DE102012206518A1 - Method and device for controlling an electric machine of an electric drive train - Google Patents

Abstract

The invention relates to a method (40) for controlling an electric machine (12) of an electric drive train, which is designed to drive a motor vehicle, wherein at least one parameter of the drive train is detected (44), which is predefined by a predefined for normal operation of the motor vehicle Value Range deviates, wherein an emergency start for the motor vehicle is requested (46), wherein the motor vehicle is started (48) in an emergency operating mode, wherein electrical energy for the electric machine (12) is provided (48), so that a predefined drive torque (28 ) and / or the motor vehicle is accelerated to a predefined vehicle speed, and wherein the emergency mode is terminated (52) by stopping the provision of the electrical energy, if the emergency start request is withdrawn.

Description

The present invention relates to a method for controlling an electric machine of an electric drive train, which is designed to drive a motor vehicle.

Furthermore, the present invention relates to a device for controlling an electric machine of an electric drive train, which is designed to drive a motor vehicle.

State of the art

Conventional vehicles with an internal combustion engine have a functionality that makes it possible to move the vehicle in emergency situations a short distance, even if the drive system is no longer functional. An example scenario is a vehicle left on a railroad crossing. When the gear is engaged, the vehicle can be moved several meters out of a danger zone (eg from an area of the railroad crossing) by turning and holding the ignition key only by the drive torque of the starter / starter motor. However, this emergency start does not take into account any possible damage to vehicle components. Therefore, there is the possibility that, for example, the starter after such an emergency start is no longer functional.

Vehicles with a purely electric powertrain (eg electric vehicles, serial hybrid vehicles (Range Extender), fuel cell vehicles) have no separate starter motor in addition to the electric drive motor, since the electric drive motor does not require an auxiliary engine to start. However, a start of the vehicle and thus of the electric drive motor is usually only made possible if sufficient drive power can be provided by the system. The drive power is provided, for example, by a drive battery of the electric drive train. To protect the traction battery, it may only be taken out under normal conditions if there is a certain minimum state of charge or if a certain temperature range is maintained. With almost empty, very cold or overheated drive battery, the vehicle may therefore no longer be started, even if a certain residual energy is available in principle. In fuel cell vehicles, for example, run-up in very cold environmental conditions may take a long time until sufficient drive power is available. In emergency situations, however, there is a need to move the vehicle out of a danger zone, regardless of possible damage to vehicle components.

Disclosure of the invention

The present invention therefore provides a method for controlling an electric machine of an electric drive train, which is designed to drive a motor vehicle, wherein at least one parameter of the drive train is detected, which differs from a predefined for normal operation of the motor vehicle range of values, wherein a Emergency start is requested for the motor vehicle, wherein the motor vehicle is started in an emergency operating mode, wherein electrical energy is provided for the electric machine, so that a predefined drive torque is set and / or the motor vehicle is accelerated to a predefined vehicle speed and wherein the emergency mode by stopping the supply of electrical energy is terminated, if the emergency start request is withdrawn.

Furthermore, the present invention provides a device for controlling an electric machine of an electric drive train, which is designed to drive a motor vehicle, wherein the device has a control device for controlling the electric machine and wherein the control device is adapted to the method of the above Kind of execute.

Advantages of the invention

The present invention increases the safety of a vehicle with an electric drive train, especially in an emergency situation. The vehicle can, for example, be moved out of a danger zone even without the use of a further / redundant drive unit by means of the electric machine of the electric drive train.

By setting a predefined drive torque and / or the acceleration of the motor vehicle to a predefined vehicle speed, the use of electrical energy is limited. This can be a potential damage to vehicle components are minimized.

The control unit according to the invention controls all components required for emergency operation, so that the emergency operation can be activated even in the event of failure of one or more control units of the drive train, sensors or other components. Thus, a very robust control of emergency operation is possible.

Of particular preference is when the emergency start is requested by a start button of the motor vehicle is pressed for a predefined period.

By using a standard control component (start button), the emergency start request can be easily and safely followed. In contrast, a special, separately executed emergency switch would not be found in panic situations or too late, since this is used only in very rare cases. In a separate emergency start switch also incurred costs for the additional switching element. Furthermore, additional wiring would be required.

In this embodiment, it is sufficient for the request of an emergency start, the start button to operate over a predefined period. The vehicle is automatically started without any further intervention. The adjustment of the drive torque can take place, for example, without consideration of the driving step selection of the motor vehicle. In addition, the parking brake can be automatically released upon detection of an emergency start request. This allows the driver of the motor vehicle, the emergency operation by a single action (pressing the start button) trigger without further interaction.

