Movement Mechanism And Experimental Study Of Multi-legged Robot Based On Hybrid-Driven Mechanism

In the field of the multi-legged robot, the high speed, high efficiency and high maneuverability are the goals of all researchers. Nowadays, most of the multi-legged robot applied full-servo open-chain legs, thus the flexibility of the foot trajectory and good maneuverability of the robot could be realized, while the efficiency and stride frequency was low due to the reciprocation of the actuators. Besides, the multi-legged robot which applied crank-driven-linkage leg could achieve high speed and high efficiency through the constant speed rotary actuation, while lack flexibility of foot trajectory and maneuverability due to the lack of servo motion. However, as a multi-DOFs linkage mechanism which has both constant speed rotary actuation and servo actuation, the hybrid-driven mechanism could realize a high speed and high efficient motion through the constant speed rotary actuation, and obtain foot trajectory flexibility through the servo actuation. Surrounding the design and experiments of the multi-legged robot based on hybrid-driven mechanism, a series of work including the basic theory of hybrid-driven mechanism, the design of hybrid-driven mechanism leg, and the simulations and experiments of the multi-legged robot based on hybrid-driven mechanism was carried out in this dissertation. The detail content and achievement were list as following:(1) Based on an analysis on the trajectory of the hybrid-driven five-bar mechanism, the necessary condition of the servo actuation for hybrid-driven mechanism to realize a smooth trajectory was proposed, namely the derivative of the servo actuation function was continuous. Then, after an investigation on the relationship between the realizing trajectory and the motivation function of the constant speed and servo actuators, the necessary and sufficient conditions of the trajectory realizing of a hybrid-driven mechanism was proposed, namely the function of the equivalent time parameter of the trajectory with respect to actual time exists and is monotonous, and then a process of numerical criterion was pointed out to improve the adaptability of the necessary and sufficient conditions. In addition, the trajectory realizing of a circle and a square was conducted through the numerical criterion and verified experiments was conducted on a hybrid-driven mechanism in double crank configuration; the error in experiments were small, which verified the feasibility of the numerical trajectory realizing method.(2) Based on the linkage group theory, a configuration synthesis on the crank-driven six-bar and eight-bar linkage mechanism leg in two segment configuration was conducted through a linkage group combination method, which provided a mass of configuration basis for the design of hybrid-driven mechanism leg. Then, based on a foot trajectory analysis on the six-bar Stephenson-III mechanism, a two-DOFs seven-bar hybrid-driven mechanism, having both constant speed rotary actuation and linear servo actuation, was designed, which had a small duty factor and could realize a up and down adjustment of the foot trajectory. Moreover, a two-DOFs eleven-bar hybrid-driven mechanism, which also had both constant speed rotary and linear servo actuation, was designed after a analysis on the trajectory of an eight-bar Jansen mechanism, and it could maintain the horizontality and the height of the bottom of the foot trajectory during the servo motivation, which coincided with the GDA principle and the walking motion of legs would be efficient.(3) Based on the seven-bar hybrid-driven mechanism, a hybrid-driven quadruped robot with modular leg was a designed. Then, a virtual prototype simulation of turning gait was conducted, and the results showed that the hybrid-driven quadruped robot could realize a turning locomotion with the action of the servo control. In addition, A linear-interpolation-based foot trajectory planning method was proposed to deal with the hybrid-driven mechanism with a linear servo actuation, and the trajectory planning experiments of straight line, large span triangle trajectory, quadrangle trajectory and ellipse trajectory were conducted, and the error in experiments were all small, which verified the feasibility of the numerical trajectory planning method. Besides, the influence of the circular elastic foot on the walking performance was studied and the results showed that the circular elastic foot could reduce the peak current of content speed actuator efficiently.(4) Based on the eleven-bar hybrid-driven mechanism, a symmetrical hexapod robot prototype was built. After an analysis of the trajectories under different servo adjustment, a turning locomotion based on a differential servo motivation of the left and right legs was proposed:the differential servo would result in a difference of switching time of left and right legs, and then a two-legs and a four-legs standing period appeared, during which a large velocity difference appeared and resulted in a step turning motion. Then the virtual prototype simulations of turning gait were conducted, and the body center trajectories were all approximate to circle, and the pitch angle, roll angle and the body center fluctuation were all small, which demonstrated that the turning locomotion was steady. In addition, the quantitative analysis of influence of the control parameters (crank angular speed, length adjustment of left and right legs) and dimension parameters (the distances between the left and right legs, and between the front and back legs) on the turning locomotion was studied, which offer a technical reference for the design of hybrid-driven hexapod robot. Finally, a manually-servo-based hybrid-driven hexapod robot prototype was designed to conduct the experiments of turning locomotion, and the results showed that the tendency of the simulations and experiments were similar, which verified the validity of the turning gait and the feasibility of the quantitative analysis of simulation.