WO2019052650A1 - Method for monitoring a field oriented control of an electric motor and electric motor - Google Patents

Method for monitoring a field oriented control of an electric motor and electric motor Download PDF

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Publication number
WO2019052650A1
WO2019052650A1 PCT/EP2017/073238 EP2017073238W WO2019052650A1 WO 2019052650 A1 WO2019052650 A1 WO 2019052650A1 EP 2017073238 W EP2017073238 W EP 2017073238W WO 2019052650 A1 WO2019052650 A1 WO 2019052650A1
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WO
WIPO (PCT)
Prior art keywords
oriented control
field oriented
electric motor
rotor
angular position
Prior art date
Application number
PCT/EP2017/073238
Other languages
French (fr)
Inventor
Florian Weigt
Alexander HAPPE
Christian Daniel POPA
Cosmin Marius CRACIUN
Original Assignee
HELLA GmbH & Co. KGaA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by HELLA GmbH & Co. KGaA filed Critical HELLA GmbH & Co. KGaA
Priority to PCT/EP2017/073238 priority Critical patent/WO2019052650A1/en
Publication of WO2019052650A1 publication Critical patent/WO2019052650A1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/14—Electronic commutators
    • H02P6/16—Circuit arrangements for detecting position
    • H02P6/18—Circuit arrangements for detecting position without separate position detecting elements
    • H02P6/182—Circuit arrangements for detecting position without separate position detecting elements using back-emf in windings

Definitions

  • the invention is related to a method for monitoring a field oriented control of an electric motor, the electric motor comprises a rotor and is driven by an electric current comprising at least a first phase, the field oriented control is based at least on an estimated rotational speed of the rotor and further on field oriented control is executed in cycles. Further on the invention is related to an electric motor, comprising a rotor and driven by an electric current comprising at least a first phase and controlled by a field oriented control, the field oriented control is based at least on an estimated rotational speed of the rotor and further on executed in cycles.
  • Electric motors are commonly used in modern technology. Especially electric motors driven by electric current are widely spread, for instance in vehicles and domestic and/or industrial applications.
  • the electric current is used to generate magnetic fields in the rotor and/or the stator of such an electric motor and as a result to set the rotor in a rotational movement.
  • the field oriented control is normally based on an estimated rotational speed of the rotor of the electric motor to correctly commutate the phases.
  • external sensors are used to measure the rotational speed of the rotor. This solution has the disadvantage that the sensor has to be included into the electric motor and therefore the electric motor cannot be constructed as compact as possible. Further on, such a sensor to measure the rotational speed of the rotor of the electric motor increases the overall complexity of an electric motor and also shortens the service intervals.
  • the object is achieved by a method for monitoring a field oriented control of an electric motor, the electric motor comprises a rotor and is driven by an electric current comprising at least a first phase, the field oriented control is based at least on an estimated status of the rotor and further on field oriented control is executed in cycles.
  • a method according to the invention is characterized in that the field oriented control is paused, that in this pause at least a first zero crossing of the first phase at a first time stamp is detected, that the field oriented control is afterwards restarted and that the additional information provided by the at least one detected first zero crossing is used to monitor the field oriented control.
  • a method according to the invention can be implemented and used by an electric motor controlled by a field oriented control.
  • the electric motor can preferably be built as a permanent magnet synchronous motor. Further, the electric motor is driven by an electric current comprising at least one phase, wherein the current is distributed at the respective parts of the electric motor, especially coils to generate magnetic fields, according to the parameters provided by the field oriented control. This distribution can be also called commutation.
  • the field oriented control is based on an estimated status of the rotor of the electric motor, for instance on an estimated rotational speed and/or on an estimated angular position of the rotor.
  • the estimated status should not differ from the actual respective status of the rotor of the electric motor, or at least the estimated status should be close to the actual status.
  • a method according to the invention can provide this, especially without the requirement of an external sensor to measure the actual status of the rotor.
  • the field oriented control is stopped. This ensures an elimination of influences of the field oriented control itself on obtaining the status information.
  • at least one first zero crossing, especially a first zero crossing of an induced voltage, induced by the on-going rotation of the rotor, of the first phase at a first time stamp is detected.
  • the field oriented control is restarted afterwards.
  • the information obtained from the detection of at least the first zero crossing and its respective first time stamp is used to monitor the field oriented control.
  • a method according to the invention provides the possibility to monitor a field oriented control. Especially the status of the rotor of the electric motor used by the field oriented control can be calculated based on simple voltage measurements, without the need of further sensors and/or probes to directly measure the status of the rotor itself. Further, the field oriented control can be improved by using the newly calculated status of the rotor as basis for the on-going control.
  • the field oriented control is based at least on an estimated rotational speed of the rotor.
  • the used estimated status of the rotor is an estimated rotational speed of the rotor.
  • step g) monitor the field oriented control by comparing the calculated rotational speed of step f) with the estimated rotational speed used by the field oriented control.
  • the field oriented control is based at least on an estimated rotational speed of the rotor of the electric motor.
  • the estimated rotational speed should not differ from the actual rotational speed of the rotor of the electric motor, or at least the estimated rotational speed should be close to the actual rotational speed.
  • a method according to the invention can provide this, especially without the requirement of an external sensor to measure the rotational speed of the rotor.
  • the first step a) describes the normal operation of the electric motor.
  • the field oriented control is active and controls the commutation of the electric current to the respective recipients inside of the electric motor.
  • the field oriented control can at least partly be implemented as a sensorless algorithm, for instance to provide an estimation of the magnetic flux within the electric motor.
  • a second step b) of this embodiment of a method according to the invention the field oriented control is paused. Therefore the control of the commutation of the electric power provided by the field oriented control is also stopped.
  • the rotor of the electric motor rotates without further impetus. Nevertheless, as the method according to the invention stops the field oriented control only for a very short time period this has very little to no effect on the operation of the electrical motor. Further, this rotation generates an induction voltage in the first phase, which can be measured.
  • a voltage especially a sinusoidal voltage
  • This voltage oscillates between a negative and a positive maximum, wherein the oscillation frequency depends on the rotational speed of the rotor.
  • Each cycle of the induced voltage therefore comprises two zero crossings, whose time difference allows to calculate the rotational speed of the rotor.
  • a first zero crossing of the first phase and a second zero crossing of the first phase respectively are detected.
  • This can for instance be done by sensors and/or probes.
  • voltage sensors and/or appropriate comparators and ADCs respectively can be used.
  • step e the field oriented control of the electric motor is restarted.
  • the two time stamp measurements done in step c) and d) provide enough information to calculate later on the rotational speed of the rotor.
  • step f) of a method according to the invention The actual calculation of the calculated rotational speed is carried out in step f) of a method according to the invention.
