40 Principles with Examples: Human Factors & Ergonomics

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By Stan Caplan, Michael Tschirhart and Jack Hipple

Abstract

Over the past ten years, there have been several 40 inventive principles lists with examples that illustrate the breadth of Genrich Altshuller's work; the founder of The Theory of Inventive Problem Solving (TRIZ).^1,2,3

The 40 principles framework has shown its robustness in its ability to capture key inventive examples across many different technologies and businesses. Though the TRIZ methodology has advanced beyond this simple characterization, these principles along with the original contradictions table both still remain as legitimate problem solving tools. Both tools offer a way to get problem owners to think in terms of overcoming contradictions as opposed to compromising and optimizing. After this basic understanding, they can move on to more sophisticated TRIZ tools and algorithms.

Human factors and ergonomics are the sciences relating to the relationship among humans and their working environments, including:

• The equipment that is operated.
• The environment it is operated in.
• The relationships among humans and the machines and processes they operate.

This entire area has become a major area of focus as the population ages and the elderly still need to drive cars, interact with machinery (even as small as a can opener) and see and interpret information on signs. Tasks that are taken for granted such as boarding an airplane or reading a speedometer in a car are not as easy for an elderly person or one with physical limitations such as arthritis. There is a classical contradiction with providing an over-the-counter medicine bottle that is easy to open for an elderly arthritic while at the same time preventing access to the same bottle with a young child that could easily open it.

Introduction

The authors have developed a list of examples for the 40 principles applied to the area of human factors and ergonomics. This is the area of science and engineering that relates to the relationships among humans and their working environments, including human-machine interfaces. With the arrival of several interfaces in multiple industries, this has become a major engineering challenge. As the population ages, the ability of individuals to access and use devices and systems is compromised by their physical abilities. Many designed systems are not suitable for all people. When a system is designed for one population, it may not be easily used by others. For example, a sophisticated display screen on a state of the art copier may be appropriate for a professional office assistant, but a manager walking by and wanting to make a few black and white copies is overwhelmed by the complexity of the copier. If the screen's display were to change based on the user, then a TRIZ separation principle has been used to resolve the contradiction of the display needing to be simple and uncomplicated. Another example is remote controls for televisions and other electronic devices. The tendency is to design complicated interfaces that can do everything when what is really needed is an interface that is appropriate for the use at that time only for the user.

In workplace ergonomics, there is a need to learn how to pre-position workplace materials in such a way as to minimize bodily stress in reaching for assembly components (a "do it in advance" TRIZ principle). Designs that minimize the potential negative impact on the worker while increasing productivity demonstrates the time honored TRIZ approach of resolving contradictions rather than finding some kind of optimum condition.

The following includes TRIZ principles for human factors and ergonomics with an area of science and engineering that relates to the relationships among humans and their working environments, including human-machine interfaces.

Principle 1: Segmentation

A. Divide an object into independent parts.

• Dividing a work process into separate steps.
• Segregate primary controls from secondary controls.
• Group menu options.

B. Make an object easy to disassemble.

• Modular furniture to avoid injury in transportation.

C. Increase the degree of fragmentation or segmentation.

• Phone numbers divided into perceptual chunks.
• Layering of information screens based on what is needed.
• Optimizing work processes through individual task analysis.

Principle 2: Taking Out

A. Separate an interfering part or property from an object or single out the only necessary part (or property) of an object.

• Navigation systems using "turn by turn" versus complex maps.
• Removing hazardous operations to an isolated location.
• Recessed start button to minimize accidental starts.
• Progressive disclosure of information.

Principle 3: Local Quality

A. Change an object's structure from uniform to non-uniform, change an external environment (or external influence) from uniform to non-uniform.

• Oversized emergency buttons.
• Simplified cell phone panels for people with motor skills problems.

B. Make each part of an object function in conditions most suitable for its operation.

• Specialized setting on websites and software.
• Offer different ways to have software provide the same function.

C. Make each part of an object fulfill a different and useful function.

• Individual office design to reflect different ergonomic needs.
• Individual televisions on airplanes.
• Mouse performs both point and scroll functions.

