Engine urea injection amount self-adaptive control system and method

Abstract

The application discloses an engine urea injection amount self-adaptive control system and method, which comprises the following steps: estimating the actual ammonia storage of a catalyst according to engine operation signals; calculating a transition coefficient according to the operation signals; identifying a current operation state based on the transition coefficient and the operation signals; calling a first control map and a second control map according to the transition coefficient and performing weighted fusion to obtain a basic injection amount and a target control amount; correcting the basic injection amount to obtain a corrected injection amount; calculating a correction upper limit; correcting the corrected injection amount to obtain a final injection amount and controlling an injection valve to perform injection according to the final injection amount. The transition coefficient is used to continuously represent the entering, stable and exiting processes of DPF active regeneration, so that the SCR urea injection control is no longer hard switched between the first control map in the normal mode and the second control map in the regeneration mode, but realizes smooth fusion of the double MAPs, thereby reducing the mutation risk of the urea injection amount.

Description

Technical Field

[0001] This invention relates to the field of engine exhaust aftertreatment control technology, and in particular to an adaptive control system and method for engine urea injection quantity. Background Technology

[0002] Diesel engines and other lean-burn engines produce nitrogen oxide (NOx) emissions during operation. Selective catalytic reduction (SCR) systems, which inject urea solution to decompose urea into ammonia, and then use the ammonia to reduce NOx in the SCR catalyst, are an important technical route for reducing NOx emissions. In actual operation, the SCR urea injection quantity needs to be balanced between NOx conversion rate and ammonia leakage. Insufficient urea injection quantity leads to a decrease in NOx conversion rate, while excessive urea injection quantity easily causes excessive ammonia leakage downstream of the SCR. Especially during DPF active regeneration, to increase DPF temperature and oxidize and capture particulate matter, the exhaust temperature, exhaust flow rate, and original NOx concentration of the engine and aftertreatment system will change significantly, causing a rapid change in the SCR system inlet boundary.

[0003] Existing technologies typically employ a MAP-based urea injection control strategy, which determines the urea injection quantity by looking up tables based on parameters such as engine operating conditions, exhaust temperature, exhaust flow rate, and nitrogen oxide concentration. Different target MAPs can also be established for normal operation mode and DPF regeneration mode. However, during the DPF active regeneration entry and exit phases, if the system performs a hard switch between the normal mode MAP and the regeneration mode MAP, it can easily cause a sudden increase or decrease in the urea injection quantity. This can lead to over-injection of urea and an increased risk of ammonia leakage during the regeneration entry phase, or insufficient urea injection and a decrease in nitrogen oxide conversion rate during the regeneration exit phase.

[0004] Furthermore, the exhaust temperature rises rapidly during DPF active regeneration, increasing the risk of desorption and oxidation of ammonia already adsorbed inside the SCR catalyst. If ammonia storage is still controlled according to the conventional upper limit, it may be impossible to prevent ammonia leakage in advance, leading to the downstream ammonia concentration exceeding the limit under regeneration thermal shock. Summary of the Invention

[0005] To address the technical problems existing in the background art, this invention proposes an adaptive control system and method for engine urea injection quantity.

[0006] The present invention proposes an adaptive control method for engine urea injection quantity, comprising: S1, acquiring engine operating signals to estimate the actual ammonia storage in the catalyst; S2. Calculate the transition coefficient based on the operating signal, and identify the current operating state based on the transition coefficient and the operating signal. The current operating state is one of the first steady state, the transition state, and the second steady state. S3. Based on the transition coefficient, the first control spectrum and the second control spectrum are called simultaneously and weighted and fused to obtain the basic injection quantity and the target control quantity. Then, the rate of change of the basic injection quantity is limited. S4. Based on the deviation between the target control quantity and the actual value in the operating signal, the base injection quantity is corrected to obtain the corrected injection quantity; S5. Dynamically reduce the upper limit of ammonia storage based on the transition coefficient and the temperature change rate in the operating signal to obtain the corrected upper limit. Compare the actual ammonia storage with the lower limit of ammonia storage and the corrected upper limit. Adjust the injection quantity based on the comparison results to obtain the final injection quantity. Control the injection valve to perform injection based on the final injection quantity.

[0007] Preferably, a safety judgment for injection is set between S1 and S2 based on the catalyst carrier temperature and downstream ammonia concentration in the operating signal. Specifically, when the catalyst carrier temperature is lower than the injection start temperature threshold or the downstream ammonia concentration reaches the ammonia leakage limit, urea injection is prohibited; when the catalyst carrier temperature is not lower than the injection start temperature threshold and the downstream ammonia concentration is lower than the ammonia leakage limit, the process proceeds to S2 after passing the safety judgment.

[0008] Preferably, step S1 specifically involves: acquiring engine operating signals, which include at least a DPF regeneration request signal, DPF differential pressure, DPF outlet temperature, upstream catalyst temperature, downstream catalyst temperature, upstream catalyst nitrogen oxide concentration, downstream catalyst nitrogen oxide concentration, downstream catalyst ammonia concentration, exhaust gas mass flow rate, engine speed, and engine torque; estimating the catalyst carrier temperature based on the upstream catalyst temperature, downstream catalyst temperature, and exhaust gas mass flow rate; and calculating the actual ammonia storage capacity of the catalyst using mass conservation recursion based on the urea injection rate, exhaust gas mass flow rate, upstream catalyst nitrogen oxide concentration, downstream catalyst nitrogen oxide concentration, downstream catalyst ammonia concentration, and catalyst carrier temperature.

[0009] Preferably, the calculation of the transition coefficient based on the operating signal in S2 specifically involves: calculating the normalized value of the DPF pressure difference based on the DPF pressure difference and the DPF regeneration trigger pressure difference threshold in the operating signal; calculating the normalized value of the DPF outlet temperature based on the DPF outlet temperature, the DPF regeneration trigger temperature threshold, and the DPF regeneration exit temperature threshold in the operating signal; calculating the normalized value of the catalyst temperature change rate based on the catalyst carrier temperature change rate and a preset temperature change rate threshold in the operating signal; calculating the normalized value of the exhaust flow rate change rate based on the exhaust mass flow rate change rate and a preset flow rate change rate threshold in the operating signal; calculating the normalized value of the nitrogen oxide concentration change rate based on the upstream nitrogen oxide concentration change rate and a preset concentration change rate threshold in the operating signal; performing a weighted summation on the normalized values ​​of the DPF pressure difference, DPF outlet temperature, catalyst temperature change rate, exhaust flow rate, and nitrogen oxide concentration change rate, and limiting the amplitude of the weighted summation result to obtain the original value of the transition coefficient; and performing a smoothing filter on the original value of the transition coefficient to obtain the transition coefficient.

[0010] Preferably, the step of identifying the current operating state based on the transition coefficient specifically involves: identifying a first steady state when the transition coefficient is less than or equal to a first threshold and the DPF regeneration request signal is invalid; identifying a transition state when the transition coefficient is greater than the first threshold and the DPF regeneration request signal is valid, or when the DPF regeneration request signal is invalid and the transition coefficient is greater than the first threshold; and identifying a second steady state when the transition coefficient is greater than or equal to a second threshold and the DPF regeneration request signal is valid, wherein the second threshold is greater than the first threshold.

