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Flatness-based Trajectory-tracking control of Dielectric Elastomer Actuators

IFAC-PapersOnLine 2020年第2期53卷 8757-8762页

作者： P.M. Scherer A. Irscheid G. Rizzello J. Rudolph Chair of Systems Theory and Control Engineering Saarland University 66123 Saarbrücken Germany Intelligent Material Systems Lab Saarland University 66123 Saarbru¨cken Germany

In recent years, actuators based on dielectric elastomers have become popular for both research and industrial applications. Due to their nonlinear behavior, they are typically used in on/off actuation. Established feedback control methods such as PID provide an effective and robust way to drive these actuators under constant setpoint requirements. However, such control methods exhibit poor trajectory tracking performance. This shortcoming is addressed in this work with a flatness-based nonlinear control design for a circular membrane actuator based on dielectric elastomers. By exploiting a nonlinear electro-mechanical model of the device, a tracking control law is designed in both feed-forward and feedback form. Moreover, it is shown how the flatness-based feed-forward control may be used to extend a conventional PID control to improve its tracking performance. The presented methods are validated and compared experimentally with a real actuator prototype. Tracking accuracy better than 10µm along a 1 mm stroke trajectory (i. e. less than 1%) is shown. This result is a significant improvement over existing PID control laws.

关键词： flatness nonlinear control feed-forward control dielectric elastomer dielectric elastomer actuator membrane actuator

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Data and computation efficient model-based fault detection for rolling element bearings using numerical differentiation

Data and computation efficient model-based fault detection f...

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Conference on control and Fault-Tolerant systems (SysTol)

作者： Amine Othmane Joachim Rudolph Chair of Systems Theory and Control Engineering Saarland University 66123 Saarbrücken Germany Laboratoire des signaux et systèmes Université Paris-Saclay CNRS CentraleSupélec 91190 Gifsur-Yvette France

A novel model-based approach for online condition monitoring of rolling element bearings based on efficient and robust numerical differentiation is proposed. The physical parameters may be identified using fault-free data. The main idea for fault detection is the design of signals, called residuals, sensitive only to faults using a simplified model of the bearing vibrations. These residuals are proportional to the force stemming from the faults and are easy to compute and implement. An approach for the design of a failure detection threshold is provided. This threshold can be designed to meet a desired probability of false alarms. The method is validated using four experimental data sets stemming from different research centers.

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Non-intrusive Time-POD for Optimal control of a Fixed-Bed Reactor for CO 2 Methanation

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IFAC-PapersOnLine 2021年第3期54卷 122-127页

作者： Jens Bremer Jan Heiland Peter Benner Kai Sundmacher Max Planck Institute Magdeburg Dpt. Process Systems Engineering Sandtorstraße 2 39106 Magdeburg Germany and Otto von Guericke University Magdeburg Chair for Process Systems Engineering Universitätsplatz 2 39106 Magdeburg (Sundmacher) Max Planck Institute Magdeburg Dpt. Computational Methods in Systems and Control Theory and Otto von Guericke University Magdeburg Fakultät für Mathematik

The optimization of a controlled process in a simulation without access to the model itself is a common scenario and very relevant to many chemical engineering applications. A general approach is to apply a black-box optimization algorithm to a parameterized control scheme. The success then depends on the quality of the parametrization that should be low-dimensional though rich enough to express the salient features. This work proposes using solution snapshots to extract dominant modes of the temporal dynamics of a process and use them for low-dimensional parametrizations of control functions. The approach is called proper orthogonal decomposition in time (time-POD). We provide theoretical reasoning and illustrate the performance for the optimal control of a methanation reactor.

关键词： Optimal control Model order reduction Proper orthogonal decomposition Fixed-bed reactor Carbon dioxide methanation Nonlinear programming Black-box model

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Redundant configuration coordinates and nonholonomic velocity coordinates in analytical mechanics

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IFAC-PapersOnLine 2018年第2期51卷 409-414页

作者： Konz, Matthias Rudolph, Joachim Chair of Systems Theory and Control Engineering Saarland University Saarbrücken66123 Germany

Several established concepts of analytical mechanics are reviewed and extended to include redundant configuration coordinates and nonholonomic velocity coordinates. The main motivation for redundant coordinates is that the resulting formulations can be global, whereas minimal coordinates might necessarily be local depending on the topology of the configuration space e.g. for SO(3). The resulting formulations for Lagrange's equations, the Gibbs-Appell equations and the coefficients of the Levi-Civita connection are derived. These are then applied to the example of the free rigid body to derive the well-known Newton-Euler equations. © 2018

关键词： Mechanics Rigid structures Analytical mechanics Energy method First principles Gibbs Appell equations Newton Euler equation Redundant configuration Redundant coordinates Rigid body

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Analysis of the parameter estimate error when algebraic differentiators are used in the presence of disturbances ⁎

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IFAC-PapersOnLine 2020年第2期53卷 572-577页

作者： A. Othmane J. Rudolph H. Mounier Université Paris-Saclay CNRS CentraleSupélec Laboratoire des signaux et systèmes 91190 Gif-sur-Yvette France Chair of Systems Theory and Control Engineering Saarland University Saarbrücken Germany

The use of algebraic differentiators in the context of asymptotic continuous-time parameter estimation is discussed. The estimation problem is analyzed within a least squares optimization context. Bounds for the error stemming from high frequency disturbances and the approximation of the derivatives are derived. It is shown that with higher frequencies the error stemming from the disturbances decreases and that the filter parameters can be used to adjust the convergence of this error to zero. An observer with assignable error dynamics for the online estimation is also proposed. A simulation is carried out to evaluate the results and compare the proposed observer with the recursive solution of the least squares problem.

