High Precision Control for Twin-Drive System Based on Mode Decoupling with Virtual Viscosity: Equivalent Controller Transform for Machine Tool

Machine tools are essential to the manufacturing industry, and the twin-drive stage, driven by two parallel-mounted motors, has recently been adopted to achieve higher precision in the system. However, this system generates a coupling force between the motors, which poses a significant challenge. Numerous advanced control strategies have been proposed to solve this issue, but they often introduce complexity and create difficulties for integration into the actual machine tools which only have limited controller architectures. This paper introduces an innovative method for transforming controllers from center-of-gravity (COG) to each axis coordination on the twin drive system. High-performance controllers originally designed for the COG coordination in the twin-drive system are adapted into individuaL-axis controllers using our proposed method. The effectiveness of the proposed method has been experimentally confirmed, achieving an 87.4 % reduction in tracking error compared to the conventional method.

I. Introduction

In recent years, the size of machine tools, illustrated in Fig. 1, has been increasing. Historically, single motors have been used to actuate the stages of these tools. However, to achieve a more accurate system, the concept of parallel twin-drive mechanisms, which employ two motors in tandem as shown in Fig. 2, has emerged. Consequently, numerous studies have been conducted to precisely control this system.