Enhanced Contour Tracking: A Time-Varying Internal Model Principle-Based Approach

Contour tracking is crucial in multiaxis motion control systems, requiring both multiaxial contouring and individual-axial servo performance. Existing methods such as cross-coupled control and task coordinate frame exhibit limitations in asymptotic tracking and system nonlinearity, respectively. This article proposes a novel time-varying internal model principle-based contouring control (TV-IMCC) to enhance contour tracking performance by simultaneously reducing axial and contour errors. The TV-IMCC methodology includes an extended position domain framework with master-slave structures for contour regulation, and a time-varying internal model principle-based controller for axial tracking precision. A novel signal conversion algorithm within the extended position domain framework decouples the original $n$-axis contouring problem into $(n-1)$ two-axis master-slave tracking problems, extending the class of contour candidates. With this, the TV-IMCC addresses time-varying dynamics in axial systems via the transformation between time and position domains. Stability analysis for the closed-loop system of the TV-IMCC is provided. Simulation and experimental results demonstrate enhanced contour tracking performance compared to existing methods, without strict requirements on master axis precision, making the TV-IMCC well suited for multiaxis macro–micro motion systems.