High-precision air temperature control considering both hardware elements and controller design

The environment with high-stability temperature is crucial for precision machinery such as lithography and laser interferometer. Some studies have investigated temperature control algorithms and temperature fluctuation attenuators to provide precision temperature control systems for them. In this paper, considering the characteristics of hardware elements and the closed control loop overall, a general control loop connected by multiple cascade loops is proposed for high-precision air temperature control to reject the disturbance from the inlet air. It is found that this disturbance and the noise generated by the non-uniform air temperature of the chamber are the two main sources affecting the control precision. Based on loop shaping, a controller with compensators is designed for the cascade control loop to make a tradeoff between the disturbance rejection and noise attenuation. The lumped parameter theoretical models of three kinds of attenuators for air temperature fluctuation are analysed for the design of precision air temperature control. An air temperature control system is used to verify the performance of the proposed controller. The results demonstrate that the controller can improve the disturbance rejection performance while reducing the sensitivity to the noise. The 1σ derivation of the chamber air temperature is decreased from 15.6 mK to 10.5 mK.