Robot control
Force control
Definition
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.
Also known as: Robot force control
Updated
Regulating contact load
When a robot presses a tool against a surface, accurate position alone does not guarantee the desired pressure. A small error in the assumed surface location can create a large force if the tool and surface are stiff. Force control makes that interaction load an explicit target.
Modern Robotics describes a quasistatic method that maps a desired end-effector wrench into joint torques using the robot Jacobian transpose, with gravity compensation. Adding a force-torque sensor permits feedback on the difference between desired and measured wrench.
Contact must support the requested force
A hand pressing on a tabletop can push into it, but cannot pull it upward without a grasp or adhesion. It may also slide if the tangential force exceeds available friction. A controller's target therefore needs to fit the actual contact constraints.
Force and motion are coupled
For wiping, the robot may regulate the normal pressing force while controlling motion along the surface. This is a use of hybrid position-force control. Alternatively, impedance control sets a compliant response. Force sensing can be noisy, and Modern Robotics notes that differentiation amplifies this noise, which influences feedback and filtering choices.
Sources
Related terms
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.
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.
Hybrid position-force control
Hybrid position-force control regulates motion in some task directions and contact force in complementary constrained directions. It separates the commands according to the motion and force freedoms permitted by the environment.
Wrench
A wrench is a six-component representation of force and moment acting on a rigid body. It combines three force components with three moment components about a specified reference point.