Research On A Quadruped Robot Walking With Variable Steps On Plane

ABSTRACT:With the progress of science and technology, the intelligent robot technology has developed rapidly. Some people predicted that the21st century will be the" robot era". In such a bad environment as nuclear power plant accidents, human could not take remedial measures on the spot, in which the intelligent robots play an important role. The ability of wheeled robot and tracked robot responded to the complex environment is limited. Walking robot could support its body with foot endpoint, which had inherent advantages to adapt to complex environments. The design of foot type robot on structure and control system played a pivotal role in robot’s capability.Studying and summarizing some achievements of the predecessors on structure of biped robot, quadruped robot, hexapod robot and multi-legged robot, developed a new structure of quadruped robot. This thesis discussed design of the quadruped robot with the hind paw. It was much more flexible in the movements in interior space under damage building structure. Its wingspan was much longer and could provide better stability at needed time. The paper designed a hydraulically actuated knuckle in the robot body. Through combining knuckle with the design of paws, robot’s function had extended.This thesis aimed at the poor walking stability, high energy consumption and strong mechanical structure impact when the robot walked on flat. It presented variable stride straight algorithm of quadruped robot based on stable gravity. The gait design of previous robot took uniformity of its centre of gravity of the velocity, or stability of its centre of gravity of the energy as a result of the existence of diagonal triangle switched into consideration. But it did not solve the contradiction between the uniformity of the velocity and stability of the energy. Based on the forecast of later two steps of locomotion, the thesis adjusted robot’s stride in advance and insured the stability of motion process. By planning the sequence of each leg’s movement and setting a time, not only the problem of the diagonal triangle switched was solved effectively, the jitter of the centre of gravity in the process was reduced further. Also the problem of deviating designed trajectory on account of accumulation of error was prevented.This thesis designed a method that determines motion trajectory of turning process according to finishing point on the basis of the variable stride straight algorithm of quadruped robot with stable gravity. Motion trajectory of robot was set as the circular arc is centered at some point. The robot did not need to stop in the walking transition state (turning or going straight) with the help of the variable stride turning algorithm. It could always keep and set velocity of center of gravity motion. Even if in the process of turning, the robot would also be able to ensure the smoothness of the gravity trajectory and the uniformity of motion rate.Based on virtual prototype technology, this thesis set up program of joint simulation of ADAMS and MATLAB. On the basis of the implement methods of algorithm, this thesis established three modules of control, calculation of kinematics and model in the MATLAB/Simulink. It designed sequential control with Stateflow. It reduced the amount of calculation and speeded up the simulation because lots of processes were only performed at a particular moment. The results of simulation were proved the validity of the straight and turning algorithm, and the modular design of program also helped the development of more complex subsequent program.Designed a trajectory algorithm without impact, further reduced the quadruped robot the impact of the foot end when in contact with the ground. The trajectory are tested on four degrees of freedom mechanical arm, proved to be correct and practical.