Dynamic modelling of a TRMS using analytical and empirical approaches

This investigation presents 1 degree of freedom (1DOF) dynamic modelling of an experimental aerodynamic test rig, a twin rotor multi-input–multi-output system (TRMS) using analytical as well as empirical approaches. The TRMS is a highly nonlinear system which can be considered as an experimental model of a complex air vehicle. Such vehicles are required to be modelled precisely to ensure satisfactory control performance to meet the demand for automation and sophistication. The TRMS is modelled in terms of vertical and horizontal 1DOF dynamics using Newtonian and Lagrangian methods based analytical approaches and neural networks based empirical approaches. The analytical modelling is carried out in two phases. In the first phase the interface circuit, DC motors and propulsive forces due to these motors are modelled. Thereafter, the dynamic equations for the remaining parts are formulated taking all the effective forces into account. Two neural network based models are developed using Levenberg–Marquardt (LM) and gradient descent (GD) algorithms. The responses of all the analytical and empirical based models are compared with that of the real TRMS to validate the accuracy of the models. The performances of the models are also compared with respect to each other.