Walking of Biped Robot with Variable Stiffness at the Ankle Joint Achieving versatile and efficient walking on biped robots is an important research objective. The impact between the foot and the ground has significant effects on the walking stability of biped robots. Research on human walking indicates that the joints in human lower limbs show different stiffness values in different phases of walking. Inspired by humans, this paper presents the realization of biped robot walking with variable stiffness at the ankle joint. A walking control scheme which combines PD control and variable impedance control is designed for the biped robot. Results of dynamic walking simulation verified that variable stiffness at the ankle joint could contribute to the improvement of walking stability and energy efficiency.

Toward a Bipedal Robot with Variable Gait Styles: Sagittal Forces Analysis in a Planar Simulation and a Prototype BallTray Mechanism Variable walking styles in bipedal robots may be used to communicate information about purpose andor personality to human viewers and may also help accommodate features of the environment. This paper presents variable gait in a simulation and results from a hardware prototype for gravitydriven rolling ball mechanism in a previously proposed bipedal design. First, optimal control inputs that produce a range of variable feasible gaits is generated on a simplified underactuated planar model. Then, a traylike mechanism that provides a curved path for a ball to roll on is presented. This mechanism is designed to replicate a notion of pelvic shift, described in Bartenieff Fundamentals, with movement of the ball (which is shaped by the tray) creating a shift of weight. Analysis of two gait styles and two tray designs shows comparable ranges of forces in the direction of travel between the simulated planar model and the hardware mechanism. This work is an important first step in generating feasible, stable and variablexe2x80x93 bipedal gaits using this hardware design.