A torque coordination control method for a double drive axle electric commercial vehicle under wheel speed loss

Abstract

The application is suitable for the technical field of electric commercial vehicle driving torque coordination control, and provides a double drive axle electric commercial vehicle torque coordination control method under wheel speed loss, comprising: obtaining vehicle state information; obtaining wheel edge equivalent speed by using drive axle motor speed conversion, calculating vehicle reference speed by using front axle left and right wheel speed, and constructing drive axle slip rate; establishing a drive axle ground driving force estimation model, fitting a local slope by using a rolling window method, and determining a slip state; updating or maintaining the reference slip rate and the wheel edge transmissible torque upper limit according to the slip state; distributing and constraining the driver demand wheel edge driving torque according to the middle axle and rear axle slip state combination; performing anti-slip torque correction on the over-slip drive axle; and generating and outputting a target driving torque. The application realizes reasonable distribution of inter-axle driving torque and over-slip suppression, and is suitable for double drive axle electric commercial vehicles without wheel speed sensors on part of the drive axles.

Description

Technical Field

[0001] This invention belongs to the field of drive torque coordination control technology for electric commercial vehicles, and particularly relates to a torque coordination control method for dual-drive axle electric commercial vehicles under wheel speed loss. Background Technology

[0002] With the continuous development of commercial vehicle electrification, pure electric commercial vehicles are playing an increasingly important role in the transportation sector. Dual-drive axle electric commercial vehicles possess advantages such as high load capacity, strong power, and high transport efficiency, and are widely used in medium- and long-distance transportation. Dual-drive axle electric commercial vehicles operate in complex environments, frequently navigating slippery, muddy, icy, and other conditions with limited traction, requiring excellent traction and anti-skid performance to ensure driving safety.

[0003] However, due to factors such as overall vehicle cost and system configuration, some drive axles of dual-drive axle electric commercial vehicles are typically not equipped with wheel speed sensors. This makes it impossible to directly obtain the wheel speed of the drive wheels on these axles, hindering the direct application of existing anti-slip control methods based on drive wheel speed and slip ratio. Therefore, accurately identifying slip states, rationally distributing drive torque between the middle and rear axles, and suppressing excessive slip are crucial for improving the driving safety of dual-drive axle electric commercial vehicles in traction-limited road conditions when drive wheel speed signals are missing.

[0004] Chinese invention patent application number 202511585856.4, entitled "Dual Electric Drive Axle Commercial Vehicle Drive Anti-Slip Control Method, System, Equipment and Medium," calculates the real-time rolling radius of the drive wheels using a reference vehicle speed and drive wheel angular velocity, combined with parameters such as vehicle load and motor torque. Based on the real-time rolling radius, drive wheel speed, and reference vehicle speed, it calculates the drive wheel slip ratio and further determines the target drive torque to achieve anti-slip control. However, this method requires drive wheel speed information. When this information is missing, it is difficult to calculate the drive wheel slip ratio and the target drive torque, thus hindering the reasonable distribution of drive torque between the middle and rear axles and the suppression of excessive slippage.

[0005] Chinese invention patent application number 202410651180.3, entitled "Vehicle Drive Anti-slip Control Method, Device, Medium, and Vehicle," utilizes information such as drive wheel speed and wheel acceleration to determine the drive wheel slip state and applies different control strategies to the drive torque according to different slip stages to achieve rapid convergence of the slip ratio. This method also relies on drive wheel speed information for both slip state determination and drive torque control, and does not address the torque coordination and distribution between the two drive axles. Therefore, in the absence of drive wheel speed signals, it is difficult to achieve a reasonable distribution of drive torque between the middle and rear axles and to suppress excessive slip.

[0006] The above methods all rely on the acquisition of drive wheel speed signals, which are difficult to apply to dual-drive axle electric commercial vehicles where some drive axles are not equipped with wheel speed sensors. Summary of the Invention

[0007] The purpose of this invention is to provide a torque coordination control method for dual-drive axle electric commercial vehicles under wheel speed loss, aiming to solve the problems mentioned in the background art.

[0008] The present invention is implemented as follows: a torque coordination control method for a dual-drive axle electric commercial vehicle under wheel speed loss includes the following steps:

[0009] Step 1: Obtain the drive axle motor speed, drive axle motor torque, and front axle left and right wheel speeds in real time via the vehicle's CAN bus;

[0010] Step 2: Calculate the equivalent speed of the drive axle wheel using the drive axle motor speed and the total transmission ratio of the transmission system. Calculate the vehicle reference speed based on the wheel speeds of the left and right front axle wheels. Calculate the drive axle slip ratio using the equivalent speed of the drive axle wheel and the vehicle reference speed.

[0011] Step 3: Establish a ground driving force estimation model for the drive axle and update the model parameters using a recursive least squares method with a forgetting factor; obtain synchronous data combinations of the estimated ground driving force and the drive axle slip ratio in real time using a rolling window method, fit the data combination within the current window to obtain the local slope of the estimated ground driving force and the drive axle slip ratio under the current window; determine the drive axle slip state based on the relationship between the local slope and the preset slope threshold.

