Modulating performance of an electric motor in a hybrid vehicle during a combustion event

Abstract

The present disclosure relates to a system for regulating performance of an electric motor in a hybrid vehicle during a combustion event. The system includes an internal combustion engine including a cylinder, an electric motor including an electric motor shaft and connected to the internal combustion engine via a drive shaft, and an inverter controller connected to the electric motor. The inverter controller includes an electronic processor configured to receive a rotational position of the electric motor shaft, determine whether a combustion event occurred in the cylinder based on the rotational position of the electric motor shaft, and perform a selected one from a group including increasing torque generated by the electric motor and decreasing torque generated by the electric motor when the combustion event occurred in the cylinder.

Description

Technical Field

[0001] This disclosure relates to systems and methods for regulating the performance of an electric motor in a hybrid vehicle during a combustion event. Background Technology

[0002] Hybrid vehicles include an internal combustion engine connected to what is commonly referred to as an "electric motor." However, it should be understood that, in the context of a hybrid vehicle powertrain, the so-called electric motor is typically a combination of one or more electrical devices. At least one of these electrical devices operates as an electric motor, and another acts as a generator. A single electrical device may also operate as a motor in one mode and as a generator in another. When the internal combustion engine comprises a small number of cylinders (e.g., three or fewer), hybrid vehicles may experience operational instability in the form of speed and current oscillations.

[0003] Currently, systems called surge dampers exist to smooth speed and current oscillations during instantaneous load changes (e.g., in hybrid vehicles, pressing or releasing the accelerator pedal, commonly referred to as the "throttle pedal"). Surge damper systems treat the hybrid vehicle's drivetrain as a spring-dampened system and control the torque delivery gradient to reduce drivetrain twist and subsequent speed oscillations. However, surge damper systems are ineffective at smoothing speed or current oscillations during steady-state operation of the internal combustion engine at a constant engine speed. Steady-state operation of the internal combustion engine occurs when it operates at a constant speed or when its speed increases linearly (e.g., after a sudden acceleration event). Summary of the Invention

[0004] The embodiments described herein particularly provide systems and methods for regulating the performance of an electric motor in a hybrid vehicle during combustion events in steady-state or transient operation of an internal combustion engine. As described in more detail below, an inverter controller connected to the electric motor uses sensor data (e.g., electric motor shaft angular acceleration data, electric motor torque variation data, and electric motor current variation data) to determine when a combustion event will occur in the cylinder of the internal combustion engine. Combustion events typically occur near the top dead center (TDC) position associated with the cylinder. When a combustion event occurs, the inverter controller can alter the performance of the electric motor to increase operational smoothness or smooth oscillations in rotational speed or current within the electric motor, thereby providing a better driving experience or protecting the components of the electric motor.

[0005] An embodiment provides a system for regulating the performance of an electric motor in a hybrid vehicle during a combustion event. The system includes: an internal combustion engine including cylinders, an electric motor including an electric motor shaft and connected to the internal combustion engine via a drive shaft, and an inverter controller connected to the electric motor. The inverter controller includes an electronic processor configured to receive the rotational position of the electric motor shaft; determine, based on the rotational position of the electric motor shaft, whether a combustion event has occurred in the cylinder; and, when a combustion event occurs in the cylinder, execute one selected from the group consisting of increasing the torque generated by the electric motor and decreasing the torque generated by the electric motor.

[0006] Another embodiment provides a method for adjusting the performance of an electric motor in a hybrid vehicle during a combustion event. The method includes receiving, with an electronic processor, the rotational position of the electric motor shaft; determining, based on the rotational position of the electric motor shaft, whether a combustion event has occurred in a cylinder of an internal combustion engine connected to the electric motor via a drive shaft; and, when a combustion event occurs in the cylinder, performing one selected from the group consisting of increasing the torque generated by the electric motor and decreasing the torque generated by the electric motor.

[0007] Other aspects, features, and embodiments will become apparent upon consideration of the detailed description and accompanying drawings. Attached Figure Description

[0008] Figure 1 This is a block diagram of a system for adjusting the performance of an electric motor in a hybrid vehicle during a combustion event, according to an embodiment.

[0009] Figure 2 for Figure 1 An illustrative example of the combustion cycle in the cylinder of a system.

[0010] Figure 3 According to the embodiments Figure 1 The diagram shows the system's inverter controller and multiple sensors from which the inverter controller receives data.

