Research On A Novel Magnetorheological Damper And Semi-active Whole-spacecraft Vibration Isolation

The harsh vibration environment during the launch phase will cause fatigue damage to the satellite structure and the on-board precision instrument.Conventional adapters for connecting satellites and rockets typically use an aluminum conical housing that features high structural stiffness and small structural damping,resulting in environmental loads to pass directly from the rocket to the satellite.As a smart device with excellent performance,the magnetorheological(MR)damper has the advantages of simple structure,continuously adjustable damping force,fast response and low energy consumption.It is considered to be one of the most promising semi-active control devices and is also an ideal actuator for aerospace applications.While the semi-active control technology has the characteristics of good stability,low energy consumption and good control effect.Based on MR damper and semi-active control technology,a whole-spacecraft vibration isolation(WSVI)system with multi-axis vibration isolation performance is presented to improve the vibration environment of satellites during launch.Aiming at the characteristics of large load mass and wide source frequency bandwidth of the WSVI system,a novel MR damper with meandering magnetic circuit(MMCMRD)is proposed.The magnetic flux path of the MMCMRD is guided by magnetically conductive and non-magnetically conductive elements.A theoretical model of the MMCMRD is built and a finite-element analysis is performed to predict the damping characteristics of the MMCMRD.Prot otypes of the MMCMRD and a conventional MR damper with the same outer dimensions are fabricated,and their damping force performance are experimentally tested and compared.The results show that the controllable range of the proposed magnetorheological damper is significantly increased,while the damping force in field-off remains unchanged.In order to apply the MMCMRD to semi-active control system design,a parametric model of MR dampers considering excitation characteristics is proposed.The damping characteristics of the MMCMRD are tested under different working conditions by changing the input current and the excitation amplitude and frequency.Based on the test results,a Tanh model describing the damping characteristics of MR damper is established,and the model parameters are identified using the genetic algorithm.On this basis,a modified model considering the excitation amplitude and excitation frequency is established.The fitting accuracy of the two models to the test results is compared,and the ability of the two models to predict the damping characteristics under other working conditions outside the test range is analyzed.The results show that the proposed model has higher fitting accuracy and stronger prediction ability,which can well describe the dynamic characteristics of the MMCMRD.In addition,the feedforward-PI hybrid control is designed based on the proposed model,and the precise damping force tracking control of the MR damper is realized.A self-inductive six-axis conical vibration isolation platform is presented,which integrates MR dampers,mold springs and sensors.Based on structural stability considerations,the platform is used to partially replace the original satellite-rocket connection(OSRC)adapter to form a novel WSVI syst em.A configuration optimization model with natural frequency and static deformation as the target and structural parameters as variables is established.The model is solved by non-dominated sorting genetic algorithm NSGA-II,and the mechanical performance optimization and structural parameter selection of the platform are completed.Furthermore,the dynamic models of the OSRC system and the proposed WSWI system are established based on the Donnell shell theory and the Newton-Euler method.The passive vibration isolation characteristics of the two systems and the influence of satellite flexibility on the transmission characteristics of the system are analyzed.The results show that the passive vibration isolation effect of the WSVI system is good,and the flexibility of the satellite has a great influence on the transmission characteristics of the system,which cannot be ignored.The dynamic model of the system and the passive vibration isolation characteristics are the basis for the design of the semi-active control system.For the vibration isolation platform with rigid load,the semi-active control simulation is carried out in Matlab/Simulink,and vibration isolation effect of Skyhook control,state feedback optimal control and two passive situations are compared and analyzed.The results show that after the maximum allowable current is applied,the resonance peak of the vibration isolation system transmissibility is significantly suppressed,but the high-frequency vibration isolation performance is deteriorated.The Skyhook control can improve this deterioration to some extent.The state feedback optimal control has the best overall vibration isolation effect,which can suppress the formant well and not deteriorate the high-frequency vibration isolation effect.Moreover,compared with the Skyhook control,the MR dampers has less power consumption under the state feedback optimal control.Furthermore,the semi-active control simulation of the WSVI system is completed and similar results are obtained.The vibration isolation platform is designed and fabricated,and an embedded controller based on DSP is developed.The WSVI semi-active control hardware-in-the-loop test system is built to carry out the ground experiments.The experimental results show that the WSVI system has good vibration isolation performance,which verifies the rationality of the design principle and the accuracy of theoretical analysis.