Discrete time control of 2 axis gimbal

Abstract

This thesis focuses on the design and performance of the sampled-data control for MIMO nonlinear Pan-Tilt platform of two-axis gimbal for UAVs based on the discrete-time extended order HGO in the presence of parametric uncertainties and external disturbance. The control laws for these systems are designed based on their continuous-time equivalent models. The Pan-Tilt platform is a two-axis serial robotic manipulator having a nonlinear dynamic model. Pan-Tilt platform also known as a gamble has potential applications in inspections, monitoring, unmanned systems and used to carry high-precision devices such as camera or range finding sensors. Stabilization needed for the two degree of freedom gimbal which is mounted on the aerial vehicle. The stabilization of the gimbal needed for the pointing payload toward the target which is attached to the gimbal while the aerial vehicle is in flight, followed by the stabilization of the platform by canceling out any modeling and parametric uncertainties or external disturbances, that may arise because of winds, vibrations of the engine, and so on. Different nonlinear techniques have been proposed and applied to the nonlinear MIMO 2- DOF gimbal with containing parametric uncertainties and external disturbances. HGO techniques are used for the two-axis gimbal to solve this problem by using the output feedback linearization to estimate the unknown states and stabilize the system states. The nonlinearities of the system are canceled by output feedback linearization however, because of the presence of nonlinearities in the system dynamic model and other parametric uncertainties, achieving high precision stabilization or trajectory tracking is difficult. To solve this problem, EHGO is introduced. The EHGO in addition to estimation of system states provides an estimate of perturbations which includes modeling uncertainties and external disturbance, both of which play a pivotal role in performance degradation of the gimbal control system. The practical implementation of EHGO using digital electronics requires discrete-time control techniques for observer and control. The EHGO is discretized by using the ADEM method in which the continuous-time system is discretized using Euler forward difference method and discrete-time control is obtained for the discretized system. The discretized control system also provides desired performance in sampled-data configuration. To evaluate the performance of the suggested algorithm extensive simulations are carried out in Matlab Simulink to show the effectiveness 7 of the proposed controller. The derived control law is effectively applied on the real time system and desired results are obtained