A drive slip control method for a hub-hydraulic hybrid vehicle

Abstract

The application provides a driving anti-skid control method for a hub hydraulic hybrid vehicle, aiming at solving the single-axis slip phenomenon caused by the uncoordinated rotation speed of the hub hydraulic hybrid system of different driving shafts. The control method comprises the following steps: S1, driving anti-skid entering and exiting condition judgment; S2, initialization of slip correction torque; S3, torque compensation control; and S4, solving of the hub hydraulic motor correction demand torque. Based on the power ground coupling characteristics of the hub hydraulic hybrid vehicle, the application can effectively solve the driving wheel slip phenomenon often occurring in the driving process of the hub hydraulic hybrid vehicle due to the different power source characteristics of each driving axle of the hub hydraulic hybrid vehicle, and effectively guarantee the driving stability of the hub hydraulic hybrid vehicle.

Description

Technical Field

[0001] This invention relates to the field of hybrid vehicle control, and more specifically to a drive anti-slip control method for hub hydraulic hybrid vehicles. Background Technology

[0002] Although the number of commercial vehicles in my country is far lower than that of passenger vehicles, commercial vehicles are applicable to a wide range of regions and are suitable for various scenarios. They undertake the main task of transporting goods and are of great significance to the development of the national economy. Traditional fuel-powered commercial vehicles have poor adaptability to various operating conditions. On soft, muddy or other bad roads, as well as in mining and mountainous areas, the drive wheels often slip, which not only affects the vehicle's passability and stability but also increases fuel consumption and deteriorates emissions. The hub hydraulic hybrid system provides all-wheel drive, which can significantly improve the vehicle's passability on low-traction roads. During braking, the vehicle can also recover regenerative braking energy through an accumulator to improve the vehicle's economy. At the same time, hydraulic auxiliary braking improves braking safety. In addition, compared with the hybrid electric system, it has advantages such as high power density, small size and weight, and low overall cost. However, hub hydraulic hybrid vehicles have a complex structure and are difficult to control. In actual use, it is often found that the hub hydraulic motor shaft slips at low speeds, especially during low-speed starts and low-speed turns. Wheel slippage not only shortens the lifespan of components such as tires but also affects vehicle reliability and stability. This is especially true for heavy-duty commercial vehicles, where wheel slippage poses a significant threat to overall vehicle safety. Therefore, developing an effective anti-slip control algorithm for hub-and-wheel hydraulic hybrid vehicles is urgently needed.

[0003] Currently available technologies include, for example, the invention patent published on December 10, 2021, publication number: CN113771834A, "A Power Domain System and Control Method for a Hub Hydraulic Hybrid Commercial Vehicle," which proposes a power domain control architecture to replace traditional distributed control, thus compensating for the shortcomings of traditional methods in coordinating the dual power sources and AMT of hub hydraulic hybrid vehicles. However, it does not propose a relevant control method for drive anti-slip. Another example is the invention patent published on April 14, 2020, publication number: CN109624732A, "A Multi-Layer Drive Anti-Slip Control Method Applicable to Electric Wheel Drive Vehicles." This invention patent adopts a multi-layer drive anti-slip strategy and discusses the entry conditions and control methods for each layer of drive anti-slip. However, this invention patent only addresses multi-motor wheel-side drive configurations and cannot solve the drive slippage problem of hub hydraulic hybrid vehicles. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a drive anti-slip control method for hub-driven hydraulic hybrid vehicles. This method calculates the maximum adhesion limit of the slipping axle by real-time observation of vehicle speed, load information, and road surface adhesion, using this as a constraint. By judging slip confirmation information and entry / exit conditions, it decides whether to implement drive anti-slip torque compensation control. Finally, by combining the steady-state torque demand of the hub-driven hydraulic motor and the slip correction torque, it calculates the corrected torque demand of the hub-driven hydraulic motor. The control method proposed in this invention effectively solves the single-axle slip phenomenon that often occurs during driving in hub-driven hydraulic hybrid vehicles due to drive redundancy and the different power source characteristics of each drive axle, resulting in uncoordinated speeds of the two drive axles. This effectively ensures the driving stability of hub-driven hydraulic hybrid vehicles.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] Step 1: Determine the conditions for driving the anti-slip entry and exit.

