Turning control device and turning control method

Abstract

A turning control device (70) is configured to execute turning processing, detection processing, and storage processing. The turning processing is processing which is for turning a turning wheel in at least one of two directions, the right turn side and the left turn side, by operating a motor. The detection processing is processing in which the detection value of an absolute angle sensor and the detection value of a rotation angle sensor are inputs while the turning processing is being executed, and which is for detecting a degree of inconsistency between a displacement amount in an axial direction of a turning shaft and a rotation angle on an input side of a conversion device. The storage processing is processing for storing, in a storage device, a correction amount for suppressing the inconsistency between the displacement amount in the axial direction of the turning shaft and the rotation angle on the input side of the conversion device.

Description

Steering control device and steering control method

[0001] The present disclosure relates to a steering control device and a steering control method.

[0002] Japanese Patent Application Laid-Open No. 2006-101494 (Patent Document 1) describes a steering system that steers steered wheels by displacing a steering shaft in the axial direction. This system includes a transmission device that converts the rotation of a motor into the axial displacement of the steering shaft. This system also detects an abnormality in the transmission device based on the rotation angle of the motor and the amount of movement of the steering shaft.

[0003] JP 2019-104488 A

[0004] In the case of the steering system described above, if an assembly error is compounded with a detection error from the sensor, there is a risk that an abnormality will be erroneously detected in the transmission device even though no abnormality has occurred.

[0005] One aspect of the present disclosure provides a steering control device. In the steering control device, a steering actuator equipped with a conversion device that converts rotation of a motor into axial displacement of a steering shaft is an operation target. The steering shaft is configured to steer steered wheels by displacing it in the axial direction. The steering control device includes an execution device and a storage device. The execution device is configured to execute a steering process, a detection process, and a storage process. The steering process is a process of operating the motor to steer the steered wheels in at least one of two directions, a right-turn direction and a left-turn direction. The detection process receives as input a detection value of an absolute angle sensor and a detection value of a rotation angle sensor while the steering process is being executed, and is a process of detecting a degree of mismatch between the axial displacement amount of the steering shaft and the rotation angle of the input side of the conversion device. The storage process is a process of storing in the storage device a correction amount for suppressing a mismatch between the axial displacement amount of the steering shaft and the rotation angle of the input side of the conversion device. The absolute angle sensor is a sensor that detects a quantity that corresponds one-to-one to the turning angle of the steered wheels. The rotation angle sensor is a sensor that detects the rotation angle on the input side of the conversion device.

[0006] Another aspect of the present disclosure provides a steering control method. In the steering control method, a steering actuator including a conversion device that converts the rotation of a motor into an axial displacement of a steering shaft is an object to be operated. The steering shaft is configured to steer the steered wheels by displacing it in the axial direction. The method includes the steps of executing a steering process, a detection process, and a storage process. The steering process is a process of operating the motor to steer the steered wheels in at least one of two directions, a right-turn direction and a left-turn direction. The detection process receives as input a detection value of an absolute angle sensor and a detection value of a rotation angle sensor while the steering process is being executed, and detects the degree of mismatch between the axial displacement of the steered shaft and the rotation angle of the input side of the conversion device. The storage process is a process of storing a correction amount for suppressing the mismatch between the axial displacement of the steered shaft and the rotation angle of the input side of the conversion device in a storage device. The absolute angle sensor is a sensor that detects a quantity that corresponds one-to-one with the steering angle of the steered wheels. The rotation angle sensor is a sensor that detects the rotation angle of the input side of the conversion device.

[0007] Fig. 1 is a block diagram showing a steering system according to one embodiment. Fig. 2 is a flowchart showing a processing procedure executed by the steering control device shown in Fig. 1. Fig. 3 is a flowchart showing a processing procedure executed by the steering control device shown in Fig. 1. Fig. 4 is a block diagram showing a manufacturing process of the steering system of Fig. 1. Fig. 5 is a flowchart showing a processing procedure executed by the turning control device shown in Fig. 4. Fig. 6 is a flowchart showing a processing procedure executed by the turning control device shown in Fig. 4. Fig. 7 is a flowchart showing a processing procedure executed by the turning control device shown in Fig. 4. Fig. 8 is a diagram showing an example of control in the manufacturing process shown in Fig. 4. Fig. 9 is a diagram showing an example of control in the manufacturing process shown in Fig. 4.

[0008] An embodiment will be described below with reference to the drawings. "Configuration of Steering System" Fig. 1 shows the configuration of a vehicle steering system 10. Steering system 10 includes a steering device 20, a turning device 30, a reaction force control device 60, and a turning control device 70.

[0009] The steering device 20 includes a steering wheel 12 and a steering shaft 14 mechanically connected to the steering wheel 12. A reaction motor 16 is mechanically connected to the steering shaft 14. The reaction motor 16 is used to apply a reaction force that resists the operation of the steering wheel 12 by the driver. The output voltage of an inverter 18 is applied to the terminals of the reaction motor 16.

[0010] The steering device 30 includes a steering shaft 32 and a pinion shaft 34. Rack teeth 32a are formed on the steering shaft 32. Pinion teeth 34a are formed on the pinion shaft 34. The rack teeth 32a and the pinion teeth 34a are engaged with each other to form a rack and pinion mechanism 36.

