Hybrid Control Strategies for Jumping Robots

The paper treats the control problem of the locomotion phases in a jumping cycle of a robot. The mechanical architecture of the leg with elastic lower segment (ATHLETE MODEL) is discussed. The dynamic model of the motion in stance phase is determined. The touch-down sequence, when the elastic foot hits the ground, is discussed and the control system is analyzed for two cases: actuator as passive damper system and actuator as semi-active damper system with ground-hook damper model. The transmissibility characteristics are analyzed. An active damper with ER fluids actuator and a skyhook viscosity controller is proposed to avoid the vibrations in the mechanical structure that can disturb the evolution of the robot. The control parameters are determined by using the circle criterion. The take-off sequence conditions in the stance phase are inferred by using the energy concept.