JP7769862B2 - Motor control device - Google Patents

Description

This invention relates to a motor control device that controls an electric motor for steering angle control.

Patent Document 1 discloses the following driving assistance technology. Specifically, the steering control unit calculates the X coordinate xc of a target passing point at the gaze-ahead distance and the X coordinate xe of an estimated passing point. The steering control unit then adds a calculation term obtained by multiplying the difference (xc-xe) between these X coordinates xc and xe by a first control gain Gl to a calculation term obtained by multiplying the yaw angle θca by a second control gain Gy to calculate the motor control variable (torque command value) Tc. The first and second control gains Gl and Gy are set to larger values the longer the hands-off time is, and if a hands-off state is not detected, the lower the level of alertness or the higher the level of absentmindedness is, the smaller the values are set.

JP 2011-57037 A

Level 2 equivalent driving assistance functions require the driver to keep their hands on the steering wheel. Therefore, in driving assistance mode, if the driver's hands are determined to be off the steering wheel for a predetermined period of time or longer, a warning is output, and if the hands remain off the steering wheel after the warning, the driving assistance mode is canceled.

For this reason, in driving assistance mode, it is necessary to accurately determine whether the vehicle is in a gripped state or a hands-off state. However, if the gripped state or hands-off state is determined based on the steering torque (torsion bar torque) detected by a torque sensor, in situations where there is little driver torque input, such as when driving in a straight line, there is a risk that the vehicle may be erroneously determined to be in a hands-off state even when the driver is gripping the vehicle.

The objective of one embodiment of this invention is to provide a motor control device that can accurately determine whether the device is in a gripped state or a hands-free state when in driving assistance mode.

One embodiment of the present invention provides a motor control device that includes a torque detection unit for detecting steering torque, a manual steering command value generation unit that generates a manual steering command value using the steering torque, an integrated angle command value calculation unit that calculates an integrated angle command value by adding the manual steering command value to an automatic steering command value provided in driving assistance mode, a control unit that controls the angle of an electric motor for steering angle control based on the integrated angle command value, and a hands-on/off determination unit that determines whether the driver is in a gripped state where the driver is gripping the steering wheel or a hands-off state where the driver is not gripping the steering wheel, where the manual steering command value generation unit is configured to generate the manual steering command value using the steering torque and a spring constant and viscous damping coefficient for generating road load torque, and where the motor control device further includes a road load characteristic change unit that changes at least one of the spring constant and the viscous damping coefficient when the hands-on/off determination unit determines that the driver is in a hands-off state for a predetermined period of time or more in the driving assistance mode.

This configuration makes it possible to accurately determine whether the device is being held or let go when in driving assistance mode.

One embodiment of the present invention is a motor control device that includes a torque detection unit for detecting steering torque, a steering angle detection unit for detecting actual steering angle, an automatic steering control unit that sets an automatic steering control amount based on an automatic steering command value given in a driving assistance mode, an assist control unit that sets an assist control amount using the steering torque, an integrated control amount calculation unit that calculates an integrated control amount by adding the automatic steering control amount and the assist control amount, and a control unit that controls an electric motor for steering angle control based on the integrated control amount, and a hands-on/off determination unit that determines whether the driver is in a gripped state where the driver is gripping the steering wheel or in a hands-off state where the driver is not gripping the steering wheel, and a hands-on/off determination unit that calculates an actual manual steering angle, which is the steering angle for manual steering based on the steering torque and the assist control amount. and an actual automatic steering angle calculation unit that calculates an actual automatic steering angle, which is the steering angle for automatic steering based on the automatic steering control amount, by subtracting the actual manual steering angle from the actual steering angle. The automatic steering control unit sets the automatic steering control amount using the automatic steering angle command value and the actual automatic steering angle, and the actual manual steering angle calculation unit calculates the actual manual steering angle using the steering torque, the assist control amount, and a spring constant and viscous damping coefficient for generating road load torque. The motor control device further includes a road load characteristic change unit that changes at least one of the spring constant and the viscous damping coefficient when the hands-on/off determination unit determines that the vehicle is in a hands-off state for a predetermined period of time or more in the driving assistance mode.

This configuration makes it possible to accurately determine whether the device is being held or let go when in driving assistance mode.

FIG. 1 is a schematic diagram showing the general configuration of an electric power steering system to which a motor control device according to an embodiment of the present invention is applied. FIG. 2 is a block diagram for explaining the electrical configuration of the motor control ECU. FIG. 3 is a block diagram showing the configuration of the manual steering command value generating unit. FIG. 4 is a graph showing an example of setting the assist torque command value T ^* _m,ad relative to the steering torque _Ttb . FIG. 5 is a schematic diagram showing an example of a reference EPS model used in the command value setting unit. FIG. 6 is a block diagram showing the configuration of the angle control unit. FIG. 7 is a schematic diagram showing an example of the configuration of a physical model of an electric power steering system. FIG. 8 is a block diagram showing the configuration of the disturbance torque estimating section. FIG. 9 is a schematic diagram showing the configuration of the torque control unit. FIG. 10 is a flowchart showing the procedure of the spring constant setting process performed by the road surface load characteristic setting unit. FIG. 11 is a block diagram for explaining the electrical configuration of a modified example of the motor control ECU. FIG. 12 is a block diagram showing the configuration of the automatic steering control unit. FIG. 13 is a schematic diagram showing an example of the configuration of a physical model of an electric power steering system. FIG. 14 is a block diagram showing the configuration of the disturbance torque estimating section.

[Description of the embodiment of the present invention]
One embodiment of the present invention provides a motor control device including: a torque detection unit for detecting steering torque; a manual steering command value generation unit for generating a manual steering command value using the steering torque; an integrated angle command value calculation unit for calculating an integrated angle command value by adding the manual steering command value to an automatic steering command value given in a driving assistance mode; a control unit for controlling the angle of an electric motor for steering angle control based on the integrated angle command value; and a hands-on/off determination unit for determining whether the driver is in a gripped state where the driver is gripping the steering wheel or in a hands-off state where the driver is not gripping the steering wheel, wherein the manual steering command value generation unit is configured to generate the manual steering command value using the steering torque and a spring constant and a viscous damping coefficient for generating a road load torque, and further including a road load characteristic change unit that changes the value of at least one of the spring constant and the viscous damping coefficient when the hands-on/off determination unit determines that the driver is in a hands-off state for a predetermined period of time or more in the driving assistance mode.

This configuration makes it possible to accurately determine whether the device is being held or let go when in driving assistance mode.

One embodiment of the present invention is a motor control device that includes a torque detection unit for detecting steering torque, a steering angle detection unit for detecting actual steering angle, an automatic steering control unit that sets an automatic steering control amount based on an automatic steering command value given in a driving assistance mode, an assist control unit that sets an assist control amount using the steering torque, an integrated control amount calculation unit that calculates an integrated control amount by adding the automatic steering control amount and the assist control amount, and a control unit that controls an electric motor for steering angle control based on the integrated control amount, and a hands-on/off determination unit that determines whether the driver is in a gripped state where the driver is gripping the steering wheel or in a hands-off state where the driver is not gripping the steering wheel, and a hands-on/off determination unit that calculates an actual manual steering angle, which is the steering angle for manual steering based on the steering torque and the assist control amount. and an actual automatic steering angle calculation unit that calculates an actual automatic steering angle, which is the steering angle for automatic steering based on the automatic steering control amount, by subtracting the actual manual steering angle from the actual steering angle. The automatic steering control unit sets the automatic steering control amount using the automatic steering angle command value and the actual automatic steering angle, and the actual manual steering angle calculation unit calculates the actual manual steering angle using the steering torque, the assist control amount, and a spring constant and viscous damping coefficient for generating road load torque. The motor control device further includes a road load characteristic change unit that changes at least one of the spring constant and the viscous damping coefficient when the hands-on/off determination unit determines that the vehicle is in a hands-off state for a predetermined period of time or more in the driving assistance mode.

This configuration makes it possible to accurately determine whether the device is being held or let go when in driving assistance mode.

