19-1 Reliable Autonomous Precise Integrated Navigation FLAPIN for Present and Future Air-Vehicles Dr. Thomas K(rhler - Daimler-Benz Aerospace AG Military Aircraft (Ottobnmn) P.O. Box 801160,81663 Muenchen, Germany Tel: +89-607-24635 Fax: +89-607-32074 E-mail: [email protected] Franz Tumbrilgel - Daimler-Benz Aerospace AC Military Aircraft (Bremen) Dr. Jllrgen Beyer - Honeywell Regelsysteme GmbH (Maintal) 1 SUMMARY 2.1 Mativntion The operation of unmanned vehicles ranging from strategic Daimler-Benz Aerospace AG - Military Aircraft (Dasa-M) is missions of auronomous hjgh altitude reconnaissanceto tactical concentrating on the following unmanned air vehicle (UAV) missions of reconnaissance and strike/attack impose new re- missions: quirements to the guidance systems in the area of reliability and safw. This includes all phases of the mission start, cruise, -Unmanned latforms with flight -attack/strike and ‘Low Level’ operation including precision profiles above the current airways (above FL 500) Their use approaches even under bad weather conditions and in a hostile lies predominantly in the areas of peace keeping and crisis environment. control and involves flight over long distances over friendly territory. The flight scenario consists basically of start cruise A reliable, continuous and precise navigation system is of and landing. Where stti and landing incl. penetration of the paramount importance for the guidance function even more for ‘controlled airspace’ will take place in a friendly envimnment unmanned air vehicles. The Project RAPIN, the name standing with the possibility of direct human control (video & data link). for ‘Reliable Autonomous Precise Integrated Navigation’, com- Human involvement during mission (with long delays) is pos- bines the navigational research activities at Daimler-Benz sible via satellite links. In case of jamming or malfimction a Aerospace AG (Dasa) Military Aircraft teamed with Honeywell ,,safe termination” function has to be implemented. ,,Safe ter- Regelsysteme GmbH in that context. RAPiN integrates ‘Laser mination” refers under these circumstances to a controlled Inertial Navigation System’ (LINS), P(Y) code ‘Global Posi- landing in a predefined uninhabited area using a steerable tioning System’ (GPS) and ‘Terrain Referenced Navigation’ parafoil. These strategic missions experience a long duration system (TRN). The data fusion concept is to combine all avail- from 1Ohr up to 48hr. able information in one MAIN filter gaining the highest accu- racy. In order to provide uncontaminated backup solutions in The navigation system has to provide the ability to guide the case of sensor failures a bank of SUB filters is working in vehicle to a ‘safe’ landing facility. The size of the emergency parallel. Each SUB filter uses a different subset of sensor landing places determines the requirement on the navigation signals. It is the objective of this paper to report on the system system accuracy. Over friendly territory this guidance function concept, the design of the prototype, and to describe the reali- is expected to be safety involved with the requirements in sation process. Subsequently the paper will present first and system layout (fail-operational) and dependability. Due to the preliminary results including flight trials on C-160 Transall high operating altitude a terrain correlation system is not appli- ANAJFRA (Autonome Navigationsanla- cable. It is assumed that a INS/GPS design with the necessary ge I’ Flugregelungsanlage) performed by the .,Wehrtechnische redundancy is appropriate. In case of general GPS unavailabil- Dienststelle 61“. The possible application of this generic sys- ity an image correlation system or a star-tracker could aid the tem varies from uninhabited reconnaissance / fighter aircraft navigation system. over transport aircrafi to rescue helicopters. - Unmanned autonomous reconnaissance alatforms which are operated at medium fo low altitudes in a military target area and cruise above FL 200. On their return phase they will operate 2 INTRODUCTION over friendly territory with the above mentioned requirements This paper describes the current research and development regarding safety. activities under the lead of Daimler-Benz Aerospace AG (Dasa) Military Aircraft in the field of fault-tolerant integrated naviga- Here a more accurate navigation system is necessary, for the tion systems. After a brief discussion of our motivation we will low level operation and the system has to cope with adverse define the goal and the statement of work of this project. Sub- conditions (manoeuvring of the airframe, jamming and other sequently we will introduce the involved partners. threats by hostile forces). Due to the expected unavailability of GPS in the operating scenario