Steering control device

Abstract

A steering control device includes control circuitry configured to execute synchronization control. The synchronization control includes: target synchronization angle calculation processing that calculates a target synchronization angle, the target synchronization angle being a steering side rotation angle that satisfies a predetermined correspondence with respect to a turning side rotation angle; target relay angle calculation processing that calculates a target relay angle, the target relay angle being located closer to a first side in a circumferential direction than a first side angle, the first side angle being one of the steering side rotation angle and the target synchronization angle and being located closer to the first side than the other of the steering side rotation angle and the target synchronization angle; and motor drive processing that, after operating a steering side motor (13) so that the steering side rotation angle reaches the target relay angle, operates the steering side motor (13) so that the steering side rotation angle reaches the target synchronization angle.

Description

TECHNICAL FIELD

[0001] The present application relates to a steering control device. BACKGROUND

[0002] In the related art, for example, as described in Japanese Patent Application Publication No. 2012-91677 (JP 2012-91677 A), a steer-by-wire steering system is known in which a power transmission path between a steering unit connected to a steering wheel and a turning unit that turns turning wheels is cut off. A steering control device that controls such a steering system controls the steering system so that a positional relationship between a steering angle of the steering wheel and a turning angle of the turning wheels is a predetermined correspondence relationship when an ignition switch is in an on state. Specifically, the steering control device turns the turning wheels so that a turning angle corresponding to the steering angle is achieved by operating a turning side motor provided in the turning unit. On the other hand, when the steering wheel is steered while the ignition switch is in an off state, the steering control device does not turn the turning wheels. As a result, the positional relationship between the steering angle and the turning angle deviates from the predetermined correspondence relationship.

[0003] Therefore, for example, Japanese Patent Application Publication No. 2006-321434 (JP 2006-321434 A) discloses a steering system in which, for example, immediately after the ignition switch is turned on in a case where the steering wheel has been steered while the ignition switch has been in an off state, the steering wheel is rotated so that the steering angle reaches an angle corresponding to the turning angle. By performing such a synchronization operation, deviation of the positional relationship between the steering angle and the turning angle from the predetermined correspondence relationship after the ignition switch is turned on is prevented. SUMMARY

[0004] In the configuration described in JP 2006-321434 A, the synchronization operation is performed so that the steering angle directly becomes close to the angle corresponding to the turning angle. Therefore, in this configuration, the direction in which the steering wheel is rotated in the synchronization operation varies depending on the direction in which the steering angle deviates from the turning angle. That is, the manner of operation in the synchronization operation is different.

[0005] Here, assume that the steering wheel is often steered to the right when the ignition switch is in the off state, for example, due to the driver's habit when getting in the vehicle. In this case, when it is assumed that the driver accidentally steers the steering wheel to the left while the ignition switch is in the off state, the direction in which the steering wheel is rotated in the synchronization operation is opposite to the direction in which the steering wheel is generally rotated in the synchronization operation. As a result, for example, the driver can feel uneasy (i.e., unsafe) as to whether the steering angle has reached the angle corresponding to the turning angle when the synchronization operation is actually performed.

[0006] The present application provides a steering control device capable of preventing a driver from feeling uneasy when a synchronization operation is performed.

[0007] The steering control device according to an aspect of the present application is configured to control a steering system having a structure in which a power transmission path between a steering unit connected to a steering wheel and a turning unit that turns a turning wheel is cut off. The steering control device includes control circuitry configured to perform synchronization control for adjusting a steering-side rotation angle, which is a rotation angle that can be converted into a steering angle of the steering wheel, by operating a steering-side motor such that a positional relationship between the steering-side rotation angle and a turning-side rotation angle, which is a rotation angle that can be converted into a turning angle of the turning wheel, is a predetermined correspondence relationship. The steering unit includes the steering-side motor configured to rotate the steering wheel. The synchronization control includes: target synchronization angle calculation processing that calculates a target synchronization angle, which is a steering-side rotation angle that satisfies the predetermined correspondence relationship with respect to the turning-side rotation angle; target relay angle calculation processing that calculates a target relay angle, which is located closer to a first side in a circumferential direction than a first-side angle, which is one of the steering-side rotation angle and the target synchronization angle and is located closer to the first side than the other of the steering-side rotation angle and the target synchronization angle; and motor drive processing that operates the steering-side motor such that the steering-side rotation angle reaches the target synchronization angle after operating the steering-side motor such that the steering-side rotation angle reaches the target relay angle.

[0008] With this configuration, when the synchronization control is performed, the steering wheel is rotated such that the steering-side rotation angle reaches the target synchronization angle after reaching the target relay angle, and thus the rotation direction of the steering wheel is changed while the synchronization operation is performed. That is, the synchronization operation is a two-step operation. Regardless of the relative positional relationship between the steering-side rotation angle and the target synchronization angle, the target relay angle is set to be closer to the first side in the circumferential direction than a first-side angle, which is one of the steering-side rotation angle and the target synchronization angle and is located closer to the first side than the other of the steering-side rotation angle and the target synchronization angle. Therefore, regardless of the relative positional relationship between the steering-side rotation angle and the target synchronization angle, the synchronization operation is performed such that the steering wheel is rotated to the first side in the circumferential direction and then rotated to a second side in the circumferential direction opposite to the first side. Thus, since the synchronization operation is performed in the same operation manner regardless of the relative positional relationship between the steering-side rotation angle and the target synchronization angle, it is possible to prevent a driver from feeling uneasy.

