Steering control device

Abstract

A steering control device (50) controls a steering system including a reaction force motor (22) that applies a steering reaction force to a steering shaft (14), and a steering motor (42) that rotates a wheel (34) in a state in which power transmission from the steering shaft (14) is blocked. A steering control device (50) includes a processor (52) that executes a reaction force setting process and a reaction force applying process. In the reaction force setting process, the processor (52) sets the steering reaction force using the predetermined component reflection process. In the reaction force application process, the processor (52) operates the reaction force motor (22) such that the reaction force motor (22) applies the steering reaction force set by the reaction force setting process.

Description

Technical Field

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

[0002] For example, Japanese Unexamined Patent Application Publication No. 2020-142704 (JP 2020-142704 A) describes a so-called steer-by-wire system (hereinafter referred to as SBW) in which the power transmission between the steering wheel and the steering wheel is blocked. In SBW, the road surface reaction force, that is, the force received by the steering wheel from the road surface, is not transmitted to the steering wheel. Therefore, it is difficult for the driver to have a moderate steering feel corresponding to the road surface reaction force.

[0003] Therefore, the control device described in JP 2020-142704 A sets the reaction force applied to the steering wheel according to a predetermined frequency component of the current in the motor that steers the steering wheel. The current flowing through the motor reflects the road surface reaction force. Therefore, using the above-mentioned control device, the road surface reaction force can be transmitted to the steering wheel.

[0004] However, in the case where the system including SBW is unstable, when the reaction force applied to the steering wheel is set according to the predetermined frequency component as described above, control may not be properly performed. In addition, in the case where control cannot be properly performed, the vibration of the steering wheel may become greater than the vibration caused by the above-mentioned road surface reaction force. Summary of the invention

[0005] In one aspect of the present disclosure, a steering control device is configured to control a steering system, the steering system including a reaction force motor and a steering motor, the reaction force motor applies a steering reaction force to a steering shaft, the steering motor steers a steering wheel in a state where power transmission from the steering shaft is blocked. The steering control device includes a processor configured to perform a reaction force setting process, a reaction force application process, and a linkage process. In the reaction force setting process, the processor sets the steering reaction force using a predetermined component reflection process. In the reaction force application process, the processor operates the reaction force motor so that the reaction force motor applies the steering reaction force set by the reaction force setting process. In the predetermined component reflection process, the processor reflects a predetermined component of a frequency signal applied to the steering wheel in the steering reaction force. In the linkage process, the processor changes another of the first pair of variables according to one of the first pair of variables, the first pair of variables including a variable reflecting a specified variable and determining a change in the steering reaction force relative to the operation of the steering shaft. The reflection of the specified variable specifies a way of extracting the predetermined component.

[0006] The above-mentioned predetermined component is a frequency component having information on the road surface. Therefore, in the above-mentioned configuration, since the steering reaction force is set using the predetermined component reflection process, the road surface information can be conveyed to the driver.

[0007] Meanwhile, in the case where the steering reaction force relative to the operation of the steering shaft changes greatly, the gain of the steering reaction force relative to the operation of the steering shaft is greater than the case where the steering reaction force relative to the operation of the steering shaft changes little, and therefore, the steering system is more likely to become unstable. In the case where the steering system is likely to become unstable, the steering system may actually become unstable in the case where the component with the road surface information is large. Therefore, in the above configuration, one of the variables reflecting the specified variable and determining the change of the steering reaction force relative to the operation of the steering shaft is changed according to the other of the variables reflecting the specified variable and determining the change of the steering reaction force relative to the operation of the steering shaft. Thus, it is possible to suppress the degree of reflection of the predetermined component in the steering reaction force from becoming too large to cause instability of the steering system.

[0008] The processor may be configured to perform an axial force gradient calculation process. In the axial force gradient calculation process, the processor may calculate an axial force gradient; the axial force gradient may be a ratio of a change in a force resisting a rotation of a steering shaft relative to a change in a rotation angle of the steering shaft. In the linkage process, the processor may also change another of a second pair of variables according to one of the second pair of variables, the second pair of variables including a reflection of a specified variable and an axial force gradient.

[0009] In the case where the axial force gradient is large, the gain of the steering reaction force relative to the change in the steering angle is greater than in the case where the axial force gradient is small, and therefore, the steering system is more likely to become unstable. In the case where the steering system is likely to become unstable, in the case where the component with the road surface information is large, the steering system may actually become unstable. Therefore, in the above configuration, one of the reflection specified variable and the axial force gradient is changed according to the reflection of the other of the specified variable and the axial force gradient. Thereby, it is possible to suppress the degree of reflection of the predetermined component in the steering reaction force from becoming too large to cause instability of the steering system.

[0010] The reaction force setting process may include an assist amount setting process and an axial force setting process. In the axial force setting process, the processor may set an axial force that resists the driver's rotation operation of the steering shaft. In the assist amount setting process, the processor may set an assist amount that assists the driver in turning the steering shaft. The steering reaction force may be determined based on a value obtained by subtracting the assist amount from the axial force.

[0011] In a steering system that performs power transmission between a steering shaft and a rotating shaft, the axial force from the steering wheel becomes a force that hinders the driver's rotational operation of the steering shaft. Therefore, the assist amount is the amount of steering assistance by the driver. On the other hand, in the above configuration, in a state where the power transmission between the steering shaft and the rotating shaft is blocked, the axial force that resists the rotational operation of the steering shaft can be virtually realized by control. Therefore, the assist amount can be set with the same concept as that of a steering system that performs power transmission between a steering shaft and a steering wheel.

[0012] In the axial force gradient calculation process, the processor may calculate an amount of change of the axial force set by the axial force setting process with respect to a change in the rotation angle of the steering shaft.

[0013] In the above configuration, by calculating the amount of change of the axial force set by the axial force setting process relative to the change of the rotation angle of the steering shaft, the actual axial force gradient of the steering shaft can be calculated with high accuracy.

[0014] In the linkage process, the processor can use the axial force gradient as an input to change the reflection specified variable. In this configuration, the predetermined component can be reflected within a range that can suppress the steering system from becoming unstable under the current axial force gradient.

