Research On Key Technologies For Reconfigurable CNC Controller

The reconfigrable Computer Numerical Controller (CNC) is a key technology in reconfigurable manufacturing systems. The reconfigurable technology could help improving the flexibility and the resource configuration in CNC to rapidly meet the machining process requirement. In this dissertation, servral theory and application problems in the reconfigurable CNC controller are studied.A reconfigurable Numerical Control (NC) pipeline architechture is proposed based on the analysis of the functions in CNC controllers. The pipeline is consists of a NC pipeline thread, a driver and a NC Microcode Processor (NCMP). In this architecture, the NC Canonical Command (NCCC) interface and the NC Microcode (NCM) interface are defined to ensure the interchangeabilty of different modules and the reconfigurability of the pipeline. The primary controlling functions from code interpretation to NCM generation are encapsulated in the NC pipeline thread with high portability. NC Mircrocodes are simplified operating codes aimed for the real-time execution of CNC functions in NCMP. Experiments demonstrate that the NC pipeline architecture could realize the reconfigurable CNC controller efficiently.Feedrate plan is an important module in CNC controllers, which affects the efficiency, the smoothness of movements, and many other aspects in the machining process. In this dissertation, a type of Acceleration and Deceleration (ACC/DEC) algorithms is mathematically abstracted, and a Generic Look-Ahead Feedrate Plan (GLAFP) scheme is proposed for this type algorithms. The optimizing properties of GLAFP are theoretically proved. The complete algorithms for linear, modified exponential and S-curve ACC/DEC are derivated under the GLAFP scheme. The proposed scheme is verified by experiments.The machining of micro-lines is very common in the complex surface maching programs. The speed limit algorithm for the intersection of straight lines and feedrate modification algorithm for the continuously deviating micro-lines based on the contour error of servo systems are developed. These algorithms can intelligently control the feedrate according to the feature of the machining path. The proposed feedrate control methods along with the S-curve ACC/DEC algorithm can be reconfigured in the GLAFP architecture as a feedrate plan module for the smooth machining of micro-lines.The resampling interpolation enables the coarse interpolation running in a batch and non-real-time pattern. This could not only enhance the performance but also benefits the design of CNC controllers. The linear resampling interpolation and the curve-subdivision-based resampling interpolation are proposed. The analysis shows that the subdivision algorithm can generate more smooth result than the linear algorithm. The reconfigurable logic is designed for accelerate the execution of resampling algorithms. The applications of resampling interpolation in the threading and electronic cam functions are illustrated as examples.For the implementaionn of reconfigurable CNC controller, several reconfigurable schemes for the hardware and software with different granularities are proposed. Three prototype reconfigurable controllers based on the NC pipeline architechture are developed. The experiments and the applications prove that the NC pipeline architechture is a platform independent, open, reconfigurable and efficient solution for the CNC controller design.