Multi-working-condition braking energy recovery control method for pure electric land leveler

Abstract

The invention discloses a multi-working-condition braking energy recovery control method for a pure electric land leveler. The method comprises the steps that system key parameters are collected; acquiring a basic correction torque based on a preset curve: generating a ramp angle correction torque Tslopeinit based on the ramp angle theta, looking up a table of a shovel blade pressure correction torque Tloadinit based on the shovel blade pressure P, and forming a basic correction system adaptive to the working condition; calculating a demanded braking torque based on the pedal operating state; correcting the total required torque in combination with working conditions; energy recovery dynamic judgment is implemented, the maximum regenerative braking torque Tmotormax of the motor and the maximum rechargeable torque Tbattmax of the battery are combined, and under the working conditions of the flat road and the downhill, Ttotalreqt is determined according to the maximum regenerative braking torque Tmotormax of the motor and the maximum rechargeable torque Tbattmax of the battery; and when 0, energy recovery is executed, the recovery torque does not exceed the maximum value of the two, forward torque is output under the uphill working condition, and electric braking and energy recovery are not conducted. Through a double-correction mechanism of the ramp angle and the shovel blade pressure, the method is precisely adaptive to the working conditions of leveling, uphill, downhill and different operation loads, the problem of single working condition in the prior art is solved, and the complex operation requirements of the pure electric land leveler are met.

Description

Technical Field

[0001] This invention relates to an energy recovery control method, and more particularly to a multi-condition braking energy recovery control method for a pure electric grader. Background Technology

[0002] As an important category of new energy construction machinery, the range and energy efficiency of pure electric graders are core issues of concern in the industry. Braking energy recovery technology, which converts the kinetic energy generated during vehicle braking into electrical energy stored in the battery, is one of the key technologies for improving the range of pure electric graders.

[0003] However, pure electric graders operate in complex and varied environments, frequently handling different conditions such as flat roads, uphill slopes, and downhill slopes. Furthermore, the blade operation generates additional load, and electric braking is limited by both the motor's external characteristics and the battery's regenerative braking capacity. Existing regenerative braking strategies often fail to adequately consider these complex factors, resulting in low energy recovery efficiency or impacting vehicle safety and operational smoothness under certain conditions. Therefore, a control strategy that can adapt to complex working conditions while balancing safety and energy recovery efficiency is urgently needed. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to propose a multi-condition braking energy recovery control method for pure electric graders. By coordinating multi-dimensional parameters, differentiating working conditions, and intelligent braking distribution, the method improves the endurance and operational reliability of pure electric graders.

[0005] Technical solution: This invention includes the following steps:

[0006] S1: Collect key parameters of the system, including motor speed, battery SOC value, battery temperature, ramp angle θ, blade pressure P, throttle pedal physical opening α and opening change rate dα / dt, and brake pedal opening a.

[0007] S2: Obtain the basic correction torque based on the preset curve: Generate the slope angle correction torque T_slope_init based on the slope angle θ and the blade pressure correction torque T_load_init based on the blade pressure P, forming a basic correction system adapted to the working conditions;

[0008] S3: Calculate the required braking torque based on pedal operation state: When the accelerator pedal is operated, the working mode is switched according to dα / dt. When dα / dt≥0, the driving torque is calculated using the drive curve f_drive(α). When dα / dt<0, the system enters the mixing zone and calculates the torque according to the fusion formula. Calculate the total required torque, where w is the fusion weight, w=1-α, and β is the braking request degree calculated based on the pedal release speed and the current α. When the brake pedal is operated, the braking force is distributed in stages according to the brake pedal opening degree a. When a<70%, electric braking is given priority and mechanical braking is supplemented. When a≥70%, mechanical braking is given priority and electric braking is assisted.

[0009] S4: Combine working conditions to correct total demand torque: For three working conditions, θ=0, uphill, θ>0, and downhill, θ<0, T_slope_init and T_load_init are superimposed respectively to complete the correction of total demand torque, forming a torque control mechanism that coordinates working conditions, load and slope.

