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With the growing popularization of Electric Vehicle (EVs), Electro-mobility (in terms of where to charge EV) has become an increasingly important research problem in smart cities. One of the major concerns is the anxiety of EVs, as drivers may suffer from discomfort due to long charging time. In this paper, we leverage the battery switch technology to provide an even faster charging than plug-in charging service, by cycling switchable (fully recharged) batteries at Charging Stations (CSs). Upon that, a cost-efficient Publish/Subscribe (P/S) system is provisioned, to facilitate the design of distributed charging manner for privacy guarantee. The proposed communication framework utilizes Mobile Edge Computing (MEC)-functioned Road Side Units (RSUs) to bridge, process, and aggregate the information flow between CSs and EVs. We further design an advanced reservation-based charging system, in which the knowledge of EVs' reservations is utilized to predict how likely a CS will be congested. This benefits to a smart transportation planning on where to charge, in order to improve charging comfort. Results show the advantage of our enabling technology comparing to other benchmark solutions, in terms of minimized waiting time for the battery switch (as the benefit for EV drivers), and a higher number of batteries switched (as the benefit for CSs). [ABSTRACT FROM AUTHOR]

Traffic-aware base station (BS) sleeping is a promising approach to increase the energy efficiency (EE) of cellular networks. Both deep sleep and discontinuous transmission (DTX) can be applied to improve network EE. This paper studies the optimal BS operation when both deep sleep and DTX are employed. Queuing theory and stochastic geometry theory are jointly applied to model network performance considering both traffic dynamics and stochastic channel quality. We firstly propose a scaling law of transmit power that assures network coverage. Then, we characterize the resource utilization of active BSs when various percentages of BSs are switched into deep sleep, and analyze the overload probability of the remaining active BSs. Finally, we investigate the impact of BS deep sleep and DTX micro sleep on network EE. Both analytical and simulation results show that there is a tradeoff between deep sleep and DTX micro sleep. Switching BSs into deep sleep would increase the load of the remaining active BSs and reduce their energy saving achieved with DTX. When the power consumption of BS in DTX micro-sleep mode is considerably low, switching BSs into deep sleep might increase the overall energy consumption, and it is not always the best practice to switch as many BSs into deep sleep as possible to maximize network EE. [ABSTRACT FROM AUTHOR]

Device-to-device (D2D) communication is a promising technology to achieve high spectrum efficiency, low energy consumption, and enhanced system capacity. In D2D communications, the channel allocation plays a crucial role to avoid interference, which usually involves a centralized coordination. With the increasing number of devices or terminals as well as the dynamic network environment, the computation and information exchange during the centralized channel allocation would be a big burden for wireless networks. We tackle this problem by proposing a distributed channel allocation method with blind rendezvous to enable collision-free concurrent transmissions over multiple channels. Specifically, we first present a receiver-oriented channel allocation algorithm to reduce interference and then propose a sender-jump blind channel rendezvous algorithm based on channel hopping techniques. The proposed channel allocation method allows each sender–receiver pair to obtain an appropriate channel for collision-free transmissions requires no centralized coordination. Theoretical analysis, simulation results and test-bed experiments validate the proposed solution. Our findings reported in this paper may help network designers to contribute in the development of high-density Internet of Things. [ABSTRACT FROM AUTHOR]

In this paper, we compare the performance of time-switching relaying (TSR) and power-splitting relaying (PSR) protocols in two-hop networks with a battery-assisted energy-harvesting (EH) amplify-and-forward relay. In this battery-assisted relay framework, the EH relay augments the harvested energy with energy drawn from a battery. Using expressions derived for throughput and average battery energy consumption, we investigate maximization of throughput for given battery energy availability per time slot and minimization of battery energy consumption for target throughput requirement. When only statistical channel knowledge is available, PSR results in better throughput performance at practical signal-to-noise ratios. However, in the typical low battery energy and low target throughput regime, it is TSR that is more battery energy efficient. When second-hop instantaneous channel knowledge is available, we observe dramatical energy savings that increases lifetime of nodes. Simulation results are presented to demonstrate accuracy of the derived expressions. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive sliding mode control (SMC) loop design for single-phase interleaved totem pole (ILTP) power factor correction (PFC) converters in electric vehicle onboard charger applications is proposed. The major objectives of the proposed SMC are to improve the converter dynamics, ensure a tight output voltage regulation under fast load fluctuations, and maintain a unity power factor. The sliding mode coefficients are selected to ensure both small signal and large signal stability for the robustness of the converter in wide operating conditions. As verification to the proof-of-concept, a hardware prototype of a single-phase ILTP PFC is developed and tested to validate the effectiveness of loop design by the load transient tests. The steady state results exhibit a power factor >0.995 and total harmonic distortion <3% at 800 W load power. At a 25% step-change in load power, SMC achieves 80 ms settling time, which is approximately 200 ms faster than the conventional PI control. [ABSTRACT FROM AUTHOR]

Cell voltage equalization is inevitable to ensure years of safe operation of series-connected energy storage cells, such as lithium-ion batteries and supercapacitors (SCs). Although various kinds of cell voltage equalizers have been proposed, most equalizer topologies require multiple switches and/or a multiwinding transformer, resulting in complex circuitry and poor modularity. In this paper, a single-switch single-transformer equalizer using a forward–flyback resonant inverter (FFRI) with a voltage multiplier is proposed. The required switch count of the proposed equalizer is the minimum without impairing modularity due to the single-switch circuitry with no need for a multiwinding transformer. An experimental equalization test performed for eight SCs connected in series successfully demonstrated the equalization performance of the proposed equalizer. The FFRI can be extended as a “resonant input cell,” and by combining one of resonant input cells and a voltage multiplier, a single-switch resonant equalization charger that is basically a charger with an equalization function is also derived. An experimental charging test using the resonant equalization charger was also performed, and its equalization-charging performance was demonstrated. [ABSTRACT FROM AUTHOR]