[0015] The predetermined component reflection processing may include a predetermined component extraction processing and an extraction change processing. In the predetermined component extraction processing, the processor may extract the predetermined component based on the reflection specified variable. In the extraction change processing, the processor may change the reflection specified variable. In the axial force setting processing, the processor may set the axial force based on the axial force specified variable, and the axial force specified variable specifies the relationship between the axial force and the change in the rotation angle of the steering shaft. In the linkage processing, the processor may use the reflection specified variable as an input to change the axial force specified variable.

[0016] In the above configuration, the axial force gradient can be set within a range that can suppress the steering system from becoming unstable at the current reflection degree of the predetermined component.

[0017] The reaction force setting process may include a basic assist amount setting process and an axial force setting process. In the axial force setting process, the processor may set an axial force that resists the driver's rotational operation of the steering shaft. In the basic assist amount setting process, the processor may use the steering torque as input to set a basic assist amount for assisting the driver in turning the steering shaft. The steering reaction force may be determined based on the value obtained by subtracting the basic assist amount from the axial force. In the linkage process, the processor may also change another of the second pair of variables based on one of the second pair of variables, the second pair of variables including reflecting a specified variable and an assist gradient. The assist gradient may be a ratio of a change in the basic assist amount to a change in the steering torque.

[0018] In a steering system that performs power transmission between a steering shaft and a rotating shaft, the axial force from the steering wheel becomes a force that hinders the driver's rotational operation of the steering shaft. Therefore, the assist amount is the amount of steering assistance by the driver. On the other hand, in the above configuration, in a state where the power transmission between the steering shaft and the rotating shaft is blocked, the axial force that resists the rotational operation of the steering shaft can be virtually realized by control. Therefore, the assist amount can be set with the same concept as that of a steering system that performs power transmission between a steering shaft and a steering wheel.

[0019] In the case where the assist gradient is large, the steering system is more likely to become unstable than in the case where the assist gradient is small. In the case where the steering system is likely to become unstable, the steering system may actually become unstable in the case where the component with the road surface information is large. Therefore, in the above configuration, one of the reflection specified variable and the assist gradient is changed according to the reflection specified variable and the assist gradient. Thereby, it is possible to suppress the reflection degree of the predetermined component in the steering reaction force from becoming too large to cause instability of the steering system.

[0020] In the linkage process, the processor can use the assist gradient as an input to change the reflection specified variable. In this configuration, the predetermined component can be reflected within a range that can suppress the steering system from becoming unstable at the current assist gradient.

[0021] The predetermined component reflection process may include a predetermined component extraction process and an extraction change process. In the predetermined component extraction process, the processor may extract the predetermined component according to the reflection specified variable. In the extraction change process, the processor may change the reflection specified variable. In the linkage process, the processor may use the reflection specified variable as input to change the auxiliary gradient.

[0022] In the above configuration, the assist gradient can be set within a range that can suppress the steering system from becoming unstable at the current reflection degree of the predetermined component. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, wherein like symbols represent like elements, and wherein:

[0024] Figure 1 is a diagram showing the configuration of a steering system according to a first embodiment;

[0025] Figure 2 is a block diagram showing a process performed by a control device according to the first embodiment;

[0026] Figure 3is a block diagram showing a process performed by a control device according to the first embodiment;

[0027] Figure 4 is a block diagram showing a process performed by a control device according to the first embodiment;

[0028] Figure 5 is a block diagram showing a process performed by a control device according to a second embodiment;

[0029] Figure 6 is a block diagram showing a process performed by a control device according to a second embodiment;

[0030] Figure 7 is a block diagram showing a process performed by a control device according to a third embodiment;

[0031] Figure 8 is a block diagram showing processing performed by a control device according to a fourth embodiment; and

[0032] Fig. 9 is a block diagram showing processing executed by a control device according to a modification of the fourth embodiment. DETAILED DESCRIPTION

[0033] First embodiment

[0034] A first embodiment will be described below with reference to the drawings.

[0035] Prerequisite Configuration

[0036] Figure 1 The steering device 10 of the vehicle shown in 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 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 resists the force of the driver's operation on 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 as a force opposite to the steering to the steering wheel 12 through the steering shaft 14. The reaction force motor 22 is connected to the steering shaft 14 through the reaction force reduction mechanism 26. For example, a three-phase synchronous electric motor is used as the reaction force motor 22. For example, the reaction force reduction mechanism 26 is composed of a worm and a worm wheel.

[0037] The steering actuator 30 is an actuator for steering the steering wheel 34 in response to the driver's steering intention indicated by the driver's operation of the steering wheel 12. The steering actuator 30 includes a rack shaft 32, a steering motor 42, a steering inverter 44, a steering transmission mechanism 46, and a conversion mechanism 48. For example, a three-phase surface magnet synchronous electric motor (SPM) is used as the steering motor 42. The steering transmission mechanism 46 is composed of a belt transmission mechanism. The rotational power of the steering motor 42 is transmitted to the conversion mechanism 48 through the steering transmission mechanism 46. The conversion mechanism 48 converts the transmitted rotational power into displacement power in the axial direction of the rack shaft 32. The steering wheel 34 rotates by the displacement of the rack shaft 32 in the axial direction of the rack shaft 32.

[0038] The steering control device 50 controls the steering wheel 12 and the steering wheel 34 as targets. That is, the steering control device 50 controls the steering reaction force that resists the driver's steering as a control variable for the steering wheel 12 as a control target. In addition, the steering control device 50 controls the turning angle as a control variable for the steering wheel 34 as a control target. The turning angle is the movement angle of the tire as the steering wheel 34.

