Magellan Preliminary Design Review

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MagellanPreliminary Design Review

• Charlie Reverte
• Zachary Omohundro
• Chris Baker
• Chin Keong Ling
• Aaron Morris
• 12/11/2002

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Operational
Requirements

• Deployment and recovery through a 10 borehole
• Un-tethered
• Semi-autonomous
• Rugged and waterproof
• Drive on land and water
• Traverse obstacles up to 8
• Carry mapping payload
• Reasonable range
• Purged and Pressurized
• Expendable

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Concept Image
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Mechanical
Specifications

• 2 segment 4 wheeled rover
• Solid drive axles
• Steering via actuated center link
• Inflatable wheels

• Single purged and pressurized volume
• Deployable sensor payload
• Docking mechanism
• Compact deployment configuration

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Electrical
Specifications

• Source 24 volt Li-ion batteries
• Target 1 KWh capacity
• Locomotion and Actuation Motors (24VDC)
• Front Drive
• Rear Drive
• Pneumatic Pump
• Sensing
• 24VDC Laser Scanner
• Computing
• PC/104 form factor
• Wireless Ethernet
• Hard disk drive
• Includes 5 conversion/regulation for secondary
  sensors.

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Sensing
Specifications

• Primary mapping payload
• Laser rangefinder
• Purged and pressurized
• Linear potentiometer to sense laser orientation
• Analog magnetic compass
• Navigation sensors
• Drive motor encoder counters
• Intrinsically safe steering potentiometer
• 3 axis accelerometers
• Tilt sensor
• Obstacle avoidance
• Motor current sensors
• Ultrasonic sensors
• 3 front, 3 rear, 1 overhead
• Primary mapping sensor tilt scan
• Internal state sensors
• Battery status
• Chassis pressure monitor
• Wheel pressure monitor

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External Sensor Layout
Major Subsystems

• Rear 3 sonar configuration is identical

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High Level Software
Specifications

• Autonomy
• Preprocessed topological graph of map from
  Voronoi
• Node waypoint selection from graph search
  algorithm
• Cost D(edge) batt/D interesting
  D(Origin)
• Waypoint following once oriented
• Track D(traveled) and battery consumption
• Correct edge costs, use A or D to plot course
  to origin
• Unexpected Voids Enter Exploration Mode
• Take Unknown Crosscuts until
• Exploration_Interest(Battery) lt Battery Consumed
• Dead End
• Return To LPC, Relay, Await

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Navigation
Specifications

• Navigation
• Node to Node Transition
• Feature Identification Corridor and Crosscut
• Partial Carmen Construction for Reverse
• Wall Centering and Obstacle Avoidance
• Morphin algorithm

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On-board / Off-board Software
Specifications

• On-board
• Voronoi Map and Feature ID (Bayes Classifier)
• Logging All Sensor Data Time Stamped
• Morphin
• A or D path changes (shortest path home)
• Carmen Map for reverse
• Off-board
• Preprocessing
• Carmen Map Software
• Sensor Realization for Teleoperation GUI

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Chassis Layout
Major Subsystems
Battery Pack

• Front Segment
• 2 Identical battery packs
• Drive motor and pneumatic pump
• PC/104 Stack
• Sensor payload mounting
• Rear Segment
• 2 Identical Battery packs
• Drive motor and pneumatic reservoir
• Docking Mechanism

Drive
Pump
Battery Pack
Air and Elec. Lines
Battery Pack
Tank
Drive
Battery Pack
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Drive Layout
Major Subsystems

• Identical drives in both segments
• Single drive shaft
• O-Ring pressure seal
• Bevel gear transmission
• High gear ratio DC brushed motor

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Steering Mechanism
Major Subsystems

• Single central steering joint
• Dual pneumatic cylinder actuation
• Wire/Pneumatic tubing pass-throughs
• /- 30o turn angle
• Intrinsically-safe potentiometer for steering
  angle measurement

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Chassis Pressure System
Major Subsystems

• 1 Pump, 1 High pressure reservoir
• 1 Valve per wheel
• Solenoid valves to control pneumatic cylinders
• 1 External valve/connector for initial
  pressurization venting
• High pressure venting prevents mine air intake
• Redundant pressure monitoring with certified
  pressure monitoring system
• Both segments and the mapping sensor (one
  pressure volume) purged and pressurized prior to
  deployment
• Wheels, cylinders, never directly connected to
  internal pressure volume

TANK
Pump
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Inflatable Wheels
Major Subsystems

• Sphere and torus shaped internal pressure volume
• Enclosed in wheel sleeve
• Stability/traction
• Abrasion resistance
• Central pump drives independent wheel circuits

• Wheels inflated in mine
• Air supplied by base station via detachable
  snorkel
• Wheels are vacuum deflated for recovery
• Extra air is vented to mine