  • the exact relation between the time difference of two zero crossings and the rotational speed of the rotor is known. It depends for instance of the type of the rotor, especially the number of electric poles used in the electric motor. The time difference itself can be easily calculated as difference of the two measured time stamps.
  • step f) the information of a calculated rotational speed of the rotor of the electric motor is present.
  • This calculated rotational speed is used in the last step g) of a method according to the invention. It is actually compared with the estimated rotational speed used in the field oriented control. Deviations between these two values of the rotational speed can for instance be used to measure the quality of the field oriented control, especially, how good the estimations are, which lead to the estimated rotational speed. Further on, the calculated rotational speed can also be used as new estimated rotational speed to improve the commutation provided by the field oriented control.
  • a method according to this embodiment of the invention provides the possibility to monitor a field oriented control based on an estimated rotational speed of the rotor. Especially the rotational speed of the rotor of the electric motor can be calculated, without the need of further sensors and/or probes to directly measure this rotational speed. Further, the field oriented control can be improved by using the newly calculated rotational speed of the rotor as basis for the on-going control.
  • a method according to the invention can be characterized in that the detected zero crossings in step c) and step d) have the same direction in respect to the sign of the voltage.
  • the induced voltage oscillates between a negative and a positive maximum. Therefore each cycle of the induced voltage comprises two zero crossings, wherein the direction changes, one zero crossing is in the direction of the positive maximum, the next in the direction of the negative maximum.
  • it can be ensured, that a complete cycle of the induced voltage is covered by the measurements done in step c) and d) of a method according to the invention. By this, the accuracy of the calculation of the rotational speed in step f) can be improved.
  • a method according to the invention can be characterized in that after step c) the field oriented control is restarted and before step d) the field oriented control is paused. By doing so, the duration in which the electric motor is driven without field oriented control can be minimized. The impact of a method according to the invention on the operation of an electric motor can thereby be reduced.
  • a method according to the invention can be characterized in that the field oriented control is additionally based on an estimated angular position of the rotor, that in step f) a calculated angular position of the rotor based on the measured time stamps in steps c) and d) is calculated, and that in step g) the calculated angular position of the rotor is compared to the estimated angular position used in the field oriented control.
  • the field oriented control is additionally based on an estimated angular position of the rotor, that in step f) a calculated angular position of the rotor based on the measured time stamps in steps c) and d) is calculated, and that in step g) the calculated angular position of the rotor is compared to the estimated angular position used in the field oriented control.
  • the field oriented control is based at least in an estimated angular position of the rotor.
  • the used estimated status of the rotor is an estimated angular position of the rotor.
  • step I) monitors the field oriented control by comparing the calculated angular position of step I) with the estimated angular position used by the field oriented control.
  • the field oriented control is based at least on an estimated angular position of the rotor of the electric motor.
  • the estimated angular position should not differ from the actual angular position of the rotor of the electric motor, or at least the estimated angular position should be close to the actual angular position.
  • a method according to the invention can provide this, especially without the requirement of an external sensor to measure the angular position of the rotor.
  • the first step h) describes the normal operation of the electric motor.
  • the field oriented control is active and controls the commutation of the electric current to the respective recipients inside of the electric motor.
  • the field oriented control can at least partly be implemented as a sensorless algorithm, for instance to provide an estimation of the magnetic flux within the electric motor.
  • a second step i) of this embodiment of a method according to the invention the field oriented control is paused. Therefore the control of the commutation of the electric power provided by the field oriented control is also stopped.
  • the rotor of the electric motor rotates without further impetus. Nevertheless, as the method according to the invention stops the field oriented control only for a very short time period this has very little to no effect on the operation of the electrical motor. Further, this rotation generates an induction voltage in the first phase, which can be measured.
  • a voltage is induced in the lines of the first phase.
  • This voltage oscillates between a negative and a positive maximum, wherein the oscillation frequency depends on the rotational speed of the rotor.
  • Each cycle of the induced voltage therefore comprises two zero crossings, wherein each time stamp of the two zero crossings allow to calculate the angular position of the rotor.
  • a first zero crossing of the first phase is detected.
  • This can for instance be done by sensors and/or probes.
  • voltage sensors and/or appropriate comparators and ADCs respectively can be used.
  • step k the field oriented control of the electric motor is restarted.
  • the time stamp measurement done in step j) provides enough information to calculate later on the angular position of the rotor.
  • step I) of a method according to this embodiment of the invention The actual calculation of the calculated angular position is carried out in step I) of a method according to this embodiment of the invention.
  • the exact relation between the time stamp of a zero crossing and the angular position of the rotor is known. It depends for instance of the type of the rotor, especially the position of electric poles used in the electric motor.
  • step I) the information of a calculated rotational speed of the rotor of the electric motor is present.
  • This calculated angular position is used in the last step m) of a method according to this embodiment of the invention. It is actually compared with the estimated angular position used in the field oriented control. Deviations between these two values of the angular position can for instance be used to measure the quality of the field oriented control, especially, how good the estimations are, which lead to the estimated angular position. Further on, the calculated angular position can also be used as new estimated angular position to improve the commutation provided by the field oriented control.
  • a method according to this embodiment of the invention provides the possibility to monitor a field oriented control based on an estimated angular position of the rotor.
  • the angular position of the rotor of the electric motor can be calculated, without the need of further sensors and/or probes to directly measure this angular position. Further, the field oriented control can be improved by using the newly calculated angular position of the rotor as basis for the on-going control.
  • a method according to the invention can be characterized in that the electric current comprises two or more phases, preferably three phases, and that steps b) to g) or steps i) to m) are executed for each of the two or more phases.
  • an electric current with two or more phases, especially three phases provides the electric power to drive the electric motor.
  • the method can be characterized in that steps b) to g) or steps i) to m) are performed for each of the two or more phases in a consecutive order of the two or more phases.
  • steps b) to g) or steps i) to m) are performed for each of the two or more phases in a consecutive order of the two or more phases.
  • steps b) to g) or steps i) to m) are performed for each of the two or more phases in a consecutive order of the two or more phases.
  • steps b) to g) or steps i) to m) are performed for each of the two or more phases in a consecutive order of the two or more phases.
  • a method according to the invention can be characterized in that restarting the field oriented control of the electric motor in step e) and/or k) is performed according to status data of the electric motor.
  • the field oriented control is used to provide a commutation of the phases of the electric current such that an operation of the electric motor can be ensured.
  • the field oriented control is paused and afterwards restarted.
  • a method according to the invention can be characterized in that a time interval between the execution of step b) and the first zero crossing detected in step c) or a time interval between the execution of step i) and the first zero crossing detected in step j) is adjusted according to status data of the electric motor. It is especially preferable that the time duration, in which the field oriented control is disabled, is as short as possible. Therefore it is advantageously, if the time interval between the pausing of the field oriented control in step b) and the first zero crossing measured in step c) or the time interval between the execution of step i) and the first zero crossing detected in step j) respectively is as short as possible. This can be achieved by adjusting the time interval according to status data of the electric motor. Status data in the sense of the invention can for instance be the electric power consumption, the rotational speed of the rotor or similar data.
