Patent Description:
There are conventionally known vehicle control devices like this one: The electronic control unit (ECU) of <CIT> (<CIT>), for example, controls a motor of an electric power steering system installed in a vehicle. The ECU has dual-system magnetic detection elements. The ECU generates motor rotation angle information from a first rotation angle signal generated by a magnetic detection element of a first system and a second rotation angle signal generated by a magnetic detection element of a second system. The ECU calculates the position of a steering wheel from the motor rotation angle information.

The ECU compares first motor rotation angle information obtained from the first rotation angle signal and second motor rotation angle information obtained from the second rotation angle signal. When the first motor rotation angle information and the second motor rotation angle information match, the ECU executes assistive control of assisting the steering of the steering wheel using information on the position of the steering wheel obtained from the motor rotation angle information. When the first motor rotation angle information and the second motor rotation angle information do not match, the ECU detects an abnormality of the magnetic detection element of the first system or the magnetic detection element of the second system.

Document <CIT> discloses a steering system in a vehicle including a plurality of subsystems provided with a control unit. The control unit includes a storage unit storing steer angle information regarding a steer angle of one of a steering mechanism and a steered mechanism when the steering mechanism or the steered mechanism stops, an abnormality determiner determining abnormality of the motor rotation detection value and the detection circuit in the plurality of subsystems at a start time of a motor based on a comparison of at least two parameters, and a steer angle calculator calculating the steer angle based on the parameters having been determined by the abnormality determiner as not abnormal.

The ECU of <CIT> can detect that one of the dual-system magnetic detection elements is abnormal. However, the ECU of <CIT> cannot identify which of the dual-system magnetic detection elements is abnormal. Thus, driving of the motor may fail to start even when one of the dual-system magnetic detection elements is normal.

A vehicle control device according to one aspect of the present invention according to claim <NUM>, includes: dual-system control circuits that control power supply to dual-system winding sets of a motor having the winding sets, for each system independently; and dual-system rotation detection circuits each of which detects a rotation speed of the motor. The control circuits are each configured to calculate an absolute rotation angle of the motor using the rotation speed of the motor, and each of the control circuits is configured to, when a power source is turned off, store an absolute rotation angle of the motor at that time and, when the power source is turned on, start after confirming that both of the dual-system rotation detection circuits are normal. At least one of the control circuits is configured to start when the power source is turned on and an absolute value of a difference between an absolute rotation angle of the motor that was stored when the power source was turned off last time and an absolute rotation angle of the motor that is calculated when the power source is turned on this time is equal to or smaller than a given threshold value, regardless of whether it is detected that an abnormality has occurred in one of the dual-system rotation detection circuits or an abnormality of the dual-system rotation detection circuits is not determinable.

According to this configuration, when the absolute value of the difference between the absolute rotation angle of the motor that was stored when the power source was turned off and the absolute rotation angle of the motor that is calculated when the power source is turned on next time is equal to or smaller than the given threshold value, the rotation detection circuit of the corresponding system can be said to be normal. Therefore, the control system of the first system or the second system can start appropriately to start executing motor control.

In the vehicle control device according to the above-described aspect, the dual-system control circuits may be a control circuit of a first system and a control circuit of a second system, and the dual-system rotation detection circuits may be a rotation detection circuit of the first system and a rotation detection circuit of the second system. The control circuit of the first system may be configured to provide, to the control circuit of the second system, the rotation speed of the motor detected by the rotation detection circuit of the first system, and receive the rotation speed of the motor detected by the rotation detection circuit of the second system. The control circuit of the second system may be configured to provide, to the control circuit of the first system, the rotation speed of the motor detected by the rotation detection circuit of the second system, and receive the rotation speed of the motor detected by the rotation detection circuit of the first system. The dual-system control circuits may be configured to determine an abnormality of the dual-system rotation detection circuits by comparing the rotation speeds of the motor detected by the dual-system rotation detection circuits. The dual-system control circuits may have a master-slave relationship, with the control circuit of the first system being a master and the control circuit of the second system being a slave, and a case where an abnormality of the dual-system rotation detection circuits is not determinable may be a case where the control circuit of the first system does not start when the power source is turned on.

According to this configuration, even in the case where the control circuit of the first system that is the master does not start when the power source is turned on, the rotation detection circuit of the second system can be said to be normal when the absolute value of the difference between the absolute rotation angle of the motor that was stored when the power source was turned off last time and the absolute rotation angle of the motor that is calculated when the power source is turned on this time is equal to or smaller than the given threshold value. Therefore, the control circuit of the second system that is the slave can start alone.

In the vehicle control device according to the above-described aspect, the motor may be a driving source of a mechanical device, and the mechanical device may have a sensor that detects an absolute position of a constituent element that operates in conjunction with the motor. Only the control circuit of the first system may be connected to the sensor. The control circuit of the first system may be configured to, when the power source is turned on and it is detected that an abnormality has occurred in one of the dual-system rotation detection circuits or an abnormality of the dual-system rotation detection circuits is not determinable, execute a process of calculating the absolute rotation angle of the motor using the absolute position of the constituent element detected through the sensor, and a process of transmitting the absolute position of the constituent element detected through the sensor to the control circuit of the second system.

According to this configuration, when the power source is turned on and an abnormality of one of the dual-system rotation detection circuits is detected or an abnormality of the dual-system rotation detection circuits is not determinable, the control circuit of the first system and the control circuit of the second system can calculate the absolute rotation angle of the motor using the absolute position of the constituent element of the mechanical device.

In the vehicle control device according to the above-described aspect, the mechanical device may be a steering system of a vehicle. The constituent element may be a turning shaft that turns a turning wheel of the vehicle. The sensor may be a stroke sensor that detects an absolute position of the turning shaft in an axial direction.

According to this configuration, when the power source is turned on and an abnormality of one of the dual-system rotation detection circuits is detected or an abnormality of the dual-system rotation detection circuits is not determinable, the control circuit of the first system and the control circuit of the second system can calculate the absolute rotation angle of the motor using the absolute position of the turning shaft that is a constituent element of the steering system.

In the vehicle control device according to the above-described aspect, the motor may be a turning-side motor that generates a turning force for turning the turning wheel of the vehicle. The dual-system control circuits may include a first turning control circuit that controls power supply to a winding set of a first system of the turning-side motor and a second turning control circuit that controls power supply to a winding set of a second system of the turning-side motor, and the winding set of the first system and the winding set of the second system may be provided as a dual-system winding sets.

As in this configuration, the turning-side motor is sometimes required to start as far as possible, even with a single system. Such requirement can be met.

In the vehicle control device according to the above-described aspect, the motor may be an assist motor that generates an assistive force for assisting operation of a steering wheel. The dual-system control circuits may include a first assistance control circuit that controls power supply to a winding set of a first system of the assist motor and a second assistance control circuit that controls power supply to a winding set of a second system of the assistance motor, and the winding set of the first system and the winding set of the second system may be provided as the dual-system winding sets.

As in this configuration, the assist motor is sometimes required to start as far as possible, even with a single system. Such requirement can be met.

The vehicle control device of the present invention can start more appropriately when the power source is turned on.

A first embodiment in which a vehicle control device is embodied in a steer-by-wire steering system will be described below. The steering system is a mechanical device.

As shown in <FIG>, a steering system <NUM> of the vehicle has a steering shaft <NUM> coupled to a steering wheel <NUM>. The steering system <NUM> further has a turning shaft <NUM> extending along a vehicle width direction (the left-right direction in <FIG>). Turning wheels <NUM> are coupled to the ends of the turning shaft <NUM> through tie rods <NUM>. As the turning shaft <NUM> moves linearly, a turning angle θw of the turning wheels <NUM> changes. The steering shaft <NUM> and the turning shaft <NUM> constitute a steering mechanism of the vehicle. In <FIG>, only the turning wheel <NUM> on one side is shown.

