13:30
Prostheses
Chair: Bart Verkerke
13:30
15 mins
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DESIGN OF WALKMECH : AN ENERGY EFFICIENT TRANSFEMORAL PROSTHESIS
Ramazan Unal, Sebastiaan Behrens, Raffaella Carloni, Edsko Hekman, Stefano Stramigioli, Bart Koopman
Abstract: In this study, we present the principle design of a fully-passive transfemoral prosthesis for normal walking, inspired by the power flow in human natural gait. The working principle of the mechanism is based on three parts, which are responsible of the energetic coupling between the knee and ankle joints. The design parameters of the prosthesis have been determined according to the energy absorption intervals of the natural human gait. Test results show that significant amount of energy can be stored to deliver for ankle push-off generation.
The research interest on transfemoral prostheses is clearly motivated by their crucial impact to human life. In particular, a still open challenge is the design of a prosthesis that can both adapt to various walking conditions and can be energy efficient with respect to the metabolic energy consumption and external actuation. Therefore, we proposed a fully-passive transfemoral prosthesis design that is inspired by the power flow in human gait as in [1].
According to power flow through the joints, functions of the joints can be explained by dividing gait into three phases: Stance; the knee absorbs a certain amount of energy during flexion and generates as much as the same energy for its extension. In the meantime, the ankle joint absorbs energy, due to the weight bearing. Push-off; the knee starts absorbing energy, while the ankle generates the main part of the energy for the push-off, which is about the 80% of the overall energy generation. Swing; the knee joint absorbs energy due to kinetic energy of shank during late swing phase, while the energy flow in the ankle joint is negligible.
In this study, we present a mechanism that can cover the energy absorption phases and deliver the total energy at the ankle joint for push-off. This mechanism has three distinct parts:
Linkage mechanism, CL that couples the knee and ankle joints kinematically and is responsible for the exchange of the energy between the two joints during push-off.
Coupling elastic element, C2 that couples the upper and lower leg and is responsible for the absorption and transfer of the energy during swing phase and for a part of absorption during stance phase.
Ankle elastic element, C3 that connects the foot and lower leg and is responsible for the main part of the absorption during stance phase.
According to the power analysis and biological leg dimensions, we set the design parameters for the prosthesis and realize the prototype for normal walking in order to examine the power absorption capacity on healthy and amputee subjects. Primary functional tests have shown promising results towards to fully passive energy efficient transfemoral prosthesis.
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13:45
15 mins
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HUMAN ASSISTED BALANCE CONTROL OF UNDERACTUATED LOWER EXTREMITY EXOSKELETONS
Letian Wang, Edwin van Asseldonk, Herman van der Kooij
Abstract: ABSTRACT
Assisted by lower extremity exoskeletons, walking disabled people can stand up again and regain their walking abilities. It is a wise design to underactuate certain joints of the exoskeleton in order to achieve lighter weight, lower power consumption and as a consequence, better mobility. A reasonable choice is to leave the ankle joints passive[1, 2]. In this way, the gait can still be realized by actuating the hip and knee joints while less weight is put at the end of the leg, where has the most effect on the inertia of the leg. However, the sacrifice of underactuated ankle is the performance on the balance control especially during stance.
We believe, human subject inside such exoskeleton with unimpaired upper body abilities , can assist the exoskeleton to enhance the balance using the upper body movement given properly designed exoskeleton controllers. In this way, less assistive devices, e.g. crutches, are needed for assisting the balance.
Experiments are designed to test the ability of human subjects to assist the controller to balance a virtual human-exoskeleton system under random perturbation (push or pull in sagittal and lateral plane) during stance. The virtual exoskeleton has three degrees of freedom (DoFs) at hip, one DoF at knee and one DoF at ankle. Hip endo-exo and ankle dorsiflexion are passive while the rest joints are actively controlled by PD controllers and model predictive controllers[3]. The human subject is given visual feedback of the posture of the virtual human-exoskeleton. A mapping from the trunk of the human subject to the trunk of the virtual human is provided so that the human subject is able to manipulate the centre of mass of the virtual human-exoskeleton.
