Steering control device

Abstract

To provide a steering control device which can suppress such a situation that torque that can be output by a motor is not restricted in a case where an abnormality in a power source is detected.SOLUTION: A steering control device is connected to a main power source via a power source device having an auxiliary power source. The steering control device includes a turning side control unit which controls the operation of a turning side motor by controlling the drive of a drive circuit connected to at least one of the main power source and the auxiliary power source. The connection state of the drive circuit to the main power source and the auxiliary power source is switched by the power source device so as to shift to the backup state with detection of a fall of the main power source. The turning side control unit is configured to start output restriction processing in the shift of backup until switching of the connection state by the power source device so as to shift to the backup state with detection of the fall is completed after detection of the fall of the main power source.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a steering control device. [Background technology]

[0002] For example, a vehicle is equipped with a steering device described in Patent Document 1. The steering device described in Patent Document 1 is a so-called steer-by-wire type steering device in which the power transmission path between the steering wheel of the vehicle and the steered wheels of the vehicle is separated. The steering device is equipped with a power supply device. The power supply device supplies power to each component of the steering device, such as the reaction motor, the steering actuator, and the control device. The power supply device includes a main power supply and a backup power supply. The backup power supply is used as a backup in the event of an abnormality in the power supply device, such as a failure or malfunction of the main power supply.

[0003] However, since there is a limit to the power that the backup power supply can supply, the steering device executes an output limiting process that controls to limit the output of the steering actuator while the backup power supply is in operation. This allows the steering device to continue steering the steered wheels as much as possible through backup by the backup power supply when an abnormality occurs in the power supply device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-83058 Summary of the Invention [Problem to be solved by the invention]

[0005] In the case of Patent Document 1, the vehicle is designed so that the power limit that the backup power supply can supply is not exceeded even if steering of the steered wheels through backup by the backup power supply must continue. Here, there is a need for a way to prevent a situation in which output limiting processing for the output of the steering actuator is not executed when the vehicle is in backup mode by the backup power supply. [Means for solving the problem]

[0006] A steering control device that solves the above problem is a steering control device that is connected to a first power source mounted on a vehicle via a power supply device having a second power source, and that controls a steering device mounted on the vehicle, and includes a drive circuit that drives a motor to supply power supplied by being connected to at least one of the first power source and the second power source, and is equipped with a control unit that controls the operation of the motor by controlling the drive circuit, and the connection state of the drive circuit to the first power source and the second power source is such that, when a state in which power is supplied from the first power source is defined as a first state, the connection state is switched by the power supply device so as to transition to a second state in which power is supplied from the second power source upon detection of an abnormality in the first power source, and the control unit has a function of executing an output limiting process, which is a process for limiting the torque that the motor can output after detecting an abnormality in the first power source, compared to before the abnormality was detected, and the output limiting process is configured to be started after detecting an abnormality in the first power source, but before the power supply device has completed switching the connection state so as to transition to the second state upon detection of the abnormality.

[0007] According to the above configuration, when the power supply device completes switching of the connection state to transition to the second state in response to the detection of an abnormality in the first power supply, the control unit has already started the output limiting process. This makes it possible to prevent a situation in which the control unit does not limit the torque that can be output by the motor when the power supply device has completed switching of the connection state. Therefore, it is possible to prevent a situation in which the torque that can be output by the motor is not limited when an abnormality in the power supply is detected.

[0008] In the above steering control device, the output limiting process is a process of limiting the torque output by the motor so that it does not exceed an output limit value, and it is preferable that the output limit value is a value less than the limit of the power supply performance of the second power supply, assuming that the power supply performance defined by the power supply capacity or power supply voltage of the second power supply is lower than that of the first power supply.

[0009] According to the above configuration, in the second state, it is possible to prevent the power supply performance of the second power supply from being exceeded. As a result, even if an abnormality in the first power supply is detected, the motor can continue to operate favorably. This is particularly effective when the power supply performance of the second power supply is lower than that of the first power supply.

[0010] In the above steering control device, the power supply device includes a power supply control unit having a function of switching the connection state so as to transition to the second state upon detection of an abnormality in the first power supply, and it is preferable that the control unit is connected to the power supply control unit via a line so as to be able to communicate with the power supply control unit, and is configured to obtain information from the power supply control unit via the line indicating that the switching of the connection state has been completed when transitioning to the second state.

[0011] In the above configuration, the control unit can determine the state of the power supply device, such as whether it is in the first state or the second state, based on information obtained from the power supply control unit via the line. This allows the control unit to operate taking the state of the power supply device into consideration. However, communication delays occur in communication between the control unit and the power supply control unit. Causes of communication delays include, for example, line path or communication errors. As an example, assume that the control unit is configured to start limiting the torque that can be output by the motor after determining, based on information obtained from the power supply control unit, that switching of the connection state to the second state has been completed. In this case, during the communication delay, while switching of the connection state to the second state has been completed, the control unit has not started limiting the torque that can be output by the motor.

[0012] In contrast, with the above configuration, when the control unit detects an abnormality in the first power supply, it can start limiting the torque that can be output by the motor earlier than obtaining information from the power supply control unit that switching of the connection state to the second state has been completed. Therefore, in a configuration in which the control unit and the power supply control unit communicate with each other, it is possible to reduce the likelihood of a situation in which the torque that can be output by the motor is not limited in the second state to which the transition occurs upon detection of an abnormality in the first power supply.

[0013] Specifically, in the above steering control device, it is preferable that the control unit is configured to execute the output limiting process while the power supply of the vehicle that allows connection to the first power supply so that the vehicle can operate is in an on state.

[0014] In the above steering control device, it is preferable that the control unit includes a control circuit that executes processing related to the output limiting processing, and the control circuit is connected to at least one of the first power source and the second power source, and is configured to be constantly connected to at least one of the first power source and the second power source via a connection circuit that the power supply device has, regardless of the state of the first power source, while the vehicle's power source is on.

[0015] According to the above configuration, if an abnormality in the first power source is detected while the vehicle is powered on, power is continuously supplied to the control circuit included in the control unit. In this case, the control circuit can preferably start output limiting processing when the first power source fails. [Effects of the Invention]

[0016] According to the steering control device of the present invention, when a power supply abnormality is detected, it is possible to make it less likely that the torque that can be output by the motor will be unrestricted. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 2 is a diagram showing a schematic configuration of a steering device. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the steering device. [Figure 3] FIG. 2 is a block diagram showing the electrical configuration of the steering device, particularly the electrical configuration of a steering-side control unit. [Figure 4] FIG. 2 is a block diagram showing the functions of a main control unit of a steering-side control unit, particularly a control circuit. [Figure 5] FIG. 2 is a diagram illustrating the function of a limiting control unit among the functions of the control circuit. [Figure 6] 1A is a diagram showing the power supply voltage, FIG. 1B is a diagram showing the state of the start switch, FIG. 1C is a diagram showing the state of the power supply device, and FIG. 1D is a diagram showing the output limit value, in accordance with an embodiment. [Figure 7] 10A shows the power supply voltage, FIG. 10B shows the state of the start switch, FIG. 10C shows the state of the power supply device, and FIG. 10D shows the output limit value for the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0018] A steering control device 1 according to one embodiment will be described. As shown in FIG. 1, steering device 2, which is the control target of steering control device 1, is configured as a steer-by-wire type steering device for a vehicle. Steering device 2 includes a steering unit 4 and a turning unit 6. Steering unit 4 is steered by a driver via a steering wheel 3 of the vehicle. Steering unit 6 steers left and right steerable wheels 5 of the vehicle in accordance with the steering input to steering unit 4 by the driver. Note that steering device 2 of this embodiment has a structure in which the power transmission paths between steering unit 4 and turning unit 6 are mechanically separated at all times. In other words, the power transmission paths between steering actuator 12, which will be described later, and turning actuator 31, which will be described later, are mechanically separated at all times.

