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X14 Vertical Profiling Float
| PART Summary | |
|---|---|
| Vehicle | X14 ROV Sub-Optimal |
| Contributors | Jason Zheng, Ulysses Hennelly |
The Vertical Profiling Float serves as a float that is capable of completing two vertical profiles after being deployed by the ROV. This float utilizes a buoyancy engine to control the displacement of seawater and thus achieve a vertical profile.
- Priorities
- Standard Parts
- Ease of replacement/modularity
- Less jank esp. Since we’re dealing with 40PSI
- Quick prototype
- Despite calculations showing that minimal amount of inflation -> rise, unsure, thus need to quickly build a float to ensure the basic design was sound
- Considerations
- Holds pressure up to and beyond 40 PSI
- Light weight in order to maintain neutral buoyancy without having to add a lot of foam/mass to maintain neutral buoyancy
The float is composed of three separate components, the electronics/battery housing, the solenoid/pipe as well as the pressure accumulator. These components all slot into a 3D printed bracket which holds the components in place for mounting to a polycarbonate tube. This tube then has a handle attached for the ROV to hold onto while positioning the float.
The pipes are standard brass fittings with some plastic tubing that is rated to 40 PSI. The housing for the electronics as well as pressure accumulation tank is made out of PVC. The mounting bracket is made of PLA 3D printed filament. The outer clear tube is ordered from McMaster-Carr and is made of polycarb.
https://materovcompetition.org/content/mate-floats - Previous year’s float competition. Provided useful reference info for initial idea brainstorm
- Initial idea of using syringes for buoyancy was revised after considerations.
- Multiple meetings were held.
- Syringe idea deemed possible but pressurized air was also deemed an option
- 2 ideas held, after more discussion whilst buying parts, we figured pressurized air was a) easier than figuring out motorized syringes + b) more margin for error.
- Multiple meetings were held.
- Solenoids became leaky internally as they were used so replacement solenoids were ordered.
- When pressurized up to 40 PSI, the tank would leak to ~37 PSI and the bladder would become visibly inflated.
- Initial pressure accumulators that were repurposed airsoft gun cartridges were deemed impractical and replaced with plastic accumulation tanks
- Metal cartridges were heavier than plastic which would require additional foam instead of additional mass.
- Foam would have soaked up water which would be iffy.
- Dimensions of metal cartridges were a) too small and b) not in a great form factor
- Would have required multiple and harder to refill.
- Also can daisy chain plastic cartridges.
- Metal cartridges were heavier than plastic which would require additional foam instead of additional mass.
- Epoxy did not bond well to some surfaces so parts had to be cleaned up, roughened and re-epoxied.
- Cap - wire = epoxy peeled off - different epoxy used
- Solenoid wires epoxy started to peel off - not enough epoxy
- Electronics housing was re-made to fit with the mounting plate and also to make replacement of electronics easier.
An Electric teammate created an arduino nano circuit to run the solenoids via the battery.
- Some parts had to be re-made properly due to issues when modifying/assembling the parts for the system.
- Electronic feedback caused components to fry so feedback diodes were placed into the circuit
Initial prototyping and component purchase should have been completed sooner. This would have given us more time to properly create housing for the system.
- SID + Fuse Calculations
- Reverse Diode Protection
- Also python script for measuring how little volume change -> time to ascend/descend
Buoyancy Engine Design:
- Air is compressed to 40 PSI and sent into the pressure accumulator via the quick disconnect connector. At this point, the valve next to the quick disconnect remains closed. After being dropped off in the correct location in the pool, pressurized air is released into the bladder. The flow of the air is constricted via the first solenoid to allow for enough air to remain for the second vertical profile. This causes the system to float to the surface. Then, the second solenoid is fired to vent the air in the bag via the check valve which prevents water from back flowing. This causes the system to sink. This cycle is repeated for the second vertical float.
- The system is maintained at a slightly negative buoyancy when the bladder is half-inflated to ensure that a minimal amount of additional inflation of the bladder is required for the system to perform the first profile.
Operation details:
- Switch on housing is flicked and the Arduino Nano starts a timer for the circuit to start inflating. Meanwhile, the ROV positions the float into the correct position within the 60sec time. The float is released by the ROV when the bladder is inflated and the float starts its vertical profile. The float completes the two vertical profiles by inflating and deflating the bladder as described above.
Search keywords.
The vertical-profiling float serves as a float that is capable of completing two vertical profiles after being deployed by the ROV. It utilizes a buoyancy engine to control the displacement of seawater and thus control the vertical height of the float. This buoyancy engine is composed of 3 separate modules. Firstly is the pressure accumulator that powers the system. Secondly is the pneumatic control system composed of the solenoids and bladder. This system controls the pressurized airflow to and from the bladder. The bladder's volume varies, which modulates the buoyancy of the buoy. The last module is the electrical housing, which controls the solenoid actuation timing. Our design approach focused on rapid prototyping and testing for the development and construction of the float. To accelerate the design process we used standard parts like PVC piping that could be locally sourced. We also developed a basic python program that helped us determine the movement of the float given a few parameters like mass and volume. This program aided us in estimating the time to surface of 1 second in a 6-meter pool given a 2.5% increase in volume. This program proved the viability of our design before any physical testing. After the initial prototype took only 3 seconds to surface, we became confident in our design approach. With this newfound confidence, prototypes started construction. These prototypes failed on many occasions, which helped us locate issues before the competition. One such issue was that our solenoids began to leak over time when the accumulator was pressurized at 40 psi. This proved to be a fundamental issue with the product thus the issue was bypassed by replacing the solenoids and purchasing a larger accumulator. Another issue was that the decreased hydrostatic pressure at the surface of the pool led to the bladder not deflating fully. Removal of the check valve to reduce barriers proved moderately successful. Together with the additional pressurized air volume provided by the larger accumulator and modification of the float buoyancy, this issue was resolved. In the end, our rapid failures and resulting solutions culminated in a successful test, and the fundamental design was finalized. We then turned our focus toward creating a proper housing and mounting system for the float.
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