bluuebunny/crossref_metadata_2025_split huggingface dataset:
Teleoperated equipment for emergency response applications at the savannah river site
Authors: Fogle Robert F. , Heckendorn Frank M. 
Published: July 2007

AbstractThe Robotics Development Group (RDG) of the Westinghouse Savannah River Company (WSRC) is developing an array of teleoperated vehicles and support equipment to be used in emergency response applications. Teleoperators have been used to monitor and map radiation areas, perform decontamination tasks, and handle radioactive material. Other possible scenarios include video surveillance, remote sensing, and fire fighting. The primary justification for developing teleoperated vehicles and support hardware is to eliminate or significantly reduce personnel exposure to radioactive or other hazardous activities. This article discusses past, present, and future applications that use teleoperated equipment and current development work on several mobile teleoperators at the U.S. Department of Energy's (DoE) Savannah River Site (SRS).
Path feasibility and modification
Authors: Young Kuu‐Young , Wu Chi‐Haur 
Published: July 2007

AbstractKinematic feasibility of a planned robot path is restrained by the kinematic constraints of the robot executing the task, such as workspace, configuration, and singularity. Since these kinematic constraints can be described utilizing the geometry of the given robot, corresponding regions within the robot workspace can be expressed in geometrical representation. Consequently, geometric information can be derived from the planned path and the geometric boundaries of these regions. Then, by utilizing the geometric information and proper modification strategies, a Cartesian robot path that is kinematically infeasible can be modified according to different task requirements. To demonstrate the proposed feasibility and modification schemes, simulations for a 6R robot manipulator are executed.
Model for robot motion performance
Authors: Wygant Robert M. , White Bob E. 
Published: July 2007

AbstractExperimental studies were conducted on the Prab Model E, General Electric P‐50, and Cincinnati T3 robots to develop a model to predict performance times for motions in the X, Y, and Z axes. Based on this analysis, it was determined that some robots have a definite point where the programmed velocity does not affect the time to move from one point to another.
Design of robust PD‐type control laws for robotic manipulators with parametric uncertainties
Authors: Shahruz S. M. , Langari G. , Tomizuka M. 
Published: July 2007

AbstractIn this article, design of a simple robust control law that achieves desired positions and orientations for robotic manipulators with parametric uncertainties is studied. A discontinuous control law is proposed, which consists of a high‐gain linear proportional plus derivative (PD) term and additional terms that compensate for the effect of gravitation. The stability of the robotic system under the proposed control law is proved by LaSalle's stability theorem. Furthermore, by the theory of singularly perturbed systems, it is shown that if the proportional and derivative gain matrices are diagonal with large positive elements then the system is decoupled into a set of first‐order linear systems. Simulation results are presented to illustrate the application of the proposed control law to a two‐link robotic manipulator.
Dynamic analysis and determination of the joint characteristics of parallel‐drive robot manipulators
Authors: Chen C. C. , Yeh M. K. , Sung C. K. 
Published: July 2007

AbstractThis article presents a theoretical and experimental study on structural dynamic response and determination of the joint characteristics of a five degree‐of‐freedom industrial robot manipulator with a parallel‐drive mechanism. The joints were modeled as a linear spring in parallel with a viscous damper while the link members were assumed to be rigid in this study. The dynamic equations of motion of the robot manipulator were derived using the principle of virtual work. Based on these equations, the complex structural characteristics of the manipulator were simplified by carefully arranging the manipulator in proper arm configurations to avoid coupling effects among joints. Hence, the joint stiffness and damping ratio of each joint were determined experimentally. Meanwhile, the dynamic responses of the robot manipulator were also investigated. Good correlation between computer simulations and experimental results was achieved. From the experimental study, an additional troublesome flexural mode of about 10 Hz that tends to dominate the whole dynamic response and influence the positioning accuracy of the manipulator was found due to the weakness of the structural member at the base rotation joint, which was not modeled in the dynamic equations. The results of this study will be useful in providing a basis for improving the design of mechanical components and the articulating members of industrial robot manipulators.
Path planning in the presence of obstacles based on task requirements
Authors: Wu Tzung‐Hsien , Young Kuu‐Young 
Published: July 2007

AbstractWe propose a novel and efficient scheme for planning a kinematically feasible path in the presence of obstacles according to task requirements. By employing geometrical analysis, we derive expressions to describe the relationship between the planned path, kinematic constraints, and obstacles in the robot workspace. The freedom available according to task requirements is then utilized to modify the infeasible portions of the planned path. We use a 6R (revolute) wrist‐partitioned type of robot manipulator and a spherical obstacle as a case study to demonstrate the proposed scheme. We then extend our results to general wrist‐partitioned types of robot manipulators and arbitrarily‐shaped or multiple obstacles. © 1994 John Wiley & Sons, Inc.
Efficient quadrature multichannel processor algorithms for MCD applications
Authors: Corden I. R. , Carrasco R. A. 
Published: July 2007

