Vertical accelerations of the body of a motor vehicle when crossing a speed bump
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Cracow University of Technology, Faculty of Mechanical Engineering, Institute of Automotive Vehicles and Internal Combustion Engines
Publish date: 2015-03-09
Archiwum Motoryzacji 2015;67(1):47–60
The article comprises results of determining the vertical accelerations of a selected point in the body of a VW Passat B5 passenger car when the car crossed a speed bump with various speeds. The measurements were carried out for two sets of shock absorbers, which differed from each other in vibration damping characteristics. The force-displacement and force-velocity (damping) characteristics of the shock absorbers having been removed from the motor vehicle were determined by rig testing. For comparison, the condition of the shock absorbers when installed in the vehicle was assessed by the EUSAMA diagnostic method. The speed bump had a trapezoidal profile and it was crossed by the vehicle with speeds of 20 km/h, 30 km/h, and 40 km/h. The accelerations were measured with the use of various measuring equipment, including Crossbow VG 440CA-200 and VBOX RLVBIMU03 measurement units and an HBM B12/200 acceleration sensor. The results have been presented in the form of time histories of the vertical acceleration of the car body, with highlighting the differences that occurred in the instrument readouts. Moreover, simulation tests were carried out with the use of the V-SIM program for the actual distribution of mass among individual vehicle wheels as well as stiffness and damping coefficients of the wheel suspension system determined on a test stand for both the shock absorber sets. The differences in the results obtained by individual test methods have been evaluated and the reasons that caused the differences to occur have been specified.