Vehicle motion control method and system based on rotating speeds of front shaft and rear shaft

Abstract

The invention discloses a vehicle motion control method and system based on rotating speeds of front and rear axles. The method comprises the following steps: collecting running parameters of a vehicle; calculating the target rotating speeds of the front-axle motor and the rear-axle motor at the current moment, and calculating the rotating speed difference between the target rotating speeds of the front-axle motor and the rear-axle motor at the current moment and the target execution rotating speed at the previous moment; calculating the maximum synchronization number of the motor, and calculating the single-step rotating speed coordination quantity of front and rear shaft motors; calculating a motor torque reduction coefficient, and calculating a target execution rotating speed of the front and rear axle motor at the current moment; controlling the front-rear shaft motor to execute the corresponding target execution rotating speed at the current moment, and updating the target execution rotating speed of the front-rear shaft motor at the previous moment to the target execution rotating speed at the current moment; and the operation is repeated until the front axle motor and the rear axle motor are judged to enter a rotating speed stable state. According to the invention, the target execution rotating speed of the front-axle motor or the rear-axle motor at the current moment can be synchronously adjusted to the target rotating 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 power configuration for electric vehicles. This configuration has strong power but also has higher control complexity than a single motor. The speed control of the dual motors must meet the kinematic requirements of the vehicle. Otherwise, if the speed difference between the front and rear axles is not synchronized, it will induce wheel slip, which will lead to low safety performance during vehicle driving. 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 rotational speed of the front and rear axles, which is used to synchronize the rotational 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, comprising: collecting the vehicle's operating parameters, including the target execution speeds of the front axle motor and the rear axle motor at the last moment; further, the initial value of the target execution speeds of the front axle motor and the rear axle motor at the last moment is 0.

[0005] Based on the collected parameters, the target speeds of the front axle motor and the rear axle motor at the current moment are calculated, and 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 is calculated respectively;

[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] 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;

[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 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.

[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 speed at the center of the vehicle based on the accelerator pedal opening;

[0013] Calculate the target driving 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 speed at the center of the vehicle includes: the target vehicle speed at the center of the vehicle 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 axle and the rear axle 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 at 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 of 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 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 multiplied by the rear axle transmission ratio.

[0018] According to the above technical scheme, 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 a 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 of 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 scheme, 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 change in high-voltage current of the vehicle based on the single-step speed coordination of the front axle motor and the rear axle motor;

[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 the 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 the 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 a speed stable state is the same;

[0038] Among them, the calculation method of the time required for the front axle motor to enter a stable speed state includes: the time required for the front axle motor to enter a stable speed 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 a stable speed state includes: the time required for the rear axle motor to enter a stable speed 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, so that after multiple rounds of cyclic operation, the front axle motor and the rear axle motor simultaneously enter a stable speed state, avoiding wheel slip caused by the asynchronous speed difference between the front and rear axles, thereby 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 not greater than its corresponding speed change capability, which can prevent the front axle motor or the rear axle motor from overloading and causing motor damage.

[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 briefly introduces 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 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 It 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 solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with 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 used to limit the present invention.

[0047] It should be noted that the illustrations provided in the embodiments of the present invention are only used to illustrate the basic concept of the present invention in a schematic manner. Therefore, the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout type may also be more complicated.

[0048] In the present invention, it is also necessary to explain that, if the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, if the terms "first" and "second" appear, they are only used for description and distinction purposes, and cannot be understood 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. Further, the target execution speed of the front axle motor at the last moment W1(k-1) f and the target execution speed W1(k-1) of the rear axle motor at the previous moment r The initial value of is 0.

[0052] Specifically, the vehicle operation parameters also include: accelerator pedal opening α, front wheel turning angle θ, wheelbase l of the front and rear axles of the vehicle, tire radius R, front axle transmission ratio i f , rear axle transmission ratio i r , Front axle motor speed variation capability ΔW1 fmax , rear axle motor speed variation capability ΔW1 rmax , front axle conversion factor β f , rear axle conversion factor β r , vehicle high voltage current change protection limit ΔIlimt. Further, the above operating parameters can be obtained through actual measurement, bench calibration or empirical values.

