KR100867826B1 - Method for control regenerative braking of electric vehicle - Google Patents

Abstract

The present invention relates to a regenerative braking control method of an electric vehicle, by using a feedforward controller and a feedback controller at the same time to calculate the regenerative braking torque capable of maximum charging of the battery in real time, the fast response characteristics according to the use of the feedforward controller It is possible to eliminate the instability caused by the measurement error of the system through the feedback controller, and maximize the regenerative braking amount without system shutdown even in the presence of system modeling error due to the simultaneous use of the feedforward controller and the feedback controller. The present invention relates to a regenerative braking control method of an electric vehicle.

Electric Vehicle, Fuel Cell, Hybrid, Regenerative Braking, Feedforward Control, Feedback Control

Description

Control method for regenerative braking of electric vehicle {Method for control regenerative braking of electric vehicle}

1 is a view showing a conventional torque signal transmission state at the time of regenerative braking of the vehicle,

2 is a flowchart illustrating a process of receiving a brake signal from a PCU and outputting the signal to a MCU after processing a map;

3 is a diagram illustrating weak field control of the MCU;

4 is a configuration diagram of a power net of a fuel cell battery hybrid system;

5 is a diagram illustrating a torque signal transmission state according to the present invention at the time of regenerative braking of a fuel cell battery hybrid vehicle;

6 is a diagram illustrating a control algorithm according to the present invention, illustrating a control algorithm for feedforward control and feedback control.

7 is a diagram illustrating signal input / output states of a feedforward controller and a feedback controller in the present invention;

8 is a flowchart of a torque calculation process performed by a feedforward controller of the present invention;

9 is a flowchart illustrating a correction factor calculation process performed by the feedback controller of the present invention;

10 is a diagram illustrating an example in which regenerative braking torque is adjusted by a PCU.

<Explanation of symbols for the main parts of the drawings>

1: PCU 2: MCU

10: VCU 20: PCU

21: feedforward controller 25: feedback controller

30: MCU

The present invention relates to a regenerative braking control method of an electric vehicle, and more particularly, by using a feedforward controller and a feedback controller simultaneously to calculate the regenerative braking torque capable of maximum charging of the battery in real time, Fast response characteristics can be obtained, and instability due to measurement error of the system can be eliminated through the feedback controller, and the simultaneous use of the feedforward controller and the feedback controller enables the regenerative braking amount without system shutdown even in the presence of system modeling error. It relates to a regenerative braking control method of an electric vehicle that can maximize the.

The global automotive industry has been growing rapidly, especially for gasoline and diesel internal combustion engines for more than 100 years, but is facing tremendous changes, coupled with environmental regulations, energy security threats and fossil fuel depletion.

Therefore, countries around the world, especially developed countries, are participating in the fierce competition for the development of eco-friendly vehicles, and each automobile manufacturer has made great efforts to avoid falling behind in the competition for technology development of future cars that require eco-friendly and high-efficiency advanced technologies. I'm leaning.

In particular, in response to the demand for developing more environmentally friendly products while solving the problem of depletion of fossil fuels, automakers have been actively researching electric vehicles that use driving motors as a power source.

Electric vehicles such as hybrid vehicles and fuel cell vehicles are currently the most actively researched fields.

Here, the hybrid vehicle in the broad sense means to drive the vehicle by combining two or more different power sources efficiently, but in most cases, the vehicle is driven by the power of an engine and a high voltage battery using fuel such as gasoline or diesel. A vehicle that obtains driving power by a motor is referred to as a hybrid electric vehicle (HEV).

In the hybrid electric vehicle, the optimum operating area of the engine and the driving motor is used, thereby improving fuel efficiency of the entire driving system as well as recovering energy from the driving motor to charge the high voltage battery, thereby enabling efficient use of energy.

In addition, the fuel cell is a device that converts the chemical energy of the fuel into electrical energy directly in the cell without converting the chemical energy into heat by combustion, and is a pollution-free power generation device that has been recently studied with interest.

In a vehicle equipped with a fuel cell, hydrogen is used as a fuel to supply the fuel cell to generate electricity, and the vehicle is driven by operating a driving motor with electricity generated by the fuel cell.

