Steering system

Abstract

This steering system (100) comprises an operation member (110), a first motor (121) that operates the operation member (110), a first control device (131) that controls the first motor (121), a second motor (122) that operates the operation member (110), a second control device (132) that controls the second motor (122), and a third control device (133) that transmits target values to the first control device (131) and the second control device (132) for driving the first motor (121) and the second motor (122). The third control device (133) comprises: a response difference determination unit (141) that determines whether or not a deviation amount, which is the magnitude of the difference between the response timing of the first motor (121) and the response timing of the second motor (122), based on the transmitted target values, is within a prescribed range; and a control adjustment unit (142) that adjusts the deviation amount so as to fall within a prescribed range when the deviation amount is outside the prescribed range.

Description

Steering system

[0001] The present invention relates to a steering system that steers a steered wheel by operating one operating member by controlling two or more motors respectively.

[0002] For example, Patent Document 1 describes a technique for correcting and synchronizing the driving timings of two motors. Specifically, a technique is described in which two control systems respectively connected to two motors receive synchronization signals from each other to generate a signal indicating a deviation, and detect the deviation of the driving timing of the motors.

[0003] Japanese Patent Application Laid-Open No. 2017-189037

[0004] However, in the technique described in Patent Document 1, although the synchronization of the driving timings of the motors is performed, the driving timings of the motors are not synchronized in consideration of the difference in responsiveness of the control arithmetic units that control the motors respectively and the difference in motor characteristics. Therefore, it is impossible to cope with the deviation of the driving timing of the motor due to performance differences such as motors, speed reducers, or control systems, differences in changes over time, performance differences in communication in the control system, and the like.

[0005] The present invention has been made in view of the above problems, and provides a steering system that adjusts the deviation amount of the responses of two or more motors to be within a predetermined range.

[0006] A steering system according to one aspect of the present invention is a steering system that steers a steered wheel, and includes an operating member that operates when steering the steered wheel, a first motor that operates the operating member, a first control device that controls the first motor, a second motor that operates the operating member, a second control device that controls the second motor, and a third control device that transmits target values for driving the first motor and the second motor to the first control device and the second control device. The third control device includes a response difference determination unit that determines whether or not a deviation amount, which is the magnitude of the difference between the response timing of the first motor and the response timing of the second motor based on the transmitted target values, is within a predetermined range, and a control adjustment unit that adjusts the deviation amount to be within the predetermined range when the deviation amount is outside the predetermined range.

[0007] According to the present invention, the stability of the operating state is improved when a single operating member is operated by multiple motors.

[0008] Figure 1 is a diagram showing the overall configuration of the steering system. Figure 2 is a block diagram showing the functional configuration of the steering system. Figure 3 is a block diagram showing another example 1 of the functional configuration of the steering system. Figure 4 is a block diagram showing another example 2 of the functional configuration of the steering system.

[0009] The following describes embodiments of the steering system according to the present invention with reference to the drawings. Note that the following embodiments are examples provided to illustrate the present invention and are not intended to limit it. For example, the shapes, structures, materials, components, relative positional relationships, connection states, numerical values, formulas, the content of each step in the method, and the order of each step shown in the following embodiments are examples and may include content not described below. Furthermore, geometric expressions such as parallel and orthogonal may be used, but these expressions do not indicate mathematical rigor and include substantially acceptable errors and deviations. Similarly, expressions such as simultaneous and identical also include substantially acceptable ranges.

[0010] Furthermore, the drawings are schematic diagrams that have been appropriately emphasized, omitted, or had their proportions adjusted to illustrate the present invention, and therefore differ from the actual shapes, positional relationships, and proportions. Also, the X, Y, and Z axes shown in the drawings represent orthogonal coordinates arbitrarily set for the purpose of explaining the drawings. In other words, the Z axis is not necessarily an axis along the vertical direction, and the X and Y axes are not necessarily located in the horizontal plane.

[0011] Furthermore, in the following, multiple inventions may be described comprehensively as a single embodiment. Also, some of the content described below is described as an optional component relating to the present invention.

