Differential protection method and device and vehicle

Abstract

The invention relates to the technical field of electric driving systems of electric automobiles, in particular to a differential protection method and device and a vehicle. The method comprises the steps that the current wheel speed difference of driving wheels on the two sides corresponding to a differential is obtained; if the current wheel speed difference is larger than the preset wheel speed difference, the actual demand torque of a driving motor corresponding to the differential mechanism and the duration of outputting the actual demand torque are obtained; and executing a protection action on the differential mechanism according to the actual demand torque and / or the duration. Therefore, the problems that in the prior art, the protection strategy setting reasonability of the differential mechanism is poor, frequent starting is prone to occurring, and the service life of the differential mechanism is shortened are solved.

Description

Technical Field

[0001] This application relates to the technical field of electric drive systems for electric vehicles, and particularly to a differential protection method, device, and vehicle. Background Art

[0002] In new energy vehicles, the ESP (Electronic Stability Program) function can protect the differential. However, when the ESP is turned on and effective, there is a response delay in the transmission of the torque reduction signal to the IPU (Intergrated Power Unit, motor controller unit). During this delay time, the speed difference will rise beyond the differential boundary; at the same time, the ESP fails or cannot effectively protect the differential in the fault state, resulting in a failure risk.

[0003] In related technologies, CN115675108A discloses a vehicle active protection control method, device, electronic device, and storage medium, which can directly obtain the differential of the left / right half shafts of the reducer, and start the first differential protection when the differential meets the first preset condition; start the second differential protection when the differential meets the second preset condition; and then reduce the torque at the motor output end according to the first differential protection or the second differential protection. CN116039400A discloses a differential protection method, device, electric vehicle, and storage medium, which can directly obtain the rotational speed difference between the rotational speed half shafts in the differential and the output torque of the drive motor; match the torque threshold of the drive motor according to the rotational speed difference, and determine whether the rotational speed difference is within a preset protection interval and whether the output torque is greater than the torque threshold; when the rotational speed difference is within the preset protection interval and the output torque is greater than the torque threshold, activate the differential protection function of the differential, and use the differential protection function to reduce the output torque of the drive motor to the target torque, otherwise do not activate the differential protection function.

[0004] However, although the related technologies can add a differential protection function to new energy vehicles and consider torque limitation and response strategies at the same time, there are still problems such as poor rationality in setting the protection strategy of the differential, easy frequent activation, and reduced service life of the differential. Summary of the Invention

[0005] One of the purposes of this application is to provide a differential protection method to solve the problems in the related technologies that the rationality of setting the protection strategy for the differential is poor, it is easy to be frequently activated, and the service life of the differential is reduced; the second purpose is to provide a differential protection device; the third purpose is to provide a vehicle.

[0006] To achieve the above purposes, the technical solutions adopted in this application are as follows:

[0007] A differential protection method includes the following steps: obtaining the current wheel speed difference between the two driving wheels corresponding to the differential; if the current wheel speed difference is greater than a preset wheel speed difference, obtaining the actual required torque of the drive motor corresponding to the differential and the duration of outputting the actual required torque; performing a protection action on the differential according to the actual required torque and / or the duration.

[0008] According to the above technical means, the embodiments of the present application can achieve the protection of the differential according to the actual required torque and / or the duration of the drive motor. Since the differential can still operate for a period of time when the wheel speed difference of the differential is large and will not immediately damage the differential, and the allowable operating duration is different under different required torques, the embodiments of the present application can use the speed difference, the actual required torque and / or the duration as the trigger conditions for the differential protection strategy, rather than simply using the speed difference as the trigger condition, which can effectively improve the rationality of setting the differential protection strategy, reduce the opening frequency of the differential, thereby avoiding the frequent opening of the differential, and at the same time can avoid the risk of differential ablation caused by long-term operation, effectively improve the service life of the differential, and further improve driving safety.

[0009] Further, the performing a protection action on the differential according to the actual required torque and / or the duration includes: judging whether the differential protection condition is satisfied according to the actual required torque and / or the duration; if the differential protection condition is satisfied, controlling the output torque of the drive motor to be reduced to a target torque.

[0010] According to the above technical means, the embodiments of the present application can judge whether the differential protection condition is currently satisfied, and protect the differential when the protection condition is satisfied, so that the drive motor reduces torque, avoids the frequent opening of the differential protection function, and improves the service life of the differential.

[0011] Further, the protection condition includes: the actual required torque is less than or equal to a first torque threshold, greater than or equal to a second torque threshold and the duration is greater than a duration threshold, where the first torque threshold is greater than the second torque threshold; the actual required torque is greater than the first torque threshold.

[0012] Further, before judging whether the differential protection condition is satisfied according to the actual required torque and / or the duration, it further includes: obtaining an ability boundary curve and a forced boundary curve; determining the first torque threshold according to the current wheel speed difference and the ability boundary curve, and determining the second torque threshold according to the first torque threshold; determining the maximum torque of the drive motor according to the current wheel speed difference and the forced boundary curve; determining the duration threshold according to the current speed difference.

