15.1 Project Proposal

Introduction:
Automatons are similar to robots, though unlike a robot, they typically use only one input and are composed of more joints. Essentially, Automatons are moving mechanical devices, oftentimes made out of metal, that achieve complex and mesmerizing motion from simple inputs. For example the Silver Swan is a well-known 250 year old automaton that is wound up once per day for a thirty second show.

Problem Statement:
This project will focus on building an avian automaton that will achieve wing, mouth, head, tail, and vertical motion using a single crank. Individual simple joints (i.e. prismatic or rotary) cannot achieve the prescribed motions from a single input, so several 4-bar mechanisms (rockers and sliders) and transmissions must be used.

Mechanism
In order to achieve this collection of motions through the use of one input, there will be a series of mechanisms that all connect to the same shaft through the use of gear trains. This singular shaft will be connected to the motor to produce a rotational movement that will be used to convert to the subsequent rotational and linear motion to move the various systems of the automaton. Additionally, the motor will be connected to an arduino that will allow the team to control the speeds at which the motion occurs, as well as other features such as LED for the eyes.

In order to give the most realistic visual motion to the automaton, a Cam/Follower, four bar rocker, klann linkage mechanism, cam lobe mechanism, and system of gears will be utilized.

Cam/Follower - Used for the wings of the automaton. This mechanism was chosen because of its ability to have a slow “build up” and quick drop, due to the shape of the Cam, visually showing a similar motion to flapping seen in real life birds
Four Bar Rocker - Used for the Head/Beak of the automaton. This mechanism was chosen because of its ability to utilize vertical and horizontal from a singular input and will be connected to the original rotating axle through the use of a crossed helical gear in order to convert rotation 90 degrees.
Klann Linkage Mechanism - Used for the legs and motion of the automaton. This mechanism was chosen because of its common use to produce motion in a robot and will be connected to the original rotating axle through the use of a gear train and a crossed helical gear.
Cam Lobe Mechanism - Used for the rear tail feather of the automaton. This mechanism was chosen because of its ability to produce varied motion through its system. The lobes placed at intentionally varying degrees will simulate non-uniformity for the tail, often seen in birds in real life. Once again a crossed helical gear will most likely be used in order to create motion in a new axle, 90 degrees offset from the original rotating axle.

Proposed Scope:
The scope of the project is to brainstorm, design, and fabricate a fully functional animal automaton that is capable of producing lifelike motion such as wing flapping, head blobbing, and potentially other structural movements like the tail, spine, etc. These motions will be sourced from a single motor input and given the project’s budget and time constraints, the final assembly’s target will be a prototype that demonstrates a synchronized system driven by one rotating crank through a system of cam followers, four-bar linkages, and a gear train connecting all in one.

Prior to fabrication, several analyses will need to be conducted such as gruebler equation and degrees of freedom check will be performed on each subsystem in order to determine that the overall mechanism is properly constrained and behaves as intended. Grashof condition check will be applied to the four-bar linkages to confirm crank-rocker behavior for the wing and head subsystems, ensuring continuous rotation. Position analysis will then be conducted on the four-bar rocker mechanism governing head motion to select appropriate link lengths with full range of motion. Gear ratio analysis will be performed on the gear train and belt system to properly distribute and phase the motion between subsystems so that each body part moves in a coordinated sequence. The critical joints and link connections will also need to ve heavily evaluated with input loads. Torque and power requirements will be addressed as well for motor selection. Lastly, a bill of materials (BOM) will be finalized alongside a full motion CAD model to guide a clear direction during the fabrication process through 3D printing, laser cutting, and other hands-on manufacturing processes.

Other interests that the team has is stylizing the animal body structure for a cleaner aesthetic such as painted or hand-colored surfaces on the animal body and structural base to bring the automaton to life as a piece of mechanical art. Natural environment features such as decorative trees, foliage, rocks, or a habitat-themed base platform could also be added to contextualize the animal within a realistic scene and elevate the overall display quality. We also hope to integrate programmable motion control with sensors or LEDs to simulate ambient environmental effects such as glowing eyes.

Preliminary Design

Shown above are some rough drafts of the most basic elements of our prototype. The diagram marked ‘Wing Model’ uses a simple crank rocker design to make the gold segment, which we intend to attach the wing to, move in a realistic flapping motion. A preliminary estimation of the link lengths required is also listed above.

In addition to the wing model, we have a neck model, containing a crank slider mechanism with spring forcing the block right. We also aim to have the gold segment buffer out the motion to prevent jerkiness, potentially by setting it within a slider connected to the crank shaft. The blue link seen in this image is meant to be the same, or along the same axis, as the blue link in the wing model. We will also transfer via pulley the circular motion from the wing crankshaft to the neck model crankshaft. This way, we will have multiple complex motions happening from the same input.

Lastly, this is the most basic of models, and in order to make a more realistic wing motion, we will need to have more links attached to the undersides of the wings to guide its motion, likely connecting to the original shown wing link. These will likely be using several cam-followers mounted to a shared axel below the model. Klann linkages would prove useful for legs, and cam lobes with asymmetrical lobes could be used to simulate the quick flicking motions of a tail.