Jan Leuridan

High Resolution Order Tracking at Extreme Slew Rates Using Kalman Tracking Filters

The analysis of the periodic components in noise and vibration signals measured on rotating equipment such as car power trains, must be done more and more under rapid changes of an axle, or reference RPM. Normal tracking filters (analog or digital implementations) have limited resolution in such situations; wavelet methods, even when applied after resampling the data to be proportional to an axle RPM, must compromise between time and frequency resolution. The authors propose the application of nonstationary Kalman filters for the tracking of periodic components in such noise and vibration signals. These filters are designed to accurately track signals with a known structure among noise and signal components of different, “unknown,” structure. The tracking characteristics of these filters, i.e., the predicted signal amplitude versus time values versus exact signal amplitude versus time values, can be tailored to accurate tracking of harmonics buried in other signal components and noise, even at high rates of change of the reference RPM. A key to the successful construction is the precise knowledge of the structure of the signal to be tracked. For signals that vary with an axle RPM, an accurate estimate of the instantaneous RPM is essential, and procedures to this end will also be presented.

Multiple input orthogonal polynomial parameter estimation

Abstract The object of this paper is the development of a so-called global modal parameter estimation technique capable of analysing frequency response functions (FRFs) between several input and response stations simultaneously. The technique analyses the FRFs in their natural domain, the frequency domain. Highly consistent estimates of all modal parameters, including repeated modes, can be obtained. The effect of modes outside the analysis band can also be accounted for by explicitly locating these modes, by including residual terms, or by a combination of both. The use of orthogonal polynomials improves the numerical properties of the calculation procedure. It also reduces the order of the identification problem. All pertinent equations have a size which is proportional to the number of modes in the data, and are independent of the number of response and input stations for which data are analysed simultaneously. As a consequence, the technique lends itself readily to implementation with microcomputers.

Virtual engineering at work: the challenges for designing mechatronic products

The product race has become an innovation race, reconciling challenges of branding, performance, time to market and competitive pricing while complying with ecological, safety and legislation constraints. The answer lies in “smart” products of high complexity, relying on heterogeneous technologies and involving active components. To keep pace with this evolution and further accelerate the design cycle, the design engineering process must be rethought. The paper presents a mechatronic simulation approach to achieve this goal. The starting point is the current virtual prototyping paradigm that is widely adopted and that continues to improve in terms of model complexity, accuracy, robustness and automated optimization. Two evolutions are discussed. A first one is the extension to multi-physics simulation answering the design needs of the inherent multi-disciplinarity of “intelligent” products. Integration of thermal, hydraulic, mechanical, haptic and electrical functions requires simulation to extend beyond the traditional CAD-FEM approach, supporting the use of system, functional and perception models. The second evolution is the integration of control functions in the products. Where current industrial practice treats mechanical system design and control design as different design loops, this paper discusses their integration in a model-based design process at all design stages, turning concepts such as software-in-the-loop and hardware-in-the-loop into basic elements of an industrial design approach. These concepts are illustrated by a number of automotive design engineering cases, which demonstrate that the combined use of perception, geometric and system models allows to develop innovative solutions for the active safety, low-emission and high-comfort performance of next-generation vehicles. This process in turn poses new challenges to the design in terms of the specification and validation of such innovative products, including their failure modes and fault-tolerant behaviour. This will imply adopting a model-based system engineering approach that is currently already common practice in software engineering.

Frequency domain direct parameter identification for modal analysis: State space formulation

Abstract This paper outlines the theoretical development of a modal identification technique for the dynamic behaviour of linear time-invariant systems. Using a state space formulation for the equations of motion for a mechanical structure, an algorithm is developed to identify its state transition matrix from measured multiple input/multiple output relations (frequency response functions). From the identified matrix quantities, it is possible to derive a modal model of natural frequencies, damping values, mode shapes and modal participation factors. Aspects of data reduction via singular value analysis are discussed to extract valid state variables from the entire set of response stations. Emphasis is put on the application of this frequency domain direct parameter identification technique for the analysis of non-uniformly sampled frequency response functions, as generated for example when automated stepped-sine excitation is applied for modal testing of mechanical structures.

