Method and assistance system for automatically controlling an electric vehicle drive system having an auto-hold function, and correspondingly designed motor vehicle

Abstract

The invention relates to a method and an assistance system (10) for automatically controlling a drive system (2) of an electrically driven motor vehicle (1). In the method, limitation of a tilt compensating torque (18) which is generated by means of the electric drive (3) of the motor vehicle (1) and is active during driving is suspended when the motor vehicle (1) stops on a slope. The invention further relates to a correspondingly designed motor vehicle (1).

Description

[0001] Method and assistance system for automatically controlling an electric vehicle drive system with an auto-hold function and correspondingly configured

[0002] motor vehicle

[0003] The present invention relates to a method and an assistance system for automatically controlling a drive system of an electrically powered motor vehicle. The invention also relates to a correspondingly configured motor vehicle.

[0004] Driving maneuvers on uphill and downhill gradients can generally be challenging. For example, stopping and starting comfortably and precisely, as well as remaining stationary, can be problematic with conventional manually controlled motor vehicles. Firstly, continuously manually applying the brake pedal to hold the vehicle stationary can be strenuous. Secondly, for example, on an uphill gradient, it can potentially lead to an undesirable rollback, or on a downhill gradient, the vehicle's speed can increase surprisingly quickly or in a way that cannot be precisely controlled by the accelerator pedal after the brake is released. In some cases, the vehicle may have to move off against the partial resistance of a mechanical or hydraulic brake, i.e., a friction brake, which does not seem optimal in terms of both energy consumption and wear.

[0005] For example, DE 102012 223 867 A1 describes a method for holding a motor vehicle on an inclined surface. In this method, the motor vehicle is initially held by a motor torque generated by an electric drive motor, with the performance of a corresponding drive system being monitored. If the performance drops to or by a certain amount, an alternative holding system, in particular a conventional braking system, is activated to hold the motor vehicle.

[0006] As another example, DE 10 2019 103 375 A1 describes a control unit for a motor vehicle comprising an electric motor for driving wheels of the vehicle and a friction brake. The control unit is configured to determine that a one-pedal feel function is to be provided via an accelerator pedal and / or a creep function is to be provided via a brake pedal. Furthermore, the control unit is configured to operate the electric motor and the friction brake in combination, at least temporarily, to provide these functions.

[0007] However, the solutions adopted so far leave room for further improvement.

[0008] The object of the present invention is to enable a particularly comfortable and precise operation of a motor vehicle for longitudinal guidance on gradients with at least partially manual control.

[0009] This problem is solved by the subject matter of the main claim and the subsidiary claims or the independent claims. Further possible embodiments of the invention are disclosed in the subclaims, the description, and the figures. Features, advantages, and possible embodiments presented in the description for one of the subject matter of the independent claims are to be regarded at least analogously as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the subclaims.

[0010] The method according to the invention can be used for the automatic control of a drive system of a motor vehicle that is driven by one or more electric machines. For example, one electric machine can be provided to drive several wheels. Likewise, several electric drive machines can be provided, each driving exactly one wheel of the motor vehicle. The method according to the invention can be used for the individual or joint or coordinated control of the possibly several electric drive machines. In the method according to the invention, the inclination of a surface currently being traveled on by the motor vehicle, for example a busy road or a busy path - and thus also the corresponding inclination of the motor vehicle itself - is continuously monitored in the longitudinal direction. The inclination in the longitudinal direction can therefore be an inclination in the direction of travel oropposite to the direction of travel of the motor vehicle, i.e. in or opposite to its longitudinal direction. A positive incline or gradient here means that the motor vehicle is traveling uphill or is on an incline. A negative incline or gradient here means that the motor vehicle is traveling downhill or is on a downward slope. The incline can be determined or monitored, for example, by means of an incline sensor on the motor vehicle and / or using position data that indicates the current position of the motor vehicle and corresponding predefined map data that indicates local inclines. Based on the current local incline, a corresponding incline compensation torque is automatically generated to at least partially compensate for a downhill torque caused by the incline.a corresponding downhill force acting on the vehicle caused by the incline is determined or calculated. Depending on the situation, this incline compensation torque can be a positive, i.e., driving, or a negative, i.e., braking or inhibiting torque. The incline compensation torque can be generated by the electric motor or incorporated into a balance or balance calculation to determine a currently set total target torque, i.e., into a corresponding control or determination of a corresponding operating point of the electric motor.

