Use of LMS Test Lab for acoustic and vibration measurements on a

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					                   LMS Users Conference




       Use of LMS Test Lab for
        acoustic and vibration
         measurements on a
         VW Golf windscreen

Group Research                            VOLKSWAGEN AG
Vehicle Dynamics
                                                                                               Acoustics and vibration of a Windscreen
                                                                                               LMS User Conference Munich - March 22 & 23 , 2006

                                                                                       Agenda
Meschke/Fahrzeugdynamik/LMS-Conference-Windscreen-230306.ppt / 23.02.2006




                                                                                  ■ Introduction
                                                                                  ■ Objectives of Research Project INMAR
                                                                                  ■ Vehicle Investigations
                                                                                  ■ Modal Analysis
                                                                                  ■ Active vibration attenuation
                                                                                  ■ Summary




                                                                            Group Research                                                         VOLKSWAGEN AG
                                                                            Vehicle Dynamics
                                                                                               Acoustics and vibration of a Windscreen
                                                                                               LMS User Conference Munich - March 22 & 23 , 2006

                                                                                       Introduction
Meschke/Fahrzeugdynamik/LMS-Conference-Windscreen-230306.ppt / 23.02.2006




                                                                                  ■ Volkswagen Group Research serves to all brands within the
                                                                                    Volkswagen Group (Volkswagen, Audi, Skoda, Seat etc.)
                                                                                  ■ Research and Development consist of about 9500 People
                                                                                  ■ 550 Researchers work on e.g. Power-trains, Fuel strategy, Multimedia,
                                                                                    Environment and Vehicle Research
                                                                                  ■ Volkswagen Group Research is involved in the EU-Project INMAR
                                                                                          ■ One of the objectives is to improve acoustics and vibration behavior by
                                                                                            use of “Intelligent Materials for Active Noise Reduction”
                                                                                          ■ Reduction of Windscreen vibrations and
                                                                                            interior acoustics with Piezo actuators
                                                                                            is investigated



                                                                            Group Research                                                             VOLKSWAGEN AG
                                                                            Vehicle Dynamics
                                                                                               Acoustics and vibration of a Windscreen
                                                                                               LMS User Conference Munich - March 22 & 23 , 2006

                                                                                       Objectives of Volkswagen within INMAR Subproject “Windscreen”
Meschke/Fahrzeugdynamik/LMS-Conference-Windscreen-230306.ppt / 23.02.2006




                                                                                          ■ Reduction of noise transmission caused by vibration of windows
                                                                                          ■ Development of different new active windshield concepts with the
                                                                                            integration of an active interface between the window and its framework
                                                                                                 ■ Testing and evaluation of active windshield systems under
                                                                                                   automotive conditions in the lab and on the road
                                                                                                 ■ Measurement of window vibration and sound radiation without and
                                                                                                   with controlled driven piezo-element actuators




                                                                            Group Research                                                               VOLKSWAGEN AG
                                                                            Vehicle Dynamics
                                                                                               Acoustics and vibration of a Windscreen
                                                                                               LMS User Conference Munich - March 22 & 23 , 2006

                                                                                  Vehicle Investigations                                         ■ Noticeable booming noise around 120 Hz
Meschke/Fahrzeugdynamik/LMS-Conference-Windscreen-230306.ppt / 23.02.2006




                                                                                                                                                   on front seats corresponds with certain
                                                                                                                                                   accelerations on windscreen
                                                                                                                                                 ■ Modal analysis conducted to determine
                                                                                                                                                   mode shapes and parameters for FEA
                                                                                                                                                   calculations
                                                                                                     Sketch Windscreen:
                                                                                                   Position of accelerometers


                                                                                                         Accelerometer 1                                         Microphone front left
                                                                                   120 Hz
                                                                                                                                                   120 Hz




                                                                                                         Accelerometer 2                                        Microphone front right




                                                                                                  Test road      Roller test; anechoic chamber              Test road       Roller test; anechoic chamber


                                                                            Group Research                                                                                                   VOLKSWAGEN AG
                                                                            Vehicle Dynamics
                                                                                               Acoustics and vibration of a Windscreen
                                                                                               LMS User Conference Munich - March 22 & 23 , 2006

                                                                                  Vehicle Investigations
Meschke/Fahrzeugdynamik/LMS-Conference-Windscreen-230306.ppt / 23.02.2006




                                                                                  ■ Accelerations of points 1 and 3 around 10
                                                                                    dB higher than acceleration at point 2 (mid
                                                                                    of windscreen)
                                                                                                                                                            Sketch Windscreen:
                                                                                                                                                          Position of accelerometers

