Steering control device and control data adaptation method

Abstract

To provide a steering control device that can prevent the steering feel of a driver from deteriorating.SOLUTION: An end stopper 100 is fixed to a steering shaft. The end stopper 100 rotates together with an intermediate stopper 90 in accordance with the rotation of the steering shaft. When a protrusion 92 of the intermediate stopper 90 comes into contact with a protrusion 72, the rotation of the intermediate stopper 90 is restricted; therefore, the end stopper 100 rotates not together with the intermediate stopper 90. When the intermediate stopper 90 switches from a state in which the intermediate stopper is rotated together with the steering shaft to a state in which the intermediate stopper is not rotated together with the steering shaft, load torque applied to the steering shaft increases in a stepwise manner. The assist amount set by a steering control device is adapted such that a gradient, which is a ratio of an increase in an absolute value of the assist amount relative to an increase in an absolute value of steering torque, matches a value that compensates for the increase in the load torque.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a steering control device and a method for adapting control data. [Background technology]

[0002] The following Patent Document 1 describes a device for mechanically limiting the rotational range of a steering shaft in a steer-by-wire system. More specifically, the device includes a first rotating member that rotates in conjunction with the steering shaft, and a second rotating member that rotates with the first rotating member. The device also includes a restricting member that contacts the second rotating member and prevents the rotation of the second rotating member when the rotation angle of the second rotating member reaches a predetermined angle. Then, when the first rotating member rotates a predetermined amount from the steering angle at which the rotation of the second rotating member is prevented by the restricting member, the first rotating member and the second rotating member come into contact with each other such that the second rotating member prevents the rotation of the first rotating member. This prevents the rotation of the first rotating member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-69844 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above device, the magnitude of the torque that hinders the rotation of the steering shaft differs between a state in which the second rotating member is rotated by the rotation of the first rotating member and a state in which only the first rotating member rotates. Therefore, when switching from one of the above two states to the other, the torque applied to the steering shaft changes stepwise, which may cause a deterioration in the steering feel. [Means for solving the problem]

[0005] Means for solving the above problems and their effects will be described below. 1. A steering control device that operates a reaction force actuator that applies a reaction force to a steering shaft that is rotated in response to steering by a driver while power transmission to steered wheels is cut off, the reaction force actuator comprising a first rotating member that rotates in conjunction with the steering shaft, a second rotating member that is rotated along with the first rotating member, and a regulating member that contacts the second rotating member when the rotation angle of the second rotating member reaches a predetermined angle, thereby preventing the rotation of the second rotating member, and is configured such that the first rotating member and the second rotating member come into contact with each other such that the second rotating member prevents the rotation of the first rotating member when the first rotating member rotates a predetermined amount from the angle at which the rotation of the second rotating member is prevented, and the steering control device a reaction force command value setting process, and an operation process, wherein the operation process is a process of operating the reaction force actuator in accordance with a reaction force torque command value that is a command value of a torque variable indicating the reaction force, and the reaction force command value setting process is a process of setting the reaction force torque command value, and a decrease in the absolute value of the reaction force torque command value relative to an increase in the absolute value of a steering torque that is input to the steering shaft by a driver is set so as to compensate for a fluctuation in the load torque applied to the steering shaft when the steering shaft switches from one of a state in which the first rotating member rotates the second rotating member together with the second rotating member and a state in which the first rotating member rotates without rotating the second rotating member together with the second rotating member to the other.

[0006] In the above configuration, the load torque applied to the steering shaft when the first rotating member rotates the second rotating member is different from the load torque applied to the steering shaft when the first rotating member rotates without rotating the second rotating member. Therefore, when switching from one of the state where the first rotating member rotates the second rotating member and the state where the first rotating member rotates without rotating the second rotating member to the other, a step-like fluctuation occurs in the load torque. If a step-like fluctuation occurs in the load torque, a step-like fluctuation may occur in the steering torque. Therefore, in the above configuration, the decrease amount of the absolute value of the reaction torque command value relative to the increase amount of the absolute value of the steering torque is set so as to compensate for the step-like fluctuation in the load torque. This makes it possible to suppress a decrease in the steering feel of the driver when switching from one of the state where the first rotating member rotates the second rotating member and the state where the first rotating member rotates without rotating the second rotating member to the other.

