Research On Bounding Gait For Quadruped Robot With Half-circular Compliant Legs

Robots with half-circular compliant legs combine the advantages of legged robots and wheeled robots. Its half-circular, compliant leg designs were found to have robust mechanical properties and good dynamic performance, which has attracted substantial researchers. For its research, scholors mainly do research from static control and dynamic control. Research work about static control is relatively mature,while in the dynamic control of motion, such as running,jumping and so on, the main problem is the energy efficiency is low and stability will deteriorate when robots move at a high speed, so to improve energy efficiency and high-speed stability of the robots is necessary. Researches have showed passive walking is an effective way to improve energy efficiency. In paper, based on the mechanisms of bionics and numerical simulation methods, we carried out the dynamic characteristics of passive jumping movement of robots with half-circular compliant legs.Firstly, based on the Castigliano’s theorem, the leg stiffness is getted in order to establish a dynamical model of half-circular compliant legs. Then briefly introduce the bounding gait and analysis four motion phases of a cycle bounding motion and apply the model of half-circular compliant legs to build a passive bounding plane model of quadruped. Using Euler-Lagrange method, the each phase dynamics of the model during the passive bounding motion and each of phase transition conditions are obtained according to bounding motion.Secondly, define the Poincare mapping and fixed point of half-circular compliant legs model and plane model during passive bounding motion. The Newton-Raphson method is used to find the fixed point of the two models. Then use dimensional analysis to determine the dimensionless parameters of the model, greatly improving the simulation efficiency. As to the half-circular compliant legs model, analyzed the height mapping, pointed out the distribution and performance of speed and height of fixed points and studied the impact on system by spring stiffness. As to plannar model, carried out the analysis of the distribution of fixed points under different energy levels, the relationship of speed and energy and studied the impact on system by the moment of inertia, spring stiffness and half body length. matlab numerial simulation proves reasonable configuration of initial conditions can achieve stable passive jumping movement and have anti-interference ability,Finally, according to the obtained energy mapping rules, a control strategy based on energy level is established, and the actual robot’s motion control is near to the stable fixed point of the passive jumping gait, and the energy efficiency is improved. Then The equivalent SLIP model and torsion spring model of the half-circular compliant leg model is established, and a virtual simulation platform is built and use energy motion control to complete motion simulation, which verifies the results of numerical analysis. A prototype was built and basic jumping movement is achieved in the prototype.