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When Rankine or Coulomb theories are used to design a retaining wall, it is accepted that the retaining wall will experience a lateral displacement. By allowing the wall to move laterally, the earth pressure decreases on the active side of the wall and wall and earth pressure increases on the passive side, and therefore, more economical walls can be obtained when the lateral displacement is allowed. This lateral displacement is usually not calculated when designing a retaining wall. An experimental investigation is carried out to study the lateral displacement of a retaining wall subjected to dynamic loads with different load amplitude vibration, absolute frequencies, backfill sand relative densities, and different distances between the retaining wall and the loading source. The objectives of this study are to trace the lateral displacement of retaining wall under dynamic loads other than earthquakes such as the traffic load caused by trucks or railroads by direct measurement of displacements. The model footing used in this study is square. On a cohesionless soil, the tests were carried out using a dynamic load. The studied variables were as follows: three load amplitudes (0.25, 0.5, and 1 ton), three vibration frequencies (0.5, 1, and 2 Hz), two relative densities of sandy soil (30% loose sand and 70% dense sand), and three different distances between the foundation and the retaining wall. Observations show that the lateral displacement increased by increasing the load amplitude and decreased by increasing the distance between the foundation and the retaining wall. There is insignificant consequence of frequency on the cumulative lateral displacement. The lateral displacement decreased by increasing the density of sandy soil.

The utilization of unmanned aerial vehicles (UAVs) is on the rise across various industries. In such a scenario, the issue of flight safety for these UAVs becomes increasingly paramount. Currently, UAVs exhibit shortcomings in flight attitude perception compared to more mature manned aircraft, especially concerning the position sensing of flight actuation, which poses significant safety risks. Mature position monitoring solutions for flight actuation used in manned aircraft cannot be directly integrated into systems of UAV due to compatibility issues. This necessitates the development of new position sensing technologies to address this challenge. Triboelectric nanogenerators, with their advantages of miniaturization, self‐powering capabilities, and the ability to generate voltage‐level electrical signals, are chosen to form a part of the position detection system for sensors in UAVs. In this study, a self‐powered displacement sensor is developed that utilizes frictional charge separation signals. This sensor is specifically designed to monitor the position status of the flight actuators in UAV. With a compact volume of <11.1 cm3 and a weight of <9.5 g, this sensor is lightweight efficient and adaptable for practical applications. [ABSTRACT FROM AUTHOR]

In intelligent transportation, various types of sensors are used both in traffic control systems as well as in the control, safety, and entertainment systems of the vehicles themselves. In the process of educating future designers and developers of such systems, it is necessary to familiarize them with the operation and parameters of sensors. The recent years of the COVID-19 pandemic have disturbed this process due to the need to conduct classes remotely. This article presents the general concept of a laboratory stand for testing sensors of electrical and non-electrical quantities, which can be used both in stationary and remote learning. Additionally, the practical implementation of two laboratory stands for testing current and linear displacement sensors was also presented. Both stands have been tested in the remote access mode. The tests showed some shortcomings in the management software but also confirmed the correctness of the adopted concept of their implementation. [ABSTRACT FROM AUTHOR]

In this paper, a sensorless method of detecting the spool position of a high-speed on/off solenoid valve is presented. The method depends on analyzing the time-current curve of the solenoid coil passing current and measuring the maximum stroke of the valve spool, such that the dynamic behavior of the valve is estimated and the spool displacement curve is plotted. A mathematical model of the solenoid valve is developed and the effect of the hydraulic force on the valve spool is studied. Experimental results show that the proposed method error is less than 7% when compared to valve spool displacement measured by the commonly used linear variable displacement transducer.

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Wireless microwave sensors provide a practical alternative where traditional contact-based measurement techniques are not possible to implement or suffer from performance deterioration. Resonating elements are commonly used in these sensors as the sensing concept relies on the resonance properties of the employed structure. This work presents some simple guidelines for designing displacement sensors based on spiral resonator (SR) tags. The working principle of this sensor is based on the variation of the coupling strength between the SR tag and a probing microstrip loop with the distance between them. The performance of the sensor depends on the main design parameters, such as tag dimensions, filling factor, number of turns, and the size of probing loop. The guidelines provided herein can be used for the initial phase of the design process by helping to select a preliminary set of parameters according to the desired application requirements. The provided conclusions are supported using electromagnetic simulations and analytical expressions. Finally, a corrected equivalent circuit model that takes into account the phenomenon of the resonant frequency shift at small distances is provided. The findings are compared against experimental measurements to verify their validity.

