Rigid–Flexible Coupling Dynamic Modeling and UDO-LQR-Based Stable Control of the Ground Mobile Platform Pointing System with Uncertain Disturbances

The ground mobile platform pointing system (GMPPS) suffers from poor stability and low pointing accuracy under uncertain disturbances due to nonlinear rigid–flexible coupling and structural uncertainties. A UDO-LQR control strategy is proposed, achieving superior control performance compared with the conventional PID control. In this work, a rigid–flexible coupled nonlinear dynamic model of the GMPPS with disturbances is established using Lagrange’s equations of the second kind. Based on the torque compensation equivalence principle, the electromechanical coupling equations are derived. An uncertainty disturbance observer (UDO) is designed to estimate the state variables corresponding to unmodeled disturbances, and a linear quadratic regulator (LQR) is employed to effectively suppress uncertain disturbances, achieving attitude stabilization of the pointing system (PS). The proposed UDO-LQR (UDO-augmented-LQR) strategy delivers an 83.79% performance improvement in azimuth and a 70.45% improvement in elevation in terms of RMSE compared with PID under standard road profile excitations, making it suitable for stable control of the PS under field road conditions compared to the PID control scheme.