| 摘要 |
A process control system (1) according to the present invention uses analog control circuitry in which a differential amplifier stage (54) is incorporated into the feedback path rather than the feedforward path to enable the control of highly non-linear processes that may also exhibit high levels of hysteresis. Such processes often have superior performance characteristics that conventional control circuitry cannot exploit. The present invention additionally incorporates an automatic control circuit which varies the gain of various stages of the control circuitry when the output of the process is within a predetermined range. An embodiment of the present invention is used to control a non-linear proportional valve (18) with severe hysteresis. The valve regulates the pressure within pressure-driven ophthalmic surgical instruments (42) which must be controlled extremely precisely to enable successful eye surgery. <IMAGE> |
