JP7610474B2 - Electric Linear Actuator - Google Patents

Description

The present invention relates to a method for controlling an electric linear actuator that converts the rotational motion of an electric motor into linear motion.

Electric linear actuators have been considered for use in, for example, electric brake devices and electric press devices. As a conventional electric brake device, for example, Patent Document 1 proposes an electric actuator with a speed change function that uses a planetary roller screw structure included in a planetary rolling element.

JP 2012-057681 A

In general, in applications such as electric brakes that use electric linear actuators, precise control of the actuator is often required. In such cases, when using an electric linear actuator with a speed change mechanism such as that described in Patent Document 1, for example, if the correlation between the drive amount (amount of rotation, number of rotations) of the electric motor during operation and the operation amount (linear amount) of the linear motion of the linear actuator (i.e., equivalent to the equivalent lead corresponding to the linear amount of the linear motion relative to the amount of rotation of the electric motor) is different from expected, problems such as reduced controllability and responsiveness may occur.

For example, the linear actuator with a speed change mechanism described in Patent Document 1 has a speed change function in which, when the reaction force when the actuator applies a load to an object exceeds the spring force that applies the frictional force that rotates the multiple planetary rollers and the sun roller (or rotation input shaft) that is the rotation axis at the center of the multiple planetary rollers together, the planetary rollers rotate in the planetary reduction structure provided in the planetary roller screw structure, and a planetary reduction effect occurs in which a difference in rotation speed occurs between the planetary carrier that supports the multiple planetary rollers and the sun roller, thereby reducing the equivalent lead. In this case, there is a discontinuity in the equivalent lead based on the speed change ratio (the change ratio of the equivalent lead) in the speed change function. If the linear actuator is given such a speed change function, it is preferable because, like the clearance between the friction material and the brake rotor in an electric brake device, the equivalent lead can be relatively large until the linear actuator comes into contact with the object to which the load is applied, improving responsiveness, and after the load is applied, the equivalent lead becomes relatively small, allowing even a small motor with a small output torque to generate a large load. However, a structure that immediately changes the speed of the linear motion mechanism using the speed change function when the load is no longer zero must achieve the above-mentioned speed change operation using extremely minute spring forces and spring deformation amounts, which is extremely difficult from a manufacturing standpoint, and in order to build a stable speed change mechanism, a structure that changes speed while a certain amount of load is applied may be necessary. However, when it is necessary to control a small actuator load, such as during light braking operations in an electric brake device, the above-mentioned speed change operation may make it difficult to control the actuator load with high precision.

In addition, for example, in the gear shifting operation in the structure described in Patent Document 1, due to the nonlinear hysteresis characteristics between the displacement caused by friction and the spring force, there may be a problem that the gear shift occurs at different times, for example, when the load applied to the actuator is increased (pressure increase) and decreased (pressure decrease).

The object of this invention is to provide an electric linear actuator that can drive an electric motor with high precision by taking into account the discontinuous stiffness that occurs based on the gear ratio in the transmission mechanism in order to solve the problems of the conventional technology described above.

In order to achieve the above object, the electric linear actuator according to the present invention comprises:
the electric motor; a linear motion mechanism that converts a rotational motion of the electric motor into a linear motion; a control device that drives the electric motor to control a load that the linear motion mechanism applies to an object by the linear motion; and a speed change mechanism having a speed change function that changes the correspondence relationship between the linear motion amount of the linear motion and the rotation amount of the electric motor at a predetermined load;
The control device includes:
An estimator that estimates a load applied by the linear motion mechanism;
a load controller that uses a control gain for a control calculation in a process of deriving a drive amount of the electric motor, the control gain being multiplied by at least one or more of a deviation between the estimated value of the load and a target value of the load, an integral value of the deviation, and a differential value of the deviation, and calculates a motor drive amount using a control gain that discontinuously changes in response to a transition of at least one of the estimated value of the load and the target value at at least one point in a state in which at least one of the estimated value of the load and the target value is not zero;
a control gain adjustment unit that adjusts a control gain used in the load controller in accordance with a load condition;
has.

With the above configuration, the electric linear actuator of the present invention can drive the electric motor with high precision by setting the control gain in consideration of the discontinuous stiffness that occurs based on the gear ratio in the gear change mechanism under load conditions that cause gear changes.

In the above configuration, the speed change mechanism has the speed change function including a first equivalent lead state in which the amount of linear motion has a predetermined correlation with the amount of rotation of the electric motor, and a second equivalent lead state in which the amount of linear motion has a smaller correlation with the amount of rotation of the electric motor compared to the first equivalent lead state,
the shifting function has a nonlinearity in which, in a process in which the load applied by the linear motion mechanism increases, the shifting function switches from the first equivalent lead state to the second equivalent lead state when the load exceeds a first shift load, which is the predetermined load, and, in a process in which the load applied by the linear motion mechanism decreases, the shifting function switches from the second equivalent lead state to the first equivalent lead state when the load falls below a second shift load, which is the predetermined load different from the first shift load;
the control gain includes a first discontinuous point where a transition of the control gain with respect to the transition of the load becomes discontinuous, and the control gain on a side where the load is smaller than the first discontinuous point is smaller than the control gain on a side where the load is larger than the first discontinuous point;
The shift function having nonlinearity of the shift mechanism and the control gain may satisfy either of the following conditions i) and ii).
i) the first shift load of the shift function is greater than the second shift load, and the first discontinuity point of the control gain is closer to the first shift load than to the second shift load.
ii) the second shift load of the shift function is greater than the first shift load, and the first discontinuity point of the control gain is closer to the second shift load than to the first shift load.
As a result, in a load region where it is unstable as to whether a gear shift will occur or not, if the motor is driven assuming that the equivalent lead is small even though the equivalent lead is large, the actuator load will change significantly, which can result in unstable operation. Therefore, by operating the motor as if the equivalent lead was large at least in the region where gear shifting is unstable, the above-mentioned unstable actuator operation can be prevented.

In the above configuration, the linear motion mechanism includes:
a rotation input member, a planetary carrier supported concentrically with the rotation input member for free rotation, and a planetary rolling element supported rotatably on the planetary carrier;
an elastic member that applies a fastening force by which the planetary rolling bodies do not rotate about their axes and the rotation input member and the planetary carrier rotate synchronously by an elastic force, and that causes the fastening force to be lost by a reaction force of a load applied by the linear motion mechanism, causing the planetary rolling bodies to rotate about their axes and generating a difference in the amount of rotation between the rotation input member and the planetary carrier,
the elastic member has a nonlinear deformation characteristic in which, in a process in which the load applied by the linear motion mechanism increases, the deformation of the elastic member is completed when the load exceeds a predetermined first deformation load, and, in a process in which the load applied by the linear motion mechanism decreases, the deformation of the elastic member begins when the load falls below a second deformation load different from the first deformation load;
the control gain includes a second discontinuous point where a transition of the control gain with respect to the transition of the load becomes discontinuous, and the control gain on a side where the load is smaller than the second discontinuous point becomes larger than the control gain on a side where the load is larger than the second discontinuous point;
The deformation characteristic and the control gain of the elastic member of the linear motion mechanism may satisfy either of the following conditions i) and ii):
i) The first deformation load of the elastic member is greater than the second deformation load, and the second discontinuity of the control gain is closer to the second deformation load than to the first deformation load.
ii) the second deformation load of the elastic member is greater than the first deformation load, and the second discontinuity of the control gain is closer to the first deformation load than to the second deformation load.
As a result, in a load region where it is unstable as to whether or not spring deformation will occur in a gear shifting function using a spring elastic member, if the motor is driven assuming that the spring will deform when in fact it does not, the actuator load will change significantly, which can result in unstable operation. Therefore, by operating the motor as if the spring is not deforming at least in the region where spring deformation is unstable, it is possible to prevent the above-mentioned unstable actuator operation.

