Common-Rail Pressure Control via Second Filter and PWM Dynamics
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Solution Overview
Problem
In common rail systems of internal combustion engines, load shedding leads to unexpected opening of the pressure-limiting valve due to increased engine speed, causing rapid rail pressure rise and potential instability, exacerbated by the limitations of existing PID control systems and electrical parameters of the control unit.
Innovation Solution
A second actual rail pressure is determined using a second filter, and upon detecting load shedding, a higher PWM signal is temporarily applied to accelerate the closing of the suction throttle, preventing unintended pressure relief valve opening and improving actuator dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PID controller is used to regulate rail pressure, then the pressure regulation is maintained under normal operation, but the response time is too slow to prevent unexpected pressure-limiting valve opening during load shedding
Solution Approach 1:
The control system performs preliminary detection of load shedding conditions by monitoring engine load and speed parameters before the pressure crisis occurs. When load shedding is detected, the system proactively activates enhanced control modes (PWM specification, second filter) to prevent the pressure-limiting valve from opening, rather than reacting after the problem occurs.
Solution Approach 2:
The system dynamically switches between different control strategies based on operating conditions. Under normal operation, standard PID control is used. When load shedding is detected, the system transitions to an enhanced dynamic response mode with adjusted PWM specifications and additional filtering, allowing the suction throttle to close faster and prevent pressure buildup.
2Productivity
If the engine speed increases during load shedding, then the delivery rate of the high-pressure pump increases, but this causes the rail pressure to rise rapidly to dangerous levels
Solution Approach 1:
The system uses feedback from engine speed and load sensors to detect load shedding conditions. The second filter processes the rail pressure signal with a smaller time constant to provide rapid feedback on pressure changes. This feedback mechanism allows the control system to identify when engine speed increases cause problematic pressure rises and respond accordingly by adjusting the PWM signal to the suction throttle.
Solution Approach 2:
The system applies preliminary anti-action by detecting the conditions that lead to excessive pressure (engine speed increase during load shedding) and counteracting them before the pressure reaches dangerous levels. The enhanced PWM specification and second filter work together to preemptively close the suction throttle, preventing the pressure-limiting valve from opening in the first place.
3Speed
If the PWM signal is increased to accelerate the suction throttle closing, then the actuator dynamics improve, but the electrical parameters of the control unit (maximum current, power loss) are severely restricted
Solution Approach 1:
The enhanced PWM specification is applied periodically and temporarily only during load shedding events, rather than continuously. The system activates the second filter and enhanced PWM mode only when load shedding is detected, and deactivates them when normal operation resumes. This periodic application minimizes the electrical energy burden on the control unit while still providing the necessary actuator acceleration when needed.
Solution Approach 2:
The system dynamically adjusts the PWM signal based on real-time detection of load shedding conditions. During normal operation, standard PWM values are used. When load shedding is detected, the system temporarily switches to enhanced PWM specifications to accelerate the suction throttle response, then returns to normal PWM operation after the event resolves. This dynamic adjustment ensures electrical parameters are not continuously stressed.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach prevents unintentional opening of the pressure relief valve and ensures safer pressure regulation by enhancing the dynamic response of the high-pressure control circuit, allowing the suction throttle to recover from sticking issues and maintaining stable rail pressure.
Implementation Method 1
a second actual rail pressure is determined from the rail pressure via a second filter
Implementation Method 2
The control signal is implemented electrically as a PWM signal (pulse-width modulated)
Data Source
Figure 1
Figure 2
Figure 3A~3D
AI summary
The invention relates to a control and regulation method for an internal combustion engine (1) provided with a Common-Railsystem, wherein rail pressure (pCR) is regulated in normal operation. The invention is characterised in that a second actual rail pressure is determined by a second filter, load shedding is recognised when the second actual rail pressure exceeds a first threshold value and is controlled by recognising a load shedding of the rail pressure (pCR), wherein the PWM-signal (PWM) is set by a PWM-specification to a PWM value which is higher than in normal operation.