Method and apparatus for operating an electric machine, drive arrangement

Abstract

The invention relates to a method for operating an electric machine (4), in particular a drive machine (2), having a rotor (7) which is rotatably mounted in a housing and a housing-fixed stator (5), wherein the stator (5) has multiphase drive windings (6), wherein the phases of the drive windings (6) are energized in accordance with a rated torque and a rotational angle of the rotor (7), and wherein the rotational angle of the rotor (7) is determined in at least one operating range of the electric machine (4) in accordance with an induced electric motor back electromotive force (BEMF) in the drive windings. It is proposed that the rotational angle of the rotor (7) is determined in at least one further operating range which is different from the operating range by means of signal injection (SI).

Description

Technical Field

[0001] The present invention relates to a method for operating an electric motor, particularly a drive motor, having a rotor rotatably supported in a housing and a stator fixed in the housing, wherein the stator has multi-phase drive windings, wherein phases of the drive windings are energized according to the rated torque and rotation angle of the rotor, and wherein the rotation angle of the rotor is determined according to the electric reaction force induced in the drive windings in at least one operating range of the motor.

[0002] In addition, the present invention relates to a device for operating an electric motor, particularly a drive motor, the motor having a rotor rotatably supported in a housing and a stator fixed in the housing, wherein the stator has multi-phase drive windings.

[0003] Furthermore, the present invention relates to a drive device having the aforementioned motor. Background Technology

[0004] Methods of the type mentioned at the beginning have been disclosed in the prior art. For operating a motor, especially one constructed as a perpetually excited synchronous machine, it is important to know the current rotation angle of the rotor so that the phase can be optimally energized according to the current rotation angle to generate torque. To detect the rotation angle, it is known to use position sensors based on physical effects, such as Hall effect sensors, GMR sensors, AMR sensors, or TMR sensors, which detect the rotor's rotation angle. However, these sensors require additional structural space. Furthermore, such sensors are sensitive to positional tolerances between the sensor and signal sensors (e.g., signal sensors in the form of sensor magnets) arranged on the rotor. For example, if large bearing clearances exist, such as in the case of hydrodynamic sliding bearings, such sensors often cannot determine the rotation angle accurately enough.

[0005] Furthermore, methods for determining the rotation angle without such sensors have been disclosed. In particular, a so-called anti-EMF method is used, which determines the rotation angle by utilizing the inductive electric reaction force in the drive winding, where a distinction is made between the calculated reaction force and the measured reaction force. In calculating the inductive electric reaction force, the known applied voltage at the phase and the resulting measured engine current in the phase are used to calculate the inductive electric reaction force using a mathematical model of the motor; that is, the voltage induced in the phase by at least one rotating permanent magnet of the rotor. In the second case, in the method of measuring the inductive electric reaction force, it is known that the phases of the drive winding are either switched on or off without current for a predetermined duration. Then, the voltage induced in this phase between the star contacts of the drive winding and the terminals of this phase is measured, and its zero-crossing point is determined. Based on this, information about the rotation angle is determined. However, this method requires that the star contacts of the machine be directed outwards, or that the star contacts in the electronic components be simulated using a resistor network. The latter leads to increased costs in electronic components and also takes up space on the circuit boards of controllers or power electronics. However, it remains a more commonly used method. Summary of the Invention

[0006] The method according to the invention has the advantage of ensuring improved rotation angle detection throughout the entire operating range of the motor. To this end, the invention proposes that the rotor rotation angle be obtained by means of signal injection in at least one additional operating range different from the first operating range. Signal injection, through the manipulation of the drive winding by superimposing a high-frequency voltage signal, leads to increased iron losses in the motor, resulting in a significant decrease in motor efficiency, particularly in operating ranges with low torque or low phase current. However, it is also possible, with the signal injection method, to perform the determination of the rotation angle from a stationary state or at zero speed. Therefore, by the additional application of the signal injection method, the speed can be reliably determined throughout the entire speed range of the motor. Here, the motor can be constructed not only as an inner rotor machine with a rotor rotatably supported within the stator, but also as an outer rotor machine with a stator located within a rotor rotatably supported. For example, the motor can be constructed as an actuator for movable elements (e.g., covers, doors, hydraulic or pneumatic adjustment elements, sliding sunroofs, or the like) in motor vehicles, but it can also be used as a drive motor for motor vehicles. Preferably, a method for operating an electric motor is used, which drives a pump, fan, compressor, or other components, especially those requiring speed regulation. Because this advantageous method also ensures regulated operation even at zero speed, it is also conceivable to use this method for position regulation applications.

