A hub hydraulic hybrid vehicle shift power interruption-free coordination control method

Abstract

The application provides a hub hydraulic hybrid vehicle gear shifting non-power interruption coordination control method, aiming at overcoming the problem of power interruption in the gear shifting process of a hub hydraulic hybrid system. The control method comprises the following steps: S1, judging the allowable working mode of the gear shifting non-power interruption coordination control; S2, judging the condition of the gear shifting non-power interruption coordination control; S3, calculating the torque compensation amount of the front axle hub hydraulic motor in the gear shifting process; and S4, setting the torque compensation change amount limit threshold of the hub hydraulic motor. Based on the power ground coupling characteristics of the hub hydraulic hybrid vehicle, the application effectively eliminates the system power interruption phenomenon in the gear shifting process of the intermediate shaft gearbox, improves the driving power and smoothness of the vehicle, further consumes hydraulic energy in the vehicle driving process, ensures that the high-pressure accumulator has more energy storage space for the potential next brake recovery, fully utilizes the redundancy driving characteristics of the hub hydraulic hybrid power, and improves the comprehensive quality of the hybrid vehicle.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hub hydraulic hybrid vehicle control, and particularly relates to a power interruption-free coordination control method for gear shifting process of hub hydraulic hybrid vehicle. BACKGROUND

[0002] The driving condition of commercial vehicle is more complex than that of passenger vehicle, and it often works on low adhesion road surface such as mountain road, soft road in the countryside, ice and snow road surface, etc. The traditional all-wheel drive form can improve the passability of vehicle on low adhesion road surface, but the parasitic power brought by it has certain influence on the economy of vehicle. The hub hydraulic hybrid system drives timely all-wheel, which can not only significantly improve the passability of vehicle on low adhesion road surface, but also can realize regenerative braking energy recovery through accumulator when the vehicle brakes to improve the economy of vehicle, and can improve the braking safety through hydraulic auxiliary braking. In addition, compared with oil-electric hybrid system, the hub hydraulic hybrid system has the advantages of high power density, small mass and volume, low comprehensive cost, etc. However, the engine driving power chain of hub hydraulic hybrid system is interrupted in the gear shifting process of multi-gear transmission, which is similar to traditional fuel vehicle, resulting in the power interruption of vehicle driving system, and the output torque of vehicle is lower than the expected torque of driver in the gear shifting moment, which is not conducive to the power performance of vehicle, and also affects the smoothness and comfort of vehicle driving. Therefore, in order to give full play to the advantages of hub hydraulic hybrid driving, it is necessary to design a gear shifting power interruption-free coordination control method for the power interruption problem of hub hydraulic hybrid system in gear shifting process.

[0003] In the prior art, there are few invention patents related to the shift coordination control technology of the hub hydraulic hybrid power system. For example, the invention patent with the publication number CN113771834A, which was published on December 10, 2021, provides a hub hydraulic hybrid commercial vehicle power domain system architecture scheme and proposes a method for dynamic coordination control in the power domain during the shift process to make up for the lack of coordination control of the hub hydraulic hybrid vehicle multi-power source and AMT. However, the invention patent only qualitatively outlines the hub hydraulic motor torque compensation target and does not propose a specific control method, and does not consider the actual output torque of the engine affected by accessories, which has poor practical application value. For another example, the invention patent with the publication number CN115126832A, which was published on September 30, 2022, is a double-motor planetary gear hybrid power transmission, and the invention patent with the publication number CN114771235A, which was published on July 22, 2022, is a hybrid power drive device for a hybrid electric vehicle and a control method thereof. The hybrid power system drive and transmission device proposed in the above invention patents can realize a no-power interruption shift process through multi-power source cooperation, but there are significant differences between the vehicle objects and drive system configurations applied in the invention patent and the above invention patents. The above invention patents use multi-power source power to timely couple and drive a single drive shaft, while the hub hydraulic hybrid power dual power sources are timely coupled to the ground to drive respective drive shafts. Therefore, the no-power interruption shift process realized by the above invention patents does not have reference value for the hub hydraulic hybrid vehicle research object. SUMMARY

