Actuator/Sensor Layout Optimization Design And Vibration Control Of Large Flexible Space Structures

With the vigorous development of the aerospace industry,flexible structures for various purposes are widely used in space vehicles and science platforms,due to the nonlinear dynamics such as large flexibility,low natural frequencies,weak self-damping,and high vibration frequency of these structures,in the process of orbit transformation and attitude adjustment with the center body,it is more susceptible to environmental interference such as electromagnetic radiation and solar pressure in complex space environments.Unlike traditional small-sized spacecraft and flexible appendixes,it is difficult to stopping the vibration in a short time rely on self-damping,causing the positioning,measurement and even structural failure of the spacecraft.As an important emerging technology in the engineering field in recent years,active vibration control technology is an effective means of vibration suppression in aerospace,road and bridge engineering,exploration drilling and vehicles fields.This topic is summarized and expanded on the research on the dynamics modeling and control law design of a flexible spacecraft of a space research institute.Based on this,the main contents are:Firstly,the dynamic model of the spacecraft with flexible appendixes fixed to the center body is introduced.The vibration control equations and measurement equations of the spacecraft flexible appendixes are established by the finite element method and the Lagrange method.Based on the Newton-Eulerian method,the attitude dynamics equation of the spacecraft with flexible appendixes is established.Using the finite element analysis,four basic units,including rods,beams,plates and concentrated masses,are constructed,and combining a order-reduced flexible space structure model;All above lay the foundation for subsequent system structure design and simulation analysis.For the layout optimization problem of the actuator/sensor on the flexible space structure,considering the actuator/sensor layout,although as many sensors and actuators as possible are installed,more comprehensive modal information can be obtained,resulting in a larger control effect,but if the number and location of the layout are unreasonable,the control effect will be reduced and the system energy consumption will be increased.The energy correlation matrix of the system modal control force can be obtained from the structural dynamics equations in the order reduced system state space.Considering the controllability/observability and energy consumption of the system,a successive reduction optimazition criterion is proposed,and the actuator/sensor layout scheme is optimized.By measuring the fitness value parameter of the group,the problem that the genetic algorithm may fall into the local suboptimal solutions solving the iterative process,the crossover operator and the mutation operator are adaptively changed to obtain the global optimal solution.Aiming at the problem of active vibration suppression of flexible space structures,two kinds of vibration suppression controllers based on independent modal space theory are designed.First,the modal filter is designed to pre-filter the modal information collected from the physical space;the modal observer is designed to obtain the modal displacement and the modal velocity from the modal acceleration.Secondly,based on the independent decoupling of each mode in the independent modal space theory,an independent modal space controller based on optimal control and an independent modal space controller based on H? suhoptimil control are designed,consititute a complete closed-loop active vibration control system for flexible space structures.Finally,the simulation model is established to simulate the effect of the control system when the spacecraft center body adjusts the attitude or the transient impact of the space environment.The theoretical analysis of the observation and control spillovers in the design process is given,and the preliminary solution is given.The numerical simulation results are analyzed to illustrate the feasibility of the control system.