Vehicle motion control method and system based on front and rear axle speeds

Abstract

The present invention discloses a vehicle motion control method and system based on the front and rear axle speeds, wherein the method includes: collecting vehicle operating parameters; calculating the target speeds of the front and rear axle motors at the current moment, calculating the speed difference between the target speeds of the front and rear axle motors at the current moment and the target execution speeds at the previous moment; calculating the maximum motor synchronization number, calculating the single-step speed coordination amount of the front and rear axle motors; calculating the motor torque reduction coefficient, calculating the target execution speeds of the front and rear axle motors at the current moment; controlling the front and rear axle motors to execute the corresponding target execution speeds at the current moment, updating the target execution speeds of the front and rear axle motors at the previous moment to the target execution speeds at the current moment; repeating the above operations until it is determined that the front and rear axle motors have both entered a speed stable state. The present invention can synchronously adjust the target execution speed of the front or rear axle motor at the current moment to the target speed at the current moment.

Description

Technical Field

[0001] The present invention relates to the field of motor drive technology, and in particular to a vehicle motion control method and system based on front and rear axle rotation speeds. Background Art

[0002] Dual-motor drive on the front and rear axles is a common powertrain configuration for electric vehicles. While this configuration offers significant power, it also requires greater control complexity than a single-motor configuration. Dual-motor speed control must comply with vehicle kinematics. Otherwise, if the speed difference between the front and rear axles is out of sync, wheel slip will occur, compromising vehicle safety. Summary of the Invention

[0003] The main purpose of the present invention is to provide a vehicle motion control method and system based on the front and rear axle speeds, which are used to synchronize the speed difference between the front axle motor and the rear axle motor of the vehicle.

[0004] The technical solution adopted by the present invention is: a vehicle motion control method based on the front and rear axle speeds, including: collecting the vehicle's operating parameters, including the target execution speeds of the front axle motor and the rear axle motor at the previous moment; further, the initial value of the target execution speeds of the front axle motor and the rear axle motor at the previous moment is 0.

[0005] Based on the collected parameters, calculate the current target speed of the front axle motor and the rear axle motor, and calculate the speed difference between the current target speed of the front axle motor or the rear axle motor and the target execution speed at the previous moment;

[0006] Calculating the maximum synchronization number of the front and rear axle motors based on the speed difference, and calculating the single-step speed coordination amount of the front axle motor or the rear axle motor based on the maximum synchronization number of the front and rear axle motors and the speed difference corresponding to the front axle motor or the rear axle motor;

[0007] Calculating the front and rear axle motor torque reduction coefficients based on the single-step speed coordination amount of the front axle motor or the rear axle motor, and calculating the target execution speed of the front axle motor or the rear axle motor at the current moment based on the single-step speed coordination amount of the front axle motor or the rear axle motor and the front and rear axle motor torque reduction coefficients;

[0008] Controlling the front axle motor or the rear axle motor to execute the corresponding target execution speed at the current moment, and updating the target execution speed of the front axle motor or the rear axle motor at the previous moment as the target execution speed at the current moment;

[0009] Repeat all the above operations until it is determined that both the front axle motor and the rear axle motor enter a stable speed state.

[0010] According to the above technical solution, the operating parameters also include: accelerator pedal opening, front wheel angle, vehicle wheelbase, tire radius, front axle transmission ratio, rear axle transmission ratio, front axle motor speed variation capability, rear axle motor speed variation capability, front axle conversion factor, rear axle conversion factor, and vehicle high-voltage current variation protection limit. Furthermore, the above operating parameters can be obtained through actual measurement, bench calibration, or empirical values.

[0011] According to the above technical solution, the method for calculating the target speed of the front axle motor or the rear axle motor at the current moment includes:

[0012] Calculate the target vehicle center speed based on the accelerator pedal opening;

[0013] Calculate the target speeds of the front and rear axles based on the Ackerman steering model and the target vehicle center speed;

[0014] The target speed of the front axle motor or the rear axle motor at the current moment is calculated based on the target driving speed of the front axle or the rear axle, the tire radius, and the front axle transmission ratio or the rear axle transmission ratio.

