A control method and system for suppressing engine stop noise and vibration of a hybrid vehicle

Abstract

This invention discloses a control method and system for suppressing engine shutdown noise and vibration in hybrid vehicles. In series mode, upon receiving a shutdown command, the intake manifold pressure is assessed. If the intake manifold pressure exceeds a threshold, a pre-shutdown idle speed control phase is initiated, temporarily cutting off fuel supply to the engine, setting the engine target torque to zero, and the generator executes closed-loop idle speed control torque. If the intake manifold pressure is less than or equal to the threshold, a forced shutdown control phase is initiated, cutting off fuel supply to the engine, setting the engine target torque to the shutdown torque, and providing the generator shutdown torque based on engine speed. When the engine speed approaches zero, engine shutdown is complete. The control method employed in this invention effectively solves the engine shutdown noise and vibration problem. Simultaneously, during the shutdown process, the generator load converts the engine's mechanical energy into electrical energy and stores it in a high-voltage battery, achieving shutdown energy recovery and rapid shutdown.

Description

Technical Field

[0001] This invention belongs to the field of automotive engine shutdown control, and more specifically, relates to a control method and system for suppressing engine shutdown noise and vibration in hybrid vehicles. Background Technology

[0002] To improve fuel economy, power, and emissions performance, hybrid vehicles are playing an increasingly important role in the development of new models by various manufacturers. Traditional car engines operate under very simple conditions before shutdown, primarily idling. The shutdown process involves first cutting off the fuel supply, then using the engine's own friction pump load to stop the engine. In contrast, hybrid vehicle engine shutdown has two new characteristics: firstly, the operating conditions before shutdown are more diverse, such as potentially operating under high-power generator conditions; secondly, to improve fuel economy and achieve rapid shutdown, hybrid vehicle engine shutdown typically involves cutting off the fuel supply and then using a generator directly connected to the engine, combined with the engine's own friction pump load, to achieve engine shutdown. These two new characteristics result in noticeable noise and vibration issues during engine shutdown in hybrid vehicles under certain operating conditions. Currently, some manufacturers use a two-dimensional lookup table of engine speed and speed change rate to determine the generator shutdown torque to optimize this problem. However, because engine speed and speed change rate require low-pass filtering to remove signal glitches in engineering applications, there is a certain lag, and the actual control effect cannot be fully realized. Summary of the Invention

[0003] To address the aforementioned shortcomings of existing technologies, this invention proposes a control method for suppressing engine shutdown noise and vibration in hybrid vehicles. Tests and analyses were conducted on the engine shutdown noise and vibration problem in hybrid vehicles, and a control strategy was developed. This method not only solves the engine shutdown noise and vibration problem but also achieves the goals of shutdown energy recovery and rapid shutdown.

[0004] In a first aspect, embodiments of the present invention disclose a control method for suppressing engine shutdown noise and vibration in hybrid vehicles, comprising: in series mode, upon receiving a shutdown command, judging the intake manifold pressure value; if the intake manifold pressure is greater than a threshold value, entering the pre-shutdown idle speed control stage; if the intake manifold pressure is less than or equal to the threshold value, entering the forced shutdown control stage.

[0005] Furthermore, during the pre-stop idle speed control phase, the engine temporarily stops fuel supply, the engine target torque is set to zero, and the generator executes closed-loop idle speed control torque.

[0006] Furthermore, during the forced shutdown control phase, the engine fuel is cut off, the engine target torque is set to the shutdown torque, the generator shutdown torque is determined based on the engine speed, and the engine shutdown is completed when the engine speed approaches 0.

[0007] Furthermore, the control process of the pre-stop idling control phase includes: selection of target speed and speed control.

[0008] Furthermore, the selection of the target speed is based on the following factors: the speed request based on the engine coolant temperature, the speed request of engine accessories, and the speed request of the transmission.

[0009] Furthermore, the speed control method includes the following steps:

[0010] S1: Calculate the feedforward control torque;

[0011] S2: Calculate the internal mold control torque;

[0012] S3: Calculate the speed control torque based on the feedforward control torque and the internal mold control torque.

