Steering control device

Abstract

To provide a steering control device that can appropriately control driving of a motor even when a power supply voltage is decreased.SOLUTION: A steering control device 10 controls a motor 30 including a first winding group 30A and a second winding group 30B. The steering control device 10 includes a first control unit 10A, a second control unit 10B, and a switch 10C. The first control unit 10A operates by consuming power from a first power supply 20A. The second control unit 10B operates by consuming power from the first power supply 20A or a second power supply 20B. The switch 10C switches the power supply of the second control unit 10B between the first power supply 20A and the second power supply 20B. When a monitor value of the power supply voltage of only one of the first control unit 10A and the second control unit 10B is decreased, a driving mode of the motor 30 transitions depending on whether the power supply of the second control unit 10B is the first power supply 20A or the second power supply 20B.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, as described in Patent Document 1, for example, there is known a steering control device that controls a motor that is a generating source of assist torque applied to a steering mechanism of a vehicle. The motor has two systems of coils. The steering control device has two sets of drive circuits and a microcomputer corresponding to the two systems of coils, respectively. Each microcomputer controls the respective drive circuits in accordance with the steering torque, thereby independently controlling the power supply to the two systems of coils. The assist torque is the sum of the torques generated by the coils of each system. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-195089 Summary of the Invention [Problem to be solved by the invention]

[0004] The power supply voltage may drop for some reason, and the steering control device is required to appropriately control the drive of the motor even when the power supply voltage drops. [Means for solving the problem]

[0005] A steering control device that can solve the above problem controls a motor that is a drive source for a steering device of a vehicle and has a first winding group and a second winding group. The steering control device includes a first control unit that operates by consuming power from a first power source and is configured to control the power supply to the first winding group, a second control unit that operates by consuming power from the first power source or a second power source different from the first power source and is configured to control the power supply to the second winding group, and a switch that switches the power source of the second control unit between the first power source and the second power source. The steering control device is configured so that when a monitored value of only one of the power source voltages of the first control unit and the second control unit drops, the drive mode of the motor transitions depending on whether the power source of the second control unit is the first power source or the second power source.

[0006] With this configuration, when the monitored value of the power supply voltage of only one of the first control unit and the second control unit drops, the motor drive mode is set depending on whether the power supply of the second control unit is the first power supply or the second power supply. Therefore, even when the monitored value of the power supply voltage of only one of the first control unit and the second control unit drops, the drive of the motor can be appropriately controlled.

[0007] In the above steering control device, the motor may be an assist motor configured to generate an assist torque that assists steering wheel operation. In this case, when the power source of the second control unit is the second power source, the steering control device may be configured to transition the drive mode of the motor from full assist mode to half assist mode when only the monitored value of either the first control unit or the second control unit decreases. The full assist mode is a drive mode in which equal torque is generated in both the first winding group and the second winding group. The half assist mode is a drive mode in which power supply to an abnormal winding group of the first winding group or the second winding group, where the monitored value has decreased, is permanently stopped, and a torque equal to or less than the maximum torque that can be generated only by the normal winding group where the monitored value has not decreased.

[0008] According to this configuration, when the power source of the second control unit is the second power source, the motor drive mode transitions from full assist mode to half assist mode when the monitored value of only one of the first control unit and the second control unit drops. Therefore, when the power source of the second control unit is the second power source, even when the monitored value of the power source voltage of only one of the first control unit and the second control unit drops, the motor drive can be appropriately controlled in half assist mode.

[0009] In the above steering control device, if the power source of the second control unit is the second power source, when a hardware abnormality that does not involve a decrease in the monitored value occurs in either the first control unit or the second control unit, the drive mode of the motor may be configured to transition from the full assist mode to the half assist mode.

[0010] According to this configuration, when the power source of the second control unit is the second power source, even if a hardware abnormality occurs in either the first control unit or the second control unit that does not result in a decrease in the monitor value, the drive of the motor can be appropriately controlled in half assist mode.

[0011] In the above steering control device, the motor may be an assist motor configured to generate an assist torque that assists steering wheel operation. In this case, the steering control device may be configured such that, when the power source of the second control unit is the first power source, the drive mode of the motor transitions from full assist mode to single-system assist stop mode when the monitored value of only one of the first control unit and the second control unit decreases. The full assist mode is a drive mode in which equal torque is generated in both the first winding group and the second winding group. The single-system assist stop mode is a drive mode in which power supply to an abnormal winding group, of the first winding group and the second winding group, in which the monitored value has decreased is temporarily stopped, and half of the torque required of the motor is generated only by the normal winding group in which the monitored value has not decreased.

[0012] According to this configuration, when the power source of the second control unit is the first power source, the motor drive mode transitions from full assist mode to single assist stop mode when the monitored value of only one of the first control unit and the second control unit drops. Therefore, when the power source of the second control unit is the first power source, even when the monitored value of the power source voltage of only one of the first control unit and the second control unit drops, the motor drive can be appropriately controlled in single assist stop mode.

