Steering control device

Abstract

A steering control device is disclosed. A steering control device (1) controls a steering device (2) as a target, the steering device (2) including a steering actuator (12) and a turning actuator (31) having a structure in which a power transmission path is cut off from the steering actuator (12). The steering control device (1) includes a control unit. The control unit is configured to execute: turning side synchronization control when an absolute value of a deviation amount is a value within a first range; steering side synchronization control when the absolute value of the deviation amount is a value within a second range, the value within the second range being a value larger than the value within the first range; and at least one of the turning side synchronization control and the steering side synchronization control when the absolute value of the deviation amount is a value within a third range, the value within the third range being a value between the value within the first range and the value within the second range.

Description

TECHNICAL FIELD

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

[0002] There is a so-called steer-by-wire steering device in which a power transmission path between a steering wheel of a vehicle and a turning wheel of the vehicle is cut off. Such a steering device includes a steering actuator that operates to apply a steering reaction force to the steering wheel and a turning actuator that operates to turn the turning wheel. When the vehicle is running, a steering control device that controls the steering device as a target generates the steering reaction force by controlling power supply to the steering actuator and turns the turning wheel by controlling power supply to the turning actuator.

[0003] In the steer-by-wire steering device, the rotational position of the steering wheel is not limited by the turning position of the turning wheel. Therefore, although the electric power of the vehicle is cut off, the steering wheel can be rotated when subjected to some external force. Since the turning wheel does not turn during this period, a situation in which the positional relationship between the rotational position of the steering wheel and the turning position of the turning wheel deviates from a predetermined correspondence relation can occur.

[0004] As a remedial measure, for example, a steering control device of Japanese Unexamined Patent Application Publication No. 2006-321434 (JP 2006-321434 A) executes a correction process on the rotational position of the steering wheel at the time when the electric power of the vehicle is turned on. In the steering control device, the rotational position of the steering wheel at the time when the electric power of the vehicle is turned off is stored. The steering control device calculates an amount of deviation of the rotational position of the steering wheel by comparing the rotational position of the steering wheel at the time when the electric power of the vehicle is turned off and the rotational position of the steering wheel at the time when the electric power of the vehicle is turned on. Then, the steering control device operates the steering actuator so that the amount of deviation assumes a zero value. SUMMARY

[0005] The fact is that the correction process executed by the steering control device of JP 2006-321434 A can improve the deviation of the positional relationship between the steering wheel and the turning wheel. The method for correcting the positional relationship between the steering wheel and the turning wheel is not limited to the method of the correction process executed by the steering control device of JP 2006-321434 A, and there is still room to propose other methods that are more useful.

[0006] A turning control device according to an aspect of the present application controls a turning device as a target, the turning device including a turning actuator that operates to apply a turning reaction force to a steering wheel of a vehicle, and a turning actuator that has a structure in which a power transmission path from the turning actuator is cut off and operates to turn a turning wheel of the vehicle. The turning control device includes a control unit that performs synchronization control that controls operation of at least one of the turning actuator and the turning actuator such that a positional relationship between a rotation position of the steering wheel and a turning position of the turning wheel satisfies a predetermined correspondence relationship. The control unit is configured to perform processing including deviation amount determination processing that determines a magnitude of an absolute value of a deviation amount of the positional relationship from the predetermined correspondence relationship at a time of power-on of the vehicle, and synchronization control processing that performs the synchronization control based on a determination result of the deviation amount determination processing, the synchronization control being at least one of turning side synchronization control that performs correction processing on the turning position by operating the turning actuator, and turning side synchronization control that performs correction processing on the rotation position by operating the turning actuator. The control unit is configured to perform the following operation in the synchronization control processing: in terms of whether the deviation amount is large or small, when the absolute value of the deviation amount is a value within a first range, the turning side synchronization control is performed, the value within the first range being a small value; in terms of whether the deviation amount is large or small, when the absolute value of the deviation amount is a value within a second range, the turning side synchronization control is performed, the value within the second range being a value larger than the value within the first range; and when the absolute value of the deviation amount is a value within a third range, at least one of the turning side synchronization control and the turning side synchronization control is performed, the value within the third range being a value between the value within the first range and the value within the second range.

[0007] According to this aspect, the turning side synchronization control has an advantage that correction processing on the positional relationship between the steering wheel and the turning wheel can be performed when the steering wheel is not rotated. This advantage can be used in a case where the absolute value of the deviation amount is the value within the first range and is relatively small. The turning side synchronization control has an advantage that correction processing on the positional relationship between the steering wheel and the turning wheel can be easily performed. This advantage can be used in a case where the absolute value of the deviation amount is the value within the second range and is relatively large. In a case where the absolute value of the deviation amount is the value within the third range, at least one of the turning side synchronization control and the turning side synchronization control is specified to be performed, so that the advantage of each control mode can be utilized according to a required effect. Thus, as a method of performing correction processing on the positional relationship between the steering wheel and the turning wheel, a method of utilizing the advantages of the turning side synchronization control and the turning side synchronization control can be proposed.

[0008] In the above aspect, the control unit can be configured to execute the steering side synchronization control when the absolute value of the amount of deviation is a value of the second range or a value within the third range. The control unit can be configured such that the steering side synchronization control is executed as a correction process involving two actions of rotating the steering wheel in one direction and then rotating the steering wheel in a direction opposite to the one direction when the absolute value of the amount of deviation is a value within the second range, and such that the steering side synchronization control is executed as a correction process involving one action of rotating the steering wheel in one direction when the absolute value of the amount of deviation is a value within the third range.

[0009] According to this configuration, the correction process involving two actions of the steering side synchronization control has an advantage that it is less likely to cause discomfort to the driver even if the steering wheel is rotated by a relatively large amount. On the other hand, the correction process involving one action of the steering side synchronization control has an advantage that the correction process of the rotational position of the steering wheel can be completed in a short time compared to the correction process involving two actions. In this case, the advantage of the correction process involving two actions can be used in a case where the steering side synchronization control can be executed and the absolute value of the amount of deviation is a value within the second range that is a large value. The advantage of the correction process involving one action can be used in a case where the steering side synchronization control can be executed and the absolute value of the amount of deviation is a value within the third range that is a small value. This configuration is effective for utilizing the advantages of each of the correction processes involving one action or two actions of the steering side synchronization control.

[0010] In the above aspect, the control unit can be configured to execute the steering side synchronization control and the turning side synchronization control among the turning side synchronization control and the steering side synchronization control when the absolute value of the amount of deviation is a value within a fourth range, the value within the fourth range being a small value among the values within the third range, in terms of whether the values within the third range are large or small, and to execute both the turning side synchronization control and the steering side synchronization control when the absolute value of the amount of deviation is a value within a fifth range, the value within the fifth range being a larger value among the values within the third range than the value within the fourth range, in terms of whether the values within the third range are large or small.

[0011] According to this configuration, the advantages of the turning side synchronization control and the steering side synchronization control can be used in a case where at least one of the turning side synchronization control and the steering side synchronization control is executed and the absolute value of the amount of deviation is a value within the fifth range that is a large value. The advantage of the steering side synchronization control can be used in a case where at least one of the turning side synchronization control and the steering side synchronization control is executed and the absolute value of the amount of deviation is a value within the fourth range that is a small value. This configuration is effective for utilizing the advantages of the turning side synchronization control and the steering side synchronization control.

[0012] In the above-described configuration, the control unit is configured to, when the absolute value of the amount of deviation is a value within the fifth range, execute the turning-side synchronization control before the absolute value of the amount of deviation assumes a value within the first range, and execute the turning-side synchronization control after the absolute value of the amount of deviation assumes a value within the first range, as the turning-side synchronization control and the turning-side synchronization control.

[0013] According to this configuration, the advantage of the turning-side synchronization control that can be utilized in the case where the absolute value of the amount of deviation is relatively large can be more appropriately used in the case where both the turning-side synchronization control and the turning-side synchronization control are executed and the absolute value of the amount of deviation is a value within the fifth range as a large value. This configuration is effective from the viewpoint of facilitating execution of the correction process on the positional relationship between the steering wheel and the turning wheel.

[0014] In the above-described aspect, the control unit can be configured to, when the turning-side synchronization control is executed, execute the correction process on the turning position after the electric power of the vehicle is turned on and the vehicle starts running, and to, when the turning-side synchronization control is executed, execute the correction process on the turning position after the electric power of the vehicle is turned on and before the vehicle starts running.

[0015] According to this configuration, the turning-side synchronization control has an advantage that the time required for the vehicle to start running after the electric power of the vehicle is turned on can be shortened. This advantage can be more effectively used in the case where the absolute value of the amount of deviation is a value within the first range and is relatively small. The turning-side synchronization control has an advantage that the behavior of the vehicle is less likely to cause discomfort to the driver. This advantage can be more effectively used in the case where the absolute value of the amount of deviation is a value within the second range and is relatively large. In this case, the correction process on the positional relationship between the steering wheel and the turning wheel can produce a shortening effect of the period from when the electric power of the vehicle is turned on until the vehicle starts running and a reduction effect of the possibility that the behavior of the vehicle causes discomfort to the driver.

