DE102014220922A1 - Method for fault tolerant rotation angle detection - Google Patents

Abstract

The invention relates to methods for fault tolerant signal detection with at least three sensors, wherein the sensors detect angular positions of a rotor of an electric motor, wherein a commutation of the electric motor is performed depending on the detected by the sensors angular position of the rotor, wherein for fixed states of the signals of the three sensors Angle positions are stored for the rotor, wherein states are stored with a defective sensor, wherein a sequence of states is detected, wherein the detected states are compared with the stored states, and wherein based on the comparison, a defective sensor is detected.

Description

The invention relates to a method according to claim 1, an evaluation circuit according to claim 11 and an electric motor according to claim 12.

State of the art

Cost-effective angle sensing principles are known from the prior art, which consist only of Hall switches. For example, in electric scooters, three phase-shifted Hall switches are installed inside the electric motor in order to realize a control signal for a commutation of the electric drive. If one of the three Hall sensors fails, a reliable commutation of the electric motor with the known method is difficult.

Disclosure of the invention

The object of the invention is to provide a method for a fault-tolerant rotation angle detection for a commutation of an electric motor.

The object of the invention is achieved by the method according to claim 1, the evaluation circuit according to claim 11 and the electric motor according to claim 12. Further developments are specified in the dependent claims.

An advantage of the method described is that, if one sensor fails, a sufficiently good commutation of the electric motor continues to be achieved. This is achieved by an estimation of the rotational angle of the rotor in the event of a failure of a sensor due to the sequence of signal states of the sensors.

For this purpose, at least three sensors are provided, wherein the sensors detect angular positions of a rotor of an electric motor, wherein a commutation of the electric motor is performed depending on the detected by the sensors angular position of the rotor, wherein for fixed states of the signals of the three sensors angular positions are stored for the rotor wherein states are also stored with a defective sensor, wherein a sequence of states is detected, wherein the detected states are compared with the stored states, and wherein based on the comparison, a defective sensor is detected.

In one embodiment, after detecting a defective sensor, a sequence of the detected states is compared with stored sequences of states, and it is determined on the basis of the comparison which sensor is defective. As a result, a safe and easy detection of the defective sensor is possible.

In one embodiment, the sequence of detected states is compared with stored sequences of the states for specified operating states of the electric motor with a defective sensor, and wherein the comparison determines the defective sensor. As a result, a quick determination of the defective sensor is achieved.

In a further embodiment, when a defective sensor is detected for at least one state, a corrected angle value relative to a fault-free case is stored, and the corrected angle value is used for the state. As a result, the angle detection is further specified.

In a further embodiment, a sequence of detected states is compared with stored sequences of states, one of a plurality of possible error situations being identified based on the comparison, an allocation table being provided for the possible error situations, angles being stored in the assignment table for the states and wherein the mapping table stored for the detected error situation is used to use the angle stored in the mapping table for the detected state. This makes the process more precise and easier.

In a further embodiment, upon detection of a condition for a defective sensor, angle values for preceding states and / or angle values for the following states are also corrected, wherein in particular the angle values are corrected in such a way that an angle error, in particular via an electrical revolution of the rotor, is minimized.

In a further embodiment, the information which sensor has failed is transferred to a subsystem. The subsystem can represent a speed detection.

In one embodiment, a commutation is performed controlled for a start of an electric drive at least during a first rotation of the electric motor.

In one embodiment, an evaluation circuit is provided with a status determination, wherein the status determination is designed to determine a state, wherein a state comprises signals from three sensors for determining an angular position of a rotor, wherein a fault location is provided, wherein the fault location is formed, to detect an error situation due to a sequence of states, wherein a Selection unit is provided, wherein the selection unit is adapted to allocate the states fixed angles depending on the detected error situation, and wherein an allocation unit is provided, wherein the allocation unit is adapted to output depending on the state of the selected by the selection unit angle for the state.

The method and the evaluation circuit can be used in an electric motor, in particular in an electric motor of an electric scooter.

The invention will be explained in more detail below with reference to FIGS. Show it

1 a schematic representation of an electric motor with a control circuit,

2 a schematic representation of a waveform of the three sensors of the control circuit of the electric motor,

3 a table with signal states for normal operation,

4 a first error table for signal states with a fault of the third sensor, which is stuck at a low signal level,

5 a second error table for signal states with a fault of the third sensor, which is stuck at a high signal level, and

6 an evaluation circuit for a fault-tolerant detection of a rotation angle of the rotor,

