Hybrid vehicle engine start-stop control method, system, hybrid vehicle and storage medium

Abstract

This invention discloses a hybrid vehicle engine start-stop control method, system, hybrid vehicle, and storage medium, comprising: S1, acquiring parameters required for calculating predicted power; S2, calculating predicted power based on the parameters acquired in S1; S3, determining whether the battery discharge power emitted by the power control unit is less than or equal to the predicted power; if so, proceeding to S4; otherwise, the process ends; S4, requesting and controlling engine start; S5, setting the engine operating point according to the required power and vehicle speed; S6, setting the engine charging SOC threshold according to the required power and vehicle speed; S7, determining whether the engine should be stopped based on whether the battery SOC has reached the charging threshold, the current required power, and the vehicle speed; if the stop condition is met, proceeding to S8; if the stop condition is not met, returning to S5; S8, requesting and controlling engine stop. This invention solves the problems of smoothness and power performance when switching between EV mode and HEV mode in hybrid vehicles.

Description

Technical Field

[0001] This invention belongs to the field of hybrid vehicle technology, specifically relating to a hybrid vehicle engine start-stop control method, system, hybrid vehicle, and storage medium. Background Technology

[0002] For hybrid electric vehicles (HEVs) with a dual-motor system, one motor is a generator, and the other is a drive motor. Based on the battery capacity and whether the engine can directly drive the vehicle, they are classified as HEVs, PHEVs, and REEVs. When the battery capacity of a HEV is 0.5kWh-2kWh, it typically lacks a charging function, and the engine can directly drive the vehicle. When the battery capacity is larger, such as 10kWh-60kWh, it is rechargeable, and the engine can directly drive the vehicle; this is called a PHEV. When the battery capacity is also large, such as 10kWh-60kWh, it is rechargeable, and the engine cannot directly drive the vehicle; this is called a REEV. The hybrid electric vehicles mentioned can be ordinary hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or range-extended hybrid electric vehicles (REEVs). When the battery SOC is too low or the battery discharge power is too low, the engine needs to be started to supplement the power. At this time, the torque smoothness and power when switching from EV mode to HEV need to be considered, as well as the switching frequency, the NVH experience brought by the engine operating point, and the overall fuel consumption.

[0003] For example, patent document CN114174139A discloses a hybrid vehicle and its engine start-stop control method and device, which comprehensively discusses the start-stop control method for hybrid vehicle engines, including start-stop strategies related to energy management, driving behavior, and engine events. Regarding engine start-stop caused by battery SOC, this method sets a battery SOC protection limit; if the SOC is below the limit, the engine starts; if it exceeds the limit, the engine stops. This method does not fully consider the comprehensive evaluation of energy recovery and traffic jam conditions, which is detrimental to overall fuel consumption. Regarding battery discharge power and required power, this method only compares the discharge power with the required power; if the discharge power is lower, the engine starts or stops. It does not predict the vehicle's required power in advance, resulting in insufficient power demand before requesting engine power supplementation, which can easily cause problems with torque smoothness and power performance.

[0004] Therefore, it is necessary to develop a hybrid vehicle engine start-stop control method, system, hybrid vehicle, and storage medium. Summary of the Invention

[0005] The present invention aims to improve at least one of the technical problems existing in the prior art or related art.

[0006] The purpose of this invention is to provide a method, system, hybrid vehicle, and storage medium for starting and stopping a hybrid vehicle engine.

[0007] In a first aspect, the hybrid vehicle engine start-stop control method of the present invention includes the following steps:

[0008] S1. Obtain the parameters required to calculate the predicted power, including the current actual torque of the drive motor Tq_real_TM, the current actual speed of the drive motor n_TM, the drive motor request torque Tq_req_TM that the power control unit will output, and the total power demand of other high-voltage components P_other.

[0009] S2. Calculate the predicted power based on the parameters obtained in S1. The calculation formula is as follows:

[0010] P_req_pre=Tq_real_TM*n_TM / 9550+Tq_req_TM*(dn_TM / dt)*△t / 9550+P_other

[0011] Where P_req_pre is the battery discharge power after time Δt, i.e., the predicted power; dn_TM / dt is the rate of change of the drive motor speed; and Δt is the prediction time.

[0012] S3. Determine whether the battery discharge power issued by the power control unit is less than or equal to the predicted power P_req_pre. If yes, proceed to S4; otherwise, the process ends.

