Anti-skid control method and system for double-electric-drive-axle tractor, driving system and tractor

Abstract

The invention relates to a double-electric-drive-axle tractor anti-skid control method and system, a driving system and a tractor. The control method comprises the steps that a first parameter and a second parameter are obtained; the first parameters comprise a front axle wheel speed, a middle axle wheel speed, a rear axle wheel speed and a vehicle speed; the second parameters comprise an accelerator pedal state, a brake pedal state, an energy recovery gear state and a gear state; according to the front axle wheel speed, the middle axle wheel speed and the rear axle wheel speed, the slip rate of middle axle wheels and the slip rate of rear axle wheels are determined; determining the slipping state of the vehicle according to the front axle wheel speed, the rear axle wheel speed and the vehicle speed; determining a vehicle driving state according to the second parameter; determining a torque control strategy according to the driving state of the vehicle; and according to the torque control strategy, the torque of the middle axle motor and the torque of the rear axle motor are adjusted till the slip rate of middle axle wheels and the slip rate of rear axle wheels are smaller than or equal to a preset first threshold value.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicles, and in particular to an anti-skid control method and system for a dual-electric drive axle tractor, a drive system and a tractor. Background Art

[0002] At present, most pure electric heavy trucks are remodeled by replacing the engine with the motor, and are in the stage of "oil to electricity". Some manufacturers have launched "dual-motor" drive models based on economic considerations, while our company adopts a distributed drive mode, which lacks the torque distribution function between the shafts of mechanical transmission. Therefore, anti-skid control during driving and braking is very important. Due to the complexity and uncertainty of road conditions, such as wet, icy, uneven, the vehicle is prone to wheel slip during driving and braking.

[0003] The traditional response method of the drive system is to use independent systems such as ASR and TCS. By limiting the total torque, the limit will be too low and the vehicle will stop. This will not only reduce the vehicle's power performance and braking effect, but may also cause the vehicle to lose control and cause a safety accident.

[0004] The traditional response method of the braking system adopts independent systems such as ABS and EBS. Due to the characteristics of energy recovery in electric vehicles, when the driver only uses energy recovery for braking, the drive axle may slip due to reasons such as slippery road surface. However, if the driver does not step on the brake pedal, the ABS and EBS functions cannot be activated at this time, resulting in an accident.

[0005] There are mainly the following ways to prevent skidding when driving and braking commercial vehicles:

[0006] Drive anti-skid control mode:

[0007] Once the Acceleration Sl ip Regulation (ASR) system determines that the drive wheel is slipping, it will take a variety of control measures, such as reducing the output power of the engine, reducing the power output of the engine by adjusting the throttle opening, reducing the amount of fuel injection, etc. Braking the slipping drive wheel, reducing its speed by applying a certain braking force, and restoring the drive wheel to a normal rotation state.

[0008] Traction Control System (TCS): monitors wheel speed in real time. When the driving wheel speed exceeds the set threshold (i.e. slippage), it controls wheel slippage by reducing engine power output or braking the slipping wheel. For example, when accelerating on a slippery road, TCS detects wheel slippage and reduces the engine's fuel supply or applies brakes to the slipping wheel.

[0009] When the above two methods are applied to dual electric drive axle vehicles, if a single axle slips, the vehicle power will be reduced as a whole, and both the slipping axle and the non-slipping axle will be torque-limited simultaneously, which makes it impossible to maximize the grip. If both axles slip at the same time, the power will be limited uniformly according to the axle with the most serious slip. If the torque limit is too low, the vehicle will stop, which will make it more difficult to start after stopping.

[0010] Braking anti-skid control mode:

[0011] Anti-lock Braking System (ABS): prevents wheels from locking during braking and keeps them rolling, thereby improving braking effect and vehicle handling. When a wheel is about to lock, ABS will automatically adjust the brake pressure to keep the wheel rolling and sliding.

[0012] Electronic Stability Control (ESC): When braking and steering, the vehicle's driving posture is adjusted by braking individual wheels to prevent skidding and loss of control.

