Acceleration Schedule Research Articles

Robust acceleration schedule design for gas turbine engine using multilayer perceptron network with adaptive sample class weighting

The acceleration schedule is crucial for generating acceleration control references for the gas turbine engine (GTE) and ensuring optimal acceleration performance. However, under harsh operating conditions, GTEs may encounter difficult-to-diagnose pressure sensor faults, which lead to inaccurate control references and decreased acceleration performance. This paper proposes a data-driven robust acceleration schedule (RAS) design method to tackle this issue, including fault data augmentation and adaptive sample class weighting (ASCW). Fault data augmentation generates multiple pressure fault sample classes from a normal acceleration schedule dataset. Due to the redundant pressure sensor configuration, the RAS can reconstruct these classes and generate accurate control references when a single pressure sensor fails. The ASCW employs a multilayer perceptron network to reconstruct the normal and fault sample classes accurately. Proportional integral regulation adjusts their weights during training to ensure balanced reconstruction precision. Simulation cases were conducted to verify the effectiveness of the RAS under actual GTE conditions, including engine-model mismatches, performance deterioration, flight envelope, and measurement uncertainty. The results demonstrate that the RAS ensures superior acceleration performance of GTEs across the full flight envelope in both normal and single pressure sensor fault scenarios. Additionally, the ASCW achieves reconstruction precision of 0.068 %, 0.080 %, 0.080 %, 0.082 %, and 0.077 % for normal and fault sample classes, respectively, prioritizing the precision of the normal sample class and balancing the precision of fault sample classes.

Surge-Elimination Strategy for Aero-Engine Transient Control

Abstract The fundamental principle of the transient state control method for turbofan engines, which is based on the acceleration ratio of high-pressure rotational speed (N-dot), involves sacrificing a portion of the safety margin to obtain satisfactory acceleration performance. However, it could induce surge in the engine's compressor. To prevent the destructive damage caused by surge to both the engine and its components, a surge-elimination control strategy for the engine based on an N-dot controller is proposed. First, the engine mathematical model, which incorporates the effects of engine volumetric dynamics, stall zone characteristics, and combustion chamber flameout characteristics, is established to simulate surge mechanism. Subsequently, the acceleration schedule of the N-dot is calculated by employing sequential quadratic programming (SQP) algorithm to solve the multiconstraint optimization problem, while designing the transition state controller of N-dot based on a high-order filter. Finally, the surge detection logic and surge-elimination strategy based on the μ-correction method are proposed and designed to realize active control of surge elimination. The simulation results demonstrate that the N-dot control method offers significant advantages in mitigating the steady-state errors resulting from inevitable engine degradations. The surge state is effectively suppressed by the proposed surge-elimination control method, and the surge duration is significantly shorten during the acceleration phases. Furthermore, compared to the one without any surge-elimination control, the proposed method decreases the acceleration time by 5.53%.

A fault-tolerant acceleration control strategy for turbofan engine based on multi-layer perceptron with exponential Gumbel loss

The acceleration performance of turbofan engine is mainly limited by the surge boundary of high-pressure compressor (HPC). A certain amount of surge margin (SM) is reserved between the boundary and the acceleration schedule (AS) of acceleration control to avoid the risk caused by intake distortion, etc. However, the performance improvement by low SM design is the requirement for advanced engines. Hence it must execute a fault-tolerant strategy for the impact of sensor error, fuel metering error, etc. This paper proposes a method by adopting four ASs for weighted average to replace the single AS. The weights are altered by the multi-layer perceptron with reference to the real-time fuel results from four ASs, intake condition and rotor speed. For safety and accuracy, an exponential Gumbel loss function is introduced into the model training. The simulation results demonstrate that the method can significantly tolerate the impact of a single fault and the normal deviations of other factors without causing SM of HPC to be less than 3.6%. These also indicate that the acceleration time on the ground does not exceed acceptable 5 s, with a median that is 0.34 s less than the minimum method of two ASs within the flight envelope.

