Objective measurement of the start-motion quality of a forklift truck

Abstract

An objective index is developed for the estimation of ride quality during a forklift truck start. After consultation with test drivers, start-motion quality is defined and three governing parameters selected: engagement shock in the driving direction, vertical vibration, and pitch vibration. Subjective evaluation of the starting motion and objective measurements of vehicle vibration were performed on five forklift trucks with various load capacities. The vibration measured at the driver's seat was changed into a perceptual amount by using the frequency weighting curves and the fourth power dose method suggested in ISO 2631-1 (Mechanical Vibration and Shock-evaluation of Human Exposure to Whole-body Vibration—Part 1: General Requirements. International Organization for Standardization). Regression between the perceptual vibrations, expressed as a vibration dose value, and the subjective rating scores yielded an index equation in the form of Steven's psychophysical power law: ψ=1.912 φ −0.601, where ψ is the sensation magnitude of start-motion quality and φ is the stimulus magnitude of the vibration dose value.