Steering control device

Abstract

The present application provides a kind of steering control device in redundancy structure, even if one vehicle speed information is abnormal, can stably continue steering control.The present application has: multiple communication lines (41, 42), transmit vehicle speed information as information related to vehicle speed;And multiple operation parts (51, 53), are connected in a communicable manner, are connected separately corresponding to multiple communication lines (41, 42), respectively based on the vehicle speed information received via corresponding communication line (41, 42) to operate transmission ratio, multiple operation parts (51, 53) respectively determine whether the received vehicle speed information is valid, in the case of determining that vehicle speed information is invalid by at least one of multiple operation parts (51, 53), respectively change the operation control of transmission ratio from the vehicle speed sensing control based on vehicle speed information to the specific control of not based on vehicle speed information to operate transmission ratio.

Description

Steering control unit Technical Field

[0001] This invention relates to a steering control device. Background Technology

[0002] Steering control devices include those that perform vehicle speed-sensing control, calculating the transmission ratio (gear ratio) between the steering wheel's operating angle and the steering wheel's turning angle based on vehicle speed. In vehicle speed-sensing control, the transmission ratio is large in the low-speed range and small in the high-speed range. For example, Japanese Patent Application Publication No. 2020-29194 discloses a steering control device that determines the transmission ratio based on vehicle speed-sensing control.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2020-29194

[0006] For example, in steer-by-wire systems where the control components and steering mechanism are not mechanically linked, sometimes two processing units (e.g., microcomputers) are integrated into a single ECU to ensure system redundancy. In such a redundant structure, the two processing units perform calculations independently, allowing steering control to continue even if one unit malfunctions. In this redundant structure, the calculation results are compared between the two processing units, including in speed-sensing control where the calculated gear ratio is also compared. However, in speed-sensing control, if the input information (vehicle speed information) from one unit is abnormal, a large difference can occur between the calculation results, making it difficult to determine the gear ratio. Summary of the Invention

[0007] The purpose of this invention is to provide a steering control device that can stably continue steering control even if a vehicle speed information is abnormal in a redundant structure.

[0008] The steering control device of the present invention is a steering control device for controlling a steering device, the steering device being configured to change the transmission ratio between the operating angle of the operating member and the steering angle of the steering wheel by operating the steering motor. The steering control device includes: multiple communication lines for transmitting vehicle speed information as information related to vehicle speed; and multiple arithmetic units interconnected in a communicable manner, each individually connected to one of the multiple communication lines, each calculating the transmission ratio based on the vehicle speed information received via the corresponding communication line. The multiple arithmetic units each determine whether the received vehicle speed information is valid. If at least one of the multiple arithmetic units determines that the vehicle speed information is invalid, the calculation control of the transmission ratio is changed from vehicle speed sensing control based on the vehicle speed information to specific control that calculates the transmission ratio without based on the vehicle speed information.

[0009] Invention Effects

[0010] For example, if a fault such as a broken line occurs in one of the multiple communication lines, the vehicle speed information transmitted through the faulty communication line may be invalid. According to the present invention, if invalid vehicle speed information is transmitted through a portion of the multiple communication lines and the anomaly is detected by at least one arithmetic unit, the transmission ratio calculation control (calculation mode) in all arithmetic units is switched from vehicle speed sensing control to specific control. Thus, the transmission ratio is calculated by each of the multiple arithmetic units independently of the vehicle speed information, thereby suppressing instability and complexity in the transmission ratio calculation control (e.g., decreased responsiveness of the calculation process). That is, even if the vehicle speed information is abnormal, steering control continues without control confusion because the transmission ratio is calculated without using the vehicle speed information. Thus, according to the present invention, in the redundant structure, steering control can continue stably even if one piece of vehicle speed information is abnormal. Attached Figure Description

[0011] Figure 1 is a configuration diagram of a steering system including the steering control device of this embodiment.

[0012] Figure 2 is a configuration diagram of the steering control device of this embodiment.

[0013] Figure 3 is a graph showing the relationship between vehicle speed and transmission ratio in the vehicle speed sensing control of this embodiment.

[0014] Figure 4 is a graph showing the relationship between the operating angle and the transmission ratio in the operating angle sensing control of this embodiment.

[0015] Figure 5 is a flowchart illustrating an example of the control process in this embodiment.

[0016] Figure 6 is a configuration diagram of a modified example of the steering control device of this embodiment.

[0017] Figure 7 is a configuration diagram of a modified example of the steering control device of this embodiment.