In one embodiment of the present invention, if the spring constant and the viscous damping coefficient whose value is changed by the road load characteristic change unit is defined as a road load variable, when, in the driving assistance mode, the hands-on/off determination unit determines that the vehicle is in a hands-off state for a predetermined period of time, the road load characteristic change unit gradually increases the value of the road load variable from that point on while the hands-off state determination continues, and when the road load variable reaches a predetermined upper limit, the unit maintains the value of the road load variable at the upper limit.

In one embodiment of the present invention, in the driving assistance mode, when the hands-on/off determination unit determines that the vehicle is in a hands-off state for a predetermined period of time or more and then changes its determination result to a gripped state, the road load characteristic change unit gradually decreases the value of the road load variable from that point onwards while the hands-on/hands-off determination result continues to be that the vehicle is in a gripped state, and when the road load variable reaches a predetermined lower limit, maintains the road load variable at the lower limit.

Detailed Description of the Embodiments of the Invention
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[1] General Configuration of Electric Power Steering System FIG. 1 is a schematic diagram showing the general configuration of an electric power steering system to which a motor control device according to an embodiment of the present invention is applied.

The electric power steering system 1 includes a steering wheel (handle) 2 as a steering member for steering the vehicle, a steering mechanism 4 that steers steered wheels 3 in conjunction with the rotation of the steering wheel 2, and a steering assist mechanism 5 that assists the driver in steering. The steering wheel 2 and the steering mechanism 4 are mechanically connected via a steering shaft 6 and an intermediate shaft 7.

The steering shaft 6 includes an input shaft 8 connected to the steering wheel 2 and an output shaft 9 connected to the intermediate shaft 7. The input shaft 8 and output shaft 9 are connected via a torsion bar 10 so as to be able to rotate relative to each other.

A torque sensor 12 is disposed near the torsion bar 10. The torque sensor 12 detects the steering torque (torsion bar torque) _Ttb applied to the steering wheel 2 based on the relative rotational displacement amount between the input shaft 8 and the output shaft 9. In this embodiment, the steering torque _Ttb detected by the torque sensor 12 is detected as a positive value for torque for steering leftward, and a negative value for torque for steering rightward, and the magnitude of the steering torque _Ttb increases as the absolute value increases.

The steering mechanism 4 consists of a rack-and-pinion mechanism that includes a pinion shaft 13 and a rack shaft 14 as the steering shaft. The steered wheels 3 are connected to each end of the rack shaft 14 via tie rods 15 and knuckle arms (not shown). The pinion shaft 13 is connected to the intermediate shaft 7. The pinion shaft 13 rotates in conjunction with the steering of the steering wheel 2. A pinion 16 is connected to the tip of the pinion shaft 13.

The rack shaft 14 extends linearly in the left-right direction of the vehicle. A rack 17 that meshes with the pinion 16 is formed in the axial middle of the rack shaft 14. The pinion 16 and rack 17 convert the rotation of the pinion shaft 13 into axial movement of the rack shaft 14. By moving the rack shaft 14 in the axial direction, the steered wheels 3 can be steered.

When the steering wheel 2 is steered (rotated), this rotation is transmitted to the pinion shaft 13 via the steering shaft 6 and intermediate shaft 7. The rotation of the pinion shaft 13 is then converted into axial movement of the rack shaft 14 by the pinion 16 and rack 17. This causes the steered wheels 3 to turn.

The steering assist mechanism 5 includes an electric motor 18 for generating a steering assist force (assist torque), and a reducer 19 for amplifying the output torque of the electric motor 18 and transmitting it to the steering mechanism 4. The reducer 19 is made up of a worm gear mechanism including a worm gear 20 and a worm wheel 21 that meshes with the worm gear 20. The reducer 19 is housed in a gear housing 22 that serves as a transmission mechanism housing. Hereinafter, the reduction ratio (gear ratio) of the reducer 19 may be represented by N. The reduction ratio N is defined as the ratio θ _wg /θ _{ww of the rotation angle θ wg of} the worm gear 20 to the rotation angle θ _ww of the worm wheel 21.

The worm gear 20 is driven to rotate by the electric motor 18. The worm wheel 21 is connected to the output shaft 9 so that it can rotate integrally with the output shaft 9.

When the worm gear 20 is driven to rotate by the electric motor 18, the worm wheel 21 is driven to rotate, applying motor torque to the steering shaft 6 and rotating the steering shaft 6 (output shaft 9). The rotation of the steering shaft 6 is then transmitted to the pinion shaft 13 via the intermediate shaft 7. The rotation of the pinion shaft 13 is converted into axial movement of the rack shaft 14, thereby turning the steered wheels 3. In other words, by driving the worm gear 20 to rotate by the electric motor 18, steering assistance by the electric motor 18 and steering of the steered wheels 3 become possible. The electric motor 18 is provided with a rotation angle sensor 23 for detecting the rotation angle of the rotor of the electric motor 18.

The torque applied to the output shaft 9 (one example of a drive target of the electric motor 18) includes motor torque from the electric motor 18 and disturbance torque other than the motor torque. The disturbance torque _Tlc other than the motor torque includes steering torque _Ttb , road load torque (road reaction torque) _Trl , friction torque _Tf, etc.

The steering torque _Ttb is a torque applied to the output shaft 9 from the steering wheel 2 side by a force applied to the steering wheel 2 by the driver (driver torque) or a force generated by steering inertia.

The road load torque T _rl is a torque applied to the output shaft 9 from the steered wheels 3 via the rack shaft 14 due to the self-aligning torque generated in the tires, forces generated by the suspension and tire/wheel alignment, frictional forces of the rack and pinion mechanism, etc.

The vehicle is equipped with a CCD (Charge Coupled Device) camera 25 that captures images of the road ahead in the vehicle's direction of travel, a GPS (Global Positioning System) 26 for detecting the vehicle's position, a radar 27 for detecting road shapes and obstacles, a map information memory 28 that stores map information, and a vehicle speed sensor 29 for detecting the vehicle speed V.

The CCD camera 25, GPS 26, radar 27, map information memory 28, and vehicle speed sensor 29 are connected to a host ECU (Electronic Control Unit) 201 that performs driving assistance control. Based on the information obtained from the CCD camera 25, GPS 26, radar 27, and vehicle speed sensor 29, as well as map information, the host ECU 201 performs surrounding environment recognition, vehicle position estimation, route planning, etc., and determines control target values for steering and drive actuators.

In this embodiment, the driving modes include a normal mode and a driving assistance mode. In the driving assistance mode, the host ECU 201 sets an automatic steering command value θ ^* _c,ad for driving assistance. In this embodiment, the driving assistance is lane centering assist (LCA) for maintaining the vehicle position in the center of the lane. The automatic steering command value θ ^* _c,ad is a target value of the steering angle for driving the vehicle along the center of the lane. The automatic steering command value θ ^* _c,ad is set based on, for example, the vehicle speed, the lateral deviation from the target driving line, and the yaw deviation of the vehicle from the target driving line. The process of setting such an automatic steering command value θ ^* _c,ad is well known, so a detailed description thereof will be omitted here. In the normal mode, the host ECU 201 sets the automatic steering command value θ ^* _c,ad to zero.

Furthermore, the host ECU 201 outputs a mode signal S _mode indicating whether the driving mode is the normal mode or the driving assistance mode. The mode signal S _mode , the automatic steering command value θ ^* _c,ad , and the vehicle speed V set by the host ECU 201 are provided to the motor control ECU 202 via the in-vehicle network. The steering torque T _tb detected by the torque sensor 12 and the output signal of the rotation angle sensor 23 are input to the motor control ECU 202. The motor control ECU 202 controls the electric motor 18 based on these input signals and information provided by the host ECU 201.

[2] Motor control ECU 202
FIG. 2 is a block diagram for explaining the electrical configuration of the motor control ECU 202. As shown in FIG.

The motor control ECU 202 includes a microcomputer 40, a drive circuit (inverter circuit) 31 controlled by the microcomputer 40 and supplying power to the electric motor 18, and a current detection circuit 32 for detecting the current flowing through the electric motor 18 (hereinafter referred to as "motor current I _m,int ").

