General Mass Property Measurement Equipment for Large-Sized Aircraft

Abstract

The accurate measurement of aircraft mass properties, such as the mass, centroid, and moment of inertia (MOI), plays a key role in the precise control of aircraft. In order to obtain high-precision information on the parameters of the mass, centroid, and MOI of an aircraft using a single instrument, an integrated mass property measurement system was developed in this study by analyzing and comparing the latest technologies, especially the function-switching device, which switches the measurement states between the center of mass and the MOI. The purpose of mass property measurement was achieved through single clamping. In addition, the system has strong versatility and expansion and can be used with different tooling or adapter rings to measure the mass properties of aircraft with different shapes. In this paper, the main mechanical structure of the measurement system, the measurement method of relevant mass parameters, and the solution method of the transformation matrix are introduced, and the standard parts and the aircraft were verified experimentally. The test results showed that the mass measurement accuracy was 0.03%, the centroid measurement error was within ±0.2 mm, and the measurement accuracy of the MOI was within 0.2%, all of which meet the high-precision measurement requirements for the mass properties.

Research on the Pose Error Compensation Technology for the Mass and Centroid Measurement of Large-Sized Aircraft Based on Kinematics

“…Before the measurement, the four load cells are adjusted to the same height. Record the output value of the load cell in the no-load state and the load state, respectively, noted as P 1 i and P 2 i [ 14 ], namely: where M g is the equipment work parts mass, and M z is the total mass of the equipment tooling and the measured object.…”

“…The theoretical 2D coordinates of the centroid of the measured object in the sensors’ coordinate system can be measured through the principle of moment balance, combined with the position information and output data of the load cell. where x si , y si are the coordinates of the i th cell in the XOY plane of the coordinate system where it is located, and Δ P i is the difference between the measured values before and after the i th cell loads the measured object, denoted as Δ P i = P 2 i − P 1 i [ 14 ].…”

“…A multi-station measurement idea that can self-compensate the results is proposed on the basis of the mass and centroid measurement system introduced in the paper [ 14 ]. The idea is realized by the multi-station switching device in [ 14 ].…”

“…In view of the above situation, a multi-station measurement idea which can compensate for the pose error is proposed based on the equipment described in [ 14 ], After the initial calibration, the conversion of measurement results into the measured object’s own coordinate system without a laser tracker is realized by the homogeneous coordinate transformation matrix based on the kinematic concept. At the same time, this function can also effectively suppress product pose errors caused by assembly errors introduced by the measurement system or the object under test.…”

Research on error separation method of center of gravity measurement system for large-sized solid of revolution

“…The multi-point weighing method uses three or more load cells to support the measuring platform together, and the center of gravity can be measured by the principle of static moment balance based on the relative position of each sensor. This method boasts a simple structure, high measurement accuracy, and the ability to measure the specimen's mass simultaneously, making it widely used in the field of large-size specimen measurement [7][8][9].…”