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System Level
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Total Costs 3 fully powered and steering, 4 idler modules Prototyping Costs (1 fully powered and steering, tested on bench): –Power Electronics = 183.50 –Control System = 279.19 –Mechanical = 221.90 –TOTAL = 684.59 Production Costs: –Power Electronics = 382.34 –Control System = 128.59 –Mechanical = 657.04 –PCB Setup Cost = 200.00 –TOTAL = 1367.97 TOTAL = $2052.56
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Mechanical
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High Performance Motor Module
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Low Performance Motor Module
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http://robots.mit.edu/publications/papers/2000_09_Yu,_Dub_Skw.pdf
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Airtrax.com
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100 kg Stress Study
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Out of Date
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Maxonmotorusa.com RE-30
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www.superdroidrobots.com
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Power Electronics
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Knowing the requirements for the motor from the mechanical subsystem such as required torque and motor speed, a compatible motor is the Maxon RE-30 60 Watt DC Motor (310007). Out of Date
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Datasheet for Maxon RE-30 http://www.maxonmotorusa.com/files/catalog/2005/pdf/05_080_e.pdf Operating Voltage = 24V Max Continuous Current = 3.81 A Terminal Resistance =.611 Ohms Terminal Inductance =.00012 H Speed Constant = 369 rpm/V Out of Date
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Using the formula from “Robot DNA Series - Building Robot Drive Trains” by Dennis Clark and Michael Owings to determine PWM frequency for this motor, Where >> is a factor of at least 10. Out of Date
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Using a formula from Maxon Precision Motors Inc. to calculate the current ripple seen on the DC bus: Where U is the supply voltage and the EMF is the speed constant divided by the speed. Out of Date
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The motor will have the feature of a power-off electronic brake through the use of a DPDT relay. Diagram of Motor with Safety Relay When power is applied the relay will allow the motor to be powered by the H-Bridge. Without power the relay contacts will be wired such that the motor terminals are shorted.
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Omron G2R Relay example: Contact specifications on Omron G2R DPDT Relay http://www.components.omron.com $5-$10 depending on mounting and options (LEDs)
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Coil Specification on Omron G2R DPDT Relay 21.8 mA @ 24 VDC Current Draw http://www.components.omron.com
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H-Bridge frequency needs to be at least 8 kHz, however higher frequencies help reduce current ripple and increase efficiency. Examples of compatible H-Bridges: Freescale Semiconductor H-Bridge Section of Datasheet, page 1/32 http://www.freescale.com/files/analog/doc/data_sheet/MC33887.pdf Out of Date
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STMicroelectronics Dual Full Bridge Driver Section of datasheet, page 1/13 http://www.st.com/stonline/products/literature/ds/1773.pdf STMicroelectronics Dual Full Bridge Driver Section of datasheet, page 7/13 http://www.st.com/stonline/products/literature/ds/1773.pdf Out of Date
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National Semiconductor LMD18200 Section of datasheet, page 1/14 http://cache.national.com/ds/LM/LMD18200.pdf
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Allegro Full-Bridge Power MOSFET Controller http://www.allegromicro.com/sf/3940/ Available from Digikey; <$5 Out of Date
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Infineon N-Channel MOSFET http://rocky.digikey.com/WebLib/Infineon/Web%20Data/IPP14N03LA_Rev1.2.pdf Available from Digikey; ~$1 Out of Date
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Estimated Power Systems Loads
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Potential Deep Cycle Batteries; PVX-340T costs $105. http://store.solar-electric.com/cosuagmba.html Out of Date
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Potential battery datasheet giving 1 hour rate of discharge 13.2 Ah at 1 hour http://www.vision-batt.com/newpdf/D/CP12180D.pdf Out of Date
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Table from datasheet (page 2/2) giving voltage sag levels at different drain currents http://www.vision-batt.com/newpdf/D/CP12180D.pdf Out of Date
