Adding eyelids to the Eyepot makes it possible to convey emotion. I want to open the eyelids of the Eyepot as far as possible and close them fully. The visible eye surface should be covered completely by the eyelids when closed and preferably a little bit further so that we can't see inside the animatronic itself.
The eyelids need to go somewhere when fully opened, and that place is inside, specifically around the eyeball. This might sound very logical and unnecessary for me to mention, but it is important as we arrive at our next challenge.
Having such large eyelids will take up quite some space. The problem is that when we open up the eyes by rotating the eyelids inwards, the eyelids will collide with our eye linkages, making it impossible to open the eyelids fully while the linkages are in the way.
Figure 1. Sideview of the eyelid crashing into linkage (Own work)
A way to solve this problem is to reposition the linkages. The following image shows how redesigning the eyeball and therefore moving the linkages solves the eyelid problem.
Figure 2. Sideview of the redesigned eyeball (Own work)
I created a paper prototype out of paper, an insulation board, and some flat thumbtacks to test my new design.
For this test, I used thin paper for lack of something better. I would suggest using thicker paper or cardboard if you want to create your own linkage prototype. The warping of the paper, when pushed, caused it to move off of the thumbtacks. Sometimes it wasn't clear if the linkage didn't work or that the paper was warping too much.
Figure 3. Paper prototype created to test linkages 1, 2, and 6 (Own work)
In the video above, I demonstrate three linkages I created. The test started with just two linkages; linkage number 1 and number 2.
Linkage number 1, a parallel linkage, is the same design used for the eye prototype. This is the design where the eyelids collide with the links as they open. Linkage number 2 is my redesign to combat the colliding problem from linkage 1. I created this prototype since I expected that repositioning the links away from the alignment with the eye's pivot point would disturb the movement. And it did.
As I discovered that my redesigned linkage didn't work how I intended it to, I tested out a few other designs. The linkage that worked is linkage number 6. This linkage was created last, but since there was no place left on the board, it had to go next to 1 :')
Linkage number 1 is still a parallel linkage, like number 2. The difference is that the linkages are placed inside the eye while keeping its alignment.
Figure 4. Sideview eyeball with the linkages placed inside (Own work)
The following video demonstrates three other linkages which I'm not going to be using.
Figure 5. Paper prototype created to test linkages 3,4, and 5 (Own work)
For linkage number 3, I extended the servos horn, which didn't work. For linkage number 4, I matched the positioning of the links attached to the eye. This design worked, but the eye didn't have much rotation freedom as the links collided with each other. For linkage 5, I scaled up the servo part, but rotation became less again.
Figure 6. Full Paper prototype created to test linkages (Own work)
List of figures
Van den Brand, J. (2021, March 9). Sideview of the eyelid crashing into linkage (Own work) [Image].
Van den Brand, J. (2021, March 9). Sideview of the redesigned eyeball (Own work) [Image].
Van den Brand, J. (2021, March 9). Paper prototype created to test linkages 1, 2, and 6 (Own work) [Video].
Van den Brand, J. (2021, March 9). Sideview eyeball with the linkages placed inside (Own work) [Image].
Van den Brand, J. (2021, March 9). Paper prototype created to test linkages 3,4, and 5 (Own work) [Video].
Van den Brand, J. (2021, March 9). Full Paper prototype created to test linkages (Own work) [Video].
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