It is an essential step in model-based damage identification to accurately determine the parameters which localize and quantify damage from the measured changes of vibration characteristics. This task is formulated as...
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ISBN:
(纸本)0912053941
It is an essential step in model-based damage identification to accurately determine the parameters which localize and quantify damage from the measured changes of vibration characteristics. This task is formulated as an inverse problem and optimisation or regression methods are used. The resulting inverse problem is usually illposed and therefore requires regularization. Usually, the assumption is made that disturbances e.g. caused by measurement noise have a normal distribution. If this assumption is true a weighted Least Squares (LS) estimator yields the best unbiased estimation. If not, a second issue in solving the inverse problem arises which is the high sensitivity of least squares regression methods to statistical outliers or systematic errors in the residual data, for example caused by expansion errors or by linearization errors. Therefore robust regression methods in combination with regularization are applied to solve the inverse problem in order to get reliable and stable solutions for damage identification. The difference between the least squares method and robust regression is worked out. The methods are compared in different simulation studies, performed on the two-storey "Steelquake" structure, which was a benchmark structure of the European COST-F3-Action. Finally, the identification procedure is performed with measured data from the Steelquake-structure, which has been damaged by an artificial earthquake. The conclusion is that the robust regression shows more stable results.
This paper presents the hardware in the loop simulation of an Adaptive Headlight System for motor vehicles. The headlamp orientation control system rotates the right and left low beam headlights independently. It also...
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The design of mechatronic systems requires extensive knowledge from various disciplines that has to be mastered, applied, and cross-linked. In the various softwares employed, knowledge is formalised and saved for reus...
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The design of mechatronic systems requires extensive knowledge from various disciplines that has to be mastered, applied, and cross-linked. In the various softwares employed, knowledge is formalised and saved for reuse. Academic education has to teach students how to work with software systems while taking into account the theoretical contents and methods and using examples that have a strong relation to research. The research projects serve as innovation pools where new concepts and innovative ideas are developed and realized. An example taken from the lecture course on simulation technology will illustrate the way the students are imparted knowledge on methods of generating and analyzing the equations describing mechatronic systems and also the manner in which they acquire the ability to perform simulations and assess the results.
In conventional cross-coupled controller design,the method usually ignored the inherent characteristic of time-vary- ing parameters and model uncertainties in *** this paper,a cross-coupled controller(CCC)using an H~...
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In conventional cross-coupled controller design,the method usually ignored the inherent characteristic of time-vary- ing parameters and model uncertainties in *** this paper,a cross-coupled controller(CCC)using an H~∞control scheme has been proposed to reduce the contouring error for an X-Y ***,the proposed CCC design,which is a typical Multi- Input Multi-Output(MIMO)system with linear time varying(LTV)characteristics,has been verified as being internally stable. The simulations are carried on Matlab simulink to verify the proposed method,and the results showed that the proposed method can reduce the contouring error significantly compared with the conventional one.
It is of high importance to avoid scratches in lapping process. A Grain Size Sensitivity (GSS) model is put forward in this paper. The GSS is a relative parameter which defines the relative change of the depth of cutt...
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It is of high importance to avoid scratches in lapping process. A Grain Size Sensitivity (GSS) model is put forward in this paper. The GSS is a relative parameter which defines the relative change of the depth of cutting, influenced by the change of the size of grain powders, by which it is possible to evaluate quantificationally the capability of lapping machines in avoiding scratches. It is useful for designing and using lapping machines. The simulating of lapping processes based on GSS model is carried out. The transferring of error is also discussed and a new structure of lapping plate with spring cells developed by the authors is introduced.
Switched controllers can often outperform traditional adaptive control. The paper starts with a brief overview of the development of the field of switched controllers. After that, it describes an original control arch...
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ISBN:
(纸本)9608457564
Switched controllers can often outperform traditional adaptive control. The paper starts with a brief overview of the development of the field of switched controllers. After that, it describes an original control architecture based on controller and estimator switching. This architecture uses state-feedback control with switched controllers to cope with controlled system dynamics changes. If conventional observer were used to estimate the unmeasurable state variables, the control performance would deteriorate because the estimation results could be corrupted by disturbances acting at various points of the controlled system. To overcome this problem, the proposed architecture includes also a bank of switched estimators. Each of these estimators is tuned for a specific input point of a disturbance. Switching logic is used to select the most suitable estimator that yields the most reliable estimate in any particular control situation. A considerable deal of attention is devoted to extensive testing of the proposed architecture using computer simulation. The testing results are promising.
The SHM methodology offers the possibility to assess the integrity of a structure without using visual inspections. This is of great advantage especially in areas where the accessibility of the structure is not given,...
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ISBN:
(纸本)0912053941
The SHM methodology offers the possibility to assess the integrity of a structure without using visual inspections. This is of great advantage especially in areas where the accessibility of the structure is not given, e.g. aero- and astronautics applications. In this paper the Stochastic Subspace based Fault Detection Method (SSFDM) and Ultrasonic Guided Waves are applied to detect and to localise damage. Piezo-electric sensors and actuators are used to measure the structural response and to excite the structure respectively. The input signal for the SSFDM is a band limited white noise signal, whereas the input signal for the Ultrasonic Waves is a narrow band Gaussianmodulated sinusoidal pulse. The SSFDM as a global vibration-based method should decide whether the structure is damaged or not while, in the case of damage, the ultrasonic waves should determine the damage position. This multi-scale combination of global and local approach improves the performance of the Structural Health Monitoring. Experiments are carried out on a stiffened aluminium plate and on a GFRP-plate. Damage scenarios such as artificially introduced cracks as well as delaminations are investigated and could be reliably detected even in an early state. Further investigations have been carried out on the simulation of wave propagation to find an appropriate sensor placement.
In the conventional valve controlled hydraulic elevator, when the cabin moves downwards, the entire potential energy of cabin is wasted and converted into fluid heat by throttling. Thus the energy consumption of a tra...
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In the conventional valve controlled hydraulic elevator, when the cabin moves downwards, the entire potential energy of cabin is wasted and converted into fluid heat by throttling. Thus the energy consumption of a traditional hydraulic elevator is much higher with comparison to that of the traction elevator. To reduce the energy consumption and power installation requirements, energy-regenerative hydraulic elevators have been developed since 1997. Different methods of energy recovery were introduced for the new design of energy-regenerative system. Experimental studies were carried out to compare the energy consumption of different system designs of hydraulic elevator
The grain size and its identity of abrasives are of high importance to obtain the damage-free and low roughness surfaces in traditional polishing processes. The undesirable scratches will appear on the surface of work...
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The grain size and its identity of abrasives are of high importance to obtain the damage-free and low roughness surfaces in traditional polishing processes. The undesirable scratches will appear on the surface of workpiece, if the grain size of abrasives is of high decentralization, or some abnormal larger grains or impurities are interfused in polishing process. And it is very difficult to polish curved surfaces. A new polishing technology, which is called as polishing with flotative abrasive balls, is put forward in this paper, in order to solve the problems mentioned above. Some primary experiments and theoretical analyses are carried out. It is found that the contact pressure between workpiece and abrasive grains may be easily controlled, as a result, the depth of cutting may also be easily controlled and it is not sensitive to the grain size of abrasives. The new technology may also be used in the polishing of curved surfaces.
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