Spatial Position Measurement Research Articles

Saliency-Based Rotor Spatial Position Displacement Self-Sensing for Self-Bearing Machines.

Self-bearing machines do not contain physical bearings but magnetic bearings. Both rotor rotary and spatial positions displacement are required in these types of machines to control the rotor position while it is levitating. Self-bearing machines often use external sensors for x (horizontal) and y (vertical) spatial position measurement, which will result in additional cost, volume, complexity, and number of parts susceptible to failure. To overcome these issues, this paper proposes a xy-position estimation self-sensing technique based on both main- and cross-inductance variation. The proposed method estimates x and y position based on inductive saliency between two sets of three-phase coils. The proposed idea is applied on a combined winding self-bearing machine which does not require additional suspension force winding. No additional search coil placement for xy-position estimation is required. Therefore, the proposed algorithm can result in a compact size self-bearing machine that does not require external sensors for xy-position measurement and suspension force winding.

Optic-electronics stereo system for spatial position measurement of railway track

Optic-electronics stereo system for spatial position measurement of railway track

Spatial Position Measurement of Multiple Targets Using a Line Lasers and a Plane Array Camera

To solve the testing problem of simultaneous overlapping and distinguish positions of multiple targets in weapon testing system, this paper proposes a method for measuring the spatial position of multiple targets based on a combination of line laser and single plane array camera, sets up the spatial position calculation model of multiple targets; studies a charge threshold crosstalk model for multiple targets with different spatial positions, and calculates the crosstalk probability at different target altitudes in terms of the imaging charge threshold. In the spatial position calculation model, error analysis of the parameter is carried out using a differential method. The factors that influence spatial position measurement errors are analyzed on the basis of the crosstalk probability. By testing the three-dimensional coordinates of flight target, we use the traditional two plane array cameras intersection testing method and a combination of multiple line lasers and single plane array camera method to compare the three-dimensional coordinates testing results when the flight target passes under the same conditions. The results show that the average errors are less than 6.8 mm, the testing system can work steadily and can distinguish effectively positions of multiple targets.

Error Analysis of a Kind of 3D Laser Ball Bar

Laser tracker instruments are used wildly in the measurement of spatial position, but the instruments have complicated structure and high manufacture cost. In this paper, a kind of 3D laser ball bar instrument for measuring spatial position was introduced, of which measuring principle is a passive laser tracking method. Based on the analysis of error sources, the compensation model of 3D laser ball bar was established according to multi-body system error modelling method. Then, a series of calibration methods for measurement errors are proposed, such as the angular error of two rotary stages, transit tilt and laser axis tilt. Measurement experiments indicate that the positioning error of X-axis is reduced from 20μm to 8μm and the positioning error of Z-axis is reduced from 61 μm to 28μm after error compensation.

A Novel Measurement System Based on Binocular Fisheye Vision and its Application in Dynamic Environment

This paper describes the development of a novel measurement system of calculating the three-dimensional (3D) coordinates of a target with image information taken from stereo fisheye cameras. The system has the characteristics of high precision, wide of view, long-distance control, dynamic angles compensation and high frame rate measurement. In order to improve the robustness and precision of the system, a detailed uncertainty analysis of the spatial positioning was made. Moreover, a novel method named Dynamic Angles Compensation Method (DACM) is proposed for first time to complete spatial position measurement in the dynamic environment by angles compensation. This method uses a tilt angle sensor that is installed in the birocular measurement system horizontally to calculate the pitch and roll angles of the measurement system, which is the foundation for calculating the conversion equation to compensate the measurement coordinates error caused by the dynamic environment. Using real data acquired by equipment, we performed experiments covering all the necessary stages to obtain a high-performance stereo fisheye vision system. The validity and accuracy of the proposed method are demonstrated with the statistical analyses of the experimental results.

Spatial Position Measurement System for Surgical Navigation Using 3-D Image Marker-Based Tracking Tools With Compact Volume.

We develop a spatial position measurement system using three-dimensional (3-D) image marker-based tracking tools targeted at surgical navigation in minimally invasive surgery. We generate 3-D image markers with spatial information encoded to 2-D images, design tracking tools with the 3-D image markers, and analyze the tracking tools' theoretical spatial errors, which are primarily limited by the spatial distribution of reconstructed fiducial 3-D markers. A pattern analysis-based positional measurement algorithm is developed to calculate the tool's spatial information using its spatial configuration. Evaluation experiments were conducted to demonstrate the accuracy and effectiveness of the proposed system. Furthermore, surgical navigation feasibility studies were performed. With a patient-image registration algorithm, a navigation interface that shows preoperative medical data and intraoperative information about the tool can intuitively and accurately assist surgeons. The results demonstrate that the proposed tracking tools, which have compact volume and spatial positional information, are of potential use in minimally invasive surgery in a limited space.

