Exhaust temperature safety control method and system for engine DPF regeneration cooling stage

Abstract

The invention discloses an engine DPF regeneration cooling stage exhaust temperature safety control method and system, and relates to the technical field of diesel engine aftertreatment system control. According to the technical key points, linear controllable adjustment of exhaust flow is achieved through collaborative composite slope control, high-temperature heat stored in parts such as DOC, DPF and SCR of an aftertreatment system is released in order along with stable airflow and taken away at a constant speed, and severe temperature fluctuation and high-frequency thermal shock caused by sudden change of cold and hot airflow in the prior art are completely avoided; irreversible faults such as shedding of an SCR carrier catalytic coating, aging failure of a temperature sensor probe and thermal deformation air leakage of a sealing gasket are effectively avoided, and the thermal aging rate of a post-processing core component is reduced, so that the service life of the whole machine of a post-processing system is prolonged, the long-term operation reliability of the post-processing system is improved, and meanwhile, the equipment maintenance cost and shutdown loss of a terminal user are reduced.

Description

Technical Field

[0001] This invention relates to the field of diesel engine aftertreatment system control technology, and in particular to a method and system for safe control of exhaust temperature during the regeneration and cooling stage of an engine DPF. Background Technology

[0002] To meet emission regulations regarding particulate matter emissions, diesel engines must be equipped with a diesel particulate filter (DPF). This filter uses a wall-flow trapping structure to intercept carbon particulate matter in the exhaust to meet legal emission limits. As carbon soot accumulates in the DPF, the engine exhaust back pressure gradually increases, leading to poor fuel economy and reduced power. Therefore, periodic parking regeneration is necessary. At the end of parking regeneration, the oxidation catalyst (DOC), DPF, and selective catalytic reduction (SCR) carrier in the aftertreatment system are all at temperatures above 600°C. The overall temperature of the aftertreatment system must be reduced to below a safe threshold through a cooling process to prevent thermal damage to surrounding wiring harnesses and pipes caused by high-temperature components, and to eliminate safety hazards caused by high temperatures in the tailpipe.

[0003] The current industry-standard DPF regeneration cooling control solution has the following complete implementation process:

[0004] The first step involves the engine control unit (ECU) determining, based on parameters such as carbon load model and regeneration runtime, that DPF parking regeneration is complete. Upon completion, it immediately triggers a mode switching command, directly switching the engine operating state from "regeneration control mode" to "rapid cooling mode." The second step involves the ECU simultaneously outputting two step-like control signals during the mode switching command: one is a speed control signal, which abruptly and seamlessly reduces the engine speed from the high speed during the regeneration phase (industry-standard range 1600 rpm to 2000 rpm, typical value 1800 rpm) to a preset low cooling speed (industry-standard range 1200 rpm to 1600 rpm, typical value 1500 rpm); the other is a throttle control signal, which instantly and without buffering switches the small throttle opening used to control exhaust oxygen concentration during the regeneration phase to a fully open state. This maximizes intake air volume to rapidly increase exhaust flow, relying on the large exhaust flow to remove heat from the aftertreatment system, achieving rapid cooling. However, the existing technical solution has the following drawbacks in actual implementation:

[0005] Firstly, when the existing solution switches execution modes, the combination of the instantaneous full opening of the throttle and the step drop in engine speed causes a sudden increase in engine exhaust flow rate several times over in a short period of time. At this time, the temperature at the DOC inlet and DPF inlet upstream of the aftertreatment system will drop rapidly with the large flow of fresh air due to the rapid increase in fresh air volume. However, the DPF and SCR ceramic carriers themselves have extremely strong thermal inertia, and the large amount of high-temperature heat stored inside them cannot be cooled down simultaneously and rapidly. The sudden increase in high-speed exhaust flow will directly wash over the high-temperature carrier, rapidly and concentratedly blowing the heat stored in the carrier wall and internal pores to the downstream pipeline of the aftertreatment system. This causes the temperature at the SCR inlet, SCR outlet, and even the tailpipe to show an abnormal peak of "first rising sharply and then slowly decreasing", making it impossible to achieve the core control goal of a stable and monotonous decrease in exhaust temperature during the cooling process.

[0006] Secondly, on the one hand, the abnormal peak temperature of the tailpipe caused by the existing solution is very likely to exceed the 500℃ human contact safety limit and the ignition threshold of flammable and explosive materials. The regeneration scenarios of diesel vehicles parked in the parking area are mostly closed / semi-closed environments such as depots and garages. The overheated tailpipe will not only cause serious burns to the operators and maintenance personnel nearby, but may also ignite the surrounding oil, cardboard boxes, and flammable and explosive materials, causing fires or even explosions, posing a great safety risk to production. On the other hand, the abnormal temperature rise peak will cause the downstream SCR carrier, temperature sensor, gasket and other components of the aftertreatment to experience a sudden temperature rise and fall of more than 200℃ within tens of seconds, forming a violent thermal shock. Under long-term cycle, it will lead to irreversible failures such as the peeling of the SCR carrier catalytic coating, aging and failure of the temperature sensor probe, and thermal deformation and leakage of the gasket, which will significantly reduce the long-term operational reliability and service life of the aftertreatment system and significantly increase the maintenance costs of the end users. Therefore, we propose a safe control method and system for exhaust temperature during the engine DPF regeneration cooling stage. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] To address the shortcomings of existing technologies, this invention provides a method and system for safe control of exhaust temperature during the regeneration and cooling stage of an engine DPF. By progressively and collaboratively controlling engine speed and throttle opening, a smooth transition in engine operating state is achieved, enabling the orderly release and removal of heat from the exhaust system. This eliminates abnormal temperature rise downstream of the aftertreatment system during the DPF regeneration and cooling stage from the root, and achieves a stable and monotonous decrease in exhaust temperature from the high regeneration temperature to the safe temperature, ensuring the safety and controllability of the entire cooling process.

