Rotor position detection

Abstract

The invention relates to the detection (42) of a rotor position ([gamma] EM) of an electric motor (10) comprising at least one stator (12), at least one rotor (14) rotatable relative to the stator in order to change the rotor position ([gamma] EM), and at least two motor phases (16). The rotor position ([gamma] EM) is detected on the basis of a rotor position reference value ([psi] b) which is calculated from an electrically operated variable (30) of the at least two motor phases (16), the electrically operated variable (30) being applied to a reference frame (22) fixed relative to the stator in order to calculate the rotor position reference value ([psi] b). The invention also relates to an analysis device (34) and a drive device (26).

Description

Technical Field

[0001] The invention relates to rotor position detection according to the preamble of claim 1. The invention also relates to an evaluation device and a drive device. Background Art

[0002] DE 10 2013 004 954 A1 describes a method for operating a multiphase electric machine having a rotor and a rotary encoder operatively connected to the rotor. The actual rotational angle of the rotor is determined as a function of a measured rotational angle determined by means of the rotary encoder and a rotational angle offset. In this case, it is provided that, in order to determine the rotational angle offset, the rotor is brought to a certain rotational speed and then an active short circuit of the electric machine is initiated, wherein an actual current vector is determined as a function of the current intensity of a current flowing in at least two of the phases of the electric machine and a measured rotational angle determined by means of a rotational angle sensor using a dq transformation, and the rotational angle offset is calculated as a function of the actual current vector and a reference current vector.

[0003] EP 3 473 346 A1 describes a method for determining a measurement offset of a rotor position sensor assigned to a rotor of an electric machine, the method comprising the steps of applying a short circuit to a stator winding of the electric machine, detecting the current of the stator winding in the short-circuited state, and determining the measurement offset as a function of a current vector angle in a dq reference frame. The current vector angle is calculated by a phase-locked loop.

[0004] The object of the invention is to detect the rotor position more accurately and quickly. The computational workload should be reduced and the computation should be less susceptible to fluctuations and interruptions. Summary of the invention

[0005] At least one of these objects is achieved by a rotor position detection having the features according to claim 1. This can improve the stability of the rotor position detection to fluctuations of the electrical manipulated variable. Furthermore, frequency overshoots and phase overshoots can be reduced in the presence of errors in the input signal. Furthermore, the rotor position can be determined more accurately. The rotor position can be determined more independently of asymmetries in the electric motor and the motor control and of the measuring technology.

[0006] Detecting the rotor position may result in a more efficient and more convenient operation of the electric motor.The rotor position is preferably a rotational position of the rotor rotatable relative to the stator about a rotation axis.

[0007] The rotor position detection may be performed after the electric motor is installed and / or before the electric motor is put into operation. The rotor position detection may be performed regularly or irregularly during the operation of the electric motor.

[0008] The rotor position detection can be a check of the rotor position measured by the rotor position sensor. The measured rotor position can be corrected by the rotor position detection. Due to manufacturing tolerances, deviations of the measured rotor position from the actual rotor position can occur. Deviations can be detected and / or compensated by the rotor position detection.

[0009] The electric motor may be controlled by a motor controller. The motor controller may include power electronics. The motor controller may have an inverter circuit with semiconductor switching elements for controlling the electric motor. The semiconductor switching elements may be actively switched. The electric motor may have at least three motor phases. The motor controller may have a total of three half bridges. The motor controller may include six semiconductor switching elements.

[0010] In a preferred embodiment of the invention, it is advantageous if the rotor rotates relative to the stator at least during the detection of at least one of the electrical manipulated variables. This allows a direct measurement of the electrical manipulated variable.

[0011] In a particular embodiment of the invention, it is advantageous if, during the detection of at least one of the electrical operating variables, the electric motor is at least temporarily operated in an active short-circuit operation or in a freewheeling operation. The short-circuit operation or the freewheeling operation can be switched by the motor controller. The short-circuit operation may occur due to an electrical short circuit of all motor phases. In the short-circuit operation, half of the semiconductor switching elements may be actively switched and thus closed. In the freewheeling operation, all semiconductor switching elements may not be switched and thus open.