  • a method according to the invention can be characterized in that as status data of the electric motor the estimated rotational speed of the rotor used in the field oriented control and/or the calculated rotational speed of the rotor calculated in step f) and/or the estimated angular position of the rotor used in the field oriented control and/or the calculated angular position of the rotor calculated in step I) is used.
  • the estimated and/or the calculated rotational speed and/or the estimated and/or the calculated angular position respectively speed can both be used to predict the time stamps of the zero crossings.
  • the restarting of the field oriented control can be performed and respectively estimated especially easily based on the estimated and/or the calculated rotational speed and/or the estimated and/or the calculated angular position respectively.
  • the time interval between the pausing of the field oriented control and the measurement of the first zero crossing can be estimated especially easily based on the estimated and/or the calculated rotational speed and/or the estimated and/or the calculated angular position
  • a method according to the invention can be characterized in that steps b) to g) or steps i) to m) are repeatedly executed every 20000, preferably every 7500, especially every 500, cycles of the field oriented control.
  • a field oriented control normally is executed in cycles.
  • the algorithm of the field oriented control is repeatedly executed, and the respective executions are separated in time by one cycle length each.
  • a cycle length can be for instance less than 1 ms, preferably less than 0,5 ms. Especially, the cycle length can be 0,05 ms.
  • Each execution of a method according to the invention needs electrical energy and especially
  • an electric motor comprising a rotor driven by an electric current comprising at least a first phase and controlled by a field oriented control, the field oriented control is based at least on an estimated status of the rotor and further on executed in cycles.
  • An electric motor according to the invention can be characterized in that electric motor comprises monitor means to execute a method according to the first aspect of the invention.
  • monitor means can be for instance a computer unit, sensors and data
  • an electric motor according the second aspect of the invention can provide the same advantages as described above in respect to a method according the first aspect of the invention.
  • an electric motor according to the invention can be characterized in that the electric motor is a permanent magnet synchronous motor (PMSM).
  • PMSM permanent magnet synchronous motor
  • permanent magnets are used in the rotor to provide magnetic fields. This provides the advantage that no or at least less electric connections have to be provided to the rotor.
  • An electric motor built as a permanent magnet synchronous motor can therefore be constructed very straightforward.
  • FIG. 1 A flow chart of the inventive method
  • Fig. 2 an electric motor according to the invention
  • Fig. 3 measured data during an execution of an inventive method.
  • FIG 1 a flowchart of a method according to the invention is shown.
  • the single steps a) to g) or steps h) to m) are represented with capital letters A to M.
  • the first three steps a) and h), b) and i) and c) and j) are identical in the two preferred embodiments of a method according to the invention.
  • the steps d) to g) and k) to m) respectively are shown of separated branches of the flowchart. It is noted, that these two embodiments can be performed alternatively or complementary.
  • Figure 2 shows an inventive electric motor 1 , which is able to carry out a method according to the invention as shown in Figure 1 .
  • Figure 3 some data is shown which is
  • FIG. 2 schematically shows an electric motor 1 .
  • the electric motor 1 comprises at least a rotor 2 and is driven by electric current 5 with three phases 6, 7, 8.
  • the electric motor 5 is constructed as a permanent magnet synchronous motor
  • CMOS in which permanent magnets are used in the rotor 2 to generate magnetic fields.
  • a field oriented control 10 is used to commutate the three phases 6, 7, 8 of the electric current 5 such, that a continuous, smooth and powerful operation of the electric motor 5 can be provided.
  • the field oriented control 10 can be executed in cycles 1 1 , for instance in cycles 1 1 of 0,05 ms, see for instance Figure 3.
  • the electric motor 1 further comprises monitor means 50, for instance a computer unit and sensors 51 , for an execution of a method according to the invention.
  • this field oriented control 10 is paused.
  • the rotor 2 of the electric motor 1 normally contains a huge amount of torque, and so it keeps rotating with an almost unchanged rotational speed 3, starting at an initial angular position 4.
  • This second step b) or i) is preferably executed an adjustable time interval 14 before a predicted first zero crossing 30, see Figure 3.
  • any status data of the electric motor 1 can be used, preferably the estimated rotational speed 12 and/or the estimated angular position 13 of the rotor 2 used in the field oriented control 10 and/or the calculated rotational speed 20 of the rotor 2 calculated in step f) and/or the calculated angular position 21 of the rotor 2 calculated in step I) respectively.
  • the electric motor 1 comprises several phases 6, 7, 8, the method according to the invention can be executed for each of the phases 6, 7, 8, preferably in a consecutive order.
  • a first zero crossing 30 and a second zero crossing and their respective time stamps 31 , 41 are detected, see Figure 3, in which especially the signals for the time stamps 31 , 41 are shown.
  • the actual measurement of the induced voltage is not shown.
  • the zero crossings 30, 40 have the same direction in respect to the sign of the induced voltage.
  • the zero crossings 30, 40 can for instance be detected by sensors 51 , especially voltage sensors and/or appropriate comparators and ADCs respectively.
  • the field oriented control 10 was paused, therefore no electric current 5 is applied.
  • the electric current of the first phase 15 is shown, which consequently shows a flat line during the pause of the field oriented control 10.
  • step e) of a method according to the invention see E in Figure 1 .
  • Electric current 5 is again commutated and distributed by the field oriented control 10 to the respective parts of the electric motor 1 , see Figure 3.
  • the field oriented control 10 can also be reactivated between the execution of steps c) and d) (not shown).
  • a calculated rotational speed 20 and preferably also a calculated angular position 21 is calculated.
  • the time difference 52 between the first timestamp 31 and the second time stamp 41 is used, see Figure 3.
  • the field oriented control 10 is monitored, especially by comparing the calculated rotational speed 20 with the estimated rotational speed 12 an preferably also by comparing the calculated angular position 21 with the estimated angular position 13, see the respective double arrows in Figure 2.
  • this comprises the possibility to check whether the estimated rotational speed 12 and/or the estimated angular position 13 are correct within the limits.
  • the field oriented control can be corrected by using the calculated rotational speed 20 and/or the calculated angular position 21 .
  • a first zero crossing 30 and its respective time stamp 31 is detected, see Figure 3.
  • the zero crossing 30 can for instance be detected by sensors 51 , especially voltage sensors and/or appropriate comparators and ADCs respectively.
  • the field oriented control 10 was paused, therefore no electric current 5 is applied. It is again referred to the lower part of Figure 3, in which the electric current of the first phase 15 is shown.
  • step k) of a method according to the invention see K in Figure 1 .
