Control device and steering apparatus

Abstract

To provide: a control device capable of improving steering performance in a steering apparatus; and a steering apparatus including the control device.SOLUTION: A control device is mounted on a steering apparatus of a steer-by-wire system that includes a steering mechanism including a steering wheel steered by a steering person, a turning mechanism including a first turning wheel and a second turning wheel, and a turning side motor for driving the turning mechanism, and that is mounted on a vehicle. The control device includes a turning side control section for controlling a control target including the turning side motor. The turning side control section includes a model following control section for generating correction torque for correcting input torque input to the control target, on the basis of output of the control target and a nominal model based on a configuration of the control target. The model following control section is configured such that a transfer function of the control target is restricted to a transfer function of the nominal model in a frequency band where a gain in a gain characteristic of a complementary sensitivity function with respect to a modeling error between the control target and the nominal model is approximately 1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device and a steering device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, a separate type power steering device that is not mechanically connected, that is, a steering device of a so-called steer-by-wire system, is known (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4639500 Summary of the Invention [Problem to be solved by the invention]

[0004] In the steering device as described above, further improvement in steering performance has been desired.

[0005] In view of the above circumstances, an object of the present invention is to provide a control device that can improve the steering performance of a steering device, and a steering device including such a control device. [Means for solving the problem]

[0006] One embodiment of the control device of the present invention is a control device mounted on a steer-by-wire type steering device mounted on a vehicle, the control device including a steering mechanism having a steering wheel steered by a driver, a steering mechanism having a first steered wheel and a second steered wheel, and a steering-side motor driving the steering mechanism, and the control device includes a steering-side control unit that controls a control object including the steering-side motor. The steering-side control unit has a model following control unit that generates a correction torque that corrects an input torque input to the control object based on an output of the control object and a nominal model based on a configuration of the control object. The model following control unit is configured so that a transfer function of the control object is constrained to a transfer function of the nominal model in a frequency band where a gain in a gain characteristic of a complementary sensitivity function for a modeling error between the control object and the nominal model is approximately 1. Effect of the Invention

[0007] According to one aspect of the present invention, the steering performance of a steering device can be improved. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a steering device according to a first embodiment. [Diagram 2] FIG. 2 is a diagram showing a schematic view of a part of the steering mechanism in the first embodiment. [Diagram 3] FIG. 3 is a diagram that diagrammatically shows a part of the first turning-side motor in the first embodiment. [Figure 4A] FIG. 4A is a diagram showing a schematic view of a part of the first turning side motor and a part of the first turning side control section in the first embodiment. [Figure 4B] FIG. 4B is a diagram showing a schematic view of a part of the second turning side motor and a part of the second turning side control section in the first embodiment. [Diagram 5] FIG. 5 is a block diagram showing the configuration of the control device in the first embodiment. [Figure 6]FIG. 6 is a block diagram showing the configuration of the command value generating unit in the first embodiment. [Figure 7] FIG. 7 is a block diagram showing a configuration of a part of the command value generating unit in the first embodiment. [Figure 8] FIG. 8 is a graph showing the relationship between the vehicle response characteristics and the feeling that the driver gets when steering the vehicle. [Figure 9] FIG. 9 is a block diagram showing the configuration of the cooperative control unit in the first embodiment. [Figure 10] FIG. 10 is a graph showing the gain characteristic of the frequency domain setting unit in the first embodiment. [Figure 11] FIG. 11 is a block diagram showing the configuration of the steering reaction force control unit in the first embodiment. [Figure 12A] FIG. 12A is a graph showing an example of the relationship between the steering torque and the self-aligning torque. [Figure 12B] FIG. 12B is a graph showing an example of the relationship between the assist torque and the steering torque. [Figure 13] FIG. 13 is a block diagram showing a partial configuration of the first steering side control unit in the first embodiment. [Figure 14] FIG. 14 is a diagram showing a simplified model of the first control object in the first embodiment. [Figure 15] FIG. 15 is a graph illustrating the gain characteristic of the complementary sensitivity function and the gain characteristic of the reciprocal of the modeling error between the transfer function of the first controlled object and the transfer function of the first nominal model. [Figure 16] FIG. 16 is a block diagram showing a configuration of a portion of the second steering side control unit in the first embodiment. [Figure 17] FIG. 17 is a diagram illustrating a steering device according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] First Embodiment A steering device 100 of this embodiment shown in FIG. 1 is mounted on a vehicle. The steering device 100 is a steer-by-wire type steering device. As shown in FIG. 1, the steering device 100 includes a steering mechanism 10 including a steering wheel 11 steered by a driver, a steering mechanism 20 having a first steered wheel 21 and a second steered wheel 22, a first steering side motor 31, a second steering side motor 32, a first steering side motor 33, a second steering side motor 34, a control device 50, a steering torque sensor 81, a steering angle sensor 82, a first rotation sensor 83, a second rotation sensor 84, a first battery 85a, and a second battery 85b. The control device 50 includes a first steering side control unit 51, a second steering side control unit 52, a first steering side control unit 53, and a second steering side control unit 54. The first battery 85a supplies power to the first steering side control unit 51 and the first turning side control unit 53. The second battery 85b supplies power to the second steering side control unit 52 and the second turning side control unit .

[0010] When a driver who drives a vehicle, i.e., a steerer, steers the steering mechanism 10 via the steering wheel 11, the first turning side motor 33 and the second turning side motor 34 are driven by the control device 50, and the first turning side motor 33 and the second turning side motor 34 drive the steering mechanism 20. By driving the steering mechanism 20, the angle of the first turning wheel 21 and the angle of the second turning wheel 22 are changed, and the traveling direction of the vehicle changes. The first turning wheel 21 and the second turning wheel 22 are a pair of tires on the front side of the vehicle. The angle of the first turning wheel 21 and the angle of the second turning wheel 22 are steering angles.

[0011] The steering mechanism 10 has a steering wheel 11, an input shaft 12, an output shaft 13, a torsion bar 14, and a first transmission mechanism 15. The input shaft 12 is a shaft extending from the steering wheel 11 that is steered by a driver. The output shaft 13 is connected to the input shaft 12 via the torsion bar 14. The first transmission mechanism 15 is connected to the output shaft 13. The input shaft 12 and the output shaft 13 are arranged coaxially. The input shaft 12 and the output shaft 13 are rotatable around the same central axis. In the following description, a virtual axis passing through the common central axis of the input shaft 12 and the output shaft 13 is referred to as a rotation axis R. The input shaft 12 and the output shaft 13 are rotatable relative to each other within a range in which the torsion bar 14 can be twisted. The torsion bar 14 connects the input shaft 12 and the output shaft 13. The torsion bar 14 can be twisted around the rotation axis R. The rotation angle of the input shaft 12 around the rotation axis R is equal to the steering angle θ of the steering wheel 11. h The steering angle θ h is detected by the steering angle sensor 82. The rotation angle of the output shaft 13 around the rotation axis R is the output angle θ s It is.

[0012] The first transmission mechanism 15 connects the output shaft 13 to the first steering-side motor 31 and the second steering-side motor 32. The first transmission mechanism 15 transmits the rotational torque of the first steering-side motor 31 and the rotational torque of the second steering-side motor 32 to the output shaft 13 as torque around the rotation axis R. The first transmission mechanism 15 is, for example, a reduction mechanism including a worm gear. The output shaft 13 is rotated by the first steering-side motor 31 and the second steering-side motor 32 via the first transmission mechanism 15 to obtain an output angle θ s By controlling the torque T, the amount of twist of the torsion bar 14 around the rotation axis R can be controlled. This makes it possible to control the force around the rotation axis R transmitted from the torsion bar 14 to the steering wheel 11 via the input shaft 12, and therefore the steering reaction force transmitted to the driver via the steering wheel 11. The steering reaction force is calculated by the steering torque T h is equal to.

[0013] Steering torque T his detected by a steering torque sensor 81. The steering torque sensor 81 detects the amount of twist of the torsion bar 14 around the rotation axis R, thereby detecting the steering torque T h Detects the steering torque T h is a torsion bar torque generated in the torsion bar 14, and is a torsion moment about the rotation axis R. In this embodiment, the rotation angle of the output shaft 13, i.e., the output angle θ s It is possible to detect

[0014] The steering mechanism 20 has a first steered wheel 21, a second steered wheel 22, a steering linkage 23, knuckle arms 24a, 24b, and second transmission mechanisms 25a, 25b. The steering linkage 23 has a rack shaft 23c and tie rods 23a, 23b. The rack shaft 23c extends in the left-right direction of the vehicle, i.e., in the vehicle width direction. As shown in FIG. 2, bushes 23d, 23e are provided on the portion of the rack shaft 23c on the side where the first steered wheel 21 is arranged. Although not shown, a bush is provided on the portion of the rack shaft 23c on the side where the second steered wheel 22 is arranged, similar to the portion of the rack shaft 23c on the side where the first steered wheel 21 is arranged. Note that in FIG. 2, the elasticity and viscosity of the first steered wheel 21 are represented as a bush element RB between the road surface RS and the first steered wheel 21.

[0015] As shown in FIG. 1, the first steered wheel 21 is connected to one end of the rack shaft 23c via a tie rod 23a and a knuckle arm 24a. The second steered wheel 22 is connected to the other end of the rack shaft 23c via a tie rod 23b and a knuckle arm 24b. The second transmission mechanism 25a connects the rack shaft 23c to the first steered side motor 33. The second transmission mechanism 25b connects the rack shaft 23c to the second steered side motor 34. The second transmission mechanism 25a is connected to a portion of the rack shaft 23c that is closer to the first steered wheel 21 in the vehicle width direction. The second transmission mechanism 25b is connected to a portion of the rack shaft 23c that is closer to the second steered wheel 22 in the vehicle width direction. The second transmission mechanism 25a is a reduction mechanism having a pinion gear that meshes with the rack shaft 23c. The second transmission mechanism 25b is a reduction mechanism having a pinion gear that meshes with the rack shaft 23c.

[0016] As shown in Fig. 2, the first steered wheel 21 is provided with a suspension 40. The suspension 40 has a transverse link 41 and a tension rod 42. The transverse link 41 is provided with a bush 41a. The tension rod 42 is provided with a bush 42a. Although not shown in the figures, the second steered wheel 22 is also provided with a suspension 40, similar to the first steered wheel 21.

[0017] The first steering side motor 31 is controlled by the first steering side motor 31. The second steering side motor 32 is controlled by the second steering side motor 32. The first steering side motor 31 and the second steering side motor 32 are capable of driving the steering mechanism 10. The first turning side motor 33 is controlled by a first turning side control unit 53. The second turning side motor 34 is controlled by a second turning side control unit 54. The first turning side motor 33 and the second turning side motor 34 drive the steering mechanism 20.

[0018] As shown in FIG. 3, the first turning-side motor 33 has a rotor 35a and a stator 35b. The rotor 35a is rotatable around the central axis J. In the following description, the direction in which the central axis J extends is simply referred to as the "axial direction", the radial direction around the central axis J is simply referred to as the "radial direction", and the circumferential direction around the central axis J is simply referred to as the "circumferential direction". The stator 35b is located radially outside the rotor 35a. The stator 35b surrounds the rotor 35a. The stator 35b has a plurality of coils 36 arranged around one circumference in the circumferential direction. In this embodiment, twelve coils 36 are provided. The twelve coils 36 are composed of four U-phase coils U1a, U1b, U2a and U2b, four V-phase coils V1a, V1b, V2a and V2b, and four W-phase coils W1a, W1b, W2a and W2b.

[0019] As shown in FIG. 4A, the stator 35b in the first turning-side motor 33 has coil groups 37 of a plurality of systems. In this embodiment, the coil groups 37 in the first turning-side motor 33 are provided with two coil groups, a first coil group 37a of the first system and a second coil group 37b of the second system. The first coil group 37a of the first system has two U-phase coils U1a, U1b, two V-phase coils V1a, V1b, and two W-phase coils W1a, W1b. The second coil group 37b of the second system has two U-phase coils U2a, U2b, two V-phase coils V2a, V2b, and two W-phase coils W2a, W2b. That is, two coils 36 are provided in one phase of each system. The two coils 36 of each phase of each system are connected to each other by a crossover wire 36b. In the first coil group 37a of the first system, the U-phase coils U1a, U1b, the V-phase coils V1a, V1b, and the W-phase coils W1a, W1b are connected to each other by a Y connection. In the second coil group 37b of the second system, the U-phase coils U2a, U2b, the V-phase coils V2a, V2b, and the W-phase coils W2a, W2b are connected to each other by a Y connection.

[0020] 3, in the first turning-side motor 33, the first coil groups 37a, 37b of different systems are arranged rotationally symmetrically about the central axis J. This ensures redundancy of the first turning-side motor 33. In other words, even if a malfunction occurs in one of the coil groups 37 of the multiple systems, the first turning-side motor 33 can be suitably driven using the coil groups 37 of the other systems.

[0021] In this specification, "coil groups are in different systems" includes the case where current is supplied to each coil group independently for each system, i.e., the first coil group 37a and the second coil group 37b are each supplied with three-phase AC current independently.

[0022] In this embodiment, the first coil group 37a and the second coil group 37b are arranged in two-fold symmetry with each other around the central axis J. That is, when the first coil group 37a is rotated 180° around the central axis J, the positions of the coils 36 of each phase in the first coil group 37a match the positions of the coils 36 of each phase in the second coil group 37b in the circumferential direction. In this way, by arranging the first coil group 37a and the second coil group 37b in two-fold symmetry with each other around the central axis J, the coils 36 of the first coil group 37a and the coils 36 of the second coil group 37b, which are in the same phase, can be easily arranged apart from each other, and the mutual inductance generated between the first coil group 37a and the second coil group 37b can be easily suppressed to a small value. Therefore, it is easy to increase the magnetic independence of the two coil groups 37 of different systems. Therefore, it is easy to improve the controllability of torque ripple and the like by model following control, which will be described later.

[0023] In addition, the coil groups 37 may be arranged in any number of rotations symmetry as long as they are arranged in rotational symmetry around the central axis J. For example, when three coil groups 37 are provided, the three coil groups 37 may be arranged in three-fold symmetry around the central axis J. In this case, when one coil group 37 is rotated 120° around the central axis J, the positions of the coils 36 of each phase in the one coil group 37 match the positions of the coils 36 of each phase in the other coil group 37 in the circumferential direction. In this case, as in the case of the two coil groups 37 described above, it is easy to suppress the mutual inductance generated between the three coil groups 37. Therefore, it is easy to increase the magnetic independence of the three coil groups 37 of different systems. Therefore, it is easy to improve the controllability of the torque ripple and the like by the model following control described later.

[0024] In this embodiment, the coils 36 in the first coil group 37a of the first system and the coils 36 in the second coil group 37b of the second system are arranged to sandwich the central axis J in the radial direction. The coils 36 in the first coil group 37a and the coils 36 in the second coil group 37b arranged to sandwich the central axis J in the radial direction are coils of the same phase. That is, for example, the U-phase coil U1a of the first coil group 37a and the U-phase coil U2a of the second coil group 37b are arranged to sandwich the central axis J in the radial direction, the V-phase coil V1a of the first coil group 37a and the V-phase coil V2a of the second coil group 37b are arranged to sandwich the central axis J in the radial direction, and the W-phase coil W1a of the first coil group 37a and the W-phase coil W2a of the second coil group 37b are arranged to sandwich the central axis J in the radial direction.

