Actuator Device And Method For Compensating For A Stray Magnetic Field In The Case Of An Actuator Device

Abstract

An electromagnetic actuator device includes an actuator having an actuator coil and a tappet that can be moved in and against a longitudinal direction. The actuator device includes a sensor device having a transmitter element arranged on the tappet and a sensor element for generating a measurement signal, containing information about a current actual position of the tappet, depending on a magnetic field generated by the transmitter element. The actuator device includes a control unit with a controller, which applies a control voltage to the actuator coil for generating an electromagnetic field during operation in dependence on a position signal based on the measurement signal, so that the tappet moves into a target position. During operation, a stray magnetic field is generated by the at actuator coil, an adaptation of the measurement signal is performed to compensate for the influence on the measurement signal caused by the stray field.

Claims

1. An electromagnetic actuator device comprising: an actuator with at least one actuator coil for generating at least one electromagnetic field and with a tappet movable in and against a longitudinal direction in dependence on the at least one generated electromagnetic field; a sensor device comprising a transmitter element and a sensor element, the transmitter element arranged on the tappet, the sensor element designed to generate a measurement signal, which contains information about a current actual position of the tappet along the longitudinal direction, in dependence on a magnetic field generated by the transmitter element; and a control unit with a controller, which is set up so as to apply a control voltage to the at least one actuator coil for generating the at least one electromagnetic field during operation in dependence on a position signal on the basis of the measurement signal, so that the tappet moves from the current actual position into a target position, wherein during operation, a stray magnetic field, which influences the measurement signal, is generated by the at least one actuator coil, and wherein the control unit has a compensating device, which is set up so as to determine a variable correlated with the stray magnetic field and to adapt the measurement signal in dependence on this variable and transmit it to the controller, the adaptation of the measurement signal performed in such a way as to compensate for the influence of the measurement signal caused by the stray field.

2. The actuator device as claimed in claim 1 comprising a linear actuator.

3. The actuator device as claimed in claim 1, wherein the variable correlated with the stray magnetic field is an actuator current flowing in the at least one actuator coil as a result of the control voltage.

4. The actuator device as claimed in claim 3, wherein an estimating unit is arranged in the control unit is, the estimating unit is set up so as to determine the variable correlated with the stray magnetic field on the basis of at least one state variable of the actuator.

5. The actuator device as claimed in claim 4, wherein the estimating unit determines the variable correlated with the stray magnetic field on the basis of at least one of the following state variables: the last detected actuator current, the actuator temperature, the electrical resistance of the at least one actuator coil, the inductance of the at least one actuator coil, the position and speed of the tappet, the control voltage of the actuator.

6. The actuator device as claimed in claim 1, wherein the compensating device is set up in such a way that it determines a correction variable from the determined variable on the basis of a correction function and adapts the measurement signal on the basis of the correction variable.

7. The actuator device as claimed in claim 6, wherein the correction variable determined on the basis of the correction function is corrected with calibrating values, the calibrating values being an offset and/or a gain factor.

8. The actuator device as claimed in claim 1, wherein the transmitter element is designed as a permanent magnet.

9. The actuator device as claimed in claim 1, wherein the sensor element is designed as a magnetic field sensor.

10. The actuator device as claimed in claim 1, wherein the transmitter element is arranged on the tappet in such a way that the direction of the magnetic field generated by the transmitter element and the direction of the stray magnetic field at a measuring position at which the sensor element is arranged are oriented in the same direction.

11. A method for compensating for a stray magnetic field of an actuator device, the actuator device comprising: an actuator with at least one actuator coil for generating at least one electromagnetic field and with a tappet movable in and against a longitudinal direction in dependence on the at least one generated magnetic field, a sensor device comprising a transmitter element and a sensor element, the transmitter element arranged on the tappet and a measurement signal, which contains information about a current actual position of the tappet along the longitudinal direction, being generated by the sensor element in dependence on a magnetic field generated by the transmitter element, and a control unit with a controller, by which a control voltage is applied to the at least one actuator coil for generating the at least one electromagnetic field in dependence on a position signal on the basis of the measurement signal, so that the tappet is moved from the current actual position into a target position and wherein a stray magnetic field, which influences the measurement signal, is generated by the at least one actuator coil, comprising the following steps: detecting a variable correlated with the stray magnetic field by a compensating device, generating a correction variable on the basis of the detected variable, adapting the measurement signal by applying the correction variable to the measurement signal, and transmitting the position signal on the basis of the adapted measurement signal to the controller.

12. The method of claim 11, in which a correction variable is determined by the compensating device from the determined variable on the basis of a correction function and the measurement signal is adapted on the basis of the correction variable and wherein the correction variable determined on the basis of the correction function is corrected with calibrating values, the calibrating values being an offset and/or a gain factor.

13. The method as claimed in claim 12, in which, to determine the calibrating values, the tappet is moved into predetermined and known calibrating positions once with an energized actuator and once with a de-energized actuator, and the position of the tappet is detected in each case by the sensor device and the value for the calibrating position determined for a respective calibrating position by the correction function is compared with the actual value of the calibrating position and the offset and gain factor are determined from this.

