Operational Envelope Research Articles

Polytrauma in a Jet Pilot After Low-Altitude Ejection Without Parachute Deployment

BACKGROUND: Ejection seats are designed to be a lifesaving device for aircrew in emergencies. Modern ejection seats are widely prevalent in fighter and bomber aircraft and are occasionally associated with acceleration injury from axial loading (Gz) during the catapult phase of ejection, limb flail injury due to windblast, or parachute landing fall, especially if the ejection is outside of the seat’s performance envelope. CASE REPORT: We present the first known case in the medical literature of a military pilot who survived a low-altitude, high-angulation (>90° of bank angle) ejection where the pilot’s ejection seat parachute did not deploy due to contact with the ground before completion of the ejection sequence. The patient’s initial exam upon arrival at a trauma center was significant for a Glasgow Coma Scale of 3T, with evidence of cranial and extremity trauma. The patient presented with respiratory acidosis and required upsizing of his endotracheal tube placed in the field. The patient’s injury list included bilateral subdural and subarachnoid hemorrhages, a Hangman’s fracture, spinal burst fractures, and extensive extremity fractures. After a prolonged hospital stay, the patient was discharged to rehabilitation. The patient made a functional and neurological recovery, including return to independent completion of his activities of daily living. DISCUSSION: This case provides evidence of favorable outcome after a low-altitude, high-angulation ejection without parachute deployment. This case details the medical and traumatic pathology medical personnel should expect from an ejection that occurs outside of the seat’s performance envelope. Zivkovic MM, Inman BL, Figlewicz MR, Burchett JA, Nowadly CD. Polytrauma in a jet pilot after low-altitude ejection without parachute deployment. Aerosp Med Hum Perform. 2024; 95(11):862–866.

Nonlinear model predictive dynamic positioning of a remotely operated vehicle with wave disturbance preview

Exploiting preview information of disturbances within robot control is an effective method of handling state perturbations. For underwater vehicles operating in wave-dominated environments, disturbances significantly influence vehicle response and pose a threat to operational safety. In consideration of this, a complete end-to-end control architecture is developed in this work for disturbance rejection during station keeping tasks under wave perturbations, encompassing a nonlinear model predictive controller (NMPC) combined with a deterministic sea wave predictor (DSWP). The wave predictor exploits a continuous measurement of the wave elevation at a location upstream of the vehicle to form a forecast of the temporal evolution of the wave elevation at the vehicle location. The predicted wave parameters are then used to estimate the impending wave-induced hydrodynamic loading, enabling explicit consideration of accurate short-term disturbance forecasts within the controller, ensuring this preview is incorporated in the optimised control sequence. Experimental testing confirms the validity of the wave predictor, producing RMSE as low as 0.017 m. The proposed strategy is then simulated under various wave conditions, optimising control actions inclusive of the preview information. The NMPC outperforms a similar disturbance mitigating feed-forward controller, with average improvements of up to 52% and is found to perform best even with noisy, lower accuracy wave predictions, as well as with communication time delays, providing a high degree of robustness. This demonstrates the potential of the proposed control framework to effectively tackle disturbance mitigation of underwater vehicles subject to large magnitude wave disturbances, expanding the operational envelop of autonomous systems towards forbidding ocean environments.

Resilience in emerging complex intelligent systems: A case study of search and rescue

AbstractAs artificial intelligence (AI) is becoming part of complex systems and critical infrastructures, perspectives on resilience may need to be revisited. This paper focuses on the challenges and approaches in engineering design for achieving resilience in complex and increasingly intelligent systems (CoIS). Building on a case study of a system situated in the context of search and rescue (SAR) operations at sea as well as scenarios of SAR operations supported by AI solutions, it outlines challenges for organisational and engineering design in contexts where flexibility, adaptability, and high reliability are important. The findings point at resilience as a system property, made up of the constituent systems, their interaction and coordination in a system‐of‐systems framework. AI and autonomy in CoIS represent potentially a double‐edged sword; while AI and autonomy contribute to system capabilities and resilience, they can also introduce limitations in terms of, for instance, confined operational envelopes. Achieving resilience in CoIS thus requires a holistic approach that considers constituent systems as well as their interplay, organisational factors, and the judicious balance of AI and human‐based solutions.

