High Precision Control for Twin-Drive Machine Tool Based on Mode Decoupling With Virtual Viscosity

The size of machine tools has been increasing to meet the demand for larger workpieces, and recently, the parallel twin-drive stage, actuated by two motors, has been employed to drive the larger stage more precisely. However, the twin-drive stage faces the issue of coupling forces between the two motors, which degrades tracking performance. This article proposes a novel mode decoupling method to address the problem of coupling forces and achieve higher precision control of the twin-drive stage. The twin-drive stage is modeled as a simple two-inertia system, and a novel virtual viscosity is introduced to transform the coupling system into the translational and rotational modes. In addition, the feedforward implementation of the virtual viscosity and the controller conversion for the actual control architecture of the machine tool are proposed for practical implementation. Simulations and experiments are conducted to verify the proposed method, and the experimental results under machining condition show that the tracking performance is improved by 21.9% with the proposed method compared to the default controller of the actual machine tool.