A method for regulating engine output power of a dual-motor hybrid vehicle

Abstract

This invention provides a method for adjusting the output power of a dual-motor hybrid vehicle engine. Based on the engine's initial operating point within the range of its universal characteristic curve and the adjustment amount of the required output power, the engine's output power is adjusted using either torque-following control or power-following control. The advantage of this invention is that it changes the control from controlling the optimal fuel consumption point to controlling the optimal fuel consumption region, reducing engine speed fluctuations, achieving better dynamic fuel consumption, and thus reaching the goal of optimal fuel consumption under cyclic operating conditions.

Description

Technical Field

[0001] This invention relates to the field of hybrid vehicle technology, and more specifically, to a method for adjusting the output power of a dual-motor hybrid vehicle engine. Background Technology

[0002] Currently, in practical market applications, non-plug-in hybrid electric vehicles (HEVs) mainly fall into two categories: series-parallel configurations, such as Honda's iMMD; and power-split configurations, such as Toyota's THS. In series mode of either series or series-parallel configurations, the engine generates electricity through a generator, which then powers the drive motor to power the vehicle. Ideally, in series mode, the generator's output power would perfectly match the drive motor's power requirements. However, considering differences in hardware performance, calculation deviations, and measurement errors, such an ideal energy flow diagram cannot be achieved in practice. Therefore, a high-voltage battery is needed to regulate and compensate throughout the process. This results in three degrees of freedom that can be adjusted: the engine's operating point, the high-voltage battery's operating point, and the drive motor's operating point. Different control methods will produce different efficiency outputs.

[0003] Current solutions from various parties focus on static fuel consumption as the control target, while some mention considering the SOC (State of Charge) of the high-voltage battery and appropriately charging it. However, none of them address the dynamic characteristics of the engine. When the engine is dynamically adjusting, its fuel consumption is significantly higher than the static fuel consumption. Clearly, the lower the fuel consumption rate, the better the economy. Therefore, in actual driving conditions, the fuel consumption will be much higher than the value calculated using static fuel consumption.

[0004] Invention Patent Content

[0005] To address the aforementioned technical problems, this invention provides a method for adjusting the standby power of a dual-motor hybrid electric vehicle engine. This method fully utilizes the characteristics of high-voltage batteries to adjust and compensate for the power demand of the drive motor, and employs a torque-following control method to reduce fluctuations in the engine's standby power and minimize dynamic losses, thereby optimizing the overall energy consumption of the system.

[0006] The present invention solves the technical problem by adopting the following technical solution:

[0007] A method for adjusting the output power of a dual-motor hybrid vehicle engine includes the following steps:

[0008] S1. Find the initial operating point A corresponding to the current engine power on the optimal fuel economy curve;

[0009] S2. When the engine's initial operating point A is within the optimal fuel consumption range, and the vehicle speed is between 20km / h and 120km / h, the engine's output power is controlled using a torque-following method to reduce engine speed fluctuations. Specifically:

[0010] S21. When the engine's standby output power increases:

[0011] (1) Find the maximum power value W1 in the region with the same speed as the initial operating point A within the optimal fuel consumption range;

[0012] (2) Compare the engine's output power with the maximum power value W1:

[0013] When the engine's output power is less than or equal to the maximum power value W1, the engine speed is kept constant, the engine torque increases accordingly, and the engine's operating point moves from the initial operating point A to the operating point B that meets the engine's output power requirement.

[0014] When the engine's required output power exceeds the maximum power value W1, on the optimal fuel economy curve, the engine's operating point shifts from the initial operating point A to the operating point C that meets the engine's required output power; or

[0015] S22. When the engine's standby output power decreases:

[0016] (1) Find the minimum power value W2 that is the same as the initial operating point A speed in the region with the optimal fuel consumption;

[0017] (2) Compare the engine's output power with the minimum power value W2:

[0018] When the engine's output power is greater than or equal to the minimum power value W2, the engine speed is kept constant, the engine torque decreases accordingly, and the engine's operating point moves from the initial operating point A to the operating point D that meets the engine's output power requirement.

[0019] When the engine's required output power is less than the minimum power value W2, on the optimal fuel economy curve, the engine's operating point moves from the initial operating point A to the operating point E that meets the engine's required output power; or

[0020] S3. When the engine's initial operating point A is outside the optimal fuel consumption region, the engine's output power is controlled using a power follower method, specifically:

[0021] The engine's operating point moves from the initial operating point A on the optimal fuel economy curve to the operating point F that meets the engine's power output requirements.

