The dashpot-type isochronous governor (which may be modified by droop) is the standard hydraulic governor in current use for prime movers. This governor is designed to give proportional-plus-integral (actually, rate-responsive) control. The governor has the advantages of giving constant speed control where desired; it can be adjusted to compensate for a low value of damping in the engine system to be controlled, and it has a dashpot including a needle valve whereby one of the governor constants can be varied readily. Disadvantages of hydraulic governors in common use are the poor adjustability of control parameters; too small needle valve openings for normal applications; sensitivity of the dashpot to variations in the viscosity of dashpot oil causing corresponding variations in control parameters; floating (receiving or proportioned pistons that can and do stick; and the relative noninterchangeability of the governors from one type of engine to another. In the new governor described in the paper the foregoing problems and others not mentioned are all solved with the aid of a technique for hydraulic addition. In contrast to current governors, governor parameters including governor time lag can be adjusted independently. Load control can be introduced to the governor without the need of an extra servomotor. Nonlinearities are incorporated to improve performance. This governor is a radical departure from existing units greatly increasing the flexibility and reliability of the speed governor.

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