[0012] Figure 1 is a diagram showing the overall configuration of the steering system 100. Figure 2 is a block diagram showing the functional configuration of the steering system 100. The steering system 100 is a system that can steer the steering wheels 200 mounted on a vehicle such as a passenger car based on signals output by operating an operating member 210. In this embodiment, the steering system 100 is a so-called linkless steer-by-wire system in which the operating member 210 and the steering wheels 200 are not connected by mechanical elements such as links, and the steering wheels 200 are steered based solely on signals. The steering system 100 includes an operating member 110, a first motor 121, a second motor 122, a first control device 131, a second control device 132, and a third control device 133. In this embodiment, the steering system 100 also includes an operating amount output device 134 and an automatic driving device 135.

[0013] The operating member 110 is a member that operates in response to the output of the first motor 121 and the output of the second motor 122 to generate thrust and steer the steering wheels 200. The type of operating member 110 is not limited, but in this embodiment, the operating member 110 is a rack bar, with rack teeth provided around both ends in the longitudinal direction. The rack bar generates thrust in the axial direction in response to the output of the first motor 121 and the output of the second motor 122, and steers the two steering wheels 200 simultaneously via tie rods or the like connected to both ends of the rack bar.

[0014] The first motor 121 and the second motor 122 are electric motors that work together to operate a single operating member 110. The mechanism by which the first motor 121 and the second motor 122 operate the operating member 110 is not limited, but in this embodiment, two pinion shafts that mesh with each other are arranged on the rack teeth provided at two locations on the rack bar. In addition, two reduction gears are attached to the pinion shafts, respectively, to reduce the rotational output of the first motor 121 and the second motor 122 and rotate the pinion shafts. Through these mechanisms, the first motor 121 and the second motor 122 operate the operating member 110.

[0015] The first motor 121 and the second motor 122 operate based on steering signals output from the control input output device 134 or from the automatic driving device 135 when the driver operates the control member 210. The first motor 121 and the second motor 122 may be collectively referred to as "motors." The type of steering signal is not limited, but examples include signals indicating target torque and target steering angle. The target steering angle can be determined, for example, by a known method (such as a map) based on the steering angle and vehicle speed when the driver steers the control member 210.

[0016] The first control device 131 is a so-called ECU (Electronic Control Unit) that controls the first motor 121. The second control device 132 is an ECU that controls the second motor 122, similar to the first control device 131. In this embodiment, the first control device 131 and the second control device 132 perform feedback control so that the driving state of the first motor 121 and the second motor 122 approaches a target value (for example, a target current value) output by the third control device 133 based on the steering signal. Note that the first control device 131, the second control device 132, and the third control device 133 may be collectively referred to as "control devices".

[0017] The third control unit 133 is a so-called ECU that transmits target values ​​for driving the first motor 121 and the second motor 122 to the first control unit 131 and the second control unit 132. The communication method for transmitting the target values ​​from the third control unit 133 to the first control unit 131 and the second control unit 132 is not limited. For example, communication may be performed using a so-called CAN (Controller Area Network) that uses a standard protocol for in-vehicle networks to perform communication between control units. Alternatively, communication may be performed using a communication standard other than CAN.

[0018] Each control unit is equipped with a processor, and by having the processor execute a program, it realizes motor control, communication between control units, and conversion from steering signals to target values. The third control unit 133 realizes a response difference determination unit 141 and a control adjustment unit 142 by having the processor execute a synchronization program. In this embodiment, the third control unit 133 is equipped with a target value transmission unit 143 as a processing unit.

[0019] The response difference determination unit 141 determines whether the difference between the response timing of the first motor 121 based on the target value transmitted by the third control device 133 and the response timing of the second motor 122 is within a predetermined range. The response timing of the second motor 122 can be exemplified by the timing of the motor's torque output, torque change, or motor stop.

[0020] In this embodiment, the response difference determination unit 141 acquires a first required time, which is the time required for communication between the third control device 133 and the first control device 131, and a second required time, which is the time required for communication between the third control device 133 and the second control device 132, and determines the magnitude of the difference between the first required time and the second required time as the deviation amount. The specific method for acquiring the first required time and the second required time is not limited. For example, if the clocks of the control devices are synchronized, a packet containing information indicating the transmission time may be transmitted, and the difference between the received time and the transmission time in the packet may be used as the time required for communication. Alternatively, the response difference determination unit 141 may use the magnitude of the difference between the time from when the third control device 133 transmits a first transmission signal to the first control device 131 to transmit a target value, until when the first transmission signal is successfully received, and the time from when the third control device 133 transmits a second transmission signal to the second control device 132 to transmit a target value, until when the second transmission signal is successfully received, as the deviation amount. Specifically, when the control device is communicating using CAN, the time difference between transmission and acknowledgment packets can be defined as the delay amount.