Frequency-modulated continuous-wave (FMCW) methods and switched antenna arrays (SAAs) are very attractive for application in automotive radar because of their low hardware complexity. In traditional SAA radar, the receiving antenna array elements are successively switched according to their natural spatial order [referred to as sequential SAAs (SSAAs)]. For radars using both SSAA and FMCW methods, the phase difference caused by the target azimuth and time delay will be difficult to distinguish, thus resulting in delay–space coupling, which may lead to degradation of the road target observation. In this paper, randomized SAA (RSAA) FMCW radar is proposed. The new radar scheme has high delay/space resolution for target location detection and character extraction, and can also solve the coupling problem. The signal model of RSAA FMCW radar is derived and compared with that of SSAA radar. The influence of the antenna-array switching mode on the radar performance is also analyzed. A conventional zero-padding algorithm and a new clustering FOCUSS algorithm are both introduced for the signal processing of the new radar scheme. The numerical results illustrate the performance of RSAA FMCW radar in high-resolution target imaging and delay–space decoupling. [ABSTRACT FROM PUBLISHER]

When a mobile operator migrates its network from the third generation (3G) system to Long Term Evolution (LTE), both 3G and LTE will coexist for a period of time. Since the 3G circuit-switched (CS) voice mechanism is more mature and available than that for the LTE Voice over Internet Protocol (VoIP), the operator may consider CS fallback (CSFB) as a solution for providing reliable voice calls. According to the 3G Partnership Project (3GPP) CSFB procedure, when a mobile user in the LTE network has an incoming or an outgoing call, the user equipment (UE) falls back from LTE to Universal Mobile Telecommunications System (UMTS). When the call is complete and released, the UE immediately returns to LTE. If the next activity for the UE is another voice call, immediately switching from UMTS to LTE may not be efficient. In this case, the UE has to perform another CSFB. To resolve this issue, we suggest delaying the returns to avoid unnecessary CSFBs, which is called delayed return (DR). Based on the measurements from the real UMTS and LTE networks, we develop an analytic model for investigating the performance of the CSFB with DR. This paper indicates that the DR scheme can effectively reduce the CSFB costs by up to 60%. [ABSTRACT FROM PUBLISHER]

This paper presents a six-phase current reconstruction scheme for dual traction inverters in hybrid electric vehicles (HEVs) with a single dc-link current sensor. During the phase current reconstruction, one of the inverters is proposed to operate using active vectors, whereas the other inverter operates using nonactive vectors. An advanced phase-shift scheme for all pulsewidth-modulated (PWM) signals based on the sequence of duty cycles is implemented. PWM signals are considered in three types: large, medium, and small duty cycles. Then, the minimum phase-shift scheme is applied to each type of PWM signal to ensure the minimum duration of the active vector for stable current reconstruction. With this proposed phase-shift scheme, the maximum allowable modulation index and dc-link voltage utilization are improved. In addition, the relationship between the minimum required time for stable phase current reconstruction and the maximum allowable modulation index is derived theoretically. The effectiveness of the proposed method is verified by both simulation and experimental results. With this scheme, cost and volume of dual inverters in HEVs are reduced, considering the lower number of current sensors. [ABSTRACT FROM PUBLISHER]

This paper presents the design guideline of a bidirectional isolated Ćuk converter with an active-snubber circuit, which is used as a cell level tester for multiple automotive dc energy storage devices (ESDs), such as ultracapacitors, Li-ion batteries, and NiMH batteries. The converter interfaces those automotive dc ESD cells with 24-V dc systems, and it realizes bidirectional power flow with two main switches. Based on the ratings of those dc ESD cells, the designed converter operates at a very low voltage range, i.e., from 1.5 to 6 V, with current as high as 300 A. The detailed operation principle and major features, such as soft switching and energy recovery, are analyzed under continuous current mode. Based on the analysis, the design guideline of the dc–dc converter is presented. A 1.2-kW laboratory prototype has been built and tested with full power rating. Both simulation and experimental results are presented to verify the analysis. [ABSTRACT FROM PUBLISHER]

In this paper, a control strategy is presented for a high-performance capacitively loaded loop (LLC) multiresonant dc–dc converter in a two-stage smart charger for neighborhood electric vehicle (NEV) applications. It addresses several aspects and limitations of LLC resonant dc–dc converters in battery charging applications, such as very wide output voltage range while keeping the efficiency maximized, implementation of the current mode control at the secondary side, and optimization of burst mode operation for current regulation at very low output voltage. The proposed control scheme minimizes both low- and high-frequency current ripples on the battery while maintaining stability of the dc–dc converter, thus maximizing battery life without penalizing the volume of the charger. Experimental results are presented for a prototype unit converting 390 V from the input dc link to an output voltage range of 3–72 V dc at 650 W. The prototype achieves a peak efficiency value of 96%. [ABSTRACT FROM PUBLISHER]

In an earlier paper, a simple and fast bit loading algorithm for orthogonal frequency-division-multiplex (OFDM) systems was presented. A drawback of the algorithm is that the solution obtained is suboptimal. This drawback is removed in this paper, where we show that the algorithm can be improved and turned into an optimal algorithm with a negligible impact on the computational complexity. [ABSTRACT FROM PUBLISHER]

In this correspondence paper, a decode-forward relay system with a source, a relay, and a destination is considered. A new switching superposition-coded (NSSC) relay scheme is proposed to improve error performance by increasing the equivalent squared minimum distance. On the receiver side, a low-complexity linear-combining successive-interference-cancellation decoder is proposed for the NSSC scheme. The theoretical and simulation results show that the NSSC scheme achieves better performance compared to the existing superposition-coded relay schemes. [ABSTRACT FROM AUTHOR]

