hHoneycomb, a self-reconfigurable cleaning robot, is designed based on tiling theory, to overcome the significant challenges experienced by the fixed morphology cleaning robot. It consists of four regular hexagonal units and the units are connected by a planar revolute joint which helps in reconfiguration. This platform attains six distinct configurations (bar, bee, arch, wave, worm, and pistol) and these configurations have circular arcs and irregular concave and convex boundary that would help in accessing various obstacles in the cleaning space. This work addresses the mechanical design, system-level modeling, reconfiguration of the platform via hinged joint mechanism, mobility of the platform, polyhex based tiling set, and power consumption during reconfiguration. The strength of the mechanical structure is studied based on the structural analysis of the system using finite element method. Based on the natural frequency and deformation pattern, the proposed design is validated and... [more]

Contributed by the low cost, the simulation method is considered an attractive option for the optimization and design of the supersonic combustor. Unfortunately, accurate and satisfactory modeling is time-consuming and cost-consuming because of the complex processes and various working conditions. To address this issue, a mathematical modeling for the combustor on the basis of the clustering algorithm, machine learning algorithm, and model migration strategy is developed in this paper. A general framework for the migration strategy of the combustor model is proposed among the similar combustors, and the base model, which is developed by training the machine learning model with data from the existing combustion processes, is amended to fit the unexampled combustor using the model migration strategy with a few data. The simulation results validate the effectiveness of the development strategy, and the migrated model is proved to be suitable for the new combustor in higher accuracy with l... [more]

This study proposed a combined solar-assisted heat pump (SAHP) system that could operate in the serial mode or parallel mode. For this proposed system, a stable year-round operation could be achieved without the assistance of electric heating or low-temperature heat pump. By analyzing the heat balance equations, a correlation of the combined SAHP system for the two modes switched was obtained, which provided a theoretical basis for the optimal operation of this system. In addition, the performance of the proposed system applied in a university bathroom in Xi’an district was investigated using TRNSYS. The results illustrated that compared to the serial and parallel systems, the proposed system exhibited a good performance on energy efficiency. The annual average coefficient of performance (COP) of the proposed system was 5.7, obviously higher than those of the serial system and the parallel system, which were 3.3 and 4.3, respectively. Therefore, the results in this study could provide... [more]

Quadruped robots can be used to transport loads or conduct rescue missions on tough terrain. In addition to flexibility and adaptability to complex terrain, the hydraulic driven quadruped robots also have the important characteristic of energy consumption. This paper studies the trot gait motions of the quadruped robot SCalf. The energy model including the mechanical power and heat rate is established, which can be used to obtained the energy consumption of the robot. Compared with a cubic spline interpolation reference trajectory, a foot trajectory based on Fourier series is studied to reduce the joints energy consumption, and the parameters of the foot trajectory are acquired by the Pattern Search method. The effectiveness of the energy efficient trajectory is verified by simulations and verified on the robot prototype.

This paper presents a numerical investigation of ignition and combustion stabilization of a novel design of a solid-fuel ramjet (SFRJ) motor with and without swirl flow. The proposed design includes two solid fuels, retaining the simple design of the classic SFRJ. Numerical simulations of unsteady, turbulent, reactive, and swirling flow coupled with solid-fuel pyrolysis have been performed using an in-house CFD solver. Experiments on SFRJ were conducted via a connected-pipe test facility to validate the developed code. Furthermore, the code was validated for chemical reactions, heat diffusion, and swirl flow by using benchmark test cases of shock-induced, semi-infinite plate, and dump combustor with swirl flow, respectively. Then, the proposed and classic designs were simulated for the same inflow conditions and configurations, and the results were analyzed and discussed. It is found that the mixing degree, reactant residence time, mass flux, ignition delay time, and regression rate im... [more]

A balanced voltage distribution for each break is required for normal operation of a multi-break vacuum circuit breaker (VCB) This paper presented a novel 363 kV/5000 A/63 kA sextuple-break VCB with a series-parallel structure. To determine the static voltage distribution of each break, a 3D finite element method (FEM) model was established to calculate the voltage distribution and the electric field of each break at the fully open state. Our results showed that the applied voltage was unevenly distributed at each break, and that the first break shared the most voltage, about 86.3%. The maximum electric field of the first break was 18.9 kV/mm, which contributed to the reduction of the breaking capacity. The distributed and stray capacitance parameters of the proposed structure were calculated based on the FEM model. According to the distributed capacitance parameters, the equivalent circuit simulation model of the static voltage distribution of this 363 kV VCB was established in PSCAD.... [more]

