Steering control system

Abstract

To provide a steering control device capable of inhibiting a change in torsional rigidity between a steering wheel and a turning wheel.SOLUTION: A PU 52 controls torque of a turning motor 42 by feedback control in which a turning angle of a turning wheel 34 is set as a control amount and a target turning angle is set as a target value of the control amount. The PU 52 applies a counterforce to a steering wheel 12 in accordance with a shaft force. The PU 52 calculates an angle shaft force in accordance with a target turning equivalent angle. The PU 52 calculates a current shaft force in accordance with a current of the turning motor 42. PU 52 uses, as the shaft force, a weighted mean process value of the angle shaft force and the current shaft force. The PU 52 changes a gain of the feedback control according to a ratio of the current shaft force to the shaft force.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] For example, Patent Document 1 below describes a control device that controls a steering wheel and a steering wheel while the power transmission between the steering wheel and the steering wheel is interrupted. This control device applies a reaction torque, which is a torque opposite to the torque applied by the driver to operate the steering wheel, to the steering wheel according to the axial force. Here, the control device calculates the axial force by adjusting the distribution ratio between the angular axial force, which is the axial force corresponding to the target value of the angle, and the current axial force, which is the axial force corresponding to the current of the motor that steers the steering wheel.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when a large external force is applied to the steering wheel, the current of the motor increases. Therefore, when a large external force is applied to the steering wheel, the current axial force changes greatly. On the other hand, since the angular axial force is an amount corresponding to the target value, it does not change significantly even when a large external force is applied to the steering wheel. Therefore, the reaction force applied to the steering wheel when a large external force is applied to the steering wheel changes according to the distribution ratio between the angular axial force and the current axial force. This is a concern that causes the driver to feel a change in the torsional rigidity between the steering wheel and the steering wheel.

Means for Solving the Problems

[0005] The following describes the means and effects of solving the above-mentioned problems. The steering system is applied to a steering system comprising a reaction force motor that applies a reaction force to the steering wheel and a steering motor that steers the steering wheels, and is configured to perform steering control processing, angular axial force calculation processing, motor axial force calculation processing, distribution processing, reaction force control processing, and gain variable processing when power transmission between the steering wheel and the steering wheels is interrupted, wherein the steering control processing is a process that operates the steering motor according to an operation amount of feedback control, where the equivalent steering angle is the control amount and the target equivalent steering angle is the target value of the control amount, the equivalent steering angle is a variable indicating the steering angle, the target equivalent steering angle is the target value of the equivalent steering angle, and the angular axial force calculation processing is a process that calculates the angular axial force using the value of the angular variable for axial force as input, and The steering control device comprises an angle variable for axial force, which is a variable indicating the angle of the steering device and is referenced when calculating the angle axial force; a motor axial force calculation process, which calculates the motor axial force using the value of a torque variable, which is a variable indicating the torque of the steering motor, as input; a distribution process, which calculates the distributed axial force according to a weighted average of the angle axial force and the motor axial force; a reaction force control process, which controls the torque of the reaction force motor according to the distributed axial force; and a variable gain process, which changes the gain of the feedback control according to the distributed axial force, and sets the gain when the ratio of the motor axial force to the distributed axial force is large to be greater than or equal to the gain when the ratio is small.

[0006] In the above configuration, the gain is varied according to the ratio of motor axial force to the distributed axial force, while the gain when the ratio is large is set to be greater than or equal to the gain when the ratio is small. Therefore, when the ratio is large, deviation of the steering angle from the target steering angle is suppressed more quickly compared to when the ratio is small. The greater the deviation between the steering angle and the target steering angle, the larger the amount of feedback control tends to be. Therefore, changing the above gain leads to suppressing an increase in the magnitude of the motor axial force. Consequently, when the above ratio is large, the reaction force applied to the steering wheel when a large external force is applied to the steering wheel can be suppressed to be larger than when the ratio is small.

[0007] 2. The steering control device described in paragraph 1 above, wherein the distribution process includes a process to change the ratio of the motor axial force to the distributed axial force according to the value of the distribution angle variable, and the distribution angle variable is a variable that indicates the angle of the steering device and is a variable that is referenced when calculating the ratio.

