DE102019126113A1 - Procedure for calibrating a synchronous motor - Google Patents

Abstract

The invention relates to a method for calibrating a synchronous motor, which has a sensor device for detecting a rotational position of its rotor, which sensor device has several sensors arranged in a stator, distributed over an inner circumference and a rotor-fixed sensor magnet, the rotor of the synchronous motor in a rotationally fixed manner in a first step is connected to a torque and angle of rotation measuring shaft, which measuring shaft is further connected to an external motor, in a second step the external motor is operated in such a way that it drives the rotor by means of the measuring shaft at a constant speed, in a third step at least one coil strand of the stator is energized, while on the one hand a sinusoidally changing torque-angle of rotation curve of the rotor by means of the torque and angle of rotation measuring shaft and on the other hand an angular position of the rotor by means of the sensor device are detected, and in a fourth step at least a pole point of a rotor magnet attached to the rotor is assigned to a maximum and / or a minimum of the torque-angle of rotation curve immediately following the maximum in its angular position of the angular position of the rotor detected by the sensor device.

Description

The invention relates to a method for calibrating a synchronous motor, which is preferably used in a clutch actuation device of a motor vehicle.

From the prior art it is through the DE 102 15 428 A1 known in principle to determine the rotor position of a synchronous motor by determining the amount of the current vector required to achieve a defined deflection of the rotor for a large number of current vectors that are distributed over an electrical revolution of the synchronous motor. The position of the rotor can be calculated from the position of the minima of the amounts determined in this way, taking into account the direction of rotation of the rotor. Applying a brake ensures that grooving forces and machine vibrations do not play a role.

Furthermore, state of the art is through the DE 10 2017 128 891 A1 , the DE 10 2016 212 175 A1 , the DE 10 2013 205 905 A1 , the DE 10 2013 208 986 A1 , the DE 10 2013 211 041 A1 , the DE 10 2013 213 948 A1 , the DE 10 2013 222 366 A1 as well as the DE 10 2016 207 241 A1 known.

There are consequently already known designs with which the basic structure of a sensor-controlled EC motor is shown. In principle, there is a requirement in these designs that the stator field must be generated as a function of the rotor position in order to achieve the maximum electromagnetic torque, high dynamics and functional reliability. In particular, with the current remaining constant, the torque is at its maximum when the stator and rotor fields are within an electrical period at an angle of 90 ° to one another. This increases the efficiency and dynamics of the engine. The functional reliability can be improved that a more precise position control of the rotor is carried out.

However, a disadvantage of the previously implemented methods for calibrating synchronous motors has been found to be that the method steps carried out are highly susceptible to the effects of frictional forces. Although the friction can be partially corrected by averaging or other methods, it is necessary, however, that the existing friction is known in terms of its magnitude or is at least identical in both directions of rotation of the rotor. These methods are particularly unsuitable for synchronous motors in which the friction is different in the two opposite directions of rotation.

It is therefore the object of the present invention to eliminate the disadvantages known from the prior art and, in particular, to provide a reliable calibration method for calibrating a synchronous motor that is as independent as possible of external friction influences.

This is achieved according to the invention by the subject matter of claim 1. Accordingly, a method for calibrating a synchronous motor is implemented, the synchronous motor having a sensor device for detecting a rotational position of its rotor, which sensor device also has a plurality of sensors arranged in a stator, distributed over an inner circumference and a sensor magnet fixed to the rotor, with the rotor in a first step of the synchronous motor is non-rotatably connected to a torque and angle of rotation measuring shaft, which measuring shaft is further connected to an external motor, in a second step the external motor is operated in such a way that it drives the rotor by means of the measuring shaft at a constant speed, in a third step At least one coil strand of the stator is energized, while on the one hand a sinusoidally changing torque-angle of rotation curve of the rotor by means of the torque and angle of rotation measuring shaft and on the other hand an angular position of the rotor (/ of the sensor magnet) by means of the sensor device and in a fourth step at least one pole point (preferably two pole points) of a rotor magnet attached to the rotor at a maximum and / or a minimum of the torque-angle-of-rotation curve immediately following the maximum in its angular position of the angular position detected by the sensor device Rotor is assigned.

As a result, by coupling the synchronous motor to the external motor, a reliable, friction-independent drive of the rotor is achieved during the measuring steps. In addition, there is a reliable, manufacturing tolerance-independent assignment of the actual angular position of the pole points in relation to the angular position of the rotor, so that the synchronous motor can be controlled particularly efficiently during operation. Since the respective pole position on the rotor is exactly at the maximum or the minimum (depending on the direction of magnetization), the pole positions can therefore ideally be precisely determined. This means that the assignment to the stator coils for exactly one pole pair, i.e. two pole positions, can be determined for each full wave of the sinusoidal oscillation.

Further advantageous designs are claimed with the subclaims and explained in more detail below.

