Research On Strapdown Gravimeter Stabilized Platform Control

High-resolution measurements of strap-down airborne gravimeter are limited by the vibration noise from aircraft and the effect of angular motion. The aim of this thesis is to implement horizon servo tracking in a two-axial stabilized platform. In this thesis, we design a mathematical model according system characteristics; obtain command signals of angular positions by applying trust region method to solve nonlinear equations; analyze the methods for solving command signals of angular velocity; present a fuzzy sliding-mode control strategy based on the tuning parameters of particle swarm optimization; validate the control effect of system through simulation; implement horizon servo tracking of attitude angle with an accuracy better than 0.1661°.The following contents are mainly research in this thesis:?1? Based on the characteristics that the system runs at low speed with a heavy load, a two-mass servo system model which takes Stribeck friction model as friction torque input is designed, and a self-tuning PID fuzzy adaptive control algorithm and sliding mode variable structure control algorithm are proposed. Through theoretical analyses and simulations, the effect of control coefficients in system control and obtain system control parameters is also analyzed, which satisfies certain accuracy criteria.?2? A horizon error model of stabilized platform is created; the necessity of applying attitude information of strap-down gravimeter is validated to solve command signals of angular position of platform; the decoupling of command signals of angular position in a two-axial stabilized platform are implemented by applying trust region method to solve nonlinear equations; the methods to solve command signals of angular velocity are analyzed based on proving the non-differentiability of the instructions. The reasonability of the methods is also proved by simulation results.?3? A fuzzy control adaptive law and sliding-mode control parameters are optimized using particle swarm optimization. A control algorithm for reducing system dithering is implemented using fuzzy approximation method. On the basis of the carrier attitude information during the airborne gravity measurement somewhere in China, the simulation of servo tracking in a two-axial stabilized platform is also carried out. The control precision of instruction angle signal approaching is finally implemented less than 0.0038 rad.The experimental results show that by applying the trust region method to solve nonlinear equations, the accuracy of the numeric solutions are better than 10^-4 rad, and the solving speed reaches 10^-2 s. Based on the satisfaction of fuzzy sliding-mode control precision of particle swarm optimization, the horizon servo tracking in a stabilized platform that runs at low speed with a heavy load can be implemented.