[0012] Step 4: Update or maintain the reference slip ratio and the upper limit of the torque that can be transmitted to the wheel side of the drive axle according to the slip state of the drive axle;

[0013] Step 5: Based on the combination of slip states of the middle and rear axles, implement corresponding distribution and constraint strategies for the driver's required wheel-side drive torque to obtain the target drive torque after distribution and constraint of the middle and rear axles;

[0014] Step 6: For the drive axle that is still in an overslip state after the inter-axle drive torque distribution and constraint, generate anti-slip correction torque based on the deviation between the real-time slip ratio of the drive axle and the reference slip ratio, and correct the target drive torque after distribution and constraint.

[0015] Step 7: The target driving torque generated in Step 5 after allocation and constraint is superimposed with the corresponding anti-slip correction torque to generate the final target driving torque, and then output to the corresponding drive axle motor for execution.

[0016] A further technical solution involves using the following formula in step 2 to calculate the equivalent speed of the drive axle wheel side based on the drive axle motor speed and the overall transmission ratio of the transmission system:

[0017] (1)

[0018] In the formula, To drive the equivalent speed of the axle wheel, This refers to the motor speed. This refers to the gear ratio of the transmission. Main reducer transmission ratio, This refers to the gear ratio of the wheel-side reducer;

[0019] The formula for calculating the vehicle's base speed based on the wheel speeds of the left and right front axles is as follows:

[0020] (2)

[0021] In the formula, The vehicle's base speed. and These are the angular velocities of the left and right non-driving wheels, respectively. The radius of the wheel's rolling radius;

[0022] The formula for calculating the slip ratio of the drive axle, using the equivalent rotational speed of the drive axle wheel and the vehicle's reference speed, is as follows:

[0023] (3)

[0024] In the formula, This refers to the slip ratio of the drive axle.

[0025] A further technical solution, in step 3, specifically includes the establishment of the drive axle ground driving force estimation model, which includes:

[0026] The drive torque of the drive axle wheel is obtained by converting the drive axle motor torque through the transmission ratio of the transmission system. :

[0027] (4)

[0028] In the formula, For the drive motor torque, For drive axle transmission efficiency;

[0029] Drive axle ground driving force Satisfy the following formula:

[0030] (5)

[0031] In the formula, This is the equivalent rotational inertia of the transmission system to the wheel edge. This is the equivalent angular acceleration of the drive axle wheel side.

[0032] A further technical solution, in step 3, is as follows: the specific method for updating the model parameters using the recursive least squares method with a forgetting factor is as follows:

[0033] No. Observations used for model updates at specific times for:

[0034] (6)

[0035] In the formula, For the first The regression vector at time step, and , For the first The driving torque at the wheel side of the drive axle at any given moment. For the first The equivalent angular acceleration of the drive axle wheel at any given moment; Let be the parameter vector to be estimated, and , The driving torque coefficient, The equivalent angular acceleration coefficient of the drive axle wheel edge; For the first Momentary noise;

[0036] The parameter vector is updated online using a recursive least squares method with a forgetting factor, and the estimation error is:

[0037] (7)

[0038] In the formula, For the first The time estimation error, For the first Estimates of the time parameter vector;

[0039] The recursive formula is:

[0040] (8)

[0041] In the formula, For the first Gain vector at time step and The first With the The covariance matrix at time t, For the first The estimated value of the parameter vector at time. Forgetting factor, It is the identity matrix;

[0042] Obtain the estimated value of the ground driving force of the drive axle for:

[0043] (9).

[0044] A further technical solution involves determining the drive axle slip state in step 3 based on the relationship between the local slope and a preset slope threshold, specifically including:

[0045] Based on the preset slope threshold and With local slope The relationship between the two factors determines the slip state of the drive axle. The slope threshold is used to distinguish between underslip and ideal slip. The slope threshold is the dividing line between ideal slip and excessive slip, and ;when At that time, the drive axle is in an underslip state; when At that time, the drive axle is in an ideal slip state; when At that time, the drive axle is in an excessive slip state.

[0046] A further technical solution, specifically step 4 includes:

[0047] When the drive axle is in an underslip state, the drive axle reference slip ratio and the upper limit of the wheel-side transmittable torque are not updated.

[0048] When the drive axle is in an ideal slip state, the maximum value of the estimated ground driving force of the drive axle within the current window is multiplied by the tire rolling radius to obtain the upper limit of the current wheel-side transmittable torque. The corresponding drive axle slip ratio is used as the drive axle reference slip ratio. The formula for calculating the upper limit of wheel-side transmittable torque is as follows:

[0049] (10)

[0050] In the formula, This represents the upper limit of the torque that can be transmitted by the wheel. This represents the maximum value of the estimated ground driving force.

