Optimal Five-bar Legged Design for Energy-Efficient Bipedal Robot

摘要

Legged robots have high mobility for application with uneven terrain. Bipedal robots require a lower number of actuators with less complication of control system. The five-bar mechanisms are widely applied in robotic legs to enable the leg movement to be actuated by the motors located on the robot body (instead of at the leg joints) to minimize the inertia of the moving legs. For attaining a desired foot position with respect to the two actuated joints of each leg, there are two non-trivial solutions obtained from the inverse kinematics. For both solutions, the parameters of the five-bar linkage are optimized using the derivative-free method by considering the energy consumption of the stance leg. Based on the optimized leg parameters, the zero-moment point (ZMP) along the foot support is derived by using the table-cart model. The ZMP generator for shifting the center of mass (COM) forward according to the stride is simulated with the dynamic model of the leg for predicting the motor torques varying in the stance phase and comparing between both solutions. Based on the optimal five-bar parameters, the small-scaled leg prototype was built, and the experiment was conducted to evaluate the trajectory and the actuation torque of each joint varying against the stride.