Steering system

Abstract

A steering system is provided that can execute abnormality control even if a main power supply also becomes abnormal when a backup power supply becomes abnormal. The steering system (1) of the present invention comprises: a steering device (14) having a steering motor (50) supplied with power from at least one of a main power supply (70) and a backup power supply (90); and a control device (62) for controlling the steering device (14) based on a steering request. The control device (62) is configured to: when the backup power supply (90) is normal, if it is determined that the voltage of the main power supply (70) is less than a first threshold value, execute abnormality control based on the power supplied to the steering motor (50) from at least one of the main power supply (70) and the backup power supply (90); and when the backup power supply (90) is abnormal, if it is determined that the voltage of the main power supply (70) is less than a second threshold value greater than the first threshold value, execute abnormality control based on the power supplied to the steering motor (50) from the main power supply (70).

Description

Technical Field

[0001] The present invention relates to a steer-by-wire system mounted on a vehicle. Background Art

[0002] In a fail-safe manner, a proposed method for providing a backup power supply and making the system redundant (duplexed) is to provide a backup power supply in a steering-by-wire system. For example, in the vehicle steering control system described in Japanese Patent Application Laid-Open No. 2004-338657, if the voltage of the main power supply drops, the power supply to the steering shaft drive motor switches from the main power supply to the backup power supply.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-338657

[0004] However, in the above-mentioned device, there is no specific description of a countermeasure for a situation in which the voltage of the main power supply gradually decreases due to a failure / abnormality of the main power supply after the backup power supply becomes abnormal. The present invention aims to provide a steering system that can perform abnormality control even if the main power supply also becomes abnormal in the event of an abnormality in the backup power supply. Summary of the Invention

[0005] The steering system of the present invention is a wire-controlled steering system, which comprises: a main power supply and a backup power supply; a steering device having a steering motor powered by at least one of the main power supply and the backup power supply, and steering the wheels by the force of the steering motor; and a control device that detects the voltage of the main power supply, supplies power from the main power supply to the steering motor, and controls the steering device based on a steering request, wherein the control device is constructed such that when the backup power supply is normal, if it is determined that the voltage of the main power supply is less than a first threshold value, abnormal control is performed based on the power supply to the steering motor from at least one of the main power supply and the backup power supply; and when the backup power supply is abnormal, if it is determined that the voltage of the main power supply is less than a second threshold value that is greater than the first threshold value, abnormal control is performed based on the power supply from the main power supply to the steering motor.

[0006] According to the present invention, since the second threshold value is a value greater than the first threshold value (a high value), when the voltage of the main power supply decreases under the condition that the backup power supply is abnormal, the abnormal control is executed earlier than when the voltage of the main power supply decreases under the condition that the backup power supply is normal. Thus, in a situation where power supply based on the backup power supply cannot be performed, the abnormal control can be started before the voltage of the main power supply decreases to a level that makes the abnormal control incapable of execution. Since the abnormal control can be started earlier, that is, since the abnormal control can be started while the voltage of the main power supply is high, the execution time required for the abnormal control can be ensured. According to the present invention, in the case of an abnormal backup power supply, even if the main power supply also becomes abnormal, the abnormal control can be executed. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a diagram schematically showing the overall structure of the steering system of the embodiment.

[0008] Figure 2 FIG. 1 is a schematic diagram of a power source in a steering system according to an embodiment.

[0009] Figure 3 It is a schematic diagram showing the structure of the backup power supply of the embodiment.

[0010] Figure 4 This is a time chart for explaining the change in the voltage of the main power supply and the start timing of the avoidance running control in the embodiment.

[0011] Figure 5 This is a time chart for explaining the change in the voltage of the main power supply and the start timing of the avoidance running control in the embodiment.

[0012] Figure 6 This is a flowchart showing the flow of control in the embodiment.

[0013] Description of Reference Numerals

[0014] 1…steering system; 10…wheel; 14…steering device; 50a, 50b…steering motor; 62a, 62b…steering ECU (control device); 70…main power supply; 90…backup power supply; 90b…first voltage detection unit; 90c…second voltage detection unit; 91…capacitor; 95…microcomputer. DETAILED DESCRIPTION

[0015] Below, as a mode for implementing the claimed invention, a steering system, as an embodiment of the present invention, is described in detail with reference to the accompanying drawings. First, the structure and control of the steering system ([A]-[C]) are described. The detailed structure of the backup power supply ([D]) and the abnormality control ([E]) are then explained. Furthermore, in addition to the following embodiment, the present invention can be implemented in various forms, including various modifications and improvements based on the knowledge of those skilled in the art.

[0016] [A] Steering system structure

[0017] like Figure 1 As schematically shown, a steering system 1 of the embodiment mounted on a vehicle is a system for steering two wheels (front wheels) 10, each serving as a steerable wheel. The steering system 1 is a steer-by-wire system including an operating device 12 and a steering device 14 that are mechanically independent of each other.

