Method for controlling a two-speed AWD vehicle

Abstract

A method for controlling a two-speed AWD vehicle is disclosed. According to the present embodiment, control of an electric vehicle can be carried out by outputting an AWD control torque to a driveshaft by means of a detailed torque control in a 4H or 4L mode.

Description

The present invention relates to a method for controlling a two-speed AWD vehicle, which aims to enable the two-speed AWD vehicle to drive in an optimized state. Electronic all-wheel drive (EWD) is a system that distributes a vehicle's drive power to the front and rear wheels using an electronic control unit. Instead of a mechanical connection, the electronic AWD manages the drive power using a sensor and an electric motor. The electronic AWD captures data in real time by recording a vehicle's speed, wheel rotation speed, steering angle, accelerator pedal input, road conditions, and the like. Furthermore, the electronic control unit (ECU) uses the collected data to calculate an optimal distribution of drive power. Depending on requirements, the electronic control unit distributes the drive power to the front and rear wheels, or to the front left and right wheels and the rear left and right wheels. To achieve the aforementioned operation, the vehicle is equipped with an electric clutch or an electric motor, and the electronic clutch transmits power to the wheels or interrupts power transmission. Additionally, a hybrid AWD system drives specific wheels using an electric motor. The electronic AWD improves fuel efficiency by driving only the front wheels under normal conditions. When needed, the electronic AWD can quickly switch to all-wheel drive, instantly adjusting the drive power to changes in road conditions with high responsiveness and thus preventing wheel slippage. Because the electronic AWD can be structurally simplified and requires fewer components than the conventional mechanical AWD, the electronic AWD enables a weight reduction. The electronic AWD can adjust the power distribution ratio between a main drive shaft and an auxiliary drive shaft depending on the driving situation. For example, in a front-wheel drive (2WD) vehicle, 100% of the power is distributed to the front wheels and 0% to the rear wheels. Furthermore, electronic all-wheel drive (AWD) allows for varying power distribution to the front wheels. This means that a maximum of 50% of the power can be distributed to the front wheels and 50% to the rear wheels. General passenger cars are driven in 4A mode (all-wheel drive automatic mode), which actively and autonomously adapts the torque distribution between the front and rear wheels to the driving situation. However, off-road special vehicles, such as large SUVs, also offer a switch-activated 4H mode (4WD high gear mode) and a 4L mode (4WD low gear mode), thus providing a function for directly connecting a shaft with maximum torque. When the 4H / 4L mode is activated, the off-road special vehicle does not reach an optimized control state that takes into account all the different driving conditions of the vehicle, resulting in a phenomenon where the drive force is simply transmitted to a driveshaft with maximum torque. In this case, excessive torque can be transmitted to the driveshaft and drive system, which can reduce service life and increase energy consumption. Therefore, countermeasures are necessary. [Document of related technology] (Patent document 1) Korean Patent No. 10-2440674 (September 1, 2022) The present invention is intended to solve these problems and aims to provide a method for controlling a two-speed AWD vehicle, wherein the method is able to control a minimum torque required to directly connect a driveshaft in an optimal condition in a 4H or 4L mode of the two-speed AWD vehicle. This problem is solved by a method according to claim 1. A method for controlling a two-speed AWD vehicle according to an embodiment of the present invention comprises: a first step ST100 of selecting a 4H mode or a 4L mode and enabling the driving of a two-speed AWD vehicle; and a second step ST200 of performing a control to output an AWD control torque transmitted to a driveshaft as a minimum torque value according to the mode selected from the 4H mode or the 4L mode. The second step ST200 further includes: a traction control step ST210 of calculating the total traction torque to output a maximum value (Max) for torque control according to different driving situations of the two-speed all-wheel drive vehicle; a TCB control step ST220 to control the torque generated when the two-speed all-wheel drive vehicle is in a low-speed, high-steer driving condition; and a handling control step ST230 of calculating the handling control torque based on a driving mode that corresponds to the cornering characteristics of the two-speed all-wheel drive vehicle. In the traction control step ST210, different gain values ​​are applied based on the shift positions of the two-speed AWD vehicle. In the traction control step ST210, a minimum torque value (β) is applied to the gain value of the two-speed AWD vehicle, and the maximum value (Max) is selected from calculated result torque values. In the second step ST200, the torque