CN111186424B - Composite brake control system and method based on motor brake characteristics - Google Patents

Abstract

The invention discloses a composite brake control system and a composite brake control method based on motor brake characteristics, which realize real-time query and monitoring by calibrating the motor brake characteristics; the braking torque is corrected by referring to the braking torque of the motor and the actual braking torque of the motor, so that the accurate control of the braking torque of the motor is realized; closed-loop control of the electro-hydraulic braking torque is realized through active pressurization control, and electro-hydraulic combined braking is accurately responded; the speed of oil entering the energy accumulator is changed by controlling the response state of the energy accumulator control valve, so that pedal feeling simulation is realized. The invention realizes the consistency of pedal feeling and braking working condition in the braking process and the braking stability of the composite braking system, and has the function of feedback compensation.

Description

Composite brake control system and method based on motor brake characteristics

Technical Field

The invention belongs to the technical field of automobile hydraulic and motor composite braking, and particularly relates to a composite braking control system and method based on motor braking characteristics.

Background

The composite braking system generally comprises a motor braking system, a hydraulic braking system and a coordination control module, and in order to achieve that the response to the braking intention of a driver and the stability and the safety of the braking process are not lost in the process of recovering the braking energy of the electric automobile, the motor and the hydraulic braking system are subjected to coordination control to jointly complete the braking of the automobile. In the process of composite braking, the most central problem is the consistency of braking stability and braking feeling when the motor and the hydraulic pressure perform braking together. In the prior art, the braking torque of a motor is calculated based on real-time feedback signals of the motor, and then the required braking force is responded by controlling the hydraulic braking torque, so that the feedback compensation function is not provided.

Disclosure of Invention

In order to solve the problem of consistency of stability and braking feeling when a motor and hydraulic pressure perform braking together in a composite braking process, the invention provides a composite braking control system and method based on motor braking characteristics, and the composite braking control system and method have a feedback compensation function.

In order to achieve the technical purpose, the invention provides the following technical scheme:

a composite braking control method based on motor braking characteristics comprises the following steps:

step (1), judging the SOC of an energy storage component when a vehicle is in a braking working condition, and carrying out pure hydraulic braking when the SOC is more than 96%; when the SOC is less than or equal to 96 percent, executing the step (2);

step (2), if the emergency braking is carried out, executing pure hydraulic braking; otherwise, determining whether the motor can brake, and executing pure hydraulic braking when the motor cannot brake; when the motor can brake, whether pure electric braking or electrohydraulic composite braking is carried out is determined according to whether hydraulic braking force is needed or not; when the emergency brake is not performed, the pedal feeling is simulated, and the consistency of the pedal feeling and the brake working condition is realized.

Further, the process of whether the motor can brake is as follows: obtaining a reference target value of the motor braking efficiency eta by instantly calibrating a braking MAP graph, inquiring the MAP graph according to the reference target value of the braking efficiency eta, and obtaining a reference motor braking torque T_{m_ref}From T_{m_ref}It is determined whether the motor is capable of braking.

Further, when T is_{m_ref}When the value is 0, the motor can not brake; when T is_{m_ref}>When 0, the motor can brake, the required braking torque T is compared_{P_com}Braking torque T with reference motor_{m_ref}It is determined whether hydraulic braking force is required.

Further, when T is_{m_ref}>T_{P_com}When the braking is performed, the pure motor braking is performed, and the ECU brakes the torque T by the actual motor_{m_real}And reference motor braking torque T_{m_ref}Correcting the motor braking torque; the motor braking torque correction is realized by receiving a motor control signal delta S by a motor controller_mIs carried out by_m＝f(ΔT_m)，ΔT_m＝T_{m_ref}-T_{m_real}。

Further, when T is_{m_ref}≤T_{P_com}In time, the electro-hydraulic composite braking is carried out, and the hydraulic braking torque T is referred_{h_ref}In combination with the actual wheel cylinder pressure T_{h_real}Correcting hydraulic braking torque; the hydraulic braking torque correction is realized by receiving a hydraulic control signal delta S by an ECU_hBy controlling a hydraulic control module, wherein Δ S_h＝f(ΔT_h)，ΔT_h＝T_{h_ref}-T_{h_real}Reference hydraulic braking torque T_{h_ref}＝T_{P_com}-T_{m_ref}Actual wheel cylinder pressure T_{h_real}Collected by a wheel cylinder pressure sensor.

