WO2015043882A1

WO2015043882A1 - Method for controlling a drive-off process

Info

Publication number: WO2015043882A1
Application number: PCT/EP2014/068468
Authority: WO
Inventors: Till FÖRSTER; Stefan HASSLER; Thorsten STÜTZLE
Original assignee: Siemens Aktiengesellschaft
Priority date: 2013-09-30
Filing date: 2014-09-01
Publication date: 2015-04-02
Also published as: US20160244073A1; DE102013219743A1; RU168142U1; CN105593057A; EP3024689A1

Abstract

The invention relates to a method for controlling a drive-off process of an electrically driven vehicle, the electric motor of which is fed via a converter, wherein a holding torque necessary to prevent the vehicle from rolling back is determined. By using sensors for determining carriage masses and sensors for determining route inclinations, the holding torque can be precisely determined. In order to achieve a drive-off process of the electrically driven vehicle that is gentle on the electric motor, according to the invention, as long as a determined rotational motor speed (n) is less than a specified limit rotational speed (n₁), a traction torque (M_T) is limited by a control unit of the vehicle to a limit torque (M_G) dependent on the holding torque (M_F), and the traction torque (M_T) is increased beyond the limit torque (M_G) by the control unit only once the rotational motor speed (n) is greater than the limit rotational speed (n₁).

Description

description

The invention relates to a method for controlling a starting operation of an electrically driven vehicle, in which a holding torque necessary for preventing the vehicle from rolling back is determined. Electric motors, especially three-phase motors, electrically driven vehicles, are often powered by a converter. The inverter generates an output voltage from an input voltage, which is output in the form of pulses with adjustable pulse duration and / or adjustable pulse height to an electric motor of the vehicle. Preferably, this is

Output voltage is a three-phase system with variable frequency and voltage amplitude.

The motor speed of a three-phase motor is dependent - depending on the frequency and voltage of the power supply - given the load characteristic. The engine speed increases in particular with increasing frequency of the output voltage. Therefore, the engine speed can be controlled by regulating the frequency and voltage of the output voltage generated by the inverter.

It is an object of the present invention to provide a method with which a machine-friendly starting operation of an electrically driven vehicle is made possible.

This object is achieved by a method of the type mentioned above, according to the invention, as long as a determined engine speed is less than a predetermined first limit speed, a traction torque is limited by a control unit of the vehicle to a dependent of the holding torque torque limit and the traction torque of the Control unit is increased beyond the limit torque only when the engine speed is greater than the first limit speed. The invention is based on the consideration that during a starting process of the vehicle a strong thermal load of the converter, in particular of a semiconductor component of the converter, can occur, which can shorten a service life of the converter.

Furthermore, the invention is based on the consideration that at low frequencies the output voltage generated by the converter and thus also at low engine speeds, as they occur during a starting process of a vehicle, a conducting phase of a semiconductor component of the converter is relatively long. Consequently, the semiconductor device can heat up in a conductive phase for a relatively long time and reach a high temperature when the engine speed is low. A maximum reached during a conducting phase of the semiconductor device temperature of the semiconductor device may be set from that at the respective engine speed

Depend on traction moment. With increasing traction torque, said temperature can increase.

At a higher frequency of the output voltage generated by the inverter and thus also at a higher engine speed, a conductive phase of the semiconductor device is shorter, which is why the semiconductor device heats up shorter in a conducting phase. As a result, it is possible that a maximum temperature of the semiconductor component reached during a conducting phase of the semiconductor component assumes a lower value at a higher engine speed, even in the case of a higher set traction torque, than at a low engine speed.

The traction torque can be understood to be that part of the drive torque generated by one or more electric motors of a vehicle, which acts in total on wheels of the vehicle and can contribute to a transmission of tractive force to a track surface. The vehicle may include a single car, among others. But it can also include several mutually coupled cars. At least one vehicle of the vehicle has an electric drive, wherein the electric drive comprises at least one electric motor, which is fed via an inverter.

The vehicle may be e.g. to act a rail vehicle or a motor vehicle. If the vehicle is a motor vehicle, the vehicle may e.g. an electrically powered truck or passenger car and one or more attached to the truck or passenger cars without own drive include. If the vehicle is a rail vehicle, the vehicle may include one or more powered cars and one or more cars without their own drive.

The vehicle is equipped with an electric drive having one or more electric motors. These are powered by one or more inverters, each one

Electric motor can be powered by a converter or fed by a converter several electric motors.

A holding torque can be the minimum traction torque to be applied by the electric motor in order to prevent the vehicle from rolling back, for example at a section gradient. Rolling back can generally be considered as rolling against a direction of travel established by a driver or automatic control. The start of a starting process can be defined as the point in time at which, after stopping the vehicle, the traction torque is increased or a braking torque is reduced - whichever comes first. A braking torque may be a torque generated by one or more brake systems, which acts in total on wheels or wheel axles of the vehicle. The braking torque may, for example, have the purpose of the vehicle, in particular on a route gradient or a line gradient, to keep at a standstill. A brake system may comprise one or more brakes, in particular one brake per wheel or wheel axle of the vehicle. In particular, if the vehicle is a rail vehicle, the vehicle may have additional brakes, which may develop braking forces directly between the vehicle and the track surface. When using these additional brakes, the braking torque may be a sum of a torque generated by the further brakes and the torque generated by the brake systems, which acts on the wheels or wheel axles of the vehicle.

Before starting the starting process, the traction torque is expediently zero so that unnecessary heating of the electric motor and / or the converter can be avoided. In addition, the braking torque before starting the start-up is usefully at least as large as the holding torque, so that a rolling back of the vehicle is prevented. A control unit can be understood as a device which is prepared for controlling the traction torque. The control unit can in particular be an automatic

Traction control include. Furthermore, the control unit can be prepared for controlling one or more brake systems, in particular for applying and / or releasing one or more brakes.

A limit torque may be a value of the traction torque to which the traction torque is limited by the control unit, the value u.a. may be dependent on the determined holding torque. Appropriately, the limit torque is above the holding torque, so that the vehicle can be accelerated from a standstill in the direction of travel, in particular without rolling back.

