RU2436037C1 - Absolute angle transducer - Google Patents

Abstract

FIELD: physics. ^ SUBSTANCE: absolute angle transducer includes a magnetic system connected to a rotary shaft, a reader device (containing transducer elements and a signal processing circuit and mounted with a clearance relative to the magnetic system). The magnetic system is represented by an encoding magnetic disc containing concentrically arranged tracks with magnetic elements assembled in accordance with Gray code. Part of the magnetic elements are shifted towards the outer half of the tracks with the other part shifted towards the tracks inner half. The transducer elements are represented by a line of magnetoresistive transducer elements that are designed as Winston bridges with collinearly arranged magnetoresistive strips with the axis of easy magnetisation along their longer side. The bridge arms are spaced apart so that the two opposite arms of the bridge are opposed the track outer half magnetic elements while the other two opposite arms are opposed to the track inner half magnetic elements. ^ EFFECT: enhanced radiation resistance and the signal processing circuit simplification. ^ 3 dwg

Description

The invention relates to measuring equipment and can be used for contactless determination of the position of the motor shaft.

Known Honeywell sensors, in which magnetoresistive sensitive elements such as HMC 1501 and HMC 1512 (application note AN 211, Honeywell, Solid State Electronics Center, www.magneticsensor.com) are used as a reader.

The disadvantages of such sensors are the complexity of the signal processing circuit and the need to use a Hall sensor with low radiation resistance.

Absolute encoders of the SICK series ARS 60 and ATM 60 ATM 90 (www.stegmann.com) are known, which use a coding disk in combination with optical and magnetoresistive technologies and gear technology. Information from the coding disk is easily converted to digital form, but the device of such an encoder is quite complex, contains a large number of rubbing parts, has a limited temperature range and speed, and the sensitive elements - phototransistors and Hall sensors - do not have radiation resistance.

Also known is a non-contact programmable sensor of absolute angular position of 360 °, described in RF patent No. 2312363 C1 of January 31, 2006, which we took as a prototype. The sensor consists of two parts that are not mechanically interconnected and isolated from each other with a constant air gap in the space between them, one part is a rotor assembly, the other part is a stator - a set of stationary mechanical and electronic parts that represent information about the rotor angular position through the contact interface with a magnet. The information is processed using the arctangent function of the signals of the integrated cruciform array of planar Hall elements that are sensitive to the gradient of the components of the working magnetic field.

The disadvantages of such sensors, which use Hall sensors as a sensitive element (reader), are low sensitivity to the magnetic field, high sensitivity to thermal influences, low radiation resistance and the complexity of the signal processing circuit associated with the conversion of the analog signal to digital form.

The technical result of the invention is the creation of a radiation-resistant absolute angle sensor with noise immunity, increased sensitivity and a simpler signal processing circuit.

The specified technical result is achieved by the fact that in the absolute sensor of the angle of rotation, including a magnetic system associated with a rotating shaft, a reader containing sensing elements and a signal processing circuit installed with a gap relative to the magnetic system, the magnetic system is made in the form of an encoding magnetic disk containing concentric tracks with magnetic elements that are mounted in accordance with the Gray code, with one part of the magnetic elements shifted to the outside half, and the other to the inner half of the tracks, and the sensitive elements represent a line of magnetoresistive sensitive elements (MRE), which are made in the form of Winston bridges with collinear magnetoresistive strips with the axis of easy magnetization along their long side, and the shoulders of the bridge are spatially spaced so that two opposing shoulders of the bridge are opposed to the magnetic elements of the outer half of the track, and two other opposing shoulders are opposed to the magnetic elements of the inner half of the track and.

The essence of the proposed technical solution lies in the fact that a multipole output signal is generated in the absolute angle sensor due to the spatial separation of the shoulders of the Winston bridge and the separate exposure of the fields of magnetic elements to them in a strictly defined sequence (Gray code). This sequence is ensured by the action of the coding magnetic disk either on one half of the Winston bridge (active unit) or on the second - (active zero) regardless of the sign of the magnetic field, but in the direction perpendicular to the OLR and the flowing sensor current, which ensures the maximum change in the resistance value in two shoulders of the Winston bridge (anisotropic magnetoresistive effect (AMP effect).

The invention is illustrated by drawings.

In FIG. 1 shows fragments of coding disks 1a - optical, used in analogues and 1b - magnetic disk with a Gray code, where:

1 - tracks located concentrically relative to the center of the disk;

2 - the outer half of the track magnetic coding disk;

3 - the inner half of the track magnetic coding disk;

4 - magnetic elements.

In FIG. 2 shows the topology of the Winston bridge according to the known connection diagram of its shoulders (figa) and the proposed connection diagram (fig.2b), where:

5 - shoulder of the Winston bridge (highlighted);

6 - magnetoresistive strips from which the shoulders of the Winston bridge are formed;

a, b, c, d - symbol of the shoulders of the Winston bridge;

OLN is the axis of easy magnetization.

