Torque distribution method for two-speed dual-motor HEV hybrid system

Abstract

A new two-speed dual-motor HEV hybrid system torque distribution method: S1. Calculate the required power (P) based on acceleration demand. Calculate the maximum power (P) of the engine with battery assistance, the maximum power (P) without battery assistance, and the maximum and minimum power (P) of the engine in the economic zone based on the vehicle's acceleration demand under each operating mode. S2. When P demand < maximum power (P), proceed to S3. When P demand > maximum power (P), P demand outputs full throttle power. S3. When P demand < maximum power (P), proceed to S4. When maximum power (P) without battery assistance < P demand < maximum power (P), P demand outputs a high throttle power range. S4. When P demand < maximum power (P in the economic zone), proceed to S5. When maximum power (P in the economic zone) < P demand < maximum power (P without battery assistance), P demand outputs a medium throttle power range. S5. When P demand < minimum power (P in the economic zone), P demand outputs a lower throttle power range.

Description

Technical Field

[0001] This invention relates to the field of hybrid two-speed dual-motor systems, specifically to a torque distribution method for a two-speed dual-motor HEV hybrid system. Background Technology

[0002] As human society progresses, people are increasingly concerned about energy security and air pollution. With the continuous increase in the number of cars worldwide and the rising fuel consumption and emission standards in various countries, hybrid vehicles play a crucial role in reducing fuel consumption and emissions. Hybrid systems effectively address the issues of long electric driving range and charging times. The two-speed dual-motor HEV hybrid system is a prime example of a hybrid system, better integrating vehicle power, fuel economy, and driving comfort, thus making a greater contribution to low-carbon travel.

[0003] The conventional hybrid system approach calculates the driver's required torque based on the vehicle's acceleration power demand, and then distributes the torque among various components (engine, generator, drive motor, etc.) according to the hybrid mode. This approach can easily result in a messy torque distribution, weak system integration, and a lot of repetitive verification work. Furthermore, it only emphasizes the engine's economic operating range without providing a detailed explanation of the generator and drive motor's high-efficiency operating range. Summary of the Invention

[0004] This invention provides a torque distribution method for a two-speed dual-motor HEV hybrid system. Under various hybrid operating conditions, this invention distributes the corresponding power of each throttle position using a four-demand grading method. Then, it obtains the driver's demand power for each throttle position based on the vehicle's acceleration power requirements and acceleration level requirements. The driver's demand power distribution allows the engine to operate within its economic zone.

[0005] The technical solutions to the above problems are as follows:

[0006] The torque distribution method for a two-speed dual-motor HEV hybrid system includes the following steps:

[0007] S1, P demand power is calculated based on vehicle speed acceleration demand, and the maximum available power of the engine with power battery assistance P maximum power, the maximum available power of the engine without power battery assistance P maximum power, the upper limit of the engine's economic zone power P maximum power and the lower limit of the engine's economic zone power P minimum power, MG1 generator high-efficiency zone power, and MG2 drive motor high-efficiency zone power are calculated based on the vehicle speed acceleration demand under various hybrid modes.

[0008] S2, determine whether the current P demand is less than the maximum P assist power. If the result is yes, proceed to S3. Otherwise, if the current P demand is greater than the maximum P assist power, output the full throttle demand power.

[0009] S3, determine whether the current P demand is less than the maximum power of P without power assist. If the result is yes, proceed to S4; otherwise, when the maximum power of P without power assist is less than the current P demand is less than the maximum power of P with power assist, the P demand outputs the power range of the large throttle demand.

[0010] S4, determine whether the current P demand is less than the maximum power of the P economic zone. If the result is yes, proceed to S5; otherwise, when the maximum power of the P economic zone < the current P demand < the maximum power of P without power assist, the P demand output is in the throttle demand power range.

[0011] S5 determines whether the current P demand is less than the minimum power of the P economic zone. If the result is yes, that is, the current P demand is less than the minimum power of the P economic zone, the P demand output is within a smaller throttle demand power range.