[0051] When the drive axle is in an overslip state, the reference slip ratio of the drive axle and the upper limit of the torque that can be transmitted at the wheel end obtained in the most recent ideal slip state remain unchanged.

[0052] In a further technical solution, step 5 specifically includes:

[0053] The slip state of the drive axle is divided into three types: underslip state, ideal slip state, and overslip state, which are denoted as state A, state B, and state C, respectively.

[0054] When the drive axle slip state combination is AA, AB, AC, BA, CA, a slip ratio approach strategy is adopted to increase the torque distribution coefficient of the drive axle on the side with lower slip ratio and decrease the torque distribution coefficient of the drive axle on the side with higher slip ratio. During the slip ratio approach process, when the drive axle in the underslip state approaches the ideal slip state, further torque distribution is stopped, and the drive axle torque distribution coefficient of the previous moment is maintained.

[0055] When implementing the slip ratio approaching strategy, the control objective for inter-axle torque distribution is to make the slip ratio deviation between the middle and rear axles approach zero.

[0056] (11)

[0057] In the formula, The difference in slip ratio between the middle and rear axles and These are the drive axle slip ratios for the middle and rear axles, respectively.

[0058] According to the definition of drive axle slip ratio, the first individual drive axle slip ratio Represented as

[0059] (12)

[0060] In the formula, For the first The equivalent wheel side angular velocity of each drive axle For the middle bridge, For the rear axle;

[0061] Differentiating equation (12) yields:

[0062] (13)

[0063] in, For the first The equivalent wheel angular acceleration of each drive axle For the longitudinal acceleration of the vehicle, For the first The derivative of the slip ratio of each drive axle;

[0064] Based on equations (11) and (13), the rate of change of slip deviation of the drive axle is obtained. for:

[0065] (14)

[0066] No. The ground driving force of the first drive axle and the first The driving torques of each drive axle wheel side satisfy the following relationship:

[0067] (15)

[0068] In the formula, For the first Ground driving force of each drive axle For the first Drive torque at the wheel side of each drive axle For the first The rotational inertia of each drive axle is equivalent to that of the wheel.

[0069] The driver requires wheel-side drive torque of The inter-bridge dynamic torque distribution coefficient is When the slip ratio approach strategy is adopted, the wheel-side drive torques of the middle axle and the rear axle are respectively:

[0070] (16)

[0071] Substituting equations (15) and (16) into equation (14), we obtain the dynamic relationship of the drive axle slip ratio deviation:

[0072] (17)

[0073] Change rate of drive axle slip ratio deviation The value is zero, and the longitudinal acceleration of the vehicle in equation (17) is zero. The relevant terms are treated as disturbance terms, and a slip ratio approach correction term is introduced to obtain the dynamic torque distribution coefficient:

[0074] (18)

[0075] In the formula, For the slip ratio to approach the gain, Boundary layer thickness, It is a saturation function;

[0076] When the slip state combination of the drive axle is BB, BC, CB, CC, and a slip ratio approach strategy is not adopted, the drive torque of the middle and rear axle wheels is constrained based on the upper limit of the transmittable torque of each drive axle wheel. The resulting drive torques of the middle and rear axle wheels after constraint are denoted as follows: and ;

[0077] Will and After calculating the overall transmission ratio of the corresponding drive axle transmission system, the target driving torque after the corresponding distribution constraints is obtained:

[0078] (19)

[0079] In the formula, , , , , These are the target torque of the motor, the transmission ratio of the gearbox, the transmission ratio of the main reducer, the transmission ratio of the wheel-side reducer, and the transmission efficiency after the middle bridge is constrained. , , , , These are the target torque of the motor after the rear axle is constrained, the transmission ratio of the gearbox, the transmission ratio of the main reducer, the transmission ratio of the wheel-side reducer, and the transmission efficiency.

[0080] In a further technical solution, in step 6, the slip ratio deviation is:

[0081] (20)

[0082] In the formula, For the first The slip ratio deviation of each drive axle For the first Real-time slip rate of each drive axle For the first Reference slip ratio of each drive axle;

[0083] Based on the slip ratio deviation, PID control is used to generate the motor anti-slip correction torque:

[0084] (twenty one)

[0085] In the formula, For the first Anti-slip correction torque for the motor of each drive axle , , The first The proportional coefficient, integral coefficient, and differential coefficient of the anti-slip torque correction for each drive axle.

[0086] In a further technical solution, the final target driving torque calculation formula in step 7 is as follows:

[0087] (twenty two)

[0088] in, For the first The ultimate target driving torque of each drive axle For the first The target torque of the motor after the drive axle is assigned constraints.

[0089] The torque coordination control method for dual-drive axle electric commercial vehicles under wheel speed loss conditions provided by this invention has the following beneficial effects:

[0090] (1) Anti-slip control can be achieved without relying on the wheel speed information of the drive wheel. The reference vehicle speed is calculated by using the wheel speeds of the left and right wheels of the front axle, and the equivalent speed of the drive axle wheel is calculated by combining the drive axle motor speed and the total transmission ratio of the transmission system. The drive axle slip ratio is then obtained, which effectively solves the control problem under the condition of missing wheel speed and improves the fault tolerance of the system.

