Steering control method and steering device

Abstract

In the steering control method of the present invention, the current state of the vehicle, i.e., the current state (S1), is detected, a target value of the state of the vehicle, i.e., the target state (S2), is set, and based on the deviation between the current state and the target state, a first steering command value and a second steering command value with a time difference are calculated, which are used as steering command values ​​(S3 to S5) for driving a steering mechanism for steering the steering wheel of the vehicle, a first steering motor driving the steering mechanism is driven based on the first steering command value, and a second steering motor driving the steering mechanism is driven based on the second steering command value (S7).

Description

Technical Field

[0001] The invention relates to a steering control method and a steering device. Background Art

[0002] Patent Document 1 listed below describes a steering device that calculates a steering angle command value by multiplying a deviation between a target steering angle and an actual steering angle by a predetermined gain, and drives a steering motor based on the steering angle command value.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-177943

[0006] Problems to be solved by the invention

[0007] However, if a steering command value is generated based on a deviation between a target state, i.e., a target vehicle state, and an actual current state, i.e., a current state, and the steering motor is driven with the generated steering command value, the steering motor may vibrate due to a transient response of the steering command value to a change in the target state or the current state. Summary of the invention

[0008] An object of the present invention is to suppress vibration of a steering motor when generating a steering command value based on a deviation between a target state that is a target of vehicle states and a current state that is an actual current state and driving the steering motor with the generated steering command value.

[0009] In a steering control method of one embodiment of the present invention, the current state of the vehicle, i.e., the current state, is detected, a target value of the state of the vehicle, i.e., the target state, is set, and a first steering command value and a second steering command value with a time difference are calculated based on a deviation between the current state and the target state. These steering command values ​​are used as steering command values ​​for driving a steering mechanism for steering a steering wheel of the vehicle, and a first steering motor driving the steering mechanism is driven based on the first steering command value, and a second steering motor driving the steering mechanism is driven based on the second steering command value.

[0010] Effects of the Invention

[0011] According to the present invention, when a steering command value is generated based on a deviation between a target state and an actual current state of the vehicle and a steering motor is driven with the generated steering command value, vibration of the steering motor can be suppressed.

[0012] The objects and advantages of the present invention will be embodied and realized by utilizing the elements and combinations thereof shown in the scope of the claims. The above general description and the following detailed description are only examples and illustrations and should not be understood as limiting the present invention as the scope of the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic configuration diagram schematically showing an example of a steering device according to an embodiment.

[0014] Figure 2 This is a block diagram showing an example of the functional configuration of the motor control unit according to the first embodiment.

[0015] Figure 3A This is a timing chart of an example of the first steering command value and the second steering command value without providing a time difference.

[0016] Figure 3B This is a timing chart showing an example of the first steering command value and the second steering command value in which the time difference is set.

[0017] Figure 3C yes Figure 3B Magnified image of .

[0018] Figure 4 This is a flowchart of an example of the steering control method according to the first embodiment.

[0019] Figure 5 This is a block diagram showing an example of the functional configuration of the motor control unit according to the second embodiment.

[0020] Figure 6 This is a block diagram showing an example of a functional configuration of a motor control unit according to a modification of the second embodiment. DETAILED DESCRIPTION

[0021] (First Embodiment)

[0022] (constitute)

[0023] Hereinafter, an example of a case where the steering device of the present invention is applied to an electric power steering system will be described, but the present invention is not limited to the electric power steering system. The present invention can be widely applied to a steering device that generates a steering command value based on a deviation between a target state, i.e., a vehicle state, and an actual current state, i.e., a current state, and drives a steering motor with the generated steering command value. For example, the steering device of the present invention can be applied to a steer-by-wire system in which a steering wheel and a steering wheel can be mechanically separated.

[0024] Figure 1 It is a schematic diagram showing an example of the structure of an electric power steering system 1 to which the steering device according to the present embodiment is applied.

[0025] In the electric power steering system 1, the host control unit 101 sets the control mode of the electric power steering system 1. The host control unit 101 outputs a control mode signal Smode indicating the control mode.

[0026] As a control mode of the electric power steering system 1 , there is a normal control mode in which the electric motors 18 a and 18 b generate a steering assist force corresponding to the steering torque Td applied to the steering shaft 6 and apply the steering assist force to the steering shaft.

[0027] In addition, for example, the control mode of the electric power steering system 1 may also include: automatic driving control for enabling the vehicle to drive autonomously based on the vehicle's surrounding environment and the vehicle's driving state, automatic parking control for moving from the current position to the target parking position, emergency avoidance control for avoiding obstacles in the direction of travel, and lane departure prevention control (lane keeping control) for preventing the vehicle from deviating from the driving lane.

[0028] When the control mode is automatic driving control, automatic parking control, emergency avoidance control, or lane departure prevention control, the host control unit 101 calculates and outputs a target steering angle θad which is a target value of the steering angle of the steered wheels 3 .

