Steering control device

Abstract

The steering control device (50) includes a software processing device. The software processing device is configured to perform an assist amount setting process, an axial force setting process, and a reaction force applying process. In the assist amount setting process, the assist amount is set using an output value of the first damping process that outputs a first damping correction amount having a correlation with the steering angular velocity. In the axial force setting process, the axial force is set using an output value of the second damping process that outputs a second damping correction amount having a positive correlation with the steering angular velocity. In the reaction force application process, a value obtained by subtracting the axial force from the assist amount is input, and the reaction force motor (22) is operated.

Description

Technical Field

[0001] The present disclosure relates to steering control devices. Background Art

[0002] For example, Japanese Unexamined Patent Application Publication No. 2022-160308 (JP 2022-160308 A) discloses a steering control device mounted on a wire steering system. The control device sets a steering force and an axial force, which is a force in the direction in which the driver steers the steering wheel. The control device controls the torque of a motor that applies a reaction force to the steering wheel according to a value obtained by subtracting the axial force from the steering force. Summary of the invention

[0003] Incidentally, the inventors have found a phenomenon in which the steering system is unstable such as vibration of the steering wheel in the case where the torque of the motor is increased.

[0004] Hereinafter, means for solving the above problems and their effects will be described.

[0005] Configuration 1. An aspect of the present disclosure relates to a steering control device including a software processing device. The software processing device sets a steering system as a control target. The steering system includes: a reaction force motor configured to apply a steering reaction force to a steering shaft; and a steering motor configured to steer a steering wheel in a state where power transmission from the steering shaft is cut off. The software processing device is configured to perform an assist amount setting process, an axial force setting process, and a reaction force application process. In the assist amount setting process, an assist amount is set while using an output value of a first damping process, wherein the assist amount is an amount of assisting a driver in rotating the steering shaft. In the axial force setting process, an axial force is set while using an output value of a second damping process, wherein the axial force is a force that resists a driver's rotational operation of the steering shaft. In the reaction force application process, a value obtained by subtracting the axial force from the assist amount is an input, and the reaction force motor is operated. In the first damping process, a first damping correction amount having a correlation with a steering angular velocity is an output. In the second damping process, a second damping correction amount having a positive correlation with the steering angular velocity is output.

[0006] In the above configuration, since the second damping process is newly provided, it is possible to suppress the steering system from becoming unstable in the case where the second damping correction amount is used.

[0007] Configuration 2. In the steering control device according to configuration 1, the software processing device may be configured to perform a second gain adjustment process that adjusts a second gain as a gain of the second damping process according to a value of a torque-related variable. The torque-related variable may be a variable having a correlation with the torque of the reaction force motor.

[0008] The torque correlation coefficient has a positive correlation with the torque of the reaction force motor and the steering torque, which is the torque input to the steering shaft by the driver. When the absolute value of the torque of the reaction force motor is large, when the absolute value of the steering torque is too large, etc., the steering system may become unstable. Therefore, in the above configuration, in the case of understanding that the steering system may become unstable, the gain of the second damping process can be adjusted according to the situation by the torque correlation coefficient. Therefore, an appropriate gain can be set when suppressing the steering system from becoming unstable.

[0009] Configuration 3. In the steering control device according to configuration 2, in the second gain adjustment process, in addition to the value of the torque-related variable, the second gain can be adjusted according to the vehicle speed. In the above configuration, the second gain is set according to the vehicle speed. Therefore, compared with the case where the second gain is set without referring to the vehicle speed, the second gain can be set more appropriately according to the situation where stability may be reduced.

[0010] Configuration 4. In the steering control device according to any one of configurations 1 to 3, in the assist amount setting process, the assist amount may be set while using output values ​​of a plurality of compensation processes including the first damping process. The software processing device may be configured to perform a compensation gain adjustment process that adjusts a compensation gain that is a gain of at least one of the plurality of compensation processes according to a value of a torque-related variable. The torque-related variable may be a variable having a correlation with the torque of the reaction force motor.

[0011] The torque correlation coefficient has a positive correlation with the torque of the reaction force motor and the steering torque, which is the torque input to the steering shaft by the driver. When the absolute value of the torque of the reaction force motor is large, when the absolute value of the steering torque is too large, etc., the steering system may be unstable. Therefore, in the above configuration, in the case of understanding that the steering system may be unstable, the gain of the compensation process can be adjusted according to the situation by the torque correlation coefficient. Therefore, the output of the compensation process can be adjusted to an appropriate value according to the situation that the stability may be reduced.

[0012] Configuration 5. In the steering control device according to configuration 4, in the compensation gain adjustment process, the compensation gain may be adjusted according to the vehicle speed in addition to the value of the torque-related variable. In the above configuration, the compensation gain is set according to the vehicle speed. Therefore, compared with the case where the compensation gain is set without referring to the vehicle speed, the compensation gain can be set more appropriately according to the situation where stability may be reduced.

