Improving CNC contouring accuracy by integral sliding mode control

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• 作者：Xue-Cheng Xi ; Geok-Soon Hong ; Aun-Neow Poo
• 关键词：Computer numerical control (CNC) ; Contouring accuracy ; Contour error ; Tracking error ; Integral sliding mode control
• 刊名：Mechatronics
• 出版年：2010
• 出版时间：June 2010
• 年：2010
• 卷：20
• 期：4
• 页码：442-452
• 全文大小：1031 K

文摘

In this paper, an integral sliding mode controller (ISMC), based on input–output models, is proposed as a refinement from a two-degree-of-freedom controller with independent objectives for tracking and regulation. Thus, the knowledge of pole placement can be utilized in ISMC. The robustness is improved by a disturbance estimation, which results in an equivalent control. To eliminate the problem of chattering, two measures adopted are an appropriate choice of the sliding surface and an integral control action. It was found that the choice of a slower natural frequency of the sliding surface dynamics than that of the open loop can ease the problem of chattering. The choice of k_i, the integral control coefficient, is based on the two-degree-of-freedom controller. Root locus is used in assisting in choosing an appropriate value of k_i to ensure the closed-loop stability. The proposed ISMC was implemented and experimentally tested in a mini-CNC machine. The contouring accuracy of the mini-CNC machine was greatly improved by the proposed ISMC. Furthermore, no chattering was observed, which is beneficial to machine actuators.