[0091] (2) The parameters of the driving axle ground driving force estimation model are updated online using the recursive least squares method with forgetting factor. The data combination of driving axle ground driving force estimation value and driving axle slip ratio is linearly fitted by the rolling window method. According to the relationship between local slope and preset slope boundary threshold, the slip state is divided into underslip state, ideal slip state and overslip state. The estimation accuracy is high and the state judgment is accurate and reliable.

[0092] (3) Differentiated control is implemented according to the slip state of the drive axle. At the same time, based on the slip rate approach strategy, the torque distribution coefficient between the axles is dynamically adjusted with the goal of making the slip rate deviation between the middle axle and the rear axle approach zero, so as to achieve the coordination of the slip rates of the middle axle and the rear axle and take into account the power and stability of the whole vehicle.

[0093] (4) A two-layer control architecture combining inter-bridge drive torque distribution and constraint with anti-slip correction torque is adopted. First, macro-coordination is achieved through inter-bridge torque distribution and constraint. Then, the anti-slip correction torque of the motor is generated by PID control based on the slip rate deviation of the drive bridge that is still in the over-slip state. The target drive torque after distribution and constraint is corrected. It has fast response, high accuracy, and effectively suppresses single-bridge over-slip.

[0094] (5) The influence of the rotational inertia of the transmission system equivalent to the wheel side during acceleration is considered in the calculation of the ground driving force of the drive axle. The control model is more in line with the actual physical characteristics of the dual drive axle electric commercial vehicle and has high engineering practical value. Attached Figure Description

[0095] Figure 1 The overall control architecture diagram of a torque coordination control method for dual-drive axle electric commercial vehicles under wheel speed loss provided by an embodiment of the present invention;

[0096] Figure 2 A diagram showing the estimated ground driving forces;

[0097] Figure 3 A schematic diagram illustrating the slip state of the drive axle;

[0098] Figure 4 This is a graph showing the variation of the drive axle torque distribution coefficient.

[0099] Figure 5 The diagram shows the effect of coordinated control of driving torque under restricted road conditions (where a is the time-domain curve of the torque of the middle and rear axle drive motors, and b is the time-domain curve of the slip rate of the middle and rear axle drive axles). Detailed Implementation

[0100] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0101] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0102] like Figure 1 As shown in Table 1, this invention provides a torque coordination control method for a dual-drive axle electric commercial vehicle under wheel speed loss conditions. The method is designed using a dual-drive axle pure electric commercial vehicle as an example. The basic parameters of the vehicle are shown in Table 1.

[0103] Table 1 Basic parameters of the vehicle

[0104]

[0105] The method specifically includes the following steps:

[0106] Step 1: Obtain vehicle status information;

[0107] The vehicle's CAN bus is used to acquire real-time data on the drive axle motor speed, drive axle motor torque, and the wheel speeds of the left and right front axles (the front axle is a non-drive axle). The drive axle motor speed and torque are obtained from feedback by the corresponding motor controller, while the wheel speeds of the left and right front axles are acquired by wheel speed sensors.

[0108] Step 2: Construct the drive axle slip ratio;

[0109] The equivalent speed of the drive axle wheel side is calculated by using the drive axle motor speed and the overall transmission ratio of the transmission system. The calculation formula is as follows:

[0110] (1)

[0111] In the formula, This refers to the motor speed. This refers to the gear ratio of the transmission. Main reducer transmission ratio, This refers to the gear ratio of the wheel-side reducer.

[0112] Calculate the vehicle's base speed based on the wheel speeds of the left and right front axles. The calculation formula is as follows:

[0113] (2)

[0114] In the formula, and These are the angular velocities of the left and right non-driving wheels, respectively. This is the rolling radius of the wheel.

[0115] The slip ratio of the drive axle is calculated using the equivalent rotational speed of the drive axle wheel and the vehicle's reference speed. The calculation formula is as follows:

[0116] (3)

[0117] In the formula, This refers to the slip ratio of the drive axle.

[0118] Step 3: Identify the slippage state of the drive axle;

[0119] A model for estimating the ground driving force of the drive axle is established, and the model parameters are updated using a recursive least squares method with a forgetting factor. Synchronous data of the estimated ground driving force and the drive axle slip ratio are acquired in real time using a rolling window method. The data within the window are fitted to obtain the local slope. The drive axle slip state is determined based on the relationship between the local slope and a preset slope threshold. Specifically:

[0120] The drive torque of the drive axle wheel is obtained by converting the drive axle motor torque through the transmission ratio of the transmission system. :

[0121] (4)

[0122] In the formula, For the drive motor torque, This refers to the drive axle transmission efficiency.

