Modelling and vibration control of a twin rotor system: A particle swarm optimisation approach

The construction and operation of twin rotor multi-input multi-output system (TRMS) in many aspects resemble that of a helicopter, with a significant cross-coupling between longitudinal and lateral directional motions. Moreover, flexible motion due to the unsymmetrical mass distribution of the system causes structural vibration while in operation. Command shaping is an effective control strategy to reduce vibration of flexible dynamic systems. Designing a conventional command shaper requires a priori knowledge of the system characteristics. This paper investigates a new method to extract parametric model of the system and to design a command shaper for vibration reduction of the system using particle swarm optimization (PSO) algorithm. Each parameter set, that forms the model or controller, is represented as a particle in the particle swarm. In order to control the global search and convergence to the global best solution, a derivative of particle swarm algorithm that uses time-varying inertia weight factor and time-varying acceleration coefficients is used in this work. The effectiveness of the proposed algorithms is verified and their performances in vibration suppression are assessed both in time and frequency domains.