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Glossary of Robotics
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actuation
The mechanism or system that generates motion in a robot, typically through motors that produce torque (rotational force) at the joints.
actuator
Mechanical devices that convert energy (pneumatic, hydraulic, or electrical) into motion. In this context, they’re the “muscles” of a robot that enable movement and manipulation.
angular velocity
How fast something is rotating (in radians per second).
articulated robot
A robot with multiple joints connected by links, similar to how human limbs are jointed. These can achieve complex movements through multiple articulations.
C
cartesian coordinates
A coordinate system using X, Y, and Z axes to describe positions in 3D space (named after mathematician René Descartes). This is how we typically describe where something is in the world.
Cartesian space control
A control method where you specify the desired position and orientation of the robot's hand (end-effector) in 3D space, and the control system automatically calculates which joint angles are needed to achieve it. What it is: A...
Cartesian velocities
The combination of linear and angular velocities of the end-effector expressed in Cartesian coordinates. Cartesian velocities represent the motion of the robot's end-effector in 3D space, combining both linear velocity (how...
centrifugal effects
The apparent outward force felt by objects in rotating systems. As a robot’s arm spins, the centrifugal effect creates additional stresses on the joints. The Basics Centrifugal effect is the apparent outward force experienced by...
cobot
A robot designed to work safely alongside humans in a shared workspace. Cobots combine sensors, compliant control, and safety features (e.g., force limiting, speed/distance monitoring, soft padding) so that human–robot...
coordinate frame
An origin point with defined axes, used as a reference system to describe locations and orientations. The robot base has one frame, the camera might have another, and the end-effector has yet another.
coupling forces
Forces that result from the interaction between different joints. Because robot joints are connected, moving one joint can create unexpected forces in adjacent joints. The Basics Coupling forces are indirect forces that arise...
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degrees of freedom (DOF)
The number of independent ways a robot can move. A human arm has multiple degrees of freedom (shoulder, elbow, wrist rotation, etc.), allowing it to reach a point in space in many different configurations.
Denavit-Hartenberg (DH) parameters
A standardized mathematical notation for describing the geometry of robot links and joints that uses four parameters per joint. This provides a systematic way to represent complex robotic structures. Instead of writing out...
dynamics
The study of motion that includes forces and mass. Unlike kinematics, dynamics accounts for the physical forces required to make a robot move, considering gravity, inertia, and momentum.
E
encoder
A sensor that measures the rotation angle of a joint. Internal encoders track how much each joint has rotated, providing crucial feedback about the robot’s position. What it is: A sensor attached to each joint that measures...
end-effector
The business end of a robot—the part that does the work, such as a hand, gripper, or tool attached to the robot’s arm.
ends mode
Ends Mode is an operational mode where a joint (or actuator) moves at a commanded constant speed until it reaches a predefined positional limit (end stop) or timeout. It does not use force/torque feedback to adapt to contact;...
Euler angles
A way to represent 3D orientation using three rotation angles applied in a specific sequence around the coordinate axes. Euler angles are a set of three angles that describe the 3D orientation (rotation) of an object. Instead...
exoskeleton
A wearable robotic framework that amplifies human strength and movement, helping people lift heavier loads or overcome physical limitations. An exoskeleton is a wearable robotic suit that wraps around your body and amplifies...
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Five-Bar Linkage System
A mechanical structure composed of five rigid bars (links) connected by five joints, typically in a closed chain. This configuration is commonly used in precision positioning devices because it provides smooth, predictable...
force sensors
Devices that measure forces and torques applied to a robot or its end-effector. They provide critical feedback for force/impedance control, collision detection, safe interaction with humans and environments, and haptic feedback....
force-torque sensor
A six-degree-of-freedom sensor at a robot’s wrist that measures the forces (linear pushes/pulls) and torques (rotational forces) applied to the end-effector. This allows robots to sense when they’re in contact with objects and...
forward kinematics
A calculation that determines where the end-effector (hand/gripper) is positioned in space based on knowing all the joint angles. Think: “If I know the angle of every joint, where is my hand pointing?” The opposite of inverse...
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G-Force
The acceleration of the robot expressed in multiples of gravitational acceleration (9.8 m/s²). Fifty Gs means the robot accelerates at 50 times the acceleration you’d experience in free fall. This extreme acceleration requires...
generalized coordinates
A set of independent parameters (typically joint angles) that completely describe a robot’s internal configuration. If you know all the generalized coordinates, you know exactly what shape the robot is in. The Basics Generalized...
gravity compensation
Gravity compensation is the calculation and application of motor torques needed to counteract gravity, allowing a robot to hold its configuration without drooping or sagging. By computing the gravitational force acting on each...
