METHOD AND DEVICE FOR ADJUSTING AN ACTUATOR MEMBER OF A POSITIONING SYSTEM WITH AN ELECTRONICALLY COMMUTATED ACTUATOR DRIVE

Abstract

A method is proposed for adjusting an actuator (300) of a positioning system (100). The positioning system (100) has an electronically commutated actuator drive (200) which is coupled to the actuator (300), wherein the actuator drive (200) has a permanent magnetic rotor (210), wherein the rotor (210) has a first shaft (212) which extends along a pole axis (290) of the rotor (210). The actuator drive (200) additionally has an electronically commutated stator (230), wherein the stator (230) can be energized using a space phasor (260), wherein the space phasor (260) has an electric phase and an amplitude, wherein the space phasor (260) is aligned with respect to the first shaft (212) of the rotor (210) around a difference phasing. In order to be able to actuate a predefined position of the actuator, even without sensors to determine the position of the first shaft (212) of the rotor (210), the following steps of the method are thereby provided: setting the difference phasing of the space phasor (260) to an operating difference phasing; setting the amplitude to an operating amplitude, wherein the operating difference phasing and the operating amplitude are set in such a way that the operating difference phasing is less than 45 and that a torque is generated at the rotor (210) suitable for starting up the predefined position of the actuator (300). The invention further relates to a device for adjusting an actuator (300) of a positioning system (100) and a computer program product which contains a program code which, when it is executed by a data processing unit, implements the method according to the invention.

Claims

1-15. (canceled)

16. A method for adjusting an actuator member of a positioning system, wherein the positioning system has an electronically commutated actuator drive which is coupled to the actuator member, wherein the actuator drive has a rotor with permanent magnets, wherein the rotor has a first axis which extends along a pole axis of the rotor, and wherein the actuator drive has an electronically commutated stator, wherein the stator can be energized with a space phasor, wherein the space phasor has an electric phase .sub.el and an amplitude A, wherein the space phasor is oriented about a differential phasing relative to the first axis of the rotor, characterized in that the method comprises the following steps for controlling a predefined position of the actuator member: setting the differential phasing of the space phasor to an operating differential phasing .sub.O, setting the amplitude A to an operating amplitude A.sub.O, wherein the operating differential phasing .sub.O and the operating amplitude A.sub.O are set such that the operating differential phasing .sub.O is less than 45, and that a torque is generated which acts on the rotor and is suitable for approaching the predefined position of the actuator member.

17. The method according to claim 16, characterized in that the positioning system comprises means for detecting a position value L of the position of the first axis.

18. The method according to claim 17, characterized in that the means comprise at least one calibration step for determining a position value L.

19. The method according to claim 16, characterized in that at the predefined position of the actuator member, the actuator member is fully opened and/or the actuator member comes to rest on a mechanical stop.

20. The method according to claim 16, characterized in that the predefined position of the actuator member is reached in less than 300 ms, in particular in less than 100 ms.

21. The method according to claim 16, characterized in that the control for rotating the electrical phase el of the space phasor takes place such that the depiction of the phase control values over the control time gives a curve which can be differentiated at any time, i.e. in particular the left-side derivative at any time corresponds to the right-side derivative.

22. The method according to claim 16, characterized in that the method is performed only after the occurrence of a defined event, wherein without the occurrence of the defined event for adjusting the position of the actuator member, the space phasor is oriented relative to the first axis of the rotor by a differential phasing which lies in a range between 45 and 135, in particular in a range from 70 to 110.

23. The method according to claim 16, characterized in that the means for detecting a position value L of the position of the first axis are at least one sensor arranged on the actuator member and/or at least one sensor arranged on the actuator drive.

24. The method according to claim 16, characterized in that the positioning system comprises a memory for storing position values L of the position of the first axis, and that on occurrence of the defined event, a position value L is retrieved from the memory in order to set the operating differential phasing .sub.O.

25. The method according to claim 16, characterized in that the defined event is a malfunction of the sensor or the failure of the sensor.

26. The method according to claim 16, characterized in that the predefined position of the actuator member is a position in which the actuator member comes to rest on a mechanical stop, wherein a differential phase angle of the electrical phase .sub.el of the space phasor results from the difference between a first electrical phase 1 of the space phasor at the predefined position and a second electrical phase 2 of the space phasor which the space phasor has at the position value L retrieved from the memory plus a multiple of 360, in particular plus 720.