  • Electric current 5 is again commutated and distributed by the field oriented control 10 to the respective parts of the electric motor 1 .
  • the field oriented control 10 is monitored, especially by comparing the calculated angular position 21 with the estimated angular position 13, see the respective double arrow in Figure 2. On the one hand this comprises the possibility to check whether the estimated angular position 13 is correct within the limits. On the other hand, if the estimated angular position 13 is exceeding the limits, the field oriented control can be corrected by using the calculated angular position 21 .
  • the steps b) to g) or i) to m) of a method according to the invention can be repeatedly executed every 20000, preferably every 7500, especially every 500, cycles 1 1 of the field oriented control 10.
  • a method according to the invention provides the possibility to monitor a field oriented control 10. Especially the rotational speed 3 and/or the angular position 4 of the rotor 2 of the electric motor 1 can be calculated, without the need of further sensors and/or probes to directly measure this rotational speed 3 and/or angular position 4. Further, the field oriented control 10 can be improved by using the newly calculated rotational speed 20 and/or angular position 21 of the rotor 2 as basis for the on-going control.

Abstract

The invention is related to a method for monitoring a field oriented control (10) of an electric motor (1), the electric motor (1) comprises a rotor (2) and is driven by an electric current (5) comprising at least a first phase (6), the field oriented control (10) is based at least on an estimated status of the rotor (2) and further on is executed in cycles (11). Further on the invention is related to an electric motor (1), comprising a rotor (2) driven by an electric current (5) comprising at least a first phase (6) and controlled by a field oriented control (10), the field oriented control (10) is based at least on an estimated status (12, 13) of the rotor (2) and further on executed in cycles (11).

Description

Method for monitoring a field oriented control of an electric motor and electric motor
Description
The invention is related to a method for monitoring a field oriented control of an electric motor, the electric motor comprises a rotor and is driven by an electric current comprising at least a first phase, the field oriented control is based at least on an estimated rotational speed of the rotor and further on field oriented control is executed in cycles. Further on the invention is related to an electric motor, comprising a rotor and driven by an electric current comprising at least a first phase and controlled by a field oriented control, the field oriented control is based at least on an estimated rotational speed of the rotor and further on executed in cycles.
Electric motors are commonly used in modern technology. Especially electric motors driven by electric current are widely spread, for instance in vehicles and domestic and/or industrial applications. The electric current is used to generate magnetic fields in the rotor and/or the stator of such an electric motor and as a result to set the rotor in a rotational movement.
In the aforementioned electric motors, electrical phases of the electric current have to be connected to the electric motor in such a way that the magnetic fields are generated at the right positions and in the correct order in time. For this purpose, it is known to implement a field oriented control (FOC). The field oriented control is used to provide a commutation of the phases of the electric current such that an operation of the electric motor can be ensured.
The field oriented control is normally based on an estimated rotational speed of the rotor of the electric motor to correctly commutate the phases. According to known solutions in the state of the art, external sensors are used to measure the rotational speed of the rotor. This solution has the disadvantage that the sensor has to be included into the electric motor and therefore the electric motor cannot be constructed as compact as possible. Further on, such a sensor to measure the rotational speed of the rotor of the electric motor increases the overall complexity of an electric motor and also shortens the service intervals.
It is an object of the present invention to overcome aforesaid problems at least partially. Particularly, it is an object of the present invention to provide a simplified and/or more reliable and/or more precise solution for a method for monitoring a field oriented control of an electric motor and an electric motor, wherein especially sensors to measure a rotational speed of the rotor of the electric motor can be avoided.
Aforesaid object is achieved by a method according to independent claim 1 and by an electric motor according to claim 13. Further features and details of the invention result from the subclaims, the description and the figures. Features and details discussed with respect to the inventive method are also correlated with the inventive electric motor and the other way round in each case.
Particularly, the object is achieved by a method for monitoring a field oriented control of an electric motor, the electric motor comprises a rotor and is driven by an electric current comprising at least a first phase, the field oriented control is based at least on an estimated status of the rotor and further on field oriented control is executed in cycles. A method according to the invention is characterized in that the field oriented control is paused, that in this pause at least a first zero crossing of the first phase at a first time stamp is detected, that the field oriented control is afterwards restarted and that the additional information provided by the at least one detected first zero crossing is used to monitor the field oriented control.
A method according to the invention can be implemented and used by an electric motor controlled by a field oriented control. The electric motor can preferably be built as a permanent magnet synchronous motor. Further, the electric motor is driven by an electric current comprising at least one phase, wherein the current is distributed at the respective parts of the electric motor, especially coils to generate magnetic fields, according to the parameters provided by the field oriented control. This distribution can be also called commutation. To provide this commutation, the field oriented control is based on an estimated status of the rotor of the electric motor, for instance on an estimated rotational speed and/or on an estimated angular position of the rotor. To ensure a smooth and powerful operation of the electric motor, the estimated status should not differ from the actual respective status of the rotor of the electric motor, or at least the estimated status should be close to the actual status. A method according to the invention can provide this, especially without the requirement of an external sensor to measure the actual status of the rotor.
To provide the necessary information for a monitoring of the field oriented control, as a first element of a method according to the invention, the field oriented control is stopped. This ensures an elimination of influences of the field oriented control itself on obtaining the status information. Next, at least one first zero crossing, especially a first zero crossing of an induced voltage, induced by the on-going rotation of the rotor, of the first phase at a first time stamp is detected. To ensure a further operation of the electric motor, the field oriented control is restarted afterwards. Especially, according to the invention the information obtained from the detection of at least the first zero crossing and its respective first time stamp is used to monitor the field oriented control. This can be done for instance such that the information is used to calculate a calculated status of the rotor, wherein this calculated status is compared to the estimated status used in the field oriented control. This comparison allows detecting deviations of the estimated status used by the field oriented control from the actual status of the rotor and therefore to identify possible malfunction sources.
In summary, a method according to the invention provides the possibility to monitor a field oriented control. Especially the status of the rotor of the electric motor used by the field oriented control can be calculated based on simple voltage measurements, without the need of further sensors and/or probes to directly measure the status of the rotor itself. Further, the field oriented control can be improved by using the newly calculated status of the rotor as basis for the on-going control. In a first preferred embodiment of a method according to the invention, the field oriented control is based at least on an estimated rotational speed of the rotor. In other words, in this embodiment of a method according to the invention the used estimated status of the rotor is an estimated rotational speed of the rotor. A method according to this embodiment of the invention comprises the following steps:
a) perform the field oriented control of the electric motor,
b) pause the field oriented control of the electric motor,
c) detect a first zero crossing of the first phase at a first time stamp,
d) detect a second zero crossing of the first phase at a second time stamp, e) restart the field oriented control of the electric motor,
f) calculate a calculated rotational speed of the rotor based on the measured time stamps in steps c) and d), and
g) monitor the field oriented control by comparing the calculated rotational speed of step f) with the estimated rotational speed used by the field oriented control.
