IAI’s MICRO / MINI UAV SYSTEMS – DEVELOPMENT APPROACH

Avi Abershitz* Israel Aircraft Industries, Lod, 70100, Israel

David Penn, Amit Levy, Aviv Shapira , Zvi Shavit† Israel Aircraft Industries, Lod, 70100, Israel

Technological developments in the fields of computers, sensors, navigation, communications, photography, MEMS etc. now facilitates the production of Mini and even Micro UAVs, and the potential for these small UAVs has been demonstrated. These new developments in the domain of mini and micro UAVs have a potential for civil (Para-military) missions, based on technologies which until recently were non-existent. They can be utilized for various missions such as "over the hill" surveillance and reconnaissance, biological or chemical agent sensing and detection, damage assessment and as a communications relay. In addition to these military or paramilitary applications they could also be considered for border patrol, air sampling, police surveillance, crowd control etc.

I. Introduction

M INI UAVs are proliferating as an important aid used by military units for instantaneous and immediate online intelligence. These miniaturized air vehicles are identified to play a key role in the future of ground warfare,

low intensity conflict, urban warfare and law enforcement operations. It gives the operator a better idea of what might be over the next hill or in case of urban warfare what is around the next corner. Mini UAVs are now seriously considered for use in the operations of the military, police, fire departments units etc. Potential applications for these vehicles are Intelligence, Surveillance and Reconnaissance (ISR), search and rescue, pipeline inspection, perimeter control and border guard, biological or chemical agent sensing and detection and also to serve as a communications relay.

These UAV systems are designed to be operated by users with little or no experience. They must therefore be easy to operate and simple to deploy, so that any person familiar with a PC would be capable of operating it. Simplicity of operation is a major factor that will influence the popularity and the increase in applications of such systems. Mini and Micro UAVs must be capable of being launched and landed in almost any type of terrain and be affordable so that total loss, or damage to the vehicle would be bearable. In order to assure a low system cost and a short time to integrate, test and verify the system; it was determined that the majority of components must be commercially available off-the-shelf (COTS).

This paper presents an overview of the development programs currently underway in IAI, for micro and mini UAVs and their supporting systems. The Mini-UAV line includes the "BIRDY" with a wingspan of less than 1M and weighing about 1 kg, which began flying in 2002; and the BIRDEYE –500 in the 5kg class, which has demonstrated commercial capabilities. This paper also describes some demonstrations, which were performed on behalf of the military and the police, including flights over Neunen and over the central station of Amsterdam.

The micro-UAV Mosquito-1.5 in the 500 grams class with a wingspan of 300 millimeters has now reached the status of autonomous flight and operational capability. The Mosquito whose performance is limited to range of 1 mile and operational altitude of 500 feet, flew in January 2003 and achieved an endurance of over 45 minutes while providing on-line video information.

A new phase in micro / mini UAV development is presented with emphasis on reliability and safety, extending upwards to twin engine, electrical, mini UAVs in the 12kg class. The potential use of fuel cells is also evaluated.

This paper addresses the technological challenges and achievements, and describes the various development stages including flight-testing. It considers reliability and safety issues and the operation of this type of vehicle with * Manager – Autonomous Systems, Engineering Division. † Preliminary Design Department, Engineering Division.

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Infotech@Aerospace26 - 29 September 2005, Arlington, Virginia

AIAA 2005-7034

Copyright © 2005 by A. Abershitz. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.

respect to regulations. The concept of a total system approach is emphasized including an examination of cost effectiveness (performance versus cost) for various applications.

II. Mini UAV family – development process The challenge in developing mini UAVs lies in the requirement that a UAV should be small, lightweight, and

simple to operate, so that any human with no special skills of operating UAVs can operate it. Also the fact that it must be affordable dictates two further considerations; firstly that the price of the aircraft should be as low as possible and secondly that the operating costs must be low. In order to achieve these goals a gradual development approach was chosen in which the influence of each part and subsystem comprising the mini UAV system was considered and examined. A decision was taken to use “Commercial Off The Shelf” (COTS) components where available. The rationale behind this decision was to assure low cost of the system (no investment in developing the subsystem and components) and thus ensure a minimum time for integration, testing and verification of the system.

The study of critical systems incorporated understanding the characteristics of COTS components, integrating them into the system and analyzing their capabilities by ground and flight tests with commercial R/C model aircraft. These components included for example: - miniature video cameras, low weight and low power video transmitters, low cost GPS, electrical motors and different types of batteries. Only those parts unavailable as COTS were required to be developed.

