Pneumatic control system

Abstract

An improved pneumatic control system suitable for use in providing servo control of one or more active devices in an analytical instrument includes a series pass element that effects partial regulation of an unregulated voltage to remove any high frequency supply voltage variations (including but not limited to a ripple component), but need not regulate the low frequency voltage variations, the effects of which are compensated by a loop gain compensation scheme operable in a servo control loop. A digital signal processor employed in the servo control loop uses a voltage sense signal representative of the regulated supply line voltage to generate a correcting term for use in a proportional integral derivative (PID) control algorithm operating in control loop firmware. The correcting term causes an inverse proportional change in the control loop gain. The duty cycle of the drive signal provided to the active device is accordingly modulated, when necessary, to account for changes indicated by the voltage sense signal. The power in the drive signal is therefore made independent of variations in the regulated supply line voltage. As a result, the active device is operated with greater efficiency and accuracy.

Dependencies are inferred from the claim text.