Unmanned System Data Protocol and Format - DJI Phantom 4

4.5 - Research Assignment: Unmanned System Data Protocol and Format

There are many commercial unmanned aerial systems (UAS) on the market that currently incorporate a multitude of sensors that require data systems, protocols, and storage methods to make them an effective and functional system.  One system currently on the market that incorporates this technology is the DJI Phantom 4 (P4).  The P4 officially went on sale March 15, 2016 (Martin, 2016).  The P4 has an impressive sensor suite that allows for it to handle a multitude of functions.  According to Jim Martin (2016), the P4 has the following capabilities based on the sensors on board:

•          An Obstacle Sensing System that uses ultrasonic sensors plus two front facing and two downward facing cameras allowing it to see and avoid people, buildings, or other obstacles.
•          An Active Track function that lets the system track a moving subject without GPS navigation.
•          A TapFly function that allows the user to fly the system with a smartphone by tapping where the user wants it to go, in a well-lighted environment, allowing the avoidance technology to handle the flight path.
•          A vision positioning system with an effective range of up to 10 meters.
•          A 4K camera that is attached to a gimbal that can record slow motion video capture of 120 frames per second at 1080 pixels.
•          An intelligent flight battery with a capacity of 5350mAh, and a flight time of 28 minutes.

The P4 allows the data collected by the sensors to be stored in several ways.  One way data can be collected and stored is by an onboard micro SD card, with a max capacity of 64 gigabytes (DJI, 2016b).  DJI has developed the DJI GO app for Apple iOS and Android devices that uses a real-time HD downlink to see what the camera sees (DJI, 2016a).  According to DJI (2016a), the following data from sensors can be downloaded the DJI GO app:

•          The aircraft’s position and heading.
•          Images and videos.
•          Fight log data through the Flight Record feature.

The DJI GO app has the following specifications:

•          Equivalent isotropically radiated power (EIRP) of 100mW
•          Power Spectral Density of 6.9mW/MHz and a live view working frequency of 2.4GHz ISM
•          A live view quality of 720p at 30 frames per second with a latency of 220ms, depending on the conditions and mobile device.
•         Required operating systems of iOS 8.0 or later and Android 4.1.2 or later (DJI, 2016b).

As mentioned previously the P4 is equipped with an obstacle sensing system, vision positioning system, and a 4K camera.  The Obstacle Sensing System has a sensory range of 2 to 49 feet and must have a surface with a clear pattern and adequate lighting of greater than 15 lux, for its operating environment (DJI, 2016b).  The vision positioning system has an altitude and operating range of 0 to 33 feet, along with the same lighting requirements as the Obstacle Sensing System (DJI, 2016b).  According to DJI (2016b), the 4K camera specifications are:

•          12 megapixels, attached to a gimbal with a 3-axis stabilization and pitch of -90^o to +30^o.
•          A lens with an operating field of view (FOV) of 94^o 20mm.
•          An ISO range of 100 to 3200 for video and 100 to 1600 for photos.
•          A shutter speed of 8s to 1/8000s with a maximum image size of 4000x3000 pixels.
•         A max video bitrate of 60 Mbps
•         JPEG and DNG photo files and MP4 and MOV (MPEG-4 AVC/H.264) movie files.
•          An operating temperature range of 32 to 104 degrees Fahrenheit.

In order to power the P4 it is incorporated with an intelligent flight battery system.  The intelligent flight battery weighs 462 grams; is a LiPo 4S battery with 15.2 volts; has energy of 81.3Wh; and has a maximum charging power of 100W with an operating temperature of 14 to 104 degrees Fahrenheit (DJI, 2016b).  

The P4 also has several other sensors that are built into the airframe to assist in flight operations.  In order to assist the global positioning system (GPS) the P4 has dual inertial measurement units (IMUs) and dual compass modules.  The data these sensors receive is run through algorithms to check for accuracy, any inaccurate data is then discarded without affecting the flight of the system (DJI, 2016c). 

The P4 is controlled by the DJI Phantom 4 remote control.  It has an operating frequency of 2.400 GHz to 2.483 GHz with an operating voltage of 7.4 volts at 1.2 amps; a maximum transmission distance of 3.1 miles; can operate in temperatures from 32^o to 104^o Fahrenheit with a 6000mAh LiPo 2S battery; and has a FCC transmitter EIRP of 23 dBm (DJI, 2016b).  Last, according to DJI (2016b), the P4 has the following specifications:

·         Weighs 1380 grams with a maximum speed of 20 meters per second.

•          An ascent speed of 6 meters per second with a descent speed of 4 meters per second.
•          Can operate at a maximum of 19,685 feet or 6,000 meters above sea level.

•          Has a vertical and horizontal hover accuracy of +/- .1 meters and +/- .3 meters respectively when vision positioning is active.

            The DJI Phantom 4 is an excellent commercial UAS for an end user who wants to use it for aerial videography and photography.  There are a couple of changes I would make to the system.  First, it appears that the camera cannot be switched out with the gimbal it is attached to.  I would make it so it can be used with several different brands of cameras, such as GoPro and Sony, and other thermal infrared, multispectral, and hyperspectral sensors.  I think it would be good for DJI to also find another means of data storage for the Phantom 4.  I think this would be an important feature to consider incase the micro SD card becomes damaged during flight, and if the DJI GO app becomes inoperable during an operation.  DJI might consider adding cloud storage solutions for data after flight operations, too.  DJI could try to incorporate other solid state drives (SSD) into the system for storage solutions, such as the Microsemi Corporation’s low power mSATA SSD that has 64GB single-level cell (SLC) flash capacity in a 50mm x 30mm compact size, designed for unmanned aerial vehicles (Unmanned Systems Technology, 2015).

References:

DJI. (2016a). DJI GO - Capture and Share Beautiful Content Using this New App. Retrieved June 26, 2016, from DJI: http://www.dji.com/product/goapp

DJI. (2016b). DJI Phantom 4 - Spec, FAQ, Tutorials and Downloads. Retrieved June 26, 2016, from DJI: http://www.dji.com/product/phantom-4/info#specs

DJI. (2016c). Phantom 4 - DJI's smartest flying camera ever. Retrieved June 26, 2016, from DJI: http://www.dji.com/product/phantom-4

Martin, J. (2016, April 20). DJI Phantom 4 release date, price, specs: the drone that can fly itself and avoid obstacles. Retrieved June 26, 2016, from PC Advisor: http://www.pcadvisor.co.uk/new-product/gadget/dji-phantom-4-release-date-price-specs-3636067/

Unmanned Systems Technology. (2015, August 13). Microsemi Introduces Secure Solid State Drive for High-Security Embedded Applications. Retrieved June 26, 2016, from Unmanned Systems Technology: http://www.unmannedsystemstechnology.com/2015/08/microsemi-introduces-secure-solid-state-drive-for-high-security-embedded-applications/