Control of automatic start of a motor vehicle going uphill with μ-disengagement

Abstract

A method for controlling the automatic start of a motor vehicle comprising an electronically controllable locking differential when driving uphill with μ-disengagement is described. The method comprises the following steps: determining the positive gradient of the underlying surface; defining an initial locking torque according to the determined positive gradient and according to the component of torque required for the vehicle to travel uphill with only the first drive wheel driven; if a reference speed V Ref At 0 and critical speed V Crit According to SR xx =(V xx ‑V Ref ) / V Crit Calculate the slip ratio SR of the first driving wheel xx xx , and if the reference speed V Ref Above critical speed V Crit According to SR xx =(V xx ‑V Ref ) / V Ref Calculate the slip ratio SR of the first driving wheel xx xx ; and limiting the locking torque of the electronically controllable locking differential according to the slip ratio of the first drive wheel.

Description

Technical Field

[0001] The invention relates to a method and a device for controlling the automatic start of a motor vehicle comprising an electronically controllable locking differential on a slope or uphill with μ (friction coefficient) disengagement. The invention also relates to a motor vehicle with an electronically controllable locking differential. Background Art

[0002] During a μ-disengagement uphill start, i.e. when there are differences in the friction coefficients of the underlying surfaces at the left and right wheels of the vehicle, a critical situation regarding vehicle stability may arise depending on the drive torque engagement conditions at the wheels. In particular, the vehicle's ability to move forward in the desired direction may be adversely affected.

[0003] Most motor vehicles currently available on the market have an open differential and are equipped with ESP (Electronic Stability Control), traction control (ETC—Engine Traction Control) and brake traction control, which uses brake pressure on the pulley to simulate a locking differential. Vehicles with electronically controllable locking differentials are also now available.

[0004] An inaccurate locking torque can easily cause undesired vehicle movements, which are independent of the locking device on the drive shaft. It is necessary to take into account the fact that when the vehicle is started uphill in μ-disconnection (especially with a manual transmission), it is very easy to apply excessive torque to the drive train, especially when only a part of the drive torque can be converted into propulsion due to lack of grip.

[0005] Excessive torque causes one or both wheels of the corresponding axle to rotate, with the result that the lateral and longitudinal forces available to one or more rotating wheels are greatly reduced. If the wheel with a high coefficient of friction of the lower surface on the drive axle starts to rotate, the lateral stability of the axle is adversely affected and the vehicle starts to perform a yaw motion due to gravity and the uneven drive forces acting on the drive wheels. These effects may lead to the following situation. If too low a locking torque is applied to the electronically controllable locking differential, there is a risk that the motor vehicle will roll back downwards because sufficient drive torque has not yet been transferred from the drive wheel with a low coefficient of friction of the lower surface to the drive wheel with a high coefficient of friction of the lower surface. Applying too high a locking torque to the electronically controllable locking differential can have the following effect: If the drive axle is pointed uphill, that is to say, for example, a motor vehicle with front-wheel drive is driven uphill, the vehicle starts a yaw motion about the lower axle (for example the rear axle), which is similar to an inverted pendulum. Once this movement has started, it is difficult to stop and the vehicle will be positioned laterally relative to the lower surface or, in the worst case, will slide down in a rotational movement. This situation is uncontrollable. If the axis of the driven axle is not pointing uphill, such as in the case of a motor vehicle with front-wheel drive driven backwards uphill, the motor vehicle begins a yaw movement about the higher axis, similar to a normal pendulum. In addition, if the longitudinal force of the drive wheels is reduced due to excessive rotation, there is a risk of rolling back downwards.

[0006] The above example shows that it is important to apply the right level of locking torque to the electronically controllable locking differential and to do so at the right time. In addition, it is critical to carefully adjust the function of the drive wheels with a high coefficient of friction on the underlying surface, as too much or too little locking torque can have a negative impact.

