Energy-recoverable landing strategy for small-scale jumping robots

Small-scale jumping robots widely employ the pause-and-leap locomotion strategy. They use elastic elements to enhance the jumping performance, which is promising for locomotion over rugged terrain. However, these robots typically lose a significant amount of mechanical energy during landing, which is initially accumulated for takeoff, resulting in wasted energy. Here, we propose a landing strategy that uses a jumping mechanism with controlled mono-stable or bi-stable characteristics to achieve the energy recoverable landing. By adjusting the jumping mechanism to an appropriate bi-stable state before landing, the robot's extended leg retracts to its pre-jump configuration upon touchdown, enabling the recapture of mechanical energy within the springs. We develop analytical models for the touchdown collision and landing dynamics. A 165 g robot prototype is constructed, featuring integrated sensing, actuation, and computations. Both simulations and experiments are conducted to explore the effects of various factors on the landing behavior. Experiments demonstrate successful landings with energy recovery ratio exceeding 50% across different landing trajectories. This landing strategy holds significant potential for enhancing the locomotion efficiency of future small-scale jumping robots.