[0039] For the control of the control variable, the steering control device 50 involves the steering torque Th detected by the torque sensor 60. The steering torque Th is the torque applied to the steering shaft 14 by the driver's operation of the steering wheel 12. For the control of the control variable, the steering control device 50 involves the rotation angle θa detected by the steering side rotation angle sensor 62, and the rotation angle θa is the angle of the rotation shaft of the reaction force motor 22. In addition, for the control of the control variable, the steering control device 50 involves the currents ius, ivs, iws flowing through the reaction force motor 22. For example, the currents ius, ivs, iws can be detected as the voltage drop amount of the shunt resistor provided to the corresponding branch of the reaction force inverter 24. For the control of the control variable, the steering control device 50 involves the rotation angle θb detected by the turning side rotation angle sensor 64, and the rotation angle θb is the angle of the rotation shaft of the steering motor 42. In addition, for the control of the control variable, the steering control device 50 involves the currents iut, ivt, iwt flowing through the steering motor 42. For example, the currents iut, ivt, iwt may be detected as the amount of voltage drops across shunt resistors provided to the respective branches of the steering inverter 44. The steering control 50 is dependent on the vehicle speed V detected by the vehicle speed sensor 66.

[0040] The steering control device 50 includes a PU 52 and a storage device 54. The PU 52 is a software processor such as a CPU, a GPU, and a TPU. The storage device 54 may be a nonvolatile memory in which electrical rewriting is impossible. In addition, the storage device 54 may be a nonvolatile memory in which electrical rewriting is possible, or may be a storage medium such as a disk medium.

[0041] Overview of Controls

[0042] Figure 2 2 shows the processing performed by the steering control device 50. For example, when the PU 52 repeatedly executes the program stored in the storage device 54 at a predetermined cycle, the Figure 2 The process shown in .

[0043] The steering angle calculation process M10 includes a process for converting the rotation angle θa into a cumulative angle including a range exceeding 360 degrees by, for example, counting the number of revolutions of the reaction force motor 22 from a steering neutral position, which is the position of the steering wheel 12 when the vehicle moves straight. The steering angle calculation process M10 includes a process for calculating the steering angle θs by multiplying the cumulative angle obtained by the conversion by a conversion factor based on the rotation speed ratio of the reaction force speed reduction mechanism 26.

[0044] The rotation corresponding angle calculation processing M12 includes the following processing: for example, by counting the number of revolutions of the steering motor 42 from the rack neutral position which is the position of the rack shaft 32 when the vehicle moves in a straight line, the rotation angle θb is converted into a cumulative angle including a range exceeding 360 degrees. The rotation corresponding angle calculation processing M12 includes the following processing: by multiplying the cumulative angle obtained by the conversion by a conversion factor according to the reduction ratio of the steering transmission mechanism 46, the lead of the conversion mechanism 48, etc., the rotation corresponding angle θp is a quantity that is proportional to the rotation angle. As an example, in the case of an angle on the right side of the rack neutral position, the rotation corresponding angle θp is positive, and in the case of an angle on the left side of the rack neutral position, the rotation corresponding angle θp is negative.

[0045] The target rotation corresponding angle calculation process M18 is a process for calculating the target rotation corresponding angle θp* based on the steering angle θs and the vehicle speed V.

[0046] The assist amount setting process M20 is a process for calculating 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 direction of the driver's steering. When the force for assisting the steering by the driver is large, the magnitude of the assist amount Ta is set to a large value.

[0047] The axial force setting process M22 is a process for setting the axial force F using the vehicle speed V, the q-axis current iqt of the steering motor 42, and the target rotation corresponding angle θp* as inputs. The axial force F is a value representing the force acting on the rack shaft 32 through the steering wheel 34 by control. However, for the axial force F, it is not necessary to intend to estimate the force acting on the rack shaft 32 with high accuracy. For example, as the axial force F, the force acting on the rack shaft 32 may be virtually determined. The axial force F is an axial force obtained from the conversion into the torque applied to the steering shaft 14. That is, the axial force F is an axial force obtained from the conversion into the torque applied to the steering shaft 14 when assuming a state in which power transmission can be performed between the steering wheel 34 and the steering shaft 14. The axial force F is an amount acting in the direction opposite to the direction of the driver's steering. The axial force setting process M22 may be a process for calculating the axial force F so that the absolute value of the axial force F is larger when the absolute value of the target rotation corresponding angle θp* is larger. In addition, for example, the axial force calculation process M22 may be a process in which the axial force F is calculated so that the absolute value of the axial force F is larger when the vehicle speed V is higher. In addition, the axial force calculation process M22 may be a process in which the axial force F is calculated so that the absolute value of the axial force F is larger when the absolute value of the q-axis current iqt is larger. The q-axis current iqt is calculated by the PU 52 based on the rotation corresponding angle θp and the currents iut, ivt, and iwt.

[0048] 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 reaction torque Ts. The target reaction torque Ts is a target value of torque applied to the steering shaft 14 by the reaction motor 22 .

[0049] The reaction force operation signal generation process M26 is a process for generating an operation signal MSs for the reaction force inverter 24 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. More specifically, the reaction force operation signal generation process M26 includes a process for converting the target reaction force torque Ts into the target torque of the reaction force motor 22. In addition, the reaction force operation signal generation process M26 includes a process for calculating the operation signal MSs for the reaction force inverter 24 so that the current flowing through the reaction force motor 22 approaches the current determined by the target reaction force torque Ts through the feedback control of the current. In fact, the operation signal MSs includes the corresponding operation signals for the six switching elements of the reaction force inverter 24. Since the torque of the reaction force motor 22 becomes the target reaction force torque Ts, the steering reaction force relative to the force for the rotation of the steering wheel 12 is "(-1)Ts".

[0050] The rotation feedback process M30 is a process of substituting a manipulated variable in feedback control in which the rotation corresponding angle θp is used as a control variable and the target rotation corresponding angle θp* is used as a target value of the control variable into the target rotation torque Tt*. The target rotation torque Tt* satisfies a constant ratio with respect to the torque of the steering motor 42.

[0051] The rotation operation signal generation process M32 is a process for generating an operation signal MSt for the steering inverter 44 to control the torque of the steering motor 42 so that the torque of the steering motor 42 becomes a value that satisfies a constant ratio with respect to the target rotation torque Tt*. More specifically, the rotation operation signal generation process M32 includes a process for converting the target rotation torque Tt* into a target torque of the steering motor 42. In addition, the rotation operation signal generation process M32 includes a process for calculating the operation signal MSt for the steering inverter 44 so that, through feedback control of the current, the current flowing through the steering motor 42 approaches the current determined by the target torque. In fact, the operation signal MSt includes corresponding operation signals for the six switching elements of the steering inverter 44.