The stability of a deep composite roof is a powerful guarantee for the safe and efficient production of a coal mine. The coal−rock combination, the single rock or coal bodies have different bearing capacity; thus, we can accurately obtain the deformation field evolution and failure mechanisms of the combination, which is useful in the deformation control of a composite roof. In this study, based on the digital speckle correlation method (DSCM), a uniaxial compression test was applied to coal−rock combinations with different height ratios. The results revealed that the compressive strength, elastic modulus, and secant modulus of the combination gradually decreased, while the decreasing amplitude weakened with the increase of coal height. Additionally, the strain field map of the combination had different characteristics in different stages. As the height of the coal body continuously increased, the gradient of the strain cloud and the area of local strain increase moved upwards. Moreove... [more]

Fault diagnosis and maintenance of a whole-building system is a complex task to perform. A wide range of available building fault detection and diagnosis (FDD) tools are only capable of performing fault detection using behavioral constraints analysis. However, the validity of the detected symptom is always questionable. In this work, we introduce the concept of the contextual test with validity constraints, in the context of building fault diagnostics. Thanks to a common formalization of the proposed heterogeneous tests, rule-, range-, and model-based tests can be combined in the same diagnostic analysis that reduces the whole-building modeling effort. The proposed methodology comprises the minimum diagnostic explanation feature that can significantly improve the knowledge of the building facility manager. A bridge diagnosis approach is used to describe the multiple fault scenarios. The proposed methodology is validated on an experimental building called the center for studies and desi... [more]

The paper presents a comparative study of two solar string inverters based on the Quasi-Z-Source (QZS) network. The first solution comprises a full-SiC two-level QZS inverter, while the second design was built based on a three-level neutral-point-clamped QZS inverter with Silicon based Metal−Oxide−Semiconductor Field-Effect Transistors (Si MOSFETs). Several criteria were taken into consideration: the size of passive elements, thermal design and size of heatsinks, voltage stress across semiconductors, and efficiency investigation. The Photovoltaic (PV)-string rated at 1.8 kW power was selected as a case study system. The advantages and drawbacks of both solutions are presented along with conclusions.

A new protection scheme based on applying a combination of wavelet multi-resolution singular spectrum entropy and support vector machine is proposed to identify different types of grid faults in a three-phase grid-tied photovoltaic system. In this technique, discrete wavelet transform with multi-resolution singular spectrum entropy is utilized to extract the unique features of three-phase voltage signals at the point of common coupling. The three-phase voltage signals are decomposed to provide detail and approximation coefficients of wavelet transform. Then, various features between different types of grid faults can be extracted by a combination of multi resolution analysis and spectrum analysis with entropy as the output. The constructed features vector is utilized as input data of a support vector machine classifier to identify and classify various types of faults. The results illustrate that the proposed intelligent technique not only recognizes different types of grid faults corre... [more]

Aerodynamics of the Darrieus wind turbine is an extremely complex issue requiring the use of very advanced numerical methods. Additional structural components of this device, such as, for example, a rotating shaft disturb the flow through the rotor significantly impairing its aerodynamic characteristics. The main purpose of the presented research is to validate the commonly-used unsteady Reynolds averaged Navier−Stokes (URANS) approach with the shear stress transport (SST) k-ω turbulence model based on the particle image velocimetry (PIV) studies of a two-bladed rotor operating at the moderate tip speed ratio of 4.5. In the present numerical studies, a two-dimensional turbine rotor with a diameter of 1 m was considered. The following parameters were evaluated: instantaneous velocity fields; velocity profiles in the rotor shadow and aerodynamic blade loads. The obtained numerical results are comparable with the reference experimental results taken from the literature. The second purpose... [more]

Growing competition in the market for energy raw materials needed for power generation has led to an increasing number of measures being undertaken in the mining sector to reduce the unit costs of mining production. One of the areas that offer considerable savings in this regard is the utilisation of the technical resources owned by mines. This article is therefore focussed on analysing the utilisation effectiveness of these machines, based on the data recorded by industrial automation systems, as well as on measurements from independent surveying and chemical analysis of the excavated material’s quality. For this purpose, a methodology was developed to use the data about the operational parameters of the machines in order to analyse the effectiveness of their utilisation. It was assumed that the reliability of this assessment would depend mainly on the quality of the data used to conduct it. It was also assumed that using independent data sources for the analysis would provide objecti... [more]

The thermodynamic cycle, as a significant tool derived from equilibrium, could provide a reasonable and rapid energy profile of complicated energy systems. Such a function could strongly promote an in-depth and direct understanding of the energy conversion mechanism of cutting-edge industrial systems, e.g., carbon capture system (CCS) However, such applications of thermodynamics theory have not been widely accepted in the carbon capture sector, which may be one of the reasons why intensive energy consumption still obstructs large-scale commercialization of CCS. In this paper, a kind of thermodynamic cycle was developed as a tool to estimate the lowest regeneration heat (Qre) of a benchmark solvent (MEA) under typical conditions. Moreover, COPCO2, a new assessment indicator, was proposed firstly for energy-efficiency performance analysis of such a kind of CCS system. In addition to regeneration heat and second-law efficiency (η2nd), the developed COPCO2 was also integrated into the exis... [more]