Results show that the virtual human-exoskeleton can withstand larger perturbation under the balance assistance of the human subject compared the case of no balance assistance. The results also suggest the performance of the balance assistance by human subjects can be increased by training and learning.
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14:00
15 mins
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VOLUNTARY CLOSING PROSTHESES - AN UPDATE
Dick Plettenburg, Gerwin Smit, Mona Hichert
Abstract: In order to meet the needs of a person with an arm defect, many, sometimes conflicting, requirements have to be fulfilled. These requirements can be summarized into three basic demands: cosmesis, comfort, and control [1, 2]. In the control domain natural, intuitive, subconscious control is strived for. To achieve this type of control proper feedback needs to be present [3]. This implies control according to the voluntary closing principle. In body-powered, body-controlled prostheses voluntary closing control enables proprioceptive feedback of position, velocity, and force to the user through the bodies own proprioceptive system, comparable to the way we use a tool, e.g. a tennis racket [4, 5].
The Delft Institute of Prosthetics and Orthotics has started several projects to develop body-powered, body-controlled voluntary closing prostheses. Current projects include:
- a voluntary closing hand for toddlers, with an emphasize on the reduction of glove forces acting. Recently a master thesis project has started;
- a voluntary closing prehensor similar in looks to the already existing and successful appealing prehensor [6], where the main challenge is a variable advantage mechanism to promote fast sizing of powerful grasps. Recently a master thesis project has started;
- a wrist-operated voluntary closing prehensor, which will incorporate novel hydraulics. In a master thesis project very interesting initial results have been obtained [7];
- a study into the psychophysical properties of shoulder harnesses, where the main challenge is to identify the optimal force and excursion windows. Initial experiments [8, 9] indicate that the currently available body powered prostheses require too large operating forces. A PhD-project is started to further investigate the optimal range for operating forces and displacements.
Ultimately, we aim at voluntary closing hands that provide adaptive grasp patterns. Adaptivity enhances the natural appearance [cosmesis], and at the same time reduces the need for high pinch forces [comfort, control]. A PhD-project has resulted in a very promising first prototype [10].
REFERENCES
[1] D.H. Plettenburg, “Basic requirements for upper extremity prostheses: the WILMER approach.” In: Proceedings of the 20th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, October 29 – November 1, 1998, Hong Kong SAR, China. Chang H.K., Zhang Y.T. [eds.], Vol.5/6, ISBN 0-7803-5164-9, pp. 2276 – 2281, 1998
[2] D.H. Plettenburg, Upper extremity prosthetics. Current status and evaluation. VSSD, The Netherlands, ISBN-13: 978-90-71301-75-9, 133 + 8 pp., 2006
[3] N. Wiener, Cybernetics, or control and communication in the animal and the machine. John Wiley & Sons, Inc., New York, USA, 1948
[4] D. Simpson, “The choice of control system for the multimovement prosthesis: extended physiological proprioception.” In: The control of upper-extremity prostheses and orthoses. Herberts P., Kadefors R., Magnusson R, Petersen I. [eds.], Charles C. Thomas, Springfield, Illinois, ISBN 0-398-02869-9, pp. 146 – 150, 1974
[5] J.A. Doubler, D.S. Childress, “An analysis of extended physiological proprioception as a prosthesis-control technique.” Journal of Rehabilitation Research and Development, Vol. 21, No. 1. BPR 10-38, pp. 5 – 18, 1984
[6] D.H. Plettenburg, “The WILMER Appealing Prehensor” Journal of Prosthetics and Orthotics, Vol. 18, No. 2, pp. 43 – 45, 2006
[7] D.H. Plettenburg, J. Nieuwendijk, G. Smit, “A new voluntary closing hook prosthesis” In: Proceedings of the University of New Brunswick’s International Conference on Advanced Limb Prosthetics, August 14-19, 2011, Fredericton, NB, Canada, ISBN 978-1-55131-160-91, pp. 110-113
[8] D.H. Plettenburg, M. Hichert, G. Smit, “Feedback in voluntary closing arm prostheses” In: Proceedings of the University of New Brunswick’s International Conference on Advanced Limb Prosthetics, August 14-19, 2011, Fredericton, NB, Canada, ISBN 978-1-55131-160-91, pp. 74-78
[9] M.L. Valk, “Towards better perception. A first pterspective on the perception of operating force and cable displacement in shoulder harness controlled body powered prostheses”. MSc-Thesis, Delft University of Technology, 2012
[10] G. Smit, D.H. Plettenburg, “Design of a hydraulic hand prosthesis with articulating fingers” In: Proceedings of the University of New Brunswick’s International Conference on Advanced Limb Prosthetics, August 14-19, 2011, Fredericton, NB, Canada, ISBN 978-1-55131-160-91, pp. 24-26
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14:15
15 mins
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INTELLIGENT VIBROTACTILE SYSTEM FOR SPATIAL PERCEPTION
Jing Yu, Miguel Reyes Adame, Knut Möller
Abstract: According to the latest figures from the World Health Organization, 285 million people are visually impaired worldwide: 39 million are blind and 246 million have low vision. For them, a regular cane and guide dog are the widely accepted travel assistive devices. Advances of technology and better knowledge in human 3D world perception permit the design and development of wearable and portable devices assisting visually impaired.