[0013] In the above steering control device, if the power source of the second control unit is the first power source, when the monitor values of both the first control unit and the second control unit decrease, the first control unit may be configured to temporarily stop supplying power to the first winding group, and the second control unit may be configured to temporarily stop supplying power to the second winding group.

[0014] If the power supply for the second control unit is the first power supply, a drop in the voltage of the first power supply is considered to be due to a drop in the monitored values of both the first control unit and the second control unit. The voltage drop of the first power supply 20A may be temporary. According to the above configuration, power supply to the first winding group and the second winding group can be temporarily stopped to wait for the monitored value of the power supply voltage to return to a normal level.

[0015] In the above steering control device, when the power supply of the second control unit is the first power supply, the drive mode of the motor may be transitioned from the full assist mode to a half assist mode when a hardware abnormality that does not result in a decrease in the monitored value occurs in either the first control unit or the second control unit. The half assist mode is a drive mode in which power supply to a winding group of an abnormal system in which the hardware abnormality has occurred is permanently stopped, and a torque equal to or less than the maximum torque that can be generated by only the winding group of a normal system in which the hardware abnormality has not occurred is generated.

[0016] According to this configuration, when the power source of the second control unit is the first power source, even if a hardware abnormality occurs in either the first control unit or the second control unit that does not result in a decrease in the monitor value, the drive of the motor can be appropriately controlled in half assist mode. [Effects of the Invention]

[0017] According to the steering control device of the present invention, even if the power supply voltage drops, the drive of the motor can be appropriately controlled. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a block diagram of an embodiment of a steering control device. [Figure 2] FIG. 2 is a circuit diagram of the first control unit and the second control unit of FIG. [Figure 3] FIG. 3 is a transition diagram showing the transition of the drive mode of the motor of FIG. [Figure 4] FIG. 4 is a graph showing the relationship between the amount of assistance required of the motor of FIG. 1 and the amount of assistance output by the motor of FIG. [Figure 5] FIG. 5 is a schematic diagram showing the connection state between the power supply and the steering control device when the switch in FIG. 1 is in the first connection state. [Figure 6] FIG. 6 is a schematic diagram showing the connection state between the power supply and the steering control device when the switch in FIG. 1 is in the second connection state. [Figure 7] FIG. 7 is a diagram showing the transition of the motor drive mode for each connection state of the switches in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment of a steering control device will be described below. As shown in FIG. 1, the steering control device 10 operates by consuming power from a main power supply 20 mounted on a vehicle. The main power supply 20 has a first power supply 20A and a second power supply 20B. The first power supply 20A and the second power supply 20B are, for example, batteries, which are DC power supplies. The steering control device 10 is one of the vehicle control devices, and controls a motor 30, which is a drive source for a steering device of the vehicle. The steering device is, for example, an electric power steering device. The steering wheel and the steered wheels of the vehicle are connected so that power can be transmitted.

[0020] Motor 30 is an assist motor that generates an assist torque that assists steering wheel operation. The assist torque is torque in the same direction as the steering wheel operation. Motor 30 is a three-phase brushless motor that has two winding groups, namely, a first winding group 30A and a second winding group 30B. First winding group 30A and second winding group 30B each have a U-phase winding, a V-phase winding, and a W-phase winding. The torque of motor 30 is applied to a steering shaft or a steered shaft via a reducer. The steering shaft is connected to the steering wheel so as to be rotatable together with it. The steered shaft steers the steered wheels in conjunction with the operation of the steering wheel.

[0021] The steering control device 10 controls the power supply to the motor 30. The steering control device 10 has a first control unit 10A, a second control unit 10B, and a switch 10C. The first control unit 10A is connected to a first power supply 20A via a first power supply line L1. The first control unit 10A operates by consuming power from the first power supply 20A. The first control unit 10A controls the power supply to the first winding group 30A of the motor 30.

[0022] The switch 10C switches the power supply of the second control unit 10B between the first power supply 20A and the second power supply 20B. The switch 10C is, for example, a mechanical relay and has a first fixed contact 40A, a second fixed contact 40B, a third fixed contact 40C, and a movable contact 40D. The first fixed contact 40A is connected to a connection point P on the first power supply line L1 via a second power supply line L2. The second fixed contact 40B is connected to the second power supply 20B via a third power supply line L3. The third fixed contact 40C is connected to the second control unit 10B via a fourth power supply line L4. The movable contact 40D is connected to the third fixed contact 40C.