[0029] For example, in the automatic driving control, the upper control unit 101 sets a target driving trajectory as a trajectory for driving the vehicle based on the surrounding environment of the vehicle and the driving state of the vehicle, and calculates a steering angle for driving the vehicle along the target driving trajectory as the target steering angle θad. Specifically, for example, the lane dividing lines (lane markings) on the left and right sides of the road in front of the vehicle are detected, and the target driving trajectory passing through a predetermined position in the lane width direction relative to the detected lane dividing lines is calculated, and the steering angle for driving the vehicle along the calculated target driving trajectory is calculated as the target steering angle θad.

[0030] In addition, for example, in automatic parking control, the upper control unit 101 sets a target driving trajectory for moving the vehicle to the parking target position based on the relative position relationship between the current position of the vehicle and the parking target position, and calculates the steering angle used to make the vehicle travel along the target driving trajectory as the target steering angle θad.

[0031] In addition, for example, in emergency avoidance control, the host control unit 101 calculates a steering angle for avoiding an obstacle in the vehicle's traveling direction as the target steering angle θad. In addition, for example, in lane departure prevention control, the host control unit 101 calculates a steering angle for preventing the vehicle from departing from the driving lane as the target steering angle θad.

[0032] The selection of the control mode in the upper control unit 101 can also be performed by the driver selecting a selection switch (not shown) connected to the upper control unit 101. Alternatively, a sensor for detecting the distance to an obstacle in front of the vehicle can be provided, and when an obstacle is detected within a specified distance in the direction of travel of the vehicle during automatic driving control, the automatic driving control can be automatically changed to emergency avoidance control, etc., and the selection can be made according to the vehicle condition. In addition, when the position of the vehicle is in a parking lot and the speed is below a specified speed suitable for parking, etc., the automatic parking control can be automatically started according to the vehicle condition, and the selection can be automatically made according to the position of the vehicle and the vehicle condition. As described above, the method for selecting the control mode in the upper control unit 101 can be appropriately changed.

[0033] The target steering angle θad and the control mode signal Smode generated by the host control unit 101 are provided to the motor control unit 102 via, for example, an in-vehicle network.

[0034] The steering shaft 6 includes an input shaft 8 connected to the steering wheel 2 and an output shaft 9 connected to the intermediate shaft 7. The input shaft 8 and the output shaft 9 are connected to each other via a torsion bar 10 so as to be relatively rotatable. A torque sensor 12 is arranged near the torsion bar 10. The torque sensor 12 detects the steering torque (actual steering torque) Td applied to the steering wheel 2 as the current state of the vehicle, i.e., the current state, based on the relative rotation displacement of the input shaft 8 and the output shaft 9 (i.e., the twisting amount of the torsion bar). The actual steering torque Td is an example of the "current steering torque" described in the scope of the claim.

[0035] In the present embodiment, the actual steering torque Td detects, for example, a torque for left-hand steering as a positive value and a torque for right-hand steering as a negative value. The larger the absolute value, the larger the magnitude of the actual steering torque Td.

[0036] The steering mechanism 4 includes a rack-and-pinion mechanism including a pinion shaft 13 and a rack shaft 14 as a steering shaft. The steered wheels 3 are connected to each end of the rack shaft 14 via a steering tie rod 15 and a knuckle arm (not shown). The pinion shaft 13 is connected to the intermediate shaft 7. The pinion shaft 13 rotates in conjunction with the steering of the steering wheel 2. A pinion 16 is connected to the front end of the pinion shaft 13.

[0037] The rack shaft 14 extends linearly along the left-right direction of the vehicle. A rack 17 meshing with the pinion 16 is formed in the axial middle portion of the rack shaft 14. The rotational motion of the pinion shaft 13 is converted into the axial linear motion of the rack shaft 14 by the pinion 16 and the rack 17. By moving the rack shaft 14 in the axial direction, the steering wheel 3 can be steered. When the steering wheel 2 is steered (rotated), the rotation is transmitted to the pinion shaft 13 via the steering shaft 6 and the intermediate shaft 7. Moreover, the rotation of the pinion shaft 13 is converted into the axial movement of the rack shaft 14 by the pinion 16 and the rack 17. As a result, the steering wheel 3 is steered.

[0038] The steering assist mechanism 5 includes a first motor 18a and a second motor 18b for generating a steering assist force (assist torque), and a first speed reducer 19a and a second speed reducer 19b for amplifying (amplifying) the output torque of the first motor 18a and the second motor 18b and transmitting the amplified output torque to the steering mechanism 4.

[0039] The first reducer 19a has a worm gear mechanism including a worm gear 20a and a worm wheel 21a meshing with the worm gear 20a. The first reducer 19a is housed in a gear box 22a as a transmission mechanism housing. Hereinafter, the reduction ratio (gear ratio) of the first reducer 19a is sometimes represented by N. The reduction ratio N is defined as the ratio of the angular velocity ωwg of the worm gear 20a to the angular velocity ωww of the worm wheel 21a, ωwg / ωww.

[0040] The second speed reducer 19b has the same structure as the first speed reducer 19a, and has a worm gear mechanism including a worm gear 20b and a worm wheel 21b meshing with the worm gear 20b in a gear case 22b.

