CN113879272B - Vehicle brake control method based on electronic parking system - Google Patents
Vehicle brake control method based on electronic parking system Download PDFInfo
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- CN113879272B CN113879272B CN202010630549.4A CN202010630549A CN113879272B CN 113879272 B CN113879272 B CN 113879272B CN 202010630549 A CN202010630549 A CN 202010630549A CN 113879272 B CN113879272 B CN 113879272B
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- clamping force
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
- B60T13/74—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with electrical assistance or drive
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
- B60T8/17—Using electrical or electronic regulation means to control braking
- B60T8/172—Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters
Abstract
The invention aims to provide a vehicle brake control method based on an electronic parking system, which uses a brake master cylinder pressure signal or a brake pedal stroke signal or a control signal generated by an electronic controller related to automatic driving as a target deceleration signal of a vehicle, and controls clamping force generated by an EPB according to the target deceleration signal, so that the vehicle deceleration can follow the target deceleration signal. The follow-up of the vehicle deceleration and a target deceleration signal is realized through an EPB system, and the deceleration control effect is equivalent to that of a traditional hydraulic braking system; fast response to the target deceleration signal.
Description
Technical Field
The invention relates to the field of active safety of motor vehicles, in particular to a vehicle brake control method based on an electronic parking system.
Background
In recent years, with the continuous development of the technology in the field of intelligent driving, safety and comfort become important factors considered in the industry. Vehicles are beginning to be equipped with more and more electronic control systems, wherein wheel-end electronic parking devices (EPBs) have become the standard configuration for more and more passenger cars. EPBs are used not only for parking, but also for the purpose of braking the vehicle in an emergency (emergency braking).
In the existing vehicle equipped with the EPB, when the emergency service braking needs to be completed under the condition of failure of a hydraulic system and the like, a driver triggers an EPB system switch, and an EPB controller provides the maximum vehicle deceleration under the premise of avoiding locking of wheels. The control method has the following disadvantages:
1. emergency braking can only be achieved when the driver triggers a switch, which is not used correctly by all drivers in an emergency.
2. Only a constant deceleration can be provided during emergency braking and the intention of the driver to decelerate cannot be followed. The main reason is that the wheel end EPB device (EPB caliper or drum EPB mechanism) is a self-locking device, and when the vehicle deceleration needs to be changed from high to low, no reliable control method exists so far.
On the other hand, autonomous driving places higher demands on redundant braking functions beyond the main braking system. If a suitable control method can be found to enable the EPB system to be used as a controllable redundant brake system, it is of great significance to improve the safety and comfort of the vehicle and to reduce the cost and weight of the brake system.
Disclosure of Invention
In order to solve the above problems, the present invention provides a vehicle brake control method based on an electronic parking system, which controls a motor to clamp, release or stop according to the relationship between the current clamping force and the target clamping force, so as to realize the following of the vehicle deceleration and the target deceleration signal, and solve the problems occurring in the background art.
The invention aims to provide a vehicle brake control method based on an electronic parking system, which uses a brake master cylinder pressure signal or a brake pedal stroke signal or a control signal generated by an electronic controller related to automatic driving as a target deceleration signal of a vehicle, and controls clamping force generated by an EPB according to the target deceleration signal, so that the vehicle deceleration can follow the target deceleration signal.
The further improvement lies in that: the clamping force is generated by a wheel end electronic parking device (EPB) with a self-locking characteristic.
The further improvement lies in that: clamping process EPB clamping force vs drive motor current relationship:
F N =k*I mot ，
wherein: f N : EPB clamping force, k: coefficient of proportionality, I mot : the motor current.
Under the conditions of different temperatures or working voltages, the k values are different, and the k values are obtained through experimental measurement;
in the process of controlling the release of the EPB, the formula F cannot be directly adopted because the EPB adopts a self-locking transmission mechanism N =k*I mot Calculating the clamping force according to the release current of the motor; clamping force F at the beginning of release 0 Under the state, the calculation of the residual clamping force of the calipers in the motor release process is divided into two stages of unlocking and releasing:
starting motor and releasing to motor releasing turns C 0 The period is called unlocking stage, the residual clamping force and the number of releasing turns of the motor C x Direct correlation:
F r = F 0 – (m 0 *C x +n 0 ) ，
wherein: f r : residual clamping force of the releasing process, F 0 : the clamping force at the beginning of the releasing process,
m 0 and n 0 Are all equal to F 0 A corresponding constant, which can be obtained by experimental calibration;
the number of the backspacing circles of the motor can be calculated by a motor model through the current and the voltage of the motor,
motor release exceeding number of turns C 0 The residual clamping force then has a linear relationship with the motor current:
F r =k r *I r ，
wherein: f r : residual clamping force during release, k r : clamping force to current ratio coefficient during release, I r : releasing the current.