According to a further embodiment, the emergency start is requested by the start button of the motor vehicle is operated with a predefined pressure.

In the present embodiment, a pressure or force is exerted on the start button. This is preferably done via pressure sensors, which are integrated in the start button. For this purpose, capacitive, piezoresistive, piezoelectric active principles or even electroactive polymers can be used. The emergency start request is made as soon as the pressure on the start button reaches or exceeds a predefined value. This allows a very simple and cost-effective implementation of an emergency start switch.

In a further alternative embodiment, the emergency start is requested if a predefined pressure on the start key is exceeded for a predefined time.

Thus, the triggering of the emergency start can be made even more reliable.

In a further alternative embodiment, the emergency start is requested by not only the actuation of the start button and an accelerator pedal of the motor vehicle in the attack or in a "kickdown" area is actuated.

In this embodiment, a secure detection of an emergency start is ensured. The likelihood of confusion with standard situations in normal driving decreases.

According to another embodiment, the emergency start request is canceled by terminating the operation of the start key.

In this embodiment, the emergency start is requested by operating the start key. Subsequently, the motor vehicle is started in an emergency operation mode, i. electrical energy is provided to the electric machine. The emergency operating mode of the motor vehicle is maintained as long as the start button is kept pressed. As soon as the actuation of the start button is ended, the provision of electrical energy and thus the emergency mode is also terminated. This allows a very simple handling or operation of the emergency operation by the driver of the vehicle.

In a further embodiment, the emergency start is requested by an activation of the emergency start in a driver information system of the motor vehicle.

In this embodiment, for example, a warning may be issued in the driver information system when the driver tries to start the vehicle in a state where, for example, sufficient charge capacity is no longer present in the traction battery. The driver can decide (for example in an emergency situation) by means of a dialog-based query to start the vehicle nevertheless, even if this may cause damage to vehicle components. Due to the dialog-based query in the driver information system, no separate controls are needed for triggering the emergency start. Since the emergency start is explicitly requested via a button in the driver information system, there is no likelihood of confusion with other standard situations. This can ensure that the motor vehicle is started only on explicit request of the driver in an emergency operating mode.

In a further embodiment, the emergency start request is withdrawn if the emergency start is deactivated in the driver information system.

The explicit entry in a dialog of the driver information system to end the emergency start, a clear control of emergency operation is possible.

In a further embodiment, the activation and / or deactivation of the emergency start is supported by additional warnings in the driver information system which, for example, the driver. inform you that an emergency start will be triggered in a few seconds. This measure leads to a safe handling of the emergency start. Operating errors could, for example, be withdrawn again after the warning has appeared.

According to a further embodiment, after requesting the emergency start, a plausibility check of the emergency start request is carried out, the motor vehicle being started as a function of the plausibility check.

With the aid of the plausibility check, the control of the emergency operation can be made more reliable. This is particularly important because at a start of the vehicle in an emergency vehicle components can be destroyed. In the case of the plausibility check, for example, the information can be used as to whether the brake pedal is actuated or in which position a gear selection lever of the motor vehicle is located. Accordingly, a start of the motor vehicle in the emergency operating mode is prevented if the emergency start request does not seem plausible (for example, pressing the start button while pressing the brake pedal).

In another embodiment, the electrical energy is provided by a traction battery of the motor vehicle, wherein operating restrictions that are defined for the traction battery in the normal operation of the motor vehicle are canceled.

In normal operation, it is necessary to limit the discharge of the traction battery, so that always a residual charge amount of 20% to 30% of the nominal battery capacity is maintained. Below this limit, the proportion of harmful chemical side reactions increases, which leads to a shortening of the life of the traction battery. In emergency situations, component protection only has a minor significance. In these, the motor vehicle must be operable without regard to possible damage in an emergency operating mode in order to minimize risks to the vehicle occupants. Thus, when the emergency mode is activated, the normal mode limits are overridden and the traction battery is depleted of the required energy regardless of the SOC (state of charge) or SOH (state of health) to generate an emergency torque using the powertrain.

In a further embodiment, the electrical energy is provided by a low-voltage battery of the motor vehicle.

For example, in situations where the traction battery is completely discharged due to a fault, alternatively or in addition to the traction battery, the low voltage battery (eg, the "12V car battery") may be used as a redundant power source for the emergency mode of operation. This assists a reliable starting of the motor vehicle in an emergency situation.

