A control method and system of a virtual center differential lock and a vehicle

Abstract

The present application relates to a kind of virtual central differential lock control method and system and car, wherein the virtual central differential lock control method, it includes the following specific steps: after receiving locking instruction, front axle enters rotational speed control mode, rear axle enters torque control mode;If no unlocking request is received, then the torque of front axle torque and rear axle torque is judged, when the front axle torque is greater than the rear axle torque, front axle adopts torque control mode, rear axle adopts rotational speed control mode, when the rear axle torque is greater than the front axle torque, rear axle adopts torque control mode, and front axle adopts rotational speed control mode, until unlocking request is received, only then exit central differential lock locking mode.The present application can solve the problem that the torque distributed on two axes cannot be accurately and real-time controlled according to the two-axis situation in the prior art, prevent power loss when one axis slips or is suspended, and at the same time, the control ability of the vehicle can be improved, and vehicle skidding out of control can be avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automobile control technology, in particular to a control method and system of a virtual central differential lock and an automobile. BACKGROUND

[0002] In the era of fuel vehicles, the power of the vehicle is output by the engine, so a complex mechanical structure is needed to realize four-wheel drive control. The current mainstream four-wheel drive systems include part-time four-wheel drive, full-time four-wheel drive and on-demand four-wheel drive. The part-time four-wheel drive relies on a transfer case to realize the conversion between two-wheel drive and four-wheel drive modes. Since the transfer case does not have a differential function, such a four-wheel drive system does not need a central differential lock. The state of such a four-wheel drive system in the four-wheel drive mode is the same as the effect after the central differential lock is locked. The full-time four-wheel drive system connects the front and rear axles by a central differential. At all times, it is in four-wheel drive mode. The central differential of the four-wheel drive system has a central differential lock, which is used to lock the differential when one axle of the vehicle slips, so that the power is transmitted to the non-slip axle. The on-demand four-wheel drive can be understood as a part-time four-wheel drive that automatically switches modes. It automatically determines whether to enter the four-wheel drive mode under specific conditions.

[0003] The traditional full-time four-wheel drive system mainly consists of a PTU power transmission device, an intermediate transmission shaft, front and rear axle differentials, a central differential and other components. For hard off-road vehicles, in order to improve the passability of the vehicle, the front axle differential lock, rear axle differential lock and central differential lock are needed to lock the front and rear axle differentials and central differential at a certain time to prevent the engine from transmitting all the power to the slipping or suspended wheels when the vehicle slips or the wheels are suspended, thereby assisting the vehicle to escape. The traditional full-time four-wheel drive system and central differential lock need to rely on a transmission shaft that penetrates the entire vehicle body and a central differential on the transmission shaft. This transmission shaft will occupy a large amount of space in the vehicle chassis, and will increase the cost and complexity of the mechanical structure of the vehicle. For new energy vehicles, since the battery is generally arranged in the chassis part of the vehicle, this transmission shaft will occupy a large amount of battery space, affecting the vehicle's endurance. Since the traditional central differential lock rigidly connects the front and rear drive axles, it also has a significant defect: when the vehicle speed is high, the vehicle will produce a large resonance, and if the driver turns the steering wheel sharply or at a large angle, it will cause an impact between the transmission system and the suspension system, resulting in chassis rupture and vehicle loss of control.

[0004] Patent CN111071059A provides a four-wheel drive control mode for a dual-motor electric vehicle. This invention realizes the switching between two-wheel drive mode and four-wheel drive mode for a dual-motor electric vehicle through manual operation of an electronic button or key switch. After switching to four-wheel drive mode, the vehicle can always maintain four-wheel drive form during the entire driving process. The torque required to drive the vehicle is reasonably distributed to the front and rear drive motors in a certain proportion under the control of the controller to ensure normal operation of the vehicle. This scheme fully utilizes the advantages of dual motors and realizes a four-wheel drive system without a central transmission shaft. However, this system has the following problems:

[0005] 1. The system is a simple torque control. The torque is distributed to the two drive shafts in a certain proportion according to the transmission ratio of the front and rear axle reducers. It is not possible to accurately and real-time control the torque distributed on the two shafts according to the two shaft conditions. When one shaft slips or is suspended, the torque will still be transmitted to the shaft, and the power will be lost through the shaft.