Furthermore, the electro-hydraulic compound braking realizes closed-loop control through active pressurization; the closed-loop control process comprises the following steps: and performing linear fitting calibration on the flow-pressure characteristics of the booster motor and the wheel cylinder to obtain the target pressure of the wheel cylinder response, determining the working angular displacement of the booster motor under different target pressures, and controlling the target pressure of the brake wheel cylinder by the working angular displacement of the booster motor so as to control the pressure of the brake wheel cylinder.

Further, the simulated pedal feel is specifically: deriving a reference master cylinder pressure F from the pedal displacement x_{m_ref}Combined with actual master cylinder pressure F_{m_real}And obtaining a duty ratio signal for controlling the control valve of the energy accumulator.

A composite brake control system based on motor brake characteristics comprises a hydraulic control module, wherein the hydraulic control module is connected with an oil path of a brake main cylinder, a main cylinder pressure sensor and a main oil path control valve are sequentially arranged on the oil path, a branch connected with an active energy accumulator is arranged on the oil path between the main cylinder pressure sensor and the main oil path control valve, and an energy accumulator control valve is arranged on the branch; the hydraulic control module is connected with a wheel cylinder through an oil way, and a wheel cylinder pressure sensor is arranged on the oil way;

the system also comprises an ECU (electronic control unit), wherein the ECU is connected with a pedal displacement sensor, a master cylinder pressure sensor, an energy accumulator control valve, an active energy accumulator, a main oil way control valve, a wheel cylinder pressure sensor, a hydraulic control module and a motor controller.

The invention has the beneficial effects that:

(1) according to the invention, through pure electric machine control and electro-hydraulic composite control, the fluctuation of intervention and quitting of the electro-hydraulic composite control is weakened, and when the pure electric machine control is carried out, the ECU carries out motor braking torque correction by the actual motor braking torque and the reference motor braking torque; when electro-hydraulic compound control is carried out, hydraulic braking torque correction is carried out by combining reference hydraulic braking torque with actual wheel cylinder pressure; the accuracy of brake pressure response is improved, and the brake smoothness is improved. And when the pure electric machine is controlled, a reference target value of the motor braking efficiency is obtained through instantaneous calibration, the MAP is inquired according to the reference target value of the braking efficiency, a reference motor braking torque is obtained, zero-delay inquiry of the reference braking torque is realized, the response speed and the convergence speed of control are improved, and the braking accuracy is improved.

(2) The invention obtains the reference master cylinder pressure by the pedal displacement, obtains the duty ratio signal for controlling the energy accumulator control valve by combining the actual master cylinder pressure, and controls the oil inlet and outlet of the active energy accumulator by controlling the opening and closing of the energy accumulator control valve, thereby realizing the consistency of the pedal feeling and the braking working condition.

Drawings

FIG. 1 is a schematic diagram of a hybrid braking control system based on motor braking characteristics according to the present invention;

FIG. 2 is a block diagram of a composite braking control logic based on motor braking characteristics according to the present invention;

FIG. 3 is a diagram of the braking characteristics of the motor of the present invention;

FIG. 4 is a graph of pedal displacement versus reference master cylinder pressure for the present invention;

FIG. 5 is a graph of master cylinder pressure bias versus duty cycle signal in accordance with the present invention.