Virtualizing a Post-Moore’s Law Analog Mesh Processor: The Case of a Photonic PDE Accelerator

Innovative processor architectures aim to play a critical role in future sustainment of performance improvements under severe limitations imposed by the end of Moore’s Law. The Reconfigurable Optical Computer (ROC) is one such innovative, Post-Moore’s Law processor. ROC is designed to solve partial differential equations in one shot as opposed to existing solutions, which are based on costly iterative computations. This is achieved by leveraging physical properties of a mesh of optical components that behave analogously to lumped electrical components. However, virtualization is required to combat shortfalls of the accelerator hardware. Namely, (1) the infeasibility of building large photonic arrays to accommodate arbitrarily large problems and (2) underutilization brought about by mismatches in problem and accelerator mesh sizes due to future advances in manufacturing technology. In this work, we introduce an architecture and methodology for lightweight virtualization of ROC that exploits advantages borne from optical computing technology. Specifically, we apply temporal and spatial virtualization to ROC and then extend the accelerator scheduling tradespace with the introduction of spectral virtualization. Additionally, we investigate multiple resource scheduling strategies for a system-on-chip (SoC)-based PDE acceleration architecture and show that virtual configuration management offers a speedup of approximately 2×. Finally, we show that overhead from virtualization is minimal, and our experimental results show two orders of magnitude increased speed as compared to microprocessor execution while keeping errors due to virtualization under 10%.

Баллистическая оценка полетов серии «Аполлон» к Луне

Materials from the US sources on the Apollo program were considered, and the presented data were evaluated from the point of view of external ballistics equations, flights of spacecraft to the Moon and their return to the Earth. The evaluation made it possible to determine inconsistency of the data (mass characteristics) in different documents relating to one object in the Apollo 11 mission. Inconsistencies were also found in the ballistic schemes for launching into the departure trajectory to the Moon, mooning, undocking and docking in the lunar orbit, braking maneuver to enter the lunar orbit, acceleration maneuver for returning to the Earth and braking maneuver for landing on the Earth’s surface. Analysis of the lunar missions’ documents formed the basis to ask questions that were not previously raised in such a formulation, and no answers were given to them. In particular, significant discrepancies in the initial data were found in the official documents on the US lunar missions. Reference orbit altitude before the second activation of the Saturn-5 3rd stage, the first space velocity at the Florida peninsula inclination and the second space velocity seem to be strange. Significant doubts are caused by acceleration schedule, projection of the flight path to the Earth and remoteness of the first stage impact area from the launch pad. In terms of the F-1 engines of the Saturn-5 launch vehicle first stage, thrust indicators of one engine and the total thrust of the first stage are not consistent. A conclusion is made that at present it is almost impossible to put into practice some of the maneuvers demonstrated in the US documents.

A multi-input based full envelope acceleration schedule design method for gas turbine engine based on multilayer perceptron network

Acceleration schedule design is a crucial task in gas turbine engine (GTE) control system design as it dramatically influences the acceleration performance of GTE. The corrected parameter based (CPB) method is the traditional solution for acceleration schedule design, which is simple to implement but could not fully exploit GTE acceleration performance in full envelope. It even fails to prevent the GTE from exceeding its surge margin boundary in some envelope points. In this paper, aiming to improve full envelope acceleration performance of GTE, a novel multi-input based (MIB) method for high-precision acceleration schedule design is proposed. Firstly, the full envelope acceleration schedule (FEAS) design problem is represented, and the CPB method is realized as a baseline. Then, the proposed MIB method is formulated, which integrates a combined input selection (CIS) strategy and a multilayer perceptron (MLP) network. With a weighted integration loss function to evaluate sensors of GTE, the CIS strategy determines appropriate inputs to design a high-precision and robust FEAS. The MLP network is employed to further enhance the FEAS precision. Finally, effectiveness of the proposed method is verified through a series of simulations and flight data verification. Compared with the CPB, the simulation results of acceleration processes under random envelope points indicate that the high-precision MIB method significantly improves acceleration performance of GTE and reduces its possibility of violating the surge margin boundary. Acceleration performances of the two methods are further compared under 1000 random envelope points, and similar results show the effectiveness of the MIB. Moreover, the CIS strategy performs better than other input selection strategies and contributes to enhancing the FEAS design precision and robustness. The MLP network is more qualified to improve FEAS precision than other classical machine learning models.