We started by searching and testing miniaturized autopilot and video transmitters. We found a small and basic autopilot and a commercial video transmitter / receiver for indoor usage. An electrical engineer converted the output power of the video transmitter so that it was capable of transmitting for a distance of about 3 km. Having succeeded this far, the strategy for developing mini UAVs at the Engineering Division of IAI involved the following steps: (1) studying the characteristics of critical systems, (2) development of BIRDY Version-I, (3) development of BIRDY version-II (see Fig. 1), (3) development of a mini UAV BIRD-EYE 500 (see Fig 2).

Figure 1: BIRDY Version II Figure 2: BIRD-EYE 500

Figure 3: Hand Launching Figure 4: BIRD-EYE 500 Flight Test to 12 km

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Based on the experience obtained during the BIRDY development we concluded the full development of BIRD-EYE 500 within 5 months. The process included design and manufacture of the aircraft, design and manufacture of the gimbals and payload, assembly and integration of the avionics and flight-testing. For the first flights we used landing gear for takeoff and landing, which was performed automatically. When this phase was completed, we continued with hand launching (see Fig.3) and landing on the belly of the fuselage.

III. Flight testing and further development of mini UAVs

A. BIRDY The study started with testing these systems on a commercial model aircraft. We tested communications and

video transmission over a distance of at least 3km. Once these systems/components showed satisfactory results, it was decided to build the BIRDY version I, in order to study the aerodynamic characteristics of a small size UAV. This UAV weighs 600 gr. and its wingspan is 60 cm. After successful flight tests of this vehicle and an understanding of its aerodynamics characteristics, the next stage involved the integration of a COTS autopilot system, communications and video transmission system, and the testing of various electric motors and batteries. These changes caused an increase in the total aircraft weight and more room was needed for the subsystems, which obliged us to increase the airframe dimensions. The aircraft body and wing were up scaled to accommodate all the system and fly for at least one hour. This process ended with building a prototype of BIRDY Version-II (now named BIRD-EYE-100). This mini UAV was flown autonomously by waypoint control for a distance of 2 Km while transmitting live video.

B. BIRD-EYE 500 After completing the development of BIRDY Version-II, a new mini UAV was developed based on military

requirements found on the Internet. This mini UAV was named BIRD-EYE-500 (previously named SPY-THERE) and its total takeoff weight is 5 kg. An electrical motor powers the aircraft and its flight endurance is 1.5 hours. It carries a high quality camera, which is housed in two axes gimbals. A lightweight airframe was also designed and manufactured. The airframe comprises few subassemblies for quick and easy assembly and for readiness in the field. The aircraft flies autonomously by means of a preprogrammed waypoint route. The mini UAV can perform HOLD over a desired point in order to loiter over it. A simple and friendly user Ground Control Station (GCS) based on a rugged laptop, displays a map and designated waypoints; the position of the aircraft and its trajectory based on GPS are shown over it. Extensive flight-testing was conducted in order to calibrate the PID control loop of the autopilot. We also had to gain confidence and improve reliability, which resulted in a flight of more than 12 km. Fig. 4 shows the Ground Control Station and the UAV on the map, as it flies toward the red waypoint alongside the road. Fig. 5 shows the telemetry data for the north and east flight path. This UAV was also demonstrated to the police of the Netherlands and is described later.

Figure 5: Telemetry of flight test to 12 km

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C. Development of launching and recovery systems During the development we incorporated automatic takeoff and landing capabilities and tested it successfully.

When this phase was achieved, we developed an autonomous takeoff by using a bungee system (see Fig 6). This is based on two rubber bands which are hooked to the ground about 4 meters apart while the other ends are connected to a hook on the fuselage belly. When the aircraft is released by hand, the autopilot senses speed and pushes the electric motor to maximum power. Once the aircraft passes the ground hooks, the ropes falls away.

Since it was requirement to land on any type of terrain we needed a recovery capability. For this purpose we included a small parachute that is activated once the UAV is over the landing area. When the parachute is deployed it stops the forward velocity and the aircraft sinks down safely. At the same time, an aircushion is inflated and comes out under the fuselage to absorb the impact when the aircraft touches the ground (see Fig. 7).

Figure 6: Bungee launch Figure 7: Parachute and aircushion recovery

IV. Demonstrations of mini UAVs

D. Demonstration in the Netherlands The police of the Netherlands and in particular the head of the police of Amsterdam wished to examine the use

of mini UAVs for police activities. IAI took up the challenge of performing this demonstration according to the police requirements. The demonstrations were conducted over a period of five days and involved flying and following traffic on highways and also following a train. We also had to find a herd of sheep in a field and a barrel on fire. Most of the flight took place in the city of Neunen and over the central station of Amsterdam, involving flying over high buildings and inspecting boats entering the harbour.

