Patent Application
20250136176
This application claims priority to Japanese Patent Application No. 2023-184775 filed on Oct. 27, 2023. The disclosure of the above-identified application, including the specification, drawings, and claims, is incorporated by reference herein in its entirety.
The present disclosure relates to a steering control device.
There is a so-called steer-by-wire steering device in which power transmission between a steering wheel and turning wheels is cut off. The steering device includes a reaction force motor that is a generation source of a steering reaction force to be applied to a steering shaft, and a turning motor that is a generation source of a turning force for turning the turning wheels. A control device of the steering device generates the steering reaction force through control of electric power supply to the reaction force motor, and turns the turning wheels through control of electric power supply to the turning motor.
For example, the control device of Japanese Unexamined Patent Application Publication No. 2020-83059 (JP 2020-83059 A) executes an output restriction process that restricts an output of a turning motor when an output restriction condition is met. Examples of the output restriction condition include that a temperature of the turning motor exceeds a temperature threshold value, and that a voltage supplied to the turning motor falls below a voltage threshold value. Through the execution of the output restriction process, a temperature rise of the turning motor or power consumption of the turning motor is restricted.
In conventional control devices having the function of restricting the output of the turning motor, including the control device of JP 2020-83059 A, there is a concern as follows: When the restriction on the output of the turning motor is canceled as the output restriction condition fails to be met or a specified output restriction cancelation condition is met, the output of the turning motor may change rapidly. A rapid change in the output of the turning motor constitutes a factor in causing abnormal sound or vibration.
One aspect of the present disclosure is a steering control device. The steering control device is configured to control electric power supply to a turning motor that drives a steering device that turns a turning wheel of a vehicle. The steering control device includes: a target rotation angle calculation circuit or unit configured to calculate, according to a steering angle of a steering wheel, a target rotation angle of a shaft that rotates in conjunction with a turning action of the turning wheel; an offset angle calculation circuit or unit configured to calculate an offset angle relative to the target rotation angle when a specific event occurs in a state where there is a discrepancy between the target rotation angle and a real angle of the shaft; a final target rotation angle calculation circuit or unit configured to calculate a final target rotation angle of the shaft by subtracting the offset angle from the target rotation angle; and a feedback control circuit or unit configured to execute feedback control that adapts the real angle to the final target rotation angle. The offset angle calculation circuit or unit is configured to calculate an estimated rotation angle deviation based on a value of a current of the turning motor immediately before the specific event occurs, and is configured to calculate the offset angle by subtracting the real angle and the estimated rotation angle deviation from the target rotation angle.
According to this configuration, when the specific event occurs, the final target rotation angle does not match the present value of the real angle of the shaft. Therefore, while the absolute value of the current supplied to the turning motor decreases rapidly, the absolute value of the current supplied to the turning motor does not instantly reach “0.” Thus, a rapid change in the output of the turning motor and, by extension, a rapid change in the turning angle of the turning wheel due to the absolute value of the current supplied to the turning motor instantly reaching “0” can be made less likely.
In the above-described steering control device, the offset angle calculation circuit may be configured to gradually reduce the offset angle toward zero after calculating the offset angle. According to this configuration, the real angle of the shaft can be adapted to the final target rotation angle while a rapid change in the output of the turning motor is made less likely.
In the above-described steering control device, the feedback control circuit may be configured to execute proportional control that controls the real angle in proportion to a deviation of the real angle from the final target rotation angle. When the estimated rotation angle deviation is “Δθp{circumflex over ( )}” the value of the current of the turning motor immediately before the specific event occurs is “Ib,” a proportional gain of the feedback control unit is “Gp,” a rated current of the turning motor is “It,” and a rated pinion torque is “Tp,” the offset angle calculation circuit may be configured to calculate the estimated rotation angle deviation based on the following Formula (A):
According to this configuration, the estimated rotation angle deviation of the shaft can be calculated as an angle corresponding to correction by the proportional control from the last time to the present time.
In the above-described steering control device, the specific event may be that execution of a current restriction process in which a current supplied to the turning motor is restricted is ended. When the current restriction process for the turning motor is executed as in this configuration, a discrepancy occurs between the target rotation angle and the real angle. According to this configuration, a rapid change in the output of the turning motor can be made less likely when the execution of the current restriction process is ended.
