METHOD FOR OPERATING A MOTOR VEHICLE, DEVICE FOR A MOTOR VEHICLE, MOTOR VEHICLE

Description

[0001] The invention relates to a method for operating a motor vehicle comprising an electric machine having at least three phases, an electrical energy storage device and power electronics comprising several switching elements, wherein the switching elements of the power electronics are controlled to electrically connect the phases to the energy storage device in order to generate a generator-like deceleration torque.

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

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

[0004] Documents CN 102 457 182 A, JP 2012 060710 A, US 2015 / 239350 A1, and DE 10 2016 207280 A1 disclose methods and devices for operating a motor vehicle. Methods and motor vehicles of the type mentioned above are known from the prior art. For example, motor vehicles increasingly have at least one electric motor as their drive unit. The electric motor typically has a stator with at least three phases. The phases are arranged around a rotor of the electric motor in such a way that the rotor can be driven or rotated by a suitable current applied to the phases. To achieve a targeted current application to the phases, power electronics with several switching elements are provided, wherein the phases are connected / connectable to an electrical energy storage device of the motor vehicle via the power electronics.For example, the power electronics feature a half-bridge with two switching elements for each of the phases.

[0005] When the electric machine is operated in generator mode, the rotation of the rotor induces alternating voltages in the phases, generating a regenerative braking torque. The switching elements of the power electronics are then activated to electrically connect the phases to the energy storage device, thus generating this regenerative braking torque. Disclosure of the invention

[0006] The method according to the invention, with the features of claim 1, has the advantage that a particularly suitable control of the switching elements of the power electronics can be implemented situationally. According to the invention, a driving situation of the motor vehicle is determined, wherein, depending on the determined driving situation, a control method is selected from a group of at least two possible control methods, and wherein the switching elements are controlled depending on the selected control method. Depending on which control method is selected, the switching elements are controlled by different control signals. For example, when a first of the control methods is selected, the switching elements are controlled by different control signals than when a second of the control methods is selected.Because the control signals differ, the regenerative operation of the electric machine is affected differently by the selected control method. It is assumed that a different control method is particularly suitable depending on the vehicle's driving situation. The control methods are preferably predetermined or fixed. For each possible control method, there is at least one vehicle driving situation in which the respective control method would be selected. Preferably, the control signals for controlling the switching elements are determined as a function of the selected control method, the rotor speed, and / or the rotor angle.

[0007] According to the invention, a block clocking method is selected as the control method. Block clocking methods are generally known and are also referred to as six-step mode or fundamental frequency clocking (FFC). If the block clocking method is selected, the controlled switching elements are switched once in a conducting state and once in a non-conducting state during each revolution of the rotor. The controlled switching elements are switched with a time offset from each other. The duration during which the controlled switching elements are conducting corresponds to the duration during which they are non-conducting. If the switching elements are controlled according to the block clocking method, a particularly high regenerative deceleration torque is generated, resulting in rapid deceleration of the vehicle.

[0008] According to the invention, the block timing method is selected when an emergency braking situation is detected. An emergency braking situation is understood to be a driving situation in which the fastest possible deceleration of the vehicle is desired. Because the block timing method generates a high regenerative deceleration torque, it is particularly suitable as a control method when an emergency braking situation is detected. Preferably, when the emergency braking situation is detected, at least one friction braking device of the vehicle is also activated to generate a friction braking torque.

[0009] According to a preferred embodiment, a space vector pulse width modulation (SVPWM) method is selected as the control method. SVPWM methods are generally known and are also referred to as space vector pulse width modulation. In SVPWM, the controlled switching elements are driven by pulse width modulation. The duty cycle of the pulse width modulated control corresponds to the rotor's position angle. Compared to block clocking, the use of SVPWM results in increased recuperation efficiency. The efficiency of converting the vehicle's kinetic energy into electrical energy is therefore greater.

[0010] Preferably, a space vector pulse-width modulation (PWM) method that achieves high recuperation efficiency is selected when a standard driving situation is determined. A standard driving situation can be assumed, for example, when a comfort deceleration is to be implemented. The high recuperation efficiency is achieved, for example, by appropriately specifying a setpoint for a torque-generating current and a setpoint for a flux-generating current. The torque-generating current and the flux-generating current are also commonly referred to as Iq and Id, respectively. In field-oriented control of electric machines, the space vector is described by the torque-generating current and the flux-generating current.