[0011] The steering device 30 includes a steering actuator ACT. The steering actuator ACT includes a steering motor 40, an inverter 42, a transmission mechanism 44, and a conversion mechanism 46. The transmission mechanism 44 transmits the rotation of the steering motor 40 to the conversion mechanism 46, for example, via a belt. The conversion mechanism 46 includes, as an example, a ball screw mechanism. The conversion mechanism 46 converts the rotational displacement from the transmission mechanism 44 into a displacement in the axial direction of the steering shaft 32. The transmission mechanism 44 and the conversion mechanism 46 are conversion devices that convert the rotational power of the steering motor 40 into a displacement power in the axial direction of the steering shaft 32.

[0012] The steerable wheels 50 are steered by the axial displacement of the steered shaft 32. The range of axial displacement of the steerable shaft 32 is determined by the rack housing 48. In other words, the maximum value of the steering angle of the steerable wheels 50 on the right-turning side and the maximum value on the left-turning side are determined by the position at which the displacement of the steered shaft 32 is prevented by the rack housing 48.

[0013] The reaction force control device 60 includes a PU 62 and a storage device 64. The control object of the reaction force control device 60 is the steering device 20, and the operation object is the reaction force motor 16. The reaction force control device 60 controls the control amount of the control object by the PU 62 executing a program stored in the storage device 64.

[0014] Steering control device 70 includes PU 72 and storage device 74. The control object of steering control device 70 is steered wheels 50, and the operation object is steering actuator ACT. Steering control device 70 controls the control amount of the control object by PU 72 executing a program stored in storage device 74. To control the control amount, steering control device 70 references the rotation angle of steering motor 40 detected by rotation angle sensor 82. To control the control amount, steering control device 70 references absolute angle θa detected by absolute angle sensor 84. Absolute angle θa is the rotation angle of pinion shaft 34. Absolute angle θa is a variable that has a one-to-one correspondence with the steering angle. For example, absolute angle θa has a positive value in the case of a right-turning side, and a negative value in the case of a left-turning side. For example, if the maximum value of the steering angle on the right-turning side is greater than one rotation of pinion shaft 34, absolute angle θa can be an angle exceeding 360°. The steering control device 70 refers to the currents iut, ivt, and iwt that flow through the steering motor 40. Note that the currents iut, ivt, and iwt may be detected as the amount of voltage drop across a shunt resistor provided in each leg of the inverter 42.

[0015] Reaction force control device 60 and steering control device 70 are capable of communicating with each other. "Processing of steering control device" Figure 2 shows the procedure of processing that is executed when steering control device 70 is started up as a trigger. The processing shown in Figure 2 is realized by PU 72 repeatedly executing a program stored in storage device 74, for example, at a predetermined interval. Note that below, the step number of each processing step is represented by a number preceded by "S".

[0016] In the series of processes shown in FIG. 2 , the PU 72 first determines whether the power supply of the steering control device 70 has been switched from off to on (S10). If the PU 72 determines that the power supply has been switched (S10: YES), the PU 72 determines whether correction data 74a is stored in the storage device 74 (S12). If the PU 72 determines that correction data 74a is stored (S12: YES), the PU 72 sets the operation mode to the normal control mode (S14). The normal control mode is a mode in which normal control is performed in which the steering angle is the control variable. On the other hand, if the PU 72 determines that correction data 74a is not stored (S12: NO), the PU 72 sets the operation mode to the inspection mode (S16). The inspection mode is a mode in which processing such as acquiring the correction data 74a is performed.

[0017] PU 72 temporarily terminates the series of processes shown in Figure 2 when the processes of S14 and S16 are completed or when a negative determination is made in the process of S10. Figure 3 shows the procedure of the processes executed by steering control device 70. The processes shown in Figure 3 are realized by PU 72 repeatedly executing a program stored in storage device 74, for example at a predetermined interval, in the normal control mode.

[0018] In the series of processes shown in FIG. 3 , the PU 72 first determines whether the operation mode is the normal control mode (S20). If the PU 72 determines that the operation mode is the normal control mode (S20: YES), the PU 72 acquires the steering equivalent angle θp (S22). The steering equivalent angle θp is a variable that has a one-to-one correspondence with the steering angle of the steered wheels 50. The steering equivalent angle θp is, for example, the rotation angle of the pinion shaft 34. The steering equivalent angle θp is calculated by the PU 72 based on a process of integrating the rotation angle θt. For example, the steering equivalent angle θp has a positive value when turning right and a negative value when turning left. Note that in this embodiment, the resolution of the steering equivalent angle θp is higher than the resolution of the absolute angle θa. That is, the steering equivalent angle θp can express a smaller steering angle than the absolute angle θa. The PU 72 also acquires the latest absolute angle θa detected by the absolute angle sensor 84 (S24). The PU 72 also reads out the correction amount Δc from the correction data 74a stored in the storage device 74 (S26).

[0019] Then, PU 72 determines whether the absolute value of the value obtained by subtracting absolute angle θa and correction amount Δc from steering equivalent angle θp is greater than a threshold value (S28). If PU 72 determines that the absolute value is greater than the threshold value (S28: YES), it determines that an abnormality has occurred (S30). In other words, if the absolute value of the difference between steering equivalent angle θp and absolute angle θa is large, there is a possibility that the rotation of steering motor 40 is not being properly converted into axial displacement of steering shaft 32. Then, PU 72 notifies the user of the abnormality by operating user interface 78 shown in FIG. 1 (S32).

[0020] When the PU 72 completes the process of S32 or when a negative determination is made in the processes of S20 and S28, the PU 72 temporarily ends the series of processes shown in Fig. 3. "Acquisition of correction data 74a" The correction data 74a is stored in the storage device 74 before the steering device 30 is mounted on the vehicle.

