DE102016014552A1 - Method for operating an electrical machine of a vehicle - Google Patents

Abstract

The invention relates to a method for operating an electric machine (5) of a vehicle (1), in which - upon actuation of a brake pedal by means of a sensor unit (2) a desired braking torque request (MSoll) is detected, - the detected desired braking torque request (MSoll ) is transmitted to a control unit (3) of an assistance system, wherein the control unit (3) calculates an actual braking torque (MIst_1) to be set on the basis of the detected desired braking torque request (MSoll), - the actual braking torque (MIst_1) to be set by the Control unit (3) to an electrical machine control (4) is transmitted, which controls the electric machine (5) and - in the electric machine (5) depending on the actual braking torque to be set (MIst_1) an actual braking torque (MIst_2) is provided , According to the invention, the electrical machine controller (4) cyclically detects and / or determines the actual braking torque (MIst_2) in the electric machine (5) and compares it with a defined maximum permissible actual braking torque, - a safety function in the electrical machine control (4) is activated when the actual braking torque (MIst_2) exceeds the maximum permissible actual braking torque and - when the safety function is activated, preventing the actual braking torque (MIst_2) from being set in the electric machine (5).

Description

The invention relates to a method for operating an electric machine of a vehicle according to the preamble of claim 1.

Method for operating an electric machine of a vehicle, which is in particular an electric drive unit of the vehicle, are known from the prior art. For example, in the DE 101 62 362 A1 describes a method for managing the regenerative braking of a motor vehicle by means of a torque control, which is realized via internal interactions between a powertrain control module and a brake control unit of the motor vehicle.

Furthermore, generally as an assistance system coupled to the electrical machine, e.g. As an electronic stability program, in short: ESP, which calculates a braking torque request in a vehicle. In order to minimize the risk of dangerous malfunctions, the electronic stability program is developed with a safety mechanism which complies with certain standards, in particular the so-called ISO 26262 , corresponds. The safety mechanism detects slipping on vehicle wheels. If the slip on the vehicle wheels exceeds a critical limit value, the electronic stability program of a power electronics unit of the vehicle signals this limit value. Ensuring the security mechanism requires high signal integrity.

The invention is based on the object to provide a comparison with the prior art improved method for operating an electric machine of a vehicle.

The object is achieved with the features specified in claim 1.

Advantageous embodiments of the invention are the subject of the dependent claims. In a method for operating an electric machine of a vehicle, a desired braking torque request is detected when a brake pedal is actuated by means of a sensor unit. The detected desired braking torque request is transmitted to a control unit of an assistance system of the vehicle, wherein the control unit calculates an actual braking torque to be set on the basis of the detected desired braking torque request and transmits the actual braking torque to be set to an electrical machine control which controls the electric machine. The electric machine here is an electric drive of the vehicle and the electrical machine control is a power electronics for controlling the electric drive. In the electric machine, an actual braking torque is provided as a function of the actual braking torque to be set.

According to the invention, the electric machine control system cyclically detects and / or determines the braking torque set in the electric machine and compares it with a defined, maximum permissible actual braking torque, with a safety function being activated in the electric machine control if the set braking torque is the maximum permissible braking torque Is actual braking torque exceeds, and with the activated safety function prevents the placement of the braking torque in the electric machine, in particular is physically prevented.

In the method, the setting of the braking torque is limited, so that the risk of incorrect placement of the braking torque is reduced. This makes it possible to reduce signal integrity for a control signal which is transmitted from the control unit of the assistance system to the electrical machine control. Thus, an implementation of a control function in the vehicle is greatly simplified. Furthermore, by means of the method, an improved stability of the vehicle during braking processes is achieved compared to the prior art, in particular if the vehicle is braked on road surfaces with a high coefficient of friction.

Embodiments of the invention will be explained in more detail below with reference to a drawing.

Showing:

1 a block diagram of a vehicle.

The only 1 shows a block diagram of a vehicle 1 , The vehicle 1 includes a sensor unit 2 , a control unit 3 , an electrical machine control 4 and an electric machine 5 ,

To brake the vehicle 1 the driver depresses a brake pedal. The operation of the brake pedal is by the sensor unit 2 detected, which includes, for example, a pedal travel sensor. The sensor unit 2 then transmits a set braking torque request M _setpoint generated by the driver by actuating the brake pedal to the control unit 3 which a single control unit of an assistance system or a control unit network of an electric drive train of the vehicle 1 represents. The assistance system is, for example, a brake assist to assist a driver when braking the vehicle 1 and coupled to a brake device, not shown.