In the above configuration, the control gain adjustment unit includes a pressure increase control gain which is the control gain at the time of pressure increase when the load increases, a pressure decrease control gain which is the control gain at the time of pressure decrease when the load decreases, and a control gain switching unit which determines which of the pressure increase control gain or the pressure decrease control gain is to be referenced,
The control gain switching unit may switch the control gain based on at least a transition in the motor angle so as to refer to a control gain for a pressure increase control gain when the motor is rotating toward the pressure increase side, and to refer to a control gain for a pressure decrease control gain when the motor is rotating toward the pressure decrease side.
As a result, when a linear actuator mechanism is adopted that has nonlinear characteristics that differ between pressure increase and pressure decrease, such as the first and second shift loads and the first and second deformation loads, and that stably exhibits pressure increase characteristics when pressure is increased and exhibits pressure decrease characteristics when pressure is decreased in a load region between the first and second shift loads, or in a load region between the first and second deformation loads, the actuator can be operated with higher accuracy.

In the above configuration, the control gain adjustment unit has a first control gain which is a control gain of the electric motor when an equivalent lead corresponding to a direct motion amount of the linear motion with respect to an amount of rotation of the electric motor is large, a second control gain which is the control gain when the equivalent lead is small and the elastic member is deformed, and a third control gain which is the control gain when the equivalent lead is small and the elastic member has reached a deformation limit, and a control gain switching unit which switches between any one of the first to third control gains and uses them as a reference;
The electric linear actuator further comprises:
a change gradient calculation unit that derives a gradient of a change in either the motor angle or the estimated load relative to a change in the other;
a change gradient comparison unit that stores the gradient of change derived by said change gradient calculation unit, compares the stored gradient of change with a gradient of change newly derived by said change gradient calculation unit after said storage, and determines that a discontinuity in control gain exists when the gradient has changed by a predetermined value or more;
the control gain switching unit uses the first to third control gains, and when there are a plurality of discontinuous points, performs a control according to at least one of the plurality of discontinuous points determined by the change gradient comparing unit,
When the load is changed in a pressure increasing direction while the first control gain is being referenced, if it is determined that the discontinuous point has occurred, the second control gain is referenced;
when the pressure is increased while the second control gain is being referenced, if it is determined that the discontinuity has occurred, the third control gain is referenced, and when the pressure is decreased, if it is determined that the discontinuity has occurred, the first control gain is referenced;
In a state where the third control gain is being referenced, if there is a change in the pressure reducing direction and it is determined that the discontinuous point has occurred, the second control gain may be referenced.
As a result, the actuator can be operated with higher accuracy by adopting an appropriate control gain even in a region where the actuator stiffness is unstable, such as a linear actuator mechanism having nonlinear characteristics that differ between when the pressure is increased and when the pressure is decreased, such as the first and second shift loads and the first and second deformation loads, and a load region between the first and second shift loads and the first and second deformation loads.

In the above configuration, the control device
an estimator for estimating a rotation angle of the electric motor;
a stiffness parameter storage unit that stores a history of changes in the rotation amount of the electric motor and the estimated load when a predetermined amount of change in the load occurs within a range that includes at least the load corresponding to a discontinuity point of the pre-stored control gain;
The control device further comprises:
The control system may further include a nonlinear stiffness estimator that estimates a discontinuity point of the control gain from the change history of the angle of the electric motor and the estimated load, and updates the control gain based on the estimated discontinuity point.
As a result, by reflecting in the control gain the results of estimating at least the change in discontinuity point from the correlation between the motor rotation amount and load of the actual electric linear actuator with respect to characteristic fluctuations in the control gain that may occur due to, for example, changes in the contact state of each component of the electric linear actuator or wear of the components, it becomes possible to control the electric linear actuator with higher accuracy at least from the next operation onwards (estimated by updating from log information).

In the above configuration, the control device
An estimator for estimating a rotation angle of the electric motor,
When a predetermined amount of change in the load or the amount of rotation of the electric motor occurs, an amount of change in either the load or the amount of rotation of the electric motor is estimated and stored;
The control device further comprises:
The stored amount of change may be compared with an amount of change newly estimated after the storage, and if these amounts of change are greater than a predetermined amount, it may be determined that a discontinuity has occurred in the control gain between the angle and load of the electric motor, and the control gain may be updated based on the determined point of discontinuity.
As a result, by reflecting in the control gain the results of estimating at least the change in discontinuity point from the correlation between the motor rotation amount and the load of the actual electric linear actuator regarding characteristic fluctuations in the control gain that may occur due to, for example, changes in the contact state of each component part of the electric linear actuator or wear of the parts, it becomes possible to control the electric linear actuator with higher accuracy at least from the next operation onwards (real-time estimation).

The electric linear actuator of the present invention takes into account discontinuous stiffness that occurs based on the speed change ratio in the speed change mechanism, making it possible to drive the electric motor with high precision.

1 is a block diagram showing a schematic configuration of an electric linear actuator according to one embodiment of the present invention. FIG. 13 is a block diagram showing a schematic configuration of an electric linear motion actuator according to another embodiment of the present invention. 3 is a schematic diagram of a linear motion mechanism having a speed change mechanism in each of the electric linear motion actuators described above. FIG. FIG. 4 is a block diagram of an example of a load controller included in the control device in each of the electric linear motion actuators described above. FIG. 11 is a block diagram of another example of the load controller included in the control device in each of the electric linear motion actuators described above. 5 is an example of a characteristic diagram illustrating a control gain of a control gain adjustment unit included in the load controller. 11 is a characteristic diagram illustrating another example of a control gain of a control gain adjustment unit included in the load controller. 11 is yet another example of a characteristic diagram illustrating a control gain of a control gain adjustment unit included in the load controller. 11 is yet another example of a characteristic diagram illustrating a control gain of a control gain adjustment unit included in the load controller. 11 is yet another example of a characteristic diagram illustrating a control gain of a control gain adjustment unit included in the load controller. FIG. 3B is an example of a block diagram illustrating the load controller shown in FIG. 3A in more detail. 3B is another example of a block diagram illustrating the load controller shown in FIG. 3A in more detail. 5 is a waveform diagram showing an example of operation when a load is generated in the electric linear actuator. FIG.

<<Configuration of electric brake device>>
An electric brake device 1A to which an electric linear actuator 1 according to one embodiment of the present invention is applied will be described. Fig. 1A shows an example of the configuration of the electric brake device 1A including an electric brake control device 100A as an example of a control device 100, a brake actuator 500A as an example of an actuator 500 using a linear mechanism, and a brake instruction means 300A such as a brake pedal as an example of an instruction means 300. In this embodiment, the electric brake device 1A is used for braking a vehicle.

<<Configuration of Brake Actuator 500A>>
The brake actuator 500A is composed of an electric motor 510, a linear motion mechanism 520 that converts the rotational motion of the electric motor 510 into linear motion (linear motion) of a friction material 560 described later, an angle sensor 530 that detects and outputs the amount of rotation (number of rotations) or rotation angle (hereinafter also referred to as the motor angle) of the rotor of the electric motor 510, a brake rotor 570 that rotates integrally with the wheel and is an object of load, a friction material 560 that is pressed against the brake rotor 570 to apply a load (or linear load; in this embodiment, also referred to as the brake load) to generate a braking force on the vehicle (wheel), a load sensor 540 that detects and outputs the brake load, a reducer 550 that reduces the number of rotations of the electric motor 510 and outputs it to the linear motion mechanism 520, and a speed change mechanism 580. Note that a configuration without the reducer 550 may be used depending on the performance requirements of the brake.

