Experimental Prototype Research Articles

Detecting and Attributing Change in Climate and Complex Systems: Foundations, Green’s Functions, and Nonlinear Fingerprints

Detection and attribution (DA) studies are cornerstones of climate science, providing crucial evidence for policy decisions. Their goal is to link observed climate change patterns to anthropogenic and natural drivers via the optimal fingerprinting method (OFM). We show that response theory for nonequilibrium systems offers the physical and dynamical basis for OFM, including the concept of causality used for attribution. Our framework clarifies the method’s assumptions, advantages, and potential weaknesses. We use our theory to perform DA for prototypical climate change experiments performed on an energy balance model and on a low-resolution coupled climate model. We also explain the underpinnings of degenerate fingerprinting, which offers early warning indicators for tipping points. Finally, we extend the OFM to the nonlinear response regime. Our analysis shows that OFM has broad applicability across diverse stochastic systems influenced by time-dependent forcings, with potential relevance to ecosystems, quantitative social sciences, and finance, among others. Published by the American Physical Society 2024

Justifying the structure of the improved mechanism for manual control of motor vehicles’ pedals

Due to the challenging military situation in Ukraine, the demand for tailored and flexible pedal control systems for individuals with physical disabilities is especially important. Standard pedal configurations often fail to meet the specific needs of drivers with limited mobility, making vehicle operation both difficult and potentially unsafe. The development of specialized manual control devices, such as hand-operated pedals or adjustable foot controls, is crucial for ensuring that these drivers can manage their vehicles with accuracy and safety. Such innovations not only improve accessibility but also foster greater autonomy and inclusion, empowering disabled drivers to navigate the roads with confidence and ease. This article aims to review existing prototypes of manual control mechanisms for vehicle pedals and to develop an improved device that enables simultaneous control of three pedals – accelerator, brake, and clutch – with one hand. As a result of a patent review of several existing prototypes of control mechanisms, it was concluded that the vast majority of them provide control for only two pedals – the accelerator and brake. This means they can only be used in motor vehicles with automatic transmissions or electric cars. Only a few mechanisms were designed to control three pedals, but they required using both the driver’s hands, directly affecting driving safety. Therefore, improving existing designs of the mechanisms for controlling three pedals by transferring all control functions to one hand of a driver remains relevant. The research methodology involves the use of classical methods from the theory of mechanisms and machines to conduct the structural synthesis of an improved multi-link hinge-lever mechanism and its kinematic analysis, aimed at determining the main parameters of pedals’ movements in a vehicle under various control inputs from the driver’s hand. The results obtained can be utilized by researchers and engineers to enhance manual control mechanisms for vehicle pedals and in the practical implementation processes. The prospects for future research on this topic are in developing an experimental prototype of the control mechanism and its testing and adjustment for different vehicle modifications to improve running smoothness and driving comfort and safety.

Simulation and Modeling of Data Transmission Process in Boreholes Using Intelligent Drill Pipe for a Laboratory Experiment

Currently, most oil and gas wells are drilled by continuously transmitting downhole measured information (directional and geological information) in real-time to the surface to monitor and steer the well along a pre-defined path. The intelligent drill pipe method can transmit data over longer distances and at a higher rate than other methods, such as mud pulse telemetry, acoustic telemetry, and electromagnetic telemetry. Nevertheless, it is expensive and requires boosters along the drill string. In the available literature, academic research rarely addresses the data transmission process in boreholes using intelligent drill pipes. Furthermore, there is a need for an effective and validated model to study various controllable parameters to enhance the efficiency of the intelligent drill pipe telemetry without the need to develop several physical lab or field prototypes. This paper presents the development of a model based on MATLAB Simulink to simulate the process of data transmission in boreholes utilizing intelligent drill pipes. Laboratory experimental prototype measurements have been used to test the model’s effectiveness. A good correlation is found between the measured lab data and the model’s predictions for the signals transmitted contactless through intelligent drill pipes with a correlation coefficient (R2) above 0.9. This model can enhance data transmission efficiency via intelligent drill pipes, study different concepts, and eliminate the need to develop several unnecessarily expensive and time-consuming physical lab prototypes.

