Engine shutdown control method and related device

Abstract

The invention discloses an engine stop control method and a related device, and the method comprises the steps: responding to an obtained stop instruction, determining a first reverse torque opposite to the torque direction of an engine, and controlling the engine according to the first reverse torque. And if the rotating speed of the engine is smaller than or equal to the idle speed of the engine, the current rotating speed of the engine in the ith second and the optimal rotating speed of the engine in the ith second are obtained, the second reverse torque in the ith second is determined according to the difference between the current rotating speed of the engine in the ith second and the optimal rotating speed of the engine in the ith second, and the engine is controlled according to the second reverse torque in the ith second. If the rotating speed of the engine is smaller than or equal to the first rotating speed threshold value, an output shaft of the engine is locked through a brake till the rotating speed of the engine does not change any more. Therefore, the engine is controlled in different modes in different stages of the shutdown process of the engine, so that the requirements corresponding to the different stages are met, and the vibration suppression effect is improved.

Description

Technical Field

[0001] The present invention relates to the field of vehicle technology, and in particular to an engine shutdown control method and related devices. Background Art

[0002] With the development of automobile technology and new energy technology, there are more and more hybrid vehicles. For some types of hybrid vehicles, such as hybrid vehicles using dedicated hybrid transmission (DHT) systems, when the engine is stopped, the torque generated by the change in engine speed acts on the wheel end, causing the body to vibrate, which brings a bad riding experience to users.

[0003] The system used in hybrid vehicles (referred to as hybrid system) usually includes components such as an engine, a drive motor, and a generator. In related technologies, vibration is usually suppressed by outputting compensating torque from the drive motor. However, this method cannot be applied to all stages of hybrid vehicle engine shutdown, and the effect of suppressing vibration is poor. Summary of the invention

[0004] In view of the above problems, the present application provides an engine shutdown control method and related devices, which are used to solve the problem of poor vibration suppression effect during engine shutdown.

[0005] Based on this, this application discloses the following technical solutions:

[0006] In a first aspect, an embodiment of the present application provides an engine shutdown control method, which is applied to a hybrid vehicle, wherein the hybrid vehicle includes an engine and a brake, wherein the engine is used to provide power for the hybrid vehicle, and the brake is used to lock an output shaft of the engine, and the method includes:

[0007] In response to obtaining a stop command, determining a first reverse torque opposite to the torque direction of the engine, and controlling the engine according to the first reverse torque, wherein the first reverse torque is used to reduce the engine speed, and the direction of the first reverse torque is opposite to the torque direction of the engine;

[0008] If the engine speed is less than or equal to the engine idle speed, the current engine speed at the ith second and the optimal engine speed at the ith second are obtained, and the second reverse torque at the ith second is determined according to the ith second difference between the current engine speed at the ith second and the optimal engine speed at the ith second, and the engine is controlled according to the second reverse torque at the ith second, the optimal engine speed at the ith second is an engine speed among a plurality of engine speeds corresponding to the ith second, and the vehicle vibration value at the ith second corresponding to the optimal engine speed at the ith second is the smallest, the direction of the second reverse torque is opposite to the torque direction of the engine, and the ith second is one second within the duration when the engine speed is less than or equal to the engine idle speed;

[0009] If the engine speed is less than or equal to a first speed threshold, the output shaft of the engine is locked by the brake until the engine speed no longer changes. The first speed threshold is less than the engine idle speed. The first speed threshold is determined based on entering a speed oscillation range during the process of the engine speed decreasing.

[0010] Optionally, if the engine speed is less than or equal to a second speed threshold, and the engine speed is greater than a first speed threshold, the second speed threshold is less than the engine idle speed, and the second speed threshold is determined based on entering a maximum vehicle vibration interval during a decrease in the engine speed, the method further includes:

[0011] determining a third reverse torque at the jth second according to the optimal engine speed at the jth second, wherein the jth second is one second within a period in which the engine speed is less than or equal to the engine idle speed, and the third reverse torque at the jth second is greater than the second reverse torque at the jth second;

[0012] The engine is controlled according to the third reverse torque at the j-th second.

[0013] Optionally, determining the third reverse torque at the jth second according to the optimal engine speed at the jth second includes:

[0014] determining a compensation torque at the jth second according to a jth second difference between the current engine speed at the jth second and the optimal engine speed at the jth second, wherein the direction of the compensation torque is the same as the direction of the second reverse torque, and the compensation torque is used to reduce the jth second difference until it is less than a first difference threshold, wherein the first difference threshold is determined based on the current engine speed at the jth second being close to the optimal engine speed at the jth second;

[0015] The third reverse torque at the jth second is determined according to the second reverse torque at the jth second and the compensation torque at the jth second.

[0016] Optionally, the compensation torque at the jth second is determined by:

[0017] Obtaining a j-1 second difference, a sampling period, and a compensation parameter, wherein the j-1 second difference is the difference between the current engine speed at the j-1 second and the optimal engine speed at the j-1 second, the sampling period is the time interval between the j-1 second and the j-1 second, and the compensation parameter includes a proportional parameter, an integral parameter, and a differential parameter;

[0018] Determine the compensation proportion parameter value, the compensation integral parameter value and the compensation differential parameter value respectively corresponding to the j-th second according to the j-1th second difference, the j-th second difference, the sampling period and the compensation parameter;

[0019] The compensation torque at the jth second is determined according to the compensation proportion parameter value, the compensation integral parameter value and the compensation differential parameter value respectively corresponding to the jth second.

