| Micro-nano remote sensing satellites have developed rapidly in recent years due to their inherent high observation frequency,low development cost,short developing cycle,and flexible application.Due to the particularity of satellite activities,the core key technologies must be simulated and verified on the ground.The three-axis air floating platform is the key equipment for remote sensing satellite ground simulation,which shorten the satellite development cycle and improved technological maturity.Since satellites run in a microgravity environment,they are basically free from other external forces except universal gravitation.Therefore,the movement of satellites on the ground must eliminate the effects of gravity,magnetic forces,and other external forces such as the environment and temperature.Excessive torque will affect the effect of satellite attitude simulation and subsequent imaging experiments.Therefore,reducing the unbalanced torque and developing the automatic balance system have become the key issues of the three-axis air-floating platform technology.This program mainly studies the design and implementation of a three-axis air-floating platform automatic balancing control system and automatic balancing algorithm.This paper first uses the Euler angle description method to construct a dynamic and kinematic model of air-floating platform,and conducts targeted analysis and simplification.Based on this model,an automatic balance adjustment scheme for the gravity unbalancing torque of the air-floating platform is designed.The system is divided into a centroid measurement system and an adjustment execution system.The method of online identification of the centroid position is described,including the compound pendulum model and the least square method.With the improvement of the regulation accuracy,the influence of other interference torques on the air-floating platform has become larger.This paper discusses the causes,quantitative analysis and compensation measures of several common interference torques.The feasibility analysis of the least squares centroid identification method based on the dynamic model is carried out.Secondly,in response to the high precision and low speed requirements of the gravity imbalance torque adjustment of the air-floating platform,a firefly algorithm optimized BP neural network PID control algorithm was designed for real-time control of the automatic balancing adjustment process.A two-step tuning balance strategy of coarse adjustment and fine adjustment was formulated,the principles of PID controller,BP neural network and firefly optimization algorithm and the design of the parameter model were clarified.The firefly algorithm was used to improve the local minimum and convergence speed of the BP neural network.For slow problems,the two-level optimization algorithm is proved to have a good effect of controlling the automatic balance control through modeling and simulation experiments.Finally,an air-floating platform control system was developed.The process of constructing the control system of the air-floating platform includes hardware electronics equipment selection,control system construction,control system software development,upper and lower computer communication link establishment,and balancing algorithm programming.The software program including the control algorithm is developed based on the VxWorks embedded operating system.It is entered into the embedded computer on the desk and the embedded system is used to implement automatic balance control.Finally,the final joint adjustment experiment and auto-balancing experiment of the air-floating platform control system were completed on this system.The experimental results show that the automatic adjustment of the platform can be completed within 600s,and the offset of the three-axis centroid is reduced to the order of 10-6 or less,which verifies the effectiveness of the automatic adjustment system and algorithm of the air floating platform in this subject. |
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