[0006] 2. As described in 1, when one shaft slips or is suspended, power will still be distributed to the shaft, causing the wheel to spin. If the vehicle is in a slipping state at this time, there is a risk of losing control. SUMMARY

[0007] One of the purposes of the present invention is to provide a control method for a virtual central differential lock to solve the problem of being unable to accurately and real-time control the torque distributed on the two shafts according to the two shaft conditions in the prior art, prevent power from being lost through the shaft when one shaft slips or is suspended, and improve the control ability of the vehicle to avoid vehicle slipping and losing control. The second purpose is to provide a virtual central differential lock system. The third purpose is to provide an automobile.

[0008] To achieve the above purposes, the technical solutions adopted by the present invention are as follows:

[0009] A control method for a virtual central differential lock, comprising the following specific steps:

[0010] S1: receiving a locking instruction;

[0011] S2: the front axle enters a rotational speed control mode, and the rear axle enters a torque control mode until the target wheel speed difference between the front drive axle and the rear drive axle is reached;

[0012] S3: determining whether a unlocking request is received. If yes, go to step S8. If no, go to step S4;

[0013] S4: determining whether the front axle torque is greater than the rear axle torque. If yes, go to step S5. If no, return to step S2;

[0014] S5: the front axle enters a torque control mode, and the rear axle enters a rotational speed control mode until the target wheel speed difference between the front drive axle and the rear drive axle is reached;

[0015] S6: determining whether the unlocking request is received, if yes, entering step S8, if no, entering step S7;

[0016] S7: determining whether the rear axle torque is greater than the front axle torque, if yes, returning to step S2, if no, returning to step S5;

[0017] S8: exiting the central differential lock locking mode, and the process ends.

[0018] According to the above technical means, the purpose of the present application is to provide a control method for realizing the inter-axle differential lock function by controlling the speed of the dual motor of the electric vehicle. The essential function of the central differential lock is to make the front and rear drive axles of the vehicle rigidly connected by locking the central differential, so that most or even all of the torque can be transmitted to the drive axle that is not slipping, and the adhesion of the axle can be fully utilized to generate traction. Among them, the drive axle can be a front drive axle and / or a rear drive axle. The present application realizes the virtual rigid connection of the front and rear drive axles without the transmission shaft by switching from torque control to speed control of the front and rear axles. At present, many new energy vehicles use dual motor drive, and the power output is distributed in the front and rear axles, and the motor has the characteristics of fast response speed and sensitive control. Therefore, compared with the traditional differential lock, a virtual central differential lock based on computer control without transmission shaft has significant advantages in vehicle layout, mechanical structure and cost. Moreover, due to the flexibility brought by computer control, the control method of the present application can overcome the defects caused by the rigid connection of the traditional central differential lock. In the present application, the drive axle is composed of a main reducer, a differential, a wheel transmission device and a drive axle housing, etc. The transmission shaft is an important part of the wheel transmission device, and in the front and rear drive vehicle, the front drive axle includes the front axle, and the rear drive axle includes the rear axle. Therefore, in this paper, for example, the front axle is in torque control mode, which is equivalent to the front drive axle being in torque control mode, and the rear axle is in speed control mode, which is equivalent to the rear drive axle being in speed control mode.

[0019] Specifically, in general cases, the two motors of the vehicle provide power according to the general mode, i.e. most of the torque is distributed to one of the motors, and generally according to the vehicle speed, the torque is distributed to the motor with higher efficiency at this speed, and the other motor outputs a small part of the power.

[0020] After the user presses the central differential lock button, the vehicle will enter the initial state of the central differential lock locking mode, at this time the torque control is maintained on the rear axle, and the speed control is performed on the front axle, and the control is performed to make the speed of the front drive axle consistent with that of the rear drive axle.

[0021] In the central differential lock locking state, the active power control unit continuously judges the torque output of the front axle motor and the rear axle motor, and distributes the torque control shaft and the speed control shaft according to the torque size, wherein the driving axle with larger torque is the torque control axle, and the driving axle with smaller torque is the speed control axle.

[0022] The user presses the central differential lock button again, the central differential lock locking mode ends, and the motor control mode of the vehicle is switched to the general mode.