[0018] The operating device 12 includes a steering wheel 20, a steering shaft 22, a steering column 24, and a reaction force imparting mechanism 28. The steering wheel 20 is an operating component for steering operation (steering operation) by the driver. The steering shaft 22 is a shaft component with the steering wheel 20 mounted on the front end. The steering column 24 is a component that holds the steering shaft 22 in a rotatable state and is supported by an instrument panel reinforcement (not shown). The reaction force imparting mechanism 28 is a mechanism that uses the reaction force motor 26, which is an electric motor supported by the steering column 24, as a power source to impart a reaction force (strictly speaking, a reaction force torque, but the conventional term "operation reaction force" will be used below) relative to the steering operation to the steering wheel 20 via the steering shaft 22. The reaction force imparting mechanism 28 is a mechanism of a general structure including a reducer, etc., and therefore the description of the specific structure of the reaction force imparting mechanism 28 is omitted.

[0019] The reaction motor 26 is a three-phase brushless DC motor with magnets attached to the outer circumference of the rotating shaft and coils arranged in the housing opposite these magnets. The reaction motor 26 is a dual-system motor, with two sets of coils arranged for each magnet. Hereinafter, one system of the dual-system reaction motor 26 will be referred to as the reaction motor 26a, and the other as the reaction motor 26b. Reaction motor 26a has a motor rotation angle sensor 30a that detects the rotation angle (which can be considered a "relative angle" or "phase") within one rotation, in order to switch the energized phase of its power supply. Similarly, reaction motor 26b has a motor rotation angle sensor 30b. Hereinafter, the motor rotation angle sensors 30a and 30b will be collectively referred to as the "motor rotation angle sensor 30." Therefore, the operating device 12 can be considered a dual-system device serving as a redundant system (hereinafter, referred to as "operating device 12a" or "operating device 12b").

[0020] The operating device 12 includes an operating angle sensor 32 that detects the operating angle of the steering wheel 20 as the steering operation amount. When the steering wheel 20 is in a forward-moving state, the operating angle of the steering wheel 20 is determined by the left and right rotation angles (which can be considered "absolute angles") from the neutral position.

[0021] Furthermore, the steering system 1, similar to a typical so-called power steering system, includes a torsion bar 34 mounted on the steering shaft 22 and operating torque sensors 36a and 36b (hereinafter sometimes collectively referred to as "operating torque sensors 36") for detecting operating torque, which is the operating force applied by the driver to the steering wheel 20, based on the amount of twisting of the torsion bar 34. Two operating torque sensors 36 are provided to support the dual systems of the operating device 12.

[0022] The wheels 10 are steerably supported on the vehicle body via a steering knuckle 40, which is a structural element of the suspension system. The steering device 14 integrally steers each of the wheels 10 by rotating the steering knuckle 40. The steering device 14 has a steering actuator 42 as a main structural element.

[0023] The steering actuator 42 includes a steering rod 46, a housing 48, and a rod moving mechanism 52. The steering rod 46 (also sometimes referred to as a "rack") is a component whose ends are connected to the left and right steering knuckles 40 respectively via connecting rods 44. The housing 48 is a component that supports the steering rod 46 so that it can move left and right and is fixed to the vehicle body. The rod moving mechanism 52 is a mechanism for moving the steering rod 46 left and right using the steering motor 50, which is an electric motor, as a driving source. The rod moving mechanism 52 is mainly composed of a ball screw mechanism composed of a ball groove with a thread provided on the steering rod 46 and a nut that is threadedly engaged with the ball groove via a bearing ball and rotated by the steering motor 50. Since it is a mechanism of general structure, a detailed description of the rod moving mechanism 52 is omitted here.

[0024] The steering motor 50, like the reaction force motor 26, is a dual-system, three-phase brushless DC motor. One of the two systems may be referred to as the steering motor 50a, and the other as the steering motor 50b. The steering motor 50a includes a motor rotation angle sensor 54a for detecting the rotation angle (which can be considered a "relative angle" or "phase") within one rotation, in order to switch the energized phase during its power supply. Similarly, the steering motor 50b includes a motor rotation angle sensor 54b. Hereinafter, the motor rotation angle sensors 54a and 54b may be collectively referred to as the "motor rotation angle sensor 54." Therefore, the steering system 14 can be considered a dual-system system serving as a redundant system (hereinafter, referred to as the "steering system 14a" or the "steering system 14b"). Furthermore, the steering motors 50a and 50b each have their own current sensors 56a and 56b (hereinafter, referred to as the "current sensor 56") for detecting the current IS actually supplied to them, creating a one-to-one correspondence between the motors and the sensors.

[0025] The steering device 14 also includes a steering angle sensor 58 for detecting a steering angle as a steering amount of the wheels 10 by detecting the left and right movement amounts of the steering rod 46 from a neutral position (a position when the vehicle is moving forward).

[0026] Control of the operating device 12, specifically the control of the operating reaction force, i.e., the control of the reaction force motor 26 of the operating device 12, is performed by operating electronic control units (hereinafter referred to as "operating ECUs") 60a and 60b, which serve as controllers or operating controllers, corresponding to the dual systems of the operating device 12. Hereinafter, the operating ECUs 60a and 60b will sometimes be collectively referred to as the operating ECUs 60. Each operating ECU 60 comprises a computer including a CPU, ROM, RAM, and the like, and an inverter serving as a driver (drive circuit) for the reaction force motor 26.