[0011] Preferably, step S3 specifically involves: simultaneously calling the first control graph and the second control graph based on the transition coefficient; the first control graph outputs a first basic injection quantity, a first target conversion rate, a first target leakage quantity, and a first target storage quantity; the second control graph outputs a second basic injection quantity, a second target conversion rate, a second target leakage quantity, and a second target storage quantity; the first basic injection quantity and the second basic injection quantity are weighted and summed according to the transition coefficient to obtain the basic injection quantity; the first target conversion rate and the second target conversion rate are weighted and summed according to the transition coefficient to obtain the target conversion rate; the first target leakage quantity and the second target leakage quantity are weighted and summed according to the transition coefficient to obtain the target leakage quantity; the first target storage quantity and the second target storage quantity are weighted and summed according to the transition coefficient to obtain the target storage quantity; the target control quantity includes the target conversion rate, the target leakage quantity, and the target storage quantity; and the change rate of the basic injection quantity is limited so that the change in the basic injection quantity between adjacent control cycles does not exceed a preset increase change threshold and a preset decrease change threshold.

[0012] Preferably, step S3 further includes: when the DPF regeneration request signal in the operating signal disappears and the upstream temperature of the catalyst or the temperature of the catalyst support is lower than the preset exit temperature threshold, instead of immediately switching to the first control spectrum, the transition coefficient is controlled to gradually decrease according to a preset decreasing rate, and the weighted fusion of the first control spectrum and the second control spectrum continues to be performed in the transition state until the transition coefficient reaches the first value corresponding to the first steady state.

[0013] Preferably, step S4 specifically involves: calculating the actual conversion rate based on the upstream and downstream nitrogen oxide concentrations of the catalyst in the operating signal; correcting the base injection quantity after the rate of change limit based on the deviation between the target conversion rate and the actual conversion rate in the target control quantity to obtain a first corrected injection quantity; correcting the first corrected injection quantity based on the deviation between the target leakage quantity in the target control quantity and the actual leakage quantity in the operating signal to obtain a second corrected injection quantity; and outputting the second corrected injection quantity as the corrected injection quantity.

[0014] Preferably, step S5 specifically involves: determining the lower and upper limits of ammonia storage based on the dynamic difference between nitrogen oxide concentration and ammonia storage quantity in the operating signal; calculating the regeneration thermal shock safety margin based on the transition coefficient and the temperature change rate in the operating signal; subtracting the regeneration thermal shock safety margin from the upper limit of ammonia storage to obtain the corrected upper limit; comparing the actual ammonia storage quantity with the lower and corrected upper limits; increasing the corrected injection quantity when the actual ammonia storage quantity is lower than the basic lower limit; decreasing the corrected injection quantity when the actual ammonia storage quantity is higher than the corrected upper limit; maintaining the corrected injection quantity when the actual ammonia storage quantity is between the lower and corrected upper limits to obtain the final injection quantity; and generating a pulse width modulation signal based on the final injection quantity to drive the injection valve to perform injection.

[0015] The present invention also provides an engine urea injection quantity adaptive control system, which applies the above-mentioned engine urea injection quantity adaptive control method and includes: a pattern recognition module for acquiring operating signals and identifying the current operating state, wherein the current operating state includes at least a first steady state, a transition state and a second steady state; The estimation module is used to estimate the actual ammonia storage capacity inside the SCR catalyst based on the operating signals. The safety assessment module is used to assess the safety of urea injection based on the SCR carrier temperature and the concentration of ammonia leakage downstream of the SCR. The optimal MAP storage module is used to store the first control map in normal mode and the second control map in regeneration mode; The regeneration transition fusion module is used to calculate the regeneration transition coefficient based on at least one of the following after passing the safety judgment: DPF regeneration request signal, DPF pressure difference, DPF outlet temperature, SCR carrier temperature change rate, exhaust mass flow rate change rate, and SCR upstream nitrogen oxide concentration change rate. Based on the regeneration transition coefficient, the control targets output by the first control spectrum in normal mode and the second control spectrum in regeneration mode are weighted and fused to obtain the transition basic urea injection quantity and the transition target control quantity. The slope limiting module is used to limit the slope of the transition base urea injection volume; The steady-state correction module is used to correct the injection amount of transitional base urea after slope limitation based on the nitrogen oxide conversion rate deviation, so as to obtain the first corrected injection amount. The leakage correction module is used to correct the first correction injection quantity based on the ammonia leakage concentration deviation to obtain the second correction injection quantity; The boundary shrinkage module is used to solve the lower limit and upper limit of ammonia storage based on the dynamic difference between nitrogen oxide concentration and actual ammonia storage, and to dynamically shrink the upper limit of ammonia storage according to the regeneration transition coefficient and the temperature change rate of SCR carrier to obtain the corrected upper limit. The deep correction module is used to compare the actual ammonia storage amount with the lower limit of ammonia storage and the upper limit of correction, and to correct the second correction injection amount according to the comparison result to obtain the final urea injection amount. The execution module is used to convert the final urea injection quantity into a pulse width modulation signal to drive the urea injection valve to perform injection.

[0016] In this invention, by utilizing the transition coefficient to continuously characterize the DPF active regeneration entry, stabilization, and exit processes, the SCR urea injection control no longer involves hard switching between the first control chart in normal mode and the second control chart in regeneration mode. Instead, it achieves smooth fusion of the two MAPs, thereby reducing the risk of abrupt changes in urea injection volume. The smoothing fusion factor is used to adjust the base injection volume and target NO output of the first control chart in normal mode and the second control chart in regeneration mode. x The conversion rate, target ammonia leakage, and target ammonia storage are weighted and integrated to ensure continuous control targets throughout the normal operation, regeneration transition, regeneration stabilization, and regeneration exit transition phases. By limiting the slope of the base injection quantity, sudden increases or decreases in injection quantity between adjacent control cycles are avoided, improving the response stability of the urea injection actuator and reducing the risk of ammonia leakage and insufficient nitrogen oxide conversion caused by sudden changes in injection quantity. The regeneration thermal shock safety margin is calculated based on the SCR carrier temperature change rate, transition coefficient, and exhaust mass flow rate change rate. Based on this safety margin, the upper limit of ammonia storage is dynamically reduced, ensuring that the actual ammonia storage inside the SCR is far from the ammonia leakage boundary before the active regeneration thermal shock of the DPF occurs. Attached Figure Description

[0017] Figure 1 This is a block diagram of the engine urea injection quantity adaptive control system proposed in this invention; Figure 2 A schematic diagram of the engine hardware architecture involved in the proposed engine urea injection quantity adaptive control system. Figure 3 This is a flowchart of the adaptive control method for engine urea injection quantity proposed in this invention. Detailed Implementation

[0018] Example 1

[0019] Reference Figure 1 The present invention proposes an adaptive control system for engine urea injection quantity, which is applied to, for example... Figure 2 The engine hardware architecture shown includes an engine body 1, an exhaust aftertreatment module 2, a sensor network module 3, an electronic control unit (ECU) 4, and a urea injection actuator 5.

[0020] The exhaust aftertreatment module 2 includes a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and a selective catalytic reduction (SCR) catalyst. The sensor network module 3 includes a DPF differential pressure sensor, a DPF outlet temperature sensor, an SCR upstream temperature sensor, an SCR downstream temperature sensor, and an SCR upstream NO sensor. x Sensors, downstream NO of SCR x Sensors, downstream ammonia sensor for SCR, and exhaust mass flow sensor.

[0021] This system is integrated into the electronic control unit ECU 4, which includes a pattern recognition module, an estimation module, a safety determination module, an optimal MAP storage module, a regenerative transition fusion module, a slope limiting module, a steady-state correction module, a leakage correction module, and a boundary contraction module.

