Nonlinear Control of Linear Sliders Using Cascade Control Based on Operator Theory

Recently, The demand for smart devices, including smartphones, has been rapidly expanding, along with the development of higher performance devices, and this trend is expected to continue in the future. For the manufacture of these devices, miniaturization of semiconductor devices and improvement of productivity are required. Precise control of semiconductor lithography equipments is critical for the manufacture of ultra small semiconductor devices. Semiconductor lithography equipments use linear motor stages, and this paper describes a high precision perfect tracking control of these stages. Perfect tracking control is a control method that ensures the system constantly follows a command value, even as it changes over time, and requires a high level of accuracy. But the dynamic characteristics of linear motors are strictly nonlinear, which requires nonlinear control for precise control. Therefore, operator theory, which compensates for the stability of nonlinear control systems, is used to control the position of stage. In this paper, we propose a new control system design method using cascade control based on operator theory to achieve model reduction. Experimental results show that the proposed method improves the tracking performance compared with previous studies.