Research And Development Of Motion Control Algorithm For Multi-axis CNC System

Numerical control technology is the critical technology of modern equipment manufacturing industry, and CNC motion control technology also pays a decisive role in the performance of manufacture equipment. With the rapid development of industry, the advanced manufacturing technology puts higher request on CNC system. For meeting the requirement of the advanced manufacturing technology and implementing the high-performance CNC system, the paper researches about the flexible acceleration and deceleration algorithm (ACC/DEC algorithm), look-ahead algorithm, jerk-limited acceleration interpolation algorithm, motion smooth processing and tangent interpolation algorithm of CNC system. The main research work of this paper is as follows:By analyzed the characteristics of simplified S shape ACC/DEC algorithm for flexible control, a method of quickly classifying the S shape ACC/DEC feedrate profile based on the relationship between the length and speed of curves is proposed in the paper. Meanwhile, the simple calculation formula of simplified S shape ACC/DEC algorithm is derived, which establishes the theoretical foundation for realizing the speed planning and look-ahead algorithm.At present, in most CNC system the tool path often contains a large number of small consecutive line blocks. So the adaptive look-ahead algorithm for consecutive line blocks is proposed in the paper. By establishing the mathematical model of small line blocks’velocity, the optimal velocities of consecutive line blocks are achieved. Meanwhile, the less number of line blocks for look-ahead calculation is calculated with the optimal velocities, which helps to optimize the look-ahead algorithm.Based on the time-sharing interpolation algorithm, the linear and circular interpolations based on error control are researched. Also, by proposing a NURBS look-ahead algorithm based on the changes of curvature in NURBS curve, the NURBS interpolation algorithm is implemented.For the issue of feedrate profile variation caused by interpolation error, a motion smooth processing algorithm is proposed. The feedrate profile is divided into symmetry and asymmetry feedrate profile according to the characteristics of speed curve in different types of motion. For symmetry feedrate profile, the achievement of motion smooth processing is by adjusting the motion parameters to eliminate interpolation error. And for asymmetry feedrate profile, it is by constructing error compensation sequence to elimination interpolation error in each interpolate time.Finally, by established the motion control of tangent interpolation model, the tangent interpolation algorithms about linear, circular, NURBS and consecutive line blocks are implemented.Experimental results and simulation results based on CNC leather cutting machine and motion controller based on OMAPL138+FPGA show that the proposed motion control algorithm can effectively improve the processing efficiency and quality of CNC equipment.