Limited Power Source Research Articles

Power-Aware Mobile Multimedia: a Survey (Invited Paper)

With the fast-paced development of computing technologies, mobile devices have almost sufficient computation and communication capabilities to support mobile multimedia applications such as multimedia streaming, VoIP, and mobile TV. However, most existing mobile devices are powered by battery with limited energy resource. To support multimedia on battery-powered mobile devices, how to efficiently utilize the limited power source and other limited network resources has become one of the major challenges in mobile multimedia system design. It has been shown that achieving a satisfactory user experience needs a systematic consideration of both video source adaptation and network transmission adaptation, indicating that the core of mobile multimedia system design is how to achieve a good balance of the power consumption between computation usage and communication usage. In other words, it depends on how to jointly select video source parameters and channel parameters based on the video content characteristics, available network resources, and underlying network conditions, given the fact that the power management schemes as well as the nonlinear battery effects also affect the system power consumption of mobile devices. In this paper, we review the recent advances in power-aware mobile multimedia, especially the adaptation technologies applied in video coding and delivery. In addition, the major research challenges in the field are demonstrated and discussed, which include power-management for mobile devices, rate-distortion-complexity optimized video codec design, and computational complexity and power aware cross-layer design and optimization. At the end, we propose a number of future research directions for audiences to continue investigation in this field.

An Energy Model for Simulation Studies of Wireless Sensor Networks using OMNeT++

Simulation is frequently used to evaluate the performance of networking algorithms and techniques in wireless communication networks. However, performance aspects such as the transmission delay, the channel utilization, or the throughput provide only limited information about the feasibility of the particular approach. This is especially the case when investigating Wireless Sensor Networks (WSNs), which stress energy-efficiency due to extremely limited power source in sensor nodes. Thus, a precise evaluation of the energy efficient performance is demanded. In this paper, we present a generic energy model developed for the simulation framework OMNeT++. The model allows to accurately evaluate the energy performance (in terms of energy consumption or network lifetime) of sensor networks (or in principle any wireless network), taking into account the energy consumption of both the radio transceiver and the CPU. The energy model can be calibrated to arbitrary types of sensor nodes if power measurements are available for the node type. The applicability of the developed energy model is demonstrated in a selected application scenario: the analysis of the energy consumption in IEEE 802.15.4 star networks. Additionally, we outline the need for more complex metrics compared to the energy consumption of single nodes to evaluate the lifetime of the whole sensor network.

Towards estimating lifetime of ad hoc wireless networks

Ad hoc wireless networks possess highly constrained energy resources. The available energy resources should thus be used efficiently, in order to satisfy the requirements. Hence, the protocols at all the layers of the protocol stack should be energy aware and energy efficient. However, all the existing protocols are not energy aware and perform poorly in the presence of a limited power source. Even the energy aware protocols proposed for ad hoc networks do not consider all the characteristics of the underlying batteries. Hence, they fail to efficiently utilize the available energy. There also exist a few protocols, which, though battery unaware, unknowingly prove to be energy efficient. Thus, a mechanism is required to measure the efficiency of the protocols of ad hoc networks, in terms of the network lifetime. To the best of our knowledge, there has been no reported work till date for analyzing the lifetime of the ad hoc networks for various protocols. The protocols at all the layers of the protocol stack together decide the discharge of the battery source of a node. However, assuming that only the MAC protocols decide the battery performance, we focus on measuring the energy efficiency of MAC protocols. This paper primarily provides a novel generalized analytical model for estimating lifetime of ad hoc networks, in the presence of the following two kinds of MAC protocols: (i) reservation-based TDMA protocols and (ii) a specific class of CSMA protocols that try to follow a pattern, such as a round-robin scheduling, for packet transmission. Our model uses discrete-time Markov chain with probabilistic recovery to model the batteries of the ad hoc nodes. We found that our analytical model accurately estimates the lifetime of the network for various MAC protocols. We prove through analytical and simulation studies that energy awareness is crucial in deciding the performance of the MAC protocols for both homogeneous and heterogeneous ad hoc wireless networks.

