Research On The Attitude Control System For Nano-Satellites Based On Micro-Reaction Wheels Units

With the development of miniaturized satellite technology,nano-satellite begins to assume more and more scientific research tasks,even to the area for undertaking civilian and military tasks.It makes higher requirements to the miniaturized satellite attitude control platform.However,due to the quality,size,power consumption and other restrictions of nano-satellite,the performance of the indicators on the nano-satellite has not been desired,neither for its control system accuracy.The project of micro-reaction wheels unit design is the main direction of attitude control development.Because of its own unreliability,the orbit injection of the satellite has repeatedly failed.Based on the actual needs of nano-satellites,this paper studies the current situation and trend of domestic and foreign research,making a study on the reaction wheel unit through theoretical calculation and computer simulation.The main results of this paper are as follows:(1)Aiming at the design constraints and performance requirements of ZDPS-2 satellites,establishing mathematical model of mass efficiency of micro-reaction wheel using this model to make quantitative comparative analysis to 3 commonly used mass block of momentum wheel structures.The result shows the best on quality efficiency in the application of beam mass block.This paper establish unbalanced mathematical model of micro-reaction wheel,combining structure design makes parameter analysis of dynamic unbalance on structural design parameters as well as the requirements of machining error.According to the above analysis,reaction wheel unit design scheme has been optimized,wheel unit structure design,circuit and control software design has been completed,and all the performance has been tested and analyzed.The 2 units of 8 momentum wheels developed were applied to two ZDPS-2 satellites respectively.Presently,they have been running in orbit for nearly two years,accomplishing the mission objectives and life assessment.(2)The design of realizing attitude stabilization and maneuver of ZDPS-2 satellite by the use of micro-reaction wheels unit has been put forward.In view of the ZDPS-2 satellite's own issues,such as carrying large deployable mechanism,the inertia ratio of satellite and wheel unit is large,a control scheme of wheel unit with magnetic torque actuator is proposed,and the control algorithm is designed.Within 12 months,all the software and hardware development and test verification work are completed.ZDPS-2 satellite adopts the attitude scheme control based on the reaction wheel unit,completing the three-axis stabilization control.The main technical indicators meet the requirements of the mission objections.The main function and performance coincides with the ground simulation analysis,which ensures the long term stability of ZDPS-2 in orbit,and meets the task requirements successfully.Some flaws like frequent saturation of momentum wheel are found in orbit.To solve these flaws,two other shapes of wheel unit are analyzed and compared.The optimization scheme of the magnetic flux feedback and the reaction wheel speed management is proposed.The simulation results show that the scheme can achieve better results.(3)In view of the application of the earth to ground optical remote sensing satellite,like high accuracy staring imaging,multi observation sequence imaging,regional scanning imaging,a series of issue have been studied,such as high precision control and fast maneuver control.In the scheme of attitude maneuvering,two solutions are provided,the control mode of "bang-bang +terminal PDM with no path planning and the control mode of "feedforward + full PD" with path planning.The advantages and disadvantages of the both sets of schemes are provided.For the gaze control of the ground,the paper also gives two sets of design schemes of "the sliding mode control" and "feedforward +PD".Related simulation analysis is carried out to compare the advantages and disadvantages of the two methods.Then a set of control scheme is given by combining attitude maneuver and staring control.In the area scan scheme,a small angle attitude maneuver control scheme is proposed,proving the effectiveness of the system.To sum up,this paper combines ZDPS satellite engineering application requirements,carrying our further research on reaction wheel design and attitude control system based on reaction wheel unit.The above research findings have been successfully applied on ZDPS-2 satellite on orbit,providing key technologies for the next generation high-precision remote sensing nano-satellite.