[0021] Figure 4 shows the hardware configuration when correction data 74a is acquired. As shown in Figure 4, steering control device 70 is connected to facility-side terminal 90. Facility-side terminal 90 comprises PU 92 and storage device 94. Facility-side terminal 90 causes PU 92 to execute a program stored in storage device 94, thereby causing steering control device 70 to execute processing to acquire correction data 74a.

[0022] The procedure for the process for acquiring the correction data 74a is shown in Fig. 5. The process shown in Fig. 5 is realized by the PU 72 repeatedly executing a program stored in the storage device 74, for example, at predetermined intervals.

[0023] In the series of processes shown in FIG. 5 , the PU 72 first determines whether the operation mode is the inspection mode (S40). If the PU 72 determines that the operation mode is the inspection mode (S40: YES), it determines whether the end contact process is being executed (S42). If the PU 72 determines that the end contact process is not being executed (S42: NO), it determines whether an end contact command has been input from the facility-side terminal 90 to the steering control device 70 (S44). If the PU 72 determines that a command has been input (S44: YES), it receives data indicating the guard values ​​Δ1 to Δ3 output from the facility-side terminal 90 (S46). The PU 72 also receives the change angles θp1 and θp2 output from the facility-side terminal 90 (S48). The PU 72 then starts the end contact process (S50).

[0024] Next, PU 72 acquires the steering equivalent angle θp (S52). Then, PU 72 calculates a target steering equivalent angle θp*, which is a target value of the steering equivalent angle θp (S54). Next, PU 72 calculates a target torque Tt* corresponding to the operation amount by feedback control, in which the steering equivalent angle θp is the control amount and the target steering equivalent angle θp* is the target value of the control amount (S56). Target torque Tt* is the torque of steering motor 40.

[0025] Then, PU 72 outputs to inverter 42 an operation signal MSt for inverter 42 to bring the torque of steering motor 40 closer to target torque Tt* (S58). On the other hand, if PU 72 determines that end contact processing is being executed (S42: YES), it determines whether end contact processing has been completed (S60). If PU 72 determines that end contact processing has not yet been completed (S60: NO), it proceeds to processing of S52.

[0026] On the other hand, if the PU 72 determines that the end contact process has been completed (S60: YES), if a negative determination is made in the processes of S40 and S44, or if the process of S58 is completed, the PU 72 temporarily terminates the series of processes shown in FIG. 5.

[0027] Fig. 6 shows details of the processing of S54. In the series of processing shown in Fig. 6, the PU 72 determines whether the control mode of the steered wheels 50 in the end contact processing is the right turn mode (S70). The right turn mode is a mode in which processing is executed to steer the steered wheels 50 to the right turn side. As an example, the PU 72 sets the right turn mode at the start of the processing of S70.

[0028] When the PU 72 determines that the vehicle is in the right turn mode (S70: YES), it determines whether the target steering equivalent angle θp* is equal to or greater than the change angle θp1 (S72). When the PU 72 determines that the target steering equivalent angle θp* is less than the change angle θp1 (S72: NO), it assigns a guard value Δ1 to the change amount Δ (S74). The change amount Δ determines the amount of change in the target steering equivalent angle θp* per predetermined time. In other words, the change amount Δ determines the rate of change of the target steering equivalent angle θp*. On the other hand, when the PU 72 determines that the target steering equivalent angle θp* is equal to or greater than the change angle θp1 (S72: YES), it assigns a guard value Δ2 to the change amount Δ (S76). The guard values ​​Δ1 and Δ2 are set to positive values, and the guard value Δ1 is set to a value greater than the guard value Δ2.

[0029] When the processing of S74 and S76 is completed, the PU 72 assigns a value obtained by adding the change amount Δ to the target steering equivalent angle θp* to the target steering equivalent angle θp* (S78).The PU 72 then determines whether the logical product of the following conditions (A) and (B) remains true for a certain period of time (S80).

[0030] Condition (A) is a condition that the previous value "θp(n-1)" of steering equivalent angle θp and the current value "θp(n)" match. Condition (B) is a condition that the absolute value of q-axis current iqt flowing through steering motor 40 is equal to or greater than threshold value Ith. Threshold value Ith is set to a value greater than the expected absolute value of q-axis current iqt when steered wheels 50 are turned when the steering angle is in an intermediate region between the upper limit value on the right-turning side and the upper limit value on the left-turning side.

[0031] The above conditions (A) and (B) are conditions for determining that the steering angle has reached the upper limit value on the right-turn side. If the PU 72 determines that the logical product of conditions (A) and (B) remains true for a certain period of time (S80: YES), the PU 72 assigns the current value "θp(n)" of the steering equivalent angle θp to the target steering equivalent angle θp* (S82). The PU 72 then determines whether the control mode is the right-turn mode (S84). If the PU 72 determines that the control mode is the right-turn mode (S84: YES), the PU 72 assigns the current value "θp(n)" to the right-side upper limit value θpR and sets the control mode to the left-turn mode (S86).

[0032] On the other hand, if the PU 72 determines that the control mode is not the right turn mode (S70: NO), it determines whether or not the control mode is the left turn mode (S88). If the PU 72 determines that the control mode is the left turn mode (S88: YES), it determines whether or not the target steering equivalent angle θp* is equal to or less than the change angle θp2 (S90). If the PU 72 determines that the target steering equivalent angle θp* is greater than the change angle θp2 (S90: NO), it assigns "(-1)·Δ1" to the change amount Δ (S92). On the other hand, if the PU 72 determines that the target steering equivalent angle θp* is equal to or less than the change angle θp2 (S90: YES), it assigns "(-1)·Δ2" to the change amount Δ (S94).

