What is a soft ramp, and why does the throttle not open suddenly?
The GS740-3P applies the position command not as a step but along a controlled ramp. This way the actuator moves smoothly to the target even when the potentiometer is turned quickly. The aim is to reduce sudden jumps at the throttle butterfly, shock loading in the cable and the risk of speed oscillation (hunting). The ramp time is not stated numerically in the product data.
A sudden change of position creates three problems:
- Mechanical shock: the cable, the terminal and the throttle lever joint take a shock load with every abrupt movement; connections loosen over time.
- Speed oscillation: while the engine's own mechanical governor responds to a sudden throttle change it may overshoot and undershoot (hunting). In a system with high gain or an abrupt response, oscillation starts.
- Equipment strain: on a piston pump a sudden change in flow creates a pressure surge in the line.
The ramp spreads the command over time and softens all of these. The system reaches the target a little later but without a jump. In applications such as drilling where three pumps run at the same time, this protects both the line and the engine.
The ramp time is not declared as a parameter that the user can change; during installation the thing that affects response speed is more the cable routing and friction. Keeping the route short and gently curved brings out the effect of the ramp to best advantage.
The full topic: Electronic speed and throttle control on a diesel engine