Steering system

Abstract

A steering system (10) includes a steering operation shaft (31) in which power transmission to and from a steering wheel (11) is prohibited, and which turns a steering wheel (12) of a vehicle, a steering operation motor (32) that generates a steering operation force, which is a torque applied to the steering operation shaft (31) to turn the steering wheel (12), and a control device that controls the steering operation motor (32). When a rotational position of the steering wheel (11) is different from a rotational position corresponding to a turning position of the steering wheel (12), the control device executes, by the steering operation motor (32), a process for correcting the turning position of the steering wheel (12) to a position corresponding to the rotational position of the steering wheel (11).

Description

TECHNICAL FIELD

[0001] The present application relates to a steering system for a vehicle. BACKGROUND

[0002] There is a steering system called steer-by-wire in which there is no mechanical power transmission between a steering wheel and a steering wheel. The steering system includes a reaction mechanism having a reaction motor that is a source of a steering reaction force applied to a steering shaft, and a steering operation mechanism having a steering operation motor that is a source of a steering operation force for turning a steering wheel. When the vehicle is running, a control device of the steering system generates the steering reaction force by power supply control of the reaction motor, and turns the steering wheel by power supply control of the steering operation motor.

[0003] In the steering system of steer-by-wire, the steering wheel is not restricted by the steering operation mechanism. Therefore, when a certain external force is applied to the steering wheel in the case where the power of the vehicle is turned off, the steering wheel can be rotated. At this time, since the steering wheel is not working, the positional relationship between the steering wheel and the steering wheel is different from the original positional relationship according to a predetermined steering angle ratio. The steering angle ratio refers to the ratio between the steering angle of the steering wheel and the steering angle of the steering wheel.

[0004] Therefore, for example, in the steering system of Japanese Unexamined Patent Application Publication No. 2006-321434 (JP 2006-321434 A), when the power of the vehicle is turned on, a correction process of the rotational position of the steering wheel is performed. The control device of the steering system stores the rotational position of the steering wheel at the time when the power of the vehicle is turned off. The control device calculates the amount of deviation of the rotational position of the steering wheel by comparing between the rotational position of the steering wheel at the time when the power of the vehicle is turned off and the rotational position of the steering wheel at the time when the power of the vehicle is turned on, and causes the reaction motor to be driven so that the amount of deviation becomes zero (0). SUMMARY

[0005] According to the steering system of JP 2006-321434 A, the deviation of the positional relationship between the steering wheel and the steering wheel is certainly improved. However, in order to correct the positional relationship between the steering wheel and the steering wheel, the steering wheel is automatically rotated at the time when the power of the vehicle is turned on. The driver can feel uncomfortable with the automatic rotation of the steering wheel. In addition, during the period from the time when the power of the vehicle is turned on to the time when the correction process of the rotational position of the steering wheel is completed, the driver cannot start the vehicle. Therefore, the driver can feel stress.

[0006] The present application provides a steering system that can reduce the discomfort or stress of the driver for the correction process of the positional relationship between the steering wheel and the steering wheel.

[0007] The steering system according to the aspect of the application includes a steering operation shaft in which power transmission to and from a steering wheel is prohibited, and which turns a steering wheel of a vehicle, a steering operation motor that generates a steering operation force that is a torque applied to the steering operation shaft to turn the steering wheel, and a control device that controls the steering operation motor. In a case where at least one of start of the vehicle and turning of the steering wheel is performed for the first time after power of the vehicle is turned on, when a rotation position of the steering wheel is different from a rotation position corresponding to a turning position of the steering wheel, the control device performs, by the steering operation motor, a process for correcting the turning position of the steering wheel to a position corresponding to the rotation position of the steering wheel.

[0008] With this configuration, when at least one of start of the vehicle and turning of the steering wheel is performed for the first time after power of the vehicle is turned on, the turning position of the steering wheel is automatically adjusted to a position corresponding to the rotation position of the steering wheel. Therefore, compared to a case where the turning position is automatically adjusted in a stopped state or a non-turning state, discomfort or stress of the driver for an automatic adjustment operation of the turning position of the steering wheel is reduced.

[0009] In the above aspect, the steering system can further include a steering shaft that rotates with operation of the steering wheel, and a reaction motor that generates a steering reaction force that is a torque applied to the steering shaft and acting in a direction opposite to a steering direction. The control device can have a function of performing, by the reaction motor, a correction process of rotating the steering wheel to reduce an amount of deviation of the rotation position of the steering wheel from a correct rotation position corresponding to the turning position of the steering wheel, in a case where power of the vehicle is turned on and the rotation position of the steering wheel is different from the correct rotation position. The control device can perform the correction process when the amount of deviation is equal to or greater than a predetermined allowable amount, and can perform, without performing the correction process, a process for correcting the turning position of the steering wheel to a position corresponding to the rotation position of the steering wheel when the amount of deviation is smaller than the predetermined allowable amount.

[0010] With this configuration, when power of the vehicle is turned on and the amount of deviation of the rotation position of the steering wheel from the turning position of the steering wheel is equal to or greater than a predetermined allowable amount, the correction process of the rotation position of the steering wheel is performed. By the performance of this correction process, the amount of deviation of the rotation position of the steering wheel is reduced. Therefore, it is possible to suppress discomfort to the driver while starting the vehicle.

[0011] When the power of the vehicle is turned on and the amount of deviation of the rotational position of the steering wheel with respect to the steering position of the steering wheel is smaller than a predetermined allowable amount, the correction process of the rotational position of the steering wheel is not performed. When at least one of the start of the vehicle and the steering of the steering wheel is performed for the first time, the steering position of the steering wheel is automatically adjusted to a position corresponding to the rotational position of the steering wheel. The steering wheel is not automatically rotated when the power of the vehicle is turned on, so that the driver does not feel uncomfortable. In addition, the driver does not have to wait for the completion of the correction process of the rotational position of the steering wheel. Therefore, the driver does not feel stress.

