Steering control device

Abstract

A steering control device (60) controls a steering device (10). The steering device (10) includes a processor (62) configured to perform a dead zone amount calculation process and an overlay process. And a dead zone amount calculation process for calculating a dead zone amount by using the steering angle as an input, the dead zone amount being an amount by which the steering angle changes when the steered wheel (40) is not steered in the steering direction. The superimposition process is a process of superimposing the dead zone compensation torque on the torque of the motor (50) when the magnitude of the dead zone amount is greater than zero. The dead zone compensation torque increases the torque of the motor (50) in the direction in which the steered wheel (40) steers in accordance with the rotation of the steering shaft (14).

Description

Technical Field

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

[0002] For example, a control device for correcting a target steering angle according to a steering direction is described in Japanese Unexamined Patent Application Publication No. 2023-73790. In this device, when the planned steering direction is the right steering direction, the target steering angle is corrected by a backlash amount which is a value for the right steering direction. The backlash amount is the maximum value of an amount by which the steering angle of the steering wheel does not change even when the steering angle changes. Summary of the invention

[0003] In the case where the target steering angle is corrected as described above, there is a concern that an appropriate manipulated variable cannot be calculated because the target value deviates from the steering angle of the steering wheel intended to be actually controlled. Specifically, for example, in the case where a manipulated variable for feedforward control is calculated based on the target steering angle, there is a concern that the size of the manipulated variable becomes too large. The present disclosure provides a steering control device that improves the controllability of the steering angle.

[0004] A steering control device according to one aspect of the present disclosure is a steering control device for controlling a steering device. The steering device includes a steering shaft, a steering wheel of a vehicle, and a motor, the steering wheel turns as the steering shaft rotates, and the motor is configured to rotate the steering shaft. The steering device includes a processor configured to perform a dead zone amount calculation process and a superposition process. The dead zone amount calculation process is a process for calculating a dead zone amount using a steering angle as an input, and the dead zone amount is the amount of change in the steering angle when the steering wheel does not turn in the steering direction. The steering angle is the rotation angle of the steering shaft. The superposition process is a process as follows: when the size of the dead zone amount is greater than zero, a dead zone compensation torque is superimposed on the torque of the motor. The dead zone compensation torque is a torque that increases the torque of the motor in the direction in which the steering wheel turns according to the rotation of the steering shaft.

[0005] In the above configuration, when the dead zone amount is greater than zero, the dead zone compensation torque is superimposed on the torque of the motor. Therefore, by designing the dead zone compensation torque, it is possible to compensate for the reduction in responsiveness of the steering angle caused by the non-zero dead zone amount. Therefore, compared with the case of correcting the target value of the steering angle, it is possible to more directly compensate for the reduction in responsiveness of the steering angle caused by the dead zone amount other than zero, and thus it is possible to improve the controllability of the steering angle.

[0006] In a steering control device according to one aspect of the present disclosure, the superposition process may include a dead zone compensation torque calculation process. The dead zone compensation torque calculation process may be a process in which the size of the dead zone compensation torque is changed according to the dead zone amount under the condition that the size of the dead zone compensation torque is equal to or greater than the size of the dead zone compensation torque when the size of the dead zone amount is small when the size of the dead zone amount is large.

[0007] In the above configuration, the magnitude of the dead zone compensation torque varies according to the magnitude of the dead zone amount, and therefore, the dead zone compensation torque can be adjusted to a value more suitable for improving the controllability of the steering angle than when the magnitude of the dead zone compensation torque is fixed.

[0008] The steering control device according to an aspect of the present disclosure may further include a storage device in which a dead zone width is stored for each of the vehicle speeds that are different from each other. The dead zone width may be the amount of change in the steering angle after the rotation direction of the steering shaft is switched from one of the right turn direction and the left turn direction to the other of the right turn direction and the left turn direction and before the steering wheel is turned. The dead zone compensation torque calculation process may include a dead zone width selection process. The dead zone width selection process may be a process in which a dead zone width corresponding to the vehicle speed is selected from a plurality of dead zone widths stored in the storage device according to the vehicle speed. The dead zone compensation torque calculation process may be a process in which the size of the dead zone compensation torque is changed according to the ratio band under the condition that the size of the ratio of the dead zone amount to the dead zone width selected by the dead zone width selection process is large and the size of the dead zone compensation torque is equal to or greater than the size of the dead zone compensation torque when the size of the ratio is small.

[0009] The dead zone bandwidth may vary according to the vehicle speed. Therefore, in the above configuration, the magnitude of the dead zone compensation torque varies according to the magnitude of the ratio of the dead zone amount to the dead zone width. Thus, even if the dead zone width varies according to the vehicle speed, the maximum value of the dead zone compensation torque can be fixed.

[0010] In a steering control device according to an aspect of the present disclosure, a dead zone amount calculation process may include a steering direction determination process. The steering direction determination process may be a process of determining whether the steering direction is a right turn direction or a left turn direction based on a direction of change in a target value of a steering angle. The dead zone amount calculation process may be a process of calculating a dead zone amount based on a steering direction determined by the steering direction determination process.

[0011] In the above configuration, the dead zone amount is calculated according to the change in the target value. Therefore, it is possible to superimpose an appropriate dead zone compensation torque to improve the controllability of the steering angle with respect to the target value.

[0012] In a steering control device according to an aspect of the present disclosure, a dead zone amount calculation process may include a steering direction determination process. The steering direction determination process may be a process of determining whether the steering direction is a right turn direction or a left turn direction based on the sign of the difference between the target value of the steering angle and the steering angle. The dead zone amount calculation process may be a process of calculating the dead zone amount based on the steering direction determined by the steering direction determination process.

