Showing papers by "Technische Universität Darmstadt published in 1992"

Fault diagnosis of machines via parameter estimation and knowledge processing

Abstract: For further improvement of the reliability and safety of machines the automatic early detection and localization of faults is of high interest. The conventional approach is to monitor some important variables like temperatures, pressures, vibrations and to generate alarms if certain limits are exeeded. However, developing internal faults are in this way only detected at a rather late stage. By applying static and dynamic process models and common process input and output measurements the inherent relationships and redundancies can be used to detect faults earlier and to localize them better. Changes in process and signal parameters are very well suited for fault detection. The paper describes a general methodology for machines and other processes by using few measurements, dynamic process and signal models and parameter estimation to generate symptoms. The detected symptoms are fed into a knowledge based fault diagnosis procedure. Analytical and heuristic knowledge is treated via fault-symptom trees, process history and plausibility measures. The considered machines consist of a motor, a drive chain and a working process or load. They may be electrical motor or combustion engine driven pumps, fans or machine tools with gear or belt drive chains. The described methodology was developed and tested experimentally for several machines. As one example, experimental results are shown for a d.c. motor powered feed drive of a machine tool.

Input-dependent stability of joint torque control of tendon-driven robot hands

Abstract: The input-dependent stability observed during torque control experiments using the first joint of the Darmstadt-HAND is discussed. Friction and compliance existing in tendon-sheath drive systems introduce a hysteresis nonlinearity between the joint torque output and the actuator displacement. Although this transmission characteristic is close to the well-known backlash behavior of the gears situated between a motor and a load shift, this hysteresis loop exhibits input-dependent characteristics in the backlash region of the transmission system, with springlike behavior within a portion of the backlash region. Experiments confirmed that there is a close relationship between the input-dependent backlash characteristics and the input-dependent stability. Based on these experiments, the authors describe the transmission characteristic using a simple model and explore the system stability using sinusoidal-input-describing-functions (SIDF). A nondimensional stability-criterion-map that successfully predicts the experimental results is presented. >

Network Design Formulations in Schedule Synchronization

Abstract: This paper deals with problems in schedule synchronization for public transit networks. First we reformulate the problem of minimizing waiting times of passengers changing communication routes at certain transfer stations in a network. In this problem all transit lines only meet at certain points or transfer stations. A second problem, in addition, considers the case where different lines partly use the same tracks implicating that security distances have to be observed.

Excitation-energy dependence of the giant dipole resonance width.

Abstract: High-energy \ensuremath{\gamma} rays have been measured in coincidence with heavy fragents in deeply inelastic reactions of $^{136}\mathrm{Xe}$${+}^{48}$Ti at 18.5 MeV/nucleon. The giant dipole resonance (GDR) strength function is deduced from an analysis of the photon spectra within the statistical model. The GDR width \ensuremath{\Gamma} is studied as a function of the fragment excitation energy ${\mathit{E}}^{\mathrm{*}}$. A saturation at about \ensuremath{\Gamma}=10 MeV is observed for ${\mathit{E}}^{\mathrm{*}}$/A\ensuremath{\ge}1.0 MeV/nucleon.

Ac technique for simultaneous study of local and global linear responses near the glass transition : the case of doped Ca2+/K+/NO3-

Abstract: We describe what we believe may be the first linea response experiment which simultaneously measures global and local relaxation kinetics in a viscous liquid near its glass transition temperature. The system chosen for study is the model Ca 2+ /K + /NO 3 - ionic liquid {2Ca(NO 3 ) 2 .3KNO 3 , or CKN}

Ultratrace analysis — Facts and fiction

Abstract: Ultratrace analysis is a term which still awaits a clear definition but it is gaining rising importance especially for hightech materials and processes. Relevant ultratrace levels of importance depend largely on the investigated matrix but generally range below 1 ppm. Some factors leading to fiction in ultratrace analysis are discussed such as: On the other hand, some of the most fascinating aspects of ultratrace analysis are elucidated:

A heated membrane for a capacitive gas sensor

Abstract: Interdigital capacitors covered with a gas-sensitive layer are suitable for the integration of gas sensors with microelectronic technologies. They can be temperature stabilized by mounting them on a heated membrane. Usually one faces the problem of significant temperature gradients across the membrane for large-area sensors. In this work a heater arrangement capable of maintaining an almost even temperature distribution on the heated membrane is presented. An analytical approach and finite-element simulations are used to estimate heating power distribution for a square-shaped membrane. A test chip was designed and fabricated. The fabrication process is fully compatible with standard bipolar processing.

