A method of preventing unintended acceleration control in a dual planetary row hybrid vehicle

Abstract

The application discloses a kind of prevent double planetary row structure hybrid vehicle unintended acceleration control method, specifically includes: parking power generation working condition, driver needs deep brake pedal to enter parking power generation mode, can avoid the security risk caused by unintended acceleration when parking power generation.Driving working condition, considering the influence of the chargeable capacity of current battery, the driving and braking capacity of MG2, the demand power of driver and other factors, the power of engine is corrected in real time, so as to avoid the occurrence of unintended acceleration condition in driving working condition.Braking working condition, considering the influence of the chargeable capacity of current battery, the demand power of driver, the power generation capacity of MG2 and other factors, when the power of engine cannot be converted into electric power by MG2 and MG1, timely set the power correction factor of engine to 0, prohibit engine power output, avoid the unintended acceleration of vehicle caused by the power of engine mechanical path in braking working condition, improve driving safety.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of vehicle control, and particularly relates to a method for preventing unintended acceleration control of a double planetary row structure hybrid vehicle. BACKGROUND

[0002] The planetary gear mechanism is compact and flexible, and is a power coupling and splitting device with three input (output) ports and two degrees of freedom. The double planetary row hybrid system has the advantages of simple structure and stepless speed change function, and the engine and transmission shaft are decoupled, so that the engine can always work in the economic zone. For the bus working condition of frequent start-stop and low average speed, it is a good hybrid power technology route. However, due to the two degrees of freedom of the power system, the energy management of the double planetary row system has always been a hot and difficult point of research.

[0003] The double planetary row hybrid system decouples the engine and the transmission shaft, so that part of the power of the engine is transmitted to the output shaft through a mechanical path, and part of the power of the engine is used to charge the battery or drive the vehicle to run through an electric power path, reducing the multiple conversion of energy. Compared with the series plug-in hybrid system, it has better economy. However, for the double planetary row structure hybrid system, the mechanical structure determines that the power of the engine must have two transmission paths, one is a mechanical path, and the other is an electric path. When the power of the mechanical path is greater than the required driving power of the driver, it will cause the risk of unintended acceleration of the vehicle, which seriously affects the driving safety. The existing method basically explains the energy management method of the double planetary row system from the perspective of how to improve the efficiency of the engine, but few related documents involve the influence of the torque of the engine mechanical path on driving safety and how to avoid the occurrence of unintended acceleration conditions caused by the torque of the engine mechanical path. SUMMARY

[0004] The present application is proposed to solve the above problems, and provides a method for preventing unintended acceleration of a double planetary row structure hybrid vehicle. The method can adjust the output power of the engine in real time under various working conditions such as parking power generation, driving and braking, so as to adjust the torque of the engine mechanical path in real time, effectively avoid the driving torque of the engine mechanical path from being used to drive the vehicle to run, and greatly improve the driving safety of the double planetary row structure hybrid vehicle. The control method is used on the double planetary row hybrid system.

[0005] The double planetary hybrid system specifically comprises: the sun gear S1 of the planetary gear set I is connected with the adjusting motor, the carrier C1 of the planetary gear set I is connected with the engine, the ring gear R1 is connected with the carrier C2 of the planetary gear set II, the sun gear S2 of the planetary gear set II is connected with the driving motor, the outer ring gear R2 is connected with the vehicle frame, the main function of the adjusting motor is to adjust the engine operating point, the driving motor is mainly used for driving, and the power of the engine and the driving motor is coupled through R1 and the carrier C2 and then output to the vehicle wheel through the main reducer;

[0006] Different control strategies are adopted based on different working conditions, and specifically include:

[0007] In the parking power generation working condition, and after the vehicle meets the necessary conditions of the parking power generation mode, when it is detected that the brake pedal opening is greater than the opening threshold and the duration is greater than the time threshold, the parking power generation mode is entered, otherwise the parking power generation mode is prohibited.

[0008] In the driving working condition, and when the vehicle is in the hybrid mode, when it is detected that the engine target power is greater than the sum of the demand power and the maximum charging power P BatMaxChrg of the battery, and / or the driving motor fails, and / or the battery cell voltage exceeds the threshold, the power correction factor K of the engine is calculated, the target power of the engine is corrected, and the power of the engine mechanical path is less than or equal to the demand power of the driver until the power of the engine mechanical path is less than or equal to the demand power of the driver.

[0009] In the braking working condition, when it is detected that the sum of the engine power and the demand braking power of the driver is greater than the maximum charging power P BatMaxChrg of the battery, and / or the driving motor fails, and / or the battery cell voltage exceeds the threshold, the power correction factor K of the engine is calculated and K is set to 0, so that the engine power output is prohibited, and unintended acceleration is prevented.

