Robot control
Admittance control
Definition
Admittance control converts measured or estimated interaction forces into a desired robot motion through a specified dynamic model. An inner motion controller then follows that reference.
Also known as: Robot admittance control
Updated
Turning a push into a motion command
A typical admittance controller receives a force or wrench, applies a virtual mass-spring-damper model, and calculates a position or velocity adjustment. This lets a motion-controlled arm yield when someone pushes its handle instead of holding the handle rigidly in place.
The ros2_control implementation provides force-torque sensing, selectable Cartesian axes, virtual mass, damping, and stiffness settings. Its documentation also describes position and velocity interfaces and tool-weight compensation. These are examples of one implementation, rather than requirements for every admittance controller.
How it differs from impedance control
Impedance control specifies a force response to motion, commonly through torque commands, as explained in MIT's manipulation notes. An admittance implementation uses force as the input to a motion-generating model. The intended external response may be similar, but the sensing requirements and inner control loops differ.
Practical constraints
Measured force must be interpreted in the correct frame and distinguished from effects such as tool weight. The requested motion must stay within the robot's reachable region and joint limits. Filter delay and the response of the inner motion loop affect contact behavior, so selecting small virtual mass or high stiffness does not by itself establish stable interaction with a rigid surface.
Sources
Related terms
Impedance control
Impedance control shapes the dynamic relationship between a robot’s motion and the forces it exchanges with its environment. A common goal is for the robot to respond like a chosen mass, spring, and damper at a joint or end effector.
Force control
Force control regulates the force or wrench a robot applies to its environment. It may use a robot model, measured interaction forces, or both to produce joint commands that achieve a desired contact load.
End effector
An end effector is the part of a robot positioned to perform a task at the end of a manipulator, such as a gripper, hand, suction tool, or welding tool. Its pose and interaction forces are often the quantities a task controller regulates.
Torque control
Torque control regulates the turning effort delivered by an actuator or robot joint. It provides an actuation interface from which motion, force, and impedance controllers can produce the joint torques their tasks require.