[0013] When the above two methods are applied in dual electric drive axle models, the above functions cannot be activated in the case of pure energy recovery, so additional functions are needed to control the braking slip during the electric recovery process.

[0014] The above problems need to be solved urgently. Summary of the invention

[0015] The invention discloses an anti-skid control method and system for a dual-electric drive axle tractor, a drive system and a tractor, aiming to solve the technical problems existing in the prior art.

[0016] The present invention adopts the following technical solutions:

[0017] In a first aspect, the present invention provides an anti-skid control method for a dual-electric drive axle tractor, the tractor comprising a middle axle motor, a rear axle motor, a front axle wheel, a middle axle wheel and a rear axle wheel; the middle axle motor is used to drive the middle axle wheel to rotate; the rear axle motor is used to drive the rear axle wheel to rotate, and the control method comprises the following steps:

[0018] Acquire vehicle driving parameters, the vehicle driving parameters including a first parameter and a second parameter; the first parameter includes a front axle wheel speed, a middle axle wheel speed, a rear axle wheel speed and a vehicle speed; the second parameter includes an accelerator pedal state, a brake pedal state, an energy recovery gear state and a gear state;

[0019] Determining the slip rate of the middle axle wheel and the slip rate of the rear axle wheel according to the front axle wheel speed, the middle axle wheel speed and the rear axle wheel speed;

[0020] determining a slip state of the vehicle according to the front axle wheel speed, the rear axle wheel speed and the vehicle speed;

[0021] determining a vehicle driving state according to the second parameter, wherein the vehicle driving state includes a driving state and a braking state;

[0022] If the slipping state of the vehicle is a slipping state, then determining a torque control strategy according to the driving state of the vehicle;

[0023] The torque of the mid-axle motor and the rear-axle motor is adjusted according to the torque control strategy until the slip rate of the mid-axle wheel and the slip rate of the rear-axle wheel are less than or equal to a preset first threshold.

[0024] In a second aspect, the present invention further provides an anti-skid control system, comprising:

[0025] A parameter acquisition module, used to acquire vehicle driving parameters, the vehicle driving parameters including a first parameter and a second parameter; the first parameter includes a front axle wheel speed, a middle axle wheel speed, a rear axle wheel speed and a vehicle speed; the second parameter includes an accelerator pedal state, a brake pedal state, an energy recovery gear state and a gear state;

[0026] A first calculation module, used for determining the slip rate of the middle axle wheel and the slip rate of the rear axle wheel according to the front axle wheel speed, the middle axle wheel speed and the rear axle wheel speed;

[0027] A slip state determination module, used for determining the slip state of the vehicle according to the front axle wheel speed, the rear axle wheel speed and the vehicle speed;

[0028] A driving state determination module, used to determine the driving state of the vehicle according to the second parameter, wherein the driving state of the vehicle includes a driving state and a braking state;

[0029] A control strategy generating module, used for determining a torque control strategy according to the driving state of the vehicle when the vehicle is in a slipping state;

[0030] An execution module is used to adjust the torque of the mid-axle motor and the rear-axle motor according to the torque control strategy until the slip rate of the mid-axle wheel and the slip rate of the rear-axle wheel are less than or equal to a preset first threshold.

[0031] In a third aspect, the present invention further provides a drive system, comprising:

[0032] Controller, mid-axle motor control unit, rear-axle motor control unit, front axle, mid-axle and rear axle;

[0033] The middle bridge motor control unit is used to control the rotation of the middle bridge wheels through the middle shaft;

[0034] The rear axle motor control unit is used to control the rotation of the rear axle wheels through the rear axle;

[0035] The controller is used to execute the control method described above.

[0036] In a fourth aspect, the present invention further provides a tractor, which comprises the above-mentioned drive system.