[0007] The present invention relates to a hub hydraulic hybrid vehicle, wherein the rear axle of the hub hydraulic hybrid vehicle is driven by an engine, and the engine power is transmitted to the rear axle drive axle through a multi-speed automatic transmission, while the front axle is driven by a hydraulic drive system and hub hydraulic motors.

[0008] If it is necessary to enter the anti-slip control mode, the vehicle controller should first determine that the vehicle is in a driving state, the EBS is fault-free and the wheel speed monitored by the vehicle controller is reliable, the clutch is engaged, and the multi-speed automatic transmission is not shifting. In addition, the vehicle controller should also check the slip confirmation signal.

[0009] The vehicle controller monitors the rotational speed of each wheel on the front and rear axles, taking into account the differences in wheel rotational speed caused by turning, obstacle crossing, and changes in tire pressure. The vehicle controller determines the relative average wheel speed n between the average rotational speed of the wheels on both sides of the rear axle and the average rotational speed of the wheels on both sides of the front axle. relative The absolute value is greater than the rated slip wheel speed n calibration When the vehicle enters anti-slip control, the slip confirmation signal is set to 1, activating the drive anti-slip function, and the relative average wheel speed n relative The expression is shown in equation (1); to avoid the vehicle stability deteriorating due to frequent intervention of the drive anti-slip control, when the relative average wheel speed n relative Half of the calibrated slip wheel speed When the front and rear axle speeds are determined to be consistent, the drive anti-slip control must be disengaged and the slip confirmation signal set to 0.

[0010]

[0011] Entry condition: |n relative |>ncalibration ................................(2)

[0012] Exit conditions:

[0013] In equation (1), n front_left n front_right n rear_left n rear_right These represent the rotational speeds of the wheels on the left, right, left, and right sides of the front axle, respectively.

[0014] Step 2: Initialize the slip correction torque.

[0015] After determining that the drive anti-slip control has been activated, the slip correction torque T is initialized. com (0) is 0 Nm; when the slip confirmation signal is set to 0, no drive anti-slip control is required, and the slip correction torque T com (t) is always set to 0 Nm;

[0016] Step 3: Torque compensation control.

[0017] When the vehicle controller determines that the average wheel speed of the rear axle is higher than the average wheel speed of the front axle, and the slip confirmation signal is 1, the vehicle controller executes the front axle torque increase control function, first by increasing the slip correction torque T. com (0) is set to 10 Nm, the initial value t(0) of the torque increase timer is set to 0, then torque increase adjustment is performed and timing begins. Each simulation step adjusts the torque value T by sliding it from the previous moment. com (t-1) adds stepping torque increment ΔT to the hub hydraulic motor. com_rise As shown in equation (4), until the corrected torque value T com (t) reaches the upper limit of torque compensation T com_hi Or the torque increase time t exceeds the upper limit of the torque increase duration t rise_lim Then the torque increase stops, where the step torque increment ΔT com_rise The relative average wheel speed n relative The PID control output is obtained as shown in equation (5);

[0018] T com (t)=T com (t-1)+ΔT com_rise ....................................(4)

[0019]

[0020] In equation (5), K p K iK d These represent the proportional coefficient, integral coefficient, and differential coefficient, respectively.

[0021] When the vehicle controller determines that the average wheel speed of the rear axle is lower than the average wheel speed of the front axle, and the slip confirmation signal is 1, the vehicle controller executes the front axle torque reduction control function, first by adjusting the slip correction torque T. com (0) is set to -10Nm, the initial value t(0) of the torque reduction timer is set to 0, then torque reduction adjustment is performed and timing begins. Each simulation step adjusts the torque value T by sliding it from the previous moment. com (t-1) Reduced stepping torque of the hub hydraulic motor ΔT com_reduce As shown in equation (6), until the corrected torque value T com (t) is below the lower limit of torque compensation T com_lo Or the torque reduction time t exceeds the upper limit of torque reduction duration t reduce_lim Then the torque reduction stops, where the step torque reduction ΔT com_reduce The relative average wheel speed n relative The PID control output is obtained as shown in equation (7);

[0022] T com (t)=T com (t-1)-ΔT com_reduce ...................................(6)

[0023]

[0024] Step 4: Determine the required torque for the wheel hub hydraulic motor correction.

