Design and characterization of a compliant-joint robotic jumping leg

Abstract

Biological systems employ compliant joints to allow robust contact with the surroundings and to increase locomotive efficiency. In this experiment, we designed a three-link robotic leg with a compliant calf tendon that was acutated by a DC motor at the hip and measured the effect of compliance on the force profile and energy consumption for a single jump. The lengths of the femur, tibia, and foot were 150 mm, 210 mm, and 60 mm respectively. Overall vertical leg stiffness was varied from 472 N/m to 3980 N/m. Using a 40 degree angle ramp for the motor acutation profile, adding compliance tended to distribute force over time at a smaller magnitude which resulted in longer contact time with the ground. Total impulse was found to vary and peaked at a value of 3.42 Ns for a overall leg stiffness of 1180 N/m. The findings suggest that these systems can be optimized for performance by tuning the stiffness of compliant joints.