End Position Detection with the Aid of Two-Position Controller

Abstract

A method for end position detection in an electromagnetic, bistable actuator (101) includes applying excitation energy to the actuator (101) with the aid of a two-position controller while an armature (103) of the actuator (101) is in an end position, and determining at least one value of a switching frequency of the two-position controller.

Claims

1-4: (canceled)

5. A method for end position detection in an electromagnetic, bistable actuator (101), comprising: applying excitation energy to the actuator (101) with the aid of a two-position controller while an armature (103) of the actuator (101) is in an end position; and determining at least one value of a switching frequency of the two-position controller.

6. The method of claim 5, further comprising comparing the determined value of the switching frequency with a first predetermined value and a second predetermined value, wherein the switching frequency assumes the first predetermined value when the armature (103) is in a first end position, and the switching frequency assumes the second predetermined value when the armature (103) is in a second end position.

7. The method of claim 6, further comprising: detecting a position of the armature (103) as the first end position when the determined value of the switching frequency corresponds to the first predetermined value; and detecting the position of the armature (103) as the second end position when the determined value of the switching frequency corresponds to the second predetermined value.

8. An end position detection arrangement, comprising: an electromagnetic, bistable actuator (101); a control unit; and a two-position controller configured for applying excitation energy to the actuator (101) when an armature (103) of the actuator (101) is in an end position, wherein the control unit is configured for determining at least one value of a switching frequency of the two-position controller.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] A preferred exemplary embodiment of the invention is represented in FIG. 1. Identical reference numbers label identical or functionally identical features. Specifically:

[0022] FIG. 1 shows the time profile of excitation variables of an actuator.

DETAILED DESCRIPTION

[0023] Reference will now be made to embodiments of the invention, one or more examples of which are shown in the drawings. Each embodiment is provided by way of explanation of the invention, and not as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be combined with another embodiment to yield still another embodiment. It is intended that the present invention include these and other modifications and variations to the embodiments described herein.

[0024] An actuator 101 represented in FIG. 1 includes an armature 103, which is axially displaceable via application of an excitation voltage. The axial position x of the armature 103 is plotted as a function of the time tin the lower diagram in FIG. 1. If the armature 103 is in a first end position represented on the left in FIG. 1, the axial position x of the armature 103 assumes an axial position x.sub.1. The armature 103 assumes an axial position x.sub.2 when the axial position x of the armature 103 is in a second end position represented on the right in FIG. 1.

[0025] In the upper diagram of FIG. 1, the progression of an excitation voltage u is plotted as a function of the time t. The excitation voltage u is generated by a two-position controller. Therefore, the excitation voltage u alternates between 0 and an upper limiting value, as a square wave signal.

[0026] The progression represented in the middle diagram results for the excitation current i as a function of the time t. A mean current i.sub.soll is predefined as a reference variable for the two-position controller. The excitation current i then oscillates between an upper switching threshold and a lower switching threshold in a current band i.sub.H around the mean current i.sub.soll.

[0027] t.sub.on designates the switch-on time of the excitation voltage u and/or the time duration in which u assumes the upper limiting value in each case. Correspondingly, t.sub.off designates the time period in which the excitation voltage u assumes the value 0 in each case.

[0028] The switching frequency f is

[00001]$f=\frac{1}{t_{\mathrm{on}}-t_{\mathrm{off}}}.$

[0029] The switching frequency f that sets in when the armature 103 assumes the first end position is greater than the switching frequency f that sets in when the armature 103 assumes the second end position. The reason therefor is the inductance, which has changed due to the different position of the armature 103. By evaluating the switching frequency f, it can therefore be determined whether the armature 103 assumes the first end position or the second end position. In particular, the evaluation of the frequency f makes it possible to differentiate between the two end positions.

[0030] Modifications and variations can be made to the embodiments illustrated or described herein without departing from the scope and spirit of the invention as set forth in the appended claims. In the claims, reference characters corresponding to elements recited in the detailed description and the drawings may be recited. Such reference characters are enclosed within parentheses and are provided as an aid for reference to example embodiments described in the detailed description and the drawings. Such reference characters are provided for convenience only and have no effect on the scope of the claims. In particular, such reference characters are not intended to limit the claims to the particular example embodiments described in the detailed description and the drawings.

REFERENCE NUMBERS

[0031] 101 actuator [0032] 103 armature