To produce a good machine tool, the thermally induced error in the machine during machining plays a crucial role and is an important issue needing to be resolved. The thermal error may account for 70% of the total error. There are three main approaches to solving the thermal error problem: preventing heat flows from hot components, designing a thermally stable structure for the machine, and compensating the thermal error using thermal error models. The first two approaches can be carried out in the primary design stage of machine tools, and they have been used in the manufacture of commercial products. The third approach, the strategy of thermal error compensation, is the most effective and popular approach. However, there are still many unsolved problems. Among these problems, the cutting conditions have a significant influence on the modeling precision of the thermal error. In this study, we develop an integral model based on the integrated grey system theory (IGST) in conjunction with a genetic-algorithm (GA)-optimized back-propagation neural network (BPNN) to investigate the influence of cutting conditions on a machine tool's thermal error. The model is chosen on account of its high ability in dealing with a small amount of training data. Results show that a single thermal error modeling formula cannot make accurate predictions for different cutting conditions. Suitable adjustment of the modeling parameters or the use of a multiple modeling scheme is needed. [ABSTRACT FROM AUTHOR]

The use of wireless sensors for bridge assessment has been investigated extensively in the past decades. However, in most field applications, current sensors and sensing systems still rely on wired connectivity for communication and power. This is the case even though tethered sensors require extensive cabling throughout a structure resulting in long installation processes, and their maintenance may increase the total cost of Structural Health Monitoring systems and impede their broader use, especially when rapid infrastructure assessment is needed. One possible explanation of this slow adoption of wireless sensors is the use of sensing units that have not been tested for decades as their wired counterparts. This paper presents a suite of wireless sensors that were developed through the transformation of established wired sensors into wireless units. The objective was to explore whether it was possible to transform such wired sensors into wireless units and then confirm successful transformation with laboratory and field applications. The sensors presented here focus on accurate measurements of displacement, strain, and acceleration with units that are rugged, have a long service life and are used primarily for rapid structural assessment. With this transformation, the authors wanted to accomplish the goal of rapid installation and sensing reuse, and achieve accurate wireless measurements guaranteed by the wired sensors of established sensing vendors. In this study, the wireless sensors were tested first in laboratory conditions along with wired sensors for comparison and then were successfully tested in the field. [ABSTRACT FROM AUTHOR]

A novel microwave system for measuring linear displacements and velocities with sub-millimeter resolution and for the implementation of near-field chipless radiofrequency identification (chipless-RFID) systems with very high data capacity is presented. The system is based on a reader, consisting of a half-wavelength straight resonator coupled (through capacitor gaps) to a pair of access lines, and a microwave encoder, in relative motion to the reader and consisting of a linear chain of strips orthogonally oriented to the chain axis. By displacing the encoder over the half-wavelength resonator of the reader, with the encoder strips parallel oriented to the reader axis, the relative velocity and position between the encoder and the reader can be inferred. For that purpose, the reader is fed by a harmonic signal tuned to the resonance frequency that results when an encoder strip is perfectly aligned with the reader. The encoder motion amplitude modulates the feeding signal at the output port, and both the position and the velocity are measured from the peaks, or dips, of the resulting envelope function. Moreover, by making certain strips inoperative, the system can be used for coding purposes. Due to the small period of the encoder (0.6 mm), a high per-unit-length data density in these near-field chipless-RFID tags (i.e., 16.66 bits/cm) is achieved. To illustrate the functionality and potential of the approach, 100-bit chipless-RFID tags with various ID codes are implemented and read. [ABSTRACT FROM AUTHOR]