Advantageously, an engine speed is determined repeatedly, in particular at fixed time intervals. To determine the engine speed, for example, an engine speed sensor will be used. A speed of the vehicle may be proportional to the engine speed, in this regard, additionally or alternatively, the speed may be measured, wherein a speed measurement is hereinafter understood for the sake of simplicity as determining the engine speed.

A limit speed may be a design-related speed value. The limit speed may depend in particular on a type of inverter. Furthermore, the limit speed may depend on the limit torque. The limit speed can in particular be greater, the greater the limit torque.

The higher a temperature of the semiconductor component achieved during a starting phase during a conducting phase of a semiconductor component of the converter, the lower the lifetime of the semiconductor component can be. Advantageously, the traction torque is therefore controlled by the control unit such that a maximum temperature of the semiconductor component achieved during a conducting phase of a semiconductor component of the converter remains below a predetermined temperature value.

This process feature can be e.g. realize that a calculated in dependence on several parameters temperature of the semiconductor device is stored in the form of a particular multi-dimensional table in the control unit. For each of the parameters on which the calculated temperature depends, a set of possible parameter values may be present in the table.

The calculated temperature can be dependent on: the holding torque, the traction torque, the braking torque, the engine speed and / or the type of converter parameters that depend on the model. At fixed time intervals, the calculated temperature of the semiconductor component can be taken with the aid of the known and / or determined parameter values of the table. The calculated temperature can be calculated with the specified temperature value to be compared. Subsequently, the limit torque can be increased or decreased by the control unit.

The temperature of the semiconductor component may, for example, relate to a temperature at a contact surface with a bonding wire. The bonding wire can be prepared to connect the semiconductor component in an electrically conductive manner to one or more components, in particular to terminals of a chip housing which can surround the semiconductor component. Preferably, the bonding wire is soldered or welded to the semiconductor device.

The semiconductor device and the bonding wire may have different materials. The bonding wire may e.g. consist essentially of aluminum. The semiconductor component preferably consists essentially of silicon.

Different, in particular material-dependent coefficients of thermal expansion of the bonding wire and of the semiconductor component can, after a certain number of switching cycles of the semiconductor component, lead to a crack on the contact surface of the bonding wire and thereby to a failure of the converter. The number of switching cycles after which the converter may fail may depend on: a material of the bonding wire, a material of the semiconductor component, a geometry of the bonding wire, a geometry of the semiconductor component and / or operating parameters of the converter. The semiconductor component can in particular

Be bipolar transistor with insulated gate (insulated gate bipolar transistor).

In an advantageous embodiment of the invention, the limit torque is below the maximum of 1.3 times the

Arresting torque and 0.3 times the maximum adjustable by the control unit traction value. At these values It is also possible to achieve converter-friendly start-up, even with a steep grade gradient or when starting off on the mountain.

Furthermore, the limit torque is preferably above the maximum of 1.2 times the holding torque and 0.2 times the maximum adjustable by the control unit

Traction value. This ensures that the limit torque is not too low and, in spite of the converter protection, a quick start-up is possible.

The fact that the limit torque is determined by means of a maximum function, it can be achieved that the limit torque is set at small values of the holding torque of the control unit to a fixed predetermined value. Furthermore, it can be achieved that the limit torque at high values of

Arresting torque of the control unit is set to a dependent of the holding torque, in particular above the holding torque value. In this way, an advantageous compromise between a converter protection and a speedy start can be achieved.

In a variant of the invention, a torque band having a maximum value and a minimum value of the traction torque may be stored in the control unit. Preferably, the traction torque is adjustable only within this torque band, as long as the determined engine speed is less than the predetermined first limit speed. In this way it can be avoided that the traction torque is set by an external intervention to a destructor value. The traction torque may be e.g. be adjustable by the driver or by an external control unit.

The maximum value of the torque band can in particular be the maximum of 1.3 times the holding torque and 0.3 times the maximum that can be set by the control unit

Traction value. The minimum value of the torque band can in particular be the maximum of 1.2 times the hold-down torque. ment and 0.2 times the maximum traction value that can be set by the control unit.

If such a torque band is stored in the control unit, in the absence of an external intervention, for example by the driver or by the external control unit, the traction torque can be kept constant by the control unit at a predetermined value, as long as the determined engine speed is less than the first limit speed. The predefined value may, in particular, be the mean value of the maximum value and the minimum value.

Advantageously, the traction torque is held by the control unit above a minimum torque, preferably between the minimum torque and the limit torque, as soon as the traction torque is at least as large as the minimum torque. As a result, it can be achieved that a dwell time of the vehicle is shortened in a state with a low engine speed. It makes sense for the minimum torque to be smaller than the limit torque.

The minimum torque can be dependent on the holding torque. Preferably, the minimum torque is greater than the holding torque. As a result, despite possible inaccuracies in determining the holding torque or in spite of the influence of other influences, such as, for example, Head wind or friction, prevent the vehicle - even without a holding effect of a brake - rolls back. The minimum torque can be set by a given percentage of the

Arresting torque, for example 10%, be greater than the holding torque. However, if the determined holding torque is below a specified threshold, in particular if the holding torque is zero, the minimum torque may be a fixed value, eg 15% of the maximum traction value that can be set by the control unit. A further variant of the invention provides that the limit torque and / or the minimum torque can be adjusted by the driver, in particular in stages. Expediently, it is possible for the driver to completely remove a limitation of the traction torque, in particular in the event of an exceptional operational situation.

In a preferred embodiment of the invention, the traction torque is increased by the control unit until reaching a predetermined second limit speed as soon as the engine speed is greater than the first limit speed. As a result, a higher speed and / or acceleration of the vehicle can be achieved. At the same time, despite an increase in the traction torque, the maximum temperature reached during a conducting phase of the semiconductor device semiconductor device due to a shorter duration of the conductive phase may be lower than in the period in which the engine speed is less than the first limit speed. The traction torque is preferably increased linearly, in particular proportionally, to the engine speed as soon as the engine speed is greater than the first limit speed and as long as the engine speed is less than the second limit speed.