[0018] Explanation of reference numerals in the attached figures:

[0019] 1 Steering system; 10 Steering device; 11 Steering control device; 2 Operating device; 3 Steering device; 35 Steering motor; 41 First communication line; 42 Second communication line; 43 First sub-communication line; 44 Second sub-communication line; 5 Steering ECU; 51 First microcomputer (first arithmetic unit); 52 First drive circuit; 53 Second microcomputer (second arithmetic unit); 54 Second drive circuit; 7 ECU (vehicle speed arithmetic unit); 71 Microcomputer (first vehicle speed arithmetic unit); 72 Microcomputer (second vehicle speed arithmetic unit); 8 Wheel speed sensor. Detailed Implementation

[0020] Hereinafter, as a specific embodiment, the steering control device 11, as an embodiment of the present invention, will be described in detail with reference to the accompanying drawings. It should be noted that, in addition to the embodiments described below, the present invention can also be implemented in various forms with various modifications and alterations based on the knowledge of those skilled in the art. Furthermore, in the description, the microcomputer is simply referred to as a "microcomputer".

[0021] As shown in Figure 1, the steering control device 11 is a device that controls the steering device 10. The steering device 10 is configured to change the transmission ratio between the operating angle of the steering wheel 21 (which is an operating member) and the steering angle of the front wheel 9F (which is a steering wheel) by the operation of the steering motor 35. The steering system 1 is composed of the steering device 10 and the steering control device 11 that controls it. The steering system 1 is a steer-by-wire system.

[0022] (Steering mechanism)

[0023] The steering system 10 includes mechanically independent operating devices 2 and steering mechanisms 3. The steering mechanism 3 turns a pair of front wheels 9F, which serve as steering wheels. It should be noted that, hereinafter, the front wheels 9F and rear wheels 9R are sometimes collectively referred to as wheels 9. Furthermore, the drive wheel is, for example, the rear wheel 9R. In addition, each wheel 9 is equipped with a wheel speed sensor 8 for detecting wheel speed. The wheel speed sensor 8 is equivalent to a sensor that detects information related to vehicle speed.

[0024] The operating device 2 includes a steering wheel 21, a steering shaft 22, a steering column 23, a reaction force applying mechanism 24, and an operating angle sensor 25. The steering wheel 21 is an operating component for the driver to perform steering operations. The steering shaft 22 is a shaft component on which the steering wheel 21 is mounted. The steering column 23 is a component that holds the steering shaft 22 in a rotatable position and supports it to the instrument panel reinforcement (not shown).

[0025] The reaction force applying mechanism 24 is powered by a reaction force motor 26, which is an electric motor supported on the steering column 23, and applies a reaction force (hereinafter also referred to as "operation reaction force") relative to steering operation to the steering wheel 21 via the steering shaft 22. The reaction force applying mechanism 24 is a mechanism with a general structure including a reducer, etc. A rotation angle sensor 26a is provided in the reaction force motor 26. The operation angle sensor 25 is a sensor that detects the operation angle of the steering wheel 21 to determine the amount of steering operation.

[0026] Furthermore, in the steering system 1, similar to a typical power steering system, a torsion bar 27 is assembled on the steering shaft 22. The operating device 2 has an operating torque sensor 28 for detecting the operating torque, which is the operating force applied by the driver to the steering wheel 21, based on the amount of torsion of the torsion bar 27.

[0027] Each of the wheels 9 is steerably supported on the vehicle body via a steering knuckle 39, which is a component of the suspension system. The steering mechanism 3 steers the pair of front wheels 9F together by rotating the steering knuckle 39. The steering mechanism 3 has a steering actuator 30 as its main component.

[0028] The steering actuator 30 includes a steering rod 31, a housing 32, a rod movement mechanism 33, and a steering motor 35. The steering rod 31 (also referred to as a "rack rod") is a component whose two ends are connected to the left and right steering knuckles 39 respectively via connecting rods 34. The housing 32 is a component that supports the steering rod 31 so that it can move left and right and is fixedly held to the vehicle body.

[0029] The lever movement mechanism 33 is used to move the steering lever 31 left and right, driven by the steering motor 35, which is an electric motor. The lever movement mechanism 33 is primarily a ball screw mechanism consisting of a ball groove and a nut screwed into the steering lever 31. The nut engages with the ball groove via bearing balls and is rotated by the steering motor 35. Since it is a generally constructed mechanism, a detailed description of the lever movement mechanism 33 is omitted.

[0030] The steering motor 35 is equipped with a rotation angle sensor 35a and a current sensor 35b that detects the current supplied to it. Furthermore, the steering device 3 has a steering angle sensor 36 that detects the amount of movement of the steering stick 31 from the neutral position to the left and right respectively in order to detect the steering angle (steering amount) of the front wheels 9F. Thus, the steering device 3 is configured as a steer-by-wire type steering device that is mechanically independent of the operating force of the steering wheel 21 and uses the force of the steering motor 35 to turn the front wheels 9F.

