Control of activated sludge treatment process using pre-compensated multi-variable quantitative feedback theory-based controller

This paper deals with the design of a pre-compensated multi-variable quantitative feedback theory (QFT)-based fully populated matrix controller for an activated sludge treatment process (ASTP) of a waste water treatment plant (WWTP). The regulation of the concentration of biochemical oxygen demand ([Formula: see text]) and ammonium-ion ([Formula: see text]) is the control objective. The plant dynamics are obtained using physical laws available in the literature. The parametric uncertainty is quantified from the measurement data obtained from a real ASTP of an oil refinery. The model is duly cross-validated. A novel technique is proposed to design a pre-compensator that will enhance the diagonal dominance of the plant transfer function matrix. A diagonal controller and a pre-filter, are then designed using a sequential multi-input multi-output (MIMO) QFT-based methodology to meet a set of performance specifications such as relative stability, disturbance rejection, robust tracking and so forth. The simulation results validate the effectiveness of the proposed control scheme. A comparative analysis with reported works shows that the proposed control scheme outperforms some of the reported control strategies.

Quantitative Feedback Theory Velocity Control of a Single-rod Pump-controlled Actuator Using a Novel Flow Compensation Circuit

This paper employs the quantitative feedback theory (QFT) to design a robust fixed-gain linear velocity controller for a newly developed single-rod pump-controlled actuator. The actuator operates in four quadrants, with a load force becoming resistive or assistive alternatively. The controller also satisfies tracking, stability and sensitivity specifications in the presence of a wide range of system parametric uncertainties. Its performance is examined on an instrumented John Deere JD-48 backhoe. The experimental results show that the controller can maintain the actuator velocity within an acceptable response envelope, despite variation in load mass as high as 163 kg and the hydraulic circuit switching between operating quadrants.