[0023] The switch 10C switches the connection state of the movable contact 40D with the first fixed contact 40A and the second fixed contact 40B based on a command from the first control unit 10A or the second control unit 10B. The connection states include a first connection state and a second connection state. The first connection state is a state in which the movable contact 40D is connected to the first fixed contact 40A. That is, in the first connection state, the first power source 20A and the second control unit 10B are connected via the first power line L1, the second power line L2, and the fourth power line L4. The second connection state is a state in which the movable contact 40D is connected to the second fixed contact 40B. That is, in the second connection state, the second power source 20B and the second control unit 10B are connected via the third power line L3 and the fourth power line L4.

[0024] The second control unit 10B operates by consuming power from the first power supply 20A or the second power supply 20B. The second control unit 10B controls the power supply to the second winding group 30B of the motor 30. The first control unit 10A and the second control unit 10B can communicate with each other. The first control unit 10A and the second control unit 10B exchange information via a communication line.

[0025] <Configuration of the first control unit 10A> Next, the configuration of the first control unit 10A will be described. As shown in FIG. 2, the first control unit 10A has a first microcomputer 51A, a first pre-driver 52A, and a first inverter 53A.

[0026] The first microcomputer 51A includes a CPU (Central Processing Unit) and a memory. The memory is a computer-readable medium that stores a program that describes processes or instructions for the computer. In this embodiment, the computer is the CPU. The memory includes RAM (Random Access Memory) and ROM (Read Only Memory). The CPU performs various controls by executing the program stored in the memory at a predetermined calculation cycle.

[0027] The first microcomputer 51A operates by consuming power from the first power supply 20A. However, the voltage supplied to the first microcomputer 51A is converted to a voltage suitable for operation of the first microcomputer 51A by a power supply circuit provided in the first control unit 10A.

[0028] The first microcomputer 51A executes assist control. The assist control is a control for causing the motor 30 to generate an assist torque. The first microcomputer 51A calculates a target assist torque to be generated by the first winding group 30A based on, for example, the steering torque τ and the vehicle speed V. The steering torque τ is detected by a torque sensor mounted on the vehicle. The vehicle speed V is detected by a vehicle speed sensor mounted on the vehicle.

[0029] The first microcomputer 51A calculates a current command value according to the target assist torque and performs current feedback control to make the value of the current supplied to the first winding group 30A follow the current command value. The first microcomputer 51A performs the current feedback control to generate a command signal S1 for the first pre-driver 52A. The command signal S1 is, for example, a PWM (Pulse Width Modulation) signal.

[0030] The first pre-driver 52A operates by consuming power from the first power supply 20A. The first pre-driver 52A generates a drive signal S2 for operating the first inverter 53A based on a command signal S1 generated by the first microcomputer 51A.

[0031] The first pre-driver 52A includes an abnormality detection circuit. The abnormality detection circuit monitors the voltage supplied from the first power supply 20A, i.e., the power supply voltage of the first pre-driver 52A. The first pre-driver 52A stops operating when the abnormality detection circuit detects a drop in the power supply voltage. The abnormality detection circuit determines that the power supply voltage has dropped when, for example, the power supply voltage is equal to or lower than a threshold voltage. The threshold voltage is set, for example, based on the voltage required for proper operation of the first pre-driver 52A. The abnormality detection circuit monitors not only the power supply voltage but also various abnormalities in the first pre-driver 52A. The abnormalities include a hardware abnormality in the first pre-driver 52A.

[0032] The first pre-driver 52A generates a monitoring result signal S3 at a predetermined calculation period and transmits the generated monitoring result signal S3 to the first microcomputer 51A. The monitoring result signal S3 includes information indicating, for example, the monitored value of the power supply voltage, whether or not the power supply voltage has dropped, and whether or not an abnormality has occurred in the first pre-driver 52A. The first microcomputer 51A receives the monitoring result signal S3 and can recognize the monitored value of the power supply voltage, whether or not the power supply voltage has dropped, and whether or not an abnormality has occurred in the first pre-driver 52A based on the received monitoring result signal S3.

[0033] The first inverter 53A converts DC power from the first power supply 20A into three-phase AC power. The first inverter 53A has a plurality of switching elements. The switching elements are, for example, field-effect transistors (FETs). The DC power from the first power supply 20A is converted into three-phase AC power by the switching elements performing switching operations based on the drive signal S2 generated by the first pre-driver 52A. A current corresponding to the command signal S1 is supplied to the first winding group 30A via the first inverter 53A, causing the first winding group 30A to generate torque corresponding to the target assist torque.

[0034] The first inverter 53A has three legs corresponding to the three phases. The first leg corresponding to the U phase has two FETs 61 and 62 connected in series. The second leg corresponding to the V phase has two FETs 63 and 64 connected in series. The third leg corresponding to the W phase has two FETs 65 and 66 connected in series. The first to third legs are connected in parallel with each other between the + terminal of the first power supply 20A and ground. "+B" in FIG. 2 indicates the power supply voltage. The power supply voltage is, for example, a battery voltage.