[0013] According to the above technical means, before determining whether the current situation meets the differential protection condition, the embodiments of the present application can obtain the ability boundary line curve, the forced boundary curve, the first and second torque thresholds, the maximum torque of the drive motor, and the duration threshold. Thus, the first and second torque thresholds can be obtained through the ability boundary line curve and the forced boundary curve, the current differential state can be judged through the first and second torque thresholds, and the differential protection process can be controlled by using the above values, rather than simply using the rotational speed difference as the trigger condition for differential protection. Therefore, the rationality of the differential protection strategy setting can be effectively improved.

[0014] Further, controlling the output torque of the drive motor to decrease to the target torque includes: determining the target decreasing gradient of the output torque of the drive motor according to the current rotational speed; controlling the output torque of the drive motor to decrease to the target torque according to the target decreasing gradient.

[0015] According to the above technical means, the embodiments of the present application can determine the target decreasing gradient of the output torque of the drive motor according to the current rotational speed, and control the output torque to output to the corresponding target torque according to this decreasing gradient, ensuring the smooth and stable torque response of the whole vehicle, improving the differential protection stability, and thus enhancing the driving experience.

[0016] Further, after performing the protection action on the differential according to the actual required torque and / or the duration, it further includes: judging whether the differential protection exit condition is met according to the current rotational speed difference, the actual required torque, and / or the duration; if the protection exit condition is met, determining the target increasing gradient of the output torque of the drive motor according to the current rotational speed difference, and controlling the output torque of the drive motor to increase to the actual required torque according to the target increasing gradient.

[0017] According to the above technical means, the embodiments of the present application can judge whether the current differential protection meets the exit condition, and exit the differential protection when the condition is met, thereby avoiding the risk of differential ablation caused by long-term operation, effectively improving the service life of the differential, and enhancing the rationality of the differential protection setting; at the same time, it can ensure that the vehicle reasonably responds to the torque request when exiting the differential protection, improving the driving stability of the vehicle, and thus enhancing the driving experience and passenger comfort.

[0018] Further, before performing the protection action on the differential according to the actual required torque and / or the duration, it further includes: obtaining the current vehicle speed of the vehicle; if the current vehicle speed is greater than the preset vehicle speed, the protection action on the differential is not performed; otherwise, the protection action on the differential is performed according to the actual required torque and / or the duration.

[0019] According to the above technical means, the embodiments of the present application can judge whether to activate differential protection based on driving safety. When the vehicle driving speed does not meet the differential protection conditions, the differential protection is not activated, thereby avoiding torque limitation other than the anti-lock braking system, improving driving safety and vehicle driving stability, and meeting the actual use requirements.

[0020] Further, the obtaining of the current wheel speed difference between the two driving wheels corresponding to the differential includes: obtaining the wheel speed signals of the two driving wheels; when the wheel speed signals of the two driving wheels both meet the preset normal conditions, calculating the current wheel speed difference according to the wheel speed signals of the two driving wheels; when any one of the wheel speed signals of the current wheel speed difference meets the preset abnormal conditions, calculating the current wheel speed difference according to the wheel speed signal that meets the preset normal conditions and the current rotational speed of the driving motor.

[0021] According to the above technical means, the embodiments of the present application can distinguish the obtaining methods of the current wheel speed difference under normal and abnormal conditions, so as to obtain more accurate wheel speed difference data, improve the reliability of the wheel speed difference calculation result, and meet the actual needs.

[0022] A differential protection device includes: an obtaining module, configured to obtain the current wheel speed difference between the two driving wheels corresponding to the differential; a comparing module, configured to, when the current wheel speed difference is greater than a preset wheel speed difference, obtain the actual required torque of the driving motor corresponding to the differential and output the duration of the actual required torque; an executing module, configured to perform a protection action on the differential according to the actual required torque and / or the duration.

[0023] Further, the executing module is further configured to: judge whether the differential protection conditions are met according to the actual required torque and / or the duration; if the differential protection conditions are met, control the output torque of the driving motor to be reduced to a target torque.

[0024] Further, the protection conditions include: the actual required torque is less than or equal to a first torque threshold, greater than or equal to a second torque threshold and the duration is greater than a duration threshold, where the first torque threshold is greater than the second torque threshold; the actual required torque is greater than the first torque threshold.

[0025] Further, the executing module is further configured to: obtain an ability boundary curve and a forced boundary curve; determine the first torque threshold according to the current wheel speed difference and the ability boundary curve, determine the second torque threshold according to the first torque threshold; determine the maximum torque of the driving motor according to the current wheel speed difference and the forced boundary curve; determine the duration threshold according to the current rotational speed difference.

[0026] Further, the output torque of the driving motor is controlled to be reduced to a target torque, and the execution module is further configured to: determine a target decreasing gradient of the output torque of the driving motor according to the current rotational speed; control the output torque of the driving motor to be reduced to the target torque according to the target decreasing gradient.

[0027] Further, the execution module is further configured to: determine whether a protection exit condition of the differential is satisfied according to the current rotational speed difference, the actual required torque, and / or the duration; if the protection exit condition is satisfied, determine a target increasing gradient of the output torque of the driving motor according to the current rotational speed difference, and control the output torque of the driving motor to increase to the actual required torque according to the target increasing gradient.

[0028] Further, the execution module is further configured to: obtain the current vehicle speed; if the current vehicle speed is greater than a preset vehicle speed, do not perform the protection action on the differential; otherwise, perform the protection action on the differential according to the actual required torque and / or the duration.

