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The first prototype consisted of a four bar linkage that opened and closed the jaws of a cam cleat. Velcro straps were utilized about the wrist to attach the device to the user. As shown in Figure 1, the design is meant to be motorized to enable a powered gripper for the impaired user. A tie rod was going to be used to to attach a servo motor horn to link 3 (L3).
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Another key factor with this final design was the addition of a case over the mechanism. This would prevent any unwanted snags with the linkage while operating complex movements during sailing. Figure 6 also shows the chosen actuation method for this design. A Hall effect sensor was embedded into the top corner of the 3D printed plastic, and when rising edge signals are generated and sent to a microcontroller, the device can open and close via the servo motor on command. Having a magnetic ring attached to the thumb of the user allows him or her to tap the corner of the device and cause the servo to move to the opposite of its current state, which could be open or closed. The toggle switch logic was designed to work the same physically for both opening and gripping on the rope.
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