Patent ID: 8903609

Claim:
A hybrid motor driven power steering system for a commercial vehicle comprising: a Motor Driven Power Steering (MDPS) unit configured to generate motor output torque corresponding to a portion of detected driver torque, wherein the MDPS unit is mounted to a steering column connecting a steering wheel; an Electro-Hydraulic Power Steering (EHPS) unit configured to generate hydraulic output torque, to create, together with the motor output torque of the MDPS unit, an output required for steering the commercial vehicle; a ball nut type gear box configured to include a hydraulic cylinder having a large hydraulic area and a ball nut to generate real output torque of a piston using hydraulic pressure supplied from the EHPS unit; a link configured to be operated by the output torque generated at the ball nut type gear box to operate a tie rod connected to left and right wheels; and two torsion bars configured to be respectively installed in at least two different positions of the steering column to detect a road surface reaction force which is introduced to the ball nut type gear box and transferred to the steering wheel.