Method for operating an electric drive system of a vehicle and electric drive system

Abstract

The invention relates to a method for operating an electric drive system (1) of a vehicle having an electric machine (2), a traction battery (3), and a pulse-controlled inverter (4), wherein the pulse-controlled inverter (4) converts a direct current from the traction battery (3) into a three-phase current for the electric machine (2) during operation of the electric drive system (1), wherein the three-phase current is modulated by means of a function generator (40) controlled by a control device (5) in such a way that a torque oscillation is modulated onto a torque generated by the electric machine (2), which torque oscillation generates haptic feedback perceptible to a driver of the vehicle, wherein the type and / or strength of the haptic feedback indicates a distance between a current driving state of the vehicle and a driving dynamics limit range.

Description

The present invention relates to a method of operating an electric drive system of a vehicle. In another aspect, the present invention relates to an electric drive system.In electrically driven vehicles, as are known from the prior art, the drive torque of an electric drive device, which has at least one electric machine, is significantly more harmonic and has less interference variables than a vehicle having an internal combustion engine. At the same time, higher system powers can be achieved with the aid of the at least one electric machine of the electric drive device. By means of the extended possibilities of longitudinal and transverse distribution, a neutral driving behavior of the vehicle can be shifted further in the direction of the physical driving dynamic limit range. The dynamic driving limit range of the vehicle is thereby narrowed, so that the possibilities of asymptotically approaching this limit range "from below" are made significantly more difficult. This circumstance may have a negative effect on driving safety.DE 601 33 712 T2 discloses a feedback system for a hybrid or electric vehicle, wherein torque pulses are generated in a targeted manner by means of an electric machine in order thereby to generate haptic feedback, which signals to the driver that a driving state has occurred, which requires increased attention.DE 10 2021 131 529 A1 discloses a method for operating an electric drive system of a vehicle having an electric machine, wherein the current is modulated by means of a function generator which is actuated by a control device in such a way that a torque oscillation is modulated onto a torque generated by the electric machine, said torque oscillation generating a haptic feedback perceptible to a driver of the vehicle. The type and / or the strength of the haptic feedback indicates a distance of a current driving state of the vehicle from a driving dynamic boundary region.The object of the present invention is to provide a further improved method for operating an electric drive system of a vehicle, which method makes it possible in particular to increase driving safety.This object is achieved by a method for controlling an electric drive device of a vehicle having the features of claim 1.According to the invention, a method for operating an electric drive system of a vehicle having an electric machine, a traction battery and a pulse inverter is provided, wherein the pulse inverter converts a direct current of the traction battery into a three-phase current for the electric machine during operation of the electric drive system, wherein the three-phase current is modulated by means of a function generator which is controlled by a control device in such a way that a torque vibration is modulated onto a torque generated by the electric machine, which vibration generates a haptic feedback perceptible to a driver of the vehicle, wherein a distance of a current driving state of the vehicle from a driving-dynamic boundary region is indicated by the type and / or strength of the haptic feedback, and wherein the torque vibration is modulated onto the torque of the electric machine in such a way that the ignition behavior of an internal combustion engine is emulated with non-uniform ignition distances. The modulating of a torque oscillation provided in the invention thus generates a haptic feedback perceptible to the driver, which indicates the distance of the current driving state from the driving dynamic limit range and thus enables the driver an intuitive reaction for the return to a safe driving state. The method according to the invention thus contributes to an increase in driving safety.In one specific embodiment, it is proposed that the distance of the current driving state of the vehicle from the driving dynamic limit range is indicated by adapting a frequency range and / or an amplitude and / or a signal shape of the torque vibration modulated onto the torque. The smaller the distance of the current driving state from the driving dynamic limit range, the more perceptible is then advantageously the haptic feedback for the driver, which is generated by the torque oscillation additionally modulated onto the torque of the electric machine, so that the driver can intuitively react to an approach to the driving dynamic limit range. In the case of a large distance of the current driving state from the driving dynamic boundary region of the vehicle, no haptic feedback or only a small haptic feedback can be generated, since the vehicle is then in a safe driving state under driving dynamic aspects.In one specific embodiment, it is proposed that the torque vibration be modulated onto the torque of the electric machine in such a way that the ignition behavior of an internal combustion engine is emulated with asymmetrically shortened ignition distances.In one embodiment, there is the possibility that the torque vibration is modulated onto the torque of the electric machine in such a way that the passing over profiled roadway markings is emulated.In one specific embodiment, it is provided that the torque vibration is modulated onto the torque of the electric machine in such a way that pulsating antilock braking of the vehicle is emulated.According to a further aspect, the present invention relates to an electric drive system for a vehicle, comprising an electric machine which is designed to generate a torque for driving the vehicle during operation, a traction battery, a pulse inverter which is designed to convert a direct current of the traction battery into a three-phase current for the electric machine during operation, and a control device which is designed to control the operation of the electric drive system.According to the invention, it is proposed that the electric drive system comprises a function generator that can be controlled by the control device, wherein the function generator is designed to modulate the three-phase current for the