[0021] Furthermore, the response difference determination unit 141 can acquire the first communication count, which is at least one of the number of normal communications and the number of communication errors between the third control device 133 and the first control device 131, and the second communication count, which is at least one of the number of normal communications and the number of communication errors between the third control device 133 and the second control device 132, and determine the magnitude of the difference between the first communication count and the second communication count as the deviation amount. For example, the control device may be equipped with counters that count the number of normal communications and the number of communication errors, and the number of communication errors occurring during a predetermined period may be defined as the first communication count and the second communication count, respectively, with the smaller number indicating a faster communication speed and proceeding with processing. Alternatively, the number of normal communications occurring during a predetermined period may be defined as the first communication count and the second communication count, respectively, with the larger number indicating a faster communication speed and proceeding with processing.

[0022] Furthermore, the response difference determination unit 141 may obtain the first communication number by subtracting the first error number (related to the number of normal communications between the third control device 133 and the first control device 131) from the first error number (related to the number of communication errors), and the second communication number by subtracting the second error number (related to the number of communication errors) from the second error number (related to the number of communication errors), and determine the magnitude of the difference between the first communication number and the second communication number as the deviation amount. The normal number (related to the number of normal communications) and the error number (related to the number of communication errors) mean that at least one of the number of normal communications and the number of communication errors counted by the counter may be multiplied by a weight (coefficient). In other words, the normal number may be obtained by multiplying the number of normal communications by a weight (including 1), and the error number may be obtained by multiplying the number of communication errors by a weight (including 1).

[0023] The control adjustment unit 142 adjusts the deviation amount determined by the response difference determination unit 141 to fall within a predetermined range if the deviation amount is outside the predetermined range. The adjustment method of the control adjustment unit 142 is not limited. For example, as shown in Figure 2, the control adjustment unit 142 may change the current feedback gain of the control device that controls the fast-responding motor to reduce its responsiveness and match the response timing with the control device that controls the slow-responding motor. Alternatively, as shown in Figure 3, the control adjustment unit 142 may instruct the target value transmission unit 143 to delay the timing of transmitting the target value to the control device that controls the fast-responding motor and match the response timing with the control device that controls the slow-responding motor. Furthermore, the control adjustment unit 142 can also speed up the response by applying a phase lead to the target value transmission signal to the control device that controls the slow-responding motor and match the response timing with the control device that controls the fast-responding motor.

[0024] The target value transmission unit 143 is a processing unit that transmits target values ​​for operating the first motor 121 and the second motor 122 based on the steering signal output from the control amount output device 134 when the driver operates the control member 210 during manual operation, or the steering signal output from the automatic operation device 135 during automatic operation. The method for converting the steering signal to a target value is not limited. For example, the target value transmission unit 143 may acquire an assist map from a storage device that converts the target torque included in the steering signal and the target current included in the target value, and transmit the target value based on the assist map. Alternatively, the target value transmission unit 143 may have a function that can calculate a target value based on the parameters included in the steering signal, and transmit the target value calculated based on the function.

[0025] It should be noted that the present invention is not limited to the embodiments described above. For example, other embodiments of the present invention may be realized by arbitrarily combining the components described herein, or by excluding some of the components. Furthermore, modifications obtained by applying various modifications to the above embodiments that a person skilled in the art could conceive of without departing from the spirit of the present invention, that is, the meaning indicated by the wording in the claims, are also included in the present invention.

[0026] For example, implementing a program corresponding to each process performed by a control device also constitutes an implementation of the present invention. Of course, implementing a recording medium on which such a program is stored also constitutes an implementation of the present invention.

[0027] Furthermore, the first motor 121 and the second motor 122 are motors that operate by vector control, and the response difference determination unit 141 may, as shown in Figure 4, acquire a first delay time, which is the current delay time obtained by step-inputting a voltage to one of the multiple axes of the first motor 121, and a second delay time, which is the current delay time obtained by step-inputting the same voltage to the same axis of the second motor 122 as the axis to which the voltage was step-inputted to the first motor 121, and determine the magnitude of the difference between the first delay time and the second delay time acquired by the delay time acquisition unit as the amount of deviation. This makes it possible to grasp the delay of the entire channel, including the delay of communication. In this case, since the motor may rotate when a voltage is input, it is necessary to impose restrictions such as executing only when the vehicle is stopped.