The electric motor 510 is, for example, a permanent magnet synchronous motor, and such a configuration is considered to be suitable as it saves space, is highly efficient, and provides high torque. However, the invention is not limited to this, and other examples include DC motors using brushes, reluctance motors that do not use permanent magnets, and induction motors. It may also be a radial gap motor with magnetic poles in the direction of the rotational diameter, or an axial gap motor with magnetic poles in the direction of the rotational axis.

In this embodiment, the linear motion mechanism 520 is a linear motion mechanism incorporating a speed change mechanism 580 in which the equivalent lead changes depending on the linear load applied. In particular, it is preferable to use a planetary roller screw structure in which the equivalent lead changes as the planetary carrier 524 and multiple planetary rolling elements 523 are fastened or separated by the reaction force of the linear load as shown in FIG. 2 described below, as this structure is simple and space-saving. Alternatively, a linear motion mechanism can be used that combines a planetary reducer as described above equipped with a speed change mechanism and various mechanisms capable of converting rotational motion into linear motion, such as a ball screw or a ball ramp mechanism.

In this embodiment, the speed change mechanism 580 includes a spring member 581 (an example of an elastic member) and a stopper 583 shown in FIG. 2, which will be described later. Note that the speed change mechanism 580 is not limited to being built into the linear motion mechanism 520 as in this embodiment, but may be, for example, in the reducer 550 outside the linear motion mechanism 520, or may be the reducer 550, or may be another mechanism that can produce a speed change function.

The angle sensor 530 in FIG. 1A is, for example, a resolver or a magnetic encoder, and using these is considered to be preferable due to their high accuracy and reliability. However, it is not limited to these, and various sensors such as an optical encoder can also be applied. Alternatively, as another configuration, it is possible to apply angle sensorless estimation without using an angle sensor, for example, by estimating the motor angle from the relationship between voltage and current in a control device described later.

The load sensor 540 is a sensor that detects distortion or deformation in response to the load applied by the actuator, for example, and is considered to be suitable for use as it is inexpensive and highly accurate. However, the load sensor is not limited to this, and a pressure-sensitive medium such as a piezoelectric element can also be used. Alternatively, a torque sensor that detects the braking torque of the brake rotor, or, in the case of an electric vehicle brake device, an acceleration sensor that detects the longitudinal deceleration of the vehicle, can also be used.

As other elements not shown, the brake actuator 500A may be provided with a power supply device that supplies power to each part, and various sensors such as thermistors, depending on requirements. The brake actuator 500A can also be used as a parking brake actuator by providing a mechanism, such as a solenoid or DC motor, that locks the part to which the power of the actuator, such as the linear motion mechanism 520, is transmitted.

<<Configuration of electric brake control device 100A>>
The electric brake control device 100A is composed of a brake controller 110A that performs brake control calculations which is an example of a load controller 110 that performs load control calculations, a motion state estimator 120 that calculates the operating state of the motor, a brake force estimator 130A that estimates the brake force which is an example of a load force estimator 130 that estimates the load force, a motor controller 140 that controls the motor current flowing through the electric motor 510 to obtain a predetermined motor output, a motor driver 150 that supplies power to the motor, and a current sensor 160 that detects the motor current.

The motion state estimator 120 includes at least an angle estimator 121 that estimates the angle (motor angle) of the electric motor rotor, and an angular velocity estimator 123 that estimates the angular velocity of the motor angle. Alternatively, instead of having these estimators, the motion state estimator 120 may be provided with a function for estimating a predetermined differential integral value such as the electric motor angular acceleration, and a function for estimating disturbances. The motor angle may be, for example, an electrical angle phase used for current control, or a total rotation angle corrected for overlap and underlap of an angle sensor used for angle control, and the angle estimator 121 has a function for appropriately determining a required physical quantity based on a control configuration. In addition, the motor angle and angular velocity may be, for example, a rotation angle (rotation speed) of a predetermined part of a reducer determined based on a reduction ratio, or a position or speed determined based on an equivalent lead of a screw mechanism, instead of the electric motor rotor. The configuration for estimating the physical quantity may use, for example, a configuration such as a state estimation observer, or may be a direct calculation such as a back calculation based on a differential or inertia equation.

The current sensor 160 may be, for example, a sensor consisting of an amplifier that detects the voltage across a shunt resistor installed in the current path, or a non-contact sensor that detects magnetic flux around the current path. Alternatively, the current sensor 160 may be configured to detect the terminal voltage of an element that configures a motor driver. The current sensor 160 may be installed between the phases of the electric motor, or one or more current sensors may be installed on the low side or high side. Alternatively, a current value may be calculated based on motor characteristics such as inductance and resistance value without installing a current sensor, and feedforward control may be performed.

The brake controller 110A has a function of calculating an operation amount for the brake actuator 500A to follow a predetermined command input (specifically, a brake force command value or a press force command value; in Figs. 3A and 3B, a load command value) and converting it into a motor drive signal. It mainly controls the stroke position [or (linear) stroke amount (corresponding to the movement amount of the friction material 560)] of the so-called rod of the component that performs the linear motion of the linear motion mechanism 520, and is equipped with a brake force control unit 113A (an example of a load force control unit 113 for controlling the load force generated by conversion to linear motion of the linear motion mechanism) for controlling the brake force generated by the contact between the friction material 560 and the brake rotor 570, and a control gain adjustment unit 115 for adjusting the control gain calculated in the brake force control unit 113A according to the load condition.

The braking force control unit 113A (i.e., the load force control unit 113) may have a function of determining the motor drive amount of the electric motor 510 so as to control the linear stroke amount of the linear mechanism 520 converted from the motor rotation amount (or motor angle) based on, for example, the equivalent lead when a screw mechanism is used, the reduction ratio when a reducer is provided, or various specifications of the actuator 500. Alternatively, the braking force control unit 113A may have a function of providing a stroke sensor (not shown) separately and performing feedback control to make the sensor signal follow a predetermined target value. In addition, the braking force control unit 113A may also have a function of setting the stroke amount so that a predetermined gap can exist between the friction material 560 and the brake rotor 570 so that they do not come into contact as much as possible when the brake is released. The stroke amount that can become the predetermined gap can be set, for example, as a position where the motor is rotated a predetermined amount from the motor angle where the estimated braking force estimated by the braking force estimator 130A becomes a predetermined value, or a position where the motor is rotated a predetermined amount after the estimated braking force stops changing with the transition of the motor angle (or after the amount of change becomes smaller than a predetermined value). In addition, the braking force control unit 113A may function to set the stroke state where the gap is close to zero or a value smaller than zero, for example, in order to control extremely slight braking forces that may be difficult to detect using a load sensor that detects the braking force or the torque sensor described above.

In this embodiment, specifically, the brake force control unit 113A has a function of determining the motor drive amount so that the brake force when the friction material 560 and the brake rotor 570 are brought into contact is controlled to follow a predetermined target value. In this embodiment, the pressing force between the friction material 560 and the brake rotor 570 is detected by the load sensor 540, and an example is shown in which the brake force is estimated from the output of the load sensor 540 by a brake force estimator 130A (described later) (estimated brake force), but the brake force can also be controlled using a torque sensor or the like that detects the braking torque of the brake rotor described above.

The control gain adjustment unit 115 has a function of adjusting the control gain applied when calculating the operation amount in the braking force control unit 113A to a control gain that takes into account the nonlinear characteristics that arise mainly due to the speed change mechanism 580 present in the linear motion mechanism in this embodiment, using the motor rotation amount determined from the motor angle of the electric motor 510 and the brake load, which is an example of the actuator load, etc. This nonlinear characteristic will be described next.