The microcomputer 40 is equipped with a CPU and memory (ROM, RAM, non-volatile memory, etc.), and by executing a predetermined program, functions as multiple functional processing units. These multiple functional processing units include a rotation angle calculation unit 41, a reduction ratio division unit 42, a hands-on/off determination unit 43, a road load characteristic setting unit 44, a manual steering command value generation unit 45, an integrated angle command value calculation unit 46, an angle control unit 47, and a torque control unit 48.

The rotation angle calculation unit 41 calculates the rotor rotation angle θ _m,int of the electric motor 18 based on the output signal of the rotation angle sensor 23. The reduction ratio division unit 42 converts the rotor rotation angle θ _m,int into a rotation angle (actual steering angle) θ _{c, int of the output shaft 9 by dividing the rotor rotation angle θ m} ,int by the reduction ratio N.

The hands-on/off determination unit 43 determines whether the driver is in a gripped state (hands-on) in which the driver is gripping the steering wheel 2, or a hands-off state (hands-off) in which the driver is not gripping the steering wheel 2. The hands-on/off determination unit 43 may estimate a driver torque, which is the torque applied by the driver to the steering wheel 2, based on, for example, the steering torque T _tb and the actual steering angle θ _c,int or the rotor rotation angle θ _m,int , and determine the driver torque as being in a gripped state if the driver torque is equal to or greater than a predetermined threshold, and determine the driver torque as being in a hands-off state if the driver torque remains below the threshold for a predetermined time or more. In this case, the driver torque is determined to be in a gripped state until the driver torque is determined to be in a hands-off state after the driver torque changes from a state equal to or greater than the threshold to a state less than the threshold. As such a hands-on/off determination unit 43, for example, a "steering wheel operation state determination unit" described in Patent Publication No. 2017-114324, Patent Publication No. 2018-165156, Patent Publication No. 2020-142703, Patent Publication No. 2020-59361, Patent Publication No. 2020-59362, etc. can be used.

The hands-on/off determination unit 43 may determine, for example, that the vehicle _{is in a gripped state when the steering torque Ttb is} equal to or greater than a predetermined threshold, and that the vehicle is in a hands-off state when the steering torque _Ttb remains below the threshold for a predetermined period of time or longer. In this case, the vehicle is determined to be in a gripped state until the vehicle is determined to be in a hands-off state after the steering torque Ttb changes from a state equal to or greater than the threshold to a state below the threshold.

The road load characteristic setting unit 44 sets the spring constant k and viscous damping coefficient c used by the manual steering command value generation unit 45 in driving assistance mode based on the hands-on/off determination result of the hands-on/off determination unit 43.

The manual steering command value generating unit 45 is provided to set a steering angle corresponding to the steering wheel operation as a manual steering command value θ ^* _c,md when the driver operates the steering wheel 2. The manual steering command value generating unit 45 generates the manual steering command value θ ^* _c,md using the vehicle speed V and the steering torque _Ttb detected by the torque sensor 12. Details of the operation of the manual steering command value generating unit 45 will be described later.

The integrated angle command value calculation unit 46 adds the manual steering command value θ ^* _c, md to the automatic steering command value θθ ^* _c, ad set by the host ECU 201 to calculate an integrated angle command value θ ^* _c,int .

The angle control unit 47 calculates a motor torque command value T ^* _m,int , which is a target value for the motor torque of the electric motor 18, based on the integrated angle command value θ ^* _c,int . The torque control unit 48 drives the drive circuit 31 so that the motor torque of the electric motor 18 approaches the motor torque command value T ^* _m,int . In other words, the control unit consisting of the angle control unit 47 and the torque control unit 48 drives and controls the drive circuit 31 so that the actual steering angle θc _,int (rotational angle θc _,int of the output shaft 9) approaches the integrated angle command value θ ^* _c,int . Details of the operations of the angle control unit 47 and the torque control unit 48 will be described later.

Figure 3 is a block diagram showing the configuration of the manual steering command value generation unit 45.

The manual steering command value generation unit 45 includes an assist torque command value setting unit 51 and a command value setting unit 52.

The assist torque command value setting unit 51 sets an assist torque command value T ^* _m,md , which is a target value of the assist torque required for manual operation. The assist torque command value setting unit 51 sets the assist torque command value T ^* _m,md based on the vehicle speed V and the steering torque _Ttb detected by the torque sensor 12. An example of setting the assist torque command value T ^* _m,md relative to the steering torque _Ttb is shown in FIG. 4.

The assist torque command value T ^* _m,md is set to a positive value when a steering assist force for steering leftward is to be generated from the electric motor 18, and is set to a negative value when a steering assist force for steering rightward is to be generated from the electric motor 18. The assist torque command value T ^* _m,md is positive for a positive value of the steering torque _Ttb , and negative for a negative value of the steering torque _Ttb . The assist torque command value T ^* _m,md is set so that its absolute value increases as the absolute value of the steering torque _Ttb increases. The assist torque command value T ^* _m,md is set so that its absolute value decreases as the vehicle speed V increases.

The assist torque command value setting unit 51 may calculate the assist torque command value T ^* _m,md by multiplying the steering torque _Ttb by a preset constant.

In this embodiment, the command value setting unit 52 sets the manual steering command value θ ^* _c.md using a reference EPS model.

Figure 5 is a schematic diagram showing an example of a reference EPS model used by the command value setting unit 52.

This reference EPS model is a single-inertia model that includes the lower column. The lower column corresponds to the output shaft 9 and the worm wheel 21. In Fig. 5, _Jc is the inertia of the lower column, _θc is the rotation angle of the lower column, and _Ttb is the steering torque. This reference EPS model is a model for generating (estimating) the rotation angle _θc of the lower column when the steering torque _Ttb , the torque N·T ^* _{m,md that} acts on the output shaft 9 from the electric motor 18 based on the assist torque command value T ^* _m,md , and the road load torque _Trl are applied to the lower column. The road load torque _Trl is expressed by the following equation (1) using a spring constant k and a viscous damping coefficient c.

T _rl = -k・θ _c -c (dθ _c /dt) …(1)
The spring constant k and the viscous damping coefficient c are set by the road load characteristic setting unit 44. The operation of the road load characteristic setting unit 44 will be described in detail later.

The equation of motion for the reference EPS model is expressed as follows:

J _c・d ² θ _c /dt ² = T _tb +N・T ^* _{m, md} −k・θ _c −c (dθ _c /dt) …(2)
The command value setting unit 52 substitutes the steering torque _Ttb detected by the torque sensor 12 into _Ttb , and substitutes the assist torque command value T ^* _m,md set by the assist torque command value setting unit 51 into T ^* _m,md , and calculates the rotation angle _θc of the lower column by solving the differential equation of formula (2).The command value setting unit 52 then sets the obtained rotation angle _θc of the lower column as the manual steering command value θ ^* _c,md .

Figure 6 is a block diagram showing the configuration of the angle control unit 47.

The angle control unit 47 calculates a motor torque command value T ^* _m,int based on the integrated angle command value θ ^* _c,int . The angle control unit 47 includes a low-pass filter (LPF) 61, a feedback control unit 62, a feedforward control unit 63, a disturbance torque estimating unit 64, a torque adding unit 65, a disturbance torque compensating unit 66, a reduction ratio dividing unit 67, and a reduction ratio multiplying unit 68.

The reduction ratio multiplication unit 68 converts the motor torque command value T ^* _m,int calculated by the reduction ratio division unit 67 into an output shaft torque command value T ^* c,int (=N·T ^* _m,int ) acting on the output shaft 9 by multiplying the motor torque command value T ^* _{m,int by} the reduction ratio N of the reducer 19.

The low-pass filter 61 performs low-pass filtering on the integrated angle command value θ ^* _c,int . The integrated angle command value θ ^* _c,intf after the low-pass filtering is provided to the feedback control unit 62 and the feedforward control unit 63.