[0009] (II) Technical Solution

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A method for safe control of exhaust temperature during the regeneration and cooling stage of an engine DPF, applied to a diesel engine aftertreatment system, includes the following steps:

[0012] S1. When the engine control unit determines that the diesel engine particulate filter (DPF) parking regeneration meets the completion conditions through the preset parking regeneration completion judgment parameters, it does not perform the operation of step-by-step switching the engine operating mode from the regeneration mode to the traditional cooling mode, but starts the progressive collaborative composite control cooling strategy.

[0013] S2. The engine control unit synchronously executes coordinated composite slope control of engine speed and throttle opening, controlling the engine speed to smoothly and continuously decrease from the high regeneration speed corresponding to parking regeneration according to the composite descent slope, while controlling the throttle to smoothly and continuously open from the small opening corresponding to regeneration mode according to the composite opening slope; wherein, the composite descent slope and the composite opening slope are pre-calibrated for coordinated matching.

[0014] S3. During the entire process of implementing the progressive collaborative composite control cooling strategy, the engine control unit continuously monitors the real-time measurement values ​​of at least one temperature sensor in the aftertreatment system, obtains temperature change characteristic parameters that characterize the temperature change trend based on the real-time measurement values, and then calculates the real-time correction slope based on the temperature change characteristic parameters. The total value of the composite descent slope and the composite opening slope is dynamically adjusted through the real-time correction slope.

[0015] S4. When the engine control unit detects that the real-time measured values ​​of all temperature sensors in the aftertreatment system have dropped below the preset safety threshold, it determines that the regeneration cooling process of the diesel engine particulate filter (DPF) is complete, terminates the progressive collaborative composite control cooling strategy, and controls the engine to switch to idle operation.

[0016] Preferably, in step S2, the rules for generating the composite descent slope and the composite opening slope are as follows:

[0017] The composite descent slope of the engine speed is generated by combining the base descent slope and the real-time correction slope according to a preset mathematical relationship, wherein the base descent slope can be calibrated.

[0018] The composite opening slope of the throttle valve is generated by combining the basic opening slope and the real-time correction slope according to a preset mathematical relationship, wherein the basic opening slope can be calibrated.

[0019] The preset mathematical relationship includes any one of the following: addition operation, weighted average operation, maximum value operation, and minimum value operation.

[0020] Preferably, in step S2, the cooperative matching calibration rule for the composite opening slope and the composite descent slope is as follows:

[0021] The basic opening slope and the basic descent slope are positively correlated. When the rate of decrease in engine speed increases, the throttle opening rate increases synchronously, and when the rate of decrease in engine speed decreases slows down, the throttle opening rate slows down synchronously.

[0022] Preferably, in step S1, the preset parking regeneration completion determination parameters include at least one of the real-time carbon load value of the particulate filter DPF and the cumulative running time of parking regeneration.

[0023] Preferably, in step S3, the temperature sensors of the aftertreatment system are installed in the upstream and downstream pipelines of the aftertreatment system. The temperature sensors include at least one of the following: oxidation catalyst (DOC) inlet temperature sensor, diesel engine particulate filter (DPF) inlet temperature sensor, selective catalytic reduction (SCR) inlet temperature sensor, and selective catalytic reduction (SCR) outlet temperature sensor.

[0024] The engine control unit prioritizes collecting real-time measurements from temperature sensors in the downstream pipelines of the aftertreatment system.

[0025] Preferably, in step S3, during the initial operation phase after the gradual collaborative composite control cooling strategy is activated, the engine control unit executes the basic slope control mode, including:

[0026] In the initial stage of the cooling strategy activation, the engine control unit sets the real-time correction slope corresponding to the composite descent slope and the composite opening slope to 0, so that the composite descent slope is equal to the basic descent slope and the composite opening slope is equal to the basic opening slope. According to the calibrated basic descent slope and basic opening slope, the engine speed is synchronously controlled to reduce smoothly and the throttle valve to open smoothly.

[0027] Preferably, in step S3, the temperature change characteristic parameter is the first derivative of the temperature measurement value; the specific process of calculating the real-time correction slope based on the temperature change characteristic parameter and dynamically adjusting the composite slope through the real-time correction slope is as follows:

[0028] When the engine control unit detects that the real-time measurement value of the target temperature sensor shows an upward trend, it calculates and generates a real-time correction slope with a negative value through a preset control algorithm. The preset control algorithm includes any one or more combinations of lookup table method, proportional control algorithm, and PID control algorithm.

[0029] Substitute the negative real-time correction slope into the calculation of the compound descent slope and the compound opening slope respectively, and simultaneously reduce the total value of the compound descent slope and the compound opening slope, thereby simultaneously slowing down the rate of engine speed reduction and the rate of throttle opening.

[0030] During the cooling process, the above dynamic adjustment is continuously performed until the engine control unit detects that the temperature change rate of the target temperature sensor remains negative for a continuous preset time period, and the absolute value of the temperature change rate is lower than the preset change rate threshold. At this point, it is determined that the exhaust temperature has entered a stable monotonically decreasing channel, and the real-time correction slope is returned to zero, restoring the basic slope control mode.

[0031] Preferably, in step S4, the preset safety threshold is pre-calibrated based on the allowable temperature limit of each component of the post-processing system and the safe temperature limit of the tailpipe outlet.

[0032] A safety control system for exhaust temperature during the regenerative cooling stage of an engine DPF includes an engine control unit, an engine body, a throttle valve, and an aftertreatment system. The engine control unit is communicatively connected to the engine body, the throttle valve, and the aftertreatment system.

[0033] The engine control unit is a programmable control unit configured to:

[0034] The system determines whether the diesel engine particulate filter (DPF) parking regeneration meets the completion conditions by using preset parking regeneration completion parameters, and initiates a progressive collaborative composite control cooling strategy when the completion conditions are met.