[0022] The pattern recognition module is used to acquire operating signals and identify the current operating state, which includes at least a first steady state in normal mode, a second steady state in regeneration mode, and a transition state; the transition state includes regeneration entry transition state and regeneration exit transition state. The estimation module is used to estimate the actual ammonia storage capacity inside the SCR catalyst based on the operating signals. The safety determination module is used to determine the safety of urea injection based on the SCR carrier temperature and the downstream ammonia leakage concentration. The optimal MAP storage module is used to store the first control map in normal mode and the second control map in regeneration mode. The regeneration transition fusion module, after passing the safety determination, calculates a transition coefficient based on at least one of the following: DPF regeneration request signal, DPF differential pressure, DPF outlet temperature, SCR carrier temperature change rate, exhaust mass flow rate change rate, and upstream nitrogen oxide concentration change rate. Based on the transition coefficient, it weights and fuses the control targets output from the first control map in normal mode and the second control map in regeneration mode to obtain the basic injection quantity and target control quantity of urea in the transition state. The slope limitation module is used to limit the slope of the basic injection quantity of urea in the transition state. The steady-state correction module corrects the gradient-limited base urea injection rate based on the nitrogen oxide conversion rate deviation, yielding a first corrected injection rate. The leakage correction module corrects the first corrected injection rate based on the ammonia leakage concentration deviation, yielding a second corrected injection rate. The boundary contraction module calculates the lower and upper limits of ammonia storage based on the dynamic differences between the nitrogen oxide concentration and the actual ammonia storage, and dynamically contracts the upper limit of ammonia storage according to the regeneration transition coefficient and the SCR carrier temperature change rate, yielding a corrected upper limit. The depth correction module compares the actual ammonia storage with the lower and corrected upper limits, and corrects the second corrected injection rate based on the comparison results, yielding the final urea injection rate. The execution module converts the final urea injection rate into a pulse width modulation signal to drive the urea injection valve to perform injection.

[0023] In this embodiment, both the first control graph (i.e., the optimal MAP for normal mode) and the second control graph (i.e., the optimal MAP for regeneration mode) are pre-generated and stored in the electronic control unit ECU 4. The optimal MAP takes at least one of the following as inputs: SCR carrier temperature, exhaust mass flow rate, air speed, engine speed, and engine torque, and outputs: base urea injection quantity, target nitrogen oxide conversion rate, target ammonia leakage, and target ammonia storage quantity. The generation process of the optimal MAP for normal mode and the optimal MAP for regeneration mode is briefly described below: At each steady-state calibration point, the system first determines the candidate range of urea injection rate by dynamically increasing the urea dosage. The dynamic urea dosage relationship is shown in equation (1):

[0024] In the formula, For the first j Urea injection mass flow rate during the second dynamic dosage increase ； For the first Urea injection mass flow rate after dynamic dosage increase; This is the dynamic addition ratio coefficient.

[0025] When NO x When the conversion rate increase is less than the set threshold, or when the downstream ammonia concentration of the SCR approaches the ammonia leakage limit, the dynamic dosage increase should be stopped. The NO content during dynamic dosage increase should be monitored. x The conversion rate is shown in equation (2):

[0026] In the formula, For the first j NO during the second dynamic dosage increase x Conversion rate; For the first j+ NO after 1 dynamic dosage increase x Conversion rate; NO x Conversion rate improvement threshold.

[0027] Collected SCR downstream Concentration and The relationship between leakage limits is shown in equation (3):

[0028] In the formula, For the first j SCR downstream during the second dynamic dosage increase concentration; for Leakage proximity limit factor; for Leakage limits.

[0029] This yields the candidate range for urea injection rate, as shown in equation (4):

[0030] In the formula, The urea injection mass flow rate to be optimized; This is the lower limit of the urea injection mass flow rate; This represents the upper limit of the urea injection mass flow rate.

[0031] Subsequently, the urea injection rate was used as the optimization variable, as shown in equation (5):

[0032] In the formula, Optimize variables for multiple objectives; This refers to the mass flow rate of urea injection.

[0033] Then, the multi-objective optimization function is defined as shown in equation (6):

[0034] In the formula, Optimize function vectors for multiple objectives; Let this be the first objective function; The second objective function; The mass flow rate of urea injection is the optimization variable; the superscript T indicates vector transpose.

[0035] Wherein, the first objective function is The minimum unconverted rate is achieved, as shown in equation (7):

[0036] In the formula, Let be the first objective function, used to characterize Non-conversion rate; To optimize variables Corresponding SCR downstream concentration; To optimize variables The corresponding SCR upstream concentration.

[0037] The second objective function is Minimum leakage, as shown in equation (8):

[0038] In the formula, The second objective function is used to characterize The relative level of leakage; To optimize variables Corresponding SCR downstream concentration; for Leakage limits.

[0039] The optimization constraints used are as follows: Equations (9), (10), (11), (12), and (13):

[0040] In the formula, Optimize the urea injection mass flow rate variables; The maximum permissible urea injection mass flow rate.

[0041]

[0042] In the formula, The SCR carrier temperature; This is the threshold temperature for urea injection.

[0043]

[0044] In the formula, For SCR internal Storage lower limit; For SCR internal actual Storage capacity; For SCR internal Storage limit. This constraint is used to ensure the internal storage capacity of the SCR. The storage capacity is within a reasonable range.

[0045]

[0046] In the formula, To meet Pareto feasible solution set for leakage limit constraints; For the Pareto solution set, the first There are 10 candidate solutions; For the first The SCR downstream of each candidate solution concentration; for Leakage limits.

[0047] After multi-objective optimization, the Pareto optimal solution set is obtained. The system first eliminates infeasible solutions where the downstream ammonia concentration of the SCR exceeds the ammonia leakage limit, and obtains the feasible solution set, as shown in equation (14):

[0048] In the formula, Number the final selected optimal solution; To meet Pareto feasible solution set for leakage limit constraints; For the first The candidate solutions correspond to The conversion rate; argmax represents the candidate solution number selected to maximize the objective function.

[0049] Select from the feasible solution set The candidate solution with the highest conversion rate is taken as the optimal solution, as shown in equation (15):

[0050] In the formula, Number the final selected optimal solution; To meet Pareto feasible solution set for leakage limit constraints; for Leakage limits; For the first The SCR downstream of each candidate solution concentration; This indicates the selection of candidate solution numbers that minimize the objective function.

[0051] When there are multiple candidate solutions When the conversion rate difference is less than the preset threshold, the candidate solution with the downstream ammonia concentration of SCR that is closest to but does not exceed the ammonia leakage limit is selected, as shown in equation (16):

[0052] In the formula, This is the optimal MAP for the current operating mode; The optimal urea injection mass flow rate; To be optimal Conversion rate; For optimal SCR downstream concentration; For the optimal SCR internal Storage quantity; superscript This represents the optimal value obtained through optimization.

[0053] Finally, the optimal solution corresponds to the urea injection rate, Conversion rate Leakage and The storage amount is written to the optimal MAP corresponding to the operating mode, as shown in equation (17):

[0054] In the formula, This represents the urea injection quality requirement value during the kth control cycle. For the first k Final urea injection mass flow rate under each control cycle; To control the cycle.

[0055] It should be noted that the optimal MAP generation process can be completed offline or in a model-in-the-loop environment, and the generated optimal MAP for normal mode and optimal MAP for regeneration mode are stored in the ECU. During real-time control, the ECU does not need to re-execute the complete multi-objective optimization, but instead calls the corresponding MAP according to the current operating conditions and performs smooth fusion of the two MAPs based on the regeneration transition coefficient.

