Trash Can Robot

Notes for a trash can style robot. The R2D2 body shape has alot going for it from a technical / usefullness standpoint. Being a short squat body, it's center of gravity is low. The legs that are attached at the top of the body, combined with the center leg create a good tripod stance that places the center of mass well within it's perimiter. This makes motion much more stable. When the legs are moved forward of the center leg it allows the robot to have greater stability when manipulating objects right infront of it. Though not really shown in the movies, the legs can also be used to walk, thus allowing for clearing of obsticals a standard wheeled robot would otherwise not be able to traverse.

Initial prototype for developing modules that can be used to make the final R2D2 style robot.

Bearing selection for support of wheel shafts on each side of the wheels.

Found 4 - 10x35x?mm bearings at ABC Electronics.

For starters I'm going to make differential drive circular robot.

The drive wheels are offset back from the mid-line of the robot so it isn't able to spin in it's circumfrance. That isn't much of an issue.

Body Ideas

Looking around I find plastic 55 Gallon barrels. One could combine one of these with a top for a trashcan to make a silly body.

Size

Circumfrence will be about 24 inches with protrusions for the drive wheels.
All measurements will be in refference to a center line from the front to the rear, and the center point.
Large enough to have a full AT Motherboard based PC on board.

Will need to modify AT PC case to make it more suitable for use on the robot.

Separate out functional blocks so they can be mounted on the robot chasis.
Provide shock absorbtion for hardisks and motherboard assemblies.
Provide needed cooling fans.
Support expansion cards.

Modules needed for prototype

Main Processor - AT PC Motherboard
Drive Motor Controller Board

MCB02PIN.pcb

Touch Sensor Controller

TSB02PIN.pcb

IR Sensor Controller

IRB02PIN.pcb

Sonar Sensor Controller

Defered to a latter date.

Keypad Controller

Not likely needed anymore due to using PC keyboard.

LCD Display Controller

Not likely needed anymore due to getting LCD screen for PC.

LED Display Controller

8x8 LED Display
LCB01PIN.pcb + LAR01PIN.pcb

RS-232 to 485DA Converter Board

SRB01.PIN.pcb

AT PC-Power Supply
Controller Power Supply - 20A @ 5VDC
Battery Pack
Charger/Battery monitor

Monitors the voltages of the batteries and the states of the battery chargers.
Resistor/divider networks with compairators driving logic opto-isolators.

Voltages checked

10	Battery out
10.5	Battery low

Drive/Battery Base - Look into placing batteries and recharger in the space between the drive motors and the casters.

Do I go to 48VDC main battery pack? Yes

Batteries:

4 - 12VDC 12AH sealed lead acid batteries.

Logic Power Supply

5 VDC Supply

2 - 48VDC to 5VDC 50W Converters
See if the system can run with only one 5VDC converter.
If both converters are needed, place the PC on one and the microcontrollers, floppydisk and harddisk on the other.

12 VDC Supply

2 - 48VDC to 12VDC 50W Converters
First converter will power Motherboard/Video Board.
Second converter will supply the HD and FD.

-5 VDC Supply

1 - 48VDC to 5VDC 50W Converter with the + connected to system ground, and - as the -5VDC rail.

-12 VDC Supply

1 - 48VDC to 12VDC 50W Converter with the + connected to system ground, and - as the -12VDC rail.

Provide a power good signal.
Connect up the outputs of the 4 supplies and power good signal into a PC AT power connector.
For power distribution, use wires solidered to a PCB. This is the easiest, and cheepest solution.

PC AT Power connector wire set.
+48VDC Motor Wire Set
???

Battery Charger Circuit Design

Looks like I can use the 15VDC supplies. They are tuneable from 13.9VDC to 18.8VDC. This allows me to power a charger circuit that has 3VDC drop in it's current control.

Power Supply Mounting Board

RC Servo Power Supply

+5VDC Supply, Ground common to Logic Supply

1 - 48VDC to 5VDC 50W Converter

Motor Controllers

LMD18200 H-Bridge controler chip

To keep the chips from seeing the 58.8VDC battery charge voltage: Initially have a switch to disconnect them from the battery bank while charging is taking place. Latter use solid state relays to control when they are tied to the battery bank. One could switch the battery charger on and off via a solid state relay, and also control the connection of the battery pack to the H-Bridge controler chips.

AN alternate protection scheme is to just use a set of diodes in series to produces a voltage trop of 3-5 volts.

If a different and higher voltage H-Bridge controller is used, then this isn't a problem.

Second possibility for motor controller.

http://www.inconnect.com/~dennis/osmc/osmcdes.html - OSMC Open Source Motor Controller. 50 or 100 Amps at up to 85VDC.

PRO:

more capacity.
Cheep DC-DC converters from meci.com $9 each for 48VDC Input to 5VDC and 12VDC outputs in 50W models.

