Final Report Summary - RANGE (Simulation of random non-Gaussian excitations in environmental testing and computer modelling for better product engineering of vehicle systems)
The IIF project RANGE relates to dynamic systems, such as vehicles, whose motion depends on the excitation applied, with this excitation being generated by environmental or technological effects. Hence, how accurately the excitation is simulated becomes a key point in design and testing. The excitation is often a random signal, i.e. it is not a unique time function but a collection of unpredictable realizations that still can be modeled if inherent characteristics governing behavior of such excitations are understood properly.
Modern computer systems made it possible to exercise analytical and experimental simulation of random excitations by digital synthesis. A common technique is to apply the Inverse Fast Fourier Transform (IFFT) with randomized phases to the specified power spectral density (PSD) that describes frequency spectrum of the excitation. That is how a Gaussian random excitation can be modeled. However, not all real excitations are Gaussian and the PSD is not a full description of random signals. There is another basic characteristic - probability density function. If it is different from that of the Gaussian model, the random excitation cannot be simulated by the classic IFFT.
The core of the project is a modification of the IFFT simulation to make it non-Gaussian by developing methods of IFFT phase manipulation. Dr. Alexander Steinwolf, the nominated visiting researcher, has been working on this problem for many years and his developments on kurtosis control were recognized and implemented by shaker equipment manufacturers in the USA, but not in Europe. An essential part of product development in the host organization also belongs to the shaker testing area. Thus, an important transfer of knowledge from the foreign expert to the European host could be realized. The cooperation between the project participants resulted also in using new characteristics more advanced than kurtosis to outclass current non-Gaussian random simulation methods. The cooperation also resulted in joint publications, that received substantial attention when presented at international conferences.
The following work was performed since the beginning of the project:
- Development of method 1: Polynomial transform with time-frequency domain swapping.
- Development of method 2: Analytical solution for phases based on kurtosis equation.
- Testing and performance comparison of two phase selection methods.
- Simulation of differences in non-Gaussian behaviour not described by kurtosis.
- Comparison of two phase selection methods in terms of accelerated fatigue shaker testing.
- Comparison of two phase selection methods for realistic excitation of car body vibration.
- Shaker testing with fatigue damage spectrum (FDS) as a criterion of mission signal synthesis.
The main results are, on the one hand, an initial commercially available implementation of non-Gaussian random control, and, on the other hand, a new method which enables qualification testing using damage equivalent non-Gaussian random vibration excitations. It is moreover possible to achieve an accelerated lifetime test, where the time-to-failure at a particular resonance frequency is decreased in a controlled manner, by increasing the kurtosis while the PSD level is preserved.
Products of vehicle manufacturing industries in Europe and elsewhere are getting more and more complex, containing very delicate and critical subsystems like avionics, car electronics, etc., that may be the cause of product failure. The required robustness of such systems is however in direct conflict with demands for lightweight solutions, which are often of inferior mechanical quality. So, to perform design for reliability, while maintaining high standards on packaging and light weight, becomes increasingly important. This requires, due to less over-design space, much better knowledge and incorporation of realistic excitation signals. Dr. Alexander Steinwolf, the nominated Visiting Researcher, was the first to prove the necessity of high-kurtosis random vibration testing of vehicles and their components, to suggest methods capable of doing this non-Gaussian upgrade, and to verify experimentally how it works in the frame of current shaker control procedures. Siemens Industry Software hosted Dr Steinwolf as a Marie Curie IIF fellow for two years. His work in Belgium was a valuable transfer of important knowledge to the Host Organization and an essential contribution to European excellence and European competitiveness. Some very concrete deliverables were realized during the RANGE project. An initial version of LMS Test.Lab Kurtosis Control was released to the market. Together with the LMS SCADAS data acquisition hardware, customers can now perform more realistic testing. In addition, prototype code was developed for a next generation software that would allow even more advanced kurtosis control that makes the link to fatigue damage. It is expected that, through the wide base of Siemens PLM LMS customers throughout Europe, the RANGE project will contribute to the objective of having better European products which will be of longer life as they have been tested against more realistic environmental conditions. Also it would help to reduce some of the design conservatism and to avoid over-design with less materials used and energy saved.
The fellow worked closely together with hosting institution staff members of the research team (Dr. Herman Van der Auweraer, Dr. Bart Peeters, Dr. Karl Janssens, Dr. Bram Cornelis), the product management team (Dr. Alex Carrella, Ludo Gielen) and the software development team (Eddy Faignet, Johan De Rue):
- To ensure the uptake of the technology as in-house knowledge;
- To define the way the developed RANGE technology will be presented to prospective customers and to fine-tune the research activities based on feedback from early-visibility customers;
- To ensure the uptake of the technology as a commercial software deliverable.
During the project, the fellow was involved systematically in high-quality industrial projects and case studies running at SISW. This allowed to bridge the gap between academic research and industrial applications. It was a bi-directional process of, first, confronting the academic research with real problems that matter and hence driving research breakthroughs into relevance and, second, inversely allowing to upscale basic research methods from lab-scale validations to industrial-scaled applications.
