CN110470322A - A kind of eddy current type absolute encoder and its working method - Google Patents

Abstract

The invention provides an eddy current type absolute encoder, which comprises an annular coding disc and an annular reading disc, which are relatively concentrically arranged, parallel to each other, and provided with a distance. A number of reflective conductors are arranged on the code disc, which are distributed on two concentric circular code tracks, and the number of reflectors in the two code tracks is different. The reading disc is equipped with four sets of planar coils, which are distributed on two concentric circular code tracks. The interval between the two planar coils in each group is an even multiple of 1/2 the measurement wavelength, and the interval between the two sets of planar coils is Odd multiples of 1/4 measurement wavelength. The planar coil forms an integral component with the measuring circuit. The angle value is obtained by calculating the phase difference of the two code tracks. At the same time, a working method of the eddy current absolute encoder is provided. The invention not only can realize absolute angle measurement, but also has the characteristics of low cost, anti-vibration, wide temperature range, and insensitivity to magnetic targets and magnetic field changes, and can be applied in various complex and strong interference environments.

Description

An eddy current absolute encoder and its working method

technical field

The invention relates to a non-contact encoder. Specifically, it is an eddy current absolute encoder and its working method.

Background technique

An encoder is a sensor that converts angular position or angular displacement into an electrical signal and outputs it according to certain rules. It is widely used in various rotary mechanisms and is a commonly used angle and angular position sensor.

According to the different reading methods, the encoder can be divided into two types: contact type and non-contact type. Contact encoders due to wear, short operating life and unreliability have been eliminated and replaced by non-contact encoders. Non-contact encoders have high speed, long life and reliable operation, so they are the first choice in today's encoder field.

According to different encoding methods, encoders can be divided into two types: incremental and absolute: incremental encoders convert the angular displacement of rotation into periodic electrical pulse signal output, and use the number of pulses to represent angular displacement. size. The absolute encoder converts each angular position (that is, the angle) into a unique number corresponding to it, so its indication value is only related to the angular position at the time of measurement, and has nothing to do with the process before the measurement.

According to different working principles, non-contact encoders currently mainly have two forms: photoelectric encoders and magnetic encoders. The photoelectric encoder has high precision and fast speed, and is the mainstream in the encoder field. However, the photoelectric encoder has high environmental requirements, poor shock resistance, and narrow temperature range. Magnetoelectric encoder is a new type of angle or angular displacement measurement sensor. Its principle is to use magnetoresistance or Hall elements to measure the angle or angular displacement of rotating magnetic elements. It has low cost, anti-vibration, anti-corrosion , anti-pollution, anti-interference and wide temperature characteristics, it can be applied to industrial fields where traditional photoelectric encoders cannot adapt.

However, magnetic encoders work on the principle of magnetic induction, and the magnetic signal is the measurement medium. Therefore, the magnetic encoder is very sensitive to the surrounding magnetic objects or the fluctuation of the magnetic field of the environment, and the performance drops seriously, so it is limited in practical use.

Contents of the invention

The present invention aims at the defects of existing magnetic encoders that are sensitive to magnetic objects and magnetic field fluctuations, and proposes an eddy-current absolute encoder based on the transverse variable-area eddy current effect and its working method. The eddy current can be used to measure the absolute angle and angular position. It not only has the characteristics of low cost, anti-vibration, anti-corrosion, anti-pollution, anti-interference and wide temperature of the magnetic encoder, but also has the characteristics of magnetic objects and magnetic fields from the working principle. The excellent characteristics of insensitivity to changes make it more stable and reliable to work in a magnetic field environment, so it has wider practicability.

The present invention is achieved through the following technical solutions:

According to one aspect of the present invention, an eddy current absolute encoder is provided, comprising an annular coding disc and an annular reading disc arranged relatively concentrically and in parallel, and a distance is provided between the encoding disc and the reading disc; wherein :

The surface of the code disc is provided with two concentric ring code tracks a, and multiple reflective conductors with different numbers are respectively arranged on the two ring code track a; multiple reflective conductors on the same ring code track a have the same Shape and size, and distributed evenly along the circumference, the fan angle corresponding to the interval between two adjacent reflective conductors in the circumferential direction is called the measurement wavelength of the code track; because the number of reflective conductors on the two ring code tracks a is different, so The measurement wavelengths of the two ring code tracks a are also different;

The surface of the reading disc is provided with two ring code tracks b corresponding to the two ring code tracks a on the code disc, and the measurement wavelength of the two ring code tracks b is the same as that of the corresponding ring code track a; Four planar coils are respectively arranged on the ring code track b; the shape and size of the four planar coils on the same ring code track b are the same, and the four planar coils are divided into two groups, and the two planar coils in each group are on the circumference The spacing in the directions is an even multiple of the 1/2 measurement wavelength of the code track, and the circumferential spacing of the two groups of planar coils is an odd multiple of the 1/4 measurement wavelength of the code track.

