Hardware & control
End effector
An end effector is a task-specific device attached to a robot manipulator’s mechanical interface so the robot can act on its environment, such as a gripper, hand or welding tool. It is distinct from the wrist or mounting flange, and from the tool centre point, which is only a coordinate frame used to plan the device’s motion.
Also known as: End-effector, Robot end effector, End effectors
Updated
Device, interface and tool centre point
ISO 8373:2021 treats the end effector as a device attached to the manipulator’s mechanical interface to perform a task. The manipulator includes its links, joints and actuators but excludes the end effector itself. A gripper is therefore an end effector; the wrist and mounting flange that support it are parts of the manipulator.
The tool centre point (TCP) is different again. Universal Robots defines a TCP as a translation and rotation from the tool flange to a point on the tool. Changing that transform changes how motion is calculated, not which hardware is attached.
The term broadens in humanoid control
For hardware descriptions, a humanoid hand or gripper is the clearest end-effector example. Kinematics and control also use “end effector” for a terminal link or task frame. Modern Robotics attaches such a frame to the end of a kinematic chain.
That broader usage lets a controller treat hands and feet as task frames. A foot may be a moving end effector during swing and a constrained support contact after touchdown. Technical records should say whether “end effector” means the physical device, terminal link or selected frame.
Data needs the tool context
An end-effector trajectory is incomplete without the frame in which its pose is expressed. Training data should preserve the flange-to-tool transform, TCP convention, tool identity, opening or grasp state, payload properties, and any tactile or force channels.
The same wrist pose can produce different contacts after a hand, gripper or tool change. Keeping the tool geometry and calibration with the trajectory prevents those physically different actions from being treated as equivalent.
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Related terms
Hardware & control
Actuator
An actuator is a robot’s power mechanism that converts electrical, hydraulic, pneumatic or other supplied energy into controlled mechanical force, torque or motion. In a humanoid, actuators drive joints, often through transmissions; they are distinct from the joints and sensors, and their arrangement need not correspond one-to-one with the robot’s degrees of freedom.
Hardware & control
Degree of freedom
A degree of freedom (DoF) is one independent parameter needed to specify a robot’s configuration; equivalently, a robot’s DoF is the dimension of its configuration space. It describes possible motion, not the number of motors. Joint constraints, closed kinematic chains and environmental contacts can make joint count, actuator count and controllable motion differ.
Hardware & control
Impedance control
Impedance control regulates the dynamic relationship between a robot’s motion error and the force or torque it exerts, usually by giving the robot virtual stiffness, damping and sometimes inertia. It lets an end effector or limb yield predictably during contact instead of trying to hold an exact position regardless of interaction forces.
Hardware & control
Whole-body control
Whole-body control coordinates a humanoid’s full multibody state, actuated joints and environmental contacts to pursue several motion or force objectives while respecting constraints such as balance, joint limits and friction. It is a family of hierarchical or optimisation-based methods, not one algorithm; implementations may output joint positions, accelerations or torques.