[0019] The steering unit 4 includes a steering shaft 11 and a steering actuator 12. The steering shaft 11 is connected to the steering wheel 3. The steering actuator 12 includes a steering-side motor 13, which is a drive source, and a steering-side reduction mechanism 14. The steering-side motor 13 is a reaction motor that applies a steering reaction force, which is a force that resists steering, to the steering wheel 3 via the steering shaft 11. The steering-side motor 13 is connected to the steering shaft 11 via the steering-side reduction mechanism 14, which is made up of, for example, a worm and wheel. For example, a three-phase brushless motor is used as the steering-side motor 13 in this embodiment.

[0020] The steered unit 6 includes a pinion shaft 21, a rack shaft 22 serving as a steered shaft, and a rack housing 23. The pinion shaft 21 and the rack shaft 22 are connected at a predetermined cross angle. A rack-and-pinion mechanism 24 is formed by meshing pinion teeth 21a formed on the pinion shaft 21 with rack teeth 22a formed on the rack shaft 22. In other words, the pinion shaft 21 corresponds to a rotation axis that can be converted into a steering angle, which is the steering position of the steered wheels 5. The rack housing 23 accommodates the rack-and-pinion mechanism 24. An end of the pinion shaft 21 opposite the end connected to the rack shaft 22 protrudes from the rack housing 23. Both ends of the rack shaft 22 protrude from both axial ends of the rack housing 23. Tie rods 26 are connected to both ends of the rack shaft 22 via rack ends 25 formed as ball joints. The ends of the tie rods 26 are connected to knuckles (not shown) to which the left and right steered wheels 5 are attached.

[0021] The steering unit 6 includes a steering actuator 31. The steering actuator 31 includes a steering-side motor 32, which is a drive source, a transmission mechanism 33, and a conversion mechanism 34. The steering-side motor 32 applies a steering force to the rack shaft 22 to turn the steered wheels 5 via the transmission mechanism 33 and the conversion mechanism 34. The steering-side motor 32 transmits rotation to the conversion mechanism 34 via the transmission mechanism 33, which is, for example, a belt transmission mechanism. The transmission mechanism 33 converts the rotation of the steering-side motor 32 into reciprocating motion of the rack shaft 22 via the conversion mechanism 34, which is, for example, a ball screw mechanism. A three-phase brushless motor, for example, is used as the steering-side motor 32 in this embodiment. In this embodiment, the steering-side motor 32 is an example of a motor.

[0022] In the steering device 2 configured as described above, the steering actuator 31 applies motor torque as a steering force to the rack shaft 22 in response to the steering operation by the driver, thereby changing the steering angle of the steered wheels 5. At this time, the steering actuator 12 applies a steering reaction force that resists the steering by the driver to the steering wheel 3. In other words, in the steering device 2, the steering torque Th required to steer the steering wheel 3 is changed by the steering reaction force, which is the motor torque applied from the steering actuator 12.

[0023] The reason for providing the pinion shaft 21 is to support the rack shaft 22 together with the pinion shaft 21 inside the rack housing 23. In other words, the rack shaft 22 is supported movably along its axial direction and is pressed toward the pinion shaft 21 by a support mechanism (not shown) provided in the steering device 2. In this way, the rack shaft 22 is supported inside the rack housing 23. However, another support mechanism may be provided to support the rack shaft 22 in the rack housing 23 without using the pinion shaft 21.

[0024] As shown in Fig. 1, the steering-side motor 13 and the steered-side motor 32 are connected to the steering control device 1. The steering control device 1 controls the operation of each of the motors 13, 32. In this way, the steering control device 1 controls the steering device 2 to operate so as to perform the desired function as a steer-by-wire type steering device.

[0025] Detection results of various sensors are input to the steering control device 1. The various sensors include, for example, a torque sensor 41, a steering side rotation angle sensor 42, a turning side rotation angle sensor 43, and a vehicle speed sensor 44.

[0026] The torque sensor 41 is provided on the steering shaft 11 at a position closer to the steering wheel 3 than the steering side reduction mechanism 14. The torque sensor 41 detects steering torque Th, which is a value indicating the torque applied to the steering shaft 11 by the driver's steering. The steering torque Th is detected in relation to the torsion of a torsion bar 41a provided midway along the steering shaft 11. The steering side rotation angle sensor 42 is provided on the steering side motor 13. The steering side rotation angle sensor 42 detects rotation angle θa, which is the angle of the rotation shaft of the steering side motor 13, within a range of 360 degrees. The turning side rotation angle sensor 43 is provided on the turning side motor 32. The turning side rotation angle sensor 43 detects rotation angle θb, which is the angle of the rotation shaft of the turning side motor 32, within a range of 360 degrees. The vehicle speed sensor 44 detects vehicle speed V, which is the traveling speed of the vehicle.

[0027] <Electrical configuration of steering control device 1> As shown in Fig. 2, the steering control device 1 has a steering side control unit 50 that controls the power supply to the steering side motor 13, and a turning side control unit 60 that controls the power supply to the turning side motor 32. The steering side control unit 50 and the turning side control unit 60 transmit and receive information to each other via a local network 70 such as serial communication. The steering side control unit 50 is provided as part of the configuration of the steering unit 4. In addition, the turning side control unit 60 is provided as part of the configuration of the turning unit 6.

[0028] The steering-side control unit 50 is equipped with a central processing unit (CPU) and memory (not shown), and the CPU executes a program stored in the memory at predetermined calculation cycles. This allows various processes to be performed. The calculation cycle of the steering-side control unit 50 may be set taking into consideration the calculation cycle of a power supply control unit 88 (described later) or the communication cycle of a dedicated signal line 90 (described later). For example, the calculation cycle of the steering-side control unit 50 is designed to be shorter than the calculation cycle of the power supply control unit 88 (described later) or the communication cycle of a dedicated signal line 90 (described later).

[0029] The steering-side control unit 50 is configured to have two control systems, a main control unit 50a and a sub-control unit 50b, which combine a CPU and a memory to execute various processes. In this embodiment, the steering-side control unit 50 operates in a master-slave control system in which the main control unit 50a is the master control unit and the sub-control unit 50b is the slave control unit. The same applies to the turning-side control unit 60. In other words, the turning-side control unit 60 has two control units, a main control unit 60a and a sub-control unit 60b, which combine a CPU and a memory to execute various processes, and these are configured to operate in a master-slave control system. The control units 50a, 50b of the steering-side control unit 50 and the control units 60a, 60b of the turning-side control unit 60 are configured to be able to communicate with each other via a local network 70.

