|Collision Sense and Avoid||- Sense and Avoid|
The ASTM F-38 Committee has issued a published standard for DSA collision avoidance, (F2411-04 DSA Collision Avoidance) that requires a UAV to be able to detect and avoid another airborne object within a range of + or - 15 degrees in elevation and + or -110 degrees in azimuth and to be able to respond so that a collision is avoided by at least 500 ft. The 500 ft safety bubble is derrived from the commonly accepted definition of what constitutes a Near Mid Air Collision. This gives airframe and avionic / DSA electronics manufacturers a target for certification. It is likely that the ASTM standard will be incorporated by reference in eventual FAA certification requirements.
A very good paper on collision avoidance systems, titled SAFETY
ANALYSIS METHODOLOGY FOR UNMANNED AERIAL
from presentation on " Small sense and avoid system" by Dr John F. McCalmont, USAF Research Laboratory at UAV 2007 Conference in Paris.
Above and three images below from a presentation by Col Gary Hopper of the USAF Research Laboratory at the UAV 2007 Conference in Paris
Sense and Avoid system detection test: spot the aircraft against the background...
Above and below from presentation by Steve Umbaugh on " M2CAS Multi-mode collision avoidance system" at the UAV 2007 Conference in Paris.
This aircraft, seen at the AUVSI Conference 2008 in San Diego, uses several microphones mounted on the protruding rods on the wings to detect aircraft.
Above, the requirements on a Sense and Avoid system, as expressed by Captain Thomas Mildenberger of the Airline Pilots " European Cockpit Association" in his presentation at the UAV 2007 Conference in Paris.
Above from the presentation by Commander Max Snow on " NATO developments in sense and avoidfunctional requirements" at the UAV 2007 Conference in Paris.
Collision “Sense and Avoid” capabilities are likely to become an essential feature of an Unmanned Air Vehicle, if it is to operate in commercial air space. Such a system must:
For more information, see http://www.uavm.com/uavregulatory/collisionavoidance.html .
New Mexico State University Aerostar UAS currently being used for sense-and-avoid technology demonstrations.
This is an example of a collision detection system, based on the use of millimetre wave primary and secondary RADAR systems, coupled with a high resolution CCD imager with a zoom lens, to accurately locate an oncoming air vehicle identified by the primary RADAR.
The RingCam is an omnidirectional camera, which captures 360-degrees of video. It is constructed of inexpensive 1394 digital cameras (each 640x480). The RingCam differs from existing omnidirectional cameras, like the OmniCam, in that it is much higher resolution (3000x480), and significantly cheaper. It requires a single 1394 cable to interface to a PC. Images from each camera are stitched together in real-time to form a high resolution panorama.
This camera concept could be used to provide a form of 360 degree visual coverage of the environment outside of the Unmanned Aircraft.
Below, one can see an example of a way in which a Collision Sense and Avoid radome mounted system can be implemented on a UA, in this case, on a Northrop Grumman / IAI Hunter RQ-5A. Note that this unit is actually a directional radio system, used in a GCS - UA radio link.
The Hunter RQ-5A Tactical Unmanned Air Vehicle in service with the US Army.
Another view of the Hunter UAV, " new UAV 2.bmp"
Navy STTR FY2007 - Topic N07-T025
Opens: February 20, 2007 - Closes: March 21, 20076:00am EST
N07-T025 TITLE: Autonomous UAV Collision Avoidance
TECHNOLOGY AREAS: Air Platform, Sensors, Electronics
ACQUISITION PROGRAM: US Marine Corps PMA-263
The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.
OBJECTIVE: To develop a radar sensor compatible with small UAVs that permits safe/reliable autonomous flight in civilian airspace.
DESCRIPTION: The goal of this topic is to develop a radar based collision avoidance sensor suite (RCASS) compatible with small UAVs (< 11 foot wingspan, i.e. Silver Fox class size) for collision avoidance supporting autonomous flights in air spaces co-located with manned air space. Current UAV flights are severely restricted to avoid potential collision with other air platforms. Federal Aviation Administration (FAA) Regulation 7610.4  states that remotely operated aircraft must have an equivalent level of safety, comparable to see-and-avoid requirements for manned aircraft, to satisfy FAA safety requirements. UAVs operating like manned aircraft in the National Air Space have additional FAA requirements. The RCASS must be effective against all air traffic, with or without transponder-based collision avoidance systems such as TCAS  or ADS-B .
One component of the RCASS may include omni-directional Radar . The RCASS system design must provide an energy density per unit solid angle supporting detection at ranges compatible with collision avoidance. Further, the design must satisfy typical small UAV payload constraints. For system design purposes assume < 10% of payload volume, weight, with 200 cc, 1.1 Kg, and < 40 W as an upper bound.
The RCASS must also be electromagnetically compatible with traditional UAV sensors including EO/IR, magnetic detectors, as well as on-board avionics (including GPS) and wireless communication systems.
For autonomous UAV flight in heavy air traffic environments, the UAV must sense or be aware of the coarse 3-D trajectories of neighboring air traffic relative to its own flight trajectory. The RCASS processor will update and maintain its own internal map of the neighborhood air picture, as well as optimizing its actual 3-D trajectory path with its pre-planned 3-D trajectory as a constraint. The RCASS is a point solution and does not require modifications to the external air traffic control system in CONUS or worldwide.
ONR is interested in any intelligent autonomous systems that would be able to perform the sense and avoid function while adhering to the size, weight and power constraints of small UAVs. The Navy will only fund proposals that are innovative and involve technical risk.
PHASE I: Provide an initial system design that demonstrates scientific merit and capabilities of the proposed Radar based RCASS system for small UAVs. This includes a calculation of the RCASS awareness volume surrounding the UAV. The volume is to be determined in part by the limited detection ranges of the sensors. It must support the slower response time of UAVs relative to nearby higher speed military and civilian aircraft kinematics. The Phase I study also includes a high level design of the Radar sensors to support the RCASS awareness volume, as well as a high level design of the RCASS hardware (supporting the < 10% of the volume, weight, and power allocated to the UAV’s normal payload). A software simulation of the collision avoidance function in a heavy civilian traffic environment with the limitations of the proposed RCASS system design will demonstrate the efficacy of the approach.
PHASE II: Design, build, and test an affordable RCASS for a small UAV. Demonstrate collision avoidance. In this phase, a live field test with a surrogate manned aircraft must be documented. Obtain FAA guidance for PHASE III transition.
PHASE III: Obtain FAA certification for autonomous flight in CONUS with UAVs equipped with RCASS. Also demonstrate a manufacturing process that supports volume cost savings to enhance the affordability for dual usages.
PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Autonomous UAV operation lowers man power costs and is key to ubiquitous deployment by the commercial sector. Commercial applications include surveillance of private oil and gas pipelines, the national electronic grid, crop assessment (farming), forest fire fighting, automotive traffic surveillance, and sky based communication networks.
1. FAA, FAA Order 7610.4, available from www.faa.gov , 2006.
2. FAA, " Introduction to TCAS Version 7," US Department of Transportation, Federal Aviation Administration, 2000.
3. RTCA, " Minimum Aviation System Performance Standards For Automatic Dependent Surveillance Broadcast (ADS-B)" , RTCA/DO-242A, Washington DC, 2002
4. Skolnik, M., " Improvements for Air-Surveillance Radar," IEEE Radar Conference, pp 18-21, Waltham, MA, 1999.