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28th International Symposium on Automation and Robotics in Construction, ISARC 2011

作者： Heikkilä, Rauno Hovila, Jani Ahola, Jari M. Nevala, Kalervo Scháfer, Timo University of Oulu Construction Technology Research Center Oulu Finland VTT'Technical Research Centre of Finland Networked Intelligence Oulu Finland Department of Mechanical Engineering Laboratory of Mechatronics and Machine Diagnostics University of Oulu Oulu Finland

A large research program of digital product process has been active (2008-2012) in Finland. The goal of the program has been to increase customer orientation and productivity in company networks that design and deliver products, systems and services to global markets. For small and medium sized companies the developing of multitechnical products usually has to be done in a network of companies. This requires a lot of data transfer and integration between various computer systems. To improve these processes the research project "Developing the digital product process of multitechnical products to improve the designing and manufacturing of small series product" (Monidigi) has been started. The aim of the Monidigi research was to improve the design process by using solely digital product information that is handled by proper product lifecycle management systems. The product development is guided by the philosophy of the digital prototype that is tested in a virtual working environment. Products are modeled in 3D and developed by various simulations and analyses before real prototypes are made. This allows a flexible design process and coordinated change management. Digital product processes allow easy data transfer, collaborated engineering and modern manufacturing in a network of companies. Several examples and development possibilities and the state of the art in construction industry are introduced and evaluated.

关键词： Data transfer

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Intelligent scaling of features in fault diagnosis

Intelligent scaling of features in fault diagnosis

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7th International Conference on Condition Monitoring and machinery Failure Prevention Technologies 2010, CM 2010/MFPT 2010

作者： Juuso, Esko Lahdelma, Sulo Control Engineering Laboratory Department of Process and Environmental Engineering P.O.Box 4300 FI-90014 University-of-Oulu Finland Mechatronics and Machine Diagnostics Laboratory Department of Mechanical Engineering P.O.Box 4200 FI-90014 University-of-Oulu Finland

ISBN: (纸本)9781618390134

Automatic fault detection with condition indices enables reliable condition monitoring to be combined with process control. Useful information on different faults can be obtained by selecting suitable features. Generalised norms can be defined by the order of derivation, the order of the moment and sample time. These norms have the same dimensions as the corresponding signals. The nonlinear scaling used in the linguistic equation approach extends the idea of dimensionless indices to nonlinear systems. Condition indices are obtained from short samples by means of the scaled values and linear equations. Indices, which are used in the same way as the process measurements in process control, detect differences between normal and faulty conditions and provide an indication of the severity of the faults. The generalised norms represent the norms from the minimum to the maximum in a smoothly increasing way. The new nonlinear scaling methodology based on generalised norms and skewness provides good results for the automatic generation of condition indices. Additional sensitivity is achieved for the values which differ only slightly from the centre values. For cavitation, the new approach provides four levels from cavitation-free to clear cavitation. For the supporting rolls of a lime kiln, it provides an efficient indication of faulty situations. Sensitivity is also improved for small fluctuations. All the supporting rolls can be analysed using the same approach throughout the data set. The results of both the applications are consistent with the vibration severity criteria: good, usable, still acceptable, and not acceptable. Warning and alarm limits can be defined and fault types can also be identified with fuzzy set systems and specialised condition indices.

关键词： Cavitation

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Generalised lp norms in vibration analysis of process equipments

Generalised lp norms in vibration analysis of process equipm...

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7th International Conference on Condition Monitoring and machinery Failure Prevention Technologies 2010, CM 2010/MFPT 2010

作者： Lahdelma, Sulo Juuso, Esko Mechatronics and Machine Diagnostics Laboratory Department of Mechanical Engineering University of Oulu P.O. Box 4200 FI-90014 Finland Control Engineering Laboratory Department of Process and Environmental Engineering University of Oulu P.O. Box 4300 FI-90014 Finland

ISBN: (纸本)9781618390134

Advanced signal processing methods combined with automatic fault detection enable reliable condition monitoring for long periods of continuous operation. Rapid changes in acceleration become emphasised upon the derivation of the signal x(2) . The aim is to detect faults at an early stage by using the absolute values of the dynamic part of the signals. Generalised norms p M p can be defined by the order of derivation ( ), the order of the norm ( p ) and sample time ( ), where and p are real numbers. These norms have the same dimensions as the corresponding signals. A need for maintenance is indicated for lime kilns, which are essential parts of the chemical recovery cycle in a pulp mill. These large machines with very slow rotational speeds must run at different production capacities and speeds. The generalised norms provide an efficient indication of faulty situations in the supporting rolls. Surface damage and alignment problems are clearly detected and in the present system also identified with two norms of different order obtained from the signals x(4) . An early indication of friction increase is also achieved. The data set covers the following cases: (1) surface problems, (2) good conditions after grinding, (3) misalignment, (4) stronger misalignment, (5) very good conditions after repair work, and (6) very good conditions one year later. Maintenance was done for one of the supporting rolls. All the rolls can be analysed using the same features throughout the data set. All the faults, friction and minor fluctuations were validated by listening to the recorded acceleration signals and analysing time domain signals and frequency spectra with an oscilloscope and a real time analyser.

