Method, computing unit and computer program for operating a vehicle with an electric motor by means of a control element

Abstract

The present invention relates to a method for operating a vehicle with an electric motor by means of an operating element, comprising determining a current target torque of the electric motor as a function of a current operating element position using a first relationship (1v) between the operating element position (S FP ) and the target torque (M S ), wherein the first relationship (1v) has a first point (Su), which is given by a first control element position and a zero torque, and a second point (R), which is given by a second control element position and a first minimum target torque, and, if a second minimum target torque of the electric motor is received, which differs from the first minimum target torque, determining a second relationship (1v') between the control element position (S FP ) and the target torque (M S), wherein the second relationship (1v', 1v''') has a third point (F), which is given by the current control element position and the current target torque, and a fourth point (R'), which is given by a third control element position and the second minimum target torque.

Description

[0001] The present invention relates to a method for operating a vehicle with an electric motor by means of an operating element as well as a computing unit and a computer program for carrying out the method. Background of the invention

[0002] In an electric vehicle or a hybrid vehicle with an electric drive option, deceleration of the vehicle can be achieved by operating the accelerator pedal (control element) below a predetermined threshold. Regenerative braking is initiated at this accelerator pedal position and the electric motor operates as a generator and thus as an electromotive brake. This eliminates the need to switch to the brake pedal in most driving situations. The regenerative braking torque (negative torque) of the electric motor can be increased by further reducing the accelerator pedal's pressure until the maximum regenerative braking torque (minimal negative torque) is reached with the accelerator pedal depressed.

[0003] DE 10 2006 044 773 A1 relates to a method for operating a drive device for a hybrid vehicle, which has an electric motor and an internal combustion engine. A drive torque can be specified by actuating a control element of the drive device, which can be freely adjusted between a minimum and maximum position, by the driver. During coasting of the hybrid vehicle, the minimum position of the control element essentially corresponds to the torque loss of the internal combustion engine and / or the auxiliary units and forms an accelerator pedal contact point.

[0004] The recuperation torque curve versus accelerator pedal position (i.e., the dependence of the recuperation torque on the accelerator pedal position) can also be influenced by the driver by selecting a recuperation level or a driver profile (e.g., SPORT or ECO). Furthermore, additional factors, such as information about vehicles ahead (distance, speed, acceleration, etc.) or environmental information (gradient, speed limits, road layout, road surface, etc.), can be used to dynamically adapt the recuperation torque curve.

[0005] Such an adjustment can result in a different target torque being calculated during vehicle deceleration with an unchanged accelerator pedal position, thereby changing the driving behavior without the driver having to vary the accelerator pedal actuation. Such a change in the target torque is understandable to the driver if it represents a reaction to their input (e.g., changing the recuperation level or the driving profile). However, if the curve is changed without driver interaction, e.g., due to environmental information, there is a possibility that the changed driving behavior will surprise the driver or represent behavior that is incomprehensible to them. Disclosure of the invention

[0006] According to the invention, a method for operating a vehicle with an electric motor by means of an operating element, as well as a computing unit and a computer program for implementing the method, are proposed, having the features of the independent patent claims. Advantageous embodiments are the subject of the subclaims and the following description.

[0007] In this process, a current target torque of the electric motor is first determined as a function of a current control element position from a first relationship between the control element position and the target torque. The first relationship can, for example, be a predetermined relationship or standard relationship stored in a computing unit executing the method, such as a vehicle control unit.

[0008] In general, a relationship between a control element position and a target torque of a drive motor can be given either in the form of a characteristic curve or a characteristic map or a calculation rule and can be stored, for example, in a control unit (e.g. engine management) of the vehicle. Particularly in vehicles with an electric motor, the relationship can comprise three areas: an area for driving the vehicle (drive area), in which a positive target torque is present; an area for a coasting mode of the vehicle (coasting area), in which the target torque is zero; and a further area for decelerating the vehicle (deceleration area), in which a negative target torque is present, so that the electric motor operates as a generator and recuperates the vehicle's kinetic energy.

[0009] The invention relates to the deceleration range of such a relationship and presents an improved adaptation of the same when a change in the maximum recuperation torque (minimum (signed) target torque) is requested or specified during vehicle deceleration. The invention takes into account a current position of the control element when adapting the relationship, so that a current target torque is not affected.