[0016] The steering control device having these aspects can utilize the advantages of the turning-side synchronization control and the turning-side synchronization control as a method of executing the correction process on the positional relationship between the steering wheel and the turning wheel. BRIEF DESCRIPTION OF DRAWINGS

[0017] 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:

[0018] Figure 1 is a schematic configuration diagram of a steer-by-wire steering device;

[0019] Figure 2 is a flowchart showing a flow of a start synchronization process related to the synchronization control;

[0020] Figure 3 This is a flowchart illustrating the normal correction process related to synchronization control;

[0021] Figure 4 It is a table describing the processing involved in synchronization control;

[0022] Figure 5 Parts (a) and (b) show the operating mode of processing method A related to synchronization control;

[0023] Figure 6 Parts (a) and (b) show the operating mode of processing method B related to synchronization control;

[0024] Figure 7 This is a view showing the operating mode of processing method C related to synchronization control, in parts (a) to (c); and

[0025] Figure 8 Parts (a) to (c) show the operating mode of processing method D related to synchronization control. Detailed Implementation

[0026] An embodiment of the steering control device will now be described with reference to the accompanying drawings. Figure 1 As shown, the steering device 2, which serves as the control target of the steering control device 1, is configured as a steer-by-wire type vehicle steering device. The steering device 2 includes a steering section 4 and a rotation section 6. The steering section 4 is steered by the driver via the vehicle's steering wheel 3. The rotation section 6 rotates the vehicle's left and right steering wheels 5 according to the steering input by the driver to the steering section 4. The steering device 2 of this embodiment has a structure in which the power transmission path between the steering section 4 and the rotation section 6 is always mechanically cut off. This means that the power transmission path between the steering actuator 12 (described later) and the rotation actuator 31 (described later) is always mechanically cut off.

[0027] The steering unit 4 includes a steering shaft 11 and a steering actuator 12. The steering shaft 11 is connected to the steering wheel 3. The steering actuator 12 has a steering-side motor 13 as a drive source and a steering-side reduction mechanism 14. The steering-side motor 13 is a reaction force motor that applies a steering reaction force, which is a force resisting steering, to the steering wheel 3 via the steering shaft 11. The steering-side motor 13 is connected to the steering shaft 11 via the steering-side reduction mechanism 14, which is formed, for example, by a worm and a worm gear set. A three-phase brushless motor is used, for example, as the steering-side motor 13 in this embodiment.

[0028] The rotating section 6 includes a pinion shaft 21, a rack shaft 22 as a rotating shaft, and a rack housing 23. The pinion shaft 21 and the rack shaft 22 are coupled together at a predetermined crossing angle. Pinion teeth 21a formed on the pinion shaft 21 and rack teeth 22a formed on the rack shaft 22 are engaged with each other to form a rack and pinion mechanism 24. Accordingly, the pinion shaft 21, which corresponds to its rotation angle, can be converted into a rotation axis of a rotation angle θi, which is a rotational position of the rotating wheels 5. The rack housing 23 accommodates the rack and pinion mechanism 24. One end of the pinion shaft 21 on a side opposite to the side coupled to the rack shaft 22 protrudes from the rack housing 23. Both ends of the rack shaft 22 protrude from both ends of the rack housing 23 in the axis direction. A tie rod 26 is coupled to each end of the rack shaft 22 through a rack end 25 formed by a ball joint. A front end of the tie rod 26 is coupled to a knuckle (not shown) on which the left and right rotating wheels 5 are respectively mounted.

[0029] The rotating section 6 includes a rotating actuator 31. The rotating actuator 31 includes a rotating side motor 32 as a drive source, a transmission mechanism 33, and a conversion mechanism 34. The rotating side motor 32 applies a rotating force for rotating the rotating wheels 5 to the rack shaft 22 through the transmission mechanism 33 and the conversion mechanism 34. The rotating side motor 32 transmits rotation to the conversion mechanism 34 through the transmission mechanism 33 formed by, for example, a belt transmission mechanism. The transmission mechanism 33 converts the rotation of the rotating side motor 32 into reciprocating motion of the rack shaft 22 through the conversion mechanism 34 formed by, for example, a ball screw mechanism. A three-phase brushless motor is employed as the rotating side motor 32 of the present embodiment.

[0030] In the steering device 2 thus configured, when a motor torque is applied as a rotating force from the rotating actuator 31 to the rack shaft 22 in accordance with a steering operation by the driver, the rotation angle θi of the rotating wheels 5 is changed. At the same time, a steering reaction force against the steering by the driver is applied from the steering actuator 12 to the steering wheel 3. Accordingly, in the steering device 2, a steering torque Th required to steer the steering wheel 3 is changed by the steering reaction force as the motor torque applied from the steering actuator 12.

[0031] The reason for providing the pinion shaft 21 is to support the rack shaft 22 together with the pinion shaft 21 in the rack housing 23. Specifically, the rack shaft 22 is supported so as to be movable in the axis direction thereof and is pressed against the pinion shaft 21 by a support mechanism (not shown) provided in the steering device 2. Accordingly, the rack shaft 22 is supported in the rack housing 23. Alternatively, the pinion shaft 21 can not be used, and other support mechanisms that support the rack shaft 22 in the rack housing 23 can be provided.

[0032] Electrical configuration of the steering device 2

[0033] As Figure 1As shown in FIG. 1, the steering-side motor 13 and the turning-side motor 32 are connected to the steering control device 1. The steering control device 1 controls the operation of the steering-side motor 13 and the turning-side motor 32. The main power supply 41 is connected to the steering control device 1, i.e., the steering device 2. The main power supply 41 is a storage battery installed in the vehicle, and serves as a power supply for the operation of the motors 13, 32 and as a power supply for the operation of the steering control device 1, i.e., the steering device 2.

[0034] A start signal Sig showing the on or off state of a start switch 42, e.g., an ignition switch, of the vehicle is input to the steering control device 1. The start switch 42 is provided between the steering control device 1 and the main power supply 41. The start switch 42 is manipulated to activate a travel driving source, e.g., an engine, of the vehicle, and thereby start various functions to allow the operation of the vehicle. The electric power from the main power supply 41 is switched between supply and cutoff by the manipulation of the start switch 42. In this embodiment, the operation state of the steering device 2 is related to the operation state of the vehicle.

[0035] Further, the detection results of various sensors are input to the steering control device 1. Examples of the various sensors include a vehicle speed sensor 43, a steering torque sensor 44, a steering-side rotation angle sensor 45, and a turning-side rotation angle sensor 46.

[0036] The vehicle speed sensor 43 detects a vehicle speed V as a travel speed of the vehicle. The steering torque sensor 44 detects a steering torque Th as a value showing the torque applied to the steering shaft 11 by the steering operation of the driver. The steering-side rotation angle sensor 45 detects a rotation angle Θs as an angle of a rotation axis of the steering-side motor 13 in a range of 360 degrees. The turning-side rotation angle sensor 46 detects a rotation angle Θt as an angle of a rotation axis of the turning-side motor 32 in a range of 360 degrees.

[0037] Specifically, the steering torque sensor 44 is provided at a portion of the steering shaft 11 on the side of the steering wheel 3 relative to the steering-side reduction mechanism 14. The steering torque sensor 44 detects the steering torque Th based on the torsion of a torsion bar (not shown) provided at an intermediate point on the steering shaft 11. For example, when the vehicle is steered to the right, the steering torque Th is detected as a positive value, and when the vehicle is steered to the left, the steering torque Th is detected as a negative value.

[0038] A steering-side rotation angle sensor 45 is installed in the steering-side motor 13. The rotation angle θs of the steering-side motor 13 is used to calculate the steering angle θh. The steering-side motor 13 and the steering shaft 11 are interlocked with each other via a steering-side reduction mechanism 14. Therefore, there is a correlation between the rotation angle θs of the steering-side motor 13 and the rotation angle of the steering shaft 11, and extended to, there is a correlation between the rotation angle θs of the steering-side motor 13 and the steering angle θh, which is the rotation angle used to display the rotational position of the steering wheel 3. Therefore, the steering angle θh can be obtained based on the rotation angle θs of the steering-side motor 13. For example, when the vehicle turns right, the rotation angle θs is detected as a positive value, while when the vehicle turns left, the rotation angle θs is detected as a negative value.

