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3D printing

A way to make a physical object from a digital 3D model. This works similar to normal printing, but in stead of ink it uses plastic or other suitable materials. Printing is done by adding molten plastic, drop by drop, in successive layers. The droplet solidifies as soon as it is added. This method is called additive manufacturing.

A/D converter (analog-to-digital converter)

A piece of electronics that measures input voltage and outputs a corresponding discrete value for use with digital electronics.

absolute data (ABSO Data)

a way for an encoder to determine the position of an actuator without relying on previous movements. It gives the position relative to a fixed home position, and maintains its value even after power loss.

AC (alternating current)

Electrical current where the direction of flow reverses periodically. This in contrast to DC (direct current), where the flow is always in the same direction. Typical wall sockets provide AC (alternating 50 or 60 times per second in most countries), while typical batteries provide DC. Although many low power devices work on DC so they can work on batteries, they can still be powered from an AC wall socket by means of an adaptor that converts AC to DC.


The precision with which a robot or actuator can actually move to a specified location in space. It specifies a margin of error. Accuracy may vary over the reach of an actuator and, most pronounced, over the whole assembly.

Ackermann steering

An optimized steering mechanism where the inner wheel turns more than the outer wheel in order to avoid slip. Since the inner wheel follows a smaller circle when turning than the outer wheel, it should turn more than the outer wheel.

active compliance

when a robot assembly changes its planned behavior in response to signals from its force sensors. This is especially important for robots that work with humans in order to avoid injury and to acomplish its task regardless of minor disturbances. See also compliance.

active joint

a joint that can be controlled directly by an actuator. As opposed to a passive joint, that cannot be controlled other than by connected links.

actual position

the position of an endpoint of a robot assembly in the real world, as opposed to the position requested or held in the memory of the controller. These differ slighly due to inaccuracies in the physical movements of the robot and in the encoders.


a device that applies a force in the real world, either to make something move, or to maintain position. It is usually a motor or servo mechanism, sometimes a hydraulic or pneumatic mechanism.

adaptive behavior

modification of actions to take into account any changes in the environment. This usually involves high level techniques like machine learning or artificial intelligence.

additive manufacturing

a method of contruction where an object is created by adding successive layers of material. 3D printing is one of the best known examples of additive manufacturing.

AGV (automated guided vehicle)

a vehicle that navigates automatically based on visual markers or wires on the floor, or uses vision or laser to determine their location. Most commonly they are used in warehouse settings to move around pallets of products.

AI (artificial intelligence)

emulation of intelligence by means of computers or other machines. In practice, this encompasses only fragmented parts of human intelligences (playing chess, computer vision). Emulation of the full scope of human intelligence is called strong-AI or AGI (artificial general intelligence).


standard unit of electric current. Sometimes abbreviated to amp or amps.


a robot resembling a human being, both in appearance and behaviour.


the electrode where current flows into a device, e.g. the "-" side of a battery, or the "+" side of a diode or LED. See also cathode, which is the opposite end. See also current for the direction of flow.

APC (absolute pulse coder)

a system that stores encoder pulse counts in persistent memory, so when there is a power loss or when the robot is turned off and on, it can recallibrate.


an open source electronics platform providing hardware and software especially suited for hobby projects and robotics due to the small size of its components. It includes credit-card sized single board computers and controllers (boards), extention boards (shields) that provide motor controllers, gps and ethernet functionallity amongst others, as well as accessories.


a set of rigid bars connected through electronically controlled mechanical joints. The end-effector or gripper does not form part of the arm.


used to describe any (part of a) robot assembly that has static parts (e.g. rods) connected by one or more joints. Each joint adds to the degree of freedom of the assembly, making it easier to work in confined spaces or reach objects from different angles.

Describes a jointed device, such as a jointed manipulator. The joints provide rotation about a vertical axis, and elevation out of the horizontal plane. This allows a robot to be capable of reaching into confined spaces

assembly robot

a robot designed specifically for assembly lines, where it joins parts or components into completed products.


a device that moves or acts though mechanical ingenuity rather than electronic control.


acting without human supervision and making its own decisions.


imaginary reference line. It can be the line in 3D space around which a rotary joint rotates or along which a linear motor moves. An axis is relative to some reference, usually some part of a robot assembly. This reference may be either fixed or movable. In the latter case, the axis moves as if fixated to the reference part when this moves.

back-pressure sensor

a sensor that measures the instantaneous torque that a motor applies.

base link

the stationary base structure of a robot arm that supports the first joint.