Optimization design of dead time in the four-switch buck-boost LLC resonant converter

Purpose The purpose of this study is to solve the problem of longer dead-time in the rear bridge leg switches and lower efficiency in the Four-Switch Buck-Boost LLC Resonant Converter. Design/methodology/approach The paper adopts time-domain analysis to derive the time-domain expression for optimal dead time, analyzing the conditions for achieving soft switching of the transistors. It further explores the relationship between the dead time of the bridge arm switching transistors and the input/output of the converter under different operating conditions. Specifically, the dead time of the upper bridge arm transistors increases with the converter input voltage and decreases with the output current. In contrast, the dead time of the lower bridge arm transistors is independent of the converter output current and decreases with increasing converter input voltage. Findings By simulating and constructing a 500 W experimental prototype, experimental results indicate that designing the dead time of the switch according to the optimal dead time proposed in this paper significantly improves efficiency when the converter operates from heavy load to full load. When the transformer takes minimum input, maximum input and intermediate bus voltage inputs respectively, its peak efficiency is increased by 0.6%, 1.7% and 1.1%, respectively, compared to the traditional four-switch Buck–Boost LLC resonant converter. Originality/value Experimental validation confirms the correctness of the optimal dead time design and analyzes the impact of different operating conditions of the converter on the dead time. This is of significant importance for the rational design of switch dead times and the enhancement of converter efficiency.

Technical–Economic Analyses of Electric Energy Generation by Biogas from Anaerobic Digestion of Sewage Sludge from an Aerobic Reactor with the Addition of Charcoal

This study aimed to obtain the energy recovery potential of the biogas produced from anaerobic digestion (AD) of the sludge from a wastewater treatment plant (WWTP), including the use of biochar as an additive for substrate co-digestion and catalyst for methane production. We carried out the following steps: chemical–physical laboratory analyses of sludge samples; the building, operation, and monitoring of an experimental prototype of a batch bioreactor of 2.5 L for the AD of the sludge (with and without the addition of charcoal); qualitative measurements of biogas; the study of charcoal morphology; and the projection of useful energy generation from the AD sludge after treatment. A study on the economic viability and avoided greenhouse gas (GHG) emissions was performed based on the experimental results. The substrate showed alterations in all the physicochemical parameters evaluated after AD, such as a reduction of 35% in the biochemical oxygen demand (BOD) analysis; the experiment carried out using biochar showed positive results regarding the speed of CH4 production and a greater potential for energy recovery. Enterprises from 2000 kW onwards would present an internal rate of return (IRR) equal to or higher than the minimum attractiveness rate (MAR) of 15%. The USD 95.28/MWh tariff presented economic feasibility for the studied scenarios. WWTPs that produce enough sludge to generate power of 2000 kW would need to process the waste of 117,200 inhabitants with charcoal addition and 136,000 without charcoal. It would be possible to avoid the emission of 2307.97 tCO2/year (2000 kW). According to the results obtained, this study revealed that using alternative energies based on anaerobic digestion and biochar can generate positive results regarding methane production, and its application as an energy source in a WWTP proved to be economically viable at a specific level of power production.

Modeling and implementation of a position-sensitive fiber optic spark sensor with spectral radiation converter

Through numerical modeling of the optical part of the developed position-sensitive fiber-optic spark sensor with a spectral radiation converter, it was demonstrated that the sensor’s angular resolution in the range of ±18° is 3°. The spectral characteristics of the fluorescent glass plate with silver molecular clusters, which was used as the radiation converter in both numerical modeling and the experimental prototype, were investigated. Based on the developed optical sensor design, an experimental prototype was assembled. Testing of the prototype showed that it is capable of etecting sparks at a distance of 1000mm within an angular range of ±18° with an angular resolution of 3°. The results obtained from modeling and prototype testing are consistent and can be utilized in the development of sensors and emergency systems.

