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Singularities in differential-algebraic systems with unilateral constraints

ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik 2010年第S3期78卷

作者： M. Arnold DLR Institute of Robotics and System Dynamics P.O. Box 1116 D - 82230 Wessling Germany

Inequality (unilateral) constraints may introduce various types of singularities in differential-algebraic systems ([5]). In the present paper we consider contact conditions that are formulated as unilateral constraints for position and velocity coordinates in a mechanical multibody system. If the surfaces of the bodies being in contact are worn then the contact conditions result often in constraints that are only piecewise differentiable. We discuss a regularization that considers qualitatively the elastic deformation of the bodies.

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Computation of Kalman decompositions of periodic systems

Computation of Kalman decompositions of periodic systems

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2003 European Control Conference, ECC 2003

作者： Varga, A. German Aerospace Center DLR - Oberpfaffenhofen Institute of Robotics and System Dynamics WesslingD-82234 Germany

ISBN: (纸本)9783952417379

We consider the numerically reliable computation of reachability and observability Kalman decompositions of a periodic system with time-varying dimensions. These decompositions generalize the controllability/observability Kalman decompositions for standard state space systems and have immediate applications in the structural analysis of periodic systems. We propose a structure exploiting numerical algorithm to compute the periodic controllability form by employing exclusively orthogonal similarity transformations. The new algorithm is computationally efficient and strongly backward stable, thus fulfils all requirements for a satisfactory algorithm for periodic systems. © 2003 EUCA.

关键词： Numerical methods

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Coprime factor reduction of H∞ controllers

Coprime factor reduction of H∞ controllers

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2003 European Control Conference, ECC 2003

作者： Varga, A. German Aerospace Center DLR - Oberpfaffenhofen Institute of Robotics and System Dynamics WesslingD-82234 Germany

ISBN: (纸本)9783952417379

We consider the efficient solution of the coprime factorization based H∞ controller approximation problems by using frequency-weighted balancing related model reduction approaches. It is shown that for a class of frequency-weighted performance preserving coprime factor reduction as well as for a relative error coprime factor reduction method, the computation of the frequency-weighted controllability and observability grammians can be done by solving Lyapunov equations of the order of the controller. The new approach can be used in conjunction with accuracy enhancing square-root and balancing-free techniques developed for the balancing related coprime factors based model reduction. © 2003 EUCA.

关键词： Observability

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Application of an optimization-based design process for robust autoland control laws

Application of an optimization-based design process for robu...

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AIAA Guidance, Navigation, and Control Conference and Exhibit 2001

作者： Looye, Gertjan Joos, Hans-Dieter Willemsen, Dehlia German Aerospace Center DLR-Oberpfaffenhofen Institute for Robotics and Mechatronics D-82234 Wessling Germany DLR-Braunschweig Institute for flight system dynamics Germany

ISBN: (纸本)9781563479786

The design of a robust autoland controller using an optimization based design process is described. A modular controller architecture is developed first. Inner loops are based on Dynamic Inversion, speed and longitudinal path tracking loops are based on the Total Energy Control system. Functions for lateral path tracking, ILS guidance, flare and runway alignment are based on classical PID structures. The free parameters in the controller functions are tuned using multi-objective optimization. Performance criteria are directly derived from the imposed design requirements and computed from linear or nonlinear analysis (e.g. eigen-values, simulations). Robustness is addressed via a multi-model approach, via optimization criteria (e.g. gain/phase margins), and, as a new contribution, via statistical criteria computed from on-line Monte-Carlo analysis. The design process and selected architecture have been applied to a wide-body as well as a small passenger aircraft to demonstrate controller robustness and efficiency of the process. In both cases, JAR-AWO specifications had to be met. The latter design was successfully flight tested. © 2001 by the German Aerospace Center dlr.

关键词： Design

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Accuracy enhancing methods for the frequency-weighted balancing related model reduction

Accuracy enhancing methods for the frequency-weighted balanc...

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IEEE Conference on Decision and Control

作者： A. Varga B.D.O. Anderson Institute of Robotics and System Dynamics German AeroSpace Center DLR-Oberpfaffenhofen Wessling Germany Information Sciences and Engineering Australian National University Canberra ACT Australia

In this paper we develop computational techniques with enhanced accuracy for two frequency-weighted model reduction approaches, namely, balanced truncation, and singular perturbation approximation. New stability-enforcing choices of the frequency-weighted grammians can guarantee the stability of reduced models for two-sided frequency weights. Several numerical examples show the effectiveness of the new approximation techniques.

关键词： Frequency Reduced order systems Stability Robustness Bismuth Robots Aerodynamics Reliability engineering Australia Microcomputers

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On Robust Sensitivity Functions and Related Problems

On Robust Sensitivity Functions and Related Problems

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第十九届中国控制会议

作者： J．Ackermann Institute of Robotics and System Dynamics German Aerospace Research Center DLR-Oberpfaffenhofen D-82230 Wessling Germany

In this paper, we prove that, for an interval system, the maximal H ∞ norm of its sensitivity function is achieved at twelve (out of sixteen) Kharitonov vertices. We also study the envelope of the Nyquist plots generated by a family of stable transfer functions with multilinearly correlated uncertainties and show that the outer Nyquist envelope is generated by the Nyquist plots of the vertices of this family. We then apply this result to calculating the maximal H ∞ norm and verifying the strict positive realness condition for uncertain transfer function families.

