WO2011006742A1

WO2011006742A1 - Electronically commutated electric motor having rotor position capturing and method

Info

Publication number: WO2011006742A1
Application number: PCT/EP2010/058803
Authority: WO
Inventors: David Fricker
Original assignee: Robert Bosch Gmbh
Priority date: 2009-07-13
Filing date: 2010-06-22
Publication date: 2011-01-20
Also published as: DE102009027662A1

Abstract

The invention relates to an electronically commutated electric motor having a stator and a rotor particularly designed as a permanent magnet. The rotor position capturing device is designed for determining the rotor position as a function of a voltage induced in at least one stator winding of the stator. According to the invention, the electronically commutated electric motor comprises a rotor position capturing device. The rotor position capturing device is implemented for capturing a rotor position of the rotor and generating a rotor position signal representing a rotor position of the rotor.

Description

description

title

Electronically commutated electric motor with rotor position detection and processQ

State of the art

The invention relates to an electronically commutated electric motor with a

Stator and a particular permanent magnetic trained rotor.

From DE 698 23 494 T2, an electronically commutated electric motor is known, wherein in the electronically commutated electric motor, a rotor position of the rotor can be detected as a function of a voltage induced in the stator coils of the electric motor.

Disclosure of the invention

According to the invention, the electronically commutated electric motor of the type mentioned in the introduction with a stator and with a rotor which is in particular designed to be permanent magnetic, preferably has a rotor position detection device. The rotor position detection device is designed to detect a rotor position of the rotor and to generate a rotor position signal, which represents a rotor position of the rotor.

The rotor position detection device may for example be part of a control unit of the electric motor. The control unit may, for example, generate control signals for generating a rotating magnetic field and output these via a power output stage to the stator and thus generate the rotating magnetic field by means of the stator.

The rotor position detection device is preferably designed to determine the rotor position as a function of a voltage induced in at least one stator coil of the stator. As a result, advantageously a rotor position sensor, for example a Hall sensor can be saved.

The electronically commutated electric motor, preferably the control unit of the electric motor, particularly preferably the rotor position detection device of the electric motor, is designed to detect at least one stator coil current and to detect the current position of the stator coil. at least one stator coil of the stator induced voltage as a function of a time derivative of the at least one Statorspulenstromes to determine.

By virtue of the detection thus formed, in particular determination of the induced voltage as a function of the time derivative of the stator coil current, it is advantageously possible to energize the stator coils, and thus not only during a non-energized state of a stator coil, by means of the rotor magnetic field, for example in the form of a counter-electromotive force (back EMF) generated induced voltage to determine the rotor position are used. Further advantageously, the rotor position can be detected continuously during a whole rotor revolution. Further advantageously, a signal can be continuously available over the rotor circulation, from which the rotor position of the rotor can be determined.

In a preferred embodiment of the electric motor, the rotor position detection device is designed to use the time derivative of the stator coil current for determining the rotor position at a time at which a Statorspulenspannung switched to the stator coil is sufficiently small or equal to zero.

More preferably, the rotor position detection device is designed to use the inductance of the at least one stator coil for determining the rotor position. By using the time derivative of the stator coil current to a

When the stator coil voltage across the stator coil is sufficiently low or equal to zero, the induced voltage generated in the stator coil can preferably only be determined as a function of the time derivative of the stator coil current, more preferably additionally as a function of the stator coil inductance.

In a preferred embodiment, the rotor position sensing device is configured to use a time derivative of the stator coil current to determine the rotor position at a first instant in which a positive stator coil voltage is connected to the stator coil and a derivative of the stator coil current to determine the rotor position to a second Use the time at which a negative stator coil voltage is connected to the stator coil, in particular to the positive Satatorspulenspannung reversed. More preferably, the rotor position detection device is designed, the inductive cient voltage as a function of the time derivative of the stator coil current at the first time and at the second time to determine.

In another embodiment, the electric motor is designed to detect a DC link current instead of a stator coil current and to determine the induced voltage as a function of the DC link current.

The voltage induced in the stator coil is then calculated as follows for a stator coil string:

(1) U = RI + L-dI / dt + U _Ind

The power output stage can, for example, have an H-bridge for each stator coil. The power output stage is preferably designed to switch at least or exactly three mutually different stator coil voltages to the stator coil, a supply voltage, a supply voltage directed inversely to the supply voltage or a zero voltage, which is preferably centered between the supply voltage and the supply voltage directed inversely thereto. This results in the following equations:

(2) U _dc = RI _pos + L-dI _pos / dt + U _Ind

(3) -U _dc = RI _neg + L-dI _neg / dt + U _lnd

Mean in it

U, _nd = Induced voltage,

R = ohmic resistance of the stator coil,

L = inductance of the stator coil,

Ip _os = current through the stator coil, positive,

l _neg = current through the stator coil, negative,

U _dc = supply voltage.

