To analyze the vibration behavior of an unbalanced flexible rotor considering both internal dampi... more To analyze the vibration behavior of an unbalanced flexible rotor considering both internal damping and a constant driving torque, the Laval-rotor-model is applied. The resulting set of nonlinear ordinary differential equations is transformed into a dimensionless formulation to enable numerical integration using an explicit Runge-Kutta-schema. Applying this approach it is possible to study two different phenomena, the well known “stalling” effect of the shaft that occurs just below the bending critical speed when the drive torque is too weak to pass the resonance as well as the effect of self-excitation that occur at very high speeds because of negative damping. It is shown that both problems can be solved, if the radial displacements of the shaft are controlled by a shaft seal. The latter is modeled as a lumped system – considering mass, stiffness and viscosity effects. The seal influences both the horizontal and vertical displacement of the shaft, and the speed of rotation. Becaus...
As a first example this chapter presents the application of the general design methodology for AN... more As a first example this chapter presents the application of the general design methodology for ANC-systems (proposed in Chap. 8) to a particular interior noise problem in an aircraft cabin. To show the practical use of the proposed (matrix) design approach, considering the mechatronic background of feed-forward ANC presented in part I as well as the ANC-system design tools discussed in Chap. 7, this chapter reports on five successive design steps that were performed to support the development of a robust active noise system (ANS) for a special working area (WA) of a certain military aircraft (MA). The chapter starts with a motivation and a description of the requirements. Afterwards, the output of all design steps, beginning with the feasibility study and ending with the robustness study, will be summarized. The project was intended to support the activities of Airbus Germany. It was carried out at the professorship for Mechatronics of Helmut-Schmidt-University/University of the Fed...
Essence of the invention is the integration of at least a microphone together with at least one a... more Essence of the invention is the integration of at least a microphone together with at least one acceleration sensor, and other sensors for relevant measurement variables with an arithmetic unit and non-volatile memory an intelligent microphone module and a cascadable construction of subunits by automatic time synchronization, the time-synchronous data collection from all intelligent microphone modules allow.
The paper present a short overview on active control of low frequency interior noise in aircraft ... more The paper present a short overview on active control of low frequency interior noise in aircraft cabins caused by internal and external sources such as engines or turbulent air ow. For propeller driven aircraft as well as for jet powered aircraft the latter are the most dominant sources for the generation of airborne and structure-borne noise inside the aircraft cabin. Especially in the low frequency range active noise treatments can be applied e ectively to reduce the interior sound pressure level. The application can be based on feedforward controller or a feedback controller. Both structures can include self-adaptive algorithms in order to track changings of the disturbing noise eld. Practical applications are known from commercial aircraft based on systems with distributed sensors and actuators. The combination of all components yields the conclusion that active control of aircraft interior noise can be interpreted as a mechatronic approach.
Multifunctional composites including polymer electrolyte coated carbon fibres and polymer matrix ... more Multifunctional composites including polymer electrolyte coated carbon fibres and polymer matrix systems gained recent interest in light-weight design related research areas. Compared to classical fibre reinforced plastics, the interphase, made by electropolymerisation on the fibre surface, represents a new, third material phase. The coating serves as ion-conducting separator in structural batteries and as insulating layer in energy transmitting multifunctional composites. The importance of this study is related to the fact, that multifunctional applications, based on such composites, are exposed to temperature changes in many cases. The coating material, acting as thin interphase, shows a significant temperature dependant Young’s modulus, determining the overall macroscopic behaviour under thermal loads. The new influences on the effective elastic properties of the composite are determined in this work in a 3D microstructural simulation approach based on a unit cell geometry. For t...