[0015] According to the above technical solution, the method for calculating the target vehicle center speed includes: the target vehicle center speed is equal to the accelerator pedal opening multiplied by a preset proportional coefficient;

[0016] The method for calculating the target driving speeds of the front and rear axles includes: the target driving speed of the front axle is equal to the target vehicle speed at the center of the vehicle divided by the turning radius of the center of the vehicle multiplied by the turning radius of the front axle; the target driving speed of the rear axle is equal to the target vehicle speed at the center of the vehicle divided by the turning radius of the center of the vehicle multiplied by the turning radius of the rear axle; wherein the turning radius of the center of the vehicle is equal to the square average of the product of the wheelbase of the front and rear axles of the vehicle and the turning angle of the front wheels and half the wheelbase of the front and rear axles of the vehicle, the turning radius of the front axle is equal to the wheelbase of the front and rear axles of the vehicle divided by the cosine value of the front wheel turning angle, and the turning radius of the rear axle is equal to the wheelbase of the front and rear axles of the vehicle multiplied by the tangent value of the front wheel turning angle;

[0017] The method for calculating the target speed of the front axle motor or the rear axle motor at the current moment includes: the target speed of the front axle motor at the current moment is equal to the target driving speed of the front axle divided by the tire radius and then multiplied by the front axle transmission ratio; the target speed of the rear axle motor at the current moment is equal to the target driving speed of the rear axle divided by the tire radius and then multiplied by the rear axle transmission ratio.

[0018] According to the above technical solution, the method for calculating the speed difference between the target speed of the front axle motor or the rear axle motor at the current moment and the target execution speed at the previous moment includes: the speed difference corresponding to the front axle is equal to the target speed of the front axle motor at the current moment minus the target execution speed of the front axle motor at the previous moment; the speed difference corresponding to the rear axle is equal to the target speed of the rear axle motor at the current moment minus the target execution speed of the rear axle motor at the previous moment.

[0019] According to the above technical solution, the method for calculating the maximum synchronization number of the front and rear axle motors includes:

[0020] Selecting the larger value of the speed difference between the current target speed of the front axle motor or the rear axle motor and the target execution speed at the previous moment;

[0021] The maximum synchronization number of the front and rear axle motors is calculated based on the larger amplitude value, the front axle motor speed change capability, and the rear axle motor speed change capability.

[0022] According to the above technical solution, the method of selecting the larger amplitude value includes: the larger amplitude value is the larger value of the absolute value of the speed difference corresponding to the front axle and the absolute value of the speed difference corresponding to the rear axle;

[0023] The method for calculating the maximum synchronization number of the front and rear axle motors includes: the maximum synchronization number of the front and rear axle motors is equal to the larger amplitude value divided by the smaller value of the front axle motor speed change capability and the rear axle motor speed change capability.

[0024] According to the above technical solution, the method for calculating the single-step speed coordination amount of the front axle motor or the rear axle motor includes: the single-step speed coordination amount of the front axle motor is equal to the corresponding speed difference of the front axle divided by the maximum synchronization number of the front and rear axle motors; the single-step speed coordination amount of the rear axle motor is equal to the corresponding speed difference of the rear axle divided by the maximum synchronization number of the front and rear axle motors.

[0025] According to the above technical solution, the absolute value of the single-step speed coordination amount of the front axle motor is not greater than the speed change capability of the front axle motor; the absolute value of the single-step speed coordination amount of the rear axle motor is not greater than the speed change capability of the rear axle motor.

[0026] According to the above technical solution, the method for calculating the torque reduction coefficient of the front and rear axle motors includes:

[0027] Calculate the vehicle's high-voltage current change based on the front and rear axle motors' single-step speed coordination;

[0028] The front and rear axle motor torque reduction coefficients are calculated based on the vehicle's high-voltage current change and the vehicle's high-voltage current change protection limit.

[0029] According to the above technical solution, the method for calculating the change in high-voltage current of the whole vehicle includes: the change in high-voltage current of the whole vehicle is equal to the value obtained by multiplying the single-step speed coordination amount of the front axle motor by the front axle conversion coefficient plus the value obtained by multiplying the single-step speed coordination amount of the rear axle motor by the rear axle conversion coefficient;

[0030] The method for calculating the torque reduction coefficient of the front and rear axle motors includes: the torque reduction coefficient of the front and rear axle motors is equal to the smaller value of the absolute value of the high-voltage current change of the whole vehicle and the high-voltage current change protection limit of the whole vehicle divided by the high-voltage current change of the whole vehicle.

[0031] According to the above technical solution, the method for calculating the target execution speed of the front axle motor and the rear axle motor at the current moment includes:

[0032] Calculating a single-number speed increment of the front axle motor or the rear axle motor based on a single-step speed coordination amount of the front axle motor or the rear axle motor and a torque reduction coefficient of the front and rear axle motors;

[0033] The target execution speed of the front axle motor or the rear axle motor at a current moment is calculated based on the odd-number speed increment of the front axle motor or the rear axle motor and the target execution speed of the front axle motor or the rear axle motor at a previous moment.