Thermal error plays a deterministic role in the machining precision of computer-numericalcontrol (CNC) tool machinery. Previously, three ways had been proposed to overcome thermal error problems: prevention, restraint, and compensation. The first two ways may be performed in the initial design stage. The last one includes the challengeable features of caseby- case simulation of cutting paths, searching for characteristic temperature points, thermal deformation measurement, and establishing an accurate thermal model. Different from most of the previous studies concerning mathematical thermal models, which have many restrictions and disadvantages, in this study, we propose a novel hybrid thermal error modelling scheme of the Grey system theorem and deep-learning neural network. Specifically, a linear-guideway grinding machine, never seen in previous thermal-error-compensation-related studies, was chosen as the target to identify the usefulness of our proposed scheme. Results show that the proposed hybrid model has a comprehensive prediction ability of thermal behavior for the target CNC grinding machine. [ABSTRACT FROM AUTHOR]

Laser sensors can be used to measure distances to objects and their related parameters (displacements, position, surface profiles and velocities). Laser sensors are based on many different optical techniques, such as triangulation, time-of-flight, confocal and interferometric sensors. As laser sensor technology has improved, the size and cost of sensors have decreased, which has led to the widespread use of laser sensors in many areas. In addition to traditional manufacturing industry applications, laser sensors are increasingly used in robotics, surveillance, autonomous driving and biomedical areas. This paper outlines some of the recent efforts made towards laser sensors for displacement, distance and position.

The degradation of onshore, reinforced-concrete wind turbine foundations is usually assessed via above-ground inspections, or through lengthy excavation campaigns that suspend wind power generation. Foundation cracks can and do occur below ground level, and while sustained measurements of crack behaviour could be used to quantify the risk of water ingress and reinforcement corrosion, these cracks have not yet been monitored during turbine operation. Here, we outline the design, fabrication and field installation of subterranean fibre-optic sensors for monitoring the opening and lateral displacements of foundation cracks during wind turbine operation. We detail methods for in situ sensor characterisation, verify sensor responses against theoretical tower strains derived from wind speed data, and then show that measured crack displacements correlate with monitored tower strains. Our results show that foundation crack opening displacements respond linearly to tower strain and do not change by more than ±5 μm. Lateral crack displacements were found to be negligible. We anticipate that the work outlined here will provide a starting point for real-time, long-term and dynamic analyses of crack displacements in future. Our findings could furthermore inform the development of cost-effective monitoring systems for ageing wind turbine foundations. [ABSTRACT FROM AUTHOR]

A fiber cavity ring-down (FCRD) displacement sensor with picometer resolution using frequency-shifted interferometry (FSI) was developed. Compared with the traditional time-domain FCRD-based displacement sensor, the proposed sensor is based on space-domain measurement by combing FCRD with FSI, which reduces the requirements of the laser source and detector, showing low cost and high sensitivity. A piece of single-mode fiber wrapped on the piezoelectric transducer was used as the sensor head and displacement was monitored by measuring the ring-down distance. The experimental results show that the sensitivity of the displacement sensor is measured to be 0.246 (km−1·nm−1). Taking advantage of using differential detection method to eliminate direct current noise and the same-path interference to cancel common-mode noise, high stability of 0.06% was achieved. Due to the high sensitivity and good stability, the displacement resolution of 10 pm was achieved, which is about 3 orders of magnitude higher than that of traditional laser interferometry-based displacement sensors. [Display omitted] • A space-domain FCRD-based displacement sensor was proposed and investigated for achieving picometre level resolution. • A sensitivity of 0.246 (km-1·nm-1) was achieved, which was higher than that of traditional FCRD displacement sensor. • A displacement sensor with resolution of 10 pm was achieved due to high sensitivity and high stability. [ABSTRACT FROM AUTHOR]

The novel fiber-optic low coherence sensor with thin diamond films is demonstrated. The undoped and boron-doped diamond films were elaborated by the use of the microwave plasma enhanced chemical vapor deposition (μPE CVD) system. The optical signal from the Fabry–Pérot cavity made with the application of those thin films is sensitive to displacement. The sensor characterization was made in the range of 0–600 μm. The measurements were performed using two superluminescent diodes (SLD) with central wavelengths of 1290 mm and 1550 mm and the output signal was analyzed by the measurement of the modulation change of spectral pattern. Furthermore, very good coefficient of the determination R 2 > 0.9565 and the visibility of optical measured signal equal to 95.6% were achieved. [ABSTRACT FROM AUTHOR]