[0012] In the above aspect, as the process for correcting the steering position of the steering wheel to a position corresponding to the rotational position of the steering wheel, the control device can control the steering operation motor so that the steering position of the steering wheel is gradually changed toward the position corresponding to the rotational position of the steering wheel.

[0013] With this configuration, the steering position of the steering wheel is gradually changed toward the position corresponding to the rotational position of the steering wheel. Since sudden movement of the steering wheel is suppressed, the driver is less likely to feel uncomfortable.

[0014] With the steering system of the above aspect, the driver's discomfort or stress with respect to the correction process of the positional relationship between the steering wheel and the steering wheel can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0015] Features, advantages, and technical and industrial significance of exemplary embodiments of the present application will be described below with reference to the accompanying drawings, wherein like numerals denote like elements, and wherein:

[0016] Figure 1 is a configuration diagram showing an embodiment of a steering system;

[0017] Figure 2 is a flowchart showing a process procedure of synchronization control of a reaction force control unit of the embodiment;

[0018] Figure 3 (a) and (b) of FIG. 10 are front views showing a first example of a change in the rotational position of the steering wheel when the power of the vehicle is turned on in the embodiment;

[0019] Figure 4 (a) and (b) of FIG. 11 are front views showing a second example of a change in the rotational position of the steering wheel when the power of the vehicle is turned on in the embodiment;

[0020] Figure 5 is a block diagram showing a configuration of a steering operation control unit according to the embodiment;

[0021] Figure 6Timing diagrams are shown, wherein (a) is a timing diagram showing the on / off state of a flag indicating the completion of the synchronous control of the reaction force control unit of the embodiment; (b) is a timing diagram showing the time variation of the angle difference between the target pinion angle and the pinion angle in the embodiment; (c) is a timing diagram showing the time variation of the gain in the embodiment; (d) is a timing diagram showing the time variation of the release amount relative to the angle difference between the target pinion angle and the pinion angle in the embodiment; (e) is a timing diagram showing the target pinion angle and the pinion angle at the completion of the synchronous control of the reaction force control unit of the embodiment; and (f) is a timing diagram showing the time variation of the final target pinion angle; and

[0022] Figure 7 This is a flowchart illustrating the synchronous control process of the steering operation control unit according to an embodiment. Detailed Implementation

[0023] The first implementation of the steering system will be described below. For example... Figure 1 As shown, the steering system 10 for a vehicle includes: a reaction force unit 20 that applies a steering reaction force to the steering wheel 11 of the vehicle; and a steering operation unit 30 that steers the steering wheels 12, 12 of the vehicle. The steering reaction force is a torque acting in the opposite direction to the driver's operation of the steering wheel 11. By applying a steering reaction force to the steering wheel 11, an appropriate responsiveness can be provided to the driver.

[0024] The reaction force unit 20 includes a steering shaft 21 connected to the steering wheel 11, a reaction motor 22, a reduction mechanism 23, a rotation angle sensor 24, a torque sensor 25, and a reaction force control unit 27.

[0025] The reaction motor 22 is the source of the steering reaction force. For example, a three-phase brushless motor is used as the reaction motor 22. The reaction motor 22 is connected to the steering shaft 21 via a reduction gear 23. The torque generated by the reaction motor 22 is applied to the steering shaft 21 as the steering reaction force.

[0026] A rotation angle sensor 24 is mounted on the reaction motor 22. The rotation angle sensor 24 detects the rotation angle θ of the reaction motor 22. a A torque sensor 25 is disposed in a portion of the steering shaft 21 between the reduction gear 23 and the steering wheel 11. The torque sensor 25 detects the steering torque T applied to the steering shaft 21 by the rotation of the steering wheel 11. h .

[0027] The reaction force control unit 27 is based on the rotation angle θ of the reaction motor 22 detected by the rotation angle sensor 24. a To calculate the steering angle θs the steering operation angle θ s is the rotation angle of the steering shaft 21. The reaction force control unit 27 counts the number of rotations of the reaction motor 22 with the motor neutral point as a reference. The motor neutral point indicates the rotation angle θ a of the reaction motor 22 corresponding to the steering neutral position of the steering wheel 11. The reaction force control unit 27 calculates an integrated angle, which is an angle obtained by integrating the rotation angle θ a with the motor neutral point as an origin, and multiplies the calculated integrated angle by a conversion factor based on the reduction ratio of the reduction mechanism 23, so as to calculate the steering operation angle θ s of the steering wheel 11. The motor neutral point is stored in the reaction force control unit 27 as the steering operation angle midpoint information.

[0028] The reaction force control unit 27 executes reaction force control for generating a steering reaction force corresponding to the steering torque T h by drive control of the reaction motor 22. The reaction force control unit 27 calculates a target steering reaction force based on the steering torque T h detected by the torque sensor 25, and calculates a target steering operation angle of the steering wheel 11 based on the calculated target steering reaction force and the steering torque T h . The reaction force control unit 27 obtains a difference between the steering operation angle θ a calculated based on the rotation angle θ s of the reaction motor 22 and the target steering operation angle, and controls the power supply to the reaction motor 22 so as to eliminate the difference. The reaction force control unit 27 vector controls the reaction motor 22 using the rotation angle θ a of the reaction motor 22 detected by the rotation angle sensor 24.

[0029] The steering operation unit 30 includes a steering operation shaft 31, a steering operation motor 32, a reduction mechanism 33, a pinion shaft 34, a rotation angle sensor 35, and a steering operation control unit 36. The steering operation shaft 31 extends along the vehicle width direction (left-right direction in the vehicle). The left and right steered wheels 12, 12 are connected to opposite ends of the steering operation shaft 31 via tie rods 13, 13, respectively. Figure 1

[0030] ​The steering operation motor 32 is the source of steering force. For example, a three-phase brushless motor is used as the steering operation motor 32. The steering operation motor 32 is connected to the pinion shaft 34 via a reduction gear 33. The pinion teeth 34a of the pinion shaft 34 mesh with the rack teeth 31a of the steering operation shaft 31. The torque generated by the steering operation motor 32 is applied as the steering force to the steering operation shaft 31 via the pinion shaft 34. The steering operation shaft 31 rotates along the vehicle width direction as the steering operation motor 32 rotates. Figure 1 The steering wheel 12 moves (left or right). As the steering operating shaft 31 moves, the steering angle θ of the steering wheels 12 and 12 changes. w Change.

