Slip Control During Slope Descent for a Rover with Plowing Capability

Daniel Loret de Mola Lemus
master's thesis, tech. report CMU-RI-TR-13-10, Robotics Institute, Carnegie Mellon University, July, 2013


Download
  • Adobe portable document format (pdf) (3MB)
Copyright notice: This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. These works may not be reposted without the explicit permission of the copyright holder.

Abstract
Recent efforts in planetary robotic exploration aim toward craters, skylights, and other depressions with challenging terrain conditions. The access to such places requires traversing on extreme slopes where high levels of slip greatly hamper rover mobility and control. To successfully reach valuable targets such as water ice and mineral outcrops in these locations, slip must be promptly arrested. The work presented here develops an automatic system for a plowing-capable rover that controls slip during descent on steep unconsolidated slopes.

The slip control system is implemented around the robot’s plow, and has two main components: a slip estimation subsystem and the slip controller. Slip estimation is performed through a visual odometry algorithm based on monocular optical flow. Two approaches were explored for the slip controller: PID and fuzzy logic control. The design of the controllers was aided by a model of the rover-terrain system formulated specifically for this purpose.

Field testing was carried out on conditions relevant to lunar crater exploration. The experimental results showed that the control system is able to keep slip to a minimum for different commanded vehicle speeds and slopes as steep as 31°. As a consequence, this work expands current rover mobility and control capabilities by enabling precise descent on steep slopes of unconsolidated material.

Keywords
Slip, slope descent, fuzzy logic, control, slip control, slip estimation, plowing, tracked rover

Notes
Associated Center(s) / Consortia: Space Robotics Initiative and Field Robotics Center
Associated Project(s): Lunar Ice Discovery Initiative
Number of pages: 108

Text Reference
Daniel Loret de Mola Lemus, "Slip Control During Slope Descent for a Rover with Plowing Capability," master's thesis, tech. report CMU-RI-TR-13-10, Robotics Institute, Carnegie Mellon University, July, 2013

BibTeX Reference
@mastersthesis{Loret_de_Mola_Lemus_2013_7437,
   author = "Daniel {Loret de Mola Lemus}",
   title = "Slip Control During Slope Descent for a Rover with Plowing Capability",
   booktitle = "",
   school = "Robotics Institute, Carnegie Mellon University",
   month = "July",
   year = "2013",
   number= "CMU-RI-TR-13-10",
   address= "Pittsburgh, PA",
}