[0037] The technical solution adopted by the present invention can achieve the following beneficial effects:

[0038] The present invention mainly provides an anti-skid control method for a dual-electric drive axle tractor, which determines the vehicle driving state based on the accelerator pedal state, brake pedal state, energy recovery gear state and gear state, and determines the torque control strategy according to different vehicle driving states when the vehicle slips, so as to maximize the use of the adhesion coefficient, adapt to different driving states, improve transportation efficiency and reduce accident risks; and the vehicle driving state is determined by the energy recovery gear state, then the larger braking force in the energy recovery gear state is optimized; by transferring and adjusting the torque between the middle axle motor and the rear axle motor torque, rather than controlling the dual motor torque in the control mode of a single motor, it is avoided that the torque is too low to cause the vehicle to stop. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments, which constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions explain the present invention and do not constitute improper limitations on the present invention. In the drawings:

[0040] Figure 1 The present invention is a schematic flow chart of an anti-skid control method for a dual-electric drive axle tractor. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. In the description of the present invention, it should be noted that the term "or" is usually used in the sense of including "and / or", unless the content clearly indicates otherwise.

[0042] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or a magnetic connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance. In the description of the present invention, the meaning of "multiple" is at least two, such as two, three or more, etc., unless otherwise clearly and specifically limited.

[0043] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] In order to solve the problems existing in the prior art, the embodiments of the present application provide a dual electric drive axle tractor anti-skid control method, system, drive system and tractor.

[0045] A method for preventing slip of a dual electric drive axle tractor, the tractor comprises a middle axle motor, a rear axle motor, a front axle wheel, a middle axle wheel and a rear axle wheel; the middle axle motor is used to drive the middle axle wheel to rotate; the rear axle motor is used to drive the rear axle wheel to rotate, such as Figure 1 As shown, the following steps are included:

[0046] Obtain vehicle driving parameters, which include a first parameter and a second parameter; the first parameter includes the front axle wheel speed, the middle axle wheel speed, the rear axle wheel speed and the vehicle speed; the second parameter includes the accelerator pedal state, the brake pedal state, the energy recovery gear state and the gear state; specifically, the vehicle speed is the average vehicle speed, that is, the average of the front axle wheel speed, the middle axle wheel speed and the rear axle wheel speed, and its calculation is mainly derived from the EBS (Electronic Brake Systems) vehicle speed and the VCU (Vehicle Control Unit) vehicle controller, which is calculated by motor speed*speed ratio*tire rolling radius.

[0047] Determining the slip ratio of the middle axle wheel and the slip ratio of the rear axle wheel according to the front axle wheel speed, the middle axle wheel speed and the rear axle wheel speed;

[0048] Determine the skidding state of the vehicle based on the front axle wheel speed, the rear axle wheel speed and the vehicle speed;

[0049] Determining a vehicle driving state according to the second parameter, the vehicle driving state including a driving state and a braking state;

[0050] If the vehicle is in a slipping state, then a torque control strategy is determined according to the vehicle driving state;

[0051] The torque of the mid-axle motor and the rear-axle motor is adjusted according to the torque control strategy until the slip rate of the mid-axle wheel and the slip rate of the rear-axle wheel are less than or equal to a preset first threshold; preferably, the first threshold can be 5% to 10%, specifically, it can be selected according to different vehicle loads.

[0052] The present invention provides an anti-skid control method for a dual-electric drive axle tractor. The method determines the vehicle driving state based on the accelerator pedal state, the brake pedal state, the energy recovery gear state and the gear state, and determines the torque control strategy according to different vehicle driving states when the vehicle slips. The method can maximize the use of the adhesion coefficient, adapt to different driving states, improve transportation efficiency and reduce accident risks. The vehicle driving state is determined by the energy recovery gear state, and the larger braking force in the energy recovery gear state is optimized. The torque is transferred and adjusted between the middle axle motor and the rear axle motor torque, rather than controlling the dual motor torque in a single motor control manner, to avoid vehicle parking due to excessively low torque.

[0053] The steps of determining the torque control strategy according to the vehicle driving state include:

[0054] If the vehicle driving state is the driving state, and one of the slip ratios of the middle axle wheels and the rear axle wheels is greater than the first threshold and the other is less than the first threshold, then the following driving control strategy is executed: the middle axle and the rear axle with the higher slip ratio are reduced according to the first torque adjustment value, and the torque of the one with the lower slip ratio is increased according to the first torque adjustment value;

[0055] If the vehicle is in a braking state, and one of the slip rates of the middle axle wheels and the rear axle wheels is greater than a first threshold and the other is less than the first threshold, then, before the brake pedal is applied, the following braking control strategy is executed: the torque of the middle axle and the rear axle with a higher slip rate is reduced according to a first torque adjustment value, and the torque of the middle axle and the rear axle with a lower slip rate is increased according to the first torque adjustment value.