[0013] Furthermore, the calculation method for the feedforward control torque in step S1 includes:

[0014] S11: Calculate the target rotational speed change rate;

[0015] S12: Convert the target rotational speed change rate into the target angular acceleration;

[0016] S13: Calculate the feedforward control torque based on the target angular acceleration and engine rotational inertia.

[0017] Furthermore, the calculation method for the internal mold control torque in step S2 includes:

[0018] S21: Calculate the speed difference between the target speed and the actual speed, and convert the unit to rad / s;

[0019] S22: Calculate the actual rate of change of rotational speed and convert the actual rate of change of rotational speed into actual angular acceleration;

[0020] S23: Select the time constant t TimeConstant and D-direction coefficient k d ;

[0021] S24: Calculate the torque in the P direction, the torque in the I direction, and the torque in the D direction respectively.

[0022] Furthermore, the calculation method for the speed control torque mentioned in step S3 is as follows:

[0023] T SpeedControl =T Feedforward +T p +T i +T d

[0024] Among them, T FeedforwardFor feedforward control torque, T p For the torque in direction P, T i For the torque in the I direction, T d This refers to the torque in the D direction.

[0025] Secondly, another embodiment of the present invention discloses a control system for suppressing engine shutdown noise and vibration in hybrid vehicles. In the control method for suppressing engine shutdown noise and vibration in hybrid vehicles, the control system is used to calculate and output control commands during the pre-stop idle speed control stage and the forced stop control stage. The system includes: a vehicle controller, an engine, an engine controller, a generator, a generator controller, a high-voltage battery, a battery controller, and a transmission mechanism.

[0026] The vehicle controller interacts with the engine controller, generator controller, and battery controller via a control link to exchange control signals. The engine is mechanically connected to the generator via the transmission mechanism. During shutdown, the generator converts the engine's mechanical energy into electrical energy, which is then stored in the high-voltage battery via a high-voltage link.

[0027] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0028] This invention analyzes the noise and vibration problems associated with series shutdown in hybrid vehicles, identifying intake manifold pressure as the core factor affecting this issue. Using intake manifold pressure as input, the shutdown process is divided into two stages: pre-shutdown idling and forced shutdown, with separate controls for engine and generator shutdown. Having resolved the engine shutdown noise and vibration problem, the generator converts the engine's mechanical energy into electrical energy, which is then stored in a battery via high-voltage wiring, achieving energy recovery during shutdown and enabling rapid shutdown. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the engine shutdown strategy in series mode for hybrid vehicles according to an embodiment of the present invention.

[0030] Figure 2 This is a flowchart of the speed control method according to an embodiment of the present invention;

[0031] Figure 3 This is a flowchart of the method for calculating the feedforward control torque according to an embodiment of the present invention;

[0032] Figure 4 This is a flowchart illustrating the method for calculating the internal mold control torque according to an embodiment of the present invention.

[0033] Figure 5 This is a system link diagram of the engine shutdown process in the series mode according to an embodiment of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0035] This invention addresses the issue of engine noise and vibration during hybrid vehicles.

[0036] In the series mode of a hybrid vehicle, the engine may be in a high-power, high-speed power generation state before it stops. At this time, the pressure in the engine intake manifold is relatively high. If the generator is directly controlled to shut down the engine under such conditions, there will be obvious noise and vibration problems.

[0037] Extensive data testing and analysis revealed that high pressure in the intake manifold after engine shutdown is the direct cause of engine noise and vibration issues. When the intake manifold pressure is high after engine shutdown, the engine output torque is greater, and the engine speed is higher. If, according to the shutdown command, the throttle is closed directly, and the shutdown load torque of the P1 motor is applied to the engine, the engine speed will drop rapidly, and the shutdown kinetic energy will be greater, easily causing abnormal noise during shutdown. Real-world testing on a certain vehicle model showed that a intake manifold pressure exceeding 55 kPa after engine shutdown results in significant noise and vibration problems. This threshold is related to the engine's hardware design, and the threshold varies between different engines.

[0038] Based on the above test analysis results, in order to solve the problem of engine shutdown noise and vibration, this embodiment of the invention provides a control method for suppressing engine shutdown noise and vibration in hybrid vehicles, the method comprising the following steps:

[0039] In series mode, upon receiving a shutdown command, the intake manifold pressure value is determined.

