Inverse Simulation of a Full- Scale Helicopter Using Finite Difference Technique

Abstract

Inverse simulation is a computational method that determines the control inputs required for a dynamic system to achieve a desired output. In case of helicopter dynamics, inverse simulation is used to obtain the pilot control inputs required for the helicopter to accomplish a desired maneuver. Complex configuration of helicopter makes its model inversion is significantly more difficult than fixed wing aircrafts. In this paper, a general method, used to define any helicopter maneuver in earth axes system, is introduced. An algorithm, for solving the helicopter inverse simulation problem at a given maneuver by using the differentiation approach, is presented. This method is based on converting the model nonlinear differential equations to algebraic difference equations which can be solved at each time step by an iterative scheme. The accuracy of this technique is improved by increasing the order of the finite difference scheme and decreasing the time step. The verification of the inverse simulation results is achieved by supplying the resultant control inputs to the direct simulation code and the helicopter flies in the desired maneuver.