Research On Motion Performance Analysis And Force Control Of Spherical Wrist By Two Constant Transmission Ratios

With the development and integration of various disciplines,which has promoted theinnovation of intelligent robot technology,the application field of robot are gradually expanding from traditional industrial manufacturing to aerospace,medical services and other areas.Compared with the manufacturing industry,the work environment of these areas is unstructured,dangerous and other characteristics.completing the tasks in this complex environment,it is more stringent performance requirements of the robot.The wrist is an key components connecting arm and hand,which is used to change the working attitude of the manipulator.Because of the complex design and technical difficulties,it has become the bottleneck of the robot's application and expansion in the extreme environment.In order to improve the operating capacity of the robot,it is of great significance to study the high performance wrist module.In this paper,a 3-DOF decoupled spherical wrist by two constant transmission ratios highly integrated with two ball basket universal joints was proposed,which drive the upper and lower biasing of the rotating body to compose pitch-yaw motion and rotation of the suspension end.The structural characteristics and transmission relationship of three motions were analyzed,the structure design of the decoupled spherical wrist by two constant transmission ratios was finished,the lower dimensional positive and inverse kinematics equations of spherical wrist were established,both the structural decoupling principle and decoupling principle by two constant transmission ratios were investigated,Jacobian matrix and singularity of spherical wrist were deduced.The accuracy of the model and positioning was verified by the motion simulation module.Compared with the cross universal wrist,the decoupling by two constant transmission ratios simplified the complexity of kinematics,and the Jacobian matrix was simple in form.The motion performance of two kinds of spherical wrist with different transmission structure was analyzed and compared.The angular velocity and the angular acceleration transfer formula were deduced.With the angular velocity and angular acceleration transfer characteristics of the two wrist compared by applying a certain driving input,the angular output characteristics of spherical wrist were evaluated.The static angular resolution of the wrist were defined,and the static angular resolution of the wrist were solved by the decomposition motion along the longitude and latitude directions.The manipulability expression of spherical wrist was given,the ? was optimized by the quantification index,and the flexibility and motion ability of the spherical wrist were evaluated.Force control method of spherical wrist based on inner velocity loop was proposed.A friction model of spherical wrist was established.Based on compensation of the gravity of spherical wrist end actuator and joint friction,the environment interaction force information measured was converted to the desired speed information of driving space which control spherical wrist to realize rapid tracking contacting force.In the Simulink environment,the simulation analysis was carried out to verify the effectiveness of the force control algorithm.The simulation results demonstrated that the proposed method can effectively improve the tracking ability and compliance of spherical wrist system.