Steering control device

Abstract

To provide a steering control device configured to shorten a time required for a process for learning a midpoint.SOLUTION: A PU 52 maximally displaces a steering shaft 14 to a right turning side, by operating a reaction force motor 22. When a steering angle is not changed any more, the PU 52 sets the steering angle at that time to an upper limit value at the right turning side. The PU 52 calculates an upper limit value at a left turning side, on the basis of the upper limit value at the right turning side and a mechanical end interval. The PU 52 sets [1 / 2] of the sum of the upper limit value at the right turning side and the upper limit value at the left turning side as a midpoint.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 below describes a steer-by-wire system which is a system in which the power transmission between the steering wheel and the steering shaft is interrupted. The control device described in the document calculates a midpoint based on the steering angle when the steering shaft is displaced to the maximum on the left turn side and the steering angle when the steering shaft is displaced to the maximum on the right turn side.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the case of the above device, in order to calculate the midpoint, it is necessary to displace the steering shaft to the maximum on both the right turn side and the left turn side. Therefore, the execution time of the process for calculating the midpoint becomes long.

Means for Solving the Problems

[0005] Hereinafter, means for solving the above problems and their effects will be described. 1. A steering control device in which a reaction force motor that applies a reaction force to the steering shaft is an operation target in a state where power transmission between the steering wheel and the steering shaft is interrupted, and is configured to execute an end contact process, an end determination process, a maximum displacement variable acquisition process, and a midpoint learning process. The end contact process is a process of displacing the steering shaft to the maximum extent to either the right rotation side or the left rotation side by operating the reaction force motor. The end determination process is a process of determining whether the steering shaft has been displaced to the maximum extent. The maximum displacement variable acquisition process is a process of acquiring the value of the maximum displacement variable. The maximum displacement variable is a variable obtained based on being determined to have been displaced to the maximum extent by the end determination process. The midpoint learning process is a process of learning the midpoint of the rotation angle of the steering shaft based on the value of the maximum displacement variable.

[0006] The range in which the steering shaft can be displaced can be grasped in advance. Therefore, according to the value of the maximum displacement variable obtained when displaced to the maximum extent, it is also possible to grasp the variable value indicating the steering angle by displacing to the maximum extent to either the other side. This means that based on the value of the maximum displacement variable, the upper limit values of the steering angles on both the one side and the other side can be grasped. Therefore, in the above configuration, the midpoint is learned based on the value of the maximum displacement variable. Thereby, compared with the case of executing the process of displacing the steering shaft to the maximum extent to both the right rotation side and the left rotation side, the time required for the process of learning the midpoint can be shortened.

[0007] 2. The value of the maximum displacement variable is the integrated value of the rotation angle of the reaction force motor when it is determined by the end determination process that the maximum displacement has occurred. The midpoint learning process is the process of learning the midpoint based on the rotatable angle of the steering shaft determined in advance and the integrated value as an input variable, according to the steering control device described in 1 above.

[0008] The integrated value indicates the upper limit value of the steering angle in any one of the above. Therefore, according to the rotatable angle of the steering shaft and the integrated value, the upper limit value and the midpoint of the steering angle of the other one can be grasped.

[0009] 3. It is configured to execute an initial value acquisition process, the end fitting process includes a process of controlling the rotational speed of the reaction force motor to a target rotational speed, the maximum displacement variable is the elapsed time until it is determined that the maximum displacement has occurred by the end fitting process, the initial value acquisition process is a process of acquiring an integrated value of the rotational angle of the reaction force motor at the start of the measurement of the elapsed time, and the midpoint learning process is a process of learning the midpoint based on the value of the maximum displacement variable as an input variable and the integrated value at the start. The steering control device according to item 1 above.

[0010] According to the target rotational speed and the elapsed time, the displacement amount of the steering shaft can be grasped. Therefore, according to the elapsed time and the value acquired by the above initial value acquisition process, the steering angle when displaced to any one of the above can be grasped. Therefore, according to the above configuration, the midpoint can be learned.