[0035] Of the six FETs 61 to 66, three FETs 61, 63, and 65 are arranged on the power supply side, while the remaining three FETs 62, 64, and 66 are arranged on the ground side. Each of the six FETs 61 to 66 is provided with a free wheel diode 67. Each free wheel diode 67 is connected in parallel with the corresponding FET 61 to 66. The cathode of each free wheel diode 67 is connected to the power supply side relative to the corresponding FET 61 to 66. The anode of each free wheel diode 67 is connected to the ground side relative to the corresponding FET 61 to 66.

[0036] In the first leg corresponding to the U phase, a U-phase node Pu established between FET 61 and FET 62 is connected to the U-phase winding of the first winding group 30A via a U-phase power line 71u. In the second leg corresponding to the V phase, a V-phase node Pv established between FET 63 and FET 64 is connected to the V-phase winding of the first winding group 30A via a V-phase power line 71v. In the third leg corresponding to the W phase, a W-phase node Pw established between FET 65 and FET 66 is connected to the W-phase winding of the first winding group 30A via a W-phase power line 71w.

[0037] The DC power supplied from the first power supply 20A is converted into three-phase AC power by switching each of the FETs 61-66 on and off based on a drive signal S2 generated by the first pre-driver 52A. The drive signal S2 includes six drive signals α1-α6 corresponding to the six FETs 61-66, respectively. The three-phase AC power is supplied to the windings of each phase of the first winding group 30A via a U-phase power line 71u, a V-phase power line 71v, and a W-phase power line 71w.

[0038] The U-phase connection point Pu is also connected to the first pre-driver 52A via a U-phase signal line 72u. The V-phase connection point Pv is also connected to the first pre-driver 52A via a V-phase signal line 72v. The W-phase connection point Pw is also connected to the first pre-driver 52A via a W-phase signal line 72w. The first pre-driver 52A detects the potentials generated at the U-phase connection point Pu, the V-phase connection point Pv, and the W-phase connection point Pw as the terminal voltages of each phase of the first winding group 30A.

[0039] <Configuration of second control unit 10B> As shown in FIG. 2, the second control unit 10B has a configuration similar to that of the first control unit 10A. Specifically, the second control unit 10B includes a second microcomputer 51B, a second pre-driver 52B, and a second inverter 53B. The second microcomputer 51B and the second pre-driver 52B operate by consuming power from the first power supply 20A or the second power supply 20B. The second inverter 53B converts DC power from the first power supply 20A or the second power supply 20B into three-phase AC power. The three-phase AC power is supplied to the windings of each phase of the second winding group 30B.

[0040] <Drive mode of motor 30> Next, a description will be given of the drive modes of the motor 30. The drive modes include, for example, a full assist mode, a half assist mode, a single assist stop mode, and a dual assist stop mode.

[0041] The full assist mode is a drive mode when both systems are normal, and causes both the first winding group 30A and the second winding group 30B of the motor 30 to generate equal torque.

[0042] Half-assist mode is a drive mode used when an abnormality has been confirmed in one of the two systems and there is no possibility of restoring the system to normal. Half-assist mode is also a drive mode in which power supply to the winding group in the abnormal system is permanently stopped and torque is generated that is less than the maximum torque that can be generated by the winding group in the normal system alone.

[0043] The single-system assist stop mode is a drive mode used when an abnormality occurs in one of the two systems but the abnormality has not been confirmed and there is a possibility of recovery to a normal state. The single-system assist stop mode is also a drive mode in which power supply to the winding group of the abnormal system is temporarily stopped and half of the torque required of the motor 30 is generated by only the winding group of the normal system.

[0044] The dual-assist stop mode is a drive mode used when abnormalities in both systems are confirmed and there is no possibility of returning to a normal state. The dual-assist stop mode is a drive mode in which power supply to both the first winding group 30A and the second winding group 30B of the motor 30 is stopped.

[0045] The abnormality includes, for example, a temporary abnormality that can be recovered from and a permanent abnormality that is difficult to recover from. The temporary abnormality includes, for example, a temporary drop in the power supply voltage. The permanent abnormality includes, for example, a hardware abnormality in the control unit (10A, 10B). The hardware abnormality includes, for example, a failure in at least one of the six FETs 61 to 66 of the inverter (53A, 53B). Depending on the location of the hardware abnormality, the monitored value of the power supply voltage monitored by the pre-driver (52A, 52B) may drop. The power supply voltage is, for example, a battery voltage.

[0046] As shown in FIG. 3, when both systems are normal, the microcomputers (51A, 51B) control the driving of the motor 30 in the full assist mode. When a temporary abnormality occurs in one of the two systems while the full assist mode is selected as the drive mode, the microcomputers (51A, 51B) switch the drive mode from the full assist mode to the one-system assist stop mode.