[0123] Considering the effect of the transmission system's rotational inertia during acceleration, the ground driving force of the drive axle Satisfy the following formula:

[0124] (5)

[0125] In the formula, This is the equivalent rotational inertia of the transmission system to the wheel edge. This is the equivalent angular acceleration of the drive axle wheel side.

[0126] To avoid the impact of fluctuations caused by directly calculating the ground driving force of the drive axle, a ground driving force estimation model for the drive axle is established, and the recursive least squares method with a forgetting factor is used to update the model parameters in real time. Observations used for model updates at specific times for:

[0127] (6)

[0128] In the formula, For the first The regression vector at time step, and , For the first The driving torque at the wheel side of the drive axle at any given moment. For the first The equivalent angular acceleration of the drive axle wheel at any given moment; Let be the parameter vector to be estimated, and , The driving torque coefficient, The equivalent angular acceleration coefficient of the drive axle wheel edge; For the first Momentary noise.

[0129] The parameter vector is updated online using a recursive least squares method with a forgetting factor, and the estimation error is:

[0130] (7)

[0131] In the formula, For the first The time estimation error, For the first The estimated value of the time parameter vector.

[0132] The recursive formula is:

[0133] (8)

[0134] In the formula, For the first Gain vector at time step and The first With the The covariance matrix at time t, For the first The estimated value of the parameter vector at time. Forgetting factor, It is an identity matrix.

[0135] Obtain the estimated value of the ground driving force of the drive axle for:

[0136] (9)

[0137] like Figure 2 As shown, the estimated value of the ground driving force of the drive axle has a high degree of consistency with the actual value, which can meet the requirements.

[0138] A rolling window method is used to obtain synchronous data combinations of multiple sets of estimated drive axle ground driving force values ​​and drive axle slip ratios within the current window. Linear fitting is then performed on these data combinations to obtain the local slopes of the estimated drive axle ground driving force values ​​and drive axle slip ratios within the current window. .

[0139] Furthermore, based on the preset slope threshold... and ( ,in The slope threshold is used to distinguish between underslip and ideal slip. (The slope threshold separating ideal slip from excessive slip) and local slope The relationship between the two factors determines the slip state of the drive axle. When At that time, the drive axle is in an underslip state; when At that time, the drive axle is in an ideal slip state; when At this time, the drive axle is in an excessive slip state. The diagram illustrates the division of drive axle slip states. Figure 3 .

[0140] Step 4: Determine the control parameters;

[0141] Based on the slip state of the drive axle, the reference slip ratio of the drive axle and the upper limit of the torque that can be transmitted at the wheel end are updated or maintained according to the corresponding strategy.

[0142] When the drive axle is in an underslip state, the drive axle reference slip ratio and the upper limit of the wheel-side transmittable torque are not updated.

[0143] When the drive axle is in an ideal slip state, the maximum value of the estimated ground driving force of the drive axle within the current window is multiplied by the tire rolling radius to obtain the upper limit of the current wheel-side transmittable torque. The corresponding drive axle slip ratio is used as the drive axle reference slip ratio. The formula for calculating the upper limit of wheel-side transmittable torque is as follows:

[0144] (10)

[0145] In the formula, This represents the upper limit of the torque that can be transmitted by the wheel. This represents the maximum value of the estimated ground driving force.

[0146] When the drive axle is in an overslip state, the reference slip ratio of the drive axle and the upper limit of the torque that can be transmitted at the wheel end obtained in the most recent ideal slip state remain unchanged.

[0147] Step 5: Inter-bridge drive torque distribution and constraints;

[0148] Based on the combination of slip states of the middle and rear axles, a corresponding distribution and constraint strategy is implemented for the wheel-side drive torque required by the driver to obtain the target drive torque after distribution and constraint of the middle and rear axles.

[0149] The slip state of the drive axle is divided into three types: underslip state, ideal slip state, and overslip state, which are denoted as state A, state B, and state C, respectively.

[0150] Based on the slip combinations of the middle and rear axles, corresponding distribution and constraint strategies are implemented for the driver's required wheel-side drive torque. When the drive axle slip combinations are AA, AB, AC, BA, and CA, a slip ratio approach strategy is adopted to increase the torque distribution coefficient of the drive axle with the lower slip ratio and decrease the distribution coefficient of the drive axle with the higher slip ratio. During the slip ratio approach process, when the under-slip drive axle approaches the ideal slip state, further torque distribution is stopped, and the drive axle torque distribution coefficient from the previous moment is maintained to reduce the risk of the drive axle transitioning from an under-slip state to an over-slip state.

[0151] When implementing the slip ratio approaching strategy, the control objective for inter-axle torque distribution is to make the slip ratio deviation between the middle and rear axles approach zero.

[0152] (11)

[0153] In the formula, The difference in slip ratio between the middle and rear axles and These are the drive axle slip ratios for the middle and rear axles, respectively.