[0009] In the steering control device according to the aspect, a lower limit of the amount of rotation can be set based on visibility of rotation of the steering wheel and can be set to the minimum amount of rotation; and in a case where the absolute value of the angle difference between the steering-side rotation angle and the target synchronization angle is greater than the predetermined angle difference, the target relay angle calculation process can calculate, as the target relay angle, an angle located at a position closer to the first side than the first side angle by the minimum amount of rotation.

[0010] With this configuration, the target relay angle is prevented from excessively separating from the second side angle, which is the other of the steering-side rotation angle and the target synchronization angle and is located at a position closer to the second side in the circumferential direction than the first side angle. Thus, an increase in time required for the synchronization operation can be suppressed.

[0011] In the steering control device according to the aspect, a lower limit of the amount of rotation can be set based on visibility of rotation of the steering wheel and can be set to the minimum amount of rotation; an amount of rotation greater than the minimum amount of rotation can be set as the intermediate amount of rotation; and in a case where the absolute value of the angle difference between the steering-side rotation angle and the target synchronization angle is equal to or smaller than the predetermined angle difference, the target relay angle calculation process can calculate, as the target relay angle, an angle located at a position closer to the first side than the first side angle by the intermediate amount of rotation.

[0012] With this configuration, the target relay angle is prevented from excessively approaching the first side angle, which is one of the steering-side rotation angle and the target synchronization angle and is located at a position closer to the first side in the circumferential direction than the other of the steering-side rotation angle and the target synchronization angle (i.e., the second side angle). Thus, it is possible to make the driver recognize that the synchronization operation is a two-step operation.

[0013] In the steering control device according to the aspect, the intermediate amount of rotation can be an amount of rotation equal to or smaller than a total value of the minimum amount of rotation and the predetermined angle difference. With this configuration, the target relay angle is prevented from excessively separating from the first side angle, which is one of the steering-side rotation angle and the target synchronization angle and is located at a position closer to the first side in the circumferential direction than the other of the steering-side rotation angle and the target synchronization angle (i.e., the second side angle). Thus, an increase in time required for the synchronization operation can be suppressed.

[0014] According to an aspect of the present application, it is possible to prevent the driver from feeling uneasy about the synchronization operation. 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, in which like numerals denote like elements, and wherein:

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

[0017] Figure 2 is a flowchart showing a processing routine of the synchronization control performed by the steering control device;

[0018] Figure 3A is a schematic diagram showing an example of the synchronization operation when the angle difference between the steering angle and the target synchronization angle is large;

[0019] Figure 3B is a schematic diagram showing an example of the synchronization operation when the angle difference between the steering angle and the target synchronization angle is large;

[0020] Figure 3C is a schematic diagram showing an example of the synchronization operation when the angle difference between the steering angle and the target synchronization angle is large;

[0021] Figure 4A is a schematic diagram showing an example of the synchronization operation when the angle difference between the steering angle and the target synchronization angle is small;

[0022] Figure 4B is a schematic diagram showing an example of the synchronization operation when the angle difference between the steering angle and the target synchronization angle is small;

[0023] Figure 4C is a schematic diagram showing an example of the synchronization operation when the angle difference between the steering angle and the target synchronization angle is small;

[0024] Figure 5A is a schematic diagram showing another example of the synchronization operation when the angle difference between the steering angle and the target synchronization angle is large;

[0025] Figure 5B is a schematic diagram showing another example of the synchronization operation when the angle difference between the steering angle and the target synchronization angle is large;

[0026] Figure 5C is a schematic diagram showing another example of the synchronization operation when the angle difference between the steering angle and the target synchronization angle is large;

[0027] Figure 6A is a schematic diagram showing another example of the synchronization operation when the angle difference between the steering angle and the target synchronization angle is small;

[0028] Figure 6B is a schematic diagram showing another example of the synchronization operation when the angle difference between the steering angle and the target synchronization angle is small; and

[0029] Figure 6C is a schematic diagram showing another example of the synchronization operation when the angle difference between the steering angle and the target synchronization angle is small. DETAILED DESCRIPTION

[0030] Hereinafter, a steering control device according to an embodiment of the present application will be described with reference to the drawings. As shown in Figure 1 The steering system 2 controlled by the steering control device 1 is configured as a steer-by-wire system in this embodiment. The steering system 2 includes a steering unit 4 manipulated by a driver via a steering wheel 3 and a turning unit 6 that turns a turning wheel 5 in accordance with the driver's manipulation of the steering unit 4. The steering wheel 3 is rotationally asymmetric in shape about its center of rotation in this embodiment.

[0031] The steering unit 4 includes a steering shaft 11 connected to the steering wheel 3 and a steering-side actuator 12 that applies a steering reaction force as a force resisting steering to the steering wheel 3 via the steering shaft 11.

