Fuel Injector PWM Signal Adaptation to Prevent Latch-Up
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Solution Overview
Problem
Current fuel injection control systems in vehicles are prone to latch-up due to spurious pulses and programming errors, leading to incorrect injector control and potential engine damage, especially at high PWM frequencies where existing filters are ineffective.
Innovation Solution
A method and computer system that adapt control signals by detecting and modifying pulse durations to filter out spurious pulses, ensuring the control signal remains within predetermined intervals, thereby preventing latch-up and correcting programming errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the PWM control signal frequency is increased to improve injection control precision, then the injection precision is improved, but spurious pulses become shorter in duration and existing filters become ineffective
Solution Approach 1:
The patent applies preliminary action by detecting and correcting spurious pulses in the PWM control signal before they reach the control circuit. The microcontroller monitors the PWM signal for abnormal pulses (duration shorter than minimum threshold or longer than maximum threshold) and corrects them by adjusting the duty cycle, ensuring only valid control signals are sent to the control circuit. This preventive approach maintains reliability while allowing high PWM frequencies for precision control.
Solution Approach 2:
The patent implements feedback by continuously monitoring the PWM control signal characteristics (pulse duration, duty cycle) and comparing them against predetermined thresholds. When spurious pulses are detected through this feedback mechanism, the system automatically corrects the duty cycle to eliminate the abnormal pulses, creating a closed-loop control system that maintains reliability at high frequencies.
2Reliability
If a filter is added to filter out spurious pulses, then the control circuit reliability is improved, but the filter cannot effectively filter very short-duration pulses at high PWM frequencies
Solution Approach 1:
The patent replaces the mechanical/analog filter approach with a digital signal processing solution implemented in the microcontroller. Instead of using physical filter components that have fixed frequency characteristics, the system uses software-based detection and correction of spurious pulses by monitoring pulse duration and duty cycle parameters, enabling effective filtering at high PWM frequencies where analog filters fail.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the duty cycle parameter of the PWM signal based on detected pulse characteristics. When spurious pulses are identified (abnormal duration or duty cycle values), the system modifies the duty cycle parameter to correct the signal, providing adaptive filtering that remains effective across varying PWM frequencies including high-frequency operations.
3Adaptability or versatility
If the duty cycle of PWM control signals is allowed to vary freely between 0 and 100%, then the control flexibility is improved, but spurious pulses may cause latch-up of the control circuit
Solution Approach 1:
The patent applies preliminary anti-action by implementing protective measures against latch-up before it occurs. The microcontroller monitors the PWM signal for conditions that could cause latch-up (extreme duty cycle values, abnormal pulse durations) and takes corrective action by adjusting the duty cycle to safe ranges, preventing control circuit latch-up while maintaining necessary control flexibility for normal operation.
Solution Approach 2:
The patent uses feedback by continuously monitoring PWM signal parameters (duty cycle, pulse duration) and comparing them against safety thresholds. When the duty cycle approaches extreme values or abnormal patterns are detected, the feedback mechanism triggers corrective adjustment of the duty cycle, creating a self-regulating system that maintains stability while allowing flexible control within safe operating ranges.
Data Source
AI summary
Disclosed is a method for adapting a control signal of a control circuit for at least one injector of a combustion engine of a motor vehicle, the control signal being a voltage-pulse signal of variable frequency varying between a minimum frequency and a maximum frequency and which is characterized over a given period by its duty cycle. For a given period of the control signal, the method includes determining the start time of the given period and of detecting the first pulse in the given period from the start time and, when the duration of the detected first pulse is included in a minimum time interval beginning at the start of the given period and the duration of which is dependent on the maximum frequency, modifying the duration of the detected first pulse so that the duration becomes equal to the duration of the minimum time interval.