Motor control device

Abstract

This motor control device comprises a manual steering command value generation unit for generating a manual steering command value, and a hands on / off determination unit for determining whether the state of the driver is a gripping state in which the driver is gripping the steering wheel, or a hands-free state in which the driver is not gripping the steering wheel. The manual steering command value generation unit is configured to generate a manual steering command value on the basis of an equation of motion. The motor control device further comprises a coefficient value change unit for changing the value of at least one coefficient from among the coefficients included in the equation of motion, in accordance with the determination results from the hands on / off determination unit.

Description

Technical Field

[0001] This invention relates to a motor control device that controls an electric motor for rudder angle control.

Background Art

[0002] Patent Document 1 below discloses a motor control device including a manual steering command value calculation unit that calculates a manual steering command value using steering torque, an integrated angle command value calculation unit that adds the manual steering command value to an automatic steering command value to calculate an integrated angle command value, and a control unit that controls the electric motor based on the integrated angle command value.

[0003] The manual steering command value calculation unit of Patent Document 1 calculates the manual steering command value using a reference EPS model. Specifically, the manual steering command value calculation unit calculates the manual steering command value based on a motion equation including a spring constant and a viscous damping coefficient for applying a virtual reaction force as coefficients. The spring constant and the viscous damping coefficient are presumably designed so that an appropriate steering reaction force is generated when the driver intervenes in steering.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the motor control device described in Patent Document 1, although the reaction force characteristics when the driver intervenes in steering can be designed, the return characteristics (characteristics in which the manual steering command value converges to zero) when the driver releases the hand from the steering wheel and returns to automatic driving after the steering intervention are left to chance. In other words, when returning to automatic driving, the manual steering command value converges to zero according to the characteristics designed for the steering reaction force at the time of steering intervention.

[0006] When designing the spring constant and viscous damping coefficient with priority given to the return characteristic in the reverse direction, the reaction force characteristic during steering intervention will become a matter of course.

[0007] An object of an embodiment of the present invention is to provide a motor control device capable of separately setting the reaction force characteristic during steering intervention and the return characteristic after release.

Means for Solving the Problem

[0008] An embodiment of the present invention includes a manual steering command value generation unit that generates a manual steering command value, an integrated angle command value calculation unit that adds the manual steering command value to an automatic steering command value given in the automatic driving mode to calculate an integrated angle command value, 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 gripping state of gripping the steering wheel or in a released state of not gripping the steering wheel. The manual steering command value generation unit is configured to generate the manual steering command value based on the equation of motion, and further includes a coefficient value change unit that changes the value of at least one coefficient among the coefficients included in the equation of motion according to the determination result of the hands-on / off determination unit. A motor control device is provided.

[0009] With this configuration, it becomes possible to separately set the reaction force characteristic during steering intervention and the return characteristic after release.

Brief Description of the Drawings

[0010]

Figure 1

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Figure 5

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Figure 10

Figure 11

MODE FOR CARRYING OUT THE INVENTION

[0011] [Description of Embodiment of the Present Invention] One embodiment of the present invention includes a manual steering command value generation unit that generates a manual steering command value, an integrated angle command value calculation unit that adds the manual steering command value to an automatic steering command value given in the automatic driving mode to calculate an integrated angle command value, 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 gripping state of gripping the steering wheel or a released state of not gripping the steering wheel. The manual steering command value generation unit is configured to generate the manual steering command value based on the equation of motion, and further includes a coefficient value change unit that changes the value of at least one coefficient among the coefficients included in the equation of motion according to the determination result of the hands-on / off determination unit, and provides a motor control device.

[0012] In this configuration, it becomes possible to separately set the reaction force characteristics during steering intervention and the return characteristics after release.

[0013] In one embodiment of the present invention, the equation of motion includes inertia, spring constant, and viscous damping coefficient as coefficients, and the coefficient value changing unit is configured to change at least one value among the inertia, the spring constant, and the viscous damping coefficient according to the determination result of the hands-on / off determination unit.

[0014] In one embodiment of the present invention, the hands-on / off determination unit is configured to determine a gripping state if the steering torque is equal to or greater than a predetermined threshold value, and to determine a released state when a state in which the steering torque is less than the threshold value continues for a predetermined time or more.

[0015] [Detailed Description of Embodiment of the Present Invention] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. [1] Schematic Configuration of Electric Power Steering System FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering system to which a motor control device according to an embodiment of the present invention is applied.

