WO2020193054A1

WO2020193054A1 - Method for operating a drive system of an electric vehicle, and drive system for an electric vehicle

Info

Publication number: WO2020193054A1
Application number: PCT/EP2020/055154
Authority: WO
Inventors: Andreas Erban
Original assignee: Robert Bosch Gmbh
Priority date: 2019-03-27
Filing date: 2020-02-27
Publication date: 2020-10-01
Also published as: DE102019204205A1

Abstract

The invention relates to a method for operating a drive system (100) of an electric vehicle, comprising an electric machine (54), an inverter unit (30) for actuating the electric machine (54), which has a torque control unit (32) and actuation unit (52), wherein the torque control unit (32) detects an actual rotational speed (40) of the electric machine (54) and calculates a control deviation (46) from the actual rotational speed (40) of the electric machine (54) and from a target rotational speed (62); a controller (42) of the torque control unit (32) calculates a correction torque (44) from the control deviation (46); the torque control unit (32) calculates a target torque (51) from the correction torque (44) and a specified torque (50); the actuation unit (52) calculates a target current (57) from the target torque (51); and the actuation unit (52) actuates the electric machine (54) with the target current (57). The invention also relates to a drive system (100) for carrying out the method for an electric vehicle.

Description

Method for operating a drive system of an electric vehicle and

Drive system for an electric vehicle

The invention relates to a method for operating a

Drive system of an electric vehicle, which has a transmission with at least one axle differential of at least one driven axle of the

Electric vehicle, an electric machine for driving the transmission and an inverter unit for controlling the electric machine, which one

Has torque control unit and a control unit comprises. The

The invention also relates to a drive system for an electric vehicle, which comprises a transmission with at least one axle differential of at least one driven axle of the electric vehicle, an electric machine for driving the transmission and an inverter unit for controlling the electric machine, which has a torque control unit and a control unit .

State of the art

DE 10 2011 088 729 A1 relates to a speed window-based one

Control strategy for an electric machine. A motor controller is disclosed which is used to control an electric machine, in particular to drive a

Vehicle is used. The engine controller includes an input terminal for inputting a value that is desired to be supplied by the electric machine

Torque in the indicative desired setpoints and for entering a limit variable indicative of a mechanical operating limit of the electrical machines. Furthermore, the engine control comprises a processor for outputting a torque indicative of a torque actually to be delivered by the electric machine in the actual setpoint, the processor being designed to determine the actual setpoint based on the desired setpoint and the limit variable. The motor controller is designed as a converter for converting a direct current into an operating current for the electric machine, the operating current being an in particular three-phase alternating current and the converter is designed so that it generates the operating current based on the actual target value.

DE 10 2016 203 113 A1 relates to a control system for distributing a drive torque and a vehicle with such a system

Control system. The distribution of a

Drive torque between a left and a right drive wheel of a motor vehicle via a differential gear. The drive torque is provided by an electric motor coupled to the differential gear. The provided drive torque is generated by a speed excitation of the

Electric motor and an adjustable braking intervention on one of the drive wheels distributed in such a way that when there are different on the left and right

Drive wheel acting coefficients of friction to a ground in contact with the drive wheels, the respectively available drive torque on the drive wheel with the higher coefficient of friction is higher than on the drive wheel on which the lower coefficient of friction is presented. In this way, an effective propulsive torque is largely transmitted via that of the drive wheels which has the higher coefficient of friction. The invention also relates to a motor vehicle which comprises such a control system. The

The control system comprises a control unit and sensors for detecting the wheel speeds, wheel brakes for braking the drive wheels individually and / or at least one actuator unit for the adjustable actuation of the wheel brakes assigned to the drive wheels.

A device for controlling a motor, in particular one

Vehicle engine is known from EP 2 810 132 B1.

Vehicles with an electric drive and an axle differential connected to it and provided on a driven axle have very high dynamics with regard to the drive torques that occur. This can lead to very different wheel speeds between the left and right wheels of a driven axle, especially with inhomogeneous coefficients of friction. The resulting high

Differential speed places a strong mechanical load on the

Axle differential of the driven axle. It can damage the axle differential and, in the worst case, result in a Total failure of the drive train. The driving comfort also suffers due to the noises occurring and the vibrations associated with them.

