JP7688902B2 - Vehicle steering system control device - Google Patents

Description

The present invention relates to a control device for a vehicle steering system.

One type of vehicle steering system is the Steer By Wire (SBW) system, which mechanically separates a steering mechanism (FFA: Force Feedback Actuator) having a steering wheel operated by the driver from a steering mechanism (RWA: Road Wheel Actuator) that steers the steered wheels. In the SBW system, the steering mechanism and the steering mechanism are electrically connected via a control device (ECU: Electronic Control Unit), and the steering wheel operation is transmitted to the steering mechanism by an electric signal to steer the steered wheels, while the steering mechanism generates a steering reaction force to give the driver an appropriate steering feel. The steering mechanism generates the steering reaction force by a reaction force actuator equipped with a reaction force motor, and the steering mechanism steers the steered wheels by a steering actuator equipped with a steering motor. The reaction force actuator and the steering wheel are mechanically connected via a column shaft, and the reaction force (torque) generated by the reaction force actuator is transmitted to the driver via the column shaft and the steering wheel.

In SBW systems where the steering mechanism and the turning mechanism are mechanically separated, in order to avoid problems (such as cable breakage) caused by cables for electrical equipment such as airbags and horns mounted on the steering wheel, a steering end point that is the limit of steering possible is provided in the steering mechanism, and an upper limit is set for the steering angle of the steering wheel. The following Patent Document 1 discloses a technology that increases the steering reaction force when the steering angle is equal to or greater than a steering angle threshold, thereby restricting the steering wheel operation by the driver.

JP 2017-024624 A

In a configuration provided with a stopper (rotation limiting mechanism) that physically sets the steering end point, which is the limit of possible steering, it is conceivable that by applying a steering reaction force that increases with an increase in the steering angular speed, it is possible to suppress a collision occurring at the steering end point when the driver turns the steering wheel further near the steering end point. In such a configuration, if a steering reaction force that exceeds the torque applied to the steering wheel by the driver when turning the steering wheel is applied, there may be an instantaneous transition from further turning to turning back. If such an instantaneous return occurs from further turning, the steering reaction force may become zero, or a steering reaction force that tries to turn the wheel further may be generated, causing a collision at the steering end point, which may cause discomfort or strangeness to the driver.

The present invention was made in consideration of the above problems, and aims to provide a control device for a vehicle steering system that can suppress the steering reaction force from being zero or the steering reaction force from being momentarily increased when the steering wheel is turned further and then turned back instantaneously.

In order to achieve the above object, a control device for a vehicle steering system according to one aspect of the present invention is a control device for a vehicle steering system having a rotation limiting mechanism provided at the steering end of a steering wheel, a reaction force device that drives a reaction force motor that applies a steering reaction force to the steering wheel, and a steering device that drives a steering motor according to the steering angle of the steering wheel, and is provided with a steering torque target value generation unit that generates a steering torque target value that is a target value of the steering torque for obtaining the steering reaction force, and the steering torque target value generation unit is provided with a torque calculation unit that performs processing at predetermined intervals and generates a first torque value that increases as the steering angular velocity of the steering wheel increases, and an output value selection unit that selects either the first torque value or a second torque value that is the first torque value generated in the previous processing, depending on at least whether the steering wheel has been turned back.

According to the above configuration, when the steering wheel is turned further and then instantly turned back, the second torque value generated by the torque calculation unit in the previous process and held in the output value selection unit is output, thereby preventing the steering reaction force from becoming zero or preventing the steering reaction force from momentarily trying to turn further.

As a preferred embodiment of the control device for a vehicle steering system, the output value selection unit preferably selects the second torque value when the multiplication value of the steering angle and the steering angle velocity changes from a positive value to a negative value and the amount of change in the steering angle is equal to or less than a predetermined amount of change threshold.

According to the above configuration, it is possible to determine whether the steering wheel is being turned further or returned to its original position using the steering angle and the steering angle speed. In addition, by selecting the second torque value when the steering wheel is turned from an instantaneous turning further to a return position and the amount of change in the steering angle is equal to or less than the threshold amount of change, it is possible to prevent the steering reaction force from becoming zero or to prevent the steering reaction force from momentarily trying to turn further.

As a desirable aspect of the control device for a vehicle steering system, it is preferable that the output value selection unit selects the second torque value when the multiplication value of the steering angle and the steering angular velocity becomes a negative value from a positive value, and the time during which the multiplication value is a negative value is equal to or less than a predetermined time threshold value.

According to the above configuration, it is possible to determine whether the steering wheel is being turned further or returned to its original position using the steering angle and the steering angle velocity. Also, when the steering wheel is turned further and then instantly returned to its original position, and the time during which the product of the steering angle and the steering angle velocity is a negative value is equal to or less than a time threshold, the second torque value is selected, thereby making it possible to prevent the steering reaction force from becoming zero or to prevent the steering reaction force from momentarily trying to turn further.

As a preferred embodiment of the control device for a vehicle steering system, the first torque value is a value that increases with an increase in energy proportional to the square of the steering angular velocity.

According to the above configuration, the first torque value increases as the steering angular speed increases.

As a preferred embodiment of the control device for a vehicle steering system, the torque calculation unit preferably generates a third torque value whose value increases as the steering angle increases, and multiplies the third torque value by the torque value selected by the output value selection unit.

The above configuration provides a torque value that has both a characteristic of increasing with an increase in steering angular velocity and a characteristic of increasing with an increase in steering angle.