[0056] Example 2 like Figure 2 Based on the above system settings, the present invention proposes an adaptive control method for engine urea injection quantity, which specifically includes the following steps: S1. Collect engine operating signals to estimate the actual ammonia storage in the catalyst. The specific process is as follows: First, within each control cycle, the system collects operating signals from the engine and aftertreatment system. The collected engine operating signals include at least the DPF regeneration request signal, DPF differential pressure, DPF outlet temperature, upstream catalyst temperature, downstream catalyst temperature, upstream nitrogen oxide concentration, downstream nitrogen oxide concentration, downstream ammonia concentration, exhaust mass flow rate, engine speed, and engine torque. Based on the collected operating signals, a state vector can be obtained, as shown in equation (1):

[0057] In the formula, For the first k Operating state vector under each control cycle; For the first k DPF regeneration request signal under each control cycle; For the first k DPF pressure difference under each control cycle; For the first k DPF outlet temperature under each control cycle; The upstream temperature of the SCR during the k-th control cycle; For the first k SCR downstream temperature under each control cycle; For the first k SCR upstream under each control cycle concentration; For the first k SCR downstream under each control cycle concentration; For the first k SCR downstream under each control cycle concentration; For the first k Exhaust mass flow rate under each control cycle; For the first k Engine speed under each control cycle; For the first k Engine torque under each control cycle.

[0058] Then, the catalyst carrier temperature is estimated based on the upstream temperature of the catalyst, the downstream temperature of the catalyst, and the exhaust mass flow rate, as shown in equation (2):

[0059] In the formula, For the first k SCR carrier temperature under each control cycle; For the first k-SCR carrier temperature during one control cycle; To control the cycle; The thermal inertia time constant of the SCR carrier; For the first k Equivalent exhaust temperature under each control cycle.

[0060] in, The calculation formula is as shown in equation (3):

[0061] In the formula, For the first k Equivalent exhaust temperature under each control cycle; For the first k Temperature weighting coefficients under each control cycle; For the first k SCR upstream temperature under each control cycle; For the first k SCR downstream temperature under each control cycle.

[0062] The calculation formula is as shown in equation (4):

[0063] In the formula, For the first k Exhaust mass flow rate under each control cycle; The preset maximum exhaust mass flow rate; This is a function that takes the minimum value.

[0064] Finally, based on the urea injection rate, exhaust mass flow rate, upstream nitrogen oxide concentration, downstream nitrogen oxide concentration, downstream ammonia concentration, and catalyst carrier temperature, the actual ammonia storage capacity of the catalyst is calculated recursively using mass conservation. The mass flow rate of ammonia generated from urea decomposition and entering the SCR system can be obtained from equation (5):

[0065] In the formula, For the first k Entering the SCR system under each control cycle Mass flow rate; for Molar mass; This refers to the molar mass of urea. This represents the mass fraction of urea in an aqueous urea solution. The mass flow rate of urea injection during the k-th control cycle; coefficient 2 indicates that 1 mol of urea can generate .

[0066] participate The mass flow rate of ammonia consumed in the reduction reaction can be obtained from equation (6):

[0067] In the formula, For the kth control cycle, participate The reduction reaction consumes Mass flow rate; For the first k SCR upstream under each control cycle concentration; For the first k SCR downstream under each control cycle concentration; For the first k Exhaust mass flow rate under each control cycle; The average molar mass of the exhaust gas; for Molar mass; 106 is the conversion factor for converting ppm concentration to volume fraction.

[0068] The downstream ammonia leakage mass flow rate of the SCR can be obtained from equation (7):

[0069] In the formula, For the first k SCR downstream under each control cycle Leakage mass flow rate; For the first k SCR downstream under each control cycle concentration; For the first k Exhaust mass flow rate under each control cycle; The average molar mass of the exhaust gas; for Molar mass; 106 is the conversion factor for converting ppm concentration to volume fraction.

[0070] The mass flow rate of ammonia oxidation or desorption loss at high temperature can be obtained by equation (8):

[0071] In the formula, For the first k Under each control cycle Mass flow rate loss due to oxidation or desorption; To match the temperature of the SCR carrier and airspeed Related Loss coefficient; For the first The actual internal operation of SCR under each control cycle Storage capacity.

[0072] The actual ammonia storage capacity inside the SCR is calculated recursively, as shown in equation (9):

[0073] In the formula, For the first k The actual internal operation of SCR under each control cycle Storage capacity; For the first The actual internal operation of SCR under each control cycle Storage capacity; To control the cycle; For the first k Entering the SCR system under each control cycle Mass flow rate; For the first k Participate in each control cycle The reduction reaction consumes Mass flow rate; For the first k SCR downstream under each control cycle Leakage mass flow rate; For the first k Under each control cycle Oxidation or desorption results in loss of mass flow rate.

[0074] Because the actual ammonia storage capacity cannot be directly measured, this step uses mass conservation recursion (taking into account spray decomposition, ... The four major losses are reduction consumption, downstream leakage, and high-temperature oxidation / desorption loss. Using existing conventional sensors ( (Temperature, flow rate) can be calculated in real time without the need for expensive [equipment / feedback]. The sensor is placed inside the SCR, which effectively reduces hardware costs.

[0075] S2. Calculate the transition coefficient based on the operating signal, and identify the current operating state based on the transition coefficient and the operating signal. The current operating state is one of the first steady state, the transition state, and the second steady state. This includes the following sub-steps: S21. Calculate the transition coefficient: The system calculates the transition coefficient based on the DPF regeneration request signal, DPF differential pressure, DPF outlet temperature, SCR carrier temperature change rate, exhaust mass flow rate change rate, and SCR upstream... The concentration change rate is used to calculate the regeneration transition coefficient. For ease of calculation, the normalized value of the DPF pressure difference is first calculated, as shown in equation (10):

[0076] In the formula, For the first kNormalized DPF differential pressure value under each control cycle; For the first k DPF pressure difference under each control cycle; The differential pressure threshold for DPF regeneration triggering; This means that the calculation result will be limited to between 0 and 1.

[0077] Then calculate the normalized value of the DPF outlet temperature, as shown in equation (11):

[0078] In the formula, For the first k Normalized DPF outlet temperature under each control cycle; For the first k DPF outlet temperature under each control cycle; The DPF regeneration exit temperature threshold; The DPF regeneration trigger temperature threshold; This means that the calculation result will be limited to between 0 and 1.

[0079] The normalized value of the SCR catalyst temperature change rate is calculated as shown in equation (12):

[0080] In the formula, For the first k Normalized value of SCR catalyst temperature change rate under each control cycle; For the first k SCR carrier temperature change rate under each control cycle; The threshold for the temperature change rate of the SCR carrier; This means that the calculation result will be limited to between 0 and 1.

[0081] The normalized value of the rate of change of exhaust flow is calculated as shown in equation (13):

[0082] In the formula, For the first k Normalized value of the rate of change of exhaust mass flow rate under each control cycle; For the first k Rate of change of exhaust mass flow rate under each control cycle; The threshold for the rate of change of exhaust mass flow rate; This means that the calculation result will be limited to between 0 and 1.

[0083] Calculate SCR upstream The normalized value of the concentration change rate is shown in equation (14):

[0084] In the formula, For the first k SCR upstream under each control cycle Normalized value of concentration change rate; For the first k SCR upstream under each control cycle Concentration change rate; upstream of SCR Concentration change rate threshold; This means that the calculation result will be limited to between 0 and 1.