[0035] Synchronously execute the coordinated composite slope control of engine speed and throttle opening, calculate and generate composite descent slope and composite opening slope, and send speed control command to engine body and throttle opening control command;

[0036] The system acquires real-time measurements from temperature sensors, obtains temperature change characteristic parameters, generates a real-time correction slope, and performs dynamic feedback adjustment.

[0037] The system compares the real-time temperature sensor readings of the aftertreatment system with the preset safety threshold to determine whether the cooling process is complete, and controls the engine to switch to idle speed after cooling is complete.

[0038] Preferably, the engine control unit includes:

[0039] The regeneration completion determination module is used to obtain preset parking regeneration completion determination parameters, determine whether parking regeneration meets the completion conditions, and output a cooling strategy start command.

[0040] The coordinated slope control module is used to calculate and generate the basic descent slope and the basic opening slope, and to calculate the composite descent slope and the composite opening slope by combining the real-time correction slope, and output coordinated control commands to the engine body and the throttle body respectively.

[0041] The temperature feedback adjustment module is used to acquire the real-time measurement value of the temperature sensor of the post-processing system, calculate the temperature change characteristic parameters, generate a real-time correction slope through a preset control algorithm, and output it to the collaborative slope control module to complete the dynamic adjustment.

[0042] The cooling completion determination module compares the real-time measurement values ​​of all temperature sensors in the aftertreatment system with the preset safety threshold to determine whether the cooling process is complete, and outputs an idle speed switching command to the engine body.

[0043] The aftertreatment system includes an oxidation catalyst (DOC), a diesel engine particulate filter (DPF), and a selective catalytic reduction (SCR) connected in sequence. Multiple temperature sensors that communicate with the engine control unit are installed on the piping of the aftertreatment system.

[0044] (III) Beneficial Effects

[0045] 1. After DPF parking regeneration is completed, this invention abandons the step-like mode switching logic of existing technologies. Through the coordinated composite slope control of engine speed and throttle opening, the engine speed is smoothly and continuously reduced from the high regeneration speed, and the throttle opening is synchronously and smoothly reduced from the small opening. At the same time, through the positive correlation and coordinated matching calibration of the two, the exhaust flow is ensured to increase linearly and smoothly, thus avoiding the concentrated purging of upstream high-temperature carriers by sudden airflow changes. It achieves a smooth and monotonous decrease in exhaust temperature from the high regeneration temperature to the safe threshold during the cooling process, thereby fundamentally eliminating the safety risks of personnel burns and ignition of flammable and explosive materials caused by tailpipe overheating. It solves the core safety hazards of the cooling stage of parking regeneration in existing technologies, and significantly improves the safety of personnel operation and equipment operation in closed / semi-closed parking regeneration scenarios such as depots and garages.

[0046] 2. Through coordinated composite slope control, linear and controllable adjustment of exhaust flow is achieved, allowing the high-temperature heat stored in components such as DOC, DPF, and SCR in the aftertreatment system to be released and carried away at a constant speed with a smooth airflow. This completely avoids the drastic temperature fluctuations and high-frequency thermal shocks caused by sudden changes in hot and cold airflows in existing technologies. It effectively prevents irreversible failures such as SCR carrier catalytic coating peeling, temperature sensor probe aging and failure, and gasket thermal deformation and leakage, reducing the thermal aging rate of the core components of the aftertreatment system. This extends the overall service life and long-term operational reliability of the aftertreatment system, while reducing equipment maintenance costs and downtime losses for end users.

[0047] 3. Throughout the entire cooling strategy execution process, real-time measurements from the aftertreatment system's temperature sensors are continuously collected. Using temperature change characteristic parameters, which characterize temperature trends, as the core basis, a preset control algorithm is used to calculate and correct the slope in real time. Simultaneously, the control slopes of engine speed and throttle are dynamically adjusted, constructing a feedback control mechanism that sequentially progresses from signal acquisition, feature extraction, correction calculation, dynamic adjustment, to effect verification. In the initial cooling stage, a base slope is used to ensure basic cooling efficiency. When a temperature rise is detected, a negative correction slope is immediately used to slow the control process. Once the temperature enters a stable, monotonically decreasing channel, the basic control mode is restored. This gives the cooling process a strong adaptability to various operating conditions, allowing for dynamic adjustment of control intensity based on real-time exhaust temperature status. While ensuring cooling efficiency, the exhaust temperature safety boundary is locked throughout the process, improving the intelligence level, all-scenario adaptability, and control accuracy of the control strategy.

[0048] 4. Since all the control logic of this invention is based on the existing mass-produced hardware architecture of diesel engines, it fully reuses the original engine control unit (ECU), speed sensor, electronic throttle, after-treatment system temperature sensor and other hardware devices. There is no need to add any sensors, actuators or other hardware facilities to the engine and after-treatment system, nor is there any need to modify the mechanical architecture and wiring harness layout of the vehicle. All control functions can be realized by simply reprogramming and reconstructing the internal control logic of the ECU and calibrating the parameters. It has strong engineering applicability and market promotion value. Attached Figure Description

[0049] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0050] Figure 1 This is a flowchart illustrating the safety control strategy for exhaust temperature during the DPF regeneration cooling stage in this embodiment of the invention.

[0051] Figure 2 This is a schematic diagram of the exhaust temperature safety control system in an embodiment of the present invention. Detailed Implementation

[0052] This application provides a method and system for safe control of exhaust temperature during the regenerative cooling stage of an engine DPF, overcoming the defect of abnormal downstream temperature rise caused by the step-cooling mode switching in the prior art.