Controller area network with flexible data rate (CAN-FD) has been introduced to support higher data rates for intelligent automotive systems. To achieve a robustness in the electronic functions of electronic systems, CAN-FD transmitters should provide a good symmetry between the differential signaling on the CAN bus radiating a low electromagnetic emission (EME). This paper proposes a new CAN-FD transmitter which achieves good symmetry on the CAN-FD signals. Also, a so-called ``Ping-Pong” driving scheme is introduced. Without using complex circuits and after-calibration process, this method can match accurate turn-on/off timing of the transmitter signals. The proposed CAN-FD transmitter was fabricated using a $0.18\,\mu {\text{m}}$ automotive Bipolar-CMOS-DMOS process. The measurement results show that the proposed CAN-FD transmitter improves the voltage symmetry of the CAN bus at 5 Mbps, achieving a low EME. [ABSTRACT FROM AUTHOR]

To overcome the problem that the balancing performance of existing switched-capacitor (SC) cell balancing systems drops along with the increase in the number of series-connected battery cells, a novel SC cell balancing circuit is presented in this paper. The same as other SC balancing systems, only a pair of complementary square-wave signals is required to control the proposed circuit. With resonant SC design, all switches employed in the proposed balancing circuit operate under zero-current switching. The equivalent model is derived to reveal the balancing performance of the proposed balancing circuit. The system feasibility and theoretical analysis are verified by both of simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, an innovative method to minimize the intermediate dc-link capacitance in a cascaded two-stage combination of a three-phase six-switch power factor correction (PFC) and phase-shifted full-bridge (PSFB) dc/dc stage is introduced and analyzed. The proposed strategy has a significant impact on the minimization of the overall system weight and volume. Fundamentally, the method is based on minimizing the switching fundamental component of the dc-link current and is established by imposing a separate constraint on the phase duty ratios without compromising the unity PFC action. Furthermore, the control loop takes care of regulating the intermediate dc-link voltage along with the final output voltage. A 6 kW laboratory prototype of the integrated three-phase PFC and PSFB dc/dc as a part of auxiliary power unit in more-electric airplanes is developed and designed to validate the proposed algorithm. The experimental results show a conversion efficiency of 95.4% at full load, input total harmonic distortion of 4.1%, power factor of 0.998, output voltage ripple of ±1%, and a reduction of dc-link capacitor by 60%. [ABSTRACT FROM AUTHOR]

With the emerging automated tasks in vehicle domain, the development of in-vehicle communications is increasingly important and subjected to new applications. The use of vehicular power lines has been a promising alternative to in-vehicle communications because of elimination of extra data cables. In this paper, we focus on the latest HomePlug Green PHY (HPGP) and explore its opportunity to support time-critical in-vehicle applications. Specifically, we apply network calculus to evaluate the worst access and queuing delay of various priority flows in vehicle bus networks. In order to maximize the bandwidth utility and satisfy the end-to-end hard delay requirements, we further propose a bandwidth efficient fair rate scheduling and delay sensitive traffic shaper. Performance evaluation supplemented by numerical and simulation results is also provided to show the advantage of HPGP and the proposed traffic shaper over the existing industry solutions. [ABSTRACT FROM PUBLISHER]

This paper investigates the inverter nonlinearities in a drive system based on silicon carbide metal-oxide-semiconductor field-effect transistor (SiC-mosfets) and compares its performance with that of an equivalent silicon insulated-gate bipolar transistor (Si-IGBT) system. Initially, a novel comprehensive analytical model of the inverter voltage distortion is developed. Not only voltage drops, dead time, and output capacitance, but also switching delay times and voltage overshoot of the power devices are taken into account in the model. Such a model yields a more accurate prediction of the inverter's output voltage distortion, and is validated by experimentation. Due to inherent shortcomings of the commonly used double pulse test, the switching characteristics of both SiC-mosfets and Si-IGBTs in the pulse width modulation inverter are tested instead, such that the actual performances of the SiC and Si devices in the motor drive system are examined. Then, the switching performance is incorporated into the physical model to quantify the distorted voltages of both the SiC-based and Si-based systems. The results show that, despite its existing nonlinearities, the SiC-based drive has lower voltage distortion compared to the conventional Si-based drive as a result of its shorter switching times and smaller voltage drop, as well as a higher efficiency. Finally, the overriding operational advantages of the SiC-based drive over its Si-based counterpart is fully demonstrated by comprehensive performance comparisons. [ABSTRACT FROM PUBLISHER]

DC-link voltage fluctuation, originated from the single-phase power supply, has a significant impact on the railway traction drive system. Instead of employing a large LC filter to suppress the fluctuation, software solutions are of more interests, since they do not add additional components to the system. A state-of-the-art feedforward strategy predicts the dc-link voltage pattern based on its repetitive nature and directly modifies the duty cycle fed to the inverter to eliminate the impact of the fluctuation. Yet this strategy requires a symmetrical and consistent pulse pattern. In this paper, a compensation approach for synchronous space vector modulation with multiple pulse patterns is proposed. It utilizes the prediction of the dc-link voltage pattern and, based on the volt–second balancing principle, modifies the switching instants corresponding to different pulse patterns. Simulation and experimental results show that the proposed method can significantly eliminate the impact of the fluctuation. [ABSTRACT FROM PUBLISHER]