A Conceptual Model for Automation of Small Ports

Abstract For large ports and terminals, the loading and discharge operations have to a great extent been automated already. However, for the vast number of small ports, for instance all Norwegian ports, this large-scale automation is not possible due to the small size of the ports compared to the cost of introducing full automation. Still, these small ports are important logistics hubs in the transport system. They facilitate the shift from congested roads to the sea by allowing the goods to arrive closer to the final destination by using smaller, possibly autonomous, vessels. However, this puts pressure on the ports to facilitate reduced laytime in the port, to increase the port efficiency and to improve interoperability towards hinterland systems and terminals. For small ports, this means that manual and automated work processes need to exist side by side, and that it will be important to get an overview of which processes to automate and which will remain manual, in addition to the handling of the hand-over between humans and automation. This paper describes a conceptual model that can be used by small ports as a starting point on their way to introduce automation of their services supporting the cargo flow through the port. The model includes a description of port functions, tasks and responsibilities and use the concept of operational envelope to define the overall capabilities of the system, including both automation and human. This will be the starting point for how to structure the description of an operation centre that monitor and control the maritime terminal operations. The starting point for this work is a use case analysis performed in some small ports in Norway, and their need to optimize the utilization of their assets. The work is done as part of the AutoPort project which is a research project funded by the Norwegian Research Council (project number 337211). The goal of this work is to describe a methodology on how to identify the interface between automation and human operators when it comes to small ports and the movement of cargo through its terminals, and by this give a description on how different levels of automation can be implemented. The methodology consists of several steps, including definition of the context (big picture of the use case, actors and their roles, and communication), the scenario (port activities and processes), and the use cases including the control tasks performed by the automated systems.

Low-carbon high-strength engineered geopolymer composites (HS-EGC) with full-volume fly ash precursor: Role of silica modulus

In this study, the influence of the silica modulus of alkaline activators on the overall performances of pure fly ash (FA)-based High-Strength Engineered/Strain-Hardening Geopolymer Composites (HS-EGC/SHGC) was comprehensively studied. The developed HS-EGC successfully presented simultaneous high compressive strength (over 90 MPa) and high tensile ductility (over 6.0 %) for the first time. Tensile strain-hardening and over-saturated cracking phenomena were observed for all the HS-EGC mixes. It was found that the increase of the silica modulus from 1.0 to 2.0 reduced the tensile strength and strain energy density of HS-EGC, but the most distinguished overall mechanical index was achieved in the mix with the silica modulus of 1.5. Additionally, the underlying mechanism behind the mechanical performances was explored by Back Scattering Electron and Energy Dispersive Spectroscopy (BSE-EDS) tests. According to the data comparison from literature review, the good sustainability and market potential of the developed material were successfully demonstrated, and the developed HS-EGC pushed the performance envelope of pure FA-based EGC materials. The findings could help promote the future development and practical applications of this strain-hardening geopolymer material with both good sustainability and high mechanical performances.

Dynamic operating envelopes embedded peer-to-peer-to-grid energy trading

A novel decentralized peer-to-peer-to-grid (P2P2G) trading mechanism considering distribution network integrity is proposed. In order to direct prosumers’ peer-to-peer (P2P) trading behavior to be grid-friendly, the proposed method incorporates Dynamic Operating Envelopes (DOEs) into the existing P2P2G trading. Moreover, DOEs are determined through negotiations between the distribution system operator (DSO) and prosumers alongside the process of P2P trading, avoiding compromising prosumers’ privacy and network parameters leakage. To reduce communication costs during P2P trading, a variant of the alternating direction method of multipliers (ADMM), i.e., communication-censored ADMM (COCA) is used to solve the P2P2G trading problem. Finally, the DOE price is shown to be comprised of several economically interpretable components. Simulations validate the effectiveness of the proposed mechanism.