[0013] In the above configuration, the dead zone amount is calculated according to the sign of the difference between the target value and the steering angle. Therefore, it is possible to superimpose an appropriate dead zone compensation torque to improve the controllability of the steering angle with respect to the target value.

[0014] In a steering control device according to an aspect of the present disclosure, the processor may be configured to perform a steering process. The steering process may be a process of manipulating the torque of a motor according to a manipulated variable for feedback control, in which a steering angle of a steering wheel is a controlled variable and a target value of the steering angle is a target value of the controlled variable. The superposition process may be a process of superimposing a dead zone compensation torque on a torque according to the manipulated variable.

[0015] In the above configuration, by superimposing the dead zone compensation torque, feedback control according to the dead zone can be added to the feedforward control. Therefore, the responsiveness of the steering angle can be improved compared to the case where only feedback control is performed.

[0016] The steering control device according to aspects of the present disclosure may further include a storage device in which a stiffness coefficient is stored for each of different vehicle speeds. The stiffness coefficient may be a ratio of a steering angle to a steering angle. The processor may be configured to perform a stiffness coefficient selection process and a steering angle acquisition process. The stiffness coefficient selection process is a process in which a stiffness coefficient corresponding to the vehicle speed is selected from a plurality of stiffness coefficients stored in the storage device according to the vehicle speed.

[0017] The stiffness coefficient varies according to the vehicle speed. Therefore, in the above configuration, by using the stiffness coefficient according to the vehicle speed, the steering angle can be estimated with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] 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:

[0019] Figure 1 is a diagram showing a configuration of a steering system according to a first embodiment;

[0020] Figure 2 It is shown Figure 1A diagram showing the relationship between the steering control angle and the steering angle in the steering system shown;

[0021] Figure 3 It is shown by Figure 1 A block diagram of a process performed by a steering control device shown;

[0022] Figure 4 It is shown by Figure 1 A flowchart of the process performed by the steering control device shown;

[0023] Figure 5 It is shown by Figure 1 A flowchart of the process performed by the steering control device shown;

[0024] Figure 6 is an example Figure 5 A diagram of a portion of the process shown;

[0025] Figure 7 It is shown by Figure 1 A flowchart of the process performed by the steering control device shown;

[0026] Figure 8 It is shown by Figure 1 A flowchart of the process performed by the steering control device shown;

[0027] Fig. 9 It is shown by Figure 1 A flowchart of the process performed by the steering control device shown;

[0028] Fig.10 is exemplified by Figure 1 A timing diagram of the processing performed by the steering control device shown; and

[0029] Fig.11 is a flowchart showing the procedure of a process executed by the steering control device according to the second embodiment. DETAILED DESCRIPTION

[0030] First embodiment

[0031] A first embodiment will be described below with reference to the drawings.

[0032] Prerequisite Configuration

[0033] Figure 1The steering device 10 shown includes a steering wheel 12. A steering shaft 14 is coupled to the steering wheel 12. The end of the steering shaft 14 on the opposite side of the steering wheel 12 is coupled to a steering gear box 20. The sector shaft of the steering gear box 20 is coupled to one end of a link arm 22. The other end of the link arm 22 is coupled to one end of a trailing link 24. The other end of the trailing link 24 is coupled to one end of a knuckle arm 26. The other end of the knuckle arm 26 is coupled to a kingpin shaft 28 of a right steering wheel 40 (R). The kingpin shaft 28 of the right steering wheel 40 (R) and the kingpin shaft 28 of the left steering wheel 40 (L) are coupled through a tie rod arm 30 and a tie rod 32.

[0034] The rotational force of the motor 50 is transmitted to the steering shaft 14. As an example, the motor 50 is a synchronous electric motor. The output voltage of the inverter 52 is applied to the terminals of the motor 50.

[0035] The steering control device 60 includes a PU 62 and a storage device 64. The PU 62 is a software processing device such as a CPU, a GPU, and a TPU. The storage device 64 may be a non-volatile memory that cannot be electrically rewritten. In addition, the storage device 64 may be a non-volatile memory that can be electrically rewritten, or a storage medium such as a disk medium. The PU 62 executes the program stored in the storage device 64, and thereby the steering control device 60 performs processing for controlling the controlled object.

[0036] The controlled object of the steering control device 60 is the steering device 10. For the control of the controlled object, the steering control device 60 refers to the rotation angle θm of the motor 50 detected by the rotation angle sensor 70. In addition, the steering control device 60 refers to the yaw rate γ detected by the yaw rate sensor 71. In addition, the steering control device 60 refers to the currents iu, iv, iw flowing through the terminals of the motor 50. For example, the currents iu, iv, iw can be detected as the voltage drop amount at the shunt resistor provided on the branch of the inverter 52. The steering control device 60 refers to the vehicle speed V detected by the vehicle speed sensor 84 through the network 72.

[0037] The steering control device 60 is capable of communicating with the high-level ECU 80 through the network 72. The high-level ECU 80 performs a process of generating a command for intervening in the steering of the vehicle independently of an instruction of a steering manipulation due to the operation of the steering wheel 12. In other words, the high-level ECU 80 performs an autonomous steering process. In order to perform the autonomous steering process, the high-level ECU 80 acquires image data of the vehicle surroundings captured by the camera device 82. In addition, the high-level ECU 80 is aware of, for example, an intention instruction related to the execution of the autonomous steering process and input by the driver through the interface 86.

[0038] Characteristics of the steering device 10

[0039] The above-described steering device 10 includes a complicated link mechanism, and therefore, a so-called backlash in which the steering wheel 40 does not rotate in response to the rotation of the steering shaft 14 is large.