Preferably, a measurement circuit is also provided on the reading plate, and the measurement circuit forms an integrated component with the planar coils, and is used to provide excitation signals for all the planar coils, and at the same time obtain the changing parameters of the planar coils and output corresponding electrical signals, The electrical signal is used to derive the measured angular position.

Preferably, the measurement circuit uses an exciter to provide an excitation signal for the planar coil and directly outputs an analog signal; the number of the exciter is the same as the number of the planar coil, wherein each planar coil corresponds to an exciter, so that the processing high speed of the process.

Preferably, an interface socket is also provided on the reading plate, and the interface socket is used for connecting an external power supply and outputting measurement results.

Preferably, the reflective conductor is made of metal, and is prepared by a PCB manufacturing method or a mechanical processing method.

Preferably, the planar coil is manufactured by a multi-layer PCB manufacturing method.

Preferably, the distance between the coding disc and the reading disc is 0.5mm.

Preferably, the outer diameters and inner diameters of the coding disc and the reading disc are the same or similar to each other.

According to another aspect of the present invention, a working method of the eddy current absolute encoder described in any one of the above is provided, including the following steps:

S1, differential processing: differential processing (i.e. subtraction) is performed on the analog signals output by the two planar coils in each group of planar coils on the reading plate after excitation to obtain four differential signals;

S2, calculate the tangent: for the four-way differential signal obtained after the differential processing, perform ratio processing on the two-way differential signals on the same ring code track b, so as to obtain the tangent values of the two ring code track b respectively;

S3, calculate the phase: perform the arctangent calculation on the two tangent values obtained after calculating the tangent respectively, so as to obtain the phase values of the two ring code tracks b;

S4, calculating the phase difference: performing differential calculation (i.e. subtraction) on the two phase values obtained after calculating the phase, so as to obtain the phase difference of the two ring code tracks b;

S5, calculate the angle: multiply the phase difference of the two ring code tracks b obtained after calculating the phase difference by a fixed constant to obtain the final measured angle value; the constant is the product of the measured wavelengths of the two ring code tracks b It is directly proportional to, and inversely proportional to the difference between the measured wavelengths of the two ring code tracks b, and the proportional coefficient is 1/(2π).

The working method of the eddy current absolute encoder according to claim 9, is characterized in that: also comprises the following steps:

S6, communication output: output the measured angle value obtained after calculating the angle to the host computer through the interface socket set on the reading panel.

Compared with the prior art, the present invention has the following beneficial effects:

The eddy current absolute encoder and its working method provided by the present invention can not only realize absolute angle measurement, but also have the characteristics of low cost, anti-vibration, wide temperature range, and insensitivity to magnetic targets and magnetic field changes, and can be applied to various In a complex and highly disturbed environment.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

Figure 1 is a schematic diagram of the composition and structure of an eddy current absolute encoder provided in an embodiment of the present invention;

Fig. 2 is a schematic diagram of the composition and structure of the code disc provided in the embodiment of the present invention;

Fig. 3 is a schematic diagram of the composition and structure of the reading plate provided in the embodiment of the present invention;

Fig. 4 is a schematic diagram of the corresponding relationship between the reading disk and the coding disk provided in the embodiment of the present invention;

Fig. 5 is a schematic flowchart of the overall working method of the eddy current absolute encoder provided in the embodiment of the present invention.

In the figure, 1 is the code disc, 2 is the reading disc, 3-1 and 3-2 are the two circular code tracks on the code disc respectively, 4 is the reflective conductor, 5 is the planar coil, 6 is the measuring circuit, 7 is the interface socket.

