Automobile control method based on slip rate

Abstract

The invention provides a vehicle control method based on a slip rate, which comprises the following steps: acquiring state information of a current vehicle, the state information of the current vehicle comprising the slip rate; judging whether the state information of the current vehicle meets a preset adjusting condition or not; when the preset adjusting condition is met, whether the speed of the current vehicle meets a preset speed condition or not is judged; if yes, energy recovery revocation is executed, and if not, a torque adjusting strategy is executed to adjust the motor torque, so that control over the vehicle is achieved, the vehicle speed is slowly reduced, and vehicle running instability caused by sudden revocation of electric braking is avoided.

Description

Technical Field

[0001] The invention relates to the field of automobile control methods, and in particular to an automobile control method based on slip rate. Technical Field

[0003] Electric braking, also known as energy recovery, refers to changing the direction of the motor power supply during the sliding or braking process, using the original vehicle motor as a generator to slow down the vehicle. It is an energy management method that converts mechanical energy into electrical energy. ABS (Anti-locked Braking System), also known as the car anti-lock braking system, refers to a control system that prevents the wheels of a car from locking; the principle of ABS is to detect the slip rate of each wheel, and when the wheel is about to lock, it will reduce the braking force of the wheel by removing the braking force of the wheel to avoid locking.

[0004] When a hybrid or pure electric vehicle is accelerating, the motor converts electrical energy into mechanical energy to drive the vehicle. When coasting or braking, the motor can be used as a generator to convert mechanical energy into electrical energy. The braking process of a conventional vehicle is to convert mechanical energy into heat energy through the friction between the friction plate and the brake disc / brake drum to achieve vehicle deceleration. Among them, electric braking decelerates the vehicle by converting mechanical energy into electrical energy, and ABS reduces the braking force of a certain wheel by removing the braking force of that wheel to prevent locking. It can be seen that the adjustment direction of electric braking and ABS is opposite. However, the electric braking and ABS of current pure electric vehicles do not interact with each other or interact in a breakpoint manner, which will cause ABS to make wrong judgments and cause the wheels to lose control.

[0005] A car without interaction. When the driver steps on the brake pedal while the vehicle is driving, the electric brake is effective, that is, the motor will consume part of the vehicle's kinetic energy and convert it into electrical energy. For the entire vehicle, the vehicle is pushing the wheels to rotate (power generation process). At this time, the wheels are pushed by the vehicle's inertia, and the wheel speed is slowing down. Assuming that the critical point of a wheel locking has been reached, ABS needs to remove the braking force of the wheel to prevent the wheel from locking, and conflict with the effective electric brake. Specifically, the electric brake is working, and the effect is that the wheel speed is getting slower and slower, while ABS wants to reduce the wheel slowing down by reducing the braking force.

[0006] A car with breakpoint interaction. When ABS is effective, the electric brake will be immediately withdrawn. At this time, the performance of the whole vehicle is that the speed suddenly increases during the braking process. Because the reason is transmission braking + electric braking, the electric brake is suddenly withdrawn, the driving experience is not good and rear-end collisions are prone to occur. Summary of the invention

[0007] The purpose of the present invention is to provide a car control method based on slip rate in view of the deficiencies in the prior art. When ABS is not in operation, the slip rate and the tendency of wheel locking are judged to control the size of the electric braking torque, so as to slowly reduce the vehicle speed and avoid vehicle driving instability caused by sudden cancellation of electric braking.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] A vehicle control method based on slip ratio comprises the following steps:

[0010] Acquiring current vehicle status information, wherein the current vehicle status information includes a slip rate;

[0011] Determine whether the current vehicle status information meets the preset adjustment conditions;

[0012] When the preset adjustment condition is met, it is determined whether the current vehicle speed meets the preset speed condition; if so, energy recovery cancellation is executed; if not, the torque adjustment strategy is executed to adjust the motor torque to achieve control of the vehicle.

[0013] As a preferred embodiment, the current vehicle status information also includes the activation status of the brake and the activation status of the ABS;

[0014] The preset adjustment condition is: the slip ratio is greater than a set threshold, the brake is in an activated state, and the ABS is in an inactivated state.

[0015] As a preferred embodiment, the obtaining of the current vehicle status information includes:

[0016] Obtain the wheel's running speed, wheel angular velocity and wheel rolling radius;

[0017] The slip rate is calculated according to the running speed of the wheel, the wheel angular velocity and the wheel rolling radius.

[0018] As a preferred embodiment, the preset vehicle speed condition is: the vehicle speed is less than 20 km / h.

