HYBRID ELECTRIC VEHICLE AND METHOD OF MOTOR CONTROL FOR THE SAME

Abstract

A hybrid vehicle (HEV) provides an improved sensation of acceleration. An example method for controlling an engine of an HEV which includes a first motor directly connected to an engine and a second motor located at an input side of a transmission, may include determining a requested torque, determining a compensation torque for compensating an acceleration loss in a shift process based on the requested torque, a torque of the second motor, a torque of the engine and information on the shift, determining an available torque of the first motor, and determining a final torque of the first motor based on the compensation torque and the available torque.

Claims

1. A method for controlling a motor of a HEV comprising a first motor directly connected to an engine and a second motor located at an input side of a transmission, the method comprising: determining, by a control unit, a requested torque; determining, by the control unit, a compensation torque for compensating acceleration loss in a shift process based on the requested torque, a torque of the second motor, a torque of the engine, and transmission information; determining, by the control unit, an available torque of the first motor; and determining, by the control unit, a final torque of the first motor based on the compensation torque and the available torque.

2. The method of claim 1, wherein determining the final torque comprises determining a lower torque between the compensation torque and the available torque to be the final torque.

3. The method of claim 1, wherein determining the compensation torque comprises subtracting the torque of the second motor and the engine torque from the requested torque.

4. The method of claim 3, wherein the subtraction is conducted for a torque phase in a power on upshift.

5. The method of claim 1, wherein the transmission information comprises at least one of a shift class, a shift phase, a current gear position in the transmission, a target gear position in the transmission, and a shift progress rate.

6. The method of claim 1, wherein determining the available torque comprises: determining available power for the first motor based on a discharge limit of a battery and power consumption of the second motor; and determining the available torque based on the available power and a temperature and a rotational speed of the first motor.

7. The method of claim 6, wherein determining the available torque is performed according to a predetermined maximum-torque map.

8. The method of claim 1, further comprising determining the final torque of the first motor to be zero, when at least one of a predetermined vehicle-speed condition and a first-motor temperature condition is not satisfied.

9. The method of claim 1, further comprising the determined final torque being output from the first motor.

10. A non-transitory computer-readable medium having stored therein instructions executable by a processor, including instructions executable to perform the method of claim 1.

11. A hybrid electric vehicle comprising: a first motor directly connected to an engine; a second motor located at an input side of a transmission; and a first control unit configured to determine a compensation torque for compensating acceleration loss in a shift process, an available torque of the first motor, and a final torque of the first motor based on the compensation torque and the available torque; wherein the compensation torque is determined based on a requested torque, a torque of the second motor, a torque of the engine, and transmission information.

12. The hybrid electric vehicle of claim 11, wherein the first control unit determines a lower of the compensation torque and the available torque to be the final torque.

13. The hybrid electric vehicle of claim 11, wherein the first control unit determines the final torque by subtracting the torque of the second motor and the engine torque from the requested torque.

14. The hybrid electric vehicle of claim 13, wherein the first control unit determines the compensation torque for a torque phase in a power on upshift.

15. The hybrid electric vehicle of claim 11, wherein the transmission information comprises at least one of a shift class, a shift phase, a current gear position in the transmission, a target gear position in the transmission, and a shift progress rate.

16. The hybrid electric vehicle of claim 11, wherein the first control unit determines an available power for the first motor based on discharge limit of a battery and power consumption of the second motor, and determines the available torque based on the available power and a temperature and a rotational speed of the first motor.

17. The hybrid electric vehicle of claim 16, wherein the determination of the available torque is made according to a predetermined maximum-torque map.

18. The hybrid electric vehicle of claim 11, wherein the first control unit determines the final torque of the first motor to be zero, when at least one of a predetermined vehicle-speed condition and a first-motor temperature condition is not satisfied.

19. The hybrid electric vehicle of claim 11, further comprising a second control unit configured to control the first motor based on a torque command corresponding to the final torque.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0039] FIG. 1 represents a structure of a powertrain of a conventional HEV.

[0040] FIG. 2 represents an example of a quick acceleration process of the conventional HEV.

[0041] FIG. 3 represents an example of a power train of a HEV applicable to embodiments of the present disclosure.

[0042] FIG. 4 represents an example of a control scheme for a HEV according to an embodiment of the present disclosure.

[0043] FIG. 5 represents an example of a controller for reducing acceleration loss in a shift process according to an embodiment of the present disclosure.

[0044] FIG. 6 represents a quick acceleration process to which acceleration-loss-reducing control is applied in a HEV according to an embodiment of the present disclosure.

[0045] FIG. 7 represents an example of torque limit for a motor.