[0053] Example 1 is a method for linear and stable exhaust temperature control during the parking regenerative cooling stage of a diesel engine DPF:

[0054] To address the technical problems caused by traditional step-cooling control modes, such as abnormal downstream temperature rise, sudden exhaust temperature changes, component thermal shock, and safety hazards, the main approach is to replace step-cooling control with progressive synergistic composite control. This achieves synchronous and linear adjustment of engine speed and electronic throttle opening, combined with dynamic temperature feedback correction, ensuring a steady increase in exhaust flow and a monotonous decrease in exhaust temperature, with no sudden changes or abnormal peaks throughout the process. Specifically:

[0055] First, the precise criteria for determining the completion of parking regeneration are clearly defined to avoid control failure caused by cooling occurring too early or too late. Second, a collaborative composite slope control logic for engine speed and throttle body is designed to solve the problem of sudden flow changes. Then, a temperature feedback adjustment mechanism is added to improve the control's adaptive capability. Finally, a unique criterion for determining the completion of cooling is set to ensure a safe end to the cooling process.

[0056] This system is applicable to the cooling stage after DPF regeneration in diesel engines meeting China VI and above emission standards. It is implemented solely based on the original vehicle hardware, without any additional hardware, architectural modifications, or wiring changes. The applicable hardware is all standard equipment from the original vehicle, including the engine control unit (ECU), which is the original core controller with pre-programmed logic and parameter calibration. The diesel engine itself is the original standard diesel engine, the electronic throttle is the original standard linear adjustment electronic throttle, the aftertreatment system is the original standard DOC+DPF+SCR integrated aftertreatment system, the temperature sensors are the original standard 4-channel sensors for DOC inlet, DPF inlet, SCR inlet, and SCR outlet, and the CAN bus is the original standard communication line with a signal transmission delay of less than 10ms.

[0057] During implementation, the first step is to determine the completion of DPF parking regeneration. The design principle is to ensure the accuracy of regeneration completion through dual-parameter determination, avoiding misjudgment that could lead to premature or delayed cooling. During implementation, the engine control unit collects two original vehicle determination parameters in real time at a high frequency of 100Hz. Both parameters must be met simultaneously to determine that parking regeneration is complete. The first determination parameter is that the real-time carbon load of DPF is not greater than 0.5g / L, and the second determination parameter is that the cumulative running time of DPF parking regeneration is not less than 30 minutes. At the same time, the traditional step-cooling control mode is strictly prohibited. Specifically, this traditional mode prohibits directly stepping down the engine speed from the parking regeneration high speed to the cooling speed, prohibits directly and instantly opening the electronic throttle to full, and prohibits achieving rapid cooling through a step-change in exhaust flow.

[0058] Subsequently, a progressive and coordinated composite control cooling strategy is initiated. This strategy replaces the traditional abrupt control with a stepless and linear coordinated control logic, thereby avoiding sudden changes in exhaust flow. When implemented, the engine control unit immediately initiates this strategy without delay at the same moment it determines that parking regeneration is complete. This strategy is the only technical means to achieve a linear and stable decrease in exhaust temperature.

[0059] Next, engine speed and electronic throttle valve coordinated composite slope control is implemented. This is achieved through the composite calculation of the base slope and the real-time correction slope to synchronize the adjustment of engine speed and throttle opening, ensuring linear growth of exhaust flow and avoiding downstream temperature rise caused by sudden flow changes. During implementation, the engine control unit synchronously performs coordinated composite slope control on engine speed and electronic throttle opening without time or rate difference. The only control rule is that the composite downward slope of engine speed equals the base downward slope plus the real-time correction slope, and the composite opening slope of electronic throttle equals the base opening slope plus the real-time correction slope. The two composite slopes share the same real-time correction slope to ensure synchronized adjustment throughout the process, which is the rule for generating the composite slope. The only parameter calibration is that the base downward slope of engine speed is 20 r / min / s with a calibration range of 5 to 50 r / min / s, and the base opening slope of electronic throttle is 10% / s with a calibration range of 1% to 50% / s, completing the calibration of the base slope support parameters.

[0060] The unique rule for coordinated matching is that when the rate of decrease in engine speed increases, the opening rate of the electronic throttle increases synchronously and proportionally; when the rate of decrease in engine speed decreases, the opening rate of the electronic throttle decreases synchronously and proportionally. This ensures that the process of decreasing engine speed is completely synchronized with the process of opening the electronic throttle, and the exhaust flow increases linearly and smoothly without sudden changes, fluctuations, or abrupt changes. This implementation process accurately implements the technical features of the coordinated matching calibration rule in claim 3, and at the same time echoes the relevant limitations on the deployment and acquisition of temperature sensors in claim 5, laying the foundation for subsequent temperature feedback adjustment.

[0061] Then, dynamic temperature feedback adjustment is performed, mainly by real-time acquisition of temperature signals, analysis of temperature change trends, and dynamic correction of the composite slope to ensure that the exhaust temperature is always in a stable downward channel to cope with temperature fluctuations under different operating conditions. During implementation, the engine control unit acquires the real-time measurement value of the SCR outlet temperature sensor at a high frequency of 100Hz throughout the process, which is the most sensitive measurement point downstream of the aftertreatment. Simultaneously, it acquires the other three temperature sensors as auxiliary signals, thus prioritizing the acquisition of downstream temperature sensor signals.

[0062] The exhaust temperature trend is determined by calculating the first derivative of the measured temperature in real time. When the first derivative is greater than 0, the exhaust temperature shows an upward trend; when the first derivative is equal to 0, the exhaust temperature shows a stable trend; and when the first derivative is less than 0, the exhaust temperature shows a downward trend. The only closed-loop regulation algorithm adopts the PID algorithm. In the initial cooling stage, i.e., from 0 to 2 seconds, the real-time correction slope is 0, and linear control is performed only according to the basic slope, thus completing the limitation of the basic slope control mode in the initial stage. When the exhaust temperature shows an upward trend, the engine control unit immediately calculates and outputs a negative real-time correction slope, simultaneously reducing the total value of the two composite slopes, and simultaneously slowing down the rate of engine speed reduction and the electronic throttle opening rate to suppress abnormal exhaust temperature rise. When the exhaust temperature shows a monotonically decreasing trend for 5 consecutive seconds and the absolute value of the temperature change rate is less than 5℃ / s, the real-time correction slope returns to 0, restoring the basic slope control mode, thus implementing all the technical features of temperature change characteristic parameters, real-time correction slope calculation, and dynamic adjustment.