[0025] Each coil 36 has one lead wire 36a extending in the axial direction. The lead wire 36a extending from the U-phase coil U1a in the first coil group 37a is connected to a U-phase bus bar 38Ua via a connection terminal 38Us. The lead wire 36a extending from the V-phase coil V1a in the first coil group 37a is connected to a V-phase bus bar 38Va via a connection terminal 38Vs. The lead wire 36a extending from the W-phase coil W1a in the first coil group 37a is connected to a W-phase bus bar 38Wa via a connection terminal 38Ws. The lead wire 36a extending from the U-phase coil U1b, the lead wire 36a extending from the V-phase coil V1b, and the lead wire 36a extending from the W-phase coil W1b in the first coil group 37a are connected to a neutral bus bar 39a via a connection terminal 39Sa.

[0026] The lead wire 36a extending from the U-phase coil U2a in the second coil group 37b is connected to the U-phase bus bar 38Ub via a connection terminal 38Us. The lead wire 36a extending from the V-phase coil V2a in the second coil group 37b is connected to the V-phase bus bar 38Vb via a connection terminal 38Vs. The lead wire 36a extending from the W-phase coil W2a in the second coil group 37b is connected to the W-phase bus bar 38Wb via a connection terminal 38Ws. The lead wire 36a extending from the U-phase coil U2b, the lead wire 36a extending from the V-phase coil V2b, and the lead wire 36a extending from the W-phase coil W2b in the second coil group 37b are connected to the neutral bus bar 39b via a connection terminal 39Sb.

[0027] The structure of the second turning-side motor 34 is similar to that of the first turning-side motor 33. As shown in FIG. 4B, the second turning-side motor 34 has a stator 35c. The stator 35c in the second turning-side motor 34 has coil groups 37 of multiple systems, similar to the stator 35b in the first turning-side motor 33. In this embodiment, the coil groups 37 in the second turning-side motor 34 are provided with two coil groups 37, a first coil group 37a of the first system and a second coil group 37b of the second system. Although not shown, in the second turning-side motor 34, the coil groups 37 of the different systems are arranged in rotational symmetry around the central axis of the second turning-side motor 34, similar to the coil groups 37 in the first turning-side motor 33. For example, in the second turning-side motor 34, the first coil group 37a and the second coil group 37b are arranged in two-fold symmetry around the central axis J. Thereby, similarly to the first turning side motor 33, redundancy of the second turning side motor 34 can be ensured.

[0028] A first output angle θ which is the rotation angle of the first turning-side motor 33 g1 is detected by the first rotation sensor 83. The second output angle θ g2 is detected by the second rotation sensor 84. The rotation angle of each steered-side motor is the rotation angle of the rotor 35a of each steered-side motor about the central axis R. g1 is equal to the rotation angle of the pinion gear attached to the output shaft of the first steering-side motor 33, i.e., the pinion absolute angle. g2 is equal to the rotation angle of the pinion gear attached to the output shaft of the second steered-side motor 34, i.e., the pinion absolute angle. As shown in FIG. 4A, the first output angle θ g1 is input to a first processor 53a (described later) in the first turning side control unit 53. As shown in FIG. 4B, the second output angle θ g2 is input to a second processor 54a in the second steering side control unit 54, which will be described later.

[0029] The structure of the first steering-side motor 31 and the structure of the second steering-side motor 32 may be similar to the structure of the first turning-side motor 33, or may be different from the structure of the first turning-side motor 33. The first steering-side motor 31 and the second steering-side motor 32 may have multiple systems of coil groups, or may have only one system of coil groups.

[0030] <Control device> The control device 50 controls each part of the steering device 100. In this embodiment, the control device 50 controls the first turning side motor 33 and the second turning side motor 34 to control the steering mechanism 20, and controls the first steering side motor 31 and the second steering side motor 32 to control the steering reaction force transmitted to the steering wheel 11 through the steering wheel 11. The first steering side control unit 51 controls the first steering side motor 31. The second steering side control unit 52 controls the second steering side motor 32. The first steering side control unit 53 controls the first turning side motor 33. The second turning side control unit 54 controls the second turning side motor 34. The first steering side control unit 51 and the first turning side control unit 53 are capable of mutual communication. The second steering side control unit 52 and the second turning side control unit 54 are capable of mutual communication. Therefore, in a steer-by-wire type steering device 100 in which the steering mechanism 10 and the turning mechanism 20 are not mechanically connected, the steering mechanism 10 and the turning mechanism 20 can be suitably controlled.

[0031] [Steering side control unit] 5, the first steering side control unit 51 has a command value generating unit 55a, a cooperative control unit 56a, and a steering reaction force control unit 57a. The second steering side control unit 52 has a command value generating unit 55b, a cooperative control unit 56b, and a steering reaction force control unit 57b. In other words, the control device 50 includes the command value generating units 55a and 55b, the cooperative control units 56a and 56b, and the steering reaction force control units 57a and 57b.

[0032] (Command value generator) The command value generating unit 55a generates the turning-side motor angle command value θ gr1 The command value generating unit 55b generates the turning-side motor angle command value θgr2 The steering motor angle command value θ gr1 is the first output angle θ of the first steering-side motor 33 g1 The steering motor angle command value θ gr2 is the second output angle θ of the second steering-side motor 34 g2 The steering motor angle command value θ gr1 is equal to the rotation angle of the pinion gear attached to the output shaft of the first turning-side motor 33, i.e., the target value of the pinion absolute angle. gr2 is equal to the rotation angle of the pinion gear attached to the output shaft of the second turning-side motor 34, i.e., the target value of the pinion absolute angle. gr2 In the following description, description of the configuration of the command value generator 55b that is the same as that of the command value generator 55a may be omitted.

[0033] 6, the command value generating unit 55a includes a yaw rate phase compensating unit 55c, a yaw rate stabilizing compensating unit 55d, and a VGR control unit 55e. The yaw rate phase compensating unit 55c calculates a time constant T c The yaw rate γ(V) of a vehicle is a parameter indicating a change in the yaw angle, which is the swing angle in the left-right direction of the vehicle. In other words, the yaw rate γ(V) is the angular velocity when the vehicle swings in the left-right direction. V is the running speed of the vehicle, that is, the vehicle speed. The transfer function Y1(s) of the vehicle yaw rate phase compensation unit 55c is expressed by the following equation (1).

[0034]

number

[0035] The yaw rate stabilization compensation unit 55d adjusts the rotation angle of the first steering-side motor 33, that is, the first output angle θ g1 The steering angle θ h The yaw rate γ(V) is stabilized by approximating the transfer characteristic from the yaw rate γ(V) to a first-order transfer characteristic. The yaw rate γ(V) is input to the yaw rate stabilization compensation unit 55d. As shown in FIG. 7, the yaw rate stabilization compensation unit 55d has a differentiator 55f, a gain adjuster 55g, a compensation unit 55h, and a subtractor SU5. The gain adjuster 55g applies a gain K to the value of the yaw rate γ(V) differentiated by the differentiator 55f. γ The output from the gain adjuster 55g is input to the compensation unit 55h. The transfer function Y2(s) of the compensation unit 55h is expressed by the following equation (2).

[0036]

number

[0037] The output from the compensation unit 55h is input to the subtractor SU5. The subtractor SU5 subtracts the output from the compensation unit 55h from the output from the yaw rate phase compensation unit 55c. The subtractor SU5 outputs a steering-side motor angle command value θ gr As shown in FIG. 6, the steering-side motor angle command value θ gr is input to the VGR control unit 55e.

[0038] Here, the steering angle θ h Transfer function G from to yaw rate γ(V) θ γ(s) is expressed by the following equation (3).

[0039]

number

[0040] The transfer function G expressed by the above formula (3) θ γ Multiplying (s) by the right-hand term of equation (2) gives the following equation (4).

[0041]

number

[0042] The transfer function obtained when the value output from gain adjuster 55g is fed back to equation (4) above is expressed as the left term of equation (5) below.

[0043]

number

[0044] In the left term of the above equation (5), {2ξ(V)+K γ If {2ξ(V)}=2, the left term of equation (5) becomes the right term of equation (5), and it can be seen that the damping coefficient becomes 1 and the transfer function becomes stable. γ (V)}=2 so that K γ Once (V) is determined, the steering angle θ h Transfer function G from to yaw rate γ(V) θ γ In this embodiment, the yaw rate γ(V) can be stabilized by K r A differentiator 55f and a gain adjuster 55g are provided to feed back the value multiplied by (V)s, and the right-hand term of the above equation (2) is inserted between the gain adjuster 55g and the subtractor SU5 in the yaw rate phase compensation unit 55c and the yaw rate stabilization compensation unit 55d, respectively, to obtain the transfer function Gθ γ (s) is stabilized as shown on the right side of equation (5).

[0045] The transfer function Y1(s) of the yaw rate phase compensation unit 55c shown in the formula (1) excluding the right-hand term of the formula (2) is (s+ω n ) 2 / (T c Therefore, the transfer function obtained by multiplying the yaw rate phase compensation unit 55c and the yaw rate stabilization compensation unit 55d is (s+ω n ) 2 / (T c s+1) and the right-hand term of equation (5), i.e., 1 / (s+ω n ) 2 The denominator of 1 / (T c s+1). This results in a steering angle of θ h The transfer characteristic from the steering angle θ to the yaw rate γ(V) can be approximated to a first-order transfer characteristic. h is calculated by the right term of the equation (2) included in the yaw rate phase compensation unit 55c. g1 The feedback yaw rate γ(V) is converted into a command value of the first output angle θ by the compensation unit 55h. g1 Therefore, the value output from the yaw rate stabilization compensation unit 55d is the first output angle θ g1 The steering motor angle command value θ gr It becomes.

[0046] In the yaw rate phase compensation unit 55c, the linear transfer function approximated as above, that is, 1 / (T c s+1) time constant T c is set to a desired value by feedforward control. This improves the steering feel when the driver steers the steering wheel 11, making it easier for the driver to drive the vehicle. cis determined based on the relationship shown in the graph of FIG. 8. FIG. 8 shows the relationship between the vehicle response characteristics and the feeling when the driver steers the vehicle. In FIG. 8, the horizontal axis represents the lateral acceleration time constant T a The vertical axis represents the yaw rate time constant T b The lateral acceleration time constant T a is the steering angle θ h The yaw rate time constant T b is the steering angle θ h is a time constant in a transfer function from the yaw rate γ(V) to the yaw rate γ(V). The yaw rate phase compensation unit 55c calculates, for example, 1 / (T c s+1) time constant T c The yaw rate phase compensation unit 55c adjusts the time constant T c The value of T is set to the yaw rate time constant T b In other words, the value is set to about 0.04 seconds or more and 0.10 seconds or less. This makes it possible to improve the feeling that the driver gets when steering the steering wheel 11.

[0047] The VGR control unit 55e sets a virtual gear ratio from the first steered-side motor 33 to the first steered wheels 21, and calculates a steered-side motor angle command value θ gr As shown in FIG 6, the VGR control unit 55e adjusts the steering-side motor angle command value θ gr and the self-aligning torque estimate SAT h The self-aligning torque estimate SAT is input. his an estimate of the total value of the self-aligning torque that the steering mechanism 20 receives via the first steered wheel 21 and the second steered wheel 22. The self-aligning torque means a torque that acts in the direction in which the steering wheel 11 returns due to the elasticity of the first steered wheel 21 and the elasticity of the second steered wheel 22 that are twisted when the steering wheel 11 is steered to change the angle of the first steered wheel 21 and the second steered wheel 22. In this embodiment, the self-aligning torque estimate value SAT h is a first self-aligning torque estimate SAT generated at the first steered wheel 21 estimated by the first steering side control unit 53. h1 and a second self-aligning torque estimated value SAT generated at the second steered wheel 22 estimated by the second steering side control unit 54. h2 The first self-aligning torque estimate SAT h1 is an estimated value of the disturbance including the reaction force of the first steered wheel 21. The second self-aligning torque estimated value SAT h2 is an estimate of a disturbance including a reaction force of the second steered wheel 22. h1 is output from a first model following control unit 63, which will be described later. h2 is output from a second model following control unit 68, which will be described later.

[0048] The VGR control unit 55e calculates the self-aligning torque estimated value SAT in order to virtually realize the steering angle being shifted by the forces applied from the first steered wheel 21 and the second steered wheel 22 in the same manner as when the steering mechanism 10 and the steering mechanism 20 are mechanically connected. h Based on this, the steering motor angle command value θ gr Specifically, the VGR control unit 55e corrects the corrected steered-side motor angle command value θ based on the following equation (6). gra Calculate.

[0049]

number

[0050] In the case where the steering mechanism 10 and the turning mechanism 20 are mechanically connected, when the turning mechanism 20 receives a self-aligning torque through the first turning wheel 21 and the second turning wheel 22, the output shaft 13 in the steering mechanism 10 rotates according to the magnitude of the self-aligning torque. h / (K s +C s s) is a value of SAT when the steering mechanism 10 and the turning mechanism 20 are mechanically connected. h This corresponds to the angle at which the output shaft 13 rotates due to the self-aligning torque when the self-aligning torque is generated. Therefore, the steering side motor angle command value θ gr From SAT h / (K s +C s s) to obtain the steering motor angle command value θ gr is a value when the steering mechanism 10 and the turning mechanism 20 are virtually mechanically connected, that is, the turning-side motor angle command value θ gra This allows the steering feel felt by the steerer steering the steering wheel 11 in the steer-by-wire steering device 100 to be similar to that of a power steering device in which the steering mechanism 10 and the turning mechanism 20 are mechanically connected. Therefore, for example, it is possible to generate an appropriate time delay in the movement of the vehicle in response to the steering of the steering wheel 11, and it is possible to suppress the responsiveness from the steering of the steering wheel 11 to the change in the angle of the first turning wheel 21 and the angle of the second turning wheel 22 becoming too sensitive. This makes it possible to improve the affinity of the steering performance of the steering device 100 to the steerer's senses, making it easier for the steerer to turn the steering wheel 11. In addition, the elastic element K s and the viscous element C sBy adjusting the above, the elasticity and viscosity between the virtually connected steering mechanism 10 and the steered mechanism 20 can be arbitrarily set. s and C. s By adjusting these factors to values ​​that make steering easier for the helmsman, the helmsman can steer the steering wheel 11 more easily.

[0051] The VGR control unit 55e calculates the steering-side motor angle command value θ gra Variable gear ratio VGR(θ gra , V) to obtain the steering motor angle command value θ gra1 That is, θ gra1 =θ gra ·VGR(θ gra ,V) holds. Variable gear ratio VGR(θ gra , V) is a virtually set gear ratio between the first steered side motor 33 and the first steered wheel 21, and the steered side motor angle command value θ gra and the vehicle speed V. Variable gear ratio VGR(θ gra , V) is the steering angle θ h The angle is appropriately set depending on how the angle of the first steered wheels 21 is changed relative to the target position.

