A prototype of a powered knee orthotic device was developed to determine whether fractional external torque and power support to the knee relieves the biomechanical loads and reduces the muscular demand for a subject performing sit-to-stand movements. With this demonstrator, consisting of the subsystems actuation, kinematics, sensors, and control, all relevant sensor data can be acquired and full control is maintained over actuator parameters. A series-elastic actuator based on a direct current motor provides up to 30Nm torque to the knee via a hinge joint with an additional sliding degree of freedom. For reasons of feasibility under everyday conditions, user intention is monitored by employing a noninvasive, nonsticking muscle activity sensor to replace electromyographic sensors, which require skin preparation. Furthermore, foot plates with force sensors have been developed and included to derive ground reaction forces. The actual knee torque needed to provide the desired support is based on an inverse dynamics model using ground reaction forces signals and leg kinematics. A control algorithm including disturbance feed forward has been implemented. A demonstration experiment with two subjects showed that 23% of moment support in fact leads to a similar reduction in activation of the main knee extensor muscle.

This paper presents a medical robotic system for tool positioning tasks in orthopaedic surgery. The system consists of an 7 DOF upper limb exoskeleton, which is attached to the arm and back of an orthopaedic surgeon, and a real-time control system with an optical tracking camera. The objective is to guide the surgeon during an operation task to follow a predefined trajectory with a surgical tool. Therefore, a control algorithm is introduced to minimize the positioning error between the desired and actual pose (position and orientation) of the tool tip. The required joint velocities for positioning tasks are obtained by solving the inverse kinematic problem of the serial kinematic chain using an extended Jacobian method. For the computation of the Jacobian matrix, a geometric approach is chosen to solve the forward kinematics problem of the manipulator links. The over-determined kinematic system of the redundant robotic manipulator is determined using basic kinematic constraints of the human joint angles. Results of the inverse kinematics solution are evaluated with simulations of positioning trajectories for drilling tasks of the robotic manipulator and show a deviation of the desired path of less than 0.8 mm. The implemented end-effector positioning controller produces satisfactory results and enables future extensions for intuitive human-machine interaction control.

Series Elastic Actuators (SEA) provide good characteristics for man-machine cooperation. Also, zero-torque control becomes possible. The paper presents an example of a series elastic actuator on an active knee ankle foot orthosis (KAFO) to support elderly people. A conventional DC motor with a planetary gearing and cylindrical spring is attached to the knee joint of the orthosis. A state space controller with disturbance observer is used to control the sit-to-stand (STS) movement. It becomes clear, that the slender design of the actuator is useful but for convenient daily activities a smaller SEA is needed. This could be accomplished by using special spring designs produced by the selective laser melting method.

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.

The development of the upper jaw during growth is influenced by the function and position of the tongue and perioral soft tissues, and the pressures exerted by them. Accurate determination of the forces exerted by the tongue would provide relevant information about this influence. To date, our ability to obtain continuous recordings of the tongue pressure during certain functions is limited. In this paper, an easy-to-employ and accurate telemetric system for such functional measurements is presented. The system, consisting of four piezoresistive pressure sensors, a microcontroller, a telemetric module and batteries, is integrated within a removable orthodontic plate and transmits the measured data out of the oral cavity to a receiver.

The development of the upper jaw during growth is influenced by the function and position of the tongue and perioral soft tissues, and the pressures exerted by them. Accurate determination of the forces exerted by the tongue would provide relevant information about this influence. To date, our ability to obtain continuous recordings of the tongue pressure during certain functions is limited. In this paper, an easy-to-employ and accurate telemetric system for such functional measurements is presented. The system, consisting of four piezoresistive pressure sensors, a microcontroller, a telemetric module and batteries, is integrated within a removable orthodontic plate and transmits the measured data out of the oral cavity to a receiver.