A Camera Stabilized Platform Based on the Feedforward Strap-Down Control with Approximate Dead-Zone Model and a Compensator with LESO

Abstract

A feedforward strap-down control with a compensator base on the linear extended state observer (LESO) is proposed for a miniaturized camera stabilized platform, which reduces the influence of the dead zone in speed regulation and uncertainties in parameters to reduce the level of angular bias to the field of vision (FOV) in a low-cost stabilized platform. Firstly, the feedforward control is inspired by an approximate linear model proposed for the dead zone to improve the response velocity of the system when tracking the varying reference. Then, the compensator, combining the LESO and proportional differential (PD) law, is designed to eliminate the disturbances including the model bias in the dead zone, inaccuracy in the plant model, and external disturbance. Moreover, the observation performance of the LESO is improved by a preprocessor based on a tracking differentiator (TD) to deal with the time delay and nonlinearities in sampling the state variables. Meanwhile, the complex and uncertain control plant is also simplified by an approximate model combining a disturbance compensator for practical application. Finally, the feasibility of the proposed controller is verified and analyzed by the simulation, and its effectiveness is simultaneously validated by the 2-DOF camera stabilized platform.