Range Of Differences Research Articles

Robust Least Squares Approach to Passive Target Localization Using Ultrasonic Receiver Array

A precise range difference (RD)-based passive target localization algorithm is proposed for mobile robot applications. To effectively solve the real-time issue, the nonlinear relation between the RD information and the target location is removed by introducing the target range as an auxiliary variable to be estimated. Then, the RD-based localization problem is formulated in the setting of linear estimation. The resultant linear measurement model contains the stochastic parametric uncertainty which causes the severe performance degradation of the conventional linear least squares (LS) method when the RD measurement noise is not negligible. To cope with this problem, the recently developed linear robust LS (RoLS) estimation theory is applied for the passive target localization problem. Using the geometric relation among the ultrasonic receivers, a systematic way to determine the design parameters of the RoLS estimator is suggested. It is shown that the proposed method can provide the nearly unbiased target location estimates for the whole location area. The proposed solution is very practical because it is preferable for real-time robot applications owing to its linear recursive structure. Through the computer simulations and actual experiments, it is shown that the proposed algorithm guarantees the superior localization performance and the fast convergence compared to the existing one.

Orbit Determination of Geostationary Earth Orbit Satellite by Transfer with Differenced Ranges between Slave-Slave Stations

In order to more restrict the transverse orbit error, a new method named “differenced ranges between slave stations by transfer”, similar to Very Long Baseline Interferometry (VLBI) observation, has been developed in the Chinese Area Positioning System (CAPS). This method has the number of baselines added, the baseline length increased and the data volume enlarged. In this article, the principle of “differenced ranges between slave stations by transfer” has been described in detail, with the clock offset between slave stations and system error which affects the precision of the differenced ranges observation being discussed. Using this method, the differenced observation of the SINOSAT-1 satellite with C-band between slave stations from 6 to 13 June 2005 was conducted. Then a comparison was made between the accuracy of orbit determination and orbit prediction. A conclusion can be drawn that the combination of pseudo-range receiving the own-station-disseminated signal and the differenced range observation between slave-slave stations has a higher orbit determination and prediction accuracy than using only the former.

Comparison of Active, Passive, and Proprioceptive Neuromuscular Facilitation Stretching for Improving Glenohumeral Internal Rotation

The purpose of this study was to compare the eff ectiveness of active, passive, and proprioceptive neuromuscular facilitation (PNF) stretching techniques on improving internal rotation of the shoulder in asymptomatic individuals. From a convenience sample of college students, including individuals on a particular athletic team, 42 asymptomatic individuals volunteered to participate. A stretching intervention was implemented during which participants performed 3 shoulder stretches by either passive, active, or PNF techniques. The results revealed signifi cant diff erences in range of motion (ROM) over time for internal rotation among the diff erent stretching protocols (P � .01). However, the stretching protocol implemented, whether passive, active, or PNF, did not signifi cantly aff ect ROM for internal rotation. The current fi ndings revealed that active, passive, and PNF stretching over time can elicit increases in internal rotation within the glenohumeral joint, and these changes are apparent after 1 week of stretching intervention.

Passive Range-Difference Estimation in a Dispersive Medium

Passive source localization can be achieved by utilizing the range-difference (RD) measurements between the source and several spatially separated sensors. When the signal propagation medium is nondispersive, the RD is typically obtained from time-difference-of-arrival (TDOA) between sensor outputs. However, for a dispersive medium which corresponds to in-solid localization, the TDOA information is not reliable. In this correspondence, two RD estimation algorithms for dispersive medium are derived and analyzed, assuming that the dispersion curve is available. Computer simulations are included to contrast the estimation performance of the two methods with the Cramer-Rao lower bound (CRLB) for different conditions.

Semidefinite Programming Approach for Range-Difference Based Source Localization

A common technique for passive source localization is to utilize the range-difference (RD) measurements between the source and several spatially separated sensors. The RD information defines a set of hyperbolic equations from which the source position can be calculated with the knowledge of the sensor positions. Under the standard assumption of Gaussian distributed RD measurement errors, it is well known that the maximum-likelihood (ML) position estimation is achieved by minimizing a multimodal cost function which corresponds to a difficult task. In this correspondence, we propose to approximate the nonconvex ML optimization by relaxing it to a convex optimization problem using semidefinite programming. A semidefinite relaxation RD-based positioning algorithm, which makes use of the admissible source position information, is proposed and its estimation performance is contrasted with the two-step weighted least squares method and nonlinear least squares estimator as well as Cramer-Rao lower bound.

Ind

Tengkawang is one of the leading commodity of non timber forest products in West Kalimantan. Tengkawang commodity ls sold in the form of dry seed mainly for export. Meanwhile, the processed products derived from tengkawang such as tengkawang oil are sent back to Indonesia as imported finished and half-finished items. This investigation was mainly aimed at assessing the effect of growth site, species, and diameter of tengkawang producing trees on the seed productivity. The target was to procure reliable data/information on productivity and technical growth increment which can befurther useful as a guidance in developing tengkawang-seed busines. The result revealed that the highest productivity of tengkawang seeds indicated by the trees with a diameter in the range of 60 -90 cm. The results revealed that, the seed production was 555,7 kg per tree per harvest. The highest seed productivity was indicated by Shorea stenoptera Burk trees growing in Sanggau, i.e. 620,9 kg per trees per harvest. It is suggested that based on the honestly significant difference's range test, the promising development of tengkawang cultivation in rank by species from the most until the least was consecutively Shorea stenoptera Burk, Shorea stenoptera Burk Forma Ardikusuma, and Shorea palembanica Miq. respectively, All species grow in Sintang and Sanggau.

Least squares range difference location

An array of n sensors at known locations receives the signal from an emitter whose location is desired. By measuring the time differences of arrival (TDOAs) between pairs of sensors, the range differences (RDs) are available and it becomes possible to compute the emitter location. Traditionally geometric solutions have been based on intersections of hyperbolic lines of position (LOPs). Each measured TDOA provides one hyperbolic LOP. In the absence of measurement noise, the RDs taken around any closed circuit of sensors add to zero. A bivector is introduced from exterior algebra such that when noise is present, the measured bivector of RDs is generally infeasible in that there does not correspond any actual emitter position exhibiting them. A circuital sum trivector is also introduced to represent the infeasibility; a null trivector implies a feasible RD bivector. A 2-step RD Emitter Location algorithm is proposed which exploits this implicit structure. Given the observed noisy RD bivector /spl Delta/, (1) calculate the nearest feasible RD bivector /spl Delta//spl circ/, and (2) calculate the nearest point to the (/sub 3//sup n/) planes of position, one for each of the triads of elements of /spl Delta//spl circ/. Both algorithmic steps are least squares (LS) and finite. Numerical comparisons in simulation show a substantial improvement in location error variances.