[0013] Configuration 6. In the steering control device according to any one of Configurations 2 to 5, the torque-related variable may be the steering torque. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0015] Figure 1 is a diagram showing a configuration of a steering system according to an embodiment of the present disclosure;

[0016] Figure 2 It is shown by Figure 1 A block diagram of a process performed by a control device shown in;

[0017] Figure 3 It is shown by Figure 1 A block diagram of a process performed by a control device shown in FIG.

[0018] Figure 4 It is shown by Figure 1 A block diagram of a process performed by a control device shown in FIG. DETAILED DESCRIPTION

[0019] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0020] Prerequisite Configuration

[0021] Figure 1The steering device 10 of the vehicle shown in the figure is a wire-controlled steering 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 applies a force that resists the force of the driver operating the steering wheel 12. The reaction force actuator 20 has 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 to the steering wheel 12 via the steering shaft 14, and the steering reaction force is a force that resists the steering operation. 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 adopted as the reaction force motor 22. The reaction force reduction mechanism 26 is, for example, a worm and a worm wheel.

[0022] The steering actuator 30 has the purpose of steering the steering wheel 34 in response to the driver's steering manipulation intention indicated by the driver operating 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. As an example, a three-phase surface permanent magnet synchronous motor (SPM) is used as the steering motor 42. The steering transmission mechanism 46 is 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 the displacement power of the rack shaft 32 in the axial direction. The steering wheel 34 is steered by the displacement of the rack shaft 32 in the axial direction.

[0023] 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 be an electrically rewritable non-volatile memory or a storage medium such as a disk medium. When the program stored in the storage device 54 is executed by the PU 52, the steering control device 50 controls the control target.

[0024] The control targets of the steering control device 50 are the steering wheel 12 and the steering wheel 34. That is, the steering control device 50 controls the steering reaction force that resists the driver's steering, and the steering reaction force is the control amount of the steering wheel 12 as the control target. In addition, the steering control device 50 controls the steering angle, which is the control amount of the steering wheel 34 as the control target. The steering angle is the cutting angle of the tire of the steering wheel 34.

[0025] The steering control device 50 controls the control amount with reference to the steering torque Th detected by the torque sensor 60. The steering torque Th is applied to the steering shaft 14 by the driver through the operation of the steering wheel 12. The steering control device 50 controls the control amount with reference to the rotation angle θa detected by the steering side rotation angle sensor 62, that is, the angle of the rotation shaft of the reaction force motor 22. In addition, the steering control device 50 controls the control amount with reference to the currents ius, ivs, and iws flowing through the reaction force motor 22. For example, the currents ius, ivs, and iws can be detected as the voltage drop of the shunt resistor provided in the corresponding branch of the reaction force inverter 24. The steering control device 50 controls the control amount with reference to the rotation angle θb detected by the steering side rotation angle sensor 64, that is, the angle of the rotation shaft of the steering motor 42. In addition, the steering control device 50 controls the control amount with reference to the currents iut, ivt, and iwt flowing through the steering motor 42. For example, the currents iut, ivt, and iwt may be detected as voltage drops of shunt resistors provided in corresponding branches of the steering inverter 44. The steering control device 50 refers to the vehicle speed V detected by the vehicle speed sensor 66.

[0026] Overview of Control

[0027] Figure 2 The processing executed by the steering control device 50 is shown. Figure 2 The processing shown in FIG. 5 is realized by the PU 52 repeatedly executing a program stored in the storage device 54, for example, in a predetermined cycle.

[0028] The steering angle calculation process M10 includes, for example, counting the number of rotations of the reaction force motor 22 from the steering neutral position, i.e., the position of the steering wheel 12 when the vehicle is traveling straight, to convert the rotation angle θa into an integral angle including a range exceeding 360 degrees. The steering angle calculation process M10 includes a process of multiplying the integral angle obtained by the conversion by a conversion coefficient based on the rotation speed ratio of the reaction force reducing mechanism 26 to calculate the steering angle θs.

[0029] The steering equivalent angle calculation process M12 includes the following processes: for example, the number of rotations of the steering motor 42 starting from the rack neutral position, that is, the position of the rack shaft 32 when the vehicle is traveling straight, is counted to convert the rotation angle θb into an integral angle including a range exceeding 360 degrees. The steering equivalent angle calculation process M12 includes the following processes: the integral angle obtained by the conversion is multiplied by the reduction ratio of the steering transmission mechanism 46 and the conversion coefficient according to the lead of the conversion mechanism 48, etc., to calculate the steering equivalent angle θp according to the steering angle of the steering wheel 34. The steering equivalent angle θp is a quantity that is proportional to the steering angle. As an example, when the angle is on the right side of the rack neutral position, the steering equivalent angle θp is positive, and when the angle is on the left side thereof, the steering equivalent angle θp is negative.

[0030] In the target steering equivalent angle calculation process M18, the steering operation angle θs and the vehicle speed V are inputs, and the target steering equivalent angle θp* is output. For example, in the target steering equivalent angle calculation process M18, the target steering equivalent angle θp* may be calculated as a value having the same sign as the steering operation angle θs. In the target steering equivalent angle calculation process M18, the target steering equivalent angle θp* may be changed according to the steering operation angle θs under the condition that the target steering equivalent angle θp* when the absolute value of the steering operation angle θs is large is equal to or greater than the target steering equivalent angle θp* when the absolute value of the steering operation angle θs is small.