[0040] If the intake manifold pressure is greater than the threshold, the engine will enter the pre-stop idle speed control phase.

[0041] If the intake manifold pressure is less than or equal to the threshold value, the system will enter the forced shutdown control phase.

[0042] In this embodiment, when the VCU (Vehicle Control Unit) shutdown control module receives a shutdown command, it first checks the intake manifold pressure. Assuming the intake manifold pressure is 60 kPa, the engine speed is 1100 rpm, and the intake manifold pressure threshold is 55 kPa, the intake manifold pressure exceeds the threshold, triggering a pre-shutdown idle speed control phase. During this pre-shutdown idle speed control state, the intake manifold pressure is gradually reduced, preventing engine stalling noises caused by a rapid drop in engine speed.

[0043] After a certain period of time or when the intake manifold pressure is less than the calibrated limit, for example, when the intake manifold pressure drops to 54 kPa and begins to fall below the intake manifold pressure threshold of 55 kPa for pre-stop idle speed, the pre-stop idle speed control will switch to the forced stop control stage.

[0044] Figure 1 The diagram shows the engine shutdown strategy flowchart in the series mode of a hybrid vehicle.

[0045] In one implementation, during the pre-stop idle speed control phase, the engine is temporarily de-energized, the engine target torque is set to zero, and the generator executes closed-loop idle speed control torque to maintain the engine speed at the target speed, with the aim of slowly reducing the intake manifold pressure.

[0046] Furthermore, after entering the forced shutdown control phase, the engine fuel is cut off, the engine target torque is set to the shutdown torque, the generator shutdown torque is determined based on the engine speed, and the engine shutdown is completed when the engine speed approaches 0.

[0047] In this embodiment of the invention, the shutdown process is divided into two stages: pre-shutdown idling and forced shutdown, using intake manifold pressure as input. By controlling the pre-shutdown idling stage, engine shutdown noise and vibration are effectively suppressed.

[0048] The control procedures for the pre-stop idle speed control phase and the forced stop control phase are explained below.

[0049] (I) Pre-stop Idle Speed ​​Control Phase

[0050] In one implementation, during the pre-stop idling control phase, the generator executes closed-loop idling control torque, and the control process includes: selection of target speed and speed control.

[0051] The factors considered in selecting the target speed include: the speed request based on engine coolant temperature, the speed request of engine accessories, and the speed request of the transmission.

[0052] Specifically, the higher the engine's target speed, the better its speed stability; conversely, the lower the target speed, the worse the speed stability and the more prone the speed fluctuations. Engine coolant temperature primarily affects the engine's own friction pumping losses and is related to engine mechanical losses. For example, at extremely low temperatures of -20°C, the engine's target speed needs to be increased to improve speed stability. Engine accessory speed requests refer to the demands of external loads directly connected to the engine flywheel on the target speed, such as mechanical compressor loads. When the air conditioning is on, the engine's target speed needs to be increased to improve speed stability. The transmission also requests the engine's target speed based on factors such as transmission oil temperature and creeping requirements to meet the needs of maintaining transmission oil temperature and improving creeping functionality.

[0053] Furthermore, the speed control employs a control method combining internal model and feedforward, including:

[0054] S1: Calculate the feedforward control torque;

[0055] S2: Calculate the internal mold control torque;

[0056] S3: Calculate the speed control torque based on the feedforward control torque and the internal mold control torque.

[0057] Figure 2 The diagram shown is a flowchart of the speed control method.

[0058] Furthermore, the calculation method for the feedforward control torque in step S1 includes:

[0059] S11: Calculate the target rotational speed change rate.

[0060] Specifically, the rate of change of the target rotational speed is calculated by differentiating the target rotational speed. The rate of change of the target rotational speed is expressed as dn. Target It indicates that the unit is r / min / s, and its calculation formula is:

[0061]

[0062] Where, n target The target engine speed is n, which typically ranges from 0 to 6000 r / min. (t-1)target Δ is the target engine speed in the previous calculation cycle. t This is the time interval between two calculation cycles, typically 10ms.

[0063] S12: Convert the target rotational speed change rate into the target angular acceleration.

