Method for controlling the battery of a mild hybrid vehicle

Abstract

Method for controlling the battery of a mild hybrid vehicle which has: a first step in capturing traffic conditions based on the vehicle's driving state; and a second step of setting a target SOC of an energy storage device based on the detected traffic condition, wherein the first step comprises: a step 1-1 of setting a first area of ​​interest based on the number of times the vehicle stops; and a step 1-2 of detecting the number of times stop and go does not operate due to a low SOC of the energy storage device within the first area of ​​interest, wherein the second step comprises a step 2-1 of comparing the number of times Stop and Go does not act with a first and second reference value that were previously set, wherein a step 2-2 of increasing the target SOC of the energy storage device is performed if the number of times Stop and Go does not act is greater than the first reference value, A step 2-3 (S230) of lowering the target SOC of the energy storage device is performed if the number of times Stop and Go does not operate is less than the preset second reference value, and the first reference value is greater than the second reference value.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to and the benefit under 35 USC § 119(a) of Korean Patent Application No. 10-2014-0135309, filed on October 7, 2014, which is hereby incorporated by reference for all purposes as if fully disclosed herein. BACKGROUND OF THE INVENTION 1. Field of the Invention

[0002] The present invention relates to a method for controlling the battery of a mild hybrid vehicle, and more particularly to a method for determining a target state of charge (SOC) of an energy storage device of a mild hybrid vehicle based on traffic conditions. 2. Description of the state of the art

[0003] Vehicle manufacturers have strived to improve fuel economy and develop environmentally friendly vehicles in response to increasing social concern about rising oil prices and the environment, and hybrid systems that regenerate and utilize vehicle deceleration energy have been developed to meet this demand.

[0004] In the prior art, in order to control the battery state of charge of a hybrid vehicle, the compensation value for an engine torque is calculated from the output of a motor based on information such as the state of charge (SOC) of the battery, the performance of a low-voltage battery that supplies power to an electric field load side of the vehicle, a driving environment (an inclination angle and external temperature), and the like, and then finally an operating point (an engine torque output point according to a current engine speed) of an engine is determined based on the calculated compensation value.

[0005] However, the prior art control method does not consider road / traffic conditions, and thus does not maximize the stop-and-go function, which has a significant impact on improving fuel efficiency, and the function of utilizing renewable energy. For example, in cases where the battery state of charge is maintained at a single target SOC, the stop-and-go function cannot be sufficiently utilized in heavy traffic congestion. In contrast, maximum renewable energy must be utilized under road / traffic conditions that have a large amount of renewable energy, but unnecessary engine power generation occurs to manage the battery, thereby increasing fuel consumption.

[0006] Patent Document 1, mentioned below, discloses a technology for controlling idle stop and go and behavior based on information sent from a traffic control center, but does not disclose a technical feature of the present invention in which a target SOC of an energy storage device of a mild hybrid vehicle is set based on a vehicle's driving condition. Patent Document 2 also discloses a start-stop system, while Patent Documents 3, 4, and 5 describe other methods for battery and idle control in vehicles with start-stop systems. Citation listPatent documents (Patent document 1) KR 10 2005 0 048 278 A (Patent document 2) DE 10 2012 104 995 A1 (Patent document 3) DE 10 2012 220 529 A1 (Patent document 4) DE 10 2007 024 471 A1 (Patent document 5) US 2014 / 0 156 132 A1 SUMMARY OF THE INVENTION

[0007] One aspect of a method for controlling the battery of a mild hybrid vehicle according to an embodiment of the present invention is to address at least the aforementioned problems and / or disadvantages and to obtain at least the advantages described below.

[0008] One aspect of the present invention is to provide a method for controlling a battery of a mild hybrid vehicle that can specify a target SOC of an energy storage device of the mild hybrid vehicle by sensing road traffic conditions that vary in real time, thereby improving the fuel efficiency of the mild hybrid vehicle. These objects are achieved by the methods for controlling the battery of a mild hybrid vehicle according to claims 1 and 2.

[0009] Aspects of the present invention are not limited to the aforementioned aspect, and other aspects not mentioned will be clearly understood by those skilled in the art from the following statements.

[0010] A method for controlling the battery of a mild hybrid vehicle according to a first embodiment of the present invention includes: a first step of detecting traffic conditions based on the driving state of the vehicle; and a second step of setting a target SOC of an energy storage device based on the detected traffic conditions, the first step including: a step 1-1 of setting a first region of interest based on the number of times the vehicle stops; and a step 1-2 of detecting the number of times stop and go is not operated due to a low SOC of the energy storage device within the first region of interest.