[0031] A rotation angle sensor 35 is mounted on the steering operating motor 32. The rotation angle sensor 35 detects the rotation angle θ of the steering operating motor 32. b The steering operation control unit 36 ​​executes steering operation control to turn the steering wheels 12, 12 according to the steering state via drive control of the steering operation motor 32. The steering operation control unit 36 ​​bases its control on the rotation angle θ of the steering operation motor 32 detected by the rotation angle sensor 35. b To calculate the pinion angle θ p The pinion angle θ p This is the rotation angle of the pinion shaft 34. Furthermore, the steering operation control unit 36 ​​uses the target steering angle or steering angle θ calculated by the reaction force control unit 27. s To calculate the target pinion angle, which is the pinion angle θ p The target value. Note that the target pinion angle is calculated from the viewpoint of achieving a predetermined steering angle ratio. The steering operation control unit 36 ​​obtains the target pinion angle and the actual pinion angle θ. p The steering control unit 36 ​​uses the rotation angle θ of the steering operation motor 32 detected by the rotation angle sensor 35 to eliminate the difference between the two. b Vector control steering operation motor 32.

[0032] Here, in the steering system 10 with on-line steering, the steering wheel 11 is not restricted by the steering operation unit 30. Therefore, the following events may occur.

[0033] That is, when the power of the vehicle is turned on, the steering wheel 11 is synchronized with the steering wheels 12, 12. Therefore, the positional relationship between the steering wheel 11 and the steering wheels 12, 12 is maintained in the positional relationship according to the predetermined steering manipulation angle ratio. However, when a certain external force is applied to the steering wheel 11 in a case where the power of the vehicle is turned off, the steering wheel 11 can rotate. At this time, the steering operation shaft 31 does not work. Therefore, the positional relationship between the steering wheel 11 and the steering wheels 12, 12 can be different from the original positional relationship according to the predetermined steering manipulation angle ratio.

[0034] Therefore, when the power of the vehicle is turned on again, the steering system 10 performs synchronization control for synchronizing the rotational position of the steering wheel 11 with the steering positions of the steering wheels 12, 12 as an initial operation. It is conceivable that the steering system 10 performs the following processing as an example of the synchronization control.

[0035] For example, in a case where the steering wheel 11 is rotated counterclockwise (in the positive direction) by a predetermined angle in a case where the power of the vehicle is turned off, when the power of the vehicle is turned on again, the steering wheel 11 is rotated clockwise (in the negative direction) by a predetermined angle by the drive control of the reaction motor 22. As a result, the positional relationship between the steering wheel 11 and the steering wheels 12, 12 returns to the original positional relationship according to the predetermined steering manipulation angle ratio.

[0036] When the power of the vehicle is switched from on to off, the reaction force control unit 27 stores the steering manipulation angle θ s calculated immediately before the power of the vehicle is turned off in the storage device 27a as a reference steering manipulation angle. The reference steering manipulation angle serves as a reference for determining whether the steering wheel 11 rotates during the period when the power of the vehicle is turned off.

[0037] When the power of the vehicle is switched from off to on, the reaction force control unit 27 determines whether the position adjustment of the steering wheel 11 is necessary by comparison between the reference steering manipulation angle stored in the storage device 27a and the steering manipulation angle θ s calculated immediately after the power of the vehicle is turned on.

[0038] In a case where the reference steering manipulation angle, which is the steering manipulation angle θ s immediately before the power of the vehicle is turned off, and the steering manipulation angle θ s immediately after the power of the vehicle is turned on again, match each other, the reaction force control unit 27 determines that the position adjustment of the steering wheel 11 is not necessary. Obviously, since the steering manipulation angle θ s does not change, the steering wheel 11 does not rotate during the period from when the power of the vehicle is turned off to when the power of the vehicle is turned on again. The reaction force control unit 27 starts to perform the usual reaction force control for generating the steering reaction force in accordance with the steering torque T h .

[0039] the steering handle 11 immediately after the power supply of the vehicle is turned on again s the reference steering handle angle and the steering handle angle θ s do not match each other, the reaction force control unit 27 determines that the position adjustment of the steering handle 11 is necessary, and performs the position adjustment of the steering handle 11. The reaction force control unit 27, for example, obtains the difference between the reference steering handle angle and the steering handle angle θ s immediately after the power supply of the vehicle is turned on, and controls the power supply to the reaction force motor 22 to eliminate the difference. Specifically, the reaction force control unit 27 sets the reference steering handle angle as a target steering handle angle that is a target value of the steering handle angle θ s , and performs feedback control of the steering handle angle θ s so that the steering handle angle θ s follows the set target steering handle angle. When the target steering handle angle and the current steering handle angle θ s match each other, the position adjustment of the steering handle 11 is completed.

[0040] The reaction force control unit 27 can use the following value as the reference steering handle angle. That is, the reaction force control unit 27 acquires the pinion angle θ p from the steering operation control unit 36, and calculates the steering handle angle θ p corresponding to the acquired pinion angle θ s based on the steering handle angle degree ratio, the pinion angle θ p being the rotation angle of the pinion shaft 34 immediately after the power supply of the vehicle is switched from off to on. The reaction force control unit 27 uses the steering handle angle θ p corresponding to the calculated pinion angle θ s as the reference steering handle angle. Also in this way, the rotation position of the steering handle 11 can be corrected to a position corresponding to the steering position of the steered wheels 12, 12.

[0041] However, in order to correct the positional relationship between the steering handle 11 and the steered wheels 12, 12, the steering handle 11 is automatically rotated at the time of the power supply of the vehicle being turned on. The driver can feel discomfort with the automatic rotation of the steering handle. In addition, during the period from the power supply of the vehicle being turned on to the completion of the correction process of the rotation position of the steering handle, the driver cannot start the vehicle. Therefore, the driver can feel stress.