[0004] To solve the problems in the prior art, the present application provides a shift no-power interruption coordination control method for a hub hydraulic hybrid vehicle, which fully utilizes the ground coupling characteristics of the multi-power source power of the hub hydraulic hybrid vehicle and the rapid response characteristics of the hub hydraulic motor, effectively eliminates the phenomenon of obvious system power interruption during the shift process of the intermediate shaft transmission, improves the vehicle driving power and smoothness, and further consumes the stored hydraulic energy of the vehicle during vehicle driving, thereby ensuring more energy storage space for the high-pressure accumulator for potential next brake recovery, optimizing system energy consumption, improving vehicle fuel economy, fully utilizing the redundancy driving characteristics of the hub hydraulic hybrid power, and improving the overall quality of the hybrid electric vehicle.

[0005] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0006] Step one, judging the allowable working mode of the shift no-power interruption coordination control,

[0007] The application is a kind of wheel hub hydraulic hybrid vehicle, in which the middle axle and rear axle are driven by an engine, the power of the engine is transmitted to the output of the middle axle and rear axle drive axle through a multi-gear automatic transmission, the front axle is driven by a hydraulic system and a wheel hub hydraulic motor, and the middle axle transmission mechanism has power interruption during gear shifting when the wheel hub hydraulic hybrid vehicle is driven in engine direct drive, running with liquid filling, and combined drive modes. When the wheel hub hydraulic hybrid vehicle is driven in the running with liquid filling mode, the wheel hub hydraulic motor responds to the negative working torque, and the selected gear shifting without power interruption coordination control allowable working mode is engine direct drive and combined drive modes to avoid frequent positive and negative mutations of the working torque of the wheel hub hydraulic motor.

[0008] Step two, judging the gear shifting without power interruption coordination control condition,

[0009] When the vehicle controller of the wheel hub hydraulic hybrid vehicle receives a hard-wired signal that the pure fuel mode switch is not enabled, and when the vehicle controller receives a vehicle speed signal that the vehicle speed is higher than the minimum stable vehicle speed for engine starting, and when the vehicle controller receives a battery management system feedback power battery state of charge SOC signal value that is higher than the allowable lower limit value of the power battery state of charge SOC, and when the vehicle controller receives a middle axle transmission mechanism control unit feedback signal that the middle axle transmission mechanism is in the gear shifting process, the gear shifting without power interruption coordination control is performed. Otherwise, the gear shifting without power interruption coordination control is not performed or is exited.

[0010] Step three, calculating the front axle wheel hub hydraulic motor torque compensation amount during gear shifting,

[0011] In the allowable working mode of the gear shifting without power interruption coordination control, the engine outputs the required driving energy for the wheel hub hydraulic hybrid vehicle, and also provides power or energy for the related accessories of the wheel hub hydraulic hybrid vehicle, and at the same time, the idle state of the engine itself must be maintained. Therefore, according to formula (1), the current actual torque T eng_real of the engine is directly used as the current engine actual power output reference value T eng , the compensation torque amount T Com of the front axle wheel hub hydraulic motor during gear shifting is small, and even negative torque is compensated. Based on this, the current actual torque T eng_real of the engine and the current requested torque T eng_ask of the engine are comprehensively considered to calculate the compensation torque during gear shifting, and the compensation torque amount T Com of the front axle wheel hub hydraulic motor during gear shifting is calculated.

[0012] T com = T ask -T eng..................................... (1)

[0013] T eng = x · T eng_real + (1 - x) · T eng_ask ........................ (2)

[0014] In the formula, T ask is the total demand torque for driving the vehicle, and x is an engine torque adjustment coefficient for the transfer case shift process. The engine torque adjustment coefficient x continuously changes within a sustained step after entering the shift process, and the specific value is determined according to actual calibration tests.

