Steering control device and steering control method

Abstract

A steering control device (40) executes input-dependent variable calculation processing, arbitration processing, operation processing, target value setting processing, and reflection processing. The input-dependent variable calculation processing is processing of calculating a value of an input-dependent variable according to an intention of a driver to steer. The arbitration processing is processing of inputting the value of the input-dependent variable and an external request value and outputting a value of a target steered angle variable. The operation processing is processing of inputting the value of the target steered angle variable and operating an actuator. The target value setting processing is processing of inputting the value of the target steered angle variable output by the arbitration processing and outputs a target yaw rate. The reflection processing is processing of reflecting, to an operation of the steered angle by the operation processing, an operation amount of feedback control in which the target yaw rate is a target value of a control amount.

Description

Steering control device and steering control method

[0001] The present disclosure relates to a steering control device and a steering control method.

[0002] The following Patent Document 1 describes a device that suppresses deviation of the vehicle's traveling direction based on the difference between a standard yaw rate corresponding to the steering angle and a detected yaw rate.The following Patent Document 2 describes a device that controls a motor that steers steered wheels based on a cooperative steering command value that takes into account both a manual steering command value corresponding to steering by the driver and an automatic steering command value.

[0003] JP 2021-14221 A JP 2020-168918 A

[0004] When the steered wheels are steered based on the coordinated steering command value as described above, there is a risk that deviation of the traveling direction may not be appropriately suppressed if a standard yaw rate set in accordance with the steering angle is used.

[0005] One aspect of the present disclosure provides a steering control device. The steering control device is configured to execute an input-dependent variable calculation process, an arbitration process, an operation process, a target value setting process, and a reflection process. The input-dependent variable calculation process is a process for calculating a value of an input-dependent variable in response to a steering intention indicated by a driver's operation of an input unit. The input-dependent variable is a variable indicating a steering angle of steered wheels of a vehicle in response to the steering intention. The arbitration process is a process in which a value of the input-dependent variable and an external requirement value are input, and a value of a target steering angle variable is an output. The target steering angle variable is a target value of the steering angle. The external requirement value is a variable indicating a requirement value for the steering angle independent of the steering intention. The operation process is a process in which a value of the target steering angle variable is input, and an actuator is operated. The actuator is configured to impart to the steered wheels a power for steering the steered wheels. The target value setting process is a process in which the value of the target steering angle variable output by the arbitration process is an input and a target yaw rate is an output. The reflection process is a process in which the yaw rate is a controlled variable and a feedback control operation amount, in which the target yaw rate is a target value of the controlled variable, is reflected in the steering angle operation by the operation process, and is executed when a value in which the external requirement value is superimposed on at least the value of the input-dependent variable is substituted for the target steering angle variable output by the arbitration process.

[0006] Another aspect of the present disclosure provides a steering control method. The steering control method includes steps of executing an input-dependent variable calculation process, an arbitration process, an operation process, a target value setting process, and a reflection process. The input-dependent variable calculation process is a process of calculating a value of an input-dependent variable in response to a steering intention indicated by a driver's operation of an input unit. The input-dependent variable is a variable indicating a steering angle of steered wheels of a vehicle in response to the steering intention. The arbitration process is a process in which a value of the input-dependent variable and an external demand value are input, and an output is a value of a target steering angle variable. The target steering angle variable is a target value of the steering angle. The external demand value is a variable indicating a demand value for the steering angle independent of the steering intention. The operation process is a process in which a value of the target steering angle variable is input, and an actuator is operated. The actuator is configured to apply a power to the steered wheels to turn the steered wheels. The target value setting process is a process in which the value of the target steering angle variable output by the arbitration process is an input and a target yaw rate is an output. The reflection process is a process in which the yaw rate is a controlled variable and a feedback control operation amount, in which the target yaw rate is a target value of the controlled variable, is reflected in the steering angle operation by the operation process, and is executed when a value in which the external requirement value is superimposed on at least the value of the input-dependent variable is substituted for the target steering angle variable output by the arbitration process.

[0007] Fig. 3 is a diagram showing the configuration of a steering control system according to a first embodiment; Fig. 4 is a block diagram showing processing executed by the steering control device in Fig. 1; Fig. 5 is a diagram showing the configuration of a steering control system according to a second embodiment; Fig. 6 is a block diagram showing processing executed by the steering control device in Fig. 3; Fig. 7 is a block diagram showing processing executed by the steering control device according to a third embodiment;

[0008] <First embodiment> A first embodiment will be described below with reference to the drawings. "Prerequisite configuration" As shown in FIG. 1, a steering device 10 includes a steering wheel 12. The steering wheel 12 is an input unit through which the driver inputs steering intentions. A transmission shaft 14 is connected to the steering wheel 12. Therefore, when the steering wheel 12 rotates, the transmission shaft 14 rotates integrally. The rotational power of the transmission shaft 14 is transmitted to a turning shaft 16. The turning shaft 16 extends in the vehicle width direction (the left-right direction in FIG. 1). Turnable wheels 20 are connected to both ends of the turning shaft 16 via tie rods 18.