[0007] 2. A steering control device as described in 1 above, wherein the reaction force command value setting process includes an assist amount setting process and an axial force setting process, the axial force setting process is a process for setting an axial force which is a force resisting the rotation operation of the steering shaft by the driver, the assist amount setting process is a process for setting an assist amount, the assist amount being an amount by which the driver assists in rotating the steering shaft, the reaction force torque command value is an amount determined according to a value obtained by subtracting the assist amount from the axial force, and the assist amount setting process is set so that an increase in the absolute value of the assist amount relative to an increase in the absolute value of the steering torque compensates for a fluctuation in the load torque applied to the steering shaft when switching from one of the two to the other.

[0008] The greater the increase in the absolute value of the assist amount relative to the increase in the absolute value of the steering torque, the more the steering torque can be suppressed from increasing abruptly. In the above configuration, focusing on this point, the fluctuation of the load torque is compensated for by setting the increase in the absolute value of the assist amount relative to the increase in the absolute value of the steering torque.

[0009] 3. A steering control device as described in claim 2, wherein the assist amount setting process includes a process of setting the assist amount using map data, the map data including data used to set the assist amount when the steering angle is within a predetermined angle region and data used to set the assist amount when the steering angle is outside the predetermined angle region, and the predetermined angle region includes the steering angle at which the first rotating member switches from one of a state in which the first rotating member rotates together with the second rotating member and a state in which the first rotating member rotates without rotating together with the second rotating member.

[0010] In the above configuration, by preparing map data dedicated to a specified angle region, it is possible to use map data optimized from a perspective other than suppressing fluctuations in load torque when switching from one of the above to the other, except around the timing of switching from one to the other.

[0011] 4. A method for adapting control data used in the assist amount setting process in the steering control device described in 2 above, wherein the control data is data for defining a mapping that includes the steering torque as an input variable and the assist amount as an output variable, and the method for adapting control data includes an operation process for rotating the steering shaft in various ways, a detection process for detecting fluctuations in the load torque applied to the steering shaft in association with the operation process, and an assist update process for updating the control data so as to increase the increase in the absolute value of the assist amount relative to the increase in the absolute value of the steering torque if the fluctuation in the load torque is greater than or equal to a predetermined value.

[0012] When the load torque changes stepwise due to switching from one of the above to the other, a step change may occur in the steering torque. In this case, the increase in the absolute value of the assist amount relative to the increase in the absolute value of the steering torque is increased, thereby suppressing the step change in the steering torque.

[0013] 5. A method for adapting control data as described in claim 4, further comprising an axial force updating process, in which the absolute value of the axial force is increased so as to compensate for a decrease in the absolute value of the reaction torque command value caused by execution of the assist updating process.

[0014] When the increase in the absolute value of the assist amount relative to the increase in the absolute value of the steering torque is increased, the absolute value of the assist amount becomes large. Therefore, there is a risk that the reaction force applied to the steering shaft becomes excessively small. Therefore, in the above configuration, the absolute value of the axial force is increased and corrected in association with the assist update process, so that the reaction force applied to the steering shaft can be prevented from becoming excessively small. [Brief description of the drawings]

[0015] [Figure 1] 1 is a diagram showing a configuration of a steering system according to a first embodiment. [Diagram 2] FIG. 2 is an exploded perspective view showing a configuration of a portion of the reaction force actuator according to the embodiment. [Diagram 3] FIG. 2 is an exploded perspective view showing a configuration of a portion of the reaction force actuator according to the embodiment. [Figure 4] 2 is a cross-sectional view showing a configuration of a portion of the reaction force actuator according to the embodiment. FIG. [Diagram 5] 5A to 5C are diagrams illustrating the operation of a stopper function of the reaction force actuator according to the embodiment. [Figure 6] 4 is a block diagram showing details of a part of the processing executed by the control device according to the embodiment. FIG. [Figure 7] 4 is a flowchart showing a control parameter adaptation process according to the embodiment. [Figure 8] 13 is a diagram illustrating an example of adjustment of the assist gradient according to the embodiment. FIG. [Figure 9] FIG. 13 is a diagram showing the relationship between the operation of the stopper function of the reaction actuator and torque. [Figure 10] 10 is a flowchart showing a procedure of a process executed by a control device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] <First embodiment> Hereinafter, the first embodiment will be described with reference to the drawings. "Prerequisite configuration" A vehicle steering device 10 shown in FIG. 1 is a steer-by-wire type 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, a three-phase synchronous motor is used for the reaction force motor 22. The reaction force reduction mechanism 26 is formed of, for example, a worm and wheel.