Adaptive Feed-Forward Control of Low Frequency Interior Noise, 2012
Active reduction of disturbing noise requires the generation of appropriate control signals in or... more Active reduction of disturbing noise requires the generation of appropriate control signals in order to drive the canceling sources. For this purpose we have to organize the signal processing of data provided by sensors. These data contain information about the disturbance as well as about the systems state. Because we assume that we are able to work with reference signals that are well correlated to the disturbing noise, the upcoming chapter is restricted to signal processing in feed-forward control systems. It starts with a mathematical preparation, because we will use some concepts of matrix calculus, see (Zurmuhl in Matrizen und ihre technischen Anwendungen, Springer, Berlin, 1964) or (Strang in Introduction to linear algebra, Cambridge University Press, Wellesley, 1993). It is continued with an introduction to feed-forward control signal processing, before we discuss active control of both harmonic excitations and stochastic disturbances. Besides the topic of optimal control, attention is paid to adaptive control that enables the controller to track down non-stationary effects, e.g. the change of the operational speed of a turbo-machinery, or changes in the system response that can be caused by a change of environmental conditions such as ambient pressure, air temperature or humidity as well as by the warming-up of the electro-acoustic equipment. Adaptive feed-forward control of harmonic disturbances is discussed in frequency domain, whereas we will present four time domain approaches for adaptive feed-forward control of stochastic disturbances. However, this chapter is far away from presenting the basics of digital signal processing and digital filters as described in (Antoniou in Digital filters: analysis and design, McGraw-Hill, New York, 1979), (Bose in Digital filters—theory and applications, Elsevier, New York, 1985), (Diniz in Adaptive filtering—algorithms and practical implementations, Springer, New York, 2008), (Haykin in Adaptive filter theory, Prentice Hall, London, 1996), (Hess in Digitale Filter—Eine Einfuhrung, Teubner, Stuttgart, 1989), (Johnson in Digitale Signalverarbeitung, Hanser, Munchen in Cooperation with Prentice Hall International, London, 1991), and (Lucker in Grundlagen digitaler Filter—Eine Einfuhrung in die Theorie linearer zeitdiskreter Systeme und Netzwerke, 1980) to review the theory of adaptive filtering as presented in (Farhang-Boroujeny in Adaptive filters—theory and applications, Wiley, New York, 1998), (Honig and Messerschmidt in Adaptive filters—structure, algorithms and applications, Kluwer Academic, Boston, 1984), (Sayed in Fundamentals of adaptive filtering, Wiley, Hoboken, 2003) and (Widrow and Stearns in Adaptive signal processing, Prentice Hall International, London, 1985) or to discuss DSP implementations, see (Akpan et al. in Active noise and vibration control literature survey: controller technologies. DREA-CR-1999-177, Contractor Report, Defence Research Establishment Atlantic, Dartmouth NS (CAN); MARTEC Ltd, Halifax NS (CAN); Sherbrooke Univ, Sherbrooke QUE (CAN), 1999) and (Chassaing in Digital signal processing and applications with the C6713 and C6416 DSK, Wiley, Canada, 2005). Its intension is to provide a basis for adaptive feed-forward control of low frequency interior noise that also includes algorithmic formulations of the control schemes. The content of the upcoming chapter is therefore oriented on (Kuo and Morgan in Active noise control systems—algorithms and DSP implementations, Wiley, Canada, 1996) and (Elliott in Signal processing for active noise control, Academic Press, London, 2001)—two fundamental books about signal processing for ANC that are (without detailed algorithmic formulations) summarized in (Kuo and Morgan in Proc. IEEE 87(6):943–973, 1999) and (Elliott in Tokhi and Veres (eds.) Active sound and vibration control, Institution of Electrical Engineers, London, pp. 57–72, 2002).
An active noise control system is developed for the loadmaster area of a propeller driven transpo... more An active noise control system is developed for the loadmaster area of a propeller driven transport aircraft. The loadmaster area is a small semi-enclosed volume connected to the large cargo hold. This coupling of a small room with a large room yields to new questions when an active noise control system is designed: Which effects does the coupling have on the noise field inside the small loadmaster area? Which influence do these effects have on the active noise control system? How complex is the uncertainty induced by the coupling to the large cargo? The analysis of this coupling was done in two ways. The first one, an energy based method, is used to analyze the acoustical energy flow between the loadmaster area and the cargo hold. The second one, a substructure technique, is used to study the influence on the eigenfrequencies and eigenmodes of such a coupled system. Afterwards, the theoretic results were confirmed with an experimental forced vibration analysis. The most important r...
