Closed-loop Configuration Research Articles

Environmental control system (ECS) design approach for collective nuclear, biological, and chemical (NBC) protection in military aircraft: A review

This comprehensive review paper delves into Environmental Control System (ECS) design strategies tailored for collective Nuclear, Biological, and Chemical (NBC) protection in military aircraft, exploring key elements such as hardening, air-tight construction, and filtering within the framework of open-loop or closed-loop ECS configurations. Initially, the paper elucidates the NBC protection requirements stipulated in commonly applied regulations such as MIL-HDBK-516C, DEFSTAN, and EMACC, highlighting the imperative for ventilation air to be devoid of contaminants, as mandated by these regulations. Subsequently, the paper delineates the strategic framework for NBC defense in the military aerospace industry, emphasizing the principles of avoidance, protection, and decontamination. A comparative analysis between individual and collective protection strategies underscores the comprehensiveness of the latter, prompting a recommendation for ECS design approaches grounded in the principles of collective protection, namely hardening, air-tight construction, and filtering. Furthermore, the paper provides insights into the configurations of open-loop and partial closed-loop ECS, elucidating their architectures for NBC protection. A comparative evaluation of these configurations enables the identification of pertinent parameters crucial for informed selection. In conclusion, the paper posits that the partial closed-loop ECS configuration exhibits greater promise in delivering enhanced NBC protection compared to the open-loop configuration, particularly in military aircraft applications operating in NBC environments.

Model-Based Sensor Fault Detection and Diagnosis in Closed-Loop Power Converters for Electric Vehicles

Electric Vehicle (EV) involves electric motors equipped with closed loop powered conversion systems which use the energy from storage batteries for vehicle propulsion and rely on sensor measurements as feedback to the controller. Therefore, sensor fault detection and diagnosis are an essential process that ensures performance and safety of EVs. From the National Renewable Energy Laboratory (NREL) study it is confirmed that electrical vehicle’s fault percentages vary, however, sensor faults constitute approximately 20-30% of total faults in them. Thus, sensor fault detection is critical for effective EV operation and requires the utmost focus from EV manufacturers and operators. Model-based techniques and Kalman Filter (KF) make it possible to detect faults on sensors in closed-loop EV power converter. It involves the use of mathematical model, sensor data and KF to identify fault before it becomes a threat and guarantees proper function of the vehicle. In this article, a state-space model of a CUK converter is developed, and an LQR closed-loop control system is designed for the power converter. A sensor fault detection method was developed for the system which is then simulated and tested under sensor bias fault conditions for both open and closed-loops control for determining the difference between them. The results showed a distinctive feature extracted between these two systems in the presence of system disturbances and noise applied to the sensor readings. The second section of simulation results in a closed-loop configuration validated the mathematical equations used for sensor fault detection, demonstrating their resistance to false alarms caused by system or component faults in addition to its ability to diagnose faults.

Energy, exergy, environmental, and economic (4E’s) analysis of a solar driven humidification-dehumidification desalination system: An experimental investigation

A solar-driven humidification-dehumidification (SDH-DH) desalination system has shown to be a highly efficient and viable solution to meet the freshwater needs of a community. However, the solar air heater based on flat plate collector, imposes constraints on their efficiency. The current work focuses on the development of an SDH-DH desalination system. This system is comprised of a solar air heater that utilizes a double-ends open evacuated tube collector, a humidifier equipped with cellulose pad packing material, and a dehumidifier based on a direct evaporative cooler. The current SDH-DH desalination system is operated in two modes, namely open loop and closed loop, at four distinct process air flow rates. The system's performance indices are evaluated based on energy, exergy, environmental and economic analysis. The solar air heater is capable of generating hot air at an approximate average temperature of 100 °C, while maintaining an airflow rate of 150 kg/h. This enhances the efficiency of the humidifier, resulting in a freshwater production rate of about 2.43 L/m2/day at a cost of 0.027 $/L. Moreover, the use of an evaporative cooler-based dehumidifier effectively mitigates the issue of fouling that arises during the condensation process. The system achieved the maximum mean energy efficiency of 25.39 % and exergy efficiency of 4.59 % in a closed loop configuration, with an air flow rate of 150 kg/h. The total CO2 reduction amounts to 119.08 tons during the designated duration.