Preferably, the traction torque when reaching the second limit speed assumes the maximum traction value that can be set by the control unit. Preferably, the

Traction torque is kept constant on said traction value after the maximum control unit adjustable traction value is accepted by the control unit until the maximum engine power is reached.

Advantageously, the first limit speed is set by the control unit as a function of the holding torque. This makes it possible that a speed range within which the traction torque is limited for the purpose of converter protection, depending on the situation is adaptable. In particular, the First limit speed can be set by the control unit to an even greater value, the greater the holding torque. The ratio of the second limit speed to the first limit speed is preferably equal to the ratio of the maximum traction value that can be set by the control unit to the limit torque. In an advantageous variant of the invention, a gradient parameter dependent on a path inclination angle is determined. It makes sense that the path inclination angle refers to a section of the track on which the vehicle is located. In particular, the path inclination angle may be a value averaged over an entire length of the vehicle.

The slope parameter may e.g. the route inclination angle itself. Alternatively, the slope parameter may be a component of earth acceleration that is dependent on the path inclination angle and that is aligned parallel to the section. From the slope parameter can easily a component of the gravitational acceleration, as

Hangabtriebsbeschleunigung acts on the vehicle to be determined.

A positive value of the slope parameter may represent a positive path slope angle, wherein the positive path slope angle may occur at a grade slope. A negative slope parameter may represent a negative path slope angle, where the negative path slope angle may occur at a path gradient. Track gradient and line gradient are to be understood as related to the direction of travel of the vehicle. The gradient parameter can be determined, for example, with the aid of an acceleration sensor. In particular, the acceleration sensor may be an element of an inertial measurement unit which, in addition to the acceleration sensor, has at least one further acceleration sensor and / or at least one rotation rate sensor. In order to achieve, for example, a higher accuracy in the determination of the gradient parameter, the gradient parameter can be determined with the aid of a plurality of acceleration sensors. In addition, at least one rotation rate sensor can be used in the determination of the gradient parameter.

Furthermore, it is advantageous if a mass of the vehicle is determined. If the vehicle has air suspension, the mass may be e.g. be determined from a measurement of air pressure. Does the vehicle with a suspension system with

Coil springs, so the mass can be determined for example from measurements of axial lengths of the coil springs.

Conveniently, the retention torque is calculated from the mass of the vehicle and from the slope parameter. Advantageously, the control unit is prepared to calculate the holding torque from the mass and the pitch parameter.

Advantageously, a car pitch parameter is determined for each car of the vehicle. As a result, it can be taken into account that the carriages can stand on sections with different line inclination angles. In order to be able to determine the respective carriage pitch parameter, each of the carriages can be equipped with at least one own acceleration sensor.

Preferably, one car mass is determined for each car of the vehicle. From the car masses a total mass of the vehicle can be calculated. Zeckmäßigerweise the control unit is prepared to calculate the total mass of the vehicle.

Preferably, the respective car mass as well as the respective car pitch parameter for each car of the vehicle calculates a carriage holding torque. The holding torque of the vehicle is expediently calculated by summing up all determined carriage holding moments.

In an advantageous embodiment variant, a substitute value calculation is present in the control unit which, if one or more individual values fail, resort to substitute values and / or substitute algorithms. For example, in the event of unavailability of a carriage pitch parameter, e.g. Because of a failure of an acceleration sensor, a car pitch parameter may be extrapolated or interpolated from one or more other car pitch parameters. If one car is positioned both in front of and behind the car whose car grading parameter is not available, then the missing carriage pitch parameter can be set equal to the mean value of the car pitch parameters of these two carriages. If the wagon whose wagon pitch parameter is not available is adjacent to only one wagon, the missing wagon pitch parameter may be set equal to the wagon pitch parameter of the adjacent wagon.

Furthermore, it is advantageous if the substitute value calculation in the case of the failure of one or more individual values during the determination of the carriage masses relies on replacement values and / or replacement algorithms. Thus, e.g. If the carriage mass of a wagon is unavailable, a maximum mass, in particular a maximum permissible maximum mass, of the wagon may be used as the wagon mass.

The respective car-holding torque may, inter alia, be greater than zero, if a component of a weight force of the respective carriage counteracts the direction of travel of the vehicle, that is, for example, when the car - based on the direction of travel - is at a route gradient. The respective car holding torque may be, inter alia, less than zero, if a component of the weight of the respective car in driving direction of the vehicle acts, so for example if the car - based on the direction of travel - is located at a distance gradient. A summation of all determined car-holding torque for calculating the holding torque of the vehicle is carried out usefully taking into account a sign of the respective car-holding torque. If the determined holding torque is less than zero, it is expediently set to zero by the control unit.

Advantageously, the gradient parameter or the carriage gradient parameters are determined repeatedly, in particular at fixed time intervals. It makes sense to calculate the holding torque of the vehicle from the last ascertained gradient parameter or from the last calculated car gradient parameters. As a result, changes in the gradient parameter or the carriage gradient parameters which occur during the startup process can be taken into account and the current retention torque can always be calculated.

Appropriately, a brake is released from the control unit for starting. The braking torque then drops from a starting braking torque to zero. A further advantageous embodiment of the invention provides that the slope of the traction torque takes place as a function of a decreasing braking torque. The control unit thus controls the increase of the traction torque as a function of the braking torque, whose time course can be stored in the control unit, for example by the time course of a release command is deposited in dependence on an initial braking torque. By such a synchronization heating of the inverter can be kept low.

Conveniently, the traction torque increases at least over a temporal portion to the extent to which the braking torque decreases. The temporal section comprises at least at least half the time it takes to completely release the brake.

It is advantageous if the brake is released by the control unit before the traction torque is increased by the control unit, in particular beginning at zero. As a result, an unnecessarily long holding action of the brake can be avoided.

The holding action of the brake is e.g. at the latest from the time point at which the traction torque is as large as the limit torque, because it is possible that the holding effect of the brake from this time only hinders the start, but is no longer needed to prevent the rolling back of the vehicle.

It is advantageous if the traction torque is controlled by the control unit such that the traction torque first reaches the limit torque when the braking torque reaches zero. This makes it possible to avoid that the braking torque counteracts the traction torque and thus hinders starting when the traction torque reaches the limit torque.

