Peak Power Requirements Research Articles

Nonlinear cavity dumping of a high finesse frequency mixing module

We present a novel generic approach for pulsed light generation in the visible spectrum. We demonstrate how the circulating field of a high finesse laser can be efficiently cavity dumped through sum-frequency mixing with externally injected high peak power single pass pulses. Periodically poled KTP is used as the nonlinear medium to minimize the peak power requirement of the injected beam. The experimental setup consists of a high finesse 1342 nm Nd:YVO4 laser cavity and a passively Qswitched Nd:YAG laser. Yellow pulses at 593 nm are generated.

Theory of frequency modulated thermal wave imaging for nondestructive subsurface defect detection

This letter provides the theory and mathematical analysis in support of a recently proposed frequency modulated thermal wave imaging for nondestructive subsurface defect detection in solids. The authors illustrate how the technique simultaneously combines the advantages of both conventional pulse based thermography as well as modulated lock-in thermography. A specimen is heated for launching thermal waves into the sample, not at a single frequency (lock-in) or at all frequencies (pulse), but in a desired range of frequencies. While peak power requirement is reduced, phase images obtained retain known advantages. Experimental results from a carbon fiber reinforced plastic sample are presented in support.

Design of Compliant Mechanisms for Minimizing Input Power in Dynamic Applications

In this paper, we investigate power flow in compliant mechanisms that are employed in dynamic applications. More specifically, we identify various elements of the energy storage and transfer between the input, external load, and strain energy stored within the compliant transmission. The goal is to design compliant mechanisms for dynamic applications by exploiting the inherent energy storage capability of compliant mechanisms in the most effective manner. We present a detailed case study on a flapping mechanism, in which we compare the peak input power requirement in a rigid-body mechanism with attached springs versus a distributed compliant mechanism. Through this case study, we present two approaches: (1) generative-load exploitation and (2) reactance cancellation, to describe the role of stored elastic energy in reducing the peak input power requirement. We propose a compliant flapping mechanism and its evaluation using nonlinear transient analysis. The input power needed to drive the proposed compliant flapping mechanism is found to be 50% less than a rigid-link four-bar flapping mechanism without a spring, and 15% less than the one with a spring. This reduction of peak input power is primarily due to the exploitation of elasticity in compliant members. The results show that a compliant mechanism can be a better alternative to a rigid-body mechanism with attached springs.

The PVT, an Elastic Conservative Transmission

This paper presents an innovative transmission called the passively variable transmission (PVT) that has a high torque ratio for large loads and a low velocity ratio for small loads. The change in these ratios depends passively on the load, in contrast to the continuous variable transmission (CVT), where the transmission ratio is controlled explicitly. Another difference from the CVT is that the PVT is elastic and the term transmission ratio is therefore not applicable. A theory section formulates alternative ways of describing the torque and velocity relations for elastic conservative transmisions as well as other important properties. This theory is used to analyze and illustrate the characteristics of a PVT. The theory is also used to compare the PVT with another novel elastic conservative transmission, called load sensitive CVT. The nonlinearities and elasticity of the PVT make it difficult to control using linear control theory. Feedback linearization was therefore used to design a torque controller, and experimental results show low impedance at small loads. Further, the controller tracks a reference torque well as long as the reference rate does not cause motor saturation. The abilities of the PVT are also illustrated by comparing it with an actuator having a traditional transmission. The load case is recorded joint torques and angles from the carpus joint of a walking horse. Simulation show that the required peak power is reduced by more than 20% and the product of the maximum torque and the maximum angular velocity is reduced by approximately 30%.

An Efficient Robotic Tendon for Gait Assistance

A robotic tendon is a spring based, linear actuator in which the stiffness of the spring is crucial for its successful use in a lightweight, energy efficient, powered ankle orthosis. Like its human analog, the robotic tendon uses its inherent elastic nature to reduce both peak power and energy requirements for its motor. In the ideal example, peak power required of the motor for ankle gait is reduced from 250 W to just 77 W. In addition, ideal energy requirements are reduced from nearly 36 J to just 21 J. Using this approach, an initial prototype has provided 100% of the power and energy necessary for ankle gait in a compact 0.95 kg package, seven times less than an equivalent motor/gearbox system.