[0015] Step four, calibrate the wheel hub hydraulic motor torque compensation change limit threshold,

[0016] After solving the front axle wheel hub hydraulic motor torque compensation amount before the shift process, the wheel hub hydraulic motor torque compensation amount is not limited, and the final output torque of the wheel hub hydraulic motor may jump, which further deteriorates the ride comfort of the wheel hub hydraulic motor torque compensation process. Therefore, in the actual torque compensation process of the wheel hub hydraulic motor, the wheel hub hydraulic motor feedback current actual torque T mot_real is introduced, and the demand wheel hub hydraulic motor torque compensation change amount ΔT com is calculated every step.

[0017] ΔT com = T com - T mot_real ......................................... (3)

[0018] If ΔT com is too large, the fast response characteristics of the wheel hub hydraulic motor will cause the wheel hub hydraulic hybrid vehicle to present strong longitudinal impact and poor comfort, and if ΔT com is too small, the power interruption phenomenon of the transfer case shift process cannot be completely eliminated, so the wheel hub hydraulic motor torque compensation change amount is further limited as shown in formula (4),

[0019] ΔT Lo ≤ ΔT com ≤ ΔT Hi ...................................... (4)

[0020] In the formula, ΔT LoThe wheel hub hydraulic motor torque compensation amount per step length decrease limit threshold, ΔT Hi The wheel hub hydraulic motor torque compensation amount per step length increase limit threshold, the specific value is determined according to actual calibration test.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] 1. The wheel hub hydraulic hybrid vehicle gear shifting power interruption free coordination control method realizes the engine driving power cut-off during the intermediate shaft gearbox shifting process, effectively eliminates the obvious interruption of system power, makes the vehicle output driving torque meet the driver's expected torque, and improves the power and smoothness of vehicle driving.

[0023] 2. The wheel hub hydraulic hybrid vehicle gear shifting power interruption free coordination control method realizes further consumption of the vehicle stored hydraulic energy during vehicle driving, ensures that the high-pressure accumulator has more energy storage space for the next potential brake recovery, optimizes the energy consumption of the system, and further improves the fuel economy of the vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0024] The description of the embodiments will become easy to understand below in combination with the drawings, in which:

[0025] Figure 1 The figure is a schematic diagram of the power system structure of the wheel hub hydraulic hybrid vehicle according to the embodiment of the present application.

[0026] Figure 2 The figure is a schematic diagram of the gear shifting power interruption free coordination control process of the wheel hub hydraulic hybrid vehicle according to the embodiment of the present application.

[0027] Figure 1 The figure is a schematic diagram of the power system structure of the wheel hub hydraulic hybrid vehicle according to the embodiment of the present application. DETAILED DESCRIPTION

[0028] The embodiments of the present application will be described in detail below, and the examples of the embodiments are shown in the drawings, in which the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0029] A wheel hub hydraulic hybrid vehicle gear shifting power interruption free coordination control method will be described below with reference to the drawings, but the present application is not limited to these embodiments.

[0030] Step one, the judgment of the allowable working mode of the shift without power interruption coordination control,

