Electric motor drive apparatus and electric power steering apparatus having the same

1. An electric motor drive apparatus, which drives an electric motor having a plurality of winding sets, comprising:

a plurality of inverter sections, each of which is arranged corresponding to one of the winding sets, a unit including each of the inverter sections and corresponding one of the winding sets being referred to as a system;

a plurality of relays, each of which controls a power supply to one of the inverter sections; and

a control unit that controls the inverter sections and the relays,

wherein the control unit includes:

an obtaining section that obtains a winding current that flows through each of the systems;

a determination section that determines whether a fault occurs in the systems based on the winding current flowing through each of the systems;

a specifying section that specifies one of the systems in which the fault occurs as a faulty system when the determination section determines that the fault occurs in the systems, one of the systems other than the faulty system being referred to as a properly-operating system;

an interrupting section that controls one of the relays corresponding to the faulty system to interrupt the power supply to the faulty system; and

a vibrating section that controls the inverter section of the properly-operating system to add a vibration to an output torque from the electric motor after the determination section determines that the fault occurs in the faulty system, the vibrating section gradually increases a vibration component of the vibration added to the output torque from the electric motor.

2. The electric motor drive apparatus according to claim 1 ,

wherein each of the inverter sections is driven based on a current command value,

wherein the vibrating section adds a predetermined current to the current command value of the inverter section of the properly-operating system so that the vibration is added to the output torque, and

wherein the predetermined current added to the current command value of the inverter section of the properly-operating system corresponds to the vibration component of the vibration added to the output torque.

3. The electric motor drive apparatus according to claim 1 ,

wherein the vibration component of the vibration added to the output torque is set based on an elapsed time after the fault occurs in the faulty system.

4. The electric motor drive apparatus according to claim 1 ,

wherein the vibration component of the vibration added to the output torque is set based on the number of operation times of an ignition switch of a vehicle after the fault occurs in the faulty system.

5. The electric motor drive apparatus according to claim 1 ,

wherein the vibration component of the vibration added to the output torque is set based on a travel distance of a vehicle after the fault occurs in the faulty system.

6. The electric motor drive apparatus according to claim 5 ,

wherein the travel distance is estimated based on a speed of the vehicle.

7. The electric motor drive apparatus according to claim 1 ,

wherein the motor performs a steering assist for a driver of a vehicle, and

wherein the vibrating section controls the inverter section of the properly-operating system to skip an adding of the vibration to the output torque when an absolute value of a steering torque, which is applied to a steering wheel of the vehicle by the driver, is smaller than a predetermined value.

8. An electric power steering apparatus comprising

the electric motor drive apparatus according to claim 1 .