[0041] The worm gear 20a of the first speed reducer 19a is driven to rotate by the first motor 18a. In addition, the worm wheel 21a is connected to the output shaft 9 so as to be rotatable as a whole. When the worm gear 20a is driven to rotate by the first motor 18a, the worm wheel 21a is driven to rotate. As a result, the motor torque of the first motor 18a is applied to the steering shaft 6, so that the steering shaft 6 (output shaft 9) rotates.

[0042] On the other hand, the worm gear 20b of the second speed reducer 19b is driven to rotate by the second motor 18b. In addition, the worm wheel 21b is connected to the output shaft 9 so as to be rotatable as a whole. When the worm gear 20b is driven to rotate by the second motor 18b, the worm wheel 21b is driven to rotate. As a result, the motor torque of the second motor 18b is applied to the steering shaft 6, so that the steering shaft 6 (output shaft 9) rotates.

[0043] The rotation of the steering shaft 6 is transmitted to the pinion shaft 13 via the intermediate shaft 7. The rotational motion of the pinion shaft 13 is converted into an axial linear motion of the rack shaft 14. Thus, the steering wheel 3 is steered by the motor torque of the first motor 18a and the second motor 18b. In addition, the steering wheel 2 also rotates with the rotation of the steering shaft 6.

[0044] As described above, the steering mechanism 4 for steering the steered wheels 3 is driven by the motor torque of the first motor 18 a and the second motor 18 b , so that the steered wheels 3 can be steered.

[0045] in addition, Figure 1 The configuration of the first motor 18a and the second motor 18b shown is an example, but the present invention is not limited thereto. For example, the first motor 18a and the second motor 18b may be double-winding motors in which two sets of windings are wound in the same motor housing and a common rotor is rotated. In this case, a single reducer is configured as the first reducer 19a and the second reducer 19b.

[0046] in addition, Figure 1 The electric power steering system of the steering column assist type in which the motor is connected to the steering shaft is exemplified, but the present invention is not limited to the electric power steering system of the steering column assist type. The present invention can also be applied to the electric power steering system of the single pinion assist type and the double pinion assist type in which the motor is connected to the pinion shaft, and the rack assist type in which the motor is arranged on the rack.

[0047] In the case of the double pinion assist system, a second pinion meshing with the rack 17 may be added, one of the first motor 18a and the second motor 18b may be connected to the pinion 16 and the other may be connected to the second pinion.

[0048] The first motor 18 a and the second motor 18 b are provided with rotation angle sensors 23 a and 23 b for detecting the rotation angles of the rotors of the first motor 18 a and the second motor 18 b , respectively.

[0049] The actual steering torque Td detected by the torque sensor 12 and the output signals of the rotation angle sensors 23a and 23b are input to the motor control unit 102. The motor control unit 102 controls the first motor 18a and the second motor 18b based on these input signals and information provided from the host control unit 101 on the vehicle side.

[0050] Specifically, the motor control unit 102 calculates the actual steering angle of the current steering wheel 3 (hereinafter sometimes referred to as "actual steering angle") as the current state of the vehicle, i.e., the current state, based on the output signals of the rotation angle sensors 23a and 23b. The actual steering angle is an example of "current steering angle" described in the scope of the claims. In addition, the motor control unit 102 obtains the actual steering torque Td detected by the torque sensor 12 as the current state.

[0051] Furthermore, the motor control unit 102 obtains the target steering angle θad provided from the upper control unit 101 as the target value of the state of the vehicle, i.e., the target state. In addition, the steering torque target value, i.e., the target steering torque, is set. In addition, since the first motor 18a and the second motor 18b are mechanically connected via the first reducer 19a, the output shaft 9, and the second reducer 19b, the steering angle detected by the motor control unit 102 based on the output signals of the rotation angle sensor 23a and the rotation angle sensor 23b is substantially the same value. Therefore, it is also possible to omit any one of the rotation angle sensor 23a and the rotation angle sensor 23b and use only the other.

[0052] The motor control unit 102 causes the first motor 18 a and the second motor 18 b to generate and distribute the total torque required to drive a steering mechanism for steering the steered wheels 3 based on the deviation between the current state and the target state.

[0053] The motor control unit 102 can cause the first motor 18a and the second motor 18b to generate the first steering command value i1 and the second steering command value i2 of torque through at least one of proportional control (P control), integral control (I control), and differential control (D control) of the deviation between the current state and the target state.

[0054] In addition, the overall torque required for driving the steering mechanism may be distributed between the first steering command value i1 and the second steering command value i2 in a ratio of, for example, 50:50 (i.e., making the first steering command value i1 equal to the second steering command value i2), or one of them may be larger than the other.

[0055] The motor control unit 102 drives the first motor 18 a based on the first steering command value i1 , and drives the second motor 18 b based on the second steering command value i2 .

