Model-based prototype design, construction and operation of closed-loop control system of solid waste treatment unit

Abstract

Solid waste treatment unit (SWTU) is important for waste disposal, and used in bioregenerative life support system (BLSS) for deep space exploration. It is vital for SWTU to robustly operate at a prescribed level with low power consumption. Nevertheless, traditional expertise-experience-experiment methods by trial-and-error have significant drawbacks in SWTU prototype design, construction and operation for this target. In this study, model-based approaches were carried out by system dynamics, ecological thermodynamics, parameter sensitivity analysis and dynamic behavior optimization in combination with digital simulation as follows: SWTU was firstly designed as a closed-loop control system of SWTU with a robust feedback controller developed from a proper stored-energy Lyapunov function. The sensitivity of six parameters in the model was analyzed and ordered. Parameters with the greatest impact were selected to further optimize the cost functions of design requirements by dynamic behavior optimization. Results of digital simulation on kinetic models were applied for model-based prototype design, construction and operation of SWTU. The 370-day experiment in BLSS showed that, when weak and strong disturbances occurred, the SWTU prototype with optimum structural and processing parameters was automatically controlled and regulated by the robust feedback controller to restore the CO₂ concentration in the gas phase of SWTU back to the nominal level with prescribed dynamic behavior characteristics, and reduced power consumption by 20%–35 % via calculation. The research can also give a new paradigm for design, construction and operation of SWTU prototype used for solid waste disposal in both ground and space scenarios.