Electric power steering controller and control method

An electric power steering controller for a vehicle for assisting steering torque of a driver applied to a steering wheel, comprising:

• a motor for generating an assistant torque to assist steering torque of a driver, speed detecting means for detecting a speed of the vehicle,
• steering torque detecting means for detecting the steering torque of a driver,
• steering angle detecting means for detecting a steering angle of the steering wheel,
• acceleration detecting means for detecting acceleration of said motor,
• current detecting means for detecting current of said motor,
• first reaction torque estimating means for estimating a first road surface reaction torque obtained by passing a signal through a low pass filter, wherein the signal is computed from the steering torque detected by the steering torque detecting means, the acceleration of said motor detected by said acceleration detecting means, and the current of said motor detected by said current detecting means,
• second reaction torque estimating means for estimating a second road surface reaction torque using the speed of the vehicle detected by said speed detecting means, and the steering angle detected by said steering angle detecting means, and
• return torque compensating means for computing a first auxiliary return torque signal to control the assistant torque of said motor depending on the first road surface reaction torque estimated by said first reaction torque estimating means, and for computing a second auxiliary return torque signal to control the assistant torque of said motor depending on the second road surface reaction torque estimated by said second reaction torque estimating means, wherein said return torque compensating means controls the assistant torque of said motor in a direction for the steering wheel to return to an original position using both of the first and second auxiliary return torque signals.

An electric power steering controller for assisting a steering torque of a driver applied to a steering wheel, comprising:

• a motor for generating an assistant torque to assist steering torque of a driver,
• steering torque detecting means for detecting the steering torque of a driver,
• steering angle detecting means for detecting a steering angle of the steering wheel,
• reaction torque estimating means for estimating a road surface reaction torque using the steering torque detected by said steering torque detecting means, and
• return torque compensating means for computing a first auxiliary return torque signal to control the assistant torque of said motor depending on the road surface reaction torque estimated by said reaction torque estimating means, and for computing a second auxiliary return torque signal to control the assistant torque of said motor depending on the steering angle detected by said steering angle detecting means, wherein said return torque compensating means controls an auxiliary torque of said motor in a direction for the steering wheel to return to an original position, using both of the first and second auxiliary return torque signals.

An electric power steering controller for a vehicle to assist a steering torque applied by a driver to a steering wheel, comprising:

• a motor for generating an assistant torque to assist steering torque of a driver,
• speed detecting means for detecting speed of the vehicle,
• steering torque detecting means for detecting the steering torque of a driver,
• steering angle detecting means for detecting a steering angle of the steering wheel,
• acceleration detecting means for detecting acceleration of said motor,
• current detecting means for detecting a current of said motor,
• reaction torque estimating means for estimating a road surface reaction torque obtained by passing a signal through a low pass filter, wherein the signal is computed from the steering torque detected by said steering torque detecting means, the acceleration of said motor detected by said acceleration detecting means, and the current of said motor detected by said current detecting means, and
• return torque compensating means for computing a first auxiliary return torque signal to control the assistant torque of said motor depending on the road surface reaction torque estimated by said reaction torque estimating means, and for computing a second auxiliary return torque signal to control the assistant torque of said motor depending on the speed of the vehicle detected by said speed detecting means, and the steering angle detected by said steering angle detecting means, wherein said return torque compensating means controls the assistant torque of said motor in the direction for the steering wheel to return to an original position, using both the first and second auxiliary return torque signals.

An electric power steering control method for vehicle to assist a steering torque applied by a driver to a steering wheel by using a motor generated torque, comprising:

• estimating a first road surface reaction torque from a steering torque,
• estimating a second road surface reaction torque from a steering angle,
• computing a first auxiliary return torque signal from the first road surface reaction torque,
• computing a second auxiliary return torque signal from the second road surface reaction torque, and
• controlling the assistant torque of the motor depending on the first and second auxiliary return torque signals so the steering wheel returns to an original position.