[0011] 4. The steering control device according to item 3 above, wherein the target rotational speed is a constant value. In the above configuration, by setting the target rotational speed to a constant value, the displacement amount of the steering shaft can be easily grasped from the elapsed time as compared with the case of changing the target rotational speed.

[0012] 5. It is configured to execute a midpoint control process, and the midpoint control process is a process of displacing the steering shaft to the learned midpoint position without displacing it to the maximum on either the right turn side or the left turn side from the state where it is displaced to the maximum on any one of them by the end fitting process. The steering control device according to any one of items 1 to 4 above.

[0013] In the above configuration, after the completion of midpoint learning, the steering angle can be quickly shifted to the midpoint.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0015] <The First Embodiment> Hereinafter, the first embodiment will be described with reference to the drawings. 「Premise Configuration」 The vehicle steering device 10 shown in FIG. 1 is a steer-by-wire device. The steering device 10 includes a steering wheel 12, a steering shaft 14, a reaction force actuator 20, and a turning actuator 30. The steering shaft 14 is connected to the steering wheel 12. The reaction force actuator 20 applies a force that resists the force with which the driver operates the steering wheel 12. The reaction force actuator 20 includes a reaction force motor 22, a reaction force inverter 24, and a reaction force reduction mechanism 26. The reaction force motor 22 applies a steering reaction force, which is a force that resists steering, to the steering wheel 12 via the steering shaft 14. The reaction force motor 22 is connected to the steering shaft 14 via the reaction force reduction mechanism 26. As an example, the reaction force motor 22 is a three-phase surface permanent magnet synchronous motor. The reaction force reduction mechanism 26 is formed, for example, of a worm and wheel.

[0016] Steering actuator 30 steers steerable wheels 34 in accordance with the driver's steering intention, which is indicated by the driver's operation of steering wheel 12. Steering actuator 30 includes rack shaft 32, steering motor 42, steering inverter 44, steering transmission mechanism 46, and conversion mechanism 48. Steering motor 42 is, for example, a three-phase synchronous motor. Steering transmission mechanism 46 is made up of a belt transmission mechanism. Rotational power of steering motor 42 is transmitted to conversion mechanism 48 by steering transmission mechanism 46. Conversion mechanism 48 converts the transmitted rotational power into axial displacement power of rack shaft 32. The axial displacement of rack shaft 32 causes steerable wheels 34 to turn.

[0017] The reaction force control device 50 includes a PU 52 and a storage device 54. The PU 52 is a software processing device such as a CPU and a GPU. The storage device 54 may be an electrically non-rewritable non-volatile memory. Alternatively, the storage device 54 may be an electrically rewritable non-volatile memory or a storage medium such as a disk medium.

[0018] The control target of the reaction force control device 50 is the steering wheel 12. The reaction force control device 50 controls the steering reaction force that resists the driver's steering, which is the control amount of the steering wheel 12.

[0019] The reaction force control device 50 refers to the steering torque Th detected by the torque sensor 56 for the control of the control amount. The steering torque Th is the torque applied to the steering shaft 14 by the driver through the operation of the steering wheel 12. The reaction force control device 50 refers to the rotation angle θa, which is the angle of the rotation shaft of the reaction force motor 22, detected by the steering-side rotation angle sensor 58 for the control of the control amount. Further, the reaction force control device 50 refers to the currents ius, ivs, iws flowing through the reaction force motor 22 for the control of the control amount. The currents ius, ivs, iws may be detected, for example, as the voltage drop amounts of shunt resistors provided in each leg of the reaction force inverter 24.

[0020] The steering control device 60 includes a PU 62 and a storage device 64. The PU 62 is a software processing device such as a CPU and a GPU. The storage device 64 may be a non-volatile memory that is electrically non-rewritable. Further, the storage device 64 may be a non-volatile memory that is electrically rewritable and a storage medium such as a disk medium.