[0031] (Steering control unit)

[0032] As shown in Figure 2, the steering control device 11 includes a first communication line 41, a second communication line 42, and a steering ECU 5 that controls the steering device 3 according to steering requests. The first communication line 41 and the second communication line 42 (hereinafter also referred to as "communication lines 41, 42") are wiring (communication buses) that transmit vehicle speed information as information related to vehicle speed. Specifically, communication lines 41, 42 are communication lines that connect the steering ECU 5 to the ECU 7. The ECU 7 is an electronic control unit equipped with one or more processors and one or more memories, etc.

[0033] ECU7 is equivalent to a vehicle speed calculation unit that calculates the vehicle speed based on the detection values ​​of wheel speed sensors 8. ECU7 is, for example, a brake ECU that controls braking force and periodically calculates the vehicle speed based on wheel speed. The detection values ​​of the wheel speed sensors 8 located at each wheel 9 are input to ECU7 via sensor communication lines 81 and 82, respectively.

[0034] In this embodiment, each wheel speed sensor 8 is connected to the microcomputer (equivalent to the "first vehicle speed calculation unit") 71 of the ECU 7 via sensor communication line 81, and to the microcomputer (equivalent to the "second vehicle speed calculation unit") 72 of the ECU 7 via sensor communication line 82. Each microcomputer 71 and 72 of the ECU 7 calculates the vehicle speed based on the detection values ​​from the multiple wheel speed sensors 8. That is, the ECU 7, like the steering ECU 5, is a redundant structure with multiple microcomputers (computation units) 71 and 72, each capable of independent computation. The microcomputers 71 and 72 independently calculate the vehicle speed and control the braking force.

[0035] Microcomputer 71 is connected to the first microcomputer 51 of the steering ECU 5 via the first communication line 41. Microcomputer 71 sends the first vehicle speed information, as a calculation result, to the first microcomputer 51 via the first communication line 41. Microcomputer 72 is connected to the second microcomputer 53 of the steering ECU 5 via the second communication line 42. Microcomputer 72 sends the second vehicle speed information, as a calculation result, to the second microcomputer 53 via the second communication line 42.

[0036] For example, due to differences in vehicle speed calculation and processing by each microcomputer, communication status, or the condition of communication lines (such as length), the first and second vehicle speed information may sometimes be different values, and may sometimes be transmitted at different time intervals. It should be noted that even if only one microcomputer for calculating vehicle speed is configured in ECU7, and the same vehicle speed information is simultaneously output from that microcomputer to two communication lines 41 and 42, the different values ​​of vehicle speed information received by each microcomputer 51 and 53 may still occur due to the condition of communication lines 41 and 42 (e.g., presence or absence of a disconnection).

[0037] The steering ECU 5 is an electronic control unit equipped with multiple processors and multiple memories. While a diagram of the communication lines is omitted, the steering ECU 5 is communicatively connected to each ECU and sensor. Communication within the vehicle uses CAN (Car Area Network or Controllable Area Network). Furthermore, the vehicle in this embodiment is equipped with an autonomous driving ECU 90 that performs controls related to autonomous driving. Additionally, the vehicle is equipped with various sensors such as wheel speed sensors 8 and acceleration sensors.

[0038] The steering ECU 5 executes steering control for steering the front wheels 9F based on steering requests, i.e., the steering wheel 21 operation angle during manual driving or instructions from the automatic driving ECU 90 during automatic driving. The steering ECU 5 obtains the steering wheel 21 operation angle based on the rotation angle of the reaction motor 26 detected by the rotation angle sensor 26a. Based on the operation angle, the steering ECU 5 determines the target front wheel steering angle that becomes the steering angle of the front wheels 9F.

[0039] The steering ECU 5 determines the target rotation angle, which is the target rotation angle of the steering motor 35, based on the target front wheel steering angle. The steering ECU 5 detects the actual rotation angle of the steering motor 35 (hereinafter also referred to as the "actual rotation angle") via the rotation angle sensor 35a and determines the rotation angle deviation, which is the deviation of the actual rotation angle from the target rotation angle. If the torque generated by the steering motor 35 is referred to as the steering torque, the steering ECU 5 determines the steering torque that should be generated according to the feedback control law based on the rotation angle deviation. The first microcomputer 51 and the second microcomputer 53 of the steering ECU 5 respectively perform the above calculations.

[0040] If the current supplied to the steering motor 35 is called the steering current, then the steering torque and the steering current are approximately proportional. Based on this relationship, the steering ECU 5 determines the steering current to be supplied to the steering motor 35 according to the determined steering torque, and supplies this steering current to the steering motor 35. The configuration related to the supply of steering current in the steering ECU 5 will be described later.