[0008] In the above configuration, an appropriate ratio can be set according to the value of the distribution angle variable. 3. A steering control device as described in 2 above, configured to perform a target steering angle calculation process and a target steering angle calculation process, wherein the target steering angle calculation process is a process that calculates the target steering angle according to the steering angle and the steering angle ratio, and the target steering angle calculation process is a process that calculates the target steering angle according to the steering angle and the steering angle ratio, and the value of the angle variable is the target steering angle.

[0009] In the above configuration, the target steering angle is set to a value that matches the actual steering angle in order to achieve the desired steering angle ratio. Then, the aforementioned ratio can be set to an appropriate value according to the target steering angle. 4. The steering control device according to any one of 1 to 3 above includes a steering control process which calculates the manipulated amount according to the output value of a proportional element that takes the difference between the equivalent steering angle and the target equivalent steering angle as input, and a gain variable process which makes the gain of the proportional element variable.

[0010] In the above configuration, the responsiveness of the proportional element can be increased when the proportion is large. 5. The variable gain processing is a steering control device according to any one of 1 to 4 above, which includes processing to change the gain using the ratio of the motor axial force to the distributed axial force as input, and processing to change the gain using the vehicle speed as input.

[0011] In the above configuration, by changing the gain according to the vehicle speed in addition to the ratio, the controllability of the steering angle can be made appropriate according to the vehicle speed. [Brief explanation of the drawing]

[0012] [Figure 1] This diagram shows the configuration of a steering device and a steering control device according to one embodiment. [Figure 2] This block diagram shows the process performed by the steering control device in the same embodiment. [Figure 3] This is a block diagram showing the details of the axial force calculation process according to the same embodiment. [Figure 4] This is a flowchart showing the procedure for the feedback processing according to the embodiment. [Modes for carrying out the invention]

[0013] One embodiment of a steering control device will be described with reference to the drawings. "Prerequisite configuration" The steering system 10 of the vehicle shown in Figure 1 is a steer-by-wire system. The steering system 10 comprises a steering wheel 12, a steering shaft 14, a reaction force actuator 20, and a steering actuator 30. The steering shaft 14 is connected to the steering wheel 12. The reaction force actuator 20 is an actuator that applies a force that opposes the force applied by the driver to operate the steering wheel 12. The reaction force actuator 20 comprises 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 opposes 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 consists of, for example, a worm and wheel.

[0014] The steering actuator 30 is an actuator that steers the steering wheels 34 in accordance with the driver's steering intention, as 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 synchronous motor is used for the steering motor 42. The steering transmission mechanism 46 consists 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 axial displacement power of the rack shaft 32. The axial displacement of the rack shaft 32 causes the steering wheels 34 to steer.

[0015] The steering control device 50 controls the steering wheel 12 and the steering wheels 34. Specifically, the steering control device 50 controls the steering reaction force that opposes the driver's steering, which is the control amount of the steering wheel 12 as the control target. The steering control device 50 also controls the steering angle, which is the control amount of the steering wheels 34 as the control target. The steering angle is the turning angle of the tires, which are the steering wheels 34.

[0016] The steering control device 50 refers to the steering torque Th detected by the torque sensor 60 for controlling 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 for controlling the control amount. Also, the steering control device 50 refers to the currents ius, ivs, iws flowing through the reaction force motor 22 for controlling 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 inverter 24 for reaction force. 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 steered side rotation angle sensor 64 for controlling the control amount. Also, the steering control device 50 refers to the currents iut, ivt, iwt flowing through the steering motor 42 for controlling 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 inverter 44 for steering. The steering control device 50 refers to the vehicle speed V detected by the vehicle speed sensor 66.

[0017] 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, GPU, and TPU. The storage device 54 may be a non-volatile memory that cannot be electrically rewritten. Also, the storage device 54 may be a non-volatile memory that can be electrically rewritten and a storage medium such as a disk medium.

[0018] "Outline of Control" Fig. 2 shows the process executed by the steering control device 50. The process shown in Fig. 2 is realized by the PU 52 repeatedly executing, for example, at a predetermined period, the program stored in the storage device 54.