[0085] Then, the normalized values ​​of DPF pressure difference, DPF outlet temperature, catalyst temperature change rate, exhaust flow rate change rate, and nitrogen oxide concentration change rate are weighted and summed, and the weighted summation result is limited to obtain the original value of the transition coefficient; the calculation formula is as shown in equation (15):

[0086] In the formula, For the first k Original value of regeneration transition coefficient under each control cycle; For the first k DPF regeneration request signal under each control cycle; For the first k Normalized DPF differential pressure value under each control cycle; For the first k Normalized DPF outlet temperature under each control cycle; For the first k Normalized value of SCR carrier temperature change rate under each control cycle; For the first k Normalized value of the rate of change of exhaust mass flow rate under each control cycle; For the first k SCR upstream under each control cycle Normalized value of concentration change rate; These are the weighting coefficients; This means that the calculation result will be limited to between 0 and 1.

[0087] Finally, to avoid abrupt changes in the transition coefficients, a first-order inertial filter is applied, as shown in formula (16):

[0088] In the formula, For the first k Transition coefficient under each control cycle; For the first Regeneration transition coefficient under each control cycle; To control the cycle; For the first k Transition coefficient filtering time constant under each control cycle; For the first k The original value of the transition coefficient under each control cycle.

[0089] Among them, the transition coefficient filtering time constant The calculation is as shown in equation (17):

[0090] In the formula, For the first k Transition coefficient filtering time constant under each control cycle; The transition coefficient rise filter time constant for the regeneration entry stage; The transition coefficient decreases during the regeneration exit phase filtering time constant; For the first k Original values ​​of the transition coefficient under each control cycle; For the first Transition coefficient under each control cycle.

[0091] S22. Identify the current operating state: The current operating state is based on the transition coefficient. DPF regeneration request signal And a preset threshold is used for division. As shown in equation (18):

[0092] In the formula, For the first k Operating status under each control cycle; This represents the first steady state under normal conditions. To enter a transitional state for regeneration; This represents the second steady state under DPF regeneration mode. To exit the transition state for regeneration; For the first k Transition coefficient under each control cycle; The first threshold; The second threshold; For the first k DPF regeneration request signal under each control cycle.

[0093] When the transition coefficient is less than or equal to the first threshold and the DPF regeneration request signal is invalid, it is identified as the first steady state; when the transition coefficient is greater than the first threshold and the DPF regeneration request signal is valid, or when the DPF regeneration request signal is invalid and the transition coefficient is greater than the first threshold, it is identified as the transition state; when the transition coefficient is greater than or equal to the second threshold and the DPF regeneration request signal is valid, it is identified as the second steady state, where the second threshold is greater than the first threshold.

[0094] By using the above state division, the present invention can avoid hard switching based solely on 0 / 1 mode flags, enabling SCR urea injection control to have continuous transition capability during the DPF active regeneration entry and exit stages.

[0095] In addition, it is worth emphasizing that there is a step between S1 and S2 to determine the injection safety based on the catalyst carrier temperature and downstream ammonia concentration in the operating signal.

[0096] The system determines the safety of urea injection based on the SCR carrier temperature and the downstream ammonia concentration. The temperature-based injection start-up condition is shown in equation (19):

[0097] In the formula, For the first k Temperature-based spray start determination flag under each control cycle; For the first k SCR carrier temperature under each control cycle; This is the threshold temperature for urea injection. When Greater than or equal to hour, Take 1; when Less than hour, Take 0.

[0098] The ammonia leak restriction conditions for starting the spray are as shown in equation (20):

[0099] In the formula, This serves as the ammonia leak initiation and discharge determination flag for the kth control cycle. For the downstream of SCR in the kth control cycle concentration; for Leakage limit. When Less than hour, Take 1; when Greater than or equal to hour, Take 0.

[0100] The final start-up enable signal is shown in equation (21):

[0101] In the formula, For the first k The final injection start-up enable signal under each control cycle; For the first k Temperature-based spray start-up determination flag under each control cycle; For the firstk The ammonia leak start-up judgment indicator under each control cycle.

[0102] When the SCR catalyst support temperature is lower than the injection temperature threshold (i.e.) If the downstream ammonia concentration of the catalyst reaches the ammonia leakage limit, urea injection is prohibited and step S2 is not executed; if the SCR catalyst carrier temperature is not lower than the start-up temperature threshold and the downstream ammonia concentration of the catalyst is lower than the ammonia leakage limit, step S2 can be executed after a safety determination.

[0103] S3. Based on the transition coefficient, simultaneously call the first control map (i.e., the optimal MAP for normal mode) and the second control map (the optimal MAP for regeneration mode) and perform weighted fusion to obtain the basic injection quantity and the target control quantity. Then, limit the rate of change of the basic injection quantity. Specifically, this includes the following steps: S31. Based on the transition coefficient, simultaneously call the first control chart and the second control chart, as follows: To reduce the impact of MAP switching, this embodiment calculates a smoothing fusion factor based on the transition coefficient, and then fuses the outputs of the optimal MAP in normal mode (i.e., the first control graph) and the optimal MAP in regeneration mode (i.e., the second control graph) accordingly. The smoothing fusion factor is shown in equation (22):

[0104] In the formula, For the first k Smoothing fusion factor under each control cycle; For the first k Transition coefficient under each control cycle.

[0105] The optimal MAP output vector in normal mode is shown in equation (23):

[0106] In the formula, For the first k Optimal MAP output vector in normal mode under each control cycle; For the first k The first basic injection volume of urea in normal mode of each control cycle; For the first k Under normal control cycle The primary goal is conversion rate; For the first k Under normal control cycle The primary target leakage amount; For the first k Under normal control cycle The first target storage amount.

[0107] The optimal MAP output vector in regeneration mode is given by equation (24):

[0108] In the formula, For the first k The optimal MAP output vector of regeneration mode under each control cycle; For the first k The second basic injection volume of urea in the regeneration mode of each control cycle; For the first k Regeneration mode in one control cycle The second target is conversion rate; For the first k Regeneration mode in one control cycle The second target leakage amount; For the first k Regeneration mode in one control cycle The second target storage amount.

[0109] The dual-MAP fusion output vector is calculated as shown in equation (25):

[0110] In the formula, For the first k The transition target output vector after fusion under each control cycle; For the first k Smoothing fusion factor under each control cycle; For the first k Optimal MAP output vector in normal mode under each control cycle; For the first k The optimal MAP output vector for regeneration mode under each control cycle.

[0111] The fused transition target output vector is calculated as shown in equation (26):

[0112] In the formula, For the first k The transition target output vector after fusion under each control cycle; For the first k The basic injection volume of urea under each control cycle; For the first k Under each control cycle The target conversion rate; For the first k Under each control cycle The target leakage amount; For the first k Under each control cycle The target storage amount.

[0113] S32. The first and second basic injection quantities are weighted and summed according to the transition coefficient to obtain the basic injection quantity, as shown in equation (27):

[0114] In the formula, For the first k The basic injection volume of urea under each control cycle; For the first k Smoothing fusion factor under each control cycle; For the first k The first basic injection volume of urea in normal mode under each control cycle; For the first k The second basic injection volume of urea in regeneration mode under each control cycle.

[0115] S33, Calculation The target conversion rate is as shown in equation (28):

[0116] In the formula, For the first k Under each control cycle The target conversion rate; For the first k Smoothing fusion factor under each control cycle; For the first k Normal mode target under each control cycle Conversion rate; For the first k Regeneration mode target under each control cycle Conversion rate.