[0031] In the description of "B is changed according to A under the condition that B when A is large is equal to or greater than B when A is small", when A is large and when A is small mean a relative size relationship when the two are compared. For example, "when A is large" corresponds to "when A is a first value", and "when A is small" corresponds to "when A is a second value less than the first value". According to the above description, B when A is the first value may be greater than B when A is the second value according to the settings of the first value and the second value.

[0032] In the assist amount setting process M20, the steering torque Th and the vehicle speed V are inputs, and the assist amount Ta is output. The assist amount Ta is an amount in the same direction as the driver's steering direction. When the force assisting the driver's steering increases, the magnitude of the assist amount Ta is set to a large value.

[0033] In the axial force setting process M22, the vehicle speed V, the q-axis current iqt of the steering motor 42 and the target steering equivalent angle θp* are inputs, and the axial force F is output. The axial force F is a value representing the force acting on the rack shaft 32 via the steering wheel 34 through control. However, the axial force F is not necessarily intended to estimate the force acting on the rack shaft 32 with high accuracy. The axial force F can be, for example, an actually determined force acting on the rack shaft 32. The axial force F is converted into a torque added to the steering shaft 14. That is, when the power transmission between the steering wheel 34 and the steering shaft 14 is assumed to be in a possible state, the axial force F is converted into a torque added to the steering shaft 14. The axial force F is a quantity acting in the direction opposite to the driver's steering direction. The q-axis current iqt is calculated by PU 52 based on the steering equivalent angle θp and the currents iut, ivt and iwt.

[0034] In the subtraction process M24 , a value obtained by subtracting the axial force F from the assist amount Ta is substituted into the target reaction torque Ts. The target reaction torque Ts is a target value of torque added to the steering shaft 14 by the reaction motor 22 .

[0035] In the operation signal generation process M26 for reaction force, an operation signal MSs for the reaction force inverter 24 is generated to control the torque of the reaction force motor 22 so that the torque added to the steering shaft 14 is the target reaction force torque Ts. Specifically, the operation signal generation process M26 for reaction force includes a process of converting the target reaction force torque Ts into a target torque of the reaction force motor 22. In addition, the operation signal generation process M26 for reaction force includes the following process: the operation signal MSs for the reaction force inverter 24 is calculated by feedback control of the current so that the current flowing through the reaction force motor 22 is close to the current determined according to the target torque. In practice, the operation signal MSs is for each of the six switching elements of the reaction force inverter 24. The target reaction force torque Ts is generally a quantity having an opposite sign to the auxiliary amount Ta. This is because the absolute value of the axial force F is generally greater than the absolute value of the auxiliary amount Ta.

[0036] In the steering feedback process M30 , the operation amount of feedback control in which the steering equivalent angle θp is the control amount and the target steering equivalent angle θp* is the target value of the control amount is substituted into the target steering torque Tt*. The target steering torque Tt* has a constant ratio with the torque of the steering motor 42 .

[0037] In the operation signal generation process M32 for steering, an operation signal MSt for the steering inverter 44 is generated to control the torque of the steering motor 42 so that the torque of the steering motor 42 is a value having a constant ratio with the target steering torque Tt*. Specifically, the operation signal generation process M32 for steering includes the following process: converting the target steering torque Tt* into the target torque of the steering motor 42. In addition, the operation signal generation process M32 for steering includes the following process: calculating the operation signal MSt for the steering inverter 44 through feedback control of the current so that the current flowing through the steering motor 42 is close to the current determined according to the target torque. In practice, the operation signal MSt is for each of the six switching elements of the steering inverter 44.

[0038] Auxiliary quantity setting process

[0039] Figure 3 Details of the assist amount setting process M20 are shown. In the phase delay compensation process M40, the phase of the steering torque Th is delayed. For example, in the phase delay compensation process M40, phase compensation for the steering torque Th can be performed to adjust the frequency characteristics of the phase difference between the two sides of the torsion bar included in the torque sensor 60. The steering torque Th after the phase compensation, that is, the output value of the phase delay compensation process M40 is the steering torque Thr. The phase delay compensation process M40 includes a filter process M42 and a filter coefficient setting process M44.

[0040] The filter processing M42 includes a phase delay filter and a low-pass filter. The transfer function of the phase delay filter is "(1+α·T1·s) / (1+T1·s)". The transfer function of the low-pass filter is "1 / (1+T2·s)". The value obtained by performing processing on the steering torque Th by the phase delay filter and the low-pass filter is the steering torque Thr.

[0041] In the filter coefficient setting process M44, filter coefficients α, T1 of the phase delay filter and filter coefficient T2 of the low pass filter are set. In the filter coefficient setting process M44, the assist gradient R and vehicle speed V described below are inputs, and filter coefficients α, T1 and T2 are outputs.