[0019] The steering angle calculation process M10 converts the rotation angle θa into an integrated angle including a range exceeding 360 degrees 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 moving straight ahead. The steering angle calculation process M10 calculates the steering angle θs by multiplying the converted integrated angle by a conversion coefficient based on the rotation speed ratio of the reaction force reduction mechanism 26.

[0020] The equivalent steering angle calculation process M12 converts the rotation angle θb into an integrated angle including a range exceeding 360 degrees by counting the number of rotations of the steering motor 42 from the rack neutral position, which is the position of the rack shaft 32 when the vehicle is moving straight ahead. The equivalent steering angle calculation process M12 calculates the equivalent steering angle θp corresponding to the steering angle of the steering wheel 34 by multiplying the converted integrated angle by a conversion coefficient according to the reduction ratio of the steering transmission mechanism 46 and the lead of the conversion mechanism 48. The equivalent steering angle θp is a quantity in a proportional relationship with the steering angle. Note that, as an example, the equivalent steering angle θp is positive when it is an angle on the right side of the rack neutral position and negative when it is an angle on the left side.

[0021] The steering angle ratio setting process M14 is a process of setting the value of a steering angle ratio variable Dst that determines the steering angle ratio, which is the ratio of the steering angle θs to the equivalent steering angle θp, according to the steering angle θs and the vehicle speed V. The target steering angle calculation process M16 is a process of calculating the target steering angle θs* according to the values of the equivalent steering angle θp and the steering angle ratio variable Dst. The ratio of the target steering angle θs* to the equivalent steering angle θp is the steering angle ratio determined by the value of the steering angle ratio variable Dst.

[0022] The target equivalent steering angle calculation process M18 is a process of calculating the target equivalent steering angle θp* according to the steering angle θs and the value of the steering angle ratio variable Dst. The ratio of the steering angle θs to the target equivalent steering angle θp* is the steering angle ratio indicated by the steering angle ratio variable Dst.

[0023] The steering force setting process M20 calculates the steering force Tb* using the steering torque Th and vehicle speed V as inputs. The steering force Tb* is a quantity in the same direction as the driver's steering. The magnitude of the steering force Tb* is set to a larger value when a greater force is required to assist the driver's steering. The steering force setting process M20 may include a process that calculates a larger steering force Tb* the larger the absolute value of the steering torque Th. Alternatively, the steering force setting process M20 may include a process that calculates a larger steering force Tb* the smaller the vehicle speed V.

[0024] The distributed axial force calculation process M22 takes the vehicle speed V, the q-axis current iqt of the steering motor 42, and the target steering equivalent angle θp* as inputs and calculates the distributed axial force F acting on the rack shaft 32 through the steering wheels 34. The distributed axial force F is converted into the torque applied to the steering shaft 14. The distributed axial force F is a quantity that acts in the opposite direction to the driver's steering direction.

[0025] The target reaction force calculation process M24 is a process that substitutes the value obtained by subtracting the distributed axial force F from the steering force Tb* into the target reaction force torque Ts*. The target reaction force torque Ts* is the target value of the torque that the reaction force motor 22 applies to the steering shaft 14.

[0026] The reaction force control signal generation process M26 generates 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 reaction force torque Ts*. Specifically, the reaction force control signal generation process M26 includes a process to convert the target reaction force torque Ts* into the target torque of the reaction force motor 22. Furthermore, the reaction force control signal generation process M26 includes a process to calculate the operation signal MSs for the reaction force inverter 24 in order to bring the current flowing through the reaction force motor 22 closer to the current determined by the target torque through current feedback control. In reality, the operation signal MSs is an operation signal for each of the six switching elements of the reaction force inverter 24.

[0027] The steering feedback process M30 is a process that substitutes the manipulated variable of the feedback control, which has the equivalent steering angle θp as the controlled variable and the target equivalent steering angle θp* as the target value of the controlled variable, into the target steering torque Tt*. The target steering torque Tt* has a constant ratio with the torque of the steering motor 42.