[0012] This invention, based on the driver's power requirements, employs a four-level demand classification method (power demand, balance demand, economic demand, and charging demand) to differentiate the power ranges for high throttle, medium throttle, low throttle, and even lower throttle by assigning four power demands: P (maximum power assist), P (maximum power without power assist), P (maximum power in the economic zone), and P (minimum power in the economic zone). Simultaneously, based on the driver's required power at each speed and the vehicle's resistance power (calculated from factors such as wind resistance, ground resistance, and acceleration resistance), the invention obtains the vehicle acceleration at each speed, with 'a' representing maximum power assist, 'a' representing maximum power without power assist, 'a' representing maximum power in the economic zone, and 'a' representing minimum power in the economic zone. Appropriate power adjustments are made to the acceleration at different speeds at the same throttle position to ensure vehicle smoothness. Furthermore, the invention further subdivides the driver's required power at each speed and throttle position by considering the perceived acceleration at each speed and the maximum power demand at each throttle position (derived from the highest achievable speed at each throttle position).

[0013] This invention allocates power to each throttle position using a four-level demand classification method (power demand, balance demand, economy demand, and charging demand) under various hybrid operating conditions. It then determines the driver's power demand at each throttle position based on vehicle acceleration performance and acceleration feel requirements. This driver-demand power allocation ensures that the high-efficiency power zones of the engine, MG1 generator, and MG2 drive motor overlap and work together to improve system efficiency. When the high-efficiency power zones of each component in the hybrid system are allocated, the corresponding torque distribution is simultaneously completed. Attached Figure Description

[0014] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0015] like Figure 1 As shown, the torque distribution method for a two-speed dual-motor HEV hybrid system of the present invention includes the following steps:

[0016] S1, P demand power is calculated based on vehicle speed acceleration demand, and the maximum available power of the engine with power battery assistance P maximum power, the maximum available power of the engine without power battery assistance P maximum power, the upper limit of the engine's economic zone power P maximum power and the lower limit of the engine's economic zone power P minimum power, MG1 generator high-efficiency zone power, and MG2 drive motor high-efficiency zone power are calculated based on the vehicle speed acceleration demand under various hybrid modes.

[0017] S2, determine whether the current P demand is less than the maximum P assist power. If the result is yes, proceed to S3. Otherwise, if the current P demand is greater than the maximum P assist power, output the full throttle demand power.

[0018] S3, determine whether the current P demand is less than the maximum power of P without power assist. If the result is yes, proceed to S4; otherwise, when the maximum power of P without power assist is less than the current P demand is less than the maximum power of P with power assist, the P demand outputs the power range of the large throttle demand.

[0019] S4, determine whether the current P demand is less than the maximum power of the P economic zone. If the result is yes, proceed to S5; otherwise, when the maximum power of the P economic zone < the current P demand < the maximum power of P without power assist, the P demand output is in the throttle demand power range.

[0020] S5 determines whether the current P demand is less than the minimum power of the P economic zone. If the result is yes, that is, the current P demand is less than the minimum power of the P economic zone, the P demand output is within a smaller throttle demand power range.

[0021] Preferably, in step S1, the maximum power of P assistance is calculated in the following ways depending on the operating conditions:

[0022] Pure electric mode: P-assisted maximum power = P3 maximum power * ηP3;

[0023] Series boost: Maximum boost power of P = Maximum power of P3 * ηP3 = (Power of P1 * ηP1 + Maximum discharge of P battery * η battery) * ηP3;

[0024] P1 power = P engine's maximum power in the economic zone * η engine;

[0025] Parallel booster: P booster maximum power = P engine maximum * η engine + P battery maximum discharge * η battery * ηP;

[0026] In the above formulas, Passisted maximum power is the maximum usable power of the engine under the assistance of the power battery, P1 power is the power of the MG1 generator, P3 maximum power is the maximum power of the MG2 drive motor, Pdemand is the power demanded by the driver, Pbattery discharge maximum is the maximum power of battery discharge, Pbattery charging maximum is the maximum power of battery charging, ηP1 is the power generation efficiency of MG1, ηP3 is the power efficiency of the MG2 drive motor, ηbattery is the battery efficiency, ηengine is the engine efficiency, Pengine maximum is the upper limit of the engine's power output, that is, the maximum mechanical power that the engine can output when the operating range is not limited, ηP is the battery discharge efficiency, Pengine economic zone maximum power is the upper limit of the power output that the engine can stably output in the operating range with optimal fuel economy, and P is the engine power.

[0027] Preferably, in step S1, the maximum power of P without assistance is calculated in the following ways depending on the operating conditions:

[0028] Pure electric mode: P demand = P3 high-efficiency power zone * ηP3

[0029] Series range extender: P demand = P3 high-efficiency power zone * ηP3 = P1 high-efficiency power zone * ηP1 * ηP3

[0030] P1 power = P engine economic zone * η engine

[0031] Parallel direct drive: P demand = P engine maximum * η engine

[0032] In the above formulas, P1 is the power of MG1 generator, P3 is the power of MG2 drive motor, P demand is the power demand of the driver, ηP1 is the power generation efficiency of MG1 generator, ηP3 is the power efficiency of MG2 drive motor, η engine is the engine efficiency, and P is the engine power.

