DE102009027662A1 - Electronically commutated electric motor with rotor position detection and method - Google Patents

Abstract

The invention relates to an electronically commutated electric motor with a stator and a rotor, in particular a permanent magnet. The rotor position detection device is designed to determine the rotor position as a function of a voltage induced in at least one stator coil of the stator. According to the invention, the electronically commutated electric motor 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.

Description

State of the art

The The invention relates to an electronically commutated electric motor with a stator and a particular permanent magnetic trained Rotor.

From the 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 aforementioned Type with a stator and with a particular permanent magnetic formed rotor preferably a rotor position detecting device on. The rotor position detecting device is formed, a Rotor position of the rotor to capture and a rotor position signal to generate, which represents a rotor position of the rotor.

The Rotor position detecting device may for example be part be a control unit of the electric motor. The control unit can For example, control signals for generating a rotating magnetic field generate, and this via a power output stage to the Output stator and so by means of the stator, the magnetic rotating field produce.

The Rotor position detection device is preferably formed the rotor position as a function of one in at least one Stator coil of the stator induced voltage to determine. Thereby may advantageously be a rotor position sensor, such as a Hall sensor be saved.

Of the electronically commutated electric motor, preferably the control unit of the electric motor, particularly preferably the rotor position detecting device the electric motor is formed, at least one Statorspulenstrom to detect and in at least one stator coil of the stator induced voltage as a function of a time derivative to determine the at least one stator coil current.

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

In a preferred embodiment of the electric motor the rotor position detecting device formed, the temporal Derivation of the stator coil current for determining the rotor position at a time when one on the stator coil switched stator coil voltage is sufficiently small or equal to zero is.

Further Preferably, the rotor position detection device is formed, the inductance of the at least one stator coil for determining the rotor position.

By drawing on the time derivative of the stator coil current at a time when the stator coil voltage exceeds the stator coil is sufficiently small or equal to zero, the induced voltage generated in the stator coil preferably only in Dependence of the time derivative of the stator coil current, more preferably additionally depending on Stator coil inductance can be determined.

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 Time to use, in which a - in particular the positive Satatorspulenspannung reversed - negative Statorspu lens voltage is connected to the stator coil. More preferably, the rotor position detection device is designed to determine the induced voltage as a function of the time derivative of the stator coil current at the first time and at the second time.

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

The voltage induced in the stator coil is then calculated as follows for a stator coil string: U = R * I + L * dI / dt + U _Ind (1)

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 in the middle between the supply voltage and the supply voltage directed inversely thereto. This results in the following equations: U _dc = R * I _pos + L * dI _pos / dt + U _Ind (2) - U _dc = R · I _neg + L · dI _neg / dt + U _Ind (3)

U_ind

= Induzierte Spannung,

R

= Ohmscher Widerstand der Statorspule,

L

= Induktivität der Statorspule,

I_pos

= Strom durch die Statorspule, positiv,

I_neg

= Strom durch die Statorspule, negativ,

U_dc

= Versorgungsspannung.

Mean in it

U _ind

= Induced voltage,

R

= Ohmic resistance of the stator coil,

L

= Inductance of the stator coil,

I _pos

= Current through the stator coil, positive,

I _neg

= Current through the stator coil, negative,

U _dc

= Supply voltage.

If a zero voltage is applied to the stator coil, the induced voltage is calculated as follows:

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:

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

According to the invention, in the method 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. This can be advantageous over - a rotor circulation away - time-continuous detection result of the induced voltage for determining the rotor position are available.

Prefers In the method, the time derivative of the stator coil current used to determine the rotor position at a time, in which an operating voltage across the stator coil low or is equal to zero. As a result, the induced voltage can be advantageous using a small number of measured variables respectively. A measured variable is in this embodiment a stream. Further embodiments of measured variables are voltages, resistance values, inductance values, or time-varying electrical quantities.

Prefers becomes an inductance in the method of determining the rotor position the at least one stator coil used. The calculation of induced voltage can then be advantageous according to the advance calculated formulas are calculated. Preferred is in the process a time derivative of the stator coil current for determining the Rotor position used at a first time, in which the Statorspulenspannung switched on the stator coil, for example the operating voltage is positive. Further preferred is in the Method is a time derivative of the stator coil current for determining the rotor position used at a second time, in which the stator coil voltage switched to the stator coil negative is. The voltage induced in the stator coil is preferred Dependence of the time derivative of the stator coil current determined at the first time and at the second time.