[0027] Similarly, control of the steering system 14, specifically the steering angle, i.e., control of the steering motor 50 of the steering system 14, is performed by steering electronic control units (hereinafter sometimes referred to as "steering ECUs") 62a and 62b, serving as respective controllers or steering controllers, corresponding to the dual systems of the steering system 14. Hereinafter, the steering ECUs 62a and 62b will sometimes be collectively referred to as the steering ECUs 62. Each steering ECU 62 consists of a computer including a CPU, ROM, RAM, etc., and an inverter serving as a driver (drive circuit) for the steering motor 50.

[0028] The operating device 12a, steering device 14a, operating ECU 60a, and steering ECU 62a constitute one system, while the operating device 12b, steering device 14b, operating ECU 60b, and steering ECU 62b constitute another system. That is, the steering system 1 is a dual-system steering system. Therefore, the operating device 12a and steering device 14a are connected via a dedicated communication line 64a, and the operating device 12b and steering device 14b are connected via a dedicated communication line 64b (hereinafter, the dedicated communication lines 64a and 64b may be collectively referred to as "dedicated communication lines 64"). Furthermore, to enable communication with the operating devices 12 and steering devices 14 of other systems, each operating device 12 and steering device 14 is connected to a CAN (car area network or controller area network) 66, which serves as a shared communication line.

[0029] Furthermore, in the steering system 1, the operating device 12a, steering device 14a, operating ECU 60a, and steering ECU 62a constitute the main system, while the operating device 12b, steering device 14b, operating ECU 60b, and steering ECU 62b constitute the subsystem. The steering device 14a and steering motor 50a can be considered the steering main system 14a and steering main system 50a, respectively, while the steering device 14b and steering motor 50b can be considered the steering subsystem 14b and steering subsystem 50b. Similarly, the operating device 12a and reaction force motor 26a can be considered the operating main system 12a and reaction force main system 26a, respectively, while the operating device 12b and reaction force motor 26b can be considered the operating subsystem 12b and reaction force subsystem 26b. Furthermore, the operating ECU 60a and steering ECU 62a can be considered the control main system 60a and control main system 62a, respectively, while the operating ECU 60b and steering ECU 62b can be considered the control subsystem 60b and control subsystem 62b, respectively.

[0030] [B] Power supply in the steering system

[0031] like Figure 2 As shown schematically, the steering system 1 of the embodiment includes a main power supply unit (hereinafter referred to as the "main power supply") 70 as a main power source, and a backup power supply unit (hereinafter referred to as the "backup power supply") 90 as a backup power source, serving as power sources for the operating device 12 and the steering device 14. The main power supply 70 includes a DC-DC converter 74 and a battery 76. The battery 76 is also referred to as an auxiliary battery. The backup power supply 90 includes a capacitor 91 as an electrical storage device. In the accompanying drawings, the grounding wires from the operating device 12 and the steering device 14 are not shown.

[0032] The vehicle equipped with the steering system 1 is a hybrid vehicle, and power is supplied from a drive system power supply 80 to a DC-DC converter 74. The DC-DC converter 74 converts the voltage applied from the drive system power supply 80 into a drive voltage for the steering system 1. A battery 76 is connected in parallel with the DC-DC converter 74 and stores the electrical energy of the voltage transformed by the DC-DC converter 74. Furthermore, if the vehicle equipped with the steering system 1 is not a hybrid vehicle or an electric vehicle, power may be supplied not from the drive system power supply 80 but from, for example, an AC generator, or the main power supply 70 may include an AC generator.

[0033] Power is supplied from the main power supply 70 via the operation ECU 60b to the reaction force motor 26b of the operation subsystem 12b, and from the main power supply 70 via the steering ECU 62b to the steering motor 50b of the steering subsystem 14b. Power is supplied from the backup power supply 90 via the operation ECU 60a to the reaction force motor 26a of the operation main system 12a, and from the backup power supply 90 via the steering ECU 62a to the steering motor 50a of the steering main system 14a. As will be described later, during normal power supply, power is supplied from the main power supply 70 via the backup power supply 90 to the reaction force motor 26a and the steering motor 50a.

[0034] The backup power supply 90 receives power from the main power supply 70, and this power is used to charge the capacitor 91. The backup power supply 90 performs this charging and allows the power from the main power supply 70 to pass through, thereby enabling power to be supplied from the main power supply 70 to the reaction force motor 26a and the steering motor 50a. Therefore, during normal power supply, power is supplied from the main power supply 70 to the reaction force motor 26a of the operation main system 12a and the steering motor 50a of the steering main system 14a. In addition, during normal power supply, power is also supplied from the main power supply 70 to the reaction force motor 26b of the operation subsystem 12b and the steering motor 50b of the steering subsystem 14b. Hereinafter, the power supply from the main power supply 70 via the backup power supply 90 will be referred to as power supply from the main power supply 70.