The present invention provides a control device for a vehicle steering system that can suppress the steering reaction force from being zero or from being generated as a steering reaction force that tries to momentarily increase the steering force when the steering wheel is turned further and then turned back instantaneously.

FIG. 1 is a configuration diagram showing an example of an outline of an SBW system including a control device according to a first embodiment. FIG. 2 is a schematic diagram showing a hardware configuration of the ECU. FIG. 3 is a diagram illustrating an example of a control block configuration of the control device according to the embodiment. FIG. 4 is a block diagram showing an example of the configuration of the steering torque target value generating unit. FIG. 5A is a diagram showing an example of the characteristics of the base map. FIG. 5B is a diagram showing an example of the characteristics of the torque value Tref_basic. FIG. 6A is a diagram showing an example of a characteristic of a damper gain map. FIG. 6B is a diagram showing an example of the characteristics of the torque value Tref_a+Tref_b. FIG. 7 is a region diagram for explaining the steering direction in the present disclosure. FIG. 8 is a block diagram showing an example of the configuration of the damping torque calculation unit. FIG. 9 is a diagram showing an example of the characteristics of an angle sensitive gain map. FIG. 10 is a diagram showing an example of the characteristics of the angular velocity sensitive gain map. FIG. 11 is a diagram showing an example of the characteristics of the torque value calculated in the damping torque calculation section. FIG. 12 is a block diagram illustrating an example of the configuration of the steering direction determination unit according to the first embodiment. FIG. 13 is a diagram showing an example of a control block configuration for explaining a processing mode of a calculation processing unit in the steering direction determination unit according to the first embodiment. FIG. 14 is a block diagram showing a first modified example of the damping torque calculation unit. FIG. 15 is a diagram showing an example of the characteristics of an energy sensitive gain map. FIG. 16 is a block diagram showing a second modified example of the damping torque calculation unit. FIG. 17 is a block diagram illustrating an example of the configuration of a steering direction determination unit according to the second embodiment. FIG. 18 is a diagram showing an example of a control block configuration for explaining a processing mode of a calculation processing unit in the steering direction determination unit according to the second embodiment.

Below, a detailed description of a form for carrying out the invention (hereinafter, referred to as an embodiment) will be given with reference to the drawings. Note that the present invention is not limited to the following embodiment. Furthermore, the components in the following embodiment include those that a person skilled in the art can easily imagine, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiment can be combined as appropriate.

(Embodiment 1)
1 is a configuration diagram showing an example of an outline of an SBW system including a control device according to embodiment 1. The SBW system includes a reaction force device 30 constituting a steering mechanism having a steering wheel operated by a driver, a steering device 40 constituting a steering mechanism for steering steered wheels, and a control device 50 for controlling both devices.

The SBW system does not have an intermediate shaft that is mechanically connected to the column shaft (steering shaft, handle shaft) 2, which is found in general electric power steering devices. Instead, the operation of the steering wheel 1 by the driver is transmitted as an electrical signal, specifically, the steering angle θh output from the reaction device 30.

The reaction force device 30 includes a reaction force motor 31 and a speed reduction mechanism 32 that reduces the rotational speed of the reaction force motor 31. The reaction force device 30 transmits the vehicle's motion state transmitted from the steered wheels 5L, 5R to the driver as a steering reaction force. The reaction force motor 31 applies the steering reaction force to the steering wheel 1 via the speed reduction mechanism 32.

The reaction force device 30 further includes a steering angle sensor 33 and a torque sensor 34. The steering angle sensor 33 detects the steering angle θh of the steering wheel 1. The torque sensor 34 detects the steering torque Th of the steering wheel 1. Hereinafter, the steering angle θh detected by the steering angle sensor 33 is also referred to as the "actual steering angle θh_act," and the steering torque Th detected by the torque sensor 34 is also referred to as the "actual steering torque Th_act."

In this disclosure, the column shaft 2 is provided with a stopper (rotation limiting mechanism) 35 that physically sets the steering end point that is the limit of possible steering. In other words, the magnitude (absolute value) of the steering angle θh is limited by the stopper 35.

The steering device 40 includes a steering motor 41, a speed reducing mechanism 42 that reduces the rotational speed of the steering motor 41, and a pinion rack mechanism 44 that converts the rotational motion of the steering motor 41 into linear motion. The steering device 40 drives the steering motor 41 in response to the steering angle θh, and imparts the driving force to the pinion rack mechanism 44 via the speed reducing mechanism 42, and steers the steered wheels 5L and 5R via the tie rods 3a and 3b. An angle sensor 43 is disposed near the pinion rack mechanism 44 and detects the steering angle θt of the steered wheels 5L and 5R. Instead of the steering angle θt of the steered wheels 5L and 5R, for example, the motor angle of the steering motor 41 or the position of the rack may be detected and the detected value may be used. Hereinafter, the steering angle θt detected by the angle sensor 43 is also referred to as the "actual steering angle θt_act".

In order to coordinately control the reaction force device 30 and the turning device 40, the control device 50 generates a voltage control command value Vref1 for driving and controlling the reaction force motor 31 and a voltage control command value Vref2 for driving and controlling the turning motor 41 based on information such as the steering angle θh and turning angle θt output from both devices, as well as the vehicle speed Vs detected by the vehicle speed sensor 10.