Hybrid systems with lead–acid battery and proton-exchange membrane fuel cell

Hybrid systems, based on a lead–acid battery and a proton-exchange membrane fuel cell (PEMFC) give the possibility to combine the advantages of both technologies. The benefits for different applications are discussed and the practical realisation of such systems is shown. Furthermore a numerical model for such a hybrid system is described and results are shown and discussed. The results show that the combination of lead–acid batteries and PEMFC shows advantages in case of applications with high peak power requirements (i.e. electric scooter) and applications where the fuel cell is used as auxiliary power supply to recharge the battery. The high efficiency of fuel cells at partial load operation results in a good fuel economy for recharging of lead–acid batteries with a fuel cell system.

Full-Lagrangian Schemes for Dynamic Analysis of Electrostatic MEMS

Dynamic analysis of microelectromechanical systems (MEMS) is characterized by the nonlinear coupling of electrical and mechanical domains. The nonlinear coupling between the two domains gives rise to several interesting dynamic phenomena besides the well established pull-in phenomenon in electrostatic MEMS. For proper understanding and detailed exploration of MEMS dynamics, it is important to have a reliable and efficient physical level simulation method. In this paper, we develop relaxation and Newton schemes based on a Lagrangian description of both the mechanical and the electrical domains for the analysis of MEMS dynamics. The application of a Lagrangian description for both mechanical and electrostatic analysis makes this method far more efficient than standard semi-Lagrangian scheme-based analysis of MEMS dynamics. A major advantage of the full-Lagrangian scheme is in the accurate computation of the interdomain coupling term (mechanical to electrical) in the Jacobian matrix of the Newton scheme which is not possible with a semi-Lagrangian scheme. The full-Lagrangian based relaxation and Newton schemes have been validated by comparing simulation results with published data for cantilever and fixed-fixed MEM beams. The Newton scheme has been used for the dynamic analysis of two classes of comb-drives widely used in MEMS, namely, transverse and lateral comb-drives. Several interesting MEM dynamic phenomena and their possible applications have been presented. Spring-hardening and softening of MEM devices has been shown. The existence of multiple resonant peaks in MEM devices has been analyzed under different electrical signals and their possible applications in multiband/passband MEM filters/oscillators is discussed. Switching speed is a serious constraint for capacitive based RF-MEM switches. We have shown that a DC bias along with an ac bias at the resonant frequency can give very fast switching at a considerably less peak power requirement.

Electrofishing Power Requirements in Relation to Duty Cycle

Under controlled laboratory conditions we measured the electrical peak power required to immobilize (i.e., narcotize or tetanize) fish of various species and sizes with duty cycles (i.e., percentage of time a field is energized) ranging from 1.5% to 100%. Electrofishing effectiveness was closely associated with duty cycle. Duty cycles of 10–50% required the least peak power to immobilize fish; peak power requirements increased gradually above 50% duty cycle and sharply below 10%. Small duty cycles can increase field strength by making possible higher instantaneous peak voltages that allow the threshold power needed to immobilize fish to radiate farther away from the electrodes. Therefore, operating within the 10–50% range of duty cycles would allow a larger radius of immobilization action than operating with higher duty cycles. This 10–50% range of duty cycles also coincided with some of the highest margins of difference between the electrical power required to narcotize and that required to tetanize fish. This observation is worthy of note because proper use of duty cycle could help reduce the mortality associated with tetany documented by some authors. Although electrofishing with intermediate duty cycles can potentially increase effectiveness of electrofishing, our results suggest that immobilization response is not fully accounted for by duty cycle because of a potential interaction between pulse frequency and duration that requires further investigation.

New Solitary-wave Solutions for the Higher Order Nonlinear Schrödinger Equation with Both Real and Imaginary Raman Terms

We find new solitary-wave solutions of the higher order nonlinear Schrödinger equation with both real and imaginary Raman terms, which can model an ultrashort pulse propagation through optical fibers, under some constraint among the model coefficients. The physical conditions such as the wavelength needed to launch the pulse, the types of optical fibers, and the required peak power, are obtained from the constraints for the solitary-wave solutions. - PACS number(s): 42.65.Tg, 42.81Dp, 02.30.Jr, 42.79.Sz.

Modeling and Control of Oxygen Transfer in High Purity Oxygen Activated Sludge Process

A dynamic mathematical model for the high purity oxygen activated sludge process, which incorporates structured biomass, gas–liquid interactions and control systems, was developed. The model was calibrated using pilot plant data associated with the development of the West Point Treatment Plant near Seattle, Wash. The calibrated model was used to simulate oxygen transfer rates for various operating conditions. Simulations showed that an optimal control system can reduce aerator power by 33% as compared to a conventional design, and reduce average oxygen feed gas by as much as 18%. Vent gas purity control dramatically reduced the peak aerator horsepower required to maintain set point dissolved oxygen concentration during high loadings. Step feed operation reduced the stag-to-stage variation in aerator horsepower and also reduced the required peak power. Predicted power savings for a 605,000 m³/day plant were $500,000 per year at current power costs.