[0011] In the method according to the invention, the inclination compensation torque is then generated by corresponding automatic control of the electric machine. The inclination compensation torque is therefore applied or realized here as a motor drive torque or motor braking torque by means of the electric machine. This can be done effectively, for example, by forming a torque balance from different torques and adjusting or controlling the electric machine so that a resulting net or target total torque is produced. The respective inclination compensation torque can be included as at least one component in this torque balance or this net or target total torque. Likewise, depending on the situation, an accelerator pedal torque and / or a brake pedal torque and / or a creep torque and / or the like can be taken into account or incorporated. The accelerator pedal torque is a drive torque that is dependent on the current position orcorresponds to the current degree of actuation of the accelerator pedal or is determined or derived therefrom. The accelerator pedal torque can also already include or contain a specified or preset creep torque in a sub- or partial balance. This creep torque can be a positive drive torque that results without actuation of the accelerator pedal, i.e., in its base or zero position. The brake pedal torque can be a negative, i.e., braking or decelerating drive torque, which corresponds to the current position or the current degree of actuation of the vehicle's brake pedal or is determined or derived therefrom.

[0012] The inclination compensation torque is or will be automatically limited to a predefined maximum value or - positive or negative depending on the situation - maximum value as long as the motor vehicle is moving, i.e. as long as the speed of the motor vehicle relative to the surface it is traveling on is greater than zero. The predefined maximum value is not sufficient to hold the motor vehicle against all inclines or gradients present or occurring in public traffic areas or on normal roads or traffic routes. A inclination compensation torque equal to the predefined maximum value can therefore, for example, fully compensate for a slope downforce torque up to an incline of, for example, up to 4%, up to 7%, up to 12% or the like.This means that for a given accelerator or brake pedal position, the same speed of the motor vehicle would only always be achieved regardless of whether the motor vehicle is driving on a level surface, i.e. on a level surface or on an incline or a decline, if the gradient there corresponds at most to the stated value.

[0013] The motor vehicle also has an automatic hold function. In the method according to the invention, when the automatic hold function of the motor vehicle is activated, which prevents or is intended to prevent avoidable rolling away of the motor vehicle when stationary, the limitation of the inclination compensation torque is automatically lifted when the motor vehicle comes to a stop on a downhill slope from a previous movement or has just come to a stop - and in particular only then. In this case, for example, the predetermined maximum amount can be ignored or increased or set to 100% of the torque that can be applied by the electric machine and is directed counter to the downhill force or torque, in this case in particular a corresponding braking torque. The hold function can be or have been activated manually, for example, by a driver or vehicle occupant of the motor vehicle.For this purpose, the motor vehicle can, for example, have a corresponding control element, such as a button or a switch, or a corresponding user interface (HMI: Human Machine Interface). By removing the limitation of the inclination compensation torque when stationary, the motor vehicle is then held stationary by the inclination compensation torque regardless of the inclination, even when the brake pedal is released, i.e. not manually operated by the driver of the motor vehicle, as long as the accelerator pedal is not manually operated by the driver. If the driver therefore releases the brake pedal after the motor vehicle has come to a standstill on the gradient, the total torque command in relation to the local incline remains negative or zero. The total torque command indicates at least an assumed command of the driver ora corresponding total torque, which can be determined - at least in part - based on the driver's operating actions, i.e. the actuations or degrees of actuation of the accelerator pedal and the brake pedal, in particular depending on the situation or context. In the situation described, a driver's intention to stop can therefore initially be recognized based on the actuation of the brake pedal with a corresponding force. After the motor vehicle has come to a standstill, the driver's intention can still be recognized as that the motor vehicle should stop, i.e. remain stationary, as long as the driver does not actuate the accelerator pedal. This driver intention is then implemented here, even when the brake pedal is released, by a corresponding increase in the inclination compensation torque above the maximum amount active while the motor vehicle is moving.

