Abstract
In this paper, the purpose is to establish a control strategy for an under-actuated one-legged hopping robot constructed from three links with two actuators and flat-shaped foot. To act like a human, the robot will go through an under-actuated phase in which the foot rotates around the under-actuated toe on the ground before taking off. By this special feature, it can perform human-like hops with longer hopping distance than a fully actuated robot. First we derive the robot system’s dynamics, and implement the control method from reference. By choosing particular mass and length parameters, zero dynamics turn into a simple pendulum motion, which causes the robot to hop. Next, kinematics are analyzed to design the control target during flight phase. Finally, close-loop control is used to simulate the center of mass act as a spring damper system to stabilize the robot in the landing phase and complete the hop cycle. In conclusion, the simulation results demonstrate that it can achieve under-actuated hopping by the control strategy, and performance can be changed by modifying the control parameters.