A novel proportional-derivative (PD) law based fuzzy logic principles assisted controller for simultaneously controlling indoor temperature and humidity using a direct expansion (DX) air conditioning (A/C) system

A novel Proportional-Derivative (PD)law based Fuzzy Logic Controller (PFC) for a variable speed (VS) direct expansion (DX) air conditioning (A/C) system has been developed. There were two coupled control loops in this controller, i.e., varying supply fan speed to control indoor dry-bulb temperature (Tdb), and compressor speed indoor wet-bulb temperature (Twb). To weaken the coupling effect between the two loops, fuzzy logic principles were deployed. Furthermore, a PD law was used instead of a Proportional-Integral-Derivative (PID) law, in the PFC, which helped simplify not only calculation but also the structure of the PFC. The controller developed was validated by carrying out the controllability tests with the experimental conditions covering the normal operational range of a VS DX A/C system. The experimental results of the controllability tests suggested that the novel PFC developed is capable of realizing the simultaneous control of indoor temperature and humidity satisfactorily, in terms of control accuracy and sensitivity.