Critical Slip of Three-phase Cage Induction Motor Supplied from Limited Power Source

The peculiarities and characteristics of a cage induction motor supplying from limited power source (mobile electric power station, diesel power plant, wind power station and etc.) change virtually in comparison with the case when motor is supplied from unlimited voltage source. The critical slip expression of the cage induction motor operating from the limited power-supply source taking into account the inner complex impedance of power-supply source and other cable parameters has been derived. It is shown that critical slip formula, when motor is supplied from a high-capacity power-supply source (the inner complex impedance is not taken into account) and through short cable (the cable impedance is not taken into account) absolutely coincides with well-known formula. The algorithm for calculations of the induction motor characteristics taking into account the parameters of the supply circuit and the suitable length and cross-section of the supply cable has been created. Ill.1, bibl. 6 (in English; summaries in English, Russian and Lithuanian).

A Time-Sharing Motor Control for Wearable Robot

To utilize limited USB bus power for robot control, total power of a robot including multi motors should be restricted. Namely, power of each motor should be reduced. To tackle this problem, a time sharing motor control is proposed in this paper. This technique drives just one of motors whose required power is less than a limited power source, and switches a driven motor with very short period like a multi task system in UNIX. As a result, human beings recognize robot motions with natural feeling even only a motor is driven at once. To confirm the proposed approach, a wearable robot named as wearable telecommunicator T2 including 3 RC servo motors is employed with USB bus power.

Nonsymmetric Groove Pattern Design for Precise Micro-Spindles

As the fluid dynamic bearing spindles are to be actively adopted to various small form factor mobile applications, mechanical specifications for the motors have been aggressively changed to pursue the fierce information technology sector market trend. One of the major technological challenges for the spindles to be successfully employed in the applications is the reduction of power consumption since the most of the mobile applications operate with a limited power source at relatively lower voltage. Recognizing implication of the power consumption that of course affects stiffness of the spindle, few of options for mechanical designers are available but either lowering rotational speed or adopting thinner lubricant. In the present work, a novel design solution for alleviating side effect of the lower stiffness spindle is introduced and verified.

Critical Slip in Maximum Electromagnetic Power of a Motor for Borehole Prospecting Mechatronic Devices

The extraordinary conditions for borehole motors such as: wide operating medium temperature change interval from –20oC up to +250oC, hydrostatic pressure changes from atmospheric up to 210 MPa, operating medium – dielectric liquid, limited power source, long geophysical, cable of up to 10,000 m non-constant load, due to the operating cycle have influence on their reliable operating, maximum power transmission, and change of characteristics. In this particular case, it is important to know the maximum electromagnetic power, which may be created by the motor. The critical slip and maximum electromagnetic power of the induction motor with a solid rotor supplied from a limited power-source and through the complex circuit, taking into account the parameters of the motor and supply circuit, as well as the operating peculiarities, have been derived. The study of computed characteristics of the borehole motor, taking into account the above-mentioned conditions, show that the motor supplied from a limited power-supply source and through the complex circuit should be investigated inseparably from the whole system.

Web Bazaar. A Location-Dependent Secured Mobile Web Service System

Web services has evolved to be a promising technology for developing application in open, loosely coupled and distributed computing environments and in mobile commerce. One of the key requirements of the web services to meet user expectation is its secure universal accessibility free from temporal and spatial constraints. To access the web services from anywhere and anytime in a secured manner, a suitable mobile web services architecture is needed which must overcome the limitations of the mobile environment (service discovery, low bandwidth, insecurity, limited power source and scalability bottleneck). This paper exploits the advances in wireless broadcast discipline and proposes a new architecture that overcomes a number of problems in discovering and using web services. At the same time it also proposes a new location based signature scheme to add an extra dimension to the authentication of the mobile transactions.