[0056] At this time, when the target state or the current state changes, vibration may occur in the first motor 18a and the second motor 18b. For example, when the gain in the P control, I control, and D control is large, when the target state or the current state changes, the first steering command value i1 and the second steering command value i2 become larger, and thus vibration may occur in the transient response of the first steering command value i1 and the second steering command value i2 to the change in the target state or the current state, and vibration may occur in the first motor 18a and the second motor 18b.

[0057] On the other hand, if a small gain is set to suppress such vibration, the ability of the current state to follow the target state will be reduced.

[0058] Furthermore, even when the target state or the current state has changed significantly, the above-mentioned vibration may occur regardless of the magnitude of the gain.

[0059] Therefore, the motor control unit 102 of the present invention sets a time difference between the first steering command value i1 and the second steering command value i2. That is, the motor control unit 102 generates the first steering command value i1 and the second steering command value i2 with a time difference. For example, one of the second steering command value i2 and the first steering command value i1 is output with a delay relative to the other.

[0060] In this way, when the time difference is set between the first steering command value i1 and the second steering command value i2, the generation of a part of the torque can be delayed compared to the case where the time difference is not set (that is, the case where the entire torque for driving the steering mechanism is generated simultaneously according to the change in the deviation between the current state and the target state). As a result, a phenomenon similar to the delay caused by the viscous resistance can be reproduced, so that the vibration generated by the transient response of the first steering command value i1 and the second steering command value i2 can be attenuated by the viscous resistance.

[0061] As a result, the vibrations of the first steering command value i1 and the second steering command value i2 can be converged at an early stage, and the vibrations generated in the first electric motor 18 a and the second electric motor 18 b can be suppressed.

[0062] Hereinafter, the motor control unit 102 will be described in detail. Figure 2 1 is a block diagram of an example of the functional structure of the motor control unit 102 of the first embodiment. As described above, the steering angles detected by the motor control unit 102 based on the output signals of the rotation angle sensor 23a and the rotation angle sensor 23b are substantially the same. Figure 2 In the block diagram of FIG. 1 , the rotation angle sensor is only the rotation angle sensor 23a.

[0063] The rotation angle calculation unit 110 calculates the rotor rotation angle θma of the first motor 18a based on the output signal of the rotation angle sensor 23a. The reduction ratio division unit 111 converts the rotor rotation angle θma into the rotation angle (actual steering angle) θa of the output shaft 9 by dividing the rotor rotation angle θma calculated by the rotation angle calculation unit 110 by the reduction ratio N. The actual steering angle θa calculated by the reduction ratio division unit 111 is provided to the subtractor 112.

[0064] The subtractor 112 calculates a deviation (steering angle deviation) Δθ=(θad−θa) of the actual steering angle θa from the target steering angle θad supplied from the host control unit 101 , and outputs the deviation to the third steering command value calculation unit 113 .

[0065] The third steering command value calculation unit 113 calculates a third steering command value i3 as a steering command value for driving the steering mechanism 4 by at least one of P control, I control, and D control for the steering angle deviation Δθ. The third steering command value calculation unit 113 outputs the third steering command value i3 to the command value setting unit 117.

[0066] On the other hand, the target state setting unit 114 sets the target steering torque Te. For example, the target state setting unit 114 may set the target steering torque Te according to the lateral acceleration generated by the vehicle. For example, the target state setting unit 114 may set the target steering torque Te to a larger value as the lateral acceleration increases, so that the steering torque required for steering becomes larger as the lateral acceleration increases.

[0067] The subtractor 115 calculates a deviation (steering torque deviation) ΔT=(Te−Td) of the actual steering torque Td from the target steering torque Te set by the target state setting unit 114 , and outputs the deviation to the fourth steering command value calculation unit 116 .

[0068] The fourth steering command value calculation unit 116 calculates a fourth steering command value i4 as a steering command value for driving the steering mechanism 4 by performing at least one of P control, I control, and D control on the steering torque deviation ΔT. The fourth steering command value calculation unit 116 outputs the fourth steering command value i4 to the command value setting unit 117 .

[0069] The command value setting unit 117 sets a basic steering command value i0 based on the third steering command value i3 and the fourth steering command value i4. The basic steering command value i0 is a steering command value that causes the electric motor to generate torque that maintains the overall driving force applied to the steering mechanism 4.

[0070] For example, the command value setting unit 117 may set either the third steering command value i3 or the fourth steering command value i4 as the basic steering command value i0 based on the control mode signal Smode. For example, when the control mode indicated by the control mode signal Smode is any one of the automatic driving control, the automatic parking control, the emergency avoidance control, and the lane departure prevention control, the third steering command value i3 may be set as the basic steering command value i0, and when the control mode is the normal control mode, the fourth steering command value i4 may be set as the basic steering command value i0.

[0071] In addition, for example, the command value setting unit 117 may set the basic steering command value i0 based on the sum of the third steering command value i3 and the fourth steering command value i4. For example, the command value setting unit 117 may set the basic steering command value i0 as the average value and the weighted sum of the third steering command value i3 and the fourth steering command value i4.

[0072] The distributor 118 distributes the basic steering command value i0 set by the command value setting unit 117 into a first steering command value i1 and a second steering command value i2 having a time difference therebetween, and outputs them to the first motor drive circuit 119 and the second motor drive circuit 129 , respectively.