In the above-described steering control device, the specific event may be that a power source of the vehicle is turned on. According to this configuration, a rapid change in the output of the turning motor can be made less likely in the case where there is a discrepancy between the target rotation angle and the real angle when the vehicle power source is turned on.
In the above-described steering control device, the steering device may be a steer-by-wire steering device in which power transmission between the steering wheel and the turning wheel is cut off. This steering control device is suitable for a steer-by-wire steering device.
In the above-described steering control device, the steering device may be an electric power steering device in which the steering wheel and the turning wheel are coupled to each other so as to transmit power. The electric power steering device may have a variable-gear-ratio function of changing a steering gear ratio that is a ratio of a turning angle of the turning wheel to the steering angle of the steering wheel.
This steering control device is suitable for an electric power steering device having a variable-gear-ratio function.
The steering control device of the present disclosure can make a rapid change in the output of the turning motor less likely.
Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein:
One embodiment of a steering control device will be described below.
As shown in
The steering mechanism 3 has a steering shaft 11, a reaction force motor 12, and a speed reducer 13. The steering wheel 5 is coupled to the steering shaft 11 so as to be integrally rotatable. The reaction force motor 12 is a generation source of a steering reaction force to be applied to the steering shaft 11. The steering reaction force is a force in the opposite direction from a steering direction of the steering wheel 5. The reaction force motor 12 is, for example, a three-phase brushless motor. The speed reducer 13 decelerates rotation of the reaction force motor 12 and transmits the decelerated rotation to the steering shaft 11.
The turning mechanism 4 has a pinion shaft 21, a turning shaft 22, and a housing 23. The housing 23 rotatably supports the pinion shaft 21. The housing 23 reciprocably houses the turning shaft 22. Power transmission between the turning shaft 22 and the steering wheel 5 is cut off. The pinion shaft 21 is provided so as to intersect with the turning shaft 22. Pinion teeth 21a of the pinion shaft 21 mesh with rack teeth 22a of the turning shaft 22. At both ends of the turning shaft 22, tie rods 25 are coupled through rack ends 24 formed by ball joints. Leading ends of the tie rods 25 are coupled to knuckles (not shown) on which the turning wheels 6 are mounted.
The turning mechanism 4 includes a turning motor 31, a transmission mechanism 32, and a conversion mechanism 33. The turning motor 31 is a generation source of a turning force to be applied to the turning shaft 22. The turning force is a force for turning the turning wheels 6. The turning motor 31 is, for example, a three-phase brushless motor. The transmission mechanism 32 is, for example, a belt transmission mechanism. The transmission mechanism 32 transmits rotation of the turning motor 31 to the conversion mechanism 33. The conversion mechanism 33 is, for example, a ball screw mechanism. The conversion mechanism 33 converts the rotation transmitted through the transmission mechanism 32 into movement of the turning shaft 22 in an axial direction.
As the turning shaft 22 moves in the axial direction, a turning angle θw of the turning wheels 6 is changed. Since the pinion teeth 21a of the pinion shaft 21 are meshed with the rack teeth 22a of the turning shaft 22, the pinion shaft 21 rotates in conjunction with the movement of the turning shaft 22. The pinion shaft 21 is a shaft or a rotating body that rotates in conjunction with a turning action of the turning wheels 6.
The reaction force control device 1A controls the operation of the reaction force motor 12. The reaction force control device 1A has a processing circuit including one of the following three Configurations A1, A2, and A3:
A1. One or more processors that operate according to a computer program that is software.
Each processor includes a central processing unit (CPU) and a memory.
A2. One or more dedicated hardware circuits, such as application-specific integrated circuits (ASICs), that execute at least some of various processes.
Each ASIC includes a CPU and a memory.
A3. A hardware circuit combining Configurations A1 and A2.
The memory is a medium that is readable by a computer, and stores programs describing processes or commands for the computer. In this embodiment, the computer is a CPU. The memory includes a random-access memory (RAM) and a read-only memory (ROM). The CPU executes various modes of control by executing programs stored in the memory on a specified calculation cycle.