[0007] Document DE 10 2006 021 652 A1 describes a device and a method for assisting a starting process of a motor vehicle from a standstill when a μ-separation situation exists. It is proposed that, when a difference in the coefficient of friction of the underside surface between the sides is detected, the brake pressure is reduced in the wheel brakes of the drive wheels assigned to the side of the underside surface with the higher coefficient of friction of the underside surface, while the brake pressure is maintained in the wheel brakes of the drive wheels assigned to the side of the vehicle with the lower coefficient of friction of the underside surface.

[0008] DE 10 2015 212 948 A1 describes a method for improving the acceleration behavior of a vehicle. In this context, a stability control system is used to induce a braking torque acting on the drive wheels of the vehicle in order to reduce the slip of the drive wheels. In addition, an index is determined to indicate that a first drive wheel of the vehicle is on a first side of an underlying surface, the first side of the underlying surface allowing a lower frictional engagement with the first drive wheel than a second side of the underlying surface allowing a lower frictional engagement with a second drive wheel of the vehicle. Summary of the invention

[0009] A method for controlling a vehicle includes: when the vehicle is stationary, setting an initial locking torque of an electronic limited slip differential according to a road gradient, and after detecting vehicle motion, setting the locking torque according to a slip ratio of the slowest drive wheel. Ref At 0 and critical speed V Crit According to SR xx =(V xx -V Ref ) / V Crit Calculate the slip ratio SR xx , and in response to the parameter speed being greater than the critical speed, according to SR xx =(V xx -V Ref ) / V Ref Calculate the slip ratio SR xx . The initial locking torque may be greater than a lower limit value of the torque capacity required for the vehicle to travel uphill on a road grade with only one drive wheel driven. The initial locking torque may be less than an upper limit value of the torque capacity so that the powertrain torque does not cause the slowest drive wheel to rotate. The locking torque may be maintained in response to the slip ratio being within an allowable slip ratio range. The locking torque may be reduced in response to the slip ratio increasing above a maximum allowable slip ratio. The locking torque may be increased in response to the slip ratio decreasing below a minimum allowable slip ratio.

[0010] The vehicle control system includes a sensor and a controller. The sensor determines the road grade and the drive wheel speed. The controller is programmed to set the initial locking torque of the electronic limited slip differential according to the road grade when the vehicle is stationary, and to set the locking torque according to the slip ratio of the slowest drive wheel in response to detecting vehicle motion. The controller may be responsive to a reference speed V Ref At 0 and critical speed V Crit According to SR xx =(V xx -V Ref ) / V Crit Calculate the slip ratio SR of the slowest driving wheel xx , and in response to the reference speed being greater than the critical speed, according to SR xx =(V xx -V Ref ) / V Ref Calculate the slip ratio SR of the slowest driving wheel xx . BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 shows a schematic side view of a motor vehicle starting from a slope;

[0012] Figure 2 Shows Figure 1 A schematic top view of a motor vehicle shown in ;

[0013] Figure 3 shows a schematic side view of a motor vehicle starting on a slope;

[0014] Figure 4 Shows Figure 3 A schematic top view of a motor vehicle is shown;

[0015] Figure 5 shows a schematic side view of a motor vehicle starting on a slope;

[0016] Figure 6 Shown in different locations Figure 5 A schematic top view of a motor vehicle shown in ;

[0017] Figure 7 A schematic diagram of a variant of the method according to the invention is shown in the form of a flow chart;

[0018] Figure 8 A schematic diagram of a motor vehicle according to the invention is shown. DETAILED DESCRIPTION

[0019] Embodiments of the present disclosure are described herein. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take various alternative forms. The drawings are not necessarily to scale; certain features may be exaggerated or minimized to show the details of a particular component. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art to use the present invention in various ways. As will be understood by those of ordinary skill in the art, the various features shown and described with reference to any one of the figures may be combined with the features shown in one or more other figures to produce embodiments that are not explicitly shown or described. The combination of features shown provides representative embodiments for typical applications. However, various combinations and modifications of features consistent with the teachings of the present disclosure may be desirable for specific applications or implementations.