关键词： Condition monitoring

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Cavitation indices in power control of Kaplan water turbines

Cavitation indices in power control of Kaplan water turbines

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6th International Conference on Condition Monitoring and machinery Failure Prevention Technologies 2009

作者： Juuso, Esko Lahdelma, Sulo Control Engineering Laboratory Department of Process and Environmental Engineering University of Oulu P.O.Box 4300 FI-90014 Finland Mechatronics and Machine Diagnostics Laboratory Department of Mechanical Engineering University of Oulu P.O.Box 4200 FI-90014 Finland

ISBN: (纸本)9781618390097

Cavitation is harmful to water turbines and may cause shutdowns for several weeks. The real-time detection of cavitation risk is increasingly important, and even narrow cavitation-free power ranges can be utilised in load optimisation. Higher derivative signals x(a),a =3 or 4, calculated from acceleration signals x(2)are very suitable for detecting impacts. Generalised moments and their lp norms, ||τ Mαp||, detect the normal operating conditions, which are free of cavitation, and also provide an early indication of cavitation risk. On-line cavitation monitoring is based on cavitation indices calculated from a moving maximum of the lp norms obtained from samples. Data compression is very efficient, as the detailed analysis only requires feature values with a short sample time, τ = 3s. The absolute mean, i.e. the order of moment p = 1, is very good in normal operating conditions and in the high power range. The cavitation indicator also provides warnings on short periods of cavitation if the power is not too low. This is readily suitable for intelligent sensors where a good solution is to use analogue signals x (4). The optimal norm (p = 2.75) is only needed in the low power range. Power control minimises the cavitation risk by dividing the load between three turbines, whose conditions are normal, bad and very good. Each turbine has three operating modes: low, normal and high power. In the normal area, a cavitation free power level is taken as an operating point. The low and high operating areas are defined by local minima of the cavitation indices. The control system has a feedforward controller, which allocates the load to the turbines by means of knowledge-based cavitation indices, and a feedback controller, which is based on the linguistic equation (LE) approach. Each turbine has a P type LE controller which is adapted to the operating conditions by the scaling functions. The cumulative time in the strong cavitation provides an indication of possible damage to be

关键词： Cavitation

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Generalised moments and lp norms in vibration analysis

Generalised moments and lp norms in vibration analysis

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6th International Conference on Condition Monitoring and machinery Failure Prevention Technologies 2009

作者： Lahdelma, Sulo Juuso, Esko Mechatronics and Machine Diagnostics Laboratory Department of Mechanical Engineering University of Oulu P.O.Box 4200 FI-90014 Finland Control Engineering Laboratory Department of Process and Environmental Engineering University of Oulu P.O.Box 4300 FI-90014 Finland

ISBN: (纸本)9781618390097

The signals x(3) and x(4) are very suitable for the condition monitoring, and real order derivatives x(α) provide additional possibilities. Generalised moments τM αp and their lp norms are defined by the order of derivation (α), the order of the moment (p) and sample time (τ), which all are real numbers. The lp norms have the same dimensions as the corresponding signal. Optimal parameters α, p and τ, have been obtained for a Kaplan water turbine, which was analysed in a wide power range. A short sample time, τ=3 s, and relatively small requirements for the frequency ranges make this approach feasible for on-line analysis and power control. High correlation to the knowledge-based cavitation index is achieved with the relative max( 3 M42.75). In the problematic low power range, absolute average and rms values result in considerably lower R2 values even when α=4, and the corresponding norms with α=3 are inacceptable. The second example is a centrifuge, which has very fast rotating roller bearings. The sensitivities of the norms with different values for the order α, and the order p are compared. The sample time 3.9 ms corresponds to two rotations. A good order of derivation and proper frequency ranges are beneficial for fault detection. The norms based on the signal x(4) provide the best results: good results are already obtained in the frequency range 10-1000 Hz. The absolute mean x(α) av can be used if the order α is proper and the frequency range is sufficient. This is readily suitable for intelligent sensors where a good solution is to use analog signals x(4) and combine peak values x (4)p and absolute averages x(4) av. These methodologies are not limited to vibration analysis.