[0010] S5: Implement dynamic energy recovery determination. Combine the maximum regenerative braking torque of the motor T_motor_max and the maximum rechargeable torque of the battery T_batt_max. Under flat road and downhill conditions, energy recovery is performed when T_total_req<0, and the recovered torque does not exceed the maximum value of the two. Under uphill conditions, positive torque is output, and electric braking and energy recovery are not performed.

[0011] The preset rule for T_slope_init is: when θ>0, positive holding torque; when θ<0, negative braking torque; when θ=0, T_slope_init=0. The values ​​of the positive holding torque and the negative braking torque are both calibrated based on the grader's overall vehicle mass and slope resistance coefficient.

[0012] The preset rule for T_load_init is: when P=0, T_load_init=0; when P reaches the rated operating pressure, T_load_init is at its maximum value; and the T_load_init corresponding to the intermediate pressure value is fitted to form a continuous mapping curve through multiple sets of operating test data.

[0013] The domain of the drive curve f_drive(α) is α∈[0%,100%] and the output range is [0,T_drive_max]. The domain of the braking curve f_brake(β) is β∈[0%,100%] and the output range is [T_brake_min,0]. The domain of the braking torque curve f_brake(a) is a∈[0%,100%] and the output range is [0,T_brTq_max]. Wherein, T_drive_max is the rated drive torque of the motor, and T_brake_min is the maximum regenerative braking negative torque of the motor.

[0014] When releasing the accelerator pedal on a flat road, first calculate... When ΔT≤0, T_total_req=0 is directly determined, and electric braking and energy recovery are not started; when ΔT>0, T_total_req is calculated according to the fusion formula of the mixing zone, and then energy recovery determination is performed.

[0015] When pressing the brake pedal on a flat road... The electric braking torque first calls the minimum value between T_motor_max and T_batt_max, and the insufficient part is made up by the mechanical braking torque.

[0016] When operating the accelerator pedal on an uphill slope, When operating the brake pedal, Through bidirectional torque superposition.

[0017] When releasing the accelerator pedal on a downhill slope, first calculate... If ΔT≤0, then follow Calculate; if ΔT>0, then proceed according to... Calculate; if If so, energy recovery will be carried out. In this case, electric braking and energy recovery will not be performed.

[0018] When braking on a downhill slope... If the absolute value of the superposition of T_slope_init and T_load_init is greater than or equal to f_brake(a), then braking is completed only by electric braking and all energy is recovered.

[0019] The fusion weight w ranges from [0,1]. When α=100%, w=0; when α=0, w=1. The intermediate opening is dynamically calculated using the linear interpolation formula w=1-α / 100%.

[0020] Beneficial effects: The present invention has the following advantages:

[0021] (1) Adaptable to various working conditions: Through the dual correction mechanism of slope angle and blade pressure, it can accurately adapt to flat roads, uphill, downhill and different working load conditions, solve the problem of single working conditions of existing technology, and meet the complex operation needs of pure electric graders.

[0022] (2) Safety and smoothness are both taken into account: the slope angle correction torque is used to prevent the vehicle from rolling back uphill and speeding downhill, and the pedal fusion logic is used to achieve smooth switching between driving and braking, ensuring driving safety and smooth operation.

[0023] (3) Energy recovery efficiency optimization: Based on different working conditions and operating states, the control torque is precisely adjusted to maximize the recovery of braking energy while meeting braking requirements, effectively improving the range of pure electric graders;

[0024] (4) Scientific and reasonable control logic: By integrating preset characteristic curves with dynamic weights, the control complexity is simplified, ensuring the executability and stability of the strategy;

[0025] (5) Reduce wear on mechanical brakes, increase the service life of mechanical brake pads, and extend the maintenance cycle. Attached Figure Description

[0026] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0027] The invention will now be further described with reference to the accompanying drawings.