According to a further embodiment, the electrical energy is provided such that the drive torque is increased until the predefined vehicle speed is reached.

This type of cruise control ensures that the motor vehicle can also move on a steep slope. The motor vehicle can thus be moved reliably out of a danger zone.

In a further embodiment, the electrical energy is provided in such a way that an electric current which supplies the electric machine with the electrical energy does not exceed a predefined threshold value.

By limiting the battery current can be avoided that, for example, with a stuck vehicle and high starting current a fire hazard caused by the overheating of the traction battery.

According to a further embodiment, the emergency operating mode and the provision of electrical energy is terminated if a brake pedal of the motor vehicle is actuated.

Due to the possibility of being able to stop the motor vehicle at any time by an actuation of the brake pedal, the safety of the motor vehicle is increased. In addition, the operation of the brake pedal is a simple and intuitive solution for the termination of emergency operation.

According to a further aspect of the invention, the device according to the invention further comprises an electrical power supply unit, which is designed to supply the control unit with electrical energy.

The control unit for emergency operation is decoupled by the independent power supply from the rest of the electrical system of the motor vehicle. Thus, an emergency start activation can also take place if, for example, a low-voltage battery of the motor vehicle has failed. This increases the robustness and safety of the emergency operating system.

According to a further embodiment, the device according to the invention further comprises a low-voltage battery and a DC-DC converter, which is adapted to one of the low-voltage battery available Asked provide electrical energy for the operation of the electrical machine.

The low-voltage battery additionally protects the power supply of the drive train in an emergency situation, even if the traction battery is completely discharged or electrically disconnected, for example. The DC-DC converter ensures that the voltage of the low-voltage battery is transformed to a high-voltage level of the drive train.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the invention.

Brief description of the drawings

1 shows in schematic form an inventive device for controlling an electric machine of an electric drive train, which is adapted to drive a motor vehicle; and

2 shows a flowchart for illustrating an embodiment of a method according to the invention for controlling an electric machine of an electric drive train.

Embodiments of the invention

1 shows a device 10 for controlling an electric machine 12 , which is adapted to drive a vehicle not shown in detail with a purely electric drive train. For example, this category of vehicles includes pure electric vehicles, serial range extender vehicles and fuel cell vehicles. The device according to the invention 10 is used to move the vehicle a short distance in emergency situations, even if the drive system is no longer functional in a normal operating mode. As a result, the vehicle can, for example, be moved out of a danger zone.

The device 10 has a controller 14 , a traction battery 16 , a low-voltage battery 18 and a DC-DC converter 20 on. With the help of the traction battery 16 and the low voltage battery 18 can electrical energy for the operation of the electric machine 12 to be provided. Furthermore, the device 10 a power electronics 22 on, over which the electric machine 12 is controlled. Finally, the device points 10 an electrical power unit 24 on, which is a standalone power supply to the controller 14 guaranteed. As an electrical power supply unit 24 For example, a 9 V battery can be used. This decouples the control unit 14 from the rest of the electrical system of the vehicle. This is the control unit 14 ready for use, even if the low-voltage battery 18 that the control unit 14 usually supplied with electrical energy has failed. This is particularly important because the control unit 14 assumes the control of an emergency operation of the vehicle in an emergency situation.

If the vehicle has been left lying on a railroad crossing, for example, the driver of the vehicle will request an emergency start in order to move the vehicle out of this danger zone. The request for the emergency start is preferably carried out by an actuation of a start button of the motor vehicle over a predefined period of time.

Alternatively or additionally, the pressure with which the start button is actuated can also be evaluated. In this embodiment, the emergency start request is detected when the start key is pressed with at least one predefined pressure over the predefined time period. In a further alternative embodiment, the activation of the emergency start takes place via a dialog-based query in a driver information system of the vehicle.

Upon detection of the emergency start request, an emergency start request is made 26 to the control unit 14 forwarded. To set up an emergency operation of the motor vehicle, the control unit 14 at the power electronics 22 or on the electric machine 12 a target torque 28 one. In addition, the controller gives 14 for the traction battery 16 or the low-voltage battery 18 an electrical nominal power 30 before, for the provision of the target torque 28 on the electric machine 12 is needed. In the emergency mode is by the control unit 14 first checked if the traction battery 16 is able to power the vehicle. For the realization of the emergency operation it is sufficient to drive the vehicle for a short period of time (for example <60 s) at walking speed. But only a very low drive power and a small amount of energy is needed.