[0052] Here, the rotation angle of the first turning-side motor 33, i.e., the first output angle θ g1 and the angle (steered angle) of the first steered wheels 21 do not have a linear relationship, and the first output angle θ g1 The amount of change in the angle of the first steered wheels 21 varies depending on the magnitude of the first output angle θ g1 The larger the angle of the first steered wheels 21, the more difficult it becomes to change the angle of the first steered wheels 21. Therefore, the first steered-side motor 33 is simply notified of the steered-side motor angle command value θ gra When the steering angle θ h Depending on the size of the deflection, the amount of change in the angle of the first steered wheels 21 will change, which may make it difficult for the driver to steer the steering wheel 11.

[0053] In contrast, for example, the variable gear ratio VGR(θ gra, V) at the steering angle θ h The steering motor angle command value θ obtained based on gra and the angle of the first steered wheel 21 are set as variables such that the relationship between them is linear. h ) can be changed in angle of the first steered wheel 21 in proportion to the rotational speed of the steering wheel 11. This makes it easier for the driver to steer the steering wheel 11.

[0054] Also, for example, when the steering wheel 11 is turned greatly to abruptly change the traveling direction of the vehicle, it may be preferable to change the angle of the first steered wheels 21 more greatly as the rotation angle of the steering wheel 11 becomes larger. In such a case, the variable gear ratio VGR(θ gra , V) is expressed as the steering motor angle command value θ gra When the steering motor angle command value θ is equal to or larger than a certain value, gra The larger the steering motor angle command value θ gra By setting the variable such that the amount of change in the angle of the first steered wheel 21 is greater than the amount of change in the angle of the first steered wheel 21, the angle of the first steered wheel 21, i.e., the steering angle, can be changed more significantly when the steering wheel 11 is suddenly turned by a large amount. This makes it possible to suitably change the traveling direction of the vehicle, for example, when the driver suddenly changes the traveling direction of the vehicle to take emergency avoidance action.

[0055] The steering motor angle command value θ output from the VGR control unit 55e gra1 is an output value output from the command value generating unit 55a. As shown in FIG. gra1 is input to the first steering side control unit 53.

[0056] The command value generating unit 55b, in the same manner as the above-mentioned command value generating unit 55a, generates the turning-side motor angle command value θ gra2 The steering motor angle command value θ gra2 is the second output angle θ, which is the rotation angle of the second steering-side motor 34. g2 is the command value.

[0057] (Cooperative control unit) The cooperative control units 56a, 56b perform calculations for cooperatively controlling the first turning side motor 33 and the second turning side motor 34. In the following explanation, the cooperative control unit 56a will be explained as a representative of the cooperative control units 56a, 56b, and explanations of the configuration of the cooperative control unit 56b that is similar to that of the cooperative control unit 56a may be omitted.

[0058] 9, the cooperative control unit 56a has a compensation torque calculation unit 56c and a frequency domain setting unit 56d. The compensation torque calculation unit 56c calculates the first self-aligning torque estimate SAT h1 and the second self-aligning torque estimate value SAT output from the second steering side control unit 54. h2 is entered.

[0059] First self-aligning torque estimate SAT h1 and the second self-aligning torque estimate SAT h2 The sum of these values, i.e. the estimated self-aligning torque SAT h can be regarded as the total value of the torque required to drive the steering mechanism 20, and can be regarded as the total value of the motor torque that needs to be output by the two motors, the first steering-side motor 33 and the second steering-side motor 34. Here, the first self-aligning torque estimate SAT h1 can be regarded as the value of the motor torque required for the first turning side motor 33, which is closer to the first turning wheel 21 than the second turning side motor 34. h2 can be regarded as the value of the motor torque required for the second turning side motor 34, which is closer to the second turning wheel 22 than the first turning side motor 33. Since the reaction force received from the first turning wheel 21 and the reaction force received from the second turning wheel 22 are often different from each other, the first self-aligning torque estimated value SAT h1 and the second self-aligning torque estimate SAT h2In this case, the motor torque of the first turning side motor 33 and the motor torque of the second turning side motor 34 are different from each other. Therefore, a bias in the motor torque occurs between the first turning side motor 33 and the second turning side motor 34, and the load on one turning side motor becomes larger than that on the other turning side motor, and the amount of heat generated in the other turning side motor becomes larger than the amount of heat generated in the one turning side motor.

[0060] The first self-aligning torque estimate SAT is calculated by two steering motors. h1 and the second self-aligning torque estimate SAT h2 The total torque, i.e. the estimated self-aligning torque SAT h Therefore, in order to eliminate the bias between the motor torque of the first turning side motor 33 and the motor torque of the second turning side motor 34, each of the motor torques of the turning side motors must be equal to or greater than the first self-aligning torque estimate value SAT h1 and the second self-aligning torque estimate SAT h2 In other words, the motor torque of the first steering-side motor 33 should be half the total torque of T SM1 and the motor torque T of the second steering side motor 34 is SM2 Then, T SM1 =T SM2 =(SAT h1 +SAT h2 ) / 2. First self-aligning torque estimate SAT h1 and the second self-aligning torque estimate SAT h2 The first self-aligning torque estimate SAT h1 and the second self-aligning torque estimate SAT h2 The correction interference torque required to correct the total torque to half the value of T m1 Then, (SAT h1 +SAT h2 ) / 2=SAT h1 -T m1 =SAT h2 +T m1 Therefore, T m1 =(SATh1 -SAT h2 ) / 2. The compensation torque calculation unit 56c calculates the correction interference torque T m1 Calculate the correction interference torque T m1 is subtracted from the motor torque of the first steering-side motor 33 to obtain the correction interference torque T m1 to the motor torque of the second turning side motor 34, the bias between the motor torque of the first turning side motor 33 and the motor torque of the second turning side motor 34 can be eliminated.

[0061] The frequency domain setting section 56d sets a frequency domain for cooperatively controlling the first turning side motor 33 and the second turning side motor 34. The frequency domain setting section 56d calculates the corrected interference torque T m1 Correction of interference torque T m2 and outputs the converted signal to the first steering side control unit 53. In this embodiment, the frequency domain setting unit 56d is a low-pass filter. The corrected interference torque T m2 is expressed by the following equation (7).

[0062]

number

[0063] The frequency domain setting unit 56d is a low-pass filter that exhibits the characteristics shown in Fig. 10. In Fig. 10, the vertical axis indicates the gain [dB] in the frequency domain setting unit 56d, and the horizontal axis indicates the steering frequency f [Hz]. The steering frequency f is a function of the steering angle θ h As shown in FIG. 10, the cutoff frequency ω1 is a frequency that is smaller than the mechanical resonance frequency ω rThe resonant frequency ω r For example, the cutoff frequency ω1 is about 1 Hz or more and 50 Hz or less. For example, the cutoff frequency ω1 is about 1 Hz or more and 5 Hz or less. In the region where the steering frequency f is equal to or less than the cutoff frequency ω1, the gain in the frequency domain setting unit 56d is 0 dB, that is, the gain in the transfer function of the frequency domain setting unit 56d is approximately 1. Therefore, in the region equal to or less than the cutoff frequency ω1, T m2 =T m1 In a region where the steering frequency f is higher than the cutoff frequency ω1, the gain in the frequency region setting unit 56d becomes smaller than 1, and T m2 <T m1 In the region where the steering frequency f is higher than the cutoff frequency ω1, the higher the steering frequency f, the smaller the gain. Therefore, the higher the steering frequency f, the smaller the correction interference torque T m2 becomes smaller.

[0064] As described above, the cooperative control unit 56a calculates the first self-aligning torque estimate value SAT h1 and a second self-aligning torque estimate value SAT, which is a value output from a second model following control unit 68 described later. h2 Correction of interference torque T based on m2 In this embodiment, the cooperative control unit 56a generates a first self-aligning torque estimate SAT h1 and the second self-aligning torque estimate SAT h2 Half the difference between the two, i.e., the correction interference torque T m1 The interference torque T m2 The first self-aligning torque estimate SAT h1 corresponds to the "first estimated value." The second self-aligning torque estimated value SAT h2 corresponds to the “second estimate.”

[0065] The cooperative control unit 56b, like the cooperative control unit 56a, controls the correction interference torque T m2The correction interference torque T m2 The value of the correction interference torque T m2 In the following description, the correction interference torque T m2 Correction of interference torque T m2R and the correction interference torque T m2 Correction of interference torque T m2L It is sometimes called.

[0066] (Steering reaction force control unit) The steering reaction force control units 57a and 57b control the steering reaction force transmitted to the driver via the steering wheel 11. As shown in FIG. 5, the steering reaction force control units 57a and 57b each control a steering angle θ h is input. The steering reaction force control unit 57a controls the first steering-side motor 31. The steering reaction force control unit 57b controls the second steering-side motor 32. The steering reaction force control unit 57a sends half the value of the desired steering reaction force as a command value to the first steering-side motor 31 and controls the first steering-side motor 31. The steering reaction force control unit 57b sends half the value of the desired steering reaction force as a command value to the second steering-side motor 32 and controls the second steering-side motor 32. The first steering-side motor 31 and the second steering-side motor 32 are controlled by the respective steering reaction force control units 57a and 57b, and the output shaft 13 is rotated by the two steering-side motors, thereby generating a steering reaction force, i.e., a steering torque T h is adjusted to a desired value. The steering reaction force control unit 57a and the steering reaction force control unit 57b have the same configuration except that the steering-side motors they control are different. Therefore, in the following description, the steering reaction force control unit 57a will be described as a representative of the steering reaction force control units 57a and 57b, and a description of the same configuration of the steering reaction force control unit 57b as the steering reaction force control unit 57a may be omitted.

[0067] As shown in FIG. 11, the steering reaction force control unit 57a has a steering reaction force setting unit 70, an angle control unit 71, a state feedback unit 72, a third model following control unit 73, a torque conversion unit 74, subtractors SU6, SU7, SU8, SU9, and an adder AD4.

[0068] The steering reaction force setting unit 70 sets a target steering reaction force. The steering reaction force setting unit 70 is configured to set a steering angle θ h and self-aligning torque estimate SAT h is input. Self-aligning torque estimate SAT h is the first self-aligning torque estimate SAT h1 and the second self-aligning torque estimate SAT h2 The result is calculated by adding together the above in an adder AD4 and inputted to a steering reaction force setting unit 70.

[0069] The steering reaction force setting unit 70 includes a low-pass filter 70a. The low-pass filter 70a filters the self-aligning torque estimated value SAT h At least a portion of the components with frequencies higher than a predetermined cutoff frequency is removed from the self-aligning torque estimated value SAT. The predetermined cutoff frequency is, for example, about 10 Hz. The frequency of the self-aligning torque SAT is about 10 Hz or lower. Therefore, the low-pass filter 70a removes at least a portion of the components with frequencies higher than 10 Hz from the self-aligning torque estimated value SAT. h By removing the self-aligning torque estimate SAT h The accuracy of the self-aligning torque estimation value SAT input to the steering reaction force setting unit 70 can be further improved. h The frequency components higher than 10 Hz included in include components due to, for example, a reaction force of vehicle motion. In this embodiment, the steering reaction force setting unit 70 uses a low-pass filter 70a to distinguish between the reaction force of vehicle motion and tire contact information, i.e., the self-aligning torque SAT, in the frequency domain, and obtains a more accurate self-aligning torque estimated value SAT h The target steering reaction force is set using

[0070] In this embodiment, the first steering-side motor 31 and the second steering-side motor 32 adjust the output angle θ of the output shaft 13. s By adjusting the difference in the rotation angle between the input shaft 12 and the output shaft 13 connected by the torsion bar 14, the steering reaction force, i.e., the steering torque T h Therefore, the steering reaction force setting unit 70 controls the steering torque T h The output angle θ of the output shaft 13 required to make the target value s Here, the target value of the steering torque T h is expressed by the following equation (8).

[0071]

number

[0072] Steering torque T h The target value of T hr And the output angle θ s The target value of θ sr Then, from the above (8), the output angle target value θ sr is expressed by the following equation (9).

[0073]

number

[0074] Here, the steering torque T h The relationship between the self-aligning torque SAT and the steering torque T can be expressed, for example, as shown in the graph in Fig. 12A. In Fig. 12A, the horizontal axis represents the self-aligning torque SAT, and the vertical axis represents the steering torque T h For example, in an electric power steering device in which a steering mechanism and a turning mechanism are mechanically connected, the steering torque T h and the assist torque T output from the electric power steering device asThe sum of these two torques can be considered to be approximately equal to the self-aligning torque SAT. as and steering torque T h The relationship between the steering torque T and the steering angle θ can be expressed, for example, as shown in the graph in FIG. h and the vertical axis is the assist torque T as SAT≒T h +T as From the relationship, the assist torque T as For the curve of steering torque T h The curve created by adding up the self-aligning torque SAT is the curve shown by the dashed line in FIG. 12B. As a result, the self-aligning torque SAT and the steering torque T h A graph showing the relationship between

[0075] The steering reaction force setting unit 70 calculates the input self-aligning torque estimated value SAT based on the relationship shown in the graph of FIG. h The steering torque T corresponding to the value h The value of this is the steering torque target value T hr The steering reaction force setting unit 70 calculates the calculated steering torque target value T hr and the input steering angle θ h Substituting this into the above equation (9), the output angle target value θ sr As shown in FIG. 11, the output angle target value θ sr is input to the subtractor SU9. The subtractor SU9 subtracts the output angle target value θ sr from the current output angle θ s The result is output to angle control unit 71.

[0076] The angle control unit 71 performs PD control to obtain the output angle target value θ sr and output angle θ s The difference between the third input torque T r3 The third controlled object 75 is a controlled object including the first steering-side motor 31. The transfer function P m3(s) is expressed, for example, by the following equation (10).

[0077]

number

[0078] The PD gain in the angle control section 71 is set so that the torque value output from the angle control section 71 is equal to the steering torque target value T hr That is, the third input torque T output from the angle control unit 71 is adjusted to a value that is half the value of r3 is T hr The third input torque T output from the angle control unit 71 is equal to r3 is input to the subtractor SU7. The subtractor SU7 subtracts the third input torque T r3 The third correction torque T output from the third model following control unit 73 is f3 The subtractor SU7 also subtracts the third input torque T r3 , the current steering torque T h Half the value of T h Add / 2. T h The value of / 2 is multiplied by the gain K of the torque conversion unit 74. t The subtractor SU6 multiplies the steering angle θ h The subtractor SU6 receives the steering angle θ h from output angle θ s The steering torque T h Half the value of T h / 2 can be calculated.

[0079] The force generated by the twisting of the torsion bar 14 is distributed as a reaction force and applied to the first steering-side motor 31 and the second steering-side motor 32. The first steering-side motor 31 and the second steering-side motor 32 each receive a steering torque T h Therefore, as described above, the third input torque T r3 For T h By adding the value of / 2, the reaction force that the first steering-side motor 31 receives from the torsion bar 14 can be compensated for.

[0080] The output from the subtractor SU7 is input to the adder AD5 and the third model following control unit 73. The adder AD5 outputs to the third controlled object 75 a value obtained by adding the output from the state feedback unit 72 to the output from the subtractor SU7.