[0023] In order to more clearly illustrate the technical solutions, in the following description, the torque control axle is the driving axle with torque as the control quantity, and the speed control axle is the driving axle with speed as the control quantity; wherein the speed control is a closed-loop control, and the specific logic is that when the shaft speed is less than the target speed, the active power control unit increases the motor torque output; when the shaft speed is greater than the target speed, the active power control unit reduces the motor torque output, so that the speed is consistent with the target speed. The target speed of the speed control axle is followed by the speed of the torque control axle; the torque control axle is the main response axle, which directly responds to the control signal from the accelerator pedal.

[0024] Further, in the speed control mode, it is judged whether the vehicle is in steering driving in steps S2 and S5, if yes, the differential control mode is entered, and if not, the same speed control mode is entered.

[0025] Further, in the differential control mode, the target wheel speed difference between the front driving axle and the rear driving axle is calculated; in the same speed control mode, the target wheel speed difference between the front driving axle and the rear driving axle is zero.

[0026] Further, it is judged whether the vehicle is in steering driving according to whether the steering wheel has a steering angle.

[0027] Further, the differential control mode is specifically controlled as follows:

[0028] Sa1: calculating the target wheel speed difference according to the front wheel steering angle;

[0029] Sa2: controlling the front driving axle speed or the rear driving axle speed to make the front driving axle speed and the rear driving axle speed difference meet the target wheel speed difference.

[0030] Further, the specific operation of controlling the front driving axle speed or the rear driving axle speed is as follows:

[0031] Sb1: when the front axle is in the speed control mode, the front axle motor is controlled to make the front driving axle speed greater than the rear driving axle speed; when the rear axle is in the speed control mode, the rear axle motor is controlled to make the rear driving axle speed less than the front driving axle speed;

[0032] Sb2: determine whether the difference between the front drive axle speed and the rear drive axle speed is equal to the target wheel speed difference, if yes, the process ends, if not, return to step Sb1.

[0033] Further, the step S4 first acquires the front axle torque and the rear axle torque, and then compares the sizes of the two; wherein the steps of acquiring the front axle torque and the rear axle torque are as follows:

[0034] S41: acquire the driving current of the front axle motor and the rear axle motor respectively;

[0035] S42: acquire the speed data of the front drive axle and the rear drive axle according to the driving current of the front axle motor and the rear axle motor;

[0036] S43: calculate the front axle torque and the rear axle torque by combining the speed data of the front drive axle and the rear drive axle, the characteristic curve of the front axle motor and the rear axle motor, and the corresponding algorithm;

[0037] S44: the front axle motor control unit and the rear axle motor control unit upload the calculated torque data to the main power control unit, and determine whether the front axle torque is greater than the rear axle torque.

[0038] The application also provides a virtual central differential lock system applied to the control method of the virtual central differential lock, the virtual central differential lock system comprising a collection module, a control module and an execution module, the execution module comprising a front axle motor, a rear axle motor, an accelerator pedal and a start-stop control button, the front axle motor, the rear axle motor and the start-stop control button being in communication connection with the collection module, and the front axle motor, the rear axle motor, the accelerator pedal and the collection module being in communication connection with the control module.

[0039] Further, the control module comprises a vehicle body controller, a main power control unit, a front axle motor control unit, a rear axle motor control unit and a chassis controller, the vehicle body controller being in communication connection with the main power control unit, and the main power control unit being in communication connection with the front axle motor control unit, the rear axle motor control unit and the chassis controller respectively.

[0040] The application also provides an automobile comprising a vehicle body, wherein the vehicle body is provided with the virtual central differential lock system.

[0041] The application also provides a storage medium for a computer, wherein the storage medium stores a program, and the program is executed by a processor to realize the control method of the virtual central differential lock.

[0042] The application has the following beneficial effects:

[0043] 1. The driver's operation of the accelerator will always respond to the drive shaft with greater adhesion, effectively avoiding the situation where the axle is slipping or floating after the axle rotates due to the small resistance after responding to the driver's operation of the accelerator. At the same time, due to the closed-loop control of the speed control bridge, a large speed signal input to the motor control unit of the speed control bridge will cause the controller to react sharply, outputting excessive current to the motor, which will not be conducive to the normal operation of the motor and will reduce the service life of the motor. After using this logic, the rotational resistance of the drive shaft with smaller adhesion is smaller, the current required for speed control is smaller, and the working condition is more favorable to the motor.