[0033] The PU 72 also proceeds to the process of S78 when the processes of S92 and S94 are completed. The process of S80, which is executed upon completion of the processes of S92 and S94, is a process for determining whether the steering angle has reached the upper limit value on the left turning side.

[0034] Thereafter, if the determination in S84 is negative, the PU 72 assigns the current value "θp(n)" to the left upper limit value θpL and sets the control mode to the midpoint movement mode (S96).Then, the PU 72 assigns "½" of the sum of the right upper limit value θpR and the left upper limit value θpL to the midpoint θpmd (S98).

[0035] Thereafter, the PU 72 determines whether the steering equivalent angle θp coincides with the midpoint θpmd by making a negative determination in the processing of S88 (S100). When the PU 72 determines that the steering equivalent angle θp does not coincide with the midpoint θpmd (S100: NO), it assigns a guard value Δ3 to the change amount Δ (S102). The guard value Δ3 is a positive value and is set to a value greater than the guard value Δ2. The guard value Δ3 may be equal to the guard value Δ1. Then, the PU 72 assigns a value obtained by adding the change amount Δ to the target steering equivalent angle θp* to the target steering equivalent angle θp* (S104).

[0036] On the other hand, if the PU 72 determines that the steering equivalent angle θp coincides with the midpoint θpmd (S100: YES), it acquires the latest absolute angle θa detected by the absolute angle sensor 84 (S106). Next, the PU 72 determines whether the absolute value of the absolute angle θa is equal to or less than the threshold value θath (S108). The process of S108 is a process for determining whether the absolute angle θa has been acquired normally. That is, if the process of S100 returns a positive determination, it is considered that the absolute angle θa is close to zero. Therefore, if the absolute angle θa deviates significantly from zero, it is considered that some kind of abnormality exists.

[0037] When the PU 72 determines that the absolute value is equal to or smaller than the threshold value θath (YES in S108), it substitutes the absolute angle θa for the correction amount Δa, and then stores the correction amount Δa in the storage device 74 (S110). As a result, the storage device 74 transitions from a state in which the correction data 74a indicating the correction amount Δa is not stored to a state in which it is stored.

[0038] The PU 72 then completes the end contact process (S112). Note that the PU 72 temporarily ends the series of processes shown in FIG. 6 when it completes the processes of S86, S98, S104, and S112, or when it makes a negative determination in the processes of S80 and S108.

[0039] Incidentally, PU 72 may refer to the correction amount Δa to evaluate the reliability of the steering equivalent angle θp before executing control in which the steering equivalent angle θp is the controlled variable. Specifically, PU 72 may evaluate the reliability of the steering equivalent angle θp to be high, for example, when the absolute value of the difference between the absolute angle θa corrected by the correction amount Δa and the steering equivalent angle θp is equal to or less than a threshold value. PU 72 may also execute processing to assign the absolute angle θa corrected by the correction amount Δa to the initial value of the steering equivalent angle θp when steering control device 70 is started. In this way, correction amount Δa is referenced by PU 72 so that PU 72 can execute control in which the steering equivalent angle θp is the controlled variable.

[0040] 7 shows a procedure for a process for acquiring the correction amount Δc, which is executed during the end contact process. The process shown in FIG. 7 is realized by the PU 72 repeatedly executing a program stored in the storage device 74, for example, at a predetermined interval.

[0041] In the series of processes shown in Figure 7, the PU 72 first determines whether or not the end contact process is being executed (S120). If the PU 72 determines that the end contact process is being executed (S120: YES), the PU 72 calculates the steering-equivalent angular velocity ωp (S122). The steering-equivalent angular velocity ωp is the rate of change of the steering-equivalent angle θp. Next, the PU 72 determines whether or not the logical product of the following condition (C) and condition (D) is true (S124).

[0042] Condition (C) is a condition that the steering equivalent angle θp is within a predetermined angle range. The predetermined angle range is included in a range in which the rate of change of the target steering equivalent angle θp* is defined by the guard value Δ1.

[0043] Condition (D) is a condition that the absolute value of the difference between the target steering angular velocity ωp* and the steering equivalent angular velocity ωp is equal to or less than a threshold value ωth. The target steering angular velocity ωp* is the rate of change of the target steering equivalent angle θp*. The target steering angular velocity ωp* is determined by the guard value Δ1. Condition (D) is a process for determining whether the rate of change of the steering equivalent angle θp has stabilized.

[0044] If the PU 72 determines that the logical product is true (S124: YES), it acquires the absolute angle θa (S126). The PU 72 also acquires the steering equivalent angle θp (S128). The PU 72 then determines whether the control mode is the right turn mode (S130). If the PU 72 determines that the control mode is the right turn mode (S130: YES), it determines whether the value obtained by subtracting the absolute angle θa from the steering equivalent angle θp is smaller than a minimum value ΔMIN (S132). The initial value of the minimum value ΔMIN is set to a value equal to or greater than the maximum value expected for the value obtained by subtracting the absolute angle θa from the steering equivalent angle θp.