[0029] Further, the acquisition module is further configured to: obtain the wheel speed signals of the two driving wheels; if the wheel speed signals of the two driving wheels both meet the preset normal conditions, calculate the current rotational speed difference according to the wheel speed signals of the two driving wheels; if any one of the wheel speed signals of the current rotational speed difference meets the preset abnormal conditions, calculate the current rotational speed difference according to the wheel speed signals that meet the preset normal conditions and the current rotational speed of the driving motor.

[0030] A vehicle includes: a memory, a processor, and a computer program stored on the memory and executable on the processor, and the processor executes the program to implement the differential protection method as described in the above embodiments.

[0031] Advantages of the present application:

[0032] (1) In the embodiments of the present application, the protection of the differential can be achieved according to the actual required torque and / or the duration of the driving motor. Since the differential can still operate for a period of time when the rotational speed difference of the differential is large and will not immediately damage the differential, and the allowable operating duration is different under different required torques, the embodiments of the present application can use the rotational speed difference, the actual required torque, and / or the duration as the trigger conditions for the differential protection strategy, rather than simply using the rotational speed difference as the trigger condition, which can effectively improve the rationality of the differential protection strategy setting, reduce the opening frequency of the differential, thereby avoiding the frequent opening of the differential, and at the same time can avoid the risk of differential ablation caused by long-term operation, effectively improve the service life of the differential, and further improve driving safety;

[0033] (2) The embodiments of the present application can determine whether the differential protection condition is currently met, and protect the differential when the protection condition is met, causing the driving motor to reduce torque, avoiding frequent activation of the differential protection function, and improving the service life of the differential;

[0034] (3) Before determining whether the differential protection condition is currently met, the embodiments of the present application can obtain the ability boundary line curve, the forced boundary curve, the first and second torque thresholds, the maximum torque of the driving motor, and the duration threshold. Thus, the first and second torque thresholds can be obtained through the ability boundary line curve and the forced boundary curve, the current differential state can be judged through the first and second torque thresholds, and the above values can be used to control the differential protection process, rather than simply using the rotational speed difference as the trigger condition for differential protection, thereby effectively improving the rationality of the differential protection strategy setting;

[0035] (4) The embodiments of the present application can determine the target decrease gradient of the output torque of the driving motor according to the current rotational speed, so as to control the output torque to output to the corresponding target torque according to this decrease gradient, ensure the smooth and stable torque response of the whole vehicle, improve the stability of differential protection, and thus improve the driving experience;

[0036] (5) The embodiments of the present application can judge whether the current differential protection meets the exit condition, and exit the differential protection when the condition is met, thereby avoiding the risk of differential ablation caused by long-term operation, effectively improving the service life of the differential, and improving the rationality of differential protection settings; at the same time, it can ensure that the vehicle reasonably responds to the torque request when exiting the differential protection, improving the driving stability of the vehicle, and thus improving the driving experience and passenger comfort;

[0037] (6) The embodiments of the present application can judge whether to activate the differential protection based on driving safety. When the vehicle driving speed does not meet the differential protection condition, the differential protection is not activated, thereby avoiding torque limitation other than the anti-lock braking system, improving driving safety and vehicle driving stability, and meeting the actual use requirements;

[0038] (7) The embodiments of the present application can distinguish the acquisition methods of the current wheel speed difference under normal and abnormal conditions, thereby obtaining more accurate wheel speed difference data, improving the reliability of the wheel speed difference calculation result, and meeting the actual needs.

[0039] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a schematic flowchart of the differential protection method of the present application;

[0041] Figure 2Schematic diagram of the differential-torque curve of the present application;

[0042] Figure 3 Schematic diagram of the process of the active protection function of the differential of the present application;

[0043] Figure 4 Schematic diagram of the differential protection device in the present application;

[0044] Figure 5 Schematic diagram of the vehicle of the present application. Detailed implementation manners

[0045] The following will describe the implementation manners of the present application with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be understood that the preferred embodiments are only for explaining the present application, rather than for limiting the protection scope of the present application.

[0046] It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present application in a schematic manner. Therefore, only the components related to the present application are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0047] With the development of new energy vehicles, the components of the electric drive device can include a motor controller, a motor, a reducer, etc. Among them, the reducer has transmission gears and a differential. The differential is composed of planetary gears, a differential case, half-axle gears, etc.; the power of the motor enters the differential through the drive shaft, directly drives the driven gear, and then the planetary gears drive the left and right half-axles to drive the left and right wheels respectively. When the vehicle turns, the adhesion coefficients of the left and right wheel contact surfaces are different, and the rotational speeds of the two drive wheels are different, forcing the planetary gears to rotate self, resulting in different rotational speeds of the two half-axles, and thus realizing different vehicle speeds.

[0048] When the rotational speeds of the left and right half-axles are equal, the planetary gears are only in a state of revolution. However, when there is a difference in the rotational speeds of the two half-axles, the planetary gears enter a state of self-rotation. At this time, if a large torque is continuously transmitted, it will cause serious heat generation and temperature rise of the differential, and there is a risk of damaging the differential; thus, new energy vehicles can consider adding the ESP function to protect the differential.