[0032] The steering-side actuator 12 includes a steering-side motor 13 as a drive source and a speed reducer 14. For example, a worm gear mechanism is employed as the speed reducer 14. The steering-side motor 13 is connected to the steering shaft 11 via the speed reducer 14. The steering-side actuator 12 includes a restriction mechanism 15 that mechanically restricts the steering angle θh of the steering wheel 3 from exceeding a threshold angle. For example, the threshold angle is set in advance based on the transmission ratio (θh / θi) between the steering angle θh and the turning angle θi of the turning wheel 5. For example, an appropriate structure such as that described in JP 2012-91677 A can be employed as the restriction mechanism 15.

[0033] The turning unit 6 includes a pinion shaft 21, a rack shaft 22 connected to the pinion shaft 21, a rack housing 23 that houses the rack shaft 22 so that the rack shaft 22 can reciprocate, and a rack-and-pinion mechanism 24 that includes the pinion shaft 21 and the rack shaft 22. The rack shaft 22 and the pinion shaft 21 are arranged in the rack housing 23 at a predetermined cross angle. The rack-and-pinion mechanism 24 has a configuration in which pinion teeth 21a formed in the pinion shaft 21 and rack teeth 22a formed in the rack shaft 22 mesh with each other. Thus, the pinion shaft 21 rotates with the reciprocation of the rack shaft 22. A tie rod 26 is connected to both ends of the rack shaft 22 via a ball joint 25, respectively. The end of the tie rod 26 is connected to a knuckle (not shown) to which the turning wheel 5 is assembled.

[0034] The turning unit 6 includes a turning-side actuator 31 that applies a turning force to the rack shaft 22 to turn the turning wheel 5. The turning-side actuator 31 includes a turning-side motor 32 as a drive source, a belt mechanism 33, and a ball screw mechanism 34. The turning-side actuator 31 applies the turning force to the turning unit 6 by transmitting the rotation of the turning-side motor 32 to the ball screw mechanism 34 via the belt mechanism 33 and causing the ball screw mechanism 34 to convert the rotation into reciprocation of the rack shaft 22.

[0035] In the steering system 2 having the above-described configuration, the rack shaft 22 is reciprocated and the turning angle θi of the turning wheel 5 is changed by applying a turning force from the turning-side actuator 31 in accordance with a steering operation of the driver. At this time, a steering reaction force against the steering of the driver is applied to the steering wheel 3 from the steering-side actuator 12.

[0036] The electrical configuration according to this embodiment will be described below. The steering control device 1 operates the steering-side motor 13 and the turning-side motor 32. The steering control device 1 includes a central processing unit (CPU) and a memory, which are not shown. In other words, the steering control device 1 includes control circuitry. The steering control device 1 performs various controls by causing the CPU to execute a program stored in the memory in each predetermined operation cycle. The steering control device 1 operates with electric power supplied from a battery 41 installed in the vehicle.

[0037] A start signal Sig indicating an on state or an off state of a start switch 42, such as an ignition switch, of the vehicle is input to the steering control device 1. Detection results from various sensors are input to the steering control device 1. The various sensors include, for example, a vehicle speed sensor 43, a torque sensor 44, a steering-side rotation angle sensor 45, a turning-side rotation angle sensor 46, and a pinion angle sensor 47.

[0038] The vehicle speed sensor 43 detects a vehicle speed V, which is a running speed of the vehicle. The torque sensor 44 detects a steering torque Th applied to the steering shaft 11. The steering-side rotation angle sensor 45 detects a rotation angle θs of a rotation shaft of the steering-side motor 13, which is a relative angle in a range of 360°. The turning-side rotation angle sensor 46 detects a rotation angle θt of a rotation shaft of the turning-side motor 32, which is a relative angle. The pinion angle sensor 47 detects a pinion angle θpd, which is a rotation angle of the pinion shaft 21, as an absolute angle in a range including a range exceeding 360°.

[0039] As described above, the pinion shaft 21 rotates with the reciprocation of the rack shaft 22, that is, with the turning of the turning wheel 5. Therefore, the pinion angle θpd is a rotation angle that can be converted into the turning angle θi of the turning wheel 5 and corresponds to the turning-side rotation angle. For example, when the pinion angle θpd is an angle on the right side of a pinion angle midpoint θp0, the pinion angle θpd is detected as a positive value, and when the pinion angle θpd is an angle on the left side of the pinion angle midpoint θp0, the pinion angle θpd is detected as a negative value, the pinion angle midpoint θp0 being an angle when the vehicle is traveling straight ahead.

[0040] The steering control device 1 calculates a steering angle θh as a rotation angle of the steering shaft 11 based on the rotation angle θs of the steering-side motor 13. The steering angle θh corresponds to a steering-side rotation angle. Specifically, the steering control device 1 counts the number of turns of the steering-side motor 13, for example, from a steering midpoint θho and calculates a total angle as an angle obtained by summing the values of the rotation angle θs with the steering midpoint θho serving as the origin. The steering midpoint θho is the steering angle θh when the steering wheel 3 is located at the center of the steerable range. The steering control device 1 calculates the steering angle θh of the steering wheel 3 by multiplying the total angle by a conversion factor based on the speed ratio of the reducer 14. The steering angle θh is detected as a positive value when the steering angle θh is an angle to the right of the steering midpoint θho, and the steering angle θh is detected as a negative value when the steering angle θh is an angle to the left of the steering midpoint θho, for example.

