Design And Analysis Of Motion Controller For A New Relining Manipulator Of Ball Mill

Ball mill is an important equipment in mine ore dressing,the inner lining are very easy to wear and damage due to the impact of the grinding media and material.In the actual project,enterprises will change the lining regularly depend on the degree of wear and damage.Domestic mining enterprises generally use the lifting operation to replace lining,this backward way is very time consuming,prolong mill downtime and the labor intensity of the workers is great,also personal security is not guaranteed.In this paper,in order to develop a set of motion control system of Multi-DOF manipulator for relining,taking a domestic ore enterprise‘s ball mill and lining as object.The main research contents include:Establish the coordinate system of manipulator's each joint according to D-H parameter method and derive the formula for calculating the forward kinematics,then solving the inverse kinematics of manipulator,firstly it difficult to use the inverse transform of homogeneous matrix method to derive the closed form solution since the structure is not meet Pieper criterion.So in this paper,a method of Jacobian matrix iterative based on forward kinematics is elaborated.However,this method is tedious and time-consuming,also have only one solution,so it is not suitable for engineering application.In the observation of the inverse kinematics solution of each target point,find the 5 axis of manipulator almost maintained at 92 degrees.So the closed form solution can be obtained successfully by use the inverse transform of homogeneous matrix method again with taking 6 axis as a external axis.Research on trajectory generation of the manipulator,in order to make the manipulator will not be affected by the impact force in the process of operation,it's need to ensure that the joint's acceleration is continuous.The specific design of the relining manipulator which based on the research in robotics is optimized,trajectory planning in joint space using five order polynomial interpolation method,linear position planning in Cartesian space using trapezoidal acceleration curve in polynomial fitting,linear pose planning using spherical linear interpolation method that based on quaternion.At last,the PTP and CP trajectory simulation are done in the environment of Matlab and Solidworks Mtion.The simulation results show that the trajectory is smooth and the operation is stable.Using Newton-Euler method to derive the manipulator's dynamics equation,and its gravity,inertia,coriolis and centrifugal force are analyzed in detail.Finally come to the conclusion:the torque of gravity occupy a leading position of the dynamic characteristics,inertia and joint 1's coriolis and centrifugal force also affect the manipulator trajectory accuracy.The design of the manipulator's controller is carried out.Firstly,use PD control method based on Gravity Compensation to design manipulator's control law by take each joint regarded as independent joint.And the dynamic inverse operation of the manipulator is obtained by using the dynamic inverse operation and the Euler equation,then establish the simulation model of the control system in the Matlab\Simulink.From the trajectory tracking response,the simple linear control has a high steady-state accuracy for relining manipulator,but there are some errors in the trajectory tracking.To further improve the manipulator's trajectory accuracy,using a model-based computed torque method.Computating dynamic parameters to "offset" system's nonlinear factors,a decoupled and linear system is obtained,then establish simulation model.The simulation results show that the trajectory tracking accuracy of each joint is less than 1%,and the steady state error is much lower than 1%,that method has obvious effect on improving the control precision of the manipulator.