The control device 50 is supplied with power from the battery 12 and receives an ignition key signal via the ignition key 11. The control device 50 is also connected to a CAN (Controller Area Network) 20 that transmits and receives various vehicle information, and the vehicle speed Vs can also be received from the CAN 20. Furthermore, the control device 50 can also be connected to a non-CAN 21 that transmits and receives communications other than the CAN 20, analog/digital signals, radio waves, etc.

Specifically, the control device 50 is, for example, an ECU (Electronic Control Unit) mounted on the vehicle. The ECU is mainly composed of a CPU (including an MCU, MPU, etc.). Figure 2 is a schematic diagram showing the hardware configuration of the ECU. Cooperative control of the reaction device 30 and the steering device 40 is mainly executed by a program inside the CPU of the ECU.

Figure 3 is a diagram showing an example of the control block configuration of the control device according to the embodiment. In Figure 3, the reaction force device 30 includes a reaction force motor 31 and the above-mentioned configuration, as well as a PWM (pulse width modulation) control unit 37, an inverter 38, and a motor current detector 39. The steering device 40 includes a PWM control unit 47, an inverter 48, and a motor current detector 49, as well as a steering motor 41 and the above-mentioned configuration. The control device 50 realizes each control block of a reaction force control system 60 that controls the reaction force device 30, and a steering control system 70 that controls the steering device 40. The reaction force control system 60 and the steering control system 70 cooperate to control the reaction force device 30 and the steering device 40.

Note that some or all of the components of the control device 50 may be realized by hardware. The control device 50 may include, for example, a RAM (random access memory) or a ROM (read only memory) as shown in FIG. 2 in order to store data, programs, etc. The control device 50 may also include a PWM control unit 37, an inverter 38, a motor current detector 39, a PWM control unit 47, an inverter 48, and a motor current detector 49.

As shown in FIG. 3, the control device 50 includes, as control blocks, a steering torque target value generating unit 200, a steering torque control unit 400, a current control unit 500, a steering angle target value generating unit 600, a steering angle control unit 700, and a current control unit 800. The steering torque target value generating unit 200, the steering torque control unit 400, and the current control unit 500 are control blocks that make up the reaction force control system 60. The steering angle target value generating unit 600, the steering angle control unit 700, and the current control unit 800 are control blocks that make up the steering control system 70.

The reaction force control system 60 performs control so that the actual steering torque Th_act detected by the torque sensor 34 follows the steering torque target value Th_ref, which is the target value of the steering torque of the reaction force device 30.

The steering torque target value generating unit 200 generates the steering torque target value Th_ref.

The steering torque control unit 400 generates a motor current command value Ih_ref, which is a control target value of the current supplied to the reaction force motor 31. The steering torque control unit 400 calculates a motor current command value Imc such that the deviation Th_err between the steering torque target value Th_ref and the actual steering torque Th_act approaches zero.

The current control unit 500 controls the current of the reaction force motor 31. The current control unit 500 calculates a voltage control command value Vh_ref such that the deviation Ih_err between the motor current command value Ih_ref output from the steering torque control unit 400 and the actual current value (motor current value) Ih_act of the reaction force motor 31 detected by the motor current detector 39 approaches zero.

In the reaction force device 30, the reaction force motor 31 is driven and controlled via the PWM control unit 37 and the inverter 38 based on the voltage control command value Vh_ref.

The steering control system 70 performs control so that the actual steering angle θt_act detected by the angle sensor 43 follows the target steering angle value θt_ref.

The steering angle target value generating unit 600 generates the steering angle target value θt_ref based on the steering angle θh.

The steering angle control unit 700 generates a motor current command value It_ref, which is a control target value for the current supplied to the steering motor 41. The steering angle control unit 700 calculates the motor current command value It_ref such that the deviation θt_err between the steering angle target value θt_ref and the actual steering angle θt_act approaches zero.

The current control unit 800 controls the current of the steering motor 41. The current control unit 800 calculates a voltage control command value Vt_ref such that the deviation It_err between the motor current command value It_ref output from the steering angle control unit 700 and the actual current value (motor current value) It_act of the steering motor 41 detected by the motor current detector 49 approaches zero.

In the steering device 40, the steering motor 41 is driven and controlled via the PWM control unit 47 and the inverter 48 based on the voltage control command value Vt_ref.

In this embodiment, the steering torque control unit 400, the current control unit 500, the steering angle target value generation unit 600, the steering angle control unit 700, and the current control unit 800 may be configured to realize each control in the reaction force control system 60 or the steering control system 70, and are not limited by the configuration of each control block. The configuration of the steering torque target value generation unit 200 according to this embodiment will be described below with reference to FIG. 4.

Figure 4 is a block diagram showing an example of the configuration of a steering torque target value generating unit according to the embodiment. As shown in Figure 4, the steering torque target value generating unit 200 according to the present embodiment includes, as its main components, a basic map unit 210, a damper torque generating unit 220, and a damping torque generating unit 230.

In this disclosure, the sign extraction unit 280 shown in FIG. 4 extracts the sign of the steering angle θh. Specifically, for example, the value of the steering angle θh is divided by the absolute value of the steering angle θh. As a result, the sign extraction unit 280 outputs "1" when the sign of the steering angle θh is "+", and outputs "-1" when the sign of the steering angle θh is "-". Specifically, the sign extraction unit 280 generates, for example, a sign function Sgn(θh) of the steering angle θh.