[0063] Finally, the cooling process is terminated with a unique determination and control procedure. This is achieved by comparing the temperatures at all measurement points to ensure that the entire aftertreatment system has cooled to a safe temperature, avoiding potential safety hazards caused by localized high temperatures. During implementation, the engine control unit compares the real-time measurements of all temperature sensors with a preset safety threshold. This preset safety threshold is uniquely calibrated to 200℃. This value is pre-calibrated based on the allowable temperature limits of the aftertreatment components and the safe temperature limit of the tailpipe outlet. The unique rule for determining cooling completion is that the real-time measurements of all temperature sensors are consistently below 200℃ for at least 3 seconds. Once the condition is met, the engine control unit immediately terminates the progressive collaborative composite control cooling strategy and smoothly switches the diesel engine to idle speed at 800r / min ± 50r / min. This process, which involves setting the preset safety threshold, is implemented without any additional hardware and is achieved solely through ECU programming.

[0064] In the specific implementation process, 1. Triggering conditions: When the ECU determines that the DPF parking regeneration meets the completion conditions (such as based on the carbon load model, regeneration time, etc.), it does not immediately execute the traditional cooling mode, but instead starts the progressive collaborative composite control cooling strategy of the present invention.

[0065] 2. Synergistic composite slope control:

[0066] Speed ​​control: The ECU controls the engine speed, starting from the high regeneration speed (e.g., 1800 r / min) and gradually decreasing it. The decreasing slope n_slope is not a fixed value, but is composed of a base decreasing slope (n_bas) and a real-time correction slope (n_cor) according to a preset mathematical relationship, i.e., n_slope = F(n_bas, n_cor). The base decreasing slope n_bas can be set according to the system target, for example, it can be selected in the range of 5-50 (r / min) / s. As a preferred implementation, the total decreasing slope is obtained by addition, i.e., n_slope = n_bas + n_cor.

[0067] Throttle control: Simultaneously, the ECU controls the throttle to open smoothly; its opening slope θ_slope is also composed of the basic opening slope θ_bas and the real-time correction slope θ_cor according to the above-mentioned preset mathematical relationship, that is, θ_slope=G(θ_bas,θ_cor); the basic opening slope θ_bas supports parameter calibration, for example, it can be selected in the range of 1-50% / s, and is matched with the speed reduction slope n_slope; as a preferred implementation, the total opening slope is obtained by addition, that is, θ_slope=θ_bas+θ_cor.

[0068] 3. Real-time monitoring and feedback adjustment:

[0069] During the cooling process, the ECU continuously monitors the measured values ​​and trends of at least one temperature sensor on the aftertreatment system (such as SCR inlet T6 and SCR outlet T7), such as the first derivative.

[0070] In the initial stage, the system only uses the basic slope for control, that is, n_cor=0, θ_cor=0, at which time n_slope=n_bas, θ_slope=θ_bas;

[0071] If an upward trend in the temperature signal is detected, the ECU immediately calculates a correction slope based on a preset control algorithm. The preset control algorithm includes, but is not limited to, lookup table method, proportional control, PID control or a combination thereof. Any control strategy that can output a corresponding correction slope based on the temperature change trend is applicable to this invention. Typically, a negative correction slope (n_cor < 0, θ_cor < 0) is assigned to reduce the total slope and make the process smoother.

[0072] This feedback adjustment continues until the rate of change of the downstream temperature (e.g., T7) remains negative for a continuous period of time (e.g., 5 seconds) and its absolute value is below a certain threshold (e.g., 5℃ / s). At this point, it is determined that the temperature has entered a stable downward channel, and the correction slope returns to zero.

[0073] 4. Completion conditions: When all temperature sensor readings drop below the preset safety threshold, the cooling process ends and the engine can be switched to idle.

[0074] Example 2 is a linear and stable exhaust temperature control system for the DPF (Diesel Power Filter) during the parking regenerative cooling stage of a diesel engine.

[0075] This provides a complete hardware platform and functional support for the control method in Example 1. Relying on the original vehicle hardware architecture, it integrates four functional modules through the engine control unit to achieve full-process coordination of signal acquisition, logic operation, command output, and closed-loop adjustment, ensuring the accurate implementation of the control method. First, the system hardware composition is clearly defined, reusing the original vehicle's standard hardware without the need for additional equipment, thus reducing implementation costs. Second, four functional modules corresponding one-to-one with the control method steps are integrated inside the ECU to ensure precise matching between module functions and method steps. Finally, a clear signal interaction logic is designed to ensure smooth and delay-free signal transmission between components and modules, achieving full-process control.

[0076] This embodiment corresponds exactly to the method in Embodiment 1, and is implemented solely based on the original vehicle hardware. The system hardware components in this embodiment are all standard original vehicle components without any additional hardware. The engine control unit (ECU) serves as the core controller of the system, with pre-programmed logic and all parameter calibrations completed. The diesel engine receives speed control commands from the ECU and performs linear speed adjustment. The electronic throttle receives opening control commands from the ECU and performs linear opening adjustment. The aftertreatment system is the original vehicle's standard DOC+DPF+SCR integrated aftertreatment system. The temperature sensors are the original vehicle's standard four-channel sensors, namely the DOC inlet, DPF inlet, SCR inlet, and SCR outlet temperature sensors. The CAN bus provides real-time communication between the ECU and all hardware components, and the signal transmission is without delay, packet loss, or distortion.