Inductive power transfer (IPT) technology has been approved to be convenient and reliable interface for charging and discharging the electric vehicles (EVs). Precise model for such system can help designers and researchers to anticipate, optimize, and evaluate its behavior amid the development. Thus, this paper presents a physics-based co-simulation platform for the bidirectional IPT system (BIPTS) in EVs’ applications. The platform is established through the coupling between finite element and circuit analysis. The power electronic converters and controllers are developed in Simulink; and the power pads are modeled in Magnet environment. The two parts are lined together through the compatible Simulink plug-in tool. In addition, a state-space dynamic mathematical model for the same BIPTS is derived and implemented in MATLAB environment. A 1.2 kW BIPTS is analyzed under different dynamics by both models and the results are compared. The effect of the nonlinearities and the magnetic material characteristics on the BIPTS's performance is assessed, in terms of errors and harmonics analysis. The analysis considered both the full and light loading operating conditions in the system. Finally, a small-scale prototype for a BIPTS is built, tested, and compared with the co-simulation results for verification purposes. The proposed co-simulation could provide accurate prediction for the system's dynamics, during both charging and discharging operation. The scheme is generic and can be easily expanded to different pad structures, compensation networks, and converter topologies. [ABSTRACT FROM PUBLISHER]

This paper proposes an interleaved equalization architecture for series-connected lithium-ion battery strings, which can deliver energy from a battery module to the cells in the next adjacent battery module, resulting in an enhancement of the equalization current and efficiency. Particularly, the global equalization is achieved without the need of additional stage circuits to balance among modules, leading to a small size and low cost. A two-module equalizer based on resonant LC converter and buck converter with soft switching is implemented to verify the validity of the proposed interleaved architecture. Furthermore, a self-learning fuzzy logic control (SLFLC) algorithm is employed to online regulate the equalization period based on the voltage difference among cells and the cell voltage, not only greatly abbreviating the balancing time but also effectively preventing overequalization. The SLFLC has the outstanding advantages of high balancing precision, easy implementation, and strong robustness. Experimental results demonstrate that the proposed equalizer has good balancing performances with soft switching and high efficiency, and achieves zero-voltage gap among cells. Moreover, the proposed SLFLC algorithm abridges the total equalization time by about 27%, and reduces the equalization cycles by about 59% compared with the traditional control algorithm. [ABSTRACT FROM AUTHOR]

In heterogeneous networks, a dense deployment of base stations (BSs) leads to increased total energy consumption, and, consequently, increased cochannel interference (CCI). In this paper, to deal with this problem, self-organizing mechanisms are proposed, for joint channel and power allocation procedures, which are performed in a fully distributed manner. A dynamic channel allocation mechanism is proposed, in which the problem is modeled as a noncooperative game, and a no-regret learning algorithm is applied for solving the game. In order to improve the accuracy and reduce the effect of shadowing, we propose another channel allocation algorithm executed at each user equipment (UE). In this algorithm, each UE reports the channel with minimum CCI to its associated BS. Then, the BS selects its channel based on these received reports. To combat the energy consumption problem, BSs choose their transmission power by employing an on–off switching scheme. Simulation results show that the proposed mechanism, which is based on the second proposed channel allocation algorithm and combined with the on–off switching scheme, balances load among BSs. Furthermore, it yields significant performance gains up to about $40.3\%$, $44.8\%$ , and $70.6\%$ in terms of average energy consumption, UE's rate, and BS's load, respectively, compared to a benchmark based on an interference-aware dynamic channel allocation algorithm. [ABSTRACT FROM PUBLISHER]

This paper deals with a synthesis of space-vector pulsewidth modulation (SVPWM) control methods applied for an H-bridge inverter feeding a three-phase permanent-magnet synchronous machine (PMSM) in electric-vehicle (EV) applications. First, a short survey of existing architectures of power converters, particularly those adapted to degraded operating modes, is presented. Standard SVPWM control methods are compared with three innovative methods using EV drive specifications in the normal operating mode. Then, a rigorous analysis of the margins left in the control strategy is presented for a semiconductor switch failure to fulfill degraded operating modes. Finally, both classic and innovative strategies are implemented in numerical simulation; their results are analyzed and discussed. [ABSTRACT FROM PUBLISHER]

This paper presents the design and control of a high-efficiency multiphase dc–dc converter for a truck auxiliary power unit (APU) fed by a fuel-cell stack. The power-stage design methodology and the operation of the designed power stage used to achieve high efficiency are described in detail. To operate the designed converter as a truck APU, the mode transfer control scheme, where smooth transitions of the voltage and current control modes are necessary, is proposed, and the current controller design procedure is described. A 5-kW four-phase dc–dc converter prototype is built with the proposed power-stage configuration, and the proposed control strategy is applied to control the dc–dc converter. The efficiency of the converter is more than 99.5% at near 10% load and above 98% from 10% to 100% load range. Simulations and experimental results are provided to verify the feasibilities of dc–dc converter operation and the proposed control strategy in the truck APU application. [ABSTRACT FROM PUBLISHER]

Contact discovery is a fundamental premise of information exchange in delay-tolerant networks (DTNs). However, the intermittent connectivity nature of DTNs makes energy-efficient contact discovery a tough challenge. To save energy, a node should work in low-power mode most of the time since contacts with the other nodes may rarely happen. However, such a strategy will probably fail to detect many contacts with relatively short durations, leading to system performance degradation. In this paper, we consider a specific type of DTN, i.e., the pocket switched networks (PSN), in which the nodes' mobility pattern shows a strong social property. In a PSN, although the end-to-end path may be disconnected for the majority of time, several nodes periodically gather at certain hot spots and form well-connected clusters. Based on such mobility pattern, cooperation among nodes is utilized in our contact discovery design. The nodes that have already joined a cluster collaboratively wake up to discover new contacts. With local synchronization and complementary consideration of possible traffic congestion, both the theoretical analysis and simulation results show that our cooperative duty cycling (CDC) greatly reduces the energy consumption while achieving comparable data delivery performance. [ABSTRACT FROM PUBLISHER]