BCI (brain computer interface)

a system that allows you to control a machine or a computer program by mere thought. It usually measures brain waves through electrodes that are place on the scalp or that are directly connected to certain neurons inside the brain. Also called any combination of brain/mind machine/computer interface and many other names.

BEAM robotics

a form of robotics using simple analog electronics to make things move and behave in certain ways, in contrast to the use of digital controllers and microprocessors. The term (which stands for Biology, Electronics, Aesthetics and Mechanics) was coined by Mark Tilden, also known for his WowWee Robosapien.

bevel gear

a gear with its teeth placed at an angle, used to transfer the rotational force of its shaft to a shaft with another orientation. Mostly, the shaft are mounted at a 90 degree angle, and the teeth of the meshed gears are placed at an angle of 45 degrees.

bi-directional communication

communication between two entities, where both talk as well as listen, as opposed to uni-directional communication, where only one is doing the talking, and the other is only listening.

bill of materials (BOM)

a list of parts or components required to build a product.


a representation for numbers using only two digits (0 and 1) in stead of the usual 10 (0 through 9)


the study of biological systems in order to mimic them to create or improve artificial materials and machines. Sometimes also called bionics.


mechanically or electronically replacing or enhancing anatomical structures or physiological processes. A functional prostetic hand is a good example.

BMI (brain machine interface)

See BCI (brain computer interface).


electronics board that lets you plug-in and connect electronic component without soldering. It is therefore reusable and allows for rapid testing and prototyping.

CAD (computer-aided design)

using computer applications to design objects (usually mechanical or electronic parts). This allows for accurate 3D designs, easy modification and simulation. Apart from the shape of the objects, it may also define materials, weights, loads, stress, motion paths, etc. Often, the digital design is then used to control machines that can manufacture the objects or parts mostly automatically. This is called CAM (computer-aided manufacturing).


using computers to design and manufacture (mechanical or electronic) parts and objects. See CAD (computer-aided design) and CAM computer-aided manufacturing).

CAM (computer-aided manufacturing)

using computers to control manufacturing tools and related machines to automate production. This allows for great precision in the creation of complex objects and helps the production process to be more efficient in the use of materials, energy and time. Often, CAD (computer-aided design) models are used as input for the CAM process.

ńĆapek, Karel

the Czech author who introduced the term robot to describe the artificial people in his play R.U.R. (Rossum's Universal Robots) in 1920. When the play premiered in 1921, the term was copied rapidly into other languages.

cartesian robot

a robot assembly with only prismatic joints, normally arranged perpendicular to each other. This results in a highly rigid structure that can manipulate heavy loads. See also prismatic joint.


the electrode where current leaves a device, e.g. the "+" side of a battery, or the "-" side of a diode or LED. See also anode, which is the opposite end. See also current for the direction of flow.

centrifugal force

force pointing in the outward direction of a rotating object, caused by mass on the rotating object that wants to escape the rotation.


flattened edge between two (usually perpendicular) surfaces. The flattened edge will usually be at 45 degrees.

closed loop

cyclic control method, where feedback from sensors on the robot assembly is used for continuous adjustments in the steering of the robot.


the mental process of information processing. It usually includes all higher level mental processes like reasoning, language, calculating, problem solving, decision making, etc.

cognitive model

an descriptive approximation of the cognitive process of (usually) a human being. See also cognition.

command position

the targeted end position of a robot assembly.


a program that converts program text into machine code that can be directly executed by hardware. Thus, a C-compiler can transform C program text into machine language.


the yielding of a robot assembly in response to external force. High compliance means it moves easily with an applied force, while low compliance means the structure stays more rigid.

compliant robot

a robot that adapts to external forces, either passively (accepting the force to change the position of the robot joints) or actively (replanning motion and position to avoid external stress).

compound gear

two or more gears of different sizes fixed to the same axis, thus rotating at the same speed.

compound gear reduction

a reduction of rotational speed obtained by a gear train with compound gears. See also compound gear.


material that allows electric current to flow though it.


restrictions on the motion of an assembly.

contact sensor

a sensor that signals physical contact with an object.