[0047] When the one-system assist stop mode is selected as the drive mode, if a return determination condition is met before an abnormality is confirmed, the microcomputer (51A, 51B) returns the drive mode from the one-system assist stop mode to the full assist mode.

[0048] When an abnormality occurs in the normal system while the single-system assist stop mode is selected as the drive mode, the microcomputer (51A, 51B) switches the drive mode from the single-system assist stop mode to the dual-system assist stop mode.

[0049] When a permanent abnormality occurs in one of the two systems while the full assist mode is selected as the drive mode, the microcomputer (51A, 51B) switches the drive mode from the full assist mode to the half assist mode.

[0050] When an abnormality occurs in the normal system while the half assist mode is selected as the drive mode, the microcomputer (51A, 51B) switches the drive mode from the half assist mode to the both system assist stop mode.

[0051] As shown in Fig. 4, when the drive mode of the motor 30 is the full assist mode, the first winding group 30A and the second winding group 30B each generate an assist amount that is half the assist amount required of the motor 30. In other words, the assist amount required of the motor 30 is the sum of the assist amount generated by the first winding group 30A and the assist amount generated by the second winding group 30B. The motor 30 generates an assist amount equivalent to the assist amount required of the motor 30. The assist amount is expressed as a percentage when the maximum assist torque that the motor 30 can output is set to 100%.

[0052] When the drive mode of the motor 30 is the half-assist mode, the normal winding group generates an assist amount equal to the assist amount required of the motor 30. The normal winding group is the first winding group 30A or the second winding group 30B. However, the maximum assist amount that can be output by one winding group is half of the maximum assist amount that the motor 30 can output. In other words, if the maximum assist amount that the motor 30 can output is 100%, the maximum assist amount that can be output by one winding group is 50%. Therefore, when the assist amount required of the motor 30 exceeds 50%, the assist amount output by the motor 30 is maintained at 50%, regardless of the assist amount required of the motor 30.

[0053] When the drive mode of the motor 30 is the single-system assist stop mode, the winding group of the normal system generates an assist amount that is half the assist amount required of the motor 30. Therefore, for example, if the assist amount required of the motor 30 is 100%, the assist amount output by the motor 30 will be 50%. Also, for example, if the assist amount required of the motor 30 is 50%, the assist amount output by the motor 30 will be 25%.

[0054] When the drive mode of the motor 30 is the dual-assist stop mode, neither the first winding group 30A nor the second winding group 30B generates an assist amount. That is, regardless of the assist amount required of the motor 30, the assist amount output by the motor 30 is maintained at 0%.

[0055] The assist performance increases in the order of full assist mode, half assist mode, and single-system assist stop mode. <Example of Transition of Drive Mode of Motor 30> Next, an example of a transition of the drive mode of the motor 30 in response to a drop in the monitored value of the power supply voltage will be described.

[0056] As shown in FIG. 5, when the connection state of the switch 10C is the first connection state, power from the first power supply 20A is supplied to the first control unit 10A and the second control unit 10B. 6, when the connection state of the switch 10C is the second connection state, power from the first power supply 20A is supplied only to the first control unit 10A. Also, when the connection state of the switch 10C is the second connection state, power from the second power supply 20B is supplied only to the second control unit 10B.

[0057] When the connection state of the switch 10C is the first connection state or the second connection state, there are two possible patterns in which the monitor value of the power supply voltage drops. In the first pattern, the monitor values of the power supply voltages of both systems drop simultaneously. In the second pattern, the monitor value of the power supply voltage of only one system drops. The monitor value of the power supply voltage is the value of the power supply voltage monitored by the first pre-driver 52A and the second pre-driver 52B.

[0058] <First connection state> When the connection state of the switch 10C is the first connection state shown in FIG. 5, the first control unit 10A and the second control unit 10B are each supplied with power from the same first power supply 20A. Therefore, when the voltage of the first power supply 20A actually drops, the monitored values of the power supply voltages of both systems also drop simultaneously. That is, in the first connection state, a drop in the voltage of the first power supply 20A does not generally cause a drop in the monitored value of only one of the power supply voltages. In FIG. 7, a drop in the monitored value of only one of the power supply voltages is referred to as a "one-system voltage drop."

[0059] Therefore, if the monitored values of the power supply voltages of both systems drop simultaneously, it is assumed that the voltage of the first power supply 20A has dropped. However, the voltage drop of the first power supply 20A may be temporary. For this reason, as shown in FIG. 7, the first control unit 10A and the second control unit 10B temporarily stop executing the assist control when the monitored value of the power supply voltage drops. The first control unit 10A and the second control unit 10B resume executing the assist control when the monitored value of the power supply voltage returns to a normal level. In FIG. 7, the resumption of execution of the assist control is referred to as "assist return."

