Method for operating an electric motor vehicle, computer program product and electric motor vehicle

Abstract

A method for operating an electric motor vehicle is described, which has at least one electric motor supplied with energy by at least one traction battery, wherein the electric motor has a torque-speed characteristic map, wherein a plurality of speed levels are defined, each having a minimum speed and a maximum speed, wherein two adjacent speed levels overlap, wherein a speed level is specified, wherein a control variable is calculated in which a ratio between a difference between the current speed and the minimum speed of the corresponding speed level on the one hand and a difference between the maximum speed and the minimum speed of the speed level on the other hand is used, wherein the control variable is used to control at least one actuator.

Description

[0001] A method for operating an electric vehicle, a computer program product, and an electric vehicle are described.

[0002] Methods for operating an electric motor vehicle, computer program products and electric motor vehicles of the type mentioned above are known in the prior art.

[0003] Electric vehicles are perceived by many drivers as less emotionally engaging than vehicles with combustion engines, a perception attributable to several technical and sensory factors. A key aspect is the absence of the characteristic engine noise, which in combustion engines not only provides acoustic feedback about performance and driving conditions but is also often associated with a sense of dynamism and sportiness. The deep rumble of a large-displacement engine or the revving of a turbocharger creates an emotional connection to the vehicle for many people, often established in early childhood—a connection largely absent in electric vehicles. While artificially generated soundscapes exist for electric cars, these are often perceived as less authentic.

[0004] Another factor is the altered driving experience. While combustion engines, with their specific performance characteristics including acceleration lag, speed-dependent vibrations, gear changes, and speed-dependent power delivery, offer haptic feedback, electric motors deliver immediate and linear acceleration. Although this directness objectively offers greater efficiency and better performance, many drivers miss the familiar interplay of engine speed, accelerator pedal position, and transmission ratio, which is perceived as intuitive and emotionally engaging. Driving an electric vehicle can therefore seem technically impressive, but less dynamic.

[0005] Furthermore, the absence of a mechanical connection between the engine, transmission, and drivetrain—for example, through the elimination of a manual gearbox—contributes to altered perceptions, as gear changes in combustion engine vehicles are often considered an integral part of the driving experience. Highly automated driving modes, regenerative braking systems, and one-pedal driving approaches can also diminish the feeling of direct control over the vehicle.

[0006] Automakers have developed various approaches to make the driving experience of electric vehicles more emotional. These include artificially generated gear changes that simulate an interruption in torque delivery through software control. Some manufacturers also offer driving modes that modify the electric motor's responsiveness to resemble the speed-dependent power delivery of an internal combustion engine. These measures aim to create a familiar connection between driver and vehicle by generating sensory stimuli associated with classic sports cars or high-performance vehicles.

[0007] However, such simulations often come at the cost of diminishing the inherent advantages of an electric motor. Artificially reducing torque to mimic combustion engines reduces the normally seamless and instantaneous power delivery of an electric motor and can impair its efficiency.

[0008] From DE 10 2021 201 424 A1, a method for virtualizing the characteristics of a vehicle with an internal combustion engine in an electric vehicle is known, comprising the following: receiving vehicle driving information of the electric vehicle at a controller, determining a current vehicle driving mode based on the input vehicle driving information by the controller, determining a virtual engine speed in the determined vehicle driving mode using the vehicle driving information by the controller, outputting a control signal to virtualize characteristics of an internal combustion engine (ICE) drive system corresponding to a current vehicle driving mode, based on the determined virtual engine speed by the controller, and virtualizing the characteristics of the ICE drive system corresponding to the current vehicle driving mode.by controlling the operation of a virtualization device according to the control signal output by the controller.

[0009] German patent DE 10 2011 108 956 A1 describes a method for informing a driver about the operating state of a motor vehicle, whereby a virtual engine speed and a virtual gear position are determined from at least one first operating parameter describing the operating state of the motor vehicle. US patent 2012 / 0 106 748 A1 discloses a system for generating noise simulations of a multi-speed vehicle.

[0010] The task therefore is to further develop procedures for operating an electric vehicle, computer program products and electric vehicles of the type mentioned above in such a way that an emotional driving experience is made possible in an electric vehicle without having the disadvantages of known emulations of a motor vehicle with an internal combustion engine.

[0011] The problem is solved by a method for operating an electric motor vehicle according to claim 1, a computer program product according to dependent claim 9, and an electric motor vehicle according to dependent claim 10. Further embodiments and developments are the subject of the dependent claims.

[0012] A method for operating an electric motor vehicle is described, which has at least one electric motor supplied with energy by at least one traction battery, wherein the electric motor has a torque-speed characteristic map, wherein a plurality of speed levels are defined, each having a minimum speed and a maximum speed, wherein two adjacent speed levels overlap, wherein a speed level is specified, wherein a control variable is calculated in which a ratio between a difference between the current speed and the minimum speed of the corresponding speed level on the one hand and a difference between the maximum speed and the minimum speed of the speed level on the other hand is used, wherein the control variable is used to control at least one actuator.

