Transcript Introduction to Ergonomics

Introduction to Ergonomics
Engineering
 Definitions
 Process:
Problem symptom or need
Problem Definition,
Statement of Desired Outcome
Analysis (Experimentation?)
Synthesis of Alternative
Solutions
Decision (Selection)
Process Example
 What are the design
considerations for a
prosthetic Leg?
Ergonomics - Introduction
 Derived from the Greek “nomos” – natural
laws, “ergon” – work
 Definition – discipline that uses knowledge
of human abilities to design systems, jobs,
tools, and products for the safe and efficient
execution of work.
 Ergonomic Objective:
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Worker Capacity <= Job Demands
Ergonomics - Introduction
 Worker Capacity <= Job Demands
 Methods:
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Workplace and Equipment Design
Tool Design
Design of Work Methods
Matching Capabilities and Limitations of Worker
Ergonomics – Introduction
 Why Important?
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Specialization / Automation
Diversity of Workforce / Labor Laws
Gender
 Aging Population
 Injured, Disabled workers
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Increase Productivity / Competitive Advantage
Prevent Injury / Reduce workers Comp Costs
Societal Quality of Life
Ergonomics and Physiology
 Relevant Subject Areas
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Muscular
Nervous
Circulatory
Digestive
Psychosocial
Cognitive
Sensory
Ergonomics and Physics
 Force
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Regularly exerted ON the body and BY the body
F=ma
Acts in a linear direction
Muscles generate force
Ergonomics and Physics
 Torque
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M=F*D
Acts as a moment about a fixed point
Muscles in conjunction with tendons, joins, and
ligaments generate torque.
Ergonomics and Physics
 Pressure
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Imparted BY the body and ON the body
P=F/A
Examples
Occupational Injury
 Difference between Ergonomics and Safety?
 Cumulative Trauma Disorders (CTD)
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Definition: Bodily injury associated with
repeated biomechanical stress over time.
Occupational Injury
 Risk Factors for Cumulative Trauma
Disorders
Cumulative Trauma Disorders
 Bursitis
 Tendonitis
 Tenosynovitis
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Tendon injury involving the synovial sheath,
caused when excessive amounts of synovial fluid
are created due to extreme repetition. Sheath
becomes swollen or painful.
Cumulative Trauma Disorders
 De Quervain’s Disease
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Tenosynovitis in the tendons at the base of the
thumb.
Finkelstein Test
Cumulative Trauma Disorders
 Trigger Finger (Flexor Tendonitis)
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Tendon swelling interferes with the normal
movement of the tendons through the synovial
sheath and can cause the finger to click, catch, or
lock in position
Cumulative Trauma Disorders
 Carpal Tunnel Syndrome
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Impaired nervous function in the first three digits
manifested as numbness, tingling, pain, and loss
of dexterity.
Median nerve inside the wrist becomes
compressed due to inflammation or thickening of
adjacent tendon sheaths. Inflammation may be
caused by overexertion or repeated unsafe wrist
orientations.
Tool Design Guidelines
 Improper Tool Design May Cause:
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Increased grip forces (CTD)
Unwanted postures (CTD)
Acute Trauma (Burns, cuts, lacerations,
abrasions, fractures, strains, sprains, dislocations,
etc.)
Reduced Productivity
Tool Design Guidelines
 Situations to avoid
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Sustained Ulnar/Radial Wrist deviation
Excessive or repeated flexion/extension of hand and
wrist
Excessive force
Impact shocks
Tissue compression from sharp edges or misdirected
forces
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Ischemia – obstruction of blood flow to the tissues and eventual
numbness or tingling
Tool Design Guidelines
 Types of Grip
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Power
Precision
 Design for Population
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Gender
Left/Right Handedness
Tool Design Guidelines
 Handle
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Diameter
Length
Shape
Surface (material)
Angulation
Grip Span
 Weight
Examples
 Pliers
 Knives
 Scissors
Engineering Design Constraints
 Example: The Vibration Dilemma
The Future
 Workplace and Equipment Design