A multi-centre survey reveals variations in the standard treatments and treatment modifications for head and neck cancer patients during Covid-19 pandemic

BackgroundThe onset of the COVID-19 pandemic necessitated rapid changes to the practice of head and neck oncology in UK. There was a delay between the onset of the pandemic and the release of guidelines from cancer societies and networks, leading to a variable response of individual centres. This survey was conducted to assess the pre-Covid-19 pandemic standard of practice for head and neck oncology patients and the treatment modifications introduced during the first wave of the pandemic in UK. MethodologyThe UK National Cancer Research Institute (NCRI) Head and Neck Clinical Studies Group initiated a multi-centre survey using questionnaire to investigate the effect on feeding tube practice, radiotherapy (RT) fractionation and volumes, use of chemotherapy in the neo-adjuvant, concurrent and palliative setting, the use of immunotherapy in the palliative setting, access to radiology and histopathology services, and availability of surgical procedures. Results30 centres were approached across UK; 23 (76.7%) centres responded and were included in the survey. There were differences in the standard practices in feeding tube policy, RT dose and fractionation as well as concurrent chemotherapy use. 21 (91%) participating centres had at least one treatment modification. 15 (65%) centres initiated a change in radical RT; changing to either a hypofractionation or acceleration schedule. For post-operative RT 10 centres (43.5%) changed to a hypofractionation schedule. 12 (52.2%) centres stopped neo-adjuvant chemotherapy for all patients; 13 (56.5%) centres followed selective omission of chemotherapy in concurrent chemo-radiotherapy patients, 17 (73.9%) centres changed first-line chemotherapy treatment to pembrolizumab (following NHS England’s interim guidance) and 8 (34.8%) centres stopped the treatment early or offered delays for patients that have been already on systemic treatment. The majority of centres did not have significant changes associated with surgery, radiology, histopathology and dental screening. ConclusionThere are variations in the standard of practice and treatment modifications for head and neck cancer patients during Covid-19 pandemic. A timely initiative is required to form a consensus on head and neck cancer management in the UK and other countries.

Sequential ensemble optimization based on general surrogate model prediction variance and its application on engine acceleration schedule design

The Efficient Global Optimization (EGO) algorithm has been widely used in the numerical design optimization of engineering systems. However, the need for an uncertainty estimator limits the selection of a surrogate model. In this paper, a Sequential Ensemble Optimization (SEO) algorithm based on the ensemble model is proposed. In the proposed algorithm, there is no limitation on the selection of an individual surrogate model. Specifically, the SEO is built based on the EGO by extending the EGO algorithm so that it can be used in combination with the ensemble model. Also, a new uncertainty estimator for any surrogate model named the General Uncertainty Estimator (GUE) is proposed. The performance of the proposed SEO algorithm is verified by the simulations using ten well-known mathematical functions with varying dimensions. The results show that the proposed SEO algorithm performs better than the traditional EGO algorithm in terms of both the final optimization results and the convergence rate. Further, the proposed algorithm is applied to the global optimization control for turbo-fan engine acceleration schedule design.

PERCEPATAN JADWAL KONSTRUKSI DAN PENGARUHNYA TERHADAP BIAYA PENYELESAIAN PROYEK KONSTRUKSI

Means of transportation at present is very important to continue to be built effectively and efficiently to the level of fluency and accuracy of time toward the goal easier and faster and to meet minimum service standards of the highway. In line with that so that the toll road remain in the minimum service standards need to be additional road capacity to effectively and efficiently for that it is necessary to study whether the possible acceleration of road capacity expansion projects, so that the level of minimum service standards can be maintained and to what extent the effect of accelerating the schedule project on development costs.One method that can be used to analyze the effect of accelerating the project towards the costs is to analyze the exchange of money and time (time cost trade off).Variables used in the calculation of "Acceleration Schedule of Construction and Completion Costs Effect on Construction Project "is the direct labor, equipment, overtime working hours, method of construction, all have an influence on the different costs, acceleration (crash) or compression of time that have done the job and the biggest costs related to the work that has the greatest cost , a benefit if the toll road opened in advance of the acceleration due to a smaller project compared to the costs required for expediting the project construction on this project, based on the cost of the acceleration is not necessary because the costs to perform a greater acceleration when compared with a benefit.