[0020] The method for controlling the automatic start of a motor vehicle on an uphill slope or a slope according to the invention relates to a motor vehicle comprising an electronically controllable, in particular electronically closed-loop controllable, locking differential. The method relates to a μ-separation case, in which a first lower surface friction coefficient is present at a first drive wheel and a second lower surface friction coefficient is present at a second drive wheel. In this case, the first lower surface friction coefficient is higher than the second lower surface friction coefficient. The method comprises the following steps: First, a positive slope or rise of the lower surface and an orientation of the motor vehicle are determined. Subsequently, an initial locking torque is defined as a function of the determined positive slope and as a function of the component (e.g. percentage) of the torque required for the vehicle to travel uphill when only the first driven wheel is driven.

[0021] In particular, when the vehicle starts and the wheels begin to rotate, the locking torque of the electronically controllable locking differential is limited according to the slip ratio of the first drive wheel. Crit After that, the system can go to other functions. Subsequent functional control of the locking torque can be performed based on the powertrain torque alone. After the vehicle starts, in particular to ensure vehicle stability and traction, the locking torque can be adjusted based on the slip ratio of the first drive wheel and the initial locking torque.

[0022] If the reference speed V Ref Between zero and critical speed V Crit Between(0 <V Ref <V Crit ), then according to SR xx =(V xx -V Ref ) / V Crit Calculate the slip ratio SR of the first driving wheel xx xx , if the reference speed V Ref Above critical speed V Crit (V Ref >V Crit ), then according to SR xx =(V xx -V Ref ) / V Ref Calculate the slip ratio SR of the first driving wheel xx xx In this case, V xx is the speed of the driving wheel, V Ref The speed of the non-driven, rotating wheels. This is usually the minimum speed of the non-driven axle in a vehicle with two-wheel drive. Crit Characterizes the speed at which the slip ratio is stable (ie, the stability of the motor vehicle is ensured).

[0023] The term control within the scope of the present invention may also essentially include closed-loop control.

[0024] The method described has the advantage that when starting uphill with μ-disengagement, the starting behavior of the motor vehicle is optimized and the rolling back of the motor vehicle is minimized, while the stability of the vehicle takes precedence at all times. Undesired yaw movements of the motor vehicle are avoided in this way.

[0025] The solution proposed by the invention can be used as an alternative to a brake-based electronic stability control system in conjunction with starting on a slope, or also as a backup option. The method according to the invention can preferably be used in conjunction with a traction control system. In this case, a traction control system is essentially not required with respect to the stability of the vehicle in conjunction with the method according to the invention.

[0026] In an advantageous variant, a longitudinal acceleration sensor is used to determine the positive gradient, for example when the vehicle is stationary. The sensor may be part of a stability control system (ESP).

[0027] The initial locking torque is preferably limited between an upper limit value and a lower limit value. The lower limit value can be selected such that a downward roll of the motor vehicle is minimized or excluded. The upper limit value can be selected such that when the clutch is released, the first drive wheel does not rotate and / or only the second drive wheel rotates. This refinement has the advantage that the reaction speed is significantly increased compared to a brake-based electronic stability control system, in particular since the preventive torque cannot be limited within the scope of a brake-based electronic stability control system.

[0028] The locking torque can be defined by an open-loop or closed-loop control process. Furthermore, a range of additional slip ratios can be defined such that the first drive wheel provides sufficient force to bring the vehicle uphill and at the same time ensures lateral stability. In other words, a permissible slip ratio range can be defined to the effect that the first drive wheel provides sufficient force to bring the motor vehicle uphill and the boundary condition of ensuring lateral stability of the motor vehicle is met. In this way, undesired yaw movements are avoided.

[0029] The defined range can be used in particular as a trailing range. For example, if the tire is within the permissible slip ratio range, the current blocking torque should be maintained. The definition of the permissible slip ratio range which ensures the lateral stability of the tire and takes into account the lateral forces has the advantage over a system having only one fixed locking torque that a more flexible reaction to certain existing situations can be made or can be allowed to be made.