[0017] The steering actuator 30 steers the steered wheels 34 in accordance with the driver's steering intention indicated by the driver's operation of the steering wheel 12. The steering actuator 30 comprises a rack shaft 32, a steering motor 42, a steering inverter 44, a steering transmission mechanism 46, and a conversion mechanism 48. As an example, a three-phase surface permanent magnet synchronous motor (SPM) is used for the steering motor 42. The steering transmission mechanism 46 is formed of a belt transmission mechanism. The steering transmission mechanism 46 transmits the rotational power of the steering motor 42 to the conversion mechanism 48. The conversion mechanism 48 converts the transmitted rotational power into displacement power in the axial direction of the rack shaft 32. The axial displacement of the rack shaft 32 causes the steered wheels 34 to be turned.

[0018] The steering control device 50 controls the control amount of the steering wheel 12 and the steered wheels 34, which are the control objects. That is, the steering control device 50 controls the steering reaction force that resists the steering by the driver, which is the control amount of the steering wheel 12, which is the control object. The steering control device 50 also controls the steering angle, which is the control amount of the steered wheels 34, which are the control object. The steering angle is the turning angle of the tires, which are the steered wheels 34.

[0019] The steering control device 50 refers to the steering torque Th detected by the torque sensor 60 in order to control 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 steering 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 62 in order to control the control amount. The steering control device 50 also refers to the currents ius, ivs, iws flowing through the reaction force motor 22 in order to control the control amount. The currents ius, ivs, iws may be detected as the voltage drop amount of a shunt resistor provided in each leg of the reaction force inverter 24, for example. The steering control device 50 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 64 in order to control the control amount. The steering control device 50 also refers to the currents iut, ivt, iwt flowing through the steering motor 42 in order to control the control amount. The currents iut, ivt, iwt may be detected, for example, as voltage drop amounts of shunt resistors provided in the respective legs of the steering inverter 44. The steering control device 50 refers to the vehicle speed V detected by the vehicle speed sensor 66.

[0020] The steering control device 50 includes a PU 52 and a storage device 54. The PU 52 is a software processing device such as a CPU, a GPU, or a TPU. The storage device 54 may be an electrically non-rewritable non-volatile memory. The storage device 54 may also be an electrically rewritable non-volatile memory, or a storage medium such as a disk medium.

[0021] "Configuration of reaction force actuator 20" FIG. 2 shows a partial configuration of the reaction force actuator 20. As shown in FIG. As shown in Fig. 2, the reaction force actuator 20 includes a housing 70 fixed to a 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 a washer 80, an intermediate stopper 90, a washer 82, an end stopper 100, a wave washer 84, and a C-shaped retaining ring 86.

[0022] The housing 70 is provided with a protrusion 72 as a restricting member for restricting the rotation of the intermediate stopper 90 . As shown in FIG. 3, the intermediate stopper 90 is provided with a protrusion 92 whose rotation is limited by the protrusion 72 .

[0023] FIG. 4 shows a partial cross-sectional configuration of the reaction force actuator 20. As shown in FIG. 4, an elastic force in the right direction in the figure is applied to the end stopper 100 by the wave washer 84. As a result, an elastic force in the right direction is applied to the intermediate stopper 90 via the washer 82. Meanwhile, the steering shaft 14 has a reduced diameter portion at the end on the left side in the figure. The washer 80, the intermediate stopper 90, and the washer 82 are disposed in 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 moving to the right in the figure is applied to the intermediate stopper 90 by the washer 82, and an elastic force moving to the left in the figure is applied by the washer 80.

[0024] 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 rotates with it.

[0025] "Restriction of rotation of steering shaft 14" FIG. 5 shows the movement of the intermediate stopper 90 in response to the rotation of the steering shaft 14. The upper part of Fig. 5 shows a case where the steering shaft 14 rotates to the right turning side. The left end of the upper part of Fig. 5 shows a state where the steering angle θs, which is the rotation angle of the steering shaft 14, is a value corresponding to the end of the left turning side. The upper part of Fig. 5 shows a state where the steering shaft 14 rotates to the right turning side as it moves to the right in the figure. In particular, the right end of the upper part of Fig. 5 shows a state where the steering angle θs is a value corresponding to the end of the right turning side.

[0026] As shown in the upper part of FIG. 5, when the steering shaft 14 turns right from the end on the left turning side, the intermediate stopper 90 is rotated along with the rotation of the end stopper 100. The center of the upper part of FIG. 5 shows a state in which the protrusion 92 of the intermediate stopper 90 contacts the protrusion 72 of the housing 70. As a result, the intermediate stopper 90 cannot turn further to the right. Therefore, the end stopper 100 rotates independently along with the rotation of the steering shaft 14. Then, 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 turn further to the right. This state is shown at the right end of the upper part of FIG. 5. In this state, the steering shaft 14 cannot rotate further to the right. The steering angle θs at this time becomes the upper limit value on the right turning side.