[0016] The electric power steering system 1 includes a steering wheel (handle) 2 as a steering member for steering a vehicle, a steering mechanism 4 that steers the steered wheels 3 in conjunction with the rotation of the steering wheel 2, and a steering assist mechanism 5 for assisting the driver's steering. The steering wheel 2 and the steering mechanism 4 are mechanically connected via a steering shaft 6 and an intermediate shaft 7.

[0017] 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 the output shaft 9 are connected so as to be relatively rotatable via a torsion bar 10.

[0018] A torque sensor 12 is disposed near the torsion bar 10. The torque sensor 12 detects a steering torque (torsion bar torque) T applied to the steering wheel 2 based on the relative rotational displacement amount between the input shaft 8 and the output shaft 9. tb In this embodiment, the steering torque T detected by the torque sensor 12 tb is detected such that, for example, a torque for steering in the left direction is detected as a positive value, a torque for steering in the right direction is detected as a negative value, and the magnitude of the steering torque T tb increases as the absolute value thereof increases.

[0019] The steering mechanism 4 is composed of a rack and pinion mechanism including a pinion shaft 13 and a rack shaft 14 as a steering shaft. At each end of the rack shaft 14, a steering wheel 3 is connected via a tie rod 15 and a knuckle arm (not shown). The pinion shaft 13 is connected to the intermediate shaft 7. The pinion shaft 13 is configured to rotate in conjunction with the steering of the steering wheel 2. A pinion 16 is connected to the tip of the pinion shaft 13.

[0020] The rack shaft 14 extends linearly along the left - right direction of the vehicle. A rack 17 that meshes with the pinion 16 is formed at an intermediate portion in the axial direction of the rack shaft 14. By this pinion 16 and rack 17, the rotation of the pinion shaft 13 is converted into the axial movement of the rack shaft 14. By moving the rack shaft 14 in the axial direction, the steering wheel 3 can be steered.

[0021] When the steering wheel 2 is steered (rotated), this rotation is transmitted to the pinion shaft 13 via the steering shaft 6 and the intermediate shaft 7. Then, the rotation of the pinion shaft 13 is converted into the axial movement of the rack shaft 14 by the pinion 16 and the rack 17. Thereby, the steering wheel 3 is steered.

[0022] The steering assist mechanism 5 includes an electric motor 18 for generating a steering assist force (assist torque), and a speed reducer 19 for amplifying the output torque of the electric motor 18 and transmitting it to the steering mechanism 4. The speed reducer 19 consists of a worm gear mechanism including a worm gear 20 and a worm wheel 21 meshing with the worm gear 20. The speed reducer 19 is housed in a gear housing 22 as a transmission mechanism housing. In the following, the reduction ratio (gear ratio) of the speed reducer 19 may be represented by N. The reduction ratio N is the ratio θ ww of the rotation angle θ wg of the worm gear 20 to the rotation angle θ wg of the worm wheel 21, defined as θ ww / θ

[0023] The worm gear 20 is rotationally driven by the electric motor 18. Also, the worm wheel 21 is integrally rotatably connected to the output shaft 9.

[0024] When the worm gear 20 is rotationally driven by the electric motor 18, the worm wheel 21 is rotationally driven, motor torque is applied to the steering shaft 6, and the steering shaft 6 (output shaft 9) rotates. Then, the rotation of the steering shaft 6 is transmitted to the pinion shaft 13 via the intermediate shaft 7. The rotation of the pinion shaft 13 is converted into an axial movement of the rack shaft 14. Thereby, the steering wheel 3 is steered. That is, by rotationally driving the worm gear 20 with the electric motor 18, steering assist by the electric motor 18 and steering of the steering wheel 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.

[0025] As the torque applied to the output shaft 9 (an example of the drive target of the electric motor 18), there are motor torque by the electric motor 18 and disturbance torque other than the motor torque. The disturbance torque T lc other than the motor torque includes the steering torque T tb , the road surface load torque (road surface reaction torque) T rl , the friction torque T f , and the like.

[0026] Steering torque T tb is the torque applied to the output shaft 9 from the steering wheel 2 side by the force (driver torque) applied to the steering wheel 2 by the driver, the force generated by steering inertia, etc.

[0027] Road surface load torque T rl is the torque applied to the output shaft 9 via the rack shaft 14 from the steered wheel 3 side by the self-aligning torque generated in the tire, the force generated by the suspension and tire-wheel alignment, the frictional force of the rack and pinion mechanism, etc.