[0013] The control variable determines the difference between the current speed of at least one electric motor and a lower speed limit of a selected speed stage, divided by the speed spread of the corresponding speed stage. The control variable can be expressed mathematically as follows: Control variable = (current RPM - RPM stage X,min) / (max RPM stage X - RPM stage X,min)

[0014] Depending on the design, a varying number of speed levels can be defined, e.g., two to eight speed levels, which corresponds to the usual gear ratios of most internal combustion engine-powered vehicles with manual or automatic transmissions. Internal combustion engine vehicles with fewer or considerably more gear ratios are also known, but the majority have between six and nine gear ratios. Accordingly, a possible further development provides for between two and nine, and in particular six to nine, speed levels.

[0015] In vehicles with internal combustion engines, the usable gear ratios overlap for certain speed ranges, allowing a specific speed to be maintained in multiple gears. For example, with a typical 6-speed transmission, all gears between second and fifth gear can be used at 50 km / h.

[0016] The definition of a speed stage can be compared to the definition of a gear stage in a motor vehicle. In an electric vehicle, which usually has a single-speed or two-speed transmission, the vehicle's speed is linearly dependent on the speed, meaning that the speed of at least one electric motor is proportional to the vehicle's speed.

[0017] The corresponding control variable can be used to emulate the driving feel of a combustion engine vehicle by means of at least one actuator, without any other limitations on the availability of power and torque from the electric motor. In this way, the emotional driving experience of a combustion engine can be combined with the advantages of an electric vehicle.

[0018] With this method, the emotionalization of the driving behavior is achieved solely in terms of the rotational speed of the at least one electric motor, introducing simulated stages into the motor's performance map. Modulation of torque and / or power output is permissible in this mode only to improve drivability, in order to maintain the advantages of the underlying electric vehicle drive system.

[0019] Because the torque characteristics of at least one electric motor still apply, electric vehicle-specific functions such as the short-term activation of overtorque, high drive dynamics, and instantaneous response from any operating point can still be represented. The known replicas or simulations of an internal combustion engine powertrain, such as typical operating behavior or torque build-up, are not represented by this method.

[0020] The procedure can be selected and deselected by the driver of the motor vehicle as a driving mode.

[0021] In a first further development, it is envisaged that the actuator is part of a loudspeaker.

[0022] In this way, the control variable can serve as a control variable for a tone or noise to be emitted via one or more loudspeakers. Since the control variable is a relative and dimensionless quantity, and a specific control variable can occur at each speed level, or at least most of the speed levels, essentially the same noises or tones can be emitted at the corresponding speed levels.

[0023] In a further, more advanced embodiment, it is provided that the actuator is part of a vibration-generating device.

[0024] The vibrations enhance sensory perception, which is an important part of the driving experience for many drivers.

[0025] In a further, more advanced embodiment, it is provided that when the electric vehicle is stationary, sounds, noises and / or vibrations are introduced into the interior and, in some embodiments, into the exterior of the vehicle via loudspeakers.

[0026] This allows for appropriate acoustic behavior and / or haptic feedback to be achieved even when stationary, if a machine is to be simulated that does not have a zero speed during operation, e.g., an internal combustion engine, since the electric drive itself has no speed when stationary and therefore cannot provide any perceptible feedback.

[0027] In a further, more advanced embodiment, it is provided that higher-frequency oscillations are introduced into the three-phase current via three-phase modulation of an inverter of at least one electric drive.

[0028] This means that vibrations can be generated via the electric drivetrain.

[0029] The deliberate introduction of these vibrations into the three-phase current also depends on the control signal and, with its vibration frequency, matches the depicted acoustic behavior of the electric vehicle.

[0030] In this way, it is possible to simulate vibrations depending on the control variable.

[0031] In a further refined embodiment, it is provided that when a maximum speed of a speed stage is reached, a switch is made to a higher speed stage and / or when a minimum speed of a speed stage is reached, a switch is made to a lower speed stage.

[0032] This gear change can therefore occur automatically if the driver falls below or exceeds the minimum or maximum engine speed of the respective gear, or is in automatic gear change mode.

[0033] In further training, the automatic step change mode can select the step that best reflects this operating condition based on the current speed or rotational speed of at least one electric motor and the load requirement of the driver.

[0034] The current engine speed is selected in such a way that it is set as far away as possible from the respective maximum or minimum engine speed of that speed. A load-dependent shift to higher or lower engine speeds may be provided, for example, to a lower engine speed during sporty driving.

