Increased Pinch Force of Body Powered Prosthetic Hand with Pneumatic Force Servo
D. Schelvis (TU Delft - Mechanical Engineering)
D. H. Plettenburg – Mentor
Frans van Der Helm – Graduation committee member
Tim Horeman – Graduation committee member
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Abstract
In the Netherlands, there are around 3750 patients suffering from an upper limb deficiency. Many different prosthetic hands have been designed to give these people the function of their hand back. Of the people who own such a prosthetic hand, about forty percent does not wear their hand and about half of the wearers does not use all of the functionalities the hand offers. The main reasons for this is that the hands have too much weight, are too complex to control and offer no feedback. The goal of this study is to create a low-weight prosthetic hand that is easy to control and provides feedback to the user. Therefore, this study presents a Force Demand Valve (FDV) that can be used with the Delft Cylinder Hand (DCH). This FDV increases the pinch force to operation force ratio by more than 200% with the use of pressurized CO2. This mechanism does not change the size or the weight of the hand itself, because it is attached near the elbow. Also, both the closing speed and the feedback to the user have not noticeably changed with the use of the FDV, compared to the DCH being used without FDV. The main disadvantage of the mechanism, is that the gas consumption is high. This consumption, however, can be decreased by making the FDV smaller, by increasing the activation force of the FDV and by providing a threshold in which the FDV will not exhaust gas when constant forces are applied for a longer period. Concluding from a user experiment, the mechanism designed in this study will make the DCH available for daily use to a wider range of people compared to the DCH without FDV.