[0034] According to the above technical solution, the method for calculating the odd-number speed increment of the front axle motor or the rear axle motor includes: the odd-number speed increment of the front axle motor is equal to the product of the single-step speed coordination amount of the front axle motor and the torque reduction coefficient of the front and rear axle motors; the odd-number speed increment of the rear axle motor is equal to the product of the single-step speed coordination amount of the rear axle motor and the torque reduction coefficient of the front and rear axle motors;

[0035] The method for calculating the target execution speed of the front axle motor or the rear axle motor at the current moment includes: the target execution speed of the front axle motor at the current moment is equal to the odd speed increment of the front axle motor plus the target execution speed of the front axle motor at the previous moment; the target execution speed of the rear axle motor at the current moment is equal to the odd speed increment of the rear axle motor plus the target execution speed of the rear axle motor at the previous moment.

[0036] According to the above technical solution, the method for judging whether the front axle motor or the rear axle motor has entered a stable speed state includes: simultaneously satisfying that the target execution speed of the front axle motor at the current moment is equal to the target speed of the front axle motor at the current moment, and the target execution speed of the rear axle motor at the current moment is equal to the target speed of the rear axle motor at the current moment.

[0037] According to the above technical solution, the time required for the front axle motor or the rear axle motor to enter the speed stable state is the same;

[0038] Among them, the calculation method of the time required for the front axle motor to enter the speed stable state includes: the time required for the front axle motor to enter the speed stable state is equal to the target execution speed of the front axle motor at the previous moment divided by the odd speed increment of the front axle motor; the calculation method of the time required for the rear axle motor to enter the speed stable state includes: the time required for the rear axle motor to enter the speed stable state is equal to the target execution speed of the rear axle motor at the previous moment divided by the odd speed increment of the rear axle motor.

[0039] Another aspect of the present invention provides a vehicle motion control system based on the rotational speeds of the front and rear axles, which executes the above-mentioned vehicle motion control method based on the rotational speeds of the front and rear axles.

[0040] The beneficial effects of the present invention are as follows: the vehicle motion control method and system based on the front and rear axle speeds provided by the present invention synchronously coordinate the speed difference between the execution speed of the front axle motor or the rear axle motor at the previous moment and the target speed at the current moment by setting the single-step speed coordination amount of the front axle motor or the rear axle motor, and realize that the front axle motor and the rear axle motor enter a stable speed state at the same time after multiple rounds of cycle operation, thereby avoiding wheel slip caused by the asynchronous speed difference between the front and rear axles and improving the safety of the vehicle.

[0041] Furthermore, in the present invention, the single-step speed coordination amount of the front axle motor or the rear axle motor is no greater than its corresponding speed change capability, which can prevent the front axle motor or the rear axle motor from overloading and causing damage to the motor.

[0042] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 is a flow chart of a vehicle motion control method based on front and rear axle speeds according to an embodiment of the present invention;

[0045] Figure 2 This is a step diagram of a vehicle motion control method based on front and rear axle rotation speeds according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present 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 only used to explain the present invention and are not intended to limit the present invention.

[0047] It should be noted that the illustrations provided in the embodiments of the present invention are only schematic illustrations of the basic concept of the present invention. Therefore, the drawings only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0048] In the present invention, it should also be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" and the like are used to indicate positions or locations based on those shown in the accompanying drawings. These terms are intended solely to facilitate the description of the present application and to simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present application. Furthermore, the terms "first" and "second" are used solely for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.

[0049] Example 1

[0050] This embodiment provides a vehicle motion control method based on the front and rear axle speeds, the process is as follows: Figure 1 shown.

[0051] S1. Collect the vehicle's operating parameters, including the target execution speed of the front axle motor or the rear axle motor at the last moment. and the target execution speed of the rear axle motor at the previous moment The initial value of is 0.

[0052] Specifically, the vehicle operating parameters also include: accelerator pedal opening , front wheel angle , the wheelbase of the vehicle's front and rear axles , tire radius , front axle transmission ratio , rear axle transmission ratio , Front axle motor speed change capability , rear axle motor speed change capability , front axle conversion coefficient , rear axle conversion coefficient , vehicle high voltage current change protection limit Furthermore, the above operating parameters can be obtained through actual measurement, bench calibration or empirical values.

[0053] S2. Calculate the current target speeds of the front axle motor and the rear axle motor based on the collected parameters. Correspondingly, calculate the speed difference between the current target speed of the front axle motor or the rear axle motor and the target execution speed at the previous moment.

[0054] S201, calculate the target speed of the front axle motor at the current moment and the target speed of the rear axle motor at the current moment .

[0055] Specifically, based on the accelerator pedal opening Calculate the target vehicle center speed , the specific calculation methods include:

[0056]

[0057] That is, the target speed of the vehicle center Equal to the accelerator pedal opening Multiply by the preset proportional coefficient .

