Engine stepless continuous in-cylinder braking method and system based on dynamic closed-loop control

Abstract

The invention discloses an engine stepless continuous in-cylinder braking method based on dynamic closed-loop control, and relates to a vehicle braking control system or a component thereof, when a vehicle operation condition is a braking condition, the braking power P1 is calculated by combining the stress condition of the vehicle under the current operation condition; dynamic braking demand calculation correction is conducted on the braking power P1 to obtain corrected braking power P2, the corrected braking power P2 is converted into a negative torque control pulse spectrum of the engine, and target air inlet pressure is calibrated based on the negative torque control pulse spectrum; performing air flow calculation according to the target air inlet pressure to obtain an air inlet flow demand; and the air inlet flow demand is converted into throttle valve flow, and a throttle valve opening degree target is obtained through calculation according to the throttle valve flow. The invention further discloses an engine stepless continuous in-cylinder braking system based on dynamic closed-loop control. The problems that in-cylinder braking modes in the prior art are correspondingly lagged, complex long downhill cannot be met, and energy loss is too large are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to a vehicle brake control system or a part thereof, and more particularly to an engine stepless continuous cylinder braking method and system based on dynamic closed-loop control. BACKGROUND

[0002] In order to realize the braking force of the vehicle during the downhill process and improve the braking safety performance of the vehicle, in addition to the braking system of the vehicle itself, engine braking is usually used; the commonly used engine braking mode is cylinder braking, which mainly gives the vehicle a reverse force through the negative work of the engine, thereby increasing the braking capacity of the vehicle. The control of the cylinder braking is usually activated according to the vehicle on / off / message request, engine operating state and the like, and the braking work is open-loop output after activation, which may not match the actual demand of the vehicle braking power, and the actual cylinder braking power is too large or too small.

[0003] The existing cylinder braking control technology has the following problems: 1) response lag: the traditional on-off type braking power error reaches ±35%, which leads to frequent switching of mechanical braking on long downhill sections, and the risk of overheating of the brake drum increases by 47%; 2) extensive control: the step-by-step braking only supports 3-5 fixed power outputs, which cannot meet the demand of complex slope, and the torque fluctuation reaches ±200Nm when the slope changes by more than 10%; 3) energy loss: excessive braking leads to an increase of 8.2% in fuel consumption. SUMMARY

[0004] The technical problem to be solved by the present application is to solve the problems of the prior art, such as the response lag of the cylinder braking mode, the inability to meet the complex long downhill, and the excessive energy loss, by providing an engine stepless continuous cylinder braking method and system based on dynamic closed-loop control.

[0005] The engine stepless continuous cylinder braking method based on dynamic closed-loop control identifies the operating condition of the vehicle, calculates a braking power P1 in combination with the force condition of the vehicle under the current operating condition when the operating condition is in a braking condition; performs dynamic braking demand calculation on the braking power P1 to obtain a dynamic negative torque target, calculates a corrected braking power P2 according to the dynamic negative torque target, converts the corrected braking power P2 into a negative torque control pulse spectrum of the engine, and calibrates a target intake pressure based on the negative torque control pulse spectrum; performs air flow calculation according to the target intake pressure to obtain an intake flow demand; converts the intake flow demand into a throttle flow, and calculates a throttle opening target according to the throttle flow, and controls the throttle to act according to the throttle opening target.

[0006] Preferably, the force conditions of the vehicle under the current operating conditions include driving resistance power, kinetic energy change power, and engine friction power; the braking power P1 is the difference between the sum of driving resistance power and kinetic energy change power and the engine friction power.

[0007] Preferably, the driving resistance power is composed of the sum of rolling resistance power, aerodynamic resistance power, and gravity distribution resistance power, and its specific expression is as follows: Pfag=m×g×u×v×cosθ+1 / 2×ρ×Cd×A×v 3 +m×g×v×sinθ; In the formula, m is the vehicle mass, g is the gravitational acceleration, v is the vehicle speed, θ is the slope angle of the road the vehicle is currently traveling on, u is the rolling coefficient, ρ is the air density, Cd is the drag coefficient, and A is the frontal area.

[0008] Preferably, the power of the kinetic energy change is calculated using the following formula: Ek = δ × m × v × a; In the formula, δ is the rotational mass coefficient and a is the acceleration.

[0009] Preferably, the dynamic negative torque target is calculated using the following formula: Tnega = Tmax × (1 - e) -λ×P1 )+Ki×dP1 / dt In the formula, Tnega is the dynamic negative torque target, Tmax is the maximum braking torque, λ is the attenuation coefficient, and Ki is the coefficient of the i integral.

[0010] Preferably, the airflow rate is calculated using the velocity density method based on the target intake pressure.

[0011] Preferably, if the vehicle is equipped with a high-precision map / radar module, the engine's operating conditions can be predicted based on terrain using the high-precision map module.