[0039] A rotation angle sensor 46 is installed in the rotation-side motor 32. The rotation angle θt of the rotation-side motor 32 is used to calculate the pinion angle θp. The rotation-side motor 32 and the pinion shaft 21 are interlocked with each other via a transmission mechanism 33, a conversion mechanism 34, and a rack and pinion mechanism 24. Therefore, there is a correlation between the rotation angle θt of the rotation-side motor 32 and the pinion angle θp, which is the rotation angle of the pinion shaft 21. Thus, the pinion angle θp can be obtained based on the rotation angle θt of the rotation-side motor 32. The pinion shaft 21 meshes with the rack shaft 22. Correspondingly, there is also a correlation between the pinion angle θp and the amount of movement of the rack shaft 22. Therefore, the pinion angle θp is the value of the rotation angle θi that reflects the rotational position of the rotating wheel 5. For example, when the vehicle turns right, the rotation angle θt is detected as a positive value, while when the vehicle turns left, the rotation angle θt is detected as a negative value.

[0040] Function of steering control device 1

[0041] like Figure 1 As shown, the steering control device 1 has a steering-side control unit 50 and a rotation-side control unit 60. The steering-side control unit 50 controls the power supply to the steering-side motor 13. The rotation-side control unit 60 controls the power supply to the rotation-side motor 32.

[0042] In the steering control device 1, the steering-side control unit 50 and the rotation-side control unit 60 each include a CPU (not shown) and a memory. In both the steering-side control unit 50 and the rotation-side control unit 60, the CPU executes a program stored in the memory in a cycle of predetermined calculation periods. Therefore, various processes are performed. The steering-side control unit 50 and the rotation-side control unit 60 send and receive information from each other via a local network 47, such as a serial communication network. In this embodiment, the steering-side control unit 50 and the rotation-side control unit 60 are examples of control units.

[0043] Specifically, the steering torque Th, the vehicle speed V, and the rotation angle θs are input into the steering side control unit 50. Based on the steering torque Th and the vehicle speed V, the steering side control unit 50 calculates a target reaction force torque as a target value of the steering reaction force. Then, the steering side control unit 50 controls the steering side motor 13 so that a motor torque according to the target reaction force torque is generated. Thus, the steering reaction force is applied to the steering portion 4.

[0044] Further, the steering side control unit 50 converts the rotation angle θs into a cumulative angle including a range exceeding 360 degrees by, for example, counting the number of rotations of the steering side motor 13 from a steering neutral position, which is a position of the steering wheel 3 when the vehicle is traveling straight ahead. Then, the steering side control unit 50 calculates the steering angle θh by multiplying the cumulative angle obtained by the conversion by a conversion factor based on the speed ratio of the steering side reduction mechanism 14. The steering angle θh thus obtained is output to the turning side control unit 60 through the local network 47.

[0045] The vehicle speed V, the rotation angle θt, and the steering angle θh are input into the turning side control unit 60. The turning side control unit 60 converts the rotation angle θt into a cumulative angle including a range exceeding 360° by, for example, counting the number of rotations of the turning side motor 32 from a rack neutral position, which is a position of the rack shaft 22 when the vehicle is traveling straight ahead. Then, the turning side control unit 60 calculates the pinion angle θp as an actual rotation angle of the pinion shaft 21 by multiplying the cumulative angle obtained by the conversion by a conversion factor based on the speed ratio of the transmission mechanism 33, the lead of the conversion mechanism 34, and the speed ratio of the rack and pinion mechanism 24.

[0046] Further, the turning side control unit 60 calculates a target pinion angle θp* as a target value of the pinion angle θp based on the steering angle θh. In this case, the turning side control unit 60 calculates the target pinion angle θp* corresponding to the steering angle θh based on a steering angle ratio. The steering angle ratio refers to a ratio between the steering angle θh and the pinion angle θp reflecting the turning angle θi, and changes as, for example, the steering angle θh and the vehicle speed V change. The turning side control unit 60 calculates a target turning torque as a target value of the turning force by performing feedback control so that the pinion angle θp adapts to the target pinion angle θp*. Then, the turning side control unit 60 controls the turning side motor 32 so that a motor torque according to the target turning torque is generated. Thus, the turning force is applied to the turning portion 6. Thus, the turning side control unit 60 controls the steering apparatus 2 so that the positional relationship between the steering angle θh and the turning angle θi satisfies a predetermined correspondence determined in accordance with the steering angle ratio.

[0047] The start switch 42 is in the off state

[0048] When the start switch 42 is off, the steering wheel 3 can be rotated when subjected to some external force. In this case, since the start switch 42 is off, the turning side control unit 60 does not rotate the turning wheel 5 by the control of the turning side motor 32. Therefore, the positional relationship between the steering angle θh and the turning angle θi deviates from the predetermined correspondence relationship. The same applies to the case where the turning wheel 5 is rotated when subjected to some external force while the start switch 42 is off.

[0049] As a remedy, the steering control device 1 is configured to execute synchronization control when the positional relationship between the steering angle θh and the turning angle θi, i.e., the positional relationship between the steering angle θh and the pinion angle θp, is not the predetermined correspondence relationship, so that the positional relationship satisfies the predetermined correspondence relationship. The steering control device 1 executes the synchronization control of at least one of the steering side synchronization control and the turning side synchronization control.

[0050] The steering side synchronization control is the control of the steering actuator 12 by the control operation of the steering side motor 13. Specifically, in the steering side synchronization control, the correction process is executed on the rotational position of the steering wheel 3 so that the positional relationship between the steering angle θh and the pinion angle θp satisfies the predetermined correspondence relationship. The steering side synchronization control is executed as the start synchronization process, which is one of the processes executed by the steering side control unit 50 at the timing after the start switch 42 is turned on and before the vehicle starts running.

[0051] The turning side synchronization control is the control of the turning actuator 31 by the control operation of the turning side motor 32. Specifically, in the turning side synchronization control, the correction process is executed on the rotational position of the turning wheel 5 so that the positional relationship between the steering angle θh and the pinion angle θp satisfies the predetermined correspondence relationship. The turning side synchronization control is executed as the normal correction process, which is one of the processes executed by the turning side control unit 60 at the timing when the start switch 42 is turned on and after the vehicle starts running.

[0052] Start synchronization process

[0053] Figure 2 is one example of a flowchart of the process procedure of the start synchronization process executed by the steering side control unit 50. The steering side control unit 50 executes the following start synchronization process by executing the periodic process on the loop of the control cycle. The trigger for the start of the start synchronization process is the turning on of the start switch 42, and the start of the power supply to the steering control device 1.

[0054] In the start synchronization processing, the steering side control unit 50 calculates the deviation amount Δθ (step S10). This processing is processing for detecting a state variable that serves as a reference for determining the degree of deviation of the positional relationship between the steering angle θh and the pinion angle θp at the time when the start switch 42 is turned on from the predetermined correspondence relationship. In this embodiment, the deviation amount Δθ is the magnitude of the absolute value of the deviation amount of the positional relationship between the steering angle θh and the pinion angle θp at the time when the start switch 42 is turned on from the predetermined correspondence relationship. For example, the deviation amount Δθ is calculated as the absolute value of the difference between the steering angle θh and the rotation conversion angle θp_s that is obtained based on the steering angle ratio as a value corresponding to the pinion angle θp. The rotation side control unit 60 obtains the rotation conversion angle θp_s that corresponds to the pinion angle θp by calculation based on the steering angle ratio.

[0055] Further, while the start switch 42 is off, as long as the main power source 41 is connected, the steering side control unit 50 of this embodiment holds the value of the steering angle θh at the point when the start switch 42 is off and monitors the rotation of the steering side motor 13. When the steering side motor 13 rotates while the start switch 42 is off, the next time the start switch 42 is turned on, the steering side control unit 50 calculates the steering angle θh that has changed by an amount corresponding to this rotation of the steering side motor 13. The same applies to the rotation side control unit 60. Specifically, also while the start switch 42 is off, as long as the main power source 41 is connected, the rotation side control unit 60 holds the value of the pinion angle θp at the point when the start switch 42 is off and monitors the rotation of the rotation side motor 32. When the rotation side motor 32 rotates while the start switch 42 is off, the next time the start switch 42 is turned on, the rotation side control unit 60 calculates the pinion angle θp that has changed by an amount corresponding to this rotation of the rotation side motor 32. Therefore, the pinion angle θp calculated when the start switch 42 is turned on is output to the steering side control unit 50 as the rotation conversion angle θp_s calculated based on the steering angle ratio.

[0056] Subsequently, the steering side control unit 50 determines whether the deviation amount Δθ is equal to or smaller than the first threshold value θ1 (Δθ ≤ θ1) (step S11). This processing corresponds to a deviation amount determination processing for determining whether the steering side synchronization control needs to be executed.

[0057] In this embodiment, the first threshold value θ1 is set to the maximum value among values obtained through experiments in a range such that even when the vehicle is caused to start traveling with the deviation amount Δθ, such behavior of the vehicle is unlikely to cause discomfort to the driver. In this embodiment, a value equal to or smaller than the first threshold value θ1 corresponds to a value within the first range.