[0021] The control target of the steering control device 60 is the steered wheels 34. The steering control device 60 controls the steering angle, which is the control amount of the steered wheels 34. The steering angle is the cut angle of the tire as the steered wheel 34.

[0022] The steering control device 60 refers to the rotation angle θb, which is the angle of the rotation shaft of the steering motor 42, detected by the steering-side rotation angle sensor 66 for the control of the control amount. Further, the steering control device 60 refers to the currents iut, ivt, iwt flowing through the steering motor 42 for the control of the control amount. The currents iut, ivt, iwt may be detected, for example, as the voltage drop amounts of shunt resistors provided in each leg of the steering inverter 44.

[0023] "Configuration of Reaction Force Actuator 20" Fig. 2 shows a partial configuration of the reaction force actuator 20. As shown in Fig. 2, the reaction force actuator 20 includes a housing 70 fixed to the vehicle. The steering shaft 14 is inserted into the housing 70. The housing 70 rotatably supports the steering shaft 14. The steering shaft 14 is inserted into a plurality of ring-shaped members. The ring-shaped members include washers 80, an intermediate stopper 90, washers 82, an end stopper 100, wave washers 84, and a C-shaped retaining ring 86.

[0024] The housing 70 is provided with a protrusion 72 as a regulating member for regulating the rotation of the intermediate stopper 90. The intermediate stopper 90 is provided with a protrusion 92 whose rotation is restricted by the protrusion 72.

[0025] Fig. 3 shows a partial cross-sectional configuration of the reaction force actuator 20. As shown in Fig. 3, an elastic force in the right direction in the figure is exerted on the end stopper 100 by the wave washer 84. As a result, an elastic force in the right direction is exerted on the intermediate stopper 90 via the washer 82. On the other hand, the steering shaft 14 has a reduced-diameter portion at the left end in the figure. The washers 80, the intermediate stopper 90, and the washer 82 are arranged at the reduced-diameter portion of the steering shaft 14. Therefore, the displacement of the washer 80 to the right in the figure is restricted. Therefore, an elastic force that advances to the right in the figure is exerted on the intermediate stopper 90 by the washer 82, and an elastic force that advances to the left in the figure is exerted on the intermediate stopper 90 by the washer 80.

[0026] The end stopper 100 is fixed to the steering shaft 14. Therefore, as the steering shaft 14 rotates, the end stopper 100 rotates integrally with the steering shaft 14. As the end stopper 100 rotates, the intermediate stopper 90 is rotated along.

[0027] "Rotation Regulation of Steering Shaft 14" Figure 4 shows the operation of the intermediate stopper 90 as the steering shaft 14 rotates. The upper part of Figure 4 shows the case where the steering shaft 14 rotates to the right rotation side. The left end of the upper part of Figure 4 shows a state where the steering angle θh, which is the rotation angle of the steering shaft 14, is a value corresponding to the left rotation side end. And in the upper part of Figure 4, as it moves to the right in the figure, it shows a state where the steering shaft 14 rotates to the right rotation side. In particular, the right end of the upper part of Figure 4 shows a state where the steering angle θh is a value corresponding to the right rotation side end.

[0028] As shown in the upper part of Figure 4, when the steering shaft 14 rotates from the left rotation side end to the right, the intermediate stopper 90 is carried along as the end stopper 100 rotates. The center of the upper part of Figure 4 shows a state where the protrusion 92 of the intermediate stopper 90 contacts the protrusion 72 of the housing 70. Thereby, the intermediate stopper 90 cannot rotate further to the right. Therefore, as the steering shaft 14 rotates, the end stopper 100 rotates alone. And when the protrusion 102 of the end stopper 100 contacts the protrusion 92 of the intermediate stopper 90 as the steering shaft 14 rotates further, the end stopper 100 cannot rotate further to the right. This state is shown at the right end of the upper part of Figure 4. In this state, the steering shaft 14 cannot rotate further to the right. The steering angle θh at this time becomes the upper limit value on the right rotation side.