value calculated in the TCB control step ST220 is applied to the maximum value (Max) and a minimum value (Min) is selected from the calculated result values, and the AWD control torque is calculated by calculating the minimum value (Min) and a handling torque value output in the handling control step ST230 together. The traction control step ST210 further includes: a basic anticipatory torque control step ST211 of correcting a load distribution ratio by assigning a weight value to ensure performance according to the gear position and driving mode; a roll prevention torque control step ST212 of classifying levels according to an uphill driving condition and gradient angle of a hillside road when the two-speed AWD vehicle is traveling uphill or downhill; a hill start assist torque control step ST213 of preventing wheel slip when the two-speed AWD vehicle starts moving; and a low-gear shift torque control step ST214 of executing a control to output a low-gear shift torque for each gear position when the two-speed AWD vehicle shifts into a low gear position. In the roll prevention torque control step ST212, the uphill driving condition is determined based on longitudinal acceleration, lateral acceleration, wheel speed, steering angle, accelerator pedal opening degree and brake pressure information. In the ST213 hill start assist torque control step, a vehicle speed criterion and a torque control value are set differently according to the driving mode of the two-speed AWD vehicle. In the launch assist torque control step ST213, a torque control value is classified for each gear shift position according to the accelerator pedal opening degree of the two-speed AWD vehicle, and a launch assist torque output is based on a speed of the two-speed AWD vehicle. In the shift torque control step for low gears ST214, an entry point is controlled in a non-braking or non-acceleration state in which a target shift position is lower than an actual shift position. The TCB control step ST220 is determined based on the driving mode of the two-speed AWD vehicle, longitudinal acceleration information, lateral acceleration information, wheel speed information, and vehicle speed. In the handling control step ST230, the cornering torque is calculated according to a cornering weight value according to a lateral acceleration, a yaw rate and a steering angle according to the cornering characteristics of the two-speed AWD vehicle. The 4H or 4L mode of the two-speed AWD vehicle is classified as follows: a P shift-stop mode, in which the two-speed AWD vehicle switches to 2WD when in a P shift-stop state; a D / R / N shift-stop mode to control a driver's driving when the two-speed AWD vehicle is in a D shift-stop state, an R shift-stop state, or an N shift-stop state; a gearshift standby mode to limit the torque that occurs when the two-speed AWD vehicle suddenly shifts from a low shift position to a high shift position or from a high shift position to a low shift position; a low-speed optimized driving mode, in which a minimum torque value is output to the driveshaft in the 4A mode of the two-speed AWD vehicle;and a driving mode optimized for high speeds, in which a maximum torque value is output to the driveshaft in the 4A mode of the two-speed AWD vehicle. Preferred embodiments are explained in more detail below with reference to the accompanying drawings. These show: Fig. 1 a flowchart illustrating a method for controlling a two-speed AWD vehicle according to the present embodiment. Fig. 2 a flowchart illustrating a detailed configuration of a traction control step in the method for controlling a two-speed AWD vehicle according to the present embodiment. Fig. 3 a view illustrating detailed configurations of modes 4H and 4L in the method for controlling a two-speed AWD vehicle according to the present embodiment. Fig. 4 a view briefly illustrating a process for calculating the AWD control torque by a second step in the method for controlling a two-speed AWD vehicle according to the present embodiment. The advantages and features of the present invention and the methods for achieving these advantages and features will become clear with reference to the exemplary embodiments described in detail below in conjunction with the accompanying drawings. However, the present invention is not limited to the exemplary embodiments disclosed herein, but can be implemented in various forms. The exemplary embodiments of the present invention are provided so that the present invention is fully disclosed and a person with average technical knowledge in the field to which the present invention relates can fully understand its scope. The present invention is defined exclusively by the scope of the accompanying claims. Throughout the entire description, the same reference numerals denote the same components. A configuration in which one component is "connected" or "coupled" to another includes both a configuration in which one component is directly connected or coupled to another component and a configuration in which another component is positioned between them. In contrast, no components are positioned between components when one component is "directly connected" or "directly coupled" to another