Control method for avoiding squeal of vehicle brakes

Abstract

The application discloses a control method for avoiding vehicle braking squeal, which comprises the following steps: presetting a speed interval of vehicle driving, controlling the vehicle to brake in the speed interval; presetting a pressure control interval of braking and an SP curve algorithm of a brake controller; when being in the pressure control interval, automatically distributing front and rear axle braking pressures through the control of the brake controller, and performing front and rear axle pressure differential braking control; when being out of the pressure control interval, performing pressure control according to the SP curve algorithm preset by the brake controller; and the application can automatically distribute the front and rear axle braking pressures according to the braking torque equivalent principle, and can avoid the pressure interval prone to generating braking noise through the pressure differential braking control on the front and rear axles, so that the braking comfort of the vehicle is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle control, in particular to a control method for avoiding vehicle brake squeal. BACKGROUND

[0002] Integrated brake control system is more and more widely used in passenger cars, as an integrated and intelligent electric brake system, which combines basic brake assist and single wheel pressure regulation function together, has compact configuration and stronger brake performance, and can realize more brake control functions. At present, most passenger cars use friction brake, that is, brake force is generated by the contact friction force between the friction plate and the brake disc (or brake drum) in the brake, and the kinetic energy of the vehicle is converted into heat energy during braking, so as to achieve the purpose of vehicle braking and speed reduction. During vehicle braking, when the vehicle speed is low (usually less than 10kph), in a specific brake pressure interval range, the brake will produce brake squeal, which reduces the driving experience of the vehicle. The present application proposes an integrated brake control system pressure control method for avoiding brake squeal, that is, when the vehicle speed and brake pressure interval meet the requirements of the present application, the front and rear axle brake pressures are automatically distributed according to the brake torque equivalence principle, and the pressure differential control of the front and rear axles is performed to avoid the pressure interval prone to brake noise, so as to avoid brake noise and improve the driving quality of the vehicle. SUMMARY

[0003] The present application aims to provide a control method for avoiding vehicle brake squeal to solve the problems in the background art.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a control method for avoiding vehicle brake squeal, comprising:

[0005] presetting a speed interval of vehicle driving, and controlling the vehicle to brake in the speed interval;

[0006] presetting a pressure control interval of brake and an SP curve algorithm of brake controller;

[0007] when in the pressure control interval, automatically distributing the front and rear axle brake pressures through the control of brake controller, and performing front and rear axle pressure differential brake control;

[0008] when out of the pressure control interval, performing pressure control according to the SP curve algorithm preset by the brake controller.

[0009] Further, when in the pressure control interval, automatically distributing the front and rear axle brake pressures through the control of brake controller, and performing front and rear axle pressure differential brake control, further comprising:

[0010] setting a pressure fluctuation interval and a pressure fluctuation detection time;

[0011] starting the brake pressure detection in the pressure control interval with the pressure fluctuation detection time as a period;

[0012] When the detected brake pressure fluctuation in a period is within the pressure fluctuation interval, the front and rear axle brake pressures are automatically distributed to perform the front and rear axle pressure differential brake control.

[0013] If the detected brake pressure fluctuation exceeds the pressure fluctuation interval, the pressure control is performed according to the SP curve algorithm preset by the brake controller.

[0014] Further, the pressure fluctuation interval and the pressure fluctuation detection time are set, and the method further comprises that the pressure fluctuation interval is ±0.2 bar, and the pressure fluctuation detection time is 20 ms.

[0015] Further, a speed interval at which the vehicle travels is preset, and the vehicle is controlled to brake in the speed interval, and the method further comprises that the speed interval is 1.5 kph≤vehicle speed≤10 kph.

[0016] Further, the method comprises that the brake includes driver-initiated braking and upper controller-requested braking.

[0017] Further, a pressure control interval of the brake is preset, and the method further comprises that the pressure control interval is 4 bar≤pressure≤6 bar.

[0018] Further, when in the pressure control interval, the front and rear axle brake pressures are automatically distributed by the control of the brake controller to perform the front and rear axle pressure differential brake control, and the method further comprises that:

[0019] According to the brake torque equivalence principle, the front and rear axle brake pressures are automatically distributed by the control of the brake controller to control the front and rear axles of the vehicle to establish different brake pressures, and the algorithm of the brake pressure distribution is as follows:

[0020] ;

[0021] wherein, not in the pressure control interval;

[0022] the total brake torque of the front and rear axles of the vehicle, the brake pressure, the Cp values of the front and rear brakes respectively, the front and rear axle brake pressures after distribution respectively.