[0058] The target speeds of the front and rear axles are calculated based on the Ackerman steering model and the target vehicle center speed. The specific calculation method includes:

[0059]

[0060] The target speed of the front axle Equal to the target vehicle center speed Divide by the turning radius of the vehicle center Multiply it by the turning radius of the front axle .

[0061]

[0062] The target speed of the rear axle Equal to the target vehicle center speed Divide by the turning radius of the vehicle center Multiply the turning radius of the rear axle .

[0063] Target driving speed based on the front axle or target speed of the rear axle , tire radius , front axle transmission ratio or rear axle ratio Calculate the target speed of the front axle motor or the rear axle motor at the current moment. The specific calculation method includes:

[0064]

[0065] That is, the target speed of the front axle motor at the current moment Equal to the target driving speed of the front axle Divide by the tire radius Multiply by the front axle ratio .

[0066]

[0067] That is, the target speed of the rear axle motor at the current moment Equal to the target driving speed of the rear axle Divide by the tire radius Multiply by the rear axle ratio .

[0068] S202: Calculate the speed difference between the current target speed of the front axle motor or the rear axle motor and the target execution speed at the previous moment.

[0069] Specifically, the speed difference of the front axle The calculation methods include:

[0070]

[0071] That is, the target speed of the front axle motor at the current moment Subtract the target execution speed of the front axle motor at the previous moment .

[0072] Speed ​​difference corresponding to the rear axle The calculation methods include:

[0073]

[0074] That is, the target speed of the rear axle motor at the current moment Subtract the target execution speed of the rear axle motor at the previous moment .

[0075] S3, calculate the maximum synchronization number of the front and rear axle motors based on the speed difference , based on the maximum number of synchronous motors of the front and rear axles , the speed difference corresponding to the front axle motor or the rear axle motor is used to calculate the single-step speed coordination amount of the front axle motor or the rear axle motor.

[0076] S301, calculate the maximum synchronization number of the front and rear axle motors .

[0077] Specifically, select the larger value of the speed difference Specific methods include:

[0078]

[0079] Larger values Equal to the corresponding speed difference of the front axle The absolute value of the rear axle corresponding speed difference The larger of the absolute values ​​of .

[0080] Based on the larger value , Front axle motor speed change capability , rear axle motor speed change capability Calculate the maximum number of synchronous motors for the front and rear axles , the specific calculation methods include:

[0081]

[0082] That is, the maximum number of synchronous motors of the front and rear axles Equal to the larger value of the amplitude In addition to the front axis motor speed change capability Ability to change the speed of the rear axle motor The smaller value in .

[0083] S302, calculate the single-step speed coordination value of the front axle motor And the single-step speed coordination of the rear axle motor .

[0084] Specifically, the single-step speed coordination of the front axle motor is Calculation methods include:

[0085]

[0086] That is, the single-step speed coordination of the front axle motor Equal to the speed difference of the front axle Divide by the maximum number of synchronous motors .

[0087] Single-step speed coordination of the rear axle motor The calculation methods include:

[0088]

[0089] That is, the single-step speed coordination of the rear axle motor Equal to the speed difference of the rear axle Divide by the maximum number of synchronous motors .

[0090] Further, by It can be deduced that ,

[0091] Further simplified to ,

[0092] Finally got .

[0093] From the above evolution results, it can be seen that the single-step speed coordination of the front axle motor is The absolute value is not greater than the front axle motor speed change capability , the single-step speed coordination of the rear axle motor The absolute value is not greater than the rear axle motor speed change capability In this embodiment, this design is to avoid the front and rear axle motors from over-operating and causing damage to the motors.

[0094] S4. Calculate the front and rear axle motor torque reduction coefficient based on the single-step speed coordination of the front axle motor or the rear axle motor , based on the single-step speed coordination of the front axle motor or the rear axle motor and the motor torque reduction coefficient Calculate the target execution speed of the front axle motor or the rear axle motor at the current moment.

[0095] S401, calculate the front and rear axle motor torque reduction coefficient .

[0096] Specifically, based on the motor single-step speed coordination of the front axle motor Coordination value of the single-step speed of the rear axle motor Calculate the change in high voltage current of the entire vehicle , the calculation methods include:

[0097]

[0098] That is, the change in high voltage current of the vehicle Equal to the single-step speed coordination of the front axle motor Multiply by the front axle conversion factor The obtained value is added to the single-step speed coordination value of the rear axle motor Multiply by the rear axle conversion factor The obtained value, among which, the front axle conversion coefficient and rear axle conversion factor is the calibration value.