Day-ahead dynamic operating envelopes using stochastic unbalanced optimal power flow

Driven by the energy transition, distribution networks are dealing with increasing uptake of distributed energy resources, including solar photovoltaic generation. Residential rooftop solar allows customers to minimize exposure to price increases in the market, which has led to high penetration of PV in regions with high amounts of solar hours such as Australia. Eventually, this leads to congestion in the network, either due to voltage rise, or due to overcurrent in lines or transformers. Distribution utilities are now moving on from static export limits for customers in congested networks, to dynamic limits that are based on the state of the network. It is considered thoughtful to give customers advance warning, e.g. day-ahead, of the moments and degrees of export limitation, despite uncertainty surrounding the future state of the network. Therefore, in this paper, we consider the application of general polynomial chaos expansion based stochastic unbalanced optimal power flow to the day-ahead determination of dynamic export limits. We perform a numerical study on a European style low voltage feeder and illustrate the impact of fairness principles on chance-constrained stochastic nonlinear optimization without the need of sampling, linearizing the power flow equations, or applying relaxations. Case studies show the necessity of considering unbalanced study of distribution system. It was observed that equality measures reduce the overall output of the system in an attempt to achieve equal relative injection, while alpha fairness with a higher value of alpha is a compromise between the efficiency and fairness in DOEs.

Development and Testing of a Helicon Plasma Thruster Based on a Magnetically Enhanced Inductively Coupled Plasma Reactor Operating in a Multi-Mode Regime

A disruptive Electric Propulsion system is proposed for next-generation Low-Earth-Orbit (LEO) small satellite constellations, utilizing an RF-powered Helicon Plasma Thruster (HPT). This system is built around a Magnetically Enhanced Inductively Coupled Plasma (MEICP) reactor, which enables acceleration of quasi-neutral plasma through a magnetic nozzle. The MEICP reactor features an innovative design with a multi-dipole magnetic confinement system, generated by neodymium iron boron (NdFeB) permanent magnets, combined with an azimuthally asymmetric half-wavelength right (HWRH) antenna and a variable-section ionization chamber. The plasma reactor is followed by a solenoid-free magnetic nozzle (MN), which facilitates the formation of an ambipolar potential drop, enabling the conversion of electron thermal energy into ion beam energy. This study explores the impact of an inhomogeneous magnetic field on the heating mechanism of the HPT and highlights its multi-mode operation within a pulsed power range of 200 to 500 W of RF. The discharge state, characterized by high-energy electron-excited ions and low-energy excited neutral particles in the plasma plume, was analyzed using optical emission spectroscopy (OES). The experimental testing campaign, conducted under pulsed power excitation, reveals that, as RF input power increases, the MEICP reactor transitions from inductive (H-mode) to wave coupling (W-mode) discharge modes. Spectrograms, electron temperature, and plasma density measurements were obtained for the Helicon Plasma Thruster within its operational envelope. Based on OES data, the ideal specific impulse was estimated to exceed 1000 s, highlighting the significant potential of this technology for future LEO/VLEO space missions.

Ground Vacuum Facility to Simulate Low Earth Orbit Plasma Environment

This paper presents a large vacuum facility (6-ft-diameter, 10-ft-long chamber) equipped with a magnetic filter-type low Earth orbit plasma source. A recommended operating envelope for the plasma source was established through single-point measurements by varying the discharge currents of the plasma source and the gas flow rates. A three-axis translation stage was fabricated and tested with 2D and 3D scans of the simulated plasma environment. The measured plasma density during this study was between 1.63×1012−3.1×1012 m−3 for the electrons and 7.54×1012−1.82×1013 m−3 for the ions, whereas the electron and ion temperatures ranged from 0.55 to 2.06 eV and 1 to 3 eV, respectively. The simulated plasma environment compares well with orbital equivalents, specifically the F layers of the ionosphere.

Sensitivity analysis and fuel performance of a control rod withdrawal in the generic fluoride-salt-cooled high temperature reactor