In the case of a connection of a zero voltage to the stator coil, the calculated

Induced voltage from:

(4) o = RI _o + L- ^ + U _Ind , and thus

dt

(5) ^U ' _nä = -RhL ^ The above-described determination of the induced voltage as a function of the positive and depending on the negative operating voltage can be carried out, for example, as follows:

(6) ^R. I _{p∞ + L} - ^ + U " _d = -R ^. I _mi -L - ^ - U _I ""

The invention also relates to a method for determining a rotor position of a rotor of an electronically commutated electric motor. The electronically commutated electric motor has a stator and the aforementioned rotor. In the method, the rotor position is determined as a function of a voltage induced in at least one stator coil. The induced voltage is preferably the counter-electromotive force (back EMF) caused by the rotor magnetic field.

In the method according to the invention, at least one stator coil current of a stator coil of the stator is detected and the voltage induced in the at least one stator coil is determined as a function of a time derivative of the at least one detected stator coil current. As a result, a time-continuous detection result of the induced voltage for determining the rotor position can advantageously be available over a rotor circulation.

Preferably, in the method, the time derivative of the stator coil current is used for determining the rotor position at a time at which an operating voltage across the stator coil is low or equal to zero. This can cause the induced

Voltage advantageously take place using a small number of measured variables. A measured variable is a current in this exemplary embodiment. Further embodiments of measured variables are voltages, resistance values, inductance values, or time-variable electrical variables.

Preferably, in the method for determining the rotor position, an inductance of the at least one stator coil is used. The calculation of the induced voltage can then advantageously be calculated according to the formulas described above. In the method, a time derivation of the stator coil current is preferably used to determine the rotor position at a first instant in which the stator coil voltage switched to the stator coil, for example, the stator coil operating voltage, is positive. More preferably, in the method, a time derivation of the stator coil current is used to determine the rotor position at a second time, in which the stator coil voltage switched to the stator coil voltage is negative. The voltage induced in the stator coil is preferably determined as a function of the time derivative of the stator coil current at the first time and at the second time.

The values of the stator coil currents at the first and second times can, for example, in each case be kept in a buffer as a basis for calculating the further formation of the time derivative.

Further embodiments will become apparent from the dependent claims and from the features described in the following description of the figures, which in each case can be combined to achieve the effect of the invention.

The invention will now be described below with reference to figures and further embodiments.

Figure 1 shows an embodiment of an electronically commutated electric motor with a rotor position detection in response to a determined over a time derivative of a stator coil, induced in the stator coil voltage;

Figure 2 shows waveforms of voltage, current and differentiated current for a stator coil according to equations (5) and (6a) already mentioned;

FIG. 3 shows a method for detecting a rotor position as a function of a differentiated rotor coil current.

FIG. 1 shows an exemplary embodiment of an electronically commutated electric motor 1. The electric motor 1 has a stator 3 and a permanent magnet rotor 5. The stator 3 has three stator coils, namely a stator coil 7, a stator coil 9 and a stator coil 11.

The electric motor 1 also has a power output stage 12, wherein the power output stage 12 is connected on the input side via a connection 60 to a control unit 14, hereinafter also referred to as the processing unit 14. The control unit 14 can be formed, for example, by a microprocessor, a microcontroller or a field-programmable gate array (FPGA). The output stage 12 is connected on the output side via a current sensor 17 to the stator coils 7, 9 and 11. The power output stage 12 has in this embodiment in B6 circuit GE switched on power transistors. The power output stage 12 thus has 6 power transistors, in this case metal-insulator-semiconductor field-effect transistors (MIS-FET or MOS-FET), namely the transistors 20, 22, 24, 26, 28 and 30.

The source terminal of the transistor 22 is connected to the drain terminal of the transistor 20 via a connection node 38, the source terminal of the transistor 26 is connected via a connection node 36 to the drain terminal of the transistor 24, a source terminal of the transistor 30 is connected via a connection node 34 with a drain terminal of Transistor 28 connected. The source terminals of the transistors 20, 24 and 28 are each connected to a ground potential-carrying connection node 44. The drain terminals of the transistors

22, 26, and 30 are connected to a positive potential terminal 42, respectively.