[0033] Preferably, in step S1, the maximum power of the P economic zone is calculated in the following ways depending on the operating conditions:

[0034] Pure electric mode: P demand = P3 high-efficiency power zone * ηP3

[0035] Series range extender: P demand = P3 high-efficiency power zone * ηP3 = P1 high-efficiency power zone * ηP1 * ηP3

[0036] P1 power = P engine economic zone upper limit * η engine

[0037] Parallel direct drive: P demand = P engine maximum economic zone * η engine

[0038] In the above formulas, P1 is the power of MG1 generator, P3 is the power of MG2 drive motor, P demand is the power demand of the driver, ηP1 is the power generation efficiency of MG1 generator, ηP3 is the power efficiency of MG2 drive motor, η engine is the engine efficiency, and P is the engine power.

[0039] Preferably, in step S1, the minimum power of the P economic zone is calculated in the following ways depending on the operating conditions:

[0040] Pure electric mode: P demand = P3 high-efficiency power zone * ηP3

[0041] Series charging: P demand = P3 high-efficiency power zone * ηP3 = P engine economic zone * η engine - P battery discharge

[0042] Parallel charging: P demand = P engine economic zone lower limit * η engine - P battery discharge

[0043] In the above formulas, P3 is the power of the MG2 drive motor, P demand is the power required by the driver, ηP3 is the efficiency of the MG2 drive motor, η engine is the engine efficiency, ηP is the battery discharge efficiency, P is the engine power, and P battery discharge is the battery discharge power.

[0044] In addition to the four-demand grading method mentioned above, the two-stage dual-motor HEV hybrid system can also adopt the following operating modes:

[0045] 1) Pure electric mode: The vehicle is driven by the P3 motor powered by the discharge of the power battery.

[0046] P demand = P3 power * ηP3;

[0047] 2) Series mode: The engine drives the P1 generator to generate electricity and the power battery to discharge, which together or separately supplies power to the P3 drive motor to drive the vehicle.

[0048] Series assist: The engine drives the P1 generator to generate electricity, and the power battery discharges to supply power to the P3 motor to drive the vehicle.

[0049] P demand = P3 power * ηP3 = (P1 power * ηP1 + P battery discharge * η battery) * ηP3;

[0050] P1 power = P engine * η engine;

[0051] Series range extender: The engine drives the P1 generator to generate electricity, which powers the P3 motor to drive the vehicle.

[0052] P demand = P3 power * ηP3 = P1 power * ηP1 * ηP3;

[0053] P1 power = P engine economic zone * η engine;

[0054] Series charging: The engine drives the P1 generator to generate electricity, which powers the P3 motor to drive the vehicle and simultaneously charges the power battery.

[0055] P demand = P3 power * ηP3 = (P1 power * ηP1 - P battery charging) * ηP3;

[0056] 3) Parallel mode: The vehicle is driven by the combined discharge of the engine and the power battery.

[0057] Parallel-assisted system: The vehicle is driven by a combination of the engine and the power battery.

[0058] P demand = P engine maximum * η engine + P battery discharge * η battery;

[0059] Parallel direct drive: The vehicle is driven directly by the engine;

[0060] P demand = P engine * η engine;

[0061] Parallel charging: The engine directly drives the vehicle while simultaneously charging the battery.

[0062] P demand = P engine * η engine - P battery charge;

[0063] In this model, the parameters are the same as those in the four-level demand classification method mentioned above, and will not be repeated here.

[0064] The above-mentioned four-demand classification method (power demand, balance demand, economy demand, and charging demand) based on driver power demand distinguishes the power ranges of high throttle, medium throttle, low throttle, and even lower throttle by categorizing P (maximum power assist), P (maximum power without power assist), P (maximum power in the economic zone), and P (minimum power in the economic zone) into four power demand categories. Simultaneously, based on the driver's power demand at each speed and the vehicle's resistance power (calculated from factors such as wind resistance, road resistance, and acceleration resistance), the vehicle acceleration at each speed is calculated, with a (maximum power assist), a (maximum power without power assist), a (maximum power in the economic zone), and a (minimum power in the economic zone). Appropriate power adjustments are made to the acceleration at different speeds at the same throttle position to ensure vehicle smoothness. The driver's power demand at each speed and throttle position is further subdivided by considering the acceleration feel at each speed and the maximum power demand at each throttle position (derived from the highest achievable speed at each throttle position).