[0042] In the basic assistance amount setting process M46, the steering torque Thr and the vehicle speed V are inputs, and the basic assistance amount Tab is an output. In the basic assistance amount setting process M46, the basic assistance amount Tab is set to a value having a positive correlation with the steering torque Thr. The basic assistance amount setting process M46 may be a process in which, for example, the mapping calculation of the basic assistance amount Tab is performed by the PU 52 in a state in which mapping data is pre-stored in the storage device 54. In the mapping data, the steering torque Thr and the vehicle speed V are input variables, and the basic assistance amount Tab is an output variable.

[0043] The mapping data is a set of discrete values ​​of input variables and values ​​of output variables corresponding to each of the values ​​of the input variables. In addition, the mapping calculation may be a process in which, when the value of the input variable matches any one of the values ​​of the input variables of the mapping data, the corresponding value of the output variable of the mapping data is set as the calculation result. In addition, the mapping calculation may be a process in which, when the value of the input variable does not match any one of the values ​​of the input variables of the mapping data, a value obtained by interpolating a plurality of values ​​of the output variable included in the mapping data is set as the calculation result. In addition, in place of the above, the mapping calculation may be a process in which, when the value of the input variable does not match any one of the values ​​of the input variables of the mapping data, the value of the output variable of the mapping data corresponding to the closest value among the plurality of values ​​of the input variable included in the mapping data is set as the calculation result.

[0044] The basic assistance amount setting process M46 includes a process of calculating and outputting an assistance gradient R. The assistance gradient R indicates a ratio of a change in the basic assistance amount Tab to a change in the steering torque Thr.

[0045] In the phase advance compensation process M50, the phase of the assist amount Ta is advanced. The phase advance compensation process M50 may be a process that, for example, performs phase compensation on the assist amount Ta to adjust the response delay of the change of the steering wheel 12 to the change of the steering torque Th. The phase advance compensation process M50 includes a differential calculation M52, a gain setting process M54, and a multiplication process M56.

[0046] In the differential calculation M52, the first-order time differential value dTh of the steering torque Th is calculated. In the gain setting process M54, the assist gradient R and the vehicle speed V are inputs, and the gain Gad is output. In the gain setting process M54, mapping calculation of the gain Gad can be performed in a state where mapping data is pre-stored in the storage device 54. In the mapping data, the assist gradient R and the vehicle speed V are input variables, and the gain Gad is an output variable.

[0047] In the multiplication process M56, the time differential value dTh is multiplied by the gain Gad. The product of the time differential value dTh and the gain Gad is the phase advance compensation amount Tad which is the output of the phase advance compensation process M50.

[0048] In the hysteresis processing M60, the hysteresis correction amount Thys is calculated. The hysteresis correction amount Thys is an amount for setting the assist amount Ta to different values ​​as the steering wheel 12 is turned back and forth. In the hysteresis processing M60, the steering angle θs and the vehicle speed V are inputs, and the hysteresis correction amount Thys is an output. As an example, in the hysteresis processing M60, the PU 52 performs mapping calculation on the hysteresis correction amount Thys in a state where mapping data is pre-stored in the storage device 54. In the mapping data, the steering angle θs and the vehicle speed V are input variables, and the hysteresis correction amount Thys is an output variable.

[0049] In the first damping process M70, a first damping correction amount Tdampa0 is calculated that has a negative correlation with the rotation speed of the steering wheel 12. The first damping correction amount Tdampa0 is a correction amount for applying a viscous resistance to the operation of the steering wheel 12 by control. The first damping process M70 includes a differential calculation M72 and a first correction amount setting process M74.

[0050] In the differential calculation M72, the first-order time differential value of the steering angle θs is calculated. The time differential value is the steering speed ωs. In the first correction amount setting process M74, the first damping correction amount Tdampa0 having a negative correlation with the steering speed ωs is calculated. The first damping correction amount Tdampa0 has a torque dimension. In the first correction amount setting process M74, the mapping calculation of the first damping correction amount Tdampa0 can be performed by the PU 52 in a state where the mapping data is pre-stored in the storage device 54. In the mapping data, the steering speed ωs is an input variable, and the first damping correction amount Tdampa0 is an output variable.

[0051] In the first gain adjustment process M76, the steering torque Th and the vehicle speed V are inputs, and the first gain G1 is an output. As an example, in the first gain adjustment process M76, the PU 52 performs a map calculation on the first gain G1 in a state where map data is pre-stored in the storage device 54. In the map data, the steering torque Th and the vehicle speed V are input variables, and the first gain G1 is an output variable.

[0052] In the multiplication process M78, the value obtained by multiplying the first damping correction amount Tdampa0 by the first gain G1 is substituted into the first damping correction amount Tdampa. In the steering return process M80, the return correction amount Trv is calculated. The return correction amount Trv is a correction amount for returning the steering wheel 12 to the neutral position. The return correction amount Trv has a torque dimension. The steering return process M80 includes a differential calculation M81, a target steering speed setting process M82, a deviation calculation process M83, a basic compensation amount calculation process M84, a speed gain setting process M85, a torque gain setting process M86, and a multiplication process M87.