[0020] Optionally, the optimal engine speed at the i-th second is determined by:

[0021] Obtain a sampling period, where the sampling period is the time interval between the i-th second and the i-1-th second;

[0022] Determining the engine speed gradient at the i-th second according to the sampling period, the current engine speed at the i-1th second, and the current engine speed at the i-th second;

[0023] Obtaining vehicle vibration values ​​corresponding to different engine speed gradients at the i-th second, determining the engine speed gradient corresponding to the minimum vehicle vibration value from the plurality of vehicle vibration values, and obtaining the optimal engine speed gradient at the i-th second;

[0024] The optimal engine speed at the i-th second is determined according to the optimal engine speed gradient at the i-th second.

[0025] Optionally, the method further comprises:

[0026] If the difference between the engine speed and the engine idle speed is less than a second difference threshold, a fuel cut-off command is issued, wherein the second difference threshold is determined based on the engine speed being close to the engine idle speed, and the fuel cut-off command is used to stop the fuel release process; wherein the engine speed when the shutdown command is obtained is greater than the engine speed when the fuel cut-off command is issued.

[0027] In a second aspect, an embodiment of the present application provides an engine shutdown control device, the device comprising: the device comprising: a first control unit, a second control unit and a third control unit;

[0028] The first control unit is used to determine a first reverse torque opposite to the torque direction of the engine in response to obtaining a stop instruction, and control the engine according to the first reverse torque, wherein the first reverse torque is used to reduce the engine speed, and the direction of the first reverse torque is opposite to the torque direction of the engine;

[0029] The second control unit is used for obtaining the current engine speed at the ith second and the optimal engine speed at the ith second if the engine speed is less than or equal to the engine idle speed, determining the second reverse torque at the ith second according to the ith second difference between the current engine speed at the ith second and the optimal engine speed at the ith second, and controlling the engine according to the second reverse torque at the ith second, wherein the optimal engine speed at the ith second is one engine speed among a plurality of engine speeds corresponding to the ith second, and the vehicle vibration value at the ith second corresponding to the optimal engine speed at the ith second is the smallest, the direction of the second reverse torque is opposite to the torque direction of the engine, and the ith second is one second within the duration when the engine speed is less than or equal to the engine idle speed;

[0030] The third control unit is used to lock the output shaft of the engine by the brake until the engine speed no longer changes if the engine speed is less than or equal to a first speed threshold, and the first speed threshold is less than the engine idle speed, and the first speed threshold is determined based on the engine speed entering a speed oscillation range during a speed drop process.

[0031] In a third aspect, an embodiment of the present application provides a vehicle, the vehicle comprising a processor and a memory:

[0032] The memory is used to store a computer program and transmit the computer program to the processor;

[0033] The processor is configured to execute the method according to the first aspect of claim 1 according to the computer program.

[0034] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium is used to store a computer program, and the computer program is used to execute the method described in the first aspect above.

[0035] In a fifth aspect, an embodiment of the present application provides a computer program product comprising a computer program, which, when executed on a computer device, enables the computer device to execute the method described in the first aspect above.

[0036] It can be seen from the above technical solutions that the present application has at least the following beneficial effects:

[0037] In response to obtaining a shutdown command, a first reverse torque opposite to the torque direction of the engine is determined, and the engine is controlled according to the first reverse torque, so as to quickly reduce the engine speed to the engine idle speed. The shutdown process is essentially a process of reducing the engine speed to 0. The vehicle vibration is small in the stage from obtaining the shutdown command to the engine idle speed. Rapidly reducing the engine speed can shorten the duration of the shutdown process. If the engine speed is less than or equal to the engine idle speed, the current engine speed at the ith second and the optimal engine speed at the ith second are obtained, and the second reverse torque at the ith second is determined according to the ith second difference between the current engine speed at the ith second and the optimal engine speed at the ith second. The engine is controlled according to the second reverse torque at the ith second. The vehicle vibration value at the ith second corresponding to the optimal engine speed at the ith second is the smallest, so that the engine speed at each moment decreases along the trajectory of the change of the optimal engine speed over time, reducing the vibration of the vehicle caused by the change in speed, and improving the riding experience of the user at this stage. If the engine speed is less than or equal to the first speed threshold, the output shaft of the engine is locked by the brake until the engine speed no longer changes. The first speed threshold is determined based on the engine speed entering the speed oscillation range during the process of engine speed reduction, thereby reducing the additional vibration caused by the engine gear oscillation phenomenon and preventing the engine from reversing, thereby reducing engine losses. In this way, different methods are used to control the engine at different stages of the engine shutdown process to meet the corresponding needs of different stages and improve the effect of suppressing vibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 A flow chart of an engine shutdown control method provided in an embodiment of the present application;

[0040] Figure 2 A schematic diagram of a process for outputting a minimum vibration speed trajectory through a particle swarm algorithm provided in an embodiment of the present application;

[0041] Figure 3 A schematic diagram of a process for outputting a minimum vibration speed trajectory through a dynamic programming algorithm provided in an embodiment of the present application;

[0042] Figure 4 A schematic diagram of a DHT system structure provided in an embodiment of the present application;

[0043] Figure 5 A schematic diagram of an engine speed variation curve provided in an embodiment of the present application;

[0044] Figure 6 A schematic diagram of the structure of an engine shutdown control device provided in an embodiment of the present application;

[0045] Figure 7 A schematic diagram of the structure of a computer device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0046] The embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be construed as being limited to the embodiments described herein. Instead, these embodiments are provided to provide a more thorough and complete understanding of the present application. It should be understood that the drawings and embodiments of the present application are only for exemplary purposes and are not intended to limit the scope of protection of the present application.

[0047] In the related art, the compensation torque is usually calculated in the same way in all stages, and the vibration is suppressed by outputting the compensation torque through the driving motor. However, after research, it is found that the engine shutdown process can be divided into multiple stages, and different stages have different characteristics. If the same method is used to adjust different stages, it is impossible to make targeted adjustments to the needs generated in different stages of the shutdown process, resulting in poor vibration suppression effect. The following takes the engine shutdown process including four stages as an example to explain them separately.

