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Monocular Vision System for Fixed Altitude Flight of Unmanned Aerial Vehicles.

Huang KL, Chiu CC, Chiu SY, Teng YJ, Hao SS - Sensors (Basel) (2015)

Bottom Line: The UAV flight system can be set to fly at a fixed and relatively low altitude to obtain the same resolution of ground images.A forward-looking camera is mounted on the upside of the aircraft's nose.Experimental results show that the proposed system enables UAVs to obtain terrain images at constant resolution, and to detect the relative altitude along the flight path.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Electronic Engineering, Chung Cheng Institute of Technology, National Defense University, Taoyuan 33551, Taiwan. 1040510304@ndu.edu.tw.

ABSTRACT
The fastest and most economical method of acquiring terrain images is aerial photography. The use of unmanned aerial vehicles (UAVs) has been investigated for this task. However, UAVs present a range of challenges such as flight altitude maintenance. This paper reports a method that combines skyline detection with a stereo vision algorithm to enable the flight altitude of UAVs to be maintained. A monocular camera is mounted on the downside of the aircraft's nose to collect continuous ground images, and the relative altitude is obtained via a stereo vision algorithm from the velocity of the UAV. Image detection is used to obtain terrain images, and to measure the relative altitude from the ground to the UAV. The UAV flight system can be set to fly at a fixed and relatively low altitude to obtain the same resolution of ground images. A forward-looking camera is mounted on the upside of the aircraft's nose. In combination with the skyline detection algorithm, this helps the aircraft to maintain a stable flight pattern. Experimental results show that the proposed system enables UAVs to obtain terrain images at constant resolution, and to detect the relative altitude along the flight path.

No MeSH data available.


Architecture of the UAV FCS.
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sensors-15-16848-f001: Architecture of the UAV FCS.

Mentions: This section introduces the architecture of the flight control system (FCS) utilized for automatic flight (Figure 1). The FCS hardware can be divided into the flight vehicle platform (FVP) and ground control station (GCS). The FVP is equipped with two video transmitters operating on different frequencies, a forward-looking camera, downward-looking camera, and GPS data transmitter. The videos obtained from the forward- and downward-looking cameras are transmitted by different transmitters to video receivers at the GCS. The control signal of the remote controller and the image signal are transmitted in the form of an electromagnetic wave. The velocity of electromagnetic wave is 3 × 108 m/s. When the distance between UAV and GCS is 200 m, the transmission time of electromagnetic wave is approximately 0.67 × 10−6 s. Thus, the communication latency of the control and video signals can be ignored. This study uses video transmitters on 1.2 GHz and 5.8 GHz frequencies to avoid wireless interference. The video is then converted to digital images by a USB video capture card. The images captured from the forward-looking camera are transmitted to the GCS computer, which is programmed to detect the skyline. The aircraft carries out a stable automatic flight with the aid of the skyline-detection algorithm [16]. The continuous images captured from the downward-looking camera in stable flight are also transmitted to the GCS computer. Two consecutive images from the downward-looking camera are treated as images captured by two cameras, as in a stereo vision system. Finally, the altitude between the aircraft and the ground is calculated by the proposed algorithm. Details of the FVP, GCS, and remote-control operation are described in the following sub-sections.


Monocular Vision System for Fixed Altitude Flight of Unmanned Aerial Vehicles.

Huang KL, Chiu CC, Chiu SY, Teng YJ, Hao SS - Sensors (Basel) (2015)

Architecture of the UAV FCS.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541911&req=5

sensors-15-16848-f001: Architecture of the UAV FCS.
Mentions: This section introduces the architecture of the flight control system (FCS) utilized for automatic flight (Figure 1). The FCS hardware can be divided into the flight vehicle platform (FVP) and ground control station (GCS). The FVP is equipped with two video transmitters operating on different frequencies, a forward-looking camera, downward-looking camera, and GPS data transmitter. The videos obtained from the forward- and downward-looking cameras are transmitted by different transmitters to video receivers at the GCS. The control signal of the remote controller and the image signal are transmitted in the form of an electromagnetic wave. The velocity of electromagnetic wave is 3 × 108 m/s. When the distance between UAV and GCS is 200 m, the transmission time of electromagnetic wave is approximately 0.67 × 10−6 s. Thus, the communication latency of the control and video signals can be ignored. This study uses video transmitters on 1.2 GHz and 5.8 GHz frequencies to avoid wireless interference. The video is then converted to digital images by a USB video capture card. The images captured from the forward-looking camera are transmitted to the GCS computer, which is programmed to detect the skyline. The aircraft carries out a stable automatic flight with the aid of the skyline-detection algorithm [16]. The continuous images captured from the downward-looking camera in stable flight are also transmitted to the GCS computer. Two consecutive images from the downward-looking camera are treated as images captured by two cameras, as in a stereo vision system. Finally, the altitude between the aircraft and the ground is calculated by the proposed algorithm. Details of the FVP, GCS, and remote-control operation are described in the following sub-sections.

Bottom Line: The UAV flight system can be set to fly at a fixed and relatively low altitude to obtain the same resolution of ground images.A forward-looking camera is mounted on the upside of the aircraft's nose.Experimental results show that the proposed system enables UAVs to obtain terrain images at constant resolution, and to detect the relative altitude along the flight path.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Electronic Engineering, Chung Cheng Institute of Technology, National Defense University, Taoyuan 33551, Taiwan. 1040510304@ndu.edu.tw.

ABSTRACT
The fastest and most economical method of acquiring terrain images is aerial photography. The use of unmanned aerial vehicles (UAVs) has been investigated for this task. However, UAVs present a range of challenges such as flight altitude maintenance. This paper reports a method that combines skyline detection with a stereo vision algorithm to enable the flight altitude of UAVs to be maintained. A monocular camera is mounted on the downside of the aircraft's nose to collect continuous ground images, and the relative altitude is obtained via a stereo vision algorithm from the velocity of the UAV. Image detection is used to obtain terrain images, and to measure the relative altitude from the ground to the UAV. The UAV flight system can be set to fly at a fixed and relatively low altitude to obtain the same resolution of ground images. A forward-looking camera is mounted on the upside of the aircraft's nose. In combination with the skyline detection algorithm, this helps the aircraft to maintain a stable flight pattern. Experimental results show that the proposed system enables UAVs to obtain terrain images at constant resolution, and to detect the relative altitude along the flight path.

No MeSH data available.