Detailed ways

The following is a detailed description of the embodiments of the present invention: this embodiment is implemented on the premise of the technical solution of the present invention, and provides detailed implementation methods and specific operation processes. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

An embodiment of the present invention provides an eddy current absolute encoder, the eddy current absolute encoder includes an annular encoding disc and an annular reading disc; wherein:

The outer diameter and the inner diameter of the coding disc and the reading disc are the same or close to each other, arranged relatively concentrically, parallel to each other, and separated by a small distance, preferably about 0.5mm;

A plurality of reflective conductors are arranged on the surface of the code disc, distributed on two concentric circular code tracks a; the reflective conductors on the same circular code track a have the same shape and size, are evenly distributed along the circumference, and two adjacent The sector angle corresponding to the spacing of two reflective conductors in the circumferential direction can be called the measurement wavelength of the code track; the number of reflective conductors of the two ring code tracks a is different, so the measurement wavelengths of the two code tracks are also different;

The reading disk is designed with eight planar coils, which are divided into two groups and distributed on two concentric ring code tracks b corresponding to the code disk, and four planar coils are respectively arranged on each ring code track b; The shape and size of the four planar coils on a code track are the same, and the shape and size of the reflective conductor corresponding to the code track on the code disc can be the same or different; the four planar coils on the same circular code track b are further divided into Two groups, the interval between the two planar coils of each group in the circumferential direction is an odd multiple of the 1/2 measurement wavelength of the code track, and the circumferential interval of the two groups of planar coils is an odd multiple of the 1/4 measurement wavelength of the code track.

Further, the reflective conductor is made of metal, which can be manufactured by PCB technology or mechanical processing technology.

Further, the shape of the reflective conductor can be any regular shape and size.

Further, the planar coil is manufactured by a multi-layer PCB process.

Further, the planar coil can be in any regular shape.

Further, the reading plate is also provided with a measuring circuit, which forms an integrated component with the planar coils, provides excitation signals for all the planar coils, and simultaneously obtains the changing parameters of the planar coils and outputs corresponding electrical signals, which are obtained after processing and calculation. The angle and angular position to be measured.

Further, the measurement circuit uses an exciter to provide an excitation signal for the planar coil and directly outputs an analog signal; the number of exciters is the same as that of the planar coil, and each planar coil corresponds to an exciter, thereby ensuring a high speed of the processing process .

Further, the reading panel is also provided with an interface for connecting an external power supply and outputting measurement results.

The embodiment of the present invention also provides a working method of the eddy current absolute encoder, the working process includes differential processing, tangent calculation, phase calculation, phase difference calculation, angle calculation and communication output process.

The specific process is as follows:

(1) Differential processing:

Differential processing (that is, subtraction) is performed on the analog signals output by the two planar coils in each group on the reading plate after excitation, and four differential signals are obtained. Two differential frequency signals for each code channel can effectively suppress the space. Interference of point magnetic field, improve signal quality, improve measurement accuracy and anti-interference ability.

(2) Calculate the tangent:

For the four differential signals obtained after the differential processing, the ratio processing is performed on the two differential signals on the same code channel to obtain the tangent signal of the code channel, and the two tangent values of the two code channels can be obtained.

(3) Calculate the phase:

The two paths of tangent values obtained after calculating the tangent are respectively subjected to arctangent calculation to obtain the phase values of the two code channels.

(4) Calculate the phase difference:

Perform differential calculation (subtraction) on the phase values of the two code channels obtained after the phase calculation, so as to obtain the phase difference of the two code channels.

(5) Calculate the angle:

Multiply the phase difference of the two code channels obtained after calculating the phase difference by a fixed constant to obtain the final measured angle value; the constant is proportional to the product of the measured wavelengths of the two code channels, and is proportional to the The difference between the measured wavelengths is inversely proportional, with a proportionality factor of 1/(2π).

(6) Communication output:

Output the angle value obtained after calculating the angle to the host computer through the interface socket.