Micro-Fabricated Thin-Film Fuel Cells for Portable Power Requirements

AbstractFuel cells have gained renewed interest for applications in portable power since the energy is stored in a separate reservoir of fuel rather than as an integral part of the power source, as is the case with batteries. While miniaturized fuel cells have been demonstrated for the low power regime (1-20 Watts), numerous issues still must be resolved prior to deployment for applications as a replacement for batteries. As traditional fuel cell designs are scaled down in both power output and physical footprint, several issues impact the operation, efficiency, and overall performance of the fuel cell system. These issues include fuel storage, fuel delivery, system startup, peak power requirements, cell stacking, and thermal management. The combination of thin-film deposition and micro-machining materials offers potential advantages with respect to stack size and weight, flow field and manifold structures, fuel storage, and thermal management. The micro-fabrication technologies that enable material and fuel flexibility through a modular fuel cell platform will be described along with experimental results from both solid oxide and proton exchange membrane, thin-film fuel cells.

Dualband spectral-spatial RF pulses for prostate MR spectroscopic imaging.

Although MR spectroscopic imaging (MRSI) of the prostate has demonstrated clinical utility for the staging and monitoring of cancer extent, current acquisition methods are often inadequate in several aspects. Conventional 180 degrees pulses can suffer from chemical shift misregistration, and have high peak-power requirements that can exceed hardware limits in many prostate MRSI studies. Optimal water and lipid suppression are also critical to obtain interpretable spectra. While complete suppression of the periprostatic lipid resonance is desired, controlled partial suppression of water can provide a valuable phase and frequency reference for data analysis and an assessment of experimental success in cases in which all other resonances are undetectable following treatment. In this study, new spectral-spatial RF pulses were developed to negate chemical shift misregistration errors and to provide dualband excitation with partial excitation of the water resonance and full excitation of the metabolites of interest. Optimal phase modulation was also included in the pulse design to provide 40% reduction in peak RF power. Patient studies using the new pulses demonstrated both feasibility and clear benefits in the reliability and applicability of prostate cancer MRSI.

Induction accelerator architectures for heavy-ion fusion

The approach to heavy-ion-driven inertial fusion studied most extensively in the US uses induction modulators and cores to accelerate and confine the beam longitudinally. The intrinsic peak-current capabilities of induction machines, together with their flexible pulse formats, provide a suitable match to the high peak-power requirement of a heavy-ion fusion target. However, as in the RF case, where combinations of linacs, synchrotrons, and storage rings offer a number of choices to be examined in designing an optimal system, the induction approach also allows a number of architectures, from which choices must be made. We review the main classes of architecture for induction drivers that have been studied to date. The main choice of accelerator structure is that between the linac and the recirculator, the latter being composed of several rings. Hybrid designs are also possible. Other design questions include which focusing system (electric quadrupole, magnetic quadrupole, or solenoid) to use, whether or not to merge beams, and what number of beams to use – all of which must be answered as a function of ion energy throughout the machine. Also, the optimal charge state and mass must be chosen. These different architectures and beam parameters lead to different emittances and imply different constraints on the final focus. The advantages and uncertainties of these various architectures will be discussed.

Practical spread spectrum pulse compression for ultrasonic tissue imaging

Spread spectrum pulse compression is a signal processing algorithm that enhances critical system performance parameters such as signal-to-noise ratio, peak power requirements, minimum detectable signal, and total dynamic range. For this research, a digital, real-time, Barker coded, bi-phase modulator was designed and constructed, as well as a simple ultrasonic test tank containing both synthetic targets and excised goat's liver. Upon reception and demodulation of the spread spectrum ultrasonic echo, cross-correlation with a sidelobe suppression filter was performed. Due to limitations such as narrow bandwidth, and very short minimum ranges, a practical ultrasonic pulse compression system must be restricted to short code lengths. For 13 bit Barker code compression, the expected increase in signal-to-noise ratio of 11 dB was realized; at the same time greater than 30 dB of instantaneous dynamic range was maintained.

