KR20120109097A - Auto cruise control method for electric vehicle - Google Patents

Abstract

PURPOSE: An auto cruise control method of an electric vehicle is provided to minimize energy consumption by automatically driving a motor in an optimal condition. CONSTITUTION: A brake controller receives driving information for auto cruise control. The brake controller determines brake time based on the driving information. The brake controller calculates brake torque for maintaining the distance between vehicles at the brake time. A vehicle controller determines regenerative brake torque for the brake torque. The vehicle controller outputs a motor torque command by generating the motor torque command. A motor controller generates the regenerative brake torque by controlling motor torque. A battery is charged by a motor in a regenerative torque generation state. [Reference numerals] (AA) Vehicle speed, vehicle interval information input(ACC); (BB) Brake(brake pedal input); (CC) Required braking power calculation, regenerative braking torque tolerable amount sending; (DD) Regenerative braking torque determination; (EE) Regenerative braking torque control; (FF) Hydraulic braking power determination; (GG) Regenerative braking torque implementation amount sending; (HH) Hydraulic braking power generation; (II) Regenerative braking power generation

Description

AUTO CRUISE CONTROL METHOD FOR ELECTRIC VEHICLE}

The present invention relates to an auto cruise control method, and more particularly, to an auto cruise control method capable of maximizing fuel economy improvement in an electric vehicle in which regenerative braking is performed.

As is known, eco-friendly vehicles such as hybrid cars that run with engines and motors as driving sources, fuel cell cars that drive by driving motors with generated power of fuel cells, and pure electric vehicles that drive motors with power charged in batteries In electric vehicles, fuel economy (mileage) is improved through regenerative braking (RB), which converts kinetic energy into electrical energy when braking is required.

That is, in the electric vehicle braking the vehicle is made by hydraulic braking by the hydraulic braking device and electric regenerative braking, and the fuel consumption can be improved by charging the battery by using a motor that is the vehicle driving source as the generator during the regenerative braking.

In the case of fuel cell vehicles, a fuel cell hybrid system equipped with a battery or a super cap as a secondary power source as well as a fuel cell as a main power source has been developed.The regenerative power by the motor is stored in the power storage means during regenerative braking. I use it.

The regenerative braking serves as an auxiliary braking means of the electric vehicle. Typically, the regenerative braking is operated after the hydraulic braking in the initial stage of braking is operated first for safety according to the driver's brake operation.

In the case of regenerative braking, proper distribution between the braking force by the hydraulic braking device, that is, the hydraulic braking force, and the electric braking force by switching the power generation operation and rotational resistance of the motor, that is, the regenerative braking force, is essential.

1 is a diagram illustrating a process of braking an electric vehicle, and FIG. 2 is a diagram illustrating an operation state of hydraulic braking and regenerative braking during braking of an electric vehicle. When the driver presses the brake pedal with the will of braking, the total braking force required as below is distributed as the sum of the hydraulic braking force and the regenerative braking force.

Total Braking Force = Hydraulic Braking Force + Regenerative Braking Force (Motor Generation and Battery Charging)

(Total braking requirement = hydraulic braking amount + regenerative braking amount)

In addition, as shown in FIG. 2, at the beginning and the end of the braking, the hydraulic pressure of the hydraulic braking system is controlled (solenoid valve control) according to the driver's required braking torque, and the braking is performed by the hydraulic braking force. Distribute the regenerative braking force to achieve the maximum possible regenerative braking within the allowable range.

Referring to FIG. 1, the braking process will be described in more detail. First, when the driver presses the brake pedal so that the braking intention is input to the brake controller, that is, the EBS ECU (brake on), the stroke amount detected by the sensor as a pedal input value. The EBS ECU receives the (pressure amount) and calculates the driver's required braking force based on this.

After the initial hydraulic braking is performed according to the driver's required braking force, the total braking force is distributed to the hydraulic braking force and the regenerative braking force so that the regenerative braking can be performed as much as possible. Is sent to the vehicle controller (HCU: Hybrid Control Unit or VCU: Vehicle Control Unit) which is the highest level controller, and the vehicle controller transmits information (transmission lever position information, etc.) of the transmission controller (TCU), and the battery controller (BMS). The regenerative braking torque and the regenerative braking torque to be generated by the motor are determined based on the information of the battery management system (such as battery status information) and the regenerative braking torque allowance information transmitted from the EBS ECU.

