Mechanism analysis and decoupling modeling of positioning errors in fully-closed-loop feed drive system for horizontal machining centers

Fully-closed-loop feed drive systems (FCL-FDS) possess theoretically higher positioning accuracy, yet thermally induced errors caused by varying temperature fields still significantly impair machining precision. Due to the unclear error mechanisms and complex coupling, existing compensation methods show limited applicability and generalization in FCL-FDS. Focusing on the Z-axis feed system of a horizontal machining center, this study systematically reveals the mechanism, composition, and influencing factors of positioning errors in FCL-FDS, and proposes an error decoupling strategy. Errors are decoupled into geometric error, initial temperature error, thermal expansion error, and thermal drift error. On this basis, a hybrid modeling method combining deformation mechanisms with small-sample data-driven calibration is developed to enhance model interpretability and predictive accuracy. Compensation experiments demonstrate that the proposed method reduces positioning errors from −2.53 ∼ 14.83 μm to −1.47 ∼ 2.71 μm, with an 81.66 % reduction. This research provides an effective and generalizable framework for error mechanism analysis and compensation modeling in FCL-FDS.