[0073] For example, the allocating unit 118 calculates the first steering command value i1 and the second steering command value i2 by allocating the basic steering command value i0 at a predetermined ratio (e.g., 50:50). Then, one of the first steering command value i1 and the second steering command value i2 is delayed by a predetermined time difference D from the other and is output.

[0074] The first motor drive circuit 119 and the second motor drive circuit 129 supply the motor drive current based on the first steering command value i1 and the motor drive current based on the second steering command value i2 to the first motor 18a and the second motor 18b, respectively, to drive the first motor 18a and the second motor 18b. Thus, the electric power corresponding to the first steering command value i1 and the second steering command value i2 is supplied to the first motor 18a and the second motor 18b, respectively. Thus, the first motor 18a and the second motor 18b are driven by the driving force corresponding to the first steering command value i1 and the second steering command value i2, respectively.

[0075] Figure 3A 1 is a timing chart of an example of a first steering command value i1 and a second steering command value i2 without providing a time difference. Figure 3B 1 is a timing chart of an example of a first steering command value i1 and a second steering command value i2 with a time difference. Figure 3C yes Figure 3BThe solid line represents the first steering command value i1, and the dotted line represents the second steering command value i2.

[0076] exist Figure 3A to Figure 3C In this example, the second steering command value i2 is a command value having the same waveform as the first steering command value i1. Figure 3A In , because no time difference is set, the waveforms completely overlap (match). On the other hand, in Figure 3B , Figure 3C In the example, since the time difference is set, the second steering command value i2 is delayed by the time difference D from the first steering command value i1.

[0077] according to Figure 3A It can be seen that when the time difference is not set, the first steering command value i1 and the second steering command value i2 require time for the vibration to converge. Figure 3B and Figure 3C It can be seen that the vibrations of the first steering command value i1 and the second steering command value i2 converge earlier when the time difference is provided.

[0078] In addition, the time difference between the first steering command value i1 and the second steering command value i2 is preferably a phase difference between the first steering command value i1 and the second steering command value i2 greater than 0 [deg] and less than 90 [deg]. The reason is as follows.

[0079] As described above, the convergence of the vibration of the first steering command value i1 and the second steering command value i2 is caused by the viscous resistance, which is a differential term proportional to the speed. In addition, since the signal phase advances by 90 [deg] through differentiation, when the phase of one of the first steering command value i1 and the second steering command value i2 is advanced by 90 [deg] compared with the phase of the other, the command value of one becomes the differential term of the command value of the other. Therefore, when the phase difference between the first steering command value i1 and the second steering command value i2 becomes 90 [deg], the components of the command value of the one whose phase advances by 90 [deg] all become viscous resistance components, so the effect of viscous resistance is the largest.

[0080] Therefore, even if the time difference D is further increased, the effect of the viscous resistance will not increase, and the disadvantage caused by the control delay will increase. Thus, it is preferable that the phase difference between the first steering command value i1 and the second steering command value i2 is greater than 0 [deg] and less than 90 [deg].

[0081] Therefore, the time difference D may be set to be greater than 0 and less than a quarter of the vibration period generated in the transient response to the change of the first steering command value i1 and the second steering command value i2. For example, the time difference D may be set to be greater than 0 and less than a quarter of the vibration period of the highest frequency that is considered to be generated in the transient response to the change of the first steering command value i1 and the second steering command value i2.

[0082] For example, assuming that the highest frequency vibration considered to be generated in the transient response to the change of the first steering command value i1 and the second steering command value i2 is any one of 20, 30, 50 and 100 [Hz], the time difference D between the first steering command value i1 and the second steering command value i2 can also be set to any one of 12.5, 8.33, 5.00, 2.5 [msec], which is less than the value consistent with the above vibration frequency.

[0083] Figure 4 This is a flowchart of an example of the steering control method according to the first embodiment.

[0084] In step S1, the rotation angle sensor 23a, the rotation angle calculation unit 110, and the speed reduction ratio division unit 111 detect the actual steering angle θa. In addition, the torque sensor 12 detects the actual steering torque Td.

[0085] In step S2, the host control unit 101 sets the target steering angle θad. In addition, the target state setting unit 114 sets the target steering torque Te.

[0086] In step S3 , the third steerage command value calculation unit 113 calculates a third steerage command value i3 based on the steer angle deviation Δθ between the target steer angle θad and the actual steer angle θa.

[0087] In step S4 , the fourth steering command value calculation unit 116 calculates a fourth steering command value i4 based on the steering torque deviation ΔT between the target steering torque Te and the actual steering torque Td.

[0088] In step S5 , the command value setting unit 117 sets the basic steering command value i0 based on the third steering command value i3 and the fourth steering command value i4 .

[0089] In step S6 , the allocating unit 118 allocates the basic steering command value i0 into a first steering command value i1 and a second steering command value i2 having a time difference therebetween.