[0046] FIG. 8 represents a flowchart of an example of motor-control procedures for reducing acceleration loss in a shift process.

DETAILED DESCRIPTION

[0047] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings, and the same or similar elements will be given the same reference numerals regardless of reference symbols, and redundant description thereof will be omitted. In the following description, the terms “module” and “unit” for referring to elements are assigned and used interchangeably in consideration of convenience of explanation, and thus, the terms per se do not necessarily have different meanings or functions. Further, in describing the embodiments disclosed in the present specification, when it is determined that a detailed description of related publicly known technology may obscure the gist of the embodiments disclosed in the present specification, the detailed description thereof will be omitted. The accompanying drawings are used to help easily explain various technical features and it should be understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the present disclosure should be construed to extend to any alterations, equivalents and substitutes in addition to those which are particularly set out in the accompanying drawings.

[0048] Although terms including ordinal numbers, such as “first”, “second”, etc., may be used herein to describe various elements, the elements are not limited by these terms. These terms are generally only used to distinguish one element from another.

[0049] When an element is referred to as being “coupled” or “connected” to another element, the element may be directly coupled or connected to the other element. However, it should be understood that another element may be present therebetween. In contrast, when an element is referred to as being “directly coupled” or “directly connected” to another element, it should be understood that there are no other elements therebetween.

[0050] A singular expression includes the plural form unless the context clearly dictates otherwise.

[0051] In the present specification, it should be understood that a term such as “include” or “have” is intended to designate that the features, numbers, steps, operations, elements, parts, or combinations thereof described in the specification are present, and does not preclude the possibility of addition or presence of one or more other features, numbers, steps, operations, elements, parts, or combinations thereof.

[0052] In addition, the term “unit” or “control unit” included in the names of a hybrid control unit (HCU), a motor control unit (MCU), etc. is merely a widely used term for naming a controller that controls a specific vehicle function, and does not mean a generic functional unit. For example, each controller may include a communication device that communicates with another controller or a sensor to control a function assigned thereto, a memory that stores an operating system, a logic command, input/output information, etc., and one or more processors that perform determination, calculation, decision, etc. necessary for controlling a function assigned thereto.

[0053] Before a method for controlling a motor to reduce acceleration loss in a shift process according to an embodiment of the present disclosure is described, a structure of a HEV and a control scheme applicable to embodiments of the present disclosure are described.

[0054] FIG. 3 represents an example of a powertrain of a HEV applicable to embodiments of the present disclosure.

[0055] Since a structure of a powertrain of a HEV applicable to the embodiments is similar in many aspects to the structure of the parrel hybrid system represented in FIG. 1, differences will be mainly described below.

[0056] In FIG. 1, the HSG 121 is connected to the engine 110 via pulleys. However, in the powertrain of FIG. 3, a motor 122 corresponding to the HSG 121 is located between the engine clutch 130 and the engine 110 to be directly connected to the engine 110. It is advantageous that torque-control performance of the motor 122 can be improved due to the direct connection to the engine 110, and, due to no increase in rpm by a pulley ratio, the motor 122 can output a torque in spite of the engine 110 running in high rpm.

[0057] For the sake of describing convenience, in the following description, the motor 122 directly connected to the engine 110 is referred to as “first motor”, and the driving motor 140 connected to an input side of the transmission 150 is referred to as “second motor.”

[0058] Since the elements from the engine clutch 130 to in-between the wheels are similar to those of FIG. 1 described above, repetitive descriptions are omitted.

[0059] FIG. 4 represents an example of a control scheme for the HEV according to an embodiment of the present disclosure.

[0060] In reference to FIG. 4, in the HEV to which embodiments of the present disclosure can be applied, the internal combustion engine 110 may be controlled by an engine control unit 210, the first motor 122 and the second motor 140 by a motor control unit (MCU) 220 for their torques, and the engine clutch 130 by a clutch control unit 230. The engine control unit 210 may also be referred to as an engine management system (EMS). In addition, the transmission 150 is controlled by a transmission control unit 250.

[0061] Each control unit is connected to a hybrid control unit (HCU) 240 controlling the whole process of mode changes as an upper control unit, and, according to control of the HCU 240, provides to the HCU 240 information on driving-mode change, gear shift, control of the engine clutch 130, etc., and/or information necessary for engine-stop control, or performs actions according to control signals.

[0062] For example, the HCU 240 determines whether to perform a change in-between EV-HEV modes according to a driving state of the HEV. To this end, the HCU 240 determines when to open (i.e., disengage) the engine clutch 130, and performs a hydraulic pressure control for the opening. Also, the HCU 240 determines a state (lock-up, slip, open, etc.) of the engine clutch 130, and controls when to stop injecting fuel into the engine 110. Also, for the engine-stop control, the HCU may control regeneration of rotational energy of the engine by transmitting to the MCU 220 a torque command for controlling a torque of the first motor 122. In particular, in regards to embodiments of the present disclosure, the HCU 240 may determine an output torque of the first motor 122 for reducing acceleration loss in a power-on upshift.