[0009] The transmission shaft 14 is arranged to intersect with the steered shaft 16. The transmission shaft 14 and the steered shaft 16 are formed with teeth that mesh with each other. The meshing of these teeth enables the transmission of power from the transmission shaft 14 to the steered shaft 16. In other words, the rotational power of the transmission shaft 14 is converted into power that displaces the steered shaft 16 in the axial direction. The displacement of the steered shaft 16 in the axial direction is transmitted to the steered wheels 20 via tie rods 18. This changes the steering angle of the steered wheels 20. The steering angle refers to the turning angle of the tires.

[0010] The steering device 10 also includes an assist motor 30. The assist motor 30 generates an assist force that assists the driver in steering. The rotational power of the assist motor 30 is applied to a drive shaft 34. The drive shaft 34 and the steered shaft 16 have meshed teeth formed thereon. The meshing of these teeth enables power transmission from the drive shaft 34 to the steered shaft 16. In other words, the rotational power of the drive shaft 34 is converted into axial displacement power of the steered shaft 16. As a result, the rotational power of the assist motor 30 is converted into axial displacement power of the steered shaft 16 via the drive shaft 34. More specifically, the assist motor 30 is, for example, a three-phase brushless motor. The output voltage of an inverter 32 is applied to the terminals of the assist motor 30.

[0011] The steering control device 40 controls the control amount of the steering device 10, which is the object of control. In order to control the control amount, the steering control device 40 refers to the steering torque Th input to the steering wheel 12. The steering torque Th is detected by a torque sensor 50. The torque sensor 50 is a sensor that detects the steering torque Th according to the degree of torsion of a torsion bar 52, which is part of the transmission shaft 14. The steering control device 40 also refers to the vehicle speed V detected by a vehicle speed sensor 54. The steering control device 40 also refers to the rotation angle θa of the assist motor 30 detected by a rotation angle sensor 56. The steering control device 40 also refers to the currents iu, iv, and iw flowing through the assist motor 30.

[0012] The steering control device 40 includes a PU 42 and a storage device 44. The PU 42 is a software processing device such as a CPU, a GPU, and a TPU. The storage device 44 includes a storage medium such as an electrically rewritable nonvolatile memory and a disk medium. A steering control program 44a is stored in the storage device 44. The steering control device 40 controls the control amount by the PU 42 executing the steering control program 44a stored in the storage device 44.

[0013] The steering control device 40 is capable of communicating with the ADASECU 70. The ADASECU 70 executes a process for assisting the steering of the vehicle based on objects outside the vehicle. The ADASECU 70 acquires information about objects outside the vehicle by acquiring image data Do that indicates an image of the area in front of the vehicle captured by the camera 80. Here, the objects outside the vehicle are not limited to objects that exist above the road surface, such as vehicles and guardrails located ahead, but also include white lines and the like. The ADASECU 70 determines whether to execute the assist process depending on whether steering assistance is required, as instructed by an input operation on the user interface 82.

[0014] The ADASECU 70 includes a PU 72 and a storage device 74. The PU 72 executes an assist program 74a stored in the storage device 74, thereby performing a process for assisting steering.

[0015] "Processing Executed by Steering Control Device 40" Fig. 2 shows processing executed by the steering control device 40. The processing shown in Fig. 2 is realized by the PU 42 executing the steering control program 44a, for example, at a predetermined interval.

[0016] The target steering torque setting process M10 is a process for calculating a target steering torque Th*, which is a target value of the steering torque Th, based on the axial force Taf. The axial force Taf is a force applied to the steered shaft 16. The axial force Taf is an amount converted into torque of the transmission shaft 14. The target steering torque setting process M10 includes a process for setting the target steering torque Th* to a different value depending on the vehicle speed V, even if the axial force Taf is the same. This setting is intended to allow the driver to experience an optimal steering feel depending on the vehicle speed V.

[0017] The steering operation amount calculation process M12 is a process for calculating a steering operation amount Ts*, which is a control operation amount for which the steering torque Th is a control amount. The steering operation amount calculation process M12 includes a process for calculating a control operation amount for feedback control in which the steering torque Th is a control amount and the target steering torque Th* is a target value of the control amount, thereby calculating the steering operation amount Ts* in accordance with the control operation amount. The steering operation amount calculation process M12 may further include a process for calculating a control operation amount for open-loop control in which the target steering torque Th* is a target value of the control amount, thereby calculating the steering operation amount Ts* in accordance with the control operation amount. The control amount for feedback control is, for example, an amount for increasing the absolute value of the torque required for the assist motor 30 when the signs of the steering torque Th and the target steering torque Th* are both positive and the steering torque Th is greater than the target steering torque Th*. Note that the steering operation amount Ts* is, for example, an amount converted into a torque applied to the transmission shaft 14.