[0025] The calculated slip correction torque T com (t) and the steady-state torque demand T of the hub hydraulic motor determined by the vehicle controller hmot Adding (t) together, as shown in equation (8), we can obtain the required torque T for the hub hydraulic motor correction. hmot_adj (t);

[0026] T hmot_adj (t)=T hmot (t)+T com (t)........................................(8)

[0027] Furthermore, the vehicle controller estimates the road adhesion limit of a single front axle wheel by observing the current vehicle speed, vehicle weight, and road adhesion. And adjust the required torque T of the wheel hub hydraulic motor. hmot_adj (t) is subject to amplitude limitation, as shown in equation (9).

[0028]

[0029] In the formula, r represents the rolling radius of the front axle wheel.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The present invention proposes a drive anti-slip control method for hub hydraulic hybrid vehicles, which fully considers the drive characteristics of hub hydraulic hybrid vehicles. Based on the observation constraint fusion feedback control idea, the method adjusts the compensation torque of the hub hydraulic motor. The calculated corrected torque of the hub hydraulic motor has high accuracy and good effect. It can effectively solve the single-axle slip phenomenon that often occurs in the driving process of hub hydraulic hybrid vehicles due to the incoordination of the two drive shaft speeds, thereby effectively ensuring the driving stability of hub hydraulic hybrid vehicles.

[0032] 2. The drive anti-slip control method for hub hydraulic hybrid vehicles proposed in this invention comprehensively considers both torque increase and torque decrease, which can not only solve the problem of hub hydraulic motor slippage, but also the problem of hub hydraulic motor slippage.

[0033] 3. The drive anti-slip control method for hub hydraulic hybrid vehicles proposed in this invention can effectively avoid the deterioration of vehicle stability caused by frequent intervention of drive anti-slip control by reasonably setting the entry and exit conditions of drive anti-slip control. Attached Figure Description

[0034] The following description of the embodiments, taken in conjunction with the accompanying drawings, will make the embodiments readily understood, wherein:

[0035] Figure 1 This is a schematic diagram of the power system structure of a hub-driven hydraulic hybrid vehicle according to an embodiment of the present invention;

[0036] Figure 2 This is a flowchart of a wheel hub hydraulic hybrid vehicle drive anti-skid control method according to an embodiment of the present invention;

[0037] Figure 1 Explanation of the designation numbers: 1-Front axle wheel, 2-Hole hydraulic motor, 3-Accumulator, 4-Power domain controller, 5-Rear axle wheel, 6-Main reducer and differential assembly, 7-Universal joint, 8-Multi-speed AMT assembly, 9-Power take-off, 10-Engine assembly, 11-Hydraulic variable pump, 12-Hydraulic combination valve assembly. Detailed Implementation

[0038] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0039] A drive anti-slip control method for hub-driven hydraulic hybrid vehicles is described below with reference to the accompanying drawings, but the invention is not limited to these embodiments.

[0040] Step 1: Determine the conditions for driving the anti-slip entry and exit.

[0041] For a hub-driven hydraulic hybrid vehicle, see attached reference. Figure 1 The rear axle of the hub hydraulic hybrid vehicle is driven by a 10-engine, and the power of the 10-engine is transmitted to the rear axle drive axle through an 8-speed AMT. The front axle is driven by a hydraulic drive system and two hub hydraulic motors.

[0042] If you need to access the drive anti-slip control, please refer to the attached document. Figure 2 Step 1: The vehicle controller should first determine that the vehicle is in a driving state, the EBS is fault-free and the wheel speed monitored by the vehicle controller is reliable, the clutch is engaged, and the multi-speed automatic transmission is not shifting. In addition, the vehicle controller should also check the slip confirmation signal.

[0043] The vehicle controller monitors the rotational speed of each wheel on the front and rear axles, taking into account the differences in wheel rotational speed caused by turning, obstacle crossing, and changes in tire pressure. The vehicle controller determines the relative average wheel speed n between the average rotational speed of the wheels on both sides of the rear axle and the average rotational speed of the wheels on both sides of the front axle. relative The absolute value is greater than the rated slip wheel speed n calibration When the vehicle enters anti-slip control, the slip confirmation signal is set to 1, activating the drive anti-slip function, and the relative average wheel speed n relative The expression is shown in equation (1); to avoid the vehicle stability deteriorating due to frequent intervention of the drive anti-slip control, when the relative average wheel speed n relative Half of the calibrated slip wheel speed When the front and rear axle speeds are determined to be consistent, the drive anti-slip control must be disengaged and the slip confirmation signal set to 0.