[0022] Furthermore, the engine is a turbocharged engine.

[0023] Furthermore, when the engine's initial operating point A is within the optimal specific fuel consumption range and the vehicle speed is greater than 120 km / h, a power following control method is adopted.

[0024] Furthermore, the operating point B and the operating point D that meet the engine's power output requirements are located within the optimal specific fuel consumption region.

[0025] Furthermore, the operating point C and the operating point E that meet the engine's power output requirements are located within the optimal specific fuel consumption region or outside the optimal specific fuel consumption region.

[0026] Furthermore, the operating point F that meets the engine's power output requirements is located either outside the optimal fuel consumption region or within the optimal fuel consumption region.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) Select different series control methods according to the vehicle's dynamic operating conditions to reduce engine speed fluctuations, reduce fuel consumption increase under dynamic operating conditions, and achieve optimization in the actual cycle.

[0029] (2) By adopting torque following control method, the control of the optimal fuel consumption point is changed to the control of the optimal fuel consumption area, which further reduces the speed fluctuation of the engine and obtains better dynamic fuel consumption, thereby achieving the goal of optimal fuel consumption under cyclic conditions. Attached Figure Description

[0030] Figure 1 This is the ideal series energy flow diagram of the present invention.

[0031] Figure 2 This is the energy flow diagram for pure electric driving according to the present invention.

[0032] Figure 3 This is a series energy flow diagram for charging the high-voltage battery of the present invention.

[0033] Figure 4 This is a series energy flow diagram of the high-voltage battery during discharge according to the present invention.

[0034] Figure 5 This is a schematic diagram illustrating the engine start-up threshold under different SOCs according to the present invention.

[0035] Figure 6 This is a schematic diagram illustrating the specific fuel consumption selection in the engine output power control method of the present invention.

[0036] Figure 7 This is a schematic diagram illustrating the adjustment of the engine when its output power is increased according to the present invention.

[0037] Figure 8This is a schematic diagram illustrating the adjustment when the engine output power of the present invention is reduced.

[0038] Figure 9 This is a schematic diagram of the vehicle speed selection range for the engine output power control method of the present invention.

[0039] In the diagram: 1-Engine; 2-Generator; 3-Drive motor; 4-High-voltage battery. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0041] This invention provides a method for adjusting the output power of a dual-motor hybrid vehicle engine, such as... Figure 6 As shown, it includes the following steps:

[0042] S1. Find the initial operating point A corresponding to the current power of engine 1 on the optimal fuel economy curve;

[0043] S2. When the initial operating point A of engine 1 is within the optimal fuel consumption range, and the vehicle speed is between 20km / h and 120km / h, the output power of engine 1 adopts a torque following control method to reduce the speed fluctuation of engine 1. Specifically:

[0044] S21. When the output power of engine 1 increases:

[0045] (1) Find the maximum power value W1 in the region with the same speed as the initial operating point A within the optimal fuel consumption range;

[0046] (2) Compare the output power of engine 1 with the maximum power value W1:

[0047] When the output power of engine 1 is less than or equal to the maximum power value W1, the speed of engine 1 is kept constant, the torque of engine 1 increases accordingly, and the operating point of engine 1 moves from the initial operating point A to the operating point B that meets the output power requirement of engine 1.

[0048] When the required output power of engine 1 is greater than the maximum power value W1, on the optimal fuel economy curve, the operating point of engine 1 moves from the initial operating point A to the operating point C that meets the required output power of engine 1; or

[0049] S22. When the output power of engine 1 decreases:

[0050] (1) Find the minimum power value W2 that is the same as the initial operating point A speed in the region with the optimal fuel consumption;

[0051] (2) Compare the output power of engine 1 with the minimum power value W2:

[0052] When the output power of engine 1 is greater than or equal to the minimum power value W2, the speed of engine 1 is kept constant, the torque of engine 1 decreases accordingly, and the operating point of engine 1 moves from the initial operating point A to the operating point D that meets the output power requirement of engine 1.

[0053] When the required output power of engine 1 is less than the minimum power value W2, on the optimal fuel economy curve, the operating point of engine 1 moves from the initial operating point A to the operating point E that meets the required output power of engine 1; or

[0054] S3. When the initial operating point A of engine 1 is outside the optimal specific fuel consumption region, the output power of engine 1 adopts a power follower control method, specifically:

[0055] The operating point of engine 1 moves from the initial operating point A on the optimal fuel economy curve to the operating point F that meets the power output requirements of engine 1.

