Adaptive Knee Orthosis with Power Support to assist the Elderly

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The aim of this cooperative research project is to develop scientific knowledge for the development of an adaptive knee orthosis with power support to ease mobility for the elderly. Conventional stationary supports such as rising chairs and stair lifts may become obsolete once an uprising and stair climbing aid is available which is easily applied at the body, comfortable in use and intuitive to operate. The independent recognition of support demand characterizes the adaptive nature of the active orthosis. This kind of mechatronic assistance system could support the elderly in their mobility. Furthermore, therapeutic use is conceivable.In the first phase of research, a serial-elastic actuator (SEA) and special kinematics have been developed to follow the physiological knee motion and test orthoses were built. By means of surface electromyography it was verified that under external power support during the transfer movement, the activation of the knee extensors is reduced accordingly. Hence, the orthosis actually relieves the user when standing up from a sitting position. The autonomous control of the sit-to-stand process is implemented using a model of the user with orthosis and force measurement at the foot-plate of the orthosis as input variable. This allows both, the power and the transparency of the orthosis perceived by the user to be scaled dynamically. For situational awareness, a mechanical muscle activity sensor is designed for use around the thigh. Inertial sensors provide redundant orientation determination of the orthosis and enhance situational awareness in the future.The current demonstrator is still rather large and the system is controlled by a number of external devices, so that a practice-oriented testing is difficult. In the second research phase, bionically inspired distributed string-actuators are developed that allow significant weight and space reduction. Similar to the kinematics and sensors, they will be integrated in the framework of the orthosis as much as possible. This field test demonstrator should then be subject of intensive tests for further scientific issues such as the redistribution of biomechanical loads under motor support at the knee. Possible tripping and falling risks induced by the orthosis are examined. The results will be used in the future as a basis for the development of mobility-enhancing assistance systems.