Figure 5A is a diagram showing an example of the characteristics of the basic map. The steering angle |θh| and the vehicle speed Vs that have been subjected to absolute value processing in the absolute value calculation unit 260 are input to the basic map unit 210. The basic map unit 210 uses the basic map shown in Figure 5A to generate a torque value Tref_a with the vehicle speed Vs as a parameter. The torque value Tref_a is used to generate a basic steering reaction force according to the steering angle |θh| and the vehicle speed Vs.

The torque value Tref_basic has an angle-sensitive characteristic that increases or decreases according to the steering angle |θh|. More specifically, the torque value Tref_basic increases as the steering angle |θh| increases, as shown in FIG. 5A. The torque value Tref_basic also has a vehicle-speed-sensitive characteristic that increases or decreases according to the vehicle speed Vs. More specifically, the torque value Tref_basic increases as the vehicle speed Vs increases, as shown in FIG. 5A. In other words, the reaction force obtained by the torque value Tref_basic derived by the basic map shown in FIG. 5A increases as the amount of operation of the steering wheel 1 by the driver (steering angle θh) increases, and increases as the vehicle speed (vehicle speed Vs) increases. Note that the basic map shown in FIG. 5A has a vehicle-speed-sensitive characteristic, but is not limited to this.

Figure 5B is a diagram showing an example of the characteristics of the torque value Tref_a. The torque value Tref_a shown in Figure 5B is obtained by multiplying the torque value Tref_basic output from the basic map unit 210 by the sign function Sgn(θh) output from the sign extraction unit 280 in the multiplier 293. Note that a configuration without the sign extraction unit 280 may be used in which the torque value Tref_a is obtained using a basic map corresponding to the positive and negative steering angles θh, as shown in Figure 5B.

The damper torque generation unit 220 includes a damper gain map unit 221 and a multiplication unit 222. FIG. 6A is a diagram showing an example of the characteristics of the damper gain map. The vehicle speed Vs is input to the damper gain map unit 221. The damper gain map unit 221 generates the damper gain DG using the damper gain map shown in FIG. 6A.

As shown in FIG. 6A, the damper gain DG has a vehicle speed-sensitive characteristic that increases or decreases according to the vehicle speed Vs. The damper torque generation unit 220 multiplies the angular velocity of the steering wheel 1 (hereinafter also referred to as "steering angular velocity ωh") calculated by differentiating the steering angle θh (differentiation unit 270) by the damper gain DG output from the damper gain map unit 221 (multiplication unit 222), and outputs the result as a torque value Tref_b.

The torque value Tref_b output from the damper torque generating unit 220 is added to the torque value Tref_a (addition unit 291). This makes it possible to compensate for the steering reaction force in proportion to the steering angular velocity ωh.

Figure 6B is a diagram showing an example characteristic of the torque value Tref_a+Tref_b. The torque value Tref_a+Tref_b is obtained by adding the torque value Tref_a to the torque value Tref_b output from the damper torque generating unit 220. In Figure 6B, the solid line shows the torque value Tref_a+Tref_b when the steering angular velocity ωh is a positive value (ωh>0), and the dashed line shows the torque value Tref_a+Tref_b when the steering angular velocity ωh is a negative value (ωh<0). Also in Figure 6B, the dashed line shows the torque value Tref_a.

Figure 7 is a region diagram for explaining the steering direction in this disclosure. In Figure 7, the horizontal axis represents the steering angle θh, and the vertical axis represents the steering angular velocity ωh.

Area A ((θh, ωh) = (+, +)) shown in Figure 7 indicates that the steering wheel 1 is turned to the right (θh > 0) and is being turned further to the right (ωh > 0). Area B ((θh, ωh) = (+, -)) shown in Figure 7 indicates that the steering wheel 1 is turned to the right (θh > 0) and is being turned back to the left (ωh < 0). Area C ((θh, ωh) = (-, -)) shown in Figure 7 indicates that the steering wheel 1 is turned to the left (θh < 0) and is being turned further to the left (ωh < 0). Area D ((θh, ωh) = (-, +)) shown in Figure 7 indicates that the steering wheel 1 is turned to the left (θh < 0) and is being turned back to the right (ωh > 0). Also, in FIG. 7, the steering angle θh axis (ωh = 0) indicates that the steering wheel 1 is neither turned further nor turned back ((θh, ωh) = (θh, 0)), and the steering angular velocity ωh axis (θh = 0) indicates that the steering wheel 1 is in the center position ((θh, ωh) = (0, ωh)).

The torque value Tref_b output from the damper torque generating unit 220 is a positive value in regions A and D where the steering angular velocity ωh>0, and a negative value in regions B and C where the steering angular velocity ωh<0. As a result, when the steering angular velocity ωh>0, that is, in region A where the steering wheel 1 is turned to the right (θh>0) and further turned to the right, or in region D where the steering wheel 1 is turned to the left (θh<0) and turned back to the right, the torque value Tref_a is added to |Tref_b| as shown by the solid line in FIG. 6B. When the steering angular velocity ωh<0, that is, in region B where the steering wheel 1 is turned to the right (θh>0) and turned back to the left, or in region C where the steering wheel 1 is turned to the left (θh<0) and turned further to the left, the torque value Tref_a is subtracted from |Tref_b| as shown by the dashed line in FIG. 6B.

