Research On Ground Micro-gravity Simulation Method Of Space Operation Based On The Hybrid Magnetic Suspension System

The characteristics of the space environment for spacecraft launch and operation imply that the shuttle mission has high risk and high cost.Thus the spacecraft and its components cannot afford repeated experiments in space.As a result,ground experiments and verification are especially important.The formation of a microgravity environment that results from the motion characteristic and the relationship between time and space of the spacecraft and stars such as the earth is the necessary ground facilities for the spacecraft design,manufacture,testing,especially process validation and recurrence of running and operation.At present,the ground simulation system of a space microgravity environment has a variety of construction ways,such as passive suspension method,free-fall method,airfloating method,liquid-floating method and so on.A novel simulating method for the microG experiment with magnetism + liquid-float system has newly been introduced by the research team of Northwestern Polytechnical University,it combines an electromagnetic system and liquid-float system together.This simulating method can be a perfect solution for the shortage of the existing liquid-float system,and has the ability to simulate long-time,three-dimensional(3D)microgravity effect,provide a wide range of six degrees of freedom(DOF)movement space,and adjust suspension height freely.One of the core technologies of this method is: a non-contact force(the electromagnetic force)is introduced as an accurate compensation to achieve the experimental purpose.As an important participant,with the support of National High Technology Research and Development Program of China(863 Project),we focus on the hybrid magnetic suspension system based on the distributed electromagnetic coil array,the system has the characteristics of large-gap operating range,precise control,axial force uniformly.We focus on the accurate compensation control under large air-gap.The key techniques of the hybrid suspension system,such as working mechanism,system composition,electromagnetic force modeling,motion control strategy and experimental platform are studied deeply,and the main research contents and achievements are shown as follows:The design concept of axial uniform electromagnetic field is proposed based on the requirement of accurate compensation under large-gap,and a novel hybrid suspension system has been designed.The electromagnetic properties of the system has been studied.Taking the maximum magnetic suspension force as the optimization targets,the sizes of the system were optimized,the general design method of hybrid suspension system structure is obtained.A model describing the structure parameters was established,the influence mechanism of system parameters and electromagnetic force is studied,and construction scheme and key technology are expounded.The influence of hybrid levitation system structure parameters and electromagnetic force is studied.The space magnetic field distribution of the distributed electromagnetic coil array is quantitative simulated.The mathematical model of the hybrid levitation system was established based on the magnetic circuit method and virtual displacement method,which illuminates the relationship between the electromagnetic force vector and the different work units.The calculation precision of the electromagnetic force model is verified by the simulation and experiments,and it shows that this modeling method can effectively describe the electromagnetic force,and the eddy current loss,the equivalent area of air-gap and other factors will also influence the electromagnetic force model under large air-gap suspension.In view of the hybrid suspension system with nonlinear and big lag,the dynamic model is studied,a hybrid PID control method based on equilibrium linearization is proposed to compensate the hysteresis effect of the system.The dynamic nonlinear controller has been designed based on position control.Through the simulation and experiment,the dynamic nonlinear controller has faster response speed and smaller dynamic error compared with the traditional PID controller,and can make the system stable suspension under big air-gap.In the related theoretical research,the experiment platform was developed,the axial acceleration sensor and the three-dimensional space position measuring device were used for acquisition the motion state and location information.Experiments were carried out.The hybrid levitation system dynamics model were verified,The magnetic field uniformity test,accurate control the electromagnetic test,microgravity simulation tests were carried out respectively.The system scheme,the dynamic compensation control strategy and the theoretical research results in this paper have been verified by the experiment results.To sum up,the hybrid magnetic suspension platform under large air-gap,the system dynamics model and the dynamic nonlinear controller discussed in this paper can realize the stable suspension control suspension,and the precision compensation of gravity in motion.This study has great significance to the practical engineering application of "electromagnetic force system + liquid flotation suspension microgravity ground simulation method".