An active orthosis was designed to support users with reduced muscle strength with an additional knee joint torque to improve the independency in everyday activities. In two persons the hypothesis was tested that less muscle activity is necessary when standing up with the active support of a motorized orthosis. The orthosis is a custom-made knee-ankle-foot orthosis and is equipped with a series elastic actuator. A reduced EMG activity in the m. rectus femoris was found when supported by the active orthosis in the sitto-stand task. The unchanged kinetics and kinematics show that the subject's sit-to-stand (STS) strategy is not influenced by the external torque; therefor amplifying torque generation seems to be a promising way of support.

Zusammenfassung Aktive Kniegelenkorthesen können eingesetzt werden, um älteren Menschen im Alltag ein selbstbestimmtes Leben im vertrauten Umfeld zu ermöglichen. Als Antrieb für solche Geräte erweisen sich seriell-elastische Antriebe (SEA) als vorteilhaft, da sie im engen Kontakt zum Menschen besser regelbar sind als direkt gekoppelte getriebeunterstützte DC-Motoren. Sie weisen darüber hinaus in vielen Fällen ein besseres Systemleistungsgewicht als fluidische Antriebe oder elektrodynamische Direktantriebe auf. Im Folgenden werden die Auswahl und Auslegung eines SEA für eine aktive Kniegelenkorthese, seine Regelung mit einem Zustandsregler sowie erste experimentelle Ergebnisse präsentiert und diese in den Stand der Technik eingeordnet.

The purpose of the present study was to analyze the neuromuscular responses during the performance of a sit to stand [STS] task in water and on dry land.10 healthy subjects, five males and five females were recruited for study. Surface electromyography sEMG was used for lower limb and trunk muscles maximal voluntarty contraction [MVC] and during the STS task.Muscle activity was significantly higher on dry land than in water normalized signals by MVC from the quadriceps-vastus medialis [17.3%], the quadriceps – rectus femoris [5.3%], the long head of the biceps femoris [5.5%], the tibialis anterior [13.9%], the gastrocnemius medialis [3.4%], the soleus [6.2%]. However, the muscle activity was higher in water for the rectus abdominis [−26.6%] and the erector spinae [−22.6%].This study for the first time describes the neuromuscular responses in healthy subjects during the performance of the STS task in water. The differences in lower limb and trunk muscle activity should be considered when using the STS movement in aquatic rehabilitation.

Abstract This contribution presents a new approach of estimating the joint torques for an active orthosis. The new approach combines inverse dynamics and measured ground reaction forces. The joint torques can easily be computed from the ground reaction forces, but the measurement is usually flawed. An obsererver is employed to estimate the disturbance of the measurements and restore the original joint torques. A model of the human lower extremity is presented and additional seat forces are introduced to model the seat. Simulation results on the Sit-to-Stand movement illustrate the effectivity of the new approach.