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Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK
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PublicationRichtlinien für die Gestaltung von visuellem Biofeedback in der neurologischen Gangrehabilitation nach Schlaganfall( 2010)
;Brüning, M. ;Hussein, S. ;Bardeleben, A. ;Schmidt, H. ;Krüger, J.Hesse, S. -
PublicationVisuelles Biofeedback für die gerätegestützte neurologische Gangrehabilitation nach Schlaganfall( 2010)
;Brüning, M. ;Hussein, S. ;Bardeleben, A. ;Schmidt, H. ;Krüger, J.Hesse, S. -
PublicationStructural analysis method for optimized design of complex kinematic structures using static and dynamic models and application to a robotic walking simulator( 2010)
;Brüning, M. ;Hussein, S. ;Schmidt, H.Krüger, J.This paper describes an approach for structural analysis for design improvements of complex, e.g. hybrid, kinematic structures utilizing static and dynamic models. It is suitable to locate improvement potentials in existing mechanisms, facilitate goal-oriented design of new mechanisms or for a simulation-based controller synthesis e.g. a compliance-controller. To receive a model close to reality, mechanical influences, which are commonly neglected in conventional robot models, are analyzed regarding their relevance and if suitable integrated into the model. Investigated effects are the mechanical compliances of links and gears, compliances of the actuators resulting from the control circuits as well as non-linear frictional influences of the actuators. The kinematic and dynamic model is realized as an iterative solution instead of a closed analytic solution with extensive symbolic expressions. This leads to an analysis with clearly arranged aspects, further more the model is suitable for usage in a real-time control. The mechanical influences are analyzed analytically. The derived dynamic modeling is based on the Newton-Euler formulation. The approach is applied to the robotic walking simulator HapticWalker, a device for robot assisted gait rehabilitation. It consists of two identical hybrid parallel-serial manipulators. The forces calculated by the use of the developed model are in a good congruence with measured values. An obviously improved correspondence between measured and calculated values is achieved by the non-linear friction model of the actuators. -
PublicationMultimodal biofeedback architecture for an electromechanical gait rehabilitation device( 2009)
;Hussein, S. ;Schmidt, H. ;Hesse, S.Krüger, J. -
PublicationGeschwindigkeitsbasierte, adaptive Kraftregelung für ein elektromechanisches Trainingsgerät zur Gangrehabilitation( 2009)
;Hussein, S. ;Schmidt, H. ;Hesse, S.Krüger, J. -
PublicationEffect 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. -
PublicationGround reaction forces during different floor walking in robot assisted gait training( 2009)
;Hussein, S. ;Schmidt, H. ;Hesse, S.Krüger, J. -
PublicationAdaptive 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. -
PublicationMuscle coordination in healthy subjects during floor walking and stair climbing in robot assisted gait training( 2008)
;Hussein, S. ;Schmidt, H. ;Volkmar, M. ;Werner, C. ;Helmich, I. ;Pioko, F. ;Krüger, J.Hesse, S.The aim of gait rehabilitation is a restoration of an independent gait and improvement of daily life walking functions. Therefore the specific patterns, that are to be relearned, must be practiced to stimulate the learning process of the central nervous system (CNS). The Walking Simulator HapticWalker allows for the training of arbitrary gait trajectories of daily life. To evaluate the quality of the training a total of 9 subjects were investigated during free floor walking and stair climbing and during the same tasks in two different training modes on the HapticWalker: 1) with and 2) without vertical center of mass (CoM) motion. Electromyograms (EMG) of 8 gait relevant muscles were measured and muscle activation was compared for the various training modes. Besides the muscle activation as an indicator for the quality of rehabilitation training the study investigates if a cancellation of the vertical CoM movement by adaption of the footplate trajectory is feasible i.e. the muscle activation patterns for the two training modes on the HapticWalker agree. Results show no significant differences in activation timing between the training modes. This indicates the feasibility of using a passive patient suspension and emulate the vertical CoM motion by trajectory adaption of the footplates. The muscle activation timing during HapticWalker training shows important characteristics observed in physiological free walking though a few differences can still remain. -
PublicationMuscle activation of stroke patients during stair climbing in robot assisted gait training( 2008)
;Hussein, S. ;Schmidt, H. ;Volkmar, M. ;Krüger, J.Hesse, S.For central nervous system (CNS) impaired patients, e.g. after stroke, the achievement of an independent, stable gait function and endurance in walking is essential for independent mobility in daily life. Modern concepts of rehabilitation favor a task specific repetitive training, that facilitates natural motion and muscle activation patterns, i.e. in addition to commonly practiced floor walking other gait motions of daily living (ADL), such as stair climbing, should be trained. In gait rehabilitation of severely affected non-ambulatory patients, a guided training must be applied as no or only little voluntary motor control is left in the affected side. The rehabilitation robot HapticWalker is the first device that allows for robot assisted guided training of arbitrary foot trajectories, e.g. also stair climbing. The goal of this study was to assess the effect of guided training in stair climbing condition on the HapticWalker on the movement and muscle activation patterns of stroke patients. Generally rhythmic and phasic muscle activation patterns were observed, which is an important factor in gait rehabilitation. The training of stair climbing condition on the HapticWalker also facilitated body weight shift in all patients and proper activation of weight bearing muscles. The HapticWalker currently lacks a lateral hip guidance facility, hence individual differences in the ability of controlling hip movement and body weight shift depending on the level of gait ability were observed.