Reference numerals: 1. a pedal displacement sensor; 2. a brake master cylinder; 3. a master cylinder pressure sensor; 4. an accumulator control valve; 5. an active accumulator; 6. a main oil passage control valve; 7. an ECU; 8. a wheel cylinder pressure sensor; 9. a rear wheel; 10. a front wheel; 11. a motor controller; 12. a motor; 13. and a hydraulic control module.

Detailed Description

The technical solution of the present invention will be further described with reference to the accompanying drawings, but the scope of the present invention is not limited thereto.

As shown in fig. 1, a composite brake control system based on motor braking characteristics includes a master cylinder 2, a hydraulic control module 13, an ECU7, a rear wheel 9, a front wheel 10, a motor controller 11 and a motor 12, the master cylinder 2 is connected with the hydraulic control module 13 through an oil path, and the oil path is sequentially provided with a master cylinder pressure sensor 3 and two main oil path control valves 6, an oil path between the master cylinder pressure sensor 3 and the main oil path control valves 6 is provided with a branch path, the branch path is connected with an active energy accumulator 5, and the branch path is provided with an energy accumulator control valve 4; the hydraulic control module 13 is connected with wheel cylinders of the rear wheel 9 and the front wheel 10 through an oil path, and a wheel cylinder pressure sensor 8 is arranged on the oil path. The brake master cylinder 2 is mechanically connected with a pedal, and the pedal is provided with a pedal displacement sensor 1. The motor 12 is mechanically connected with the front wheel 10; the motor controller 11 is connected to the motor 12 through a high-voltage circuit.

The pedal displacement sensor 1, the master cylinder pressure sensor 3, the accumulator control valve 4, the active accumulator 5, the main oil way control valve 6, the wheel cylinder pressure sensor 8, the hydraulic control module 13 and the motor controller 11 are in signal connection with the ECU 7.

The mechanical part of the hydraulic control module is a mechanical part of a vehicle-mounted hydraulic control unit; the pedal displacement sensor 1 is a high-precision and high-sensitivity displacement sensor, has signal acquisition capacity of 0.01 second/time and is used for acquiring pedal displacement signals; the master cylinder pressure sensor 3 is a high-precision and high-sensitivity oil pressure sensor, the signal acquisition capacity reaches 0.01 second/time, and the pressure signal of the brake master cylinder 2 is acquired in real time; the active energy accumulator 5 is an energy accumulator provided with an independent driving module inside, and can flexibly control oil to enter and exit the energy accumulator, so that the purposes of pressure energy storage and volume storage are achieved; the energy accumulator control valve 4 is a two-position two-normally-off electromagnetic valve and is controlled by a PWM signal of the ECU7, so that the flow and the speed of oil entering the energy accumulator are changed by the electromagnetic valve, the pedal feeling is simulated during non-emergency braking (ABS), and the consistency of the pedal feeling and the braking working condition is realized.

The simulation pedal feeling is specifically processed as follows:

step (1), analyzing the braking condition of the vehicle, determining whether the braking is emergency braking, if not, closing the two main oil way control valves 6, and executing step (2); in the event of emergency braking, the accumulator control valve 4 is closed, and the state of purely hydraulic braking (prior art) is entered, in which no pedal feel simulation is performed.

Step (2), the pedal displacement sensor 1 and the master cylinder pressure sensor 3 respectively acquire the pedal displacement x and the actual master cylinder pressure F_{m_real}And sent to the ECU 7; FIG. 4 shows the pedal displacement x and the reference master cylinder pressure F obtained by the experiment_{m_ref}Relating pedal feel to braking conditions to generate a reference target value in the simulation, i.e. a reference master cylinder pressure F_{m_ref}(ii) a From actual master cylinder pressure F_{m_real}With reference master cylinder pressure F_{m_ref}Obtaining the master cylinder pressure deviation delta F_mA duty ratio signal D is obtained through a functional relation shown in FIG. 5 (obtained through experiments), the ECU7 converts the duty ratio signal D into a PWM signal, the opening and closing of the energy accumulator control valve 4 is controlled, and the purpose of changing the flow and the speed of oil entering the energy accumulator is achieved; the method specifically comprises the following steps:

F_{m_ref}＝f(x)

F_{m_ref}-F_{m_real}＝ΔF_m

D＝f(ΔF_m)

step (3), returning to step (1);

and (4) when braking is finished, the active energy accumulator 5 finishes oil return by means of the driving module when the energy accumulator control valve 4 is opened.

