Method for controlling an electric drive, control unit, and vehicle

Abstract

The invention relates to a method (100) for controlling an electric drive (20) which is designed to generate a torque (M) on a wheel (30) of an axle (31) of a vehicle (10), having the steps of: - receiving a delay request signal (V1, V2, V3, V4) (S1); - analyzing and classifying the delay request signal (V1, V2, V3, V4) in order to form a classified delay request signal (VK) (S2); - determining a gradient threshold (GL1, GL2) of a torque gradient (G1, G2) of the electric drive (10) on the basis of the classified delay request signal (VK) (S3a, S3b); and - actuating the electric drive (20) using a drive actuation signal (A) in order to generate a negative torque (M) on the wheel (30) of the vehicle axle (31) (S4a, S4b) on the basis of the determined gradient threshold (GL1, GL2). The invention additionally relates to a control unit (60) for a vehicle (10) and to a vehicle (10), in particular a utility vehicle, for carrying out the method.

Description

[0001] Method for controlling an electric drive, control unit and vehicle

[0002] The invention relates to a method for controlling an electric drive configured to generate a torque at a wheel of a vehicle axle. The invention further relates to a control unit for a vehicle and a vehicle, in particular a commercial vehicle, for implementing the method.

[0003] US 2018 / 0 154 777 A1 discloses a braking control method and a device therefor, wherein a control unit of the device is configured to receive driving environment information from at least one sensor and to assess an emergency braking requirement. The control unit is also configured to activate a regenerative braking function and a friction braking function to decelerate the vehicle. Furthermore, the control unit is configured to monitor the rotational speed of at least one wheel of the vehicle and to adapt the regenerative braking and the friction braking based on the monitored rotational speed.

[0004] According to the features of independent claim 1, a method for controlling an electric drive is proposed, wherein the electric drive is designed to generate a torque at a wheel of a vehicle axle of a vehicle, comprising the steps:

[0005] - Receipt of a delay request signal;

[0006] - Evaluation and classification of the delay request signal into a classified delay request signal;

[0007] - Determination of a gradient limit value of a torque gradient of the electric drive as a function of the classified deceleration request signal; and

[0008] - Control of the electric drive by means of a drive control signal to generate a negative torque at the wheel of the vehicle axle according to the determined gradient limit value. The proposed method enables dynamic, flexible, and situation-appropriate adjustment of torque generation at the wheel of the vehicle axle. The proposed method allows a deceleration effect in response to a deceleration request signal to be better tailored to the current driving situation. For example, the deceleration effect can be influenced depending on the situation in favor of component-sparing braking of the vehicle or in favor of a shortened braking distance of the vehicle. Depending on the situation, both requirements can be considered individually to varying degrees.

[0009] The electric drive is designed to generate a torque at a wheel on a vehicle axle of a vehicle. The torque can be generated by means of the electric drive at one or more wheels of one or more vehicle axles, so that the electric drive can be designed, for example, as an individual wheel drive or as a central drive for several vehicle axles. A common electric drive can also be provided for each wheel of a vehicle axle, so that there is one electric drive per vehicle axle. The electric drive can be designed to be able to generate positive torques and negative torques at the at least one wheel, wherein an acceleration effect can be achieved by a positive torque and a deceleration effect can be achieved by a negative torque.For controlled acceleration or deceleration, a drive control signal is provided, which is converted by the electric drive into torque generation. The drive control signal can be generated, for example, by a control unit that can convert acceleration request signals or deceleration request signals received at an input of the control unit into a corresponding drive control signal at an output of the control unit. If the vehicle has multiple electric drives for the wheels of the vehicle axles, the control unit can be configured to coordinate the drive control signals of the multiple electric drives with one another in such a way that a coordinated acceleration or deceleration effect is achieved.For example, depending on certain driving situations, such as cornering, drive control signals can be provided for the electric drives, which lead to different torques at individual wheels of the vehicle axles.

[0010] The vehicle can, in particular, be a commercial vehicle. For example, the commercial vehicle can be a towing vehicle, a trailer vehicle, or a vehicle combination comprising a towing vehicle and a trailer vehicle. The aforementioned advantages of the method can offer significant optimization potential, particularly for commercial vehicles, since commercial vehicles often have a higher total mass than passenger vehicles and thus subject vehicle components to greater stress. It can therefore be all the more advantageous to be able to dynamically and flexibly prioritize an increased service life of the vehicle's drive components or a high deceleration effect.An advantageous application of the method results for a vehicle combination comprising a towing vehicle having an electric drive for generating torque at a wheel of a vehicle axle of the towing vehicle, and a trailer coupled to the towing vehicle having an electric drive for generating torque at a wheel of a vehicle axle of the trailer vehicle. This allows the respective deceleration effects of the towing vehicle and trailer vehicle to be coordinated with one another, so that, for example, the trailer vehicle can be reliably prevented from pushing onto the towing vehicle due to a lower deceleration effect on the trailer vehicle.It is conceivable, for example, that a common drive control signal is transmitted to the electric drives of the towing vehicle and the trailer vehicle, or that an individual drive control signal is generated for the electric drive of the towing vehicle and for the electric drive of the trailer vehicle based on the classified deceleration request signal and the determined gradient limit value, in order to be able to individually take different vehicle properties into account, for example. However, it is also fundamentally possible, for example, to combine a towing vehicle having a combustion engine with a trailer vehicle having an electric drive or to combine a towing vehicle having an electric drive with a non-powered trailer vehicle in order to apply the method to a vehicle combination.According to one possible design, the trailer vehicle can be designed as a semi-trailer and the towing vehicle as a tractor unit.

[0011] A deceleration request signal can be generated based on a current driving situation. For example, a braking request signaled by the driver or a dangerous situation detected by the vehicle can be converted into a deceleration request signal. The signal strength, signal profile, or signal type of the deceleration request signal can vary depending on the driving situation. Therefore, the deceleration request signal can be evaluated and classified based on signal properties, for example, based on signal profiles, using the control unit described above, so that the classified deceleration request signal can, for example, allow conclusions to be drawn about a specific driving situation.