A corrective intervention of known wheel control systems z. B. ESP-TCS, comes only after a period of time d. H. belated to take effect. The reason for this is, among other things, long signal transit times, which are also referred to as latencies, between the control units involved in the work chain in the vehicle.

Disclosure of the invention

A method for operating a drive system of a

Electric vehicle proposed. The drive system comprises a transmission with at least one axle differential of at least one driven axle of the electric vehicle, an electric machine for driving the transmission and an inverter unit for controlling the electric machine. The

The inverter unit has a torque control unit and a control unit.

From the torque control unit, an actual speed of the electrical

Machine detected. The torque control unit calculates a control deviation from the actual speed of the electrical machine and a target speed. A correction torque is calculated from the control deviation by a regulator of the torque control unit. A target torque is calculated by the torque control unit from the correction torque and a default torque. A target current is calculated from the target torque by the control unit. The electrical machine is calculated by the control unit with the

Target current controlled.

In the method according to the invention, a control loop directly in the inverter unit ensures immediate, fast, subordinate speed control of the electrical machine and thus supports an external control loop for controlling the wheel speeds. In this way, excessively high wheel speeds or excessively high differential speeds between the individual driven wheels of a drive axle are avoided right from the start. The subordinate speed control in the inverter unit is now automatically active under certain conditions. Because of the lower Differential speeds between the driven wheels will be

Axle differential in the axle driven by the electric machine is less mechanically stressed.

According to an advantageous embodiment of the invention, the

Torque control unit on a protection unit. The target speed is calculated by the protection unit.

The target speed can, for example, from the protection unit

Speed signals from all wheels of the electric vehicle are calculated, in particular by averaging.

The target speed can also be determined by the protection unit exclusively from speed signals from wheels on a non-driven axle of the

Electric vehicle can be calculated, in particular by averaging.

According to another advantageous embodiment of the invention, the

Target speed from a separate ESP system (electronic

Stability program) and to the torque control unit of the

Transferring inverter unit. In doing so, a situation-related appropriate

Target speed from the ESP system to the inverter unit via a

corresponding data interface transmitted. The fast subordinate

Speed control takes place within the inverter unit. The additional

The communication effort between the ESP system and the inverter unit remains manageable.

According to a preferred development of the invention, a control mode signal is generated by a separate ESP system and transmitted to the torque control unit of the inverter unit. The control mode signal signals the

Inverter unit possible driving states of the electric vehicle, for example free rolling, TCS intervention (Traction Control System), ABS intervention

(Anti-lock braking system) or DTC intervention (Drag Torque Control).

According to a preferred embodiment of the invention, the

Specified torque from a separate vehicle control unit (VCU, Vehicle Control Unit) and transmitted to the torque control unit of the inverter unit.

A drive system for an electric vehicle is also proposed. The drive system includes a transmission with at least one

Axle differential of at least one driven axle of the electric vehicle, an electric machine for driving the transmission and an inverter unit for controlling the electric machine. The inverter unit has a

Torque control unit and a control unit.

The torque control unit detects an actual speed of the electrical machine. The torque control unit calculates a control deviation from the actual speed of the electrical machine and a target speed. The

The torque control unit has a regulator which calculates a correction torque from the control deviation. The torque control unit calculates a target torque from the correction torque and a default torque. The

The control unit calculates a target current from the target torque. The

Control unit controls the electrical machine with the calculated target current.

According to an advantageous embodiment of the invention, the

Torque control unit on a protection unit. The

Protection unit the target speed.

According to another advantageous embodiment of the invention, the drive system also includes a separate ESP system (electronic

Stability program). The ESP system calculates the target speed and transmits the target speed to the torque control unit of the inverter unit.

According to a preferred embodiment of the invention, this includes

Drive system also has a separate vehicle control unit (VCU, Vehicle Control Unit). The vehicle control unit calculates the specified torque and transmits the specified torque to the torque control unit of the inverter unit.

