Richard Kuchar

The DLR Robot Motion Simulator Part I: Design and setup

In recent years a new generation of motion simulators, based on serial kinematics industrial robots, emerged as alternative to the currently prevalent Steward-platforms. This paper presents the newest addition to this: The DLR Robot Motion Simulator.

Design, Implementation and Flight-Tests of Incremental Nonlinear Flight Control Methods

This paper presents the design and implementation of incremental backstepping (IBS) flight control laws for the attitude control and stabilization on a fixed-wing aircraft. The design consists of multiple functionalities such as command-filtered backstepping, angle of attack control and body attitude control, that are based around an incremental control inner loop that tracks the angular rates of the aircraft. The results include flight data of an integrated IBS design that validate simulation results of control laws shown previously in literature. The results show that it is possible to implement robust nonlinear flight control laws that are easy to tune and require only little knowledge about the system dynamics parameters.

Design and Flight Testing of Incremental Nonlinear Dynamic Inversion-based Control Laws for a Passenger Aircraft

This paper describes the design, implementation and flight testing of flight control laws based on Incremental nonlinear Dynamic Inversion (INDI). The method compares commanded and measured accelerations to compute increments on the current control deflections. This results in highly robust control solutions with respect to model uncertainties as well as changes in aircraft dynamic characteristics of failure cases during flight. At the same time, the complexity of the algorithms is similar to classical ones. The key for practical implementation is in ensuring synchronization between angular acceleration and control deflection measurements or estimates. The underlying theory and practical design methods of INDI are very well understood, but implementation and testing has remained limited to sub-scale UAVs. The main contribution of this paper is to present the design and validation of manual attitude control functions for a Cessna Citation II experimental aircraft, covering control structure design, application of INDI, design optimization, robustness analyses, software implementation, ground and flight testing. For comparison, also control laws based on classical Nonlinear Dynamic Inversion were implemented and flown. The flight tests were highly successful and marked the first successful demonstration of INDI on a CS-25 certified aircraft. The flight test results proved that INDI clearly outperforms NDI and provided valuable lessons-learnt for future applications.

Stability and Control Investigations in Early Stages of Aircraft Design

This paper provides an overview of current activities of DLR (German Aerospace Center) with respect to stability and control investigations in the context of early stages of aircraft design. For this purpose, DLR follows an interdisciplinary and multi-level design approach. Using an integration framework in combination with a central data exchange format, largely automated process chains are set up that combine calculation and simulation capabilities of the multitude of disciplines required in early aircraft design. Rather than using empirical relations and assumptions based on experience, the underlying methods applied by the tools are mainly based on physical model representations. The major aim of this design approach is to generate all relevant data needed for stability and control investigations, including aerodynamic damping derivatives and to assemble them within a flight dynamics model. Not only does this approach allow for an early consideration of stability and control characteristics, but it also respects interdisciplinary effects and enables automated design changes. This paper describes the infrastructure used for setting up the described process. It presents disciplinary tools used to calculate engine performance maps, calculate aerodynamic performance maps and structural properties, generate flight dynamics models with associated control laws and to assess aircraft handling qualities. Furthermore, this paper provides application examples of early stability and control considerations, using integrated interdisciplinary process chains. This comprises a handling qualities assessment under uncertainty considerations and vertical tailplane sizing for a blended wing body. In addition, engine and split flap sizing processes for an unmanned combat aerial vehicle are shown. The interdisciplinary design approach presented here, serves to find a well justified early configuration and reduces the risk of later design changes.

A versatile Simulation environment for Design Verification, System Integration Testing and Pilot Training of a diamond-shaped Unmanned Aerial Vehicle

The OpenInnovation/Sagitta project – under the lead management of Airbus Defence and Space and the active participation of numerous academic institutions\footnote[2]{TU Munich, University of the Armed Forces Munich, TH Ingolstadt, TU Chemnitz and the German Aerospace Center (DLR)} – has its focus on the contribution of innovative technologies within the scope of unmanned aviation. As part of the project, the Sagitta Demonstrator UAV has been constructed, tested and finally flight tested at the Overberg flight test range in South Africa. Before the actual flight tests were performed, intensive simulation and integration testing activities as well as operator training sessions in advance of its maiden flight had to be performed along with the general progress of the project. This paper is dedicated to the description of the general setup of the employed Simulation and Integration Testing environment (SIT) for this aircraft, continued with a specific focus on the implementation of the flight dynamics model (FDM), landing gear model (LDG) and respective systems models as well as the data flow between these entities. The utilized setup and fault insertion capabilities are presented, that provided a good preparation base for all involved personnel. Finally the respective models embedded within the overall simulation setup are compared with currently available flight test results.

A Rapid-prototyping process for Flight Control Algorithms for Use in over-all Aircraft Design

This paper describes the development and current status of a fully automated aircraft model integration and preliminary control law design process for use in aircraft over-all design. This process allows addressing flight control algorithms as a prime design variable from the earliest design stages, and facilitates multi-disciplinary aircraft over-all dynamic design analyses in for example Multi-disciplinary Design Optimization. The approach taken in this work is to address the flight control algorithms at a specification level (e.g. dynamic response parameters) and newly synthesize according algorithms adapted to the current aircraft design configuration by means of a rapid-prototyping process. This in turn enables the use of dynamic analyses in all disciplines involved (flight loads, systems, performance) from the earliest design stages, increasing accuracy, reducing conservativeness in multidisciplinary optimization, and reducing risk by increasing compatibility with dynamic analyses performed in detailed design stages. In order to ensure the latter, the proposed control law prototyping process has been developed to naturally evolve into detailed design of the flight control system.