Date of Completion
Accurate tracking of hand grip force is an important consideration needed for a robust understanding in the study of human biomechanics. One aspect where it proves useful is in hand-arm vibration, such as from gripping a power tool. Depending on how firmly the user is gripping the tool, they may change their exposure levels to the tool vibration, which can lead to potential disorders such as Hand-Arm Vibration Syndrome (HAVS).
A small, battery powered portable force unit has been developed to supply power to, and condition, the signals from eight thin-film force sensors. This gives a better understanding of the grip force used on many different tool applications that were previously immeasurable. Using this information, knowledge can be gained in determining how much of a role grip force plays in the onset of the aforementioned disease.
Using the portable force unit, two different applications are explored. The first uses an instrumented handle in conjunction with thin-film sensors to ascertain how well the thin-film sensors model the overall grip strength recorded by the handle. Using varying numbers of sensors to map the hand, a conversion factor was determined to calculate the actual grip force represented by the waveforms of the thin-film sensors. The observed results of this experiment indicated that the use of eight to four thin-film force sensors yield conversion factors that are similar, therefore using four sensors gives a similar estimated force response, while minimizing sensor bulk.
The second application is in field work. Several grip force measurements were made in the field while subjects were using pneumatic power tools. A subject calibration of the thin-film sensors was performed using the same instrumented handle mentioned previously and the unit allowed for the thin-film sensors to be used in the actual tool use measurement. Using the conversion factors from the laboratory on the data collected in the field, a better understanding of grip force was obtained. This understanding is from a real work environment rather than a laboratory tool simulation conducted by lab personnel unfamiliar with the tool, which could bias the results. Applying this method of tracking grip force is expected to provide a better understanding of how grip force plays a role in HAVS and how tool handle designs can be improved.
Tornifoglio, Shane Vincent, "Development and Application of a Portable System to Reliably Measure Grip Forces Using Thin-Film Force Sensors" (2012). Master's Theses. Paper 269.