Engineers Find New Way to Test Car Body Strength During Real Driving
Researchers have developed a method to measure how much a vehicle's body flexes and distorts while driving on test tracks, not just in labs. The technique could help automakers catch structural problems earlier and improve ride quality—but only works reliably at certain frequencies, a limitation engineers must now account for in their designs.
Originaltitel: A New Approach to Identify Rigid Body Rotations When Measuring the Body Distortion of a Full Vehicle
Bilverktygsmakare kan nu validera kroppssteifhet under körtester med en ny metod som kombinerar två signalbehandlingsansatser — E-line och Diagonal — för att identifiera när mätningarna blir opålitliga på grund av stela rotationer. Opening Distortion Fingerprint (ODF) tillsammans med Multi Stethoscope mäter dynamisk deformation i varje öppning och tvärsektion, men den traditionella E-line-metoden gäller endast vid små rotationer. Forskargruppen från Knite, Saab och Chalmers utvecklade ett verktyg för att från testdata bestämma vid vilken frekvens resultat blir ogiltiga — ett problem som tidigare inte lösts experimentellt. Metoden validerades på fullskaleignefordon och förenklat laboratorieexperiment. För utvecklingsteam är detta kritiskt för att förstå körningsmekaniken hos fordons styvhet utan att förlita sig enbart på statiska beräkningar eller dyra simuleringer. Metoden förkortar utvecklingstiden genom att ge tillförlitlig testvalidering på banan.
<div class="section abstract"><div class="htmlview paragraph">When developing a vehicle, the overall body stiffness is an important parameter to be estimated for several automotive attributes. As a complement to the traditional experimental and computational static torsional stiffness assessment, an improved method has been developed to evaluate the body stiffness when driving the vehicle on a test track. This method, valid for both test and simulation, is called Opening Distortion Fingerprint (ODF) and uses the so-called Multi Stethoscope (MSS) to measure the dynamic distortion in each body closure opening and cross section.</div><div class="htmlview paragraph">For evaluating the distortion, from both test and Multi Body Dynamics (MBD) simulation data, the Evaluation-line (E-line) method is used. The E-line method is a linear approach. Consequently, it is only valid in the absence of large rigid body rotations of the vehicle body. Therefore, to assess the validity of the ODF method, it is crucial to identify the frequency at which the distortion results become invalid due to rigid body rotations. To identify this frequency range, in an MBD simulation the total distance output parameter can be requested and used. But for a dynamic full vehicle test, it is a major challenge to measure the total distance. Several tests have been performed without success.</div><div class="htmlview paragraph">To calculate this frequency range from test data, this paper presents a new approach. In this methodology two different signal processing methods (E-line and Diagonal) are combined. To check the validity of the new approach, full vehicle test data has been evaluated. In addition, a simplified beam lab experiment is presented, highlighting the difference between test and MBD simulation when measuring the distortion at large rotations.</div></div>