[0035] As an example of a disconnection, consider Figure 2 The situation is such that the connection between the main power supply 70 and the backup power supply 90 is disconnected at the location indicated by the hollow arrow. In this situation, the main power supply 70 cannot supply power to the reaction force motor 26a and the steering motor 50a. The backup power supply 90 supplies power to the reaction force motor 26a and the steering motor 50a based on the electrical energy stored in the capacitor 91. The backup power supply 90 supplies power from the capacitor 91 when it is not receiving power at an appropriate voltage from the main power supply 70. The power supply from the capacitor 91 is referred to as the power supply from the backup power supply 90.

[0036] In the steering system 1 of the embodiment, power is supplied only from the main power supply 70 to the reaction force motor 26b constituting the operating subsystem 12b and the steering motor 50b constituting the steering subsystem 14b. In contrast, power can be selectively supplied from the main power supply 70 and the backup power supply 90 to the reaction force motor 26a constituting the operating main system 12a and the steering motor 50a constituting the steering main system 14a. Moreover, during standby operation, the power supply (power supply) to the reaction force motor 26a and the steering motor 50a is switched from the main power supply 70 to the backup power supply 90, and power is supplied to the reaction force motor 26a and the steering motor 50a from the backup power supply 90. Details of the backup power supply 90 will be described later.

[0037] [C] Steering system control

[0038] Hereinafter, regarding the control of the steering system 1 , the steering control, which is the control of the steering device 14 , and the reaction force control, which is the control of the reaction force applying mechanism 28 of the operating device 12 , will be described in sequence.

[0039] (a) Steering control

[0040] Steering control is used to steer the wheels 10 based on a steering request, that is, the operating angle of the steering wheel 20 during manual driving. Steering control is performed by the steering ECU 62. Specifically, there are two types of steering control: independent steering control (sometimes simply referred to as "independent control"), in which the steering ECU 62a and the steering ECU 62b, acting as dual-system controllers, independently perform control; and coordinated steering control (sometimes simply referred to as "coordinated control"), in which these ECUs 62a and 62b coordinate control. The following describes independent steering control and coordinated steering control.

[0041] i) Independent steering control

[0042] During independent steering control, the steering ECU 62a controls the steering main system 14a, while the steering ECU 62b controls the steering subsystem 14b. In other words, the steering ECU 62a and the steering ECU 62b perform the same control in parallel. The following description of the independent steering control will collectively describe the steering controls of the steering ECUs 62a and 62b as a single system. In the following description of independent steering control, the suffixes a and b are omitted from reference numerals when the distinction between the main system and the subsystem is unclear.

[0043] The motor rotation angle of the reaction motor 26 and the steering angle of the steering wheel 20 are in a relationship that results in a predetermined gear ratio. When the vehicle is started, the motor rotation angle is calibrated based on the steering angle detected by the steering angle sensor 32. The steering ECU 60 obtains the steering angle of the steering wheel 20 based on the motor rotation angle detected by the motor rotation angle sensor 30 of the reaction motor 26. During independent steering control, the steering ECU 62 receives steering angle information from the steering ECU 60 of the same system. Based on the steering angle, the steering ECU 62 determines a target steering angle, which serves as the target steering angle for the wheels 10.

[0044] The steering ECU 62 determines a target motor rotation angle, which serves as a target motor rotation angle for the steering motor 50, based on the determined target steering angle. The steering ECU 62 detects the actual motor rotation angle of the steering motor 50 via the motor rotation angle sensor 54 and determines a motor rotation angle deviation, which is the deviation of the motor rotation angle from the target motor rotation angle. The torque generated by the steering motor 50 is referred to as steering torque. The steering ECU 62 determines the steering torque to be generated based on a feedback control rule based on the motor rotation angle deviation.

[0045] The current supplied to the steering motor 50 is referred to as the steering current. Steering torque and the steering current are generally proportional. Based on this relationship, the steering ECU 62 determines the steering current to be supplied to the steering motor 50 based on the determined steering torque and supplies the steering current to the steering motor 50. Furthermore, the steering ECU 62 transmits steering current information to utilize the steering current value in controlling the reaction force imparting mechanism 28 of the operating device 12 and in coordinated steering control.

[0046] ii) Coordinated steering control

[0047] Coordinated steering control is performed during normal power supply from the main power supply 70 to the steering main system 14a and the steering subsystem 14b. Coordinated steering control takes into account smooth operation of the steering device 14, specifically the steering actuator 42, and ensures that the steering main system 14a and the steering subsystem 14b generate the same force. In other words, coordinated steering control coordinates the operation of the steering motor 50b of the steering subsystem 14b with the steering motor 50a of the steering main system 14a.

[0048] During coordinated steering control, the steering ECU 62a, which constitutes the main control system, transmits information regarding the steering current it supplies to the steering motor 50a to the steering ECU 62b, which constitutes the sub-control system. The steering ECU 62b does not determine the steering current it supplies to the steering motor 50b, but instead supplies the steering current to the steering motor 50b based on the received information.