[0028] like Figure 1 As shown, the multi-condition braking energy recovery control method for a pure electric grader in this embodiment includes the following steps:

[0029] S1: Collect key parameters of the system, including motor speed, battery SOC value, battery temperature, ramp angle θ, blade pressure P, accelerator pedal physical opening α and opening change rate dα / dt, and brake pedal opening a.

[0030] The maximum capacity of electric braking is determined by two parameters:

[0031] Motor external characteristic limiting torque T_motor_max (v): determined according to the motor speed v, characterizing the maximum regenerative braking torque that the motor can provide at different speeds;

[0032] Battery receiving capacity limiting torque T_batt_max (SOC,Temp): Calculated in real time by the battery management system (BMS) based on the battery SOC value and temperature Temp, corresponding to the maximum rechargeable power of the battery.

[0033] S2: Obtain the basic correction torque based on the preset curve

[0034] The preset curves include:

[0035] Accelerator pedal drive curve α represents the physical opening of the accelerator pedal, with a domain of α∈[0%,100%] and an output range of [0,T_drive_max]. It represents the correspondence between driving demand and pedal opening.

[0036] Accelerator pedal braking curve β is the virtual braking request degree, defined in the domain β∈[0%,100%], with an output value range of [0,T_brake_max] and a negative output value. It represents the correspondence between braking demand and virtual braking request degree. β is calculated based on the pedal release speed and the current α.

[0037] Brake pedal braking torque curve : a is the brake pedal opening, defined in the domain a∈[0%,100%], and output in the domain [0,T_brTq_max], representing the correspondence between braking torque and brake pedal opening.

[0038] The system pre-defines the correspondence between different slope angles θ and the initial torque T_slope_init. It collects the real-time slope angle θ through a slope sensor and obtains the slope angle correction torque T_slope_init by looking up a table based on the slope angle θ. Similarly, it pre-defines the correspondence between different blade pressures P and the initial torque T_load_init. It collects the real-time P through a blade pressure sensor and obtains the blade pressure correction torque T_load_init by looking up a table based on the blade pressure P.

[0039] The default rules for slope angle correction torque T_slope_init are as follows: when θ>0 (uphill), T_slope_init is a positive holding torque (used to prevent the vehicle from rolling backward); when θ<0 (downhill), T_slope_init is a negative braking torque (used to maintain a constant speed downhill and prevent speeding); when θ=0 (flat road), T_slope_init=0.

[0040] The preset rules for the blade pressure correction torque T_load_init are: T_load_init=0 when P=0; T_load_init is at its maximum when P is at its maximum value; T_load_init corresponding to intermediate pressure values ​​is determined by fitting experimental data.

[0041] S3: Calculate the required braking torque based on the pedal operation state:

[0042] When the accelerator pedal is operated, the operating mode is determined based on dα / dt. When dα / dt ≥ 0 (pedal depressed or held), the drive torque is calculated using the drive curve T_drive = f_drive (α). When dα / dt < 0 (pedal released), the system enters the mixing zone and operates according to the fusion formula. Calculate the total required torque, where w is the fusion weight, determined by (1-α). When α=0 (pedal fully released), w=1, and the braking curve is fully adopted. β is the braking request degree calculated based on the pedal release speed and the current α.

[0043] The domain of the drive curve f_drive (α) is α∈[0%,100%], and the output range is [0,T_drive_max]; the domain of the braking curve f_brake (β) is β∈[0%,100%], and the output range is [0,T_brake_max] with a negative output value; the domain of the braking torque curve f_brake (a) is a∈[0%,100%], and the output range is [0,T_brTq_max].

[0044] When the brake pedal is operated, the total required braking torque is calculated based on the brake pedal opening 'a' using the braking torque curve f_brake(a). When 'a' < 70% (normal braking), electric braking is given priority. If the electric braking torque is insufficient, the shortfall is supplemented by mechanical braking to ensure that the braking torque meets the braking torque requirement corresponding to the brake pedal opening. When 'a' ≥ 70% (emergency braking), mechanical braking is given priority, with electric braking as an auxiliary supplement to ensure braking safety.