[0048] In the first stage, when the engine shutdown command is received, the first stage is entered. Since the duration of the engine speed reduction determines the length of the shutdown process, in order to shorten the duration of the shutdown process, the engine speed needs to be quickly reduced to the engine idle speed in the first stage (that is, equivalent to quickly reducing the engine speed). When the engine idle speed is reached, a fuel cut-off and flameout command is sent to cut off the positive torque output by the engine.

[0049] In the second stage, when the fuel cut-off and flameout command is sent, the vehicle enters the second stage. The engine no longer outputs positive torque, and the engine speed decreases over time. Different engine speed decreases correspond to different vehicle vibrations. In order to reduce the vibration generated by the vehicle, the engine speed needs to be controlled by outputting a reverse torque in the opposite direction of the engine torque, so that the vehicle vibration corresponding to the engine speed at a certain moment is minimized, thereby reducing the impact of the engine speed on the vibration.

[0050] During the maximum vehicle vibration stage, due to the physical structural relationship between the engine and the vehicle transmission system, the vehicle vibration is maximum when the engine speed enters a certain speed range. When the vehicle enters the maximum vibration stage in this speed range, additional means are required to suppress the vibration amplification in this speed range.

[0051] In the third stage, when the engine speed drops below this speed range, it enters the third stage. The engine speed is close to 0, and the engine gear oscillation will occur, causing the engine to reverse, which will not only cause additional vibration to the body but also damage the engine.

[0052] It can be seen that different stages of the engine shutdown process produce different demands. Calculating the reverse torque in the same way cannot meet different demands, and the vibration suppression effect is not good.

[0053] Based on this, an embodiment of the present application provides an engine shutdown control method and related devices, which control the engine in different ways at different stages of the engine shutdown process to meet the corresponding needs of different stages and improve the effect of suppressing vibration.

[0054] The engine shutdown control method provided in the present application can be applied to a hybrid electric vehicle with engine shutdown control capability, wherein the hybrid electric vehicle may include an engine, a vehicle controller, a drive motor, a generator, a transmission system, etc.

[0055] See also Figure 1 , Figure 1 The following is a flow chart of the engine shutdown control method provided in the embodiment of the present application. For the convenience of description, the following embodiment is introduced by taking the execution subject of the engine shutdown control method as a hybrid vehicle as an example. Figure 1 As shown, the method includes S101-S103.

[0056] S101: In response to obtaining a stop instruction, determining a first reverse torque opposite to the torque direction of the engine, and controlling the engine according to the first reverse torque.

[0057] A hybrid electric vehicle (HEV) is a vehicle that combines two power sources, a traditional engine and a drive motor. The engine provides power to the hybrid vehicle by outputting positive torque. The engine speed is the number of revolutions per minute of the engine crankshaft, usually in revolutions per minute (r / min). During hybrid driving, the engine speed remains high. A shutdown command is a command that instructs the engine to shut down. When the shutdown command is obtained, the engine shutdown process begins. The engine shutdown process is the process of reducing the high engine speed to 0. When the engine speed drops to 0 and remains unchanged, the shutdown process ends.

[0058] In response to obtaining the shutdown command, the shutdown process enters the first stage. The first stage is the process from obtaining the shutdown command to the engine speed dropping to the engine idle speed. The engine idle speed refers to the lowest stable speed when the engine is running under no load or very low load conditions. At this speed, the engine does not provide power output. In order to shorten the total duration of the engine shutdown process and improve the efficiency of the engine's response to the shutdown command, the engine speed needs to be quickly reduced to the engine idle speed in the first stage.

[0059] In the first stage, the first reverse torque for reducing the engine speed can be determined by the difference between the current engine speed and the engine idle speed, for example, the difference can be the current engine speed minus the engine idle speed, wherein the direction of the first reverse torque is opposite to the torque direction of the engine.

[0060] Specifically, the first reverse torque can also be determined by Active Disturbance Rejection Control (ADRC), which includes the following three parts:

[0061] Tracking Differentiator (TD): used to smooth the change curve of engine speed and generate tracking signal.

[0062] Extended State Observer (ESO): used to estimate the system state (engine speed) and total disturbance (load changes, external interference, etc.).

[0063] Linear State Error Feedback (LSEF) control law: used to generate a first reverse torque so that the current engine speed tracks the first reverse torque.

[0064] ADRC has a faster response speed and control performance, which can quickly reduce the engine speed to the engine idle speed and shorten the duration of the shutdown process.

[0065] As an implementation, in a hybrid vehicle including a dedicated hybrid transmission (DHT), an integrated starter generator (ISG) may be used to apply a first reverse torque to quickly reduce the engine speed until the engine is idle.

[0066] In a possible implementation, if the difference between the engine speed and the engine idle speed is less than a second difference threshold, a fuel cut-off and flameout instruction is issued.

[0067] The second difference threshold is determined based on the engine speed approaching the engine idle speed. When the difference between the engine speed and the engine idle speed is less than the second difference threshold, it means that the engine speed has been reduced to the speed level corresponding to the engine idle speed. At this time, a fuel cut-off and flameout command is issued to stop the fuel release process to cut off the positive torque output by the engine. The engine speed when the shutdown command is obtained is greater than the engine speed when the fuel cut-off and flameout command is issued. It should be emphasized that after the fuel cut-off and flameout command is obtained to the engine speed, the fuel cut-off and flameout command is not issued before the difference between the engine speed and the engine idle speed is less than the second difference threshold.

[0068] For example, when the shutdown command is obtained, the engine speed is 1500r / min, the engine idle speed is 650r / min, and the second difference threshold is 5r / min. In the first stage, when the engine speed drops from 1500r / min to 652r / min, a fuel cut-off command is issued to stop the fuel release, so that the engine stops outputting positive torque.