The steering system <NUM> has a reaction force motor <NUM> and a speed reduction mechanism <NUM>. The reaction force motor <NUM> is a generation source of a steering reaction force. A steering reaction force refers to a force that acts in the opposite direction from a direction in which the steering wheel <NUM> is operated by a driver. A rotating shaft of the reaction force motor <NUM> is coupled to the steering shaft <NUM> through the speed reduction mechanism <NUM>. A torque of the reaction force motor <NUM> is applied to the steering shaft <NUM> as a steering reaction force. Applying the steering reaction force to the steering wheel <NUM> can give the driver an appropriate sense of resistance.

The reaction force motor <NUM> is, for example, a three-phase brushless motor. The reaction force motor <NUM> has a winding set N11 of a first system and a winding set N12 of a second system. The winding set N11 of the first system and the winding set N12 of the second system are wound around a common stator (not shown). The winding set N11 of the first system and the winding set N12 of the second system are equivalent to each other in electrical characteristics.

The steering system <NUM> has a turning-side motor <NUM> and a speed reduction mechanism <NUM>. The turning-side motor <NUM> is a generation source of a turning force. A turning force refers to a motive force for turning the turning wheels <NUM>. A rotating shaft of the turning-side motor <NUM> is coupled to a pinion shaft <NUM> through the speed reduction mechanism <NUM>. Pinion teeth 33a of the pinion shaft <NUM> are meshed with rack teeth 13a of the turning shaft <NUM>. A torque of the turning-side motor <NUM> is applied to the turning shaft <NUM> through the pinion shaft <NUM> as a turning force. The turning shaft <NUM> moves along the vehicle width direction according to rotation of the turning-side motor <NUM>.

The turning-side motor <NUM> is, for example, a three-phase brushless motor. The turning-side motor <NUM> has a winding set N21 of a first system and a winding set N22 of a second system. The winding set N21 of the first system and the winding set N22 of the second system are wound around a common stator (not shown). The winding set N21 of the first system and the winding set N22 of the second system are equivalent to each other in electrical characteristics.

The steering system <NUM> has a reaction force control device <NUM>. The reaction force control device <NUM> controls driving of the reaction force motor <NUM> that is a control target. The reaction force control device <NUM> executes reaction force control of generating a steering reaction force according to a steering torque Th in the reaction force motor <NUM>. The reaction force control device <NUM> calculates a target steering reaction force based on the steering torque Th detected through a torque sensor <NUM>. The torque sensor <NUM> is provided on the steering shaft <NUM>. The reaction force control device <NUM> controls power supply to the reaction force motor <NUM> such that the actual steering reaction force applied to the steering shaft <NUM> matches the target steering reaction force. The reaction force control device <NUM> controls power supply to the dual-system winding sets in the reaction force motor <NUM>, for each system independently.

The reaction force control device <NUM> has a first system circuit <NUM> and a second system circuit <NUM>. The first system circuit <NUM> controls power supply to the winding set N11 of the first system in the reaction force motor <NUM> according to the steering torque Th detected through the torque sensor <NUM>. The second system circuit <NUM> controls power supply to the winding set N12 of the second system in the reaction force motor <NUM> according to the steering torque Th detected through the torque sensor <NUM>.

The steering system <NUM> has a turning control device <NUM>. The turning control device <NUM> controls driving of the turning-side motor <NUM> that is a control target. The turning control device <NUM> executes turning control of generating, in the turning-side motor <NUM>, a turning force for turning the turning wheels <NUM> according to a steering state. The turning control device <NUM> takes in a steering angle θs detected through a steering angle sensor <NUM> and a stroke Xw of the turning shaft <NUM> detected through a stroke sensor <NUM>. The stroke Xw is a shift amount with reference to a neutral position of the turning shaft <NUM> and is a state variable reflecting the turning angle θw. The steering angle sensor <NUM> is provided between the torque sensor <NUM> of the steering shaft <NUM> and the speed reduction mechanism <NUM>. The stroke sensor <NUM> is provided near the turning shaft <NUM>.

The turning control device <NUM> calculates a target turning angle of the turning wheels <NUM> based on the steering angle θs detected through the steering angle sensor <NUM>. The turning control device <NUM> calculates the turning angle θw based on the stroke Xw of the turning shaft <NUM> detected through the stroke sensor <NUM>. The turning control device <NUM> controls power supply to the turning-side motor <NUM> such that the turning angle θw calculated based on the stroke Xw matches the target turning angle. The turning control device <NUM> controls power supply to the dual-system winding sets in the turning-side motor <NUM>, for each system independently.

The turning control device <NUM> has a first system circuit <NUM> and a second system circuit <NUM>. The first system circuit <NUM> controls power supply to the winding set N21 of the first system in the turning-side motor <NUM> based on the steering angle θs detected through the steering angle sensor <NUM> and the stroke Xw of the turning shaft <NUM> detected through the stroke sensor <NUM>. The second system circuit <NUM> controls power supply to the winding set N22 of the second system in the turning-side motor <NUM> based on the steering angle θs detected through the steering angle sensor <NUM> and the stroke Xw of the turning shaft <NUM> detected through the stroke sensor <NUM>.

The reaction force control device <NUM> and the reaction force motor <NUM> may be integrally provided so as to constitute a so-called mechano-electric reaction force actuator. The turning control device <NUM> and the turning-side motor <NUM> may be integrally provided so as to constitute a so-called mechano-electric turning actuator.

Next, a power supply path to the reaction force control device <NUM> and the turning control device <NUM> will be described. Various kinds of on-board control devices, including the reaction force control device <NUM> and the turning control device <NUM>, are each supplied with electricity from a direct-current power source <NUM> installed in the vehicle. The direct-current power source <NUM> is, for example, a battery. Various sensors, including the torque sensor <NUM>, the steering angle sensor <NUM>, and the stroke sensor <NUM>, are also each supplied with electricity from the direct-current power source <NUM>.

The first system circuit <NUM> and the second system circuit <NUM> of the reaction force control device <NUM> and the first system circuit <NUM> and the second system circuit <NUM> of the turning control device <NUM> are each connected to the direct-current power source <NUM> through a start switch SW of the vehicle. The start switch SW is, for example, an ignition switch or a power switch. The start switch SW is operated when starting or stopping a driving source for traveling of the vehicle, such as an engine. When the start switch SW is turned on, electricity from the direct-current power source <NUM> is supplied through the start switch SW to the first system circuit <NUM> and the second system circuit <NUM> of the reaction force control device <NUM> as well as to the first system circuit <NUM> and the second system circuit <NUM> of the turning control device <NUM>. Turning the start switch SW on means turning the vehicle power source on. Turning the start switch SW off means turning the vehicle power source off.

The first system circuit <NUM> and the second system circuit <NUM> of the reaction force control device <NUM> and the first system circuit <NUM> and the second system circuit <NUM> of the turning control device <NUM> are connected to the direct-current power source <NUM> through power source relays 60A, 60B, 60C, 60D. When the power source relays 60A, 60B, 60C, 60D are turned on, electricity from the direct-current power source <NUM> is supplied to the first system circuit <NUM> and the second system circuit <NUM> of the reaction force control device <NUM> as well as to the first system circuit <NUM> and the second system circuit <NUM> of the turning control device <NUM> through the power source relays 60A, 60B, 60C, 60D.

The first system circuit <NUM> of the reaction force control device <NUM> controls turning on and off of the power source relay 60A. When the start switch SW is switched from on to off, the first system circuit <NUM> executes power latching control of maintaining the power source relay 60A in an on-state for a given period. This allows the first system circuit <NUM> to operate even after the start switch SW is turned off. When the given period has elapsed, the first system circuit <NUM> can shut off power supply to itself by switching the power source relay 60A from on to off.