[0042] Therefore, in the present embodiment, from the viewpoint of reducing the discomfort or stress of the driver with the correction process of the positional relationship between the steering handle and the steered wheels, when the power supply of the vehicle is switched from off to on, the following process is performed as an initial operation.

[0043] As Figure 2 shown in the flowchart, the reaction force control unit 27 first calculates an amount of deviation Δθ of the steering position of the steering wheel 11 with respect to the steering position of the steered wheels 12, 12 (step S101). The amount of deviation Δθ is also an amount of rotation of the steering wheel 11 required to correct the steering position of the steering wheel 11 to a steering position corresponding to the steering position of the steered wheels 12, 12. The reaction force control unit 27 calculates the amount of deviation Δθ using, for example, the following equation (A).

[0044] Δθ = |θ s0 - θ s | (A)

[0045] Note that "θ s0 " is a reference steering angle stored in the storage device 27a immediately before the power of the vehicle is turned off last time. "θ s " is a steering angle immediately after the power of the vehicle is turned on. The sign of the steering angle θ s is, for example, negative in the right steering direction and positive in the left steering direction with respect to the steering neutral position (θ s = 0°) of the steering wheel 11.

[0046] Then, the reaction force control unit 27 determines whether the amount of deviation Δθ has a value smaller than an angle threshold value θ th (step S102). The angle threshold value θ th is set based on, for example, an angle at which the steering position of the steered wheels 12, 12 is not uncomfortable for the driver when corrected to match the steering position of the steering wheel 11 at the time of vehicle start. Further, the angle threshold value θ th may be regarded as an allowable amount with respect to the amount of deviation Δθ.

[0047] When the amount of deviation Δθ has a value smaller than the angle threshold value θ th (step S102: Yes), the reaction force control unit 27 sets the value of the flag F to "1" (step S103), and ends the processing. In this case, the steering wheel 11 is not automatically rotated.

[0048] The flag F is information indicating whether the initial operation by the reaction force control unit 27 is completed. The initial value of the flag F is "0". When the amount of deviation Δθ has a value not smaller than the angle threshold value θ th (step S102: No), the reaction force control unit 27 performs synchronization control (step S104).

[0049] The synchronization control is control for correcting the rotational position of the steering wheel 11 to a position corresponding to the steering position of the steering wheels 12, 12. The reaction force control unit 27 controls the electric power supply to the reaction motor 22 so that the deviation amount Δθ calculated in the previous step S101 becomes "0". More specifically, the reaction force control unit 27 sets a reference steering angle θ s0 as a target steering angle, and performs feedback control of the steering angle θ s so that the steering angle θ s follows the set target steering angle. When the steering angle θ s matches the target steering angle, the execution of the synchronization control is completed. The synchronization control can be regarded as a correction process of rotating the steering wheel 11 so that the deviation amount Δθ becomes zero.

[0050] When the execution of the synchronization control is completed, the reaction force control unit 27 sets the value of the flag F to "1" (step S103), and ends the process. When the power supply of the vehicle is switched from off to on, the steering operation control unit 36 executes the following process triggered by the fact that the value of the flag F set by the reaction force control unit 27 is switched from the initial value "0" to "1".

[0051] That is, in a case where the steering angle θ s calculated by the reaction force control unit 27 is an angle corresponding to the pinion angle θ p which is the rotational angle of the pinion shaft 34, the steering operation control unit 36 starts to execute the usual steering operation control for generating a steering operation force in accordance with the target steering angle θ s * or the steering angle θ s . In contrast, in a case where the steering angle θ s calculated by the reaction force control unit 27 is not an angle corresponding to the pinion angle θ p which is the rotational angle of the pinion shaft 34, the steering operation control unit 36 controls the electric power supply to the steering operation motor 32 so as to correct the pinion angle θ p to an angle corresponding to the steering angle θ s . As a result, the steering positions of the steering wheels 12, 12 are synchronized with positions corresponding to the rotational position of the steering wheel 11.

[0052] Next, the behavior of the steering wheel 11 and the steering wheels 12, 12 during the period from when the power supply of the vehicle is turned on to when the rotational position of the steering wheel 11 is synchronized with the steering positions of the steering wheels 12, 12 will be described for two cases.

[0053] Note that, as a premise, immediately after the power supply of the vehicle is turned on, the steering wheels 12, 12 are positioned at the steering neutral position (steering angle θw =0°). Initially, the steering wheel 11 should be positioned at the neutral steering position (steering angle θ) corresponding to the vehicle's straight-line forward motion. s =0°). Furthermore, as the steering angle θ s With steering angle θ w The steering angle ratio is "1:1", meaning the value of the steering angle ratio is "1".

[0054] First, the first scenario will be described. For example... Figure 3 As shown in (a), immediately after the vehicle's power is turned on, the steering wheel 11 is held at a position where the steering wheel 11 has been rotated clockwise (in the negative direction) by an angle α relative to the steering position of the steering wheels 12, 12, which has an angle α less than an angle threshold θ. th The value of . That is, the deviation Δθ of the rotational position of the steering wheel 11 relative to the steering position of the steering wheels 12, 12 is the angle α. In this case, synchronous control of the steering wheel 11 is not performed, and the state of the steering system 10 changes to a state where normal reaction force control and normal steering operation control can be performed. Thereafter, as Figure 3 As shown in (b), the steering positions of the steering wheels 12, 12 are synchronized with the rotation position of the steering wheel 11. Here, since the steering angle ratio is "1", the steering wheels 12, 12 turn clockwise by an angle α.

