Optimal energy consuming planning for a home‑based microgrid with mobility constraint of electric vehicles and tractors

This research deals with the energy management problem to minimize the cost of non-renewable energy for a small-scale microgrid with electric vehicles (EV) and electric tractors (ET). The EVs and ETs function as batteries in the power system, while they often have to leave it for their mobility and agricultural work. Each State of Charge (SoC), which is the charge rate of the battery from 0 to 1, and the operating time of ETs are optimized under the assumption that the required electrical energy, the arrival and departure time of EVs, and the working time of ETs are given by users, but they include uncertainties. In this paper, we deal with these uncertainties by constraints for robust energy planning and expected optimization based on scenarios, and show that the scheduling of the SoC assuming the worst case and the optimal home-based power consumption planning that considers the cost of each scenario corresponding to each variation can be obtained. Our proposed method is formulated as a mixed integer linear programming (MILP), and numerical simulations show that the optimal cooperative operation among multiple houses can be obtained and its global optimal or sub-optimal solution can be quickly obtained by using CPLEX.     

Dynamic replication of web contents

The phenomenal growth of the World Wide Web has brought huge increase in the traffic to the popular web sites. Long delays and denial of service experienced by the end-users, especially during the peak hours, continues to be the common problem while accessing popular sites. Replicating some of the objects at multiple sites in a distributed web-server environment is one of the possible solutions to improve the response time/latency. The decision of what and where to replicate requires solving a constraint optimization problem, which is NP-complete in general. In this paper, we consider the problem of placing copies of objects in a distributed web server system to minimize the cost of serving read and write requests when the web servers have limited storage capacity. We formulate the problem as a 0-1 optimization problem and present a polynomial time greedy algorithm with backtracking to dynamically replicate objects at the appropriate sites to minimize a cost function. To reduce the solution search space, we present necessary conditions for a site to have a replica of an object in order to minimize the cost function. We present simulation results for a variety of problems to illustrate the accuracy and efficiency of the proposed algorithms and compare them with those of some well-known algorithms. The simulation results demonstrate the superiority of the proposed algorithms.     

Effectiveness Analysis of DVFS and DPM in Mobile Devices

The demand for high-performance embedded processors in multimedia mobile electronics is growing and their power consumption thus increasingly threatens battery lifetime.It is usually believed that the dynamic voltage and frequency scaling (DVFS) feature saves significant energy by changing the performance levels of processors to match the performance demands of applications on the fly.However,because the energy efficiency of embedded processors is rapidly improving,the effectiveness of DVFS is expected to change.In this paper,we analyze the benefit of DVFS in state-of-the-art mobile embedded platforms in comparison to those in servers or PCs.To obtain a clearer view of the relationship between power and performance,we develop a measurement methodology that can synchronize time series for power consumption with those for processor utilization.The results show that DVFS hardly improves the energy efficiency of mobile multimedia electronics,and can even significantly worsen energy efficiency and performance in some cases.According to this observation,we suggest that power management for mobile electronics should concentrate on adaptive and intelligent power management for peripheral devices.As a preliminary design,we implement an adaptive network interface card (NIC) speed control that reduces power consumption by 10% when NIC is not heavily used.Our results provide valuable insights into the design of power management schemes for future mobile embedded systems.     

High-speed maneuvering target detection approach based on joint RFT and keystone transform

Increasing the integration time is an effective method to improve small maneuvering target detection performance in radar applications.However,range migration and Doppler spread caused by maneuvering target motion during the integration time make it difficult to improve the coherent accumulation of target’s energy and detection performance.In this study,a new method based on Radon Fourier transform(RFT) and keystone transform(KT) for high-speed maneuvering target detection is proposed.The proposed algorithm utilizes second-order KT to correct the range curvature,and the improved dechirping method to compensate for the Doppler spread.RFT is then used to correct the range walk for target coherent detection.The method is capable of correcting the range migration and the time-varied Doppler frequency of the target without knowing its velocity and acceleration.The advantage of the proposed method is that it can increase the coherent integration time and improve detection performance under the condition of Doppler frequency ambiguity.Compared with the second-order RFT algorithm,the computational burden of the proposed method is greatly reduced under the premise that the two methods have similar estimation accuracy of range,velocity and acceleration.Numerical experiments demonstrate the validity of the proposed algorithm.     