Autonomous Optimal Absolute Orbit Keeping through Formation Flying Techniques

In this paper, the problem of autonomous optimal absolute orbit keeping for a satellite mission in Low Earth Orbit using electric propulsion is considered. The main peculiarity of the approach is to support small satellite missions in which the platform is equipped with a single thruster nozzle that provides acceleration on a single direction at a time. This constraint implies that an attitude maneuver is necessary before or during each thrusting arc to direct the nozzle into the desired direction. In this context, an attitude guidance algorithm specific for the orbit maneuver has been developed. A Model Predictive Control scheme is proposed, where the attitude kinematics are coupled with the orbital dynamics in order to obtain the optimal guidance profiles in terms of satellite state, reference attitude, and thrust magnitude. The proposed control scheme is developed exploiting formation flying techniques where the reference orbit is that of a virtual spacecraft that the main satellite is required to rendezvous with. In addition to the controller design, the closed-loop configuration is presented supported by numerical simulations. The efficacy of the proposed autonomous orbit-keeping approach is shown in several application scenarios.

An open-loop hybrid photovoltaic solar thermal evacuated tube energy system: A new configuration to enhance techno economic of conventional photovoltaic solar thermal system

One inherent problem of the conventional hybrid photovoltaic solar thermal system is the gradual loss of module power efficiency with low energy harvesting due to steady increase in module temperature with repeated circulation of the cooling water as a result of its closed loop configuration. This poor energy harvesting couple with high initial investment has made investment in this technology unattractive. This study proposes an enhanced hybridisation of the Photovoltaic Solar Thermal System collector with an evacuated tube based on an open-loop cooling configuration and unique flow control strategy. The aim is to improve cooling of solar panel leading to higher energy harvesting and utilisation that improves economic viability that will promote faster adoption. A numerical model is formulated using TRNSYS 18 software to assess the techno economics of the hybrid system. The model is validated using the verification and experimental methods. Overall, the findings show that the enhanced hybridisation and flow control strategy has resulted in higher annual renewable power generation and utilisation by 10 % than the basic hybrid Photovoltaic Solar Thermal system. This has resulted in significant economic savings, cutting operating expenses by 48 %. The ability to tailor the intended use of the system to meet with hot water and electrical power demand of different residential building is another attribute of proposed system that improve its energy harvesting reducing it payback period and doubling it economic benefit hence promoting it fast adaptability.

Design and performance of a novel closed-loop erosion-corrosion tester

In this paper, the authors present a novel closed-loop erosion-corrosion tester designed for the study of wear damage on rotary components, specifically the impellers of centrifugal pumps. This tester improves upon standard slurry pot erosion testers by using a closed loop configuration that allows for the constant use of new particles, thus eliminating the particle blunting limitation faced by these testers. The shape of the sample holder is also altered and allows for better particle distribution and the simultaneous testing of 4 samples at different impingement angles. The tests were carried out on a AISI 1045 carbon steel to verify the repeatability of results. A study on the erosion and erosion-corrosion resistance was then performed on a 304 L stainless steel and a ferritic high chromium cast iron. Results showed that the high chromium cast iron exhibited higher erosion and erosion-corrosion resistance except at 90° angles where its brittle nature made it more vulnerable to erosion and prone to cracking which also affected its corrosion resistance.

