The Research On Control Precision Model Of SCARA Robot For Multi-point High-speed Assembly

For the industrial robot that has the requirement of continuous path control, the trajectory error of end effecter comes mainly from the control and the structure, the error from trajectory control is mainly caused by the interpolation algorithm error of the path planning and Kinematics computing Traditional interpolation methods include linear and circular interpolation, these methods always can not meet the requirement of high-speed and high-precision of robot trajectory planning. For such a problem, this paper presents the method adaptive NURBS interpolation for industrial robots trajectory control, the paper mainly include:The paper takes the SCARA industrial robot as the object of the research, it gets the forward kinematics transformation matrix and the inverse kinematics solve equations, then establishes the trajectory model for the high-speed and multi-points assembly task of the end actuator.The paper presents the method of adaptive NURBS interpolation, and analysis the application in the trajectory interpolation for SCARA robot in Cartesian space. The NURBS interpolation process includes:teaching to obtain data points, generating the control points of NURBS curve, the node density of the curve parameters, density of spatial data points, and joint data generation. After generating the control points, the corresponding NURBS fitting curve can be obtained according to the formula of NURBS curves, there is error between the fitting curve the desired trajectory. For the chord error caused by the feed step of interpolation, the article use the adaptive method to automatically adjusts the velocity of the end effecter according to the different curvature. It has been carried out the velocity curve of the effecter versus time, which can ensure the chord error is in the scope of permitted. The paper got the parameters of the joint space corresponding to the various interpolation points by inverse kinematics computing, and mapped the curve of movement displacement and velocity versus time of each joint. The inverse kinematics computing produced the calculation error due to the approximate value calculation process, so it brought the error to the trajectory control.Through simulation modeling, the paper analyzed the error caused by the NURBS curve fitting, the error caused by adaptive step, and the error caused by inverse kinematics computing, and did a comprehensive analysis of the robot trajectory control, then the paper did a comparative analysis between the method proposed in this paper and the traditional linear interpolation method, which proved that the adaptive NURBS interpolation method can ensure the accuracy much better of the trajectory control in the high-speed assembly of SCARA robot.