Then, the motor control unit (MCU) controls the regenerative braking torque of the motor according to the torque command of the vehicle controller (the regenerative braking torque is generated in the motor), and transmits the actual amount of motor torque to the EBS ECU through the vehicle controller. do.

In addition, the EBS ECU determines the hydraulic braking force while referring to the actual generation amount of the motor torque, and generates the necessary hydraulic braking force by controlling the hydraulic pressure of the hydraulic braking device.

2 shows an example in which the operation of the initial hydraulic braking, the distribution of the hydraulic braking and regenerative braking, the regenerative braking, and the final hydraulic braking are performed during vehicle braking. The distribution of the hydraulic braking and the regenerative braking for a predetermined time after the initial hydraulic braking is It shows that it is done.

Meanwhile, even in the case of the electric vehicle described above, an auto cruise control (ACC) system that can drive the vehicle at a constant speed is intended to be applied. The auto cruise control system sets a speed desired by the driver. It is a system that controls the vehicle to run at a set speed without any additional operation.

When the auto cruise control system is applied, the driving speed of the vehicle can be automatically maintained at a constant speed by a simple operation on a highway or a car road with less traffic, and the operation of the accelerator pedal is greatly reduced. There is an advantage that the convenience of driving is improved, such as to reduce fatigue.

3 is a view showing the ACC function, when there is no preceding vehicle is a constant speed running at the speed set by the driver, when there is a preceding vehicle, the vehicle is driven at the speed of the preceding vehicle while maintaining the set inter-vehicle distance with the preceding vehicle If the preceding vehicle disappears, the vehicle accelerates to the set speed and then runs at constant speed.

However, there are the following problems in applying the ACC function to the electric vehicle capable of regenerative braking.

First, there is no integrated control of regenerative braking function and ACC function.

That is, when the preceding vehicle appears while driving, auto cruise control is performed to maintain the set distance between vehicle and the vehicle speed based on information such as the distance between the preceding vehicle and the vehicle speed.However, in the electric vehicle, the ACC function and the regenerative braking function are separate functions. Only exists.

In addition, the regenerative braking system is an auxiliary braking means, and for the sake of safety during the braking of the vehicle, the hydraulic braking is operated first and then the regenerative braking is operated (the braking of FIG. 1 and FIG. 2 is performed without prior vehicle information). There is a limit that large kinetic energy is not recovered and dissipated by heat.

Secondly, when the driver presses the accelerator pedal after braking, re-acceleration occurs. When the driver accelerates by pressing the accelerator pedal, there is a problem in that a fuel economy difference occurs according to the driver's driving tendency and excessive consumption of driving energy occurs.

Accordingly, the present invention has been made to solve the above problems, and an object thereof is to provide an auto cruise control method for an electric vehicle that can maximize fuel efficiency improvement in applying the ACC function to the electric vehicle.

In order to achieve the above object, according to the present invention, the set inter-vehicle distance with the preceding vehicle is maintained based on the driving information including the inter-vehicle distance and the vehicle speed by the control of the controller during the auto cruise control operation in the electric vehicle The vehicle braking is performed, but the regenerative braking, in which the motor generation and the battery charging are performed at the time of braking, is performed immediately without the initial hydraulic braking so that the vehicle braking is performed by the regenerative braking. Provide a control method.

The regenerative braking may include: receiving, by the brake controller, driving information for auto cruise control; Determining, by the brake controller, the braking timing based on the driving information, calculating a braking torque for maintaining the distance between the brakes and transmitting the braking torque to the vehicle controller; Determining, by the vehicle controller, a regenerative braking torque for satisfying the braking torque, and generating and outputting a motor torque command accordingly; Generating a regenerative braking torque by controlling the motor torque according to the torque command of the vehicle controller; And a process of charging the battery by generating a motor when regenerative torque is generated.

