The Design And Experimental Study Of Leg Mechanism Based On Hybrid-driven

As the scope of mobile robot application is constantly expanding, such as jungle warfare in the mountains, desert wetland investigation, disaster prevention and so on, the demand of robot flexible mobility and environmental adaptability is higher and higher. The research and exploration in the multi-legged moving mechanism become an urgent problem to be solved in the current multi-legged robot research field. Traditionally, multi-legged robot applies servo controlled open-chain mechanism as multi-legged moving mechanism. Because the joint drive needs to act continuously and overcome constantly inertia power, the energy loss in the process of the reversible switch is great. Hence, it is difficult to achieve rapid gait of the robot. Based on the experimental test and the theoretical research on the bionic joint quadruped robot in the past, it puts forward the design concept called "the hybrid-driven multi-legged moving mechanism". Hybrid-driven multi-legged moving mechanism is a kind of the mechanism with multiple degrees of freedom. It is driven by high-power source of the unidirectional continuous rotation and servo-power source. The high-power source drives the crank to rotate continuously. The servo-power source adjusts continually the trajectory of the end point, so as to realize the gait control of multi-legged robot. This paper integrated the advantages of traditional mechanical system with the advantages of servo mechanical system, and it designed the quadruped robot based on the hybrid-driven mechanism. It could not only realize fast moving, but also have a good ability of flexibility.This paper first reviewed the development of the mobile robot and the hybrid-driven mechanism, and analyzed the current bottleneck problems of multi-legged robot in the research field. In order to improve the efficiency of mobile robot, the hybrid-driven mechanism was introduced in the design of the robot leg mechanism. The research content is mainly as follows:the configuration synthesis of the planar closed-chain linkage, the kinematics analysis of the hybrid-driven mechanism, electromechanical coupling modeling and virtual prototype simulation technology, the trajectory planning method of mechanism actuator and experimental research, etc.The configuration synthesis of the planar closed-chain linkage analyzed two configuration syntheses. One was the configuration synthesis of the single degree of freedom linkage; the other was the configuration synthesis of the two degree of freedom linkage. Besides, it offered all kinds of thumbnail form and structure diagram. Then it analyzed the classification of the planar four-bar linkage and hybrid-driven five-bar linkage, focusing on the structural analysis of the hybrid-driven seven-bar linkage.The kinematics analysis of the hybrid-driven mechanism was divided into the forward kinematics analysis and the inverse kinematics analysis. The forward kinematics analysis was as follows:Firstly, the structural form of mechanism and size parameters were known. Then the law of motion of driving linkage was given. Finally, the result could obtain the displacement of driven bar and its velocity and acceleration. Meanwhile, it gained the workspace of the actuators and the trajectory curves. It analyzed the speed characteristics of the mechanism and the main factors affecting the speed characteristics by making use of Jacobi matrix. The inverse kinematics analysis was as follows:the trajectory of the actuator and the speed of constant speed motor were known, the result could obtain the angular displacement of the servo motor, the angular velocity and angular acceleration.The electromechanical coupling modeling and virtual prototype simulation technology established the dynamic equations of hybrid-driven mechanism by taking advantage of Lagrange method. Since the dynamic characteristics of the motor directly affected the kinematic accuracy of the overall mechanism in the actual process, it was necessary to introduce the dynamic equation of the motor for electromechanical coupling modeling. In the ADAMS software, simulation analysis was carried out on the electromechanical coupling model, and it obtained the changing curves of both motor current and crank angular velocity under different voltage.The experimental study on the trajectory planning method of actuator introduced respectively two methods. One was the trajectory planning method based on the inverse kinematics analysis. The other was based on trajectory curves. The above two methods were studied experimentally, basing on the hybrid-driven five-bar linkage experimental platform, the results showed error curve of circular trajectory. Due to the particularity of the seven-bar linkage configuration, the specific trajectory of robot leg mechanism was achieved by method of trajectory curves. Basing on the experimental platform of robot leg mechanism, the experimental study of four different trajectories was carried out, of which the result verified the feasibility of the method.Finally, the paper summarized the main conclusions of the research work, and put forward some prospects for follow-up work, in the hope of further research on hybrid-driven mechanism.