[0052] Axial force setting process

[0053] Figure 3 The details of the axial force setting process M22 are shown.

[0054] The angular axis force setting process M40 is a process in which the angular axis force Fr is calculated using the target rotation corresponding angle θp* and the vehicle speed V as inputs. The angular axis force Fr is an estimated value of the axial force specified by an arbitrarily set vehicle model, etc. The angular axis force Fr is calculated as an axial force in which the road surface information is not reflected. The road surface information is information about minute roughness that does not affect the lateral behavior of the vehicle, the step size that affects the lateral behavior of the vehicle, and the like. For example, the angular axis force setting process M40 may be a process in which the absolute value of the angular axis force Fr increases as the absolute value of the target rotation corresponding angle θp* increases. In addition, for example, the angular axis force setting process M40 may be a process in which the absolute value of the angular axis force Fr increases as the vehicle speed V increases.

[0055] More specifically, the angular axis force setting process M40 is a process of performing map calculation on the angular axis force Fr using an angular axis force map M40a in which the target rotation corresponding angle θp* and the vehicle speed V are used as inputs and the angular axis force Fr is used as an output variable.

[0056] The mapping data is a combination of discrete values ​​of input variables and values ​​of output variables respectively corresponding to the values ​​of the input variables. In addition, the mapping calculation may be a process in which, when the value of the input variable is consistent with one of the values ​​of the input variable in the mapping data, the corresponding value of the output variable in the mapping data is adopted as the calculation result. In addition, the mapping calculation may be a process in which, when the value of the input variable is inconsistent with any of the values ​​of the input variable in the mapping data, a value obtained by interpolating among multiple values ​​of the output variable included in the mapping data is adopted as the calculation result. Alternatively, the mapping calculation may be a process in which, when the value of the input variable is inconsistent with any of the values ​​of the input variable in the mapping data, the value of the output variable in the mapping data corresponding to the value closest to the value of the input variable among multiple values ​​of the input variable included in the mapping data is adopted as the calculation result.

[0057] The current axial force setting process M42 is a process in which the current axial force Fi is calculated as the q-axis current iqt of the steering motor 42. The current axial force Fi is an estimated value of the axial force actually acting on the rack shaft 32 that is operated to rotate the steering wheel 34, that is, an estimated value of 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-mentioned road surface information. For example, the current axial force setting process M42 is a process in which the current axial force Fi is calculated so that the torque applied to the rack shaft 32 by the steering motor 42 is balanced with the torque corresponding to the force applied to the rack shaft 32 by the steering wheel 34. That is, the current axial force setting process M42 is a process in which the current axial force Fi is calculated so that the absolute value of the current axial force Fi is larger when the absolute value of the q-axis current iqt is larger.

[0058] More specifically, the current axial force setting process M42 is a process of performing map calculation on the current axial force Fi using a current axial force map M42a in which the q-axis current iqt is used as an input variable and the current axial force Fi is used as an output variable.

[0059] The distribution ratio calculation process M46 is a process in which the ratio Di is calculated using the vehicle speed V and the target rotation corresponding angle θp* 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 equal to or greater than zero and equal to or less than 1. For example, the distribution ratio calculation process M46 may be a process in which the PU 52 performs a mapping calculation on the ratio Di in a state in which the mapping data is stored in the storage device 54. The mapping data is data in which the vehicle speed V and the target rotation corresponding angle θp* are used as input variables and the ratio Di is used as an output variable.

[0060] The second distribution ratio calculation process M48 is a process of calculating a second ratio “10043Di” by subtracting the ratio Di from “1.” The second ratio is a ratio of the angular axial force Fr to the sum of the angular axial force Fr and the current axial force Fi.

[0061] The first ratio multiplication process M50 is a process of multiplying the current axial force Fi by the ratio Di. The second ratio multiplication process M52 is a process of multiplying the angular axial force Fr by the second ratio. The addition process M54 is a process of substituting the value obtained by adding the output value of the first ratio multiplication process M50 and the output value of the second ratio multiplication process M52 into the axial force F. That is, the axial force F has a value obtained by weighted average processing of the angular axial force Fr and the current axial force Fi.

[0062] Auxiliary amount setting process

[0063] Figure 4 The details of the assist amount setting process M20 are shown.

[0064] The basic assistance amount setting process M60 is a process in which the basic assistance amount Tab is set using the steering torque Th and the vehicle speed V as inputs. In the basic assistance amount setting process M60, the basic assistance amount Tab is set to a value that is positively correlated with the steering torque Th. For example, the process may be a process in which the PU 52 performs a mapping calculation on the basic assistance amount Tab in a state in which mapping data is pre-stored in the storage device 54. The mapping data is data in which the steering torque Th and the vehicle speed V are used as input variables and the basic assistance amount Tab is used as an output variable.

[0065] The road information processing M70 is a process for superimposing information related to a road surface reaction force, which is a force applied from the road surface to the steering wheel 34, on the steering wheel 12. The road information processing M70 includes a bandpass filter M72, a filter coefficient setting process M74, and a gain multiplication process M76. The q-axis current iqt is input to the bandpass filter M72. The q-axis current iqt is input to the bandpass filter M72 as a component including a vibration component of the steering wheel 34 caused by the road surface reaction force. The bandpass filter M72 is a process for selectively extracting a signal in a vibration frequency band caused by the roughness of the road surface. The gain multiplication process M76 is a process for substituting a value obtained by multiplying the output value of the bandpass filter M72 by the gain G into the road surface information torque Ti. The filter coefficient setting process M74 is a process for setting the filter coefficient τi of the bandpass filter M72 according to the vehicle speed V. The filter coefficient τi is a variable for specifying the frequency band transmitted by the bandpass filter M72, or a variable for specifying an attenuation method. For example, the variable for specifying the frequency band transmitted may be a variable for specifying a center frequency. In addition, for example, the variable for specifying an attenuation method may be an attenuation factor. Here, the filter coefficient τi is described as one variable, but may actually include multiple variables.

[0066] The synthesis process M80 is a process of subtracting the road surface information torque Ti from the basic assist amount Tab. The value calculated in this way is the assist amount Ta.