[0044] 2. Due to the flexibility of computer control, through algorithm and parameter calibration, the virtual differential lock can actively differential the front and rear axles when the vehicle turns, overcoming a series of problems caused by the rigid connection of the front and rear axles of the traditional central differential lock, and reducing the impact of the transmission mechanism when the vehicle turns after the central differential lock is locked.

[0045] 3. Since the virtual central differential lock does not require a transmission shaft, a large amount of chassis space can be saved for battery placement, effectively reducing the layout difficulty of electric vehicle equipment and improving the battery capacity of electric vehicles.

[0046] 4. The virtual differential lock will simplify the mechanical structure of the vehicle transmission system, which will reduce the failure rate and maintenance difficulty of the vehicle, and reduce the manufacturing cost of the vehicle.

[0047] 5. Due to the introduction of speed control, the rotational speed of the front and rear drive axles can remain consistent regardless of friction, and if the adhesion of a certain axle is insufficient, it will not lose adhesion, which will effectively reduce the phenomenon of slipping, pushing, etc., and improve the driving safety of the vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 Flowchart of the control method of the virtual central differential lock of the present application;

[0049] Figure 2 Flowchart of the differential control of the present application;

[0050] Figure 3 Flowchart of the determination of the size of the front axle torque and the rear axle torque of the present application;

[0051] Figure 4 Flowchart of another embodiment of the control method of the virtual central differential lock of the present application;

[0052] Figure 5 State transition diagram of the central differential lock of the present application;

[0053] Figure 6 Structural block diagram of the control system of the virtual central differential lock of the present application. DETAILED DESCRIPTION

[0054] The present application is herein described, by way of example only, with reference to the accompanying drawings. There is shown in these drawings, by way of non-limiting example thereof:

[0055] It is to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting; it being understood that unless otherwise specified the singular includes the plural thereof and reference to a particular numerical value includes at least that particular value, unless otherwise stated. When a value is expressed as an approximate value, it will be understood that the value includes any value that falls within the range of the approximate value unless otherwise stated. While the present application has been described with reference to one or more particular embodiments thereof, the description is illustrative of the application and is not intended to be limiting. Various modifications thereof can occur to those skilled in the art to which the application pertains; the application is therefore to be limited only by the scope of the appended claims, and not by the foregoing description.

[0056] As shown in FIG. 1, the control method of the virtual center differential lock according to the present embodiment includes the following specific steps: Figure 1

[0057] S1: receiving a locking instruction;

[0058] The vehicle body controller receives the center differential lock locking signal, at which time the vehicle body controller will send an inquiry signal to the main power control unit to inquire about the current working state of the center differential lock;

[0059] If the main power control unit feedbacks the vehicle body controller that the center differential lock is in the unlocked state, the vehicle body controller sends the center differential lock locking signal to the main power control unit, and the main power control unit enters the center differential lock locking control mode; if the main power control unit feedbacks the vehicle body controller that the center differential lock is in the locked state, step S2 is entered;

[0060] S2: the front axle enters the rotational speed control mode, and the rear axle enters the torque control mode, until the target speed difference between the front drive axle and the rear drive axle is reached;

[0061] The main power control unit converts the accelerator pedal signal into a torque signal and outputs it to the rear axle motor control unit, which controls the rear axle motor to output the corresponding driving torque, and then reads the rotational speed of the rear drive axle and feeds back the rotational speed to the main power control unit; the main power control unit controls the front axle motor control unit to enter the rotational speed control mode, and feeds the rotational speed of the rear drive axle to the front axle motor control unit, which enters the closed-loop rotational speed control to control the rotational speed of the front drive axle to be consistent with that of the rear drive axle;

[0062] ​The motor control unit of the front and rear axle will monitor the driving motor output torque in real time after entering the central differential lock locking mode, and output the torque size information to the main power control unit for torque control axle switching decision judgment.

[0063] Determine whether the vehicle is in steering driving, if yes, enter the differential control mode, if not, enter the same speed control mode.