On the other hand, the fuel cell vehicle (or fuel cell battery hybrid vehicle) is equipped with a vehicle controller (Vehicle Control Unit, hereinafter referred to as "VCU") that is responsible for the overall control of the vehicle, and the controller for each device constituting the system Equipped.

As described above, in a fuel cell vehicle, a controller is provided for each device so that a plurality of controllers perform cooperative control with the VCU as an upper controller while the vehicle is in operation. At this time, the upper controller is connected to the lower controller while the controllers exchange information with each other. It is supposed to deliver a command.

Related controllers that control motor operation using the VCU as an upper controller are largely a power distribution controller (also called a hybrid controller) (hereinafter referred to as a power control unit, hereinafter referred to as' PCU ') and a motor controller (Motor Control Unit, hereinafter,' MCU ').

Normally, the VCU calculates the driving torque and the braking torque by reflecting the driver's intention by operating an accelerator pedal or brake pedal, and the PCU (or FHCU: Fuel Cell Hybrid Control Unit) is a fuel cell controller which is an energy source and power distribution function of a high voltage battery. The MCU is a power module for rotating the drive motor to generate a three-phase PWM by receiving DC current, and is responsible for driving the motor and regenerative braking.

In addition, the electric motor plays a role of recovering and storing kinetic energy by regenerative braking when the vehicle is decelerated in addition to the purpose of driving the vehicle.

That is, the electric vehicle uses a part of the braking force for generating power during braking and uses the generated electric energy for charging the battery, so that a part of the kinetic energy according to the traveling speed of the car is driven by the generator. By using it as the energy required, the reduction of kinetic energy (that is, the driving speed) and the generation of electric energy are realized at the same time.

This type of braking method is called regenerative braking, and the generation of electrical energy during regenerative braking can be achieved by reverse driving a separate generator or drive motor.

Meanwhile, the regenerative braking process according to the prior art in an electric vehicle equipped with a fuel cell battery hybrid system (using a fuel cell and a high voltage battery) is as follows.

1 is a diagram illustrating a torque signal transmission state during regenerative braking of a vehicle, wherein the PCU 1 is a vehicle speed (calculated from the motor rotational speed) and a pedal angle of a brake pedal (hereinafter referred to as a brake pedal angle). The shift gear (PRND) signal of the shift gear is input.

Accordingly, the PCU 1 converts and calibrates the input brake pedal angle signal (hereinafter, referred to as a brake signal) (0V to 5V) as shown in FIG. 2 to be calibrated, and calibrated brake signal (0% to 0%). 100%) is multiplied by the scale value according to the vehicle speed (map processing according to the vehicle speed) and transmitted to the MCU 2 as shown in FIGS. 1 and 2.

When the maximum voltage threshold is exceeded at the time of regenerative braking, the MCU 2 reduces the regenerative braking amount through the field weakening control as shown in FIG. 3 to secure the stability of the system.

However, according to the conventional regenerative braking process, there is an instability due to the measurement error of the system, and there is a problem in maximizing the regenerative braking amount due to the shutdown of the system in the presence of a modeling error.

In addition, the lack of response characteristics also requires improvement.

Accordingly, the present invention is invented to solve the above problems, by using the feed forward controller and the feedback controller at the same time to calculate the regenerative braking torque capable of maximum charging of the battery in real time, according to the use of the feed forward controller Fast response characteristics can be obtained, and instability caused by the measurement error of the system can be eliminated through the feedback controller, and the simultaneous use of the feedforward controller and the feedback controller enables the regenerative braking amount without system shutdown even in the presence of system modeling error. The purpose is to provide a regenerative braking control method for electric vehicles that can be maximized.

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

In order to achieve the above object, the present invention includes the steps of calculating the regenerative braking torque generated value reflecting the driver's will based on the current vehicle speed, brake pedal angle, and shift stage signal; Calculating, by the feedforward controller, the maximum regenerative braking torque through the maximum regenerative braking torque extraction map based on the regenerative braking torque generation value and the current vehicle speed and the maximum charging power value of the battery; Calculating, by a feedback controller, a correction factor for eliminating system modeling errors occurring in the feedforward controller, and correcting the maximum regenerative braking torque using the calculated correction factor; And regenerative braking using the corrected torque value as the final regenerative braking torque value capable of maximum charging of the high voltage battery.

