The Robotics Glossary : 9 (more!) Robotics Terms You Need to Know

Lacey Trebaol
Nov 6, 2019 9:22:47 AM

In Part 1 of the Robotics Glossary, we defined 18 terms that, when known, ease communication in this domain in a tangible way. Now, in Part 2, we're adding 9 additional terms to the list. We hope you enjoy!

Admittance Control: Admittance control is a way to control the position of a robot link based on external force and torque. The robot behaves as a mass-spring-damper system. When a force/torque is applied to the robot, the robot complies in the direction of the force/torque. The amount of compliance can be configured using the stiffness parameter and the and vectors of compliance can be configured using motion constraints. Admittance control is typically used in applications such as peg-in-hole, pin insertion, sanding, or polishing.


Degree of Freedom (DOF): A DOF is an independent parameter that defines a configuration of a mechanical system.

A rigid body in space has six parameters that define six degrees of freedom. These include:

  • Translation: X, Y, and Z
  • 3 Rotations: Pitch, Roll, and Yaw

6 DOF DiagramJoints define how connected rigid bodies are allowed to move relative to each other. When a system of rigid bodies is connected with joints, the total Degrees of Freedom is defined by the DOF of each rigid body, minus the internal constraints defined by the joints.

DOF Diagram

Free-Spin-in-Z Constraint: A Free-Spin-in-Z constraint is a common 5 constraint configuration on a 6 DOF link where the rotation about one vector, typically Z, is unconstrained.


Hexapod: See Stewart Platform.

Industrial Robot (vs Collaborative Robot): An industrial robot is a class of robots that are used to automate a manufacturing process with minimal human assistance on the manufacturing floor. One of the main differences between an industrial robot and a collaborative robot (cobot) is that cobots are designed to work alongside humans, while industrial robots do work in place of the employees.

To learn more about how cobots differ from industrial robots, view this post from Universal Robots.

Link: In robotics, a link is a physical or simulated segment of a kinematic chain (a rigid body).

Robot Arm Link DiagramPrismatic Joint: Not all joints are purely rotational. A prismatic joint allows for linear sliding motion along (and sometimes also rotation about) an axis between 2 bodies.

Prismatic_jointPrismatic joint seen in 2-dimensional form. Only linear motion is possible.
Image source.

Process Applications: Process applications are a class of applications that usually require a robot to follow a defined trajectory at a certain speed and tool orientation accurately and repeatedly. Examples include dispensing, gluing, deburring, polishing, welding, and sewing. For simple applications, the trajectory can be defined using conventional waypoints and circle moves. For more complex applications in which the trajectory is difficult to define by teaching waypoints, offline simulation software is usually used to define the trajectory based on a CAD model of the part.


Stewart Platform: A Stewart Platform or Hexapod is a 6 DOF parallel manipulator system actuated by a combination of prismatic, ball, and sometimes spherical joints to move a platform relative to the base. Example uses include flight simulators, ship-to-ship/ship-to-asset gangway stabilization, remote positioning systems, machine tool positioning, and more. Stewart platforms are typically chosen for applications that require rigid 6 DOF actuation of large forces or payloads, but that do not require full rotation about pitch, roll, or yaw vectors.


Are there other terms you’d like us to add? Do you have any questions about what’s included in this post? Leave us a comment below! We’ll be creating a larger glossary on our website and want to be sure it’s as comprehensive and helpful as possible.


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