In a preferred embodiment of the invention, the traction torque is increased by the control unit such that the sum of traction torque and braking torque remains constant, in particular above the holding torque. It makes sense that the sum of traction torque and braking torque remains constant only from the time when the traction torque is increased.

Further, the traction torque can be increased by the control unit such that the sum of traction torque and braking torque remains constant and at least as large as the limit torque, in particular equal to the limit torque.

The sum of traction torque and braking torque may relate in particular to the amount of a vector sum, since the Traction torque and the braking torque during the starting process can act in different directions.

Furthermore, it is advantageous if the traction torque, in particular starting from zero, is increased as soon as the braking torque falls below the limit torque. This makes it possible that despite a drop in the braking torque, the sum of traction torque and braking torque remains at least as large as the limit torque.

In an advantageous embodiment of the invention, a first time at which the braking torque is dropped to zero, is calculated in advance. From the first point in time, a temporally preceding second point in time can be calculated. In a preferred manner, the moment of traction, which increases at the second time, in particular starting from zero, at the maximum permissible rate, reaches the limit torque for the first time. In this way, a period of counteracting traction torque and braking torque can be reduced.

The maximum allowed rate at which the traction torque is increased may be less than a technically maximum rate at which the traction torque can be increased. The maximum allowed rate may be a rate limited for reasons of passenger comfort, in particular with regard to avoiding sudden jerking movements, and / or for the purpose of sparing a drive train of the vehicle.

If the engine speed was already greater than the first limit speed and the engine speed has fallen below the first limit speed, for example due to braking, then it is advantageous if the traction torque is limited by the control unit to the limit torque as long as the engine speed is less than the first limit speed. In particular, when the engine speed falls below the first limit speed, the traction torque from the control unit may be maintained at the limit torque as long as the engine speed is less than the first limit speed. It is also advantageous when the traction torque is increased by the control unit beyond the limit torque as soon as the engine speed is again greater than the first limit speed. In a further advantageous variant of the invention, the traction torque is a negative traction torque, which is preferably used for electric braking of the vehicle. With respect to the previously described advantageous developments of the invention, an amount of the negative traction torque is decisive for controlling the traction torque by the control unit. As a result, a converter-friendly electrical braking can be achieved.

It is expedient if the control of the traction torque by the control unit during electric braking can be deactivated by the driver or is automatically deactivated in emergency braking, so that a rapid deceleration of the vehicle, in particular to its standstill, is possible.

The invention also relates to a control system for an electrically driven vehicle having at least one electric motor, a converter for supplying the electric motor and a control unit for controlling the converter, which is prepared to determine a holding torque necessary for preventing the vehicle from rolling back.

An inverter-sparing control system is inventively achieved in that the control unit is prepared to control the inverter so that, as long as a determined engine speed is less than a predetermined first limit speed, a traction of the vehicle is limited to a dependent of the holding torque limit torque and the traction torque is only increased beyond the limit torque when the engine speed is greater than the first limit speed. The description of advantageous embodiments of the invention given hitherto contains numerous features which are reproduced in some detail in the individual subclaims. However, these features may conveniently be considered individually and summarized to meaningful further combinations. In particular, these features can be combined individually and in any suitable combination with the method according to the invention and the device according to the invention.

The above-described characteristics, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of the embodiments, which will be explained in more detail in connection with the drawings. The embodiments serve to illustrate the invention and do not limit the invention to the combination of features specified therein, not even with respect to functional features. In addition, suitable features of each embodiment may also be explicitly considered isolated, removed from one embodiment, incorporated into another embodiment to complement it, and / or combined with any of the claims.

Show it:

1 shows an electrically driven vehicle with three cars on three different sections with different track inclination angles,

2 shows exemplary time courses of a

Traktionsmoments and a braking torque for a starting process in which a holding torque is zero,

3 shows exemplary temporal courses of the

Traktionsmoments and the braking torque for a Start-up process, in which the holding torque is greater than zero,

4 shows an exemplary course of the traction torque as a function of a motor rotational speed for the starting process from FIG. 2,

5 shows an exemplary course of the traction torque as a function of the engine speed for the starting process from FIG. 3,

6 shows an exemplary time profile of a temperature of a bipolar transistor of an inverter and

7 shows a further exemplary time profile of the temperature of the bipolar transistor at a higher engine speed.

1 shows a schematic representation of an electrically driven vehicle 2 with three cars 4. The vehicle 2 is a rail vehicle. Seen from the viewer right car 4 is designed as a driven car 4 and the other two cars 4 are executed without own drive.

The vehicle 2 has two electric motors 6, designed as three-phase motors, which are fed by a converter 8. The converter 8 comprises a bipolar transistor with insulated gate electrode (not shown in FIG. 1).

The vehicle 2 also has a control system 9, which comprises a control unit 10, which is used to control a

Traktionsmoments the vehicle 2 is prepared. In particular, the control unit 10 is prepared by controlling the inverter 8 to control the traction torque. Furthermore, for each of its electric motors 6, the vehicle 2 has an engine speed sensor 12 which is used to measure an engine rotational speed. number of the respective electric motor 6 is prepared.

The three cars 4 of the vehicle 2 are each equipped with an air suspension system, not shown in FIG 1. In addition, each of the car 4 has two brake systems 13, which are controllable by the control unit 10. Each of the brake systems 13 includes two brakes, which are not shown in FIG 1 for the sake of clarity. Each of the three carriages 4 has an acceleration sensor 14, which is prepared for measuring an acceleration of the carriage 4 aligned parallel to a track section 16. The acceleration sensors 14 are connected to the control unit 10 via a data line system (not shown in FIG. 1) and prepared for transmission of the ascertained accelerations to the control unit 10.

The three cars 4 of the vehicle 2 are each with a

Pressure sensor 20 is provided, which is prepared for measuring a prevailing in the air suspension system of the respective carriage 4 pressure. The pressure sensors 20 are connected via the data line system to the control unit 10 and prepared for transmission of the determined pressure to the control unit 10.