Principle 4: Asymmetry

A. Change the shape of an object from symmetrical to asymmetrical.

• Left and right handed designed products.
• One way insertion for two different parts.

B. If an object is asymmetrical, increase its degree of asymmetry.

• Differ shapes to prevent improper insertion of parts.

Principle 5: Merging

A. Bring closer together (or merge) identical or similar objects, assemble identical or similar parts to perform parallel operations.

• Combine different functions in one piece of office equipment.
• Joystick changes both direction and speed.
• Electronic chips mounted on both sides of a circuit board or subassembly.
• Using touch screens for audio and climate controls at the same time.

B. Make operations contiguous or parallel; bring them together in time.

• Bring together through multi-tasking.
• Group associated controls and functions.

Principle 6: Universality

A. Make a part or object perform multiple functions; eliminate the need for other parts.

• Universal design for a broad range of people.
• Common personal computer operating systems.
• Common procedure standards.
• Multiple back-up methods.
• Icon and label conventions.
• Conventions for links on websites.

Principle 7: Nested Doll

A. Place one object inside another; in turn, place each object inside the other.

• Nesting with menu hierarchies.
• Nesting within graphic displays.

B. Make one part pass through a cavity in the other.

• Radio graphical user interface (GUI). A selection (such as a radio station or MP3 file / song) that appears as one item among many on a search list that may pass through to the main screen where it is presented as the current status / selection.

Principle 8: Anti-weight

A. To compensate for the weight of an object, merge it with other objects that provide lift.

• An assembly line counterweights.

B. To compensate for the weight of an object, make it interact with the environment (use aerodynamic, hydrodynamic, buoyancy and other forces).

• Lift / carry an object. Center of gravity is close to the sagittal plane of the human body.

Principle 9: Preliminary Anti-action

A. If necessary to do an action with both harmful and useful effects, this action should be replaced with anti-actions to control harmful effects.

• Use of dead-man controls.
• Pre-flash to eliminate red eye in photography.
• Safety interlocks to prevent access to hazardous equipment.
• Insulation on local hot spots.

B. Create beforehand stresses in an object that will oppose known and undesirable working stresses later on.

• Introduce tension to avoid kickbacks.
• Stress induced training to prepare for actual conditions.
• Close eyes before entering a dark room.
• Synchronous vs. asynchronous defibrillators.

Principle 10: Preliminary Action

A. Perform (before it is needed) the required change of an object (either fully or partially).

• Pre-arrange components to make assembly easier.
• Format the report before the data is available.

B. Pre-arrange objects such that they can come into action from the most convenient place and without losing time for their delivery.

• Employee pre-training for hazardous operations.
• Job planning to avoid accidents.

Principle 11: Beforehand Cushioning

A. Prepare emergency means beforehand to compensate for the relatively low reliability of an object.

• Shoe cushion inserts.
• Confirmation dialogue box.
• Navigation destiny entry to avoid need for constant attention.
• Undo button.
• A lockout.

Principle 12: Equipotentiality

A. In a potential field, limit position changes (such as a change in operating conditions to eliminate the need to raise or lower objects in a gravity field).

• Spring loaded parts.
• Spring loaded self-leveling device ("levelator").
• Workplace design for sliding objects.
• Gravity feed soda can dispenser.

Principle 13: The Other Way Around

A. Invert the action(s) used to solve the problem (instead of cooling an object, heat it).

• Start / stop buttons.

B. Make movable parts (or the external environment) fixed and fixed parts movable).

• Electric can opener.

C. Turn the object (or process) upside down.

• Parts come to the operator.
• Users help design products.
• Write the user manual before writing the computer program.

Principle 14: Spheroidality – Curvature

A. Instead of using rectilinear parts, surfaces or forms, use curvilinear ones; move from flat surfaces to spherical ones; from parts shaped as a cube (parallelepiped) to ball-shaped structures.

• Smooth work surfaces to minimize sharp points.
• Smooth work flow angles to avoid sudden turns.
• Ergonomic work stations.
• Use of curved surfaces in handles and grips.

B. Use rollers, balls, spirals, domes.

• Rotaries in gauges.