As shown in fig. 2, the composite braking control method based on the motor braking characteristics, which performs the braking force control simultaneously during the process of performing the simulated pedal feel control, specifically includes the following steps:

step (1), a driver steps on a brake pedal to touch a pedal displacement sensor 1 to form a pedal displacement signal, and the ECU7 calculates a required braking torque T_{P_com}And the natural pedal vibration error is allowed during the process that the driver steps on the brake pedal.

Step (2), braking torque T is braked according to the demand_{P_com}Judging the working conditions of the vehicle, including braking working conditions and other working conditions, when T is_{P_com}>When the vehicle working condition is 0, the vehicle working condition is a braking working condition, the ECU7 detects the energy recovery condition, namely the SOC of the energy storage components (such as a storage battery and a super capacitor), and when the SOC of the energy storage components is less than or equal to 96%, the step (3) is executed; when SOC of energy storage component>At 96%, the motor does not participate in braking, the braking process is pure hydraulic braking, and the wheel cylinder pressure sensor 8 acquires the actual wheel cylinder pressure moment T_{h_real}The hydraulic control module 13 brakes the torque T according to the demand_{P_com}With actual wheel cylinder pressure T_{h_real}Performing hydraulic braking force closed-loop control (prior art); in the pure hydraulic braking process, the ECU7 monitors the actual wheel cylinder pressure torque T in real time_{h_real}A change in (c).

Step (3), performing braking requirement analysis, firstly determining whether braking is emergency braking (ABS), if so, executing pure hydraulic braking, otherwise, determining whether the motor can perform braking by the ECU7 through the current vehicle driving state information instant calibration braking MAP (as shown in fig. 3), and the process is as follows:

obtaining a reference target value of the motor braking efficiency eta through instantaneous calibration, inquiring a MAP (MAP) by the reference target value of the rotating speed and the braking efficiency eta to obtain a braking torque reference target value, namely a reference motor braking torque T_{m_ref}(ii) a Because a core factor of the working state of the motor 12 is the working efficiency of the motor, the method for determining the working efficiency of the motor of the invention predicts the working efficiency of the current motor according to the working efficiency of the motor at the previous moment, and the specific calculation method is as follows:

P_t-1＝U_t-2I_t-2cosφ_t-2

wherein, P is the motor power, U is the motor output voltage, I is the motor output current, and phi is the motor rotation angle.

When T is_{m_ref}When the brake is equal to 0, the motor can not brake, and pure hydraulic brake is executed; when T is_{m_ref}>When 0, the motor can brake, the required braking torque T is compared_{P_com}Braking torque T with reference motor_{m_ref}And determining whether hydraulic braking force is needed or not, and dividing the braking working condition into pure motor braking and electro-hydraulic composite braking.

When T_{m_ref}>T_{P_com}In the process, the braking process is purely electric braking, the motor 12 provides all braking torque, and the ECU7 obtains the actual motor braking torque T through the calculation of the recovered current and the electromotive force_{m_real}Combined with reference motor braking torque T_{m_ref}And correcting the braking torque, specifically:

T_{m_ref}-T_{m_real}＝ΔT_m

ΔS_m＝f(ΔT_m)

wherein, f (Δ T)_m) Is that the independent variable is the moment deviation Delta T of the motor_mCorrection function of, Δ S_mAs motor control signals, i_a、i_b、i_cFor the current of the three-phase winding of the machine, e_a、e_b、e_cThe motor is the electromotive force of the three-phase winding end of the motor, and omega is the angular speed of the motor rotor.

