الصفحات الشخصية - what is...
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Islamic University of Gaza - Palestine
WHAT is ERGONOMICS
Islamic University of Gaza - Palestine
What ergonomics “does” can be summed up in three
questions:
• Who (Human) was it designed for?
• What (Task) was it designed for?
• What environment was it designed to function with?
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Steps to identify and anticipate ergonomic problems
1. Become aware of problem
2. Analyze task and conditions
3. Identify problem
4. State needs and goals
5. Select candidate solution
6. Engineering control or managerial control
7. Implement solution
8. Check success
Yes- problem solved now return to step 2 or 5
Islamic University of Gaza - Palestine
Six Pillars of Ergonomic Design “Wisdom”
1. User Orientation: Design and application of tools, procedures, and systems must be user-oriented, rather than just “task” oriented
2. Diversity: Recognition of diversity in human capabilities and limitations, rather than “stereotyping” workers/users
3. Effect on Humans: Tools, procedures, and systems are not “inert”, but do influence human behaviour and well-being
What is Ergonomics? “Wisdom”
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Six Pillars of Ergonomic Design “Wisdom”
4. Objective Data: Empirical information and evaluation is key in design process, rather than just use of “common
sense”
5. Scientific Method: test and retest hypothesis with real data, rather than “anecdotal” evidence or “good
estimates”
6. Systems: object, procedures, environments, and people are interconnected, affect one another, and do not exist
in “isolation”
What is Ergonomics? “Wisdom” (cont.)
Islamic University of Gaza - Palestine
Life-Cycle of Products, Procedures, and Systems
1. Initial Idea: driven by customers, technology change,
competitors, problems, needs
2. Requirements: user, manufacturer, standards,
government, cost, profit, marketing/sales
3. Concepts: design alternatives, comparison, choose best
one
4. Design: detail parts, integrating with rest of system,
prototype testing, optimization
What is Ergonomics? -Life-Cycle of Products-
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Life-Cycle of Products, Procedures, and Systems
5. Manufacturing: material, processes, assembly
6. Distribution/Sale: shipping, display, delivery, installation,
warranty
7. Use: security, safety, access, maintenance, repair
8. Disposal: toxicity, recycling, reusability, upgrade
What is Ergonomics? - Life-Cycle of Products- (cont.)
Islamic University of Gaza - Palestine
Biomechanics
“Biomechanics uses the laws of physics and engineering
concepts to describe motion undergone by the various
body segments and the forces acting on these body parts
during normal daily activities” (Frankel and Nordin, 1980)
Occupational Biomechanics
“Occupational biomechanics is …. the study of the physical
interruption of workers with their tools, machines, and
materials so as to enhance the worker’s performance
while minimizing the risk of musculoskeletal disorders.”
(Chaffin et al., 1999)
What is Occupational Biomechanics?
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Biomechanics – What is it?
• The mechanical bases of biological systems.
• The application of mechanical laws to living structures.
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OCCUPATIONAL ERGONOMICS
& BIOMECHANICS
Biomechanical
Modeling Methods
Anthropometric
MethodsBioinstrumentation
Methods
Classifying and
Evaluating Work
Mechanical Work
Capacity
Evaluation
Methods
Kinesiology
Methods
Worker
Selection
Criteria & Training
Hand Tool
Design
Guidelines
Workplace &
Machine
Guidelines
Seating Design
Guidelines
Material
Handling Limits
Improved Performance &
Reduced Risk of Mechanical Trauma[Chaffin et al, 1999]
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Occupational Biomechanics
• Occupational Biomechanics is a sub-discipline within the general field of biomechanics which studies the physical
interaction of workers with their tools, machines and
materials so as to enhance the workers performance while
minimizing the risk of musculoskeletal injury.
• Motivation:
– About 1/3 of U.S. workers perform tasks that require
high strength demands
– Costs due to overexertion injuries - LIFTING
– Large variations in population strength
– Basis for understanding and preventing overexertion
injuries
Islamic University of Gaza - Palestine
Kinesiology – Is it the same as biomechanics?
• Kinesis (motion) + -logy (science, study of)
• Applied anatomy and mechanics
• Rasch & Burke (1978). Kinesiology
=anatomy (science of structure)
+physiology (science of body function)
+mechanics (science of movement)= science of movement of the human body.
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Kinesiology (cont.)