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Docking Mechanism
Major Subsystems

• Passive hook and catch mechanism
• disengages when robot is level
• engaged by driving catch into hook

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Docking Mechanism
Major Subsystems
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Docking Mechanism
Major Subsystems
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Docking Mechanism
Major Subsystems
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Base Station
Major Subsystems

• Purged and pressurized
• For deployment in gas filled mines
• Video
• Low light panospheric camera
• Downward facing camera
• Assists docking maneuvers
• Light
• LED rings around camera lenses
• Tether to surface
• Winch cable (pass through to robot)
• Ethernet (fiber)
• 2 video cables
• Snorkel (pass through to robot)
• Base station power
• Borehole anchoring mechanism
• Can anchor on sides of borehole like Ferret for
  stability during docking
• Compass
• Gives orientation of base station to assist
  docking
• Wireless Ethernet

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Power Configuration
Major Subsystems
Rear Segment
Front Segment
5 Regulated
Additional Sensors
CPU
Batt 3
Batt 1
Laser
Batt 2
Batt 4
Air Pump
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Status and Control Electronics
Specifications

• Battery health monitor
• One in each segment
• Locomotion and actuation control
• Front/Rear drive
• RS-485 motor controller
• Steering
• Direct CPU control
• Plain motor amplifier
• Pneumatic pump
• Pneumatic manifold control
• Relay amplifier

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Status and Control Electronics
Major Subsystems
Rear Segment
Front Segment
Steering Control
Pneumatic Control
CPU
Pot
Pump
Digital Out
Valves
Valves
Rear Battery Monitor
Voltage
A/D
Current
Rear Drv Controller
Front Battery Monitor
Voltage
PID
A/D
RS-485
RS-485
Current
Amp
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Sensor Layout
Major Subsystems
Front Segment
Rear Segment
Rear-Left Wheel Pressure
Front-Left Wheel Pressure
CPU
A/D
A/D
Serial
Inertial Sensing
I/O Card
3 1 Ultrasonic Sensors
RS-485
3 Ultrasonic Sensors
RS-485
A/D
3-axis accel
A/D
Steering Angle Pot
Laser Angle Pot
Battery Voltage Current
A/D
Drive Encoder
DIO
Laser
RS-422
Gravimetric Sensing
DIO
Drive Encoder
Battery Voltage Current
Electromagnetic Sensing
A/D
2-axis tilt
A/D
Rear Segment Pressure
Front Segment Pressure
Analog Compass
RS-485
RS-485
A/D
Current Thermal Sensing
A/D
Rear-Right Wheel Pressure
Front-Right Wheel Pressure
Current Thermal Sensing
A/D
A/D
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Primary Sensor Deployment
Major Subsystems

• Primary mapping sensor deployed pneumatically
• Dual redundant pneumatic actuators
• Deployment device also serves as tilt module

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Performance Goals
Operations

• gt 1 kWh battery life
• Li-ion 142 Wh/kg, 357 Wh/L ? 7 kg, 2.8 L
• lt 70 lbs final mass
• gt 1 mph top speed
• lt 200 W average power consumption
• 2.5 mile maximum straight line travel
• 2 mile maximum safe straight line travel
• .5 mile radius maximum circular traverse
• gt 50 deployments MTBF
• lt 20K
• lt 2 Person field team

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Deployment
Operations

• Drill Borehole
• Deploy Ferret to examine mine conditions
• Power on computer and systems
• Purge and pressurize cylinders and laser
• Lower robot and base station
• Inflate front wheels when front segment clears
  ceiling
• Deploy primary mapping sensor
• Lower front wheels onto floor and drive forward
• Inflate rear wheels
• Disengage docking mechanism and detach snorkel
• Begin mine exploration

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Recovery
Operations

• Teleoperate robot to engage docking mechanism
• Raise base station and robot
• Deflate wheels in mid air
• Stow primary mapping sensor
• Raise robot
• Retrieve data for post processing
• Inspect robot and recharge air and power

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Failure Scenarios
Operations
Failure Mode Effect








Failure Mode Consequence Response
Wheel puncture/Loss of drive actuator Loss of mobility in that direction Deflate axle, use body as a reaction/steering tail
Slow pressure loss Robot becoming unsafe, or wheel is deflating Open reservoir to maintain pressure level
Rapid loss of main pressure Robot unsafe Full systems shutdown
Computer Lockup Robot shuts down Reboot w/ watchdog
Navigation Sensor Failure Robot effectively blind Attempt immediate return to base with sonar and internal map
Proximity Sensor Failure Robot likely to hit obstacles Attempt immediate return to base with navigation sensor and internal map
Loss of steering actuator Reduced mobility Only actuate remaining functional steering piston
Violation of room and pillar assumption Wall centering is no longer valid Follow a single wall to continue mapping