[0045] If the PU 72 determines that the subtracted value is smaller than the minimum value ΔMIN (YES at S132), it assigns the subtracted value to the minimum value ΔMIN (S134). On the other hand, if the PU 72 determines that the control mode is the left turn mode (NO at S130), it determines whether the subtracted value is larger than the maximum value ΔMAX (S136). The initial value of the maximum value ΔMAX is set to a value equal to or smaller than the minimum value expected for the value to be subtracted.

[0046] If the PU 72 determines that the subtracted value is greater than the maximum value ΔMAX (S136: YES), it assigns the subtracted value to the maximum value ΔMAX (S138). The PU 72 determines whether the steering equivalent angle θp has reached the left-turn side end of the predetermined angle range (S140). If the PU 72 determines that the steering equivalent angle θp has reached the end (S140: YES), it assigns "1 / 2" of the sum of the maximum value ΔMAX and the minimum value ΔMIN to the correction amount Δc (S142). The PU 72 then determines whether the absolute value of the correction amount Δc is equal to or less than a threshold value Δth (S144). If the PU 72 determines that the correction amount Δc is equal to or less than the threshold value Δth (S144: YES), it stores the correction amount Δc in the storage device 74 (S146). Data indicating the correction amount Δc is part of the correction data 74a.

[0047] The PU 72 temporarily terminates the series of processes shown in FIG. 7 when it completes the processes of S134 and S146 or when it makes negative determinations in the processes of S120, S124, S132, S136, S140, and S144.

[0048] <Operation of this embodiment> Figure 8 illustrates the end contact process. As shown in Figure 8, when an end contact command is input from the facility-side terminal 90, the PU 72 increases the target steering equivalent angle θp* at a speed defined by the guard value Δ1 from time t1 onwards. This controls the steering equivalent angle θp, which indicates the steering angle of the steered wheels 50, to follow the target steering equivalent angle θp*. At time t2, when the target steering equivalent angle θp* reaches the change angle θp1, the PU 72 changes the rate of change of the target steering equivalent angle θp* to a speed defined by the guard value Δ2. Thereafter, when the target steering equivalent angle θp* reaches the right upper limit value θpR at time t3, the steering equivalent angle θp no longer increases. Therefore, at time t4, the PU 72 reduces the target steering equivalent angle θp* to the steering equivalent angle θp.

[0049] The PU 72 then decreases the target steering equivalent angle θp* at a speed defined by the guard value Δ1. When the target steering equivalent angle θp* reaches the change angle θp2 at time t5, the PU 72 changes the rate of decrease of the target steering equivalent angle θp* to a speed defined by the guard value Δ2. When the steering equivalent angle θp reaches the left upper limit value θpL at time t6, the steering equivalent angle θp stops changing. Therefore, at time t7, the PU 72 increases the target steering equivalent angle θp* to the steering equivalent angle θp. Thereafter, the PU 72 increases the target steering equivalent angle θp* at a speed defined by the guard value Δ3. When the steering equivalent angle θp reaches the midpoint θpmd, the PU 72 acquires the absolute angle θa. When the absolute value of the absolute angle θa is equal to or less than the threshold value θath, the PU 72 stores the absolute angle θa as the correction amount Δa in the storage device 74.

[0050] Furthermore, the PU 72 monitors the deviation between the steering equivalent angle θp and the absolute angle θa during the end contact processing. The PU 72 updates the minimum value ΔMIN when the control mode is the right turn mode and the steering equivalent angle θp is within a predetermined angle region defined by the rotation angles θ1 and θ2 in FIG. 8 . As a result, the minimum value ΔMIN becomes the minimum value of the value obtained by subtracting the absolute angle θa from the steering equivalent angle θp when the control mode is the right turn mode and the steering equivalent angle θp is within the predetermined angle region. Furthermore, the PU 72 updates the maximum value ΔMAX when the control mode is the left turn mode and the steering equivalent angle θp is within the predetermined angle region. As a result, the maximum value ΔMAX becomes the maximum value of the value obtained by subtracting the absolute angle θa from the steering equivalent angle θp when the control mode is the left turn mode and the steering equivalent angle θp is within the predetermined angle region.

[0051] Figure 9 shows the changes over time of the subtracted value, maximum value ΔMAX, and minimum value ΔMIN. As shown in Figure 9, the minimum value ΔMIN and maximum value ΔMAX represent the magnitude of the difference between the steering equivalent angle θp and the absolute angle θa when turning right and when turning left, respectively. Therefore, by calculating the correction amount Δc based on the minimum value ΔMIN and maximum value ΔMAX, it is possible to prevent erroneous determinations that an abnormality has occurred in the process of Figure 3.

[0052] The above embodiment further provides the following actions and effects. (1) PU 72 calculates correction amount Δc using both the difference between the steering equivalent angle θp and the absolute angle θa in the right turn mode in which steered wheels 50 are steered in a first direction and the difference between the steering equivalent angle θp and the absolute angle θa in the left turn mode in which steered wheels 50 are steered in a second direction. A difference may occur in the amount of axial displacement of steering shaft 32 relative to the amount of rotation of steering motor 40 between the right turn mode and the left turn mode. In this case, it is desirable to reflect in correction amount Δc the difference between the steering equivalent angle θp and the absolute angle θa in the mode in which the error is larger. In contrast, by reflecting in correction amount Δc the difference between the steering equivalent angle θp and the absolute angle θa in both the right turn mode and the left turn mode, the difference between the steering equivalent angle θp and the absolute angle θa in the mode in which the error is larger can be reflected in correction amount Δc.