[0030] Each control unit 50a, 50b of the steering-side control unit 50 calculates a reaction force control amount, which is a target for the steering reaction force of the steering wheel 3 to be generated through the steering-side motor 13, based on various information. The various information includes, for example, detection results of the various sensors described above and information obtained from the turning-side control unit 60 via the local network 70. Each control unit 50a, 50b controls the supply of power to the steering-side motor 13 based on the reaction force control amount. Furthermore, each control unit 60a, 60b of the turning-side control unit 60 calculates, based on various information, a steering control amount, which is a target for the steering force to be generated through the turning-side motor 32. The various information includes, for example, detection results of the various sensors described above and information obtained from the steering-side control unit 50 via the local network 70. Each control unit 60a, 60b controls the supply of power to the turning-side motor 32 based on the steering control amount.

[0031] A main power supply 45 serving as a first power supply is connected to the steering control device 1, i.e., the steering device 2. The main power supply 45 is, for example, a secondary battery mounted on the vehicle. The main power supply 45 serves as a power source for supplying power to operate the motors 13, 32, and also serves as a power source for supplying power to operate the steering control device 1, i.e., the steering device 2.

[0032] A vehicle start switch 46, such as an ignition switch, is provided between the steering device 2 and the main power supply 45. The start switch 46 is provided midway on the power supply line L2, which branches off from a connection point P0 of the power supply line L1, one of two power supply lines L1 and L2 connecting the steering device 2 and the main power supply 45. The start switch 46 is operated to activate various functions so that a drive source for running the vehicle, such as an engine, can be operated to enable vehicle operation. The conduction of the power supply line L2 is turned on and off through operation of the start switch 46. In this embodiment, the operating state of the steering device 2, which can perform the desired functions as a steer-by-wire steering device, is associated with the operating state of the vehicle. Note that the power supply line L1 is basically always on, but the conduction of the power supply line L1 is indirectly turned on and off as a function of the steering device 2 depending on the operating state of the steering device 2. In other words, the operating state of the steering device 2 is associated with the on and off conduction of the power supply lines L1 and L2, which is the state of the power supply from the main power supply 45.

[0033] In the steering device 2, the power supply lines L1 and L2, i.e., the main power supply 45, are connected to the main control unit 50a of the steering side control unit 50 in particular via the power supply device 80. Furthermore, the power supply lines L1 and L2, i.e., the main power supply 45 are directly connected to the sub-control unit 50b of the steering side control unit 50 in particular without going through the power supply device 80. The same is true for the turning side control unit 60, where the power supply lines L1 and L2, i.e., the main power supply 45 are connected to the main control unit 60a of the turning side control unit 60 in particular via the power supply device 80. Furthermore, the power supply lines L1 and L2, i.e., the main power supply 45 are directly connected to the sub-control unit 60b of the turning side control unit 60 in particular without going through the power supply device 80. In other words, in this embodiment, a single power supply device 80 is shared between the steering side control unit 50 and the turning side control unit 60. The power supply device 80 is configured to be able to communicate with the main control units 50 a and 60 a of the steering-side control unit 50 and the turning-side control unit 60 via a dedicated signal line 90 .

[0034] <Connection of power lines L1 and L2> Fig. 3 shows the configuration for supplying power in detail. Here, the explanation will focus on the configuration related to the turning-side control unit 60. The configuration related to the steering-side control unit 50 is basically the same as the configuration related to the turning-side control unit 60.

[0035] As shown in Fig. 3, power from the main power supply 45 is supplied to a drive circuit 61a of the main control unit 60a via a power supply line L11 branching off from a connection point P11 of the power supply line L1. The drive circuit 61a is a circuit that handles larger power and includes, for example, an inverter that converts DC power from the main power supply 45 into AC power. Power from the main power supply 45 is supplied to a control circuit 62a of the main control unit 60a via a power supply line L21 branching off from a connection point P12 of the power supply line L2. The control circuit 62a is a circuit for controlling the steering-side motor 13 and includes, for example, a CPU and a memory.

[0036] Furthermore, power from the main power supply 45 is supplied to a drive circuit 61b of the sub-controller 60b via a power line L12 branching off from a connection point P11 of the power line L1. The drive circuit 61b has the same configuration as the drive circuit 61a. Power from the main power supply 45 is supplied to a control circuit 62b of the sub-controller 60b via a power line L22 branching off from a connection point P12 of the power line L2. The control circuit 62b has the same configuration as the control circuit 62a.

[0037] The steering-side control unit 50 has a configuration corresponding to the steered-side control unit 60. That is, the steering-side control unit 50 has a configuration corresponding to a drive circuit 61a and a control circuit 62a for the main control unit 50a. The steering-side control unit 50 has a configuration corresponding to a drive circuit 61b and a control circuit 62b for the sub-control unit 50b.

[0038] <Configuration of power supply device 80> As shown in FIG. 3, the power supply device 80 includes an auxiliary power supply 81 as a second power supply, an electric circuit 82, switches 83, 84, and 85, diodes 86 and 87, and a power supply control unit 88.

[0039] The auxiliary power supply 81 is, for example, a capacitor that functions similarly to a secondary battery. The auxiliary power supply 81 serves as the power source for power supplied to operate the steering-side motor 32 and the steering-side control unit 60. The same is true for the steering unit 4, where the auxiliary power supply 81 serves as the power source for power supplied to the steering-side motor 13 and the steering-side control unit 50. The main power supply 45 and the auxiliary power supply 81 differ in power supply performance related to the performance of the power that can be supplied. The power supply capacity of the auxiliary power supply 81, which is the amount of charge that can be stored to supply power, is set smaller than that of the main power supply 45. Furthermore, the power supply voltage of the auxiliary power supply 81, which is the voltage used to supply power, is set smaller than that of the main power supply 45. In other words, the power supply performance of the auxiliary power supply 81 is configured to be lower than that of the main power supply 45.

[0040] As expressed by the following equation (A), the power supply voltage V2 of the auxiliary power supply 81 is set to a value higher than the voltage V0 required to properly operate each motor 13, 32 or each control unit 50, 60, and lower than the power supply voltage V1 of the main power supply 45.

[0041] V1>V2>V0 …(A) Inside the power supply device 80, the auxiliary power supply 81 is connected to a connection point P11 of the power supply line L11 via a power supply line L111 branching off from a connection point P13 of the power supply line L11. Also inside the power supply device 80, the auxiliary power supply 81 is connected to a connection point P11 of the power supply line L11 via a power supply line L112 branching off from a connection point P14 of the power supply line L11. However, the connection point P14 is located downstream of the connection point P13, that is, closer to the steering side control unit 60. The auxiliary power supply 81 functions to assist in the supply of power to the turning side control unit 60 in accordance with the state of power supply by the main power supply 45. In this embodiment, the auxiliary power supply 81 has the function of backing up the supply of power to the turning side control unit 60 in place of the main power supply 45, on the condition that the power supplied by the main power supply 45 decreases. The same applies to the steering side control unit 50. In other words, the auxiliary power supply 81 has the function of backing up the supply of power to the steering-side control unit 50 in place of the main power supply 45 on the condition that the power supplied by the main power supply 45 decreases.