Advantages of the invention The invention represents a control concept which is a combination of an external speed specification and an internal speed control in the

Includes inverter unit. This counteracts the approach of long signal propagation times, which are also referred to as latencies, which are particularly common in the case of a given architecture in the control unit network consisting of ESP, VCU and

Inverter unit often causes problems. In previous solutions, when the wheels spin, the drive torque of the at least one electric machine is reduced via the classic TCS control of the ESP. The sole reduction of the drive torque through the TCS function, however, only comes into effect with a delay due to the latencies, so that heavily spinning

Drive wheels with a low coefficient of friction can be the result. In the

solution according to the invention occur through the fast underlying

Speed control directly in the inverter unit does not show any significant latencies. Thus, high speed differences of the wheels as well as spinning of the drive wheels, especially during a starting phase of the

Electric vehicle, largely avoided. The control concept according to the invention is therefore advantageously used to protect a transmission, in particular one

Axle differential of a driven axle of an electric vehicle

Brief description of the drawings

Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

Show it:

Figure 1 shows a drive system for an electric vehicle according to a first

Embodiment,

Figure 2 shows a drive system for an electric vehicle according to a second

Embodiment and

Figure 3 shows a drive system for an electric vehicle according to a third

Embodiment.

Embodiments of the invention In the following description of the embodiments of the invention, the same or similar elements are denoted by the same reference numerals, a repeated description of these elements being dispensed with in individual cases. The figures represent the subject matter of the invention only schematically.

FIG. 1 shows a drive system 100 for an electric vehicle according to a first embodiment. The drive system 100 according to the first embodiment is used in particular in an electric vehicle with a classic ESP-TCS architecture. The drive system 100 according to the first

Embodiment is only suitable for use in electric vehicles

Front-wheel drive or rear-wheel drive.

The drive system 100 comprises a transmission (not shown here) with an axle differential of a driven axle of the electric vehicle. The

Drive system 100 further comprises an electric machine 54 for driving the transmission and an inverter unit 30 for controlling the electric machine 54. The inverter unit 30 has a torque control unit 32 and a control unit 52. The inverter unit 30 is connected to a battery, not shown here, which provides a direct voltage.

The drive system 100 also includes an ESP system 14, which has a TCS module 16 (Traction Control System). The ESP system 14 also has a wheel speed module 18 for detecting a speed signal 20 of a front left wheel, a speed signal 22 of a front right wheel, a speed signal 24 of a rear left wheel and a speed signal 26 of a rear right wheel.

The drive system 100 also includes a vehicle control device 10. The ESP system 14 determines a TCS target torque 28 and transmits this to the vehicle control device 10. The vehicle control device 10 has a torque module 12, which is generated, for example, from a position of an accelerator pedal of the electric vehicle and from the TCS Setpoint torque 28 calculates a default torque 50 and transmits it to torque control unit 32. The torque control unit 32 has a protection unit 34 to which the speed signals 20, 22, 24, 26 detected by the wheel speed module 18 are transmitted and which calculates a setpoint speed 62 of the electrical machine 54. In the present case, the protection unit 34 calculates the setpoint speed 62 exclusively from speed signals 20, 22, 24, 26 from wheels of a non-driven axle of the electric vehicle.

The torque control unit 32 detects an actual speed 40 of the electrical machine 54. The actual speed 40 and the setpoint speed 62 become one

Subtraction point 36 is supplied, from which a control deviation 46 is calculated as the difference between the actual speed 40 and the target speed 62.

The torque control unit 32 has a regulator 42 to which the

Control deviation 46 is supplied. The protection unit 34 also calculates a mode signal 43 and transmits this to the controller 42. The controller 42 calculates a correction torque 44 from the control deviation 46 and the mode signal 43.

The correction torque 44 and the default torque 50 are one

Summation point 48 supplied, from which a target torque 51 is calculated as the sum of the correction torque 44 and the preset torque 50. The control unit 52 calculates a target current 57 from the target torque 51 and controls the electrical machine 54 with the target current 57.