[0055] Next, the second scenario will be described. For example... Figure 4 As shown in (a), immediately after the vehicle's power is turned on, the steering wheel 11 is held at a position where the steering wheel 11 has been rotated clockwise (in the negative direction) by an angle β relative to the steering position of the steering wheels 12, 12, which has an angle β equal to or greater than an angle threshold θ. th The value of is . That is, the deviation Δθ of the rotational position of the steering wheel 11 relative to the steering position of the steering wheels 12 is the angle β. In this case, synchronous control of the steering wheel 11 is performed. For example... Figure 4 As shown in (b), through the execution of synchronization control, the rotational position of the steering wheel 11 is synchronized with the steering position of the steering wheels 12. Here, since the value of the steering angle ratio is "1", the steering wheel 11 rotates counterclockwise by an angle β, which is the deviation Δθ. After the execution of synchronization control is completed, the state of the steering system 10 changes to a state where normal reaction force control and normal steering operation control can be performed.

[0056] Note that when the value of the deviation Δθ is less than the angle threshold θ thAs in the above first case, the steered wheels 12, 12 are slightly automatically steered with the execution of the adjustment process of the steering position. Therefore, for example, the driver can feel uncomfortable with the operation of the steered wheels 12, 12 depending on the timing of the execution of the adjustment process of the steering position.

[0057] Therefore, in the present embodiment, the following configuration is adopted as the steering operation control unit 36 from the viewpoint of further reducing the driver's discomfort. As shown in FIG. 4, the steering operation control unit 36 includes a target pinion angle calculation unit 41, a pinion angle calculation unit 42, an angle difference calculation unit 43, a subtracter 44, a pinion angle feedback control unit 45, and a energization control unit 46. Figure 5

[0058] The target pinion angle calculation unit 41 calculates a target pinion angle θ s * based on the target steering angle θ s * calculated by the reaction force control unit 27. p The target pinion angle calculation unit 41 calculates the target pinion angle θ s * by, for example, dividing the steering angle θ p * by a predetermined steering angle ratio. The steering angle ratio is a ratio of the steering angle θ w to the steering angle θ s .

[0059] The pinion angle calculation unit 42 calculates a pinion angle θ b based on the rotation angle θ p of the steering operation motor 32 detected by the rotation angle sensor 35. The pinion angle θ p is a rotation angle of the pinion shaft 34. The pinion angle calculation unit 42 calculates the pinion angle θ b by, for example, dividing the rotation angle θ p of the steering operation motor 32 by a value of a reduction ratio of the reduction mechanism 33.

[0060] The angle difference calculation unit 43 calculates an angle difference Δθ p , which is a difference between the target pinion angle θ p * calculated by the target pinion angle calculation unit 41 and the pinion angle θ p calculated by the pinion angle calculation unit 42. Note that the angle difference calculation unit 43 calculates a final angle difference Δθ p by correcting a value of the angle difference Δθ p in accordance with the vehicle speed V and the steering angle velocity ω. The angle difference calculation unit 43 will be described in detail later. pf

[0061] ​​Subtractor 44 calculates the target pinion angle θ calculated by target pinion angle calculation unit 41. p *The final angle difference Δθ calculated by angle difference calculation unit 43 pf The difference between them is taken as the final target pinion angle θ. p *

[0062] The pinion angle feedback control unit 45 receives the final target pinion angle θ calculated by the subtractor 44. p * and the actual pinion angle θ calculated by pinion angle calculation unit 42 p The pinion angle feedback control unit 45 executes the pinion angle θ p Feedback control makes the actual pinion angle θ p Following the final target pinion angle θ p *To calculate the pinion angle command value T p *

[0063] The power-on control unit 46 will compare the pinion angle command value T calculated by the pinion angle feedback control unit 45 with the pinion angle command value T. p The corresponding current is supplied to the steering motor 32. Specifically, the energizing control unit 46 is based on the pinion angle command value T. p * The current command value for the steering operating motor 32 is calculated. Furthermore, the power supply control unit 46 detects the current value supplied to the steering operating motor 32 using a current sensor installed in the power supply path of the steering operating motor 32. The power supply control unit 46 obtains the deviation between the current command value and the current value supplied to the steering operating motor 32, and controls the power supply to the steering operating motor 32 to eliminate this deviation. As a result, the rotation of the steering operating motor 32 is related to the pinion angle command value T. p *Corresponding angle.

[0064] Next, the angle difference calculation unit 43 will be described in detail. For example... Figure 5 As shown, the angle difference calculation unit 43 includes a subtractor 51, a previous value holding unit 52, a switch 53, a release amount calculation unit 54, and a subtractor 55.

[0065] Subtractor 51 calculates the angle difference Δθ p The angle difference Δθ p The target pinion angle θ is calculated by the target pinion angle calculation unit 41. p *The pinion angle θ calculated by pinion angle calculation unit 42 p The difference between them.

[0066] Previous value holding unit 52 receives the final angle difference Δθ calculated by angle difference calculation unit 43. pf And maintain that final angle difference Δθ pfThe angle difference calculation unit 43 calculates the final angle difference Δθ within a predetermined calculation cycle. pf And whenever the final angle difference Δθ is calculated by the angle difference calculation unit 43 pf At that time, the final angle difference Δθ held by the previous value holding unit 52 is updated. pf That is, the final angle difference Δθ held by the previous value holding unit 52. pf This represents the final angle difference Δθ relative to the current value calculated by the angle difference calculation unit 43. pf The previous value (the final angle difference Δθ one calculation cycle prior) pf The initial value held in the previous value holding unit 52 is "0".

[0067] Switch 53 receives the angle difference Δθ calculated by subtractor 51. p and the final angle difference Δθ held by the previous value holding unit 52 pf As a data input, switch 53 also receives the value of flag F set by reaction force control unit 27 as a control input. Switch 53 selects the angle difference Δθ calculated by subtractor 51 based on the value of flag F. p Or the final angle difference Δθ held by the previous value holding unit 52 pf When the value of flag F is "0", switch 53 selects the angle difference Δθ calculated by subtractor 51. p When the value of flag F is "1" (more precisely, when the value of flag F is not "0"), switch 53 selects the final angle difference Δθ held by the previous value holding unit 52. pf .