[0064] Specifically, the target angular acceleration is represented by a. Targget It indicates that the unit is rad / s 2 The calculation formula is as follows:

[0065]

[0066] S13: Calculate the feedforward control torque based on the target angular acceleration and engine rotational inertia.

[0067] Specifically, the engine's moment of inertia is represented by J, and the feedforward control torque is represented by T. Feedforward The formula for calculating the feedforward control torque is as follows:

[0068] T Feedforward =J*a Target *k Feedforward +T Compensation

[0069] Among them, J*a Target k represents the inertial torque component in the feedforward control torque. Feedfororward This is the coefficient for the inertial torque component, typically a value between 0 and 1; T Compensation This is the basic compensation torque component in the feedforward control torque, typically a small torque value between 0 and 10 Nm.

[0070] Figure 3 The flowchart shown is a method for calculating feedforward control torque.

[0071] Examples are provided based on steps S11 to S13 above:

[0072] Assuming that the final target engine speed requirement is determined to be 1000 r / min after comprehensively considering factors such as engine coolant temperature, engine accessory speed, and transmission speed, and with a calculation period of 10 ms, if the target engine speed changes from 1000 r / min to 995 r / min, then the target speed change rate dn is calculated according to step S11. Target The value is -500 r / min / s. Further, according to step S12, the target rotational speed change rate is converted into the target angular acceleration, and the calculated target angular acceleration value is -52.3 rad / s². 2 Furthermore, assuming that in step S13, k Feedforward =0.2, T Compensation =0, J=0.17, then the calculated feedforward control torque is -1.78Nm.

[0073] Furthermore, such as Figure 4 As shown, the calculation method for the internal mold control torque in step S2 includes:

[0074] S21: Calculate the speed difference between the target speed and the actual speed, and convert the unit to rad / s.

[0075] Specifically, the target rotational speed is represented by n. Target The actual rotational speed is represented by n. actThe difference in speed (in rad / s) between the target speed and the actual speed is expressed in n. Error-rad The calculation formula is as follows:

[0076]

[0077] S22: Calculate the actual rate of change of rotational speed and convert it into actual angular acceleration.

[0078] Specifically, the actual rate of change of rotational speed is denoted by dn. act The actual angular acceleration is represented by a. act The calculation formula is as follows:

[0079]

[0080]

[0081] Where, n act The current actual engine speed, typically ranging from 0 to 6000 r / min, n (t-1)act Δ represents the actual engine speed in the previous calculation cycle. t This is the time interval between two calculation cycles, typically 10ms.

[0082] S23: Select the time constant t TimeConstant and D-direction coefficient k d .

[0083] Where, k d This refers to the coefficient in the D-axis of PID (proportional-integral-derivative control), based on the speed difference n between the target speed and the actual speed. Error-rpm and the rate of change of the target speed difference dn Target The actual rate of change of rotational speed dn act The difference dn error The value is obtained by looking up a table, and its range is usually between 0 and 1.

[0084] It should be noted that in step S21, n Errar-rad This refers to the difference in rotational speed between the target rotational speed (in rad / s, radians per second) and the actual rotational speed. Here, n is involved in step S23. Error-rpm It refers to the speed difference between the target speed and the actual speed, which is expressed in r / min (revolutions per minute).

[0085] Furthermore, based on n Error-rpm and dn error Look up the table to select the time constant t timeconstant (unit: s), t timeconstantIt is the calibration value, and its value range is usually between 0 and 1.

[0086] n Error-rpm =n target -n act

[0087] dn error =dn Target -dn act

[0088] S24: Calculate the torque in the P direction, the torque in the I direction, and the torque in the D direction respectively.

[0089] Wherein, the torque in direction P is represented by T. p It means that k p The coefficient for P in PID control, its value range depends on the engine's moment of inertia J and the calibrated time constant t. timeconstant The formula for calculating the torque in direction P is:

[0090]

[0091] T p =k p *n Error-rad

[0092] Furthermore, the torque in the I direction is represented by T. i It means that k i For the coefficients in the I-direction of PID control, t SamplpTime The system's calculation period is typically 10ms. The formula for calculating the torque in the I direction is:

[0093]

[0094] T i =∑(k i *n Error-rad *t SampleTime )

[0095] Furthermore, the torque in the D direction is represented by T. d It means that k d Let D be the coefficient in PID control, and the formula for calculating the torque in the D direction is:

[0096] T d =k d *dn error

[0097] Examples based on steps S21 to S24 above:

[0098] Assuming the calculation period Δ t The calculation period is 10ms, during which the target engine speed n is... Target The actual rotational speed is 995 r / min, n.act The engine speed is 1090 r / min; the target engine speed n in the previous calculation cycle. (t-1)target The actual rotational speed n is 1000 r / min. (t-1)act The speed is 1100 r / min.