AbstractThe forthcoming third generation of satellites incorporating multichannel demodulator (MCD) processors, and the needs apparent within aviation systems, induce the requirement for efficient band processing algorithms with specific regard to the quadrature processing arrangement.This paper presents a coherent z‐domain formulation of the pertinent digital transmultiplexer algorithms for the on‐board processing (OBP) scenario, with a view to establishing a set of desirable algorithmic properties suitable for the preferred complex oriented quadrature processing algorithms. Stemming from the principles set forth, an ensemble of new algorithms based upon mixes of Hilbert transforming and real transform algorithms is presented, wherein the established concepts relating to the telephone network transmultiplexer algorithms are able to be exploited in certain cases. Further, the computational load of one of the methods is lower than that of a known prominent OBP related technique. The computational necessities of the various algorithms are laid down for comparative purposes in addition to the mathematical descriptions.
On‐board baseband switch development using A high speed optical ring
Authors: Pontano B. A. , Redman W. A. , Inukai T. , Razdan R. , Paul D. K. 
Published: July 2007

AbstractThis paper presents work performed at COMSAT Laboratories to develop a prototype on‐board baseband switch. The switch design is modular to accommodate different service types, and the architecture features a high‐speed optical ring operating at 1 Gb/s to route input (up‐link) channels to output (down‐link) channels. The switch is inherently a packet switch, but can process either circuit‐switched or packet‐switched traffic. If the traffic arrives at the satellite in a circuit‐switched mode, the input processor packetizes it and passes it on to the switch. The main advantage of the packet approach lies in its simplified control structure. Details of the switch architecture and design, and the status of its implementation, are presented.
Efficient modulation techniques for satellite telemetry—receiver design and performance evaluation
Authors: Luise M. , Reggiannini R. , Vitetta G. M. 
Published: July 2007

AbstractIn this paper we address the design of the data demodulator for high‐efficiency satellite communications suited for telemetry applications. We choose Gaussian minimum shift keying as the modulation format and analyse its relative merits with respect to the more traditional filtered offset quadrature phase‐shift keying scheme, when applied to medium‐to‐high data rate telemetry. Our study encompasses both geostationary orbits and the more challenging low earth orbit scenarios, and investigates the acquisition and tracking performance of the receiver with the aid of computer simulations. In particular, we present design criteria leading to the development of efficient, low‐complexity schemes for symbol timing and carrier phase/frequency recovery and we analyse the impact of these synchronization algorithms on the system performance. Next, we discuss the demodulator performance degradation when the transmitted signal is passed through on‐board solid‐state or travelling‐wave‐tube power amplifiers. The paper is concluded by a comparative analysis of the above modulation schemes, with special emphasis on their power and spectral efficiency.
An assessment of the efficiency performance of linearization schemes in the Australian mobilesat system
Authors: Wilkinson T. A. 
Published: July 2007

AbstractThe efficiency of class C type amplifiers with digital predistortion linearizers is discussed. It is shown, by simulation with the AUSSAT MOBILESAT modulation schemes as examples, that the maximum efficiency from such a linearizer amplifier combination is significantly reduced for non‐constant envelope modulation schemes on that achievable with constant envelope schemes. This aspect is often neglected when linearizer performance with such amplifers is discussed. The results are generally applicable to Cartesian feedback linearization also.
Performance of a satellite modem transmitting convolutionally and differentially encoded 8PSK signals
Authors: Clark A. P. , Cheung S. W. 
Published: July 2007

AbstractThe paper studies a digital satellite modem for mobile systems. The modem transmits a convolutionally and differentially encoded eight‐phase‐shift‐keyed (CDE8PSK) signal over a satellite link and employs a near‐maximum‐likelihood decoder at the receiver. The signal can tolerate phase ambiguities that are multiples of 4 radians, which normally result from the carrier recovery loop at the receiver. However, the carrier recovery loop is not considered here. The high‐power amplifier (HPA) at the earth‐station transmitter may introduce non‐linear distortion to the CDE8PSK signal, and predistortion may or may not be used. Several different earth‐stations are assumed to have simultaneous access to a given transponder on the satellite, in an arrangement of frequency division multiple access, but the satellite transponder is assumed to be linear. Thus the CDE8PSK signals that occupy the immediately adjacent frequency bands can introduce adjacent‐channel interference (ACI) to the desired CDE8PSK signal. Extensive computer‐simulation tests have been carried out to evaluate the effects of non‐linear distortion with predistortion, in the presence of ACI, on the tolerance of the modem to additive white Gaussian noise. Four different bandwidths of the transmitted signal are considered, together with three different arrangements of the demodulator. The predistorter operates on the baseband signal at the input to the modulator and assumes a prior knowledge of the HPA characteristics. In all simulation tests, an equivalent baseband model of the transmission system is used, and the results are used to determine the preferred modem design.
The application of a bistatic intersystem interference model to radio systems co‐ordination and satellite systems optimization
Authors: McGuinness R. 
Published: July 2007