The motor controller 11 receives a motor control signal and controls the motor braking torque by controlling the recovered current; and (4) returning to the step (1). In the pure motor braking process, the ECU7 monitors the required braking torque T_{P_com}。

When T_{m_ref}≤T_{P_com}In the process, the braking process is electro-hydraulic composite braking, namely the motor 12 cannot bear all braking torque, and the motor braking torque T is referred to by inquiring a motor braking MAP_{m_ref}The actual braking torque of the motor 12 is excessively fast in transient response and is easy to generate large fluctuation when the motor is controlled; by the required braking torque T_{P_com}Braking torque T with reference motor_{m_ref}Obtaining a reference hydraulic braking torque T_{h_ref}By reference to the hydraulic braking torque T_{h_ref}Combined with actual wheel cylinder pressure torque T_{h_real}And correcting the braking torque, specifically:

T_{P_com}-T_{m_ref}＝T_{h_ref}

T_{h_ref}-T_{h_real}＝ΔT_h

ΔS_h＝f(ΔT_h)

wherein, f (Δ T)_h) Is independent variable as hydraulic moment deviation Delta T_hCorrection function of, Δ S_hIs a hydraulic control signal.

The ECU7 receives the hydraulic control signal, controls the hydraulic braking torque by controlling the hydraulic control module 13, returns to the step (1), realizes the closed-loop control of the electro-hydraulic composite braking torque, the control algorithm is the active pressure boost control with the correction function, the realization of the control function depends on the hydraulic control module 13, and the concrete process is as follows:

firstly, a plunger hydraulic pump in a hydraulic control module 13 converts the rotary motion of an eccentric shaft of a booster motor into the linear motion of a piston, so as to generate an oil pumping effect; because the pressurization mode is cam type piston pressurization, the pressurization process is a nonlinear process, the predicted values of the rotation speed of the pressurization motor, the pressure and the flow of pump oil are found through linear fitting, and the predicted values participate in hydraulic brake control, and the process is called a flow-pressure characteristic calibration process.

Secondly, because the final pressure response of the hydraulic braking control is at the end of the wheel cylinder, linear fitting calibration is also carried out on the flow-pressure characteristic of the wheel cylinder.

And thirdly, by the calibration, the target pressure of the wheel cylinder response can be obtained, and the working angular displacement of the booster motor when different target pressures are determined.

And fourthly, controlling the target pressure of the brake wheel cylinder by controlling the working angle displacement of the booster motor, controlling the pressure of the brake wheel cylinder by the target pressure, accurately boosting the process, reducing the overshoot of the pressure at the end of the wheel cylinder, and providing a more accurate hydraulic signal for the booster motor controller.

In the electro-hydraulic combined braking process, the ECU7 monitors the actual wheel cylinder pressure T_{h_real}。

The braking force control method based on the motor characteristics can accurately respond the braking force of the motor, improve the stability in the braking process, realize the accurate control of hydraulic pressure through active pressurization control, and improve the accuracy of hydraulic response of the wheel cylinder end.

The above detailed description of the embodiments according to the present invention is provided. Technical solution according to the present invention, a person skilled in the art may propose various alternative structures and implementations without changing the spirit of the present invention. Therefore, the above-described embodiments and the accompanying drawings are only exemplary illustrations of the technical solutions of the present invention, and should not be construed as all of the present invention or as limitations or limitations on the technical solutions of the present invention.

