Investigation of Chinook helicopter operations with an external slung load after cable failure

2010 ◽  
Vol 114 (1156) ◽  
pp. 345-365
Author(s):  
M. D. Pavel
Keyword(s):  
Linear Model ◽  
Air Force ◽  
Integrated Approach ◽  
Suspension System ◽  
Operating Costs ◽  
Load Following ◽  
System A ◽  
Non Linear ◽  
External Loads

Abstract The Royal Netherlands Air Force (RNLAF) conducts frequent operations of Chinook helicopters with external slung loads. The normal RNLAF practice is for large external loads to be underslung by means of a two-strop suspension system backed up by a third point of suspension, the so-called ‘redundant HUSLE (Helicopter Underslung Load Equipment)’ comprising a redundant set of slings which come into action if one of the normal strops fails. The redundant HUSLE is relatively expensive in terms of time and operating costs. The present work has investigated the behaviour of a Chinook helicopter with an underslung load following failure of a front or rear strop, to determine whether the three-point suspension system can be safely replaced by a two-point suspension, eliminating the redundant HUSLE. The paper will demonstrate that although in general the redundant HUSLE results in a less violent helicopter reaction to a cable failure, it does not necessarily guarantee safety. It is concluded that flying with loads up to around two tonnes could be done safely with a two-point suspension system. A novel feature of this analysis of helicopter operations with slung loads is the integrated approach used for simulating pilot-in-the-loop load failures using a full non-linear model.

Effect of Non-Linear Components on the Performance of a Hydro -Pneumatic Slow-Active Suspension System

1996 ◽  
Vol 210 (1) ◽  
pp. 23-34 ◽  
Author(s):  
S M El-Demerdash ◽  
D A Crolla
Keyword(s):  
Linear Model ◽  
Linear Models ◽  
Ride Comfort ◽  
Active Suspension ◽  
Front Wheel ◽  
Suspension System ◽  
Approximation Technique ◽  
Active System ◽  
Working Space ◽  
Non Linear

In this work, the effects of component non-linearities on the ride performance of a hydro-pneumatic slow-active suspension system are studied theoretically. Based on the quarter car linear model, linear optimal control theory is used to calculate the feedback and feedforward gains. These gains are used in both linear and non-linear models with and without preview control. The Pade approximation technique is used to represent the preview time resulting from a preview sensor mounted on the vehicle front bumper to measure the road irregularities ahead of the front wheel. The results on a typical major road showed that at similar r.m.s. values of suspension working space, the non-linear slow-active system with preview provided a 28 per cent improvement in ride comfort and a 17 per cent reduction in dynamic tyre load compared with a passive system. However, the inclusion of non-linear effects of the components increases the ride comfort acceleration by 10 per cent and suspension working space by 12 per cent compared to the equivalent linear model at approximately equal values of r.m.s. dynamic tyre load.

Modelling of a Controlled Pneumatic Swing-Plug Train Door

1995 ◽  
Vol 209 (2) ◽  
pp. 87-92 ◽  
Author(s):  
Y W Post ◽  
H J van Oostveen ◽  
A J J van der Weiden
Keyword(s):  
Linear Model ◽  
Computer Simulations ◽  
Mathematical Description ◽  
Measured Data ◽  
System A ◽  
Non Linear ◽  
Set Up ◽  
Linearized Model ◽  
Simulation Package

In this paper, a mathematical description will be given for a controlled pneumatic swing-plug train door. On the basis of the significant dynamics in the door system, a non-linear model is derived and implemented into the simulation package ‘SystemBuild'. Computer simulations of a closing procedure show that this non-linear model closely correlates with measured data of an experimental set-up. Linearization of the model gives rise to a drastic simplification. This linearized model is used to predict the influences of parameters on the door's behaviour.