[0018] The axial force calculation process M14 is a process for calculating the axial force Taf by adding the steering torque Th to the steering operation amount Ts*. Note that since the steering torque Th is the torque applied to the transmission shaft 14, in this embodiment the axial force Taf is a value obtained by converting the force applied in the axial direction of the steered shaft 16 into the torque applied to the transmission shaft 14.

[0019] The reference model calculation process M16 is a process in which the axial force Taf is input and the target steering equivalent angle θp0*, which is a target value of the steering equivalent angle θp, is output. In detail, the reference model calculation process M16 is a process in which the target steering equivalent angle θp0* is used to output the target steering equivalent angle θp0* using an equation in which the steering equivalent angle θp in the model equation expressed by the following equation (c1) is replaced with the target steering equivalent angle θp0*.

[0020] Taf = K θp + C θp' + J θp'' (c1) The model expressed by the above equation (c1) models the value that the steering equivalent angle θp indicates when a torque of an amount equal to the axial force Taf is input to the transmission shaft 14. The steering equivalent angle θp is a variable that indicates the steering angle of the steered wheels 20. The steering equivalent angle θp has a positive correlation with the steering angle. The steering equivalent angle θp may be the rotation angle of the transmission shaft 14, for example.

[0021] In the above equation (c1), the viscosity coefficient C models the friction of the steering device 10, etc. The inertia coefficient J models the inertia of the steering device 10, etc. The elastic coefficient K models the specifications of the suspension, wheel alignment, etc. of the vehicle on which the steering device 10 is installed. This model does not need to accurately represent the actual steering device 10 or the vehicle on which the steering device 10 is installed. This model may be a reference model designed to make the behavior of the steering angle relative to the input ideal. When a reference model is used, the steering feeling can be adjusted by designing the reference model.

[0022] The arbitration process M18 is a process that receives as input the target steering equivalent angle θp0* and the assist correction amount Δθp and outputs the target steering equivalent angle θp*. The assist correction amount Δθp is a correction amount for the target steering equivalent angle θp0* that is output from the ADASECU 70 when the ADASECU 70 is executing steering assist processing. The assist processing may be, for example, processing for preventing the vehicle from deviating from its lane. In that case, the assist correction amount Δθp is an amount for finely correcting the target steering equivalent angle θp0* in order to prevent the vehicle from deviating from its lane.

[0023] Specifically, arbitration processing M18 includes gain multiplication processing M18a and addition processing M18b. Gain multiplication processing M18a is processing for outputting a value obtained by multiplying the assist correction amount Δθp by a gain G. Addition processing M18b is processing for substituting a value obtained by multiplying the target steering equivalent angle θp0* by the gain G into the target steering equivalent angle θpa*. When assist processing is started, PU 72 gradually increases gain G from "0" toward "1". Furthermore, when assist processing is ended, PU 72 gradually decreases gain G from "1" toward "0".

[0024] The target yaw rate setting process M20 is a process in which the target steering equivalent angle θpa* and the vehicle speed V are input and the target yaw rate yr* is output. The target yaw rate yr* is the yaw rate yr that is expected when the vehicle travels on a flat road surface without being affected by airflow, with the steering angle at the target steering equivalent angle θpa* and the vehicle speed V.

[0025] The PU 42 matches the sign of the target yaw rate yr* with the sign of the target steering equivalent angle θpa*. The PU 42 changes the target yaw rate yr* in accordance with the vehicle speed V under the condition that the absolute value of the target yaw rate yr* when the vehicle speed V is high is equal to or greater than the absolute value of the target yaw rate yr* when the vehicle speed V is low. The PU 42 changes the target yaw rate yr* in accordance with the target steering equivalent angle θpa* under the condition that the absolute value of the target yaw rate yr* when the absolute value of the target steering equivalent angle θpa* is high is equal to or greater than the absolute value of the target yaw rate yr* when the absolute value of the target steering equivalent angle θpa* is low.

[0026] In the description "changing B according to A while satisfying the condition that when A is large, B is equal to or greater than B when A is small," the case where A is large and the case where A is small refer to the relative relationship of magnitude when comparing the two. For example, "when A is large" corresponds to the case where "A is a first value," and "when A is small" corresponds to the case where "A is a second value smaller than the first value." Furthermore, the above description means that, depending on the settings of the first and second values, B when A is the first value may be larger than B when A is the second value.