In this paper, an active suspension system utilizing a low-cost high-performance linear switched reluctance actuator with proportional-derivative (PD) control is presented. With the tracking differentiator (TD) calculating the displacement and its derivatives directly under the presence of noise, velocity and acceleration can be evaluated, and accurate position control can be achieved. Comparison is made between linear and nonlinear PD control methods in terms of various system parameters and road profiles. A nonlinear PD controller with better dynamic responses is evaluated and developed for real-time suspension application. The proposed PD control schemes are simulated, tested, and analyzed to prove its robustness and reliability. Finally, a quarter-car active suspension system prototype is built to demonstrate the effectiveness of the proposed control schemes with experiment results. [ABSTRACT FROM PUBLISHER]

The femtocell is becoming a promising solution to face the explosive growth of mobile broadband usage in cellular networks. Although each femtocell only covers a small area, a massive deployment is expected to form networked femtocells in the near future. One immediate challenge is to provide seamless mobility support for networked femtocells with minimal support from mobile core networks. In this paper, we propose efficient local mobility management schemes for networked femtocells based on X2 traffic forwarding under the Third-Generation Partnership Project Long-Term Evolution Advanced (3GPP LTE-A) framework. Instead of implementing the path switch operation at core network entity for each handover, a local traffic forwarding chain is constructed to use the existing Internet backhaul and the local path between the local anchor femtocell and the target femtocell for ongoing session communications. Both analytical studies and simulation experiments are conducted to evaluate the proposed schemes and compare them with the original 3GPP scheme. The results indicate that the proposed schemes can significantly reduce the signaling cost and relieve the processing burden of mobile core networks with the reasonable distributed cost for local traffic forwarding. In addition, the proposed schemes can enable fast session recovery to adapt to the self-deployment nature of the femtocells. [ABSTRACT FROM PUBLISHER]

A direct instantaneous force control with improved efficiency for the linear switched reluctance actuator (LSRA) is proposed in this paper. Four-quadrant operation is investigated for application in the active suspension system. Force ripple minimization is considered as the primary objective due to the direct impact on passenger ride comfort. An adaptive force distribution function based on the instantaneous force feedback is proposed to achieve a ripple-free system. The choice of switching parameters for improved operation efficiency is examined. The optimal switching positions are online adjusted with respect to the force demand. Simulation and experimental results are presented to verify the effectiveness of the proposed control strategy. [ABSTRACT FROM PUBLISHER]

This paper presents a high-gain boost converter (three-level converter and transformerless converter) for fuel cell (FC) vehicle applications. An original nonlinear control law based on the flatness principle for distributed dc generation is studied. Utilizing the flatness property, we propose simple solutions to the system performance and stabilization problems. The design controller parameters are straightforward and autonomous at the operating point. To validate the proposed method, a prototype FC power converter (1.2-kW three-level boost converter) is developed in the laboratory. The proposed control law is implemented with a digital estimate in a dSPACE 1104 controller card. The experimental results from the laboratory using a 1200-W and 46-A polymer electrolyte membrane FC (PEMFC) verify that this is a good control scheme. [ABSTRACT FROM PUBLISHER]

Fuel consumption of traditional ground vehicles is significantly affected by how the vehicles are driven. This paper focuses on the servo-loop control design of a Pulse-and-Gliding (PnG) strategy to minimize fuel consumption in automated car following. A switching-based framework is proposed for real-time implementation. The corresponding controller was synthesized for ideal conditions and subsequently enhanced to compensate for practical factors such as powertrain dynamics, speed variations, and plant uncertainties. Simulations in both uniform and naturalistic traffic flows demonstrate that, compared with a linear quadratic (LQ)-based benchmark controller, the PnG controller improves fuel economy up to 20%. The significant fuel saving is achieved while maintaining precise range bounds so that the negative impact on safety/traffic flow is contained. The developed algorithm can potentially be embedded in adaptive cruise control systems to achieve fuel-saving function. [ABSTRACT FROM PUBLISHER]

Effective data broadcasting is essential in vehicular networks not only for road-safety message dissemination but also to aid routing and cooperative driving applications through periodic beaconing and to spread network initialization advertisements that are mandatory to support infotainment applications. Broadcast data are neither acknowledged nor retransmitted in case of failure, which raises the possibility of frame loss due to channel errors and collisions with multiple simultaneous broadcasts. This paper aims at modeling periodic broadcasting on the control channel of IEEE Std. 802.11p vehicular networks with multichannel architecture. Unlike previous related work, the proposed novel analytical approach accounts for mutual influence among nodes, frequent periodic updates of broadcasted data, standard network advertisement procedures, and 802.11p prioritized channel access with multichannel-related phenomena under various link quality conditions. [ABSTRACT FROM PUBLISHER]

In this paper, we propose an analytical framework for determining the outage probability of random and best relay selection schemes given a Poisson field of relay nodes and the presence of path loss and fading. For relay selection, relays geographically close to the source and destination are preferred to others. This selection guideline ensures a target quality of service (QoS) and reduces the signaling overhead and the relay selection delay. A spatial region called the QoS region is obtained for the random relay selection and is shown to shrink as the distance between the source and the destination increases and the interfering node density increases. When the QoS region for random relay selection is not large enough and cannot probabilistically ensure a reliable relay therein, the best relay selection is employed since the required relay node density and selection range for a desired QoS can be reduced for the best relay selection. The gain of the best relay selection with respect to the random relay selection is quantified in terms of relay node density reduction and coverage extension due to selection diversity. [ABSTRACT FROM PUBLISHER]

