KR100534718B1 - Regeneration braking control method for 4 wheel hybrid electric vehicle - Google Patents

Abstract

It is possible to recover proper regenerative energy from the front and rear motors by distributing the braking torque for the front and rear wheels during braking of the 4WD hybrid electric vehicle to which the non-electronic brake system is applied.

When the braking control is detected, a process of detecting the current vehicle speed, a process of calculating the maximum regenerative braking torque possible under the current vehicle speed condition, and the calculated regenerative braking torque are fixed to the front wheel motor and the rear wheel motor in consideration of vehicle stability. Calculating the efficiency of the front wheel motor and the rear wheel motor according to the distributed regenerative braking torque and the motor speed, determining a maximum regenerative braking energy amount that can be charged to the battery, and charging the battery with the determined regenerative braking energy amount. And controlling the regenerative braking by distributing to the front wheel motor and the rear wheel motor so as to obtain the greatest regenerative braking energy within the limit.

Description

Regenerative braking control method for 4-wheel hybrid electric vehicle {REGENERATION BRAKING CONTROL METHOD FOR 4 WHEEL HYBRID ELECTRIC VEHICLE}

The present invention relates to a four wheel drive (hereinafter referred to as '4WD') hybrid electric vehicle, and more particularly, braking torque for front and rear wheels during braking of a 4WD hybrid electric vehicle to which a non-electronic brake system is applied. The present invention relates to a regenerative braking control method of a four-wheel hybrid electric vehicle that enables recovery of proper regenerative energy from a front / rear motor through distribution of.

In general, a hybrid electric vehicle is equipped with a power source consisting of an engine and a motor, and by applying a structure in which the above power source is properly combined with the front wheels, fuel efficiency is supported by the power of the motor operated by the voltage of the battery when the vehicle starts or accelerates. Induces improvement.

The 4WD hybrid electric vehicle is composed of an engine and a motor mounted on the front wheel of the vehicle and a separate motor mounted on the rear wheel.

Therefore, according to the driving situation, the electric vehicle mode for driving the vehicle only by the motor mounted on the rear wheel, the driving mode in which only the engine of the front wheel operates, the hybrid mode in which the engine of the front wheel acts as the main power source, and the motor of the front wheel assists the power. It is possible to implement a 4WD hybrid driving mode in which both the engine, the motor and the rear wheel motor are operated.

In the hybrid electric vehicle as described above, regenerative braking control for recovering regenerative energy during braking is applied.

The regenerative braking control is one of the main technologies of the hybrid electric vehicle. Unlike the general internal combustion engine vehicle, the regenerative braking operates the drive motor for the hybrid as a generator when the vehicle decelerates. By converting the mechanical kinetic energy of the vehicle into electrical energy and storing it in the battery, it is a braking method that can increase the fuel efficiency of the vehicle and save energy.

Therefore, the design of the regenerative braking system in hybrid electric vehicles is one of very important problem.

In the conventional hybrid electric vehicle, the regenerative braking is very limited when the existing hydraulic friction braking system is used as a braking system and additionally regenerative braking is applied, that is, when the electronic brake and the brake position sensor are not mounted. There is a limit to what is done.

Moreover, the research on the regenerative braking algorithm for the electric 4WD hybrid electric vehicle without the electronically controlled brake and brake position sensor is very insufficient. Therefore, in order to actively recover the regenerative braking energy from the electric 4WD hybrid electric vehicle, the appropriate regenerative braking energy is applied. The description of the algorithm is essential.

Conventional regenerative braking control gives a constant regenerative braking torque based on the speed of the vehicle based on the brake signal, prioritizing the purpose of drawing as much regenerative braking as possible, but the driver feels excessive braking. The compromise is made considering that it must not be lost.

However, in the case of the electric 4WD hybrid electric vehicle which is not equipped with the above electronically controlled brake and brake position sensor, the regenerative braking is performed in such a manner that the regenerative braking torque is added to the general hydraulic braking force, so that the front and rear wheels are used. Depending on the regenerative braking torque applied to the driver, excessive braking feeling can be felt by the driver or the regenerative braking torque is given to the front / rear wheels with a large difference in the characteristic curve of the front / rear motors. There is a problem that impairs the stability of the vehicle such as a spin.

