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Abstract

An adaptive control device (77) and method (102-108) for control of the operation of an actuator (72), and particularly thermally-powered actuator (72) of the type used in a variable-air-volume diffuser (71). The preferred adaptive control device is an expert system circuit which controls a heater (74) provided on a thermally-powered actuator (72) to implement an adaptive process (102-108) in which a sensed variable, such as room air temperature, is driven toward a target temperature control range (.+-.0.25.degree. F.). Most preferably, the process steps (106) include driving the room air temperature toward a gross (broader) temperature control range (.+-.1.0.degree. F.) by moving a diffuser damper assembly (80) to a substantially fully open or substantially fully closed position. Thereafter, and while inside the gross temperature control range, the process steps (107, 108) include adjustments to the position of the damper assembly (80) are made only when a sensed parameter, preferably the supply air flow rate, is in a stable condition. Most preferably, the damper (80) is temporarily 'kicked' farther open or farther closed than necessary, to minimize hysteresis effects, and then adjusted to a posiiton which tends to drive the room air temperature into the narrower, targeted temperature control range.

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First Claim