Conventional brake systems using a mechanical-structure-based contact switch with a metal spring suffer from frequent malfunction problems over time caused by unstable contacts stemming from loose tension of the spring, a faulty air gap, and damage to the contact point due to overcurrent from load. In this paper, a novel contactless switch for brake systems using an eddy-current displacement sensor is proposed, fabricated, and verified to have reliable performance that overcomes conventional contact switch problems. A proposed contactless switch was fabricated using automotive-grade surface-mount devices (SMDs) on both sides of an FR-4 printed circuit board for low-cost implementation. The measurement result shows a switching speed of less than 49.7 \mu\s, on average, which is approximately ten times faster than conventional mechanical-structure-based contact switches. The overall dimension of the proposed switch is 36 mm \times 26 mm \times 64 mm, which can fit into most brake switch housings. The operating input voltage range is from +8 V to +22 V, with the temperature ranging from -40\ ^\circ\C to +85\ ^\circ\C, showing reliable performance under harsh environment test for automobile applications. [ABSTRACT FROM PUBLISHER]

Various types of cell voltage equalizers that exchange charges among cells have been proposed for series-connected lithium-ion cells. During equalization, cells are possibly cycled not only over a conventional period that ranges from seconds to hours but at a high frequency that is equal to the operating frequency of the equalizers as well. This paper investigates how the high-frequency cycling occurs and the factor that affects the life performance of the cells during high-frequency cycling. Experiments on charge–discharge cycling at frequencies of 1–100 kHz were performed for lithium-ion cells. The capacity of cells cycled at frequencies below 10 Hz significantly deteriorated, whereas the capacity decay of cells cycled at higher frequencies were identical to the corresponding calendar degradation. Simulation analyses revealed that the cycling current at high frequencies served only to charge and discharge the double-layer capacitance C \rm dl, whereas the current that flows through the charge-transfer resistance Rct, indicating the charge-transfer process, dominated at low frequencies. A correlation between the degradation trend and current distribution to Cdl and Rct was observed, implying that the calendar degradation and the degradation due to the charge-transfer process were the major causes of capacity decay in the frequency range below 10 Hz. [ABSTRACT FROM PUBLISHER]

In this paper, a switched control strategy for an antilock braking system (ABS), which has conventional hydraulic actuators equipped with on/off valves, is presented. The investigated system contains the continuous dynamics of the vehicle and the inherent discontinuous characteristics of the on/off valves. Accordingly, a novel approach based on nonlinear state feedback and a switching strategy renders a controller that assures that the wheel slip converges into the target equilibrium set. Then, the convergence condition of the closed-loop system is analyzed using Lyapunov theory in the Filippov framework, and the influence of controller parameters on the system is also discussed. It is shown that the proposed controller has few tuning parameters, and each parameter has an explicit physical meaning. Both the illustrative hardware-in-the-loop simulation and experimental results show that the switched control approach is robust enough to guarantee a good performance, even if the uncertainties of the actuator characteristics, road-adhesion coefficient, and vehicle speed are considered. [ABSTRACT FROM PUBLISHER]

This paper presents an innovative torque control strategy for a switched reluctance machine (SRM) operating in continuous-conduction mode (CCM). The proposed strategy was first designed to control the torque in discontinuous-conduction mode and then extended to operate in CCM as well. With CCM, the torque can be increased at high speed without modifying the number of turns, the source voltage, or the converter; it is achieved through the control. Reviews of past control strategies, as well as the principle of this mode and its influence on the machine performance, are presented. The advantages and drawbacks of the proposed strategy are outlined. In particular, the power and torque densities of the SRM are improved so that this machine becomes comparable with ac machines without the drawback of field weakening. A new control law has been studied and implemented; simulation and experimental results are provided to demonstrate the effectiveness of the proposed control. [ABSTRACT FROM PUBLISHER]

In this paper, we investigate the performance of networks built from single-channel devices that use wireless access in vehicular environment protocols. We consider several traffic combinations, each of which presents a mix of traffic classes, over control and service channels. Our results show that time switching between the channels causes synchronization of backoff processes, which increases the frame collision probability, in particular for small sizes of contention windows. We also evaluate the impact of the interruption of the backoff process by inactive channel time, which gives rise to a probability distribution with repeated tails and a coefficient of variation larger than 1. Our model can also be used to evaluate different sets of enhanced distributed channel access parameters and to select the channel duty cycle according to the policy of the network operator. [ABSTRACT FROM PUBLISHER]

Wireless mesh networking (WMN) is regarded as a low-cost technology for rapid wireless network deployment. However, in a single-channel WMN, the overlapped transmission ranges between relaying mesh points could introduce serious interference. Using multiple radios over multiple channels can decrease the interference and improve the capacity of a WMN, but it increases the cost of a mesh point. One possible solution to balance between interference, hence performance, and cost is utilizing fewer radios that switch among multiple channels instead of using per-channel radios. In this paper, we propose a channel-switching method, called the traffic-aware switching scheme (TRASS), for a mesh point with a limited number of radios. TRASS utilizes the existing IEEE 802.11 mechanisms, i.e., hybrid-coordination-function-controlled channel access and power saving, to avoid packet loss during channel switching. A TRASS mesh point monitors the occupied channel time to schedule radios that switch among channels. The implemented TRASS demonstrates 75% throughput improvement by (2, 1), i.e., two-channel single-radio, over (1, 1). (3, 2) and (3, 1) achieve 69.8% and 39.7%, respectively, of the throughput of (3, 3) in the simulated TRASS. [ABSTRACT FROM PUBLISHER]