1 shows a schematic representation of an arrangement with an electric motor 1 , a control circuit 2 , a commutator circuit 3 , a sensor arrangement 4 and an evaluation circuit 6 , The electric motor 1 can be used for example in an electric scooter as a drive motor. The electric electric motor 1 is designed, for example, as a three-phase or three-phase EC motor. At the electric motor 1 only one stator is indicated with three winding strands electrically offset by 120 ° each. An associated permanent magnetic rotor is not shown. In the example shown, the winding strands are connected in a star connection, but also a triangular connection of the winding strands is possible. The winding strands are via strand connections with a commutator circuit designed as a semiconductor bridge 3 connected. The commutator circuit 3 consists of six power semiconductors by the control circuit 2 with control signals and depending on the rotational position, that is supplied by the mechanical rotation angle of the rotor. In addition, the control circuit 2 a torque control signal 7 fed to the control circuit 2 taken into account for influencing the torque.

To generate a magnetic stator rotary field are from the control circuit 2 the power semiconductors of the commutator circuit 3 in each cyclically changing combinations driven by the winding terminals either with a positive or a negative terminal of a DC voltage source 8th connected or high impedance from the DC voltage source 8th be separated. To determine the angle of rotation of the rotor, the sensor arrangement 4 intended. The sensor arrangement 4 has a first, second and third sensor 9 . 10 . 11 on. The first, second and third sensor 9 . 10 . 11 may be formed, for example in the form of a Hall sensor. The three sensors 9 . 10 . 11 are offset by 120 ° about the electrical axis of rotation of the rotor. In the case of Hall sensors, each sensor can define at least two rotational angles of the rotor, one by a rising edge and one by a falling edge. This can be done using the three sensors 9 . 10 . 11 in each case at least one predetermined rotational angle of the rotor of 60 °, 120 °, 180 °, 240 °, 300 ° and 360 ° are detected.

2 shows a schematic representation of a first waveform 12 of the first sensor 9 , a second waveform 13 of the second sensor 10 and a third waveform 14 of the third sensor 11 , The waveforms 12 . 13 . 14 are plotted over the electrical rotation angle of the rotor. At a rotation angle of 0 °, the first sensor points 9 a transition from a high level to a low level, ie a falling edge. The second waveform 13 of the second sensor 10 is at a high level. The third waveform 14 of the third sensor 11 is at a low level. At an angle of 60 °, the third waveform increases 14 from a low level to a high level with a rising edge. At a rotation angle of 120 °, the second signal curve decreases 13 from a high level to a low level with a falling edge. At an angle of 180 ° increases the first waveform 12 from a low level to a high level with a rising edge. At an angle of 240 °, the third waveform falls 14 from a high level to a low level with a falling edge. At an angle of 300 ° increases the second waveform 13 from a low level to a high level with a rising edge. At 360 °, which at the same time represent 0 ° for a new electrical revolution of the rotor, the first signal curve decreases 12 from a high level to a low level with a falling edge. Thus, using the rising and falling edges of the waveforms 12 . 13 . 14 six defined electrical rotation angle positions of the rotor are detected.

3 shows in a table 22 a temporal course of the signal states of the waveforms 12 . 13 . 14 the sensors 9 . 10 . 11 , In a zeroth state, which corresponds to the angle range between 0 ° and 60 ° of the rotational angle of the rotor, the first signal waveform points 12 a low level, which is represented by the number 0. The second waveform 13 has a high level, which is represented by the number 1. The third waveform 14 has a low level represented by the number 0. In addition, the signal states of the signal curves are in the table 12 . 13 . 14 for a first, second, third, fourth and fifth state. The first state relates to the angular range between 60 ° and 120 °, the second state concerns the angular range between 120 ° and 180 °, the third angular range relates to the state between 180 ° and 240 °, the fourth angular range relates to the state between 240 ° and 300 ° ° and the fifth state relates to the angular range between 300 ° and 360 ° of the electrical rotation angle of the rotor. In zero state 0, an angle of 30 ° is assumed for the rotor. In the first state 1, an angle of 90 ° is assumed for the rotor. In the second state 2, an angle of 150 ° is assumed for the rotor. In the third state 3, an angle of 210 ° is assumed for the rotor. In the fourth state 4, an angle of 270 ° is assumed for the rotor. In the fifth state 5, an angle of 330 ° is assumed for the rotor.

In the event of a malfunction of a sensor, signal states occur which do not occur during normal operation. These failures are: each sensor has a high voltage level or each sensor has a low voltage level. The first fault 20 corresponds to the situation where all three sensors have a low signal level. The second wrong state 21 corresponds to the state in which all sensors have a high signal level. Both wrong states 20 . 21 can be assigned regardless of further information no angle value of the rotor.