[0011] The second step may preferably include a step 2-1 of comparing the number of times that Stop and Go are not operated with the first and second reference values, a step 2-2 of increasing the target SOC of the energy storage device may preferably be performed when the number of times that Stop and Go are not operated is greater than the first reference value, a step 2-3 of decreasing the target SOC of the energy storage device may preferably be performed when the number of times that Stop and Go are not operated is less than the preset second reference value, and the first reference value may preferably be greater than the second reference value.

[0012] A method for controlling the battery of a mild hybrid vehicle according to a second embodiment of the present invention includes: a first step of detecting traffic conditions based on the driving state of the vehicle; and a second step of setting a target SOC of an energy storage device based on the detected traffic condition, wherein the first step preferably includes: a step 1-3 of setting a second region of interest for detecting the trend of an SOC of the energy storage device; and a step 1-4 of calculating an average of the SOC of the energy storage device within the second region of interest.

[0013] The second step may preferably include a step 2-4 of comparing an absolute value of the difference between the calculated average SOC of the energy storage device and the target SOC of the energy storage device with a third reference value set beforehand.

[0014] The second step may preferably further include a step 2-5 of comparing the calculated average SOC of the energy storage device and the target SOC of the energy storage device when the absolute value of the difference between the calculated average SOC of the energy storage device and the target SOC of the energy storage device is greater than the preset third reference value; a step 2-6 of decreasing the target SOC of the energy storage device may preferably be performed when the calculated average SOC of the energy storage device is greater than the target SOC of the energy storage device, and a step 2-7 of increasing the target SOC of the energy storage device may preferably be performed when the calculated average SOC of the energy storage device is less than the target SOC of the energy storage device.

[0015] The battery control method may preferably further include a third step of storing the set target SOC of the energy storage device in a memory.

[0016] The methods for controlling the battery of a mild hybrid vehicle according to embodiments of the present invention may set a target SOC of an energy storage device based on traffic conditions detected based on the driving state of a vehicle to prevent fuel consumption caused by unnecessary engine power generation, thereby improving fuel efficiency.

[0017] Effects of the present invention are not limited to the one described above, and other effects not mentioned will be clearly understood by those skilled in the art from the following findings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings in which: Fig. 1 is a block diagram illustrating a configuration of a battery charge state control device of a mild hybrid vehicle; Fig. 2 is a diagram illustrating signals input to an electronic control unit in the battery state of charge control device of the mild hybrid vehicle; Fig. 3 is a flowchart illustrating a general method for controlling the battery of a mild hybrid vehicle according to the present invention in a time-based sequence; Fig. 4 is a flowchart illustrating a method for controlling the battery of a mild hybrid vehicle according to a first embodiment of the present invention in a time-based order; Fig. 5 and Fig. 6 are views for explaining the method of controlling the battery of a mild hybrid vehicle according to the first embodiment of the present invention; Fig. 7 is a flowchart illustrating a method for controlling the battery of a mild hybrid vehicle according to a second embodiment of the present invention in a time-based order; Fig. 8 and Fig. 9 are views for explaining the method of controlling the battery of a mild hybrid vehicle according to the second embodiment of the present invention; and Fig. 10 is a view for generally explaining an operation for managing battery energy according to a method for controlling the battery of a mild hybrid vehicle according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings, wherein the same or similar elements are designated by the same reference numerals and an overlapping description thereof is omitted.

[0020] Furthermore, in the following description of the present invention, a detailed description of known technologies incorporated therein will be omitted if doing so would impair the clarity of the subject matter of the present disclosure. Furthermore, it should be noted that the accompanying drawings are provided only for easy understanding of the technical idea of ​​the present invention, and the spirit of the present invention should not be construed as limited by the accompanying drawings.

[0021] An overall configuration of a mild hybrid device according to the present invention will be described with reference to Fig. 1 and Fig. 2, before describing a method for controlling a battery of a mild hybrid vehicle according to the present invention. Fig. 1 is a block diagram illustrating a configuration of the battery state of charge control device of a mild hybrid vehicle. Fig. 2 is a diagram illustrating signals input to an electronic control unit in the battery state of charge control device of the mild hybrid vehicle.