The TCS setpoint torque 28 is sent to the inverter unit 30 after coordination with other requirements in the vehicle control device 10. In addition, interfaces for detecting the speed signals 20, 22, 24, 26 of the

Wheel speed module 18 available. The dynamic protection function for the axle differential takes place at least during the latency phase in the

Inverter unit 30 based solely on actual speed 40 and speed signals 20, 22, 24, 26.

From the speed signals 20, 22, 24, 26 of the non-driven wheels, the wheel speeds and an estimated value for the

Derive the vehicle speed of the electric vehicle. In the simplest case, this can be achieved by averaging using the speed signals 20, 22, 24, 26 of the two non-driven wheels of the electric vehicle happened. The two non-driven wheels are assumed to be in

Roll drive case almost slip-free. The estimate for the

The vehicle speed serves as a reference variable for forming the setpoint speed 62. Since the setpoint speed 62 primarily depends on the vehicle speed and does not have high dynamics, the latency for detecting the speed signals 20, 22, 24, 26 has no disruptive influence here.

The target speed 62 is formed as a function of the vehicle speed and is selected in such a way that the difference in speed between the driven wheels, and thus across the axle differential, remains moderate when driving off on a smooth surface on one side. The target speed 62 should also be selected in such a way that the traction and the lateral force potential of the driven wheels are maintained on a homogeneous road surface.

As long as a request from the TCS module 16 to lower the

Drive torque has not yet reached the inverter unit 30 because of the latency, the inverter unit 30 automatically takes over the adaptation of the target torque 51 for the electrical machine 54 if necessary

If the wheel speed of the driven wheels is greater than the setpoint value and the resulting control deviation 46 exceeds a predetermined threshold, the controller 42 calculates the correction torque 44, which is then superimposed on the current preset torque 50 specified externally by the vehicle control unit 10.

This reduces the excess of drive torque and stabilizes the spinning wheel or both spinning wheels. In the simplest case, a P controller or a PDT1 controller can be used as controller 42. If necessary, the parameters of the controller 42 are selected as a function of the estimated vehicle speed. The operating point is taken over by the vehicle control unit 10 and by the ESP system 14. There is only a rapid dynamic correction of the target torque 51 by the controller 42. By evaluating the wheel speeds, can be

Driving situations such as starting on one-sided smooth surface as well as cornering can be closed and the parameters of the controller 42 can be adapted accordingly. FIG. 2 shows a drive system 100 for an electric vehicle according to a second embodiment. The drive system 100 according to the second

Embodiment is used in particular in an electric vehicle with an extended ESP-TCS architecture. The drive system 100 according to the second embodiment is suitable for use in electric vehicles with front-wheel drive or with rear-wheel drive or with all-wheel drive.

The drive system 100 comprises a transmission (not shown here) with an axle differential of a driven axle of the electric vehicle. A further axle differential of a second driven axle can also be provided. The drive system 100 further comprises an electric machine 54 for driving the transmission and an inverter unit 30 for controlling the

electric machine 54. The inverter unit 30 has a

Torque control unit 32 and a control unit 52. The inverter unit 30 is connected to a battery, not shown here, which is a

Provides DC voltage.

The ESP system 14 also has a TCS setpoint generator 60. The TCS setpoint generator 60 calculates a setpoint speed 62 of the electrical machine 54, which is transmitted to the torque control unit 32. The TCS setpoint generator 60 also generates a control mode signal 64. The torque control unit 32 has a protection unit 34 to which the control mode signal 64 is transmitted.

The drive system 100 also includes a vehicle control device 10. The ESP system 14 determines a TCS target torque 28 and transmits this to the vehicle control device 10. The vehicle control device 10 has a torque module 12 that, for example, from a position of an accelerator pedal of the electric vehicle and a specified torque 50 is calculated from the TCS setpoint torque 28 and transmitted to the torque control unit 32.

The torque control unit 32 has a regulator 42 to which the

Control deviation 46 is supplied. The protection unit 34 calculates a mode signal 43 from the control mode signal 64 and transmits this to the controller 42. The controller 42 calculates a correction torque 44 from the control deviation 46 and the mode signal 43.