[0117] Calculate the transition state The target leakage amount is as shown in equation (29):

[0118] In the formula, For the first k Under each control cycle The target leakage amount; For the first k Smoothing fusion factor under each control cycle; For the first k Normal mode target under each control cycle Leakage amount; For the first k Regeneration mode target under each control cycle Leakage amount.

[0119] Calculate the transition state The target storage amount is as shown in equation (30):

[0120] In the formula, For the first k Transitional target under each control cycle Storage capacity; For the first k Smoothing fusion factor under each control cycle; For the first k Normal mode target under each control cycle Storage capacity; For the first k Regeneration mode target under each control cycle Storage capacity.

[0121] The above processing utilizes a smoothing fusion factor to adjust the first / second base injection quantity outputs of the optimal MAP in normal mode and the optimal MAP in regeneration mode. Target conversion rate The target leakage amount and the target storage amount of NH3 are weighted and fused to ensure that there are continuous control targets for the normal operation, regeneration transition, regeneration stabilization and regeneration exit transition stages.

[0122] S34. To avoid large transient changes in urea injection volume after dual MAP fusion, the slope of the basic injection volume is further limited as shown in equation (31):

[0123] In the formula, For the first k The basic injection volume of urea after slope limitation under each control cycle; For the first The basic injection volume of urea after slope limitation under each control cycle; For the first k The basic injection volume of urea in the transition state under each control cycle; The maximum allowable increase in a single control cycle; The maximum allowable decrease in a single control cycle; This is the amplitude limiting function.

[0124] The aforementioned slope limitation can prevent sudden increases or decreases in injection volume between adjacent control cycles, improve the response stability of the urea injection actuator, and reduce the risk of ammonia leakage and insufficient nitrogen oxide conversion caused by sudden changes in injection volume.

[0125] Furthermore, when the DPF regeneration request signal in the operating signal disappears and the upstream temperature of the catalyst or the catalyst support temperature is lower than the preset exit temperature threshold, the system does not immediately switch to the optimal MAP in normal mode. Instead, it controls the transition coefficient to gradually decrease according to a preset decreasing rate, and continues to perform a weighted fusion of the optimal MAP in normal mode and the optimal MAP in regeneration mode in the transition state until the transition coefficient reaches the first value corresponding to the first steady state (i.e., Only when After filtering, it drops to Under these conditions, and only when the state machine determines that the system has fully returned to a normal stable state, does the system completely leave the optimal MAP for regeneration mode and rely solely on the optimal MAP for normal mode. This constraint ensures that when regeneration exits, the urea injection quantity decreases gradually with the decrease in exhaust temperature and the return of flow rate, rather than decreasing abruptly, thus allowing for the consumption of residual ammonia in the SCR catalyst and The reduction reaction provides ample buffer time, preventing emissions from exceeding limits the moment the aftertreatment system exits regeneration.

[0126] S4. Based on the deviation between the target control quantity and the actual value in the operating signal, correct the base injection quantity to obtain the corrected injection quantity; specifically, this includes the following steps: S41. Calculate the actual conversion rate based on the nitrogen oxide concentrations upstream and downstream of the catalyst in the operating signal, as shown in equation (32):

[0127] In the formula, For the first k Under each control cycle The actual conversion rate; For the upstream of SCR in the k-th control cycle concentration; For the first k SCR downstream under each control cycle concentration.

[0128] S42. Based on the deviation between the target conversion rate and the actual conversion rate in the target control quantity, the base injection quantity after the rate of change limitation is corrected. This part is based on... The urea injection correction for conversion rate deviation is given by equation (33):

[0129] In the formula, For the first k Based on each control cycle Urea injection correction amount for conversion rate deviation; for Conversion rate deviation correction factor; For the first kTransient state under each control cycle The target conversion rate; For the first k Under each control cycle The actual conversion rate; For the first k The base injection volume after slope limitation under each control cycle.

[0130] Based on the above corrections, the first corrected injection amount is obtained, as shown in equation (34):

[0131] In the formula, For the first k First corrected injection quantity under each control cycle; For the first k The basic injection volume of urea after slope limitation under each control cycle; For the first k Based on each control cycle Urea injection correction amount for conversion rate deviation.

[0132] S43. Based on the deviation between the target leakage amount in the target control quantity and the actual leakage amount in the operating signal, the first corrective injection quantity is corrected. This part is based on... The urea injection correction for leakage deviation is given by equation (35):

[0133] In the formula, For the first k Based on each control cycle Urea injection correction amount for leakage deviation; for Leakage correction factor; For the first k Under each control cycle, the actual downstream SCR concentration; For the first k Transient state under each control cycle The target leakage amount; for Leakage limits; For the first k First corrected injection quantity under each control cycle; This is the function for finding the maximum value.

[0134] based on The urea injection correction amount for leakage deviation is used to obtain the second corrected injection amount, as shown in equation (36):

[0135] In the formula, For the first k Second corrected injection quantity under each control cycle; For the first k First corrected injection quantity under each control cycle; For the first k Based on each control cycle Urea injection correction amount for leakage deviation.

[0136] S44. The second corrected injection quantity is output as the corrected injection quantity.

[0137] S5. Based on the transition coefficient and the temperature change rate in the operating signal, dynamically reduce the upper limit of ammonia storage to obtain a corrected upper limit. Compare the actual ammonia storage volume with the lower limit and the corrected upper limit. Adjust the injection volume based on the comparison results to obtain the final injection volume. Control the injection valve to perform injection based on the final injection volume. Specifically, this includes the following steps: S51, based on the operating signal Concentration and Solving the dynamic characteristics of storage capacity Storage lower limit and Storage limit. The calculation process is as follows: Because during the active regeneration of the DPF, the rapid temperature rise of the SCR catalyst may lead to the rapid desorption or oxidation of adsorbed ammonia. This embodiment is based on the regeneration thermal shock safety margin. The upper limit of storage capacity is dynamically reduced.

[0138] Expected downstream of SCR Concentration as shown in formula (37):

[0139] In the formula, For the first k Expected downstream SCR under one control cycle concentration; For the first k SCR upstream under each control cycle concentration; For the first k Transient state under each control cycle Target conversion rate.

[0140] based on Transformation target solution The lower limit of storage is as shown in equation (38):

[0141] In the formula, For the first k SCR internal control cycle Storage baseline; For the firstk SCR system airspeed under each control cycle; To match the temperature of the SCR carrier Related Reduction reaction coefficient; For the first k SCR upstream under each control cycle concentration; For the first k Expected downstream SCR under one control cycle concentration; It is the natural logarithm function.

[0142] in, The calculation is as shown in equation (39):

[0143] In the formula, For the first k SCR system airspeed under each control cycle; For the first k Exhaust volume flow rate under each control cycle; This represents the effective volume of the SCR catalyst.

[0144] If the system collects exhaust mass flow rate, the exhaust volume flow rate can be converted by the following formula (40).

[0145]

[0146] In the formula, For the first k Exhaust volume flow rate under each control cycle; For the first k Exhaust mass flow rate under each control cycle; For the first k Exhaust density under each control cycle.

[0147] based on Leakage limit solution Storage limit, as shown in equation (41):

[0148] In the formula, For the first k SCR internal control cycle Storage limit; For the current SCR support temperature and space velocity, the SCR catalyst can stably adsorb [the following]. Saturated storage capacity; for Leakage limits; For SCR carrier temperature and space velocity related Leakage sensitivity coefficient.