The tunnel collapse problem of coal mine is very common and its damage is very serious. It also seriously endangers people's lives and property safety. At present, a variety of instruments are used for tunnel roof structure health monitoring in most of the coal mines at home and abroad. In this paper, a displacement sensor using optical fiber grating technology was designed, which could be used to prevent the problem of coal mine tunnel collapse by monitoring the coal mine tunnel roof displacement. Firstly, finite element analysis was demonstrated to simulate the stress and displacement of coal mine tunnel roof to determine where to install the sensor. Then the characteristics of the fiber Bragg grating sensor were analyzed in detail and the sensor structure was designed according to the actual requirements in the coal mine. At last, the feasibility of the whole system was experimentally verified. The cross-sensitivity of the temperature and displacement issue with FBG sensors could be eliminated by using matched pairs of FBG. The measuring range of 50 mm and the measurement resolution up to 0.06 mm could be obtained with the proposed sensor. [ABSTRACT FROM AUTHOR]

Some advanced fiber-optic amplitude modulated reflection displacement sensors and refractive index sensors have been developed. An improved three-fiber displacement sensor has been investigated as a refractive index sensor by computer simulations in a large interval of displacement. Some new regularities have been revealed. A reflection fiber-optic displacement sensor of novel configuration, consisting of double optical-pair fibers with a definite angle between the measuring tips of fibers in the pairs has been proposed, designed, and experimentally investigated to indicate and measure the displacement and refractive index of gas and liquid water solutions. The proposed displacement sensor and refractive index sensor configuration improves the measuring sensitivity in comparison with the known measuring methods. The refractive index sensor sensitivity Snsub = 4×10−7 RIU/mV was achieved. The displacement sensor sensitivity is Ssub = 1702 mV/µm in air (n = 1.00027).

As the demand for high speed and highly accurate machines has significantly increased, error motions from thermal change, which is up to 70 % of the total machining error, is found to be the main hurdles to overcome in improving the accuracy of CNC machine tools. In this research work, the authors installed four eddy current displacement sensors in the spindle structure near to the front bearing to monitor the spindle offset in the bearing level, which is mainly attributable to the thermal error motions of the spindle. In addition, another three capacitance sensors are mounted on the machine table level and aligned with the x-, y-, and z-axis of the machine to monitor the spindle shift in the table level to find out the correlation between temperature change and the thermal error motions of the spindle. To measure the temperature changes, we attached thermal sensors in the machine and cooling system. The estimation of the spindle thermal displacement based on temperature data from these thermal sensors can provide more information for the monitoring of thermal error motions of the spindle. [ABSTRACT FROM AUTHOR]

Highlights: [•] Novel elastomer with record value of magneto-piezoresistive sensitivity. [•] Model of the coupling between magnetoelasticity and piezoresistivity. [•] Innovative magneto-piezoresistive sensor of displacement. [Copyright &y& Elsevier]

Certain projects require the weighting of a particular structure, any industrial instrument being incompatible with the problem to be solved. In these cases new measuring instruments must be conceived. The paper presents some basic concepts regarding the development of such instruments. The study is dedicated to the weighting of the rail mounted structures. Experiments may be conducted in static or dynamic conditions. Basically, the strain gage technology offers the means to develop customized weighting instruments. The weighting operation implies the insertion of a sensor between the mass and the ground. Several solutions were studied, being presented a first method which uses strain gages and another solution based on displacement sensors. Both solutions are thoroughly analysed, by taking into account various parasitic effects. Finding the criteria to automatically process the experimental data for a load in motion along the measuring beam was an important target of the study. Numerical data were used to verify the range of the strains, of the stresses and of the deflections. Variations of the strains and displacements were graphically presented in order to have a higher degree of relevancy which leads to a more explicit interpretation and comparison of the solutions. The concepts presented in the paper may be used for rail wagons, rail mounted cranes and other rail mounted structures. [ABSTRACT FROM AUTHOR]