In this embodiment of a method according to the invention, the field oriented control is based at least on an estimated rotational speed of the rotor of the electric motor. To ensure a smooth and powerful operation of the electric motor, the estimated rotational speed should not differ from the actual rotational speed of the rotor of the electric motor, or at least the estimated rotational speed should be close to the actual rotational speed. A method according to the invention can provide this, especially without the requirement of an external sensor to measure the rotational speed of the rotor.
The first step a) describes the normal operation of the electric motor. The field oriented control is active and controls the commutation of the electric current to the respective recipients inside of the electric motor. Especially, the field oriented control can at least partly be implemented as a sensorless algorithm, for instance to provide an estimation of the magnetic flux within the electric motor.
In a second step b) of this embodiment of a method according to the invention, the field oriented control is paused. Therefore the control of the commutation of the electric power provided by the field oriented control is also stopped. The rotor of the electric motor rotates without further impetus. Nevertheless, as the method according to the invention stops the field oriented control only for a very short time period this has very little to no effect on the operation of the electrical motor. Further, this rotation generates an induction voltage in the first phase, which can be measured.
As mentioned above, by the rotation of the rotor of the electric motor, a voltage, especially a sinusoidal voltage, is induced in the lines of the first phase. This voltage oscillates between a negative and a positive maximum, wherein the oscillation frequency depends on the rotational speed of the rotor. Each cycle of the induced voltage therefore comprises two zero crossings, whose time difference allows to calculate the rotational speed of the rotor.
Therefore, in the next two steps c) and d) a first zero crossing of the first phase and a second zero crossing of the first phase respectively are detected. This can for instance be done by sensors and/or probes. Preferably, voltage sensors and/or appropriate comparators and ADCs respectively can be used.
In the next step e), the field oriented control of the electric motor is restarted. The two time stamp measurements done in step c) and d) provide enough information to calculate later on the rotational speed of the rotor. A restart of the field oriented control as soon as possible, especially only shortly after the measurement of the time stamp of the second zero crossing, therefore ensures a minimum influence of the
measurements done during the execution of a method according to the invention on the operation of the electric motor.
The actual calculation of the calculated rotational speed is carried out in step f) of a method according to the invention. The exact relation between the time difference of two zero crossings and the rotational speed of the rotor is known. It depends for instance of the type of the rotor, especially the number of electric poles used in the electric motor. The time difference itself can be easily calculated as difference of the two measured time stamps. After step f), the information of a calculated rotational speed of the rotor of the electric motor is present.
This calculated rotational speed is used in the last step g) of a method according to the invention. It is actually compared with the estimated rotational speed used in the field oriented control. Deviations between these two values of the rotational speed can for instance be used to measure the quality of the field oriented control, especially, how good the estimations are, which lead to the estimated rotational speed. Further on, the calculated rotational speed can also be used as new estimated rotational speed to improve the commutation provided by the field oriented control.
In summary, a method according to this embodiment of the invention provides the possibility to monitor a field oriented control based on an estimated rotational speed of the rotor. Especially the rotational speed of the rotor of the electric motor can be calculated, without the need of further sensors and/or probes to directly measure this rotational speed. Further, the field oriented control can be improved by using the newly calculated rotational speed of the rotor as basis for the on-going control.
Further on, a method according to the invention can be characterized in that the detected zero crossings in step c) and step d) have the same direction in respect to the sign of the voltage. As mentioned above, the induced voltage oscillates between a negative and a positive maximum. Therefore each cycle of the induced voltage comprises two zero crossings, wherein the direction changes, one zero crossing is in the direction of the positive maximum, the next in the direction of the negative maximum. In other words, by using zero crossings with the same direction in respect to the sign of the voltage, it can be ensured, that a complete cycle of the induced voltage is covered by the measurements done in step c) and d) of a method according to the invention. By this, the accuracy of the calculation of the rotational speed in step f) can be improved.
In addition, a method according to the invention can be characterized in that after step c) the field oriented control is restarted and before step d) the field oriented control is paused. By doing so, the duration in which the electric motor is driven without field oriented control can be minimized. The impact of a method according to the invention on the operation of an electric motor can thereby be reduced.
Further on, a method according to the invention can be characterized in that the field oriented control is additionally based on an estimated angular position of the rotor, that in step f) a calculated angular position of the rotor based on the measured time stamps in steps c) and d) is calculated, and that in step g) the calculated angular position of the rotor is compared to the estimated angular position used in the field oriented control. By implementing an additional usage of an estimated angular position as basis for the field oriented control, the commutation provided by the field oriented control can be improved. The information provided by the time stamps measured in step c) and d) of a method according to the invention, allows also to calculate an angular position of the rotor. This is due to the fact that, as already mentioned above the relation between the zero crossings and the rotation of the rotor is known. By widening the comparison of the results of the calculation, calculated rotational speed and calculated angular position, to the estimations on which the field oriented control is based, estimated rotational speed and estimated angular position, an overall improvement of the field oriented control can be achieved. For instance, in addition to the calculated rotational speed, also the calculated angular position can be used for the further execution of the field oriented control.
In a second preferred embodiment of a method according to the invention, the field oriented control is based at least in an estimated angular position of the rotor. In other words, in this embodiment of a method according to the invention the used estimated status of the rotor is an estimated angular position of the rotor. A method according to this embodiment of the invention comprises the following steps:
h) perform the field oriented control of the electric motor,
i) pause the field oriented control of the electric motor,
j) detect a first zero crossing of the first phase at a first time stamp,
k) restart the field oriented control of the electric motor, I) calculate a calculated angular position of the rotor based on the measured time stamp in step j), and
m) monitor the field oriented control by comparing the calculated angular position of step I) with the estimated angular position used by the field oriented control.
In this embodiment of a method according to the invention, the field oriented control is based at least on an estimated angular position of the rotor of the electric motor. To ensure a smooth and powerful operation of the electric motor, the estimated angular position should not differ from the actual angular position of the rotor of the electric motor, or at least the estimated angular position should be close to the actual angular position. A method according to the invention can provide this, especially without the requirement of an external sensor to measure the angular position of the rotor.
The first step h) describes the normal operation of the electric motor. The field oriented control is active and controls the commutation of the electric current to the respective recipients inside of the electric motor. Especially, the field oriented control can at least partly be implemented as a sensorless algorithm, for instance to provide an estimation of the magnetic flux within the electric motor.
In a second step i) of this embodiment of a method according to the invention, the field oriented control is paused. Therefore the control of the commutation of the electric power provided by the field oriented control is also stopped. The rotor of the electric motor rotates without further impetus. Nevertheless, as the method according to the invention stops the field oriented control only for a very short time period this has very little to no effect on the operation of the electrical motor. Further, this rotation generates an induction voltage in the first phase, which can be measured.