[0069] If the fuel cut-off command is issued when the engine speed is high, the engine speed will drop suddenly due to the loss of engine power, resulting in greater vibration and impact. At the same time, when the engine speed is high, it will cause wear on the engine and reduce the engine life. If the fuel cut-off command is issued when the engine speed is lower than the engine idle speed, the engine will output positive torque for a long time during the shutdown process, making the torque compensation effect more difficult, resulting in poor vibration suppression effect.

[0070] Issuing a fuel cut-off command when the engine speed is close to the engine idle speed can prevent additional impact caused by engine stalling, reduce engine wear, and at the same time reduce the duration of engine positive torque output, thereby improving the effect of suppressing vibration.

[0071] S102: If the engine speed is less than or equal to the engine idle speed, obtain the current engine speed at the ith second and the optimal engine speed at the ith second, determine the second reverse torque at the ith second based on the ith second difference between the current engine speed at the ith second and the optimal engine speed at the ith second, and control the engine based on the second reverse torque at the ith second.

[0072] The ith second is one second in the duration when the engine speed is less than or equal to the engine idle speed. For example, if the engine speed is equal to the engine idle speed, it is the 0.3 second, and the ith second can be 0.35 seconds.

[0073] The optimal engine speed at the i-th second is an engine speed among multiple engine speeds corresponding to the i-th second, and the vehicle vibration value at the i-th second corresponding to the optimal engine speed at the i-th second is the smallest, and the direction of the second reverse torque is opposite to the torque direction of the engine.

[0074] The second reverse torque can be used to control the current engine speed at the ith second to be close to the optimal engine speed at the ith second, thereby minimizing the vehicle vibration generated at the ith second and reducing the vehicle vibration.

[0075] As an implementation manner, in a hybrid vehicle including a dedicated hybrid transmission (DHT), the second reverse torque may be applied by an integrated starter generator (ISG).

[0076] In a possible implementation, the embodiment of the present application provides a method for obtaining the optimal engine speed at the i-th second, see A1-A4:

[0077] A1: Get the sampling period.

[0078] The sampling period is the time interval between the ith second and the (i-1)th second.

[0079] A2: Determine the engine speed gradient at the i-th second based on the sampling period, the current engine speed at the i-1th second, and the current engine speed at the i-th second.

[0080] The engine speed gradient at the ith second reflects how fast the engine speed changes at the ith second.

[0081] Specifically, the engine speed gradient at the i-th second can be obtained by the following formula:

[0082]

[0083] A3: Obtain vehicle vibration values ​​corresponding to different engine speed gradients at the i-th second, determine the engine speed gradient corresponding to the minimum vehicle vibration value from multiple vehicle vibration values, and obtain the optimal engine speed gradient at the i-th second.

[0084] The vehicle vibration value is a quantitative indicator of vehicle vibration and can be obtained through the acceleration sensor. At the i-th second, different engine speed gradients correspond to different vehicle vibration values. The engine speed gradient with the smallest vehicle vibration value is the situation with the optimal engine speed drop speed (minimal vehicle vibration) at the corresponding moment.

[0085] A4: Determine the optimal engine speed at the i-th second based on the optimal engine speed gradient at the i-th second.

[0086] By determining the optimal engine speed gradient at the ith second, the variation range of the engine speed at each moment can be determined, thereby determining the optimal engine speed at the ith second.

[0087] By determining the engine speed corresponding to the minimum vehicle vibration value as the optimal engine speed, the vehicle vibration level corresponding to the optimal engine speed at each moment is minimized, thereby improving the effect of suppressing vehicle vibration in the second stage during engine shutdown.

[0088] Specifically, the optimal engine speed at the i-th second can be obtained through the minimum vibration speed trajectory. The minimum vibration speed trajectory is a change curve that reflects the change of engine speed over time. Each point on the curve is the optimal engine speed at the corresponding moment.

[0089] The embodiment of the present application does not limit the method for determining the minimum vibration speed trajectory, and two determination methods, a particle swarm algorithm and a dynamic programming algorithm, are used below to illustrate.

[0090] Determination method 1: Particle swarm algorithm, see Figure 2 , Figure 2 The figure is a flow chart of outputting the minimum vibration speed trajectory through the particle swarm algorithm. First, the initial position and initial speed of the particle are determined according to the engine state, and the engine speed gradient and vehicle vibration value are used as the fitness function of the particle swarm algorithm. The individual optimal position and the global optimal position are recorded according to the size of the fitness, and the speed and position of each example are updated according to the goal of minimum fitness until the number of iterations is reached or the fitness is less than the minimum fitness, the update process is stopped, and the minimum vibration speed trajectory is generated. Among them, the minimum fitness is used to characterize that the vehicle vibration value corresponding to the engine speed gradient is the minimum.

[0091] Determination method 2: Dynamic programming algorithm, see Figure 3 , Figure 3 This is a flow chart of outputting the minimum vibration speed trajectory through a dynamic programming algorithm. The cost function is determined from the engine speed gradient and the vehicle vibration value. The engine speed and torque vibration are selected as state quantities. The second reverse torque output by the motor is the drag distance of the inefficient engine. The engine idle speed is used as the starting point to drag the engine speed to 0 as the end point. The corresponding cost function value is determined, and the minimum speed trajectory is generated with the minimum cost function value as the goal. Among them, the minimum cost function value is used to characterize the minimum vehicle vibration value corresponding to the engine speed gradient.

[0092] As an implementation method, the first stage can also be used as the calibration range of the minimum vibration speed curve, that is, the minimum vibration speed curve can also include an interval of rapidly reducing the engine speed from obtaining a shutdown command to the engine speed reaching the engine idle speed, thereby reducing vehicle vibration while satisfying the requirement of rapidly reducing the engine speed.