关键词： Algebraic differentiators parameter estimation least squares algorithm time-varying linear observers

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Learning References with Gaussian Processes in Model Predictive control applied to Robot Assisted Surgery

Learning References with Gaussian Processes in Model Predict...

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European control Conference (ECC)

作者： Janine Matschek Tim Gonschorek Magnus Hanses Norbert Elkmann Frank Ortmeier Rolf Findeisen Laboratory for Systems Theory and Automatic Control Otto-von-Guericke Univ. Magdeburg Chair of Software Engineering Otto-von-Guericke Univ. Magdeburg Fraunhofer-Institute for Factory Operation and Automation Magdeburg

ISBN: (数字)9783907144022

ISBN: (纸本)9781728188133

One of the key benefits of model predictive control is the capability of controlling a system proactively in the sense of taking the future system evolution into account. However, often external disturbances or references are not a priori known, which renders the predictive controllers shortsighted or uninformed. Adaptive and learning based prediction models can provide suitable predictions to the controller and therefor can be applied to overcome this issue. We propose to learn references for model predictive controllers via Gaussian processes. To illustrate the approach, we consider robot assisted surgery, where a robotic manipulator must follow a learned reference position based on optical tracking measurements.

关键词： Predictive models Gaussian processes Robots Predictive control Task analysis control systems Tracking

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Flatness-based control of a rigid body carried by multiple heavy ropes

Flatness-based control of a rigid body carried by multiple h...

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89th Annual Meeting on the International Association of Applied Mathematics and Mechanics, GAMM 2018

作者： Irscheid, Abdurrahman Gerbet, Daniel Rudolph, Joachim Chair of Systems Theory and Control Engineering Saarland University Saarbrücken Germany

Flatness-based trajectory planning for the distributed-parameter system consisting of a rigid body carried by multiple heavy ropes is discussed. The suspension points (controlled ends) of the ropes are assumed to be freely movable. The other ends of the ropes are parametrized by a flat output of the nonlinear boundary system at the load that describes the motion of the rigid body. This parametrization is then used to express the solution of the linearized partial differential equations for the heavy ropes under small angle approximations around a vertical equilibrium configuration by the means of operational calculus. It is shown that the system trajectories of the ropes depend on distributed delays and advances of the flat output trajectory at the load-side boundary system. Evaluating the derived parametrization of the heavy ropes at the controllable ends yields the desired open-loop controller by using a planned trajectory for the flat output. This control can be used to realize a desired transition of the load position and orientation in finite time. The introduced method is illustrated for the example of a linear infinite-dimensional model of two heavy ropes carrying a rigid rod. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

关键词： Calculations

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Flatness-Based Feed-Forward control Design for Solenoid Actuators Considering Eddy Currents

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IFAC-PapersOnLine 2019年第15期52卷 567-572页

作者： Tristan Braun Johannes Reuter Joachim Rudolph ZF Friedrichshafen AG Corporate Research & Development 88038 Friedrichshafen Germany Institute of System Dynamics Konstanz University of Applied Sciences 78462 Konstanz Germany Chair of Systems Theory and Control Engineering Saarland University Campus A5 1 66123 Saarbrücken Germany

Flatness-based feed-forward control of solenoid actuators is considered. For precise motion planning and accurate steering of conventional solenoids, eddy currents cannot be neglected. The system of ordinary differential equations including eddy currents, that describes the nonlinear dynamics of such actuators, is not differentially flat. Thus, a distributed parameter approach based on a diffusion equation is considered, that enables the parametrization of the eddy current by the armature position and its time derivatives. In order to design the feedforward control, the distributed parameter model of the eddy current subsystem is combined with a typical nonlinear lumped parameter model for the electrical and mechanical subsystems of the solenoid. The control design and its application are illustrated by numerical and practical results for an industrial solenoid actuator.

关键词： differential flatness feed-forward control motion planning distributed parameter systems diffusion equation eddy currents solenoid valves

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An Algebraic Approach to the Identification of Linear systems with Fractional Derivatives

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IFAC-PapersOnLine 2017年第1期50卷 6214-6219页

作者： Gehring N. Rudolph J. Chair of Automatic Control Technical University of Munich Munich Germany Chair of Systems Theory and Control Engineering Saarland University Saarbrücken Germany

Identification of fractional-order systems is considered from an algebraic point of view. The approach presented allows for a simultaneous estimation of model parameters and fractional (or integer) orders from input and output data. It is exact in that no approximations are required. Using the Laplace transform, algebraic manipulations are performed on the operational representation of the system. The unknown parameters and fractional orders are calculated solely from convolutions of known signals. A generalized Voigt model describing a viscoelastic material and a diffusion-wave equation representing a fractional partial differential equation are used to illustrate the approach. © 2017

关键词： algebraic approaches fractional derivatives fractional-order systems parameter identification system identification

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A Novel Observer Approach for Self Sensing of Single-Coil Digital Valves

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IFAC-PapersOnLine 2017年第1期50卷 782-787页

作者： Braun T. Reuter J. Rudolph J. Institute of System Dynamics Konstanz University of Applied Sciences Konstanz 78462 Germany Chair of Systems Theory and Control Engineering Saarland University Campus A5 1 Saarbrücken 66123 Germany

Observer-based self sensing for digital (on–off) single-coil solenoid valves is investigated. Self sensing refers to the case where merely the driving signals used to energize the actuator (voltage and coil current) are available to obtain estimates of both the position and velocity. A novel observer approach for estimating the position and velocity from the driving signals is presented, where the dynamics of the mechanical subsystem can be neglected in the model. Both the effect of eddy currents and saturation effects are taken into account in the observer model. Practical experimental results are shown and the new method is compared with a full-order sliding mode observer. © 2017

关键词： Observer design Self sensing actuators Singular perturbation analysis

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