WO2014040781A1 - Method for operating a vehicle driven by an electric motor - Google Patents

Description

 Description title

 Method for operating an electric motor driven vehicle

The invention relates to a method for operating a multi-axle vehicle with electric drive motors on the left or right wheel of a common vehicle axle.

State of the art

Electric motor drive concepts are known in motor vehicles with wheel-individually arranged electric drive motors. Here, the left and right vehicle wheels are driven by a respective electric drive motor on a common vehicle axle. It is both the drive of the front wheels and the rear wheels or all vehicle wheels into consideration. The electric drive motors must be controlled so that the respective output drive torque corresponds to a desired torque, which is dependent on the current driving situation.

Disclosure of the invention

The invention is based on the object in a multi-axle vehicle with at least two wheel-individual electric drive motors to ensure the driving stability even in the event of a disturbance of the output drive torque.

This object is achieved with the features of claim 1. The dependent claims indicate expedient developments.

The method according to the invention relates to a multiaxial vehicle with at least two electric, wheel-specific drive motors which are located on the left or right vehicle wheel of a common vehicle axle of the vehicle Vehicle are located. Basically, it may be a vehicle with only electric motor drive, which may also be hybrid vehicles with a combination of electric motor drive with an internal combustion engine into consideration. The two wheel-specific electric drive motors are located either on the front axle, the

Rear axle or on both or all axles of the vehicle. The vehicle has at least two vehicle axles, possibly also vehicles with more than two vehicle axles into consideration.

The electric drive motors on the two wheels of a vehicle axle can be controlled individually, so that the output drive torque can be adapted to the current situation. In case of a fault or a fault in the output drive torque of an electric

Drive motor emerging nuisance to the vehicle's vertical axis, but at least reduce, gets in the vehicle

compensating yaw moment provided by an adjustable vehicle aggregate. The error in the provision of the

Drive torque in the electric drive motor is detected based on a deviation of the generated by the drive motor, actual actual drive torque of a predetermined target torque. If such a deviation is present or if the deviation exceeds a predetermined threshold value, the compensating yaw moment is generated by the adjustable vehicle aggregate as a compensatory measure. This ensures that the yawing moment caused by the malfunction of the electric drive motor does not lead to a driving instability. The compensating yaw moment of the adjustable vehicle assembly counteracts the Störgiermoment caused by the power failure of the drive motor.

The malfunction is usually one

Derating, so that the actual output drive torque is smaller than the target torque. Basically comes as a power failure but also a higher drive torque compared to the target torque into consideration.

Furthermore, both power disturbances on only one electric drive motor and on a plurality of electric drive motors come into consideration.

Decisive is the resulting disturbing moment about the vertical axis, which passes through the power failure of the electric drive motors is created and which is at least partially compensated via the intervention via the vehicle unit.

The fault can occur in a control or control unit, via which the electric drive motor is controlled, in a power output stage, in

Range of the wiring or in the electric drive motor itself. The compensating moments can be applied so that the propulsion of the vehicle is maintained.

With the adjustable vehicle aggregate, over which the compensating

Yaw moment is generated, it is a vehicle device that is not identical to the electric drive motor, which has the power failure. The adjustable vehicle unit may be one of the other electric drive motors in the vehicle. In principle, however, any vehicle aggregate through which the driving dynamics of the vehicle can be influenced, for example the vehicle brake, comes into consideration

wheel-individual intervention for the generation of different wheel braking torques, to a traction control system (ASR) for setting wheel-individual

Drive torque or an active steering system to specify a

Radlenkwinkels that may differ from the driver's specification by the engagement of a superposition gear. The intervention for the production of the

compensating yaw moment can either be done via a direct control of the vehicle unit or a parent

Driver assistance system, such as an electronic stability program (ESP), in which various vehicle components or aggregates are interconnected to a parent unit.

If, for example, a power loss on an electric drive motor is detected on a vehicle wheel, then the output drive torque can be reduced correspondingly to the electric drive motor of the opposite vehicle wheel on the same vehicle axle, in particular to the same height. As a result, the emergence of Störgiermomentes counteracted. If an electric drive motor is arranged on each wheel of the axles on two vehicle axles, then this can be done

Drive torque can be increased on the wheel of the other axle on the same side of the vehicle. This produces a compensating yaw moment, which is contrary to the Störgiermoment. This embodiment has the advantage that the propulsion of the vehicle is not reduced.