[0011] Figure 4 This is an illustrative example of determining the occurrence of a combustion event based on data on changes in the shaft angular acceleration of an electric motor.

[0012] Figure 5 This is an illustrative example of determining the occurrence of a combustion event based on data on changes in the torque of an electric motor.

[0013] Figure 6 For use during a combustion event according to an embodiment Figure 1 The flowchart shows a method for adjusting the performance of the electric motor in a hybrid vehicle using a system. Detailed Implementation

[0014] Before explaining any embodiment in detail, it should be understood that this disclosure is not intended to limit its application to the details of the construction and arrangement of the components set forth in the following description or illustrated in the following drawings. Embodiments can have other configurations and can be practiced or carried out in various ways.

[0015] Multiple hardware and software-based devices and multiple different structural components can be used to implement various embodiments. Furthermore, embodiments may include hardware, software, and electronic components or modules, which, for the purposes of discussion, may be described and illustrated as if most components were implemented solely in hardware. However, those skilled in the art will recognize from this detailed description that, in at least one embodiment, the electronic aspects of the invention may be implemented in software executable by one or more processors (e.g., stored on a non-transitory computer-readable medium). For example, the “control unit” and “controller” described in the specification may include one or more electronic processors, one or more memory modules including a non-transitory computer-readable medium, one or more communication interfaces, one or more application-specific integrated circuits (ASICs), and various connections (e.g., system buses) connecting the various components.

[0016] Figure 1 An example of a system 100 for regulating the performance of an electric motor in a hybrid vehicle during a combustion event is provided. System 100 includes a hybrid vehicle 105. Although the hybrid vehicle 105 is described as a four-wheeled vehicle, it can encompass various types and designs of vehicles. For example, the hybrid vehicle 105 can be a car, motorcycle, truck, bus, semi-tractor, etc.

[0017] The hybrid vehicle 105 includes an internal combustion engine 110 and an electric motor 125. The internal combustion engine 110 includes one or more cylinders (e.g., cylinder 120) that generate combustion events by moving pistons up and down to rotate the internal combustion engine shaft 122 (crankshaft). Figure 2 The diagram provides an illustrative example of the combustion cycle in a cylinder. When the piston is at or near top dead center (TDC), in... Figure 2 A combustion event occurs between step "2. Compression" and step "3. Power". In some embodiments, the internal combustion engine 110 includes a limited number of cylinders (e.g., three cylinders or fewer). It should be understood that Figure 1 The three cylinders described herein are purely illustrative, and the internal combustion engine 110 may include, with Figure 1The electric motor 125 includes a generator. The generator charges a battery (not shown). The battery provides the electric motor 125 with the power required to rotate the electric motor shaft 130. An inverter controller 135 is connected to the electric motor 125 (e.g., the inverter controller 135 may be mounted on or included in the housing of the electric motor 125) and controls the functions of the electric motor 125, including the rate at which the electric motor 125 rotates the electric motor shaft 130. The electric motor shaft 130 and the internal combustion engine shaft 122 are connected by a drive shaft 140 via one or more couplers. The drive shaft 140 is connected to a transmission (not shown), and the rotational torque of the drive shaft 140, distributed by the transmission and axles, causes the rotation of the drive wheels of the hybrid vehicle 105.

[0018] Figure 3 for Figure 1 A block diagram of an inverter controller 135 of a system and sensors that provide data to the inverter controller 135. The inverter controller 135 includes multiple electrical and electronic components that provide power, operational control, and protection to components and modules within the inverter controller 135. The inverter controller 135 particularly includes an electronic processor 300 (such as a programmable electronic microprocessor, microcontroller, or similar device), a memory 305 (e.g., a non-transitory machine-readable medium), and an interface 310. The electronic processor 300 is communicatively connected to the memory 305 and the interface 310. In some embodiments, the electronic processor 300, in coordination with software stored in the memory 305 and information from sensors, is configured to implement, in particular, the methods described herein.

[0019] Inverter controller 135 may be implemented in several independent controllers (e.g., programmable electronic controllers), each configured to perform a specific function or sub-function. Furthermore, inverter controller 135 may contain submodules including additional electronic processors, memory, or application-specific integrated circuits (ASICs) for handling communication functions, signal processing, and the applications of the methods listed below. In other embodiments, inverter controller 135 includes additional, fewer, or different components.

