Automatic control of water cooled suits from differential temperature measurements Final report
S. J. Troutman, Paul W. Webb · NASA Technical Reports Server (NASA)
An automatic controller based on temperature changes (AT controller) was designed to regulate the temperature of water used to cool a man doing treadmill w o r k w h i l e wearing a water cooled clothing assembly.Inputs to the AT controller were: a) the difference between suit inlet and suit outlet water temperature (hea,t removal rate at fixed water flow); and b) four selected skin temperatures.Experiments were conducted to establish the correct weighting and damping factors for smooth and accurate control.Further experiments evaluated the AT controller during quiet periods, during steady w o r k at a moderate level, and during intermittent work.Long term accuracy and stability w e r e established during a final experiment lasting 16 hours, in which the subject slept, ate meals, worked, and rested.The advantages of the AT controller are that it provides relief from the responsibility for regulating one's own thermal state; guarantees low sweat rates and no dehydration at the same time as it prevents chilling and discomfort; provides maximum heat removal and minimum heat storage; and gives good long term stability at low metabolic levels. 1.' 3.