CNC控制器速度及加減速規劃之研究

Abstract

CNC工具機產生路徑誤差的原因相當複雜，輸入伺服系統的參考 命令直接影響路徑誤的產生。參考命令包含了路徑插值與加減速的計 算。路徑插值主要是獲得精確的路徑，為了更精確有效的計算複雜的 曲線，所以發展更高次的曲線插值。但若速度命令變化過大時，馬遠 瞬間大扭力輸出，會造成系統的振動，所以為了提高精度並使運動更 加平滑，必需加入適當的加減速規則。 本論文中對於路徑插值方面，藉由已經發展的Linear、 Parabolic DDA插值法則進而提出 Cubic DDA插值法則。應用高次的DDA插值，對 高次複雜的曲線能產生更精確的路徑。在加減速規則方面，發展前加 減速和多段混合(Blended)的速度曲線，規則出數種更平滑的速度曲 線並且討論由於混合(Blended)速度曲線規劃所產生的轉角誤差。最後 利用電腦模擬以上所提的方法，驗證方法具有可行性。

In the motion control, the reference command to the servo system directly influences the contouring error. The generation of the reference command includes path planning and the acceleration/deceleration planning. In order to obtain more accurate contouring path, we have to develop a higher order interpolation curve rather than a simple linear one. On the other hand, when the speed command varies drastically, the servo motor will consequently provide large torque to meet the change, and that will always cause the system to vibrate because of large jerk is induced. Therefore, it is necessary to develop an appropriate acceleration/deceleration planning for smooth and accurate motion. According to the concept of pre-acceleration/deceleration scheme, several kinds of acceleration/deceleration curve including linear curve, S-curve, and linear plus S-curve are discussed and compared. Considering the planning of speed curves within every two consecutive blocks together, we also examine several kinds of blended speed curves. The performance of different blended curves are compared in the view of corner error; an error control strategy is also developed by adjusting the acceleration time or the time-delay between two consecutive blocks. At last, every algorithm is simulated to verify its feasibility. In this thesis, we also extend the algorithm of liner and parabolic DDA to a new higher order one, called cubic DDA.