[0060] If the monitor value of the power supply voltage of only one system drops, there is a high probability that a hardware abnormality accompanying the drop in the monitor value of the power supply voltage has occurred. The hardware abnormality may include, for example, a failure in at least one of the six FETs 61 to 66 of the inverter (53A, 53B). However, it is also possible that the monitor value of the power supply voltage is temporarily dropping rather than there being a hardware abnormality.

[0061] Therefore, if the monitored value of the power supply voltage falls within a set range, the control unit of the abnormal system will temporarily stop executing the assist control, taking into consideration the possibility that the monitored value of the power supply voltage is temporarily low. The control unit of the normal system, whose monitored value of the power supply voltage has not fallen, will continue executing the assist control. That is, the drive mode of the motor 30 will transition to the single-system assist stop mode. The control unit of the abnormal system will resume executing the assist control once the monitored value of the power supply voltage returns to a normal level.

[0062] The setting range is, for example, equal to or higher than a first operation stop voltage at which the microcomputers (51A, 51B) stop operating and equal to or lower than a second operation stop voltage at which the pre-drivers (52A, 52B) stop operating, and the value of the second operation stop voltage is higher than the value of the first operation stop voltage.

[0063] The control unit of the abnormal system is either the first control unit 10A or the second control unit 10B, and the control unit of the normal system is the other of the first control unit 10A or the second control unit 10B.

[0064] If an abnormality occurs in the first pre-driver 52A or the second pre-driver 52B, the drive mode of the motor 30 transitions to half assist mode. The control unit of the abnormal system where the abnormality occurred stops executing assist control. After the drive mode of the motor 30 transitions to half assist mode, the control unit of the abnormal system does not resume assist control. The abnormality in the first pre-driver 52A and the second pre-driver 52B is a permanent abnormality, a hardware abnormality that does not involve a drop in the monitor value of the power supply voltage. The control unit of the normal system where no abnormality has occurred continues to execute assist control.

[0065] <Second connection state> When the connection state of the switch 10C is the second connection state shown in FIG. 6, the first control unit 10A and the second control unit 10B are supplied with power from different power sources. That is, the first control unit 10A is supplied with power from the first power source 20A. The second control unit 10B is supplied with power from the second power source 20B. Therefore, the probability that the monitored value of the power supply voltage monitored by the first control unit 10A and the monitored value of the power supply voltage monitored by the second control unit 10B will decrease simultaneously is low. However, in the second connection state, a voltage drop in either the first power source 20A or the second power source 20B may cause a decrease in the monitored value of only one of the power supply voltages.

[0066] As shown in FIG. 7, when the voltage of either the first power supply 20A or the second power supply 20B drops, only the monitor value of the power supply voltage of one system drops. Furthermore, when a hardware abnormality accompanying a drop in the monitor value of the power supply voltage occurs in either the first control unit 10A or the second control unit 10B, only the monitor value of the power supply voltage of one system drops. Examples of hardware abnormalities include a failure of at least one of the six FETs 61-66 of the inverter (53A, 53B). However, it is difficult to determine whether a drop in the monitor value of the power supply voltage of one system is due to an actual drop in the power supply voltage or a hardware abnormality.

[0067] Therefore, when the monitor value of the power supply voltage of only one system drops, the drive mode of the motor 30 transitions to half assist mode. That is, the control unit of the abnormal system in which the monitor value of the power supply voltage has dropped stops executing assist control, for example, when the monitor value drops to or below the operation stop voltage of the pre-drivers (52A, 52B). The control unit of the normal system in which the monitor value of the power supply voltage has not dropped continues to execute assist control. After the drive mode of the motor 30 transitions to half assist mode, the control unit of the abnormal system does not resume assist control. The control unit of the abnormal system is either the first control unit 10A or the second control unit 10B, and the control unit of the normal system is the other of the first control unit 10A and the second control unit 10B.

[0068] The assist performance increases in the order of full assist mode, half assist mode, and single-system assist stop mode. Furthermore, as mentioned above, when the connection state of switch 10C is the second connection state shown in FIG. 6, it is difficult to determine whether a drop in the monitored value of the power supply voltage of one system is due to an actual drop in the power supply voltage or a hardware abnormality. Therefore, when only the monitored value of the power supply voltage of one system drops, priority is given to assist performance, and the drive mode of motor 30 is transitioned to half assist mode rather than single-system assist stop mode. Single-system assist stop mode is a drive mode that takes into account the possibility of a temporary drop in the power supply voltage.