[0099] In step S21, according to the calculation formula The speed difference n was calculated. Error-rad It is -9.94 rad / s.

[0100] In step S22, according to the formula The actual speed change rate dn was calculated. act =-1000r / min / s, according to the formula Convert it into actual angular acceleration a act -104.7 rad / s 2 .

[0101] In step S23, the speed difference n between the target speed and the actual speed is calculated. Error-rpm =995-1090=-95r / min. Based on the example in step S1, the target rotational speed change rate dn Target Given a speed of -500 r / min / s, based on the aforementioned assumption, the actual speed change rate dn act If the target speed difference is -1000 r / min / s, then the difference dn between the target speed difference rate of change and the actual speed difference rate of change is... error =500r / min / s.

[0102] Assuming the calibration table of the time constant is shown in Table 1, the coefficient k in the D direction of PID control... d The calibration table is shown in Table 2. Based on the previous n Error-rpm =-95r / min, dn error =500 r / min / s, the time constant t is obtained from the table. timeconstant =0.6s, k d =0.001.

[0103] Table 1 Time Constant Calibration Table

[0104]

[0105] Table 2 k d Calibration table

[0106]

[0107] In step 24, calculate T according to the corresponding formula. p T i and T d .

[0108] Calculate the torque in direction P: Based on the aforementioned assumptions, the engine's moment of inertia J is 0.17, and the time constant t... timeconstant =0.6, n Error-rad The value is -9.94 rad / s, so T is calculated using the formula. p = -5.63 Nm.

[0109] Calculate the torque in the I direction: Based on the aforementioned assumptions, the engine's moment of inertia J is 0.17, and the time constant t... timeconstant =0.6, n Error-rad The value is -9.94 rad / s, and the calculation period is t. SampleTime If it is 10ms, then T is obtained according to the calculation formula. i = -0.05Nm.

[0110] Calculate the torque in direction D: Based on the aforementioned assumptions, k is obtained from the table. d =0.001, dn error =500 r / min / s, then T is obtained according to the calculation formula. d =0.5Nm.

[0111] Furthermore, in step S3 above, the speed control torque T is calculated. SpeedControl The method is as follows:

[0112] T SpeedControl =T Feedforward +T p +T i +T d

[0113] Based on the example above, T has already been calculated. Feedforward = -1.78, T p = -5.63 Nm, T i = -0.05 Nm, T d =0.5Nm, and the speed control torque T is calculated using the above formula. SpeedControl = -6.96 Nm.

[0114] (II) Forced Shutdown Control Phase

[0115] After entering the forced shutdown control phase, the engine fuel is cut off, the engine target torque is set to the shutdown torque, and the generator shutdown torque is given based on the engine speed. When the engine speed approaches 0, the engine shutdown is completed.

[0116] In one implementation, after entering the forced shutdown control phase, the VCU sends a fuel cut-off command to the engine and simultaneously looks up the generator shutdown torque according to the engine speed; when the engine speed approaches 0 r / min, the engine shutdown is completed.

[0117] Assuming the engine speed is 900 r / min at this time, the generator shutdown torque is shown in Table 3 based on the engine speed. Therefore, the generator shutdown torque at this time is -75 Nm.

[0118] As the engine speed decreases, the shutdown torque first decreases and then increases. The absolute value of the shutdown torque is relatively small in the initial and final stages of shutdown to ensure a smooth shutdown process; the absolute value of the shutdown torque is relatively large in the middle stage of shutdown, with the aim of rapid shutdown and shutdown energy recovery.

