A control unit functionally comprises a first steering-torque application control part which commands a steering actuator of a vehicle to execute application of a steering torque determined by a first steering characteristic CH1 and a second steering-torque application control part which commands the steering actuator of the vehicle to execute application of a steering torque determined by a second steering characteristic CH2. In a case where the vehicle travels at a curved portion of the lane, the first steering characteristic CH1 is set such that a first steering-force increase part L1 is located further toward an allowed right-end point E.sub.GR as a vehicle speed becomes higher and the second steering characteristic CH2 is set such that a magnitude of a torque maintenance part L4 becomes lower as a radius of curvature of the curved portion of the lane becomes smaller, like CH2H-CH2L.

An auxiliary power supply device includes a parasitic diode forming a parallel circuit together with a second switching element and connected in a forward direction to a main power supply, and a parasitic diode forming a parallel circuit together with a fourth switching element and connected in a reverse direction to an auxiliary power supply. When a state parameter indicates that a reaction force that interferes with operation of an assist motor is applied, an electronic control unit turns ON a first switching element, turns OFF the second switching element, turns ON a third switching element, and turns OFF the fourth switching element. A regenerative current from the assist motor flows to the auxiliary power supply via an inverter, the third switching element, and the parasitic diode.

An auxiliary power supply device includes a parasitic diode forming a parallel circuit together with a second switching element and connected in a forward direction to a main power supply, and a parasitic diode forming a parallel circuit together with a fourth switching element and connected in a reverse direction to an auxiliary power supply. When a state parameter indicates that a reaction force that interferes with operation of an assist motor is applied, an electronic control unit turns ON a first switching element, turns OFF the second switching element, turns ON a third switching element, and turns OFF the fourth switching element. A regenerative current from the assist motor flows to the auxiliary power supply via an inverter, the third switching element, and the parasitic diode.

A controller controls a steering motor in accordance with a pinion angle command value calculated in response to a steering state. The steering motor produces a driving force to a steering operation mechanism. The controller calculates a target pinion angle in accordance with the steering state and the pinion angle command value by performing feedback control such that an actual pinion angle corresponds to the target pinion angle. The controller includes a compensation control circuit which calculates compensation amounts reflected in the pinion angle command value so as to compensate for an inertia component, a viscosity component, and a spring component of the steering operation mechanism in accordance with the target pinion angle. The compensation control circuit adds the compensation amounts to the target pinion angle so as to calculate the final target pinion angle to be used for the calculation of the pinion angle command value.

Methods and systems are provided for a vehicle adapted to be operated based on fuel combustion or electric power. In one example, an accessory train of the vehicle, including an air conditioning pump and a power steering pump, may be operated according to a first mode or according to a second mode based on a power system of the vehicle. When in the second mode, the vehicle may be instructed to coordinate operation of the air conditioning pump and the power steering pump.

Methods and systems are provided for a vehicle adapted to be operated based on fuel combustion or electric power. In one example, an accessory train of the vehicle, including an air conditioning pump and a power steering pump, may be operated according to a first mode or according to a second mode based on a power system of the vehicle. When in the second mode, the vehicle may be instructed to coordinate operation of the air conditioning pump and the power steering pump.

An input torque fundamental component computation circuit includes: a torque command value computation circuit that computes a torque command value corresponding to a target value for steering torque that is to be input by a driver for drive torque obtained by adding the steering torque to an input torque fundamental component; and a torque F/B control circuit that computes the input torque fundamental component through execution of torque feedback control for causing the steering torque to follow the torque command value. A target steering angle computation circuit computes a target steering angle on the basis of the input torque fundamental component. A steering-side control circuit computes target reaction force torque on the basis of execution of angle feedback control for causing a steering angle to follow a target steering angle. The torque command value computation circuit computes the torque command value in consideration of the grip state amount.

An input torque fundamental component computation circuit includes: a torque command value computation circuit that computes a torque command value corresponding to a target value for steering torque that is to be input by a driver for drive torque obtained by adding the steering torque to an input torque fundamental component; and a torque F/B control circuit that computes the input torque fundamental component through execution of torque feedback control for causing the steering torque to follow the torque command value. A target steering angle computation circuit computes a target steering angle on the basis of the input torque fundamental component. A steering-side control circuit computes target reaction force torque on the basis of execution of angle feedback control for causing a steering angle to follow a target steering angle. The torque command value computation circuit computes the torque command value in consideration of the grip state amount.

A technique for reducing an operation noise even when a high-pass filter is used for controlling a motor is provided. A controller is used in a motor control system for driving a motor by using a drive circuit and an inverter. The controller includes a current control block. The controller performs feedforward control by using a current value, compensates for a term of a self-inductance of the motor included in a current control block by an inverse model, compensates for a phase characteristic of a transfer function of the inverse model by an advance component, and corrects a gain characteristic of the transfer function of the inverse model by a function of a physical quantity obtained based on an angular velocity of the motor, thereby compensating for a phase delay and a gain reduction of a torque output generated by the self-inductance.

An electric power steering apparatus includes a function to switch a control system of the motor between a torque control system of a torque system to control a motor output torque and a position and speed control system of a steering angle system to control a steering angle of a steering in accordance with an ON/OFF of a post-diagnosis automatic steering command being a judgment result of an automatic steering execution judging section; and a characteristic calculating section to calculate a fade gain signal F1 that applies a first fade characteristic of the torque system, a fade gain signal F2 that applies a second fade characteristic of the steering angle system, and a fade gain signal F3 that applies a third fade characteristic of the steering angle speed, sensitive to the steering torque.