Based on the direction of travel 22, the driven carriage 4 is located on a section 16 which is a gradient

- And thus a negative path inclination angle 24 - has. The front of the two cars 4 without its own drive is located on a flat stretch 16. The rear of the two of the two cars 4 without its own drive is located on a section 16 which has a slope

- And thus a positive path inclination angle 24 - has. The path inclination angle 24 of the section 16 with the slope is greater in magnitude than the path inclination angle 24 of the section 16 with the slope. In FIG. 1, changes in the path inclination angle 24 between the respective track sections 16 are abrupt and the track inclination angles 24 are greater in the gradient or gradient than they may actually be in the case of adhesive railways, which merely serves to illustrate.

Of the acceleration sensors 14 of the three carriages 4, a respective acceleration of the respective carriage 4, which is dependent on the path inclination angle 24, is determined at fixed time intervals, which is aligned parallel to the track section 16 on which the carriage 4 is located. Acceleration is a component of gravitational acceleration that acts as downhill acceleration. The ascertained accelerations are then transmitted to the control unit 10. In the same time intervals, the engine speeds of the electric motors 6 are determined by means of the two engine speed sensors 12.

From the pressure sensors 20 of the three carriages 4, the pressure prevailing in the air-damping system of the respective carriage 4 is determined and transmitted to the control unit 10. The control unit 10 calculates a mass of the respective carriage 4 from the transmitted pressures. Furthermore, the control unit 10 calculates the total mass of the vehicle 2 from the individual carriage masses.

From the three calculated car masses as well as from the transmitted accelerations of the three cars 4 is calculated by the control unit 10 for each car 4 a car-holding torque and calculated by adding up all calculated car-holding torques taking into account their respective signs, a holding torque that prevents a Rolling back of the vehicle 2 is necessary. To start the vehicle 2, the control unit 10 controls the brake systems 13 such that the brakes of the brake systems 13 are released. Consequently, the brake torque generated by the brake systems 13 to wheels 26 of the vehicle 2 of Starting from an initial value that is greater than the determined holding torque, reduced to zero. In addition, the control unit 10 controls the inverter 8 such that, during the deceleration of the braking torque, the traction torque acting on the wheels 26 of the vehicle 2 is increased starting from zero.

2 shows a diagram in which schematically exemplary time profiles of a traction torque M _T and a braking torque M _B during a starting process of the rail vehicle described in FIG 1 are shown.

The diagram comprises an ordinate axis and an abscissa axis. On the ordinate axis a moment M is plotted. A time t is plotted on the abscissa axis.

Furthermore, the diagram relates to a starting process in which the rail vehicle-in contrast to FIG. 1-is located on a flat stretch of road, so that a determined holding torque M _F is zero.

The retention torque is zero over the entire time period shown, since in Adhäsions railways changes in a track inclination angle - based on typical car lengths of rail vehicles - done on large length scales, the rail vehicle in the period shown, however, only covers a distance of a few car lengths.

First, the traction torque M _{T is} zero and a generated by the braking systems 13 of the rail vehicle braking torque M _B is constant at an initial value which is greater than zero.

The starting process begins at time t ₀ , at which the control unit 10 controls the brake systems 13 of the vehicle 2 in such a way that the brake systems 13 release their brakes. From time t ₀ , the braking torque M _B decreases starting from the starting value. In Figure 2, the braking torque M _{B takes} the simplicity half at a constant rate. In fact, the rate at which the braking torque M _B drops, but may be temporally fluctuating. The control unit 10 predicts a first time t ₂ at which the braking torque M _{B will have} fallen to zero. Starting from the first time t ₂ , a second time ti is calculated. This second time ti is characterized by the fact that the maximum permitted rate increased traction torque M _T at the first time t _{2 reaches} a limit torque M _G , provided that the traction torque M _{T is} increased starting at zero at time ti.

From the time ti, the traction torque M _{T is increased} by the control unit 10 starting at zero. As predicted, the braking torque M _B drops to zero at time t ₂ and the traction torque M _T reaches the limit torque M _G at time t ₂ . As soon as the traction torque M _{T is} greater than the braking torque M _B and, in addition, frictional resistances in bearings of the vehicle 2 have been overcome, ie between the time t ₁ and the time t ₂ , the rail vehicle begins to travel in the direction of travel and assumes an engine speed of the two electric motors 6 starting at zero too. The limit torque M _G is set by the control unit 10 such that during a conducting phase of the

Bipolar transistor of the inverter 8 maximum reached temperature of the bipolar transistor remains below a predetermined temperature value. In the present case, the limit torque M _{G is} equal to 0.25 times the maximum traction value M _en d which can be set by the control unit 10.

Until the time t ₂ , the traction torque M _{T is increased} at a mean rate equal to a maximum allowed rate, this maximum allowed rate being less than a technically maximum possible rate at which the

Traction torque M _T can increase. Rather, the maximum allowed rate is one for reasons of passenger comfort, in particular dere in order to avoid sudden jerking, as well as to protect a drive train of the vehicle 2 limited rate. The average rate at which the traction torque M _{T is} increased is greater in magnitude than the rate at which the

Braking torque M _B drops.

At the beginning of the increase of the traction torque M _T at the time ti occurs a small, practically instantaneous jump of the traction torque M _T , whose height is about 5% of the maximum adjustable by the control unit 10 traction value M _end and the faster increase of the traction M _T serves. In a jump of the traction torque M _T in such a small amount, there is no noticeable jerking movements due to damping by a suspension system of the vehicle 2, nor is there any noticeable wear on the drive train of the vehicle 2. When a minimum torque M _m i _n is exceeded,

Traction torque M _T for the rest of the starting process of the control unit 10 over the minimum torque M _m i _n held, the minimum torque M _m i _n in the present case is equal to 0.15 times the maximum of the control unit 10 adjustable traction value M _en d ,

From the time t ₂ at which the traction torque M _{T is} as large as the limit torque M _G , the traction torque M _{T is kept} constant by the control unit 10 at the limit torque M _G until the engine speed reaches a predetermined first limit speed.