[0022] As in Fig. 1, the mild hybrid device according to the present invention may include an engine 100, a motor generator 200, an inverter 300, an energy storage device 400, a DC-DC converter 500, a low-voltage battery 600, a belt 700, and an electronic control unit (ECU, not illustrated).

[0023] The motor-generator 200 cooperates with the engine 100 through the belt 700 and can act both as a starter motor for starting the engine 100 and as a generator that can produce an alternating voltage.

[0024] Specifically, the motor generator 200 receives drive power through the inverter 300 and assists with engine power when acting as a starter motor, and supplies electrical power generated during braking of a vehicle to the energy storage device 400 when acting as a generator.

[0025] Specifically, the hybrid device has a stop-and-go function that automatically stops the engine while a vehicle is stopped for a long time and restarts when the vehicle starts. In some cases, stop-and-go is also referred to as idle stop-and-go (ISG).

[0026] In stop-and-go operation, the hybrid device supplies a voltage charged in the energy storage device 400 through the converter 500 to the low-voltage battery 600 when the charged voltage of the energy storage device 400 is higher than or equal to a reference voltage during a stop.

[0027] The inverter 300, which controls the electric power input to or output from the motor generator 200, has the functions of converting electric power supplied from the energy storage device 400 and supplying the converted electric power to the motor generator 200, or the functions of converting electric power generated by the motor generator 200 and supplying the converted electric power to the energy storage device 400.

[0028] The energy storage device 400 may be formed with a supercapacitor module including a plurality of supercapacitors and has the functions of collecting regeneratively braked electrical energy from the motor generator 200 when the vehicle is decelerating and assisting with engine torque by supplying electrical energy to the motor generator 200 when the vehicle is accelerating. Furthermore, the energy storage device 400 may be a high-voltage lithium-based battery, such as a lithium-ion battery, a lithium polymer battery, or the like.

[0029] As in Fig. 2, the electronic control unit has the functions of controlling the elements of the hybrid device based on input signals calculated by various types of sensors arranged in the vehicle, such as the state of the energy storage device (a battery charging rate or a battery temperature), the state of the transmission, the speed of the vehicle, an amount of movement of the accelerator pedal, an amount of movement of the brake pedal, and the like.

[0030] Hereinafter, a method for controlling the battery of a mild hybrid vehicle according to the present invention will be described with reference to Fig. 3 and the above description of the overall configuration of the hybrid device. Fig. 3 is a flowchart illustrating a general method for controlling the battery of a mild hybrid vehicle according to the present invention in a time sequence.

[0031] As in Fig. 3, the method for controlling the battery of a mild hybrid vehicle according to the present invention includes a first step S100 of detecting traffic conditions and a second step S200 of setting the target state of charge (SOC) of the energy storage device 400. Specifically, in the first step S100, the traffic condition is detected based on the driving state of the vehicle, rather than being acquired and detected from a configuration external to the vehicle such as a traffic control center as described in the aforementioned prior art document, and a detailed description thereof will be given below. Furthermore, in the second step S200, the target SOC of the energy storage device 400 is set based on the traffic condition detected in the first step S100.

[0032] In addition, a third step S300 of storing the set target SOC of the energy storage device 400 in a memory is preferably added after the first and second steps S100 and S200. That is, when the vehicle is stopped, the set target SOC of the energy storage device 400 is stored in an inactive memory of the electronic control unit to prevent the set target SOC from being deleted. When a driver restarts the vehicle, the previous target SOC of the energy storage device 400 stored in the memory is read, and the target SOC of the energy storage device 400 is preferably set based on the previous target SOC. That is, an optimal target SOC of the energy storage device can be applied by learning a road condition under which the driver frequently drives the vehicle, thereby improving fuel efficiency.

[0033] In the cases of the first step S100 of detecting the traffic condition based on the running state of the vehicle, two embodiments can be specifically considered, and specific contents of each embodiment will be described below.

[0034] First, a method for controlling the battery of a mild hybrid vehicle according to a first embodiment of the present invention will be described. Fig. 4 is a flowchart illustrating the method for controlling the battery of a mild hybrid vehicle according to the first embodiment of the present invention in chronological order, and Fig. 5 and Fig. 6 are views for explaining the method for controlling the battery of a mild hybrid vehicle according to the first embodiment of the present invention. As shown in Fig. 4, the first step S100 in the method for controlling the battery of a mild hybrid vehicle according to the first embodiment of the present invention may include step 1-1 (S110) of setting a first region of interest based on the number of times a vehicle stops and step 1-2 (S120) of detecting the number of times stop and go is not operating. As shown in Fig. 5, stop and go is set not to operate in a mild hybrid system for an energy storage device when the SOC of the energy storage device is less than or equal to a predetermined numerical value (a lower limit for stop and go), and a target SOC of the energy storage device is set based on the state of charge of the energy storage device 400 and the traffic condition.

