Key Engineering Materials Vols. 295-296

Abstract: With the development of modern engineering such as micro-electro-mechanical system (MEMS) and new material, the deformation measurement of 3D displacement field is required. Moiré interferometry has become common for measuring the deformations of two-dimension in-plane displacement field. To solve the problem of 3D displacement field, a system for measuring the deformations of 3D displacement field is designed. By using this system, we can measure the out-of-plane displacement by appending a set of electronic speckle interference system based on Moiré interferometry system. Adjusting the incident angle of the incident light, the transmitting direction of the first order diffracted wave in a Moiré interferometry system is assigned to deviate with a small angle from the vertical direction of the specimen surface. Thus the first order diffracted wave is separated from the place of the appended interference field. The striated patterns of the deformations of 3D displacement field can be obtained at the same time. These striated patterns are recorded respectively by three CCD cameras and are stored and processed by a computer. The synchronous measuring method brings certain amount of measuring errors into the measurement of in-plane displacement. This measuring error is analyzed in theory. When real-time measurement is not required, this system can be changed into another system in which the in-plane and the out-of-plane displacement field are measured by time sharing to reduce the measuring errors. The theoretical derivation and a part of experimental results for verification are presented.

Abstract: For many reasons, the study of differential frequency measurement had disappeared for some years. This paper applies the differential frequency measurement previously used to measure transmission error to static differential frequency measurement. A new method called method of duality for gear and electric wave is proposed to explain the differential frequency measurement in a new way to discover its essence. A novel angular displacement sensor is designed. The composite error is ±17″ based on the static differential frequency measurement.

Abstract: Requirement for precision measurement becomes extremely advanced as industrial needs advances. CMM (Coordinate Measuring Machine) is one of the most adequate measuring machines to meet the requirement. As the precision of CMM becomes higher, it is important to improve the sensitivity of probe. We developed a contact type probe which consisted of a QPD (quadratic photo diode), a ball lens, and a laser diode to detect the displacement of stylus. The probe system has a resolution of 31nm.

Abstract: A portable three-dimensional vision coordinate measuring system is proposed in this paper. It consists of a light pen, a CCD camera and a laptop computer. The light pen is a hand-held probe with three point light sources using LEDs and a spherical touch stylus arranged in one line. The CCD camera takes the image of LEDs on the light pen and the 3D coordinates of measured point at the center of touch stylus are obtained by computing the positions of LEDs in the image when the probe contacts the object surface. The equations of the vision measurement system are derived by using perspective of three collinear points and spatial analytic geometry. The measuring device can be set up easily on an industrial site and the measurement is convenient. The object surface can be simple, complex, or hidden from the view of camera. The effectiveness of the mathematical model and validity of the measuring system are confirmed by experiments.

Abstract: In order to increase the precision of a high speed dynamic autocollimator, which uses quadrate detector, we propose a new method to compensate the residual measuring errors. For this purpose, a multi-tooth rotary table with precision of 0.2 seconds of arc is used to calibrate the autocollimator. From the calibration data, a polynomial interpolation compensation algorithm is used. As a result, the measuring accuracy is increased to the order of 0.8 seconds of arc and the sampling speed is not affected.

Abstract: This paper describes a measurement method for three-dimensional (3D) slit width deviations of long precision slot dies, which are essential for process control in manufacturing. A sensor unit consisting of two laser probes with their measurement axes aligned along the same Z-directional line but with opposite measurement directions, is placed between the two parts of the slot die to scan the two opposing surfaces of the parts along the X- and Y-axes. The variation of the sum of the laser probe outputs, which shows the deviation of the distance between the two surfaces, corresponds to the deviation of the slit width in the Z-direction. The 3D slit width deviations can be obtained accurately through scanning the entire surface in the X Y plane. In addition, the surface flatness of the parts can also be measured accurately by adding one more probe. Measurement experiments have been conducted on a precision grinding machine. The measurement results have indicated that the 3D slit width deviations and flatness can be measured with a repeatability error of less than 1 micron, which meets the requirement for quality control of slot dies.

Abstract: Ensuring the safety of running trains is the main condition of railways exploitation for transport of passengers and cargoes all over the world. This is determined by the growth of moving speed in railways and by the wear of the rolling stock. As the moving speed increases, the requirements of quality of railways and of the rolling stock become stricter. This entails the necessity of optimal use of rolling stock without decreasing the movement safety. In particular, in Russia, occurs the wear of car and locomotive stock. A similar situation exists in railways of India, Australia and some former socialist countries.

Abstract: A new method for measurement of dynamic angular error of photoelectric shaft encoder using trigger photoelectric collimator is proposed. The photoelectric shaft encoder rotates at an invariable or variable speed less than forty degrees per second. The dynamic angular error is measured. The standard uncertainty of this method is less than 0.5 arc second.

Abstract: Outer ring tilted or offset axially, caused by improperly fixing relatively to the inner ring, will produce remarkable systematic errors in measured radial clearance of a bearing. Analyzing their effects in detail on the results of measured radial clearances, they are found to be the main sources affecting the measurement accuracy. Measures for removing them are proposed. Based on these, a novel type of instrument for measurement of radial clearances of ball bearings has been developed. It could avoid the two kinds of systematic errors. The measuring principle, structures and working procedures of the instrument are presented. Test results show that the test time is less than 15 seconds per a part and the indication stability is between ±1.0 µm.

Abstract: A relative detecting method is proposed to detect the synchronous error of several long stroke hydraulic cylinders by using a short stroke displacement sensor, which has the advantages of low cost, easy to install and convenient in operation compared with an absolute detecting one. A synchronous model test system is established and on-line detection and control is realized by utilizing computer technology. A strategy named as Fuzzy-PID control and a program developed for this system are used for compensation of the synchronous errors. An effective new method for detection and control of synchro operation of hydraulic cylinders is presented for a deep ocean mining heave compensation system.