[0040] Figure 2 The relationship between the steering angle θh and the steering angle θt is shown. The steering angle θh is the rotation angle of the steering shaft 14. On the other hand, the steering angle θt is the movement angle of the tire associated with the steering wheel 40. In addition, Figure 2 The neutral position O shown is a point where the steering angle θh and the steering angle θt are both zero. This means that the steering angle θh and the steering angle θt both indicate the straight-ahead direction. In the following, it is assumed that the rotation angle in the right-turn direction is positive, and the rotation angle in the left-turn direction is negative.

[0041] like Figure 2 As shown, even when the steering angle θh changes from the neutral position O to the right turn direction, the steering angle θt does not change until the steering angle θh reaches point A. Then, when the steering angle θh becomes a value greater than point A, the steering angle θt increases.

[0042] Furthermore, even if the steering angle θh is reduced at point B, the steering angle θt does not change. In other words, even if the steering direction is switched to the left at point B, the steering angle θt does not change. The steering direction is the rotation direction of the steering shaft 14. Then, when the steering angle θh exceeds point C and becomes a smaller value, the steering angle θt decreases.

[0043] Then, at point D, the steering angle θt becomes zero. Point E is a value obtained by further displacing the steering angle θh in the left turn direction after the steering angle θt becomes zero. Even when the steering angle θh increases at point E, the steering angle θt does not change until the steering angle θh reaches point F. When the steering angle θh further increases beyond point F, the steering angle θt increases.

[0044] In this way, in the case of being at point B, even if the steering angle θh changes between point B and point C, the steering angle θt does not change. In addition, for example, in the case of being at point E, even if the steering angle θh changes between point E and point F, the steering angle θt does not change. In this way, due to the backlash of the steering device 10, there is a region where the steering angle θt does not change in response to the change in the steering angle θh, that is, a dead zone region. The dead zone region is not a region including a fixed value of the steering angle θh, but a region that can change according to the history of the change in the steering angle θh.

[0045] The displacement of the steering angle θh from point B to point C occurs in the return switch from the right turn. In addition, the displacement of the steering angle θh from point E to point F occurs in the return switch from the left turn. Figure 2 The dead zone width α shown is the length of a dead zone region in which the steering angle θt does not change in response to a change in the steering manipulation angle θh at the time of a return switch from a right turn or a left turn.

[0046] Control overview of steering control

[0047] Figure 3 Some of the processes performed by the steering control device 60 are shown. Figure 3 The illustrated processing is realized when the PU 62 repeatedly executes a program stored in the storage device 64 at predetermined time periods, for example.

[0048] The feedback process M10 is a process that takes the target steering angle θt* and the steering angle θt as inputs and takes the feedback manipulated variable Tfb as output. The feedback manipulated variable Tfb is a manipulated variable for feedback control with the steering angle θt as a controlled variable and the target steering angle θt* as a target value of the controlled variable. The target steering angle θt* is calculated by the high-level ECU 80. When the automatic driving mode is selected by the operation of the interface 86, the high-level ECU 80 calculates the target trajectory that the vehicle should travel based on the image data about the surroundings of the vehicle from the camera device 82. Then, the high-level ECU 80 calculates the target steering angle θt* so that the actual travel path of the vehicle approaches the target trajectory.

[0049] The steering angle estimation process M12 is a process that takes the steering angle θh as an input and takes the steering angle θt as an output. The steering angle θt is an estimated value. The steering angle θh is calculated by the PU 62 through an integration process of the rotation angle θm.

[0050] The dead zone compensation torque calculation process M14 is a process that uses the dead zone compensation torque Tdz in the dead zone area as an output, and the dead zone compensation torque Tdz is a manipulated variable used for feedforward control. The addition process M16 is a process that distributes the sum of the feedback manipulated variable Tfb and the dead zone compensation torque Tdz to the torque command value Trq*. The torque command value Trq* is a command value of the torque of the motor 50. The manipulation signal generation process M18 is a process that generates a manipulation signal MS for controlling the torque of the motor 50 to be close to the torque command value Trq* and outputs the manipulation signal MS to the inverter 52. The manipulation signal generation process M18 can be a process that makes the currents iu, iv, iw close to the current command value according to the torque command value Trq*.

[0051] The dead zone position calculation process M20 is a process for calculating the dead zone position Δα. The dead zone position Δα indicates Figure 2 The position of the variable within the deadband region is shown. Figure 2 The position Δα within the dead zone when the combination of the steering angle θh and the steering angle θt is at the point P is illustrated.

[0052] Control constant learning process M22

[0053] The control constant learning process M22 is a process of learning a control constant, which is a constant indicating the rotational displacement of the steered wheel 40 relative to the steering shaft 14 .

[0054] Figure 4 A procedure for preprocessing of the control constant learning process M22 is shown. Figure 4 The illustrated processing sequence is realized when the PU 62 repeatedly executes, for example, at predetermined time periods, a program stored in the storage device 64. Hereinafter, the step numbers of the processing are represented by numbers prefixed with "S".

[0055] exist Figure 4 In the processing sequence shown, the PU 62 first acquires the steering angle θh and the vehicle speed V (S10). Next, the PU 62 determines whether the absolute value of the steering angle θh is equal to or greater than the learning minimum value θL and equal to or less than the learning maximum value θH (S12). The learning minimum value θL is set based on the lower limit of the steering angle θh that allows the learning process described later to be correctly performed. In addition, the learning maximum value θH is set based on the upper limit of the steering angle θh that allows the learning process described later to be correctly performed. In setting the learning maximum value θH, it is considered that the running of the vehicle is unstable in the case where the steering angle θh is too large.

