Model-based optimisation and predictive control of a turbocharged diesel engine with variable geometry compressor

Abstract

This paper presents a model-based optimisation and preliminary control design for a diesel engine equipped with variable geometry turbocharger (VGT), exhaust gas recirculation (EGR), and variable geometry compressor (VGC) systems. Starting from a validated model of the engine air path dynamics, a model-based optimisation is conducted at steady state conditions. The optimisation results define a simple feed-forward control strategy, which shows how the VGC can be used to increase the stability range of the compressor by means of shifting the surge limit of the machine while providing opportunity to improve fuel efficiency and turbo-lag. A design of feedback control is then investigated by coordinating the available actuators to track the desired performance variables derived from the steady state optimisation, and ensure the stability of the compressor during transient. The regulation is formulated as a receding horizon optimisation problem, which is cast as a constrained quadratic programming to reduce the computational load. The proposed controller is implemented into the nonlinear engine model, followed by an analysis of the simulation results.