The feedback control unit 62 is provided to bring the actual steering angle θ _c,int calculated by the reduction ratio division unit 42 closer to the integrated angle command value θ ^* _c,intf after low-pass filtering. The feedback control unit 62 includes an angle deviation calculation unit 62A and a PD control unit 62B. The angle deviation calculation unit 62A calculates the deviation Δθ _c,int (= θ ^* _c,intf - _{θ c,int} ) between the integrated angle command value θ ^* _{c ,} intf and the actual steering angle θ c,int calculated by the reduction ratio division unit 42 (see FIG. 2 ). Note that the angle deviation calculation unit 62A may also calculate the deviation (θ ^* c _{,intf -} ^θ c,int ) between the integrated angle command value θ ^* _c,intf and the steering angle estimation value ^θ _c,int calculated by the disturbance torque estimator 64 as the angle deviation Δθ _c,int .

The PD control unit 62B calculates a feedback control torque T _fb, int by performing a PD calculation (proportional differential calculation) on the angle deviation Δθ _c,int calculated by the angle deviation calculation unit 62A. The feedback control torque T _fb,int is provided to a torque addition unit 65.

The feedforward control unit 63 is provided to improve the control response by compensating for a delay in response due to the inertia of the electric power steering system 1. The feedforward control unit 63 includes an angular acceleration calculation unit 63A and an inertia multiplication unit 63B. The angular acceleration calculation unit 63A calculates the target angular acceleration ^{d2θ *} _c,intf / ^dt2 by second-order differentiating the integrated angle command value θ ^* _c,intf .

The inertia multiplication unit 63B calculates the feedforward control torque T ff,int (=J· ^{d 2} θ ^* _c,intf /dt ² ) by multiplying the target angular acceleration d ² θ ^* _c,intf /dt ² calculated by the angular acceleration calculation unit 63A by _the inertia J of the electric power steering system 1. The inertia J can be determined, for example, from a physical model (see FIG. 7 ) of the electric power steering system 1, which will be described later. The feedforward control torque T _ff,int is provided to the torque addition unit 65 as an inertia compensation value.

The torque adder 65 calculates a basic torque command value (T _fb,int +T _ff,int ) by adding the feedforward control torque T _{ff ,int} to the feedback control torque T fb,int.

The disturbance torque estimator 64 is provided to estimate nonlinear torque (disturbance torque: torque other than motor torque) that occurs as a disturbance in the plant (the object controlled by the electric motor 18). The disturbance torque estimator 64 estimates the disturbance torque (disturbance load) T lc , the steering angle θ c,int, and the steering angle differential value (angular velocity) dθ _c ,int /dt based on the steering torque command value T ^* _{c ,int} (= N·T ^* _m,int ), which is an input value to the plant, and the actual steering angle θ _{c, int,} which is an output from the plant. The estimated values of the disturbance torque T _lc , the steering angle θ _c,int , and the steering angle differential value (angular velocity) dθ _c,int /dt are represented by ^T _lc , ^θ _c,int , and d^θ _c,int /dt, respectively. Details of the disturbance torque estimator 64 will be described later.

The disturbance torque estimated value ^T _lc calculated by the disturbance torque estimating section 64 is given to the disturbance torque compensating section 66 as a disturbance torque compensation value.

The disturbance torque compensation unit 66 calculates the output shaft torque command value T ^* _c,int (= _Tfb,int +Tff _,int -^ _Tlc ) by subtracting the disturbance torque estimated value ^ _Tlc from the basic torque command value (Tfb _,int + _Tff, int). This provides the output shaft torque command value T ^* _c,int (torque command value for the output shaft 9) compensated for the disturbance torque.

The output shaft torque command value T ^* _c,int is given to a reduction ratio division unit 67. The reduction ratio division unit 67 calculates a motor torque command value T ^* _m,int by dividing the output shaft torque command value T ^* _c,int by the reduction ratio N. This motor torque command value T ^* _m,int is given to the torque control unit 48 (see FIG. 2).

The disturbance torque estimation unit 64 will be described in detail. The disturbance torque estimation unit 64 is configured by a disturbance observer that estimates the disturbance torque T _lc , the steering angle θ _c,int , and the angular velocity dθ _c,int /dt using, for example, a physical model 101 of the electric power steering system 1 shown in FIG.

This physical model 101 includes a plant (an example of a motor-driven object) 102 that includes an output shaft 9 and a worm wheel 21 fixed to the output shaft 9. A steering torque _Ttb is applied to the plant 102 from the steering wheel 2 via the torsion bar 10, and a road load torque _Trl is also applied from the steered wheels 3 side.

Furthermore, the plant 102 is given an output shaft torque command value T ^* _c,int (=N·T ^* _m,int ) via the worm gear 20, and is given a friction torque _Tf due to friction between the worm wheel 21 and the worm gear 20.

If the inertia of the plant 102 is J, the equation of motion for the inertia of the physical model 101 is expressed by the following equation (3):

d ² θ _c,int /dt ² is the angular acceleration of the plant 102. N is the reduction ratio of the reducer 19. _{T lc} indicates a disturbance torque other than the motor torque applied to the plant 102. In this embodiment, the disturbance torque T _lc is shown as the sum of the steering torque T _tb , the road load torque T _rl , and the friction torque T _f , but in reality, the disturbance torque T _lc includes torques other than these.

The state equation for the physical model 101 in Figure 7 is expressed by the following equation (4):

In the above equation (4), x is the state variable vector, _u1 is the known input vector, _u2 is the unknown input vector, and y is the output vector (measurement value). In the above equation (4), A is the system matrix, _B1 is the first input matrix, _B2 is the second input matrix, C is the output matrix, and D is the direct feedthrough matrix.

The state equation is expanded to a system including the unknown input vector _u2 as one of the states. The state equation of the expanded system (expanded state equation) is expressed by the following equation (5).

In the above equation (5), x _e is a state variable vector of the extended system, and is expressed by the following equation (6).

In the above equation (5), A _e is the system matrix of the extended system, B _e is the known input matrix of the extended system, and C _e is the output matrix of the extended system.

From the extended state equation (5) above, a disturbance observer (extended state observer) expressed by the following equation (7) is constructed.

In equation (7), ^x _e represents the estimated value of x _e . Furthermore, L is the observer gain. Furthermore, ^y represents the estimated value of y. ^x _e is expressed by the following equation (8).

In equation (8), ̂θ _c,int is an estimate of θ _c,int , and ̂T _lc is an estimate of T _lc .

The disturbance torque estimation unit 64 calculates the state variable vector ^x _e based on the equation (7) above.

Figure 8 is a block diagram showing the configuration of the disturbance torque estimation unit 64.

The disturbance torque estimation unit 64 includes an input vector input unit 81, an output matrix multiplication unit 82, a first addition unit 83, a gain multiplication unit 84, an input matrix multiplication unit 85, a system matrix multiplication unit 86, a second addition unit 87, an integration unit 88, and a state variable vector output unit 89.

The steering torque command value T ^* _c,int (=N·T ^* _m,int ) calculated by the reduction ratio multiplication unit 68 (see FIG. 6) is given to the input vector input unit 81. The input vector input unit 81 outputs an input vector _u1 .

The output of the integrator 88 is the state variable vector ^x _e (see equation (8) above). At the start of the calculation, an initial value is given as the state variable vector ^x _e . The initial value of the state variable vector ^x _e is, for example, 0.

The system matrix multiplication unit 86 multiplies the state variable vector ^x _e by the system matrix A _e . The output matrix multiplication unit 82 multiplies the state variable vector ^x _e by the output matrix C _e .

The first adder 83 subtracts the output (C e · ^x e ) of the output matrix multiplier 82 from the output vector (measured value) y, which is the actual steering angle θ _c,int calculated by the reduction ratio divider 42 (see FIG. ₂ ). In other words, the first adder 83 calculates the difference ( _y - ^y) between the output vector y and the output vector estimated value ^y (=C _e · ^x _e ). The gain multiplier 84 multiplies the output (y - ^y) of the first adder 83 by the observer gain L (see equation (7) above).

