German Research Center for Artificial Intelligence: Portable exoskeleton helps stroke patients to move again

The use of robots has long been part of everyday life in medicine, and robotic systems are also playing an increasingly important role in rehabilitation. In the now completed project RECUPERA-Reha, the Robotics Innovation Center of the German Research Center for Artificial Intelligence (DFKI) under the direction of Prof. Dr. med. Dr. Frank Kirchner made a breakthrough in the field of rehabilitation robotics: Together with Rehaworks GmbH, he developed a mobile exoskeleton for upper body assistance especially for rehabilitative therapy after a stroke.For more than three years, an interdisciplinary DFKI research team worked on the conception of an innovative portable whole body exoskeleton for external support of the human musculoskeletal system. Based on this, it developed a robotic subsystem that can be used for medical rehabilitation in the medium term. As an application scenario, the scientists chose therapy for stroke patients. They were able to show that exoskeletons can be used to implement classical therapeutic measures, for example by enabling applications of “Assistive Daily Living” such as grasping and lifting objects.

 

(DFKI GmbH, Foto: Annemarie Popp)

“After a stroke helps physiological training, which brings people back to certain movements. Only then can healthy areas of the brain take over the functions of the destroyed areas. Our exoskeletons provide patients with intensive and sustained training that enables them to regain lost motor skills, “says neurobiologist and project manager Dr. Ing. Elsa Andrea Kirchner. The developed whole-body exoskeleton kinematically records approximately the entire range of motion of the human body. The upper body construction is used for rehabilitation, which is supported by the flexible leg construction. In contrast, the subsystem does not carry itself, but is attached to a wheelchair. To build up the exoskeletons, the DFKI scientists developed innovative methods in lightweight construction as well as in drive technology and control technology. The mechatronic approaches combined them with a new system for the online evaluation of electroencephalography and electromyography (EEG / EMG) signals, providing an assessment of the patient’s condition and multi-level regulatory support.

Three different control modes for a variable upper body assistance

For the robotic subsystem, the researchers investigated various approaches to rehabilitative therapy, which they evaluated in a user study of stroke patients. The patient in the exoskeleton or a third person can operate the system and choose between three different modes of control: In the first mode, the movement of one arm allows the other to move with it, performing exactly the same movement as the arm moved by the patient. In this way, the exoskeleton can be used for a mirror therapy, which offers not only visual, but also proprioceptive stimulation – ie the stimulation of one’s own body perception. The second mode allows the control of movement by a third person, eg the therapist, trained by leadership and thus in the sense of a repetitive therapy as often as possible executable. In the third mode, the exoskeleton can be controlled based on the patient’s muscle activity (which is still marginal in the patient population). This is done by measuring the electromyography signals (EMG signals), from which the system can deduce the movement intent of the patient and intuitively support him in his movements.

“With RECUPERA-Reha, we have been able to embark on a new path in human-robot interaction that can lead to a sustainable improvement in rehabilitation. We hope that we can develop the exoskeletons in the years to come, in order to make them even easier and more flexible, and at the same time provide even more support if needed, “says Professor Frank Kirchner.