MEBB 314 Unit hhhhhhhhhhhhgggggghhhV.pptx

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Industrial Engineering
(Course Code - MEBB 314)
By-
Dr. Shailesh M Pandey
Assistant Professor
Department of Mechanical and Aerospace Engineering
National Institute of Technology, Delhi

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Unit-V
Introduction to Ergonomics

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Ergonomics (Human Engineering)
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 Ergonomics is the study of the interaction between people and machines and the factors
that affect the interaction.
 Its purpose is to improve the performance of systems by improving human machine
interaction. This can be done by ‘designing-in’ a better interface or by ‘designing-out’ factors
in the work environment, in the task or in the organisation of work that degrade human–
machine performance.
The task of ergonomics is to develop such conditions for workers, which are necessary to
reduce physical workload, to improve working postures, facilitate instrument handling, and
thus improves the quality of working life, maximize efficiency of production operators and
minimize human errors.
Ergonomics is defined as the application of human biological sciences in conjunction with
engineering sciences to the worker and his working environment so as to obtain maximum
satisfaction for the worker which, at the same time, enhances productivity.
Ergonomics is a multi-disciplinary science comprises subjects like anatomy, psychology,
physiology, sociology, engineering, physics and medicine.

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Focus of Ergonomics
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 The focus is on the interaction between the person and the machine and the design of the
interface between the two.
 Every time we use a tool or a machine we interact with it via an interface (a handle, a
steering wheel, a computer keyboard and mouse, etc.). We get feedback via an interface (the
dashboard instrumentation in a car, the computer screen, etc.) The way this interface is
designed determines how easily and safely we can use the machine.

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Objectives of Ergonomics
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Optimize the integration of man and machine in order to increase the productivity and
accuracy with lesser amount of physical and mental strains.
It involves the design of:
a work place suitable for the worker.
machinery and controls, so as to minimize mental and physical strain on the worker to enable
the improvement in efficiency.
a favourable environment for performing the task most effectively.
task and work organization.

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Importance of Ergonomics in equipment design
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 Ergonomics in equipment design focuses on making tools, machines, and devices
compatible with human abilities, limitations, and needs.
 When applied effectively, ergonomic design ensures that equipment is safe, efficient,
comfortable, and user-friendly, ultimately enhancing performance and reducing risks.
Various reasons why ergonomics is important in equipment design?
1. Enhances User Comfort:
• Properly designed equipment fits the user’s body and minimizes strain.
• Reduces discomfort, fatigue, and stress during operation.
 Example: An ergonomically designed chair provides lumbar support to reduce back pain.

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2. Improves Safety:
• Reduces the risk of injuries, particularly musculoskeletal disorders (MSDs) caused by
repetitive strain or awkward postures.
• Helps prevent accidents due to poor control layouts, excessive force, or confusing
interfaces.
 Example: A power tool with a grip designed to reduce wrist twisting lowers injury risk.
3. Boosts Productivity:
• Comfortable and intuitive equipment design helps users work faster and more accurately.
• Less time is lost to fatigue, discomfort, or error correction.
 Example: A well-designed keyboard can increase typing speed while reducing errors and
wrist strain.

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4. Reduces Human Error:
• Equipment designed with ergonomics in mind is easier to understand, control, and
monitor.
• Reduces cognitive load, leading to fewer operational mistakes.
 Example: Clear labeling and intuitive controls on a medical device help prevent misuse.
5. Improves User Satisfaction and Acceptance:
• Ergonomically designed tools are more comfortable and enjoyable to use.
• Leads to higher job satisfaction and better compliance with procedures.
 Example: Workers are more likely to use protective gear if it's comfortable and well-
designed.

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6. Lowers Costs Over Time:
Reduces costs associated with:
• Injuries and absenteeism
• Equipment misuse or damage
• Poor performance and downtime
 Example: Fewer worker compensation claims when equipment is ergonomically safe.

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Role of Ergonomics in design of work systems
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The work system comprises a combination of people and work equipment acting together in
the work process to perform the work task at the work place in the work environment under
the conditions imposed by the work task.
Various ergonomic principles which should be considered during design of various work
systems are-
1. Design of work space & work equipment in relation to body dimensions:
a. Working height should be adopted to the body dimensions of the operator and to the kind of
work performed.
b. Seat and working desk should be designed as a unit to achieve the preferred body posture.
c. Sufficient space should be provided for body movements.
d. Grips and hands should suit the structure of the hand.

