Study On Suppression Of Spacecraft Solar Array Vibration Induced By Sun-tracking Drive With Magnetorheological Torque Compensation

The solar array system is a major power supply device of spacecraft in orbit.The micro-vibration problem of solar array systems has received wide attention in the research fields of space.Especially,the vibration of solar array induced by the sun-tracking drive has become one of the key problems restricting the attitude stability and pointing accuracy of high-precision spacecraft.The traditional controls for the drive induced solar array vibration(DISAV)were from the perspective of improving drive stability by applying kinds of vibration control algorithms to the solar array drive assembly(SADA).These studies usually neglected the explicit evaluation of the vibration disturbance to the spacecraft.Moreover,the complex algorithms of vibration control increase the interference in the normal sun-tracking drive,which may increase the failure risk of the sun-tracking work.Thus,many researchers studied the vibration control of the solar array system with external actuators.Due to the advantages of fast response,low energy consumption,easy to control,failure protection,and so on,the vibration control with a magnetorheological(MR)device has become a very promising scheme for vibration suppression of solar array system.To solve the micro-vibration of solar array system induced by the unsteable sun-tracking drive,this thesis proposes an acvtive vibration suppression approach using a disc-type MR actuator.In order to better suppress the solar array vibration with the MR actuator,the modeling and analysis of the vibration disturbing the spacecraft,the feasibility of the vibration control using an MR actuator,and the design and control of the MR actuator are studied in this thesis.It is of great significance to improve the attitude stability and pointing accuracy of high-precision spacecraft.The contents and conclusions of the study are summarized as follows:(1)The vibration of solar array and its disturbance to spacecraft is investigated under the unstable drive considering the rigid-flexible coupling effect.Based on the existing solar array system dynamics model,the system constraints is taken into account to abtain the contrained expressions.Then,the force analysis among spacecraft,SADA and solar array is developed with the Newton's third law.The relationships between the forces/torques on spacecraft and the system constraints,by which an explicit disturbance model is established for the description of the vibration disturbing the spacecraft.According to the system dynamic model and the disturbance model,the rotaty vibration,flexible vibration and disyurbance of DISAV are systematically analyzed.The generation mechanism of the vibration disturbance is revealed.And the influence of the SADA parameters on vibration disturbance is analyzed.These provide theoretical basis for the vibration suppression of DISAV.(2)A novel suppression approach considering reliability and effectiveness is proposed for the DISAV using an MR actuator.An insertion scheme and structural form of MR actuator with strong implementing feasibility is determined by analyzing the MR actuator design,installation and the affect of the additional mass on spacecraft.Then,the system dynamic model is built for the solar array system inserted with an MR actuator,the system.Based on thhe dynamic model,the spectrum analysis is developed to study the damping characteristics of the system.And,the failure protection of the MR actuator is investigated when the control fails.Also,a good control of MR actuator is assumped,by which an active torque compensation strategy with offset reference value is proposed for the suppression of the DISAV.And,a torque compensation controller based on the minimal control synthesis(MCS)algorithm is designed considering the solar array system uncertainty.The suppression of the DISAV is simulated and analyzed with the active torque compensation.(3)Refined design of disk-type MR actuator is developed considering the influence of the centrifugal action and the plug flow region of MR fluid.For disk-type MR device,the influence of centrifugal actuation on the MR fluid with rotating shear motion is investigated.On the basic of the investigation,the modification of a fundamental three-dimensional MR fluid constitutive model is made using the stress decomposition method.On this basis,the plug flow region of the MR fluid is furtherly considered in deriving the torque calculation model of the MR actuator.The stress boundary of MR fluid in working gap is analyzed for the solution of thr stress.Combined with the torque calculation model and magnetic circuit analysis method,the key dimensions of the magnetic circuit of the MR actuator are calculated.Then,the magnetic circuit simulation and optimization of the designed MR actuator are carried out by using the joint simulation of MATLAB and ANSYS.The precise design method is validated by comparing with the experimental results of prototype performance analysis.(4)A torque tracking control method of MR actuator combing polynomial feedforward and sliding mode feedback is proposed.Combining with the Bingham constitutive model and?_y-B characteristic of MR fluid,a polynomial model of the output torque of MR actuator relative to the control current is established.The control model is abtained by reverse derivation of the polynomial model subsequently.The parameters of the polynomial model are identified using the test data.The model is verified and analyzed.On the basis of the inverse polynomial model control,a current compensation strategy is proposed by a discrete sliding mode feedback with torque tracking error as input.And,a piecewise sliding mode control method with variable control parameters is applied considering the periodic change characteristics of the desired torque of solar array vibration suppression.A controller based on polynomial feedforward and sliding mode feedback is designed for the control of MR actuator,whose accuracy of the torque tracking is verified by experiments.Then,an MR actuator-in-the-loop test is carried out for the suppression of the DISAV.The suppression effect is verified for the control of DISAV with torque compensation of the MR actuator.