[0030] In an advantageous variant, if the slip ratio of the first drive wheel is within the range of permissible slip ratios, the locking torque is maintained. If the slip ratio of the first drive wheel exceeds the range of permissible slip ratios, the locking torque may be permissibly or optionally reduced. Additionally or alternatively, if the slip ratio of the first drive wheel is below the range of permissible slip ratios, the locking torque is increased. The increase or decrease of the locking torque may be performed by proportional control.

[0031] Within the scope of the method according to the invention, a traction control system can be applied. An electronic stability control system can be assisted by a traction control system. If appropriate, in this case, the traction control system can replace the electronic stability control system. In view of the above advantages, the method according to the invention has the following advantages and benefits:

[0032] Compared to brake-based electronic stability control solutions, rollback during the start-up process is avoided or reduced more effectively. In addition, electronic stability control systems may have larger yaw angles. This can be attributed to the relative inaccuracy of the brake pressure at the brake torque interface in the case of brake-based electronic stability control systems. Another reason is that the preventive locking torque cannot be defined depending on the positive slope, which increases the reaction time. The fixed locking torque leads to amplified yaw movements in the case of an electronic locking differential, which is particularly noticeable when a vehicle with rear-wheel drive is driven backwards uphill or a vehicle with front-wheel drive is driven forwards uphill. Basically, the present invention can provide a solution that is suitable for the respective driving situation, in particular for the specifically existing positive slope, the slip ratio and the respective driving direction, and is adjusted individually.

[0033] Compared to brake-based electronic stability control systems, the invention has the advantage, inter alia, that the risk of rolling back during starting is reduced or eliminated by the possibility of defining the initial locking torque before the wheels start to rotate. Rollback is defined as the distance the vehicle rolls downhill before sufficient drive is generated for uphill movement. Another advantage compared to brake-based electronic stability control systems is smaller yaw movements, since the electronically controlled differential locks are designed to allow relatively slow and precise adjustment of the locking torque. This in turn reduces yaw movements and accelerations.

[0034] Compared to solutions with a fixed locking torque, the present invention has the advantage of being adaptive and preventing excessive yaw movements. As a result, the stability of the vehicle is ensured and maintained. Basically, a fixed locking torque could lead to excessive yaw movements (i.e., spinning the vehicle) on a positive slope or to insufficient drive power. In contrast, the present invention adapts to the friction of the specific underlying surface, the rise or positive slope of the underlying surface, the grip of the wheels and the load condition of the vehicle and controls the necessary drive (i.e., the driving force or power of the vehicle) accordingly to adapt to the specific situation.

[0035] According to the invention, a device for controlling the automatic start of a motor vehicle going uphill in a μ-separation situation, wherein a first coefficient of friction of the lower surface is present at the first drive wheel and a second coefficient of friction of the lower surface is present at the second drive wheel, the first coefficient of friction of the lower surface being higher than the second coefficient of friction of the lower surface, comprises a device for determining a positive slope or rise of the lower surface. The device also comprises a device for defining an initial locking torque according to the determined positive slope and according to a component (e.g. a percentage) of the torque required for the vehicle to drive uphill with only the first drive wheel driven. Furthermore, the device also comprises a device for determining a positive slope or rise of the lower surface according to the determined positive slope and according to a component (e.g. a percentage) of the torque required for driving the vehicle ... Ref Between 0 and critical speed V Crit According to SR xx =(V xx -V Ref ) / V Crit To calculate the slip ratio SR of wheel xx xx , and if the reference speed V Ref Above critical speed V Crit， According to SR xx =(V xx -V Ref ) / V Ref Calculate the slip ratio SR of wheel xx xx The device further comprises a device for limiting the locking torque according to the slip ratio of the first drive wheel. The device according to the invention is preferably configured to perform the method according to the invention as described above.