Given an object, its positioning in the space is a main concern in structural monitoring and a required feedback in structural health monitoring, structural control and robotics. In addition, to make the sensor unit wireless is a crucial issue for advanced applications. This paper deals with the exploitation of wireless transmission technology to long-term monitoring GPS (Global Positioning System) receivers - like the Leica GMX 902 and the Leica GRX 1200-pro. These GPS receivers consist of five parts: antenna, receiver, user client computer, interface and power supply. The antenna is mounted on the object to be monitored and is connected with the receiver by a coaxial-cable through which the radio frequency signals are transmitted. The receiver unit acquires, tracks and demodulates the satellite signals and provides, through an interface which in this paper is made wireless, the resulting GPS raw data to the user client computer for being further processed by a suitable positioning algorithm. The power supply reaches the computer by a wired link, while the other modules rely on batteries re-charged by power harvesting devices. Two wireless transmission systems, the 24XStream and the CC1110, are applied to replace the cable transmission between the receiver and the user client computer which up to now was the only market offer. To verify the performance and the reliability of this wireless transmission system, some experiments are conducted. The results show a successful cable replacement. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel interface concept for eddy current displacement sensors. A measurement method and a new front-end circuit are also proposed. The front-end circuit demonstrates excellent thermal stability, high resolution, and low-power consumption. The proposed idea is analytically investigated. The demodulation principle, as well as the interface implementation, is also addressed. This interface is being introduced for measuring submicrometer displacements in medium- to high-resolution applications. The interface system consumes less than 12 mW and has an extremely low thermal drift. The interface circuit will be implemented as a system-in-a-package (SIP). The full-scale range of displacement is 1 mm with 50-kHz signal bandwidth and 11-bit resolution (less than 500 nm). The signal conditioning circuit utilizes a standard 0.35-μm complementary metal-oxide semiconductor (CMOS) technology. Simulation resuIts, which were achieved on the basis of experimental results of testing a prototype coil, also confirm the high performance of the interface system, as expected from analytical results. Compared with previous reports, this low-power interface system demonstrates a much lower temperature drift. [ABSTRACT FROM AUTHOR]

Wireless microwave sensors provide a practical alternative where traditional contact-based measurement techniques are not possible to implement or suffer from performance deterioration. Resonating elements are commonly used in these sensors as the sensing concept relies on the resonance properties of the employed structure. This work presents some simple guidelines for designing displacement sensors based on spiral resonator (SR) tags. The working principle of this sensor is based on the variation of the coupling strength between the SR tag and a probing microstrip loop with the distance between them. The performance of the sensor depends on the main design parameters, such as tag dimensions, filling factor, number of turns, and the size of probing loop. The guidelines provided herein can be used for the initial phase of the design process by helping to select a preliminary set of parameters according to the desired application requirements. The provided conclusions are supported using electromagnetic simulations and analytical expressions. Finally, a corrected equivalent circuit model that takes into account the phenomenon of the resonant frequency shift at small distances is provided. The findings are compared against experimental measurements to verify their validity. [ABSTRACT FROM AUTHOR]

In eddy-current displacement sensing, existing techniques mostly involve a high-frequency sinusoidal carrier wave and deal with the demodulation of this signal. In this paper, we give a new design idea. We use switching circuits, in which the sensing coil is included as an inductor and driven by a switching voltage, and some baseband sensor output is readily available. Thus, no explicit demodulation is needed, and the electronics are simplified. We give three designs of such switching circuits. The first is based on coil inductance, the second is also based on coil inductance but is different from the first in many ways, and the third is based on eddy-current power loss. These circuits are tested on hardware electronics. The results seem to indicate that the presented techniques would permit performances comparable to those achieved by existing techniques. [ABSTRACT FROM AUTHOR]

This paper presents a structural health monitoring system for monitoring, with reduced visual impact, one historical building structure. The system is based on fiber Bragg gratings and comprises 19 displacement sensors and 5 temperature sensors. All the sensors were custom made according to the monitoring points' characteristics. The results obtained over the first year of monitoring are presented. The objective of this work is to gather data that will bring a deeper knowledge of how this structure behaves and to help planning the recovering interventions in this historical building. [ABSTRACT FROM PUBLISHER]

We have developed a new algorithm based on the extended Kalman filter in order to improve the resolution of a self-mixing (SM) optical displacement sensor. This noncontact sensor, which provides vibration measurement with a very high accuracy, can be used for online quality control, for example, measuring the damping of excited mechanical structures. This SM sensor subject to weak feedback has been tested in comparison with a commercial vibrometer in order to measure the frequency response function (FRF) of a plate with a passive damping to be characterized, and to show the efficiency of a damping treatment. [ABSTRACT FROM PUBLISHER]