[0012] The torque at the wheel of the vehicle axle can be generated by the electric drive according to a torque gradient, for example, predetermined by the control system. A torque gradient can be understood as a degree of change in torque as a function of time, for example a gradient in the torque curve or, in simple terms, a speed of the torque increase. Higher torque gradients can be associated with a greater deceleration effect, but due to the design characteristics and mode of operation of electric drives, they are also associated with greater component loads on the drive than lower torque gradients. It can therefore be technically expedient to limit the torque gradient of the electric drive in order to protect the components of the electric drive and, in particular, to protect them from damage caused by a very high torque gradient.For this purpose, for example, a gradient limit value can be defined and stored, for example, in the control unit. The gradient limit value can correspond to a limitation of the degree of change in torque over time. In other words, once the gradient limit value is reached, an even faster torque increase can be specifically excluded. In principle, it is conceivable to define such a gradient limit value as a fixed characteristic value for an electric drive, depending on the type. However, in the present case, it is proposed to determine a gradient limit value of the torque gradient of the electric drive depending on the classified deceleration request signal. Accordingly, the gradient limit value can be dynamically defined depending on the prevailing driving situation and a resulting specific deceleration request signal.This has the advantage that, depending on the situation, a balance can be struck between a desired deceleration effect and desired component protection in terms of control technology. Determining the gradient limit can, for example, involve selecting a specific gradient limit from a plurality of predefined gradient limits, where a majority can be formed, for example, by two or more gradient limits. Alternatively or additionally, a specific gradient limit can be calculated using a predefined algorithm or calculation pattern depending on the classified deceleration request signal. For example, it is also conceivable to interpolate between predefined gradient limits in order to optionally determine an individual gradient limit.

[0013] According to one embodiment, the vehicle can have a brake control unit for controlling the vehicle's braking functions, and the reception, evaluation, and classification of the deceleration request signal into a classified deceleration request signal can be carried out by the brake control unit. The brake control unit can form the control unit described above or a part of the control unit described above, which is configured to convert a deceleration request signal received at an input of the brake control unit into a corresponding drive control signal. Thus, no additional control unit is required to carry out the aforementioned method steps, and the method can be implemented using existing control components of the vehicle.The vehicle's brake control unit is typically already configured to receive a deceleration request signal, so that only the evaluation and classification of the deceleration request signal to determine a suitable gradient limit value needs to be performed in order to be able to implement the method with the brake control unit. According to a further refinement of the aforementioned embodiment, the vehicle can further comprise a drive control unit for controlling the electric drive, wherein.

[0014] - the determination of the gradient limit value of the torque gradient of the electric drive is carried out as a function of the classified deceleration request signal by means of the brake control unit and / or by means of the drive control unit; and

[0015] - the electric drive is controlled by means of the drive control signal to generate the negative torque according to the determined gradient limit value by means of the drive control unit.

[0016] Accordingly, according to a first variant, the gradient limit value can be determined by means of the brake control unit and transmitted to the drive control unit. According to the previously described embodiment, the deceleration request signal can be classified in the brake control unit, so that immediate further processing by assigning the gradient limit value to the classified deceleration request signal can be carried out in a technically advantageous manner in the brake control unit. According to a second variant, the gradient limit value can be determined in the drive control unit. The properties of the vehicle's electric drive or drives can be precisely stored in the drive control unit, so that the gradient limit value can be determined in a technically advantageous manner in the drive control unit.By combining the first and second variants, a third variant can provide for the gradient limit to be determined in the brake control unit and in the drive control unit. For example, individual steps for determining the gradient limit can be divided between the brake control unit and the drive control unit. For example, a gradient limit can be determined in each of the brake control unit and the drive control unit, and the determined gradient limit values ​​can be compared with one another and / or combined into a common gradient limit in order to be able to determine the gradient limit reliably and / or precisely.

[0017] The drive control unit and the brake control unit can jointly form a control unit of the vehicle, for example, the control unit described above. The drive control unit and the brake control unit can be connected to one another via signaling, for example, wired or wireless, in order to be able to transmit, for example, a classified deceleration request signal and / or a gradient limit value from the brake control unit to the drive control unit. In principle, according to other embodiments, it is also conceivable, for example, to carry out the method exclusively by means of the drive control unit or exclusively by means of the brake control unit. Furthermore, it is possible, for example, for sensory signals or predictive information from other control units of the vehicle to be included in the evaluation and classification of the deceleration request signal.For example, the vehicle may have vehicle environment sensors whose sensor signals are evaluated by another control unit with regard to a hazardous situation for the vehicle. On this basis, they can contribute to a classification of the deceleration request signal, for example, by transmitting an evaluation result to the brake control unit and / or the drive control unit. The evaluation result can, for example, contribute to a plausibility check of the classified deceleration request signal or directly to the classification.

[0018] According to one embodiment, during the evaluation and classification of the deceleration request signal into a classified deceleration request signal, it can be determined whether a potential emergency braking situation exists. This creates a defined decision basis for determining a gradient limit value that allows prioritizing the deceleration effect using the negative torque generated at the wheel of the vehicle axle, for example, over component protection of the electric drive. An emergency braking situation can, for example, be a driving situation in which maximum deceleration is desired, for example, to avoid an anticipated collision.For example, a binary classification can be performed, according to which the classification result is either a potential emergency braking situation or no potential emergency braking situation. In this case, "no potential emergency braking situation" or "no emergency braking situation" can be understood, for example, as a normal braking situation in which no increase or maximization of the deceleration effect beyond a level of a standard deceleration effect typical in normal operation is required. The method can be implemented very easily with a binary classification, since only one classification is performed according to two states, and depending on the classified state, one can choose between two gradient limit values, for example.In particular, with such a binary classification, limit values ​​can generally be selected based on component load aspects, with the exception of rarer emergency situations. For example, it can be provided that a separate gradient limit value is determined only in a potential emergency braking situation, which deviates from a standard gradient limit value intended for normal operation. For example, such a standard gradient limit value can be stored in the drive control unit described above, and in a potential emergency braking situation, the brake control unit described above can specify a different gradient limit value or transmit a request to the drive control unit to determine a different gradient limit value.It is also conceivable to define further classification results regarding a potential emergency braking situation, for example, according to the states "no emergency braking situation," "emergency braking situation with potential property damage," or "emergency braking situation with potential personal injury." This allows for a differentiated classification and allows the intended deceleration effect to be weighted differently compared to component protection.

