Modeling and Simulation of an Elastic Passive Joint for Non-flipping Jumping Robot

To enhance the environmental adaptability of small-sized robots, jumping is commonly employed to achieve high mobility and obstacle-clearing capabilities. However, the prevalent problem of flipping in jumping robots limits their practical applications. Instead of adding extra control mechanisms and actuators, we propose an elastic passive joint (EPJ) to mitigate flipping. By incorporating a revolute joint, a switch, and a spring at the base of the hindleg, the leg can rotate around the body during the take-off phase, with the spring absorbing angular kinetic energy to reduce excessive angular velocity. We conducted dynamic modeling and a series of simulations to optimize the EPJ's position and stiffness. The simulation results indicate that with the EPJ in operation, adjusting the axis position slightly results in a zero-point for angular velocity. Additionally, the optimal spring stiffness of 1566 N/m ensures a non-flipping jump, which decreases the jumping height but improves the jumping distance.