The reaction force control device 1A takes in detection results of on-board sensors. These sensors include a vehicle speed sensor 41, a torque sensor 42, and a rotation angle sensor 43. The vehicle speed sensor 41 detects a vehicle speed V. The vehicle speed V is a state variable reflecting a travel state of the vehicle. The torque sensor 42 is provided on the steering shaft 11. The torque sensor 42 is located on the side of the steering wheel 5 relative to a part of the steering shaft 11 at which the speed reducer 13 is coupled. The torque sensor 42 detects a steering torque Th applied to the steering shaft 11. The steering torque Th is calculated based on an amount of twisting of a torsion bar 42a that is provided in the steering shaft 11. The rotation angle sensor 43 is provided on the reaction force motor 12. The rotation angle sensor 43 detects a rotation angle θa of the reaction force motor 12.
The reaction force control device 1A controls the operation of the reaction force motor 12 using the detection results of the vehicle speed sensor 41, the torque sensor 42, and the rotation angle sensor 43. The reaction force control device 1A controls electric power supply to the reaction force motor 12 so as to make the reaction force motor 12 generate a steering reaction force according to the steering torque Th. The reaction force control device 1A is a processing device that controls the driving of the reaction force motor 12 according to a steering state of the steering wheel 5.
The turning control device 1B controls the operation of the turning motor 31. As with the reaction force control device 1A, the turning control device 1B has a processing circuit including one of the three Configurations A1, A2, and A3 described earlier. The turning control device 1B takes in detection results of on-board sensors. These sensors include a rotation angle sensor 44. The rotation angle sensor 44 is provided on the turning motor 31. The rotation angle sensor 44 detects a rotation angle θb of the turning motor 31.
The turning control device 1B controls the operation of the turning motor 31 using the detection result of the rotation angle sensor 44. The turning control device 1B controls electric power supply to the turning motor 31 such that the turning wheels 6 are turned according to the steering state of the steering wheel 5. The turning control device 1B is a processing device that controls the driving of the turning motor 31 according to the steering state of the steering wheel 5.
The turning control device 1B determines whether the turning wheel 6 is in contact with an obstacle. One example of obstacles is a curbstone. The turning control device 1B determines that the turning wheel is in contact with an obstacle when specified determination conditions are met. Examples of the determination conditions include that a state where a value of an actual current supplied to the turning motor is equal to or larger than a current threshold value continues for a predetermined time. When it is determined that the turning wheel 6 is in contact with an obstacle, the turning control device 1B executes specified control to make overheating of the turning motor 31 less likely. The specified control includes a current restriction process that restricts the current supplied to the turning motor 31. The current restriction process is one example of an under-high-load process that is executed when a high load acts on the turning motor 31.
Next, the configuration of the reaction force control device 1A will be described. As shown in
The steering angle calculation unit 51 calculates a steering angle θs of the steering wheel 5 based on the rotation angle θa of the reaction force motor 12 detected through the rotation angle sensor 43. The reaction-force-torque command value calculation unit 52 calculates a reaction-force-torque command value T* based on the steering torque Th and the vehicle speed V. The reaction-force-torque command value T* is a target value of the steering reaction force that should be generated by the reaction force motor 12. The steering reaction force is a torque in the opposite direction from the steering direction of the steering wheel 5. The absolute value of the reaction-force-torque command value T* becomes larger as the absolute value of the steering torque Th becomes larger and as the vehicle speed V becomes lower.
The current application control unit 53 supplies electric power according to the reaction-force-torque command value T* to the reaction force motor 12. Specifically, the current application control unit 53 calculates a current command value for the reaction force motor 12 based on the reaction-force-torque command value T*. The current application control unit 53 detects a value of a current Ia that occurs in an electric power supply path to the reaction force motor 12 through the current sensor 54 provided in the electric power supply path. The value of the current Ia is a value of the current supplied to the reaction force motor 12. The current application control unit 53 obtains a deviation of the value of the current Ia from the current command value and controls the electric power supply to the reaction force motor 12 so as to eliminate this deviation. Specifically, the current application control unit 53 executes feedback control of the current Ia such that the value of the current Ia adapts to the current command value. The feedback control is, for example, PID control. The PID control includes proportional control (P-control), integral control (I-control), and derivative control (D-control). Feedback gains that are control parameters of the feedback control include a proportional gain, an integral gain, and a derivative gain. Through the feedback control of the current Ia, the reaction force motor 12 generates a torque according to the reaction-force-torque command value T*.