[0077] The system functional modules are pre-programmed and integrated by the ECU and uniquely correspond to the claims. The engine control unit integrates four core functional modules internally through pre-logic programming. Each module works collaboratively, seamlessly connects, and interacts without delay, fully executing all control methods of Embodiment 1.

[0078] The first module is the DPF parking regeneration completion determination module, which is used to accurately determine the completion of parking regeneration and provide a trigger signal for the start of the cooling strategy. The only parameters collected during implementation are the real-time carbon load of DPF and the cumulative running time of parking regeneration. The only determination rule is that the carbon load is not greater than 0.5g / L and the running time is not less than 30 minutes. The only instruction output is to immediately output the cooling strategy start instruction when the parking regeneration is determined to be complete, while strictly prohibiting the output of traditional step-type cooling control instructions.

[0079] The second module is the collaborative composite slope control module, which receives the start command and the correction slope signal, generates precise collaborative control commands, and realizes synchronous linear adjustment of engine speed and throttle. During implementation, the signal input is the start command received from the parking regeneration completion judgment module and the real-time correction slope from the temperature feedback adjustment module. The only calculation logic is to calculate and generate the composite decrease slope of engine speed and the composite opening slope of electronic throttle. The only command output is to output the linear control command of engine speed and the linear control command of electronic throttle opening with no time difference. The only execution rule is to strictly follow the collaborative matching rule to ensure that the engine speed and opening are synchronously adjusted throughout the entire process.

[0080] The third module is the temperature feedback adjustment module, which is used to collect temperature signals, analyze temperature trends, and generate correction slopes to provide feedback support for collaborative control. During implementation, the data collected are the real-time measurements from four temperature sensors. The only calculation logic is to calculate the first derivative of the temperature measurement in real time to determine the temperature change trend. The only adjustment algorithm is the PID closed-loop control algorithm to calculate and generate the real-time correction slope. The only signal output is to feed the real-time correction slope back to the collaborative composite slope control module to achieve dynamic adjustment throughout the entire process.

[0081] The fourth module is the cooling completion determination and process termination module, which is used to determine the cooling completion status and output a termination command to ensure the safe end of the cooling process. During implementation, the comparison parameters are the real-time measurement values ​​of all temperature sensors and the preset safety threshold of 200℃. The only determination rule is that all temperatures are below 200℃ and remain stable for 3 seconds. The only command output is to immediately output a cooling strategy termination command and an idle speed switching command when the cooling is determined to be complete, control the engine to smoothly switch to idle speed operation, and completely terminate the entire control process.

[0082] The system's unique signal interaction logic involves the temperature sensor transmitting a real-time temperature measurement signal to the temperature feedback adjustment module, which in turn transmits a real-time correction slope signal to the collaborative composite slope control module. The collaborative composite slope control module then transmits linear control commands to the diesel engine and electronic throttle in real time. Finally, the cooling completion determination and process termination module transmits process termination commands to the vehicle control system in real time. The entire process is characterized by zero signal delay, zero packet loss, and zero distortion, ensuring precise control, rapid response, and reliable execution. This supports the requirements for communication between the ECU and various components, command issuance, and signal acquisition.

[0083] Example 3 is a temperature exhaust control method with sensor fault redundancy handling:

[0084] As a subordinate optimized embodiment of Embodiment 1, this embodiment solves the control interruption problem of the basic method of Embodiment 1 in the case of temperature sensor failure, improves the reliability and environmental adaptability of the solution, and adds a sensor failure judgment and redundancy processing mechanism on the basis of all technical solutions of Embodiment 1 to ensure that the cooling control process can still be executed normally and the exhaust temperature can still drop steadily when a single or multiple sensors fail.

[0085] First, the criteria for judging sensor failures are clearly defined to accurately identify various failure states. Second, a hierarchical redundancy processing strategy is designed, and solutions are formulated for single-channel and multi-channel failures respectively. Finally, the redundancy processing mechanism is seamlessly integrated with the basic control flow of Example 1 to ensure that the original core control logic is not changed.

[0086] This embodiment adds a temperature sensor fault redundancy processing mechanism based on all technical solutions, implementation steps, parameter calibration, and judgment logic of Embodiment 1. It is applicable to fault scenarios such as signal loss, signal distortion, and signal exceeding limits of the temperature sensor. The unique sensor fault judgment rule in this embodiment is that the engine control unit collects four temperature sensor signals in real time. If any of the following conditions are met, the corresponding sensor is judged to be faulty: the temperature sensor signal is completely lost with no effective signal output; the temperature sensor measurement value exceeds the preset normal measurement range, i.e., -40℃ to 600℃; or the temperature sensor signal is distorted and the signal fluctuation amplitude is greater than 100℃ / s. This judgment rule accurately identifies sensor faults through three dimensions: signal integrity, rationality, and stability, and avoids control misjudgment caused by fault signals.

[0087] The fault redundancy sole handling strategy is based on the concept of redundancy backup. It ensures that effective temperature signals can still be obtained under fault conditions, maintaining the continuity of cooling control. When a single temperature sensor fails, the engine control unit automatically switches to redundant temperature measurement signals and uses the weighted average calculation of the effective signals from the other three temperature sensors to replace the faulty sensor signal, maintaining the normal operation of the cooling control strategy throughout. When multiple temperature sensors fail, the engine control unit immediately starts the preset redundant cooling control program and performs linear cooling control according to the basic slope, maintaining a stable decrease in exhaust temperature throughout until the cooling completion judgment condition is met. This handling strategy does not change the core control logic of Embodiment 1 and can effectively cope with fault scenarios, ensuring that the core advantages of the basic method are not affected.

