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Aiming at the requirements of short-range, high-precision, and high-speed measurement of coaxial helicopter wingtip distance measurement, a millimeter-wave radar wingtip distance measurement scheme is proposed, and the ranging accuracy of frequency-modulated continuous wave millimeter-wave radar is improved by optimizing the frequency estimation method and the beat-frequency signal processing process. The multi-antenna data coherent superposition method and the correlation search for the estimated frequency are used to shorten the measurement period, and at the same time, the ranging accuracy of the millimeter-wave radar can be improved, and the single measurement time can be guaranteed. Based on frequency refinement, frequency offset method, phase method, amplitude method and fitted approximation method, the frequency estimation of millimeter wave radar differential frequency signal is combined with the influence of bandwidth, measured target shape and material on ranging to improve millimeter wave radar ranging performance comprehensively. Through simulations and experiments, the accuracy, stability, time consuming and application conditions of the optimized algorithm are comprehensively evaluated, and the feasibility of millimeter wave radar wingtip ranging is verified.

To obtain a method for measuring thread functional diameter, a new probe based on the synthetic measurement principle is designed to quantify the practical effect of each parameter in all axial sections. The probing element is an axial slice of a standard thread with a certain thickness; hence, the slice has a determined lead angle and curvature radius. When threads with different diameters are measured by slices, the maximum error caused by the lead angle and curvature radius can approach 99 μm according to the simulation results. To solve this problem, a measurement error model is established by analyzing the relationship between the contact points of the measuring tip and thread. By simulations and experiments, our results show that most of the effect of lead angle and curvature radius can be compensated. Using six slices with different pitches, a precise detection of 192 kinds of threads is achieved after error compensation within the range of M65–M300.

To achieve the aim of precise position measurement of a target micro-sphere, approximately 0.2mm in diameter, a laser confocal probe, on an active focus adjusting principle, was introduced in this paper. For finding the effect way to improve the output signal, a mathematical modal of the photoelectric signal was proposed. Based on the mathematical modal, the diameter of the pinhole was decided and the optical path was adjusted, which forward the performance of the probe. The tuning fork stimulating, inductive coils and the pinhole adjuster device were designed according to the theoretical analysis, which were more convenient to the measure task. The stability of the intact oscillating unit was tested; and the optical and mechanical performance of the probe was validated by experiments using gage blocks combining with a calibrated micro-driven table. Besides, a more accurate signal processing method was suggested in this paper.

A method for measuring surfaces of rotation in a cylindrical coordinate system by using multiple measuring columns and a rotary table is proposed. This method possesses lots of advantages such as high data collection efficiency and collision avoidance. The key techniques discussed in detail include the determination of coordinate system offsets of the columns with regards to the rotary table, the determination of the effective radii of the probing systems, error compensation, collision avoidance and protection measures, workpiece centering and data processing. The practice and experiments show that the measuring uncertainty of the machines is less than 0.01 mm which meets the general requirement in most cases.

The confocal probe is a kind of non-contact measurement probes. Through an optical system containing an oscillating tuning fork, it converts displacement measurement to time difference measurement. For the measuring precision, the oscillation stability and swing of the tuning fork are important. Based on analysis, the relationship between the measuring precision and the frequency and amplitude of the tuning fork is described, and the means to obtain stable frequency and amplitude is introduced.