Design and Implementation of Discrete Time Observer Based Backstepping Controller for a 2DOF Servomechanism

The two degrees of freedom servomechanism has many applications, including in gimbaled seekers. These mechanisms require closed-loop control to perform properly. In this paper, an observer-based multi-input-multi-output hybrid controller is designed for a two-degree-of-freedom servomechanism. Since in the model presented in this paper, disturbances on the mechanism are considered, so an extended state observer to estimate disturbance term to improve the controller performance. Also, due to the nonlinearity and two input- two output dynamics of these mechanisms, the use of combined nonlinear multivariate control methods to control the angle in these mechanisms will increase efficiency. For this purpose, nonlinear auxiliary control inputs are first determined in the first step. Then, in the second step, the nonlinear control input vector is determined using the multi-input-multi-output linear feedback method. In this step, a discrete time observer is used to estimate the uncertainty. The simulation results show that the proposed observer accurately estimates the disturbance and provides it to the controller. The controller designed using this information is able to control the output angles. Also, the results of the controller implementation designed in the processor in the loop test are presented.