Energy-based Residual for Collision Detection Using a Velocity Observer

Robot collision detection is addressed with an energy monitoring residual signal that uses only joint position measurements. The residual is evaluated by estimating joint velocity with a reduced-order observer. The observer uses in turn the momentum-based residual as additional input, acting as a virtual sensor of the external torque. We show the effectiveness of this method by comparing it in simulation with numerical differentiation of encoder measurements under nominal and uncertain conditions.