A disturbance observer for the sigma.7 haptic device

This paper presents a disturbance observer for the sigma.7 haptic device. External torques on the haptic device links are observed to distinguish between intended user interaction and accidental collisions of the links. Collisions can be unintentional contact of the human operator, e.g. with his knee, other people accidentally getting in contact with the haptic device or objects falling on it. The observer is based on the dynamic model of the device and sensor measurements from the joint's position sensors and an integrated force/torque sensor. Is is implemented concurrently with a control algorithm that uses the force/torque sensor to effectively reduce the inertia and friction of the sigma.7. Furthermore, forces and torques applied on the grasping unit by the human operator are observed. Experiments are done with the sigma.7 customized for the German Aerospace Center (DLR) by Force Dimension.