[0007] According to a preferred extension of the invention, the operating range is distinguished based on the motor's speed, torque, and / or stator current in the motor's drive windings. This allows for a simple determination of which method for calculating the rotation angle to execute in which operating state. Here, the operating range is distinguished based on the motor's torque, stator current, and / or speed. Since the speed, torque, and / or stator current are typically known in the controller that operates the motor, the operating range can be defined with minimal additional cost.

[0008] Preferably, an operating range is selected for high speeds above a pre-defined first limit speed, and another operating range is selected for low speeds below the limit speed. This allows the rotational angle to be determined by means of inductive electro-reaction force (BEMF) when the speed is above the limit speed. Conversely, at lower speeds, including the limit speed, the rotational angle is determined by means of signal injection. This is particularly advantageous when low speeds also include the stationary state of the motor. Therefore, preferably, another operating range is selected for speeds from zero up to the limit speed. This achieves the aforementioned advantage that the current rotational angle can be reliably detected by signal injection at low speeds, and that the current rotational angle can be detected by means of inductive electro-reaction force at higher speeds, i.e., above the first limit speed, which is difficult or impossible to detect at low speeds.

[0009] Furthermore, preferably, an additional operating range is selected for high torques exceeding a predetermined limit torque, and an operating range is selected for low torques below the limit torque. As the torque decreases, the remaining losses of the motor also decrease, making the losses generated by high-frequency signal injection increasingly dominant. Therefore, it is advantageous to perform signal injection under high torque conditions. By switching to an operating range where the rotation angle is determined by inductive electromagnetic reaction force, the losses caused by signal injection are eliminated, thereby improving the efficiency of the motor at low torque.

[0010] Furthermore, it is preferable to select an operating range for high stator currents exceeding a predetermined limit stator current, and another operating range for low stator currents below the limit stator current. Typically, the stator current is related to a set torque, thus the advantages listed above regarding considering torque also apply to considering stator current. Preferably, the signal injection method is used in a stationary state or at low speeds. In motors requiring high stator currents to apply the signal injection method, it is preferable to operate within this operating range with high torque. Alternatively, even at low torques, it is preferable to set a large stator current by injecting a large proportion of the forming field current (d current).

[0011] Preferably, the electric reaction force is calculated from the point where a predetermined second limit speed of the rotor is reached or exceeded, wherein the second limit speed is higher than the first limit speed. Preferably, optionally, the electric reaction force is also calculated based on the current torque using measured conductor current and adjusted conductor voltage of the drive winding. Therefore, as the first limit speed is exceeded, the rotation angle is determined based on the induced electric reaction force. Here, it is preferable to first measure the induced electric reaction force. This provides particularly robust detection of the rotation angle; however, especially as the speed increases, a "blank period" is required, which reduces the maximum usable power of the motor and leads to an increase in the load on the intermediate circuit of the motor, which can also result in acoustic defects. If the rotor speed first exceeds the first limit speed, the rotation angle is first determined by measuring the electric reaction force induced in the drive winding. If the speed further exceeds the second limit speed, the rotation angle is determined by calculating the induced electric reaction force. If a limit speed is also determined based on the current torque, it is preferable to consider another limit speed higher than the second limit speed. When the torque is higher than a predetermined limit torque and the speed is between a second speed and another speed, the signal injection method is preferred. If the speed exceeds another limit speed above the second limit speed, the electric reaction force is calculated to determine the rotation angle, regardless of the current or required torque.

[0012] Furthermore, when the rotational speed exceeds a predetermined second limit, it is preferable to measure the inductive electric reaction force. This, as described above, ensures robust detection of the rotational angle.

[0013] According to a preferred extension of the invention, a conversion hysteresis is pre-given for exceeding and not exceeding the corresponding limiting speed and / or limiting torque. This conversion hysteresis is achieved by pre-given two different values ​​for the limiting speed and limiting torque, wherein switching between, for example, a first operating range and a second operating range occurs only when the higher of the two values ​​is exceeded but the lower of the two values ​​is not exceeded.

[0014] A key feature of the device according to the invention is that the controller is specifically configured to execute the method according to the invention during normal use. This results in the advantages already mentioned.

[0015] The key feature of the drive device according to the invention is the device according to the invention. This also leads to the advantages already mentioned. Attached Figure Description

[0016] The invention will be described in more detail below with reference to the accompanying drawings. For this purpose, it is shown that:

[0017] Figure 1 A simplified top view of a motor vehicle, and

[0018] Figure 2 A graph used to illustrate advantageous methods for using motors to operate motor vehicles. Detailed Implementation

[0019] Figure 1 A simplified schematic diagram of a motor vehicle 1 is shown, which has a motor 4 serving as a drive unit 2. This drive unit is either directly coupled to or coupled to the drive wheels 3 of the motor vehicle via a transmission. The motor 4 has a housing-fixed stator 5 and a rotor 7. The stator has, in particular, multi-phase drive windings 6. The rotor is arranged coaxially with the stator 5 and is supported in a rotatable manner. Furthermore, the motor 4 is equipped with a controller 8, which includes power electronics 9 by means of which the phases of the drive windings 6 are controlled.

