Steering control device

Abstract

To provide a steering control device which enables phase compensation appropriate for stabilizing a steering system regardless of a type of a travel mode.SOLUTION: Phase delay compensation processing M60 outputs steering torque Thr obtained by phase delay compensation using steering torque Th as an input. Basic assist amount setting processing M66 sets a basic assist amount Tab using the steering torque Thr as an input. Torque of a reaction force motor is controlled by using a value obtained by subtracting axial force from an assist amount Ta according to the basic assist amount Tab. The phase delay compensation processing M60 includes filter coefficient setting processing M64. The filter coefficient setting processing M64 sets filter coefficients α, T1, and T2 according to a travel mode.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] For example, the following Patent Document 1 describes a control device that controls an electric power steering device. This control device sets the torque of the motor that generates the assist force while utilizing phase compensation processing. This setting aims to stabilize the steering system, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-144887 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the appropriate phase compensation method for stabilizing the steering system may differ depending on the vehicle driving mode. In particular, in the case of a steering system in which the power transmission between the steering shaft and the steered wheels is cut off, the system is likely to become unstable because the steering does not receive resistance from the steered wheels. Therefore, the stability of the system is sensitively affected by the driving mode. [Means for solving the problem]

[0005] Means for solving the above problems and their effects will be described below. 1. A steering control device which controls a steering system having a reaction motor which applies a steering reaction force to a steering shaft and a steering motor which steers steered wheels, and is configured to execute a reaction force setting process, a phase compensation process, and a reaction force applying process, wherein the reaction force setting process is a process of setting the steering reaction force using the phase compensation process, the reaction force applying process is a process of operating the reaction force motor so as to achieve the reaction force set by the reaction force setting process, and the phase compensation process is a process of performing phase compensation of the steering reaction force in different manners when the vehicle's driving mode is different.

[0006] In the above configuration, by performing phase compensation in different ways when the driving mode differs, it is possible to perform appropriate phase compensation for stabilizing the steering system regardless of the type of driving mode.

[0007] 2. The steering control device according to claim 1, wherein the driving modes in which the phase compensation method is different include a mode in which an abnormality has been diagnosed and a normal mode. Vehicle control including the steering system tends to differ between a mode diagnosed as having an abnormality and a normal mode. Therefore, the appropriate phase compensation method for stabilizing the steering system may differ depending on whether or not there is an abnormality. Therefore, in the above configuration, the phase compensation method is changed between a mode diagnosed as having an abnormality and a normal mode. This makes it possible to perform appropriate phase compensation for stabilizing the steering system regardless of whether or not there is an abnormality.

[0008] 3. A steering control device as described in claim 2, wherein the phase compensation process is a process for compensating the phase of the steering reaction force in accordance with the value of a phase compensation defined variable and includes a variable change process, the phase compensation defined variable is a variable that determines how the phase compensation is performed, the variable change process includes a process for changing the value of the phase compensation defined variable in accordance with the vehicle speed, the mode in which an abnormality is diagnosed includes a mode in which an abnormality is diagnosed in the detected value of the vehicle speed, and the phase compensation process includes a process for executing the phase compensation in the mode in which an abnormality is diagnosed in the detected value of the vehicle speed, using the value of the phase compensation defined variable as a value for the abnormality.

[0009] In the above configuration, appropriate phase compensation is performed according to the vehicle speed. However, if there is an abnormality in the detected value of the vehicle speed, phase compensation according to the vehicle speed that is performed when there is no abnormality cannot be performed appropriately. Therefore, in the above configuration, if there is an abnormality in the detected value of the vehicle speed, phase compensation dedicated to the abnormality is performed. As a result, even if there is an abnormality in the detected value of the vehicle speed, the steering system can be stabilized by the phase compensation process.

[0010] 4. A steering control device described in any one of 1 to 3 above, wherein the driving modes in which the phase compensation is performed in different ways include an intervention mode and a non-intervention mode, the intervention mode is a mode in which control intervenes in the steering of the steered wheels depending on relationship information between the vehicle and the outside of the vehicle, and the non-intervention mode is a mode in which the intervention is not performed, the phase compensation process is a process of compensating for the phase of the steering reaction force depending on the value of a phase compensation defining variable, the phase compensation defining variable is a variable that determines the way of the phase compensation, and the phase compensation process includes a process of performing the phase compensation depending on the value of the phase compensation defining variable that differs between the intervention mode and the non-intervention mode.

[0011] When the steering of the steered wheels is intervened by control, the conditions required to keep the steering system stable may be different from those when steering is performed only by a human. Therefore, in the above configuration, the manner of phase compensation is changed between the intervention mode and the non-intervention mode. This makes it possible to stabilize the steering system regardless of whether the intervention mode is selected or not.