[0069] Even if an abnormality occurs in the first pre-driver 52A or the second pre-driver 52B, the drive mode of the motor 30 transitions to half assist mode. The control unit of the abnormal system in which the abnormality occurred stops executing assist control. After the drive mode of the motor 30 transitions to half assist mode, the control unit of the abnormal system does not resume assist control. The abnormality in the first pre-driver 52A and the second pre-driver 52B is a permanent abnormality, a hardware abnormality that does not involve a drop in the monitored value of the power supply voltage. The control unit of the normal system in which no abnormality has occurred continues to execute assist control.

[0070] <Effects of the embodiment> This embodiment has the following advantages. (1) When the monitor value of the power supply voltage of only one of the first control unit 10A and the second control unit 10B drops, the drive mode of the motor 30 transitions depending on whether the power supply of the second control unit 10B is the first power supply 20A or the second power supply 20B. Therefore, even when the monitor value of the power supply voltage of only one of the first control unit 10A and the second control unit 10B drops, the drive of the motor 30 can be appropriately controlled. The monitor value is the value of the power supply voltage detected by the first pre-driver 52A and the second pre-driver 52B.

[0071] (2) When the power source for second control unit 10B is second power source 20B, the drive mode of motor 30 transitions from full assist mode to half assist mode when the monitored value of the power supply voltage for only one of first control unit 10A and second control unit 10B drops. When switch 10C is in the second connection state of FIG. 6, the power source for second control unit 10B is second power source 20B. Therefore, when the power source for second control unit 10B is second power source 20B, even when the monitored value of the power supply voltage for only one of first control unit 10A and second control unit 10B drops, the drive of motor 30 can be appropriately controlled in half assist mode.

[0072] (3) When the power source for second control unit 10B is second power source 20B, if a hardware abnormality occurs in either first control unit 10A or second control unit 10B that is not accompanied by a drop in the monitored value of the power supply voltage, the drive mode of motor 30 transitions from full assist mode to half assist mode. Therefore, when the power source for second control unit 10B is second power source 20B, even if a hardware abnormality occurs in either first control unit 10A or second control unit 10B that is not accompanied by a drop in the monitored value of the power supply voltage, the drive of motor 30 can be appropriately controlled in half assist mode.

[0073] (4) When the power source for second control unit 10B is first power source 20A, the motor drive mode transitions from full-assist mode to single-assist stop mode when the monitored value of the power supply voltage for only one of first control unit 10A and second control unit 10B drops. When switch 10C is in the first connection state of FIG. 5, the power source for second control unit 10B is first power source 20A. Therefore, when the power source for second control unit 10B is first power source 20A, even when the monitored value of the power supply voltage for only one of first control unit 10A and second control unit 10B drops, the drive of motor 30 can be appropriately controlled in single-assist stop mode.

[0074] (5) If the power source of the second control unit 10B is the first power source 20A, when the monitored values of the power source voltages of both the first control unit 10A and the second control unit 10B drop, it is considered that the voltage of the first power source 20A has dropped. The voltage drop of the first power source 20A may be temporary. Therefore, if the power source of the second control unit 10B is the first power source 20A, when the monitored values of the power source voltages of both the first control unit 10A and the second control unit 10B drop, the first control unit 10A temporarily stops supplying power to the first winding group 30A, and the second control unit 10B temporarily stops supplying power to the second winding group 30B. In other words, the first control unit 10A and the second control unit 10B temporarily stop executing the assist control. This allows them to wait for the monitored values of the power source voltages to return to a normal level. Once the monitored values of the power source voltages return to a normal level, the first control unit 10A and the second control unit 10B resume executing the assist control.

[0075] (6) When the power source for second control unit 10B is first power source 20A, if a hardware abnormality occurs in either first control unit 10A or second control unit 10B that is not accompanied by a drop in the monitored value of the power supply voltage, the drive mode of motor 30 transitions from full assist mode to half assist mode. Therefore, when the power source for second control unit 10B is first power source 20A, even if a hardware abnormality occurs in either first control unit 10A or second control unit 10B that is not accompanied by a drop in the monitored value of the power supply voltage, drive of motor 30 can be appropriately controlled in half assist mode.

[0076] <Other embodiments> This embodiment may be modified as follows. The first control unit 10A and the second control unit 10B may switch the drive mode of the motor 30 based on an abnormality detection signal from another control device mounted on the vehicle. The abnormality detection signal is, for example, an electrical signal indicating an abnormality in various devices mounted on the vehicle. The relationship between the type of abnormality and the drive mode of the motor 30 is set appropriately according to product specifications, etc.

[0077] The first control unit 10A and the second control unit 10B may monitor the monitored values of each other's power supply voltages and switch the drive mode of the motor 30 taking into consideration the monitored values of each other's power supply voltages.

[0078] The first control unit 10A and the second control unit 10B may monitor each other's status and take each other's status into consideration when switching the drive mode of the motor 30. The status may include, for example, the operating status of the first control unit 10A and the second control unit 10B, or the presence or absence of an abnormality.

