Bit-stream Based Predictive Controllers for Linear and Nonlinear systems

Abstract

Controller design based on model predictive controller (MPC) is being widely applied in industry and studied by academia during past few decades. In recent years, with the wide application of networked control systems, bit-stream based control design method is getting increasing attention from researchers . The present study essentially focus on designing continuous time MPC and implement them in bit-stream environment. This is called as bit-stream MPC. The performance of bit-stream based MPC is investigated both via simulations and experiments. The study begins with a review of model predictive control in discrete time domain and the bit-stream technique. To successfully implement bit-stream controllers, several functions are initially implemented in MATLAB which can convert the analog or multi-bit digital signals into single bit. Then the discrete time MPC is adopted with bit-stream technique. Although the discrete time MPC has been very popular amongst practitioners during the past few decades, the controller still has some disadvantages such as choice of sampling time and numerical sensitivities. To overcome the limitations and difficulties associated with discrete time controllers, continuous time approach to controller design was preferred. Therefore, the next part of the research begins with designing controllers in continuous time domain. Initially continuous time model predictive controller (CMPC) was designed for linear systems based on the state space model of the system and then it is combined with bit-stream technique. In practice most of the systems are nonlinear to some extent. Therefore the next part of the study focuses on the design of CMPC for nonlinear systems (NLCMPC) based on state space models of the system. And also bit-stream technique is used on the NLCMPC. The last phase of the research deals with hardware implementation of bit-stream based CMPC using HILINK. An experimental prototype of DC servo motor has been considered for such implementation. The performance of bit-stream based linear CMPC has been implemented using HILINK and the tracking performance of such controllers is investigated by considering different types of references.