[0028] The vehicle is equipped with a CCD (Charge Coupled Device) camera 25 for photographing the road ahead in the traveling direction of the vehicle, a GPS (Global Positioning System) 26 for detecting the vehicle position, a radar 27 for detecting the road shape and obstacles, a map information memory 28 storing map information, and a vehicle speed sensor 29 for detecting the vehicle speed V.

[0029] The CCD camera 25, GPS 26, radar 27, map information memory 28, and vehicle speed sensor 29 are connected to a host ECU (ECU: Electronic Control Unit) 201 for performing automatic driving control. The host ECU 201 performs peripheral environment recognition, own vehicle position estimation, route planning, etc. based on the information obtained by the CCD camera 25, GPS 26, radar 27, and vehicle speed sensor 29 and the map information, and determines the control target values for steering and drive actuators.

[0030] In this embodiment, as driving modes, there are a normal mode and an automatic driving mode. The host ECU 201 sets an automatic steering command value θ * c,ad for automatic driving (including driving support) in the automatic driving mode. In this embodiment, the automatic driving control is control for driving the vehicle along a target traveling route. The automatic steering command value θ * c,adis the target value of the steering angle for driving the vehicle along the target driving route. The process of setting such an automatic steering command value θ * c,ad is well-known, so detailed description is omitted here. In the normal mode, the upper ECU 201 sets the automatic steering command value θ * c,ad to zero.

[0031] In addition, the upper ECU 201 outputs a mode signal S mode indicating whether the driving mode is the normal mode or the automatic driving mode. The mode signal S mode , the automatic steering command value θ * c,ad set by the upper ECU 201 and the vehicle speed V 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 the information provided from the upper ECU 201.

[0032] [2] Motor control ECU 202 Figure 2 is a block diagram for explaining the electrical configuration of the motor control ECU 202.

[0033] The motor control ECU 202 includes a microcomputer 40, a drive circuit (inverter circuit) 31 controlled by the microcomputer 40 to supply 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 ").

[0034] The microcomputer 40 includes a CPU and memory (such as ROM, RAM, non-volatile memory, etc.), and functions as a plurality of functional processing units by executing a predetermined program. These plurality of functional processing units include a rotation angle calculation unit 41, a reduction ratio division unit 42, a hands-on / off determination unit 43, a coefficient value 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.

[0035] Based on the output signal of the rotation angle sensor 23, the rotation angle calculation unit 41 calculates the rotor rotation angle θ of the electric motor 18. m,int The reduction ratio division unit 42 divides the rotor rotation angle θ by the reduction ratio N to convert the rotor rotation angle θ into the rotation angle (actual steering angle) θ of the output shaft 9. m,int m,int c,int

[0036] The hands-on / off determination unit 43 determines whether the driver is in a gripping state (hands-on) of gripping the steering wheel 2 or a released state (hands-off) of not gripping the steering wheel 2. The hands-on / off determination unit 43 estimates, for example, the driver torque, which is the torque applied by the driver to the steering wheel 2, based on the steering torque T tb and the actual steering angle θ c,int or the rotor rotation angle θ m,int and determines that it is a gripping state if the driver torque is equal to or greater than a predetermined threshold value, and determines that it is a released state when the state where the driver torque is less than the threshold value continues for a predetermined time or more. In this case, it is determined to be in a gripping state until it is determined to be in a released state after the driver torque changes from a state equal to or greater than the threshold value to less than the threshold value. As such a hands-on / off determination unit 43, for example, the "steering wheel operation state determination unit" described in JP-A-2017-114324, JP-A-2018-165156, JP-A-2020-142703, JP-A-2020-59361, JP-A-2020-59362, etc. can be used.

[0037] ​​​The hands-on / off determination unit 43 determines, for example, that the gripping state is established if the steering torque T tb is equal to or greater than a predetermined threshold value, and may determine that the released state is established when the state in which the steering torque T tb is less than the threshold value continues for a predetermined time or longer. In this case, after the steering torque T tb changes from a state equal to or greater than the threshold value to less than the threshold value, the gripping state is determined until the released state is determined. The hands-on / off determination unit 43 may be a hands-on / off determination unit having a hysteresis characteristic that determines hands-on if the steering torque T tb is equal to or greater than a first threshold value (for example, 1 Nm), and determines hands-off if the steering torque T tb is equal to or less than a second threshold value (for example, 0.5 Nm) different from the first threshold value.

