Exhaust Controller for Urea Injection Optimization
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Solution Overview
Problem
Existing exhaust purification devices face challenges in optimally controlling the injection amount of urea water in selective reduction catalysts due to sensitivity of NOx sensors to both NOx and ammonia, leading to difficulties in suppressing ammonia slip and maintaining high NOx reduction rates.
Innovation Solution
A controller is developed that calculates future predicted values of control output based on a plant model, using a predicted value calculating means, evaluation function value calculating means, and extremum searching means to optimize the control input values, thereby quickly and precisely matching target values despite large response delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional feedback control is used to control urea water injection amount, then the control system is simple, but the response delay causes oscillations and inability to quickly match target values
Solution Approach 1:
The patent applies preliminary action by calculating future predicted values of the control output using a plant model before the actual control action is taken. The predicted value calculating means computes what the ammonia concentration will be at future time points based on current and past control inputs, allowing the controller to anticipate the system response and adjust the urea water injection amount proactively to achieve the target value without oscillations.
2Measurement precision
If extremum searching optimization is applied, then control precision is improved, but computational load increases
Solution Approach 1:
The patent reduces computational load by performing preliminary calculations of future predicted values using a pre-established plant model. Instead of performing complex optimization calculations in real-time, the controller uses the predicted values to determine the optimal control input, significantly reducing the computational burden while maintaining high control precision for the urea water injection amount.
Solution Approach 2:
The patent applies partial action by focusing the extremum searching optimization only on the critical control parameter (urea water injection amount) rather than optimizing all system parameters simultaneously. This selective optimization approach achieves sufficient control precision for the ammonia concentration while keeping the computational load manageable for implementation in exhaust purification systems.
3Measurement precision
If ammonia concentration is detected downstream of selective reduction catalyst, then NOx reduction rate can be monitored, but ammonia slip cannot be suppressed due to sensor sensitivity to both NOx and ammonia
Solution Approach 1:
The patent applies preliminary action by calculating future predicted values of ammonia concentration at multiple time points before the actual control action is executed. The predicted value calculating means uses the plant model to forecast ammonia concentration trends, allowing the controller to adjust the urea water injection amount in advance to prevent ammonia slip while maintaining high NOx reduction rates, without relying on real-time sensor differentiation.
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 stable and precise control of the exhaust purification process, reducing oscillations and overshoot, and improving the NOx reduction rate while minimizing ammonia slip, even in adverse environments with limited computational resources.
Implementation Method 1
a selective reduction catalyst that selectively reduces NOx in the exhaust by adding a reducing agent is provided in an exhaust channel
Implementation Method 2
a selective reduction catalyst of urea addition type that uses urea water as a reducing agent generates ammonia from the urea thus added, and selectively reduces NOx in the exhaust with this ammonia
Data Source
AI summary
A controller for controlling a plant comprises a predictor for calculating a predicted value of the future of a control output value based on a provisional value of a control input value including a periodic reference signal by using a plant model indicating the dynamic characteristics of the control output value from the control input value of the plant, an evaluation function value calculator for calculating an evaluation function value including the predicted value of the future of the calculated control output value, an extreme value search optimizer for calculating a provisional value of such a control input value as that the evaluation function value becomes the extreme value on the basis of a product of the calculated evaluation function value and a periodic reference signal, and an adder for calculating a control input value including the provisional value of the calculated control input value.