Next, the configuration of the turning control device 1B will be described. As shown in
The pinion angle calculation unit 61 calculates a pinion angle θp based on the rotation angle θb of the turning motor 31 detected through the rotation angle sensor 43. The pinion angle θp is a rotation angle of the pinion shaft 21 and corresponds to a real angle of the pinion shaft 21 that is an actual angle thereof. The turning motor 31 and the pinion shaft 21 operate in conjunction with each other through the transmission mechanism 32, the conversion mechanism 33, and the turning shaft 22. Thus, there is a correlation between the rotation angle θb of the turning motor 31 and the pinion angle θp. Using this correlation, the pinion angle θp can be obtained from the rotation angle θb of the turning motor 31. The pinion shaft 21 is meshed with the turning shaft 22. Thus, there is also a correlation between the pinion angle θp and an amount of movement of the turning shaft 22. Therefore, the pinion angle θp is a value reflecting the turning angle θw of the turning wheels 6.
The target pinion angle calculation unit 62 calculates a target pinion angle θp1* based on the steering angle θs calculated by the steering angle calculation unit 51. The target pinion angle θp1* is a target rotation angle of the pinion angle θp. The target pinion angle calculation unit 62 calculates the target pinion angle θp1* such that a steered angle ratio that is set according to the product specifications etc. is realized. The steered angle ratio is a ratio of the turning angle θw to the steering angle θs.
The target pinion angle calculation unit 62 sets the steered angle ratio according to, for example, a travel state of the vehicle, such as the vehicle speed V, and calculates the target pinion angle θp1* according to this set steered angle ratio. The target pinion angle calculation unit 62 calculates the target pinion angle θp1*such that the turning angle θw relative to the steering angle θs becomes larger as the vehicle speed V becomes lower. The target pinion angle calculation unit 62 calculates the target pinion angle θp1* such that the turning angle θw relative to the steering angle θs becomes smaller as the vehicle speed V becomes higher. To realize the steered angle ratio that is set according to the travel state of the vehicle, the target pinion angle calculation unit 62 calculates the target pinion angle θp1* according to the steered angle ratio by calculating a correction angle relative to the steering angle θs and adding the calculated correction angle to the steering angle θs.
Depending on the product specifications etc., the target pinion angle calculation unit 62 may calculate the target pinion angle θp1* such that the steered angle ratio becomes “1:1” regardless of the travel state of the vehicle.
The offset determination unit 63 takes in the steering torque Th that is detected through the torque sensor 42 and a value of a current restriction flag Flim that is set by the restriction process unit 69 to be described later. Based on the steering torque Th and the value of the current restriction flag Flim, the offset determination unit 63 determines whether the situation is such that the target pinion angle θp1* should be offset.
The offset determination unit 63 determines that the situation is such that the target pinion angle θp1* should be offset, when steering back is performed in a situation where the turning wheel 6 is hitting an obstacle, i.e., a situation where the current restriction process for the turning motor 31 is being executed. Based on the value of the current restriction flag Flim, the offset determination unit 63 determines whether the current restriction process for the turning motor 31 is being executed. The offset determination unit 63 determines whether steering back has been performed through a comparison between the steering torque Th that is detected through the torque sensor 42 and a steering torque threshold value. The steering torque threshold value is stored in the memory. When the situation is such that the target pinion angle θp1* should be offset, the offset determination unit 63 sets the value of an offset determination flag Fofs to “on.”
When the turning wheel 6 is not hitting an obstacle, i.e., when the current restriction process for the turning motor 31 is not being executed, the offset determination unit 63 determines that the situation is not such that the target pinion angle θp1* should be offset. When the situation is not such that the target pinion angle θp1* should be offset, the offset determination unit 63 sets the value of the offset determination flag Fofs to “off.”