[0154] According to the definition of drive axle slip ratio, the first individual drive axle slip ratio It can be represented as

[0155] (12)

[0156] In the formula, For the first The equivalent wheel side angular velocity of each drive axle For the middle bridge, For the rear axle (parameters related to subsequent locations) The positions of these terms all have the same meaning.

[0157] Differentiating equation (12), we get:

[0158] (13)

[0159] in, For the first The equivalent wheel angular acceleration of each drive axle For the longitudinal acceleration of the vehicle, For the first The derivative of the slip ratio of each drive axle;

[0160] Based on equations (11) and (13), the rate of change of slip deviation of the drive axle is obtained. for:

[0161] (14)

[0162] No. The ground driving force of the first drive axle and the first The driving torques of each drive axle wheel side satisfy the following relationship:

[0163] (15)

[0164] In the formula, For the first Ground driving force of each drive axle For the first Drive torque at the wheel side of each drive axle For the first The rotational inertia of each drive axle is equivalent to that of the wheel.

[0165] The driver requires wheel-side drive torque of The inter-bridge dynamic torque distribution coefficient is When the slip ratio approach strategy is adopted, the wheel-side drive torques of the middle axle and the rear axle are respectively:

[0166] (16)

[0167] Substituting equations (15) and (16) into equation (14), we obtain the dynamic relationship of the drive axle slip ratio deviation:

[0168] (17)

[0169] Change rate of drive axle slip ratio deviation The value is zero, and the longitudinal acceleration of the vehicle in equation (17) is zero. Treating the relevant terms as disturbance terms and introducing a slip ratio approach correction term, the dynamic torque distribution coefficient can be obtained:

[0170] (18)

[0171] In the formula, For the slip ratio to approach the gain, Boundary layer thickness, It is a saturation function.

[0172] When the drive axle slip state combination is BB, BC, CB, CC, and a slip rate approximation strategy is not adopted, the drive torque of the middle and rear axle wheels is constrained based on the upper limit of the transmittable torque of each drive axle wheel. The resulting drive torques of the middle and rear axle wheels after constraint are denoted as follows: and .

[0173] Will and After calculating the overall transmission ratio of the corresponding drive axle transmission system, the target driving torque after the corresponding distribution constraints is obtained:

[0174] (19)

[0175] In the formula, , , , , These are the target torque of the motor, the transmission ratio of the gearbox, the transmission ratio of the main reducer, the transmission ratio of the wheel-side reducer, and the transmission efficiency after the middle bridge is constrained. , , , , These are the target torque of the motor after the rear axle is constrained, the transmission ratio of the gearbox, the transmission ratio of the main reducer, the transmission ratio of the wheel-side reducer, and the transmission efficiency.

[0176] Step 6: Drive axle anti-slip torque correction;

[0177] For drive axles that are still in an overslip state after the distribution and constraint of inter-axle drive torque, anti-slip correction torque is generated based on the deviation between the real-time slip ratio of the drive axle and the reference slip ratio, and the target drive torque after distribution and constraint is corrected.

[0178] The slip ratio deviation is:

[0179] (20)

[0180] In the formula, For the first The slip ratio deviation of each drive axle For the first Real-time slip rate of each drive axle For the first Reference slip ratio of each drive axle.

[0181] Based on the slip ratio deviation, PID control is used to generate the motor anti-slip correction torque:

[0182] (twenty one)

[0183] In the formula, For the first Anti-slip correction torque for the motor of each drive axle , , The first The proportional coefficient, integral coefficient, and differential coefficient of the anti-slip torque correction for each drive axle.

[0184] Step 7: Generate and output the target driving torque;

[0185] The target driving torque generated in step 5 after allocation and constraint is superimposed with the corresponding anti-slip correction torque to generate the final target driving torque:

[0186] (twenty two)

[0187] in, For the first The ultimate target driving torque of each drive axle For the first The target torque of the motor after the drive axle is assigned constraints;

[0188] Finally, the target driving torque is output to the corresponding drive axle motor for execution.

[0189] To verify the effectiveness of this method, it was validated in the Trucksim / Simulink co-simulation environment. The simulation condition was set as a uniform low-adhesion road surface with a road adhesion coefficient of 0.2, and the vehicle started from a standstill with 60% accelerator pedal opening. The dynamic torque distribution coefficient of the drive axle is as follows: Figure 4 As shown, this method can adjust the inter-axle drive torque distribution ratio in real time according to the difference in slip state between the middle and rear axles, achieving dynamic and coordinated distribution of drive torque between the middle and rear axles. The effect of coordinated drive torque control is as follows: Figure 5 a and Figure 5 As shown in b, this method can effectively adjust the motor drive torque, keeping the drive axle slip ratio at a low level and ensuring the vehicle's driving safety under road conditions with limited adhesion.