[0041] When the battery 41 is connected in a state in which the start switch 42 is in the off state, the steering control device 1 according to the embodiment holds the value of the steering angle θh at the point in time at which the start switch 42 is turned off and monitors the rotation of the steering-side motor 13. When the steering-side motor 13 rotates in a state in which the start switch 42 is in the off state, the steering control device 1 calculates the steering angle θh whose value is changed corresponding to the rotation at the next time when the start switch 42 is turned on.

[0042] The steering control device 1 calculates a target reaction torque as a target value of the steering reaction force based on the steering torque Th and the vehicle speed V. Then, the steering control device 1 operates the steering-side motor 13 so that a motor torque corresponding to the target reaction torque is generated. Thus, the steering reaction force is applied to the steering unit 4.

[0043] The steering control device 1 counts the number of turns of the turning-side motor 32, for example, from a pinion angle midpoint θpo and calculates a total angle as an angle obtained by summing the values of the rotation angle θt with the pinion angle midpoint θpo serving as the origin. The steering control device 1 calculates a turning corresponding angle θpc that can be converted into a turning angle θi of the turning wheel 5 by multiplying the total angle by a conversion factor based on the speed ratio of the belt mechanism 33, the lead of the ball screw mechanism 34, and the speed ratio of the rack and pinion mechanism 24. That is, the turning corresponding angle θpc indicates the rotation angle of the pinion shaft 21 and is substantially the same as the pinion angle θpd. The turning corresponding angle θpc corresponds to a turning-side rotation angle. The turning corresponding angle θpc is a positive value when the turning corresponding angle θpc is an angle to the right of the pinion angle midpoint θpo, and the turning corresponding angle θpc is a negative value when the turning corresponding angle θpc is an angle to the left of the pinion angle midpoint θpo, for example.

[0044] The steering control device 1 calculates a target turning corresponding angle θp* as a target value of the turning corresponding angle θpc on the basis of the steering angle θh. For example, the steering control device 1 calculates the target turning corresponding angle θp* by dividing the steering angle θh by a value obtained in accordance with the transmission ratio that varies in accordance with the steering angle θh and the vehicle speed V. The steering control device 1 calculates a target turning torque as a target value of the turning force by performing feedback control so that the turning corresponding angle θpc coincides with the target turning corresponding angle θp*. Then, the steering control device 1 operates the turning side motor 32 so that a motor torque corresponding to the target turning torque is generated. Thus, the turning force is applied to the turning unit 6. That is, the steering control device 1 controls the steering system 2 so that the positional relationship between the steering angle θh and the turning angle θi of the turning wheel 5 is a predetermined corresponding relationship determined in accordance with the transmission ratio.

[0045] When the steering wheel 3 is steered in a state in which the start switch 42 is off, the steering control device 1 does not turn the turning wheel 5 by operating the turning side motor 32. As a result, the positional relationship between the steering angle θh and the turning angle θi of the turning wheel 5 deviates from the predetermined corresponding relationship.

[0046] Thus, when the positional relationship between the steering angle θh and the pinion angle θpd is not the predetermined corresponding relationship, the steering control device 1 performs synchronization control for adjusting the steering angle θh by operating the steering side motor 13 so that the positional relationship between the steering angle θh and the pinion angle θpd is the predetermined corresponding relationship. The synchronization control is performed as a two-step operation in which the steering wheel 3 is rotated to a first side in the circumferential direction and then rotated to a second side in the circumferential direction. In this embodiment, the right side is the first side in the circumferential direction and the left side is the second side in the circumferential direction.

[0047] Specifically, the steering control device 1 performs the synchronization control immediately after the start switch 42 is turned on. When the synchronization control is performed, the steering control device 1 first performs a target synchronization angle calculation process of calculating a target synchronization angle θsy* that is a steering angle θh satisfying the predetermined corresponding relationship with respect to the pinion angle θpd. Subsequently, the steering control device 1 performs a target relay angle calculation process of calculating a target relay angle θrl* that is a target angle of the steering wheel 3 in a first step of the synchronization operation. Then, the steering control device 1 performs a motor drive process of operating the steering side motor 13 so that the steering angle θh reaches the target relay angle θrl* and then operating the steering side motor 13 so that the steering angle θh reaches the target synchronization angle θsy*.

[0048] In the target synchronization angle calculation processing, the steering control device 1 calculates the target synchronization angle θsy* based on the pinion angle θpd. Specifically, the steering control device 1 calculates the target synchronization angle θsy* by multiplying the pinion angle θpd detected immediately after the start switch 42 is turned on by the transmission ratio at the time when the vehicle speed V is zero.

[0049] In the target relay angle calculation processing, the steering control device 1 calculates an angle located at a position closer to the right side than one of the actual steering angle θh based on the rotation angle θs of the steering-side motor 13 and the target synchronization angle θsy* (hereinafter referred to as a first-side angle θx) as the target relay angle θrl*. The first-side angle θx of the one of the actual steering angle θh and the target synchronization angle θsy* is located at a position closer to the right side (i.e., the first side) than the other of the actual steering angle θh and the target synchronization angle θsy*. The steering control device 1 according to this embodiment changes the method of calculating the target relay angle θrl* in accordance with the absolute value of the angle difference Δθ between the steering angle θh and the target synchronization angle θsy*.