[0020] like Figure 3 As described herein, the electronic processor 300 can communicate with one or more sensors via interface 310. The one or more sensors include an electric motor shaft position sensor 315 (e.g., a resolver or encoder), an electric motor speed sensor 320, a torque sensor 325 (e.g., a transducer), and a current sensor 330 (e.g., an ammeter or multimeter). It should be understood that, although in Figure 1Not explicitly stated, but the electric motor shaft position sensor 315, electric motor speed sensor 320, torque sensor 325, and current sensor 330 are included in system 100. In some embodiments, the electric motor shaft position sensor 315, electric motor speed sensor 320, and torque sensor 325 are located on or near the electric motor shaft 130. In some embodiments, the current sensor 330 is mounted within the electric motor 125 (specifically, within the generator).

[0021] In some embodiments, the electronic processor 300 determines the actual rotational position associated with a cylinder (e.g., cylinder 120). The actual rotational position is the location where a combustion event occurs within the rotational cycle of the electric motor shaft 130. In some embodiments, the actual rotational position associated with cylinder 120 must be re-determined when the generator and motor included in electric motor 125 are disengaged, or when electric motor 125 and internal combustion engine 110 are disengaged. For example, in some embodiments, when the hybrid vehicle 105 does not include a clutch between internal combustion engine 110 and electric motor 125, the actual rotational position associated with cylinder 120 is determined or re-determined by the electronic processor 300 during the manufacture of hybrid vehicle 105, maintenance of hybrid vehicle 105, or both. In some embodiments, when the hybrid vehicle 105 includes a clutch between internal combustion engine 110 and electric motor 125, the actual rotational position associated with cylinder 120 is determined or re-determined by the electronic processor 300 when the clutch is engaged.

[0022] In some embodiments, the electronic processor 300 determines the actual rotational position based on one or more selected from the group consisting of electric motor shaft angular acceleration data, electric motor torque variation data, and electric motor current variation data.

[0023] For example, in some embodiments, the electronic processor 300 determines the actual rotational position based on angular acceleration data of the motor shaft obtained using, for example, data from the motor speed sensor 320. Continuing the example above, when the angular acceleration (gradient of angular velocity) of the motor shaft 130 changes from negative to positive, the electronic processor 300 determines the rotational position of the motor shaft 130 via, for example, the motor shaft position sensor 315. In some embodiments, the rotational position of the motor shaft 130 determined when the angular acceleration of the motor shaft 130 changes from negative to positive is determined as the actual rotational position. Figure 4 This is an illustrative example of determining the occurrence of a combustion event based on data on changes in the shaft angular acceleration of an electric motor. Figure 4 This describes data collected from hybrid vehicles with internal combustion engines having a single cylinder. From... Figure 4 As can be seen from this, during the compression stroke of the cylinder (in Figure 2 During the compression phase (as explained in section 2.), the angular acceleration of the electric motor shaft is negative, and during the expansion stroke after cylinder ignition (in... Figure 2 (As explained in section 3. Work) During this period, the angular acceleration of the electric motor shaft is positive.

[0024] In another example, the electronic processor 300 determines the actual rotational position based on motor torque variation data received from, for example, a torque sensor 325. When the torque gradient of the motor shaft 130 changes from positive to negative, the electronic processor 300 determines the rotational position of the motor shaft 130 via, for example, a motor shaft position sensor 315. In some embodiments, the rotational position of the motor shaft 130 determined when the torque gradient of the motor shaft 130 changes from positive to negative is determined as the actual rotational position. Figure 5 This is an illustrative example of determining the occurrence of a combustion event based on data on changes in the torque of an electric motor. Figure 5 This describes data collected from hybrid vehicles with internal combustion engines having a single cylinder. From... Figure 5 As can be seen from this, during the compression stroke of the cylinder (in Figure 2 During the compression phase (as explained in section 2.), the torque gradient of the electric motor shaft is positive, and during the expansion stroke after cylinder ignition (in... Figure 2 During the period described in "3. Work" (as explained in the previous section), the torque gradient of the electric motor shaft is negative. It should be understood that the method for determining the actual rotational position described herein is illustrative, and other methods may exist for the electronic processor 300 to determine the actual rotational position based on one or more selected from the group containing electric motor shaft angular acceleration data, electric motor torque variation data, and electric motor current variation data.

[0025] In some of the examples provided above, the change in gradient is evaluated or otherwise assessed. In some cases, the change occurs from positive to negative. In others, it occurs from negative to positive. In many cases, the specific change is not important, and simply evaluating the change in gradient sign is sufficient. Furthermore, when the gradient changes from negative to positive or from positive to negative, evaluating when the gradient crosses zero may be sufficient.