In this context, it is also advantageous if, in the third step, only one coil strand of the stator of the three-phase synchronous motor is energized (while the two other coil strands of the stator remain de-energized).

As an alternative to this, it is also advantageous if three coil strands of the stator of the three-phase synchronous motor are energized in the third step, two of the three coil strands being supplied / operated with the same current value with the same flow direction. This makes the calibration particularly reliable.

It is always a prerequisite that the alignment of the stator field is known and lies in the direction of the stator coils of a coil strand. For this purpose, only one coil strand is energized in principle with synchronous motors whose switching allows it. An exception are star motors / synchronous motors in star connection with center tap, where this is not possible. Therefore, in these star motors, all three coil strands are energized in such a way that one coil strand has the maximum current and the other two coil strands have a lower current. This aligns the magnetic field in the direction of the stator coil that is most energized.

Ideally, the other two coil strands are flown through in such a way that the magnetic field is strengthened in the direction of the stator coil with the strongest flow.

In addition, it is expedient if, in the fourth step, several pole positions of several rotor magnets are assigned in their angular position to the angular position of the rotor detected by the sensor device. As a result, the control of the synchronous motor is implemented even more efficiently.

Furthermore, it is advantageous if, in or after the fourth step, a data record comprising the fixed assignment of the angular position of the at least one pole point to the angular position of the rotor is stored / stored in a control unit of the synchronous motor (by an external computer unit).

In other words, according to the invention, a method for determining the rotor position based on torque oscillations (of the rotor) is implemented. The calibration method according to the invention determines the relationship between a sensor angle and the rotor position, including the individual pole positions. To carry out the process, the EC motor (synchronous motor) is connected to an external motor via a torque and angle measuring shaft. The synchronous machine is supplied with voltage in such a way that either one or three strings of the three-phase EC motor are energized. This depends on the motor connection. If all three strands are energized, two of three strands have a current that is as large as possible with the same flow direction. The external motor drives the motor at a constant speed. The energization of the stator coils creates a magnetic field, the vector of which runs exactly along the stator coils of the strand with the most current. The forces that act on the rotor as a result are dependent on the angular position of the rotor in an electrical period, which means that they differ in size and sign. A torque is generated over the circumference of the rotor, which is recorded by the external torque measuring shaft. The angle information on the torques is recorded by means of the external angle sensor.

The invention will now be explained in more detail below with reference to a figure.

It shows the only one 1 a flow chart to illustrate a calibration method according to the invention according to a preferred embodiment.

The exemplary embodiment is merely of a schematic nature and is therefore used exclusively for understanding the invention.

In the 1 a flowchart is shown to illustrate the individual method steps of the method according to the invention. The method according to the invention is a calibration method for calibrating a synchronous motor. The synchronous motor is implemented as an EC motor (/ brushless DC motor). The synchronous motor has a typical structure and is also preferably used in a clutch actuation device of a motor vehicle. The synchronous motor consequently preferably serves to engage and disengage a clutch of a motor vehicle drive train, which is not shown here for the sake of clarity.

The synchronous motor furthermore typically has a stator and a rotor which is arranged so as to be rotatable relative to the stator. The rotor comprises several permanent magnets which are arranged evenly distributed in the circumferential direction and which interact with several coils of the stator during operation. The coils are divided into three coil strands, which are controlled with the formation of a three-phase synchronous motor.

Furthermore, the synchronous motor comprises a sensor device, which sensor device includes a plurality of sensor devices received in the stator Has circumferentially distributed arranged sensors. The sensors are designed, for example, as magnetoresistive sensors. The respective sensors interact with at least one rotor-fixed sensor magnet.

In a first step a) of the method according to the invention, the rotor / a rotor shaft of the synchronous motor that directly accommodates the rotor is connected to a torque and angle of rotation measuring shaft (also simply referred to as measuring shaft for short). The measuring shaft is consequently equipped with at least one sensor for detecting a torque transmitted by the measuring shaft and a sensor for detecting an angular position / a rotation angle of the measuring shaft. The measuring shaft is attached directly to the rotor shaft in a torque-proof manner. With its end area facing away from the rotor of the synchronous motor, the measuring shaft is connected to an external motor. This external motor is preferably also designed as an electric motor.

In a second step b) of the method according to the invention, the external motor is switched on and operated in such a way that it drives / moves the rotor at a constant speed (in a specific direction of rotation).

In a third step c), while the rotor is being driven at the constant speed, in a first partial embodiment only one of the three coil strands of the synchronous motor is energized. In a further partial embodiment, all three coil strands of the synchronous motor are even energized, with two of the three strands then being energized with the same current value and the same flow direction. As a result, two of the three coil strands are energized with the same current value and the third coil strand with a higher current value than the other two coil strands, so that the stator field is aligned in the direction of the strand with the most current.