[0053] In the differential calculation M81, the steering angle θs is an input, and the steering speed ωs, that is, the first-order time differential value of the steering angle θs, is an output. In the target steering speed setting process M82, the steering angle θs and the vehicle speed V are inputs, and the target steering speed ωs* is an output. In the target steering speed setting process M82, the PU 52 can perform a mapping calculation on the target steering speed ωs* in a state where the mapping data is pre-stored in the storage device 54. In the mapping data, the steering angle θs and the vehicle speed V are input variables, and the target steering speed ωs* is an output variable. In the deviation calculation process M83, the deviation Δω between the target steering speed ωs* and the steering speed ωs is calculated. In the basic compensation amount calculation process M84, the basic compensation amount Trvb is calculated with the deviation Δω as an input. In the speed gain setting process M85, the vehicle speed V is an input, and the speed gain Gv is an output. In the speed gain setting process M85, the speed gain Gv can be mapped by the PU 52 in a state where the mapping data is pre-stored in the storage device 54. In the mapping data, the vehicle speed V is an input variable, and the speed gain Gv is an output variable. In the torque gain setting process M86, the steering torque Th is an input variable, and the torque gain Gt is an output. In the torque gain setting process M86, the torque gain Gt can be mapped by the PU 52 in a state where the mapping data is pre-stored in the storage device 54. In the mapping data, the steering torque Th is an input variable, and the torque gain Gt is an output variable. In the multiplication process M87, the value obtained by multiplying the basic compensation amount Trvb by the speed gain Gv and the torque gain Gt is substituted into the return correction amount Trv.

[0054] In the road information processing M90, information related to the road surface reaction force is superimposed on the steering wheel 12, and the road surface reaction force is a force added from the road surface to the steering wheel 34. The road information processing M90 includes a bandpass filter M92, a gain multiplication processing M94, and a filter coefficient setting processing M96. The q-axis current iqt is input to the bandpass filter M92. The q-axis current iqt is input to the bandpass filter M92 as a variable including the vibration component of the steering wheel 34 due to the road surface reaction force. In the bandpass filter M92, the signal in the vibration frequency band caused by the unevenness of the road surface is selectively extracted. In the gain multiplication processing M94, the value obtained by multiplying the output value of the bandpass filter M92 by the gain G is substituted into the road surface information torque Ti. In the filter coefficient setting processing M96, the vehicle speed V is input, and the filter coefficient τi of the bandpass filter M92 is output. The filter coefficient τi can be a variable or an attenuation coefficient for limiting the frequency band passed by the bandpass filter M92. The variable used to define the frequency band may be, for example, the center frequency. Although the filter coefficient τi is described as one variable, in practice a plurality of filter coefficients may be used.

[0055] In the synthesis process M100, the advance compensation amount Tad, the hysteresis correction amount Thys, the first damping correction amount Tdampa and the return correction amount Trv are added to the basic assist amount Tab, and the road surface information torque Ti is subtracted from the basic assist amount Tab. The value calculated in this way is the assist amount Ta.

[0056] Axial force setting process

[0057] Figure 4Details of the axial force setting process M22 are shown. In the angular axial force setting process M110, the target steering equivalent angle θp* and the vehicle speed V are inputs, and the angular axial force Fr is output. The angular axial force Fr is an estimated value of the axial force defined by a randomly set vehicle model or the like. The angular axial force Fr is calculated as an axial force in which road surface information is not reflected. The road surface information is information about minor unevenness that does not affect the behavior of the vehicle in the lateral direction, steps that affect the behavior of the vehicle in the lateral direction, and the like. In the angular axial force setting process M110, the target steering equivalent angle θp* can be calculated as a value having the same sign as the angular axial force Fr. In the angular axial force setting process M110, the angular axial force Fr can be changed according to the target steering equivalent angle θp* under the condition that the absolute value of the angular axial force Fr when the absolute value of the target steering equivalent angle θp* is large is equal to or greater than the absolute value of the angular axial force Fr when the absolute value of the target steering equivalent angle θp* is small. Furthermore, for example, in the angular axial force setting process M110, the angular axial force Fr may be changed according to the vehicle speed V under the condition that the absolute value of the angular axial force Fr when the vehicle speed V is large is equal to or greater than the absolute value of the angular axial force Fr when the vehicle speed V is small. In the angular axial force setting process M110, the PU 52 performs mapping calculation on the angular axial force Fr in a state where mapping data is pre-stored in the storage device 54. In the mapping data, the target steering equivalent angle θp* and the vehicle speed V are input variables, and the angular axial force Fr is an output variable.

[0058] In the current axial force setting process M112, the q-axis current iqt of the steering motor 42 is the input, and the current axial force Fi is the output. The current axial force Fi is an estimated value of the actual axial force acting on the rack shaft 32 that operates to steer the steering wheel 34, that is, the actual axial force transmitted to the rack shaft 32. The current axial force Fi is calculated as an axial force in which road surface information is reflected. For example, in the current axial force setting process M112, assuming that the torque added to the rack shaft 32 by the steering motor 42 is balanced with the torque according to the force added to the rack shaft 32 by the steering wheel 34, the current axial force Fi is calculated. In the current axial force setting process M112, the current axial force Fi is changed under the condition that the absolute value of the current axial force Fi when the absolute value of the q-axis current iqt is large is equal to or greater than the absolute value of the current axial force Fi when the absolute value of the q-axis current iqt is small.