[0011] According to a preferred embodiment, a space vector pulse-width modulation (SWM) method, which results in lower recuperation efficiency, is selected when the driving situation involves downhill driving and / or driving with the energy storage system at least substantially charged. It is assumed that the energy storage system's state of charge should not exceed a predetermined maximum charge threshold. Exceeding this threshold can occur, for example, when the electric machine is operated as a generator during a prolonged downhill drive and / or when the energy storage system is already at least substantially charged. Selecting the SWM method with the lower recuperation efficiency prevents the maximum charge threshold from being exceeded.The low recuperation efficiency is also preferably achieved by appropriately setting the target values ​​for the torque-generating current and the flux-generating current. In the space vector pulse-width modulation method, which results in high recuperation efficiency, different target values ​​are specified than in the space vector pulse-width modulation method, which results in lower recuperation efficiency.

[0012] Preferably, the release speed of an actuator, which can be used to impose an acceleration torque on the vehicle, is monitored to determine the driving situation. For example, it is determined that the emergency braking situation exists when the release speed exceeds a predetermined release speed threshold. If the release speed falls below the predetermined release speed threshold, the standard situation is determined to be the driving situation.

[0013] Preferably, to determine the driving situation, the actuation speed and / or the actuation force of an actuator, by which the deceleration torque for the vehicle can be determined, is monitored. If a user of the vehicle wishes to initiate emergency braking, it can be assumed that they will actuate the actuator particularly quickly and with particular force. By monitoring the actuation force and / or the actuation speed, it is therefore possible to reliably determine whether or not an emergency braking situation exists.

[0014] Preferably, the driving situation is determined based on data acquired by the vehicle's environmental sensors. Preferably, these sensors acquire visual data from the vehicle's surroundings. Based on this data, it can be determined, for example, whether an emergency braking situation exists. For instance, an emergency braking situation is determined when the environmental sensors detect that the distance between the vehicle and another vehicle or object in the vehicle's vicinity falls below a predefined threshold.

[0015] Preferably, the state of charge of the energy storage system is monitored to determine the driving situation. This makes it possible to determine whether the driving situation involves driving with the energy storage system at least substantially charged or not.

[0016] Preferably, the gradient of a road on which the vehicle is traveling is monitored to determine the driving situation. This allows it to be determined whether the driving situation is downhill or not. Preferably, the gradient is detected by a sensor device on the vehicle. This sensor device is, for example, a yaw rate sensor. Alternatively or additionally, the vehicle's position is determined based on navigation satellite signals received by the vehicle's navigation unit. To determine the gradient, the determined position is then compared with a map that contains information on the gradient for various possible positions.

[0017] The device according to the invention for a motor vehicle, comprising an electric machine with at least three phases, an electrical energy storage device, and power electronics comprising several switching elements, wherein the phases of the electric machine are electrically connected / connectable to the energy storage device via the power electronics, is characterized by the features of claim 10 by a control unit specifically designed to carry out the method according to the invention during intended use. The advantages already mentioned also result from this. Further preferred features and combinations of features result from the foregoing and from the claims. Preferably, the device comprises at least one sensor device that is communicatively connected to the control unit and is configured to acquire data that correlates with the driving situation of the motor vehicle.The control unit is then trained to determine the driving situation based on the data collected.

[0018] The motor vehicle according to the invention comprises an electric machine having at least three phases, an electric energy storage device and power electronics comprising several switching elements, wherein the phases of the electric machine are electrically connected / connectable to the energy storage device by the power electronics, and is characterized by the features of claim 11 by the device according to the invention.

[0019] This also results in the advantages already mentioned. Further preferred features and combinations of features result from what has been described above and from the claims.

[0020] The invention will be described in more detail below with reference to the drawings. These show Figure 1 shows a motor vehicle in a simplified representation and Figure 2 shows a method for operating the motor vehicle.

[0021] Figure 1 Figure 1 shows a simplified representation of a motor vehicle 1. The motor vehicle 1 has four wheels 2 and 3, with wheels 2 belonging to a front axle 4 and wheels 3 to a rear axle 5. The motor vehicle 1 has a drive arrangement 6 with an electric drive motor 7.

[0022] The drive machine 7 has a rotor (not shown) which is fixedly mounted on a drive shaft 8 of the motor vehicle 1. The drive shaft 8 is connected to the wheels 2 of the front axle 4 via a differential gear 9 and shafts 10 and 11, preventing rotation. The drive machine 7 also has a stator (not shown) with three phases. The phases are arranged around the rotor in such a way that the rotor can be driven or rotated by applying a suitable current to the phases.

[0023] To achieve targeted current supply to the phases, the motor vehicle 1 has power electronics 12. The phases of the drive motor 7 are connected / connectable to an electrical energy storage device 13 of the motor vehicle 1 via the power electronics 12. For this purpose, the power electronics 12 has a half-bridge with two switching elements for each of the phases of the drive motor 7.