[0038] The coefficient value setting unit 44 sets the lower column inertia J c , the spring constant k, and the viscous damping coefficient c, which are used by the manual steering command value generation unit 45 during the automatic driving mode, based on the hands-on / off determination result of the hands-on / off determination unit 43.

[0039] The manual steering command value generation 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 generation unit 45 generates the manual steering command value θ tb using the vehicle speed V and the steering torque T * c,md detected by the torque sensor 12. Details of the operation of the manual steering command value generation unit 45 will be described later.

[0040] The integrated angle command value calculation unit 46 adds the manual steering command value θ * c,ad to the automatic steering command value θθ * c,md set by the upper ECU 201 to calculate the integrated angle command value θ * c,int .

[0041] The angle control unit 47 calculates the motor torque command value T, which is the target value of the motor torque of the electric motor 18, based on the integrated angle command value θ * c,int * m,int * m,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. That is, the control unit composed 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 θ c,int (the rotation angle θ of the output shaft 9 c,int ) 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.

[0042] FIG. 3 is a block diagram showing the configuration of the manual steering command value generation unit 45.

[0043] The manual steering command value generation unit 45 includes an assist torque command value setting unit 51 and a command value setting unit 52.

[0044] The assist torque command value setting unit 51 sets the assist torque command value T, which is the 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 T tb detected by the torque sensor 12. An example of setting the assist torque command value T * m,md for the steering torque T tb is shown in FIG. 4. * m,md

[0045] The assist torque command value T * m,md is set to a positive value when the electric motor 18 should generate a steering assist force for leftward steering, and is set to a negative value when the electric motor 18 should generate a steering assist force for rightward steering. The assist torque command value T​​​* m,md is positive for positive values of the steering torque T tb and negative for negative values of the steering torque T tb . The assist torque command value T * m,md is set such that its absolute value increases as the absolute value of the steering torque T tb increases. The assist torque command value T * m,md is set such that its absolute value decreases as the vehicle speed V increases.

[0046] Note that the assist torque command value setting unit 51 may calculate the assist torque command value T tb by multiplying a constant preset for the steering torque T * m,md .

[0047] In this embodiment, the command value setting unit 52 sets the manual steering command value θ * c.md using a reference EPS model.

[0048] FIG. 5 is a schematic diagram showing an example of the reference EPS model used by the command value setting unit 52.

[0049] This reference EPS model is a single inertia model including a lower column. The lower column corresponds to the output shaft 9 and the worm wheel 21. In FIG. 5, J c is the inertia of the lower column, θ c is the rotation angle of the lower column, and T tb is the steering torque. This reference EPS model is based on the steering torque T tb and the assist torque command value T * m,md and the output shaft torque command value N·T * m,md acting on the output shaft 9 from the electric motor 18, and the road surface load torque T rl when they are applied to the lower column, and the rotation angle θ cis a model for generating (estimating) the road surface load torque T rl is represented by the following equation (1) using the spring constant k and the viscous damping coefficient c.

[0050] T rl = -k·θ c - c(dθ c / dt) …(1) The equation of motion of the reference EPS model is represented by the following equation (2).

[0051] J c ·d 2 θ c / dt 2 = T tb + N·T * m,md - k·θ c - c(dθ c / dt) …(2) The values of the lower column inertia J c , the spring constant k, and the viscous damping coefficient c, which are the coefficients of the equation of motion of Equation (2), are set by the coefficient value setting unit 44. Details of the operation of the coefficient value setting unit 44 will be described later.

[0052] The command value setting unit 52 substitutes the steering torque T tb detected by the torque sensor 12 into T tb and substitutes the assist torque command value T * m,md set by the assist torque command value setting unit 51 into T * m,md to solve the differential equation of Equation (2), thereby calculating the rotation angle θ c of the lower column. Then, the command value setting unit 52 sets the obtained rotation angle θ c of the lower column as the manual steering command value θ * c,md .

[0053] Figure 6 is a block diagram showing the configuration of the angle control unit 47.

[0054] The angle control unit 47 has an integrated angle command value θ * c,intBased on this, the motor torque command value T * m,int is calculated. The angle control unit 47 includes a low-pass filter (LPF) 61, a feedback control unit 62, a feed-forward control unit 63, a disturbance torque estimation unit 64, a torque addition unit 65, a disturbance torque compensation unit 66, a reduction ratio division unit 67, and a reduction ratio multiplication unit 68.

