PID Control for Diesel Exhaust Purification
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Solution Overview
Problem
During automatic regeneration of a diesel particulate defuser (DPD) with a vehicle running, sudden deceleration and acceleration cause fluctuations in boost pressure, leading to interruptions in post injection, which prolong the time to reach the target regeneration temperature and disrupt PID control, making it difficult to accurately control post injection.
Innovation Solution
The exhaust gas purifying system detects temperature deviations and uses PID control to manage post injection amounts, continuing integral control without resetting during exhaust brake valve closures and resuming with accumulated operation when the valve is opened, ensuring consistent temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If post injection is interrupted when exhaust brake valve is closed during sudden deceleration, then fuel consumption is reduced, but PID control is disrupted and regeneration time increases
Solution Approach 1:
The integral term of PID control accumulates temperature deviation information in advance during periods when post injection is interrupted (such as when exhaust brake valve is closed). This accumulated integral term is then utilized when post injection resumes, allowing the control system to quickly respond and maintain regeneration efficiency without wasting fuel during deceleration periods.
2Stability of the object's composition
If PID control is reset to zero when exhaust brake valve is closed, then control stability is improved during valve closure, but control precision deteriorates after valve opening due to loss of accumulated integral term
Solution Approach 1:
The integral term continuously accumulates temperature deviation information even when the exhaust brake valve is closed and post injection is interrupted. This preliminary accumulation ensures that when the valve opens and post injection resumes, the control system already has accumulated correction data, maintaining both stability during valve closure and precision after resumption.
3Measurement precision
If post injection is continued during exhaust brake valve closure, then temperature control precision is maintained, but fuel consumption increases unnecessarily
Solution Approach 1:
The system dynamically adjusts post injection timing based on exhaust brake valve status and driving conditions. Post injection is interrupted when the exhaust brake valve is closed during sudden deceleration to avoid unnecessary fuel consumption, while the PID control's integral term dynamically accumulates temperature deviation information to ensure rapid resumption and maintain temperature control precision when the valve opens.
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 allows for accurate control of post injection amounts based on driving conditions, maintaining the exhaust gas temperature at the target regeneration temperature even during repeated acceleration and deceleration, thereby reducing regeneration time and improving control precision.
Implementation Method 1
An exhaust gas temperature sensor disposed downstream of the DOC is used to detect the temperature of the exhaust gas flowing into the CSF
Implementation Method 2
The DOC includes an active catalyst for oxidizing unburned fuel
Implementation Method 3
The DOC includes an active catalyst for oxidizing unburned fuel
Implementation Method 4
The CSF captures PM in the exhaust gas
Implementation Method 5
a turbo charger operating during the acceleration causes a sharp rise of a boost pressure, increasing an amount of air flowing through the DPD
Implementation Method 6
an exhaust brake valve is designed to close in order to prevent an exhaust gas temperature from dropping
Data Source
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AI summary
An exhaust gas purifying system is provided to, during automatic regeneration with a vehicle running, control post injection accurately through PID control even when acceleration and deceleration are repeated or when an exhaust brake valve is closed. An exhaust pipe 20 for a diesel engine 10 is connected to a DPD 25. To automatically regenerate the DPD 25, an exhaust gas temperature is detected, a deviation of the detected exhaust gas temperature from a target regeneration temperature is evaluated, and an amount of post injection is controlled through PID control according to the deviation. When, during the automatic regeneration with a vehicle running, an exhaust brake valve 24 is closed, the post injection is interrupted. While the exhaust brake is being closed, an operation of an integral control term is continued with the PID control, and when the exhaust brake valve 24 is opened, the integral control term operated without interruption is used as an initial amount of operation.