Minimum energy storage for power system with high wind power penetration using p-efficient point theory

Minimum energy storage （ES） and spinning reserve （SR） for day-ahead power system scheduling with high wind power penetration is significant for system operations. A chance-constrained energy storage optimization model based on unit commitment and considering the stochastic nature of both the wind power and load demand is proposed. To solve this proposed chance-constrained model, it is first converted into a deterministic-constrained model using p-efficient point theory. A single stochastic net load variable is developed to represent the stochastic characteristics of both the wind power and load demand for convenient use with the p-efficient point theory. A probability distribution function for netload forecast error is obtained via the Kernel estimation method. The proposed model is applied to a wind-thermal-storage combined power system. A set of extreme scenarios is chosen to validate the effectiveness of the proposed model and method. The results indicate that the scheduled energy storage can effectively compensate for the net load forecast error, and the increasing wind power penetration does not necessarily require a linear increase in energy storage.     

A new energy optimal control scheme for a separately excited DC motor based incremental motion drive

This paper considers minimization of resistive and frictional power dissipation in a separately excited DC motor based incremental motion drive （IMD）. The drive is required to displace a given, fixed load through a definite angle in specified time, with minimum energy dissipation in the motor windings and minimum frictional losses. Accordingly, an energy optimal （EO） control strategy is proposed in which the motor is first accelerated to track a specific speed profile for a pre-determined optimal time period. Thereafter, both armature and field power supplies are disconnected, and the motor decelerates and comes to a halt at the desired displacement point in the desired total displacement time. The optimal time period for the initial acceleration phase is computed so that the motor stores just enough energy to decelerate to the final position at the specified displacement time. The parameters, such as the moment of inertia and coefficient of friction, which depend on the load and other external conditions, have been obtained using system identification method. Comparison with earlier control techniques is included. The results show that the proposed EO control strategy results in significant reduction of energy losses compared to the existing ones.     

Joint resource allocation for lifetime-aware cooperative multi-carrier DF system

In this paper,we study the problem of optimal resource allocation for lifetime maximization in an orthogonal-frequencydivision multiplexing(OFDM)system with decode-and-forward relay.The goal is to minimize total energy cost of the system by jointly optimizing power allocation,subcarrier pairing and relay selection.We present a heuristic solution that is composed of two parts.The first part is an optimal power allocation approach to allocate power to a subcarrier pair of the source and the relay.The second part is a modified Hungarian algorithm to make subcarrier pairing and relay selection.Evaluations show that the presented scheme outperforms other schemes in the total transmitted data and the network lifetime.     

A novel ESD power supply clamp circuit with double pull-down paths

Electrostatic-discharge(ESD)protection design is one of the key challenges of advanced CMOS processes.RC-triggered and MOSFET-based power supply ESD clamp circuits have been widely used to obtain the desired ESD protection ability.In this paper,a MOSFET-based ESD power clamp circuit with only10 ns RC time constant for 0.18-μm process is presented.A double pull-down path is proposed to avoid false triggering,reject power supply noise and reduce energy consumption.The performance of the novel clamp circuit is excellent,consuming very small layout area.The simulation results show that this clamp circuit can be used in industry.     

