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Robotics

Robotics is the engineering of robots: machines that sense their surroundings, decide what to do with a computer, and act through motors and other actuators, with some degree of autonomy. International standard ISO 8373 defines industrial robots as reprogrammable manipulators with three or more programmable axes and service robots as robots doing useful tasks for people. NASA's Perseverance rover shows sensing, computing and acting working together on Mars.

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Standard definitions

ISO 8373:2021 defines an industrial robot as an automatically controlled, reprogrammable, multipurpose manipulator programmable in three or more axes, fixed in place or on a mobile platform, for industrial automation. 'Degree of autonomy' is the ability to perform intended tasks based on current state and sensing without human intervention. The 2021 revision also makes medical robots a category of their own.

Control loop

  1. Sensors estimate state (joint angles, position, obstacles).
  2. A controller compares the estimate with the goal and computes actuator commands.
  3. Actuators apply forces or torques; sensing repeats, closing the feedback loop.

Perseverance's driving illustrates the loop at a slow cadence: stop, image the terrain in stereo, assess hazards from the 3D views, choose a path, drive, repeat.

Common misconception: Autonomy is not all-or-nothing. For service robots the IFR describes a spectrum, from partial autonomy with human–robot interaction to full autonomy without active human intervention.
Full explanation — the complete reference version every reading depth is based on

Sense, decide, act

  1. Sense: sensors such as cameras measure the robot's surroundings and its own position.
  2. Decide: a computer runs a program that turns those measurements into commands.
  3. Act: actuators — electric motors, hydraulic or pneumatic cylinders — convert energy into motion.

ISO 8373 describes this as a 'degree of autonomy': the ability to perform intended tasks based on current state and sensing, without human intervention. For service robots, the International Federation of Robotics notes that this ranges from partial autonomy, with people interacting with the robot, to full autonomy.

Kinds of robot

  • Industrial robots: automatically controlled, reprogrammable, multipurpose manipulators programmable in three or more axes, used for automation in industry.
  • Service robots: robots in personal or professional use that perform useful tasks for people or equipment.
  • Medical robots: since ISO 8373:2021, a third category alongside industrial and service robots.
  • By mechanical structure: Cartesian (three sliding joints), SCARA (two parallel rotary joints), articulated (three or more rotary joints, like an arm).

Degrees of freedom

Each independently driven joint adds a degree of freedom. NASA's Perseverance rover has a 2.1 m arm with five: shoulder azimuth, shoulder elevation, elbow, wrist and turret, each turned by a rotary actuator motor. Its six hazard-avoidance cameras take stereo pictures of the ground, so the rover can choose its own path without asking the team on Earth about every move, and its duplicated Rover Compute Element means there is always a spare 'brain'.

DOF=∑joints(independent motions per joint)\text{DOF} = \sum_{\text{joints}} (\text{independent motions per joint})

For a serial arm of single-axis joints, the degrees of freedom equal the number of joints.

Worked example

A Cartesian robot has three prismatic joints moving along x, y and z, so it has 3 degrees of freedom and can reach any point in a box-shaped workspace — but cannot tilt its tool. Perseverance's arm, with five rotary joints, can both position its turret and turn it to point instruments at a rock.

How we know

The definitions come from the international robotics vocabulary standard, ISO 8373, as quoted by the International Federation of Robotics (the standard itself is sold, not freely published). The Perseverance details come from NASA's published description of the rover's components.

Assumptions and limits

Definitions differ between uses: the IFR, for example, counts medical robots with service robots in its statistics, deviating from ISO 8373. Autonomy is also partial in practice — Perseverance chooses its own path on a drive, but the mission team on Earth still commands where it goes, what it photographs and which instruments it uses.

Common misconception: Misconception: 'a robot must look like a person'. Most robots are arms, vehicles or cleaning machines. What makes something a robot is programmable, actuated behaviour with some autonomy, not a human shape.
Info: Connections: robots depend on Sensors to perceive, Computers to decide and Energy sources to move; Perseverance is robotics applied to exploring the Solar System; and AI agents follow the same perceive–decide–act loop in software.

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Sources and methodology

  • ISO 8373:2021 defines an industrial robot as an automatically controlled, reprogrammable, multipurpose manipulator, programmable in three or more axes, which can be fixed in place or fixed to a mobile platform for use in automation applications in an industrial environment. (awaiting scientific review)
  • According to ISO 8373, robots require a degree of autonomy, defined as the ability to perform intended tasks based on current state and sensing, without human intervention. (awaiting scientific review)
  • ISO 8373 defines a service robot as a robot in personal use or professional use that performs useful tasks for humans or equipment. (awaiting scientific review)
  • ISO 8373:2021 defines medical robots as a third category alongside industrial and service robots, although the International Federation of Robotics includes medical robots in its service-robot statistics. (awaiting scientific review)
  • An actuator is a device, operated by a source of energy such as electric current, hydraulic fluid pressure or pneumatic pressure, that converts that energy into motion; it is the mechanism by which a control system acts upon its environment. (awaiting scientific review)
  • Industrial robots are classified by mechanical structure: for example, a Cartesian robot has three prismatic (sliding) joints, a SCARA robot has two parallel rotary joints, and an articulated robot has three or more rotary joints. (awaiting scientific review)
  • NASA's Perseverance Mars rover has a 2.1-metre (7-foot) robotic arm with five degrees of freedom — shoulder azimuth, shoulder elevation, elbow, wrist and turret joints — driven by rotary actuator motors. (awaiting scientific review)
  • Perseverance's six hazard-avoidance cameras detect hazards such as large rocks, trenches and sand dunes; when driving, the rover stops frequently to take new stereo images, and the 3D views let it decide where to drive without consulting the team on Earth about every move. (awaiting scientific review)
  • Perseverance's computer, the Rover Compute Element, is duplicated so that there is always a spare 'brain', and its memory is built to tolerate extreme radiation in space and on Mars. (awaiting scientific review)

Claims marked “awaiting scientific review” cite the sources listed but have not yet been signed off by a scientific reviewer.

Content status: published 1 October 2026.

  • Scientific review: this version has not yet been signed off by a scientific reviewer.
  • The Advanced explanation has not yet been reviewed for age suitability.