Figure 8a: Over the central railway station Figure 8b: Train leaving the station

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Figure 8c: Over high building

Figure 8: Video photos from flight over Amsterdam

Figure 8 shows three photos taken during the flight over Amsterdam’s central station area. BIRD-EYE 500 flew

autonomously towards waypoints that were assigned over the digital (scanned) map of Amsterdam. The specified waypoints and places to fly to were selected by the police officer.

V. New power plant studies One of the main aspects of mini UAVs is the energy for the motor. It is assumed that the motor will be electrical

for ease of operation, maintenance, logistics and safety compared to gasoline. Two directions were considered and investigated: - fuel cells and solar cells.

E. Fuel cells The Engineering Division of Israel Aircraft Industries (IAI) wishes to demonstrate an all-electric mini-UAV

powered by fuel cells (FC). The demonstration is intended to provide proof of concept that fuel cell technology can be adapted to a wide range of future all-electric UAV designs. The rapidly emerging fuel cell power technologies which are intended for the automotive industry, can be used to launch a new revolutionary electrical propulsion system for UAVs.

The fuel cell is a very promising energy supply. It can be seen from the comparison table (Fig. 10) that fuel cells provide much more energy than the current high technology batteries, and there are already some products on the market which we are studying, and considering using for demonstration.

The main advantages are low noise and low emissions. In the case of using pure hydrogen fuel, the result is zero emission or low emission. Other advantages of an all electric aircraft are: - high reliability, low maintenance, only slight reduction in engine performance due to altitude, and easy start up of engine.

The Engineering Division is leading this R&D program and a preliminary design of the UAV to demonstrate the use of fuel cells is completed, and the proposed aircraft is shown in Fig. 9. The demonstration will involve the development and ground testing of a fuel cell engine with respect to propulsion and other requirements, and its integration into a purpose designed mini-UAV, which will be flight tested.

The planned mini-UAV project stages are is as follows: Fuel cell engine development/purchase. Design and production of a fuel cell Mini-UAV that meets the requirements, taking into account the fuel

cell propulsion system, avionics, aerodynamics and structure. Flight test of the all-electric Mini-UAV with Li-ion batteries. Integration of the fuel cell propulsion system on board. Flight test with the fuel cell propulsion

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Figure 9: Proposed UAV to fly with fuel cells energy

Fuel Cells Technology 200 watts/kg, Hydrogen gravimetric efficiency 6%

Figure 10: Comparison table - Li-Ion Vs. Fuel Cell

F. Solar Energy Cells For a long time man has tried to take advantage of the unlimited energy of the sun: - it is powerful and available,

and most important it is free!. As time progresses, technology is advancing and solar cells are becoming more and more efficient and therefore more applications across the world are becoming “solar” by the day. With the evolvement of batteries in the past few years, a solar electric system is becoming more favorable than ever.

The Engineering Division of IAI has developed an autonomous unmanned air-vehicle that exploits the sun’s energy for long endurance. The term “long endurance” takes on a new meaning with the new tactical solar UAV called “Sunrider” (Fig. 11). A typical mission for the “Sunrider” will start on March and will end somewhere in September. Theoretical calculations performed during preliminary design indicate that under standard atmospheric conditions, the energy absorbed during the day in these months, should suffice for night operations. Therefore IAI will introduce a world breaking solar UAV which promises a LOW COST and LONG ENDURANCE system. Next year, a demonstrator should roll off the drawing board and into the skies.

The demonstrator will use state of the art electric components such as: - very high efficiency solar cells, advance high capacity batteries, high power electric engine and an autonomous flight control system. Redundant energy is stored during the day for night operation. The demonstrator will carry a 1.5 Kg payload and 5.5 Kg Li-Poly batteries. With a span of more than 5.5 meters and a cruise velocity of approximately 25 knots, endurance will

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surpass the 24-hour barrier. In the wintertime when the sun is low and the winds are strong, non-rechargeable batteries are used, but only one-day endurance can be achieved.

Solar energy is certainly the future, and it is safe to say that the “Sunrider” is opening the door for many future solar UAVs.

Figure 11: The Sunrider UAV

VI. Micro UAVs This section describes the development of the Mosquito Micro Air Vehicle (MAV). The present configuration,

the Mosquito 1.5 is an electrically powered 450 grams MAV with a wingspan of 340 mm. The maximum-recorded endurance is 58 min. The Mosquito 1.5 is shown in fig. 12.

