“…A common way to estimate it, is via the grasping force at the interaction point, by dedicated force/torque sensors, even if in industrial applications there exists several cases where the human operator interacts directly with the payload, such as with lifting or assist devices. In [Lamy et al, 2009], the authors designed a handle for intuitive co-manipulation, where a 6-dof force/torque sensor was covered by a soft foam: when held delicately through a precision grip, the foam acts as a mechanical filter, and the system reflects low inertia; conversely, when held firmly through a power grasp, resulting from higher impedance in the arm because of muscle co-contraction [Napier, 1956], the squeezed foam does not filter, the system exhibits higher inertia, the gains are lowered and the system remains stable.…”