Method for investigating closed-loop hydraulic transmission with accumulator maintenance of overpressure in the suction line of a pump

The aim of the study is to verify the operability, reliability and functionality of a closed-loop hydrostatic transmission, which enhances the durability of the hydraulic drive by isolating the working fluid from atmospheric air and maintaining excess pressure at the pump inlet. The selected research object is a closed-loop hydrostatic transmission configuration, where drain leakage return is carried out by an ejector pump, while a hydropneumatic accumulator serves as a closed hydraulic reservoir that maintains excess pressure. Theoretical relationships for the designed components of the hydraulic system were derived using mathematical modelling by equations of normal dimensionless hydraulic numbers and a Microsoft Excel package. Design methods of continuity and modification were applied to construct the test bench. Based on existing research, the influence of various contaminants on the system failure characteristics was determined, and the positive effect of the purity of the working fluid on the durability and reliability of the hydraulic drive was highlighted. An overview of existing open, combined open-closed and closed hydrostatic transmissions revealed their disadvantages in terms of ensuring fluid purity. A proposed hydraulic schematic formed the basis for designing and manufacturing a test stand for investigating the closed-loop hydrostatic transmission. Criteria for selecting the pneumatic-hydraulic accumulator were defined, and a methodology for calculating parameters was substantiated. A versatile design of the ejector pump, operating under various flow pressure conditions, was developed, including replaceable components for the flow section (nozzles, mixing chambers, throats and confusers). The test program and methodology involve four test algorithms: stand preparation, tests without drain leakage, tests with maximum allowable drain leakage, and tests with intermediate drain leakage volumes, resulting in a total of one hundred sixty experiments. This study allows the feasibility of applying the presented closed-loop hydrostatic transmission in various types of machinery to be assessed.

Equilibria, Stability, and Sensitivity for the Aerial Suspended Beam Robotic System Subject to Parameter Uncertainty

This article studies how parametric uncertainties affect the cooperative manipulation of a cable-suspended beam-shaped load by means of two aerial robots not explicitly communicating with each other. In particular, this article sheds light on the impact of the uncertain knowledge of the model parameters available to an established communicationless force-based controller. First, we find the closed-loop equilibrium configurations in the presence of the aforementioned uncertainties, and then, we study their stability. Hence, we show the fundamental role played in the robustness of the load attitude control by the internal force induced in the manipulated object by nonvertical cables. Furthermore, we formally study the sensitivity of the attitude error to such parametric variations, and we provide a method to act on the load position error in the presence of uncertainties. Eventually, we validate the results through an extensive set of numerical tests in a realistic simulation environment, including underactuated aerial vehicles and sagging-prone cables, and through hardware experiments.

Centrifugal Compressor Surge In Innovative Heat Pump - Part 1: Fluid Dynamic And Vibrational Analysis

Abstract In the current energy scenario, it is necessary to reduce fossil fuel consumption to achieve the far-sighted and stringent decarbonization goals. To date, heat is mainly produced through fossil fuels. Alternatively, electrically driven heat pumps can exploit renewable power to recover environmental and waste heat, offering energy efficient and environmentally friendly heating and cooling for applications ranging from domestic and commercial buildings to process industries. Centrifugal compressors are already used as prime movers of the working fluid in heat pumps, thanks to their industrial replicability, compact size, affordable costs, and good performance in terms of efficiency and low noise. However, they are subject to instabilities such as surge and stall like any other dynamic compressor and these phenomena develop quite differently than in classic open-loop systems such as gas turbines. In fact, such peculiarity is mainly due to the closed loop configuration with real gases in two-phase conditions, occurring in typical heat pump cycles. The aim of this paper is to experimentally investigate the behavior of a centrifugal compressor installed into an innovative close loop heat pump system under stable and unstable conditions from both vibrational and fluid-dynamic points of view. The impact of the main process parameters on the evolution of the instability is shown, highlighting how surge cycles change by varying system operating conditions. The experimental results shown in this paper can be a basis for the future development of validated mathematical models of closed loop heat pumps systems equipped with dynamic compressors.