As mentioned above, by the rotation of the rotor of the electric motor, a voltage, especially a sinusoidal voltage, is induced in the lines of the first phase. This voltage oscillates between a negative and a positive maximum, wherein the oscillation frequency depends on the rotational speed of the rotor. Each cycle of the induced voltage therefore comprises two zero crossings, wherein each time stamp of the two zero crossings allow to calculate the angular position of the rotor.
Therefore, in the next step j) a first zero crossing of the first phase is detected. This can for instance be done by sensors and/or probes. Preferably, voltage sensors and/or appropriate comparators and ADCs respectively can be used.
In the next step k), the field oriented control of the electric motor is restarted. The time stamp measurement done in step j) provides enough information to calculate later on the angular position of the rotor. A restart of the field oriented control as soon as possible, especially only shortly after the measurement of the time stamp of the first zero crossing, therefore ensures a minimum influence of the measurements done during the execution of a method according to this embodiment of the invention on the operation of the electric motor.
The actual calculation of the calculated angular position is carried out in step I) of a method according to this embodiment of the invention. The exact relation between the time stamp of a zero crossing and the angular position of the rotor is known. It depends for instance of the type of the rotor, especially the position of electric poles used in the electric motor. After step I), the information of a calculated rotational speed of the rotor of the electric motor is present.
This calculated angular position is used in the last step m) of a method according to this embodiment of the invention. It is actually compared with the estimated angular position used in the field oriented control. Deviations between these two values of the angular position can for instance be used to measure the quality of the field oriented control, especially, how good the estimations are, which lead to the estimated angular position. Further on, the calculated angular position can also be used as new estimated angular position to improve the commutation provided by the field oriented control. In summary, a method according to this embodiment of the invention provides the possibility to monitor a field oriented control based on an estimated angular position of the rotor. Especially the angular position of the rotor of the electric motor can be calculated, without the need of further sensors and/or probes to directly measure this angular position. Further, the field oriented control can be improved by using the newly calculated angular position of the rotor as basis for the on-going control.
In particular, a method according to the invention can be characterized in that the electric current comprises two or more phases, preferably three phases, and that steps b) to g) or steps i) to m) are executed for each of the two or more phases. In this preferably embodiment an electric current with two or more phases, especially three phases, provides the electric power to drive the electric motor. By executing the steps b) to g) or steps i) to m), especially the two steps c) and d) or the step j), the advantages described above can be provided for each of the phases. The overall accuracy of a field oriented control monitored by a method according to the invention can therefore be improved further.
In an improved embodiment of a method according to the invention, the method can be characterized in that steps b) to g) or steps i) to m) are performed for each of the two or more phases in a consecutive order of the two or more phases. In this preferred embodiment of a method according to the invention, in each execution cycle of the method, a particular phase is surveyed. This reduces the workload and therefore increases the speed of the execution, especially for instance of the calculations done in step f) or I) respectively. A hindrance for the operation of the electric motor caused by a method according to the invention can therefore be avoided.
Further, a method according to the invention can be characterized in that restarting the field oriented control of the electric motor in step e) and/or k) is performed according to status data of the electric motor. The field oriented control is used to provide a commutation of the phases of the electric current such that an operation of the electric motor can be ensured. During the measurement of the one or more zero crossings, the field oriented control is paused and afterwards restarted. By performing this restart according to status data of the electric motor, a smooth and especially correct restart and/or reinitialization of the field oriented control can be ensured. The normal operation of the electric motor can therefore be continued without any negative influence caused by using a method according to the invention.
In addition, a method according to the invention can be characterized in that a time interval between the execution of step b) and the first zero crossing detected in step c) or a time interval between the execution of step i) and the first zero crossing detected in step j) is adjusted according to status data of the electric motor. It is especially preferable that the time duration, in which the field oriented control is disabled, is as short as possible. Therefore it is advantageously, if the time interval between the pausing of the field oriented control in step b) and the first zero crossing measured in step c) or the time interval between the execution of step i) and the first zero crossing detected in step j) respectively is as short as possible. This can be achieved by adjusting the time interval according to status data of the electric motor. Status data in the sense of the invention can for instance be the electric power consumption, the rotational speed of the rotor or similar data.
In an especially preferred embodiment, a method according to the invention can be characterized in that as status data of the electric motor the estimated rotational speed of the rotor used in the field oriented control and/or the calculated rotational speed of the rotor calculated in step f) and/or the estimated angular position of the rotor used in the field oriented control and/or the calculated angular position of the rotor calculated in step I) is used. The estimated and/or the calculated rotational speed and/or the estimated and/or the calculated angular position respectively speed can both be used to predict the time stamps of the zero crossings. Therefore the restarting of the field oriented control can be performed and respectively estimated especially easily based on the estimated and/or the calculated rotational speed and/or the estimated and/or the calculated angular position respectively. Additionally also the time interval between the pausing of the field oriented control and the measurement of the first zero crossing can be estimated especially easily based on the estimated and/or the calculated rotational speed and/or the estimated and/or the calculated angular position
respectively. Especially short time intervals can be chosen.
Further on, a method according to the invention can be characterized in that steps b) to g) or steps i) to m) are repeatedly executed every 20000, preferably every 7500, especially every 500, cycles of the field oriented control. A field oriented control normally is executed in cycles. In other words, the algorithm of the field oriented control is repeatedly executed, and the respective executions are separated in time by one cycle length each. A cycle length can be for instance less than 1 ms, preferably less than 0,5 ms. Especially, the cycle length can be 0,05 ms. Each execution of a method according to the invention needs electrical energy and especially
computational power. Additionally, a sudden change in the parameters of the electric motor is often unlikely. Therefore it is preferably, to execute the steps b) to g) or steps i) to m) not for each cycle of the field oriented control, but only every 20000, preferably every 7500, especially every 500, cycles of the field oriented control. By this, electrical energy and especially computational power can be saved, without losing the advantages of a method according to the invention described above.
According to another aspect of the invention the object is achieved by an electric motor, comprising a rotor driven by an electric current comprising at least a first phase and controlled by a field oriented control, the field oriented control is based at least on an estimated status of the rotor and further on executed in cycles. An electric motor according to the invention can be characterized in that electric motor comprises monitor means to execute a method according to the first aspect of the invention. Such monitor means can be for instance a computer unit, sensors and data
connections, both wired and wireless. By the possibility to execute a method according the first aspect of the invention, an electric motor according the second aspect of the invention can provide the same advantages as described above in respect to a method according the first aspect of the invention.
Further on, an electric motor according to the invention can be characterized in that the electric motor is a permanent magnet synchronous motor (PMSM). In this particular electric motor, permanent magnets are used in the rotor to provide magnetic fields. This provides the advantage that no or at least less electric connections have to be provided to the rotor. An electric motor built as a permanent magnet synchronous motor can therefore be constructed very straightforward.