[0012] 5. A steering control device as described in any one of 1 to 4 above, wherein the reaction force setting process includes an assist amount setting process and an axial force setting process, the axial force setting process is a process for setting an axial force which is a force that resists the rotation operation of the steering shaft by the driver, the assist amount setting process is a process for setting an assist amount according to a detection value of a steering torque, the assist amount is an amount that assists the driver in rotating the steering shaft, and the steering reaction force is an amount determined according to a value obtained by subtracting the assist amount from the axial force, the phase compensation process includes a phase lag compensation process, and the phase lag compensation process is a process for delaying the phase of the detection value used for setting the assist amount in accordance with a lag specifying variable, and the lag specifying variable is a variable that specifies the phase lag compensation process and takes different values ​​when the driving mode is different.

[0013] In the above configuration, the manner of phase compensation by the phase lag compensation process is changed depending on the different driving modes, so that appropriate phase lag compensation can be achieved depending on the driving mode. 6. A steering control device described in any one of 1 to 5 above, wherein the reaction force setting process includes an assist amount setting process and an axial force setting process, the axial force setting process is a process for setting an axial force which is a force resisting the rotation operation of the steering shaft by the driver, the assist amount setting process is a process for setting an assist amount and includes the phase compensation process and a basic assist amount setting process, the assist amount is an amount by which the driver assists in rotating the steering shaft, the basic assist amount setting process is a process for setting a basic assist amount according to a detection value of the steering torque input to the steering shaft, the phase compensation process includes a phase lead compensation process, and the phase lead compensation process is a process for calculating an advance correction amount of the basic assist amount in accordance with an advance specified variable using the detection value as an input and for the assist amount setting process to set the assist amount from the basic assist amount, the steering reaction force is an amount determined according to a value obtained by subtracting the assist amount from the axial force, and the phase lead specified variable is a variable that specifies the phase lead compensation process and takes different values ​​when the driving mode is different.

[0014] In the above configuration, the manner of phase compensation by the phase lead compensation process is changed for different driving modes, so that appropriate phase lead compensation can be achieved depending on the driving mode. [Brief description of the drawings]

[0015] [Figure 1] 1 is a diagram showing a configuration of a steering system according to a first embodiment. [Diagram 2] FIG. 2 is a block diagram showing a process executed by a control device according to the embodiment. [Diagram 3] FIG. 2 is a block diagram showing a process executed by a control device according to the embodiment. [Figure 4] 4 is a flowchart showing a procedure of a process executed by a control device according to the embodiment. [Diagram 5] 10 is a flowchart showing a procedure of a process executed by a control device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] <First embodiment> Hereinafter, the first embodiment will be described with reference to the drawings. "Prerequisite configuration" A vehicle steering device 10 shown in FIG. 1 is a steer-by-wire type device. The steering device 10 includes a steering wheel 12, a steering shaft 14, a reaction force actuator 20, and a turning actuator 30. The steering shaft 14 is connected to the steering wheel 12. The reaction force actuator 20 is an actuator that applies a force that resists the force with which the driver operates the steering wheel 12. The reaction force actuator 20 includes a reaction force motor 22, a reaction force inverter 24, and a reaction force reduction mechanism 26. The reaction force motor 22 applies a steering reaction force, which is a force that resists steering, to the steering wheel 12 via the steering shaft 14. The reaction force motor 22 is connected to the steering shaft 14 via the reaction force reduction mechanism 26. As an example, a three-phase synchronous motor is used for the reaction force motor 22. The reaction force reduction mechanism 26 is, for example, a worm and wheel.

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

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

[0019] The steering control device 50 refers to the steering torque Th detected by the torque sensor 60 in order to control the control amount. The steering torque Th is the torque applied to the steering shaft 14 by the driver through the operation of the steering wheel 12. The steering control device 50 refers to the rotation angle θa, which is the angle of the rotation shaft of the reaction force motor 22, detected by the steering side rotation angle sensor 62 in order to control the control amount. The steering control device 50 also refers to the currents ius, ivs, iws flowing through the reaction force motor 22 in order to control the control amount. The currents ius, ivs, iws may be detected as the voltage drop amount of a shunt resistor provided in each leg of the reaction force inverter 24, for example. The steering control device 50 refers to the rotation angle θb, which is the angle of the rotation shaft of the steering motor 42, detected by the steering side rotation angle sensor 64 in order to control the control amount. The steering control device 50 also refers to the currents iut, ivt, iwt flowing through the steering motor 42 in order to control the control amount. The currents iut, ivt, iwt may be detected as voltage drops across shunt resistors provided in the respective legs of the steering inverter 44, for example.

[0020] The steering control device 50 is capable of communicating with the braking ECU 70. The braking ECU 70 controls the vehicle's braking device. The braking ECU 70 acquires wheel speeds ωw1 to ωw4, which are the speeds of the four wheels detected by wheel speed sensors 72. If there is no abnormality in the wheel speeds ωw1 to ωw4, the braking ECU 70 transmits this to the steering control device 50. If there is an abnormality in the wheel speeds ωw1 to ωw4, the braking ECU 70 notifies the steering control device 50 of that fact.