[0026] In some embodiments, when the internal combustion engine 110 is a four-stroke engine, intermediate changes in the sign of the gradient associated with the torque of the electric motor shaft 130, the angular acceleration of the electric motor shaft 130 (angular velocity gradient of the electric motor shaft 130), or the gradient associated with the current of the electric motor 125 may not correspond to a combustion event. For example, when the exhaust valve or intake valve in the internal combustion engine 110 is open, the electric motor shaft 130 may experience angular acceleration even if no combustion event occurs. However, a change in the sign of the gradient associated with a combustion event will be associated with a larger rate of change in the angular velocity of the electric motor shaft 130, the torque of the electric motor shaft 130, or the current of the electric motor 125 compared to a change in the sign of the gradient not associated with a combustion event. Therefore, in some embodiments, the electronic processor 300 may determine that a change in the sign of the gradient is associated with a combustion event when the absolute value of the rate of change of the angular velocity of the electric motor shaft 130, the torque of the electric motor shaft 130, or the current of the electric motor 125 is greater than a predetermined threshold.

[0027] In some embodiments, when the internal combustion engine 110 includes multiple cylinders, the electronic processor 300 may receive the number of cylinders included in the internal combustion engine 110, the position associated with each cylinder, or both. For example, in a three-cylinder internal combustion engine, the electronic processor 300 may receive information specifying that the internal combustion engine 110 has three cylinders and determining that there is a 240-degree separation between each combustion event. In some embodiments, the electronic processor 300 receives information as input from a technician via a user interface of a device, such as an inverter controller 135, in communication with the device.

[0028] In some embodiments where the internal combustion engine 110 includes multiple cylinders, the electronic processor 300 may determine the actual rotational position of each cylinder based on one or more selected from the group consisting of electric motor shaft angular acceleration data, electric motor torque variation data, and electric motor current variation data. In other embodiments where the internal combustion engine 110 includes multiple cylinders, the electronic processor 300 may determine the actual rotational position of a single cylinder (e.g., cylinder 120) based on one or more selected from the group consisting of electric motor shaft angular acceleration data, electric motor torque variation data, and electric motor current variation data, and determine the actual rotational position of each cylinder (other than cylinder 120) based on the actual rotational position associated with cylinder 120 and the aforementioned received information. For example, the electronic processor 300 may determine that the actual rotational position associated with cylinder 120 is five degrees and receive information indicating that the internal combustion engine 110 has three cylinders. Based on the received information and the actual rotational position associated with cylinder 120, it may determine that a combustion event occurs at five degrees, 245 degrees, and 485 degrees.

[0029] Figure 6A method 700 for adjusting the performance of an electric motor in a hybrid vehicle during a combustion event is described. In some embodiments, method 700 begins at step 705 when an electronic processor 300 receives, for example, the rotational position of an electric motor shaft 130 from an electric motor shaft position sensor 315. In some embodiments, at step 710, the electronic processor 300 determines whether a combustion event has occurred in a cylinder (e.g., cylinder 120) based on the rotational position of the electric motor shaft 130 (the received rotational position of the electric motor shaft 130). For example, the electronic processor 300 can determine whether a combustion event has occurred in cylinder 120 by comparing the received rotational position with the actual rotational position associated with cylinder 120. The electronic processor 300 can retrieve the actual rotational position associated with cylinder 120 from memory 305. In some embodiments, when the actual rotational position matches the received rotational position, the electronic processor 300 determines that a combustion event has occurred.

[0030] In some embodiments, when a combustion event occurs in cylinder 120, electronic processor 300 performs an action selected from the group consisting of increasing and decreasing the torque generated by electric motor 125. In some embodiments, the increase in torque is proportional to the angular rotational acceleration of drive shaft 140 caused by the combustion event. In some embodiments, the amount by which electronic processor 300 increases torque is a value included in memory 305. The combustion event instantaneously increases the rotational speed of drive shaft 140 and the speed of hybrid vehicle 105. By increasing the torque generated by electric motor 125, the rotational speed of drive shaft 140 (and therefore the speed of hybrid vehicle 105) will remain more constant. By reducing speed oscillations in the rotational speed of drive shaft 140, electronic processor 300 reduces the likelihood that the driver or passengers of hybrid vehicle 105 will perceive any operational instability (e.g., noise or speed oscillations) associated with hybrid vehicle 105. By reducing speed oscillations in the rotational speed of the drive shaft 140, the electronic processor 300 reduces the chance of damage to the coupler connecting the electric motor 125, the drive shaft 140, and the internal combustion engine 110 caused by harmonics generated by speed oscillations. However, the increased torque generated by the electric motor 125 during a combustion event results in larger current oscillations in the electric motor 125, and these current oscillations can damage components included in the electric motor 125.