[0012] A continuously variable in-cylinder braking system for implementing the aforementioned engine continuously variable in-cylinder braking method based on dynamic closed-loop control is characterized by comprising a working condition identification module, a demand calculation engine module, a dynamic distributor, a negative torque mapper, an air circuit controller, a throttle actuator, and a closed-loop correction module.

[0013] Preferably, it also includes a prediction control module.

[0014] Beneficial effects The engine stepless continuous cylinder braking method of the application has the advantages that the application realizes engine stepless continuous cylinder braking control by the brake force dynamic distribution method in combination with the negative torque continuous mapping technology, optimizes the cylinder braking effect, and solves the problems of the corresponding lag of the cylinder braking mode in the prior art, the inability to meet complex long downhill, and excessive energy loss. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The figure is a flowchart of the engine stepless continuous cylinder braking method of the application. Figure 2 The figure is a structural diagram of the engine stepless continuous cylinder braking system of the application. DETAILED DESCRIPTION

[0016] The application will be further described below in combination with the embodiments, but does not constitute any limitation to the application, and any limited number of modifications made by anyone within the scope of the claims of the application is still within the scope of the claims of the application. Embodiment one Referring to Figure 1 The engine stepless continuous cylinder braking method based on dynamic closed-loop control of the application identifies the operation condition of the vehicle by the ECU receiving the key input information of the vehicle operation, such as the vehicle weight signal, the vehicle speed signal, the slope signal, and the cylinder braking signal from the vehicle control unit HCU. When the cylinder braking signal is set, it indicates that the operation condition of the vehicle is in the braking condition, and the braking power P1 is calculated in combination with the force condition of the vehicle under the current operation condition. When the high-precision map / radar module is arranged on the vehicle, the operation condition of the engine is predicted based on the terrain by the high-precision map module.

[0017] The braking power P1 is composed of various resistance powers. Specifically, the force condition of the vehicle under the current operation condition includes the running resistance, the kinetic energy change, and the engine friction, and correspondingly, the powers generated by these resistances include the running resistance power, the kinetic energy change power, and the engine friction power. The running resistance power is composed of the sum of the rolling resistance power, the aerodynamic resistance power, and the gravity distribution resistance power. Therefore, it can be known from the above force analysis that: P1=fr+fa+fg+Ek-Pf.

[0018] P1 is the braking power; fr+fa+fg represents the running resistance power, fr is the rolling resistance, fa is the aerodynamic resistance, and fg is the gravity distribution resistance; Ek is the kinetic energy change power; and Pf is the engine friction power.

[0019] Further, the kinetic energy change power Ek, also referred to as the vehicle kinetic energy correction amount, when Ek>0, the vehicle accelerates, the kinetic energy increases, and the braking demand decreases; when Ek<0, the vehicle decelerates, the kinetic energy decreases, and the braking demand increases. The specific calculation is obtained by the following formula: Ek=δ×m×v×a; In the formula, δ is the rotational mass coefficient, and a is the acceleration.

[0020] The driving resistance power can be calculated by the following formula: Pfag=m×g×u×v×cosθ+1 / 2×ρ×Cd×A×v 3 +m×g×v×sinθ.

[0021] In the formula, m is the vehicle mass, g is the gravity acceleration, v is the vehicle speed, θ is the slope angle of the current driving road of the vehicle, u is the rolling coefficient, ρ is the air density, Cd is the wind resistance coefficient, and A is the windward area.

[0022] The engine controller (ECU) receives the braking power P1 and performs corresponding decision control. Specifically, first, the dynamic braking demand calculation is performed on the braking power P1 to dynamically adjust the braking power P1 to obtain a dynamic negative torque target. In the present application, the braking power P1 is dynamically adjusted by a negative torque continuous mapping function, and the negative torque continuous mapping function is specifically: Tnega=Tmax×(1-e -λ×P1 )+Ki×dP1 / dt.

[0023] In the formula, Tnega is the dynamic negative torque target; Tmax is the maximum braking torque; λ is the attenuation coefficient, the empirical value is 0.023, and can be set as a calibrated value; Ki is the coefficient of i integration.

[0024] Then, based on the power and torque conversion formula, the corrected braking power P2 is calculated according to the dynamic negative torque target, and the negative torque control pulse of the engine is converted according to the corrected braking power P2, and the target intake pressure is obtained based on the negative torque control pulse calibration. Finally, the air flow is calculated using the speed density method according to the target intake pressure to obtain the intake flow demand, and the intake flow demand is converted into the throttle flow, and the throttle opening target is calculated according to the throttle flow. After outputting the throttle opening target, the throttle is controlled according to the throttle opening target to act. The throttle opening is closed-loop corrected according to the actual intake flow and the throttle flow, and the opening of the throttle is adjusted in real time. Based on the above strategy, the test results are shown in Table 1, which shows that the braking stability is improved obviously.