[0056] Preferably, the first torque adjustment value is calculated by the following formula:

[0057] △F=P*(the larger of the middle axle slip rate or the rear axle slip rate - the first threshold)+i*load coefficient, wherein △F is the first torque adjustment value, P is the proportional coefficient, P=1000*(the larger of the middle axle slip rate or the rear axle slip rate - the first threshold), i=50Nm, and the load coefficient is 1-10. Specifically, the load coefficient is calculated based on the following formula: F=ma, wherein F is the wheel-side driving force, a is the vehicle acceleration, and m is the estimated vehicle mass; the mass of the vehicle in the empty state is 10t, and the total overload mass is 100t, then the load coefficient is 1-10, and the specific value of the load coefficient is determined by the estimated vehicle mass, such as when the estimated vehicle mass is 70t, the load coefficient is 7.

[0058] Among them, the reduction rate of reducing the first torque adjustment value is S1; the increase rate of increasing the first torque adjustment value is S2; S1=2S2; specifically, the rate of torque reduction or increase is determined according to the requested torque, vehicle speed, and transmission gear, for example, 100Nm / 100ms; it can be adjusted according to needs and is not limited here; preferably, when the vehicle is in a braking state, the reduction rate of the first torque adjustment value is greater than the reduction rate of the first torque adjustment value when the vehicle is in a driving state.

[0059] In some preferred embodiments, the constant torque control strategy further includes:

[0060] If the slip rate of the middle axle wheel and the slip rate of the rear axle wheel are both greater than the first threshold, then the torque values ​​of the middle axle motor and the rear axle motor are reduced;

[0061] If the slip ratio of the middle axle wheel and the slip ratio of the rear axle wheel are both less than or equal to the first threshold, then no torque adjustment is performed. Based on different slip ratios, different adjustments are performed to ensure normal driving of the vehicle while maintaining control of the slip ratio and maintaining a large driving force.

[0062] In some preferred embodiments, the step of determining the torque control strategy according to the vehicle driving state further includes:

[0063] Determine whether the vehicle is in a turning state. If so, reduce the first torque adjustment value in the driving control strategy and the braking control strategy by 0-20%. The specific selection is linear matching according to the steering wheel angle range (0-100%). For example, if the steering wheel angle is 50%, the first torque adjustment value is reduced by 10%. When turning, the resistance received by the vehicle is increased due to the angle between the front axle wheels and the forward direction. Therefore, when turning, the road surface provides greater resistance to the tires. Therefore, if the anti-skid torque is set according to straight driving, it will be over-adjusted. Therefore, for turning slip conditions, the torque limit value will be smaller.

[0064] In some preferred embodiments, the step of determining the slip rate of the middle bridge according to the first parameter comprises:

[0065] The first slip ratio of the middle axle is calculated according to the wheel speed of the front axle and the wheel speed of the middle axle; specifically, the first slip ratio of the middle axle wheel=(middle axle wheel speed-front axle wheel speed) / front axle wheel speed.

[0066] The second slip rate of the middle axle is calculated according to the following formula: the second slip rate of the middle axle = 0.377*middle axle motor speed*middle axle wheel radius) / (middle axle gear ratio*front axle wheel speed), wherein the middle axle gear ratio refers to the speed ratio corresponding to the gear of the middle axle gearbox.

[0067] The first slip rate of the middle bridge is compared with the second slip rate of the middle bridge to confirm the slip rate of the middle bridge; based on the slip rates obtained by different parameters, and the stable value of the slip rate fluctuation is used as the final slip rate value, the accuracy of the slip rate is improved, thereby improving the accuracy of torque control.