[0021] The steering control device 50 is capable of communicating with a host ECU 80. The host ECU 80 executes a process of generating a command to intervene in the steering of the vehicle, independent of a steering command by the operation of the steering wheel 12. In order to execute the process of intervening in the steering, the host ECU 80 acquires image data of the surroundings of the vehicle captured by a camera 82. The host ECU 80 also grasps an indication of intent to intervene in the steering, input by the driver via an interface 84, such as whether or not to intervene in the steering.

[0022] The steering control device 50 includes a PU 52 and a storage device 54. The PU 52 is a software processing device such as a CPU, a GPU, or a TPU. The storage device 54 may be an electrically non-rewritable non-volatile memory. The storage device 54 may also be an electrically rewritable non-volatile memory, or a storage medium such as a disk medium.

[0023] "Control Overview" 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 a program stored in the storage device 54, for example, at a predetermined interval.

[0024] The steering angle calculation process M10 includes a process of converting the rotation angle θa into an integrated angle including a range exceeding 360 degrees, for example, by counting the number of rotations of the reaction force motor 22 from a steering neutral position, which is the position of the steering wheel 12 when the vehicle is moving straight. The steering angle calculation process M10 includes a process of multiplying the integrated angle obtained by conversion by a conversion coefficient based on the rotation speed ratio of the reaction force reduction mechanism 26 to calculate the steering angle θs.

[0025] The turning equivalent angle calculation process M12 includes a process of converting the rotation angle θb into an integrated angle including a range exceeding 360 degrees, for example, by counting the number of rotations of the steering motor 42 from the rack neutral position, which is the position of the rack shaft 32 when the vehicle is traveling straight. The turning equivalent angle calculation process M12 includes a process of multiplying the integrated angle obtained by conversion by a conversion coefficient according to the reduction ratio of the turning transmission mechanism 46 and the lead of the conversion mechanism 48, etc., to calculate the turning equivalent angle θp according to the turning angle of the steered wheels 34. The turning equivalent angle θp is an amount proportional to the turning angle. Note that, as an example, the turning equivalent angle θp is positive when it is an angle to the right of the rack neutral position, and negative when it is an angle to the left of the rack neutral position.

[0026] The target turning equivalent angle calculation process M40 is a process for calculating a target turning equivalent angle θp* in accordance with the steering angle θs and the vehicle speed V. The assist amount setting process M20 is a process 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 steering direction of the driver. The magnitude of the assist amount Ta is set to a large value when the force assisting the steering by the driver is to be increased.

[0027] The axial force setting process M22 is a process that calculates the axial force F acting on the rack shaft 32 through the steered wheels 34 using the vehicle speed V, the q-axis current iqt of the steering motor 42, and the target steering equivalent angle θp* as inputs. The axial force F is a value that expresses the force acting on the rack shaft 32 through the steered wheels 34 by control. However, the axial force F does not necessarily have to be intended to estimate the force acting on the rack shaft 32 with high accuracy. The axial force F may be, for example, a virtually determined force acting on the rack shaft 32. The axial force F is converted into a torque applied to the steering shaft 14. That is, it is converted into a torque applied to the steering shaft 14 when it is assumed that the power transmission between the steered wheels 34 and the steering shaft 14 is possible. The axial force F is an amount that acts in the opposite direction to the steering direction of the driver. The axial force setting process M22 may be a process that calculates the axial force F so that the absolute value of the axial force F increases as the absolute value of the target steering equivalent angle θp* increases. For example, the axial force setting process M22 may be a process for calculating the axial force F such that the absolute value of the axial force F increases as the vehicle speed V increases. The axial force setting process M22 may be a process for calculating the axial force F such that the absolute value of the axial force F increases as the absolute value of the q-axis current iqt increases. Here, the q-axis current iqt is calculated by the PU 52 in accordance with the steering equivalent angle θp and the currents iut, ivt, and iwt.

[0028] 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 Ts1. The target reaction torque Ts1 is a target value of the torque that the reaction motor 22 applies to the steering shaft 14.

[0029] The target steering angle setting process M26 is a process for setting a target steering angle θs* using the target reaction torque Ts1 and the steering torque Th as inputs. The target steering angle setting process M26 is a process for setting a target steering angle θs* using a model. The model determines the target steering angle θs* using the sum of the target reaction torque Ts1 and the steering torque Th as inputs. The model may be a model in which a steering angle corresponding to an ideal steering angle according to an input torque is modeled in advance by experiments or the like, on the premise that a steering device in which the steering wheel 12 and the steered wheels 34 are mechanically connected to each other. The target steering angle setting process M26 is a process for calculating an input torque by adding the target reaction torque Ts1 and the steering torque Th, and then calculating the target steering angle θs* from the input torque based on the model.