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Control Power Distribution Board Functional Decomposition
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Amp DUAC Connector http://catalog.tycoelectronics.com/TE/bin/TE.Connect?C=1&PN=794657-4&M=BYPN&LG=1&I=13 <$1 9A Current (MAX)
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Parvus PC104 Power Supply http://www.parvus.com/products/Transportation/Board-LevelOEM/PRV-0617/
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Tenergy Sc 3500 mAh high capacity High Drain (10C) NiMH Rechargeable batteries “Up to 35 Amps 10C high drain current rate” ~$5.00 per cell http://www.all-battery.com/ To power some of the feedback devices a voltage other than the control voltage may be needed. This can be obtained by common DC-DC converters which regulate the voltage to a desired level. Out of Date
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Example Control Power Battery http://rocky.digikey.com/WebLib/B&B%20Battery/Web%20Data/BP7-12.pdf Typically used in UPS applications, $16 from Digikey Page 1 of datasheet
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DC-DC Converter capable of 3.3V, 5V, and 12V outputs from a wide input voltage range Section of datasheet, page 1/12 http://cache.national.com/ds/LM/LM2825.pdf Out of Date
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For speed feedback an encoder with quadrature output is needed for accurate speed and direction signals. US Digital Encoder with Quadrature output, 5V input 400-1200 pulses per revolution, ~30$ Lower cost versions available ($20) via “Low cost push-on hub” http://www.usdigital.com/data-sheets/E4%20Data%20Sheet.pdf
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With a resolution of 400 pulses per revolution, the maximum error in position feedback will be: Increasing the number of pulses to 1200 decreases the error by a factor of 3. On a 7” diameter wheel, that corresponds to.055” of accuracy
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Potential RTD: Honeywell HRTS-5760-B-T-0-12 Section of datasheet, page 1/3 http://catalog.micro.honeywell.com/AUTHOR/images/honeywell/temp/HRTS.pdf Out of Date
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Control System
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Comm Protocol Pugh Chart
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Controls Subsystem
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Microchip PIC 18F2431 Microprocessor
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Motor Control Graphical User Interface The MC-GUI graphical user interface allows users to configure the motor and a wide range of system parameters for a selected motor type, including speed, rotation direction, current, heatsink temperature, fault status and much more. Available at no cost, this Windows® based software program supports Microchip’s motor control demonstration boards to provide a complete solution that helps reduce design time.
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Data Monitor and Control Interface Software
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A (Baseline)BCDE Microcontroller BASIC Stamp II Atmel AVR (ATmega 8) Motorola Coldfire MCF5307 89C4051 (8051 Architectur e) PIC18F2 431 Clock Speed0111 PWM capabilities01111 Cost00 1 Power Consumption0111 I/O Ports01111 Flash Memory01011 I2C capability00101 H-Bridge Technology00001 Ease of Programability01111 Commercial Portability01101 Sum05658 Rank53231 Figure – Control Subsystem Concept Screening
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A (Baseline )BCDE MicrocontrollerWeight BASIC Stamp II Atmel AVR (ATmega 8) Motorola Coldfire MCF530 7 89C4051 (8051 Architectur e) PIC18F2431 Clock Speed0.0532444 PWM capabilities0.1534444 Cost0.233222 Power Consumption0.0534444 I/O Ports0.134444 Flash Memory0.0534344 I2C capability0.1533434 H-Bridge Technology0.1533334 Ease of Programability0.0534444 Commercial Portability0.0534434 Total33.4 3.253.6 Rank52241 Continue?No Yes Figure – Control Subsystem Concept Selection
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Figure – Microcontroller Comparison Chart
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Figure – PM DC Motor Simulation
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Figure – Open Loop Response of the Simulated PM DC Motor X axis = time (s) Y axis = voltage (V)
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Resources http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=55&mid=10&la ng=en&pageId=74 http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1 335&dDocName=en010271 http://ww1.microchip.com/downloads/en/DeviceDoc/39616b.pdfhttp://ww1.microchip.com/downloads/en/DeviceDoc/39616b.pdf (Datasheet)
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Safety
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