[0020] Power electronics 9 is connected to an energy storage device 10 via a controller 8. This energy storage device provides the electrical energy necessary for operating the motor 4 and, if necessary—if the motor 4 can also operate in a generator-generating manner—receives electrical energy. During motor operation, the controller 8 manipulates the power electronics 9 to energize, in particular, three phases of the drive windings 6 of the motor 4, thereby loading the rotor 7 with a pre-given torque. The motor 4 is, in particular, an electrically commutated / electronically commutated motor, wherein the phases are controlled according to the current rotation angle of the rotor 7. During operation, the rotation angle is continuously determined by the controller 8. For this purpose, the controller 8 specifically performs… Figure 2 The method is simplified as shown in the figure.

[0021] Figure 2The torque T of motor 4 is shown in the graph of rotational speed n. Here, a typical maximum torque curve for the motor is also shown, in which the motor has maximum torque at low speeds, decreasing as speed increases. According to this method, the rotation angle of rotor 7 is determined sensorlessly. In principle, sensorless methods are known, in which the induced electric reaction force in the drive winding is considered, because the rotor position and thus the rotation angle are directly derived from the direction of the voltage vector (Spannungszeiger) belonging to the reaction force. Here, a distinction is made between calculated and measured induced electric reaction forces. In the first case, the reaction force, i.e., the voltage induced in the drive winding 6 by the rotating permanent magnet or in the phase of the drive winding 6, is calculated using a mathematical model of motor 4 from the known applied voltage and measured engine current. In the second case, the phase of drive winding 6 is either switched on or off without current for a predetermined duration. Then, if the phases are connected to each other at the star contacts, the induced voltage between the star contacts and the terminals of that phase is measured, and its zero-crossing point is determined. It is also possible to simultaneously connect all three phases without current, so that the rotation angle can then be calculated directly from the three measured phase voltages. Here, it is not necessary to measure the star contact potential.

[0022] Furthermore, the rotation angle can be determined without sensors using a signal injection method. This method utilizes the anisotropy of motor 4, specifically the difference in inductance in the rotor direction and transverse to rotor 7, to estimate the rotation angle. For this purpose, a high-frequency voltage signal is superimposed by the controller onto the phase of the drive winding that has been manipulated to drive the motor. This leads to increased iron losses in the motor, which significantly reduces the efficiency of motor 4, especially in operating ranges with low torque or low phase current. Here, in the current case, the signal injection method is executed from a stationary state to determine the rotation angle.

[0023] like Figure 2 As shown, under the current circumstances, depending on the current operating range of motor 4, and especially based on stator current, torque, and / or speed, controller 8 switches between signal injection method SI and method based on inductive electric reaction force. Here, in particular, it is also based on speed that the inductive electric reaction force is calculated (BEMF-C) or measured (BEMF-M).

[0024] Here, in the current situation, it is proposed that if the current rotational speed is lower than the pre-defined limit rotational speed n... G1 Then, the signal injection method is executed. Furthermore, if the current rotational speed is at the limit speed n... G1 With another limiting speed n G2 Between and above the limit torque TG Then, the signal injection method is executed. If the current torque is lower than the limit torque T... G And the speed is above the limit speed n G1 Within the specified speed range, operation is first activated using the measured inductive electric reaction force (BEMF-M). If the speed n is further increased, thus exceeding the second limit speed n... G3 According to this embodiment, the second limiting speed is higher than the limiting speed n. G1 And less than the limiting speed n G2 Then, the process switches to: determining the rotor's rotation angle using calculated induced electro-reaction force (BEMF-C). This occurs after exceeding the limiting speed n. G2 Regardless of the set torque, the inductive electric reaction force is obtained by calculating the inductive electromagnetic reaction force (BEMF-C).

[0025] The advantageous method has the following benefits: the rotation angle can be determined from the stationary state of the rotor 7, and thus the regulated dynamic operation of the motor 4 associated with high stator current and / or torque can be achieved. In this case, the additional losses caused by high-frequency injection play a secondary role compared to other losses. If, for example, the torque required to operate the motor 4 stationary under low load is reduced, the other losses also decrease, and the losses caused by high-frequency injection become increasingly dominant. By switching to determining the rotation angle by means of inductive electromagnetic reaction force, these losses caused by high-frequency injection are eliminated and the efficiency of the entire system increases. If the rotation angle can only be determined by high-frequency excitation of the motor 4 from a certain height of stator current, operation can be guaranteed across the entire current range by switching between the methods.

