Method for operating a motor vehicle, device for a motor vehicle, motor vehicle

Abstract

The invention relates to a method for operating a motor vehicle (1) having an electric machine (7) having at least three phases, an electrical energy store (13) and power electronics (12) having a plurality of switching elements, wherein the switching elements of the power electronics (12) are actuated for electrically connecting a phase to the energy store (13) for generating a generator-like retarding torque. It is provided that a driving situation of the motor vehicle (1) is determined, wherein an actuation method is selected from a group of at least two possible actuation methods depending on the determined driving situation, and wherein the switching elements are actuated in accordance with the selected actuation method.

Description

TECHNICAL FIELD

[0001] The invention relates to a method for operating a motor vehicle having an electric machine having at least three phases, an electrical energy store and a power electronics having a plurality of switching elements, wherein the switching elements of the power electronics are actuated for electrically connecting the phases to the energy store for generating a generator-like retarding torque.

[0002] Furthermore, the invention relates to a device with a controller.

[0003] Furthermore, the invention relates to a motor vehicle with such a device. BACKGROUND

[0004] Methods and motor vehicles of the type mentioned in the opening part are known from the prior art. For example, motor vehicles increasingly have at least one electric machine as a drive machine. The electric machine usually has a stator with at least three phases. The phases are arranged distributed around a rotor of the electric machine in such a way that the rotor can be driven or said to be rotated by a suitable energization of the phases. In order to achieve a targeted energization of the phases, a power electronics having a plurality of switching elements is provided, wherein the phases are connected / connectable to an electrical energy store of the motor vehicle by means of the power electronics. The power electronics has, for example, a half-bridge with two switching elements for each of the phases.

[0005] If the electric machine is operated generator-like, an alternating voltage is induced into the phases by the rotation of the rotor and a generator-like retarding torque is generated. Here, the switching elements of the power electronics are actuated for electrically connecting the phases to the energy store for generating a generator-like retarding torque. SUMMARY

[0006] The method according to the application having the features of claim 1 has the advantage that depending on the situation a particularly suitable actuation of the switching elements of the power electronics can be achieved. To this end according to the application the driving situation of the motor vehicle is ascertained, wherein depending on the ascertained driving situation an actuation method is selected from a group of at least two possible actuation methods, and wherein the switching elements are actuated according to the selected actuation method. Depending on the selected actuation method the switching elements are actuated by different actuation signals. For example, when the first of the actuation methods is selected the switching elements are actuated by different actuation signals than when the second of the actuation methods is selected. Since the actuation signals differ from one another, the generator-like operation of the electric machine is influenced differently by the selection of the actuation method. It is based here on the fact that depending on the driving situation of the motor vehicle different ones of the actuation methods are particularly suitable. The actuation method is preferably a predetermined or fixed actuation method. Here, for each of the possible actuation methods there is at least one driving situation of the motor vehicle in which the respective actuation method is selected. Preferably, the actuation signals for actuating the switching elements are ascertained depending on the selected actuation method, the rotational speed of the rotor and / or the rotor position angle of the rotor.

[0007] According to a preferred embodiment it is provided that the block clock method is selected as the actuation method. The block clock method is known in principle and is also referred to as Six Step Mode or Fundamental Frequency Clocking (FFC). If the block clock method is selected, the actuated switching elements are switched conductively and non-conductively respectively during each revolution of the rotor. Here, the actuated switching elements are switched out of phase with respect to one another in time. The duration of the conduction of the actuated switching elements corresponds to the duration of the non-conduction of the actuated switching elements. If the switching elements are actuated according to the block clock method, a particularly high generator-like deceleration torque arises, so that the motor vehicle is rapidly decelerated.

[0008] Preferably, the block clock method is selected when an emergency braking situation is ascertained as the driving situation. The emergency braking situation is to be understood as the driving situation in which it is desired to decelerate the motor vehicle as quickly as possible, in particular as fast as possible. Since a high generator-like deceleration torque arises by means of the block clock method, the block clock method is particularly suitable as the actuation method when the emergency braking situation is ascertained. Preferably, at least one frictional brake device of the motor vehicle is also actuated for generating a frictional braking torque when the emergency braking situation is ascertained.

