| 1. |
|
|
| 2. |
- Ahlin, Kjell, et al.
(author)
-
A smart way to analyze dynamic data
- 2003
-
In: Sound & Vibration. - : Acoustical Publications, Inc.. - 1541-0161 .- 2693-1443. ; :February, s. 20-22
-
Journal article (other academic/artistic)abstract
- In recent years MATLAB® has become a common software tool for general computational mathematics, in universities as well as in industry. In the field of noise and vibration analysis, MATLAB is very common in universities, but perhaps a little less common in the industrial world. In this article some ideas are presented on how MATLAB can be successfully used for analyzing experimental noise and vibration data. Through the introduction of toolboxes in this field, the less experienced user can take advantage of the powerful functionality of MATLAB, either as the main tool or as a complement to the many excellent menu driven systems available on the market. Some of the advantages and disadvantages of using MATLAB versus menu driven systems are also discussed.
|
|
| 3. |
- Ahlin, Kjell, et al.
(author)
-
Comparing Road Profiles with Vehicle Perceived Roughness
- 2004
-
In: International Journal of Vehicle Design. - Geneva, Switzerland : Inderscience Enterprises. - 0143-3369 .- 1741-5314. ; 36:2-3, s. 270-286
-
Journal article (peer-reviewed)abstract
- Accurate road profiles are useful in vehicle design, such as for simulation of durability and ride quality. Laser/inertial profilometers typically record I mm wide profiles. The question is how well such a profile matches perceived vehicle wheel roughness. The objective here was to create a more representative wheel track longitudinal profile. Simulated and measured wheel vibration was compared on a 6km long road. Simulations were made for several definitions of the profile. Results for single laser sensor profiles showed reasonable likeness to truck perceived roughness. By far the best likeness (14.5% better) was achieved when the profile was based on triangular 25%-50%-25% weighted data from three sensors in the wheel track. Clearly, vehicle engineers can benefit from using multiple laser profile sensors, instead of a single sensor. This will improve test accuracy, thus reducing vehicle design project lead times and costs.
|
|
| 4. |
- Ahlin, Kjell
(author)
-
Comparison of Test Specifications and Measured Field Data
- 2006
-
In: Sound and Vibration. - Bay Village, Ohio, USA : Acoustical. - 0022-460X. ; 40:9, s. 22-25
-
Journal article (peer-reviewed)abstract
- It is not always obvious how to compare a given test specification with measured field data. This article presents a systematic method based on the shock response spectrum and the fatigue damage spectrum. A random-on-random test specification for tracked vehicles, AECTP 400, is used as an example.
|
|
| 5. |
- Ahlin, Kjell, et al.
(author)
-
Simulation of forced response in linear and nonlinear mechanical systems using digital filters
- 2006
-
Conference paper (peer-reviewed)abstract
- There exist many methods to calculate forced response in mechanical systems. Some methods are slow and the errors introduced are unknown. The paper presents a method that uses digital filters and modal superposition. It is shown how aliasing can be avoided as well as phase errors. The parameters describing the mechanical system are residues and poles, taken from FEA models, from lumped MCK systems, from analytic solutions or from experimental modal analysis. Modal damping may be used. The error in the calculation is derived and is shown to be only a function of the sampling frequency used. When the method is applied to linear mechanical systems in MATLAB it is very fast. The method is extended to incorporate nonlinear components. The nonlinear components could be simple, like hardening or stiffening springs, but may also contain memory, like dampers with hysteresis. The simulations are used to generate test data for development and evaluation of methods for identification of non-linear systems.
|
|
| 6. |
- Brandt, Anders, et al.
(author)
-
A Digital Filter Method for Forced Response Computation
- 2003
-
Conference paper (peer-reviewed)abstract
- Transient forced response of mechanical structures is usually computed using time domain integration. This is often computationally costly, and the numerical precision and stability are concerns. In the present paper, a novel method based on modal superposition, using a new digital filter implementation, is presented. Poles and residues of the model are used as input data, which allows for using data from a finite element model, a lumped parameter model, or from experimental modal analysis. Modal damping can be used if the damping matrix is unknown. With the proposed method, the frequency dependant error can easily be computed, and can be chosen arbitrarily small by selecting proper sampling frequency (time increment). The method is applicable to all linear structures and can be used for stationary or transient input data. Simulation results show that the new method is superior to the alternative methods, at less computational cost.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Brandt, Anders, et al.
(author)
-
Main principles and limitations of current order tracking methods
- 2005
-
In: SOUND AND VIBRATION. - BAY VILLAGE : ACOUSTICAL PUBL INC. - 0022-460X. ; , s. 19-22:March, s. 19-22
-
Journal article (peer-reviewed)abstract
- Order tracking is a widely used tool for analysis of vibrations generated in vehicle drivetrain components, since many vibrations are related to engine RPMs. In recent years, offline order tracking has become suitable due to enhanced computer speeds. Many methods, some patented, for both online and offline order tracking have been presented over the years. This article reviews some basic ideas behind current methods and compares their main advantages and limitations. Some basic time-frequency concepts and time window effects are reviewed. Questions on suitable tachometers and their number of pulses per revolution are also addressed. The possibility of processing RPM dependent data without tachometers is also discussed.
|
|
| 10. |
|
|