Here, the calculation of the correction coefficient, the current limit value of the HDC input and output stage, the voltage limit value of the HDC input and output stage, the current measurement value of the HDC input and output stage, and the value measured by monitoring the voltage measurement value of the HDC input and output stage It is characterized by calculating using them.

Preferably, the calculation of the correction coefficient, the error of the HDC output stage current measurement value and the HDC output stage current limit value, the error of the HDC input stage current measurement value and the HDC input stage current limit value, the HDC output stage voltage measurement value and the HDC output stage voltage limit value Error of the HDC input stage voltage measurement value and the HDC input stage voltage limit value, respectively, characterized in that it calculates the correction coefficient according to each error through each map.

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

4 is a diagram illustrating a power net configuration of a hybrid fuel cell battery system, wherein the current / voltage of the high voltage DC-DC converter (HV DCDC, hereinafter referred to as “HDC”) input stage, and the current of the HDC output stage are shown. It shows voltage measurement.

5 is a diagram illustrating a torque signal transmission state according to the present invention at the time of regenerative braking of a fuel cell battery hybrid vehicle, and includes a regenerative braking torque signal transmission method formed between the VCU 10, the PCU 20, and the MCU 30. Is showing.

6 is a diagram illustrating a control algorithm according to the present invention, which is a schematic diagram illustrating a control algorithm for feedforward control and feedback control used in the present invention, and is compensated through feedforward control and feedback control. The algorithm for calculating the maximum regenerative braking torque is shown.

In addition, Figure 7 is a view showing the signal input and output state of the feed forward controller and the feedback controller in the present invention, Figure 8 is a flow chart of the torque calculation process performed by the feed forward controller of the present invention, Figure 9 is a view of the present invention A flowchart illustrating a correction factor calculation process performed by the feedback controller.

In the present invention, the regenerative braking torque generation, transmission, and the generated signal flow has been improved, unlike in the related art. By using the feedforward controller 21 and the feedback controller 25 simultaneously, the maximum voltage of the high voltage battery in real time is achieved. The regenerative braking torque that can be charged is calculated.

The feedforward controller 21 calculates the maximum chargeable regenerative braking torque in real time based on the current vehicle speed and the maximum chargeable power amount of the battery.

In addition, the feedback controller 25 receives a current value and a voltage value (refer to FIG. 4) measured at the HDC input / output stage in real time and calculates a correction coefficient for removing a system modeling error occurring at the feedforward controller 21. And, using this correction coefficient to control the final amount of torque input to the MCU 30 so that the system is not shut down.

Hereinafter, a control process according to the present invention will be described in detail with reference to the accompanying drawings.

First, as shown in FIG. 5, the vehicle controller VCU 10 receives the current vehicle speed, the pedal angle of the brake pedal (hereinafter referred to as the brake pedal angle), and the shift gear PRND signal of the shift gear. Based on this, the regenerative braking torque value (hereinafter referred to as 'VCU regenerative braking torque generation value') that reflects the driver's will (calculated torque value through the map from the brake pedal angle) is calculated. ).

Accordingly, the PCU 20 adjusts the VCU regenerative braking torque generation value transmitted from the VCU 10 according to the current vehicle speed and the battery state as shown in FIG. 5 to transmit the adjusted regenerative braking torque value to the MCU 30. do.

The regenerative braking torque value calculation in the PCU 10 is performed by the feedforward controller 21 and the feedback controller 25, which will be described in more detail with reference to FIGS. 6 to 9.

First, the feedforward controller 21 receives the VCU regenerative braking torque generation value and the current vehicle speed and the maximum charging power value of the battery based on the maximum regenerative braking torque extraction map 22 based on the maximum regenerative braking torque Tm. Will be calculated.