[0009] According to a preferred embodiment provision is made for selecting the space vector pulse width modulation method as the control method. The space vector pulse width modulation method is known in principle and is also referred to as space vector pulse width modulation (SVPWM). In the space vector pulse width modulation method the controlled switching elements are controlled in a pulse width modulated manner. Here, the duty cycle of the control in a pulse width modulated manner corresponds to the rotor position angle of the rotor. By using the space vector pulse width modulation method an improved recuperation efficiency can be achieved compared to the block clock method. As a result, the conversion of the kinetic energy of the motor vehicle into electrical energy is more efficient.

[0010] Preferably, when the standard driving condition is ascertained as the driving condition, then the space vector pulse width modulation method which leads to a high recuperation efficiency is selected. When the comfortable deceleration should be carried out as the deceleration, then the standard driving condition can be inferred, for example. Here, the high recuperation efficiency is achieved, for example, by a suitable presetting of the target value of the current for forming the torque and the target value of the current for forming the magnetic flux. The current for forming the torque and the current for forming the magnetic flux are also referred to as Iq or Id, respectively. The space vector is described in the field-oriented regulation of the electric machine by the current for forming the torque and the current for forming the magnetic flux.

[0011] According to a preferred embodiment provision is made for selecting the space vector pulse width modulation method which leads to a lower recuperation efficiency when the downhill driving and / or the driving in the case of an at least substantially fully charged energy store is ascertained as the driving condition. Here, the basis is that the state of charge of the energy store should not exceed a predefined maximum charge threshold. For example, when the electric machine is operated as a generator in the case of a long downhill driving and / or in the case of an energy store which is already at least substantially fully charged, then an exceeding of the maximum charge threshold can occur. By selecting the space vector pulse width modulation method with a low recuperation efficiency, the exceeding of the maximum charge threshold is avoided. The low recuperation efficiency is preferably also achieved by a suitable presetting of the target value of the current for forming the torque and the target value of the current for forming the magnetic flux. Here, in the space vector pulse width modulation method which leads to a high recuperation efficiency, different target values are predefined than in the space vector pulse width modulation method which leads to a lower recuperation efficiency.

[0012] Preferably, for ascertaining the driving condition the release speed of the adjustment element is monitored by means of which an acceleration torque for the motor vehicle can be predefined. For example, when the release speed exceeds a predefined release speed threshold, then it is determined that an emergency braking condition exists. If the release speed is below the predefined release speed threshold, then in particular the standard condition is ascertained as the driving condition.

[0013] Preferably, the driving situation is ascertained in order to monitor the actuating speed and / or the actuating force of the adjustment element by means of which the deceleration torque for the motor vehicle can be predefined. If the user of the motor vehicle wants to initiate an emergency braking, it can be assumed that he will actuate the adjustment element particularly quickly and particularly intensively. Thus, by monitoring the actuating force and / or the actuating speed it can be reliably determined whether an emergency braking situation exists as a driving situation.

[0014] Preferably, the driving situation is ascertained from data detected by means of an environmental sensor device of the motor vehicle. Preferably, visual data in the environment of the motor vehicle are detected by means of the environmental sensor device. From the data detected by means of the environmental sensor device it can be determined, for example, whether an emergency braking situation exists. For example, when it is determined by means of the environmental sensor device that the distance of the motor vehicle to another vehicle or to an object in the environment of the motor vehicle is below a predefined distance threshold, it is ascertained that an emergency braking situation exists.

[0015] Preferably, the state of charge of the energy store is monitored in order to ascertain the driving situation. Thereby it can be determined whether driving with an at least substantially fully charged energy store exists as a driving situation.

[0016] Preferably, the gradient of the road on which the motor vehicle is driving is monitored in order to ascertain the driving situation. Thereby it can be determined whether downhill driving exists as a driving situation. Preferably, the gradient is detected by means of a sensor device of the motor vehicle. The sensor device is then, for example, a rotational rate sensor. As an alternative or in addition, the position of the motor vehicle is ascertained from navigation satellite signals detected by means of a navigation unit of the motor vehicle. In order to ascertain the gradient, the ascertained position is then compared with a map in which for different possible positions a gradient or a slope is stored respectively.