[0099] Based on the change of high voltage current of the whole vehicle , vehicle high voltage current change protection limit Calculate the torque reduction coefficient of the front and rear axle motors , the calculation methods include:

[0100]

[0101] That is, the front and rear axle motor torque reduction coefficient Equal to the change in high voltage current of the entire vehicle The absolute value of the vehicle high voltage current change protection limit The smaller value of the two divided by the change in the vehicle's high-voltage current .

[0102] S402: Calculate the target execution speed of the front axle motor at the current moment and the target execution speed of the rear axle motor at the current moment .

[0103] Specifically, based on the single-step speed coordination of the front axle motor Or the single-step speed coordination of the rear axle motor and motor torque reduction factor Calculates the single-digit speed increments of the front axle motor or single-digit speed increments for the rear axle motor , the calculation methods include:

[0104]

[0105] That is, the odd speed increment of the front axle motor Equal to the single-step speed coordination of the front axle motor and motor torque reduction factor The product of the rear axle motor's single-digit speed increment Equal to the single-step speed coordination of the rear axle motor and motor torque reduction factor The product of .

[0106] Based on single-digit speed increments for the front axle motor or single-digit speed increments for the rear axle motor , the target execution speed of the front axle motor at the previous moment Or the target execution speed of the rear axle motor at the previous moment Calculate the target execution speed of the front axle motor at the current moment Or the target execution speed of the rear axle motor at the current moment , the calculation methods include:

[0107]

[0108] That is, the target execution speed of the front axle motor at the current moment Equal to the odd number of speed increments of the front axle motor Add the target execution speed of the front axle motor at the previous moment ; The target execution speed of the rear axle motor at the current moment Equal to the odd-numbered speed increment of the rear axle motor Add the target execution speed of the rear axle motor at the previous moment .

[0109] S5: Control the front axle motor or the rear axle motor to execute the corresponding target execution speed at the current moment, and update the target execution speed of the front axle motor or the rear axle motor at the previous moment as the target execution speed at the current moment. By performing this step, the current target execution speed of the front axle motor or the rear axle motor is synchronized to approach the current target speed of the front axle motor or the rear axle motor.

[0110] S6. Repeat all the above operations until it is determined that the front axle motor and the rear axle motor both enter a state of having the same rotational speed.

[0111] Specifically, the method for determining that the front axle motor and the rear axle motor both enter a state of having the same rotational speed includes:

[0112] Compare the target execution speed of the front axle motor at the current moment and the target speed of the front axle motor at the moment , the target execution speed of the rear axle motor at the current moment and the target speed of the rear axle motor at the moment If both are the same, it is determined that the front axle motor and the rear axle motor have entered the same speed state.

[0113] Furthermore, the time required for the front axle motor to enter the same speed state is The time required for the rear axle motor to reach the same speed Similarly, the proof process of this conclusion is as follows.

[0114] Among them, the time required for the front axle motor to enter the same speed state The calculation methods include:

[0115]

[0116] That is, the time required for the front axle motor to enter the same speed state Equal to the target execution speed of the front axle motor at the previous moment Divide the odd-number speed increment of the front-axis motor by .

[0117] The time required for the rear axle motor to reach the same speed state The calculation methods include:

[0118]

[0119] That is, the time required for the rear axle motor to enter the same speed state Equal to the target execution speed of the rear axle motor at the previous moment Divide by the odd-number speed increment of the rear motor .

[0120] right Derived ,

[0121] Further simplified to .

[0122] From the above evolution results, we can know that the time required for the front axle motor to enter the state of the same speed is The time required for the rear axle motor to reach the same speed Equal, equal to the larger value of the speed difference In addition to the front axis motor speed change capability and rear axle motor speed variation capability The smaller value of and the motor torque reduction factor The product of .

[0123] Example 2

[0124] This embodiment provides another vehicle motion control method based on the front and rear axle speeds, the steps are as follows: Figure 2 shown.

[0125] T1. Calculate the target vehicle speed at the center of the vehicle .

[0126] Specifically, based on the accelerator pedal opening Get the target vehicle center speed .

[0127] T2. Calculate the target driving speed of the front axle and the target speed of the rear axle .

[0128] Specifically, based on the Ackerman steering model, the vehicle center target speed Target driving speed mapped to the front axle and the target speed of the rear axle .

[0129] T3. Calculate the target speed of the front axle motor and the target speed of the rear axle motor .

[0130] Specifically, based on the target driving speed of the front axle or target speed of the rear axle , tire radius , front axle transmission ratio or rear axle ratio , calculate the target speed of the front axle motor Or the target speed of the rear axle motor .

[0131] T4. Calculate the speed difference corresponding to the front axle Speed ​​difference with the rear axle .