[0028] The steering control signal generation process M32 generates 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 is a value that has a constant ratio with the target steering torque Tt*. Specifically, the steering control signal generation process M32 includes a process to convert the target steering torque Tt* into a target torque for the steering motor 42. Furthermore, the steering control signal generation process M32 includes a process to calculate the operation signal MSt for the steering inverter 44 in order to bring the current flowing through the steering motor 42 closer to the current determined by the target torque by current feedback control. In reality, the operation signal MSt is an operation signal for each of the six switching elements of the steering inverter 44.

[0029] "Axial force calculation process" Figure 3 shows the details of the distribution axial force calculation process M22. The angle-axis force calculation process M40 calculates the angle-axis force Fr using the target steering equivalent angle θp* and vehicle speed V as inputs. The angle-axis force Fr is the ideal value of the axial force defined by the vehicle model set arbitrarily. The angle-axis force Fr is calculated as an axial force that does not reflect road surface information. Road surface information refers to information such as minute bumps that do not affect the lateral behavior of the vehicle and steps that do affect the lateral behavior of the vehicle. For example, the angle-axis force calculation process M40 may be calculated so that the absolute value of the angle-axis force Fr increases as the absolute value of the target steering equivalent angle θp* increases. Alternatively, for example, the angle-axis force calculation process M40 may be calculated so that the absolute value of the angle-axis force Fr increases as the vehicle speed V increases.

[0030] The current axial force calculation process M42 calculates the current axial force Fi as the q-axis current iqt of the steering motor 42. The q-axis current iqt is calculated by PU52 according to the steering equivalent angle θp and the currents iut, ivt, and iwt. The current axial force Fi is an estimated value of the axial force that actually acts on the rack shaft 32, which operates to steer the steering wheels 34, i.e., the axial force actually transmitted to the rack shaft 32. The current axial force Fi is calculated as an axial force that reflects the above road surface information. For example, the current axial force calculation process M42 calculates the current axial force Fi by assuming that the torque applied to the rack shaft 32 by the steering motor 42 is balanced by the torque corresponding to the force applied to the rack shaft 32 through the steering wheels 34. In other words, the current axial force calculation process M42 calculates the absolute value of the current axial force Fi to be a larger value as the absolute value of the q-axis current iqt increases.

[0031] The distribution ratio calculation process M46 is a process that calculates a ratio Di using the vehicle speed V and the target steering angle θs* as inputs. The ratio Di is the ratio of the current axial force Fi to the sum of the angular axial force Fr and the current axial force Fi. The ratio Di has a value between zero and 1. The distribution ratio calculation process M46 can be, for example, a process in which the PU 52 performs a map calculation on the ratio Di when the map data is stored in the memory device 54. Here, the map data is data in which the vehicle speed V and the target steering angle θs* are input variables and the ratio Di is the output variable.

[0032] Map data is a set of data consisting of discrete values ​​of input variables and corresponding values ​​of output variables for each of the input variable values. The map operation can be performed by taking the value of the corresponding output variable of the map data as the calculation result if the value of the input variable matches any of the input variable values ​​of the map data. Alternatively, if the value of the input variable does not match any of the input variable values ​​of the map data, the map operation can be performed by taking the value obtained by interpolating the values ​​of multiple output variables included in the map data as the calculation result. Or, if the value of the input variable does not match any of the input variable values ​​of the map data, the map operation can be performed by taking the value of the output variable of the map data corresponding to the closest value among the multiple input variable values ​​included in the map data as the calculation result.

[0033] The second distribution ratio calculation process M48 calculates the second ratio "1-Di" by subtracting the ratio Di from "1". The second ratio is the ratio of the angular axial force Fr to the sum of the angular axial force Fr and the current axial force Fi.

[0034] The first ratio multiplication process M50 multiplies the current axial force Fi by the ratio Di. The second ratio multiplication process M52 multiplies the angular axial force Fr by the second ratio. The addition process M54 adds the output value of the first ratio multiplication process M50 and the output value of the second ratio multiplication process M52 and assigns the result to the distributed axial force F. In other words, the distributed axial force F is a weighted average of the angular axial force Fr and the current axial force Fi.