[0090] In step S7 , the first motor drive circuit 119 and the second motor drive circuit 129 drive the first motor 18 a and the second motor 18 b based on the first steering command value i1 and the second steering command value i2 , respectively.

[0091] (Second Embodiment)

[0092] The motor control unit 102 of the first embodiment calculates a basic steering command value i0 for causing the motor to generate torque that provides the entire driving force applied to the steering mechanism 4, and distributes the basic steering command value i0 into a first steering command value i1 and a second steering command value i2 with a time difference.

[0093] The motor control unit 102 of the second embodiment makes the structure for calculating the steering command value redundant in two systems, and independently calculates the first steering command value i1 and the second steering command value i2 in each system, and outputs the first steering command value i1 and the second steering command value i2 with a time difference to the first motor drive circuit 119 and the second motor drive circuit 112.

[0094] Figure 5 This is a block diagram showing an example of the functional configuration of the motor control unit 102 according to the second embodiment.

[0095] The first system S1 includes a rotation angle calculation unit 110, a reduction ratio division unit 111, a subtractor 112, a third steering command value calculation unit 113, a target state setting unit 114, a subtractor 115, a fourth steering command value calculation unit 116, a command value setting unit 117, a first motor drive circuit 119, a first motor 18a, and a rotation angle sensor 23a.

[0096] The second system S2 also has the same structure as the first system S1, and includes: a rotation angle calculation unit 120, a reduction ratio division unit 121, a subtractor 122, a third steering command value calculation unit 123, a target state setting unit 124, a subtractor 125, a fourth steering command value calculation unit 126, a command value setting unit 127, a second motor drive circuit 129, a second motor 18b, and a rotation angle sensor 23b.

[0097] The rotation angle calculation unit 110, the reduction ratio division unit 111, the subtractor 112, the third steering command value calculation unit 113, the target state setting unit 114, the subtractor 115, the fourth steering command value calculation unit 116, and the command value setting unit 117 of the second embodiment are respectively the same as the rotation angle calculation unit 110, the reduction ratio division unit 111, the subtractor 112, the third steering command value calculation unit 113, the target state setting unit 114, the subtractor 115, the fourth steering command value calculation unit 116, and the command value setting unit 117 of the first embodiment.

[0098] However, the command value setting unit 117 of the second embodiment outputs the first steering command value i1 instead of the basic steering command value i0. That is, the command value setting unit 117 sets the first steering command value i1 based on the third steering command value i3 and the fourth steering command value i4.

[0099] Therefore, the third steering command value calculation unit 113, the fourth steering command value calculation unit 116, and the command value setting unit 117 are changed to calculate the first steering command value i1, which corresponds to the torque generated by the first motor 18a in the total torque of the driving force applied to the steering mechanism 4 (for example, 50% of the total torque).

[0100] In addition, the rotation angle calculation unit 120, the reduction ratio division unit 121, the subtractor 122, the third steering command value calculation unit 123, the target state setting unit 124, the subtractor 125, the fourth steering command value calculation unit 126, and the command value setting unit 127 of the second system S2 are respectively the same as the rotation angle calculation unit 110, the reduction ratio division unit 111, the subtractor 112, the third steering command value calculation unit 113, the target state setting unit 114, the subtractor 115, the fourth steering command value calculation unit 116, and the command value setting unit 117 of the first system S1.

[0101] However, the rotation angle calculation unit 120 of the second system S2 calculates the rotor rotation angle θmb of the second motor 18b based on the output signal of the rotation angle sensor 23b. The reduction ratio division unit 121 converts the rotor rotation angle θmb into the actual steering angle θb by dividing the rotor rotation angle θmb by the reduction ratio N. The subtractor 122 calculates the steering angle deviation Δθ=(θad-θb) of the actual steering angle θb relative to the target steering angle θad.

[0102] Furthermore, the command value setting unit 127 sets the second steering command value i2 based on the third steering command value i3 and the fourth steering command value i4.

[0103] Thus, the third steering command value i3 and the fourth steering command value i4 for setting the first steering command value i1 are calculated by the third steering command value calculation unit 113 and the fourth steering command value calculation unit 116 of the first system S1.

[0104] On the other hand, the third steering command value i3 and the fourth steering command value i4 for setting the second steering command value i2 are calculated by the third steering command value calculation unit 123 and the fourth steering command value calculation unit 126 of the second system S2.

[0105] In a structure in which the first system S1 and the second system S2 independently calculate the first steering command value i1 and the second steering command value i2, respectively, by having a time difference between the moment when the signals of the target steering angle θad and the actual steering torque Td are input into the first system S1 and the moment when they are input into the second system S2, the first steering command value i1 and the second steering command value i2 with a set time difference can be output.

[0106] For example, the motor control unit 102 may be implemented by two electronic control units consisting of a control unit of the first system S1 and a control unit of the second system S2. Furthermore, the control unit of the first system S1 may receive signals of the target steering angle θad, the control mode signal Smode, and the actual steering torque Td from the upper control unit 101 and the torque sensor 12, and the control unit of the second system S2 may receive these signals from the control unit of the first system S1.