This paper presents a theoretical and experimental analysis on the application of power-line communication (PLC) on a cruise ship. The authors have developed an accurate model of the power grid of a ship when it is used as a PLC channel. The model is developed based on a theoretical approach and validated by a thorough measurement campaign. The accuracy of the model is addressed by a comparison between simulation results and measured data, and its use gives an insight into the performance of the power network to be used as PLC channel. [ABSTRACT FROM PUBLISHER]

Considering the advantages of contactless fault diagnosis, a novel sound based fault diagnosis method for railway point machines (RPMs) is proposed. Firstly, a denoising method based on empirical mode decomposition (EMD) is proposed. The useful intrinsic mode functions (IMFs) are selected using kurtosis and energy criteria to reconstruct the denoised signal. Then, multi-scale fractional permutation entropy (MFPE) is proposed inspired by fractional calculus, which is more powerful than the classical multi-scale permutation entropy (MPE). And a two-scale algorithm is developed to avoid neglecting the information contained at the end of the signals in the coarse-graining process. Finally, the feasibility and superiority of the proposed method (D-FMPE-T) based on denoising method and two-scale algorithm are verified using support vector machine optimized by particle swarm optimization (PSO-SVM) through comparing with some commonly used feature extraction and classification methods. Besides, CWRU is also utilized for verification of the superiority of the proposed method. Experiment results show that the proposed method performs best. The identification accuracies on normal-reverse and reverse-normal switching processes, and CWRU data sets reach 99.3%, 99%, and 99.17% respectively, demonstrating the feasibility and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

We consider an energy-harvesting cognitive radio (CR) system coexisting with an unslotted primary user (PU) system. The secondary user (SU) either harvests energy from the PU transmissions or transmits when the PU is sensed to be idle. In this paper, we optimize the sensing intervals to balance between energy harvesting and spectrum access, considering the PU traffic statistics that affects both the energy arrival and consumption in addition to the opportunistic spectrum access. We propose to use different sensing intervals if the SU decides to transmit or harvest energy. The harvesting and transmission durations can be used to optimize the tradeoff between maximizing the utilization of PU spectrum opportunities and harvesting sufficient energy to transmit. We determine a closed-form expression for the probability of SU being active as a function of the PU traffic statistics and SU's access and harvest durations. Optimal transmission and harvesting durations have been found to maximize the CR throughput while protecting the PU. Furthermore, we enhance the system capability by considering that the SU can choose to purchase energy from the PU during the discovered PU idle periods in addition to the energy harvested opportunistically. It can further exploit the difference in the PU busy and idle durations as per its energy needs. The average energy cost spent in a time slot is minimized to achieve a given SU transmission rate while adhering to the PU collision constraint. [ABSTRACT FROM AUTHOR]

A nonisolated single-stage on-board charger for electric vehicles has been proposed to increase system efficiency and power density in previous works. However, its ability to achieve high efficiency is limited by variations in the electric utility and battery, especially during the step-down operation. This paper proposes an advanced control algorithm that improves system efficiency in the step-down mode by controlling each switch asymmetrically using a phase-shift control. The proposed algorithm consists of only one controller, which prevents transient states from causing variations in the controller. The algorithm decreases the magnitude and ripple of the inductor current, which improves the charging efficiency by approximately 4.1% over at the 3.7-kW full load that of the conventional algorithm in the step-down mode, and measured total harmonic distortion and power factor are 3.2% and 0.995, respectively. [ABSTRACT FROM AUTHOR]

This paper proposes a novel integrated synchronous buck converter for the auxiliary power supply system of electric vehicles, which achieves multiple independently regulated outputs with reduced switching components in comparison with the conventional separate buck converters. In order to obtain a better understanding of the proposed converter, operational principle and performance characteristics of a simplified dual-output buck converter are introduced in detail, as an example. The analysis shows that zero-voltage-switching operation and lower conduction losses could be attained. In addition, its dynamic behavior is similar to the conventional buck converter and thus the controller design is simple. Finally, experimental results based on a prototype circuit in which two inductors are integrated into one magnetic core to achieve further reduced cost are demonstrated to verify the advantages. [ABSTRACT FROM PUBLISHER]

Channel rendezvous is a vital step to form a cognitive radio network (CRN). It is intractable to guarantee rendezvous for secondary users (SUs) within a short finite time in asynchronous, heterogeneous, and anonymous CRNs. However, most previous heterogeneous algorithms rely on explicit SUs' identifiers (IDs) to guide rendezvous, which is not fully distributed. In this paper, we exploit the mathematical construction of sunflower sets to develop a single-radio sunflower set (SSS)-based pairwise rendezvous algorithm. We propose an approximation algorithm to construct disjoint sunflower sets. Then, the SSS leverages the variant permutations of elements in sunflower sets to adjust the order of accessing channels instead of SUs' IDs, which is more favorable for anonymous SUs in distributed environments. We also propose a multiradio-sunflower-set-based pairwise rendezvous algorithm to bring additional rendezvous diversity and accelerate the rendezvous process. Moreover, for the case with more than two SUs, we propose a multiuser collaborative scheme in which SUs cooperatively exchange and update their channel-hopping sequences until rendezvous. We derive the theoretical upper and lower bounds of rendezvous latency of the proposed algorithms. Extensive simulation comparisons with the state-of-the-art blind-rendezvous algorithms are conducted, incorporating the metrics of maximum and expected time-to-rendezvous. The simulation results show that our algorithms can achieve rendezvous faster than previous works. [ABSTRACT FROM PUBLISHER]