[0013] S4. Request and control engine start;

[0014] S5. Set the engine operating point according to the required power and vehicle speed, where the required power...

[0015] = P_req_pre + P_batt_charge, where P_batt_charge is the battery charging power;

[0016] S6. Set the engine charging SOC threshold SOC_charge_Limit according to the required power and vehicle speed;

[0017] S7. Based on whether the battery SOC has reached the charging threshold SOC_charge_Limit, the current power demand and vehicle speed, determine whether the engine should be shut down. If the shutdown conditions are met, proceed to S8; otherwise, return to S5.

[0018] S8. Request and control engine shutdown.

[0019] Optionally, S4 specifically refers to: the power control unit controlling the engine to start according to the engine starting strategy.

[0020] Optionally, in step S5, an acceptable engine NVH limit is selected based on the vehicle speed, and the optimal operating range for efficiency η_EN is selected under this NVH limit condition. Within this operating range, the intermediate speed is selected as the target engine speed, and the engine torque is calculated based on the required power.

[0021] Optionally, in step S6, the SOC_charge_Limit when the vehicle is in traffic jam is higher than the SOC_charge_Limit when the vehicle is in normal driving conditions.

[0022] Optionally, S8 specifically refers to: the power control unit controlling the engine to shut down according to the shutdown strategy.

[0023] Secondly, the hybrid vehicle engine start-stop control system of the present invention includes a memory and a controller. The memory stores a computer-readable program, which, when invoked by the controller, can execute the steps of the hybrid vehicle engine start-stop control method of the present invention.

[0024] Thirdly, the hybrid vehicle described in this invention employs the hybrid vehicle engine start-stop control system as described in this invention.

[0025] Fourthly, the present invention provides a storage medium storing a computer-readable program, which, when invoked by a controller, can execute the steps of the hybrid vehicle engine start-stop control method described in the present invention.

[0026] This invention has the following advantages: By predicting vehicle driving power demand and combining the power battery's SOC value and charging / discharging power value, this invention rationally requests engine start-up or shutdown, solving the problems of smoothness and power performance when switching between EV and HEV modes in hybrid vehicles, achieving the same experience as EV vehicles; it rationally sets the engine operating point based on vehicle speed, engine NVH, and the engine's optimal economic curve, finding a balance between NVH and economy; and it dynamically sets the engine charging SOC threshold based on vehicle speed and power demand, solving the problem that a single engine charging SOC threshold cannot adapt to energy recovery under traffic jams and high-speed conditions. This invention improves the driving experience of hybrid vehicles. Attached Figure Description

[0027] Figure 1 This is a diagram of the local network architecture for CAN communication involved in this embodiment.

[0028] Figure 2 This is a schematic diagram of the dual-motor hybrid power system involved in this embodiment.

[0029] Figure 3 This is the control flowchart for this embodiment.

[0030] In the diagram, 1. Engine Management System, 2. Dual Motor Controller Assembly, 3. Power Control Unit, 4. Power Battery Management System, 5. Engine, 6. Generator, 7. Clutch, 8. Drive Motor, 9. Power Battery. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings.

[0032] like Figure 1 The diagram shown illustrates the partial CAN communication network architecture used in this embodiment, including an engine management system 1, a dual-motor controller 2, a power control unit 3, and a battery management system 4. The engine management system 1 is the management system for the engine 5, responsible for engine 5 control and status monitoring. The dual-motor controller 2 is the controller for the generator 6 and the drive motor 8, responsible for the control and status monitoring of both. The power control unit 3 is the powertrain controller, responsible for powertrain control including energy management, high-voltage power supply / discharge, hybrid mode management, and driver demand analysis. The battery management system 4 is the management system for the power battery 9, responsible for power battery control and status monitoring. The engine management system 1, dual-motor controller 2, power control unit 3, and battery management system 4 interact via a CAN network.