[0053] (2) The first region, which is the angle region for calculating the difference between the steering equivalent angle θp and the absolute angle θa in the right turn mode, is the same as the second region, which is the angle region for calculating the difference between the steering equivalent angle θp and the absolute angle θa in the left turn mode. In this way, by making the angle region for calculating the difference between the steering equivalent angle θp and the absolute angle θa the same for the right turn mode and the left turn mode, it is possible to grasp the difference between the above-mentioned difference between the right turn mode and the left turn mode.

[0054] (3) The PU 72 calculates the correction amount Δc by averaging the maximum value ΔMAX and the minimum value ΔMIN. This allows the correction amount Δc to reflect both the degree to which the absolute angle θa deviates to the right or the degree to which it deviates to the left with respect to the steering equivalent angle θp.

[0055] (4) PU 72 detects the difference between the steering equivalent angle θp and the absolute angle θa when the steering equivalent angular velocity ωp is stable. This allows the difference to be detected with higher accuracy than when the difference between the steering equivalent angle θp and the absolute angle θa is detected when the steering equivalent angular velocity ωp is unstable.

[0056] (5) When the PU 72 determines that the absolute value of the correction amount Δc is equal to or less than the threshold value Δth, the PU 72 stores the correction amount Δc in the storage device 74. This prevents an inappropriate value from being stored in the storage device 74 as the correction amount Δc due to some abnormality.

[0057] (6) The PU 72 sets the operation mode to the inspection mode when the correction amount Δc is not stored in the storage device 74. This prevents normal control of the steered wheels 50 from being performed in a state where the correction amount Δc is not stored in the storage device 74.

[0058] (7) The PU 72 performs the process of calculating the difference between the steering equivalent angle θp and the absolute angle θa in order to calculate the correction amount Δc during the end contact process. This allows the process of calculating the midpoint and the process of calculating the correction amount Δc to be performed simultaneously.

[0059] (8) The guard value Δ3 is set to a value greater than the guard value Δ2. This reduces the time required to reach the midpoint θpmd compared to when the guard value Δ2 is used in the midpoint movement mode.

[0060] (9) In this embodiment, a system is employed in which guard values ​​Δ1 to Δ3 are input to steering control device 70 from facility-side terminal 90. This makes it possible to flexibly set the right turning speed and the like to appropriate values ​​in accordance with requirements such as the schedule of the manufacturing process of steering device 30.

[0061] (10) In this embodiment, a system is employed in which change angles θp1, θp2 are input to steering control device 70 from facility-side terminal 90. This makes it possible to flexibly set the required time for right turn mode, etc., to an appropriate value in accordance with requirements such as the schedule for the manufacturing process of steering device 30.

[0062] (11) In this embodiment, the steering equivalent angle θp, which is determined by integrating the rotation angle θt of steering motor 40, is used as the control variable for feedback control in the midpoint movement mode. The steering equivalent angle θp has a higher resolution than the absolute angle θa. Therefore, the steering angle of steered wheels 50 can be controlled to the midpoint with high precision.

[0063] (12) On the condition that the absolute value of the absolute angle θa when the steering equivalent angle θp reaches the midpoint θpmd is equal to or less than the threshold value θath, the PU 72 stores the absolute angle θa as the correction data 74a in the storage device 74. This prevents the absolute angle θa from being stored when the steering angle of the steered wheels 50 is not at the midpoint due to some abnormality.

[0064] <Other Embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0065] "Regarding the detection process" The first region, which is the angle region in which the difference between the steering equivalent angle θp and the absolute angle θa is calculated in the right turn mode, and the second region, which is the angle region in which the difference between the steering equivalent angle θp and the absolute angle θa is calculated in the left turn mode, do not necessarily have to be the same region. For example, the first region may include the second region. Also, for example, the first region and the second region may be regions on the right turn side and the left turn side of the neutral position, respectively.

[0066] The angle region for detecting the degree of mismatch between the axial displacement of the steering shaft 32 and the rotation angle of the input side of the conversion device does not necessarily have to be the angle region for which the target steering angular velocity ωp* is determined by the guard value Δ1.

[0067] The averaging process of the degree of mismatch between the axial displacement of the steering shaft 32 and the rotation angle of the input side of the converter in the right turn mode and the degree of mismatch in the left turn mode is not limited to the process exemplified in the above embodiment. For example, the PU 72 may obtain the maximum value ΔMAX and the minimum value ΔMIN in both the first region and the second region and calculate the average of these maximum values ​​ΔMAX and minimum values ​​ΔMIN. Furthermore, for example, the PU 72 may sample three or more degrees of mismatch in the combined region of the first region and the second region and calculate the average value. Note that the locations at which the degree of mismatch is sampled are preferably defined by rotation angle. Furthermore, the number of samples in the first region is preferably the same as the number of samples in the second region.

[0068] The detection process does not necessarily have to be a process for detecting the degree of mismatch in the right turn mode and the degree of mismatch in the left turn mode. The detection process may be a process for detecting only one of the two degrees of mismatch in the right turn mode and the degree of mismatch in the left turn mode.

[0069] Regarding the rotational speed on the input side: The rotational angle on the input side of the conversion device that converts the rotation of steering motor 40 into a change in the steering angle of steered wheels 50 is not limited to rotational angle θt. For example, if a transmission is provided between steering motor 40 and the belt provided in transmission mechanism 44, the rotational angle may be the rotational angle of the output shaft of that transmission.