Tonotopy and periodotopy in the auditory midbrain of cat and Guinea fowl

Abstract: A laminar functional organization has been demonstrated in the auditory midbrain of mammals and birds. In the midbrain of cat a fine structure of the tonotopic organization could be demonstrated, covering a frequency range of 1/6 octave in each of the functional laminae. Neurons in the midbrain of various animals have been found to be selective for certain modulation frequencies (BMF) relevant for the perception of periodicity pitch. An orderly topographical distribution of BMF could be demonstrated in the laminae of the ICC of the cat, approximately orthogonal to the tonotopic fine-structure within the laminae. An orderly spatial representation of BMF could be demonstrated also in the midbrain of Guinea fowl.

The influence of spatial polarization distribution on spot poled PVDF membrane hydrophone performance.

Abstract: The influence of spatial polarization distribution on spot poled PVDF membrane hydrophone performance was calculated and then experimentally verified using a one-dimensional model based on acoustic wave propagation through a layered medium. It is shown that the sensitivity of the hydrophone is markedly dependent on the spatial polarization distribution. It is also shown that there can be a significant difference between the voltage sensitivities measured in the same hydrophone probe depending on which electrode is actually facing the acoustic source. The measurements carried out in the frequency range 1–20 MHz indicate that this difference, while negligible below 2 MHz, may exceed 1.6 dB at higher frequencies. The model developed can also be used to determine the “effective” piezoelectric constant d33 of the PVDF material as a continuous function of frequency. Moreover, the model predicts the existence of a negative slope in the frequency response of the spot poled membrane hydrophone. The experimental confirmation of this prediction underscores the importance of using swept frequency methods during calibration measurements.

Remarks on depth selective CEMS — Backscattering measurements

Abstract: Depth Selective Conversion Electron Mossbauer (MB) Spectroscopy measurements usually are done in backscattering geometry under bad geometrical conditions due to low resonant count rates Furthermore in the case of iron these investigations are often done on samples enriched with57Fe, partially polarized Because of these conditions the spectra are modified more or less strongly by the cosine smearing effect and/or saturation effects due to high enrichment of57Fe We have investigated these effects in the case of an α-Fe-metal sample using a high transmission orange spectrometer

Real-Time Simulation of Drive Chaines for Use in Dynamical Engine Test Stands

Abstract: In this paper, a dynamical engine test stand is presented which may be used as an advanced tool for combustion engine optimization and control. To simulate the dynamics of load changes occuring in a driving vehicle, a model of the car body including drive line, differential and wheels and a driver simulation have been developed and implemented on the test stand. Simulation results are presented and discussed.

DaDaMo-a conceptual data model for electronic design applications

Abstract: DaDaMo is a conceptual data model for design applications requiring complex modelling techniques. By the integration and extension of semantic and object-oriented modelling concepts, DaDaMo provides modelling mechanisms considering especially the requirements of complex design applications. These mechanisms are described in detail and their adequacy in particular for electronic design applications is shown. Additionally, experiences in using DaDaMo and the consideration of international standardization efforts are reported. >

A heavy-ion beam current monitor with a wide dynamic range☆

Abstract: We present a new current monitor concept for relativistic heavy-ion beams based on secondary electron emission. The detector is capable of measuring beam intensities from single particles up to several 109 Hz.

Mössbauer backscattering spectrometer for mineralogical analysis of the mars surface

Abstract: A Mossbauer spectrometer for the mineralogical analysis of the Mars surface is under development. This instrument will be installed on a Mars-Rover, included in the Soviet Union Mars-94/96 Mars mission. Due to power and mass restrictions the electromechanical drive and the electronic components have been extremely miniaturized in comparison to standard systems. Solid state detectors (PIN-diodes) are used for γ- and x-ray detection. The whole spectrometer is controlled by a microprocessor (transputer). An additional application as x-ray fluorescence spectrometer is proposed.

Modulation of effects of lipopolysaccharide on macrophages by a major outer membrane protein of Proteus mirabilis as measured in a chemiluminescence assay.

Abstract: Our previous studies have shown that a major protein isolated from purified cell walls of Proteus mirabilis (39-kDa protein) is a strong modulator of the specific immune responses to lipopolysaccharide (LPS) from this bacterium. When the protein is mixed with LPS before immunization of mice, the responses of antibody-producing cells specific for LPS are greatly enhanced and converted predominantly to the immunoglobulin G isotype. In the present study, the immunomodulating effects of the 39-kDa protein were tested at the level of interaction of LPS with macrophages. Activation of macrophages was determined by measuring the production of oxygen radicals in a chemiluminescence assay with lucigenin as the amplifier. LPS from P. mirabilis induced strong oxidative metabolism in both peritoneal and bone marrow-derived murine macrophages. These responses were inhibited in a dose-dependent manner by mixing LPS with increasing amounts of the protein. In contrast, bovine serum albumin and methylated bovine serum albumin enhanced the response of macrophages dramatically when complexed with LPS. The inhibiting activity of the 39-kDa protein was also observed with LPS from Escherichia coli K-12.