[0027] The lower part of Fig. 5 shows a case where the rotation angle of the steering shaft 14 rotates to the left turning side. The left end of the lower part of Fig. 5 shows a state where the steering angle θs is a value corresponding to the end of the right turning side. The lower part of Fig. 5 shows a state where the steering shaft 14 rotates to the left turning side as it moves to the right side in the figure. In particular, the right end of the lower part of Fig. 5 shows a state where the steering angle θs is a value corresponding to the end of the left turning side.

[0028] As shown in the lower part of FIG. 5, when the steering shaft 14 turns left from the end on the right turning side, the intermediate stopper 90 is rotated along with the rotation of the end stopper 100. The center of the lower part of FIG. 5 shows a state in which the protrusion 92 of the intermediate stopper 90 contacts the protrusion 72 of the housing 70. As a result, the intermediate stopper 90 cannot turn left any further. Therefore, the end stopper 100 rotates independently along with the rotation of the steering shaft 14. Then, 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 turn left any further. This state is shown at the right end of the lower part of FIG. 5. In this state, the steering shaft 14 cannot turn left any further. The steering angle θs at this time becomes the upper limit value on the left turning side.

[0029] "Control Overview" Fig. 6 shows the process executed by the steering control device 50. The process shown in Fig. 6 is realized by the PU 52 repeatedly executing a program stored in the storage device 54, for example, at a predetermined interval.

[0030] The steering angle calculation process M10 includes a process of converting the rotation angle θa into an integrated angle including a range exceeding 360 degrees, for example, by counting the number of rotations of the reaction force motor 22 from a steering neutral position, which is the position of the steering wheel 12 when the vehicle is moving straight. The steering angle calculation process M10 includes a process of multiplying the integrated angle obtained by conversion by a conversion coefficient based on the rotation speed ratio of the reaction force reduction mechanism 26 to calculate the steering angle θs.

[0031] The turning equivalent angle calculation process M12 includes a process of converting the rotation angle θb into an integrated angle including a range exceeding 360 degrees, for example, by counting the number of rotations of the steering motor 42 from a rack neutral position, which is the position of the rack shaft 32 when the vehicle is traveling straight. The turning equivalent angle calculation process M12 includes a process of multiplying the integrated angle obtained by conversion by a conversion coefficient according to the reduction ratio of the turning transmission mechanism 46 and the lead of the conversion mechanism 48, etc., to calculate the turning equivalent angle θp according to the turning angle of the steered wheels 34. The turning equivalent angle θp is an amount proportional to the turning angle. Note that, as an example, the turning equivalent angle θp is positive when it is an angle to the right of the rack neutral position, and negative when it is an angle to the left of the rack neutral position.

[0032] The target turning equivalent angle calculation process M18 is a process for calculating a target turning equivalent angle θp* in accordance with the steering angle θs and the vehicle speed V. The assist amount setting process M20 is a process that calculates the assist amount Ta using the steering torque Th and the vehicle speed V as inputs. The assist amount Ta is an amount in the same direction as the steering direction of the driver. The magnitude of the assist amount Ta is set to a large value when the force assisting the steering by the driver is to be increased. The assist amount setting process M20 is a process in which the PU 52 performs map calculations to calculate the assist amount Ta with map data M20a stored in the storage device 54. The map data M20a is data that uses the steering torque Th and the vehicle speed V as input variables and the assist amount Ta as an output variable.

[0033] Here, map data refers to a set of data consisting of discrete values ​​of input variables and values ​​of output variables corresponding to each of the input variable values. Furthermore, the map calculation may be a process in which, when the value of an input variable matches any of the values ​​of the input variables in the map data, the value of the output variable in the corresponding map data is used as the calculation result. Furthermore, the map calculation may be a process in which, when the value of an input variable does not match any of the values ​​of the input variables in the map data, the value obtained by interpolating the values ​​of multiple output variables included in the map data is used as the calculation result. Alternatively, the map calculation may be a process in which, when the value of an input variable does not match any of the values ​​of the input variables in the map data, the value of the output variable in the map data that corresponds to the closest value among the values ​​of multiple input variables included in the map data is used as the calculation result.

