actuator
In plain wordsThe 'muscle' of a machine: a motor or similar device that turns electrical, hydraulic or air power into movement, such as turning a robot's joint or closing its gripper.
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Robotics and engineering
A component that converts energy — electrical, hydraulic, pneumatic, thermal or chemical — into mechanical motion or force on command from a controller, producing the physical actions of a robotrobot, n.: A machine that senses its surroundings, decides what to do and physically acts, moving itself or handling objects, with some independence from a human operator. Factory arms, robot vacuums and self-driving cars are all robots., vehicle or machine. Robots mostly use electric motors (brushless motors with position encoders, often paired with high-ratio reducers such as harmonic or planetary gears), hydraulic cylinders for very high force, as in the original hydraulic Atlas humanoid, and pneumatic cylinders or suction for cheap, compliant grippers. Designs trade torque density, speed, precision, efficiency, cost and back-drivability, the ability to be pushed back by external forces, which matters for safety and for sensing contact. Series elastic actuators put a spring between motor and load to measure and control force; quasi-direct-drive or 'proprioceptive' actuators use low gear ratios so that motor current reveals contact forces, a design favored in agile legged robotslegged robot, n.: A robot that walks on legs instead of rolling on wheels, such as a four-legged 'robot dog' or a two-legged humanoid, so it can climb stairs and cross rough ground.. Research actuators include artificial muscles, shape-memory alloys and soft pneumatic chambers.
The knee actuator overheats on stairs, so we cap the gait's peak torque.
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AI agents (by analogy)
In the classic definition of an intelligent agentintelligent agent, n.: In AI theory, a decision-maker, such as a robot, a self-driving car, a chess program or a helpful piece of software, that notices what is going on around it and responds in ways that serve its goals., whatever the agent uses to act on its environment — motors and grippers for a robot, or messages, tool callstool call, n.: A single request from an AI model to use one of its tools — naming the tool and filling in the details — which the surrounding software then carries out and reports back on. and file writes for a software agent — paired with the sensors that supply its percepts.
Origin
From 'actuate' (Medieval Latin actuare, to put into action). Series elastic actuators were introduced by Gill Pratt and Matthew Williamson in 1995; the sensors-and-actuators description of agents was popularized by Stuart Russell and Peter Norvig's textbook Artificial Intelligence: A Modern Approach (first edition 1995).
Related
- robotrobot, n.: A machine that senses its surroundings, decides what to do and physically acts, moving itself or handling objects, with some independence from a human operator. Factory arms, robot vacuums and self-driving cars are all robots.
- end effectorend effector, n.: The tool at the end of a robot arm that actually touches the world, such as a gripper, suction cup, welding torch, paint sprayer or robotic hand.
- degrees of freedomdegrees of freedom, n.: The number of independent ways something can move. A robot arm with six motorized joints has six; a free-floating object can slide three ways and turn three ways.
- proprioceptionproprioception, n.: A robot's sense of its own body: where its joints are, how fast they are moving and how hard its motors are pushing, measured by internal sensors rather than cameras.
- legged robotlegged robot, n.: A robot that walks on legs instead of rolling on wheels, such as a four-legged 'robot dog' or a two-legged humanoid, so it can climb stairs and cross rough ground.
- intelligent agentintelligent agent, n.: In AI theory, a decision-maker, such as a robot, a self-driving car, a chess program or a helpful piece of software, that notices what is going on around it and responds in ways that serve its goals.
- PID controllerPID controller, n.: The most common automatic controller in industry. It corrects a machine using three ingredients: how far off it is now, how long it has been off, and how fast the error is changing.
Sources
- Pratt, G. A. & Williamson, M. M. (1995). Series elastic actuators. Proc. IEEE/RSJ IROS 1995.
- Russell, S. & Norvig, P. (1995). Artificial Intelligence: A Modern Approach. Prentice Hall.
Mentioned in
robotrobot, n.: A machine that senses its surroundings, decides what to do and physically acts, moving itself or handling objects, with some independence from a human operator. Factory arms, robot vacuums and self-driving cars are all robots., roboticsrobotics, n.: The science and engineering of building robots and making them work: designing their bodies, sensors and motors, and writing the software that lets them see, plan and move safely., collaborative robotcollaborative robot, n.: A robot designed to work safely right next to people without a safety cage, for example by moving gently and stopping at once if it bumps into someone., degrees of freedomdegrees of freedom, n.: The number of independent ways something can move. A robot arm with six motorized joints has six; a free-floating object can slide three ways and turn three ways., end effectorend effector, n.: The tool at the end of a robot arm that actually touches the world, such as a gripper, suction cup, welding torch, paint sprayer or robotic hand., legged robotlegged robot, n.: A robot that walks on legs instead of rolling on wheels, such as a four-legged 'robot dog' or a two-legged humanoid, so it can climb stairs and cross rough ground., PID controllerPID controller, n.: The most common automatic controller in industry. It corrects a machine using three ingredients: how far off it is now, how long it has been off, and how fast the error is changing., proprioceptionproprioception, n.: A robot's sense of its own body: where its joints are, how fast they are moving and how hard its motors are pushing, measured by internal sensors rather than cameras.