[0029] The lower part of Figure 4 shows the case where the rotation angle of the steering shaft 14 rotates to the left rotation side. The left end of the lower part of Figure 4 shows a state where the steering angle θh is a value corresponding to the right rotation side end. And in the lower part of Figure 4, as it moves to the right in the figure, it shows a state where the steering shaft 14 rotates to the left rotation side. In particular, the right end of the lower part of Figure 4 shows a state where the steering angle θh is a value corresponding to the left rotation side end.

[0030] As shown in the lower part of FIG. 4, when the steering shaft 14 turns left from the end on the right-turning side, the intermediate stopper 90 rotates as the end stopper 100 rotates. The center of the lower part of FIG. 4 shows a state in which the protrusion 92 of the intermediate stopper 90 contacts the protrusion 72 of the housing 70. This prevents the intermediate stopper 90 from turning further to the left. Therefore, the end stopper 100 rotates independently as the steering shaft 14 rotates. Then, when the steering shaft 14 rotates further and the protrusion 102 of the end stopper 100 contacts the protrusion 92 of the intermediate stopper 90, the end stopper 100 cannot turn further to the left. This state is shown at the right end of the lower part of FIG. 4. In this state, the steering shaft 14 cannot rotate further to the left. The steering angle θh at this time is the upper limit on the left-turning side.

[0031] "N-point learning value" As shown in FIG. 1, storage device 54 of reaction force control device 50 stores steering side N-point learning data 54a indicating an N-point learning value, which is a learned value of steering angle θh when traveling straight. Storage device 64 of steering control device 60 stores steering side N-point learning data 64a indicating an N-point learning value, which is a learned value of steering angle when traveling straight. As an example, steering side N-point learning data 64a is stored in storage device 64 before shipping of steering device 10. Meanwhile, in this embodiment, reaction force control device 50 executes processing to acquire the N-point learning value when reaction force control device 50 is started for the first time after shipping. Reaction force control device 50 also executes processing to acquire the N-point learning value when steering control device 60 is started immediately after steering side N-point learning data 54a is lost in storage device 54 due to battery replacement, for example. The conditions under which reaction force control device 50 and steering control device 60 start communication for steering the vehicle include a condition that each of them holds an N-point learning value.

[0032] The process in which the reaction force control device 50 acquires the N-point learning value is performed, for example, by displacing the steering angle θh up to its upper limit on the right-turning side. This will be described below. "N-point learning process" FIG. 5 shows the procedure of the process at the time of activation of the reaction force control device 50. The process shown in FIG. 5 is realized by the PU52 executing the program stored in the storage device 54 triggered by the activation of the reaction force control device 50. In the following, the step numbers of each process are represented by numbers with "S" attached at the beginning.

[0033] In the series of processes shown in FIG. 5, the PU52 first determines whether or not the steering side N-point learning data 54a is stored (S10). When the PU52 determines that the steering side N-point learning data 54a is not stored (S10: NO), it sets the control mode to the N-point learning mode (S12). On the other hand, when the PU52 determines that the steering side N-point learning data 54a is stored (S10: YES), it sets the control mode to the normal control mode (S14). The normal control mode is a mode for executing processes related to the steering of the vehicle in cooperation with the steering control device 60. However, at the start of the normal control mode, initial check processes such as whether communication with the steering control device 60 can be executed normally are performed.

[0034] When the PU52 completes the processes of S12 and S14, it temporarily ends the series of processes shown in FIG. 5. FIG. 6 shows the procedure of the process related to the acquisition of the steering side N-point learning data 54a. The series of processes shown in FIG. 6 is realized by the PU52 repeatedly executing the program stored in the storage device 54 at a predetermined period, for example.

[0035] In the series of processes shown in FIG. 6, the PU52 first determines whether or not it is in the N-point learning mode (S20). When the PU72 determines that it is in the N-point learning mode (S20: YES), it determines whether or not the operation mode in the N-point learning mode is the right turn mode (S22). The operation mode is set to the right turn mode when the control mode switches to the N-point learning mode. When the PU52 determines that it is in the right turn mode (S22: YES), it substitutes the value obtained by adding a predetermined amount Δ to the target steering angle θh* for the target steering angle θh* (S24). Then, the PU72 determines whether or not the logical product of the following conditions (A) to (C) has been true for a certain period of time (S26).