[0036] The motor vehicle according to the invention comprises an electronically controllable, in particular electronically closed-loop controllable, locking differential and a device as described above. In an advantageous variant, the motor vehicle according to the invention comprises an electronic stability control system and / or a traction control system.

[0037] The motor vehicle according to the invention can have two-wheel drive or all-wheel drive.

[0038] The device according to the invention and the motor vehicle according to the invention have the properties and advantages described with reference to the method according to the invention.

[0039] Other features, properties and advantages of the present invention are described in more detail below according to exemplary embodiments and with reference to the accompanying drawings. All features described above and below are advantageous individually and in any desired combination with each other. The exemplary embodiments described below constitute only examples, which, however, do not limit the subject matter of the present invention.

[0040] Against this background, the object of the present invention is to provide an advantageous method for controlling an automatic start of a motor vehicle comprising an electronically controllable locking differential uphill with μ-disengagement, and a device suitable for this purpose and a correspondingly advantageous motor vehicle.

[0041] Figure 1 An underlying surface 1 with a positive gradient or rise is shown. A motor vehicle 2 with rear-wheel drive is driving forward uphill on the underlying surface 1. Arrow 3 characterizes a relatively high force vector exerted by the rear wheels with a low slip level. Figure 2 The lower surface 10 relative to the right side of the vehicle 2 is shown to have a low lower surface friction coefficient, while the lower surface 11 relative to the left side of the vehicle 2 has a high lower surface friction coefficient. Therefore, a μ-split situation exists. In this case, the left rear wheel applies a higher force during launch, as shown by force vector 3, while the right rear wheel applies a lower force than the left rear wheel, as shown by vector 4. This can be attributed to the fact that the right rear wheel has a higher slip than the left rear wheel due to the different lower surface friction coefficients.

[0042] Due to the different force vectors 3 and 4, there is a risk of yaw motion. The resulting yaw motion Figure 2 In the example shown, the transverse forces 5 and 6 are compensated, thus avoiding yaw movements. Figure 1 and Figure 2 The example shown relates to a specific set locking torque. In this case, the locking torque is equal to the value of the drive torque of the wheel with a high coefficient of friction of the underlying surface, and in the example shown, the lateral stability of the motor vehicle 2 can be maintained at the left rear drive wheel. In particular, after a drive open-loop or closed-loop control process, the excess torque from the engine is compensated by the drive wheel with a low coefficient of friction of the underlying surface, in this example the right rear drive wheel. In the example shown, the vehicle is accelerated in a trouble-free manner without yaw movements.

[0043] Figure 3 and 4 An example of excessive slip is shown where the drive axle is pointing downhill (ie, lower than the non-drive axle). Figure 3 The motor vehicle 2 is shown during starting uphill or on a slope. The vehicle 2 has rear-wheel drive and is driving forward uphill. Figure 3 In FIG, a vehicle is schematically shown from the side. Figure 4 Shown from above Figure 3 The center of gravity of the motor vehicle 2 is defined by reference numeral 9 . The force of gravity acting at the center of gravity of the motor vehicle is defined by vector 7 .

[0044] exist Figure 3 and Figure 4In the example shown, the two rear wheels rotate due to excessive drive torque and excessive locking torque. As shown by arrows 13 and 14, the rear axle loses longitudinal and lateral drive ability, or the longitudinal and lateral drive ability is significantly reduced. At the same time, the lateral force of the left rear wheel 16 required to compensate for the yaw movement is reduced. Due to gravity, the vehicle 2 rotates around the front wheel (the example is shown as around the left front wheel) due to the high friction coefficient of the underlying surface. This brings about a movement similar to that of a pendulum. This yaw movement may occur suddenly. This yaw movement is represented by arrow 8 and can be attributed to gravity 7 on the one hand and to unequal drive forces 13 and 14 on the other hand.

[0045] Figure 5 and Figure 6 A schematic diagram of a vehicle with rear wheel drive and driven rearward uphill is shown. The drive axle is therefore pointing uphill or above the non-drive axle. Figure 5 In FIG, a vehicle is schematically shown from the side. Figure 6 , the vehicle is schematically shown from above. In the example shown, the two rear wheels rotate when starting.