[0025]

[0026] Example 2 like Figure 2 As shown, an engine continuously variable in-cylinder braking system for implementing the above-mentioned engine continuously variable in-cylinder braking method based on dynamic closed-loop control includes a working condition identification module, a demand calculation engine module, a dynamic distributor, a negative torque mapper, an air circuit controller, a throttle actuator, a closed-loop correction module, and a predictive control module.

[0027] The system comprises the following modules: a working condition identification module for identifying the vehicle's operating conditions; a demand calculation engine module for calculating braking power P1 when the vehicle is in braking condition, based on the force conditions under which the vehicle operates; a dynamic distributor for dynamically calculating braking demand based on braking power P1 to obtain a dynamic negative torque target, and calculating a corrected braking power P2 based on the dynamic negative torque target; a negative torque mapper for converting the corrected braking power P2 into an engine negative torque control pulse spectrum, and calibrating the target intake pressure based on the negative torque control pulse spectrum; an air circuit controller for calculating airflow based on the target intake pressure to obtain the intake flow demand; converting the intake flow demand into throttle flow, and calculating the throttle opening target based on the throttle flow; a throttle actuator for controlling the throttle to operate according to the throttle opening target; and a closed-loop correction module for feeding back the actual throttle opening to the ECU, performing closed-loop adjustment based on the actual intake flow and throttle flow, correcting the throttle opening in real time.

[0028] This invention achieves stepless continuous in-cylinder braking control of the engine by using a dynamic braking force distribution method combined with negative torque continuous mapping technology. This optimizes the in-cylinder braking effect and solves the problems of lag in the in-cylinder braking method in the prior art, which cannot meet the requirements of complex long downhill slopes and results in excessive energy loss.

[0029] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention, and these will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A method of engine continuously variable in-cylinder braking based on dynamic closed loop control, characterized in that, Identify the operating condition of the vehicle, when the operating condition is in the braking condition, calculate the braking power P1 in combination with the force condition of the vehicle in the current operating condition; Dynamic braking demand calculation is performed on the braking power P1 to obtain a dynamic negative torque target, a corrected braking power P2 is calculated according to the dynamic negative torque target, and a negative torque control pulse of the engine is converted according to the corrected braking power P2, and the target intake pressure is calibrated based on the negative torque control pulse; According to the target intake pressure, the air flow is calculated to obtain the intake flow demand; The throttle flow is converted into the throttle flow, and the throttle opening target is calculated according to the throttle flow, and the throttle is controlled according to the throttle opening target to act.

2. The engine continuously variable cylinder deactivation method based on dynamic closed loop control according to claim 1, characterized in that, The force condition of the vehicle in the current operating condition includes driving resistance power, kinetic energy change power and engine friction power; The braking power P1 is the difference between the sum of the driving resistance power and the kinetic energy change power and the engine friction power.

3. The engine continuously variable cylinder deactivation method based on dynamic closed loop control according to claim 2, characterized in that, The driving resistance power is composed of rolling resistance power, aerodynamic resistance power and gravity distribution resistance power, and its specific expression is: Pfag = m x g x u x v x cos θ + 1 / 2 x p x Cd x A x v 3 + m x g x v x sin θ; In the formula, m is the vehicle mass, g is the acceleration of gravity, v is the vehicle speed, θ is the slope angle of the current driving road of the vehicle, u is the rolling coefficient, ρ is the air density, Cd is the wind resistance coefficient, and A is the windward area.

4. The engine continuously variable cylinder deactivation method based on dynamic closed loop control according to claim 3, characterized in that, The kinetic energy change power is calculated by: Ek=δ×m×v×a; In the formula, δ is the rotational mass coefficient, and a is the acceleration.

5. The dynamic closed loop control based engine continuously variable in-cylinder brake method according to claim 1, wherein, The dynamic negative torque target is calculated by: Tnega = Tmax x (1 - e -λ×P1 ) + Ki x dP1 / dt In the formula, Tnega is the dynamic negative torque target, Tmax is the maximum braking torque, λ is the attenuation coefficient; Ki is the coefficient of i integration.

6. The dynamic closed loop control based engine continuously variable in-cylinder brake method according to claim 1, wherein, The air flow is calculated using the speed density method according to the target intake pressure.

7. The dynamic closed loop control based engine stepless continuous in-cylinder braking method according to claim 1, wherein, If the high-precision map / radar module is provided on the vehicle, the operating condition of the engine is predicted based on the terrain through the high-precision map module.

8. An engine continuously variable cylinder deactivation system for implementing the engine continuously variable cylinder deactivation method based on dynamic closed loop control according to any one of claims 1 to 7, characterized in that It includes operating condition identification module, demand calculation engine module, dynamic distributor, negative torque mapper, air path controller, throttle actuator and closed loop correction module.

9. The engine continuously variable in-cylinder brake system according to claim 8, characterized by, It also includes a pre-judgment control module.

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