The propeller engine uses the rotation of the propeller to push the air behind the aircraft, which would produce the reaction force to propel the aircraft forward. The propeller is generally made up of multiple propeller blades and a propeller hub. The overall balance of the assembly needs to be measured to ensure that the unbalanced synthetic torque generated by the individual blades is within a reasonable range when the propeller engine is rotating. Therefore, it is essential to measure the static torque of each propeller blade after production and before assembly. Due to the unique irregular shape of the propeller, the radial torque varies at different rotation angles. Moreover, the variable pitch propellers with adjustable blade angles have been widely used, so the measurement of the radial static torque of the propeller at different working angles also needs to be addressed. The existing propeller blade static torque measurement devices are mainly based on the principle of torque balance, which has the advantages of low measurement error, high stability, and repeatability, and the results can be traced using weights.
In this paper, a propeller static torque measurement device is developed for the new composite variable pitch propeller, which can achieve the measurement of both propeller axial static torque and radial multi-angle static torque measurement. Besides, a specified gauge is developed for the device and the performance parameters of the device are tested by the gauge and the actual blades to verify the feasibility of the device.
The measurement requirements for civil aircraft components when using laser radar are always large-scale, high precision, high efficiency and so on, so several measuring stations are needed to construct a large-scale measuring network. Thus how to set up the layout of the stations is very important as it has direct influence with the precision. In this paper we develop a layout optimization method to solve the question in order to meet the requirements for precision and efficiency. The math model of the optimization is constructed by using the precision as constraints, and the solution is given to get the exact number and division of the laser radar. The initial layout can be obtained by the region growing algorithm to carry on the characteristics of discrete information and extract the discrete point method. And then we use the measurement uncertainty to optimize the results and the division. The experimental results show that compared with the experience-based manual layout, this method is more feasible and effective in obtaining large range and small number of measurement area division results and reasonable stations measurement stations. This experiment has verified the rationality, the correctness, the precision and effectiveness of the relevant methods.
The rocket sled is a large-scale, high-precision ground dynamic simulation test equipment that uses a powerful rocket booster to push the test object at high speed on a special slide which is similar to a railroad track. It is mainly used for dynamic performance analysis of such as speed and acceleration. There are several targets along the sled and the ultra-long position parameters of the targets are very important for the dynamic test. Thus it is a worldwide problem to get the position parameters precisely. This paper states a measuring method for position parameters of large rocket sled by using the fusion of multiple measurement systems. At present, the methods of obtaining dynamic parameters mainly include high-speed photography and photoelectric detection position marking method. We use a laser tracker and a total station to set a collaborative network which can integrate the advantages of the both systems. The mathematic model is established by using the global coordinate control field as the constraint equations. In order to solve the equations we use the iterative optimization algorithm, and the weights for each value are given. The experiment is designed under field environment and The results show that the measurement error is kept at 3mm within the range of 3km by comparing with the standard length of the reference ruler. This experiment has verified the high-precision and high-efficiency of the ultra-long position measuring method.
KEYWORDS: 3D modeling, Global Positioning System, Optimization (mathematics), Instrument modeling, Distance measurement, Data modeling, Control systems, Sensing systems, Assembly equipment, Process modeling
Digital measurement technology used for aircraft assembly is to meet the requirements of each link in the aircraft assemble process, to integrate digital measurement into the aircraft assemble process, and to improving the accuracy of component assembly. At present, the measurement process involves a large number of departments such as design, manufacturing, product process, inspection, and assembly, which would result in a huge workload and volume of measurement data. In this context, a variety of digital measurement equipment, such as laser trackers, indoor GPS, laser scanners, photogrammetry systems, and laser radar, are used to from a collaborative measurement system, which is built to complete resource fusion and data fusion, so as to form a solution for on-site assembly with high precision, efficiency and flexibility. Firstly, according to the measurement process requirements, digital measurement technology should be integrated into all aspects of aircraft assembly, and a 3D measurement process model construction method is proposed. Then, in the process model, a digital method using multiple measurement devices is proposed. The corresponding algorithm and a method of calculating iterative initial values is proposed to improve the accuracy. Finally, a collaborative measurement platform based on laser tracker and indoor GPS is designed for the assembly process for the large part of an aircraft. The accuracy of the algorithm is verified, which proves the correctness and reliability of the method provided in this paper.