Integrating a Fischer Tropsch process into a pulp mill - A techno-economic assessment

To reduce the greenhouse gas emissions of the transport sector, synthetic fuels based on CO2 and H2 are one viable option. This paper evaluates the integration of a Fischer Tropsch process into a pulp mill to improve efficiency and to lower CO2 emissions. Different syngas preparation technologies, plant sizes, and gas loop designs are considered. The processes were simulated with a chemical process simulation software to retrieve mass and energy balances. Based on the simulations, the processes are evaluated regarding economics, CO2 emissions, and efficiency indicators.The Power-to-Fuel efficiency reaches almost 40 % for closed loop configuration with reverse water gas shift reactor for carbon monoxide production. For the open loop configuration the efficiency is tremendously lower. In closed loop configurations, the carbon efficiency reaches 80 %. The levelized cost of syncrude ranges from 3.28 to 7.69 €/kg. The most important impact on syncrude price comes from electricity price, investment cost, and efficiency of water electrolysis. Integrating the Fischer Tropsch process into the pulp mill shows advantages in terms of Power-to-Fuel efficiency and CO2 emissions but not necessarily in terms of economics.

Operating mode dependent energy transfer efficiency in a quantum well waveguide

In this paper, we delve into the intricate interplay between optical fields with varying relative phases in a closed-loop configuration semiconductor quantum well waveguide with four distinct energy levels, and how it impacts the Fraunhofer diffraction patterns obtained via four-wave mixing. By harnessing a strong control field, a standing wave driving field, and two weak probe and signal fields, we drive the waveguide to generate these patterns with maximum efficiency. To achieve this, we consider three distinct light-matter interaction scenarios, where the system is first set up in either a lower electromagnetically induced transparency or a coherent population trapping state, followed by a final state that enables electron spin coherence (ESC) induction. Our results reveal that the efficiency of Fraunhofer diffraction in the quantum well waveguide can be enhanced significantly under specific parameter regimes via the spin coherence effect. Further investigation of the light-matter interaction in the ESC zone, where only one of the control fields is a standing wave field, demonstrates that spin coherence facilitates more efficient transfer of energy from the probe light to the third and fourth orders, highlighting its crucial role in shaping the diffraction patterns.

Initial evaluation of USP apparatus 4 for measuring dissolution profile of man-made vitreous fibers

We report the successful evaluation of a US Pharmacopeia Apparatus 4 (USP-4) system in measuring the dissolution profiles of man-made vitreous fibers (MMVF)11Man-made vitreous fibers (MMVF) is the terminology commonly used in the European Union to refer to mineral wool fibers, it is also the terminology used in the classification entries for these materials in Regulation (EC) No 1272/2008 classification, labelling and packaging of substances and mixtures as the term synthetic vitreous fibers (SVF) is also used in literature and other jurisdictions to refer to mineral wool fibers.. Glass and stone wool fibers with different (high- and low-) solubility profiles were tested in closed-loop configuration using a sodium/potassium phosphate buffer solution or an acetate buffer, respectively. Results confirm a need to operate in diluted conditions to avoid silicon saturation in the simulant solution and suppression of fiber dissolution. A clear fiber-to-fiber differentiation with good cell-to-cell reproducibility was achieved. These findings support the continued development of a USP-4 protocol for MMVF in vitro acellular testing.

LoRaWAN-based Petroleum Pipeline Leakage Detection System Using Pressure Profile under a Pump Proximity Effect Condition

Leakages in pipeline is an important problem that can occur at any stage of the pipeline lifespan due to ageing, improper installation, or human related factors like bunkering or vandalization. Several invasive and non-invasive techniques are being used which have proven to be successful. However, this study focuses on leakage in an area of the pipeline network that is most often overlooked. This area is within the first 100 meters of the pipeline network to the excitation pump and is often prone to leakages due to high pressure. This study shows that even at no leak conditions pressure profile of a short pipeline in a closed loop configuration can vary by as much 59.93 percent. The study also examined the impact of single leak, double leaks, and triple leaks on the pipeline network with pressure loss compared to the no leak condition ranging from about 10 percent to as high as 60 percent.