The control unit 3 calculated as a function of the desired braking torque request M _Soll to be set actual braking torque M _{Ist_1} , which to the electrical machine control 4 is transmitted. In particular, the actual braking torque M _{Ist_1 to be set is} divided and sent to a hydraulic service brake and to the electrical machine control 4 transmitted. Depending on the actual braking torque to be set M _{Ist_1} is in the electric machine 5 an actual braking torque M _{ist_2 is} set. The electric machine 5 in this case represents an electric drive of the vehicle 1 For example, the electric machine 5 designed as a permanent magnet synchronous machine with a number of phase strands. Alternatively, the electric machine 5 also be designed as an asynchronous machine. The electrical machine control 4 is a power electronics for controlling the electrical machine 5 ,

That in the electric machine 5 asked, actual braking torque M _{Ist_2} is cyclical from the electrical machine control 4 detected and / or determined and compared with a specified maximum allowable actual braking torque M _{Ist_1} . This is in the electrical machine control 4 carried out. If the set actual braking torque M _{Ist_2 exceeds} the maximum permissible actual braking torque M _{Ist_1} , then in the electrical machine control 4 a safety function is activated, in which the electrical machine control 4 assumes a safe state in which the electric machine 5 the braking torque M _{Ist_2 is} not physically or at least only a lower braking torque M _{Ist_2} can set, which is a stability of the vehicle 1 not endangered. The safe state is, for example, by short-circuiting all phases of the permanent-magnet synchronous machine or by opening all lines of the electrical machine control 4 achieved when the electric machine 5 is designed as an asynchronous machine.

The setting of the actual braking torque M _{Ist_2} is in this case limited such that a destabilization of the vehicle 1 avoided in a malfunction or at least limited to road surfaces with a small coefficient of friction. This reduces a probability of a dangerous malfunction, so that a safety integrity of the signals to be transmitted from the control unit 3 to the electrical machine control 4 is reduced. In addition, a calculation of a so-called hardware metric within the assistance system and the electrical machine control 4 simplified. Furthermore, the maximum permissible actual braking torque M _{Ist_1 is set} outside a recuperation range. Ie. Recuperation is not affected.

LIST OF REFERENCE NUMBERS

1

vehicle

2

sensor unit

3

control unit

4

electrical machine control

5

electric machine

M _{is_1}

to be set actual braking torque

M _{is_2}

actual braking torque

M _Soll

Target braking torque request

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10162362 A1 [0002]

Cited non-patent literature

• ISO 26262 [0003]

Claims (3)

Method for operating an electrical machine ( 5 ) of a vehicle ( 1 ), in which - when a brake pedal is actuated by means of a sensor unit ( 2 ) a desired braking torque request (M _setpoint ) is detected, - the detected setpoint braking torque request (M _setpoint ) to a control unit ( 3 ) of an assistance system, the control unit ( 3 ) is calculated on the basis of the detected desired braking torque request (M _setpoint ) to be set actual braking torque (M _{Ist_1} ), - to be set actual braking torque (M _{Ist_1} ) from the control unit ( 3 ) to an electrical machine control ( 4 ) transmitting the electric machine ( 5 ) and - in the electrical machine ( 5 ) is provided as a function of the actual braking torque (M _{Ist_1} ) an actual braking torque (M _{Ist_2} ), characterized in that the electrical machine control ( 4 ) in the electric machine ( 5 ) actual cyclic torque (M _{Ist_2} ) cyclically detected and / or determined and compared with a specified maximum allowable actual braking torque, - a safety function in the electrical machine control ( 4 ) is activated when the actual braking torque (M _{Ist_2} ) exceeds the maximum permissible actual braking torque and - when the safety function is activated, setting the actual braking torque (M _{Ist_2} ) in the electric machine ( 5 ) is prevented. A method according to claim 1, characterized in that the setting of the actual braking torque (M _{Ist_2} ) in the designed as a permanent _magnet synchronous machine electric machine ( 5 ) is physically prevented by closing all phase phases of the permanent-magnet synchronous machine. A method according to claim 1, characterized in that the setting of the actual braking torque (M _{Ist_2} ) in the formed as an asynchronous, electrical machine ( 5 ) by opening all lines of the electrical machine control ( 4 ) is physically prevented.

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