[0017] A motor vehicle has an electric machine having at least three phases, an electrical energy store and a power electronics having a plurality of switching elements, wherein the phases of the electric machine are electrically connectable to the energy store by means of the power electronics, a device according to the application for the motor vehicle according to the features of claim 12 is distinguished by a controller which is specifically designed for carrying out a method according to the application in the case of a prescribed use. The advantages already mentioned are thereby also obtained. Further preferred features and feature combinations result from the foregoing description and from the claims. Preferably, the device has at least one sensor device which is connected in terms of communication technology to the controller and is designed for detecting data relating to a driving situation of the motor vehicle. The controller is then designed for ascertaining the driving situation from the detected data.

[0018] The motor vehicle according to the application has an electric machine having at least three phases, an electrical energy store and a power electronics having a plurality of switching elements, wherein the phases of the electric machine are electrically connected / connectable to the energy store by means of the power electronics and are characterized in terms of the features of claim 13 and in terms of the device according to the application. The advantages already mentioned thereby also result. Further preferred features and feature combinations result from the foregoing explanations and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0019] The application is explained in more detail below on the basis of the drawings. Therein:

[0020] Figure 1 A motor vehicle is shown in a simplified diagram, and

[0021] Figure 2 A method for operating a motor vehicle is shown. DETAILED DESCRIPTION

[0022] Figure 1 A motor vehicle 1 is shown in a simplified diagram. The motor vehicle 1 has four wheels 2 and 3, wherein the wheels 2 belong to a front axle 4 and the wheels 3 belong to a rear axle 5. The motor vehicle 1 has a drive 6 with an electric drive machine 7.

[0023] The drive machine 7 has a not shown rotor which is arranged in a rotationally fixed manner on a drive shaft 8 of the motor vehicle 1. The drive shaft 8 is currently connected in a rotationally fixed manner to the wheels 2 of the front axle 4 by means of a differential gear 9 and shafts 10 and 11. The drive machine 7 furthermore has a not shown stator with three phases. The phases are arranged so as to be distributed around the rotor, such that the rotor can be driven or rotated by suitable energization of the phases.

[0024] In order to achieve a targeted energization of the phases, the motor vehicle 1 has a power electronics 12. The phases of the drive machine 7 are connected / connectable to an electrical energy store 13 of the motor vehicle 1 by means of the power electronics 12. To this end, the power electronics 12 has a half-bridge with two switching elements for each of the phases of the drive machine 7.

[0025] The drive machine 7 can be operated as a generator. If the drive machine 7 is operated as a generator, an alternating voltage is induced into the phases by the rotating rotor and a generator-like deceleration torque is generated which decelerates the motor vehicle 1. The induced alternating voltage can be rectified into a direct voltage for charging the energy store 13 by suitably actuating the switching elements of the power electronics 12.

[0026] The motor vehicle 1 furthermore has a device 14. The device 14 has a controller 15 which is configured to actuate the switching elements of the power electronics 12.

[0027] The device 14 furthermore has a data memory 16 in which different control methods are stored. The data memory 16 is connected to the controller 15 in terms of communication technology in order to provide the controller 15 with one or more of the control methods.

[0028] The motor vehicle 1 furthermore has a first adjustment element 17, wherein by actuating the first adjustment element 17 a predefinable acceleration torque for the motor vehicle 1 can be given. The first adjustment element 17 is thus an accelerator pedal 17 of the motor vehicle 1. In order to generate the predefinable acceleration torque, the controller 15 actuates the switching elements of the power electronics 12 in such a way that phases are energized in order to drive the rotor by energizing the phases.

[0029] The motor vehicle 1 furthermore has a second adjustment element 18, by which a predefinable deceleration torque for the motor vehicle 1 can be given. The second adjustment element 18 is thus a brake pedal 18 of the motor vehicle 1. In order to generate the predefinable deceleration torque, the controller 15 actuates the switching elements of the power electronics 12 in order to generate the deceleration torque by generator-like operation of the drive machine 7. As an alternative thereto, at least one not shown friction brake is actuated in order to generate the deceleration torque or the power electronics 12 are not only actuated but also at least one friction brake is actuated, so that the at least one friction brake and the drive machine 7 jointly generate the deceleration torque.