[0055] The reduction ratio multiplication unit 68 multiplies the motor torque command value T * m,int calculated by the reduction ratio division unit 67 by the reduction ratio N of the speed reducer 19, thereby obtaining the output shaft torque command value T * m,int acting on the output shaft 9 * c,int (= N·T * m,int ).

[0056] The low-pass filter 61 performs low-pass filter processing on the integrated angle command value θ * c,int . The integrated angle command value θ after the low-pass filter processing * c,intf is given to the feedback control unit 62 and the feed-forward control unit 63.

[0057] The feedback control unit 62 is provided to make the actual steering angle θ c,int calculated by the reduction ratio division unit 42 (see FIG. 2) approach the integrated angle command value θ after the low-pass filter processing * c,intf . 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,intf between the integrated angle command value θ c,int and the actual steering angle θ calculated by the reduction ratio division unit 42 c,int (= θ * c,intf - θ c,int ). Note that the angle deviation calculation unit 62A calculates the deviation between the integrated angle command value θ * c,intfand the deviation (θ c,int -^θ * c,intf ) between the steering angle estimated value ^θ calculated by the disturbance torque estimator 64 c,int is calculated as the angle deviation Δθ c,int .

[0058] The PD control unit 62B performs PD calculation (proportional derivative calculation) on the angle deviation Δθ calculated by the angle deviation calculation unit 62A c,int to calculate the feedback control torque T fb,int . The feedback control torque T fb,int is given to the torque addition unit 65

[0059] The feedforward control unit 63 is provided to compensate for the response delay due to the inertia of the electric power steering system 1 and improve the response of the control. 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 d * c,intf θ 2 by second-order differentiating the integrated angle command value θ * c,intf / dt 2 .

[0060] The inertia multiplication unit 63B multiplies 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 to calculate the feedforward control torque T ff,int (=J·d 2 θ * c,intf / dt 2 ). The inertia J is obtained, for example, from the physical model of the electric power steering system 1 (see FIG. 7) described later. The feedforward control torque T ff,int is given to the torque addition unit 65 as an inertia compensation value

[0061] The torque addition unit 65 adds the feedforward control torque T fb,int to the feedback control torque T ff,int to calculate the basic torque command value (T fb,int +T ff,int ).

[0062] The disturbance torque estimation unit 64 is provided to estimate the non-linear torque (disturbance torque: torque other than the motor torque) generated as a disturbance in the plant (the controlled object of the electric motor 18). The disturbance torque estimation unit 64 estimates the disturbance torque (disturbance load) T * c,int (=N·T * m,int ), the actual steering angle θ c,int which is the output of the plant, and the steering angle derivative value (angular velocity) dθ lc / dt based on the output shaft torque command value T c,int c,int lc / dt. The estimated values of the disturbance torque T c,int , the steering angle θ c,int and the steering angle derivative value (angular velocity) dθ lc / dt are represented by ^T c,int , ^θ c,int and d^θ lc / dt respectively. Details of the disturbance torque estimation unit 64 will be described later.

[0063] The estimated disturbance torque value ^T fb,int calculated by the disturbance torque estimation unit 64 is given to the disturbance torque compensation unit 66 as a disturbance torque compensation value.

[0064] The disturbance torque compensation unit 66 subtracts the estimated disturbance torque value ^T ff,int from the basic torque command value (T lc +T * ) to calculate the output shaft torque command value T c,int fb,int (=T ff,int +T lc -^T * ). Thus, the output shaft torque command value T c,int with the disturbance torque compensated is obtained.(Torque command value for output shaft 9) is obtained.

[0065] Output shaft torque command value T * c,int is given to the reduction ratio division unit 67. The reduction ratio division unit 67 divides the output shaft torque command value T * c,int by the reduction ratio N to calculate the motor torque command value T * m,int This motor torque command value T * m,int is given to the torque control unit 48 (see FIG. 2).

[0066] The disturbance torque estimation unit 64 will be described in detail. The disturbance torque estimation unit 64 is composed of, for example, a disturbance observer that uses the physical model 101 of the electric power steering system 1 shown in FIG. 7 to estimate the disturbance torque T lc , the steering angle θ c,int and the angular velocity dθ c,int / dt.