The input matrix multiplication unit 85 multiplies the input vector u1 output from the input vector input unit ₈₁ by the input matrix B _e . The second addition unit 87 adds the output (B e · _u1 ) of the input matrix multiplication unit 85, the output (A _e · ^x _e ) of the system matrix multiplication unit 86, and the output (L(y - ^y)) of the gain multiplication unit 84 to calculate the differential value d^x _e /dt of the state variable vector. The integrator 88 integrates the output (d^x _e /dt) of the second addition unit 87 to calculate the state variable vector ^x _e . The state variable vector output unit 89 calculates the disturbance torque estimate ^T _lc , the steering angle estimate ^θ _c,int, and the angular velocity estimate d^θ _c,int /dt based on the state variable vector ^x _e .

Unlike the extended state observer described above, a typical disturbance observer consists of an inverse model of the plant and a low-pass filter. The plant's equation of motion is expressed by equation (3) as described above. Therefore, the inverse model of the plant is expressed by equation (9) below.

The inputs to a general disturbance observer are J· ^d2θc _,int / ^dt2 and N·T ^* _m,int , and because the second-order differential value of the actual steering angle _θc,int is used, it is significantly affected by noise from the rotation angle sensor 23. In contrast, the extended state observer of the above-described embodiment estimates the disturbance torque in an integral manner, and therefore can reduce the influence of noise due to differentiation.

In addition, the disturbance torque estimation unit 64 may be a general disturbance observer consisting of an inverse model of the plant and a low-pass filter.

Figure 9 is a block diagram showing the electrical configuration of the torque control unit 48. The torque control unit 48 includes a motor current command value calculation unit 91, a current deviation calculation unit 92, a PI control unit 93, and a PWM (Pulse Width Modulation) control unit 94.

The motor current command value calculation unit 91 calculates the motor current command value I ^* _{m ,int} by dividing the motor torque command value T ^* m,int calculated by the angle control unit 47 by the torque constant _Kt of the electric motor 18 .

The current deviation calculation unit 92 calculates the deviation ΔI m _, int (=I ^* _{m,int -I m,int) between the motor current command value I * m,int} obtained by the motor current command value calculation unit 91 and the motor current ^I _m , _int detected by the current detection circuit 32.

The PI control unit 93 performs a PI calculation (proportional-plus-integral calculation) on the current deviation ΔI _m,int calculated by the current deviation calculation unit 92, to generate a drive command value for guiding the motor current I _m,int flowing through the electric motor 18 to the motor current command value I ^* _m,int . The PWM control unit 94 generates a PWM control signal with a duty ratio corresponding to the drive command value, and supplies it to the drive circuit 31. As a result, power corresponding to the drive command value is supplied to the electric motor 18.

Next, the operation of the road load characteristic setting unit 44 will be described in detail. In driving assistance mode, the road load characteristic setting unit 44 performs a spring constant setting process to set the spring constant k, and a viscous damping coefficient setting process to set the viscous damping coefficient c. These processes will be described below.

Figure 10 is a flowchart showing the steps of the spring constant setting process performed by the road surface load characteristic setting unit 44. The spring constant setting process shown in Figure 10 is started each time the driving assistance mode is started, and is repeated at predetermined calculation intervals until the driving assistance mode is canceled.

In the following, ΔT is the time equivalent to one calculation cycle (sampling time). T _off is the duration of the hands-off state. _{k min} is the preset minimum spring constant. The normal value of the spring constant k is set as the minimum spring constant k _min . k _max is the preset maximum spring constant. k _decrease is the preset amount of decrease in the spring constant in one calculation cycle. k _increase is the preset amount of increase in the spring constant in one calculation cycle. The initial value of k is k _min . The initial value of _{T off} is 0.

The road load characteristic setting unit 44 determines whether the hands-on/off determination unit 43 determines whether the hands-off state is present (step S1).

If the hands-on/off determination unit 43 determines that the vehicle is in a gripped state (step S1: NO), the road load characteristic setting unit 44 sets the duration _Toff of the hands-off state to zero (step S2).Then, the road load characteristic setting unit 44 determines whether the spring constant k is greater than the minimum spring constant _kmin (step S3).

If the spring constant k is greater than the minimum spring constant _kmin (step S3: YES), the road load characteristic setting unit 44 sets the spring constant k to a value obtained by subtracting the spring constant decrease amount _kdecrease from the spring constant k (step S4). However, if the value obtained by subtracting the spring constant decrease amount _kdecrease from the spring constant k is smaller than the minimum spring _{constant kmin} , the road load characteristic setting unit 44 sets the minimum spring constant _kmin as the spring constant k. Then, the road load characteristic setting unit 44 ends the processing for the current calculation cycle.

If it is determined in step S3 that the spring constant k is equal to _or less than the minimum spring constant kmin (step S3: NO), the road load characteristic setting unit 44 sets the minimum spring constant _kmin as the spring constant k (step S5), and then ends the processing for the current calculation cycle.

In step S1, if the hands-on/off determining unit 55 determines that the driver is in the hands-off state (step S1: YES), the road load characteristic setting unit 44 sets Toff to a value obtained by adding ΔT to the duration _Toff of the hands- _off state (step S6). That is, the duration _Toff of the hands-off state is updated.

Next, the road load characteristic setting unit 44 determines whether the duration _Toff of the hands-off state is longer than a predetermined time _TLCA (step S7). If the duration _Toff of the hands-off state is shorter than the predetermined time _TLCA , that is, if _Toff ≦ _TLCA (step S7: NO), the road load characteristic setting unit 44 proceeds to step S3.

In step S7, if it is determined that the duration _Toff of the hands-off state is longer than the predetermined time _TLCA , that is, if it is determined that _Toff > _TLCA (step S7: YES), the road load characteristic setting unit 44 determines whether the spring constant k is smaller than _{the maximum} spring constant kmax (step S8). If the spring constant k is smaller than _{the maximum} spring constant kmax (step S8: YES), the road load characteristic setting unit 44 sets the spring constant k to a value obtained by adding the spring constant increase amount _kincrease to the spring constant k (step S9). However, if the value obtained by adding the spring constant increase amount _kincrease to the spring constant k is greater than the maximum spring constant _kmax , the road load characteristic setting unit 44 sets the spring constant k to the _maximum spring constant kmax. Then, the road load characteristic setting unit 44 ends the processing for the current calculation cycle.

If it is determined in step S8 that the spring constant k is _equal to or greater than the maximum spring constant kmax (step S8: NO), the road load characteristic setting unit 44 sets the _maximum spring constant kmax as the spring constant k (step S10: NO), and the gain setting unit 73 ends the processing for the current calculation cycle.

The viscous damping coefficient setting process is similar to the spring constant setting process of Fig. 10. However, in the viscous damping coefficient setting process, the spring constant k, spring constant minimum value _kmin , spring constant maximum value _kmax , spring constant decrease amount _kdecrease , and spring constant increase amount _kincrease of Fig. 10 are replaced with the viscous damping coefficient c, viscous damping coefficient minimum value _cmin , viscous damping coefficient maximum value _cmax , viscous damping coefficient decrease amount _cdecrease , and viscous damping coefficient increase amount _cincrease , respectively.

When the driving mode is the normal mode, the road load characteristic setting unit 44 sets the spring constant k to the minimum spring constant _kmin and sets the viscous damping coefficient _c to the minimum viscous damping coefficient c. In other words, in the normal mode, the spring constant k and the viscous damping coefficient c are not changed.

In the above-described embodiment, in the driving assistance mode, when the hands-on/off determination unit 55 determines that the driver is in a hands-off state for a predetermined period of time or more, the road load characteristics (spring constant k and viscous damping coefficient c) used by the command value setting unit 52 are increased. When the road load characteristics k, c are increased, the manual steering command value θ ^* _c,md relative to the driver torque (driver input) is reduced. This reduces the amount of rotation of the output shaft 9 based on the driver torque, making it easier for the torsion bar 10 to twist even with a relatively small rotation of the steering wheel 2 operated by the driver. This increases the steering torque _Ttb and the driver torque, improving the accuracy of the hands-on/off determination by the hands-on/off determination unit 55. This makes it possible to prevent or suppress erroneous determination that the driver is in a hands-off state despite the driver gripping the steering wheel 2 in situations where the driver torque input is low, such as when driving in a straight line.