[0067] The axial force gradient calculation process M90 is a process that uses the vehicle speed V, the target rotation corresponding angle θp*, and the q-axis current iqt as inputs to calculate the axial force gradient dF. The axial force gradient dF is a variable indicating the ratio of the change in the axial force F to the change in the steering angle θs. Figure 3 As shown, the angular force Fr is calculated using the target rotation corresponding angle θp* and the vehicle speed V as input. The target rotation corresponding angle θp* is a variable related to the steering angle θs. Accordingly, the ratio of the change in the angular force Fr to the change in the steering angle θs can be calculated based on the target rotation corresponding angle θp* and the vehicle speed V.

[0068] At the same time, Figure 3 In the illustrated process, the current axial force Fi is set independently of the variable indicating the angle. However, there is a relationship between the change in the current axial force Fi and the change in the steering angle θs because, for example, the q-axis current iqt is implemented by feedback control in which the rotation corresponding angle θp is used as a control variable. Therefore, using the target rotation corresponding angle θp* and the q-axis current iqt as inputs, the ratio of the change in the current axial force Fi to the change in the steering angle θs can be known.

[0069] Specifically, the axial force gradient calculation process M90 may be a process that uses the vehicle speed V, the target rotation corresponding angle θp*, and the q-axis current iqt as inputs to perform a mapping calculation on the axial force gradient dF. The mapping uses the vehicle speed V, the target rotation corresponding angle θp*, and the q-axis current iqt as input variables, and uses the axial force gradient dF as an output variable.

[0070] Operation and Effects of Implementation Methods

[0071] PU 52 sets the target reaction torque Ts by subtracting the axial force F from the assist amount Ta. Then, the torque of the reaction motor 22 is controlled according to the target reaction torque Ts. The axial force F is a value that can be adjusted by control design. Therefore, the steering reaction force applied to the driver can be freely designed by control design. However, when the change in the axial force F is large relative to the change in the steering angle θs, the stability of the steering system is more likely to decrease. Therefore, when the stability of the steering system is likely to decrease, in the case where the amplitude in a predetermined frequency band increases due to the road surface information torque Ti, the steering system may actually become unstable.

[0072] Therefore, the PU 52 sets the filter coefficient τi according to the axial force gradient dF. Therefore, it is possible to suppress an excessive increase in amplitude in a frequency band that causes instability. Accordingly, it is possible to suppress the steering system from becoming unstable due to the road surface information torque Ti.

[0073] Second embodiment

[0074] The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0075] Figure 5 The details of the assist amount setting process M20 are shown. Figure 5 For convenience, Figure 4 The same step numbers are used to represent corresponding processes in the illustrated processes.

[0076] In this embodiment, if Figure 5 As shown, the axial force gradient dF is not used as an input in the filter coefficient setting process M74 of the road information process M70.

[0077] Figure 6 The details of the axial force setting process M22 are shown. Figure 6 For convenience, Figure 3 Corresponding processes shown in are denoted by the same step numbers.

[0078] like Figure 6As shown, in the angular axis force setting process M40, the filter coefficient τi of the road information process M70 is used as an input. More specifically, the angular axis force setting process M40 includes the following process: the value of the mapping identification variable Vm1 is calculated based on the filter coefficient τi. At the same time, in an embodiment, there are multiple angular axis force mappings M40a, in which the target rotation corresponding angle θp* and the vehicle speed V are used as input variables, and the angular axis force Fr is used as an output variable. In addition, the angular axis force setting process M40 includes the following process: based on the mapping identification variable Vm1, determine which of the multiple angular axis force mappings M40a is used in the mapping calculation of the angular axis force Fr.

[0079] In addition, in the current axial force setting process M42, the filter coefficient τi of the road information process M70 is used as an input. More specifically, the current axial force setting process M42 includes the following process: calculating the mapping identification variable Vm2 based on the filter coefficient τi. At the same time, in the present embodiment, there are multiple types of current axial force mappings M42a, in which the q-axis current iqt is used as an input variable and the current axial force Fi is used as an output variable. In addition, the current axial force setting process M42 includes the following process: based on the mapping identification variable Vm2, determining which of the multiple current axial force mappings M42a is used in the mapping calculation of the current axial force Fi.

[0080] Operation and Effects of Implementation Methods

[0081] The PU 52 changes the map for setting the axial force F according to the filter coefficient τi of the road information processing M70. Thus, the ratio of the change in the axial force F set by the axial force setting processing M22 to the change in the steering angle θs is changed according to the filter coefficient τi. Thus, the generation of the axial force gradient that makes the steering system unstable due to the road surface information torque Ti can be suppressed.

[0082] Third embodiment

[0083] The third embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0084] In the present embodiment, as an input to the road information processing M70, an assist gradient R is used instead of the axial force gradient dF. The assist gradient R is a ratio of a change in the basic assist amount Tab to a change in the steering torque Th.

[0085] Figure 7 The details of the assist amount setting process M20 are shown. Figure 7 For convenience, Figure 5 Processes corresponding to the processes shown in are denoted by the same step numbers.

[0086] Figure 7 The filtering process M100 shown in FIG. 6 is a process of receiving the steering torque Th and outputting the steering torque Thr. As an example, the filtering process M100 may be a process of delaying the phase of the steering torque Th. For example, the filtering process M100 may be a process for performing phase compensation of the steering torque Th to adjust the frequency characteristics of the phase difference between both sides of the torsion bar included in the torque sensor 60.

[0087] The road information processing M70 includes three bandpass filters M72a, M72b, and M72c that are different from each other in transmission band. The gain multiplication processing M76a is a processing of multiplying the output value of the bandpass filter M72a by the gain G1. The gain multiplication processing M76b is a processing of multiplying the output value of the bandpass filter M72b by the gain G2. The gain multiplication processing M76c is a processing of multiplying the output value of the bandpass filter M72c by the gain G3. The addition processing M78 is a processing of substituting the value obtained by adding the output values ​​of the gain multiplication processing M76a, M76b, and M76c into the road surface information torque Ti.