[0010] Further, the parking power generation working condition refers to that the electric quantity of the high-voltage battery is low after the vehicle is parked stably, and the high-voltage battery is charged by using the engine power under the condition that no external charging gun is connected. In the parking power generation working condition, the detection method that the brake pedal opening is greater than the opening threshold and the duration is greater than the time threshold specifically comprises: when the vehicle meets the necessary conditions of the parking power generation mode, whether the brake pedal opening is greater than the opening threshold is detected; if not, the parking power generation mode is prohibited, if yes, whether the duration that the brake pedal opening is greater than the opening threshold is greater than the time threshold is continuously detected; if yes, the parking power generation mode is entered, if not, the parking power generation mode is prohibited, and the necessary conditions of the parking power generation mode specifically comprise that the driver pulls the handbrake and / or deeply presses the brake pedal, selects the forward gear, and presses the climbing switch for 3 times within 4s.

[0011] The calculation of the power correction factor K of the engine specifically comprises that the power difference between the engine mechanical path power and the target power of the driver is obtained by table lookup.

[0012] Further, the driving condition includes two conditions of pure electric driving and hybrid mode driving, in the pure electric condition, since the engine is stopped, the power and torque without mechanical path are output to the transmission shaft, in the hybrid mode, the engine is started and works with a certain power to drive the vehicle or charge the power battery, the engine will have the torque and power with mechanical path output to the transmission shaft. In the driving condition, further comprising: according to the required power P Drv calculating the target power P Eng,raw of the engine; if P Drv is less than P Eng,raw , further calculating the power P Eng,M with mechanical path of the engine at this time; if P Eng,M at this time is greater than P Drv , detecting whether the target power of the engine is greater than the sum of the required power and the maximum charging power P BatMaxChrg of the battery, whether the motor MG2 is faulty and the battery cell voltage.

[0013] Further, the braking condition refers to the condition that the driver releases the accelerator pedal, the vehicle is sliding or braking. In the braking condition, further comprising: if the engine power is not 0, detecting whether the sum of the engine power and the required braking power of the driver is greater than the maximum charging power P BatMaxChrg of the battery, whether the driving motor is faulty and the battery cell voltage.

[0014] The beneficial effects of the present application: the present application elaborates the control method for preventing the unintended acceleration of the double planetary row structure hybrid vehicle in the three conditions of parking power generation, driving and braking. The method considers the influence of various factors such as the current required power of the driver, the chargeable capacity of the battery, the driving and braking capacity of the driving motor, etc., and corrects the target power of the engine in real time, to avoid the condition that the power with mechanical path of the engine is greater than the required driving power of the driver. The method is verified by the real vehicle, which is not only feasible, but also greatly improves the driving safety of the double planetary row structure hybrid vehicle, and can effectively avoid the occurrence of the unintended acceleration condition. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on the drawings shown.

[0016] Figure 1 It is a structure diagram of the double planetary row hybrid system.

[0017] Figure 2 Control method flow chart for parking power generation working condition.

[0018] Figure 3 Control method flow chart for driving working condition.

[0019] Figure 4 Control method flow chart for braking working condition. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0021] The structure of the double planetary row hybrid power system is shown in Figure 1 The sun gear S1 of the planetary row I is connected with the regulating motor MG1, the carrier C1 is connected with the engine, and the ring gear R1 is connected with the carrier C2 of the planetary row II. The sun gear S2 of the planetary row II is connected with the driving motor MG2, and the outer ring gear R2 is connected with the vehicle frame. The structure is a typical input power split type hybrid power system, the main function of the motor MG1 is to regulate the engine operating point, and the driving motor MG2 is mainly used for driving. The power of the engine and the driving motor MG2 is coupled through the ring gear R1 and the carrier C2 and then output to the vehicle wheel through the main reducer. The characteristic parameter of the planetary row I of the double planetary row system is k1, and the characteristic parameter of the planetary row II is k2.

[0022] The double planetary row system is a typical power split type hybrid power topology structure. The real-time power of the engine is distributed in two paths. A part of the power is directly transmitted to the driving wheel through the meshing of the planetary gear, and this path is called the mechanical path. Another part of the power is transmitted to the regulating motor MG1 through the sun gear S1, and the regulating motor MG1 converts this part of the power into electrical energy, and this path is called the electrical path. The engine speed and the vehicle speed are decoupled, but the proportional relationship between the power of the engine mechanical path and the power of the electrical path changes in real time with the change of the vehicle speed.

