vibration measurements car

Automotive - NVH Testing

The duration of product development processes from concept to series production is getting shorter and shorter. This is particularly the case in the automotive industry, where the switch to electromobility is accelerating change. New components and the use of lightweight construction require extensive vibration analyzes.
Even if components and entire component groups are increasingly and always more precisely examined for their properties by numerical simulations, real measurements on models are still required to validate these calculations. Non-contact measurement techniques such as laser vibrometry have the advantage that they do not influence the vibrations of the components and deliver very good results in a very short time with little effort.

The superior signal quality of the Optomet infrared technology guarantees the best possible measurement result even on problematic surfaces. This makes the devices suitable for measuring any component, regardless of its material and nature. The simple handling of the measuring device and software saves valuable time and helps to reduce the development time. Whatever application you want to measure non-contact vibrations, be it in the wind tunnel, on the rotation test rig or in the acoustic laboratory, for modal tests, for the development of components such as sensors or drives, the Optomet team will be happy to assist you in selecting the suitable vibrometry solution and implementing it.

Aeroacoustics

Aeroacoustics deals with the noise caused by the flow. Turbulent flows, flows through and around structures create vibrations on components. These vibrations, in turn, are responsible for the generation and emission of sound waves, some of which people perceive as unpleasant. Ever stricter immission regulations also increase the need for a noise-reducing design.
Noise reduction is particularly important in the aerospace and automotive industries. Examples of noise sources are, for example, engine noises on aircraft or wind noises on motor vehicles and high-speed trains. These are perceived as the more disruptive the more other sources of noise disappear, as is apparent from the replacement of internal combustion engines in motor vehicles by electric drives.


The airborne sound perceived as noise is picked up by microphones or entire arrays of microphones. However, when it comes to identifying the possible sound sources, measurement methods with better spatial resolution, such as scanning laser Doppler vibrometry, are required.


With the Optomet Laser Scanning Vibrometers, both small structures and entire vehicles can be examined contactlessly and with high accuracy. The user-friendly OptoSCAN software enables the measurement to be carried out quickly and offers a wide range of meaningful evaluations and clear two-dimensional and animated displays for this task. For example, the correlation of the forms of vibration with the frequencies recorded in airborne noise can be used to draw important conclusions about the location and the type of sound generation, and suitable design measures for noise suppression can be taken.


The infrared laser technology (SWIR) of the Optomet Scanning Vibrometer guarantees a sufficient signal level for a reliable vibration measurement even at larger measuring distances of more than 10 meters. Even dark or reflective curved measuring surfaces can be measured without a reflection-enhancing treatment. Measurements through thick glass surfaces between vibrometer and measurement object are also possible without impairments.

 

 

Brake noise

The dynamic behavior of brakes under load is crucial for the overall assessment of brake systems. Brake noise, brake squeal and the entire brake acoustics have a major impact on the performance and comfort of the vehicle. For example, premature and unexpected wear and tear can significantly impair the efficiency of the brake system and thus driving safety.

The comfort of the occupants is also of increasing importance in automotive development. For vehicle buyers, especially in the premium segment, acoustic comfort is often an important argument for or against a purchase. In addition, brake noise is perceived as the more annoying, the more other noise sources are eliminated, as is the case, for example, when internal combustion engines are increasingly to be replaced by electric drives.

The cause of the brake squeal is the friction between the brake disc and the brake pads and the resulting excitation of vibration modes at frequencies that are perceived as unpleasant by the human ear. In brake development, finite element models are used to determine such modes and to suppress their occurrence by suitably adapting the brake geometry or other design measures.

The Optomet Scanning Laser Doppler Vibrometer allows the contactless detection and analysis of the occurring vibration forms of the surfaces of the brake disc and caliper, as well as their 3-dimensional animated representation. This enables the model calculations to be precisely compared with and validated by the actual vibration behaviour.

To investigate the brake characteristics, the brake can be excited to vibrate with a modal hammer, or the brake vibrations can be measured under operating conditions. The first method provides all modes of the braking system, but the influence of fastenings and couplings on the vibration behaviour is neglected, as well as typical modes experienced by the driver in the actual car. In the second method scanning laser technology is used to advantage in the operational vibration analysis of the system consisting of brake discs and calipers on brake test benches under conditions that are as close to reality as possible. However, the targeted stimulation of squeaking noises is usually not easily repeatable. With Optomet Scanning Laser Vibrometers it is possible to automatically limit the measurement to the time window in which the squeaking actually occurs. This means a considerable relief and time saving in the optimization process.

The Optomet SWIR laser vibrometer technology is ideally suited for the measurement of brake systems and components in vehicle construction. The decisive advantage of the Optomet solution compared to conventional HeNe-based systems is particularly evident when measuring brake discs on the test bench. Back-to-back tests by SWIR and HeNe vibrometers have shown that due to the excessive noise level, HeNe systems are unable to provide measurement data of sufficient quality. The resonances to be examined are lost in the noise. The use of the Optomet SWIR laser vibrometer technology, on the other hand, brings about a dramatic improvement and in these applications delivers results with noise levels that are 40 dB to 50 dB below the resonance peaks.

 

 

Electric Drives

Modern cars have many electric drives built in, some of which are in the direct area of perception of the occupants of the car, such as electric windows, electric sunroof, servo motors for outside mirrors, wiper motor or seat adjusters. Other drives operate without being perceived directly, such as fuel and coolant pumps or blower motors.

Beyond their desired function, these drives an also be a source of objectionable noise. Such extraneous noise can become clearly audible, especially in electric or hybrid vehicles where the combustion engine as one of the main sources of noise is eliminated.

Laser vibrometers from Optomet are ideal in assisting design and test engineers in localizing, visualizing, quantifying and eliminating such sources of undesirable noise. 
 

 

 

Haptic Displays

In the age of tablets and smartphones, we have long become used to swiping instead of typing. However, many users find it difficult to type on virtual keyboards because they cannot see through their fingertip which point on the touch screen is being touched.

Safety issues arise when touch-sensitive displays are used during the operation of a vehicle. One solution is haptic displays which make keys and slide controls physically perceptible on the display. They provide tactile feedback to a user’s finger during the execution of his or her commands without the need to look at the screen.

Optomet laser Doppler vibrometers are indispensable tools during the development of such haptic displays as well as for their quality assurance in production.
 

 

 

Where does the annoying noise come from?

Particularly in vehicles in which a large number of components are installed, unwanted vibrations occur repeatedly, which the driver and his passengers often perceive as structure-borne or airborne noise as disturbing noises. Using so-called NVH tests, which stand for "noise, vibration, roughness" engineers try to localize the sound sources and then eliminate them. The aim is to provide the user with the most comfortable, noise-optimized product possible.

Laser scanning vibrometers from Optomet with their high spatial resolution and their high signal-to-noise ratio on any surface are particularly suitable for locating the sources of vibration. With the simple and intuitive software for the measurement process, the meaningful 3D visualization of the data and the fast automated scanning process, product surfaces can be examined in a very short time.
The numerous options for displaying and exporting the measurement data facilitate communication with colleagues. Based on the results, engineers can, for example, rethink component connections or geometries and increase damping at suitable points.

 

 

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