Hummingbird

Hummingbird Flying

Hummingbird helicopter in autonomous flight

Hummingbird with ground station GPS antenna

Research Goals

Autonomous helicopters are a promising research area due to their advanced capabilities and great flexibility. Besides having the ability to hover, which allows one to operate in areas unaccessible to other vehicles, an unmanned autonomous helicopter can perform tasks which would be exceedingly difficult or hazardous for a manned vehicle. Possible applications for this technology include close-up inspection of power lines, terrain surveying, search-and-rescue missions, filming movies, and the investigation and clean-up of hazardous waste sites.

The ultimate goal of this research at Stanford is to demonstrate the practicality of using inexpensive robot helicopters to perform tasks without the need for highly trained human operators. This research will bring the concept of object-based, task-leve l control to a new and exciting application environment.

The Hummingbird Helicopter

HUMMINGBIRD is a small autonomous helicopter build by a team at the ARL. It consists of a heavily modified "60 size" remote control model helicopter with a 2.76 cu.in. engine. Navigational sensing is provided entirely by a pair of Trimble Global Positio ning System receivers operating using Differential Carrier Phase calculations. By using four separate antennas, HUMMINGBIRD is able to sense its attitude as well as position with GPS.

As an additional sensor, HUMMINGBIRD has an onboard camera system to gather additional information about its environment. Using this system, HUMMINGBIRD is capable of object location, identification, and retrieval using a retractable tether with a magnet ic manipulator.

HUMMINGBIRD's current flight capabilities include autonomous take-off, hover, trajectory following, and landing. The ability to fly autonomously and retrieve a small ferromagnetic disk was sufficient to win the 1995 International Aerial Robotics Competition sponsored by the Association of Unmanned Vehicle Systems International (AUVSI). Stanford was the first and only team in the six years of this competition to successfully retrieve and move a target disk.

Additional Information

Helicopter Statistics

Body Size	60
Body Length	62 inches
Rotor Diameter	61 inches
Overall Weight	46 pounds
Engine Size	2.76 cubic inches
Engine Power	4.75 HP
Navigational Sensors	TANS Vector Differential Carrier Phase GPS

Current Capabilities

Dynamic Target Tracking and Following
Servoing from Vision Feedback
Autonomous Hover, Trajectory Following, and Landing
Object Location and Identification using Vision
Ferromagnetic Disk Retrieval

Future Capabilities

Autonomous Take-Offs
Parallel Camera Stereo Vision
Motion-Based Stereo Vision
Real-Time User Interaction
Human-Robot Team Mission Tasks

Global Positioning System

One of the greatest problems with controlling an autonomous helicopter is sensing position and attitude. Since a small, inexpensive vehicle is being used, it has neither the payload nor the financial budget to use exceedingly high quality inertial guidance systems. Navigation using differential carrier phase Global Positioning System (DCPGPS), is an active area of research within ARL, and offers an practical solution to these problems.

The Global Positioning System is an excellent sensor offering a wide variety of configurations. In its normal civilian configuration, it provides accuracies of roughly 100 meters in both position and altitude. Various (mainly differential) methods have been proposed and implemented for increasing this precision to about a meter. Stanford's use of carrier phase measurements allow accuracy on the order of centimeters. When carrier phase techniques are used in conjunction with multiple antenna, vehicle attitude can also be determined.