component. The term "and / or" encompasses all combinations of one or more of the elements mentioned. The terms used in this description serve to explain the exemplary embodiments and not to limit the present invention. Unless expressly stated otherwise in this description, a singular form also includes a plural form. The terms "have (comprise)" and / or "having (comprise)" used in the description are intended to specify the presence of the mentioned components, steps, processes, and / or elements, but do not exclude the presence or addition of one or more further components, steps, processes, and / or elements. The terms "first", "second", and similar can be used to describe different components, but the components are not limited by these terms. These terms are merely used to distinguish one component from another. A method for controlling a two-speed AWD vehicle according to the present embodiment is described with reference to the drawings. For reference, Fig. 1 is a flowchart illustrating a method for controlling a two-speed AWD vehicle according to the present embodiment; Fig. 2 is a flowchart illustrating a detailed configuration of a traction control step in the method for controlling a two-speed AWD vehicle according to the present embodiment; Fig. 3 is a view illustrating detailed configurations of modes 4H and 4L in the method for controlling a two-speed AWD vehicle according to the present embodiment; and Fig. 4 is a view briefly illustrating a process of calculating the AWD control torque by a second step in the method for controlling a two-speed AWD vehicle according to the present embodiment. With reference to the attached Figs. 1, 2, 3 to 4, the method for controlling a two-speed AWD vehicle according to the present embodiment comprises a first step ST100 of selecting a 4H mode or a 4L mode and enabling the two-speed AWD vehicle to be driven, and a second step ST200 of performing a control to output an AWD control torque which is transmitted to a driveshaft as a minimum torque value according to the mode selected from the 4H mode or the 4L mode. In particular, the present embodiment segments the mode into five types of modes (a P-position stop mode, a D / R / N-position stop mode, a shift standby mode, a low-speed optimized driving mode 4L, and a high-speed optimized driving mode 4H) in the event that the two-speed AWD vehicle switches to mode 4H or 4L. Furthermore, based on these five segmented mode types, the AWD control torque (Tqt) transmitted to the driveshaft in 4H or 4L mode can be controlled to output a minimum torque value. In this case, stable driving of the vehicle can be achieved when a large driving force is required for light off-road driving or towing, or when driving through rough terrain. In the first step ST100 according to the present embodiment, the two-speed AWD vehicle can drive in any mode selected from the 4H mode or the 4L mode. The 4H mode is a 4WD high-gear mode and is used when the two-speed AWD vehicle is driving on unpaved roads, surfaces with low traction, or slippery surfaces, such as snow-covered roads in winter, where the two-speed AWD vehicle is at risk of losing traction. In 4H mode, all wheels of the two-speed AWD vehicle must be driven. The 4L mode is a 4WD low-gear mode and is used when the two-speed AWD vehicle is traveling on a completely unpaved surface that requires strong traction at all wheels, especially when the vehicle needs to travel at speeds of 20 km / h or less. However, the road or surface conditions mentioned above are not limited to these and can vary. The second step ST200 according to the present embodiment further comprises a traction control step ST210 for calculating the total traction torque (TC_Tq) to output a maximum value (Max) for torque control according to various driving situations of the two-speed AWD vehicle, a TCB control step ST220 for controlling the torque (TCB_Tq) generated when the two-speed AWD vehicle is in a low-speed, high-steering driving condition, and a handling control step ST230 for calculating a handling control torque (h_Tqt) based on a driving mode that corresponds to the cornering characteristics of the two-speed all-wheel drive vehicle. For information: TCB is defined as "Tight Corner Braking". The traction control step ST210 is provided to improve traction performance through anticipatory torque control according to different driving situations of the two-speed AWD vehicle, with the torque value being continuously calculated and simultaneously output. In the present embodiment, different gain values ​​(α) are applied to the output value calculated in the traction control step ST210, based on the gear positions of the two-speed AWD vehicle, wherein the gain value (α) decreases when the two-speed AWD vehicle switches from a low gear position to a high gear position. For example, the gain value (α) can be 1 in the first and second switch positions, and less than 1 in the third switch position. However, the specific numerical value can vary depending on the settings. In the traction control step ST210, a minimum torque value (β) is applied to the gain value (α) of the two-speed AWD vehicle, and the maximum value (Max) is selected from the calculated