The offset angle calculation unit 64 takes in the pinion angle θp calculated by the pinion angle calculation unit 61, the target pinion angle θp1* calculated by the target pinion angle calculation unit 62, and the value of the offset determination flag Fofs set by the offset determination unit 63. The offset angle calculation unit 64 calculates an offset angle θofs when the value of the offset determination flag Fofs is “on.” As shown in the following Formula (1), the offset angle θofs is, for example, a difference between the target pinion angle θp1* and the pinion angle θp.
After calculating the offset angle θofs, the offset angle calculation unit 64 gradually reduces the offset angle θofs toward “0” as time passes.
When the value of the offset determination flag Fofs is “off,” the offset angle calculation unit 64 does not calculate the offset angle θofs, or sets the value of the offset angle θofs to “0.”
The final target pinion angle calculation unit 65 takes in the target pinion angle θp1* calculated by the target pinion angle calculation unit 62 and the offset angle θofs calculated by the offset angle calculation unit 64. The final target pinion angle calculation unit 65 calculates a final target pinion angle θp2* based on the target pinion angle θp1* and the offset angle θofs. As shown in the following Formula (2), the final target pinion angle θp2* is a difference between the target pinion angle θp1* and the offset angle θofs. The final target pinion angle θp2* corresponds to a final target rotation angle of the pinion shaft 21.
When the offset angle θofs is not calculated by the offset angle calculation unit 64, or when the value of the offset angle θofs is set to “0” by the offset angle calculation unit 64, the target pinion angle θp1* calculated by the target pinion angle calculation unit 62 is set as is as the final target pinion angle θp2*.
The pinion angle feedback control unit 66 takes in the final target pinion angle θp2* calculated by the final target pinion angle calculation unit 65 and the pinion angle θp calculated by the pinion angle calculation unit 61. The pinion angle feedback control unit 66 calculates a turning torque command value Tp* through feedback control of the pinion angle θp such that the pinion angle θp adapts to the final target pinion angle θp2*. The turning torque command value Tp* is a command value for the torque generated by the turning motor 31, and is a target value of the turning force.
The feedback control is, for example, PID control. The PID control includes proportional control (P-control), integral control (I-control), and derivative control (D-control). The proportional control is a control method that controls the pinion angle θp in proportion to a deviation of the pinion angle θp from the final target pinion angle θp2*. The integral control is a control method that controls the pinion angle θp in proportion to a time integral of the deviation of the pinion angle θp from the final target pinion angle θp2*. The derivative control is a control method that controls the pinion angle θp in proportion to a time derivative of the deviation of the pinion angle θp from the final target pinion angle θp2*. Feedback gains that are control parameters of the feedback control include a proportional gain, an integral gain, and a derivative gain.
The current application control unit 67 supplies electric power according to the turning torque command value Tp* to the turning motor 31. Specifically, the current application control unit 67 calculates a current command value for the turning motor 31 based on the turning torque command value Tp*. The current application control unit 67 detects the value of a current Ib that occurs in an electric power supply path to the turning motor 31 through the current sensor 68 provided in the electric power supply path. The value of the current Ib is a value of the current supplied to the turning motor 31. The current application control unit 67 obtains a deviation of the value of the current Ib from the current command value, and controls the electric power supply to the turning motor 31 so as to eliminate this deviation. Specifically, the current application control unit 67 executes feedback control of the current Ib such that the value of the current Ib adapts to the current command value. The feedback control is, for example, PID control. The PID control includes proportional control (P-control), integral control (I-control), and derivative control (D-control). Feedback gains that are control parameters of the feedback control include a proportional gain, an integral gain, and a derivative gain. Through the feedback control of the current Ib, the turning motor 31 generates a torque according to the turning torque command value Tp*.
The restriction process unit 69 determines whether the turning wheel 6 is hitting an obstacle. The restriction process unit 69 determines that the turning wheel 6 is hitting an obstacle, for example, when the following two Determination Conditions B1 and B2 are both met:
In Determination Condition B1, “Ib” is the value of the current of the turning motor 31, and “Ith” is a current threshold value. The current threshold value Ith is set based on the following perspective: When the turning wheel 6 is hitting an obstacle, it is difficult to perform steering forth. Steering forth is steering the steering wheel 5 so as to turn the turning wheel 6 toward the side of hitting the obstacle. In a situation where the turning wheel 6 is hitting an obstacle, the harder one tries to further turn the turning wheel 6 toward the side of hitting the obstacle, the further the absolute value of the current Ib of the turning motor 31 increases. Thus, it can be said that the larger the absolute value of the current Ib of the turning motor 31 is, the higher the probability is that the turning wheel 6 is hitting an obstacle. Therefore, the value of the current Ib of the turning motor 31 is a value indicating the degree of certainty of a situation where the turning wheel 6 is hitting an obstacle. Based on this perspective, the current threshold value Ith is set by an experiment or a simulation.