[0088] The gain setting process M75a is a process of calculating the gain G1 using the vehicle speed V and the assisting gradient R as inputs. The gain setting process M75a may be a process in which the PU 52 performs a map calculation for the gain G1 in a state in which the map data is stored in the storage device 54. The map data is data in which the vehicle speed V and the assisting gradient R are used as input variables and the gain G1 is used as an output variable.

[0089] The gain setting process M75b is a process of calculating the gain G2 using the vehicle speed V and the assisting gradient R as inputs. The gain setting process M75b may be a process in which the PU 52 performs a map calculation for the gain G2 in a state in which the map data is stored in the storage device 54. The map data is data in which the vehicle speed V and the assisting gradient R are used as input variables and the gain G2 is used as an output variable.

[0090] The gain setting process M75c is a process of calculating the gain G3 using the vehicle speed V and the assisting gradient R as inputs. The gain setting process M75c may be a process in which the PU 52 performs a map calculation for the gain G3 in a state in which the map data is stored in the storage device 54. The map data is data in which the vehicle speed V and the assisting gradient R are used as input variables and the gain G3 is used as an output variable.

[0091] Operation and Effects of Implementation Methods

[0092] PU 52 uses the steering torque Thr and the vehicle speed V as inputs to calculate the basic assist amount Tab. PU 52 sets the target reaction torque Ts according to the value obtained by subtracting the axial force F from the basic assist amount Tab. Then, the torque of the reaction motor 22 is controlled according to the target reaction torque Ts. The assist gradient R, which is the ratio of the change in the basic assist amount Tab to the change in the steering torque Thr, is a value that can be adjusted by the control design. Therefore, the steering reaction force applied to the driver can be freely designed by the control design. However, as the assist gradient R is larger, the stability of the steering system is more likely to decrease. Therefore, when the stability of the steering system is likely to decrease, the steering system may actually become unstable when the amplitude within a predetermined frequency band increases due to the road surface information torque Ti.

[0093] Therefore, the PU 52 sets the gains G1 to G3 according to the assist gradient R. Thus, an excessive increase in the amplitude in the frequency band that causes instability can be suppressed. Therefore, the steering system can be suppressed from becoming unstable due to the road surface information torque Ti.

[0094] Fourth embodiment

[0095] The fourth embodiment will be described below with reference to the drawings, focusing on differences from the third embodiment.

[0096] Figure 8 The details of the assist amount setting process M20 are shown. Figure 8 For convenience, Figure 7 Processes corresponding to the processes shown in are denoted by the same step numbers.

[0097] like Figure 8 As shown, in the gain setting processes 75a, 75b, 75c according to the present embodiment, the assist gradient R is not used as an input. In contrast, in the basic assist amount setting process M60, the basic assist amount Tab is set using the gains G1 to G3 as inputs.

[0098] More specifically, the basic assistance amount setting process M60 is a process of calculating the basic assistance amount Tab by selectively using a plurality of mapping data M60a identified by a mapping identification variable Vma. The mapping data M60a is data in which the steering torque Thr is used as an input variable and the basic assistance amount Tab is used as an output variable. The plurality of mapping data M60a includes a plurality of pieces of data that are different from each other in the assistance gradient R. The mapping identification variable Vma is set according to the vehicle speed V and the gains G1 to G3.

[0099] Operation and Effects of Implementation Methods

[0100] The PU 52 changes the map data M60a used in the calculation of the basic assist amount Tab according to the gains G1 to G3 of the road information processing M70. Therefore, the assist gradient R changes according to the gains G1 to G3. Thus, the generation of such an assist gradient R that causes the steering system to become unstable due to the road surface information torque Ti can be suppressed.

[0101] Correspondence

[0102] The correspondence between the contents in the above-mentioned embodiments and the contents described in “Summary of the Invention” is as follows.

[0103] The reaction force setting process corresponds to the assist amount setting process M20, the axial force setting process M22, and the subtraction process M24. The reaction force application process corresponds to the reaction force operation signal generation process M26. The predetermined component reflection process corresponds to the road information process M70. The linkage process corresponds to inputting the axial force gradient dF to Figure 4 The filter coefficient setting process M74 in the embodiment. In addition, the linkage process corresponds to inputting the filter coefficient τi into Figure 6 The angular axis force setting process M40 and the current axis force setting process M42 in the linkage process correspond to the auxiliary gradient R input to Figure 7 The linkage processing corresponds to inputting the gains G1 to G3 into the Figure 8 The auxiliary amount setting process M20.

[0104] The axial force gradient calculation process corresponds to the axial force gradient calculation process M90. The linkage process corresponds to inputting the axial force gradient dF into Figure 4 The filter coefficient setting process M74 in the embodiment. In addition, the linkage process corresponds to inputting the filter coefficient τi into Figure 6 Angular axis force setting processing M40 and current axis force setting processing M42 in.

[0105] Linkage processing corresponds to Figure 4 The processing illustrated in FIG. 1 reflects the specified variable corresponding to the filter coefficient τi.

[0106] The predetermined component extraction process corresponds to the bandpass filter M72. The extraction change process corresponds to the filter coefficient setting process M74. The axial force designation variable corresponds to the map identification variables Vml, Vm2. The linkage process corresponds to Figure 6 The processing illustrated in .

[0107] The basic assist amount setting process corresponds to the assist amount setting process M20.

[0108] The linkage process corresponds to inputting the auxiliary gradient R into Figure 7 Gain setting processing M75a, M75b, M75c.

[0109] The linkage process corresponds to inputting the gains G1 to G3 to Figure 8 The auxiliary amount setting process M20.

[0110] Other Implementations

[0111] The embodiment may be performed while being modified as follows. The embodiment and the following modifications may be performed while being combined with each other within the range where there is no technical inconsistency.

[0112] Predetermined component extraction processing

[0113] The variable indicating the frequency signal to be applied to the steering wheel 34 and being the extraction object of the predetermined component is not limited to the q-axis current iqt. For example, the torque of the steering motor 42 may be employed.

[0114] Extract change processing

[0115] As the extraction changes are processed, Figure 5 The process of changing the filter coefficient τi only according to the vehicle speed V has been exemplified in FIG. 1 , but is not limited to this.