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2. Design in relation to the body posture:
a. Design of work should be such that so as to avoid unnecessary strain in muscles, joints and
respiratory and circulatory systems.
b. The operator should be able to alternate between sitting and standing.
c. Body postures should not cause work fatigue from prolonged static muscular tension.
3. Design in relation to the muscular strength:
a. Strength requirements should be within physiological desirable limits.
b. Maintenance of prolonged static tension in the same muscle should be avoided.

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4. Design in relation to the body movement:
a. Body movements should be in harmony with each other.
b. A good balance should be established among body movement. Motion should be preferred to
prolonged immobility.
c. Movements with great accuracy requirements should not entail exertion of considerable
muscular strength.
d. Execution and sequencing of movements should be facilitated by guiding devices.
5. Design of signals, displays and controls:
a. Signals and displays should be selected, designed and laid out in a manner compatible with
the characteristics of human perception.
b. Controls shall be selected, designed and laid out in such a way as to be compatible with the
movement of that part of the body by which they are operated.
c. Control movement, equipment response and display information should be mutually
compatible.

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6. Design of the work environment:
a. The work environment should be designed and maintained so that physical, chemical,
biological conditions have no adverse effect on people, but serve to ensure their health, as well
as their capacity and readiness to work.
b. Work environment should include adequate work space, emission of pollutants, appliances
consuming oxygen, thermal conditions, air temperature, air humidity, air velocity, thermal
radiation, intensity of physical work involved, absence of undesirable reflections, noise,
distribution of working hours, vibrations, exposure to dangerous materials.

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7. Design of work process:
a. The design of work process should safe for workers health and safety, promote their well
being and facilitate task performance, in particular by avoiding overloading (produce fatigue)
and underloading (results in monotony).
b. The physical and psychological stresses exerted depend not only on factors considered in
above but also on the content and repetitiveness of operations and on the workers control over
the work process.
c. While designing the work process, particular attention should be paid to the following-
i. Variations in vigilance and work capacity over day and night.
ii. Difference in work capacity among operators, and changes with the age.
iii. Individual development.

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Concept of man-machine-systems
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 A man-machine system also known as human-machine system. It is a system in which human
beings and machines interact and work together to achieve a specific goal.
 Systems can be improved by-
• Designing the user-interface to make it more compatible with the task and the user. This
makes it easier to use and more resistant to errors that people are known to make.
• Changing the work environment to make it safer and more appropriate for the task.
• Changing the task to make it more compatible with user characteristics.
• Changing the way work is organised to accommodate people’s psychological, and social
needs.
 It combines:
• Human capabilities (e.g., thinking, decision-making, sensing)
• Machine capabilities (e.g., computing, mechanical power, data storage)

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Components of man-machine-systems
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1. Human Components:
 The human body is part of the physical world and obeys the same physical laws as other
animate and inanimate objects.
 The goal of ergonomics at this level is to optimise the interaction between the body and its
physical surroundings. This means ensuring that physical space requirements are met (using
data on human ‘anthropometry’) and that internal and external forces acting on the body are
not harmful.
 Ergonomic problems often arise because, although the operator is able to carry out the task,
the effort required overloads the sustaining and supportive processes of the body and causes
fatigue, injury or errors.

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Various human components are-
i. The effectors:
The three primary effectors are the hands, the feet and the voice. More generally, the
musculoskeletal system and body weight can be regarded as effectors – no purposeful physical
activity of the limbs can be carried out without maintenance of the posture of the body and
stabilisation of the joints.
ii. The senses:
The senses are the means by which we are made aware of our surroundings. Human beings are
often said to have five senses – sight, hearing, touch, taste and smell. Vision and hearing are
the most relevant to ergonomics, although smell is important in detecting leaks, fires, and so
on.

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iii. Central processes:
 In order to carry out work activities, we require energy and information.
 Physiological processes provide energy to the working muscles and dissipate waste products.
 The brain can be regarded as an information processing centre, that contains low-level
programs to control the basic sensory-motor work activities and higher-level cognitive
processes that make possible the planning, decision making and problem solving activities of
work.
 The human operator can be thought of both as a user and as a source of energy. An
understanding of these basic processes is essential in work design to determine workers’
capacity for physical work and to investigate the factors (such as climate and individual
differences) that influence work capacity.

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iv. Energy and information:
 Finally, energy and information can only lead to purposeful work activity if the human is
sufficiently motivated.
 Motivation is the force that directs behaviour and is here regarded as a supportive process.
Some would argue that motivation lies in the realm of occupational psychology rather than
ergonomics. Although this may be true, the ergonomist cannot ignore such a fundamental
determinant of human behaviour – no work system can operate in a goal-directed and
purposeful way if the human component itself is not goal-directed and purposeful.

