Research On Gait Planning And Uneven Terrain's Walking Method Of Crab-like Robot

Theroy analysis and experimental study have been developed in this paper aiming at solving the leg impact and body stability problem during walking on the uneven terrains.The structure schemes of the crablike robot including modularization joints, elastic toe, walking legs and body structure are proposed. And the motion performance of the leg and body has been studied and simulated by forward kinematics and inverse kinematics. Based on joint angle constraints of walking leg, the reachable workspaces of the leg and body are worked out using searching method.The trajectory problem of the leg is studied and the tip trajectory is planned using cubic spline curve. An adaptive trajectory planning strategy and trajectroy database are put forward as well as the calling mechanism of database. The simulation which is made for testing the motion on the uneven terrain proves that the crablike robot has favorable environmental adaptability.The pace order and gait's parameters of the crablike robot are planned based on the analysis of crab's motion traits and a new gait planning method is put forward. According to the statistic stability, the walking legs have been distributed along Z-form and the alternating equal-phase wave gait is proposed after considering the effect of variable phase factor of the successive legs within a tetrapod group. The paper establishs the gait's parameter function, calculates the duty factors of the legs and analyzes the changing effects of duty factor and phase factor using energy comsumption ratio. The results of gait's simulation show that the energy comsumption ratio increases linearly with the duty factor. When the duty factor is 0.454, the phase factor is equal to 0.25 and the robot can walk with better moving stability and lower energy comsumption ratio than the double tetrapod one.The compliance control method of the crablike robot is proposed in this paper. Based on position impedance control method, the simulation model of control is established through analyzing the contact model between legs and environment. The simulation results indicate that the impact force is restrained during walking by using compliance control without leg fluctuation. That means the compliance control method is suitable for the walking control of the robot. Because the environment impacts on the transferring legs and supporting legs are different, especially the effect of different force signal, the fuzzy controlor is applied to the position control of a single joint and the simulation is carried out. The simulation results show that the fuzzy controler has strong robustness for the variation of force and is suitable for the controler of joint's position control. And the compliance control of the robot is realized in the paper.The experimental platform for the crablike prototype is developed and the experiments of the motion performance on the complex terrain have been made sufficiently for the deep study. Gaits'experiments using real-time simulation system dSPACE and moving tests on flat groud and slope are carried out. Through the contrast experiments between alternating equal-phase wave gait and double tetrapod gait, the feasibility of the alternating equal-phase wave gait is proved. The results show that the velocity of alternating equal-phase wave gait changed smoothly with small fluction of gravity centre and the robot can receive favorable gait stability.The influence of the leg's impact force is eliminated by using control strategy. Through compliance control experiment, the variation of system stiffness is tested. And the compliance control tests show that the robot can receive nice compliance performance and this method can provide a good buffer effect when the legs are subject to the impact force.The robot has high motion stability with stronge terrain adaptation. The crablike robot can also keep stable in complex environment because of its redundant structure and complete the operation even if some joints'are disabled.