[0119] Table 3 Comparison of Engine Speed ​​and Generator Shutdown Torque

[0120] Engine speed (r / min) 0 200 300 600 1200 Generator shutdown torque (Nm) 0 -7 -50 -120 -30

[0121] This invention, based on the engine's operating state, divides the shutdown process into two stages: pre-shutdown idling and forced shutdown. In the pre-shutdown idling control stage, the engine fuel supply is not interrupted, the engine target torque is set to zero, and the generator executes closed-loop idling control torque to maintain the engine speed at the target speed, aiming to slowly reduce the intake manifold pressure. After a certain period or when the intake manifold pressure falls below the calibrated limit, the forced shutdown stage begins, controlling the engine fuel supply to be cut off, and calculating the generator shutdown torque command based on the engine speed.

[0122] Based on the same inventive concept, another embodiment of the present invention discloses a control system for suppressing engine shutdown noise and vibration in hybrid vehicles. In the control method for suppressing engine shutdown noise and vibration in hybrid vehicles, the control system is used to calculate and output control commands during the pre-stop idle speed control phase and the forced stop control phase.

[0123] Specifically, the system includes: a vehicle control unit (VCU), an engine, an engine control system (EMS), a generator, a generator control unit (GCU), a high-voltage battery, a battery control system (BMS), and a transmission mechanism (i1).

[0124] The vehicle controller interacts with the engine controller, generator controller, and battery controller via a control link to exchange control signals.

[0125] The engine is mechanically connected to the generator through the transmission mechanism. During shutdown, the generator converts the engine's mechanical energy into electrical energy, which is then stored in the high-voltage battery via a high-voltage link.

[0126] Figure 5 The diagram shows the system link diagram for the engine shutdown process in series mode.

[0127] Specifically, in Figure 5In the control process shown, the VCU interacts with the EMS, GCU, and BMS via control signals in the control link. A mechanical connection exists between the generator and the engine, allowing the conversion of the engine's mechanical energy into electrical energy during shutdown. A high-voltage connection exists between the generator and the battery, enabling the transfer of electrical energy to the battery. The connection between the mechanical and high-voltage links forms the hardware foundation for rapid shutdown and shutdown energy recovery using the generator. During shutdown, the system status, such as intake manifold pressure, needs constant monitoring, and shutdown torque is calculated based on these statuses. Whether in the shutdown idle control phase or the forced shutdown control phase, the VCU needs to calculate and output the final control command based on the status of the EMS, GCU, and BMS.

[0128] In the control link, the VCU is connected to the EMS, GCU and BMS respectively; during the shutdown control process, the VCU calculates the fuel cut-off command and generator shutdown torque based on the current status signals of the EMS, GCU and BMS, and then controls the engine and generator to perform engine shutdown.

[0129] In the mechanical link, the engine is directly connected to the generator via a transmission mechanism. During the series shutdown control process, the VCU controls the engine to cut off fuel, while simultaneously controlling the generator to provide a shutdown load. The engine's own friction pumping load and the generator's shutdown load work together to achieve engine shutdown.

[0130] In the high-voltage link, the engine shutdown process only involves the transfer of electrical power between the generator and the high-voltage battery. According to the engine speed and generator shutdown torque comparison table in Table 3, the generator torque is negative when the engine is shut down, indicating that the generator is acting as a load to convert mechanical energy into electrical energy during the engine shutdown process, that is, the generator is in "generating mode". According to the structure of the power system, this part of the electrical energy is stored in the high-voltage battery through the high-voltage wiring harness.

[0131] Specifically, since the speed range of electric motors is usually 0-12000 r / min and the speed range of engines is usually 0-6000 r / min, in order to better utilize the capabilities of engines and electric motors, transmission mechanisms are usually used to match the speeds of engines and generators.

[0132] Figure 5 In this context, i1 represents a transmission mechanism, which can be a gear mechanism.

[0133] Preferred, Figure 5 The transmission mechanism i1 in the diagram is a speed-increasing gear mechanism.

[0134] In this embodiment of the invention, during engine shutdown in a hybrid vehicle in series mode, the mechanical energy of the engine is converted into electrical energy by a generator, and then stored in the battery through a high-voltage wiring harness, achieving the purpose of shutdown energy recovery and rapid shutdown. During shutdown, the P1 motor recovers shutdown energy to generate electricity. The results of analyzing multiple sets of test data are shown in Table 4. The comparison reveals that during shutdown from 900 r / min to 0 r / min, the shutdown time is reduced from 0.802 s to 0.42 s, representing an efficiency improvement of approximately 48%.