[0014] The present invention enables the convenient implementation of an automatic holding function, i.e., a so-called auto-hold function, on downhill gradients. At the same time, the maximum amount of the incline compensation torque maintained during travel enables comfortable, expected, and easily controllable starting on inclines. The invention enables starting on a downhill gradient from a standstill, precisely controlled using the accelerator pedal. This avoids both a rapid increase in speed, which the driver cannot control using the accelerator pedal, caused by quickly releasing a conventional friction brake, and starting against the braking force of such a friction brake. The latter thus also avoids creaking noises that might otherwise occur, which could potentially unsettle the driver and / or impair the comfort of using the motor vehicle.The invention ultimately enables smooth, jerk-free, comfortable and precise starting on a slope, controlled by the accelerator pedal in combination with an auto-hold function.

[0015] In one possible embodiment of the present invention, the tilt compensation torque, particularly both while the motor vehicle is moving and when it is stationary, is generated entirely by the electric motor. In other words, no mechanical or hydraulic braking system, i.e., no friction brake of the motor vehicle, is used to generate the tilt compensation torque or part of it. This allows the described advantages to be realized particularly effectively and comprehensively.

[0016] The present invention also relates to an assistance system for a motor vehicle for implementing an inclination compensation torque while driving and an automatic hold function, i.e., an auto-hold function of the motor vehicle when stationary, in particular when the brake pedal is fully or partially released on a downhill slope or on a downhill stretch. The assistance system according to the invention has a detection or monitoring device for detecting or monitoring the current, i.e., local, inclination of a surface currently being traveled by the motor vehicle. This device can, for example, be or comprise a corresponding inclination sensor and / or an input interface for detecting corresponding inclination data, i.e., for example, sensor data from such an inclination sensor.The assistance system also includes a data processing device for determining and outputting a respective inclination compensation torque to be generated by an electric drive motor of the motor vehicle based on the respective inclination. The assistance system can thus be configured, for example, to directly control the electric motor accordingly or to send a signal indicating the respective inclination compensation torque to be generated to a drive control unit for the electric motor. For this purpose, the assistance system can also have a corresponding output interface.

[0017] The assistance system according to the invention is configured to execute, in particular automatically, the method according to the invention. For this purpose, the data processing device can comprise a processing device, such as a microprocessor, microchip, microcontroller, or the like, and a computer-readable data memory coupled thereto. A corresponding operating or computer program can then be stored in this data memory, which codes or implements the method steps, measures, or sequences described in connection with the method according to the invention, or corresponding control instructions. This operating or computer program can be executable by means of the processing device in order to execute the corresponding method or to effect its execution.

[0018] In one possible embodiment of the present invention, the assistance system is configured to also monitor the position of the accelerator pedal of the motor vehicle and, upon actuation of the accelerator pedal by the driver, thereby ending the standstill, to restore the limitation of the inclination compensation torque to the predefined maximum value following the thus-ending standstill. In other words, the assistance system is configured to reduce the maximum possible - positive or negative - value of the inclination compensation torque again - for example, from 100% - to the lower predefined maximum value after the limitation of the inclination compensation torque has been lifted during the current standstill of the motor vehicle on a downhill slope or during the standstill of the motor vehicle ending with the detected actuation of the accelerator pedal.This means that the described behavior of the vehicle can be reliably realized both when stationary and while driving.

[0019] In one possible development of the present invention, the assistance system is configured to gradually reduce the maximum possible value or amount when the limitation is restored or the inclination compensation moment is correspondingly reduced down to the maximum amount specified for the moving state of the motor vehicle. In other words, when the vehicle comes to a standstill or when it starts moving again from a standstill, the maximum possible value or amount of the inclination compensation moment is not set abruptly, i.e., not suddenly, to the specified maximum amount. Rather, this occurs over a certain period of time. For example, the maximum possible amount of the inclination compensation moment can be gradually reduced continuously or in stages, in particular over a large number of intermediate values. This reliably prevents an abrupt change in the behavior of the vehicle.The vehicle then does not shoot forward suddenly or abruptly, but can move off slowly and in a controlled manner. This ultimately allows a particularly high level of comfort to be achieved in a particularly reliable manner.

[0020] In a possible further development of the present invention, the assistance system is configured to linearly reduce the maximum possible value or amount of the inclination compensation moment when the limitation of the inclination compensation moment is restored. The assistance system is configured to select, specify, or adjust the gradient of this linear reduction depending on the amount of the inclination compensation moment last generated or active while stationary, so that the time period over which the reduction to the predetermined maximum amount occurs increases more slowly than linearly with the amount of the inclination compensation moment last generated while stationary. In other words, the reduction of the maximum possible amount of the inclination compensation moment can always occur linearly on gradients of different strengths or different sizes, but at different rates of change or speeds of change.The reduction occurs more quickly on a steeper or larger gradient, i.e., over a shorter overall period of time, than would be the case if the same gradient were used on a gentler or smaller gradient. This prevents the vehicle from taking too long to return to its normal driving behavior after starting on a particularly steep or steep gradient. This can enable or support comfortable and precise driving and steering of the vehicle for the driver, even in such situations.