[0107] Thus, a time difference can be set between the time when the target steering angle θad and the actual steering torque Td signals are input to the first system S1 and the time when they are input to the second system S2. In addition, in this case, the target steering angle θad, the control mode signal Smode, and the actual steering torque Td signals input to the control unit of the first system S1 are the same, and are signals that differ only in the time of input.

[0108] Figure 6 1 is a block diagram showing an example of the functional structure of the motor control unit 102 of the modified example of the second embodiment. A time difference may be set between the first steering command value i1 and the second steering command value i2 by providing a delay unit after the command value setting unit 117 of the first system S1 or the command value setting unit 127 of the second system S2. Figure 6 In the example of FIG. 1 , a delay unit 130 for delaying the second steering command value i2 is provided after the command value setting unit 127. The delay time of the delay unit 130 may be a fixed value or a variable value corresponding to the vibration frequency of the second steering command value i2 (i.e., the change speed of the second steering command value i2). For example, the delay time may be set to be shorter as the frequency is higher (the change speed is faster).

[0109] (Effects of Embodiments)

[0110] (1) The torque sensor 12, the rotation angle sensor 23a, and the motor control unit 102 detect the current state of the vehicle. The motor control unit 102 sets a target state, which is a target value of the state of the vehicle, and calculates a first steering command value and a second steering command value having a time difference therebetween based on a deviation between the current state and the target state, as steering command values ​​for driving a steering mechanism 4 for steering a steering wheel 3 of the vehicle, and drives the first motor 18a driving the steering mechanism 4 based on the first steering command value, and drives the second motor 18b driving the steering mechanism 4 based on the second steering command value.

[0111] This makes it possible to attenuate vibrations generated by transient responses of the first steering command value and the second steering command value, thereby suppressing vibrations generated in the first electric motor 18 a and the second electric motor 18 b .

[0112] (2) The current state may be the current steering angle of the host vehicle, and the target state may be a target steering angle set as a target value of the steering angle of the host vehicle.

[0113] Thereby, the first electric motor 18a and the second electric motor 18b can be driven so that the actual steering angle of the host vehicle becomes the target steering angle.

[0114] (3) A target driving trajectory may be set as a trajectory for causing the host vehicle to travel, and a steering angle for traveling along the target driving trajectory may be calculated as the target steering angle.

[0115] As a result, the first motor 18 a and the second motor 18 b can be driven so that the host vehicle travels along the target travel trajectory.

[0116] (4) The target steering angle may be calculated as a steering angle for the vehicle to avoid an obstacle in the direction of travel or a steering angle for preventing the vehicle from deviating from the driving lane. Thus, the first motor 18a and the second motor 18b may be driven in such a manner that the vehicle avoids an obstacle in the direction of travel or does not deviate from the driving lane.

[0117] (5) The current steering angle of the vehicle, i.e., the current steering angle, and the current steering torque of the vehicle, i.e., the current steering torque, may be detected as the current state. The motor control unit 102 sets the target value of the steering angle of the vehicle, i.e., the target steering angle, and the target value of the steering torque of the vehicle, i.e., the target steering torque, as the target state, and calculates the first steering command value and the second steering command value based on either the deviation between the current steering angle and the target steering angle or the deviation between the current steering torque and the target steering torque.

[0118] Thus, the first and second motors 18a and 18b can be driven based on either the deviation between the current steering angle and the target steering angle or the deviation between the current steering torque and the target steering torque according to the control mode of the electric power steering system applied to the steering device.

[0119] (6) The current steering angle, which is the current steering angle of the vehicle, and the current steering torque, which is the current steering torque of the vehicle, may be detected as the current state.

[0120] It is also possible to set a target value of the steering angle of the vehicle, i.e., the target steering angle, and a target value of the steering torque of the vehicle, i.e., the target steering torque, as target states, calculate a third steering command value based on a deviation between a current steering angle and the target steering angle, calculate a fourth steering command value based on a deviation between a current steering torque and the target steering torque, and calculate a first steering command value and a second steering command value based on the sum of the third steering command value and the fourth steering command value.

[0121] As a result, the first electric motor 18a and the second electric motor 18b can be driven so as to reduce the deviation between the current steering angle and the target steering angle and the deviation between the current steering torque and the target steering torque.

[0122] (7) The time difference between the first steering command value and the second steering command value may be set to a value greater than 0 and less than a quarter of a period of the highest frequency vibration that is expected to occur in a transient response to a change in the steering command value.

[0123] Thereby, it is possible to provide a time difference suitable for the frequency of vibration of the first steering command value and the second steering command value.

[0124] (8) The motor control unit 102 may set a basic steering command value based on the deviation between the current state and the target state, and distribute the basic steering command value into the first steering command value and the second steering command value at a predetermined ratio. Thus, the first motor 18a and the second motor 18b may generate a torque that provides the overall driving force for the steering mechanism 4.

[0125] (9) The motor control unit 102 may calculate the first steering command value based on the deviation between the current state and the target state, and calculate the second steering command value based on the deviation between the current state and the target state separately from the calculation of the first steering command value.