The plus potential corresponds to the previously mentioned positive operating voltage, the ground potential corresponds to the negative operating voltage.

The terminals 42 and 44 are each via a current sensor 18 with a vehicle electrical system

16 connected. The electrical system can be, for example, a vehicle electrical system of a motor vehicle.

The control terminals, in particular gate terminals of the transistors 20, 22, 24, 26, 28 and 30 are each connected to the processing unit 14 via the multi-channel connection 60. The connection lines of the control terminals of the transistors

28 and 30 are shown in dashed lines. The processing unit 14 may be formed for example by a microprocessor, a microcontroller, a Field Programmable Gate Array (FPGA), or via an analog or digital signal processing circuit. The processing unit 14 may be part of a control unit of the electric motor 1, for example.

The connection node 34 is connected via the current sensor 17 to the first terminal of the stator coil 7. The connection node 36 is connected via the current sensor 17 to a first terminal of the stator coil 9. The connection node 38 is connected via the current sensor 17 to a first terminal of the stator coil 1 1. The second terminals of the stator coils 7, 9 and 11 are each connected to a star point terminal 40. It is conceivable - instead of the star connection of the stator coils 7, 9, and 1 1 - also a delta connection of the stator coils 7, 9, and 1 1. The power transistors 30 and 28 may each have the plus potential or the ground potential. potential via the connection node 34 and the current sensor 17 to the stator coil 7 switch. The transistors 24 and 26 can switch the plus potential or the ground potential via the connection node 36 and the current sensor 17 to the stator coil 9. The transistors 20 and 22 can switch the plus potential or the ground potential via the current sensor 17 to the stator coil 11. The current sensor 17 is designed to detect the stator coil current of the stator coil 7, the stator coil current of the stator coil 1 and the stator coil current of the stator coil 1 1 -in each case independently of one another-in particular by means of shunt resistors, and via the multi-channel connecting line 61, in particular in the form of a voltage dropping across the shunt resistors to output a current signal representative of the stator coil currents. The current sensor 17 is connected to the processing unit 14 via the multi-channel connection 61. The current sensor 17 may, unlike in this embodiment shown in dashed lines instead of shunt resistors, for example, comprise inductive current sensors, which are each designed to generate the current signal.

The current sensor 18 is connected on the output side via connecting lines 58 and 59 to the processing unit 14. The connecting lines 58 and 59 take a drop across the measuring resistor 19 voltage. The measuring resistor 19 is an example of part of the current sensor 18 and, for example, a shunt resistor. The measuring resistor 19 is in this embodiment in the plus

Arranged wire, conceivable is also an arrangement in the ground line or a detection with two measuring resistors in both lines. For example, instead of the measuring resistor 19, the current sensor 18 can inductively detect the current flowing through the current sensor 18 and generate an output signal corresponding to the current. The processing unit 14 is connected on the input side to the ground potential thus connection 44 via a connecting line 57. The processing unit 14 can thus detect the current flowing from the electrical system 16 via the current sensor 18 to the power output stage 12, in particular the intermediate circuit current. The current sensor 17 is designed to detect the currents of the stator coils 7, 9 and 11 independently of one another. The processing unit 14 is designed to receive the currents detected by the current sensors 18 and / or 17 on the input side and to temporally differentiate the currents received on the input side and to provide the differentiation result thus formed for further arithmetic operations, for example by means of a buffer. The processing unit 14 For example, it is designed to calculate the voltages induced in the stator coils 7, 9 and 11 according to the previously mentioned formulas (5) and / or (6a).

The processing unit 14 is further configured to use the induced in the stator coils 7, 9 and 1 1 voltage to determine the rotor position of the rotor 5 and so the rotor position of the rotor 5 in dependence of the induced voltage and thus also in dependence of the time derivative of the current determine. To determine the rotor position of the rotor 5, the processing unit 14 may, for example, form the argument of the complex space vector of the induced voltage. The argument of the complex space vector of the induced voltage corresponds to the angle of the complex space vector in polar coordinates. The processing unit 14 may, for example, for determining the argument of the complex space vector of the induced voltage, use a CORDIC method, a PLL (Phase Locked Loop) method or another particularly analogous method for determining the space vector's argument. The processing unit in this embodiment comprises a rotor position detection unit 15 configured to perform part or all of the above-mentioned arithmetic operations for determining the rotor position and to generate a rotor position signal representing the rotor position. The processing unit 14 can control the power output stage 12 and the stator 3 for generating the magnetic rotary field as a function of the rotor position signal.