[0056] In the case where the PU 62 determines that the above absolute value is equal to or greater than the learning minimum value θL and equal to or less than the learning maximum value θH (S12: Yes), the PU 62 determines whether the condition that the absolute value of the steering angular velocity ωh is equal to or less than the threshold value ωth1 is satisfied (S14). The steering angular velocity ωh is the speed of change of the steering steering angle θh. The PU 62 calculates the steering angular velocity ωh using the time series data on the steering steering angle θh. The condition that the absolute value of the steering angular velocity ωh is equal to or less than the threshold value ωth1 is one of the execution conditions of the learning process described later. This condition is a condition indicating that the steering steering angle θh is stable.

[0057] In the case where the PU 62 determines that the absolute value of the steering angular velocity ωh is equal to or less than the threshold value ωth1 (S14: YES), the PU 62 determines whether the combination of the steering angle θh and the steering angle θt is outside the dead zone area (S16). The input in this process is the dead zone in-position Δα output by the dead zone in-position calculation process M20. In the case where the absolute value of the dead zone in-position Δα is less than "1 / 2" of the dead zone width αi described later, the PU 62 determines that the combination of the steering angle θh and the steering angle θt is in the dead zone area.

[0058] In the case where the PU 62 determines that the combination of the steering steering angle θh and the steering angle θt is not in the dead band region ( S16 : YES), the PU 62 determines whether the following condition (A) is satisfied ( S18 ).

[0059] Condition (A): Figure 4 The condition that the absolute value of the steering angular velocity ωh after the timing of the predetermined period of time before the current execution timing of the processing sequence in and before the current timing is equal to or smaller than the threshold value ωth2.

[0060] In the case where the PU 62 determines that the condition (A) is satisfied (S18: YES), the PU 62 acquires the yaw rate γ (S20). Next, the PU 62 assigns the value obtained by multiplying the yaw rate γ by "(1+A·V·V) / V / I" to the steering angle θt (S22). This process is a process in which the PU 62 estimates the steering angle θt based on the yaw rate γ. Here, the stability coefficient A and the wheelbase I are used.

[0061] Next, the PU 62 stores the steering angle θt estimated by the process of S22 in the storage device 64 in association with the steering direction, the vehicle speed V, and the steering operation angle θh (S24). Once the PU 62 completes the process of S24, or makes a negative determination in the process of S12, S14, S16, or S18, the PU 62 ends. Figure 4 The processing sequence shown.

[0062] Figure 5 The procedure of the control constant learning process M22 is shown. Figure 5 The illustrated processing sequence is realized when the PU 62 repeatedly executes a program stored in the storage device 64 at, for example, a predetermined period of time.

[0063] exist Figure 5 In the processing sequence shown, the PU 62 determines whether the data stored in the storage device 64 by the process of S24 has been secured to an amount that satisfies the learning condition (S30). As an example, the learning condition is a condition that the number of values ​​stored by the process of S24 in each of the following states 1 to 4 is a predetermined number. A plurality of predetermined numbers may be adopted.

[0064] State 1: When the steering direction is the right turn direction, the steering angle θh is equal to or greater than the learned minimum value θL and equal to or less than the learned maximum value θH.

[0065] State 2: When the steering direction is the right turn direction, the steering angle θh is equal to or greater than "-θH" and equal to or less than "-θL".

[0066] State 3: When the steering direction is the left turn direction, the steering angle θh is equal to or greater than the learned minimum value θL and equal to or less than the learned maximum value θH.

[0067] State 4: When the steering direction is the left turn direction, the steering angle θh is equal to or greater than "-θH" and equal to or less than "-θL".

[0068] In the case where PU 62 determines that the data has been secured to an amount that satisfies the learning condition (S30: Yes), PU 62 assigns "1" to the variable i that identifies the above data (S32). Next, PU 62 reads data, which is data in the sampled data stored in the storage device 64 through the processing of S24 and in which the vehicle speed V is in the area Ai (S34). According to the variable i, the area Ai shows one of the areas A1, A2, ... Areas A1, A2, ... are areas where the vehicle speeds V are different from each other. For example, area A3 is an area from 30km / h to 40km / h, and area A4 is an area from 40km / h to 50km / h. Then, PU 62 calculates the stiffness coefficient ki (S36). The stiffness coefficient is a coefficient that determines the ratio of the change in the steering angle θt to the change in the steering angle θh when the combination of the steering angle θh and the steering angle θt is not in the dead zone.

[0069] Figure 6 Each of the black circles shown indicates a combination of the steering angle θh and the steering angle θt stored by the process of S24. As an example, the PU 62 uses the least square method to evaluate a straight line that minimizes the deviation from the sampling point indicating the combination of the steering angle θh and the steering angle θt. Then, the PU 62 assigns the slope of the straight line to the stiffness coefficient ki. The stiffness coefficient ki is a learning value when the vehicle speed V is a value in the region Ai.

[0070] return Figure 5 PU 62 extracts the data read out by the process of S34 and the data that the steering direction is the right turn direction (S38). Then, PU 62 calculates the right turn direction based on the data extracted by the process of S38. Figure 6The right-turn straight line L1 shown (S40). The right-turn straight line L1 is a straight line having a slope of the stiffness coefficient ki calculated by the process of S36 and an intercept b1. The process of S40 is a process of evaluating the intercept b1 when the difference between the extracted data and the right-turn straight line L1 is minimized. The right-turn straight line L1 is an approximate expression for approximating the relationship between the steering angle θh and the steering angle θt when the steering direction is the right-turn direction.

[0071] Next, PU 62 extracts data from the data read by the process of S34 and data that the steering manipulation direction is the left turn direction (S42). Then, PU 62 calculates the left turn straight line L2 based on the data extracted by the process of S42 (S44). The left turn straight line L2 is a straight line having a slope of the stiffness coefficient ki calculated by the process of S42 and an intercept b2. The process of S44 is a process of evaluating the intercept b2 when the difference between the extracted data and the left turn straight line L2 is minimized. The left turn straight line L2 is an approximate expression for approximating the relationship between the steering manipulation angle θh and the steering angle θt when the steering manipulation direction is the left turn direction.

