The Research And Realization Of Alogorithm On Complex Track In Motion Control

Motion control technology, which determines the machining efficiency, accuracy and quality, is crucially important technology in CNC system. The CNC machine tools move towards to the direction of high speed and high accuracy. So in order to develop high performance motion controller with Chinese intellectual property rights, the thesis researches several key technologies in motion control system. In NC machining, workpiece will be decomposed into machining points list, the machine tool advances along the points track and accomplishes the machining. So how to propose the machining trajectory based on points list and how to plan the machining velocity are the keystones of this thesis. Usually, the points list can be fitted through spline curves, which can ensure the smoothness of machining surfaces, and also the points list can be connected directly using micro segment lines, which is a simpler method. Some regular complex curves, such as spiral line, can be machined according to specified algorithm without dividing it into points list. So, the literature focused on how to machine every segment between two points, how to generate the whole trajectory and how to control the velocity. Based on these questions, the thesis designed and analyzed the motion control algorithms and motion control system. And experiments are designed and implemented to validate the performance of designed system.In modern NC machining, interpolation of complex profile curve requires high speed and high accuracy. Based on B spline curve theory, this thesis presents a modified algorithm in cubic B spline curve interpolation. This proposed algorithm gives a new method which is based on pre-judgement of machining velocity to calculate the tangent vectors of spline curve junction. The tangent vectors are used to establish the spline curve equations with time as parameter. These equations can make trajectory generation and velocity generation simultaneously done. The experiment simulation results show that the algorithm has high calculation efficiency and meet the requirement of high accuracy and feedrate smoothing.In modern NC machining, interpolation of spatial motion such as spatial arc and spiral line is significant. Based on quaternion interpolation algorithm and S curve velocity planning, a method which can be used to machine spatial arc and spiral line was presented. This method uses a quaternion to describe the arc interpolation in three-dimensional space. The arc information is transformed into the information of spherical interpolation. By doing this, the arc or spiral line trajectory can be particularly generated. The S curve feedrate profile will be used in the velocity generation process, which makes the machine impact is very low. In the velocity generation process, all the line measurement will be translated into angular measurement in order to using quaternion interpolation. The experiment simulation results show that this method which has high calculation efficiency and low impact is a good way to machine the spatial arc and spiral line.CNC system usually uses continuous small scale line usually in micron to instead smooth curve. But this method would reduce the efficiency of machining due to the every line need a speeding up or down process. So, how to Figure out micro segment line machining in CNC system is important to the machining quality and efficiency. The thesis asserted a new algorithm to adjust the feedrate automatically to achieve maximum productivity with no expense of surface quality. This new algorithm considers the Geometric connectivity of these lines together with the S curve feedrate profile planning, then gives an iterate process to solve the problem. According to simulation and experiment, it showed that the algorithm improved the machining efficiency significantly.In order to realize all the new motion control algorithms, the whole control system was built up. And the function and performance of the motion control system were illustrated carefully. All the modules, which charged the different functions of the system, were introduced and analyzed in detail. The framework of software system of motion controller was also introduced. And some experiments were conducted in order to validate the control system and motion control algorithms. All the experiment details and data were presented in the thesis.In conclusion, the research in this dissertation enriches the theory and method of the motion control algorithm for machine tools, and provides new hardware and software structure of motion control system, which was proved to have a high performance.