Electric power steering device

An electric power steering device comprising a control device configured to calculate a current command value on the basis of steering torque given through an operation of a steering shaft and to calculate a voltage command value on the basis of the current command value, a power converter configured to supply a motor with power converted on the basis of the voltage command value outputted from the control device, and a current detector configured to detect current supplied to the motor, the electric power steering device being configured to generate assist torque to the steering shaft by driving of the motor, wherein

• the control device includes
• a q-axis current command value calculation circuitry and a d-axis current command value calculation circuitry configured to calculate the current command value,
• a motor control signal calculation circuitry configured to calculate the voltage command value on the basis of a q-axis current command value calculated by the q-axis current command value calculation circuitry and a d-axis current command value calculated by the d-axis current command value calculation circuitry, and
• a control steering angle calculation circuitry configured to calculate a steering angle of the steering shaft on the basis of a rotation position of the motor,
• the q-axis current command value calculation circuitry includes
• a base current command value calculation circuitry configured to calculate a base q-axis current command value as a reference, on the basis of the steering torque,
• a q-axis current limitation value calculation circuitry configured to calculate a q-axis current limitation value such that, in a case where an absolute value of the steering angle calculated by the control steering angle calculation circuitry is equal to or greater than a predetermined first steering angle threshold, the q-axis current limitation value decreases with increase in the absolute value of the steering angle, and
• a q-axis current guard processing circuitry configured to receive the base q-axis current command value calculated by the base current command value calculation circuitry and the q-axis current limitation value calculated by the q-axis current limitation value calculation circuitry,
• the q-axis current guard processing circuitry is configured to, in a case where the steering angle is equal to or greater than the first steering angle threshold and the base q-axis current command value is greater than the q-axis current limitation value, set the q-axis current command value on the basis of the q-axis current limitation value instead of the base q-axis current command value,
• the q-axis current guard processing circuitry is configured to, in a case where the steering angle is equal to or smaller than −1×the first steering angle threshold and the base q-axis current command value is smaller than −1×the q-axis current limitation value, set the q-axis current command value on the basis of −1×the q-axis current limitation value instead of the base q-axis current command value,
• the q-axis current guard processing circuitry is configured to output the q-axis current command value to the motor control signal calculation circuitry, and
• the motor control signal calculation circuitry includes
• a feedback control circuitry configured to acquire actual q-axis current and actual d-axis current by converting the current detected by the current detector, and to calculate a reference voltage command value as a reference for causing the actual q-axis current and the actual d-axis current to respectively follow the q-axis current command value inputted from the q-axis current command value calculation circuitry and the d-axis current command value inputted from the d-axis current command value calculation circuitry,
• a voltage limitation value calculation circuitry configured to calculate a voltage limitation value such that, in a case where the absolute value of the steering angle calculated by the control steering angle calculation circuitry is equal to or greater than a predetermined second steering angle threshold smaller than the first steering angle threshold and a product of the steering angle and an angular velocity of the steering shaft is positive, the voltage limitation value decreases with increase in the absolute value of the steering angle, and in a case where the absolute value of the steering angle is smaller than the second steering angle threshold or the product of the steering angle and the angular velocity of the steering shaft is equal to or smaller than 0, the voltage limitation value becomes equal to or greater than maximum voltage that the motor can output,
• a voltage guard processing circuitry configured to receive the reference voltage command value calculated by the feedback control circuitry and the voltage limitation value calculated by the voltage limitation value calculation circuitry, and to output the voltage command value so that an absolute value of the voltage command value does not exceed the voltage limitation value, and
• wherein the control device further comprises one or more processors configured to implement the q-axis current command value calculation circuitry, the d-axis current command value calculation circuitry, the motor control signal calculation circuitry and the control steering angle calculation circuitry.

An electric power steering device comprising a control device configured to calculate a current command value on the basis of steering torque given through an operation of a steering shaft and to calculate a voltage command value on the basis of the current command value, a power converter configured to supply a motor with power converted on the basis of the voltage command value outputted from the control device, and a current detector configured to detect current supplied to the motor, the electric power steering device being configured to generate assist torque to the steering shaft by driving of the motor, wherein

• the control device includes
• a q-axis current command value calculation circuitry and a d-axis current command value calculation circuitry configured to calculate the current command value,
• a motor control signal calculation circuitry configured to calculate the voltage command value on the basis of a q-axis current command value calculated by the q-axis current command value calculation circuitry and a d-axis current command value calculated by the d-axis current command value calculation circuitry, and
• a control steering angle calculation circuitry configured to calculate a steering angle of the steering shaft on the basis of a rotation position of the motor,
• the q-axis current command value calculation circuitry includes
• a base current command value calculation circuitry configured to calculate a base q-axis current command value as a reference, on the basis of the steering torque,
• a q-axis current limitation value calculation circuitry configured to calculate a q-axis current limitation value such that, in a case where an absolute value of the steering angle calculated by the control steering angle calculation circuitry is equal to or greater than a predetermined first steering angle threshold, the q-axis current limitation value decreases with increase in the absolute value of the steering angle, and
• a q-axis current guard processing circuitry configured to receive the base q-axis current command value calculated by the base current command value calculation circuitry and the q-axis current limitation value calculated by the q-axis current limitation value calculation circuitry,
• the q-axis current guard processing circuitry is configured to, in a case where the steering angle is equal to or greater than the first steering angle threshold and the base q-axis current command value is greater than the q-axis current limitation value, set the q-axis current command value on the basis of the q-axis current limitation value instead of the base q-axis current command value,
• the q-axis current guard processing circuitry is configured to, in a case where the steering angle is equal to or smaller than −1×the first steering angle threshold and the base q-axis current command value is smaller than −1×the q-axis current limitation value, set the q-axis current command value on the basis of −1×the q-axis current limitation value instead of the base q-axis current command value,
• the q-axis current guard processing circuitry is configured to output the q-axis current command value to the motor control signal calculation circuitry,
• the motor control signal calculation circuitry includes
• a feedback control circuitry configured to acquire actual q-axis current and actual d-axis current by converting the current detected by the current detection circuitry, and to calculate a reference voltage command value as a reference for causing the actual q-axis current and the actual d-axis current to respectively follow the q-axis current command value inputted from the q-axis current command value calculation circuitry and the d-axis current command value inputted from the d-axis current command value calculation circuitry,
• a voltage limitation value calculation circuitry configured to calculate a voltage limitation value such that, in a case where the absolute value of the steering angle calculated by the control steering angle calculation circuitry is equal to or greater than a predetermined second steering angle threshold smaller than the first steering angle threshold, the voltage limitation value decreases with increase in the absolute value of the steering angle, and
• a voltage guard processing circuitry configured to receive the reference voltage command value calculated by the feedback control circuitry and the voltage limitation value calculated by the voltage limitation value calculation circuitry,
• the voltage guard processing circuitry is configured to, in a case where the steering angle is equal to or greater than the second steering angle threshold and the reference voltage command value is greater than the voltage limitation value, output, as the voltage command value, the voltage limitation value instead of the reference voltage command value,
• the voltage guard processing circuitry is configured to, in a case where the steering angle is equal to or smaller than −1×the second steering angle threshold and the reference voltage command value is smaller than −1×the voltage limitation value, output, as the voltage command value, −1×the voltage limitation value instead of the reference voltage command value, and
• wherein the control device further comprises one or more processors configured to implement the q-axis current command value calculation circuitry, the d-axis current command value calculation circuitry, the motor control signal calculation circuitry and the control steering angle calculation circuitry.