[0058] When the steering side control unit 50 determines in step Sll that the deviation amount Δθ is equal to or smaller than the first threshold value θl (step Sll: YES), the steering side control unit 50 determines that the steering side synchronization control need not be executed. Based on the determination result of YES in step Sll, the steering side control unit 50 ends the startup synchronization processing by considering that the startup synchronization processing has been completed. In this case, the steering side control unit 50 generates a synchronization processing completion flag FLG as information indicating that the startup synchronization processing has been completed, and outputs the synchronization processing completion flag FLG to the turning side control unit 60 through the local network 47. Thereafter, the steering side control unit 50 executes the steering side control during the power-on period of the online control steering apparatus 2.

[0059] On the other hand, when the steering side control unit 50 determines in step Sll that the deviation amount Δθ is not equal to or smaller than the first threshold value θl (step Sll: NO), the steering side control unit 50 determines that the steering side synchronization control needs to be executed. Based on the determination result of NO in step Sll, the steering side control unit 50 determines whether the deviation amount Δθ is greater than the sum of the first threshold value θl and the second threshold value θ2 (Δθ > θl + θ2) (step S12). This processing corresponds to a deviation amount determination processing for determining the specific content of the correction processing of the steering side synchronization control when it is determined that the steering side synchronization control needs to be executed.

[0060] In this embodiment, the second threshold value θ2 is set to the maximum value among the values within a range obtained through experiments such that even when the steering wheel 3 is rotated to make the deviation amount Δθ close to a zero value, such rotation of the steering wheel 3 is unlikely to cause discomfort to the driver. Thus, a value greater than the sum of the threshold values θl, θ2 indicates that both making the vehicle start traveling at this deviation amount Δθ and rotating the steering wheel 3 so as to make the deviation amount Δθ close to a zero value are likely to cause discomfort to the driver. In this embodiment, a value greater than the sum of the threshold values θl, θ2 corresponds to a value within the second range.

[0061] When the steering side control unit 50 determines in step S12 that the deviation amount Δθ is greater than the sum of the threshold values θl, θ2 (step S12: YES), the steering side control unit 50 determines to execute the regular synchronization control as the steering side synchronization control. In this case, the steering side control unit 50 executes the regular synchronization control such that the deviation amount Δθ assumes a zero value (Δθ = 0) (step S13). This processing corresponds to a synchronization control processing executed based on the determination results of steps Sll, S12 corresponding to the deviation amount determination processing. In the regular synchronization control, a correction processing is executed on the rotational position of the steering wheel 3 by rotating the steering wheel 3 such that the deviation amount Δθ assumes a zero value before the vehicle starts traveling. In this embodiment, the regular synchronization control is specified as a correction processing involving two actions of rotating the steering wheel 3 in one direction and then rotating the steering wheel 3 in a direction opposite to this one direction.

[0062] Specifically, for the regular synchronization control, the steering side control unit 50 calculates a synchronization target steering angle θh* that is the steering angle θh at which the deviation amount Δθ assumes a zero value. In this case, the steering side control unit 50 calculates, as the synchronization target steering angle θh*, a value of the turning conversion angle θp_s used for calculating the deviation amount Δθ.

[0063] Further, the steering side control unit 50 calculates a relay target steering angle θhr* that is the steering angle θh used as a relay point at the time of obtaining the synchronization target steering angle θh*. In this case, the steering side control unit 50 calculates, as the relay target steering angle θhr*, an angle obtained by further changing one of the steering angle θh and the synchronization target steering angle θh* on the positive value side toward the positive value side by a predetermined amount.

[0064] Then, the steering side control unit 50 executes feedback control so that the steering angle θh matches the relay target steering angle θhr*, and thus controls the steering side motor 13 so as to rotate the steering wheel 3. This can be referred to as a first stage of the regular synchronization control in relation to the regular synchronization control. Accordingly, a rotational force toward the positive value side of the steering angle θh is applied to the steering wheel 3. Thus, the steering side control unit 50 controls the operation of the steering actuator 12 so that the steering wheel 3 rotates in one direction of the right direction.

[0065] Subsequently, when the steering angle θh matches the relay target steering angle θhr*, the steering side control unit 50 executes feedback control so that the steering angle θh matches the synchronization target steering angle θh*, and thus controls the steering side motor 13 so as to further rotate the steering wheel 3. This can be referred to as a second stage of the regular synchronization control executed after the first stage in relation to the regular synchronization control. Accordingly, a rotational force toward the negative value side of the steering angle θh is applied to the steering wheel 3. Thus, the steering side control unit 50 controls the operation of the steering actuator 12 so that the steering wheel 3 rotates in the left direction that is the direction opposite to the right direction.

[0066] Thereafter, when the steering angle θh matches the synchronization target steering angle θh*, the steering side control unit 50 ends the regular synchronization control, that is, the processing of step S13, and ends the start synchronization processing by considering that the start synchronization processing has been completed. In this case, as when "Yes" is determined in step Sll, the steering side control unit 50 generates and outputs the synchronization processing completion flag FLG to the turning side control unit 60, and then executes the steering side control during the power-on period of the steer-by-wire steering apparatus 2.

[0067] On the other hand, when the steering side control unit 50 determines in step S12 that the deviation amount Δθ is not greater than the sum of the threshold values θ1, θ2 (step S12: No), the steering side control unit 50 determines that the deviation amount Δθ is equal to or smaller than the sum of the threshold values θ1, θ2. Based on the determination result of "No" in step S12, the steering side control unit 50 determines whether the deviation amount Δθ is greater than the first threshold value θ1 and equal to or smaller than the second threshold value θ2 (θ1 < Δθ ≤ θ2) (step S14). This processing corresponds to deviation determination processing for determining whether the deviation amount Δθ is within a range of a value equal to or smaller than the smaller one of the threshold values θ1, θ2.

[0068] In this embodiment, a value greater than the first threshold value θ1 and equal to or smaller than the second threshold value θ2 indicates that starting the vehicle to travel at the deviation amount Δθ can cause discomfort to the driver, but rotating the steering wheel 3 so as to make the deviation amount Δθ close to the zero value is unlikely to cause discomfort to the driver. In this embodiment, a value equal to or smaller than the sum of the threshold values θ1, θ2 corresponds to a value within the third range. A value greater than the first threshold value θ1 and equal to or smaller than the second threshold value θ2 corresponds to a value within the fourth range, which is the smaller one of the values within the third range in terms of whether the value is large or small.

[0069] When the steering side control unit 50 determines in step S14 that the deviation amount Δθ is greater than the first threshold value θ1 and equal to or smaller than the second threshold value θ2 (step S14: Yes), the steering side control unit 50 determines to execute the first simplified synchronization control as the steering side synchronization control. In this case, the steering side control unit 50 executes the first simplified synchronization control so that the deviation amount Δθ assumes a zero value (Δθ = 0) (step S15). This processing corresponds to synchronization control processing executed based on the determination result of steps S11, S12, S14 corresponding to the deviation determination processing. In the first simplified synchronization control, a correction processing is executed on the rotational position of the steering wheel 3 by rotating the steering wheel 3 so that the deviation amount Δθ assumes a zero value before the vehicle starts to travel. In this embodiment, the first simplified synchronization control is specified as a correction processing involving one action of rotating the steering wheel 3 in one direction.

[0070] Specifically, for the first simplified synchronization control, the steering side control unit 50 calculates a synchronization target steering angle θh* that is the steering angle θh at which the deviation amount Δθ assumes a zero value. In this case, as when the regular synchronization control is executed, the steering side control unit 50 calculates a value of the turning conversion angle θp_s used to calculate the deviation amount Δθ as the synchronization target steering angle θh*.

[0071] Then, the turning side control unit 50 executes feedback control so that the steering angle θh matches the synchronization target steering angle θh* and thus controls the turning side motor 13 so as to rotate the steering wheel 3. Accordingly, a rotation force toward the synchronization target steering angle θh* is applied to the steering wheel 3. Thus, the turning side control unit 50 controls the operation of the turning actuator 12 so that the steering wheel 3 rotates in one of the leftward direction and the rightward direction.

[0072] Thereafter, when the steering angle θh matches the synchronization target steering angle θh*, the turning side control unit 50 ends the first simplified synchronization control, that is, the process of step S15, and ends the start synchronization process by considering that the start synchronization process has been completed. In this case, as when "Yes" is determined in step Sll, the turning side control unit 50 generates and outputs the synchronization process completion flag FLG to the turning side control unit 60, and then executes the turning side control during the energization of the steer-by-wire steering apparatus 2.