[0023] In the free state, the relationship between the engine mechanical path torque and the electrical path torque is:

[0024]

[0025] T S —Sun gear torque; T R —Carrier torque; T H —Outer ring gear torque, k—Characteristic parameter of planetary row.

[0026] The relationship between the mechanical path power of the engine and the electric path power is:

[0027]

[0028] In the formula: λ - power separation factor, P R1 - mechanical path power; P eng - engine power; T eng - engine torque; i - main reducer speed ratio, v - vehicle speed; n eng - engine speed; k1 - planetary gear set I characteristic parameter, r - wheel radius.

[0029] From the above formula (2), when the engine speed is constant, the higher the vehicle speed, the greater the mechanical path power; when the vehicle speed is constant, the lower the engine speed, the greater the mechanical path power. Although the mechanical path power and the electric path power are proportional to each other in real time, during driving, a part of the engine power must be transmitted to the drive shaft through the mechanical path.

[0030] In addition, for a hybrid vehicle with a double planetary gear set structure, there are two power sources, a high-voltage battery and an engine. When driving, if the driver's demand power is higher than the maximum discharge power of the battery, the engine starts, and a part of the engine power is directly used to drive the vehicle through the mechanical path; another part is converted into electric energy by the adjusting motor MG1 and then converted into mechanical energy by the drive motor MG2 to drive the vehicle. When braking, the drive motor MG2 recovers the braking energy, and if the engine is still driving at this time, a part of the engine power is transmitted to the drive motor MG2 through the mechanical path and converted into electric power by the drive motor MG2 to charge the battery; another part is converted into electric energy by the adjusting motor MG1 and directly charges the battery. However, regardless of the working condition, the given target power of the engine needs to consider the influence of various factors such as the current driver's demand power, the charge and discharge capacity of the battery, the power generation capacity of the adjusting motor MG1, the driving and power generation capacity of the drive motor MG2, etc., to ensure that the total power of the engine meets the current driver's demand and the charging demand of the high-voltage battery, and prevent the occurrence of unexpected acceleration conditions.

[0031] The present application adopts different control methods based on different working conditions to prevent the occurrence of vehicle unexpected acceleration caused by the mechanical path power of the engine. The following will elaborate the control method of preventing vehicle unexpected acceleration from three working conditions: parking power generation condition, driving condition and braking condition.

[0032] (1) Parking power generation condition

[0033] The parking power generation refers to that when the vehicle is parked, the electric quantity of the high-voltage battery is low, and the high-voltage battery is charged by using the engine power without external charging gun. As can be seen from formula (1), when the parking power generation, the engine has no mechanical path power because the vehicle speed is 0, but the mechanical path torque is directly transmitted to the transmission shaft, and then the vehicle can be driven to run.

[0034] The control method flow chart of the parking power generation working condition is shown in Figure 2 The necessary conditions for triggering the vehicle to enter the parking power generation mode include that the driver pulls the hand brake or deeply presses the brake pedal, selects the forward gear, and continuously presses the hill start switch for 3 times within 4 seconds. After the above conditions are met, the driver needs to deeply press the brake pedal to reach a time threshold N seconds, the drive motor MG1 starts the engine, the engine drives the regulating motor MG1 to generate power at a certain power, if the driver releases the brake pedal within N seconds, the parking power generation mode is exited; otherwise, after N seconds, the driver can release the brake pedal, and the engine can still charge the battery.

[0035] According to the above control method, first, after the hand brake is pulled, the driver needs to deeply press the brake pedal within N seconds to allow the engine to start and perform parking charging. Since the driver deeply presses the brake pedal and pulls the hand brake, it can be ensured that the mechanical path torque of the engine cannot drive the vehicle during the engine starting process and the power generation process, thereby preventing unintended acceleration. On the other hand, when the hand brake is broken, if the driver releases the brake pedal after N seconds, the mechanical path torque of the engine will drive the vehicle to run, but this phenomenon can obviously alert the driver to remind the driver to immediately exit the parking charging mode.

[0036] Therefore, by using the above control method, the unintended acceleration of the vehicle can be effectively prevented when the hand brake is normal, and the driver can be alerted to exit the parking power generation mode in time when the hand brake is broken, thereby ensuring the torque safety of the vehicle in the parking power generation working condition.

[0037] (2) Driving working condition

[0038] The driving working condition includes two working conditions of pure electric driving and hybrid mode driving. In the pure electric working condition, the engine is stopped, so there is no mechanical path power and torque output to the transmission shaft. In the hybrid mode, the engine is started and works at a certain power to drive the vehicle or charge the power battery, and the engine will necessarily have mechanical path torque and power output to the transmission shaft. In this working condition, if the mechanical path torque of the engine is greater than the required torque of the driver, there will be a risk of torque out of control, which will cause the vehicle to accelerate unintentionally and seriously threaten the driving safety of the vehicle.