[0190] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A torque coordination control method for a dual-drive axle electric commercial vehicle under wheel speed loss, characterized in that, Includes the following steps: Step 1: Obtain the drive axle motor speed, drive axle motor torque, and front axle left and right wheel speeds in real time via the vehicle's CAN bus; Step 2: Calculate the equivalent speed of the drive axle wheel using the drive axle motor speed and the total transmission ratio of the transmission system. Calculate the vehicle reference speed based on the wheel speeds of the left and right front axle wheels. Calculate the drive axle slip ratio using the equivalent speed of the drive axle wheel and the vehicle reference speed. Step 3: Establish a ground driving force estimation model for the drive axle, and update the model parameters using the recursive least squares method with a forgetting factor; The synchronous data combination of the estimated ground driving force of the drive axle and the slip ratio of the drive axle is obtained in real time by using the rolling window method. The data combination in the current window is fitted to obtain the local slope of the estimated ground driving force of the drive axle and the slip ratio of the drive axle in the current window. The slip state of the drive axle is determined according to the relationship between the local slope and the preset slope threshold. Step 4: Update or maintain the reference slip ratio and the upper limit of the torque that can be transmitted to the wheel side of the drive axle according to the slip state of the drive axle; Step 5: Based on the combination of slip states of the middle and rear axles, implement corresponding distribution and constraint strategies for the driver's required wheel-side drive torque to obtain the target drive torque after distribution and constraint of the middle and rear axles; Step 6: For the drive axle that is still in an overslip state after the inter-axle drive torque distribution and constraint, generate anti-slip correction torque based on the deviation between the real-time slip ratio of the drive axle and the reference slip ratio, and correct the target drive torque after distribution and constraint. Step 7: The target driving torque generated in Step 5 after allocation and constraint is superimposed with the corresponding anti-slip correction torque to generate the final target driving torque, and then output to the corresponding drive axle motor for execution. In step 2, the formula for calculating the equivalent speed of the drive axle wheel side using the drive axle motor speed and the total transmission ratio of the transmission system is as follows: （1） In the formula, To drive the equivalent speed of the axle wheel, This refers to the motor speed. This refers to the gear ratio of the transmission. Main reducer transmission ratio, This refers to the gear ratio of the wheel-side reducer; The formula for calculating the vehicle's base speed based on the wheel speeds of the left and right front axles is as follows: （2） In the formula, The vehicle's base speed. and These are the angular velocities of the left and right non-driving wheels, respectively. The radius of the wheel's rolling radius; The formula for calculating the slip ratio of the drive axle, using the equivalent rotational speed of the drive axle wheel and the vehicle's reference speed, is as follows: （3） In the formula, For drive axle slip ratio; In step 3, the establishment of the ground driving force estimation model for the drive axle specifically includes: The drive torque of the drive axle wheel is obtained by converting the drive axle motor torque through the transmission ratio of the transmission system. : （4） In the formula, For the drive motor torque, For drive axle transmission efficiency; Drive axle ground driving force Satisfy the following formula: （5） In the formula, This is the equivalent rotational inertia of the transmission system to the wheel edge. This is the equivalent angular acceleration of the drive axle wheel side.

2. The torque coordination control method for dual-drive axle electric commercial vehicles under wheel speed loss as described in claim 1, characterized in that, In step 3, the specific method for updating the model parameters using the recursive least squares method with a forgetting factor is as follows: No. Observations used for model updates at specific times for: （6） In the formula, For the first The regression vector at time step, and , For the first The driving torque at the wheel side of the drive axle at any given moment. For the first The equivalent angular acceleration of the drive axle wheel at any given moment; Let be the parameter vector to be estimated, and , The driving torque coefficient, The equivalent angular acceleration coefficient of the drive axle wheel edge; For the first Momentary noise; The parameter vector is updated online using a recursive least squares method with a forgetting factor, and the estimation error is: （7） In the formula, For the first The time estimation error, For the first Estimates of the time parameter vector; The recursive formula is: （8） In the formula, For the first Gain vector at time step and The first With the The covariance matrix at time t, For the first The estimated value of the parameter vector at time. Forgetting factor, It is the identity matrix; Obtain the estimated value of the ground driving force of the drive axle for: （9）。 3. The torque coordination control method for dual-drive axle electric commercial vehicles under wheel speed loss as described in claim 2, characterized in that, In step 3, the slip state of the drive axle is determined based on the relationship between the local slope and a preset slope threshold, specifically including: Based on the preset slope threshold and With local slope The relationship between the two factors determines the slip state of the drive axle. The slope threshold is used to distinguish between underslip and ideal slip. The slope threshold is the dividing line between ideal slip and excessive slip, and ;when At that time, the drive axle is in an underslip state; when At that time, the drive axle is in an ideal slip state; when At that time, the drive axle is in an excessive slip state.