[0059] Specifically, in the current axial force setting process M112, the PU 52 performs map calculation on the current axial force Fi in a state where map data is pre-stored in the storage device 54. In the map data, the q-axis current iqt is an input variable, and the current axial force Fi is an output variable.

[0060] In the distribution ratio calculation process M114, the vehicle speed V and the target steering equivalent angle θp* are inputs, and the ratio Di is the output. The ratio Di is the ratio of the current axial force Fi to the sum of the angle axial force Fr and the current axial force Fi. The ratio Di has a value of zero or greater and one or less. For example, the distribution ratio calculation process M114 can be the following process: in a state where the mapping data is pre-stored in the storage device 54, the PU 52 performs a mapping calculation on the ratio Di. In the mapping data, the vehicle speed V and the target steering equivalent angle θp* are input variables, and the ratio Di is an output variable.

[0061] In the second distribution ratio calculation process M116, the ratio Di is subtracted from “1” to calculate a second ratio “1-Di.” 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.

[0062] In the first ratio multiplication process M118, the current axial force Fi is multiplied by the ratio Di. In the second ratio multiplication process M120, the angle axial force Fr is multiplied by the second ratio. In the additional process M122, the value obtained by adding the output value of the first ratio multiplication process M118 and the output value of the second ratio multiplication process M120 is substituted into the axial force F0. That is, the axial force F0 is a weighted average processed value of the angle axial force Fr and the current axial force Fi.

[0063] In the second damping process M130, a second damping correction amount Tdampb0 having a positive correlation with the rotation speed of the steering wheel 12 is calculated. The second damping correction amount Tdampb0 is a correction amount for compensating for the phase delay of the axial force F0 by control. The second damping correction amount Tdampb0 may be a correction amount for reducing the damping component caused by the current axial force Fi, etc. The second damping process M130 includes a differential calculation M132 and a second correction amount setting process M134.

[0064] In the differential calculation M132, the first-order time differential value of the steering angle θs is calculated. The time differential value is the steering speed ωs. In the second correction amount setting process M134, the second damping correction amount Tdampb0 having a positive correlation with the steering speed ωs is calculated. The second damping correction amount Tdampb0 has a torque dimension. In the second correction amount setting process M134, the mapping calculation of the second damping correction amount Tdampb0 can be performed by the PU 52 in a state where the mapping data is pre-stored in the storage device 54. In the mapping data, the steering speed ωs is an input variable, and the second damping correction amount Tdampb0 is an output variable.

[0065] In the second gain adjustment process M136, the steering torque Th and the vehicle speed V are inputs, and the second gain G2 is an output. As an example, in the second gain adjustment process M136, the PU 52 performs a map calculation on the second gain G2 in a state where map data is pre-stored in the storage device 54. In the map data, the steering torque Th and the vehicle speed V are input variables, and the second gain G2 is an output variable.

[0066] In the multiplication process M138, the value obtained by multiplying the second damping correction amount Tdampb0 by the second gain G2 is substituted into the second damping correction amount Tdampb. In the addition process M139, the value obtained by adding the second damping correction amount Tdampb to the axial force F0 is substituted into the axial force F.

[0067] Functions and effects of this embodiment

[0068] The PU 52 subtracts the axial force F from the assist amount Ta to set a target reaction force torque Ts. The torque of the reaction force motor 22 is controlled according to the target reaction force torque Ts.

[0069] Here, in the case where the correction amount of the compensation process, such as the first damping correction amount Tdampa and the advance compensation amount Tad (which is a variable for calculating the assist amount Ta) is not reflected, or in other cases, stability is reduced. For example, such a situation occurs when the torque input to the steering wheel 12 is too large. That is, for example, when the above torque exceeds the range detectable by the torque sensor 60, the time differential value dTh is zero. Therefore, the advance compensation amount Tad cannot be set to an appropriate value. In addition, for example, when the basic assist amount Tab is too large, the magnitude of the axial force F is relatively small, and the steering operation of the steering wheel 12 may be unstable. In particular, when the lower limit protection process is performed on the magnitude of the reaction force resisting the driver's operation of the steering wheel 12, the correction amount of the compensation process may not be reflected by the lower limit protection value.

[0070] The PU 52 adds the second damping correction amount Tdampb to the axial force F0. Therefore, for example, when the assist amount Ta is too large, as the correction for the axial force F increases, the magnitude of the reaction force against the driver's operation of the steering wheel 12 is suppressed from becoming too small. Therefore, the reduction in the stability of the steering device 10 can be suppressed.

[0071] According to the present embodiment described above, the following actions and effects can also be obtained: The second damping process M130 is newly provided to the axial force setting process M22. Therefore, a process of advancing the phase can be realized.