27. A device for adjusting an actuator member of a positioning system, wherein the positioning system has an electronically commutated actuator drive which is coupled to the actuator member, wherein the actuator drive has a rotor with permanent magnets, wherein the rotor has a first axis which extends along a pole axis of the rotor, and wherein the actuator drive has an electronically commutated stator, wherein the stator can be energized with a space phasor, wherein the space phasor has an electrical phase .sub.el and an amplitude A, wherein the space phasor can be oriented about a differential phasing relative to the first axis of the rotor, characterized in that the device is configured to approach a predefined position of the actuator member in that: the space phasor can be controlled such that the differential phasing can be set to an operating differential phasing .sub.O, wherein the space phasor can be controlled such that the amplitude A can be set to an operating amplitude A.sub.O, wherein the operating differential phasing .sub.O and the operating amplitude A.sub.O can be set such that the operating differential phasing .sub.O is less than 45, and the space phasor generates a torque acting on the rotor and suitable for approaching the predefined position of the actuator member.

28. The device according to claim 27, characterized in that the device is configured to approach a predefined position of the actuator member in a normal operating mode, in that the space phasor can be oriented relative to the first axis of the rotor about a differential phasing of more than 45, in particular about a differential phasing of more than 70, wherein the amplitude A can be set such that the space phasor generates a torque acting on the rotor and suitable for approaching a predefined position, and that the device is furthermore configured to approach the predefined position of the actuator member only after occurrence of a defined event, in that the operating differential phasing .sub.O and the operating amplitude A.sub.O can be set such that the operating differential phasing .sub.O is less than 45, and that the space phasor generates a torque acting on the rotor and suitable for approaching the predefined position.

29. The device according to claim 27, characterized in that the positioning system comprises means for detecting a position value L of the position of the first axis, wherein the means for detecting the position value L are at least one sensor arranged on the actuator member and/or at least one sensor arranged on the actuator drive, wherein the positioning system comprises a memory for storing position values L of the position of the first axis, and wherein on occurrence of the defined event, a position value L is retrieved from the memory in order to set the operating differential phasing .sub.O, and wherein the defined event is a malfunction of the sensor or the failure of the sensor.

30. A computer program product which contains a program code which, if executed on a data processing unit, performs the method according to claim 16.

Description

DRAWINGS

[0042] Further features and advantages of the present invention will become clear to the person skilled in the art from the description below of exemplary embodiments, which should not however be interpreted so as to restrict the invention, and with reference to the enclosed drawings.

[0043] The drawings show:

[0044] FIG. 1a a diagrammatic depiction of a positioning system;

[0045] FIG. 1b a depiction of the torque exerted by the stator on the rotor for various amplitudes and differential phasings of the space phasor running around the stator, and a depiction of the counter-torque acting on the actuator member as a function of the rotary angle of the actuator member;

[0046] FIG. 2 a depiction of various space phasor vectors which exert the same torque on the rotor;

[0047] FIG. 3a a depiction of the method process in normal operation;

[0048] FIG. 3b a depiction of the method process after occurrence of the defined event;

[0049] FIG. 4 a depiction of the control of the electrical phasing of the space phasor from a first position to the position at the predefined position of the actuator member.

[0050] All figures are merely diagrammatic depictions of devices or methods or their constituents according to the invention, according to exemplary embodiments of the invention. In particular, distances and size ratios are not shown to scale in the figures. In the various figures, corresponding elements carry the same reference numerals.

[0051] FIG. 1a shows a positioning system 100 which can be controlled by a control unit (not shown). The positioning system comprises an electronically commutated actuator drive 200, e.g. a brushless electric motor.

[0052] The actuator drive 200 is coupled to an actuator member 300 via a gear mechanism 280 with a gear ratio G=n1:n2. The actuator drive 200 has a rotor 210 with permanent magnets, wherein the rotor has a first axis 212 which extends along a pole axis 290 of the rotor 210. The first axis 212 is normally designated the d-axis. The rotor 210 in addition has a second axis 214 oriented perpendicular to the first axis 212, which thus also stands perpendicular to the pole axis 290 and is conventionally known as the q-axis (in the rotor coordinate system).

