Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Patient adaptive control of end-effector based gait rehabilitation devices using a haptic control framework
    ( 2011)
    Hussein, S.
    ;
    Krüger, J.
    Robot assisted training has proven beneficial as an extension of conventional therapy to improve rehabilitation outcome. Further facilitation of this positive impact is expected from the application of cooperative control algorithms to increase the patient's contribution to the training effort according to his level of ability. This paper presents an approach for cooperative training for end-effector based gait rehabilitation devices. Thereby it provides the basis to firstly establish sophisticated cooperative control methods in this class of devices. It uses a haptic control framework to synthesize and render complex, task specific training environments, which are composed of polygonal primitives. Training assistance is integrated as part of the environment into the haptic control framework. A compliant window is moved along a nominal training trajectory compliantly guiding and supporting the foot motion. The level of assistance is adjusted via the stiffness of the moving window. Further an iterative learning algorithm is used to automatically adjust this assistance level. Stable haptic rendering of the dynamic training environments and adaptive movement assistance have been evaluated in two example training scenarios: treadmill walking and stair climbing. Data from preliminary trials with one healthy subject is provided in this paper.
  • Publication
    Effect of different training modes on ground reaction forces during robot assisted floor walking and stair climbing
    ( 2009)
    Hussein, S.
    ;
    Schmidt, H.
    ;
    Hesse, S.
    ;
    Krüger, J.
    The HapticWalker is a robotic walking simulator for neurological gait rehabilitation. The device is based on the end-effector principle, i.e. the patients' feet are fixed on two footplates, his trunk is secured via a suspension harness. The footplates (end-effectors) of the robot guide the feet of the patient on freely programmable trajectories. Currently two different training modes are provided for each foot trajectory on the HapticWalker. Firstly training trajectories based on real motion capture data can be used. Secondly the vertical center of mass (CoM) motion can be incorporated into the foot trajectory. The latter method leaves the absolute position of the CoM constant, while the relative movement between CoM and feet remains the same as in free walking. Thereby the v ertical CoM motion can be actively supported by using a fixed passive suspension, any type of controlled body weight support will then be accomplished via force controlled footplates. To characterize the training on the machine in position controlled mode, muscle activities as well as ground reaction force data of healthy subjects were collected. This article presents preliminary results from the investigation of ground reaction force data of healthy subjects. Therefore data of 10 healthy subjects was used to compare HapticWalker training modes vs. free walking on level ground and upstairs without any assistive devices and the aforementioned two HapticWalker training modes against each other. Amplitude and timing of force peaks during heel strike, foot flat and push off in vertical ground reaction forces were used for the assessment. In spite of a footplate, which does not provide a separate metatarsal joint for relative motion between fore and hind foot, during heel strike and push off the known characteristic peaks at the beginning and the end of the stance phase can be clearly distinguished. Though compared to free walking a slower and premature rise and slower decline of ground reaction for- ces can be seen due to the stiff guidance of the feet in position controlled mode. No significant differences appeared between the two described HapticWalker training modes.
  • Publication
    Multimodal biofeedback architecture for an electromechanical gait rehabilitation device
    ( 2009)
    Hussein, S.
    ;
    Schmidt, H.
    ;
    Hesse, S.
    ;
    Krüger, J.
  • Publication
    Adaptive control of an end-effector based electromechanical gait rehabilitation device
    ( 2009)
    Hussein, S.
    ;
    Schmidt, H.
    ;
    Krüger, J.
    In industrialized countries stroke is the major cause for physical disabilities in adults. In various clinical studies gait therapy with the help of the electromechanical Gait Trainer GT-I proved to enhance the rehabilitation outcome for subacute stroke patients. This paper presents control methods that were developed to enable variability during treatment in order to further improve gait therapy with this class of devices. The algorithms suitable for the Gait Trainer GT-I are analyzed in a simulation study. Therefore models which simulate the practicing subjects behaviour were developed. A purely mechanical mass-damper system models the passive subjects behaviour while motor learning models were adopted to simulate patient adaptation different types of footplate gui dance characteristics. Several adaptive approaches have been developed for other rehabilitation devices in the past. In this work two controllers were developed and evaluated. The first features a one dimensional control window along the footplate trajectory within which the patient is only slightly guided. Outside the window a force field draws the subject back to the window. The second algorithm extends the window controller with a human motor learning strategy for to adapt the window size and thereby the assistance provided to the subjects. They were tested in a simulation study with different human behaviour models, the results are presented in this paper.
  • Publication
    Ground reaction forces during different floor walking in robot assisted gait training
    ( 2009)
    Hussein, S.
    ;
    Schmidt, H.
    ;
    Hesse, S.
    ;
    Krüger, J.
  • Publication
    Gait machines and robots to support motor rehabilitation after stroke
    ( 2007)
    Schmidt, H.
    ;
    Hussein, S.
    ;
    Werner, C.
    ;
    Bernhardt, R.
    ;
    Hesse, S.
    ;
    Krüger, J.
    The group at Klinik Berlin/Charite University Hospital in Berlin, Germany, began studies to promote motor recovery after stroke in the early 1990s. Following the introduction of treadmill training with partial body-weight support, the group designed an electromechanical gait trainer, GT I, based on movable foot plates that relieve therapist effort (e.g., when assisting the movement of the paretic limbs) and intensify patient gait training (GT). Preliminary results of a recent multicenter trial of 155 acute stroke patients showed that the GT I effectively promotes gait ability and competence in activities of daily living. The experimental group received 20 min of GT and 25 min of physiotherapy (PT) and the control group received 45 min of PT every day for 4 weeks. The laboratory's next step was the HapticWalker, a robotic walking simulator with freely programmable foot plates which was designed and built in close collaboration with the Fraunhofer Institute IPK. On this machine patients can, for example, additionally train for stair climbing and perturbations. The foot plates can be operated in full guidance or compliance control modes, thus reducing foot support according to the patient's learning success. Entnommen aus TEMA