[0034] The axial force setting process M22 is a process that calculates the axial force F acting on the rack shaft 32 through the steered wheels 34 using the vehicle speed V, the q-axis current iqt of the steering motor 42, and the target steering equivalent angle θp* as inputs. The axial force F is a value that expresses the force acting on the rack shaft 32 through the steered wheels 34 by control. However, the axial force F does not necessarily have to be intended to estimate the force acting on the rack shaft 32 with high accuracy. The axial force F may be, for example, a virtually determined force acting on the rack shaft 32. The axial force F is converted into a torque applied to the steering shaft 14. That is, it is converted into a torque applied to the steering shaft 14 when it is assumed that the power transmission between the steered wheels 34 and the steering shaft 14 is possible. The axial force F is an amount that acts in the opposite direction to the steering direction of the driver. The axial force setting process M22 may be a process that calculates the axial force F so that the absolute value of the axial force F increases as the absolute value of the target steering equivalent angle θp* increases. For example, the axial force setting process M22 may be a process for calculating the axial force F such that the absolute value of the axial force F increases as the vehicle speed V increases. The axial force setting process M22 may be a process for calculating the axial force F such that the absolute value of the axial force F increases as the absolute value of the q-axis current iqt increases. Here, the q-axis current iqt is calculated by the PU 52 in accordance with the steering equivalent angle θp and the currents iut, ivt, and iwt.

[0035] The subtraction process M24 is a process of substituting a value obtained by subtracting the axial force F from the assist amount Ta into the target torque Ts. The target torque Ts is a target value of the torque that the reaction force motor 22 applies to the steering shaft 14.

[0036] The reaction force operation signal generation process M26 is a process for generating an operation signal MSs for the reaction force inverter 24 in order to control the torque of the reaction force motor 22 so that the torque applied to the steering shaft 14 becomes the target torque Ts. More specifically, the reaction force operation signal generation process M26 includes a process for converting the target torque Ts into a target torque of the reaction force motor 22. The reaction force operation signal generation process M26 also includes a process for calculating an operation signal MSs for the reaction force inverter 24 in order to make the current flowing through the reaction force motor 22 approach a current determined from the target torque Ts by current feedback control. Note that the operation signal MSs is actually an operation signal for each of the six switching elements of the reaction force inverter 24. By making the torque of the reaction force motor 22 the target torque Ts, the absolute value of the steering reaction force resisting the force that tries to rotate the steering wheel 12 becomes equal to the absolute value of the target torque Ts. Furthermore, the sign of the steering reaction force that resists the force that tries to rotate the steering wheel 12 is usually opposite to the sign of the assist amount Ta. This is because the absolute value of the axial force F is usually greater than the absolute value of the assist amount Ta.

[0037] The steering feedback process M30 is a process for substituting the operation amount of 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, into the target steering torque Tt*. The target steering torque Tt* has a constant ratio with the torque of the steering motor 42.

[0038] The steering operation signal generation process M32 is a process for generating an operation signal MSt for the steering inverter 44 in order to control the torque of the steering motor 42 so that the torque of the steering motor 42 becomes a value having a constant ratio with respect to the target steering torque Tt*. In particular, the steering operation signal generation process M32 includes a process for converting the target steering torque Tt* into a target torque of the steering motor 42. The steering operation signal generation process M32 also includes a process for calculating an operation signal MSt for the steering inverter 44 in order to bring the current flowing through the steering motor 42 close to a current determined from the target torque by current feedback control. Note that the operation signal MSt is actually an operation signal for each of the six switching elements of the steering inverter 44.

[0039] "Map data M20a compatibility" The steps for generating the map data M20a are shown in Fig. 7. In the following, each step will be designated by a number preceded by the letter "S".

[0040] 7, first, conventional map data that is map data already used in the steering control system is acquired (S10). Here, it is preferable that the acquired map data corresponds to a steering system specification that is as close as possible to the specification of this embodiment.

[0041] Next, the steering wheel 12 is operated (S12). The step of S12 may be a step in which a person operates the steering wheel 12. Alternatively, the step of S12 may be a step in which an adaptation device rotates the steering shaft 14. When the step of S12 is performed, an assist amount setting process M20, an axial force setting process M22, and a subtraction process M24 are executed, and a reaction force is applied to the steering wheel 12. However, the map data M20a in the assist amount setting process M20 is the data acquired in the step of S10.

[0042] Next, it is determined whether the variation in the torque applied to the steering wheel 12 is equal to or greater than a threshold value Tth (S14). The step of S14 may be, for example, a step in which the adaptation device compares the magnitude of the amount of change in the absolute value of the detection value of the torque sensor with the threshold value Tth. In this case, the threshold value Tth may be set according to the lower limit value at which a person feels uncomfortable operating the steering wheel 12. Alternatively, the step of S14 may be a step in which it is determined whether a person feels uncomfortable operating the steering wheel 12. In this case, the threshold value Tth is the magnitude of the torque variation at which a person feels uncomfortable operating the steering wheel 12.

