Subsystem Build & Test
Table of Contents
The Subsystem Build and Test directory contains our documents.
Team Vision for Subsystem Level Build & Test PhaseDuring this phase our team aimed to continue testing using currently available parts, source the items on our B>O>M>, and begin construction on the Ppod, Labview Code, and controls systems. Continued testing was able to provide necessary information about our system to be considered in build decisions going forward such as base plate design.
Test Results Summary
Solenoid and Piston
Running the Solenoid to its absolute extremes we found that the solenoid valve was maxing out of the system at the 40 Hz range. This was determined by listening to the clicking from the cycling of the valve. Fallowing this discovery that we weren’t going to get the right frequency led us to the decision that we needed to get the other solenoid valve.
The new valve:
- Ordered and received the solenoid Feb. 24 2016
- Looked at components and reviewed data sheet
Running tests for the system we found that the response of our piston we have currently does not work because it requires a pressurization of 60 psi for our 20 lbs mass and is resulting in our piston cycling with decaying amplitudes. This leads us to believe that we need to move form our current piston to the one from McMaster Carr to run at lower cfm’s and get out of the compressible region.
Moving forward I hope to obtain a better testing result from the new piston and try to find an experimental time constant.
Damping and Simulation Testing
The mass being shaken on our real test rig is about 23lbs. The mass we used during simulation testing was about 20lbs.
Predictions Before Testing
1. Acceleration results in the data would be fairly similar at 80psi versus 100psi.
2. As more mass is added to the baseplate, the system will see better damping response.
Using the data to take the average acceleration at each pressure and frequency tested:
Since the vibration application I used accounted for gravity, having acceleration values around 9.8m/s on the tabletop meant that the system was being properly isolated from the table.
Observations and Solutions After Testing
1. Observation: The pressure needed to allow the piston to function is 80psi -100psi because our valve constraints. Therefore, we were only able to test at 800 and 100psi.
Solution: Once we receive our new piston, which will have a larger bore size, we should be able to test at a range of pressures.
2. Observation: Our sine wave generator can get us to our 100Hz required frequency with no issues.
3. Observation: The maximum frequency that our entire current system could run was 23Hz. Any frequency past 23Hz was irresponsible. The system as a whole became unresponsive at around 23Hz.
Solution: Our new piston will have a larger bore size and smaller volume to be able to handle pressure intake and outputs at higher frequencies (20Hz and up).
4. Observation: The solenoid could go up to 40Hz when acting alone.
Solution: The new solenoid we've just purchased will be tested for specifications and used for testing. This new solenoid is capable of functioning up to 109Hz.
6. Observation: Our current baseplate did not dramatically outweigh our ~20lb top assembly. Any test data collected past 10 Hz was considered inaccurate because the system became too jumpy and began sliding off of the damping hemispheres .Solution: Once we are able to machine out ~40lb steel baseplate we will be able to create a more stable test and permanently attach the Sorbothane hemispheres. This will give us more accurate data and keep our system from jumping along the tabletop.
Labview CodeDuring this phase we began to explore the critical functions of our labview code and control structure.The chief concern was to create a program which would monitor run time and automatically adjust it's outputs to the appropriate frequency and acceleration values.
The above image shows the block diagram for the critical components used to monitor and control the outputs from the program to the test rig.
Shown above is an example of the sine wave output changing frequency as it the time of the test changes.
Accelerometer and Gyrometer
In order to start working with the accelerometer board, we used an arduino uno and a breadboard. This will give us the ability to experiment with the board before installing it on the rig using a labview DAQ.
- Testing of the accelerometer and gyrometer are currently in process
- Working with arduino uno to validate the board and am having some difficulty compiling the code
- Contacted packaging science vibration test lab to request time with their system for calibration and validation
- Full scale test of emergency stop is complete
- Emergency stop was able to stop a large motor immediately
Takeaways from the test:
- Button controls the hot wire only
- Button immediately stops the flow of electricity completely
- Ready to install on the test rig
Assembly Construction & Design UpdateDuring this phase, after further consulting with the machine shop, some changes were necessary in the construction of the P Pod. The initial plan of welding was removed due to the inability to hold a small tolerance. Then, once I spoke with the machine shop and the Brinkman lab, a new solution arose.
In this updated design there are a few key features.
- Screws: To ensure the accuracy of the interior rails, they will be fixed to the outer sheet metal using a number of screws. This allows for some adjustability, with a larger hole in the sheet metal. Interference of holes has also been addressed by carefully choosing the holes depth and diameter.
- Base Holes: There are threaded holes on the base of the P Pod which allow it to be secured to the oscillating base. This ensures it remains even more secure, but adds some difficulty for removal.
- Tolerancing: All parts has been updated based on cubesat standards. The drawings were updated accordingly and moved to the MSD title block format.
- "Calibration" Square: During the assembly and machining process, a "calibration" square, the same dimensions of the rails of the CubeSat, will be made, to ensure the real CubeSat can slide in without issue, or risk of damage.
- CubeSat: P16102's Cubesat's are updated into the model, so no more plain and ugly orange/brown blocks.
Ideally, this would have been under construction by now, but as the previously explained difficulties arose, the timeline was pushed back. We do have all materials necessary to complete this on hand, minus the screws. Once the P Pod is complete, then the frame will be constructed. Since the P Pod is the primary concern, this timeline and process is reasonable.
Bill of MaterialsAll items with N* are ready to order, were temporarily held up by change of screws. Minimize orders frequency to reduce shipping cost. Shipping cost will be added to bill of materials, once values are quantified.
Risk and Problem Tracking
- We have been able to take away 3 Risks from our list based off the fact that we no longer see them as a risk
Plans for next phaseTeam Shared vision
- Solenoid Valve Validated
- System tested to dampen vibrations and prevent movement
Testing in process:
- Accelerometer and gyrometer board
- Position sensor
- Piston Received
- All more parts and materials sourced
Build of Rig:
- Top half assembly and PPod 60% completed
- Labview code ready to connect and output to DAQ device to out put frequency and amplitude commands.
1. Continue to work with accelerometer board and validate on packaging science test rig with the position sensor
2. Work with the team to understand and use the new solenoid valve and controller
1. Work with new solenoid to get an understanding of how it works
2. Order and work with the new Piston
1. Continue thorough testing of system with accelerometer, solenoid and new piston
2. Assist with solenoid
1. Complete construction of P Pod
2. Order the rest of the necessary parts
1. Implement DAQ connections into labview code
2. Test Solenoid with sine wave output