As shown in FIG. 6B, the torque value Tref_a+Tref_b increases with the magnitude of the steering angle θh, and the closer the steering angle θh approaches the steering end point where it is limited by the stopper (rotation limiting mechanism) 35, the smaller the increase in torque increase with respect to the change in steering angle θ becomes. In other words, the torque value Tref_a+Tref_b has a characteristic that the rate of change gradually decreases as the steering angle θh increases. For this reason, the driver is likely to turn the steering wheel 1 more near the steering end point, and a sudden more-turn steering may cause a collision (hereinafter also referred to as a "high-speed collision") at the steering end point, causing discomfort or strangeness to the driver.

As shown in FIG. 4, the present disclosure includes a damping torque generating unit 230 that generates a damping torque that increases the rise of the steering reaction force as the steering angular velocity ωh increases, and the torque value Tref_d generated by the damping torque generating unit 230 is added to the torque value Tref_a+Tref_b, and then multiplied by the sign function Sgn(θh) output from the sign extracting unit 280. This suppresses sudden further steering near the steering end. The specific configuration and operation of the damping torque generating unit 230 according to the embodiment will be described below.

Figure 8 is a block diagram showing an example of the configuration of the damping torque calculation unit. In the example configuration shown in Figure 8, the damping torque calculation unit 240 includes, as its main components, an angle-sensitive gain map unit 241, an angular velocity-sensitive gain map unit 242, a steering direction determination unit 250, and an output value selection unit 251.

The damping torque calculation unit 240 performs the processing described below for each predetermined period Δt. The predetermined period Δt is determined, for example, by the processing sampling interval in the CPU of the ECU that constitutes the control device 50. The predetermined period Δt is, for example, about 1 ms to 4 ms. Note that the predetermined period Δt may be, for example, one sampling period of the ECU, or multiple sampling periods. In other words, the damping torque calculation unit 240 may perform steering direction determination processing at one sampling interval of the ECU, or may perform processing at multiple sampling intervals.

The sign extraction unit 243 shown in FIG. 8 extracts the sign of the steering angular velocity ωh. Specifically, for example, the value of the steering angular velocity ωh is divided by the absolute value of the steering angular velocity ωh. As a result, the sign extraction unit 243 outputs "1" when the sign of the steering angular velocity ωh is "+", and outputs "-1" when the sign of the steering angular velocity ωh is "-". Specifically, the sign extraction unit 243 generates, for example, a sign function Sgn(ωh) of the steering angular velocity ωh.

Figure 9 is a diagram showing an example of the characteristics of the angle-sensitive gain map. The steering angle |θh| that has been subjected to absolute value processing in the absolute value calculation unit 248 is input to the angle-sensitive gain map unit 241. The angle-sensitive gain map unit 241 generates a torque value (third torque value) according to the angle-sensitive gain map shown in Figure 9.

The angle-sensitive gain map shown in FIG. 9 has an angle-sensitive characteristic in which the gain Ga increases or decreases according to the steering angle |θh|. More specifically, as shown in FIG. 9, the gain Ga increases as the steering angle |θh| increases in the region equal to or greater than a predetermined steering angle threshold |θth|. In other words, the angle-sensitive gain map shown in FIG. 9 has a characteristic in which the gain Ga increases monotonically as the steering angle |θh| becomes larger beyond the steering angle threshold |θth|, that is, as the steering angle |θh| approaches the terminal angle. The steering angle threshold |θth| may be set to an angle a predetermined angle before the terminal angle |θend| (for example, |θth|=|θend|-10 [deg]).

Figure 10 is a diagram showing an example of the characteristics of the angular velocity sensitive gain map. The steering angular velocity |ωh| that has been subjected to absolute value processing in the absolute value calculation unit 249 is input to the angular velocity sensitive gain map unit 242. The angular velocity sensitive gain map unit 242 generates a torque value (first torque value) according to the angular velocity sensitive gain map shown in Figure 10.

The angular velocity sensitive gain map shown in FIG. 10 has an angular velocity sensitive characteristic in which the gain Gv increases or decreases according to the steering angular velocity |ωh|. More specifically, as shown in FIG. 10, the gain Gv increases as the steering angular velocity |ωh| increases. In other words, the angular velocity sensitive gain map shown in FIG. 10 has a characteristic in which the gain Gv monotonically increases as the steering angular velocity |ωh| increases.

Figure 11 is a diagram showing an example of the characteristics of the torque value calculated in the damping torque calculation unit. The damping torque calculation unit 240 multiplies the torque value (third torque value) generated by the angle-sensitive gain map unit 241 by the torque value (first torque value) generated by the angular velocity-sensitive gain map unit 242, or the torque value (second torque value) held by the output value selection unit 251 described later (multiplication unit 244). As a result, as shown in Figure 11, in a region equal to or greater than a predetermined steering angle threshold |θth|, an angular velocity-sensitive characteristic is obtained in which the torque value increases as the steering angle |θh| increases and increases or decreases according to the steering angular velocity |ωh|. More specifically, the torque value calculated in the damping torque calculation unit 240 has a characteristic that the torque value increases as the steering angle |θh| exceeds the steering angle threshold θth and approaches the terminal angle, and the rate of increase (rate of change) increases as the steering angular velocity |ωh| becomes faster.

The damping torque calculation unit 240 further multiplies the output value of the multiplication unit 244 by the sign function Sgn(ωh) of the steering angular velocity ωh (multiplication unit 245) to output the torque value Tref_d.

