Part 4| Creating an animatronic - The eye mechanism

For the eye to move, we need to attach it to some servos with links. To come up with placement for the servos, I created some sketches.

Figure 1. Eye rotation mechanism sketches

In order to make the eye look left and right, a servo will be placed behind the eye. The pivot point of the servo is aligned with the pivot point of the eye. The horn (double servo arm) of the servo is elongated to ensure identical motion transfer. This will make animating and rigging the eye easier since the servo's rotation is the same as the eye's; no calculation necessary.

This linkage setup is called a parallel linkage. the input force and movement are the same as the output force and movement.

A mechanical linkage is an assembly of bodies connected to manage forces and movement.

(robotpark academy, 2015)

Figure 2. Dual-arm VS. Single-arm (Own work)

It would be expected that the same design would work to make the eye move up and down (rotated 90 degrees), but the placement of the first servo will limit the movement of the second servo's horn unless we place it further away. Since the amount of space we have is limited due to the Eyepot's size, I opt for a single servo arm instead. The link in charge of pitching the eye will only be connected via the highest link instead of both connection points.

List of figures

1. Van den Brand, J. (2021, March 8). Eye rotation mechanism sketches [Image].

2. Van den Brand, J. (2021, March 8). Dual-arm VS. Single-arm [Image].

List of references

1. robotpark academy. (2015, January 8). Robotic Mechanisms - LINKAGES - Simple Planar Linkages 51009. Robotpark. http://www.robotpark.com/academy/robotic-mechanisms-linkages-simple-planar-linkages-51009/