[0063] It should be understood that the described control units and the function of each control unit and the way of distinguishing each control unit from the others are only examples and they are not limited by their names. For example, the HCU 240 may be integrated into one of the other control units so that the corresponding function can be provided by the integrated control unit, or the function may be distributed and integrated into two or more other control units.

[0064] The above-described structure of the HEV illustrated in FIGS. 3 and 4 is only an example, and it is obvious to a person of ordinary skill in the art that a HEV applicable to embodiments of the present disclosure is not limited to this structure.

[0065] In an embodiment of the present disclosure, when a HEV accelerated from stop with the accelerator pedal pressed over a predetermined threshold, it is suggested to control a toque of the first motor and thus compensate acceleration loss, so that the acceleration performance and the sensation of acceleration are improved.

[0066] FIG. 5 represents an example of the control unit 240 for reducing acceleration loss in a shift process according to an embodiment of the present disclosure.

[0067] In reference to FIG. 5, to reduce the acceleration loss, the HCU 240 may determine a torque of the first motor based on various input information, and transmit a torque command corresponding to the determined torque to the MCU 220, and the MCU 220 may control the first motor 122 based on the torque command.

[0068] To this end, the HCU 240 may receive a discharge limit of a battery, a state of charge (SOC), a vehicle speed, an APS value, a brake-pedal-position-sensor (BPS) value, an engine-clutch state, an engine torque, a torque of the second motor, a shift class/phase, a target gear position in the transmission, a current gear position in the transmission, a shift progress rate, power consumption of the second motor, a temperature of the first motor, a rotational speed of the first motor, etc. as the input information.

[0069] The discharge limit of the battery and the SOC may be obtained from a battery management system (BMS), the vehicle speed from a vehicle-speed sensor, and the APS value and the BPS value from respective corresponding sensors. Also, the engine-clutch state may be obtained from the clutch control unit 230, the engine torque from the engine control unit 110, and the shift class/phase, the target gear position, the current gear position, and the shift progress rate from the transmission control unit 250. In addition, the torque of the second motor, the power consumption of the second motor, the temperature of the first motor, and the rotational speed of the first motor may be obtained from the motor control unit 220. It should be understood that the sources of the above-described information are only examples and the present disclosure is not limited thereto, so that sensed information may be transmitted via other control unit or after processed.

[0070] Also, the HCU 240 may comprise a requested-torque calculating unit 241, an acceleration-loss calculating unit 242, a first-motor-available-output calculating unit 243, and a first-motor-torque calculating unit 244.

[0071] The requested-torque calculating unit 241 may determine a torque requested by a driver based on the APS value, the BPS value, the discharge limit of the battery, and the SOC of the battery.

[0072] The acceleration-loss calculating unit 242 may calculate a base target torque of the first motor for compensating acceleration loss in an upshift process based on the driver's requested torque, the shift class/phase, the current gear position, the target gear position, the shift progress rate, the engine torque, and the second motor torque information.

[0073] The process of the acceleration-loss calculating unit 242 is described in reference to FIG. 6. FIG. 6 represents a quick acceleration process to which acceleration-loss-reducing control is applied in the HEV according to an embodiment of the present disclosure.

[0074] In reference to FIG. 6, a compensation torque for compensating acceleration loss may be defined as much torque as the sum of the engine torque and the second-motor torque does not satisfy the driver's requested torque. In other words, the compensation torque may have the value obtained by subtracting the engine torque and the second-motor torque from the driver's requested torque. Accordingly, the acceleration-loss calculating unit 242 may determine a compensation torque and decide it to be the base torque of the first motor, where it is determined based on the transmission information that the current shift is a power-on upshift and corresponds to a torque phase.

[0075] The first-motor-available-output calculating unit 243 may determine an available output (torque) of the first motor based on the discharge limit of the battery, the power consumption of the second motor, the temperature of the first motor and the rotational speed of the first motor. In detail, the first-motor-available-output calculating unit 243 determines first-motor available power which is available power which can be supplied to the first motor, by subtracting the power consumption of the second motor from the discharge limit of the battery. The maximum torque which can be exerted within the first-motor available power under the situation of the rotational speed and the temperature of the first motor may be the first-motor available torque.