C. Go from linear to rotary motion. Use centrifugal forces.

• Produce linear motion of the cursor on the computer screen using a mouse or a trackball.
• Replace wringing clothes to remove water with spinning clothes in a washing machine.
• Spherical casters instead of cylindrical wheels to move furniture.
• Spherical casters on luggage and vacuums.

Principle 15: Dynamics

A. Allow (or design) the characteristics of an object, external environment or process to change to be optimal or to find an optimal operating condition.

• Adjustable steering wheels and seats.
• Unlearning "sounding out words" to enable speed reading.

B. Divide an object into parts capable of movement relative to each other.

• The butterfly or foldable computer keyboard.

C. If an object (or process) is rigid or inflexible, make it movable or adaptive.

• Use gooseneck connections.
• Use coiled cords / tubes / hoses to allow flexible positioning.
• Use a flexible sigmoid scope for medical examination.

Principle 16: Partial or Excessive Actions

A. If 100 percent of an object is hard to achieve by using a given solution method then, use slightly less or slightly more of the same method. The problem may be considerably easier to solve.

• Apply a safety factor over design.
• Design processes where hazardous operations are done in steps.
• Increase sampling rate of inspection.
• Introduce irrelevant stimuli on vigilance tasks.

Principle 17: Another Dimension

A. To move an object in a two- or three-dimensional space.

• Braille for the blind.
• Finger swipe cell phone operation versus a push button.

B. Use a multi-story arrangement of objects instead of a single-story arrangement.

• Add auditory or tactile feedback to visual feedback.
• Use shelves above a work surface.

C. Tilt or re-orient the object, lay it on its side.

• Re-orient a dump truck.
• An automobile rotisserie - rotate the car body to work on the underbody.

D. Use another side of a given area.

• Use three dimensional imaging to design tasks.
• Use a shelf hanging below a work surface.

Principle 18: Mechanical Vibration

A. Cause an object to oscillate or vibrate.

• Use vibration rather than mechanical force to dislodge an object.
• Use tactile feedback.

B. Increase its frequency (even up to the ultrasonic).

• Distribute powder with vibration.

C. Use an object's resonant frequency.

• Use a rough road shoulder to alert drivers.

D. Use piezoelectric vibrators instead of mechanical ones.

• Quartz crystal oscillations drive high accuracy clocks.

E. Use combined ultrasonic and electromagnetic field oscillations.

• Use vibration and sound to alert a cell phone user of incoming calls.

Principle 19: Periodic Action

A. Instead of continuous action, use periodic or pulsating actions.

• Do hazardous tasks a little at a time.
• Replace a continuous siren with a pulsed sound.

B. If an action is already periodic, change the periodic magnitude or frequency.

• Use auditory alerts.
• Replace a continuous siren with a sound that changes amplitude and frequency.

C. Use pauses between impulses to perform a different action.

• Press and hold down buttons.

Principle 20: Continuity of Useful Action

A. Carry on work continuously; make all parts of an object work at full load, all the time.

• Avoid lengthy machine startups.
• Employ emergency backups.

B. Eliminate all idle or intermittent actions or work.

• Eliminate repetitive motion.

Principle 21: Skipping

A. Conduct a process or a certain stage (destructible, harmful or hazardous operations) at high speed.

• Minimize duration of error consequences.
• Redesign processes to avoid hazardous operations.
• Run hazardous chemical reactions at high speed to minimize inventory.

Principle 22: "Blessing in Disguise" or "Turn Lemons into Lemonade"

A. Use harmful factors (particularly, harmful effects of the environment or surroundings) to achieve a positive effect.

• Stop system progress to prevent more errors.
• The Environmental Protection Agency regulates product changes; new product gives competitive advantage.

B. Eliminate the primary harmful action by adding it to another harmful action to resolve the problem.

• Loud noise (such as a radio) and fatigue are each bad for drivers, but combined they can cancel some negative effects for drowsy drivers.
• Make a component fragile looking to discourage abuse.

Principle 23: Feedback

A. Introduce feedback (referring back, cross-checking) to improve a process or action.

• Provide instant and relevant information to operators to provide safe operation.