[0045] S4: Adjust the total required torque based on operating conditions:

[0046] Flat road condition (θ=0):

[0047] When operating the accelerator pedal: ;

[0048] Under flat road conditions, calculate the initial torque difference when releasing the accelerator pedal: .

[0049] If dα / dt≥0: ;

[0050] If dα / dt < 0 and ΔT > 0, calculate according to the fusion formula. If ΔT≤0, then directly determine It does not perform electric braking or energy recovery.

[0051] When operating the brake pedal: .

[0052] When pressing the brake pedal on a flat road, press Calculate the total required braking torque; if When the torque is less than the electric braking torque, braking is performed entirely by electric braking. When the braking torque exceeds the electric braking torque, braking is achieved through a combination of electric braking and mechanical braking. Energy recovery occurs whenever electric braking is involved.

[0053] Uphill working condition (θ>0):

[0054] When operating the accelerator pedal: ; For positive torque, and Together they counteract the component of the vehicle's weight and the component of the blade's load, preventing the vehicle from rolling backward;

[0055] When operating the brake pedal: ;

[0056] When releasing the accelerator pedal or pressing the brake pedal during uphill driving, there is no electric braking energy recovery because the required torque is the driving torque.

[0057] Downhill working condition (θ<0):

[0058] ;

[0059] When operating the brake pedal: ;

[0060] Press the brake pedal:

[0061] according to Calculate the total demand braking torque and superimpose it. , Prevent vehicles from speeding and losing control;

[0062] like In this case, the mechanical brakes will not function, and braking will be performed entirely by electric braking.

[0063] like If the speed is insufficient, the mechanical brakes will compensate, keeping the vehicle speed within a stable range.

[0064] When braking on a downhill slope, T_slope_init, T_load_init, and the mechanical brake need to participate in the torque correction corresponding to the brake pedal opening. Furthermore, the execution of T_slope_init must satisfy the following condition: if its absolute value exceeds... Then according to Perform regenerative braking; otherwise, press Enter. implement.

[0065] When operating the accelerator pedal: ;

[0066] When releasing the accelerator pedal on a downhill slope, first calculate... If ΔT≤0, then follow Perform the calculation; if ΔT>0, then proceed as follows: Perform the calculation. If If so, energy recovery will be carried out. If the current condition is not met, then electric braking and energy recovery will not be performed. During energy recovery, it is necessary to determine whether the current exceeds the limit. If the value exceeds the limit, then follow the... Perform regenerative braking; if it does not exceed the limit, then follow the procedure. Perform braking energy recovery;

[0067] S5: Energy Recovery Decision and Execution:

[0068] Uphill driving condition: The corrected total torque demand is positive torque, and electric braking and energy recovery are not performed;

[0069] Flat / downhill conditions: When the corrected total required torque T_total_req < 0, determine whether its absolute value exceeds the maximum value of the motor's maximum regenerative braking torque T_motor_max and the battery's maximum rechargeable torque T_batt_max. If it exceeds, brake energy recovery is performed according to the maximum value; otherwise, it is performed according to T_total_req. When T_total_req ≥ 0, electric braking and energy recovery are not performed.

Claims

1. A multi-condition braking energy recovery control method for a pure electric grader, characterized in that, Includes the following steps: S1: Collect key parameters of the system, including motor speed, battery SOC value, battery temperature, ramp angle θ, blade pressure P, throttle pedal physical opening α and opening change rate dα / dt, and brake pedal opening a. S2: Obtain the basic correction torque based on the preset curve: Generate the slope angle correction torque T_slope_init based on the slope angle θ and the blade pressure correction torque T_load_init based on the blade pressure P, forming a basic correction system adapted to the working conditions; S3: Calculate the required braking torque based on pedal operation state: When the accelerator pedal is operated, the working mode is switched according to dα / dt. When dα / dt≥0, the driving torque is calculated using the drive curve f_drive(α). When dα / dt<0, the system enters the mixing zone and calculates the torque according to the fusion formula. Calculate the total required torque, where w is the fusion weight, w=1-α, and β is the braking request degree calculated based on the pedal release speed and the current α. When the brake pedal is operated, the braking force is distributed in stages according to the brake pedal opening degree a. When a<70%, electric braking is given priority and mechanical braking is supplemented. When a≥70%, mechanical braking is given priority and electric braking is assisted. S4: Combine working conditions to correct total demand torque: For three working conditions, θ=0, uphill, θ>0, and downhill, θ<0, T_slope_init and T_load_init are superimposed respectively to complete the correction of total demand torque, forming a torque control mechanism that coordinates working conditions, load and slope. S5: Implement dynamic energy recovery determination. Combine the maximum regenerative braking torque of the motor T_motor_max and the maximum rechargeable torque of the battery T_batt_max. Under flat road and downhill conditions, energy recovery is performed when T_total_req<0, and the recovered torque does not exceed the maximum value of the two. Under uphill conditions, positive torque is output, and electric braking and energy recovery are not performed.

