Varying the front plate

This page focuses specifically of the effects of changing the distance of the front piece. The experiments crudely change the distance of this area by inserting a spacer and visualizing how the spacing affects grabbing different objects.

Results found from these experiments are based on look and feel, not quantitative data. Measurements of the objects being grappled were measured and recorded.

Inserted Item

The inserted item was a 12mm thick by 21mm width eraser for simplicity and speed of testing

Test Item sizes

Node that for competition the maximum item size to grapple is 5cm

Results

Discussion

There was much less adaptability at 21 mm compared to 12 mm, more force was required. This is because when the spacing gets too large, and the item diameter gets too big, the tangential contact surface is closer to the tips of the claw rather than the inside pivot point. The best adapability was seen when the contact point was at or a little below the pivot points, i.e. the inner pivot points and the center point of the object form a straight line or a triangle facing inwards

Both 12mm and 21mm felt very stiff compared to no spacer. This can be attributed to the fact that the rubbers had a high co-efficient of friction when compared to the PLA base. Also note that with the spacing, there is a greater force/contact area on the tip piece rather than the inner link, this is important because all of the gripper material will be on the gripper piece and not the inner link.

The larger front results in a less adaptive movement whilst achieving the same grip strength. This is beneficial as this also results in less lead screw length required for the adaptive movement. thus shortening the mechanism overall.

One disadvantage of this gripper is that there is less depth from the tip of the tips to the front. This did not appear to be a major disadvantage

Conclusion

Increasing the front of the gripper base appeared to have a positive effect on the gripper, up to a certain distance. a distance of 15mm will be used in the next prototype, with rubberization