Nonlinear adaptive temperature and humidity control of a 30m3 climate chamber for VOC emission detection in the presence of uncertainties

Abstract

Volatile organic compounds (VOCs) are major air pollutants and pose significant hazards to human health. The climate chamber is widely used for VOC emission detection. The reliability of detection results depends on whether the temperature and humidity in the chamber strictly satisfy the required standards, which imposes requirements on temperature and humidity control in practice, while the climate chamber system exhibits highly nonlinear dynamic characteristics with strong multivariable coupling and significant uncertainties, making precise control theoretically challenging. To address this issue, an adaptive nonlinear temperature and humidity controller for the climate chamber used for VOC emission detection is proposed. Although the climate chamber model exhibits a complex pure‐feedback structure with these characteristics, the implicit function theorem is employed to enable direct construction of the control law via backstepping without additional decoupling or linearization. Meanwhile, model uncertainties associated with the water mass in the temperature control tank and that in the dew‐point humidity generator, including unknown control coefficients, are considered. For the first time, the Nussbaum gain technique combined with an adaptive method is employed in the climate chamber closed‐loop system to compensate for these uncertainties. In addition, actuator faults in the heating equipment are considered to reflect practical operation. Finally, the effectiveness of the proposed control method is verified through theoretical analysis and comparative simulations.