In the following, preferred embodiments of the invention are described based on supportive figures. Thereby, the features described in the claims and in the description, can be each single or in every combination be essential for the invention. It is shown in schematically:
Fig. 1 A flow chart of the inventive method,
Fig. 2 an electric motor according to the invention, and
Fig. 3 measured data during an execution of an inventive method.
In Figure 1 a flowchart of a method according to the invention is shown. The single steps a) to g) or steps h) to m) are represented with capital letters A to M. The first three steps a) and h), b) and i) and c) and j) are identical in the two preferred embodiments of a method according to the invention. The steps d) to g) and k) to m) respectively are shown of separated branches of the flowchart. It is noted, that these two embodiments can be performed alternatively or complementary. Figure 2 shows an inventive electric motor 1 , which is able to carry out a method according to the invention as shown in Figure 1 . In Figure 3 some data is shown which is
representative for an execution of a method according to the invention for one of the phases 6, 7, 8. In the following, all three Figures 1 to 3 are therefore described together, wherein the details of the different Figures are emphasised.
Figure 2 schematically shows an electric motor 1 . The electric motor 1 comprises at least a rotor 2 and is driven by electric current 5 with three phases 6, 7, 8. Preferably, the electric motor 5 is constructed as a permanent magnet synchronous motor
(PMSM), in which permanent magnets are used in the rotor 2 to generate magnetic fields. To drive the electric motor 1 with electric current 5, a field oriented control 10 is used to commutate the three phases 6, 7, 8 of the electric current 5 such, that a continuous, smooth and powerful operation of the electric motor 5 can be provided. This is for instance the case in the starting step a), h) of a method according to the invention, see A, H in Figure 1 . The field oriented control 10 can be executed in cycles 1 1 , for instance in cycles 1 1 of 0,05 ms, see for instance Figure 3. The electric motor 1 further comprises monitor means 50, for instance a computer unit and sensors 51 , for an execution of a method according to the invention.
In a second step b) or i), see B, I in Figure 1 , of a method according to the invention, this field oriented control 10 is paused. The rotor 2 of the electric motor 1 normally contains a huge amount of torque, and so it keeps rotating with an almost unchanged rotational speed 3, starting at an initial angular position 4. This second step b) or i) is preferably executed an adjustable time interval 14 before a predicted first zero crossing 30, see Figure 3. For an adjustment of this time interval 14 any status data of the electric motor 1 can be used, preferably the estimated rotational speed 12 and/or the estimated angular position 13 of the rotor 2 used in the field oriented control 10 and/or the calculated rotational speed 20 of the rotor 2 calculated in step f) and/or the calculated angular position 21 of the rotor 2 calculated in step I) respectively. If, as depicted, the electric motor 1 comprises several phases 6, 7, 8, the method according to the invention can be executed for each of the phases 6, 7, 8, preferably in a consecutive order.
In the following, a first preferred embodiment of a method according to the invention comprising the steps a) to g), see A to G in Figure 1 , is described.
In the next two steps c) and d), see C and D in Figure 1 , of a this method according to the invention, a first zero crossing 30 and a second zero crossing and their respective time stamps 31 , 41 are detected, see Figure 3, in which especially the signals for the time stamps 31 , 41 are shown. The actual measurement of the induced voltage is not shown. Preferably, the zero crossings 30, 40 have the same direction in respect to the sign of the induced voltage. The zero crossings 30, 40 can for instance be detected by sensors 51 , especially voltage sensors and/or appropriate comparators and ADCs respectively. As in step b), the field oriented control 10 was paused, therefore no electric current 5 is applied. In the lower part of Figure 3, the electric current of the first phase 15 is shown, which consequently shows a flat line during the pause of the field oriented control 10.
After the detection of the second zero crossing 40 and of the respective second time stamp 41 , the field oriented control 10 is restarted in step e) of a method according to the invention, see E in Figure 1 . Electric current 5 is again commutated and distributed by the field oriented control 10 to the respective parts of the electric motor 1 , see Figure 3. For a further improvement, the field oriented control 10 can also be reactivated between the execution of steps c) and d) (not shown).
In the following step f), see F in Figure 1 , a calculated rotational speed 20 and preferably also a calculated angular position 21 is calculated. For this, especially the time difference 52 between the first timestamp 31 and the second time stamp 41 is used, see Figure 3.
In the last step g) of a method according to the invention, see G in Figure 1 , the field oriented control 10 is monitored, especially by comparing the calculated rotational speed 20 with the estimated rotational speed 12 an preferably also by comparing the calculated angular position 21 with the estimated angular position 13, see the respective double arrows in Figure 2. On the one hand this comprises the possibility to check whether the estimated rotational speed 12 and/or the estimated angular position 13 are correct within the limits. On the other hand, if the estimated rotational speed 12 and/or the estimated angular position 13 are exceeding the limits, the field oriented control can be corrected by using the calculated rotational speed 20 and/or the calculated angular position 21 .
In the following, a second preferred embodiment of a method according to the invention comprising the steps h) to m), see H to M in Figure 1 , is described.
After the pausing of the performed field oriented control 10 in step i), see I in Figure 1 , in the next step j), see J in Figure 1 , of a this method according to the invention, a first zero crossing 30 and its respective time stamp 31 is detected, see Figure 3. The zero crossing 30 can for instance be detected by sensors 51 , especially voltage sensors and/or appropriate comparators and ADCs respectively. As in step i), the field oriented control 10 was paused, therefore no electric current 5 is applied. It is again referred to the lower part of Figure 3, in which the electric current of the first phase 15 is shown.
After the detection of the first zero crossing 30 and of the respective first time stamp 31 , the field oriented control 10 is restarted in step k) of a method according to the invention, see K in Figure 1 . Electric current 5 is again commutated and distributed by the field oriented control 10 to the respective parts of the electric motor 1 .
In the following step I), see L in Figure 1 , a calculated angular position 20 is
calculated. For this, especially the time stamp 31 and the known internal structure of the rotor 2, for instance the number and the positions of the permanent magnets and/or the magnetic coils, is used, see Figure 3.
In the last step m) of this embodiment of a method according to the invention, see M in Figure 1 , the field oriented control 10 is monitored, especially by comparing the calculated angular position 21 with the estimated angular position 13, see the respective double arrow in Figure 2. On the one hand this comprises the possibility to check whether the estimated angular position 13 is correct within the limits. On the other hand, if the estimated angular position 13 is exceeding the limits, the field oriented control can be corrected by using the calculated angular position 21 .
For a further general improvement of embodiments, the steps b) to g) or i) to m) of a method according to the invention can be repeatedly executed every 20000, preferably every 7500, especially every 500, cycles 1 1 of the field oriented control 10.