[0049] When the ESP is turned on and effective, there is a response delay when the torque reduction signal is transmitted to the IPU. During this delay time, the speed difference will rise beyond the differential boundary; and when the ESP fails or is in a faulty state, the differential cannot be effectively protected. Therefore, new energy vehicles need to add a differential protection function. At the same time, for problems such as insufficient vehicle dynamic performance and poor vehicle stability in special scenarios when the above two functions act simultaneously, torque limitation and response strategies need to be considered.

[0050] In the related art, only the relationship between the differential threshold and torque is considered. The vehicle will enable the limit protection when the preset conditions are met, resulting in frequent activation of the differential protection and affecting the overall vehicle performance. At the same time, this method does not consider the torque change rate when the differential protection is turned on and off, and does not pre-set the recommended torque change rate under each differential, so the problem of vehicle jitter when the differential protection enters and exits cannot be solved. In addition, in the related art, there is also a problem that the wheel speed difference is not obtained in the case of a certain rotational speed failure, and this method does not consider the time threshold for triggering the differential protection, the vehicle speed threshold for enabling the differential protection function while ensuring passenger safety, and does not consider the up and down torque gradients under different differentials.

[0051] To solve the above problems, the present application can provide a differential protection method, device, vehicle and storage medium. Specifically, Figure 1 FIG. is a schematic flowchart of a differential protection method provided by an embodiment of the present application.

[0052] As Figure 1 shown, the differential protection method includes the following steps:

[0053] In step S201, obtain the current wheel speed difference between the two driving wheels corresponding to the differential.

[0054] It can be understood that the controller of the embodiment of the present application can obtain the current wheel speed difference between the two driving wheels on both sides of the vehicle by detecting the left and right wheel speeds of the two driving wheels on both sides of the vehicle. Among them, the embodiment of the present application can use at least one method to obtain the current wheel speed difference, specifically as follows:

[0055] In the embodiment of the present application, obtaining the current wheel speed difference between the two driving wheels corresponding to the differential includes: obtaining the wheel speed signals of the two driving wheels; if the wheel speed signals of the two driving wheels both meet the preset normal conditions, calculate the current wheel speed difference according to the wheel speed signals of the two driving wheels; if any one of the wheel speed signals of the current wheel speed difference meets the preset abnormal conditions, calculate the current wheel speed difference according to the wheel speed signal that meets the preset normal conditions and the current rotational speed of the drive motor.

[0056] Among them, the preset normal conditions and preset abnormal conditions can be set according to the actual situation, and no specific limitation is made thereto.

[0057] It can be understood that the embodiments of the present application can use the wheel speed signals of the two driving wheels to make judgments, distinguish normal conditions and abnormal conditions to obtain the wheel speed difference: Under normal conditions, the embodiments of the present application can directly detect the wheel speed signals of the driving wheels and calculate the wheel speed difference; if any wheel speed signal is invalid at this time, that is, any driving wheel is in a preset abnormal condition, the embodiments of the present application can use the VCU (Vehicle Control Unit, vehicle controller) to calculate the speed of the other wheel (abnormal wheel) through the wheel speed signal that meets the preset normal condition and the motor speed feedback by the IPU, and then analyze the wheel speed difference between the two driving wheels: wheel speed difference = |the wheel speed of any one of the left and right wheels - the motor speed feedback by the IPU / speed ratio|; if both wheel speed signals are abnormal at this time and the differential protection function cannot be executed, the embodiments of the present application can perform a fault report, for example, an ABS (Anti-lock Brake System) fault can be displayed on the instrument panel, etc.

[0058] In step S202, if the current wheel speed difference is greater than the preset wheel speed difference, obtain the actual required torque of the drive motor corresponding to the differential and the duration of outputting the actual required torque.

[0059] Among them, the value of the preset wheel speed difference can be set according to the actual situation, and no specific limitation is made thereto.

[0060] It can be understood that after obtaining the current wheel speed difference, the embodiments of the present application can compare the current wheel speed difference with the preset wheel speed difference; when the current wheel speed difference is greater than the preset wheel speed difference, obtain the actual required torque of the drive motor corresponding to the differential and obtain the duration required to output the actual required torque; among them, the embodiments of the present application can use at least one method to obtain the actual required torque of the drive motor corresponding to the differential and the duration of outputting the actual required torque, such as table lookup and comparison, etc., and no specific limitation is made thereto.

[0061] In step S203, perform a protection action on the differential according to the actual required torque and / or the duration.

[0062] It can be understood that the embodiments of the present application can perform corresponding differential protection actions according to the actual required torque and / or the duration of outputting the actual required torque after obtaining the actual required torque and / or the duration of outputting the actual required torque.

[0063] Specifically, performing a protection action on the differential according to the actual required torque and / or the duration includes: judging whether the differential protection condition is met according to the actual required torque and / or the duration; if the differential protection condition is met, control the output torque of the drive motor to be reduced to the target torque.

[0064] Among them, the protection conditions include: the actual required torque is less than or equal to the first torque threshold, greater than or equal to the second torque threshold and the duration is greater than the duration threshold, wherein the first torque threshold is greater than the second torque threshold; the actual required torque is greater than the first torque threshold.

