A Biomechanical Model of Ergonomic Design and Selection of Hand Tools

Research Trainee: Jia-Hua Lin, PhD Student in Industrial and Systems Engineering at the University of Wisconsin at Madison

Faculty Researcher: Robert G. Radwin, PhD, Professor of Industrial and Systems Engineering and Biomedical Engineering at the University of Wisconsin at Madison

This study develops a biomechanical model to predict the capacity for a human operator to react against the impulsive reaction force produced by power nutrunners. The human operator will be represented as a single-degree-of-freedom mechanical system that contains mass, spring, and damping elements. It is hypothesized that these parameters are dependent upon the operator’s posture, the tool’s shape, and the tool’s orientation. An apparatus will be constructed to deliver an impulse that is similar to actual power tool operation. Five different handles and load conditions will be tested. Subjects will hold a handle while the resulting handle displacement to the impulse is recorded. The stiffness, mass, and damping elements corresponding to a specific work location and orientation is determined from the displacement by calculating frequency and amplitude changes. A computer program will be developed to estimate the hand force and hand displacement from this biomechanical model. The model will be validated in laboratory and field experiments using actual tools. The research team has already successfully conducted pilot tests for pistol grip nutrunners used on a vertical surface to demonstrate that the proposed method is feasible. The enhanced model will add knowledge about the operator response and result in better tools and workstations, reducing the physical strain experienced by power tool operators.


Publications resulting from this project:
Lin J-H, Radwin RG, Fronczak FJ, Richard TG. Forces associated with pneumatic power screwdriver operation: statics and dynamics. Ergonomics. 2003;46(12):1161-1177. doi:10.1080/0014013031000139518.

Lin J-H, Radwin RG, Richard TG. A single-degree-of-freedom dynamic model predicts the range of human responses to impulsive forces produced by power hand tools. J Biomech. 2003;36(12):1845-1852.

Lin J-H, Radwin RG, Richard TG. Development and Validation of a Dynamic Biomechanical Model for Power Hand Tool Torque Build-up Reaction Force. Proceedings of the Human Factors and Ergonomics Society Annual Meeting. 2000;44(29):29-32. doi:10.1177/154193120004402908.

Lin JH, Radwin RG, Richard TG. Dynamic biomechanical model of the hand and arm in pistol grip power handtool usage. Ergonomics. 2001;44(3):295-312. doi:10.1080/00140130118167.

Lin J-H, Radwin RG, Richard TG. Handle dynamics predictions for selected power hand tool applications. Hum Factors. 2003;45(4):645-656.

Lin JH, Radwin RG, Nembhard DA. Ergonomics applications of a mechanical model of the human operator in power hand tool operation. Journal of Occupational and Environmental Health. 2005;2(2):111-9. DOI: 10.1080/15459620590913155.

Grants resulting from this project:
UAW/GM Center for Human Resources. (PI: Radwin). Ergonomics Criteria for Industrial Power Hand Tools. 2005-2007.


Research trainee’s current position:
Jia-Hua Lin completed his PhD in 2001 and is currently an Affiliate Associate Professor in the Department of Environmental and Occupational Health Sciences at the University of Washington, and an Ergonomist at the Washington State Department of Labor and Industries.