Sensing and Actuation for Polar Mobile Robot

1
Sensing and Actuation for Polar Mobile Robot

• Eric L. Akers, Hans P. Harmon,
• Richard S. Stansbury (Presenter), and Arvin Agah
• ITTC, University of Kansas
• September 20, 2004

2
Overview

• Introduction
• Mobile Platform
• Virtual Prototyping
• Software
• Computing and Connectivity
• Sensors
• Actuation
• Evaluation

3
Introduction

• Polar Radar for Ice Sheet Measurement (PRISM)
• Measurement of ice sheet properties in polar
  environments
• Mobile robot to aid data collection
• Transports radar equipment
• Tows antenna array
• Precise movement for data collection
• Environmental challenges
• cold temperatures, harsh winds, blowing snow.

4
Mobile Platform

• Requirements
• Operation at -30 degrees C to 40 degrees C.
• Operate at altitudes from 0m to 3000m above sea
  level.
• Transport 300kg of equipment.
• Support 40Us of rack-mount space.
• Max ATV Buffalo
• Six-wheeled ATV with optional tracks
• Amphibious (sealed)
• Protective enclosure designed and constructed
• Tank-like skid steering.

5
Mobile Platform Max ATV Buffalo
6
Virtual Prototyping

• MSC.visualNastran
• 3D simulation package.
• Evaluation of design parameters and rover
  performance
• Payload placement
• Wheels vs. Tracks
• Turning radius.
• Maximum climbable slope.

7
Virtual Prototyping
Virtual Prototype of PRISM Rover
8
Software

• JAVA
• Portability.
• Object oriented design.
• PRISM Robot API
• Interfaces for robot components.
• Events and Event Listeners
• Forward data updates.
• Propagate error notification
• Sensor and actuator drivers
• Instantiate API defined components.
• Utilizes manufacturers proprietary communication
  languages.

9
Computing and Connectivity

• RS-232 to USB Hub
• Supports up to 16 sensors and Actuators
• 16-Port Switch
• Connects onboard computers
• GoBook Max Ruggedized Laptop
• Pentium III 750 MHz running Windows XP
• Operates at -30 degrees C.
• Shock-mounted hard drives.
• Waterproof

10
Sensors Requirements

• Task
• Centimeter-level position accuracy.
• Video for remote operation and outreach.
• Environmental
• Survive in polar environment.
• Determine weather conditions
• Detect and avoid human-made and
  naturally-occurring obstacles
• Proprioception
• Current state heading, position, orientation.
• Internal temperature
• Fuel level

11
Sensor Suite

• Global Positioning
• Topcons Legacy-E RTK GPS System
• Obstacle Detection
• SICK LMS221 Laser Range Finder
• Tilt and Temperature
• PNI Corp. TCM2-50

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Sensor Suite

• Heading
• BEI Systron-Donner MotionPak II Gyroscope
• Weather
• Rainwise WS-2000 Weather Station
• Vision
• Pelco Esprit pan/tilt/zoom camera

13
Sensors Hardware Integration
External Sensors
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Sensors - Hardware Integration
Internal Sensors
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Actuation

• Three components to control
• Left and right brake.
• Throttle
• Linear actuators
• Electromagnetic motors.
• No gears.
• 20 µm resolution
• Controlled by microcontroller with RS-232
  interface

16
Evaluation

• Field experimentation
• Greenland 2003 North GRIP Camp
• Individual sensor tests and data collection
• Greenland 2004 Summit Camp
• Integrated tests with radar system.
• Climate Survivability
• Sensors operated in polar environment.
• Rover would become stuck occasionally when
  turning in soft snow.
• Batteries drained quickly and were replaced with
  power supplies.

17
Evaluation

• GPS Relative Accuracy
• Measured distance between two points vs. known
  distance
• Relative Accuracy
• x 0.006 0.004 meters
• y 0.010 0.007 meters
• z 0.022 0.016 meters

18
Evaluation

• GPS Visibility
• Measured number of GPS and GLONASS satellites
  available at the North Grip camp for a 24-hour
  period.

19
Evaluation

• Obstacle Image vs. LMS221 Image Snowmobile

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Evaluation

• Obstacle Image vs. LMS221 Image Sastrugi

21
Evaluation

• Waypoint Navigation
• Demonstrates the integration of sensors,
  actuation, and platform.
• Waypoints assigned in a pattern similar to its
  data collection pattern on the ice.
• Thresholds
• Waypoint arrival 1 meter
• Heading on target 10 degrees

22
Evaluation
23
Future Work

• Additional fault tolerance.
• Tighten waypoint path for greater accuracy.
• Reduce rover payload to improve performance in
  soft snow.
• Additional field experiments in Greenland and
  Antarctica.

24
Conclusion

• Mobile robot constructed for collection of radar
  data in polar regions.
• Robust suite of sensors was selected.
• Vehicle automation has been developed and
  verified using waypoint navigation.

25
Acknowledgements

• This work was supported by the National Science
  Foundation (grant OPP-0122520), the National
  Aeronautics and Space Administration (grants
  NAG5-12659 and NAG5-12980), the Kansas
  Technology Enterprise Corporation, and the
  University of Kansas.