[0043] If it is determined in step S14 that the torque variation is equal to or greater than the threshold value Tth, the adapting device increases the assist gradient, which is the increase in the absolute value of the assist amount Ta relative to the increase in the absolute value of the steering torque Th (S16). That is, the adapting device increases the assist gradient of the map data M20a used in the assist amount setting process M20. As a result, in step S12, the assist amount setting process M20 becomes a process for setting the assist amount Ta using the map data M20a with the changed assist gradient.

[0044] In Fig. 8, the assist amount Ta before correction is indicated by a two-dot chain line, and the assist amount Ta after correction is indicated by a solid line. As shown in Fig. 8, the change amount b of the assist amount Ta relative to the change amount ΔTh of the steering torque Th after correction is larger than the change amount a of the assist amount Ta relative to the change amount ΔTh of the steering torque Th before correction. In other words, the assist gradient is corrected to increase.

[0045] Returning to FIG. 7, the adaptation device corrects and increases the axial force F (S18). That is, when the assist gradient increases, the absolute value of the assist amount relative to the steering torque Th increases, and therefore the absolute value of the steering reaction force, which is the absolute value of the value obtained by subtracting the assist amount Ta from the axial force F, decreases. Therefore, the adaptation device corrects and increases the absolute value of the axial force F to compensate for the decrease in the steering reaction force. However, the increase correction of the absolute value of the axial force F is made so as not to offset the increase correction of the assist gradient.

[0046] When the step of S18 is completed or when a negative judgment is made in the step of S14, the compatible device judges whether or not all patterns have been completed for the operation of the steering wheel 12 (S20). If there is a pattern that has not yet been executed (S20: NO), the process returns to the step of S12. On the other hand, when it is judged that all patterns have been completed (S20: YES), the series of steps shown in FIG. 7 is temporarily terminated.

[0047] "Actions and Effects of the Present Embodiment" 9 shows the transition of the load torque, which is the torque caused by friction that tries to prevent the rotation of the steering shaft 14. Note that FIG. 9 corresponds to the operation in the upper part of FIG.

[0048] 9, when the state in which the intermediate stopper 90 is rotated together with the rotation of the end stopper 100 changes to the state in which the end stopper 100 rotates independently, the load torque increases stepwise. This is because a new frictional force with the intermediate stopper 90 is added when the end stopper 100 rotates.

[0049] Here, the PU 52 calculates the assist amount Ta by using the map data M20a. The map data M20a is data in which the assist gradient has been adapted by the process shown in FIG. 7. Therefore, when the load torque increases stepwise, the absolute value of the steering torque Th increases stepwise, but the assist amount Ta increases rapidly accordingly. Therefore, the fluctuation of the steering torque Th is suppressed. Therefore, the driver is prevented from feeling a stepwise increase in the load torque by operating the steering wheel 12.

[0050] According to the present embodiment described above, the following actions and effects can be obtained. (1) When the assist gradient is increased in the adaptation process of the map data M20a, the absolute value of the axial force F is increased. This makes it possible to prevent the absolute value of the steering reaction force from becoming excessively small due to the increase in the assist gradient.

[0051] <Second embodiment> The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0052] In this embodiment, the map data M20a is provided according to whether or not the steering angle θs is within a predetermined angle region including the steering angle θs at the time when the intermediate stopper 90 switches from being rotated by the end stopper 100 to being not rotated by the end stopper 100.

[0053] Fig. 10 shows the procedure of the switching process of the map data M20a according to this embodiment. The series of processes shown in Fig. 10 is realized by the PU 52 repeatedly executing a program stored in the storage device 54, for example, at a predetermined interval. In the following, the step number of each process is represented by a number preceded by "S."

[0054] In the series of processes shown in Fig. 10, the PU 52 first obtains the steering angle θs (S30). Then, the PU 52 determines whether the steering angle θs is in a region that is equal to or larger than the first angle θsL and equal to or smaller than the second angle θsH (S32). This region includes the steering angle θs at the time when the intermediate stopper 90 switches from a state in which it is rotated by the end stopper 100 to a state in which it is not rotated by the end stopper 100. It is desirable to set this region as narrow as possible under the condition that includes the variation in the steering angle θs at the time of switching due to tolerance.