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Components of man-machine-model
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2. Machine Components:
 A ‘machine’ can be any man-made device that augments work capacity. The prototypical
human–machine system of ergonomics is illustrated by the car driver or machine operator
where the machine component and the links between the human and the machine (the
displays and controls) are tangible.
• Recent developments in information technology have shifted much of the attention of
ergonomics to information systems in which the work system is abstract and has no unique
spatial location. A piece of software on a computer network is an example of such a
machine.

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The various machine components are-
i. The controlled process:
 This is the basic operation of the machine on its local environment as controlled by the
human.
 Digging a vegetable garden with a spade is an example of such a process. Nuclear fission is
another example of a controlled process that is used to produce electricity in a nuclear power
station.
 In information systems, the controlled process is often more difficult to categorise because of
the abstract nature of the concepts used in these systems. Automatically sorting files,
sending electronic mail and searching a database for an item of information or a
directory for a particular entry are examples of controlled processes in information systems.

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ii. Displays:
 In simple work systems, the display is often just the action of the machine on its local
environment. The process is its own display (as in chopping wood with an axe).
 With increasing technological sophistication, the distance between the controlled process
and the human component is increased and artificial displays have to be designed.
 Driving a motor car or operating a lathe are intermediate in the sense that the display comes
both directly from the controlled process (the view of the road or the action of a machine tool
on a part) and indirectly from gauges, dials, etc.

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iii. Controls:
 Human interaction with machines depends on the provision of suitable controls, which can
be acted on by the effectors.
 With simple technology, the machine component itself is often the control. The handle of an
axe is a lever that enables the cutting edge to be accelerated towards the target via the
pivoting action at the hand–handle interface. At this level, the design requirements centre
around the interaction of the effectors and the control and the mechanical advantage provided
by the design of the control.
 Controls are also an important source of feedback during the execution of control actions.
 For example, the resistance to cutting of a saw tells us something about the sharpness of the
blade or the hardness of the wood, the resistance to turning of a motorcar steering wheel
provides feedback about the road surface or the tyre pressures.

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3. Environment:
 This refers to the place and the circumstances in which work is carried out and consists of the
physical workspace, the physical environment and the social and technical constraints under
which the work is done.
The various elements that affect environment are-
i. Workspace:
 The workspace is the three-dimensional space in which work is carried out.
 In simple work systems, the workspace may be just the place in which work is being carried
out at any point in time as we move from one location to another.
 In more complex systems, workspaces usually become fixed and this introduces design
issues such as the need to determine the workspace dimensions.

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ii. The physical environment:
 Many aspects of the physical environment can affect workers. Ergonomists are most
interested in those that have an influence on the way the human and machine components
interact.
 Noise, vibration, lighting and climate are of most concern to the ergonomist. Contamination
and pollution of the environment are matters best dealt with by industrial hygienists, because
they presumably have direct effects on health irrespective of any other work system factors.
iii. Work organisation:
 Work organisation at its most basic level refers to the immediate organisation of human–
machine interaction – the rate of work, whether the human works at his own pace or whether
the machine sets the pace and whether people work alone or are dependent on others.
 More broadly, it refers to the organisational structure in which the work activity is embedded,
the technical system and the social system which supports it.

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Characteristics of man-machine-systems
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The man-machine system consists of the man, the machine and system environment.
It is essentially artificial by nature and is specifically developed to fulfil some purpose or
specific aim.
It has specific inputs and outputs which are appropriately balanced.
 It is variable in size and complexity and is dynamic in performance.
Subsystems of man machine system interact with and effects the other parts.
The man-machine system becomes more efficient when inputs and out puts are adequately
balanced.
Environmental factors or system environment effects system performance.

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Classification of man-machine-systems
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1. Manual Systems:
• They are essentially man directed systems. These are flexible in nature and small in size.
• Simple tools and equipment are used and the efficiency is dependent upon the human factor.
• A large variability is possible in a manual system as every worker may select different
method to do the same job.
2. Mechanical Systems:
• They are more complex and inflexible in nature than manual systems.
• The machine component is power driven and human activity is information processing,
decision making and controlling occasionally knows semi automatic systems, they have
components which are well integrated. This is the feature which renders these systems rather
inflexible.
• An automobile and a machine tool operated by driver or operator are good examples of his
class.

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Classification of man-machine-systems
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3. Automatic Systems:
• A complex system in which all operational functions are performed by automatic devices is
known as automatic system.
• Operational functions are sensing information processing decision making and action. It is
completely inflexible in nature and cannot be adopted to uses other that the one for which it
has be designed.
• The human element/component performs the jobs of monitoring, programming the function,
maintenance and up keep.
• An automatic telephone exchange, a digital computer and automatic screw cutting, machines
are good examples of automatic systems.

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