[0021] In a further possible embodiment of the present invention, the assistance system is designed to recognize a driver's instruction to stop the motor vehicle while the motor vehicle is moving on a downhill slope if the current sum of the accelerator pedal torque, in particular including the creep torque, the brake pedal torque and the inclination compensation torque is less than the current negated downhill torque. In order to decelerate the motor vehicle on a downhill slope, the said sum must be negative. However, the downhill torque is positive on a downhill slope because it accelerates the motor vehicle in its downhill direction of travel. Accordingly, the driver's instruction to stop can only be recognized if the amount of the said sum is greater than the amount of the downhill torque. In this case, the instruction oran intention of the driver of the motor vehicle with regard to its state of motion is interpreted to mean that the driver wants to bring the motor vehicle to a standstill. This can be the case, for example, if the driver depresses the brake pedal so hard that the corresponding brake pedal torque is greater in magnitude than the sum of the creep torque and the slope drag torque - at least if the driver does not depress the accelerator pedal at the same time. If such a driver intention to stop is detected, then, for example, the removal of the limitation of the inclination compensation torque can already be prepared or, for example below a predetermined maximum speed, a gradual removal of the limitation of the inclination compensation torque, i.e. a gradual, in particular linear, increase or increase in the actually applied and / or the maximum possible amount of the inclination compensation torque can be initiated or started.This can assist in stopping the vehicle and / or reduce any jolt when the vehicle comes to a standstill.

[0022] In a further possible embodiment of the present invention, the assistance system is configured to automatically deactivate the creep torque active during the previous movement of the motor vehicle when the motor vehicle comes to a standstill, particularly on a downhill slope, or has just come to a standstill. In other words, once the motor vehicle has stopped, the creep torque can be reduced to zero. This can simplify the calculation of a total target torque to be set and / or the corresponding control of the electric motor.

[0023] In a possible further development of the present invention, the assistance system is configured to automatically and gradually reactivate the creep torque upon actuation of the accelerator pedal of the motor vehicle by its driver. In other words, the assistance system can cause the creep torque to be gradually increased with or upon starting off the motor vehicle to the predetermined value that existed during the movement of the motor vehicle prior to the standstill or that is predetermined for a movement of the motor vehicle. Such a gradual increase or restoration of the creep torque, i.e. extending over a certain period of time, i.e. gradually occurring, can prevent an abrupt acceleration of the motor vehicle. This can make the movement of the motor vehicle more comfortable for the driver and can be controlled more easily and precisely using the accelerator pedal.

[0024] The present invention also relates to a motor vehicle having an electric drive motor, an accelerator pedal, a brake pedal, and the assistance system according to the invention. Accordingly, the motor vehicle according to the invention can thus be configured to execute, in particular automatically, the method according to the invention. The motor vehicle according to the invention can in particular be the motor vehicle mentioned in connection with the method according to the invention and / or the assistance system according to the invention or correspond thereto. Accordingly, the motor vehicle according to the invention can thus, for example, have the aforementioned inclination sensor and / or the aforementioned drive control unit.

[0025] Further features of the invention may emerge from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures alone, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0026] The drawing shows:

[0027] Fig. 1 is a schematic representation of a motor vehicle equipped with a

[0028] Tilt compensation and an auto-hold function; and Fig. 2 is a schematic diagram illustrating the operation of the functions of the motor vehicle.

[0029] Fig. 1 shows a schematic representation of a motor vehicle 1 with a drive system 2. The drive system 2 is electric here, i.e., comprises an electric machine 3 that can be supplied by a traction battery 4 of the motor vehicle 1. By means of the drive system 2, in particular the electric machine 3, a torque can be applied to driven wheels 5 of the motor vehicle 1. This can be controlled by a driver 6 in an at least partially manual driving mode. For this purpose, the motor vehicle 1 has, indicated here by way of example, an accelerator pedal 7 and a brake pedal 8, which can be operated, i.e., actuated, by the driver 6. By actuating the accelerator pedal 7, the driver 6 can initiate the generation of an accelerating torque, i.e., a positive drive torque, while by actuating the brake pedal 8, they can initiate or cause the generation of a braking torque, i.e., a negative drive torque.