The first system circuit <NUM> detects turning on and off of the start switch SW by, for example, monitoring a voltage across ends of the start switch SW. When the voltage across the ends of the start switch SW falls below a given voltage threshold value, the first system circuit <NUM> detects that the start switch SW has been turned on. When the voltage across the ends of the start switch SW is equal to or higher than the given voltage threshold value, the first system circuit <NUM> detects that the start switch SW has been turned off.

The second system circuit <NUM> of the reaction force control device <NUM> controls turning on and off of the power source relay 60B. The second system circuit <NUM> executes power latching control in the same manner as the first system circuit <NUM>. When the start switch SW is switched from on to off, the second system circuit <NUM> maintains the power source relay 60B in an on-state for a given period.

The first system circuit <NUM> of the turning control device <NUM> controls turning on and off of the power source relay 60C. The first system circuit <NUM> executes power latching control in the same manner as the first system circuit <NUM> of the reaction force control device <NUM>. When the start switch SW is switched from on to off, the first system circuit <NUM> maintains the power source relay 60C in an on-state for a given period.

The second system circuit <NUM> of the turning control device <NUM> controls turning on and off of the power source relay 60D. The second system circuit <NUM> executes power latching control in the same manner as the first system circuit <NUM> of the reaction force control device <NUM>. When the start switch SW is switched from on to off, the second system circuit <NUM> maintains the power source relay 60D in an on-state for a given period.

Among the constituent elements of the steering system <NUM>, constituent elements that are required to operate also after the start switch SW is turned off, such as the torque sensor <NUM>, the steering angle sensor <NUM>, and the stroke sensor <NUM>, are connected to the direct-current power source <NUM> through at least one of the power source relays 60A, 60B, 60C, 60D. Therefore, also when the start switch SW is off, if at least one of the power source relays 60A, 60B, 60C, 60D is on, power supply to the constituent elements, such as the torque sensor <NUM>, the steering angle sensor <NUM>, and the stroke sensor <NUM>, is continued.

Next, the configuration of the reaction force control device will be described in detail. As shown in <FIG>, the reaction force control device <NUM> has the first system circuit <NUM> and the second system circuit <NUM>. The first system circuit <NUM> has a first reaction force control circuit 41A and a motor driving circuit 41B. The second system circuit <NUM> has a second reaction force control circuit 42A and a motor driving circuit 42B.

The first reaction force control circuit 41A is formed by a processing circuit including (<NUM>) one or more processors that operate in accordance with a computer program (software); (<NUM>) one or more dedicated hardware circuits, such as application-specific integrated circuits (ASICs), that execute at least some of various processes; and (<NUM>) a combination of (<NUM>) and (<NUM>). The processor includes a central processing unit (CPU). The processor includes memories, such as a random-access memory (RAM) and a read-only memory (ROM). The memories store program codes or commands configured to make the CPU execute processes. The memories, i.e., non-transitory computer-readable media include all available media that can be accessed by a general-purpose or special-purpose computer.

The first reaction force control circuit 41A calculates a target steering reaction force to be generated in the reaction force motor <NUM> based on the steering torque Th detected through the torque sensor <NUM>, and calculates a first current command value for the winding set N11 of the first system according to this calculated value of the target steering reaction force. The first current command value is set to a value of half (<NUM>%) of a current amount (<NUM>%) that is required to generate the target steering reaction force in the reaction force motor <NUM>. The first reaction force control circuit 41A generates a driving signal (PWM signal) to the motor driving circuit 41B by executing current feedback control of adapting the actual value of the current supplied to the winding set N11 of the first system to the first current command value.

The motor driving circuit 41B is a PWM inverter in which two switching elements, such as field-effect transistors (FET), connected in series constitute a leg as a basic unit, and three legs corresponding to the respective three phases (U, V, W) are connected in parallel. The motor driving circuit 41B converts direct-current power supplied from the direct-current power source <NUM> into three-phase alternating-current power as the switching elements of the respective phases switch based on a driving signal generated by the first reaction force control circuit 41A. The three-phase alternating-current power generated by the motor driving circuit 41B is supplied to the winding set N11 of the first system of the reaction force motor <NUM> through a power supply path of each phase formed by a busbar, a cable, or the like. Thus, the winding set N11 of the first system generates a torque according to the first current command value.

The second reaction force control circuit 42A has basically the same configuration as the first reaction force control circuit 41A. The second reaction force control circuit 42A calculates a target steering reaction force to be generated in the reaction force motor <NUM> based on the steering torque Th detected through the torque sensor <NUM>, and calculates a second current command value for the winding set N12 of the second system according to this calculated value of the target steering reaction force. The second current command value is set to a value of half (<NUM>%) of a current amount that is required to generate the target steering reaction force in the reaction force motor <NUM>. The second reaction force control circuit 42A generates a driving signal to the motor driving circuit 42B by executing current feedback control of adapting the actual value of the current supplied to the winding set N12 of the second system to the second current command value.

The motor driving circuit 42B has basically the same configuration as the motor driving circuit 41B. The motor driving circuit 42B converts direct-current power supplied from the direct-current power source <NUM> into three-phase alternating-current power based on a driving signal generated by the second reaction force control circuit 42A. The three-phase alternating-current power generated by the motor driving circuit 42B is supplied to the winding set N12 of the second system of the reaction force motor <NUM> through a power supply path of each phase formed by a busbar, a cable, or the like. Thus, the winding set N12 of the second system generates a torque according to the second current command value. The reaction force motor <NUM> generates a torque that is a total of the torque generated by the winding set N11 of the first system and the torque generated by the winding set N12 of the second system.

There is a master-slave relationship between the first system circuit <NUM> and the second system circuit <NUM> of the reaction force control device <NUM>. In this case, for example, the first system circuit <NUM> functions as the master and the second system circuit <NUM> functions as the slave.

Next, the configuration of the turning control device <NUM> will be described in detail. As shown in <FIG>, the turning control device <NUM> has the first system circuit <NUM> and the second system circuit <NUM>. The first system circuit <NUM> has a first turning control circuit 51A and a motor driving circuit 51B. The second system circuit <NUM> has a second turning control circuit 52A and a motor driving circuit 52B.

The first turning control circuit 51A has basically the same configuration as the first reaction force control circuit 41A. The first turning control circuit 51A calculates a target turning angle of the turning wheels <NUM> based on the steering angle θs detected through the steering angle sensor <NUM>. The first turning control circuit 51A calculates the turning angle θw based on the stroke Xw of the turning shaft <NUM> detected through the stroke sensor <NUM>. The first turning control circuit 51A calculates a target turning force to be generated in the turning-side motor <NUM> through execution of angle feedback control of adapting the turning angle θw calculated based on the stroke Xw to the target turning angle, and calculates a third current command value to the winding set N21 of the first system of the turning-side motor <NUM> according to this calculated value of the target turning force. The third current command value is set to a value of half (<NUM>%) of a current amount that is required to generate the target turning force in the turning-side motor <NUM>. The first turning control circuit 51A generates a driving signal to the motor driving circuit 51B by executing current feedback control of adapting the actual value of the current supplied to the winding set N21 of the first system to the third current command value.

The motor driving circuit 51B has basically the same configuration as the motor driving circuit 41B. The motor driving circuit 51B converts the direct-current power supplied from the direct-current power source <NUM> into three-phase alternating-current power based on a driving signal generated by the first turning control circuit 51A. The three-phase alternating-current power generated by the motor driving circuit 42B is supplied to the winding set N21 of the first system of the turning-side motor <NUM> through a power supply path of each phase formed by a busbar, a cable, or the like. Thus, the winding set N21 of the first system generates a torque according to the third current command value.

