Implementation of a computer-controlled life support system in the acceleration research environment.

Electronic control of the G-valve and pressure breathing regulator is being implemented in some advanced life support systems used in aircrew protection. This technological improvement, however, has not reached its full potential in the research environment. A computer-controlled life support system interface providing programmable schedules for G-suit inflation and positive pressure breathing during +Gz (PBG) was developed. Output pressures from a G-valve and pressure breathing regulator (Carleton Technologies) were controlled by a Macintosh computer running LabVIEW software. Required pressures were determined as functions of single or multiple control inputs (i.e. +Gz level, a pressure signal, time, etc.). Subject safety was ensured via hardware limitations and status checks incorporated into the software. Experiments conducted at +1 Gz and at various +Gz levels evaluated the computer software-life support hardware interface. Open-loop algorithms allowed independent control of multiple regulators using simple (single input) and complex (multiple input with adaptive loop) control structures. The system provided accurate and reproducible G-suit and mask pressures. Time of inflation, peak pressure attained, and deflation rate were effectively controlled at all +Gz levels. The ability to alter the pressure schedules independent of +Gz or time allowed comprehensive control over all parameters necessary to conduct acceleration research involving advanced life support systems.