electric machine in such a way thata torque oscillation is modulated onto the torque generated by the electric machine, said torque oscillation generating a haptic feedback perceptible to a driver of the vehicle, wherein a distance of a current driving state of the vehicle from a driving dynamic boundary region is indicated by the type and / or strength of the haptic feedback, andthe torque vibration is modulated onto the torque of the electric machine in such a way that the ignition behavior of an internal combustion engine is emulated with non-uniform ignition distances, in particular with asymmetrically shortened ignition distances.The function generator can preferably be formed integrally with the pulse inverter.Further features and advantages of the present invention will become apparent from the following description of a preferred exemplary embodiment with reference to the attached FIG. 1, which shows an electric drive system 1 of a vehicle, not shown here in any more detail, in a schematically greatly simplified form.The electric drive system 1 comprises at least one electric machine 2 which generates a torque during operation in order to drive and / or decelerate the vehicle. Furthermore, the electric drive system 1 has a traction battery 3, in which energy for the operation of the electric machine 2 can be stored electrochemically. A further, particularly important component of the electric drive system 1 is a pulse inverter 4, which is electrically connected to the traction battery 3 and to the electric machine 2. The pulse inverter 4 has the task of converting, during the operation of the electric drive system 1, a direct current which is made available by the traction battery 3 into a three-phase current for the operation of the electric machine 2 by interconnecting three or more alternating current circuits, the so-called phases U, V and W.For controlling the operation, the electric drive system 1 further has a control device 5 which is connected to the electric machine 2, the traction battery 3 and the pulse inverter 4. During operation, the control device 5 receives corresponding data from a multiplicity of sensor means and / or further control devices of the vehicle and processes these continuously. Some of these data have a direct or indirect relationship to the driving dynamics of the vehicle and can thus provide information about how far the current driving state approaches a driving dynamics boundary region which is defined by the steering angle and / or the vehicle rotation rate and / or wheel speeds and / or the range of the longitudinal acceleration and / or the lateral acceleration shortly before the force closure boundary is reached.In an electrically driven vehicle, the drive torque of the electric drive device 1 with the at least one electric machine 2 is significantly more harmonic and less subject to interference variables than a vehicle with an internal combustion engine. At the same time, higher system powers can be achieved with the aid of the at least one electric machine 2 of the electric drive device 1. By means of the extended possibilities of longitudinal and transverse distribution, a neutral driving behavior of the vehicle can be shifted further in the direction of the driving dynamic limit range. The dynamic driving limit range of the vehicle is thereby narrowed, so that the possibilities of asymptotically approaching this limit range "from below" are made significantly more difficult. This can have a disadvantageous effect on driving safety.In order to increase the driving safety of the vehicle, a method for operating the electric drive system 1 is presented below, which makes it possible to remedy the aforementioned problem.As already explained above, during the operation of the electric drive system 1, the pulse inverter 4 converts a direct current of the traction battery 3 into a three-phase current for the electric machine 2, so that the electric machine 2 provides a torque to drive the vehicle. In the method, it is now provided that the three-phase current for the electric machine is modulated by means of a function generator 40, which is controlled by the control device 5 and can be integrated into the pulse inverter 4, for example, in such a way that a torque oscillation is modulated onto the torque generated by the electric machine 2. This modulated torque oscillation in turn generates a haptic feedback that is perceptible to a driver of the vehicle, the distance of the current driving state of the vehicle from the driving dynamic limit range being indicated by the type and / or strength of the haptic feedback. Modulating the torque oscillation generates a haptic feedback that is perceptible to the driver, which indicates to the driver the distance of the current driving state from the driving dynamic limit range and thus enables the driver an intuitive reaction for the return to a safe driving state. The control device 5 continuously processes corresponding data from sensor means and / or further control units, which provide information about the distance of the current driving state of the vehicle from the driving dynamic limit range, and controls the function generator 40 accordingly, so that as the driving dynamic limit range is approached, the haptic feedback becomes more perceptible to the driver, so that he can react to this accordingly.In this case, it is possible that, by adapting a frequency range and / or an amplitude and / or a signal shape of the torque oscillation modulated onto the torque, the distance of the current driving state of the vehicle from the driving dynamic limit range is indicated. The smaller the distance of the current driving state from the driving dynamic limit range, the more perceptible is then advantageously the haptic feedback for the driver, which is generated by the torque vibration additionally modulated onto the torque of the electric machine 2. In the case of a large distance of the current driving state from the driving dynamic boundary region of the vehicle, it is also not possible to generate haptic feedback or only very weakly perceptible haptic feedback, since the vehicle is then in a safe driving state under driving dynamic aspects.In one specific embodiment, it is proposed that the torque vibration be modulated onto the torque of electric machine 2 in such a way that the ignition behavior of an internal combustion engine is emulated with non-uniform ignition distances, in particular with asymmetrically shortened ignition distances.In one embodiment, there is the possibility that the torque vibration is modulated onto the torque of the electric machine 2 in such a way that the passing over of profiled roadway markings is emulated.In one specific embodiment, it is provided that the torque vibration is modulated onto the torque of electric machine 2 in such a way that pulsating antilock braking of the vehicle is emulated.