[0072] In addition to the first damping process M70 provided in the assist amount setting process M20, the second damping process M130 is provided in the axial force setting process M22. Therefore, the first damping correction amount Tdampa and the second damping correction amount Tdampb can be set according to the difference in each purpose and thus facilitate adaptation.

[0073] The PU 52 sets the second gain G2 according to the steering torque Th. First, the steering torque Th is a variable indicating whether the detection target is within the range detectable by the torque sensor 60. Second, the steering torque Th is a torque-related variable having a positive correlation with the torque of the reaction force motor 22. Therefore, the size of the second damping correction amount Tdampb can be adjusted according to whether the detection target is within the range detectable by the torque sensor 60 and according to whether the target reaction torque Ts has a size that can be achieved by the reaction force motor 22.

[0074] The PU 52 sets the second gain G2 according to the vehicle speed V. Therefore, compared with the case where the second gain G2 is set without referring to the vehicle speed V, the second gain G2 can be set more appropriately according to the situation where stability may be reduced.

[0075] The degree to which the first damping correction amount Tdampa0 output from the first damping process M70 included in the assist amount setting process M20 is reflected in the assist amount Ta is adjusted by the first gain G1. Therefore, the first damping correction amount Tdampa obtained by multiplying the first damping correction amount Tdampa0 by the first gain G1 can be set to an appropriate size to suppress a decrease in the stability of the steering device 10.

[0076] The PU 52 sets the first gain G1 according to the vehicle speed V. Therefore, compared with the case where the first gain G1 is set without referring to the vehicle speed V, the first gain G1 can be set more appropriately according to the situation where stability may be reduced.

[0077] Correspondence

[0078] The correspondence between the matters in the above embodiment and the matters described in the "Means for Solving the Problem" column is as follows. In the following, the correspondence for each number of the solution means described in the "Means for Solving the Problem" column is shown. [1 to 3] The reaction force application process corresponds to the subtraction process M24 and the operation signal generation process M26 for the reaction force. The torque correlation coefficient corresponds to the steering torque Th. [4 to 5] The compensation process corresponds to the phase delay compensation process M40, the phase advance compensation process M50 and the first damping process M70. The compensation gain adjustment process corresponds to the second gain adjustment process M136.

[0079] Other Implementations

[0080] The embodiment can be implemented with the following modifications. The embodiment and the following modification examples can be implemented in combination with each other within the scope of technical consistency.

[0081] Torque correlation coefficient

[0082] The torque correlation coefficient is not necessarily the steering torque Th. The torque correlation coefficient may be, for example, the torque of the reaction force motor 22 calculated based on the current flowing through the reaction force motor 22. In addition, for example, when performing a process of performing feedback control on the steering torque Th to a target value, the torque correlation coefficient may be the same target value. In addition, for example, the torque correlation coefficient may be the target reaction torque Ts.

[0083] Second gain adjustment process

[0084] The input to the second gain adjustment process is not necessarily the torque correlation coefficient and the vehicle speed V. For example, the input to the second gain adjustment process may be only the torque correlation coefficient.

[0085] Compensation gain adjustment process

[0086] The gain adjustment target by the compensation gain adjustment process is not limited to the second damping correction amount Tdampb0. The gain adjustment target by the compensation gain adjustment process may be, for example, the advance compensation amount Tad. In addition, for example, the gain adjustment target by the compensation gain adjustment process may be both the second damping correction amount Tdampb0 and the advance compensation amount Tad.

[0087] The input to the compensation gain adjustment process is not necessarily the torque correlation coefficient and the vehicle speed V. For example, the input to the compensation gain adjustment process may be only the torque correlation coefficient.

[0088] Phase advance compensation processing

[0089] exist Figure 3 In the embodiment, the input of the gain setting process M54 is the vehicle speed V and the assist gradient R, but is not limited thereto. For example, the input of the gain setting process M54 may be only the assist gradient R. Furthermore, for example, the input of the gain setting process M54 may be only the vehicle speed V.

[0090] A low pass filter may be provided between the differential calculation M52 and the multiplication process M56. In the multiplication process M56, instead of multiplying the time differential value dTh by the gain Gad, map data in which the time differential value dTh is an input variable and the advance compensation amount Tad is an output variable may be provided.

[0091] The phase advance compensation process does not need to include a process of calculating the time differential value dTh. For example, instead of the calculation of the time differential value dTh, a process in which the input of the phase advance compensation process is the steering torque Th may be included.

[0092] First damping treatment

[0093] The first correction amount setting process M74 is not limited to the process of calculating the first damping correction amount Tdampa0 having a negative correlation with the steering manipulation speed ωs. In the first correction amount setting process M74, the first damping correction amount Tdampa0 may be set to a value having a positive correlation with the steering manipulation speed ωs, for example, based on a predetermined variable such as the value of the target reaction torque Ts.

[0094] Axial force setting process

[0095] The angular axial force setting process M110 is not necessarily a process for performing a mapping calculation on the angular axial force Fr. For example, in the angular axial force setting process M110, a value obtained by multiplying the target steering equivalent angle θp* by a gain may be substituted into the angular axial force Fr. The gain may be a variable according to the vehicle speed V.