For a component-saving operation (normal operation) of the traction battery 16 It is necessary to limit the discharge of energy, so that always a residual charge amount of 20% to 30% of the nominal battery capacity is maintained.

Below this limit, the proportion of harmful chemical side reactions increases, which leads to a shortening of the service life. If no consideration is given to component protection (emergency situation), this residual energy can be used for emergency operation. The associated performance is sufficient to power the vehicle in an emergency situation for a short period of time.

The same applies at very low or very high ambient / battery temperatures. For example, in emergency mode, threshold values that are a temperature range for the traction battery 16 in normal operation, override. Thus, the traction battery 16 put into operation without consideration of the battery temperature.

In summary, when the emergency mode is activated, the restrictions on normal operation and the traction battery are removed 16 a required electrical power 32 regardless of SOC (State of Charge) or SOH (State of Health) taken to by means of the electric machine 12 the target torque 28 to create.

In situations where the traction battery 16 due to a fault is completely discharged, or the electrical connection between the electric machine 12 and the traction battery 16 is interrupted, alternatively or additionally, the low-voltage battery 18 be used as a redundant energy source. As a low voltage battery 18 For example, the well-known 12 V car battery can be used. This is dimensioned so that it is able to drive the starter motor of conventional vehicles even in adverse environmental conditions. This means that the energy of the low-voltage battery 18 in principle sufficient for an emergency operation comparable to conventional vehicles. In normal operation, the low-voltage battery 18 through the electric machine 12 charged. For this feeds the DC-DC converter 20 Energy from a high-voltage network, with the electric machine 12 is coupled to a low-voltage grid that uses the low-voltage battery 18 is coupled. For the emergency mode, the DC-DC converter must 20 be designed so that it can be operated in an emergency at least briefly in the opposite direction. This turns the low voltage of the low voltage battery 18 transformed to a high voltage level and the electrical power 32 provided in the high-voltage network. Thus, the emergency mode requires a bidirectional implementation of the DC-DC converter 20 to the energy of the low-voltage battery 18 to be able to feed into the high-voltage network.

The electric power 32 is provided such that the electric machine 12 the predefined setpoint torque 28 generated. Alternatively, the electrical power 32 also be provided so that the vehicle is accelerated to a predefined vehicle speed. It is sufficient to limit the predefined vehicle speed to, for example, a walking speed. Optionally, alternatively or additionally, the drive torque of the electric machine 12 continuously increased until a specified minimum speed is reached. This type of cruise control ensures that the vehicle can move on a steep slope in an emergency situation. Advantageously, the battery current is limited, so that is excluded that, for example, in a stuck vehicle and high starting current a fire hazard due to overheating of the traction battery 16 or the low-voltage battery 18 arises.

The target torque 28 is only requested as long as the driver has the emergency start request 26 (for example, by permanently pressing the start button) maintains. When the start button is released, the emergency start ends immediately. In addition, the driver can always stop the vehicle at a faulty detection or release of the emergency operation by pressing the brake. Of particular preference is when the control unit 14 alone controls the components needed for emergency operation. Thus, the emergency operation can be activated, even if other control units, sensors or other components have failed.

2 shows a flowchart for explaining an embodiment of a method according to the invention 40 , The procedure 40 serves to control the electric machine 12 the electric drive train, which is adapted to drive the motor vehicle.

In a first step 42 the start button of the motor vehicle is briefly operated by the driver to start the vehicle.

In a further step 44 a check is made as to whether the operating parameters of the drive train are moving in a value range predefined for the normal operation of the motor vehicle. If this is not the case (for example, is the remaining charge of the traction battery 16 less than 20% to 30% of the nominal battery capacity), the drive system does not report a start release, since a component-sparing normal operation with sufficient drive power is not possible.

If the driver of the vehicle is in an emergency situation, the vehicle must be moved in an emergency operation, regardless of possible damage. The driver sends in one step 46 the emergency start request 26 to the drive system of the motor vehicle. This is done, for example, by pressing the start button over a predefined period. Using standard operating components simplifies the activation of the emergency start. This is particularly important in panic situations, because, for example, a special switch for the emergency start would not or found too late. Alternatively, the activation of the emergency start can also be done by a dialog-based query in the driver information system of the motor vehicle. As soon as the emergency start request 26 is detected, in addition, a warning in the driver information system can be issued, which informs the driver that an emergency start is triggered in a few seconds. This can be avoided any possible malfunctions and component damage caused by the motor vehicle. After detection of the emergency start request 26 In addition, a plausibility check can be carried out. This can, for example, check whether currently the brake pedal is pressed.