[0019] According to one embodiment, the deceleration request signal can be evaluated and classified into a classified deceleration request signal according to hazard levels with different hazard potential values. This enables improved fine-tuning of the required deceleration effect and a reduction in component stress. Classifying the deceleration request signal according to hazard levels with different hazard potential values ​​can enable individual optimization of torque provision and a differentiated, situation-appropriate vehicle response. According to one embodiment, the hazard potential value can be a risk parameter that, for example, includes a percentage probability of an accident occurring and / or an anticipated extent of damage and can be calculated and signaled as a representative key figure.Classifying the deceleration request signal according to hazard levels with different hazard potential values ​​enables a gradual classification of the deceleration request signal, whose properties can indicate a driving situation with different hazard levels. According to a simplified example, in which classification can be based on the vehicle's anticipated collision risk, the hazard levels could be:

[0020] - no risk of collision, for example when braking due to reaching a speed-limited section of road;

[0021] - low risk of collision, for example when braking due to the end of a traffic jam visible in the distance;

[0022] - medium risk of collision, for example when braking due to the end of a traffic jam after a bend; and / or

[0023] - high risk of collision, for example if you want to brake due to an accident situation directly in front of the vehicle.

[0024] According to other examples, the danger levels can also represent different categories of

[0025] - vehicle defects, such as engine failures or lighting defects,

[0026] - vehicle environments, such as city traffic or highways, or

[0027] - Road conditions, for example, uneven, wet, or icy roads. It is also conceivable to further subdivide the emergency braking situation described above into different danger levels, for example, based on the likelihood of property damage or personal injury.

[0028] According to one embodiment, the gradient limit value can be determined depending on the classified deceleration request signal such that the gradient limit value is designed to ensure or increase a minimum service life of drive components of the electric drive. This allows a component-protecting deceleration effect to be realized, depending on the situation, in order to extend the achievable operating time of the drive components of the electric drive. A minimum service life can, for example, initially be a predetermined operating time of a drive component, whereby an increase in the minimum service life can generally be viewed as an increase in the service life of the drive component beyond the minimum service life.For example, for a classified deceleration request signal that represents a low hazard level or no emergency braking situation, a component-optimized, stronger limitation of the torque gradient can be implemented compared to a deceleration-optimized, weaker, less restrictive limitation of the torque gradient. In other words, the gradient limit value for ensuring or increasing the minimum service life of the drive components can be lower than a gradient limit value for increasing a deceleration effect, as explained below. A lower gradient limit value allows for smaller degrees of change in torque over time, so that, in simple terms, a gradient limit value for ensuring or increasing the minimum service life of the drive components allows for slower changes in torque than a gradient limit value for increasing a deceleration effect.The drive components of the electric drive whose minimum service life can be advantageously ensured or increased with a low gradient limit value can be, for example, shaft bearings in the motor and / or transmission, gear sets with gearing, and housing parts of the electric drive. Furthermore, adverse influences on the component strengths of the shafts can be avoided. Furthermore, the minimum service life of power semiconductors in an inverter of the electric drive can be ensured or increased with a low gradient limit value. According to one example of the embodiment, a gradient limit value suitable for ensuring or increasing the minimum service life of drive components of the electric drive can be, for example, between 5,000 Nm / s and 50,000 Nm / s, for example, approximately 10,000 Nm / s.According to one embodiment, the gradient limit value can be determined such that the gradient limit value is designed to maximize the service life of drive components of the electric drive. This allows for optimization of component protection within technically feasible limits.

[0029] According to one embodiment, the gradient limit can be determined depending on the classified deceleration request signal such that the gradient limit is designed to increase the deceleration effect. This allows an appropriate deceleration response to be implemented depending on the situation, for example, to enable a shorter braking distance in a driving situation with increased hazard potential. A shortened service life or potential damage to the drive components can be deliberately permitted, for example, to accommodate the emergency nature of the driving situation through an increased deceleration effect.For example, for a classified deceleration request signal representing a high hazard level or an emergency braking situation, a deceleration-optimized, weaker, less restrictive torque gradient limitation can be applied compared to a component-optimized, stronger torque gradient limitation. In other words, the gradient limit value for increasing the deceleration effect can be higher than the previously explained gradient limit value for ensuring or increasing the minimum service life of the drive components. A higher gradient limit value enables greater degrees of change in torque over time, so that, in simple terms, a gradient limit value for increasing a deceleration effect allows faster changes in torque than a gradient limit value for ensuring or increasing the minimum service life of the drive components.According to one example of the embodiment, a gradient limit suitable for ensuring or increasing the minimum service life of drive components of the electric drive can be, for example, between 150,000 Nm / s and 250,000 Nm / s, in particular approximately 200,000 Nm / s. According to one refinement of the embodiment, the gradient limit can be determined such that the gradient limit is designed to maximize the deceleration effect. This allows optimization of the deceleration effect within technically feasible limits, for example, up to a maximum load capacity of the drive components of the electric drive. Suitable gradient limit values ​​for maximizing the deceleration effect can be determined, for example, by means of load tests.

[0030] According to one embodiment, the gradient limit can be determined depending on the classified deceleration request signal such that the gradient limit lies between a gradient limit for ensuring or increasing a minimum service life of drive components of the electric drive and a gradient limit for increasing the deceleration effect. In particular, the gradient limit can lie between a gradient limit for maximizing the service life of drive components of the electric drive and a gradient limit for maximizing the deceleration effect. Accordingly, gradient limit values ​​between two defined gradient limit values ​​can also be determined, for example, selected or calculated. This can enable improved fine-tuning of the required deceleration effect and the reduction of component stress.In addition, individual optimization of torque delivery and a differentiated, situation-appropriate vehicle response can be enabled. The gradient limit between the gradient limit for ensuring or increasing the minimum service life of drive components of the electric drive and the gradient limit for increasing the deceleration effect can be determined, for example, in response to a gradually classified deceleration request signal, for example, selected depending on classified hazard levels with different hazard potential values. Furthermore, the gradient limit can be calculated as an intermediate value, for example, according to specified criteria or by interpolation between two predefined gradient limits.

