REMOTE VIBRATION MEASUREMENTS - COMPENSATION OF WAVE-FORM DISTORTION DUE TO WHOLE-BODY TRANSLATIONS

Remote vibration measurements using the laser Doppler technique are a practical and increasingly popular alternative to the use of contactin g transducers. This study concerns aspects of non-contact measurements that result when the vibrating target additionally undergoes larger s cale whole body translation. The characteristics of a single remote me asurement of steady state vibration on a body undergoing whole body tr anslation are investigated in both the time and frequency domains, whe re waveform distortion and whole body target displacement induced harm onics are observed. A technique which compensates for the relative who le body displacement between the target and a remote transducer is int roduced, in which two simultaneous remote measurements are combined to derive a closer estimate of the measurement which would be made by a contacting transducer attached to the target surface. A substantial im provement in the data quality obtainable from a single remote measurem ent is demonstrated using a numerical simulation and in experimental d ata captured remotely from a golf club head during and immediately fol lowing an impact with a golf ball. Remote measurements are particularl y suited to analysis of impacting bodies and the displacement compensa tion technique is thus developed in this paper to investigate transien t pulse propagation effects. The improvement in data quality obtained is demonstrated using data pertaining to the deformation of a golf bal l during an impact in which the whole ball accelerates forwards rapidl y. (C) 1998 Academic Press.