Online adaptive compensation of the ARMin Rehabilitation Robot

Robot-assisted arm therapy is increasingly applied in neurorehabilitation. The reason for this development over the last decades was that robots relieve the therapist from hard physical work while the training intensity can be increased. Importantly, an increase in training intensity is closely linked to functional improvements of the patient. However, usability of the robot for therapists was hardly considered an important factor in rehabilitation robot development so far. We believe that usability of the robot is a key factor for acceptance of the device by therapists. In this paper, an online adaptive compensation for the ARMin rehabilitation robot is presented, which aims at improving usability of the robot. Therefore, we expect ARMin therapy to become even more effective than conventional therapy at a level that is also relevant for the patient. Additionally, improved usability relieves the therapist from unnecessary/time-consuming tasks linked to robot handling. For the ARMin, the new online adaptive compensation takes over automatic updates of changed upper and lower arm lengths as well as adaptation of shoulder angle settings to fit the patient's anthropometry. Simultaneously, the model-based compensation in ARMin is directly updated to account for hardware changes. Importantly, the online adaptive compensation provides improved performance of ARMin even at the borders of the workspace. In experiments, we could show that the adaptive online compensation relieves the force and position controller from additional burdens and increases the robot performance drastically especially at the workspace border.