Claims (8)

1. A composite braking control method based on motor braking characteristics is characterized by comprising the following steps:

step (1), judging the SOC of an energy storage component when a vehicle is in a braking working condition, and carrying out pure hydraulic braking when the SOC is more than 96%; when the SOC is less than or equal to 96 percent, executing the step (2);

step (2), if the emergency braking is carried out, executing pure hydraulic braking; otherwise, determining whether the motor can brake, and executing pure hydraulic braking when the motor cannot brake; when the motor can brake, whether pure electric braking or electrohydraulic composite braking is carried out is determined according to whether hydraulic braking force is needed or not; when the emergency brake is not performed, the pedal feeling is simulated, and the pedal feeling is consistent with the brake working condition;

the process of whether the motor can brake is as follows: obtaining the reference of the motor braking efficiency eta by an instantaneous calibration braking MAP graphInquiring MAP graph according to the reference target value of the braking efficiency eta to obtain the reference motor braking torque T_{m_ref}From T_{m_ref}Determining whether the motor can brake;

the simulated pedal feel is specifically: deriving a reference master cylinder pressure F from the pedal displacement x_{m_ref}Combined with actual master cylinder pressure F_{m_real}And obtaining a duty ratio signal for controlling the control valve of the energy accumulator.

2. The compound brake control method based on motor brake characteristics according to claim 1, wherein when T is T_{m_ref}When the value is 0, the motor can not brake; when T is_{m_ref}>0, the motor can brake, and the required braking torque T is compared_{P_com}Braking torque T with reference motor_{m_ref}It is determined whether hydraulic braking force is required.

3. The compound brake control method based on motor brake characteristics according to claim 2, wherein when T is T_{m_ref}>T_{P_com}When the braking is performed, the pure motor braking is performed, and the ECU brakes the torque T by the actual motor_{m_real}And reference motor braking torque T_{m_ref}And correcting the motor braking torque.

4. The compound brake control method based on motor braking characteristics according to claim 3, wherein the motor braking torque correction is a reception of a motor control signal Δ S by a motor controller_mIs carried out by_m＝f(ΔT_m) Moment deviation of motor Δ T_m＝T_{m_ref}-T_{m_real}。

5. The compound brake control method based on motor brake characteristics according to claim 2, wherein when T is T_{m_ref}≤T_{P_com}In time, the electro-hydraulic composite braking is carried out, and the hydraulic braking torque T is referred_{h_ref}In combination with the actual wheel cylinder pressure T_{h_real}And correcting the hydraulic braking torque.

6. The compound brake control method based on motor brake characteristics according to claim 5, wherein the hydraulic brake torque correction is a hydraulic control signal Δ S received by the ECU_hBy controlling a hydraulic control module, wherein Δ S_h＝f(ΔT_h) Hydraulic moment deviation Δ T_h＝T_{h_ref}-T_{h_real}Reference hydraulic braking torque T_{h_ref}＝T_{P_com}-T_{m_ref}Actual wheel cylinder pressure T_{h_real}Collected by a wheel cylinder pressure sensor.

7. The compound brake control method based on the motor brake characteristics according to claim 5, wherein the electro-hydraulic compound brake realizes closed-loop control by active pressurization; the closed-loop control process comprises the following steps: and performing linear fitting calibration on the flow-pressure characteristics of the booster motor and the wheel cylinder to obtain the target pressure of the wheel cylinder response, determining the working angular displacement of the booster motor under different target pressures, and controlling the target pressure of the brake wheel cylinder by the working angular displacement of the booster motor so as to control the pressure of the brake wheel cylinder.

8. A compound brake control system of a compound brake control method based on motor brake characteristics according to any one of claims 1 to 7, characterized by comprising a hydraulic control module, wherein the hydraulic control module is connected with a brake main cylinder oil path, a main cylinder pressure sensor and a main oil path control valve are sequentially arranged on the oil path, a branch path connected with an active energy accumulator is arranged on the oil path between the main cylinder pressure sensor and the main oil path control valve, and an energy accumulator control valve is arranged on the branch path; the hydraulic control module is connected with a wheel cylinder through an oil way, and a wheel cylinder pressure sensor is arranged on the oil way;

the system also comprises an ECU (electronic control unit), wherein the ECU is connected with a pedal displacement sensor, a master cylinder pressure sensor, an energy accumulator control valve, an active energy accumulator, a main oil way control valve, a wheel cylinder pressure sensor, a hydraulic control module and a motor controller.

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