[0036] Condition (A) is a condition that the absolute value of the steering torque Th is equal to or less than a predetermined value. This condition indicates that the driver is not operating the steering wheel 12. Condition (B) is a condition that the previous value "θh(n - 1)" and the current value "θh(n)" of the steering angle θh are the same. The steering angle θh is calculated by the PU52 based on the rotation angle θa as an input variable. The calculation process of the steering angle θh by the PU52 includes the following processes. That is, the calculation process includes a process of converting the rotation angle θa into an integrated angle including a range exceeding 360° by counting the number of rotations of the reaction force motor 22 from the steering neutral position, which is the position of the steering wheel 12 when the vehicle is going straight. Further, the calculation process includes a process of calculating the steering angle θh by multiplying the obtained integrated angle by a conversion coefficient based on the rotation speed ratio of the reaction force reduction mechanism 26. Note that the steering angle θh is positive when it is an angle on the right side of the steering neutral position, for example, and negative when it is an angle on the left side.

[0037] Condition (C) is a condition that the absolute value of the q-axis current iqs flowing through the reaction force motor 22 is equal to or greater than the threshold value Ith. The threshold value Ith is set to a value larger than the value assumed as the absolute value of the q-axis current iqs when displacing the steering angle θh when the steering angle is in the intermediate region between the upper limit value on the right turn side and the upper limit value on the left turn side. For example, when the feedback control in the process of S34 described later includes a proportional term, the threshold value Ith may be set to be equal to or greater than the output value of the proportional term when the absolute value of the difference between the target steering angle θh* and the steering angle θh becomes a predetermined amount Δ. Further, the threshold value Ith may be a value for determining that the windup phenomenon of the integral term occurs when the feedback control in the process of S34 includes an integral term. Note that the q-axis current iqs is calculated by the PU52 based on the rotation angle θa and the currents ius, ivs, iws as input variables.

[0038] The fact that the above logical product is true is a condition for determining that the steering angle has reached the upper limit value on the right turn side. That is, if condition (A) is satisfied, it is understood that the driver is not prevented from rotating the reaction motor 22 to rotate the steering shaft 14. Therefore, when condition (A) is satisfied and the upper limit value on the right turn side is reached, condition (B) is satisfied. Further, when the upper limit value on the right turn side is reached, since the absolute value of the difference between the target steering angle θh* and the steering angle θh cannot be reduced, the absolute value of the torque of the reaction motor 22 increases, and condition (C) is satisfied.

[0039] When PU52 determines that the state where the logical product of conditions (A) to (C) is true has continued for a certain period of time (S26: YES), it substitutes the current value "θh(n)" of the steering angle θh into the target steering angle θh* (S28). Then, it substitutes the current value "θh(n)" into the right upper limit value θhR (S30).

[0040] PU72 switches the operation mode to the midpoint movement mode (S32). When PU52 completes the process of S32 and when a negative determination is made in the process of S26, it calculates a target torque Ts* corresponding to the operation amount by feedback control in which the steering angle θh is the control amount and the target steering angle θh* is the target value of the control amount (S34). The target torque Ts* is the target value of the torque of the reaction motor 22.

[0041] Then, PU52 outputs an operation signal MSs of the reaction inverter 24 to the reaction inverter 24 in order to make the torque of the reaction motor 22 approach the target torque Ts* (S36). On the other hand, when a negative determination is made in the process of S22, PU52 substitutes the value obtained by subtracting the mechanical end interval θLR from the right upper limit value θhR into the left upper limit value θhL (S38). The mechanical end interval θLR indicates the magnitude of the displaceable angular range of the steering angle θh. This angular range is the change range of the steering angle θh from the state shown at the left end in the upper part of FIG. 4 to the state shown at the right end. PU52 acquires the mechanical end interval θLR by reading the mechanical end interval data 54b stored in the storage device 54.