[0023] Further, according to the brake torque equivalence principle, the front and rear axle brake pressures are automatically distributed by the control of the brake controller to control the front and rear axles of the vehicle to establish different brake pressures, and the method further comprises that:

[0024] Generally, the braking torque of the front wheels is greater than that of the rear wheels, so the front axle brake pressure is greater than the rear axle brake pressure;

[0025] Through the control of the brake controller, the inlet electromagnetic valve of the front axle corresponding wheel cylinder is fully opened, and the inlet electromagnetic valve of the rear axle corresponding wheel cylinder is partially opened.

[0026] Further, the pressure control is performed according to the SP curve algorithm preset by the brake controller, including that the brake pressures of the four wheel cylinders are consistent.

[0027] Further, the pressure control is performed according to the SP curve algorithm preset by the brake controller, including that the pressure control is performed according to the algorithm of the brake controller, and the parameters in the algorithm of the brake controller include an SP control curve, wherein the SP control curve includes a preset brake pedal stroke S and brake pressure P, and the brake pedal stroke S and the brake pressure P are set correspondingly.

[0028] Compared with the prior art, the present application has the beneficial effects that: the present application can automatically distribute the front and rear axle brake pressures according to the braking torque equivalence principle, and avoid the pressure interval prone to producing brake noise through differential pressure brake control of the front and rear axles, thereby improving the braking comfort of the vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A control method flowchart for avoiding vehicle brake screeching in an embodiment of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more; the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" and the like are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0032] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0033] Please refer to the drawings in the specification, the present application provides a technical solution: as Figure 1 The control method for avoiding vehicle brake squeal comprises the following steps:

[0034] S102, preset the speed range of the vehicle, control the vehicle to brake in the speed range;

[0035] S104, preset the pressure control range of braking and the SP curve algorithm of the brake controller;

[0036] S106, when in the pressure control range, through the control of the brake controller, automatically distribute the front and rear axle brake pressure, and perform front and rear axle pressure differential brake control;

[0037] S108, when outside the pressure control range, execute pressure control according to the SP curve algorithm preset by the brake controller.

[0038] In the above embodiment, during the vehicle braking process, when the vehicle speed is low (usually less than 10kph), the brake will produce brake squeal in a specific brake pressure range, which reduces the driving experience of the vehicle. In view of the brake squeal problem of the brake during the vehicle braking process, the present application considers the pressure range of the vehicle speed and the driver stepping on the brake pedal or the upper controller requesting braking, and automatically distributes the front and rear axle brake pressure according to the brake torque equivalence principle, and avoids the pressure range prone to brake noise by performing pressure differential brake control on the front and rear axles, so as to avoid brake squeal during braking.

[0039] Optionally, step S106 further comprises the following steps:

[0040] S202, set the pressure fluctuation range and the pressure fluctuation detection time;

[0041] S204, start brake pressure detection in the pressure control range with the pressure fluctuation detection time as the period;

[0042] S206, when the detected brake pressure fluctuation in a period is located in the pressure fluctuation range, automatically distribute the front and rear axle brake pressure, and perform front and rear axle pressure differential brake control;

[0043] S208, if the detected brake pressure fluctuation exceeds the pressure fluctuation interval, performing pressure control according to the SP curve algorithm preset by the brake controller.

[0044] Specifically, a pressure fluctuation interval and a pressure fluctuation detection time are set, wherein the pressure fluctuation interval is preferably ±0.2 bar, and the pressure fluctuation detection time is 20 ms.

[0045] In the above embodiment, the pressure fluctuation interval refers to that when the brake pressure requested by the driver is within the pressure control interval 4-6 bar of the brake, the timing starts, and within the pressure fluctuation detection time of one cycle 20 ms, if the brake pressure requested by the driver fluctuates within ±0.2 bar, the brake pressure fluctuation does not exceed the pressure fluctuation interval, and if the brake pressure fluctuation exceeds ±0.2 bar within one cycle 20 ms, the detected brake pressure fluctuation exceeds the pressure fluctuation interval, and then the pressure control is performed according to the SP curve algorithm of the brake controller.

[0046] Optionally, a speed interval at which the vehicle travels is preset, and the vehicle is controlled to brake in the speed interval, and the speed interval is 1.5 kph≤vehicle speed≤10 kph.

[0047] Optionally, the brake includes driver-initiated braking and upper controller-requested braking.

[0048] In the above embodiment, the driver-initiated braking is that the driver steps on the brake pedal, and the brake controller is preferably an integrated brake control system, which controls the motor to rotate by reading the internal brake pedal stroke signal, establishes brake pressure in the four wheel cylinders according to the brake demand of the driver, and completes the process of brake assist; the upper controller-requested braking is that the advanced auxiliary driving controller such as the adaptive cruise controller, the automatic parking controller, etc. issues a brake request, and the integrated brake control system responds to the brake request and establishes brake pressure in the four wheel cylinders.