[0072] Next, the PU 62 assigns the absolute value of the difference between the intercept b1 and the intercept b2 to the dead band width αi (S46). The dead band width αi is a learning value when the vehicle V is a value in the region Ai. Then, the PU 62 determines whether the stiffness coefficients k1, k2, ... and the dead band widths α1, α2, ... have been completed for all regions A1, A2, ... associated with the vehicle speed V (S48). In the case where the PU 62 determines that there is an area where learning has not been completed (S48: No), the PU 62 increments the variable i (S50) and returns to the process of S34.

[0073] On the other hand, in the case where the PU 62 determines that the learning has been completed for all areas (S48: YES), the learned data is stored in a predetermined area of ​​the storage device 64 (S52). Once the PU 62 completes the processing of S52, or in the case of a negative determination in the processing of S30, the PU 62 ends. Figure 5 The processing sequence shown.

[0074] Incidentally, before the above learning is completed, the PU 62 uses preset default values ​​as the stiffness coefficient ki and the dead zone width αi. The default values ​​are stored in advance in the storage device 64. In addition, it is also possible to set the vehicle speed V to zero and not Figure 6 In this case, the learning of the dead zone width α0 in the area A0 can be performed alone using a well-known technique.

[0075] Steering angle estimation processing

[0076] Figure 7 The process of the steering angle estimation process M12 is shown. Figure 7 The illustrated processing is realized when the PU 62 repeatedly executes a program stored in the storage device 64 at predetermined time periods, for example.

[0077] exist Figure 7 In the processing sequence shown, first, the PU 62 acquires the steering angle θh and the vehicle speed V (S60). Next, the PU 62 selects the stiffness coefficient ki based on the vehicle speed V acquired by the processing of S60 (S62). For example, in the case where the vehicle speed V is a value in the area A2, the PU 62 selects the stiffness coefficient k2.

[0078] Next, PU 62 assigns the value obtained by dividing the steering steering angle θh by the stiffness coefficient ki to the steering angle θt0 (S64). Next, PU 62 calculates the steering angle θt by correcting the steering angle θt0 as appropriate (S66). That is, in the case where the steering angle θt0 is located in the dead zone area, PU 62 assigns the latest value of the steering angle θt to the steering angle θt. On the other hand, in the case where the steering angle θt0 is not in the dead zone area, PU 62 assigns the value obtained by adding the difference between the current value of the steering angle θt0 and the latest value of the steering angle θt to the latest value of the steering angle θt to the current value of the steering angle θt. Whether the steering angle θt0 is within the dead zone area is determined based on whether the size of the dead zone position Δα calculated by the dead zone position calculation processing M20 is less than "1 / 2" of the dead zone width αi. That is, in the processing of S66, the dead zone position Δα is used as an input.

[0079] Once the PU 62 completes the processing of S66, the PU 62 ends. Figure 7 The processing sequence shown.

[0080] Dead zone position calculation processing M20

[0081] Figure 8 The procedure of the dead zone position calculation process M20 is shown. Figure 8 The illustrated processing is realized when the PU 62 repeatedly executes a program stored in the storage device 64 at predetermined time periods, for example.

[0082] exist Figure 8 In the processing sequence shown, first, the PU 62 acquires the vehicle speed V (S70). Next, the PU 62 selects the dead zone width αi corresponding to the vehicle speed V acquired by the process of S70 (S72). For example, when the vehicle speed V is a value in the area A2, the PU 62 selects the dead zone width α2.

[0083] Next, PU 62 assigns the value obtained by subtracting the latest value "θh(n-1)" of the steering angle θh from the current value "θh(n)" of the steering angle θh to the latest value "Δα(n-1)" of the position Δα in the dead zone to the temporary position X (S74). Next, PU 62 determines whether the temporary position X is equal to or greater than "(-1)·αi / 2" and equal to or less than "αi / 2" (S76). This process is a process of determining whether the combination of the steering angle θh and the steering angle θt is within the dead zone area. In the case where PU 62 determines that the temporary position X is equal to or greater than "(-1)·αi / 2" and equal to or less than "αi / 2" (S76: Yes), PU 62 assigns the temporary position X to the dead zone position Δα (S77).

[0084] On the other hand, in the case where the PU 62 makes a negative determination in the process of S76, the PU 62 determines whether the temporary position X is greater than "αi / 2" (S78). In the case where the PU 62 determines that the temporary position X is greater than "αi / 2" (S78: Yes), the PU 62 assigns "αi / 2" to the position Δα within the dead zone (S80). On the other hand, in the case where the PU 62 determines that the temporary position X is less than "αi / 2" (S78: No), the PU 62 assigns "(-1)·αi / 2" to the position Δα within the dead zone (S82).

[0085] Once the PU 62 completes the processing of S77, S80 or S82, the PU 62 ends. Figure 8 The processing sequence shown.

[0086] Dead zone compensation torque calculation processing M14

[0087] Fig. 9 The procedure of the dead zone compensation torque calculation process M14 is shown. Fig. 9 The illustrated processing is realized when the PU 62 repeatedly executes a program stored in the storage device 64 at predetermined time periods, for example.

[0088] exist Fig. 9 In the processing sequence shown, first, the PU 62 acquires the vehicle speed V ( S90 ). Next, the PU 62 selects the dead zone width αi corresponding to the vehicle speed V selected by the processing of S90 ( S92 ).