[0019] As a preferred embodiment, the executing energy recovery cancellation includes:

[0020] Electric brake is disabled.

[0021] As a preferred embodiment, the execution torque adjustment strategy includes:

[0022] Obtaining the slip ratio again, and determining whether the slip ratio obtained again is in a preset state;

[0023] If yes, increase the motor torque and re-determine whether the vehicle status information meets the preset adjustment conditions;

[0024] If not, the motor torque is reduced and the vehicle status information is re-determined to see whether it meets the preset adjustment conditions.

[0025] As a preferred embodiment, the preset state is that the slip ratio obtained again does not increase compared with the slip ratio obtained last time.

[0026] As a preferred embodiment, increasing the motor torque includes:

[0027] Increases the motor's torque by 20%.

[0028] As a preferred embodiment, reducing the motor torque includes:

[0029] Reduce the torque of the motor by 20%.

[0030] Compared with the prior art, this technical solution has the following advantages:

[0031] During the vehicle's coasting or braking process, when the slip rate of a certain wheel is greater than the set threshold, the electric brake is increased or decreased by judging the vehicle speed to achieve a gradual withdrawal of the electric brake. This ensures that the electric brake is not effective during ABS operation and there will be no adjustment conflict or vehicle jumping due to sudden withdrawal.

[0032] The present invention is further described below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A method flow chart of the vehicle control method based on slip ratio according to the present invention;

[0034] Figure 2 The figure is a logic diagram of the vehicle control method based on slip ratio according to the present invention. DETAILED DESCRIPTION

[0035] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles of the present invention defined in the following description can be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not deviate from the spirit and scope of the present invention.

[0036] like Figure 1 As shown, the vehicle control method based on slip ratio comprises the following steps:

[0037] Acquiring current vehicle status information, wherein the current vehicle status information includes a slip rate;

[0038] Determine whether the current vehicle status information meets the preset adjustment conditions;

[0039] When the preset adjustment condition is met, it is determined whether the current vehicle speed meets the preset speed condition; if so, energy recovery cancellation is executed; if not, the torque adjustment strategy is executed to adjust the motor torque to achieve control of the vehicle.

[0040] The current vehicle status information is used to reflect the slip rate, ABS status and brake status of the current vehicle, wherein the slip rate is greater than the set threshold, and the ABS is not started, and the brake is started, then the current vehicle status information meets the preset adjustment conditions, and the electric brake is started at this time. Then, by judging the vehicle speed, the torque adjustment strategy is executed to increase or decrease the motor torque corresponding to the electric brake, so as to achieve a slow push out of the electric brake, so that the electric brake is not effective during the operation of the ABS and there will be no adjustment conflict, and there will be no jumping of the vehicle due to sudden withdrawal. Therefore, it is relatively safe. It has been found through experiments that if the slip rate is exited at 20%, there will be no conflict when the ABS is restarted.

[0041] The technical solution of the present invention is introduced and described in detail below through specific embodiments.

[0042] See Figure 2 , the vehicle control method based on slip ratio comprises the following steps:

[0043] Step 1: Under the driving state of the vehicle, obtain the current state information of the vehicle, wherein the state information includes the slip rate, the activation state of the brake and the activation state of the ABS.

[0044] The slip ratio is used to measure the proportion of the tire's sliding component during driving, and can reflect the wheel state, such as pure rolling, rolling and sliding, and locking pure sliding. When the wheel is purely rolling, the wheel speed is equal to the vehicle speed, and the slip ratio is 0, indicating that there is no relative sliding between the tire and the ground. When the wheel is rolling and sliding, the vehicle speed is greater than the wheel speed, and the slip ratio is between 0 and 100%, indicating that the tire also has sliding components while rolling. When the wheel is locked and purely sliding, the wheel speed is zero and the slip ratio is 100%, indicating that the tire has completely stopped rotating and sliding friction is generated with the ground.

[0045] The brake activation state includes a brake state and a brake inactivation state, wherein when the driver steps on the brake pedal, it is called a brake state, and when the brake pedal is not stepped on, it is called a brake inactivation state.

[0046] During the braking process, if the wheels tend to lock or have already locked, the ABS system will intervene quickly to prevent the wheels from locking by adjusting the oil pressure or braking force of the brake system. This process can be called ABS activation. Under normal circumstances, the ABS system is in standby mode and will not actively intervene in the braking process. Only when the wheels tend to lock will the ABS be activated. Therefore, if the wheels do not tend to lock during the braking process, the ABS can be considered to be in an inactive state.