[0031] According to one embodiment, a brake pedal signal, an accelerator pedal signal, a driver monitoring signal, and / or vehicle status information can be included in the evaluation and classification of the deceleration request signal to form a classified deceleration request signal. This enables a differentiated evaluation of the deceleration request signal and a precise, reliable classification. The aforementioned signals and information can, for example, be triggers, influencing factors, and / or indicators of a deceleration requirement or desired deceleration. Inclusion of one of the aforementioned signals or information can occur, for example, by comparing it with reference signals or information, by specifying defined conditions regarding the signals or information for classification, or by incorporating it into predefined calculation methods.A deceleration request can be indicated, for example, by releasing the accelerator pedal and / or applying pressure to the brake pedal, and can be detected based on the accelerator and brake pedal signal changes associated with the release or loading. A momentary or dynamic characteristic of the brake pedal signal and / or the accelerator pedal signal can be included in the evaluation and classification of the deceleration request signal. A driver monitoring signal can be generated, for example, by a sensory driver monitoring system that is configured, for example, to detect a critical driver condition, such as an unexpected health impairment, and can, for this purpose, have an optical monitoring unit with connected image processing.Using the driver monitoring signal, for example, a potential emergency braking situation or a high-risk hazard level can be reported, and the deceleration request signal can be classified accordingly. Vehicle status information can be generated, for example, using a sensory and / or predictive vehicle monitoring system that is configured, for example, to detect a critical vehicle condition, such as a vehicle defect, or to perform predictive collision detection or trajectory prediction. Vehicle status information can also relate to a current vehicle property, such as the vehicle's total mass or driving speed, which is known or can be signaled to a control unit for implementing the method.Using the vehicle status information, for example, a potential emergency braking situation or a high-risk hazard level can be reported, and the deceleration request signal can be classified accordingly. The brake pedal signal, the accelerator pedal signal, the driver monitoring signal, and / or the vehicle status information can also be evaluated together in combination or in subcombinations to provide a classified deceleration request signal. For example, it is also conceivable to perform a plausibility check of a classified deceleration request signal using one or more of the aforementioned signals or one or more of the aforementioned information in order to increase the reliability of the classification.It is possible that, given a specific classification of the deceleration request signal, further sensor data from the driver monitoring or vehicle monitoring system may be specifically queried in order to verify the classification result or to provide further evidence of a specific vehicle situation.

[0032] According to one embodiment, the deceleration request signal can be evaluated and classified into a classified deceleration request signal based on a signal profile of the brake pedal signal and / or based on a signal profile of the accelerator pedal signal. This allows for simple implementation of the evaluation and classification of the deceleration request signal, whereby, for example, an emergency braking situation or different danger levels can be reliably identified based on the signal profile or the signal profiles. A signal profile can, for example, correspond to a profile of the accelerator pedal signal as a function of time or a profile of the brake pedal signal as a function of time, whereby a combined consideration of the two signal profiles as a function of time and in dependence on one another can also be carried out for the evaluation and classification.For evaluation and classification, certain characteristics or patterns of the signal curve(s) can be considered, for example, gradients, extreme points, or inflection points. For example, a negative gradient of the accelerator pedal signal and / or a positive gradient of the brake pedal signal can be detected and evaluated, whereby the gradient can define a rate of change in the signal strength as a function of time. When evaluating the signal curves together, a changeover time between a release of the accelerator pedal and a loading of the brake pedal can also be taken into account for the evaluation. In principle, it is conceivable to consider instantaneous absolute values ​​of the brake pedal signal and / or the accelerator pedal signal alternatively or additionally.However, a temporal signal curve or a relative signal change as a function of time can be more meaningful and thus advantageous for a differentiated classification of the delay request signal.

[0033] According to one embodiment, depending on the classified deceleration request signal, a friction brake system of the vehicle can be controlled by the drive control signal in addition to controlling the electric drive of the wheel of the vehicle axle. This allows an additional deceleration effect to be achieved by the vehicle's friction brake system. Furthermore, individual coordination of torque generation by the electric drive and the vehicle's friction brake system, for example, individual distribution of the deceleration request to optimize the deceleration effect, can be enabled.For example, the electric drive and the friction brake system can be individually controlled depending on the classified deceleration request signal in such a way that the minimum service life of the drive components of the electric drive and / or the minimum service life of the brake components of the friction brake system are ensured or increased, or in such a way that a maximum deceleration effect is achieved by increasing the gradient limit value and maximum utilization of the electric drive and by maximum utilization of the friction brake system. For example, the above-described control unit can be configured to provide the drive control signal and to control the friction brake system, wherein the control unit can advantageously be formed by the above-described brake control unit configured to control braking functions of the vehicle or can comprise the above-described brake control unit.The above-described signals and information relating to a brake pedal signal, an accelerator pedal signal, a driver monitoring signal, and / or vehicle status information can advantageously be used not only to evaluate and classify the deceleration request signal, but also, for example, to determine a suitable control scheme for the coordinated control of the electric drive and the friction brake system. For example, a state of the vehicle's friction brake system can be taken into account when determining the control scheme. For example, to achieve a high or maximized deceleration effect, a higher load on the electric drive with a high gradient limit value can be applied if the friction brake system is operated with deactivated friction pairs, for example, after long periods of inactivity, and the friction brake has therefore not yet been sufficiently conditioned.

[0034] The invention also relates to a control unit for a vehicle for carrying out the method according to one of the features described above, wherein the control unit is configured to receive a deceleration request signal, evaluate it, and classify it into a classified deceleration request signal, determine a gradient limit value of a torque gradient of the electric drive as a function of the classified deceleration request signal, and provide a drive control signal for the electric drive to generate a negative torque according to the determined gradient limit value at a wheel of a vehicle axle. The above-described advantages of a situation-appropriate adaptation of torque generation at the wheel of the vehicle axle and a deceleration effect better tailored to a given driving situation can also be achieved with such a control unit.The control unit can, for example, be configured to generate a drive control signal, wherein the control unit can convert incoming acceleration request signals or deceleration request signals at an input of the control unit into a corresponding drive control signal. If the vehicle has multiple electric drives for the wheels of the vehicle axles, the control unit can be configured to coordinate the drive control signals of the multiple electric drives with one another in such a way that a coordinated acceleration or deceleration effect occurs. The control unit can be configured to receive a deceleration request signal, for example, be signal-connected to a vehicle system that is configured to generate a deceleration request signal, for example, to an accelerator pedal system, a brake pedal system, a driver monitoring system, and / or a vehicle monitoring system.The control unit can be configured to evaluate and classify the deceleration request signal based on signal properties and / or signal profiles. For example, the control unit can be configured to include a brake pedal signal, an accelerator pedal signal, a driver monitoring signal, and / or vehicle status information in the evaluation and classification of the deceleration request signal. According to one embodiment, the control unit can be formed by a single control unit, for example, a brake control unit. According to further embodiments, it is conceivable for the control unit to have multiple control units, for example, two or more control units. For example, the control unit can have a brake control unit and a drive control unit. The brake control unit and the drive control unit can be interconnected via signaling.Furthermore, the control unit can have additional control units or be connected to other control units for signaling purposes, which, for example, enable the determination of hazard potential values ​​of driving situations using sensors or predictions, so that the deceleration request signal can be evaluated and classified according to hazard levels with different hazard potential values.

