Team Vision for Detailed Design Phase
- Complete and document at least one feasibility analysis for each major system
- Create all drawings and models needed to communicate the full RCS structural design
- Create all electrical schematics needed to fully communicate every electrical system on the RCS and the charging system in the Robofish
- Create software flowcharts that describe the software intended for the RCS
- Complete the Bill of Materials with every component needed to realize the design
- Create a procurement plan and cost accounting system to be used in MSD 2 for acquiring and tracking components
- Write a test plan that lays out all project requirements and how it will be determined that they are met. The plan should contain procedures for all needed tests
- Implement an issue management system to track all known and completed issues
- Create a project closure plan that can be passed to another team that describes what we have done and where information can be found
- Continue to update the risk management system to track all known and closed risks
- Draft a schedule for MSD 2 to describe a high level picture of due dates and resource allocation
What is left to complete:
- Lengthen the connector guide surface length to position the Robofish before the attachment screw
- Add component to run attachment motor in reverse for releasing the Robofish
- Complete the MSD II Project Plan
- Pick out specific fuses for RCS circuit
- Reach out to local companies to see if they have surplus material we can use
- Ensure all electronic components are in the BOM
Progress made for the detailed design phase as of 11/22/16:
Prototyping, Engineering Analysis, Simulation
OverviewFeasibility analyses have been performed on all major systems of the RCS design. This section describes all analyses performed. A summary can be downloaded through the link below.
Image ProcessingQuestion: How far can the RoboFish see underwater?
The intended colour of the pole to be used as the object the RoboFish attaches initially to the RCS is red. Therefore a pole was painted this colour, and the code on the Raspberry Pi was modified so that it would detect a significant hue range of red. The fish currently uses a Raspberry camera, and the resolution set to 480 x 300. The small resolution helps reduce noise, as small red particulates can make for false positives. The code goes through 9 distinct stages of image processing to ensure that the colour red is highly detectable under varying conditions.
The Raspberry Pi was then placed underwater, and coded so that when it does detect this colour, that it would open its jaw. The link to the modified and updated Image Processing code (Python) has been provided here.
The testing proved that after approximately 5 meters, the fish camera loses the red object detection.
A sample snapshot was taken to show the image processing code result with a red pole underwater at a distance of 1.5 meters.
A concern with this approach which was implemented by the previous MSD group is the fact that it relies being able to see the pole in the first place. Therefore, if the camera is not facing the RCS, the RoboFish is unable to detect the location of the RCS. This has been identified in the updated Risk Assessment below, whereby the code must be modified so that the RoboFish will rotate, check, swim ahead, and complete a systematic process in order to identify the location of the RCS eventually. With this in mind, the threshold of the battery for it to be considered "low" and therefore requires charging must be increased to a level that would allow enough energy for the RoboFish to at least complete the entire process of this search.
Question: How much buoyancy force is needed to keep the RCS afloat and what contained volume of air is necessary to provide that?
Question: How much force is needed to completely submerge the RoboFish?
The RoboFish's buoyancy is controlled through the Arduino. This was temporarily set to maximum through C++ on Visual Studio, then re-uploaded to the micro-controller.
The fish was unable to lift 5 pounds when set to fully buoyant.
Question: Can the station remain stable when subjected to small tilts?
Two main forces are considered to determine the stability of the station: the buoyancy force and the force due to gravity. Each of these forces acts at different locations depending on the tilt of the station. The force due to gravity will always act at the center of mass (COM) of the station and the buoyancy force will always act at the center of buoyancy (COB) of the station. Based on assumptions made, these forces will always be equal and opposite but the COM and COB will change. When coupled, these forces form a moment that varies in magnitude based on the locations that the forces act. Up to a certain angle of tilt, this moment is called the restoring moment as it restores the RCS to its non-tilted position.
It is concluded that the station will remain stable to at least 10° of tilt. It will likely remain stable far past that but due to the assumptions made, this analysis would not apply.
- Force of buoyancy and force due to gravity are equal and opposite, always acting in the vertical (y) direction
- The floats remain level with the surface of the water no matter the tilt of the station (relatively accurate to about 15° of tilt)
- All floats on the station remain at least partially submerged (true to about 10-15° of tilt)
- The floats on the station are symmetric about the y-axis
- The COM x coordinate lies at the center of the RCS
Solar HarvestingQuestion: How large of a solar panel area is required to charge the Robofish once per day on an average Rochester day?
The solar panel we currently have is .68 m^2. According to the calculations this one panel will provide sufficient power on an average Rochester day. However, to include a large margin of safety and to improve performance so that the RCS operates on nearly any day the station was designed with two panels.
Question: A solar panel was inherited from a previous team. How much power is it capable of harvesting on an average Rochester day? Would two panels harvest sufficient energy to charge the Robofish once per day?
A test was performed at 4 different times in four different conditions to determine the harvesting capabilities of the Grape Solar 100W panel. The panel was laid flat on the ground outdoors for each test.
Requirement: 148 Wh to fully charge Robofish
Assumption: 11 hours of sunlight each day
The conditions are defined as follows:
Worst Case - Raining, full cloud coverage, in shade of building
Average - Cloudy day
Best Case - Sunny, few clouds
Solar Feasibility Conclusions
Two solar panels will provide sufficient energy harvesting to charge the fish once a day on an average Rochester day. The graph below shows that in all but the worst case condition, enough energy will be harvested.