[0012] In a particular embodiment of the invention, it is advantageous if at least one of the electrical operating variables is detected by a short circuit current in short circuit operation and / or an open circuit voltage in freewheeling operation. The open circuit voltage may be formed by a phase voltage of at least one of the motor phases.

[0013] The rotor position reference value may be the angle of the current vector of the short-circuit current and / or the angle of the voltage vector of the open-circuit voltage in a reference frame fixed to the stator. The rotor position reference value may be the difference angle between the current vector of the short-circuit current and the measured rotor position.

[0014] The rotor position can be specified by the field of view angle corresponding to the d-axis in a reference frame fixed relative to the stator (dq reference frame). For example, based on the open circuit voltage, the voltage vector of the open circuit voltage can be offset by 90° relative to the field of view angle. In the case of an electrical operating variable formed by a short-circuit current, during short-circuit operation, there may be an offset between the current vector of the short-circuit current and the field of view angle of 180°. Alternatively, the offset between the current vector of the short-circuit current and the field of view angle can be detected by comparison with a reference frame, in particular a reference frame including a reference motor.

[0015] In an advantageous embodiment of the invention, it is provided that the rotor position is calculated by the phase locked loop by including a feedback variable. This allows the rotor position to be calculated more accurately and independently of fluctuations and disturbances. The feedback variable can be based directly or indirectly on the measured rotor position. The feedback variable can be based directly or indirectly on a rotor position reference value.

[0016] Alternatively or additionally, the rotor position can be calculated based on at least one characteristic value of the electrical operating variable. The characteristic value can be a maximum value, a minimum value and / or a zero point. During the rotor position detection, a known relationship between the characteristic value and the actual rotor position can be used. The known relationship can be stored in a retrievable manner for rotor position detection. The rotor position can be calculated by comparing it with the known relationship. The relationship can link the actual rotor position to the characteristic value for different time points in the time series. During the adjustment process during the rotor position detection, the measured rotor position can be measured for different time points in the time series, and the rotor position can be compared with multiple reference values ​​of the time series of the known relationship.

[0017] The phase locked loop may include at least one P element, I element and / or D element that performs control.

[0018] In a particular embodiment of the invention, it is advantageous if the position measuring device is arranged to detect the measured rotor position.The position measuring device may comprise at least one rotor position sensor.

[0019] The rotor position can be calculated based on the measured rotor position of the position measuring device.

[0020] In an advantageous embodiment of the invention, it is provided that an offset angle between the rotor position and the measured rotor position is calculated based on the rotor position reference value.

[0021] In an advantageous embodiment of the invention, it is provided that the rotor position is calculated based on the measured rotor position and the offset angle. Preferably, the offset angle used for calculating the rotor position is stored in a retrievable manner during operation of the electric motor. The rotor position can be calculated based on the sum or difference of the measured rotor position and the offset angle. During the calculation, the difference or sum value can be formed using filtered values, in particular average values, of the measured rotor position and / or the difference or sum value can be filtered, in particular averaged, over several values. The rotor position can also be calculated under different operating conditions. The offset angle can be formed based on the operating conditions.

[0022] Furthermore, at least one of the previously specified objects is achieved by an analysis device having a first receiving unit for receiving a measured rotor position, a second receiving unit for receiving at least one electrically manipulated variable, and a computing unit for executing a method having at least one of the previously described features. A unit is understood to be a physically present device-side implementation. Different units can be structurally separate from one another or structurally combined.

[0023] Furthermore, at least one of the above objects is achieved by a drive device having an electric motor and an analysis device as described above, the electric motor comprising at least one stator and at least one rotor that can rotate relative to the stator to change the rotor position and at least two motor phases. The drive device can be arranged in a vehicle. The electric motor can provide a drive torque to propel the vehicle.