[3] Modification of Motor Control ECU 202 FIG. 11 is a block diagram for explaining the electrical configuration of a modification of the motor control ECU 202. As shown in FIG.

The motor control ECU 202 includes a microcomputer 40A, a drive circuit (inverter circuit) 31 controlled by the microcomputer 40A and supplying power to the electric motor 18, and a current detection circuit 32 for detecting the current flowing through the electric motor 18 (hereinafter referred to as "motor current I _m,int ").

The microcomputer 40A is equipped with a CPU and memory (ROM, RAM, non-volatile memory, etc.), and by executing predetermined programs, functions as multiple function processing units. These multiple function processing units include an assist control unit 111, an automatic steering control unit 112, an integrated torque calculation unit (integrated control amount calculation unit) 113, a torque control unit (control unit) 114, an actual steering angle calculation unit 115, a hands-on/off determination unit 116, an actual automatic steering angle calculation unit 117, and a road load characteristic setting unit 118.

The assist control unit 111 sets an assist torque command value (assist control amount) T ^* _m,md , which is a target value of the assist torque required for manual steering. The assist control unit 11 sets the assist torque command value T ^* _m,md based on the vehicle speed V and the steering torque _Ttb detected by the torque sensor 12. The assist control unit 111 sets the assist torque command value T ^* _m,md in a similar manner to that of the assist torque command value setting unit 51 in FIG. 2 .

The automatic steering control unit 112 sets an automatic steering torque command value (automatic steering control amount) T ^* _m,ad required for automatic steering, using the automatic steering angle command value θ ^* _c,ad given by the host ECU 201 and an actual automatic steering angle _θc,ad described later. Details of the automatic steering control unit 112 will be described later.

The integrated torque calculation unit 113 calculates an integrated torque command value (integrated control amount) T ^* _m,int by adding the automatic steering torque command value T ^* _m,ad to the assist torque command value T ^* _m,md .

The torque control unit 114 drives the drive circuit 31 so that the motor torque of the electric motor 18 approaches the integrated torque command value T ^* _m,int . The configuration of the torque control unit 114 is the same as the configuration of the torque control unit 48 shown in Figure 9 above, so a description thereof will be omitted.

The actual steering angle calculation unit 115 calculates the rotation angle θ _c,int of the output shaft 9 based on the output signal of the rotation angle sensor 23. Specifically, the actual steering angle calculation unit 115 includes a rotation angle calculation unit 115A and a reduction ratio division unit 115B. The rotation angle calculation unit 115A calculates the rotor rotation angle θ _m,int of the electric motor 18 based on the output signal of the rotation angle sensor 23. The reduction ratio division unit 115B converts the rotor rotation angle θ _m,int to the rotation angle (actual steering angle) θ _{c,int of the output shaft 9 by dividing the rotor rotation angle θ m, int} calculated by the rotation angle calculation unit 115A by the reduction ratio N of the reducer 19.

The actual steering angle θ _c,int includes the steering angle for manual steering based on the steering torque T _tb and the assist torque command value T ^* _m,md (hereinafter referred to as the "actual manual steering angle θ _c,md "), and the steering angle for automatic steering based on the automatic steering torque command value T ^* _m,ad (hereinafter referred to as the "actual automatic steering angle θ _c,ad ").

The hands-on/off determination unit 116 determines whether the device is in a gripped state or a hands-off state using a method similar to that used by the hands-on/off determination unit 42 in Figure 2.

The actual automatic steering angle calculation unit 117 calculates the actual automatic steering angle θ _{c, ad included in the actual steering angle θ c,} int. Specifically, the actual automatic steering angle calculation unit 117 includes an actual manual steering angle calculation unit 117A and a subtraction unit 117B. The actual manual steering angle calculation unit 117A calculates the actual manual steering angle θ _c,md based on the steering torque T _tb , the assist torque command value T ^* _m,md, and the spring constant k and viscous damping coefficient c set by the road surface load characteristic setting unit 118. The subtraction unit 117B calculates the actual automatic steering angle θ _c,ad by subtracting the actual manual steering angle θ _c,md calculated by the actual manual steering angle calculation unit 117A from the actual steering angle θ _c,int calculated by the actual steering angle calculation unit 115. This actual automatic steering angle θ _c,ad is given to the automatic steering control unit 112 .

In this embodiment, the actual manual steering angle calculation unit 117A calculates the actual manual steering angle θ _c,md using a reference model of the electric power steering system 1 (reference EPS model).

The actual manual steering angle calculation unit 117A calculates the actual manual steering angle θ _c,md using, for example, the reference EPS model shown in FIG. 5 described above.

Referring to FIG. 5, the road load torque T _rl is expressed by the above-mentioned equation (1) using the spring constant k and the viscous damping coefficient c.

The spring constant k and viscous damping coefficient c are set by the road load characteristic setting unit 118. In driving assistance mode, the road load characteristic setting unit 118 sets the spring constant k and viscous damping coefficient c based on the hands-on/off determination result of the hands-on/off determination unit 116. The method for setting the spring constant k and viscous damping coefficient c by the road load characteristic setting unit 118 is the same as the method for setting the spring constant k and viscous damping coefficient c by the road load characteristic setting unit 44 in Figure 2 described above, and therefore a description thereof will be omitted.

The equation of motion of the reference EPS model in Fig. 5 is expressed by the above-mentioned equation (2). The actual manual steering angle calculation unit 116A calculates the rotation angle _θc of the lower column by solving the differential equation of equation (2), and sets the obtained rotation angle _θc as the actual manual steering angle θc _,md .

The automatic steering control unit 112 is described in detail below.

Figure 12 is a block diagram showing the configuration of the automatic steering control unit 112.

The automatic steering control unit 112 calculates an automatic steering torque command value T ^* _{m ,ad} using the automatic steering angle command value θ ^* c, _ad and the actual automatic steering angle θc,ad. The automatic steering control unit 112 includes a low-pass filter (LPF) 161, a feedback control unit 162, a feedforward control unit 163, a disturbance torque estimating unit 164, a torque adding unit 165, a disturbance torque compensating unit 166, a reduction ratio dividing unit 167, and a reduction ratio multiplying unit 168.

The reduction ratio multiplication unit 168 converts the automatic steering torque command value T ^* _m,ad calculated by the reduction ratio division unit 167 into an automatic output shaft torque command value N·T ^* _{m,ad (=T*c,ad)} acting on the output shaft 9 (worm wheel 21) by multiplying the automatic steering torque command value T ^* _m,ad calculated by the reduction ratio division unit 167 by the reduction ratio ^N of _{the reducer 19} .

The low-pass filter 161 performs low-pass filtering on the automatic steering angle command value θ ^* _c,ad . The automatic steering angle command value θ ^* _c,adf after the low-pass filtering is provided to the feedback control unit 162 and the feedforward control unit 163.

The feedback control unit 162 is provided to bring the actual automatic steering angle θ _c,ad calculated by the actual automatic steering angle calculation unit 117 (see FIG. 11) closer to the automatic steering angle command value θ ^* _c,adf after low-pass filter processing. The feedback control unit 162 includes an angle deviation calculation unit 162A and a PD control unit 162B. The angle deviation calculation unit 162A calculates the deviation Δθ _c,ad (= θ ^* _c,adfd - _{θ c,ad} ) between the automatic steering angle command value θ ^* _c,adf and the actual automatic steering angle θ c _, ad. In addition, the angle deviation calculation unit 162A may calculate the deviation (θ ^* _c,adfd - ^θc _, ad) between the automatic steering angle command value θ ^* _c,adf and the actual automatic steering angle estimated value ^θc _,ad calculated by the disturbance torque estimation unit 164 as the angle deviation Δθc _,ad .

The PD control unit 162B calculates a feedback control torque T _fb, ad by performing a PD calculation (proportional differential calculation) on the angle deviation Δθ _c,ad calculated by the angle deviation calculation unit 162A. The feedback control torque T _fb,ad is provided to a torque addition unit 165.

