Performance based approach to investigate

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• ATM Seminar 2013 • Olga Gluchshenko • Performance based approach to investigate resilience and robustness of an ATM System
Performance based approach to investigate
resilience and robustness of an ATM System
DLR - German Aerospace Center
Institute of Flight Guidance
Olga Gluchshenko, Peter Foerster
Tenth USA/Europe Seminar on ATM R&D June 10-13, 2013 in Chicago, IL, USA
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• ATM Seminar 2013 • Olga Gluchshenko • Performance based approach to investigate resilience and robustness of an ATM System
Outline
• Terminology framework
• Decision-making chain
• Measures of resilience and robustness
• New modeling approach and performance based approach
• Conclusions
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• ATM Seminar 2013 • Olga Gluchshenko • Performance based approach to investigate resilience and robustness of an ATM System
Usage of terms in different domains
Disturbance and perturbation are used to denote:
1.
a cause
2.
an effect
3.
a cause and an effect, respectively
term
used in synonymic
sense
Robustness
Resilience
Resilience
Stability
Resistance
Recovery
Stability
Elasticity
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• ATM Seminar 2013 • Olga Gluchshenko • Performance based approach to investigate resilience and robustness of an ATM System
Usage of terms in different domains
1. ”the time required for a system to return to an equilibrium or steady-state following
a perturbation“ - has been termed as ”engineering resilience“ (Holling 1996)
2. ”the ability of a system to absorb changes of state variables, driving variables, and
parameters, and still persist“ - has been named ”ecological resilience“ (Holling 1996)
 ”Resilience engineering is a paradigm for safety management that focuses on how to
help people cope with complexity under pressure to achieve success“ (Hollnagel 2006)
”Resilience is the intrinsic ability of a system to adjust its functioning prior to, during,
or following changes and disturbances, so that it can sustain required operations under
both expected and unexpected conditions“(Hollnagel 2006, EUROCONTROL 2009)
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• ATM Seminar 2013 • Olga Gluchshenko • Performance based approach to investigate resilience and robustness of an ATM System
Usage of terms in different domains
Oxford Dictionary: robust (adj.)
- sturdy in construction;
- able to withstand or overcome adverse conditions;
- uncompromising and forceful;
Oxford Dictionary: resilient (adj.)
- able to recoil or spring back into shape after bending, stretching,
or being compressed;
- able to withstand or recover quickly from difficult conditions;
Edward J. Rykiel, Towards a definition of ecological disturbance,
Australian Journal of Ecology, Volume 10, Issue 3, pages 361–365, September 1985
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• ATM Seminar 2013 • Olga Gluchshenko • Performance based approach to investigate resilience and robustness of an ATM System
Terminology framework
an ATM System
System is a framework of objects and relations with particular attributes (Bruns 1991)
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• ATM Seminar 2013 • Olga Gluchshenko • Performance based approach to investigate resilience and robustness of an ATM System
Terminology framework
Assumptions:
• an ATM System (the whole ATM system or any of its subsystems, for instance, a
planning system, an airport etc.) is driven by economic interests of the participating
stakeholders, i.e. it is performance oriented;
an ATM System
• its performance is evaluated by means of a set of (key) performance indicators that
describe a state of the system;
• an evaluation is always done by one evaluator that represents either a
person/organization point of view or one collaborative point of view expressed by
a reference state (otherwise - set of independent views or evaluations);
• the evaluator defines time scales - how long a description of the (reference) state
by means of the specified set of (key) performance indicators will be valid.
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• ATM Seminar 2013 • Olga Gluchshenko • Performance based approach to investigate resilience and robustness of an ATM System
Terminology framework
an ATM System
Current state of a system is defined by the current values of its performance indicators.
Reference state of a system is the specified set of performance indicators values.
A reference state relative to the current state of the system can be either an actual
reference state or a potential reference state . A potential reference state may be
realistic or nonrealistic with respect to the existing operational conditions.
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• ATM Seminar 2013 • Olga Gluchshenko • Performance based approach to investigate resilience and robustness of an ATM System
Terminology framework
disturbance
an ATM System
Disturbance – (a cause) a phenomenon, factor, or process, either internal or
external, which may cause a stress in a system; is relative to the specified
reference state and considered system; is categorised and quantified by type,
frequency, intensity and duration.
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Terminology framework
disturbance
an ATM System
*the scale in which the system is defined and observed is a most important factor
determining the level of detail required in characterizing disturbances and their
impact on the system;
*in a hierarchically structured system, a disturbance at any level can be
“absorbed” by moving up the hierarchy.
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Terminology framework
disturbance
an ATM System
lethal stress
survival stress
no stress
Stress – (an effect – a reaction of a system) the state of a system caused by a
disturbance which differs from the reference state and is characterised by deviation
from this reference condition; can be