[0024] The drive motor 7 can be operated in generator mode. When the drive motor 7 is operated in generator mode, an alternating voltage is induced in the phases by the rotating rotor, generating a regenerative deceleration torque that slows the vehicle 1. By appropriately controlling the switching elements of the power electronics 12, the induced alternating voltage can be converted into a direct voltage for charging the energy storage device 13.

[0025] The motor vehicle 1 also has a device 14. The device 14 has a control unit 15 which is configured to control the switching elements of the power electronics 12.

[0026] The device 14 also includes a data storage device 16 in which different control methods are stored. The data storage device 16 is connected to the control unit 15 via communication technology in order to provide the control unit 15 with one or more of the control methods.

[0027] The motor vehicle 1 also has a first actuating element 17, whereby an acceleration torque for the motor vehicle 1 can be specified by actuating the first actuating element 17. The first actuating element 17 is therefore an accelerator pedal 17 of the motor vehicle 1. In order to generate the specified acceleration torque, the control unit 15 controls the switching elements of the power electronics 12 such that the phases are energized in order to drive the rotor by energizing the phases.

[0028] The motor vehicle 1 also has a second actuating element 18 by which a deceleration torque for the motor vehicle 1 can be specified. The second actuating element 18 is therefore a brake pedal 18 of the motor vehicle 1. To generate the specified deceleration torque, the control unit 15 activates the switching elements of the power electronics 12 to generate the deceleration torque by operating the drive motor 7 in generator mode. Alternatively, preferably at least one friction brake device (not shown) is activated to generate the deceleration torque, or both the power electronics 12 and the at least one friction brake device are activated, so that the at least one friction brake device and the drive motor 7 jointly generate the deceleration torque.

[0029] The device 14 also has several sensor devices 19, 20, 21, 22, 23, 24 and 25.

[0030] A first sensor device 19 is configured to detect the velocity of a displacement of the first actuator 17. The first sensor device 19 is connected to the control unit 15 via communication technology in order to provide the control unit 15 with the detected velocity of the displacement of the actuator 17.

[0031] A second sensor 20 is configured to detect the velocity of a displacement of the second actuator 18. The second sensor 20 is connected to the control unit 15 via communication technology in order to provide the control unit 15 with the detected velocity of the displacement of the second actuator 18. Alternatively or additionally, the second sensor 20 is configured to detect an actuation force of the second actuator 18 and provide it to the control unit 15.

[0032] A third sensor device 21 is designed to detect the gradient of a road on which the motor vehicle 1 is traveling. For example, the third sensor device 21 is a yaw rate sensor 21. The third sensor device 21 is connected to the control unit 15 via communication technology in order to provide the control unit 15 with the detected gradient.

[0033] A fourth sensor 22 is configured to monitor the state of charge of the energy storage device 13. The fourth sensor 22 is connected to the control unit 15 via communication technology in order to provide the control unit 15 with the detected state of charge.

[0034] The fifth 23, sixth 24, and seventh 25 sensor devices are each environmental sensors 23, 24, and 25 of the motor vehicle 1. Together, the environmental sensors 23, 24, and 25 form an environmental sensor system 26 of the motor vehicle 1 and are designed to detect the 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 control unit 15 via communication technology in order to provide the control unit 15 with environmental data detected by the environmental sensors 23, 24, and 25.

[0035] The following refers to Figure 2 An advantageous method for operating the motor vehicle 1 is explained in more detail using a flowchart.

[0036] In a first step S1, data is recorded by the sensor devices 19, 20, 21, 22, 23, 24 and 25 and made available to the control unit 15.

[0037] In a second step S2, the control unit 15 determines a driving situation of the motor vehicle 1 based on the data recorded by the sensor devices 19, 20, 21, 22, 23, 24 and 25.

[0038] For example, the control unit 15 determines that an emergency braking situation exists when the speed of movement of the first actuator 17 towards an unactuated state, i.e., the release speed of the first actuator 17, exceeds a release speed threshold. The control unit 15 also determines that an emergency braking situation exists when the speed of movement of the second actuator 18 in an actuation direction, i.e., the actuation speed of the second actuator 18, exceeds an actuation speed threshold.The control unit 15 also determines that the emergency braking situation exists if, based on the data acquired by the environmental sensors 26, it is determined that a distance between the motor vehicle 1 on the one hand and another vehicle in the vicinity of the motor vehicle 1 and / or an object in the vicinity of the motor vehicle 1 falls below a predetermined distance threshold.