AbstractThis paper presents results from a new theoretical model to estimate bistatic rain scatter interference between terrestrial radio relay systems and earth‐satellite systems operating at the same frequency. The current model used by the CCIR was developed in the early 1970s when system packing density was low and the large earth‐station antennas allowed the consideration of narrow beam approximations. This resulted in a small common volume of intersection of the two beams and large circular contours. The recent increase in microwave communications traffic and the improvements in technology have meant that very small aperture terminals (VSATs) can be employed, and hence the model must allow for the consideration of sidelobes, low gain antennas and non‐uniform rain cells intersecting much larger common volumes. Aspects of the new model are discussed and different assumptions made by the CCIR model are examined. Results from the new model show that the contours are smaller and non‐circular and result in much smaller co‐ordination areas.
Improving FH and FH/PN spread spectrum communications through PN M‐ary phase sequences and signal editing
Authors: Ng W. H. , Ungar J. L. 
Published: July 2007

AbstractPseudo‐noise (PN) or direct sequence (DS) modulation, frequency hopping (FH) and their combination (i.e. the hybrid FH/PN approach) are common spread spectrum (SS) communications techniques used to achieve anti‐jamming (AJ) and/or low probability of intercept (LPI). This study investigates the following FH and FH/PN related issues: (i) derive and apply M‐ary phases of PN sequences to increase the AJ and transmission efficiency, (ii) use of erasure channel to reduce received errors and unreliable data, (iii) employ error correction coding and signal editing (SE) to improve communication surviv‐ability, and (iv) adopt surface acoustic wave (SAW) devices to simplify the synchronization procedure in PN correlation. A special example is also given to illustrate the potential AJ improvement when an SS communications system employs both concatenated coding and concatenated SE techniques.
A frequency scanning satellite system for land mobile communications
Authors: Russo P. , D'Ippolito A. , Ruggieri M. , Volpicella N. , Scialino G. , Vatta S. , Jones T. 
Published: July 2007

AbstractA frequency scanning system for mobile applications has been assessed for a European mission at L‐band. Feasibility evaluations, electrical design and analysis have been performed for both the antenna and the entire repeater. Efforts have also been made to solve accommodation, thermal and mechanical problems, so as to demonstrate the actual feasibility of the frequency scanning concept in user‐oriented applications. The very promising results obtained are presented in this paper.
A multi‐carrier demodulator architecture for SMS/IBS
Authors: Barton S. K. , Al‐Jalili Y. O. 
Published: July 2007

AbstractThis paper describes a multi‐carrier demodulator (MCD) architecture which is capable of demodulating a mixture of signals of different data rates, such as are found in present day transparent transponders. No extra restrictions are placed on the signal transmission rates, bandwidths, channel spacings, frequency stabilities, independent timing, etc. beyond what is already specified by INTELSAT and EUTELSAT. The only exception to this is that no signal should straddle the centre frequency of the existing 72 MHz bandwidth transponders. The system is a refinement of the ‘frequency domain’ filtering approach described in References 7 and 8. The main improvement is in performing the symbol timing recovery in the frquency domain before converting to the time domain. This leads to reductions in computational complexity in both the timing recovery and the frequency to time conversion process. All of these functions can be performed by standard DSP processors. Only the initial time to frequency domain transform requires ASIC technology.
An engineering approach for site shielding calculations
Authors: Van Dooren G. A. J. , Herben M. H. A. J. 
Published: July 2007

AbstractIn this paper, two models to approximately calculate the field distribution in the vicinity of a perfectly conducting finite width screen are discussed. The first model is based on the geometrical theory of diffraction (GTD), and is simplified such that the magnitude of the individual ray contributions can be easily calculated. The second model is based on a graphical approach. Coefficients that are representative for the dimensions of the obstacle and the relative position of the observation point are used together with standardized equations to calculate the field strength in the shadow region behind the screen. Also a modification of the current CCIR procedure for knife‐edge diffraction is proposed, such that it can be applied to a finite width screen.Results of all models are compared with more accurate and complex results from a model based on the uniform theory of diffraction (UTD). All models proposed are simple to apply and present an essential extension to currently available engineering models. It is found that the GTD model has the best performance with respect to the UTD approach. The graphical method, however, is more user friendly than the GTD model, because fewer intermediate results need to be calculated. Moreover, the use of this method yields a field‐strength distribution for the whole shadow region of the obstacle instead of the field at just a single point. Further, it is found that the modified CCIR approach can also be used with good accuracy.The models discussed answer some questions formulated by the CCIR concerning site shielding, and extend the currently available engineering models for this interference reduction technique.
A co‐designed coding, modulation and equalization scheme for the transmission of 155‐52 Mbit/s data over a 72 MHz intelsat transponder. Part 2: Equalization
Authors: Peile R. E. , Rajput S. A. , Welch L. R. 
Published: July 2007