Survival – if the system can respond by perturbation without modification to
change the current state;

Lethal – if the system cannot or should not respond by perturbation to change the
current state and has to be modified;
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Terminology framework
disturbance
an ATM System
lethal stress
survival stress
no stress
Perturbation – (an effect - an action of a system) the response of a system to the
possible or current significant undesirable changes of the state of the system
caused by a disturbance.
Perturbation aims at preventing of the changes and/or at minimizing of deviation
of the current values from the reference values of performance indicators.
In the case when stress is unavoidable, but survival, perturbation can be
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Terminology framework
disturbance
an ATM System
lethal stress
permanent perturbation
survival stress
no stress
transient perturbation

Transient – if it enables temporary deviation which becomes zero over time
with return to the reference state;

Permanent – if deviation becomes fixed over time leading to a state of the
system different from the reference state.
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Terminology framework
Robustness – the ability of a system to
experience no stress since a disturbance
disturbance
Robustness
of system
had occurred, i.e. the system is robust
against the disturbance;
is relative to the specified reference state
an ATM System
of the system and a particular disturbance.
lethal stress
permanent perturbation
survival stress
no stress
transient perturbation
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Terminology framework
Resilience – the ability of a system to
respond on a disturbance within a time
horizon by transient perturbation, i.e.
the system is resilient against the
disturbance over the considered time
horizon;
is relative to the specified reference
state of the system and a particular
disturbance.
disturbance
Robustness
of system
an ATM System
lethal stress
permanent perturbation
survival stress
no stress
transient perturbation
Resilience of system
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Terminology framework
Uncertainties:
1. type, frequency, intensity,
duration and time of occurrence
disturbance
Robustness
of system
2. type of stress
an ATM System
3. type of perturbation
lethal stress
permanent perturbation
Modification
of system
New reference
state of system
survival stress
no stress
transient perturbation
Resilience of system
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Terminology framework
disturbance
stress time Ts
reference
state
stress
state
state of
system
time
magnitude of
perturbation
perturbation
time T p
time
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Terminology framework - reference state:
At the moment of its specification
‐
an actual reference state, when the current values of the performance indicators are in the specified set of performance indicators values
or
‐
a potential reference state, when at least one of the current values of the performance indicators is not in the specified set of performance indicators values
‐
a realistic potential reference state
‐
a nonrealistic potential reference state
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Terminology framework - actual reference state
Uncertainties:
1. type, frequency, intensity,
duration and time of occurrence
disturbance
Robustness
of system
2. type of stress
an ATM System
3. type of perturbation
lethal stress
permanent perturbation
Modification
of system
New reference
state of system
survival stress
no stress
transient perturbation
Resilience of system
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Terminology framework - realistic potential ref. state
Uncertainties:
1. type, frequency, intensity,
duration and time of occurrence
disturbance
2. type of stress
an ATM System
3. type of perturbation
lethal stress
permanent perturbation
Modification
of system
New reference
state of system
survival stress
transient perturbation
Resilience of system
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Terminology framework - nonrealistic potential ref. state
Uncertainties:
1. type, frequency, intensity,
duration and time of occurrence
disturbance
2. type of stress
an ATM System
lethal stress
permanent perturbation
Modification
of system
New reference
state of system
survival stress
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System properties and according decision-making chain
consider/modify
system
set PI,reference
state
measure
robustness
control PI
yes
resilience
set ∆ t
control PI
yes
no