[0053] The actuator drive 200 also has an electronically commutated stator 230 which in the embodiment shown has a pole pair count of 1. The stator thus has three energizable coils 232A, 232B, 232C which are arranged offset by 120 to each other. Correspondingly, with a pole pair count of 2, a total of six energizable coils would be provided, each offset by 60 to each other. The stator 230, or the coils 232A, 232B, 232C can be energized with a space phasor 260. The space phasor 260 can be described by polar coordinates. With regard to a positionally fixed coordinate system of the stator 230, the space phasor 260 can be unambiguously determined by an electrical phase .sub.el which describes an angular value to a reference axis in the stator 230, and by an amplitude A which indicates the length of the space phasor 260 and is proportional to the size of the current loading the stator 230. The electrical phase .sub.el may assume any arbitrary positive or negative value, wherein in the positionally fixed coordinate system of the stator 230, the space phasor 260 always points in the same direction after a multiple of 360. Thus the direction of the space phasor 260 in the positionally fixed coordinate system of the stator 260 can only reflect the electrical phase .sub.el of the space phasor 260 up to a multiple of 360. With regard to the rotor 210, the space phasor 260 has a differential phasing , wherein the differential phasing is the angle by which this space phasor 260 is rotated relative to the first axis 212 of the rotor 210 (in the positionally fixed coordinate system of the rotor 210). The differential phasing may by definition assume any angle between 180 and +180. The rotor 210 with permanent magnets is now forced, due to the stator magnetic field caused by energizing of the stator coils 232, to orient itself with its pole axis 290 along this stator magnetic field. Thus a rotation of the space phasor 260 and the stator magnetic field co-rotating with the space phasor 260 causes a mechanical rotation of the rotor 210. The rotor 210 is thus rotated when the stator magnetic field applies a force or a torque resulting from this force on the rotor 210. In the state without a counter-torque, this can only be the case if the stator magnetic field and hence the space phasor 260 are rotated about a differential phasing of more than 0 relative to the first axis 212 of the rotor 210.

[0054] Viewed in a coordinate system of the stator 230, the rotor 210 with its mechanical angle phase thus follows the electrical phase of the space phasor 260 as long as the space phasor 260 has a sufficient amplitude A to overcome any counter-torque acting on the rotor 210. Assuming a state free from counter-torque, the mechanical phasing of the rotor, or the rotor position or the position of the first axis 212 of the rotor 210, is therefore unambiguously coupled to the electrical phasing .sub.el of the space phasor 260. The term position value L of the position of the first axis 212 of the rotor 210 can therefore be understood to be the mechanical angular rotation of the rotor 210 starting from an original state of 0.

[0055] The drawing shows as an example two different space phasors 260 which have the same differential phasing relative to the rotor 210, but different lengths i.e. different amplitudes A. The space phasor designated 260A has a smaller amplitude A1 than the space phasor designated 260B with its amplitude A2. Also, space phasors 260 are shown which are designated i.sub.q and i.sub.d. Here the space phasor 260 designated i.sub.d is oriented along the first axis of the rotor 210 and has a differential phasing of 0. The space phasor 260 designated i.sub.q is oriented along the second axis 214 of the rotor 210 and has a differential phasing of 90. In general, each space phasor 260 can be depicted as a linear combination of the space phasor 260 designated i.sub.q and the space phasor 260 designated i.sub.d. The electrical phase .sub.el of the space phasors 260 shown is here insignificant for the time being.

[0056] The right-hand part of FIG. 1a shows the actuator member 300 coupled to the actuator drive 200. The actuator member may for example be a throttle valve, a general-purpose actuator member, a charge movement valve, a control of an exhaust gas recirculation valve, or a screen wiper motor, or any other element arranged on an actuator member. The actuator member 300 is spring-loaded in the exemplary embodiment shown. A first abutment 310 for a first spring 312 is provided, wherein the first spring 312 is configured to move the actuator member 300 to the first abutment 310. Also, a second abutment 320 is provided for a second spring 322 which acts in the opposite direction to the first spring 312. In the exemplary embodiment shown, the actuator member 300 is for example in a position which is horizontal in the figure, i.e. a closed position resting on the first abutment 310. It can be moved counterclockwise up to a mechanical stop 380 about a mechanical phase or mechanical adjustment angle . Such a movement can be provoked by rotation of the rotor 210 of the actuator drive 200. In non-energized state of the actuator drive 200, the actuator member 300 moves to a position in which the forces of the first spring 312 and the second spring 322 cancel each other out. In order to move the actuator member out of this position in one of the two directions, a torque is then necessary which acts against the springs. In the exemplary embodiment shown, a sensor 350 is provided on the actuator member which detects a position value of the actuator member 300.