[0056] In a hybrid electric vehicle, in series mode, when the power demand of the drive motor 3 is less than the starting threshold of the engine 1, it operates on pure electric power. In this case, the high-voltage battery 4 supplies power to the drive motor 3, and the energy flow direction is as follows: Figure 2 As shown. When the power demand of the drive motor 3 is greater than or equal to the starting threshold of the engine 1, the engine 1 operates, driving the generator 2 to generate electricity, and the generator 2 supplies power to the drive motor 3. The starting threshold of the engine 1 is a calibration value, which can be obtained according to methods commonly used by those skilled in the art. Preferably, for example, a baseline value of the starting threshold of the engine 1 is first obtained. The baseline value can be obtained using software simulation or based on the starting threshold of the engine 1 of an older vehicle model. Then, the baseline value is corrected according to "GB / T 19753-2021 Test Method for Energy Consumption of Light Hybrid Electric Vehicles" to obtain the calibration value. For example, for a certain vehicle model, such as Figure 5 The figure shows the calibration values ​​of the high-voltage battery 4 at different SOCs and vehicle speeds. The horizontal axis represents vehicle speed, and the vertical axis represents the power demand of the drive motor 3. When the power demand of the drive motor 3 is less than the starting threshold of the engine 1, that is, when the power demand of the drive motor 3 is below the calibration curve, pure electric driving is used. When the power demand of the drive motor 3 is greater than or equal to the starting threshold of the engine 1, that is, when the power demand of the drive motor 3 is above the calibration curve (inclusive), the engine 1 starts.

[0057] After engine 1 starts working, when the output power of generator 2 just meets the power requirement of drive motor 3, the energy flow direction is as follows: Figure 1As shown, the ideal state of the series mode is achieved. However, considering differences in hardware performance, calculation deviations, and measurement errors, such an ideal energy flow diagram cannot actually be achieved, and high-voltage battery 4 is needed for adjustment and compensation. When the output power of generator 2 is greater than the required power of drive motor 3, that is, when the power of engine 1 is greater than the required power of drive motor 3, generator 2 supplies power to drive motor 3 and simultaneously charges high-voltage battery 4. The excess energy of generator 2 is absorbed by high-voltage battery 4, and its energy flow direction is as follows. Figure 3 As shown. When the output power of generator 2 is less than the required power of drive motor 3, that is, when the power of engine 1 is less than the required power of drive motor 3, high-voltage battery 4 discharges, and together with generator 2, supplies power to drive motor 3. The insufficient energy of generator 2 is supplemented by high-voltage battery 4, and its energy flow direction is as follows. Figure 4 As shown. When the high-voltage battery 4 charges or discharges to adjust the power demand of the drive motor 3, the energy flow among the generator 2, high-voltage battery 4, and drive motor 3 reaches a balance, that is, the energy flow among the engine 1, high-voltage battery 4, and drive motor 3 reaches a balance. When the power demand of the drive motor 3 changes, or the power demand of the high-voltage battery 4 changes, or both the power demand of the drive motor 3 and the high-voltage battery 4 change, the output power of the engine 1 needs to be adjusted to restore balance and meet the changing power demand of the drive motor 3, thereby satisfying the vehicle's driving requirements. For example, if the SOC of the high-voltage battery 4 is too low, or the vehicle's acceleration decreases causing a sudden decrease in the power demand of the drive motor 3, or if the SOC of the high-voltage battery 4 is too high, or the vehicle's acceleration increases causing a sudden increase in the power demand of the drive motor 3, the output power of the engine 1 needs to be adjusted.

