Development and feasibility flight test of obstacle detection and collision warning system for civil helicopters

Abstract

Helicopters mainly fly at low altitude under visual flight rules and many accidents occurred when helicopters have struck power lines in good weather conditions. Pilots sometimes have difficulty to see long thin objects such as power lines even with good visibility.

In order to enhance detection ability, many kinds of obstacle detection and collision warning systems are now under development. ENRI is also trying to find a solution to reduce these kinds of accidents for civil helicopters. Such a system requires detection ability for obstacles at 800m with visibility enhancement under all bad weather conditions. It must also perform all of the process in real time within 1 second.

This paper describes the results of feasibility flight tests of a system developed by ENRI. The paper is divided into five parts, according to research topic, as follows;

(1) Section 2 describes ground tests of an IR camera capable to detecting power lines, with built-in image processing. IR imager provides a shape of obstacles such as power lines, locate as far as 1,000m away. Image processing enhances the shape of objects such as power lines within 100msec.

(2) Section 3 describes millimeter wave radar hardware and software. The radar emits 20.17dBm and the maximum range achieved is more than 800m. Nearest target extraction is installed in radar signal processing.

(3) Section 4 describes the development of a radar antenna, because there are few choices for this application. A primary source using slot array performs with -20dB reflection losses. A number of Fresnel reflector antennas are also manufactured. Folded reflector antennas provide 36 dBi of gain with back side feed.

(4) Section 5 describes the concept of a total system using a CCD camera, an infrared camera, and a millimeter wave radar. We present a solution to show color fusion images plus an IR images with distance information from the radar.

(5) Section 6 describes the results of feasibility test. The system detects obstacles such as power lines located at 800m range with image enhancement. Its refresh rate exceeds 8 frames per second with smooth flow of the processed movie.

We conclude that the proto-type system indicates the feasibility of power line detection using millimeter wave radar and an IR camera.