Fatigue evaluation in maintenance and assembly operations by digital human simulation

TL;DR

This paper introduces a novel digital human simulation framework that models fatigue and physical capacity changes over time, enhancing ergonomic assessment in manual operations like airplane assembly.

Contribution

It proposes the Virtual Human Status concept and a fatigue model based on existing endurance time data to simulate physical capacity variations during tasks.

Findings

The fatigue model accurately predicts decreases in muscle strength.

Simulation results align with laboratory experiments.

Framework effectively assesses work difficulty based on physical capacity.

Abstract

Virtual human techniques have been used a lot in industrial design in order to consider human factors and ergonomics as early as possible. The physical status (the physical capacity of virtual human) has been mostly treated as invariable in the current available human simulation tools, while indeed the physical capacity varies along time in an operation and the change of the physical capacity depends on the history of the work as well. Virtual Human Status is proposed in this paper in order to assess the difficulty of manual handling operations, especially from the physical perspective. The decrease of the physical capacity before and after an operation is used as an index to indicate the work difficulty. The reduction of physical strength is simulated in a theoretical approach on the basis of a fatigue model in which fatigue resistances of different muscle groups were regressed from 24 existing maximum endurance time (MET) models. A framework based on digital human modeling technique is established to realize the comparison of physical status. An assembly case in airplane assembly is simulated and analyzed under the framework. The endurance time and the decrease of the joint moment strengths are simulated. The experimental result in simulated operations under laboratory conditions confirms the feasibility of the theoretical approach.