[0089] PU 62 determines whether the value obtained by subtracting the latest value "θt*(n-1)" of the target steering angle θt* from the current value "θt*(n)" of the target steering angle θt* is positive (S94). This process is a process for determining whether the steering manipulation direction is the right turn direction. In the case where PU 62 determines whether the above value obtained by subtraction is positive (S94: Yes), PU 62 allocates the value obtained by subtracting the position Δα in the dead zone from "1 / 2" of the dead zone width αi selected by the process of S92 to the dead zone amount Dα (S96). The dead zone amount Dα obtained by the process of S96 is the maximum amount by which the steering angle θt does not change when the steering manipulation angle θh changes in the right turn direction.

[0090] Next, the PU 62 determines whether the dead zone amount Dα is greater than zero (S98). When the PU 62 determines that the dead zone amount Dα is greater than zero (S98: Yes), the PU 62 assigns the sum of the value obtained by dividing the dead zone amount Dα by the dead zone width αi and the prescribed torque TdzA and the offset TdzB to the dead zone compensation torque Tdz (S100).

[0091] On the other hand, in the case where PU 62 makes a negative determination in the process of S94, PU 62 determines whether the value obtained by subtracting the latest value "θt*(n-1)" of the target steering angle θt* from the current value "θt*(n)" of the target steering angle θt* is negative (S102). This process is a process for determining whether the steering manipulation direction is a left turn direction. In the case where PU 62 determines that the above value obtained by subtraction is negative (S102: Yes), PU 62 assigns the value obtained by subtracting the position Δα in the dead zone from "-1 / 2" of the dead zone width αi selected by the process of S92 to the dead zone amount Dα (S104). The absolute value of the dead zone amount Dα obtained by the process of S104 is the maximum amount by which the steering angle θt does not change when the steering manipulation angle θh changes in the left turn direction, and the maximum amount refers to the maximum value of the absolute value. Here, the dead zone amount Dα is equal to or less than zero.

[0092] When the PU 62 determines that the dead zone amount Dα is less than zero ( S106 : YES), the PU 62 allocates to the dead zone compensation torque Tdz a value obtained by subtracting the offset amount TdzB from a value obtained by adding the prescribed torque TdzA to the dead zone amount Dα divided by the dead zone width αi ( S108 ).

[0093] On the other hand, in the case where the PU 62 makes a negative determination in the process of S98 or S106, the PU 62 assigns "0" to the dead zone compensation torque Tdz (S110). Once the PU 62 completes the process of S100, S108, or S110, or makes a negative determination in the process of S102, the PU 62 ends. Fig. 9 The processing sequence shown.

[0094] Operation and Effects of Implementation Methods

[0095] Fig.10 FIG. 2 shows an example of the transition of the dead zone compensation torque Tdz according to the embodiment. Fig.10 As shown, at time t1 when PU62 determines that the steering direction has changed from the right turn direction to the left turn direction based on the target steering angle θt*, PU62 sets the dead zone compensation torque Tdz as the torque for left turn. Fig.10 , it is assumed that the steering angle θt is not within the dead zone region immediately before time t1. Therefore, the dead zone amount Dα at time t1 is "-αi". Therefore, at time t1, PU 62 gradually changes the dead zone compensation torque Tdz from "0" to "-TdzA-TdzB". Then, PU 62 gradually reduces the size of the dead zone compensation torque Tdz until the dead zone amount Dα becomes zero. At time t2 when the dead zone amount Dα becomes zero, PU 62 gradually changes the dead zone compensation torque Tdz from "-TdzB" to "0".

[0096] Thereafter, at time t3 when PU 62 determines that the steering manipulation direction has changed from the left turn direction to the right turn direction based on the target steering angle θt*, PU 62 sets the dead zone compensation torque Tdz to the torque for right turn. The dead zone amount Dα at time t3 is "αi". Therefore, at time t3, PU 62 gradually changes the dead zone compensation torque Tdz from "0" to "TdzA+TdzB". Then, PU 62 gradually reduces the size of the dead zone compensation torque Tdz until the dead zone amount Dα becomes zero. At time t4 when the dead zone amount Dα becomes zero, PU 62 gradually changes the dead zone compensation torque Tdz from "-TdzB" to "0".

[0097] In this way, when the steering angle θt is in the dead zone region, the PU 62 uses the dead zone compensation torque Tdz as the manipulated variable for feedforward control to control the torque of the motor 50. Therefore, compared with the case where the torque of the motor 50 is controlled using only the feedback manipulated variable Tfb, the responsiveness of the steering angle θt can be improved.

[0098] In particular, the dead zone compensation torque Tdz is a manipulated variable used for feedforward control, and therefore, the torque command value Trq* is easily designed to be an appropriate amount compared to the case of coping by correcting the target steering angle θt* when the steering angle θt is in the dead zone region.

[0099] In the above-described embodiment, the following operations and effects can also be obtained.

[0100] (1-1) Dead zone compensation torque Tdz is set based on a value obtained by dividing the dead zone amount Dα by the dead zone width αi. As a result, the maximum absolute value of the dead zone compensation torque Tdz can be made constant regardless of the size of the dead zone width αi.

[0101] (1-2) The PU 62 determines the steering direction according to the direction of change of the target steering angle θt*. Thus, the controllability of the steering angle θt according to the steering direction desired by the high-level ECU 80 can be improved.

[0102] (1-3) The PU 62 estimates the steering angle θt using the stiffness coefficient ki according to the vehicle speed V. Thus, the stiffness coefficient ki can be set to an appropriate value according to the vehicle speed V, and the accuracy of the estimation of the steering angle θt can be improved.

[0103] (1-4) The PU 62 learns the dead zone width αi according to the vehicle speed V. Thus, compared with a case where the dead zone width αi is a value independent of the vehicle speed V, the position Δα within the dead zone can be calculated with higher accuracy.

[0104] Second embodiment

[0105] Hereinafter, with reference to the drawings, the second embodiment will be described mainly based on the differences from the first embodiment.