Design and Implementation of An Energy-Efficient Extension Board with Integrated Overcurrent Protection for Home Appliances

Electrical extension boards are a major cause of electrical fires in homes, university hostels, offices, and other key applications worldwide, often due to overloading beyond their rated capacity. Additionally, users frequently forget to turn off appliances like televisions, portable fans, or electric irons, resulting in unnecessary energy waste. These Extension boards, commonly used to power multiple electrical appliances, are widespread in homes and universities, but overloading them can lead to overheating, burning, and potential fire hazards. This is often due to exceeding the board’s rated capacity, which reduces load resistance and increases current flow, particularly in parallel connected domestic loads. To address this risk, this paper presents an innovative energy efficient extension board equipped with overcurrent protection. The system continuously monitors the current drawn by connected appliances and automatically isolates them via a relay mechanism when the load exceeds the rated capacity of 13 amperes. The overcurrent status is displayed on an LCD. A microcontroller, interfaced with a current sensor and relay, manages the process, ensuring the safety of the extension boards and home appliances. Additionally, a buzzer notifies the user of the system's status. Furthermore, the system features a timer function to manage energy consumption based on user defined settings. Both simulation and experimental prototype were employed to verify the design, and the results showed a strong correlation between the expected and actual performance, demonstrating the practicality of the proposed system.

A Fixed‐Time Composite Control With Variable Exponent Coefficients for Stewart Parallel Mechanism Tracking in Task Space

ABSTRACTTo improve tracking control performance in the task space of the Stewart parallel mechanism (SPM) with uncertainties of modeling errors and external disturbances in our developed rust removal sandblasting robot for the surface roughness processing of a bridge's steel box girder, a fixed‐time composite control with variable exponent coefficients (VEC‐FxTCC) approach for multi‐input multi‐output (MIMO) nonlinear robotic systems is developed. Firstly, by devising only one regulation term with a variable exponent coefficient (VEC) function in the system's Lyapunov differential inclusion, a novel VEC fixed‐time stability theorem for the MIMO nonlinear dynamic system is proposed and proven. Secondly, based on the proposed theorem, VEC‐FxTCC is formed by designing and combining a VEC fixed‐time disturbance observer (VEC‐FxTDOB) and a VEC fixed‐time super‐twisting control (VEC‐FxTSTC), in order to achieve fast, steady, and uniformly bounded‐time convergence for SPM's end‐effector tracking, while avoiding singularity. Finally, the effectiveness of the proposed VEC‐FxTCC approach is validated through the simulations and the rust removal sandblasting robot prototype experiments.

Experimental study of friction damping connections for prefabricated self-centering rocking structural elements

Self-centering rocking structural systems provide solutions for prefabricated buildings to achieve better seismic resilience. A well-designed connection of the self-centering rocking structural elements is critical to provide stable supplemental damping to the system. In this study, an innovative friction damping connection was proposed that could better match the gap-opening-closing motion of the rocking elements. Firstly, prototype experiments were carried out to investigate the connection’s mechanical behavior. The brake pad-stainless steel interface exhibited smooth sliding without chatter, stick-slip, or damage. The average static and kinetic friction coefficients were 0.30 and 0.28, respectively, showing negligible dependence on surface pressure, amplitude, or frequency. Then, the proposed connections were applied to the prefabricated shear wall-rocking coupling beam subassembly. Quasi-static cyclic loading tests on 5 full-scale specimens of the subassembly showed typical flag-shaped hysteresis curves, and the connections performed well as expected. Moreover, the theoretical analysis accurately reflected the hysteretic behavior of the specimen. Adjusting the connection’s frictional force changed the initial damping moment ratio (IDMR) of the coupling beam, determining the rocking system’s energy dissipation and self-centering capability. A reasonable IDMR value ranged from 0.8 to 0.9.

Influence of Winding Configurations and Stator/Rotor Pole Combinations on Field Back-EMF Ripple in Switched Flux Hybrid Excited Machines

