Small Vehicle, Small Sensors

      The initial criteria for a sense and avoid sensor are going to be physical.  A small unmanned aerial vehicle (UAV) weighing less than 55 pounds is not going to have the available cargo allowance to add much weight in sensors and maintain usefulness for its mission.  The sensor must provide enough range and accuracy to the UAV to be worth installing but also must be light enough and efficient enough to not cause the UAV to drain its power source at an unacceptable rate.  The next criteria deal with the goals of the sensor.  Being installed on a small UAS, it can be determined the UAV will not be operational in an airspace which has manned aircraft equipped with cooperative sensors such as ADS-B or TCAS-II.  According to the National Aeronautics and Space Administration (NASA), UAVs which operate at these higher altitudes are going to require systems which use cooperative and non-cooperative sensors for sense and avoid procedures (NASA, 2016).  Small UAS are going to be more concerned with other small UAS (sUAS) and objects from the environment which the operator cannot see to avoid.  To accomplish sensing objects in this domain, it is recommended to use a small radar sensor with a moderate range, minimal weight, and minimal power drain.  Once such sensor system has been developed by Aerotenna. 

Figure 1. Aerotenna (2017) µSharp 360° equipped to a sUAS.  Retrieved from https://aerotenna.com/aerotenna-releases-360-sense-avoid-radar-advances-drones-closer-autonomous-flight/

      There are other radar sensor systems on the market for use on sUAS, but Aerotenna’s µSharp 360° actually provides sensor coverage in a complete 360° arc around the sUAS (Aerotenna, 2017).  The reason full circle coverage is important is the maneuverability of sUAS.  It is not unusual for a vehicle to be brought to a stop and then accelerated in a completely different direction.  The sensor will give the system the data needed to prevent the operator form turning into a hazard which originally was not in its flight path.  The sensor has a range of 120 meters, giving it the moderate range needed for sUAS as they traverse a domain littered with hazards (Aerotenna, 2017).   Perhaps the best aspects of the sensor are the size and weight.  The µSharp 360° only weighs 243g and is only 115 mm by 115mm (Aerotenna, 2017).  This makes is applicable to just about any sUAS with a UART or CAN I/O port and room on the vehicle.  So, what is the down side to the sensor?  It would have to be the cost.  Since the µSharp 360° is relatively new and the only 360-degree sensor on the market, the price is high.  In order to equip your sUAS with the µSharp 360° you will have to spend $2,500.  This makes the sensor as much if not more expensive as most commercially available sUAS which would employ the µSharp 360°.  Until the price comes down, it would probably be cheaper to replace/repair the sUAS after the collision than to purchase the sensor. 

  References

Aerotenna. (2017, December 2). uSharp - 360 Sense-and-Avoid Radar. Retrieved from Aerotenna: https://aerotenna.com/datasheets/AerotennauSharp360Datasheet.pdf

NASA. (2016, September 13). Unmanned Aircraft Systems (UAS) Integration in the National Airspace System (NAS) Project. Retrieved from National Aeronautical Space Administration: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160013707.pdf