The current sensors are arranged in this embodiment to detect the currents through the stator coils, or one of the power output stage 12 supplied total current. Also conceivable is a current detection for at least one, preferably for each of the transistors 20, 22, 24, 26, 28 and 30. Also conceivable is a current detection of DC link currents, or a common DC circuit current in the case of an H-circuit. It is conceivable that the power output stage 12 has an H circuit for each of the stator coils.

Independently or depending on the above-described rotor position detection, an electronically commutated electric motor may have at least one stator coil, preferably two stator coils, more preferably three stator coils. The stator coils are each connected to an H-circuit of a power output stage. The electronically commutated electric motor thus controlled by means of H circuits can preferably be advantageously contained for driving a fan, for example a cooling fan in a motor vehicle. Further advantageous possibilities for forming a Electric drives are a fan for air conditioning of a motor vehicle or a power steering of a motor vehicle.

An H circuit of a power output stage comprises two transistor half bridges, wherein an output of a first transistor half-bridge with a first terminal of a stator coil and an output of a second half-bridge with a second terminal of

Stator coil can be connected.

For an electric motor with two stator coils, the space vector of the induced voltages can be calculated as follows:

U ind ges ⁼ ^ ind A + ^{l '} ^ ind B In this mean

U, _nd _g _es = space vector induced voltage of all stator coils

U, _nd _ _A = space vector induced voltage coil A, real part

U _ιnC ι_ _B = space vector induced voltage coil B, imaginary part

In an electric motor with a stator connected in B6 circuit with three stator coils U, V and W, three complex space vectors of combinations of the coil strands can be formed as follows:

U _ιndJ = U _{and U} + (ILd (VIIW),

U _lnd _ ₂ = U _lnd _ _V + (U, _nd (W || U),

U = U _l nd_3 nd_W _l + (U _l nd (U || v)

U _md (U || V) means, for example, induced voltage of a parallel circuit of

Coils U and V.

A complex space vector of all induced voltages can be calculated as follows:

^U ^T jmd_ge _S - e ^e '° - U ^U md _l + ⁺ e ^e ' ^{2π / 3} - U ^U md_ 2 + ⁺ e ^e ' ^{4π / 3} - U ^U ind _3 ^■ FIG. 2 shows an exemplary embodiment of one possible embodiment Voltage and a possible associated current waveform of a current through a stator coil of the electronically commutated electric motor described in Figure 1. Shown is a diagram with an abscissa 82 and an ordinate 70. The abscissa 82 corresponds to a time axis, the ordinate 70 corresponds to a Statorspulenspannung, for example, the switched from the power amplifier 12 to one of the stator coils 7, 9, or 1 1 Sta- torspulenspannung. The diagram with the ordinate 70 is subordinated to a diagram which shows a current profile of a stator coil current through the stator coil.

The diagram with the current waveform 1 12 has an ordinate 72, which represents the current of the current waveform 1 12.

The diagram with the current waveform 1 12 is a subordinate diagram, which has a curve 1 14. The curve 1 14 represents a differentiated current profile of the current waveform 1 12.

The diagram with the differentiated current profile 1 14 has an abscissa 86, which represents a time profile, and an ordinate 74, which represents the differentiated one

Current represents, up. Shown are also time sections 90, 92 and 94, which extend over all three diagrams with the curves 1 10, 1 12 and 1 14. The period 90 represents a period in which the voltage applied to the stator coil such as the stator coil 7, 9 or 11 is positive. The positive voltage causes - as can be seen from the curve of the stator coil current 1 12 - an increase in the stator coil current through the stator coil. The time derivative of the stator coil current in the time interval 90 shows the curve 1 14 in the period 90. The curve 1 14 of the time derivative of the current corresponds in the time portion 90 of a straight line.

During the period 92, the power output stage 12 switches a negative voltage to the stator coil. The voltage curve is shown corresponding to the time section 92. The current profile 1 12 shows in the period 92 - corresponding to the voltage curve - a linear drop.

The curve 1 14 shows during the period 92 a constant course. During the period 94, the power output stage 12 does not switch any potential

Connections 40 or 44 to the stator coil. The current flow 1 12 increases during this period of time. The time derivative of the current waveform 1 12 in the period 94 is represented by the curves course 1 14 in the period 94 accordingly.