This study proposes a generalized voltage pumping module (GVPM) and a GVPM-enabled converter design approach for electric vehicles. The designed GVPM has high flexibility and can be applied to most high step-up converters for extra voltage pumping yet with low component stresses. The proposed GVPM design method is presented, rationalized and analyzed in a generalized structure, which is followed by eight specific application examples, where typical step-up converters are employed to be structurally coupled with the proposed GVPM design approach for design guideline and methodological validation. Through theoretical analyses and experimental verification, the proposed voltage pumping approach is proven to be able to work synergistically with most types of DC-DC converters, demonstrating its advantageous features and wide applicability for voltage pumping of step-up converters. [ABSTRACT FROM AUTHOR]

To improve the mode switching quality of the power-split hybrid electric vehicle (PS-HEV), a compound torque coordinated control strategy is proposed. Aiming at the problem of engine dynamic response lag, the engine real-time torque estimator is designed, and then the torque ripple at the output end of the power coupling mechanism is reduced through the basic motor torque compensation. On this basis, considering the existence of non-ideal communication networks in actual vehicle control systems, the tremendous impact of communication network time delay and interruption on the mode switching stability and vehicle fuel consumption has been deeply revealed. Then the compound coordinated control strategy including the BP-smith predictive controller, motor torque change rate limiting module, network transmission mechanism with fixed communication priority and fault-tolerant torque coordinated control module is put forward and verified by simulation and hardware-in-the-loop test. The results show that the compound coordinated control strategy could still guarantee the system stability, mode switching smoothness and vehicle fuel economy under the interference of stochastic communication delay and interruption. [ABSTRACT FROM AUTHOR]

Although multiple channels are supported in the physical layer, the IEEE 802.11 MAC-layer mechanism is designed for a single channel. Exploiting multiple channels enhances spatial reuse and reduces transmission collisions and, thus, improves network throughput. Designing a multichannel MAC protocol is much more difficult than designing a single-channel MAC protocol. New challenges, such as the channel allocation problem and the missing receiver problem, must be overcome. Existing multichannel MAC protocols suffer from either higher hardware cost (because of applying multiple transceivers) or lower channel utilization (due to limited transmission opportunity). In this paper, a fully distributed channel-hopping solution, i.e., the cyclic-quorum-based multichannel MAC protocol, is proposed. We use the cyclic quorum in a novel way and the proposed protocol has several attractive features. First, only a single transceiver is needed for each node. Second, any sender is guaranteed to meet its receiver in a short time. Third, each node's channel-hopping sequence is derived from its node ID. This avoids exchanging control messages, such as each node's hopping sequence or available channel list. Fourth, multiple transmission pairs can accomplish handshaking simultaneously. The proposed protocol is simple and efficient. Simulation and real system implementation results verify that our mechanism is a promising multichannel MAC protocol for mobile ad hoc networks. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicle (UAV) swarms have attracted great interests in numerous civil and military scenarios due to their flexible deployment and mobility. The increased network size poses a challenge for the network scalability. Clustering as an effective scheme, is able to provide efficient communication and network performance. In order to adapt to the change of network topology, the link subsistence probability is used to evaluate the mobility of UAVs. However, the UAVs usually perform tasks collaboratively, which leads to their movements are typically group-based. To this end, a coalition game theoretic framework is proposed to cluster UAVs into coalitions in a distributed autonomous manner, based on the group and the mobility information. The proposed game allows the UAVs with the same group, as much as possible, into one coalition under some constraints, such as cluster size and cluster diameter. To solve the game, each UAV makes its decision whether to switch based on the coalition value. Finally, some comparisons are provided to illustrate the efficiency of the proposed algorithm. [ABSTRACT FROM AUTHOR]

With growing concern about environmental issues and an emerging green communications paradigm, cognitive radio (CR) networks (CRNs) have to be considered from the energy efficiency perspective. In this paper, we focus on scheduling in CRNs, in which a cognitive base station (CBS) makes frequency allocations to the CRs at the beginning of each frame. A cognitive scheduler must consider the diversity among CRs' queues and channel capacities in terms of number of bits and the channel switching cost from one frequency to another. Taking all these into account, we formulate the scheduling problem as an energy efficiency maximization problem, which is a nonlinear integer programming (NLP) problem and is thereby hard to solve. We seek alternate computationally easier solutions. To this aim, we propose a polynomial-time heuristic algorithm, i.e., the energy-efficient heuristic scheduler (EEHS), which allocates each idle frequency to the CR that attains the highest energy efficiency at this frequency. Next, we reformulate the original problem first as a throughput maximization problem subject to energy consumption restrictions and then as an energy consumption minimization problem subject to minimum throughput guarantees. These two schedulers also have the power to provide fairness in resource allocation. We analyze the energy efficiency and successful transmission probability of the proposed schedulers under both contiguous and fragmented spectrum scenarios. Performance studies show that, compared with a pure opportunistic scheduler with a throughput maximization objective, proposed schedulers can attain almost the same throughput performance with better energy efficiency. [ABSTRACT FROM PUBLISHER]

Cell voltage equalizers are necessary to ensure years of operation for series-connected supercapacitors (SCs) by eliminating cell voltage imbalance. Conventional equalizers require numerous switches and/or magnetic components; hence, the circuit complexity and size tend to increase. In this paper, a double-switch single-transformer equalizer, which is based on the combination of a half-bridge inverter and a voltage multiplier, is proposed. The operation of the proposed equalizer is analyzed in detail, and a dc equivalent circuit is mathematically derived. Experimental equalization tests were performed for eight SCs connected in series under a voltage-imbalanced condition. The energy of the series-connected SCs was preferentially redistributed to SCs with low voltages, and eventually, the voltage imbalance was eliminated, demonstrating the equalization performance. Simulation-based equalizations using the derived dc equivalent circuit were also performed under the same condition as the experiments. The experimental and simulation results were in good agreement, indicating that the derived dc equivalent circuit can adequately express real equalization profiles. [ABSTRACT FROM PUBLISHER]