[0049] Thus, the steering system 1 of the embodiment includes: a main power supply 70 and a backup power supply 90; a steering system 14 having a dual-system steering motor 50, a main system and a subsystem, which steers the wheels 10 using the force generated by the steering motor 50; and a steering ECU 62 (control device) that controls the operation of the main system and the subsystem of the steering motor 50 to control the steering system 14 based on a steering request. The steering system 1 is configured to selectively supply power to the main system of the steering motor 50 from the main power supply 70 and the backup power supply 90, while supplying power only to the subsystem of the steering motor 50 from the main power supply 70. The steering ECU 62 is configured to operate the subsystem of the steering motor 50 in coordination with the main system of the steering motor 50 during normal power supply, when power is supplied from the main power supply 70 to the main system and subsystem of the steering motor 50. During backup power supply, when power is supplied from the backup power supply 90 to the main system of the steering motor 50, the steering ECU 62 independently controls the main system and the subsystem of the steering motor 50.

[0050] (b) Reaction force control

[0051] Reaction force control is used to provide the driver with a sense of steering operation. In the steering system 1, reaction force control is configured such that, during normal power supply, the main control system 12a and the sub-control system 12b independently and concurrently apply the same operational reaction force to the steering wheel 20. The following description of the reaction force control involves a unified description of the reaction force application process performed by the operation ECU 60a, which constitutes the main control system, and the reaction force application process performed by the operation ECU 60b, which constitutes the sub-control system.

[0052] The operation ECU 60 determines the operational reaction force based on two components: the steering load-based component FS and the operational force-reduction-based component FA. The steering load-based component FS represents the steering force (steering torque of the steering motor 50) required to steer the wheels 10 and is determined based on the steering current supplied to the steering motor 50. Although detailed description is omitted, a greater steering current is recognized as a greater steering load on the wheels 10, and a greater value is determined for the steering load-based component FS. Furthermore, information regarding the actual steering current supplied to the steering motor 50 is transmitted from the steering ECU 62 to the operation ECU 60 in the same system via a dedicated communication line 64.

[0053] On the other hand, the operating force reduction component FA can be considered as a component for providing the driver with a so-called operational feel in the power steering system. In a power steering system, an assist torque corresponding to the operating torque is generally applied to the steering shaft 22. The operating ECU 60 detects the operating torque via the operating torque sensor 36. Based on the operating reaction force, the operating ECU 60 determines a reaction force current, which is a current supplied to the reaction force motor 26, and supplies this determined reaction force current to the reaction force motor 26.

[0054] [D] Detailed structure of backup power supply

[0055] like Figure 3 As shown, the backup power supply 90 includes a power line 90a, a capacitor 91, a charging circuit 92, a discharging circuit 93, an interface circuit 94, a microcomputer 95, and switches 96, 97, and 98. The power line 90a connects the input terminal 9a and the output terminal 9b of the backup power supply 90. The input terminal 9a is connected to the positive electrode of the main power supply 70, and the output terminal 9b is connected to the operating device 12 (operating ECU 60a) and the steering system 14 (steering ECU 62a). A switch 96 is provided on the power line 90a.

[0056] Capacitor 91 is connected in parallel with main power supply 70 via power supply line 90a. The positive electrode of main power supply 70 is connected to one terminal of capacitor 91 via switches 96 and 97 and charging circuit 92. Furthermore, the positive electrode of main power supply 70 is connected to one terminal of capacitor 91 via switches 96 and 98 and discharge circuit 93. Charging circuit 92 and discharge circuit 93 are connected in parallel.

[0057] The charging circuit 92 is a charging circuit for storing power in the capacitor 91. When switches 96 and 97 are turned on (connected) and switch 98 is turned off (shutoff), charging of the capacitor 91 from the main power supply 70 begins via the power line 90a, a diode 921 disposed between the power line 90a and the charging circuit 92, and the charging circuit 92. The discharging circuit 93 is a discharging circuit for discharging the power stored in the capacitor 91 to supply power to the operating device 12 and the steering device 14 when power is required from the capacitor 91 due to a failure of the main power supply 70, for example. When switches 96 and 97 are turned off and switch 98 is turned on, power is supplied from the capacitor 91 to the operating device 12 and the steering device 14 via the discharging circuit 93, a diode 931 disposed between the power line 90a and the discharging circuit 93, and the power line 90a.

[0058] Interface circuit 94 is a circuit connected to microcomputer 95. It has the function of converting the voltage of main power supply 70 (power line 90a) and the voltage of capacitor 91 into levels and outputting them to microcomputer 95, and the function of outputting control signals from microcomputer 95 to switches 96 to 98. In other words, interface circuit 94 is a circuit for microcomputer 95 to monitor voltage and a circuit for outputting control signals from microcomputer 95 to switches 96 to 98.

[0059] The backup power supply 90 also includes a first voltage detection unit (also referred to as a voltage detection circuit or voltmeter) 90b for detecting the voltage of the main power supply 70, and a second voltage detection unit (also referred to as a voltage detection circuit or voltmeter) 90c for detecting the voltage of the capacitor 91. The first voltage detection unit 90b and the second voltage detection unit 90c can be said to include an interface circuit 94. The microcomputer 95 detects the voltage of the main power supply 70 and the voltage of the capacitor 91 via the first voltage detection unit 90b and the second voltage detection unit 90c. Furthermore, the operation ECU 60 and the steering ECU 62 are configured to detect the voltage of the main power supply 70 without using the microcomputer 95 (through other means). In other words, the operation ECU 60 and the steering ECU 62 each include a voltage detection unit for detecting the voltage of the main power supply 70.

