Method, device and automobile for improving braking performance based on full active suspension

Abstract

The application relates to a method, device and automobile for improving braking performance based on a full active suspension, and the method comprises the following steps: acquiring signals such as a reference vehicle speed and a braking master cylinder pressure change rate, and determining whether to enter an emergency braking state; if it is determined that it is not an emergency state, only activating a vehicle body posture controller; if it is determined that it is an emergency braking state, activating the vehicle body posture controller and simultaneously activating a braking enhancement controller. The vehicle body posture controller applies a first vertical active force through the active suspension to suppress a vehicle braking nodding angle and improve braking comfort; the braking enhancement controller applies a second vertical active force through the active suspension to reduce slip rate fluctuation and improve the braking performance of an anti-lock braking system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle chassis dynamics control, in particular to a method and device for improving braking performance based on full active suspension and a vehicle. BACKGROUND

[0002] In order to improve the braking stability and efficiency of the vehicle, the anti-lock braking system (ABS) has been widely used in various passenger cars and commercial vehicles. The core function of ABS is to prevent wheel lock by real-time monitoring and controlling the wheel slip ratio during braking.

[0003] The introduction of full active suspension provides the possibility to improve braking performance. However, the current braking system and active suspension system are often designed and operated as independent subsystems, lacking effective control coordination. In most mass-produced vehicles, the braking system still uses traditional hydraulic systems, which have a higher response bandwidth than high-performance full active suspensions, making it difficult to actively cooperate with full active suspensions for precise actuation. In recent years, although the research on full active suspension is still in its infancy, there are few studies on enhancing ABS braking performance through active suspension.

[0004] Therefore, the present application proposes an algorithm for full active suspension, which can reduce the fluctuation of wheel acceleration and improve braking effect without coordinating the ABS and full active suspension systems. SUMMARY

[0005] In view of the problems in the prior art, the present application aims to provide a method and device for improving braking performance based on full active suspension, which can reduce the fluctuation of wheel acceleration and improve the braking effect of the vehicle.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A method for improving braking performance based on full active suspension, comprising the following steps:

[0008] Obtaining relevant vehicle parameters based on vehicle sensors, including wheel speed, brake master cylinder pressure change rate, and longitudinal acceleration signal;

[0009] Determining the braking state of the current vehicle according to the obtained relevant vehicle parameters;

[0010] If the current braking state of the vehicle is determined to be non-emergency braking, the vehicle attitude controller outputs a first vertical active force to ensure the longitudinal attitude of the vehicle body is level. If the current braking state of the vehicle is determined to be emergency braking, the vehicle attitude controller outputs a first vertical active force to ensure the longitudinal attitude of the vehicle body is level. At the same time, the brake enhancement controller identifies the wheel slippage trend based on the wheel acceleration signal and applies a second vertical active force to the wheel. The first vertical active force and the second vertical active force are superimposed to form the total vertical active force output by the suspension. The total vertical active force acts on the wheel to reduce the fluctuation of wheel acceleration and wheel speed during emergency braking.

[0011] The design process of the braking enhancement controller algorithm includes:

[0012] Establish the tire dynamics equations and slip ratio calculation formulas:

[0013]

[0014] Where J is the moment of inertia of the wheel. Let F be the wheel angular acceleration, μ be the road adhesion coefficient, and s be the slip ratio. The conversion relationship between μ and s is obtained by looking up a table or polynomial fitting. z For the vertical load on the wheel, r d K is the rolling radius of the wheel. b The braking force T is the braking pressure applied to the wheel end. b The conversion factor, P b For braking pressure, v x For vehicle speed, ωr d This refers to wheel speed.