A free-float bike-sharing system faces various operational challenges to maintain good service quality while optimizing the operational cost. The primary problems include the fulfillment of the users demand at all stations, and the replacement of faulty bikes presented in the system. This study focuses on a free-float bike-sharing system rebalancing problem (FFBP) with faulty bikes using battery electric vehicles (BEVs). The target inventory of bikes at each station is obtained while minimizing the total traveling time through the presented formulation. Using CPLEX solver, the model is demonstrated through numerical experiments considering the various vehicle and battery capacities, and a cost−benefit analysis is performed for BEV and conventional internal combustion engine vehicles (ICEVs) while taking the BEV manufacturing and indirect emission into account. The results show that the annual cost incurred on an ICEV is 56.9% more as compared to the cost of using an equivalent BEV. Sin... [more]

To address the problem of the supply−demand imbalance caused by network transmission losses in integrated power and heating systems (IPHS), this paper presents an optimal economic dispatch strategy to minimize system operation cost and realize coordination and optimization between power and heat. Firstly, an innovative economic dispatch model considering transmission losses is developed, where both power and heat transmission losses models are established with good precision together. In addition, the coordination equation is derived from the formulated nonlinear, multi-constrained coupling optimization problem, where the coordination relationship of units’ outputs is clearly analyzed in an analytic way. Then, a double- λ -iteration algorithm is proposed, which can not only effectively solve the nonlinear coupling optimization problem but also decrease computation burden with faster convergence rate. Finally, simulations performed on five case studies illustrate the satisfying perf... [more]

With the development of in-wheel technology (IWT), the design of the electric vehicles (EV) is getting much improved. The anti-lock braking system (ABS), which is a safety benchmark for automotive braking, is particularly important. Installing the braking motor at each fixed position of the wheel improves the intelligent control of each wheel. The nonlinear ABS with robustness performance is highly needed during the vehicle’s braking. The anti-lock braking controller (CAB) designed in this paper considered the well-known adhesion force, the resistance force from air and the wheel rolling friction force, which bring the vehicle model closer to the real situation. A sliding mode wheel slip ratio controller (SMWSC) is proposed to yield anti-lock control of wheels with an adaptive sliding surface. The vehicle dynamics model is established and simulated with consideration of different initial braking velocities, different vehicle masses and different road conditions. By comparing the brakin... [more]

Harmonic stability of double-fed induction generators (DFIGs) now has become a significant topic because of its harmful impact on power quality issues of the system. Since the double pulse width modulation (PWM) converter is one of the main harmonic sources in DFIGs, it may cause harmonic instability with increasing harmonic contents. Thus, the modeling and stability analyses of PWM converters in DFIGs are essential steps to assess the harmonic stability of DFIGs. Aiming at dual PWM converters, which include the grid side converter (GSC) and the rotor side converter (RSC), this paper divides converters into two parts: circuit modules and control modules. Closed-loop input impedance models of each module are then derived by means of transfer functions. Hence, the stability of the system can be readily predicted through Nyquist diagrams. The contributions of parameters to the system’s harmonic stability are also identified. Finally, time-domain simulations are conducted in a real-time di... [more]

In this study, fast Fourier transform and inverse transform are adopted for noise reduction filtering the data of load rejection pressure of a single unit in a one-tube, four-unit pumped storage power station. Five-spot triple smoothing method is used to extract the time-average and pulsation value of the water hammer pressure of the spiral case and draft tube inlet. The reasonable correction formula is put forward, and the pulsating pressure rise rate of the spiral case (4.44%) and the draft tube inlet (−1.22%) are obtained. A mathematical model is also established for the transition process of the water conveyance and power generation system of the pumped storage power station, and the field single-unit load rejection condition is simulated. The simulation results are consistent with the measurements, and the accuracy of the calculation model in predicting the time-average pressure of water hammer is verified. Thus, the extreme successive load rejection conditions can be simulated ba... [more]

The wind energy conversion system (WEC) has been increasingly proposed to capture wind energy producing electrical power in high efficiency. One of the most important factors that has significant influence on the overall efficiency is the performance of generators in a fixed-speed wind turbine. The efficiency of the generator strongly depends on the operating speed. Therefore, the generator should be controlled to operate at the rated speed to increase the overall efficiency. In this paper, a continuously variable transmission (CVT) was employed to maintain the speed of the generator by controlling the transmission ratio. By employing a position control system based on an electro-hydraulic actuator (EHA), the speed ratio could be tuned continuously to keep the generator at rated speed. Here, an adaptive fuzzy sliding mode control (AFSC) was developed to control the proposed EHA CVT. Mathematical analysis was also carried out to investigate the global stability of the system. Finally, e... [more]

