HID Joystick Control for K10 Series Rover

1
HID Joystick Control for K10 Series Rover Gregg
Carpenter, University of Vermont, Burlington
Vermont Mentor Dr. Terry Fong, Intelligent
Robotics Group, NASA Ames
BACKGROUND In order to more precisely control
the position and orientation of the K10 series
rover during field testing, a dynamic Human
Interface Device, or HID, was implemented using a
Universal Serial Bus, or USB, compliant joystick.
The motivation behind this interface is that it
could be easily utilized in the field either
connected directly to the local brain of the
rover, or connected via a base control terminal
on the wireless communications network at the
test site, using a standard protocol which is
well supported on most operating system
platforms thus being consistent with the
decision to maintain platform portability for the
development source code instruction set for the
K10 series.
METHODS In order to implement the software
client for the HID, the software language C was
used to develop the source code instruction set.
The Simple Direct media Layer, or SDL, libraries
were utilized as they offered both USB and
joystick functionalities in an easy to use tool
set for the C language. Mappings were
developed in order to translate the movements of
the joystick, by the operator, to software
commands which interfaced with the K10 locomotion
control software.
START
USB Joystick
NO
JOYSTICK?
END
YES
LAST_TRIGGER FALSE
CHECK FOR PRESSED BUTTONS ASSIGN BUTTON STATES
INCREMENT COMMAND COUNTER
COMMAND COUNTER ISSUE COUNT?
YES
TRIGGER PRESSED?
YES
K10 Blue
NO
NO
CURVATURE X3 VELOCITY Y(LOW_MAXTHROTTLEHIGH
_MAX)
YES
Two distinct modes of operation were devised and
executed for joystick control point-turn mode,
in which the rover rotates in-place either
clockwise or counter clockwise, and continuous
drive mode, in which the rover moves either
forward or backward while being able to execute a
turn in either direction. Both modes of
operation utilized a unique mapping of the
joystick motion, while using existent software,
already utilized by the K10 navigation and
locomotion systems, to execute the joystick
commands.
LAST_TRIGGER TRUE TRIGGER FALSE?
ISSUE STOP COMMAND
ISSUE VELOCITY CURVATURE COMMANDS
NO
EMERGENCY STOP BUTTON PRESSED?
YES
ISSUE EMERGENCY STOP COMMAND
NO
POINT_TURN BUTTON PRESSED?
YES
STOP COMMAND ISSUED
NO
RESULTS The result of the project has been a
robust joystick client for the K10 rover that has
native support for three separate specific HID
USB joysticks and generic support for any USB
joystick with at least basic functionality. This
client has been used successfully both for the
control, and testing, of the rover, as well as
its locomotion control subsystems, at both the
marscape test site at NASA Ames research
center, and at the Haughton Crater field survey
site in Devon Island, Nunavut, in the Canadian
arctic.
X0 POINT_TURN BUTTON PRESSEDgt
YES
TRIGGER PRESSED?
LAST_TRIGGER TRUE
YES
NO
NO
POINT_TURN BUTTON PRESSED?
NO
LAST_TRIGGER FALSE
YES
Xgt0?
YES
POINT_TURN RIGHT COMMAND
NO
YES
Xgt0?
CONCLUSIONS The usefulness of the joystick
interface was most apparent in its ability to
provide high-speed, real-time testing of the
locomotor control and coordination of motor
commands in a way that was more dynamic and
flexible than the commands that would be sent
from the rovers internal navigation software.
The ability to also maneuver easily and quickly
in test environments, in cases where current
navigation software would be impractical, also
played to the strengths of the joystick HID.
POINT_TURN LEFT COMMAND
NO
YES
NO
STOP COMMAND ISSUED
Xgt0?
ACKNOWLEDGEMENTS Special thanks to Terry Fong,
Matt Deans, Hans Utz, and Joel Croteau, as well
as the Exploration Systems Mission Directorate,
Maricela Varma, the Education Associates Office,
and the entire Intelligent Robotics Group and The
Vermont Space Grant Consortium.