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haptic devices
Technology that provides force feedback, allowing users to physically “feel” virtual or remote environments. Used in surgical robots and VR systems to transmit touch sensations. Haptic devices are tools that simulate touch and...
Homogeneous Transformation
A 4×4 matrix that captures both the rotation and translation (movement) between two coordinate frames. It’s a unified way to describe where something is and which way it’s pointing. Think of it as a complete descriptor of one...
humanoid robot
A humanoid robot is a robotic system intentionally designed to resemble the human body in form, degrees of freedom, sensors, and behavior. The design goal is to operate effectively in human environments, interact safely with...
hydraulic
A system powered by pressurized fluid (typically oil). Similar to pneumatics but capable of producing higher forces, often used in heavy industrial equipment.
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inertia
The resistance of an object to changes in motion. More massive or awkwardly shaped objects have greater inertia and require more force to accelerate. The Basics Inertia is the resistance to change in motion—an object's...
inverse kinematics
Determining what joint angles are needed to position the end-effector at a specific target location. Think: “I want my hand at this point in space—what angles do I need?” The opposite of forward kinematics. What it is: The...
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Jacobian matrix
A mathematical tool that relates joint velocities (how fast each joint is moving) to end-effector velocities (how fast the hand is moving). It also importantly relates the forces applied at joints to the forces felt at the...
joint
The connection point between two links that allows controlled motion. In robotics, joints are deliberately simplified to either rotate or slide. The Basics A joint is a connection point between two links that allows controlled...
joint space control
A robotic control approach that operates at the individual joint level, commanding each motor to move to specific angles. Traditional industrial robots use this method. Modern robots tend to use Cartesian space control. What it...
joint space control
A traditional control approach that commands each individual motor to achieve specific angles. Uses proportional-integral-derivative (PID) controllers to drive each joint independently. Common in industrial robots. Joint space...
K
kinematic chain
The sequence of connected links and joints in a robot arm. Calculating the kinematic chain means multiplying transformation matrices to determine the position of the robot’s tool relative to a target. A kinematic chain is...
kinematics
The branch of mechanics that describes motion without considering the forces that cause it. In robotics, it focuses on how joints and links move in space—essentially the geometry of motion. Think of it as describing where a...
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linear velocity
How fast something is moving in a straight line through space (in meters per second).
link
A rigid body or segment that forms part of a robot’s structure. Links are the “bones” of the robot and don’t deform during operation. The Basics A link is a rigid structural segment of a robot—the solid "bones" that form the...
Local Minima (in motion planning)
A trap condition where the robot gets stuck in a sub-optimal position—like a ball rolling into a small dip when there’s a deeper valley elsewhere. Good planning algorithms help avoid these traps. Local minima occur when a robot...
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mass matrix
A mathematical representation of how the robot’s mass and inertia are distributed across its structure. It’s essential for understanding the forces needed to accelerate the robot. What it is: A mathematical representation that...
modular robotics
A design approach where robots are composed of discrete, interchangeable units that can be connected in different configurations to achieve different shapes and functions. Modular robotics is the "construction kit approach"—a...
moving coil actuators
Electrical motors that use a coil of wire suspended in a magnetic field to produce motion. Unlike traditional motors with rotating shafts, moving coil actuators are designed for direct linear or short-distance motion, making...
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nominal trajectory
A planned path computed from a starting point to a destination, taking into account constraints like steering angles and vehicle dynamics. For autonomous parking, this is the ideal parking path calculated before execution...
non-holonomic System
A system where the possible paths of motion are constrained by the current state, meaning you cannot move in any direction at any time. A classic example is a car: it cannot move sideways (parallel park) without moving forward...
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operational (task) space control
A more intuitive control method that treats the end-effector as being attracted to a goal position by a virtual force (like magnetic attraction). The robot naturally finds its own path to the target without explicitly...
operational coordinates (task coordinates)
The position and orientation of the end-effector in space relative to a reference point. In 3D, this requires 6 parameters: three for location (x, y, z) and three for orientation (roll, pitch, yaw—like airplane movements). The...
Operational Space (or Task-Space) Control
A control method where the robot's hand (end-effector) is treated as if it's attracted to a goal position by a virtual force (like a magnet pulling it toward a target). Instead of calculating exact joint angles, the system lets...
optical encoders
Sensors that measure position by detecting light pulses passing through or reflecting off a calibrated disk or pattern. “Low-mass” encoders minimize the weight added to moving parts, which is crucial for high-speed systems where...
orthonormal
A property of rotation matrices: their rows and columns are perpendicular unit vectors. This means the inverse of the matrix is simply its transpose—a major computational convenience.