The second turning control circuit 52A has basically the same configuration as the first reaction force control circuit 41A. The second turning control circuit 52A calculates a target turning angle of the turning wheels <NUM> based on the steering angle θs detected through the steering angle sensor <NUM>. The second turning control circuit 52A calculates the turning angle θw based on the stroke Xw of the turning shaft <NUM> detected through the stroke sensor <NUM>. The second turning control circuit 52A calculates a target turning force to be generated in the turning-side motor <NUM> through execution of angle feedback control of adapting the turning angle θw calculated based on the stroke Xw to the target turning angle, and calculates a fourth current command value to the winding set N22 of the second system of the turning-side motor <NUM> according to this calculated value of the target turning force. The fourth current command value is set to a value of half (<NUM>%) of a current amount that is required to generate the target turning force in the turning-side motor <NUM>. The second turning control circuit 52A generates a driving signal to the motor driving circuit 52B by executing current feedback control of adapting the actual current value supplied to the winding set N22 of the second system to the fourth current command value.

The motor driving circuit 52B has basically the same configuration as the motor driving circuit 41B. The motor driving circuit 52B converts the direct-current power supplied from the direct-current power source <NUM> into three-phase alternating-current power based on a driving signal generated by the second turning control circuit 52A. The three-phase alternating current power generated by the motor driving circuit 52B is supplied to the winding set N22 of the second system of the turning-side motor <NUM> through a power supply path of each phase formed by a busbar, a cable, or the like. Thus, the winding set N22 of the second system generates a torque according to the fourth current command value. The turning-side motor <NUM> generates a torque that is a total of the torque generated by the winding set N21 of the first system and the torque generated by the winding set N22 of the second system.

There is a master-slave relationship between the first system circuit <NUM> and the second system circuit <NUM> of the turning control device <NUM>. In this case, for example, the first system circuit <NUM> functions as the master and the second system circuit <NUM> functions as the slave.

Next, communication paths inside the reaction force control device <NUM> and the turning control device <NUM> and communication paths between the reaction force control device <NUM> and the turning control device <NUM> will be described.

As shown in <FIG>, the first reaction force control circuit 41A and the second reaction force control circuit 42A exchange pieces of information with each other through a communication line L1. These pieces of information include information on an abnormality of the first reaction force control circuit 41A, the second reaction force control circuit 42A, or the motor driving circuits 41B, 42B. These pieces of information also include values of flags showing various states. The first reaction force control circuit 41A and the second reaction force control circuit 42A control the driving of the reaction force motor <NUM> by collaborating with each other based on the pieces of information exchanged therebetween.

The first turning control circuit 51A and the second turning control circuit 52A exchange pieces of information with each other through a communication line L2. These pieces of information include information on an abnormality of the first turning control circuit 51A, the second turning control circuit 52A, or the motor driving circuits 51B, 52B. These pieces of information also include values of flags showing various states. The first turning control circuit 51A and the second turning control circuit 52A control the driving of the turning-side motor <NUM> by collaborating with each other based on the pieces of information exchanged therebetween.

The first reaction force control circuit 41A and the first turning control circuit 51A exchange pieces of information with each other through a communication line L3. These pieces of information include information on an abnormality of the first reaction force control circuit 41A, the first turning control circuit 51A, and the motor driving circuits 41B, 51B. These pieces of information also include values of flags showing various states. The first reaction force control circuit 41A and the first turning control circuit 51A operate in conjunction with each other based on the pieces of information exchanged therebetween.

The second reaction force control circuit 42A and the second turning control circuit 52A exchange pieces of information with each other through a communication line L4. These pieces of information include information on an abnormality of the second reaction force control circuit 42A, the second turning control circuit 52A, or the motor driving circuits 42B, 52B. These pieces of information also include values of flags showing various states. The second reaction force control circuit 42A and the second turning control circuit 52A operate in conjunction with each other based on the pieces of information exchanged therebetween.

Next, driving modes of the reaction force motor <NUM> and the turning-side motor <NUM> will be described. The driving modes include a collaborative driving mode, an independent driving mode, and a single-system driving mode.

The collaborative driving mode is a driving mode that is entered at normal times when the first system circuits <NUM>, <NUM> and the second system circuits <NUM>, <NUM> are operating normally. The first system circuit <NUM> and the second system circuit <NUM> share pieces of information, such as a command value and a limit value, and generate an equal torque in both of the winding set N11 of the first system and the winding set N12 of the second system of the reaction force motor <NUM>. The first system circuit <NUM> and the second system circuit <NUM> share pieces of information, such as a command value and a limit value, and generate an equal torque in both of the winding set N21 of the first system and the winding set N22 of the second system of the turning-side motor <NUM>.

In the case where there is a master-slave relationship between the first system circuit <NUM> and the second system circuit <NUM> of the reaction force control device <NUM>, when the collaborative driving mode is selected as the driving mode, the slave controls driving of the reaction force motor <NUM> using a command value calculated by the master. In the case where there is a master-slave relationship between the first system circuit <NUM> and the second system circuit <NUM> of the turning control device <NUM>, when the collaborative driving mode is selected as the driving mode, the slave controls driving of the turning-side motor <NUM> using a command value calculated by the master.

The independent driving mode is a driving mode that is entered when the operation of one of the four control circuits (41A, 42A, 51A, 52A) has stopped momentarily but an abnormality is not confirmed and there is a possibility of restoration to normal operation. In the independent driving mode, for example, when there is a possibility that one control circuit that has stopped operating may restore normal operation, the other three control circuits generate a torque in the corresponding winding sets based on their own calculation results without using information obtained through inter-system communication.

In the case where there is a master-slave relationship between the first system circuit <NUM> and the second system circuit <NUM> of the reaction force control device <NUM>, when the independent driving mode is selected as the driving mode, the master-slave relationship between the first system circuit <NUM> and the second system circuit <NUM> is temporarily dissolved. In the case where there is a master-slave relationship between the first system circuit <NUM> and the second system circuit <NUM> of the turning control device <NUM>, when the independent driving mode is selected as the driving mode, the master-slave relationship between the first system circuit <NUM> and the second system circuit <NUM> is temporarily dissolved.

The single-system driving mode is a driving mode that is entered when an abnormality of one of the four control circuits (41A, 42A, 51A, 52A) has been confirmed and there is no possibility of restoration to normal operation. For example, when an abnormality of the first system circuits <NUM>, <NUM> is confirmed, a torque is generated in the reaction force motor <NUM> and the turning-side motor <NUM> by the second system circuits <NUM>, <NUM> alone. When an abnormality of the second system circuits <NUM>, <NUM> is confirmed, a torque is generated in the reaction force motor <NUM> and the turning-side motor <NUM> by the first system circuits <NUM>, <NUM> alone.

In the case where there is a master-slave relationship between the first system circuit <NUM> and the second system circuit <NUM> of the reaction force control device <NUM>, when the single-system driving mode is selected as the driving mode, the master-slave relationship between the first system circuit <NUM> and the second system circuit <NUM> is temporarily dissolved. In the case where there is a master-slave relationship between the first system circuit <NUM> and the second system circuit <NUM> of the turning control device <NUM>, when the single-system driving mode is selected as the driving mode, the master-slave relationship between the first system circuit <NUM> and the second system circuit <NUM> is temporarily dissolved.

At normal times when not experiencing an abnormality, the control circuits (41A, 42A, 51A, 52A) control driving of the motors (<NUM>, <NUM>) in the collaborative driving mode. When an abnormality determination condition is met in a state where the collaborative driving mode is selected as the driving mode, each control circuit switches the driving mode from the collaborative driving mode to the independent driving mode. When a restoration determination condition is met before an abnormality is confirmed in a state where the independent driving mode is selected as the driving mode, each control circuit restores the driving mode from the independent driving mode to the collaborative driving mode. When an abnormality confirmation condition is met in a state where the independent driving mode is selected as the driving mode, each control circuit switches the driving mode from the independent driving mode to the single-system driving mode.