CON:

Weight, quite heavy battery weight.
Cost

Main Brain

PC Motherboard, AT

System will be upgraded as heavier duty processing is added. Especially after vision systems are added.
ASUS SP3G Motherboard

IDE
Fast SCSI-2
FD
2 Serial
1 Parallel

486DX2-66 Processor
16MBytes Ram
Cirrus Logic based LCD VGA Controller and 9.5 in diagonal 16 Gray scale display.
NIC ?
Mini-AT Keyboard.
1.44MB Floppy disk
?? [IDE/SCSI] HD
2Serial/1Parallel on ISA Bus Card.

Control software

Linux os with Real Time extensions.

Real Time Linux http://luz.cs.nmt.edu/~rtlinux/.

I may not need the real time extensions with clever driver design.

Another RT Linux

hegel.ittc.ukans.edu/projects/kurt/ - KURT Kansas University Real Time Linux.

Drivers

No special drivers needed yet.

Input devices

PC Joystick tied to a rope to serve at a leader line. Software would look at the joystick's deflection, and move the robot to zero it out.
IR Remote input

Video Inputs

Direct digital input is prefered.
Suppliers.

Digital Compas

Use one for general orientation.
The Vector 2XG has motorola SPI serial link interface. How many bits output does it give? Possibly use a serial to parallel register to have it dump it's data to so it can be read off by the host CPU. It would clock it's data out, then interupt the CPU to say it has new data. From the descriptions given, this seams to be supported. A 16bit register would be needed, along with an interupt line.

Data is clocked into a 16 bit serial to parallel register.
Host is interupted on an interupt line.
The outputs of the register are put onto the IO bus when the register is selected for read.

Suppliers.

IR Ranging.

Sharp GP2D02 distance sensor. About $22. Ranges from 8cm to 80cm, 5-10 degree field of view.
Use multiples for ranging and object detection at short range.
(www.acroname.com/robotics/parts/parts.html)
(www.hobbyrobot.com/info/gp2d02) has a lot of good information on the opperation and use of th GP2D02 distance sensor.
Other sources?

Sonar Ranging

(www.acroname.com/robotics/parts/parts.html) Poloroid modules.
Other sources?

Computer Systems

Main brain
Wheel Motion Controler
Touch Sensor Controlers

Touch Sensors

Body pannels are all supported so they are able to serve as touch sensors.
Possible methods of supporting body pannels

Velcro for attaching pannel

Use a micro switch (SW1 or SW2) at each corner of a pannel for sensing if the pannel being pressed on. These micro switcheas only need to be depresssed a mm to activate.

Shiming of the micro switch can be done via layers of tape, or shaved off rubber feet.

The foam needs to be very soft to allow a large velcro attachment area while still being soft enough to allow light touches to be sensed.
Panels: Center front, left & right front, center rear, left & right rear, left side front, left side rear, right side front, right side rear for a total of 10 pannels around the perimiter. Likely there will be pannels on the two legs, around the three feet, on the bottom of the body, and on the dome .

Use the natural spongeyness of velcro to provide the motion needed to depress a short throw micro-switch.
If needed the velcro spongeyness could be extended by a second layer or foam backing.
CON: May be hard to push.
CON: May stay pushed in after being pushed.
PRO: Holds pannel in place without screws showing.
PRO: Easy removal of a pannel.
CON: No touch sensing when a pannel is removed.

Switch Wiring Harness

Use ribbon cable for wiring, 1 common wire plus 1 wire per switch.
Solder wires to switches.
Use a IDC connector at the end of the ribbon cable to connect the wires to a header on the PCB.

One group of 4 switches (enough to do a normal rectangular pannel) plus 1 group of 4 status LEDs can be placed on one 10 conductor ribbon cable.

Switches, 1 Common Wire plus 4 switch wires.
LEDs, 1 Common Wire plus 4 LED wires. Current limit on the Common wire for LED versus Port IO pin, likely 10-20mA. Scann the LEDs in sequential fashion to give even current draw.

PRO: Allows easy connection/disconnection of switch harnesses to PCB.
PRO: Wiring harness will look neat and good without much effort.

Locomotion

Software Features

Motion is monitered via multiple inputs. Dead reaconing from the propulsion motors. Inertial motion from the inertial motion sensors. Vison system inputs. GPS Receiver with differential corrections where available.

Each foot has a tread belt driven by a motor.

All three feet are identicle. The differences are in what is above the mounting points.
Stock Drive Products (http://www.sdp-si.com) has 3/8in dual sided drive belts available in custom widths from sleeves they stock. 3 to 4 inch wide belts could be ordered. They also have timing pully stock so you can cut your own custom width timing pullies.

An alternate idea is to design the foot so it uses only a single sided belt. This would require the belt to be driven by a pully mounted on the outside, but this is dooable. It has the advantage of making all the pullies on the inside simple flat tubes rather than keyed pullies.

The center leg is stearable.

Stearing the foot is handled through the mounting point mechains that hold the foot.

The two main legs are steared through differential drive.
All legs all drive motors and electronic brakes.