[0064] When the vehicle is in steering driving, the speed control is differential control, and the target wheel speed difference between the front drive axle and the rear drive axle is calculated;

[0065] Sa1: Calculate the target wheel speed difference according to the front wheel steering angle;

[0066] Determine whether the vehicle is in steering driving according to whether the steering wheel has a steering angle; When the vehicle is steering, the chassis controller recognizes that the front wheel steering angle is not 0, and the chassis controller will send this steering angle data to the main power control unit, and the main power control unit calculates the target wheel speed difference according to the front wheel steering angle;

[0067] If the vehicle is in a turning state, the speed difference between the speed control shaft and the torque control shaft will be formed according to the front wheel angle to adapt to the wheel speed difference between the front and rear axles due to different turning radii when the vehicle is turning. As shown in Figure 2

[0068] Sa2: Control the front drive axle speed to make the front drive axle speed and the rear drive axle speed difference meet the target wheel speed difference.

[0069] The specific operation of controlling the front drive axle speed is as follows:

[0070] Sb1: When the front axle is in speed control mode, it means that the front axle is a speed control axle, and the front axle motor is controlled to make the front drive axle speed greater than the rear drive axle speed;

[0071] Sb2: Determine whether the front drive axle speed and the rear drive axle speed difference is equal to the target wheel speed difference, if yes, the process is ended, if not, return to step Sb1.

[0072] At this point, when the front axle is in speed control mode, the front axle is a speed control axle, and the front drive axle speed can be directly adjusted to make the front drive axle and the rear drive axle reach the target wheel speed difference;

[0073] When in steering driving, the motor control unit of the speed control axle controls the speed of the corresponding axle of this axle according to the data, and the speed of the corresponding axle of the torque control axle to form a target wheel speed difference, to compensate for the speed difference between the front and rear axles due to different turning radii of the trajectory when the vehicle is turning.

[0074] ​When in straight driving, enter the same speed control mode, control the front drive axle and the rear drive axle to have the same speed, and the target wheel speed difference between the front drive axle and the rear drive axle is zero;

[0075] S3: judge whether the unlocking request is received, if yes, enter step S8, if not, enter step S4;

[0076] The vehicle body controller receives the central differential lock unlocking signal, at this time the vehicle body controller initiates an inquiry signal, if the main power control unit feedbacks that the vehicle body controller is currently in the central differential lock locking state, enter step S4, if at this time it is in the unlocking state, the main power control unit does not respond. The vehicle body controller sends a central differential lock unlocking signal to the main power control unit, enter step S8, and the main power control unit exits the central differential lock locking control mode.

[0077] S4: judge whether the front axle torque is greater than the rear axle torque, if yes, enter step S5, if not, return to step S2;

[0078] Dynamic perception and control of the driving axle torque. This function relies on reading the driving motor current, driving axle speed, and combining certain algorithms to calculate the output torque of the driving motor.

[0079] In step S4, the front axle torque and the rear axle torque are first obtained, and then the sizes of the two are compared; as shown in the figure, Figure 3 The steps of obtaining the front axle torque and the rear axle torque are as follows:

[0080] S41: the current sensor obtains the driving currents of the front axle motor and the rear axle motor respectively, and transmits them to the front axle motor control unit and the rear axle motor control unit;

[0081] S42: obtain the corresponding front axle speed data and rear axle speed data according to the driving currents of the front axle motor and the rear axle motor;

[0082] S43: calculate the front axle torque and the rear axle torque by combining the speed data of the front axle and the rear axle with the characteristic curves of the front axle motor and the rear axle motor and the corresponding algorithm;

[0083] S44: the front axle motor control unit and the rear axle motor control unit upload the calculated torque data to the main power control unit, and judge whether the front axle torque is greater than the rear axle torque.

[0084] When the output torque of the speed control shaft is greater than the output torque of the torque control shaft by a certain threshold value, it indicates that the adhesion of the speed control shaft is greater than the adhesion of the torque control shaft, at this time the speed control shaft with greater adhesion is set as the torque control shaft, and the torque control shaft with smaller adhesion is set as the speed control shaft, so as to realize the state switching of the driving axle.