[0106] Fig.11 The procedure of the dead zone compensation torque calculation process M14 according to the second embodiment is shown. Fig.11 The illustrated processing is realized when the PU 62 repeatedly executes a program stored in the storage device 64 at predetermined time intervals, for example. Fig.11 In the process shown, for convenience, Fig. 9 Corresponding processes to those shown are denoted by the same step numbers.

[0107] exist Fig.11 In the processing sequence shown, in the case where the PU 62 completes the processing of S92, the PU 62 determines whether the value obtained by subtracting the steering angle θt from the target steering angle θt* is positive (S94a). The processing of S94a is a process for determining whether the steering manipulation direction is the right turn direction. In the case where the PU 62 determines that the above value obtained by subtraction is positive (S94a: Yes), the PU 92 transitions to the processing of S96.

[0108] On the other hand, in the case where the PU 62 determines that the above value obtained by subtraction is equal to or less than zero (S94a: No), the PU 62 determines whether the value obtained by subtracting the steering angle θt from the target steering angle θt* is negative (S102a). The process of S102a is a process for determining whether the steering manipulation direction is the left turn direction. In the case where the PU 62 determines that the above value obtained by subtraction is negative (S102a: Yes), the PU 62 transitions to the process of S104. On the other hand, once the PU 62 makes a negative determination in the process of S102a, the PU 62 ends. Fig.11 The processing sequence shown.

[0109] Correspondence

[0110] The correspondence between the matters in the above-mentioned embodiment and the matters described in the "Summary of the Invention" is shown as follows. The dead zone position calculation processing M20 and the processing of S92 to S96, S102 and S104 constitute an example of the dead zone amount calculation processing. In addition, the dead zone position calculation processing M20 and the processing of S92, S94a, S96, S102a and S104 constitute an example of the dead zone amount calculation processing. The dead zone compensation torque calculation processing M14 and the addition processing M16 constitute an example of the superposition processing. The processing of S72 and S92 constitutes an example of the dead zone width selection processing. The processing of S94 and S102 constitutes an example of the steering control direction determination processing. The processing of S94a and S102a constitutes an example of the steering control direction determination processing. The feedback processing M10 and the control signal generation processing M18 constitute an example of the steering processing. The processing of S62 constitutes an example of the stiffness coefficient selection processing. The processing of S64 and S66 constitutes an example of the steering angle acquisition processing.

[0111] Other Implementations

[0112] The following modifications may be performed on the embodiment. As long as there is no technical inconsistency, the embodiment and the following modifications may be implemented in combination with each other.

[0113] Dead zone compensation torque calculation and processing

[0114] In the dead zone compensation torque calculation process, it is not necessary to calculate the dead zone compensation torque Tdz using the offset TdzB.

[0115] In the dead zone compensation torque calculation process, the dead zone compensation torque Tdz does not need to be calculated as a value proportional to the value obtained by dividing the dead zone amount Dα by the dead zone width αi. For example, in the dead zone compensation torque calculation process, the dead zone compensation torque Tdz may be calculated as a value proportional to the square of the above value obtained by division.

[0116] The dead zone compensation torque calculation process does not need to be a process of calculating a value obtained by inputting the above-mentioned value obtained by division into an elementary function. For example, the dead zone compensation torque calculation process may also be a process of performing map calculation of the dead zone compensation torque Tdz by the PU 62 in a state where the map data is stored in advance in the storage device 64. In this case, the relationship between the value obtained by division and the dead zone compensation torque Tdz may be adjusted to an arbitrary relationship that cannot be expressed by an elementary function.

[0117] Even in this case, the dead zone compensation torque calculation process may be a process of changing the dead zone compensation torque Tdz according to the dead zone amount Dα under the condition that the dead zone compensation torque Tdz when the dead zone amount Dα is large is equal to or greater than the dead zone compensation torque Tdz when the dead zone amount Dα is small.

[0118] In the description of "B is changed according to A under the condition that B is equal to or greater than B when A is small", "when A is large" and "when A is small" refer to the relative size relationship when comparing the two situations. 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". In addition, the above description means that, according to the setting of the first value and the second value, B when A is the first value can be greater than B when A is the second value. In addition, the above description means changing B according to A so that A when B is large is greater than A when B is small.

[0119] Incidentally, in the map data, a value obtained by division may be employed as an input variable, and alternatively, the dead zone amount Dα and the dead zone width αi may be employed as input variables.

[0120] In the dead zone compensation torque calculation process, the dead zone compensation torque Tdz does not need to be calculated considering the dead zone width αi. For example, the dead zone compensation torque calculation process may be a process of calculating the dead zone compensation torque Tdz based on the dead zone amount Dα without referring to the dead zone width αi.

[0121] Dead zone position calculation and processing

[0122] The dead zone position calculation process M20 does not need to be a process of calculating the dead zone position Δα using the dead zone width αi according to the vehicle speed. For example, a process of calculating the dead zone position Δα using a single dead zone width that does not depend on the vehicle speed may be employed.

[0123] Steering angle θt

[0124] The steering angle estimation process M12 does not need to be a process of estimating the steering angle using the stiffness coefficient ki learned according to the vehicle speed V. For example, a process of estimating the steering angle using the stiffness coefficient ki that does not depend on the vehicle speed may be employed.

[0125] The steering angle θt as a controlled variable for feedback control does not need to be an estimated value. For example, the steering angle θt may be a detection value of a sensor that detects the steering angle.

[0126] Motor torque control

[0127] In the control in which the steering angle is a controlled variable and the target value of the steering angle is a target value of the controlled variable, the drive circuit of the motor 50 does not need to operate according to the manipulated variable. For example, the drive circuit of the motor 50 may operate according to the manipulated variable of the feedforward control depending on the target value. In this case, in the dead zone, the PU 62 may superimpose the dead zone compensation torque Tdz on the manipulated variable for the feedforward control calculated even outside the dead zone area.