[0035] In a further, more advanced embodiment, it is provided that switching from one speed level to another is done by manual input.

[0036] This allows the driver to manually select the current engine speed, taking into account the available range for that speed. This can be done by interacting with a control element in the vehicle interior, such as steering wheel paddle shifters.

[0037] In a further refinement, it is provided that a change in longitudinal acceleration is made when switching from one speed stage to another.

[0038] A brief change in longitudinal acceleration when transitioning from one stage to another serves to add emotional impact.

[0039] The change in longitudinal acceleration during the gear change can factorially model the control variable for at least one electric motor depending on the respective driving condition, so that a clearly perceptible short-term change in acceleration occurs in each case.

[0040] In a further, more advanced version, it is envisaged that the tax variable includes factors and / or addends.

[0041] In this configuration, the mathematical control variable can be modeled by factoring and adding constant parameters, so that the range of values ​​corresponds to any machine to be simulated, for example, that of a typical reciprocating internal combustion engine (e.g., 700 ... 8000 rpm) or that of an aircraft engine (e.g., 11000 ... 17000 rpm).

[0042] In particular, the factors can be greater or less than 1, and the summands can be positive or negative.

[0043] In a further, more advanced design, it is envisaged that energy recuperation takes place during thrust operation, taking into account the control variable.

[0044] For the vehicle's overrun mode, the applied deceleration torque with which the vehicle recuperates can therefore also depend on the value of the control variable in the respective speed stage, e.g. the higher the current value of the control variable, the higher the applied negative torque of the electric motor.

[0045] In a further, more advanced embodiment, it is provided that the current modeled value of the control variable or a value derived from the control variable is displayed in the motor vehicle.

[0046] A first independent subject matter relates to a computer program product comprising a computer-readable storage medium on which instructions are embedded which, when executed by at least one computing unit, cause that at least one computing unit to be equipped to execute the procedure of the aforementioned type.

[0047] The process can be executed on one or more computing units, so that certain process steps are executed on one computing unit and other process steps on at least one other computing unit, whereby calculated data can be transmitted between the computing units if necessary.

[0048] Another independent item concerns an electric motor vehicle with a computer program product of the type described above.

[0049] Further advantages, features, and details will become apparent from the following description, in which – possibly with reference to the drawing – at least one embodiment is described in detail. Identical, similar, and / or functionally equivalent parts are identified by the same reference numerals.

[0050] They show schematically: Fig. 1. A top view of an electric motor vehicle, as well as Fig. 2 a torque-speed characteristic map of the electric motor of the electric vehicle Fig. 1.

[0051] Fig. Figure 1 shows a top view of an electric vehicle.

[0052] The electric vehicle 2 has a traction battery 4 and an electric motor 6. In alternative configurations, more than one traction battery and more than one electric motor can be provided. The traction battery 4 supplies the electric motor 6 with energy to propel the electric vehicle 2 by means of the electric motor 6.

[0053] The electric motor 6 is connected to a controller 8, which has a processing unit 8.1 and a memory 8.2. A computer program product is loaded in the memory 8.2, which implements the procedure described below. The controller 8 receives information from the electric motor 6 about the current speed of the electric motor and can calculate a control variable S using the processing unit 8.1, which is defined as follows: Control variable = (current RPM - RPM stage X,min) / (max RPM stage X - RPM stage X,min)

[0054] In alternative configurations, the control variable S can be manipulated using factors and / or summands in order to emulate different drive types.

[0055] The control variable S is used to control a loudspeaker 12 via a loudspeaker actuator 12.1. Alternatively or additionally, vibration generators with corresponding actuators can be provided, which can generate corresponding vibrations depending on the control variable S. An inverter of the electric motor 6 (not shown) can also be used as an actuator by inducing high-frequency voltage and current fluctuations in the electric motor, causing the drive train of the electric vehicle 2 to vibrate. Vibrations can also be generated in the electric vehicle 2 via special loudspeakers.

[0056] The control variable S generally describes the current rotational speed of a conventional drive motor at a corresponding speed level. This value can be used to enhance the driving experience of the electric vehicle 2 by generating acoustic and / or haptic signals that can be perceived by the driver and possibly other occupants of the vehicle.

[0057] In particular, it may be provided that at a very low rotational speed, i.e. in a state in which the electric vehicle 2 is stationary or only rolling slowly, a certain noise is generated that, for example, emulates an internal combustion engine at a standstill.

[0058] The control variable can be manipulated by factors and summands, allowing a variety of different drives to be emulated, for example, an internal combustion engine or internal combustion engines with different numbers of cylinders, or other drive types such as turbines or the like. In certain embodiments, the corresponding emulations can be selected by the driver of the electric vehicle 2.

