Flight Mechanics, Flight Control and Aeroelasticity

LAPAZ - Luft-Arbeits-Plattform für die Allgemeine Zivilluftfahrt

LAPAZ is a three-and-a-half-year (Jan. 1, 2007 - Aug. 31, 2010) project funded under the National Aeronautics Research Program (LUFO IV) to develop an automatic flight control system for aerial workhorses.

 

Introduction

For a wide range of tasks in geo-exploration, environmental protection, disaster control, fisheries, coastal and border surveillance, there is a worldwide need for powerful, efficient and cost-effective aerial workhorses. They must be able to fly specified flight profiles with high precision and maneuver safely close to the ground or obstacles. Typical payloads are in the range of 150 - 300 kg.

The problem with today's workplanes is their size, the often multi-member crew and the associated costs. Better suited are specially designed, single-engine workplanes with a takeoff weight of about 1 ton. The STEMME aviation company is developing such aircraft, but the highly reliable, automatic flight control systems needed for aerial work have yet to be developed. Control systems of business, commercial and military aircraft either lack the required functionalities or are too heavy and too expensive. Commercial autopilots for small sport aircraft fall far short of meeting the requirements for dynamics, functionality, reliability and precision.

Objectives

The aim of the research project is to develop and demonstrate a reliable and high-precision control system. This will be modular, fault-tolerant and scalable so that it can be easily adapted to new types of tasks. In addition, the requirements for a safety-critical system are to be met at a cost that is in line with the market.

 

Project Plan

AP1000RequirementsDefinition of the "High Level Specifications". This includes the requirements for the airborne workhorse in terms of functional scope, safety requirements and mission spectrum, as well as defining the requirements for individual system components such as sensors, actuators, etc.
AP2000Aircraft development & measurement flightsIntegration of relevant system components such as extended measurement sensors into the demonstration aircraft. Execution of required measurement flights to identify the STEMME S6 system.
AP3000Flight control & flight control lawsParameter identification and development of flight mechanical models of the demonstration aircraft. Design of flight control structure and development of flight control software.
AP4000Computer PlatformHardware and software development and verification of the flight control computer platform.
AP5000Software and hardware verificationIntegration of the control software developed under AP3000 into the computer platform designed under AP4000. Verification of the functionality of the overall platform using appropriate test environments.
AP6000Integration & Flight TestIntegration of the flight control platform into the demonstration aircraft and execution of test flights for certification.
AP7000EvaluationFinal evaluation of test results regarding flight characteristics and behavior of the integrated hardware.

Tasks of the TU Berlin

The task of the TU Berlin is the development and implementation of the flight control software. To this end, it is primarily involved in the project areas AP1000, AP3000, AP5000, AP6000 and AP7000. In addition to defining top level specifications for the flight control system and the corresponding sensor technology, the department develops flight mechanical models based on the test data from AP2000, which serve as the basis for designing the controller structure and the control laws.

In view of a later implementation, e.g. as an OPV (optionally piloted vehicle), the process of software development is carried out as close as possible to the RTCA/DO-178 guidelines for software in safety-critical applications. The designed control algorithms are implemented accordingly in computer code and the specifications defined under AP1000 are verified by means of a real-time simulation environment.

Results

The three-year LAPAZ technology project funded by the German Federal Ministry of Economics and Technology as part of the 4th Aeronautics Research Program has ended extremely successfully with the flight testing of the novel LAPAZ automatic flight control system for aerial work aircraft. The TU Berlin was responsible for the development of the controller functions and the flight-mechanical modeling required for this. After careful testing of the control laws in the simulator and in the laboratory and integration of the system into a modified Stemme S15, the flight control system was subjected to an extensive test program (approx. 40 hours of flight tests). A detailed description of the results can be found in our press release.

 

Project Partners

  • STEMME AG
  • Institut für Luftfahrtsysteme (ILS) der Universität Stuttgart
  • Institut für Luft- und Raumfahrttechnik (ILR) der TU Berlin