The electronic brakes are needed so it can lock the treads in position for walking.

www-personal.engin.umich.edu/~johannb/ - XXXX
web.cs.cmu.edu/afs/cs.cmu.edu/user/thrun/public_html/index.html - XXXX

Parts Table

Assemblies
#	Robot Part Number	Use Area	Description	Supplier Part Number	Count	At	Order Count	Total
1	CTRL1		Main Computer
1	CTRL2		Motor Controler
?	CTRL3		Touch Sensor Controler
?	LedInd1		8 LED Indicator Board
?	LedInd2		4 LED Indicator Board
1	WH1		24VDC Power Supply Wiring Harness
1	WH2		AC Power Wiring Harness
1	WH3		Robot Wiring Harness
1	MBP		Main Battery Pack	self

Chips
#	Robot Part Number	Use Area	Description	Supplier Part Number	Count	At	Order Count	Total
?	IC1		RS-485 Tranceiver, Low-Power, Slew-Rate-Limited, Input/Output Enables, MAXIM # MAX487CPA, 8-Pin Plastic DIP.	MAX487CPA-ND	?	2.81
?	IC2		Scenix SX-28 MCU
Resistors
#	Robot Part Number	Use Area	Description	Supplier Part Number	Count	At	Order Count	Total

Capacitors
#	Robot Part Number	Use Area	Description	Supplier Part Number	Count	At	Order Count	Total

Switches
#	Robot Part Number	Use Area	Description	Supplier Part Number	Count	At	Order Count	Total
?	SW1		Detector Switch: Panel 5mm W/Mounting Hole, , Panasonic: ESE-105HS1. Look into issue of switch having electrical contacts on the body bottom where it would contact metal on a chasis mounting. Use a thin plastic sheet to separate switch from metal surfaces.	P8097SCT-ND	10	5.17	30
?	SW2		Left hand version of above SW1	P8098SCT-ND	10	5.17	30
Fans
#	Robot Part Number	Use Area	Description	Supplier Part Number	Count	At	Order Count	Total
1	FAN1		Motor Controller Cooling Fan, 12VDC?
1	FAN2		DC-DC Converter Cooling Fan, 12VDC
Wood
#	Robot Part Number	Use Area	Description	Supplier Part Number	Count	At	Order Count	Total
2	W1, W2		Wood Disk, 24" diameter, 3/4" plywood		have
2	W3, W4		Motor mount wall, 14"x6"x3/4" hardwood		have
2	W5, W6		Outter beering support wall, 10"x6"x3/4" hardwood		have
2	W7, W8		Motor box side wall, 13"x6"x3/4" hardwood		have
1	W9		Battery box divider, 8.5"x6"x3/4" hardwood		have
1	W10		Battery box bottom, 14.5"x9"x1/4" plywood		have
1	W11		Caster Block, 13"x3"x3/4" hardwood		have
2	W12, W13		Caster block standoffs, Size to fit

Metal
#	Robot Part Number		Description	Supplier Part Number	Count	At	Order Count	Total

Misc.
#	Robot Part Number		Description	Supplier Part Number	Count	At	Order Count	Total
4	B1-B4	MBP	12V 12AH Lead-Acid Battery		have
2	Mot1, Mot2		Drive motors with gear reduction and quadrature encoders.		have
2	Wheel1, Wheel2		Wheels, 7"Lawnmower tires		have
2	Wheel3, Wheel4		Casters, 2.5" diameter ballbearing casters.		have
4	Bearing1 - Bearing4		Ballbearings with 10mm inside diameter to fit over gearbox output shaft and support weight of robot instead of gearbox bearings.		have
xxx
#	Robot Part Number	Use Area	Description	Supplier Part Number	Count	At	Order Count	Total

xxx
#	Robot Part Number	Use Area	Description	Supplier Part Number	Count	At	Order Count	Total

xxx
#	Robot Part Number	Use Area	Description	Supplier Part Number	Count	At	Order Count	Total

Appendix A - PCB Sub Assemblies

Reset Circuit

Remote switch which if not present, the circuit can't be reset without power cycling it.

Clock/Programming Circuit

On boards that use a oscillator chip, a jumper connecting the OSC1 pint to the oscillator output is forced to be removed before programming can take place, and replaced before normal opperation resumes.

Serial Link Circuit

Provides a multi-drop serial link between devices.
Connectors:

JA: 4 pin Header

Pin #	Description
1	+5VDC
2	Serial Side A
3	Serial Side B
4	Ground

Parts:

RS-485 Tranceiver with Driver and Receiver Enables, Low Slew Rate, Low-Power
3 Pin Header Strip

Appendix B - Serial Links, See: Serial Links Descriptions.

Appendix C - Wire Color Coding to be followed where feasable in the prototype.

Appendix D - Kepco Power Supply Modules. The power supply modules that I'm using to make up the PC AT power supply from.

Appendix E - Voice input possibilities.

www.software.ibm.com/is/voicetype/dev_linux.html - ViaVoice SDK for Linux.

Appendix F - Pinout of Quadrature Encoder on motors.

Pin #	Color	Use
1	Green	Ground
2	na	no wire
3	White	Channel 2
4	Blue	+5VDC
5	Yellow	Channel 1

Appendix G - .

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