Soft Ramp
A soft ramp means applying the position or speed command along a controlled slope instead of as an abrupt step. Even if the potentiometer is turned all at once, the actuator moves to the target at a limited rate. This reduces mechanical shock, overshoot and unnecessary current draw.
In a system without a ramp the error is at its maximum the instant the command changes; the controller drives the actuator at full power. The result is sudden tension in the cable, shock at the linkage and the throttle opening all at once. On a diesel this sudden opening means smoke and wasted fuel.
- If the ramp time is too long the system becomes sluggish; if it is too short the protective effect of the ramp is lost.
- A ramp reduces overshoot with less loss of speed than reducing gain does; this is why the two are tuned together.
On the GS740-3P the soft ramp is an integral part of the closed-loop P controller and is factory set. In the field this corresponds to the following: even if you turn the potentiometer quickly, the throttle lever opens in a controlled way. This behaviour is not a delay fault but a deliberate design choice that protects the mechanics and the engine. If an application requires sudden speed changes, the consequences of this on the mechanical and engine side must be evaluated separately.
The context in which this term is used: Electronic speed and throttle control on a diesel engine