[0042] PU52 substitutes "1 / 2" of the sum of the right upper limit value θhR and the left upper limit value θhL into the midpoint θhmd (S40). PU52 determines whether the steering angle θh matches the midpoint θhmd (S42). When PU72 determines that the steering angle θh does not match the midpoint θhmd (S42: NO), it substitutes the value obtained by subtracting a predetermined amount Δ from the target steering angle θh* into the target steering angle θh*. Then, PU52 proceeds to the process of S34.

[0043] On the other hand, when PU72 determines that the steering angle θh matches the midpoint θhmd (S42: YES), it ends the N-point learning mode (S46). Note that when PU72 completes the processes of S36 and S46, and when it makes a negative determination in the process of S20, it temporarily ends the series of processes shown in FIG. 6.

[0044] "Actions and Effects of the Present Embodiment" When the steering-side N-point learning data 54a is not stored at startup, PU52 sets the control mode to the N-point learning mode. In the N-point learning mode, PU52 increases the target steering angle θh* at a speed defined by a predetermined amount Δ. As a result, the steering angle θh is controlled to follow the target steering angle θh*. When the steering angle θh reaches the right upper limit value, the steering angle θh no longer increases. Therefore, PU52 recognizes the steering angle θh at that time as the right upper limit value θhR.

[0045] Then, PU52 calculates the left upper limit value θhL based on the right upper limit value θhR and the mechanical end interval θLR. And PU52 calculates the midpoint θhmd based on the right upper limit value θhR and the left upper limit value θhL.

[0046] In this way, the PU 52 calculates the midpoint θhmd only by the process of maximally displacing the steering shaft 14 to the right, which reduces the processing time required to calculate the midpoint θhmd compared to the case where both the process of maximally displacing the steering shaft 14 to the right and the process of maximally displacing the steering shaft 14 to the left are performed.

[0047] According to the present embodiment described above, the following actions and effects can be further obtained. (1) The PU 52 determines whether the steering shaft 14 has been displaced to the maximum extent based on whether the logical product of the above conditions (A) to (C) is true. This makes it possible to determine with high accuracy whether the steering shaft 14 has been displaced to the maximum extent.

[0048] That is, for example, if the logical product of the above conditions (B) and (C) is true and it is determined that the steering angle θh has been fully displaced, there is a risk that the system will erroneously determine that the steering angle θh has been fully displaced if the driver applies force to the steering wheel 12 so as not to displace the steering angle θh. Also, for example, if the logical product of the above conditions (A) and (B) is true and it is determined that the steering angle θh has been fully displaced, there is a risk that the system will erroneously determine that the steering angle θh has been fully displaced if there is an abnormality in the power supply to the reaction force motor 22.

[0049] <Second embodiment> The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0050] Figure 7 shows the procedure for processing related to acquisition of the steering-side N-point learning data 54a. The series of processes shown in Figure 7 are realized by the PU 52 repeatedly executing a program stored in the storage device 54, for example, at a predetermined interval. For convenience, the same step numbers are assigned to processes in Figure 7 that correspond to the processes shown in Figure 6.

[0051] In the series of processes shown in FIG. 7, when the PU72 makes an affirmative determination in the process of S22, it determines whether it is the first cycle in the right turn mode (S50). When the PU52 determines that it is the first time (S50: YES), it substitutes the steering angle θh into the initial value θh0 (S52). When the PU52 completes the process of S52 and when it makes a negative determination in the process of S50, it proceeds to the process of S24. When the PU52 completes the process of S24, it adds the cycle Tc to the counter T (S54). The cycle Tc is the execution cycle of the series of processes shown in FIG. 7. The counter T is a variable that measures the period during which the processes of S34 and S36 are executed in response to the process of S24. Then the PU52 proceeds to the process of S26.