The Values of the stator coil currents at the first and second times for example, each in a cache as a basis for calculating the further formation of the time derivative be kept in stock.

Further Embodiments emerge from the dependent Claims and from the in the following description of the figures described features, each for achieving the effect of the invention can be combined.

The Invention will now be described below with reference to figures and others Embodiments described.

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

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

3 shows a method for detecting a rotor position in response to a differentiated rotor coil current.

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

The electric motor 1 also has a power output stage 12 on, where the power output stage 12 on the input side via a connection 60 with a control unit 14 connected, hereinafter also processing unit 14 called. The control unit 14 may for example be formed by a microprocessor, a microcontroller or a Field Programmable Gate Array (FPGA). The power output stage 12 is output side via a current sensor 17 with the stator coils 7 . 9 and 11 connected. The power output stage 12 has power transistors connected in B6 circuit in this embodiment. 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 on.

The source terminal of the transistor 22 is connected to the drain terminal of the transistor 20 via a connection node 38 connected, the source terminal of the transistor 26 is via a connection node 36 with the drain terminal of the transistor 24 connected, a source terminal of the transistor 30 is via a connection node 34 with a drain terminal of the transistor 28 connected. The source connections of the transistors 20 . 24 and 28 are each connected to a ground potential connecting node 44 connected. The drain terminals of the transistors 22 . 26 and 30 are each leading to a plus potential the connection 42 connected.

The Plus potential corresponds to the positive one mentioned above Operating voltage, the ground potential corresponds to the negative operating voltage.

The connections 42 and 44 are each via a current sensor 18 with a wiring 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 via the multi-channel connection 60 with the processing unit 14 connected. 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 can for example be part of a control unit of the electric motor 1 be.

The connection node 34 is about the current sensor 17 with the first connection of the stator coil 7 connected. The connection node 36 is about the current sensor 17 with a first connection of the stator coil 9 connected. The connection node 38 is about the current sensor 17 with a first connection of the stator coil 11 connected. The second connections of the stator coils 7 . 9 and 11 are each with a Stempunktanschluss 40 connected. It is conceivable - instead of the star connection of the stator coils 7 . 9 , and 11 - Also a delta connection of the stator coils 7 . 9 , and 11 , The power transistors 30 and 28 can each have the plus potential or the ground potential via the connection node 34 and the current sensor 17 on the stator coil 7 turn. The transistors 24 and 26 can the plus potential or the ground potential via the connection node 36 and the current sensor 17 on the stator coil 9 turn. The transistors 20 and 22 can the plus potential or the ground potential via the current sensor 17 on the stator coil 11 turn. The current sensor 17 is formed, the stator coil current of the stator coil 7 , the stator coil current of the stator coil 9 and the stator coil current of the stator coil 11 - Each independently - in particular by means of shunt resistors, to detect and on the multi-channel connection line 61 in particular in the form of a voltage drop across the shunt resistors, to output a current signal representing the stator coil currents. The current sensor 17 is about the multi-channel connection 61 with the processing unit 14 connected. The current sensor 17 can - in contrast to the dashed lines in this embodiment shown - instead of shunt resistors, for example, comprise inductive current sensors, which are each designed to generate the current signal.

The current sensor 18 is on the output side via connecting cables 58 and 59 with the processing unit 14 connected. The connection lines 58 and 59 grab one over the measuring resistor 19 decreasing voltage. The measuring resistor 19 is an example of the current sensor 18 and, for example, a shunt resistor. The measuring resistor 19 is arranged in this embodiment in the plus line, is also conceivable an arrangement in the ground line or a detection with two measuring resistors in both lines. The current sensor 18 For example, instead of the measuring resistor 19 through the current sensor 18 Inductively detect flowing current and generate an output signal corresponding to the current. The processing unit 14 On the input side, it is also connected to the ground potential 44 over a connecting line 57 connected. The processing unit 14 can be so from the electrical system 16 via the current sensor 18 to the power output stage 12 flowing current, in particular DC link current capture. The current sensor 17 is formed, the currents of the stator coils 7 . 9 and 11 each independently. The processing unit 14 is formed by the current sensors 18 and or 17 to receive detected currents on the input side and to differentiate the temporally received currents received on the input side and to provide the differentiation result thus formed for further arithmetic operations - for example by means of an intermediate memory. The processing unit 14 is formed, for example, in the stator coils 7 . 9 and 11 induced voltages according to the previously mentioned formulas (5) and / or (6a) to calculate.