[0027] As an example, the target yaw rate setting process M20 may be a process in which the PU 42 calculates the target yaw rate yr* using a map in a state in which map data is stored in the storage device 44. The map data is data in which the target steering equivalent angle θpa* and the vehicle speed V are input variables and the target yaw rate yr* is an output variable.

[0028] 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. Furthermore, the map calculation may be a process in which, when the value of an input variable matches one of the input variable values ​​in the map data, the value of the output variable in the corresponding map data is used as the calculation result. Furthermore, when the value of an input variable does not match any of the input variable values ​​in the map data, the map calculation may be a process in which the value obtained by interpolating the values ​​of multiple output variables included in the map data is used as the calculation result. Alternatively, when the value of an input variable does not match any of the input variable values ​​in the map data, the map calculation may be a process in which the value of the output variable in the map data that corresponds to the closest value of the input variable values ​​included in the map data is used as the calculation result.

[0029] The deviation calculation process M22 calculates the deviation between the target yaw rate yr* and the yaw rate yr. The yaw rate feedback process M24 receives the output value of the deviation calculation process M22 and outputs a yaw rate correction amount Δθc. The yaw rate correction amount Δθc is a feedback control manipulated variable in which the yaw rate yr is a controlled variable and the target yaw rate yr* is a target value of the controlled variable. The yaw rate correction amount Δθc may be an output value of a proportional element corresponding to the output value of the deviation calculation process M22. The yaw rate correction amount Δθc may also be the sum of the output value of a proportional element corresponding to the output value of the deviation calculation process M22 and the output value of an integral element. The yaw rate correction amount Δθc may also be the sum of the output value of a proportional element, the output value of an integral element, and the output value of a derivative element corresponding to the output value of the deviation calculation process M22. The yaw rate correction amount Δθc may also be the sum of the output value of a proportional element, the output value of an integral element, and the output value of a derivative element corresponding to the output value of the deviation calculation process M22. However, the feedback control for calculating the yaw rate correction amount Δθc is not limited to the classical control.

[0030] The target steering equivalent angle setting process M26 is a process in which a value obtained by adding the yaw rate correction amount Δθc to the target steering equivalent angle θpa* is assigned to the target steering equivalent angle θp*. The steering angle calculation process M30 is a process in which the rotation angle θa of the assist motor 30 is input and the steering equivalent angle θp is output. The steering angle calculation process M30 includes a process of integrating the rotation angle θa. In this integration process, the steering equivalent angle when the vehicle is traveling straight is set to "0".

[0031] The angle manipulated variable calculation process M32 is a process in which the steering equivalent angle θp and the target steering equivalent angle θp* are input and the assist torque Ta* is output. The assist torque Ta* is a manipulated variable of control in which the steering equivalent angle θp is the controlled variable. The angle manipulated variable calculation process M32 includes a process of calculating a manipulated variable of feedback control in which the steering equivalent angle θp is the controlled variable and the target steering equivalent angle θp* is the target value of the controlled variable, thereby calculating the assist torque Ta* in accordance with the manipulated variable. The angle manipulated variable calculation process M32 may further include a process of calculating a manipulated variable of open-loop control in which the target steering equivalent angle θp* is the target value of the controlled variable, thereby calculating the assist torque Ta* in accordance with the manipulated variable.

[0032] The assist operation process M34 is a process for outputting an operation signal MS to the inverter 32 in order to control the torque of the assist motor 30 in accordance with the assist torque Ta*. Note that the operation signal MS actually becomes an operation signal for each arm of each leg of the inverter 32.

[0033] <Actions and Effects of the Present Embodiment> The PU 42 of the steering control device 40 calculates the target steering equivalent angle θp0* in accordance with the steering torque Th input to the transmission shaft 14. The PU 72 of the ADASECU 70 calculates the assist correction amount Δθp for assisting steering in accordance with the image data Do. The PU 42 sets the target yaw rate yr* based on the target steering equivalent angle θpa*, which is a value obtained by correcting the target steering equivalent angle θp0* with the assist correction amount Δθp. The PU 42 corrects the target steering equivalent angle θpa* with the yaw rate correction amount Δθc, which is a manipulation amount for bringing the yaw rate yr closer to the target yaw rate yr*, thereby setting the final target steering equivalent angle θp*. The PU 42 then controls the steering equivalent angle θp to approach the target steering equivalent angle θp*.