[0116] The extraction change process is not limited to the process of changing the filter coefficient of the band pass filter. For example, the process of changing the gain G according to a variable such as the vehicle speed V may be adopted.

[0117] exist Figure 7 In , only two of the gains G1 to G3 can be changed according to the auxiliary gradient R. In addition, for example, in Figure 7 In , only one of the gains G1 to G3 may be changed according to the auxiliary gradient R. In addition, for example, in Figure 7 and Figure 8 In the example, only two of the gains G1 to G3 may be changed according to the vehicle speed V. In addition, for example, in Figure 7 and Figure 8 In the embodiment of the present invention, only one of the gains G1 to G3 may be changed according to the vehicle speed V.

[0118] The predetermined component extraction process is not limited to a process having a bandpass filter corresponding to one frequency band or a bandpass filter corresponding to three frequency bands. In the case where there are bandpass filters corresponding to a plurality of arbitrary frequency bands respectively in the predetermined component extraction process, the extraction change process may be performed as follows. For example, the extraction change process may be a process of changing the filter coefficient of the bandpass filter according to the vehicle speed V, etc. In addition, for example, the extraction change process may be a process of changing only the filter coefficients of some of the bandpass filters corresponding to the plurality of frequency bands respectively according to the vehicle speed V, etc.

[0119] Predetermined component reflection processing

[0120] The predetermined component reflecting process does not need to be a process of calculating the road surface information torque Ti by multiplying the output value of the band pass filter by a gain. For example, a process of using the output value of the band pass filter as the road surface information torque Ti may be adopted.

[0121] Axis force setting process

[0122] The angular force setting process M40 need not be a process of performing a mapping calculation of the angular force Fr using the angular force map M40a. For example, the angular force setting process M40 may be a process of substituting a value obtained by multiplying the target rotation corresponding angle θp* by a gain into the angular force Fr. The gain may vary according to the vehicle speed V.

[0123] The inputs of the angular force setting process M40 do not need to be the target rotation corresponding angle θp* and the vehicle speed V. For example, the vehicle speed V may be excluded from the angular force setting process M40. Furthermore, for example, the angle variable in the steering system as the input variable of the angular force setting process M40 is not limited to the target rotation corresponding angle θp*. For example, the angle variable in the steering system may be the rotation corresponding angle θp. Furthermore, for example, the angle variable in the steering system may be the steering angle θs.

[0124] The current axial force setting process M42 is not limited to the process of performing map calculation of the current axial force Fi using the current axial force map M42a. For example, the current axial force setting process M42 may substitute a value obtained by multiplying the q-axis current iqt by a gain into the current axial force Fi.

[0125] The input of the current axial force setting process M42 is not limited to the q-axis current iqt. For example, as the input of the current axial force setting process M42, the q-axis current iqt and the vehicle speed V may be used. In addition, for example, as the input of the current axial force setting process M42, angle variables in the steering control system may be included, such as the target rotation corresponding angle θp*, the rotation corresponding angle θp, and the steering angle θs.

[0126] The axial force setting process does not need to include both the angular axial force setting process M40 and the current axial force setting process M42. For example, only one of the angular axial force setting process M40 and the current axial force setting process M42 may be included.

[0127] Axial force gradient calculation and processing

[0128] The axial force gradient calculation process is not limited to the process of calculating the axial force gradient dF using the vehicle speed V, the target rotation corresponding angle θp*, and the q-axis current iqt as inputs. For example, in the axial force gradient calculation process, the angular axial force Fr may be used as an input instead of the target rotation corresponding angle θp*. In addition, for example, in the axial force gradient calculation process, the current axial force Fi may be used as an input instead of the q-axis current iqt.

[0129] Linkage processing

[0130] exist Figure 4 In the example, the axial force gradient dF is used as an input to change the filter coefficient τi, but the present disclosure is not limited thereto. For example, the axial force gradient dF may be used as an input to change the gain G. In addition, for example, the axial force gradient dF may be used as an input to change both the filter coefficient τi and the gain G.

[0131] exist Figure 6 In the example, the value of the mapping identification variable Vm1 for identifying which of the multiple angular axis force mappings M40a is used is set according to the filter coefficient τi, but the present disclosure is not limited thereto. For example, a protection process for limiting the magnitude of the change in the angular axis force Fr may be provided, and the protection value for the protection process may be changed according to the filter coefficient τi.

[0132] exist Figure 6 In the example, the value of the mapping identification variable Vm2 for identifying which of the multiple current axial force mappings M42a is used is set according to the filter coefficient τi, but the present disclosure is not limited thereto. For example, a protection process for limiting the magnitude of the change in the current axial force Fi may be provided, and the protection value for the protection process may be changed according to the filter coefficient τi.

[0133] The axial force specified variable does not need to be composed of a variable related to the current axial force Fi and a variable related to the angular axial force Fr. For example, a protection process that limits the magnitude of the change in the axial force F may be provided, and the protection value used for the protection process may be changed according to the filter coefficient τi. In this case, the axial force specified variable is the protection value of the axial force F.

[0134] In the case where the gain G is changed according to the vehicle speed V or the like described in the “extraction change process”, the value of the axial force designation variable may be changed according to the gain G.

[0135] exist Figure 7 In FIG. 1 , the gains G1 to G3 are changed according to the auxiliary gradient R, but the present disclosure is not limited thereto. For example, the filter coefficient τi may be changed according to the auxiliary gradient R.

[0136] exist Figure 8In the embodiment, the gains G1 to G3 are input to the basic assist amount setting process M60, but the present disclosure is not limited thereto. For example, only two of the three gains G1 to G3 may be input to the basic assist amount setting process M60. In addition, for example, only one of the gains G1 to G3 may be input to the basic assist amount setting process M60.

[0137] The reflection specified variables input to the basic assist amount setting process M60 are not limited to the gains G1 to G3. Figure 8 In the process, a filter coefficient setting process may be performed in which the PU 52 sets the respective filter coefficients of the bandpass filters M72a, M72b, M72c according to the vehicle speed, etc., and the filter coefficients may be input to the basic assist amount setting process M60.