Similar to armature back electromotive force (armature back-EMF), the back-EMF also exists in the field winding of hybrid excited machines. However, the existence of field back electromotive force (field back-EMF) is harmful to the safe and stable operation of machine systems, e.g., higher losses, lower efficiency, higher torque ripple, and reduced control performance. This paper systematically investigates the influence of armature/field winding configurations together with stator/rotor pole combinations on the field back-EMF ripple in hybrid excited machines with switched-flux stators. The two-dimensional (2D) time-stepping finite element modeling and prototyping experiments are used for the research. The investigated field and armature coil pitches equal to 1, i.e., non-overlapped windings. The influential factors that are investigated in this paper mainly include the number of layers of field/armature windings, the number of field/armature coils, and the stator/rotor pole combinations. The results show that the field back-EMF’s harmonic order and peak-to-peak value are closely associated with field/armature winding configurations and stator/rotor pole combinations under various conditions. Finally, for validation of the results predicted by the finite element method, a prototype machine is built and tested. Overall, non-overlapped double-layer armature and field windings are recommended for the hybrid excited switched flux machines with various stator/rotor pole combinations to realize relatively lower field back-EMF under different conditions.

A New Concept of Reconfigurable Antenna Structure Based on an Array of RF-MEMS Switches

A geometrical reconfigurable structure based on RF Micro-electro-mechanical switches (RF-MEMS) is proposed in this work. The structure is composed of an array of gold metallic patches interconnected together utilizing RF-MEMS switches in order to change its geometry and, consequently, the scattering parameters. In particular, the reconfigurability is achieved by activating multiple RF-MEMS switches, which enables the change in electrical length and, consequently, the resonance frequency of the structure. As a proof of concept, an experimental antenna prototype composed of an array of 7×7 elements interconnected by a set of RF-MEMS switches has been designed, fabricated numerically, and experimentally assessed. The structure can be set as an antenna or as other basic radio frequency components. The obtained experimental results are in good agreement with the simulations, with an error of less than 5% for the considered radiating structures. The quite promising results demonstrate the potential and flexibility of the proposed structure.

Multi-objective optimization approach for permanent magnet machine via improved soft actor–critic based on deep reinforcement learning

As awareness of environmental protection grows, the development of electric vehicles has emerged as a prominent area of research. Naturally, optimizing Permanent Magnet (PM) machines is critical for enhancing the power performance of electric vehicles, as they are essential components of these vehicles. Benefitting from the advantage of Deep Neural Network (DNN), optimizing the PM machine by leveraging DNN has drawn great attention from industry and academia. To increase the torque of the PM machine and reduce torque ripple from a structural design perspective, this paper proposes a Multi-objective Optimization approach for PM machine via improved Soft Actor Critic (called MOPM-SAC) based on Deep Reinforcement Learning (DRL). MOPM-SAC consists of two core components: a surrogate model based on DNN and a SAC algorithm. Specifically, the SAC algorithm based on DNN is used to optimize the PM machine. The surrogate model is established by training the DNN to use Finite Element (FE) simulation samples, which possesses higher accuracy than other methods, such as Support Vector Machine (SVM), Random Forest (RF), and so on. Moreover, the SAC algorithm integrates a trained DNN as the state transition function within the DRL environment, which enhances the optimization algorithm’s generalization ability in the context of PM machines. In addition, the reward function is designed based on optimization requirements to guide the agent in the SAC algorithm toward learning the optimal strategy. Finally, a 75 kW prototype is manufactured and tested. The effectiveness of the proposed method is validated through FE simulations and prototype experiments.

Z source based switched capacitor nine level boost inverter with a modified modulation strategy

This article presents a Z source (ZS) based switched capacitor multilevel inverter (SC-MLI) with low capacitors charging inrush currents utilizing a modified modulation strategy. The topology generates nine output voltage levels with quadruple voltage gain utilizing eight power switches, five capacitors, two inductors, four discrete diodes, and a single DC source. The voltage gain can be further increased by applying shoot through (ST) states to the frontend ZS-network. Owing to its high voltage gain, the topology is suitable for low voltage renewable energy sources such as photovoltaics (PV), and fuel cells (FC). A modified modulation strategy is presented based on the conventional level shifted sinusoidal pulse width modulation (LS-SPWM). The proposed modulation strategy improves the dc-link utilization at higher modulation index. A detailed mathematical analysis is provided for the gain calculation based on the modified modulation strategy. A comparative study is implemented to verify the merits of the proposed topology. A simulation model is implemented utilizing MATLAB / Simulink to verify the topology characteristics. The power losses and efficiency calculations are presented using Altair PSIM. Furthermore, an experimental prototype is constructed to verify the simulation findings. The topology is tested with different loading conditions at numerous modulation index values and ST duty ratios. Furthermore, step change conditions are implemented to test the topology response. The effect of the ZS network on the switched capacitors charging inrush currents is validated. The proposed topology shows an overall advantage in terms of the output characteristics as well as the hardware requirements.