[0065] Driver's power requirement is converted into driver's torque requirement:

[0066] Based on the vehicle speed and hybrid mode (pure electric, series, parallel), the power allocation for each component utilizes the engine's economical power range, the MG1 generator's high-efficiency power range, and the MG2 drive motor's high-efficiency power range as much as possible, maximizing the overlap of these three components' high-efficiency ranges to improve system efficiency. Due to the hybrid two-speed dual-motor structure, the MG1 generator speed has a certain speed ratio to the engine speed, and the MG2 drive motor speed has a certain speed ratio to the wheel speed. In parallel mode, the MG2 drive motor speed and engine torque can be converted into corresponding wheel-side torque through a certain speed ratio. Simultaneously, the two-speed dual-motor hybrid system, with its two gears, allows for two high-efficiency speed ranges for both the engine and generator through upshifting, improving overall fuel economy. Therefore, the power allocation for each component in the hybrid system is determined, and the corresponding torque allocation is completed simultaneously, ensuring the driver's required torque is met at the same time. Once the power demand of the engine, generator P1, and drive motor P3 is allocated, the total torque demand of the driver (wheel-side torque) can be obtained by converting the power and torque using the power-torque conversion formula: T=P*9550 / n, under a certain vehicle speed where the speeds of the engine, generator P1, and drive motor P3 are all determined.

[0067] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be described in more detail with reference to the accompanying drawings. The described embodiments are some, but not all, of the embodiments of the present invention. The embodiments described with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be simply construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for torque distribution in a two-gear dual-motor HEV hybrid system, characterized in that, Includes the following steps: S1, P demand power is calculated based on vehicle speed acceleration demand, and the maximum available power of the engine with power battery assistance P maximum power, the maximum available power of the engine without power battery assistance P maximum power, the upper limit of the engine's economic zone power P maximum power and the lower limit of the engine's economic zone power P minimum power, MG1 generator high-efficiency zone power, and MG2 drive motor high-efficiency zone power are calculated based on the vehicle speed acceleration demand under various hybrid modes. In step S1, the maximum power of P assistance is calculated in the following ways depending on the operating conditions: Pure electric mode: P-assisted maximum power = P3 maximum power * ηP3; Series boost: Maximum boost power of P = Maximum power of P3 * ηP3 = (Power of P1 * ηP1 + Maximum discharge of P battery * η battery) * ηP3; P1 power = P engine's maximum power in the economic zone * η engine; Parallel booster: P booster maximum power = P engine maximum * η engine + P battery maximum discharge * η battery * ηP; In the above formulas, Passisted maximum power is the maximum usable power of the engine under the assistance of the power battery, P1 power is the power of the MG1 generator, P3 maximum power is the maximum power of the MG2 drive motor, Pbattery discharge maximum is the maximum discharge power of the battery, ηP1 is the power generation efficiency of MG1, ηP3 is the power efficiency of the MG2 drive motor, ηbattery is the battery efficiency, ηengine is the engine efficiency, Pengine maximum is the upper limit of the engine's power output, that is, the maximum mechanical power that the engine can output when the operating range is not limited, ηP is the battery discharge efficiency, and Pengine economic zone maximum power is the upper limit of the power value that the engine can stably output in the operating range with optimal fuel economy. S2, determine whether the current P demand is less than the maximum P assist power. If the result is yes, proceed to S3. Otherwise, if the current P demand is greater than the maximum P assist power, output the full throttle demand power. S3, determine whether the current P demand is less than the maximum power of P without power assist. If the result is yes, proceed to S4; otherwise, when the maximum power of P without power assist is less than the current P demand is less than the maximum power of P with power assist, the P demand outputs the power range of the large throttle demand. S4, determine whether the current P demand is less than the maximum power of the P economic zone. If the result is yes, proceed to S5; otherwise, when the maximum power of the P economic zone < the current P demand < the maximum power of P without power assist, the P demand output is in the throttle demand power range. S5 determines whether the current P demand is less than the minimum power of the P economic zone. If the result is yes, that is, the current P demand is less than the minimum power of the P economic zone, the P demand output is within a smaller throttle demand power range.

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