The purpose of this study is to develop boundary conditions with respect to input parameter uncertainty for fuel performance assessment of a control rod withdrawal transient in a fluoride-salt-cooled high-temperature reactor (FHR). Sensitivity analysis was performed to determine how certain key input parameters impacted the uncertainty of the outputs needed for the boundary conditions. The generated boundary conditions can be used in fuel performance codes to obtain failure probabilities and fuel performance envelopes. To accomplish this, we utilized a KP-AGREE model of the generic fluoride-salt-cooled high-temperature reactor (gFHR) and a pebble bed benchmark developed by Kairos Power. The key boundary conditions that were developed included the total power, maximum fuel region temperature, maximum fuel kernel temperature, and maximum moderator (graphite) temperature within the core. The sensitivity analysis was run until the Sobol indices and output converged within a 95 % confidence level; it was found that the coolant inlet temperature consistently had the highest impact on the uncertainty of the key core temperature values. The maximum bound of these temperatures also did not exceed 1123.5 °C for the fuel kernel and 973.7 °C for the moderator after the transient, demonstrating that there is a large margin between the predicted fuel and moderator temperature and accepted safety limits, given a 1650 °C limit for Tristructural Isotropic (TRISO) fuel. These boundary conditions were implemented into a BISON model to demonstrate their use in fuel performance and obtain a brief failure profile of the fuel. The maximum magnitude of the hoop stress on the SiC layer was −12.02 MPa, resulting in a failure probability of 4.90·10−19. Thus, the fuel performance simulations also emphasized the robustness of the TRISO fuel design utilized in the gFHR, as the predictions reveal substantial margin of the TRISO particles relative to temperature limits during the control rod withdrawal. The limiting temperature is expected to be the reactor vessel temperature and the fuel is not expected to be challenged at all by mechanical failure of the SiC layer during these events.

Neural adaptive performance guaranteed formation control for USVs with event-triggered quantized inputs

ABSTRACT This study presents an adaptive fault-tolerant performance guaranteed formation control strategy with event-triggered quantised inputs (EDQI) for unmanned surface vessels (USVs) in the presence of model uncertainties and actuator faults. Firstly, a prescribed performance formation guidance control law is proposed to allow formation tracking errors to evolve within the performance envelope and convergence to prescribed steady regions at an appointed time. Then, minimal-parameter-learning-based neural networks (MLP-NN) are used to tackle model uncertainties. To reduce the frequency of actuator updates and the communication burden on the channel, a dynamic memory event-triggered quantised input strategy is investigated. In addition, adaptive estimators and auxiliary design signals are built to compensate for the effects caused by input quantisation and actuator faults. It is proved that all closed-loop signals are bounded and formation errors can converge to the prescribed region at an appointed time. Finally, the effectiveness of the proposed controllers is verified by numerical simulations.

Cylinder-piston application for surge prevention and energy efficiency in an industrial compression unit

Compressions are prevalent in industrial applications and are notable for their substantial energy consumption. Therefore, the simulation and analysis of the compression process are essential for maintenance and energy conservation efforts. These systems are prone to potentially unstable surge conditions, necessitating the use of traditional anti-surge valves that result in considerable energy losses. Ensuring the near-optimal operation of these systems is critical to minimizing energy consumption.In this article, a conceptual framework for a cylinder-piston mechanism is delineated, intended for design and operation as an active surge control system. Additionally, a modular quasi-one-dimensional model is articulated for the transient simulation of an industrial compression system, which integrates models for both the anti-surge and active control systems. The manuscript presents a novel design, featured by a cylinder-piston system integrated with a robust controller, posited as a potential alternative to traditional anti-surge systems. The effectiveness of this design in expanding the operational envelope of the compression system and surge prevention is rigorously examined. Moreover, a thermodynamic model, grounded in the fundamental laws of mass, momentum, and energy conservation, is applied to each component of the system. Furthermore, the manuscript explores the benefits of the innovative design in achieving a marked decrease in energy wastage. Simulation results from a test scenario reveals that the implementation of the cylinder-piston design, as opposed to the conventional anti-surge system, can diminish energy losses and associated pollutant emissions by approximately 33 percent.

Flow-Based Assessment of the Impact of an All-Electric Aircraft on European Air Traffic

The consequences of new airspace entrants, such as novel aircraft concepts with innovative propulsion systems, on air traffic management operations need to be carefully identified. This paper aims to assess the impact of future aircraft with different performance envelopes on the European air traffic network from a flow-based perspective. The underlying approach assumes that all certification-related questions concerning airworthiness have been resolved and do not take into account any economic factors related to airline operations. For example, for an innovative propulsion system, a short range all-electric aircraft is considered in this study. Aircraft trajectory calculations are based on the dataset of base of aircraft data (BADA), which are developed and maintained by EUROCONTROL. The new design concept is integrated into BADA as well, resulting in a new set of coefficients for the all-electric aircraft. In addition to the adjusted parameters which affect airborne performances, ground-related aspects are also taken into account. This includes assumptions on operational procedures, charging capacities and adaptions in infrastructure. Investigations are carried out at the trajectory level as well as at the airport and the entire network.