The output value of the multiplication unit 244 increases as the amount of operation of the steering wheel 1 by the driver (steering angle θh) increases, and increases as the speed of operation of the steering wheel 1 by the driver (steering angular velocity ωh) increases, due to the characteristics shown in FIG. 11. As a result, the steering reaction force obtained by the torque value Tref_d increases as the amount of operation of the steering wheel 1 by the driver (steering angle θh) increases, and increases as the speed of operation of the steering wheel 1 by the driver (steering angular velocity ωh) increases.

As described above, the torque value (first torque value) generated by the angular velocity sensitive gain map unit 242 increases as the steering angular velocity |ωh| increases. However, if the steering reaction force applied by the reaction force device 30 exceeds the steering force applied by the driver to the steering wheel 1 when the driver steers the steering wheel 1, there may be an instantaneous transition from further turning to returning to the original position. Specifically, there may be a transition from area A to area B, or from area C to area D, as shown in FIG. 7. If such a momentary return occurs from further turning of the steering wheel 1, the steering reaction force becomes zero, or a steering reaction force that momentarily tries to further turn the wheel is generated, which may cause a high-speed collision at the steering end due to the stopper (rotation limiting mechanism) 35, causing discomfort or an unpleasant feeling to the driver.

In the present disclosure, when the steering wheel 1 is turned back from an instantaneous further turning as described above, the previous value (second torque value) of the torque value (first torque value) output from the angular velocity sensitive gain map unit 242 is output. This makes it possible to prevent the steering reaction force from becoming zero or the steering reaction force that tries to momentarily turn the steering wheel 1 back from an additional turning, when the steering wheel 1 is turned back from an additional turning. Below, a detailed description is given of the configuration and operation that can prevent the steering reaction force from becoming zero or the steering reaction force that tries to momentarily turn the steering wheel 1 back from an additional turning.

Figure 12 is a block diagram showing an example of the configuration of a steering direction determination unit according to embodiment 1. Figure 13 is a diagram showing an example of a control block configuration for explaining the processing mode of the calculation processing unit in the steering direction determination unit according to embodiment 1.

The steering angle θh and the steering angular velocity ωh are input to the steering direction determination unit 250. The multiplication unit 252 multiplies the steering angle θh and the steering angular velocity ωh together.

The sign determination unit 253 determines the sign of the multiplication result of the steering angle θh and the steering angular velocity ωh, and generates the sign function Sgn.

When the sign function Sgn is a positive value (+), it indicates that the vehicle is in area A or area C shown in FIG. 7. In other words, when the sign function Sgn is a positive value (+), it indicates that the steering wheel 1 is turned to the right (θh>0) and has been turned further to the right (ωh>0), or that the steering wheel 1 is turned to the left (θh<0) and has been turned further to the left (ωh<0).

On the other hand, when the sign function Sgn is a negative value (-), it indicates that the vehicle is in area B or area D shown in FIG. 7. In other words, when the sign function Sgn is a negative value (-), it indicates that the steering wheel 1 is turned to the right (θh>0) and then turned back to the left (ωh<0), or that the steering wheel 1 is turned to the left (θh<0) and then turned back to the right (ωh>0).

The calculation processing unit 254 performs the steering direction determination process described below every predetermined period Δt.

The output value selection unit 251 shown in FIG. 8 holds the torque value (second torque value) generated by the angular velocity sensitive gain map unit 242 in the previous process (processing a predetermined period of time Δt ago). Specifically, the torque value (second torque value) held by the output value selection unit 251 is the output value of the output value selection unit 251 in the previous process (steering direction determination processing a predetermined period of time Δt ago). The output value selection unit 251 is configured, for example, by the RAM of the ECU that constitutes the control device 50.

In the configuration of the calculation processing unit 254 shown in FIG. 13, the output value selection unit 251 is controlled to select and output the previous output value (second torque value) held by the output value selection unit 251 when the sign function Sgn transitions from a positive value (+) to a negative value (-), i.e., when the steering wheel 1 is turned back from a state in which it has been turned further, and when the amount of change in the steering angle θh from the previous value is equal to or less than a predetermined change amount threshold Δθth (e.g., 3 [deg]). The change amount threshold Δθth is stored, for example, in the ROM of the ECU constituting the control device 50.

By repeatedly executing the above-mentioned steering direction determination process at predetermined intervals Δt, when the steering wheel 1 is turned further and then turned back instantaneously, it is possible to prevent the steering reaction force from becoming zero or the steering reaction force from being generated that tries to turn the wheel more instantaneously. This makes it possible to prevent a high-speed collision at the steering end caused by the stopper (rotation limiting mechanism) 35, and to prevent the driver from feeling uncomfortable or unnatural.

In addition, the configuration of the damping torque calculation unit can be changed to the following configuration instead of the configuration shown in FIG. 8.

Figure 14 is a block diagram showing a first modified example of the damping torque calculation unit. In the first modified example shown in Figure 14, the damping torque calculation unit 240a includes, as its main components, an energy calculation unit 246 and an energy-sensitive gain map unit 247.

The steering angular velocity ωh is input to the energy calculation unit 246. The energy calculation unit 246 calculates the energy Eg generated by the handle operation (steering) using the following formula.

Eg=J×ωh ^2/2

In the above formula, J represents the moment of inertia. The moment of inertia J is stored, for example, in the ROM of the ECU that constitutes the control device 50.