[0028] Furthermore, if the first motor 121 and the second motor 122 are motors that operate by dq control, the response difference determination unit 141 may control the first control device 131 and the second control device 132, respectively, to input voltage in steps for the d axis and acquire the delay time. When voltage is input to the d axis, the motor does not rotate, so it is possible to acquire the delay time even when the vehicle is running.

[0029] (Summary) The steering system 100 of the first embodiment is a steering system 100 for steering a steering wheel 200, and comprises an operating member 110 that operates when steering the steering wheel 200, a first motor 121 that operates the operating member 110, a first control device 131 that controls the first motor 121, a second motor 122 that operates the operating member 110, a second control device 132 that controls the second motor 122, and a third control device 133 that transmits target values ​​for driving the first motor 121 and the second motor 122 to the first control device 131 and the second control device 132, respectively, wherein the third control device 133 comprises a response difference determination unit 141 that determines whether the amount of deviation, which is the magnitude of the difference between the response timing of the first motor 121 and the response timing of the second motor 122 based on the transmitted target value, is within a predetermined range, and a control adjustment unit 142 that, if the amount of deviation is outside the predetermined range, adjusts the amount of deviation so that it falls within the predetermined range.

[0030] According to the first embodiment, relative differences in the responses of multiple motors, such as output timing, can be monitored, and adjustment control can be performed to reduce the timing difference. Furthermore, since the relative differences in responses can be monitored in real time, relative differences in responses due to changes in the control device and motors over time can also be detected, and the difference in response timing can be reduced.

[0031] The steering system 100 in the second embodiment includes the first embodiment, and the response difference determination unit 141 acquires a first required time, which is the time required for communication between the third control device 133 and the first control device 131, and a second required time, which is the time required for communication between the third control device 133 and the second control device 132, and determines the magnitude of the difference between the first required time and the second required time as the amount of deviation.

[0032] According to the second embodiment, based on the phenomenon discovered by the inventor that the delay in the motor's response largely depends on the communication time between control devices, channels with shorter communication times can be treated as having faster motor response.

[0033] The steering system 100 of the third embodiment includes the second embodiment, and the response difference determination unit 141 defines the magnitude of the difference between the time from when the third control device 133 transmits a first transmission signal to the first control device 131 for transmitting a target value until the first reply signal, which is returned when the first transmission signal is successfully received, and the time from when the third control device 133 transmits a second transmission signal to the second control device 132 for transmitting a target value until the second reply signal, which is returned when the second transmission signal is successfully received, as the amount of deviation.

[0034] According to the third embodiment, by monitoring the time required for round-trip communication, it becomes possible to accurately determine the time taken for communication even if there is a discrepancy in the clocks provided by each control device.

[0035] The steering system 100 of the fourth embodiment includes the first embodiment, and the response difference determination unit 141 obtains a first communication count, which is at least one of the number of normal communications and the number of communication errors between the third control device 133 and the first control device 131, and a second communication count, which is at least one of the number of normal communications and the number of communication errors between the third control device 133 and the second control device 132, and determines the magnitude of the difference between the first communication count and the second communication count as the amount of deviation.

[0036] According to the fourth embodiment, based on the fact that the difference between the first number of communications and the second number of communications, as discovered by the inventor, affects the communication time between control devices, channels with a large difference between the number of normal communications and the number of communication errors can be processed as having a faster motor response.

[0037] The steering system 100 of the fifth embodiment includes the first embodiment, and the response difference determination unit 141 obtains the first communication number by subtracting the first error number, which is related to the number of normal communications between the third control device 133 and the first control device 131, from the first error number, which is related to the number of communication errors, and the second communication number by subtracting the second error number, which is related to the number of normal communications between the third control device 133 and the second control device 132, from the second error number, which is related to the number of communication errors, and determines the magnitude of the difference between the first communication number and the second communication number as the amount of deviation.

