Patent ID: 8142371

Claim:
A walking assist device comprising: a lifting force transmitting portion which is put in contact with the trunk of a user so as to allow an upward lifting force to be applied to the trunk of the user; a pair of left and right foot attachment portions fitted to the feet of the legs of the user; and a pair of left and right leg links connecting the foot attachment portions to the lifting force transmitting portion, respectively, each of the leg links including a thigh frame extending from the lifting force transmitting portion via a first joint, a crus frame extending from each foot attachment portion via a second joint, and a third joint that interconnects the thigh frame and the crus frame so that the frames freely bend and stretch and each of the leg links being provided with a rotary actuator mounted on the thigh frame and with a power transmission system which transmits a driving force of the rotary actuator to the third joint to apply a driving torque around a joint axis of the third joint thereto, wherein the power transmission system includes a driving crank arm fixed coaxially with an output shaft of the rotary actuator, a driven crank arm fixed to the crus frame coaxially with the joint axis of the third joint, and a connecting rod pivotally attached to the driving crank arm and to the driven crank arm at one end and the other end; and wherein each of the leg links includes: a rod transmitting force measuring means which measures a rod transmitting force, which is a translational force acting on the connecting rod in a longitudinal direction thereof according to the driving force of the rotary actuator, on the basis of an output of a rod transmitting force measurement force sensor fixed to the connecting rod; a controlled variable desired value setting means which sets a controlled variable desired value that is a desired value of a controlled variable requested to control the lifting force to a desired lifting force, where the controlled variable is one of the rod transmitting force and the driving torque applied to the third joint by the rod transmitting force; and an actuator control means which feedback-controls the driving force of the rotary actuator according to a value of the rod transmitting force measured by the rod transmitting force measuring means and the set controlled variable desired value so that the controlled variable coincides with the controlled variable desired value set by the controlled variable desired value setting means.