[0026] In addition to stator current and torque, such as Figure 2 As shown, rotational speed can also be used as a standard for switching. In a stationary state and / or at low speeds, a signal injection method is used. For motors requiring high stator current to perform the signal injection method, this range is traversed with high torque. Alternatively, even at low torque, a large stator current can be set by injecting a large proportion of the forming field current.

[0027] Advantageously, a flux estimator or a linear or nonlinear observer method can be used when calculating the inductive electric reaction force. This avoids the blanking period required for measurement and the resulting drawbacks, such as increased load on the intermediate loop or decreased torque. In principle, the signal injection method can also be applied at high speeds. However, this requires maintaining a certain voltage reserve, which reduces the maximum possible torque of motor 4 at high speeds.

[0028] When switching between operating ranges SI, BEMF-M, and BEMF-C, the currently estimated or calculated rotation angle is passed to the next method so that it can be used to correctly initialize the integrator, delay circuit, etc. To obtain the values ​​required for initialization, the rotation angle is calculated using other parameters (such as current or voltage) based on the mathematical model of motor 4, if necessary.

[0029] This embodiment describes the use of motor 4 as a drive unit for motor vehicle 1. However, according to another embodiment (not shown here), motor 4 is proposed to be used as a drive unit or actuator, for example, for hydraulic or pneumatic adjustment elements, sliding window glass, or a sliding sunroof of a motor vehicle, or for other applications, and is also used outside of motor vehicle manufacturing. In particular, the method for operating motor 4 described above is especially applicable to motor 4 used as a speed-regulating drive unit, for example, as a drive unit for a pump, fan, compressor, or the like.

Claims

1. A method for operating an electric motor (4), said motor having a rotor (7) rotatably supported in a housing and a stator (5) fixed to the housing, wherein, The stator (5) has a multi-phase drive winding (6), wherein phases of the drive winding (6) are energized according to the rated torque and rotation angle of the rotor (7), and wherein the rotation angle of the rotor (7) is determined according to the induced electro-reaction force (BEMF) in the drive winding in at least one operating range of the motor (4), characterized in that the rotation angle of the rotor (7) is determined by means of signal injection (SI) in at least one additional operating range different from the first operating range. Wherein, if the current rotational speed is lower than the first predetermined limit rotational speed n G1 Then execute the signal injection method; if the current rotational speed is at the first limit rotational speed n... G1 With another limiting speed n G2 Between and above the limit torque (T) G If so, the signal injection method will be executed. If the current torque is lower than the limit torque (T) G And the rotational speed is higher than the first limit speed n. G1 Within the specified speed range, operation is first switched on using the measured inductive electric reaction force (BEMF-M). If the current torque is lower than the limit torque (T) G ), from reaching or exceeding the predetermined second limit speed (n) of the rotor (7) G3 ) to calculate the electric reaction force (BEMF-C), where the second limiting speed (n G3 ) higher than the first limiting speed (n) G1 ).

2. The method according to claim 1, characterized in that, The operating range is distinguished based on the rotational speed (n) of the motor (4), the torque (T) of the motor (4), and / or the stator current in the drive winding (6) of the motor (4).

3. The method according to claim 1, characterized in that, For a speed higher than the first predetermined limit speed n G1 The high-speed selection is a certain operating range, which is within the first limiting speed n. G1 The following low-speed options are available in different operating ranges.

4. The method according to claim 1, characterized in that, For a torque higher than the predetermined limit torque (T) G For high torque, select an additional operating range, for the limit torque (T) G The following low torque selection is available in the operating range.

5. The method according to claim 1, characterized in that, For high stator currents exceeding a predetermined limit stator current, an additional operating range is selected; for low stator currents below the predetermined limit stator current, an operating range is selected.

6. The method according to claim 1, characterized in that, When the pre-given second limit speed n is exceeded G3 At that time, the electro-reaction force described in (BEMF-M) is measured.

7. The method according to claim 1, characterized in that, These represent exceeding and not exceeding the corresponding limit speed and / or limit torque (T), respectively. G Pre-defined conversion lag.

8. The method according to claim 1, characterized in that, The motor (4) is a drive unit (2).

9. A device for operating an electric motor (4), said motor having a rotor (7) rotatably supported in a housing and a stator (5) fixed to the housing, wherein, The stator (5) has multiphase drive windings and is characterized by a controller (8) specifically arranged to perform the method according to any one of claims 1 to 8 during normal use.

10. A drive unit having a motor (4) having a rotor (7) rotatably supported in a housing and a stator (5) fixed to the housing, wherein, The stator (5) has a multiphase drive winding (6), characterized in that the device is according to claim 9.

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