[0030] The steering angle feedback process M28 is a process for calculating a feedback correction amount Tfb by inputting the steering angle θs and the target steering angle θs*. The feedback correction amount Tfb is a manipulation amount of the feedback control in which the steering angle θs is a control amount and the target steering angle θs* is a target value of the control amount.

[0031] The superimposition process M30 is a process for substituting a value obtained by adding a feedback correction amount Tfb to the target reaction torque Ts for the target reaction torque Ts. However, when an intervention torque Tin is input from the host ECU 80, the superimposition process M30 is a process for substituting a value obtained by adding the feedback correction amount Tfb and the intervention torque Tin to the target reaction torque Ts for the target reaction torque Ts. The intervention torque Tin is a correction amount of the target reaction torque Ts1 that the host ECU 80 uses to intervene in the steering.

[0032] The reaction force operation signal generation process M32 is a process for generating an operation signal MSs for the reaction force inverter 24 in order to control the torque of the reaction force motor 22 so that the torque applied to the steering shaft 14 becomes the target reaction force torque Ts. More specifically, the reaction force operation signal generation process M32 includes a process for converting the target reaction force torque Ts into a target torque of the reaction force motor 22. The reaction force operation signal generation process M32 also includes a process for calculating an operation signal MSs for the reaction force inverter 24 in order to make the current flowing through the reaction force motor 22 approach a current determined from the target reaction force torque Ts by current feedback control. Note that the operation signal MSs is actually an operation signal for each of the six switching elements of the reaction force inverter 24. By making the torque of the reaction force motor 22 the target reaction force torque Ts, the steering reaction force resisting the force that tries to rotate the steering wheel 12 becomes "(-1)·Ts".

[0033] The target turning equivalent angle calculation process M40 is a process for calculating a target turning equivalent angle θp* in accordance with the steering angle θs and the vehicle speed V. The steering feedback process M42 substitutes the operation amount of the feedback control in which the steering equivalent angle θp is used as a control amount and the target steering equivalent angle θp* is used as a target value of the control amount for the target steering torque Tt. The target steering torque Tt has a constant ratio with the torque of the steering motor 42.

[0034] The steering operation signal generation process M44 is a process for generating an operation signal MSt for the steering inverter 44 in order to control the torque of the steering motor 42 so that the torque of the steering motor 42 becomes a value having a constant ratio with respect to the target steering torque Tt. In particular, the steering operation signal generation process M44 includes a process for converting the target steering torque Tt into a target torque of the steering motor 42. The steering operation signal generation process M44 also includes a process for calculating an operation signal MSt for the steering inverter 44 in order to bring the current flowing through the steering motor 42 close to a current determined from the target torque by current feedback control. Note that the operation signal MSt is actually an operation signal for each of the six switching elements of the steering inverter 44.

[0035] "Assist amount setting process" FIG. 3 shows details of the assist amount setting process M20. The phase lag compensation process M60 is a process for delaying the phase of the steering torque Th. This may be a process for the purpose of performing phase compensation on the steering torque Th in order to adjust the frequency characteristic of the phase difference between both sides of a torsion bar provided in the torque sensor 60, for example. The phase-compensated steering torque Th, which is the output value of the phase lag compensation process M60, is the steering torque Thr. The phase lag compensation process M60 includes a filter process M62 and a filter coefficient setting process M64.

[0036] The filter processing M62 includes a phase lag filter and a low-pass filter. The transfer function of the phase lag filter is "(1+α·T1·s) / (1+T1·s)". The transfer function of the low-pass filter is "1 / (1+T2·s)". The steering torque Thr is the value obtained by processing the steering torque Th through the phase lag filter and the low-pass filter.

[0037] The filter coefficient setting process M64 sets the filter coefficients α and T1 of the phase lag filter and the filter coefficient T2 of the low-pass filter. The filter coefficient setting process M64 sets the filter coefficients α, T1, and T2 according to the assist gradient R and the vehicle speed V. In detail, the filter coefficient setting process M64 is, for example, a process in which the PU 52 performs map calculations of the filter coefficients α, T1, and T2 in a state in which map data is stored in the storage device 54. The map data is of the following three types of data. One is data in which the assist gradient R and the vehicle speed V are input variables and the filter coefficient α is an output variable. Another is data in which the assist gradient R and the vehicle speed V are input variables and the filter coefficient T1 is an output variable. The other is data in which the assist gradient R and the vehicle speed V are input variables and the filter coefficient T2 is an output variable.

[0038] The map data is a set of data consisting of discrete values ​​of input variables and values ​​of output variables corresponding to each of the input variable values. The map calculation may be a process in which, when the value of an input variable matches any of the values ​​of the input variables in the map data, the value of the output variable in the corresponding map data is used as the calculation result. The map calculation may be a process in which, when the value of an input variable does not match any of the values ​​of the input variables in the map data, the value obtained by interpolating the values ​​of multiple output variables included in the map data is used as the calculation result. Alternatively, the map calculation may be a process in which, when the value of an input variable does not match any of the values ​​of the input variables in the map data, the value of the output variable in the map data that corresponds to the closest value among the values ​​of multiple input variables included in the map data is used as the calculation result.

