Vibration Behavior of a Vehicle

 

By order of the technical department of AUDI AG the service company ID (ID = Ingenieurtechnische Dienstleistungen, equivalent for Engineering service) which is located in Kinding, Altmühltal, Germany, examines the oscillation behavior of a vehicle with the central point of body and chassis. ROGA-Instruments GX-1 is used for mobile and stationary operation. The front end with its several data interfaces permits easy and fast data transfer to the respective data analysis programs. ID is a firm which offers measurement and testing services for automotive industry and their suppliers, and for branches like engineering and plant manufacturing. Central point of their activities is the examination of modal and operational oscillations and analysis and finding solutions for actual problems.

 

There are lots of measurements to do. Not only in the field like observations of oscillations of a vehicle with up to 350 measuring points (triaxial each) but also in stationary applications like modal analysis for bodies, parts of chassis and engines and so on. To solve actual problems modal analysis software is a very useful tool. It is possible to replay sequences in a kind of slow motion which were not reproducible.

 

TEAC in the Field

 

Time synchronous acquisition of 96 channels

 

For time synchronous acquisition of all accelerations of the wheel suspensions a GX-1 with 64 channels and another one with 32 channels were used in synchronized operation. This was necessary because an ABS full braking and the reaction time of the suspension are never reproducible. For this reason a later synchronization of several measurement rides is not feasible. All measured accelerations were computed to distances by filtering and double integration. A method was used which does not produce phase shifting nor settling phenomena of filters. Aided by this kind of analysis the sequence of the phenomena which has to be observed could be described. Based on this knowledge combined with the computed operational oscillations a perfect solution could be found.

Especially useful for this kind of observation was the compact housing, the small amount of needed energy and the high stability of GX-1.

Mr. Lindner who owns ID pointed out the usefulness of the high flexibility of data exchange formats of the GX-1 . Especially for a service company which works for several customers and has to be compatible to many different systems this is a real benefit.

 

Animation of a Wheel Suspension During an ABS Full Braking

 

Because ID uses the GX-1 or very different measurement tasks like driving comfort, stability examinations, acoustical observations, road profile measurement and more engineers and technicians of ID appreciated the modular structure of the GX-1. Either acceleration, microphone, DMS, rotation or digital I/Os any of the modules can be combined freely. Furthermore the number of channels can be extended with respective units so it can be perfectly fit to any need.

GX-1 is also usable as front end for wide spread examinations of oscillations on the road and on shakers. Models with up to 350 measuring points can be analyzed. The structure shown in the upper right is a so called "trimmed body". This is a complete vehicle with removed engine, chassis and suspensions. Electro dynamic shakers provide the excitation.

ID is developing a system which is able to detect noise that could be heard during driving and which can be generated by respective excitation. At the wheel base movements in three directions are applied. The intensity of the applied movements is high enough to stimulate noise at the suspension and the inner of the body. The method to interpret the measured values is still under development.

The measurements are achieved with GX-1 units. Furthermore this allows excitations with wide bandwidths which reach the intensity of the real road excitation. So this permits to use this very cost effective exciters for simulated operational oscillations examinations.

 

Model Analysis "Trimmed Body" (First Bending)

 

The combination of GX-1 and DASYLab offers a lot new applications. As shown in the following circuit diagram GX-1 can be configured for any measurement task. In this application ID has measured accelerations also. An ICP supply unit was used to supply the sensors with the necessary voltage. For a first glance over the measured data time signals and online computed amplitude spectra were visualized. Data were stored simultaneously in two different formats. This was a must because the measured raw data had to be in a customer compatible format which allows ID the further processing.

Furthermore DASYLab makes automatic processing of measurement sequences possible and even the results can be put into a report automatically. Quite a nice feature for test applications.

 

DASYLab Circuit Diagram: Data of 32 Channels Saved in Two Formats