• Old (pre-1980) usage
– Title of a functional (applied) anatomy + biomechanics
course (“Kinesiology”).
• Continue to see that use
– many programs now put extra descriptors in the title for
clarification (e.g., “Anatomical Kinesiology”, “Functional
Anatomy and Kinesiology”).
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Kinesiology (cont.)
• Current (post-1980) usage
– One of several terms used to characterize the discipline
or field (e.g., “Department of Kinesiology”).
• Other terms include “Exercise Science and Physical
Education”, “Exercise and Sport Sciences”, “Human
Movement Studies”, or “Movement Science”.
– Potentially an umbrella term for any form of anatomical,
physiological, psychological, or mechanical analysis of
human movement.
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Biomechanics: Does it exist in more than one field?
• Exercise and sport biomechanics
• Orthopedic biomechanics
• Occupational biomechanics
• Biomechanics of other biological systems
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• Exercise and sport biomechanics
– improving athletic performance, reduction of athletic
injuries
Biomechanics: Does it exist in more than one field?
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• Orthopedic biomechanics
– artificial limbs, joints, and orthoses to improve functional
movement capacity
– study of natural and artificial biological tissues
Biomechanics: Does it exist in more than one field?
Islamic University of Gaza - Palestine
• Occupational Biomechanics
– Ergonomics and Human Factors
– reduction of workplace injuries
Biomechanics: Does it exist in more than one field?
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• Biomechanics of other biological systems
– Comparative biomechanics (e.g., swimming in fish,
locomotion in apes)
– Equine (horse) and canine (dog) racing performance
Biomechanics: Does it exist in more than one field?
Islamic University of Gaza - Palestine
What do we have in common?
• Application of fundamental mechanical principles to the
study of structure and function of living systems.
• Common measurement and analysis tools.
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Divisions of
Mechanics
(Bio)mechanics
Statics Dynamics Fluids
Kinematics Kinetics
Linear Angular
Deformable
Solids
Stress Strain
Islamic University of Gaza - Palestine
Why Study Biomechanics?
• From a mechanical perspective…
– How do we generate and control our movements?
– What mechanical and/or anatomical factors determine or
limit movement outcomes?
– How can we make our movements “better”?
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Problems (example)
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Free-Body Diagrams
• Free-body diagrams are schematic representations of a
system identifying all forces and all moments acting on
the components of the system.
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2-D Model of the Elbow
From Chaffin, DB and Andersson, GBJ (1991) Occupational Biomechanics.
17.0 cm
35.0 cm
180 N
10 N
Unknown Elbow force
and moment
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From Chaffin, DB and Andersson, GBJ (1991) Occupational Biomechanics. Fig 6.7
2-D Model of the Elbow
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Assumptions Made in 2-D Static Analysis
• Joints are frictionless
• No motion
• No out-of-plane forces (Flatland)
• Known anthropometry (segment sizes and weights)
• Known forces and directions
• Known postures
• 1 muscle
• Known muscle geometry
• No muscle antagonism (e.g. triceps)
• Others
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3-D Biomechanical Models
• These models are difficult to build due to the increased
complexity of calculations and difficulties posed by
muscle geometry and indefiniteness.
• Additional problems introduced by indefinity; there are
fewer equations of equilibrium (balance) than unknowns
muscle forces.
• While 3-D models are difficult to construct and validate,
3-D components of lifting, especially lateral bending,
appear to significantly increase risk of injury.
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From Biomechanics to Task Evaluation
• Biomechanical analysis yields external moments at
selected joints
• Compare external moments with joint strength
(maximum internal moment)
– Typically use static data, since dynamic strength
data are limited
– Use appropriate strength data (i.e. same posture)
• Two Options:
– Compare moments with an individuals joint
strength
– Compare moments with population distributions to
obtain percentiles (more common)
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Task Evaluation and Ergonomic Controls
• Demand (moments) < Capacity (strength)
• Are the demands excessive?
– Is the percentage capable too small?
– What is an appropriate percentage? [95% or 99%
capable commonly used]
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• Strategies to Improve the Task:
– Decrease Demand (D)
• Forces: masses, accelerations (increase or decrease,
depending on the specific task)
• Moment arms: distances, postures, work layout
– Increase Capacity (C)
• Design task to avoid loading of relatively weak joints
• Maximize joint strength
• Use only strong workers
Task Evaluation and Ergonomic Controls (cont.)