[0065] It can be understood that the embodiment of the present application can compare the actual required torque and / or duration with the differential protection condition. When the differential protection condition is met, that is, the required torque is less than or equal to the first torque threshold, greater than or equal to the second torque threshold and the duration is greater than the duration threshold, the output torque of the drive motor is controlled to be reduced to the target torque; wherein, the embodiment of the present application can use at least one method to obtain the first and second torque thresholds, as follows:

[0066] In an embodiment of the present application, before determining whether the differential protection condition is met based on the actual required torque and / or duration, it also includes: obtaining a capacity boundary curve and a forced boundary curve; determining a first torque threshold based on the current wheel speed difference and the capacity boundary curve, and determining a second torque threshold based on the first torque threshold; determining the maximum torque of the drive motor based on the current wheel speed difference and the forced boundary curve; and determining a duration threshold based on the current speed difference.

[0067] It can be understood that the embodiment of the present application can obtain the capacity boundary line Tn and the forced boundary curve Tq through the differential test, determine the time threshold according to the current speed difference; then confirm the first and second torque thresholds through the current wheel speed difference and the capacity boundary curve, and determine the maximum torque value of the drive motor through the current wheel speed difference and the forced boundary curve; wherein, the differential-torque curve schematic diagram of the torsion limit line, the capacity boundary curve and the forced boundary curve of the embodiment of the present application can be as follows Figure 2 shown.

[0068] Specifically, (1) confirmation of the first torque threshold, the second torque threshold and the duration threshold: the embodiment of the present application can calibrate and select strategy area I and strategy area II of the differential protection strategy.

[0069] Strategy area I: The embodiment of the present application can select c%*Tn≤T≤Tn as strategy area I according to the protection strategy; wherein c is obtained by calibrating the actual climbing performance, which can meet the requirement of the whole vehicle passing through a 16.6% roller ramp, and the general value range is 70% to 90%; according to the relationship between the first torque threshold and the second torque threshold, the embodiment of the present application can determine the first torque threshold to be Tn and the second torque threshold to be c%*Tn.

[0070] Strategy Region II: After the torque exceeds the threshold time t (t1, t2... t5), the torque is restricted according to a linear strategy. T > Tn is Strategy Region II. Among them, other methods can also be used to restrict the torque in the embodiments of the present application, and specific limitations are not made here. The duration threshold t can be the time that can meet the vehicle climbing performance at different wheel speed differences. In the embodiments of the present application, the time t can be set so that the frequency of triggering the differential protection intervention is not higher than 5 Hz. The relationship table between the wheel speed difference and the ability boundary curve in the embodiments of the present application can be as shown in Table 1 below:

[0071] Table 1

[0072] Wheel speed difference n n1 n2 n3 n4 n5 Capacity boundary curve Tn Tn1 Tn2 Tn3 Tn4 Tn5

[0073] It should be noted that when there is no threshold time, in the embodiments of the present application, the torque can be directly restricted according to the torque change rate c% * Tn set corresponding to the differential value calculated at the previous moment.

[0074] (2) Confirmation of the maximum torque value of the drive motor:

[0075] In the embodiments of the present application, the maximum torque value of the drive motor can be determined according to the current wheel speed difference and the forced boundary curve. Among them, the corresponding relationship table between the current wheel speed difference and the forced boundary curve can be as shown in Table 2 below:

[0076] Table 2

[0077] Wheel speed difference n n1 n2 n3 n4 n5 Forced boundary curve Tq Tq1 Tq2 Tq3 Tq4 Tq5

[0078] After the above steps, the embodiments of the present application can determine the first torque threshold, the second torque threshold, the time threshold, and the maximum torque value.

[0079] It should be noted that in order to ensure the reasonable response of the vehicle to the torque request when triggering and exiting the differential protection, and to ensure the stability of the vehicle driving and the comfort of passengers, in the embodiments of the present application, the torque increase gradient and the torque decrease gradient at different wheel speed differences can be obtained through vehicle calibration means. By changing the different torque increase and decrease gradients requested by the VCU for the motor, the motor speed can be selected.

[0080] Specifically, for the comfort of driving and the stability of the vehicle during the torque response of the motor, in the embodiments of the present application, the torque increase gradient k and the torque decrease gradient a can be set at different left and right wheel speed differences. Among them, the change rate of the motor speed without torque oscillation does not exceed 50 rpm. The torque increase gradients at different differentials can be set as k1, k2... k, and the torque decrease gradients a can be set as a1, a2... a5. The calibration table according to the vehicle driving performance can be as shown in Table 3 below.

[0081] Table 3

[0082] Wheel speed difference n n1 n2 n3 n4 n5 Capacity boundary curve Tn Tn1 Tn2 Tn3 Tn4 Tn5 Forced boundary curve Tq Tq1 Tq2 Tq3 Tq4 Tq5 Torque increase gradient k k1 k2 k3 k4 k5 Torque decrease gradient a a1 a2 a3 a4 a5

[0083] In the embodiment of the present application, controlling the output torque of the drive motor to decrease to the target torque includes: determining the target decrease gradient of the output torque of the drive motor according to the current speed; controlling the output torque of the drive motor to decrease to the target torque according to the target decrease gradient.