The processing unit 14 is further formed in the stator coils 7 . 9 and 11 induced voltage for determining the rotor position of the rotor 5 and thus the rotor position of the rotor 5 as a function of the induced voltage and thus as a function of the time derivative of the current to determine. To determine the rotor position of the rotor 5 can the processing unit 14 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 For example, to determine the argument of the complex space vector of the induced voltage, a CORDIC method, a PLL (PLL = Phase-Lo cked-loop) or another particularly analogous method for determining the argument of the space vector. The processing unit has a rotor position determination unit in this embodiment 15 which is 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 the power output stage depending on the rotor position signal 12 and the stator 3 to drive to generate the magnetic rotating field.

The current sensors are arranged in this embodiment, the currents through the stator coils, or one of the power output stage 12 to detect 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 link current in the case of an H-circuit. It is conceivable that the power output stage 12 for each of the stator coils has an H-circuit.

Independently or depending on the previously described rotor position detection can an electronically commutated electric motor at least one Stator coil, preferably two stator coils, more preferably three Have stator coils. The stator coils are each with a H circuit connected to a power amplifier. The so by means of H circuits controlled electronically commutated electric motor may be preferred for Driving a fan, such as a cooling fan be advantageously included in a motor vehicle. Further advantageous Possibilities for forming an electric drive are a Blower for air conditioning of a motor vehicle or a power steering system of a motor vehicle.

A 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 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} = U _{ind_A} + i · U _{ind_B}

U_{ind_ges}

= Raumzeiger induzierte Spannung aller Statorspulen

U_{ind_A}

= Raumzeiger induzierte Spannung Spule A, Realteil

U_{ind_B}

= Raumzeiger induzierte Spannung Spule B, Imaginärteil

Mean in it

U _{ind_ges}

= Space vector induced voltage of all stator coils

U _{ind_A}

= Space vector induced voltage coil A, real part

U _{ind_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 can be formed from combinations of the coil strands as follows: U _{ind_1} = U _{ind_U} + (U _ind (V || W), U _{ind - 2} = U _{ind - V} + (U _ind (W | U)) U _{ind_3} = U _{ind_W} + (U _ind (U || V),

U _ind (U || V) means, for example, induced voltage of a parallel connection of the coils U and V.

A complex space vector of all induced voltages can be calculated as follows: U _{ind_ges} = e ⁱ⁰ · U _{ind_1} + e ^{i2Π / 3} · U _{ind_2} + e ^{i4Π / 3} · U _{ind_3} .

2 shows an embodiment of a possible voltage and a possible associated current flow of a current through a stator coil of in 1 described electronically commutated electric motor. 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 stator coil voltage, for example, that of the power output stage 12 on one of the stator coils 7 . 9 , or 11 switched stator coil voltage. The diagram with the ordinate 70 is a subordinate diagram showing a current waveform of a stator coil current through the stator coil.

The diagram with the current flow 112 has an ordinate 72 on which the current of the current flow 112 represents.

The diagram with the current profile 112 is a subordinate diagram, which is a curve 114 having. The curve 114 represents a differentiated current profile of the current profile 112 ,

The diagram with the differentiated current profile 114 has an abscissa 86 , which represents a time course, and an ordinate 74 , which represents the differentiated current, on. Shown are also time periods 90 . 92 and 94 , which in each case over all three diagrams with the curves 110 . 112 and 114 extend. The period of time 90 represents a period of time in which the on the stator coil, for example, the stator coil 7 . 9 or 11 switched voltage is positive. The positive voltage causes - how to the curve of the stator coil current 112 can take - an increase of the stator coil current through the stator coil. The time derivative of the stator coil current in the time period 90 shows the curve 114 in the time period 90 , The curve 114 the time derivative of the current corresponds to the time period 90 a straight line.

During the period 92 switches the power output stage 12 on the stator coil a negative voltage. The voltage curve is the time period 92 shown accordingly. The current course 112 shows in the time period 92 - according to the voltage curve - a linear drop.

The curve 114 shows during the period 92 a constant course. During the period 94 switches the power output stage 12 no potential of connections 40 or 44 on the stator coil. The current course 112 rises during this time period. The time derivative of the current flow 112 in the time period 94 is by means of the curve 114 in the time period 94 reproduced accordingly.

Also shown are three diagrams, namely a diagram with a voltage curve 116 , one the voltage curve 116 corresponding current curve 118 , where the current flow 118 a DC link current, for example, detected by the in 1 illustrated current sensor 18 , can represent.