In addition, the case where the amount of regenerative energy input to the battery, such as when the vehicle rapidly decelerates at a high speed, may enter an amount of energy input to the battery more than the amount of rated current that can be actually charged in the battery. The heat generated by the internal resistance of the battery itself is caused by excessive heat generated causes problems such as shortening the life of the battery and deterioration of efficiency.

The present invention has been invented to solve the above problems, the object of the present invention is to distribute the braking torque for the front and rear wheels based on the current vehicle speed during braking of the 4WD hybrid electric vehicle to which the non-magnetic brake system is applied. It is possible to recover proper regenerative energy from the rear wheel motor.

According to an aspect of the present invention, there is provided a 4WD hybrid electric vehicle, comprising: detecting a current vehicle speed when a braking control is detected; Calculating the maximum possible regenerative braking torque at the current vehicle speed condition; Distributing the calculated regenerative braking torque to a front wheel motor and a rear wheel motor at a predetermined ratio in consideration of vehicle stability; Determining the maximum amount of regenerative braking energy chargeable in the battery by calculating the efficiency of the front wheel motor and the rear wheel motor according to the distributed regenerative braking torque and the motor speed; Regenerative braking of the four-wheel hybrid electric vehicle comprising controlling the regenerative braking by distributing the determined amount of regenerative braking energy to the front wheel motor and the rear wheel motor to obtain the largest regenerative braking energy within the battery charge limit. Provide control method.

In other words, the braking torque ratio of the front and rear wheels is distributed so that the total braking force ratio of the front and rear wheels can be kept constant in consideration of stability based on the current vehicle speed during braking of the 4WD hybrid electric vehicle, and the maximum regenerative chargeable to the battery is possible. The regenerative braking energy amount is determined according to the braking energy, and the regenerative braking amount of the front / rear motor is distributed.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As can be seen in Figure 1, the regenerative braking control apparatus for a 4WD hybrid electric vehicle according to the present invention includes a driving information detection unit 10, an ECU (Electric Control Unit; 20), a TCU (Torque Control Unit; 30), an HCU ( Hybrid Control Unit; 40), Battery 50, Battery Management System; BMS (Motor Control Unit; 80), Engine 80, First Inverter 90, Second Inverter 100, It is composed of one motor 110, the second motor 120 and CVT (Continuously Variable Transmission; 30).

The driving information detection unit 10 detects a driving request signal of the driver, such as an acceleration position sensor (APS) signal for a driver's start and acceleration request, a brake pedal signal for controlling braking, and an signal of an inhibitor switch for shift stage selection.

The ECU 20 controls general operations of the operation of the engine 80 according to the driver's driving request signal, engine state information such as coolant temperature, engine torque, and the control of the HCU 40, which is an upper controller.

The TCU 30 detects information such as a current vehicle speed, a gear ratio, a clutch state, and controls the overall operation of adjusting the output torque of the CVT 130 according to the control of the upper controller 40.

The HCU 70 controls each of the controllers as an upper controller, and when the braking signal is detected, the regenerative braking force is maintained so that the total braking force for the front wheel and the rear wheel can be kept constant in consideration of the stability of the vehicle based on the current vehicle speed. Control the distribution by calculating the torque.

The battery 50 is composed of a high-capacity high-voltage battery that supplies driving voltage to the front wheel motor 110 and the rear wheel motor 120 for power assistance in a 4WD hybrid electric vehicle, and the regenerative energy recovered from the front wheel and the rear wheel during braking control. And by the output of the engine 80.

The BMS 60 comprehensively detects information such as voltage, current, and temperature of the battery 50 to control the SOC state of the battery and to control the amount of output current, and to charge the battery 50 by regenerative braking energy. To control.

The MCU 70 distributes and controls the regenerative braking torques of the front wheel motor 110 and the rear wheel motor 120 under the control of the HCU 40, which is an upper controller.