[0084] It can be understood that in the embodiment of the present application, the motor request torque sent by the VCU can be linearly limited to a preset value according to the decrease torque gradient of each wheel speed difference; wherein, in the embodiment of the present application, the target decrease gradient of the output torque is determined by the current speed. As shown in Table 3, then, according to the target decrease gradient, the output torque of the drive motor is controlled to decrease to the corresponding target torque, so as to protect the differential and reduce the wheel speed difference.

[0085] Specifically, if the calculated wheel speed difference ≥ n1, then it is judged whether the actual torque used by the current vehicle, the duration recorded by the controller, and the threshold time are satisfied. When c% * Tn ≤ T actual demand torque ≤ Tn and the duration both reach the threshold, the differential protection function is triggered in Strategy Region I: linearly limit the motor request torque sent by the VCU to the preset value c% * Tn according to the decrease torque gradient a of each wheel speed difference in the embodiment of the present application to protect the differential, thereby reducing the wheel speed difference.

[0086] In the embodiment of the present application, before performing the protection action on the differential according to the actual demand torque and / or the duration, it further includes: obtaining the current vehicle speed; if the current vehicle speed is greater than the preset vehicle speed, the protection action on the differential is not performed; otherwise, the protection action on the differential is performed according to the actual demand torque and / or the duration.

[0087] Among them, the preset vehicle speed can be calibrated according to the actual vehicle running conditions, and no specific limitation is made thereto.

[0088] It can be understood that when the vehicle is in a high-speed driving state or in use scenarios such as sand, snow, or turning, from the perspective of the vehicle's safety strategy, considering the vehicle stability and the safety of the passengers and drivers, the torque limitation of non-ESP systems should be avoided; therefore, as Figure 3 shown, the embodiment of the present application can consider the differential protection activation vehicle speed, and compare the actual vehicle speed with the activation vehicle speed to judge whether to perform the differential protection action.

[0089] In the embodiment of the present application, after performing the protection action on the differential according to the actual demand torque and / or the duration, it further includes: judging whether the protection exit condition of the differential is satisfied according to the current speed difference, the actual demand torque, and / or the duration; if the protection exit condition is satisfied, determining the target increase gradient of the output torque of the drive motor according to the current speed difference, and controlling the output torque of the drive motor to increase to the actual demand torque according to the target increase gradient.

[0090] It can be understood that when the left - right wheel speed difference is lower than the wheel speed difference threshold, or the left - right wheel speed difference exceeds the wheel speed difference threshold but the duration and the required torque do not reach the threshold for activating the differential protection, the embodiments of the present application can consider that the current vehicle meets the differential protection exit condition, and thus can exit the differential protection. At this time, the torque request in response to the VCU can linearly respond according to the torque increase gradient k in the above - mentioned embodiments.

[0091] Specifically, when the left - right wheel speed difference is lower than the wheel speed difference threshold, or the left - right wheel speed difference exceeds the wheel speed difference threshold but the duration and the required torque do not reach the threshold for activating the differential protection, the embodiments of the present application will exit the differential protection. At this time, the torque request in response to the VCU linearly responds according to the torque increase gradient k at each wheel speed difference designed in the present application.

[0092] The differential protection method proposed according to the embodiments of the present application has at least the following advantages:

[0093] (1) The embodiments of the present application can realize the protection of the differential according to the actual required torque and / or the duration of the drive motor. Since the differential can still operate for a period of time when the wheel speed difference of the differential is large and will not immediately damage the differential, and the allowable operating duration is different under different required torques, the embodiments of the present application can use the speed difference, the actual required torque and / or the duration as the trigger conditions for the differential protection strategy, rather than simply using the speed difference as the trigger condition. This can effectively improve the rationality of the differential protection strategy setting, reduce the opening frequency of the differential, thus avoiding the frequent opening of the differential, and at the same time can avoid the risk of differential ablation caused by long - time operation, effectively improving the service life of the differential, and further improving the driving safety.

[0094] (2) The embodiments of the present application can judge whether the current differential protection condition is met, and protect the differential when the protection condition is met, so that the drive motor reduces torque, avoiding the frequent activation of the differential protection function and improving the service life of the differential.

[0095] (3) The embodiments of the present application can obtain the ability boundary line curve, the forced boundary curve, the first and second torque thresholds, the maximum torque of the drive motor and the duration threshold before judging whether the current differential protection condition is met. Thus, the first and second torque thresholds can be obtained through the ability boundary line curve and the forced boundary curve, the current differential state can be judged through the first and second torque thresholds, and the differential protection process can be controlled using the above - mentioned values, rather than simply using the speed difference as the trigger condition for differential protection. This can effectively improve the rationality of the differential protection strategy setting.