[0035] The invention also relates to a vehicle, in particular a commercial vehicle, for carrying out the method according to one of the features described above, wherein the vehicle has an electric drive configured to generate a torque at a wheel of a vehicle axle of the vehicle, a device for generating a deceleration request signal, and a control unit according to one of the features described above. A device for generating a deceleration request signal can, for example, be an accelerator pedal system, a brake pedal system, a driver monitoring system, and / or a vehicle monitoring system. Even with such a vehicle, the aforementioned advantages of situation-appropriate adaptation of torque generation at the wheel of the vehicle axle and a deceleration effect better tailored to the prevailing driving situation can be achieved.The advantages mentioned can offer a high optimization potential, particularly for commercial vehicles, since commercial vehicles often have a higher total mass than passenger vehicles and therefore a greater load on vehicle components. It can therefore be all the more advantageous to be able to dynamically and flexibly prioritize an increased service life of the vehicle's drive components or a high deceleration effect.

[0036] According to one embodiment, the vehicle can have more than one vehicle axle with a wheel that can be driven by the electric drive. For example, the vehicle can have two or more vehicle axles that have a wheel that can be driven by the electric drive. The electric drive can be designed, for example, as a central drive for wheels on two or more vehicle axles. In principle, however, it is also conceivable to design the electric drive as an individual wheel drive or to provide a common electric drive for the wheels of a vehicle axle. The electric drive can be configured to be able to generate positive torques and negative torques on the at least one wheel in accordance with a drive control signal, wherein an acceleration effect can be achieved by a positive torque and a deceleration effect can be achieved by a negative torque.

[0037] According to one embodiment, the vehicle can be designed as a towing vehicle, as a trailer vehicle, or as a vehicle combination comprising a towing vehicle and a trailer vehicle. In this case, the towing vehicle and / or the trailer vehicle can have an electric drive that is designed to generate a torque on a wheel of a vehicle axle of the vehicle. According to an advantageous embodiment, the towing vehicle and the trailer vehicle of a vehicle combination can each have such an electric drive that can be controlled with a drive control signal according to the features described above. As a result, the respective deceleration effect of the towing vehicle and trailer vehicle can be coordinated with one another, so that, for example, the trailer vehicle can be reliably prevented from being pushed onto the towing vehicle due to a lower deceleration effect on the trailer vehicle.In this case, it is conceivable, for example, that a common drive control signal can be transmitted to the electric drives of the towing vehicle and the trailer vehicle, or that an individual drive control signal is generated for the electric drive of the towing vehicle and for the electric drive of the trailer vehicle based on the classified deceleration request signal and the determined gradient limit value, in order to be able to take different vehicle properties into account individually, for example. However, it is also fundamentally possible, for example, to provide a vehicle combination with a towing vehicle having a different drive, for example a combustion engine, and a trailer vehicle having an electric drive, or to provide a vehicle combination with a towing vehicle having an electric drive and a non-powered trailer vehicle.According to one possible design, the trailer vehicle can be designed as a semi-trailer and the towing vehicle as a tractor unit.

[0038] The invention permits various embodiments and is explained in more detail below using exemplary embodiments with the accompanying drawings. They show schematically: Fig. 1 shows a flowchart of a method for controlling an electric drive according to one exemplary embodiment;

[0039] Fig. 2 shows an exemplary curve of a torque as a function of time according to two different torque gradients;

[0040] Fig. 3 shows an exemplary curve of an accelerator pedal signal and a brake pedal signal as a function of time according to two different driving situations;

[0041] Fig. 4 shows a control unit for a vehicle according to an embodiment; Fig. 5 shows a vehicle with a control unit according to an embodiment;

[0042] Fig. 6 shows a vehicle with a control unit according to a further embodiment.

[0043] Fig. 1 shows a simplified and schematic flow diagram of a method 100 for controlling an electric drive 20, which is set up to generate a torque M, for example shown in Fig. 2, at a wheel 30 of a vehicle axle 31 of a vehicle 10, for example shown in Fig. 5. In a first step S1 of the method 100, a deceleration signal Vi, V2, V3, V4, for example shown in Fig. 4, is received. In a second step S2 of the method 100, the deceleration request signal Vi, V2, V3, V4 is evaluated and classified to form a classified deceleration request signal VK. Subsequently, a gradient limit value Gn, GL2 of a torque gradient G1, G2 of the electric drive 20 is determined as a function of the classified deceleration request signal VK (see also Fig. 4). According to the method shown in Fig.In the exemplary embodiment shown in Fig. 1, for example, a binary classification with the classification result "emergency braking situation" or "no emergency braking situation" can be provided as the classified deceleration request signal VK. The binary classification is represented in Fig. 1 by means of the condition C1 in the form of a system query for an emergency braking situation, which, if the answer Y is positive, leads to a third step S3b of the method 100 and, if the answer N is negative, leads to a third step S3a of the method 100. Step S3a of the method 100 can correspond to a determination of a first gradient limit value Gn, and step S3b of the method 100 can correspond to a determination of a second gradient limit value GL2.Subsequently, according to a fourth step S4a or a fourth step S4b of the method 100, the electric drive 20 is controlled by means of a drive control signal A to generate a negative torque M according to the determined gradient limit value GLI, GL2 at the wheel 30 of the vehicle axle 31. With the end of the method E, the previously described method 100 is initially terminated, but can be restarted by receiving a further deceleration request signal Vi, V2, V3, V4. With the proposed method 100, a flexible adaptation of a torque generation at the wheel 30 of the vehicle axle 31 of the vehicle 10 to a driving situation and a deceleration request resulting from the driving situation can be achieved, so that a deceleration effect W can be optimized depending on the situation.The deceleration effect W can, for example, be influenced depending on the situation in favor of a component-friendly deceleration of the vehicle 10 or in favor of an increased braking effect of the vehicle 10, whereby both requirements can be taken into account individually to different extents depending on the situation. According to the exemplary embodiment in Fig. 1, a binary classification of the deceleration request signal V1, V2, V3, V4 can be carried out to form a classified deceleration request signal VK. According to other embodiments, it is also conceivable, for example, to classify the deceleration request signal V1, V2, V3, V4 according to hazard levels GS with different hazard potential values ​​GP.