[0035] "Steering feedback processing" Figure 4 shows the procedure for the steering feedback process M30. The process shown in Figure 4 is realized by the PU 52 repeatedly executing a program stored in the memory device 54, for example, at a predetermined period. In Figure 4, the step number of each process is represented by a number preceded by "S".

[0036] In the series of processes shown in Figure 4, PU52 first obtains the vehicle speed V (S10). Next, PU52 obtains the ratio Di (S12). Also, PU52 substitutes the value obtained by subtracting the steering equivalent angle θp from the target steering equivalent angle θp* into the deviation Δθ (S14).

[0037] Then, PU52 substitutes the sum of the output value of the proportional element that takes the deviation Δθ as input, the output value of the differential element that takes the time derivative of the deviation Δθ as input, and the output value of the integral element that corresponds to the deviation Δθ, into the target steering torque Tt* (S16).

[0038] Here, PU52 variably sets the proportional gain Kp, which is the gain of the proportional element, according to the ratio Di and the vehicle speed V. Here, PU52 sets the proportional gain Kp when the ratio Di is large to be greater than or equal to the proportional gain Kp when the ratio Di is small. This process can be performed by PU52 performing a map calculation on the proportional gain Kp while the map data is stored in the storage device 54. The map data is data in which the ratio Di and the vehicle speed V are input variables and the proportional gain Kp is the output variable.

[0039] Furthermore, PU52 variably sets the differential gain Kd, which is the gain of the differential element, according to the ratio Di and the vehicle speed V. Here, PU52 sets the differential gain Kd when the ratio Di is large to be greater than or equal to the differential gain Kd when the ratio Di is small. This process can be performed by PU52 performing a map calculation on the differential gain Kd while the map data is stored in the storage device 54. The map data is data in which the ratio Di and the vehicle speed V are input variables and the differential gain Kd is the output variable.

[0040] Furthermore, PU52 variably sets the integral gain Ki, which is the gain for the integral element, according to the ratio Di and the vehicle speed V. Here, PU52 sets the integral gain Ki when the ratio Di is large to be greater than or equal to the integral gain Ki when the ratio Di is small. This process can be performed by PU52 performing a map calculation on the integral gain Ki while the map data is stored in the storage device 54. The map data is data in which the ratio Di and vehicle speed V are input variables and the integral gain Ki is the output variable.

[0041] Furthermore, when PU52 completes the process in S16, it temporarily terminates the series of processes shown in Figure 4. "The operation and effects of this embodiment" PU52 calculates the angular axial force Fr according to the target steering angle θp*. PU52 also calculates the current axial force Fi according to the q-axis current iqt. PU52 calculates the distributed axial force F from the angular axial force Fr and current axial force Fi according to the ratio Di. PU52 calculates the target reaction torque Ts* by subtracting the distributed axial force F from the steering force Tb*, which determines the assist force etc. according to the steering torque Th. Then, PU52 controls the torque of the reaction motor 22 according to the target reaction torque Ts*. As a result, the larger the magnitude of the distributed axial force F, the larger the reaction force applied to the steering wheel 12 can be.

[0042] Incidentally, when a large external force is applied to the steering wheel 34, causing the equivalent steering angle θp to deviate significantly from the target equivalent steering angle θp*, the magnitude of the q-axis current iqt increases. When the magnitude of the q-axis current iqt increases, the magnitude of the current axial force Fi also increases. In that case, when a large external force is applied to the steering wheel 34, there is concern that the torsional stiffness of the steering angle of the steering wheel 34 will differ with respect to the steering torque Th applied to the steering wheel 12, depending on the magnitude of the ratio Di.

[0043] Therefore, PU52 increased the gain of the steering feedback process M30 when the ratio Di was large compared to when the ratio Di was small. As a result, when the ratio Di is large, compared to when the ratio Di is small, the tendency for the steering equivalent angle θp to deviate from the target steering equivalent angle θp* when a large external force is applied to the steering wheel 34 is suppressed more quickly. This suppresses an increase in the magnitude of the current axial force Fi. Therefore, when a large external force is applied to the steering wheel 34, it is possible to suppress the difference in the torsional stiffness of the steering angle of the steering wheel 34 with respect to the steering torque Th applied to the steering wheel 12, depending on the magnitude of the ratio Di.

