SU1323850A1 - Angular displacement differential transducer - Google Patents

Abstract

The invention relates to a measurement technique and aims to expand the measurement range while maintaining the linearity and uniqueness of the conversion function of a differential capacitive angular displacement sensor, the MOBILE electrode 1 of which is made in the shape of an acute sector, and the fixed electrodes 2. and 3 are bounded from the inside by a circle with an axis 6 rotation of the movable electrode. The stationary electrodes are separated from each other by an insulating gap in the form of a flat spiral 7, the ends of which lie on the inner 4 and outer 5 circles, bounding the stationary electrodes, and section 10 in the form of a segment connecting the ends 8 and 9 of this spiral, respectively. one straight with the center of the indicated circles. When rotating movable electrode 1 around axis 6, perpendicular to its plane, there is a change in the area of mutual overlap of this electrode and stationary electrodes 2 and 3. Thanks to the spiral form of the insulating gap between stationary electrodes 2 and 3, described by the corresponding mathematical expression, there is an unambiguous linear variation of the partial capacitances between them and the movable electrode of the sensor. 1 z.P. f-ly. 2 Il. with S (L with y with 00 ate

Description

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The invention relates to a measuring technique and can be used when measuring angular movements, for example, the working bodies of robots or automatic machines in the range from 0 to 360.

The purpose of the invention is to expand the measurement range while maintaining the linearity of the conversion function by appropriately profiling the electrodes of the capacitive sensor.

FIG. 1 shows a differential capacitive angular displacement sensor, a longitudinal section; in fig. 2 - the same, top view.

The differential capacitive angular displacement sensor contains a flat podvrshny electrode 1, having the shape of a sector of a circle with an acute angle at the apex, and two stationary electrodes 2 and 3, located in a plane parallel to the plane of the moving electrode.

The stationary electrodes 2 and 3 are bounded from inside and outside by circles .4 and 5 with a center lying on the axis 6 of rotation of the movable electrode, perpendicular to its plane and passing through the sector apex. Isol

the conversion function is violated only in the case where the mobile

the cyop gap separating the non-electrode is above the linear

moving electrodes 2 and 3. one from the other, made in the form of a flat spiral 7, the ends 8 and. 9 which lie on the inner A and outer 5 circumference, bounding the stationary electrodes, respectively, and has a straight line section 10 in the form of a segment connecting the ends 8 and 9 of the helix 7.

To obtain a linear transformation function, it is necessary that the radius R of a flat helix separating stationary electrodes 2 and 3 be described, for example, by the following mathematical expression

 35

40

section 10 separating stationary electrodes 2 and 3. Therefore, the range of displacements measured by the proposed sensor is (), where Cf is the angle at the apex of the sector of movable electrode 1, which can actually be 300-350.

When a capacitive sensor is turned on in a measurement circuit, for example, a Mos-Gu or compensated-bridge measuring circuit that implements one of the following P-conversion functions, where, 2,3: -C.

L

Ron-VR 4R | -R,) ff,

(one)

where R and R are the radii of the inner and outer circles, respectively, bounding the stationary electrodes;

| 3 the angular coordinate of the point of the spiral, in which its radius is determined,

50

p - .. 1 .....

,,.,

ps with;: 7s - ;. 7

the linear dependence of the output signal on the measured angular displacement is obtained, invariant to the value

varying in the range of the 55 dielectric constant of the medium, not from O to 2. The gap between the electrodes and the temperature. Differential capacitive sensors change the active area, the angular displacements work as follows. The use of the proposed differential sensor ...

When the angular position changes from the moving electrode 1, which rotates relative to its top in a plane parallel to the plane of the fixed electrodes 2 and 3, the area of their mutual overlap changes. Since the stationary electrodes are limited by concentric circles whose center lies on the axis of rotation of the movable electrode, the sum of active areas of the stationary electrodes and the sum of partial capacitances, Zch between the respective electrodes of the sensor, keeps the pile value regardless of the angular position 0 of the movable electrode 1. due to the spiral-shaped interface between the stationary electrodes 2 and 3, leads to an unambiguous increase in one partial capacitance due to a decrease in the other, which determines the differential law varying partial capacitances in the sensor with variable active electrode area. The monotonic change in the partial capacitances, and hence the

the conversion function is violated only in the case where the mobile

35

40

45

section 10 separating stationary electrodes 2 and 3. Therefore, the range of displacements measured by the proposed sensor is (), where Cf is the angle at the apex of the sector of movable electrode 1, which can actually be 300-350.

When a capacitive sensor is turned on in a measurement circuit, for example, a Mos-Gu or compensated-bridge measuring circuit that implements one of the following P-conversion functions, where, 2,3: -C.

50

1-1

p - .. 1 .....

,,.,

ps with;: 7s - ;. 7

the linear dependence of the output signal on the measured angular displacement is obtained, invariant to the value

in comparison with the known ones, it will almost double the range of measured angular displacements while maintaining the linearity of the conversion characteristic.

Claims (2)

Invention Formula 1, Differential capacitive angular displacement sensor comprising a flat movable electrode having the shape of a sector of a circle and mounted rotatably around an axis perpendicular to the plane of this electrode and passing through the apex of the sector, two fixed electrodes located in a plane parallel to the plane of the moving electrode, and bounded outside by a circle with a center lying on the axis of rotation of the movable electrode is about the fact that, in order to expand the measuring range, the movable electrode It is made with a sharp angle at the top of the sector, and fixed electrodes are bounded internally by a circle with a center lying on the axis of rotation Compiled by S. Scrushnik Editor A. Revin Tekhred L. Oliynyk, Proofreader S. Shekmar Order 2953/43 Circulation 677 Subscription VNIIPI USSR State Committee for inventions and discoveries t13035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4 moving electrode, and separated from each other by insulating gaps in the form of a flat helix, the ends of which lie on the inner and outer circumferences bounding the stationary electrodes, and a straight line connecting the ends of this helix, which are located on the same straight line with the center of the circles . / O 0 2. The sensor according to claim 1, characterized in that, in order to increase the linearity of the conversion characteristic, the radius Rtn of the flat helix 5 is determined by the extrusion / O 20 R on 1 / R2 + / 3 ( where R and Rj L 25 2n the radii of the inner and outer circumferences bounding the stationary electrodes; the angular coordinate of the point of the helix at which its radius is determined, varying from 0 to 27. R FI.1