[0068] Release amount calculation unit 54 calculates the release amount θ pr Using the release rate θ pr So that the pinion angle θ calculated by the pinion angle calculation unit 42 can be obtained. p The value begins to move towards the target pinion angle θ calculated by the target pinion angle calculation unit 41. p The true value of * gradually changes the final target pinion angle θ. p The value of *. Release amount θ pr It is when the final angle difference Δθ calculated by the angle difference calculation unit 43 pf The angle difference Δθ for each calculation cycle as the value gradually changes towards "0" p The change in quantity.

[0069] The release amount calculation unit 54 includes a first gain calculation unit 61, a second gain calculation unit 62, a maximum value selection unit 63, and a multiplier 64. The first gain calculation unit 61 calculates a first gain G1 based on the vehicle speed V. As the vehicle speed V increases from "0", the first gain calculation unit 61 calculates a first gain G1 with a larger value. After the vehicle speed V reaches a predetermined vehicle speed threshold, the first gain calculation unit 61 sets the value of the first gain G1 to a predetermined value (e.g., "1"), regardless of the vehicle speed V. The vehicle speed threshold is set from the perspective of determining whether a stopped vehicle has started.

[0070] The second gain calculation unit 62 calculates a second gain G2 based on the steering angular velocity ω. As the vehicle angular velocity ω increases from "0", the second gain calculation unit 62 calculates a second gain G2 with a larger value. After the steering angular velocity ω reaches a predetermined angular velocity threshold, the second gain calculation unit 62 sets the value of the second gain G2 to a predetermined value (e.g., "1"), regardless of the steering angular velocity ω. The angular velocity threshold is set from the viewpoint of determining whether the driver has operated the steering wheel 11.

[0071] The maximum value selection unit 63 receives the first gain G1 calculated by the first gain calculation unit 61 and the second gain G2 calculated by the second gain calculation unit 62, and selects the one with the larger value among the first gain G1 and the second gain G2.

[0072] Multiplier 64 multiplies the angle difference Δθ selected by switch 53. p The release amount θ is calculated by multiplying by either the first gain G1 or the second gain G2 selected by the maximum value selection unit 63. pr .

[0073] Subtractor 55 operates by measuring the angle difference Δθ selected by switch 53. p Subtract the release amount θ calculated by the release amount calculation unit 54 from the middle. pr To calculate the final angle difference Δθ pf .

[0074] Therefore, when the vehicle's power supply switches from off to on, the steering operation control unit 36 ​​operates as follows. When the vehicle's power supply is on, during the period from the start of the initial operation of the reaction force control unit 27 to its completion, the value of flag F is "0". Therefore, switch 53 selects the angle difference Δθ calculated by subtractor 51. p When the vehicle speed V and steering angular velocity ω are both "0", the values ​​of the first gain G1 and the second gain G2 are both "0". This is due to the release amount θ. pr The value is also "0", therefore the angle difference Δθ selected by switch 53 is... p (Here, the angle difference Δθ is calculated by subtractor 51)p ) is used as the final angle difference Δθ pf That is, the angle difference Δθ calculated by subtractor 51 immediately after the vehicle's power is turned on. p It is preserved.

[0075] Then, the subtractor 44 calculates the target pinion angle θ from the target pinion angle calculation unit 41. p *Subtract the final angle difference Δθ calculated by subtractor 55. pf (Here, the angle difference Δθ is calculated by subtractor 51 immediately after the vehicle's power is turned on.) p To calculate the final target pinion angle θ p * At this point, the final angle difference Δθ calculated by subtractor 55 pf Having an angle difference Δθ calculated by subtractor 51 p The same value. Therefore, as expressed in the following equation (B3), the final target pinion angle θ p The value of * has the same as the pinion angle θ calculated by pinion angle calculation unit 42. p The same value. Therefore, steering wheels 12 remain stationary and are not turned. The following equation (B3) is based on the following equations (B1) and (B2).

[0076] Δθ p =θ p *–θ p (B1)

[0077] θ p *=Δθ p +θ p (B2)

[0078] θ p *(Final) = θ p *-Δθ pf =(Δθ) p +θ p )-Δθ pf =θ p (B3)

[0079] Next, as Figure 6 As shown in (a), when the initial operation of the reaction force control unit 27 is completed (time T1), the value of flag F switches from "0" to "1". Therefore, switch 53 selects the final angle difference Δθ held by the previous value holding unit 52 as the reference value. pf angular difference Δθ p Here, when the vehicle speed V and steering angular velocity ω are both "0", the values ​​of the first gain G1 and the second gain G2 are both "0", as shown below. Figure 6 As shown in (c). At this time, as Figure 6As shown in (d), the release amount θ pr The value is also "0". Therefore, the angle difference Δθ selected by switch 53 p (Here, the angle difference Δθ is maintained by the previous value holding unit 52) p ) is used as the final angle difference Δθ pf That is, the final angular difference Δθ immediately following the switch of the value of flag F from "0" to "1". pf (Here, the angle difference Δθ is calculated by subtractor 51 immediately after the vehicle's power is turned on.) p ) is preserved.

[0080] Then, the subtractor 44 calculates the target pinion angle θ from the target pinion angle calculation unit 41. p *Subtract the final angle difference Δθ held by the previous value holding unit 52. pf The previous value (here, the angle difference Δθ calculated by subtractor 51 immediately after the vehicle's power is turned on) p To calculate the final target pinion angle θ p * At this point, the final angle difference Δθ held by the previous value holding unit 52 pf The previous value has an angle difference Δθ calculated by subtractor 51 immediately after the vehicle's power is switched on. p The same value. Therefore, as... Figure 6 As shown in (e) and (f), the final target pinion angle θ p The value of * has the pinion angle θ calculated by the pinion angle calculation unit 42 immediately after the vehicle's power is switched on. p The same value. Therefore, steering wheels 12 remain stationary and are not turned.

[0081] In this state, when the vehicle starts in a steering hold state with the steering wheel 11 held in a predetermined rotation position (time T2), for example, the multiplier 64 uses the angle difference Δθ selected by the switch 53. p (Here, the angle difference Δθ is maintained by the previous value holding unit 52) p The release amount θ is calculated by multiplying it by the first gain G1 corresponding to the vehicle speed V. pr Subtractor 55 operates by measuring the angle difference Δθ selected by switch 53. p (Here, the angle difference Δθ is maintained by the previous value holding unit 52) p Subtract the release amount Δθ pr To calculate the final angle difference Δθ pf That is, the final angle difference Δθ calculated by subtractor 55. pf The value of θ reduced the amount of release. pr .