[0057] Since the rotor 210 is unambiguously coupled to the actuator member 300 via the gear mechanism 280, by determining the position of the actuator member 300 i.e. the adjustment angle , also the position value L of the first axis 212 of the rotor, i.e. the mechanical phase of the first axis 212 of the rotor 210 or the rotor position, can be unambiguously established. The mechanical phase a of the actuator member 300 is linked to the position value L of the first axis 212 of the rotor 210 via the following relation:

=L/G,

wherein G is the translation ratio G=n1:n2 of the gear mechanism 280.

[0058] Assuming that the space phasor 260 is sufficiently energized at any time to drag the rotor 210 with it, i.e. the force of the stator 230 acting on the rotor 210 is greater than e.g. the counter-force from the first spring 312 which increases as the actuator member 300 opens further, then the mechanical phase of the actuator member 300 is also unambiguously coupled to the electrical phase .sub.el of the space phasor 260, following the relation:

=L/(G*NP),

wherein NP is the pole pair count of the stator.

[0059] With a pole pair count of NP=1 and a gear ratio of G=40:1, one rotation of the space phasor 260 by 3600 corresponds to one revolution of the first axis 212 of the rotor 210 by also 3600, and causes a mechanical rotation of the actuator member 300 by an adjustment angle of 90. It is evident that other gear ratios are also possible, e.g. G=20:1.

[0060] FIG. 1b shows on the right-hand side a depiction of the counter-torque T.sub.C acting on the rotor 210 as a function of the adjustment angle of the actuator member 300. For the sake of simplicity, a linear correlation is assumed for the functional connection between the counter-torque T.sub.C and the adjustment angle of the actuator member 300, as given for example for a spring in Hookes' law. Evidently, a different functional correlation may exist between the counter-torque T.sub.C and the rotary angle or adjustment angle . In order therefore to adjust the actuator member in the direction of a greater adjustment angle , a greater counter-torque T.sub.C at the rotor 210 must be overcome. Such a torque T.sub.C is finally provided by the actuator drive 200. This means that as the adjustment angle of the actuator member 300 increases, the torque exerted by the space phasor 260 on the rotor 210 must also increase.

[0061] FIG. 1b shows on the left-hand side a depiction of the torque T.sub.M exerted on the rotor 210 by the stator 230 for different amplitudes A and differential phasing of the space phasor 260 energizing the stator 230. The differential phasing is here shown from 180 to +180. As already described above, for a differential phasing of 0 under ideal conditions, a state exists in which no torque is exerted by the space phasor 260 on the first axis 212 of the rotor 210, since the space phasor 260 and the first axis 212 are in this case arranged co-linear to each other.

[0062] In other words, in this case the space phasor 260 has no component in the direction of the q-axis, i.e. the second axis 214 of the rotor 210, which alone can exert a torque on the rotor 210. With a differential phasing of 90 and +90, the torque exerted by the space phasor 260 on the first axis 212 of the rotor 210 is at a maximum. In other words, consequently, with a differential phasing of around 90, i.e. a fixed amplitude, the greatest torque can be achieved, or for a predefined torque T.sub.M to be achieved, this can be achieved at a differential phasing of 90 with a smaller amplitude than at any other differential phasing . Thus the actuator drive 200 can be operated for optimum efficiency with a differential phasing of around 90, since the smallest power consumption or smallest amplitude of the space phasor 260 is thus required to achieve a predefined torque T.sub.M.

[0063] Looking now at the left- and right-hand sides of FIG. 1b together, for each adjustment angle of the actuator member 300, a counter-torque T.sub.C can be determined which must be exerted by the magnetic field of the stator 230, provoked by the space phasor 260, on the rotor 210 in order to achieve or maintain the adjustment angle of the actuator member 300. In order to achieve or maintain the adjustment angle of 27 shown as an example on the right-hand side, a value T1 of the counter-torque T.sub.C is required. Above the diagram, the adjustment angle position of the actuator member 300 for some adjustment angles is shown diagrammatically.

[0064] Thus a space phasor 260 must be provided which generates a torque T.sub.M of T1 against the rotor 210. Finally, for each adjustment angle , T.sub.M=T.sub.C. As shown on the left-hand side of FIG. 1b, this can be achieved with a space phasor 260 with an amplitude A3 for a differential phasing of for example 5 or 175. If a space phasor with an amplitude A2 is used, wherein A2 is less than A3, the differential phasing necessary to achieve T1 is for example 25 or 155. If however a space phasor 260 is used with an efficiency-optimised amplitude A1 which is less than A2, the torque T1 is reached only with a differential phasing of 90.