[0149] S52. Calculate the regeneration thermal shock safety margin based on the transition coefficient and the temperature change rate in the operating signal. Subtract the regeneration thermal shock safety margin from the upper limit of ammonia storage to obtain the corrected upper limit. The calculation process is as follows: Because the rapid temperature rise of the SCR support during the active regeneration of DPF may lead to rapid desorption or oxidation of adsorbed ammonia, this embodiment further calculates the regeneration thermal shock safety margin, as shown in equation (42):

[0150] In the formula, For the first k Safety margin for regenerative thermal shock under each control cycle; This is the safety margin coefficient corresponding to the temperature change rate of the SCR carrier; This is the safety margin coefficient corresponding to the regeneration transition coefficient; This is the safety margin coefficient corresponding to the rate of change of exhaust mass flow rate; For the first k SCR carrier temperature change rate under each control cycle; The threshold for the temperature change rate of the SCR carrier; For the first k Regeneration transition coefficient under each control cycle; For the first k Rate of change of exhaust mass flow rate under each control cycle; The threshold for the rate of change of exhaust mass flow rate; This is the function for finding the maximum value.

[0151] Calculate the upper limit of correction for ammonia storage under DPF regeneration perturbation constraints, as shown in equation (43):

[0152] In the formula, For the first k Under DPF regenerative disturbance constraints in one control cycle Storage correction limit; For the first k SCR internal control cycle Storage limit; For the first k Safety margin for regenerative thermal shock under each control cycle.

[0153] The safety margin calculated above dynamically shrinks the upper limit of ammonia storage, thus limiting the internal capacity of the SCR. The actual storage capacity is moved away from the ammonia leakage boundary in advance before the DPF active regeneration thermal shock arrives, forcing the actual storage capacity to be reduced to a safer level, effectively avoiding the instantaneous "ammonia wave" caused by the large-scale desorption / oxidation of adsorbed ammonia at high temperature.

[0154] To prevent excessive contraction of the upper limit, an ammonia storage correction upper limit with a minimum safety interval can also be used, as shown in equation (44):

[0155] In the formula, For the first k Under DPF regenerative disturbance constraints in one control cycle Storage correction limit; For the first k SCR internal control cycle Storage lower limit; To preset the minimum safety interval; For the first k SCR internal control cycle Storage limit; For the first k Safety margin for regenerative thermal shock under each control cycle; This is the function for finding the maximum value.

[0156] S53, will Actual storage capacity and Compare the lower limit of storage and the upper limit of correction; when the actual Storage volume less than When the storage limit is reached, the corrected injection amount is increased using formula (45);

[0157] In the formula, For the first k Ammonia storage depth correction amount under each control cycle; Increase the injection ratio when ammonia storage is insufficient; For the first k Second corrected injection quantity under each control cycle; For the first k SCR internal control cycle The actual storage capacity; For the first k SCR internal control cycle Lower limit of storage.

[0158] when When the actual storage amount is higher than the correction limit, the correction injection amount is reduced using formula (46);

[0159] In the formula, For the first k Ammonia storage depth correction amount under each control cycle; The injection rate is reduced when ammonia storage is too high. For the first k Second corrected injection quantity under each control cycle; For the first k SCR internal control cycle The actual storage capacity; For the first k Under DPF regenerative disturbance constraints in one control cycle Storage correction limit.

[0160] when When the actual storage amount is within the safe range between the lower limit of ammonia storage and the upper limit of correction, the corrected injection amount is maintained to obtain the final injection amount, as shown in equation (47):

[0161] In the formula, For the first k Ammonia storage depth correction amount under each control cycle; For the first k SCR internal control cycle Storage lower limit; For the first k SCR internal control cycle The actual storage capacity; For the first k Under DPF regenerative disturbance constraints in one control cycle Storage correction limit.

[0162] S54. Determine the final injection volume, as shown in equation (48):

[0163] In the formula, For the first k The final injection volume of urea under each control cycle; For the first k Second corrected injection quantity under each control cycle; For the first k Ammonia storage depth correction amount under each control cycle; This refers to the maximum permissible injection mass flow rate of the urea injection system. This is the amplitude limiting function.

[0164] The present invention can, through the above settings, The actual storage capacity is strictly limited to the lower limit of ammonia storage (preservation capacity). The ammonia level is between the lower limit and the adjusted upper limit (leakage prevention). If it falls below the lower limit, the amount is increased (to fill the storage gap); if it rises above the adjusted upper limit, the amount is reduced (forced ammonia unloading). Through this double-boundary clamping correction, the SCR always maintains an optimal ammonia storage level that is "just enough but never redundant," ensuring rapid response. Its ability to adapt to transient changes also minimizes the risk of high-temperature leaks.

[0165] S55. Generate a pulse width modulation signal based on the final injection volume to drive the injection valve to perform injection.

[0166] The required urea injection mass within one control cycle is given by equation (49):

[0167] In the formula, This refers to the mass of urea injected in a single application. This is the flow characteristic function of the urea injection valve; Pressure is applied to supply urea; This refers to the opening time of the injection valve.

[0168] The flow characteristics of the urea injection valve are expressed as shown in equation (50):

[0169] In the formula, For the first k Injector valve opening time under each control cycle; It is the inverse function of the urea injection valve flow characteristic function; For the first k Urea supply pressure under each control cycle; For the first k The required urea injection quality value within each control cycle.

[0170] Then, the injection valve opening time is calculated inversely based on the target urea injection mass, as shown in equation (51):

[0171] In the formula, For the first k PWM duty cycle under each control cycle; For the first k Injector valve opening time under each control cycle; This is the PWM control cycle.

[0172] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An adaptive control method for engine urea injection quantity, characterized in that, include: S1. Collect engine operating signals to estimate the actual ammonia storage in the catalyst; S2. Calculate the transition coefficient based on the operating signal, and identify the current operating state based on the transition coefficient and the operating signal. The current operating state is one of the first steady state, the transition state, and the second steady state. S3. Based on the transition coefficient, the first control spectrum and the second control spectrum are called simultaneously and weighted and fused to obtain the basic injection quantity and the target control quantity. Then, the rate of change of the basic injection quantity is limited. S4. Based on the deviation between the target control quantity and the actual value in the operating signal, the base injection quantity is corrected to obtain the corrected injection quantity; S5. Dynamically reduce the upper limit of ammonia storage based on the transition coefficient and the temperature change rate in the operating signal to obtain the corrected upper limit. Compare the actual ammonia storage with the lower limit of ammonia storage and the corrected upper limit. Adjust the injection quantity based on the comparison results to obtain the final injection quantity. Control the injection valve to perform injection based on the final injection quantity.

2. The adaptive control method for engine urea injection quantity according to claim 1, characterized in that, Between S1 and S2, there is a safety judgment for injection based on the catalyst carrier temperature and downstream ammonia concentration in the operation signal. Specifically, when the catalyst carrier temperature is lower than the injection start temperature threshold or the downstream ammonia concentration reaches the ammonia leakage limit, urea injection is prohibited; when the catalyst carrier temperature is not lower than the injection start temperature threshold and the downstream ammonia concentration is lower than the ammonia leakage limit, the safety judgment is passed and the process proceeds to S2.

3. The adaptive control method for engine urea injection quantity according to claim 1, characterized in that, S1 specifically involves: acquiring engine operating signals, which include at least the DPF regeneration request signal, DPF differential pressure, DPF outlet temperature, upstream catalyst temperature, downstream catalyst temperature, upstream catalyst nitrogen oxide concentration, downstream catalyst nitrogen oxide concentration, downstream catalyst ammonia concentration, exhaust mass flow rate, engine speed, and engine torque; estimating the catalyst carrier temperature based on the upstream catalyst temperature, downstream catalyst temperature, and exhaust mass flow rate; and calculating the actual ammonia storage capacity of the catalyst using mass conservation recursion based on the urea injection rate, exhaust mass flow rate, upstream catalyst nitrogen oxide concentration, downstream catalyst nitrogen oxide concentration, downstream catalyst ammonia concentration, and catalyst carrier temperature.