                                                                               Acceleration normal to windshield   Acceleration normal to windshield Acceleration normal to windshield
                                                                               Point 1                             Point 2                           Point 3




                                                                            Group Research                                                                            VOLKSWAGEN AG
                                                                            Vehicle Dynamics
                                                                                               Acoustics and vibration of a Windscreen
                                                                                               LMS User Conference Munich - March 22 & 23 , 2006
                                                                                                                                                                                                                                 72 km/h stone pavement on test rig; windscreen vibrations

                                                                                  Vehicle Investigations                                                                  0,0005
Meschke/Fahrzeugdynamik/LMS-Conference-Windscreen-230306.ppt / 23.02.2006




                                                                                                                                                                                                                                                                                                       windscreen
                                                                                                                                                               0,00045
                                                                                                                                                                                                                                                                                                       with masses


                                                                                  ■ Windscreen vibrations (mean of                                                        0,0004




                                                                                                                         mean velocity over all points [m/s]
                                                                                                                                                               0,00035

                                                                                    all points measured) reduced by                                                       0,0003
                                                                                                                                                                                                                                                                 = 0,13 mm/s

                                                                                    4,2 dB by use of masses applied                                            0,00025
                                                                                                                                                                                                                                                                bei 118 Hz




                                                                                    to the windscreen surface
                                                                                                                                                                          0,0002


                                                                                                                                                               0,00015



                                                                                  ■ Reduction of sound pressure                                                           0,0001


                                                                                                                                                               0,00005

                                                                                    level at co-driver seat due to                                                                                      0
                                                                                                                                                                                                             50   60   70   80          100 110 120 130 140
                                                                                                                                                                                                                                   9072 km/h stone pavement on test150 windscreen 180 190 200
                                                                                                                                                                                                                                                                    rig: 160 170 vibrations                   210     220   230   240   250

                                                                                    masses around 2,2 dB                                                                                              0,35                                                             Hz


                                                                                                                                                                                                                                                                                                        windscreen

                                                                                  ■ There is a potential to improve                                                                                    0,3                                                                                              with masses




                                                                                                                                                               sound pressure at refence point [Pa]
                                                                                    interior noise by attenuating
                                                                                                                                                                                                      0,25




                                                                                    windscreen vibrations
                                                                                                                                                                                                       0,2                                                         = 0,05 Pa
                                                                                                                                                                                                                                                                 bei 118 Hz


                                                                                                                                                                                                      0,15



                                                                                                                                                                                                       0,1



                                                                                                                                                                                                      0,05



                                                                                                                                                                                                        0
                                                                                                                                                                                                             50   60   70   80     90   100   110   120   130    140   150     160   170   180   190    200    210    220   230   240   250
                                                                                                                                                                                                                                                                        Hz




                                                                            Group Research                                                                                                                                                                                                   VOLKSWAGEN AG
                                                                            Vehicle Dynamics
                                                                                               Acoustics and vibration of a Windscreen
                                                                                               LMS User Conference Munich - March 22 & 23 , 2006

                                                                                  Modal Analysis on Vehicle Windscreen
Meschke/Fahrzeugdynamik/LMS-Conference-Windscreen-230306.ppt / 23.02.2006




                                                                                  ■ Modal Analysis with Test Lab
                                                                                  ■ Excitation with Impact Hammer
                                                                                  ■ Different reference (driving) points

                                                                                         Point 18                       Point 22
                                                                                                                                   2nd Mode shape Eigenfrequency 117 Hz




                                                                                                    Reference point 7




                                                                                                                                   3rd Mode shape Eigenfrequency 148 Hz
                                                                            Group Research                                                               VOLKSWAGEN AG
                                                                            Vehicle Dynamics
                                                                                               Acoustics and vibration of a Windscreen
                                                                                               LMS User Conference Munich - March 22 & 23 , 2006

                                                                                  Modal Analysis on a Windscreen Test rig
Meschke/Fahrzeugdynamik/LMS-Conference-Windscreen-230306.ppt / 23.02.2006




                                                                                  ■ Modal Analysis with Impact Hammer
                                                                                    and Shaker
                                                                                  ■ Eigenfrequencies of Mode shapes of Test
                                                                                    rig differ slightly form those of Vehicle




                                                                                               Eigenfrequency of 2nd Mode shape
                                                                                               (acoustically relevant) at 106 Hz

                                                                            Group Research                                                         VOLKSWAGEN AG
                                                                            Vehicle Dynamics
                                                                                               Acoustics and vibration of a Windscreen
                                                                                               LMS User Conference Munich - March 22 & 23 , 2006

