Method and device for operating a brushless DC motor

Patent metadata

Field	Value
Publication number	US-9748875-B2
Application number	US-201414785755-A
Country	US
Kind code	B2
Filing date	Apr 17, 2014
Priority date	Apr 26, 2013
Publication date	Aug 29, 2017
Grant date	Aug 29, 2017

Abstract

A method for operating a three-phase brushless DC motor with a pulse-width modulation controlled electronic commutation in the event of a malfunction. A maximum number (n) of commutation steps, a direction of motor rotation and at least two possible operating end states are specified, and one of the operating end states is chosen. Following indication of a malfunction, the rotor of the brushless DC motor is rotated at the specified maximum number (n) of commutation steps in the specified direction of motor rotation and the brushless DC motor is then set to the operating end state selected.

First claim

The invention claimed is:

1. A method of operating a three-phase brushless DC motor with a pulse-width-modulation-controlled electronic commutation in an event of a malfunction, the method comprising:
predefining a maximum number (a) of commutation steps, a direction of rotation of the motor, and at least two possible operating end states that can be selected in the event of the malfunction, wherein the at least two possible operating end states of the brushless DC motor include a braking state of the brushless DC motor and a freewheeling state of the brushless DC motor in which a converter for the brushless DC motor has a maximum impedance state;
selecting one of the at least two possible operating end states as a selected operating end state in the event of the malfunction:
upon an indication of the malfunction, rotating a rotor of the brushless DC motor by the predefined maximum number (a) of commutation steps in the predefined direction of rotation of the motor, and then setting the brushless DC motor to the selected operating end state;
when a first operating end state of the at least two possible operating end states is selected, using a control unit to put the converter in the maximum impedance state causing the brushless DC motor to be in a freewheeling state; and
when a second operating end state of the at least two possible operating end states is selected, using the control unit to put the converter in a state causing the brushless DC motor to be in a braking state.

2. The method according to claim 1 , which comprises, following the indication of the malfunction, rotating the rotor of the brushless DC at a maximum modulation factor of the commutated pulse-width-modulation.

3. The method according to claim 1 , which comprises:
predefining a current threshold value for a motor current of the brushless DC motor and an interruption period; and
following the indication of the malfunction, continuously measuring the motor current and rotating the rotor of the brushless DC at a maximum modulation factor of the commutated pulse-width-modulation as long as the motor current does not exceed the current threshold value, and changing a level of the pulse-width-modulation signal for the interruption period when the motor current exceeds the current threshold value.

4. The method according to claim 1 , which comprises acquiring at least one sensor signal indicating a rotor position of the rotor, and monitoring a number of commutation steps performed following the indication of the malfunction by way of the at least one sensor signal.

5. The method according to claim 4 , which comprises predefining a disconnection period and, following the indication of the malfunction, setting the brushless DC motor into the selected operating state if the at least one sensor signal does not change during a period exceeding the disconnection period.

6. The method according to claim 1 , which comprises predefining a high-resistance state between outputs of actuation electronics of the brushless DC motor as the first possible operating end state.

7. The method according to claim 6 , which comprises predefining a low-resistance state between the outputs of the actuation electronics of the brushless DC motor as the second possible operating end state.

8. The method according to claim 6 , which comprises predefining a low-resistance state between outputs of actuation electronics of the brushless DC motor as a possible operating end state.

9. A motor control device for controlling a three-phase brushless DC motor with a pulse-width-modulation-controlled electronic commutation in an event of a malfunction, the motor control device comprising:
a converter having an electrical half-bridge with two electronic switches for each phase of the brushless DC motor; and
a control unit for controlling the electronic switches;
said control unit having interfaces for receiving the indication of the malfunction, the commutated pulse-width-modulation signal, the selection of an operating end state including at least a first operating end state and a second operating end state, and at least one sensor signal indicating a rotor position of the rotor of the brushless DC motor;
said control unit being configured to evaluate the at least one sensor signal to detect performed commutation steps and to store the predefined maximum number of commutation steps, the predefined direction of rotation of the motor and, for each of the possible operating end states, a switching state, assigned to the respective operating end state of the electronic switches;
said control unit being configured to control the converter to be in a maximum impedance state causing said brushless DC motor to be in a freewheeling state when said first operating end state is selected; and
said control unit being configured to control the converter to be in a state causing said brushless DC motor to be in a braking state when said second operating end state is selected.

10. The motor control device according to claim 9 , wherein said control unit is configured, following the indication of the malfunction, to count the detected commutation steps and to adjust the switch state, associated with the selected operating end state, of the electronic switches if a number of the counted commutation steps reaches the predefined maximum number.

11. The motor control device according to claim 10 , wherein said control unit comprises a counter register and said control unit is configured to initialize a memory content of said counter register with the predefined maximum number of commutation steps and, following the indication of the malfunction, to decrement the memory content by one for each detected commutation step.

12. The motor control according to claim 9 , wherein said control is configured, following the indication of the malfunction, to acquire a period after each detected commutation step, during which the at least one sensor does not change.

13. The motor control device according to claim 12 , wherein a disconnection period is stored in said control unit and said control unit is configured to adjust the switch state, associated with the selected operating end state, of the electronic switches if the at least one sensor signal does not change during a period exceeding the disconnection period.

Assignees

• Conti Temic Microelectronic Gmbh
• Continental Automotive Gmbh

Inventors

• Arabackyj Marc
• Jerichow Edgar
• Kuhn Mathias
• Guertler Thomas
• Pschorr Andreas
• Loerincz Robert

Classifications

• H02P6/12 Primary

  Monitoring commutation; Providing indication of commutation failure · CPC title

• H02P6/16

  Circuit arrangements for detecting position · CPC title

• H02P29/032

  Preventing damage to the motor, e.g. setting individual current limits for different drive conditions · CPC title

• H02P29/0241

  the fault being an overvoltage · CPC title

• H02P29/022

  Electricity · mapped topic