[0081] In this embodiment, the third model following control unit 73 is a model following controller configured to perform model following control. The third model following control unit 73 controls the third input torque T r3 The third correction torque T f3 is generated based on the output of the third controlled object 75 and the third nominal model NM3. In this embodiment, the third correction torque T f3 is the third input torque T r3 The third nominal model NM3 is an internal model used as a model for constraining the third controlled object 75 when controlling the third controlled object 75.

[0082] In this embodiment, the third model following control unit 73 controls the output angle θ s Based on the third correction torque T f3 and generates a third input torque T r3 The third model following control unit 73 has a third inverse nominal model 73a, a filter 73b, and a subtractor SU8.

[0083] When the transfer function of the filter 73b is Q3(s), the third model following control unit 73 calculates a transfer function P m3 (s) is the transfer function P of the third nominal model NM3 nc In this embodiment, Q3(s) is equal to the complementary sensitivity function T3(s) of the inner loop configured by third model following control unit 73. Q3(s), i.e., complementary sensitivity function T3(s), has a gain of approximately 0 dB, i.e., a gain of approximately 1 in the transfer function, in the frequency band passed by filter 73b.

[0084] In this specification, "the transfer function of the controlled object is constrained to the transfer function of the nominal model" means that the controlled object is controlled so that the transfer function of the controlled object appears to be the transfer function of the nominal model when, for example, the input / output relationship is viewed. In addition, in this specification, "the gain is approximately 1" includes, in addition to the case where the gain is 1, for example, the case where the gain is 0.8 or more and 1.2 or less. The numerical range is, for example, a range in which the gain of the substantial disturbance suppression characteristic can be adjusted to 1, taking into account the positive efficiency and the negative efficiency of the worm gear, when the reduction mechanism connected to each motor has a worm gear. Since the efficiency of the worm gear is about 0.8, it is necessary to adjust the gain to ±0.2 with respect to the target value 1.

[0085] The third inverse nominal model 73a is an inverse model of the third nominal model NM3 used to constrain the third controlled object 75. The transfer function P nc (s) is expressed, for example, by the following equation (11). nc -1 (s) is expressed by the following equation (12).

[0086]

number

[0087]

number

[0088] The output of the third controlled object 75 is input to the third inverse nominal model 73a. Specifically, the third inverse nominal model 73a is s The third inverse nominal model 73a is obtained by using the above formula (12) and the input output angle θ s Based on the torque T p3 The torque T p3 is equal to the value of the torque input to the third nominal model NM3 when the output value of the third nominal model NM3 is the same as the output value of the third controlled object 75.

[0089] The subtractor SU8 subtracts the output of the subtractor SU7 from the output of the third inverse nominal model 73a to obtain a differential torque T a3 The torque difference T output from the subtractor SU8 is generated. a3 is filtered by the filter 73b and input to the gain adjuster 73c. ​​The gain adjuster 73c multiplies the output value from the filter 73b with a feedback gain K to obtain the third correction torque T f3 The third correction torque T f3 is output to the subtractor SU7.

[0090] The state feedback unit 72 calculates the apparent transfer function of the third controlled object 75 based on the output of the third controlled object 75 as a transfer function P of the third nominal model NM3. nc To get closer to (s), the state compensation value V s3 The third input torque T r3 The apparent transfer function of the third controlled object 75 is, for example, the transfer function of a portion located inside the feedback loop created by the third model following control unit 73 when the portion is regarded as one portion. Specifically, in this embodiment, the apparent transfer function of the third controlled object 75 is the transfer function of the entire portion from the subtractor SU7 to the output of the third controlled object 75, and is the transfer function of the portion combining the state feedback unit 72 and the third controlled object 75. In this embodiment, the state feedback unit 72 calculates the third correction torque T f3 and before being input to the third control target 75. r3 For the state compensation value V s3 Provide feedback.

[0091] State compensation value V s3 includes a compensation value that compensates for at least a part of the inertial force generated in the third controlled object 75, the viscous force generated in the third controlled object 75, and the frictional force generated in the third controlled object 75. More specifically, the state compensation value V s3 includes a compensation value that compensates for at least a part of the inertial force generated in the first steering-side motor 31, the viscous force generated in the first steering-side motor 31, and the frictional force generated in the first steering-side motor 31. In this embodiment, the state compensation value V s3 is a compensation value including the inertial force generated in the first steering-side motor 31, the viscous force generated in the first steering-side motor 31, and the frictional force generated in the first steering-side motor 31.

[0092] The state feedback unit 72 includes an inertia compensator 72a, a viscosity compensator 72b, and a friction compensator 72c. The inertia compensator 72a calculates an output angle θ of the output shaft 13 rotated by the first steering-side motor 31. sThe viscous compensator 72b calculates a compensation value for compensating for at least a part of the inertial force generated in the first steering-side motor 31 based on the output angle θ s The friction compensator 72c calculates a compensation value for compensating for at least a part of the viscous force generated in the first steering-side motor 31 based on the output angle θ s Based on this, a compensation value that compensates for at least a part of the frictional force generated in the first steering-side motor 31 is calculated. In this embodiment, the state compensation value V s3 The compensation value calculated by the inertia compensator 72a, the compensation value calculated by the viscosity compensator 72b, and the compensation value calculated by the friction compensator 72c are output to an adder AD5 to calculate the third correction torque T f3 The third input torque T after being corrected by r3 is added to.

[0093] The state feedback unit 72 calculates the state compensation value V s3 By adding this, the inertia, viscosity, and friction in the steering system including the steering wheel 11 and the first steering-side motor 31 can be adjusted to desired values, and the steering reaction force received by the helm 11 from the steering wheel 11 can be adjusted to a value that makes steering easier for the helmsman. Therefore, the steering feel felt by the helmsman can be improved.

[0094] Furthermore, by providing the state feedback unit 72, the third controlled object 75 to be controlled by feedback from the third model following control unit 73 can be made to appear close to the third nominal model NM3 which is included as an internal model. As a result, when performing model following control by the third model following control unit 73, the third controlled object 75 can be regarded as a model close to the third nominal model NM3, and the modeling error between the third controlled object 75 and the third nominal model NM3 can be reduced. Therefore, when the gain in the gain characteristic of Q3(s) is set to approximately 1, the transfer function P m3 (s) is the transfer function P ncThe frequency band in which the steering force can be constrained to (s) can be widened. Therefore, the model following control by the third model following control unit 73 can be performed in a wider frequency band, and the steering feel felt by the steerer can be further improved.

[0095] In this embodiment, in each of the steering reaction force control section 57a ​​and the steering reaction force control section 57b, the third input torque T r3 T hr / 2, and the output angle of the first steering-side motor 31 and the output angle of the second steering-side motor 32 are controlled by model following control to obtain an output angle θ of the output shaft 13. s The target steering torque T hr This allows the steering reaction force transmitted to the driver to be adjusted to a suitable value.

[0096] [Steering side control unit] The first turning side control unit 53 controls the turning side motor angle command value θ gra1 The second steering side control unit 54 controls the first controlled object 65a including the first steering side motor 33 based on the steering side motor angle command value θ gra2 Based on this, it controls a second controlled object 65b including the second turning side motor 34. In the following explanation, the first turning side control unit 53 will be explained as a representative of the first turning side control unit 53 and the second turning side control unit 54, and explanations of the configuration of the second turning side control unit 54 that is similar to that of the first turning side control unit 53 may be omitted.

[0097] As shown in Fig. 4A, the first turning side control unit 53 has a first processor 53a and a plurality of inverter circuits 58. The plurality of inverter circuits 58 supply power independently to the plurality of coil groups 37 in the first turning side motor 33. This ensures redundancy of the first turning side control unit 53 and redundancy of the first turning side motor 33. In other words, even if a malfunction occurs in one of the plurality of inverter circuits 58 and power cannot be supplied to a certain coil group 37, power can be supplied to the other coil groups 37 by the other inverter circuits 58, and the first turning side motor 33 can be driven suitably.

[0098] In this embodiment, two inverter circuits 58 are provided: a first inverter circuit 58a and a second inverter circuit 58b. The first inverter circuit 58a supplies power independently to the first coil group 37a in the first turning-side motor 33. The second inverter circuit 58b supplies power independently to the second coil group 37b in the first turning-side motor 33.

[0099] As shown in FIG. 4B, the second turning side control unit 54 has a second processor 54a and a plurality of inverter circuits 59. The plurality of inverter circuits 59 supply power independently to the plurality of coil groups 37 in the second turning side motor 34. This ensures redundancy of the second turning side control unit 54 and redundancy of the second turning side motor 34, similar to the first turning side control unit 53 and the first turning side motor 33. In this embodiment, the inverter circuit 59 includes two inverter circuits, a first inverter circuit 59a and a second inverter circuit 59b. The first inverter circuit 59a supplies power independently to the first coil group 37a in the second turning side motor 34. The second inverter circuit 59b supplies power independently to the second coil group 37b in the second turning side motor 34.

[0100] The first processor 53a and the second processor 54a are semiconductor integrated circuits, and are also called central processing units (CPUs) or microprocessors. The first processor 53a and the second processor 54a sequentially execute computer programs that are stored in a ROM (not shown) and contain instructions for controlling motor drive, to realize desired processing.

[0101] As shown in FIG. 5, the first processor 53a receives a steering-side motor angle command value θ gra1 and the correction interference torque T m2R As shown in Fig. 13, the first processor 53a has an angle control section 61, a state feedback section 62, a first model following control section 63, subtractors SU1, SU2, and adders AD1, AD2. That is, the first turning side control section 53 has an angle control section 61, a state feedback section 62, a first model following control section 63, subtractors SU1, SU2, and adders AD1, AD2. The turning side motor angle command value θ input to the first processor 53a gra1 is input to the subtractor SU1. The subtractor SU1 subtracts the steering side motor angle command value θ gra1 to the first output angle θ of the first steering-side motor 33 g1 The angle control unit 61 performs PD control to subtract the first input torque T r1 and outputs it to the subtractor SU2.

[0102] The subtractor SU2 subtracts the first input torque T r1 The correction torque T output from the first model following control unit 63 is f1 The output from the subtractor SU2 is input to an adder AD1 and a first model following control unit 63. The adder AD1 adds the output from the subtractor SU2 and the output from the state feedback unit 62, and outputs the result to the adder AD2. The adder AD2 adds the disturbance torque T d1and outputs the sum of these to the first controlled object 65a. In this embodiment, the first controlled object 65a includes the first turning-side motor 33, the first steered wheel 21, and the bushes 23d, 23e, 41a, and 42a provided in the steering mechanism 20. In this embodiment, the first controlled object 65a includes the portion of the vehicle from the first turning-side motor 33 to the first turning wheel 21. The output of the first controlled object 65a is a first output angle θ of the first turning-side motor 33. g1 It is.

[0103] As shown in Fig. 14, the first controlled object 65a can be represented by a simplified model in which the first steered-side motor 33 and the first steered wheel 21 are connected by a virtual spring 20a. In Fig. 14, the spring constant K Bush1 is a parameter corresponding to the equivalent spring constant of the elastic element including each of the bushes 23d, 23e, 41a, and 42a included in the first controlled object 65a. Bush1 The stiffness of the vehicle body is also included. Tire1 is the angle of the first steered wheel 21.

[0104] In this embodiment, the first model following control unit 63 is a model following controller configured to perform model following control. As shown in FIG. 13, the first model following control unit 63 controls a first input torque T r1 Correction torque T f1 is generated based on the output of the first controlled object 65a and a first nominal model NM1 based on the configuration of the first controlled object 65a. f1 is the first input torque T r1 The first nominal model NM1 is an internal model used as a model for constraining the first controlled object 65a when controlling the first controlled object 65a.

[0105] In this embodiment, the first model following control unit 63 controls the first output angle θ of the first turning-side motor 33. g1 Based on the correction torque T f1 and generates the first input torque Tr1 The first model following control unit 63 has a first inverse nominal model 63a, a filter 63b, a noise removal filter 63c, and subtractors SU3 and SU4.

[0106] When the transfer function of the filter 63b is Q1(s), the first model following control unit 63 calculates a transfer function P SAW1 (s) is the transfer function P of the first nominal model NM1. na In this embodiment, Q1(s) is equal to the complementary sensitivity function T1(s) of the inner loop formed by the first model following control unit 63.

[0107] The first inverse nominal model 63a is an inverse model of the first nominal model NM1 used to constrain the first controlled object 65a. In this embodiment, the transfer function P na (s) is expressed by the following equation (13). The transfer function P na -1 (s) is expressed by the following equation (14).

[0108]

number

number

[0109] As shown in the above equation (13), the transfer function P na (s) is the function F na In this embodiment, the transfer function P na (s) is the function F na Consists of only (s).

[0110] The first nominal model NM1 is derived based on the simplified first controlled object 65a shown in Fig. 14. In order to obtain the self-aligning torque SAT1, which is the force generated by the first steered wheel 21, from the model shown in Fig. 14, the first output angle θ of the first steered-side motor 33 is calculated from the output torque of the first steered-side motor 33 not including the self-aligning torque SAT1 based on the simplified steering system characteristics. g1 This improves the accuracy of estimating the self-aligning torque SAT1, and enables a design that compensates for the steering characteristics caused by the compliance of the vehicle. Based on the simplified model shown in FIG. 14, the output torque T g1 to the first output angle θ of the first steering-side motor 33 g1 The transfer characteristic up to is calculated as follows:

[0111]

number

[0112] Here, the gear ratio from the first steering side motor 33 to the first steering wheel 21 is about 300, so K Bush1 / G 2can be considered to be almost zero. Using this, the right-hand term of the above equation (15) can be rearranged to obtain the transfer function P na (s) can be derived.

[0113] Transfer function P of the first nominal model NM1 na The first term of (s), that is, 1 / (J n1 s 2 +B n1 s) is a term related to the mechanical characteristics of the first steering-side motor 33. na The first term in (s) affects the responsiveness of the first turning side motor 33. When active front steering control is performed, for example, the time constant is 0.05 seconds, and therefore the control responsiveness is required to be one tenth of that. To achieve this responsiveness, it is desirable to compensate for the inertia of the first turning side motor 33 and the friction of the first turning side motor 33, and to keep the mechanical responsiveness of the first turning side motor 33 in a high state. This can be achieved by providing a state feedback unit 62. Also, the transfer function P na J in the first paragraph of (s) n1 and B. n1 is a parameter that sets the motor characteristic of the first turning-side motor 33 as seen by the first model following control section 63 after compensation is performed by providing the state feedback section 62. n1 and B. n1 It is possible to improve the robust stability of the first model following control section 63 by adjusting the above. As a result, it is possible to achieve both responsiveness and robust stability.