Shown are also three diagrams, namely a diagram with a voltage curve 1 16, a voltage waveform 1 16 corresponding current waveform 1 18, wherein the current waveform 1 18 a DC link current, for example, detected by the current sensor 18 shown in Figure 1, can represent. Shown is also a waveform 120, which represents a time derivative of the current waveform 1 18 of the DC link current. Shown are also time sections 96 and 98, which each extend through the curves of the curves 1 16, 1 18 and 120. It can be seen that during the time interval 96, when a positive potential, for example the potential of the terminal 42, is switched to a stator coil, the DC link current 18 increases accordingly. During the period 98, in which the potential of the terminal 44 is switched by means of the power output stage 12 to the stator coil, the DC link current 18 1 takes a negative value and increases.

Figure 3 shows an embodiment of a method for detecting a rotor position of a rotor of an electronically commutated electric motor with a stator and the rotor. In a method step 100, at least one stator coil current of a stator coil of the stator is detected at a point in time during which a zero voltage is applied to the stator coil. In a subsequent method step 102, a time derivative of the detected stator coil current is formed. In a method step 104, a voltage induced in the at least one stator coil is determined as a function of the time derivative of the at least one detected stator coil current-in particular by multiplying the time derivative of the stator coil current by a stator coil inductance of the stator coil. In a method step 106, a rotor position of the rotor is determined as a function of the determined induced voltage.

A magnetic rotating field for rotational movement of the rotor can - in a further, not shown, process step - are advantageously generated in dependence on the determined induced voltage.

Claims

claims

1. Electronically commutated electric motor (1) with a stator (3) and with a particular permanent magnetic rotor (5), wherein the electric motor (1) has a rotor position detecting device (14, 15) which is formed, a rotor position of the rotor (5), and to generate a rotor position signal representing a rotor position of the rotor (5), wherein the rotor position detecting device (14, 15) is formed, the rotor position in response to a in at least one stator coil (7, 9 , 1 1) to determine induced voltage

characterized in that

the rotor position detection device (14, 15) is designed to detect at least one stator coil current (1 12, 1 18) and to determine the voltage induced in at least one stator coil (7, 9, 11) of the stator as a function of a time derivative ( 1 14, 120) of the at least one Statorspulenstromes (1 12, 1 18) to determine.

2. Electric motor (1) according to claim 1,

characterized in that

the rotor position detection device (14, 15) is adapted to use the time derivative (1 14) of the stator coil current (1 12) to determine the rotor position at a time (94) at which a stator coil voltage switched to the stator coil is sufficiently small or equal Is zero.

3. Electric motor (1) according to claim 2,

characterized in that

the rotor position detection device (14, 15) is designed to use the inductance of the at least one stator coil (7, 9, 11) to determine the rotor position.

4. Electric motor (1) according to one of the preceding claims,

characterized in that the rotor position detecting device (14, 15) is formed,

a time derivative (120) of the stator coil current (1 18) for determining the rotor position at a first time (96), in which the on Stator coil switched stator coil voltage is positive and a derivative (120) of the stator coil current (1 18) for determining the rotor position at a second time (98) to use, in which the stator coil switched to the stator coil voltage, in particular to the positive stator coil voltage is negative, and the induced voltage as a function of the time derivative of the stator coil current at the first time (96) and the second time (98) to determine.

5. Method (100, 102, 104, 106) for determining a rotor position of a rotor (5) of an electronically commutated electric motor (1) with a stator (3) and the rotor (5), in which the rotor position in dependence on at least a stator coil (7, 9, 1 1) induced voltage is determined (106),

characterized in that

at least one Statorspulenstrom (1 12) of a stator coil (7, 9, 1 1) is detected and in the at least one stator coil (7, 9, 1 1) induced voltage as a function of a time derivative (1 14) of the at least one detected

Stator coil current (1 12) is determined (104).

6. The method according to claim 5,

characterized in that

the time derivative (1 14) of the stator coil current (1 12) for determining the rotor position at a time (94), in which a Statorspulenspannung (1 10) over the stator coil (7, 9, 1 1) is low or equal to zero.

7. The method according to claim 6,

characterized in that

an inductance of the at least one stator coil (7, 9, 11) is used to determine the rotor position.

8. The method according to any one of claims 5 to 7,

characterized in that

a time derivative (120) of the stator coil current (1 18) is used for determining the rotor position at a first time (96), in which a Statorspulenspannung (1 10) connected to the stator coil (7, 9, 1 1) is positive, and a time derivative (120) of the stator coil current for determining the rotor position at a second time (98) is used, in which a to the stator coil (7, 9, 1 1) switched stator coil voltage (1 10) is negative, and the voltage induced in the stator coil as a function of the time derivative (120) of the stator coil current (1 18) at the first time (96) and the second Time (98) is determined.