[0088] Example 4 is a method for exhaust temperature control with real-time correction of exhaust flow rate:

[0089] This is a subordinate optimized embodiment of Embodiment 1, used to improve the accuracy of exhaust temperature control in the basic method of Embodiment 1 and solve the problem of exhaust temperature control deviation caused by exhaust flow fluctuations under different operating conditions. Based on the collaborative composite slope control of Embodiment 1, a real-time exhaust flow acquisition and correction mechanism is added. The composite slope is dynamically adjusted by the exhaust flow change rate, so that the cooling rate is fully adaptive to the exhaust flow change. The design process is as follows: first, clarify the exhaust flow acquisition method and calculation logic to obtain real-time flow change data; second, design the linkage correction rules between flow and slope to establish the correspondence between flow change and composite slope adjustment; finally, integrate the flow correction mechanism into the feedback adjustment process of Embodiment 1 to achieve dual-dimensional collaborative control of temperature and flow.

[0090] This embodiment adds a real-time exhaust flow correction mechanism to all technical solutions in Embodiment 1. By collecting engine exhaust flow signals in real time, the collaborative composite slope is dynamically corrected to further improve the accuracy of exhaust temperature control. The exhaust flow acquisition and calculation in this embodiment involves acquiring exhaust flow data in real time, analyzing flow change trends, and providing accurate basis for slope correction. During implementation, the engine control unit collects engine exhaust flow sensor signals in real time, calculates the exhaust flow change rate in real time, and dynamically corrects the real-time correction slope based on the exhaust flow change rate to ensure that the rate of engine speed reduction and the electronic throttle opening rate are perfectly matched with the real-time exhaust flow change. The only rule for dynamic correction is to establish a positive correlation between flow change and cooling rate to ensure accurate matching between exhaust flow and exhaust temperature control. During implementation, when the exhaust flow is on an upward trend, the total value of the composite slope is increased simultaneously to accelerate the cooling rate; when the exhaust flow is on a downward trend, the total value of the composite slope is decreased simultaneously to slow down the cooling rate; when the exhaust flow is stable, the basic slope control mode is maintained and dynamic correction is not performed. The implementation of this rule does not change the core control steps of Embodiment 1, but only adds a flow correction item in the composite slope calculation stage.

[0091] Example 5 is a temperature control system with fault diagnosis and information storage:

[0092] This is a subordinate optimized embodiment of Embodiment 2, which solves the problems of difficult troubleshooting and inconvenient maintenance of the basic system in Embodiment 2, and improves the reliability and maintainability of the system throughout its entire life cycle. Based on the system hardware and functional modules of Embodiment 2, a fault diagnosis and information storage module is added to realize real-time fault diagnosis, information storage and code output, providing accurate basis for after-sales maintenance. The design process is to first clarify the scope of system fault diagnosis, covering various faults such as hardware, modules and signal interaction.

[0093] Secondly, fault diagnosis algorithms and fault code rules are designed to ensure accurate fault identification and classification.

[0094] Finally, a fault information storage and output mechanism was designed to enable the traceability of fault information.

[0095] This embodiment adds a fault diagnosis and information storage module to all system hardware, functional modules, and signal interaction of Embodiment 2, so as to realize real-time fault diagnosis, real-time fault information storage, and real-time fault code output.

[0096] The design principle of the fault diagnosis and information storage module in this embodiment is to monitor the operating status of each link of the system in real time, accurately identify faults and record relevant information, and provide support for fault diagnosis and maintenance. In practice, the functions of this module include real-time fault diagnosis, that is, real-time monitoring of system hardware, functional modules and signal interaction faults to generate unique fault codes; fault information storage, that is, real-time storage of fault codes, fault occurrence time, fault type and fault component information; and fault information output, that is, real-time output of fault codes through the vehicle CAN bus to support vehicle fault diagnostic instruments to read.

[0097] Finally, it should be noted that the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for safe control of exhaust temperature during the regeneration and cooling stage of an engine DPF, applied to a diesel engine aftertreatment system, the method comprising the following steps: S1. When the engine control unit determines that the diesel engine particulate filter (DPF) parking regeneration meets the completion conditions through the preset parking regeneration completion judgment parameters, it does not perform the operation of step-by-step switching the engine operating mode from the regeneration mode to the traditional cooling mode, but starts the progressive collaborative composite control cooling strategy. S2. The engine control unit synchronously executes coordinated composite slope control of engine speed and throttle opening, controlling the engine speed to smoothly and continuously decrease from the high regeneration speed corresponding to parking regeneration according to the composite descent slope, while controlling the throttle to smoothly and continuously open from the small opening corresponding to regeneration mode according to the composite opening slope; wherein, the composite descent slope and the composite opening slope are pre-calibrated for coordinated matching. S3. During the entire process of implementing the progressive collaborative composite control cooling strategy, the engine control unit continuously monitors the real-time measurement values ​​of at least one temperature sensor in the aftertreatment system, obtains temperature change characteristic parameters that characterize the temperature change trend based on the real-time measurement values, and then calculates the real-time correction slope based on the temperature change characteristic parameters. The total value of the composite descent slope and the composite opening slope is dynamically adjusted through the real-time correction slope. S4. When the engine control unit detects that the real-time measured values ​​of all temperature sensors in the aftertreatment system have dropped below the preset safety threshold, it determines that the regeneration cooling process of the diesel engine particulate filter (DPF) is complete, terminates the progressive collaborative composite control cooling strategy, and controls the engine to switch to idle operation.

2. The method for safe control of exhaust temperature during the regeneration cooling stage of an engine DPF according to claim 1, characterized in that, In step S2, the rules for generating the composite descent slope and the composite opening slope are as follows: The composite descent slope of the engine speed is generated by combining the base descent slope and the real-time correction slope according to a preset mathematical relationship, wherein the base descent slope can be calibrated. The composite opening slope of the throttle valve is generated by combining the basic opening slope and the real-time correction slope according to a preset mathematical relationship, wherein the basic opening slope can be calibrated. The preset mathematical relationship includes any one of the following: addition operation, weighted average operation, maximum value operation, and minimum value operation.