[0132] Specifically, based on the target speed of the front axle motor Or the target speed of the rear axle motor , the target execution speed of the front axle motor at the previous moment Or the target execution speed of the rear axle motor at the previous moment , calculate the speed difference corresponding to the front axle Speed ​​difference with the rear axle .

[0133] T5. Calculate the maximum value of the speed difference .

[0134] Specifically, based on the speed difference corresponding to the front axle Speed ​​difference with the rear axle Calculate the maximum value of the speed difference .

[0135] T6. Calculate the maximum synchronization number of the front and rear axle motors .

[0136] Specifically, based on the larger value of the speed difference , Front axle motor speed change capability , rear axle motor speed change capability Calculate the maximum number of synchronous motors for the front and rear axles .

[0137] T7. Calculate the single-step speed coordination of the front axle motor Coordination value of single-step speed of rear axle motor .

[0138] Specifically, based on the maximum synchronization number of the front and rear axle motors , the speed difference corresponding to the front axle Or the speed difference of the rear axle Calculate the front axle motor single-step speed coordination Or the rear axle motor single-step speed coordination .

[0139] T8. Calculate the change in high voltage current of the vehicle .

[0140] Specifically, based on the front axle motor single-step speed coordination Or the rear axle motor single-step speed coordination Calculate the change in high voltage current of the entire vehicle .

[0141] T9. Calculate the torque reduction coefficient of the front and rear axle motors .

[0142] Specifically, based on the change in high voltage current of the vehicle , vehicle high voltage current change protection limit Calculate the torque reduction coefficient of the front and rear axle motors .

[0143] T10, calculate the odd speed increment of the front axle motor and rear axle motor single speed increments .

[0144] Specifically, based on the front axle motor single-step speed coordination Or the rear axle motor single-step speed coordination , motor torque reduction factor Calculate the single-digit speed increment of the front axle motor Or single speed increment of rear axle motor .

[0145] T11. Calculate the target execution speed of the front axle motor at the current moment and the target execution speed of the rear axle motor at the current moment .

[0146] Specifically, based on the single-digit speed increment of the front axle motor Or single speed increment of rear axle motor , the target execution speed of the front axle motor at the previous moment Or the target execution speed of the rear axle motor at the previous moment , calculate the target execution speed of the front axle motor at the current moment Or the target execution speed of the rear axle motor at the current moment .

[0147] T12. Determine whether the front axle motor and the rear axle motor are both in a stable speed state.

[0148] Specifically, determine whether the front axle motor and the rear axle motor both meet the target execution speed at the current moment equal to the target speed at the current moment. If so, determine that the front axle motor and the rear axle motor are both in a stable speed state. If either the front axle motor or the rear axle motor does not meet the stable speed state, re-execute this method from step T1.

[0149] Furthermore, the vehicle center target speed in this embodiment , target driving speed of the front axle and the target speed of the rear axle , target speed of the front axle motor and the target speed of the rear axle motor , the speed difference corresponding to the front axle Speed ​​difference with the rear axle , the speed difference is large , Maximum number of synchronous motors of front and rear axles , front axle motor single-step speed coordination Coordination value of single-step speed of rear axle motor , Change in vehicle high voltage current , front and rear axle motor torque reduction coefficient , odd speed increment of front axle motor and rear axle motor single speed increments , the current target execution speed of the front axle motor and the target execution speed of the rear axle motor at the current moment The specific calculation method of the parameters and the method of determining whether the front axle motor and the rear axle motor are both in a stable speed state in step T12 are the same as those in Example 1 and will not be repeated here.

[0150] Example 3

[0151] This embodiment provides a vehicle motion control system based on the front and rear axle rotational speeds, which executes the vehicle motion control method based on the front and rear axle rotational speeds in embodiment 1 or embodiment 2.

[0152] In summary, the present invention provides a method and system for vehicle motion control based on the front and rear axle speeds, which synchronously adjust the target execution speed of the front axle motor or the rear axle motor at the current moment to the corresponding target speed at the current moment through a cyclic operation, thereby achieving consistency in the stable moments of the front and rear axle speeds and avoiding vehicle safety problems caused by the speed difference between the front and rear axles.