Examples of abnormalities include temporary abnormalities from which recovery is possible, such as an abnormality in inter-system communication, an abnormality in communication within the same system, a difference in command values between the systems, and a decrease in a current limit value.

Next, the configuration of the turning control device <NUM> will be supplementarily described. The turning control device <NUM> further has the following configurations (A1) to (A6).

(A1) The first system circuit <NUM> and the second system circuit <NUM> start as the vehicle power source turns on. At start-up, the first system circuit <NUM> and the second system circuit <NUM> calculate the rotation angle of the turning-side motor <NUM> as an absolute angle. The turning angle θw is an absolute angle. The first system circuit <NUM> and the second system circuit <NUM> start after confirming that the rotation angle of the turning-side motor <NUM> has been calculated normally.

(A2) The first system circuit <NUM> has a rotation detection circuit 51C (TC: turn counter). The second system circuit <NUM> has a rotation detection circuit 52C. The rotation detection circuits 51C, 52C take in electrical signals generated by the rotation angle sensor of the turning-side motor <NUM> on a given sampling cycle. The electrical signals are electrical signals corresponding to the rotation angle of the turning-side motor <NUM>. The electrical signals include sine signals (sin signals) that change in a sine wave form relative to the rotation angle of the turning-side motor <NUM>, and cosine signals (cos signals) that change in a cosine wave form relative to the rotation angle of the turning-side motor <NUM>. The rotation detection circuits 51C, 52C calculate the rotation direction and the rotation speed of the turning-side motor <NUM> based on the sine signals and the cosine signals.

The rotation detection circuits 51C, 52C plot a coordinate (cosθb, sinθb) that is a combination of values of a sine signal and a cosine signal on an orthogonal coordinate system of "cosθb" and "sinθb," and detect the rotation direction of the turning-side motor <NUM> based on transition of a quadrant in which the plotted coordinate is located. The symbol "θb" represents the rotation angle of the turning-side motor <NUM>. The rotation detection circuits 51C, 52C determine the quadrant in which the plotted coordinate is located based on whether the values of "sinθb" and "cosθb" are positive or negative. For example, when the coordinate has transitioned from the first quadrant to the second quadrant, the rotation detection circuits 51C, 52C determine that the rotation direction of the turning-side motor <NUM> is a positive direction. For example, when the coordinate has transitioned from the first quadrant to the fourth quadrant, the rotation detection circuits 51C, 52C determine that the rotation direction of the turning-side motor <NUM> is a reverse direction.

The rotation detection circuits 51C, 52C each has a counter. The rotation detection circuits 51C, 52C increase or decrease the count values by a certain value each time the quadrant in which the coordinate (cosθb, sinθb) that is a set of the values of a sine signal and a cosine signal is located switches. For example, the certain value is a positive natural number, such as one or two. When the rotation direction of the turning-side motor <NUM> is the positive direction, the rotation detection circuits 51C, 52C increase the count values by the certain value each time the coordinate transitions by one quadrant. When the rotation direction of the turning-side motor <NUM> is the reverse direction, the rotation detection circuits 51C, 52C decrease the count values by the certain value each time the coordinate transitions by one quadrant. The rotation detection circuits 51C, 52C detect the rotation speed of the turning-side motor <NUM> based on the count value.

The first turning control circuit 51A detects an abnormality of the two rotation detection circuits 51C, 52C by comparing count values of the two rotation detection circuits 51C, 52C. When the count values of the two rotation detection circuits 51C, 52C match, the first turning control circuit 51A determines that the two rotation detection circuits 51C, 52C are normal. When the count values of the two rotation detection circuits 51C, 52C do not match, the first turning control circuit 51A determines that one of the two rotation detection circuits 51C, 52C or both of the two rotation detection circuits 51C, 52C are abnormal.

The second turning control circuit 52A determines an abnormality of the two rotation detection circuits 51C, 52C in the same manner as the first turning control circuit 51A.

(A3) The first turning control circuit 51A is connected to the stroke sensor <NUM>. The first turning control circuit 51A takes in electrical signals generated by the stroke sensor <NUM>. The stroke sensor <NUM> serves to detect the absolute position of the turning shaft <NUM> in an axial direction. For example, the stroke sensor <NUM> may be of a kind provided on the pinion shaft <NUM>. This kind of stroke sensor <NUM> detects the rotation angle of the pinion shaft <NUM> as an absolute angle. The rotation angle of the pinion shaft <NUM> can be converted into a stroke of the turning shaft <NUM> or a rotation angle of the turning-side motor <NUM>.

Depending on the product specifications, the second turning control circuit 52A is not connected to the stroke sensor <NUM>. In this case, the second turning control circuit 52A cannot take in electrical signals generated by the stroke sensor <NUM>.

(A4) The first turning control circuit 51A has a function of detecting battery reset. Battery reset means that power supply from the direct-current power source <NUM>, such as a battery, is interrupted. For example, when electricity from the direct-current power source <NUM> stops, the first turning control circuit 51A detects battery reset. As with the first turning control circuit 51A, the second turning control circuit 52A has a function of detecting battery reset.

(A5) The accuracy of the count numbers of the rotation detection circuits 51C, 52C cannot be guaranteed when, for example, the following cases B1 to B3 apply at start-up of the first turning control circuit 51A.

A case where battery reset has occurred. When electricity from the direct-current power source <NUM> stops, the rotation detection circuits 51C, 52C cannot count the rotation speed of the turning-side motor <NUM>.

A case where an abnormality of the rotation detection circuits 51C, 52C is detected. In this case, it is unclear whether the rotation speed of the turning-side motor <NUM> is a correct value.

A case where an abnormality of the rotation detection circuits 51C, 52C cannot be determined. In this case, it is unclear whether the rotation speed of the turning-side motor <NUM> is a correct value.

In the case of B1 to B3, therefore, the first turning control circuit 51A calculates an offset angle with reference to a neutral position of the turning shaft <NUM> using the detection result of the stroke sensor <NUM>. The neutral position is the position of the turning shaft <NUM> when the vehicle is in a state of moving straight ahead. The offset angle is the stroke of the turning shaft <NUM> with reference to the neutral position of the turning shaft <NUM> or the rotation angle of the pinion shaft <NUM>. The first turning control circuit 51A transmits the offset angle to the second turning control circuit 52A through the communication line L2. The first turning control circuit 51A stores the offset angle, and calculates the rotation angle of the turning-side motor <NUM> as an absolute angle based on the offset angle.

(A6) When these cases B1 to B3 do not apply, the first turning control circuit 51A calculates the rotation angle of the turning-side motor <NUM> as an absolute angle using the offset angle stored at start-up.

Next, states of the turning control device <NUM> will be described.

As shown in <FIG>, states of the turning control device <NUM> are represented by, for example, the following items (C1) to (C6):.

(C1) "Inter-microcomputer communication" is communication between the first turning control circuit 51A and the second turning control circuit 52A. States of the inter-microcomputer communication include normal and abnormal.

(C2) "Driving state" includes a driving state of the first turning control circuit 51A and a driving state of the second turning control circuit 52A. "Main" in <FIG> represents the first turning control circuit 51A that is the master. "Sub" in <FIG> represents the second turning control circuit 52A that is the slave. Driving states include the collaborative driving mode, the independent driving mode, and the single-system driving mode described earlier, and shutdown. Shutdown includes shutdown due to a non-rotation-angle-related failure and shutdown due to a rotation-angle-related failure.