关键词： Vibration analysis

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Adaptive features in condition monitoring systems

Adaptive features in condition monitoring systems

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6th International Conference on Condition Monitoring and machinery Failure Prevention Technologies 2009

作者： Strackeljan, Jens Lahdelma, Sulo Otto-von-Guericke-Universität Magdeburg Fakultät für Maschinenbau Institut für Mechanik Universitätsplatz 2 30106 Magdeburg Germany Mechatronics and Machine Diagnostics Laboratory Department of Mechanical Engineering University of Oulu P.O.Box 4200 FI-90014 Finland

ISBN: (纸本)9781618390097

This paper presents some aspects concerning the problems of adaptive monitoring systems. Each automatic monitoring system has to be adapted if it is installed in a new environment. Characteristic of solving the monitoring task, the number of fault classes and free parameters in the internal classier are potential switchers to adjust the system. We discuss general problems in the field, such as fault simulation, provide the necessary definitions of different levels of adaptivity, describe the state of the art and give some hints about how the implementation of intelligent data pre-processing can improve the transfer of data from an existing system to a new one. As an application we use the detection of fault in a roller bearing using the derivative x(4) to obtain a higher sensitivity in the monitoring system.

关键词： Condition monitoring

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Development of an accuracy assessment phantom for surgical navigators

Development of an accuracy assessment phantom for surgical n...

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Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)

作者： Tapani Koivukangas Jani Katisko Kalervo Nevala Yrjo Louhisalmi John Koivukangas Department of Mechanical Engineering University of Oulu Oulu Finland Hospital Physicist Department of Neurosurgery Oulu University Hospital Oulu Finland Mechatronics and Machine Diagnostics Laboratory Technical Research Centre of Finland University of Oulu Oulu Finland Department of Neurosurgery and Chief of the Neurosurgery Research Unit Oulu University Hospital Oulu Finland

The objective of this study was to design a calibration phantom for a surgical navigator used in a hospital environment. It addresses two major issues: the design of an accuracy phantom and the accuracy analysis of the surgical navigator in a hospital setting. The designed phantom was used to assess the accuracy of the optical tracking modality of the surgical navigator used at Oulu University Hospital, Oulu, Finland. The phantom functioned according to the design criteria, it was easy to use and it had enough calibration points that were localized by the navigator according to the accuracy assessment protocol to assess the accuracy error. The distances measured from a fixed origin with the surgical navigator were compared to the known phantom calibration point coordinates. The mean error was within the manufacturer specifications of 1.00 mm. The analysis done using the designed phantom and accuracy assessment protocol showed that the error increased with the distance from the center of the phantom. The accuracy assessment protocol using the present phantom proved to be a suitable method for accuracy analysis of a surgical navigator in a hospital setting.

关键词： Imaging phantoms Surgery Navigation Hospitals Calibration Protocols Neurosurgery Surges Optical sensors Manufacturing

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Vibration Analysis of Cavitation in Kaplan Water Turbines

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IFAC Proceedings Volumes 2008年第2期41卷 13420-13425页

作者： Sulo Lahdelma Esko K. Juuso Mechatronics and Machine Diagnostics Laboratory Department of Mechanical Engineering P.O. Box 4200 FI-90014 University of Oulu Finland Control Engineering Laboratory Department of Process and Environmental Engineering P.O. Box 4300 FI-90014 University of Oulu Finland

Cavitation is harmful to water turbines and may cause operation delays of several weeks. The real-time detection of cavitation risk is increasingly important, and even narrow cavitation-free power ranges can be utilised in load optimisation. Higher derivative signals x (3) and x (4) calculated from acceleration signals are very suitable for detecting impacts. This paper introduces a generalised moment which is defined by three parameters: the sensitivity of the moment improves when the order p of the moment increases, especially when short sample time τ is used. In this study, sufficently good results were obtained with moments where the order of derivation α = 4, p ≈ 4, and τ = 3 s . These moments detect the normal operating conditions, which are free of cavitation, and also provide a clear indication for cavitation risk at an early stage. Sufficiently long signals are required for producing reliable maximum moments and data for analysing short-term cavitation. On-line cavitation monitoring is feasible with this approach since the analysis does not need high frequency ranges and the sample times are very short. The moment can be analysed first, and it is then possible to obtain the cavitation index if the moment value exceeds the threshold. Data compression is very efficient as the detailed analysis only requires the feature values of the appropriate samples.

关键词： cavitation vibration analysis higher order derivatives feature extraction water turbine

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