This paper presents a systematic design framework for selecting the sensors in an optimised manner, simultaneously satisfying a set of given complex system control requirements, i.e. optimum and robust performance as well as fault tolerant control for high integrity systems. It is worth noting that optimum sensor selection in control system design is often a non-trivial task. Among all candidate sensor sets, the algorithm explores and separately optimises system performance with all the feasible sensor sets in order to identify fallback options under single or multiple sensor faults. The proposed approach combines modern robust control design, fault tolerant control, multiobjective optimisation and Monte Carlo techniques. Without loss of generality, it's efficacy is tested on an electromagnetic suspension system via appropriate realistic simulations.Keywords: Optimised sensor selection, Robust control, Fault tolerant control, Magnetic levitation, Multi-objective optimisation, Electromagnetic Suspension
IntroductionOptimum sensor selection in practical control system design can be complex process especially if the selection is done with respect to a number of properties in order to achieve robust optimum performance and reliability properties.A typical closed-loop control system is shown in Fig. 1. Typically, a system to be controlled has a number of candidate control inputs (actuators) and outputs (sensors) that could be used to control it by proper controller design using one of the existing modern control methods. Moreover the system suffers from input disturbances and uncertainties or model inaccuracies. Additionally, faults highly The problem of sensor/actuator selection has been addressed before in the literature [5] but none of the methods consider simultaneous satisfaction of the aforementioned properties except in [6] where the authors have consider both optimum performance and sensor fault tolerance using Linear Quadratic Gaussian (LQG) control. Therefore the problem is to find the 'best' set of sensors, Y o , subject to the aforementioned control properties i.e. optimum performance, robustness, fault tolerance and minimum number of sensors.The novelty in this paper relies in the fact that optimum robust performance with sensor fault tolerance is achieved by combining robust control methods, Fault Tolerant Control (FTC), MultiObjective OPtimisation (MOOP) and Monte Carlo (MC) method as illustrated in Fig. 2.Robust control design in a practical control system has a vital role because real systems have