According to a further advantageous embodiment, the compensating torque depends on the duration of the deviation of the drive torque from the power-driven drive motor from the desired torque. Here can

basically between a short-term and a permanent one

Disturbance are distinguished. In the case of a short-term power failure, a momentary impulse is optionally sufficient as the compensating moment, which is generated for example via a second electric drive motor by reducing or increasing the drive torque. Constant power disturbances become the compensating moment

advantageously also applied permanently. Conveniently, the duration of the compensating torque is adapted to the duration of the power disturbance.

According to a further advantageous embodiment, the functionality of one or more driver assistance systems is maintained during the duration of the deviation of the drive torque from the desired torque. This is to avoid that the functionality of a vehicle dynamics control system at a detected fault in the vehicle or the electric drive motor

is restricted. Once such a fault is detected in the electric drive motor or a component for controlling the electric drive motor, it may be advantageous to prevent degradation or restriction of the functionality of the vehicle dynamics control system, at least for the duration of the power failure of the electric drive motor or allow only a slight restriction to ensure that the unwanted Störgierbewegung can be compensated by the vehicle dynamics control system. In addition, by maintaining the

Functionality ensures that the measures taken to generate the compensating moment do not in turn lead to an undesirable driving condition in the vehicle.

Maintaining the functionality of one or more

Driver assistance systems or vehicle dynamics control systems are for example ensured by the fact that during the period of the deviation of the Drive torque from the target torque the faulty electrical

Drive motor plausibility checks for one or more vehicle wheels, in particular for the wheel with the faulty electric drive motor either exposed or adjusted by widening of limits. Suspending or adjusting the plausibility check can

optionally be additionally limited to the speed ranges in which the faulty drive torque is relatively high and exceeds a threshold or limit. Furthermore, it is possible to provide additional sensor signals representing the state of motion of the vehicle during driving while maintaining the functionality of the driver assistance system or vehicle dynamics control system

consider. For example, the threshold or limit values for the plausibility check of a yaw rate signal can be widened in order to obtain a value during the duration of the drive torque generated incorrectly

Functionality restriction to avoid.

The method according to the invention is carried out in a control unit in the vehicle.

Further advantages and expedient embodiments can be taken from the further claims, the description of the figures and the drawings. Show it:

1 is a schematic representation of a two-axle motor vehicle with two wheel-individual electric drive motors on the rear axle,

2 shows a motor vehicle with two wheel-individual electric drive motors on the front axle,

3 shows a motor vehicle with wheel-specific drive motors on the

 Front axle and the rear axle,

4 is a block diagram showing the system structure for generating a

Compensating torque in the event of a deviation of the drive torque generated by an electric drive motor of a target torque. In the figures, the same components are provided with the same reference numerals.

1 to 3 each show a motor vehicle 1, the forward direction is marked with the arrow F. It is in the motor vehicle 1 to an electric motor driven vehicle, the embodiments according to FIGS. 1 to 3 differ by the drive concept.

According to FIG. 1, two electric drive motors 4, 5 are arranged on the rear axle 3 of the vehicle 1, which permit a wheel-individual drive. The electric drive motors are designed, for example, as wheel hub motors. The front axle 2 is in the embodiment of FIG. 1 without drive. 2, two electric drive motors 6, 7 at the

Front axle 2 arranged, which are each assigned to a wheel on the front axle. In the embodiment of FIG. 3 is a vehicle 1 with a total of four electric drive motors 4, 5, 6, 7, which are assigned to the vehicle wheels on the rear axle and the front axle.

It is in the illustrated in Figures 1 to 3 motor vehicles 1 is preferably an exclusively electric motor drive. In principle, however, are also hybrid drives, in which in addition to the illustrated electric drive motors also another drive source, in particular an internal combustion engine comes, what an exclusive drive on the additional drive source or a mixed operation with a drive both via the additional drive source and via a or more electric drive motors allows.

In the event that in one of the electric drive motors not the desired target torque is generated, but the actual generated

Drive torque deviates from the nominal torque, for example, due to an error or damage in the electric drive motor, in the rule or

Control unit or the power electronics, countermeasures are taken to create a compensating moment. This ensures that due to the deviation in the defective electric drive motor no resulting yaw moment is generated about the vehicle vertical axis, which would represent a disturbance torque. In Figs. 1 to 3 is in each case with arrows 8 and 9 at different

Vehicle wheels a different moment (solid arrow 8) on a drive motor and a compensating moment (dashed arrow 9) registered on another drive motor. The deviating moment on the relevant vehicle wheel is the respective associated electrical

 Drive motor generates, which is affected by an error. The deviation at the moment according to arrow 8 is in particular a reduction compared to the desired torque, which in principle also comes into consideration an increased moment. 1 is via the electric drive motor 4 on the left rear wheel an actual