At this time, the regenerative braking energy amount is determined according to the maximum regenerative braking energy that can be charged in the battery 50, and the regenerative braking amount of the front wheel motor 110 and the rear wheel motor 120 is distributedly controlled.

The engine 80 is operated by the control of the ECU 20, and the output shaft is directly connected to the CVT 130 through the front wheel motor 110.

The first inverter 90 converts the DC voltage applied from the battery 50 into an alternating current three-phase voltage through an insulated gate bipolar transistor (IGBT) as a switching means under the control of the MCU 70 to output the engine 80. The front wheel motor 110 is directly connected to the shaft, and the regenerative energy recovered from the front motor 110 is supplied to the battery 50 at a charging voltage.

The second inverter 100 drives the rear wheel motor 120 by converting the DC voltage applied from the battery 50 into an AC three-phase voltage through an IGBT, which is a switching means, under the control of the MCU 70. The regenerative energy recovered by 120 is supplied to the battery 50 at a charging voltage.

An operation of recovering the regenerative braking energy from the front / rear motors in the 4WD hybrid electric vehicle according to the present invention including the above function will be described with reference to FIG. 2.

In the state where the 4WD hybrid electric vehicle is driving, the HCU 40 determines whether the braking request signal is detected through the driving information detector 10 (S100).

At this time, if the braking request signal is not detected, the vehicle behavior is maintained according to the signal such as the APS signal and the signal of the inhibitor switch for the shift stage selection, and if the braking request signal is detected, the current traveling vehicle speed is read (S110). .

Then, the speed W_f of the front wheel motor 110 and the speed W_r of the rear wheel motor 120 are read (S111), and the regenerative braking torque of the front wheel motor 110 is set to an initial value (R_f = 0) ( S112).

In addition, the regenerative braking torque of the front wheel motor 110 is determined in consideration of the accuracy of the regenerative braking control, the processing speed of the controller, and the like (S113) to determine the regenerative braking torque of the front wheel motor 110 for regenerative braking control. It determines (R_f = R_f + D_R_f) (S114).

As described above, when the regenerative braking torque of the front wheel motor 110 is determined (R_f = R_f + D_R_f), the regenerative braking torque of the rear wheel motor 120 is considered in consideration of the gear ratio i_f of the front wheel, the gear ratio i_r of the rear wheel, and stability. The regenerative braking torque of the rear wheel motor 120 is determined by applying the selected brake torque ratio A of the front and rear wheels and the regenerative braking torque R_f of the front wheel motor 110. [R_r = (i_f / i_r) * A * R_f] (S115).

Subsequently, it is determined whether the determined regenerative braking torque of the rear wheel motor 120 has a value smaller than the maximum torque set in the rear wheel motor 120 (R_r ≦ R_r_max) (S116).

If it is determined that the regenerative braking torque of the rear wheel motor 120 determined above has a value smaller than the maximum torque, the efficiency [Eff_f] of the front wheel motor 110 is determined from the speed W_f and the regenerative braking torque R_f of the front wheel motor 110. (W_f, R_f) is calculated, and the efficiency Eff_r (W_r, R_r) of the rear wheel motor 120 is calculated from the speed W_r and the regenerative braking torque R_r of the rear wheel motor 120 (S117).

As described above, when the efficiency [Eff_f (W_f, R_f) for the front wheel motor 110 and the efficiency [Eff_r (W_r, R_r) for the rear wheel motor 120 are determined, the regenerative braking voltage (P = R_f * W_f * Eff_f) is determined therefrom. + R_r * W_r * Eff_r) is calculated (S118).

It is determined whether the calculated regenerative braking voltage P has a value less than or equal to the battery charge limit voltage P_L (P ≦ P_L) (S119).

When the regenerative braking voltage P is determined to have a value less than or equal to the charging limit voltage P_L of the battery, the regenerative braking torque R_f of the front wheel motor 110 and the regenerative braking torque R_r of the rear wheel motor 120 are determined. And regenerative braking voltage P is set (S120).