Peak power bi-directional transfer from high speed flywheel to electrical regulated bus voltage system: a practical proposal for vehicular technology

This paper provides a design outline and implementation procedure for a secondary energy storage unit (SESU) that can be used to meet the peak energy requirements of an electric vehicle during both acceleration and regenerative braking. The life cycle of the electric vehicle's batteries can be extended considerably by supplying peak energy requirements from a secondary source. A simulation study was conducted to determine the peak power and energy requirements over the SAE recommended electric vehicle test procedure. A scaled prototype SESU was built using flywheel energy storage, and tests were performed to determine the energy transfer capabilities of a flywheel coupled high speed permanent magnet synchronous machine through the proposed system's energy storage tank. Results are presented that indicate the necessity of the energy storage tank. An evaluation of the proposed system is also included which indicates the practicality of the system when compared to conventional regenerative control techniques.

Hydronic radiant cooling — preliminary assessment

A significant amount of the electrical energy used to cool non-residential buildings equipped with all-air systems is drawn by the fans that transport the cool air through the thermal distribution system. Hydronic systems reduce the amount of air transported through the building by separating the tasks of ventilation and thermal conditioning. Due to the physical properties of water, hydronic systems can transport a given amount of thermal energy and use less than 5% of the otherwise necessary fan energy. This improvement alone significantly reduces the energy consumption and peak-power requirement of the air conditioning system. Radiant cooling has never penetrated the US markets significantly. The scope of this survey is to show the advantages of radiant cooling in combination with hydronic thermal distribution systems, as compared to the commonly-used all-air systems. The report describes the development, thermal comfort issues, and cooling performance of the hydronic systems. The peak-power requirement is also compared for hydronic systems and conventional all-air systems.

Study on the constant voltage damping system for circular accelerators

The constant voltage damping system is discussed. This damping system provides effective damping but with a considerably reduced peak power requirement.

Heteronuclear Broadband Spin-Flip Decoupling with Adiabatic Pulses

The application of adiabatic pulses for heteronuclear broadband decoupling is described. It is shown that superior cyclicity can be achieved even when excitation-free intervals are inserted between successive pulses. Thanks to this feature, sample heating can be considerably reduced in comparison with the standard decoupling techniques with continuous irradiation, while the benefit of low sensitivity to RF field inhomogeneity is obtained. The peak power requirements depend not only on the decoupling bandwidth, but also on the parameters of the adiabatic pulses used. Generally, they correspond to the power requirements of broadband decoupling by WALTZ-16. Recommendations for the choice of a pulse suitable for a given application are presented. The intensity of cycling sidebands is the main trade-off of this method. Quantitative assessment of this intensity shows the limits for the pulse repetition period. Experimental verification on a 200 MHz spectrometer is described.

Switching system for single antenna operation of an S-band FMCW radar

Increasing interest is being shown in frequency modulated continuous wave (FMCW) radars due to their advantages of compact size, low peak power requirement, good range resolution and low interference to other systems. A major disadvantage of FMCW systems is the need to use two separate, well shielded antennas for transmission and reception. Several schemes have been devised to enable FMCW radars to operate with a single antenna. The authors describe a ground based S-band ocean surface remote sensing FMCW radar that has been adapted for single antenna operation by alternately switching the single antenna between the transmitter and the receiver. Even though this frequency modulated interrupted continuous wave (FMICW) system is no longer a true continuous wave radar, the essential properties of the FMCW waveform are preserved, provided some conditions on the switching speed and FMCW parameters are met. The purpose of the radar is to deduce ocean wave and current parameters by measuring ocean surface velocities. The radar was tested operationally by comparing ocean surface data from both the single antenna (FMICW) and dual antenna (FMCW) systems recorded under similar conditions.

Fluid-power Drive for Round Balers

The mechanical power-take-off (pto) drive of a large round baler was replaced with an open circuit, fluid-power drive for the purpose of providing an alternative method for transmitting and controlling power. The potential to reduce product liability associated with pto driveline injuries provided the motivation for the work. Principal components of the drive circuit included a fixed displacement axial piston pump at the tractor pto, and a gerotor motor to power the elevator chain drive shaft on the baler. A pressure relief, crossover, and oil cooler were added to the circuit for pump and motor protection. The circuit was instrumented to measure system pressure and temperature, and motor shaft speed. Peak power requirements for the fixed chamber baler reached 24.5 kW (32.8 hp) when baling mixed orchard grass hay. To maintain a reasonable system operating temperature it was estimated that 7400 kJ/h (7,000 Btu/h) of heat would have to be rejected by the oil cooler placed in the circuit. The reduced volume reservoir and 10W30 SAE grade motor in the baler drive circuit posed no apparent problems. Fluid drive design considerations and typical field trial data are reported.