The predetermined first limit speed is reached at time t ₃ . From this point on, the traction torque M _{T is increased} by the control unit 10, in particular proportional to

Engine speed increased until engine speed reaches preset second speed limit. The predetermined second limit speed is reached at time t ₄ . At this time, the traction torque M _{T takes} the maximum of the control unit 10 adjustable

Traction value M _end on. The ratio of the second limit speed to the first limit speed is equal to the ratio of the maximum of the control unit 10 adjustable traction value Mend to the limit torque M _G.

From the time t ₄ , the traction torque M _{T is} until the maximum motor power reached at the time t ₅ constant on the maximum of the control unit 10 adjustable

Traction M _end held.

The following descriptions of the further figures are essentially limited to the differences to the figure described immediately above.

3 shows a diagram in which further exemplary time profiles of the traction torque M _T and of the braking torque M _B are shown schematically. The diagram refers to a starting process in which the rail vehicle is at a line gradient, the determined holding torque M _F is therefore greater than zero. For the purpose of a simple comparability of FIG. 3 and FIG. 2, the scaling of the ordinate axes or of the abscissa axes is the same in both figures.

The initial value of the braking torque M _B , which is exactly as large as in FIG. 2, is above the determined holding torque M _F. In the present case, the holding torque M _{F is} approximately 0.5 times the maximum traction value M _{end which can be} set by the control unit 10. The limit torque M _G is equal to 1.25 times the holding torque M _F and the minimum torque M _min is the same 1.1 times the holding torque M _F.

The increase in the traction torque M _T does not start from the predicted time t _± , but from one time before lying time t _± ''. The average rate at which the traction torque M _{T is increased} from the time t _± 'is in this case set equal to the rate at which the braking torque M _B decreases, so that an amount of vector sum of the braking torque M _B and the traction torque M _T from the time ti '' until the time t ₂ remains approximately constant.

An analogous to FIG 2 increase of the traction torque M _T with the maximum allowable rate from the precalculated time point ti, would cause the braking torque M _B immediately before the time ti already below the limit torque M _G and possibly even below the holding torque M _F would be even before the traction M _{T is} built. As a result, rolling back of the vehicle 2 could not be reliably prevented.

The rail vehicle begins to travel in the direction of travel and the engine speed of the electric motors 6 increases as soon as a difference between the traction torque M _T and the holding torque M _{F is} greater than the braking torque M _B and, in addition, frictional resistances in bearings of the vehicle 2 are overcome. ie between the time t _± '' and the time t ₂ .

Since, in the present case, the limit moment M _{G is} greater than in FIG. 2 and also the average rate at which the

Traction torque M _{T is increased} to reach the limit torque M _G , is smaller than in FIG 2, in the present case, a period for reaching the limit torque M _G from the beginning of increasing the traction torque M _T from zero to longer than in FIG.

As can be seen from a comparison of FIG. 3 and FIG. 2, a period in which the traction torque M _{T is} on the

Limit moment M _G is held in FIG is longer than in FIG 2. This 3 because in this case the limit torque M _G is greater than in FIG 2 and thus takes place a longer boundary of the traction moment M _T, in order to conserve the inverter 8 , Furthermore, it can be seen from the comparison of FIG. 3 and FIG. 2 that a period in which an increase in the traction torque M _T proportional to the engine rotational speed takes place is shorter in FIG. 3 than in FIG. 2, which is due to the fact that the increase proportional to the engine rotational speed at a higher

Traction torque M _T starts.

4 shows a diagram in which an exemplary course of the traction torque M _T as a function of the engine speed n is shown schematically. The diagram relates to the time course of the traction torque M _T , which is shown in FIG 2, and to the starting situation, which is described in connection with FIG.

The diagram comprises an ordinate axis and an abscissa axis. On the ordinate axis a moment M is plotted. On the abscissa axis, the engine speed n is plotted. As long as the engine speed n is less than the predetermined first limit speed n _{i (} the traction torque M _T from the control unit 10 to the limit torque M _G , which is 0.25 times the maximum of the control unit 10 adjustable

Traction value M _end is set. As described in connection with FIG 2, the rail vehicle begins to drive in the direction of travel, as soon as the traction torque M _{T is} greater than the braking torque M _B and in addition frictional resistance in bearings of the vehicle 2 are overcome, ie even before the time t ₂ at which the Traction torque M _{T is} equal to the limit torque M _G. Since traction is already built up before the rail vehicle begins to travel in the direction of travel, the traction torque M _T at the engine speed zero is already at a value greater than zero, but less than the limit torque M _G. As the engine speed n increases in proportion to the speed of the vehicle 2, this decreases

Traction torque M _T until reaching the limit torque M _G at time t ₂ with increasing speed n, in particular linearly to the speed n, too. After reaching the limit torque M _G is the

Traction torque M _{T held} constant by the control unit 10 to the limit torque M _G until the engine speed n at time t _{3 reaches} the predetermined first limit speed ni. Once the engine speed n has exceeded the predetermined first limit speed ni and as long as the engine speed n is smaller than the predetermined second limit speed n ₂ , the traction torque M _{T is increased} by the control unit 10 in proportion to the engine speed n.

When the second limit speed n _{2 is reached} at the time t ₄ , the traction torque M _{T is} equal to the maximum traction value M _end that can be set by the control unit 10. As long as the maximum engine power has not yet been reached, this becomes

Traction torque M _{T held} constant on the adjustable by the control unit 10 traction value M _end . From the time t ₅ at which the maximum engine power is reached, the traction torque M _T is reduced inversely proportional to the engine speed n, while the maximum engine power is maintained.

FIG. 5 shows a diagram in which a schematically another exemplary course of the traction torque M _{T is shown} as a function of the engine speed n. The diagram relates to the time course of the traction torque M _T , which is shown in FIG 3, as well as to the starting situation, which is described in connection with FIG. For the purpose of a simple comparability of FIG. 5 and FIG. 4, the scaling of the ordinate axes or of the abscissa axes is the same in both figures.