Indirect drive ICF design study for a 3 MJ NIF enhanced yield capability

A proposed upgrade to the National Ignition Facility is under consideration that would ultimately increase the maximum operating envelope for the laser to 3.0 MJ with a peak power of 450 TW. This upgrade would provide opportunities to address an expanded set of data needs for NNSA’s Stockpile Stewardship mission, including the potential to generate fusion yields ≥30 megajoules. A simplified model of ignition and burn is used to scope the theoretical maximum target yield as a function of laser driver energy. We examine two indirect drive ICF target designs that make use of the 3 MJ laser drive using a common model for integrated laser-hohlraum simulations. These two designs compare and contrast the impacts of two different ablator materials, pure carbon and CH. Additionally, the potential for increased backscatter from these larger scale designs is discussed.

Feasibility region analysis of active systems: investigating the lateral performance envelope of sports cars

Active systems are gaining significant importance because of their ability of enhancing handling performance, stability, and driver engagement, especially in sports cars. The upfront study of the achievable handling characteristics with a specific actuator set is crucial, given the involved development costs and time. In this context, although several recent studies have compared the cornering response associated with different chassis actuations, none of them has analysed in detail the resulting performance envelope, i.e. the feasibility region, based on the operating limit of the available hardware. This study targets the identified gap and presents a methodology for obtaining the feasibility region of chassis actuation systems, defined as the locus of the achievable understeer characteristics. The analysis considers front and rear active camber (FAC and RAC), rear-wheel-steering (RWS) and variable roll moment distribution (RMD). Simplified vehicle models with reduced number of degrees of freedom (DoFs) and other features to accurately obtain the feasibility region and the relevant dynamic response indicators in the early design stages of the vehicle are compared with a high-fidelity model based on VI-CarRealTime. The results highlight the favourable trade-off between complexity and accuracy of a 3-DoF nonlinear model accounting for suspension kinematics and compliances.

A Novel Chaos Control Strategy for a Single-Phase Photovoltaic Energy Storage Inverter

The single-phase photovoltaic energy storage inverter represents a pivotal component within photovoltaic energy storage systems. Its operational dynamics are often intricate due to its inherent characteristics and the prevalent usage of nonlinear switching elements, leading to nonlinear characteristic bifurcation such as bifurcation and chaos. In this paper, a deep investigation of a single-phase H-bridge photovoltaic energy storage inverter under proportional–integral (PI) control is made, and a sinusoidal delayed feedback control (SDFC) strategy to mitigate the nonlinear characteristics is proposed. A frequency domain mapping model of the system is established, then, by analyzing the Jacobian matrix and equilibrium points, the bifurcation diagram is formed, and finally, the stable operational domains are determined under double and triple bifurcation parameters. Through simulation experiments, the efficacy of this strategy is validated. The findings show that through the control strategy, the stable operational envelope of the inverter can be greatly expanded and the nonlinear dynamic phenomena can be notably suppressed.

Impact of phase selection on accuracy and scalability in calculating distributed energy resources hosting capacity

Hosting capacity (HC) and dynamic operating envelopes (DOEs), defined as dynamic, time-varying HC, are calculated using three-phase optimal power flow (OPF) formulations. Due to the computational complexity of such optimisation problems, HC and DOE are often calculated by introducing certain assumptions and approximations, including the linearised OPF formulation, which we implement in the Python-based tool ppOPF. Furthermore, we investigate how assumptions of the distributed energy resource (DER) connection phase impact the objective function value and computational time in calculating HC and DOE in distribution networks of different sizes. The results are not unambiguous and show that it is not possible to determine the optimal connection phase without introducing binary variables since, no matter the case study, the highest objective function values are calculated with mixed integer OPF formulations. The difference is especially visible in a real-world low-voltage network in which the difference between different scenarios is up to 14 MW in a single day. However, binary variables make the problem computationally complex and increase computational time to several hours in the DOE calculation, even when the optimality gap different from zero is set.