AbstractThis paper reports on the application of co‐designed coding, modulation and equalization techiques to an INTELSAT requirement for transmitting 155‐52 Mbit/s data over a 72 MHz satellite channel. A specific solution as regards coding, modulation and equalization is proposed and analysed that differs from ‘standard’ concatenation in that the inner decoder integrates equalization, modulation and coding. In Part 2, a novel technique for integrating decision feedback equalization into the inner decoder is described. The gains in integrating the coding and equalization are shown to be significant for channels that need equalizing.
Architecture and networking issues in satellite systems for personal communications
Authors: Ananasso Fulvio , Carosi Marco 
Published: July 2007

AbstractThe paper expands on some specific aspects of personal communications via satellite, often–although not necessarily–envisaging extensive use of ‘small’ satellites, using orbits not necessarily coinciding with the geostationary one (36,000 km), but rather at 1000–11,000 km altitude. One key point to be borne in mind is the issue of internetworking between satellite and terrestrial systems. Network integration should be carefully implemented in order to comply with ITU future public land mobile telecommunication systems (FPLMTS) requirements, also accepted in the European Telecommunication Standards Institute (ETSI) universal mobile telecommunication systems (UMTS). In addition to some insight into the technology of small satellites and associated orbits, architectures and networking aspects of most relevant systems providing personal communication services (PCS) are addressed in some detail, and potential applications highlighted. Frequency spectrum allocation is addressed in the light of the 1992 World Administrative Radio Conference (WARC‐92), taking into account also multiple access problems and regulatory issues such as Federal Communications Commission (FCC) licensing and spectrum sharing debates. Some remarks on critical technologies and cost conclude the paper.
Influences of external digital environment, markets and terminal price elasticity on personal satellite systems
Authors: Brandon William T. 
Published: July 2007

AbstractAlthough there is no doubt about the feasibility of personal communications via small satellites in low earth orbit, there is considerable uncertainty about the size of the market, whether the specific applications will be business or personal in context, about the market relationship between voice services and data services, and the implications for system design of any information that might be developed on these questions.This paper will develop the concept that the key to understanding low orbit small satellite communications systems is the message delivery time requirement of markets and that the data services market has a widely varying range of acceptable data delivery times. We estimate the distribution of data delivery time versus population of users on a global basis.A second concept to be developed in this paper is that low orbit satellites are in some respects matched to global data delivery applications because of the daylight time zones and natural delays they impose.Using the estimated market size versus message delivery time, we show that there is a significant design implication for the space segment in terms of the number of satellites, the orbit period, and the use of crosslinks. It will be further shown that the difference in complexity of data and voice services with respect to cost argues for the rapid emergence and success of data services.Finally, we will show that a preferred terminal architecture may be an accessory or applique for a personal computer, rather than a small dedicated satellite terminal, based on the extant population of personal computers. A review of the planned terminal architectures of emerging systems reveals that using a personal computer as the basis for a terminal has not yet received wide interest. In particular, the new laptop smaller computers may be the natural catalyst for personal satellite data services in facilitating the terminal.
Interference between satellite systems in non‐geostationary orbits
Authors: Nelson Robert A. , Pritchard W. L. 
Published: July 2007

AbstractSatellites are considered in arbitrary orbits, and interference between them and other satellites or earth‐stations is calculated. The composite interference from a complete system is found by summing over the set of visible satellites. One starts with the Keplerian orbital parameters and assumed antenna patterns and transmitter characteristics. Using classical orbital mechanics and a series of co‐ordinate transformations, one determines the location of any satellite in the frame of reference of any other satellite or earth‐station. Conventional interference methods are then used to find the result.
An advanced satellite communication system with on‐board fast packet switching capabilities
Authors: Del Re Enrico , Fantacci Romano 
Published: July 2007

AbstractThis paper is focused on a satellite communication system having on‐board fast packet switching capabilities. Different alternatives for the up‐link access technique and for the architecture of the onboard switching fabric are considered. In particular an efficient time division multiple access technique with slots assigned on demand and a novel switching approach are proposed. Performances in terms of mean access delay and mean on‐board switching delay are derived by analytical approaches and computer simulations.