[0044]

[0045] Entry condition: |n relative |>n calibration ............................(2)

[0046] Exit conditions:

[0047] In equation (1), n front_left n front_right n rear_left n rear_right These represent the rotational speeds of the wheels on the left, right, left, and right sides of the front axle, respectively.

[0048] Step 2: Initialize the slip correction torque.

[0049] Reference Appendix Figure 2 Step 2: After determining that the drive anti-slip control has been entered, initialize the slip correction torque T. com (0) is 0 Nm; when the slip confirmation signal is set to 0, no drive anti-slip control is required, and the slip correction torque T com (t) is always set to 0 Nm;

[0050] Step 3: Torque compensation control.

[0051] Reference Appendix Figure 2 Step 3: When the vehicle controller determines that the average wheel speed of the rear axle is higher than the average wheel speed of the front axle, and the slip confirmation signal is 1, the vehicle controller executes the front axle torque increase control function, first by increasing the slip correction torque T. com (0) is set to 10 Nm, the initial value t(0) of the torque increase timer is set to 0, then torque increase adjustment is performed and timing begins. Each simulation step adjusts the torque value T by sliding it from the previous moment. com (t-1) adds stepping torque increment ΔT to the hub hydraulic motor. com_rise As shown in equation (4), until the corrected torque value T com (t) reaches the upper limit of torque compensation T com_hi Or the torque increase time t exceeds the upper limit of the torque increase duration t rise_lim Then the torque increase stops, where the step torque increment ΔT com_rise The relative average wheel speed n relative The PID control output is obtained as shown in equation (5);

[0052] T com (t)=T com (t-1)+ΔT com_rise ....................................(4)

[0053]

[0054] In equation (5), K p K i K d These represent the proportional coefficient, integral coefficient, and differential coefficient, respectively.

[0055] When the vehicle controller determines that the average wheel speed of the rear axle is lower than the average wheel speed of the front axle, and the slip confirmation signal is 1, the vehicle controller executes the front axle torque reduction control function, first by adjusting the slip correction torque T. com (0) is set to -10Nm, the initial value t(0) of the torque reduction timer is set to 0, then torque reduction adjustment is performed and timing begins. Each simulation step adjusts the torque value T by sliding it from the previous moment. com (t-1) Reduced stepping torque of the hub hydraulic motor ΔT com_reduce As shown in equation (6), until the corrected torque value T com (t) is below the lower limit of torque compensation T com_lo Or the torque reduction time t exceeds the upper limit of torque reduction duration t reduce_lim Then the torque reduction stops, where the step torque reduction ΔT com_reduce The relative average wheel speed n relative The PID control output is obtained as shown in equation (7);

[0056] T com (t)=T com (t-1)-ΔT com_reduce .................................(6)

[0057]

[0058] Step 4: Determine the required torque for the wheel hub hydraulic motor correction.

[0059] Reference Appendix Figure 2 Step 4, calculate the slip correction torque T com (t) and the steady-state torque demand T of the hub hydraulic motor determined by the vehicle controller hmot Adding (t) together, as shown in equation (8), we can obtain the required torque T for the hub hydraulic motor correction. hmot_adj (t);

[0060] T hmot_adj (t)=T hmot (t)+T com (t)........................................(8)

[0061] Furthermore, the vehicle controller estimates the road adhesion limit of a single front axle wheel by observing the current vehicle speed, vehicle weight, and road adhesion. And adjust the required torque T of the wheel hub hydraulic motor. hmot_adj (t) is subject to amplitude limitation, as shown in equation (9).

[0062]

[0063] In the formula, r represents the rolling radius of the front axle wheel.