Energy-efficient power allocation for non-regenerative OFDM relay links

We consider a two-hop non-regenerative (amplify-and-forward) relay link with one source, one destination and one relay, in which orthogonal frequency division multiplexing (OFDM) is used. The power allocation (PA) to maximize the energy efficiency for the whole link is investigated under quality of service (Qos) require- ment and separate power constraints. An approximation method with low complexity is first proposed to convert the PA problem into a quasi-concave problem, which can obtain a tight lower bound in high SNR region. Furthermore, a more accurate approximation method with higher complexity is raised, which can approach the actual performance both in the low SNR and high SNR regions. We also introduce subcarrier pairing scheme to further enhance the energy efficiency for the link. Simulation results are shown to compare the performance of the two proposed methods.     

Novel sensor scheduling and energy-efficient quantization for tracking target in wireless sensor networks

This paper focuses on sensor scheduling and information quantization issues for target tracking in wireless sensor networks (WSNs). To reduce the energy consumption of WSNs, it is essential and effective to select the next tasking sensor and quantize the WSNs data. In existing works, sensor scheduling’ goals include maximizing tracking accuracy and minimizing energy cost. In this paper, the integration of sensor scheduling and quantization technology is used to balance the tradeoff between tracking accuracy and energy consumption. The main characteristic of the proposed schemes includes a novel filtering process of scheduling scheme, and a compressed quantized algorithm for extended Kalman filter (EKF). To make the algorithms more efficient, the proposed platform employs a method of decreasing the threshold of sampling intervals to reduce the execution time of all operations. A real tracking system platform for testing the novel sensor scheduling and the quantization scheme is developed. Energy consumption and tracking accuracy of the platform under different schemes are compared finally.     

一种单阅读器移动RFID系统性能评估方法

中小型区域RFID标签的识别通常采用阅读器网路实现,因为只有多阅读器才能静态实现阅读器对所有待识别标签的全覆盖。但这种方法面临阅读器使用成本高,阅读器间碰撞,标签识别率低等问题。为改善上述问题,提出一种运用于中小型区域的单阅读器移动RFID系统性能评估方法,该方法以标签丢失率和全识别圈数作为性能指标,在单阅读器移动RFID系统中对已有的静态防碰撞算法的性能进行评估。实验通过判断当前时隙类型确定阅读器是否成功识别标签,每消耗1个时隙阅读器位置调整一次使得信号区及其区内标签重新确定,直至阅读器结束标签识别任务。仿真结果表明该方法能很好地对各种已有标签算法在中小型区域的RFID标签识别环境中的性能进行有效评估,同时提高RFID系统效率。     

Decomposition-based multi-objective firefly algorithm for RFID network planning with uncertainty

Radio frequency identification (RFID) is widely used for item identification and tracking. Due to the limited communication range between readers and tags, how to configure a RFID system in a large area is important but challenging. To configure a RFID system, most existing results are based on cost minimization through using 0/1 identification model. In practice, the system is interfered by environment and probabilistic model would be more reliable. To make sure the quality of the system, more objectives, such as interference and coverage, should be considered in addition to cost. In this paper, we propose a probabilistic-based multi-objective optimization model to address these challenges. The objectives to be optimized include number of readers, interference level and coverage of tags. A decomposition-based firefly algorithm is designed to solve this multi-objective optimization problem. Virtual force is integrated into random walk to guide readers moving in order to enhance exploitation. Numerical simulations are introduced to demonstrate and validate our proposed method. Comparing with existing methods, such as Non-dominated Sorting Genetic Algorithm-II and Multi-objective Particle Swarm Optimization approaches, our proposed method can achieve better performance in terms of quality metric and generational distance under the same computational environment. However, the spacing metric of the proposed method is slightly inferior to those compared methods.     