Figure 15 is a diagram showing an example of the characteristics of the energy-sensing gain map. The energy Eg calculated by the energy calculation unit 246 is input to the energy-sensing gain map unit 247. The energy-sensing gain map unit 247 generates a torque value (first torque value) according to the energy-sensing gain map shown in Figure 15.

The energy-sensitive gain map shown in FIG. 15 has an energy-sensitive characteristic in which the gain Ge (Gd2) increases or decreases according to the energy Eg generated by steering the steering wheel 1. More specifically, as shown in FIG. 15, the gain Ge (Gd2) increases as the energy Eg increases. As shown in the above formula, the energy Eg is proportional to the square of the steering angular velocity ωh. In other words, the energy-sensitive gain map shown in FIG. 15 has a characteristic in which the rate at which the gain Ge (Gd2) increases (rate of change) increases as the steering angular velocity ωh increases, similar to the characteristic shown in FIG. 11.

The damping torque calculation unit 240a outputs a torque value Tref_d obtained by further multiplying (multiplication unit 245) the torque value (first torque value) generated by the energy sensitive gain map unit 247 or the torque value (second torque value) held by the output value selection unit 251 by the sign function Sgn(ωh) of the steering angular velocity ωh.

The output value of the energy-sensing gain map unit 247 becomes larger as the driver's operation speed of the steering wheel 1 (steering angle speed ωh) becomes faster, due to the characteristics of the energy-sensing gain map shown in FIG. 15. As a result, the steering reaction force obtained by the torque value Tref_d becomes larger as the driver's operation speed of the steering wheel 1 (steering angle speed ωh) becomes faster.

As described above, the first torque value (energy-sensitive gain Ge) increases as the steering angular velocity ωh increases, so if the reaction force device 30 applies a steering reaction force that exceeds the steering force applied to the steering wheel 1 by the driver when the driver turns the steering wheel 1, there may be an instantaneous transition from further turning to returning to the original position. If such a momentary return occurs from further turning of the steering wheel 1, causing the steering reaction force to become zero or a momentary steering reaction force that tries to turn the wheel further, a high-speed collision may occur at the end of the steering due to the stopper (rotation limiting mechanism) 35, causing discomfort or an odd feeling to the driver.

In the configuration with the damping torque calculation unit 240a shown in FIG. 14, similar to the configuration shown in FIG. 8, by configuring it with the steering direction determination unit 250 and output value selection unit 251 described above, it is possible to prevent the steering reaction force from becoming zero or the steering reaction force from momentarily trying to turn the steering wheel 1 back when the steering wheel 1 is turned further and then turned back instantaneously.

Figure 16 is a block diagram showing a second modified example of the damping torque calculation unit. In the second modified example shown in Figure 16, the damping torque calculation unit 240b includes an energy calculation unit 246 and an energy sensitive gain map unit 247 in the embodiment shown in Figure 14, instead of the angular velocity sensitive gain map unit 242 in the embodiment shown in Figure 8.

The damping torque calculation unit 240b multiplies the torque value (third torque value) generated by the angle sensitive gain map unit 241 by the torque value (first torque value) generated by the energy sensitive gain map unit 247 or the torque value (second torque value) held by the output value selection unit 251 (multiplication unit 244). As a result, similar to the characteristics shown in FIG. 11, in the region equal to or greater than a predetermined steering angle threshold |θth|, an angular velocity sensitive characteristic is obtained that increases as the steering angle |θh| increases and increases or decreases according to the steering angular velocity |ωh|.

The damping torque calculation unit 240b further multiplies the output value of the multiplication unit 244 by the sign function Sgn(ωh) of the steering angular velocity ωh (multiplication unit 245) to output the torque value Tref_d.

The output value of the multiplication unit 244, due to characteristics similar to those shown in FIG. 11, becomes larger as the amount of operation of the steering wheel 1 by the driver (steering angle θh) becomes larger, and also becomes larger as the operation speed of the steering wheel 1 by the driver (steering angular velocity ωh) becomes faster. As a result, the steering reaction force obtained by the torque value Tref_d becomes larger as the amount of operation of the steering wheel 1 by the driver (steering angle θh) becomes larger, and also becomes larger as the operation speed of the steering wheel 1 by the driver (steering angular velocity ωh) becomes faster.

As described above, the first torque value (energy-sensitive gain Ge) increases as the steering angular velocity ωh increases, so if the reaction force device 30 applies a steering reaction force that exceeds the steering force applied to the steering wheel 1 by the driver when the driver turns the steering wheel 1, there may be an instantaneous transition from further turning to returning to the original position. If such a momentary return occurs from further turning of the steering wheel 1, causing the steering reaction force to become zero or a momentary steering reaction force that tries to turn the wheel further, a high-speed collision may occur at the end of the steering due to the stopper (rotation limiting mechanism) 35, causing discomfort or an odd feeling to the driver.

In the configuration with the damping torque calculation unit 240b shown in FIG. 16, as in the configuration shown in FIG. 8, by configuring the steering direction determination unit 250 and output value selection unit 251 described above, it is possible to prevent the steering reaction force from becoming zero or the steering reaction force from momentarily trying to turn the steering wheel 1 back when the steering wheel 1 is turned further and then turned back instantaneously.

The torque value Tref_d output from the damping torque generating unit 230 is added to the torque value Tref_a and the torque value Tref_b in the adding units 291 and 292 shown in FIG. 4. As a result, the steering torque target value Th_ref is output from the steering torque target value generating unit 200.

