MSD Project Team P08454

Underwater Thruster Design

Anthony Squaire – Team Leader - Industrial and Systems Engineering

Alan Mattice – Lead Engineer - Mechanical Engineer

Cody Ture - Mechanical Engineer

Brian Bullen – Mechanical Engineer

Charles Trumble – Mechanical Engineer

Aron Khan – Electrical Engineer

Jeff Cowan – Electrical Engineer

Andre McRucker – Computer Engineer

Project Background•Derived from one of the most successful projects in RIT’s history: P06606

•Project mission is to design an open source thruster that can be used and/or improved for future RIT MSD projects

•Customers:

•Dresser Rand

•Dr. Hensel and the RIT Mechanical Engineering Department

•Hydroacoustics

•The design needs to be competitive with the current thruster designs in use:

•Seabotix

•TecnadyneFigure 1: ROV Design from MSD project P06606

High Level Customer Needs•Thrust must be improved over the current Seabotix Thruster

•Power consumption must be better than the Seabotix Thruster

•Mounts as easy as the Tecnadyne Thruster

•Operational in 400 ft. (173 psi) of water

•Needs to work in temperatures from 38-75 F

•Modular, open source design

•Comply with federal, state, and local laws, including the policies and procedures of RIT

Current State of Design

•Completed two design reviews and met with the customers so that they could voice their concerns

•Machine drawings are complete for specialty parts and overall thruster design

•Have ordered the high priority/long lead time parts:

•Motor, magnetic coupling, shaft bearings, o-rings, motor controller, development board for microcontroller and feasible impeller prototypes

•Have two test plans completed and started to put together additional test plans to confirm the design specifications

•A test rig is built that will test the final thruster design

•Continue to meet with the lighting team to discuss the project interface for the light and the thruster bodies

•The major concerns of the design have been identified through the two design reviews and additional meetings with the customers and changes (if needed) will be implemented to mitigate the concerns:

•Heat dissipation, condensation forming, sealing the enclosure, and containing and balancing the magnetic coupling/shaft assembly

Current State of Design cont…

Assembly Drawing

Figure 4: Section view of P08454 thruster design (Note: Does not include rear section that will house the electronics)

Figure 3: Front View of thruster

Figure 2: Rear View of thruster

Exploded Assembly Animation

Anaheim Automation: BLWRPG17 Brushless DC Motor

•Planetary Gear Ratio: 4.9 to 1

•Torque:

•117.943 oz-in @857 rpm (Geared)

•Power: 25W

•Feedback using Hall Sensors

•Weight: 1.37 lbs

•Dimensions: 2.36 in (Motor), 1.39 in (Gearbox), 1.654 in (Diameter)

•Cost: $90.00 per motor

Figure 5: Motor Picture from Anaheim Automation

Figure 6: Motor dimensions from Anaheim Automation

Magnetic Coupling

Max Continuous Torque: 71 oz-in

Max Continuous Speed: 26000 rpm

Effective Gap: 0.23 in

Inner Hub Diameter: 0.87 in (Outer)

Outer Hub Diameter: 1.73 in (Outer)

Length/ Diameter: 1.73 in/ 1.73 in

Figure 7: Proposed magnetic coupling exploded view

Containment Barrier: Made in house, using PAEK (Polyaryletherkeytone) or PEEK (Polyetheretherkeytone)

•High temperature and pressure resistance

•Relatively cheap as compared to metals like titanium

Total Cost (Coupling): $140.00 per unit

Sealing and CondensationSealing:

•Standard Viton O-rings

•Resistant to hydraulic and natural oils

•Weather resistant: can handle environment changes

•Medium Hard on the Durometer Shore A scale

Condensation:

•Silica Gel Insert

•Condensation may occur at depth due to being sealed in a moist air environment

•Hydrophilic substance that will collect any moisture from the inner air and any moisture that may condense out

Figure 8: Viton O-ring

Figure 9: Silica Gel beads

Impeller GeometryComputer Fans

•Thousands of different sizes and shapes

•Lightweight plastic is easy to modify and resistant to corrosion or deformation

•“Low Noise” fans more hydrodynamic

Final Selection

•Effective propeller comparison requires measurement of shaft speed (Hall Sensor)

•To be evaluated on final thruster housing in MSD II.

Figure 10: Solidworks Model Used for CFD Analysis

Figure 11: 120mm ”Low Noise” Silverstone Fan

Impeller Geometry

Testing for MSD II

•Similar single axis test rig

•Each of 6 designs at varying gear ratios

•USE BLEACH

Kort Nozzle

• Use of an accelerating nozzle can increase thrust by as much as 40%

•Wide blades with little clearance

Microcontroller: ATmega168

Benefits of using a Microcontroller:

•Easy to program

•Easily modifiable design for future designs

•Source code remains stored in the memory

Benefits of the ATmega168

•Low power consumption

•Sufficient PWM channels

•Numerous communication protocols

Top View

Bottom View

Figure 12: Top and Bottom Views of the ATmega168

Software Function Flowchart

User

Control ROVSelect Proper

Thruster(s)

