Fig. 2

Sit-down controller. Left: Prosthesis knee torque was controlled as a function of prosthesis knee position. A triangle-shaped profile was prescribed (yellow), and damping torque was added (blue). Right: prosthesis ankle equilibrium position was controlled as a function of prosthesis knee position (yellow). The equilibrium position was used in an impedance controller that added damping and stiffness around the equilibrium position, resulting in the prosthesis ankle position (blue). The start of the movement (standing) is indicated with circles, and the end of the movement (sitting) is indicated with squares. Black arrows indicate the progression of the movement