高速 CNC 工具機循徑運動控制的軌跡精度改進策略

Abstract

本論文針對 CNC 數值工具機運動控制所涵蓋的兩部份關鍵技術：命令產生器（Command Generator）及伺服迴路控制（Servo Loop Control）提出循徑運動的軌跡精度改進策略。 在第一部份有關命令產生器的改進策略中，本論文首先以 FIR 數位濾波器設計方法為基礎，加上運動軌跡控制之必要條件，發展一系統化之加減速機制設計程序；另外在運動控制的應用中，轉角運動為一常見之軌跡形態，本論文延續上述之加減速機制，設計一簡單之時間延遲，並依照使用者所規範之轉角速度與轉角誤差之規格提出一最佳之時間延遲。 在第二部份的單軸追蹤控制改進策略中，本論文考慮伺服系統普遍存在之延滯現象，因而加入直接速度與加速度前饋控制器（Direct Velocity and Acceleration Feedforward Controller）來增加系統追蹤之能力，並探討在驅動器飽和的情況下，採用不完全前饋控制之增益值的調整法則。而在雙軸軌跡控制的改進策略中，本論文首先求出各種不同軌跡之輪廓誤差模型，並將輪廓誤差回饋，利用交叉耦合控制，求出各軸之最佳修正量，然後，利用此修正量來補償輪廓誤差；另外，為了達到高速高精度之需求，最後本論文使用了前饋控制與交叉耦合控制之合成系統，並探討了前饋控制與交叉耦合控制之間的交互作用及此二控制器在一高速高精度之運動控制系統中所扮演的角色。 關於上述本論文所發展的 CNC工具機循徑運動控制的軌跡精度改進策略，除了理論推導之外，論文中並給定實際運動進給的條件進行模擬與實驗驗證，證明這些改進策略的實用性。

The improved strategies using the two key technology, command generator and servo loop control, in contouring accuracy for the high speed CNC motion control are investigated in this thesis. In the command generator improved strategies, we firstly develop a systematic design procedure for the Acc/Dec processor based on the discrete time finite-impulse-response (FIR) filter design technique with some necessary conditions. The proposed Acc/Dec algorithm is quite flexible and efficient, creating space for users to use more sophisticated profiles to more efficiently match the system constraints with minimum contouring errors. Then, we propose a novel motion planning around a corner to decrease the corner contouring error. The strategy just add a delay time between two successive line interpolation and does not destroy the Acc/Dec structure. According to the specification of minimum tangent velocity and corner contouring error, the design procedure of block command delay time not only compensate the corner error during command generation but also compensate the corner error yielding by servo lag. In the improved strategies of single axis tracking control , this thesis proposes a new feedforward controller called the direct velocity and acceleration feedforward controller (DVAFF) to improve the tracking performance. The controller is adapted to both minimum phase system and nonminimum phase system and it can also take the practical driving capability of actuator and saturation of D/A converter into account by tuning their gains. In the improved strategies of multi-axes synchronous contouring control, we firstly create the accurate contouring error model. Then, the cross-coupled controller is designed to compensate the contouring error using the accurate contouring error model. The hybrid system of DVAFF and cross-coupled controller is integrated to satisfy the high speed and high accuracy motion control requirement. Finally, the above improved strategies in contouring accuracy for high speed CNC motion control are verified by the simulation and experimental results.