[0135] Table 4. Shutdown Efficiency Comparison Test Table

[0136]

[0137] This invention analyzes the noise and vibration problem caused by series shutdown in hybrid vehicles, identifying intake manifold pressure as the core factor affecting this issue. By determining the intake manifold pressure value, the shutdown process is divided into two stages: pre-shutdown idling and forced shutdown, with separate controls for engine and generator shutdown. Controlling the pre-shutdown idling stage resolves the engine shutdown noise and vibration problem. During shutdown, the generator load converts the engine's mechanical energy into electrical energy, which is stored in a high-voltage battery via high-voltage wiring harness, achieving energy recovery and rapid shutdown.

[0138] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for suppressing engine shutdown noise and vibration in hybrid vehicle models, characterized in that, The method includes the following steps: In series mode, upon receiving a shutdown command, the intake manifold pressure value is determined. If the intake manifold pressure is greater than the threshold, the pre-stop idle speed control phase will be initiated. If the intake manifold pressure is less than or equal to the threshold value, the forced shutdown control phase will be initiated. During the pre-stop idle speed control phase, the engine fuel supply is temporarily cut off, the engine target torque is set to zero, and the generator executes closed-loop idle speed control torque. The control process for the pre-stop idle speed control phase includes: selection of target speed and speed control; The selection of the target speed involves the following reference factors: speed request based on engine coolant temperature, engine accessory speed request, and transmission speed request. The speed control method includes the following steps: S1: Calculate the feedforward control torque; S2: Calculate the internal mold control torque; S3: Calculate the speed control torque based on the feedforward control torque and the internal mold control torque; During the forced shutdown control phase, the engine fuel is cut off, the engine target torque is set to the shutdown torque, the generator shutdown torque is determined based on the engine speed, and the engine shutdown is completed when the engine speed approaches 0. The calculation method for the internal mold control torque in step S2 includes: S21: Calculate the speed difference between the target speed and the actual speed, and convert the unit to rad / s; S22: Calculate the actual rate of change of rotational speed and convert the actual rate of change of rotational speed into actual angular acceleration; S23: Based on the speed difference between the target speed and the actual speed, and the rate of change of the actual speed, select the time constant t. TimeConstant and D-direction coefficient k d ; S24: Based on the speed difference between the target speed and the actual speed, calculate the torque in the P direction, the torque in the I direction, and the torque in the D direction.

2. The control method for suppressing engine shutdown noise and vibration in hybrid vehicles as described in claim 1, characterized in that, The calculation method for the feedforward control torque in step S1 includes: S11: Calculate the target rotational speed change rate; S12: Convert the target rotational speed change rate into the target angular acceleration; S13: Calculate the feedforward control torque based on the target angular acceleration and engine rotational inertia.

3. The control method for suppressing engine shutdown noise and vibration in hybrid vehicles as described in claim 1 or 2, characterized in that, The calculation method for the speed control torque mentioned in step S3 is as follows: T SpeedControl =T Feedforward +T p +T i +T d Among them, T SpeedControl For speed control torque, T Feedforward For feedforward control torque, T p For the torque in direction P, T i For the torque in the I direction, T d This refers to the torque in the D direction.

4. A control system for suppressing engine shutdown noise and vibration in hybrid vehicle models, characterized in that, In the control method for suppressing engine shutdown noise and vibration of hybrid vehicles according to any one of claims 1 to 3, the control system is used to calculate and output control commands in the pre-stop idle speed control stage and the forced stop control stage; The system includes: a vehicle controller, an engine, an engine controller, a generator, a generator controller, a high-voltage battery, a battery controller, and a transmission mechanism; The vehicle controller interacts with the engine controller, generator controller, and battery controller via a control link to exchange control signals. The engine is mechanically connected to the generator through the transmission mechanism. During shutdown, the generator converts the engine's mechanical energy into electrical energy, which is then stored in the high-voltage battery via a high-voltage link.

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