[0035] The step 1-1 (S110) and the step 1-2 (S120) of the method for controlling the battery of a mild hybrid vehicle according to the first embodiment of the present invention will be explained with reference to Fig. 6. As described in Fig. 6, the first region of interest is set based on the number of times the vehicle stops; that is, based on the number of times the condition for a stop and go occurs. For example, as in Fig. 6, the first region of interest is set based on the assumption that the number of times that Stop and Go can occur is five, and the number of times that Stop and Go does not take effect because the SOC of the energy storage device 400 is less than a lower limit for Stop and Go, although the occurrence of Stop and Go is possible, is counted. The first region of interest is set to be as in Fig. 6 illustrates moving each time the condition for occurrence of stop and go takes place, thereby making it possible to continuously perform step 1-1 (S110), and a user can preferably set the first region of interest by changing a count value as required.

[0036] After step 1-1 (S110) and step 1-2 (S120) are performed, the second step S200 of setting a target SOC of the energy storage device 400 is performed. In the method for controlling the battery of a mild hybrid vehicle according to the first embodiment of the present invention, a process of comparing the number of times that Stop and Go is not operated, which is detected in step 1-2 (S120), with the first and second reference values ​​previously set, and setting the target SOC of the energy storage device 400 based on the comparison result is performed, and the first reference value is set to a higher value than the second reference value in the second step S200, as shown in Fig. 4. Describing the second step S200 in more detail, when the comparison result shows that the number of times Stop and Go is not operated is greater than the first reference value, Step 2-1 (S210) of comparing the number of times Stop and Go is not operated with the respective preset first and second reference values ​​is performed, and then Step 2-2 (S220) of increasing the target SOC of the energy storage device 400 is performed, thereby increasing the engine start frequency and the Stop and Go operation frequency. On the other hand, when the number of times Stop and Go is not operated is less than the second reference value, Step 2-3 (S230) of decreasing the target SOC of the energy storage device 400 is performed.Therefore, in this case, the first region of interest is determined to be an interval where a large amount of regenerative energy is present, and thus the target SOC of the energy storage device 400 is lowered, thereby reducing the power generation frequency of the engine and increasing the amount of regenerative energy that can be collected. When the number of times the stop and go cycle is not performed is between the first and second reference values, the target SOC of the energy storage device 400 is maintained unchanged.

[0037] A method for controlling the battery of a mild hybrid vehicle according to a second embodiment of the present invention is described. Fig. 7 is a flowchart illustrating the method for controlling the battery of a mild hybrid vehicle according to the second embodiment of the present invention in a time sequence, and Fig. 8 and Fig. 9 are views for explaining the method of controlling a battery of a mild hybrid vehicle according to the second embodiment of the present invention.

[0038] As in Fig. 7, in the method for controlling the battery of a mild hybrid vehicle according to the second embodiment of the present invention, the first step S100 may include the step 1-3 (S130) of setting a second region of interest for detecting the trend of an SOC of the energy storage device 400 and the step 1-4 (S140) of calculating the average of the SOC of the energy storage device 400.

[0039] The trend of the SOC of the energy storage device 400 can be as in Fig. 8, and the second region of interest, which is a detection region of the SOC trend of the energy storage device 400, is shown as in Fig. 9. The second region of interest may be set based on a preset time. In addition, an SOC of the energy storage device 400 may be detected during a counting operation at a predetermined interval, and the second region of interest may also be set based on a count value. As with the first region of interest, the second region of interest may be set to be as shown in Fig. 9 illustrates based on a predetermined time or a predetermined count value, thereby making it possible to continuously perform step 1-3 (S130), and the second region of interest can preferably be set to be changed as required by a user.

[0040] After step 1-3 (S130), step 1-4 (S140) of calculating the average SOC of the energy storage device within the second region of interest is performed to quantify the SOC trend of the energy storage device 400 detected within the second region of interest.