Autonomous Mars-Gravity Enabling Quadrotor

Study of various physical phenomena in reduced gravity environments is of importance to several branches of science. This paper describes the trajectory design and automation control strategy for a quadrotor to maintain an acceleration such that a payload on-board experiences Mars-gravity for a short time period. A 1-D vertical trajectory with time varying acceleration is proposed for this purpose. A detailed kinematic analysis is presented to arrive at an acceleration schedule for the quadrotor to follow this trajectory. The analysis will also enable a designer to choose an appropriate motor-propeller combination for a quadrotor to follow this trajectory, given the constraints on peak altitude of the executed trajectory and duration for which reduced gravity needs to be maintained. The efficacy of the proposed approach and automation strategy is demonstrated using a detailed 6-DoF model simulation. Since the proposed trajectory is highly unsteady, the widely used steady state thrust model for quadrotors will not suffice. Therefore, a better thrust model is developed using blade element theory where the model parameters are estimated using experiments conducted in a wind tunnel. Our kinematic analysis shows that an appropriately designed quadrotor is capable of replicating Mars gravity environment for duration of 4 seconds while executing a vertical trajectory with peak altitude less than 45 m, which is validated through simulation and a preliminary flight test.

Phân tích các kỹ thuật đánh giá chậm trễ tiến độ dự án xây dựng - Ứng dụng thực tế tại dự án Luồng cho tàu biển tải trọng lớn vào sông Hậu

Schedule delays occur frequently in construction projects around the world and Vietnam; it probably leads to damages, impacts on financial matters and even causes myriad disputes in litigation among project parties. Hence, many delay analysis techniques have been proposed and used for analyzing schedule delay problems, namely the real-time delay, concurrent delay, pacing delay, acceleration schedule, float ownership and its consumption, resource allocation and productivity loss. However, no universal technique can solve all complex project situations and is widely accepted by project participants due to the inability of existing approaches to address thoroughly all aforementioned delay issues. This paper examines current delay analysis techniques by applying a real case study to identify which is the most ideal technique to give a reliable and an accurate result that can ensure a greatly acceptable outcome in resolving delay claims. Study results revealed that currently ideal technique is still necessary improved because of its shortcomings. Further researches may also develop an effective approach in full compliance with professional softwares that can solve all identified delay schedule-related problems.

A New Method for the Design of Optimal Control in the Transient State of a Gas Turbine Engine

To improve the control performance in the transient state of a gas turbine engine, a new method based on variable replacement method (VRM) and particle swarm optimization (PSO) algorithm is proposed. Above all, an acceleration schedule under the constraints of fuel air ratio ( $FAR$ ), high pressure turbine inlet temperature ( $T_{4}$ ) and high pressure compressor surge margin ( $SM$ ) could be obtained. Then PSO is employed to optimize the acceleration controller. At the same time, the deceleration controller is designed in consideration of minimum fuel ratio unit ( ${W_{f}}/{P_{s_{3}}}$ ) limiter. At last, a simulation is carried out to verify the performance of the proposed method and the results manifest that the optimized controller can track the acceleration command quickly and accurately, while accomplish the requirement of minimum fuel ratio unit (0.005) in deceleration.