B. If feedback is already used, change its magnitude or influence.

• Flash a warning light if steady state operation is not acknowledged in "X" seconds.
• Flash an auditory alert if steady state operation is not acknowledged within a given time frame.
• Change the color of the visual effect.

Principle 24: Intermediary

A. Use an intermediary carrier article or intermediary process.

• Use cushioning.
• Use bins to transport parts between operations.
• Use pop-up windows and a dialogue box.

B. Merge one object temporarily with another (which can be easily removed).

• Chunk numbers in a sequence.
• Track changes in document creation.

Principle 25: Self-service

A. Make an object self-serve by performing auxiliary helpful functions.

• Use optical illusions.
• Use online stress measurements, adjust equipment or positions.
• Convey depth in drawing via line convergence.

B. Use waste resources, energy or substances.

• Learn from mistakes or errors.
• Excess process heat is used to heat office area.

Principle 26: Copying

A. Instead of an unavailable, expensive, fragile object, use simpler and inexpensive copies.

• Virtual reality via the computer instead of an expensive vacation.
• Listen to an audio tape instead of attending a seminar.

B. Replace an object or process with optical copies.

• Virtual training for hazardous situations.

C. If visible optical copies are already used, move to infrared or ultraviolet copies.

• Mental models of systems.

Principle 27: Cheap Short-living Objects

A. Replace an inexpensive object with a multiple of inexpensive objects, comprising certain qualities (such as service life).

• Use lightweight temporary pieces versus heavy permanent ones.
• Use temporary blocks to restrain equipment operation.

Principle 28: Mechanics Substitution

A. Replace a mechanical means with a sensory (optical, acoustic, taste or smell) means.

• Replacement of any human force with a mechanical force reduces required human energy.
• Use a bad smelling compound in natural gas to alert users to leakage, instead of a mechanical or electrical sensor.
• Use a flashing light instead of a ringing bell to indicate an incoming telephone call.

B. Use electric, magnetic and electromagnetic fields to interact with the object.

• Use artificial intelligence.
• Interaction in a television remote.

C. Change from static to movable fields from unstructured fields to those having structure.

• Use a 3G network for wireless communication.
• Wireless communication improves work flexibility.

D. Use fields in conjunction with field-activated (ferromagnetic) particles.

• Heat a substance containing ferromagnetic material by using varying magnetic fields. When the temperature exceeds the Curie point, the material becomes paramagnetic and no longer absorbs heat.

Principle 29: Pneumatics and Hydraulics

A. Use gas and liquid parts of an object instead of solid parts (inflatable, filled with liquids, air cushion, hydrostatic, hydro-reactive).

• Use comfortable shoe sole inserts filled with gel.
• Use pneumatics and hydraulics to minimize human force requirements for heavy parts.
• Make a product use forgiving.

Principle 30: Flexible Shells and Thin Films

A. Use flexible shells and thin films instead of three dimensional structures.

• Pre-packaged materials to isolate materials from human contact.
• Isolate un-needed features of a product.

B. Isolate the object from the external environment using flexible shells and thin films.

• Barriers to isolate operators from hazardous operations.
• Spam or information filter; personalize electronic information.
• Use shields.

Principle 31: Porous Materials

A. Make an object porous or add porous elements (inserts, coatings, etc.).

• Use porosity in a structure to reduce weight.

B. If an object is already porous, use the pores to introduce useful substances or functions.

• Use controlled information flow and direction.

Principle 32: Color Changes

A. Change the color of an object or its external environment.

• Use color to indicate danger or conditions.
• Use highway signs.
• Use color coding.

B. Change the transparency of an object or its external environment.

• Use color sensitive labeling.
• Use clear storage bins.

Principle 33: Homogeneity

A. Make objects interact with a given object of the same material (or material with identical properties).

• Use affinity mapping.
• Layer consistency in maps or displays.
• Train operators in similar tasks to minimize accidents from different tasks.

Principle 34: Discarding and Recovering

A. Make portions of an object that have fulfilled their functions go away (discard by dissolving, evaporating, etc.) or modify these directly during operation.

• Use automatic file deletion.
• Use lossy compression.