When the target deceleration signal changes, the target clamping force is calculated according to the following formula, the EPB motor is controlled to release or clamp, and when the actual clamping force is equal to the target clamping force, the motor is stopped, so that the following of the vehicle deceleration and the target deceleration signal is realized:
F N =(m*a*R β )/( 2*n*μ*R e )，
wherein: f N : EPB clamping force, m: vehicle mass, a: deceleration, R β : rolling radius of wheel, R e : effective braking radius, n: typical values for the number of wheels involved in electric caliper braking are 2 or 4, μ: coefficient of friction.
The further improvement lies in that: and converting the target deceleration signal into a target clamping force, and taking the target clamping force as a control target.
The invention has the beneficial effects that: the invention realizes the follow-up of the vehicle deceleration and the target deceleration signal through the EPB system, and the deceleration control effect is equivalent to the effect of the traditional hydraulic braking system; fast response to the target deceleration signal.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
Detailed Description
For the purpose of enhancing understanding of the present invention, the present invention will be further described in detail with reference to the following examples, which are provided for illustration only and are not to be construed as limiting the scope of the present invention.
As shown in fig. 1, the present embodiment provides a vehicle brake control method based on an electronic parking system, which establishes in advance a correlation between a target deceleration signal and a vehicle deceleration according to a braking demand:
a=f(s)，
wherein: a: vehicle deceleration, s: a target deceleration signal.
And (3) calculating clamping force required by the EPB corresponding to different target decelerations according to parameters such as the mass of the vehicle, the effective braking radius, the rolling radius of the wheels, the friction coefficient and the like:
F N =(m*a*R β )/( 2*n*μ*R e )，
wherein: f N : EPB clamping force, m: vehicle mass, a: deceleration, R β : rolling radius of wheel, R e : effective braking radius, n: typical values for the number of wheels involved in electric caliper braking are 2 or 4, μ: coefficient of friction.
EPB clamping force versus drive motor current:
F N =k*I mot ，
wherein: f N : EPB clamping force, k: coefficient of proportionality, I mot : the motor current.
Under the conditions of different temperatures or working voltages, the k values are different, and the k values are obtained through experimental measurement;
establishing a characteristic relation between the target deceleration signal and the EPB motor current according to the relation among the target deceleration signal, the target deceleration, the clamping force and the current:
I mot = f(s)，
wherein: i is mot : motor current, s: is the target deceleration signal.
When the target clamping force is larger than or equal to the current clamping force, the EPB motor is controlled to clamp or stop according to the clamping current corresponding to the target clamping force, and the follow-up of the vehicle deceleration and the target deceleration signal is realized.
The EPB adopts a self-locking structure, and when the motor is controlled to be released, the EPB cannot directly adopt F N =k*I mot The clamping force is calculated from the release current of the motor (the clamping force during release is also referred to herein as the residual clamping force). At the current clamping force of F 0 Under the state, the calculation of the residual clamping force of the calipers in the motor release process is divided into two stages of unlocking and releasing:
starting the motor and releasing to the number of releasing turns C of the motor 0 This period of time is referred to as the unlock phase. Experiments show that the residual clamping force and the number of releasing turns C of the motor at the stage x In the following relationship;
F r = F 0 – (m 0 *C x +n 0 )，
wherein: f r : residual clamping force during release, F 0 : clamping force at the beginning of the release process, i.e. at the end of the EPB clamping, m 0 And n 0 Are all equal to F 0 Corresponding constant, which can be obtained by experimental calibration.
The number of the backspacing turns of the motor can be calculated by a motor model through the current and the voltage of the motor.
The motor release exceeds the number of turns C 0 The residual clamping force is then linear with the current of the EPB motor:
F r =k r *I r ，
wherein: f r : residual clamping force during release, k r : clamping force to current ratio coefficient during release, I r : releasing the current.
And when the target clamping force is smaller than the residual clamping force, controlling the EPB motor to release (namely reverse), calculating the current residual clamping force according to the unlocking stage or the releasing stage where the motor releasing state is located and by combining the motor backspacing number of turns or the motor current, and stopping the motor when the residual clamping force meets the vehicle deceleration requirement.