[0114] In addition, the transfer function P na The second term of (s), that is, (s 2 +α b1 s+α k1 ) / (s 2 +β b1 s+β k1) is a term related to the compensation of compliance steer. Compliance steer is a change in the actual steering angle caused by an angle that appears as if the steering wheel has been turned on the tires when an external force acts on the contact area of ​​the vehicle tires, and this deflection causes a deflection in the suspension elements of the vehicle, such as rubber bushings. In this embodiment, compliance steer is a change in the angle of the first steered wheel 21 and the angle of the second steered wheel 22 caused by the deflection of suspension elements such as bushings 23d, 23e, 41a, 42a. The physical parameters that affect compliance steer are elastic elements such as bushings and viscous elements of the tires, and the transfer function P na In (s), K Bush1 and B. Tire1 The transfer function P na In the second paragraph of (s), K Bush1 and B. Tire1 are the ideal parameters, and α b1 ,α k1 ,β b1 ,β k1 By determining the first nominal model NM1, it is possible to make the first nominal model NM1 a model having desirable compliance characteristics. By performing model following control using the first nominal model NM1 thus obtained, it is possible to suitably compensate for the compliance steering characteristics of the vehicle. As a result, for example, regardless of where the first battery 85a and the second battery 85b are disposed in the vehicle, the running stability of the vehicle can be ensured.

[0115] In addition, K Bush1 is the transfer function P na (s) affects only the second term, and Bush1 The natural frequency of K is sufficiently higher than the frequency band of the self-aligning torque SAT1 generated in the first steered wheel 21. Bush1 has little effect on the estimation of the self-aligning torque SAT1. Bush1 The natural frequency of the self-aligning torque SAT1 is, for example, about 20 Hz or more and 30 Hz or less. The frequency band of the self-aligning torque SAT1 is, for example, about 10 Hz or less.

[0116] As shown in Fig. 13, the output of a first controlled object 65a is input to the first inverse nominal model 63a. Specifically, the first inverse nominal model 63a is input with a first output angle θ g1 The first inverse nominal model 63a is calculated based on the above formula (14) and the input first output angle θ g1 Based on the torque T p1 That is, the first model following control unit 63 uses the first nominal model NM1 based on the output of the first controlled object 65a to output the torque T p1 Calculate the torque T p1 is equal to the value of the torque input to the first nominal model NM1 when the output value of the first nominal model NM1 is the same as the output value of the first controlled object 65a.

[0117] The subtractor SU3 subtracts the output of the subtractor SU2 from the output of the first inverse nominal model 63a to obtain a differential torque T a1 That is, the subtractor SU3 generates the correction torque T f1 After being fed back, the state compensation value V s1 The first input torque T before being fed back r1 , torque T p1 Subtract the differential torque T from a1 Generates a differential torque T a1 For example, the disturbance torque T d1 and includes the self-aligning torque SAT1 of the first steered wheel 21 and the second interference torque caused by the second turning-side motor 34 driving the turning mechanism 20. The second interference torque is applied to the first controlled object 65a.

[0118] The torque difference T output from the subtractor SU3 a1 is filtered by the filter 63b and input to the subtractor SU4. a1 The differential torque T a1fThe filter 63b is, for example, a filter formed by connecting a low-pass filter and a high-pass filter in series. As a result, the differential torque T a1f is a frequency component equal to or higher than the first cutoff frequency Cf1 of the high-pass filter in the filter 63b and equal to or lower than the second cutoff frequency Cf2 of the low-pass filter in the filter 63b. a1f These include friction force, self-aligning torque SAT1 of the first steered wheel 21, disturbance torque caused by backlash of the first controlled object 65a, and torque ripple generated in the first controlled object 65a.

[0119] The subtractor SU4 subtracts the output value from the filter 63b, i.e., the differential torque T a1f The correction interference torque T m2R Subtract the correction torque T f1 Then, the correction torque T f1 The subtractor SU4 outputs the correction torque T f1 is the input of the first controlled object 65a, that is, the first input torque T r1 is fed back to.

[0120] Here, the correction interference torque T m2R As described above, the value of is the correction interference torque T m1 The torque difference T a1f The correction interference torque T is subtracted from m2R Specifically, in the region where the steering frequency f is equal to or lower than the cutoff frequency ω1, the gain in the transfer function of the frequency region setting unit 56d becomes 1, so that the correction interference torque T m2R The value of the correction interference torque T m1 This results in the subtractor SU4 calculating the differential torque T a1f The value to be subtracted from is the correction interference torque T m1In this case, the first model following control unit 63 calculates the correction interference torque T m2R Correction torque T f1 In this embodiment, the correction interference torque T m2R Correction torque T f1 The model following control performed by including the above is called "cooperative control CT1." The cooperative control CT1 corresponds to the "first control."

[0121] On the other hand, in a region where the steering frequency f is higher than the cutoff frequency ω1, the gain in the transfer function of the frequency region setting unit 56d becomes smaller than 1, so that the correction interference torque T m2R The value of the correction interference torque T m1 Therefore, compared with the case where the steering frequency f is equal to or lower than the cutoff frequency ω1, the differential torque T a1f The correction interference torque T is subtracted from m2R If the steering frequency f is higher than a certain level in the region higher than the cutoff frequency ω1, the correction interference torque T m2R is sufficiently attenuated in the frequency range setting unit 56d. In this case, the differential torque T a1f The value subtracted from the steering frequency f can be considered to be almost zero. In this way, in the region where the steering frequency f is higher than the cutoff frequency ω1, the differential torque T a1f The correction interference torque T is subtracted from m2R In other words, in the region where the steering frequency f is higher than the cutoff frequency ω1, the correction torque T f1 The correction interference torque T m2R In this embodiment, the influence of the correction torque T f1 The correction interference torque T m2R The model following control in which the influence of the correction interference torque is small is called the "non-interference control CT2." The non-interference control CT2 corresponds to the "second control." In this specification, "the influence of the correction interference torque on the correction torque is smaller than that of the cooperative control" includes the case where the correction interference torque is not input to each model following control unit.

[0122] In this manner, in this embodiment, the first model following control unit 63 can execute the cooperative control CT1 and the non-interacting control CT2. In this embodiment, as shown in Fig. 10, the cooperative control CT1 is executed when the steering frequency f is in a cooperative control region PH1 that is equal to or lower than the cutoff frequency ω1, and the non-interacting control CT2 is executed when the steering frequency f is in a non-interacting control region PH2 that is higher than the cutoff frequency ω1. In other words, the cooperative control CT1 and the non-interacting control CT2 are executed based on the steering angle θ which changes when the steering wheel 11 is steered. h The steering frequency f when the non-interference control CT2 is executed is higher than the steering frequency f when the cooperative control CT1 is executed. In this embodiment, the cooperative control CT1 and the non-interference control CT2 are automatically switched between in accordance with the steering frequency f by the low-pass filter process performed in the frequency domain setting unit 56d.

[0123] As shown in FIG. 13, the noise removal filter 63c receives the differential torque T a1f The noise elimination filter 63c receives the differential torque T a1f The noise elimination filter 63c removes at least a part of the noise from the first self-aligning torque estimate value SAT h1 The first self-aligning torque estimate SAT h1 is an estimate of the self-aligning torque SAT1 generated at the first steered wheel 21. The first self-aligning torque estimate value SAT h1 As shown in FIG. 5, these are input to the command value generating units 55a, 55b, the cooperative control units 56a, 56b, and the steering reaction force control units 57a, 57b in the first steering side control unit 51 and the second steering side control unit 52.

[0124] As shown in FIG. 13, the state feedback unit 62 calculates the output of the first controlled object 65a, that is, the first output angle θ g1Based on this, the apparent transfer function of the first controlled object 65a is calculated based on the transfer function P na To get closer to (s), the state compensation value V s1 Let the first input torque T r1 The apparent transfer function of the first controlled object 65a is, for example, the transfer function of a portion located inside the feedback loop created by the first model following control unit 63 when the portion is regarded as one portion. Specifically, in this embodiment, the apparent transfer function of the first controlled object 65a is the transfer function of the entire portion from the subtractor SU2 to the output of the first controlled object 65a, and is the transfer function of the portion combining the state feedback unit 62 and the first controlled object 65a. In this embodiment, the state feedback unit 62 calculates the correction torque T f1 After being corrected by and before being input to the first controlled object 65a, the first input torque T r1 For the state compensation value V s1 Provide feedback.

[0125] State compensation value V s1 includes a compensation value for compensating for at least a part of the inertial force generated in the first controlled object 65a, the viscous force generated in the first controlled object 65a, and the frictional force generated in the first controlled object 65a. s1 includes a compensation value that compensates for at least a part of the inertial force generated in the first turning side motor 33, the viscous force generated in the first turning side motor 33, and the frictional force generated in the first turning side motor 33. In this embodiment, the state compensation value V s1 is a compensation value including the inertial force generated in the first turning side motor 33, the viscous force generated in the first turning side motor 33, and the frictional force generated in the first turning side motor 33.

[0126] The state feedback unit 62 includes an inertia compensator 62a, a viscosity compensator 62b, and a friction compensator 62c. The inertia compensator 62a is configured to calculate a first output angle θ of the first steered-side motor 33. g1 The viscosity compensator 62b calculates a compensation value for compensating for at least a part of the inertial force generated in the first turning-side motor 33 based on the first output angle θg1 The friction compensator 62c calculates a compensation value for compensating for at least a part of the viscous force generated in the first turning-side motor 33 based on the first output angle θ g1 Based on this, a compensation value that compensates for at least a part of the frictional force generated in the first turning-side motor 33 is calculated. In this embodiment, the state compensation value V s1 The compensation value calculated by the inertia compensator 62a, the compensation value calculated by the viscosity compensator 62b, and the compensation value calculated by the friction compensator 62c are output to an adder AD1 to calculate the correction torque T f1 The first input torque T after being corrected by r1 is added to.

[0127] Next, a more detailed description will be given of the control by the first model following control unit 63. The first model following control unit 63 controls the first controlled object 65a using an inverse model of the first nominal model NM1 included as an internal model, that is, a first inverse nominal model 63a.

[0128] The first model following control unit 63 is similar in configuration to a conventional disturbance estimator (disturbance observer), but has different intended actions and effects. A conventional disturbance estimator estimates disturbance torque by making an inverse plant model, which is an internal model, a model close to the first control target 65a, and reduces the influence of disturbance by adjusting the disturbance torque in advance.

[0129] In the present embodiment, the control by the first model following control unit 63 is carried out by a feedback loop to obtain a transfer function P SAW1 (s) is the transfer function P of the first nominal model NM1 that is included as an internal model. na For example, if the first nominal model NM1 is defined so that there is no torque ripple, the transfer function P SAW1(s) is constrained to a characteristic without torque ripple, and as a result, it is possible to reduce torque ripple by applying torque ripple compensation. In addition, by making the first nominal model NM1 a low inertia model and constraining the first controlled object 65a with the first nominal model NM1, the first controlled object 65a can be treated as a low inertia model. In addition, by making the first nominal model NM1 a low viscosity model and constraining the first controlled object 65a with the first nominal model NM1, the first controlled object 65a can also be treated as a low viscosity model. By executing model following control by the first model following control unit 63, in addition to the compensation for the torque ripple of the first turning-side motor 33, for example, loss torque compensation or motor inertia compensation is performed. In the above-mentioned equations (13) and (14), J n1 and B. n1 By appropriately setting SAW1 (s) can be given the desired frequency characteristics.

[0130] The transfer function P of the first controlled object 65a SAW1 (s) and the transfer function P of the first nominal model NM1 na When the modeling error with respect to (s) is Δ(s), the transfer function P SAW1 (s) is expressed by the following equation (16).

[0131]

number

[0132] The transfer function P of the first controlled object 65a SAW1 The gain characteristic of the first controlled object 65a has peaks at, for example, two frequency values. The modeling error Δ(s) appears, for example, near the higher frequency of the two peaks in the gain characteristic of the first controlled object 65a. Therefore, as shown in FIG. 15, the reciprocal 1 / Δ(s) of the modeling error Δ(s) has a bottom in a relatively high frequency region. In FIG. 15, the modeling error Δ(s) is shown as an absolute value. When the modeling error Δ(s) becomes large, the transfer function PSAW1 (s) and the transfer function P of the first nominal model NM1 na As a result, the deviation from the first nominal model NM1 becomes large, and the control of the first controlled object 65a by the first model following control unit 63 using the first nominal model NM1 becomes unstable. Therefore, in a region where the modeling error Δ(s) is relatively small, the first controlled object 65a can be stably and suitably controlled by constraining the first controlled object 65a to the first nominal model NM1 with the gain of the complementary sensitivity function T1(s), i.e., Q1(s), set to approximately 1. The frequency characteristic of the modeling error Δ(s) is expressed by the transfer function P na J in (s) n1 and B. n1 The frequency band in which the gain of Q1(s) is approximately 1 can be adjusted by adjusting the first cutoff frequency Cf1 and the second cutoff frequency Cf2. This allows the gain of Q1(s) to be adjusted to approximately 1 in a frequency band in which the modeling error Δ(s) is small. In this embodiment, the complementary sensitivity function T1(s), i.e., the gain of Q1(s), is set within a range of 0.8 or more and less than 1.

[0133] In Fig. 15, 1 / Δ(s) is relatively high in a frequency band equal to or lower than the second cutoff frequency Cf2, and drops sharply in a frequency band higher than the second cutoff frequency Cf2. The model following control that constrains the first controlled object 65a to the first nominal model NM1 can be stably performed, for example, in a range in which 1 / Δ(s) is greater than 1, that is, in a range in which 1 / Δ(s) is greater than 0 dB. Therefore, as shown in Fig. 15, by adjusting 1 / Δ(s) to be greater than 1 in a frequency band in which the gain of Q1(s) is approximately 1, when the gain of Q1(s) is approximately 1, the first controlled object 65a can be constrained to the first nominal model NM1 and controlled stably and suitably.

[0134] For example, in order to expand the frequency band in which the first controlled object 65a can be stably and suitably controlled by constraining it to the first nominal model NM1, the second cutoff frequency Cf2 may be increased within a range in which 1 / Δ(s) is not equal to or less than 1, that is, within a frequency band lower than the frequency at which the curve showing 1 / Δ(s) intersects with the horizontal axis in FIG. 15. However, if the second cutoff frequency Cf2 is increased too much, the gain of Q1(s) may remain relatively high in a frequency band higher than the second cutoff frequency Cf2, even though 1 / Δ(s) is lowered, which may cause unstable control. In response to this, for example, by setting the order of the low-pass filter in the filter 63b to third order or higher, the gain of Q1(s) can be sharply reduced in a frequency range higher than the second cutoff frequency Cf2. As a result, even if the second cutoff frequency Cf2 is set relatively high, the gain of Q1(s) can be immediately reduced in a frequency band higher than the second cutoff frequency Cf2, thereby preventing the control of the first controlled object 65a from becoming unstable.

[0135] The robust stability of the first model following control section 63 is guaranteed when the small gain theorem shown in the following equation (17) holds between the complementary sensitivity function T1(s) and the modeling error Δ(s).

[0136]

number

[0137] In order to satisfy the above formula (17), it is necessary to set the first nominal model NM1 so that the modeling error Δ(s) is as small as possible within the frequency band in which the model following control is performed. For example, when the responsiveness to be achieved is a time constant of 0.05 seconds, it is necessary to set the first nominal model NM1 so that the modeling error Δ(s) is small up to 40 Hz, which corresponds to a frequency ten times that of the time constant. In this embodiment, for example, by capturing the first controlled object 65a as a simplified model as shown in FIG. 14 and setting the first nominal model NM1, it is possible to set the first nominal model NM1 so that the modeling error Δ(s) is small up to 40 Hz.