Assisting Directional Drilling by Calculating a Safe Operating Envelope

Summary Nowadays, complex 3D trajectories are executed with a succession of circular arcs (CAs). Although they have constant curvature, their tool face is not constant. Consequently, directional drillers must adjust the tool face regularly to reach the target entry within its tolerances. This paper investigates the use of the constant curvature and constant tool face (CTC in short) curve as an alternative to the CA to assist the directional drilling work to reach the target entry within its boundaries. The problem is addressed by calculating a safe operating envelope (SOE) to reach the boundaries of the target entry and provide a tolerance window for the curvature and tool face to support directional drilling decisions. The target entry tolerance is discretized as a polygon. From the current bit position and its direction, the possible choices of curvatures and tool faces are obtained to reach the edges of the target entry shape. The SOE can be calculated with the CA or with the CTC curve. It is, therefore, possible to compare the advantages and disadvantages of both types of curves to attain the target entry and stay within its boundaries. The CA is shorter than the CTC curve. However, it requires adjusting the tool face during the navigation, which is not the case with the CTC curve. As a result, the directional driller can control the bottomhole assembly (BHA) direction such that the well lands within the target entry limits by using set points for tool face and curvature inside the calculated SOE. Furthermore, a new way to represent the SOE is introduced. It makes use of a 3D cylindrical representation where the curvature is mapped as the height of a cylinder, while the tool face corresponds to the azimuth in the cylindrical coordinate system, and the length is linked to the radial distance. This provides a visual aid to understand the SOE. Moreover, this visualization helps to appreciate the relationship between the initial bit location and direction in the construction of the SOE and how the margins increase in a particular manner as the bit approaches the target entry polygon. The CTC curve is the natural one followed by directional positive displacement motors (PDMs) or rotary steerable systems (RSS). Potentially, the CTC curve may be a more straightforward solution to automated directional drilling control because it is easier to be followed by both PDM and RSS.

Thermoeconomic assessment of the air-cooled tropical data center through energy-saving strategies

Rapid developments in the electronic information industry drive the increased energy usage and carbon emission of data center buildings, prompting the focus on the energy efficiency and environmental sustainability. Expanded operation envelopes of tropical data centers is assessed to analyze the potential for the building energy savings and carbon emission reduction through collaborative analysis of operation modes (OMs), supply air temperature (SAT), and outdoor air temperature (OAT). The OMs of compression vary with the setpoints of SAT, in which the average exergy efficiency of compressors at alternate operation mode is 6.8 % and 8.0 % lower than that of double and single compression operations. As SAT rises from 20 °C to 32 °C, the system exergoeconomic factor increases from 5.4 % to 8.0 %, and the average carbon cost decreases by 36.5 %. Additionally, with just an 8.5 % increase in exergy cost (i.e., Case 8) at OAT rising from 30 to 34 °C, the high SAT and low refrigerant charges provide considerable exergy cost advantages versus resisting the OAT fluctuations. Dynamic operation strategies are also proposed and compared to cope with the impacts of tropical environments. Compared to the 26 °C SAT baseline, the average energy savings are 9.1–14.7 %, indicating the ability to fully utilize outdoor and indoor conditions.

Design of self-healing materials for the integration of structural health monitoring (SHM^2)

Integration of the complementary fields of structural health monitoring in self-healing materials (SHM2) has the potential to transform the traditional engineering concepts of fail safe and damaged tolerant design. Structural health monitoring seeks to embed and automate sensing capabilities within structures to determine their state and to detect degradation or damage. Once degradation or damage is detected, additional decisions and potential action are required. Reducing operational envelopes can prevent further damage accumulation or catastrophic failure or repairs can be performed to correct the degradation. Typical repair requires active involvement of personnel and potentially down time. Self-healing materials seek to avoid maintenance needs and down time through the creation of structures and materials with an imbued capability to repair damage. Together SHM^ 2 has the potential to create a closed loop where damage is detected using embedded sensors and automated analysis that can then initiate self-healing. The highly structured and controlled nature of self-healing materials presents an opportunity to design structures that additionally support health monitoring capabilities. This paper presents recent research and results informing the design of shape memory alloy (SMA) fiber reinforced metal matrix composites (MMCs) to optimize self-healing capabilities and structural health monitoring (SHM^2). Fiber pull tests were performed to analyze the strength of the interface between the SMA fibers and matrix allowing for sizing to complement both composite design and healing capabilities. Analysis was performed to understand complex failure mechanisms occurring at the interface between detwinning shape memory alloys and the metal matrix. And novel composite design was performed to support both the self-healing and damage detection capabilities of the material structure.