[0039] The basic assist amount setting process M66 is a process for setting a basic assist amount Tab using the steering torque Thr and the vehicle speed V as inputs. The basic assist amount setting process M66 sets the basic assist amount Tab to a value that has a positive correlation with the steering torque Thr. This process may be, for example, a process in which the PU 52 calculates the basic assist amount Tab using a map in a state in which map data is pre-stored in the storage device 54. The map data is data that uses the steering torque Thr and the vehicle speed V as input variables and the basic assist amount Tab as an output variable.

[0040] The basic assist amount setting process M66 includes a process of calculating and outputting an assist gradient R. The assist gradient R indicates the ratio of the change in the basic assist amount Tab to the change in the steering torque Thr.

[0041] The phase lead compensation process M70 is a process for leading the phase of the assist amount Ta. For example, the purpose of this may be to perform phase compensation on the assist amount Ta in order to adjust the response delay of the change in the steering wheel 12 in response to the change in the steering torque Th. The phase lead compensation process M70 includes a differential calculation M72, a gain setting process M74, and a multiplication process M76.

[0042] The differential calculation M72 is a process for calculating a first-order time differential value dTh of the steering torque Th. The gain setting process M74 is a process for setting a gain Gad using the assist gradient R and the vehicle speed V as inputs. As an example, the gain setting process M74 is a process for map-calculating the gain Gad in a state in which map data is pre-stored in the storage device 54. This map data is data that uses the assist gradient R and the vehicle speed V as input variables and the gain Gad as an output variable.

[0043] The multiplication process M76 is a process of multiplying the time differential value dTh by the gain Gad. The product of the time differential value dTh and the gain Gad is the lead compensation amount Tad as the output of the phase lead compensation process M70.

[0044] The synthesis process M80 is a process for adding the lead compensation amount Tad to the basic assist amount Tab. The value calculated in this way is the assist amount Ta. "Phase compensation processing by mode" Fig. 4 shows the procedure for switching the phase compensation by the phase lag compensation process M60 and the phase lead compensation process M70 depending on the mode. The process shown in Fig. 4 is realized by the PU 52 repeatedly executing a program stored in the storage device 54, for example, at a predetermined interval. In the following, the step number of each process is represented by a number preceded by "S".

[0045] 4, the PU 52 determines whether or not the braking ECU 70 has notified the PU 52 that an abnormality has occurred in the detection of the wheel speeds ωw1 to ωw4 (S10). This process is for determining whether or not the vehicle is in a mode in which an abnormality has occurred in the detection value of the vehicle speed.

[0046] When the PU 52 determines that no notification has been made (S10: NO), the PU 52 is in the normal mode and therefore acquires the wheel speeds ωw1 to ωw4 via the brake ECU 70 (S12). Then, the PU 52 calculates the vehicle speed V from the wheel speeds ωw1 to ωw4 (S14). The vehicle speed V may be, for example, a predetermined number-th largest value among the wheel speeds ωw1 to ωw4. Alternatively, the vehicle speed V may be, for example, an average value of the wheel speeds ωw1 to ωw4.

[0047] Then, the PU 52 assigns the normal mode variable value Vmn to a map specifying variable Vm that specifies a map for performing map calculations on the filter coefficients α, T1, T2 and the gain Gad (S16). As a result, the filter coefficient setting process M64 becomes a process of performing map calculations using the map data for the normal mode out of the map data for the normal mode and the map data for the abnormal mode stored in the storage device 54. Also, the gain setting process M74 becomes a process of performing map calculations using the map data for the normal mode out of the map data for the normal mode and the map data for the abnormal mode stored in the storage device 54.

[0048] On the other hand, when it is determined that a notification has been made (S10: YES), the PU 52 assigns the abnormal mode variable value Vmi to the map specifying variable Vm (S18). As a result, the filter coefficient setting process M64 becomes a process of performing map calculation using the map data for the abnormal mode out of the map data for the normal mode and the map data for the abnormal mode stored in the storage device 54. Here, the map data does not need to use the vehicle speed V as an input variable. Also, the gain setting process M74 becomes a process of performing map calculation using the map data for the abnormal mode out of the map data for the normal mode and the map data for the abnormal mode stored in the storage device 54. Here, the map data does not need to use the vehicle speed V as an input variable.

[0049] When the processes of S16 and S18 are completed, the PU 52 temporarily ends the series of processes shown in FIG. "Actions and Effects of the Present Embodiment" The PU 52 sets a 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 PU 52 sets the assist amount Ta by using a phase lag compensation process M60 and a phase lead compensation process M70. The filter coefficients α, T1, and T2 in the phase lag compensation process M60 and the gain Gad in the phase lead compensation process M70 are set according to the vehicle speed V. This makes it possible to perform appropriate phase compensation that can keep the steering system stable according to the vehicle speed V.