[0096] The input of the angular axial force setting process M110 is not necessarily the target steering equivalent angle θp* and the vehicle speed V. For example, the input of the angular axial force setting process M110 may not include the vehicle speed V. In addition, for example, the angular variable of the steering control system as the input variable of the angular axial force setting process M110 is not limited to the target steering equivalent angle θp*. For example, the angular variable of the steering control system may be the steering equivalent angle θp. In addition, for example, the angular variable of the steering control system may be the steering control angle θs.

[0097] The current axial force setting process M112 is not limited to the process of performing map calculation on the current axial force Fi. For example, in the current axial force setting process M112, a value obtained by multiplying the q-axis current iqt by the gain may be substituted into the current axial force Fi.

[0098] The input of the current axial force setting process M112 is not limited to the q-axis current iqt. For example, the input of the current axial force setting process M112 may be the q-axis current iqt and the vehicle speed V. For example, the input of the current axial force setting process M112 may include angle variables of the steering control system, such as the target steering equivalent angle θp*, the steering equivalent angle θp, and the steering control angle θs.

[0099] The input of the distribution ratio calculation process M114 is not necessarily the target steering equivalent angle θp* and the vehicle speed V. For example, the input of the distribution ratio calculation process M114 may not include the vehicle speed V. In addition, for example, the angle variable of the steering system as the input variable of the distribution ratio calculation process M114 is not limited to the target steering equivalent angle θp*. For example, the angle variable of the steering system may be the steering equivalent angle θp. In addition, for example, the angle variable of the steering system may be the steering steering angle θs.

[0100] The axial force setting process does not need to include both the angular axial force setting process M110 and the current axial force setting process M112. For example, only either one of the angular axial force setting process M110 and the current axial force setting process M112 may be included.

[0101] Steering Controls

[0102] The steering control device is not limited to a device that performs software processing. For example, a dedicated hardware circuit, such as an ASIC, may be provided that performs at least a portion of the processing performed in the above embodiment. That is, the steering control device may include a processing circuit that includes any of the following configurations (a) to (c). (a) A processing circuit that includes a processing device that performs all processing according to a program and a program storage device, such as a storage device, that stores the program. (b) A processing circuit that includes a processing device that performs a portion of the processing according to the program, a program storage device, and a dedicated hardware circuit that performs the remaining processing. (c) A processing circuit that includes a dedicated hardware circuit that performs all processing. Here, a plurality of software execution devices including a processing device and a program storage device may be provided. In addition, a plurality of dedicated hardware circuits may be provided.

[0103] other

[0104] The steering motor 42 is not necessarily a synchronous motor. For example, a generator may be used.

[0105] In each of the above embodiments, the steering device 10 has a linkless structure in which the steering wheel 12 and the steering wheel 34 are always mechanically separated from each other, but is not limited thereto. A structure in which the steering wheel 12 and the steering wheel 34 are mechanically separable from each other by a clutch may be used.

Claims

1. A steering control device (50), characterized in that: Comprising a software processing device, wherein: The software processing device sets the steering control system as a control target; The steering control system comprises: a reaction force motor (22) configured to apply a steering reaction force to the steering shaft (14); and a steering motor (42) configured to steer the steering wheel (34) in a state where power transmission from the steering control shaft (14) is cut off; The software processing means is configured to execute assist amount setting processing, axial force setting processing and reaction force applying processing; In the assist amount setting process, the assist amount is set by using the output value of the first damping process, wherein the assist amount is an amount of assisting the driver in rotating the steering shaft (14); in the axial force setting process, the axial force is set by using the output value of the second damping process, wherein the axial force is a force resisting the driver's rotation operation on the steering shaft (14); In the reaction force applying process, a value obtained by subtracting the axial force from the assist amount is input, and the reaction force motor (22) is operated; In the first damping process, a first damping correction amount having a correlation with a steering angular velocity is output; and In the second damping process, a second damping correction amount having a positive correlation with the steering angular velocity is output.

2. The steering control device (50) according to claim 1, characterized in that: The software processing device is configured to execute a second gain adjustment process of adjusting a second gain as a gain of the second damping process according to a value of a torque-related variable; and The torque-related variable is a variable that is correlated with the torque of the reaction force motor (22).

3. The steering control device (50) according to claim 2, characterized in that: In the second gain adjustment process, the second gain is adjusted according to the vehicle speed in addition to the value of the torque-related variable.

4. The steering control device (50) according to claim 1, characterized in that: in the assist amount setting process, setting the assist amount while using output values ​​of a plurality of compensation processes including the first damping process; The software processing device is configured to execute a compensation gain adjustment process of adjusting a compensation gain that is a gain of at least one compensation process among the plurality of compensation processes according to a value of a torque-related variable; and The torque-related variable is a variable that is correlated with the torque of the reaction force motor (22).

5. The steering control device (50) according to claim 4, characterized in that: In the compensation gain adjustment process, the compensation gain is adjusted according to the vehicle speed in addition to the value of the torque-related variable.

6. The steering control device (50) according to claim 2, characterized in that: The torque-dependent variable is the steering torque.

Images