Research Of Space Coordinate Measuring Technologies Based On Wireless Sensor Network

In the process of manufacture and assembling of large mechanical equipments, precision measurement of workpiece’s physical dimension and shape and position error is a key factor for ensuring high manufacturing quality of the whole equipment. In "National Medium-term and Long-term Planning Brief for Development of Science and Technology", extreme manufacturing technology is seemed to be the cutting-edge technology of advanced manufacturing technology, and design method, manufacturing technology and measurement technology for huge system should be researched specially. With the development of huge system’s industrialization, high-efficiency measurement method and system has become an urgent issue in the field of research of huge system.The dissertation was based on a research project of "key technologies of3D coordinate measuring network with high precision for extra-large space based on wireless sensor network" sponsored by the National Natural Science Foundation. The3D coordinate measuring network with high precision for extra-large space in the project, consists of two network components:laser measurement network based on multi-lateration ranging to acquire high measuring precision for geometric parameters of major equipment with dimensions of tens of meters, and wireless sensor network to achieve coarse positioning of spatial targets and offer the high-precision laser spatial coordinate measuring system measuring guide and measure automatically. Because of peak diameter of target mirror in the laser spatial coordinate measuring system is7cm, positioning accuracy of wireless positioning system for measuring guide must be better than7cm. But the wireless positioning systems currently supplied in market cannot meet the demands of the subject.In this dissertation, a systematic study in depth about high-precision spatial wireless positioning technology was carried out. The main works and its originality of this dissertation are as follows: (1)The design of a spatial wireless positioning method based on compound time-difference of arrivalThe method combined arriving time-difference of different (spread velocity) pulse signals simultaneously transmitted from one known position node (a beacon node) to a unknown position node (a mobile node) for ranging with arriving time-difference of same (spread velocity) pulse signals transmitted one after another at a certain interval from dual beacon nodes to the mobile node for range difference measurement, and then calculated estimated spatial positions of the mobile node by redundant measurement data and the maximum likelihood method algorithm, which can acquire positioning repeatability of millimeter.(2)The design of an optimization method based on spatial positioning error analysis for wireless positioning networkBy deep research on relation between structure parameters (number and layout of beacon nodes) of wireless positioning network and positioning precision of space nodes and spatial distribution model of positioning precision, a method which selected appropriate structure parameters according to3D dimension and measurement accuracy requirements (overall accuracy and local accuracy) of measured objects, can provide scientific basis for building appropriate irregular positioning network. The optimization method can be suitable for space laser coordinate measuring system, which is also based on multi-lateration ranging.(3)The construction of space wireless positioning network based on compound time-difference of arrivalSpace wireless positioning network, which is based on compound time-difference of arrival, included beacon node system, mobile node system and positioning control system. The beacon node system primarily achieved emission of radio frequency signal and ultrasonic signal, the mobile node system mainly achieved time-difference measurement of arrival, and the positioning control system primarily achieved positioning process control and measurement information processing. The hardware and software of above systems were designed in the dissertation.(4)The completion of some research experiments and calibration experiments Experimental studies the relation between analyzed propagation distance and beam angle of ultrasonic and ambient temperature with ranging accuracy, which determined ranging error correction model, and relation between propagation distance and beam angle of ultrasonic with ranging reliability, which determined ranging weights model. The positioning accuracy of the wireless positioning network based on compound time-difference of arrival has been calibrated, and ranging error correction model and ranging weights model testified. The experimental results showed that the wireless positioning network can acquire positioning repeatability of millimeter and meet measuring guide demands of high-precision laser spatial coordinate measuring system.