In any case, in the third step c), the energization of the at least one coil strand creates a magnetic field, the vector of which runs precisely along the stator coils of the coil strand that is most energized. Thus, the stator field is aligned along the energized or the most energized coil strand. The forces that act on the rotor as a result are dependent on the angular position of the rotor in an electrical period, which means that they differ in size and sign. A torque thus arises over the circumference of the rotor, which is recorded by the measuring shaft over a certain period of time (over at least one full revolution of the rotor). The angular information / angular position of the measuring shaft and thus of the rotor is also recorded by the angle sensor of the torque and angle of rotation measuring shaft.

Due to this operation of the synchronous motor due to the different energization of the coil strands, the torque generated on the rotor and recorded by the measuring shaft changes sinusoidally over the rotation angle of the rotor / the time. With the usual sinusoidal distribution of the flux density on the rotor, a sinusoidal curve of the measured torque results. A maximum of the torque is implemented when a rotor magnet with a magnetic north pole on the outside of the rotor is in the direction of rotation by 90 ° electrically in front of the stator coil that is most energized. A minimum of the torque arises in the direction of rotation by 90 ° electrically behind the stator coil that is most energized.

Thus, in the third step, by energizing the at least one coil strand of the stator by means of the measuring shaft, a sinusoidally changing torque / angle of rotation curve of the rotor and, by means of the sensor device, at the same time an angular position of the sensor magnet / an angular position of the rotor determined by the sensor magnet.

Subsequently, in a fourth step d) at least one pole point of a rotor magnet attached to the rotor is defined / determined which pole point, depending on the magnetization direction of the rotor magnet, is exactly at the maximum or at the minimum immediately following this maximum along the torque-rotation angle curve. The angular position of this at least one pole point is directly assigned to the angular position of the rotor detected by the sensor device. This can be done in a simple manner, since two pole points (a first pole point at the maximum and a second pole point at the minimum) of the rotor magnet attached to the rotor are located along a sinusoidal solid wave of the torque-angle of rotation curve.

In this embodiment, in a fifth step e), the correspondingly measured angular position of the pole is determined via an external computing unit and compared with the internal sensor signal of the synchronous motor, that is, the angular position of the sensor magnet / rotor detected by the sensor device, and fed or fed to a control unit of the synchronous motor .stored herein. The friction is not relevant with this method, since the external motor specifies the rotation and this is recorded by the external angle sensor, as well as torque maxima and minima arise independently of the friction and thus the pole positions can be determined.

In other words, according to the invention, the rotor position is detected via the torque applied to the rotor shaft. The torque is created by a fixed current supply to the stator coils. The rotor is driven externally at a constant speed, which results in a sinusoidal change in torque. The torque is recorded on a measuring shaft, at the same time the angle is recorded on the shaft. The rotor position and the individual pole positions are deduced from the minima and maxima of the torque curve. Due to the computer-aided evaluation of the sinusoidal torque curve and the assignment of the motor-internal sensor signal to the determined support points, the sensor-motor system is considered to be calibrated and can be put into operation.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• DE 10215428 A1 [0002]
• DE 102017128891 A1 [0003]
• DE 102016212175 A1 [0003]
• DE 102013205905 A1 [0003]
• DE 102013208986 A1 [0003]
• DE 102013211041 A1 [0003]
• DE 102013213948 A1 [0003]
• DE 102013222366 A1 [0003]
• DE 102016207241 A1 [0003]

Claims (5)

A method for calibrating a synchronous motor which has a sensor device for detecting a rotational position of its rotor, which sensor device has a plurality of sensors arranged in a stator, distributed over an inner circumference and a sensor magnet fixed to the rotor, wherein in a first step the rotor of the synchronous motor is rotationally fixed with a torque and rotation angle measuring shaft is connected, which measuring shaft is further connected to an external motor, in a second step the external motor is operated in such a way that it drives the rotor by means of the measuring shaft at a constant speed, in a third step at least one coil strand of the stator is energized , while on the one hand a sinusoidally changing torque-angle of rotation curve of the rotor by means of the torque and angle of rotation measuring shaft and, on the other hand, an angular position of the rotor by means of the sensor device, and in a fourth step at least one pole point one another Rotor magnets attached to the rotor are assigned to the angular position of the angular position of the rotor detected by the sensor device at a maximum and / or a minimum immediately following the maximum of the torque-angle of rotation curve. Procedure according to Claim 1 , characterized in that in the third step only one coil strand of the stator of the three-phase synchronous motor is energized. Procedure according to Claim 1 , characterized in that three coil strands of the stator of the three-phase synchronous motor are energized in the third step, two of the three coil strands being supplied with the same current value with the same flow direction. Method according to one of the Claims 1 to 3 , characterized in that, in the fourth step, several pole positions of several rotor magnets are assigned in their angular position to the angular position of the rotor detected by the sensor device. Method according to one of the Claims 1 to 4th , characterized in that in or after the fourth step a data record comprising the fixed assignment of the angular position of the at least one pole point to the angular position of the rotor is stored in a control unit of the synchronous motor.

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