Low energy body design and nonlinear control of balance in a one legged robot

Postural control of a two degree of freedom hopping robot with a novel balancing mechanism is revisited. The balancing mechanism is a concave downward-swinging body whose center of gravity lies below the hip joint. It is shown that at a specific body curvature, the linearized system is transformed from non-minimum to minimum phase, the conditions for feedback linearization of the nonlinear model satisfied and minimal mechanical power required for stability during stance observed. Control of the nonlinear postural dynamics is then attempted using feedback linearization and its performance in achieving our control objective is compared against that of a linear quadratic regulator.