(1) In the linear motion mechanism 520 of this embodiment, when the planetary carrier 524 and the rotating shaft 521 in FIG. 2 are fastened and rotate together (referred to as the integral rotation state), the equivalent lead is relatively large, and when the planetary carrier 524 and the rotating shaft 521 are separated and the planetary rolling body 523 rotates (referred to as the separated rotation state), the equivalent lead is relatively small due to the planetary deceleration effect. In other words, when the state changes between the integral rotation state and the separated rotation state, the stiffness, which is the correlation between the motor rotation amount and the brake load, becomes a discontinuous stiffness that depends at least on the presence or absence of the planetary deceleration effect. In other words, the gradient of change in either the motor rotation amount or the brake load relative to the other becomes a stiffness that transitions discontinuously at least by the deceleration ratio due to the planetary deceleration effect.

(2) For example, when using an elastic member (in this embodiment, a spring member) 581 that deforms due to the reaction force of a linear load as a means for fastening or separating the planetary carrier 524 and planetary rolling element 523 described above, the closer to zero the deformation amount of the spring member 581 is, the better in terms of performance. However, due to manufacturing reasons such as dimensional tolerances, the reality is that a structure that only deforms a predetermined amount is unavoidable. Therefore, while the spring member 581 is deforming, the rigidity of the spring member becomes discontinuous, especially when the deformation of the spring member 581 reaches its limit and it can no longer deform.

In addition, in this embodiment, for example, a function may be provided to provide a predetermined clearance between the friction material 560 and the brake rotor 570 when the braking force is set to zero. In addition, in the braking force control unit 113A, an arithmetic expression may be used to derive a motor angle or angular velocity based on the feedback deviation of the braking force as the motor drive amount for controlling the braking force to follow a desired target value, and a minor control loop may be provided separately to provide feedback of the motor angle or angular velocity.

The motor controller 140 has a function of controlling the motor current so that it follows a predetermined motor drive signal output from the brake force controller 110A (load controller 110). In order to obtain a predetermined torque at a predetermined motor angular velocity, the motor controller 140 stores the optimal current conditions in a look-up table (LUT) in advance, determines a target current value from the current motor angular velocity, and controls the motor current to the target current value. This is considered to be preferable because it allows inexpensive and highly accurate control. However, the present invention is not limited to this, and the motor controller 140 can also function to calculate the relational expressions between the currents and voltages to derive the output of the electric motor 510 and determine the drive conditions in real time.

The motor driver 150 is configured with a bridge circuit using switching elements such as FETs (Field Effect Transistors), and is considered to be suitable for low cost and high performance if configured to perform PWM (Pulse Width Modulation) control, which determines the motor application voltage based on a predetermined duty ratio (the ratio between the high time and low time of the motor application voltage). Alternatively, the motor driver 150 can be configured to perform PAM (Pulse Amplitude Modulation) control by providing a transformer circuit or the like.

The brake force estimator 130A, which is an example of the load force estimator 130, has a function of estimating the brake force generated by the contact between the brake rotor 570 and the friction material 560. Specifically, the brake force estimator 130A receives an input from the load sensor 540 and outputs an estimated brake force.

Instead of a brake pedal, the brake instruction means 300A can use various control means that can be operated by the driver, such as a volume, joystick, switch, etc.

The vehicle motion control device 700 includes an automatic brake function unit (not shown) that prevents vehicle collisions or reduces the impact of collisions, a skid prevention function unit that prevents vehicle spinning by braking at least when the vehicle is in a skid state, and an anti-skid control unit that prevents the wheels from locking due to braking and making the vehicle behavior unstable, and determines and outputs a brake operation amount to apply a predetermined amount of brakes to the vehicle. The vehicle motion control device 700 may be an integrated control device that integrates information from various on-board sensors such as a gravity sensor, an object sensor, and a GPS (Global Positioning System), not shown, and performs calculations required for the various functions. The brake operation amount determined by the vehicle motion control device 700 is also transmitted to the electric brake control device 100A as a target brake force or a part of the target brake force.

＜＜Others＞＞
A power supply device may be provided as an element not shown in the figure. In an electric brake device for an automobile, for example, the power supply device may be a low-voltage battery or a step-down converter that steps down a high-voltage battery. Alternatively, a high-capacity capacitor or the like may be used, or these may be used in parallel for redundancy. In addition, it is preferable that the motor driver and solenoid driver are directly supplied with power output, and a small step-down converter is applied within the electric brake control device 100A to step down the voltage of the various computing units and functional units, etc., or the power output may be directly supplied to the various computing units and functional units, etc., and power may be supplied via a step-up converter to either or both of the motor driver and the solenoid.

In addition, it is considered preferable that the above various computing units and functional units are configured with electronic components such as a processor such as a programmable microcomputer, an FPGA (Field Programmable Gate Array), or an ASIC (Application Specific Integrated Circuit), which are inexpensive and have high performance. The functional blocks shown in this figure are provided solely for convenience of description and do not restrict the specification of the hardware or software configuration or the division of functions, and the functions of each block may be integrated or divided as necessary. In addition, the specific configuration of the software and hardware may be configured arbitrarily as long as it does not interfere with the functions shown in this embodiment. Elements not shown in the figure may also be added as long as it does not interfere with the functions of this embodiment. For example, it is preferable to add safety mechanisms in case of failure of various functions or sensors, etc., based on the system requirements.

The electric brake device 1A can be used not only as a brake device for vehicles, but also as a brake device for stopping lifting devices, power generation devices, and energy storage devices such as flywheels.

An electric press 1B to which an electric linear actuator 1 according to another embodiment of the present invention is applied will be described. FIG. 1B shows an example of the configuration of an electric press 1B including an electric press control device 100B as an example of a control device 100, a press actuator 500B as an example of an actuator 500 using a linear mechanism, and a press controller 300B as an example of an instruction means 300. The electric press 1B is different from the electric brake device 1A of the previous embodiment in that the object to which the load is applied is the press object 590 of the press actuator 500B instead of the brake rotor 570 of the brake actuator 500A. In the electric press 1B, components with the same reference numerals as those of the electric brake device 1A have the same functions in principle, so their functions can be guessed and will not be described below.

The press controller 110B of the electric press control device 100B is an example of a load controller 110 that performs load control calculations, and performs calculations for press control, etc. The press load estimator 130B is an example of a load force estimator 130 that estimates the load force, and estimates the press force (or press load) from the drive mechanism 520 to the press object 590.

The press load control unit 113B (an example of a load controller 113) of the press controller 110B is an example of a load force control unit 113 for controlling the load force generated by the conversion of the linear motion of the linear motion mechanism to linear motion. The press load control unit 113B has a function of determining the motor drive amount so as to control the press force from the drive mechanism 520 to the press object 590 to follow a predetermined target value. In the press load control unit 113B of this embodiment, the press force is detected by the load sensor 540, and an example is shown in which the press load control unit 113B functions based on the press force (estimated press force) estimated by the press load estimator 130B from the output of the load sensor 540.

<<Structural example of linear motion mechanism 520>>
2A is a schematic diagram of a linear motion mechanism 520 having a speed change mechanism 580 in an unloaded state. A planetary carrier 524 supporting a plurality of planetary rolling elements 523 is pressed against a stopper 583 by a spring member 581, which is an elastic member, and is integrated with the rotation input shaft 521 so that the planetary rolling elements 523 do not rotate on their own axis, and the planetary carrier 524 and the rotation input shaft 521 rotate together (integral rotation state), resulting in the same operation as a general sliding screw.