[0010] The control element can, in particular, be the vehicle's accelerator pedal. Other types of control elements, such as rotary knobs, levers, etc., are also possible.

[0011] The first relationship has a first point, which is defined by a first control element position and a target torque of zero, and a second point, which is defined by a second control element position and a first minimum target torque. The first control element position represents, in particular, a lower value of a coasting range, i.e., the control element position at which no recuperation torque is yet absorbed by the electric motor. The second control element position corresponds, in particular, to an unactuated control element.

[0012] The term "sailing," particularly in electric and hybrid vehicles, refers to a driving mode in which the vehicle moves solely on kinetic energy, with its drive motor(s) neither absorbing nor releasing torque. Consequently, the target torque value during sailing is zero.

[0013] In this context, the coasting range should be understood as the adjustment range of the control element in which the target torque is zero. This means that a change in the position of the control element within the coasting range does not result in a change in the target torque, but rather, it remains at zero. By optimizing the width / size of the coasting range, for example, depending on the vehicle's speed, the utilization of its kinetic energy can be improved.

[0014] According to one embodiment, the first relationship can be given as a linear relationship corresponding to a straight line between the first point and the second point. In this case, the first relationship has a first gradient.

[0015] If, during vehicle deceleration, a second minimum target torque of the electric motor is received that differs from the first minimum target torque, the relationship is adjusted starting from the current control element position upon receipt of the second minimum target torque in order to obtain a second relationship that has a third point, which is given by the current control element position and the current target torque, and a fourth point, which is given by a third control element position and the second minimum target torque. The third control element position also corresponds in particular to an unactuated control element. This means that the current target torque does not change if the control element position remains unchanged; rather, a torque change only occurs when the control element position also changes.In this way, the driver can understand the vehicle’s deceleration behavior at any time.

[0016] According to one embodiment, the second and / or third control element position can correspond to a zero position of the control element. In this case, the minimum target torque only occurs when the driver no longer operates the control element. In this way, its adjustment range can be fully utilized.

[0017] According to one embodiment, the second relationship may include a first linear region defined as a straight line between the third point and the fourth point. In this case, the first linear region has a second gradient that differs from the first gradient.

[0018] According to one embodiment, the second relationship can comprise a second linear region which is defined as a straight line between the third point and the first point. The second linear region thus adjoins the first linear region in the direction of larger control element positions and corresponds to the first relationship there. In this case, the second linear region has a third gradient which corresponds to the first gradient but differs from the second gradient. This means that the second relationship has a kink at the current control element position, i.e. that a gradient of the target torque changes at this point, which can result in a change in the deceleration behavior during continuous actuation of the control element. In this case, the coasting region of the second relationship can be the same size as the coasting region of the first relationship.

[0019] To counteract the change in deceleration behavior, according to another embodiment, the second relationship can include a second linear range that has the same gradient as the first linear range, i.e., is defined as a straight line between the third point and a fifth point, which results from the extrapolation of the first linear range to a target torque of zero. This results in a continuous curve of the target torque over the control element position. In this case, a modified adjustment range of the control element for coasting results.

[0020] In this case, in particular, the sailing range of the second relationship can be greater than the sailing range of the first relationship if the second minimum target torque is less than the first minimum target torque, or the sailing range of the second relationship can be smaller than the sailing range of the first relationship if the second minimum target torque is greater than the first minimum target torque. In other words, the adjustment range of the control element, in which no torque is delivered or absorbed by the electric motor, can be changed, and thus the response behavior of the control element can be changed.

[0021] A computing unit according to the invention, e.g. a control unit of a motor vehicle, is configured, in particular in terms of programming, to carry out a method according to the invention.

[0022] The implementation of a method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps is also advantageous, since this entails particularly low costs, in particular if an executing control unit is also used for other tasks and is therefore already present. Finally, a machine-readable storage medium is provided with a computer program stored thereon as described above. Suitable storage media or data carriers for providing the computer program are, in particular, magnetic, optical and electrical memories, such as hard disks, flash memories, EEPROMs, DVDs, and others. Downloading a program via computer networks (Internet, intranet, etc.) is also possible. Such a download can be wired or cable-based or wireless (e.g. via a WLAN network, a 3G, 4G, 5G or 6G connection, etc.).

