NAU ME Capstone

G.A. CubeSat Team

Project Information

Description

The team will design a mounting fixture that securely attaches a 12U CubeSat to an air bearing test stand, so that a friction less environment can be achieved for testing purposes. The design must refocus the center of gravity of the entire assembly and limit tilt degree.  

Design Constraints

Customer Needs

• Reliable
• Durable
• Non-Magnetic
• Limit Space
• Limit Overall Weight
• CubeSat Easily Install/Removal
• Secure CubeSat
• Adjustable on Three Axis
• Compatible with Air Bearing Stand
• Refocus Center of Gravity
• Compatible with Different Payloads
• Compatible with Keep Out Zones
• Account for Hardware

Main Content

Engineering Requirements

• Accept CubSat (Lift Weight)
• Movability in all Axis
• Limit Tilt
• 360 Degree Rotation
• Limit Weight
• Limit Size
• Material Strength
• Lifetime Cycle

First Semester Tasks

The first semester's goal was to end the semester with a finalized design, sketched out in CAD. As well as developing different testing procedures to complete during the second semester. Throughout the semester the team completed the following:

• Developed appropriate design constraints (Customer Needs and Engineering Requirements)
  
• Generated multiple design concepts
• Evaluated designs
• Analyzed sub-functions of chosen design
• Created 3D CAD model of chosen design
• Developed a testing procedure for second semester
• Finalized a bill of materials (BOM) for the prototype of the design

Concept Generation

Black Box Model

Functional Model

Design Alternatives

Design Concept 1: Sliding Rail with Clamps

• This design attaches the CubeSat to a rail system that is able to move in both the X and Y directions
• It moves the CubeSat so that the center of gravity is in the correct location
• For this design the rail would be manually moved and placed at the certain location necessary

Design Concept 2: Power Screw with Counter Weights

• This design has four power screws with counter weights attached along the sides of the fixture
• The counter wights will move along in the X and Y directions
• The weights will allow the whole assembly to relocate the center of gravity

Design Concept 3: Pneumatic Gimble

• This design uses pneumatic cylinders placed on the corners of the fixture in order to lift the fixture / CubeSat up and at different angles
• The design would help relocate the center of gravity of the fixture in multiple different axis

Design Concept 4: Pneumatic Rod with Counter Weights

• This design uses counter weights attached to a pneumatic rod
• The rods would move in the direction of the X-Y plane
• The weights would help relocate the center of gravity of the entire assembly

Design Concept 5: Combination (Design Chosen)

• This design utilizes different components of the designs prior
• It has a clamping mechanism on the top to secure the CubeSat to the fixture
• It has a sliding fixture to move the CubeSat around
• It also utilizes conter weights attached to power screws moving in the X, Y, and Z directions

Evaluation of Designs: Decision Matrix

First Semester Conclusions

CAD Model of the Design Chosen

Estimated Bill of Materials

Quality Function Development (QFD)

Second Semester Tasks

The second semester's goal is to have a fully complete design that has been built and tested. The team will end the second semester with a prototype of the full design and will be able to give directions on how to build the actual device for the clients. As well as directions on how to set up and take down the device for testing purposes. Throughout the semester the team will complete the following:

• Build each individual sub-system
• Run tests on each sub-system
• Set up the full prototype of the design
• Test the full design
• Create a manufacturing and development plan
• Write a set-up and take-down plan to describe how to use the device
• Handoff all materials to client

Sub-Systems

Programming / Electronics

The programming/electronic system is what locates the center of gravity and calculates the necessary correction. The entire code is made up of different components, each combined into one solidified Arduino Code. The code is made up of the following subprograms:

• Subprogram to detect tilt in the system
• Subprogram that calculates the location for where each counter-weight needs to move too
• Subprogram that utilizes force sensors to detect where the center of gravity of the system is

The elctrical system contains the necessary sensors for each of the programs.

The set up for the electrical system is shown below.

Pneumatic

The pneumatic system is what powers the motors for the counter-weights to move. The set up consits of a compressor, air tank, solenoids, motors, hosing, and connectors. The compressor and air tank are external to the system, and everything else is attatched to the design.

The following image shows the set up of the system.

The prototye for the pneumatic system is shown below.

Counter-Weight

The counter-weight system relocates the center of gravity of the entire assembly. The system is composed of a powerscrew assembly, the counter-weights and a railing system.

The prototype for the counter-weight system is shown below.

Securing Mechanism

The securing mechanism system is how the CubeSat is going to be attached to the fixture. The current system is utilizing tabs that are located at the bottom of the CubeSat to slide into a railing system. This railing system would then be screwed onto the fixture.

The prototype for the railing system is shown below.

The way the CubeSat fits into the railing system is modeled within a CAD model shown below.

Entire System

Below are images showing the first step of manufacturing.

Below are images of the CAD model of the system

Final Product

The finalalized image of the fixture ontop of the testing stand is below