[0015] When the wheel acceleration is less than the longitudinal acceleration of the vehicle body, or the rate of change of wheel acceleration... At this time, the brake enhancement controller applies a downward second vertical active force to the corresponding wheel, increases the total vertical active force of the suspension output acting on the corresponding wheel, increases the wheel acceleration, thereby stabilizing the wheel acceleration relative to the vehicle body acceleration and reducing the fluctuation of the slip ratio;

[0016] When the wheel acceleration is greater than the longitudinal acceleration of the vehicle body, or the rate of change of wheel acceleration At this time, the brake enhancement controller applies an upward second vertical active force to the corresponding wheel, reduces the total vertical active force of the suspension output acting on the corresponding wheel, reduces the wheel acceleration, thereby stabilizing the wheel acceleration relative to the vehicle body acceleration and reducing the fluctuation of the slip ratio.

[0017] Furthermore, during emergency braking, the vehicle's reference speed and emergency braking time are continuously monitored. When the current reference speed is detected to be lower than the set reference speed threshold, or the emergency braking time exceeds the set reference time threshold, the brake enhancement controller stops working.

[0018] Further, the brake state determination of the current vehicle adopts a logical determination method.

[0019] Further, the body posture control algorithm adopts a control mode combining feedforward and PID feedback.

[0020] A device for improving brake performance based on a full active suspension, comprising

[0021] A parameter acquisition module is configured to acquire relevant vehicle parameters, including wheel speed, brake master cylinder pressure change rate, and longitudinal acceleration signal.

[0022] A brake state determination module is configured to determine, according to the acquired relevant vehicle parameters, whether the current vehicle is in an emergency braking state or a non-emergency braking state.

[0023] A body posture controller is configured to output a first vertical active force to ensure the longitudinal posture of the vehicle body when the current vehicle is in an emergency braking state or a non-emergency braking state.

[0024] A brake enhancement controller is configured to identify the slip trend of the wheel based on the wheel acceleration signal when the current vehicle is in an emergency braking state, and apply a second vertical active force to the corresponding wheel to reduce the wheel acceleration fluctuation and wheel speed fluctuation during emergency braking.

[0025] A superimposed output module is configured to superimpose the first vertical active force and the second vertical active force, and output a total vertical active force of the suspension acting on the wheel.

[0026] An automobile is configured with the above device.

[0027] An electronic device includes a processor and a memory, and the memory stores a computer program. When the processor executes the computer program, the above method is realized.

[0028] A storage medium stores a computer program. When the computer program is executed by a processor, the above method is realized.

[0029] In general, the present application has the following advantages:

[0030] 1) No additional sensors are required. Most mass-produced vehicles have the sensors required for the body posture control algorithm of the full active suspension and the brake enhancement algorithm based on wheel acceleration. The wheel acceleration signal can be calculated by differentiating the wheel speed signal.

[0031] 2) Strong adaptability. This method does not modify the control logic of the ABS system itself, so the decoupling degree of the brake system and the suspension system is high, and it can be adapted to all vehicles equipped with ABS systems.

[0032] 3) In the process of emergency braking, compared with the nodding posture of the vehicle body, the vehicle body keeps basically longitudinal horizontal, the driver's field of vision is more open and stable, which helps to enhance the braking confidence.

[0033] 4) Without estimating the slip ratio, the prior art method is to increase or decrease the tire vertical force according to the feedback of the slip ratio signal, so as to stabilize the slip ratio and improve the braking efficiency, and the accurate estimation of the slip ratio has the difficulty in engineering implementation. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is the flowchart of the present application.

[0035] Figure 2 is the load transfer amount and vehicle speed change diagram of the front and rear axles of the vehicle during emergency braking.

[0036] Figure 3 is the superposition diagram of the total vertical active force of the suspension during emergency braking.

[0037] Figure 4 is the force analysis diagram of the wheel during braking.

[0038] In the figure: v w is the wheel speed; ω is the wheel angular velocity; r d is the wheel rolling radius; F xb is the braking force; F z is the tire vertical load; T b is the braking torque.

[0039] Figure 5 is the relationship diagram of different road adhesion coefficients and slip ratios.