A controlled diesel drive line with hydrostatic transmission: Part 1 - mathematical model

A dynamic model of a diesel driveline consisting of a controlled proper drive, mechanical gearing, controlled hydrostatic transmission and a loading mechanism is derived. The system under consideration represents a chain of mechanisms for energy transfer with a limited power source and energy receiver. The transmitting working medium is a mass, compressible and viscous liquid and the energy transfer agent is its high pressure. A system of non-linear ordinary differential equations represents the discrete dynamic model of the complex mechanical system.

Application of Solid Oxide Fuel Cells to Aircraft

Fuels Cells are being considered for various applications on airplanes and space vehicles. It is critical that fuel cells meet the performance and airplane system-level environmental requirements. Fuels cells are being considered for replacing batteries as a non-time limited emergency power source; as a replacement for the Auxiliary Power Units (APUs); and as the primary power source for propulsion on high altitude long endurance aircraft and high altitude airships. For high altitude long endurance airplane or airship applications, fuels cells are being considered as regenerative closed loop power sources. Two major types of fuel cells, Proton Exchange Membrane Fuel Cell (PEMFC) and Solid Oxide Fuel Cell (SOFC), are the most probable choices due to their relatively high level of development and potential for commercialization. For transportation applications, the PEMFC is in the forefront because of its compact size, quick startup time and low operating temperatures (∼80°C). In the future, for aerospace applications, the SOFC should become more common because of its ability to use converted hydrocarbon fuels along with some of the impurities such as CO, its high operating temperatures (∼1,000°C) and its potential to combine with a gas turbine to gain even higher efficiency (1). For use on present day airplanes, since the operators of commercial airplanes have no desire to maintain the logistics and carry another type of fuel (e.g. Hydrogen), fuel processing is required to convert current fuels, such as Jet A, JP-5 or JP-8 to hydrogen in order to drive the fuel cells. The complexity of the fuel processing is dependent on the purity required. Here, the SOFC seems to have a definite advantage over the PEMFC.

Methods for service discovery in Bluetooth scatternets

This paper presents methods for service discovery in multi-hop Bluetooth ad hoc networks, so called scatternets. Two service discovery protocols based on filtering of service requests are proposed. Extensive simulation results are presented showing that the protocols significantly reduce network traffic. Reducing the network traffic is important as many Bluetooth devices have limited power sources and, therefore, benefit from keeping links idle in power saving modes. It is also explained how the proposed protocols can interact with reactive routing protocols and effectively assist route discovery. Finally, an implementation providing functionality for both searching and browsing for services is suggested, effectively extending the Bluetooth SDP to the scatternet.

Energy efficient routing in ad hoc disaster recovery networks

The terrorist attacks on September 11, 2001 have drawn attention to the use of wireless technology in order to locate survivors of structural collapse. We propose to construct an ad hoc network of wireless smart badges in order to acquire information from trapped survivors. We investigate the energy efficient routing problem that arises in such a network and show that since smart badges have very limited power sources and very low data rates, which may be inadequate in an emergency situation, the solution of the routing problem requires new protocols. The problem is formulated as an anycast routing problem in which the objective is to maximize the time until the first battery drains-out. We present iterative algorithms for obtaining the optimal solution of the problem. Then, we derive an upper bound on the network lifetime for specific topologies and describe a polynomial algorithm for obtaining the optimal solution in such topologies. Finally, numerical results regarding the upper bound and the algorithms are presented.

Escape in a nonideal electro-mechanical system

In this work a particular system is investigated consisting of a pendulum whose point of support is vibrated along a horizontal guide by a two bar linkage driven from a DC motor, considered as a limited power source. This system is nonideal since the oscillatory motion of the pendulum influences the speed of the motor and vice-versa, reflecting in a more complicated dynamical process. This work comprises the investigation of the phenomena that appear when the frequency of the pendulum draws near a secondary resonance region, due to the existing nonlinear interactions in the system. Also in this domain due to the power limitation of the motor, the frequency of the pendulum can be captured at resonance modifying completely the final response of the system. This behavior is known as Sommerfeld effect and it will be studied here for a nonlinear system.