[0039] If the gradient detected by the third sensor 21 exceeds a predefined gradient threshold, the control unit 15 determines that the driving situation is downhill. If the state of charge detected by the fourth sensor 22 exceeds a predefined charge threshold, the control unit 15 determines that the driving situation is driving with the energy storage device 13 at least substantially charged.

[0040] If neither the emergency braking situation, nor the downhill driving, nor the driving with at least substantially charged energy storage 13 is present, the control unit 15 determines a standard driving situation as the driving situation in step S2.

[0041] In a third step S3, the control unit 15 selects one of the control methods stored in the data memory 16, depending on the determined driving situation. If the control unit 15 determined the emergency braking situation in step S2, it selects a block timing method as the control method in step S3. If the control unit 15 determined downhill driving or driving with at least substantially charged energy storage 13 in step S2, it selects a space vector pulse width modulation method as the control method in step S3, which results in lower recuperation efficiency. However, if the control unit 15 determined the standard driving situation in step S2, it selects a space vector pulse width modulation method as the control method in step S3, which results in high recuperation efficiency.

[0042] In a fourth step S4, the control unit 15 detects that a delay torque is to be generated, for example due to an actuation of the second actuator 18.

[0043] In a fifth step S5, the control unit 15 determines control signals for controlling the switching elements of the power electronics 12. The control unit 15 determines the control signals at least as a function of the selected control method. Preferably, the control unit 15 also determines the control signals as a function of a rotational speed of the rotor and / or a rotor position angle.

[0044] In a sixth step S6, the control unit 15 then controls the switching elements of the power electronics 12 using the determined control signals in order to operate the drive motor 7 in generator mode and to generate a regenerative deceleration torque. The switching elements are thus controlled depending on the selected control method. If the emergency braking situation was determined as the driving situation in step S2, then preferably at least one of the friction brake devices (not shown) is also controlled. In this case, both a regenerative deceleration torque and a friction brake torque are generated to decelerate the vehicle 1.

Claims

1. Method for operating a motor vehicle which comprises an electrical machine (7) having at least three phases, an electrical energy store (13) and a power electronics system (12) having a plurality of switching elements, wherein the switching elements of the power electronics system (12) are actuated for electrically connecting the phases to the energy store (13) in order to produce a generator deceleration torque, characterized in that a driving situation of the motor vehicle (1) is determined, wherein, according to the driving situation thus determined, an actuation method is selected from a group of at least two potential actuation methods, and wherein the switching elements are actuated according to the actuation method selected, wherein a clocking block method is selected as the actuation method, in the event that an emergency braking situation is identified as the driving situation.

2. Method according to one of the preceding claims, characterized in that a space vector pulse-width modulation method is selected as the actuation method.

3. Method according to Claim 2, characterized in that a space vector pulse-width modulation method is selected, in the event that a standard driving situation is identified as the driving situation.

4. Method according to one of Claims 2 and 3, characterized in that a space vector pulse-width modulation method is selected, if the driving situation is identified as downhill travel and / or travel with an at least substantially charged energy store.

5. Method according to one of the preceding claims, characterized in that, for the identification of the driving situation, a release speed of an actuator (17) is monitored, by means of which an acceleration torque of the motor vehicle (1) is definable.

6. Method according to one of the preceding claims, characterized in that, for the identification of the driving situation, an operating speed and / or an operating force of an actuator (18) is monitored, by means of which the deceleration torque for the motor vehicle (1) is definable.

7. Method according to one of the preceding claims, characterized in that the driving situation is determined according to data which are detected by means of an environment sensor system (26) of the motor vehicle (1).

8. Method according to one of the preceding claims, characterized in that, for the determination of the driving situation, a state-of-charge of the energy store (13) is monitored.

9. Method according to one of the preceding claims, characterized in that, for the determination of the driving situation, a gradient of a road upon which the motor vehicle (1) is travelling is monitored.

10. Device for a motor vehicle which comprises an electrical machine (7) having at least three phases, an electrical energy store (13) and a power electronics system (12) having a plurality of switching elements, wherein the phases of the electrical machine (7) are electrically connected / connectable to the energy store (13) by means of the power electronics system (12), characterized by a control apparatus (15), which is specifically designed, in regulation use, to execute the method according to one of Claims 1 to 9.

11. Motor vehicle with an electrical machine (7) having at least three phases, particularly a drive machine (7), an electrical energy store (13) and a power electronics system (12) having a plurality of switching elements, wherein the phases of the electrical machine (7) are electrically connected / connectable to the energy store (13) by means of the power electronics system (12), characterized by a device (14) according to Claim 10.