DEVELOPMENT OF MEASURING SYSTEM OF GRAVITY CENTER IN UNBALANCED MODELS

摘要

The rotor system is core part in the unmanned helicopter, and it is important to the aviation performance, vibration and noise. In the system, rotor blade is usually manufactured manually because of its complex shape, materials, and production volume. Static balancing of the rotor blade should be controlled precisely in order to ensure the stability during the flight. But the cross section of the rotor blade is not symmetrical and very unbalance. In the industrial applications, there are many unbalanced models such as rotor blade in helicopter, small-sized precision motor, and rotating fans. In the real products, the centre of gravity does not usually accord with desired gravity centre. If the deviation of the gravity centre is large between them, it can be a major cause of vibration and noise due to the oscillating loads in the blades. Therefore the gravity centre in the rotation parts should be controlled properly to improve the static and dynamic balancing of the parts. In this research, the rotor blade of unmanned helicopter has been selected as unbalanced model to obtain the high quality of static balancing in the manufacturing process. It is more convenient to measure the static balancing than dynamic balancing, because the rotor blade has long length compared to its width. In order to achieve the purpose, a measuring system has been proposed. In the measuring system, basic principle is three point weighting method, which is one of the Multiple-point Weighting Method. And circle fitting was used for compensation of measured errors. Before measuring the centre of gravity, 3-dimensional measuring equipment was used for measuring the length and width of rotor blades. Because the resolution level of the electrical voltage obtained from the load cells is low, amplifier was used and the signal is inverted into the electro signal through the data acquisition board and transferred to the personal computer, then voltage is measured by using the measuring programme of gravity centre. From the results, the proposed measuring system gives reliable and precise data of gravity centre for the blade of unmanned helicopter.