[0065] At even smaller amplitudes, the counter-force (e.g. of the first spring 312) rotates the actuator member 300 and the rotor 210 coupled thereto back until the torque equation is again fulfilled, i.e. the counter-torque T.sub.C is compensated by the torque T.sub.M generated by the amplitude and the differential phasing .

[0066] For an adjustment angle of 72, a second counter-torque T2 applies which is greater than the first counter-torque T1. Thus it is necessary to also provide a second torque at the rotor. In the exemplary depiction, this can be achieved at a differential phasing of 90 with the amplitude A2 or a greater amplitude, wherein then a differential phasing other than 90 is sufficient.

[0067] Finally, it results from this that to achieve a torque of T1, a solution space exists with various combinations of differential phasings and amplitudes A, wherein for a differential phasing of 90 there is only one suitable amplitude A.sub.u, wherein this amplitude A.sub.u has the lowest value of all amplitudes of this solution space. At the same time, for ever smaller differential phasings, an ever greater amplitude is required in order to provide the desired torque T1. Thus the lower limit of the differential phasing down to the value 0 or the upper limit up to the value of 180 is finally determined for constructional reasons by the maximum available amplitude A.sub.o (i.e. for example by the current carrying capacity of the stator coils 232). In order to keep the installation space as small as possible and at the same time keep the energy consumption as low as possible, it is therefore normal to operate such electronically commutated motors or actuator drives 200 for optimum efficiency. In the real world, the efficiency-optimised differential phasing may deviate from 90 due to the counter-torque and internal friction forces. Thus slightly higher amounts are sensible for high rotation speeds, whereby higher moments can be achieved due to weakening of the magnetic rotor flux. The precise values for the differential phasing and the amplitude A of the space phasor 260 can be determined by various ways, e.g. using a so-called field-oriented method (FOR method) with direct measurement of the phase currents. In each case, to set the space phasor in efficiency-optimised mode, i.e. at differential phasings of around 90, continuous information on the position of the first axis 212 of the rotor 210 is required.

[0068] The electrical phase .sub.el of the space phasor 260 corresponding to each adjustment angle according to the design of the positioning system 100 is shown on a second x-axis which is arranged below the first x-axis with adjustment angles . This corresponds to the mechanical phase of the rotor 210 insofar as the rotor 210 has not undergone any slippage.

[0069] FIG. 2 shows in detail the correlation between the rotor 210 with its first axis 212 and with its second axis 214 and three different space phasors 260C, 260D and 260E. All three space phasors 260C, 260D and 260E exert the same torque on the rotor 210.

[0070] This is because all three space phasors 260C, 260D, 260E have the same vector components i.sub.C,q, i.sub.D,q and i.sub.E,q in the direction of the second axis 214 of the rotor 210. Since all three space phasors 260C, 260D, 260E however have different differential phasings .sub.C, .sub.D, and .sub.E, they must have differently sized amplitudes A.sub.C, A.sub.D, A.sub.E in order to achieve the desired torque T1. The closer the differential phasing comes to the first axis 212 of the rotor 210, the greater the amplitude A must be to generate the same vector component in the direction of the second axis 214 of the rotor 210.