Also, in the process of reaccelerating the vehicle to a set speed or reaccelerating the vehicle to maintain a set inter-vehicle distance with the preceding vehicle when there is no preceding vehicle after braking the vehicle, the controller is based on driving information including the inter-vehicle distance and the vehicle speed. It is characterized by driving the motor to the optimum operating point.

Accordingly, in the auto cruise control method of the present invention, the improved auto cruise control integrated with the regenerative braking function is implemented, thereby maximizing fuel efficiency. When braking the vehicle during the auto cruise control operation, the regenerative braking force is generated without the initial hydraulic braking, thereby increasing the energy recovery amount.

In addition, the motor controller can be operated to automatically drive the motor to the optimal operating point with low energy consumption during re-acceleration after braking during auto cruise control operation. (Motor controller based on torque command output and torque command corresponding to the optimum operating point of the vehicle controller) Motor torque control) is performed, thereby minimizing the consumption of traveling energy.

In particular, frequent braking and acceleration are required when driving in crowded city centers. At this time, it is possible to improve fuel economy through regenerative braking and optimal acceleration while automatically maintaining an appropriate inter-vehicle distance.

1 is a diagram illustrating a process of braking an electric vehicle.
2 is a view showing an operating state of hydraulic braking and regenerative braking during braking of an electric vehicle.
3 is a diagram illustrating an auto cruise control (ACC) function.
4 is a diagram illustrating a braking control process in a vehicle to which auto cruise control of the present invention is applied.
5 is a view showing the operating state of regenerative braking and hydraulic braking to obtain a braking force in the auto cruise control according to the present invention.
6 is a view for explaining a motor control method when re-acceleration after braking in the auto cruise control process according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auto cruise control (ACC) method of an electric vehicle, wherein the auto cruise function and the regenerative braking function are integrally controlled, and the distance between the vehicle and the vehicle speed with the preceding vehicle by the integrated control of the auto cruise function and the regenerative braking function. The vehicle braking is automatically performed by regenerative braking based on driving information such as braking. In particular, the vehicle is braked by regenerative braking without using hydraulic braking at the beginning of braking to maximize the energy recovery amount. Energy recovery).

FIG. 4 is a diagram illustrating a braking control process in a vehicle to which auto cruise control of the present invention is applied, and FIG. 5 is a diagram illustrating an operation state of regenerative braking and hydraulic braking for obtaining braking force during auto cruise control according to the present invention.

FIG. 4 is a view illustrating a process of braking the vehicle during normal driving and a braking process of the vehicle at the time of auto cruise control operation (ACC On). FIG. The braking process is performed in the same manner (as in FIGS. 1 and 2).

This is the same as the braking process described above with reference to FIGS. 1 and 2, and under cooperative control performed by the brake controller (EBS ECU) and the host controller (VCU or HCU), the motor controller (MCU), etc., exchange information. Proceed.

On the other hand, if there is a preceding vehicle in the state in which the auto cruise control is activated by setting the desired speed of the driver (ACC On by the predetermined operation), the distance between the vehicle and the vehicle is set based on the current driving information such as the distance between the preceding vehicle and the vehicle speed. The motor control for re-acceleration is performed at a necessary time after the vehicle braking is performed so that the vehicle braking can be maintained, and in particular, the vehicle braking is performed by regenerative braking without initial hydraulic braking during braking.

In the initial stage of braking, the braking of the vehicle is performed through a control process that performs regenerative braking without using hydraulic braking.

To this end, the brake controller is provided to receive driving information for auto cruise control such as the distance between the preceding vehicle and the vehicle speed from the information collection unit in the auto cruise control system, and requires braking of the vehicle based on the driving information during the auto cruise control operation. Ensure that regenerative braking occurs immediately.

At this time, when braking to maintain the distance between the vehicle using the driving information such as the distance between the vehicle and the vehicle speed, an appropriate regenerative braking force is generated immediately without the hydraulic braking from the beginning of braking. The braking torque is calculated and transmitted to the vehicle controller so that the distance between the vehicle can be maintained.

Accordingly, the vehicle controller determines the regenerative braking torque to satisfy the required braking torque and outputs a motor torque command accordingly, and then the motor controller generates the regenerative braking torque by controlling the motor torque according to the torque command of the vehicle controller.