Realization of Adaptive Shock Absorbers by Estimating Physical Process Coefficients of a Vehicle Suspension System

Abstract: Shock absorbers with adjustable damping coefficients used in present vehicle suspension systems are only feedforward controlled The effective damping is not measured and many changes in vehicle conditions can not taken into consideration automatically. Two methods are presented which use real-time parameter estimation and feedback to build up a parameter adaptive shock absorber system. The dynamics of the vehicle's vertical motion can be modelled theoretically. Unknown parameters of the nonlinear model like damping coefficient, stiffness, load and friction are estimated on-line in real-time. Simulations and experiments on a quarter-car test stand show the results obtained until now.

Application-specific microelectronics for mechatronic systems

Abstract: A methodology for the design of microelectronic subsystems in a mechatronic environment is presented, and its application to various problems is described. Several strategies from hardware-in-the-loop simulation over rapid prototyping of ASIC-based systems with field programmable gate arrays to the design of application-specific integrated processors are offered. The efficiency of the design system is demonstrated for three mechatronic applications: a self-controlled clutch, ignition control of a combustion engine, and a turbine compressor unit state estimator. >

Preliminary measurements of SIS 18 beam parameters

Abstract: The performance of the newly commissioned heavy-ion synchrotron SIS 18 is investigated. The fragment separator provides access to all six phase-space coordinates of the slowly extracted ion beam. Transverse beam emittances were found to be ϵ xx ′ = 1.8 π mm mrad and ϵ yy ′ = 4.0 π mm mrad for 40 Ar at 1 GeV/nucleon. A change in longitudinal momentum over extraction time is discussed. The stability of mean position and angle during resonance extraction is investigated.

The DASDBS Geokernal — An Extensible Database System for GIS

Abstract: The DASDBS Geokernel as an extensible database for GIS is introduced. The system is embedded in two larger research projects “Digital Geoscientific Maps” and the database research project DASDBS. The main requirements and concepts of database systems for GIS are discussed. Then the realization of the more performance oriented concepts within the DASDBS Geokernel are explained. These are mainly the support for complex objects and the extensibility of geometrical data types and spatial access methods.

Surface sensitivity of low energy electron Mössbauer spectroscopy (LEEMS) using 57 Fe

Abstract: Very low energy electrons (LEE) (E e ≤15 eV) are produced with high intensity directly by Mossbauerabsorption and conversion in the case of57Fe [1, 4, 5]. These electrons should be very surface sensitive due to their very low attenuation length compared to the 7.3 keV K-Conversion electrons of57Fe [5, 11]. We have examined the surface sensitivity of these resonant LEE, using nonresonant56Fe metal and56Fe stainless steel foils coated with about 20 A and 50 A57Fe, respectively. They were exposed to air after evaporation: The 20 A samples are found to be fully oxidized [5]. Depth Selective Conversion Electron Mossbauer Spectroscopy (DCEMS), performed with a high transmission orange type magnetic spectrometer [5, 6, 13] reveals a two layer structure of the 50 A samples. Low Energy Electron Mossbauer Spectroscopy (LEEMS) [5] is found to be significantly more surface sensitive than conventional DCEMS, but not as surface sensitive as Auger Electron Mossbauer Spectroscopy (AEMS) using LMM-Auger electrons of 500–600 eV, as expected due to the different mean free path. But because of the very low intensity of these Auger electrons this mode appears to be not very useful for practical application.

Isotopic effects in the disassembly of hot nuclear systems.

Abstract: The analysis of isotopic effects in the production of intermediate mass fragments from light-ion-induced reactions on heavy nuclei reveals a high degree of equilibration in the isotopic degree of freedom. The observed effects are quantitatively reproduced by the quantum statistical model based on chemical equilibrium. The nearly identical isotopic yield ratios for reactions induced by light ions (p,d,\ensuremath{\alpha}) of several GeV and by heavy ions ${(}^{12}$C${,}^{14}$N${,}^{18}$O) of 30\char21{}100 MeV/nucleon suggest that the statistical parameters of the hot nuclear systems produced in both types of reactions are very similar.

VLSI system design for automotive control

Abstract: Presents a novel VLSI approach for combustion engine control. The approach is based on a real-time solution of a thermodynamical differential equation. The control system calculates an optimum ignition point by fast measurement and real-time processing of signals as temperature, pressure, and volume of the combustion chamber. The required computational power cannot be met with standard signal processors. The design of a mechatronic system that is based on an application-specific vector architecture is presented. Each design step from the analysis of the heat release algorithm, the optimization of the algorithm and the dataform, the mapping on architecture, the physical design of the testchip set and the single chip, the chip test, and the system integration, is presented. Finally, the application at an engine test-stand and results are shown. >