Application and Implementation of LQ Design Method for the Velocity Control of Hydrostatic Transmissions

1995 ◽  
Vol 209 (4) ◽  
pp. 255-268 ◽  
Author(s):  
J Lennevi ◽  
J-O Palmberg
Keyword(s):  
Linear Model ◽  
Power Transmission ◽  
Design Method ◽  
Stiff Systems ◽  
Velocity Control ◽  
Test Rig ◽  
System A ◽  
Non Linear ◽  
Hydrostatic Transmissions ◽  
Linearized Model

Hydrostatic transmissions are inherently low damped and stiff systems which are increasingly used for the power transmission in vehicle drivetrains. For the velocity control of hydrostatic transmissions the regulator must contribute to the damping of the system. A non-linear and a linearized model of the system are presented. LQG design is applied and the obtained regulator is implemented in different ways. The implementations are compared and discussed with respect to their merits and drawbacks. Results for evaluation and validation are obtained by means of simulation of a non-linear model and experiments in a test rig.

scholarly journals Influence of the Porosity of Polymer Foams on the Performances of Capacitive Flexible Pressure Sensors

Sensors ◽  
2019 ◽  
Vol 19 (9) ◽  
pp. 1968 ◽  
Author(s):  
Sylvie Bilent ◽  
Thi Hong Nhung Dinh ◽  
Emile Martincic ◽  
Pierre-Yves Joubert
Keyword(s):  
Experimental Data ◽  
Linear Model ◽  
Dielectric Material ◽  
Pressure Sensors ◽  
Volume Ratio ◽  
Measurement Range ◽  
Polymer Foams ◽  
First Order ◽  
Non Linear ◽  
Flexible Pressure Sensors

This paper reports on the study of microporous polydimethylsiloxane (PDMS) foams as a highly deformable dielectric material used in the composition of flexible capacitive pressure sensors dedicated to wearable use. A fabrication process allowing the porosity of the foams to be adjusted was proposed and the fabricated foams were characterized. Then, elementary capacitive pressure sensors (15 × 15 mm2 square shaped electrodes) were elaborated with fabricated foams (5 mm or 10 mm thick) and were electromechanically characterized. Since the sensor responses under load are strongly non-linear, a behavioral non-linear model (first order exponential) was proposed, adjusted to the experimental data, and used to objectively estimate the sensor performances in terms of sensitivity and measurement range. The main conclusions of this study are that the porosity of the PDMS foams can be adjusted through the sugar:PDMS volume ratio and the size of sugar crystals used to fabricate the foams. Additionally, the porosity of the foams significantly modified the sensor performances. Indeed, compared to bulk PDMS sensors of the same size, the sensitivity of porous PDMS sensors could be multiplied by a factor up to 100 (the sensitivity is 0.14 %.kPa−1 for a bulk PDMS sensor and up to 13.7 %.kPa−1 for a porous PDMS sensor of the same dimensions), while the measurement range was reduced from a factor of 2 to 3 (from 594 kPa for a bulk PDMS sensor down to between 255 and 177 kPa for a PDMS foam sensor of the same dimensions, according to the porosity). This study opens the way to the design and fabrication of wearable flexible pressure sensors with adjustable performances through the control of the porosity of the fabricated PDMS foams.

Analysis of Single Buffer Random Polling System With State-Dependent Input Process and Server/Station Breakdowns

2018 ◽  
Vol 9 (1) ◽  
pp. 22-50 ◽  
Author(s):  
Thomas Y.S. Lee
Keyword(s):  
Steady State ◽  
Linear Model ◽  
Repair Process ◽  
Polling System ◽  
Steady State Analysis ◽  
Relaxation System ◽  
Polling Model ◽  
State Dependent ◽  
Non Linear ◽  
State Analysis

