P17250: Solar Powered Charging Station

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Preliminary Detailed Design

Table of Contents

1 Team Vision for Preliminary Detailed Design Phase
2 Design Overview
3 Feasibility: Prototyping, Analysis, Simulation
4 Drawings, Schematics, Flow Charts, Simulations
5 Bill of Material (BOM)
- 5.1 BOM for RCS
- 5.2 BOM for Robofish
6 Test Plans
7 Risk Assessment
8 Design Review Materials
9 Plans for Next Phase

Team Vision for Preliminary Detailed Design Phase

Planned:

Ensure the Robofish is in working condition

Complete preliminary feasibility analyses

Create full preliminary designs for all systems

Create a BOM containing components needed for preliminary designs

Create draft test plans that describe tests needed to demonstrate that the customer and engineering requirements have been met

What Occurred:

It was discovered that the Robofish has problems with its internal wiring that are preventing it from performing as intended

Feasibility analyses have been completed with the exception of the RCS guide test which was dependent on the guide geometry that was recently finalized. As an alternative a Plan B was developed and a feasibility test was run for it

Preliminary designs (schematics, flow charts, CAD models) have been completed for all major systems

A BOM has been drafted containing components that are needed to realize those designs

Test plans have been drafted. Test set up schematics will be completed next phase after feedback has been received about draft plan

Design Overview

Six Main Systems were designed in this phase:

Structure - The overall structure of the RCS including the frame and components necessary to hold and protect components from other systems

Buoyancy - The system necessary to ensure the top surface of the RCS remains above water

Robofish Docking - The system that describes how the Robofish appraches the station and positions for attachment. A painted pole is used to attract the Robofish. Plan A is to use passive guides to guide the fish into position. Plan B is to use a rotating fixture to move the fish into position

Robofish Attachment - The system that describes how the Robofish connects to the station electronically and physically

Solar Power Harvesting and Storage - The system that collects and stores energy from the sun

Robofish Power Delivery System - The system that transfers stored energy from the RCS to the batteries on the Robofish

Feasibility: Prototyping, Analysis, Simulation

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 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

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

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.

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

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

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

Robofish Docking

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

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

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 with drain holes to connect wet without causing a short

Drain holes double as an attachment point for the RCS to secure the connection with solenoids. This is required because the connection force for this connector must be small due to the small buoyancy force of the fish

Prototype Connector Design

Connector Design Download (Solidworks)

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?

Drawings, Schematics, Flow Charts, Simulations

Structure

Design Features

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

Isometric View (11/2/2016)

Side View (11/2/2016)

Most Recent CAD Files Download

Electrical

Solar Panels to RCS Power Output

Charging Schematic (10/26/2016)

Fish Side Conroller

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, which then controls some transistors or relays (details still in the air) to disconnect the load (ie the rest of the fish electronics) from the battery, and enables the charger. After a set amount of time, the charger is disconnected, the fish electronics reattached and the fish disconnects from the RCS.

Fish-side charge controller (11/03/2016)

Software

Fish Side Docking Sequence

Describes software process that must be implemented on the fish to perform the docking procedure.

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)

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.

Most Recent BOM Download