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parametric excitation
A method of adding energy to a swinging system (like a child on a swing or a brachiation robot) by changing a system parameter—such as the length of the arms—at specific intervals to increase the amplitude of the swing.
Pick-and-Place Tasks
Simple repetitive industrial tasks where a robot picks up an object from one location and places it in another. This was historically the primary use of robots. Pick-and-place is a fundamental industrial robot operation where...
PID controller (Proportional-Integral-Derivative)
A control algorithm with three components that work together: Proportional (responds to current error), Integral (corrects past errors), and Derivative (predicts future error). It’s the standard way to control individual motors...
pitch, yaw, and roll
Three rotational axes describing how an object is oriented in 3D space: Pitch: rotation about the side-to-side (lateral) axis Yaw: rotation about the vertical axis Roll: rotation about the front-to-back (forward) axis
pneumatic
A system powered by compressed air rather than electricity or liquids. Pneumatic actuators are lighter and naturally absorb impacts, making them safer around people than rigid motor-driven systems.
potential energy gradients
A concept where attractive forces pull the robot toward goals and repulsive forces push it away from obstacles. The robot moves along the “energy landscape” toward the lowest energy point (the goal). This describes...
prismatic joint
A joint that slides linearly back and forth along an axis, like a drawer opening and closing. A prismatic joint is a mechanical connection that allows linear sliding movement along a fixed axis—like a drawer, piston, or...
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Quaternions
Quaternions are a mathematical representation of 3D rotations using four parameters instead of three. This extra parameter eliminates singularities (gimbal lock) and enables smooth, continuous rotation calculations for any...
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reactionless design
A mechanical arrangement where the center of gravity of all moving parts stays fixed during operation, even as individual components move relative to each other. This prevents the robot from “pushing back” on its mounting...
Recursive Newton-Euler Formulation
A computational method for calculating reaction forces between every link in the robot chain. Used in dynamics analysis but can be computationally expensive. The Recursive Newton-Euler (RNE) formulation is a computational...
redundancy (in kinematics)
A situation where multiple joint configurations can achieve the same end-effector position. Like how you can reach for a coffee cup with your elbow high or low—both work. This creates computational complexity because there’s no...
revolute joint
A joint that rotates, like an elbow or knee. It allows rotational movement around an axis. A revolute joint is a mechanical connection that allows rotational movement around a fixed axis—similar to a hinge or pivot. Common...
Rigid Body
A solid component in a robot that doesn’t bend or deform—it maintains its shape under all conditions. Real-World Examples Rigid bodies in robots: Metal arm segments Robot links (connecting pieces) Gripper fingers Wheels and...
Rotation Matrix
A 3×3 mathematical matrix that describes how one coordinate frame is oriented relative to another. The columns represent the directional axes of one frame as seen from another frame’s perspective. A special property: multiplying...
S
singularity
A singularity is a problematic robot configuration occurring when rotation axes become aligned, resulting in the temporary loss of one degree of freedom. At this point, the robot loses the ability to move smoothly in certain...
springs mode
Springs Mode is an operational mode where a joint (or end-effector) behaves like a well-damped virtual spring: it applies forces proportional to displacement from a setpoint and includes damping to avoid oscillation. The...
statically stable gait
Statically stable gait is a locomotion pattern for modular robots where the robot moves along a straight line while maintaining stability at every instant. Unlike dynamic gaits that rely on momentum, a statically stable gait...
T
tactile sensors
Touch-sensitive devices on a robot (typically on fingertips or hands) that detect physical contact, pressure, or slippage when handling objects. The Basics Tactile sensors are touch-sensitive devices on a robot's gripper,...
torque
A rotational force that causes something to spin or rotate. In motors, torque describes how hard the motor can twist.
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velocity propagation
A recursive computational method that calculates the velocity of each link sequentially from the robot’s base outward to the end-effector. More efficient than solving the entire kinematic chain simultaneously. Velocity...
velocity-force duality
The reciprocal relationship in robotics where the Jacobian maps velocities forward, while its transpose maps forces backward. A position where velocities are amplified (low mechanical advantage) is also where forces are reduced;...
virtual work principle
A foundational concept in mechanics stating that at static equilibrium, the total work done by all forces and torques must be zero. This principle is used to derive the relationship between joint torques and end-effector forces.
visual servo control
A feedback system where cameras continuously monitor the position of a target, and this visual information is used to guide the robot’s movements in real-time. The robot constantly adjusts its arm position based on what its...
Z
zero backlash
The absence of “dead space” or slack between mechanical components. In a typical gear system, when direction changes, there’s a brief moment where the gears don’t fully engage—this is backlash. Zero backlash means every motor...