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Dual active converter (DAB) can achieve high efficiency when the voltage ratio (the ratio of the input voltage to the output voltage equivalent to the primary side) is one, but when the voltage ratio is not one, the light-load efficiency drops sharply. Based on the realization logic of DAB light-load, this article proposes a modulation method with asymmetric compression duty cycle, which only increases one degree of freedom and does not need additional components to significantly improve the light-load efficiency. First, this article introduces the existing problems and solutions of the traditional scheme and puts forward a new modulation strategy. Then, the operating modes and power characteristics are analyzed. Then, the influence of duty cycle compression on reflux power and current stress is analyzed. Finally, a prototype with an input voltage of 100–200V, an output voltage of 50 V, and a full load power of 300–600 W is built to verify the analysis. [ABSTRACT FROM AUTHOR]

This article proposes a classifier-based approximator to compensate for friction in a high accelerated positioning system. Since friction function is globally non-smooth, an unsupervised k-means clustering algorithm is adopted to classify the friction into micro and macro motion segment, then the frictions are estimated with two sub-approximator in the corresponding segment respectively. Due to the unsupervised classification of friction, the classifier-based approximator can realize universal approximation of nonlinear friction with high precision. Finally, comparative experiments on a high accelerated position system driven by voice coil motors are conducted to verify the effectiveness of the proposed method. The proposed method can reduce the root mean square error (RMSE) of tracking by 57.2%, 19.1%, and 27.4% compared with a parametric model, recurrent neural network (RNN), and incremental extreme learning machine (I-ELM), respectively. [ABSTRACT FROM AUTHOR]

The creation of context-aware services in pervasive computing environments has driven the wide development of wireless local area network (WLAN)-based indoor positioning systems. One of the main challenges in WLAN-based indoor positioning is the severe fluctuation of received signal strength (RSS), which may cause the RSS patterns to be mismatched and the positioning to be inaccurate. In this paper, an indoor positioning algorithm that combines the fingerprint scheme with mobility prediction is proposed. Since the mobility prediction is performed according to the moving speed and direction of the mobile client, the resulting location estimation is more stable compared to the use of RSS alone. Experimental results show that the proposed positioning algorithm can mitigate the impact of the RSS fluctuation and has better positioning accuracy and stability than previous fingerprint-based approaches. [ABSTRACT FROM AUTHOR]

The SC200 cyclotron is the critical component of the proton therapy system, which is being jointly developed by the Institute of Plasma Physics Chinese Academy of Sciences (ASIPP), Hefei, China, and the Joint Institute for Nuclear Research (JINR), Dubna, Russia. It is an isochronous cyclotron to accelerate H+ ions and extract proton beam energies of 75–200 MeV with the maximum beam intensity of 1 ~ μ A. The maximum magnetic field intensity of the SC200 cyclotron is 4.6 T, and the accuracy of measurements for the average isochronous field is required to be better than 10−4. The magnetic gap decreases from 37 mm at cyclotron center to 9 mm at the pole edge. Hence, the difficulty of designing a magnetic field measurement system is increased because of the required magnetic field accuracy and the narrow gap between the poles. A measurement system has been developed to measure the magnetic field distribution in the median plane of the cyclotron by the SENIS Hall probe. After the Hall probe is calibrated by NMR, the measurement accuracy can reach ± 4 × 10−4 under the magnetic field intensity of 5 T. The position of the Hall probe will be monitored by grating and optical encoder, respectively, so as to ensure its correct positions. To verify the performance of the mapping system, it has been tested in the SC200 cyclotron with the designed vacuum degree. The test results showed that the mapping system can run smoothly and meet the measurement requirements of the SC200 cyclotron. [ABSTRACT FROM AUTHOR]

Miniaturized multi-axis (force & torque) tactile sensors are paramount for the robot system to interact safely with the external environment, especially for the controlled adhesive robots. However, there exists a drawback——measurement anisotropy, which prevents sensors from performing equally well in all the directions and the high degree of integration. Based on the plate capacitive mechanism, this paper introduces a miniaturized 5-axis tactile sensing method with a novel double-layer sensitive structure. Practically, shear force is detected by measuring the change of overlap area in the upper-layer-sensing cell, while the normal force and moment can be obtained by the variable space between two plates arranged in a ${2} \times {2}$ -grid in the lower-layer-sensing cell. Moreover, in order to achieve the measurement isotropy, the relationship between the force/torque and the capacitance is clarified to facilitate the independent adjustment of the sensitivity of each axis. Based on the methodology, a miniature 5-axis flat tactile sensor is manufactured. The experimental results show that the shear sensitivity of the prepared sensor is over 0.2557pF/N within 7 N, reaching the same magnitude as normal force (0.2859pF/N over 3N range). The sensitivities of torque are over 1.8406 $({N}\cdot {m})^{-{1}}$ with a full-scale range of $0.04~{N}\cdot {m}$. The results demonstrate that the miniaturized tactile sensor is capable of isotropic measurement among 5-axis for robotic manipulation. [ABSTRACT FROM AUTHOR]

Offshore wind energy conversion system (WECS) usually adopts parallel converters to expand power capacity and improve reliability because of limited power rating of power devices, harsh marine environment, and poor maintenance accessibility. Any faulty converter is cutoff under traditional fault-tolerant control. When all parallel converters are faulty, the wind turbine must be shut down. Although simple, such a fault-tolerant control reduces system availability. Thus, a reconfigurable control for fault-tolerant of parallel wind power converters is proposed in this paper. The current reference of every phase leg in parallel converter system is reconfigured postfault according to their healthy states. The proposed reconfigurable control is realized in software level and without requiring redundant hardware. Compared with traditional fault-tolerant control, the proposed reconfigurable control only cuts off the faulty legs rather than faulty converter, and makes full use of all healthy legs. The reconfigurable control improves the availability of parallel wind power converters and provides multiple-leg fault ride-through capability to WECS, enhancing reliability and electricity generation. The simulation and experimental results validate the feasibility and effectiveness of the proposed reconfigurable control. [ABSTRACT FROM AUTHOR]

