Method to quantify ride comfort and allowable accelerations

Abstract

When the motion of a vehicle includes "shocks" or impulsive velocity changes, R.M.S. acceleration has no relation to crew comfort or injury. Existing (R.M.S. G) methods of ride assessment can show lethal accelerations as being perfectly safe, and vice versa. It follows that R.M.S. acceleration is not meaningful for nonsinusoidal "random" vibration either. This paper presents a method of evading the difficulty, using fairly well established biodynamic modeling techniques, and an extension of Allen's "shock tolerance" concept. Among other advantages, the method "automates" the assessment of ride quality so that personal judgments are not involved and the relative ride quality of different vehicles can be placed on a quantitative basis. Since this work was inspired by the problem of Navy crew tolerance to the motions of high-speed ships, the discussion is in those terms. Also, the proposed criteria should probably be scaled down for more general populations.