[0059] Fig. Figure 2 shows a torque-speed characteristic map 14 of the electric motor 6, in which the speed of the electric motor 6 is shown on the x-axis and the maximum possible torque of the electric motor 6 is shown on the y-axis.

[0060] Electric motors in electric vehicles typically exhibit a relatively constant maximum torque up to a certain speed limit. At higher speeds, the torque then decreases. According to the method described here, 14 different speed levels, levels 1 to 4, are defined within the torque-speed map, emulating a four-speed transmission in a combustion engine vehicle. Speed ​​levels 1 to 4 partially overlap, with some of these speed levels being overlapped by more than one subsequent speed level: levels 1, 2, and 3 overlap in a specific sub-range; levels 2, 3, and 4 also overlap in another specific sub-range.

[0061] The speed levels 1 to 4 are defined by their respective minimum speeds dmin1, dmin2, dmin3, dmin4 and maximum speeds dmax1, dmax2, dmax3 and dmax4, i.e., level 1 by dmin1 and dmax1, etc.

[0062] The relevant control variable S is used as in connection with Fig. 1 described depending on the respective spread of the steps, which is calculated from dmax - dmin.

[0063] Although the invention has been further illustrated and explained in detail by means of preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived from them by a person skilled in the art without departing from the scope of protection of the invention. It is therefore clear that a multitude of possible variations exist. It is also clear that the embodiments mentioned as examples are truly only examples and are not to be understood in any way as limiting, for example, the scope of protection, the possible applications, or the configuration of the invention.Rather, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete terms, whereby the person skilled in the art, with knowledge of the disclosed inventive concept, can make various changes, for example with regard to the function or the arrangement of individual elements mentioned in an exemplary embodiment, without leaving the scope of protection defined by the claims and their legal equivalents, such as a further explanation in the description. Reference symbol list 2 Electric motor vehicle 4 traction batteries 6 electric motor 8 Control 8.1 Computing unit 8.2 Memory 12 speakers 12.1 Loudspeaker actuator 14 Torque-speed characteristic map S control variable Stage 1 - Stage 4 Speed ​​level

Claims

Method for operating an electric motor vehicle (2) comprising at least one electric motor (6) supplied with energy by at least one traction battery (4), wherein the electric motor (6) has a torque-speed characteristic map (14), characterized in that a plurality of speed stages (stage 1, stage 2, stage 3, stage 4) are defined, each having a minimum speed (dmin1, dmin2, dmin3, dmin4) and a maximum speed (dmax1, dmax2, dmax3, dmax4), wherein two adjacent speed stages (stage 1, stage 2, stage 3, stage 4) overlap, wherein one speed stage (stage 1, stage 2, stage 3, stage 4) is specified, and wherein a control variable (S) is calculated in which a ratio between a difference between the current speed (dmax1, dmax2, dmax3, dmax4) and the minimum speed (dmin1, dmin2, dmin3, dmin4) of the corresponding speed stage (stage 1, stage 2, stage 3, stage 4) on the one hand and a difference between maximum speed (dmax1, dmax2,dmax3, dmax4) and minimum speed (dmin1, dmin2, dmin3, dmin4) of the speed stage (stage 1, stage 2, stage 3, stage 4) on the other hand is used, wherein the control variable (S) is used to control at least one actuator (12.1). Method according to claim 1, characterized in that the actuator (12.1) is a component of a loudspeaker (12). Method according to claim 1 or 2, characterized in that the actuator (12) is part of a vibration-generating device (6). Method according to one of the preceding claims, characterized in that when a maximum speed (dmax1, dmax2, dmax3, dmax4) of a speed stage (stage 1, stage 2, stage 3, stage 4) is reached, a change is made to a higher speed stage (stage 1, stage 2, stage 3, stage 4) and / or when a minimum speed (dmin1, dmin2, dmin3, dmin4) of a speed stage (stage 1, stage 2, stage 3, stage 4) is reached, a change is made to a lower speed stage (stage 1, stage 2, stage 3, stage 4). Method according to one of the preceding claims, characterized in that the speed level (level 1, level 2, level 3, level 4) is changed to another speed level (level 1, level 2, level 3, level 4) by manual input. Method according to claim 4 or 5, characterized in that a change in longitudinal acceleration is made when changing from one speed stage (stage 1, stage 2, stage 3, stage 4) to another speed stage (stage 1, stage 2, stage 3, stage 4). Method according to one of the preceding claims, characterized in that the control variable (S) comprises factors and / or summands. Method according to one of the preceding claims, characterized in that energy recuperation takes place during thrust operation taking into account the control variable (S). Computer program product, comprising a computer-readable storage medium (8.2) on which instructions are embedded which, when executed by at least one computing unit (8.1), cause the at least computing unit (8.1) to be configured to execute the method according to one of the preceding claims. Electric motor vehicle (2) with a computer program product according to claim 9 .

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