4. The torque coordination control method for dual-drive axle electric commercial vehicles under wheel speed loss as described in claim 3, characterized in that, Step 4 specifically includes: When the drive axle is in an underslip state, the drive axle reference slip ratio and the upper limit of the wheel-side transmittable torque are not updated. When the drive axle is in an ideal slip state, the maximum value of the estimated ground driving force of the drive axle within the current window is multiplied by the tire rolling radius to obtain the upper limit of the current wheel-side transmittable torque. The corresponding drive axle slip ratio is used as the drive axle reference slip ratio. The formula for calculating the upper limit of wheel-side transmittable torque is as follows: （10） In the formula, This represents the upper limit of the torque that can be transmitted by the wheel. This represents the maximum value of the estimated ground driving force. When the drive axle is in an overslip state, the reference slip ratio of the drive axle and the upper limit of the torque that can be transmitted at the wheel end obtained in the most recent ideal slip state remain unchanged.

5. The torque coordination control method for dual-drive axle electric commercial vehicles under wheel speed loss as described in claim 4, characterized in that, Step 5 specifically includes: The slip state of the drive axle is divided into three types: underslip state, ideal slip state, and overslip state, which are denoted as state A, state B, and state C, respectively. When the drive axle slip state combination is AA, AB, AC, BA, CA, a slip ratio approach strategy is adopted to increase the torque distribution coefficient of the drive axle on the side with lower slip ratio and decrease the torque distribution coefficient of the drive axle on the side with higher slip ratio. During the slip ratio approach process, when the drive axle in the underslip state approaches the ideal slip state, further torque distribution is stopped, and the drive axle torque distribution coefficient of the previous moment is maintained. When implementing the slip ratio approaching strategy, the control objective for inter-axle torque distribution is to make the slip ratio deviation between the middle and rear axles approach zero. （11） In the formula, The difference in slip ratio between the middle and rear axles and These are the drive axle slip ratios for the middle and rear axles, respectively. According to the definition of drive axle slip ratio, the first individual drive axle slip ratio Represented as （12） In the formula, For the first The equivalent wheel side angular velocity of each drive axle For the middle bridge, For the rear axle; Differentiating equation (12) yields: （13） in, For the first The equivalent wheel angular acceleration of each drive axle For the longitudinal acceleration of the vehicle, For the first The derivative of the slip ratio of each drive axle; Based on equations (11) and (13), the rate of change of slip deviation of the drive axle is obtained. for: （14） No. The ground driving force of the first drive axle and the first The driving torques of each drive axle wheel side satisfy the following relationship: （15） In the formula, For the first Ground driving force of each drive axle For the first Drive torque at the wheel side of each drive axle For the first The rotational inertia of each drive axle is equivalent to that of the wheel. The driver requires wheel-side drive torque of The inter-bridge dynamic torque distribution coefficient is When the slip ratio approach strategy is adopted, the wheel-side drive torques of the middle axle and the rear axle are respectively: （16） Substituting equations (15) and (16) into equation (14), we obtain the dynamic relationship of the drive axle slip ratio deviation: （17） Change rate of drive axle slip ratio deviation The value is zero, and the longitudinal acceleration of the vehicle in equation (17) is zero. The relevant terms are treated as disturbance terms, and a slip ratio approach correction term is introduced to obtain the dynamic torque distribution coefficient: （18） In the formula, For the slip ratio to approach the gain, Boundary layer thickness, It is a saturation function; When the slip state combination of the drive axle is BB, BC, CB, CC, and a slip ratio approach strategy is not adopted, the drive torque of the middle and rear axle wheels is constrained based on the upper limit of the transmittable torque of each drive axle wheel. The resulting drive torques of the middle and rear axle wheels after constraint are denoted as follows: and ; Will and After calculating the overall transmission ratio of the corresponding drive axle transmission system, the target driving torque after the corresponding distribution constraints is obtained: （19） In the formula, , , , , These are the target torque of the motor, the transmission ratio of the gearbox, the transmission ratio of the main reducer, the transmission ratio of the wheel-side reducer, and the transmission efficiency after the middle bridge is constrained. , , , , These are the target torque of the motor after the rear axle is constrained, the transmission ratio of the gearbox, the transmission ratio of the main reducer, the transmission ratio of the wheel-side reducer, and the transmission efficiency.

6. The torque coordination control method for dual-drive axle electric commercial vehicles under wheel speed loss as described in claim 5, characterized in that, In step 6, the slip ratio deviation is: （20） In the formula, For the first The slip ratio deviation of each drive axle For the first Real-time slip rate of each drive axle For the first Reference slip ratio of each drive axle; Based on the slip ratio deviation, PID control is used to generate the motor anti-slip correction torque: （21） In the formula, For the first Anti-slip correction torque for the motor of each drive axle , , The first The proportional coefficient, integral coefficient, and differential coefficient of the anti-slip torque correction for each drive axle.

7. The torque coordination control method for dual-drive axle electric commercial vehicles under wheel speed loss as described in claim 6, characterized in that, In step 7, the final target driving torque is calculated using the following formula: （22） in, For the first The ultimate target driving torque of each drive axle For the first The target torque of the motor after the drive axle is assigned constraints.

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