and the low operating altitude a terrain referenced system with its full autonomous non- jamming capability should be employed. Paper presented at the AGARD MSP Symposium on “System Design Considerations for Unmanned Tactical Aircraft (UTAJ”, held in Athens, Greece, 7-9 October 1997, and published in CP-5W. 19-2 - Unmanned tactical aircraft to fly strike and/or attack missions l demonstrate function and performance in flight tests in a conflict. Even though this class of aircraft operates pre- l produce generic specification for navigation systems for. dominately over hostile territory, it will be dispatched fcom future product applications with requirements regarding friendly bases and therefore fly partially over friendly territory. high dependability Also, to minimise collateral damage, the system accuracy and l build up supplier’s system relevant realisation know how reliability should match that of current manned aircraft. As a realisation restriction all the existing navigation compo- The navigation system has to be designed for ‘low level’ and nents have to be used unchanged, which is due to some system cruise operations with mixed traffic in the ‘controlled airspace’. implementation benefits and aviation administration require- Still being undefined it is expected that high requirements ments as well. regarding safety and accuracy have to be met. As a consequence and to compensate for the missing human on 2.2.2 Operadonal Aspect board, all these aircraft need a system architecture which allows RAPIN is focusing on military low level flight operation sce- to limit the failure probability of the whole system to the same narios, Present and future mission requirements of military air low values which are placed on manned aircraft by the civilian vehicles, stand-off-weapons, drones, transport aircraft and of certification authorities if operated over own territory or in unmanned tactical aircraft dictate accurate and dependable peace keeping missions. navigation as a means to increase survivability and mission Historically the project RAPiN was defined for a transport effectiveness. Navigation systems will be increasingly used to aircraft with ‘low-level operation’ capability as the major target deliver precise position, velocity and track data to the flight scenario. No forward looking radar was permitted in the design. control system to guide aircrafi during low level flights This caused demanding requirements on the navigation func- (approach and landing, terrain following, terrain and threat tion and the digital terrain data base regarding dependability avoidance). In this case, the navigation signals are flight safety and accuracy. critical and the dependability (integrity, continuity, survivabil- ity and availability) becomes the major system requirement. Reviewing the flight guidance requirements of unmanned air- craft leads to the conclusion that the RAPM system design has Especially in unmanned air vehicles like military reconnais- a high potential of fblfdment for UAV needs. sance UAV’s or uninhabited fighters, which have a long flight- endurance not only above war-theatres but even over inhabited Operating under military conditions the navigation system has areas, the navigation system reliability is even more important also to be operated autonomous, without support from ground than in manned aircraft. Here, no pilot can verify the correct stations (risk of jamming, detecting, and destruction of ground operation of the avionics-system and can take over system- stations). As no w state of the art navigation sensor can control if a system-failure occurs. meet the accuracy, reliability and robustness requirements, integrating well suited individual navigation sensors is pres- Thus autonomous navigation components are favourabIe for ently the only viable solution to this problem. system survivability, availability and continuity reasons. Re- dundancy will be stressed in terms of system reliability and Even the common used LMS GPS integration is on its own not integrity. Due to jamming in the hostile environment P(Y) code reliable enough. In order to achieve the position accuracy with GPS is seen to be useful as an aiding sensor albeit having to the requested reliability for ‘low level operations’ at least two play a ‘nice to have but add on’ role in the system concept. physically independent position sensors with a similar accuracy are required to co-operate with an additional autonomous navi- A secondary objective of project RAPM in that context is gation system like LINS. This kind of navigation system is answering the question whether military precise approach and where we will focus on in this paper. landing is possible in terms of accuracy using a P(Y) code GPS receiver and/or TRN instead