Study On Five-Axis Interpolation Algorithm And Numerical Control System Multitask Dispatch

Nowadays, NC system is developing to Open NC system, and more and more organizations and scholars are engaged on the research in order to develop more open, more flexible and mightier NC systems. With this trend, this paper emphasizes on a five-axis surface real-time interpolation algorithm. Also, the paper discusses the multitask dispatch of NC systems based onμC/OS-II, serial communication between PC and S3C44B0X and display on LCD of S3C44B0X.The five-axis surface real-time interpolation algorithm presented by this paper is a five-axis Surface Direct Interpolation(SDI) based on Non-Uniform Rational B-Spline (NURBS) surface. We know that a NURBS surface can be determined by two parameters, and if a series of values of one parameter are found firstly, thus a series of NURBS curves determined by another parameter can be found correspondingly. If we machine the surface along these curves orderly, the whole surface can be machined in this way. The main content of this paper includes: the theory of NURBS related with this paper, how to realize the zigzag tool path, the speed and precision control when machined along curves, smooth transition between sections when a tool traveling along a curve, how to solve the values of the two rotational axes, the remnant error control between tool paths, how to reduce the calculation complexity in terms of the property of a NURBS, and the discussion about acceleration-deceleration control and tool transition between curves.At present, NC systems are more complicated and have more tasks, so it is necessary to use a OS to manage these tasks. In our research, we use the real-time OSμC/OS-II to complete multitask dispatch. In the paper, the character, transplantation to a chip and working principium ofμC/OS-II is analyzed firstly. Then the interpolation task, surface management task and communication task etc. that will be needed in a NC system are designed. After that, we design the multitask scheduling strategy and letμC/OS-II manage and schedule these tasks. Last, we realize the five-axis surface real-time interpolation algorithm based on bi-cubic NURBS surface with C language, and simulate it in a PC with MATLAB. The results of simulation indicate that the algorithm can meet expectation. We also test the multitask dispatch based onμC/OS-II. The test is based on the platform S3CEV40 provided by Embest Company. We transplant theμC/OS-II to S3C44B0X and letμC/OS-II manage and dispatch the tasks needed by the NC system. The dispatch results satisfy our need. At the same time we realize serial communication between PC and S3C44B0X and let LCD of S3C44B0X display what we expect.