[0023] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0024] The invention is illustrated schematically in the drawings using exemplary embodiments and is described below with reference to the drawings. Short description of the drawings Fig. 1 schematically shows an example of a relationship between a position of an operating element and a target torque of a vehicle drive, the adaptation of which when the minimum target torque changes during deceleration does not take place according to an embodiment of the invention. Fig. 2 shows the relationship Fig. 1, wherein the adaptation thereof is carried out upon change of the minimum target torque during deceleration according to an embodiment of the invention. Fig. 3 shows the relationship Fig. 1, wherein its adaptation is carried out upon change of the minimum target torque during deceleration according to a further embodiment of the invention.

[0025] In the figures, identical elements are provided with identical reference symbols. Therefore, a repetitive description is omitted where appropriate. Embodiment(s) of the invention

[0026] Fig. 1 shows schematically an example of a relationship between a position of a control element S FP and a target torque M S of a vehicle drive, the adaptation of which upon change of a minimum target torque R, R' during deceleration does not take place according to an embodiment of the invention.

[0027] In the present example, the functional relationship is shown as characteristic curve 1, which represents the target torque M S an electric motor of the vehicle drive via the position of the control element SFP The control element can in particular be an accelerator pedal of a vehicle. Between an accelerator pedal position S FP from 25% to 100%, in the example shown, a positive target torque M S is output to the electric motor, which is then used to drive the vehicle (drive range 1b). The course of characteristic curve 1 is linear in drive range 1b, i.e., if the accelerator pedal is depressed more forcefully, the vehicle's drive torque increases accordingly. Drive range 1b is limited downwards by the accelerator pedal position So, at which the target torque is zero. In this case, this is a pedal travel of 25%, which must be overcome by the driver for the electric motor to deliver positive torque.

[0028] If the accelerator pedal position S FP in the range from Su = 20% to So = 25%, no target torque M Soutput (sailing range 1s). At these accelerator pedal positions, the vehicle is used in sailing mode without outputting or receiving any torque from the electric motor. In other words, the target torque M S between the accelerator pedal position Su (first control element position) and So (third control element position) is constantly at the value zero.

[0029] If the accelerator pedal position falls below S FP the value of Su = 20%, a deceleration range 1v of characteristic curve 1 comes into effect, in which a negative target torque M S(recuperation torque) is effective and the electric motor is thus operated as a generator. The generator is driven by the vehicle's kinetic energy, which allows it to be braked. With the accelerator pedal at a minimum position (second control element position), a maximum recuperation torque R (first minimum target torque) required for braking in the current driving situation is output. In the example shown, the target torque M S between the accelerator pedal position Su = 20% and the minimum accelerator pedal position S FP = 0 (zero position) and thus the braking effect of the generator is continuously increased as the pedal travel decreases.

[0030] In the example shown, an operating point F is shown in the deceleration range 1v, which symbolizes that at this operating point, e.g. due to changing ambient conditions, a stronger braking effect and thus a lower minimum target torque R' (second minimum target torque) is required. In the case shown, which is not according to the invention, a new linear curve 1v' of the target torque M S between the accelerator pedal position Su = 20% and the minimum accelerator pedal position S FP = 0. This means that at the current operating point F, with a constant accelerator pedal position of S FP = 5%, the target torque M Sis suddenly reduced, thus setting a new operating point F', even though the accelerator pedal position has not been changed. Such a change may be understandable or expected by the driver if it represents a reaction to their input (e.g., change in the recuperation level or driving profile). However, if the maximum recuperation torque is changed without driver interaction, e.g., due to environmental information, there is a possibility that the changed driving behavior will surprise the driver or represent behavior that is incomprehensible to them.

[0031] Such behavior can be avoided with the present invention, as will be shown by the following embodiments.

[0032] Fig. 2 shows the relationship (first relationship) from Fig. 1, wherein the adjustment of the deceleration range 1v upon change of the minimum target torque R, R' during a deceleration is carried out according to an embodiment of the invention in order to obtain a second relationship. In the deceleration range 1v, the operating point F is again shown. In the example shown, when a lower minimum target torque R' (second minimum target torque) is requested, a new linear curve 1v' of the target torque M S between the current accelerator pedal position (current control element position) in the operating point F (S FP = 5%) and the minimum accelerator pedal position S FP = 0 at point R'. This keeps the current operating point F constant and the target torque M S is only activated when the accelerator pedal is in S position FP<5% according to the new linear target torque curve 1v' to the second minimum target torque. If the pedal travel exceeds the accelerator pedal position S FP = 5%, the target torque M S raised according to the originally calculated curve 1v. The now effective second relationship thus comprises a first linear region 1v' as a straight line between point F and point R', and a second linear region 1v'' as a straight line between point F and point Su.