                                                                                  Active Vibration attenuation with Piezo-Actuators
Meschke/Fahrzeugdynamik/LMS-Conference-Windscreen-230306.ppt / 23.02.2006




                                                                                  Expected Results within the EU-Project:
                                                                                  ■ Potential of non-transparent Piezo-
                                                                                    actuators to attenuate window
                                                                                    vibrations and improvement of interior
                                                                                    noise by application on the window or
                                                                                    at the surrounding rim
                                                                                  ■ Amplitude reduction of acoustical
                                                                                    relevant resonances of 10 dB is an
                                                                                    aim that could be achieved
                                                                                  ■ Objective is to reduce related
                                                                                    acoustical “booms” by 5 dB
                                                                                  ■ Development of transparent
                                                                                    actuators for direct use on a window

                                                                            Group Research                                                         VOLKSWAGEN AG
                                                                            Vehicle Dynamics
                                                                                               Acoustics and vibration of a Windscreen
                                                                                               LMS User Conference Munich - March 22 & 23 , 2006

                                                                                  Active Vibration attenuation with Piezo-Actuators on Windscreen Test rig
Meschke/Fahrzeugdynamik/LMS-Conference-Windscreen-230306.ppt / 23.02.2006




                                                                                  ■ Four Piezo-Element Actuators on driver and Co-driver side
                                                                                  ■ All Actuators can be controlled individually
                                                                                  ■ Wind screen excitation by shaker (sinus or white noise)
                                                                                                                                   Locations
                                                                                                                                   of Piezo-
                                                                                                                                   Actuators




                                                                            Group Research                                                         VOLKSWAGEN AG
                                                                            Vehicle Dynamics
                                                                                               Acoustics and vibration of a Windscreen
                                                                                               LMS User Conference Munich - March 22 & 23 , 2006

                                                                                  Active Vibration attenuation with Piezo-Actuators on Windscreen Test rig
Meschke/Fahrzeugdynamik/LMS-Conference-Windscreen-230306.ppt / 23.02.2006




                                                                                  Operation mode shape due to excitation with Shaker at 108 Hz:
                                                                                  Without active vibration cancellation




                                                                                                                               [µm]  Amplitude
                                                                                                                               Amplitude [µm]



                                                                                                                                                   Position
                                                                                                                                                 Position




                                                                                  ■ Dotted lines in left figure show deflection of window in three different levels
                                                                                  ■ Second bending mode can be observed

                                                                            Group Research                                                                    VOLKSWAGEN AG
                                                                            Vehicle Dynamics
                                                                                               Acoustics and vibration of a Windscreen
                                                                                               LMS User Conference Munich - March 22 & 23 , 2006

                                                                                  Active Vibration attenuation with Piezo-Actuators on Windscreen Test rig
Meschke/Fahrzeugdynamik/LMS-Conference-Windscreen-230306.ppt / 23.02.2006




                                                                                  Operation mode shape due to excitation with Shaker at 108 Hz:
                                                                                  With active vibration cancellation by Piezo-Actuators




                                                                                                                            Amplitude [µm]
                                                                                                                            Amplitude [µm]


                                                                                                                                             Position

                                                                                  ■ Red area in left figure shows excitation with the shaker
                                                                                  ■ Reduction of bending mode can be observed (amplitudes to about 30% of
                                                                                    original values)
                                                                            Group Research                                                              VOLKSWAGEN AG
                                                                            Vehicle Dynamics
                                                                                               Acoustics and vibration of a Windscreen
                                                                                               LMS User Conference Munich - March 22 & 23 , 2006

                                                                                       Summary
Meschke/Fahrzeugdynamik/LMS-Conference-Windscreen-230306.ppt / 23.02.2006




                                                                                  ■    The Potential of Piezo-electric elements to
                                                                                       use as Actuators to attenuate vibrations of
                                                                                       a windscreen is investigated
                                                                                  ■    Resonances of windscreens can be an
                                                                                       acoustic problem. Although on a Golf V it
                                                                                       seems there is only a small problem this
                                                                                       vehicle was chosen for tests
                                                                                  ■    On a wind screen test rig a first set-up of
                                                                                       Piezo Actuators was tested. Vibrations
                                                                                       of Windscreen could be reduced to 30%
                                                                                  ■    Optimum Actuator locations and control
                                                                                       systems will be investigated by use of FEA
                                                                                  ■    Implementation of actuators on the rim will
                                                                                       be investigated

                                                                            Group Research                                                         VOLKSWAGEN AG
                                                                            Vehicle Dynamics

				
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