[0050] Specifically, in a case where the absolute value of the angle difference Δθ is greater than a predetermined angle difference θth, the steering control device 1 calculates an angle located at a position closer to the right side than the first-side angle θx by the minimum rotation amount Δθmin as the target relay angle θrl*. On the other hand, in a case where the absolute value of the angle difference Δθ is equal to or less than the predetermined angle difference θth, the steering control device 1 calculates an angle located at a position closer to the right side than the first-side angle θx by the intermediate rotation amount Δθmod as the target relay angle θrl*.

[0051] The predetermined angle difference θth is a rotation amount indicating that the steering angle θh and the target synchronization angle θsy* are separated from each other to a certain extent, and is set to a rotation amount by which the driver can easily see the rotation when the steering wheel 3 is rotated by the predetermined angle difference θth. The minimum rotation amount Δθmin is set to a rotation amount by which the driver can see the rotation when the steering wheel 3 is rotated by the minimum rotation amount Δθmin. The intermediate rotation amount Δθmod is set to a rotation amount that is greater than the minimum rotation amount Δθmin and equal to or less than a sum value obtained by adding the predetermined angle difference θth to the minimum rotation amount Δθmin.

[0052] In the motor drive processing, the steering control device 1 first sets the target relay angle θrl* as a first target steering angle and performs angle feedback control to adjust the steering angle θh to the first target steering angle. When the steering angle θh reaches the target relay angle θrl*, the steering control device 1 sets the target synchronization angle θsy* as a second target steering angle and performs angle feedback control to adjust the steering angle θh to the second target steering angle. Then, when the steering angle θh reaches the target synchronization angle θsy*, the steering-side motor 13 is stopped.

[0053] A processing routine of the synchronization control performed by the steering control device 1 will be described below. As shown in the flowchart of FIG. 10, upon acquiring various state quantities (step 101), the steering control device 1 determines whether the activation switch 42 has been switched from the off state to the on state based on the activation signal Sig (step 102). That is, in step 102, it is determined whether the activation switch 42 has just been turned on. In the case where the activation switch 42 has not been turned on immediately before (step 102: No), the steering control device 1 does not perform the subsequent processing. Figure 2

[0054] In the case where the activation switch 42 has just been turned on (step 102: Yes), the steering control device 1 calculates the target synchronization angle θsy* (step 103) and calculates the angle difference Δθ (step 104). Subsequently, the steering control device 1 determines whether the angle difference Δθ is zero (step 105), and in the case where the angle difference Δθ is zero (step 105: Yes), does not perform the subsequent processing.

[0055] On the other hand, in the case where the angle difference Δθ is not zero (step 105: No), the steering control device 1 determines whether the absolute value of the angle difference Δθ is greater than a predetermined angle difference Δθth (step 106). In the case where the absolute value of the angle difference Δθ is greater than the predetermined angle difference Δθth (step 106: Yes), the steering control device 1 calculates the target relay angle θrl* by adding the minimum rotation amount Δθmin to the first side angle θx (step 107). Then, the steering control device 1 drives the steering side motor 13 based on the target synchronization angle θsy* calculated in step 103 and the target relay angle θrl* calculated in step 107 (step 108).

[0056] On the other hand, in the case where the absolute value of the angle difference Δθ is equal to or smaller than the predetermined angle difference Δθth (step 106: No), the steering control device 1 calculates the target relay angle θrl* by adding the intermediate rotation amount Δθmod to the first side angle θx (step 109). Then, the steering control device 1 drives the steering side motor 13 based on the target synchronization angle θsy* calculated in step 103 and the target relay angle θrl* calculated in step 109 (step 108).

[0057] The operation of this embodiment will be described below. First, it is assumed that the steering angle θh is located at a position closer to the right side than the target synchronization angle θsy*. As shown in FIG. 11, when the angle difference Δθ is greater than the predetermined angle difference Δθth, the target relay angle θrl* is located at a position closer to the right side than the steering angle θh by the minimum rotation amount Δθmin. Figure 3A

[0058] When the motor drive processing is activated, the steering wheel 3 is turned to the right as shown in FIG. 12, and the steering angle θh is increased. When the steering angle θh reaches the target synchronization angle θsy*, the angle difference Δθ becomes zero. At this time, the activation switch 42 is turned on. Figure 3B ​​the thick solid arrow in FIG. 6 indicates, until the steering angle θh reaches the target relay angle θrl*. Subsequently, when the steering angle θh reaches the target relay angle θrl*, the steering wheel 3 is rotated to the left as indicated by the thick solid arrow in FIG. 6 until the steering angle θh reaches the target synchronization angle θsy*. That is, the steering wheel 3 is rotated to the right once and then to the left. Figure 3C the thick solid arrow in FIG. 6 indicates, until the steering angle θh reaches the target relay angle θrl*. Subsequently, when the steering angle θh reaches the target relay angle θrl*, the steering wheel 3 is rotated to the left as indicated by the thick solid arrow in FIG. 6 until the steering angle θh reaches the target synchronization angle θsy*. That is, the steering wheel 3 is rotated to the right once and then to the left.