It is proposed to design, simulate and implement an assistive wearable navigation device for visual impaired. This device facilitates the wearer's ability to perform normal tasks without feeling encumbered. A 3D camera captures images from the surrounding environment and after appropriate information reduction 3D representations are created. To avoid the degradation and overload of the hearing sense, the 3D information shall be transferred to the cognitive system via the stimulation of skin receptors.
This paper focuses on the evaluation of a special belt. Small vibration motors are used as a major component of the belt and the location of motors are adjustable. Tactile display presents information to the wearers.
Three parameters of the belt were evaluated. Five healthy volunteers participated in a preliminary study. According to the result, the duration of the vibration and its location could be used for spatial orientation. Then a simple computer game was developed to simulate an environment with obstacles. Healthy people were involved as test subjects and faced the task to avoid collisions in the game. Their performance under the visible and invisible circumstances was obtained and compared. In the case of blindfold, the recommended actions were directly transmitted to the subjects via the vibration motors. The belt was proved to be easy to use while no special training was required.
REFERENCES
[1] World Health Organization, “Visual impairment and blindness” - Fact Sheet N°282 (2012). Available online at: http://www.who.int/mediacentre/factsheets/fs282/en/
[2] K. Möller, F. Toth, L. Wang, J. Möller, K. O. Arras, M. Bach, S. Schumann, and J. Guttmann, “Enhanced perception for visually impaired people”, in 3rd International Conference on Bioinformatics and Biomedical Engineering (iCBBE), (IEEE, Beijing, China, 2009), 2009.
[3] K. Möller, J. Möller, K. O. Arras, M. Bach, S. Schumann, and J. Guttmann, “Enhanced perception for visually impaired people evaluated in a real time setting”, in WC 2009, IFMBE Proceedings, O. Dössel and W. C. Schlegel, Eds., (Springer, Munich, Germany, 2009), vol. 25/4, pp. 283-6, 2009.
[4] K. Möller, J. Möller, K. Arras, and M. Bach, “Intelligent information reduction to guide visually impaired people”, in 55. GMDS-Jahrestagung, P. Schmücker, et al., Eds., (Antares Verlag, Mannheim, Germany, 2010), pp. 544-5, 2010.
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14:30
15 mins
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STIFFNESS FEEDBACK BY THE COMBINATION OF VIBROTACTILE HAND OPENING AND GRASPING FORCE FEEDBACK
Heidi Witteveen, Frauke Luft, Hans Rietman, Peter Veltink
Abstract: The percentage of myoelectric forearm prostheses that is being used on a daily basis, is quite low, which is among others caused by the lack of sensory feedback to the users. Earlier studies, e.g. [1], showed the possibilities of vibrotactile stimulation to provide hand opening or grasping force feedback. For optimal object handling, the ability to determine the stiffness of an object is extremely important and it is shown that both proprioceptive and tactile information from the human hand are required for stiffness discrimination. In this study, grasping force and hand opening feedback were combined to provide stiffness feedback.