[0096] (4) The embodiments of the present application can determine the target descending gradient of the output torque of the drive motor according to the current rotational speed, so as to control the output torque to output to the corresponding target torque according to this descending gradient, ensure the smooth and stable torque response of the whole vehicle, improve the stability of differential protection, and thus improve the driving experience;

[0097] (5) The embodiments of the present application can judge whether the current differential protection meets the exit condition, and exit the differential protection when the condition is met, so as to avoid the risk of differential burning caused by long-term operation, effectively improve the service life of the differential, and improve the rationality of differential protection settings; at the same time, it can ensure that the vehicle reasonably responds to the torque request when exiting the differential protection, improve the driving stability of the vehicle, and thus improve the driving experience and passenger comfort;

[0098] (6) The embodiments of the present application can judge whether to activate the differential protection based on driving safety. When the vehicle driving speed does not meet the differential protection condition, the differential protection is not activated, so as to avoid torque limitation other than the anti-lock braking system, improve driving safety and vehicle driving stability, and meet the actual use requirements;

[0099] (7) The embodiments of the present application can distinguish the acquisition methods of the current wheel speed difference under normal and abnormal conditions, so as to obtain more accurate wheel speed difference data, improve the reliability of the wheel speed difference calculation result, and meet the actual needs.

[0100] Next, a differential protection device according to an embodiment of the present application will be described with reference to the accompanying drawings.

[0101] Figure 4 It is a block diagram of the differential protection device according to an embodiment of the present application.

[0102] As Figure 4 shown, the differential protection device 10 includes: an acquisition module 100, a comparison module 200, and an execution module 300.

[0103] Among them, the acquisition module 100 is used to acquire the current wheel speed difference between the two driving wheels corresponding to the differential; the comparison module 200 is used to acquire the actual required torque of the drive motor corresponding to the differential and the duration of outputting the actual required torque when the current wheel speed difference is greater than the preset wheel speed difference; the execution module 300 is used to perform a protection action on the differential according to the actual required torque and / or the duration.

[0104] In the embodiments of the present application, the execution module 300 is further configured to: judge whether the differential protection condition is met according to the actual required torque and / or the duration; if the differential protection condition is met, control the output torque of the drive motor to decrease to the target torque.

[0105] In the embodiments of the present application, the protection conditions include: the actual required torque is less than or equal to the first torque threshold, greater than or equal to the second torque threshold, and the duration is greater than the duration threshold, where the first torque threshold is greater than the second torque threshold; the actual required torque is greater than the first torque threshold.

[0106] In the embodiments of the present application, the execution module 300 is further configured to: obtain the capability boundary curve and the forced boundary curve; determine the first torque threshold according to the current wheel speed difference and the capability boundary curve, and determine the second torque threshold according to the first torque threshold; determine the maximum torque of the drive motor according to the current wheel speed difference and the forced boundary curve; determine the duration threshold according to the current rotational speed difference.

[0107] In the embodiments of the present application, when controlling the output torque of the drive motor to decrease to the target torque, the execution module 300 is further configured to: determine the target decreasing gradient of the output torque of the drive motor according to the current rotational speed; control the output torque of the drive motor to decrease to the target torque according to the target decreasing gradient.

[0108] In the embodiments of the present application, the execution module 300 is further configured to: judge whether the protection exit condition of the differential is satisfied according to the current rotational speed difference, the actual required torque, and / or the duration; if the protection exit condition is satisfied, determine the target increasing gradient of the output torque of the drive motor according to the current rotational speed difference, and control the output torque of the drive motor to increase to the actual required torque according to the target increasing gradient.

[0109] In the embodiments of the present application, the execution module 300 is further configured to: obtain the current vehicle speed of the vehicle; if the current vehicle speed is greater than the preset vehicle speed, do not perform the protection action of the differential; otherwise, perform the protection action on the differential according to the actual required torque and / or the duration.

[0110] In the embodiments of the present application, the acquisition module 100 is further configured to: acquire the wheel speed signals of the two driving wheels; if the wheel speed signals of the two driving wheels both meet the preset normal conditions, calculate the current wheel speed difference according to the wheel speed signals of the two driving wheels; if any of the wheel speed signals of the current wheel speed difference meets the preset abnormal conditions, calculate the current wheel speed difference according to the wheel speed signal that meets the preset normal conditions and the current rotational speed of the drive motor.

[0111] It should be noted that the foregoing explanation of the embodiments of the differential protection method is also applicable to the differential protection device of this embodiment, and will not be elaborated here.

[0112] The differential protection device proposed according to the embodiments of the present application can protect the differential according to the actual required torque and / or duration of the driving motor. Since the differential can still operate for a period of time when the wheel speed difference of the differential is large and will not immediately damage the differential, and the allowable operating duration is different under different required torques, the embodiments of the present application can use the speed difference, the actual required torque and / or the duration as the triggering conditions for the differential protection strategy, rather than simply using the speed difference as the triggering condition, which can effectively improve the rationality of setting the differential protection strategy, reduce the opening frequency of the differential, thereby avoiding the frequent opening of the differential, and at the same time can avoid the risk of differential ablation caused by long-term operation, effectively improve the service life of the differential, and further improve the driving safety.

[0113] Figure 5 The structure diagram of the vehicle provided by the embodiment of the present application. The vehicle may include: a memory 501, a processor 502, and a computer program stored on the memory 501 and executable on the processor 502; when the processor 502 executes the program, it implements the differential protection method provided in the above embodiment.

[0114] Further, the vehicle further includes: a communication interface 503 for communication between the memory 501 and the processor 502; a memory 501 for storing a computer program executable on the processor 502; the memory 501 may include a high-speed RAM (Random Access Memory) memory, and may also include a non-volatile memory, such as at least one disk memory.