Perception-aware online trajectory generation for a prescribed manoeuvre of unmanned surface vehicle in cluttered unstructured environment

This paper proposes a perception-aware online trajectory generation system that facilitates prescribed manoeuvres of an unmanned surface vehicle (USV) in a dynamic unstructured environment. The proposed system is developed based on the principles of the inverse dynamics in the virtual domain (IDVD) method and an event-triggered receding horizon control (ETRHC) mechanism. This approach transforms the underlying nonconvex constrained optimization problem into a virtual space with a differentially flat dynamics and uses relatively few decision variables to prototype feasible quasi-optimal trajectories. The closed-loop configuration is provided by a computationally efficient ETRHC mechanism that uses situational awareness of operating environment to trigger trajectory replanning if/when required. This addresses the challenge of continuously updating a closed-loop trajectory which imposes unnecessary computational burden on a system with the limited onboard resources. To investigate the performance of the proposed trajectory generating system, a dynamic unstructured environment including variable and uncertain no-fly zone areas as well as variable current vector fields are modeled. Further, different operating conditions incorporating the uncertainties of environment and sudden failure on the USV propulsion system are introduced to examine the effectiveness, agility, and robustness of the proposed trajectory generating system. A comparative study with benchmark solutions generated by the hp-adaptive Radau pseudo-spectral method is conducted to provide a detailed statistical analysis of the proposed approach robustness, computational complexity, and effectiveness. The simulation results confirm the effectiveness of the proposed trajectory generator and ability to produce a solution for online realization.

Strategic closed-loop supply chain configuration in the transition towards the circular economy of EV batteries: an evolutionary analytical framework

PurposeThis study advocates the importance of taking an evolutionary perspective in the strategic configuration of closed-loop supply chains (CLSC) in the transition to a circular economy. Building on the supply chain management and industrial dynamics research domains, an evolutionary analytical framework was developed and applied in the empirical context of the ongoing industrial transition to e-mobility.Design/methodology/approachThis study is designed as an in-depth exploratory case study to capture the multi-layer dynamic complexities and their interplay in CSLC development. The empirical investigation was based on two-year interactions between the authors and various departments in a leading European heavy vehicle manufacturer. The proposed evolutionary analytical framework was used for investigating the dynamics of four CLSC configurations through ten possible trajectories.FindingsThe findings demonstrate that the evolution of each CLSC configuration comes with multiple challenges and requirements and point out the necessity for the co-development of technologies, product design and production, and infrastructure through long-term relationships among key supply chain actors. However, this evolutionary journey is associated with multiple dilemmas caused by uncertainties in the market and technology developments. All these factors were properly captured and critically analyzed, along with their interactions, thanks to the constructs included in the proposed evolutionary analytical framework.Research limitations/implicationsThe proposed evolutionary framework is applicable for examination of SC transformation in the context of market and technology development, and is particularly relevant for transitioning from linear SC to CLSC. The framework offers a single actor perspective, as it does not directly tackle dynamics and effects of actions taken by SC actors.Practical implicationsThe developed framework can support SC managers in identifying, framing, and comparing alternative strategies for CLSC configuration in the transition process.Originality/valueThis study proposes the framework for understanding and guiding the evolutionary process of CLSC development. Its uniqueness lies in the integration of concepts from innovation and evolutionary theories coming from industrial dynamics and SCM literature streams.

Systematic realization of tunable-phase third-order oscillators

In this work, we introduce and verify general structures to obtain two-output tunable-phase oscillators using cascaded standard filter sections. In particular, a standard second-order high-pass, band-pass or all-pass filter followed by a first-order bi-linear filter section in a unity-gain closed loop configuration is shown to result in a third-order oscillator under certain conditions. The phase difference between the outputs of the two filter sections is a design parameter and can be tunable independent of the oscillation frequency or the start-up gain condition. Quadrature phase outputs can be obtained as special cases. Spice circuit simulations and experimental results are provided to verify the theory.