[0041] The steering system 1 also includes a reaction force ECU 6 that performs reaction force control to provide the driver with a feel for steering operations. The reaction force ECU 6 determines the operating reaction force based on two components: a steering load reference component FS and an operating force reference reduction component FA. The steering load reference component FS is a component related to the steering force (steering torque of the steering motor 35) required to turn the front wheels 9F, and is determined based on the steering current supplied to the steering motor 35. Although detailed descriptions are omitted, a higher steering current value indicates a greater steering load on the front wheels 9F, thus the steering load reference component FS is determined to be a larger value.

[0042] On the other hand, the operating force, based on the reduction component FA, can be considered as the component used to impart the so-called operating feel to the driver in the power steering system. In the power steering system, an auxiliary torque, generally corresponding to the operating torque, is applied to the steering shaft 22. The reaction force ECU6 detects the operating torque via the operating torque sensor 28. The reaction force ECU6 determines the reaction force current as the current supplied to the reaction force motor 26 based on the operating reaction force, and supplies the determined reaction force current to the reaction force motor 26.

[0043] (Detailed composition of the steering ECU)

[0044] The steering ECU 5 includes a base plate 50, a first microcomputer 51 serving as a first arithmetic unit, a first drive circuit 52, a second microcomputer 53 serving as a second arithmetic unit, and a second drive circuit 54. The first microcomputer 51 is a microcomputer having one or more processors and one or more memories. The first microcomputer 51 is disposed on the base plate 50 and determines the current value of the first steering current supplied to the steering motor 35 via the first drive circuit 52. The first microcomputer 51 controls the first drive circuit 52 (PWM control) so that the first steering current is supplied to the steering motor 35.

[0045] The first drive circuit 52 is a motor drive circuit that drives the steering motor 35. It is configured to include multiple switching elements to correspond to the three phases of the steering motor 35. The first drive circuit 52 is disposed on the substrate 50 and is communicatively connected to the first microcomputer 51. The first drive circuit 52 supplies power from a battery (not shown) to the steering motor 35 according to the control of the first microcomputer 51.

[0046] The second microcomputer 53, like the first microcomputer 51, is a microcomputer mounted on the substrate 50, equipped with one or more processors and one or more memories. The second microcomputer 53 determines the value of the second steering current supplied to the steering motor 35 via the second drive circuit 54. The second microcomputer 53 controls the second drive circuit 54 (PWM control) so that the second steering current is supplied to the steering motor 35. The first microcomputer 51 and the second microcomputer 53 are interconnected in a communicative manner.

[0047] The second drive circuit 54 is a motor drive circuit that drives the steering motor 35. It is configured to include multiple switching elements to correspond to the three phases of the steering motor 35. The second drive circuit 54 is disposed on the substrate 50 and is communicatively connected to the second microcomputer 53. The second drive circuit 54 supplies power from a battery (not shown) to the steering motor 35 according to the control of the second microcomputer 53.

[0048] The steering motor 35 is a dual-winding type electric motor having a winding 351 connected to the first drive circuit 52 and a winding 352 connected to the second drive circuit 54. That is, the steering motor 35 is configured to output a steering torque corresponding to the sum of the first steering current supplied from the first drive circuit 52 and the second steering current supplied from the second drive circuit 54 (also called the total steering current). The steering current supplied from the battery via the steering ECU 5 is the sum of the first steering current and the second steering current.

[0049] Thus, the first drive circuit 52 and the second drive circuit 54 (hereinafter also referred to as "drive circuits 52, 54") are configured to correspond individually to microcomputers 51 and 53, respectively, and supply steering current to the steering motor 35 through the control of the corresponding microcomputers 51 and 53. Furthermore, microcomputers 51 and 53 are configured to be communicatively connected to each other, each individually connected to communication lines 41 and 42, and calculate the gear ratio based on vehicle speed information received via the corresponding communication lines 41 and 42. Communication lines 41 and 42 independently transmit vehicle speed information as vehicle speed-related information. In this embodiment, the first communication line 41 connects the first microcomputer 51 to microcomputer 71, and the second communication line 42 connects the second microcomputer 53 to microcomputer 72.

[0050] (Transmission ratio calculation and control)

[0051] The first microcomputer 51 is connected to the first communication line 41 and obtains the first vehicle speed information via the first communication line 41. The second microcomputer 53 is connected to the second communication line 42 and obtains the second vehicle speed information via the second communication line 42. The first communication line 41 and the second communication line 42 are independent of each other.