[0055] When the PU 52 determines that the intermediate stopper 90 is outside the above-mentioned region (S32: NO), the PU 52 adopts a normal map as the map data M20a for calculating the assist amount Ta (S34). The normal map is data adapted to satisfy a requirement element unrelated to suppression of torque fluctuations caused when the intermediate stopper 90 switches from a state in which it is accompanied by the end stopper 100 to a state in which it is not accompanied by the end stopper 100. On the other hand, when the PU 52 determines that the intermediate stopper 90 is within the above-mentioned region (S32: YES), the PU 52 adopts a gradient increase map as the map data M20a for calculating the assist amount Ta (S36). The gradient increase map is data adapted with the aim of suppressing torque fluctuations caused when the intermediate stopper 90 switches from a state in which it is accompanied by the end stopper 100 to a state in which it is not accompanied by the end stopper 100. The gradient increase map has a larger assist gradient than the normal map.

[0056] When the PU 52 completes the processes of S34 and S36, the PU 52 temporarily ends the series of processes shown in Fig. 10. When switching between the gradient increase map and the normal map, it is preferable that the PU 52 executes a guard process to limit the absolute value of the change in the assist amount Ta in order to suppress a sudden change in the assist amount Ta.

[0057] <Correspondence> The correspondence between the matters in the above embodiment and the matters described in the above "Means for solving the problem" column is as follows. In the following, the correspondence is shown for each number of the solving means described in the "Means for solving the problem" column. [1] The first rotating member corresponds to the end stopper 100. The second rotating member corresponds to the intermediate stopper 90. The regulating member corresponds to the protrusion 72. The reaction force command value calculation process corresponds to the assist amount setting process M20, the axial force setting process M22, and the subtraction process M24. [2] The assist amount Ta is set using the map data M20a adapted by the process shown in FIG. 7. [3] The predetermined angle region corresponds to the angle region in S32 that is equal to or larger than the first angle θsL and equal to or smaller than the second angle θsH. [4] The control data corresponds to the map data M20a. The operation process corresponds to the process in S12. The detection process corresponds to the process in S14. The assist update process corresponds to the process in S16. [5] The axial force update process corresponds to step S18.

[0058] <Other embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0059] "Assist amount setting process" The assist amount setting process is not limited to a process of calculating the assist amount Ta using map data in which the vehicle speed V and steering torque Th are input variables and the assist amount Ta is an output variable. For example, the assist amount Ta may be calculated using a function approximator that receives the vehicle speed V and steering torque Th as inputs and outputs the assist amount Ta. In that case, in the step of S16 in FIG. 7, data that defines the function approximator as control data may be updated.

[0060] Instead of the steering torque Th as an input variable, a value obtained by subjecting the steering torque Th to a process of delaying its phase may be used. The process of delaying the phase may be a process for the purpose of performing phase compensation on the steering torque Th in order to adjust the frequency characteristics of the phase difference on both sides of a torsion bar provided in the torque sensor 60, for example.

[0061] A value calculated using the vehicle speed V and steering torque Th as inputs may be used as the basic assist amount Tab, and various corrections may be applied to this value to determine the assist amount Ta. Specifically, for example, a hysteresis correction amount, which is a correction amount for making the assist amount Ta different between turning the steering wheel 12 back and forth, may be added to the basic assist amount Tab. Also, for example, a damping correction amount, which is a correction amount negatively correlated with the rotation speed of the steering wheel 12, may be added to the basic assist amount Tab. Also, for example, a return correction amount, which is a correction amount for returning the steering wheel 12 to the neutral position, may be added to the basic assist amount Tab.

[0062] "About axial force setting process" The inputs for the axial force setting process do not necessarily have to be the q-axis current iqt, the target steering equivalent angle θp*, and the vehicle speed V. For example, the vehicle speed V does not have to be included. Also, for example, the angle variable of the steering system as an input variable is not limited to the target steering equivalent angle θp*. For example, the angle variable of the steering system may be the steering equivalent angle θp. Also, for example, the angle variable of the steering system may be the steering angle θs. Also, for example, the variable indicating the load torque of the steered wheels is not limited to the q-axis current iqt. For example, it may be an estimated value of the torque of the steering motor 42.

[0063] "Device for restricting rotation of 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 device may be provided with a plurality of intermediate stoppers that are rotated by the end stopper 100. Here, an example will be described in which a first intermediate stopper and a second intermediate stopper are provided. In this case, the first intermediate stopper and the second intermediate stopper are rotated with the rotation of the end stopper 100. Then, the protrusion of the first intermediate stopper comes into contact with the protrusion 72 of the housing 70, thereby preventing the rotation of the first intermediate stopper. As a result, only the second intermediate stopper is rotated with the rotation of the end stopper 100. Then, the protrusion of the second intermediate stopper comes into contact with the protrusion of the first intermediate stopper, thereby preventing the rotation of the second intermediate stopper. As a result, the end stopper 100 rotates alone. Then, the protrusion 102 of the end stopper 100 comes into contact with the protrusion of the second intermediate stopper, thereby preventing the rotation of the end stopper 100. That is, further rotation of the steering shaft 14 is prevented.