[0059] On the other hand, as shown in FIG. 5, when the angle difference Δθ is equal to or smaller than the predetermined angle difference Δθth, the target relay angle θrl* is located at a position closer to the right side than the steering angle θh by an intermediate rotation amount Δθmod. As shown in FIG. 5, the steering wheel 3 is rotated to the right as indicated by the thick solid arrow in FIG. 5 until the steering angle θh reaches the target relay angle θrl*. Subsequently, when the steering angle θh reaches the target relay angle θrl*, the steering wheel 3 is rotated to the left as indicated by the thick solid arrow in FIG. 5 until the steering angle θh reaches the target synchronization angle θsy*. That is, the steering wheel 3 is rotated to the right once and then to the left. Figure 4A Figure 4B and Figure 4C the thick solid arrow in FIG. 6 indicates, until the steering angle θh reaches the target relay angle θrl*. Subsequently, when the steering angle θh reaches the target relay angle θrl*, the steering wheel 3 is rotated to the left as indicated by the thick solid arrow in FIG. 6 until the steering angle θh reaches the target synchronization angle θsy*. That is, the steering wheel 3 is rotated to the right once and then to the left. Figure 3B and Figure 3C the thick solid arrow in FIG. 6 indicates, until the steering angle θh reaches the target relay angle θrl*. Subsequently, when the steering angle θh reaches the target relay angle θrl*, the steering wheel 3 is rotated to the left as indicated by the thick solid arrow in FIG. 6 until the steering angle θh reaches the target synchronization angle θsy*. That is, the steering wheel 3 is rotated to the right once and then to the left.

[0060] Subsequently, it is assumed that the target synchronization angle θsy* is located at a position closer to the right side than the steering angle θh. As shown in FIG. 7, when the angle difference Δθ is greater than the predetermined angle difference Δθth, the target relay angle θrl* is located at a position closer to the right side than the target synchronization angle θsy* by a minimum rotation amount Δθmin. Figure 5A

[0061] When the motor drive process is started, the steering wheel 3 is rotated to the right as indicated by the thick solid arrow in FIG. 6 until the steering angle θh reaches the target relay angle θrl*. Subsequently, when the steering angle θh reaches the target relay angle θrl*, the steering wheel 3 is rotated to the left as indicated by the thick solid arrow in FIG. 6 until the steering angle θh reaches the target synchronization angle θsy*. That is, the steering wheel 3 is rotated to the right once and then to the left. Figure 5B the thick solid arrow in FIG. 6 indicates, until the steering angle θh reaches the target relay angle θrl*. Subsequently, when the steering angle θh reaches the target relay angle θrl*, the steering wheel 3 is rotated to the left as indicated by the thick solid arrow in FIG. 6 until the steering angle θh reaches the target synchronization angle θsy*. That is, the steering wheel 3 is rotated to the right once and then to the left. Figure 5C the thick solid arrow in FIG. 6 indicates, until the steering angle θh reaches the target relay angle θrl*. Subsequently, when the steering angle θh reaches the target relay angle θrl*, the steering wheel 3 is rotated to the left as indicated by the thick solid arrow in FIG. 6 until the steering angle θh reaches the target synchronization angle θsy*. That is, the steering wheel 3 is rotated to the right once and then to the left.

[0062] On the other hand, as shown in FIG. 5, when the angle difference Δθ is equal to or smaller than the predetermined angle difference Δθth, the target relay angle θrl* is located at a position closer to the right side than the steering angle θh by an intermediate rotation amount Δθmod. As shown in FIG. 5, the steering wheel 3 is rotated to the right as indicated by the thick solid arrow in FIG. 5 until the steering angle θh reaches the target relay angle θrl*. Subsequently, when the steering angle θh reaches the target relay angle θrl*, the steering wheel 3 is rotated to the left as indicated by the thick solid arrow in FIG. 5 until the steering angle θh reaches the target synchronization angle θsy*. That is, the steering wheel 3 is rotated to the right once and then to the left. Figure 6A Figure 6B and Figure 6C the thick solid arrow in FIG. 6 indicates, until the steering angle θh reaches the target relay angle θrl*. Subsequently, when the steering angle θh reaches the target relay angle θrl*, the steering wheel 3 is rotated to the left as indicated by the thick solid arrow in FIG. 6 until the steering angle θh reaches the target synchronization angle θsy*. That is, the steering wheel 3 is rotated to the right once and then to the left. Figure 5B and Figure 5C the thick solid arrow in FIG. 6 indicates, until the steering angle θh reaches the target relay angle θrl*. Subsequently, when the steering angle θh reaches the target relay angle θrl*, the steering wheel 3 is rotated to the left as indicated by the thick solid arrow in FIG. 6 until the steering angle θh reaches the target synchronization angle θsy*. That is, the steering wheel 3 is rotated to the right once and then to the left.

