Manipulator impedance accuracy in position-based impedance control implementations

Compares two position-based impedance controllers obtaining desired end-effector impedances during robot interaction with the environment. It is shown that while these two controllers have similar structures, the Adept Controller yields more accurate impedances in the DC region because of the stiffness control properties of the force loop. In addition, adding a force feedforward component to offset the contact force was found to significantly reduce the impedance errors in both controllers. The effect of bandwidth and force feedforward are examined for a planar arm example for a typical set of desired impedance specifications