[0073] On the other hand, when the turning side control unit 50 determines that the deviation amount Δθ is greater than the first threshold value θl and not equal to or smaller than the second threshold value θ2 in step S14 (step S14: No), the turning side control unit 50 determines to execute the second simplified synchronization control as the turning side synchronization control. This process corresponds to a deviation amount determination process for determining that the deviation amount Δθ is a value greater than the second threshold value θ2 and equal to or smaller than the sum of the threshold values θl, θ2, that is, the deviation amount Δθ is a value equal to or smaller than the larger one of the sum of the threshold values θl, θ2.

[0074] In this embodiment, a value greater than the second threshold value θ2 and equal to or smaller than the sum of the threshold values θl, θ2 indicates that both starting the vehicle to travel at this deviation amount Δθ and rotating the steering wheel 3 so as to make the deviation amount Δθ approach a zero value are likely to cause discomfort to the driver. However, a value range greater than the first threshold value θl is included in a value range equal to or smaller than the second threshold value θ2. This means that starting the vehicle to travel at a deviation amount Δθ in a range equal to or smaller than the first threshold value θl is less likely to cause discomfort to the driver, and rotating the steering wheel 3 so as to make the deviation amount Δθ approach a zero value in a value range greater than the first threshold value θl is also less likely to cause discomfort to the driver. In this embodiment, a value greater than the second threshold value θ2 and equal to or smaller than the sum of the threshold values θl, θ2 corresponds to a value in the fifth range, which is the larger one of the values in the third range than the values in the fourth range, in terms of whether the value is large or small.

[0075] When the steering side control unit 50 determines "No" in step S14, the steering side control unit 50 executes second simplified synchronization control so that the deviation amount Δθ assumes the first threshold value θ1 (Δθ = θ1) (step S16). This processing corresponds to synchronization control processing executed on the basis of the determination result of steps S11, S12, S14 corresponding to the deviation amount determination processing. In the second simplified synchronization control, correction processing is executed on the rotational position of the steering wheel 3 by rotating the steering wheel 3 so that the deviation amount Δθ assumes the first threshold value θ1 before the vehicle starts running. In this embodiment as well, as with the first simplified synchronization control, the second simplified synchronization control is specified as correction processing involving one action of rotating the steering wheel 3 in one direction.

[0076] Specifically, for the second simplified synchronization control, the steering side control unit 50 calculates a synchronization target steering angle θh* that is the steering angle θh when the deviation amount Δθ assumes the first threshold value θ1. In this case, the steering side control unit 50 calculates, as the synchronization target steering angle θh*, a value obtained by changing the value of the turning conversion angle θp_s used to calculate the deviation amount Δθ toward the steering angle θh by the first threshold value θ1.

[0077] Then, the steering side control unit 50 executes feedback control so that the steering angle θh matches the synchronization target steering angle θh* and thus controls the steering side motor 13 so as to rotate the steering wheel 3. Thus, a rotational force toward the synchronization target steering angle θh* is applied to the steering wheel 3. Accordingly, the steering side control unit 50 controls the operation of the steering actuator 12 so that the steering wheel 3 rotates in one of the leftward direction and the rightward direction.

[0078] Thereafter, when the steering angle θh matches the synchronization target steering angle θh*, the steering side control unit 50 ends the second simplified synchronization control, that is, the processing of step S16, and ends the start synchronization processing by considering that the start synchronization processing has been completed. In this case as well, as when "Yes" is determined in step S11, the steering side control unit 50 generates and outputs the synchronization processing completion flag FLG to the turning side control unit 60, and then executes steering side control during energization of the steer-by-wire steering apparatus 2.

[0079] Normal Correction Processing

[0080] Figure 3is one example of a flowchart of a process procedure of the normal correction processing executed by the rotation-side control unit 60. The rotation-side control unit 60 executes the following normal correction processing by executing periodic processing on a cycle of the control period. The trigger for the start of the normal correction processing is the input of the synchronization processing completion flag FLG after the turning-on of the start switch 42, and the start of the supply of electric power to the steering control device 1. This means that the trigger for the start of the normal correction processing is the completion of the start synchronization processing executed by the steering-side control unit 50. Since the synchronization processing completion flag FLG is input, the rotation-side control unit 60 executes the rotation-side control during the power-on period of the online control steering device 2. Therefore, the normal correction processing is executed as one of the processes of the rotation-side control executed by the rotation-side control unit 60 during the power-on period.

[0081] In the normal correction processing, the rotation-side control unit 60 calculates the offset amount θofst(Step S20). This processing is processing for detecting a state variable that serves as a reference for determining the offset amount Δθ that remains as a result of the start synchronization processing.

[0082] In this embodiment, the offset amount θofst is an amount of the direction of the deviation of the positional relationship between the steering angle θh and the pinion angle θp from the predetermined correspondence relationship after the turning-on of the start switch 42 and the completion of the start synchronization processing executed by the steering-side control unit 50. For example, the offset amount θofst is calculated by subtracting the pinion angle θp from the target pinion angle θp* that is a value corresponding to the steering angle θh obtained on the basis of the steering angle ratio. The steering angle θh used for the calculation of the offset amount θofst is the steering angle θh outputted to the local network 47 by the steering-side control unit 50 in the first control period after the completion of the start synchronization processing.

[0083] Subsequently, the rotation-side control unit 60 determines whether the offset amount θofst is equal to a zero value (θofst = 0) (Step S21). This processing is processing for determining whether the execution of the rotation-side synchronization control is necessary. In this embodiment, the offset amount θofst is a value corresponding to the offset amount Δθ that is substantially equal to or smaller than the first threshold value θ1. This is because the offset amount Δθ that remains as a result of the start synchronization processing is substantially equal to or smaller than the first threshold value θ1. Therefore, the offset amount θofst is a value within a range in which such behavior of the vehicle is unlikely to cause discomfort to the driver even when the vehicle is caused to start running while having the offset amount θofst.

[0084] When the rotation-side control unit 60 determines in step S21 that the offset θofst is equal to the zero value (step S21: YES), the rotation-side control unit 60 determines that the rotation-side synchronous control need not be executed. Based on the determination result of "YES" in step S21, the rotation-side control unit 60 ends the normal correction processing by considering that the normal correction processing has been completed.

[0085] On the other hand, when the rotation-side control unit 60 determines in step S21 that the offset θofst is not equal to the zero value (step S21: NO), the rotation-side control unit 60 determines that the rotation-side synchronous control needs to be executed. In this case, the rotation-side control unit 60 executes the rotation offset control as the rotation-side control so that the offset θofst assumes the zero value (θofst = 0) (step S22). This processing corresponds to the synchronous control processing executed based on the determination result of steps S11, S12, S14 of the start synchronous processing corresponding to the deviation amount determination processing. In the rotation offset control, the correction processing is executed on the rotation position of the rotation wheel 5 by rotating the rotation wheel 5 so that the offset θofst assumes the zero value after the vehicle starts running.

[0086] Specifically, for the rotation offset control, the rotation-side control unit 60 calculates a compensated target pinion angle θp* obtained by subtracting the offset θofst from the target pinion angle θp* that assumes a value corresponding to the steering angle θh based on the steering angle ratio.

[0087] Then, before the offset θofst assumes the zero value, the rotation-side control unit 60 executes the feedback control as the rotation-side control during energization so that the pinion angle θp is adapted to the compensated target pinion angle θp*. This allows the vehicle to start running while having the offset θofst even when the offset θofst is not equal to the zero value. Therefore, the rotation-side control unit 60 controls the operation of the rotation actuator 31 so that the vehicle can start running while having the offset θofst.

[0088] Further, in a case where the running of the vehicle is detected based on the vehicle speed V, the rotation-side control unit 60 executes a reduction processing that gradually brings the offset θofst close to the zero value until the offset θofst assumes the zero value. In this case, for example, the rotation-side control unit 60 makes the reduction amount larger as the rotation speed or the vehicle speed V corresponding to the amount of change in the pinion angle θp is larger.

[0089] Thereafter, when the offset θofst matches the zero value, the rotation-side control unit 60 ends the rotation offset control, that is, the processing of step S22, and ends the normal correction processing by considering that the normal correction processing has been completed.

[0090] Contents of synchronous control processing

[0091] As shown in Figure 4 , the steering control device 1 performs synchronous control of four types of processing modes A, B, C, and D based on the magnitude of the deviation amount Δθ.

[0092] Processing mode A

[0093] When the deviation amount Δθ is equal to or smaller than the first threshold value θ1 Figure 4 , synchronous control is performed in processing mode A. In this case, steering-side synchronous control is not performed in the start-up synchronization processing Figure 4 , and in the normal correction processing, the rotation offset control is performed as rotation-side synchronous control.