[0042] The electric circuit 82 switches the connection state of the power supply line L11 to charge and discharge the auxiliary power supply 81. The electric circuit 82 also switches the connection state of the power supply line L11 to disconnect the auxiliary power supply 81 so that the auxiliary power supply 81 is not discharged.

[0043] The switch 83 is provided midway along the power line L11 inside the power supply device 80. The switch 83 is located upstream of the connection point P13 and closer to the main power supply 45. The switch 83 opens and closes the power line L11.

[0044] The switch 84 is provided midway along the power line L111 inside the power supply device 80. The switch 84 opens and closes the power line L111. The switch 85 is provided midway along the power line L112 inside the power supply device 80. The switch 85 opens and closes the power line L112.

[0045] A connection point P15 is set on the power supply line L112. Inside the power supply device 80, the connection point P15 of the power supply line L112 and the connection point P16 of the power supply line L21 are connected by a power supply line L113.

[0046] The diode 86 is provided midway along the power supply line L113. The cathode of the diode 86 is connected to a connection point P16 of the power supply line L21. The anode of the diode 86 is connected to a connection point P15 of the power supply line L113.

[0047] The diode 87 is provided midway along the power supply line L21. The cathode of the diode 87 is connected to a connection point P16 of the power supply line L21. The anode of the diode 87 is connected to a connection point P12 of the power supply line L21.

[0048] The diodes 86 and 87 allow power to flow from the anode to the cathode, while restricting power from flowing from the cathode to the anode. The diodes 86 and 87 form an OR circuit that supplies the power supplied by the main power supply 45 or the auxiliary power supply 81, whichever supplies the higher voltage, to the control circuit 62a. The OR circuit formed by the diodes 86 and 87 is a so-called wired OR. The OR circuit formed by the diodes 86 and 87 corresponds to a selection circuit that selects the power supplied by the main power supply 45 or the auxiliary power supply 81, whichever supplies the higher voltage, to supply power to the steering side control unit 60. In the present embodiment, the OR circuit is an example of a connection circuit.

[0049] <Functions of the power supply control unit 88> The power supply control unit 88 includes a central processing unit (CPU) and memory (not shown), and the CPU executes a program stored in the memory at each predetermined calculation cycle, thereby executing various processes.

[0050] Specifically, the power supply control unit 88 controls the switching of the connection state of the electric circuit 82 and also controls the opening and closing of the switches 83, 84, and 85. The power supply control unit 88 monitors the voltage of the main power supply 45. The power supply control unit 88 has a function of detecting the voltage of the power supplied to the power supply device 80 through the power line L11 as the power supply voltage Vb of the main power supply 45. The power supply voltage Vb is the power supply voltage at the connection point P11 of the power line L11. As expressed by the following equation (B), the power supply control unit 88 determines that the power supply voltage Vb of the main power supply 45 has dropped when the power supply voltage Vb of the main power supply 45 is lower than a threshold voltage Vth. The threshold voltage Vth is a criterion for determining a voltage drop of the main power supply 45 and is set based on a voltage V0 required for the appropriate operation of the motors 13 and 32 or the control units 50 and 60. In this embodiment, the threshold voltage Vth is set to the same value as the voltage V0.

[0051] Vb <Vth …(B) When no voltage drop of the main power supply 45 is detected, the power supply control unit 88 maintains the switches 83 and 84 in the on-closed state and maintains the switch 85 in the off-open state. Furthermore, when a voltage drop of the main power supply 45 is detected, the power supply control unit 88 switches the switches 83 and 84 from the on-closed state to the off-open state. Thereafter, the power supply control unit 88 switches the switch 85 from the off-open state to the on-closed state.

[0052] Specifically, when the power supply voltage Vb of the main power supply 45 does not drop, the switches 83 and 84 are maintained in the on-closed state, and the switch 85 is maintained in the off-open state. For example, in the steering unit 6, power from the main power supply 45 is supplied via a power supply line L11 to a drive circuit 61a in the steering-side control unit 60. In addition, power from the main power supply 45 is charged into the auxiliary power supply 81 via a power supply line L111.

[0053] If the power supply voltage Vb of the main power supply 45 has not dropped, when the start switch 46 is turned on, power from the main power supply 45 is supplied to the control circuit 62a in the turning-side control unit 60 via the power supply line L21. Incidentally, the power supply voltage Vb of the main power supply 45 is set to a power supply voltage V1 that is higher than the power supply voltage V2 of the auxiliary power supply 81, so that the power of the auxiliary power supply 81 is not basically supplied to the turning-side control unit 60 via the power supply line L113 and a part of the power supply line L21. In addition, the diode 86 prevents the power of the main power supply 45 that has passed through the power supply line L21 from flowing into the auxiliary power supply 81 via the power supply line L113.

[0054] If the main power supply 45 experiences an abnormality such as a breakdown or failure and the power supply voltage Vb of the main power supply 45 falls below the power supply voltage V2 of the auxiliary power supply 81, power from the auxiliary power supply 81 is immediately supplied to the control circuit 62a in the turning-side control unit 60 via the power supply line L113 and a part of the power supply line L21. This is because the power supply voltage V2 of the auxiliary power supply 81 becomes higher than the voltage generated in the power supply line L2. Even if the power supply from the main power supply 45 to the turning-side control unit 60 is interrupted due to a failure of the main power supply 45, the power supply to the control circuit 62a is backed up by the auxiliary power supply 81.

[0055] When the power supply voltage Vb of the main power supply 45 further decreases and falls below the threshold voltage Vth, the switches 83 and 84 are switched from an on-closed state to an off-open state. After this, the switch 85 is switched from an off-open state to an on-closed state. As a result, power from the auxiliary power supply 81 is supplied to the drive circuit 61a in the turning-side control unit 60 via the power supply line L112 and a portion of the power supply line L11. This is because, due to a failure of the main power supply 45, the power supply voltage V2 of the auxiliary power supply 81 becomes higher than the voltage generated in the power supply line L11. Therefore, even if the power supply from the main power supply 45 to the turning-side control unit 60 is interrupted due to a failure of the main power supply 45, the power supply to the drive circuit 61a in the turning-side control unit 60 is backed up by the auxiliary power supply 81.

[0056] In this case, the power supply control unit 88 generates a backup switching completion flag FLG as information indicating the completion of switching to a state in which the power supply is backed up by the auxiliary power supply 81. Subsequently, the power supply control unit 88 outputs the backup switching completion flag FLG to the turning side control unit 60, i.e., the main control unit 60a, via a dedicated signal line 90. The backup switching completion flag FLG is information indicating the completion of switching of the switches 83, 84 from an on-closed state to an off-open state due to a failure of the main power supply 45, and the completion of switching of the switch 85 from an off-open state to an on-closed state. This enables the turning side control unit 60 to determine that the state of the power supply device 80 is a state in which the power supply is backed up by the auxiliary power supply 81.