RF window which serves as a barrier between the vacuum and air sides is a very important device for RF cavity of cyclotron. But the performances of a basic RF window are not good in impedance matching characteristics and service life. In this paper, two kinds of RF window are developed to improve performances from three candidate designs as impedance matching optimization, thermal consideration during RF operation, and multipactor effect analysis. The multiple comparisons indicate that one of the designed RF windows is far better than the others, and a low-power test has verified its impedance matching characteristic. This optimal RF window may be widely used in other low energy cyclotron and similar devices. [ABSTRACT FROM AUTHOR]

Network coding is a promising technology proven to improve the performance of wireless networks. To successfully design a quality-of-service (QoS)-satisfied routing protocol with network coding, the bandwidth consumption of a coding host should be determined. Furthermore, coding opportunities should be increased to improve network capacity. Nevertheless, it is challenging to determine whether a host can be a coding host and to determine the bandwidth consumption of a coding host in a mobile ad hoc network (MANET). In this paper, we first present and define the coding conditions to identify a coding host. The bandwidth consumption of a coding host is then estimated under the contention-based wireless networks with a random access mechanism. Finally, we propose a bandwidth-satisfied and coding-aware multicast routing protocol (BCMRP). By taking into account the residual bandwidth of the carrier-sense neighbors of the forwarders, the proposed protocol can satisfy the bandwidth requirements of the requested flow and other ongoing flows. As a consequence of considering coding opportunities in multicast tree construction, the proposed multicast protocol can reduce the total bandwidth consumption. The simulation results show that BCMRP outperforms the prior multicast routing protocols in receiving ratio, admission ratio, and total bandwidth consumption. [ABSTRACT FROM AUTHOR]

Due to significant advances in wireless modulation technologies, some MAC standards such as 802.11a, 802.11b, and 802.11g can operate with multiple data rates for QoS-constrained multimedia communication to utilize the limited resources of MANETs more efficiently. In this paper, by means of measuring the busy/idle ratio of the shared radio channel, a method for estimating one-hop delay is first suggested. Then, by constructing a multicast tree, a delay-sensitive multicast protocol for real-time applications in multirate MANETs is proposed. In order to increase the network capacity, the proposed multicast protocol intends to minimize the sum of the total transmission time of the forwarders and the total blocking time of the blocked hosts, by taking the neighboring information of the forwarders into account and properly adjusting the data rates of the forwarders. Simulation results show that the proposed delay estimation method is more accurate, as compared with previous works. Besides, the proposed multicast protocol can induce higher network capacity, while satisfying the delay requirement. [ABSTRACT FROM PUBLISHER]

Wireless links are inherently lossy due to channel fading or interference. Previously, duplicate packets were transmitted on multiple routes of lossy mobile ad hoc networks (MANETs) to enhance reliability. In this paper, a multicast routing protocol that constructs multiple multicast trees and employs network coding is proposed for lossy MANETs, where each multicast tree can satisfy a predefined percentage of the bandwidth requirement. The proposed protocol can reduce the total bandwidth consumption while providing bandwidth guarantees to a requested flow and ongoing flows. As a consequence of employing network coding, no redundant packet is generated, and no scheduling algorithm for distributing packets among the multicast trees is needed. Simulation results show that the proposed protocol outperforms prior multicast routing protocols in terms of the receiving ratio, the admission ratio, and the total bandwidth consumption. [ABSTRACT FROM PUBLISHER]

Cognitive radio (CR) is introduced to improve spectrum efficiency by unlicensed usage when a licensed band is idle. These devices monitor licensed users to find spectral opportunities for transmission. A cognitive radio network (CRN) is defined as a structure, which is constructed by both licensed users and unlicensed CR users. In an effort to improve spectrum efficiency, CR users' spectrum issues have been widely studied over the last few years. However, the existing solutions are not capable of dealing with the following scenario: multiple CRNs operating simultaneously without a centralized coordinator. This issue is often referred to as a coexistence problem of heterogeneous CRNs. This problem is caused in a distributed framework of CRNs without a centralized component to negotiate spectrum usages with one another. The system characteristics of these heterogeneous networks are different; thus, the fairness issue between CR users must be considered. In this paper, a decentralized solution that does not limit the hardware capacity of a CR device is proposed as an added fairness feature. Several Markov chain models are proposed to study these unfairness conditions, and a medium access control layer approach is introduced. Numerical and simulation results are presented to verify the proposed solution. [ABSTRACT FROM PUBLISHER]

In recent years, wireless network structures and mechanisms have been proposed to enhance the efficiency of communications. Regarding the upper-layer of protocol stacks, wireless transmission control protocols (WTCPs) are proposed to deal with transmission control protocol (TCP) performance problems on wireless networks. However, some new lower-layer solutions, e.g., cognitive radio (CR) systems, cause new throughput decay problems to TCPs, which existing WTCPs do not solve. In this paper, we study throughput decay issues in CR environments and discuss three events that cause these problems. Three event handlers are proposed to improve TCP throughput. The proposed solutions are designed by numerical analysis, and performance improvement is verified by NS2. We propose an event-driven CR-TCP that combines these event handlers, which can be combined with state-of-art CR-TCP solutions. Simulation results and analysis are presented to demonstrate the effectiveness of the proposed solution. [ABSTRACT FROM AUTHOR]