Of course, the electrical energy recovered from the motor by regenerative braking is charged to the battery.

Referring to FIG. 5, in the present invention, it can be seen that braking is performed by immediately generating a regenerative braking force without initial hydraulic braking, based on driving information during auto cruise control operation. By braking the large kinetic energy of the initial braking can be recovered as electrical energy, it is possible to maximize the energy recovery.

On the other hand, after braking by the auto cruise control function, if there is no preceding vehicle based on driving information such as presence or absence of preceding vehicle, distance between the preceding vehicle, and vehicle speed, the vehicle is re-accelerated to a set speed or In the process of re-acceleration to maintain the set inter-vehicle distance, the vehicle controller causes the motor to be driven to the optimum driving point with less energy consumption, thereby minimizing the consumption of driving energy.

More specifically, Figure 6 is a view for explaining a motor control method when re-acceleration after braking in the auto cruise control process according to the present invention, the vehicle controller at the time of re-acceleration after braking, whether there is a preceding vehicle, the distance between the vehicle and the vehicle speed The required torque and the optimum operating point are determined on the basis of the driving information, and the torque command for the motor torque output corresponding to the optimum operating point is generated.

Subsequently, the motor controller receives the torque command from the vehicle controller, thereby driving the motor by controlling the motor torque according to the torque command transmitted from the vehicle controller.

Here, the optimum controller data stored in consideration of the motor efficiency is stored in advance in the vehicle controller with respect to the information such as the distance between the vehicle and the vehicle speed.

In addition, the vehicle controller may be provided to directly receive driving information such as the distance between the vehicle and the vehicle speed from the information collecting unit of the auto cruise control system or through the brake controller, and may use the battery as an input variable to determine the required torque and the optimum driving point. Status information (SOC, etc.), motor status information (motor temperature and / or motor rotational speed as shown in FIG. 3) may additionally be used.

In this way, in the present invention, by implementing the auto cruise function using the regenerative braking, it is possible to provide an advantage of increasing the fuel efficiency (one-charge mileage) of the electric vehicle in addition to the improvement of convenience that can be achieved by the auto cruise function. .

In addition, the motor controller can be operated to automatically drive the motor to the optimal operating point with low energy consumption during re-acceleration after braking during auto cruise control operation. (Motor controller based on torque command output and torque command corresponding to the optimum operating point of the vehicle controller) Motor torque control) is performed, thereby minimizing the consumption of traveling energy.

In particular, frequent braking and acceleration are required when driving in crowded city centers, whereby it is possible to improve fuel economy through regenerative braking and optimum acceleration while automatically maintaining an appropriate inter-vehicle distance.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments. Modified forms are also included within the scope of the present invention.

Claims (3)

In an electric vehicle, vehicle braking is performed to maintain a set inter-vehicle distance with the preceding vehicle based on driving information including the distance between the preceding vehicle and the vehicle speed by the control of the controller during the auto cruise control operation. A method of controlling an auto cruise of an electric vehicle, characterized in that regenerative braking at which a motor is generated and battery charging is performed immediately without initial hydraulic braking to perform vehicle braking by regenerative braking.
The method according to claim 1,
The regenerative braking is
Receiving, by the brake controller, driving information for auto cruise control;
Determining, by the brake controller, the braking timing based on the driving information, calculating a braking torque for maintaining the distance between the brakes and transmitting the braking torque to the vehicle controller;
Determining, by the vehicle controller, a regenerative braking torque for satisfying the braking torque, and generating and outputting a motor torque command accordingly;
Generating a regenerative braking torque by controlling the motor torque according to the torque command of the vehicle controller; And
A process of charging the battery by generating a motor when regenerative torque is generated;
Auto cruise control method of an electric vehicle, characterized in that carried out by.
The method according to claim 1,
If there is no preceding vehicle after braking the vehicle, in the process of re-accelerating the vehicle to a set speed or re-accelerating to maintain the set inter-vehicle distance with the preceding vehicle, the controller is optimized based on driving information including the inter-vehicle distance and the vehicle speed. An auto cruise control method for an electric vehicle, comprising driving a motor to a driving point.

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