[0044] <Correspondence> The correspondence between the matters in the above embodiment and the matters described in the "Means for Solving the Problems" section is as follows. Below, the correspondence is shown for each number of the solution means described in the "Means for Solving the Problems" section. [1,4] Steering control processing corresponds to steering feedback processing M30 and steering operation signal generation processing M32. Motor axial force calculation processing corresponds to current axial force calculation processing M42. Distribution processing corresponds to distribution ratio calculation processing M46, second distribution ratio calculation processing M48, first ratio multiplication processing M50, second ratio multiplication processing M52, and addition processing M54. Reaction force control processing corresponds to target reaction force calculation processing M24 and reaction force operation signal generation processing M26. Gain variable processing corresponds to processing S16. [2] Distribution angle variable corresponds to target steering angle θs*. [3] Target steering equivalent angle calculation processing corresponds to target steering equivalent angle calculation processing M18. The target steering angle calculation process corresponds to the target steering angle calculation process M16. [5] In the process of S16, the proportional gain Kp, the derivative gain Kd, and the integral gain Ki are changed according to the vehicle speed V and the target steering angle θs*.

[0045] <Other Embodiments> Furthermore, this embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0046] "Regarding angular variables for axial force" The angular variable for axial force used as input for the calculation process of angular axial force is not limited to the target steering equivalent angle θp*. For example, it may be the steering angle θs. Or, for example, it may be the steering equivalent angle θp. Furthermore, for example, it may be the target steering angle θs* mentioned above. However, it is desirable that the value of the angular variable for axial force is a value that is calculated without referring to the value of a variable that is correlated with the torque of the steering motor 42.

[0047] "Regarding the angle variables used for allocation" The angular variable used to determine the ratio Di of angular axial force Fr to current axial force Fi is not limited to the target steering angle θs*. For example, it may be a set of equivalent steering angle θp and steering angle θs. Alternatively, the equivalent steering angle θp may be used instead.

[0048] "Regarding the calculation process for distributed axial force" The inputs for calculating the ratio Di are not limited to vehicle speed V and target steering angle θs*. For example, the distribution angle variables described in "About Distribution Angle Variables" and vehicle speed V may be used as inputs. Alternatively, only the distribution angle variables described in "About Distribution Angle Variables" may be used as inputs. Note that it is not mandatory for the inputs for calculating the ratio Di to include the distribution angle variables.

[0049] "Regarding motor axial force" The motor axial force calculated using the value of the torque variable, which is a variable indicating the torque of the steering motor 42, as input is not limited to the current axial force Fi. For example, the axial force may be calculated using the estimated torque of the steering motor 42 as input. If the steering motor 42 is a surface magnet synchronous motor, the estimated torque of the steering motor 42 can be the value obtained by multiplying the q-axis current by the armature flux linkage constant. Also, for example, if the steering motor 42 is an embedded magnet synchronous motor, the value can be calculated according to a well-known model formula based on the d-axis current, q-axis current, d-axis inductance, q-axis inductance, and armature flux linkage constant.

[0050] "Regarding the equivalent angle of steering change" • The steering angle itself may be used as the equivalent steering angle. "Regarding steering angle control processing" It is not mandatory for the steering angle control process to include a process for calculating the target steering torque Tt* based on the sum of the output values ​​of the proportional element, the differential element, and the integral element. For example, it may include a process for calculating the target steering torque Tt* based on the sum of the output values ​​of the proportional element and the differential element, without including the output value of the integral element. Alternatively, it may include a process for calculating the target steering torque Tt* based on the sum of the output values ​​of the proportional element and the integral element, without including the output value of the differential element. Alternatively, it may include a process for calculating the target steering torque Tt* based on the output value of the proportional element, without including the output values ​​of the differential element and the integral element.

[0051] The differential element is not limited to one that takes the first-order time derivative of the difference between the controlled variable and its target value as input. For example, it may take the first-order time derivative of the controlled variable as input. In other words, a leading-derivative type controller may be used in the steering angle control process.