[0039] When the engine starts, its target power output needs to consider multiple factors, including the battery's charging and discharging power, the driver's power demand, and the electric motor's driving capability. When the driver's power demand exceeds the engine's actual power, a portion of the engine's power directly drives the vehicle via a mechanical path; the other portion is converted into electrical energy by the regulating motor MG1 and used by the drive motor MG2 to also drive the vehicle. Simultaneously, the power battery discharges, meaning the engine and the power battery work together to drive the vehicle and meet the driver's power needs. When the driver's power demand is less than the engine's actual power, if the engine's mechanical path power is also greater than the driver's power demand, the excess mechanical path power must be absorbed by the drive motor MG2, converting it into electrical power to charge the high-voltage battery; the engine's electrical path power is converted into electrical energy by the regulating motor MG1 to charge the high-voltage battery. If the power of the engine's mechanical path is less than the driver's required power, then all the power from the engine's mechanical path will be used to drive the vehicle. Simultaneously, the drive motor MG2 absorbs the electrical power from the regulating motor MG1 to propel the vehicle and meet the driver's needs. The power from the engine's electrical path is converted into electrical energy by the regulating motor MG1. Part of this electrical energy is absorbed by the drive motor MG2 to drive the vehicle, and the other part is used to charge the high-voltage battery. Therefore, for a hybrid system with a dual planetary gear set structure, energy distribution is both a key focus and a challenge. Improper energy distribution can lead to power from the engine's mechanical path being transferred to the transmission shaft, creating a safety hazard.

[0040] The flowchart of the control method for preventing unintended acceleration under driving conditions is as follows: Figure 3 As shown, based on the driver's required power P Drv Calculate the target power P of the engine Eng,raw If P Drv Greater than P Eng,raw If P Drv Less than P Eng,raw Then, the power P of the engine's mechanical path at this time can be further calculated. Eng,M If P at this time Eng,M Greater than P Drv The remaining power in the engine's mechanical path must be converted into electrical power by the drive motor MG2; otherwise, unintended acceleration will occur. Simultaneously, the power in the engine's electrical path is converted into electrical power by the regulating motor MG1. Therefore, if P... Drv Greater than P Eng,raw At this time, the drive motor MG2 must be operating normally, and the battery must be rechargeable. This is achieved when any one of the following conditions is met: the engine's target power is greater than the required power and the battery's maximum charging power P. BatMaxChrgWhen the sum of the engine power and the driver's demand braking power is greater than the maximum charging power of the battery, the drive motor MG2 fails, or the battery cell voltage is high, the engine power correction flag C is set to 1. When the power correction flag C is 1, the engine power correction factor K is calculated in real time, the target power of the engine is corrected, and the power of the engine mechanical path is less than or equal to the demand power of the driver. The power correction factor K is obtained by table lookup according to the power difference between the engine mechanical path power and the driver target power. By adopting the above reasonable control strategy, the occurrence of the unintended acceleration condition of the vehicle in the driving condition can be effectively prevented.

[0041] (3) Braking condition

[0042] The braking condition refers to the condition that the driver releases the accelerator pedal and the vehicle is sliding or braking. If the engine mechanical path still has power output at this time, and the power of the mechanical path is greater than the power of the braking feedback, it will inevitably lead to the vehicle driving rather than braking, which completely violates the driving intention of the driver and seriously endangers the driving safety. In order to prevent the occurrence of the above abnormal condition, a reasonable control strategy must be adopted to avoid the dangerous condition.

[0043] The control method flow chart for preventing unintended acceleration of the vehicle in the braking condition is shown in Figure 4 If the engine power P Eng,Act is not 0, the power of the engine must be completely converted into electrical energy to charge the battery. The power of the engine mechanical path must be absorbed by the drive motor MG2 and converted into electrical energy, and the power of the engine electrical path must be converted into electrical energy by the adjusting motor MG1. Whether it is the electrical path power or the mechanical path power, it will eventually charge the high-voltage battery. As can be seen, to achieve the above energy conversion, the high-voltage battery must be chargeable, and the drive motor MG2 must be able to generate electricity. Therefore, when any one of the following three conditions is met: the sum of the engine power and the driver's demand braking power is greater than the maximum charging power of the battery, the drive motor MG2 fails, and the battery cell voltage is high, the engine power correction flag C needs to be calculated. If C is 1, the power correction factor K of the engine is further calculated, and K is set to 0, thereby prohibiting the engine power output and preventing unintended acceleration.

