P17250: Solar Powered Charging Station
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Detailed Design

Table of Contents

Team Vision for Detailed Design Phase

Planned:

What is left to complete:

Progress Update

Progress made for the detailed design phase as of 11/22/16:

Progress Update Download

Prototyping, Engineering Analysis, Simulation

Overview

Feasibility 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.

Feasibility Summary Download

Image Processing

Question: 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.

File Download

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.

Image Processing Sample (10/27/2016)

Image Processing Sample (10/27/2016)

Image Processing Sample Result (10/27/2016)

Image Processing Sample Result (10/27/2016)

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.

Weight Estimation

Weight Estimations

Weight Estimations

File Download

Buoyancy

Question: How much buoyancy force is needed to keep the RCS afloat and what contained volume of air is necessary to provide that?

Volume of Displaced Water Needed

Volume of Displaced Water Needed

File Download

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.

Assumptions

Center of Buoyancy Calculations

Center of Buoyancy Calculations

Stability Graphs, COB based on angle of tilt and restoring force based on angle of tilt

Stability Graphs, COB based on angle of tilt and restoring force based on angle of tilt

Calculation Summary Download

Matlab Download

Solar Harvesting

Question: How large of a solar panel area is required to charge the Robofish once per day on an average Rochester day?
Area of Solar Panel Needed

Area of Solar Panel Needed

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.

File Download

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

Summary of Tests Conducting with GrapeSolar 100W Panel

Summary of Tests Conducting with GrapeSolar 100W Panel

Test Data Download

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.

Summary of Solar Calculations and Tests

Summary of Solar Calculations and Tests

Robofish Docking

Question: 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.

Scale model of Guide Design and Robofish

Scale model of Guide Design and Robofish

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.

Miniature Prototype

Miniature Prototype

Video Download (Might have to download through SVN, the file size is causing issues with this link)

Robofish Attachment

Question: Can a prototype connector be made that is capable of accepting the Robofish if its angle is not perfectly aligned?

Connector Design Features

Prototype Connector Design (Isometric View)

Prototype Connector Design (Isometric View)

Prototype Connector Design (In Installation Orientation)

Prototype Connector Design (In Installation Orientation)

RCS Connector Drawing (12/6/2016)

RCS Connector Drawing (12/6/2016)

Connector Design Download (Solidworks 2013)

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.

Does Connector Short when wet?

Does Connector Short when wet?

Drawings, Schematics, Flow Charts, Simulations

Structure

Design Features

Isometric View (12/6/2016)

Isometric View (12/6/2016)

RCS ASSY Drawing (12/6/2016)

RCS ASSY Drawing (12/6/2016)

Most Recent CAD Files Download

Guide Drawings

Guide, Left, Long Drawing (12/6/2016)

Guide, Left, Long Drawing (12/6/2016)

Guide, Left, Short Drawing (12/6/2016)

Guide, Left, Short Drawing (12/6/2016)

Guide, Right, Long Drawing (12/6/2016)

Guide, Right, Long Drawing (12/6/2016)

Guide, Right, Short Drawing (12/6/2016)

Guide, Right, Short Drawing (12/6/2016)

Guide, Under Drawing (12/6/2016)

Guide, Under Drawing (12/6/2016)

Electrical

RCS electronics
Charging Schematic (02/02/2017)

Charging Schematic (02/02/2017)

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.

Fish Electronics

Fish electronics schematic

Fish electronics schematic

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.

Software

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.

Fish Docking Sequence Program (Fish Side) (12/06/2016)

Fish Docking Sequence Program (Fish Side) (12/06/2016)

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 Docking Sequence Program (RCS Side) (12/06/2016)

Fish Docking Sequence Program (RCS Side) (12/06/2016)

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.

Fish Docking Sequence Program (Fish Side) (11/01/2016)

Fish Docking Sequence Program (Fish Side) (11/01/2016)

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.

Fish Docking Sequence Program (RCS Side) (11/01/2016)

Fish Docking Sequence Program (RCS Side) (11/01/2016)

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 from 1/24/2017 Download The most recent BOM is located at the bottom of the Subsystem Build & Test Page.

BOM for RCS

BOM for RCS

BOM for RCS

BOM for Robofish

BOM for Robofish

BOM for Robofish

Test Plans

This document details the tests necessary to prove that the customer and engineering requirements have been met.

Tests Described:

Most Recent Test Plan Download

Risk Assessment

Risk Assessment (12/6/2016)

Risk Assessment (12/6/2016)

Risk Assessment Download

Design Review Materials

Detailed Design Presentation Download

Closure Plan

A 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.

Closure Plan Download

Plans for Next Phase

MSD 2 Project Plan Download

Gate Review

Gate 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


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