[0034] Here, the target steering equivalent angle θp* is a value obtained by correcting the target steering equivalent angle θpa* by the yaw rate correction amount Δθc. The yaw rate correction amount Δθc is an operation amount for bringing the yaw rate yr closer to the target yaw rate yr*. The target yaw rate yr* is a yaw rate that is assumed to be realized when the vehicle travels on a flat road surface without being affected by airflow or the like under traveling conditions that satisfy the target steering equivalent angle θpa* and vehicle speed V. Therefore, factors that cause the yaw rate yr to deviate from the target yaw rate yr* include crosswinds blowing against the vehicle, disturbances caused by the road surface such as the gradient and bumps of the road surface, and aging of the vehicle.

[0035] The assist correction amount Δθp output by the ADASECU 70 does not take into account disturbances caused by crosswinds or road surfaces, aging of the vehicle, etc. Therefore, even if the assist correction amount Δθp is calculated to suppress lane departure, if the yaw rate correction amount Δθc is not used, there is a concern that the vehicle may depart from the lane due to the influence of crosswinds, etc.

[0036] In response to this, the PU 42 can achieve the desired steering by adopting the yaw rate correction amount Δθc. In particular, the PU 42 inputs the target steering equivalent angle θpa* output by the arbitration process M18 into the target yaw rate setting process M20. In other words, the PU 42 sets the target yaw rate yr* in accordance with the value of the most downstream variable for calculating the target steering equivalent angle θp*, excluding the correction by the yaw rate correction amount Δθc. Therefore, the target yaw rate yr* can be set to a value more appropriate for achieving the intended steering, compared to when a more upstream variable value, such as the target steering equivalent angle θp0*, is substituted into the target yaw rate setting process M20.

[0037] According to the present embodiment described above, the following further actions and effects can be obtained. (1-1) In the present embodiment, the manipulated variable of the feedback control in which the yaw rate yr is the controlled variable is adopted as the correction variable for correcting the target steering equivalent angle θpa*. This allows the feedback control in which the yaw rate yr is the controlled variable to be quickly reflected in the steering equivalent angle θp.

[0038] Second Embodiment A second embodiment will be described below with reference to the drawings, focusing on differences from the first embodiment.

[0039] "Prerequisite Configuration" The configuration of the steering control system according to this embodiment is shown in Fig. 3. In Fig. 3, members corresponding to those shown in Fig. 1 are denoted by the same reference numerals for convenience.

[0040] 3, in the steering device 10, the transmission shaft 14 is separated into an input shaft 14a connected to the steering wheel 12 and an output shaft 14b engaged with the steered shaft 16. Note that in this embodiment, the output shaft 14b is not actually required. However, for convenience of the following explanation, the output shaft 14b is provided.

[0041] A reaction motor 90 is provided on the input shaft 14a. The reaction motor 90 is a motor for applying a reaction force, which is a torque in the opposite direction to the torque input by the driver, to the steering wheel 12. The reaction motor 90 is, for example, a three-phase brushless motor. The output voltage of an inverter 92 is applied to the terminals of the reaction motor 90.

[0042] Torque from steering motor 100 is applied to steering shaft 16 via drive shaft 34. Steering motor 100 is, for example, a three-phase brushless motor. The output voltage of inverter 102 is applied to terminals of steering motor 100.

[0043] The steering control device 40 controls the steering device 10. The steering control device 40 operates the inverter 92 to control the reaction force, which is the control variable of the control object. The steering control device 40 also operates the inverter 102 to control the steering angle of the steered wheels 20, which is the control variable of the control object.

[0044] Steering control device 40 refers to rotation angle θs of reaction force motor 90 detected by rotation angle sensor 110 in order to control the reaction force, which is a control variable. Steering control device 40 also refers to currents ius, ivs, iws flowing through reaction force motor 90 in order to control the reaction force. Steering control device 40 also refers to rotation angle θt of turning motor 100 detected by rotation angle sensor 112 in order to control the steering angle, which is a control variable. Steering control device 40 also refers to currents iut, ivt, iwt flowing through turning motor 100 in order to control the steering angle.

[0045] "Processing Executed by Steering Control Device 40" Figure 4 shows processing executed by the steering control device 40. In other words, Figure 4 shows processing executed by the steering control device 40 in a state where the transmission of power from the steering wheel 12 to the steered wheels 20 is interrupted. Note that in Figure 4, processing corresponding to the processing shown in Figure 2 is denoted by the same reference numerals for convenience.

[0046] As shown in Fig. 4, the reference model calculation process M16 is a process for outputting a target steering angle θh* instead of the target steering equivalent angle θp0*. The steering angle calculation process M40 is a process in which the rotation angle θs is input and the steering angle θh is output. The steering angle calculation process M40 includes a process for integrating the rotation angle θs. In this integration process, the steering angle θh is set to zero at the neutral position.