[0126] Thus, by making the timing of inputting a signal to the electronic circuit that calculates the first steering command value different from the timing of inputting a signal to the electronic circuit that calculates the second steering command value, a time difference can be provided between the first steering command value and the second steering command value.

[0127] All examples and conditional terms recorded herein are intended for educational purposes to help readers understand the present invention and the concepts provided by the inventor for technological progress, and should be interpreted as not being limited to the above examples and conditions specifically recorded, as well as the structures of the examples in this specification related to the superiority and inferiority of the present invention. Although the embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions and modifications may be applied thereto without departing from the spirit and scope of the present invention.

[0128] Explanation of symbols

[0129] 1: Electric power steering system, 2: Steering wheel, 3: Steering wheel, 4: Steering mechanism, 5: Steering auxiliary mechanism, 6: Steering shaft, 7: Intermediate shaft, 8: Input shaft, 9: Output shaft, 10: Torsion bar, 12: Torque sensor, 13: Pinion shaft, 14: Rack shaft, 15: Steering tie rod, 16: Pinion, 17: Rack, 18a: First motor, 18b: Second motor, 19a: First speed reducer, 19b: Second speed reducer, 20a, 20b: Worm gear, 21a, 21b: Worm wheel, 22a, 22b: Gear box, 23a, 23b : Rotation angle sensor, 101: upper control unit, 102: motor control unit, 110, 120: rotation angle calculation unit, 111, 121: reduction ratio division unit, 112, 122: subtractor, 113, 123: third steering command value calculation unit, 114, 124: target state setting unit, 115, 125: subtractor, 116, 126: fourth steering command value calculation unit; 117, 127: command value setting unit, 118: distribution unit, 119: first motor drive circuit, 129: second motor drive circuit, 130: delay unit.

Claims

1. A steering control method, characterized in that: Detect the current state of the vehicle, i.e. the current state, Setting a target value of the vehicle state, i.e., a target state, Based on the deviation between the current state and the target state, a basic steering command value is set; The basic steering command value is distributed at a predetermined ratio to calculate a first steering command value and a second steering command value having a time difference therebetween as steering command values ​​for driving a steering mechanism for steering the steering wheel of the vehicle. A first steering motor for driving the steering mechanism is driven based on the first steering command value, and a second steering motor for driving the steering mechanism is driven based on the second steering command value.

2. The steering control method according to claim 1, characterized in that: The current state is a current steering angle of the vehicle, and the target state is a target steering angle set as a target value of the steering angle of the vehicle.

3. The steering control method according to claim 2, characterized in that: A target travel trajectory is set as a trajectory for causing the vehicle to travel, and a steering angle for traveling along the target travel trajectory is calculated as the target steering angle.

4. The steering control method according to claim 2, characterized in that: The target steering angle is calculated as a steering angle for the vehicle to avoid an obstacle in a traveling direction or a steering angle for preventing the vehicle from deviating from a driving lane.

5. The steering control method according to claim 1, characterized in that: detecting a current steering angle of the vehicle, that is, a current steering angle, and a current steering torque of the vehicle, that is, a current steering torque, as the current state, setting a target steering angle, which is a target value of a steering angle of the vehicle, and a target steering torque, which is a target value of a steering torque of the vehicle, as the target state, The first steering command value and the second steering command value are calculated based on either a deviation between the current steering angle and the target steering angle or a deviation between the current steering torque and the target steering torque.

6. The steering control method according to claim 1, characterized in that: detecting a current steering angle of the vehicle, that is, a current steering angle, and a current steering torque of the vehicle, that is, a current steering torque, as the current state, setting a target steering angle, which is a target value of a steering angle of the vehicle, and a target steering torque, which is a target value of a steering torque of the vehicle, as the target state, calculating a third steering command value based on a deviation between the current steering angle and the target steering angle, calculating a fourth steering command value based on a deviation between the current steering torque and the target steering torque, The first steering command value and the second steering command value are calculated based on the sum of the third steering command value and the fourth steering command value.

7. The steering control method according to any one of claims 1 to 6, characterized in that: The time difference is set to be greater than 0 and less than a quarter of a vibration period of a highest frequency that is considered to be generated in a transient response to a change in the steering command value.

8. The steering control method according to any one of claims 1 to 6, characterized in that: calculating the first steering command value based on the deviation between the current state and the target state, Separately from the calculation of the first steering command value, a second steering command value is calculated based on a deviation between the current state and the target state.

9. A steering device, characterized in that: have: A first steering motor and a second steering motor drive a steering mechanism for steering a steering wheel of the vehicle; A controller that detects a current state of the vehicle, i.e., a current state, sets a target value of the state of the vehicle, i.e., a target state, sets a basic steering command value based on a deviation between the current state and the target state, calculates a first steering command value and a second steering command value with a time difference between them by allocating the basic steering command value at a prescribed ratio as steering command values ​​for driving a steering mechanism of the vehicle, drives the first steering motor based on the first steering command value, and drives the second steering motor based on the second steering command value.

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