[0031] In some embodiments, when a combustion event occurs, the electronic processor 300 reduces the torque generated by the electric motor 125. In some embodiments, the reduction in torque is proportional to the increase in current in the electric motor 125 caused by the combustion event. In some embodiments, the amount by which the electronic processor 300 reduces torque is a value included in memory 305. As described above, current oscillations damage the hardware of the electric motor 125. Reducing the torque generated by the electric motor 125 during a combustion event reduces the current in the electric motor 125 during the combustion event and smooths out current oscillations. Reducing the torque generated by the electric motor 125 during a combustion event can increase the lifespan of the components of the electric motor 125. However, reducing the torque generated by the electric motor 125 during a combustion event will increase the oscillations in the rotational speed of the drive shaft 140 and the speed of the hybrid vehicle 105.

[0032] In some embodiments, the electronic processor 300 is configured to periodically (e.g., every ten minutes) verify the actual rotational position during a drive cycle of the hybrid vehicle 105 by varying the actual rotational position and evaluating improved or deteriorated operational smoothness. For example, the rotational position at which the spark point (combustion event) occurs may vary depending on the speed load point of the internal combustion engine 110. In some embodiments, the actual rotational position for a speed load point of the internal combustion engine 110 is learned or determined based on one or more selected from the group comprising electric motor shaft angular acceleration data, electric motor torque variation data, and electric motor current variation data. When the internal combustion engine 110 operates at different speed load points, it may advantageously be "staged controlled" or the actual rotational position may be changed by one or several degrees (e.g., from 480 degrees to 482 degrees or 478 degrees). In some embodiments, the electronic processor 300 performs method 700 using the changed actual rotational position.

[0033] In some embodiments, the electronic processor 300 determines whether the altered actual rotational position execution method 700 improves or deteriorates the operational smoothness of the hybrid vehicle 105 by measuring, for example, speed oscillations or current oscillations using the electric motor speed sensor 320 or the current sensor 330. For example, when using the altered actual rotational position execution method 700 to increase the torque generated by the electric motor 125 results in a larger speed oscillation than using the actual rotational position execution method 700 to increase the torque generated by the electric motor 125, the electronic processor 300 determines that the altered actual rotational position deteriorates the operational smoothness of the hybrid vehicle 105.

[0034] In some embodiments, when the electronic processor 300 determines that performing method 700 with a changed actual rotational position degrades the operational smoothness of the hybrid vehicle 105, the electronic processor 300 changes the actual rotational position again based on the actual rotational position and previous changes made to the actual rotational position. In some embodiments, when the electronic processor 300 determines that the changed actual rotational position improves the operational smoothness of the hybrid vehicle 105, the electronic processor 300 stores the changed actual rotational position in memory 305 and performs method 700 using the changed actual rotational position. In other embodiments, the electronic processor 300 changes the actual rotational position and evaluates the effect of the changed actual rotational position on the operational smoothness of the hybrid vehicle 105 until the electronic processor 300 determines the actual rotational position that causes maximum operational smoothness, stores the actual rotational position that causes maximum operational smoothness in memory 305, and performs method 700 using the actual rotational position that causes maximum operational smoothness.

[0035] Therefore, the embodiments described herein particularly provide systems and methods for regulating the performance of an electric motor in a hybrid vehicle during a combustion event. Various features and advantages of the embodiments are set forth in the following claims.

Claims

1. A system for regulating the performance of an electric motor in a hybrid vehicle during a combustion event, the system comprising: An internal combustion engine, the internal combustion engine including cylinders; An electric motor, the electric motor including an electric motor shaft and connected to the internal combustion engine via a drive shaft; as well as An inverter controller, connected to the electric motor, includes an electronic processor configured to... Receive the rotational position of the electric motor shaft; Whether a combustion event has occurred in the cylinder is determined based on the rotational position of the electric motor shaft; as well as When a combustion event occurs in the cylinder, one of the following is performed: increasing the torque generated by the electric motor and decreasing the torque generated by the electric motor.

