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Ergonomic

a systems approach for analyzing the physical interaction of the human worker with their work environment to maximize productivity, quality, usability, safety, health, and comfort

Work

the energy, W, transferred when a force, F, is applied to an object moving through a distance, d

Resistance force

the impeding effect exerted by one material object on another

Simple machines

a mechanism that changes the direction or magnitude of a force

Magnitude

the greatness of size or amount

Compound machine

a machine made up of two or more simple machines

Mechanical advantage

the ratio of the force produced by a machine to the force applied to it, used to assess the performance of a machine

Mathematical model

a representation of a real-world situation or system using mathematical concepts and language

Fixed pulley

a first-class lever that has an axle attached to a supporting structure and changes the direction of force

Moveable pulley

a pulley with an axle in a movable block that is supported by two parts of the same rope

Block and tackle pulley

a pulley system made up of fixed and moveable pulleys

Biomechanics

the science of movement (or mechanics) of a living body, including how muscles, bones, tendons, and ligaments work together to produce movement

Fulcrum

the point on which a lever rests or is supported and on which it pivots

Goniometer

an instrument for the precise measurement of angles

Population

all values in a data set that are collected during an observation or experiment

Mean

an average of a set of numeric data values, calculated by dividing the sum of individual values by the number of values

Median

a measure of center in a set of numerical data. The median of a list of values is the value at the center of a sorted version of the list, or the mean of the two central values, if the list contains an even number of values

Mode

the value that occurs most frequently in a given data set

Outliers

an extreme value that differs greatly from other values in a set of data. As a rule of thumb, an extreme value is an outlier if it is at least 1.5 interquartile ranges below the first quartile (Q1), or at least 1.5 interquartile ranges above the third quartile (Q3)

Interquartile range

a measure of variability equal to Q3 minus Q1. The interquartile range represents the middle 50% of data values in an ordered data set

Measurable

able to be measured. Measurable design criteria should provide a precise indicator of a quantifiable characteristic so that a design can be compared to the criteria and deemed acceptable or unacceptable

Abstraction

the process or result of taking away or removing characteristics from something to reduce it to a set of essential characteristics

Prototype

a working model used to test a design concept by making observations and necessary adjustments

Computer aided design (CAD)

a process that uses a computer to assist in designing something, such as a part, electrical circuit, or building

Solid modeling

the process of creating a solid model or three-dimensional object using modeling and design software

Additive method

a rapid prototyping method where three-dimensional objects are built by adding layer upon layer of material

Subtractive method

a solid modeling design method in which an object is created by subtracting volume from a larger object

Geometric primitives

the simplest two-dimensional or three-dimensional geometric shape

Rapid prototyping

a process, abbreviated RP, for quickly constructing a scale model of a physical part or system using three-dimensional computer-aided design models

Additive manufacturing

a rapid prototyping method where three-dimensional objects are built by adding layer upon layer of material

Filament

a slender threadlike strand or fiber used in additive manufacturing and three-dimensional printing

Extruder

a metal piece or die that is heated and forces plastic filament or metal through a shaped hole to produce a continuous ribbon of the material

Linkage

an assembly of links connected at joints used to transfer an input motion to a desired output motion, usually in a two-dimensional plane

Pins

a cylindrical machine component used as a fastener to constrain the relative movement between connected parts. In many cases, a pin is used to constrain connected parts to rotation about the axis of the pin

Curvilinear motion

a combination of linear motion in two directions resulting in curved lines of motion

Torque

a twisting force that tends to cause rotation

Gear train

a mechanism used for transmitting rotary motion and torque through interlocking teeth

Proof of concept

experimental evidence that demonstrates that a design concept is feasible

Project charter

a document issued by the project initiator or sponsor that formally authorizes the existence of a project and gives the project manager the authority to apply organizational resources to project activities