[0063] ​​​The advantages of this embodiment will be described below. (1) When the synchronous control is executed by the steering control device 1, the steering wheel 3 is rotated so that the steering angle θh reaches the target synchronous angle θsy* after reaching the target relay angle θrl*, and thus the direction of rotation of the steering wheel 3 is changed during the synchronous operation. That is, the synchronous operation is a two-step operation. The target relay angle θrl* is set to a position that is closer to the right side than one of the steering angle θh and the target synchronous angle θsy* (i.e., the first side angle θx), that is, regardless of the relative positional relationship between the steering angle θh and the target synchronous angle θsy*. One of the steering angle θh and the target synchronous angle θsy* (i.e., the first side angle θx) is positioned closer to the right side (first side) than the other of the steering angle θh and the target synchronous angle θsy*. Thus, regardless of the relative positional relationship between the steering angle θh and the target synchronous angle θsy*, the synchronous operation is executed so that the steering wheel 3 is rotated to the right side and then to the left side. Thus, since the synchronous operation is executed in the same operation manner regardless of the relative positional relationship between the steering angle θh and the target synchronous angle θsy*, it is possible to prevent the driver from feeling uneasy.

[0064] (2) When the angle difference Δθ is greater than the predetermined angle difference Δθth, the steering control device 1 calculates an angle positioned at a position closer to the right side than the first side angle θx by the minimum rotation amount Δθmin as the target relay angle θrl*. Thus, the target relay angle θrl* is prevented from being excessively separated from the other of the steering angle θh and the target synchronous angle θsy* (i.e., the second side angle). The other of the steering angle θh and the target synchronous angle θsy* (i.e., the second side angle) is positioned closer to the left side than the first side angle θx. Thus, it is possible to suppress an increase in the time required for the synchronous operation.

[0065] (3) When the angle difference Δθ is equal to or smaller than the predetermined angle difference Δθth, the steering control device 1 calculates an angle positioned at a position closer to the right side than the first side angle θx by the intermediate rotation amount Δθmod as the target relay angle θrl*. Thus, the target relay angle θrl* is prevented from being excessively close to the first side angle θx. Thus, it is possible to make it easy for the driver to recognize that the synchronous operation is a two-step operation.

[0066] (4) Since the intermediate rotation amount Δθmod is set to a rotation amount equal to or smaller than the sum of the minimum rotation amount Δθmin and the predetermined angle difference Δθth, it is possible to prevent the target relay angle θrl* from being excessively separated from the first side angle θx. Thus, it is possible to suppress an increase in the time required for the synchronous operation.

[0067] (5) The turning control device 1 executes the synchronization control immediately after the start switch 42 is switched from the off state to the on state, and thus it is possible to execute the synchronization operation at an appropriate timing. The embodiment can be modified as follows. The embodiment and the following modification example can be combined unless there is a technical contradiction.

[0068] In the above embodiment, when it is determined in step 105 that the angle difference Δθ is zero, the target relay angle calculation processing and the motor drive processing are not executed, but the present application is not limited to this. When the angle difference Δθ is equal to or smaller than a threshold value set to be slightly larger than zero, the target relay angle calculation processing and the motor drive processing can not be executed.

[0069] In the above embodiment, the synchronization control can be executed at a timing other than the timing immediately after the start switch 42 is switched from the off state to the on state. In the embodiment, the intermediate rotation amount Δθmod can be set to a rotation amount equal to or smaller than the minimum rotation amount Δθmin. The intermediate rotation amount Δθmod can be set to a rotation amount larger than a sum value of the minimum rotation amount Δθmin and the predetermined angle difference Δθth.

[0070] In the above embodiment, as long as the target relay angle θrl* is located at a position closer to the right side than the first side angle θx, the method of calculating the target relay angle θrl* can be appropriately modified. For example, when the angle difference Δθ is larger than the predetermined angle difference Δθth, an angle located at a position closer to the right side than the first side angle θx by the intermediate rotation amount Δθmod can be calculated as the target relay angle θrl*.

[0071] In the above embodiment, the target turn corresponding angle θp* is set to a value obtained by dividing the steering angle θh by a transmission ratio that varies in accordance with the steering angle θh and the vehicle speed V. However, the present application is not limited to this, and for example, the target turn corresponding angle θp* can be set to the same angle as the steering angle θh. In this case, the positional relationship between the steering angle θh and the turn angle θi of the turn wheel 5 is a one-to-one relationship.

[0072] In the above embodiment, the pinion angle θpd detected by the pinion angle sensor 47 is used as the turn side rotation angle, but the present application is not limited to this. A turn corresponding angle θpc based on the rotation angle θt of the turn side motor 32 can be used as the turn side rotation angle.

[0073] In the above embodiment, a steering sensor that directly detects the steering angle θh can be provided, and a detection value from the steering sensor can be used as the steering side rotation angle. In the above embodiment, the steering unit 4 can be configured so that the steering shaft 11 rotates in a range including more than 360°. In this case, the steering angle θh is calculated as an angle in a range including more than 360°.

[0074] In the above-described embodiment, the left side can be a first side in the circumferential direction, and the right side can be a second side in the circumferential direction. In the above-described embodiment, the steering system 2 has a disconnected structure in which the power transmission path between the steering unit 4 and the turning unit 6 is cut off. However, the present application is not limited to this, and the steering system 2 can employ a structure in which the power transmission path between the steering unit 4 and the turning unit 6 can be cut off by a clutch.