Due to standing waves the creation of artificial free-field conditions is required to detect soun... more Due to standing waves the creation of artificial free-field conditions is required to detect sound sources in weakly damped interiors. Normally sound absorbing material is mounted on the interior walls to eliminate unwanted reflections. In contrast to this time consuming procedure, the ...
The paper presents an active sound intensity probe that can be used for sound source localization... more The paper presents an active sound intensity probe that can be used for sound source localization in standing wave fields. The probe consists of a sound hard tube that is terminated by a loudspeaker and an integrated pair of microphones. The microphones are used to decompose the standing wave field inside the tube into its incident and reflected part. The latter is cancelled by an adaptive controller that calculates proper driving signals for the loudspeaker. If the open end of the actively controlled tube is placed close to a vibrating surface, the radiated sound intensity can be determined by measuring the cross spectral density between the two microphones. A one-dimensional free field can be realized effectively, as first experiments performed on a simplified test bed have shown. Further tests proved that a prototype of the novel sound intensity probe can be calibrated.
In der Elektromobilität gewinnen, wegen des Wegfalls der Geräusche des Verbrennungsmotors, die Sc... more In der Elektromobilität gewinnen, wegen des Wegfalls der Geräusche des Verbrennungsmotors, die Schallemissionen von zuvor akustisch nicht wirksamen Bauteilen an Relevanz. Wesentliche Geräuschquellen sind nach Genuit [1] dabei der Elektromotor und das Getriebe, wobei die Antriebswelle die Körperschallbrücke zum Getriebegehäuse darstellt. Von diesem werden die mechanischen Schwingungen in akustisch wahrnehmbaren Luftschall umgewandelt.
The invention describes a noise reduction system for actively blocking the sound energy input of ... more The invention describes a noise reduction system for actively blocking the sound energy input of a noise source (1) for a transport. The noise reduction system comprises at least a counter sound source (2) and at least one intensity sensor (3). The at least one counter sound source (2) and the at least one intensity sensor (3) are arranged in a measuring region (5). In the measurement region (5) a measurement of a noise intensity of the noise source (1) and a counter sound intensity of the counter sound source (2) by means of the intensity sensor (3) can be provided. Based on the measured noise intensity and the counter sound intensity, the counter sound source (2) can be controlled such that a sound energy input of the noise source (1) by means of the counter sound source (2) is reducible.
Numerical simulation can be performed; however the implementation into the design process is smal... more Numerical simulation can be performed; however the implementation into the design process is small due to the fact that the accepted validation processes are still not established. Especially the coupling to optimization problems is still not a simple approach. Also the sufficient modelling of room acoustical problems involves a number of parameters (e.g. material-based absorption coefficients) which are currently not easy to implement.
Cultural assets are witnesses of past times with versatile worth. The irreplaceability of those t... more Cultural assets are witnesses of past times with versatile worth. The irreplaceability of those treasures of art makes their protection our major task. This article reflects the commitment and results of 40 years of conservators’ research to protect canvas - objects of cultural heritage - particularly from mechanical loads. It gives a classification of mechanical loads that act upon canvas during transport, exhibition and storing in depot. Furthermore, it gives an overview of different approaches which were used over years to protect canvas from various mechanical loads. This article tends to bridge the gap between restorers’ knowledge and methods and concepts known from engineering dynamics. Restorers’ first steps using engineers’ methods are brought up and the necessity of theoretical modeling which has not started so far are pointed out.
A smart exciter coupled to cabin panels can be used as a new type of loudspeaker for emergency an... more A smart exciter coupled to cabin panels can be used as a new type of loudspeaker for emergency announcements in the aircraft cabin. The same device can also be used as a semi-active vibration control system which is effective in reducing the amplitude of structural vibration. The objective of this paper is to investigate the potential of vibration reduction using a smart exciter in combination with an optimized resistive-inductive shunt circuit, which serves as an absorbing network. First, the vibration reduction effect has been analyzed numerically using a simulation framework realized with COMSOL and MATLAB/Simulink. In a second step, the reduction effect of the smart exciter together with a resistive-inductive shunt circuit, which is produced by the Center of Applied Aeronautical Research (Zentrum für Angewandte Luftfahrtforschung GmbH, Hamburg, Germany), has been investigated experimentally. The results presented here prove that the smart exciter together with a resistive-induct...
