Heartrate as an Indicator of Optimum Control Design for Underground Mining Machines

Abstract

Machines used in low seem coal mines use manual hydraulic controls for most functions. This study addressed the optimum design of controls used for tramming (driving) a machine. For such tasks, the operator stoop walks behind the machine while pushing the controls. The study intended to determine at what height the controls should be located for a stoop walking task and what pressure would be considered maximum for control activation. Twelve male subjects were paid for their participation in the experiment. The following variables were manipulated within subjects: control pressure (10 and 20 pounds), seem height (40 and 50 in.), and control height (21, 26, 31, and 36 in.). The experiment was performed on a treadmill with a speed of 75 feet per minute. Each subject participated in 12 conditions, each lasting about 15 minutes for a total of three hours. Heartrate was measured continuously and sampled each minute. Oxygen uptake was analyzed for one subject.

For the 40 in. seem height, the lowest control height (21 in.) and the highest control force (20 lbs) produced the lowest heartrate. For a 50 in. seem height, the lowest control height (26 in.) and the lowest control force (10 lbs) produced the lowest heartrate. The applicability of the results in terms of human factors design of mining machines is discussed.