As described above, in the damping torque generating unit 230 of the present disclosure, the steering direction determining unit 250 and the output value selecting unit 251 are controlled to hold the output value (second torque value) of the output value selecting unit 251 in the previous process, and to select and output the previous output value (second torque value) held by the output value selecting unit 251 when the steering wheel 1 is turned back from a state in which it has been turned further, and when the amount of change in the steering angle θh from the previous value is equal to or less than a predetermined change amount threshold Δθth. This makes it possible to suppress the occurrence of zero steering reaction force or a steering reaction force that tries to turn the steering wheel more instantaneously when the steering wheel 1 is turned back instantaneously from a state in which it has been turned further.

(Embodiment 2)
Fig. 17 is a block diagram showing an example of the configuration of a steering direction determination unit according to embodiment 2. Fig. 18 is a diagram showing an example of a control block configuration for explaining the processing mode of a calculation processing unit in the steering direction determination unit according to embodiment 2.

In the steering direction determination unit 250a, the calculation processing unit 254a performs the steering direction determination process described below every predetermined period Δt.

In the configuration of the calculation processing unit 254a shown in FIG. 17, the output value selection unit 251 is controlled to select and output the previous output value (second torque value) held by the output value selection unit 251 when the sign function Sgn transitions from a positive value (+) to a negative value (-), i.e., when the steering wheel 1 is turned back from a state in which it has been turned further, and when the time tc during which the sign function Sgn is a negative value (-) is equal to or less than a predetermined time threshold Δtth (e.g., 0.5 [sec]). The time threshold Δtth is stored, for example, in the ROM of the ECU constituting the control device 50.

By repeatedly executing the above-mentioned steering direction determination process at predetermined intervals Δt, it is possible to prevent the steering reaction force from becoming zero or the steering reaction force from momentarily trying to turn the steering wheel 1 more when the steering wheel 1 is turned back instantaneously, as in the first embodiment. This makes it possible to prevent a high-speed collision at the steering end caused by the stopper (rotation limiting mechanism) 35, and to prevent the driver from feeling uncomfortable or unnatural.

The figures used in the above-described embodiment are conceptual diagrams for providing a qualitative explanation of the present disclosure, and are not intended to be limiting. Furthermore, the above-described embodiment is an example of a suitable implementation of the present disclosure, but is not intended to be limiting, and various modifications may be made without departing from the spirit of the present disclosure.

REFERENCE SIGNS LIST 1 Steering wheel 2 Column shaft 3a, 3b Tie rod 5L, 5R Steering wheel 10 Vehicle speed sensor 11 Ignition key 12 Battery 30 Reaction device 31 Reaction motor 32 Speed reduction mechanism 33 Steering angle sensor 34 Torque sensor 35 Stopper (rotation limiting mechanism)
40 Steering device 41 Steering motor 42 Speed reduction mechanism 43 Angle sensor 44 Pinion rack mechanism 50 Control device 60 Reaction force control system 70 Steering control system 200 Steering torque target value generation section 210 Basic map section 220 Damper torque generation section 221 Damper gain map section 222 Multiplication section 230 Damping torque generation section 240, 240a, 240b Damping torque calculation section 241 Angle sensitive gain map section 242 Angular velocity sensitive gain map section 243 Sign extraction section 244, 245 Multiplication section 246 Energy calculation section 247 Energy sensitive gain map section 248 Absolute value calculation section 250, 250a Steering direction determination section 251 Output value selection section 252 Multiplication section 253 Sign determination section 254, 254a Calculation processing section 260 Absolute value calculation section 270 Differentiation section 280 Sign extraction section 291, 292 Addition section 293 Multiplication section 400 Steering torque control section 500 Current control section 600 Turning angle target value generation section 700 Turning angle control section 800 Current control section

Claims (5)

A control device for a vehicle steering system, comprising: a rotation limiting mechanism provided at a steering end of a steering wheel; a reaction device that drives a reaction motor that applies a steering reaction force to the steering wheel; and a steering device that drives a steering motor in accordance with a steering angle of the steering wheel,
a steering torque target value generating unit that generates a steering torque target value that is a target value of the steering torque for obtaining the steering reaction force,
The steering torque target value generating unit
a torque calculation unit that performs processing at predetermined intervals and generates a first torque value that increases as the steering angular velocity of the steering wheel increases;
an output value selection unit that selects either the first torque value or a second torque value that is a held first torque value generated in a previous process, depending on at least whether the steering wheel has been turned back;
Equipped with
A control device for a vehicle steering system. the output value selection unit selects the second torque value when a multiplication value of the steering angle and the steering angular velocity becomes a negative value from a positive value and an amount of fluctuation of the steering angle is equal to or less than a predetermined amount of fluctuation threshold.
The control device for a vehicle steering system according to claim 1. the output value selection unit selects the second torque value when a multiplication value of the steering angle and the steering angular velocity becomes a negative value from a positive value and a time during which the multiplication value is a negative value is equal to or shorter than a predetermined time threshold value.
The control device for a vehicle steering system according to claim 1. The first torque value is a value that increases with an increase in energy proportional to the square of the steering angular velocity.
A control device for a vehicle steering system according to any one of claims 1 to 3. The torque calculation unit is
generating a third torque value whose value increases as the steering angle increases, and multiplying the third torque value by the torque value selected by the output value selection unit;
A control device for a vehicle steering system according to any one of claims 1 to 4.

Images