[0093] S103: If the engine speed is less than or equal to the first speed threshold, the output shaft of the engine is locked by a brake until the engine speed no longer changes.

[0094] The first speed threshold is less than the engine idle speed, and the first speed threshold is determined based on the engine speed entering a speed oscillation range during a speed drop process.

[0095] When the engine speed is less than or equal to the first speed threshold, the shutdown process enters the third stage. The engine speed is in the speed oscillation range from the first speed threshold to 0. In the speed oscillation range, the engine speed will oscillate, which will cause the engine to reverse and generate additional vibration.

[0096] Based on this, the engine output shaft can be locked by a physical structure such as a brake, so as to quickly and accurately control the engine speed to 0, thereby reducing the loss of the engine in the speed oscillation range and avoiding additional vibration. For example, the first speed threshold is 3r / min, and when the engine speed drops to 2r / min, the engine output shaft is locked by the brake.

[0097] It can be seen from the above technical solution that in response to obtaining a shutdown command, a first reverse torque opposite to the torque direction of the engine is determined, and the engine is controlled according to the first reverse torque, so as to quickly reduce the engine speed to the engine idle speed. The shutdown process is essentially a process of reducing the engine speed to 0. The vehicle vibration is small in the stage from obtaining the shutdown command to the engine idle speed. Rapidly reducing the engine speed can shorten the duration of the shutdown process. If the engine speed is less than or equal to the engine idle speed, the current engine speed at the i-th second and the optimal engine speed at the i-th second are obtained, and the second reverse torque at the i-th second is determined according to the i-th second difference between the current engine speed at the i-th second and the optimal engine speed at the i-th second. The engine is controlled according to the second reverse torque at the i-th second. The vehicle vibration value at the i-th second corresponding to the optimal engine speed at the i-th second is the smallest, so that the engine speed at each moment decreases along the trajectory of the change of the optimal engine speed over time, reducing the vibration of the vehicle caused by the change in speed, and improving the riding experience of the user at this stage. If the engine speed is less than or equal to the first speed threshold, the output shaft of the engine is locked by the brake until the engine speed no longer changes. The first speed threshold is determined based on the engine speed entering the speed oscillation range during the process of engine speed reduction, thereby reducing the additional vibration caused by the engine gear oscillation phenomenon and preventing the engine from reversing, thereby reducing engine losses. In this way, different methods are used to control the engine at different stages of the engine shutdown process to meet the corresponding needs of different stages and improve the effect of suppressing vibration.

[0098] In the second stage of the shutdown process, when the engine speed is less than or equal to the second speed threshold and greater than the first speed threshold, the shutdown process enters. Due to the physical structural relationship between the engine and the vehicle transmission system, the engine torque fluctuation is the largest in this interval, resulting in greater vehicle vibration, and it is difficult to offset the engine torque fluctuation through the second reverse torque. Based on this, the embodiment of the present application provides an engine shutdown control method in the maximum vibration interval, see B1-B2:

[0099] B1: Determine the third reverse torque at the jth second according to the optimal engine speed at the jth second.

[0100] Among them, the second speed threshold is less than the engine idle speed, and the second speed threshold is determined based on entering the maximum vehicle vibration range during the engine speed reduction process. The jth second is one second during which the engine speed is less than or equal to the engine idle speed, and the third reverse torque of the jth second is greater than the second reverse torque of the jth second.

[0101] B2: Control the engine according to the third reverse torque at the jth second.

[0102] As an implementation method, in a hybrid vehicle including a dedicated hybrid transmission (DHT), a third reverse torque may be applied by a drive motor (Torque Motor, TM) to achieve a dual-motor controlled engine shutdown process.

[0103] By applying a third reverse torque that is larger than the second reverse torque in the range of maximum vibration, it is possible to overcome the greater torque fluctuation generated by the engine in the range of maximum vehicle vibration, which makes it difficult for the current engine speed at the jth second to approach the optimal engine speed at the jth second, thereby improving the effect of suppressing vehicle vibration.

[0104] The embodiment of the present application also provides a method for determining the third reverse torque by combining the second reverse torque with the compensation torque, see C1-C2:

[0105] C1: Determine the compensation torque at the jth second based on the jth second difference between the current engine speed at the jth second and the optimal engine speed at the jth second.

[0106] The direction of the compensation torque is the same as that of the second reverse torque, and the compensation torque is used to reduce the j-th second difference until it is less than a first difference threshold, which is determined based on the current engine speed at the j-th second being close to the optimal engine speed at the j-th second.

[0107] The present application embodiment provides a specific implementation method for determining the compensation torque, see D1-D3:

[0108] D1: Get the j-1 second difference, sampling period and compensation parameters.

[0109] The j-1 second difference is the difference between the current engine speed at the j-1 second and the optimal engine speed at the j-1 second. The sampling period is the duration between the j-1 second and the j-1 second. The compensation parameters include proportional parameters, integral parameters and differential parameters.

[0110] D2: Determine the compensation proportion parameter value, compensation integral parameter value and compensation differential parameter value corresponding to the jth second according to the j-1th second difference, the jth second difference, the sampling period and the compensation parameter.

[0111] Among them, the proportional parameter is used to determine the compensation proportional parameter value, the integral parameter is used to determine the compensation integral parameter value, and the differential parameter is used to determine the compensation differential parameter value.

[0112] The values ​​of various compensation parameters can be determined by the following formula:

[0113] u p (t j )=K p *e(t j )

[0114] Among them, u p (t j ) is the compensation ratio parameter value at the jth second, K p is the proportional parameter, e(t j ) is the j-th second difference.

[0115] u i (t j )=u i (t j-1 )*K i *e(t j )*T s

[0116] Among them, u i (t j ) is the compensation integral parameter value at the jth second, u i (t j-1 ) is the compensation integral parameter value at the j-1th second, K i is the integral parameter, e(t j ) is the jth second difference, T s is the sampling period.