If the plausibility check is successful, the vehicle will be in one step 48 started in an emergency operation. In addition, electrical energy is provided for the drive train, so that a predefined drive torque is set and / or the motor vehicle is accelerated to a predefined vehicle speed. The generation of the drive torque can be done without consideration of the drive level selection. This would allow the driver to initiate emergency operation by a single action without additional step selection. This is in electric vehicles, which often have no mechanical clutch in the drive train, easy to implement. The parking brake can also be released automatically. This leads to a simple and safe handling of the emergency operation.

Once the vehicle is maneuvered out of the danger area, the driver stops in one step 50 pressing the start button. Alternatively, the driver can also operate the brake of the vehicle. This will be the emergency start request 26 withdrawn.

Subsequently, the emergency operation of the motor vehicle in one step 52 stopped and no more electrical energy provided.

With the aforementioned method, a very easy-to-use and robust emergency operating mode can be realized in a vehicle with an electric drive train. The emergency running properties are improved.

Claims (15)

Procedure ( 40 ) for controlling an electric machine ( 12 ) of an electric drive train, which is designed to drive a motor vehicle, with the steps: - detecting ( 44 ) at least one parameter of the drive train, which deviates from a value range predefined for normal operation of the motor vehicle, 46 ) an emergency start for the motor vehicle, - start ( 48 ) of the motor vehicle in an emergency operation mode, - providing ( 48 ) of electrical energy for the electrical machine ( 12 ), so that a predefined drive torque ( 28 ) is set and / or the motor vehicle is accelerated to a predefined vehicle speed, - terminate ( 52 ) of the emergency operation mode by stopping the provision of the electric power, if the emergency start request is withdrawn. Method according to claim 1, wherein the emergency start is requested ( 46 ) by actuating a start button of the motor vehicle over a predefined period of time. Method according to claim 1 or 2, wherein the emergency start is requested ( 46 ) by the start button of the motor vehicle is operated with a predefined pressure. Method according to claim 2 or 3, wherein the emergency start request is terminated by terminating ( 50 ) is canceled by pressing the start button. Method according to one of claims 1 to 4, wherein the emergency start is requested by an activation of the emergency start in a driver information system of the motor vehicle ( 46 ). Method according to claim 5, wherein the emergency start request is withdrawn if the emergency start in the driver information system is deactivated ( 50 ). Method according to one of claims 1 to 6, wherein after requesting ( 46 ) of the emergency start a plausibility check of the emergency start request is performed, and wherein the motor vehicle is started in dependence on the plausibility check ( 48 ). Method according to one of claims 1 to 7, wherein the electrical energy from a traction battery ( 16 ) of the motor vehicle ( 48 ), with operating restrictions that apply to the traction battery ( 16 ) are defined in the normal operation of the motor vehicle, be repealed. Method according to one of claims 1 to 8, wherein the electrical energy from a low-voltage battery ( 18 ) of the motor vehicle ( 48 ). Method according to one of claims 1 to 9, wherein the electrical energy is provided in such a way ( 48 ) that the drive torque is increased until the predefined vehicle speed is achieved. Method according to one of claims 1 to 10, wherein the electrical energy is provided in such a way ( 48 ) that an electrical current that the electric machine ( 12 ) supplied with the electrical energy, does not exceed a predefined threshold. Method according to one of claims 1 to 11, wherein the emergency operating mode and the provision of electrical energy is terminated ( 52 ), if a brake pedal of the motor vehicle is actuated ( 50 ). Contraption ( 10 ) for controlling an electric machine ( 12 ) of an electric drive train, which is designed to drive a motor vehicle, with a control device ( 14 ) for controlling the electric machine ( 12 ), whereby the control unit ( 14 ) is adapted to carry out the method according to any one of claims 1-12. Apparatus according to claim 13, wherein the device ( 10 ) an electrical power supply unit ( 24 ), which is adapted to the control unit ( 14 ) to provide electrical energy. Device according to claim 13 or 14, wherein the device ( 10 ) a low-voltage battery ( 18 ) and a DC-DC converter ( 20 ) adapted to receive one of the low-voltage battery ( 18 ) provided electrical energy for the operation of the electrical machine ( 12 ).

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