At the engine speed zero, the traction torque M _{T is} already at a value which is greater than the holding torque M _F , but is smaller than the limit torque M _G. The limit torque M _G , to which the traction torque is set by the control unit 10, is equal to 1.25 times the determined holding torque M _F , wherein the holding torque M _{F is} about 0.5 times the maximum of the control unit 10 adjustable traction M _end . Thus, the limit torque M _G in the present case has a greater value than in FIG 4. Accordingly, the predetermined first limit speed ni, to reach which the traction M _{T is held} on the limit torque M _G , from the control unit 10 to a larger Value as set in FIG 4, to protect the inverter 8.

The predetermined second limit speed n ₂ , until reaching the traction torque M _{T is} increased in proportion to the engine speed n after exceeding the predetermined first limit speed ni, however, is set by the control unit 10 to the same value as in FIG.

The limit torque to which the traction torque is limited as long as the engine speed n is less than the predetermined first limit speed n _{i (} is the driver gradually, in particular in three adjustment stages, adjustable.

By default, the first setting level is set. A choice of the second or third setting stage is limited to the presence of an operational exceptional situation and must be enabled by the driver by pressing an unlocking lever or an unlocking switch. In the first setting, the limitation of the

Traction moments as previously described. That is, the limitation of the traction torque M _T to limit torque M _G described in connection with FIGS. 2 to 5 relates to the first setting stage. In the second setting stage, the limit torque is set in such a way that a difference between the maximum traction value M _end which can be set by the control unit 10 and the limit torque is halved compared with the corresponding difference in the first setting stage. In the third stage, however, there is no limitation of the traction torque.

If there is an exceptional operational situation, a faster starting of the rail vehicle can be achieved by the choice of the second or the third setting.

In FIG. 2, an exemplary time profile of the

Traktionsmoments M _T 'shown in the selection of the second setting stage by means of a dashed line.

In the second setting stage, the limit torque M _G 'is set to a value which is approximately 0.62 times the maximum traction value M _en d which can be set by the control unit 10. Thereby, the difference between the maximum adjustable by the control unit 10 traction value M _en d and the limit torque M _G ', compared to the difference between the maximum adjustable by the control unit 10 traction value M _en d and the limit torque MG in the first setting stage, halved.

Since the limit torque M _G 'in the second setting stage is greater than the limiting torque M _G in the first setting stage, the precalculated instant t _± ' in the second setting stage is earlier than the predicted instant ti in the first setting stage. The traction torque M _T 'increased from the time t _± ' at the maximum permitted rate reaches the limit torque M _G 'at the instant t ₂ .

Until the time t ₃ 'at which the engine speed n reaches the first limit speed ni, the traction torque M _T ' is kept constant by the control unit 10 at the limit torque M _G '. From the time t ₃ 'is a proportional to the engine speed n increase of the traction torque M _T until the

Traction torque M _T 'at time t ₄ ' reaches the maximum adjustable by the control unit 10 traction value M _en d. From then on, the traction torque M _T 'remains constant until the maximum engine power is reached at time t ₅ maximum traction value adjustable by the control unit 10

In the second setting stage, a period in which the traction torque M _T 'is maintained at the limit torque M _G ' is longer than in the first setting stage. This is because, in the second setting stage, the limit torque M _G 'is greater than in the first setting stage and consequently a longer limitation of the traction torque M _T ' takes place in order to protect the converter 8.

Further, in the second setting stage, a period in which the increase in the engine speed n proportional increase of

Traction torque M _T 'takes place, is shorter than in the first setting stage, since the proportional to the engine speed n

Increasing at a higher traction torque M _T 'starts than in the first setting stage.

The temporal profile of the traction torque M _T 'in the second setting stage described in conjunction with FIG. 2 can be transmitted analogously to FIG.

6 shows a diagram in which an exemplary time profile of a temperature of the

Bipolar transistor of the rail vehicle described in FIG 1 is shown. The diagram comprises an ordinate axis and an abscissa axis. On the ordinate axis a temperature T is plotted. A time t is plotted on the abscissa axis.

The illustrated temperature is the temperature at a contact surface of the bipolar transistor to which a bonding wire is soldered or welded to the bipolar transistor. This temperature may be, for example, the temperature to which the control unit 10 refers when controlling the traction torque M _T. Furthermore, the illustrated temperature profile refers to a period in which an engine speed n of the two electric motors 6 is below the predetermined first limit speed rii and thus a frequency of the output voltage generated by the converter 8 is low. The period shown is so short that the engine speed n is considered to be approximately constant over this period.

During a conducting phase of the bipolar transistor, the bipolar transistor heats up and the temperature at the contact surface increases. Accordingly, the cools

Bipolartransistor during a non-conducting phase of the bipolar transistor and the temperature at the contact surface decreases.

In FIG. 6, a periodic fluctuation of the temperature between a minimum temperature and a maximum temperature is shown. The maximum temperature is a maximum temperature T _{max reached} at the contact surface during a conducting phase of the bipolar transistor. This temperature will be on

Reached the end of a leading phase. The minimum temperature is one during a non-conductive phase of the

Bipolar transistor minimum reached temperature T _m i _n at the contact surface. This temperature is reached at the end of a non-conductive phase. Consequently, the value of the minimum attained temperature T _m i _n at the contact surface depends inter alia on a duration of the non-conducting phase of the bipolar transistor. Accordingly, the value of the maximum reached temperature T _max at the contact surface depends inter alia on a duration of the conducting phase of the bipolar transistor.

The temperature profile is shown in simplified form and is merely intended to illustrate a relationship between the motor speed n dependent on the frequency of the output voltage and the maximum temperature T _{max reached} at the contact surface during a conducting phase of the bipolar transistor. For the representation of the temperature curve, it was assumed that an average temperature at the contact surface - be relied on a temporal averaging of the temperature over several temperature periods - set to a steady value and does not increase with time t. 7 shows a diagram in which a further exemplary time profile of the temperature of the bipolar transistor of the converter 8 is shown. The temperature curve shown relates to a period in which the engine speed n is above the first predetermined limit speed rii and thus the frequency of the output voltage generated by the converter 8 is higher than in FIG. 6.

For the purpose of a simple comparability of FIG. 6 and FIG. 7, the scaling of the ordinate axes or of the abscissa axes is the same in both figures.

