Engine Speed PI Control with Derivative-Limited Integral Action
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Solution Overview
Problem
Existing speed control methods for internal combustion engines face challenges in providing quick and precise responses due to intrinsic delays, such as the capacitive effect of the intake manifold, leading to instability and unpredictable behavior when using PID controllers, especially during sudden load changes or gear shifts.
Innovation Solution
A control method utilizing a PI controller with a derivative contribution that intervenes to saturate the integral controller's output based on speed error and derivative, minimizing over- and underelongations without compromising stability, by incorporating a saturator that adjusts the integral controller's input and output signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a PID controller is used to improve response speed, then the response quickness is improved, but the system stability deteriorates due to high-frequency dynamics introduced by the derivative term
Solution Approach 1:
The patent extracts the derivative term from the traditional PID controller structure and applies it specifically to the integral contribution rather than adding it as a separate parallel term. This selective extraction and repositioning of the derivative function allows capturing its beneficial quick-response特性 while avoiding the destabilizing high-frequency dynamics that would result from a full PID implementation.
Solution Approach 2:
The derivative contribution is applied locally to the integral term rather than globally to the entire controller output. This localized application means the derivative action only modifies the integral contribution, allowing precise control over where and how the derivative effect is introduced into the system, thereby maintaining stability while improving response.
2Stability of the object's composition
If the integral term is saturated to limit over- and underelongations, then the system stability is improved, but the response precision deteriorates
Solution Approach 1:
The derivative term acts in advance on the integral contribution before the integral term can generate large deviations. By anticipating the integral term's behavior and pre-adjusting it with the derivative action, the system prevents over- and underelongations before they occur, maintaining both stability and precision without needing aggressive saturation.
3Stability of the object's composition
If the integral term is reset to zero based on error sign change to limit over- and underelongations, then the system stability is improved, but the engine behavior becomes edgy and unpredictable
Solution Approach 1:
Instead of a static reset-to-zero approach, the patent implements a dynamic adjustment where the derivative term continuously modifies the integral contribution based on the current error and its rate of change. This dynamic approach maintains stability while preserving smooth, predictable engine behavior by avoiding abrupt resets.
Data Source
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AI summary
Method to control an internal combustion engine by means of a feedback control based on an engine speed error (Err) calculated between a reference value (Ref) and a measured value (Speed), wherein said control comprises a proportional contribution (P) and an integral contribution (I), the method comprising a step of saturating said integral contribution as a function of a derivative (ΔSpeed) of said measured value of the speed (Speed) of the engine and of said speed error (Err).