By adopting the technical scheme, the method has the following effects:
1. the follow-up of the vehicle deceleration and a target deceleration signal is realized through an EPB system, and the deceleration control effect is equivalent to that of a traditional hydraulic braking system;
2. fast response to the target deceleration signal.
Claims (3)
1. A vehicle brake control method based on an electronic parking system is characterized in that: using a brake master cylinder pressure signal or a brake pedal stroke signal or a control signal generated by an electronic controller related to automatic driving as a target deceleration signal of the vehicle, and controlling the clamping force generated by the EPB according to the target deceleration signal to realize that the vehicle deceleration changes along with the target deceleration signal;
clamping process EPB clamping force vs drive motor current relationship:
F N =k*I mot ，
wherein: f N : EPB clamping force, k: coefficient of proportionality, I mot : the current of the motor is measured by the motor,
under the conditions of different temperatures or working voltages, the k values are different, and the k values are obtained through experimental measurement;
in the process of controlling the release of the EPB, the EPB adopts a self-locking transmission mechanism, so that the clamping force can not be directly calculated by the release current of the motor by adopting the formula; clamping force F at the beginning of release 0 Under the state, the calculation of the residual clamping force of the calipers in the motor release process is divided into two stages of unlocking and releasing:
starting the motor and releasing to the number of releasing turns C of the motor 0 The period is called unlocking stage, the residual clamping force and the number of releasing turns of the motor C x Direct correlation:
F r = F 0 – (m 0 *C x +n 0 ) ，
wherein: f r : residual clamping force of the releasing process, F 0 : the clamping force at the beginning of the releasing process,
m 0 and n 0 Are all equal to F 0 A corresponding constant, which can be obtained by experimental calibration;
the number of the backspacing turns of the motor can be calculated by a motor model through the current and the voltage of the motor,
motor release exceeding number of turns C 0 The residual clamping force then has a linear relationship with the motor current:
F r =k r *I r ，
wherein: f r : residual clamping force of the releasing process, k r : clamping force to current ratio coefficient during release, I r : releasing the current;
when the target deceleration signal changes, the target clamping force is calculated according to the following formula, the EPB motor is controlled to release or clamp, and when the actual clamping force is equal to the target clamping force, the motor is stopped, so that the follow-up of the vehicle deceleration and the target deceleration signal is realized:
F N =(m*a*R β )/( 2*n*μ*R e )，
wherein: f N : EPB clamping force, m: vehicle mass, a: deceleration, R β Rolling radius of wheel, R e : effective braking radius, n: typical values for the number of wheels involved in electric caliper braking are 2 or 4, μ: coefficient of friction.
2. The electronic parking system-based vehicle brake control method according to claim 1, characterized in that: the clamping force is generated by a wheel end electronic parking device (EPB) with a self-locking characteristic.
3. The electronic parking system-based vehicle brake control method according to claim 1, characterized in that: and converting the target deceleration signal into a target clamping force, and taking the target clamping force as a control target.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010630549.4A CN113879272B (en) | 2020-07-03 | 2020-07-03 | Vehicle brake control method based on electronic parking system |
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| CN202010630549.4A CN113879272B (en) | 2020-07-03 | 2020-07-03 | Vehicle brake control method based on electronic parking system |
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| CN114740831B (en) * | 2022-06-09 | 2022-09-06 | 坤泰车辆系统(常州)股份有限公司 | Test method of test bench for EPB model verification and parameter matching and EPB system |
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| JP4983270B2 (en) * | 2007-01-19 | 2012-07-25 | 富士重工業株式会社 | Brake device |
| JP2013071521A (en) * | 2011-09-27 | 2013-04-22 | Advics Co Ltd | Parking brake control apparatus |
| KR101714241B1 (en) * | 2015-10-22 | 2017-03-22 | 현대자동차주식회사 | Apparatus for controlling electric parking brake and method thereof |
| KR102544381B1 (en) * | 2016-06-03 | 2023-06-19 | 에이치엘만도 주식회사 | Electronic Parking Brake System of Vehicle And Method of Driving The Same |
| DE112018001057T5 (en) * | 2017-02-28 | 2019-11-14 | ZF Active Safety US Inc. | Vehicle braking system with an electric parking brake used in case of defective gain function |
| CN110040119B (en) * | 2019-05-08 | 2020-05-12 | 清华大学 | Electronic parking braking method and device |
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