[0040] Figure 6 is the device structure block diagram of the present application.

[0041] Figure 7 is the electronic equipment structure block diagram of the present application. DETAILED DESCRIPTION

[0042] The present application will be further described in detail as follows.

[0043] As Figure 1 shown, a method for improving braking performance based on full active suspension includes the following steps:

[0044] Obtain vehicle operating state information through various sensors arranged on the vehicle, and determine whether the vehicle is in an emergency braking state.

[0045] The determination can be made in this way:

[0046] 1) Obtain signals of each wheel speed sensor, brake master cylinder pressure sensor and longitudinal acceleration sensor;

[0047] 2) Based on the above information, the system firstly estimates the current reference vehicle speed, and carries out real-time sampling and differential processing on the brake master cylinder pressure signal to obtain the pressure change rate;

[0048] 3) The system determines whether the vehicle is in an emergency braking state through logical judgment, and determines that the vehicle enters the emergency braking state when the reference vehicle speed is greater than a set threshold vehicle speed and the brake master cylinder pressure change rate is greater than a set threshold.

[0049] The determination method is simple and effective, and can quickly identify the emergency braking intention of the driver, and when the emergency braking state is determined, the full active suspension system is triggered to enter a control strategy with safety priority. The application does not limit the judgment logic, and other emergency braking determination methods can also be used.

[0050] When it is determined that it is not an emergency braking state, the full active suspension works in a comfort priority mode, and the vehicle body posture controller works alone to perform vehicle body posture leveling function, and outputs the first vertical active force to ensure the vehicle body longitudinal posture is horizontal, and does not apply the second vertical active force to ensure the vehicle ride comfort.

[0051] In the application, ensuring the horizontal of the longitudinal vehicle body can reduce the tire dynamic load fluctuation in the initial braking stage, and helps to improve the braking performance of the vehicle. Figure 2 Fig. 2 is a load transfer and vehicle speed change diagram of the vehicle in the emergency braking, wherein the load transfer calculation is the sum of the absolute values of the front axle load increase and the rear axle load decrease in braking. In the initial braking stage, the vehicle body starts to nod greatly due to the inertial force, and after the current suspension spring is compressed to a certain extent, the stored elastic potential energy is released, so the vehicle body will also have a small degree of lifting, and then the vehicle body will stabilize the nodding posture. This corresponds to the load transfer, and is manifested as a significant overshoot of the load transfer amount, which tends to be stable after a short time. If the full active suspension system is used to keep the longitudinal level of the vehicle body in the initial braking stage, the load transfer overshoot phenomenon can be effectively alleviated, that is, the vertical load overshoot fluctuation of the front and rear axles is alleviated, and the ground braking force fluctuation of the whole vehicle is reduced, and the performance and stability of the vehicle in the initial braking stage are improved.

[0052] In the embodiment of the application, the vehicle body posture controller is designed to ensure that the longitudinal posture of the vehicle body can be kept stable during braking, reduce the nodding and pitching of the vehicle, and reduce the overshoot of the tire dynamic load in the initial braking stage. The controller adopts a combination of feedforward control and PID feedback control, and specifically includes the following steps:

[0053] 1) Feedforward control: When the driver steps on the brake pedal, the feedforward controller calculates the feedforward control force in advance according to the master cylinder pressure, longitudinal acceleration and current vehicle speed signals obtained by sensors, to suppress the body "nodding" caused by the driver's operation. The feedforward control force can be obtained by looking up the table according to the master cylinder pressure, longitudinal acceleration and current vehicle speed signals;

[0054] 2) PID feedback control: According to the master cylinder pressure, longitudinal acceleration and current vehicle speed signals obtained by sensors, the body pitch angle is calculated in real time through the vehicle pitch dynamics model, and the difference between the reference pitch angle and the real-time calculated body pitch angle is transmitted to the PID feedback controller, thereby outputting the feedback control force. The feedback control force is mainly used to compensate for the feedforward control error;

[0055] 3) Control force arbitration: The feedforward control force and the feedback control force are added to obtain the total suspension output vertical control force of the body posture.

