Study On Precision Measuring Technology Of Electrical Thickness For Complex Surface Radome

As a key part in high speed & accurate guiding missile, the active self-seeking radar radome is a revolving shaped part with 3D-complex curve generatrix and made by hard-brittle materials. Due to complicated manufacturing process, its electrical characteristics always have poor quality, and in turn make direct influence to the guidance precision of the missiles. As an important electrical characteristic of radome in engineering, electrical thickness has already become a principal guideline in the electrical characteristics inspection and compensation of radome. The absence of high precision and automatic electrical thickness measuring machine, limits the development of radome manufacturing level greatly, and becomes a "bottleneck" in the development of high accurate guiding missile technology. So, solving the technological know-how and developing an electrical thickness precision measuring machine for radome, is of great significance to the development of national defense of China.In this dissertation, the electrical thickness precision and automatic measuring technology for complex-shaped quartz ceramic radome is studied deeply. Based on the difficulty in electrical thickness measuring and the relationship of electrical thickness and IPD (Insert Phase Delay), electrical thickness is obtained by IPD measurement; the electrical thickness measuring methed based on microwave transmitting principle is presented, and the whole scheme of measuring system is developed, which includes three main modules—IPD measuring system, mechanical system and computer control system. In the measuring process, by fixing IPD measuring system with moving radome, maintaining the microwave incidence angle to Brewster angle, and stable measuring after the measuring point of the radome surface moving to the given position of microwave focus point, the measuring precision of the electrical thickness can be guaranteed.Through the structure design and kinematics analysis, the mechanical system scheme which can ensure the motion of any point in the measurement zone of radome surface achieve microwave focus point accurately, safely and convenient; by deep studying the positioning and fixing technology of radome with complex shape and quartz ceramic material, the special-used fixture which positions by axial hoop and radial hoop and fixs with 3-part clamping hoop is designed; the key parts of the mechanical system are designed, and the series four-axis synchronous mechanical system with reasonable structure is developed; by analyzing the error sources of these parts, the integrated error model of the mechanical system which can describe the position error of microwave focus point and measuring point, and incidence angle error in measuring process is established, and the designed precision of the key parts is validated by this model.The computer control system which can realize precise four-axis simultaneous motion controlling, measuring track programming and measuring data processing is developed. Based on the "IPC (Industrial Personal Computer) + PMAC (Programmable Multi-Axis Controller)" opening structure, semi-closed loop servo-control mode, and the "PID (Proportional-Integral-Differential) + Notch filter" location loop control strategy and algorithm, the fluctuation-free and high accuracy controlling of the control system can be realized; by establishing the screw-pitch compensation and clearance compensation table, the position precision of the system is ensured; by applying the interface technology of PMAC and serial absolute encoder, the absolute position in each axis of the measuring machine can be controlled precisely in any case.Based on the objective-oriented developing strategy, the software system for radome precision measuring with complete function, friendly user interface, high reliability and convenient operation is developed. It can not only assist the user in measuring track programming and data processing, but also guarantee the full-scale control and operating condition real-time inspection with its powerful ability of man-machine two-way communication and hardware control.Integrated the above key techniques, the electrical thickness precision measuring machine for radome is developed successfully. The results of important characteristic parameters checkout and electrical thickness measuring test shows: the characteristic indices of the machine has achieved the designed requirement, it is stable and reliable in practical running, and can realize high precision and automatic electrical thickness measuring according to the motion track programming, the measurement precision is achieved, and the repetitive measurement precision is also very high. The machine has obtained the national defense invention patent, and passed the check and accept of the specialists. This research fruit has solved the key problem of electrical thickness precision measuring for complex-shaped quartz ceramic radome, filled up the domestic vacancy of this kind of machines, satisfied the urgent requirement of high accurate guiding missile development, and can make great contribution to the national defense of China.