A global optimization control for turbo-fan engine acceleration schedule design

A new optimization control method, which is based on the optimization employing Bezier curves of control variables, is proposed to improve engine thrust response performance. The minimum of the time consumption for control variables changing from start to end point is selected as objective function. Unlike conventional methods, the optimization variables are altered to the Bezier curves of the control variables in this scheme. This new acceleration optimization control only establishes one optimization problem for the overall acceleration process instead of establishing a series of sub optimization problems, which is usually adopted by conventional optimization controls. Hence, the proposed method is easier to overcome the disadvantage of the conventional ones, which just search for the optimal engine performance in local time period. Finally, for comparisons, the simulations for the proposed method and the conventional one have been both conducted. The simulations demonstrate that, although the conventional optimization control shows better performance in initial half part of acceleration process, however, the overall acceleration performance turns to be worse whereas for the new one, the acceleration time from idle to 95% of the maximum power is surprising decreased by 1.4 s compared to the conventional optimization control.

Disengaged scheduling for fair, protected access to fast computational accelerators

Today's operating systems treat GPUs and other computational accelerators as if they were simple devices, with bounded and predictable response times. With accelerators assuming an increasing share of the workload on modern machines, this strategy is already problematic, and likely to become untenable soon. If the operating system is to enforce fair sharing of the machine, it must assume responsibility for accelerator scheduling and resource management. Fair, safe scheduling is a particular challenge on fast accelerators, which allow applications to avoid kernel-crossing overhead by interacting directly with the device. We propose a disengaged scheduling strategy in which the kernel intercedes between applications and the accelerator on an infrequent basis, to monitor their use of accelerator cycles and to determine which applications should be granted access over the next time interval. Our strategy assumes a well defined, narrow interface exported by the accelerator. We build upon such an interface, systematically inferred for the latest Nvidia GPUs. We construct several example schedulers, including Disengaged Timeslice with overuse control that guarantees fairness and Disengaged Fair Queueing that is effective in limiting resource idleness, but probabilistic. Both schedulers ensure fair sharing of the GPU, even among uncooperative or adversarial applications; Disengaged Fair Queueing incurs a 4% overhead on average (max 18%) compared to direct device access across our evaluation scenarios.

Disengaged scheduling for fair, protected access to fast computational accelerators

Today's operating systems treat GPUs and other computational accelerators as if they were simple devices, with bounded and predictable response times. With accelerators assuming an increasing share of the workload on modern machines, this strategy is already problematic, and likely to become untenable soon. If the operating system is to enforce fair sharing of the machine, it must assume responsibility for accelerator scheduling and resource management. Fair, safe scheduling is a particular challenge on fast accelerators, which allow applications to avoid kernel-crossing overhead by interacting directly with the device. We propose a disengaged scheduling strategy in which the kernel intercedes between applications and the accelerator on an infrequent basis, to monitor their use of accelerator cycles and to determine which applications should be granted access over the next time interval. Our strategy assumes a well defined, narrow interface exported by the accelerator. We build upon such an interface, systematically inferred for the latest Nvidia GPUs. We construct several example schedulers, including Disengaged Timeslice with overuse control that guarantees fairness and Disengaged Fair Queueing that is effective in limiting resource idleness, but probabilistic. Both schedulers ensure fair sharing of the GPU, even among uncooperative or adversarial applications; Disengaged Fair Queueing incurs a 4% overhead on average (max 18%) compared to direct device access across our evaluation scenarios.

Alternate operating scenarios for NDCX-II

NDCX-II is a newly completed accelerator facility at LBNL, built to study ion-heated warm dense matter, as well as aspects of ion-driven targets and intense-beam dynamics for inertial-fusion energy. The baseline design calls for using 12 induction cells to accelerate 30–50nC of Li+ ions to 1.2MeV. During commissioning, though, we plan to extend the source lifetime by extracting less total charge. Over time, we expect that NDCX-II will be upgraded to substantially higher energies, necessitating the use of heavier ions to keep a suitable deposition range in targets. For operational flexibility, the option of using a helium plasma source is also being investigated. Each of these options requires development of an alternate acceleration schedule. The schedules here are worked out with a fast-running 1-D particle-in-cell code ASP.