[0094] Operation mode of processing mode A

[0095] As a precondition, for example, as shown in part (a) of Figure 5 , immediately after the on of the start-up switch 42, the steering angle θh has deviated from the rotation conversion angle θp_s, which is obtained as a value corresponding to the pinion angle θp based on the steering angle ratio, toward the right side as the positive value side. Therefore, the deviation amount Δθ of the rotational position of the steering wheel 3 from the rotation conversion angle θp_s is an angle Ra_h having a value equal to or smaller than the first threshold value θ1. In this case, steering-side synchronous control for the steering wheel 3 is not performed, and the vehicle is caused to start running while having the angle Ra_h as the deviation amount Δθ.

[0096] Then, as shown in part (b) of Figure 5 , at the start of running of the vehicle, the offset amount θofst is an angle Ra_p obtained as a value corresponding to the angle Ra_h of the deviation amount Δθ. Subsequently, immediately after the vehicle starts running, the rotation offset control for the rotation wheel 5 is performed so that the rotational position of the rotation wheel 5 is corrected to be in a predetermined correspondence relationship with the rotational position of the steering wheel 3 so that the angle Ra_p as the offset amount θofst assumes a zero value. For example, when the rotational position of the steering wheel 3 is to be held at a rotational position in which the deviation amount Δθ is the angle Ra_h, the rotation wheel 5 is rotated by the angle Ra_p toward the right side as the positive value side.

[0097] Processing mode B

[0098] When the deviation amount Δθ is greater than the first threshold value θ1 and equal to or smaller than the second threshold value θ2 (θ1 < Δθ ≤ θ2), synchronous control is performed in processing mode B. In this case, the first simplified synchronous control is performed in the start-up synchronization processing, and steering-side synchronous control is not performed in Figure 4 , in the normal correction processing.

[0099] Operation mode of processing mode B

[0100] As a prerequisite, for example, Figure 6 As shown in part (a), immediately after the start switch 42 is turned on, the steering angle θh has already deviated from the rotation conversion angle θp_s, which is obtained based on the steering angle ratio and corresponds to the pinion angle θp, towards the right side, which is the positive side. Therefore, the deviation Δθ between the rotational position of the steering wheel 3 and the rotation conversion angle θp_s is an angle Rb_h, the value of which is greater than the first threshold θ1 and equal to or less than the second threshold θ2. In this case, a first simplified synchronization control is performed before the vehicle starts moving, thereby rotating the steering wheel 3 so that the deviation Δθ presents a zero value.

[0101] Then, as Figure 6 As shown in part (b), a first simplified synchronization control is performed on the steering wheel 3 to correct the rotational position of the steering wheel 3 to correspond to the rotational position of the wheel 5 in a predetermined manner, such that the angle Rb_h is zero as a deviation. Therefore, the rotational position of the steering wheel 3 is rotated by an angle Rb_h toward the left, which is the negative side.

[0102] Processing method C

[0103] When the deviation Δθ is greater than the second threshold θ2 and equal to or less than the sum of thresholds θ1 and θ2 (θ2 < Δθ ≤ θ1 + θ2), synchronization control is performed in processing mode C. In this case, second simplified synchronization control is performed in the initial synchronization process, and rotational offset control is performed in the normal correction process.

[0104] Operation mode of processing method C

[0105] As a prerequisite, for example, Figure 7 As shown in part (a), immediately after the start switch 42 is turned on, the steering angle θh has already deviated from the rotation conversion angle θp_s, which is obtained based on the steering angle ratio and corresponds to the pinion angle θp, toward the right side, which is the positive side. Therefore, the deviation Δθ between the rotation position of the steering wheel 3 and the rotation conversion angle θp_s is an angle Rc_h, the value of which is greater than the second threshold θ2 and equal to or less than the sum of thresholds θ1 and θ2. In this case, a second simplified synchronization control is performed before the vehicle starts moving, thereby rotating the steering wheel 3 such that the deviation Δθ represents the first threshold θ1.

[0106] Then, as Figure 7As shown in section (b), a second simplified synchronization control is performed on the steering wheel 3 to correct the rotational position of the steering wheel 3 to correspond to a predetermined relationship with the rotational position of the wheel 5, such that the deviation Δθ represents a first threshold θ1. Therefore, the rotational position of the steering wheel 3 moves to the left, which is the negative side, so that the first threshold θ1 remains at the deviation Δθ. Here, the steering-side synchronization control of the steering wheel 3 is considered complete, and the vehicle begins to move while having the first threshold θ1 as the deviation Δθ.

[0107] After that, as Figure 7 As shown in section (c), at the start of vehicle movement, the offset θofst is the angle θ1s_p, which is obtained as a value corresponding to the first threshold θ1 of the deviation Δθ. Subsequently, immediately after the vehicle begins movement, rotational offset control for the rotating wheel 5 is performed, such that, as in the section regarding... Figure 5 In the mode described in part (b), the rotation position of the rotating wheel 5 is corrected to correspond to the rotation position of the steering wheel 3 in a predetermined manner. Therefore, when the rotation position of the steering wheel 3 is to be maintained at a rotation position where the deviation Δθ is the first threshold θ1, the rotating wheel 5 rotates by an angle θ1s_p toward the right side, which is the positive side.

[0108] Processing method D

[0109] When the deviation Δθ is greater than the sum of thresholds θ1 and θ2 (θ1 + θ2 < Δθ), synchronization control is executed in processing mode D. In this case, normal synchronization control is executed during the synchronization startup process, and not during the normal correction process. Figure 4 (None) Rotational side synchronous control.

[0110] Operation mode of processing method D

[0111] As a prerequisite, for example, Figure 8 As shown in part (a), immediately after the start switch 42 is turned on, the steering angle θh has already deviated from the rotation conversion angle θp_s, which is obtained based on the steering angle ratio and corresponds to the pinion angle θp, towards the right side, which is the positive side. Therefore, the deviation Δθ between the rotational position of the steering wheel 3 and the rotation conversion angle θp_s is the angle Rd_h, the value of which is greater than the sum of the thresholds θ1 and θ2. In this case, conventional synchronization control is performed before the vehicle starts moving, thereby rotating the steering wheel 3 so that the deviation Δθ is zero.

[0112] Then, as Figure 8As shown in section (b), the first stage of conventional synchronization control for steering wheel 3 is performed. Through this first stage, the rotational position of steering wheel 3 is corrected to further deviate from the predetermined correspondence with the rotational position of wheel 5, causing a temporary increase in the deviation Δθ. Specifically, the rotational position of steering wheel 3 moves to the right, which is the positive side, causing a deviation of a predetermined amount, angle Rdr. In this case, the deviation Δθ temporarily increases to the sum of angles Rd_h and Rdr, which has a value greater than angle Rd_h.

[0113] Subsequently, as Figure 8 As shown in part (c), the second stage of conventional synchronization control for steering wheel 3 is performed. Through this second stage of conventional synchronization control, the rotational position of steering wheel 3 is corrected to correspond to a predetermined relationship with the rotational position of wheel 5, causing the sum of angles Rd_h and Rdr to temporarily increase due to the deviation Δθ reaching zero. In this case, the rotational position of steering wheel 3 shifts to the left, which is the negative side, by the sum of angles Rd_h and Rdr.

[0114] How the implementation method works

[0115] According to the implementation method, the rotational offset control of the rotational side synchronous control has the following advantages: it can perform correction processing on the positional relationship between the steering wheel 3 and the rotating wheel 5 when the steering wheel 3 is not rotating. This advantage can be used when the deviation Δθ is equal to or less than the first threshold θ1.

[0116] For example, such as Figure 4 As shown, the synchronization control in processing method A is specified for cases where the value of the deviation Δθ is equal to or less than the first threshold θ1. In this case, as... Figure 5 As shown in parts (a) and (b), the vehicle begins to move simultaneously with a first threshold θ1 as a deviation amount Δθ, and the rotational position of the rotating wheel 5 is corrected so that the positional relationship between the steering wheel 3 and the rotating wheel 5 satisfies a predetermined correspondence after the start of driving. Therefore, by not performing synchronization control before the vehicle starts moving, the time period from when the start switch 42 is turned on until the vehicle starts moving is shortened. Furthermore, since the steering wheel 3 does not rotate automatically, this method is unlikely to cause discomfort to the driver.

[0117] Conventional synchronous control of the steering side has the following advantages: it can easily perform correction processing on the positional relationship between the steering wheel 3 and the rotating wheel 5. This advantage can be used when the value of the deviation Δθ is greater than the sum of the thresholds θ1 and θ2.