[0031] For a kind of hub hydraulic hybrid vehicle, refer to the attached Figure 1 The hub hydraulic hybrid vehicle mainly includes the following components and assemblies: 1 front axle wheel, 2 hub hydraulic motor, 3 accumulator, 4 power domain controller, 5 intermediate axle wheel, 6 rear axle wheel, 7 main reducer and differential assembly, 8 universal joint, 9 multi-gear AMT assembly, 10 power take-off, 11 engine assembly, 12 hydraulic variable pump, 13 hydraulic combination valve assembly. Refer to the attached Figure 1 It can be seen that the intermediate axle and the rear axle of the hub hydraulic hybrid vehicle are driven by the 11 engine assembly, the engine power is transmitted to the intermediate axle and the rear axle drive axle output through the 9 multi-gear AMT assembly, and the front axle is driven by the hydraulic drive system and the 2 hub hydraulic motors. When the hub hydraulic hybrid vehicle is driven to travel in the engine direct drive ICE, the on-the-road liquid filling CHEV, and the combined driving HHEV three driving modes, there is power interruption in the multi-gear AMT shift process. When the hub hydraulic hybrid vehicle is driven to travel in the on-the-road liquid filling CHEV mode, the hub hydraulic motor responds to the negative working torque. In order to avoid frequent positive and negative mutations of the hub hydraulic motor working torque, the allowable working mode of the shift without power interruption coordination control is selected as the engine direct drive ICE and the combined driving HHEV two driving modes, and the judgment condition is referred to the attached Figure 2 Step one.

[0032] Step two, the judgment of the condition of the shift without power interruption coordination control,

[0033] When the vehicle controller of the hub hydraulic hybrid vehicle receives the hard-wired signal that the pure fuel mode switch is not enabled Button ICE = 0, and when the vehicle controller receives the vehicle travel speed u higher than the minimum stable vehicle speed u lo_engon of the engine start, and when the vehicle controller receives the battery management system feedback power battery state of charge SOC signal value higher than the allowable power interruption coordination control power battery state of charge SOC lower limit value SOC lo_com , and when the vehicle controller receives the control unit of the intermediate axle transmission feedback that the intermediate axle transmission is in the shift process Shift_in_process = 1, the shift without power interruption coordination control is performed; otherwise, the shift without power interruption coordination control is not performed or exited, and the judgment condition is referred to the attached Figure 2 Step two.

[0034] Step three, calculate the hub hydraulic motor torque compensation amount before the shift process,

[0035] In the shift without power interruption coordination control allowable working mode, the engine provides power or energy for the related accessories of the hub hydraulic hybrid vehicle while driving the hub hydraulic hybrid vehicle, and at the same time, the idle state of the engine must be maintained, so according to formula (1), the current actual torque T eng_real As the current engine actual power output reference value T eng , the hub hydraulic motor compensation torque amount T Com The compensation torque analysis will be smaller, or even negative torque, based on this, reference to the attached Figure 2 Step three, that is, the engine feedback current actual torque T eng_real And the current engine request torque T eng_ask , the hub hydraulic motor compensation torque for the shift process is calculated, and the hub hydraulic motor compensation torque amount T Com The calculation formula is

[0036] T com = T ask -T eng ............................................. (1)

[0037] T eng = x·T eng_real +(1-x)·T eng_ask ............................ (2)

[0038] In the formula, T ask is the total demand torque for driving the vehicle, and x is the engine torque adjustment coefficient of the central shaft transmission during the shift process. The engine torque adjustment coefficient x of the central shaft transmission during the shift process continuously changes within the continuous step length after entering the shift process, and the specific value is determined according to the actual calibration test.

[0039] Step four, calibrate the hub hydraulic motor torque compensation change limit threshold,

[0040] After the hub hydraulic motor torque compensation amount before the shift process is solved, because the change rate of the hub hydraulic motor torque compensation amount is not limited, the final output torque of the hub hydraulic motor may jump, and the ride comfort of the hub hydraulic motor torque compensation process is deteriorated, so reference to the attached Figure 2 Step four, that is, in the actual torque compensation process of the hub hydraulic motor, the current actual torque T mot_real of the hub hydraulic motor is introduced, and the demand hub hydraulic motor torque compensation change amount ΔT com is calculated every step length, as shown in formula (3),

[0041] ΔT com = T com - T mot_real (3)

[0042] If ΔT com is too large, the hub hydraulic motor's fast response characteristics will result in the hub hydraulic hybrid vehicle presenting a strong longitudinal impact, poor smoothness, and if ΔT com is too small, the power interruption phenomenon during the transfer case shifting process cannot be completely eliminated, so the hub hydraulic motor torque compensation change is further limited as shown in equation (4),

[0043] ΔT Lo ≤ ΔT com ≤ ΔT Hi (4)

[0044] In the equation, ΔT Lo is the hub hydraulic motor torque compensation per step drop limit threshold, and ΔT Hi is the hub hydraulic motor torque compensation per step increase limit threshold, the specific value is determined according to the actual calibration test.