result torque values. The minimum torque value (β) according to the present embodiment has a torque value that varies depending on the five modes mentioned above. The reason for selecting the maximum value (Max) is that driving at low speeds in the two-speed AWD vehicle in 4H or 4L mode requires a relatively high torque compared to driving at high speeds. Therefore, as described above, the maximum value (Max) is selected. In the second step ST200, the torque value calculated in the TCB control step ST220 is applied to the maximum value (Max) and a minimum value (Min) is selected from the calculated result values, and the AWD control torque (Tqt) is calculated by calculating the minimum value (Min) and a handling torque value output in the handling control step ST230 together. In the TCB control step ST220, as described above, the minimum value (Min) is selected based on the torque value defined for the driving mode, taking accuracy and safety into account. If, for example, an intermediate value is selected, the range becomes larger, and an accurate torque value cannot be calculated. Consequently, the control torque required for the two-speed AWD vehicle cannot be calculated accurately. Therefore, in the present embodiment, the minimum value (Min) is transmitted together with the handling torque value to a separately provided control unit 100, and the control unit 100 outputs an optimal AWD control torque. For your information: The second step ST200 is based on the driving mode. For example, the second step ST200 refers to any mode selected from Eco mode, Normal mode, or Sport mode. Furthermore, the gain value (α) and the minimum torque value (β) are based on the mode of the two-speed AWD vehicle. For example, the mode can be any mode selected from modes 2H, 4A, 4H, and 4L. The TCB control step ST220 is determined based on the driving mode of the two-speed AWD vehicle, longitudinal acceleration information, lateral acceleration information, wheel speed information, and vehicle speed. The vehicle speed condition is based on a case where the vehicle speed is higher than a reference speed assigned to each driving mode. However, in Sport mode, the ESC is deactivated if wheel slip exceeds a threshold. Furthermore, in the TCB control step ST220, a determining criterion is only applied if all driving conditions of the two-speed AWD vehicle are met. For example, the case in which the driving condition is met refers to a case in which a steering angle is less than a reference angle, a case in which a steering angular velocity is less than a reference angular velocity, a case in which a yaw rate is less than a reference rate, and a case in which a lateral acceleration value is less than a reference acceleration value. The traction control step ST210 according to the present embodiment further comprises: a basic anticipatory torque control step ST211 of correcting a load distribution ratio by assigning a weight value to ensure performance according to the gear position and driving mode; a roll-prevention torque control step ST212 of classifying levels according to an uphill driving condition and a gradient angle of a hillside road when the two-speed AWD vehicle is traveling uphill or downhill; a hill-start assist torque control step ST213 of preventing wheel slip when the two-speed AWD vehicle starts moving; and a low-gear shift torque control step ST214 of executing a control to output a low-gear shift torque for each gear position when the two-speed AWD vehicle shifts into a low gear position. In the basic anticipatory torque control step ST211, a basic anticipatory torque value is calculated taking into account the corrected load distribution ratio for the torque transmitted to the two-speed AWD vehicle. The roll-prevention torque control step ST212 is applied to ensure stable traction performance when the two-speed AWD vehicle is traveling uphill or downhill. Furthermore, the uphill driving condition is determined based on longitudinal acceleration, lateral acceleration, wheel speed, steering angle, accelerator pedal opening, and brake pressure information encountered while driving the two-speed AWD vehicle. For example, the levels are classified according to the uphill driving condition of the two-speed AWD vehicle, and a specified roll-prevention torque value is output according to the driving mode. In the ST213 hill start assist torque control step, a vehicle speed criterion and a torque control value are set differently according to the driving mode of the two-speed AWD vehicle. For example, a torque control value for each gear position is classified according to the accelerator pedal opening degree of the two-speed AWD vehicle, and a hill start assist torque output is based on a speed of the two-speed AWD vehicle. The ST214 low-gear shift torque control step is used to stabilize vehicle movement due to engine braking when the two-speed AWD vehicle shifts into low gear while driving. For example, an entry point is controlled in a non-braking or non-acceleration state in which a target switching position is lower than an actual switching position. In the handling control step ST230, the cornering torque is calculated according to a cornering weight value