[0085] At this time, the rear drive axle is a torque control axle, and the front drive axle is a speed control axle. When the main power control unit identifies that the output torque of the rear axle is less than the output torque of the front axle by a certain threshold, it can be determined that the rear drive axle is in a floating or slipping state at this time, and the main power control unit will make a decision to switch the torque control axle, set the front drive axle as the torque control axle, and set the rear drive axle as the speed control axle.

[0086] S5: The front axle enters a torque control mode, and the rear axle enters a speed control mode, until a target speed difference between the front drive axle and the rear drive axle is reached;

[0087] At this time, the accelerator pedal signal will be converted into a torque signal and output to the front axle motor control unit, which controls the front axle motor to output the corresponding torque, and then reads the front axle speed and feeds it back to the main power control unit. The rear axle motor control unit enters the speed control mode under the instruction of the main power control unit and starts to receive the speed signal of the front drive axle. The rear axle motor control unit enters closed-loop speed control to control the speed of the rear drive axle to reach the target speed difference with the front drive axle.

[0088] The specific operation of controlling the speed of the rear drive axle is as follows:

[0089] Sb1: When the rear axle is in the speed control mode, control the rear axle motor to make the speed of the rear drive axle less than that of the front drive axle;

[0090] Sb2: Determine whether the speed difference between the front drive axle and the rear drive axle is equal to the target speed difference, if yes, the process ends, if not, return to step Sb1.

[0091] At this time, when the rear axle is in the speed control mode, the rear axle is a speed control axle, and the speed of the rear drive axle can be directly adjusted to make the rear drive axle reach the target speed difference with the front drive axle;

[0092] S6: Determine whether an unlocking request is received, if yes, proceed to step S8, if not, proceed to step S7;

[0093] This step is similar to step S3. The vehicle body controller receives the central differential lock unlocking signal, at this time the vehicle body controller initiates an inquiry signal, if the main power control unit feedbacks that the vehicle body controller is currently in the central differential lock state, proceed to step S7, if it is in the unlocking state at this time, the main power control unit does not respond. The vehicle body controller sends a central differential lock unlocking signal to the main power control unit, and the main power control unit exits the central differential lock control mode.

[0094] S7: Determine whether the torque of the rear axle is greater than that of the front axle, if yes, return to step S2, if not, return to step S5;

[0095] The step S4 is similar to the step S4, first obtaining the front axle torque and the rear axle torque, and then comparing the sizes of the front axle torque and the rear axle torque; if Figure 3 The step of obtaining the front axle torque and the rear axle torque is specifically as follows:

[0096] S71: The current sensor obtains the driving current of the front axle motor and the rear axle motor respectively, and transmits the driving current to the front axle motor control unit and the rear axle motor control unit;

[0097] S72: The driving current of the front axle motor and the rear axle motor is used to obtain the corresponding rotation speed data of the front axle and the rear axle;

[0098] S73: The rotation speed data of the front axle and the rear axle is combined with the characteristic curve of the front axle motor and the rear axle motor and the corresponding algorithm to calculate the front axle torque and the rear axle torque;

[0099] S74: The front axle motor control unit and the rear axle motor control unit upload the calculated torque data to the main power control unit, and judge whether the rear axle torque is greater than the front axle torque.

[0100] When the output torque of the speed control shaft is greater than the output torque of the torque control shaft by a certain threshold value, it indicates that the adhesion of the speed control shaft is greater than the adhesion of the torque control shaft, at this time, the speed control shaft with greater adhesion is set as the torque control shaft, and the torque control shaft with smaller adhesion is set as the speed control shaft, so as to realize the state switching of the driving shaft.

[0101] S8: Exit the central differential lock locking mode, and the process ends.

[0102] Within the cognitive range of those skilled in the art, when the front axle torque is equal to the rear axle torque, there are two control schemes, which are that the front axle enters the rotation speed control mode and the rear axle enters the torque control mode, or the front axle enters the torque control mode and the rear axle enters the rotation speed control mode; the two control schemes can achieve the same technical effect.