[0067] This physical model 101 includes a plant (an example of a motor drive target) 102 that includes the output shaft 9 and the worm wheel 21 fixed to the output shaft 9. The plant 102 is given the steering torque T tb from the steering wheel 2 via the torsion bar 10, and is given the road surface load torque T rl from the side of the steered wheels 3.

[0068] Furthermore, the plant 102 is given the output shaft torque command value T * c,int (= N·T * m,int ) via the worm gear 20, and is given the frictional torque T f due to the friction between the worm wheel 21 and the worm gear 20.

[0069] Assuming 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).

[0070] [Number]

[0071] d 2 θ c,int / dt 2 is the angular acceleration of the plant 102. N is the reduction ratio of the speed reducer 19. T lc represents the disturbance torque other than the motor torque applied to the plant 102. In this embodiment, the disturbance torque T lc is the steering torque T tb and the road surface load torque T rl and the frictional torque T f and is shown as the sum of them. However, in reality, the disturbance torque T lc includes torques other than these.

[0072] The state equation for the physical model 101 in FIG. 7 is represented by the following equation (4).

[0073] [Number]

[0074] 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 transmission matrix.

[0075] The above state equation is extended to a system that includes the unknown input vector u2 as one of the states. The state equation of the extended system (extended state equation) is represented by the following equation (5).

[0076] [Number]

[0077] In the above equation (5), x e is the state variable vector of the extended system and is represented by the following equation (6).

[0078]

Number

[0079] In the above formula (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.

[0080] From the extended state equation of the above formula (5), a disturbance observer (extended state observer) represented by the equation of the following formula (7) is constructed.

[0081]

Number

[0082] In formula (7), ^x e represents the estimated value of x e . Also, L is the observer gain. Also, ^y represents the estimated value of y. ^x e is represented by the following formula (8).

[0083]

Number

[0084] In formula (8), ^θ c,int is the estimated value of θ c,int , and ^T lc is the estimated value of T lc .

[0085] The disturbance torque estimation unit 64 calculates the state variable vector ^x e based on the equation of the above formula (7).

[0086] Figure 8 is a block diagram showing the configuration of the disturbance torque estimation unit 64.

[0087] The external 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.

[0088] The output shaft torque command value T * c,int (= N·T * m,int ) is given to the input vector input unit 81. The input vector input unit 81 outputs an input vector u1.

[0089] The output of the integration unit 88 is the state variable vector ^x e (see the above formula (8)). At the start of the operation, the state variable vector ^x e is given an initial value. The initial value of the state variable vector ^x e is, for example, 0.

[0090] 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 .

[0091] The first addition unit 83 subtracts the output (C c,int ·^x e ) of the output matrix multiplication unit 82 from the output vector (measured value) y which is the actual steering angle θ e calculated by the reduction ratio division unit 42 (see FIG. 2). That is, the first addition unit 83 calculates the difference (y - ^y) between the output vector y and the output vector estimated value ^y (= C e ·^x e ). The gain multiplication unit 84 multiplies the output (y - ^y) of the first addition unit 83 by the observer gain L (see the above formula (7)).

[0092] The input matrix multiplication unit 85 multiplies the input matrix B eMultiply. The second adder 87 adds the output (Be·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 adder 87 to calculate the state variable vector ^x e . The state variable vector output unit 89 calculates the estimated disturbance torque ^T e , the estimated steering angle ^θ lc , and the estimated angular velocity d^θ c,int / dt based on the state variable vector ^x c,int .

[0093] Unlike the aforementioned extended state observer, a general disturbance observer is composed of an inverse model of the plant and a low-pass filter. The equation of motion of the plant is expressed by Equation (3) as described above. Therefore, the inverse model of the plant is as follows in Equation (9).

[0094]

Equation

[0095] The inputs to a general disturbance observer are J·d 2 θ c,int / dt 2 and N·T * m,int . Since it uses the second derivative value of the actual steering angle θ c,int , it is greatly affected by the noise of the rotation angle sensor 23. In contrast, in the extended state observer of the aforementioned embodiment, since the disturbance torque is estimated in an integral type, the noise influence by differentiation can be reduced.

[0096] Note that, as the disturbance torque estimation unit 64, a general disturbance observer composed of an inverse model of the plant and a low-pass filter may be used.

[0097] FIG. 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.