The worst case condition shown was a test conducted under full cloud coverage in the shade of a building while it was raining with droplets on the panel.
Robofish DockingQuestion: Can a passive guide mechanism be designed that can guide the Robofish into a docking port if it floats up into it?
A test was performed in a bathtub using a scaled down version of the RCS guide design and Robofish. The top of the angled guides were positioned just above the water's surface as will be the case with the larger version. The model Robofish was positioned with is "grasper" below the center of the model station. The fish was then released and allowed to float up into the guides.
The guides were successfully able to guide the Robofish into the docking ports no matter what upright orientation the fish was at upon being released (when the 'grasper' was located beneath the center). While this test improves confidence, it is not conclusive. The model Robofish has simplified geometry compared to the actual Robofish and likely more relative buoyancy. Additionally, the model guides were hard plastic but the real guides will be styrofoam.
In conclusion, plan B will be carried forward into MSD 2 to be enacted in the event that the constructed guides do not perform correctly.
Question: If the guide mechanism is not capable of docking the fish from any docking orientation, can a rotating fixture be used to move the fish into place?
A miniature prototype was constructed using an Arduino with an IR sensor and printed parts.
The fish approaches the docking pole and the fixture senses it and stops beneath it. The fish sinks into the fixture which will then rotate again to position it beneath a docking port. The fish will then float straight up into the port.
In the prototype, the IR sensor is in the miniature 'fish'. If this design is adopted this would be replaced with an ultrasonic transducer in the rotating table that would be capable of sensing the presence of the fish above it.
Robofish AttachmentQuestion: Can a prototype connector be made that is capable of accepting the Robofish if its angle is not perfectly aligned?
Connector Design Features
- Funnel to accept Robofish mating connector if Robofish is misaligned
- Angled faces to guide correct pins together if Robofish is incorrectly angled
- Isolated power pins allow a connection to be made when small amounts of water are present without causing a short
- Drain holes allow excess water to drain from connector before connection is made
- An attachment screw driven by a DC motor to complete the connection process and secure the attachment. This is needed because the buoyancy of the Robofish is less than 5 lbs and is not great enough to form a solid connection
- The male connector (on the Robofish) has its attachment point on a spring which will allow for a 1-inch overshoot in the screw connection. The spring gives the system some margin for error in alignment and overshoot
- A microswitch will be used to to detect that the Robofish is in position and to begin the screw attachment process
Question: Can a prototype connector be made that is capable not shorting when connected after emerging from underwater?
A prototype connector was design with drain holes and isolated pins to make a good electrical connection to the RCS after emerging from the water. A test was performed on the prototype connector to determine whether it shorts out when wet. The results are below, a 0 represents no short. The connector performs as intended and does not short when connected wet.
Drawings, Schematics, Flow Charts, Simulations
- Eight 5-gallon containers are used for buoyancy with an estimated weight capacity of ~340 lbs
- 80-20 is used for the frame. It is reliable, strong, easy to assemble, and we have received a large quantity of it from a previous group.
- The electronics are to all be placed in a large splash resistant orange container. This container is large enough to provide room for future additions to the station
- Guides were designed to aid in the fish docking process
- In the next phase, the attachment points and the docking pole will be added to the CAD model
The RCS has an arduino pro mini on it, which is used to detect electrical connection at the charging port, secure the connectors against turbulence via microswitch triggered stepper motors which screw the connectors together, and provide emergency disconnect options.Additionally, there is a current transducer used to measure current flow out of the station into the fish, and when it falls low enough the fish will be considered charged.
The fish side controller is always off when the charging connector is disconnected. When powered (ie the fish is plugged in to charge) the arduino is powered, and a SPDT relay activates and disconnects the load (ie the rest of the fish electronics) from the battery. The arduino enables the charger. After the current is measured to have stopped flowing from the RCS to the Fish, the RCS disconnects the fish and the SPDT relay automatically reconnects the load, disconnecting the charger.
Fish Side Docking Sequence (Plan A Docking Process)
Describes software process that must be implemented on the fish to perform the docking procedure - Plan A.
RCS Side Docking Sequence (Plan A Docking Process)
Describes software process that must be implemented on the RCS to perform the docking procedure utilizing the passive guide process.
Fish Side Docking Sequence (Plan B Docking Process)
Describes software process that must be implemented on the fish to perform the docking procedure - Plan B.
RCS Side Docking Sequence (Plan B Docking Process)
Describes software process that must be implemented on the RCS to perform the docking procedure should the passive guide process not work.
Bill of Material (BOM)
The BOM is split into two sections: one contains the materials needed to construct the Robofish Charging Station and the other contains materials that were used to modify the Robofish in order to implement our charging system.
BOM for RCS
BOM for Robofish
This document details the tests necessary to prove that the customer and engineering requirements have been met.
- Depth Test
- Battery Capacity Test
- Energy Delivery Test
- Energy Harvesting Test
- Robofish Attachment Strength Test
- Buoyancy Test
- Waterproof Test
- Automated Process Test
Design Review Materials
Closure PlanA project closure plan has been created to ensure that the project is properly closed for a possible hand-off to a future team. This plan includes detailed information on the project and its processes, as well as recommendations and lessons learnt.
Plans for Next Phase
Gate ReviewGate Review Presentation: Gate Review Presentation Download
Gate Review Action Items: Gate Review Action Items Download
FMEA (Failure Mode Effect Analysis): FMEA Download
MSD 2 Project Plan - Download from project plan section from above