Figure 2(b) shows a schematic diagram of the linear motion mechanism 520 with the speed change mechanism 580 when a linear motion load of a predetermined value or more is applied. The spring member 581 is compressed by Δ due to the reaction force transmitted from the outer ring 525 to the force applied by converting the rotational force of the rotation input shaft 521 into a linear motion load via the planetary rolling body 523. As a result, the pressure of the planetary carrier 524 against the stopper 583 is released, the integration of the planetary carrier 524 and the rotation input shaft 521 is released, the planetary rolling body 523 begins to rotate (separated rotation state), and a planetary deceleration effect occurs in which a difference in rotational speed occurs between the rotation input shaft 521 and the planetary carrier 524, and the equivalent lead is reduced compared to the case of Figure 2(a).

<<Configuration Example of Load Controller 110>>
Fig. 3A shows an example of the configuration of a load controller 110 including the brake controller 110A of Fig. 1A and the press controller 110B of Fig. 1B. The load target value (command input) and estimated load in the figure become a brake force command value and an estimated brake force, respectively, when configuring the brake controller 110A, and become a press force command value and an estimated press force, respectively, when configuring the press controller 110B.

The load control unit 113 derives the motor drive amount for making the estimated load value of the actual machine follow the target load value. For example, it can calculate the deviation between the target load value and the estimated load value, and determine the operation amount that makes the deviation zero or within an acceptable error range.

The control gain adjustment unit 115 has a function of acquiring a load target value, deriving a control gain setting value corresponding to the load target value, and updating the control gain of the load control unit 113 to the control gain setting value. This control gain setting value is a value that changes discontinuously in response to discontinuous nonlinear stiffness (e.g., due to a speed change mechanism as shown in FIG. 2).

In the load control unit 113, for example, PID compensation (or PID control [Proportional Integral Differential Control]) is performed on the deviation between the estimated load value and the target load value. In this case, the control gain adjustment unit 115 may be a function to adjust one steady-state gain related to all gains of the P control [Proportional Control], I control [Integral Control], and D control [Differential Control], or a function to adjust the gains of each element of the P control, I control, and D control individually. Alternatively, for example, when a state feedback controller having a predetermined feedback loop eigenvalue is applied in the load control unit 113, the control gain adjustment unit 115 may be a function to adjust at least the time constant of the eigenvalue. These adjusted values can be derived by a predetermined calculation formula, but it is preferable to store a predetermined design value according to the load in a LUT (Look Up Table) or the like in advance and refer to the LUT or the like, since this reduces the amount of calculation.

In addition, in this embodiment, the motor drive amount indicates a motor torque command value, which is considered preferable because it allows the controller to be designed based on a simple equation of motion. However, this is not limited to this, and it is also possible to derive, for example, a motor current command value or a voltage to be directly applied to the motor.

Figure 3B shows an example of a configuration for the control gain adjustment unit 115 in Figure 3A, in which the control gain is determined by referring to an estimated load instead of a load target value as an input. Other than this difference, the configuration is the same as in Figure 3A, so a detailed description will be omitted. Note that the calculation of the control gain setting value can also be performed by using an intermediate value such as a weighted average value of the load target value and the estimated load, for example, by combining the configurations in Figures 3A and 3B.

<<Control Gain Adjustment Unit 115>>
4A to 4E show examples of nonlinear stiffness (pressure increase characteristics, pressure decrease characteristics) when linear motion mechanism 520 having speed change mechanism 580 in Fig. 2 is applied, and corresponding control gains (control gain setting values) calculated by control gain adjuster 115 in Fig. 3A and Fig. 3B (actuator load vs. motor rotation amount and control gain characteristics). In the upper diagram of each diagram, the solid line shows the pressure increase characteristics during pressure increase, and the dashed line shows the pressure decrease characteristics during pressure decrease.

Figures 4A to 4E show the control gain with respect to the actuator load (or linear load). If the point where the gradient of change in the motor rotation amount with respect to the actuator load (called the gradient of change in the motor rotation amount) or the reverse gradient of change in the actuator load with respect to the motor rotation amount changes discontinuously is defined as a discontinuous point, in this embodiment, there are two discontinuous points of stiffness in each of the boost characteristic and the decompression characteristic in the figure, and counting from the lowest actuator load, the first is a discontinuous point where a shift occurs in which the equivalent lead of the linear mechanism changes, and the second is a discontinuous point due to deformation such as the deformation limit of the spring member (elastic member) of the speed change mechanism. Here, discontinuity includes the above-mentioned discontinuity even if it shows a continuity that changes gradually when viewed microscopically, when the above-mentioned gradient of change changes extremely sharply when viewed macroscopically on a full scale. On the other hand, discontinuity between samples caused by discretization in discretized information such as LUT is not included in the above-mentioned discontinuity.

Here, for example, in cases where the deformation amount of the spring member is extremely close to zero, or where a structure is adopted in which a spring member is used that does not reach its deformation limit even when the linear motion mechanism 520 applies a maximum load, it is possible for the control gain to be such that the second discontinuity does not exist.

In general, the nonlinear stiffness of a linear mechanism during pressure increase and pressure decrease has a nonlinearity that does not match when pressure is increased or decreased, mainly due to factors such as friction at the contact points of the components where deformation occurs (the hysteresis characteristic described above), and the tendency of this mismatch varies depending on the linear mechanism used. Nonlinearity can also change due to aging or wear, and it can also change depending on the operating history, such as how much load was generated. In other words, at least in the region where the characteristics of the pressure increase side and the pressure decrease side differ in the control gain for the actuator load shown in the figure (the intermediate region), it is difficult to clearly grasp in advance what type of stiffness will be exhibited.

In FIG. 4A, when pressure is increased, at the first specified actuator load F1a when viewed from the low actuator load side, a shift occurs as the actuator changes from a rotating together state to a rotating apart state, reducing the equivalent lead and creating a discontinuous point where the gradient of change in motor rotation amount with respect to actuator load increases. In the characteristics when pressure is reduced, the equivalent lead is large at F1a and the gradient of change in motor rotation amount is relatively small compared to the characteristics when pressure is increased. In the characteristics when pressure is reduced, at actuator load F2a, which is larger than F1a, a shift occurs again as the actuator changes from a rotating together state to a rotating together state, creating a characteristic where the first discontinuous point occurs when viewed from the low actuator load side.

At this time, the control gain in the control gain adjustment unit 115 transitions from a low to a high state at the first discontinuity point when viewed from the low load side, and in the section from F1a to F2a, the control gain is in a low state, and the discontinuity point F2a on the pressure reduction side is used as the discontinuity point. This is preferable because it can prevent deterioration in controllability such as the actuator overshooting significantly when the motor is driven strongly assuming that the equivalent lead is small even when the equivalent lead is large. Note that the discontinuity point of the control gain may be a discontinuity point at a load that is sufficiently closer to F2a than F1a, or the discontinuity point may be set to a load slightly larger than F2a, taking into account the individual characteristics variations of the actuator and changes over time.

In this embodiment, high and low control gains not only mean that the absolute value of the coefficient actually multiplied is large and small, but also mean that the time constant for the eigenvalue of the control loop that is configured is small (= fast) and large (= slow).

In addition, at the second actuator load F3a when viewed from the low actuator load side during pressure increase, the spring member (elastic member) 581 of the speed change mechanism 580 reaches its deformation limit, and a discontinuous point occurs where the gradient of the change in the motor rotation amount with respect to the actuator load decreases. During pressure reduction, a predetermined actuator load F4a smaller than the F3a becomes the second discontinuous point when viewed from the low actuator load side. At this time, the control gain in the control gain adjustment unit 115 transitions from a high control gain state to a low control gain state at the second discontinuous point when viewed from the low load side, and in the section from F4a to F3a, the control gain is in a low state, and the discontinuous point adopts a characteristic having a discontinuous point of F4a on the pressure reduction side. This is preferable because it can prevent deterioration in controllability such as the actuator overshooting significantly when the motor is driven largely assuming that the equivalent lead is small even when the equivalent lead is large. The discontinuity point of the control gain may be set at a load that is sufficiently closer to F4a than to F3a, or may be set at a load slightly smaller than F4a, taking into account variations in the characteristics of individual actuators and changes over time.