Thereafter, it is determined whether the regenerative braking torque R_f of the front wheel motor 110 is determined to be equal to or greater than the maximum torque value R_f_max set in the front wheel motor 110 (R_f> R_f_max) (S121).

When the regenerative braking torque R_f of the front wheel motor 110 is determined to have a value less than or equal to the maximum torque R_f_max, the process returns to step S114 to repeat the above-described process, and the regenerative braking of the front wheel motor 110 is performed. When it is determined that the torque R_f is determined to be greater than or equal to the maximum torque R_f_max, the maximum value of the regenerative braking voltage P set in S120 is found (S122). The regeneration of the front wheel motor 110 and the rear wheel motor 120 is performed. The regenerative braking control is executed by determining the braking torques R_f and R_r (S123).

In the determination of S116, the regenerative braking torque R_r of the rear wheel motor 110 is equal to or greater than the maximum value set in the rear wheel motor 120, or the regenerative braking voltage P is greater than or equal to the charging limit voltage P_L of the battery in S119. If the value has a value, the regenerative braking voltage P is set to '0', and then the process of S120 described above is executed (S130).

As described above, the present invention provides a front wheel motor while increasing the regenerative braking torque applied to the front wheel motor 110 at the current vehicle speed condition at a predetermined interval from the current vehicle speed condition when the braking control is detected. The total regenerative braking energy of the 110 and the rear wheel motor 120 is obtained, and a case where the largest regenerative braking energy can be obtained is within the charge limit voltage of the battery, and the front wheel motor 110 and the rear wheel motor 120 Control the regenerative braking torque.

Therefore, by maintaining the ratio of the total braking force applied to the front and rear wheels as in the case of a normal engine vehicle, it maintains the driver's deceleration as it is, and can solve the problem of deterioration of the stability of the vehicle resulting from excessive difference in braking force, At the same time, the regenerative braking torque is given to the front and rear motors so that the regenerative braking energy is not applied beyond the allowable capacity which can be excessively input to the battery, thereby improving the regenerative braking efficiency.

As described above, the present invention provides stability to the behavior of the vehicle through the distribution of the regenerative braking torque for the front wheel motor and the rear wheel motor and the distribution of the regenerative braking energy to determine the amount of regenerative braking energy during regenerative braking control of the 4WD hybrid electric vehicle. Provides optimum regenerative braking efficiency maintained.

1 is a block diagram of a regenerative braking control device for a four-wheel hybrid electric vehicle according to the present invention.

2 is a flowchart of an embodiment for executing regenerative control control in a four-wheel hybrid electric vehicle according to the present invention;

Claims (4)

In the 4WD hybrid electric vehicle, Detecting a current vehicle speed when the braking control is detected; Calculating the maximum possible regenerative braking torque at the current vehicle speed condition; Distributing the calculated regenerative braking torque to a front wheel motor and a rear wheel motor at a predetermined ratio in consideration of vehicle stability; Determining the maximum amount of regenerative braking energy chargeable in the battery by calculating the efficiency of the front wheel motor and the rear wheel motor according to the distributed regenerative braking torque and the motor speed; Regenerative braking of the four-wheel hybrid electric vehicle comprising controlling the regenerative braking by distributing the determined amount of regenerative braking energy to the front wheel motor and the rear wheel motor to obtain the largest regenerative braking energy within the battery charge limit. Control method. The method of claim 1, The maximum regenerative braking torque possible under the current vehicle speed condition is calculated by applying the increase rate of the braking torque in consideration of the processing speed of the controller to the regenerative braking torque applied to the front wheel motor. Way. The method of claim 1, The regenerative braking torque of the rear wheel motor is calculated by applying the brake torque ratio of the front and rear wheels and the regenerative braking torque of the front wheel motor, which are selected in consideration of the gear ratio of the front wheel, the gear ratio of the rear wheel, and the stability. Regenerative braking control method. The method of claim 1, The regenerative braking control method of the four-wheel hybrid electric vehicle, characterized in that to initialize the determined regenerative braking energy amount when the battery chargeable regenerative braking energy amount has a value greater than or equal to the charging limit of the battery.