SISW is a company having a leading position in the European software and systems scene. It is ideally placed to transfer the results of such a project as the International Incoming Fellowship to industry at large. SISW has this transformer role and working with SISW as a visiting researcher realized a tremendous leveraging factor to the industry which would not be achieved by working in a university laboratory. This allowed making an important step further, from advancement in “State-of-the-Art” to advancement in “State-of-the-Use”.
Modern computer systems made it possible to exercise analytical and experimental simulation of random excitations by digital synthesis. A common technique is to apply the Inverse Fast Fourier Transform (IFFT) with randomized phases to the specified power spectral density (PSD) that describes frequency spectrum of the excitation. That is how a Gaussian random excitation can be modeled. However, not all real excitations are Gaussian and the PSD is not a full description of random signals. There is another basic characteristic - probability density function. If it is different from that of the Gaussian model, the random excitation cannot be simulated by the classic IFFT.
The core of the project is a modification of the IFFT simulation to make it non-Gaussian by developing methods of IFFT phase manipulation. Dr. Alexander Steinwolf, the nominated visiting researcher, has been working on this problem for many years and his developments on kurtosis control were recognized and implemented by shaker equipment manufacturers in the USA, but not in Europe. An essential part of product development in the host organization also belongs to the shaker testing area. Thus, an important transfer of knowledge from the foreign expert to the European host could be realized. The cooperation between the project participants resulted also in using new characteristics more advanced than kurtosis to outclass current non-Gaussian random simulation methods. The cooperation also resulted in joint publications, that received substantial attention when presented at international conferences.
The following work was performed since the beginning of the project:
- Development of method 1: Polynomial transform with time-frequency domain swapping.
- Development of method 2: Analytical solution for phases based on kurtosis equation.
- Testing and performance comparison of two phase selection methods.
- Simulation of differences in non-Gaussian behaviour not described by kurtosis.
- Comparison of two phase selection methods in terms of accelerated fatigue shaker testing.
- Comparison of two phase selection methods for realistic excitation of car body vibration.
- Shaker testing with fatigue damage spectrum (FDS) as a criterion of mission signal synthesis.
The main results are, on the one hand, an initial commercially available implementation of non-Gaussian random control, and, on the other hand, a new method which enables qualification testing using damage equivalent non-Gaussian random vibration excitations. It is moreover possible to achieve an accelerated lifetime test, where the time-to-failure at a particular resonance frequency is decreased in a controlled manner, by increasing the kurtosis while the PSD level is preserved.
Products of vehicle manufacturing industries in Europe and elsewhere are getting more and more complex, containing very delicate and critical subsystems like avionics, car electronics, etc., that may be the cause of product failure. The required robustness of such systems is however in direct conflict with demands for lightweight solutions, which are often of inferior mechanical quality. So, to perform design for reliability, while maintaining high standards on packaging and light weight, becomes increasingly important. This requires, due to less over-design space, much better knowledge and incorporation of realistic excitation signals. Dr. Alexander Steinwolf, the nominated Visiting Researcher, was the first to prove the necessity of high-kurtosis random vibration testing of vehicles and their components, to suggest methods capable of doing this non-Gaussian upgrade, and to verify experimentally how it works in the frame of current shaker control procedures. Siemens Industry Software hosted Dr Steinwolf as a Marie Curie IIF fellow for two years. His work in Belgium was a valuable transfer of important knowledge to the Host Organization and an essential contribution to European excellence and European competitiveness. Some very concrete deliverables were realized during the RANGE project. An initial version of LMS Test.Lab Kurtosis Control was released to the market. Together with the LMS SCADAS data acquisition hardware, customers can now perform more realistic testing. In addition, prototype code was developed for a next generation software that would allow even more advanced kurtosis control that makes the link to fatigue damage. It is expected that, through the wide base of Siemens PLM LMS customers throughout Europe, the RANGE project will contribute to the objective of having better European products which will be of longer life as they have been tested against more realistic environmental conditions. Also it would help to reduce some of the design conservatism and to avoid over-design with less materials used and energy saved.
The fellow worked closely together with hosting institution staff members of the research team (Dr. Herman Van der Auweraer, Dr. Bart Peeters, Dr. Karl Janssens, Dr. Bram Cornelis), the product management team (Dr. Alex Carrella, Ludo Gielen) and the software development team (Eddy Faignet, Johan De Rue):
- To ensure the uptake of the technology as in-house knowledge;
- To define the way the developed RANGE technology will be presented to prospective customers and to fine-tune the research activities based on feedback from early-visibility customers;
- To ensure the uptake of the technology as a commercial software deliverable.
During the project, the fellow was involved systematically in high-quality industrial projects and case studies running at SISW. This allowed to bridge the gap between academic research and industrial applications. It was a bi-directional process of, first, confronting the academic research with real problems that matter and hence driving research breakthroughs into relevance and, second, inversely allowing to upscale basic research methods from lab-scale validations to industrial-scaled applications.
SISW is a company having a leading position in the European software and systems scene. It is ideally placed to transfer the results of such a project as the International Incoming Fellowship to industry at large. SISW has this transformer role and working with SISW as a visiting researcher realized a tremendous leveraging factor to the industry which would not be achieved by working in a university laboratory. This allowed making an important step further, from advancement in “State-of-the-Art” to advancement in “State-of-the-Use”.