WHOLE-BODY VERTICAL BIODYNAMIC RESPONSE CHARACTERISTICS OF THE SEATEDVEHICLE DRIVER - MEASUREMENT AND MODEL DEVELOPMENT

The vertical driving-point mechanical impedance characteristics applic able to seated vehicle drivers are measured in the 0.625-10 Hz frequen cy range with excitation amplitudes ranging from 1.0 to 2.0 m s(-2) us ing a whole-body vehicular vibration simulator. The measurements are p erformed for seated subjects with feet supported and hands held in a d riving position. Variations in the seated posture, backrest angle, and nature and amplitude of the vibration excitation are introduced withi n a prescribed range of likely conditions to illustrate their influenc e on the driving-point mechanical impedance of seated vehicle drivers. Within the 0.75-10 Hz frequency range and for excitation amplitudes m aintained below 4 m s(-2), a four-degree-of-freedom linear driver mode l is proposed for which the parameters are estimated to satisfy both t he measured driving-point mechanical impedance and the seat-to-head tr ansmissibility characteristics defined from a synthesis of published d ata for subjects seated erect without backrest support. The parameter identification technique involves the solution of a multivariable opti mization function comprising the sum of squared magnitude and phase er rors associated with both the mechanical impedance and seat-to-head tr ansmissibility target values, subject to limit constraints identified from the anthropometric and biomechanical data. The model response, ho wever, is found to provide a closer agreement with the mechanical impe dance target values than that with the seat-to-head transmissibility. From the model, the main body resonant frequencies computed on the bas is of both biodynamic response functions are found to be within close bounds to that expected for the human body.