[0024] Further advantages and advantageous embodiments of the invention emerge from the description of the figures and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention is described in detail below with reference to the accompanying drawings. In the accompanying drawings, in detail:

[0026] Figure 1 : An electric motor of a drive device in a specific embodiment of the present invention is shown.

[0027] Figure 2 : shows a driving device in a specific embodiment of the present invention.

[0028] Figure 3 : shows the rotor position detection in a specific embodiment of the present invention.

[0029] Figure 4 : A method for determining the deviation of rotor position detection in another specific embodiment of the present invention is shown.

[0030] Figure 5 : A method for determining the deviation of rotor position detection in another specific embodiment of the present invention is shown.

[0031] Figure 6 : An alternative method for determining the deviation of the rotor position detection in another specific embodiment of the present invention is shown.

[0032] Figure 7 : shows rotor position detection in another specific embodiment of the present invention.

[0033] Figure 8 : shows rotor position detection in another specific embodiment of the present invention. DETAILED DESCRIPTION

[0034] Figure 1 1 shows an electric motor of a drive device in a specific embodiment of the present invention. The electric motor 10 comprises a stator 12 and a rotor 14, which can rotate relative to the stator about a rotation axis; and three motor phases 16, to which respective phase voltages 18 are applied for operating the electric motor 10. When the rotor 14 rotates relative to the stator 12, the rotor position γ EM , i.e., the rotational position of the rotor 14 relative to the stator 12 changes. The electrical operating variables present during operation of the electric motor 10 can be described in a reference frame 22 fixed relative to the stator with the direction of the coil as the axis, or in a reference frame 24 fixed relative to the stator that rotates at a certain rotational speed relative to the reference frame 22 fixed relative to the stator. The reference frame 24 fixed relative to the rotor spans the d-axis representing the magnetic flux density and the q-axis perpendicular thereto and representing the torque. The d-axis spans the rotor position γ relative to the axis of the coil along the reference frame 24 fixed relative to the rotor EM The corresponding field of view angle.

[0035] Figure 2 The drive device 26 in a specific embodiment of the present invention is shown. The drive device 26 comprises: an electric motor 10; a motor controller 28 for controlling the electric motor 10 via at least one electric manipulated variable 30; a position measuring device 31 having a rotor position γ for detecting the measured rotor position γ. m and an analysis device 34 having a rotor position sensor 32; and an analysis device 34 having a rotor position sensor γ m The first receiving unit 36 ​​and the second receiving unit 38 receiving the electric manipulated variable 30 and processing the measured rotor position γ m and a calculation unit 40 of the electric manipulated variable 30 .

[0036] Measured location γ m The actual rotor position γ may deviate from this, for example due to manufacturing tolerances. EM Angle of deviation θ 偏移 Such deviations of the rotor position must in particular be determined in advance and compensated for during operation of the electric motor 10 in order to identify the actual rotor position γ during operation of the electric motor 10 . EM And using this knowledge to operate the electric motor 10 as efficiently as possible.

[0037] For example, the offset angle θ may be adjusted during operation of the electric motor 10. 偏移 is stored and accessed to determine the actual rotor position γ EM .

[0038] Figure 34. The rotor position detection in a specific embodiment of the present invention is shown. With the rotor position detection 42 performed during operation of the electric motor, the rotor position γ measured by the rotor position sensor m It can be used, for example, to convert the measured value sin(γ) of the rotor position sensor 32 into m ) and cos(γ m ) is converted into the measured rotor position γ m To calculate the actual rotor position γ EM The offset angle θ is determined by the electrical operating variable 偏移 Then it is used to calculate the rotor position γ according to the measured m To calculate the actual rotor position γ EM .

[0039] Offset angle θ 偏移 It can be detected during operation of the electric motor or calculated before operation, in particular before the electric motor is put into operation for the first time. For this purpose, the rotor position reference value ψ b For calculating the offset angle θ based on the electrical manipulated variables 30 of at least two motor phases, in particular three motor phases 偏移 .

