InteSpring is working together with TU Delft, LUMC and OIM on an orthosis specific for patients with an equines foot. The current state of technology is that the patients will get a stiff orthosis which bends the foot in a neutral (90 degree) position. The hypothesis is that by applying a patient-specific negative stiffness a healthy ankle stiffness can be achieved. In this way rehabilitation to a more natural gait can be established instead of moving away from it as in the current solution.
The first prototype was to proof the working principle of the tunable stiffness. InteSpring already has the techniques to deliver exact torque characteristics for specific purposes; in this case with a cam mechanism. For this application it is needed the torque characteristic can be tuned differently for different subjects and for different measurements over time. InteSpring developed a model to achieve this in a near perfect way – good enough for the application. And so, minimizing the cost of the initial research. Since the second, current, prototype has to be tested with patients, factors as weight and hysteresis need to be eliminated as an influencing factor. To achieve this InteSpring developed several optimization models for spring and cam-shape selection while keeping the tune-ability in mind. Also, the selection of the proper bearings and optimization of the mechanism resulted in a huge improvement in terms of weight and hysteresis, 500% and 300% respectively.
This prototype will be tested as we speak and first conclusion on the stated hypothesis can be expected. In the meantime, InteSpring is already again working on an even more compact and efficient design to test specific users at home-use for a timespan of multiple months.