[0056] The algorithm of the body posture controller is only an embodiment, and the specific control mode can be flexibly adjusted according to system requirements, which is not limited in the present application.

[0057] When it is determined to be an emergency braking state, the full active suspension system enters a safety priority control mode, the body posture controller and the brake enhancement controller work simultaneously, the body posture controller outputs the first vertical active force to ensure the longitudinal posture of the vehicle body, and the brake enhancement controller applies the second vertical active force to the corresponding wheel according to the wheel slip trend, the first vertical active force and the second vertical active force are superimposed to form the total suspension output vertical active force and act on the wheel, thereby reducing the wheel acceleration fluctuation and wheel speed fluctuation during ABS braking, and indirectly enhancing the pressure regulation effect and braking performance of ABS. As shown in Figure 3 , it is a schematic diagram of superimposition of the first vertical active force and the second vertical active force during emergency braking.

[0058] Referring to Figure 4 and Figure 5 , the brake enhancement controller algorithm based on wheel acceleration is as follows:

[0059] A, the wheel dynamics equation and the slip rate calculation formula are established:

[0060]

[0061] Wherein, J is the rotational inertia of the wheel, is the angular acceleration of the wheel, μ is the road adhesion coefficient, s is the slip rate, and the conversion relationship between μ and s is obtained by looking up the table or polynomial fitting (see the attached Figure 5 , the road type is input by other systems), F z is the vertical load of the wheel, r d is the wheel rolling radius, Kb The braking force T is the braking pressure applied to the wheel end. b The conversion coefficient is typically a positive and fixed value. Its specific value can be obtained through vehicle calibration or experimental data fitting; this application does not impose any limitations on it. P b For braking pressure, v x For vehicle speed, ωr d This refers to wheel speed.

[0062] B. When the system detects that the wheel acceleration is less than the longitudinal acceleration of the vehicle body, or the rate of change of wheel acceleration... At that time, it was determined that the wheel speed was decreasing and there was a risk of a rapid increase in the slip ratio. In order to ensure that the slip ratio did not exceed the upper limit controlled by the ABS system, the brake enhancement controller was activated, driving the fully active suspension actuator to apply a downward second vertical active force to the target wheel.

[0063] Understandably, the suspension actuator applies a downward second vertical active force to the target wheel, which can rapidly increase the wheel's vertical load F in a short period of time. z From formula (1), we can see that F z Increasing the wheel speed increases the wheel angular acceleration on the left side of the formula, thus suppressing the decreasing trend of wheel speed; therefore, the wheel speed becomes more stable relative to the vehicle speed, and as shown in formula (2), the fluctuation of the slip ratio decreases; Figure 5 It can be seen that the reduction in slip ratio fluctuation keeps the road surface adhesion coefficient near its maximum value, thereby improving braking adhesion utilization while shortening braking distance.

[0064] C. When the system detects that the wheel acceleration is greater than the longitudinal acceleration of the vehicle body, or the rate of change of wheel acceleration... At that time, it was determined that the wheel speed was increasing and there was a risk of a rapid decrease in the slip ratio. In order to ensure that the slip ratio did not exceed the lower limit controlled by the ABS system, the brake enhancement controller was activated, driving the fully active suspension actuator to apply an upward second vertical active force to the target wheel.

[0065] Understandably, the suspension actuator applies a second upward vertical active force to the target wheel, which can rapidly reduce the vertical load F on the wheel in a short period of time. z From formula (1), we can see that F z Decreasing the wheel speed reduces the wheel angular acceleration on the left side of the formula, thus suppressing the upward trend of wheel speed; therefore, the wheel speed becomes more stable relative to the vehicle speed, and as shown in formula (2), the fluctuation of the slip ratio decreases; Figure 5 It can be seen that the reduction in slip ratio fluctuation keeps the road surface adhesion coefficient near its maximum value, thereby improving braking adhesion utilization while shortening braking distance.