[0153] It should be pointed out that, according to the needs of implementation, the various steps / components described in this application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0154] The size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0155] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A vehicle motion control method based on front and rear axle speeds, characterized in that: include: Collect vehicle operating parameters, including the target execution speed of the front axle motor and the rear axle motor at the previous moment; Based on the collected parameters, the target speeds of the front and rear axle motors at the current moment are calculated, and the speed differences between the target speeds of the front and rear axle motors at the current moment and the target execution speeds at the previous moment are calculated. Calculating the maximum synchronization number of the front and rear axle motors based on the speed difference, and calculating the single-step speed coordination amount of the front and rear axle motors based on the maximum synchronization number of the front and rear axle motors and the corresponding speed difference of the front and rear axle motors; Calculating the front and rear axle motor torque reduction coefficients based on the single-step speed coordination amounts of the front and rear axle motors; and calculating the target execution speeds of the front and rear axle motors at the current moment based on the single-step speed coordination amounts and the front and rear axle motor torque reduction coefficients. Control the front axle motor and the rear axle motor to execute the corresponding target execution speed at the current moment, and update the target execution speed of the front axle motor and the rear axle motor at the previous moment to the target execution speed at the current moment; Repeat all the above operations until it is determined that both the front axle motor and the rear axle motor enter a stable speed state.

2. The vehicle motion control method based on front and rear axle speeds according to claim 1, characterized in that: The operating parameters also include: accelerator pedal opening, front wheel angle, vehicle wheelbase, tire radius, front axle drive ratio, rear axle drive ratio, front axle motor speed change capability, rear axle motor speed change capability, front axle conversion coefficient, rear axle conversion coefficient, and vehicle high-voltage current change protection limit.

3. The vehicle motion control method based on front and rear axle speeds according to claim 2, characterized in that: The method for calculating the target speeds of the front axle motor and the rear axle motor at the current moment includes: Calculate the target vehicle center speed based on the accelerator pedal opening; Calculate the target driving speeds of the front and rear axles based on the Ackerman steering model and the target vehicle center speed; The target speed of the front axle motor or the rear axle motor at the current moment is calculated based on the target driving speed of the front axle or the rear axle, the tire radius, and the front axle transmission ratio or the rear axle transmission ratio.

4. The vehicle motion control method based on front and rear axle speeds according to claim 3, characterized in that: The method for calculating the target vehicle center speed of the vehicle includes: the target vehicle center speed of the vehicle is equal to the accelerator pedal opening multiplied by a preset proportional coefficient; The method for calculating the target driving speeds of the front and rear axles includes: the target driving speed of the front axle is equal to the target vehicle speed at the center of the vehicle divided by the turning radius of the center of the vehicle multiplied by the turning radius of the front axle; the target driving speed of the rear axle is equal to the target vehicle speed at the center of the vehicle divided by the turning radius of the center of the vehicle multiplied by the turning radius of the rear axle; wherein the turning radius of the center of the vehicle is equal to the square average of the product of the wheelbase of the front and rear axles of the vehicle and the turning angle of the front wheels and half the wheelbase of the front and rear axles of the vehicle, the turning radius of the front axle is equal to the wheelbase of the front and rear axles of the vehicle divided by the cosine value of the front wheel turning angle, and the turning radius of the rear axle is equal to the wheelbase of the front and rear axles of the vehicle multiplied by the tangent value of the front wheel turning angle; The method for calculating the target speed of the front axle motor or the rear axle motor at the current moment includes: the target speed of the front axle motor at the current moment is equal to the target driving speed of the front axle divided by the tire radius and then multiplied by the front axle transmission ratio; the target speed of the rear axle motor at the current moment is equal to the target driving speed of the rear axle divided by the tire radius and then multiplied by the rear axle transmission ratio.

5. The vehicle motion control method based on front and rear axle speeds according to claim 1, characterized in that: The method for calculating the speed difference between the target speed of the front axle motor and the rear axle motor at the current moment and the target execution speed at the previous moment includes: the speed difference corresponding to the front axle is equal to the target speed of the front axle motor at the current moment minus the target execution speed of the front axle motor at the previous moment; the speed difference corresponding to the rear axle is equal to the target speed of the rear axle motor at the current moment minus the target execution speed of the rear axle motor at the previous moment.

6. The vehicle motion control method based on front and rear axle speeds according to claim 5, characterized in that: The method for calculating the maximum synchronization number of the front and rear axle motors includes: Selecting the larger value of the speed difference between the current target speed of the front axle motor or the rear axle motor and the target execution speed at the previous moment; The maximum synchronization number of the front and rear axle motors is calculated based on the larger amplitude value, the front axle motor speed change capability, and the rear axle motor speed change capability.

7. The vehicle motion control method based on front and rear axle speeds according to claim 6, characterized in that: The method of selecting the larger amplitude value includes: the larger amplitude value is the larger value of the absolute value of the speed difference corresponding to the front axle and the absolute value of the speed difference corresponding to the rear axle; The method for calculating the maximum synchronization number of the front and rear axle motors includes: the maximum synchronization number of the front and rear axle motors is equal to the larger amplitude value divided by the smaller value of the front axle motor speed change capability and the rear axle motor speed change capability.