[0052] The first microcomputer 51 and the second microcomputer 53 calculate the transmission ratio (gear ratio) between the steering angle of the steering wheel 21 and the steering angle of the front wheel 9F when calculating the steering current. The transmission ratio is calculated based on the input vehicle speed information. As shown in Figure 3, the relationship between vehicle speed and transmission ratio is preset and stored in microcomputers 51 and 53 as a first mapping diagram. The first mapping diagram is used in vehicle speed sensing control; if the vehicle speed is determined, the transmission ratio is determined. Vehicle speed sensing control is a calculation control that calculates the transmission ratio based on vehicle speed information. In vehicle speed sensing control, the higher the vehicle speed, the smaller the transmission ratio.

[0053] Each microcomputer 51 and 53 calculates the transmission ratio based on the input vehicle speed information through vehicle speed sensing control. The calculation results are communicated between the microcomputers 51 and 53. For example, if the difference between the first transmission ratio calculated by the first microcomputer 51 and the second transmission ratio calculated by the second microcomputer 53 (hereinafter also referred to as the "transmission ratio calculation difference") is less than a predetermined calculation difference threshold, the first transmission ratio is set as a shared transmission ratio in both microcomputers 51 and 53. The shared transmission ratio (here, the first transmission ratio) is used in both microcomputers 51 and 53. The communication system connected to the first microcomputer 51 is referred to as the first system, and the communication system connected to the second microcomputer 53 is referred to as the second system.

[0054] Microcomputers 51 and 53 determine whether the received vehicle speed information is valid. If at least one of the microcomputers 51 and 53 determines that the vehicle speed information is invalid, the transmission ratio calculation control is changed from vehicle speed sensing control based on vehicle speed information to specific control that calculates the transmission ratio without vehicle speed information. As shown in Figure 4, the specific control in this embodiment is operation angle sensing control based on the operation angle to calculate the transmission ratio. Each microcomputer 51 and 53 has a second mapping diagram representing the relationship between the operation angle and the transmission ratio pre-stored. The second mapping diagram is used in operation angle sensing control; if the operation angle is determined, the transmission ratio is determined. In operation angle sensing control, the larger the operation angle, the larger the transmission ratio.

[0055] Each microcomputer 51 and 53 determines that either of the two speed information is abnormal (i.e., invalid) if the difference between the vehicle speed information received by the first microcomputer 51 and the vehicle speed information received by the second microcomputer 53 (hereinafter also referred to as "vehicle speed information difference") is above a predetermined vehicle speed difference threshold. For example, if a fault such as a disconnection occurs in either of the communication lines 41 and 42, or if a fault occurs in one of the microcomputers 71 and 72 of the ECU 7, the vehicle speed information transmitted through the system of the faulty party is likely to be an abnormal value. In this case, the vehicle speed information of one party is an abnormal value, while the vehicle speed information of the other party is a normal value, and the vehicle speed information difference becomes larger. Therefore, each microcomputer 51 and 53 determines that the vehicle speed information of one party is abnormal if the vehicle speed information difference is above the vehicle speed difference threshold. The two speed information that are the objects of the calculation of the vehicle speed information difference are calculated based on, for example, the detection values ​​detected by the wheel speed sensor 8 at the same timing. For example, the two speed information being compared are calculated based on the same basis (detection value).

[0056] As an example of information transmission and reception settings, the first microcomputer 51 immediately sends the vehicle speed information to the second microcomputer 53 after receiving it from the first communication line 41, and the second microcomputer 53 immediately sends the vehicle speed information to the first microcomputer 51 after receiving it from the second communication line 42. One of the microcomputers 51 and 53 that determines the validity / invalidity of the vehicle speed information immediately sends the determination result to the other microcomputer 51 and 53 after the determination is completed. Depending on the timing of the transmission and reception of vehicle speed information by each microcomputer 51 and 53, the timing of the determination by each microcomputer 51 and 53 may also be simultaneous.

[0057] Furthermore, each microcomputer 51 and 53 can, for example, identify faults in microcomputers 71 and 72 within the ECU7 or faults in communication lines 41 and 42 (e.g., disconnection, congestion) based on the output signal from the ECU7 that calculates the vehicle speed, and can also determine the validity / invalidity of the vehicle speed information based on the output signal from the ECU7. For example, if each microcomputer 51 and 53 is configured to periodically receive signals from the ECU7 (e.g., the corresponding microcomputers 71 and 72), each microcomputer 51 and 53 can identify an anomaly in the microcomputer or communication line by not receiving the signal.

[0058] Using any of the above-described determination methods, when at least one of the microcomputers 51 and 53 determines that the vehicle speed information of one party is invalid, the determination result is shared between the two microcomputers 51 and 53, and the transmission ratio calculation control (calculation method) in the two microcomputers 51 and 53 is changed from vehicle speed sensing control to operating angle sensing control. After the change, each microcomputer 51 and 53 calculates (determines) the transmission ratio based on the detection value of the operating angle sensor 25 and the second mapping map. Furthermore, even when both microcomputers 51 and 53 simultaneously determine that "the vehicle speed information of one party is invalid," the transmission ratio calculation control is changed from vehicle speed sensing control to operating angle sensing control in the two microcomputers 51 and 53 in the same manner as above. Thus, when at least one of the microcomputers 51 and 53 determines that the vehicle speed information is invalid, the transmission ratio calculation control of both microcomputers 51 and 53 is set to operating angle sensing control.

