Ride vibration environment of tracked sidewalk snowploughs: spectral classification

摘要

A spectral class is defined in the 0.5 to 40Hz frequency range to characterize the vibration at or near the seat attachment point in tracked sidewalk snowploughs during normal operating conditions. The spectral class is defined for the vibrational modes involving longitudinal (x-axis), lateral (y-axis) and vertical (z-axis) motions, and angular motions along the roll and pitch axes. The definition of this spectral class for the various vibrational modes is based upon field measured data involving 20 combinations of vehicles (Bombardier SW-48) and operating tasks associated with the use of this type of vehicle by the municipalities. The spectral class is defined by a function which approximates the amplitude of the mean power spectral density (PSD) of measured acceleration in the 0.5 40 Hz frequency range for the various vibrational modes. A spectral class defining more severe vibration conditions approximating the envelope of maximum PSD amplitude values is further proposed to be considered as input in laboratory seat performance testing. For both mean and severe vibration conditions, the frequency-weighted and unweighted rms accelerations associated with the various modes of vibration characterising the spectral class are also provided based upon the integration of the derived acceleration PSD functions. The determination of crest factors associated with the measured data is also realized on the basis of the probability distribution function of instantaneous acceleration values evaluated for all the segments of acceleration time signals of one minute duration retained to characterize the vibration.