[0041] After step 1-4 (S140), step 2-4 (S240) of comparing an absolute value of the difference between the calculated average SOC of the energy storage device 400 and a target SOC of the energy storage device 400 with a third reference value set beforehand is performed. If the comparison result in step 2-4 (S240) shows that the absolute value of the difference between the calculated average SOC of the energy storage device 400 and the target SOC of the energy storage device 400 is smaller than the third reference value, it is not necessary to change and adjust the target SOC of the energy storage device 400 because the calculated difference between the average SOC of the energy storage device 400 and the target SOC of the energy storage device 400 is not large. Accordingly, the target SOC of the energy storage device 400 is maintained as it is without change.

[0042] On the other hand, if the comparison result shows that the absolute value of the difference between the calculated average SOC of the energy storage device 400 and the target SOC of the energy storage device 400 is greater than the preset third reference value, step 2-5 (S250) of comparing the average SOC of the energy storage device 400 is performed. If the comparison result in step 2-5 (S250) shows that the average SOC of the energy storage device 400 is greater than the target SOC of the energy storage device 400, step 2-6 (S260) of lowering the target SOC of the energy storage device 400 is performed to suppress unnecessary power generation of the engine.On the other hand, when the comparison result shows that the average SOC of the energy storage device 400 is smaller than the target SOC of the energy storage device 400, step 2-7 (S270) of increasing the target SOC of the energy storage device 400 is performed to increase the charging amount of the battery by increasing the power generation of the engine.

[0043] As described above, the method for controlling the battery of a mild hybrid vehicle according to the present invention can be specifically performed based on the number of times that stop and go is not allowed to occur as in the first embodiment, or based on an average SOC of the energy storage device 400 as in the second embodiment. However, as in Fig.10, the battery control method can also be carried out by simultaneously applying the first and second embodiments.

[0044] The embodiments presented in this specification and the accompanying drawings are merely illustrative explanations of a portion of the spirit and scope of the present invention. Therefore, it is understood that the embodiments disclosed in this specification are intended to explain, but not limit, the spirit and scope of the present invention, so that the spirit and scope of the present invention are not limited by the embodiments. Modified examples and specific embodiments that would be apparent to those skilled in the art without departing from the spirit and scope contained in the specification and drawings of the present invention are included within the spirit and scope of the present invention. Description of reference numbers 100 machines 200 Motor-Generator 300 inverters 400 energy storage device 500 converters 600 low-voltage battery 700 belts

Claims

[1] A method for controlling the battery of a mild hybrid vehicle, comprising: a first step of detecting traffic conditions based on a driving state of the vehicle; and a second step of setting a target SOC of an energy storage device based on the detected traffic condition, the first step comprising: a step 1-1 of setting a first region of interest based on the number of times the vehicle stops; and a step 1-2 of detecting the number of times stop and go is not operated due to a low SOC of the energy storage device within the first region of interest, wherein the second step comprises a step 2-1 of comparing the number of times Stop and Go does not operate with a first and second reference value set beforehand, wherein a step 2-2 of increasing the target SOC of the energy storage device is performed when the number of times Stop and Go does not operate is greater than the first reference value, a step 2-3 (S230) of lowering the target SOC of the energy storage device is performed when the number of times Stop and Go is not operated is less than the preset second reference value, and the first reference value is greater than the second reference value. [2] A method for controlling the battery of a mild hybrid vehicle, comprising: a first step of detecting a traffic condition based on a driving state of the vehicle; and a second step of setting a target SOC of an energy storage device based on the detected traffic condition, the first step comprising: a step 1-1 of setting a second region of interest for detecting a history of an SOC of the energy storage device; and a step 1-2 of calculating an average of the SOC of the energy storage device within the second region of interest, where the second step comprises: a step 2-1 of comparing the absolute value of the difference between the calculated average SOC of the energy storage device and the target SOC of the energy storage device with a preset reference value, a step 2-2 of comparing the calculated average of the SOC of the energy storage device and the target SOC of the energy storage device when the comparison result in the step 2-1 shows that the absolute value of the difference between the calculated average SOC of the energy storage device and the target SOC of the energy storage device is greater than the preset reference value, a step 2-3 of lowering the target SOC of the energy storage device when the calculated average SOC of the energy storage device is greater than the target SOC of the energy storage device, and a step 2-4 of increasing the target SOC of the energy storage device when the calculated average SOC of the energy storage device is less than the target SOC of the energy storage device. [3] The method of claim 2, further comprising: a third step of storing the set target SOC of the energy storage device in a memory.

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