| Ships are driven at sea,affected by many factors such as waves and sea breeze,and are inevitably in periodic motion.This has a serious impact on maritime radar signal capture,offshore hoisting,offshore surgery implementation,ship-borne helicopter landing safety and shipboard weapon targeting accuracy.The ship stabilized platform detects and compensates the movement of the hull in the waves in real time,provides stabilized space to ground for the shipboard equipment,and has a positive effect on the level of ship equipment.This paper focuses on the hydraulically driven 3UPS/S parallel stabilized platform prototype,from the perspective of mechanism body,hydraulic drive characteristics and mechanism control method.The research is carried out on electro-hydraulic servo coordinated control of hull motion compensation for parallel stabilized platform.The main contents are as follows:Establish a non-inertial dynamics model of 3UPS/S parallel stabilized platform.Based on the dynamics modeling process of the parallel-serial hybrid mechanism,the inertial system dynamics research method is extended into the non-inertial system through the virtual low-order reference system.The Kane method is used to establish the non-inertial system dynamic model of the 3UPS/S parallel stabilized platform.In order to verify the correctness of the modeling method,non-inertial motion experimental platform were built.The experimental results show that the calculated driving force and the measured driving force are similar in magnitude and the trend is consistent,which verifies the accuracy of the dynamic model.For the 3UPS/S stabilized platform hydraulic drive unit,the fourth-order nonlinear state space model of the valve-controlled asymmetric cylinder hydraulic servo system is established by the bond-graph method.The system parameters are obtained by the static characteristic test of the servo valve and the parameter identification of the valve-controlled cylinder system.On this basis,the driving stiffness,damping and high-order characteristics of the hydraulic drive unit under quasi-static conditions are analyzed,and the response of the servo cylinder load force to the displacement deviation is tested under different conditions.The rationality of the analysis results is verified.Based on the fourth-order nonlinear state space model of the hydraulic servo drive system,the singular perturbation analysis is used to simplify the system model into a reduced-order model.In order to demonstrate the rationality of the model simplification,the load pressure boundary assumption of the hydraulic servo system and the assumption of the same signal input and output are proposed,and the exponential convergence of the system boundary layer is given.Combined with the idea of impedance control,a single-cylinder high-precision position tracking algorithm based on singular perturbation and impedance control is proposed.Simulation and experimental results verify the effectiveness of the algorithm.Research on coordinated control of stabilized platform from two aspects of motion execution level control and trajectory planning level control.According to the characteristics of hydraulic servo drive and the spatial motion characteristics of parallel mechanism,the single-channel impedance control method based on singular perturbation is extended to the task space of the mechanism.A composite impedance control method for hydraulically driven parallel mechanism is proposed.Real-time requirements,combined with Bezier curve and mechanism motion online optimization constraint algorithm,a real-time trajectory generation method for parallel mechanism is proposed.According to the proposed coordinated control algorithm,the online trajectory tracking experiment of 3UPS/S platform is carried out.The experimental results show that the coordinated control can improve the tracking accuracy and stabilized of the platform motion,and verify the effectiveness of the coordinated control method. |
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