How can you tell when a person is incapable of doing something? It’s possible to try many times and fail without asking for help. In the case of a robot intended for a particular task, giving the unit a way to signal its failure would help human handlers understand whether it needed help or repair. Researchers from Cornell and UC Berkeley developed a process by which a robot uses expressive motion to indicate “both what it wants to do and why it is incapable of doing it.” The motions are generated based on what the problem is. For example, a robot unable to pick up an object is shown shrugging its shoulder upward.
More information can be found here.