[0030] The motor vehicle 1 is also equipped with a function for automatic inclination compensation, i.e., for automatically compensating for downhill forces or corresponding moments on uphill or downhill gradients, and an automatic hold function for holding the motor vehicle 1 stationary on an incline, i.e., an ascent or descent. For this purpose, the motor vehicle 1 has an inclination sensor 9 and an assistance system 10 for implementing these functions. The assistance system 10 is coupled to the inclination sensor 9, for example, via a bidirectional interface 11 and can also monitor the positions or actuations of the accelerator pedal 7 and the brake pedal 8 and output input or control signals to the drive system 2. For processing corresponding data and generating corresponding output signals, the assistance system 10 comprises a processor 12 and a computer-readable data memory 13, indicated schematically here.

[0031] In existing vehicles, an automatic hold function can be implemented in a brake control unit, which can automatically release a friction brake based on time when starting from a standstill. However, this can lead to the vehicle, for example, shooting forward on a downhill slope, accelerating relatively quickly and in a way that cannot be controlled or controlled by the driver using the accelerator pedal. Likewise, in conventional vehicles,

[0032] Slope compensation functions, but their effectiveness is limited.

[0033] The motor vehicle 1 or its assistance system 10 avoids these problems. For illustration purposes, Fig. 2 shows a schematic diagram in which the temporal progression of various variables is shown. The time t is plotted on the abscissa, while the ordinate can have different meanings depending on the variable or parameter under consideration, in particular it can plot a speed or a torque. Specifically, for an exemplary situation in which the motor vehicle 1 is driving on a gradient, stops and then sets off again, the progressions of the vehicle speed 14, an accelerator pedal desired torque 15, a brake pedal desired torque 16, a total driver desired torque 17 and an inclination compensation torque 18 are plotted here. The vehicle speed 14 initially decreases and reaches a value of zero at a time t1, so that the motor vehicle 1 is at a standstill from time t1.The vehicle speed 14 then remains at zero from time t1 through a later time t2 until a later time t3. From time t3 onward, the motor vehicle 1 begins to move again, so that the vehicle speed 14 then increases again from zero.

[0034] The accelerator pedal command torque 15 is constant at a certain value up to time t1, which in the present example can correspond to a predetermined creep torque. This means that the driver 6 does not manually operate the accelerator pedal 7 before time t1. Higher values ​​of the accelerator pedal command torque 15 would result if the driver 6 actively operated the accelerator pedal 7. The brake pedal command torque 16 represents a deceleration request from the driver 6 in accordance with their operation of the brake pedal 8. In the example shown here, the brake pedal command torque 16 is initially zero, since the driver 6 does not operate the brake pedal 8. At a time before time t1 that is not explicitly marked, the driver 6 operates the brake pedal 8, so that the brake pedal command torque 16 then becomes negative. This expresses that a slope force acting on the gradient ora corresponding torque is to be generated to decelerate the motor vehicle 1. The brake pedal command torque 16 drops here to a certain value, which corresponds to an end position, i.e., a maximum actuation of the brake pedal 8 in the situation represented here. The combination of the accelerator pedal command torque 15, which here includes the predefined creep torque active during travel, the brake pedal command torque 16, and the inclination compensation torque 18 results in the total driver command torque 17. Since the creep torque and the inclination compensation torque 18 are constant here during travel and the driver 6 does not actuate the accelerator pedal 7, the total driver command torque 17 runs parallel to the brake pedal command torque 16 up to time t1.

[0035] The inclination compensation torque 18 is a torque that is automatically caused or initiated by the inclination compensation function of the motor vehicle 1 or the assistance system 10 and generated by the electric machine 3. In this case, the inclination compensation torque 18 is negative because, in the situation shown or represented here, the motor vehicle 1 is on a gradient. Thus, the negative inclination compensation torque 18 partially compensates for a positive downhill torque 19a that is effective in the situation. If the sign of the downhill torque 19a is reversed, this results in a negated downhill torque 19b with the same magnitude as the downhill torque 19a, but with the opposite sign compared to the latter. For further illustration, this negated downhill torque 19b is also shown here. The inclination compensation torque 18 is here before the time t1 orlimited to a predetermined negative maximum value or a predetermined maximum amount until time t1. Since the gradient in the situation represented here is supposed to be relatively large or steep, the slope downforce torque 19a cannot be fully compensated by the inclination compensation function while the motor vehicle 1 is traveling. This is immediately apparent from the fact that the negated slope downforce torque 19b is more negative than the inclination compensation torque 18 until time t1.

