Receding horizon control based on prioritised multi-operational ranges for greenhouse environment regulation

Energy demand by a controller extensively depends on how its control strategy incorporates the desired environment. For greenhouses, existing optimal environment considerations by the control strategies are fixed level reference trajectory and allowable range for control outputs. The fixed level reference approach only favours a reference trajectory taken from a specified permissible range, instead of determining the reference path within the same range requiring lowest energy demand. The classical receding horizon control (RHC) implementation is limited to a single operation range due to the fixed format for problem formulation. This paper proposes the multi-operational ranges (MOR) based control strategy for RHC, which simultaneously handles the multiple constraints explicitly defined for control output. This new approach favours the straightforward design for the multiple constraints into various operational ranges, prioritised them based on the operational preferences, and accommodate all complications specified for temperature regulation of tomatoes. The greenhouse temperature regulation by proposed MOR RHC approach was compared with the established fixed two-level reference RHC with an adaptive transition, where each level represents the desired temperature for day or night operation. Results show that MOR approach achieves significant energy savings over the fixed level reference approach under identical environmental conditions.