Set External Force Torque

SUMMARY

Set External Force Torque injects a user-supplied wrench [Fx, Fy, Fz, Tx, Ty, Tz] into the robot controller's dynamics model. This allows the robot to account for an external load that is not measured by the built-in F/T sensor.

SUPPORTED ROBOTS

This skill is currently supported on Universal Robots only. Calling this method on other robot brands will raise a NotImplementedError.

The Skill

robot.set_external_force_torque(wrench=[10.0, 0.0, 0.0, 0.0, 0.0, 0.0])

The Code

Example: Inject a 10 N Force Along the Base X Axis

from loguru import logger
from telekinesis.synapse.robots.manipulators import universal_robots

robot_ip = "192.168.1.2"  # replace with your robot's IP

robot = universal_robots.UniversalRobotsUR10E()
# Connect
robot.connect(ip=robot_ip)

wrench = [10.0, 0.0, 0.0, 0.0, 0.0, 0.0]
robot.set_external_force_torque(wrench=wrench)
logger.success(f"External force/torque set: {wrench}")

# Disconnect
robot.disconnect()

The Explanation of the Code

set_external_force_torque feeds an externally estimated wrench into the robot's dynamics model. Forces are in Newtons; torques are in Newton-meters, all in the robot base frame. Use this when an external load (e.g., from a cable bundle or magnetic fixture) is known but not measurable by the built-in sensor. The injected wrench is used by the controller to compensate for the extra load in force-control calculations.

How to Tune the Parameters

Parameter	Type	Required	Description
wrench	list[float]	Yes	External wrench [Fx, Fy, Fz, Tx, Ty, Tz]. Forces in N, torques in N·m.

Return Value

Value	Description
None	This skill returns nothing.

Where to Use the Skill

• Compensating for known external loads not captured by the F/T sensor.
• Improving force-control accuracy when the robot is attached to a cable management system.

When Not to Use the Skill

Use a different skill instead in these cases:

• Use Zero FT Sensor to remove static tool bias; this method is for injecting dynamic or directional load estimates.