[0060] The microcomputer 95 is a microcomputer for control with a CPU and the like. The microcomputer 95 monitors the voltage of the main power supply 70 and the voltage of the capacitor 91, and controls the on and off of each switch 96 to 98 based on each voltage value. The microcomputer 95 is powered by the main power supply 70 via a control system power supply circuit 951 that is separate from the power supply line 90a. If the ignition switch (key switch) 99 is turned on, the control system power supply circuit 951 is connected to the main power supply 70. The microcomputer 95 is communicatively connected to the operation ECU 60 and / or the steering ECU 62. In Figure 3 In the description, the microcomputer 95 is connected to the operation ECU 60a.

[0061] If the microcomputer 95 determines that the amount of charge in capacitor 91 is insufficient based on the voltage value of capacitor 91 (for example, if the voltage value of capacitor 91 falls below a predetermined value), the microcomputer 95 changes the control mode from the normal mode to the charging mode. The normal mode is a control mode in which switch 96 is turned on and switches 97 and 98 are turned off. The charging mode is a control mode in which switches 96 and 97 are turned on and switch 98 is turned off.

[0062] If a failure of the main power supply 70 is determined based on its voltage value, specifically if the voltage of the main power supply 70 is determined to be less than a first threshold, the microcomputer 95 changes the control mode from the normal mode (or charging mode) to the backup mode. The backup mode is a control mode in which switches 96 and 97 are opened and switch 98 is closed. The microcomputer 95 is configured to determine that the voltage of the main power supply 70 is less than the first threshold if the voltage of the main power supply 70 continues to be less than the first threshold for a predetermined period of time. When the control mode is changed to the backup mode, power is supplied from the capacitor 91 to the reaction force motor 26 and the steering motor 50 via the drivers (inverters) of the operation ECU 60a and the steering ECU 62a.

[0063] If the microcomputer 95 detects a failure (abnormality) in the capacitor 91, discharge circuit 93, or other components, it transmits information indicating a failure in the backup power supply 90 to the operation ECU 60a. For example, a failure in the capacitor 91 can be detected by the absence of a voltage increase in the capacitor 91, even in charging mode. Furthermore, a failure in the discharge circuit 93 can be detected, for example, through a preliminary check performed during vehicle startup. If a failure in the capacitor 91 or discharge circuit 93 occurs, the microcomputer 95 does not change the control mode to the backup mode, regardless of the voltage level of the main power supply 70.

[0064] Furthermore, if the microcomputer 95 itself fails, no signal (regular signal) is sent from the microcomputer 95 to the operation ECU 60a. Therefore, the operation ECU 60a does not receive any signal from the microcomputer 95 and can determine that the backup power supply 90 has failed. This allows the operation ECU 60a to detect a failure in the backup power supply 90. If the backup power supply 90 fails, the operation ECU 60a notifies the steering ECU 62 of this information, which then issues a warning to the driver. The steering ECU 62 notifies the driver of the abnormality through a display and audio, and advises the driver to visit a dealer, for example.

[0065] [E] Abnormal control

[0066] When the microcomputer 95 changes the control mode to the backup mode when the backup power supply 90 is normal, the steering ECU 62 and the operation ECU 60 also perform abnormal control at the same time as the change. Abnormal control is a control for stopping the vehicle safely, such as evasive driving control. The voltage drop of the main power supply 70 is often caused by a failure of the drive system power supply 80. In this case, the drivable time is limited. Therefore, the evasive driving control is a control that urges evasive driving in a manner that enables the vehicle to evade and stop in a safe place, for example, by outputting a warning (such as a warning display, sound) to the driver. Since the control mode is the backup mode, the steering control in the evasive driving control becomes effective by the power supply from the backup power supply 90. In addition, in the evasive driving control, for example, the remaining drivable time can also be notified to the driver.

[0067] The first threshold is a threshold used to determine the start of evasive driving when the backup power supply 90 is normal. The voltage at which the operating device 12 and the steering device 14 cannot operate is used as a reference, and the first threshold is set to a value with a margin relative to the reference (a value higher than the reference). Figure 4 As shown, when a failure of the main power supply 70 occurs during normal driving, causing the voltage of the main power supply 70 to drop. If the voltage of the main power supply 70 remains below a first threshold for a predetermined time, the microcomputer 95 switches the power supply source from the main power supply 70 to the backup power supply 90, and the steering ECU 62 and the operating ECU 60 initiate avoidance driving control. The predetermined time is set to eliminate noise (instantaneous voltage drops). By switching the control mode of the backup power supply 90 to the backup mode, power from the capacitor 91 is supplied to the operating device 12 and the steering device 14 via the power line 90a.