[0068] In some preferred embodiments, the step of determining the slip ratio of the rear axle according to the first parameter comprises:

[0069] The first slip ratio of the rear axle is calculated according to the wheel speed of the middle axle and the wheel speed of the rear axle; specifically, the first slip ratio of the rear axle wheel=(rear axle wheel speed-front axle wheel speed) / front axle wheel speed.

[0070] The second slip rate of the rear axle is calculated according to the following formula: the second slip rate of the rear axle = 0.377*rear axle motor speed*rear axle wheel radius / (rear axle gear ratio*front axle wheel speed); wherein the rear axle gear ratio refers to the speed ratio corresponding to the rear axle gearbox gear.

[0071] The first slip rate of the rear axle is compared with the second slip rate of the rear axle to confirm the slip rate of the rear axle; based on the slip rates obtained by different parameters, and the value of the slip rate fluctuation being stable as the final slip rate value, the accuracy of the slip rate is improved, thereby improving the accuracy of the torque control.

[0072] In some preferred embodiments, the step of determining the vehicle driving state according to the second parameter includes:

[0073] If the accelerator pedal state is valid, the gear state is D / M gear, and the torque of the middle axle motor and the rear axle motor is positive, or if the accelerator pedal state is valid, the gear state is R gear, and the torque of the middle axle motor and the rear axle motor is negative, then the vehicle driving state is judged to be the driving state;

[0074] If the accelerator pedal state is invalid, the brake pedal state is valid, or the energy recovery gear state is valid, then it is determined that the vehicle driving state is a braking state.

[0075] In some preferred embodiments, the step of determining the vehicle's slip state based on the front axle wheel speed, the rear axle wheel speed and the vehicle speed comprises:

[0076] The vehicle speed is ≥ the second threshold, and the rear axle wheel speed / front axle wheel speed-1> the third threshold, or,

[0077] The vehicle speed is less than the second threshold, and the rear axle wheel speed minus the front axle wheel speed is greater than the fourth threshold,

[0078] Then, the vehicle's skidding state is skidding. The diversified calculation based on vehicle speed can make judgments in abnormal situations such as signal loss, which increases its own reliability.

[0079] Preferably, the second threshold value may be selected as 5 km / h, the third threshold value may be selected as 20%, and the fourth threshold value may be selected as 5 km / h. Of course, other values ​​may be selected, depending on the specific requirements.

[0080] In some preferred embodiments, the method further includes determining the degree of slippage according to the slip rate of the middle axle or the rear axle, and adjusting the first torque adjustment value according to the degree of slippage, as follows:

[0081] If the slip rate of the middle axle or rear axle is less than 5%, no torque adjustment is performed;

[0082] If the slip ratio of the middle axle or the rear axle is greater than or equal to 5% and less than or equal to 10%, the first torque adjustment value is 30% of the calculated value;

[0083] If the slip ratio of the middle axle or the rear axle is greater than 10% and less than or equal to 15%, the first torque adjustment value is 70% of the calculated value;

[0084] If the slip ratio of the middle axle or the rear axle is greater than 15%, the first torque adjustment value is 100% of the calculated value;

[0085] Based on the adjustment of different first torque adjustment values ​​determined by different slip ratios, the slip ratio adjustment is achieved while ensuring the vehicle power to ensure the normal driving of the vehicle.

[0086] Example 2

[0087] This embodiment provides an anti-skid control system, which includes:

[0088] A parameter acquisition module, used to acquire vehicle driving parameters, the vehicle driving parameters including a first parameter and a second parameter; the first parameter includes a front axle wheel speed, a middle axle wheel speed, a rear axle wheel speed and a vehicle speed; the second parameter includes an accelerator pedal state, a brake pedal state, an energy recovery gear state and a gear state;

[0089] A first calculation module, used for determining the slip rate of the middle axle wheel and the slip rate of the rear axle wheel according to the front axle wheel speed, the middle axle wheel speed and the rear axle wheel speed;

[0090] A slip state determination module, used for determining the slip state of the vehicle according to the front axle wheel speed, the rear axle wheel speed and the vehicle speed;

[0091] A driving state determination module, used to determine the driving state of the vehicle according to the second parameter, wherein the driving state of the vehicle includes a driving state and a braking state;

[0092] A control strategy generating module, used for determining a torque control strategy according to the driving state of the vehicle when the vehicle is in a slipping state;

[0093] An execution module is used to adjust the torque of the mid-axle motor and the rear-axle motor according to the torque control strategy until the slip rate of the mid-axle wheel and the slip rate of the rear-axle wheel are less than or equal to a preset first threshold.