[0033] like Figure 2 The diagram shows the structure of the dual-motor hybrid power system involved in this embodiment, including an engine 5, a generator 6, a clutch 7, a drive motor 8, and a power battery 9. The engine 5 is directly connected to the generator 6. The generator 6's main functions are starting the engine, assisting in engine shutdown, generating electricity under the drive of the engine 5, and traction of the engine 5 to a specific speed. The drive motor 8 is connected to the vehicle through a reducer, and its main functions are driving the vehicle and energy recovery. The power battery 9's main functions are providing and storing electrical energy. The clutch 7 enables the engagement and disengagement of the engine 5 from the vehicle's power. Based on the capacity of the power battery 9 and whether the engine 5 can directly drive the vehicle, it is classified as HEV, PHEV, or REEV. The hybrid electric vehicle shown in this embodiment is a PHEV, which has three operating modes. When the clutch 7 is disengaged, the engine 5 is off, and the vehicle is driven by the drive motor 8, it is in EV mode. When the clutch 7 is disengaged, the engine 5 is running, the generator 6 generates electricity, and the vehicle is driven by the drive motor 8, it is in series drive HEV mode. When the clutch 7 is closed, the engine 5 is running, the generator 6 generates electricity or follows up, and the vehicle is driven by the drive motor 8 or directly by the engine 5, it is in parallel drive HEV mode.

[0034] Whether it's HEV, PHEV, or REEV, their power battery 9 all require starting the engine 5 when it's depleted. If the engine 5 starting time is not set properly, it will affect the smoothness and power of the vehicle's power delivery. If the engine 5's operating point is not set properly, it will result in poor fuel economy and NVH experience. When the engine 5's shutdown strategy based on SOC is not reasonable, it will lead to frequent start-stop or unreasonable energy management.

[0035] like Figure 3 As shown, in order to solve the above problems, this embodiment proposes a hybrid vehicle engine start-stop control method, including the following steps:

[0036] S1. Obtain the parameters required for calculating the predicted power, including the current actual torque of the drive motor Tq_real_TM, the current actual speed of the drive motor n_TM, the drive motor request torque Tq_req_TM that the power control unit will output, and the total power demand of other high-voltage components P_other (mainly smaller power components such as DC-DC / electric compressor).

[0037] S2. Calculate the predicted power based on the parameters obtained in S1. The calculation formula is as follows:

[0038] P_req_pre=Tq_real_TM*n_TM / 9550+Tq_req_TM*dn_TM / dt*△t / 9550+P_other

[0039] Where P_req_pre is the battery discharge power after time Δt, dn_TM / dt is the rate of change of the drive motor speed, and Δt is the prediction time (Δt is generally set to the engine start time, such as 0.5s).

[0040] S3. Check if the battery discharge power issued by the power cut-off control unit 3 is less than or equal to the predicted power P_req_pre. If yes, proceed to S4; otherwise, the process ends.

[0041] S4. Request and control the engine to start. The power control unit 3 controls the engine 5 to start according to the engine starting strategy. The engine starting strategy is existing technology, so it will not be explained further.

[0042] S5. Set the engine operating point based on power demand and vehicle speed. The NVH performance of engine 5 is related to its speed, torque, and other parameters. A performance table for engine 5 needs to be calibrated on a test bench, consisting of speed n_EN, torque T_EN, NVH_EN, and efficiency η_EN. Based on the vehicle speed, select an acceptable NVH limit for engine 5. Under this NVH limit, select the optimal operating range for efficiency η_EN. Within this operating range, select the midpoint speed as the target engine speed. The engine torque can then be calculated based on the power demand. To ensure the engine operates in its high-efficiency range, in addition to P_req_pre, the required power should also include the battery charging power P_batt_charge, i.e., engine 5 output power P_EN = P_req_pre + P_batt_charge. By adjusting P_batt_charge (P_batt_charge > 0), the engine operates at its optimal efficiency point. Because engine 5 is started in advance based on the predicted power demand, the drive motor 8 operates without torque limitations, ensuring smoothness and rapid power delivery of the entire vehicle.

[0043] S6. Set the engine charging SOC threshold (SOC_charge_Limit) based on power demand and vehicle speed. When vehicle speed is low, i.e., in traffic jams, SOC_charge_Limit should be set higher, such as 30% (PHEV, REEV). This allows for longer driving in EV mode after the battery is fully charged and the engine stops, reducing engine start-stop frequency, optimizing energy consumption, and improving customer experience. When vehicle speed is high, i.e., during normal driving, SOC_charge_Limit should be set lower, such as 20% (PHEV, REEV). This allows for normal vehicle operation, reducing energy storage and release in the battery, and optimizing energy consumption. It should be noted that the relationship between vehicle speed and the charging SOC threshold (SOC_charge_Limit) is related to vehicle weight and battery capacity, and needs to be calibrated according to the specific hybrid vehicle.

[0044] S7. Determine whether the engine should be shut down based on whether the battery SOC has reached the charging threshold SOC_charge_Limit, the current power demand, and the vehicle speed. If the shutdown conditions are met, proceed to S8; otherwise, return to S5 to continue execution.