[0138] The transfer function Q1(s) of the filter 63b is expressed as the output torque T g1 to the first output angle θ of the first steering-side motor 33 g1 The control system is designed to satisfy the above formula (17) while taking into consideration the transfer characteristics up to , that is, the modeling error not included in the above formula (15). In this embodiment, the state feedback unit 62 is provided, so that the influence of the fluctuations in various parameters of the first controlled object 65a on the formula (17) can be compensated for. Note that, although an example in which the state feedback unit 62 is implemented by a transfer function is shown in this embodiment, the state feedback unit 62 may be implemented by an extended state space representation in which the disturbance is a part of the state variables.

[0139] As shown in FIG. 5, the second processor 54a receives a steering-side motor angle command value θ gra2 and the correction interference torque T m2L As shown in Fig. 16, the second processor 54a has an angle control section 66, a state feedback section 67, a second model following control section 68, subtractors SU10, SU11, and adders AD6, AD7. That is, the second turning side control section 54 has an angle control section 66, a state feedback section 67, a second model following control section 68, subtractors SU10, SU11, and adders AD6, AD7. The turning side motor angle command value θ input to the second processor 54a gra2is input to the subtractor SU10. The subtractor SU10 subtracts the steering-side motor angle command value θ gra2 to the second output angle θ of the second steering-side motor 34 g2 The angle control unit 66 performs PD control to subtract the second input torque T r2 and outputs it to the subtractor SU11.

[0140] The subtractor SU11 subtracts the second input torque T r2 The correction torque T output from the second model following control unit 68 is f2 The output from the subtractor SU11 is input to an adder AD6 and a second model following control unit 68. The adder AD6 adds the output from the subtractor SU11 and the output from the state feedback unit 67, and outputs the result to an adder AD7. The adder AD7 adds the disturbance torque T d2 and outputs the sum of the two to the second controlled object 65b. In this embodiment, the second controlled object 65b includes the second turned-side motor 34, the second steered wheel 22, and each bush provided around the second turned wheel 22 and the second turned-side motor 34 similar to each bush 23d, 23e, 41a, 42a shown in FIG. 2. In this embodiment, the second controlled object 65b includes a portion of the vehicle from the second turned-side motor 34 to the second turned wheel 22. The output of the second controlled object 65b is a second output angle θ of the second turned-side motor 34. g2 The second controlled object 65b can be represented by a simplified model as shown in FIG. 14, similar to the first controlled object 65a. The transfer function P SAW2 (s) can be expressed in the same way as the first controlled object 65a.

[0141] The second model following control unit 68 performs model following control on the second controlled object 65b in the same manner as the first model following control unit 63. The second model following control unit 68 controls the second input torque T r2 Correction torque T f2is generated based on the output of the second controlled object 65b and a second nominal model NM2 based on the configuration of the second controlled object 65b. f2 is the second input torque T r2 The second nominal model NM2 is an internal model used as a model that constrains the second controlled object 65b when controlling the second controlled object 65b. The second model following control section 68 controls the second output angle θ g2 Based on the correction torque T f2 and generates a second input torque T r2 The second model following control unit 68 has a second inverse nominal model 68a, a filter 68b, a noise elimination filter 68c, a subtractor SU12, and an adder AD8. The filter 68b is similar to the filter 63b. The noise elimination filter 68c is similar to the noise elimination filter 63c.

[0142] The second inverse nominal model 68a is an inverse model of the second nominal model NM2 used to constrain the second controlled object 65b. In this embodiment, the transfer function P nb (s) is expressed by the following equation (18). The transfer function P nb -1 (s) is expressed by the following equation (19).

[0143]

number

number

[0144] As shown in the above equation (18), the transfer function P nb (s) is the function F nb In this embodiment, the transfer function P nb (s) is the function F nb Consists of only (s).

[0145] As shown in Fig. 16, the output of the second controlled object 65b is input to the second inverse nominal model 68a. Specifically, the second inverse nominal model 68a is input with the second output angle θ g2 The second inverse nominal model 68a is calculated by the above equation (19) and the input second output angle θ g2 Based on the torque T p2 That is, the second model following control unit 68 uses the second nominal model NM2 based on the output of the second controlled object 65b to output the torque T p2 Calculate the torque T p2 is equal to the value of the torque input to the second nominal model NM2 when the output value of the second nominal model NM2 is the same as the output value of the second controlled object 65b.

[0146] The subtractor SU12 subtracts the output of the subtractor SU11 from the output of the second inverse nominal model 68a to obtain a differential torque T a2 That is, the subtractor SU12 generates the correction torque T f2 After being fed back, the state compensation value V s2 The second input torque T before being fed back r2 , torque T p2 Subtract the differential torque T from a2 Generates a differential torque T a2 For example, the disturbance torque Td2 and includes the self-aligning torque of the second steered wheel 22 and the first interference torque caused by the first turning-side motor 33 driving the turning mechanism 20. The first interference torque is applied to the second controlled object 65b.

[0147] The torque difference T output from the subtractor SU12 a2 is filtered by the filter 68b and input to the adder AD8. a2 The differential torque T a2f It is called the differential torque T a2f includes friction force, self-aligning torque of the second steered wheel 22, disturbance torque caused by backlash of the second controlled object 65b, and torque ripple generated in the second controlled object 65b.

[0148] The adder AD8 calculates the output value from the filter 68b, i.e., the differential torque T a2f The correction interference torque T m2L Add the correction torque T f2 Then, the correction torque T f2 is output to the subtractor SU11. The correction torque T f2 is the input of the second controlled object 65b, that is, the second input torque T r2 is fed back to.

[0149] Here, the correction interference torque T m2L is the correction interference torque T input to the first model following control unit 63. m2R Similarly, the value changes according to the steering frequency f. As a result, in this embodiment, the second model following control unit 68 can execute the cooperative control CT1 and the non-interference control CT2, similar to the first model following control unit 63.

[0150] The noise removal filter 68c receives the differential torque T a2f The noise elimination filter 68c receives the differential torque T a2fThe noise elimination filter 68c removes at least a portion of the noise from the second self-aligning torque estimate value SAT h2 The second self-aligning torque estimate SAT h2 is an estimated value of the self-aligning torque generated at the second steered wheel 22. The second self-aligning torque estimated value SAT h2 As shown in FIG. 5, these are input to the command value generating units 55a, 55b, the cooperative control units 56a, 56b, and the steering reaction force control units 57a, 57b in the first steering side control unit 51 and the second steering side control unit 52.

[0151] As shown in FIG. 16, the state feedback unit 67 calculates the output of the second controlled object 65b, that is, the second output angle θ g2 Based on this, the apparent transfer function of the second controlled object 65b is calculated as the transfer function P nb To get closer to (s), the state compensation value V s2 The second input torque T r2 The apparent transfer function of the second controlled object 65b is, for example, the transfer function of a portion located inside the feedback loop created by the second model following control unit 68 when the portion is regarded as one portion. Specifically, in this embodiment, the apparent transfer function of the second controlled object 65b is the transfer function of the entire portion from the subtractor SU11 to the output of the second controlled object 65b, and is the transfer function of the portion including the state feedback unit 67 and the second controlled object 65b. In this embodiment, the state feedback unit 67 calculates the correction torque T f2 After being corrected by and before being input to the second controlled object 65b, the second input torque T r2 For the state compensation value V s2 Provide feedback.

[0152] In this embodiment, the state feedback unit 67 has an inertia compensator 67a, a viscosity compensator 67b, and a friction compensator 67c, similar to the state feedback unit 62. In this embodiment, the state compensation value V s2are compensation values ​​including the inertial force generated in the second turning side motor 34, the viscous force generated in the second turning side motor 34, and the frictional force generated in the second turning side motor 34. Each compensation value is output to an adder AD6, and is used to calculate the correction torque T f2 The second input torque T after being corrected by r2 is added to.

[0153] In this embodiment, the following ASIL Decomposition is used to satisfy the highest standard "D" among the Automotive Safety Integrity Levels (ASIL) defined in the international functional safety standard "ISO26262", that is, ASIL D. In the drive system that drives the steering mechanism 20, the two steering side motors, the first steering side motor 33 and the second steering side motor 34, are motors each having two coil groups 37, and the first steering side control unit 53 and the second steering side control unit 54 are provided with a plurality of inverter circuits 58, 59 that independently supply power to each coil group 37 in each steering side motor controlled by each steering side control unit. As a result, the motor that drives the steering mechanism 20 and the inverter circuit that drives the motor each satisfy the ASIL C standard. Therefore, by combining these, ASIL D = ASIL C (D) + ASIL C (D), and the drive system that drives the steering mechanism 20 satisfies the ASIL D standard.

[0154] When the steering mechanism 20 is driven by the first turning-side motor 33 and the second turning-side motor 34 that are driven independently as described above, if a discrepancy occurs between the driving by the first turning-side motor 33 and the driving by the second turning-side motor 34, a first interference torque caused by the first turning-side motor 33 driving the steering mechanism 20 is applied to the second control object 65b that is the control object of the second turning-side motor 34, and a second interference torque caused by the second turning-side motor 34 driving the steering mechanism 20 is applied to the first control object of the first turning-side motor 33. In other words, the output torque of the first turning-side motor 33 and the output torque of the second turning-side motor 34 interfere with each other. Therefore, it is necessary to solve the interference problem between the two turning-side motors while maintaining the independence of each turning-side motor and each inverter circuit 58, 59.

[0155] Generally, as a method for solving the interference problem between the two motor outputs as described above, a method of synchronizing the response of the speeds of the two motors is known. As a means for realizing this method, generally, there is a means for exchanging speed information between the two motors and performing control for correcting the speed of each motor. However, in order to satisfy the safety standard of the above-mentioned ASIL D, it is necessary to electrically maintain the independence of each motor and each inverter circuit. Therefore, for example, it is necessary to exchange speed information between the motors through a communication means such as CAN. However, in this case, variations and delays in communication timing occur, making it difficult to synchronize the speeds of the motors. In addition, for example, a method of synchronizing the speeds of the two motors by providing a third control unit in addition to the two control units that control the two motors can be considered. In this case, however, there are problems such as an increase in the number of parts of the control unit in the steering device or a complication of the control unit due to the need to provide the third control unit.

[0156] To address the above problem, this embodiment employs model following control for torque control of the two turning-side motors, and employs a method of synchronizing the speeds of the two turning-side motors. If the two turning-side motors are reduced to a similar nominal model, it becomes possible to compensate for the asynchronism of the speeds of the turning-side motors by making the torque command the same, even if the loads applied to the turning-side motors are different.

[0157] Specifically, in this embodiment, the first model following control unit 63 is configured so that the transfer function of the first controlled object 65a is constrained to the transfer function of the first nominal model NM1 in a frequency band where the gain in the gain characteristic of the transfer function Q1(s) of the filter 63b, that is, the complementary sensitivity function T1(s) for the modeling error Δ(s) between the first controlled object 65a including the first turning-side motor 33 and the first nominal model NM1, is approximately 1. The second model following control unit 68 is configured so that the transfer function of the second controlled object 65b is constrained to the transfer function of the second nominal model NM2 in a frequency band where the gain in the gain characteristic of the transfer function Q2(s) of the filter 68b, that is, the complementary sensitivity function T2(s) for the modeling error Δ(s) between the second controlled object 65b including the second turning-side motor 34 and the second nominal model NM2, is approximately 1. In this way, by constraining each controlled object including each steered-side motor to a nominal model by model following control, it is possible to compensate for the interference torque caused by the other steered-side motor in the control of each steered-side motor. That is, the first turning-side control unit 53 compensates for the second interference torque caused by the second turning-side motor 34 driving the steered mechanism 20 by model following control that constrains the transfer function of the first controlled object 65a to the transfer function of the first nominal model NM1 based on the configuration of the first controlled object 65a. The second turning-side control unit 54 compensates for the first interference torque caused by the first turning-side motor 33 driving the steered mechanism 20 by model following control that constrains the transfer function of the second controlled object 65b to the transfer function of the second nominal model NM2 based on the configuration of the second controlled object 65b. Therefore, it is easier to preferably synchronize the rotation speed of the first turning-side motor 33 and the rotation speed of the second turning-side motor 34 compared to the case where a communication means such as CAN is used, and the turning mechanism 20 can be preferably controlled. This makes it possible to solve the problem of interference between the two turning-side motors while maintaining the electrical independence of each turning-side motor and each turning-side control unit. Therefore, it is possible to improve the controllability of the steering device 100 and improve the steering performance of the steering device 100 while ensuring the safety of the steering device 100.Furthermore, since there is no need to provide the third control section as described above, an increase in the number of components of the control device 50 in the steering device 100 and an increase in the complexity of the control device 50 can be suppressed.

[0158] Furthermore, by performing model following control in the first model following control unit 63 and the second model following control unit 68, it is possible to compensate for torque ripple and friction of the first turning side motor 33 and the second turning side motor 34. Therefore, in advanced driver-assistance systems (ADAS) and autonomous driving of the vehicle, it is possible to control the lateral movement of the vehicle with less force.

[0159] Due to variations in the torque constants of the turning-side motors and the detection values ​​of current sensors (not shown) capable of detecting the currents supplied to the turning-side motors, it may be difficult to compensate for the asynchronism of the speeds of the turning-side motors. In response to this, in this embodiment, the gains of the complementary sensitivity functions T1(s) and T2(s), i.e., Q1(s) and Q2(s), are set within a range of 0.8 or more and less than 1. By setting the gains of Q1(s) and Q2(s) slightly smaller than 1, the strength of the model following control performed in each model following control unit can be appropriately weakened. For example, if the gain is strictly set to 1 in one model following control unit to enhance the disturbance suppression characteristic, the disturbance can be suppressed suitably for the control object including one turning-side motor, but suppressing the disturbance increases the disturbance applied to the control object including the other turning-side motor that interferes with one turning-side motor. In response to this, by appropriately weakening the strength of the model following control performed in each model following control unit as described above, disturbances can be suitably suppressed for each control object while reducing the effect of the suppression of disturbances in each control object on the other control objects as disturbances. Therefore, each control object including each turning-side motor can share the effects of the mutually interfering turning-side motors in a well-balanced manner. This makes it easier to compensate for asynchronism in the speeds of the turning-side motors even if there is variation in the torque constants of the turning-side motors and the detection values ​​of the current sensors (not shown).

[0160] According to the present embodiment, the transfer function P na (s) is the first input torque T r1 The first output angle θ of the first steering-side motor 33 relative to the g1 The transfer function P of the second nominal model NM2 corresponds to the target value of the mechanical compliance, which is the ratio of nb (s) is the second input torque T r2 The second output angle θ of the second steering-side motor 34 relative to the g2is a transfer function equivalent to a target value of mechanical compliance, which is the ratio of . That is, the model following control for controlling the first controlled object 65a including the first turning-side motor 33 and the model following control for controlling the second controlled object 65b including the second turning-side motor 34 are virtual compliance controls. Therefore, by constraining each controlled object to each nominal model, it is possible to virtually replace the mechanical compliance from the input to the output of each turning-side motor with a preferable mechanical compliance and control each controlled object. This makes it possible to suitably compensate for the compliance steering characteristic of the vehicle, the steering characteristic of the vehicle, and the body rigidity of the vehicle. Therefore, the steering performance of the steering device 100 can be further improved. By being able to compensate for the influence of the body rigidity of the vehicle, it is not necessary to provide a reinforcing material or the like separately in the vehicle in order to improve the dynamic performance of the vehicle. Therefore, the dynamic performance of the vehicle can be improved while reducing the number of parts of the vehicle. In addition, the vehicle can be made lighter by not needing to provide a reinforcing material or the like.