In summary, a method according to the invention provides the possibility to monitor a field oriented control 10. Especially the rotational speed 3 and/or the angular position 4 of the rotor 2 of the electric motor 1 can be calculated, without the need of further sensors and/or probes to directly measure this rotational speed 3 and/or angular position 4. Further, the field oriented control 10 can be improved by using the newly calculated rotational speed 20 and/or angular position 21 of the rotor 2 as basis for the on-going control.
Reference list
1 electric motor
2 rotor
3 rotational speed
4 angular position
5 electric current
6 first phase
7 second phase
8 third phase
10 field oriented control
1 1 cycle
12 estimated rotational speed
13 estimated angular position
14 time interval
15 current of the first phase
20 calculated rotational speed
21 calculated angular position
30 first zero crossing
31 first time stamp
40 second zero crossing
41 second time stamp
50 monitor means
51 sensor
52 time difference

Claims

Patent claims
1 . Method for monitoring a field oriented control (10) of an electric motor (1 ), the electric motor (1 ) comprises a rotor (2) and is driven by an electric current (5) comprising at least a first phase (6), the field oriented control (10) is based at least on an estimated status (12, 13) of the rotor (2) and further on is executed in cycles (1 1 ),
characterized in that
the field oriented control (10) is paused, that in this pause at least a first zero crossing (30) of the first phase (6) at a first time stamp (31 ) is detected, that the field oriented control (10) is restarted and that the additional information provided by the at least one detected first zero crossing (30) is used to monitor the field oriented control (10).
2. Method according to claim 1 , wherein the field oriented control (10) is based at least on an estimated rotational speed (12) of the rotor (2),
comprising the following steps:
a) perform the field oriented control (10) of the electric motor (1 ), b) pause the field oriented control (10) of the electric motor (1 ), c) detect a first zero crossing (30) of the first phase (6) at a first time
stamp (31 ),
d) detect a second zero crossing (40) of the first phase (6) at a second time stamp (41 ),
e) restart the field oriented control (10) of the electric motor (1 ), f) calculate a calculated rotational speed (20) of the rotor (2) based on the measured time stamps (31 , 41 ) in steps c) and d), and
g) monitor the field oriented control (10) by comparing the calculated rotational speed (20) of step f) with the estimated rotational speed (12) used by the field oriented control (10). Method according to claim 2,
characterized in that
the detected zero crossings in step c) and step d) have the same direction in respect to the sign of the voltage.
Method according to claim 2 or 3,
characterized in that
after step c) the field oriented control (10) is restarted and before step d) the field oriented control (10) is paused.
Method according to one of the preceding claims 2 to 4,
characterized in that
the field oriented control (10) is additionally based on an estimated angular position (13) of the rotor (2),
that in step f) a calculated angular position (21 ) of the rotor (2) based on the measured time stamps (31 , 41 ) in steps c) and/or d) is calculated, and that in step g) the calculated angular position (21 ) of the rotor (2) is compared to the estimated angular position (13) used in the field oriented control (10).
Method according claim 1 , wherein the field oriented control (10) is based at least on an estimated angular position (13) of the rotor (2)
comprising the following steps:
h) perform the field oriented control (10) of the electric motor (1 ), i) pause the field oriented control (10) of the electric motor (1 ), j) detect a first zero crossing (30) of the first phase (6) at a first time stamp (31 ),
k) restart the field oriented control (10) of the electric motor (1 ),
I) calculate a calculated angular position (21 ) of the rotor (2) based on the measured time stamp (31 ) in step j), and
m) monitor the field oriented control (10) by comparing the calculated angular position (21 ) of step I) with the estimated angular position (13) used by the field oriented control (10).
7. Method according to one of the preceding claims 2 to 6,
characterized in that
the electric current (5) comprises two or more phases (6, 7, 8), preferably three phases (6, 7, 8), and that steps b) to g) or steps i) to m) are executed for each of the two or more phases (6, 7, 8).
8. Method according to claim 7,
characterized in that
steps b) to g) or steps i) to m) are performed for each of the two or more phases (6, 7, 8) in a consecutive order of the two or more phases (6, 7, 8).
9. Method according to one of the preceding claims 2 to 8,
characterized in that
restarting the field oriented control (10) of the electric motor (1 ) in step e) and/or k) is performed according to status data of the electric motor (1 ).
10. Method according to one of the preceding claims 2 to 9,
characterized in that
a time interval (14) between the execution of step b) and the first zero crossing (30) detected in step c) or a time interval (14) between the execution of step i) and the first zero crossing (30) detected in step j) is adjusted according to status data of the electric motor (1 ).
1 1 . Method according to claim 10,
characterized in that
as status data of the electric motor (1 ) the estimated rotational speed (12) of the rotor (2) used in the field oriented control (10) and/or the calculated rotational speed (20) of the rotor (2) calculated in step f) and/or the estimated angular position (13) of the rotor (2) used in the field oriented control (10) and/or the calculated angular position (21 ) of the rotor (2) calculated in step I) is used.
12. Method according to one of the preceding claims 2 to 1 1 ,
characterized in that
steps b) to g) or steps i) to m) are repeatedly executed every 20000, preferably every 7500, especially every 500, cycles (1 1 ) of the field oriented control (10).
13. Electric motor (1 ), comprising a rotor (2) driven by an electric current (5) comprising at least a first phase (6) and controlled by a field oriented control (10), the field oriented control (10) is based at least on an estimated status (12, 13) of the rotor (2) and further on executed in cycles (1 1 ),
characterized in that
the electric motor (1 ) comprises monitor means (50) to execute a method according to one of the preceding claims to monitor the field oriented control (10).
14. Electric motor (1 ) according to claim 13,
characterized in that
the electric motor (1 ) is a permanent magnet synchronous motor.
PCT/EP2017/073238 2017-09-15 2017-09-15 Method for monitoring a field oriented control of an electric motor and electric motor WO2019052650A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
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Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005076458A1 (en) * 2004-02-06 2005-08-18 Micro-Beam Sa Method and device for controlling a synchronous motor with permanent magnets
WO2006012990A1 (en) * 2004-07-30 2006-02-09 Aesculap Ag & Co. Kg Surgical machine and method for controlling and/or regulating one such surgical machine
DE102014001184A1 (en) * 2014-01-30 2015-07-30 Otto Bock Healthcare Products Gmbh Method for operating an electric motor

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005076458A1 (en) * 2004-02-06 2005-08-18 Micro-Beam Sa Method and device for controlling a synchronous motor with permanent magnets
WO2006012990A1 (en) * 2004-07-30 2006-02-09 Aesculap Ag & Co. Kg Surgical machine and method for controlling and/or regulating one such surgical machine
DE102014001184A1 (en) * 2014-01-30 2015-07-30 Otto Bock Healthcare Products Gmbh Method for operating an electric motor

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