[0064] "About steering control devices" The steering control device is not limited to one that executes software processing. For example, it may be equipped with a dedicated hardware circuit such as an ASIC that executes at least a part of the processing executed in the above embodiment. That is, the steering control device may include a processing circuit having any of the following configurations (a) to (c). (a) A processing circuit equipped with 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 equipped with a processing device and a 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 equipped with a dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software execution devices equipped with a processing device and a program storage device. Also, there may be multiple dedicated hardware circuits.

[0065] "Others" In each of the above embodiments, the steering device 10 has a linkless structure in which the steering wheel 12 and the steered wheels 34 are mechanically separated at all times. However, the present invention is not limited to this structure, and the steering device 10 may have a structure in which the steering wheel 12 and the steered wheels 34 can be mechanically separated by a clutch. [Explanation of symbols]

[0066] 10...Steering gear 12…Steering wheel 14…Steering shaft 20…Reaction actuator 22…Reaction motor 24…Reaction force inverter 50...Steering control device 70…Housing 72...Protrusion 80,82…Washer 84…Wave washer 86...C-type retaining ring 90...Intermediate stopper 92...Protrusion 100...End stopper 102...Protrusion

Claims

1. A steering control device that operates a reaction force actuator that applies a reaction force to a steering shaft that is rotated in response to steering by a driver in a state where power transmission to steered wheels is interrupted, the reaction force actuator includes a first rotating member that rotates in conjunction with the steering shaft, a second rotating member that is rotated by the first rotating member, and a regulating member that comes into contact with the second rotating member to prevent the second rotating member from rotating when a rotation angle of the second rotating member reaches a predetermined angle, the first rotating member and the second rotating member are configured to come into contact with each other such that the second rotating member prevents the rotation of the first rotating member by rotating the first rotating member a predetermined amount from an angle at which the rotation of the second rotating member is prevented, The steering control device is configured to execute a reaction force command value setting process and an operation process, the operation process is a process of operating the reaction force actuator in accordance with a reaction force torque command value which is a command value of a torque variable indicating the reaction force, The reaction force command value setting process is a process for setting the reaction torque command value, and a decrease in the absolute value of the reaction torque command value relative to an increase in the absolute value of steering torque, which is the torque input to the steering shaft by a driver, is set so as to compensate for a fluctuation in the load torque applied to the steering shaft when the first rotating member rotates the second rotating member together with the second rotating member and a state in which the first rotating member rotates without rotating the second rotating member together with the second rotating member are switched from one to the other.

2. The reaction force command value setting process includes an assist amount setting process and an axial force setting process, the axial force setting process is a process for setting an axial force which is a force resisting a rotation operation of the steering shaft by a driver, The assist amount setting process is a process for setting an assist amount, the assist amount is an amount of assistance provided to the driver in rotating the steering shaft, the reaction torque command value is an amount determined in accordance with a value obtained by subtracting the assist amount from the axial force, 2. A steering control device according to claim 1, wherein the assist amount setting process is set so that an increase in the absolute value of the assist amount relative to an increase in the absolute value of the steering torque compensates for fluctuations in the load torque applied to the steering shaft when switching from one to the other.

3. the assist amount setting process includes a process of setting the assist amount using map data, the map data includes data used for setting the assist amount when the steering angle is within a predetermined angle region, and data used for setting the assist amount when the steering angle is outside the predetermined angle region, 3. The steering control device according to claim 2, wherein the predetermined angle region includes the steering angle at which the first rotating member switches from one of a state in which the first rotating member rotates together with the second rotating member and a state in which the first rotating member rotates without rotating together with the second rotating member to the other.

4. A method for adapting control data used in the assist amount setting process in the steering control device according to claim 2, comprising the steps of: the control data is data for defining a mapping including the steering torque as an input variable and the assist amount as an output variable, an operating step of rotating the steering shaft in various directions; a detection step of detecting a variation in a load torque applied to the steering shaft in association with the operation step; an assist updating step of updating the control data so as to increase an increase in an absolute value of the assist amount relative to an increase in an absolute value of the steering torque when the fluctuation amount of the load torque is equal to or greater than a predetermined value; A method for fitting control data having the following structure:

5. An axial force updating process is provided, 5. The method for adapting control data according to claim 4, wherein the axial force updating step is a step of increasing and correcting the absolute value of the axial force so as to compensate for a decrease in the absolute value of the reaction torque command value caused by execution of the assist updating step.

Images