[0047] The target reaction torque calculation process M42 is a process in which the steering angle θh and the target steering angle θh* are input and the target reaction torque Tr* is output. The target reaction torque calculation process M42 includes a process for calculating a manipulation amount of feedback control in which the steering angle θh is a controlled variable and the target steering angle θh* is a target value of the controlled variable, thereby calculating the target reaction torque Tr* in accordance with the manipulated variable. The target reaction torque calculation process M42 may further include a process for calculating a manipulation amount of open-loop control in which the target steering torque Th* is a target value of the controlled variable, thereby calculating the target reaction torque Tr* in accordance with the manipulated variable.

[0048] The steering operation signal generation process M44 is a process for operating the inverter 92 by inputting the target reaction torque Tr*. The steering operation signal generation process M44 includes a process for calculating a control operation amount in which the torque of the reaction motor 90 is the control amount and the target reaction torque Tr* is the target value of the control amount. The calculation of the operation amount is performed by referring to the rotation angle θs and the currents ius, ivs, and iws. The steering operation signal generation process M44 also includes a process for operating the inverter 92 in accordance with the operation amount. FIG. 4 illustrates an operation signal MSs for the inverter 92. Note that in reality, the operation signal MSs is a separate operation signal for each switching element of the inverter 92.

[0049] The target steering equivalent angle calculation process M50 is a process in which the steering angle θh and the vehicle speed V are input and the target steering equivalent angle θp0* is output. PU42 changes the target steering equivalent angle θp0* in accordance with the steering angle θh under the condition that the absolute value of the target steering equivalent angle θp0* when the absolute value of the steering angle θh is large is equal to or greater than the absolute value of the target steering equivalent angle θp0* when the absolute value of the steering angle θh is small.

[0050] Steering angle calculation process M30 is a process in which rotation angle θt of steering motor 100 is input instead of rotation angle θa, and steering equivalent angle θp is output. Angular operation amount calculation process M32 is a process in which steering equivalent angle θp and target steering equivalent angle θp* are input, and target steering torque Tt* is output instead of assist torque Ta*.

[0051] The steering operation signal generation process M34a is a process for operating inverter 102 in response to input of target steering torque Tt*. The steering operation signal generation process M34a may be a process for calculating a control operation amount in which the torque of steering motor 100 is the control amount and the value obtained by converting target steering torque Tt* into the torque of steering motor 100 is the target value of the control amount. The calculation of the operation amount references the rotation angle θt and currents iut, ivt, and iwt. The steering operation signal generation process M34a also includes a process for operating inverter 102 in accordance with the operation amount. FIG. 5 shows an operation signal MSt for inverter 102. Note that in reality, the operation signal MSt is a separate operation signal for each switching element of inverter 102.

[0052] <Functions and Effects of the Second Embodiment> The PU 42 calculates the target steering equivalent angle θp0* according to the steering angle θh. The PU 72 of the ADASECU 70 calculates the assist correction amount Δθp for assisting steering according to the image data Do. The PU 42 sets the target yaw rate yr* based on the target steering equivalent angle θpa*, which is a value obtained by correcting the target steering equivalent angle θp0* with the assist correction amount Δθp. The PU 42 corrects the target steering equivalent angle θpa* with the yaw rate correction amount Δθc, which is a manipulation amount for bringing the yaw rate yr closer to the target yaw rate yr*, thereby setting the final target steering equivalent angle θp*. The PU 42 then controls the steering angle of the steered wheels 20 to approach the target steering equivalent angle θp*.

[0053] Therefore, according to this embodiment, the same effects as those of the first embodiment are achieved. Third Embodiment Hereinafter, a third embodiment will be described with reference to the drawings, focusing on the differences from the second embodiment.

[0054] Figure 5 shows the processing executed by the steering control device 40. In other words, Figure 5 shows the processing executed by the steering control device 40 in a state where the transmission of power from the steering wheel 12 to the steered wheels 20 is interrupted. Note that in Figure 5, processing corresponding to the processing shown in Figure 4 is denoted by the same reference numerals for convenience.

[0055] In this embodiment, the output of the arbitration process M18 is the target steering equivalent angle θp*, which is input to the yaw rate feedback process M24 and the angle operation amount calculation process M32. The yaw rate correction amount ΔTaf output by the yaw rate feedback process M24 is the correction amount for the axial force Taf. That is, the axial force calculation process M14 is a process of adding the steering torque Th to the steering operation amount Ts* and substituting the result for the axial force Taf0. The axial force correction process M60 is a process of adding the yaw rate correction amount ΔTaf to the axial force Taf, which is input to the target steering torque setting process M10 and the reference model calculation process M16.

