PIM-based Digital Controller for System with Process Delay

Discretization of a controller in a process plant is a norm through a variety of means. A typical approach of industry involves converting an analog time controller to discrete time controller using PID adjustment method. Delayed system however, suffers degradation in its transient performance at certain level and form including but not limited to; higher overshoot and slower settling time. As such, process’ tuning is always mandatory as a means of compensation. Plant Input Mapping (PIM) based method aims to reduce the performance’s degradation with minimal tuning involved. In this project, an epsilon operator is used and preferred compared to z operator. Both the plant and the controller will be discretized using Step Invariant Model (SIM) and Matched Pole Zero (MPZ) technique respectively. Experiment has been done to compare the performance of discrete PID and PIM method. First order dead time (FODT) transfer function of the plant is calculated using statistical modelling method and thus, the values for continuous time (CT) PID is calculated using the open loop tuning method. Simulation of all process are generated through Simulink’s model. It is observed that the performance of PIM could rival the DT PID’s however, there is some limitation in PIM technique that makes the technique undesirable. Further modification of technique is done and proven to be significantly better than DT PID and closely simulates its continuous system counterpart.