2. The system according to claim 1, wherein, The increase in torque is proportional to the angular rotational acceleration of the drive shaft caused by the combustion event, and the decrease in torque is proportional to the increase in current in the electric motor caused by the combustion event.

3. The system according to claim 1, wherein, The system also includes a memory connected to the electronic processor, wherein the electronic processor is further configured to determine whether the combustion event has occurred in the cylinder by comparing the rotational position of the electric motor shaft with an actual rotational position associated with the cylinder and stored in the memory, based on the rotational position of the electric motor shaft.

4. The system according to claim 3, wherein, The electronic processor is configured to determine the actual rotational position associated with the cylinder based on one or more selected from a group containing electric motor shaft angular acceleration data, electric motor torque variation data, and electric motor current variation data.

5. The system according to claim 4, wherein, The electronic processor is configured to determine the actual rotational position based on the electric motor shaft angular acceleration data in the following manner. When the angular acceleration of the electric motor shaft changes from negative to positive, the rotational position of the electric motor shaft is determined to be the actual rotational position associated with the cylinder.

6. The system according to claim 4, wherein, The electronic processor is configured to determine the actual rotational position based on the electric motor torque variation data in the following manner. When the torque gradient of the electric motor shaft changes from positive to negative, the rotational position of the electric motor shaft is determined to be the actual rotational position associated with the cylinder.

7. The system according to claim 4, wherein, When the hybrid vehicle does not include a clutch between the internal combustion engine and the electric motor, the electronic processor is configured to determine the actual rotational position during the manufacture of the hybrid vehicle, the maintenance of the hybrid vehicle, or both.

8. The system according to claim 4, wherein, The electronic processor is configured to periodically verify the actual rotational position by changing the actual rotational position and evaluating improved or deteriorated operational smoothness during the hybrid vehicle's drive cycle.

9. The system according to claim 4, wherein, When the hybrid vehicle includes a clutch between the internal combustion engine and the electric motor, the electronic processor is configured to determine the actual rotational position when the clutch is engaged.

10. A method for adjusting the performance of an electric motor in a hybrid vehicle during a combustion event, the method comprising: The rotational position of the electric motor shaft is received by an electronic processor; Whether a combustion event occurs in the cylinder of an internal combustion engine is determined based on the rotational position of the electric motor shaft, which is connected to the electric motor via a drive shaft; as well as When a combustion event occurs in the cylinder, one of the following is performed: increasing the torque generated by the electric motor and decreasing the torque generated by the electric motor.

11. The method according to claim 10, wherein, Increasing the torque generated by the electric motor includes increasing the torque by a value proportional to the angular rotational acceleration of the drive shaft caused by the combustion event, and decreasing the torque generated by the electric motor includes decreasing the torque by a value proportional to the increase in current in the electric motor caused by the combustion event.

12. The method according to claim 10, wherein, The method further includes determining whether the combustion event has occurred in the cylinder by comparing the rotational position of the electric motor shaft with an actual rotational position, the actual rotational position being associated with the cylinder and stored in a memory.

13. The method of claim 12, wherein, The method further includes determining the actual rotational position associated with the cylinder based on one or more selected from the group consisting of electric motor shaft angular acceleration data, electric motor torque variation data, and electric motor current variation data.

14. The method according to claim 13, wherein, Determining the actual rotational position based on the electric motor shaft angular acceleration data includes... When the angular acceleration of the electric motor shaft changes from negative to positive, the rotational position of the electric motor shaft is determined to be the actual rotational position associated with the cylinder.

15. The method according to claim 13, wherein, Determining the actual rotation position based on the electric motor torque variation data includes... When the torque gradient of the electric motor shaft changes from positive to negative, the rotational position of the electric motor shaft is determined to be the actual rotational position associated with the cylinder.

16. The method according to claim 13, wherein, When the hybrid vehicle does not include a clutch between the internal combustion engine and the electric motor, determining the actual rotational position associated with the cylinder includes determining the actual rotational position during the manufacture of the hybrid vehicle, the maintenance of the hybrid vehicle, or both.

17. The method according to claim 16, wherein, The method also includes periodically verifying the actual rotational position by changing the actual rotational position and evaluating improved or deteriorated operational smoothness during the drive cycle of the hybrid vehicle.

18. The method according to claim 13, wherein, When the hybrid vehicle includes a clutch between the internal combustion engine and the electric motor, determining the actual rotational position associated with the cylinder includes determining the actual rotational position when the clutch is engaged.

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