Master's Thesis : Design of a stabilisation mechanism enabling compensation of parasitic accelerations due to oscillations and vibrations of a motorised multi-directional system

Abstract

The aim of this master thesis consists in pursuing a camera stabilization project for Manakeen where the internship was completed. This project consists in stabilizing a camera utilising an inertial stabilized platform, the gimbal, actuated in three degrees of freedom. The primary goal of the thesis was to finish the theoretical design of the stabilization control system of the gimbal on which is fixed a camera. To initiate the design of the control system, the dynamic behaviour of the gimbal had to be established. For this purpose, research was carried out to find the correct and accurate modeling of the gimbal behaviour. Different methods were tried to find the equations of motion describing the gimbal behaviour. First the gimbal was divided in three independent mechanical subsystems of one or two degrees of freedom. However the coupling between the different subsystems could not be neglected. Then it was try to apply the Euler’s equations to the whole gimbal. Nevertheless it was not correct to consider the gimbal as one solid submitted to torques originated from each of the three axes of rotation. Finally the Lagrange method was applied. This method proved to be the most accurate to derive the equations of motion of the gimbal. By developing Lagrange method it was found that each rotation of the gimbal was expressed in coupled equations. At first these equations were linearized around a fixed position and implemented on Matlab and Simulink. Then the time and frequency response of the system in open loop were simulated and analysed on the software. Based on these results a simple control system design of the gimbal was analysed on Simulink. These results were considered as the basis for the implementation of a more accurate modeling of the gimbal. The influence of the proportional, integrative and derivative action of a PID controller was discussed in the last section of the thesis.