[0038] According to the fifth embodiment, by assigning predetermined weights to the number of successful communications and the number of communication errors and calculating the difference, the magnitude of the difference can be processed as the difference in the motor's response timing.

[0039] The steering system 100 in the sixth embodiment includes the first embodiment, and the first motor 121 and the second motor 122 are motors that operate by vector control. The response difference determination unit 141 obtains a first delay time, which is the current delay time obtained by step-inputting a voltage to one of the multiple axes of the first motor 121, and a second delay time, which is the current delay time obtained by step-inputting the same voltage to the same axis of the second motor 122 as the axis to which the voltage was step-inputted to the first motor 121. The magnitude of the difference between the first delay time and the second delay time is determined as the amount of deviation.

[0040] According to the sixth embodiment, the response timing of the motor can be directly obtained, and the response timings of multiple channel motors can be synchronized more accurately.

[0041] The steering system 100 in the seventh embodiment includes the sixth embodiment, wherein the first motor 121 and the second motor 122 are motors that operate by dq control, and the response difference determination unit 141 derives the amount of deviation by stepping in voltage on the d axis.

[0042] According to the seventh embodiment, the response timing of the motor can be obtained without rotating the motor, so the response timing can be obtained even when the vehicle is in motion.

[0043] The technology according to the present invention can be used in a steering system that can steer each steering wheel based on a signal.

[0044] 100...Steering system, 110...Operating member, 121...First motor, 122...Second motor, 131...First control device, 132...Second control device, 133...Third control device, 134...Operated amount output device, 135...Automatic driving device, 141...Response difference determination unit, 142...Control adjustment unit, 143...Target value transmission unit, 200...Steering wheel, 210...Operating member

Claims

1. A steering system for steering a steering wheel, comprising: an operating member that operates when steering a steering wheel; a first motor that operates the operating member; a first control device that controls the first motor; a second motor that operates the operating member; a second control device that controls the second motor; and a third control device that transmits target values ​​for driving the first motor and the second motor to the first control device and the second control device, wherein the third control device comprises: a response difference determination unit that determines whether the amount of deviation, which is the magnitude of the difference between the response timing of the first motor and the response timing of the second motor based on the transmitted target value, is within a predetermined range; and a control adjustment unit that, if the amount of deviation is outside the predetermined range, adjusts the amount of deviation so that it falls within the predetermined range.

2. The steering system according to claim 1, wherein the response difference determination unit obtains a first required time, which is the time required for communication between the third control device and the first control device, and a second required time, which is the time required for communication between the third control device and the second control device, and determines the magnitude of the difference between the first required time and the second required time as the amount of deviation.

3. The steering system according to claim 2, wherein the response difference determination unit determines the magnitude of the difference between the time from when the third control device transmits a first transmission signal for transmitting a target value to the first control device until the first reply signal, which is returned when the first transmission signal is successfully received, and the time from when the third control device transmits a second transmission signal for transmitting a target value to the second control device until the second reply signal, which is returned when the second transmission signal is successfully received, is the amount of the deviation.

4. The steering system according to claim 1, wherein the response difference determination unit obtains a first communication count, which is at least one of the number of normal communications and the number of communication errors between the third control device and the first control device, and a second communication count, which is at least one of the number of normal communications and the number of communication errors between the third control device and the second control device, and determines the magnitude of the difference between the first communication count and the second communication count as the amount of deviation.

5. The steering system according to claim 1, wherein the response difference determination unit obtains a first number of communication errors by subtracting a first number of normal communication errors, which is related to the number of normal communication errors between the third control device and the first control device, and a second number of communication errors, which is related to the number of normal communication errors between the third control device and the second control device, and determines the magnitude of the difference between the first number of communication errors and the second number of communication errors.

6. The steering system according to claim 1, wherein the first motor and the second motor are motors that operate by vector control, and the response difference determination unit obtains a first delay time, which is the current delay time obtained by step-inputting a voltage to one of the multiple axes of the first motor, and a second delay time, which is the current delay time obtained by step-inputting the same voltage to the same axis of the second motor as the axis to which the voltage was step-inputted to the first motor, and determines the magnitude of the difference between the first delay time and the second delay time as the amount of deviation.

7. The steering system according to claim 6, wherein the first motor and the second motor are motors that operate by dq control, and the response difference determination unit derives the amount of deviation by stepping in voltage on the d axis.

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