Forward Action to Stabilize multiple Time-Delays MIMO Systems

In this paper, the problem of closed-loop stability of linear time-invariant systems with multiple time-delays is studied. We prove that stability of closed-loop configurations of such systems with unitary feedback can be guaranteed by means of a forward control action. The case of single-input single-output (SISO) systems is first considered, and then, an extension to the more general case of multi-input multi-output (MIMO) systems with multiple time-delays is dealt with. Numerical examples illustrating the theoretical results are also discussed.

Advanced Hybrid System for Ammonium Valorization as Liquid Fertilizer from Treated Urban Wastewaters: Validation of Natural Zeolites Pretreatment and Liquid-Liquid Membrane Contactors at Pilot Plant Scale.

This study evaluates a hybrid system combining zeolites as a sorption stage and a hollow fiber membrane contactor (HFMC) for ammonia (NH3) recovery from treated urban wastewater. Ion exchange with zeolites was selected as an advanced pretreatment and concentration step before the HFMC. The system was tested with wastewater treatment plant (WWTP) effluent (mainstream, 50 mg N-NH4/L) and anaerobic digestion centrates (sidestream, 600-800 mg N-NH4/L) from another WWTP. Natural zeolite, primarily clinoptilolite, demonstrated effective desorption of retained ammonium using a 2% NaOH solution in a closed-loop configuration, resulting in an ammonia-rich brine that enabled over 95% NH3 recovery using polypropylene HFMCs. A 1 m3/h demonstration plant processed both urban wastewaters, which were pretreated by ultrafiltration, removing over 90% of suspended solids and 60-65% of COD. The 2% NaOH regeneration brines (2.4-5.6 g N-NH4/L) were treated in a closed-loop HFMC pilot system, producing 10-15% N streams with potential use as liquid fertilizers. The resulting ammonium nitrate was free of heavy metals and organic micropollutants, making it suitable for use as liquid fertilizer. This comprehensive N management solution for urban wastewater applications can contribute to local economies while achieving reduced N discharge and circularity goals.

Development of an innovative test machine for tyre, wheel and suspension systems for automotive and industrial vehicles

Reliability and efficiency of automotive and industrial vehicles are strongly affected by the behaviour of the components involved in the interaction with the ground. For this reason, components like tyres, wheels and suspension systems are physically tested, for performance and durability assessment. Anyway, standard test machines are generally designed for testing only one specific component.The aim of this work is the design of an innovative test machine, able to perform different kinds of tests, for tyre, wheel and suspension system components, on a unique bench. The machine is a flat track type, better fit than traditional drum types in simulating real tyre-to-ground contact conditions. The core of the machine is a Gough-Stewart platform, where the flat track is fixed, which is moved by six hydraulic actuators to reproduce multiple work configurations, for extended time periods or numerous test block repetitions. After the preliminary design phase, the machine components were subjected to topology optimization and modal analysis by FEM, to reduce weights and avoid any issues related to the expected working frequencies. Given the quality of the results achieved, currently, the software design for closed-loop control configuration is under development, for the machine prototype next construction.

Diffraction grating via position dependent incident light in a closed-loop quantum system

We have proposed a new model for controlling the electromagnetically induced grating in a three-level closed-loop quantum system. The quantum system interacts with three-laser fields which one of them is the weak probe light and two of them are strong driving and coupling laser fields. These two strong laser fields have standing wave (SW) patterns in two x and y directions. This makes that the absorption and dispersion properties of the media change periodically which leads to diffraction of the transmitted light. We have shown that because of the closed-loop configuration of the quantum system the relative phase between applied lights can affect the diffraction grating pattern of the transmitted light. We have also discussed the Rabi-frequency effect of the driving and coupling lights on the different orders of the grating. We have shown that our proposed model may be used as a new tool for developing the future quantum information processing devices.