Revisiting the OSHA Hand Speed Constant
Type of DegreePhD Dissertation
Industrial and Systems Engineering
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This research focused on after-reach and over-reach in automated systems. OSHA uses a hand speed constant developed in 1935 (1.6 m/s) to calculate the “safe distance” on dual palm buttons and presence sensing devices. The 1.6 m/s value was later adopted by ANSI and RIA for “point-of-operation” safeguarding on robotic/automated systems. Several studies have found hand-speed values that exceed the 1.6 m/s value used in US safety regulations. The results of this study were: 1)For the simulated press experiment, the 95th percentile hand-speed from the lower button was 1.51 m/s and the 95th percentile hand speed from the upper buttons was 2.83 m/s. The study found that the hand speed between the UB and LB positions are significantly different, which implies that the use of a single hand speed constant for both locations is inappropriate. 2) For over-reach applications, the study found that a hand speed constant between 3.5 m/s to 3.9 m/s would protect 95% of a population age 20-30 years old in a situation with unconstrained hand position (no dual palm buttons). 3) A comparison of the speed measured by Vicon (optical motion capture) and Xsens (IMU motion capture) demonstrated a general agreement (average bias 0.19 m/s) between the two technologies. Based on this analysis, an IMU-based system could be a viable option for measuring after-reach speed on the factory floor in the future.