Fig. 2

Upper panel: Evolution of upper extremity rehabilitation robots. From stiff (high impedance) industrial manipulators to dedicated rehabilitation robots providing control at the distal effector or over each joint, including the rendering of virtual object dynamics resulting in somatosensory feedback. Further evolution of the technology will see wearable systems providing support not only during therapy sessions, but also during activities of daily living in the home environment, allowing physical interaction with real objects. Lower panel: Task-specific design of hand rehabilitation robots. Functional hand movement training should focus not only on unimanual, i.e. reach and grasp tasks (left), but should also include bimanual separate tasks (middle), as well as cooperative movement tasks that are employed, e.g., when opening a bottle (right)