[0033] Fig. 3 also shows the first connection from Fig. 1, wherein the adaptation of the deceleration range 1v upon change of the minimum target torque from R to R' during a deceleration is carried out according to a further embodiment of the invention in order to obtain a different second relationship.

[0034] In the deceleration range 1v, the operating point F is again shown, in which a lower minimum target torque R' (second minimum target torque) is requested. In the example shown, analogous to the representation in Fig. 2 a new linear curve 1v' of the target torque M S between the current accelerator pedal position at the operating point F (S FP = 5%) and the minimum accelerator pedal position S FP = 0. In addition, the gradient of the target torque curve 1v between the current accelerator pedal position S FP = 5% and the accelerator pedal position Su = 20%, in which the target torque is zero, is adapted to the gradient of the target torque curve 1v' by extrapolation. This results in a new target torque curve 1v''' between the current accelerator pedal position S FP = 5% and an accelerator pedal position Su' in which the target torque M S the value M S= 0. The now effective second relationship thus again includes the first linear region 1v' as a straight line between the point F and the point R', and another second linear region 1v''' as a straight line between the point F and the point Su'.

[0035] In the example shown, the sailing range 1s is also increased by reducing the accelerator pedal position Su = 20% to Su' ≈ 8%. However, it is also possible to keep the width / size of the sailing range 1s constant by additionally reducing the accelerator pedal position So accordingly. In this case, the drive range 1b is reduced to accelerator pedal positions S FP < 25% expanded.

[0036] By additionally adjusting the target torque curve 1v'' between the operating point F and the lower limit of the sailing range Su, a continuous change of the target torque curve 1v', 1v''' from zero to the second minimum target torque R' is achieved, which corresponds to the driver's expectations.

[0037] Although the figures only show examples in which the second minimum target torque is smaller than the first minimum target torque, the invention is applicable to all cases, in particular even if the second minimum target torque is greater than the first minimum target torque. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2006 044 773 A1

[0003]

Claims

[1] Method for operating a vehicle with an electric motor by means of an operating element, comprising the steps: Determining a current target torque of the electric motor as a function of a current control element position based on a first relationship (1v) between the control element position (S FP ) and the target torque (M S ), wherein the first relationship (1v) has a first point (Su) which is given by a first control element position and a zero torque, and a second point (R) which is given by a second control element position and a first minimum target torque when a second minimum target torque of the electric motor is received which differs from the first minimum target torque, Determining a second relationship (1v', 1v'', 1v''') between the control element position (S FP ) and the target torque (M S), wherein the second relationship (1v', 1v'', 1v''') has a third point (F), which is given by the current control element position and the current target torque, and a fourth point (R') which is given by a third control element position and the second minimum target torque. [2] Method according to claim 1, wherein the second and / or third operating element position corresponds to a zero position of the operating element. [3] Method according to claim 1 or 2, wherein the first relationship (1v) is given as a linear relationship corresponding to a straight line between the first point (Su) and the second point (R). [4] Method according to one of the preceding claims, wherein the determination of the second relationship (1v', 1v'', 1v''') between the control element position (S FP ) and the target torque (M S) comprises determining a first linear region (1v') of the second relationship as a straight line between the third point (F) and the fourth point (R'). [5] Method according to claim 4, wherein the determination of the second relationship (1v', 1v'', 1v''') between the control element position (S FP ) and the target torque (M S ) comprises determining a second linear region (1v'') as a straight line between the third point (F) and the first point (Su). [6] Method according to claim 4, wherein the determination of the second relationship (1v', 1v'', 1v''') between the control element position (S FP ) and the target torque (M S ) comprises determining a second linear range (1v''') as a straight line between the third point (F) and a fifth point (Su'), which results from the extrapolation of the first linear range (1v') to a target torque of zero. [7] Computing unit which is configured to carry out all method steps of a method according to one of the preceding claims. [8] Computer program which causes a computing unit to carry out all the method steps of a method according to one of claims 1 to 6 when it is executed on the computing unit. [9] A machine-readable storage medium having stored thereon a computer program according to claim 8.

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