August 2023
A new robotic head for our david bipedal child model.
Background
A bipedal robot one could engineer by a 3D printer presented an opportunity to test the limits of emotional toys. While it works in principle, parts of its design is at odds with the company philosophy of its idea of how to get tighter integration of people and robots, especially in an emotional capacity.
Task
The head is wholly inappropriate for use because:
- It has no face
- Can work if fitted to existing animatronic hardware that exemplifies the deign of “fred", featured in cameo at https://emotional.toys
The point where the AX12 motor (top mounting in the case - see the solidworks file) and the original head (see the solidworks file "old-head") join needs to be reused for the completely new head from this mechanical attachment. Another part of the head will mount to an existing face that has a set of servo motors, with a dimension shown in the photo "headcap-front-x -y".
The new headcap will be hollow as it needs to allow the mounting of a miniature computer just behind the box that contains the collection of servo motors. It will mount from top-bottom against the backplane of the motor box, so a connection join needs to be designed to fit. The motor box, face, can be connected to the faceplace and fit into the headcap on assembly by eye with the wire for the battery connection available to small human hands. The size and bolt-spacing for the screw-mounted joint (bolt, washer, and nut) is shown in the "computer-x -y" files. This should be M3 metal fastener stainless steel.
The motor box is shown in the correspondingly-named image files.
Notice that the computer has a ventilation port and connection to a RJ45 Gigabit Ethernet socket IEEE802.3 and a 0.9mm power socket. Ventilation needs to be extended to outside the headcap for air-intake but should be mostly invisible where possible. The headcap will be the external shell for the back of the head and support the motors toward its center of inertia and the face on the neck joint.
There will be an onboard battery on the lower part of the robot but a cable will need to come through the neck to connect with the power socket. The Ethernet socket will not connect externally but is a maintenance port when the headcap is removed.
A design is required how the headcap will fasten to the faceplate with a threaded fastener. The drive should be unique to a corresponding handtool such that only a person who has this special tool, can remove the headcap getting access to the computer and motor box. A modified version of torx (sized appropriately to the scale shown in the photos) is suggested as a place to begin.
In the original design, the faceplace was sewn onto the headcap as it has plush fabric near to the edges of the faceplate. It extends up to 3cm at the cheeks but is shorter at the brow while even at the chin. It snaps into the motor box that contains the animatronic eyes and mouth.
The bolt/nut pattern for the neck joint will be inherited from the old design, as shown in the appropriately-named files in this repository.
There is a part of the design that is unsure if it needs to be implemented in the new head; this is the i-beam style neck that mounts into the bottom of the motor box (see picture) and extends through the old padded headcap where it connected to a tubular frame. The engineering question is: does the i-beam need to be added to the connection joint at the AX12A motor?
The hand-drawn sketch is contained below.
Good luck!