[0044] Fig. 2 shows a simplified, linearized outline of an exemplary curve of a torque M as a function of time t according to two different torque gradients G1, G2. The torque M shown can be generated as a positive torque or as a negative torque at the wheel 30 of the vehicle axle 31 of the vehicle 10, wherein a positive torque curve is shown in Fig. 2 to simplify the illustration. With a first torque gradient G1, a torque Mi is reached at a time t which is smaller than a torque M2 reached with the second torque gradient G2 at the same time t. The second torque gradient G2 has a greater gradient than the first torque gradient G1. With the second torque gradient G2, a faster change in the torque M is made possible than with the first torque gradient G1. A torque gradient shown for example in Fig.A first gradient limit value GLI or a second gradient limit value GL2, schematically indicated in Fig. 4, can form an upper limit for a torque gradient Gi, G2 predetermined by the control system in order to limit a rate of change of the torque M as a function of time t. For example, the torque gradients G1, G2 sketched in Fig. 2 can each form a first gradient limit value GLI and a second gradient limit value GL2, so that further torque gradients permissible by the control system can run in an area spanned between a torque gradient G1, G2 and the t-axis. For example, a first gradient limit value GLI can be designed to ensure or increase the minimum service life L of drive components 21 of the electric drive 20, for example of shaft bearings in a motor and / or transmission of the electric drive 20.For example, a second gradient limit value GL2 can be designed to increase a deceleration effect W on the vehicle 10. For this purpose, the second gradient limit value GL2 can, for example, be higher than the first gradient limit value Gn, so that a higher rate of change of the torque M per time t is permitted or requested by the control system.

[0045] Fig. 3 shows a simplified, linearized sketch of an exemplary accelerator pedal signal curve Fi, F2 of an accelerator pedal signal I2 shown in Fig. 4 and a brake pedal signal curve Bi, B2 of a brake pedal signal I1 shown in Fig. 4 as a function of time t according to two different driving situations. The driving situation represented by a first accelerator pedal signal curve Fi, shown with a solid line, and a first brake pedal signal curve Bi, shown with a solid line, can correspond, for example, to an emergency braking situation. The first accelerator pedal signal curve Fi has a steep negative gradient until it reaches a zero value at time ti. The first brake pedal signal curve Bi has a steep gradient.The time span between times ti and t2 corresponds to a first transition time twi of the driver between a release of the accelerator pedal system generating the accelerator pedal signal I2 and a load on a brake pedal system generating the brake pedal signal I1. The transition time in an emergency braking situation can be comparatively short, so that the first transition time Twi as well as, for example, the gradients and other characteristic properties of the first accelerator pedal signal curve Fi and the first brake pedal signal curve Bi can enable detection of an emergency braking situation. In comparison, a driving situation represented, for example, by a second accelerator pedal signal curve F2 shown with a dashed line and a second brake pedal signal curve B2 shown with a dashed line can correspond, for example, to a normal braking situation that does not require emergency braking with the highest possible deceleration effect W.The second accelerator pedal signal curve F2 has a smaller negative gradient than the first accelerator pedal signal curve Fi until reaching a zero value at time ts. The second brake pedal signal curve B2 has a smaller gradient than the first brake pedal signal curve Bi. The second transition time Tw2 between times ts and t4 is longer than the first transition time Twi between times t1 and t2. Accordingly, the second transition time Tw2 as well as, for example, the gradients and other characteristic properties of the second accelerator pedal signal curve F2 and the second brake pedal signal curve B2 can enable detection of a normal braking situation versus an emergency braking situation.

[0046] Fig. 4 shows a control unit 60 for a vehicle 10 according to an exemplary embodiment. The control unit 60 has a brake control unit 40 and a drive control unit 50 connected to the brake control unit 40 for signal transmission. The brake control unit 40 is configured to control braking functions of the vehicle 10 and has a first data processing unit 41 and a first memory unit 42 connected to the first data processing unit 41. The drive control unit 50 has a second data processing unit 51 and a second memory unit 52 connected to the second data processing unit 51.

[0047] The drive control unit 50 is configured to provide a drive control signal A for an electric drive 20 of the vehicle 10. The electric drive 20 is configured to generate a torque M at a wheel 30, as shown in Fig. 4, at two wheels 30 of a vehicle axle 31 of the vehicle 10. The brake control unit 40 is configured to receive a deceleration request signal Vi, V2, V3, V4 and to evaluate and classify it into a classified deceleration request signal VK, for example by means of the first data processing unit 41, which can perform the evaluation and classification, for example, using evaluation instructions and classification rules stored in the first memory unit 42.For example, classification rules for hazard levels GS with associated hazard potential values ​​GP can be stored in the first memory unit 42, so that the evaluation and classification of the deceleration request signal (Vi, V2, V3, V4) into a classified deceleration request signal (VK) can be carried out according to hazard levels (GS) with different hazard potential values ​​(GP). According to the illustrated embodiment, the brake control unit 40 is configured to transmit the classified deceleration request signal VK to the drive control unit 50.