[0053] S2. Based on the collected parameters, calculate the target speed of the front axle motor and the rear axle motor at the current moment, and correspondingly calculate 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.

[0054] S201, calculating the target speed W of the front axle motor at the current moment f and the current target speed W of the rear axle motor r .

[0055] Specifically, the vehicle center target speed V0 is calculated based on the accelerator pedal opening α, and the specific calculation method includes:

[0056] V0=α*K

[0057] That is, the target vehicle speed V0 at the center of the vehicle is equal to the accelerator pedal opening α multiplied by the preset proportional coefficient K.

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

[0059]

[0060] That is, the target driving speed V of the front axle f Equal to the target vehicle speed V0 at the center of the vehicle divided by the turning radius at the center of the vehicle Multiply it by the turning radius of the front axle

[0061]

[0062] That is, the target speed V of the rear axle r Equal to the target vehicle speed V0 at the center of the vehicle divided by the turning radius at the center of the vehicle Multiply it by the turning radius of the rear axle l*tanθ.

[0063] Target driving speed V based on the front axle f Or the target speed V of the rear axle r , tire radius R, front axle transmission ratio i f or rear axle ratio i r 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 W of the front axle motor at the current moment f Equal to the target driving speed V of the front axle f Divide by the tire radius R and multiply by the front axle transmission ratio i f .

[0066]

[0067] That is, the target speed W of the rear axle motor at the current moment r Equal to the target driving speed V of the rear axle r Divide by the tire radius R and multiply by the rear axle transmission ratio i f .

[0068] S202: Calculate 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.

[0069] Specifically, the speed difference ΔW(k-1) corresponding to the front axle f The calculation methods include:

[0070] ΔW(k-1) f =W f -W1(k-1) f

[0071] That is, the target speed W of the front axle motor at the current moment f Subtract the target execution speed W1(k-1) of the front axle motor at the previous moment f .

[0072] The speed difference of the rear axle ΔW(k-1) r The calculation methods include:

[0073] ΔW(k-1) r =W r -W1(k-1) r

[0074] That is, the target speed W of the rear axle motor at the current moment r Subtract the target execution speed W1 of the rear axle motor at the previous moment (k-1) r .

[0075] S3: Calculate the maximum synchronization number ΔN of the front and rear axle motors based on the speed difference fr , based on the maximum synchronization number of the front and rear axle motors ΔN fr , and the speed difference corresponding to the front axle motor or the rear axle motor are 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 ΔN of the front and rear axle motors fr .

[0077] Specifically, the larger value ΔW of the speed difference is selected. frmax , the specific methods include:

[0078] ΔW frmax =max(|ΔW(k-1) f |,|ΔW(k-1) r |)

[0079] Larger value ΔW frmax Equal to the corresponding speed difference of the front axle ΔW(k-1) f The absolute value of the speed difference ΔW(k-1) corresponding to the rear axle r The larger value of the absolute value of .

[0080] Based on the larger value ΔW frmax , Front axle motor speed variation capability ΔW1 fmax , rear axle motor speed variation capability ΔW1 rmax Calculate the maximum synchronization number ΔN of the front and rear axle motors fr , the specific calculation methods include:

[0081]

[0082] That is, the maximum synchronization number of the front and rear axle motors ΔN fr Equal to the larger value of the amplitude ΔW frmax Divide the previous axis motor speed change capability ΔW1 fmax The rear axle motor speed variation capability ΔW1 rmax The smaller value in .

[0083] S302, calculate the single-step speed coordination value ΔW1 of the front axle motor f And the single-step speed coordination of the rear axle motor ΔW1 r .

[0084] Specifically, the single-step speed coordination value of the front axle motor ΔW1 f The calculation methods include:

[0085]

[0086] That is, the single-step speed coordination value of the front axle motor ΔW1 f Equal to the speed difference of the front axle ΔW(k-1) f Divide by the maximum number of synchronous motors ΔN fr .

