Hybrid Controller Switching to Increase Lithography Bandwidth
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Linear integrators in lithographic apparatus control systems are limited by a 90 degrees phase lag, which restricts the bandwidth and is undesirable for improved control characteristics.
Innovation Solution
A hybrid control system comprising a linear integrator and a linear gain in parallel, with a selector switching between integrator and gain modes based on specific conditions to optimize output signals, allowing for improved bandwidth without compromising low-frequency disturbance rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a linear integrator is used in the control system, then low-frequency disturbance rejection is improved, but the bandwidth is limited due to 90 degrees phase lag
Solution Approach 1:
The patent applies dynamics by making the control system switch between two operational modes (integrator mode and gain mode) based on real-time conditions. The selector dynamically chooses which control signal to use, transforming the static linear integrator into a dynamic hybrid system that can adapt its characteristics to overcome the fixed 90-degree phase lag limitation while maintaining low-frequency disturbance rejection capabilities
Solution Approach 2:
The patent changes the parameter of phase lag by switching between different control modes. In integrator mode, the system provides low-frequency disturbance rejection with 90-degree phase lag, while in gain mode, the phase lag is reduced. The selector switches between these modes based on the switching condition, effectively changing the phase lag parameter to expand bandwidth without sacrificing disturbance rejection
Data Source
AI summary
The invention relates to a control system comprising a controller arranged to provide an output signal on the basis of an input signal. The controller comprises a linear integrator, a linear gain and a selector. The linear integrator is arranged to provide a first control signal. The linear gain is in parallel to the linear integrator and is arranged to provide a second control signal. The selector is arranged to switch between an integrator mode in which the first control signal is used as the output signal of the controller and a gain mode in which the second control signal is used as the output signal of the controller. The selector is arranged to switch to the integrator mode when the value of the second control signal passes zero, and to switch to the gain mode when: eu<kh−1u2, wherein e is the input signal of the controller, u is the output signal of the controller, and kh is the gain of the linear gain.