Research On Key Technologies Of Mass Proterties Measurement For Large-size Aircraft

The mass properties of flight vehicle include quality, center of gravity(CG), moment of inertia(MOI) and product of inertia(POI). Precise measurement of these parameters is the premise of controlling the flight vehicle precisely, therefore, mass properties measurement has been paid more and more attention by many countries all the time. Recently, with the development of defense and military careers, flight vehicle has made an unprecedented breakthrough no matter on size or shape, which leads to the research on related technique of flight vehicle in large size, including the technique of mass properties measurement.In order to improve the precision of mass properties measurement on flight vehicle in large size, it is researched deeply from the aspects of the improvement and optimal technique of measurement method, calibration technique of sensor and revision technique of position error, with the detailed contents as follows.For drawbacks of traditional measurement method in the measurement process of CG of flight vehicle in large size, the flexible measurement method of CG is proposed, which indicated that through the adoption of measurement equipment of three-dimensional coordinate, utilizing its own automatic leveling function and the advantage on target space location of precise measurement, the method can precisely compensate on gravity line equation of test piece under certain condition effectively, and further more can still measure the CG precisely when there is great error in leveling, processing and assembling on the measurement platform. Through the experiment, the advantage of flexible measurement method was identified, and the problem on great error simply caused by traditional measurement method, when CG of flight vehicle in large size was measured.The measurement on moment of inertia and product of inertia under the coordinate system of CG by adopting inertial ellipsoid method need the tensional pendulum measurement on the test piece under6kinds of attitudes. Considering the impact of attitude error on the calculation results, if6kinds of attitudes are selected inappropriately, tiny attitude error shall greatly affect the calculation results, therefore the optimal analysis should be conducted on attitude, and the measurement plan on rotary inertia and product of inertia based on optimal attitude was proposed. Through experiment, it was identified that the impact of attitude error could be declined to the minimum on the calculation result relying on the optimal plan; therefore, the distortion of calculation result was prevented effectively, to improve the measurement precision.On-line calibration technique of multi-weighing sensor is one of the critical techniques in mass properties measurement. For the situation of encountering with ill-posed problem constantly in the calibration process by calibration method of digital parameters addition, the solutions are promoted. First, considering from the viewpoint of resolving ill conditioned calibration equation directly, the essay utilized the resolving method based on principal combining ridge and principal components estimation, which could adopt the useful information provided by the calibration equation sufficiently, eliminate the interference of redundant information, and decrease the ill conditioned degree of calibration equation, thus, to improve the resolving precision. Then, started from the viewpoint of avoiding the ill-posed problem, the essay promoted calibration method of digital sum based on digital parameters addition with minimized condition, which enable the condition numbers of design matrix of established calibration equation approaching the minimum under the situation of no information loss, so that while the calibration precision is guaranteed, and calibrated robustness shall be improved.The revision technique of measured attitude error based on kinesiology is researched. First, the essay established kinematics mode on the whole mechanical structure, and calibration equation of kinematics parameter based on pose error. Through the geometric parameter of calibrated mechanic structure, the revision on measurement pose error was achieved. In order to improve the calibration efficiency and precision, it is designed the method adopting optimal configuration, established the judgment evidence for optimal calibration configuration, and promoted the method to search the optimal calibration configuration by adopting the advanced particle swarm optimization. Finally, through experiment, it is verified that adoption of the improved particle swarm calculation could obtain the optimal calibration configuration precisely, and geometric parameter obtained from the calibration under the optimal calibration configuration can revise the pose error effectively.For the requirement of mass properties measurement on certain flight vehicle in large size, a suit of measurement system is designed and developed, which could measure the mass properties of flight vehicle in large size. After measurement on standard piece, each performance reached the design requirement. Because the system utilized the new method and technology promoted in the essay, it is verified that the correctness of critical technique researched in the essay.