[0048] According to the exemplary embodiment shown, the drive control unit 50 is configured to receive the classified deceleration request signal VK from the brake control unit 40 and, depending on the classified deceleration request signal VK, to determine a gradient limit value Gn, GL2 of a torque gradient G1, G2 of the electric drive 20. For example, two different gradient limit values ​​Gn, GL2 of the torque gradient G1, G2 of the electric drive 20 can be stored in the second memory unit 52 of the drive control unit 50, and the second data processing unit 51 can be configured to select one of the two gradient limit values ​​Gn, GL2 depending on the classified deceleration request signal VK.The electric drive 20 can then be controlled by means of the drive control signal A, taking into account the determined gradient limit value Gn, GL2, so that a torque M is generated at the wheels 30 in such a way that the determined gradient limit value Gn, GL2 of the torque gradient G1, G2 is not exceeded. For example, the brake control unit 40 can be configured to select a second gradient limit value GL2, which is higher than a first gradient limit value Gn, in the event of a deceleration request signal VK classified as a potential emergency braking situation, in order to increase the deceleration effect W of a negative torque M provided at the wheels 30.For example, the brake control unit 40 can be configured to select a first gradient limit value GL1, which is lower than a second gradient limit value GL2, in the case of a deceleration request signal VK classified as a normal braking situation, in order to ensure or increase the minimum service life L of drive components 21 of the electric drive 20. For example, the brake control unit 40 can be configured to select a second gradient limit value GL2, which is higher than a first gradient limit value Gn, in the case of a deceleration request signal VK classified as a potential emergency braking situation, in order to increase the deceleration effect W of a negative torque M provided to the wheels 30.In principle, it is also conceivable that the second data processing unit 51 of the drive control unit 50 is configured to calculate a further gradient limit value as an intermediate value between the first gradient limit value GLI and the second gradient limit value GL2 ZU in order to enable a finer tuning and weighting of a component protection of the electric drive 20 with respect to a required deceleration effect W.

[0049] The deceleration request signal Vi, V2, V3, V4 can be generated, for example, by a brake pedal system 80, an accelerator pedal system 81, a driver monitoring system 82 and / or a vehicle monitoring system 83. In addition, a brake pedal signal I1, an accelerator pedal signal I2, a driver monitoring signal I3 and / or a vehicle status information k can be included in the evaluation and classification of the deceleration request signal Vi, V2, V3, V4, for example, they can also be additionally queried or evaluated together. The brake control unit 40 can be configured to carry out the evaluation and classification of the deceleration request signal Vi, V2, V3, V4 into a classified deceleration request signal VK based on a signal curve Bi, B2 of the brake pedal signal I1 and / or based on a signal curve Fi, F2 of the accelerator pedal signal I2.The brake control unit 40 can be configured to provide, alternatively or in addition to generating a negative torque M at the wheels 30, a friction brake control signal 71 for a friction brake system 70 of the vehicle 10 in order to enable friction braking of the wheels 30.

[0050] Fig. 5 shows a vehicle 10 with a control unit 60 according to an exemplary embodiment. The vehicle 10 is illustrated as a commercial vehicle and is designed as a vehicle combination 13 with a towing vehicle 11 and a trailer vehicle 12. According to the exemplary embodiment shown, the towing vehicle 11 has two electric drives 20, which are each configured to generate a torque M at a wheel 30 of two vehicle axles 31 of the towing vehicle 11. The control unit 60 has a brake control unit 40 and a drive control unit 50. The drive control unit 50 is configured to control the electric drives 20 by means of a drive control signal A.The brake control unit 40 is configured to receive a deceleration request signal Vi, V2, V3, V4 and can, for example, be signal-connected to a brake pedal system 80, an accelerator pedal system 81, a driver monitoring system 82, and / or a vehicle monitoring system 83, each of which can represent a suitable device for generating a deceleration request signal Vi, V2, V3, V4. For example, the vehicle monitoring system 83 can be configured to monitor the environment and detect collisions of the vehicle 10, for example, using optical monitoring means to detect a potential collision object K.In this way, for example, a deceleration request signal V1, V2 already transmitted by an accelerator pedal system 81 and / or a brake pedal system 80 and a deceleration request signal VK classified as a potential emergency braking situation can be verified or evaluated directly in conjunction with the brake pedal signal I1 and / or the brake pedal signal I2 and classified into a classified deceleration request signal VK.

[0051] Fig. 6 shows a vehicle 10 with a control unit 60 according to a further exemplary embodiment. The vehicle 10 is illustrated as a commercial vehicle by way of example and is designed as a vehicle combination 13 with a towing vehicle 11 and a trailer vehicle 12. Compared to the exemplary embodiment shown in Fig. 5, in the further exemplary embodiment shown, not only the towing vehicle 11 but also the trailer vehicle 12 has an electric drive 20 which is designed to generate a torque M at wheels 32 of the driven vehicle axle 33 of the trailer vehicle 12. A drive control signal A generated by means of the drive control unit 50 can be transmitted to the electric drive 20 of the trailer vehicle 12 via a trailer control unit 90 of the trailer vehicle 12, which is connected to the drive control unit 50 of the towing vehicle 11 by a signal line.This makes it possible to enable a coordinated deceleration effect of the towing vehicle 11 and the trailer vehicle 12, for example to prevent the trailer vehicle 12 from being pushed onto the towing vehicle 11. In principle, according to alternative embodiments, it is also conceivable for only the trailer vehicle 12 to have an electric drive 20, which can be controlled, for example, with the drive control signal via the drive control unit 50 and the trailer control unit 90, while the towing vehicle 11 is driven, for example, by a different drive type, such as an internal combustion engine.

[0052] Reference symbol (part of the description):

[0053] 10 vehicles

[0054] 11 towing vehicle

[0055] 12 trailer vehicle

[0056] 13 vehicle combination

[0057] 20 electric drive

[0058] 21 Drive component

[0059] 30-wheel towing vehicle

[0060] 31 Vehicle axle towing vehicle

[0061] 32 wheel trailer vehicle

[0062] 33 vehicle axle trailer vehicle

[0063] 40 Brake control unit

[0064] 41 first data processing unit

[0065] 42 first storage unit

[0066] 50 drive control unit

[0067] 51 second data processing unit

[0068] 52 second storage unit

[0069] 60 control unit

[0070] 70 Friction brake system

[0071] 71 Friction brake control signal

[0072] 80 Brake pedal system

[0073] 81 Accelerator pedal system

[0074] 82 Driver monitoring system

[0075] 83 Vehicle monitoring system

[0076] 90 Trailer control unit

[0077] 100 Methods for controlling an electric drive

[0078] A drive control signal

[0079] Bi first brake pedal signal curve

[0080] B2second brake pedal signal curve

[0081] C1 Condition “potential emergency braking situation”

[0082] E End of the procedure

[0083] Fi first accelerator pedal signal curve

[0084] F2 second accelerator pedal signal curve Gi first torque gradient

[0085] G2 second torque gradient

[0086] GL1 first gradient limit

[0087] GI-2 second gradient limit

[0088] GP Hazard potential value

[0089] GS danger level

[0090] K potential collision object

[0091] L Minimum service life of drive components

[0092] M torque

[0093] 11 Brake pedal signal

[0094] 12 Accelerator pedal signal h Driver monitoring signal k Vehicle status information

