Control-theoretic dynamic modeling and analysis of a production system

Scope and Method of Study. This research is focused on combining the analytical and experimental based techniques to design, model and analyze a production system under the impact of a rush order using principles from classical control theory. This work provides a suite of transient performance metrics to study and assess the performance of a production system under the impact of a disturbance. A graphical root locus technique from classical control theory is introduced in the production system realm as a way to aid in designing control policies that affect the dynamic control system performance. This research additionally provides a framework by which real time data can be harnessed to generate dynamic control actions on the shop floor as a proactive mechanism in response to external and internal disturbances. This approach is tested on a three-workstation, homogeneous, tandem, single entrant line that has infinite supply of raw material to the system. This proposed model is a continuous flow aggregate model where the part discreteness constraint is relaxed.;Findings and Conclusions. In this study, PID control policy is found to perform better than a proportional control policy in terms of better control efficiency and improved profitability in the face of a rush order. Also, the degree of flexibility is also assessed by the production system's ability to respond to disturbances by studying its impact on the suite of performance metrics in terms of delay and quantization on the production system's performance. Based on this analysis, an increased quantization of capacity resulted in a stronger dead band that the controller needed to work against and results in less frequent and less alternating controller action. On the other hand, high quantization levels led to higher percentage throughput overshoot. Also, the effect of the production system delay is analyzed using the root locus plot and its effect on the production system response.