[0087] Single-step speed coordination of the rear axle motor ΔW1 r The calculation methods include:

[0088]

[0089] That is, the single-step speed coordination of the rear axle motor ΔW1 r Equal to the speed difference ΔW(k-1) corresponding to the rear axle r Divide by the maximum number of synchronous motors ΔN fr .

[0090] Further, by

[0091] Further simplified to

[0092] Finally get

[0093] From the above evolution results, it can be seen that the single-step speed coordination of the front axle motor ΔW1 f The absolute value is not greater than the front axle motor speed variation capability ΔW1 fmax , the single-step speed coordination of the rear axle motor ΔW1 r The absolute value is not greater than the rear axle motor speed variation capability ΔW1 rmaxIn this embodiment, the design is to avoid the front and rear axle motors from over-capacity operation, which may cause damage to the motors.

[0094] S4. Calculate the front and rear axle motor torque reduction coefficient τ based on the single-step speed coordination amount of the front axle motor or the rear axle motor, and calculate 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 motor torque reduction coefficient τ.

[0095] S401, calculating the torque reduction coefficient τ of the front and rear axle motors.

[0096] Specifically, based on the motor single-step speed coordination value ΔW1 of the front axle motor f And the motor single-step speed coordination value of the rear axle motor ΔW1 r Calculate the change in high-voltage current ΔI of the vehicle. The calculation method includes:

[0097] ΔI=ΔW1 f *β f +ΔW1 r *β r

[0098] That is, the change in the vehicle's high-voltage current ΔI is equal to the single-step speed coordination of the front axle motor ΔW1 f Multiply by the forward axis conversion factor β f The obtained value is added to the single-step speed coordination value ΔW1 of the rear axle motor r Multiply the rear axis conversion factor β r The obtained value, among which, the front axle conversion factor β f and the rear axle reduction factor β r is the calibration value.

[0099] The front and rear axle motor torque reduction coefficient τ is calculated based on the vehicle high voltage current change ΔI and the vehicle high voltage current change protection limit ΔIlimt. The calculation method includes:

[0100]

[0101] That is, the front and rear axle motor torque reduction coefficient τ is equal to the smaller value of the absolute value of the vehicle's high-voltage current change ΔI and the vehicle's high-voltage current change protection limit ΔIlimt divided by the vehicle's high-voltage current change ΔI.

[0102] S402, calculating the target execution speed W1(k) of the front axle motor at the current moment f and the target execution speed W1(k) of the rear axle motor at the current moment r .

[0103] Specifically, based on the single-step speed coordination value ΔW1 of the front axle motor f Or the single-step speed coordination value of the rear axle motor ΔW1 rCalculate the single-number speed increment ΔW2 of the front axle motor with the motor torque reduction coefficient τ f Or the single number speed increment of the rear axle motor ΔW2 r , the calculation methods include:

[0104]

[0105] That is, the single speed increment of the front axle motor ΔW2 f Equal to the single-step speed coordination value of the front axle motor ΔW1 f The product of the motor torque reduction coefficient τ, the rear axle motor single speed increment ΔW2 r Equal to the single-step speed coordination of the rear axle motor ΔW1 r The product of the motor torque reduction factor τ.

[0106] Based on the single speed increment ΔW2 of the front axle motor f Or the single number speed increment of the rear axle motor ΔW2 r 、The target execution speed of the front axle motor at the previous moment W1(k-1) f Or the target execution speed W1(k-1) of the rear axle motor at the last moment r Calculate the target execution speed W1(k) of the front axle motor at the current moment f Or the target execution speed W1(k) of the rear axle motor at the current moment r , the calculation methods include:

[0107]

[0108] That is, the target execution speed W1(k) of the front axle motor at the current moment f Equal to the single-digit speed increment ΔW2 of the front axle motor f Add the target execution speed W1(k-1) of the front axle motor at the previous moment f ; The target execution speed of the rear axle motor at the current moment W1(k) r Equal to the single-digit speed increment ΔW2 of the rear axle motor r Add the target execution speed W1(k-1) of the rear axle motor at the previous moment r .

[0109] S5, 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. By performing this step, the target execution speed of the front axle motor or the rear axle motor at the current moment is synchronously close to the target speed of the front axle motor or the rear axle motor at the current moment.