Claims

Method for operating an electric drive system (1) of a vehicle having an electric machine (2), a traction battery (3) and a pulse inverter (4), wherein the pulse inverter (4) converts a direct current of the traction battery (3) into a three-phase current for the electric machine (2) during operation of the electric drive system (1), wherein the three-phase current is modulated by means of a function generator (40) which is actuated by a control device (5) in such a way that a torque oscillation is modulated onto a torque generated by the electric machine (2), said torque oscillation generating a haptic feedback perceptible to a driver of the vehicle, wherein a distance of a current driving state of the vehicle from a driving-dynamic boundary region is indicated by the type and / or strength of the haptic feedback, and wherein the torque oscillation is modulated onto the torque of the electric machine (2) in such a way, the ignition behavior of an internal combustion engine is emulated with non-uniform ignition distances.Method according to Claim 1, characterized in that the distance of the current driving state of the vehicle from the driving-dynamic limit region is indicated by an adaptation of a frequency range and / or an amplitude and / or a signal shape of the torque vibration modulated onto the torque.Method according to either of Claims 1 and 2, characterized in that the torque oscillation is modulated onto the torque of the electric machine (2) in such a way that the ignition behavior of an internal combustion engine is emulated with asymmetrically shortened ignition distances.Method according to one of Claims 1 to 3, characterized in that the torque oscillation is modulated onto the torque of the electric machine (2) in such a way that the passing over of profiled roadway markings is emulated.Method according to one of Claims 1 to 4, characterized in that the torque oscillation is modulated onto the torque of the electric machine (2) in such a way that pulsating antilock braking of the vehicle is emulated.An electric drive system (1) of a vehicle, comprising - an electric machine (2) which is designed to generate a torque for driving the vehicle during operation, - a traction battery (3), - a pulse inverter (4) which is designed to convert a direct current of the traction battery (3) into a three-phase current for the electric machine (2) during operation of the electric drive system (1), and - a control device (5) which is designed to control operation of the electric drive system (1), characterized in that the electric drive system (1) comprises a function generator (40) which can be controlled by the control device (5), wherein the function generator (40) is designed to modulate the three-phase current for the electric machine (2) in such a way that - a torque oscillation is modulated onto the torque generated by the electric machine (2), said torque oscillation comprising a haptic signal, Feedback perceptible to a driver of the vehicle is generated, wherein a distance of a current driving state of the vehicle from a driving dynamic limit range is indicated by the type and / or strength of the haptic feedback, and - the torque vibration is modulated onto the torque of the electric machine (2) in such a way that the ignition behavior of an internal combustion engine is emulated with non-uniform ignition distances, in particular with asymmetrically shortened ignition distances.Electric drive system (1) according to Claim 6, characterized in that the function generator (40) is formed integrally with the pulse inverter (4).

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