[0118] For example, such as Figure 4As shown, the synchronization control in processing method D is specified for cases where the value of the deviation Δθ is greater than the sum of thresholds θ1 and θ2. In this case, as... Figure 8 As shown in sections (a) to (c), the rotational position of the steering wheel 3 is corrected so that the positional relationship between the steering wheel 3 and the rotating wheel 5 satisfies a predetermined correspondence before the vehicle begins to move. The steering wheel 3 rotates through the following two actions as basic movements: rotating towards the right side, which is the positive side, and then rotating towards the left side, which is the negative side. Therefore, the correction process for the positional relationship between the steering wheel 3 and the rotating wheel 5 can be easily performed because the correction process involves only rotating the steering wheel 3. The driver can be made aware that when the steering wheel 3 is to be rotated significantly, the rotation is accomplished through the two actions as basic movements, making it unlikely to cause discomfort to the driver even if the steering wheel 3 is rotated relatively significantly.

[0119] If the value of the deviation Δθ is greater than the first threshold θ1 and equal to or less than the sum of thresholds θ1 and θ2, at least one of the rotation-side synchronous control and steering-side synchronous control is specified to be executed so as to take advantage of the advantages of each control mode according to the desired result.

[0120] Specifically, when the deviation Δθ has a value greater than the first threshold θ1 and equal to or less than the sum of thresholds θ1 and θ2, which is greater than the second threshold θ2, the advantages of the second simplified synchronous control of rotational offset control and steering-side synchronous control can be utilized.

[0121] For example, such as Figure 4 As shown, the synchronization control in processing method C is specified for cases where the value of the deviation Δθ is greater than the second threshold θ2 and equal to or less than the sum of thresholds θ1 and θ2. In this case, as... Figure 7 As shown in parts (a) and (b), the rotational position of the steering wheel 3 is corrected such that the deviation Δθ in the positional relationship between the steering wheel 3 and the rotating wheel 5 is reduced to a first threshold θ1 before the vehicle begins to move. Then, the steering wheel 3 rotates by rotating in one of the left or right directions.

[0122] After that, as Figure 7 As shown in part (c), the vehicle starts driving while having a first threshold θ1 as a deviation amount Δθ, and the rotation position of the rotating wheel 5 is corrected so that the positional relationship between the steering wheel 3 and the rotating wheel 5 satisfies a predetermined correspondence after driving begins.

[0123] Therefore, the degree of rotation of the steering wheel 3 is limited to a minimum, so that rotating the steering wheel 3 is unlikely to cause discomfort to the driver, and the time from when the start switch 42 is turned on until the vehicle starts moving is shortened.

[0124] In the case where the deviation amount Δθ has a value larger than the first threshold value θ1 and equal to or smaller than the sum of the threshold values θ1, θ2, equal to or smaller than the second threshold value θ2, the advantage of the first simplified synchronization control of the turning side synchronization control can be utilized.

[0125] For example, as shown in FIG. 10, the synchronization control in the processing mode B is designated for the case where the value of the deviation amount Δθ is larger than the first threshold value θ1 and equal to or smaller than the second threshold value θ2. In this case, as shown in parts (a) and (b) of FIG. 10, the rotational position of the steering wheel 3 is corrected so that the positional relationship between the steering wheel 3 and the turning wheel 5 satisfies the predetermined correspondence relationship before the vehicle starts running. In this case, the steering wheel 3 is rotated by one action of being rotated in one of the leftward direction and the rightward direction. Therefore, although the steering wheel 3 is rotated before the vehicle starts running, the rotation is completed in a short time compared to when the steering wheel 3 is rotated by two actions. Figure 4 Figure 6 In the case where the value of the deviation amount Δθ is larger than the first threshold value θ1 and equal to or smaller than the second threshold value θ2, the advantage of the first simplified synchronization control of the turning side synchronization control can be utilized.

[0126] Effects of Embodiments

[0127] In this embodiment, as a method of performing the correction processing of the positional relationship between the steering wheel 3 and the turning wheel 5, a method of utilizing the advantages of the turning side synchronization control and the steering side synchronization control can be proposed.

[0128] The correction processing of two actions of the conventional synchronization control involving the steering side synchronization control has an advantage that it is less likely to cause discomfort to the driver even in the case where the steering wheel 3 is relatively largely rotated. On the other hand, the correction processing of one action of each mode of the simplified synchronization control involving the steering side synchronization control has an advantage that the correction processing of the rotational position of the steering wheel 3 can be completed in a short time compared to the correction processing involving two actions. In this case, the advantage of the correction processing involving two actions can be used in the case where the value of the deviation amount Δθ is larger than the sum of the threshold values θ1, θ2. The advantage of the correction processing involving one action can be used in the case where the value of the deviation amount Δθ is equal to or smaller than the sum of the threshold values θ1, θ2. This configuration is effective for utilizing the advantages of each correction processing involving one action or two actions of the steering side synchronization control.

[0129] In the case where the value of the deviation amount Δθ is larger than the second threshold value θ2 and equal to or smaller than the sum of the threshold values θ1, θ2, the advantages of the turning offset control and the correction processing involving one action of the steering side synchronization control can be utilized. In the case where the value of the deviation amount Δθ is larger than the first threshold value θ1 and equal to or smaller than the second threshold value θ2, the advantage of the correction processing involving one action of the steering side synchronization control can be utilized. This configuration is effective for utilizing the advantages of the turning side synchronization control and the steering side synchronization control. ​

[0130] In particular, in the case where the value of the deviation amount Δθ is greater than the second threshold value θ2 and equal to or smaller than the sum of the threshold values θ1, θ2, the advantage of the correction process involving one action can be more appropriately utilized. From the viewpoint of easily performing the correction process on the positional relationship between the steering wheel 3 and the turning wheels 5, this configuration is effective.

[0131] The turning side synchronous control with the turning offset control has an advantage that the time required for the vehicle to start running after the start switch 42 is turned on can be shortened. This advantage can be more effectively used in the case where the value of the deviation amount Δθ is equal to or smaller than the first threshold value θ1. Each mode of the conventional synchronous control and the simplified synchronous control of the turning side synchronous control has an advantage that the behavior of the vehicle is less likely to cause discomfort to the driver. This advantage can be more effectively used in the case where the value of the deviation amount Δθ is greater than the first threshold value θ1. In this case, the correction process on the positional relationship between the steering wheel 3 and the turning wheels 5 can produce the following two effects: a shortening effect of the period from when the start switch 42 is turned on until the vehicle starts running; and a reduction effect of the likelihood that the behavior of the vehicle causes discomfort to the driver.

[0132] Other Embodiments

[0133] The above-described embodiments can be changed as follows. The following other embodiments can be combined with each other within such a range that no technical inconsistency arises.

[0134] As with each mode of the simplified synchronous control, with respect to the turning side synchronous control, the conventional synchronous control can also be designated as a correction process involving one action of rotating the steering wheel 3 in one direction. With respect to the turning side synchronous control, in the conventional synchronous control, an angle obtained by further changing one of the steering angle θh and the synchronous target steering angle θh* on the negative value side by a predetermined amount toward the negative value side can also be calculated as the relay target steering angle θhr*. In the conventional synchronous control, the method of calculating the relay target steering angle θhr* can be changed depending on the positional relationship between the steering angle θh and the synchronous target steering angle θh*. Further, in the conventional synchronous control, the relay target steering angle θhr* can also be calculated so that the steering angle θh temporarily exceeds the synchronous target steering angle θh* in the first stage of the conventional synchronous control.

[0135] As with the conventional synchronous control, with respect to the turning side synchronous control, each mode of the simplified synchronous control can also be designated as a correction process involving two actions of rotating the steering wheel 3 in one direction and then rotating the steering wheel 3 in the opposite direction of the one direction.

[0136] As with the rotation offset control, with the steering side synchronization control, the control can be gradually reflected in the rotation of the steering wheel 3 while the steering wheel 3 is being steered after the start switch 42 is turned on and the vehicle starts running.

[0137] With the rotation offset control of the normal correction processing, the reduction processing of the offset amount θofst can also be executed at a timing at which the vehicle is braked or stopped after the vehicle starts running. With the rotation offset control of the normal correction processing, the reduction processing of the offset amount θofst can also be executed at a timing before the vehicle starts running, as long as the timing is after the start switch 42 is turned on and the start synchronization processing by the steering side control unit 50 is completed. In this case, even before the vehicle starts running, the rotation offset control can be executed while the steering wheel 3 is being steered. Further, the rotation offset control can be executed after the start synchronization processing is completed, regardless of the situation, the rotation offset control is after the start synchronization processing.

[0138] When the deviation amount Δθ is greater than the second threshold value θ2 and equal to or less than the sum of the threshold values θ1, θ2, the synchronization control can be executed in the processing mode B or the processing mode D. In this case, the configuration in which the synchronization control is executed in the processing mode C can be omitted. This embodiment is effective for meeting the requirement of making the positional relationship between the steering angle θh and the pinion angle θp as close as possible to the predetermined correspondence before the vehicle starts running.