Models and analytical techniques are developed to evaluate the performance of two variations of single buffers (conventional and buffer relaxation system) multiple queues system. In the conventional system, each queue can have at most one customer at any time and newly arriving customers find the buffer full are lost. In the buffer relaxation system, the queue being served may have two customers, while each of the other queues may have at most one customer. Thomas Y.S. Lee developed a state-dependent non-linear model of uncertainty for analyzing a random polling system with server breakdown/repair, multi-phase service, correlated input processes, and single buffers. The state-dependent non-linear model of uncertainty introduced in this paper allows us to incorporate correlated arrival processes where the customer arrival rate depends on the location of the server and/or the server's mode of operation into the polling model. The author allows the possibility that the server is unreliable. Specifically, when the server visits a queue, Lee assumes that the system is subject to two types of failures: queue-dependent, and general. General failures are observed upon server arrival at a queue. But there are two possibilities that a queue-dependent breakdown (if occurs) can be observed; (i) is observed immediately when it occurs and (ii) is observed only at the end of the current service. In both cases, a repair process is initiated immediately after the queue-dependent breakdown is observed. The author's model allows the possibility of the server breakdowns/repair process to be non-stationary in the number of breakdowns/repairs to reflect that breakdowns/repairs or customer processing may be progressively easier or harder, or that they follow a more general learning curve. Thomas Y.S. Lee will show that his model encompasses a variety of examples. He was able to perform both transient and steady state analysis. The steady state analysis allows us to compute several performance measures including the average customer waiting time, loss probability, throughput and mean cycle time.

Development of a Performance Rating Standard for Residential Fuel Cell Systems

2006 ◽  
Author(s):  
Michael W. Ellis ◽  
Mark W. Davis ◽  
A. Hunter Fanney ◽  
Brian P. Dougherty ◽  
Ian Doebber
Keyword(s):  
Fuel Cell ◽  
Performance Standards ◽  
Cell System ◽  
Fuel Cell System ◽  
Experimental Procedure ◽  
Cell Systems ◽  
Load Following ◽  
System A ◽  
Experimental Apparatus ◽  
Using Data

Fuel cell systems for residential applications are an emerging technology for which specific consumer-oriented performance standards are not well defined. This paper presents a proposed experimental procedure and rating methodology for evaluating residential fuel cell systems. In the proposed procedure, residential applications are classified as grid independent load following; grid connected constant power; grid connected thermal load following; and grid connected water heating. An experimental apparatus and procedures for steady state and simulated use tests are described for each type of system. A rating methodology is presented that uses data from these experiments in conjunction with standard residential load profiles to quantify the net effect of a fuel cell system on residential utility use. The experiments and rating procedure are illustrated using data obtained from a currently available grid connected thermally load following system.

Selection of models to describe the temperature-dependent development of Neoleucinodes elegantalis (Lepidoptera: Crambidae) and its application to predict the species voltinism under future climate conditions

2021 ◽  
pp. 1-9
Author(s):  
Hevellyn Talissa dos Santos ◽  
Cesar Augusto Marchioro
Keyword(s):  
Climate Change ◽  
Linear Model ◽  
Future Climate ◽  
Future Climate Change ◽  
Climate Change Scenarios ◽  
Temperature Dependent ◽  
Dependent Development ◽  
Degree Day ◽  
Non Linear ◽  
The Impact

Abstract The small tomato borer, Neoleucinodes elegantalis (Guenée, 1854) is a multivoltine pest of tomato and other cultivated solanaceous plants. The knowledge on how N. elegantalis respond to temperature may help in the development of pest management strategies, and in the understanding of the effects of climate change on its voltinism. In this context, this study aimed to select models to describe the temperature-dependent development rate of N. elegantalis and apply the best models to evaluate the impacts of climate change on pest voltinism. Voltinism was estimated with the best fit non-linear model and the degree-day approach using future climate change scenarios representing intermediary and high greenhouse gas emission rates. Two out of the six models assessed showed a good fit to the observed data and accurately estimated the thermal thresholds of N. elegantalis. The degree-day and the non-linear model estimated more generations in the warmer regions and fewer generations in the colder areas, but differences of up to 41% between models were recorded mainly in the warmer regions. In general, both models predicted an increase in the voltinism of N. elegantalis in most of the study area, and this increase was more pronounced in the scenarios with high emission of greenhouse gases. The mathematical model (74.8%) and the location (9.8%) were the factors that mostly contributed to the observed variation in pest voltinism. Our findings highlight the impact of climate change on the voltinism of N. elegantalis and indicate that an increase in its population growth is expected in most regions of the study area.

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