Project History

September 1991

Initial attitude control experiments

Attitude control testbed developed.
Used to test and tune attitude control system.
Electrical model helicopter mounted on a swiveling arm platform.
Optical encoder mounted with a frictionless bearing measures ground-truth angles in real time.
Configurable for roll, pitch, and yaw.

February 1992

Free flight and vision-based state estimator

Six-degree-of-freedom testbed developed for evaluating various position estimation and control systems.
Electrical model helicopter attached to poles by graphite rods for safety and helicopter ground-truth position estimation.
Lightweight composite material and custom designed frictionless air bearings allow unobtrusive helicopter free flight in a cone shaped area.
Mechanical stops prevent the helicopter from crashing or flying away.

September 1994

First autonomous platform

Indoor testbed developed as an intermediate step towards autonomous operation.
Used for testing the vision system, control system, sensor platform, power system, RF interference, and overall system integrity.
Allows relatively large (1.5 meter) longitudinal travel.
Severely limits helicopter travel laterally and vertically.
Helicopter is tethered with ropes which are fastened to the ground and two poles positioned on either side of the platform.
Steel rod with hooks on either end connects the ropes to the helicopter.
Steel rod is secured to the helicopter's center of gravity to eliminate any torques from restraining forces which could cause dangerous rotations.

October 1995

Autonomous Helicopter #1

Visual odometer (4 cm accuracy, 60Hz update), tracks image patches and templates with helicopter motion.
Initial computer control trials performed at relatively high (~15m) altitudes to allow safety pilot time to override computer.
Latitudinal and longitudinal controls were tested first by mixing human control for height and heading with the computer commands.
Heading and height control were enabled as the computer control proved effective in stabilizing the helicopter
GPS used for ground-truth measurements.
CNN coverage.

August 1996

Autonomous Helicopter #2

Control system for autonomous takeoff, landing and smooth trajectory following.
System tested in harsh conditions (40-45 mph wind gusts).
State estimator fusing data from a dual-frequency carrier-phase GPS receiver, 3-axis angular rate and inertial sensors, and field-rate vision-based odometry.
Custom-designed vision system capable of field-rate position sensing, multiple object tracking, color discrimination, and aerial intensity map building.
Custom-designed camera stabilization system.
3D laser line scanner.
Power system for up to 33 minutes autonomous operation.
Winner of the 1997 Unmanned Aerial Robotics Competition
Journal of Robotics and Autonomous Systems (Oct 1997) article about the competition.

July 1998

Autonomous Helicopter #3