[0056] As a result, the target steering angle θh* reflects the manipulated variable of the feedback control, in which the yaw rate yr is the controlled variable. As a result, the PU 42 controls the torque of the reaction force motor 90 so that the steering angle θh becomes appropriate for bringing the yaw rate yr closer to the target yaw rate yr*. Meanwhile, the PU 42 sets the target steering equivalent angle θp0* in accordance with the steering angle θh. As a result, the target steering equivalent angle θp* reflects the manipulated variable of the feedback control, in which the yaw rate yr is the controlled variable.

[0057] <Other Embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0058] Regarding the Input-Dependent Variable Calculation Process: In the process illustrated in Fig. 2, the target steering equivalent angle θp0* as the input-dependent variable is calculated using feedback control in which the steering torque Th is the controlled variable, but this is not limiting. For example, the target steering equivalent angle θp0* as the input-dependent variable may be calculated only from the manipulated variable of open-loop control in which the steering torque Th is the controlled variable.

[0059] 4 and 5, the target steering equivalent angle θp0* is calculated as an input-dependent variable in accordance with the steering angle θh and vehicle speed V, which indicate the driver's steering intention. However, this is not limitative. For example, the target steering equivalent angle θp0* may be calculated as an input-dependent variable in accordance with the target steering angle θh* and vehicle speed V. In this case, the driver's steering intention is expressed by the steering torque Th. The target steering angle θh* is calculated by a process in which the steering torque Th is the input and the target steering angle θh* is the output. Therefore, the target steering equivalent angle θp0* calculated by a process in which the target steering angle θh* and vehicle speed V are the input and the target steering equivalent angle θp0* is the output is an input-dependent variable.

[0060] Regarding the collaborative processing, the processing in which the output value of the processing for assisting steering of the vehicle in accordance with information about an object outside the vehicle and the value of the input-dependent variable are input, and the value of the target steering angle variable is output, is not limited to the processing exemplified in the above embodiment. For example, the processing may be processing in which a weighted average of the output value of the processing for assisting steering of the vehicle and the value of the input-dependent variable is assigned to the target steering angle variable.

[0061] The external requirement value that is input to the cooperative process is not limited to the output value of the process that assists the steering of the vehicle in accordance with information about an object outside the vehicle. For example, it may be a correction amount that corrects the target steering equivalent angle θp0* in accordance with the detection result of wheel slippage.

[0062] Regarding the operation process, the operation process is not limited to a process of operating the actuator in accordance with the operation amount of feedback control in which the steering equivalent angle θp is the control amount. For example, the operation process may be a process of operating the actuator in accordance with only the operation amount of open-loop control in which the target steering equivalent angle θp* is a target value of the control amount.

[0063] Regarding the target value setting process, the target value setting process is not limited to a process in which the target steering equivalent angle θp* and the vehicle speed V are input and the target yaw rate yr* is output. For example, if the vehicle is capable of steering both the front and rear wheels, the target values ​​of the steering equivalent angles of both the front and rear wheels and the vehicle speed V may be input variables.

[0064] Regarding the Reflection Process: The process of reflecting the manipulated variable of the feedback control, in which the yaw rate yr is the controlled variable, in the reaction force, thereby reflecting the manipulated variable in the operation of the actuator by the operation process via the value of the input-dependent variable, is not limited to the process exemplified in Fig. 5. This process may be, for example, a process of correcting the elastic coefficient K of the reference model calculation process M16 using the manipulated variable of the feedback control, in which the yaw rate yr is the controlled variable. Furthermore, this process may be, for example, a process of correcting the target steering angle θh* using the manipulated variable of the feedback control, in which the yaw rate yr is the controlled variable.

[0065] Regarding the ADASECU 70: The data containing information about objects outside the vehicle is not limited to image data. For example, it may be point cloud data generated in response to reflected laser light emitted in different directions by the LIDAR. The point cloud data is a collection of data indicating the distance between the object that reflected the laser light and the LIDAR and the direction of irradiation.

[0066] Regarding the Steering Control Device In the configuration illustrated in FIG. 3, the device that operates the reaction force motor 90 and the device that operates the steering motor 100 may be separate devices.

[0067] The ADASECU 70 and the steering control device 40 may be configured as an integrated unit. The steering control device is not limited to one that includes a PU 42 and a storage device 44 and executes software processing. For example, a dedicated hardware circuit such as an ASIC that executes at least part of the processing executed in the above embodiment may be included. In other words, the steering control device may include a processing circuit having any of the following configurations (a) to (c):

[0068] (a) A processing circuit comprising a processing device that executes all of the above processes according to a program and a program storage device such as a memory device that stores the program. (b) A processing circuit comprising a processing device and program storage device that executes part of the above processes according to a program, and a dedicated hardware circuit that executes the remaining processes.

[0069] (c) A processing circuit comprising a dedicated hardware circuit for executing all of the above processes. Here, there may be a plurality of software execution devices each comprising a processing device and a program storage device. Also, there may be a plurality of dedicated hardware circuits.