[0047] Furthermore, the obtaining of the current vehicle status information includes:

[0048] Obtain the wheel's running speed, wheel angular velocity and wheel rolling radius;

[0049] The slip rate is calculated according to the running speed of the wheel, the wheel angular velocity and the wheel rolling radius.

[0050] The slip ratio can be calculated using the following formula:

[0051]

[0052] Among them, u w is the speed of the wheel center; r r0 is the wheel rolling radius when there is no ground braking force; w w is the angular velocity of the wheel; s is the slip rate.

[0053] The slip rate is calculated by VCU through collecting vehicle speed, wheel angular velocity, and according to the tire rolling radius of the vehicle model. By collecting data 5 times, it is judged whether the slip rate increases, and the speed increase can be obtained, and it can be judged whether there is a tendency of wheel locking. If the tendency of wheel locking is decreasing, the braking torque can be increased by increasing the motor braking torque. The electric braking torque is initially set to increase by 20%, and the increase or decrease ratio of the electric braking torque can be adjusted later according to the growth trend of the slip rate. In this way, a dynamic balance is achieved, so that the electric braking torque is withdrawn before the ABS takes effect, but the electric braking torque reaches the maximum utilization before the withdrawal.

[0054] Step 2: Determine whether the current vehicle status information meets the preset adjustment conditions.

[0055] The preset adjustment condition is: the slip ratio is greater than a set threshold, the brake is in an activated state, and the ABS is in an inactivated state.

[0056] If the brake is in the activated state, it means that the electric brake is activated to reduce the speed of the vehicle. When the ABS is in the inactivated state and the slip ratio is greater than a set threshold, the execution conditions are provided for executing ABS activation and electric brake exit.

[0057] The ABS is adjusted to control the slip ratio within 10% to 30%, which ensures sufficient longitudinal braking force and maintains necessary lateral grip, thereby optimizing the braking performance and handling performance of the vehicle to obtain the best braking distance and steering controllability. Therefore, the threshold value is set to 10% to 30%, and the preferred threshold value is 20%. It can be seen that when the slip ratio is greater than the set threshold, the motor torque is adjusted to keep the slip ratio within the set threshold.

[0058] When the status information of the current vehicle meets the preset conditions, step three is executed, that is, whether the speed of the current vehicle meets the preset speed conditions; if so, energy recovery cancellation is executed; if not, the torque regulation strategy is executed to adjust the motor torque to achieve control of the vehicle.

[0059] The execution of energy recovery cancellation includes: electric braking exit. Electric braking changes the direction of motor power supply during sliding or braking, uses the original vehicle motor as an engine, thereby slowing down the vehicle, converting mechanical energy into motor and recovering energy.

[0060] It should be noted that the reference Figure 2 After adjusting the motor torque in step three, return to step two to re-judge whether the current vehicle status information meets the preset adjustment conditions until energy recovery cancellation is executed.

[0061] The preset vehicle speed condition is: the vehicle speed is less than 20 km / h, to prevent the vehicle speed from being too high and directly executing the exit of the electric brake, resulting in a bad driving experience and prone to accidents.

[0062] When the vehicle speed is greater than 20 km / h, the torque regulation strategy is executed to adjust the motor torque so that the electric brake is slowly withdrawn in the slip rate range of 10% to 30%. That is, the electric brake is not effective during the operation of the ABS, and there will be no regulation conflict, and there will be no vehicle jumping due to sudden withdrawal. Therefore, it is relatively safe.

[0063] Specifically, the execution torque adjustment strategy includes:

[0064] Obtaining the slip ratio again, and determining whether the slip ratio obtained again is in a preset state;

[0065] If yes, increase the motor torque and re-determine whether the vehicle status information meets the preset adjustment conditions;

[0066] If not, the motor torque is reduced and the vehicle status information is re-determined to see whether it meets the preset adjustment conditions.

[0067] The preset state is: the slip ratio obtained again does not increase relative to the slip ratio obtained last time. The slip ratio obtained last time refers to the slip ratio obtained in step 1. When the slip ratio obtained again does not increase relative to the slip ratio obtained last time, the torque of the motor is increased, that is, the vehicle speed is increased. Otherwise, it means that the slip ratio has changed, and the torque of the motor is reduced, that is, the vehicle speed is reduced.

[0068] The magnitude of the electric braking force directly determines how quickly the vehicle speed is reduced. The greater the electric braking force, the faster the vehicle speed is reduced. When the slip rate increases, the electric braking force is large, and the interaction between the wheel and the ground increases, so the torque of the motor needs to be reduced to reduce the vehicle speed. When the slip rate does not increase, it means that the sliding degree of the wheel relative to the ground has not increased, and the wheel still maintains a good rolling state. In this installed state, increase the vehicle speed to increase the electric braking force.

