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AIAA Science and Technology Forum and Exposition, AIAA SciTech Forum 2025

作者： Gäßler, Björn Robens, Johannes German Aerospace Center Institute for System Dynamics and Control Space Systems Department DLR German Aerospace Center Institute of System Dynamics and Control OberpfaffenhofenD-82234 Germany

ISBN: (数字)9781624107238

ISBN: (纸本)9781624107238

The Reusability Flight Experiment (ReFEx) is a technology demonstrator developed by the German Aerospace Center (dlr) for a launch vehicle with vertical takeoff and horizontal landing capabilities. Its objective is to verify key technologies critical to the reusability of a launch vehicle’s first stage and boosters. During atmospheric flight, the vehicle’s trajectory spans a wide range of Mach numbers and angles of attack. The vehicle encounters substantial shifts in dynamic pressure and highly nonlinear aerodynamic effects. These include sign changes in the control derivatives and singularities, where the lateral motion may become uncontrollable. The aerodynamic control surfaces, which are applied to control the vehicle’s attitude, exhibit strong cross-coupling and varying effectiveness. Given the uncertainties in the vehicle’s mechanical properties and aerodynamic data, a reliable control design capable of handling the uncertainties and disturbances is essential. The flight controller presented in this paper addresses these challenges by combining a cascaded control architecture based on nonlinear dynamic inversion (NDI) with an incremental NDI approach for control allocation. For fast guidance reference signal tracking the presented controller employs feed-forward control while uncertainties, disturbances and model mismatches are compensated by linear feedback controllers. A control allocation based on a damped-least squares optimization approach determines aerodynamic control surface deflections and prevents excessive control actions in the vicinity of singularities. Simulation results and Monte Carlo campaigns validate the selected control approach and demonstrate that the proposed flight controller is capable of tracking the trajectory in the presence of disturbances and uncertainties. © 2025, American institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Angle of attack

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A multishift Hessenberg method for pole assignment of single-input systems

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IEEE TRANSACTIONS ON AUTOMATIC CONTROL 1996年第12期41卷 1795-1799页

作者： Varga, A DLR-Oberpfaffenhofen Institute for Robotics and System Dynamics German Aerospace Research Establishment (DLR) Wessling Germany

A new algorithm is proposed for the pole assignment of single-input linear time-invariant systems, The proposed algorithm belongs to the family of Hessenberg methods and is based on an implicit multishift QR-like technique, The new method compares favorably in many respects (speed, memory usage) with existing numerically stable methods, Its improved vectorizability guarantees good opportunities for parallel implementation on high-performance computers.

关键词： Eigenvalues and eigenfunctions Symmetric matrices Aerodynamics Concurrent computing State feedback Control systems Controllability Robot kinematics Costs

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ROBUSTIZATION OF A LEARNING-METHOD FOR RBF NETWORKS

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NEUROCOMPUTING 1995年第1期9卷 85-94页

作者： SANCHEZ, VD German Aerospace Research Establishment DLR Oberpfaffenhofen Institute for Robotics and System Dynamics D-82230 Wessling Germany

Outliers in a given training data set can cause substantial deterioration of the approximation realized by a neural network architecture. Robustization refers to the process of enhancing a learning method to deal with data containing outliers. The robustization of a learning method for training RBF networks for function approximation is presented leading to a novel efficient robust learning method for this architecture class. Its experimental evaluation confirms the expectations created from its theoretical foundations.

关键词： FUNCTION APPROXIMATION LEARNING FROM EXAMPLES NETWORK SYNTHESIS RADIAL BASIS FUNCTIONS REGRESSION ROBUST LEARNING METHODS

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Robots in space - A survey

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ADVANCED robotics 1995年第6期9卷 625-651页

作者： Hirzinger, G DLR (German Aerospace Research Establishment) Institute for Robotics and System Dynamics Oberpfaffenhofen Wessling D-82234 Germany

The paper tries to outline the state of the art in space robotics. It discusses the technologies used in ROTEX, the first remotely controlled space robot which flew with the shuttle Columbia in April 1993, but it also gives a review of the major space robot projects envisioned by different nations for the next decade. The mechatronics and dynamics aspects of space robots including free-flying systems are briefly discussed. Broader attention is given to the telerobotic and teleoperational control loop structures, including predictive delay-compensating graphics simulation. The paper finally tries to emphasize that by task-level programming (involving 'learning by showing' on a high level) future space robots will be powerful tools for scientists and ground operators which are not robot specialists. The tele-sensor programming concept of ROTEX was a first step in this direction. We plead for flying a variety of space robot systems in the near future in order to enhance experience with and confidence in these technologies as quickly as possible.

关键词： robotics

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ROBUST DECOUPLING, IDEAL STEERING dynamics AND YAW STABILIZATION OF 4WS CARS

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AUTOMATICA 1994年第11期30卷 1761-1768页

作者： ACKERMANN, J [a]German Aerospace Research Establishment (DLR) Institute for Robotics and System Dynamics Oberpfaffenhofen D-82230 Wessling Germany

Four-wheel car steering is modeled by a single-track model with nonlinear tire characteristics. A generic control law for robust decoupling of lateral and yaw motion by yaw-rate feedback to front-wheel steering is derived. Ideal steering dynamics are achieved by velocity-scheduled lateral acceleration feedback to front-wheel steering. For robust yaw stabilization a velocity-scheduled yaw-rate feedback to rear-wheel steering is given, by which the linearized system gets velocity-independent yaw eigenvalues.