4. The adaptive control method for engine urea injection quantity according to claim 1, characterized in that, The S2 step of calculating the transition coefficient based on the operating signal specifically involves: calculating the normalized value of the DPF pressure difference based on the DPF pressure difference and the DPF regeneration trigger pressure difference threshold in the operating signal; calculating the normalized value of the DPF outlet temperature based on the DPF outlet temperature, the DPF regeneration trigger temperature threshold, and the DPF regeneration exit temperature threshold in the operating signal; calculating the normalized value of the catalyst temperature change rate based on the catalyst carrier temperature change rate and the preset temperature change rate threshold in the operating signal; calculating the normalized value of the exhaust flow rate change rate based on the exhaust mass flow rate change rate and the preset flow rate change rate threshold in the operating signal; and calculating the normalized value of the nitrogen oxide concentration change rate based on the upstream nitrogen oxide concentration change rate and the preset concentration change rate threshold in the operating signal. The normalized values ​​of DPF differential pressure, DPF outlet temperature, catalyst temperature change rate, exhaust flow rate change rate, and nitrogen oxide concentration change rate are weighted and summed, and the weighted summation result is limited to obtain the original value of the transition coefficient. The original value of the transition coefficient is then smoothed and filtered to obtain the transition coefficient.

5. The adaptive control method for engine urea injection quantity according to claim 3, characterized in that, The method of identifying the current operating state based on the transition coefficient is as follows: when the transition coefficient is less than or equal to the first threshold and the DPF regeneration request signal is invalid, it is identified as the first steady state; when the transition coefficient is greater than the first threshold and the DPF regeneration request signal is valid, or when the DPF regeneration request signal is invalid and the transition coefficient is greater than the first threshold, it is identified as the transition state; when the transition coefficient is greater than or equal to the second threshold and the DPF regeneration request signal is valid, it is identified as the second steady state, where the second threshold is greater than the first threshold.

6. The adaptive control method for engine urea injection quantity according to claim 1, characterized in that, S3 specifically involves: simultaneously calling the first control graph and the second control graph based on the transition coefficient; the first control graph outputs the first basic injection quantity, the first target conversion rate, the first target leakage quantity, and the first target storage quantity; the second control graph outputs the second basic injection quantity, the second target conversion rate, the second target leakage quantity, and the second target storage quantity; the first basic injection quantity and the second basic injection quantity are weighted and summed according to the transition coefficient to obtain the basic injection quantity; the first target conversion rate and the second target conversion rate are weighted and summed according to the transition coefficient to obtain the target conversion rate; The target leakage amount is obtained by weighted summing of the first target leakage amount and the second target leakage amount based on the transition coefficient. The first target storage quantity and the second target storage quantity are weighted and summed according to the transition coefficient to obtain the target storage quantity; the target control quantity includes the target conversion rate, the target leakage quantity and the target storage quantity; the change rate of the base injection quantity is limited so that the change of the base injection quantity between adjacent control cycles does not exceed the preset increase change threshold and the preset decrease change threshold.

7. The adaptive control method for engine urea injection quantity according to claim 6, characterized in that, S3 further includes: when the DPF regeneration request signal in the operation signal disappears and the upstream temperature of the catalyst or the temperature of the catalyst support is lower than the preset exit temperature threshold, instead of immediately switching to the first control spectrum, the transition coefficient is controlled to gradually decrease according to the preset decreasing rate, and the weighted fusion of the first control spectrum and the second control spectrum continues to be performed in the transition state until the transition coefficient reaches the first value corresponding to the first steady state.

8. The adaptive control method for engine urea injection quantity according to claim 1, characterized in that, S4 specifically involves: calculating the actual conversion rate based on the nitrogen oxide concentrations upstream and downstream of the catalyst in the operating signal; and correcting the base injection quantity after the rate of change limit based on the deviation between the target conversion rate and the actual conversion rate in the target control quantity to obtain the first corrected injection quantity. Based on the deviation between the target leakage amount in the target control quantity and the actual leakage amount in the operation signal, the first corrected injection quantity is corrected to obtain the second corrected injection quantity; The second corrected injection quantity is output as the corrected injection quantity.

9. The adaptive control method for engine urea injection quantity according to claim 1, characterized in that, Specifically, S5 involves: determining the lower limit and upper limit of ammonia storage based on the dynamic difference between the nitrogen oxide concentration and ammonia storage in the operating signal; The safety margin for regeneration thermal shock is calculated based on the transition coefficient and the rate of temperature change in the operating signal. The upper limit for ammonia storage is then subtracted from the safety margin for regeneration thermal shock to obtain the corrected upper limit. Compare the actual ammonia storage capacity with the lower limit and the adjusted upper limit of ammonia storage. When the actual ammonia storage level is lower than the lower limit of the ammonia storage baseline, the correction injection rate is increased; When the actual ammonia storage level is higher than the correction limit, reduce the correction injection amount; When the actual ammonia storage level is between the lower limit of ammonia storage and the upper limit of correction, the corrected injection rate is maintained to obtain the final injection rate. A pulse width modulation signal is generated based on the final injection volume to drive the injection valve to perform injection.

10. An adaptive control system for engine urea injection quantity, employing the adaptive control method for engine urea injection quantity as described in any one of claims 1-9, characterized in that, include: The pattern recognition module is used to collect operating signals and identify the current operating state, which includes at least a first steady state, a transitional state, and a second steady state. The estimation module is used to estimate the actual ammonia storage capacity inside the SCR catalyst based on the operating signals. The safety assessment module is used to assess the safety of urea injection based on the SCR carrier temperature and the concentration of ammonia leakage downstream of the SCR. The optimal MAP storage module is used to store the first control map in normal mode and the second control map in regeneration mode; The regeneration transition fusion module is used to calculate the regeneration transition coefficient based on at least one of the following after passing the safety judgment: DPF regeneration request signal, DPF pressure difference, DPF outlet temperature, SCR carrier temperature change rate, exhaust mass flow rate change rate, and SCR upstream nitrogen oxide concentration change rate. Based on the regeneration transition coefficient, the control targets output by the first control spectrum in normal mode and the second control spectrum in regeneration mode are weighted and fused to obtain the transition basic urea injection quantity and the transition target control quantity. The slope limiting module is used to limit the slope of the transition base urea injection volume; The steady-state correction module is used to correct the injection amount of transitional base urea after slope limitation based on the nitrogen oxide conversion rate deviation, so as to obtain the first corrected injection amount. The leakage correction module is used to correct the first correction injection quantity based on the ammonia leakage concentration deviation to obtain the second correction injection quantity; The boundary shrinkage module is used to solve the lower limit and upper limit of ammonia storage based on the dynamic difference between nitrogen oxide concentration and actual ammonia storage, and to dynamically shrink the upper limit of ammonia storage according to the regeneration transition coefficient and the temperature change rate of SCR carrier to obtain the corrected upper limit. The deep correction module is used to compare the actual ammonia storage amount with the lower limit of ammonia storage and the upper limit of correction, and to correct the second correction injection amount according to the comparison result to obtain the final urea injection amount. The execution module is used to convert the final urea injection quantity into a pulse width modulation signal to drive the urea injection valve to perform injection.

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