Int j simul model 13 (2014) 1, 5-15 ISSN 1726-4529 Original scientific paper DOI:10.2507/IJSIMM13(1)1.234 5 DECISION SUPPORT SYSTEM FOR GENERATING ERGONOMIC TOOL-HANDLES Harih, G. Laboratory for intelligent CAD systems, University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, SI-2000 Maribor, Slovenia E-Mail: gregor.harih@um.si Abstract Tool-handle design research has been previously limited to determination of diameters of cylindrical handles to increase performance, comfort and avoid acute and cumulative traumatic disorders. However, there is still lack of correct shape determination and systemization of the ergonomic design knowledge. To overcome these limitations, methodology to develop optimal sized and shaped tool- handles for a target population previously developed has been integrated into an existing ergonomics and aesthetics decision support system. The system allows a correct determination of tool-handle size and shape according to the target population and provides general ergonomics knowledge. Resulting handles consider optimal diameters for each finger to maximize maximum voluntary contraction, comfort and contact area, which can lower the risk of acute and cumulative trauma disorders. The system allows development of ergonomic tool-handles with almost no prior ergonomics knowledge and without iterative design process, which decreases the designing time. (Received in August 2012, accepted in July 2013. This paper was with the authors 2 months for 2 revisions.) Key Words: Ergonomics, Tool-Handle, Material Choice, Finite Element Method, Decision Support System 1. INTRODUCTION If the product will be human operated, the designer has to consider ergonomics in order to achieve the expected system efficiency [1]. Since most of the products are designed to be human hand operated, many authors have researched the topic of tool-handle design to define the optimal size and shape of a tool-handle. A correctly designed handle can provide safety, comfort and increased performance. Different authors used different criteria to determine optimal cylindrical handle: subjective comfort rating [2, 3]; finger force measurement [4, 5]; muscle force minimization [6] and hand anthropometrics [2, 7-12]. Few studies also used two or more criteria: finger force measurement and muscle activity [7, 10, 13]; subjective comfort rating, finger force measurement and electromyographic efficiency of muscle activity [14]. Most of the authors have focused on cylindrical or elliptical shapes of the handles. However none of them considered the anatomical shape of the hand in the optimal power grasp posture. It has been shown that handles should vary in size between hand and finger size, since maximum possible exerted finger force is diameter dependent [14]. It has been also shown that objects that follow the shape of the hand result in much lower local contact pressures, which can prevent discomfort and several disorders [15]. Authors suggested that further research of this topic should consider the shape of the hand in the optimal power grasp posture since it could improve the ergonomics of the tool-handle [11]. The mechanical behaviour of the skin and subcutaneous tissue is crucial during gripping tasks, since forces and moments are transferred from the tool to the whole hand-arm system. Skin and subcutaneous tissue have non-linear viscoelastic properties, where the skin is stiffer than the subcutaneous tissue [16]. A power-grasp produces a very uneven distribution of forces and, therefore, also pressure on the hand and fingers [17]. It has been shown, that any higher contact pressures than allowed for over a specific time can result in discomfort, pain,