To analyze the vibration behavior of an unbalanced flexible rotor considering both internal dampi... more To analyze the vibration behavior of an unbalanced flexible rotor considering both internal damping and a constant driving torque, the Laval-rotor-model is applied. The resulting set of nonlinear ordinary differential equations is transformed into a dimensionless formulation to enable numerical integration using an explicit Runge-Kutta-schema. Applying this approach it is possible to study two different phenomena, the well known “stalling” effect of the shaft that occurs just below the bending critical speed when the drive torque is too weak to pass the resonance as well as the effect of self-excitation that occur at very high speeds because of negative damping. It is shown that both problems can be solved, if the radial displacements of the shaft are controlled by a shaft seal. The latter is modeled as a lumped system – considering mass, stiffness and viscosity effects. The seal influences both the horizontal and vertical displacement of the shaft, and the speed of rotation. Becaus...
As a first example this chapter presents the application of the general design methodology for AN... more As a first example this chapter presents the application of the general design methodology for ANC-systems (proposed in Chap. 8) to a particular interior noise problem in an aircraft cabin. To show the practical use of the proposed (matrix) design approach, considering the mechatronic background of feed-forward ANC presented in part I as well as the ANC-system design tools discussed in Chap. 7, this chapter reports on five successive design steps that were performed to support the development of a robust active noise system (ANS) for a special working area (WA) of a certain military aircraft (MA). The chapter starts with a motivation and a description of the requirements. Afterwards, the output of all design steps, beginning with the feasibility study and ending with the robustness study, will be summarized. The project was intended to support the activities of Airbus Germany. It was carried out at the professorship for Mechatronics of Helmut-Schmidt-University/University of the Fed...
Essence of the invention is the integration of at least a microphone together with at least one a... more Essence of the invention is the integration of at least a microphone together with at least one acceleration sensor, and other sensors for relevant measurement variables with an arithmetic unit and non-volatile memory an intelligent microphone module and a cascadable construction of subunits by automatic time synchronization, the time-synchronous data collection from all intelligent microphone modules allow.
The paper present a short overview on active control of low frequency interior noise in aircraft ... more The paper present a short overview on active control of low frequency interior noise in aircraft cabins caused by internal and external sources such as engines or turbulent air ow. For propeller driven aircraft as well as for jet powered aircraft the latter are the most dominant sources for the generation of airborne and structure-borne noise inside the aircraft cabin. Especially in the low frequency range active noise treatments can be applied e ectively to reduce the interior sound pressure level. The application can be based on feedforward controller or a feedback controller. Both structures can include self-adaptive algorithms in order to track changings of the disturbing noise eld. Practical applications are known from commercial aircraft based on systems with distributed sensors and actuators. The combination of all components yields the conclusion that active control of aircraft interior noise can be interpreted as a mechatronic approach.
Multifunctional composites including polymer electrolyte coated carbon fibres and polymer matrix ... more Multifunctional composites including polymer electrolyte coated carbon fibres and polymer matrix systems gained recent interest in light-weight design related research areas. Compared to classical fibre reinforced plastics, the interphase, made by electropolymerisation on the fibre surface, represents a new, third material phase. The coating serves as ion-conducting separator in structural batteries and as insulating layer in energy transmitting multifunctional composites. The importance of this study is related to the fact, that multifunctional applications, based on such composites, are exposed to temperature changes in many cases. The coating material, acting as thin interphase, shows a significant temperature dependant Young’s modulus, determining the overall macroscopic behaviour under thermal loads. The new influences on the effective elastic properties of the composite are determined in this work in a 3D microstructural simulation approach based on a unit cell geometry. For t...
