Phase 3

During this phase of the project, the team designed and constructed the lifting mechanism that interfaces with the grasping mechanism and lifts the payload.

Design Constraints and Considerations

Phase 3 consists of challenging tasks, such as constructing calculations for the GLS and Mechanical Advantage, MATLAB coding, and other topics stressed throughout course research and study. Involved with this portion of the project include the following:

Form
- The weight of the claw and the grasping object was approximated in Solidworks and came to be 0.076kg. This weight is crucial as it is used in the mechanical advantage calculations.
Materials
- For all Fastener must be selected to be alloy steel
- For all links, including the ground, Pine must be selected
Phase duration
- The phase duration expresses the entirety of phase 3 with respect to time. The team was given a total of three weeks to complete phase 3. Within the three weeks, the Mechanical advantage calculations, MATLAB coding, and various other tasks were to be conducted.

Not only are explicit constraints entailed within phase 3, but there are implicit constraints the team has encountered as well, such as:

The payload must interface with the claw
The claw along with it's arms must interface with the base tower in order for it to move up and down.

As far as a team imposed constraint the team has decided on laser engraving into the wood of our final designs. The laser engraving will take place towards the end of Phase 4. Laser engraving will be a unique challenge to furthermore enhance our knowledge and experience with laser engraving.

Brainstorming Session

Design #1

This design played off of the sample arm previously provided in the project by changing the angle of the bottom link and having a support link in between

Pros:

Simple Design

Cons:

Almost no mechanical advantage
Support link would most likely bind
Would probably put too much stress on the servo

Final Design

This design was an optimization of design two based on mechanical advantage

Pros:

High mechanical advantage
Should be able to handle the weight of the claw and the payload

Cons:

Payload is tilted up when lifted

Design #2

In this design the top like would be the crank and the coupler would be perpendicular to the bottom link, which is parallel to the ground, when grabbing the payload

Pros:

Lifting from top link should avoid binding and clearance issues

Cons:

Low mechanical advantage
Payload is tilted up when lifted

Graphical Linkage Synthesis

Mechanical Advantage Calculations and MATLAB CODE

Above are the calculations for the mechanical advantage which were conducted based off the graphical linkage synthesis in the previous section.

Lifter Torque Estimator

MATLAB Code

This code estimates the excess torque available to accelerate the linkage after evaluating the torque consumed to hold the claw and object in a fixed position.

Here we can see a visual demonstration of the arm and claw interacting and moving with each other.

Photos of Arm

Open Position

Closed Position

Model Video

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