[0095] 51 Reception of a delay request signal

[0096] 52 Evaluation and classification of the delay request signal

[0097] S3a Determination of a first gradient limit

[0098] S3b Determination of a second gradient limit

[0099] S4a Provision of a first drive control signal

[0100] S4b Provision of a second drive control signal ti first time t2 second time t3 third time t4 fourth time

[0101] Twi first changeover time

[0102] T 2 second changeover time

[0103] V1 Delay request signal

[0104] V2 Delay request signal

[0105] V3 Delay request signal

[0106] V4 Delay request signal

[0107] VK classified delay request signal

[0108] W Delaying effect

Claims

Patent claims: 1 . Method (100) for controlling an electric drive (20) which is designed to generate a torque (M) at a wheel (30) of a vehicle axle (31) of a vehicle (10), comprising the steps: - reception of a delay request signal (Vi, V2, V3, V4) (S1); - Evaluation and classification of the delay request signal (V1, V2, V3, V4) into a classified delay request signal (VK) (S2); - determining a gradient limit value (Gn, G1.2) of a torque gradient (G1, G2) of the electric drive (10) as a function of the classified deceleration request signal (VK) (S3a, S3b); and Controlling the electric drive (20) by means of a drive control signal (A) to generate a negative torque (M) according to the determined gradient limit value (GLI, GL2) at the wheel (30) of the vehicle axle (31) (S4a, S4b).

2. Method (100) according to claim 1, characterized in that the vehicle (10) has a brake control unit (40) for controlling braking functions of the vehicle (10) and that the reception, evaluation and classification of the deceleration request signal (V1, V2, V3, V4) to a classified deceleration request signal (VK) (S1, S2) are carried out by means of the brake control unit (40).

3. Method (100) according to claim 2, characterized in that the vehicle (10) further comprises a drive control unit (50) for controlling the electric drive (20) and that - the determination of the gradient limit value (Gn, G1.2) of the torque gradient (G1, G2) of the electric drive (20) is carried out (S3a, S3b) as a function of the classified deceleration request signal (VK) by means of the brake control unit (40) and / or by means of the drive control unit (50); and - the control of the electric drive (20) by means of the drive control signal (50) for generating the negative torque (M) according to the determined gradient limit value (Gn , G1.2) is carried out by means of the drive control unit (50) (S4a, S4b).

4. Method (100) according to one of the preceding claims, characterized in that during the evaluation and classification of the deceleration request signal (Vi, V2, V3, V4) into a classified deceleration request signal (VK) (S2) it is determined whether a potential emergency braking situation exists (C1).

5. Method (100) according to one of the preceding claims, characterized in that the evaluation and classification of the deceleration request signal (Vi, V2, V3, V4) to a classified deceleration request signal (VK) (S2) takes place according to hazard levels (GS) with different hazard potential values ​​(GP).

6. Method (100) according to one of the preceding claims, characterized in that the gradient limit value (Gn , G1.2) is determined as a function of the classified deceleration request signal (VK) in such a way that the gradient limit value (GLI ) is designed to ensure or increase a minimum service life (L) of drive components (21 ) of the electric drive (20).

7. Method (100) according to one of the preceding claims, characterized in that the gradient limit value (Gn, G1.2) is determined as a function of the classified deceleration request signal (VK) in such a way that the gradient limit value (GL2) is designed to increase a deceleration effect (W).

8. Method (100) according to one of the preceding claims, characterized in that the gradient limit value (Gn, G1.2) is determined as a function of the classified deceleration request signal (VK) in such a way that the gradient limit value (Gn, GL2) lies between a gradient limit value (GLI) for ensuring or increasing a minimum service life (L) of drive components (21) of the electric drive (20) and a gradient limit value (G1.2) for increasing the deceleration effect (W).

9. Method (100) according to one of the preceding claims, characterized in that in the evaluation and classification of the delay request signal (Vi, V2, V3, V4) to a classified Deceleration request signal (VK) (S2) includes a brake pedal signal (h), an accelerator pedal signal (I2), a driver monitoring signal (h) and / or vehicle status information (k).

10. The method (100) according to claim 9, characterized in that the evaluation and classification of the deceleration request signal (V1, V2, V3, V4) to a classified deceleration request signal (VK) (S2) is carried out on the basis of a signal profile (Bi, B2) of the brake pedal signal (I1) and / or on the basis of a signal profile (Fi, F2) of the accelerator pedal signal (I2).

11. Method (100) according to one of the preceding claims, characterized in that, in dependence on the classified deceleration request signal (VK), in addition to controlling the electric drive (20) of the wheel (30) of the vehicle axle (31) by means of the drive control signal (A) (S4a, S4b), a friction brake system (70) of the vehicle (10) is controlled.

12. Control unit (60) for a vehicle (10) for carrying out the method (100) according to one of claims 1 to 11, wherein the control unit (60) is configured to receive a deceleration request signal (V1, V2, V3, V4), to evaluate it and to classify it into a classified deceleration request signal (VK), to determine a gradient limit value (G1, GL2) of a torque gradient (G1, G2) of the electric drive (20) as a function of the classified deceleration request signal (VK), and to provide a drive control signal (A) for the electric drive (20) for generating a negative torque (M) according to the determined gradient limit value (Gn, G1.2) at a wheel (30) of a vehicle axle (31).

13. Vehicle (10), in particular a commercial vehicle, for carrying out the method (100) according to one of claims 1 to 11, wherein the vehicle (10) has an electric drive (20) which is designed to generate a torque (M) at a wheel (30) of a vehicle axle (31) of the vehicle (10), a device for generating a deceleration request signal (V1, V2, V3, V4) and a control unit (60) according to claim 12.

14. Vehicle (10) according to claim 13, wherein the vehicle (10) has more than one vehicle axle (31) with a drive system drivable by means of the electric drive (20). wheel (30).

15. Vehicle (10) according to claim 13 or 14, wherein the vehicle (10) is designed as a towing vehicle (11), as a trailer vehicle (12) or as a vehicle combination (13) with a towing vehicle (11) and a trailer vehicle (12).

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