Structure Subsystem Build & Test
Table of Contents
Vision for Structure Subsystem Level Build & Test Phase
This phase focused on finalizing the overall structure design and optimizing its space, weight,factor of safety and displacement.
Test Results Summary
During this phase all boards and components are finalized. Using this information the platform layout was defined. When finalizing this layout, the footprint of the platform was reduced from 14" x 14" to 12" x 12" by moving the boards, battery and reaction wheel board to the corners of the platform. In addition, all mounting points were finalized to assist with the final FEA simulation.
After the design and layout was finalized, FEA was performed to validate the structures Factor of Safety and identify any additional risks. Accurate locations of the boards and their masses were utilized. Therefore, the Factor of Safety, Displacement and the Center of mass could be examined during the simulation.
Multiple iterations of this simulation were performed. Using the results, material was removed from the structure to reduce weight. The structure weight was reduced by 875 g or 1.93 pounds. After each iteration, the factor of safety, displacement and center of mass were evaluated to compare various design configurations.
Using the FEA simulation and process of removing material from the structure, a final design was found. This design has a minimum Factor of Safety of 8, minimum displacement of 1.3 mm, center of mass of .5" from the center axis and a weight of 11 lbs. All of these parameters are acceptable based on the teams requirements. However, the next section will describe risks that still exist and the plan put in place to potentially address them.
Risk and Problem Tracking
The weight of the platform is about 11 lbs. This uses assumed values for wires and various sensors. However, conservative estimates were made for these components. If the weight is greater than 12 lbs after assembly, the reaction wheel has been identified as the first component that will be removed from the design.
The maximum displacement of the structure is 1.3 mm based on the simulation. This is slightly above the 1 mm goal defined. However based on the design of the simulation, the following conclusions were made:
Not all of the components will have this max displacement based on specific location on the platform. The max displacement occurs directly in the middle of the structure
- The simulation does not account for the support added by the insulation panels which enclose the entire structure
- If it is found that any components are reaching an excessive displacement, stand-offs or lightweight bases can be made to add rigidity to individual components
Impact will be tested after assembly. If the structure does not meet the requirements for impact, the thickness of the supports can be increased to add support.
The design of the structure allows for any thickness of insulation to be used assuming the weight of the total structure remains below 12 lbs. Therefore, testing can be performed after the structure is assembled and the required thickness of insulation can be selected to meet the temperature requirements.
Plans for next phase
- Finalize Drawings
- Design Battery Mount
- Assembly Battery
- Test Battery, Solar Panel and MPPT
- Order remaining material
- Manufacture all parts
- Final BioCell test
- Assemble platform