New Tuning Approach of Discrete PI/PID Controller Applied to Bitumen System Based on Non-Minimal State Space Formulation

Abstract

This paper presents a new optimal tuning approach for discrete PI/PID compensators via Linear Quadratic (LQ) cost function by exploiting non-minimal state space (NMSS) form. In this regard, first order discrete-time transfer function (TF) of Bitumen system with samples time delays more than unity is utilized to formulate the novel NMSS-PI/PID form. The approach then develops state variable feedback (SVF) control law for PI/PID implementation on Bitumen system, sited at INSUMAT Company. The work also introduces proportionalintegral-plus (PIP) control as a well-established model-based, full state feedback control, when applied to the same Bitumen system, as benchmark. For consistent comparison, NMSS-PIP form is formulated using the same TF, then optimizing the PIP gains via LQ cost function. Here, the Bitumen temperature should not exceed ± 5% of the specified temperature (90o C-180o C) in order to achieve an accepted properties for the produced material. Moreover, overshoot behaviour is not allowed in order to avoid self-ignition for the vapor inside the Bitumen tank. Simulation results verify the applicability of the new discrete PID approach. Also both discrete PID and PIP control show satisfactory steady state response with good control action, with little significant improvement of PIP over new approach of discrete PID control. The paper shows successful implementation ‘onsite’ for the two controllers, for which all the control design criteria are met.