[0076] For example, for the maximum torque, the map of FIG. 7 may be referred to. FIG. 7 represents an example of torque limit for a motor. In reference to FIG. 7, the maximum torque of the first motor 122 may be predetermined for a range of rpm by operation type. Here, the operation type may comprise a temporary operation and a continuing operation, and since, in the embodiments of the present disclosure, the first motor 122 is not operated continuously, but temporarily to compensate acceleration loss at a torque phase in a shift process, the first-motor-available-output calculating unit 243 may refer to the max torque line of the temporary operation, the present disclosure is not limited thereto though.

[0077] The first-motor-torque calculating unit 244 may determine a final torque of the first motor 122 based on the base torque and the available torque of the first motor, and output to the motor control unit 220 a torque command corresponding to the determined torque. For example, the final torque of the first motor 122 may be determined to be the lower value between the base torque and the available torque.

[0078] The control procedures described above can be represented by the flowchart of FIG. 8.

[0079] FIG. 8 represents a flowchart of an example of motor-control procedures for reducing acceleration loss in a shift process.

[0080] In reference to FIG. 8, first, the requested-torque calculating unit 241 of the HCU 240 may determine the driver's requested torque based on the APS value, the BPS value, the vehicle speed, the discharge limit, and the SOC of the battery at S810.

[0081] Also, the HCU 240 may enter a motor control mode for reducing acceleration loss in the shift process, if a predetermined vehicle-speed condition at S820 and a predetermined first-motor temperature condition at S830 are determined to be satisfied (Yes in S830). The predetermined vehicle-speed condition may be satisfied if a vehicle speed is within a predetermined range, and the first-motor temperature condition satisfied if a temperature of the first motor 122 is below a predetermined temperature.

[0082] The reason for involving the vehicle-speed condition is because upshift such as 1.sup.st gear to 2.sup.nd generally does not occur with a sufficiently low vehicle-speed and acceleration variation is not large with the remaining available torque of the general driving source, i.e., the engine 110 and the second motor 140 comparatively large enough and the vehicle accelerated to a certain high speed (e.g., 4.sup.th-speed gear position).

[0083] Also, the reason for involving the first-motor temperature condition is because the first motor is difficult to output sufficient torque under its over-heated state despite the discharge limit of the battery high enough.

[0084] The detailed thresholds for the vehicle-speed condition and the first-motor temperature condition may be determined through a real test by vehicle, which the present disclosure is not limited to.

[0085] As both of the vehicle-speed condition (S820) and the first-motor temperature condition (S830) are determined to be satisfied (Yes in S830), the acceleration-loss calculating unit 242 and the first-motor-available-output calculating unit 243 may determine the base torque and the available torque of the first motor, respectively.

[0086] In detail, the acceleration-loss calculating unit 242 may determine the compensation torque for compensating acceleration loss based on the driver's requested torque, the shift class/phase, the current gear position, the target gear position, the shift progress rate, the engine torque, the second-motor torque information at S840A, and determine the compensation torque to be the base torque of the first motor at S850A.

[0087] Also, the first-motor-available-output calculating unit 243 may determine the first-motor available power which is the available power which can be supplied to the first motor, by subtracting the power consumption of the second motor from the discharge limit of the battery at S840B. The first-motor-available-output calculating unit 243 may determine the maximum torque exerted within the first-motor available power under the situation of the rotational speed and the temperature of the first motor to be the first-motor available torque at S850B.

[0088] The first-motor-torque calculating unit 244 may determine the lower torque between the base torque determined in the acceleration-loss calculating unit 242 and the available torque determined in the first-motor available output calculating unit 243 to be the torque of the first motor at S860.

[0089] If the vehicle-speed condition not satisfied (No in S820) or the first-motor temperature condition not satisfied (No in S830), the first-motor torque calculating unit 244 may determine the torque of the first motor to be zero at S870.

[0090] The first-motor torque calculating unit 244 may transmit to the motor control unit 220 a torque command corresponding to the determined torque, and the motor control unit 220 may control the first motor 122 to output the torque corresponding to the torque command at S880.

[0091] According to the embodiments of the present disclosure described above, acceleration loss can be reduced by controlling a torque of the first motor and thus sensation of acceleration in a shift process can be improved, in spite of the vehicle quickly accelerated by high APS values in a HEV having a multi-speed transmission.

[0092] On the other hand, the present disclosure described above may be embodied as computer-readable code on a medium in which a program is recorded. The computer-readable medium includes all types of recording devices in which data readable by a computer system is stored. Examples of the computer-readable medium include a hard disk drive (HDD), a solid-state drive (SSD), a silicon disk drive (SDD), a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, etc. Therefore, the above detailed description should not be construed as restrictive and should be considered as illustrative in all respects. The scope of the present disclosure should be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the present disclosure are included in the scope of the present disclosure.