[0094] Example 3

[0095] This embodiment provides a driving system, which includes:

[0096] Controller, mid-axle motor control unit, rear-axle motor control unit, front axle, mid-axle and rear axle;

[0097] The middle bridge motor control unit is used to control the rotation of the middle bridge wheels through the middle shaft;

[0098] The rear axle motor control unit is used to control the rotation of the rear axle wheels through the rear axle;

[0099] The controller is used to execute the control method in the above-mentioned embodiment 1.

[0100] Example 4

[0101] This embodiment provides a tractor, which includes the drive system in the above-mentioned embodiment 3.

[0102] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A method for preventing slip of a dual electric drive axle tractor, wherein the tractor comprises a middle axle motor, a rear axle motor, a front axle wheel, a middle axle wheel and a rear axle wheel; the middle axle motor is used to drive the middle axle wheel to rotate; the rear axle motor is used to drive the rear axle wheel to rotate, characterized in that: The steps include: Acquire vehicle driving parameters, the vehicle driving parameters including a first parameter and a second parameter; the first parameter includes a front axle wheel speed, a middle axle wheel speed, a rear axle wheel speed and a vehicle speed; the second parameter includes an accelerator pedal state, a brake pedal state, an energy recovery gear state and a gear state; Determining the slip rate of the middle axle wheel and the slip rate of the rear axle wheel according to the front axle wheel speed, the middle axle wheel speed and the rear axle wheel speed; determining a slip state of the vehicle according to the front axle wheel speed, the rear axle wheel speed and the vehicle speed; determining a vehicle driving state according to the second parameter, wherein the vehicle driving state includes a driving state and a braking state; If the slipping state of the vehicle is a slipping state, then determining a torque control strategy according to the driving state of the vehicle; The torque of the mid-axle motor and the rear-axle motor is adjusted according to the torque control strategy until the slip rate of the mid-axle wheel and the slip rate of the rear-axle wheel are less than or equal to a preset first threshold.

2. The anti-skid control method for a dual electric drive axle tractor according to claim 1, characterized in that: The step of determining the torque control strategy according to the vehicle driving state comprises: If the vehicle driving state is a driving state, and one of the slip ratios of the middle axle wheels and the rear axle wheels is greater than the first threshold and the other is less than the first threshold, then the following driving control strategy is executed: the middle axle and the rear axle with a higher slip ratio are reduced according to the first torque adjustment value, and the torque of the middle axle and the rear axle with a lower slip ratio are increased according to the first torque adjustment value; If the vehicle is in a braking state, and one of the slip rates of the middle axle wheels and the rear axle wheels is greater than the first threshold and the other is less than the first threshold, then, before the brake pedal is applied, the following braking control strategy is executed: the torque with higher slip rates in the middle axle and the rear axle is reduced according to the first torque adjustment value, and the torque with lower slip rates is increased according to the first torque adjustment value.

3. The anti-skid control method for a dual electric drive axle tractor according to claim 2, characterized in that: The first torque adjustment value is calculated by the following formula: △F=P*(the larger value of the middle axle slip rate or the rear axle slip rate-the first threshold)+i*load coefficient, wherein △F is the first torque adjustment value, P is the proportional coefficient, P=1000*(the larger value of the middle axle slip rate or the rear axle slip rate-the first threshold), i=50Nm, and the load coefficient is 1-10; The decreasing rate of decreasing the first torque adjustment value is S1; the increasing rate of increasing the first torque adjustment value is S2; S1=2S2.

4. The anti-skid control method for a dual electric drive axle tractor according to claim 2, characterized in that: The step of determining the torque control strategy according to the vehicle driving state also includes: It is determined whether the vehicle is in a turning state, and if so, the first torque adjustment value in the driving control strategy and the braking control strategy is reduced by 0-20%.