Claims

1. A drive anti-skid control method for hub-driven hydraulic hybrid vehicles, characterized in that, Includes the following steps: Step 1: Determine the conditions for driving the anti-slip entry and exit. The present invention relates to a hub hydraulic hybrid vehicle, wherein the rear axle of the hub hydraulic hybrid vehicle is driven by an engine, and the engine power is transmitted to the rear axle drive axle through a multi-speed automatic transmission, while the front axle is driven by a hydraulic drive system and hub hydraulic motors. If it is necessary to enter the anti-slip control mode, the vehicle controller should first determine that the vehicle is in a driving state, the EBS is fault-free and the wheel speed monitored by the vehicle controller is reliable, the clutch is engaged, and the multi-speed automatic transmission is not shifting. In addition, the vehicle controller should also check the slip confirmation signal. The vehicle controller monitors the rotational speed of each wheel on the front and rear axles, taking into account the differences in wheel rotational speed caused by turning, obstacle crossing, and changes in tire pressure. The vehicle controller determines the relative average wheel speed n between the average rotational speed of the wheels on both sides of the rear axle and the average rotational speed of the wheels on both sides of the front axle. relative The absolute value is greater than the rated slip wheel speed n calibration When the vehicle enters anti-slip control, the slip confirmation signal is set to 1, activating the drive anti-slip function, and the relative average wheel speed n relative The expression is shown in equation (1); To avoid deterioration of vehicle stability due to frequent intervention of drive anti-slip control, when the relative average wheel speed n relative Half of the calibrated slip wheel speed When the front and rear axle speeds are determined to be consistent, the drive anti-slip control must be disengaged and the slip confirmation signal set to 0. Entry condition: |n relative |>n calibration ..........................................(2) Exit conditions: In equation (1), n front_left n front_right n rear_left n rear_right These represent the rotational speeds of the wheels on the left, right, left, and right sides of the front axle, respectively. Step 2: Initialize the slip correction torque. After determining that the drive anti-slip control has been activated, the slip correction torque T is initialized. com (0) is 0 Nm; When the slip confirmation signal is set to 0, no drive anti-slip control is required, and the slip correction torque T... com (t) is always set to 0 Nm; Step 3: Torque compensation control. When the vehicle controller determines that the average wheel speed of the rear axle is higher than the average wheel speed of the front axle, and the slip confirmation signal is 1, the vehicle controller executes the front axle torque increase control function, first by increasing the slip correction torque T. com (0) is set to 10 Nm, the initial value t(0) of the torque increase timer is set to 0, then torque increase adjustment is performed and timing begins. Each simulation step adjusts the torque value T by sliding it from the previous moment. com (t-1) adds stepping torque increment ΔT to the hub hydraulic motor. com_rise As shown in equation (4), until the corrected torque value T com (t) reaches the torque compensation limit T com_hi Or the torque increase time t exceeds the upper limit of the torque increase duration t rise_lim Then the torque increase stops, where the step torque increment ΔT com_rise The relative average wheel speed n relative The PID control output is obtained as shown in equation (5); T com (t)=T com (t-1)+ΔT com_rise ........................................(4) In equation (5), K p K i K d These represent the proportional coefficient, integral coefficient, and differential coefficient, respectively. When the vehicle controller determines that the average wheel speed of the rear axle is lower than the average wheel speed of the front axle, and the slip confirmation signal is 1, the vehicle controller executes the front axle torque reduction control function, first by adjusting the slip correction torque T. com (0) is set to -10Nm, the initial value t(0) of the torque reduction timer is set to 0, then torque reduction adjustment is performed and timing begins. Each simulation step adjusts the torque value T by sliding it from the previous moment. com (t-1) Reduced stepping torque of the hub hydraulic motor ΔT com_reduce As shown in equation (6), until the corrected torque value T com (t) is below the lower limit of torque compensation T com_lo Or the torque reduction time t exceeds the upper limit of torque reduction duration t reduce_lim Then the torque reduction stops, where the step torque reduction ΔT com_reduce The relative average wheel speed n relative The PID control output is obtained as shown in equation (7); T com (t)=T com (t-1)-ΔT com_reduce ........................................(6) Step 4: Determine the required torque for the wheel hub hydraulic motor correction. The calculated slip correction torque T com (t) and the steady-state torque demand T of the hub hydraulic motor determined by the vehicle controller hmot Adding (t) together, as shown in equation (8), we can obtain the required torque T for the hub hydraulic motor correction. hmot_adj (t); T hmot_adj (t)=T hmot (t)+T com (t)........................................(8) Furthermore, the vehicle controller estimates the road adhesion limit of a single front axle wheel by observing the current vehicle speed, vehicle weight, and road adhesion. And adjust the required torque T of the wheel hub hydraulic motor. hmot_adj (t) is subject to amplitude limitation, as shown in equation (9). In the formula, r represents the rolling radius of the front axle wheel.

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