Zero-Force Drag

Letting a robot arm cancel out its own gravity and friction so a person can push it around with barely any force.

Zero-force drag is a hand-guiding mode found on collaborative arms — Universal Robots calls it Freedrive, Franka calls it Guiding mode. Once engaged, the controller computes in real time the torque needed to cancel its own gravity (gravity compensation) and joint friction (friction compensation), so the arm hangs as if weightless and a light push is enough to move it. It's implemented roughly three ways: arms with joint torque sensors apply the compensation directly in torque mode; many collaborative arms without torque sensors estimate external force from motor current instead; traditional industrial arms mount a 6-axis force sensor at the wrist and use admittance control to convert the measured force into motion. Its main use is kinesthetic teaching: a person physically guides the arm through a motion by hand, and the controller records the trajectory or saves it as demonstration data. ‘Zero-force’ refers to the force a person needs to apply being close to zero — not that the motors output no force.

ExampleOn Franka arms, holding two opposing buttons near the flange engages guiding mode, and libfranka's setGuidingMode can release only some directions (e.g., allowing translation only, locking rotation); UR's ROS 2 driver provides a freedrive_mode_controller that needs a continuous stream of True messages, exiting automatically if none arrive for 1 second by default.

Also called

Free-Drive Mode, Hand Guiding Mode, Freedrive, Guiding Mode

Related

Kinesthetic Teaching · Gravity Compensation · Friction Compensation · Admittance Control · Joint Torque Sensor · Demonstration Data

Sources

libfranka robot.h（setGuidingMode：Guiding mode can be enabled by pressing the two opposing buttons near the robot's flange）
Universal Robots ROS 2 Driver: ur_controllers 文档（FreedriveModeController / ForceModeController） (Chinese)
Enabling Scalable Kinesthetic Teaching via Observer-based Hand-guiding with Active Support (arXiv:2608.10847)

As of

2026-09