The correction torque 44 and the default torque 50 are one

The specified torque 50 is sent to the inverter unit 30 after coordination with other requirements in the vehicle control device 10. In addition, an associated control mode signal 64 is transmitted. The speed signals 20, 22, 24, 26 for the wheel speeds are not required. The

During the latency phase, speed control works only on the basis of the current actual speed 40 and the setpoint speed 62, since the new TCS setpoint torque 28 is not yet available.

The setpoint speed 62 is calculated in the TCS setpoint generator 60 of the ESP system 14. For this purpose, the setpoint wheel speed of the TCS module 16 is used to determine the associated setpoint speed 62. The

The target wheel speed of the TCS module 16 is continuously calculated and transmitted to the inverter unit 30, even when the TCS function is passive. The additionally transmitted control mode signal 64 is used to control the controller 42 in the inverter unit 30. The control deviation 46 is limited asymmetrically, since to compensate for the excess torque in the drive train, an increased reduction of the

Drive torque by the controller 42 is necessary. As long as the request from the TCS module 16 to lower the drive torque has not yet reached the inverter unit 30 because of the latency, the inverter unit 30 automatically adjusts the drive torque of the electrical machine 54 if necessary.

As soon as the resulting control deviation 46 exceeds a predefined threshold, the controller 42 calculates a correction torque 44, which is then predefined externally by the vehicle control device 10 for the current one

Default torque 50 is superimposed. This will remove the excess of the

Reduced drive torque and the spinning wheel or both

spinning wheels stabilized.

In the simplest case, a P controller or PDT1 controller can be used as controller 42. The parameters of the controller 42 are selected as a function of the vehicle speed. The vehicle speed does not have to be known exactly. Should the vehicle speed be in the

Inverter unit 30 is not already known, so this can be from the

transmitted setpoint speed 62 are determined.

The operating point is taken over by the vehicle control unit 10 and the ESP system 14. A rapid dynamic correction of the target torque 51 takes place by the controller 42. The driving situations such as starting on one-sided smooth surface as well as cornering and the associated kinematics are already taken into account in the calculation of the transmitted setpoint speed 62 in the ESP system 14.

FIG. 3 shows a drive system 100 for an electric vehicle according to a third embodiment. The drive system 100 according to the third embodiment is used in particular in an electric vehicle with an extended ESP-TCS architecture with additional wheel signal information. The

Drive system 100 according to the third embodiment is suitable for use in electric vehicles with front-wheel drive or with rear-wheel drive or with all-wheel drive The drive system 100 comprises a transmission (not shown here) with an axle differential of a driven axle of the electric vehicle. A further axle differential of a second driven axle can also be provided. The drive system 100 further comprises an electric machine 54 for driving the transmission and an inverter unit 30 for controlling the

electric machine 54. The inverter unit 30 has a

Provides DC voltage.

The ESP system 14 also has a TCS setpoint generator 60. The TCS setpoint generator 60 calculates a setpoint speed 62 of the electrical machine 54, which is transmitted to the torque control unit 32. The TCS setpoint generator 60 also generates a control mode signal 64. The torque control unit 32 has a protection unit 34 to which the control mode signal 64 is transmitted. The speed signals 20, 22, 24, 26 detected by the wheel speed module 18 are also transmitted to the protective unit 34.

The drive system 100 also includes a vehicle control device 10. The ESP system 14 determines a TCS target torque 28 and transmits this to the vehicle control device 10. The vehicle control device 10 has a torque module 12, which is generated, for example, from a position of an accelerator pedal of the electric vehicle and from the TCS Setpoint torque 28 calculates a default torque 50 and transmits it to torque control unit 32.

Subtraction point 36 is supplied, from which a control deviation 46 is calculated as the difference between the actual speed 40 and the target speed 62. The torque control unit 32 has a regulator 42 to which the

The correction torque 44 and the default torque 50 are one

The specified torque 50 is sent to the inverter unit 30 after coordination with other requirements in the vehicle control device 10. In addition, an associated control mode signal 64 is transmitted. In addition, the speed signals 20, 22, 24, 26 for the wheel speeds must be available.

