Research On The Kinematics And Dynamics Of Locust-like Hopping Robotand Design Bionic Joint*

The research of the bionic robot can be inspired from the ingenious mechanism and skillful movement of animals, which will improve the hopping performance of the robot. Locust is chosen as target animal, which is typical in intermittent hopping. Based on a mechanism model of the locust-like hopping robot, the kinematics and dynamic researching methods are proposed, and the hopping features and principles are unveiled. All these provide the theoretical basis for building realistic model of the robot.Firstly, according to the basic method of bionic research and scientists'analysis of locust, the mechanism model of locust-like hopping robot is presented. D-H method is used to conduct forward kinematics and inverse kinematics analysis to the model. By citing the biology data, the varying process of the robot body posture and taking-off velocity are obtained,and the result is similar with the motion of locust. The influence to the velocity of body center by the length of each linkage is analyzed through orthogonal test method, which can be the foundation in robot design. Based on the result of kinematics research, the motion transmission performance of the mechanism is analyzed.Secondly, the multi-rigid dynamic model of locust-like robot is built. And a torsion spring is used to imitate the energy storage structure in locust's knee joint. By constructing the dynamic formulation with Lagrange method, the driving torques in joints are calculated and they are compared with those in no-spring model. The result shows the driving torques in robot's knee joint and ankle joint can be reduced by using elastic energy storage equipment. According to the theorem of moment of momentum, it can be predicted that the robot will tumble after taking off. Through optimizing the trace of mass center, the moment of momentum can be reduced to minimum, which will make the gesture control of air-phase easier. The air-phase is modeled and restriction equation of angular velocity of each linkage is obtained.Finally, a bionic joint is designed to imitate the knee joint of locust. It contains spring as the energy storage equipment and a cam as storing and releasing device, which is optimally designed. The simulation result shows that the bionic joint can move as it is expected.