In Determination Condition B2, “T” is a time that has elapsed since the point when Determination Condition B1 was met. “Tth” is a time threshold value. The time threshold value Tth is a time required to confirm the determination result that the turning wheel 6 is hitting an obstacle.
When it is determined that the turning wheel 6 is hitting an obstacle, the restriction process unit 69 executes the current restriction process for the turning motor 31. The current restriction process is a process that restricts the current supplied to the turning motor 31 to restrict an output of the turning motor 31. Specifically, the restriction process unit 69 sets a limit value Ilim for restricting the amount of current supplied to the turning motor 31. The limit value Ilim is a value of the current that is set based on a perspective of protecting the turning motor 31 from overheating, and is an upper limit value of the amount of current supplied to the turning motor 31. The limit value Ilim is, for example, a value smaller than the current threshold value Ith.
When the limit value Ilim is calculated by the restriction process unit 69, the current application control unit 67 restricts the amount of current supplied to the turning motor 31 according to the limit value Ilim. The current application control unit 67 compares the absolute value of the current intended to be supplied to the turning motor 31 and the limit value Ilim. When the absolute value of the current intended to be supplied to the turning motor 31 is larger than the limit value Ilim, the current application control unit 67 restricts the absolute value of the current supplied to the turning motor 31 to the limit value Ilim. When the absolute value of the current intended to be supplied to the turning motor 31 is equal to or smaller than the limit value Ilim, the current application control unit 67 supplies the original current that is calculated through the feedback control of the current Ib as is to the turning motor 31.
The restriction process unit 69 sets the value of the current restriction flag Flim according to the determination result that the turning wheel 6 is hitting an obstacle. When it is determined that the turning wheel 6 is not hitting an obstacle, i.e., when at least one of the two Determination Conditions B1 and B2 is not met, the restriction process unit 69 sets the value of the current restriction flag Flim to “off.” In reality, “at least one of the two Determination Conditions B1 and B2” means “only Determination Condition B2 or both of the two Determination Conditions B1 and B2.” When it is determined that the turning wheel 6 is hitting an obstacle, i.e., when the two Determination Conditions B1 and B2 are both met, the restriction process unit 69 sets the value of the current restriction flag Flim to “on.”
The restriction process unit 69 ends the execution of the current restriction process for the turning motor 31 when a specified ending condition is met while the current restriction process for the turning motor 31 is being executed. One example of the ending condition is that steering back of the steering wheel 5 is performed. Steering back is steering the steering wheel 5 so as to turn the turning wheel 6 toward the opposite side from the side of hitting an obstacle. The restriction process unit 69 determines whether steering back has been performed, for example, through a comparison between the steering torque Th detected through the torque sensor 42 and the steering torque threshold value. When the ending condition for the current restriction process is met, the restriction process unit 69 sets the value of the current restriction flag Flim to “off.”
Next, the current restriction process for the turning motor 31 will be described. As shown in
As shown in
In
Thereafter, when the ending condition for the current restriction process is met, i.e., steering back of the steering wheel 5 is performed, the execution of the current restriction process for the turning motor 31 ends. Then, an offset process for the target pinion angle θp1* is executed. Specifically, the offset angle θofs is calculated by Formula (1) described earlier based on the target pinion angle θp1* immediately before the execution of the current restriction process ends and the pinion angle θp immediately before the execution of the current restriction process ends. Next, the final target pinion angle θp2* is calculated based on Formula (2) described earlier. Through the execution of this offset process, the final target pinion angle θp2* assumes the same value as the present pinion angle θp. In other words, the deviation of the pinion angle θp from the final target pinion angle θp2* is “0.” Therefore, through the feedback control of the pinion angle θp, a rapid change in the turning torque command value Tp* and, by extension, the amount of current supplied to the turning motor 31 is made less likely. Thus, a rapid change in the turning angle θw of the turning wheels 6 is made less likely. As a result, generation of abnormal sound accompanying a rapid change in the turning angle θw is made less likely.