2. The multi-condition braking energy recovery control method for a pure electric grader according to claim 1, characterized in that, The preset rule for T_slope_init is: when θ>0, positive holding torque; when θ<0, negative braking torque; when θ=0, T_slope_init=0. The values ​​of the positive holding torque and the negative braking torque are both calibrated based on the grader's overall vehicle mass and slope resistance coefficient.

3. The multi-condition braking energy recovery control method for a pure electric grader according to claim 1, characterized in that, The preset rule for T_load_init is: when P=0, T_load_init=0; when P reaches the rated operating pressure, T_load_init is at its maximum value; and the T_load_init corresponding to the intermediate pressure value is fitted to form a continuous mapping curve through multiple sets of operating test data.

4. The multi-condition braking energy recovery control method for a pure electric grader according to claim 1, characterized in that, The domain of the drive curve f_drive(α) is α∈[0%,100%] and the output range is [0,T_drive_max]. The domain of the braking curve f_brake(β) is β∈[0%,100%] and the output range is [T_brake_min,0]. The domain of the braking torque curve f_brake(a) is a∈[0%,100%] and the output range is [0,T_brTq_max]. Wherein, T_drive_max is the rated drive torque of the motor, and T_brake_min is the maximum regenerative braking negative torque of the motor.

5. The multi-condition braking energy recovery control method for a pure electric grader according to claim 1, characterized in that, When releasing the accelerator pedal on a flat road, first calculate... When ΔT≤0, T_total_req=0 is directly determined, and electric braking and energy recovery are not started; when ΔT>0, T_total_req is calculated according to the fusion formula of the mixing zone, and then energy recovery determination is performed.

6. The multi-condition braking energy recovery control method for a pure electric grader according to claim 1, characterized in that, When the brake pedal is pressed on a flat road, the total required braking torque = electric braking torque + mechanical braking torque - T_load_init. The electric braking torque first calls the minimum value between T_motor_max and T_batt_max, and the insufficient part is made up by the mechanical braking torque.

7. The multi-condition braking energy recovery control method for a pure electric grader according to claim 1, characterized in that, When operating the accelerator pedal on an uphill slope, When operating the brake pedal, Through bidirectional torque superposition.

8. The multi-condition braking energy recovery control method for a pure electric grader according to claim 1, characterized in that, When releasing the accelerator pedal on a downhill slope, first calculate... If ΔT≤0, then follow Calculate; if ΔT>0, then proceed according to... Calculate; if If so, energy recovery will be carried out. In this case, electric braking and energy recovery will not be performed.

9. The multi-condition braking energy recovery control method for a pure electric grader according to claim 1, characterized in that, When braking on a downhill slope... If the absolute value of the superposition of T_slope_init and T_load_init is greater than or equal to f_brake(a), then braking is completed only by electric braking and all energy is recovered.

10. The multi-condition braking energy recovery control method for a pure electric grader according to claim 1, characterized in that, The fusion weight w ranges from [0,1]. When α=100%, w=0; when α=0, w=1. The intermediate opening is dynamically calculated using the linear interpolation formula w=1-α / 100%.

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