On The Tracking Algorithm Of Driven Axis Following Capstan Axis For Cam Grinder

Cam, as a key component to realize kinds of complex mechanical movement, its machining precision is increasingly demanding. The traditional copying machining can’t adapt to the development of products, now CNC grinding machine is used to precision machining. In order to improve the theory and technology of CNC cam grinding. By the study on the movement of two axes in the process of grinding, the topic find the important factors influencing the grinding accuracy is coordinated precision between rotary C axis and reciprocating X axis. On the basis of every single axis tracking precision meet certain requirements, the grinding precision of cam is determined by the accuracy of X axis tracking C axis.Based on the above, this topic proposed profiling tracking error compensation. The actual output of C axis is transformed by function X(C), its value is subtracted from the actual output of X axis which means the location of grinding wheel center, and feedback the results to the input series of X axis. And on this basis, design the neural network PID and fuzzy PID controller as the profiling tracking error compensator. The profiling tracking error compensation and designed controllers are verified in grinding simulation platform. The main contents are as follows:1. Establish a mathematical model of cam grinding. Cam data is given by the lift table, process the lift table data using cubic spline interpolation, and make it meet the requirements of processing. The mathematical relationship between different measuring probe of the lift table and its cam profile, establish their mathematical relationship by analyzing the measuring probe’s movement respectively. Deduce the grinding model between rotation angle of C axis and feed of X axis based on the principle of reversion and velocity instant center method. All above is prepared for the later work.2. Proposal of a new compensation method which is named profiling tracking error compensation and derivation of relationship between profiling tracking error and contour error. By analyzing two traditional tracking methods and combining the advantages of theirs, profiling tracking error compensation is proposed to realize the high precision coordination of the two axes. Contour error is one of the important criteria for judging cam machining precision, and if using profiling tracking error to direct grinding, the relationship of them must be clear. By establishing the contour error model which is suitable for profiling tracking, the conclusion that profiling tracking error is less than or equal to contour error can be proved. As long as the profiling tracking error can meet the requirements of machining accuracy, the contour error also can. By reducing profiling tracking error, the contour error can be indirectly reduced, and then improve the machining precision.3. Design of profiling tracking error compensator. Once the three parameters of traditional PID controller are set, they can’t make proper adjustments to meet the requirements of precision and flexible according to the different working conditions and the shapes of cam. The intelligent control algorithms are applied to the grinding of the cam, because of the fuzzy PID controller and the artificial neural network PID controller are designed respectively. The two intelligent control algorithms can modify the three parameters of PID controller instantaneously to meet the requirements of different working conditions and shapes of cam processing.4. Verify the effectiveness of profiling tracking error compensation and the controllers by experiment. Build the grinding simulation system by using SIMULINK toolbox based on MK8312 C CNC camshaft grinder. The design procedure of the controller and parameters selection are given in detail. Compare control effect of conventional PID controller to them. The experimental results show that the profiling tracking error compensation can effectively improve the grinding accuracy, and the designed two controllers have certain advantages on the precision and disturbance resisting compared with the traditional PID control.In conclusion, this paper does the relevant study on cam grinding mathematical model, the effect of cam machining accuracy caused by tracking precision of X axis trace C axis, the relationship between profiling tracking error and contour error, the application of intelligent control algorithm in cam grinding. Naturally, there are many questions worth further discussing, such as using the optimization of processing speed to realize the increase of grinding accuracy, realizing high precision grinding by using contour’s non-indent control because of cam grinding is irreversible and so on.