关键词： Nyquist On Robust Sensitivity Functions and Related Problems

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Damping of vehicle roll dynamics by gain scheduled active steering

Damping of vehicle roll dynamics by gain scheduled active st...

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1999 European Control Conference, ECC 1999

作者： Ackermann, Jurgen Odenthal, Dirk DLR German Aerospace Center Institute of Robotics and System Dynamics WesslingD-82230 Germany

ISBN: (纸本)9783952417355

Active steering is applied to robustly reduce the rollover risk of vehicles with an elevated center of gravity. An actuator sets an auxiliary steering angle which is mechanically added to the steering angle commanded by the driver. The control law presented, is based on feedback of the roll rate and the roll acceleration. The controller gains are scheduled with the speed and the vehicle's CG height. The controller gains are found by the parameter space approach and constrained optimization in frequency domain. Robust reduction of transient rollover risk is shown by evaluation of the sensitivity function at various operating points. Simulation of a double lane change maneuver illustrates the benefits in time domain. © 1999 EUCA.

关键词： Robust control

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Nonlinear steering and braking control for vehicle rollover avoidance

Nonlinear steering and braking control for vehicle rollover ...

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1999 European Control Conference, ECC 1999

作者： Odenthal, Dirk Bunte, Tilman Ackermann, Jurgen DLR German Aerospace Center Institute of Robotics and System Dynamics Oberpfaffenhofen WesslingD-82230 Germany

ISBN: (纸本)9783952417355

Steering and braking control is applied to avoid rollover of road vehicles. The control concept presented is composed of three feedback loops: Continuous operation steering control, emergency steering control and emergency braking control. In continuous operation the roll rate and the roll acceleration are fed back by velocity scheduled gains to the front wheel steering angle. Thereby, the vehicle's roll damping is robustly improved for a wide range of speed and height of the center of gravity. The latter may change for example with a truck from ride to ride. A rollover coefficient is defined that basically depends on the lateral acceleration at the center of gravity of the vehicle's sprung mass. For critical values of this variable the emergency steering and braking system is activated. The rollover coefficient is also used for nonlinear feedback to the front wheel steering angle. The control concept is evaluated by linear sensitivity analysis and by simulations. Additionally, absolute stability of the steering control concept is verified using Popov's criterion. © 1999 EUCA.

关键词： Robust control

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An overview of hybrid simulation phenomena and their support by simulation packages 1

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2nd International Workshop on Hybrid systems: Computation and Control, HSCC 1999

作者： Mosterman, Pieter J. Institute of Robotics and System Dynamics DLR Oberpfaffenhofen P.O. Box 1116 WesslingD-82230 Germany

ISBN: (数字)9783540489832

ISBN: (纸本)3540657347

Hybrid systems combine continuous behavior evolution specified by differential equations with discontinuous changes specified by discrete event switching logic. Numerical simulation of continuous behavior and of discrete behavior is well understood. However, to facilitate simulation of mixed continuous/discrete systems a number of specific hybrid simulation issues must be addressed. This paper presents an overview of phenomena that emerge in simulation of hybrid systems, reported in previously published literature. They can be classified as (i) event handling, (ii) run-time equation processing, (iii) discontinuous state changes, (iv) event iteration, (v) comparing Dirac pulses, and (vi) chattering. Based on these phenomena, numerical simulation requires the implementation of specific hybrid simulation features. An evaluation of existing simulation packages with respect to these features is presented. © Springer-Verlag Berlin Heidelberg 1999.

关键词： Hybrid systems

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A fast and robust grasp planner for arbitrary 3D objects

A fast and robust grasp planner for arbitrary 3D objects

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IEEE International Conference on robotics and Automation (ICRA)

作者： Ch. Borst M. Fischer G. Hirzinger Institute of Robotics and System Dynamics German Aerospace Research Establishment (DLR) Wessling Germany

In order to grasp and manipulate real world objects, grasp planning systems are required, and they have to be very fast in order to be integrated in online planning systems for robots. This paper presents a method to compute a desirable grasp quality measure very fast and accurately. Based on this measure a heuristic approach towards fast planning of precision grasps for arbitrarily shaped 3D objects is described. A number of feasible grasp candidates are generated heuristically. These grasp candidates are qualified using the described grasp quality measure and the best candidate is chosen. The planned grasps are robust with respect to grasp placement. It is shown that only a relatively small number of grasp candidates has to be generated in order to obtain a good, although not optimal, grasp.

关键词： Robustness Orbital robotics Force measurement Torque measurement Fingers Power system planning Robust stability Aerodynamics Shape measurement Resists

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