19.5 - Implementation
Notes:
comment from prototype: “Your mechanical advantage calculation is interesting because it declines as you grip. For the final report, I would like to see you plot the mechanical advantage for the range and then add the value for specific points where you make contact with your different test objects. Then you can explain how at that contact moment, the force was sufficient for grasping“
1st Design Update: Changing the finger designs to be more anatomically finger-like, increasing contact surfaces to improve grasping performance. Add a second finger and change the base to accommodate this change. Begin with a distance of 3 in between the inner grounded joints.
Test the design update / new 3D prints and assess performance using manual actuation.
Order new components to ensure one motor can drive rotary input across two fingers. Use a combination of gears (1:1 ratio) and timing belts to create simultaneous rotation that mirror each other. Update the base and links to accommodate the 5 mm shafts and bearings.
New parts have arrived (spring, belts, gears, shafts and bearings) and updated 3D prints for the larger base and updated fingers are being tested.
We use the smallest torsional spring in the assortment kit to achieve desired motion profile and distinct two stages of motion
May need to update link 5(proximal link) to avoid object collision and increase distance between inner grounded joints slightly for better demonstration performance)
Update the base to use the bearings and place the gears and belt system properly.
Following the development of our initial prototype, the focus of the remaining weeks is to refine our design for improved grasping performance and integrate the actuation system. This includes geometric updates to better mimic the anatomical finger structure, the addition of a second finger to form a simple gripper, and the implementation of a single motor transmission system for simultaneous finger control.
Improving Anatomical Finger Designs and Adding a Second Finger
The first major design update focused on improving the geometry of the compliant fingers to enhance grasping performance. The original links were made to demonstrate the motion profile, but for our final product, we updated the links to increase contact surface area during grasping. This not only made our linkage mechanism more anatomically accurate in terms of appearance but also in performance. This change allowed for improved force distribution and more stable object interaction.
Specifically, link 3 and link 4 were redesigned to ensure the screw connecting the links would not collide during actuation and to create a larger finger tip respectively. These updates are shown in Figure 1 and Figure 2.
In addition to modifying the finger’s individual links, a second identical finger was introduced to create a simple two-finger gripper configuration. To accommodate this change, the base was redesigned to support both fingers while maintaining proper alignment and motion. The distance between the inner grounded joints of the two fingers was set to 3 inches to provide sufficient spacing for our test object in both long and short orientations.
A key feature of the updated base is the vertical offset between both fingers, which allows both fingers to operate within the same plane. This ensures the fingers are contacting the test object at the same height to avoid twisting the object during grasping. The two-finger configuration is shown below:
The updated components were all 3D printed and assembled to verify its intended functionality. Preliminary testing showed that we may want to experiment with the spacing between the fingers to optimize the grasping performance. Additionally, we noted that links 2 and 3 would occasionally collide with the object, preventing the distal segment of the finger to make a full closure. This seemed to result from where the proximal link 5 would be grounded, so we made note to revisit this issue to ensure proper grasping.
gear and belt testing with new base
new link 5 for collision avoidance
change base platform for more surface contact and improved belt/gear spacing
integrate motor placement
add updated BOM with shafts, bearings, gears and belts