[0068] On the other hand, when an abnormality (failure) of the backup power supply 90 is detected, the steering ECU 62 and the operation ECU 60 change the threshold of the voltage value of the main power supply 70, which is a judgment indicator for starting the avoidance driving control, from the first threshold to the second threshold. The second threshold is a value greater than the first threshold (second threshold>first threshold). Figure 5 As shown, if the voltage of the main power supply 70 drops below the second threshold for a predetermined period of time, the steering ECU 62 and the operating ECU 60 determine that the voltage of the main power supply 70 is below the second threshold and execute abnormality control, namely, evasive driving control. This allows evasive driving control to begin at an earlier time than when the backup power supply 90 is functioning properly, allowing evasive driving to be executed for a correspondingly longer period using the power of the main power supply 70. In other words, the operating device 12 and steering device 14 can be operated using the power of the main power supply 70 before the voltage drops completely, and evasive driving control can be initiated at a time when evasive driving can be completed. It can also be said that the microcomputer 95, the steering ECU 62, and the operating ECU 60 constitute a controller of the steering system 1.

[0069] Reference Figure 6 An example of the control process will be described below. First, the microcomputer 95, the steering ECU 62, and the operating ECU 60 obtain information on the voltage value of the main power supply 70 (S101). The steering ECU 62 and the operating ECU 60 determine whether the backup power supply 90 is normal based on the communication results with the microcomputer 95 (for example, the presence or absence of a fault notification signal) (S102). If the backup power supply 90 is normal (S102: Yes), the steering ECU 62 and the operating ECU 60 compare the voltage value of the main power supply 70 with a first threshold value (S103). If the voltage value of the main power supply 70 is less than the first threshold value (S103: Yes), the steering ECU 62 and the operating ECU 60 measure the duration of the state in which the voltage value of the main power supply 70 is less than the first threshold value (S104). Specifically, the steering ECU 62 and the operating ECU 60 increment the counter by 1 (S104).

[0070] Next, the steering ECU 62 and the operation ECU 60 determine whether the counter value is greater than a specified value (S105). If the counter value is greater than the specified value (S105: Yes), the steering ECU 62 and the operation ECU 60 execute avoidance driving control (S106). If the voltage value of the main power supply 70 is greater than the first threshold value (S103: No), the steering ECU 62 and the operation ECU 60 reset the counter value to 0 (S107). Furthermore, as in steps S103-S105 and S107, the microcomputer 95 compares the voltage of the main power supply 70 with the backup transition threshold value (here, the same value as the first threshold value) independently of the steering ECU 62 and the operation ECU 60. The backup transition threshold value is used to determine whether to shift the control mode to the backup mode. Specifically, if the voltage of the main power supply 70 remains below the backup transition threshold value for a specified period of time (for example, when the counter value is greater than the specified value), the microcomputer 95 shifts the control mode to the backup mode. In this example, the ECUs 60 and 62 independently determine whether to start the abnormality control and the microcomputer 95 independently determines whether to shift to the standby mode. In this example, the result is a shift to the standby mode and the start of the abnormality control (S106).

[0071] On the other hand, if the backup power supply 90 is abnormal (failed) (S102: No), the steering ECU 62 and the operation ECU 60 compare the voltage value of the main power supply 70 with the second threshold value (second threshold value > first threshold value) (S108). If the voltage value of the main power supply 70 is less than the second threshold value (S108: Yes), the steering ECU 62 and the operation ECU 60 measure the duration of the state in which the voltage value of the main power supply 70 is less than the second threshold value (S109). Specifically, the steering ECU 62 and the operation ECU 60 increment the counter by 1 (S109). Next, the steering ECU 62 and the operation ECU 60 determine whether the counter value is greater than a predetermined value (S110). If the counter value is greater than the predetermined value (S110: Yes), the steering ECU 62 and the operation ECU 60 execute avoidance driving control (S111). Furthermore, if the voltage value of the main power supply 70 is greater than the second threshold value (S108: No), the steering ECU 62 and the operation ECU 60 reset the counter value to 0 (S112). The steering ECU 62 and the operation ECU 60 repeatedly execute such processing at short time intervals.

[0072] Thus, when backup power supply 90 is normal, evasive driving control associated with a failure of main power supply 70 is initiated based on the first threshold value and executed using the power of backup power supply 90. On the other hand, when backup power supply 90 is abnormal, evasive driving control associated with a failure of main power supply 70 is initiated based on the second threshold value and executed using the power of main power supply 70. Furthermore, various determinations, such as the determination to start abnormality control, may be made by at least one of the steering ECU 62 and the operation ECU 60.

[0073] (Summarize)

[0074] The steering system 1 of this embodiment is a steer-by-wire system that includes a main power supply 70 and a backup power supply 90; a steering device 14 having a steering motor 50 that receives power from at least one of the main power supply 70 and the backup power supply 90, and steers the wheels 10 using the force of the steering motor 50; and a steering ECU 62 serving as a control device that detects the voltage of the main power supply 70, supplies power from the main power supply 70 to the steering motor 50, and controls the steering device 14 based on a steering request. The steering ECU 62 is configured to execute abnormality control based on power supplied to the steering motor 50 from at least one of the main power supply 70 and the backup power supply 90 (the selected power source) when the backup power supply 90 is normal and the voltage of the main power supply 70 is determined to be less than a first threshold value. Furthermore, if the backup power supply 90 is abnormal and the voltage of the main power supply 70 is determined to be less than a second threshold value that is greater than the first threshold value, the steering ECU 62 executes abnormality control based on power supplied to the steering motor 50 from the main power supply 70.

