Experimental Research On Measure Technique Of Spacecraft Dynamic Balance

The dynamic balance of spacecraft has an impact on the precision of its movement. Because of the deviation between the principal axis of inertia and the rotating axis, the spin spacecraft is likely to generate the swing, vibration to the rotating axis, and even the rolling by the interfering moment (such as aerodynamical moment), all of which hurt the precision and stabilization of the craft movement. For the three-axis-stablized spacecraft, the dynamic unbanlance to the axis of attitude control will generate an extra dynamic couple and cause a new attitude control error. To solve the dynamic balance issue of the non-gudgeon journal and weak stiffness objects—like spacecraft—which allows only low-speed rotation, this thesis researches on a vertical hard bearing dynamic balancing machine by gas bearing and its related technology of dynamic balance measurement.This thesis first presents the design analysis, composing principle, the solution for the dynamic unbalance and methods of data analysis and processing for the system of spacecraft dynamic balance. It conducts a thorough analysis of the principle, mechanical structure and system characteristic of the existed dynamic technologies. It also probes the key issues in the dynamic balance technology: principle of measurement, bearing technique, rotation drive, sensor and the data analysis and processing.Then the thesis establishes the system dynamical model of vertical dynamic balancing machine, analyzing its working principle and locating the influence on the dynamic balance measurement by the dynamic properties of each system component. A numeric simulation experiment further proves the validness of the principle of the dynamic balance machine and the effeciveness of its configuration method. Based on the error theory, the structure of the dynamic balance machine and the principle of measurement, it also conducts an error analysis in the dynamic balance measurement and determines the error distribution of various factors.This thesis also puts forwards a measuring method of preset unbalance as an improvement of the basic measurement of the dynamic balance machine. It proved the principle of the measuring method of preset unbalance by the principle of the vertical dynamic balancing machine. By adopting a certain initial unbalance, this method overcomes the effect by the measurement dead space, echances the ability to discriminate the minor unbalance and, accordingly, improves the measurement precision of the dynamic balance machine.Further this thesis suggests a measurement principle and method for the minor unbalance based on circumferential offset. This method can improve the precision of the dynamic balance without changing the hardware of the original dynamic balance machine.It designs a calculation method of eccentricity and deflection angle of principal axis of inertia according to the dynamic balance machine measurement, which simplifies the current testing and process of related products.While the azimuth of destination axis (such as axis of centre of figure, axis of theory) can't coincidence with the axis of dynamic balancing machine, dynamic balance of the destination axis located in the measuring coordinate can be balanced directly with basic principle of mass property and the principle of dynamic balancing machine. That would replace coordinate translation equipment and simplify working process of dynamic balance. The efficiency of dynamic balance would be increased. The numerical computations indicate that the method can be feasible.Finally, this thesis performs the experiment on the minimum resolution of dynamic unbalance, the minimum residual unbalances and spacecraft dynamic balance process with an implemented gas bearing vertical dynamic balancing machine. The experimental results indicate the correctness of the above mentioned measure method of preset unbalance, measure method of circumferential offsets, calculation method of eccentricity and deflection angle of principal axis of inertia and balancing method of the axis without same azimuth. It also proves that the gas bearing vertical dynamic balancing machine meets the designed performance, capable of an accurate and effective control on the dynamic balance of the spacecraft.