Control Stability
Stability is the system's ability to settle on the target after a disturbance without the oscillation growing. In a stable system each oscillation is smaller than the previous one and the movement dies out within a few cycles. If the amplitude of the oscillation stays constant or grows, the system is at the stability limit or unstable.
The factors that spoil stability are mostly in the physics rather than in the control parameter:
- Delay: every delay between the command and the movement that takes place eats into the stability margin. Cable friction, joint free play and mechanical flex are each a source of delay.
- Excess gain: aggressive correction, combined with delay, feeds the oscillation.
- Changing conditions: cold oil, a warming environment, a wearing cable; a setting that was stable yesterday may be marginal today.
That is why the setting is always made leaving a margin. When you see a sign of instability in the field — the speed regularly rising and falling, the actuator constantly making small movements — first check the mechanical chain: cable tension, sharp bends along the routing, the firmness of the guides and joint free play. Since the control parameters on the GS740-3P are factory set, the solution is almost always found on this side.
Context in which this term is used: Electronic speed and throttle control on a diesel engine