continuous path

end-effector movement that is fully calculated at all positions from start to end, as opposed to point-to-point, where only certain key positions are calculated, and the trajectory in between is not important.

control system

the central hardware and software that controls the whole robot, often an single board computer.


a device that steers an actuator guided by an external input signal and the actuator's feedback. This alleviates the sender of the external input signal from handling specific operating requirements of the actuator.

controller system

the central hardware and software that controls the whole robot, often an single board computer.


a mechanical structure to transport material or objects, usually by means of a belt (conveyer belt) that is spanned between two wheels that drive the belt to rotate with the materials on top.


the flow of an electric charge through a wire or other medium. By convention, the flow direction is defined as flowing from positive to negative, or as the direction as how positive particles would move. Since electrons are negatively charged, the convention says the direction of current is opposite to the stream of electrons.


a being that is part human part robot (contraction of cybernetic organism).

DC (direct current)

Electrical current where the direction of flow is always the same. This in contrast to AC (alternating current), where the flow reverses many times per second. DC current is typically provided by batteries, while wall sockets typically provide AC. Although many low power devices work on DC so they can work on batteries, they can still be powered from an AC wall socket by means of an adaptor that converts AC to DC.

gear train

an assembly of various meshed gears used to obtain a speed and/or torque reduction or increment.

gravity balanced

an assembly where the gravity effects of the links in a robot arm are compensated, usually by counter weights or springs. This releaves the joints from unnecessary torque requirements due to the weight of the links.

instantaneous torque

torque that is applied at one specific moment in time, as opposed to mean torque, which is measured over a period. Depending on their inner workings, motors do not deliver constant torque, e.g. an internal combustion engine delivers high torque at the moment of combustion, but then it wades until the next combustion.


part of a robot assembly that connects two other parts in such a way that they can move relative to each other while remaining connected. A joint may be active (invoking the motion) or passive (moves only when the other parts make it move).

joint / circular / linear / spline motion type

these are different strategies for an (industrial) robot arm controller to move its tool to a certain position.

  • joint - each joint is made to achieve its end position, without taking into account the path of the tool.
  • circular - makes the tool center point move in two half circles to reach the end position.
  • linear - makes the tool center point move in a straight line to the end position.
  • spline - makes the tool center point move along a path defined by a spline.
joint load

the total of force exercised on a joint. Typically, for a robot arm, this is the load of anything held in its gripper, plus the load of the attached assembly (links and joints) that the joint must carry. When the assembly is moving, then acceleration forces may alter the joint load.

linear joint

a joint that allows for linear sliding motion between the connected links. Also called a prismatic joint.

passive joint

a joint that cannot be controlled directly by an actuator, but moves only forced by connected links. As opposed to an active joint, that can be controlled directly by an actuator.

prismatic joint

a joint that allows for linear sliding motion between the connected links. Also called a linear joint.


a machine that is able to perform a complex task or range of tasks without the intervention of a human being, usually responding to external stimuli and with some level of autonomy. Note that this definition includes floor cleaning robots like the Roomba, but not kitchen appliances like the KitchenAid.


a motor that rotates full speed to an position indicated by the input signal and then stays in this position. Usually a servo is limited in its rotational angle (often less than 180 degrees) and is driven by PWM (pulse width modulation) to indicate the required angle.

three laws of robotics

science-fiction writer Isaac Asimov coined the following 3 laws that should be obeyed by robots:

  1. A robot may not injure a human being or, through inaction, allow a human being to come to harm.
  2. A robot must obey the orders given to it by human beings, except where such orders would conflict with the First Law.
  3. A robot must protect its own existence as long as such protection does not conflict with the First or Second Law.

Later, he added the following zeroth law:

  1. A robot may not harm humanity, or, by inaction, allow humanity to come to harm.

force that a rotational motor delivers at a given distance from the center of rotation. When expressed in Newton-Meters, it is the force (in Newton) that it exerts at 1 meter from the center of the shaft. It is calculated as force x distance, thus if a motor has a maximum torque of 5 kg·cm, it can lift up to 5 kg at the end of a 1 cm long horn, or likewise up to 1 kg at the end of a 5 cm long horn.

uni-directional communication

communication between two entities, where only one is doing the talking, and the other is only listening, as opposed to bi-directional communication, where both talk as well as listen.