Data Stream Synchronization of Distributed Measurements Systems Using GPS Technology

Global Positioning System (GPS) satellite signals are used in time and frequency metrology in general and a GPS receiver can provide a reference signal for frequency and time synchronization in particular. GPS, well known as a versatile, global tool for positioning, has also become the primary system for distributing time and frequency. GPS delivers very precise time as a by-product of their navigation methodology and the exacting timing requirements for the satellite. For measurement applications, like recording the accurate time (time stamping) and positioning (extract distances and velocity speed) are useful information for a single device. Due to the time accuracy, GPS can be used for synchronization of multiple, distributed measurement systems. The article describes the measurements set up and the result of phase-match specifications between separate, stand-alone systems, which meet figures of current inter-channel phase-match specifications.

Case Study: An Automobile Body

This chapter considers the application of correlation and validation techniques to an automobile body, commonly called a body-in-white. The automobile was a 1991 GM Saturn four door Sedan (Brughmans et al., 1992). The finite element model of this car had 46830 degrees of freedom (half model). A multi-point experimental modal analysis (EMA) survey was performed with 360 response degrees of freedom. Classical techniques for correlation analysis such as the Modal Assurance Criterion (MAC, Chapter 4) were applied. Error localisation methods identified the regions of the finite element model that caused most of the discrepancies between the model and the measurements. The Bayesian, or minimum variance, updating method (Chapter 8) reduced the difference between the finite element model and measured modal model to acceptable limits.

Integrated stepped-sine system for modal analysis

Abstract The inherent qualities of the stepped-sine excitation technique for frequency response measurements are generally accepted, but several factors have made its practical implementation as a valid alternative to todays broadband excitation methods very difficult. The dedicated hardware for harmonic testing and the incompatibility of the obtained frequency response functions with current commonly used parameter estimation methods inhibited the integration of both methods into a single modal analysis system. In order to overcome these limitations, a versatile measurement front-end, ensuring the compatibility of these procedures, as well as new multiple input parameter estimation methods have been developed. This paper discusses the integration of stepped-sine excitation into a standard modal testing system and illustrates its application with a complete dual input test example.

Use of Interface Agents for Automatic Pass-by-Noise Measurements

Global competition requires product development cycles to bring technology innovation into new products while consistently shortening time to market. In software industry, new product releases are yearly launched to commercially better exploit technology added value. Such a fast changing scenario makes it very hard for users to get acquainted with newly implemented functionalities. This problem is even more critical in case commercial software - often very technical - is used to simplify complex industrial applications. A typical example in NVH measurement is pass-by-noise testing, where complex test set-up and strict data validation procedures require several expert operators to perform the test. This paper presents a multiagent system that assists a single non-expert test engineer to correctly perform pass-by noise measurement. The proposed solution uses interface agent technology to control the data acquisition system, deal with the complex test set-up and perform automatic and on-line data validation check on measured data

Multi-agent Systems in a One-man Operation Measurement Setup

Global competition requires product development cycles to bring technology innovation into new products while consistently shortening time to market. In software industry, new product releases are yearly launched to commercially better exploit technology added value. Such a fast changing scenario makes it very hard for users to get acquainted with newly implemented functionalities. This problem is even more critical in case commercial software - often very technical - is used to simplify complex industrial applications. A typical example in NVH measurement is pass-by-noise testing, where complex test set-up and strict data validation procedures require several expert operators to perform the test. This paper presents a multiagent system that assists a single non-expert test engineer to correctly perform pass-by noise measurement. The proposed solution uses interface agent technology to control the data acquisition system, deal with the complex test set-up and perform automatic and on-line data validation check on measured data.

Holography as a quantitative modal testing technique applied to a brake drum in view of correlation with FE data

Classical Modal Testing techniques, using accelerometers, are faced with problems of mass loading and spatial resolution if lightweight structures and/or high frequency modes have to be measured. Until today, holographic techniques, such as Electronic Speckle Pattern Interferometry (ESPI) are mainly used as a qualitative rather than quantitative measurement technique and usually lack the capability to measure phases of the vibration. An approach, using ESPI, has been developed which allows to measure the response displacement of the complete structure in amplitude and phase format. If referenced to the measurement of input force, it allows to obtain the complete frequency response functions, which can then be processed by classical modal parameter identification techniques in order to extract the frequency and mode shape information. The approach has the advantage to give very high density spatial information (several thousands points measured simultaneously without mass-loading) in a numerical format directly usable for further numeric analysis. This paper explain the approach and shows how it has been used to perform a modal analysis of a brake drum, in view of a correlation analysis with the FE model of this drum. It will discuss practical aspects involved in the measurements, present obtained results and highlight possible further development and automation.