Adaptive Feed-Forward Control of Low Frequency Interior Noise, 2012
Active reduction of disturbing noise requires the generation of appropriate control signals in or... more Active reduction of disturbing noise requires the generation of appropriate control signals in order to drive the canceling sources. For this purpose we have to organize the signal processing of data provided by sensors. These data contain information about the disturbance as well as about the systems state. Because we assume that we are able to work with reference signals that are well correlated to the disturbing noise, the upcoming chapter is restricted to signal processing in feed-forward control systems. It starts with a mathematical preparation, because we will use some concepts of matrix calculus, see (Zurmuhl in Matrizen und ihre technischen Anwendungen, Springer, Berlin, 1964) or (Strang in Introduction to linear algebra, Cambridge University Press, Wellesley, 1993). It is continued with an introduction to feed-forward control signal processing, before we discuss active control of both harmonic excitations and stochastic disturbances. Besides the topic of optimal control, attention is paid to adaptive control that enables the controller to track down non-stationary effects, e.g. the change of the operational speed of a turbo-machinery, or changes in the system response that can be caused by a change of environmental conditions such as ambient pressure, air temperature or humidity as well as by the warming-up of the electro-acoustic equipment. Adaptive feed-forward control of harmonic disturbances is discussed in frequency domain, whereas we will present four time domain approaches for adaptive feed-forward control of stochastic disturbances. However, this chapter is far away from presenting the basics of digital signal processing and digital filters as described in (Antoniou in Digital filters: analysis and design, McGraw-Hill, New York, 1979), (Bose in Digital filters—theory and applications, Elsevier, New York, 1985), (Diniz in Adaptive filtering—algorithms and practical implementations, Springer, New York, 2008), (Haykin in Adaptive filter theory, Prentice Hall, London, 1996), (Hess in Digitale Filter—Eine Einfuhrung, Teubner, Stuttgart, 1989), (Johnson in Digitale Signalverarbeitung, Hanser, Munchen in Cooperation with Prentice Hall International, London, 1991), and (Lucker in Grundlagen digitaler Filter—Eine Einfuhrung in die Theorie linearer zeitdiskreter Systeme und Netzwerke, 1980) to review the theory of adaptive filtering as presented in (Farhang-Boroujeny in Adaptive filters—theory and applications, Wiley, New York, 1998), (Honig and Messerschmidt in Adaptive filters—structure, algorithms and applications, Kluwer Academic, Boston, 1984), (Sayed in Fundamentals of adaptive filtering, Wiley, Hoboken, 2003) and (Widrow and Stearns in Adaptive signal processing, Prentice Hall International, London, 1985) or to discuss DSP implementations, see (Akpan et al. in Active noise and vibration control literature survey: controller technologies. DREA-CR-1999-177, Contractor Report, Defence Research Establishment Atlantic, Dartmouth NS (CAN); MARTEC Ltd, Halifax NS (CAN); Sherbrooke Univ, Sherbrooke QUE (CAN), 1999) and (Chassaing in Digital signal processing and applications with the C6713 and C6416 DSK, Wiley, Canada, 2005). Its intension is to provide a basis for adaptive feed-forward control of low frequency interior noise that also includes algorithmic formulations of the control schemes. The content of the upcoming chapter is therefore oriented on (Kuo and Morgan in Active noise control systems—algorithms and DSP implementations, Wiley, Canada, 1996) and (Elliott in Signal processing for active noise control, Academic Press, London, 2001)—two fundamental books about signal processing for ANC that are (without detailed algorithmic formulations) summarized in (Kuo and Morgan in Proc. IEEE 87(6):943–973, 1999) and (Elliott in Tokhi and Veres (eds.) Active sound and vibration control, Institution of Electrical Engineers, London, pp. 57–72, 2002).
An active noise control system is developed for the loadmaster area of a propeller driven transpo... more An active noise control system is developed for the loadmaster area of a propeller driven transport aircraft. The loadmaster area is a small semi-enclosed volume connected to the large cargo hold. This coupling of a small room with a large room yields to new questions when an active noise control system is designed: Which effects does the coupling have on the noise field inside the small loadmaster area? Which influence do these effects have on the active noise control system? How complex is the uncertainty induced by the coupling to the large cargo? The analysis of this coupling was done in two ways. The first one, an energy based method, is used to analyze the acoustical energy flow between the loadmaster area and the cargo hold. The second one, a substructure technique, is used to study the influence on the eigenfrequencies and eigenmodes of such a coupled system. Afterwards, the theoretic results were confirmed with an experimental forced vibration analysis. The most important r...