[0098] The motor current command value calculation unit 91 divides the motor torque command value T * m,int calculated by the angle control unit 47 by the torque constant K t of the electric motor 18 to calculate the motor current command value I * m,int .

[0099] The current deviation calculation unit 92 calculates the deviation ΔI * 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 (= I * m,int - I m,int ).

[0100] The PI control unit 93 performs a PI operation (proportional integral operation) 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, electric power corresponding to the drive command value is supplied to the electric motor 18.

[0101] Next, the operation of the coefficient value setting unit 44 will be described in detail. The coefficient value setting unit 44 performs a coefficient value setting process for setting the lower column inertia J c , the spring constant k, and the viscous damping coefficient c in the automatic driving mode.

[0102] FIG. 10 is a flowchart showing the procedure of the coefficient value setting process performed by the coefficient value setting unit 44. The coefficient value setting process shown in FIG. 10 is started every time the automatic driving mode is started, and is repeatedly performed at a predetermined calculation cycle until the automatic driving mode is canceled.

[0103] Hereinafter, J c1 , k1, and c1 are, respectively, the lower column inertia J for designing the reaction force characteristics during steering intervention c , the spring constant k, and the viscous damping coefficient c. J c2 , k2, and c2 are, respectively, the lower column inertia J for designing the return characteristics after release c , the spring constant k, and the viscous damping coefficient c. J c1 , k1, and c1, and J c2 , k2, and c2 are preset and stored in the memory.

[0104] In the initial setting when the power is turned on, the coefficient value setting unit 44 sets the lower column inertia J c , the spring constant k, and the viscous damping coefficient c to J c1 , k1, and c1, respectively.

[0105] The coefficient value setting unit 44 determines whether or not the determination result of the hands-on / off determination unit 43 is in the released state (step S1).

[0106] If the determination result of the hands-on / off determination unit 43 is in the gripped state (for example, the steering torque T tb is equal to or greater than a predetermined threshold value) (step S1: NO), the coefficient value setting unit 44 sets the lower column inertia J c , the spring constant k, and the viscous damping coefficient c to J c1 , k1, and c1, respectively (step S2). Then, the process in the current calculation cycle is terminated.

[0107] Note that when shifting to step S2, the lower column inertia J c , the spring constant k, and the viscous damping coefficient c are, respectively, J c2When J, k2, and c2 are set, the coefficient value setting unit 44 sets J c2 , k2, and c2 to gradually approach J c1 , k1, and c1 over a period of about 0.5 to 1 second, and then switch to J c1 , k1, and c1. In this case, after a plurality of calculation cycles, J c2 , k2, and c2 are switched to J c1 , k1, and c1.

[0108] Also, as a method not limited to the elapsed time, when the hands-on / off determination unit 43 is a hands-on / off determination unit that determines hands-on when the steering torque T tb is equal to or greater than a first threshold value (for example, 1 Nm), and hands-off when the steering torque T tb is equal to or less than a second threshold value different from the first threshold value (for example, 0.5 Nm), the coefficient value setting unit 44 may switch the coefficient values as follows. That is, from the time when the steering torque T tb exceeds the second threshold value, the coefficient value setting unit 44 gradually approaches J c2 , k2, and c2 to J c1 , k1, and c1. Thereafter, when the steering torque T tb reaches the first threshold value, the coefficient value setting unit 44 sets J c , the spring constant k, and the viscous damping coefficient c to J c1 , k1, and c1.

[0109] In step S1, if the determination result of the hands-on / off determination unit 43 is the released state (for example, the state where the steering torque T tb is less than the threshold value continues for a predetermined time or more) (step S1: YES), J c , the spring constant k, and the viscous damping coefficient c are set to J c2 , k2, and c2, respectively (step S3). Then, the processing in the current calculation cycle is terminated.

[0110] Note that when shifting to step S3, the lower column inertia J c, as the spring constant k and the viscous damping coefficient c, respectively, J c1 , when k1 and c1 are set, the coefficient value setting unit 44 sets J c1 , k1 and c1 are gradually brought closer to J c2 , k2 and c2 over a period of about 0.5 to 1 second, and J c1 , k1 and c1 may be switched. In this case, after a plurality of calculation cycles, J c1 , k1 and c1 are J c2 , switched to k2 and c2.