In Figure 4B, when pressure is increased, at the first specified actuator load F1b when viewed from the low actuator load side, a shift occurs as the actuator transitions from an integral rotation state to a counter-rotation state, reducing the equivalent lead and creating a discontinuous point where the gradient of change in motor rotation amount with respect to actuator load increases. When pressure is reduced, at actuator load F2b, which is smaller than F1b, a shift occurs again as the actuator transitions from a counter-rotation state to an integral rotation state, creating the first discontinuous point when viewed from the low actuator load side. In the characteristics when pressure is reduced, the gradient of change in motor rotation amount is larger in the load region smaller than F1b compared to the characteristics when pressure is increased.

At this time, preferably, in the section from F2b to F1b, the control gain is low, and the discontinuity point adopted is the discontinuity point of F1b on the pressure increase side. The discontinuity point of the control gain may be a discontinuity point at a load sufficiently closer to F1b than F2b, or, taking into account the variation in characteristics between individual actuators and aging, the discontinuity point may be set to a load slightly greater than F1b. Note that the control gain in the section from F4b to F3b, where a discontinuity point occurs due to deformation of the spring member in the characteristics of both the pressure increase and pressure decrease, can be set in the same way as in the section from F4a to F3a in FIG. 4A.

In Figure 4C, when pressure is increased, the spring member (elastic member) 581 of the speed change mechanism 580 reaches its deformation limit at the second specified actuator load F3c when viewed from the low actuator load side, creating a discontinuous point where the gradient of change in motor rotation amount relative to the actuator load decreases. When pressure is decreased, a specified actuator load F4c that is greater than F3c becomes the second discontinuous point when viewed from the low actuator load side.

In this case, preferably, the control gain in the control gain adjustment unit 115 is in a low state in the section from F3c to F4c, and the discontinuity point adopted is the discontinuity point of F3c on the pressure increase side. The discontinuity point of the control gain may be a discontinuity point at a load sufficiently closer to F3c than F4c, or the discontinuity point may be set to a load slightly smaller than F3c, taking into account the variation in characteristics of individual actuators and aging. The control gain in the section from F1c to F2c, where a discontinuity point occurs due to a change in the equivalent lead, may be set in the same way as in the section from F1a to F2a in FIG. 4A.

For FIG. 4D, the control gain can be determined between actuator loads F1d and F2d in the same manner as between F1b and F2b in FIG. 4B, and between actuator loads F3d and F4d in the same manner as between F3c and F4c in FIG. 4C. FIG. 4E shows an example of the control gain when an electric linear actuator 1 having a speed change mechanism 580 is applied to an electric brake device 1A. The pressure increase characteristic, pressure decrease characteristic, and control gain in FIG. 4A are closer to a curve than a straight line.

Generally, electric brake devices have nonlinear stiffness due to the influence of nonlinear stiffness of friction materials for brakes, etc., but while the change is generally continuous, discontinuous change occurs when the linear motion mechanism 520 having the speed change mechanism 580 shown in FIG. 2 is applied. Therefore, as a control gain for that, a discontinuous point of the control gain corresponding to the discontinuous point of the stiffness due to the speed change mechanism 580 is set, and the control gain can be made to change continuously in other regions. Note that the nonlinearity due to pressure increase/decrease is described as showing the same trend as in FIG. 4A, but when an actuator showing the trend of FIG. 4B to FIG. 4D is used, the discontinuous point of the control gain can be set in the same way as in FIG. 4B to FIG. 4D. Also, an example is shown in which the section excluding the discontinuous point of the control gain has continuous nonlinearity, but the controller may be designed to be somewhat robust and simplified to change at a constant gradient, or it may be set to an approximately constant value.

<<Other Examples of Control Gain Adjustment Unit 115>>
Fig. 5A shows an example in which the nonlinear stiffness and its discontinuity points are estimated from the motor angle and the estimated load, and the control gain of the control gain adjustment unit 115 is adjusted and updated based on the estimation result. In Fig. 5A, the control gain adjustment unit 115 has a pressure increase control gain 115a in which the control gain at the time of pressure increase is stored, and a pressure decrease control gain 115b in which the control gain at the time of pressure decrease is stored, and further has a control gain switching unit 115c that determines whether the control gain at the time of pressure increase control gain 115a or the pressure decrease control gain 115b is to be referenced.

The control gain switching unit 115c can have a function of switching the control gain so that, for example, when it is determined from the transition of the motor angle that the motor is rotating on the pressure-increasing side, the control gain of the pressure-increasing control gain 115a is referenced, and when it is determined that the motor is rotating on the pressure-reducing side, the control gain of the pressure-reducing control gain 115b is referenced. Alternatively, the control gain switching unit 115c may determine whether the motor is rotating on the pressure-increasing side by a predetermined amount or more, the motor is rotating on the pressure-reducing side by a predetermined amount or more, or an intermediate state that does not correspond to either of these, and in the intermediate state, the control gain in which the control gains at the pressure-increasing and pressure-reducing times are combined at a predetermined ratio may be referenced. Alternatively, instead of the motor angle, a determination may be made as to whether the control gain is to be referenced from the pressure-increasing control gain 115a or the pressure-reducing control gain 115b from the transition of the estimated load.

Now, in FIG. 5A, in addition to having the above-mentioned control gain adjustment unit 115, and in addition to the configuration of FIG. 3A, a stiffness parameter storage unit 117 and a nonlinear stiffness estimation unit 118 are also included. The stiffness parameter storage unit 117 stores a history of changes in the amount of rotation of the electric motor 510 and the estimated load when a predetermined amount of change in the load occurs within a range that includes at least the load corresponding to the discontinuity point of the pre-stored control gain. Specifically, the stiffness parameter storage unit 117 includes a pressure increase data storage unit 117a that stores the motor angle and estimated load during pressure increase operation, and a pressure reduction data storage unit 117b that stores the motor angle and estimated load during pressure reduction operation.

The nonlinear stiffness estimation unit 118 estimates a discontinuous point in the correlation between the motor angle and the load in the control gain from the change history of the angle of the electric motor 510 and the estimated load, and updates the control gain based on the estimated discontinuous point. Specifically, the nonlinear stiffness estimation unit 118 includes a convergence calculation unit 118a that performs parameter fitting to minimize an error for a predetermined function for estimating the discontinuous point and deriving the nonlinear stiffness, for the motor angle and the estimated load stored in the stiffness parameter storage unit 117, and a control gain calculation unit 118b that derives the nonlinear stiffness based on the result of the convergence calculation unit 118a. The parameter fitting in the convergence calculation unit 118a is performed at a stage when a sufficient range of data including at least the discontinuous points of stiffness is accumulated in the stiffness parameter storage unit 117.

ここで、g1(Fnl1) = g2(Fnl1), g2(Fnl2) = g3(Fnl2) を満足させるようg1(F), g2(F), g3(F)のうち何れか２つの関数の定数項は調整され、g1(F), g2(F), g3(F)のうち前記２つを除いた１つの関数の定数項Fcは後述のパラメータフィッティングの変数に用いる。 In the convergence calculation unit 118a, the nonlinear stiffness for the motor angle θ and load F is derived as follows using a function g1(F) indicating the stiffness when the equivalent lead is large, a function g2(F) indicating the stiffness when the equivalent lead is small and the spring member deforms, a function g3(F) indicating the stiffness when the equivalent lead is small and the spring member does not deform (e.g., at the deformation limit), and a load Fnl1 where g1(F) and g2 coincide, and a load Fnl2 where g2(F) and g3(F) coincide, which correspond to two discontinuous points.