Send PWM Signalsto Driver

Send Output Signalto H-Bridge

Thruster(s) OperateForward/Reverse

Adjust VoltageBased on Feedback

-End1

*

-End2

*

-End3

*

-End4

*

-End5*

-End6*

-End7*

-End8*

-End9*

-End10*

-End11*

-End12*

-End13

*

-End14

*

3-Phase Brushless DC Motor Driver

Figure 13: ST Microelectronics L6235 motor driver

•Integrated Hall Effect sensor for the accurate feedback of ωr, direction of rotation, and position

•Rated Current: 5.6 A, Rated Voltage: 52 V

•Over Current Detection Circuitry reads the current in each high side

•Tachometer for easy implementation of closed loop control

•PWM input for speed control

3-Phase Brushless DC Motor Driver cont…

Comparing to Current Designs

•Listed above are the most important metrics when comparing the three thruster designs.

  Cost (Dollars) Thrust (lbf)

Power Consumption

(watts)Open Source

Design

Feedback from the

Motor

P08454's Design 750.00 Comparable to Both* 39 Yes Yes

Seabotix 1,000.00 4.8 (Forward), 4.4 (Reverse) 80 No No

Tecnadyne 4,000.00 12 (Forward), 4 (Reverse) 50.4 No Yes

* Numbers not yet known but design intends to be comparable to both thrusters using different impeller designs

Figure 14: Seabotix ThrusterFigure 16: Tecnadyne Thruster

Figure 15: P08454’s Thruster

Risks/Concerns•Membrane Integrity

•The membrane will have to be very thin

•Build small rig to test pressure effects on membrane

•Bearing Configuration/Life

•Will use a plain bearing to support the output shaft

•If assembly is unbalanced then bearing can wear prematurely

•O-ring Effectiveness

•Most critical piece of the housing sealing

•Need to use hydraulic o-rings to combat depth pressure

•Current Spikes at Start-up

•If start-up current peaks over 4.5A, then potential damage can occur to the power supply

•If fuses are placed on the power supply, then the risk should be mitigated

•Heat Dissipation

•An analysis has shown that the amount of heat that can be dissipated from the thruster far exceeds the heat that will be produced by it’s components

Figure 17: P06606 ROV Prototype

Concept Design Review: 19 October 2007

Questions/Concerns:

•Concerns with magnetic coupling?

•Sealing around the electrical cords, feeding power and control through same tether?

•What is the worst failure mode that could happen?

•Oil vs. Air filled?

•Power is at a premium

•How will the thruster interact with the computer interface?

•Considered using a heat sink to help dissipate heat?

Detailed Design Review: 2 November 2007

Questions/Concerns:

•What compromises are made in choosing a motor?

•Are the electronics purchasable or do they need to be bread boarded?

•Do you need to worry about heat dissipation from or warping of the magnetic couple membrane?

•Plan on running the life test rig continuously?

•Do you have a method of choosing the best impeller design?

Where to Next?

•Purchase remaining parts and place orders in the machine shop for custom parts

•Write verification test plan to confirm that the design meets all specifications

•Build prototype models

•Verify that the design meets all of the specifications using the verification test plan

•Optimize the design based on data collected during testing and adjust final design according to optimizations

•Place thrusters on Hydroacoustics ROV for testing

Figure 18: Current Hydroacoustics ROV

Figure Sources Figure 1: Concept Model of P06606’s ROV: https://edge.rit.edu/content/P08454/public/Home Figure 5: Anaheim Automation: http://anaheimautomation.com/blwrpg17_brushless_dc_planetary_gearmotors.aspx Figure 6: Anaheim Automation: http://anaheimautomation.com/blwrpg17_brushless_dc_planetary_gearmotors.aspx Figure 7: Magnetic Technologies Ltd: http://www.magnetictech.com/prod_magcoup_coax_sae.htm Figure 8: McMaster-Carr: http://www.mcmaster.com/ Figure 9: Silica Gel Beads: http://en.wikipedia.org/wiki/Image:SilicaGel.jpg Figure 10: Silverstone Tek: http://www.silverstonetek.com Figure 12: ATmega168 Microcontroller: http://www.atmel.com/dyn/resources/prod_documents/2545S.pdf Figure 13: ST Microelectronics: http://www.st.com/stonline/products/literature/an/9214.pdf Figure 14: Seabotix: http://www.seabotix.com/products/btd150.htm Figure 16: Tecnadyne: http://www.tecnadyne.com/images/Model-260-2.jpg Figure 17: P06606: http://designserver.rit.edu/Archives/P06606/web-content/Images/large_photos/SponsorROV2.jpg Figure 18: Hydroacoustics: http://hydroacousticsinc.com/marine_technology.php

Information Sources Anaheim Automation: http://www.anaheimautomation.com Seabotix Inc.: http://www.seabotix.com/products/btd150.htm Tecnadyne: http://www.tecnadyne.com/Brochure/Model%20260%20Brochure.pdf Danaher Motion: http://kmtg.kollmorgen.com/products/motors/ Huco Dynatork: http://www.huco.com ST Microelectronics: http://www.st.com Microchip: http://www.microchip.com Atmel Corporation: http://www.atmel.com McMaster-Carr: http://www.mcmaster.com/