Ultraprecision multi-axis CARIC control strategy with application to a nano-accuracy air-bearing motion stage

Multi-axis contouring control is crucial for ultraprecision manufacturing industries, contributing to meeting the ever-increasingly stringent performance requirements. In this article, a novel contouring adaptive real-time iterative compensation (CARIC) method is proposed to achieve extreme multi-axis contouring accuracy, remarkable trajectory generalization, disturbance rejection, and parametric adaptation simultaneously. Specifically, control actions generated by CARIC consist of robust feedback, adaptive feedforward, and online trajectory compensation components. Robust feedback and adaptive feedforward terms initially stabilize single-axis closed-loop control systems and adapt to parameter variations. An online contouring error prediction model subsequently captures upcoming contouring errors in advance, enabling the iterative calculation of optimal online trajectory compensation signals at each sampling instant during real-time motion. This mechanism proactively suppresses potential contouring errors before their occurrence. Comparative simulations and experiments demonstrate that the proposed CARIC method reaches the accuracy limit previously attainable only by iterative learning control (ILC) while enhancing trajectory generalization, disturbance rejection, and parametric adaptation. Notably, practical experiments on a nano-accuracy air-bearing motion stage showcase consistent 7-nm-level accuracy across various 100-mm stroke contouring tasks even under varying contours, payloads, and disturbances. Owing to these advantages, CARIC offers promising potential to enhance ultraprecision manufacturing performance through advanced motion control techniques.