Feed Forward Injection Pressure Control for Overshoot Reduction
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Solution Overview
Problem
Current feed forward techniques for injection pressure control in fuel injection systems are limited by the need for PI integrator saturation to handle system unknowns and transients, leading to overshoot and limitations in set-point dynamics and integrative gain.
Innovation Solution
A new feed forward technique that calculates a compensation for closed loop static error and separates the integrative gain from overshoot requirements, allowing the PI integrator to focus on system unknowns and tolerances, while using a proportional and integral contribution to manage load dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full compensation via feed-forward is used, then regulation error is reduced, but the PI integrator becomes overloaded during transients and causes overshoot
Solution Approach 1:
The patent segments the control function by introducing a feed-forward path that handles the compensation of known disturbances and set-point changes, while the PI integrator is reserved for handling only the residual regulation error. This segmentation prevents the integrator from being overloaded during transients, thereby eliminating overshoot while maintaining accurate regulation.
2Object-affected harmful factors
If stronger filtering is applied to the feed-forward signal, then noise is reduced, but the response overshoot increases
Solution Approach 1:
The patent introduces an intermediary low-pass filter in the feed-forward path that attenuates noise from the set-point and load signals. The filter is designed with appropriate time constants to reduce high-frequency noise while preserving the dynamic response characteristics, thus avoiding excessive overshoot in the system response.
3Reliability
If anti-windup saturation is applied to the PI integrator, then integrator overflow is prevented, but the regulation error cancellation capability is reduced
Solution Approach 1:
The patent applies preliminary action by compensating for known disturbances and set-point changes through the feed-forward path before they affect the system. This reduces the burden on the PI integrator, allowing it to operate within its linear range without requiring aggressive anti-windup saturation, thereby maintaining both integrator stability and regulation accuracy.
4Measurement precision
If the integrative gain is increased to improve regulation, then set-point dynamic response is limited
Solution Approach 1:
The patent makes the system dynamic by introducing a feed-forward path that actively responds to set-point changes and load disturbances. This allows the use of a lower integrative gain that maintains regulation accuracy while permitting faster set-point dynamic response, as the feed-forward path handles the transient compensation rather than relying solely on the integrator.
Data Source
AI summary
A control method is provided for using a feed forward technique. The method includes, but is not limited to using a setpoint value of a controlled variable to calculate a compensation of the closed loop static error, summing said contribution to the setpoint value, operating an estimation of the closed loop error to obtain a feed forward contribution.