A non-rotation-angle-related failure is an abnormality of a device that does not affect the calculation of the rotation angle of the turning-side motor <NUM> by the rotation angle sensor of the turning-side motor <NUM>, the rotation detection circuits 51C, 52C, etc. A non-rotation-angle-related failure includes a case where an abnormality is confirmed after the rotation angle of the turning-side motor <NUM> is calculated as an absolute angle and a case where an abnormality is confirmed before the rotation angle of the turning-side motor <NUM> is calculated as an absolute angle. A rotation-angle-related failure is an abnormality of a device that affects the calculation of the rotation angle of the turning-side motor <NUM> by the rotation angle sensor of the turning-side motor <NUM>, the rotation detection circuits 51C, 52C, etc..

(C3) "Battery reset" shows whether battery reset has occurred. "Reset" in <FIG> shows that battery reset has occurred. The hyphens "-" in <FIG> show that battery reset has not occurred.

(C4) "TC initial state flag" shows whether the two rotation detection circuits 51C, 52C are normal. When it is determined that the two rotation detection circuits 51C, 52C are normal, the first turning control circuit 51A sets the value of the TC initial state flag to "normal. " When the value of the TC initial state flag is set to "normal," the rotation detection circuits 51C, 52C can be used. When it is determined that one of the two rotation detection circuits 51C, 52C is abnormal, the first turning control circuit 51A sets the value of the TC initial state flag to "invalid. " When the value of the TC initial state flag is set to "invalid," the rotation detection circuits 51C, 52C cannot be used. The hyphens "-" in <FIG> show that these states need not be considered.

When the value of the TC initial state flag is "normal," the first turning control circuit 51A calculates the rotation angle of the turning-side motor <NUM> as an absolute angle using the stored offset angle. When the value of the TC initial state flag is "invalid," the first turning control circuit 51A calculates the offset angle with reference to the neutral position of the turning shaft <NUM> using the detection result of the stroke sensor <NUM>. The first turning control circuit 51A calculates the rotation angle of the turning-side motor <NUM> as an absolute angle using the calculated offset angle.

(C5) "Implementation or no implementation of TC comparison" shows whether to perform a process of comparing the count values of the two rotation detection circuits 51C, 52C. "Implementation" in <FIG> shows that the process of comparing the count values of the two rotation detection circuits 51C, 52C is performed. "No implementation" in <FIG> shows that the process of comparing the count values of the two rotation detection circuits 51C, 52C is not performed.

For example, when the first turning control circuit 51A starts in the single-system mode with the second turning control circuit 52A shut down, the process of comparing the count values of the two rotation detection circuits 51C, 52C cannot be performed. In this case, an abnormality of the rotation detection circuits 51C, 52C cannot be detected. Therefore, an offset angle with reference to the neutral position of the turning shaft <NUM> is calculated using the detection result of the stroke sensor <NUM>. Using the calculated offset angle, the first turning control circuit 51A calculates the rotation angle of the turning-side motor <NUM> as an absolute angle.

In some cases, however, after the rotation angle of the turning-side motor <NUM> is calculated as an absolute angle using the stored offset angle, the second turning control circuit 52A, for example, may shut down due to a non-rotation-angle-related failure. In this case, the state of "implementation or no implementation of TC comparison" is "implementation.

(C6) "TC initial state determination result" shows whether the rotation speed of the turning-side motor <NUM> has been continuously counted by the rotation detection circuits 51C, 52C during a period in which the vehicle power source has been off. "Continuous" in <FIG> shows that counting of the rotation detection circuits 51C, 52C has been continuously performed. "Not continuous" in <FIG> shows that counting of the rotation detection circuits 51C, 52C has not been continuously performed. The hyphens "-" in <FIG> show that these states need not be considered.

For example, when battery reset occurs, the rotation detection circuits 51C, 52C cannot count the rotation speed of the turning-side motor <NUM>. Therefore, the TC initial state determination result is "not continuous. " When the TC initial state determination result is "not continuous," the accuracy of the count numbers of the rotation detection circuits 51C, 52C cannot be guaranteed. Therefore, when the TC initial state determination result is "not continuous," an offset angle with reference to the neutral position of the turning shaft <NUM> is calculated using the detection result of the stroke sensor <NUM>. Using the calculated offset angle, the first turning control circuit 51A calculates the rotation angle of the turning-side motor <NUM> as an absolute angle.

The first turning control circuit 51A calculates the rotation angle of the turning-side motor <NUM> as an absolute angle using the stored offset angle when all of the following four conditions (D1) to (D4) are met.

When at least one of the four conditions (D1) to (D4) is not met, the first turning control circuit 51A calculates an offset angle with reference to the neutral position of the turning shaft <NUM> using the detection result of the stroke sensor <NUM>. Using the calculated offset angle, the first turning control circuit 51A calculates the rotation angle of the turning-side motor <NUM> as an absolute angle.

The second turning control circuit 52A operates basically in the same manner as the first turning control circuit 51A. However, the turning control device <NUM> has the following matters of concern.

As indicated in the bottom row of <FIG>, a situation can arise where the first turning control circuit 51A, which is the master, does not start when the vehicle power source is turned on. As the first turning control circuit 51A is maintained in the state of being shut down, the second turning control circuit 52A, which is originally the slave, starts in the single-system mode, for example.

However, since the first turning control circuit 51A is shut down, an abnormality of the rotation detection circuits 51C, 52C cannot be determined. This makes it necessary for the second turning control circuit 52A to calculate the offset angle with reference to the neutral position of the turning shaft <NUM>, and further the rotation angle of the turning-side motor <NUM> as an absolute angle, using the detection result of the stroke sensor <NUM>. However, when the second turning control circuit 52A is not configured to take in the detection result of the stroke sensor <NUM>, the second turning control circuit 52A cannot calculate the offset angle and further the rotation angle of the turning-side motor <NUM> as an absolute angle. Thus, there is a concern that the second turning control circuit 52A may be unable to start.

This event may occur also when, for example, the vehicle power source is turned on in a state where a power line that supplies electricity to the first turning control circuit 51A is broken. Therefore, this embodiment employs the following configuration.

In the case where the first turning control circuit 51A that is the master does not start when the vehicle power source is turned on, the second turning control circuit 52A that is the slave compares the rotation angle of the turning-side motor <NUM> that was stored when the vehicle power source was turned off last time and the rotation angle of the turning-side motor <NUM> that is calculated from the stored offset angle.

When the absolute value of the difference between the rotation angle of the turning-side motor <NUM> that was stored when the vehicle power source was turned off last time and the rotation angle of the turning-side motor <NUM> that is calculated from the offset angle is equal to or smaller than a given threshold value, the second turning control circuit 52A determines that there is no abnormality in the rotation detection circuits 51C, 52C. In this case, the second turning control circuit 52A starts using the rotation angle of the turning-side motor <NUM> calculated from the offset angle. This is because, if control is executed based on the rotation angle of the turning-side motor <NUM> that was stored when the vehicle power source was turned off last time, differences due to detection errors of the rotation angle sensor of the turning-side motor <NUM> may be integrated.

That is, in the case where the second turning control circuit 52A that is the slave starts in the single-system mode as indicated in the bottom row of <FIG>, the second turning control circuit 52A starts by regarding the value of the TC initial state flag of the second turning control circuit 52A as "normal" when it is confirmed that there is no abnormality in the rotation detection circuits 51C, 52C.

This is based on the premise that an event that causes a change in the turning angle θw, such as jacking up the vehicle, does not occur in the normal use state of the vehicle. When the absolute value of the difference between the rotation angle of the turning-side motor <NUM> that was stored when the vehicle power source was turned off last time and the rotation angle of the turning-side motor <NUM> that is calculated from the offset angle exceeds the given threshold value, the second turning control circuit 52A determines that there may be an abnormality in the rotation detection circuits 51C, 52C. In this case, the second turning control circuit 52A does not start.