[0049] Optionally, a pressure control interval of the brake is preset, and the pressure control interval is 4 bar≤pressure≤6 bar.

[0050] Optionally, when in the pressure control interval, the front and rear axle brake pressures are automatically distributed and controlled by the brake controller to perform front and rear axle differential brake control, and the method further comprises:

[0051] According to the brake torque equivalence principle, the front and rear axle brake pressures are automatically distributed and controlled by the brake controller to establish different brake pressures for the front and rear axles of the vehicle, and the algorithm for distributing the brake pressures is as follows:

[0052] ;

[0053] wherein, not in the pressure control interval;

[0054] is the total braking torque of the vehicle front and rear axles, is the braking pressure, respectively, the front and rear brake Cp values, respectively, the front and rear axle braking pressures after distribution.

[0055] The Cp value is a parameter used in the braking system to calculate the brake braking torque, and its physical meaning is the braking torque generated per Mpa of braking pressure, with the unit of Nm / bar.

[0056] Specifically, according to the braking torque equivalence principle, the front and rear axle braking pressures are automatically distributed by the control of the brake controller, and different braking pressures are respectively controlled for the front and rear axles of the vehicle, which also includes:

[0057] Generally, the front wheels bear more braking torque than the rear wheels, so the front axle braking pressure is greater than the rear axle braking pressure.

[0058] Through the control of the brake controller, the inlet electromagnetic valve of the front axle corresponding wheel cylinder will be completely opened, and the inlet electromagnetic valve of the rear axle corresponding wheel cylinder will be partially opened.

[0059] In the above embodiment, it is assumed that respectively, the front and rear axle braking pressures obtained by distribution, and At this time, the inlet electromagnetic valve of the front axle corresponding wheel cylinder will be completely opened, and the pressure control will be completed by the integrated brake control system. The inlet electromagnetic valve of the rear axle corresponding wheel cylinder will be partially opened, and the integrated brake control system will complete the wheel cylinder pressure control by controlling the electromagnetic valve opening degree, i.e. as the target control pressure of the integrated brake control system, as the target control pressure of the rear axle wheel cylinder. The front axle pressure is completed by the pressure closed-loop control of the integrated brake control system, and the rear axle pressure is completed by the corresponding electromagnetic valve group control.

[0060] Optionally, the pressure control is performed according to the SP curve algorithm preset by the brake controller, including that the braking pressures of the four wheel cylinders are consistent.

[0061] Optionally, the pressure control is performed according to the SP curve algorithm preset by the brake controller, and the SP curve algorithm includes an SP control curve, wherein the SP control curve includes a preset brake pedal stroke S and a braking pressure P, and the brake pedal stroke S and the braking pressure P are set correspondingly.

[0062] In the above embodiment, the SP control curve has the brake pedal stroke S as the horizontal coordinate and the braking pressure P as the vertical coordinate.

[0063] The invention will be further illustrated below with specific examples:

[0064] Example 1

[0065] During vehicle operation, the driver may press the brake pedal or the upper controller may request braking. In this embodiment, the vehicle speed is set to 8 kph, and the pressure control range is set to 4 bar ≤ pressure ≤ 6 bar.

[0066] Requested braking pressure The pressure is 5 bar. Within the pressure control range, the system begins to determine whether the braking pressure is within the pressure fluctuation range. In this embodiment, the system detects within a 20ms cycle that the driver's requested braking pressure fluctuation is 0.15 bar, which is within ±0.2 bar. Therefore, the system continues to enter the front and rear axle pressure differential braking control.

[0067] Based on the principle of equivalent braking torque, the braking pressure is automatically distributed between the front and rear axles. The distribution of braking pressure can be expressed by the following formula:

[0068] ;

[0069] This is the total braking torque of the front and rear axles of the vehicle. These are the Cp values ​​for the front and rear brakes, respectively. These are the distributed braking pressures of the front and rear axles, respectively.

[0070] Specifically, assuming the driver is currently requesting braking pressure If the value is 5 bar, then the braking torque required by the driver is... ,set up =30Nm / bar =20Nm / bar, then at this time

[0071] M 总 =5*(30+20)=250Nm, the braking pressure obtained after distribution between the front and rear axles. With the values ​​of 7 bar and 2 bar respectively, the total braking torque is M_total = 7 * 30 + 2 * 20 = 250 Nm. This achieves the effect that the total braking torque of the vehicle after distribution is equal to that before distribution.