[0052] "Regarding variable gain processing" The variable gain processing is not limited to processing that changes all of the proportional gain Kp, differential gain Kd, and integral gain Ki according to the ratio Di. This is not limited to cases where the output values ​​used by the steering angle control processing to calculate the target steering torque Tt* do not include all three output values: the output value of the proportional element, the output value of the differential element, and the output value of the integral element. For example, when the target steering torque Tt* is calculated according to the sum of the output values ​​of the proportional element and the differential element without including the output value of the integral element, only the proportional gain Kp may be changed according to the ratio Di.

[0053] "Regarding steering control devices" The steering control device is not limited to one that executes software processing. For example, it may include a dedicated hardware circuit, such as an ASIC, that executes at least a part of the processing performed 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 comprising a processing unit 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 comprising a processing unit and a program storage device that execute a part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) A processing circuit comprising a dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software execution devices comprising a processing unit and a program storage device. Also, there may be multiple dedicated hardware circuits.

[0054] "Other" It is not essential that the steering motor 42 is of the same type. For example, it could be an induction motor.

[0055] • In each of the above embodiments, the steering device 10 has a linkless structure in which the steering wheel 12 and the steering wheels 34 are mechanically separated at all times. However, it is not limited to this, and a structure in which the steering wheel 12 and the steering wheels 34 can be mechanically separated by a clutch may also be used. [Explanation of Symbols]

[0056] 10… Steering gear 12… Steering wheel 14… Steering axis 20… Reaction actuator 22… Reaction motor 24…Inverter for reaction force 30... Steering actuator 32... Rack axis 34... Steering wheel 40…Transmission mechanism 42... Steering motor 44...Inverter for steering 50... Steering control device

Claims

1. This is applied to a steering system that includes a reaction force motor that applies a reaction force to the steering wheel and a steering motor that steers the steering wheels. The system is configured to perform steering control processing, angle axial force calculation processing, motor axial force calculation processing, distribution processing, reaction force control processing, and gain variable processing when power transmission between the steering wheel and the steering wheel is interrupted. The steering control process is a process that operates the steering motor according to an input variable of feedback control, where the equivalent steering angle is the control variable and the target equivalent steering angle is the target value of the control variable. The aforementioned steering angle is a variable that indicates the steering angle. The aforementioned target steering equivalent angle is the target value of the steering equivalent angle, The aforementioned angular axial force calculation process is a process that calculates the angular axial force using the value of the angular variable for axial force as input. The aforementioned angle variable for axial force is a variable that indicates the angle of the steering device and is a variable that is referenced when calculating the angle axial force. The motor axial force calculation process is a process that calculates the motor axial force using the value of a torque variable, which is a variable indicating the torque of the steering motor, as input. The distribution process is a process that calculates the distributed axial force according to the weighted average value of the angular axial force and the motor axial force. The reaction force control process is a process that controls the torque of the reaction force motor according to the distributed axial force, The steering control device wherein the variable gain processing is a process of changing the gain of the feedback control according to the distributed axial force, and the gain when the ratio of the motor axial force to the distributed axial force is large is set to be greater than or equal to the gain when the ratio is small.

2. The distribution process includes a process to change the ratio of the motor axial force to the distributed axial force according to the value of the distribution angle variable, The steering control device according to claim 1, wherein the distribution angle variable is a variable indicating the angle of the steering device and is a variable referenced when calculating the ratio.

3. It is configured to perform a target steering angle calculation process and a target steering angle calculation process, The aforementioned target steering angle calculation process is a process that calculates the target steering angle according to the steering angle and the steering angle ratio. The aforementioned target steering angle calculation process is a process that calculates the target steering angle according to the equivalent steering angle and the steering angle ratio. The steering control device according to claim 2, wherein the value of the angle variable is the target steering angle.

4. The steering control process includes a process for calculating the manipulated amount according to the output value of a proportional element that takes the difference between the equivalent steering angle and the target equivalent steering angle as input. The steering control device according to claim 1, wherein the gain variable processing includes processing to make the gain of the proportional element variable.

5. The steering control device according to claim 1, wherein the gain variable processing includes processing to change the gain using the ratio of the motor axial force to the distributed axial force as input, and processing to change the gain using the vehicle speed as input.

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