Exhaust Gas Purification PID Control for Temperature Overshoot
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Solution Overview
Problem
Existing exhaust gas purification systems face challenges in accurately controlling idling mode automatic regeneration of diesel particulate filters during vehicle stops, leading to potential temperature overshoot when transitioning from idling to running mode regeneration due to differences in exhaust gas amounts and integral control term limitations.
Innovation Solution
The system resets the integral control term in PID control to zero during the transition from running mode to idling mode automatic regeneration and re-evaluates it after a predetermined time to prevent excessive temperature overshoot by adjusting post injection quantities based on real-time deviations from target temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PID control is used for post injection quantity during idling mode automatic regeneration, then the exhaust gas temperature can be controlled based on deviation from target temperature, but the integral control term causes excessive temperature overshoot when transitioning to running mode regeneration
Solution Approach 1:
The patent applies dynamics by making the PID control parameters adaptive rather than fixed. Specifically, the integral control term is dynamically adjusted based on the operating mode (idling vs. running regeneration). When transitioning from idling to running mode, the integral term is reset or reduced to prevent excessive overshoot, while during stable idling operation it accumulates to maintain precise temperature control. This dynamic adaptation resolves the contradiction between precision control and stability during transitions.
Solution Approach 2:
The patent changes the control parameters of the PID controller based on the regeneration mode. The integral control term (Ki) is modified depending on whether the system is in idling mode or running mode. During idling mode, the integral term operates normally to eliminate steady-state error, but when transitioning to running mode, the integral term is reset or scaled down to prevent overshoot. This parameter change strategy allows the system to maintain temperature precision in each mode while avoiding instability during transitions.
2Reliability
If post injection is increased to maintain target temperature during idling regeneration, then regeneration effectiveness improves, but fuel consumption increases and lubricating oil dilution worsens
Solution Approach 1:
The patent applies partial action by providing different levels of post injection based on the regeneration mode. During idling mode regeneration, a reduced quantity of post injection is supplied compared to running mode regeneration. This partial injection is sufficient to maintain the target temperature for effective regeneration during idling, while avoiding the excessive fuel consumption and lubricating oil dilution that would result from full-strength post injection. The system achieves adequate regeneration effectiveness with minimized substance loss.
3Duration of action of stationary object
If exhaust brake valve is closed during running mode automatic regeneration, then exhaust gas temperature is maintained for continuous regeneration, but temperature control becomes difficult when vehicle stops
Solution Approach 1:
The patent applies preliminary action by preparing the control system for mode transition before it occurs. When the vehicle is decelerating or the driver releases the accelerator, the control system anticipates the upcoming transition from running to idling mode and begins adjusting the post injection quantity in advance. This preliminary adjustment ensures that when the transition occurs, the temperature control remains stable and precise, avoiding overshoot or instability. The exhaust brake valve remains closed to maintain temperature, while the injection control is proactively adjusted to accommodate the impending mode change.
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 stabilizes idling mode regeneration and prevents exhaust gas temperature overshooting, ensuring precise control and maintaining optimal regeneration temperatures during shifts from idling to running mode.
Implementation Method 1
The DPD includes a diesel oxidation catalyst (DOC) which comprises an active catalyst for oxidizing unburned fuel
Implementation Method 2
oxidizing unburned fuel and a catalyzed soot filter (CSF) for trapping PM contained in exhaust gas
Implementation Method 3
NOx is reduced by the thus produced ammonia over a SCR catalyst and thereby purified
Implementation Method 4
The temperature of exhaust gas flowing into the CSF is detected by an exhaust gas temperature sensor
Implementation Method 5
a quantity of the post injection is PID-controlled based on the calculated deviation so that the exhaust gas temperature becomes the target regeneration temperature
Data Source
AI summary
In the exhaust gas purification system, a diesel particulate defuser (“DPD”) for trapping particulate matter (“PM”) in exhaust gas is connected to an exhaust pipe of an engine to automatically regenerate the DPD by raising a temperature of the exhaust gas from the engine by carrying out post injection when an amount of PM in the DPD exceeds a predetermined amount. Further, the system includes detecting the temperature of the exhaust gas during DPD regeneration when the DPD is automatically regenerated, calculating a deviation between the detected temperature of the exhaust gas and a target temperature for the DPD regeneration, and controlling a quantity of the post injection by resetting an integral control term used in a PID control to zero when running mode automatic regeneration is shifted to idling mode automatic regeneration after a vehicle is stopped, when PID-controlling the quantity of the post injection based on the deviation.