新颖的物联网RFID传感系统防冲突算法

基于超高频射频识别(RFID)技术构建物联网系统往往需要将多个读写器同时工作于同一区域,这种多读写器环境势必会造成多读写器冲突,严重影响系统的性能。针对常用的反向散射耦合方式,选取信干比作为系统通信质量的度量,提出基于快速功率控制和退避机制的防多读写器冲突算法。读写器依据信干比情况,动态调节自身发射功率,在保证读写器读写距离的同时,减少信号覆盖区域的冗余,实现防冲突。考虑到发射功率调节至最大时,读写器仍可能无法获取目标信干比,引入了退避机制,使读写器主动降低发射功率,其退避时间映射于目标信干比迭代比例。实验结果表明,读写器能够根据功率控制算法,动态调节发射功率并快速收敛,提高了系统的实时性和可靠性。退避算法的设计提高了读写器信道争用的公平性,而且大大降低读写器功耗,这对移动/手持读写器尤为重要。该防冲突算法有效地最小化信号覆盖区域的冗余,实现防多读写器冲突,同时能够保证读写器的目标识别距离,提高了标签识别率。     

An anti‐collision algorithm based on balanced incomplete block design in RFID systems

An important challenge in radio frequency identification (RFID) systems is the collision concern. When an interrogator send a request, it has several tags to answer to in its transmission range, and a tag collision has occurred. The interrogator must be able to recognize tags as rapidly as possible. A collision problem is a power‐consuming occurrence that diminishes the operation of RFID structure. This article proposes a tag anti‐collision power‐clustering RFID algorithm for all tag identification. The tags are boundaries into the several power level clusters based on distances of the reader. Specifically, in the proposed algorithm, tags and readers use of balanced incomplete blocks design (BIBD) to reach a fast identification. In a BIBD matrix, any two columns intersect exactly in one component that makes it possible for easy transmission of any two tags via the tag's identification in their read cycles. The aim of this article is to propose a joint organization that while decreases power consumption increases the working lifetime of RFID structure. The reader can get each tag ID by distinguishing each unit of BIBD symbols, one by one. The use of proposed algorithm brings about a great improvement in the power consumption and identification time.     

Micro genetic algorithm with spatial crossover and correction schemes for constrained three-dimensional reader network planning

Due to the fast growing electronic commerce, the constrained three-dimensional reader network planning (C3DRNP) of the radio frequency identification (RFID) system for large warehouses is a subject that is worthy of study. A micro genetic algorithm (mGA) with novel spatial crossover and correction schemes is proposed to cope with this C3DRNP problem. The proposed algorithm is computationally efficient, which allows a frequent replacement of the RFID readers in the network to account for the fast turnaround time of the stored objects in the warehouse, and guarantees 100% tag coverage to avoid missing the records of the objects.The proposed algorithm is tested and compared with the existing methods such as the particle swarm optimization (PSO) method and the conventional GA (CGA) on solving several C3DRNP problems with various network sizes. The comparison results demonstrate the computational efficiency of the mGA and the effectiveness of the novel spatial crossover and correction schemes in searching the solution.     

A mechanised 3D scanning method for item-level radio frequency identification of palletised products

The automatic, non-line-of-sight characteristics of radio frequency identification (RFID) technology for identifying multiple objects are conducive to full visibility and traceability of individual product items in a supply chain. However, practical implementation of item-level RFID-based applications necessitates solving some critical issues. Among these issues, reading tag data to identify a relatively large number of individual product items, which are usually packed in batches and distributed on pallets, is particularly a bottleneck, because it affects the accuracy and trustworthiness of batch distribution of products and all subsequent logistics operations in the supply chain. Current techniques for batch identification at item-level of palletised products suffer low reading rate and incomplete tag data acquisition, rendering the RFID systems unreliable. We address this issue by proposing a mechanised 3D scanning method for identification of tagged products in large numbers to facilitate supply chain management. The proposed method requires installing RFID readers only in the X-Y plane. The readers scan tagged products in the X and Y directions while the pallet is simultaneously rotated around to be effectively scanned in the Z direction. Different scanning patterns are adopted to alleviate the problems due to randomness of tag orientation and reader collisions. As such, 3D scanning of RFID tags for item-level applications is effectively achieved without incurring much hardware cost. The performance of the proposed method is validated using an RFID-enabled gate-door for identification of palletised apparel products with item-level RFID tagging. Experiment results show that the proposed method can achieve batch reading rates remarkably higher than those reported in literature. Moreover, a correlation between the batch reading rate and the batch density is established. Apparently, the proposed mechanised 3D scanning method for batch identification of item-level tagged product items can substantially enhance the accuracy and reliability of RFID-based supply chain management systems.     