[0115] If the memory 501, the processor 502, and the communication interface 503 are implemented independently, the communication interface 503, the memory 501, and the processor 502 can be interconnected through a bus and complete communication with each other. The bus can be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus, or an EISA (Extended Industry Standard Architecture) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For the sake of representation, Figure 5 only a thick line is used to represent it in the figure, but it does not mean that there is only one bus or one type of bus.

[0116] Optionally, in a specific implementation, if the memory 501, the processor 502, and the communication interface 503 are integrated on a chip, the memory 501, the processor 502, and the communication interface 503 can complete communication with each other through an internal interface.

[0117] The processor 502 may be a CPU (Central Processing Unit), or an ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of the present application.

[0118] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, without conflict, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0119] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of these features. In the description of the present application, the meaning of "N" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0120] Any process or method description in the flowchart or described in other ways herein may be understood to represent a module, segment, or portion of code including one or N executable instructions for implementing a customized logic function or process, and the scope of the preferred embodiments of the present application includes additional implementations, where the functions may be executed in a substantially simultaneous manner or in a reverse order according to the involved functions, rather than in the order shown or discussed, which should be understood by those skilled in the art to which the embodiments of the present application pertain.

[0121] It should be understood that each part of the present application can be implemented by hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware as in another embodiment, any one of the following techniques well known in the art or a combination of them can be used: discrete logic circuits with logic gate circuits for implementing logical functions on data signals, application specific integrated circuits with appropriate combinational logic gate circuits, programmable gate arrays, field programmable gate arrays, etc.

[0122] Those of ordinary skill in the art can understand that all or part of the steps carried out in implementing the above-described embodiment methods can be completed by a program instructing relevant hardware. The said program can be stored in a computer-readable storage medium, and when executed, it includes one or a combination of the steps of the method embodiment.

[0123] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A differential protection method, characterized in that, It includes the following steps: Obtain the current wheel speed difference between the two driving wheels corresponding to the differential; If the current wheel speed difference is greater than the preset wheel speed difference, obtain the actual required torque of the drive motor corresponding to the differential and the duration of outputting the actual required torque; Perform a protection action on the differential according to the actual required torque and / or the duration; 2. The method according to claim 1, wherein The performing a protection action on the differential according to the actual required torque and / or the duration includes: Judge whether the differential protection condition is satisfied according to the actual required torque and / or the duration; If the differential protection condition is satisfied, control the output torque of the drive motor to decrease to the target torque; 3. The method according to claim 2, characterized in that, The protection condition includes: The actual required torque is less than or equal to the first torque threshold, greater than or equal to the second torque threshold and the duration is greater than the duration threshold, where the first torque threshold is greater than the second torque threshold; The actual required torque is greater than the first torque threshold; 4. The method according to claim 2, wherein Before judging whether the differential protection condition is satisfied according to the actual required torque and / or the duration, it further includes: Obtain the ability boundary curve and the forced boundary curve; Determine the first torque threshold according to the current wheel speed difference and the ability boundary curve, and determine the second torque threshold according to the first torque threshold; Determine the maximum torque of the drive motor according to the current wheel speed difference and the forced boundary curve; Determine the duration threshold according to the current speed difference; 5. The method according to claim 2, characterized in that The controlling the output torque of the drive motor to decrease to the target torque includes: Determine the target decreasing gradient of the output torque of the drive motor according to the current speed; Control the output torque of the drive motor to decrease to the target torque according to the target decreasing gradient; 6. The method according to claim 1, wherein After performing a protection action on the differential according to the actual required torque and / or the duration, it further includes: Judge whether the protection exit condition of the differential is satisfied according to the current speed difference, the actual required torque and / or the duration; If the protection exit condition is satisfied, determine the target increasing gradient of the output torque of the drive motor according to the current speed difference, and control the output torque of the drive motor to increase to the actual required torque according to the target increasing gradient; 7. The method according to claim 1, characterized in that, Before performing a protection action on the differential according to the actual required torque and / or the duration, it further includes: Obtain the current vehicle speed; If the current vehicle speed is greater than the preset vehicle speed, do not perform the protection action on the differential; Otherwise, perform a protection action on the differential according to the actual required torque and / or the duration; 8. The method according to claim 1, wherein The obtaining the current wheel speed difference between the two driving wheels corresponding to the differential includes: Obtain the wheel speed signals of the two driving wheels; If the wheel speed signals of the two driving wheels both meet the preset normal conditions, calculate the current wheel speed difference according to the wheel speed signals of the two driving wheels; If any one of the wheel speed signals of the current wheel speed difference meets the preset abnormal condition, calculate the current wheel speed difference according to the wheel speed signal that meets the preset normal condition and the current speed of the drive motor; 9. A differential protection device, characterized in that, It includes: An acquisition module for acquiring the current wheel speed difference between the two driving wheels corresponding to the differential; A comparison module for, when the current wheel speed difference is greater than a preset wheel speed difference, acquiring the actual required torque of the drive motor corresponding to the differential and outputting the duration for which the actual required torque is output; An execution module for performing a protection action on the differential according to the actual required torque and / or the duration; 10. A vehicle, characterized in that, Comprising: A memory, a processor, and a computer program stored on the memory and executable on the processor, where the processor executes the program to implement the differential protection method according to any one of claims 1-7.

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