[0040] Offset angle θ 偏移 It may be determined from the electrical operating variable 30 as explained in detail below.

[0041] Figure 4 A method for determining the deviation of the rotor position detection in another specific embodiment of the invention is shown. The method 44 for determining the deviation is performed, for example, after assembly and before the electric motor is put into operation.

[0042] The electric motor is switched by the motor controller to short-circuit operation or freewheeling operation. The method 44 for determining the deviation will be explained below using the example of short-circuit operation. The electrical operated variables 30 are each formed by the short-circuit current during the short-circuit operation.

[0043] The short-circuit currents Ia, Ib, Ic of the three motor phases are detected and form the electrical manipulated variable 30. The short-circuit currents Ia, Ib, Ic are initially referenced to an αβ reference frame fixed to the stator as transformed short-circuit currents I α ,I β . The transformed short-circuit current I α ,I β is normalized and used as the normalized short-circuit current I' α , I' β .

[0044] In the subsequent phase locked loop 46 using the PI controller and the rotor speed ω, the normalized short circuit current I′ α , I'β , the current angle γ of the current vector in the reference frame fixed to the stator s is calculated as the rotor position reference value ψ b Then according to the rotor position reference value ψ b , the measured rotor position γ m , and are predetermined on the reference motor as the current vector and the rotor position γ EM The current reference angle θ b and at least one operating parameter P of the electric motor to calculate the offset angle θ 偏移 . Offset angle Θ 偏移 It may be determined via an operating parameter P based on the operating state of the electric motor.

[0045] Figure 5 A method for determining the deviation of the rotor position detection in another specific embodiment of the present invention is shown. Except for the differences described below, the method 44 for determining the deviation is the same as Figure 4 In the phase-locked loop 46, the measured rotor position γ is used m .

[0046] This allows the measured rotor position γ to be b With the current angle γ s The difference angle between them is calculated as the rotor position reference value ψ b , and then based on the current reference angle θ b and at least one operating parameter P of the electric motor to calculate the offset angle θ 偏移 .

[0047] Figure 6 An alternative method for determining the deviation of the rotor position detection is shown in another specific embodiment of the invention. Figure 5 Part A shown is an alternative design. Instead of a phase-locked loop, the rotor position reference ψ b An open loop with filtering 48 and subsequent system error correction 50 is used.

[0048] Figure 7 FIG. 4 shows the rotor position detection in another specific embodiment of the present invention. Figure 3 The rotor position detection is similar to that of αβ, but instead of the transformed short-circuit current in the αβ reference frame, the short-circuit currents Ia, Ib, Ic are used directly as input variables. Based on the short-circuit currents Ia, Ib, Ic, the rotor position γ is calculated in the subsequent phase-locked loop 46. EM .

[0049] Figure 84 shows the rotor position detection in another specific embodiment of the present invention. The rotor position detection 42 is performed using short-circuit currents Ia, Ib, Ic, which are related to a reference frame fixed relative to the stator and represent electrical operating variables. For the harmonic short-circuit currents Ia, Ib, Ic, at least one characteristic value K of the short-circuit currents Ia, Ib, Ic is detected. The characteristic value K can be the maximum value, minimum value and / or zero point of the harmonic short-circuit currents Ia, Ib, Ic. By using as a reference position γ r γ is calculated by the known relationship f(K) between the actual rotor position and the characteristic value K measured in advance in a reference system, in particular in a reference motor. EM , to obtain the rotor position γ according to the eigenvalue K EM For this purpose, at the time t at which the characteristic value K occurs 1 The actual rotor position is also detected as the reference position γ r and is related to the characteristic value K. The relationship f(K) can depend on various parameters, such as the rotor speed or the temperature.