[0110] S6. Repeat all the above operations until it is determined that the front axle motor and the rear axle motor both have the same rotation 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 rotation speed includes:

[0112] Compare the current target execution speed W1(k) of the front axle motor respectively f and the target speed W of the front axle motor at the previous moment f 、The current target execution speed of the rear axle motor W1(k) r and the target speed W of the rear axle motor at the previous moment r , 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 time f The time required for the rear axle motor to reach the same speed state r 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 is time f The calculation methods include:

[0115]

[0116] That is, the time required for the front axle motor to reach the same speed state f Equal to the target execution speed ΔW(k-1) of the front axle motor at the previous moment f Divide the single-number speed increment ΔW2 of the front-axis motor f .

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

[0118]

[0119] That is, the time required for the rear axle motor to reach the same speed state r Equal to the target execution speed of the rear axle motor at the previous moment ΔW(k-1) r Divide by the odd number speed increment ΔW2 of the rear motor r .

[0120] right Derived

[0121] Further simplified to

[0122] From the above evolution results, it can be seen that the time required for the front axle motor to enter the same speed state is time fThe time required for the rear axle motor to reach the same speed state r Equal, equal to the larger value of the speed difference ΔW frmax In addition to the front shaft motor speed change capability ΔW1 fmax and the rear axle motor speed variation capability ΔW1 rmax The product of the smaller value of and the motor torque reduction factor τ.

[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 center speed V0.

[0126] Specifically, the target vehicle center speed V0 of the entire vehicle is acquired based on the accelerator pedal opening α.

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

[0128] Specifically, based on the Ackerman steering model, the vehicle center target speed V0 is mapped to the front axle target speed V f and the target speed V of the rear axle r .

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

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

[0131] T4. Calculate the speed difference ΔW (k-1) corresponding to the front axle f The speed difference ΔW(k-1) corresponding to the rear axle r .

[0132] Specifically, based on the target speed W of the front axle motor f Or the target speed W of the rear axle motor r 、The target execution speed of the front axle motor at the previous moment W1(k-1) f Or the target execution speed of the rear axle motor at the previous moment W1(k-1)r , calculate the speed difference ΔW(k-1) corresponding to the front axle f The speed difference ΔW(k-1) corresponding to the rear axle r .

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

[0134] Specifically, based on the speed difference ΔW(k-1) corresponding to the front axle f The speed difference ΔW(k-1) corresponding to the rear axle r Calculate the maximum value of the speed difference ΔW frmax .

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

[0136] Specifically, based on the larger value ΔW of the speed difference frmax , Front axle motor speed variation capability ΔW1 fmax , rear axle motor speed variation capability ΔW1 rmax Calculate the maximum synchronization number ΔN of the front and rear axle motors fr .

[0137] T7, calculate the front axle motor single-step speed coordination value ΔW1 f And the rear axle motor single-step speed coordination value ΔW1 r .

[0138] Specifically, based on the maximum synchronization number ΔN of the front and rear axle motors fr , the speed difference of the front axle ΔW(k-1) f Or the speed difference of the rear axle ΔW(k-1) r Calculate the front axle motor single-step speed coordination value ΔW1 f Or the rear axle motor single-step speed coordination value ΔW1 r .

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

[0140] Specifically, based on the front axle motor single-step speed coordination amount ΔW1 f Or the rear axle motor single-step speed coordination value ΔW1 r Calculate the change in high voltage current ΔI of the entire vehicle.

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

[0142] Specifically, the front and rear axle motor torque reduction coefficient τ is calculated based on the vehicle high-voltage current change ΔI and the vehicle high-voltage current change protection limit ΔIlimt.

[0143] T10, calculate the single-digit speed increment ΔW2 of the front axle motor f and the rear axle motor single speed increment ΔW2 r .

[0144] Specifically, based on the front axle motor single-step speed coordination amount ΔW1 f Or the rear axle motor single-step speed coordination value ΔW1 r , the motor torque reduction coefficient τ calculates the single-number speed increment ΔW2 of the front axle motor f Or the rear axle motor single speed increment ΔW2 r .