[0050] However, if an abnormality occurs in the detection of the wheel speeds ωw1 to ωw4, the vehicle speed V cannot be used with high reliability in setting the filter coefficients α, T1, T2 and the gain Gad to appropriate values. Therefore, in the above-mentioned abnormality, the PU 62 sets the filter coefficients α, T1, T2 and the gain Gad to values ​​for abnormality. This allows the filter coefficients α, T1, T2 and the gain Gad to be set to values ​​appropriate for stabilizing the steering system even if the PU 52 cannot grasp the accurate vehicle speed. In other words, the filter coefficients α, T1, T2 and the gain Gad to be set to values ​​appropriate for stabilizing the steering system regardless of the magnitude of the actual vehicle speed. Here, the filter coefficients α, T1, T2 and the gain Gad may be set to values ​​that can stabilize the steering system within a range of values ​​that can be taken as the actual vehicle speed, for example.

[0051] Incidentally, under normal circumstances, the filter coefficients α, T1, T2 and the gain Gad are changed in accordance with the vehicle speed V, so that optimal phase compensation can be realized within a range in which the steering system can be stabilized.

[0052] <Second embodiment> The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0053] In this embodiment, the manner of phase compensation is changed depending on whether the host ECU 80 intervenes in steering to prevent deviation from the lane or does not intervene in steering. 5 shows a procedure for switching between phase compensation by the phase lag compensation process M60 and the phase lead compensation process M70 depending on the mode. The process shown in FIG. 5 is realized by the PU 52 repeatedly executing a program stored in the storage device 54, for example, at a predetermined interval.

[0054] In the series of processes shown in FIG. 5, the PU 52 first determines whether or not the departure prevention processing mode is selected (S20). The departure prevention processing mode is a mode in which the host ECU 80 executes control for suppressing departure from the lane based on the image data. When the PU 52 determines that the departure prevention processing mode is not selected (S20: NO), the PU 52 assigns the variable value Vmm for the manual driving mode to the map specific variable Vm (S22). As a result, the filter coefficient setting process M64 becomes a process of performing map calculation using the map data for the manual driving mode out of the map data for the manual driving mode and the map data for the departure prevention mode stored in the storage device 54. In addition, the gain setting process M74 becomes a process of performing map calculation using the map data for the manual driving mode out of the map data for the manual driving mode and the map data for the departure prevention mode stored in the storage device 54.

[0055] On the other hand, when it is determined that the departure prevention processing mode is in effect (S20: YES), the PU 52 assigns the departure prevention mode variable value Vma to the map specifying variable Vm (S24). As a result, the filter coefficient setting process M64 becomes a process of performing map calculations using the map data for the departure prevention mode out of the map data for the manual driving mode and the map data for the departure prevention mode stored in the storage device 54. In addition, the gain setting process M74 becomes a process of performing map calculations using the map data for the departure prevention mode out of the map data for the manual driving mode and the map data for the departure prevention mode stored in the storage device 54.

[0056] When the PU 52 completes the processes of S22 and S24, the PU 52 temporarily ends the series of processes shown in FIG. <Correspondence> The correspondence between the items in the above embodiment and the items described in the above "Means for solving the problem" column is as follows. In the following, the correspondence is shown for each number of the solving means described in the "Means for solving the problem" column. [1,5,6] The reaction force setting process corresponds to the assist amount setting process M20, the axial force setting process M22, the subtraction process M24, the target steering angle setting process M26, the steering angle feedback process M28, and the superposition process M30. The reaction force application process corresponds to the reaction force operation signal generation process M32. The phase compensation process corresponds to the phase lag compensation process M60 and the advance compensation process M70. The driving mode corresponds to a mode in which it has not been determined that there is an abnormality in the vehicle speed and a mode in which it has been determined that there is an abnormality. In addition, the driving mode corresponds to the departure prevention process mode and the manual driving mode. [2,3] The phase compensation regulation variable corresponds to the filter coefficient α, T1, T2, and the gain Gad. The variable change process corresponds to the filter coefficient setting process M64 and the gain setting process M74. The abnormality values ​​correspond to the filter coefficients α, T1, T2, and gain Gad that are set using a map corresponding to the abnormality mode variable value Vmi. [4] The intervention mode corresponds to the deviation prevention processing mode. The non-intervention mode corresponds to the manual driving mode. The phase compensation variable values ​​in the intervention mode correspond to the filter coefficients α, T1, T2, and gain Gad that are set using a map corresponding to the deviation prevention mode variable value Vma. The phase compensation variable values ​​in the non-intervention mode correspond to the filter coefficients α, T1, T2, and gain Gad that are set using a map corresponding to the manual driving mode variable value Vmm.