This is for the following reason: In the case where, during a period from when the vehicle power source is turned off until it is turned on again, the turning angle θw changes to such an extent that the absolute value of the difference between the rotation angle of the turning-side motor <NUM> that was stored when the vehicle power source was turned off last time and the rotation angle of the turning-side motor <NUM> that is calculated when the vehicle power source is turned on this time exceeds the threshold value, the vehicle may deflect. Deflection of the vehicle means that the vehicle that is supposed to move straight ahead deflects.

Next, a processing procedure of the second turning control circuit 52A when the vehicle power source is turned off will be described.

As shown in the flowchart of <FIG>, when the vehicle power source is turned off (IG-OFF), the second turning control circuit 52A stores the rotation angle of the turning-side motor <NUM> at that time. The rotation angle is an absolute angle. The second turning control circuit 52A determines whether the rotation angle of the turning-side motor <NUM> has been stored normally (step S101).

The second turning control circuit 52A determines that the rotation angle of the turning-side motor <NUM> has been stored normally (YES in step S101), for example, when no rotation-angle-related failure has occurred in the corresponding system before execution of the power latching control, and when no error in writing into the memory has occurred. In this case, the second turning control circuit 52A also stores that the stored rotation angle of the turning-side motor <NUM> can be used at the next start-up. After a given execution period of the power latching control has elapsed, the second turning control circuit 52A turns the power source off (step S102).

When a rotation-angle-related failure has occurred in the corresponding system before execution of the power latching control, or when an error in writing into the memory is detected, the second turning control circuit 52A determines that the rotation angle of the turning-side motor <NUM> has not been stored normally (NO in step S101). In this case, the second turning control circuit 52A also stores that the stored rotation angle of the turning-side motor <NUM> cannot be used at the next start-up (step S103). After the given execution period of the power latching control has elapsed, the second turning control circuit 52A turns the power source off (step S102).

Next, a processing procedure of the second turning control circuit 52A when the vehicle power source is turned on will be described.

As shown in the flowchart of <FIG>, when the vehicle power source is turned on (IG-ON), the second turning control circuit 52A retrieves the rotation angle of the turning-side motor <NUM> stored in the memory. The rotation angle is the rotation angle of the turning-side motor <NUM> that was stored in the memory when the vehicle power source was turned off last time. The rotation angle is an absolute angle. The second turning control circuit 52A determines whether the rotation angle of the turning-side motor <NUM> has been retrieved normally (step S201).

In the case where the rotation angle of the turning-side motor <NUM> has been retrieved normally (YES in step S201), the second turning control circuit 52A regards its own TC initial state flag (TC initial state flag of the second turning control circuit 52A) as "normal" when the driving mode thereof is the single-system driving mode. In this case, the second turning control circuit 52A calculates the rotation angle of the turning-side motor <NUM> (step S202). The second turning control circuit 52A calculates the rotation angle of the turning-side motor <NUM> as an absolute angle using the stored offset angle.

Next, when the rotation angle of the turning-side motor <NUM> having been retrieved from the memory can be used, the second turning control circuit 52A compares the rotation angle of the turning-side motor <NUM> retrieved from the memory and the rotation angle of the turning-side motor <NUM> calculated in the preceding step S202. The second turning control circuit 52A determines whether the comparison result is normal (step S203).

When the absolute value of the difference between the rotation angle of the turning-side motor <NUM> retrieved from the memory and the rotation angle of the turning-side motor <NUM> calculated in the preceding step S202 is equal to or smaller than a given threshold value, the second turning control circuit 52A determines that the comparison result is normal (YES in step S203). That the comparison result is normal also means that the second rotation detection circuits 51C, 52C are normal.

When the comparison result is normal, the second turning control circuit 52A starts executing normal control. The normal control here is control in the single-system mode. When the absolute value of the difference between the rotation angle of the turning-side motor <NUM> retrieved from the memory and the rotation angle of the turning-side motor <NUM> calculated in the preceding step S202 exceeds the given threshold value, the second turning control circuit 52A determines that the comparison result is not normal (NO in step S203). When the comparison result is not normal, the second turning control circuit 52A determines that it is not startable (S205) and ends the process. Being not startable is a state of being unable to start.

Also when the rotation angle of the turning-side motor <NUM> has not been retrieved normally (NO in step S201), the second turning control circuit 52A determines that it is not startable (S205) and ends the process.

Next, detection errors of the rotation angle sensor of the turning-side motor <NUM> will be described. Here, the following items (E1) to (E5) are assumed.

(E1) During a period in which the vehicle power source is on and a period in which the vehicle power source is off, the rotation angle of the turning-side motor <NUM> does not change from <NUM>° that is a true value. The rotation angle is an absolute angle.

(E2) The rotation detection circuits 51C, 52C are normal.

(E3) Variations of the rotation angle sensor signal at normal times is, for example, ±α°.

(E4) If the variations of the rotation angle sensor of the turning-side motor <NUM> are within an allowable range for deflection of the vehicle, the second turning control circuit 52A can start.

(E5) The allowable range for deflection of the vehicle is such a range that the rotation angle of the turning-side motor <NUM> detected through the rotation angle sensor can be determined as normal, and is, for example, ±2α°. The allowable range is set based on variations of the rotation angle that is stored in the memory when the vehicle power source is turned off and variations of the rotation angle that is calculated when the vehicle power source is turned on next time.

The following three cases F1 to F3 will be considered.

N-th time of turning on of vehicle power source.

As shown in <FIG>, when the rotation angle of the turning-side motor <NUM> stored in the memory is <NUM>° that is a true value and the rotation angle of the turning-side motor <NUM> calculated at start-up is α°, the calculated rotation angle of the turning-side motor <NUM> is within the allowable range for deflection of the vehicle, specifically, a value that is "not smaller than -2α° and not larger than 2α°. " Therefore, the second turning control circuit 52A can start.

N+<NUM>-th time of turning on of vehicle power source.

As shown in <FIG>, when the rotation angle of the turning-side motor <NUM> stored in the memory is α° and the rotation angle of the turning-side motor <NUM> calculated at start-up is -α°, the rotation angle of the turning-side motor <NUM> is within the allowable range for deflection of the vehicle, specifically, a value that is "not smaller than -α° and not larger than 3α°. " Therefore, the second turning control circuit 52A can start.

N+<NUM>-th time of turning on of vehicle power source.

As shown in <FIG>, when the rotation angle of the turning-side motor <NUM> stored in the memory is α° and the rotation angle of the turning-side motor <NUM> calculated at start-up is α°, the rotation angle of the turning-side motor <NUM> is within the allowable range for deflection of the vehicle, specifically, a value that is "not smaller than -3α° and not larger than α°. " Therefore, the second turning control circuit 52A can start.

Thus, errors in detecting the rotation angle of the turning-side motor <NUM> do not build up even when a maximum error occurs for the rotation angle of the turning-side motor <NUM> that is stored in the memory when the vehicle power source is turned off and the rotation angle of the turning-side motor <NUM> that is calculated when the vehicle power source is turned on next time.

The first embodiment offers the following advantages.

(<NUM>-<NUM>) The second turning control circuit 52A is configured to start when the vehicle power source is turned on and the absolute value of the difference between the absolute rotation angle of the turning-side motor <NUM> that was stored when the vehicle power source was turned off last time and the absolute rotation angle of the turning-side motor <NUM> that is calculated when the vehicle power source is turned on this time is equal to or smaller than the given threshold value, regardless of whether it is detected that an abnormality has occurred in one of the two rotation detection circuits 51C, 52C or an abnormality of the two rotation detection circuits 51C, 52C is not determinable.