measure
resilience
survival
stress?
yes
stress during
∆ t?
robustness
no
disturbance?
no
yes
transient
perturbation
during ∆ t?
no
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Some ways to measure resilience and robustness
Resilience:
qualitative measure
 high resilience - time of deviation is considerably longer than time of recovery;
 medium resilience - time of deviation and time of recovery are approx. equivalent;
 low resilience - time of deviation is considerably shorter than time of recovery.
www.DLR.de/fl • Chart 24 • ATM Seminar 2013 • Olga Gluchshenko • Performance based approach to investigate resilience and robustness of an ATM System
Some ways to measure resilience and robustness
Resilience:
qualitative measure
 high resilience - time of deviation is considerably longer than time of recovery;
 medium resilience - time of deviation and time of recovery are approx. equivalent;
 low resilience - time of deviation is considerably shorter than time of recovery.
quantitative measure
 degree of recovery in a specified time;
 the overall time a system needs to come back to the reference state;
 the overall costs of this “comeback”.
www.DLR.de/fl • Chart 25 • ATM Seminar 2013 • Olga Gluchshenko • Performance based approach to investigate resilience and robustness of an ATM System
Some ways to measure resilience and robustness
Robustness:
quantitative measure
 the maximal “amount” of a disturbance quantified by frequency, intensity and
duration, which can be absorbed by a system, i.e. the system has no stress;
 the minimal distance to the limits of robustness, where a system still has no stress,
for a particular disturbance of some frequency, intensity and duration.
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Modeling approach - socio-technical view on an ATM
system
An ATM System has the following properties:
‐ complex structures in space and time scales
‐ organization of processes by human with help of supporting tools
‐ dynamic, but insufficient flows of data and information
‐ hierarchical structure
‐ stochastic influences
To investigate resilience and robustness:
‐ a modeling approach has to be found
‐ consider all relevant features of the system
‐ has to be realizable
‐ a simplified generic ATM model limited by physical aspects only
‐ one level of detail
‐current methods and applications like flow models, microscopic models show
differens scope and level of detail, cover different aspects of the ATM System
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Modeling approach - socio-technical view on an ATM
system
Government and Societies
Airport
Airport Ground
Operations Unit
Ground Handlers
Airline
Airline Operation
Centre
Pilots
ANSP
ATC, Safety,
Operations Units
Controllers
ESP
Operations Unit
ATF Managers
www.DLR.de/fl • Chart 28 • ATM Seminar 2013 • Olga Gluchshenko • Performance based approach to investigate resilience and robustness of an ATM System
Performance based approach to investigate resilience
and robustness of an (ATM) System:
1. Define and describe the system and its boundary to the environment;
2. Specify the scale and the level of hierarchy to observe;
3. Define performance indicators describing a state of the system;
4. Specify the reference state of the system;
5. Indicate and classify disturbances by type (of effect), frequency, intensity and duration
keeping in mind that the scale in which the system is defined and observed is the most important factor determining the level of detail required in characterizing disturbances and their impact on the system;
6. Set the time horizon and investigate resilience or robustness of the system.
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In order to obtain a more robust or more resilient system against a
particular disturbance one has to:
-
Investigate the system
Adapt resources, processes and the behavior of the system accordingly
Find potential alternative ways that lead to the same goal, which are
as independent as possible
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Conclusions:
new terminology framework with the clear differentiation between the terms resilience and robustness
the universal character of the terminology allows a general application on socio‐technical systems on different scales proposition how to measure resilience and robustness
modeling approach focused on the abstraction of the system in the form of stakeholders on the one and the movement of the aircraft on the other hand
performance based approach to investigate resilience and robustness
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Thank you for your attention!
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