Hand opening feedback was provided through an array of eight coin motors placed along the forearm, while six levels of grasping force were fed back via six amplitude levels of a single C2 tactor. 10 healthy subjects were asked to control a virtual hand by mouse scrolling, grasping virtual objects with varying sizes and stiffness. When closing the hand, by scrolling, hand opening feedback was provided via activation of one of the coin motors. After the virtual object was being touched, grasping force feedback was provided and when scrolling further the grasping force increased. For a stiff object, hand opening was kept constant when increasing the grasping force, but for the most compliant object, each step in increasing force resulted in a decrease in hand opening. Two levels of stiffness, requiring 2 or 4 levels of increase in force to change the hand opening, were simulated in between. Subjects were asked to determine the stiffness of 50 objects using either combined hand opening and grasping force feedback, only one of both feedback methods or no feedback. The outcome parameters were the percentages correctly identified stiffness and the task durations.
The stiffness of an object could be correctly identified by the subjects in ±60% of the cases when using combined hand opening and grasping force feedback and when using hand opening feedback alone. These percentages were significantly (p<0.001) higher than those reached with force feedback only or without feedback (±25%). The task duration with combined feedback was significantly longer (5.22±1.5s) than with hand opening feedback alone (4.05±0.9s), which was also significantly longer than without feedback (0.96±0.3s).
It is shown that it is possible to provide information about object stiffness by combined hand opening and grasping force feedback or by hand opening feedback alone. Despite the longer task duration with the combined feedback, subjects preferred this combination over hand opening feedback alone. Whether this stiffness feedback is useful for myoelectric prosthesis users in daily life should be further investigated.
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14:45
15 mins
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INTERACTIONS OF TOUCH FEEDBACK WITH MUSCLE VIBRATION AND GALVANIC VESTIBULAR STIMULATION IN THE CONTROL OF TRUNK POSTURE
Erwin Maaswinkel, DirkJan Veeger, Jaap van Dieën
Abstract: Introduction: There is evidence that touch cues from any part of the body in contact with a stable external object may have a profound influence on the control of body orientation. The influence of touch has been illuminated specifically in studies of standing postural sway. However, to our knowledge, this work has not investigated the influence of touch feedback on the control of trunk posture. Therefore, the objective of the current study was to investigate the contribution of different sensory systems, in particular touch, to maintaining a seated upright posture.
Methods: 13 subjects sat on a stool and were instructed to sit as still as possible. Trunk sway was measured with a motion capture system. During selected trials, a sensory perturbation was applied in the form of vibration of the paraspinal back muscles (90 Hz) or galvanic vestibular stimulation (GVS, 1.5 mA, 1 Hz). In addition, during some trials, subjects were allowed to maintain a very light contact (< 2 N) with the actuator of a force-controlled motor with either the index finger of the dominant hand or the back (T7).
Results: Muscle vibration increased postural sway sharply. In contrast, GVS had no significant effect on seated postural sway. Touch feedback did not decrease sway in neutral conditions. However, touch through both the index finger and the back greatly reduced the effect of muscle vibration on postural sway.
Conclusion: The results presented indicate that vestibular information either does not play a significant role in maintaining a seated upright posture or is easily compensated for when the system is challenged by GVS. In contrast, local information from muscle spindles appears to play an important role, as perturbing the spindles with muscle vibration resulted in a large increase of sway. Touch appears to play a unique role as the effects are only observed when local information from muscle spindles is perturbed. When no perturbations are applied, touch provides no additional benefit to controlling the trunk in a seated upright posture. These results support the notion that different sensory systems are integrated to control trunk posture and that the contribution of these systems can be reweighted. In particular, sensory reweighting between touch and muscle spindles seems to occur when muscle spindle information is perturbed.
This research is supported by the Dutch Technology Foundation STW, which is part of the Netherlands Organisation for Scientific Research (NWO) and partly funded by the Ministry of Economic Affairs, Agriculture and Innovation. See www.neurosipe.nl - Project 10732: QDISC
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