4 shows a sequence of signal states of the sensors in the form of a second table 23 , The signal states are consecutive in time from top to bottom. When detecting the signal states, the direction of rotation of the electric motor can also change. In the second table 23 are in a first column 31 the target states are shown, which should have the sensors in a normal operation of the electric motor. The sequence of signal states should be: 0, 1, 2, 3, 4, 5, 0, 1, 2, etc. Next to the first column 31 are in other columns the values for the partially disturbed signals of the waveforms 12 . 13 . 14 shown. 0 represents a low level and 1 represents a high voltage level. Moreover, in the last column 32 the resulting actual states of the sensors are shown. By recognizing the first error state 20 , which represents a normal non-occurring signal state, is from the control circuit 2 a defective sensor detected.

5 represents a third table 24 for a sequence of states. In the third table 24 are in the first column 31 again the target states for a normal operation of the electric motor shown. In normal operation, a sequence of states should be: 0, 1, 2, 3, 4, 5. In the last column 32 are the actual states, ie the actual states shown. In addition, the values for the partially disturbed signals of the signal curves 12 . 13 . 14 shown. 0 is a low level and 1 is a high level. There is a second error condition 21 represented for an actual state. The second error condition 21 represents the not normally occurring situation that all three waveforms 12 . 13 . 14 have a high level. By recognizing the second error state 21 , which represents a normal non-occurring signal state, is from the control circuit 2 a defective sensor detected. The tables of 3 . 4 . 5 are for example in the evaluation circuit 6 stored. The evaluation circuit 6 gets from the three sensors 9 . 10 . 11 the first, second and third waveforms 12 . 13 . 14 , Thus, the evaluation circuit 6 for a correct functioning of the three sensors 9 . 10 . 11 each with a change in the level of the signal waveforms 12 . 13 . 14 , ie on a flank detect a defined angle of rotation of the rotor, as shown by 2 and 3 example. Now falls, for example, the third sensor 11 off, this recognizes the evaluation circuit 6 by comparing the from the sensors 9 . 10 . 11 supplied signal states and the table of 3 in a store 15 the evaluation circuit 6 is stored.

6 shows an embodiment of a structure of the evaluation circuit 6 , The evaluation circuit 6 become the first, second and third waveform 12 . 13 . 14 the sensors 9 . 10 . 11 fed. The waveforms 12 . 13 . 14 become a status determination 16 to hand over. The status determination 16 recognizes one of the eight possible states based on the values of the signal states. The eight possible states are given by the states 0, 1, 2, 3, 4, 5 and the two error states 20 . 21 educated. The status determination 16 gives the recognized state 17 to an allocation unit 18 , The recognized state can only be one of the states 1, 2, 3, 4, 5, 20, 21.

The one of the status determination 16 detected state, ie the states 0, 1, 2, 3, 4, 5 and the first and second error state 20 . 21 , are also due to a fault location 19 passed on. In the fault location 19 is determined by the sequence of states, which of the sensors 9 . 10 . 11 is defective. For this purpose, the sequences of the actual states of at least one electrical revolution of the rotor are checked to determine which sensor is defective. The fault location 19 knows the possible states 1, 2, 3, 4, 5, 20, 21. In addition, the error localization knows 19 the possible sequences of the states for the possible error states. Corresponding tables for the sequences of the states in the error localization are 19 stored. In addition, the fault localization knows 19 also the sequence of desired states for the desired operation of the electric motor. Based on a simple comparison of the sequence of states that have occurred and the possible sequences of the states, the error localization recognizes 19 which sensor is defective and which false signal the sensor emits. Thereby six error situations and a faultless situation can be detected. The six error situations affect the three sensors, with each sensor stuck at a high level or a low level. If two sensors are defective, usually no angle detection can be performed.

The error localization 19 recognized situation is sent to the selection block 25 passed on. In the selection block 25 is an allocation table for each of the seven possible situations 41 . 42 . 43 . 44 . 45 . 46 . 47 which assigns an angle to each of the possible states 1, 2, 3, 4, 5, 20, 21 for each of the seven possible situations. Depending on the situation detected by the error localization, the states 1, 2, 3, 4, 5, 20, 21 are assigned different angles. Both the angles for the error states 20 . 21 as well as the angles for the states 1, 2, 3, 4, 5 can, depending on the six possible situations with a defective sensor, assume different values, ie corrected angle values compared to the error-free situation. For example, the angle values may be corrected for a situation with a faulty sensor such that a total angle error is reduced, in particular minimized, over all states of one electrical revolution of the rotor. The allocation tables 41 . 42 . 43 . 44 . 45 . 46 . 47 are determined in advance and stored.