[0066] When an emergency braking state is determined, the vehicle attitude controller and the brake enhancement controller work simultaneously, i.e., the system is in the safety priority control mode, continuously monitoring the vehicle reference speed and braking duration. When the current reference speed is detected to be lower than the set reference speed threshold, or the emergency braking time exceeds the set reference time threshold, the system is determined to be in a non-emergency braking state, the brake enhancement controller stops working, and the control logic automatically exits the safety priority control mode and returns to the comfort priority control mode.

[0067] It is understandable that the brake enhancement controller disengages because in the later stages of emergency braking, the pressure adjustment frequency of the ABS controller increases, while the bandwidth of the fully active suspension actuator is generally no more than 30Hz. The brake enhancement controller needs to disengage in advance, and at the same time, the vehicle speed is low, so disengaging in advance has a limited impact on the ABS braking performance.

[0068] like Figure 6 As shown, a device for improving braking performance based on fully active suspension includes...

[0069] The parameter acquisition module 501 is used to acquire relevant vehicle parameters, including wheel speed, brake master cylinder pressure change rate, and longitudinal acceleration signal.

[0070] The braking state determination module 502 is used to determine whether the current braking state of the vehicle is an emergency braking state or a non-emergency braking state based on the relevant vehicle parameters obtained.

[0071] The vehicle attitude controller 503 is used to output a first vertical active force to ensure the longitudinal attitude of the vehicle body is level when the current braking state of the vehicle is emergency braking or non-emergency braking.

[0072] The brake enhancement controller 504 is used to identify the wheel slippage trend based on the wheel acceleration signal when the current braking state of the vehicle is emergency braking, and apply a second vertical active force to the corresponding wheel to reduce wheel acceleration fluctuations and wheel speed fluctuations during emergency braking.

[0073] The superposition output module 505 is used to superimpose and output a first vertical active force and a second vertical active force, and output the total vertical active force of the suspension acting on the wheel.

[0074] The specific implementation of each module in this embodiment can be found in the above description, and will not be repeated here. It should be noted that the device provided in this embodiment is only illustrated by the above division of functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure can be divided into different functional modules to complete all or part of the functions described above.

[0075] The automobile is provided with the device, and wheel acceleration fluctuation can be reduced, and vehicle braking effect is improved.

[0076] As Figure 7 shown in the figure, the embodiment provides an electronic device, which comprises a processor 602, a memory, an input device 603, a display 604 and a network interface 605 connected through a system bus 601. The processor 602 is used to provide computing and control capability, the memory comprises a non-volatile storage medium 606 and an internal memory 607, the non-volatile storage medium 606 stores an operating system, a computer program and a database, the internal memory 607 provides an environment for the operating system and the computer program in the non-volatile storage medium 606 to run, and the computer program is executed by the processor 602 to realize the above method.

[0077] The application further provides a storage medium, and the storage medium stores a computer program, and the computer program is executed by the processor to realize the above method.

[0078] The storage medium in the embodiment can be a disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), a U disk, a mobile hard disk and the like.

[0079] The above embodiment is a preferred embodiment of the application, but the embodiment of the application is not limited by the above embodiment, and any change, modification, replacement, combination, simplification made without departing from the spirit and principle of the application should be an equivalent replacement mode, and all should be included in the protection scope of the application.