[0117]

[0118] Among them, u d (t j ) is the compensation differential parameter value at the jth second, K p is the integral parameter, e(tj ) is the jth second difference, e(t j-1 ) is the j-1 second difference, T s is the sampling period.

[0119] As an implementation manner, the compensation torque may also be determined according to ADRC.

[0120] The compensation ratio parameter value is used to quickly respond to the current j-second difference, thereby quickly responding and adjusting the compensation torque, so that the current engine speed at the j-second quickly approaches the optimal engine speed at the j-second. Through the integral ratio parameter, the past errors are accumulated to eliminate the steady-state error, so that the current engine speed at the j-second is closer to the optimal engine speed at the j-second. The compensation differential parameter value is used to predict the change trend of the error, and the compensation torque is adjusted in advance to reduce the oscillation of the compensation torque.

[0121] D3: Determine the compensation torque at the jth second according to the compensation proportional parameter value, compensation integral parameter value and compensation differential parameter value corresponding to the jth second.

[0122] Specifically, the compensation torque at the jth second may be obtained by adding the compensation proportion parameter value, the compensation integral parameter value, and the compensation differential parameter value respectively corresponding to the jth second.

[0123] C2: Determine the third reverse torque at the jth second according to the second reverse torque at the jth second and the compensation torque at the jth second.

[0124] By combining the second reverse torque with the compensation torque, the determination process of the third reverse torque can be made more accurate, thereby improving the correction effect of the third reverse torque on the maximum vibration range of the vehicle, so that the current engine torque at the jth second is closer to the optimal engine speed at the jth second.

[0125] The following is an example of an application scenario of the engine shutdown control method provided in an embodiment of the present application.

[0126] See also Figure 4 , Figure 4It is a schematic diagram of the structure of a DHT system. Macroscopically, the DHT system consists of a power shunt module, a second power source, and a gearbox. Specifically, the power shunt module consists of an engine 1, an ISG motor 2, and a P1 planetary gear. The P1 planetary gear consists of 3 planet carriers, 4 sun gears, and 5 ring gears. The engine 1 is connected to the planet carrier 3 of the P1 planetary gear, the ISG motor 2 is connected to the sun gear of the P1 planetary gear, and the ring gear 5 of the P1 planetary gear is connected to the gearbox input shaft 17 to output power. The second power source consists of a TM motor 3 and a P2 planetary gear, and the P2 planetary gear consists of 7 sun gears, 8 planet carriers, and 5 ring gears. The TM motor 6 is connected to the sun gear 7 of the P2 planetary gear, and the ring gear 9 is locked by the planet carrier 8 to connect the gearbox input shaft 17 to output power. The gearbox consists of a C1 clutch, B1 and B2 locking clutches, and P3 and P4 planetary gears. The P3 planetary gear is composed of a ring gear 10, a planet carrier 11, and a sun gear 12. The P4 planetary gear is composed of a ring gear 13, a planet carrier 14, and a sun gear 15. 16 is the output of the DHT system.

[0127] See also Figure 5 , Figure 5 It is a schematic diagram of an engine speed change curve. When the vehicle is running, a shutdown command is obtained and the first stage is entered. The engine speed is quickly reduced to the engine idle speed by outputting the first reverse torque through the ISG motor, and when the engine speed is close to the engine idle speed, a fuel cut-off and flameout command is issued. When the engine speed is less than or equal to the engine idle speed, the second stage is entered, and the second reverse torque can be output according to the minimum vibration speed trajectory. When the engine speed is less than or equal to the second speed threshold, the vehicle enters the maximum vibration range, and the engine speed is controlled by outputting the second reverse torque through the ISG motor and the compensation torque through the TM motor. When the engine speed is less than or equal to the first speed threshold, the third stage is entered. In this stage, the second reverse torque and compensation torque are no longer output, and the output shaft of the engine is locked by the controller to prevent the engine from reversing.

[0128] See also Figure 6 , Figure 6 An engine shutdown control device provided in an embodiment of the present application includes a device 600 including: a first control unit 601 , a second control unit 602 and a third control unit 603 .

[0129] The first control unit is used to determine a first reverse torque opposite to the torque direction of the engine in response to obtaining a stop instruction, and control the engine according to the first reverse torque, wherein the first reverse torque is used to reduce the engine speed, and the direction of the first reverse torque is opposite to the torque direction of the engine;

[0130] The second control unit is used for obtaining the current engine speed at the ith second and the optimal engine speed at the ith second if the engine speed is less than or equal to the engine idle speed, determining the second reverse torque at the ith second according to the ith second difference between the current engine speed at the ith second and the optimal engine speed at the ith second, and controlling the engine according to the second reverse torque at the ith second, wherein the optimal engine speed at the ith second is one engine speed among a plurality of engine speeds corresponding to the ith second, and the vehicle vibration value at the ith second corresponding to the optimal engine speed at the ith second is the smallest, the direction of the second reverse torque is opposite to the torque direction of the engine, and the ith second is one second within the duration when the engine speed is less than or equal to the engine idle speed;

[0131] The third control unit is used to lock the output shaft of the engine by the brake until the engine speed no longer changes if the engine speed is less than or equal to a first speed threshold, and the first speed threshold is less than the engine idle speed, and the first speed threshold is determined based on the engine speed entering a speed oscillation range during a speed drop process.

