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In designing the next major prototype, we looked to reconfigure the mechanical mechanism to properly incorporate the electrical motor as well as increase the output clamping force by increasing the system's mechanical advantage. First a SolidWorks line model, shown in figure 6, was created. This was used to verify the positional analysis section of the Matlab code which was then used in determining the system's mechanical advantage. Once both of these were complete, mechanical advantage as a function of input angle, link lengths, and joint pivot points locations could be found and optimized. The graphs produced, one of which is shown in figure 7, easily highlighted that the mechanism's toggle point greatly increased the mechanical advantage of the system. If properly designed, the toggle point could be used to greatly increase the gripping and locking power of the mechanism. Finally, we designed a servo horn that could be fitted to the manufacturer's original horn. This design allowed us to easily attach the servo to the rest of the mechanism using the same screws as the other joints and zip-ties.
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Figure 7: MATLAB analysis
With the new referenced optimized link sizes suggested from the Matlab code, the Solidworks model was updated to include a more finished device encompassing an electric motor, crank slider, and updated gripper links. Figure 8 shows the model below.
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This device was designed to take advantage of the system's toggle point for an increase in mechanical advantage. As the servo turned into the closed position, the device reached the toggle point and should have locked around the rope causing the rope to be fixed within the systems jaws. Unfortunately, we found this area of operation to be too unstable and unpredictable. As the jaw was closed it would lock on the toggle point, but the jaws would not necessarily have locked on to the rope. Also opening , as the jaws we opened, the device had a tendency to change into a crossed orientation and would have to be manually reset.
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