For a reliable detection requires the fault localization 19 usually at least the detected states for a total electrical revolution of the rotor. Thus, the fault location 19 the detected situation usually only after an electrical rotation of the rotor to the selection unit 23 to hand over. Consequently, the selection unit 23 the assignment table assigned to the situation 41 . 42 . 43 . 44 . 45 . 46 usually after an electrical rotation of the rotor to the allocation unit 18 to hand over.

The allocation unit 18 determined for the state 1, 2, 3, 4, 5, 20, 21, the status of the determination 16 is made available and depends on the allocation table 41 . 42 . 43 . 44 . 45 . 46 . 47 for the state, the angle stored in the table and gives the correction angle to the control circuit 2 or to a subsystem. In the initial situation, the allocation unit can use the first allocation table 31 use, which corresponds to error-free operation of the sensors. Due to the first allocation table 31 determines the allocation unit 18 The following angle values for the states: For the zeroth state 0, an angle of 30 ° is assumed for the rotor. For the first state 1, an angle of 90 ° is assumed for the rotor. For the second state 2, an angle of 150 ° is assumed for the rotor. For the third state 3, an angle of 210 ° is assumed for the rotor. For the fourth state 4, an angle of 270 ° is assumed for the rotor. For the fifth state 5, an angle of 330 ° is assumed for the rotor. The corresponding angles are referred to the control circuit as instantaneous rotational angle position 2 or to a subsystem, such as speed sensing.

The other allocation tables have a different angle value for at least one state.

Depending on the selected design, the corrected angle value corresponds to the angle value that the state would indicate for a correctly functioning sensor.

In a further embodiment, the corrected angle value can be determined as a function of the sequence of the detected states, wherein the corrected angle value deviates from the angle value if the sensors function correctly. In addition, depending on the selected implementation, for at least one of the states that is the fault state 20 . 21 preceded and / or follow also corrected angle values are assigned, although for the preceding or following states error-free states 0, 1, 2, 3, 4, 5 were detected. Preferably, the corrected angle values are chosen such that an angle error is minimized.

In addition, the defective sensor via a signal line 20 Submitted to subsystems such as the speed detection.

With the described method, despite a defective sensor, sufficient accuracy is achieved by means of two sensors for controlling the electric motor 1 , in particular for a commutation of the electric motor 1 using the control circuit 2 and the commutator circuit 3 , reached.

Claims (12)

 A method for fault-tolerant signal detection with at least three sensors, wherein the sensors detect angular positions of a rotor of an electric motor, wherein a commutation of the electric motor is performed depending on the detected by the sensors angular position of the rotor, for fixed states of the signals of the three sensors angular positions for the Rotor are stored, whereby states are stored with a defective sensor, wherein a sequence of states is detected, wherein the detected states are compared with the stored states, and wherein based on the comparison, a defective sensor is detected.  The method of claim 1, wherein after detecting a defective sensor, a sequence of the detected states is compared with stored sequences of states, and wherein it is determined based on the comparison, which sensor is defective.  The method of claim 2, wherein the sequence of detected states is compared with stored sequences of states for specified operating conditions of the electric motor with a defective sensor, and wherein the comparison of the defective sensor is determined.  Method according to one of the preceding claims, wherein upon detection of a defective sensor for at least one state, an error value corrected against an error-free angle value is stored, and wherein the corrected angle value for the state is used.  Method according to one of the preceding claims, wherein a sequence of detected states is compared with stored sequences of states, whereby one of a plurality of possible error situations is identified based on the comparison, wherein an allocation table is provided for the possible error situations, wherein in the allocation table for the States angle are stored, and wherein the assignment table stored for the detected error situation is used to use for the detected state stored in the allocation table angle.  The method of claim 5, wherein the allocation table is determined in advance and stored. Method according to one of the preceding claims, wherein upon detection of a condition for a defective sensor, angle values for preceding states and / or angle values for the following states are also corrected, in particular corrected in such a way that an angle error is minimized.  Method according to one of the preceding claims, wherein the information which sensor has failed is transmitted to a subsystem.  The method of claim 8, wherein a speed detection is used as a subsystem. Method according to one of the preceding claims, wherein for a start of an electric drive, at least during a first rotation of the electric motor, a commutation is controlled controlled. Evaluation circuit with status determination ( 16 ), whereby the status determination ( 16 ) is configured to determine a state, wherein a state comprises signals from three sensors for determining an angular position of a rotor, wherein an error localization ( 19 ), the fault localization ( 19 ) is designed to detect an error situation on the basis of a sequence of states, wherein a selection unit is provided, wherein the selection unit is designed to assign fixed angles to the states as a function of the recognized error situation, and wherein an allocation unit ( 18 ), the allocation unit ( 18 ) is formed, depending on the state of the selection unit ( 19 ) output angle for the state.  Electric motor, in particular for an electric scooter, with an evaluation circuit according to claim 11.

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