Approaching 100 T with wire wound coils

The European effort to develop nondestructive pulsed magnets for scientific research in fields up to 100 T is now well under way. Within the network of European magnet laboratories, two routes towards 100 T have emerged from an EC-sponsored design study. In this paper, the route using wire-wound coils will be described, this is based on technology available at the participating laboratories. For magnets driven by energy limited power sources (e.g. capacitor banks), coils with internal and external reinforcement will be developed, these are likely to consist of two or three concentric coils. With an energy source of order 10 MJ, the pulse duration will be of order 10 ms. For use with a power limited supply (e.g. generators), the magnet consists of typically up to ten coils that are energised separately to generate pulses with a 100 T/50 ms flat top using a 1 GW source. A series of test coils with gradually increasing peak field will be built and tested in order to optimize design, construction techniques and predictive computations.

A Model for Determining Rider Induced Energy Losses in Bicycle Suspension Systems

SUMMARY The energy dissipated by the suspension systems used for off-road bicycles is a major concern due to the limited power source in cycling. Rider induced energy losses are those that arise from the muscular action of the rider. The purpose of this study was to develop and verify a dynamic model of a seated cyclist riding an off-road bicycle up a smooth road. With the absence of terrain irregularities, all suspension motion was rider induced. Knowing the stiffness and dissipative characteristics of the suspension elements, the power dissipated by the suspensions was calculated. Simulation results were compared to suspension deflections that were experimentally measured for a cyclist riding a commercially available dual suspension bicycle up a 6% grade at 6.5m/s. For this particular case, no fork motion was observed in the experiments which was consistent with the simulation results. For the rear suspension, the mean and amplitude of the largest harmonic were experimentally determined to be 6.6 and ±2...

An approximate nyquist transmission scheme for QPSK digital mobile communications

This paper presents the design and implementation of an approximate Nyquist transmission scheme that employs a rational-function receiving filter. A transitional Butterworth-Thomson (TBT) filter is examined as a rational-function receiving filter. This filter can easily be realized as a ceramic filter. It can also function as a channel filter to realize selectivity. Therefore, the newly proposed transmission scheme provides not only a simple and economical receiver circuit but also low power consumption. These features are suitable for mobile radios which must be as small as possible and operate with limited power sources. The effects of filter approximation error on waveform transmission characteristics and adjacent channel interference selectivity are evaluated by computer simulation, and the filter characteristics are optimized in terms of both characteristics. A ceramic receiving filter is developed with the optimum TBT characteristic. A π/4-shifted QPSK transmission experiment performed with this filter confirms that it has such superior transmission characteristics as receiving sensitivity, robustness against co-channel interference, and robustness against frequency selective fading. Such characteristics are superior to those of the conventional transmission scheme using a maximally flat receiving filter. It is verified that approximate Nyquist transmission provides improved transmission quality and spectrum utilization for digital mobile communication systems.

Dynamic Stability of a Vibrating Hammer

This paper deals with the stability of motion of an elastically suspended vibrating hammer that impacts upon an energy absorbing surface referring to the dynamical interaction between a vibrating hammer and a motor. Assuming an ideal source [1] of energy is characteristic of a motor, then the force mrω2 cosωt appears to be the vertical component of the inertia force of the mass m. The mass m is located the distance r from the axis 0 and rotates by frequency ω. Hence the basic equation of a vibrating system takes the form of a linear system. Fu [2] has investigated the regions of stability of the system as the linear system. In the case of practical use, however, a limited power source called a “nonideal source of energy” is the characteristic of a motor. Accordingly, it follows that the motion of an oscillating system with a nonideal source of energy may be formulated as a nonlinear system. The local stability of the sytem desired by a nonlinear equation is presented in our paper. Finally, the results of the regions of stability are compared with those studied in Fu.

Passage through resonance of a three-dimensionally vibrating machine energized from a limited-power source

Passage through resonance of a three-dimensionally vibrating machine energized from a limited-power source