Experimental Study of Transient Nitric Oxide, Smoke, and Combustion Noise Emissions during Acceleration of an Automotive Turbocharged Diesel Engine

The control of transient emissions from turbocharged diesel engines is an important objective for automotive manufacturers, since newly produced engines must meet the stringent criteria concerning exhaust emissions levels as dictated by the legislated Transient Cycles Certification. In the current study, experimental tests are conducted on an automotive, turbocharged diesel engine in order to investigate the formation mechanism of nitric oxide, smoke, and combustion noise emissions under various acceleration schedules experienced during daily driving conditions. To this aim, a fully instrumented test bed was set up in order to capture the development of key engine and turbocharger variables during the transient events. Analytical diagrams are provided to explain the behaviour of emissions development in conjunction with turbocharger and governor/fuel pump response. Turbocharger lag was found to be the main cause for the emission spikes during all test cases examined, with the engine calibration playing a vital role. The analysis was extended with a quasi-steady approximation of transient emissions using steady-state maps, in order to highlight the effect of dynamic engine operation on pollutants and combustion noise emissions.

Plans for Warm Dense Matter and IFE Target Experiments on NDCX-II

The Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL) is currently developing design concepts for NDCX-II, the second phase of the Neutralized Drift Compression Experiment, which will use ion beams to explore Warm Dense Matter (WDM) and Inertial Fusion Energy (IFE) target hydrodynamics. The ion induction accelerator will consist of a new short pulse injector and induction cells from the decommissioned Advanced Test Accelerator (ATA) at Lawrence Livermore National Laboratory (LLNL). To fit within an existing building and to meet the energy and temporal requirements of various target experiments, an aggressive beam compression and acceleration schedule is planned. WDM physics and ion-driven direct drive hydrodynamics will initially be explored with 30 nC of lithium ions in experiments involving ion deposition, ablation, acceleration and stability of planar targets. Other ion sources which may deliver higher charge per bunch will be explored. A test stand has been built at Lawrence Berkeley National Laboratory (LBNL) to test refurbished ATA induction cells and pulsed power hardware for voltage holding and ability to produce various compression and acceleration waveforms. Another test stand is being used to develop and characterize lithium-doped aluminosilicate ion sources. The first experiments will include heating metallic targets to 10,000 K and hydrodynamics studies with cryogenic hydrogen targets.

Developing acceleration schedules for NDCX-II*

The Virtual National Laboratory for Heavy-Ion Fusion Science is developing a physics design for NDCX-II, an experiment to study warm dense matter heated by ions near the Bragg-peak energy. Present plans call for using about thirty induction cells to accelerate 30 nC of Li + ions to more than 3 MeV, followed by neutralized drift-compression. To heat targets to useful temperatures, the beam must be compressed to a millimeter-scale radius and a duration of about 1 ns. An interactive 1-D particle-in-cell simulation with an electrostatic field solver, acceleration-gap fringe fields, and a library of realizable analytic waveforms has been used for developing NDCX-II acceleration schedules. Axisymmetric simulations with WARP have validated this 1-D model and have been used both to design transverse focusing and to compensate for injection non-uniformities and radial variation of the fields. Highlights of this work are presented here.

Design of Intelligent Acceleration Schedules for Extending the Life of Aircraft Engines

Aircraft engine controllers are designed and operated to provide desired performance and stability margins. This paper addresses the relationship between acceleration action and engine component life usage. Based upon this relationship, an intelligent approach for designing acceleration schedules that provide proper tradeoffs between performance and engine life usage is proposed. The benefit of this approach is that it is expected to maintain safety while minimizing the overall operating costs. With the advances of computer technology, engine operation models, and damage physics, it is necessary to reevaluate the control strategy for overall operating cost consideration. This paper uses the thermal--mechanical fatigue (TMF) of a critical component to demonstrate how an intelligent acceleration algorithm can drastically reduce the engine life usage with minimum sacrifice in performance. We have modeled and calculated the probability of failure due to TMF damage. A Monte Carlo simulation is also performed to evaluate the likelihood of engine damage accumulation under various operating conditions. By means of genetic search algorithms, optimal acceleration schedules can be obtained with multiple constraints. The simulation results show that a selected best acceleration schedule can provide a significant life saving in selected engine components.