关键词： AUTOMOBILES ROBUST CONTROL DECOUPLING NONLINEAR systemS

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SLIDING MODE CONTROL FOR GRADIENT TRACKING AND ROBOT NAVIGATION USING ARTIFICIAL POTENTIAL FIELDS

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IEEE TRANSACTIONS ON robotics AND AUTOMATION 1995年第2期11卷 247-254页

作者： GULDNER, J UTKIN, VI DLR Institute for Robotics and System Dynamics Wessling Germany

This paper introduces a sliding mode control strategy for tracking the gradient of an artificial potential field, The control methodology is applicable to fully actuated holonomic robotic systems with n-degrees of freedom, The controller yields exact tracking of the gradient lines and is invariant with respect to parametric uncertainty and disturbances in system dynamics, A detailed case study for mobile robots introduces the equilibrium point placement method for designing harmonic planar potential fields for circular obstacle security zones. Diffeomorph mappings can be utilized for more complex obstacle security zones, The gradient of the harmonic potential field is shown to always lead away from the obstacle security zone and to continuously approach the goal point.

关键词： Sliding mode control Navigation Control systems Mobile robots Mechanical systems Force control Security Motion control Torque control Actuators

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Learning shape from shading by a multilayer network

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IEEE TRANSACTIONS ON NEURAL NETWORKS 1996年第4期7卷 985-995页

作者： Wei, GQ Hirzinger, G Institute of Robotics and System Dynamics German Aerospace Research Establishment Oberpfaffenhofen Germany

The multilayer feedforward network has been usually used for learning a nonlinear mapping based on a set of examples of the input-output data, In this paper, we present a novel use of the network, in which the example data are not explicitly given, We consider the problem of shape from shading in computer vision, where the input (image coordinates) and the output (surface depth) satisfy only a known differential equation, We use the feedforward network as a parametric representation of the object surface and reformulate the shape from shading problem as the minimization of an error function over the network weights, The stochastic gradient and conjugate gradient methods are used for the minimization, Boundary conditions for either surface depth or surface normals (or both) can be imposed by adjusting the same network at different levels, It is further shown that the light source direction can be estimated, based on an initial guess, by integrating the source estimation with the surface estimation, Extensions of the method to a wider class of problems are discussed, The efficiency of the method is verified by examples of both synthetic and real images.

关键词： Shape Nonhomogeneous media Computer vision Differential equations Computer errors Stochastic processes Gradient methods Minimization methods Boundary conditions Light sources

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Parametric shape-from-shading by radial basis functions

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IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE 1997年第4期19卷 353-365页

作者： Wei, GQ Hirzinger, G Institute of Robotics and System Dynamics German Aerospace Research Establishment Oberpfaffenhofen Germany

In this paper, we present a new method of shape from shading by using radial basis functions to parameterize the object depth. The radial basis functions are deformed by adjusting their centers, widths, and weights such that the intensity errors are minimized. The initial centers and widths are arranged hierarchically to speed up convergence and to stabilize the solution. Although the smoothness constraint is used, ii can be eventually dropped out without causing instabilities in the solution. An important feature of our parametric shape-from-shading method is that it offers a unified framework for integration of multiple sensory information. We show that knowledge about surface depth and/or surface normals anywhere in the image can be easily incorporated into the shape from shading process. It is further demonstrated that even qualitative knowledge can be used in shape from shading to improve 3D reconstruction. Experimental comparisons of our method with several existing ones are made by using both synthetic and real images. Results show that our solution is more accurate than the others.

关键词： shape from shading radial basis functions hierarchical structure depth constraints normals constraints qualitative knowledge stochastic gradient method

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Computation of coprime factorizations of rational matrices

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LINEAR ALGEBRA AND ITS APPLICATIONS 1998年第1-3期271卷 83-115页

作者： Varga, A DLR—Oberpfaffenhofen Institute of Robotics and System Dynamics P.O.B. 1116 D-82230 Wessling F.R.G.

We propose numerically reliable state-space algorithms for computing several coprime factorizations of rational matrices: (1) factorizations with factors having poles in a given stability domain;(2) factorizations with proper stable factors;(3) factorizations with inner and J-inner denominators. The new algorithms are based on a recursive generalized Schur algorithm for pole dislocation. They are generally applicable whether the underlying descriptor state-space representation is minimal or not, and whether it is stabilizable/detectable or not. The proposed algorithms are useful in solving various computational problems for both standard and descriptor system representations. (C) 1998 Elsevier Science Inc.

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Real-time visual servoing for laparoscopic surgery

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IEEE ENGINEERING IN MEDICINE AND BIOLOGY MAGAZINE 1997年第1期16卷 40-45页

作者： Wei, GQ ARbter, K Hirzinger, G German AeroSpace Research Establishment Institute of Robotics and System Dynamics DLR Germany

The authors propose a visual tracking method for stereo laparoscopes, which is robust, simple, and operates at a maximum rate of 17 Hz. The use of a stereo laparoscope enables the robot to track the instrument in both lateral and longitudinal motions. Due to the multiplicity of problems with shape analysis, the authors do not check for the presence of any particular shape or structure. Instead, they use color information alone for instrument segmentation. The non-uniqueness of the instrument color inspires the authors to distinguish it by use of an artificial color mark. They analyzed the color distribution of typical laparoscopic images and chose a color that did not appear to mark the instrument. With color image segmentation, the mark can be correctly located in the image and used to control the robot motion. Thus, even if only a very small part of the instrument is visible, reliable data can still be obtained for robot control. The image processing component is implemented on a commercially available image processing system MaxVideo MV200 (Datacube, Inc., Danvers, MA). The robot the authors use is the AESOP 1000 (Automated Endoscope system for Optimal Positioning) (Computer Motion, Inc., Goleta, CA).

关键词： Visual servoing Minimally invasive surgery Motion control Robot control Robot motion Image segmentation Instruments Laparoscopes Image color analysis Tracking

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