[0050] In an electric motor, the measured rotor position γ m At the time t when the eigenvalue K appears w is detected and the rotor position γ EM With the measured rotor position γ m The deviation between γ is converted into a correction value κ γ . As a single time point t at which the eigenvalue K occurs 2 As an alternative to measuring at r The measured rotor position γ can also be detected in the time series m , and thus the deviation δ can be calculated for different time points in the time series γ .

[0051] Reference numerals list

[0052] 10 Electric Motor

[0053] 12 Stator

[0054] 14 Rotor

[0055] 16 Motor Phases

[0056] 18 Phase voltage

[0057] 22 Reference frame fixed relative to the stator

[0058] 24 Reference frame fixed relative to the rotor

[0059] 26 Drive unit

[0060] 28 Motor Controller

[0061] 30 Electrically operated variables

[0062] 31 Position measuring device

[0063] 32 Rotor position sensor

[0064] 34 Analysis device

[0065] 36 First receiving unit

[0066] 38 Second receiving unit

[0067] 40 computing units

[0068] 42 Rotor position detection

[0069] 43 Position calculation

[0070] 44 Methods used to determine bias

[0071] 46 Phase-locked loop

[0072] 48 Filter

[0073] 50 Calibration

[0074] f(K) Relationship

[0075] K Eigenvalue

[0076] δ γ deviation

[0077] γ EM Rotor position

[0078] γ m Measured rotor position

[0079] γ r Reference location

[0080] ψ b Rotor position reference value

[0081] κ γ Correction value

[0082] ω Rotor speed

[0083] Θ 偏移 Offset Angle

[0084] Θ b Current reference angle

[0085] P Operation Parameters

[0086] t 1 Time

[0087] t 2 Time point.

Claims

1. A rotor position (γ) of an electric motor (10) EM ), the electric motor comprising at least one stator (12) and at least one rotor (14) and at least two motor phases (16), the rotor being rotatable relative to the stator so as to change the rotor position (γ EM ),in, The rotor position (γ EM ) is based on the rotor position reference value (ψ b ), the rotor position reference value being calculated based on the electrical manipulated variables (30) of the at least two motor phases (16), It is characterized in that The electrical manipulated variable (30) is applied to a reference frame (22) fixed relative to the stator to calculate the rotor position reference value (ψ b ).

2. The rotor position detection (42) according to claim 1, characterized in that At least during the detection of at least one of the electrical operated variables (30), the rotor (14) rotates relative to the stator (12).

3. The rotor position detection (42) according to claim 1 or 2, characterized in that: During the detection of at least one of the electrical operating variables (30), the electric motor (10) is at least temporarily operated in active short-circuit operation or freewheeling operation.

4. The rotor position detection (42) according to claim 3, characterized in that At least one of the electrical operation variables (30) is detected by a short-circuit current in a short-circuit operation and / or an open-circuit voltage in a freewheeling operation.

5. Rotor position detection (42) according to any of the preceding claims, characterized in that The rotor position (γ EM ) based on the rotor position (γ) measured by the position measuring device (31) m ) to calculate.

6. The rotor position detection (42) according to claim 5, characterized in that The rotor position (γ EM ) and the measured rotor position (γ m ) between the offset angle (θ 偏移 ) is based on the rotor position reference value (ψ b ) to calculate.

7. The rotor position detection (42) according to claim 6, characterized in that The rotor position (γ EM ) based on the measured rotor position (γ m ) and the offset angle (θ 偏移 ) to calculate.

8. The rotor position detection (42) according to claim 6 or 7, characterized in that for calculating the rotor position (γ) during operation of the electric motor (10) EM ) of the offset angle (θ 偏移 ) are stored in a retrievable form.

9. An analysis device (34) having a device for receiving a measured rotor position (γ m ), a first receiving unit (36) receiving at least one electrical manipulated variable (30), and a calculation unit (40) performing a rotor position detection (42) according to any of the preceding claims.

10. A drive device (26) comprising an electric motor (10) comprising at least one stator (12) and at least one rotor (14) and at least two motor phases (16), the rotor being rotatable relative to the stator in order to change the rotor position (γ EM ).

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