[0128] Autopilot mode

[0129] In the automatic driving mode, the sensing member for acquiring information about the outside of the vehicle including the lane is not limited to the camera 82. For example, a laser radar (LIDAR) may be used.

[0130] Driving Mode

[0131] The driving mode in which the dead zone compensation torque Tdz is superimposed on the torque of the motor 50 is not limited to the automatic driving mode. For example, a manual driving mode in which the driver's steering is performed may be adopted. In this case, for example, in the processing of S94 and S102, it is only necessary to adopt the steering manipulation angle θh instead of the target steering angle θt*.

[0132] Steering Controls

[0133] The high-level ECU 80 and the steering control device 60 may be configured integrally. The steering control device is not limited to a device that performs software processing. For example, a dedicated hardware circuit may be included that performs at least some of the processing performed in the above-described embodiment, as exemplified by an ASIC. That is, the steering control circuit only needs to include a processing circuit of one of the configurations (a) to (c) described below.

[0134] (a) A processing circuit including a processing device that executes all the above-mentioned processing according to a program and a program storage device storing the program, exemplified as a storage device.

[0135] (b) A processing circuit including a processing device that executes some of the above-mentioned processing according to a program, a program storage device, and a dedicated hardware circuit that executes other processing.

[0136] (c) A processing circuit comprising dedicated hardware circuits that perform all of the above processing.

[0137] A plurality of software execution means may be provided, each of the plurality of software execution means comprising a processing means and a program storage means. In addition, a plurality of dedicated hardware circuits may be provided.

Claims

1. A steering control device (60) for controlling a steering control device (10), The steering control device (10) is characterized by comprising: Steering shaft (14); A steering wheel (40) of a vehicle, wherein the steering wheel (40) turns as the steering shaft (14) rotates; a motor (50) configured to rotate the steering shaft (14); as well as A processor (62) configured to perform a dead zone amount calculation process and a superposition process, wherein: The dead zone amount calculation process is a process for calculating a dead zone amount using a steering angle as an input, wherein the dead zone amount is an amount by which the steering angle changes when the steering wheel (40) is not turned in a steering direction; The steering control angle is the rotation angle of the steering control shaft (14); The superposition process is as follows: when the magnitude of the dead zone amount is greater than zero, the dead zone compensation torque is superimposed on the torque of the motor (50); and The dead zone compensation torque is a torque that increases the torque of the motor (50) in the direction in which the steering wheel (40) is turned according to the rotation of the steering shaft (14).

2. The steering control device (60) according to claim 1, characterized in that: The superposition process includes a dead zone compensation torque calculation process; and The dead zone compensation torque calculation process is as follows: under the condition that the size of the dead zone compensation torque is equal to or greater than the size of the dead zone compensation torque when the size of the dead zone amount is large, the size of the dead zone compensation torque is changed according to the dead zone amount.

3. The steering control device (60) according to claim 2, further comprising a storage device (64) in which a dead zone width is stored for each of vehicle speeds that are different from each other, the dead zone width being the amount by which the steering angle changes after the rotation direction of the steering shaft (14) is switched from one of the right turn direction and the left turn direction to the other of the right turn direction and the left turn direction and before the steering wheel (40) turns, characterized in that: The dead zone compensation torque calculation process includes a dead zone width selection process; The dead zone width selection process is a process of selecting the dead zone width corresponding to the vehicle speed from among the plurality of dead zone widths stored in the storage device (64) according to the vehicle speed; and The dead zone compensation torque calculation process is as follows: under the condition that when the size of the ratio of the dead zone amount to the dead zone width selected by the dead zone width selection process is large, the size of the dead zone compensation torque is equal to or greater than the size of the dead zone compensation torque when the size of the ratio is small, the size of the dead zone compensation torque is changed according to the ratio.

4. The steering control device (60) according to claim 1, characterized in that: The dead zone amount calculation process includes a steering direction determination process; The steering direction determination process is a process of determining whether the steering direction is a right turn direction or a left turn direction based on a change direction of a target value of a steering angle; as well as The dead zone amount calculation process is a process of calculating the dead zone amount according to the steering direction determined by the steering direction determination process.

5. The steering control device (60) according to claim 1, characterized in that: The dead zone amount calculation process includes a steering direction determination process; The steering direction determination process is a process of determining whether the steering direction is a right turn direction or a left turn direction based on the sign of the difference between the target value of the steering angle and the steering angle; as well as The dead zone amount calculation process is a process of calculating the dead zone amount according to the steering direction determined by the steering direction determination process.

6. The steering control device (60) according to claim 1, characterized in that: The processor (62) is configured to perform a steering process; The steering process is a process of manipulating the torque of the motor (50) according to a manipulated variable for feedback control in which a steering angle of the steering wheel (40) is a controlled variable and a target value of the steering angle is a target value of the controlled variable; and The superimposition processing is a processing of superimposing the dead zone compensation torque on the torque according to the manipulated variable.

7. The steering control device (60) according to claim 6, further comprising a storage device (64) in which a stiffness coefficient is stored for each of vehicle speeds that are different from each other, the stiffness coefficient being a ratio of the steering angle to the steering angle, characterized in that: The processor (62) is configured to perform a stiffness coefficient selection process and a steering angle acquisition process; The stiffness coefficient selection process is a process of: selecting the stiffness coefficient corresponding to the vehicle speed from among the plurality of stiffness coefficients stored in the storage device (64) according to the vehicle speed; as well as The steering angle acquisition process is a process of calculating an estimated value of the steering angle as the controlled variable using the detection value of the steering manipulation angle and the stiffness coefficient selected by the stiffness coefficient selection process.

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