DEVELOPMENT OF PROPORTIONAL-SUM-DERIVATIVE CONTROL METHODOLOGY

A newly developed proportional-sum-derivative (PSD) control methodolog y is introduced. The need for on-line local controllers that can be ad apted to existing proportional-integral-derivative (PID) controllers w ithout additional effort for re-tuning motivates this work. The PSD co ntrol methodology is founded on the basis that an increase in energy e fficiency and an enhancement in thermal comfort conditions are achieve d by means of decreasing both the energy input and the heating/cooling -cycle changeovers. The objectives of this article are to describe the PSD control methodology and to compare the performance of the PSD and PID controllers. For the case where the gain coefficients are equal, the comparison is made using cost indices based on the controller ener gy and the offset of temperature from the setpoint temperature. The re sults show that the energy cost for the PSD controller is 64% lower th an that for the PID controller. Also, because of fewer oscillations in zone temperature, the change-over to PSD results in better comfort co nditions although the steady-state zone temperature is 0.5% higher tha n that of PID control methodology. The study performed on tuning the P SD controller indicates that various forms of performance objectives, such as lowering energy cost or lowering comfort-penalty, can be achie ved. The PSD control methodology is adaptable to PID controllers that are currently in operation and should be considered in new installatio ns. Copyright (C) 1997 Elsevier Science Ltd.