[0103] In one embodiment, as shown in Figure 4 A control method of a virtual central differential lock specifically comprises the following steps:

[0104] A1: receiving a locking instruction;

[0105] A2: the front axle enters the rotation speed control mode, and the rear axle enters the torque control mode, until the target wheel speed difference between the front drive axle and the rear drive axle is reached;

[0106] A3: judging whether a unlocking request is received, if yes, entering step A7, if not, entering step A4;

[0107] A4: judging whether the front axle torque is greater than the rear axle torque, if yes, entering step A5, if not, returning to step A2;

[0108] A5: The front axle enters the torque control mode, and the rear axle enters the speed control mode until the target speed difference between the front drive axle and the rear drive axle is reached;

[0109] A6: Return to step A3;

[0110] A7: Exit the central differential lock locking mode, and the process ends.

[0111] As Figure 5 shown is a schematic diagram of the switching and shifting of the central differential lock in the locked state and the unlocked state. Only when a locking instruction is received, the central differential lock enters the locked state. When an unlocking instruction is received, the central differential lock enters the unlocked state. In the central differential lock locked state, as the torque of the front axle and the rear axle changes, the speed control mode and the torque control mode are switched between the front axle and the rear axle to achieve better driving of the vehicle.

[0112] As Figure 6 shown, the embodiment also provides a virtual central differential lock system applied to the control method of the virtual central differential lock as described above. The virtual central differential lock system includes a collection module, a control module, a front axle motor, a rear axle motor, and an execution module. The front axle motor and the rear axle motor are in communication connection with the collection module. The front axle motor, the rear axle motor, the collection module, and the execution module are in communication connection with the control module.

[0113] Further, the control module includes a vehicle body controller, a main power control unit, a front axle motor control unit, a rear axle motor control unit, and a chassis controller. The vehicle body controller is in communication connection with the main power control unit. The main power control unit is in communication connection with the front axle motor control unit, the rear axle motor control unit, and the chassis controller.

[0114] The hardware components of this control system include the vehicle body controller, the start-stop control button connected to the vehicle body controller through a hard wire, the main power control unit, the accelerator pedal connected to the main power control unit, the motor control units on the front and rear drive shafts and the drive motors controlled thereby, and the chassis controller.

[0115] The specific working mode of this system will be described in the specific embodiments below.

[0116] In a specific embodiment, the vehicle is in the virtual central differential lock locking mode. At this time, the front drive axle of the vehicle is a torque control axle, and the rear drive axle is a speed control axle. The front axle of the vehicle is slipping or floating in this state. The working process of the system at this time will be described in steps.

[0117] 1. At this time, the front drive axle is in the torque control mode, and the rear drive axle is in the speed drive mode.

[0118] 2. The front drive axle suddenly suspends or slips, at this time the torque on the front drive axle will be instantaneously reduced, and the front drive axle speed has a tendency to accelerate.

[0119] 3. At this time, the power control unit recognizes the instantaneous torque drop of the front axle, and the rear axle torque increases due to the tendency of the front axle speed to accelerate. When the front axle torque is less than the rear axle torque by a certain threshold, the front-rear axle mode switching condition is met, and the front-rear axle mode is switched.

[0120] 4. Press the start-stop button to enter the central differential lock control;

[0121] 5. At this time, the rear axle is the torque control axle, and the front axle is the speed control axle. Since the rear axle does not slip at this time, the rear axle has a large rotational resistance, and the torque signal output to the rear axle will not significantly increase the speed. The tendency of the speed to accelerate is suppressed.

[0122] 6. At this time, the front axle is in speed control mode. Since the front axle is in a suspended or slipped state at this time, the rolling resistance is small, and only a small torque is needed to maintain the same speed as the rear axle.

[0123] 7. Since the torque is mainly transmitted to the non-slip or suspended rear axle, the vehicle obtains traction through the rear axle, and finally successfully escapes the trouble.

[0124] This process realizes the simulation of the central differential lock through the controller and its software, helps the vehicle to escape the trouble, and enhances the passability of the vehicle without improving the complexity of the vehicle and occupying more chassis space.

[0125] The embodiment also provides an automobile, which comprises a vehicle body, and the vehicle body is provided with the virtual central differential lock system.

[0126] The embodiment also provides a storage medium for a computer, wherein the storage medium stores a program, and the program is executed by a processor to realize the control method of the virtual central differential lock.

[0127] The above embodiments are only preferred embodiments for fully illustrating the present application, and the protection scope of the present application is not limited thereto. Any equivalent replacement or transformation of the present application based on the present application is within the protection scope of the present application.

