Transformation Control And Vibration Suppression Of Manipulator Of The Space Station

The space station is the biggest scale spacecraft in human history, which hasbeen representing the most comprehensive, complicated, advanced and integratedlevel of astronautical technology. It plays an irreplaceable role in many technologyareas such as space life science, manned deep space explore, processing of the newmaterials and so on. In the modular structure of space station assembly process, itis highly dependent upon the space manipulator to transfer function module fromthe axial lord docking port of node module to radial berthing port of node module.However, it is known that the structure flexibility of a manipulator may inducevibration during this process. It may influence docking positioning accuracy andeven endanger safe running of space station. The dynamics and control is a criticalproblem during the process of space station assembly. This dissertation focuses onthe dynamics and control problems of space station assembly concerning dynamicmodeling, attitude control, vibration control of flexible manipulator and control offlexible joint. The main themes and contributions of the dissertation include:During the process of space station assembly, the attitude of space station andthe total instantaneous center of mass may change with time. The dynamics of thesystem is quite complex. To study the dynamics characteristics for transformationof the space station via manipulator system, a vector mechanics method wasadopted to deduce the dynamic equations. The dynamic modeling withconsideration of the eccentricity was established. The elastic deformation of theflexible manipulator is depicted by using the finite element (FE) method. Thedynamic model representing the attitude motion is established with Newton-Eulermethod. And the vibrations of the flexible manipulator can be obtained by usingthe Lagrange approach. The constrained mode expansion method is used to reducethe dimensions of dynamic equations. Vibration mode of the flexible manipulatoris analyzed systematically by using the dimension reduction model.A novel vibration control theorem named negative component synthesisvibration suppression (NCSVS) is presented for active vibration control of theflexible systems such as flexible manipulator. The NCSVS, as the name denotes,contains negative amplitude components and can eliminate unwanted flexiblemodes of vibration more quickly than CSVS. Several negative componentsynthesis vibration suppression theorems are proposed and proved exactiy. Thenew principle for suppression of multiple orders modes vibrations simultaneouslyand new robustness theorem is presented respectively by expanding on traditionalCSVS method. The CSVS theory is enriched and developed extensively in this work.The differences and relations between input shaping and component synthesisvibration suppression are considered, and then a new modified negative inputshaping (MNIS) method is presented for active vibration control of flexiblestructure. The present approach allows designing modified negative input shaperby using some negative impulses and positive impulses alternately in the sequenceof impulses. The modified negative input shaper is described by closed-formfunction of the numbers of selecting impulses, the system’s natural frequency anddamping ratio. The modified UM input shaper and modified negative input shapersare proposed for undamped systems and damped systems respectively. The risetime can be improved by comparing positive input shaper. In coparison withnegative input shaper, there is a significant advantage, i.e. in the MNIS method nonumerical optimization subject to time constraints is required and the number ofselecting impulses is free. Furthermore, to improve the performance of controlsystem, a new vibration reduction control strategy is presented, which integratesmodified negative input shaping (MNIS) technique with optimal control for activevibration control of the flexible manipulator systems. Simulation results indicatethe effectiveness of the proposed method.The high-precision trajectory tracking control for space manipulator flexiblejoint is researched. The second-order cascade dynamics equations withuncertainties disturbance and friction of flexible joint are established. A controlstrategy of active disturbance rejection control (ADRC) and double closed-loopcontrol are presented by using pseudo control variables based on cascade systems.Both the inner and outer loops are designed by active disturbance rejectioncontroller. In this method the disturbances are estimated using an extended stateobserver (ESO) and compensated during each sampling period. The designedcontroller not only satisfies the quick response speed and steady-state accuracydemands, but also effectively resists to the uncertainties disturbance and friction.Control algorithm is simple and it is easy to digital implement. The simulationresults indicate that the designed of the double closed-loop control system hashigh-precision and stronger robustness and has important engineering significance.A closed-loop control for the module transformation process of the spacestation is studied. The model reduction matrix from space to plane of the spacestation transformation via manipulator is proposed. The dynamics characteristicsof the system are analyzed, and the simulation result demonstrates that the overallmoment of inertia relative to the mass center change hugely in the transformationprocess of the space station. The scope of the eccentricity is beyond the scope ofthe geometry of the core module. A closed-loop control strategy based on theCSVS/NCSVS/MNIS method and feedback decoupling control is presented in order to reduce vibration. It is difficult to determine the frequency and dampingratio of the closed-loop control system due to the dynamics model for manipulatortransformation system of the space station with strong-decoupling, nonlinearityand time variation. The designed CSVS/NCSVS/MNIS control command isachieved which utilizes the frequency and damping ratio of the whole closed loopsystem by feedback decoupling control. As mentioned above, both analytical andnumerical results verified the effectiveness for vibration suppression during thetranslocation process of the control strategy. It shows great value in both theoryand practical applications due to the improved efficiency and stability for spacemanipulator working on orbit.