3. The method for safe control of exhaust temperature during the regeneration cooling stage of an engine DPF according to claim 2, characterized in that, In step S2, the cooperative matching calibration rule for the composite opening slope and the composite descent slope is as follows: The basic opening slope and the basic descent slope are positively correlated. When the rate of decrease in engine speed increases, the throttle opening rate increases synchronously, and when the rate of decrease in engine speed decreases slows down, the throttle opening rate slows down synchronously.

4. The method for safe control of exhaust temperature during the regenerative cooling stage of an engine DPF according to claim 1, characterized in that, In step S1, the preset parking regeneration completion determination parameters include at least one of the real-time carbon load value of the particulate filter DPF and the cumulative running time of parking regeneration.

5. The method for safe control of exhaust temperature during the regeneration cooling stage of an engine DPF according to claim 1, characterized in that, In step S3, the temperature sensors of the aftertreatment system are installed in the upstream and downstream pipelines of the aftertreatment system. The temperature sensors include at least one of the following: oxidation catalyst DOC inlet temperature sensor, diesel engine particulate filter DPF inlet temperature sensor, selective catalytic reduction (SCR) inlet temperature sensor, and selective catalytic reduction (SCR) outlet temperature sensor. The engine control unit prioritizes collecting real-time measurements from temperature sensors in the downstream pipelines of the aftertreatment system.

6. The method for safe control of exhaust temperature during the regeneration cooling stage of an engine DPF according to claim 1, characterized in that, In step S3, during the initial operation phase after the gradual collaborative composite control cooling strategy is activated, the engine control unit executes the basic slope control mode, including: In the initial stage of the cooling strategy activation, the engine control unit sets the real-time correction slope corresponding to the composite descent slope and the composite opening slope to 0, so that the composite descent slope is equal to the basic descent slope and the composite opening slope is equal to the basic opening slope. According to the calibrated basic descent slope and basic opening slope, the engine speed is synchronously controlled to reduce smoothly and the throttle valve to open smoothly.

7. A method for safe control of exhaust temperature during the regeneration cooling stage of an engine DPF according to claim 6, characterized in that, In step S3, the temperature change characteristic parameter is the first derivative of the temperature measurement value; the specific process of calculating the real-time correction slope based on the temperature change characteristic parameter and dynamically adjusting the composite slope using the real-time correction slope is as follows: When the engine control unit detects that the real-time measurement value of the target temperature sensor shows an upward trend, it calculates and generates a real-time correction slope with a negative value through a preset control algorithm. The preset control algorithm includes any one or more combinations of lookup table method, proportional control algorithm, and PID control algorithm. Substitute the negative real-time correction slope into the calculation of the compound descent slope and the compound opening slope respectively, and simultaneously reduce the total value of the compound descent slope and the compound opening slope, thereby simultaneously slowing down the rate of engine speed reduction and the rate of throttle opening. During the cooling process, the above dynamic adjustment is continuously performed until the engine control unit detects that the temperature change rate of the target temperature sensor remains negative for a continuous preset time period, and the absolute value of the temperature change rate is lower than the preset change rate threshold. At this point, it is determined that the exhaust temperature has entered a stable monotonically decreasing channel, and the real-time correction slope is returned to zero, restoring the basic slope control mode.

8. The method for safe control of exhaust temperature during the regenerative cooling stage of an engine DPF according to claim 1, characterized in that, In step S4, the preset safety threshold is pre-calibrated based on the allowable temperature limits of each component of the post-processing system and the safe temperature limit of the tailpipe outlet.

9. A safety control system for exhaust temperature during the regenerative cooling stage of an engine DPF, characterized in that, It includes an engine control unit, an engine body, a throttle valve, and an after-treatment system, wherein the engine control unit is communicatively connected to the engine body, the throttle valve, and the after-treatment system, respectively. The engine control unit is a programmable control unit configured to: The system determines whether the diesel engine particulate filter (DPF) parking regeneration meets the completion conditions by using preset parking regeneration completion parameters, and initiates a progressive collaborative composite control cooling strategy when the completion conditions are met. Synchronously execute the coordinated composite slope control of engine speed and throttle opening, calculate and generate composite descent slope and composite opening slope, and send speed control command to engine body and throttle opening control command; The system acquires real-time measurements from temperature sensors, obtains temperature change characteristic parameters, generates a real-time correction slope, and performs dynamic feedback adjustment. The system compares the real-time temperature sensor readings of the aftertreatment system with the preset safety threshold to determine whether the cooling process is complete, and controls the engine to switch to idle speed after cooling is complete.

10. A safety control system for exhaust temperature during the regenerative cooling stage of an engine DPF according to claim 9, characterized in that, The engine control unit includes: The regeneration completion determination module is used to obtain preset parking regeneration completion determination parameters, determine whether parking regeneration meets the completion conditions, and output a cooling strategy start command. The coordinated slope control module is used to calculate and generate the basic descent slope and the basic opening slope, and to calculate the composite descent slope and the composite opening slope by combining the real-time correction slope, and output coordinated control commands to the engine body and the throttle body respectively. The temperature feedback adjustment module is used to acquire the real-time measurement value of the temperature sensor of the post-processing system, calculate the temperature change characteristic parameters, generate a real-time correction slope through a preset control algorithm, and output it to the collaborative slope control module to complete the dynamic adjustment. The cooling completion determination module compares the real-time measurement values ​​of all temperature sensors in the aftertreatment system with the preset safety threshold to determine whether the cooling process is complete, and outputs an idle speed switching command to the engine body. The aftertreatment system includes an oxidation catalyst (DOC), a diesel engine particulate filter (DPF), and a selective catalytic reduction (SCR) connected in sequence. Multiple temperature sensors that communicate with the engine control unit are installed on the piping of the aftertreatment system.

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