[0082] Therefore, as Figure 6As shown in (b) and (f), the final target pinion angle θ calculated by subtractor 44 p The value of * increases the final angle difference Δθ pf The amount by which the value decreases. Afterwards, as... Figure 6 As shown in (b) and (d), the final angle difference Δθ pf The value depends on the release amount θ pr The value gradually decreases at each calculation cycle of the steering operation control unit 36. Therefore, as Figure 6 As shown in (f), the final target pinion angle θ p The value of * gradually increases at each calculation cycle of the steering operation control unit 36. Ultimately, as... Figure 6 As shown in (b) and (f), at the final angular difference Δθ pf When the value becomes "0" (time T3), the final target pinion angle θ p The value of * reaches its true value, that is, the target pinion angle θ calculated by the target pinion angle calculation unit 41. p As a result, the steering positions of the steering wheels 12, 12 are synchronized with the rotation position of the steering wheel 11.

[0083] The situation when operating the steering wheel 11 while the vehicle is stationary is the same as the situation when the vehicle is starting while the steering wheel 11 is held. That is, the final target pinion angle θ p The value of * is directed toward the target pinion angle θ calculated by the target pinion angle calculation unit 41. p The actual value of * gradually increases, which is triggered by the start of steering wheel 11 turning (time T2).

[0084] Next, we will refer to Figure 7 The flowchart describes the initial operation process performed by the steering operation control unit 36 ​​after the vehicle's power is turned on. This process is executed after the vehicle's power is turned on, triggered by the fact that the value of flag F in the reaction force control unit 27 switches from "0" to "1".

[0085] like Figure 7 As shown in the flowchart, the steering operation control unit 36 ​​is based on the steering angle θ obtained by the reaction force control unit 27. s To calculate the target pinion angle θ p *(Step S201). The steering operation control unit 36 ​​bases its data on the rotation angle θ of the steering operation motor 32 detected by the rotation angle sensor 35. b To calculate the pinion angle θ p (Step S202).

[0086] Next, the steering control unit 36 ​​determines the target pinion angle θ. p *With pinion angle θ pthe angle difference Δθ p whether it is "0" (step S203). When the angle difference Δθ p is "0" (YES in step S203), the steering operation control unit 36 ends the processing. When the angle difference Δθ p is not "0" (NO in step S203), the steering operation control unit 36 holds the target pinion angle θ p * calculated in the previous step S201 (step S204), and sets the target pinion angle θ p * to the same value as the pinion angle θ p * (step S205).

[0087] Next, the steering operation control unit 36 determines whether the vehicle has been started by, for example, comparing the vehicle speed V with a vehicle speed threshold (step S206). When it is determined that the vehicle has been started (YES in step S206), the steering operation control unit 36 transfers the processing to step S207. When it is determined that the vehicle has not been started (NO in step S206), the steering operation control unit 36 transfers the processing to step S208.

[0088] In step S208, the steering operation control unit 36 determines whether the steering wheel 11 has been operated by, for example, comparing the steering angle velocity with an angle velocity threshold. When it is determined that the steering wheel 11 has not been operated, the steering operation control unit 36 transfers the processing to the previous step S206. When it is determined that the steering wheel 11 has been operated, the steering operation control unit 36 transfers the processing to step S207.

[0089] In step S207, the steering operation control unit 36 gradually changes the target pinion angle θ p * toward the true value of the target pinion angle θ p * held in the previous step S204. When the value of the target pinion angle θ p * reaches the true value, the steering operation control unit 36 ends the processing.

[0090] The steering operation control unit 36 matches the value of the pinion angle θ p with the true value of the target pinion angle θ p * by execution of feedback control for causing the pinion angle θ p to follow the true value of the target pinion angle θ p *. As a result, the steering positions of the steering wheels 12, 12 are changed to positions corresponding to the rotational position of the steering wheel 11.

[0091] Effects of the Embodiment

[0092] Accordingly, according to the present embodiment, the following effects can be obtained.

[0093] (1) When at least one of the start of the vehicle and the steering of the steering wheel 11 is performed for the first time after the power of the vehicle is turned on, the steering positions of the steered wheels 12, 12 are automatically adjusted to positions corresponding to the rotational position of the steering wheel 11. Thus, compared to a case where the steering positions are automatically adjusted in a stopped state or a non-steering state, the driver is less likely to feel discomfort or stress about the automatic adjustment operation of the steering positions of the steered wheels 12, 12.

[0094] (2) When the power of the vehicle is turned on and the amount of deviation Δθ of the rotational position of the steering wheel 11 with respect to the steering positions of the steered wheels 12, 12 has a value equal to or greater than an angle threshold value θ th , the synchronization control of the steering wheel 11 is performed. With the execution of the synchronization control, the rotational position of the steering wheel 11 is completely synchronized with the steering positions of the steered wheels 12, 12. Thus, for example, when the vehicle is started, the steering positions of the steered wheels 12, 12 are not suddenly changed toward positions corresponding to the rotational position of the steering wheel 11. Therefore, the driver can smoothly start the vehicle without feeling discomfort.

[0095] (3) When the power of the vehicle is turned on and the amount of deviation Δθ of the rotational position of the steering wheel 11 with respect to the steering positions of the steered wheels 12, 12 is less than an angle threshold value θ th , the synchronization control of the steering wheel 11 is not performed. When at least one of the start of the vehicle and the steering of the steering wheel 11 is performed for the first time after the power of the vehicle is turned on, the steering positions of the steered wheels are automatically adjusted to positions corresponding to the rotational position of the steering wheel. Thereby, the steering wheel 11 is not automatically rotated at the time when the power of the vehicle is turned on, and thus the driver is less likely to feel discomfort. Furthermore, since the driver does not have to wait for the completion of the execution of the synchronization control of the steering wheel 11, the driver is less likely to feel stress.

