Open-Loop Throttle Control
In open-loop throttle control the system does not measure engine speed; it only takes the throttle lever to the commanded position. The result is the remote and stepless version of classic mechanical throttle cable behaviour: the same position gives a different speed when the load changes. It is simple, inexpensive and sufficient for most variable-speed work.
The logic of this approach is as follows: the operator judges the speed by eye or by ear and corrects it with the potentiometer. The complexity of a closed loop and the risk of sensor failure disappear.
- Work it suits: irrigation pumps, drilling mud pumps, construction machinery, tractors — applications where a few percent change in speed does not change the result.
- Work it does not suit: a generator that requires grid quality. Since speed directly determines frequency, the frequency drifts as the load changes.
The standard GS740 kit and the GS740-3P are in this class. The GS740-3P does have a closed loop, but that loop is on actuator position; in terms of engine speed the system is still open loop. In other words, position repeatability is high, speed stability is not. If the speed must be maintained under load, feedback that reads speed must be added.
Context in which this term is used: Electronic speed and throttle control on diesel engines