Claims

1. A hub hydraulic hybrid vehicle shift no-power interruption coordination control method characterized by, The method comprises the following steps: Step one, judging the allowable working mode of shift without power interruption coordination control, For a hub hydraulic hybrid vehicle, the front axle is driven by a hydraulic system and a hub hydraulic motor, and the middle axle and the rear axle are driven by an engine, and the power of the engine is transmitted to the output of the middle axle and the rear axle drive axle through a multi-gear automatic transmission. When the hub hydraulic hybrid vehicle is driven in engine direct drive, running with liquid filling, and combined drive modes, there is a power interruption during the shifting process of the middle axle transmission mechanism. When the hub hydraulic hybrid vehicle is driven in the running with liquid filling mode, the hub hydraulic motor responds to the negative working torque. In order to avoid frequent positive and negative mutations of the working torque of the hub hydraulic motor, the selected shift without power interruption coordination control allowable working mode is engine direct drive and combined drive mode. Step two, judging the condition of shift without power interruption coordination control, When the vehicle controller of the hub hydraulic hybrid vehicle receives a hard-wired signal that the pure fuel mode switch is not enabled, and when the vehicle controller receives a vehicle speed signal that the vehicle speed is higher than the minimum stable vehicle speed of the engine starting vehicle, and when the vehicle controller receives a battery management system feedback power battery state of charge SOC signal value that is higher than the allowable power battery state of charge SOC lower limit value, and when the vehicle controller receives a middle axle transmission mechanism control unit feedback signal that the middle axle transmission mechanism is in the shifting process, the shift without power interruption coordination control is performed. Otherwise, the shift without power interruption coordination control is not performed or is exited. Step three, calculating the front axle hub hydraulic motor torque compensation amount before shifting, In the shift-without-power-interruption coordinated control permitted operating mode, the engine provides the driving energy required for the wheel hub hydraulic hybrid vehicle's driving output, and also provides power or energy to the related accessories of the wheel hub hydraulic hybrid vehicle. At the same time, it must also maintain its own idling state. Therefore, according to equation (1), it can be seen that the engine feedback of the current actual torque T is directly used. eng_real As a reference value for the actual power output of the current engine, T eng During gear shifting, the front axle wheel hub hydraulic motor compensates for the torque T. Com The compensated torque analysis will be too low, or even result in a negative torque. Based on this, the actual torque T is determined by considering the feedback from the engine. eng_real With the engine's current requested torque T eng_ask The torque compensation during the gear shifting process is calculated, and the torque T compensated by the front axle wheel hub hydraulic motor during the gear shifting process is calculated. Com The calculation formula is （1） （2） In the formula, T ask is the total demand torque for driving the vehicle, and x is an engine torque adjustment coefficient during the transfer case gear shifting process, which continuously changes in a duration after entering the gear shifting process, and the specific value is determined according to actual calibration test. Step four, calibrating the hub hydraulic motor torque compensation change amount limit threshold, In the actual torque compensation process of the hub hydraulic motor, the current actual torque T of the hub hydraulic motor is introduced mot_real The torque compensation change amount AT of the hub hydraulic motor required by each step is calculated com As shown in formula (3), （3） The hub hydraulic motor torque compensation change amount is limited as shown in formula (4), （4） In the formula, ΔT Lo is the wheel hub hydraulic motor torque compensation amount per step decrease limit threshold, ΔT Hi is the wheel hub hydraulic motor torque compensation amount per step increase limit threshold, the specific value is determined according to actual calibration test.

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