Due to standing waves the creation of artificial free-field conditions is required to detect soun... more Due to standing waves the creation of artificial free-field conditions is required to detect sound sources in weakly damped interiors. Normally sound absorbing material is mounted on the interior walls to eliminate unwanted reflections. In contrast to this time consuming procedure, the ...
The paper presents an active sound intensity probe that can be used for sound source localization... more The paper presents an active sound intensity probe that can be used for sound source localization in standing wave fields. The probe consists of a sound hard tube that is terminated by a loudspeaker and an integrated pair of microphones. The microphones are used to decompose the standing wave field inside the tube into its incident and reflected part. The latter is cancelled by an adaptive controller that calculates proper driving signals for the loudspeaker. If the open end of the actively controlled tube is placed close to a vibrating surface, the radiated sound intensity can be determined by measuring the cross spectral density between the two microphones. A one-dimensional free field can be realized effectively, as first experiments performed on a simplified test bed have shown. Further tests proved that a prototype of the novel sound intensity probe can be calibrated.
In der Elektromobilität gewinnen, wegen des Wegfalls der Geräusche des Verbrennungsmotors, die Sc... more In der Elektromobilität gewinnen, wegen des Wegfalls der Geräusche des Verbrennungsmotors, die Schallemissionen von zuvor akustisch nicht wirksamen Bauteilen an Relevanz. Wesentliche Geräuschquellen sind nach Genuit [1] dabei der Elektromotor und das Getriebe, wobei die Antriebswelle die Körperschallbrücke zum Getriebegehäuse darstellt. Von diesem werden die mechanischen Schwingungen in akustisch wahrnehmbaren Luftschall umgewandelt.
The invention describes a noise reduction system for actively blocking the sound energy input of ... more The invention describes a noise reduction system for actively blocking the sound energy input of a noise source (1) for a transport. The noise reduction system comprises at least a counter sound source (2) and at least one intensity sensor (3). The at least one counter sound source (2) and the at least one intensity sensor (3) are arranged in a measuring region (5). In the measurement region (5) a measurement of a noise intensity of the noise source (1) and a counter sound intensity of the counter sound source (2) by means of the intensity sensor (3) can be provided. Based on the measured noise intensity and the counter sound intensity, the counter sound source (2) can be controlled such that a sound energy input of the noise source (1) by means of the counter sound source (2) is reducible.
Numerical simulation can be performed; however the implementation into the design process is smal... more Numerical simulation can be performed; however the implementation into the design process is small due to the fact that the accepted validation processes are still not established. Especially the coupling to optimization problems is still not a simple approach. Also the sufficient modelling of room acoustical problems involves a number of parameters (e.g. material-based absorption coefficients) which are currently not easy to implement.
Cultural assets are witnesses of past times with versatile worth. The irreplaceability of those t... more Cultural assets are witnesses of past times with versatile worth. The irreplaceability of those treasures of art makes their protection our major task. This article reflects the commitment and results of 40 years of conservators’ research to protect canvas - objects of cultural heritage - particularly from mechanical loads. It gives a classification of mechanical loads that act upon canvas during transport, exhibition and storing in depot. Furthermore, it gives an overview of different approaches which were used over years to protect canvas from various mechanical loads. This article tends to bridge the gap between restorers’ knowledge and methods and concepts known from engineering dynamics. Restorers’ first steps using engineers’ methods are brought up and the necessity of theoretical modeling which has not started so far are pointed out.
A smart exciter coupled to cabin panels can be used as a new type of loudspeaker for emergency an... more A smart exciter coupled to cabin panels can be used as a new type of loudspeaker for emergency announcements in the aircraft cabin. The same device can also be used as a semi-active vibration control system which is effective in reducing the amplitude of structural vibration. The objective of this paper is to investigate the potential of vibration reduction using a smart exciter in combination with an optimized resistive-inductive shunt circuit, which serves as an absorbing network. First, the vibration reduction effect has been analyzed numerically using a simulation framework realized with COMSOL and MATLAB/Simulink. In a second step, the reduction effect of the smart exciter together with a resistive-inductive shunt circuit, which is produced by the Center of Applied Aeronautical Research (Zentrum für Angewandte Luftfahrtforschung GmbH, Hamburg, Germany), has been investigated experimentally. The results presented here prove that the smart exciter together with a resistive-induct...
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