5. The anti-skid control method for a dual electric drive axle tractor according to claim 1, characterized in that: The step of determining the slip rate of the middle bridge according to the first parameter comprises: Calculating a first slip ratio of the middle bridge according to the wheel speed of the front bridge and the wheel speed of the middle bridge; The second slip ratio of the middle axle is calculated according to the following formula: the second slip ratio of the middle axle=0.377*middle axle motor speed*middle axle wheel radius) / (middle axle gear ratio*front axle wheel speed); The first slip rate of the middle bridge is compared with the second slip rate of the middle bridge to confirm the slip rate of the middle bridge.

6. The anti-skid control method for a dual electric drive axle tractor according to claim 1, characterized in that: The step of determining the slip rate of the rear axle according to the first parameter comprises: Calculating a first slip ratio of the rear axle according to the wheel speed of the middle axle and the wheel speed of the rear axle; The second slip ratio of the rear axle is calculated according to the following formula: the second slip ratio of the rear axle=0.377*rear axle motor speed*rear axle wheel radius / (rear axle gear ratio*front axle wheel speed); The first slip ratio of the rear axle is compared with the second slip ratio of the rear axle to confirm the slip ratio of the rear axle.

7. The anti-skid control method for a dual electric drive axle tractor according to claim 1, characterized in that: The step of determining the vehicle driving state according to the second parameter comprises: The accelerator pedal state is valid, the gear state is D / M gear, and the torques of the mid-bridge motor and the rear-bridge motor are positive, or the accelerator pedal state is valid, the gear state is R gear, and the torques of the mid-bridge motor and the rear-bridge motor are negative, then, it is determined that the vehicle driving state is a driving state; If the accelerator pedal state is invalid, the brake pedal state is valid, or the energy recovery gear state is valid, then it is determined that the vehicle driving state is a braking state.

8. The anti-skid control method for a dual electric drive axle tractor according to claim 1, characterized in that: The step of determining the slip state of the vehicle according to the front axle wheel speed, the rear axle wheel speed and the vehicle speed comprises: The vehicle speed is ≥ the second threshold, and the rear axle wheel speed / the front axle wheel speed-1> the third threshold, or, The vehicle speed is less than the second threshold, and the rear axle wheel speed minus the front axle wheel speed is greater than the fourth threshold, Then, the skidding state of the vehicle is skidding.

9. An anti-skid control system, characterized in that: include: A parameter acquisition module, used to acquire vehicle driving parameters, the vehicle driving parameters including a first parameter and a second parameter; the first parameter includes a front axle wheel speed, a middle axle wheel speed, a rear axle wheel speed and a vehicle speed; the second parameter includes an accelerator pedal state, a brake pedal state, an energy recovery gear state and a gear state; A first calculation module, used for determining the slip rate of the middle axle wheel and the slip rate of the rear axle wheel according to the front axle wheel speed, the middle axle wheel speed and the rear axle wheel speed; A slip state determination module, used for determining the slip state of the vehicle according to the front axle wheel speed, the rear axle wheel speed and the vehicle speed; A driving state determination module, used to determine the driving state of the vehicle according to the second parameter, wherein the driving state of the vehicle includes a driving state and a braking state; A control strategy generating module, used for determining a torque control strategy according to the driving state of the vehicle when the vehicle is in a slipping state; An execution module is used to adjust the torque of the mid-axle motor and the rear-axle motor according to the torque control strategy until the slip rate of the mid-axle wheel and the slip rate of the rear-axle wheel are less than or equal to a preset first threshold.

10. A drive system, characterized in that: include: Controller, mid-axle motor control unit, rear-axle motor control unit, front axle, mid-axle and rear axle; The middle bridge motor control unit is used to control the rotation of the middle bridge wheels through the middle shaft; The rear axle motor control unit is used to control the rotation of the rear axle wheels through the rear axle; The controller is used to execute the control method described in any one of claims 1 to 8.

11. A tractor, characterized in that: A drive system comprising the above claim 10.

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