[0058] In a hybrid electric vehicle, in series mode, the operating point of engine 1 can be freely selected, unaffected by vehicle speed, and the engine speed can be adjusted without restriction. For example... Figure 6The diagram shows the universal characteristic curve of an engine, with engine speed on the horizontal axis and engine torque on the vertical axis. The curve has a region with the lowest fuel consumption (the innermost ring), where fuel consumption is minimized. Especially for engines like turbocharged engines 1, whose optimal fuel economy region changes slowly, the static specific fuel consumption difference is small at medium speeds and loads, forming an optimal specific fuel consumption region. When the required output power of engine 1 needs adjustment, two control methods are used based on the current operating point of engine 1 within the range shown on the universal characteristic curve. When the initial operating point A of engine 1 is within the optimal specific fuel consumption region, and the vehicle speed is between 20 km / h and 120 km / h, the required output power of engine 1 is adjusted using torque following control. This method aims to keep the engine speed as constant as possible while adjusting the engine torque to meet the required output power and reduce engine speed fluctuations. When the initial operating point A of engine 1 is outside the optimal specific fuel consumption region, the required output power is adjusted using power following control. Within the optimal fuel consumption range, the control for the optimal fuel consumption point is changed to the control for the optimal fuel consumption range, so that engine 1 operates near the optimal fuel economy point, reducing the speed fluctuation of engine 1, keeping the operating point of engine 1 as stable as possible, and obtaining better dynamic fuel consumption, thereby achieving the optimal global energy consumption under actual operating conditions.

[0059] When using the torque follower control method, based on the current operating point of engine 1, the maximum power value W1 or minimum power value W2 that is the same as the initial operating point A speed in the optimal fuel consumption region is obtained. It is then determined whether controlling the speed of engine 1 to remain unchanged and only adjusting the torque of engine 1 can meet the output power of engine 1 in the optimal fuel consumption region.

[0060] When the output power of engine 1 increases, such as Figure 7 As shown, the output power of engine 1 is compared with the maximum power value W1:

[0061] When the output power of engine 1 is less than or equal to the maximum power value W1, it indicates that the engine is in the optimal fuel consumption region. By keeping the engine speed constant and adjusting only the torque of engine 1, the required output power can be achieved. Therefore, the engine speed can be kept constant while the torque of engine 1 increases accordingly. The operating point of engine 1 moves from the initial operating point A to the required operating point B that satisfies the required output power of engine 1. The required operating point B is located within the optimal fuel consumption region.

[0062] When the desired output power of engine 1 is greater than the maximum power value W1, the adjustment amount of the desired output power of engine 1 is relatively large. This indicates that within the optimal fuel economy region, keeping the engine speed constant and only adjusting the torque of engine 1 is insufficient to meet the desired output power adjustment. Therefore, to meet the desired output power adjustment of engine 1, on the optimal fuel economy curve, the operating point of engine 1 shifts from the initial operating point A to the required operating point C that satisfies the desired output power of engine 1. The required operating point C can be located within or outside the optimal fuel economy region.

[0063] When the output power of engine 1 decreases, such as Figure 8 As shown, the output power of engine 1 is compared with the minimum power value W2:

[0064] When the desired output power of engine 1 is greater than or equal to the minimum power value W2, it indicates that within the optimal fuel consumption region, keeping the engine speed constant and adjusting only the torque of engine 1 is sufficient to meet the desired output power. Therefore, the engine speed can be kept constant, and the torque of engine 1 will decrease accordingly. The operating point of engine 1 will move from the initial operating point A to the required operating point D that meets the desired output power of engine 1, and the required operating point D is located within the optimal fuel consumption region.

[0065] When the desired output power of engine 1 is less than the minimum power value W2, the adjustment amount of the desired output power of engine 1 is relatively large. This indicates that within the optimal fuel economy region, keeping the engine speed constant and only adjusting the torque of engine 1 is insufficient to meet the desired output power adjustment. Therefore, to meet the desired output power adjustment of engine 1, on the optimal fuel economy curve, the operating point of engine 1 moves from the initial operating point A to the required operating point E that meets the desired output power of engine 1. The required operating point E can be located within or outside the optimal fuel economy region.

[0066] When the initial operating point A of engine 1 is outside the optimal fuel consumption region, engine 1 operates on the optimal fuel economy curve at the system's optimal torque and speed points. It moves along the optimal fuel economy curve following the total power demand, from the initial operating point A to the operating point F that meets the required output power of engine 1, thus achieving optimal fuel economy. When the required output power of engine 1 increases, the operating point of engine 1 moves to the right along the optimal fuel economy curve from the initial operating point A to the operating point F that meets the required output power of engine 1, as shown below. Figure 7 As shown. When the required output power of engine 1 decreases, the operating point of engine 1 shifts from the initial operating point A to the left along the optimal fuel economy curve to the operating point F that meets the required output power of engine 1, as shown. Figure 8 As shown, the demand operating point F can be located either outside or within the optimal fuel consumption region.

