On a Three-Link Model of the Dynamics of Standing up and Sitting down

Motion of a biped in the sagittal plane is represented by a three-link planar model with torque actuators at every joint. With this model a method is proposed by which postural stability and four motions of the biped can be realized: sitting down, standing up, bending, and squatting. The method is used to derive open loop and feedback torques. Open loop torques are derived from the records of a man performing each of these four motions. The feedback torques are derived as linear sums of the sensed angles and angular rates. This work is relevant to estimating internal feedback gains in the human body solely from remote and external measurements.