  Supernumerary Robotic Limbs (SRLs) exhibit inherently compliant behavior due
to the elasticity present at the intersection of human tissue and the robot.
This compliance, can prominently influence the operation of some SRLs,
depending on the application. In order to control the residual vibrations of
SRLs, we have used an input-shaping method which is a computationally
inexpensive approach. The effectiveness of this method in controlling the
residual vibrations of a SRL has been proven using robustness analysis. User
studies show that reducing the vibrations using input shaping directly
increases the user satisfaction and comfort by at least 9%. It is also observed
that 36% of the users preferred unshaped commands. We hypothesize that the
shaped commands put a higher cognitive load on the user compared to unshaped
commands. This shows that when dealing with human-robot interaction, user
satisfaction becomes an equally important parameter as traditional performance
criteria and should be taken into account while evaluating the success of any
vibration-control method.
