KR19980035415A - Regenerative braking control method of electric vehicle - Google Patents

Abstract

The present invention relates to an electric motor for detecting a regenerative braking force to control the magnitude of a hydraulic pressure applied to a master cylinder so as to maintain the speed of a braking sensation equal to that of a gasoline vehicle in an electric vehicle using a braking system employing a hydraulic braking device, To a regenerative braking control method for an automobile.

The present invention includes a step of detecting a braking force of each of a gasoline vehicle and an electric vehicle, a step of determining a regenerative braking force by judging the braking / deceleration speed of each of the braking forces of the gasoline vehicle and the electric vehicle detected at the step to be the same value, The regenerative braking force is applied to the hydraulic pressure applied to the master cylinder during the operation of the hydraulic brake system so that the load can feel the same deceleration force as that of the gasoline vehicle even in an electric vehicle which is heavier than the gasoline vehicle. .

Description

Regenerative braking control method of electric vehicle

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a regenerative braking control method used for decelerating or stopping a vehicle speed in an electric vehicle, and more particularly to an electric vehicle using a brake system employing a hydraulic braking device, The present invention relates to a regenerative braking control method for an electric vehicle in which the regenerative braking force is detected so as to maintain the same, and the magnitude of the hydraulic pressure applied to the master cylinder is thereby controlled.

Generally, an electric vehicle is a vehicle that uses power supplied from a battery tray, which is a secondary battery, as a power source unlike a gasoline vehicle or a diesel vehicle that uses gasoline or heavy oil, and this is a vehicle that is recently discharged from a vehicle using gasoline or heavy oil This is because it is required to develop a vehicle which is less susceptible to pollution due to a serious pollution problem of the exhaust gas to the atmosphere.

As shown in FIG. 1, various mechanisms, such as an accelerator pedal and a brake pedal, which are operated for vehicle running control, and various sensors for detecting and outputting a vehicle state during operation of the vehicle (10) for controlling the overall operation of the vehicle in response to a signal input from the vehicle controller (10), and a control unit (12) for converting DC power output from the tray into AC power, a motor (14) for generating a rotating force by receiving AC power from the inverter (12), a motor A transmission 16 that serves to transmit or block the rotational force to the driving wheel side as a driving device, And a drive wheel 20 is connected to the transmission 16 via a drive shaft 18. The accelerator pedal 22 and the brake pedal 26 are connected to the vehicle controller 10 as an example and the variable resistors 24 and 28 are coupled to the accelerator pedal 22 and the brake pedal 26, And detects the pedal force of the accelerator pedal 22 or the brake pedal 26, converts the pedal force into an electric signal proportional thereto, and inputs the signal to the vehicle controller 10.

Thus, for example, an acceleration signal, which is converted into an electric signal in the variable resistor 24 according to the degree of depression of the driver by the accelerator pedal 22, is input to the vehicle controller 10, And transmits the torque reference value to the inverter 12 by the predetermined ATS from the motor 14 speed.

The inverter (12) controls the motor (14) to output the torque reference value.

2 is a torque characteristic curve for each RPM of the motor 14, which is divided into a driving region for driving the self-quantity, a deceleration region, and a braking region (regeneration) in which the vehicle is braked by the reverse torque of the motor 14.

In the driving range, the torque curve is determined by the accelerator pedal depth (APD).

The driving force F for driving the vehicle is expressed by the following equation (1) in the driving torque curve of FIG.

[Equation 1]

Where μ _r is the rolling resistance coefficient, μ _a A is the air resistance, W is the vehicle load, θ is the back angle, and V is the vehicle speed.

At this time, the 0% load line is the minimum driving force for driving the vehicle on the flat ground, and is a value obtained by substituting 0 g00h for? In Wsin?

3 is a driving torque characteristic curve of the motor 14 for each accelerator pedal depth. For example, the accelerator pedal depression (APD) of the accelerator pedal 22, that is, the driver applies pressure to the accelerator pedal 22, ) Shows the example of RPM and torque curve according to APD 0 ~ 100% when distance traveled is expressed as a percentage.

In FIG. 3, a bold solid line indicates a driving force load curve when the backing plate is at 0%.