[0036] As soon as the total driver request torque 17 falls below the negated slope torque 19b, a stopping request from the driver 6 is detected.

[0037] As already mentioned, motor vehicle 1 actually stops at time t1. In the situation described here, the automatic hold function is active. Therefore, at time t1, i.e., when standstill is reached, the limitation of the inclination compensation torque 18 is lifted. In other words, the system switches to unlimited or complete, i.e., 100 percent, inclination compensation. Therefore, from time t1, the inclination compensation torque 18 corresponds to the negated slope torque 19b. In addition, the creep torque 15 is also automatically deactivated when standstill is reached. This is evident from the fact that from time t1, the accelerator pedal command torque 15 is zero.

[0038] The period between time t1 and the later time t2 is referred to here as the first holding phase 20. During this first holding phase 20, the driver 6 continues to depress the brake pedal 8. However, the total driver command torque 17 is even more negative here compared to the period immediately before time t1, since the creep torque has been deactivated and the inclination compensation torque 18 is now more negative. Thus, during the first holding phase 20, the motor vehicle 1 is held stationary.

[0039] At time t2, driver 6 releases brake pedal 8 without depressing accelerator pedal 7. This mechanical process takes some time, so that brake pedal command torque 16 and, correspondingly, the total driver command torque 17 do not become abruptly but gradually more positive. In principle, if driver 6 releases brake pedal 8 very quickly or abruptly, brake pedal command torque 16 and, correspondingly, the total driver command torque 17 could also become abruptly more positive. As soon as driver 6 has completely released brake pedal 8, brake pedal command torque 16 reaches a value of zero.However, since the driver 6 has not yet depressed the accelerator pedal 7, and therefore the accelerator pedal command torque 15 is still zero, meaning that the total driver command torque 17 is also smaller than the downhill torque 19a, and the motor vehicle 1 is still stationary, the assistance system 10 assumes that the driver 6 still wishes the motor vehicle 1 to remain stationary. This is achieved here by the downhill torque 19 being fully compensated for by the inclination compensation torque 18, which can be adjusted as desired and is therefore not limited to a predetermined maximum amount. In a second holding phase 21 lying between time t2 and the later time t3, the motor vehicle 1 is therefore automatically held stationary even if the brake pedal 8 is partially or completely released. Time t3 is then followed by a starting phase 22. In this starting phase 22, the driver 6 depresses the accelerator pedal 7, possibly only minimally.In the part or section of the start-off phase 22 shown here, the degree of actuation of the accelerator pedal 7 can, for example, still be less than one percent of the maximum actuation or adjustment range of the accelerator pedal 7. Based on the actuation of the accelerator pedal 7 by the driver 6, the assistance system 10 detects a start-off request by the driver 6. Subsequently, in this case from time t3, on the one hand the limitation of the inclination compensation torque 18 is restored and, on the other hand, the creep torque is reactivated. Both of these occur gradually here, i.e. not abruptly. At time t3, the driver 6 therefore actuates the accelerator pedal 7 and thereby causes or causes the total driver command torque 17 to become greater, i.e. more positive, than the negated slope torque 19b. As a result, the motor vehicle 1 starts moving. Since the brake pedal 8 was neither actuated by the driver 6 before time t3, nor was a corresponding braking system orFriction brake was actuated or activated, but the motor vehicle 1 was held at a standstill in the second holding phase 21 merely by the inclination compensation torque 18 generated solely by means of the electric machine 3, the motor vehicle 1 can start off gently and slowly from time T3 without jerking and precisely controlled by the driver 6 solely by means of the accelerator pedal 7.

[0040] Overall, the examples described show how a driver request calculation with activated Auto-Hold function and an automatic switching of an incline or gradient compensation can be realized and applied in order to achieve improved comfort.