[0071] FIG. 3a on the left-hand side shows a control circuit for implementing a method for setting the actuator member 300 to a desired value. In a step 410, an adjustment angle default .sub.Soll or a torque default T.sub.Soll proportional thereto, which the actuator member 300 must achieve, is fed into a control 420 for the actuator drive commutation or for generating a suitable space phasor 260. This value may be temporarily stored in the control 420. Another embodiment may also be possible in which this value is stored in a separate memory 480, either in addition to storage in the control 420 or instead of storage in the control 420. The space phasor 260 energizes the stator 230 of the actuator drive 200, whereby the rotor 210 is to be rotated to a desired position value L.sub.Soll. By means of the gear mechanism 280, the actuator member 300 is thus also moved. A sensor 350 arranged on the actuator member 300 detects the position of the actuator member 300 and hence indirectly a position value L of the first axis 212 of the rotor 210. This sensor 350 may, as shown in FIG. 3a, be a rotary angle sensor orin other embodiments not shown herea position sensor for detecting a translational position. This position value L is firstly supplied to the memory 480. Secondly, with knowledge of a rotor position characteristic curve 440, it is determined how far the electrical phase .sub.el of the space phasor 260 must still be rotated in order to reach the target value .sub.Soll or the torque T.sub.Soll. Before the result is supplied to the control 420 of the actuator drive commutation, it is checked in a sensor signal evaluation means 450 if the sensor signal of the sensor 350 is plausible or even present. If the result of the check in the check step 450 is valid, the control 420 of the actuator drive commutation is informed of how much further the space phasor must be rotated in order to reach the target value .sub.Soll or T.sub.Soll. In this normal operating mode, the actuator drive 200 is preferably operated for optimum efficiency, i.e. with an operating differential phasing .sub.O which lies in a range between 45 and 135, preferably in a range between 70 and 110, and quite particularly preferably in a range between 85 and 110. Ideally, the operating differential phasing .sub.O is around 90.

[0072] The right-hand side of FIG. 3a shows diagrammatically how, with the increasing electrical phase .sub.el of the space phasor 260 on the x-axis, the amount of the amplitude A of the space phasor 260 on the y-axis must be increased in order to compensate for the counter-torque T.sub.C in efficiency-optimised mode. The amplitude A of the space phasor 260 corresponding to the electrical phase .sub.el is assigned by the control 420 using the rotor position characteristic curve.

[0073] FIG. 3b shows a state in which it was established in check step 450 that the sensor signal from sensor 350 is not plausible, or that the sensor signal has been lost completely. In this case which, in the exemplary embodiment shown of the method, corresponds to a defined event, the check step 450 triggers a retrieval of a plausible position value L from the memory 480 as depicted by arrow 452. Also, the associated value of the adjustment angle default .sub.Soll or the torque default T.sub.Soll proportional thereto which the actuator member 300 must reach, is retrieved from the control 420 and/or from the memory 480. A plausible position value L may for example be the last available valid position value L or a sliding mean or another average or calculation from several stored position values L of the memory 480. At the same time, the check step 450 sends a signal, depicted by arrow 454, to the control 420 of the actuator drive commutation which shifts the space phasor control from normal operating mode to an emergency operating mode.

[0074] In emergency operating mode, due to the absence of available plausible position signals of the actuator member 300 and/or the rotor 210 of the actuator drive 200, the space phasor 260 is no longer controlled for optimum efficiency. Also, the actuator drive commutation receives the position value L retrieved from the memory via a signal path according to the arrow 456. Starting from this position value L and the associated last space phasor 260 applied with amplitude A and differential phasing , and from the electrical phase .sub.el of the space phasor 260, the differential phasing which in normal mode is at least 45, ideally at least 70, preferably at least 90is immediately changed to an operating differential phasing .sub.O of less than 45, ideally approximately between 0 and 10, and simultaneously the amplitude A of the space phasor 260 is increased to an operating amplitude A.sub.O. The combination of operating amplitude A.sub.O and operating differential phasing .sub.O is selected such that on the first axis 212 of the rotor 210, over the total path to be covered from the current position of the actuator member 300 for the retrieved position value L to the predefined desired position of the actuator member 300, the space phasor 260 exerts a greater torque T.sub.M than the maximum counter-torque T.sub.C occurring on the path. This is indicated on the right-hand side of the diagram by the sudden transition of the rising curve 750 to the horizontal curve 760 with constant operating amplitude A.sub.O. There is also a phase jump in the differential phasing .

[0075] In other words, the method is based on a phase jump of the differential phasing and an amplitude jump of the space phasor 260. From the position value L made available from the memory 480, it is also determined by which value the electrical phase .sub.el of the space phasor 260 must be changed in order, from the position value L of the first axis 212 of the rotor 210, retrieved from the memory, to reach the position value L.sub.Ende of the first axis 212 of the rotor 210 at which the predefined position of the actuator member 300 is reached. The control 420 of the actuator drive commutation now changes the electrical phase .sub.el of the space phasor 260 until the predefined position value L.sub.Ende is reached. Because the torque T.sub.M exerted by the space phasor 260 on the rotor 210 is always greater than the maximum counter-torque T.sub.C, the rotor 210 thus follows the space phasor 260, and the actuator member 300, which is coupled to the actuator drive 200 via the gear mechanism 280, moves to the predefined position of the actuator member 300.