[0067] As a preferred option, combined with Figure 6 and Figure 9 As shown, when the total power demand changes and the output power of engine 1 needs to be adjusted, different control methods for the output power of engine 1 can be used to adjust the output power of engine 1 according to the current vehicle speed and the total power demand. Vehicle speed can generally be divided into low speed (<30km / h), medium speed (30-70km / h), medium-high speed (70-120km / h), and high speed (>120km / h). It should be noted that the speed division in this embodiment is only illustrative and not limiting; other speed division ranges can be used depending on the specific vehicle.

[0068] like Figure 9 As shown, the system can be divided into four zones based on vehicle speed and total power demand. At low speeds and low power demand (zone ①), pure electric operation is used, and engine 1 is not operating. At medium speeds and medium-high speeds with medium power demand (zone ②), engine 1 operates. Specifically, the output power of engine 1 is adjusted using either torque-following control or power-following control, depending on the zone where engine 1's initial operating point A is located. When engine 1's initial operating point A is within the optimal fuel consumption zone, torque-following control is used; when engine 1's initial operating point A is outside the optimal fuel consumption zone, demand-power-following control is used. When the total power demand is at a high power level (zone ③), or when the vehicle is at a high speed (zone ④), demand-power-following control is prioritized. For example, when the vehicle speed is greater than 120 km / h and adjustment of engine 1's output power is needed, even if engine 1's initial operating point A is within the optimal fuel consumption zone, demand-power-following control is used to promptly meet the vehicle's power requirements.

[0069] The above description is only a preferred embodiment of the present invention and is 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 adjusting the output power of a dual-motor hybrid vehicle engine, characterized in that, The specific method for adjusting the engine's output power is as follows: S1. Find the initial operating point A corresponding to the current engine power on the optimal fuel economy curve; S2. When the engine's initial operating point A is within the optimal fuel consumption range, and the vehicle speed is between 20km / h and 120km / h, the engine's output power is controlled using a torque-following method to reduce engine speed fluctuations. Specifically: S21. When the engine's standby output power increases: (1) Find the maximum power value W1 in the region with the same speed as the initial operating point A within the optimal fuel consumption range; (2) Compare the engine's output power with the maximum power value W1: When the engine's output power is less than or equal to the maximum power value W1, the engine speed is kept constant, the engine torque increases accordingly, and the engine's operating point moves from the initial operating point A to the operating point B that meets the engine's output power requirement. When the engine's output power is greater than the maximum power value W1, on the optimal fuel economy curve, the engine's operating point moves from the initial operating point A to the operating point C that meets the engine's output power requirement. S22. When the engine's standby output power decreases: (1) Find the minimum power value W2 that is the same as the initial operating point A speed in the region with the optimal fuel consumption; (2) Compare the engine's output power with the minimum power value W2: When the engine's output power is greater than or equal to the minimum power value W2, the engine speed is kept constant, the engine torque decreases accordingly, and the engine's operating point moves from the initial operating point A to the operating point D that meets the engine's output power requirement. When the engine's output power is less than the minimum power value W2, on the optimal fuel economy curve, the engine's operating point moves from the initial operating point A to the operating point E that meets the engine's output power requirement. S3. When the engine's initial operating point A is outside the optimal fuel consumption region, the engine's output power is controlled using a power follower method, specifically: The engine's operating point moves from the initial operating point A on the optimal fuel economy curve to the operating point F that meets the engine's power output requirements.

2. The method for adjusting the output power of a dual-motor hybrid vehicle engine according to claim 1, characterized in that, The engine is a turbocharged engine.

3. The method for adjusting the output power of a dual-motor hybrid vehicle engine according to claim 1, characterized in that, When the engine's initial operating point A is within the optimal fuel consumption range and the vehicle speed is greater than 120 km / h, the power following control method is adopted.

4. The method for adjusting the output power of a dual-motor hybrid vehicle engine according to claim 1, characterized in that, The operating point B and the operating point D that meet the engine's power output requirements are located within the optimal specific fuel consumption region.

5. The method for adjusting the output power of a dual-motor hybrid vehicle engine according to claim 1, characterized in that, The operating point C and the operating point E that meet the engine's power output requirements are located within the optimal specific fuel consumption region or outside the optimal specific fuel consumption region.

6. The method for adjusting the output power of a dual-motor hybrid vehicle engine according to claim 1 or 3, characterized in that, The operating point F that meets the engine's output power requirement is located either outside the optimal fuel consumption region or within the optimal fuel consumption region.

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