[0057] Incidentally, it is conceivable to provide a diode in place of the switch 85 in the power supply line L112. In this way, if the main power supply 45 fails, power from the auxiliary power supply 81 is immediately supplied to the drive circuit 61a. However, a diode causes power loss. For this reason, from the perspective of suppressing consumption of the auxiliary power supply 81, a switch 85, rather than a diode, is provided in the power supply line L112 for supplying power to the drive circuit 61a, which requires greater power.

[0058] It is also possible to provide a switch in place of the diode 86 in the power supply line L113. However, in this case, the following concern arises. After the main power supply 45 fails and the power supply from the main power supply 45 is cut off, it takes a short time for the switch in the power supply line L113 to switch from off to on. Therefore, there is a risk that the power supply to the control circuit 62a will be momentarily cut off during the period until the switch in the power supply line L113 switches from off to on, causing the control circuit 62a to be reset. In this regard, if the diode 86 is provided in the power supply line L113, when the main power supply 45 fails, power from the auxiliary power supply 81 will be immediately supplied to the control circuit 62a via the power supply line L113 and a portion of the power supply line L21. Because the power supply to the control circuit 62a is not cut off, the control circuit 62a will not be reset due to a drop in its power supply voltage.

[0059] In the steering-side control unit 60, the control circuit 62a monitors the voltage of the main power supply 45. The control circuit 62a has a function of detecting the voltage of power supplied to the drive circuit 61a through the power line L11 as the power supply voltage Vig1 of the main power supply 45. The power supply voltage Vig1 is the power supply voltage at the connection point P14 of the power line L11. In addition, the control circuit 62b monitors the voltage of the main power supply 45. The control circuit 62b has a function of detecting the voltage of power supplied through the power line L22 as the power supply voltage Vig2 of the main power supply 45. The power supply voltage Vig2 is the power supply voltage at the connection point P12 of the power line L21. Similarly, the control circuit 52b included in the main control unit 50a of the steering-side control unit 50, which has the same configuration as the steering-side control unit 60, has a function of detecting the voltage of power supplied to the drive circuit 51a through the power line corresponding to the power line L11 as the power supply voltage of the main power supply 45. Furthermore, the control circuit 52b included in the sub-controller 50b of the steering-side controller 50 has a function of detecting the voltage of the power supplied through the power line corresponding to the power line L22 as the power supply voltage of the main power supply 45.

[0060] <Functions of the main control unit 60a of the steering-side control unit 60> Fig. 4 shows part of the processing executed by the control circuit 62a for the main control unit 60a of the steering-side control unit 60. The processing shown in Fig. 4 describes part of the processing realized by the CPU executing a program stored in memory, for each type of processing realized. In this embodiment, the steering-side control unit 60, i.e., the main control unit 60a, is an example of a control unit.

[0061] As shown in Fig. 4, an activation signal Sig is input to the control circuit 62a. The activation signal Sig is a signal that indicates the on / off state of the activation switch 46. When the control circuit 62a determines that the activation switch 46 is in the off state based on the activation signal Sig, it stops control for operating the turning-side motor 32. In other words, when the activation switch 46 is in the off state, the turning-side control unit 60 cannot reflect the state of the steering unit 4, which is in a mutually separated state, in the state of the turning unit 6.

[0062] On the other hand, when the control circuit 62a determines that the start switch 46 is in the on state based on the start signal Sig, it executes control to operate the turning-side motor 32. In other words, when the start switch 46 is in the on state, the control circuit 62a executes turning-side control when energized for the steer-by-wire steering device 2 so as to reflect the state of the steering units 4, which are separated from each other, in the state of the steering unit 6. In this case, the control circuit 62a executes the processing described below.

[0063] <Normal steering control> Specifically, the control circuit 62a receives as inputs the vehicle speed V, rotation angle θb, turning-side actual current value Ib, steering angle θs, power supply voltage Vig1, and backup switching completion flag FLG. The turning-side actual current value Ib is information obtained from the drive circuit 61a. The drive circuit 61a has a current sensor (not shown). The current sensor detects the turning-side actual current value Ib obtained from the value of a current of each phase of the turning-side motor 32 flowing through a connecting wire between the drive circuit 61a and the motor coil of each phase of the turning-side motor 32. The current sensor obtains, as a current, the voltage drop across a shunt resistor connected to the source side of each switching element in an inverter included in the drive circuit 61a provided corresponding to the turning-side motor 32. The steering angle θs is information obtained from the steering-side control unit 50 via the local network 70. The steering-side control unit 50 converts the rotation angle θa into an integrated angle that includes a range exceeding 360 degrees, for example, by counting the number of rotations of the steering-side motor 13 from a steering neutral position, which is the position of the steering wheel 3 when the vehicle is traveling straight. The steering-side control unit 50 calculates the steering angle θs by multiplying the converted integrated angle by a conversion coefficient based on the rotational speed ratio of the steering-side reduction gear mechanism 14. The control circuit 62a controls the driving of the drive circuit 61a based on the vehicle speed V, the rotation angle θb, the steered-side actual current value Ib, the steering angle θs, the power supply voltage Vig1, and the backup switching completion flag FLG.

[0064] The control circuit 62a has a pinion angle calculation unit 101, a pinion angle feedback control unit ("pinion angle F / B control unit" in the drawing) 102, a limitation control unit 103, and an energization control unit 104.

[0065] The rotation angle θb is input to the pinion angle calculation unit 101. The pinion angle calculation unit 101 converts the rotation angle θb into an integrated angle that includes a range exceeding 360°, for example, by counting the number of rotations of the steered-side motor 32 from a rack neutral position, which is the position of the rack shaft 22 when the vehicle is traveling straight. The pinion angle calculation unit 101 calculates the pinion angle θp, which is the actual rotation angle of the pinion shaft 21, by multiplying the integrated angle obtained by the conversion by a conversion coefficient that is based on the rotation speed ratio of the transmission mechanism 33, the lead of the conversion mechanism 34, and the rotation speed ratio of the rack-and-pinion mechanism 24. The pinion angle θp obtained in this manner is output to the pinion angle feedback control unit 102. Note that the pinion angle θp may also be output to the steering-side control unit 50 in some cases.

[0066] Vehicle speed V, steering angle θs, and pinion angle θp are input to pinion angle feedback control unit 102. Pinion angle feedback control unit 102 calculates a steering force command value Tt*, which is a steering control amount, through feedback control of pinion angle θp so that pinion angle θp follows steering angle θs, which is pinion target angle θp*. The steering force command value Tt* obtained in this manner is output to energization control unit 104.

[0067] The limit control unit 103 receives the power supply voltage Vig1 and the backup switching completion flag FLG. The limit control unit 103 calculates the output limit value Ilim based on the power supply voltage Vig1 and the backup switching completion flag FLG. The output limit value Ilim is a value for limiting the amount of current supplied to the turning-side motor 32. In other words, the output limit value Ilim is a value for limiting the torque output by the turning-side motor 32. The output limit value Ilim is calculated so as to vary depending on the voltage of the main power supply 45, i.e., the state of the power supply device 80. The output limit value Ilim obtained in this manner is output to the energization control unit 104.