[0145] T11, calculate the target execution speed W1(k) of the front axle motor at the current moment f and the target execution speed W1(k) of the rear axle motor at the current moment r .

[0146] Specifically, based on the single-number speed increment ΔW2 of the front axle motor f Or the rear axle motor single speed increment ΔW2 r 、The target execution speed of the front axle motor at the previous moment W1(k-1) f Or the target execution speed of the rear axle motor at the previous moment W1(k-1) r , calculate the target execution speed W1(k) of the front axle motor at the current moment f Or the target execution speed W1(k) of the rear axle motor at the current moment r .

[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, in this embodiment, the target vehicle center speed V0 and the target driving speed V f and the target speed V of the rear axle r , the target speed W of the front axle motor f and the target speed W of the rear axle motor r , the speed difference of the front axle ΔW(k-1) f The speed difference ΔW(k-1) corresponding to the rear axle r , the speed difference is larger than the value ΔW frmax , Maximum synchronization number of front and rear axle motors ΔN fr , front axle motor single-step speed coordination value ΔW1f And the rear axle motor single-step speed coordination value ΔW1 r , the change in high-voltage current of the whole vehicle ΔI, the reduction coefficient of the torque of the front and rear axle motors τ, the single-number speed increment of the front axle motor ΔW2 f and the rear axle motor single speed increment ΔW2 r 、The current target execution speed of the front axle motor W1(k) f and the target execution speed W1(k) of the rear axle motor at the current moment r 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 rotation speed of the front and rear axles. The system executes the vehicle motion control method based on the rotation speed of the front and rear axles 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 issues 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, and 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 order of execution of each step in the above embodiment does not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment 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 these 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 the vehicle's 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 axle motor and the rear axle motor at the current moment are calculated, and the speed differences between the target speeds of the front axle motor and the rear axle motor at the current moment and the target execution speeds at the previous moment are calculated respectively; 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 speed difference corresponding to the front and rear axle motors; Calculating the front and rear axle motor torque reduction coefficients based on the single-step speed coordination amount 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 amount of the front and rear axle motors 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 dual speed according to claim 1, characterized in that: The operating parameters also include: accelerator pedal opening, front wheel turning angle, vehicle wheelbase, 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, and vehicle high-voltage current change protection limit.

3. The vehicle motion control method based on dual speed according to claim 2, characterized in that: The method for calculating the target rotation speed of the front axle motor and the rear axle motor at the current moment includes: Calculate the target vehicle speed at the center of the vehicle 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 dual speed according to claim 3, characterized in that: The method for calculating the target vehicle speed at the center of the vehicle includes: the target vehicle speed at the center 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 axle and the rear axle 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 at 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 of 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 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 multiplied by the rear axle transmission ratio.

5. The vehicle motion control method based on dual speed 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 dual speed according to claim 5, characterized in that: The method for calculating the maximum synchronization number of the front and rear axle motors includes: Selecting a 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 of 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 dual speed 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 dual speed 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 dual speed 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 dual speed 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 change in high-voltage current of the vehicle based on the single-step speed coordination of the front axle motor and the rear axle motor; 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 dual speed according to claim 10, characterized in that: The method for calculating the change in the high-voltage current of the whole vehicle includes: the change in the 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; 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 dual speed 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 the 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 the previous moment.

13. The vehicle motion control method based on dual speed 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 dual speed 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 a current moment is equal to the target speed of the front axle motor at a current moment, and the target execution speed of the rear axle motor at a current moment is equal to the target speed of the rear axle motor at a current moment.

15. The vehicle motion control method based on dual speed according to claim 14, characterized in that: The time required for the front axle motor and the rear axle motor to enter a stable speed state is the same; Among them, the calculation method of the time required for the front axle motor to enter a stable speed state includes: the time required for the front axle motor to enter a stable speed 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 a stable speed state includes: the time required for the rear axle motor to enter a stable speed 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 rotation speed of the front and rear axles, characterized in that: The system executes the dual-speed-based vehicle motion control method described in any one of claims 1-15.

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