Decoupled feedforward control for an air-conditioning and refrigeration system

Multiple control objectives must be met in order to satisfy the system capacity and efficiency requirements of air-conditioning and refrigeration (A/C & R) systems. Moreover, in the HVAC industry, it is generally preferred to tune multiple single-input-single-output (SISO) control loops rather than a single multiple-input-multiple-output (MIMO) control loop. This paper demonstrates that a SISO decentralized control design, presented in [1], can be enhanced with feedforward control on select control channels to improve the response to reference signals and reduce the effect of system coupling. A feedforward controller is combined with a PI feedback controller to improve the reference tracking performance of average evaporator temperature while reducing the coupling effect of changes in other input channels. Both simulation and experimental results are presented.