[0068] The energization control unit 104 receives as input the steering force command value Tt*, the rotation angle θb, the steering-side actual current value Ib, and the output limit value Ilim. The energization control unit 104 calculates a current command value Ib* for the steering-side motor 32 based on the steering force command value Tt*. The energization control unit 104 executes limiting processing to limit the current command value Ib* based on the output limit value Ilim. In this case, the energization control unit 104 compares the current command value Ib* with the output limit value Ilim. When the absolute value of the current command value Ib* exceeds the output limit value Ilim, the energization control unit 104 calculates, as the final current command value Ib*, a value obtained by limiting the current command value Ib* to the output limit value Ilim, instead of the current command value Ib*. Furthermore, when the absolute value of the current command value Ib* is equal to or less than the output limit value Ilim, the energization control unit 104 calculates a value obtained by calculation based on the steering force command value Tt* as the final current command value Ib*.

[0069] Then, the energization control unit 104 determines the deviation between the final current command value Ib* and the current value on the dq coordinate obtained by converting the steered-side actual current value Ib based on the rotation angle θb, and calculates a drive signal Sm for driving the drive circuit 61a so as to eliminate the deviation. The drive signal Sm is a gate on / off signal that determines the on / off state of each switching element of the inverter included in the drive circuit 61a. The drive signal Sm obtained in this manner is output to the drive circuit 61a. As a result, drive power corresponding to the drive signal Sm is supplied from the drive circuit 61a to the steered-side motor 32. The steered-side motor 32 then rotates by an angle corresponding to the turning force command value Tt*.

[0070] <Functions of the restriction control unit 103> Regarding steering-side control during normal operation, limiting control section 103 monitors the voltage of main power supply 45. As expressed by the following equation (C), when power supply voltage Vig1 detected as the power supply voltage of main power supply 45 is smaller than threshold voltage Vth, limiting control section 103 determines that power supply voltage Vb of main power supply 45 has dropped. The threshold voltage Vth is the same value as threshold voltage Vth in the above equation (B), i.e., the same value as voltage V0.

[0071] Vig1 <Vth …(C) When no voltage drop of main power supply 45 is detected, limiting control unit 103 determines that power supply device 80 is in a normal state, which is a first state in which power is supplied from main power supply 45. In power supply device 80, the normal state refers to a state in which switches 83 and 84 are switched to a closed state in which they are on, and switch 85 is switched to an open state in which it is off.

[0072] Furthermore, after a voltage drop in main power supply 45 is detected, while backup switching completion flag FLG is not input, limit control unit 103 determines that power supply device 80 is in a transition state before the transition to the backup state is complete. In power supply device 80, the transition state to backup refers to a state in which switches 83 and 84 are switched from an on-closed state to an off-open state, and then switch 85 is in the middle of switching from an off-open state to an on-closed state.

[0073] Furthermore, when the backup switching completion flag FLG is input after a voltage drop in the main power supply 45 is detected, the limiting control unit 103 determines that the state of the power supply device 80 has completed transition to the second state, which is the backup state. In the power supply device 80, the state in which the transition to the backup state has completed is a state in which the switches 83 and 84 have been switched from an on-closed state to an off-open state, and the switch 85 has been switched from an off-open state to an on-closed state.

[0074] In the limiting control section 103, after detecting a voltage drop in the main power supply 45, it takes some time for the backup switching completion flag FLG, which indicates the completion of switching of the state of the power supply device 80 to a state in which the power supply is backed up by the auxiliary power supply 81, to be input. This is because, in the communication on the dedicated signal line 90, a communication delay occurs, for example, due to a line path or communication error. As a result of this cause, it takes some time for the backup switching completion flag FLG output by the power supply control section 88 to be input to the steering side control section 60 (for example, the "communication cycle" in FIG. 6(c)). Another cause is that, in the power supply control section 88, processing related to the switching of the switches 83, 84, and 85 is executed over a plurality of calculation cycles. As a result of this cause, it takes some time for the power supply device 80 to complete the switching of the switches 83, 84, and 85 (for example, "about several tens of ms" in FIG. 6(a)). Therefore, for example, a difference in timing between the output and input of the backup switching completion flag FLG occurs between the "about several tens of ms" and the "communication cycle." The limiting control unit 103 is configured to take into consideration the difference in timing between the output and input of the backup switching completion flag FLG when determining the state of the power supply device 80.

[0075] Then, as shown in FIG. 5, the limiting control unit 103 calculates an output limit value Ilim according to the state of the power supply device 80, which can be determined by taking into account the difference in timing between the output and input of the backup switching completion flag FLG. The limiting control unit 103 determines that the power supply device 80 is in a normal state when the power supply voltage Vig1 is equal to or higher than the threshold voltage Vth. In this case, the limiting control unit 103 calculates a maximum value Imax as the output limit value Ilim. The maximum value Imax is set as the limit value of the torque that can be output by the steered-side motor 32, for example, as a rated current value. In other words, the main control unit 60a executes normal output limiting processing through the function of the control circuit 62a, which allows the steered-side motor 32 to generate torque up to the limit that can be output.

[0076] Furthermore, when the power supply voltage Vig1 is less than the threshold voltage Vth and the backup switching completion flag FLG has not been input, the limiting control unit 103 determines that the power supply device 80 is in a state of transitioning to backup. In this case, the limiting control unit 103 calculates the minimum value Imin as the output limit value Ilim. The minimum value Imin is a value smaller than the maximum value Imax. The minimum value Imin is set to a relatively small value within a range below the power supply performance limit of the auxiliary power supply 81, from the perspective of the amount of current that can be supplied to the turning-side motor 32 in the event of a failure of the main power supply 45. In other words, the main control unit 60a executes output limiting processing during transition to backup, through the function of the control circuit 62a, to limit the torque that can be output by the turning-side motor 32 compared to before the failure of the main power supply 45.

[0077] Furthermore, when the power supply voltage Vig1 is less than the threshold voltage Vth and the backup switching completion flag FLG has been input, the limiting control unit 103 determines that the power supply device 80 has completed transition to the backup state. In this case, the limiting control unit 103 calculates the backup limit value Ibu as the output limit value Ilim. The backup limit value Ibu is a value smaller than the maximum value Imax and larger than the minimum value Imin. The backup limit value Ibu is set to a value in a range smaller than the power supply performance limit of the auxiliary power supply 81 and larger than the minimum value Imin, from the perspective of the amount of current that can be supplied to the turning-side motor 32 in the event of a failure of the main power supply 45. In other words, the main control unit 60a, through the function of the control circuit 62a, executes output limiting processing during backup, which allows the turning-side motor 32 to generate as much torque as possible while limiting the torque that can be output by the turning-side motor 32 compared to before the failure of the main power supply 45. For example, the limit control unit 103 calculates an appropriate value as the backup limit value Ibu according to the state of the steering device 2, such as the internal temperature of the steering control device 1, the operating state of the steering side motor 32, and the remaining power of the auxiliary power supply 81.