[0096] (4) When the steering positions of the steered wheels 12, 12 are automatically adjusted to positions corresponding to the rotational position of the steering wheel 11, the steering positions of the steered wheels 12, 12 are gradually changed toward positions corresponding to the rotational position of the steering wheel 11. Since the sudden movement of the steered wheels 12, 12 is suppressed, the driver is less likely to feel discomfort.

[0097] Other Embodiments

[0098] The present embodiment can be modified as follows. As Figure 1As shown by the long and two short dashed lines, for example, when the notification device 28 is installed in the passenger compartment, the reaction force control unit 27 can notify the driver of the start and completion of the steering wheel 11 position adjustment via the notification device 28. Examples of notification operations by the notification device 28 include displaying messages as text and issuing messages via voice. This allows the driver to recognize that the steering wheel 11 is automatically rotating and automatically stopping, thereby reducing discomfort for the driver. Furthermore, the steering operation control unit 36 ​​can notify the driver of the start and completion of the automatic adjustment of the steering position via the notification device 28. This allows the driver to recognize that automatic adjustment of the steering position is being performed, thereby reducing discomfort for the driver.

[0099] In this embodiment, the rotation angle θ based on the reaction motor 22 is used. a Calculated steering angle θ s However, when a steering system 10 is configured with a steering angle sensor, the steering angle θ detected by the steering angle sensor can be used. s .

[0100] In this embodiment, the steering angle ratio is set to an appropriate value according to product specifications, etc. The steering angle ratio can be, for example, "θ". s :θ w =1:1" or "θ" s :θ w =1:3". For example, in a steering angle ratio of "θ" s :θ w In the case of a ratio of 1:3, when the steering angle θ s When the deviation is 10°, the steering angle θ w The deviation is 30°. Therefore, it is preferable to accurately synchronize the steering angle θ. s and steering angle θ w .

[0101] In this embodiment, Figure 2 In the process shown in the flowchart, when the deviation Δθ calculated in step S101 does not have a value less than the angle threshold θ th When the value is "No" in step S102, the reaction force control unit 27 rotates the steering wheel 11, causing the deviation Δθ to become "0". However, the deviation Δθ does not necessarily have to be "0". For example, an angle that will not cause discomfort to the driver when the steering positions of the steering wheels 12, 12 are corrected to match the rotation position of the steering wheel 11 when the vehicle is started can be used, i.e., for example, greater than "0" and less than the threshold θ. th The angle is within the range. Even with this configuration, the same effect as in (3) of the first embodiment can be obtained.

[0102] In the present embodiment, when the power supply of the vehicle is switched from off to on, the reaction force control unit 27 executes the process shown in the flowchart of Figure 2 However, depending on the product specifications or the like, the reaction force control unit 27 can adopt a configuration that executes the function by omitting the process shown in the flowchart of Figure 2 In this case, regardless of the value of the amount of deviation Δθ of the rotational position of the steering wheel 11 with respect to the steering position of the steering wheels 12, 12, the steering operation control unit 36 executes the process of synchronizing the steering position of the steering wheels 12, 12 with the rotational position of the steering wheel 11 at the start of the vehicle or the steering of the steering wheel 11.

[0103] In the present embodiment, the power supply of the vehicle can include, for example, an accessory power supply (ACC power supply) or an ignition power supply (IG power supply). The reaction force control unit 27 and the steering operation control unit 36 can be configured as a single control device.

[0104] In the present embodiment, an example employing a so-called rack-less structure in which there is no mechanical power transmission between the steering shaft 21 and the steering wheels 12 has been described as the steering system 10 of the vehicle. However, a structure in which the power transmission between the steering shaft 21 and the steering wheels 12 can be inhibited by a clutch can be employed. When the clutch is disengaged, the power transmission between the steering wheel 11 and the steering wheels 12 is inhibited. When the clutch is engaged, the power transmission between the steering wheel 11 and the steering wheels 12 is enabled.

Claims

1. A steering system (10) characterized by, including: a steering operation shaft (31) in which power transmission to and from a steering wheel (11) is prohibited, and which steers a steering wheel (12) of a vehicle; a steering operation motor (32) that generates a steering operation force, which is a torque applied to the steering operation shaft (31) to steer the steering wheel (12); a steering shaft (21) that rotates with operation of the steering wheel (11); and a reaction motor (22) that generates a steering reaction force, which is a torque applied to the steering shaft (21) and acts in a direction opposite to a steering direction, a control device that controls the steering operation motor (32), wherein, in a case where at least one of start of the vehicle and steering of the steering wheel (11) is performed for the first time after power of the vehicle is turned on, when a rotational position of the steering wheel (11) is different from a rotational position corresponding to a steering position of the steering wheel (12), the control device performs, by the steering operation motor (32), a process for correcting the steering position of the steering wheel (12) to a position corresponding to the rotational position of the steering wheel (11), the control device has a function of performing, by the reaction motor (22), a correction process of rotating the steering wheel (11) to reduce an amount of deviation of the rotational position of the steering wheel (11) from a correct rotational position corresponding to the steering position of the steering wheel (12), in a case where the power of the vehicle is turned on and the rotational position of the steering wheel (11) is different from the correct rotational position corresponding to the steering position of the steering wheel (12); and in a case where the power of the vehicle is turned on, when the amount of deviation is equal to or greater than a predetermined allowable amount, the control device performs the correction process, and when the amount of deviation is smaller than the predetermined allowable amount, the control device performs a process for correcting the steering position of the steering wheel (12) to a position corresponding to the rotational position of the steering wheel (11) without performing the correction process. As the process for correcting the steering position of the steering wheel (12) to a position corresponding to the rotational position of the steering wheel (11), the control device controls the steering operation motor (32) so that the steering position of the steering wheel (12) is gradually changed toward the position corresponding to the rotational position of the steering wheel (11). ​ 2. The steering system (10) according to claim 1, characterized in that ​

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