[0075] According to this configuration, since the second threshold is greater than the first threshold, if the voltage of the main power supply 70 drops while the backup power supply 90 is abnormal, abnormality control can be executed earlier than if the voltage of the main power supply 70 drops while the backup power supply 90 is normal. Thus, in a situation where power supply from the backup power supply 90 is impossible, abnormality control can be initiated before the voltage of the main power supply 70 drops to a level that makes abnormality control inoperable. Because abnormality control can be initiated earlier, that is, when the voltage of the main power supply 70 is high, the required execution time for abnormality control can be ensured. According to this configuration, even if the main power supply 70 also becomes abnormal while the backup power supply 90 is abnormal, abnormality control can still be executed.

[0076] The backup power supply 90 includes a capacitor 91, a first voltage detector 90b that detects the voltage of the main power supply 70, a second voltage detector 90c that detects the voltage of the capacitor 91, and a microcomputer 95 that switches the power supply to the steering motor 50 between the main power supply 70 and the capacitor 91 based on the detection result of the first voltage detector 90b. The microcomputer 95 is configured to switch the power supply to the steering motor 50 from the main power supply 70 to the backup power supply 90 if it determines that the voltage of the main power supply 70 is less than a backup transfer threshold. In this embodiment, the first threshold and the backup transfer threshold are set to the same value. Consequently, abnormal control is performed using the power of the backup power supply 90.

[0077] The microcomputer 95 determines whether the backup power supply 90 (capacitor 91) is functioning properly based on the control status and the detection results of the second voltage detection unit 90c. For example, if the voltage of capacitor 91 does not rise despite being in charging mode, the microcomputer 95 determines that the backup power supply 90 is abnormal. The microcomputer 95 transmits the determination result to the steering ECU 62. Furthermore, the microcomputer 95 periodically transmits signals to the steering ECU 62. If it determines that signal reception from the microcomputer 95 is interrupted (for example, if no signal is received within a specified time period), the steering ECU 62 determines that the backup power supply 90 is abnormal. In this way, the steering ECU 62, acting as a control device, detects abnormalities in the backup power supply 90.

[0078] (other)

[0079] The present invention is not limited to the above-described embodiments. For example, the power supply redundancy structure is not limited to that described above; any configuration may be employed in which at least one of the main power supply 70 and the backup power supply 90 (e.g., selectively) supplies power to the steering motor 50. Furthermore, the steering system 1 can also be applied to, for example, autonomous vehicles. In this case, for example, a steering request is output from the ECU. Abnormality control is not limited to that described above; any control performed when an abnormality occurs may be performed. The timing of the change in control mode to the backup mode and the start of abnormality control may be staggered. For example, abnormality control may be initiated before or after the change to the backup mode. Specifically, the backup transition threshold and the first threshold may be set to different values, and the predetermined time for determination (the predetermined value compared with the counter count) may be different. Furthermore, the steering system 1 may include an integrated ECU serving as an integrated controller for both systems. Furthermore, for example, the main system ECU (the operating ECU 60a and / or the steering ECU 62a) may operate in an integrated manner for both systems. Abnormality control may be performed only on the steering-related portion (the steering ECU 62) to a minimum.

Claims

1. A steering system is a wire-controlled steering system having: Main and backup power supplies; a steering device having a steering motor powered by at least one of the main power source and the backup power source, and steering the wheels by the force of the steering motor; and a control device that detects the voltage of the main power supply, supplies power from the main power supply to the steering motor, and controls the steering device based on a steering request, in, The control device is composed of: When the backup power supply is normal, if it is determined that the voltage of the main power supply is less than a first threshold, abnormal control is performed based on the power supply to the steering motor from at least one of the main power supply and the backup power supply. When the backup power supply is abnormal, if it is determined that the voltage of the main power supply is less than a second threshold value greater than the first threshold value, abnormality control is executed based on power supply from the main power supply to the steering motor.

2. The steering system according to claim 1, wherein: The backup power supply has: capacitors; a first voltage detection unit configured to detect a voltage of the main power supply; a second voltage detection unit for detecting a voltage of the capacitor; as well as The microcomputer switches the power supply to the steering motor between the main power supply and the capacitor based on the detection result of the first voltage detection unit. The microcomputer is configured to switch the power supply to the steering motor from the main power supply to the backup power supply when it is determined that the voltage of the main power supply is lower than a backup shift threshold.

3. The steering system according to claim 2, wherein: The first threshold and the standby transfer threshold are set to the same value.

4. The steering system according to claim 2 or 3, wherein: The microcomputer determines whether the backup power supply is normal based on a control status and a detection result of the second voltage detection unit.

5. The steering system according to any one of claims 2 to 4, wherein: The microcomputer periodically sends a signal to the control device. If the control device determines that the signal reception from the microcomputer is interrupted, it determines that the backup power supply is abnormal.

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