Claims

1. A control method for a virtual central differential lock, characterized in that, The specific steps include the following: S1: Lock command received; S2: The front axle enters the speed control mode and the rear axle enters the torque control mode until the target wheel speed difference is reached between the front drive axle and the rear drive axle. S3: Determine whether an unlock request has been received. If yes, proceed to step S8; otherwise, proceed to step S4. S4: Determine whether the front axle torque is greater than the rear axle torque. If yes, proceed to step S5; otherwise, return to step S2. S5: The front axle enters torque control mode and the rear axle enters speed control mode until the target wheel speed difference is reached between the front drive axle and the rear drive axle. S6: Determine whether an unlock request has been received. If yes, proceed to step S8; otherwise, proceed to step S7. S7: Determine whether the rear axle torque is greater than the front axle torque. If yes, return to step S2; otherwise, return to step S5. S8: Exit the central differential lock locking mode, process ends; In steps S2 and S5, during the speed control mode, it is determined whether the vehicle is turning. If so, the differential control mode is entered; otherwise, the same speed control mode is entered. In the differential control mode, the target wheel speed difference between the front drive axle and the rear drive axle is calculated; in the same speed control mode, the target wheel speed difference between the front drive axle and the rear drive axle is zero. The differential control mode is specifically controlled as follows: Sa1: Calculate the target wheel speed difference based on the front wheel steering angle; Sa2: Control the speed of the front drive axle or the speed of the rear drive axle so that the difference between the speeds of the front drive axle and the rear drive axle meets the target wheel speed difference. The specific operation for controlling the speed of the front drive axle or the rear drive axle is as follows: Sb1: When the front axle is in speed control mode, control the front axle motor to make the front drive axle speed greater than the rear drive axle speed; when the rear axle is in speed control mode, control the rear axle motor to make the rear drive axle speed less than the front drive axle speed. Sb2: Determine whether the difference between the front drive axle speed and the rear drive axle speed is equal to the target wheel speed difference. If yes, the process ends; otherwise, return to step Sb1.

2. The control method for the virtual central differential lock according to claim 1, characterized in that: Determine whether the vehicle is turning by observing whether the steering wheel has an angle.

3. The control method for the virtual central differential lock according to claim 1 or 2, characterized in that: In step S4, the front axle torque and the rear axle torque are first obtained, and then their magnitudes are compared; the specific steps for obtaining the front axle torque and the rear axle torque are as follows: S41: Obtain the drive current of the front axle motor and the rear axle motor respectively; S42: Obtain the corresponding speed data of the front drive axle and the rear drive axle based on the drive current of the front axle motor and the rear axle motor; S43: Combine the speed data of the front drive axle and the rear drive axle with the characteristic curves of the front axle motor and the rear axle motor and the corresponding algorithm to calculate the front axle torque and the rear axle torque. S44: The front axle motor control unit and the rear axle motor control unit upload the calculated torque data to the drive power control unit to determine whether the front axle torque is greater than the rear axle torque.

4. A virtual central differential lock system, characterized in that: The control method for the virtual center differential lock as described in any one of claims 1 to 3, wherein the virtual center differential lock system includes a data acquisition module, a control module, and an execution module, wherein the execution module includes a front axle motor, a rear axle motor, an accelerator pedal, and a start / stop control button, wherein the front axle motor, the rear axle motor, and the start / stop control button are all communicatively connected to the data acquisition module, and the front axle motor, the rear axle motor, the accelerator pedal, and the data acquisition module are all communicatively connected to the control module.

5. The virtual central differential lock system according to claim 4, characterized in that: The control module includes a body controller, a power control unit, a front axle motor control unit, a rear axle motor control unit, and a chassis controller. The body controller is communicatively connected to the power control unit, and the power control unit is communicatively connected to the front axle motor control unit, the rear axle motor control unit, and the chassis controller, respectively.

6. An automobile, comprising a vehicle body, characterized in that: The vehicle body is equipped with a virtual central differential lock system as described in claim 4 or 5.

7. A storage medium for a computer, characterized in that, The storage medium stores a program that, when executed by a processor, implements the control method for the virtual central differential lock as described in any one of claims 1 to 3.

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