[0045] S8. Request and control engine shutdown. The power control unit 3 controls engine 5 to shut down according to the shutdown strategy. The engine 5 shutdown strategy is prior art and will not be described further.

[0046] The control strategy in this embodiment is executed by the power control unit 3.

[0047] In summary, this invention, by predicting vehicle drive power demand and combining the power battery's SOC value and charging / discharging power values, rationally requests engine start-up or shutdown, solving the smoothness and power issues of switching between EV and HEV modes in hybrid vehicles, achieving the same experience as EV vehicles. Based on vehicle speed, engine NVH, and the engine's optimal economic curve, it rationally sets the engine operating point, finding a balance between NVH and economy. Furthermore, it dynamically sets the power battery-engine charging SOC threshold based on vehicle speed and power demand, solving the problem that a single engine charging SOC threshold cannot adapt to energy recovery in congested and high-speed conditions. These strategies improve the driving experience of hybrid vehicles, contributing to their promotion and application.

[0048] In this embodiment, a hybrid vehicle engine start-stop control system includes a memory and a controller. The memory stores a computer-readable program, which, when invoked by the controller, can execute the steps of the hybrid vehicle engine start-stop control method described in this embodiment.

[0049] In this embodiment, a hybrid vehicle employs a hybrid vehicle engine start-stop control system as described in this embodiment.

[0050] In this embodiment, a storage medium stores a computer-readable program, which, when invoked by a controller, can execute the steps of the hybrid vehicle engine start-stop control method described in this embodiment.

[0051] It should be noted that the above embodiments are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for starting and stopping a hybrid vehicle engine, characterized in that, Includes the following steps: S1. Obtain the parameters required to calculate the predicted power, including the current actual torque of the drive motor Tq_real_TM, the current actual speed of the drive motor n_TM, the drive motor request torque Tq_req_TM that the power control unit will output, and the total power demand of other high-voltage components P_other. S2. Calculate the predicted power based on the parameters obtained in S1. The calculation formula is as follows: P_req_pre=Tq_real_TM*n_TM / 9550+Tq_req_TM*(dn_TM / dt)*△t / 9550+P_other Where P_req_pre is the battery discharge power after time t, i.e., the predicted power; dn_TM / dt is the rate of change of the drive motor speed; Δt is the prediction time; S3. Determine whether the battery discharge power issued by the battery management system is less than or equal to the predicted power P_req_pre. If yes, proceed to S4; otherwise, the process ends. S4. Request and control engine start; S5. Set the engine operating point according to the required power and vehicle speed. Required power = P_req_pre + P_batt_charge, where P_batt_charge is the battery charging power. Select an acceptable NVH limit for the engine (5) according to the vehicle speed. Under this NVH limit, select the optimal operating range for efficiency η_EN. Under this operating range, select the intermediate speed as the target engine speed. The engine torque is calculated based on the required power. S6. Set the engine charging SOC threshold SOC_charge_Limit according to the required power and vehicle speed; the SOC_charge_Limit when the vehicle is in traffic jam is higher than the SOC_charge_Limit when the vehicle is in normal driving conditions. S7. Based on whether the battery SOC has reached the charging threshold SOC_charge_Limit, the current power demand, and the vehicle speed, determine whether the engine should be shut down. If the shutdown conditions are met, proceed to S8; otherwise, return to S5. S8. Request and control engine shutdown.

2. The hybrid vehicle engine start-stop control method according to claim 1, characterized in that: Specifically, S4 is: the power control unit (3) controls the engine (5) to start according to the engine starting strategy.

3. The hybrid vehicle engine start-stop control method according to claim 1, characterized in that: Specifically, S8 is: the power control unit (3) controls the engine (5) to stop according to the shutdown strategy.

4. A start-stop control system for a hybrid vehicle engine, characterized in that: It includes a memory and a controller, wherein the memory stores a computer-readable program that, when invoked by the controller, can perform the steps of the hybrid vehicle engine start-stop control method as described in any one of claims 1 to 3.

5. A hybrid vehicle, characterized in that: The hybrid vehicle engine start-stop control system as described in claim 4 is adopted.

6. A storage medium, characterized in that: It contains a computer-readable program that, when invoked by the controller, can execute the steps of the hybrid vehicle engine start-stop control method as described in any one of claims 1 to 3.

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