[0052] When the PU52 makes a negative determination in the process of S22, it substitutes the following value into the midpoint θhmd (S40a). [Δ·{T - (constant time)} / Tc + θh0] - θLR / 2 Here, "T - (constant time)" can be regarded as the time during which the steering angle θh has changed. Note that here, the "constant time" is preferably the constant time from the point when condition (B) is satisfied, instead of the constant time as the duration of the state in which conditions (A) to (C) are satisfied. Also, "Δ / Tc" indicates the change rate of the steering angle θh. Therefore, "Δ·{T - (constant time)} / Tc" is the amount by which the steering angle θh has turned to the right. Also, "Δ·{T - (constant time)} / Tc + θh0" indicates the right upper limit value θhR. Also, the value obtained by subtracting the mechanical end interval θLR from "Δ·{T - (constant time)} / Tc + θh0" indicates the left upper limit value θhL. Therefore, referring to the process of S40, the above formula is understood as the midpoint θhmd.

[0053] When the PU72 completes the process of S40a, it proceeds to the process of S42. <Corresponding relationship> The correspondence between the matters in the above embodiment and the matters described in the "Means for Solving the Problem" column is as follows. Below, the correspondence is shown for each number of the means for solving the problem described in the "Means for Solving the Problem" column. [1] The end contact process corresponds to the processes of S34 and S36 when the processes of S22 to S24 are being executed. The end determination process corresponds to the process of S26. The maximum displacement variable acquisition process corresponds to the process of S30 in FIG. 6 and the process of S54 when a positive determination is made in the process of S26 in FIG. 7. The midpoint learning process corresponds to the processes of S40 and S40a. [2] The midpoint learning process corresponds to the process of S40. The integrated value corresponds to the steering angle θh. The "predetermined rotatable angle of the steering shaft" corresponds to the mechanical end interval θLR. [3] The initial value acquisition process corresponds to the process of S52. The value of the maximum displacement variable corresponds to the value of the counter T when a positive determination is made in the process of S26 in FIG. 7. The target steering angular velocity corresponds to "Δ / Tc." [4] This corresponds to the target steering angle θh* changing by a predetermined amount Δ per cycle Tc. [5] The midpoint control process corresponds to the processes of S34 and S36 when the process of S44 is being executed.

[0054] <Other embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0055] "About end contact processing" The end contact process is not limited to a process in which the target steering angular velocity is set to a constant value. For example, the target steering angular velocity may be reduced during the end contact process. This makes it possible to achieve a good compromise between reducing the impact when the right upper limit value is reached and quickly reaching the right upper limit value. Furthermore, the number of times the target steering angular velocity is changed during the end contact process does not necessarily have to be once, and may be two or more times.

[0056] · The condition for determining that PU52 has reached the right upper limit value is not limited to the condition that the logical product of the above conditions (A) to (C) is true and continues for a certain period of time. The condition for determining that PU52 has reached the right upper limit value may be, for example, the condition that the above conditions (A) and (B) hold for a certain period of time. Also, for example, the condition for determining that PU52 has reached the right upper limit value may be the condition that the above conditions (B) and (C) hold for a certain period of time. Also, for example, when the threshold Ith is set as the value for determining that the windup phenomenon of the integral term has occurred, the condition for determining that PU52 has reached the right upper limit value may be the condition that the above conditions (A) and (C) hold.

[0057] · When it is determined that PU52 has reached the right upper limit value, it is not essential to execute the process of substituting the steering angle θh into the target steering angle θh*. For example, when it is determined that PU52 has reached the right upper limit value, the target steering angle θh* may be gradually decreased according to a predetermined amount Δ.

[0058] · It is not essential that the control amount of the feedback control in the end fitting process is the steering angle θh. For example, the control amount of the feedback control in the end fitting process may be the change rate of the steering angle θh.

[0059] · It is not essential that the end fitting process is a process of rotating the steering shaft 14 clockwise. For example, the end fitting process may be a process of rotating the steering shaft 14 counterclockwise.