[0132] It can be seen from the above technical solution that in response to obtaining the shutdown command, the first control unit determines the first reverse torque opposite to the torque direction of the engine, controls the engine according to the first reverse torque, and quickly reduces the engine speed to the engine idle speed. The shutdown process is essentially the process of reducing the engine speed to 0. The vehicle vibration is small in the stage from obtaining the shutdown command to the engine idle speed. Rapidly reducing the engine speed can shorten the duration of the shutdown process. If the engine speed is less than or equal to the engine idle speed, the second control unit obtains the current engine speed at the i-th second and the optimal engine speed at the i-th second, determines the second reverse torque at the i-th second according to the i-th second difference between the current engine speed at the i-th second and the optimal engine speed at the i-th second, controls the engine according to the second reverse torque at the i-th second, and the vehicle vibration value at the i-th second corresponding to the optimal engine speed at the i-th second is the smallest, so that the engine speed at each moment decreases along the trajectory of the change of the optimal engine speed over time, reduces the vibration of the vehicle caused by the speed change, and improves the riding experience of the user at this stage. If the engine speed is less than or equal to the first speed threshold, the third control unit locks the output shaft of the engine through the brake until the engine speed no longer changes. The first speed threshold is determined based on the engine speed entering the speed oscillation range during the process of engine speed reduction, thereby reducing the additional vibration caused by the engine gear oscillation phenomenon and preventing the engine from reversing, thereby reducing engine losses. In this way, different methods are used to control the engine at different stages of the engine shutdown process to meet the corresponding needs of different stages and improve the effect of suppressing vibration.

[0133] As a possible implementation, if the engine speed is less than or equal to a second speed threshold, and the engine speed is greater than a first speed threshold, the second speed threshold is less than the engine idle speed, and the second speed threshold is determined based on entering a maximum vehicle vibration interval during a decrease in the engine speed, the device further includes a second control subunit, which is used to:

[0134] determining a third reverse torque at the jth second according to the optimal engine speed at the jth second, wherein the jth second is one second within a period in which the engine speed is less than or equal to the engine idle speed, and the third reverse torque at the jth second is greater than the second reverse torque at the jth second;

[0135] The engine is controlled according to the third reverse torque at the j-th second.

[0136] As a possible implementation manner, the second control subunit is specifically configured to:

[0137] determining a compensation torque at the jth second according to a jth second difference between the current engine speed at the jth second and the optimal engine speed at the jth second, wherein the direction of the compensation torque is the same as the direction of the second reverse torque, and the compensation torque is used to reduce the jth second difference until it is less than a first difference threshold, wherein the first difference threshold is determined based on the current engine speed at the jth second being close to the optimal engine speed at the jth second;

[0138] The third reverse torque at the jth second is determined according to the second reverse torque at the jth second and the compensation torque at the jth second.

[0139] As a possible implementation manner, the second control subunit is specifically configured to:

[0140] Obtaining a j-1 second difference, a sampling period, and a compensation parameter, wherein the j-1 second difference is the difference between the current engine speed at the j-1 second and the optimal engine speed at the j-1 second, the sampling period is the time interval between the j-1 second and the j-1 second, and the compensation parameter includes a proportional parameter, an integral parameter, and a differential parameter;

[0141] Determine the compensation proportion parameter value, the compensation integral parameter value and the compensation differential parameter value respectively corresponding to the j-th second according to the j-1th second difference, the j-th second difference, the sampling period and the compensation parameter;

[0142] The compensation torque at the jth second is determined according to the compensation proportion parameter value, the compensation integral parameter value and the compensation differential parameter value respectively corresponding to the jth second.

[0143] As a possible implementation manner, the second control unit is specifically configured to:

[0144] Obtain a sampling period, where the sampling period is the time interval between the i-th second and the i-1-th second;

[0145] Determining the engine speed gradient at the i-th second according to the sampling period, the current engine speed at the i-1th second, and the current engine speed at the i-th second;

[0146] Obtaining vehicle vibration values ​​corresponding to different engine speed gradients at the i-th second, determining the engine speed gradient corresponding to the minimum vehicle vibration value from the plurality of vehicle vibration values, and obtaining the optimal engine speed gradient at the i-th second;

[0147] The optimal engine speed at the i-th second is determined according to the optimal engine speed gradient at the i-th second.

[0148] As a possible implementation, the device further includes an oil cut-off unit, which is used to:

[0149] If the difference between the engine speed and the engine idle speed is less than a second difference threshold, a fuel cut-off command is issued, wherein the second difference threshold is determined based on the engine speed being close to the engine idle speed, and the fuel cut-off command is used to stop the fuel release process; wherein the engine speed when the shutdown command is obtained is greater than the engine speed when the fuel cut-off command is issued.

[0150] See also Figure 7 , the embodiment of the present application further provides a vehicle, the vehicle comprising a memory 701 and a processor 702:

[0151] The memory is used to store a computer program and transmit the computer program to the processor;

[0152] The processor is configured to execute the method of the above method embodiment according to the computer program.

[0153] An embodiment of the present application further provides a computer-readable storage medium, characterized in that the computer-readable storage medium is used to store a computer program, and the computer program is used to execute the method of the above method embodiment.

[0154] The embodiment of the present application also provides a computer program product including a computer program, which, when executed on a computer device, enables the computer device to execute the method of the above method embodiment.

[0155] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other. For the system or device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0156] The term "including" and its variations used herein are open inclusions, i.e., "including but not limited to". The term "based on" means "based at least in part on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The relevant definitions of other terms will be given in the following description.