14. The method of claim 13, wherein the predetermined and known calibrating positions include the two end positions.

Description

DESCRIPTION OF DRAWINGS

[0045] FIG. 1 shows an actuator device with an actuator and a control unit.

[0046] Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

[0047] The electromagnetic actuator device 2, for the sake of simplicity also referred to hereinafter as the actuator device 2 for short, has an actuator 4. The actuator 4 has at least one actuator coil 6 for generating at least one electromagnetic field. Furthermore, the actuator 4 has a tappet 8, which can be moved in and against a longitudinal direction L in dependence on the at least one generated electromagnetic field. In some examples, the tappet 8 is designed like a pin.

[0048] In addition, the actuator device 2 has a sensor device 10. The sensor device 10 has a transmitter element 12 and a sensor element 14. In some examples, the transmitter element 12 is arranged on the tappet 8. The transmitter element 12 may be specifically arranged at an upper end 16 of the tappet 8. The sensor element 14 is designed so as to generate a measurement signal S.sub.M in dependence on a magnetic field 18 generated by the transmitter element 12. The measurement signal S.sub.M contains information about a current actual position of the tappet 8 along the longitudinal direction L. In some examples, the transmitter element 12 is designed as a permanent magnet. Furthermore, the sensor element 14 may be designed as a Hall sensor.

[0049] Furthermore, the actuator device 2 has a control unit 20. The control unit 20 has a controller 22. The controller 22 is set up in such a way that, during operation, dependent on a position signal S.sub.P on the basis of the measurement signal S.sub.M, a control voltage U.sub.A is applied to the at least one actuator coil 6 to generate the at least one electromagnetic field. For this purpose, the controller 22 is connected for example by a power driver 24, e.g. a voltage source, so that the control voltage U.sub.A may be provided. The control unit 20 makes it possible to move the tappet 8 from a momentary actual position into a predetermined target position, for example in the form of a signal S.sub.Target. The target position is in this case for example transmitted to the controller 22 as an input variable.

[0050] During the operation of the actuator device 2, a stray magnetic field 26 is generated by the actuator coil 6. This influences the measurement signal S.sub.M to the extent that a positionally accurate control of the actual position into the target position is affected by errors.

[0051] In order to compensate for being affected by errors in this way, in the control unit 20 includes a compensating device 28. The compensating device 28 is set up so as to determine a variable G correlated with the stray magnetic field 26 and to adapt the measurement signal S.sub.M in dependence on this variable and to transmit it to the controller 22. In some examples, an actuator current I.sub.A flowing in the at least one actuator coil 6 as a result of the control voltage is used as the variable G correlated with the stray magnetic field 26. The adaptation of the measurement signal S.sub.M is performed in such a way as to compensate for the influence of the measurement signal S.sub.M caused by the stray field. That is to say that, on account of the compensation by the compensating device 28, the controller 22 receives a position signal S.sub.P on the basis of the measurement signal S.sub.M, which is not influenced by the stray magnetic field 26. In other words, there is a position signal S.sub.P on the basis of the measurement signal S.sub.M, as if there were no interfering stray magnetic field 26.

[0052] The measurement of the variable G correlated with the stray magnetic field 26, i.e., the armature current I.sub.A, takes place for example by a current measuring unit 30, which is additionally connected to the compensating unit 28 for transmitting the armature current I.sub.A.

[0053] If the direct determination of the variable G correlated with the stray magnetic field 26 cannot be detected, or temporarily cannot be detected, the control unit 20 has an estimating unit 32. The estimating unit 32 is set up in such a way that the variable G correlated with the stray magnetic field 26 is determined on the basis of other state variables Z of the actuator 4. In some examples, these other state variables Z are also in a correlation with the armature current I.sub.A, and thus also in a correlation with the stray magnetic field 26. The other state variables are thus for example the last measured armature current I.sub.A, the control voltage U.sub.A, an actuator temperature, a measured or estimated electrical resistance and/or a measured or estimated inductance of the at least one actuator coil 6 and for example an approximate position and/or speed of the tappet 8.

[0054] A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.

LIST OF REFERENCE SIGNS

[0055] 2 Electromagnetic actuator device [0056] 4 Actuator [0057] 6 Actuator coil [0058] 8 Tappet [0059] 10 Sensor device [0060] 12 Transmitter element [0061] 14 Sensor element [0062] 16 Upper end [0063] 18 Magnetic field [0064] 20 Control unit [0065] 22 Controller [0066] 24 Power driver [0067] 26 Stray magnetic field [0068] 28 Compensating device [0069] 30 Current measurement unit [0070] 32 Estimating unit [0071] L Longitudinal direction [0072] S.sub.M Measurement signal [0073] S.sub.Target Target position signal [0074] S.sub.P Position signal [0075] I.sub.A Armature current [0076] G Variable [0077] U.sub.A Control voltage [0078] Z State variable