[0060] "Regarding the midpoint learning process" · In FIG. 6, an example is described in which PU52 repeats the processes of S38 and S40 until a positive determination is made in the process of S42 in the midpoint movement mode, but it is not limited to this. For example, when executing the process of S30, PU52 may execute the processes of S38 and S40 only once and store the value in the storage device 54.

[0061] 7 illustrates an example in which the PU 52 repeats the process of S40a in the midpoint movement mode until a positive determination is made in the process of S42, but this is not limiting. For example, when executing the process of S30, the PU 52 may execute the process of S40a only once and store the result in the storage device 54.

[0062] 6, the PU 52 may execute the following process instead of the processes of S38 and S40: That is, the PU 52 may execute a process of substituting "θhR-θLR / 2" for the midpoint θhmd.

[0063] The midpoint learning process does not necessarily have to be a process for learning the midpoint of the steering angle θh obtained by integrating the rotation angle θa. For example, if a dedicated sensor for detecting the rotation angle of the steering shaft 14 is provided, the midpoint may be learned instead.

[0064] "About steering control devices" The reaction force control device 50 and the steering control device 60 may be integrally formed. 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 embodiments by hardware processing. That is, 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 according to 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 according to 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.

[0065] "Device for restricting the rotation of the steering shaft 14" The device for restricting the rotation of the steering shaft 14 is not limited to the device exemplified in the above embodiment. For example, the end stopper 100 does not have to have an intermediate stopper that rotates with it. [Explanation of symbols]

[0066] 10...Steering device 12...Steering wheel 14...Steering shaft 16...Reduction mechanism 20...Reaction actuator 22...Reaction motor 24...Reaction force inverter 26...Reaction force reduction mechanism 30...Steering actuator 32...Rack shaft 34...Steering wheel 42...Steering motor 44...Steering inverter 46...Steering transmission mechanism 48...Conversion mechanism 50...Reaction force control device

Claims

1. A steering control device in which a reaction force motor that applies a reaction force to the steering shaft is an operation target in a state where power transmission between the steering wheel and the steering shaft is interrupted, configured to execute end abutment processing, end determination processing, maximum displacement variable acquisition processing, and midpoint learning processing, wherein the end abutment processing is a process of displacing the steering shaft to the maximum extent to either the right turn side or the left turn side by operating the reaction force motor, the end determination processing is a process of determining whether or not the steering shaft has been displaced to the maximum extent, the maximum displacement variable acquisition processing is a process of acquiring the value of the maximum displacement variable, the maximum displacement variable is a variable obtained based on being determined to have been displaced to the maximum extent by the end determination processing, the midpoint learning processing is a process of learning the midpoint of the rotation angle of the steering shaft based on the value of the maximum displacement variable. A steering control device.

2. The value of the maximum displacement variable is the integrated value of the rotation angle of the reaction force motor when it is determined by the end determination processing that the maximum displacement has occurred, the midpoint learning processing is a process of learning the midpoint based on the rotatable angle of the steering shaft determined in advance and the integrated value as an input variable. The steering control device according to Claim 1.

3. configured to execute initial value acquisition processing, the end abutment processing includes a process of controlling the rotation speed of the reaction force motor to a target rotation speed, the maximum displacement variable is the elapsed time until it is determined by the end abutment processing that the maximum displacement has occurred, the initial value acquisition processing is a process of acquiring the integrated value of the rotation angle of the reaction force motor at the start of counting of the elapsed time, the midpoint learning processing is a process of learning the midpoint based on the value of the maximum displacement variable as an input variable and the integrated value at the start time. The steering control device according to Claim 1.

4. The steering control device according to Claim 3, wherein the target rotation speed is a constant value.

5. configured to execute midpoint control processing, the midpoint control processing is a process of displacing the steering shaft to the learned midpoint position without displacing the steering shaft to the maximum extent to either the right turn side or the left turn side from the state of being displaced to the maximum extent to either one by the end abutment processing The steering control device according to Claim 1.

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