[0030] The device 14 furthermore has a plurality of sensor devices 19, 20, 21, 22, 23, 24 and 25.

[0031] A first sensor device 19 of the sensor devices is configured to detect the speed of the displacement of the first adjustment element 17. The first sensor device 19 is connected to the controller 15 in terms of communication technology in order to provide the controller 15 with the detected speed of the displacement of the adjustment element 17.

[0032] A second sensor device 20 of the sensor devices is configured to detect the speed of the displacement of the second adjustment element 18. The second sensor device 20 is connected to the controller 15 in terms of communication technology in order to provide the controller 15 with the detected speed of the displacement of the second adjustment element 18. As an alternative or in addition, the second sensor device 20 is configured to detect the actuating force of the second adjustment element 18 and to provide it to the controller 15.

[0033] A third sensor device 21 of the sensor devices is configured to detect a gradient of a road on which the motor vehicle 1 is driving. The third sensor device 21 is, for example, a rate-of-rotation sensor 21. The third sensor device 21 is connected to the controller 15 in terms of communication technology in order to provide the controller 15 with the detected gradient.

[0034] A fourth sensor device 22 of the sensor devices is configured to monitor a state of charge of the energy store 13. The fourth sensor device 22 is connected to the controller 15 in terms of communication technology in order to provide the controller 15 with the detected state of charge.

[0035] A fifth sensor device 23, a sixth sensor device 24 and a seventh sensor device 25 of the sensor devices are environmental sensors 23, 24, 25 of the motor vehicle 1. The environmental sensors 23, 24 and 25 together form an environmental sensor device 26 of the motor vehicle 1 and are configured to detect an environment of the motor vehicle 1. The environmental sensors 23, 24 and 25 are, for example, radar sensors, lidar sensors, laser sensors or camera sensors. The environmental sensors 23, 24 and 25 are connected to the controller 15 in terms of communication technology in order to provide the controller 15 with environmental data detected by the environmental sensors 23, 24 and 25.

[0036] In the following, reference is made to Figure 2 An advantageous method for operating a motor vehicle 1 is explained in more detail in terms of a flow chart.

[0037] In a first step S1, data are detected by the sensor devices 19, 20, 21, 22, 23, 24 and 25 and provided to the controller 15.

[0038] In a second step S2, the controller 15 determines a driving situation of the motor vehicle 1 from the data detected by the sensor devices 19, 20, 21, 22, 23, 24 and 25.

[0039] For example, the controller 15 determines an emergency braking situation as the driving situation when a speed of a displacement of the first adjusting element 17 in a direction towards an unactuated state of the first adjusting element 17, i.e. a release speed of the first adjusting element 17, exceeds a release speed threshold value. The controller 15 also determines an emergency braking situation when a speed of a displacement of the second adjusting element 18 in a direction of actuation, i.e. an actuation speed of the second adjusting element 18, exceeds an actuation speed threshold value. The controller 15 also determines an emergency braking situation when it is determined from data or environmental data detected by the environmental sensor device 26 that a distance between the motor vehicle 1 and another vehicle in the environment of the motor vehicle 1 and / or an object in the environment of the motor vehicle 1 is below a predefinable distance threshold value.

[0040] If the gradient detected by the third sensor device 21 exceeds a predefinable gradient threshold value, the controller 15 ascertains hill descent travel as the driving situation. If the state of charge detected by the fourth sensor device 22 exceeds a predefinable charging threshold value, the controller 15 ascertains travel with the energy store 13 at least substantially fully charged as the driving situation.

[0041] If neither an emergency braking situation, nor hill descent travel, nor travel with the energy store 13 at least substantially fully charged is present, the controller 15 ascertains standard travel as the driving situation in step S2.