基于RFID加速度传感器标签的导线舞动在线监测

针对目前各种导线舞动无线监测方式存在高功耗、高成本和不适于长期监测的缺陷,提出了一种基于射频识别(RFID)加速度传感器标签的导线舞动长期在线监测的设计方案,设计了一种RFID加速度传感器标签结构,因其工作在无源模式下,可以实现导线舞动的长期在线监测.介绍了加速度信号的处理方式,提出了基于小波变换的趋势项去除算法.在实验室环境下,对加速度传感器标签进行了通信性能测试和模拟导线舞动监测实验.测试结果表明:标签通信性能良好;模拟实验结果表明:经过处理后得到的位移信号能够准确反映模拟导线的舞动情况,实现了导线舞动的在线监测.     

酒后驾驶监控系统车载终端电子标签的设计

为了对酒后驾驶做出有效的监管,提出基于RFID和GPRS的酒后驾驶监控系统。该系统利用车载终端的有源电子标签与周围部署的固定式或执勤交警手持的RFID阅读器进行通信,实现对酒驾车辆的智能识别和稽查范围内酒驾车辆拦截、追踪。但是有源电子标签寿命有限,因此系统仅在酒精检测模块检测到驾驶员酒精浓度超标时唤醒标签,有效降低了标签功耗,延长其使用寿命。     

On the Complete Coverage Path Planning for Mobile Robots

This paper presents a generalized complete coverage path planning (CCPP) algorithm and its implementation for a mobile robot. The proposed planner contains two concerns: 1) low working time or low energy consumption, and 2) high human safety. For the first concern, we design the optimal path by incorporating two factors: time and energy costs. Describing the working time and energy in terms of a turning parameter simplifies the optimal path design either for minimizing the time or energy cost. For obstacle avoidance in the CCPP, fixed or moving objects are avoided by proposing a field method describing the effects of factors such as working dangerousness and difficulty on the current robot navigation. The human safety is simultaneously guaranteed by this method. Furthermore, a backstepping controller considering constraints imposed on the control input is established to track the optimal route. An implementation of the proposed CCPP for the experimentally mobile robot equipped with this controller is presented; the verification results demonstrate significant performance and practicality of the proposed strategy.     

基于图论的射频识别阅读器防碰撞算法

射频识别（RFID）系统的运行往往需要多个阅读器,以保证覆盖整个目标区域。在密集的阅读器的环境中,由于阅读器之间存在相互干扰,会影响整个RFID系统的工作效率,降低识别效率。针对上述问题,提出一种新的基于图论的阅读器防碰撞算法。首先把阅读器网络看成简单图,以时隙对阅读器分组,同时隙阅读器为一组,相邻阅读器分配不同的时隙,以解决阅读器因读取范围交叉重叠而引起的干扰;同时考虑组内阅读器的频率干扰问题,同样以频率对组内阅读器再分组,同频率阅读器为一组,相邻阅读器分配不同频率,以解决因干扰范围过大而引起的频率碰撞问题;然后根据分组信息,中央服务器通过配置命令将时隙和频率资源调度分配给每个阅读器;最后通过时序命令控制每组阅读器的工作顺序。仿真结果显示,相比邻近友好型防碰撞（NFRA）算法,该算法平均工作效率提升了6.5个百分点;阅读器数量为1000时系统工作效率提升了9.5个百分点。新算法能优化给定时间内工作阅读器的数量,减少闲置等待的阅读器数量。