[0041] List of reference symbols

[0042] 1 motor vehicle

[0043] 2 drive system

[0044] 3 electric machine

[0045] 4 Traction battery

[0046] 5 wheels

[0047] 6 drivers

[0048] 7 Accelerator pedal

[0049] 8 Brake pedal

[0050] 9 Tilt sensor

[0051] 10 Assistance system

[0052] 11 Interface

[0053] 12 processors

[0054] 13 Data storage

[0055] 14 Vehicle speed

[0056] 15 Accelerator pedal desired torque

[0057] 16 Brake pedal desired torque

[0058] 17 Total driver request torque

[0059] 18 Tilt compensation moment

[0060] 19a Downhill torque

[0061] 19b negated slope torque

[0062] 20 first holding phase

[0063] 21 second holding phase

[0064] 22 Start-up phase t1, t2, t3 times

Claims

Patent claims 1. A method for automatically controlling a drive system (2) of a motor vehicle (1) driven by an electric machine (3), wherein - an inclination of a surface currently travelled by the motor vehicle (1) is monitored in the longitudinal direction and, based on the respective current inclination, a corresponding inclination compensation torque (18) is determined for at least partially compensating a slope downforce torque (19a) caused by the inclination, - the inclination compensation torque (18) is generated by appropriate automatic control of the electric machine (3), wherein the inclination compensation torque (18) is limited to a predetermined maximum value as long as the motor vehicle (1) is moving, - when the automatic holding function of the motor vehicle (1) is activated, which prevents the motor vehicle (1) from rolling away when stationary, when the motor vehicle (1) comes to a standstill on a gradient after a previous movement, the limitation of the inclination compensation moment (18) is lifted, so that the motor vehicle (1) is then held at a standstill by the inclination compensation moment (18) regardless of the inclination, even when the brake pedal (8) is released, as long as an accelerator pedal (7) of the motor vehicle (1) is not actuated.

2. Method according to claim 1, characterized in that the inclination compensation torque (18) is generated entirely by means of the electric machine (3).

3. Assistance system (10) for a motor vehicle (1) for implementing an inclination compensation function while driving and an automatic holding function of the motor vehicle (1) when stationary, comprising a monitoring device (9, 12, 13) for monitoring the inclination of a surface currently traveled by the motor vehicle (1) and a data processing device (12, 13) for determining and outputting a respective inclination compensation torque (18) to be generated by an electric drive motor (3) of the motor vehicle (1) based thereon, wherein the assistance system (10) is configured to carry out the method according to one of claims 1 or 2.

4. Assistance system (10) according to claim 3, characterized in that the assistance system (10) is designed to restore the limitation of the inclination compensation torque (18) to the predetermined maximum value when an accelerator pedal (7) of the motor vehicle (1) is actuated after the vehicle has come to a standstill.

5. Assistance system (10) according to claim 4, characterized in that the assistance system (10) is designed to gradually reduce the maximum possible amount of the inclination compensation moment (18) when restoring the limitation thereof.

6. Assistance system (10) according to claim 5, characterized in that the assistance system (10) is designed to reduce the maximum possible amount of the inclination compensation moment (18) linearly when restoring the limitation thereof, wherein the gradient of the linear reduction is dependent on the amount of the inclination compensation moment (18) last generated at standstill, so that a time period over which the reduction takes place up to the predetermined maximum amount increases less than linearly with the amount of the inclination compensation moment (18) last generated at standstill.

7. Assistance system (10) according to one of claims 3 to 6, characterized in that the assistance system (10) is designed to recognize a driver's wish to stop the motor vehicle (1) during the movement of the motor vehicle (1) on a downhill slope when the current sum of the accelerator pedal torque (15), in particular including the creep torque, the brake pedal torque (16) and the inclination compensation torque (18) is smaller than the current negated slope torque (19b).

8. Assistance system (10) according to one of claims 2 to 7, characterized in that the assistance system (10) is designed to automatically deactivate the creeping moment active during the previous movement of the motor vehicle (1) when the motor vehicle (1) comes to a standstill, in particular on the downhill slope.

9. Assistance system (10) according to claim 8, characterized in that the assistance system (10) is designed to automatically and gradually reactivate the creep torque upon actuation of the accelerator pedal (7) of the motor vehicle (1).

10. Motor vehicle (1), comprising one or more electric drive motors (3), an accelerator pedal (7), a brake pedal (8), and the assistance system (10) according to one of claims 3 to 9.

Images