[0070] Regarding the Steering Control Method: The entity that executes the various controls described above is not limited to a steering control device attached to the vehicle. For example, part of the above-described processes may be executed by a mobile terminal of the driver.

[0071] Regarding the Input Unit: The input unit through which the driver inputs his / her steering intention is not limited to the steering wheel 12. For example, it may be a joystick.

[0072] Regarding the power transmission cut-off state: The configuration for realizing the power transmission cut-off state between the input unit to which the steering torque is input and the steered wheels 20 is not limited to the configuration illustrated in Fig. 4. For example, a clutch may be provided between the input shaft 14a and the output shaft 14b.

[0073] Regarding the steering device: As the actuator for steering steered wheels 20, for example, one in which assist motor 30 or steering motor 100 is arranged coaxially with steering shaft 16 may be used. Also, for example, one in which the power of assist motor 30 or steering motor 100 is transmitted to steering shaft 16 via a belt-type reducer using a ball screw mechanism may be used.

[0074] The steering device capable of changing the relationship between the steering angle and the turning angle is not limited to the steering device in which the transmission of power between the steering wheel 12 and the steered wheels 20 is blocked, as shown in Fig. 3. For example, a steering device capable of changing the relationship between the steering angle and the turning angle may be configured by using a variable gear as the gear that enables the transmission of power between the steering wheel 12 and the steered wheels 20.

Claims

1. A system configured to execute an input dependent variable calculation process, an arbitration process, an operation process, a target value setting process, and a reflection process, wherein the input dependent variable calculation process is a process for calculating a value of an input dependent variable in response to a steering intention indicated by a driver's operation of an input unit, the input dependent variable being a variable indicating a steering angle of a steered wheel of a vehicle in response to the steering intention, the arbitration process is a process in which a value of the input dependent variable and an external requirement value are input and a value of a target steering angle variable is an output, the target steering angle variable is a target value of the steering angle, and the external requirement value is a variable indicating a requirement value for the steering angle independent of the steering intention, the operation process is a process in which the value of the target steering angle variable is input and an actuator is operated, and the actuator is configured to apply a power to the steered wheels to turn the wheels, and the target value setting process is a process in which the value of the target steering angle variable output by the arbitration process is input and a target yaw rate is an output, a steering control device, wherein the reflection process is a process for reflecting an operation amount of a feedback control, in which a yaw rate is a control amount and the target yaw rate is a target value of the control amount, in an operation of the steering angle by the operation process, and is executed when at least a value obtained by superimposing the external requirement value on the value of the input dependent variable is substituted for the target steering angle variable output by the arbitration process.

2. A steering control device according to claim 1, wherein the reflection process is a process of inputting the value of the target steering angle variable corrected by the amount of operation into the operation process.

3. A steering control device as described in claim 1, configured to execute the input dependent variable calculation process, the arbitration process, the operation process, the target value setting process, the reflection process, and the reaction force setting process when power transmission between the steered wheels and the input section is cut off, the reaction force setting process being a process for setting a reaction force which is a force that resists operation of the input section by the driver, and the reflection process including a process for reflecting the operation amount in the reaction force, thereby reflecting the operation amount in the operation of the steering angle by the operation process via the value of the input dependent variable.

4. A steering control device according to claim 1, wherein the external requirement value is an output value of a process for assisting steering of the vehicle in response to information from outside the vehicle.

5. A method for controlling a vehicle speed by a vehicle driver, comprising steps of: executing an input dependent variable calculation process, an arbitration process, an operation process, a target value setting process, and a reflection process, wherein the input dependent variable calculation process is a process for calculating a value of an input dependent variable in response to a steering intention indicated by a driver's operation of an input unit; the input dependent variable is a variable indicating a steering angle of a steered wheel of a vehicle in response to the steering intention; the arbitration process is a process in which a value of the input dependent variable and an external requirement value are input and a value of a target steering angle variable is an output; the target steering angle variable is a target value of the steering angle; and the external requirement value is a variable indicating a requirement value for the steering angle independent of the steering intention; the operation process is a process in which the value of the target steering angle variable is input and an actuator is operated; the actuator is configured to impart to the steered wheels a power for steering the steered wheels; and the target value setting process is a process in which the value of the target steering angle variable output by the arbitration process is input and a target yaw rate is an output. The steering control method, wherein the reflection process is a process for reflecting an operation amount of a feedback control, in which a yaw rate is a control amount and the target yaw rate is a target value of the control amount, in an operation of the steering angle by the operation process, and is a process executed when a value in which the external requirement value is superimposed on at least the value of the input dependent variable is substituted for the target steering angle variable output by the arbitration process.

Images