When the absolute value of the difference between the absolute rotation angle of the turning-side motor <NUM> that was stored when the vehicle power source was turned off and the absolute rotation angle of the turning-side motor <NUM> that is calculated when the vehicle power source is turned on this time is equal to or smaller than the given threshold value, the rotation detection circuits 51C, 52C can be said to be normal. That is, in the case where the first turning control circuit 51A that is the master does not start when the vehicle power source is turned on, unless the turning angle θw has changed due to an external force being applied during parking or other causes, the second turning control circuit 52A that is the slave can start appropriately. Driving of the motor is controlled by the second turning control circuit 52A.

The first turning control circuit 51A may be configured to operate in the same manner as the second turning control circuit 52A.

(<NUM>-<NUM>) The steering system <NUM> has the stroke sensor <NUM> that detects the absolute position of the turning shaft <NUM> in the axial direction. When the vehicle power source is turned on and it is detected that an abnormality has occurred in one of the two rotation detection circuits 51C, 52C or an abnormality of the two rotation detection circuits 51C, 52C is not determinable, the first turning control circuit 51A can calculate the absolute rotation angle of the turning-side motor <NUM> using the detection result of the stroke sensor <NUM>.

(<NUM>-<NUM>) In the case where the first turning control circuit 51A that is the master does not start when the vehicle power source is turned on, when it is confirmed that there is no abnormality in the rotation detection circuits 51C, 52C, the second turning control circuit 52A can start using the rotation angle of the turning-side motor <NUM> stored in the memory.

(<NUM>-<NUM>) The turning-side motor <NUM> is required to start as far as possible, even with a single system. This requirement can be met.

Next, a second embodiment in which the vehicle control device is embodied in an electric power steering system will be described. Those members that are the same as in the first embodiment will be denoted by the same reference signs and detailed description thereof will be omitted.

The electric power steering system has the steering wheel <NUM> and the turning wheels <NUM> shown in <FIG> described earlier that are mechanically coupled to each other. That is, the steering shaft <NUM>, the pinion shaft <NUM>, and the turning shaft <NUM> function as a power transmission path between the steering wheel <NUM> and the turning wheels <NUM>. As the steering wheel <NUM> is steered, the turning shaft <NUM> moves linearly, causing a change in the turning angle θw of the turning wheels <NUM>.

The electric power steering system has an assist motor and an assistance control device. The assist motor is provided at the same position as the reaction force motor <NUM> or the turning-side motor <NUM> shown in <FIG> described earlier. The assist motor generates an assistive force for assisting the operation of the steering wheel <NUM>. The assistive force is a torque in the same direction as the steering direction of the steering wheel <NUM>. The assistance control device controls driving of the assist motor that is a control target.

As shown in <FIG>, an assist motor <NUM> has a winding set N31 of a first system and a winding set N32 of a second system. An assistance control device <NUM> has a first system circuit <NUM>. The first system circuit <NUM> has a first assistance control circuit 81A and a motor driving circuit 81B. The first assistance control circuit 81A controls power supply to the winding set N31 of the first system. The first assistance control circuit 81A generates a driving signal to the motor driving circuit 81B based on the steering torque Th detected through the torque sensor <NUM>.

The motor driving circuit 81B converts the direct-current power supplied from the direct-current power source <NUM> into three-phase alternating-current power based on the driving signal generated by the first assistance control circuit 81A. The three-phase alternating-current power generated by the motor driving circuit 81B is supplied to the winding set N31 of the first system of the assist motor <NUM> through a power supply path of each phase formed by a busbar, a cable, or the like.

The assistance control device <NUM> has a second system circuit <NUM>. The second system circuit <NUM> has a second assistance control circuit 82A and a motor driving circuit 82B. The second assistance control circuit 82A controls power supply to the winding set N32 of the second system. The second assistance control circuit 82A generates a driving signal to the motor driving circuit 82B based on the steering torque Th detected through the torque sensor <NUM>.

The motor driving circuit 82B converts the direct-current power supplied from the direct-current power source <NUM> into three-phase alternating-current power based on the driving signal generated by the second assistance control circuit 82A. The three-phase alternating-current power generated by the motor driving circuit 82B is supplied to the winding set N32 of the second system of the assist motor <NUM> through a power supply path of each phase formed by a busbar, a cable, or the like.

The first assistance control circuit 81A and the second assistance control circuit 82A exchange pieces of information with each other through a communication line. These pieces of information include information on an abnormality of the first assistance control circuit 81A, the second assistance control circuit 82A, or the motor driving circuits 81B, 82B. These pieces of information also include values of various flags. The first assistance control circuit 81A and the second assistance control circuit 82A control driving of the assist motor <NUM> by collaborating with each other based on the pieces of information exchanged therebetween.

The first assistance control circuit 81A has basically the same configuration as the first turning control circuit 51A shown in <FIG> described earlier. The second assistance control circuit 82A has basically the same configuration as the second turning control circuit 52A shown in <FIG> described earlier. As with the control circuits (41A, 42A, 51A, 52A) in the first embodiment, the first assistance control circuit 81A and the second assistance control circuit 82A control driving of the assist motor <NUM> in one of a collaborative driving mode, an independent driving mode, and a single-system driving mode.

There is a master-slave relationship between the first system circuit <NUM> and the second system circuit <NUM> of the assistance control device <NUM>. In this case, for example, the first system circuit <NUM> functions as the master and the second system circuit <NUM> functions as the slave.

In the case where the first assistance control circuit 81A that is the master does not start when the vehicle power source is turned on, the second assistance control circuit 82A that is the slave performs the same operation as the second turning control circuit 52A in the first embodiment.

The second assistance control circuit 82A compares the rotation angle of the assist motor <NUM> that was stored when the vehicle power source was turned off last time and the rotation angle of the assist motor <NUM> that is calculated from the stored offset angle.

When the absolute value of the difference between the rotation angle of the assist motor <NUM> that was stored when the vehicle power source was turned off last time and the rotation angle of the assist motor <NUM> that is calculated from the offset angle is equal to or smaller than a given threshold value, the second assistance control circuit 82A determines that there is no abnormality in the rotation detection circuits 51C, 52C. In this case, the second assistance control circuit 82A starts using the rotation angle of the assist motor <NUM> calculated from the offset angle.

That is, as indicated in the bottom row of <FIG>, in the case where the second assistance control circuit 82A that is the slave starts in the single-system mode, when it is confirmed that there is no abnormality in the rotation detection circuits 51C, 52C, the second assistance control circuit 82A starts by regarding the value of the TC initial state flag of the second assistance control circuit 82A as "normal.

When the difference between the rotation angle of the assist motor <NUM> that was stored when the vehicle power source was turned off last time and the rotation angle of the assist motor <NUM> that is calculated from the offset angle exceeds the given threshold value, the second assistance control circuit 82A determines that there may be an abnormality in the rotation detection circuits 51C, 52C. In this case, the second assistance control circuit 82A does not start.

Thus, the second embodiment offers the following advantage in addition to the advantages described in (<NUM>-<NUM>) to (<NUM>-<NUM>) of the first embodiment.

Claim 1:
A vehicle control device comprising:
dual-system control circuits that control power supply to dual-system winding sets (N21, N22; N31, N32) of a motor having the winding sets (N21, N22; N31, N32), for each system independently; and
dual-system rotation detection circuits each of which detects a rotation speed of the motor,
the control circuits each being configured to calculate an absolute rotation angle of the motor using the rotation speed of the motor, and each of the control circuits is configured to, when a power source is turned off, store an absolute rotation angle of the motor at that time and, when the power source is turned on, start after confirming that both of the dual-system rotation detection circuits are normal,
wherein at least one of the control circuits is configured to start when the power source is turned on and an absolute value of a difference between an absolute rotation angle of the motor that was stored when the power source was turned off last time and an absolute rotation angle of the motor that is calculated when the power source is turned on this time is equal to or smaller than a given threshold value, regardless of whether it is detected that an abnormality has occurred in one of the dual-system rotation detection circuits or an abnormality of the dual-system rotation detection circuits is not determinable.