[0138] The process of changing one of the two values ​​according to the other of the two values ​​reflecting the value of the designated variable and the variable determining the change in the steering reaction force relative to the operation of the steering shaft is not limited to the process consisting of one of the following processes A and B.

[0139] Process A: Changing one of the two values ​​according to one of the two values ​​reflecting the specified variable and the axial force gradient.

[0140] Process B: Change one of the two values ​​according to the other value reflecting the specified variable and the auxiliary gradient.

[0141] Fig. 9 An example including both process A and process B is shown. Fig. 9 For convenience, the corresponding Figure 4 The processes shown in the figure are indicated by the same reference numerals. Fig. 9 As shown, in the filter coefficient setting process M74, the filter coefficient τi is set using the vehicle speed V, the axial force gradient dF, and the assist gradient R as inputs.

[0142] Steering Controls

[0143] The steering control device is not limited to a device that performs software processing. For example, a dedicated hardware circuit exemplified by an ASIC may be included, and at least some of the processing performed in the above-mentioned embodiments may be performed. That is, the steering control device only needs to include a processing circuit having one of the following configurations (a) to (c).

[0144] (a) A processing circuit including a processor that executes all the above-mentioned processing according to a program and a program storage device that stores the program, as exemplified by the storage device.

[0145] (b) A processing circuit including a processor that executes some of the above-mentioned processing according to a program, a program storage device, and a dedicated hardware circuit that executes other processing.

[0146] (c) A processing circuit comprising dedicated hardware circuits that perform all of the above processing.

[0147] A plurality of software execution devices including a processor and a program storage device may be provided. In addition, a plurality of dedicated hardware circuits may be provided.

[0148] other

[0149] The steering motor 42 does not need to be a synchronous motor. For example, an induction motor may be used.

[0150] In the above embodiment, the steering device 10 has a linkless structure in which the steering wheel 12 and the steering wheel 34 are always mechanically separated, but is not limited thereto and may have a structure in which the steering wheel 12 and the steering wheel 34 may be mechanically separated by a clutch.

Claims

1. A steering control device (50) configured to control a steering system, the steering system comprising a reaction force motor (22) and a steering motor (42), the reaction force motor (22) applying a steering reaction force to a steering shaft (14), the steering motor (42) steering a steering wheel (34) in a state where power transmission from the steering shaft (14) is blocked, the steering control device (50) comprising a processor (52), the processor (52) being configured to execute a reaction force setting process, a reaction force applying process and a linkage process, wherein: In the reaction force setting process, the processor (52) sets the steering reaction force using a predetermined component reflection process; In the reaction force applying process, the processor (52) operates the reaction force motor (22) so that the reaction force motor (22) applies the steering manipulation reaction force set by the reaction force setting process; In the predetermined component reflection process, the processor (52) reflects a predetermined component of a frequency signal applied to the steering wheel (34) in the steering manipulation reaction force; In the linkage process, the processor (52) changes one of a first pair of variables according to another of the first pair of variables, the first pair of variables including a variable reflecting a specified variable and determining a change in the steering reaction force relative to the operation of the steering shaft (14); and The reflection designation variable designates a manner of extracting the predetermined component.

2. The steering control device (50) according to claim 1, characterized in that: The processor (52) is configured to perform an axial force gradient calculation process; In the axial force gradient calculation process, the processor (52) calculates the axial force gradient; The axial force gradient is a ratio of a change in a force resisting rotation of the steering shaft (14) relative to a change in a rotation angle of the steering shaft (14); and In the linkage processing, the processor (52) further changes one of the second pair of variables according to the other of the second pair of variables, the second pair of variables including the reflection specified variable and the axial force gradient.

3. The steering control device (50) according to claim 2, characterized in that: The reaction force setting process includes an assist amount setting process and an axial force setting process; In the axial force setting process, the processor (52) sets an axial force to resist a driver's rotation operation on the steering shaft (14); In the assist amount setting process, the processor (52) sets an assist amount for assisting the driver in turning the steering shaft (14); as well as The steering reaction force is determined based on a value obtained by subtracting the assist amount from the axial force.

4. The steering control device (50) according to claim 3, characterized in that: In the axial force gradient calculation process, the processor (52) calculates a change amount of the axial force set by the axial force setting process relative to a change in a rotation angle of the steering shaft (14).

5. The steering control device (50) according to claim 2, characterized in that: In the linkage process, the processor (52) uses the axial force gradient as input to change the response specified variable.

6. The steering control device (50) according to claim 3, characterized in that: The predetermined component reflection process includes a predetermined component extraction process and an extraction change process; In the predetermined component extraction process, the processor (52) extracts the predetermined component according to the reflection specified variable; In the extraction change process, the processor (52) changes the reflection specified variable; In the axial force setting process, the processor (52) sets the axial force according to an axial force designation variable, the axial force designation variable designating a relationship of the axial force relative to a change in the rotation angle of the steering shaft (14); as well as In the linkage process, the processor (52) changes the axial force designated variable using the reflection designated variable as an input.

7. The steering control device (50) according to claim 1, characterized in that: The reaction force setting process includes a basic assist amount setting process and an axial force setting process; In the axial force setting process, the processor (52) sets an axial force to resist a driver's rotation operation on the steering shaft (14); In the basic assistance amount setting process, the processor (52) uses the steering torque as an input to set a basic assistance amount for assisting the driver in turning the steering shaft (14); The steering reaction force is determined based on a value obtained by subtracting the basic assist amount from the axial force; In the linkage process, the processor (52) further changes one of the second pair of variables according to another of the second pair of variables, the second pair of variables including the reflection specified variable and the auxiliary gradient; and The assist gradient is a ratio of a change amount of the basic assist amount to a change amount of the steering torque.

8. The steering control device (50) according to claim 7, characterized in that: In the linkage process, the processor (52) uses the auxiliary gradient as input to change the reflection specified variable.

9. The steering control device (50) according to claim 7, characterized in that: The predetermined component reflection process includes a predetermined component extraction process and an extraction change process; In the predetermined component extraction process, the processor (52) extracts the predetermined component according to the reflection specified variable; In the extraction change process, the processor (52) changes the reflection designation variable; and In the linkage process, the processor (52) uses the reflection specified variable as input to change the auxiliary gradient.

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