[0072] At this time, the inlet solenoid valve for the corresponding wheel cylinder on the front axle will be fully open, and pressure control is accomplished by the integrated brake control system. The inlet solenoid valve for the corresponding wheel cylinder on the rear axle will be partially open, and wheel cylinder pressure control is achieved through solenoid valve opening degree control. The target control pressure for the integrated braking control system. The target control pressure of the rear axle cylinder. The front axle pressure is controlled by the pressure closed loop control of the integrated brake control system, and the rear axle pressure is controlled by the corresponding solenoid valve group.

[0073] Example Two

[0074] During the vehicle driving process, the driver steps on the brake pedal or the upper controller requests braking. In this embodiment, the vehicle speed is taken as 8 kph, and the pressure control interval is set as 4 bar≤pressure≤6 bar.

[0075] The requested brake pressure is 5 bar, and the pressure control interval is 4 bar≤pressure≤6 bar. Since 5 bar is within the interval, it is determined whether the brake pressure is within the pressure fluctuation interval. In this embodiment, the driver's requested brake pressure fluctuation is in 20 ms, which exceeds the upper limit . Therefore, the pressure control is performed according to the SP curve.

[0076] Example Three

[0077] During the vehicle driving process, the driver steps on the brake pedal or the upper controller requests braking. In this embodiment, the vehicle speed is taken as 8 kph, and the pressure control interval is set as 4 bar≤pressure≤6 bar.

[0078] The requested brake pressure is 7 bar, and the brake pressure is not within the pressure control interval 4 bar≤pressure≤6 bar. Therefore, the pressure control is performed according to the SP curve.

[0079] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A control method for avoiding squeal of a vehicle brake, characterized by, The method comprises: a preset speed interval of vehicle driving, controlling the vehicle to brake in the speed interval; a preset pressure control interval of braking and an SP curve algorithm of the brake controller; when in the pressure control interval, automatically distributing front and rear axle braking pressure through control of the brake controller to perform front and rear axle pressure differential braking control; setting a pressure fluctuation interval and a pressure fluctuation detection time; starting braking pressure detection in the pressure control interval with the pressure fluctuation detection time as a period; when the detected braking pressure fluctuation in a period is in the pressure fluctuation interval, automatically distributing front and rear axle braking pressure to perform front and rear axle pressure differential braking control; if the detected braking pressure fluctuation exceeds the pressure fluctuation interval, performing pressure control according to the preset SP curve algorithm of the brake controller.

2. The control method of claim 1, wherein, The pressure fluctuation interval is ±0.2 bar and the pressure fluctuation detection time is 20 ms.

3. The control method of claim 1, wherein, The preset speed interval of vehicle driving, controlling the vehicle to brake in the speed interval, further comprises: the speed interval is 1.5 kph ≤ vehicle speed ≤ 10 kph.

4. The control method of claim 1, wherein, The method comprises: The braking comprises driver-initiated braking and upper controller-requested braking.

5. The control method of claim 1, wherein, The preset pressure control interval of braking further comprises: the pressure control interval is 4 bar ≤ pressure ≤ 6 bar.

6. The control method of claim 1, wherein, When in the pressure control interval, automatically distributing front and rear axle braking pressure through control of the brake controller to perform front and rear axle pressure differential braking control, further comprises: According to the braking torque equivalence principle, automatically distributing front and rear axle braking pressure through control of the brake controller to control the front and rear axles of the vehicle to establish different braking pressures, and the algorithm for distributing braking pressure is as follows: M 总 = p0 x (Cp f + Cp r ) = p f x Cp f + p r x Cp r ; wherein p f , p r is not within the pressure control interval; M 总 is the total braking torque of the front and rear axles, p0 is the brake pressure, Cp f , Cp r are the front and rear brake Cp values, respectively, p f , p r are the front and rear axle brake pressures after distribution.

7. The control method of claim 6, wherein, According to the braking torque equivalence principle, automatically distributing front and rear axle braking pressure through control of the brake controller to control the front and rear axles of the vehicle to establish different braking pressures, further comprises: The front axle braking pressure is greater than the rear axle braking pressure. Through control of the brake controller, the inlet electromagnetic valve corresponding to the front axle wheel cylinder is fully opened, and the inlet electromagnetic valve corresponding to the rear axle wheel cylinder is partially opened.

8. The control method of claim 1, wherein, Performing pressure control according to the preset SP curve algorithm of the brake controller comprises: the braking pressures of the four wheel cylinders are consistent.

9. The control method of claim 8, wherein, Performing pressure control according to the preset SP curve algorithm of the brake controller, the SP curve algorithm comprises an SP control curve, wherein the SP control curve comprises a preset brake pedal stroke S and a braking pressure P, and the brake pedal stroke S and the braking pressure P are set correspondingly.

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