The speed control operates during the latency phase only on the basis of the current actual speed 40 and the setpoint speed 62, since the new TCS setpoint torque 28 is not yet available. The speed signals 20, 22, 24, 26 are used to compare the individual driving situations even more precisely to one another

distinguish. With the help of the difference in the wheel speeds on the driven axle, the situation "starting on a smooth surface on one side" can be better distinguished from the situation "starting on a homogeneous coefficient of friction" with symmetrically spinning wheels.

The target wheel speed of the TCS module 16 is continuously calculated and transmitted to the inverter unit 30, even when the TCS function is passive. The additionally transmitted control mode signal 64 is used to control the controller 42 in the inverter unit 30. In the simplest case, a P controller or PDT1 controller can be used as controller 42. The parameters of the controller 42 are selected as a function of the vehicle speed. The vehicle speed does not have to be known exactly. Should the vehicle speed be in the

Inverter unit 30 is not already known, so this can be from the

transmitted setpoint speed 62 are determined.

The invention is not restricted to the exemplary embodiments described here and the aspects emphasized therein. Rather, within the range specified by the claims, a large number of modifications are possible that are within the scope of expert knowledge.

Claims

Expectations

1. A method for operating a drive system (100) of a

Electric vehicle, comprising

a transmission with at least one axle differential of at least one driven axle of the electric vehicle,

an electric machine (54) for driving the transmission and an inverter unit (30) for controlling the electric machine (54), which has a torque control unit (32) and a control unit (52), wherein

an actual speed (40) of the electrical machine (54) is detected by the torque control unit (32);

from the torque control unit (32) from the actual speed (40) of the electrical machine (54) and a target speed (62)

Control deviation (46) is calculated;

from a regulator (42) of the torque control unit (32) from the

Control deviation (46) a correction torque (44) is calculated;

a target torque (51) is calculated by the torque control unit (32) from the correction torque (44) and a preset torque (50);

a target current (57) is calculated by the control unit (52) from the target torque (51); and

the electrical machine (54) is controlled by the control unit (52) with the target current (57).

2. The method of claim 1, wherein

the torque control unit (32) has a protection unit (34) from which the setpoint speed (62) is calculated.

3. The method of claim 2, wherein

the setpoint speed (62) is calculated by the protection unit (34) from speed signals (20, 22, 24, 26) from all wheels of the electric vehicle.

4. The method of claim 2, wherein

the target speed (62) is calculated by the protection unit (34) exclusively from speed signals (20, 22, 24, 26) from wheels of a non-driven axle of the electric vehicle.

5. The method of claim 1, wherein

the target speed (62) is calculated by an ESP system (14) and transmitted to the torque control unit (32).

6. The method according to any one of the preceding claims, wherein

a control mode signal 64 is generated by an ESP system (14) and transmitted to the torque control unit (32).

7. The method according to any one of the preceding claims, wherein

the specified torque (50) is calculated by a vehicle control unit (10) and transmitted to the torque control unit (32). A drive system (100) for an electric vehicle, comprising

the torque control unit (32) detects an actual speed (40) of the electrical machine (54);

the torque control unit (32) from the actual speed (40) of the electrical machine (54) and a target speed (62)

Control deviation (46) calculated;

the torque control unit (32) has a controller (42), which consists of the

Control deviation (46) calculates a correction torque (44);

the torque control unit (32) calculates a target torque (51) from the correction torque (44) and a preset torque (50);

the control unit (52) calculates a target current (57) from the target torque (51); and

the control unit (52) controls the electrical machine (54) with the target current (57).

8. Drive system (100) according to claim 8, wherein

the torque control unit (32) has a protection unit (34) which calculates the setpoint speed (62).

9. Drive system (100) according to one of claims 8 to 9, further

full

an ESP system (14) which calculates the setpoint speed (62) and transmits it to the torque control unit (32).

10. Drive system (100) according to one of claims 8 to 10, further comprising

a vehicle control unit (10) which calculates the specified torque (50) and transmits it to the torque control unit (32).