In this blog we will explore the latest in sense and avoid technology that is commercially available for unmanned aircraft under 55 pounds. The ability for small unmanned aircraft systems (UAS) to
perceive their surroundings and react in a in a timely and appropriate manner
is critical characteristic not only for the safety of the aircraft itself, but
also for manned aircraft sharing the airspace (Warwick, 2014). Current and
emerging technologies are understandably placing a high degree of focus in
implementing and refining UAS systems that can meet both requirements. In this
paper, a commercially available sense and avoid system that aids in obstacle
clearance will be examined.
The ‘Guidance’ sensing module, offered by the DJI Corporation (DJI,
2016a), is arguably the most capable system available at this time for
commercially available small UAS (Corrigan, 2015). The Guidance
module consists of a suite of ultrasonic sensors and cameras which feed data to
an onboard processor. Visual data is analyzed by means of an advanced computer
vision algorithm that compares imagery from the cameras to determine an objects
distance by comparing the relative perspective of the object from each camera (DJI,
2016b).
The onboard processor consists of a pair of ARM Cortex-A9
cores which are able to provide up to 4000 Dhrystone million instructions per
second while consuming less than 250 mW per CPU (ARM, 2016) making this device
ideal for small UAS with limited power resources. The processor also
incorporates various Field Programmable Gate Array (FPGA) hardware accelerators
which consists of an array of programmable logic blocks (Xilinx Inc., 2016) to
assist in rapid data processing. Such computational power supports data fusion
from all installed sensors and automatically selects the best vision algorithm
based on the camera configuration (DJI, 2016c).
An article posted by Digital Trends (Digital Trends, 2016) further describes the Guidance system as
consisting of five ultrasonic sensors facing front, rear, left, right, and down
that allows a Guidance-equipped UAS to determine its position relative to its
surrounding with an accuracy of a few centimeters (Prindle, 2015). In addition,
the Guidance also features a downward-facing visual positioning system, which
aids in GPS-denied environments, that is effective up to 65 feet above the
ground (DJI, 2016d).
A Guidance core unit
measures 78.5 mm x 53.5 mm x 14 mm with sensor measurements of 170 mm x 20 mm x
16.2 mm. The weight of a fully-equipped module (core plus five sensors with
cabling) equals approximately 337 grams. Maximum power draw is 12 watts with
all five sensors installed. Effective sensor range is described as between 0.2
to 20 meters. A complete Guidance module can be purchased for $999.00 (DJI,
2016e).
In summary, the DJI Guidance module offers a significant
improvement in sense and avoid situations for obstacle clearance in small UAS.
However, this is only part of the sense and avoid picture. The Federal Aviation
Administration (FAA) is greatly concerned about small UAS in the national
airspace and currently working with the National Air and Space Administration
(NASA) to research a myriad of emerging technologies (FAA, 2009) that will best
mitigate air traffic cooperation between manned and unmanned systems and
eventually provide a complete sense and avoid capability for small UAS and provide a measure of comfort for manned aviation.
References:
ARM. (2016). Cortex-A9
Processor. Retrieved from http://www.arm.com/cortex-a9.php
Corrigan, F.
(2015). Top Matrice 100 Programmable
Sensor Drone With SDK Review. Retrieved from http://www.dronezon.com/drone-reviews/review-of-dji-matrice-100-sdk-drone-sensors-and-collision-avoidance-system/
Digital Trends. (2016). Tech for the Way we Live. Retrieved from
http://www.digitaltrends.com/about/
DJI.
(2016a). 3D Sensing. Retrieved from
http://www.dji.com/product/guidance/features#sub-feature
DJI.
(2016b). DJI Store. Retrieved from
http://store.dji.com/product/guidance?site=brandsite&from=buy_now_bottom#/spec
DJI.
(2016c). Guidance. Retrieved from
http://www.dji.com/product/guidance
DJI. (2016d). High-Precision Visual Positioning System.
Retrieved from http://www.dji.com/product/guidance/features#sub-feature
DJI. (2016e). Multi-sensor
Fusion. Retrieved from
http://www.dji.com/product/guidance/features#sub-feature
FAA.
(2009). Literature Review on Detect,
Sense, and Avoid Technology for Unmanned Aircraft Systems. Retrieved from
http://www.tc.faa.gov/its/worldpac/techrpt/ar0841.pdf
Prindle,
D. (2015). DJI’s new Obstacle Avoidance
Tech aims to make Drones Crash Proof. Retrieved from
http://www.digitaltrends.com/cool-tech/dji-obstacle-avoidance-matrice-100-guidance/