8. The vehicle motion control method based on front and rear axle speeds according to claim 1, characterized in that: The method for calculating the single-step speed coordination amount of the front and rear axle motors includes: the single-step speed coordination amount of the front axle motor is equal to the corresponding speed difference of the front axle divided by the maximum synchronization number of the front and rear axle motors; the single-step speed coordination amount of the rear axle motor is equal to the corresponding speed difference of the rear axle divided by the maximum synchronization number of the front and rear axle motors.

9. The vehicle motion control method based on front and rear axle speeds according to claim 8, characterized in that: The absolute value of the single-step speed coordination amount of the front axle motor is not greater than the speed change capability of the front axle motor; the absolute value of the single-step speed coordination amount of the rear axle motor is not greater than the speed change capability of the rear axle motor.

10. The vehicle motion control method based on front and rear axle speeds according to claim 2, characterized in that: The method for calculating the torque reduction coefficient of the front and rear axle motors includes: Calculate the vehicle's high-voltage current change based on the front and rear axle motors' single-step speed coordination; The front and rear axle motor torque reduction coefficients are calculated based on the vehicle's high-voltage current change and the vehicle's high-voltage current change protection limit.

11. The vehicle motion control method based on front and rear axle speeds according to claim 10, characterized in that: The method for calculating the change in high-voltage current of the entire vehicle includes: the change in high-voltage current of the entire vehicle is equal to the value obtained by multiplying the single-step speed coordination amount of the front axle motor by the front axle conversion coefficient plus the value obtained by multiplying the single-step speed coordination amount of the rear axle motor by the rear axle conversion coefficient; The method for calculating the torque reduction coefficient of the front and rear axle motors includes: the torque reduction coefficient of the front and rear axle motors is equal to the smaller value of the absolute value of the high-voltage current change of the whole vehicle and the high-voltage current change protection limit of the whole vehicle divided by the high-voltage current change of the whole vehicle.

12. The vehicle motion control method based on front and rear axle speeds according to claim 2, characterized in that: The method for calculating the target execution speed of the front axle motor and the rear axle motor at the current moment includes: Calculating a single-number speed increment of the front axle motor or the rear axle motor based on a single-step speed coordination amount of the front axle motor or the rear axle motor and a torque reduction coefficient of the front and rear axle motors; The target execution speed of the front axle motor or the rear axle motor at a current moment is calculated based on the odd-number speed increment of the front axle motor or the rear axle motor and the target execution speed of the front axle motor or the rear axle motor at a previous moment.

13. The vehicle motion control method based on front and rear axle speeds according to claim 12, characterized in that: The method for calculating the odd-number speed increments of the front axle motor and the rear axle motor includes: the odd-number speed increment of the front axle motor is equal to the product of the single-step speed coordination amount of the front axle motor and the torque reduction coefficient of the front and rear axle motors; the odd-number speed increment of the rear axle motor is equal to the product of the single-step speed coordination amount of the rear axle motor and the torque reduction coefficient of the front and rear axle motors; The method for calculating the target execution speed of the front axle motor or the rear axle motor at the current moment includes: the target execution speed of the front axle motor at the current moment is equal to the odd speed increment of the front axle motor plus the target execution speed of the front axle motor at the previous moment; the target execution speed of the rear axle motor at the current moment is equal to the odd speed increment of the rear axle motor plus the target execution speed of the rear axle motor at the previous moment.

14. The vehicle motion control method based on front and rear axle speeds according to claim 1, characterized in that: The method for determining whether both the front axle motor and the rear axle motor have entered a stable speed state includes: simultaneously satisfying that the target execution speed of the front axle motor at the current moment is equal to the target speed of the front axle motor at the current moment, and the target execution speed of the rear axle motor at the current moment is equal to the target speed of the rear axle motor at the current moment.

15. The vehicle motion control method based on front and rear axle speeds according to claim 14, characterized in that: The time required for the front axle motor and the rear axle motor to enter the speed stable state is the same; Among them, the calculation method of the time required for the front axle motor to enter the speed stable state includes: the time required for the front axle motor to enter the speed stable state is equal to the target execution speed of the front axle motor at the previous moment divided by the odd speed increment of the front axle motor; the calculation method of the time required for the rear axle motor to enter the speed stable state includes: the time required for the rear axle motor to enter the speed stable state is equal to the target execution speed of the rear axle motor at the previous moment divided by the odd speed increment of the rear axle motor.

16. A vehicle motion control system based on the front and rear axle speeds, characterized in that: The system executes the vehicle motion control method based on the front and rear axle rotation speeds described in any one of claims 1-15.

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