Also shown is a curve 120 , which is a time derivative of the current profile 118 represents the DC link current. Shown are also time periods 96 and 98 , which in each case by the curves of the curves 116 . 118 and 120 run. It can be seen that the DC link current 118 during the period 96 where there is a positive potential, for example, the potential of the connection 42 is switched to a stator coil, increases accordingly. During the period 98 where the potential of the connection 44 by means of the power output stage 12 is switched to the stator coil, takes the DC link current 118 a negative value and increases.

3 shows an embodiment of a method for detecting a rotor position of a rotor of an electronically commutated electric motor with a stature and the rotor. In one process step 100 At least one stator coil current of a stator coil of the stator is detected at a time at which a zero voltage is applied to the stator coil. In a subsequent process step 102 a time derivative of the detected stator coil current is formed. In one process 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 one process step 106 a rotor position of the rotor is determined as a function of the determined induced voltage.

One magnetic rotating field for rotating the rotor can - in a further process step, not shown - advantageous generated as a function of the determined induced voltage become.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• - DE 69823494 T2 [0002]

Claims (8)

Electronically commutated electric motor ( 1 ) with a stator ( 3 ) and with a particular permanent magnetic rotor ( 5 ), wherein the electric motor ( 1 ) a rotor position detecting device ( 14 . 15 ), which is formed, a rotor position of the rotor ( 5 ), and to generate a rotor position signal indicative of a rotor position of the rotor ( 5 ), wherein the rotor position detecting device ( 14 . 15 ) is formed, the rotor position in dependence on a in at least one stator coil ( 7 . 9 . 11 ) induced voltage, characterized in that the rotor position detecting device ( 14 . 15 ) is formed, at least one stator coil current ( 112 . 118 ) and in at least one stator coil ( 7 . 9 . 11 ) of the stator induced voltage as a function of a time derivative ( 114 . 120 ) of the at least one stator coil current ( 112 . 118 ) to investigate. Electric motor ( 1 ) according to claim 1, characterized in that the rotor position detecting device ( 14 . 15 ), the time derivative ( 114 ) of the stator coil current ( 112 ), for determining the rotor position at a time ( 94 ) in which a stator coil voltage connected to the stator coil is sufficiently small or equal to zero. Electric motor ( 1 ) according to claim 2, characterized in that the rotor position detecting device ( 14 . 15 ) is formed, for determining the rotor position, the inductance of the at least one stator coil ( 7 . 9 . 11 ). Electric motor ( 1 ) according to any one of the preceding claims, characterized in that the rotor position detecting device ( 14 . 15 ), a time derivation ( 120 ) of the stator coil current ( 118 ) for determining the rotor position at a first time ( 96 ) in which the stator coil voltage switched to the stator coil is positive and a time derivative ( 120 ) of the stator coil current ( 118 ) for determining the rotor position at a second time ( 98 ), in which the stator coil voltage connected to the stator coil is negative, in particular to the positive stator coil voltage, and the induced voltage as a function of the time derivative of the stator coil current at the first time ( 96 ) and at the second time ( 98 ) to investigate. Procedure ( 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 a in at least one stator coil ( 7 . 9 . 11 ) induced voltage is detected ( 106 ), characterized in that at least one stator coil current ( 112 ) of a stator coil ( 7 . 9 . 11 ) is detected and in the at least one stator coil ( 7 . 9 . 11 ) induced voltage as a function of a time derivative ( 114 ) of the at least one detected stator coil current ( 112 ) is determined ( 104 ). Method according to Claim 5, characterized in that the time derivative ( 114 ) of the stator coil current ( 112 ) for determining the rotor position at a time ( 94 ), in which a stator coil voltage ( 110 ) above the stator coil ( 7 . 9 . 11 ) is low or equal to zero. A method according to claim 6, characterized in that for determining the rotor position, an inductance of the at least one stator coil ( 7 . 9 . 11 ) is used. Method according to one of claims 5 to 7, characterized in that a time derivative ( 120 ) of the stator coil current ( 118 ) for determining the rotor position at a first time ( 96 ) is used, in which one on the stator coil ( 7 . 9 . 11 ) switched stator coil voltage ( 110 ) 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 one on the stator coil ( 7 . 9 . 11 ) switched stator coil voltage ( 110 ) is negative, and the voltage induced in the stator coil as a function of the time derivative ( 120 ) of the stator coil current ( 118 ) at the first time ( 96 ) and at the second time ( 98 ) is determined.

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