Here, the constant terms of any two of the functions g1(F), g2(F), and g3(F) are adjusted so as to satisfy g1(Fnl1) = g2(Fnl1), g2(Fnl2) = g3(Fnl2), and the constant term Fc of one function other than the two functions among g1(F), g2(F), and g3(F) is used as a variable for parameter fitting described below.

The convergence calculation unit 118a calculates, for each data sample θ1...θk and F1...Fk (k is the number of samples) in the stiffness parameter storage unit 117 during pressure increase and decrease, two discontinuous points Fnl1, Fnl2 and variables of the constant term Fc in the equation θ=f(F) that minimize the following error function J by using a convergence calculation algorithm such as Newton's method.

The control gain calculation unit 118b derives the control gains for increasing and decreasing pressure based on the calculation results of the convergence calculation unit 118a. After the derivation of the control gains is completed, the control gains of the control gain adjustment unit 115 are updated. The control gains can be derived as control gains that are determined for each function based on the derivation results of the stiffness functions g1, g2, and g3, and are combined so as to switch under load conditions corresponding to the discontinuous points Fnl1 and Fnl2. Alternatively, the derivation process may be simplified by using a control gain that is combined so as to switch under load conditions corresponding to the discontinuous points Fnl1 and Fnl2, instead of a control gain for each function that is set in advance. In this case, the functions g1, g2, and g3 in the convergence calculation unit can also be fixed functions, resulting in a further simplified calculation process.

After the derivation of the control gain is completed, the control gain adjustment unit 115 updates the control gain discontinuity points stored in the control gain adjustment unit based on the derived control gain discontinuity points. At this time, the discontinuity points for the control gains during pressure increase and pressure decrease are determined according to the method described using Figures 4A to 4E.

The control gains for pressure increase and pressure decrease may be updated simultaneously, or each may be updated individually at any timing.

In addition to the above operations, the control device 100 may estimate and store the amount of change in either the load or the amount of rotation of the electric motor 510 relative to the other when a predetermined amount of load change or amount of rotation of the electric motor 510 occurs. Furthermore, the control device 100 may compare this stored amount of change with an amount of change newly estimated after the storage, and if these amounts of change are greater than a predetermined amount, determine that a discontinuity has occurred between the angle of the electric motor 510 and the load in the control gain, and update the control gain based on this determined discontinuity.

As an element not shown, it is preferable to provide a function for appropriately resetting internal parameters so that unnecessary motor drive commands are not calculated by the load control unit 113 when the control gain is switched by the control gain switching unit 115c of the control gain adjustment unit 115, or when the control gains 115a and 115b for pressure increase and pressure decrease are updated.

In FIG. 5B, unlike FIG. 3A etc., the control gain adjustment unit 115 includes a first control gain 115d adjusted to a control gain when the equivalent lead of the linear motion mechanism is large, a second control gain 115e adjusted to a control gain when the equivalent lead is small and the spring member is deformed, and a third control gain 115f adjusted to a control gain when the equivalent lead is small and the spring member has reached its deformation limit. In FIG. 5B, instead of using the control gain in FIG. 3A etc., the first to third control gains are appropriately switched and referenced, thereby achieving the same effect as referring to a nonlinear control gain having two discontinuities as in FIG. 3A etc. (which may include the pressure increase control gain and pressure decrease control gain in FIG. 5A). Therefore, the control gain adjustment unit 115 in FIG. 5B further includes a control gain switching unit that switches to one of the first to third control gains and references it. Also, in FIG. 5B, a discontinuity estimation unit 119 exists. The first to third control gains may each be a constant value as shown in the figure, but may also vary so that each continuously increases or decreases with respect to the load.

The discontinuity point estimation unit 119 includes a change gradient calculation unit 119a that derives the change gradient of either the motor angle or the estimated load in response to a change in the other, and a change gradient comparison unit 119b that compares an already stored change gradient with the result derived by the change gradient calculation unit and newly stores the result derived by the change gradient calculation unit.

The change gradient calculation unit 119a may be a function that evaluates the amount of change in the motor angle or the estimated load when either one of them changes by a predetermined amount. For example, specifically, for the load change amount Fdelta when the motor angle changes by a predetermined θdelta, the change gradient may be Fdelta/θdelta. Alternatively, for the angle and load change over a predetermined time dt, the change gradient may be (F(t+dt)-F(t))/(θ(t+dt)-θ(t)).

The change gradient comparison unit 119b compares the change gradient already stored with the derived change gradient, and if the comparison result shows a change of a predetermined amount or more, it can determine that a discontinuity in stiffness has occurred. If a discontinuity is determined, information about the discontinuity is transmitted to the control gain adjustment unit 115.

For example, in the pressure increase direction, when it is determined that a discontinuity has occurred while the control gain of the first control gain 115d is being referenced, the control gain switching unit 115c may transition to a state in which the control gain of the second control gain 115e is being referenced. In addition, in the pressure increase direction, when it is determined that a discontinuity has occurred while the control gain of the second control gain 115e is being referenced, the control gain switching unit 115c may transition to a state in which the control gain of the third control gain 115f is being referenced, and in the pressure reduction direction, when it is determined that a discontinuity has occurred while the control gain of the second control gain 115e is being referenced, the control gain switching unit 115c may transition to a state in which the control gain of the first control gain 115d is being referenced. In the pressure reduction direction, when it is determined that a discontinuity has occurred while the control gain of the third control gain 115f is being referenced, the control gain switching unit 115c may transition to a state in which the control gain of the second control gain 115e is being referenced.

As an element not shown, when the control gain is switched by the control gain switching unit 115c of the control gain adjustment unit 115, it is preferable to provide a function for appropriately resetting internal parameters so that unnecessary motor drive commands are not calculated by the load control unit 113.

<<Operation Example of Electric Brake Device 1A>>
FIG. 6 shows an example of operation in which a predetermined braking force is generated from an unloaded state in which a predetermined clearance is provided between the friction material 560 and the brake rotor 570. FIG. 6(a) shows an example of application of the electric linear actuator 1 described in the above embodiment to which the linear mechanism 520 having the speed change mechanism 580 described in FIG. 2 is applied. In FIG. 6(a), the braking force FF can be exerted without overshooting due to deterioration of controllability depending on the occurrence of nonlinear speed change operation, and since the equivalent lead of the linear mechanism can be changed, the braking force is generated at a relatively early time TT1 from the unloaded state. FIG. 6(b) shows an example of operation by a conventional electric linear actuator to which a linear mechanism without a speed change mechanism is applied. In FIG. 6(b), since the equivalent lead of the linear mechanism is constant, it takes a relatively long time from the unloaded state to the time TT2 at which the braking force is generated. FIG. 6(c) shows an example of operation by a conventional control method to which the linear mechanism 520 having the speed change mechanism 580 described in FIG. 2 is applied, but other than that. In FIG. 2(c), because the equivalent lead of the linear motion mechanism can be changed, braking force is generated at a relatively short time TT1 from the no-load state. However, due to the occurrence of non-linear gear shifting operation, controllability deteriorates and a relatively large overshoot occurs before the braking force FF is exerted.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

1 Electric linear actuator 1A Electric brake device (electric linear actuator)
1B Electric press device (electric linear actuator)
100 Control device 100A Electric brake control device (control device)
100B Electric press control device (control device)
113 Load controller 113A Brake force control unit (load controller)
113B Press load control unit (load controller)
115 Control gain adjustment unit 115a Pressure increase control gain 115b Pressure decrease control gain 115c Control gain switching unit 115d First control gain 115e Second control gain 115f Third control gain 117 Stiffness parameter storage unit 118 Non-linear stiffness estimation unit 119a Change gradient calculation unit 119b Change gradient comparison unit 510 Electric motor 520 Linear motion mechanism 523 Planetary rolling element 524 Planetary carrier 530 Angle sensor (estimator for estimating the amount of rotation of the electric motor)
540 Load sensor (Estimator for estimating the load applied by the linear motion mechanism)
570 Brake rotor (object)
580 Speed change mechanism 581 Spring member (elastic member) (speed change mechanism)
583 Stopper (speed change mechanism)