623 レーザと受光素子による材料の空間位置計測に関する検討

623 レーザと受光素子による材料の空間位置計測に関する検討

Research on the Splitting Measurement Method of Space Position in Three-Dimensional Field

A research on measurement method of space position in three-dimensional field was demonstrated in this paper. According to the basic methods and principles of three-dimensional spatial position measurement, optical path of splitting design was used to divide an object point, through the red and green filters, into two beams of red and green, and then, through flat mirror, rectangular prism, cube prism and other optical design, it imaged on the same CCD camera film. Standard mesh was used to determine the relationship between two different spatial coordinates and the spatial pixel coordinates in the measurement space, and then the calibration relationship between object point coordinates and pixel coordinates were determined. This calibration relationship clear the error caused by the method of measurement and the measurement system. Through the determination algorithm of spatial location in three-dimensional field, the two corresponding lines of space was obtained, and its point of intersection is the spatial coordinate.

SU-FF-T-06: 4D In-Vivo Dosimetry in Radiotherapy

Purpose: To present a novel concept of 4D in-vivo dosimetry in radiotherapy. Method and Materials: A prototype of a new system capable of simultaneous measurement of dose and spatial position has been developed. The device, controlled by a computer, consists of a probe combining two technologies: MOSFET radiation detector coupled with a magnetic positioning device. Special software that allows sampling position and dose in user defined time intervals has been developed. The preliminary tests of the new device have been performed. The tests included measurements of spatial position accuracy as well as a dosimetric evaluation of the device in beam from a Theratron teletherapy unit. In addition, some tests were performed in a 6 MV beam from a Siemens linear accelerator to assess if the electromagnetic field from the linac interferes with the performance of the 4D dosimeter system. Results: Measurements of the angular response of the probe over 3600 range in a beam have been found isotropic within +/− 7%. Measurements of dose profiles in air in a beam have been performed. They agree very well with the measurements performed using RFA300 dosimeter system and a high quality photon diode. Tests conducted in a 6 MV beam indicate that there is no interference from the linac electromagnetic field on the performance of this new 4D dosimeter system. Conclusion: The results of the preliminary tests indicate that the device can be used for in-vivo dosimetry in a and high energy beams from linear accelerators. Future work will involve technical improvements to the device, experiments in a 4D phantom and finally patient in-vivo dosimetry. This project has been supported by HTX-OCE-IRAP grant.

Measurements on a miniature spherical air bearing by using its electrical gap capacitance

In our field of research we are interested in testing a hemispherical air bearing. Its diametrical section forms a rotatable mirror plane of 10 mm diameter with two angular degrees of freedom. The bearing is used for scanning and tracking purposes in flexible automation research (robots, etc.), which requires very precise spatial position measurement by applying special laser techniques (such as interferometry). As high-performance properties such as low friction and high rotation accuracy are needed, the best results may be expected with the application of an air bearing. This report presents a method for the measurement of air bearing parameters, such as load-capacity and stiffness, by using the electrical capacitance between the bearing planes. Moreover it will be shown that this capacitive measurement method is suitable to measure the dynamic behaviour of the air gap (e.g. oscillations can be determined in real-time). The method is applied to the hemispherical air bearing type. First a relationship between air gap and bearing capacitance is deduced theoretically. Next the measurement results of two prototypes are compared and discussed. Finally an evaluation will be given in which the advantages and disadvantages are briefly summarized.

A study of the transient response of position-sensitive detectors

A distributed RC transmission-line approximation is used to analyze the transient response of a conventional Position Sensitive Detector (PSD). We develop a generalized mathematical model for different kinds of excitations illuminated on the PSD. The closed form expressions derived allow expedient evaluation of candidate PSDs capable of yielding fast time-resolved information for the spatial position measurement of short duration beams. Based on these calculations, it is shown that for very short pulse excitations having duration shorter than the time constant ( T c) of the PSD, the characteristic delay time ( T ch) must be known for distortionless measurement of the spatial position. It is also found from calculated results, for the pulse duration ( T p T c ) 0.02 that, T ch is 0.26. Model predictions compare favorably with observations.