On The Obstacle Avoidance Control Of Underactuated Redundant Robots

The underactuated robot is a kind of robot which has fewer control inputs than the DOF of system. Compared with the full drive robot, the underactuated robot has the advantages of light weight, low energy consumption and high flexibility. In recent years, the underactuated robot has become a new hot spot in the field of robot research. The redundant robot is a kind of robot whose joint space is larger than the task space. Each endpoint of this kind of robot has infinity corresponding joint configuration, which makes it achieve the endpoint task and the obstacle avoidance task at the same time. This kind of robot has the characteristics of high flexibility, high fault tolerance and so on. More complex control tasks can be achieved by making full l use of the advantages of underactuated robot and redundant robot.In this paper, the underactuated redundant robot with four joint is studied. Based on the fuzzy control theory, the fuzzy controller is designed, and the research on obstacle avoidance is carried out through simulation and experimental.Firstly, the dynamic equation with joint concentration mass and joint friction is used to analyse the coupling characteristics and the redundancy of the system. The controller is designed based on the fuzzy control theory. The passive joint is controlled by the dynamic coupling of three active joints, and the redundant features of the robot are utilized to achieve the endpoint task and obstacle avoidance task.Secondly, the proposed control strategy is verified by MATLAB and ADAMS joint simulation. The simulation task is to avoid obstacles in the process of controlling the endpoint moving from the starting position to the destination or controlling the endpoint tracking the straight line and arc trajectory. The results show that the designed control method can be used to not only finish the specified task with higher precision, but also avoid the obstacle. By comparing the simulation results without obstacles, it can be found that the robot can change its configuration in the process of moving and avoid the obstacles successfully at last.Finally, on the experimental platform, the fuzzy controller is compiled based on VC++6.0, and the interface of the host computer control software is programmed. The passive joint is coupled by three active joints to execute the task of point-to-point control and trajectory tracking. In the process of motion, the repulsion of obstacle is converted to voltage and the voltage is added to the servo motors of active joints to make the robot change the joint configuration to avoid obstacles. The experimental results are compared with the simulation results. The results show that the designed control method can be used to not only finish the specified task, but also avoid the obstacle.