[0078] In addition, with respect to the sub-controller 60b of the turning-side control unit 60, if the main power supply 45 fails, the control circuit 62b will stop control for operating the turning-side motor 32 even if the start switch 46 is in the on state. This is because the sub-controller 60b is not connected to the auxiliary power supply 81 of the power supply device 80. In other words, the control circuit 62b performs the same processing as the control circuit 62a when executing normal turning-side control as long as the main power supply 45 is not failed. Furthermore, the main control unit 50a of the steering-side control unit 50 is connected to the auxiliary power supply 81 of the power supply device 80, just like the main control unit 60a of the turning-side control unit 60. In other words, the main control unit 50a may be configured to have a limiting control unit having the same functions as the main control unit 60a, or may not be configured to have such a limiting control unit. Furthermore, the sub-controller 50b of the steering-side control unit 50 is not connected to the auxiliary power supply 81 of the power supply device 80, just like the sub-controller 60b of the turning-side control unit 60. In other words, the sub-controller 50b may be configured to execute the same processing as the main controller 50a while the main power supply 45 is operating normally.

[0079] <Operation of this embodiment> 6(a) and 6(b) show how the power supply voltage Vb monitored by the power supply control unit 88 and the power supply voltage Vig1 monitored by the main control unit 60a of the steering side control unit 60 change over time t when the start switch 46 is in the on state. When the start switch 46 is in the on state, the power supply voltage Vb and the power supply voltage Vig1 are basically maintained at the power supply voltage V1 unless the main power supply 45 fails.

[0080] In this case, as shown in Figures 6(c) and (d), the main control unit 60a determines the state of the power supply device 80 and calculates the output limit value Ilim. The main control unit 60a determines that the state of the power supply device 80 is not in backup mode ("non-BU" in the figures). The main control unit 60a calculates the maximum value Imax as the output limit value Ilim. In other words, the main control unit 60a is in a state where normal output limiting processing is executed. As a result, the steered-side motor 32 is allowed to generate torque up to the limit of what can be output.

[0081] 6(a), when the main power supply 45 fails (indicated by "power supply failure" in the figure), the power supply voltage Vb and the power supply voltage Vig1 fall below the threshold voltage Vth, for example, to zero. Such a voltage drop is detected by monitoring by the power supply control unit 88 and the main control unit 60a.

[0082] In this case, as shown in FIGS. 6(c) and 6(d), the main control unit 60a determines the state of the power supply device 80 and calculates the output limit value Ilim. The main control unit 60a determines that the state of the power supply device 80 is not in the backup state ("non-BU" in the figures) until the backup switching completion flag FLG is input. Here, the period until the backup switching completion flag FLG is input ("switching completed" in the figures) corresponds to a period consisting of "approximately several tens of milliseconds" (in FIG. 6(a)) and the "communication cycle" (in FIG. 6(c)). The state of the power supply device 80 determined by the main control unit 60a is determined to be in a backup transition state even though it is not in the backup state. The main control unit 60a calculates the minimum value Imin as the output limit value Ilim. In other words, the main control unit 60a is in a state where output limiting processing is executed during the transition to backup. As a result, the torque that can be output from the steered-side motor 32 is limited compared to before the failure of the main power supply 45.

[0083] Thereafter, as shown in FIG. 6(c), when the backup switching completion flag FLG is input (in the figure, "FLG input"), the main control unit 60a determines that the state of the power supply device 80 is in backup state (in the figure, "BU").

[0084] Next, as shown in Figure 6(d), the main control unit 60a calculates the backup limit value Ibu as the output limit value Ilim. In other words, the main control unit 60a is in a state where output limiting processing for the backup state is executed. As a result, the steered-side motor 32 is in a state where it is allowed to generate as much torque as possible while the torque that can be output is limited compared to before the failure of the main power supply 45.

[0085] According to this embodiment, when the power supply device 80 completes switching of the connection state to transition to the backup state following a failure of the main power supply 45, the main control unit 60a has already started the output limiting process at the time of transition to the backup state.

[0086] <Effects of the embodiment> (1) In this embodiment, when the power supply device 80 has completed switching of the connection state so as to transition to a backup state following a failure of the main power supply 45, it is possible to prevent the occurrence of a situation in which the torque that can be output by the steered-side motor 32 is not limited. Therefore, when the main power supply 45 fails, it is possible to make it less likely that the torque that can be output by the steered-side motor 32 will be limited.

[0087] (2) In this embodiment, the minimum value Imin of the output limit value Ilim is set to a value within a range below the limit of the power supply performance of the auxiliary power supply 81, on the premise that the power supply performance of the auxiliary power supply 81 is lower than that of the main power supply 45. This makes it less likely that the power supply performance of the auxiliary power supply 81 will be exceeded when the power supply device 80 is in backup mode. This makes it possible to continue operation of the steered-side motor 32 in an appropriate manner even if an abnormality in the main power supply 45 is detected. This is particularly effective when the power supply performance of the auxiliary power supply 81 is lower than that of the main power supply 45.

[0088] (3) In the present embodiment, the main control unit 60a of the steering side control unit 60 can determine the state of the power supply device 80 based on the backup switching completion flag FLG. This allows the main control unit 60a to operate taking into account the state of the power supply device 80. However, a communication delay occurs in communication between the main control unit 60a and the power supply control unit 88.

[0089] Here, as a comparative example, it is assumed that the main control unit 60a is configured to start limiting the torque that can be output by the steered-side motor 32 after the backup switching completion flag FLG is input. In this case, during the communication delay, the main control unit 60a has not started limiting the torque that can be output by the steered-side motor 32, although the switching of the connection state to the backup state in the power supply device 80 has been completed.

[0090] For example, as shown in FIG. 7(c), similar to FIG. 6(c) above, the main control unit 60a determines that the state of the power supply device 80 is not in a backup state ("non-BU" in the figure) until the backup switching completion flag FLG is input.

[0091] 7(d), unlike in FIG. 6(d), the maximum value Imax is calculated as the output limit value Ilim. Thereafter, when the backup switching completion flag FLG is input ("FLG input" in the figure), the main control unit 60a determines that the state of the power supply device 80 is the backup state ("BU" in the figure).

[0092] That is, in the case of the above comparative example, the main control unit 60a does not limit the torque that can be output by the steered-side motor 32 from the time when a voltage drop in the main power supply 45 is detected until the backup switching completion flag FLG is input. In particular, during the period corresponding to the "communication cycle" (in FIG. 6(c)), even though the power supply device 80 has completed switching the connection state so as to transition to the backup state, the torque that can be output by the steered-side motor 32 is not limited.

[0093] 6(c) and 6(d), when the main control unit 60a of this embodiment detects a failure of the main power supply 45, it can start limiting the torque that can be output by the steered-side motor 32 earlier than the backup switching completion flag FLG is input. Therefore, in a configuration in which the main control unit 60a and the power supply control unit 88 communicate, it is possible to make it less likely that the torque that can be output by the steered-side motor 32 will not be limited when the power supply device 80 is in backup mode.

