Hexapod Robot Closed Loop Feedback Control System Based On The Joint Variables

Hexapod robot plays very important significance in robot research field for its performance in each direction is so good that there is low demand of pavement and it can adapt to all kinds of irregular road surface. More over, its stabilityis good in moving. The research object of this paper is a kind of hexapod robot with typical structure.Based on the hexapod robot Nomad HDATS(Heavy Duty All Terrain System) of Shenzhen Depush technology Co., LTD, this paper analyzes the sports structure and tripod gait. Through the "D-H" method to establish the kinematics model of the robot joints and stems, writing the transformation matrixes between them, deducing the positive kinematics equation and the inverse kinematics equations of the hexapod robot. Using Lagrange algorithm to establish the robot dynamics equation, the paper solves the problem of inverse dynamics, calculating the driving moment needed by each joint actuators of the hexapod robot.The control of the robot is usually closed loop control system, its principle is that the robot makes independent decision to realize the independent control according to the real-time information in moving process. Robot closed loop control system requires the robot can obtain external real-time environment and its own posture, the external environment information can be obtained through the sensor in general, such as visual, touch, photoelectric position detection sensors, etc; The robot posture can be determined by angle sensor, such as horizontal gyro, compass sensor, etc. The paper studies that control system how to determine the robot posture. This thesis doesn't use angle sensor on the problem, but considers that we would be able to make sure the posture of the robot through robot joint variables. After further study, we find that common simulating steering gear used by our robot also can effectively reflect the actual value of the joint variables. Based on the above thinking and analysis, this paper designs a set of robot closed-loop control system based on information feedback of joint variables to the hexapod robot we studied which has six equal limbs with3DOF.Based on the joint variable feedback system, the basic principle of the closed-loop control system designed is to convert analog signal reflecting the real-time position of the joint steering gear output shaft into digital signal by A/D chip and send it to the single chip microcomputer. Then according to the programming algorithm, the single chip microcomputer converts the digital signal into servo motor's position information or heigth that the robot is from the ground. Finally, adding the design scheme into original control system, the controller will be able to scan real-time position information of all joint servo motors using the designed feedback system and reference to the real-time position information to judge posture of the robot and the posible situation at that time, and then decide the next movement.In general, the paper makes some research and analysis to the theory related to the hexapod robot, puts forward design scheme of the robot closed-loop control system based on the joint variable information feedback, and make group testing, the result of which achieves the expected confirming the feasibility and effectiveness of the system. The designing idea of the system is new, succeeding in solving the problem that common simulation steering gear can not be used for designing the closed-loop control system to get the robot's posture, providing some reference ideas for robot control system design in future.