Two-loop robust model predictive control for the temperature control of air-handling units

This paper presents a temperature control method for air-handling units (AHUs) using a two-loop robust model predictive control (MPC). A two-loop robust MPC employs an inner-loop controller to ensure robust stability and an outer-loop controller to improve the control performance by taking uncertainties and constraints into account. A two-loop robust MPC with multiple overlapping operating modes is developed to deal with the control of systems associated with high nonlinearities. The basic idea is to separate the operating range of these systems into several operating modes such that the local systems in each operating mode suffer less from uncertainties. The overlapping operating modes are adopted in the control scheme to avoid the controller frequently switching among these operating modes. The control scheme is used to design a robust controller for a typical AHU. Simulation results are presented and compared with that of an anti-windup proportional-integral (PI) controller.