Claims

1. A method for improving braking performance based on a full active suspension, characterized by: The method comprises the following steps: Obtaining relevant vehicle parameters based on vehicle sensors, including wheel speed, brake master cylinder pressure rate of change, and longitudinal acceleration signal; determining the braking state of the current vehicle according to the obtained relevant vehicle parameters; if the braking state of the current vehicle is determined to be a non-emergency braking state, the vehicle body posture controller outputs a first vertical active force to ensure the longitudinal posture of the vehicle body; if the braking state of the current vehicle is determined to be an emergency braking state, the vehicle body posture controller outputs a first vertical active force to ensure the longitudinal posture of the vehicle body, and simultaneously, the brake enhancement controller identifies the slip trend of the wheel based on the wheel acceleration signal and applies a second vertical active force to the wheel, the first vertical active force and the second vertical active force are superimposed to form a suspension output total vertical active force acting on the wheel, reducing the wheel acceleration fluctuation and the wheel speed fluctuation during emergency braking; The brake enhancement controller algorithm design process comprises: Establishing a wheel dynamics equation and a slip rate calculation formula: ； ； wherein, J is the moment of inertia of the wheel, ω is the wheel angular velocity, is the wheel angular acceleration, μ is the road adhesion coefficient, s is the slip ratio, μ and s the conversion relationship between them is obtained by table lookup or polynomial fitting, F z is the wheel vertical load, r d is the wheel rolling radius, K b is the conversion coefficient of brake pressure to wheel end braking torque T b P b is the brake pressure, v x is the vehicle speed, ωr d is the wheel speed;​ The brake enhancement controller applies a second vertical active force to the wheel, comprising, When the wheel acceleration is less than the vehicle body longitudinal acceleration, or the wheel angular acceleration change rate The brake enhancement controller drives the full active suspension to apply a second downward vertical active force to the corresponding wheel, increases the total suspension output vertical active force acting on the corresponding wheel, increases the wheel acceleration, so as to stabilize the wheel acceleration relative to the vehicle body acceleration and reduce the fluctuation of the slip rate. When the wheel acceleration is greater than the vehicle body longitudinal acceleration, or the wheel angular acceleration rate of change The brake enhancement controller drives the full active suspension to apply an upward second vertical active force to the corresponding wheel, reduces the total suspension output vertical active force acting on the corresponding wheel, reduces the wheel acceleration, thereby stabilizing the wheel acceleration relative to the vehicle body acceleration and reducing the fluctuation of the slip rate. In the emergency braking state, the vehicle reference speed and the emergency braking time are continuously monitored, and when it is detected that the current reference speed is lower than the set reference speed threshold or the emergency braking time exceeds the set reference time threshold, the brake enhancement controller exits the work.

2. The method of claim 1, wherein: The braking state determination of the current vehicle adopts a logical determination method.

3. The method of claim 1, wherein: The vehicle body posture control algorithm adopts a control mode combining feedforward and PID feedback.

4. Apparatus for implementing the method of improving the braking performance based on a fully active suspension according to any one of claims 1 to 3, characterized in that: The method comprises A parameter acquisition module for acquiring relevant vehicle parameters, including wheel speed, brake master cylinder pressure rate of change, and longitudinal acceleration signal; A braking state determination module for determining the braking state of the current vehicle as an emergency braking state or a non-emergency braking state according to the obtained relevant vehicle parameters; A vehicle body posture controller for outputting a first vertical active force to ensure the longitudinal posture of the vehicle body when the braking state of the current vehicle is an emergency braking state or a non-emergency braking state; A brake enhancement controller for identifying the slip trend of the wheel based on the wheel acceleration signal and applying a second vertical active force to the corresponding wheel to reduce the wheel acceleration fluctuation and the wheel speed fluctuation during emergency braking when the braking state of the current vehicle is an emergency braking state; A superimposed output module for superimposing and outputting the first vertical active force and the second vertical active force to output a suspension output total vertical active force acting on the wheel.

5. An automobile characterized by comprising: The device of claim 4 is configured.

6. An electronic device, comprising: The method comprises a processor and a memory, the memory stores a computer program, and the processor executes the computer program to realize the method of any one of claims 1-3.

7. A storage medium, characterized by The storage medium stores a computer program, and the computer program is executed by the processor to realize the method of any one of claims 1-3.

Images