The offset angle θofs decreases gradually toward “O” as time passes. Therefore, as time passes, the final target pinion angle θp2* gradually approaches the target pinion angle θp1* calculated by the target pinion angle calculation unit 62.
In the steering control device 1 thus configured, there is a concern as follows. As shown in the upper figure of
As shown in the lower figure of
As shown in the upper figure of
As shown in the lower figure of
In this embodiment, to make the rapid change in the turning angle θw due to the execution of the offset process less likely, the offset angle calculation unit 64 calculates the offset angle θofs as follows. Specifically, the offset angle calculation unit 64 calculates the offset angle θofs using the following Formula (3):
Here, “θp1*” is the target pinion angle at the time when the execution of the current restriction process ends, i.e., the present target pinion angle. “θp” is the pinion angle at the time when the execution of the current restriction process ends, i.e., the present pinion angle. “Δθp{circumflex over ( )}” is an estimated pinion angle deviation.
The estimated pinion angle deviation Δθp{circumflex over ( )} is a difference between the target pinion angle θp1* and the pinion angle θp that is the real angle with reference to the current Ib that is flowing through the turning motor 31 at present. The estimated pinion angle deviation Δθp{circumflex over ( )} is expressed by the following Formula (4). In Formula (4), “/” represents division and “.” represents multiplication.
Here, “Ib” is the last value of the current supplied to the turning motor 31, i.e., the value of the current of the turning motor 31 immediately before the execution of the current restriction process ends. The unit of the current Ib is “A (ampere).” “Gp” is the proportional gain of the pinion angle feedback control unit 66. The unit of the proportional gain Gp is “Nm/deg (newton meter per degree).” “It” is a rated current of the turning motor 31. The unit of the rated current It is “A (ampere).” The rated current It is stored in the memory. “Tp” is a rated pinion torque. The unit of the rated pinion torque Tp is “Nm (newton meter).” The rated pinion torque Tp is stored in the memory.
By using Formula (4), the offset angle calculation unit 64 can calculate the estimated rotation angle deviation Δθp{circumflex over ( )} of the pinion angle θp as an angle corresponding to correction by the proportional control from the last time to the present time.
Thus, the following workings can be produced. As shown in the upper figure of
As shown in the lower figure of
As shown in the upper figure of
As shown in the lower figure of
This embodiment offers the following advantages. The steering control device 1 has the target pinion angle calculation unit 62, the offset angle calculation unit 64, the final target pinion angle calculation unit 65, and the pinion angle feedback control unit 66. The target pinion angle calculation unit 62 calculates the target pinion angle θp1* that is the target rotation angle of the pinion shaft 21 based on the steering angle θs of the steering wheel 5. When a specified event occurs, the offset angle calculation unit 64 calculates the offset angle θofs relative to the target pinion angle θp1*. The final target pinion angle calculation unit 65 calculates the final target pinion angle θp2* that is the target rotation angle as final of the pinion shaft 21 by subtracting the offset angle θofs from the target pinion angle θp1*.
The pinion angle feedback control unit 66 executes the feedback control that makes the pinion angle θp that is the real angle of the pinion shaft 21 adapt to the final target pinion angle θp2*. The offset angle calculation unit 64 calculates the estimated pinion angle deviation Δθp{circumflex over ( )} based on the value of the current Ib of the turning motor 31 immediately before the event occurs. The estimated pinion angle deviation Δθp{circumflex over ( )} is the difference between the target pinion angle θp1* and the pinion angle θp with reference to the current Ib that is flowing through the turning motor 31 at present. The offset angle calculation unit 64 calculates the offset angle θofs by subtracting the pinion angle θp and the estimated pinion angle deviation Δθp{circumflex over ( )} from the target pinion angle θp1*.