[0059] Referring to Figure 5, an example of the control flow performed by each microcomputer 51 and 53 will be described. Each microcomputer 51 and 53 determines whether the vehicle speed information of its own system is valid (S1). If the vehicle speed information of its own system is valid (S1: Yes), each microcomputer 51 and 53 determines whether the vehicle speed information of other systems is valid (S2). If the vehicle speed information of other systems is valid (S2: Yes), each microcomputer 51 and 53 calculates the transmission ratio through vehicle speed sensing control (S3). It should be noted that when each microcomputer 51 and 53 determines the validity of the vehicle speed information based on the difference in vehicle speed information, steps S1 and S2 are executed simultaneously. That is to say, in this case, it can also be said that each microcomputer 51 and 53 determines "whether the vehicle speed information of both parties is valid" in one step. As long as it is not determined that "the vehicle speed information is invalid", each microcomputer 51 and 53 continues to perform vehicle speed sensing control.

[0060] If either microcomputer 51 or 53 determines in either step S1 or S2 that "vehicle speed information is invalid" (S1: No, or S2: No), the transmission ratio calculation control is changed to operating angle sensing control, and the transmission ratio is calculated through operating angle sensing control (S4). Thus, when at least one system determines that the vehicle speed information is invalid, both microcomputers 51 and 53 change the transmission ratio calculation control to operating angle sensing control.

[0061] (Effects of this implementation method)

[0062] For example, if a fault such as a disconnection occurs in one of the multiple communication lines, the vehicle speed information transmitted through the faulty communication line may be invalid. According to this embodiment, if invalid vehicle speed information is transmitted through one of the communication lines 41 and 42, and this anomaly is detected by at least one of the microcomputers 51 and 53, the transmission ratio calculation control (calculation method) in both microcomputers 51 and 53 is switched from vehicle speed sensing control to specific control. Thus, the transmission ratio is calculated by each microcomputer 51 and 53 regardless of the vehicle speed information, thereby suppressing instability and complexity in the transmission ratio calculation control caused by large differences in vehicle speed information (e.g., decreased responsiveness of the calculation process). In other words, even if the vehicle speed information is abnormal, steering control continues without control confusion because the vehicle speed information is not used to calculate the transmission ratio. Thus, according to this embodiment, in the redundant structure, steering control can continue stably even if one vehicle speed information is abnormal.

[0063] Furthermore, in this embodiment, the specific control is set as an angle-sensing control. In angle-sensing control, a larger operating angle results in a larger gear ratio. However, drivers tend to increase the operating angle at low speeds. As a result, before and after the change in calculation control, it is easy to set the same gear ratio as speed-sensing control, which has a larger gear ratio at lower speeds. At high speeds, drivers tend to operate with a smaller operating angle; therefore, the gear ratios of both speed-sensing control and angle-sensing control decrease. Thus, since the specific control is angle-sensing control, driver discomfort can be suppressed after the change in the calculation control of the gear ratio. It should be noted that the specific control can also be a fixed gear ratio control, where the gear ratio is set to a fixed value. In this case, vehicle speed information is not used in the calculation of the gear ratio, and steering control continues without control confusion.

[0064] (Another example of a communication line connection)

[0065] The communication line connecting ECU7 and steering ECU5 can also be configured in a manner other than those described above. For example, as shown in FIG6, the steering control device 11 may also include a first sub-communication line 43 and a second sub-communication line 44. The first sub-communication line 43 connects microcomputer 71 to second microcomputer 53. The second sub-communication line 44 connects microcomputer 72 to first microcomputer 51.

[0066] In this configuration, each microcomputer 51 and 53 can directly receive two vehicle speed information messages from the ECU 7. Therefore, each microcomputer 51 and 53 can calculate the vehicle speed information difference without waiting for vehicle speed information from the other microcomputer. The first microcomputer 51 determines whether the two vehicle speed information messages are valid based on the difference between the vehicle speed information received from the first communication line 41 and the vehicle speed information received from the second sub-communication line 44. The second microcomputer 53 determines whether the two vehicle speed information messages are valid based on the difference between the vehicle speed information received from the second communication line 42 and the vehicle speed information received from the first sub-communication line 43.