The Mosquito is designed to provide “over the hill” intelligence, biological or chemical contamination monitoring, and damage assessment. In addition to military missions, para-military and commercial applications missions were considered such as: - border patrol, air sampling, police surveillance, crowd control etc.

The Mosquito project was launched in the 3rd quarter of 2001, and the preliminary phase consisted of a literature survey and feasibility study.

Several industries and academic institutes in Israel are involved in this project which is coordinated by IAI. The primary development topics of the project are listed below:

• Air Vehicle Technology • Power Sources Technology

o Electrical o Fuels

• Propulsion Systems Technology o Electrical motor o Micro jet engine o Miniature & ultra lightweight internal combustion engine

The aerodynamic configuration of the Mosquito-1 was developed during 2002. It consists of an inverse Zimerman flying wing, which in literature showed best performances than other wing plan forms and has an aspect ratio less than 2 for higher endurance. An airfoil suitable for low Reynolds numbers was selected.

Prototype manufacturing started at the end of 2002 and the first flight in RC mode was performed in January 2003. The Mosquito-1 demonstrated good flight capabilities and 31 minutes endurance. Later, the Mosquito 1 was used as a “test-bed” for components, primary batteries and electric motors. Fig. 13 shows the RC components that were used during the early stages of the project.

Figure 12: Mosquito 1.5 Figure 13: Mosquito components

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The Mosquito 1 comprises of the following: - • Energy source: - Self developed primary and rechargeable Lithium Polymer batteries. • Battery power: - 25-45 Watt • Physical: -

o TOW: 250-300 gr. o AR = 1.8 o Wing loading = 0.95 lb/sq-ft o Max L/D efficiency = 5

• Operation: Futaba RC, hand launch, belly recovery • Flight test objectives were: -

o Flight qualities o Performance o Real time video transmission

During 2004, IAI developed the Mosquito 1.5. This MAV configuration was designed for autonomous operation. The system requirements are listed below:

• Over the hill intelligence • Real time video transmission

o Present: - Daytime color video o Future: - IR camera

• Completely autonomous operation • Simple operation – short training • Low acoustics and visibility signatures • GCS based on rugged laptop • Image display on GCS/PCU (Payload Control Unit) • Electrical propulsion • Total weight: 150-500 gr • Operational radius: - up to 1 mile • Operational altitude: 100-150 m • Endurance: 1 hr. • Compactness: - wingspan range 200-400 mm

The MAV configuration development included a detailed CFD analysis. Typical results are depicted in fig. 15.

Later on IAI carried out wind tunnel tests, which improved the analysis, thus increasing our confidence in the flying characteristics and autopilot design. Wind tunnel results are shown in fig. 14.

Figure 14: Wind tunnel test results

The Mosquito 1.5 utilizes a combination of COTS and uniquely developed components. The motor depicted in

fig. 16 is among the items developed specifically for the Mosquito. The first 12-minute autonomous flight was carried out in June 2004. Until now, over 150 flights have been

carried out.

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Figure 15: CFD analysis for Mosquito Figure 16: The motor developed for Mosquito

The internal layout of the Mosquito 1.5 is illustrated in fig. 17. Its payload consists of a gimbaled, miniature, color video camera delivering real time video imagery to the ground control station, which typically consists of a Laptop PC / PDA. Fig. 18. shows a video imagery obtained from 400 ft AGL.

Figure 17: Mosquito 1.5 Figure 18: Video transmitted from Mosquito

Figure 19: Mosquito system Backpack

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A tailored backpack was developed to allow the user immediate deployment of the system. The backpack, which is shown in the following fig. 19, consists of two Mosquito 1.5 MAVs, command and control computer, radio equipment, batteries and miscellaneous items.

VII. Conclusion Three main development stages were undertaken until a final mini UAV configuration was designed,

manufactures and tested in flight, and demonstrated in operation. The system was demonstrated to the military and to the Dutch police and included few days of flights in the vicinity of Neunen and over the central station of Amsterdam. The important conclusions are: -

• Taking advantage of the incremental development process, significantly cut R&D investment. • Using appropriate COTS components reduced development risk and system cost; so that production,

flight testing and completion of a full system was enabled in a very short time. • A very similar procedure was taken in the micro UAV development.

New developments are underway which could be incorporated in new generations of UAVs; especially in the field of electrical energy such as fuel cells and solar energy.