according to a lateral acceleration, a yaw rate and a steering angle according to the cornering characteristics of the two-speed AWD vehicle. The driving modes according to the cornering characteristics can be a neutral steering mode (NS), an understeer mode (US), an oversteer mode (OS) and a countersteer mode (CS). The NS mode refers to a situation where the actual curve radius is equal to the target curve radius of a driver, and the US mode refers to a situation where the actual curve radius is smaller than the target curve radius of the driver. Furthermore, OS mode refers to a situation where the actual curve radius is greater than the desired curve radius of the driver, and CS mode refers to a driving mode in which the direction of rotation of a steering angle is immediately changed in the OS mode state. In this embodiment, a cornering weighting value is determined based on the lateral acceleration, yaw rate, and steering angle for each of the modes US, OS, NS, and CS. Furthermore, the cornering torque is calculated for normal driving conditions, taking into account the cornering weighting value for the torque transmitted to the two-speed AWD vehicle. This torque can be applied to prevent the occurrence of motion instability caused by wheel slip resulting from a sudden transition to 2WD, even in a situation where the accelerator pedal opening is zero. In this case, both the stability and the accuracy, corresponding to driving in 4H or 4L mode of the two-speed AWD vehicle, can be stabilized. The 4H or 4L mode of the two-speed AWD vehicle is classified into: a P shift stop mode, in which the two-speed AWD vehicle switches to 2WD when in a P shift stop state; a D / R / N shift stop mode to control the driver's driving when the two-speed AWD vehicle is in a D shift state, an R shift state, or an N shift state;a drive-stage standby mode to limit the torque that occurs when the two-speed AWD vehicle suddenly shifts from the low gear position to the high gear position or from the high gear position to the low gear position; a low-speed optimized driving mode in which a minimum torque value is output to the driveshaft in the 4A mode of the two-speed AWD vehicle; and a high-speed optimized driving mode in which a maximum torque value is output to the driveshaft in the 4A mode of the two-speed AWD vehicle. In the related technique, as described above, the maximum torque is delivered to the driveshaft without detailed segmented 4H and 4L modes. However, in the present embodiment, all 4H and 4L modes are segmented into five types of modes, resulting in more optimized control within the 4H and 4L modes. For example, in P (Park) stop mode, the system switches to 2WD because predictive control of the driver's driving is not required. In D / R / N (Drive / Reverse / Neutral) stop mode, standby control is performed to anticipate the driver's driving, and torque control can be set to, for example, 300 Nm to prepare for a start caused by a sudden accelerator pedal application by the driver. The gearshift standby mode is implemented as a torque control limiting mode for the drive mode control of a two-speed AWD system. Since the low-speed optimized driving mode and the high-speed optimized driving mode require relatively high torque compared to driving at high speed, the section is divided based on speed, and optimized drive control is performed. Furthermore, the torque required for directly connecting the driveshaft is actively controlled to transmit a drive force ratio of 1:1 to the front and rear wheels. For example, in P-position stop mode, D / R / N-position stop mode, and gearshift standby mode, a motion path represented by a bold solid line in the diagram is maintained when the vehicle speed is 0. Furthermore, the high-speed optimized driving mode is activated after the vehicle speed increases to a high-speed reference speed in the low-speed optimized driving mode. Furthermore, the vehicle speed converges to 0 after the implementation of the low-speed optimized driving mode, the high-speed optimized driving mode, and the low-speed optimized driving mode. According to the embodiments of the present invention, it is possible to carry out the optimal torque control required for the direct connection of the driveshaft of the two-speed AWD vehicle, thereby improving the service life of the components and reducing energy consumption. According to the embodiments of the present invention, it is possible to further segment the driving state in 4H or 4L mode of the two-speed AWD vehicle and to perform the control according to the segmentation, thereby achieving more precise control under different conditions. Although the embodiments of the present invention have been described above, skilled persons may modify and amend the present invention in various ways by adding, changing, omitting or modifying components without departing from the essence of the present invention as disclosed in the claims, and such modification and amendment are also within the scope of the present invention. Description of reference symbols 100 Control QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature KR 10-2440674

[0014]

Claims