B. Conversely, restore consumable parts of an object directly in operation.

• Lighter-weight, less durable parts to minimize physical stress.
• Reconstruction of lost images.
• Pixel interpolation.

Principle 35: Parameter Changes

A. Change an object's physical state (to a gas, liquid or solid).

• Changes in data density.
• Gas explosion to deploy seat bag.

B. Change the concentration or consistency.

• Font, case, italics changes in documents.

C. Change the degree of flexibility.

• Seat belt lockup during a crash.
• Reaction time changes for different information.

D. Change the temperature.

• Raise the temperature above the Curie point to change a ferromagnetic substance to a paramagnetic substance.
• Raise the temperature of food to cook it (changes taste, aroma, texture, chemical properties, etc.).
• Lower the temperature of medical specimens to preserve them for later analysis.
• Cool a flexible component to make it stiff for assembly.

Principle 36: Phase Transitions

A. Use phenomena occurring during phase transitions (volume changes, loss or absorption of heat, etc.).

• Melting of weak point to stop current flow.
• Analog versus digital.
• Film to CCD conversion.

Principle 37: Thermal Expansion

A. Use thermal expansion (or contraction) of materials.

• Use heating and cooling to minimize force required to loosen joints.
• Use a differing stimulus.

B. If thermal expansion is used, use multiple materials with different coefficients of thermal expansion.

• Expand granularity.
• Replace yes / no with a scale of response.

Principle 38: Strong Oxidants

A. Replace common air with oxygen-enriched air.

• Oxidizing cleaners to reduce human effort needed.
• Use a creative outsider in an ideation session.

B. Replace enriched air with pure oxygen.

• Enrich the learning environment with visual and auditory stimulation of various sorts.
• Improved aesthetics or form.

C. Expose air or oxygen to ionizing radiation.

• Localized process radiation or ionization to avoid broad exposure or to provide enhanced local properties.

D. Use ionized oxygen.

• Focused human factor audits.

E. Replace ozonized (or ionized) oxygen with ozone.

• Enrich various hospital environments.

Principle 39: Inert Atmosphere

A. Replace a normal environment with an inert one.

• Use gas padding to minimize impacts.
• Quiet areas in the workplace.

B. Add neutral parts or inert additives to an object.

• Use "time outs" during negotiations.

Principle 40: Composite Materials

A. Change from uniform to composite (multiple) materials.

• Change lightweight composites to lower-weight and minimize human effort.
• Heterogeneous focus groups.
• Non-traditional work structures.
• Flow-optimum range of challenge.

References

1. Mann, Darrell; 40 Principles (Architecture) with Examples, The TRIZ Journal, July 2001.
2. Hipple, Jack; 40 Inventive Principles with Examples for Chemical Engineering, The TRIZ Journal, June 2005.
3. Mann, Darrell; Domb, Ellen; 40 Inventive (Business) Principles with Examples, The TRIZ Journal, September 1999.

About the Authors:

Stan Caplan is President of Usability Associates, a Human Factors consulting firm that works with companies who want customers to have a superior experience when using company products. This is accomplished through user research and application of usability design and evaluation principles and methods. Caplan founded the firm in 1998 after performing Human Factors projects and managing the Human Factors function at Eastman Kodak Company for 25 years. His experience spans development of user-centered designs for hardware, embedded software and graphical user interfaces on consumer, business, commercial and medical products and systems. Contact Stan Caplan at wood27 (at) frontier.com.

Michael Tschirhart is a Technical Fellow at Visteon Corporation where he leads Advanced Human-Machine Interface (HMI) Research and Development. Contact Michael Tschirhart at mtschirh (at) visteon.com.

Jack Hipple is a principal with Innovation-TRIZ. He is the TRIZ instructor for AIChE/ASME and does TRIZ workshops for ASQ, PDMA and the Human Factors and Ergonomics Society. He has written TRIZ articles for The TRIZ Journal, Quality World, Mechanical Engineering, World Futures Quarterly, Creativity and Innovation Management's inaugural TRIZ issue, as well as a special three-part series on TRIZ for Chemical Engineering Progress. Contact Jack Hipple at jwhinnovator (at) eartlink.net or visit http://www.Innovation-TRIZ.com.