[0070] Regarding the Right Turn Operation Processing: In the right turn operation processing, the number of times the right turn speed is changed does not necessarily have to be once, but may be two or more times.

[0071] The condition for determining that the PU 72 has reached the right upper limit value θpR is not limited to the condition that the logical product of the above conditions (A) and (B) remains true for a certain period of time. The condition for determining that the PU 72 has reached the right upper limit value θpR may be, for example, the condition that the above condition (A) remains true for a certain period of time. Furthermore, the condition for determining that the PU 72 has reached the right upper limit value θpR may be, for example, the condition that the above condition (B) remains true for a certain period of time.

[0072] When the PU 72 determines that the right upper limit value θpR has been reached, it is not necessary to execute the process of substituting the steering equivalent angle θp for the target steering equivalent angle θp*. For example, when the PU 72 determines that the right upper limit value θpR has been reached, the PU 72 may gradually decrease the target steering equivalent angle θp* in accordance with the guard value Δ1.

[0073] The control amount of the feedback control in the right turn operation processing does not necessarily have to be the steering equivalent angle θp. For example, the control amount of the feedback control in the right turn operation processing may be the rate of change of the steering equivalent angle θp. Also, for example, the control amount of the feedback control in the right turn operation processing may be the absolute angle θa.

[0074] Regarding Left Turn Operation Processing In the left turn operation processing, the number of times the left turn speed is changed does not necessarily have to be once, but may be two or more times.

[0075] The condition for determining that the PU 72 has reached the left upper limit value θpL is not limited to the condition that the logical product of the above conditions (A) and (B) remains true for a certain period of time. The condition for determining that the PU 72 has reached the left upper limit value θpL may be, for example, the condition that the above condition (A) remains true for a certain period of time. Furthermore, the condition for determining that the PU 72 has reached the left upper limit value θpL may be, for example, the condition that the above condition (B) remains true for a certain period of time.

[0076] It is not essential that the PU 72 executes the process of substituting the steering equivalent angle θp for the target steering equivalent angle θp* when it determines that the left upper limit value θpL has been reached. For example, when it determines that the left upper limit value θpL has been reached, the PU 72 may gradually decrease the target steering equivalent angle θp* in accordance with the guard value Δ1.

[0077] The control amount of the feedback control in the left turn operation processing does not necessarily have to be the steering equivalent angle θp. For example, the control amount of the feedback control in the left turn operation processing may be the rate of change of the steering equivalent angle θp. Also, for example, the control amount of the feedback control in the left turn operation processing may be the absolute angle θa.

[0078] Regarding the steering process: The steering process used to detect the degree of misalignment by the detection process is not limited to the end contact process. The steering process may be a process dedicated to detecting the degree of misalignment.

[0079] "Midpoint Calculation Process" The process of S108 is not essential to the midpoint calculation process. For example, if the control variable of the feedback control in the right turn operation process and the left turn operation process is the absolute angle θa, the PU 72 may determine the right upper limit value θpR and the left upper limit value θpL as the value of the absolute angle θa. In this case, the PU 72 may store the midpoint θpmd, which is "½" of the sum of the right upper limit value θpR and the left upper limit value θpL, in the storage device 74 as the correction data 74a.

[0080] "Regarding the end contact processing" It is not essential that the end contact processing be performed before the steering device 30 is mounted on the vehicle. For example, the end contact processing may be performed immediately after the steering device 30 is mounted on the vehicle. In that case, for example, if the steering control device 70 is mounted on the vehicle and is capable of communicating with the facility-side terminal 90, the end contact processing can be performed in the same manner as in the above embodiment.

[0081] Regarding the absolute angle sensor: The absolute angle sensor, which detects an amount that corresponds one-to-one to the steering angle of the steered wheels 50, is not limited to the sensor exemplified in the above embodiment. For example, it may be a linear stroke sensor that directly detects the amount of displacement of the steering shaft 32 in the axial direction.

[0082] It is not essential that the resolution of absolute angle θa be lower than the resolution of steering equivalent angle θp. "Regarding the steering control device" It is not essential that guard values ​​Δ1, Δ2, Δ3 be input to steering control device 70 from facility side terminal 90. For example, guard values ​​Δ1, Δ2, Δ3 may be stored in advance in storage device 74 of steering control device 70.

[0083] It is not essential that the change angles θp1, θp2 are input to the steering control device 70 from the facility-side terminal 90. For example, the change angles θp1, θp2 may be stored in advance in the storage device 74 of the steering control device 70.

[0084] The steering control device is not limited to one that executes software processing. For example, it may be provided with a dedicated hardware circuit, such as an ASIC, that executes at least part of the processing executed in the above embodiment by hardware processing. In other words, the steering control device may include a processing circuit having any of the following configurations (a) to (c): (a) A processing circuit that includes a processing device that executes all of the above processing in accordance with a program, and a program storage device, such as a memory device, that stores the program. (b) A processing circuit that includes a processing device and program storage device that executes part of the above processing in accordance with a program, and a dedicated hardware circuit that executes the remaining processing. (c) A processing circuit that includes a dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software execution devices that include a processing device and a program storage device. Also, there may be multiple dedicated hardware circuits.

[0085] "Regarding the steering control system" When the facility-side terminal 90 does not input the guard values ​​Δ1, Δ2, Δ3 and the change angles θp1, θp2 to the steering control device 70, the facility-side terminal 90 may only have the function of outputting a command to the steering control device 70 to execute the end contact processing.