[0094] (4) According to this embodiment, even if the main power supply 45 fails while the start switch 46 is on, power is continuously supplied to the control circuit 62a included in the main control unit 60a. In this case, if the main power supply 45 fails, the control circuit 62a can start controlling the torque that can be output by the steered-side motor 32.

[0095] <Other embodiments> The above embodiment may be modified as follows: In addition, the following other embodiments may be combined with each other within the scope of technical compatibility.

[0096] The diodes 86, 87 may be configured to form an OR circuit inside the turning side control unit 60, i.e., the steering control device 1. Even in this case, the power selected from the main power supply 45 and the auxiliary power supply 81, whichever supplies the larger voltage, is supplied to the turning side control unit 60.

[0097] The power supply performance of the auxiliary power supply 81 may be similar to that of the main power supply 45, or may be higher than that of the main power supply 45. For example, the power supply capacity of the auxiliary power supply 81 may be similar to that of the main power supply 45, or may be set to be larger than that of the main power supply 45. In this case, for example, the power supply voltage V2 of the auxiliary power supply 81 may be set to a value similar to that of the power supply voltage V1 of the main power supply 45, or may be set to be larger than the power supply voltage V1 of the main power supply 45.

[0098] The auxiliary power supply 81 may be an electric double layer capacitor or a secondary battery. The power supply device 80 may be configured to boost the power supplied by the main power supply 45 in addition to backing up the power supply to the control units 50 and 60 in place of the main power supply 45.

[0099] The configuration related to the backup switching completion flag FLG may be omitted. In this case, the main control unit 60a of the steering side control unit 60 may determine that the power supply device 80 is in the backup state after a time period that is assumed to have elapsed since the power supply device 80 detected a failure in the main power supply 45 and has been connected to the backup state. Also, the main control unit 60a may determine that the power supply device 80 is in the backup state when it detects a power supply voltage Vig1 that is equal to or greater than the threshold voltage Vth.

[0100] In each of the control units 50, 60, the sub-control units 50b, 60b may be eliminated, and each main control unit 50a, 60a may be configured as a single system. In this case, each main control unit 50a, 60a of only one system may have the function of detecting the required power supply voltage.

[0101] In each control unit 50, 60, each sub-control unit 50b, 60b may be configured to be connected to the main power supply 45 via a power supply device 80. In this case, each main control unit 50a, 60a of only one system only needs to have the function of detecting the required power supply voltage.

[0102] When different values ​​are calculated as the output limit value Ilim, the limit control unit 103 may have a function of gradually changing the output limit value Ilim to the different value. In this case, the effect of changes in the output limit value Ilim on the vehicle behavior can be suppressed, thereby ensuring the comfort of the vehicle occupants.

[0103] The output limit value Ilim may have multiple values ​​depending on causes other than a failure of the main power supply 45. For example, when multiple values ​​are set as candidates for the output limit value Ilim, the limit control unit 103 may have a function of selecting the minimum value from the candidates. In other words, the limit control unit 103 may be configured to ultimately calculate an output limit value Ilim that is equal to or less than the minimum value Imin when the main power supply 45 fails.

[0104] The power supply device 80 may include a power supply device for the steering unit that is connected only to the steering unit 4 including the steering side control unit 50, and a power supply device for the turning unit that is connected only to the turning unit 6 that includes the turning side control unit 60.

[0105] In the steering control device 1, either of the control units 50, 60 may constitute a single control unit having a combined function of operating the steering-side motor 13 and the steered-side motor 32.

[0106] The steering-side motor 32 may be, for example, one that is arranged coaxially with the rack shaft 22, or one that is connected to the rack shaft 22 via a worm and wheel to a pinion shaft that constitutes a rack-and-pinion mechanism.

[0107] Each control unit 50, 60 and the steering control device 1 including them may be configured with a processing circuit including: 1) one or more processors that operate according to a computer program (software); 2) one or more dedicated hardware circuits such as an application-specific integrated circuit (ASIC) that executes at least some of the various processes; or 3) a combination thereof. The processor includes a CPU and memory such as RAM and ROM, and the memory stores program code or instructions configured to cause the CPU to execute processes. Memory, i.e., a non-transitory computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. The same applies to the power supply control unit 88 and the power supply unit 80 including it.

[0108] The steering device 2 has a linkless structure in which the steering unit 4 and the steered unit 6 are mechanically separated at all times, but this is not limited to this, and for example, the steering device 2 may have a structure in which the steering unit 4 and the steered unit 6 can be mechanically separated by a clutch. Furthermore, the steering device 2 is not limited to a steer-by-wire type steering device, and may be an electric power steering device in which motor torque is applied to the steering shaft 11 or the rack shaft 22. [Explanation of symbols]

[0109] 1...Steering control device 2...Steering device 32...Steering side motor (motor) 45…Main power supply (1st power supply) 46...Start switch 60...Steering side control unit (control unit) 60a...Main control unit (control unit) 61a...Drive circuit 62a...Control circuit 80...Power supply device 81…Auxiliary power supply (second power supply) 88...Power supply control unit 90...Signal line 86,87...Diodes

Claims

1. A steering control device that is connected to a first power source mounted on a vehicle via a power source device having a second power source, and that controls a steering device mounted on the vehicle, a control unit including a drive circuit that is connected to at least one of the first power source and the second power source to drive the motor to supply the power to the motor, and that controls the operation of the motor by controlling the drive circuit; a connection state of the drive circuit to the first power source and the second power source is switched by the power supply device so that, when a state in which power is supplied from the first power source is defined as a first state, the connection state transitions to a second state in which power is supplied from the second power source upon detection of an abnormality in the first power source; the control unit has a function of executing, after detecting an abnormality in the first power supply, an output limiting process that is a process for limiting the torque that can be output by the motor compared to before the abnormality was detected, the output limiting process is configured to be started after an abnormality in the first power supply is detected, and until the power supply device has completed switching of the connection state so as to transition to the second state in response to the detection of the abnormality, The output limiting process is a process of limiting the torque output by the motor so that it does not exceed an output limit value.

2. A steering control device as described in Claim 1, wherein the output limit value is a value less than the limit of the power supply performance of the second power supply, assuming that the power supply performance defined by the power supply capacity or power supply voltage of the second power supply is lower than that of the first power supply.

3. the power supply device includes a power supply control unit having a function of switching the connection state so as to transition to the second state upon detection of an abnormality in the first power supply, A steering control device as described in claim 1 or claim 2, wherein the control unit is connected to the power supply control unit via a line so as to be able to communicate with the power supply control unit, and is configured to obtain information from the power supply control unit via the line indicating that the switching of the connection state has been completed when transitioning to the second state.

4. The steering control device according to any one of claims 1 to 3, wherein the control unit is configured to execute the output limiting process while the power supply of the vehicle that allows connection to the first power supply so that the vehicle can operate is in an on state.

5. the control unit includes a control circuit that executes processing related to the output limiting processing, 5. The steering control device according to claim 4, wherein the control circuit is connected to at least one of the first power source and the second power source, and is configured to be constantly connected to at least one of the first power source and the second power source via a connection circuit provided in the power supply device while the power source of the vehicle is on, regardless of the state of the first power source.

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