[0076] In the case of a total sensor failure (e.g. for loss of sensor supply voltage, fault in sensor transmission, conversion error), for actuator members with electrically commutated actuator drive 200, by means of the method described the controllability (positionability) of the actuator or actuator member 300 can be maintained. If a sudden total sensor failure occurs for several sensors 350 (failure of all sensors 350), controllability is retained by rapid switching to controlled operation of the actuator drive 200 in emergency mode (high amplitude A of the space phasor 260 in the direction of the first axis 212). Thus, based on the last adapted correlation between the sensor signal (valve position or adjustment angle or translational position) and the rotor position or the position of the first axis 212 of the rotor 210, the actuator member 300 can still be positioned or adjusted with great precision. In principle, using the method, normal operation with different electrical phases .sub.el can be maintained, i.e. the actuator member 300 can still be controlled in differentiated fashion and is not fixed at a single predefined position. Rather, the predefined position in each cycle of the control means the position which corresponds to the value of the adjustment angle default or torque default from step 410. This is accompanied by a higher power consumption of the stator 230 in an operating mode not optimised for efficiency.

[0077] FIG. 4 shows an optimised trajectory plan. The y-axis depicts the electrical phase .sub.el of the space phasor 260, and the x-axis depicts the time. It can now be assumed e.g. that for a first electrical phase 1, the defined event e.g. a sensor failure occurs at a first time t1, and to reach the predefined position of the actuator member 300, a second electrical phase 2 of the space phasor 260 is required which should be reached in a time At for example of less than 300 ms or less than 100 ms.

[0078] Then, on switching from normal operating mode to emergency operating mode, the control could in principle simply traverse the electrical phase along a straight (line 700 in FIG. 4) from the first electrical phase 1 to the second electrical phase 2 with constant phase change rate, or simply jump to the value 2. Here however there is a risk that, on transition from a state before the first time or on transition after reaching the second phase after the second time t2, the mechanical components, i.e. for example the rotor 210 and the actuator member 300, may be subjected to sudden and strong accelerations or brakings. This is because the rotor 210 has a certain inertia moment on accelerations or on brakings in relation to the very rapid energizing of the coil 232. In order to prevent such loads on the mechanical components of the rotor 210 and/or the actuator member 300, an algorithm may be applied for changing the electrical phase .sub.el of the space phasor 260 which ensures that on a change of the electrical phase from the first electrical phase 1 to the second electrical phase 2, no discontinuities occur in the time development. This is depicted for example in the S-shaped curve 710 in FIG. 4, which can be differentiated on the left- and right-hand sides at any time. Here, after switching to an emergency operating mode, starting from the first electrical phase 1, the electrical phase .sub.el is changed slowly at first in order then to reach a high change rate as soon as the rotor 210 with its mechanical inertia can follow the space phasor 260. Towards the end of the adjustment of the electrical phase, i.e. before reaching the second electrical phase 2, the phase change rate is then reduced and slowed ever more greatly so that the inertia moment of the rotor 210 cannot turn the same beyond the target position. Such a curve path can for example be achieved by suitable filtering for example using a low-pass filter or a band-pass filter.

[0079] Such a filter element for optimised trajectory planning in the form for example of an electronic circuit may be provided in the flow diagrams of FIGS. 3a and 3b, for example between step 410 of setting the adjustment angle default .sub.Soll or a torque default T.sub.Soll proportional thereto, and the control 420. Alternatively or additionally, it may be provided between the check step 450 and the control 420.

[0080] The actuator member 300 may for example be mounted rotatably, such as e.g. a throttle valve. Also, an embodiment (not shown here) is possible in which the actuator member 300 performs a translational movement instead of a rotational movement when the actuator drive 200 is controlled. Thus, the actuator member 300 may for example be configured as a wastegate actuator. An actuator member 300 operated translationally may on the output side have a piston rod which can be moved in translation, for example in a range from e.g. 5 mm to 300 mm, preferably from 10 mm to 30 mm. For wastegate actuators, such a translational actuator member 300 is advantageous because of the movement type. However, various other actuators are conceivable as wastegate actuators, for which a translational movement is advantageous.

[0081] It is also conceivable that the position is not detected by means of an angle sensor, but that a sensor detects the transitional position which is then converted, by means of a map or functional correlation, into the rotor position of the actuator drive 200 in order thus to commutate the actuator drive 200.