Researches On Forcefree Control Of Dexterous Robot Based On Spherical Wrist

With the continuous innovation of robot technology, robot has been widely used in aerospace, deep sea technology, nuclear industry and other fields. The working environment is complex and changeable, narrow and dangerous, and beyond the limits of human body, thus presenting great challenges to robot control. Robots often collide with the equipment, tools and other objects when interacting with unstructured environment. In order to improve the compliance and security between robot and unstructured environment, research on forcefree control strategy is of great significance. In this paper, the compliance of the newly dexterous robot is studied, mainly from joint friction compensation and forcefree control strategy to improve the flexibility. The main research contents are as follows:First of all, based on a newly developed 3-DOF highly integrated spherical wrist, a dexterous robot is design, and its 3D model is established, and its structural characteristics are introduced. The kinematics model of dexterous robot is established, include of the forward and inverse kinematic equation, thus obtaining the relations between the operating space and joint space. The jacobian matrix of the dexterous robot is derived from the differential motion principle, and the performance evaluation index is designed. The dynamic model of dexterous robot is establish, and the static force transformation relation is offered.Then, the friction compensation method is introduced and the joint friction model of dexterous robot is established. The influence of model parameters on the friction torque is analyzed. Based on energy conservation law, genetic algorithm is used to identify the friction model parameters, and the identification algorithm is designed. Simulation results show that the error of the estimated friction model and the real value is very small and verify the validity of the identification parameters.Finally, Aiming at flexibility problem of the dexterous robot when interacting with unstructured environment, a torque forcefree control and an forcefree control method based on force velocity transformation are propose. The feed forward compensation technology is adopted to eliminate gravity and friction. The interaction force of environment is measured by six dimensional force sensor, and be transformed into joint torque or the desired speeds to realize compliance movement of dexterous robot. The feasibility of torque forcefree control without six dimensional force sensor at end effecter is also analyzed. The simulink platform is established, and the two kinds of forcefree tracking control are verified, and the characteristic of forcefree control methods is analyzed.In the paper, two kinds of forcefree control are proposed, which can improves the compliance ability of the dexterous robot in unstructured environment, and enriches its working range. The dexterous robot has certain reference value in the fields of spaceflight, nuclear industry, medical treatment.