Here, the feedforward controller 21 calculates the maximum regenerative braking power value from the VCU regenerative braking torque generation value and the current vehicle speed, limits the maximum chargeable amount of the battery, and calculates a torque value corresponding to the calculated regenerative braking power value. To perform the process (see FIGS. 6 to 8).

In addition, the feedback controller 25 monitors the current limit values of the HDC input and output stages, the voltage limit values of the HDC input and output stages, the current measurement values of the HDC input stage and the output stage, and the voltage measurement values of the HDC input stage and the output stage in real time, After calculating the correction coefficients (η1, η2, η3, η4) for eliminating the system modeling error occurring in the feedforward controller 21 through the set maps 26, 27, 28 and 29, the calculated correction coefficients are calculated. The final torque amount input to the MCU 30 is adjusted.

In this case, as shown in FIG. 9, the feedback controller 25 calculates the error 1 between the HDC output stage current measurement value and the HDC output stage current limit value, and calculates the correction coefficient η 1 corresponding to the error 1 through the corresponding map 26. do.

In addition, the error 2 of the HDC input stage current measurement value and the HDC input stage current limit value, the error 3 of the HDC output stage voltage measurement value and the HDC output stage voltage limit value, and the error 4 of the HDC input stage voltage measurement value and the HDC input stage voltage limit value are calculated, respectively. Calculate the correction coefficients η2, η3, and η4 corresponding to Error 2, Error 3, and Error 4 through (27, 28, 29).

Then, the calculated maximum regenerative braking torque Tc is calculated by multiplying the correction coefficients η1, η2, η3, and η4 calculated in this manner by the maximum regenerative braking torque Tm calculated by the feedforward controller 21, and then calculating the corrected regenerative braking torque Tc. The maximum regenerative braking torque value of the high voltage battery is transmitted to the MCU 30 (see FIGS. 6 and 7).

In this way, the MCU 30 performs regenerative braking by referring to the final regenerative braking torque value Tc transmitted from the feedback controller 26 as the input torque (see FIGS. 5 and 6).

10 is a diagram illustrating an example in which regenerative braking torque is adjusted by the PCU, and it can be seen that the final regenerative braking torque is reduced by the feedback controller when the HDC input current exceeds the threshold by the feedback controller.

As described above, according to the regenerative braking control method of the electric vehicle according to the present invention, by using the feed forward controller and the feedback controller at the same time to calculate the regenerative braking torque capable of maximum charging of the battery in real time, the following advantages This will be.

1) Fast response characteristics can be obtained by using a feedforward controller.

2) By using the feedback controller, it is possible to eliminate the instability caused by the measurement error of the system.

3) By using feed forward controller and feedback controller at the same time, it is possible to maximize regenerative braking amount without system shutdown even in the presence of system modeling error.

Claims (3)

Calculating a regenerative braking torque generation value based on a current vehicle speed, a brake pedal angle, and a shift stage signal; Calculating, by the feedforward controller, the maximum regenerative braking torque through the maximum regenerative braking torque extraction map based on the regenerative braking torque generation value and the current vehicle speed and the maximum charging power value of the battery; Calculating, by a feedback controller, a correction factor for eliminating system modeling errors occurring in the feedforward controller, and correcting the maximum regenerative braking torque using the calculated correction factor; Performing regenerative braking using the corrected torque value as the final regenerative braking torque value capable of maximum charging of the high voltage battery; Regenerative braking control method of the electric vehicle comprising a The method according to claim 1, The calculation of the correction coefficient may be performed using the current monitored values of the HDC input and output stages, the voltage limit values of the HDC input and output stages, the current measurement values of the HDC input and output stages, and the voltage measured values of the HDC input and output stages. Regenerative braking control method for an electric vehicle, characterized in that calculating. The method according to claim 2, The calculation of the correction coefficient may include error of the HDC output stage current measurement value and HDC output stage current limit value, error of the HDC input stage current measurement value and HDC input stage current limit value, error of the HDC output stage voltage measurement value and HDC output stage voltage limit value, The regenerative braking control method for an electric vehicle, characterized in that the error coefficient between the HDC input stage voltage measurement value and the HDC input stage voltage limit value is calculated and calculated according to each error through each map.

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