[0161] Moreover, according to this embodiment, the first controlled object 65a includes the first steered wheel 21. The second controlled object 65b includes the second steered wheel 22. Therefore, the above-mentioned virtual compliance control can be performed taking into consideration the inertia, viscosity, rigidity, etc. of the first steered wheel 21 and the second steered wheel 22. Therefore, the compliance steer characteristic of the vehicle, the steering characteristic of the vehicle, the body rigidity of the vehicle, etc. can be more suitably compensated for, and the steering performance of the steering device 100 can be further improved.

[0162] Moreover, according to this embodiment, each of the first controlled object 65a and the second controlled object 65b includes at least one bush provided in the steering mechanism 20, such as bushes 23d, 23e, 41a, and 42a. Therefore, the above-mentioned virtual compliance control can be performed taking into consideration the rigidity and viscosity of each bush. Therefore, the compliance steer characteristic of the vehicle, the steering characteristic of the vehicle, and the body rigidity of the vehicle can be more suitably compensated for, and the steering performance of the steering device 100 can be further improved.

[0163] According to the present embodiment, the transfer function P na (s) is the function F expressed by the above equation (13). na It includes at least (s). Function F na (s) is a function obtained based on a simplified model from the first steered-side motor 33 to the first steered wheel 21 shown in FIG. 14. The transfer function P na (s) is such a function F na By including the function F(s), the first controlled object 65a can be constrained to a more suitable model by model following control. Therefore, the steering performance of the steering device 100 can be further improved. na By using (s), the dynamic characteristics of steering mechanism 20 can be included in first nominal model NM1 used in model following control. This makes it possible to ideally correct the movement of steering mechanism 20 when steering wheel 11 is steered. Therefore, even if the road surface on which the vehicle is traveling is uneven, for example, it is possible to suppress steering wheel 11 from being tilted.

[0164] Moreover, according to this embodiment, the transfer function P nb (s) is the function F expressed by the above equation (18). nb It includes at least (s). Function F nb (s) is a function obtained based on a simplified model from the second steered-side motor 34 to the second steered wheel 22, similar to the simplified model from the first steered-side motor 33 to the first steered wheel 21 shown in FIG. 14. The transfer function P nb (s) is such a function F nb By including the function F(s), the second control object 65b can be constrained to a more suitable model by model following control. Therefore, the steering performance of the steering device 100 can be further improved. nbBy using (s), the dynamic characteristics of steering mechanism 20 can be included in second nominal model NM2 used in model following control. This makes it possible to more ideally correct the movement of steering mechanism 20 when steering wheel 11 is steered. Therefore, even if the road surface on which the vehicle is traveling is uneven, for example, it is possible to more effectively prevent steering wheel 11 from being tilted.

[0165] According to the present embodiment, the first model following control unit 63 calculates the torque T p1 and the first input torque T r1 A first estimated value including the second interference torque based on the difference between the first estimated value and the second interference torque, that is, a first self-aligning torque estimated value SAT h1 The second model following control unit 68 calculates the torque T p2 and the second input torque T r2 A second estimated value including the first interference torque based on the difference between the first interference torque and the second self-aligning torque estimated value SAT h2 The steering reaction force control units 57a and 57b calculate the first self-aligning torque estimate value SAT h1 and the second self-aligning torque estimate SAT h2 The sum of these two values, that is, the estimated self-aligning torque SAT h The reaction force transmitted to the steering wheel is controlled based on the first self-aligning torque estimate value SAT h1 and the second self-aligning torque estimate SAT h2 When these are added together, the first interference torque and the second interference torque are offset, and the self-aligning torque estimate value SAT h This makes it possible to accurately estimate the total self-aligning torque acting on the first steered wheel 21 and the second steered wheel 22. Therefore, the steering reaction force transmitted to the driver, i.e., the steering torque Th can be set to a suitable value, thereby improving the steering feel for the driver.

[0166] In a steering device using a steer-by-wire system, it is necessary to avoid limiting the output of the motor due to heat generation by the motor itself, i.e., self-heating. The cause of self-heating in the motor is the resistance loss (ohmic loss) of the current flowing through the motor. The motor generates heat in proportion to the square of the current flowing through the motor. In order to suppress excessive self-heating in the motor, it is sufficient to keep the absolute value of the maximum current flowing through the motor low. Therefore, in this embodiment, in order to suitably suppress the self-heating of the first turning-side motor 33 and the self-heating of the second turning-side motor 34, it is effective to equalize the currents flowing through the two turning-side motors and to lower the absolute value of the maximum current flowing through each turning-side motor. To achieve this, in order to equalize the currents flowing through the two turning-side motors, it is sufficient to equalize the loads applied to the two turning-side motors, i.e., the motor torques of the two turning-side motors. As described above (SAT h1 +SAT h2 ) / 2=SAT h1 -T m1 =SAT h2 +T m1 Therefore, in order to equalize the motor torques of the two steered-side motors, the first input torque T r1 Corrected interference torque T m1 to obtain the second input torque T r2 Corrected interference torque T m1 can be added.

[0167] Here, it is assumed that the steering reaction force is proportional to the current flowing through each steered-side motor, and that the reaction forces of the first steered wheel 21 and the second steered wheel 22 are assisted by the first steered-side motor 33 and the second steered-side motor 34. In this case, the correction interference torque T m1 In the absence of the motor torque of the first turning side motor 33 and the motor torque of the second turning side motor 34, the sum of the motor torque of the first turning side motor 33 and the motor torque of the second turning side motor 34 is (SAT h1 +SAT h2 ) can be expressed as the correction interference torque T m1When there is a torque of the first turning side motor 33 and the motor torque of the second turning side motor 34, the sum of the motor torque of the first turning side motor 33 and the motor torque of the second turning side motor 34 is expressed as follows: h1 -T m1 )+(SAT h2 +T m1 Since the amount of heat generated in the motor is proportional to the square of the motor torque, the correction interference torque T m1 When there is no compensation interference torque T m1 For example, the total heat generated in the two steering-side motors when the correction interference torque T m1 From the equation obtained by squaring the motor torque in the above equation when there is a correction interference torque T m1 If we subtract the equation obtained by squaring the motor torque in the above equation when there is no torque, we get the following equation (20).

[0168]

number

[0169] If the above equation (20) is a negative value, the correction interference torque T m1 Compared with the case without the correction interference torque T m1 The condition for the above formula (20) to be a negative value is -SAT h2 <T m1 <SAT h1 As mentioned above, T m1 =(SAT h1 -SAT h2 ) / 2, so -SAT h2 <T m1 <SAT h1 Therefore, the corrective interference torque T m1 By controlling each steering motor using m1 The amount of heat generated by each steered side motor can be reduced compared to when the above-mentioned method is not used.

[0170] On the other hand, in order to control the two steered-side motors stably and with good responsiveness, it is effective to de-interact between the two steered-side motors by the above-mentioned model following control and compensate for the effects of torque ripple of each steered-side motor and each of the second transmission mechanisms 25a, 25b connected to each steered-side motor, and the effects of friction in each part, etc.

[0171] In response to the above, according to the present embodiment, the first model following control unit 63 and the second model following control unit 68 control the correction interference torque T m2R, T m2L Correction torque T f1 ,T f2 The first control, which includes the coordinated control CT1 and the correction torque T f1 ,T f2 The correction interference torque T m2R, T m2L and non-interference control CT2 as a second control in which the influence of heat generation in the first turning side motor 33 and the second turning side motor 34 is smaller than that of the cooperative control CT1. Therefore, the cooperative control CT1 can be adopted when emphasis is placed on suppressing heat generation in the first turning side motor 33 and the second turning side motor 34, and the non-interference control CT2 can be adopted when emphasis is placed on stability and responsiveness and non-interference between the first turning side motor 33 and the second turning side motor 34. This makes it possible to improve the steering performance of the steering device 100 by suitably improving the stability and responsiveness of each turning side motor while suppressing output limitations due to self-heating of the first turning side motor 33 and the second turning side motor 34.

[0172] In this manner, in the present embodiment, the maximum current required for the first turning side motor 33 and the second turning side motor 34 and the self-heating can be suppressed by actively utilizing the torque interference occurring between the first turning side motor 33 and the second turning side motor 34 in the cooperative control CT1. This makes it easy to reduce the power consumed by the first turning side motor 33, the second turning side motor 34, the first turning side control unit 53, and the second turning side control unit 54. In addition, even if the temperature that the first turning side motor 33 and the second turning side motor 34 can withstand is lowered, it is easy to suppress the output of the first turning side motor 33 and the second turning side motor 34 from being limited. Therefore, the manufacturing cost of the first turning side motor 33 and the second turning side motor 34 can be reduced.

[0173] The torque ripple in each steered motor, etc., occurs when the steering frequency f is greater than the resonance frequency ω r , or the resonant frequency ω r Therefore, when the steering frequency f is in the vicinity of the resonance frequency ω r , or the resonant frequency ω r When the steering frequency f is in the vicinity of the resonance frequency ω, the steering device 100 is likely to become unstable, and the running of the vehicle is likely to become unstable. r , or the resonant frequency ω r When the steering frequency f is in the vicinity of the resonance frequency ω, it is preferable to perform the non-interference control CT2 to appropriately compensate for the torque ripple, stabilize the steering device 100, and stabilize the running of the vehicle. r For example, when the steering frequency f is sufficiently far from the resonant frequency ω r When the steering frequency f is sufficiently lower than the resonance frequency ω r When the frequency is sufficiently far from the target frequency, it is preferable to suppress self-heating in each steered-side motor by performing cooperative control CT1.

[0174] In response to the above, according to the present embodiment, the cooperative control CT1 and the non-interference control CT2 are performed based on the steering angle θ h The steering frequency f when the non-interference control CT2 is executed is higher than the steering frequency f when the cooperative control CT1 is executed. Therefore, the steering frequency f is relatively high and the resonance frequency ω r When the steering frequency f is relatively low and the resonance frequency ω r When the frequency tends to deviate from the reference frequency, the first model following control unit 63 and the second model following control unit 68 can be caused to execute the cooperative control CT1. Therefore, the cooperative control CT1 and the non-interference control CT2 can be suitably switched, and the self-heating of the first turning side motor 33 and the self-heating of the second turning side motor 34 can be suppressed from becoming excessively large while stabilizing the running of the vehicle.

[0175] According to the present embodiment, the cooperative control units 56a and 56b calculate the first self-aligning torque estimated value SAT h1 and a second self-aligning torque estimated value SAT outputted from the second model following control unit 68 and including the self-aligning torque generated at the second steered wheel 22. h2 The half of the difference between the two is processed by low-pass filtering to obtain the compensation interference torque T m2R ,T m2L Therefore, the correction interference torque T m2R ,T m2L Specifically, when the steering frequency f is equal to or lower than the cutoff frequency of the low-pass filter that performs the low-pass filtering process, the value of the correction interference torque T m2R ,T m2L If the steering frequency f is higher than the cutoff frequency of the low-pass filter that performs low-pass filtering, the correction interference torque T m2R,T m2L This allows the correction interference torque T m2R ,T m2L Correction torque T f1 ,T f2 As a control that is always included in the steering frequency f, the correction torque T f1 ,T f2 Correction interference torque T m2R ,T m2L Therefore, the effect of the correction interference torque T m2R ,T m2L Correction torque T f1 ,T f2 It is not necessary to perform control to switch whether or not the control is included in the coordinated control CT1 and the non-interference control CT2, and it is possible to automatically switch between the coordinated control CT1 and the non-interference control CT2.

[0176] According to the present embodiment, the cutoff frequency in the low-pass filter processing performed by the cooperative control units 56a and 56b, i.e., the cutoff frequency ω1 in the frequency domain setting unit 56d, is set to a mechanical resonance frequency ω r Therefore, the steering frequency f is lower than the resonant frequency ω r Or, the resonant frequency ω r When the frequency range setting unit 56d is in the vicinity of m2R ,T m2L This makes it easier to reduce the steering frequency f to the resonant frequency ω r , or the resonant frequency ω r When the steering frequency f is in the vicinity of the resonance frequency ω r When the frequency range setting unit 56d is set to 1, the correction interference torque T m2R ,T m2L Without attenuating the correction torque T f1 ,T f2 This makes it easy to include the steering frequency f in the resonant frequency ω rWhen the steering frequency f is sufficiently lower than f, the control executed by the first model following control unit 63 and the second model following control unit 68 is likely to be the cooperative control CT1. In this embodiment, the first model following control unit 63 and the second model following control unit 68 execute almost complete non-interference control CT2 when the steering frequency f is 10 Hz or more and 50 Hz or less, and execute cooperative control CT1 when the steering frequency f is 5 Hz or less. In this embodiment, the first model following control unit 63 and the second model following control unit 68 mainly execute cooperative control CT1 and partially execute non-interference control CT2 to perform control to compensate for the effects of friction and torque ripple. Note that even in the cooperative control CT1, the torque ripple and friction of each steered side motor are compensated for by the model following control.

[0177] Each functional block in the first steering side control unit 51, the second steering side control unit 52, the first turning side control unit 53, and the second turning side control unit 54 described above may be implemented in each processor provided in each control unit as software such as firmware, may be implemented in each processor as hardware, or may be implemented in each processor as software and hardware. The processing of each functional block in the processor provided in each control unit is typically described in a computer program in software module units and stored in a ROM (not shown). However, when using an FPGA or the like, all or part of these functional blocks may be implemented as a hardware accelerator. In addition, the control method of the control device 50 in the above-mentioned embodiment may be implemented in a computer and performed by causing the computer to execute a desired operation.

[0178] <Second embodiment> In the following description, the same configurations as those in the above-mentioned embodiment may be appropriately denoted by the same reference numerals and description thereof may be omitted. As shown in Fig. 17, unlike the steering device 100 in the first embodiment, the steering device 200 in this embodiment does not include the second steering-side motor 32, the second turning-side motor 34, the second rotation sensor 84, and the second battery 85b. In other words, the steering device 200 includes only one each of the steering-side motor, the turning-side motor, the rotation sensor, and the battery.

[0179] Unlike the steering mechanism 20 in the first embodiment, the steering mechanism 220 of this embodiment does not have the second transmission mechanism 25b. In the steering mechanism 220 of this embodiment, the second transmission mechanism 25a is connected to the central part of the rack shaft 23c in the vehicle width direction. The other configurations of the steering mechanism 220 are similar to the other configurations of the steering mechanism 20 in the first embodiment.