The feedforward control unit 163 is provided to improve the control response by compensating for a delay in response due to the inertia of the electric power steering system 1. The feedforward control unit 163 includes an angular acceleration calculation unit 163A and an inertia multiplication unit 163B. The angular acceleration calculation unit 163A calculates the target angular acceleration ^{d2θ *} _c,adf / ^dt2 by second-order differentiating the automatic steering angle command value θ ^* _c,adf .

The inertia multiplication unit 163B calculates the feedforward control torque T ff,ad (=J ^{·d 2} θ ^* _c,adf /dt ² ) by multiplying the target angular acceleration d ² θ ^* _c,adf /dt ² calculated by the angular acceleration calculation unit 163A by _the inertia J of the electric power steering system 1. The inertia J can be determined, for example, from a physical model (see FIG. 13 ) of the electric power steering system 1, which will be described later. The feedforward control torque T _ff,ad is provided to the torque addition unit 165 as an inertia compensation value.

The torque adder 165 calculates a basic torque command value (T _fb,ad +T _ff,ad ) by adding the feedforward control torque T _{ff, ad} to the feedback control torque T fb,ad .

The disturbance torque estimation unit 164 is provided mainly to calculate an automatic disturbance torque estimated value ^T _lc ,ad, which is an estimate of the disturbance torque T _lc,ad for automatic steering included in the disturbance torque T _lc other than the motor torque acting on the driven object of the electric motor 18. The disturbance torque T _lc,ad for automatic steering refers to torque other than the motor torque that occurs as a disturbance in the driven object (plant) of the electric motor 18, assuming that only automatic steering control based on the automatic steering torque command value T ^* _m,ad is being performed.

Assuming that only automatic steering control based on the automatic steering torque command value T ^* _m,ad is being performed, the target value of the plant becomes the automatic output shaft torque command value N·T ^* _m,ad (=T ^* _c,ad ), and the output of the plant becomes the actual automatic steering angle θc _,ad . Therefore, the disturbance torque estimator 164 estimates the automatic disturbance torque ^Tlc _,ad , the actual automatic steering angle ^θc , _ad, and the derivative of the actual automatic steering angle θc _{,ad (} actual automatic angular velocity) dθc _,ad /dt based on the automatic output shaft torque command value N· _T*m,ad (= _{T*c,ad) and the actual automatic steering angle θc,ad .} Hereinafter, the estimated values of T _lc,ad , θ _c,ad and dθ _c,ad /dt will be represented as ^T _lc,ad , ^θ _c,ad and ^dθ _c,ad /dt, respectively. Details of the disturbance torque estimating unit 164 will be described later.

The automatic disturbance torque estimated value ^T _lc,ad calculated by the disturbance torque estimating section 164 is given to the disturbance torque compensating section 166 as an automatic disturbance torque compensation value.

The disturbance torque compensator 166 calculates an automatic output shaft torque command value T ^* c, _ad (= _Tfb,ad +Tff,ad-^ _Tlc,ad ) by subtracting the automatic disturbance torque estimated value ^ _Tlc,ad from the basic torque command value ( _{Tfb,ad + Tff,ad} ). This provides an automatic output shaft torque command value T ^* _c,ad (target torque for the output shaft 9) with the automatic disturbance torque compensated for.

The automatic output shaft torque command value T ^* _c,ad is given to a reduction ratio division unit 167. The reduction ratio division unit 167 calculates an automatic steering torque command value T ^* _m ,ad (target torque for the electric motor 18) by dividing the automatic output shaft torque command value T ^* _c, ad by the reduction ratio N. This automatic steering torque command value T ^* _m,ad is given to an integrated torque calculation unit 113 (see FIG. 11).

The disturbance torque estimation unit 164 will be described in detail. The disturbance torque estimation unit 164 is configured from a disturbance observer that calculates the automatic disturbance torque estimated value ^T _lc,ad , the actual automatic steering angle estimated value ^θ _c,ad and the actual automatic angular velocity estimated value ^dθ _c,ad /dt using, for example, a physical model 101A of the electric power steering system 1 shown in Fig. 13. However, Fig. 13 shows a physical model when it is assumed that only automatic steering control based on the automatic steering torque command value T ^* _m,ad is being performed.

This physical model 101A includes a plant (an example of a motor-driven object) 102A that includes an output shaft 9 and a worm wheel 21 fixed to the output shaft 9. The plant 102A is supplied with a steering torque (torsion bar torque) _Ttb , which is the torsional torque of the torsion bar 10, and is also supplied with a road load torque _Trl,ad from the steered wheels 3. Furthermore, the plant 102A is supplied with an automatic output shaft torque command value N·T ^* _m,ad from the motor via the worm gear 20, and is also supplied with a friction torque _Tf,ad due to friction between the worm wheel 21 and the worm gear 20.

If the inertia of plant 102A is J, the equation of motion for the inertia of physical model 101A is expressed by the following equation (10):

d ² θ _c,ad /dt ² is the angular acceleration of the plant 102A. N is the reduction ratio of the reducer 19. _{T lc,ad} represents the automatic disturbance torque applied to the plant 102A. In this embodiment, the automatic disturbance torque T _lc,ad is shown as the sum of the steering torque T _tb , the road load torque T _rl,ad , and the friction torque T _f,ad , but in reality, the automatic disturbance torque T _lc,ad includes torques other than these.

The state equation for the physical model 101A in Figure 13 is expressed by the following equation (11):

In the above equation (11), x is a state variable vector, u1 is a known input vector, u2 is an unknown input vector, and y is an output vector. In the above equation (11), A is a system matrix, B1 is a first input matrix, B2 is a second input matrix, C is an output matrix, and D is a direct feedthrough matrix.

The above state equation is expanded to a system that includes the unknown input vector u2 as one of its states. The state equation of the expanded system (expanded state equation) is expressed as follows:

In the above equation (12), x _e is a state variable vector of the extended system, and is expressed by the following equation (13).

In the above equation (12), A _e is the system matrix of the extended system, B _e is the known input matrix of the extended system, and C _e is the output matrix of the extended system.

From the extended state equation (12) above, a disturbance observer (extended state observer) expressed by the following equation (14) is constructed.

In equation (14), ^x _e represents the estimated value of x _e . Furthermore, L is the observer gain. Furthermore, ^y represents the estimated value of y. ^x _e is expressed by the following equation (15).

In equation (15), ^θ _c,ad is an estimated value of the actual automatic steering angle θ _c,ad , ^dθ _c,ad /dt is an estimated value of the angular velocity dθ _c,ad /dt, and ^T _lc,ad is an estimated value of the automatic disturbance torque T _lc,ad .

The disturbance torque estimation unit 164 calculates the state variable vector ^x _e based on the equation (14) above.

Figure 14 is a block diagram showing the configuration of the disturbance torque estimation unit 164.

The disturbance torque estimation unit 164 includes an input vector input unit 181, an output matrix multiplication unit 182, a first addition unit 183, a gain multiplication unit 184, an input matrix multiplication unit 185, a system matrix multiplication unit 186, a second addition unit 187, an integration unit 188, and a state variable vector output unit 189.

The automatic output shaft torque command value N·T ^* _m,ad (=T ^* _c,ad ) calculated by the reduction ratio multiplication unit 168 (see FIG. 12) is given to the input vector input unit 181. The input vector input unit 181 outputs an input vector _u1 .

The output of the integrator 188 is the state variable vector ^x _e (see equation (15) above). At the start of the calculation, an initial value is given as the state variable vector ^x _e . The initial value of the state variable vector ^x _e is, for example, 0.

The system matrix multiplication unit 186 multiplies the state variable vector ^x _e by the system matrix A _e . The output matrix multiplication unit 182 multiplies the state variable vector ^x _e by the output matrix C _e .

The first adder 183 subtracts the output (C _e · ^x _e ) of the output matrix multiplier 182 from the output vector y, which is the actual automatic steering angle θ _c,ad . In other words, the first adder 183 calculates the difference (y - ^y) between the output vector y and the output vector estimate value ^y (=C _e · ^x _e ). The gain multiplier 184 multiplies the output (y - ^y) of the first adder 183 by the observer gain L (see equation (14) above).