[0057] <Other embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0058] "About phase lag compensation processing" The filter coefficient setting process M64 is not limited to a process that uses the vehicle speed V, the assist gradient R, and the map specific variable Vm as input. For example, the input to the filter coefficient setting process M64 may be the assist gradient R and the map specific variable Vm. Also, for example, the input to the filter coefficient setting process M64 may be the vehicle speed V and the map specific variable Vm.

[0059] The phase lag filter included in the filter processing M62 is not limited to the above-mentioned filter in which the orders of the Laplace operators in the numerator and denominator are both 1. It is not essential that the filtering process M62 includes a phase lag filter and a low-pass filter. For example, it may include only a phase lag filter.

[0060] In the above embodiment, the filter coefficients α, T1, and T2 are subject to change by the filter coefficient setting process M64, but this is not limiting. For example, only two of the three filter coefficients α, T1, and T2 may be subject to change. Also, for example, only one of the three filter coefficients α, T1, and T2 may be subject to change.

[0061] "About phase lead compensation processing" The gain setting process M74 is not limited to a process that uses the vehicle speed V, the assist gradient R, and the map specific variable Vm as input. For example, the input to the gain setting process M74 may be the assist gradient R and the map specific variable Vm. Also, for example, the input to the gain setting process M74 may be the vehicle speed V and the map specific variable Vm.

[0062] A low-pass filter may be provided between the differential calculation M72 and the multiplication process M76. In this case, the filter coefficient of the low-pass filter may be changed according to the driving mode. Instead of multiplying the time differential value dTh by the gain Gad in the multiplication process M76, map data may be provided that inputs the time differential value dTh and outputs the lead compensation amount Tad. The input variables of this map data may include a variable indicating the driving mode in addition to the time differential value dTh. Also, the input variables of this map data may include a variable indicating the vehicle speed V in addition to the time differential value dTh.

[0063] The phase lead compensation process does not necessarily have to include a process of calculating the time differential value dTh. For example, instead of calculating the time differential value dTh, the phase lead compensation process may include a process of inputting the steering torque Th to a phase lead compensation filter.

[0064] "About phase compensation processing" The phase compensation process does not necessarily have to consist of the phase lag compensation process M60 and the phase lead compensation process M70. For example, the phase compensation process may include only one of the two processes, the phase lag compensation process M60 and the phase lead compensation process M70. Also, the phase compensation process may include a process other than the two processes, the phase lag compensation process M60 and the phase lead compensation process M70.

[0065] "About axial force setting process" The inputs for the axial force setting process do not necessarily have to be the q-axis current iqt, the vehicle speed V, and the target steering equivalent angle θp*. For example, the angle variable of the steering system is not limited to the target steering equivalent angle θp*, and may be the steering equivalent angle θp. Also, for example, the angle variable of the steering system may be the steering angle θs. The inputs for the axial force setting process may be only any two of the three, q-axis current iqt, the vehicle speed V, and the angle variable of the steering system. Also, the input for the axial force setting process may be only one of the above three.

[0066] "About phase compensation regulation variables with different values ​​in different modes" In the above embodiment, all of the filter coefficients α, T1, and T2 of the phase lag compensation process M60 are changed using the map specific variable Vm as an input, but this is not limited to the above. For example, only two of the three filter coefficients α, T1, and T2 may be changed using the map specific variable Vm as an input. Also, for example, only one of the three filter coefficients α, T1, and T2 may be changed using the map specific variable Vm as an input.

[0067] When both the phase lag compensation process M60 and the phase lead compensation process M70 are executed, it is not essential to change the phase compensation method for both of them depending on the mode. For example, only one of the two may be changed.

[0068] "Modes with different phase compensation methods" The mode in which an abnormality has been diagnosed and the normal mode are not limited to modes according to the presence or absence of an abnormality in the detected value of the vehicle speed V. For example, the mode may be a mode according to the presence or absence of an abnormality in the torque sensor 60. Also, for example, in a redundant system in which the steering control device 50 has a plurality of PUs 52, the mode may be a mode according to whether or not there is an abnormality in any one of the PUs 52. Also, for example, in a redundant system in which the steering control device 50 has a plurality of PUs 52, the mode may be a mode according to whether or not there is an abnormality in communication between the PUs 52.

[0069] The intervention mode and the non-intervention mode are not limited to the departure prevention processing mode and the manual driving mode. For example, the intervention mode may be a mode in which the host ECU 80 executes a process to steer the steered wheels 34 while the driver is not touching the steering wheel 12. Even in that case, for example, when the intervention torque Tin is input to the input portion of the steering torque Th instead of inputting the intervention torque Tin to the superposition processing M30, it is effective to change the filter coefficients α, T1, T2 and the gain Gad according to the mode.

[0070] In the process of S20, it is determined whether or not the departure prevention process mode is selected. However, instead of this, it may be determined whether or not the intervention torque Tin is input from the host ECU 80, for example.

