Estimation And Compensation of Angular Misalignment At Robot End Brush Roller - Workpiece Contact Interface Via Elastic Contact Force Perception

When the non-standard customized brush roller tool is used for robotic grinding of large-scale components, the clamping and positioning error of the brush roller at the end of the robot is extremely easy to cause misalignment at the brush roller - workpiece contact interface, which will affect the machining accuracy and surface quality. In order to ensure the parallel contact between the brush roller and the workpiece surface during the machining process, a calculation model of the angular misalignment at the brush roller - workpiece contact interface is proposed based on the elastic contact force perception, and then the accurate positioning of the robot end brush roller is realized by a fast compensation method. Firstly, according to the geometric force relationship between the brush roller and the workpiece, as well as the determined brush roller material properties parameters, the estimation model of angular misalignment is established. Secondly, both the axial force and normal torque at the time of initial contact detected by the force-controlled sensor are regarded as the input parameters in the model. Further, the calculated brush roller - workpiece contact offset is used as the geometric error compensation amount, and the brush roller is deflected to achieve error compensation by the robot RAPID program control command. The finite element simulation results are compared with the theoretical calculation values, and the average relative error is 15.1%. The experiment on robotic grinding and brushing of high-speed rail body indicates that the compensated angle can be reduced to 0.024° from an average of 0.179° before compensation, coupled with uniform material removal depth. The proposed method can significantly improve the contour accuracy of large-scale components.

Online harmonic error compensation of Atan2 function for a low-cost automotive sensor application

A new compensation method of harmonic distortions by using Atan2 function is introduced in this paper. It provides a simple online calibration function to determine the parameters of harmonic distortions. Thus, it can be implemented in a microcontroller with less computational capacity and can increase the accuracy of a low-cost angle position sensor for automotive applications.

Nonlinear Error Compensation Based on the Optimization of Swing Cutter Trajectory for Five-Axis Machining

In order to solve the problem of deviation between actual and theoretical machining paths due to the presence of rotation axis in five-axis machining, an interpolation algorithm based on the optimization of swing cutter trajectory and the method of corresponding nonlinear error compensation are proposed. Taking A-C dual rotary table five-axis machine tool as an example, the forward and reverse kinematic model of the machine tool is established according to the kinematic chain of the machine tool. Based on the linear interpolation of rotary axis, the generation mechanism of nonlinear error is analyzed, the modeling methods of cutter center point and cutter axis vector trajectory are proposed respectively, and the parameterized model of swing cutter trajectory is formed. The formula for the nonlinear error is obtained from the two-dimensional cutter center point trajectory. According to the established model of swing cutter trajectory, the synchronous optimization method of cutter center point trajectory and cutter axis vector trajectory is proposed, and the nonlinear error compensation mechanism is established. First, pre-interpolation is performed on the given cutter location data to obtain a model of the swing cutter trajectory for each interpolated segment. Then the magnitude of the nonlinear error is calculated based on the parameters of the actual interpolation points during formal interpolation, and the interpolation points with large errors are compensated for the nonlinear error. The simulation results show that the proposed method can effectively reduce the impact of nonlinear errors on machining, and is of high practical value for improving the accuracy of cutter position and the quality of complex free-form machining in five-axis machining.