[0067] Thus, each microcomputer 51 and 53 calculates the difference (vehicle speed information difference) between the two vehicle speed information received from ECU7 and determines whether the vehicle speed information is valid. In this configuration, if at least one of the microcomputers 51 and 53 determines that the vehicle speed information of one of them is invalid, the transmission ratio calculation control of the two microcomputers 51 and 53 is changed to operating angle sensing control.

[0068] (other)

[0069] This invention is not limited to the embodiments described above. For example, the microcomputer (computation unit) within the steering ECU5 may be three or more. In this case, it is also configured such that multiple microcomputers respectively determine whether the received vehicle speed information is valid, and if at least one of the multiple microcomputers determines that the vehicle speed information is invalid, the transmission ratio calculation control is changed from vehicle speed sensing control to specific control. For example, as shown in FIG7, in the case where a redundant structure is formed by the three microcomputers within the steering ECU5, the steering ECU5 may also include a third microcomputer 55 and a third drive circuit 56, and the third microcomputer 55 and ECU7 are connected via a third communication line 45. The wheel speed sensor 8 and ECU7 may also be connected via a sensor communication line 83. ECU7 may also have three microcomputers corresponding to the steering ECU5.

[0070] Furthermore, the steering control device 11 may also have multiple ECUs as multiple computing units. That is, the computing unit is not limited to a microcomputer, but can also be an ECU. In this case, the multiple ECUs are also connected in a communicative manner. That is, the redundant structure can be composed of multiple microcomputers or multiple ECUs. The redundant structure is a configuration in which different vehicle speed information can be input to two or more computing units (e.g., microcomputers or ECUs) at different values ​​and at different timings to perform gear ratio calculation processing.

[0071] The vehicle speed information input to microcomputers 51 and 53 does not necessarily have to be calculated by ECU7; any information related to vehicle speed is acceptable. Furthermore, ECU7 is not limited to the brake ECU; it can be any other ECU with vehicle speed calculation capabilities. Additionally, the calculation unit (microcomputer) within ECU7 can be a single unit. Furthermore, for example, when the detection value (vehicle speed-related information) from wheel speed sensor 8 is input to the steering ECU 5 via communication lines 41 and 42, the vehicle speed can be calculated by each microcomputer 51 and 53. In this case, each microcomputer 51 and 53 can compare the input detection value from wheel speed sensor 8 and determine whether the detection value is valid. Alternatively, each microcomputer 51 and 53 can calculate the vehicle speed, compare the calculation result (vehicle speed information) between microcomputers 51 and 53, and determine whether the calculation result is valid. Thus, each microcomputer 51 and 53 can obtain vehicle speed information without going through ECU7. The steering device 3 can also be a device for steering the rear wheel 9R. The steering device 10 is not limited to steer-by-wire type; it can be any device with a variable transmission ratio.

[0072] (Format of this disclosure)

[0073] This disclosure includes the following scheme.

[0074] (Option 1)

[0075] A steering control device controls a steering mechanism configured to change the transmission ratio between the operating angle of an operating member and the steering angle of a steering wheel by operating a steering motor. The steering control device includes: multiple communication lines for transmitting vehicle speed information as information related to vehicle speed; and multiple arithmetic units interconnected in a communicable manner, each individually connected to one of the multiple communication lines, each calculating the transmission ratio based on the vehicle speed information received via the corresponding communication line. The multiple arithmetic units separately determine whether the received vehicle speed information is valid. If at least one of the multiple arithmetic units determines that the vehicle speed information is invalid, the transmission ratio calculation control is changed from vehicle speed sensing control based on the vehicle speed information to specific control that calculates the transmission ratio without based on the vehicle speed information.

[0076] (Option 2)

[0077] According to the steering control device of Scheme 1, the specific control is an operation angle sensing control that calculates the transmission ratio based on the operation angle.

[0078] (Option 3)

[0079] The steering control device according to Scheme 1 or 2 includes: a wheel speed sensor for detecting wheel speed; and a vehicle speed calculation unit for calculating vehicle speed based on the detection value of the wheel speed sensor, wherein a plurality of the communication lines are connected to the vehicle speed calculation unit.

[0080] (Option 4)

[0081] According to any one of the steering control devices in Schemes 1 to 3, the plurality of computing units determine whether the vehicle speed information is valid based on the difference between the vehicle speed information transmitted through two communication lines, including the communication line connected to itself.

[0082] (Option 5)

[0083] The steering control device according to any one of Schemes 1 to 4 includes: a plurality of drive circuits, each corresponding individually to a plurality of said arithmetic units, which respectively supply steering current to the steering motor through the control of the corresponding arithmetic unit.

[0084] (Option 6)

[0085] According to the steering control device of Scheme 5, the plurality of communication lines are composed of a first communication line and a second communication line, the plurality of computing units are composed of a first computing unit connected to the first communication line and a second computing unit connected to the second communication line, and the plurality of drive circuits are composed of a first drive circuit connected to the first computing unit and a second drive circuit connected to the second computing unit.