TOrsion-Bar Antenna: A Ground-Based Detector for Low-Frequency Gravity Gradient Measurement

The Torsion-Bar Antenna (TOBA) is a torsion pendulum-based gravitational detector developed to observe gravitational waves in frequencies between 1 mHz and 10 Hz. The low resonant frequency of the torsion pendulum enables observation in this frequency band on the ground. The final target of TOBA is to observe gravitational waves with a 10 m detector and expand the observation band of gravitational waves. In this paper, an overview of TOBA, including the previous prototype experiments and the current ongoing development, is presented.

An improved switch‐capacitor based 13‐level inverter topology with reduced device count and lower TSV

AbstractAn improved dual‐source SC‐MLI topology is developed in this article for medium‐voltage and high‐power applications. This topology can perform symmetrically and asymmetrically to generate 9 levels and 13 levels, respectively. It consists of 10 unidirectional switches, a dual DC source, and two capacitors to provide high‐gain output voltage with lower TSV. Since the capacitor's voltages are self‐balanced, therefore no need for an auxiliary circuit or sensors, which brings down the complexity of the circuit. To check the viability of the proposed topology, a simple and fundamental control strategy based on nearest‐level pulse width modulation is opted for. From the comparative analysis, it was observed that the proposed topology outperformed similar topologies in terms of switch counts, cost factor, power quality, and total standing voltage. The proposed topology's feasibility is evaluated using MATLAB/Simulink under both static and dynamic loads. Furthermore, a thermal analysis is conducted in PLECS software to calculate the losses across the components and consecutively the efficiency of the proposed circuit. It has been found that the proposed topology can generate 9 levels and 13 levels while having an efficiency of over 96% in symmetric and asymmetric configurations, respectively. Finally, the simulation results are verified by using the experimental prototype to validate the performance of the improved circuit under different loading conditions.

A novel PWM plus phase shift modulation strategy for three‐level isolated dual‐active‐bridge DC–DC converters

AbstractA hybrid‐three‐level isolated dual‐active‐bridge (HTDAB) DC–DC converter is widely used for grid‐interactive power converters. However, a traditional extended‐phase‐shift (EPS) modulation scheme would cause voltage‐level‐disorder (VLD) problems in HDAB DC–DC converter system because the output voltage of HTDAB would be clamped at a high‐ or low‐level during power transmission when the inductor current changes directions. Thus, the zero voltage sequence of the HTDAB cannot be stably maintained under EPS control, which not only leads to a significant difference between the actual transmission power and the target output power but also seriously affects the stability of the system control. To address this limitation, the reasons leading to VLD are analysed in detail, that is, an inappropriate PWM switching sequence at the output zero voltage level would occur under EPS control. Then, a novel PWM plus phase shift (PPS) modulation strategy is proposed, which can eliminate VLD completely. Finally, an experimental prototype is built to verify the effectiveness of the proposed PPS modulation scheme. The experimental results demonstrate that the PPS modulation method proposed in this article can effectively eliminate level disturbances and improve system stability.

Research on passive adaptive wall-climbing cleaning and inspection robot of marine cylindrical steel structure based on conical magnetic adsorption wheel

The marine growth cleaning and structural defect detection of steel structures of offshore underwater facilities are essential parts of the inspection and maintenance of offshore platforms. However, a majority part of underwater structures of offshore facilities, such as offshore wind turbines, Jacket platforms, Jack-up platforms, etc., are cylindrical structures. Compared with the planar structures, cylindrical structures have large curvature, and less supporting area, and therefore put forward higher requirements for the performance of the attached surface working robot. This paper proposes a wall-climbing cleaning robot that can move freely on the wall of cylindrical steel structures and passively adapt to cylindrical structures with various curvatures and diameters. According to the structural characteristics of the robot, a static failure model is established to analyze the different instability forms of the robot and the minimum critical magnetic adsorption force is determined. To ensure the minimum mass and the maximum magnetic adsorption force of the conical magnetic adsorption wheelsets, the effects of air gap and cone angle on the performance of the conical magnetic adsorption wheelsets were analyzed parametrically, and the optimal structural size was obtained. Finally, the mobility and capability of the robot on the surface of the different diameter cylindrical structures has been validated through prototype experiments.

