University of Kansas 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

University of Kansas Overview Introduction Mobile Platform Virtual Prototyping Software Computing and Connectivity Sensors Actuation Evaluation

University of Kansas 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.

University of Kansas 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 40U’s of rack-mount space. Max ATV Buffalo Six-wheeled ATV with optional tracks Amphibious (sealed) Protective enclosure designed and constructed Tank-like skid steering.

University of Kansas Mobile Platform – Max ATV Buffalo

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

University of Kansas Virtual Prototyping Virtual Prototype of PRISM Rover

University of Kansas 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.

University of Kansas 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

University of Kansas 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

University of Kansas Sensor Suite Global Positioning: Topcon’s Legacy-E RTK GPS System Obstacle Detection: SICK LMS221 Laser Range Finder Tilt and Temperature: PNI Corp. TCM2-50

University of Kansas Sensor Suite Heading: BEI Systron-Donner MotionPak II Gyroscope Weather: Rainwise WS-2000 Weather Station Vision: Pelco Esprit pan/tilt/zoom camera

University of Kansas Sensors – Hardware Integration External Sensors

University of Kansas Sensors - Hardware Integration Internal Sensors

University of Kansas 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

University of Kansas 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.

University of Kansas Evaluation GPS Relative Accuracy: Measured distance between two points vs. known distance Relative Accuracy: x = ± meters y = ± meters z = ± meters

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

University of Kansas Evaluation Obstacle Image vs. LMS221 Image: Snowmobile

University of Kansas Evaluation Obstacle Image vs. LMS221 Image: Sastrugi

University of Kansas 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

University of Kansas Evaluation

University of Kansas 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.

University of Kansas 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.

University of Kansas Acknowledgements This work was supported by the National Science Foundation (grant #OPP ), the National Aeronautics and Space Administration (grants #NAG and NAG ), the Kansas Technology Enterprise Corporation, and the University of Kansas.