[0157] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0158] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0159] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0160] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An engine shutdown control method, characterized in that: Applied to a hybrid vehicle, the hybrid vehicle comprises an engine and a brake, the engine is used to provide power for the hybrid vehicle, and the brake is used to lock the output shaft of the engine, the method comprises: In response to obtaining a stop command, determining a first reverse torque opposite to the torque direction of the engine, and controlling the engine according to the first reverse torque, wherein the first reverse torque is used to reduce the engine speed, and the direction of the first reverse torque is opposite to the torque direction of the engine; If the engine speed is less than or equal to the engine idle speed, the current engine speed at the ith second and the optimal engine speed at the ith second are obtained, and the second reverse torque at the ith second is determined according to the ith second difference between the current engine speed at the ith second and the optimal engine speed at the ith second, and the engine is controlled according to the second reverse torque at the ith second, the optimal engine speed at the ith second is an engine speed among a plurality of engine speeds corresponding to the ith second, and the vehicle vibration value at the ith second corresponding to the optimal engine speed at the ith second is the smallest, the direction of the second reverse torque is opposite to the torque direction of the engine, and the ith second is one second within the duration when the engine speed is less than or equal to the engine idle speed; If the engine speed is less than or equal to a first speed threshold, the output shaft of the engine is locked by the brake until the engine speed no longer changes. The first speed threshold is less than the engine idle speed. The first speed threshold is determined based on entering a speed oscillation range during the process of the engine speed decreasing.

2. The method according to claim 1, characterized in that: If the engine speed is less than or equal to a second speed threshold, and the engine speed is greater than a first speed threshold, the second speed threshold is less than the engine idle speed, and the second speed threshold is determined based on entering a maximum vehicle vibration interval during a decrease in the engine speed, the method further includes: determining a third reverse torque at the jth second according to the optimal engine speed at the jth second, wherein the jth second is one second within a period in which the engine speed is less than or equal to the engine idle speed, and the third reverse torque at the jth second is greater than the second reverse torque at the jth second; The engine is controlled according to the third reverse torque at the j-th second.

3. The method according to claim 2, characterized in that The determining the third reverse torque at the jth second according to the optimal engine speed at the jth second includes: determining a compensation torque at the jth second according to a jth second difference between the current engine speed at the jth second and the optimal engine speed at the jth second, wherein the direction of the compensation torque is the same as the direction of the second reverse torque, and the compensation torque is used to reduce the jth second difference until it is less than a first difference threshold, wherein the first difference threshold is determined based on the current engine speed at the jth second being close to the optimal engine speed at the jth second; The third reverse torque at the jth second is determined according to the second reverse torque at the jth second and the compensation torque at the jth second.

4. The method according to claim 3, characterized in that The compensation torque at the jth second is determined by: Obtaining a j-1 second difference, a sampling period, and a compensation parameter, wherein the j-1 second difference is the difference between the current engine speed at the j-1 second and the optimal engine speed at the j-1 second, the sampling period is the time interval between the j-1 second and the j-1 second, and the compensation parameter includes a proportional parameter, an integral parameter, and a differential parameter; Determine the compensation proportion parameter value, the compensation integral parameter value and the compensation differential parameter value respectively corresponding to the j-th second according to the j-1th second difference, the j-th second difference, the sampling period and the compensation parameter; The compensation torque at the jth second is determined according to the compensation proportion parameter value, the compensation integral parameter value and the compensation differential parameter value respectively corresponding to the jth second.

5. The method according to claim 1, characterized in that The optimal engine speed at the i-th second is determined by the following method: Obtain a sampling period, where the sampling period is the time interval between the i-th second and the i-1-th second; Determining the engine speed gradient at the i-th second according to the sampling period, the current engine speed at the i-1th second, and the current engine speed at the i-th second; Obtaining vehicle vibration values ​​corresponding to different engine speed gradients at the i-th second, determining the engine speed gradient corresponding to the minimum vehicle vibration value from the plurality of vehicle vibration values, and obtaining the optimal engine speed gradient at the i-th second; The optimal engine speed at the i-th second is determined according to the optimal engine speed gradient at the i-th second.

6. The method according to any one of claims 1 to 5, characterized in that: The method further comprises: If the difference between the engine speed and the engine idle speed is less than a second difference threshold, a fuel cut-off command is issued, wherein the second difference threshold is determined based on the engine speed being close to the engine idle speed, and the fuel cut-off command is used to stop the fuel release process; wherein the engine speed when the shutdown command is obtained is greater than the engine speed when the fuel cut-off command is issued.

7. An engine shutdown control device, characterized in that: The device comprises: a first control unit, a second control unit and a third control unit; The first control unit is used to determine a first reverse torque opposite to the torque direction of the engine in response to obtaining a stop instruction, and control the engine according to the first reverse torque, wherein the first reverse torque is used to reduce the engine speed, and the direction of the first reverse torque is opposite to the torque direction of the engine; The second control unit is used for obtaining the current engine speed at the ith second and the optimal engine speed at the ith second if the engine speed is less than or equal to the engine idle speed, determining the second reverse torque at the ith second according to the ith second difference between the current engine speed at the ith second and the optimal engine speed at the ith second, and controlling the engine according to the second reverse torque at the ith second, wherein the optimal engine speed at the ith second is one engine speed among a plurality of engine speeds corresponding to the ith second, and the vehicle vibration value at the ith second corresponding to the optimal engine speed at the ith second is the smallest, the direction of the second reverse torque is opposite to the torque direction of the engine, and the ith second is one second within the duration when the engine speed is less than or equal to the engine idle speed; The third control unit is used to lock the output shaft of the engine by the brake until the engine speed no longer changes if the engine speed is less than or equal to a first speed threshold, and the first speed threshold is less than the engine idle speed, and the first speed threshold is determined based on the engine speed entering a speed oscillation range during a speed drop process.

8. A vehicle, characterized in that: The vehicle comprises a processor and a memory: The memory is used to store a computer program and transmit the computer program to the processor; The processor is configured to execute the method according to any one of claims 1 to 6 according to the computer program.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium is used to store a computer program, and the computer program is used to execute the method according to any one of claims 1 to 6.

10. A computer program product comprising a computer program, characterized in that When the method is executed on a computer device, the computer device is enabled to execute the method according to any one of claims 1 to 6.

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