Dual mode variable voltage converter configuration using single topology: design and analysis

ABSTRACT This paper introduces an optimised design procedure for a DC–DC buck, boost and buck-boost configurations in a single circuit with an integrated dissipative snubber, aiming to enhance performance and efficiency. The conventional buck-boost converter’s versatility in adjusting the output voltage is complemented by a dissipative snubber, mitigating hard switching challenges in power semiconductors. Utilising advanced control techniques for seamless transitions between step-down and step-up modes, the proposed circuit ensures optimal operation across varying input voltages. The research delves into the snubber’s impact on limiting the maximum voltage stress across the switch, considering power losses in the snubber resistor. Simulation, analysis and experimental results validate the design’s effectiveness in meeting voltage regulation requirements, showcasing its adaptability to diverse electronic applications. This optimised design methodology holds promise for improving DC–DC converter efficiency in practical applications where mitigating switching losses and optimising voltage stress are critical considerations. Also this proposed converter provides output simultaneously for buck and boost configurations. The simulation and mathematical analysis are validated using the experimental prototype.

Research on the Isolated Three‐Port DC‐DC Converter with Resonant Parameter Compensation Capability and Its Performance Optimization

AbstractIn order to eliminate the adverse effects caused by power coupling of the isolated three‐port converter (ITPC), this paper proposes a three‐port resonant converter that uses a switch‐controlled‐capacitor (SCC) and an auxiliary inductor, which has resonant parameter compensation capability (RPC‐ITPC). The topology and operational principle of RPC‐ITPC are discussed in detail. To achieve resonant‐type power decoupling, it is usually necessary to ensure that the resonant frequency of the decoupling port resonant tank is consistent with the switching frequency, which puts high demands on the accuracy of the resonant components. To address the sensitivity of resonant‐type power decoupling to the parameters of resonant components, an SCC was adopted to solve the problem. The use of SCC enables the RPC‐ITPC to have resonant parameter compensation capability. In order to further optimize the performance of the RPC‐ITPC, a triple‐phase‐shift (TPS) modulation strategy is proposed to achieve the minimum RMS value of resonant current (MRMS‐TPSMS). Under the MRMS‐TPSMS, the switching devices of the power decoupling port have difficulty achieving ZVS turn‐on. To circumvent this problem, we realize ZVS of the decoupling port switching devices via auxiliary inductor current injection. Finally, a 1 kW experimental prototype was constructed to validate the theoretical propositions presented in this study. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Analysis, Design, and Optimization of Segment‐Compensated PCB Coil for Multirelay Wireless Power Transfer System

ABSTRACTThis paper proposed a segment‐compensated printed circuit board (PCB) coil for multirelay wireless power transfer (WPT) system. The PCB coil is designed with variable width to improve the system transfer efficiency, and the segmented compensation method is applied to avoid the high voltage stress on resonant capacitors in case of the multirelay WPT system with a low load resistance operating at a constant voltage frequency. The segmented compensation capacitors are integrated into the PCB coil, so as to constitute the compact coupler used in multirelay WPT system. The optimization procedure of the segment‐compensated PCB coil is also provided. The quality factor of the PCB coil can be improved by optimizing the proportional coefficients of width variation. The voltage of capacitors can be reduced by optimizing the number of segments. A physical variable‐width PCB coil with 3 segments is constructed. The experimental prototypes of the three‐coil, four‐coil, and five‐coil WPT systems are built. The experimental results show that the voltage of the segmented compensation capacitors on each coil is almost uniformly distributed and does not exceed 250 V when the input voltage is 50 V and the load resistance is 10 Ω. Compared with the multirelay WPT system using the equal‐width PCB coil, the multirelay WPT system using the PCB coil designed in this paper has higher output power and higher efficiency.