Automotive

Signatures coming from gear box vibrations have a high frequency content. A first step is to analyze them using the standard FFT analysis. One can get furtherwith tools such as cepstrum, kurtosis and harmonic markers provided by the OROS FFT-Diagnostics tool.

The Constant Band Tracking function is also especially useful for looking at order profiles during run-ups and run-downs of the transmission train.

The OROS torsional module corresponds to a frequency to voltage converter that transforms a pulse train signal into a varying rotating speed value. This is a common cause for vibration in engines. A typical display is the varying angular velocity profile versus time. The rotating speed value signal can be analyzed: torsional modes can be deduced. Provided signals can also be processed with the Synchronous Order Analysis (SOA) module to give order tracking profiles.

Classical or hybrid transmissions are some of the major source of vibration in the drive train. Nowadays, CVT (Continously Variable Transmission) transmissions integrate a flexible transmission belt that allows an infinite number of transmission ratios. In order to carry order tracking, phase reference and rotating speed determination, the transmission ratio is based on a mathematical formula based on 2 tachometer’s inputs.

Balancing is a common application in particular for crankshaft that is often carried out during production. The OROS Balancing module enables to balance quickly and accurately. The synchronous order analysis can be controlled by NVDrive for integration into automatic balancing machines.

The objective is the engine performance optimization and faults detections. For example, injection delay, valves faults, can be identified with EngineDiag. This software module integrates the machine mechanical properties: number of cylinders, firing order and timing diagram to provide pertinent results.

Time signal, overall levels, cylinders phase alignment as well as angle-frequency representation on the machine cycle are efficient results for R&D and prototype validation.

Absorbing and damping mounts are the components through which the vibration energy is transmitted between the engine and the rest of the vehicle: their properties dimensions and positions are key and should be determined with care. The techniques used are cross spectrum, transfer functions, damping, as well as ODS (operating Deflection Shape).

Modal Analysis is one of the key step when testing component prototypes: it will determine their structural characteristics and so, will define how they will react to operating excitations. Shaker or impact hammer excitations can be used to capture the experimental datasets: the final stage is the actual OROS Modal analysis.

Sound Power is a key acoustical value to be determined for vehicles and various automotive components such as alternators and motors. For qualification and production testing, the most common procedure uses microphones and is based on sound pressure level acquisition (ISO 374x) in a free or diffuse sound field. For portable applications, sound intensity is preferably used to determine sound power. It is based upon measurements at discrete points (ISO 9614-1) or via a surface scanning (ISO 9614-2). In this case, a sound intensity probe is used.

During the NVH process, the acoustical specialist is often driven by improving the understanding and control of his product noise emission. Standard 1/3 octave analysis can be used as a first step. The Sound intensity acquisition at discrete points allows going one step further, drawing a colored noise map and acoustic iso lines. As near field holography would achieve it as well, hot spots and their corresponding frequencies will help the analyst to draw conclusions on how to reduce or control better the noise emission.

The feeling perceived when listening to a sound is a key in the quality evaluation of a product. In particular, in the automotive industry, the Sound Quality of a vehicle and its sub-components is carefully evaluated. In that process, both subjective and objective approaches are typically undertaken. For that, after in-vehicle signal acquisition, the analyst goes through pyschoacoustic parameters evaluation as well as sound design with filtered playback of signals. In that process, jury testing is typically organized and a correlation with the objective calculations processed.

In automotive and railway applications, in order to reduce and control noise emission for passengers, sources and especially their Transfer Paths contributions should be evaluated. This process requires an experimental approach to determine the frequency transfer relationship between sources, attached structures and the final target represented by the passenger. Then, it is followed by a specific Transfer Path Analysis, typically referred as TPA, to finally issue the contributions

Electric markers e-NVH excitations are spot right away (PWM, slotting…)
Spatiogram a unique tool to quickly quantify the contribution of different e-NVH excitation wavenumbers to vibrations
Sound design listen and playback the motor noise separating and designing the various sources

The different components installed in a vehicle are tested on the road to validate their integration in the vehicle (brakes, tires, turbocharger etc …). It requires a portable, rugged and easy recording system with a CAN bus interface. PC free recording is especially very useful for the toughest conditions (D-rec, Direct Recording)

Drive train and transmission components are submitted to high static and dynamic stress that create fatigue in the long term. During the prototype development and validation process, strain gauges are used to determine these parameters. They are also determined in combination with other parameters such as acceleration or rotating speed: having a way such as XPods, plug and play signal conditioning, to do that is essential.