[0069] Further, the increasing of the motor torque includes: increasing the motor torque by 20%, which means that the motor torque is increased by 20% on the current basis. The reducing of the motor torque includes: reducing the motor torque by 20%, which means that the motor torque is reduced by 20% on the current basis.

[0070] The re-acquiring the slip ratio includes: collecting the slip ratio at least twice to determine whether the slip ratio increases, and also to obtain the speed increase to determine whether there is a tendency of wheel locking. If the tendency of wheel locking is decreasing, the electric braking force can be increased by increasing the motor torque. The motor torque is initially set to increase by 20%, and the increase or decrease ratio of the motor torque can be adjusted according to the growth trend of the slip ratio. In this way, a dynamic balance is achieved, so that the electric braking torque is withdrawn before the ABS takes effect, but the electric braking torque reaches the maximum utilization degree before the withdrawal.

[0071] The slip rate is the slip rate of the wheel. The vehicle has four wheels, so in the step 1, it is necessary to obtain the slip rates corresponding to all wheels. In the electric braking condition, when the slip rate of any wheel of the vehicle is close to the set threshold (i.e., the ABS adjustment range), and the speed is too high, the electric braking will not be withdrawn immediately, and the torque of the motor corresponding to the electric braking will be adjusted so that the increase in the slip rate will not be too large, and the speed will slowly drop to within 20km / h. Before the ABS enters the working state, the electric braking force is slowly withdrawn, so as to avoid the vehicle driving instability caused by the sudden withdrawal of the electric braking, and will not make the driver feel uncomfortable. It can be seen that when the ABS is not working, by judging the slip rate and the trend of wheel locking, the torque of the motor is controlled to achieve the goal of slowly reducing the vehicle speed and avoiding the vehicle driving instability caused by the sudden withdrawal of the electric braking.

[0072] The embodiments described above are only used to illustrate the technical ideas and features of the present invention, and their purpose is to enable technicians in this field to understand the contents of the present invention and implement them accordingly. The patent scope of the present invention cannot be limited only by this embodiment, that is, any equivalent changes or modifications made according to the spirit disclosed by the present invention still fall within the patent scope of the present invention.

Claims

1. A vehicle control method based on slip ratio, characterized in that: The following steps are involved: Acquiring current vehicle status information, wherein the current vehicle status information includes a slip rate; Determine whether the current vehicle status information meets the preset adjustment conditions; When the preset adjustment condition is met, determining whether the current vehicle speed meets the preset vehicle speed condition; If it meets the requirements, energy recovery cancellation is executed. If it does not meet the requirements, the torque regulation strategy is executed to adjust the motor torque to achieve control of the vehicle.

2. The vehicle control method based on slip ratio according to claim 1, characterized in that: The current vehicle status information also includes the activation status of the brake and the activation status of the ABS; The preset adjustment condition is: the slip ratio is greater than a set threshold, the brake is in an activated state, and the ABS is in an inactivated state.

3. The vehicle control method based on slip ratio according to claim 1, characterized in that: The obtaining of the current vehicle status information includes: Obtain the wheel's running speed, wheel angular velocity and wheel rolling radius; The slip rate is calculated according to the running speed of the wheel, the wheel angular velocity and the wheel rolling radius.

4. The vehicle control method based on slip ratio according to claim 1, characterized in that: The preset vehicle speed condition is: the vehicle speed is less than 20 km / h.

5. The vehicle control method based on slip ratio according to claim 1, characterized in that: The execution of energy recovery cancellation includes: Electric brake is disabled.

6. The vehicle control method based on slip ratio according to claim 1, characterized in that: The execution torque adjustment strategy includes: Obtaining the slip ratio again, and determining whether the slip ratio obtained again is in a preset state; If yes, increase the motor torque and re-determine whether the vehicle status information meets the preset adjustment conditions; If not, the motor torque is reduced and the vehicle status information is re-determined to see whether it meets the preset adjustment conditions.

7. The vehicle control method based on slip ratio according to claim 5, characterized in that: The preset state is that the slip ratio obtained again does not increase compared with the slip ratio obtained last time.

8. The vehicle control method based on slip ratio according to claim 5, characterized in that: Increasing the motor torque comprises: Increases the motor's torque by 20%.

9. The vehicle control method based on slip ratio according to claim 5, characterized in that: The reducing the motor torque comprises: Reduce the torque of the motor by 20%.

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