Claims (6)

the electric motor; a linear motion mechanism that converts a rotational motion of the electric motor into a linear motion; a control device that drives the electric motor to control a load that the linear motion mechanism applies to an object by the linear motion; and a speed change mechanism having a speed change function that changes the correspondence relationship between the linear motion amount of the linear motion and the rotation amount of the electric motor at a predetermined load;
The control device includes:
An estimator that estimates a load applied by the linear motion mechanism;
a load controller that uses a control gain for a control calculation in a process of deriving a drive amount of the electric motor, the control gain being multiplied by at least one or more of a deviation between the estimated value of the load and a target value of the load, an integral value of the deviation, and a differential value of the deviation, and calculates a motor drive amount using a control gain that discontinuously changes in response to a transition of at least one of the estimated value of the load and the target value at at least one point in a state in which at least one of the estimated value of the load and the target value is not zero;
a control gain adjustment unit that adjusts a control gain used in the load controller in accordance with a load condition;
having
the speed change mechanism has the speed change function including a first equivalent lead state in which the amount of linear motion has a predetermined correlation with the amount of rotation of the electric motor, and a second equivalent lead state in which the amount of linear motion has a smaller correlation with the amount of rotation of the electric motor compared to the first equivalent lead state;
the shifting function has a nonlinearity in which, in a process in which the load applied by the linear motion mechanism increases, the shifting function switches from the first equivalent lead state to the second equivalent lead state when the load exceeds a first shift load, which is the predetermined load, and, in a process in which the load applied by the linear motion mechanism decreases, the shifting function switches from the second equivalent lead state to the first equivalent lead state when the load falls below a second shift load, which is the predetermined load different from the first shift load;
the control gain includes a first discontinuous point where a transition of the control gain with respect to the transition of the load becomes discontinuous, and the control gain on a side where the load is smaller than the first discontinuous point is smaller than the control gain on a side where the load is larger than the first discontinuous point;
The shift function having nonlinearity of the shift mechanism and the control gain satisfy either of the following conditions i) and ii):
Electric linear actuator.
i) the first shift load of the shift function is greater than the second shift load, and the first discontinuity point of the control gain is closer to the first shift load than to the second shift load.
ii) the second shift load of the shift function is greater than the first shift load, and the first discontinuity point of the control gain is closer to the second shift load than to the first shift load. 2. The electric linear actuator according to claim 1 ,
The linear motion mechanism includes:
a rotation input member, a planetary carrier supported concentrically with the rotation input member for free rotation, and a planetary rolling element supported rotatably on the planetary carrier;
an elastic member that applies a fastening force by which the planetary rolling bodies do not rotate about their axes and the rotation input member and the planetary carrier rotate synchronously by an elastic force, and that causes the fastening force to be lost by a reaction force of a load applied by the linear motion mechanism, causing the planetary rolling bodies to rotate about their axes and generating a difference in the amount of rotation between the rotation input member and the planetary carrier,
the elastic member has a nonlinear deformation characteristic in which, in a process in which the load applied by the linear motion mechanism increases, the deformation of the elastic member is completed when the load exceeds a predetermined first deformation load, and, in a process in which the load applied by the linear motion mechanism decreases, the deformation of the elastic member begins when the load falls below a second deformation load different from the first deformation load;
the control gain includes a second discontinuous point where a transition of the control gain with respect to the transition of the load becomes discontinuous, and the control gain on a side where the load is smaller than the second discontinuous point becomes larger than the control gain on a side where the load is larger than the second discontinuous point;
The deformation characteristic and the control gain of the elastic member of the linear motion mechanism satisfy either of the following conditions i) and ii):
Electric linear actuator.
i) The first deformation load of the elastic member is greater than the second deformation load, and the second discontinuity of the control gain is closer to the second deformation load than to the first deformation load.
ii) the second deformation load of the elastic member is greater than the first deformation load, and the second discontinuity of the control gain is closer to the first deformation load than to the second deformation load. 3. The electric linear actuator according to claim 1,
the control gain adjustment unit has a pressure increase control gain which is the control gain at the time of pressure increase when the load increases, a pressure decrease control gain which is the control gain at the time of pressure decrease when the load decreases, and a control gain switching unit which determines which of the pressure increase control gain or the pressure decrease control gain is to be referred to,
the control gain switching unit switches the control gain so as to refer to a control gain for a pressure increase control gain when the motor is rotating toward a pressure increase side, and to refer to a control gain for a pressure decrease control gain when the motor is rotating toward a pressure decrease side, based on at least a transition of the motor angle.
Electric linear actuator. 3. The electric linear actuator according to claim 2 ,
the control gain adjustment unit has a first control gain which is a control gain of the electric motor when an equivalent lead corresponding to a direct motion amount of the linear motion with respect to an amount of rotation of the electric motor is large, a second control gain which is the control gain when the equivalent lead is small and the elastic member is deformed, and a third control gain which is the control gain when the equivalent lead is small and the elastic member has reached a deformation limit, and a control gain switching unit which switches between any one of the first to third control gains and uses them as a reference;
The electric linear actuator further comprises:
a change gradient calculation unit that derives a gradient of a change in either the motor angle or the estimated load relative to a change in the other;
a change gradient comparison unit that stores the gradient of change derived by said change gradient calculation unit, compares the stored gradient of change with a gradient of change newly derived by said change gradient calculation unit after said storage, and determines that a discontinuity in control gain exists when the gradient has changed by a predetermined value or more;
the control gain switching unit uses the first to third control gains, and when there are a plurality of discontinuous points, performs a control according to at least one of the plurality of discontinuous points determined by the change gradient comparing unit,
When the load is changed in a pressure increasing direction while the first control gain is being referenced, if it is determined that the discontinuous point has occurred, the second control gain is referenced;
when the pressure is increased while the second control gain is being referenced, if it is determined that the discontinuity has occurred, the third control gain is referenced, and when the pressure is decreased, if it is determined that the discontinuity has occurred, the first control gain is referenced;
and when the pressure is reduced in a state where the third control gain is being referenced and it is determined that the discontinuous point has occurred, the second control gain is referenced.
Electric linear actuator. The electric linear motion actuator according to any one of claims 1 to 4 ,
The control device includes:
an estimator for estimating a rotation angle of the electric motor;
a stiffness parameter storage unit that stores a history of changes in the rotation amount of the electric motor and the estimated load when a predetermined amount of change in the load occurs within a range that includes at least the load corresponding to a discontinuity point of the pre-stored control gain;
The control device further comprises:
a nonlinear stiffness estimator that estimates a discontinuity point of the control gain from the change history of the angle of the electric motor and the estimated load, and updates the control gain based on the estimated discontinuity point;
Electric linear actuator. The electric linear motion actuator according to any one of claims 1 to 4 ,
The control device includes:
an estimator for estimating a rotation angle of the electric motor;
When a predetermined amount of change in the load or the amount of rotation of the electric motor occurs, an amount of change in either the load or the amount of rotation of the electric motor is estimated and stored;
The control device further comprises:
comparing the stored amount of change with an amount of change newly estimated after the storage, and determining, when these amounts of change are greater than a predetermined amount, that a discontinuity has occurred in the control gain between the angle and the load of the electric motor, and updating the control gain based on the determined discontinuity;
Electric linear actuator.

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