In FIG. Figure 3 shows the relative position of the MRE and the coding magnetic disk, where Fig. 3a shows a ruler of 8 MRE, and Fig. 3b shows the output signal.

2 - the outer half of the track magnetic coding disk;

3 - the inner half of the track magnetic coding disk;

4 - magnetic elements;

7 - a line of eight MRE.

Each track 1 is divided in half into outer 2 and inner 3 parts and provided with 4 so that the dark part of the optical disk corresponds to magnetic elements 4 mounted on the outer half of the tracks, and the light part of the optical disk corresponds to magnetic elements 4 mounted on the inner half of the tracks.

The absolute sensor of the rotation angle contains a coding magnetic disk of Fig. 1b mounted on a rotating shaft, with eight tracks 1 located concentrically relative to the center of the disk (the number of tracks may be different, which is determined by the requirements for the accuracy of determining the angle of rotation and the size of the disk). Each track 1 is divided in half into the outer 2 and inner 3 parts and is equipped with magnetic elements 4 so that the dark part of the optical disk of figa corresponds to the magnetic elements 4 of fig.1b mounted on the outer part of the tracks, and the light part of the optical disc figa - magnetic elements 4 figb mounted on the inner half of the tracks.

As a magnetoresistive sensitive element, the Winston bridge (Fig. 2) is used, consisting of four arms 5 with magnetoresistive strips 6, combined in a meander. OLS is induced by a magnetic field during the deposition of a magnetoresistive film and is directed along the strips 6. All strips are collinear to each other.

The topology of the Winston bridge is such that the shoulders of the Winston bridge, opposite in the electric circuit, are arranged in pairs adjacent and spatially spaced so that the two shoulders of the Winston bridge stand against the magnetic elements 4 of the outer half of the track 7, and the other two of the inner half of the track 8 (Fig. 3a).

In FIG. 3a shows a ruler 9 of eight magnetoresistive sensitive elements located above the coding magnetic disk, and in figure 3b, the output signal for a given position of the ruler relative to the coding magnetic disk.

The operation of the absolute angle sensor is as follows.

When power is applied when the coding magnetic disk is stationary, the magnetic elements act on one (ac) or the other (bd) half of the Winston bridges (fig.2b), as a result of which the resistance changes, and output signals of either positive or negative appear in the diagonal (out) values, as shown in Fig. 36, for the position shown in Fig. 3a. After amplification, positive signals are identified with unity, and negative signals with zero. So, in figa we have the following code: 11011010.

The proposed encoder works reliably when exposed to a magnetic field with a frequency of up to 400 kHz (for example, when the motor shaft rotates at a speed of ~ 30000 ° / s, the response frequency will be only 3 kHz).

Thus, the principle of operation of the absolute sensor is realized - determining the position of the shaft not only during its rotation, but also in a stationary state.

The high radiation resistance of the magnetoresistive sensitive elements and the coding magnetic disk is ensured by the materials used for their manufacture.

For an eight-track coding magnetic disk, we have a code of 8 digits, and the output signal will contain 256 different combinations, which will correspond to a resolution of 1.4 °. During rotation, these combinations will sequentially change and display the shaft position with an accuracy of 1.4 °. To increase accuracy, a coding magnetic disk with a large number of tracks can be used, which will provide a resolution of less than 1 °.

Due to the small size of the bridge with the simultaneous exposure to "extended" electromagnetic interference on all the shoulders of the bridge, the output signal does not change. In the case of narrowly targeted interference, it is possible to use an RFE with different sensitivity. For interference of less than 8 mT, magnetoresistive elements based on films made of an alloy of 83% Ni - 17% Fe can be used, and for interference of up to 20 mT - from an alloy of 65% Ni - 15% Fe - 20% Co. In this case, the output signal level will exceed the interference signal, which can be filtered.

Thus, the proposed solution allows you to create a radiation-resistant absolute sensor of the angle of rotation with small dimensions, with compensation for electrical and magnetic interference, providing output signals that are identifiable with both the active unit and the active zero.

Claims (1)

An absolute angle sensor, including a magnetic system associated with a rotating shaft, a reader containing sensing elements and a signal processing circuit installed with a gap relative to the magnetic system, characterized in that the magnetic system is made in the form of an encoding magnetic disk containing concentrically arranged tracks with magnetic elements that are mounted in accordance with the Gray code, with one part of the magnetic elements shifted to the outer half, and the other to the inner along the paths, and the sensitive elements represent a line of magnetoresistive sensitive elements, which are made in the form of Winston bridges with collinear magnetoresistive strips with an easy magnetization axis along their long side, and the bridge shoulders are spatially spaced so that two opposite shoulders of the bridge are opposed to the magnetic elements of the outer half paths, and two other opposite shoulders - to the magnetic elements of the inner half of the path.

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