OBSTACLE AWARENESS AND COLLISION AVOIDANCE RADAR SENSOR SYSTEM

OBSTACLE AWARENESS AND COLLISION AVOIDANCE RADAR SENSOR SYSTEM FOR LOW-ALTITUDE FLYING SMART UAV Young K. Kwag and Jung W Kang, Avionics Dept. AERC, Hankuk Aviation University, Seoul, Korea Presentation by Genya Fridlyand

OBJECTIVE Obstacle awareness and collision avoidance is considered the most important issue in the field of unmanned vehicles. While this technology is in use for manned vehicles, it is still in the development and test phase for unmanned vehicles. Objective: propose a suitable radar sensor system for unmanned aircrafts 2

UNMANNED AERIAL VEHICLES An unmanned aerial vehicle (UAV) is an unpiloted aircraft. UAVs can be remote controlled or fly autonomously based on pre-programmed flight plans or more complex dynamic automation systems [2]. 3

PROBLEMS WITH UAVS In the past seven years, the UAV average mishap rate has been 4. 28; compared to the Air Force mishap rate average during that same time of 1. 12, UAV mishaps are very high [3]. • • limited camera angles extremely poor pilot-to-airplane interface reaction time boredom 4

AVAILABLE TECHNOLOGIES Current cooperative systems in use for manned aerial vehicles include: • Traffic Alert Collision Avoidance System (TCAS) • Automatic Dependent Surveillance-Broadcast (ADS-B) 5

Traffic Alert Collision Avoidance System (TCAS) TCAS involves communication between all aircraft equipped with an appropriate transponder [4]. Each TCAS-equipped aircraft "interrogates" all other aircraft in a determined range about their position and all other craft reply to other interrogations [4]. This interrogation-and-response cycle may occur several times per second [4]. 6

Traffic Alert Collision Avoidance System (TCAS) TCAS I - first generation of collision avoidance technology; Alerts pilot of traffic; no suggestion of remedy [4]. TCAS II - used in commercial aircrafts. Offers all benefits of TCAS I. Offers the pilot direct, vocalized instructions to avoid Danger [4]. TCAS III - "next gen" of collision avoidance technology. Currently suspended; no further plans for development [4]. 7

Non-Cooperative Systems Non-cooperative systems use sensors to measure the avoidance information of the obstacles using active or passive methods Active sensors emits energy to obstacles and receives the reflecting energy. Passive sensors only receive energy radiated from obstacles. • Electro-optical sensors • Electromagnetic radar sensors 8

Sensor Characteristics [1] Condition Microwave MMW Thermal Imager Mode Active Wavelength cm cm µm Average Power High Medium Low Range/Range Available Not-Available Detection Range Unlimited 10 km 10 -15 km Component Large Small Angular Resolution Large Small Atmospheric Effects No-degraded Some degraded Degraded 9

System Requirements UAV standards/requirements Maximum speed: • 500 km/hr w/o payload • 440 km/hr with payload Payload limited to 40 kg (25 kg for optimal collision avoidance) 10

Sensor Requirements Consideration • • Real-time measurement capability (most important) Operational environment Payload constraints Air safety regulation (ELOS) 11

Real-Time Measurement Capability • Range/range rate • Bearing in azimuth • Elevation 12

Operation Environment • • • Day and night operational capability Vehicle maneuverability Endurance time in air Rain, wind, hail, lightning, etc. Electronic counter-countermeasures (ECCM) capability 13

Equivalent Level of Safety (ELOS) [1] Performance Parameter ELOS for See & Avoid Missed Distance 500 feet Field of Regard -Azimuth -Elevation Search Volume +/- 60º +/- 10º VFR Detection Range 1. 84 miles Time to Collision (11 sec avoidance maneuver) 21 sec (10 sec PRT) 23. 5 sec (12. 5 sec PRT) PRT: Pilot Reaction Time Number of Aircraft in Range Limited (5 -10) 14

Most Promising Method Non-cooperative active radar sensor used as primary collision avoidance sensor. Specifically the millimeter wave radar (MMW). However, cooperative methods such as TCAS and/or ADS-B could be considered an alternative option for the back-up system. 15

Obstacle Awareness and Collision Avoidance System (OACAS) Concept Consists of CAS radar sensor and OCAS processor. The CAS radar constitutes the antenna, transmitter/receiver, signal processor, and data processor. The OCAS processor can be contained in the radar data processor or be part of the Digital Flight Control Computer (DFCC). 16

Concept of OACAS Model [1] 17

Minimum Required Time to Collision Criteria [1] Velocity (Km/h) Time to Collision (sec) 5 11 17 23 25 S 500 0. 7 1. 5 2. 3 3. 2 3. 5 Km 600 0. 8 1. 8 2. 8 3. 8 4. 2 Km 700 1. 0 2. 1 3. 3 4. 5 4. 9 Km 800 1. 1 2. 4 3. 8 5. 1 5. 6 Km 900 1. 3 2. 8 4. 2 5. 8 6. 3 Km 1000 1. 4 3. 0 4. 7 6. 4 6. 9 Km Closing Speed Avoidanc e Mode Awarenes s Mode 18

Key Radar System Design Trade-off Parameters [1] Parameters To be traded-off Radar type Coherent or Coherent-on-receiver Power Module MPM or TRM or Magnetron Frequency Ka (35 GHz) or Ku band Antenna Type Dish or Planar type Range < Max 8 Km Resolution Range < 5 m PRF Type Low PRF <5 KHz or High PRF> 20 KHz Scan Coverage +/-90 deg in azimuth +20~-80 deg in elevation Scan Volume +/-60 deg azimuth +/-10 deg elevation Probability of Detection 90% for SW 2, RCS 1 m 2, Pfa=10 -6 19

CAS Radar Design Model (CAR) [1] 20

CAR Radar Design Parameters[1] CAS radar Design parameters meet and exceed requirements by the FAA Frequency 35 Ghz Scan Coverage 180º in Azimuth 100º in Elevation Detection Range 6. 4 Km Scan Rate 150 deg/sec PRF 2 KHz Antenna Beam Width 2. 5 deg Pulse Width 33 ns Antenna Gain 38 d. B System Bandwidth 30 MHz RCS 2~30 d. Bsm Range Resolution 5 m Prob. of False Alarm 10 e-6 Peak Power 3 Kw Prob. of Detection 90% 21

Obstacle Detection Problems There is slight discrepancy with the shape and actual size of stationary and moving objects detected by the radar. Problems can arise when extremely high accuracy is needed. 22

Conclusion After comparing both the cooperative and non-cooperative methods it was determined the non-cooperative methods are currently the most feasible. How ever the OASAS concept presented is a promising possibility of future avionics. QUESTIONS? 23

Cited Sources [1] Young K and Jung W Kang, “Obstacle Awareness and Collision Avoidance Radar Sensor System For Low-Altitude Flying Smart UAV” Korean Airspace Research Institute. Downloaded Jan 14, 2009 [2] Wikipedia, “Unmanned Arial Vehicle” http: //en. wikipedia. org/wiki/Unmanned_aerial_vehicle. Accessed on Jan 23, 2009. Last updated Jan 22, 2009. [3] Abizer Tyabji, “Unique problems associated with UAV employment” BNET Business Network; Flying Safety. Accessed on Jan 23, 2009 http: //findarticles. com/p/articles/mi_m 0 IBT/is_5_63/ai_n 19396165 Last Updated May, 2007. [4] Wikipedia, “Traffic Collision Avoidance System”, http: //en. wikipedia. org/wiki/TCAS#TCAS_I Accessed on Jan 24, 2009. Last Updated Jan 23, 2009. 24