According to this configuration, when the specific event occurs in a state where there is a discrepancy between the target pinion angle θp1* and the pinion angle θp, the final target pinion angle θp2* does not match the present value of the pinion angle θp. Therefore, while the absolute value of the current Ib supplied to the turning motor 31 decreases rapidly, the absolute value of the current Is supplied to the turning motor 31 does not instantly reach “0.” Thus, a rapid change in the output of the turning motor 31 and, by extension, a rapid change in the turning angle θw of the turning wheels 6 due to the absolute value of the current Ib supplied to the turning motor 31 instantly reaching “0” can be made less likely.
The target pinion angle calculation unit 62 corresponds to the target rotation angle calculation unit. The final target pinion angle calculation unit 65 corresponds to the final target rotation angle calculation unit. The pinion angle feedback control unit 66 corresponds to the feedback control unit.
The offset angle calculation unit 64 gradually reduces the offset angle θofs toward “0” after calculating the offset angle θofs. According to this configuration, the pinion angle θp that is the real angle of the pinion shaft 21 can be adapted to the final target pinion angle θp2* while a rapid change in the output of the turning motor 31 is made less likely.
The pinion angle feedback control unit 66 executes the proportional control that controls the pinion angle θp in proportion to the deviation of the pinion angle θp from the final target pinion angle θp2*. The offset angle calculation unit 64 calculates the estimated pinion angle deviation Δθp{circumflex over ( )}based on Formula (4) described earlier. According to this configuration, the estimated pinion angle deviation Δθp{circumflex over ( )} of the pinion shaft 21 can be calculated as an angle corresponding to correction by the proportional control from the last time to the present time.
The specific event is that the current restriction process in which the current Ib supplied to the turning motor 31 is restricted is ended. When the current restriction process for the turning motor 31 is executed as in this configuration, a discrepancy occurs between the target pinion angle θp1* and the pinion angle θp. Therefore, when the execution of the current restriction process is ended, a rapid change in the output of the turning motor 31 can be made less likely through the execution of the offset process based on Formulae (3) and (4) described earlier.
The steering device 2 is a steer-by-wire steering device in which power transmission between the steering wheel 5 and the turning wheels 6 is cut off. The steering control device 1 of this embodiment is suitable for the steer-by-wire steering device 2.
This embodiment may be implemented with the following changes made thereto. The offset process may be executed not only at the timing when the current restriction for the turning motor 31 is canceled but also at the time when the vehicle system is started, i.e., at the time when the vehicle power source is turned on.
As shown in
As shown in
In this case, however, as the deviation of the pinion angle θp from the final target pinion angle θp2* becomes “0,” the absolute value of the current Ib supplied to the turning motor 31 decreases rapidly toward “0” and instantly reaches “0.” Thus, the output of the turning motor 31 and, by extension, the turning angle θw of the turning wheels 6 may change rapidly.
To make the rapid change in the turning angle θw due to the execution of the offset process less likely, the offset angle θofs is calculated using Formula (3) described earlier. Thus, even when the execution of the offset process is started, the deviation of the pinion angle θp from the target pinion angle θp1* does not become “0.” Therefore, while the absolute value of the current Ib supplied to the turning motor 31 decreases rapidly, it does not instantly reach “0.” Thus, even when there is a discrepancy between the target pinion angle θp1* and the pinion angle θp that is the real angle when the vehicle power source is turned on, a rapid change in the output of the turning motor 31 and, by extension, a rapid change in the turning angle θw of the turning wheels 6 can be made less likely. That the power source of the vehicle is turned on corresponds to the specific event.
The steering device 2 may be an electric power steering device having a variable-gear-ratio (VGR) function. In the electric power steering device, the steering wheel 5 and the turning wheels 6 are coupled to each other so as to be able to transmit power. Specifically, the steering shaft 11 and the pinion shaft 21 are coupled to each other so as to be integrally rotatable. Some electric power steering devices have the VGR function. The VGR function is a function of changing a steering gear ratio that is the ratio of the turning angle θw of the turning wheels 6 to the steering angle θs of the steering wheel 5, for example, for the purpose of improving steerability. The electric power steering device having the VGR function has a VGR motor that is provided on the steering shaft 11. The steering gear ratio is changed through driving of the VGR motor. The steering control device 1 of this embodiment is suitable for an electric power steering device having the VGR function.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-184775 | Oct 2023 | JP | national |