The input matrix multiplication unit 185 multiplies the input vector u1 output from the input vector input unit ₁₈₁ by the input matrix B _e . The second addition unit 187 adds the output (B _e · u ₁ ) of the input matrix multiplication unit 185, the output (A _e · ^x _e ) of the system matrix multiplication unit 186, and the output (L(y - ^y)) of the gain multiplication unit 184 to calculate a differential value d^x _e /dt of the state variable vector. The integrator 188 integrates the output (d^x _e /dt) of the second addition unit 187 to calculate the state variable vector ^x _e . The state variable vector output unit 189 calculates the automatic disturbance torque estimate ^T _lc,ad , the actual automatic steering angle estimate ^θ _c,ad, and the actual automatic angular velocity estimate d^θ _c,ad /dt based on the state variable vector ^x _e .

Instead of the aforementioned extended state observer, a disturbance observer consisting of an inverse model of the plant and a low-pass filter can be used. In this case, the plant's equation of motion is expressed as equation (10) as described above.

Therefore, the inverse model of the plant is given by the following equation (16).

The inputs to the disturbance observer using the inverse model of the plant are J·d ² θ _c,ad /dt ² and N·T ^* _m,ad , and since the second-order differential value of the actual steering angle θ _c,ad is used, it is significantly affected by noise from the rotation angle sensor 23. In contrast, the above-mentioned extended state observer estimates the disturbance torque in an integral manner, which has the advantage of being able to reduce the influence of noise due to differentiation.

In this modification, the electric motor 18 is driven based on an integrated torque command value T ^* _m, int which is the sum of an automatic steering torque command value T ^* m,ad calculated based on the feedback control torque _Tfb,ad , etc. and an assist torque command value T ^* _{m, md} . Therefore, in the driving assistance mode, normally, the output shaft 9 is rotated based on the automatic steering torque command value T ^* _m,ad , and also based on the steering torque _Ttb and assist torque command value T ^* _m,md which are generated based on the driver torque.

In the driving assistance mode, when the hands-on/off determination unit 116 determines that the vehicle is in a hands-off state for a predetermined period of time or longer, the road load characteristics (spring constant k and viscous damping coefficient c) used in the actual manual steering angle calculation unit 117A are increased. When the road load characteristics k and c are increased, the absolute value of the actual manual steering angle θ _c,md relative to the driver torque, i.e., the angle at which the driver is allowed to steer in response to driving assistance, becomes smaller than normal.

As a result, the value of the actual automatic steering angle θ _c,ad used in feedback control becomes larger than normal, and is reflected in the torque command value of the motor via the feedback control torque T _fb,ad and automatic steering torque command value T ^* _m,ad in that order.

As a result, similar to the embodiment in FIG. 2 , the amount of rotation of the output shaft 9 based on the driver torque is reduced. As a result, even if the steering wheel 2 is rotated, the rotation is less likely to be transmitted, and the torsion bar 10 is more likely to twist. As a result, the steering torque _Ttb and the driver torque increase, and the accuracy of the hands-on/off determination by the hands-on/off determination unit 116 increases. This makes it possible to prevent or suppress erroneous determination that the driver is not holding the steering wheel 2 even though the driver is holding it, in situations where the driver torque input is small, such as when driving in a straight line.

In the normal mode, the assist torque command value T ^* _m,md set by the assist control unit 111 is given as the integrated torque command value T ^* _m,int to the torque control unit 114. Therefore, in the normal mode, the drive circuit 31 is driven based only on the assist torque command value T ^* _m,md .

In the above-described embodiment, in driving assistance mode, the road load characteristic setting unit 44, 118 changes both the spring coefficient k and the viscous damping coefficient c based on the hands-on/off determination result, but it may also be configured to change only one of the spring coefficient k and the viscous damping coefficient c.

In the above-described embodiment, an example was shown in which this invention was applied to motor control of a column-type EPS, but this invention can also be applied to motor control of EPS other than column types.

Although embodiments of the present invention have been described in detail, these are merely examples used to clarify the technical content of the present invention, and the present invention should not be construed as being limited to these examples. The scope of the present invention is limited only by the appended claims.

1...electric power steering device, 3...steered wheels, 4...steering mechanism, 18...electric motor, 43...hands on/off determination unit, 44...road surface load characteristic setting unit, 45...manual steering command value generation unit, 46...integrated angle command value calculation unit, 47...angle control unit, 48...torque control unit, 51...assist torque command value setting unit, 52...command value setting unit, 111...assist control unit, 112...automatic steering control unit, 113...integrated torque calculation unit (integrated control amount calculation unit), 114...torque control unit (control unit), 115...actual steering angle calculation unit, 116...hands on/off determination unit, 117...actual automatic steering angle calculation unit, 117A...actual manual steering angle calculation unit, 117B...subtraction unit, 118...road surface load characteristic setting unit, 201...host ECU 201, 202...motor control ECU

Claims (4)

a torque detection unit for detecting a steering torque;
a manual steering command value generating unit that generates a manual steering command value using the steering torque;
an integrated angle command value calculation unit that calculates an integrated angle command value by adding the manual steering command value to an automatic steering command value given in a driving assistance mode;
a control unit that controls the angle of an electric motor for steering angle control based on the integrated angle command value;
a hands-on/off determination unit that determines whether the driver is in a gripped state where the driver is gripping the steering wheel or in a hands-off state where the driver is not gripping the steering wheel,
the manual steering command value generation unit is configured to generate the manual steering command value by using the steering torque, and a spring constant and a viscous damping coefficient for generating a road surface load torque,
The motor control device further includes a road surface load characteristic change unit that increases the value of at least one of the spring constant and the viscous damping coefficient when, in the driving assistance mode, the hands-on/off determination unit determines that the vehicle is in a hands-off state for a predetermined period of time or more. A motor control device including: a torque detection unit for detecting steering torque; a steering angle detection unit for detecting an actual steering angle; an automatic steering control unit for setting an automatic steering control amount based on an automatic steering command value given in a driving assistance mode; an assist control unit for setting an assist control amount using the steering torque; an integrated control amount calculation unit for calculating an integrated control amount by adding the automatic steering control amount and the assist control amount; and a control unit for controlling an electric motor for steering angle control based on the integrated control amount,
a hands-on/off determination unit that determines whether the driver is in a gripped state where the driver is gripping the steering wheel or in a hands-off state where the driver is not gripping the steering wheel;
an actual manual steering angle calculation unit that calculates an actual manual steering angle, which is a steering angle for manual steering based on the steering torque and the assist control amount;
an actual automatic steering angle calculation unit that calculates an actual automatic steering angle, which is a steering angle for automatic steering based on the automatic steering control amount, by subtracting the actual manual steering angle from the actual steering angle,
the automatic steering control unit sets the automatic steering control amount using the automatic steering command value and the actual automatic steering angle,
the actual manual steering angle calculation unit is configured to calculate the actual manual steering angle by using the steering torque, the assist control amount, and a spring constant and a viscous damping coefficient for generating a road surface load torque,
The motor control device further includes a road surface load characteristic change unit that increases the value of at least one of the spring constant and the viscous damping coefficient when, in the driving assistance mode, the hands-on/off determination unit determines that the vehicle is in a hands-off state for a predetermined period of time or more. If the spring constant and the viscous damping coefficient, the values of which are changed by the road load characteristic changing unit, are defined as road load variables, then
3. The motor control device according to claim 1, wherein, when the hands-on/off determination unit determines that the vehicle is in a hands-off state for a predetermined period of time in the driving assistance mode, the road load characteristic change unit gradually increases the value of the road load variable from that point on while the hands-on/off determination unit determines that the vehicle is in a hands-off state, and when the road load variable reaches a predetermined upper limit value, the road load characteristic change unit maintains the value of the road load variable at the upper limit value. The motor control device of claim 3, wherein, in the driving assistance mode, when the hands-on/off determination unit determines that the driver is in a hands-off state for a predetermined period of time or more and then changes the determination result from the hands-on/off determination unit to a gripped state, the road load characteristic change unit gradually decreases the value of the road load variable from that point onwards while the hands-on/hand-on state determination result continues, and when the road load variable reaches a predetermined lower limit value, the road load variable is maintained at the lower limit value.