[0139] When the deviation amount Δθ is greater than the first threshold value θ1 and equal to or less than the second threshold value θ2, the synchronization control can be executed in the processing mode A or the processing mode C. In this case, the configuration in which the synchronization control is executed in the processing mode B can be omitted. This embodiment is effective for meeting the requirement of shortening the period from when the start switch 42 is turned on until the vehicle starts running as much as possible.

[0140] The synchronization control can be configured so that, when the deviation amount Δθ is equal to or less than a minimum threshold value θmin of the first threshold value θ1, neither the rotation side synchronization control nor the steering side synchronization control is executed. For example, the minimum threshold value θmin is set to a value within a range obtained through experiments so that such behavior of the vehicle is unlikely to cause discomfort to the driver even when the vehicle starts running with the deviation amount Δθ. In this case, a situation in which the synchronization control itself is not executed after the start switch 42 is turned on can occur.

[0141] In the synchronous control of the processing mode C, the rotation position of the steering wheel 3 can be corrected by the second simplified synchronous control to the extent corresponding to half the value of the deviation amount Δθ, and then the rotation position of the rotation wheel 5 can be corrected by the rotation offset control. Further, in the synchronous control of the processing mode C, the rotation position of the steering wheel 3 can be corrected by the second simplified synchronous control to the extent corresponding to the second threshold value θ2, and then the rotation position of the rotation wheel 5 can be corrected by the rotation offset control.

[0142] The notification device that notifies the driver that the steering side synchronous control is being executed can be provided inside the passenger compartment (for example, in the instrument panel). Examples of the notification action of the notification device include: a character display message; a voice generation message; and an electronic sound generation. Thus, the driver can know that the steering wheel 3 is to be automatically rotated or that the automatically rotating steering wheel 3 is to be stopped. This embodiment is effective for reducing the possibility that the steering side synchronous control causes the driver to feel uncomfortable.

[0143] The steering angle ratio is set to an appropriate value in accordance with the product specifications or the like. For example, the steering angle ratio can be such that "θh:θi" (i.e., "θh:θp") is "1:1" or "1:3". When "θh:θp" is "1:3", a change of 10° in the steering angle θh is accompanied by a change of 30° in the rotation angle θi. When "θh:θp" is "1:1", the rotation conversion angle θp_s substantially matches the pinion angle θp. In this case, in the step S10 of starting the synchronous processing, the deviation amount Δθ can be obtained as the absolute value of the difference between the steering angle θh and the pinion angle θp. Further, the target pinion angle θp* used in the rotation side control during energization substantially matches the steering angle θh. Thus, in the step S20 of the normal correction processing, the offset amount θofst can be obtained by subtracting the pinion angle θp from the steering angle θh.

[0144] In the steering control device 1, a single control unit can be formed to have a function in which the function of the steering side control unit 50 that operates the steering side motor 13 is combined with the function of the rotation side control unit 60 that operates the rotation side motor 32. In this case, the processing involved in the synchronous control can be configured so that, after the processing corresponding to the "Yes" determination in the step S11 of starting the synchronous processing, the processing corresponding to the steps S20, S22 of the normal correction processing is executed. Further, the processing involved in the synchronous control can be configured so that, after the processing corresponding to the step S16 of starting the synchronous processing, the processing corresponding to the steps S20, S22 of the normal correction processing is executed.

[0145] When the target reaction force torque is calculated, the steering side control unit 50 should at least use a state variable that varies depending on the operation state of the steering wheel 3. In this case, instead of using the vehicle speed V or the steering torque Th, the steering side control unit 50 can use other elements or a combination of other elements.

[0146] The steering side control unit 50 can calculate, as the target reaction force torque, a value calculated by executing torque feedback control that adapts the steering torque Th to a target steering torque calculated based on the steering torque Th.

[0147] The steering side control unit 50 can calculate the steering angle θh by considering the amount of torsion of the steering shaft 11 depending on the steering torque Th and by adding, subtracting, or the like, the amount of torsion in the rotation angle θs.

[0148] The detection result of a steering sensor provided on the steering shaft 11 for detecting the rotation angle of the steering shaft 11 can be used as the steering angle θh. The detection result of a pinion angle sensor provided on the pinion shaft 21 for detecting the rotation angle of the pinion shaft 21 can be used as the pinion angle θp.

[0149] In the above-described embodiment, for example, a motor provided on the same axis as the rack shaft 22 or a motor connected to the pinion shaft that constitutes a rack and pinion mechanism together with the rack shaft 22 through a worm and a worm gear set can be used as the rotation side motor 32.

[0150] In the above-described embodiment, the steering control device 1 can be formed of a processing circuit including: (1) one or more processors that operate according to a computer program (software); (2) one or more dedicated hardware circuits such as an application specific integrated circuit (ASIC) that execute at least some of various processes; or (3) a combination of (1) and (2). The processor includes a CPU and a memory such as a RAM or a ROM, and the memory stores program codes or commands configured to cause the CPU to execute processes. Examples of the memory, i.e., a non-transitory computer readable medium, include all available media that can be accessed by a general or a dedicated computer.

[0151] In the above-described embodiment, the steering device 2 has a linkageless structure in which the steering portion 4 and the rotation portion 6 are always mechanically cut off. However, the structure of the steering device 2 is not limited to this example, but can be a structure in which the steering portion 4 and the rotation portion 6 can be mechanically cut off from each other by a clutch. In addition, the steering device 2 can have an independently rotatable structure in which the left and right rotation wheels 5 of the rotation portion 6 can be independently rotated.

Claims

1. A steering control device (1) that controls a steering device (2) as a target, the steering device (2) comprising: a steering actuator (12) operating to apply a steering reaction force to a steering wheel (3) of a vehicle; and a turning actuator (31) having a structure in which a power transmission path from the steering actuator (12) is cut off and operating to turn a turning wheel (5) of the vehicle, the steering control device (1) characterized by including a control unit that performs synchronization control that controls operation of at least one of the steering actuator (12) and the turning actuator (31) so that a positional relationship between a rotational position of the steering wheel (3) and a turning position of the turning wheel (5) satisfies a predetermined correspondence relationship, wherein: the control unit is configured to perform a process including a deviation amount determination process that determines a magnitude of an absolute value of a deviation amount of the positional relationship from the predetermined correspondence relationship at a time of power-on of the vehicle and a synchronization control process that performs the synchronization control based on a determination result of the deviation amount determination process, the synchronization control being at least one of a turning side synchronization control that performs a correction process on the turning position by operating the turning actuator (31) and a steering side synchronization control that performs a correction process on the rotational position by operating the steering actuator (12); and the control unit is configured to perform, in the synchronization control process, the following operations: when the absolute value of the deviation amount is a value within a first range, which is a small value, the turning side synchronization control is performed in terms of whether the deviation amount is large or small; when the absolute value of the deviation amount is a value within a second range, which is a larger value than the value within the first range, the steering side synchronization control is performed in terms of whether the deviation amount is large or small; and when the absolute value of the deviation amount is a value within a third range, which is a value between the value within the first range and the value within the second range, at least one of the turning side synchronization control and the steering side synchronization control is performed.

2. The steering control device (1) according to claim 1, characterized in that: the control unit is configured to perform the steering side synchronization control when the absolute value of the deviation amount is the value within the second range or the value within the third range; and the control unit is configured so that the steering side synchronization control is performed as a correction process involving two actions of rotating the steering wheel (3) in one direction and then rotating the steering wheel (3) in a direction opposite to the one direction when the absolute value of the deviation amount is the value within the second range, and so that the steering side synchronization control is performed as a correction process involving one action of rotating the steering wheel (3) in one direction when the absolute value of the deviation amount is the value within the third range.

3. The steering control device (1) according to claim 1 or 2, characterized in that the control unit is configured to execute the turning-side synchronization control and the turning-side synchronization control of the two, when the absolute value of the deviation amount is a value within a fifth range, the value within the fifth range being a larger value than the value within the fourth range, among the values within the third range.

4. The steering control device (1) according to claim 3, characterized in that the control unit is configured to execute the turning-side synchronization control and the turning-side synchronization control of the two, when the absolute value of the deviation amount is a value within a fifth range, the value within the fifth range being a larger value than the value within the fourth range, among the values within the third range.

5. The steering control device (1) according to any one of claims 1, 2 and 4, characterized in that, the control unit is configured to execute the turning-side synchronization control and the turning-side synchronization control of the two, when the absolute value of the deviation amount is a value within a fifth range, the value within the fifth range being a larger value than the value within the fourth range, among the values within the third range. the control unit is configured to execute the turning-side synchronization control and the turning-side synchronization control of the two, when the absolute value of the deviation amount is a value within a fifth range, the value within the fifth range being a larger value than the value within the fourth range, among the values within the third range. the control unit is configured to execute the turning-side synchronization control and the turning-side synchronization control of the two, when the absolute value of the deviation amount is a value within a fifth range, the value within the fifth range being a larger value than the value within the fourth range, among the values within the third range.

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