Method for controlling a two-speed AWD vehicle, the method comprising the following steps: a first step (ST100) of selecting a 4H mode or a 4L mode and enabling the driving of a two-speed AWD vehicle; and a second step (ST200) of performing a control to output an AWD control torque transmitted to a driveshaft as a minimum torque value according to the mode selected from the 4H mode or the 4L mode. The method according to claim 1, wherein the second step (ST200) further comprises: a traction control step (ST210) of calculating the total traction torque to output a maximum value (Max) for torque control according to different driving situations of the two-speed AWD vehicle; a TCB control step (ST220) of controlling the torque generated when the two-speed AWD vehicle is in a low-speed, high-steering driving condition; and a handling control step (ST230) of calculating the handling control torque based on a driving mode corresponding to the cornering characteristics of the two-speed all-wheel drive vehicle. Method according to claim 2, wherein different gain values ​​based on the switching positions of the two-speed AWD vehicle are applied in the traction control step (ST210). Method according to claim 3, wherein in the traction control step (ST210) a minimum torque value (β) is applied to the gain value of the two-speed AWD vehicle and the maximum value (Max) is selected from calculated result torque values. Method according to claim 4, wherein in the second step (ST200) the torque value calculated in the TCB control step (ST220) is applied to the maximum value (Max) and calculated, a minimum value (Min) is selected from calculated result values, and an AWD control torque is calculated by jointly calculating the minimum value (Min) and a handling torque value output in the handling control step (ST230). A method according to any one of claims 2 to 5, wherein the traction control step (ST210) further comprises: a basic anticipatory torque control step (ST211) of correcting a load distribution ratio by assigning a weight value to ensure performance according to the gear position and driving mode; a roll prevention torque control step (ST212) of classifying levels according to an uphill driving condition and a gradient angle of a hillside road when the two-speed AWD vehicle is traveling uphill or downhill; a hill start assist torque control step (ST213) of preventing wheel slip when the two-speed AWD vehicle starts moving; and a low-gear shift torque control step (ST214) of performing a control to output a low-gear shift torque for each gear position when the two-speed AWD vehicle shifts into a low gear position. Method according to claim 6, wherein in the roll prevention torque control step (ST212) the uphill driving condition is determined based on longitudinal acceleration, lateral acceleration, wheel speed, steering angle, accelerator pedal opening degree and brake pressure information. Method according to claim 6 or 7, wherein in the start-up assistance torque control step (ST213) a vehicle speed criterion and a torque control value are set differently according to the driving mode of the two-speed AWD vehicle. Method according to one of claims 6 to 8, wherein in the start-up assistance torque control step (ST213) a torque control value is classified for each gear shift position according to the accelerator pedal opening degree of the two-speed AWD vehicle, and a start-up assistance torque output is based on a speed of the two-speed AWD vehicle. Method according to one of claims 6 to 9, wherein in the shift torque control step for low gears (ST214) an entry point is controlled in a non-braking or non-acceleration state in which a target gear shift position is lower than an actual gear shift position. Method according to any one of claims 2 to 10, wherein the TCB control step (ST220) is determined on the basis of the driving mode of the two-speed AWD vehicle, the longitudinal acceleration and lateral acceleration information, the wheel speed information and a vehicle speed. Method according to one of claims 2 to 11, wherein in the handling control step (ST230) a cornering torque is calculated according to a cornering weight value according to a lateral acceleration, a yaw rate and a steering angle according to the cornering characteristics of the two-speed AWD vehicle. A method according to any one of claims 1 to 12, wherein the 4H or 4L mode of the two-speed AWD vehicle is classified into: a P shift-stop mode in which the two-speed AWD vehicle switches to 2WD in a P gear-stop state; a D / R / N shift-stop mode for controlling the driver's driving when the two-speed AWD vehicle is in a D gear-stop state, an R gear-stop state, or an N gear-stop state; a gear-shift standby mode for limiting the torque that occurs when the two-speed AWD vehicle suddenly shifts from a low gear position to a high gear position or from a high gear position to a low gear position; a low-speed optimized driving mode in which a minimum torque value is output to the driveshaft in the 4A mode of the two-speed AWD vehicle;and a driving mode optimized for high speeds, in which a maximum torque value is output to the driveshaft in the 4A mode of the two-speed AWD vehicle.

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