[0111] Also, as a method not limited to the elapsed time, as described above, the hands-on / off determination unit 43 determines hands-on when the steering torque T tb is equal to or greater than a first threshold value (for example, 1 Nm), and hands-off when the steering torque T tb is equal to or less than a second threshold value different from the first threshold value (for example, 0.5 Nm). When the hands-on / off determination unit is such that the coefficient value setting unit 44 may switch the coefficient values as follows. That is, from the time when the steering torque T tb falls below the first threshold value, the coefficient value setting unit 44 sets J c1 , k1 and c1 are gradually brought closer to J c2 , k2 and c2. Thereafter, when the steering torque T tb reaches the second threshold value, the coefficient value setting unit 44 sets the lower column inertia J c , as the spring constant k and the viscous damping coefficient c, J c2 , k2 and c2.

[0112] When the driving mode is the normal mode, the coefficient value setting unit 44 sets the lower column inertia J c , as the spring constant k and the viscous damping coefficient c, respectively, J c1 , k1 and c1. That is, in the normal mode, the lower column inertia J c , the spring constant k and the viscous damping coefficient c are not changed.

[0113] J c2 , k2 and c2 are, for example, J c1, k1 and c1 are set as follows. For example, when the reaction force characteristics during steering intervention are used as the return characteristics after releasing (the characteristic in which the manual steering command value θ * c,md converges to zero), assume a case where the return characteristics after release are fast and an unnecessary lateral acceleration is generated in the vehicle, giving the driver a sense of unease. In such a case, J c2 is set larger than J c1 , k2 is set smaller than k1, or c2 is set larger than c1.

[0114] The dashed line Q1 in FIG. 11 shows the return characteristics when the reaction force characteristics during steering intervention are used as the return characteristics after release, and the solid line Q2 in FIG. 11 shows the return characteristics when k2 is set smaller than k1. When k2 is set smaller than k1, the convergence of the manual steering command value θ * c,md to zero becomes slower.

[0115] In the automatic driving mode, based on the hands-on / off determination result, the coefficient value setting unit 44 may change all of the lower column inertia J c , the spring constant k, and the viscous damping coefficient c, or may change any one or any combination of two of the lower column inertia J c , the spring constant k, and the viscous damping coefficient c. That is, the coefficient value setting unit 44 may change at least one of the lower column inertia J c , the spring constant k, and the viscous damping coefficient c based on the hands-on / off determination result.

[0116] In the above-described embodiment, in the automatic driving mode, at least one value of the lower column inertia J c , the spring constant k, and the viscous damping coefficient c can be changed according to the determination result of the hands-on / off determination unit 43. As a result, the reaction force characteristics during steering intervention and the return characteristics after release can be set individually.

[0117] In the foregoing embodiments, an example in the case where the present invention is applied to motor control of a column type EPS has been shown. However, the present invention can also be applied to motor control of EPS other than column type.

[0118] Although the embodiments of the present invention have been described in detail, these are merely specific examples used to clarify the technical content of the present invention. The present invention should not be construed as being limited to these specific examples, and the scope of the present invention is limited only by the appended claims.

Explanation of Reference Numerals

[0119] 1... Electric power steering device, 3... Steering wheel, 4... Steering mechanism, 18... Electric motor, 43... Hands-off determination unit, 44... Coefficient value 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, 201... Upper ECU, 202... Motor control ECU

Claims

1. A manual steering command value generation unit that generates a manual steering command value, An integrated angle command value calculation unit that adds the manual steering command value to an automatic steering command value given in the automatic driving mode to calculate an integrated angle command value, A control unit that angle-controls an electric motor for rudder angle control based on the integrated angle command value, including a hands-on / off determination unit that determines whether the driver is in a gripping state of gripping the steering wheel or a released state of not gripping the steering wheel, The manual steering command value generation unit is configured to generate the manual steering command value based on the equation of motion, A motor control device further including a coefficient value change unit that changes the value of at least one of the coefficients included in the equation of motion according to the determination result of the hands-on / off determination unit.

2. The equation of motion includes inertia, spring constant, and viscous damping coefficient as coefficients, The motor control device according to claim 1, wherein the coefficient value change unit is configured to change at least one of the values of the inertia, the spring constant, and the viscous damping coefficient according to the determination result of the hands-on / off determination unit.

3. The motor control device according to claim 1 or 2, wherein the hands-on / off determination unit is configured to determine that it is in a gripping state if the steering torque is equal to or greater than a predetermined threshold value, and to determine that it is in a released state when the state where the steering torque is less than the threshold value continues for a predetermined time or more.

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