[0046] As indicated by arrows 23 and 24, the rear axle loses longitudinal and lateral drive capacity or has a significantly reduced longitudinal and lateral drive capacity. At the same time, the lateral force on the left rear wheel 26 that is required to compensate for the yaw movement is reduced. The vehicle 2 then begins to rotate around the front wheel due to the high coefficient of friction of the underlying surface. This yaw movement can be attributed on the one hand to the gravity 7 and on the other hand to the unequal drive forces 23 and 24. As a result, the vehicle behaves like an inverted pendulum and slides down uncontrollably.

[0047] Within the scope of the method according to the invention, it is prevented Figures 3 to 6 The situation shown in the figure occurs. Figure 7 An example of a variant of the method according to the invention is schematically shown in the form of a flow chart in FIG. 30 indicates a stationary motor vehicle. Frame 31 indicates an initial start. Frame 32 indicates a critical speed V Crit The above vehicles.

[0048] Vehicle stationary is detected in step 33. In step 34, an initial locking torque is then defined depending on the positive slope of the underlying surface and the orientation of the vehicle. In step 35, the accelerator pedal is then activated, the clutch is engaged and the tires begin to move. In step 36, a μ-disengagement condition is detected and the hill start function is initiated.

[0049] In step 37, the locking torque is limited or controlled in an open or closed loop according to the relatively high slip ratio of the drive wheel of the lower surface friction coefficient. Ref Between zero and critical speed V Crit Between(0 <V Ref <VCrit ), then according to SR xx =(V xx -V Ref ) / V Crit Calculate the slip ratio SR of the first driving wheel xx xx , and if the reference speed V Ref Above critical speed V Crit (V Ref >V Crit ), then according to SR xx =(V xx -V Ref ) / V Ref Calculate the slip ratio SR of the first driving wheel xx xx .

[0050] In this case, proportional control can be performed within the range of the permissible slip ratio. In step 38, a transition to other functions is performed.

[0051] Figure 8 A schematic diagram of a motor vehicle 2 according to the invention is shown, which is equipped with an electronic locking differential and comprises a control device 20 according to the invention. The device 20 according to the invention is configured to carry out the method according to the invention. It comprises in particular a device for determining a positive gradient or rise of an underlying surface, a device for defining an initial locking torque, a device for calculating a slip ratio and a device for defining a locking torque as a function of the slip ratio. The motor vehicle can essentially be a passenger vehicle, a truck or other vehicle. The motor vehicle preferably has a two-wheel drive.

[0052] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms covered by the claims. The words used in the specification are descriptive rather than restrictive, and it should be understood that various changes can be made without departing from the spirit and scope of the present disclosure. As previously mentioned, the features of the various embodiments can be combined to form additional embodiments of the present invention that may not be explicitly described or shown. Although various embodiments may have been described as providing advantages or being superior to other embodiments or prior art implementations relative to one or more desired characteristics, a person of ordinary skill in the art recognizes that one or more features or characteristics may be excluded to achieve the desired overall system properties, depending on the specific application and implementation. Thus, embodiments described as being less desirable than other embodiments or prior art implementations relative to one or more characteristics are not outside the scope of the present disclosure and may be desirable for specific applications.

Claims

1. A method for controlling a vehicle, comprising: When the vehicle is stationary, setting an initial locking torque of the electronic limited slip differential according to a road gradient; and After vehicle motion is detected, the locking torque is set based on the slip ratio of the slowest driven wheel, where: In response to the reference speed V Ref At 0 and critical speed V Crit According to SR xx = (V xx -V Ref ) / V Crit Calculate the slip ratio SR of the slowest driving wheel xx ,and In response to the reference speed being greater than the critical speed, according to SR xx = (V xx -V Ref ) / V Ref Calculate the slip ratio SR of the slowest driving wheel xx ; Where V xx is the speed of the slowest driving wheel, V Ref is the speed of the non-driven and rotating wheels, and V Crit Characterizes the speed at which the slip ratio is stable. 2 . The method according to claim 1 , wherein the initial locking torque is greater than a lower limit value of a torque capacity required for the vehicle to travel uphill on the road gradient while driving only one driving wheel. 3 . The method of claim 1 , wherein the initial locking torque is less than an upper limit value of a torque capacity such that a powertrain torque does not cause the slowest drive wheel to rotate.