[0071] "About steering control devices" The steering control device is not limited to one that executes software processing. For example, it may be equipped with a dedicated hardware circuit such as an ASIC that executes at least a part of the processing executed in the above embodiment. That is, the steering control device may include a processing circuit having any of the following configurations (a) to (c). (a) A processing circuit equipped with a processing device that executes all of the above processing according to a program, and a program storage device such as a memory device that stores the program. (b) A processing circuit equipped with a processing device and a program storage device that executes part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) A processing circuit equipped with a dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software execution devices equipped with a processing device and a program storage device. Also, there may be multiple dedicated hardware circuits.

[0072] "Others" The steering motor 42 does not necessarily have to be a synchronous motor. For example, it may be an induction motor.

[0073] In each of the above embodiments, the steering device 10 has a linkless structure in which the steering wheel 12 and the steered wheels 34 are mechanically separated at all times. However, the present invention is not limited to this structure, and the steering device 10 may have a structure in which the steering wheel 12 and the steered wheels 34 can be mechanically separated by a clutch. [Explanation of symbols]

[0074] 10...Steering gear 12…Steering wheel 14…Steering shaft 20…Reaction actuator 22…Reaction motor 24…Reaction force inverter 30...Steering actuator 32…Rack shaft 34…Steering wheel 42...Steering motor 44…Steering inverter 50...Steering control device

Claims

1. A steering system including a reaction motor that applies a steering reaction force to a steering shaft and a steering motor that steers steered wheels is set as a control object, A reaction force setting process, a phase compensation process, and a reaction force application process are executed. the reaction force setting process is a process of setting the steering reaction force by utilizing the phase compensation process, the reaction force applying process is a process of operating the reaction force motor so as to achieve the reaction force set by the reaction force setting process, A steering control device, wherein the phase compensation process performs phase compensation for the steering reaction force in different ways when the vehicle driving mode is different.

2. 2. The steering control device according to claim 1, wherein the driving modes in which the phase compensation method is different include a mode in which an abnormality has been diagnosed and a normal mode.

3. the phase compensation process is a process for compensating the phase of the steering reaction force in accordance with a value of a phase compensation definition variable, and includes a variable change process; the phase compensation defining variable is a variable that defines a manner of the phase compensation, the variable changing process includes a process of changing a value of the phase compensation defining variable in response to a vehicle speed, The mode in which the abnormality is diagnosed includes a mode in which the abnormality is diagnosed in the detection value of the vehicle speed, 3. The steering control device according to claim 2, wherein the phase compensation process includes a process of executing the phase compensation with the value of the phase compensation defined variable set to the abnormality value in a mode in which an abnormality has been diagnosed in the detected value of the vehicle speed.

4. The driving modes in which the phase compensation method is different include an intervention mode and a non-intervention mode, the intervention mode is a mode in which a control intervenes in the steering of the steered wheels in response to relationship information between a vehicle and the outside of the vehicle, The non-intervention mode is a mode in which the intervention is not performed, the phase compensation process is a process of performing phase compensation for the steering reaction force in accordance with a value of a phase compensation definition variable, the phase compensation defining variable is a variable that defines a manner of the phase compensation, 2. The steering control device according to claim 1, wherein the phase compensation process includes a process of executing the phase compensation in accordance with a value of the phase compensation defining variable, which differs between the intervention mode and the non-intervention mode.

5. The reaction force setting process includes an assist amount setting process and an axial force setting process, the axial force setting process is a process for setting an axial force which is a force resisting a rotation operation of the steering shaft by a driver, The assist amount setting process is a process for setting an assist amount in accordance with a detected value of a steering torque, the assist amount is an amount of assistance given to a driver in rotating the steering shaft, the steering reaction force is an amount determined in accordance with a value obtained by subtracting the assist amount from the axial force, The phase compensation process includes a phase lag compensation process, the phase lag compensation process is a process of delaying a phase of the detection value used for setting the assist amount in accordance with a lag defining variable; 2. The steering control device according to claim 1, wherein the delay defining variable is a variable that defines the phase delay compensation process and has a different value when the driving mode is different.

6. The reaction force setting process includes an assist amount setting process and an axial force setting process, the axial force setting process is a process for setting an axial force which is a force resisting a rotation operation of the steering shaft by a driver, the assist amount setting process is a process for setting an assist amount, and includes the phase compensation process and a basic assist amount setting process, the assist amount is an amount of assistance given to a driver in rotating the steering shaft, the basic assist amount setting process is a process for setting a basic assist amount in response to a detection value of a steering torque input to the steering shaft, The phase compensation process includes a phase lead compensation process, the phase lead compensation process is a process in which the detection value is used as an input to calculate a lead correction amount of the basic assist amount in accordance with a lead definition variable, the lead correction amount being used by the assist amount setting process to set the assist amount from the basic assist amount; the steering reaction force is an amount determined in accordance with a value obtained by subtracting the assist amount from the axial force, The steering control device according to claim 1 , wherein the phase lead defining variable is a variable that defines the phase lead compensation process and has a different value when the driving mode is different.

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