The duration of a conducting phase of the bipolar transistor is inversely proportional to the frequency of the output voltage generated by the converter 8. Accordingly, the longer the motor rotational speed n, the shorter the duration of a conducting phase of the bipolar transistor. Accordingly, the heats up

Bipolar transistor at a higher engine speed n shorter. This can be done during a conducting phase of the

Bipolar transistor maximum reached temperature T _max at the contact surface at a higher engine speed n be lower than at a lower engine speed n - and although a rate at which the temperature increases at the higher engine speed n, may be greater, for example because that

Traction torque M _{T is} greater.

This situation can be seen in the comparison of FIG. 6 and FIG. Thus, in FIG. 7, the rate at which the temperature rises is greater than in FIG. 6. However, since the duration of a conducting phase in FIG. 7 is shorter than in FIG. 6, FIG. 7 shows the maximum reached during a conducting phase of the bipolar transistor Temperature T _max at the contact surface lower than in FIG. 6 In addition, at a higher engine speed n, the duration of a non-conducting phase of the bipolar transistor is shorter. Therefore, the bipolar transistor cools at a higher motor speed n shorter and the minimum reached during a non-conducting phase of the bipolar transistor temperature T _m i _n at the contact surface may be greater at a higher engine speed n than at a lower engine speed n. Simplified can be assumed that the duration of a non-conducting phase of the bipolar transistor in FIG. 7 is so long that an increase in the minimum attained temperature T _m i _n in FIG. 7 is negligible compared to the minimum attained temperature T _min in FIG.

Although the invention has been further illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed example, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims

claims

1. A method for controlling a starting operation of an electrically driven vehicle (2), in which a holding torque (M _F ) necessary for preventing the vehicle (2) from rolling back is determined,

characterized in that, as long as a determined engine speed (n) is less than a predetermined first limit speed (ni), a traction torque (M _T ) from a control unit (10) of the vehicle (2) to one of the holding torque (M _F ) dependent limit torque (M _G ) is limited and the

Traction torque (M _T ) of the control unit (10) only after the limit torque (M _G ) is increased when the engine speed (n) is greater than the first limit speed (ni).

2. The method according to claim 1,

characterized in that the limit moment (M _G ) below the maximum of 1.3 times the holding torque (M _F ) and 0.3 times the maximum of the control unit (10) adjustable traction value (M _en d) lies.

3. The method according to claim 1 or 2,

characterized in that the limit torque (M _G ) is above the maximum of 1.2 times the holding torque (M _F ) and 0.2 times the maximum of the control unit (10) adjustable traction value (M _en d).

4. Method according to one of the preceding claims,

characterized in that the traction torque (M _T ) of the control unit (10) until reaching a predetermined second limit speed (n ₂ ) is linearly increased to the engine speed (n) as soon as the engine speed (n) is greater than the first limit speed (ni ).

5. Method according to one of the preceding claims,

characterized in that the first limit speed (ni) of the control unit (10) in dependence on the holding torque (M _F ) is set.

6. The method according to claim 4 or 5,

characterized in that the ratio of the second

Limit speed (n ₂ ) to the first limit speed (rii) is equal to the ratio of the maximum of the control unit (10) adjustable traction value (M _en d) to the limit torque (M _G ).

7. The method according to any one of the preceding claims, characterized in that for each carriage (4) of the vehicle (2) in each case a car mass and one of a track inclination angle (24) dependent car slope parameters are determined from the car mass and from the Carriage slope parameter, a car-holding torque is calculated and the holding torque (M _F ) of the vehicle (2) is calculated by adding up all determined car-holding torque.

8. The method according to any one of the preceding claims, characterized in that a brake is released by the control unit (10) for starting and the slope of the

Traction torque (M _T ) in response to a decreasing braking torque (M _B ) takes place.

9. The method according to any one of the preceding claims, characterized in that a brake is released by the control unit (10) for starting before the

Traction torque (M _T ) is increased by the control unit (10) starting at zero.

10. The method according to any one of the preceding claims, characterized in that a brake is released by the control unit (10) for starting and the

Is traction torque (M _T) of the control unit (10) controlled such that the traction torque reaches (M _T) for the first time, the limit torque (M _G) when a braking torque (M _B) reaches the value zero.

11. The method according to any one of the preceding claims, characterized in that the traction torque (M _T ) of the control unit (10) is increased such that the sum of traction torque (M _T ) and braking torque (M _B ) remains constant, in particular equal to the limit torque (M _G ).

12. The method according to any one of the preceding claims, characterized in that a first time (t ₂ ) at which a braking torque (M _B ) has dropped to zero, is calculated in advance and from the first time (t ₂ ) a time before lying second time point (ti) is calculated, so that at the second time point (ti) rising from zero starting at maximum allowable rate

Traction torque (M _T ) at the first time (t ₂ ) reaches the limit torque (M _G ).

13. The method according to any one of the preceding claims, characterized in that at a drop in the engine speed (n) below the first limit speed (ni) the

Traction torque (M _T ) from the control unit (10) on the

Limit torque (M _G ) is maintained as long as the engine speed (n) is less than the first limit speed (ni), and the

Traction torque (M _T ) of the control unit (10) over the limit torque (M _G ) is increased as soon as the engine speed (n) is greater than the first limit speed (ni).

14. The method according to any one of the preceding claims, characterized in that the traction torque (M _T ) is a negative traction torque for electric braking.

15. Control system (9) for an electrically driven

A vehicle (2) having at least one electric motor (6), a converter (8) for feeding the electric motor (6) and a control unit (10) for controlling the inverter (8) prepared for preventing the vehicle from rolling back (2) to determine the necessary holding torque (M _F ), characterized in that the control unit (10) is prepared to control the converter (8) so that as long as a determined engine speed (n) is less than a predetermined given first limiting speed (rii), a traction torque (M _T ) of the vehicle (2) is limited to a by the holding torque (M _F ) dependent limit torque (M _G ) and the traction torque (M _T ) only then on the limit torque (M _G ) is increased when the engine speed (n) is greater than the first limit speed (ni).