[0086] Regarding the steering control method: It is not essential that all of the processes illustrated in Figures 2 to 7 be executed by the computer mounted on steering control device 70. For example, some of the processes may be executed by the computer of facility-side terminal 90.

Claims

1. A steering control device in which a steering actuator having a conversion device that converts the rotation of a motor into the axial displacement of a steering shaft is an object to be operated, the steering shaft being configured to steer the steered wheels by displacing in the axial direction, the steering control device comprising an execution device and a storage device, the execution device being configured to execute a steering process, a detection process and a storage process, the steering process being a process of steering the steered wheels in at least one of two directions, the right turning direction and the left turning direction, by operating the motor, the detection process being a process in which the detection value of an absolute angle sensor and the detection value of a rotation angle sensor when the steering process is being executed are input, and the detection process being a process of detecting the degree of inconsistency between the axial displacement amount of the steering shaft and the rotation angle of the input side of the conversion device, the storage process being a process of storing in the storage device a correction amount for suppressing inconsistency between the axial displacement amount of the steering shaft and the rotation angle of the input side of the conversion device, the absolute angle sensor being a sensor that detects an amount that corresponds one-to-one with the steering angle of the steered wheels, A steering control device, wherein the rotation angle sensor is a sensor that detects the rotation angle of the input side of the conversion device.

2. A steering control device according to claim 1, wherein the steering process is a process for steering the steered wheels in each of the two directions.

3. A steering control device as described in claim 2, wherein the detection process is a process for quantifying the degree of misalignment by averaging the degree of misalignment when the steered wheels are turned in a first direction of the two directions and the degree of misalignment when the steered wheels are turned in a second direction of the two directions.

4. A steering control device as described in claim 3, wherein the detection process is a process for detecting the degree of misalignment when the steered wheels are steered in a first direction of the two directions in a first region and when the steered wheels are steered in a second direction of the two directions in a second region, the first region and the second region being rotation angle regions of the steered wheels, and the size of the first region and the size of the second region being equal to each other.

5. A steering control device according to claim 4, wherein said first region and said second region are the same region.

6. A steering control device as described in claim 3, wherein the axial displacement of the steering shaft and the rotation angle of the input side of the conversion device are quantified by the same rotation angle, and the detection process is a process of quantifying the degree of misalignment by averaging the minimum value of the difference between the axial displacement and the rotation angle of the input side of the conversion device when the steered wheels are steered in the first direction and the maximum value of the difference when the steered wheels are steered in the second direction.

7. A steering control device as claimed in claim 1, wherein the steering process includes a process for bringing the steering speed of the steered wheels closer to a target speed, and the detection process is a process for detecting the degree of the inconsistency on the condition that the steering speed of the steered wheels is controlled to a constant speed.

8. A steering control device as described in claim 1, wherein the execution device is configured to execute a judgment process, the judgment process being a process for judging whether or not the degree of inconsistency detected by the detection process is within a predetermined range, and the execution device is configured to execute the storage process when the judgment process judges that the degree of inconsistency is within the predetermined range.

9. A steering control device as described in claim 1, wherein the execution device is configured to execute a mode setting process, the mode setting process including a process for setting the operation mode of the execution device to an inspection mode when the correction amount is not stored in the storage device, and the execution device is configured to execute the steering process, the detection process, and the storage process in the inspection mode.

10. A steering control device as described in claim 9, wherein the mode setting process includes a process for setting the operating mode to a normal control mode when the correction amount is stored in the storage device, and the execution device is configured to execute an abnormality detection process in the normal control mode, and the abnormality detection process is a process for determining that an abnormality has occurred when the detection value of the absolute angle sensor and the detection value of the rotation angle sensor are input and the degree of mismatch between the axial displacement amount of the steering shaft and the rotation angle of the input side of the conversion device falls outside an allowable range, and the degree of mismatch that is to be determined as to whether it falls outside the allowable range is a value corrected by the correction amount.

11. A steering control device as described in claim 1, wherein the steering processing includes a right turning operation processing and a left turning operation processing, the right turning operation processing being a processing for maximally displacing the steered wheels to the right turning side at a right turning speed by operating the motor, and the left turning operation processing being a processing for maximally displacing the steered wheels to the left turning side at a left turning speed by operating the motor, the execution device being configured to execute a midpoint calculation processing, and the midpoint calculation processing being a processing for calculating the midpoint between the maximum value of the steering angle of the steered wheels on the right turning side in the right turning operation processing and the maximum value of the steering angle on the left turning side in the left turning operation processing.

12. A steering control method in which a steering actuator having a conversion device that converts the rotation of a motor into the axial displacement of a turning shaft is an object to be operated, the turning shaft being configured to turn the turning wheels by displacing in the axial direction, the method having steps of executing a turning process, a detection process, and a storage process, the turning process being a process of turning the turning wheels in at least one of two directions, the right turning direction and the left turning direction, by operating the motor, the detection process being a process in which the detection value of an absolute angle sensor and the detection value of a rotation angle sensor when the turning process is being executed are input, and the detection process is a process of detecting the degree of mismatch between the axial displacement amount of the turning shaft and the rotation angle of the input side of the conversion device, the storage process being a process of storing in a storage device a correction amount for suppressing the mismatch between the axial displacement amount of the turning shaft and the rotation angle of the input side of the conversion device, the absolute angle sensor being a sensor that detects an amount that corresponds one-to-one with the turning angle of the turning wheels, and the rotation angle sensor being a sensor that detects the rotation angle of the input side of the conversion device.

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