[0042] In a third step S3, the controller 15 selects one of the control methods stored in the data store 16 as a function of the ascertained driving situation. If the controller 15 has ascertained an emergency braking situation in step S2, the controller 15 selects the block clock method as the control method in step S3. If the controller 15 has ascertained hill descent travel or travel with the energy store 13 at least substantially fully charged in step S2, the controller 15 selects the space vector pulse width modulation method which leads to a lower recovery efficiency as the control method in step S3. If the controller 15 has ascertained standard travel as the driving situation in step S2, the controller 15 selects the space vector pulse width modulation method which leads to a high recovery efficiency as the control method in step S3.

[0043] In a fourth step S4, the controller 15 detects that a deceleration torque should be generated, for example as a result of a manipulation of the second actuating element 18.

[0044] In a fifth step S5, the controller 15 ascertains a control signal for the control of the switching elements of the power electronics 12. The controller 15 ascertains the control signal at least as a function of the selected control method. Preferably, the controller 15 ascertains the control signal also as a function of the rotational speed of the rotor and / or the rotor position angle of the rotor.

[0045] The controller 15 then manipulates the switching elements of the power electronics 12 in a sixth step S6 by means of the ascertained control signal in order to operate the drive machine 7 as a generator and to generate a generator-type deceleration torque. The switching elements are thus manipulated as a function of the selected control method. If an emergency braking situation has been ascertained as the driving situation in step S2, at least one of the friction brake devices, which is not shown, is preferably additionally manipulated. A generator-type deceleration torque and also a friction brake torque are then generated for decelerating the motor vehicle 1.

Claims

1. Method for operating a motor vehicle, which motor vehicle has an electric machine (7) with at least three phases, an electrical energy store (13) and power electronics (12) with a plurality of switching elements, wherein The switching elements of the power electronics (12) are actuated for electrically connecting the phases to the energy store (13) for generating a generator-like retarding torque, characterized in that the driving situation of the motor vehicle (1) is ascertained, in that an actuation method is selected from a group of at least two possible actuation methods depending on the ascertained driving situation, and in that the switching elements are actuated according to the selected actuation method, wherein the block clock method is selected when an emergency braking situation is ascertained as the driving situation.

2. The method of claim 1, wherein, The block clock method is selected as the actuation method.

3. The method of claim 1, wherein, The space vector pulse width modulation method is selected as the actuation method.

4. The method of claim 3, wherein, The space vector pulse width modulation method which leads to a high recuperation efficiency is selected when a standard driving situation is ascertained as the driving situation.

5. The method according to claim 3 or 4, characterized in that, The space vector pulse width modulation method which leads to a low recuperation efficiency is selected when a downhill driving and / or driving with an at least substantially fully charged energy store is ascertained as the driving situation.

6. The method according to any one of claims 1 to 4, characterized in that, The release speed of an adjustment element (17) by means of which an acceleration torque for the motor vehicle (1) can be predefined is monitored in order to ascertain the driving situation.

7. The method according to any one of claims 1 to 4, characterized in that, The actuating speed and / or actuating force of an adjustment element (18) by means of which a retarding torque for the motor vehicle (1) can be predefined is monitored in order to ascertain the driving situation.

8. The method according to any one of claims 1 to 4, characterized in that, The driving situation is ascertained depending on data detected by means of an environment sensor device (26) of the motor vehicle (1).

9. The method according to any one of claims 1 to 4, characterized in that, The state of charge of the energy store (13) is monitored in order to ascertain the driving situation.

10. The method according to any one of claims 1 to 4, characterized in that, The slope of the road on which the motor vehicle (1) is driving is monitored in order to ascertain the driving situation.

11. Device for a motor vehicle, which motor vehicle has an electric machine (7) with at least three phases, an electrical energy store (13) and power electronics (12) with a plurality of switching elements, wherein The phases of the electric machine (7) are electrically connectable / disconnectable to the energy store (13) by means of the power electronics (12), characterized by a controller (15) which is specifically set up for carrying out the method according to any one of claims 1 to 10 when a prescribed use is met.

12. Motor vehicle with an electric machine (7) having at least three phases, an electrical energy store (13) and power electronics (12) having a plurality of switching elements, wherein The phases of the electric machine (7) are electrically connectable / disconnectable to the energy store (13) by means of the power electronics (12), characterized by a device (14) according to claim 11.

13. The motor vehicle of claim 12, wherein, The electric machine (7) is a drive machine (7).

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