System Level

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

Mechanical

High Performance Motor Module

High Performance Motor Module

Low Performance Motor Module

http://robots.mit.edu/publications/papers/2000_09_Yu,_Dub_Skw.pdf

http://robots.mit.edu/publications/papers/2000_09_Yu,_Dub_Skw.pdf Airtrax.com

100 kg Stress Study

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Maxonmotorusa.com

RE-30

www.superdroidrobots.com

www.superdroidrobots.com

Power Electronics

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).

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Datasheet for Maxon RE-30http://www.maxonmotorusa.com/files/catalog/2005/pdf/05_080_e.pdf

Operating Voltage = 24VMax Continuous Current = 3.81 ATerminal Resistance = .611 OhmsTerminal Inductance = .00012 H

Speed Constant = 369 rpm/V

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RLf 2

kHzf

f

L

Rf

PWM

PWM

PWM

1.8

)00012(.2

)611(.102

10

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.

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Lf

EMFUIpp

PWM2

)00012)(.000,10(2

)369/(24 RPMIpp

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.

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The motor will have the feature of a power-off electronic brake through the use of a DPDT relay.

Tit le

S ize D o c u m e n t N u m b e r R e v

D a t e : S h e e t o f

<D o c > <R e v C o d e >

<Tit le >

A

1 1Tu e s d a y , O c t o b e r 1 0 , 2 0 0 6

1 2

U 1 A

7 4 0 4

H-Bridge

Battery

DC-DC

Motor

Diagram of Motor with Safety RelayWhen 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.

Omron G2R Relay example:

Contact specifications on Omron G2R DPDT Relayhttp://www.components.omron.com

$5-$10 depending on mounting and options (LEDs)

Coil Specification on Omron G2R DPDT Relay21.8 mA @ 24 VDC Current Draw

http://www.components.omron.com

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-BridgeSection of Datasheet, page 1/32

http://www.freescale.com/files/analog/doc/data_sheet/MC33887.pdf

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STMicroelectronics Dual Full Bridge DriverSection of datasheet, page 1/13http://www.st.com/stonline/products/literature/ds/1773.pdf

STMicroelectronics Dual Full Bridge DriverSection of datasheet, page 7/13

http://www.st.com/stonline/products/literature/ds/1773.pdf

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National Semiconductor LMD18200Section of datasheet, page 1/14

http://cache.national.com/ds/LM/LMD18200.pdf

Allegro Full-Bridge Power MOSFET Controllerhttp://www.allegromicro.com/sf/3940/

Available from Digikey; <$5

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Infineon N-Channel MOSFEThttp://rocky.digikey.com/WebLib/Infineon/Web%20Data/IPP14N03LA_Rev1.2.pdf

Available from Digikey; ~$1

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Estimated Power Systems Loads

Potential Deep Cycle Batteries; PVX-340T costs $105.http://store.solar-electric.com/cosuagmba.html

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Potential battery datasheet giving 1 hour rate of discharge13.2 Ah at 1 hour

http://www.vision-batt.com/newpdf/D/CP12180D.pdf

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Table from datasheet (page 2/2) giving voltage sag levels at different drain currentshttp://www.vision-batt.com/newpdf/D/CP12180D.pdf

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Control Power Distribution Board Functional Decomposition

Amp DUAC Connectorhttp://catalog.tycoelectronics.com/TE/bin/TE.Connect?C=1&PN=794657-4&M=BYPN&LG=1&I=13

<$19A Current (MAX)

Parvus PC104 Power Supplyhttp://www.parvus.com/products/Transportation/Board-LevelOEM/PRV-0617/

Tenergy Sc 3500 mAh high capacity High Drain (10C) NiMH Rechargeable batteries“Up to 35 Amps 10C high drain current rate”~$5.00 per cellhttp://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.

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Example Control Power Batteryhttp://rocky.digikey.com/WebLib/B&B%20Battery/Web%20Data/BP7-12.pdf

Typically used in UPS applications, $16 from DigikeyPage 1 of datasheet

DC-DC Converter capable of 3.3V, 5V, and 12V outputs from a wide input voltage rangeSection of datasheet, page 1/12

http://cache.national.com/ds/LM/LM2825.pdf

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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 input400-1200 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

With a resolution of 400 pulses per revolution, the maximum error in position feedback will be:

9.

)360(400

1

error

error

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

Potential RTD: Honeywell HRTS-5760-B-T-0-12Section of datasheet, page 1/3

http://catalog.micro.honeywell.com/AUTHOR/images/honeywell/temp/HRTS.pdf

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Control System

Comm Protocol Pugh Chart

Controls Subsystem

Microchip PIC 18F2431 Microprocessor

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.

Data Monitor and Control Interface Software

 A

(Baseline) B C D E

MicrocontrollerBASIC

Stamp II

Atmel AVR

(ATmega8)

Motorola Coldfire

MCF5307

89C4051(8051

Architecture)

PIC18F2431

Clock Speed 0 -1 1 1 1

PWM capabilities 0 1 1 1 1

Cost 0 0 -1 -1 1

Power Consumption 0 1 1 1 -1

I/O Ports 0 1 1 1 1

Flash Memory 0 1 0 1 1

I2C capability 0 0 1 0 1

H-Bridge Technology 0 0 0 0 1

Ease of Programability 0 1 1 1 1

Commercial Portability 0 1 1 0 1

Sum 0 5 6 5 8

Rank 5 3 2 3 1

Figure – Control Subsystem Concept Screening

   

A (Baseline

) B C D E

Microcontroller WeightBASIC

Stamp II

Atmel AVR

(ATmega8)

Motorola Coldfire MCF530

7

89C4051(8051

Architecture)

PIC18F2431

Clock Speed 0.05 3 2 4 4 4

PWM capabilities 0.15 3 4 4 4 4

Cost 0.2 3 3 2 2 2

Power Consumption 0.05 3 4 4 4 4

I/O Ports 0.1 3 4 4 4 4

Flash Memory 0.05 3 4 3 4 4

I2C capability 0.15 3 3 4 3 4

H-Bridge Technology 0.15 3 3 3 3 4

Ease of Programability 0.05 3 4 4 4 4

Commercial Portability 0.05 3 4 4 3 4

Total 3 3.4 3.4 3.25 3.6

Rank 5 2 2 4 1

Continue? No No No No Yes

Figure – Control Subsystem Concept Selection

Figure – Microcontroller Comparison Chart

b

damping

V

Scope

R

Resistance

K

Kt

K

Ke

1s

Integrator1

1s

Integrator

1/J

Inertia

1/L

Inductance

Add1

Add

id/dt(i)

d/dt(theta)d2/dt2(theta)

Figure – PM DC Motor Simulation

Figure – Open Loop Response of the Simulated PM DC MotorX axis = time (s)

Y axis = voltage (V)

Resourceshttp://www.microchip.com/ParamChartSearch/chart.aspx?branchID=55&mid=10&lang=en&pageId=74

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1335&dDocName=en010271

http://ww1.microchip.com/downloads/en/DeviceDoc/39616b.pdf (Datasheet)

Safety