[0180] The control device 250 of this embodiment is different from the control device 50 of the first embodiment in that it does not include the second steering side control unit 52 and the second turning side control unit 54. That is, the control device 250 includes only one steering side control unit and one turning side control unit. The first steering side control unit 51 of the control device 250 of this embodiment executes control similar to the control performed by the first steering side control unit 51 and the second steering side control unit 52 in the first embodiment. The first turning side control unit 53 of the control device 250 of this embodiment executes control similar to the control performed by the first turning side control unit 53 and the second turning side control unit 54 in the first embodiment. In the control device 250 of this embodiment, the first model following control unit 63 of the first turning side control unit 53 is configured so that the transfer function of the control object is constrained to the transfer function of the nominal model in a frequency band in which the gain in the gain characteristic of the complementary sensitivity function for the modeling error between the control object including the first turning side motor 33 and the nominal model based on the configuration of the control object is approximately 1. Therefore, as described in the first embodiment, by appropriately setting the nominal model, the controlled object can be treated as a desired model. This makes it possible to suitably adjust the responsiveness of each steered wheel to the steering of the steering wheel 11. Therefore, the steering performance of the steering device 200 can be improved.

[0181] Other configurations of the control device 250 are similar to the other configurations of the control device 50 in the first embodiment. Other configurations of the steering device 200 are similar to the other configurations of the steering device 100 in the first embodiment.

[0182] The present invention is not limited to the above-described embodiment, and other configurations and methods may be adopted within the scope of the technical idea of ​​the present invention. The first nominal model may have any transfer function as long as it is a model based on the configuration of the first controlled object. The second nominal model may have any transfer function as long as it is a model based on the configuration of the second controlled object. The transfer function of the first nominal model is the above-described function F naThe transfer function of the second nominal model may be the transfer function obtained by multiplying (s) by another function. nb It may be a transfer function in which (s) is multiplied by another function. The first control object is not particularly limited as long as it includes a first turning-side motor. The second control object is not particularly limited as long as it includes a second turning-side motor. The first control object and the second control object may each include at least a part of the vehicle body. In this case, the body rigidity of the vehicle and the like can be more suitably compensated for. Only one turning-side motor and one turning-side control unit may be provided.

[0183] The present technology can be configured as follows. (1) A control device mounted on a steer-by-wire steering device mounted on a vehicle, the control device comprising: a steering mechanism having a steering wheel steered by a driver, a steering mechanism having a first steerable wheel and a second steerable wheel, and a steering side motor that drives the steering mechanism, the control device further comprising a steering side control unit that controls a control object including the steering side motor, the steering side control unit having a model following control unit that generates a correction torque that corrects an input torque input to the control object based on an output of the control object and a nominal model that is based on a configuration of the control object, the model following control unit being configured so that a transfer function of the control object is constrained to a transfer function of the nominal model in a frequency band where a gain in a gain characteristic of a complementary sensitivity function for a modeling error between the control object and the nominal model is approximately 1. (2) The control device according to (1), wherein the transfer function of the nominal model is a transfer function corresponding to a target value of mechanical compliance which is a ratio of an output angle of the steered-side motor to the input torque. (3) The turning-side motor includes a first turning-side motor and a second turning-side motor, the turning-side control unit includes a first turning-side control unit that controls a first controlled object including the first turning-side motor, and a second turning-side control unit that controls a second controlled object including the second turning-side motor, a first interference torque caused by the first turning-side motor driving the turning mechanism is applied to the second controlled object, and a second interference torque caused by the second turning-side motor driving the turning mechanism is applied to the first controlled object, the first turning-side control unit has a first model following control unit that generates a correction torque for correcting a first input torque input to the first controlled object based on an output of the first controlled object and a first nominal model based on a configuration of the first controlled object, and the second turning-side control unit generates a correction torque for correcting a first input torque input to the second controlled object based on an output of the first controlled object and a first nominal model based on a configuration of the first controlled object. 13. The control device according to claim 1, further comprising: a second model following control unit that generates a correction torque for correcting two input torques based on an output of the second controlled object and a second nominal model based on a configuration of the second controlled object, wherein the first model following control unit is configured such that a transfer function of the first controlled object is constrained to a transfer function of the first nominal model in a frequency band where a gain in a gain characteristic of a complementary sensitivity function for a modeling error between the first controlled object and the first nominal model is approximately 1, and the second model following control unit is configured such that the transfer function of the second controlled object is constrained to a transfer function of the second nominal model in a frequency band where a gain in a gain characteristic of a complementary sensitivity function for a modeling error between the second controlled object and the second nominal model is approximately 1. (4) A control device mounted on a steer-by-wire type steering device mounted on a vehicle, the steering device comprising a steering mechanism having a steering wheel steered by a driver, a steering mechanism having a first steered wheel and a second steered wheel, and a first turning-side motor and a second turning-side motor that drive the steering mechanism, the control device comprising a first turning-side control unit that controls a first controlled object including the first turning-side motor, and a second turning-side control unit that controls a second controlled object including the second turning-side motor, and a first interference torque caused by the first turning-side motor driving the steering mechanism is applied to the second controlled object. , a second interference torque caused by the second turning-side motor driving the turning mechanism is applied to the first controlled object, the first turning-side control unit compensates for the second interference torque by model following control that constrains a transfer function of the first controlled object to a transfer function of a first nominal model based on a configuration of the first controlled object, and the second turning-side control unit compensates for the first interference torque by model following control that constrains a transfer function of the second controlled object to a transfer function of a second nominal model based on a configuration of the second controlled object. (5) The control device described in (3) or (4), wherein the transfer function of the first nominal model is a transfer function equivalent to a target value of mechanical compliance which is a ratio of an output angle of the first turning side motor to the first input torque, and the transfer function of the second nominal model is a transfer function equivalent to a target value of mechanical compliance which is a ratio of an output angle of the second turning side motor to the second input torque. (6) The control device according to (5), wherein the first controlled object includes the first steered wheel, and the second controlled object includes the second steered wheel. (7) The control device according to (6), wherein each of the first controlled object and the second controlled object includes at least one bush provided in the steering mechanism. (8) The transfer function of the first nominal model is the function F na The control device according to (7) above, comprising at least (s).

number

number

[0184] The configurations and methods described in this specification can be combined as appropriate within the scope of not being mutually inconsistent. [Explanation of symbols]

[0185] 10... steering mechanism, 11... handle, 20, 220... steering mechanism, 21... first steered wheel, 22... second steered wheel, 23d, 23e, 41a, 42a... bushing, 31... first steering side motor, 32... second steering side motor, 33... first steering side motor, 34... second steering side motor, 35b, 35c... stator, 36... coil, 37... coil group, 50, 250... control device, 51... first steering side control unit, 52... second steering side control unit, 53... first steering side control unit, 54... second steering side Control unit, 56a, 56b... cooperative control unit, 57a, 57b... steering reaction force control unit, 58, 59... inverter circuit, 63... first model following control unit, 65a... first control object, 65b... second control object, 68... second model following control unit, 100, 200... steering device, CT1... cooperative control (first control), CT2... non-interference control (second control), f... steering frequency, J... center axis, NM1... first nominal model, NM2... second nominal model, T f1 ,T f2 …corrected torque, T m1 ,T m2 ,T m2L ,T m2R … Correction interference torque, T r1 …First input torque, T r2 …Second input torque, θ h …Steering angle, θ s …output angle, ω1…cutoff frequency, ω r …resonant frequency

Claims

1. A control device is provided for a steer-by-wire steering device mounted on a vehicle, the control device comprising: a steering mechanism having a steering wheel steered by a driver; a steering mechanism having a first steered wheel and a second steered wheel; and a steering-side motor that drives the steering mechanism, the control device comprising: A steering-side control unit that controls a control target including the steering-side motor, the steering-side control unit has a model following control unit that generates a correction torque for correcting an input torque input to the controlled object based on an output of the controlled object and a nominal model based on a configuration of the controlled object, the model following control unit is configured to constrain a transfer function of the control object to a transfer function of the nominal model in a frequency band in which a gain in a gain characteristic of a complementary sensitivity function with respect to a modeling error between the control object and the nominal model is approximately 1.

2. 2. The control device according to claim 1, wherein the transfer function of the nominal model is a transfer function that corresponds to a target value of mechanical compliance that is a ratio of an output angle of the steered-side motor to the input torque.

3. The steering side motor is A first steering side motor; A second steering side motor; Including, The steering side control unit is a first turning side control unit that controls a first controlled object including the first turning side motor; a second turning side control unit that controls a second controlled object including the second turning side motor; Including, a first interference torque caused by the first turning-side motor driving the turning mechanism is applied to the second control object, a second interference torque caused by the second turning-side motor driving the turning mechanism is applied to the first controlled object, the first steering-side control unit has a first model following control unit that generates a correction torque for correcting a first input torque input to the first controlled object, based on an output of the first controlled object and a first nominal model based on a configuration of the first controlled object, the second steering side control unit has a second model following control unit that generates a correction torque for correcting a second input torque input to the second controlled object, based on an output of the second controlled object and a second nominal model based on a configuration of the second controlled object, the first model following control unit is configured such that a transfer function of the first controlled object is constrained to a transfer function of the first nominal model in a frequency band in which a gain in a gain characteristic of a complementary sensitivity function with respect to a modeling error between the first controlled object and the first nominal model is approximately 1; 2. The control device according to claim 1, wherein the second model following control unit is configured such that a transfer function of the second controlled object is constrained to a transfer function of the second nominal model in a frequency band in which a gain in a gain characteristic of a complementary sensitivity function with respect to a modeling error between the second controlled object and the second nominal model is approximately 1.

4. The steering side motor is A first steering side motor; A second steering side motor; Including, The steering side control unit is a first turning side control unit that controls a first controlled object including the first turning side motor; a second turning side control unit that controls a second controlled object including the second turning side motor; Including, a first interference torque caused by the first turning-side motor driving the turning mechanism is applied to the second control object, a second interference torque caused by the second turning-side motor driving the turning mechanism is applied to the first controlled object, the first steering side control unit compensates for the second interference torque by model following control that constrains a transfer function of the first controlled object to a transfer function of a first nominal model based on a configuration of the first controlled object, 2. The control device according to claim 1, wherein the second steering side control unit compensates for the first interference torque by model following control that constrains a transfer function of the second controlled object to a transfer function of a second nominal model based on a configuration of the second controlled object.

5. a transfer function of the first nominal model is a transfer function corresponding to a target value of mechanical compliance which is a ratio of an output angle of the first turning-side motor to the first input torque, 4. The control device according to claim 3, wherein the transfer function of the second nominal model is a transfer function that corresponds to a target value of mechanical compliance that is a ratio of an output angle of the second turning-side motor to the second input torque.

6. the first controlled object includes the first steered wheel, The control device according to claim 5 , wherein the second controlled object includes the second steered wheel.

7. The control device according to claim 6 , wherein each of the first controlled object and the second controlled object includes at least one bush provided in the steering mechanism.

8. The transfer function of the first nominal model is a function F expressed by the following equation: ｎａ The control device of claim 7 comprising at least (s). [0010] where s is the Laplace transform and J ｍ１ is a parameter corresponding to the moment of inertia of the first steering side motor, and B ｍ１ is a parameter corresponding to the viscous friction coefficient of the first steering side motor, and J Ｔｙｒｅ１ is a parameter corresponding to the moment of inertia of the first steered wheel, and B Ｔｙｒｅ１ is a parameter corresponding to the viscous friction coefficient of the first steered wheel, and K Ｂｕｓｈ１ is a parameter corresponding to an equivalent spring constant of an elastic element including the bush in the first controlled object, and G １ is a parameter corresponding to the gear ratio from the first turning side motor to the first turning wheel.

9. The control device according to claim 7 , wherein the transfer function of the second nominal model includes at least a function Fnb(s) expressed by the following equation: [0025] where s is the Laplace transform and J ｍ２ is a parameter corresponding to the moment of inertia of the second steering side motor, and B ｍ２ is a parameter corresponding to the viscous friction coefficient of the second steering side motor, and J Ｔｙｒｅ２ is a parameter corresponding to the moment of inertia of the second steered wheel, and B Ｔｙｒｅ２ is a parameter corresponding to the viscous friction coefficient of the second steered wheel, and K Ｂｕｓｈ２ is a parameter corresponding to an equivalent spring constant of an elastic element including the bush in the second control object, and G ２ is a parameter corresponding to the gear ratio from the second turning side motor to the second turning wheel.

10. a steering reaction force control unit for controlling a steering reaction force transmitted to the steering wheel through the steering wheel, the first model following control unit calculates a first estimate value including the second interference torque based on a difference between a torque calculated using the first nominal model based on an output of the first controlled object and the first input torque; the second model following control unit calculates a second estimate value including the first interference torque based on a difference between a torque calculated using the second nominal model based on an output of the second controlled object and the second input torque, The control device according to claim 6 , wherein the steering reaction force control unit controls the reaction force transmitted to the steerer based on a sum of the first estimated value and the second estimated value.

11. The control device according to claim 6 , wherein the first control object and the second control object each include at least a part of a vehicle body.

12. a cooperative control unit that generates a correction interference torque based on a value output from the first model following control unit and a value output from the second model following control unit, 4. The control device according to claim 3, wherein the first model following control unit and the second model following control unit are capable of executing a first control in which the correction interference torque is included in the correction torque and a second control in which an effect of the correction interference torque on the correction torque is smaller than that of the first control.

13. The first control and the second control are switched based on a steering frequency that is a frequency of a steering angle that changes when the steering wheel is steered, The control device according to claim 12, wherein the steering frequency when the second control is executed is higher than the steering frequency when the first control is executed.

14. 14. The control device according to claim 13, wherein the cooperative control unit generates, as the corrected interference torque, a value obtained by performing low-pass filtering on half of a difference between an estimated value output from the first model following control unit and including a self-aligning torque generated at the first steered wheel and an estimated value output from the second model following control unit and including a self-aligning torque generated at the second steered wheel.

15. The control device according to claim 14, wherein a cutoff frequency in the low-pass filter processing is lower than a mechanical resonance frequency in the steering device.

16. A steer-by-wire steering device, A steering mechanism having a handle operated by a driver; A steering mechanism having a first steered wheel and a second steered wheel; a first steering side motor and a second steering side motor that drive the steering mechanism; A control device according to any one of claims 3 to 15; A steering device comprising:

17. the stator in the first turning-side motor has a plurality of coil groups, 17. The steering device according to claim 16, wherein in the first steered-side motor, the coil groups of different systems are arranged rotationally symmetrically about a central axis of the first steered-side motor.

18. 18. The steering device according to claim 17, wherein the first turning-side control section has a plurality of inverter circuits that independently supply power to the coil groups of the plurality of systems in the first turning-side motor.

19. the stator in the second turning-side motor has a plurality of coil groups, In the second turning-side motor, the coil groups of different systems are arranged rotationally symmetrically about a central axis of the second turning-side motor, 19. The steering device according to claim 18, wherein the second turning-side control section has a plurality of inverter circuits that independently supply power to the coil groups of the plurality of systems in the second turning-side motor.

20. a first steering-side motor and a second steering-side motor capable of driving the steering mechanism, The control device includes: A first steering side control unit that controls the first steering side motor; A second steering side control unit that controls the second steering side motor; having The first steering side control unit and the first turning side control unit are capable of communicating with each other, The steering device according to claim 16, wherein the second steering side control unit and the second turning side control unit are capable of communicating with each other.

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