[0079] The switch 10C is not limited to a mechanical relay, but may be a contactless relay using a semiconductor element such as a field effect transistor (FET). The contactless relay may be, for example, a contact c type, in which an a-contact type semiconductor element that turns on when current is applied and a b-contact type semiconductor element that turns off when current is applied are incorporated into a single package.

[0080] The steering control device 10 is not limited to a device equipped with a CPU and memory and executing software processing. For example, the steering control device 10 may be equipped with a dedicated hardware circuit such as an ASIC that executes at least part of the processing executed in this embodiment. In other words, the steering control device 10 may include a processing circuit having any of the following configurations (A1), (A2), and (A3).

[0081] (A1) A processing circuit including a processing device that executes all of the processes executed in this embodiment in accordance with a program, and a program storage device such as a storage device that stores the program. There may be multiple processing devices.

[0082] (A2) A processing circuit comprising a processing device and a program storage device that execute part of the processing executed in this embodiment according to a program, and a dedicated hardware circuit that executes the remaining processing. There may be multiple processing devices. There may also be multiple dedicated hardware circuits.

[0083] (A3) A processing circuit including a dedicated hardware circuit that executes all of the processes executed in the present embodiment. There may be multiple dedicated hardware circuits. The steering device may be, for example, a steer-by-wire steering device. In a steer-by-wire steering device, power transmission between the steering wheel and the steered wheels is separated. The motor 30 functions as a reaction motor that generates a steering reaction force, or as a steering motor that generates a steering force. The steering reaction force is a torque in the opposite direction to the steering wheel operation direction. The steering force is a torque for steering the steered wheels. [Explanation of symbols]

[0084] 10...Steering control device 10A...First control section 10B...Second control section 10C...Switch 20A...First power supply 20B...Second power supply 30...Motor 30A...First winding group 30B...Second winding group

Claims

1. A steering control device that is a drive source for a steering device of a vehicle and controls a motor having a first winding group and a second winding group, a first control unit configured to consume power from a first power supply and control power supply to the first winding group; a second control unit configured to consume power from the first power supply or a second power supply different from the first power supply and to control power supply to the second winding group; a switch that switches a power supply of the second control unit between the first power supply and the second power supply, A steering control device configured such that when the monitored value of the power supply voltage of only one of the first control unit and the second control unit drops, the drive mode of the motor transitions depending on whether the power supply of the second control unit is the first power supply or the second power supply.

2. The motor is an assist motor configured to generate an assist torque that assists the operation of a steering wheel, When the power source of the second control unit is the second power source, when the monitor value of only one of the first control unit and the second control unit decreases, the drive mode of the motor is transitioned from a full assist mode to a half assist mode, the full assist mode is a drive mode in which equal torque is generated in both the first winding group and the second winding group; 2. The steering control device according to claim 1, wherein the half-assist mode is a drive mode in which power supply to an abnormal winding group, of the first winding group and the second winding group, in which the monitored value has decreased is permanently stopped, and a torque equal to or less than the maximum torque that can be generated only by a normal winding group in which the monitored value has not decreased is generated.

3. 3. A steering control device according to claim 2, wherein when the power source of the second control unit is the second power source, when a hardware abnormality occurs in either the first control unit or the second control unit that does not involve a decrease in the monitored value, the drive mode of the motor transitions from the full assist mode to the half assist mode.

4. The motor is an assist motor configured to generate an assist torque that assists the operation of a steering wheel, When the power supply of the second control unit is the first power supply, when only the monitor value of either the first control unit or the second control unit decreases, the drive mode of the motor is transitioned from a full assist mode to a single-system assist stop mode, the full assist mode is a drive mode in which equal torque is generated in both the first winding group and the second winding group; 2. The steering control device according to claim 1, wherein the one-system assist stop mode is a drive mode in which power supply to an abnormal system winding group, of the first winding group and the second winding group, in which the monitored value has decreased is temporarily stopped, and half of the torque required of the motor is generated only by a normal system winding group in which the monitored value has not decreased.

5. 5. The steering control device according to claim 4, wherein, when the power source of the second control unit is the first power source, when the monitored values of both the first control unit and the second control unit decrease, the first control unit temporarily stops supplying power to the first winding group, and the second control unit temporarily stops supplying power to the second winding group.

6. When the power source of the second control unit is the first power source, if a hardware abnormality that does not involve a decrease in the monitor value occurs in either the first control unit or the second control unit, the drive mode of the motor is transitioned from the full assist mode to the half assist mode, 6. A steering control device according to claim 4 or claim 5, wherein the half assist mode is a drive mode in which power supply to the winding group of the abnormal system in which the hardware abnormality has occurred is permanently stopped, and a torque equal to or less than the maximum torque that can be generated only by the winding group of the normal system in which the hardware abnormality has not occurred is generated.

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