[0075] In the above-described embodiment, the steering control device 1 is not limited to a steering control device that includes a CPU and a memory and executes software processing. For example, a dedicated hardware circuit (for example, an ASIC) that executes at least some of the software processing executed in the above-described embodiment can be provided. That is, the steering control device can have at least one of the following configurations (a) to (c). (a) A processor that executes all processing according to a program and a program storage device such as a ROM that stores the program are provided. (b) A processor that executes some of the processing according to a program, a program storage device, and a dedicated hardware circuit that executes the other processing are provided. (c) A dedicated hardware circuit that executes all processing is provided. Here, the number of software processing circuits each including a processor and a program storage device or the number of dedicated hardware circuits can be two or more. That is, the processing can be executed by a processing circuit system including at least one of i) one or more software processing circuits and ii) one or more dedicated hardware circuits.

[0076] The technical idea that can be understood from the embodiments and modified examples and advantages thereof will be described below: (A) A steering control device in which the synchronization control is executed immediately after the start switch is switched from the off state to the on state. With the above-described configuration, it is possible to execute the synchronization operation at an appropriate time.

Claims

1. A steering control device configured to control a steering system having a structure in which a power transmission path between a steering unit (4) connected to a steering wheel (3) and a turning unit (6) that turns a turning wheel (5) is cut, characterized by comprising: control circuitry configured to execute synchronization control for adjusting a steering-side rotation angle by operating a steering-side motor (13) so that a positional relationship between the steering-side rotation angle, which is a rotation angle that can be converted into a steering angle of the steering wheel (3), and a turning-side rotation angle, which is a rotation angle that can be converted into a turning angle of the turning wheel (5), is a predetermined correspondence relationship, the steering unit (4) including the steering-side motor (13) configured to rotate the steering wheel (3), wherein the synchronization control includes: a target synchronization angle calculation process that calculates a target synchronization angle that is a steering-side rotation angle that satisfies the predetermined correspondence relationship with respect to the turning-side rotation angle; a target relay angle calculation process that calculates a target relay angle that is located closer to a first side in a circumferential direction than a first-side angle that is one of the steering-side rotation angle and the target synchronization angle and is located closer to the first side than the other of the steering-side rotation angle and the target synchronization angle; and a motor drive process that, after operating the steering-side motor (13) so that the steering-side rotation angle reaches the target relay angle, operates the steering-side motor (13) so that the steering-side rotation angle reaches the target synchronization angle, sets a lower limit of a rotation amount based on visibility of rotation of the steering wheel (3) and sets the lower limit as a minimum rotation amount; sets a rotation amount greater than the minimum rotation amount as an intermediate rotation amount; and in a case where an absolute value of an angle difference between the steering-side rotation angle and the target synchronization angle is equal to or smaller than a predetermined angle difference, the target relay angle calculation process calculates, as the target relay angle, an angle located closer to the first side than the first-side angle by the intermediate rotation amount.

2. A steering control device configured to control a steering system having a structure in which a power transmission path between a steering unit (4) connected to a steering wheel (3) and a turning unit (6) that turns a turning wheel (5) is cut, characterized by comprising: control circuitry configured to execute synchronization control for adjusting a steering-side rotation angle by operating a steering-side motor (13) so that a positional relationship between the steering-side rotation angle, which is a rotation angle that can be converted into a steering angle of the steering wheel (3), and a turning-side rotation angle, which is a rotation angle that can be converted into a turning angle of the turning wheel (5), is a predetermined correspondence relationship, the steering unit (4) including the steering-side motor (13) configured to rotate the steering wheel (3), wherein the synchronization control includes: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ a target synchronization angle calculation process that calculates a target synchronization angle that is a steering side rotation angle that satisfies a predetermined correspondence with respect to the turn side rotation angle; a target relay angle calculation process that calculates a target relay angle that is located at a position closer to a first side in a circumferential direction than a first side angle, the first side angle being one of the steering side rotation angle and the target synchronization angle and being located at a position closer to the first side than the other of the steering side rotation angle and the target synchronization angle; and a motor drive process that, after operating the steering side motor (13) so that the steering side rotation angle reaches the target relay angle, operates the steering side motor (13) so that the steering side rotation angle reaches the target synchronization angle, sets a lower limit of a rotation amount based on visibility of rotation of the steering wheel (3), and sets the lower limit as a minimum rotation amount; and in a case where an absolute value of an angle difference between the steering side rotation angle and the target synchronization angle is greater than a predetermined angle difference, the target relay angle calculation process calculates, as the target relay angle, an angle located at a position closer to the first side than the first side angle by the minimum rotation amount.

3. The steering control device according to claim 2, characterized in that: a rotation amount greater than the minimum rotation amount is set as an intermediate rotation amount; and in a case where an absolute value of an angle difference between the steering side rotation angle and the target synchronization angle is equal to or smaller than a predetermined angle difference, the target relay angle calculation process calculates, as the target relay angle, an angle located at a position closer to the first side than the first side angle by the intermediate rotation amount.

4. The turning control device according to claim 1 or 3, characterized by The intermediate rotation amount is a rotation amount equal to or smaller than a sum value of the minimum rotation amount and the predetermined angle difference.

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