[0044] The control method described in the present application is not only feasible, but also greatly improves the driving safety of the double planetary row structure hybrid vehicle, and can effectively avoid the occurrence of the unintended acceleration condition.

[0045] In accordance with the practices of the present invention, these embodiments have been described in relation to the above-described embodiments, which are intended to be illustrative only and not restrictive of the invention. Numerous modifications and adaptations will be apparent to those skilled in the art. Selection of the appropriate methodology to employ will be made by the artisan in view of what is known of the art, or can be made using routine optimization. The selection of such determinations is well within the purview of the skilled artisan. The description is thus to be considered as given for purposes of illustration and description, and not for purposes of limitation. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method of preventing unintended acceleration control in a dual planetary row architecture hybrid vehicle, characterized by, The control method is used on a double planetary row hybrid power system, and different control strategies are adopted based on different working conditions, and specifically includes the following steps: In the parking power generation working condition, and after the vehicle meets the necessary conditions of the parking power generation mode, when it is detected that the brake pedal opening is greater than the opening threshold and the duration is greater than the time threshold, the parking power generation mode is entered, otherwise the parking power generation mode is prohibited; In the driving working condition, and when the vehicle is in the hybrid mode, if it is detected that the engine target power is greater than the sum of the demand power and the maximum charging power P BatMaxChrg of the battery, and / or the driving motor fails, and / or the battery cell voltage exceeds a threshold value, a power correction factor K of the engine is calculated, the target power of the engine is corrected until the power of the engine mechanical path is less than or equal to the demand power of the driver; In braking conditions, when the sum of the engine power and the driver demanded braking power is greater than the maximum battery charging power P BatMaxChrg , and / or the drive motor is faulty, and / or the battery cell voltage exceeds a threshold value, a power correction factor K of the engine is calculated and set to 0, thus inhibiting the engine power output, preventing unintended acceleration; Under the aforementioned driving conditions, it also includes: power P based on the driver's required power. Drv Calculate the target power P of the engine Eng,raw If P Drv Less than P Eng,raw Then, the power P of the engine's mechanical path at this time can be further calculated. Eng,M If P at this time Eng,M Greater than P Drv Then, it checks whether the engine's target power is greater than the required power and the battery's maximum charging power P. BatMaxChrg The sum of these factors, including whether the drive motor is faulty and the voltage of each individual battery cell.

2. The method of claim 1, wherein, In the parking power generation working condition, the detection method that the brake pedal opening is greater than the opening threshold and the duration is greater than the time threshold is specifically as follows: when the vehicle meets the necessary conditions of the parking power generation mode, whether the brake pedal opening is greater than the opening threshold is detected; if not, the parking power generation mode is prohibited, and if yes, whether the duration that the brake pedal opening is greater than the opening threshold is greater than the time threshold is continuously detected; if yes, the parking power generation mode is entered, otherwise the parking power generation mode is prohibited.

3. The method of claim 2, wherein, The necessary conditions of the parking power generation mode are specifically that the driver pulls the handbrake and / or steps on the brake pedal, selects the forward gear, and presses the hill start switch for 3 times within 4 seconds.

4. The method of claim 2, wherein, The parking power generation working condition is that the vehicle is parked, the high-voltage battery has low power, and the engine power is used to charge the high-voltage battery without external charging gun.

5. The method of claim 1, wherein, The driving working condition includes pure electric driving and hybrid mode driving.

6. The method of claim 1, wherein, In the braking mode, further comprising: if the engine power is not 0, detecting whether the sum of the engine power and the driver demand braking power is greater than the maximum charging power P of the battery BatMaxChrg , whether the drive motor is faulty and the battery cell voltage.

7. The method of claim 6, wherein, The braking working condition is a working condition in which the driver releases the accelerator pedal, and the vehicle is sliding or braking.

8. The method according to any one of claims 1 to 7, characterized in that, The power correction factor K of the engine is specifically obtained by table lookup according to the power difference between the engine mechanical path power and the driver target power.

9. The method according to any one of claims 1 to 7, characterized in that, The double planetary row hybrid power system includes that the sun gear S1 of the planetary row I is connected with the adjusting motor, the carrier C1 of the planetary row I is connected with the engine, the ring gear R1 is connected with the carrier C2 of the planetary row II, the sun gear S2 of the planetary row II is connected with the driving motor, the outer ring gear R2 is connected with the vehicle frame, and the main function of the adjusting motor is to adjust the engine operating point. The power of the engine and the driving motor is coupled through the ring gear R1 and the carrier C2 and then output to the vehicle wheel through the main reducer.

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