In case of APD 0%, a constant drive torque is given to realize a creep phenomenon that can be automatically driven like an automatic transmission vehicle. In addition, when the vehicle speed is increased by a constant torque in the drive region and the motor RPM increases in the deceleration region Do not increase your car speed

If the APD is 70% and the motor torque is applied to the point D, the accelerator pedal 22 is released while the vehicle is running and the APD 0% curve is changed to the E point. When the torque is changed from E point to A point, % Follow the curve.

For example, as shown in Fig. 4, when the vehicle traveling at the speed of V1 is changed to the APD 0% by the driving force at the point A, the driving force is shifted from the point B to the point C as the vehicle speed decreases . This time is the regenerative braking section, and the braking effect can be obtained by the reverse torque of the motor, and the electric energy can also be obtained. The energy at this time is represented by the sum of the products in the motor / RPM curve as shown in Fig. 3 inversely converted to the gear ratio in Fig.

The torque output of the motor can regulate the output amount within the maximum reverse torque even in regenerative braking. In case of APD 0% and BPD 0%, if the reverse torque value is calculated a lot, the electric energy can gain a lot but the braking energy value should be calculated because the braking energy is large, which may impact the driver. In case of APD 0% and BPD 0% or less, it should be calculated as a value matched with the hydraulic brake.

As described above, in the electric vehicle, the variable resistor 24 sends an electric signal proportional to the leg power to the vehicle controller 10 in accordance with the power of the accelerator pedal 22 to drive the motor 14, The braking force is generated by the operation of the hydraulic pressure in response to the leg power, and the regenerative braking force due to the reverse torque of the motor is generated.

However, the electric vehicle requires a large capacity battery because it uses electricity as a power source, and accordingly, the battery tray having a large number of accumulators collects a lot of weight, so the load of the vehicle as a whole increases and the braking force It should be raised.

This is because if the braking force used in existing gasoline vehicles is used as it is, the braking distance becomes long. And since the ordinary driver is familiar with the gasoline vehicle, the deceleration of APD 0% and BPD 0% There is a need to adapt it.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a braking system for an electric vehicle in which a braking force that is the same as that of an existing gasoline vehicle, And to provide a regenerative braking control method for an electric vehicle in which the regenerative braking is compensated for.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a block diagram of a driving mechanism of an electric vehicle;

2 is a graph showing a torque characteristic curve for each RPM of a motor,

3 is a drive torque curve of the motor for each accelerator pedal depth (APD)

4 is a diagram showing a driving force for a vehicle speed,

5 is a view for explaining the regenerative brake co-operating according to the depth of the brake pedal,

6 is a schematic diagram of a hydraulic brake system,

7 is a curve showing the master cylinder hydraulic pressure by deceleration,

Fig. 8 is a curve showing the driving torque / speed in Fig. 7,

Fig. 9 is a curve showing deceleration when the regenerative braking force is added to the brake pedal depression force.

Description of the Related Art [0002]

10 - vehicle controller, 12 - inverter,

14 - motors, 16 - transmission,

18-drive shaft, 20-drive wheel,

22 - accelerator pedal, 24 - potentiometer,

26 - brake pedal, 28 - potentiometer,

30 - Brake pedal, 32 - Master bag,

34 - master cylinder

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention includes a step of detecting a braking force of each of a gasoline vehicle and an electric vehicle, a step of determining a regenerative braking force by judging the braking / deceleration speed of each of the braking forces of the gasoline vehicle and the electric vehicle detected at the step to be the same value, And further causing the regenerative braking force to be applied to the hydraulic pressure applied to the master cylinder during operation of the hydraulic brake system.

First, a method of detecting the deceleration speed of the gasoline vehicle will be described.

The braking force F of the gasoline vehicle is expressed by the following equation (2).

&Quot; (2) "

Where W _EG is the vehicle load, F _B is the brake pressure due to hydraulic pressure (Kg / f), μ _r is the rolling resistance coefficient, μaA is the air resistance coefficient, V is the vehicle speed, and g _RE is the deceleration rate.

Expression (2) is expressed by the following equation for the deceleration rate,

&Quot; (3) "

.