The determination of chemical composition of lignocellulose biomass by wet chemistry analysis is labor-intensive, expensive, and time consuming. Near infrared (NIR) spectroscopy coupled with multivariate calibration offers a rapid and no-destructive alternative method. The objective of this work is to develop a NIR calibration model for olive tree lignocellulosic biomass as a rapid tool and alternative method for chemical characterization of olive tree pruning over current wet methods. In this study, 79 milled olive tree pruning samples were analyzed for extractives, lignin, cellulose, hemicellulose, and ash content. These samples were scanned by reflectance diffuse near infrared techniques and a predictive model based on partial least squares (PLS) multivariate calibration method was developed. Five parameters were calibrated: Lignin, cellulose, hemicellulose, ash, and extractives. NIR models obtained were able to predict main components composition with R2cv values over 0.5, except f... [more]

It is well accepted that faults have significant impacts on the safe production of underground coal mines; however, the fault-slip mechanism during longwall mining through a fault still needs to be investigated. In this study, the distribution of microseismicity events during panel mining through a fault is analyzed, and 3-dimensional fast Lagrangian analysis of continua was used to study the mining stress distribution and fault-slip behavior under the two different mining directions, i.e., mining the panel through the fault from the footwall, or mining the panel through the fault from the hanging wall. The research shows that when the panel is mined through the fault from the footwall, the shear displacement of the fault is significantly greater than those created by mining the panel through the fault from the hanging wall. Under the two mining directions, the variation behaviors of the normal stress and shear stress on the fault are quite different, and fault-slips mainly occur in fa... [more]

The design of ground source heat pumps is a fundamental step to ensure the high energy efficiency of heat pump systems throughout their operating years. To enhance the diffusion of ground source heat pump systems, two different tools are developed in the H2020 research project named, “Cheap GSHPs”: A design tool and a decision support system. In both cases, the energy demand of the buildings may not be calculated by the user. The main input data, to evaluate the size of the borehole heat exchangers, is the building energy demand. This paper presents a methodology to correlate energy demand, building typologies, and climatic conditions for different types of residential buildings. Rather than envelope properties, three insulation levels have been considered in different climatic conditions to set up a database of energy profiles. Analyzing European climatic test reference years, 23 locations have been considered. For each location, the overall energy and the mean hourly monthly energy p... [more]

This paper proposes a fault diagnosis and tolerant control methods for an open-switch fault caused in a three-phase three-level neutral-point-clamped (NPC) pulse-width modulation (PWM) active rectifier. The open-switch fault in the three-level NPC active rectifier causes a distortion in the input phase current and a ripple in the DC-link capacitor voltage. Therefore, proper fault diagnosis and tolerant control methods are required to prevent additional failures and performance degradation in the rectifier system. This paper conducted a detailed analysis of the effect of the single open-switch fault on the NPC PWM active rectifier and proposed a fault diagnosis method utilizing the DC link voltage and the phase angle of the input grid voltage. Furthermore, this paper proposes a fault-tolerant control method to reduce the effect of the open-switch fault by compensating a distorted reference voltage. The effectiveness of the proposed fault diagnosis and tolerant control methods are verifi... [more]

In generation expansion planning, sustainable generation expansion planning is gaining more and more attention. Based on the comprehensive consideration of generation expansion planning economics, technology, environment, and other fields, this paper analyzes the sustainable development of power supply planning evaluation indicators and builds a multi-objective generation expansion planning decision model considering sustainable development. According to the target variables in the model, the variables such as attribute variables are divided into different subsets, and the logical relationship analysis method between different nodes is obtained based on Dynamic Bayesian network theory, which reduces the complexity of the planning model problem. The application examples show the feasibility and effectiveness of the proposed model and the solution method.

With the application of information and communication technology (ICT), the modern power system has gradually been updated to a typical cyber physical power system (CPPS). The deployment of distributed measurement devices enriches the application range of power communication services. However, due to the easy accessibility of distributed devices, it also creates favorable conditions for distributed denial-of-service (DDoS) attacks. In this paper, we focus on the security performance and defense strategies of the CPPS against DDoS attacks. In order to construct a coordinated defense in the power and information space, the cyber-attack process with a complete data flow of the CPPS needs to be described precisely. Therefore, a co-simulation technology-based platform is utilized to coordinate various layers in the CPPS and provide a unified research tool for the attack-defense test. On this basis, OPNET is used to replicate DDoS attacks in the information layer. Then, through the load freq... [more]