[0086] (Option 7)

[0087] According to the steering control device described in Scheme 6, if the difference between the vehicle speed information transmitted through the first communication line and the vehicle speed information transmitted through the second communication line is greater than a predetermined threshold, the first calculation unit and the second calculation unit respectively determine that the vehicle speed information of one of them is invalid.

[0088] (Option 8)

[0089] The steering control device according to Scheme 6 or 7 includes: a wheel speed sensor for detecting wheel speed; a first vehicle speed calculation unit for calculating vehicle speed based on the detection value of the wheel speed sensor; and a second vehicle speed calculation unit for calculating vehicle speed based on the detection value of the wheel speed sensor, wherein a first communication line connects the first vehicle speed calculation unit to the first calculation unit, and a second communication line connects the second vehicle speed calculation unit to the second calculation unit.

[0090] (Option 9)

[0091] According to the steering control device described in Scheme 8, if the difference between the vehicle speed information calculated by the first vehicle speed calculation unit and the vehicle speed information calculated by the second vehicle speed calculation unit is above a predetermined threshold, the first calculation unit and the second calculation unit respectively determine that the vehicle speed information of one of them is invalid.

[0092] (Option 10)

[0093] The steering control device according to embodiment 8 or 9 includes: a first sub-communication line connecting the first vehicle speed calculation unit to the second calculation unit; and a second sub-communication line connecting the second vehicle speed calculation unit to the first calculation unit.

Claims

1. A steering control device for controlling a steering mechanism, the steering mechanism being configured to change the transmission ratio between the operating angle of an operating member and the steering angle of a steering wheel by operating a steering motor, the steering control device comprising: multiple communication lines for transmitting vehicle speed information as information related to vehicle speed; and multiple arithmetic units interconnected in a communicable manner, each individually connected to one of the multiple communication lines, each calculating the transmission ratio based on the vehicle speed information received via the corresponding communication line, each of the multiple arithmetic units determining whether the received vehicle speed information is valid, and if at least one of the multiple arithmetic units determines that the vehicle speed information is invalid, changing the transmission ratio calculation control from vehicle speed sensing control based on the vehicle speed information to specific control that calculates the transmission ratio without based on the vehicle speed information, the specific control being operating angle sensing control based on the operating angle to calculate the transmission ratio.

2. The steering control device according to claim 1, comprising: a wheel speed sensor for detecting wheel speed; and a vehicle speed calculation unit for calculating vehicle speed based on the detection value of the wheel speed sensor, wherein a plurality of the communication lines are connected to the vehicle speed calculation unit.

3. The steering control device according to claim 1, wherein, Each of the multiple computation units determines whether the vehicle speed information is valid based on the difference between the vehicle speed information transmitted through two communication lines, including the communication line connected to itself.

4. The steering control device according to claim 1, comprising: a plurality of drive circuits, each corresponding individually to a plurality of said arithmetic units, and supplying steering current to the steering motor through the control of the corresponding arithmetic unit.

5. The steering control device according to claim 4, wherein, The plurality of communication lines are composed of a first communication line and a second communication line, the plurality of arithmetic units are composed of a first arithmetic unit connected to the first communication line and a second arithmetic unit connected to the second communication line, and the plurality of driving circuits are composed of a first driving circuit connected to the first arithmetic unit and a second driving circuit connected to the second arithmetic unit.

6. The steering control device according to claim 5, wherein, If the difference between the vehicle speed information transmitted through the first communication line and the vehicle speed information transmitted through the second communication line is greater than or equal to a predetermined threshold, the first calculation unit and the second calculation unit shall determine that the vehicle speed information of one of them is invalid.

7. The steering control device according to claim 5 or 6, comprising: a wheel speed sensor for detecting wheel speed; a first vehicle speed calculation unit for calculating vehicle speed based on the detection value of the wheel speed sensor; and a second vehicle speed calculation unit for calculating vehicle speed based on the detection value of the wheel speed sensor, wherein a first communication line connects the first vehicle speed calculation unit to the first calculation unit, and a second communication line connects the second vehicle speed calculation unit to the second calculation unit.

8. The steering control device according to claim 7, wherein, If the difference between the vehicle speed information calculated by the first vehicle speed calculation unit and the vehicle speed information calculated by the second vehicle speed calculation unit is above a predetermined threshold, the first calculation unit and the second calculation unit shall determine that the vehicle speed information of one of them is invalid.

9. The steering control device according to claim 8, comprising: a first sub-communication line connecting the first vehicle speed calculation unit to the second calculation unit; and a second sub-communication line connecting the second vehicle speed calculation unit to the first calculation unit.

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