Next, a method of detecting the deceleration speed of the electric vehicle will be described.

The braking force F of the electric vehicle is expressed by the following equation (4).

&Quot; (4) "

Expressing Equation (4) above with respect to the deceleration rate,

&Quot; (5) "

Where W _EV is the vehicle load, F _B is the brake pressure due to hydraulic pressure, μ _r ^' is the rolling resistance coefficient, and F _R is the regenerative braking force.

If the accelerator pedal and the brake pedal are not pressed, the APD is 0% and the brake pressure F _B due to the hydraulic pressure is 0 because the BPD (brake pedal depth) is 0%.

In order to give the same deceleration as that of a gasoline vehicle in an electric vehicle in this state, the deceleration rate (g _EV ) of the electric vehicle should be equal to the deceleration rate (g _EG ) of the gasoline vehicle (g _EV = g _EG ).

From this, the regenerative braking force F _R is expressed by the following equation (6).

&Quot; (6) "

This is a function according to the speed. In connection with the point C in the graph for realizing the clipping phenomenon in FIG. 4 described above, it is possible to complete the driving, deceleration, and regenerative braking graphs when APD 0% and BPD 0% Regenerative braking force can be expressed in terms of RPM and torque).

Next, the regenerative braking when the APD is 0% and the BPD is 0% or more will be described.

6, when the brake pedal 30 is depressed, the pressure regulated by the master bag 32 is transmitted to the master cylinder 34 so that the hydraulic pressure in the master cylinder 34 is transmitted to the front / So that the brake force according to the hydraulic pressure is constant. At this time, the hydraulic pressure P _m of the master cylinder is expressed by the following equation (7).

&Quot; (7) "

Where a ₁ and a ₂ are the fixed brake hardware characteristics of the front and rear wheels, W is the vehicle load, and g is the deceleration speed.

Thus, the calculation of the regenerative braking force according to the depth (?) Of the brake pedal (30) depends on the type of the master bag (32) and the pedal stroke.

1, a variable resistor 28 is attached to a brake pedal 26 in an electric vehicle, and a signal change corresponding to the pedal depth is sent to the inverter 12 through the A / D converter of the vehicle controller 10 Here, the motor 14 is controlled (the control period is a period from A to D in Fig. 5).

However, such a system has many problems when combined with the hydraulic brake system described above.

Thus, the hydraulic pressure of the master cylinder 34 is calculated for each deceleration in Equation (7), and the g value for each P _m in the gasoline vehicle is calculated.

With these two values, the regenerative braking force replenishes the shortage of the master cylinder hydraulic pressure of the electric vehicle as the load increases in the same braking deceleration city.

The deceleration rate g _EG of the gasoline vehicle is

&Quot; (8) "

The deceleration rate g _EV of the electric vehicle is

&Quot; (9) "

&Quot; (10) "

&Quot; (11) "

. Where P _m 2 is the hydraulic pressure at point A, P _m 3 is the hydraulic pressure at point C, and P _m 4 is the value obtained by converting the braking force value of the regenerative brake side to the point B at point C,

Therefore, in the electric vehicle, when the brake pedal 30 is depressed, the regenerative braking force detected as described above is added to the master cylinder 34 via the master bag 32 so that the brake pedal 30 is subjected to the same pressing force A larger braking force is exerted on the front and rear wheels through the master cylinder 34, so that even a person on an electric vehicle can feel the same deceleration as in a gasoline vehicle.

As described above, according to the present invention, the same deceleration can be obtained by the regenerative braking force even when the brake force of the gasoline vehicle is applied to an electric vehicle whose load is greater than that of the gasoline vehicle according to the weight of the battery tray. The same deceleration can be felt and the vehicle can be stably driven.

Claims (1)

A step of detecting a braking force of a gasoline vehicle and an electric vehicle, a step of determining a regenerative braking force by judging the braking / deceleration speed of each of the braking forces of the gasoline vehicle and the electric vehicle detected in the step to be equal to each other, To the hydraulic pressure applied to the master cylinder during the operation of the hydraulic brake system so that the load is the same as that of the gasoline vehicle even when the electric vehicle is heavier than the gasoline vehicle, Control method.