The Algorithm Based On Tangential-Contouring Control For Cam Grinding

As a key component of the machinery devices,the grinding precision of cam directly affects the overall performance of the engine.In recent years,the grinding precision of cam has been greatly improved with the development of CNC grinding technology.Instead of the traditional processing methods of imitating the shape,now the precision machining of the two-axis linkage system is used more frequently.The cam grinding is accomplished by controlling the cooperative movement between the rotation axis of workpiece and the wheel feed shaft.Since the grinding precision of cam is ultimately reflected in the cam contour error,precision problem of the grinding process can be regarded as control problem of the cam contour error,so the control effect of directly reducing the contour error is better than the indirect method by reducing the single axis tracking errors.In this paper,a tangential-contouring control algorithm is introduced to reduce the contour error and improve the grinding precision,and a series of improvements are proposed in order to achieve the direct and effective control of the contour error.The main research contents are as follows:1?Preparation before grinding.In order to maintain the original characteristics of the cam contour and eliminate the possible errors of the lift data,the original lift data provided by the Manufacturers is processed by smoothing and three spline interpolation.On the basis of this,the input sequence value of the system is obtained by the inversion method and linkage mathematical model.2?The tangential-contouring control algorithm is introduced.In order to facilitate the application of the tangential-contouring control algorithm in the cam grinding system,a appropriate transformation matrix is selected to realize the transformation between coordinate systems.And the position tracking compensation algorithm is proposed,which together with the tangential-contouring control controller and the position loop controller,constitute the integral contour error control algorithm to realize the further reduction in contour error.And the effectiveness of the above algorithm is verified by simulation experiment.3 ? The parameter optimization algorithm is designed for the tangential-contouringcontroller.In the integral contour error control algorithm,the parameter selection of the tangential-contouring controller directly affects the grinding precision of the cam.In order to reduce the contour error effectively,the differential evolution algorithm is used to optimize the gain coefficients of the tangential controller and the contour controller.The fitness function is the maximum absolute value of the cam contour error of the current grinding process,and the two-dimensional vector composed of gain coefficients is the individual population of evolution,whose optimal solution is obtained by iterative calculation.The simulation results show that the grinding precision of the system with optimal solution has been improved.4?The parameter adaptive control algorithm is designed for the tangential-contouring controller.Due to the complicated curvature of cam contour,it is necessary to adopt the parameter adaptive control for reducing the contour error.By using BP neural network algorithm,the output layer of network corresponds to the gain coefficients of the tangential controller and the contour controller respectively,so that the controller gain coefficients can be adaptively changed according to different grinding point and the cam contour error through correcting the weight coefficients of each layer in real time.And its effectiveness is verified by simulation experiment.In addition,the advantages and disadvantages of the parameter optimization algorithm and the parameter adaptive control algorithm are compared.The parameter optimization algorithm is more time-saving,and the parameter adaptive control algorithm has more advantages in contour error control.