Piezoresistive microcantilevers were developed to be used as displacement or force sensors associated with self-detection onboard electronic systems. The aim of this work was to realize a parallel integrated and compact detection system without the need for an optical readout scheme. The electronics developed specifically for this application, when dynamically operated, allows us to measure each piezoresistive microcantilever resonance frequency (by achieving at the same time an enhancement of the quality factor) with an accuracy of 0.1 Hz [ABSTRACT FROM PUBLISHER]

In this paper, a temperature-compensated configuration for extending the working range of fiber-Bragg grating (FBG) strain sensors has been proposed. This technique consists of the application of two FBGs to the opposite surfaces of a straight elastic beam which was bent in a horizontal direction. The difference of the two FBGs' wavelengths depends on the beam curvature, while the mean value is taken in order to compensate for the temperature effects. The sensor proposed is less fragile than the bare fiber and seems particularly suited as large displacement sensor, and for structures in which it is impossible to affix the bare fiber, such as breaks or separate elements. [ABSTRACT FROM PUBLISHER]

Abstract: Metrology applications commonly require non-contact, capacitive sensors for displacement measurements due to their nanometer resolution. In some metrology applications, for example, the measurement of roundness and spindle error motion, the displacements of stationary and rotating cylindrical artifacts are measured. Error from using a conventionally calibrated sensor with a non-flat (e.g., cylindrical) target is typically neglected, but these errors cannot be ignored for nanometer-level accuracy. The capacitance between a sensor and a cylindrical target is less than that of a sensor with a flat target, which causes four effects. As the diameter of the target shrinks, the sensitivity of the sensor increases, the sensing range decreases, the sensing range shifts towards the target, and the nonlinearity increases. These errors can be greatly reduced by either calibrating sensors with the correct target surface or by determining corrections for post-processing data. This paper quantifies and experimentally verifies these errors for a commonly used sensor, and a simulation of a nanometer-level measurement of out-of-roundness and spindle error motion demonstrates that measurement accuracy is improved with corrected sensitivities. [Copyright &y& Elsevier]

This paper describes a compact and low cost micro-opto-electro-mechanical displacement sensor. Our purpose is the fabrication of a long range, nanometer resolved encoder using a standard CMOS technology, in order to integrate the optical metrology system (photodiodes, analog and digital circuits) on a single chip. We introduce the interferometric linear encoder principle using diffraction gratings; then we present results of optical and electrical characterization of an optoASIC including photodiodes and associated electronic integrated on a standard 0.6 μm CMOS process. This CMOS circuitry is then included inside of a prototype of linear displacement encoder using the principle of diffraction gratings in reflection. Finally, we present the fabrication of micrometer and sub-micrometer diffraction gratings etched in silicon material, in order to obtain a higher encoder integration. [Copyright &y& Elsevier]

We have developed a measurement system for transverse bow in cold-rolled strip, which is convenient to issue and is accurate to about 0.1 mm deformation of tensile-stressed cold-rolled strip.This system has three parts: sensors to measure optical displacement, control, and a signal-processing computer. The system has been running well without interruption for four years. Since we applied this system to the tension leveler at the coil preparation line, the transverse bow has decreased from 0.13% to 0.038% [ABSTRACT FROM PUBLISHER]

A passive micro-displacement sensor (for ∼μm displacement) was fabricated based on a magnetoelectric laminate, in which the displacement change can result in a change of the magnetic flux around the magnetoelectric sensor. The displacement measurement was realized by measuring the magnetoelectric output voltage. The displacement detecting coefficient was ∼2.5 mV/μm at a frequency of ∼1 kHz. This passive displacement sensor possesses the advantages of low cost, high resolution, low energy consumption and good linearity and has potential for application in future displacement detectors. [ABSTRACT FROM AUTHOR]

Laser sensors can be used to measure distances to objects and their related parameters (displacements, position, surface profiles and velocities). Laser sensors are based on many different optical techniques, such as triangulation, time-of-flight, confocal and interferometric sensors. As laser sensor technology has improved, the size and cost of sensors have decreased, which has led to the widespread use of laser sensors in many areas. In addition to traditional manufacturing industry applications, laser sensors are increasingly used in robotics, surveillance, autonomous driving and biomedical areas. This paper outlines some of the recent efforts made towards laser sensors for displacement, distance and position. [ABSTRACT FROM AUTHOR]