Moment 8 generated, which deviates from the nominal torque. To compensate for a resulting yaw moment about the vehicle vertical axis, a compensating torque 9 is generated at the right rear wheel, which

rectified is like the deviating actual moment 8 on the left rear wheel. This means that the change of the effective torque on the right rear wheel is carried out in the same way as the change on the left rear wheel. Overall, a disturbing yaw moment is prevented in this way, at the same time the propulsion of the vehicle is changed. A corresponding embodiment is shown in Fig. 2, according to the left

Front wheel is deviating from the nominal torque actual torque 8 is applied to compensate for the right front wheel, a corresponding moment 9 is applied, which is rectified and equal to the same as the actual torque 8. Also in this case, the formation of parasitic yawing moments is prevented However, the propulsion of the vehicle changed.

In Fig. 3 is an example of the left rear wheel deviates from the nominal torque actual torque 8, which is offset by an oppositely directed compensating moment 9 on the left front wheel. This embodiment has the advantage that on the one hand annoying yawing moments are prevented and on the other hand, the propulsion of the vehicle is not changed.

The compensation in the above-described embodiments can be performed in various ways. It is possible to generate a compensating torque via a setting of another electric

Drive motor, so in Fig. 1 via the drive motor 5, in Fig. 2 on the Drive motor 7 and in Fig. 3 via the drive motor 6. Additionally or alternatively, however, is an intervention on another adjustable

Vehicle unit possible, for example via a vehicle dynamics control system or a driver assistance system. Here are braking interventions on the vehicle brake system into consideration, generating a compensating steering angle in an active steering system or, in hybrid vehicles, a setting on the engine torque of the additional drive unit.

FIG. 4 shows in simplified form a block diagram for carrying out the method. The block 10 symbolizes the drive system to which an error detection 1 1 is assigned. Once in the drive system - in one or more of the electric drive motors - a fault on the

Error detection 1 1 is detected, a trigger signal is transmitted to a block 12, which symbolizes a vehicle assembly, which is either another electric drive motor in the vehicle and / or another vehicle aggregate such as a vehicle dynamics control system or a driver assistance system. Basically, all vehicle units come into consideration, over which the driving condition of the vehicle or the driving dynamics can be influenced, so for example an electronic

Stability Program (ESP) or the vehicle brake, which can be controlled as part of an anti-lock braking system (ABS). In an active steering system, which with a superposition steering gear to produce a

Additional steering angle is equipped, regardless of the driver's specification, the position of the wheel steering angle can be influenced, which also a

Compensating torque can be generated, which counteracts a disturbing yaw moment. The active steering system generates a compensating force in the vehicle transverse direction.

Claims

claims 1 . Method for operating a multi-axle vehicle with electric drive motors (4 to 7) on each wheel of a common vehicle axle (2, 3), characterized in that in the case of a deviation of the drive torque generated by an electric drive motor (4 to 7) of a target torque compensating moment (9) of one  adjustable vehicle unit (12) is generated. 2. The method according to claim 1, characterized in that the  Compensating torque (9) via a modified drive torque of a second electric drive motor is generated. 3. The method according to claim 2, characterized in that the  Drive torque of the second electric drive motor on the same vehicle axle (2, 3) is changed. 4. The method according to claim 2 or 3, characterized in that the  Drive torque of one or both electric drive motors on a second vehicle axle (2, 3) is changed. 5. The method according to any one of claims 1 to 4, characterized in that the compensating moment (9) via a driver assistance system is generated, for example via an electronic stability program (ESP). 6. The method according to any one of claims 1 to 5, characterized in that the compensating moment (9) via a change of  Radbremsmomente is generated. 7. The method according to any one of claims 1 to 6, characterized in that the compensating moment is generated via a change of a Radlenkwinkels in an active steering system of the vehicle. 8. The method according to any one of claims 1 to 7, characterized in that the compensating torque (9) depends on the duration of the deviation of the drive torque of the target torque. 9. The method according to any one of claims 1 to 8, characterized in that the functionality of a driver assistance system is maintained during the duration of the deviation of the drive torque from the target torque. 10. The method according to claim 9, characterized in that during the duration of the deviation of the drive torque from the desired torque  Plausibility checks suspended and / or monitoring thresholds, for example, for wheel speeds or for the yaw rate, be widened. 1 1. Control or control device for carrying out the method according to one of claims 1 to 9. 12. vehicle with electric drive motors (4 to 7) on each wheel of a common vehicle axle (2, 3) and with a control or control device according to claim 10.