4. The method according to claim 1, wherein: maintaining the locking torque in response to the slip ratio being within an allowable slip ratio range; reducing the locking torque in response to the slip ratio increasing above a maximum allowable slip ratio; and The locking torque is increased in response to the slip ratio falling below a minimum allowable slip ratio.

5. A vehicle control system, comprising: Sensors for determining road grade and drive wheel speed; and A controller programmed to perform the following steps: When the vehicle is stationary, setting an initial locking torque of the electronic limited slip differential according to the road gradient; and In response to detecting vehicle motion, setting a locking torque based on a slip ratio of the slowest driven wheel, wherein the controller is programmed to: In response to the reference speed V Ref At 0 and critical speed V Crit According to SR xx = (V xx -V Ref ) / V Crit Calculate the slip ratio SR of the slowest driving wheel xx ,and In response to the reference speed being greater than the critical speed, according to SR xx = (V xx -V Ref ) / V Ref Calculate the slip ratio SR of the slowest driving wheel xx ; Where V xx is the speed of the slowest driving wheel, V Ref is the speed of the non-driven and rotating wheels, and V Crit Characterizes the speed at which the slip ratio is stable. 6 . The control system according to claim 5 , wherein the initial locking torque is greater than a lower limit value of a torque capacity required for the vehicle to travel uphill on the road gradient while driving only one driving wheel. 7 . The control system of claim 5 , wherein the initial locking torque is less than an upper limit value of a torque capacity such that a powertrain torque does not cause the slowest drive wheel to rotate.

8. The control system of claim 5, wherein the controller is programmed to perform the following steps: maintaining the locking torque in response to the slip ratio being within an allowable slip ratio range; reducing the locking torque in response to the slip ratio increasing above a maximum allowable slip ratio; and The locking torque is increased in response to the slip ratio falling below a minimum allowable slip ratio.

9. A vehicle comprising: an electronic limited slip differential that drives both wheels; and A controller programmed to perform the following steps: When the vehicle is stationary, setting an initial locking torque of the electronic limited slip differential according to a road gradient; and In response to detecting vehicle motion, setting a locking torque based on a slip ratio of the slowest of the two wheels, wherein the controller is programmed to: In response to the reference speed V Ref At 0 and critical speed V Crit According to SR xx = (V xx -V Ref ) / V Crit Calculate the slip ratio SR of the slowest of the two wheels xx ,and In response to the reference speed being greater than the critical speed, according to SR xx = (V xx -V Ref ) / V Ref Calculate the slip ratio SR of the slowest of the two wheels xx ; Where V xx is the speed of the slowest of the two wheels, V Ref is the speed of the non-driven and rotating wheels, and V Crit Characterizes the speed at which the slip ratio is stable. 10 . The vehicle according to claim 9 , wherein the initial locking torque is greater than a lower limit value of a torque capacity required for the vehicle to travel uphill on the road gradient while driving only one of the two wheels.

11. The vehicle of claim 9, wherein the initial locking torque is less than an upper limit value of a torque capacity such that a powertrain torque does not cause the slowest one of the two wheels to rotate.

12. The vehicle of claim 9, wherein the controller is programmed to perform the following steps: maintaining the locking torque in response to the slip ratio being within an allowable slip ratio range; reducing the locking torque in response to the slip ratio increasing above a maximum allowable slip ratio; and The locking torque is increased in response to the slip ratio falling below a minimum allowable slip ratio.

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