The above-mentioned embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

The eddy-current absolute encoder provided in the above-mentioned embodiments of the present invention comprises an annular coding disc 1 and an annular reading disc 2, as shown in FIG. 1 , wherein:

The outer diameter of the code disc 1 and the reading disc 2 is the same as or close to the inner diameter, for example, the outer diameter is 60 mm and the inner diameter is 25 mm; the encoding disc and the reading disc are arranged concentrically and parallel to each other; the encoding disc and the reading disc are separated by a small distance , preferably about 0.5mm;

As shown in Figure 2, the code disc 1 has a plurality of reflective conductors 4 arranged on the surface, distributed on two concentric ring code tracks 3-1 and 3-2; the same ring code track 3-1 or 3-2 The reflective conductors 4 on the 2 have the same shape and size, and are evenly distributed along the circumference. The fan angle corresponding to the interval between two adjacent reflective conductors 4 in the circumferential direction is called the measurement wavelength; two ring code tracks 3-1 and 3 The number of reflection conductors on -2 is different, so the measurement wavelength is also different; for example, assuming that the number of reflection conductors of the two ring code tracks 3-1 and 3-2 are 36 and 35 respectively, then the measurement wavelengths of the two code tracks are respectively λ ₁ =10° and λ ₂ =10.286°;

As shown in Figure 3, the reading plate 2 is designed with eight planar coils 5-1Sp, 5-1Sn, 5-1Cp, 5-1Cn, 5-2Sp, 5-2Sn, 5-2Cp, 5-2Cn , and are divided into two groups corresponding to the ring code tracks 3-1 and 3-2 on the code disc 1, and four planar coils 5 are respectively arranged on each ring code track 3, wherein, 5-1Sp, 5-1Sn, 5-1Cp, 5-1Cn are distributed on the ring code track 3-1, 5-2Sp, 5-2Sn, 5-2Cp, 5-2Cn are distributed on the ring code track 3-2; The shape and size of the four planar coils 5 are the same, and the shape and size of the reflective conductor 3 corresponding to the code track 3 on the code disc 1 can be the same or different; the four coils 5 on the same code track 3 are divided into two parts. Group, the interval between two adjacent planar coils 5 of each group in the circumferential direction is an odd multiple of the 1/2 measurement wavelength of the ring code track, and the circumferential interval of two groups of planar coils 5 is the 1/4 measurement wavelength of the code track odd multiples of . For example, the intervals between the planar coils 5-1Sp and 5-1Sn, 5-1Cp and 5-1Cn in the circumferential direction are _1/2 odd multiples of the measurement wavelength λ1 (that is, λ1/ ₂ , 3λ1/ ₂ , _5λ1 /2, etc.), the distance between planar coils 5-2Sp and 5-2Sn, 5-2Cp and 5-2Cn in the circumferential direction is 1/2 odd multiples of the measurement wavelength λ ₂ (such as λ ₂ /2, 3λ ₂ /2 _{. _ _} 3λ _1/4 , 5λ _1/4 , etc.), two sets of planar coils 5-2Sp and 5-2Sn, 5-2Cp and 5-2Cn are spaced in the circumferential direction as 1/4 odd multiples of the measurement wavelength λ ₂ (such as λ ₂ /4, 3λ ₂ /4, 5λ ₂ /4, etc.).

In the above embodiment, the reflective conductor 4 is a metal material, which can be made by PCB technology, using the copper clad PCB as the reflective conductor 4; it can also be made by mechanical processing technology, using metal materials through various conventional mechanical processing Means form shapes with different heights.

In the above embodiment, the shape of the reflective conductor 4 can be any regular shape, such as rectangle, sector, rhombus, trapezoid, etc., and the sector shape is given priority; the reflective conductor 4 can be of any size, and its width is given priority It is better to measure 1/2 to 3/5 of the wavelength of the code channel.

In the above embodiments, the planar coil 5 is manufactured by multi-layer PCB technology.

In above-mentioned embodiment, described planar coil 5 can be any regular shape, such as rectangle, sector, rhombus, trapezoidal etc.; About 1/2 is better.

In the above embodiment, the reading plate 2 is further provided with a measuring circuit 6 for providing excitation signals to all the planar coils 5 , and at the same time acquiring changing parameters of the planar coils 5 and outputting corresponding electrical signals.

In the foregoing embodiment, the measuring circuit 6 uses an exciter to provide an excitation signal for the planar coil 5 and directly outputs an analog signal; the number of the exciter is the same as that of the planar coil 5, and each planar coil 5 corresponds to an exciter. Guaranteed high speed of processing.

In the above embodiment, the reading panel is further provided with an interface socket 7 for connecting an external power supply and outputting measurement results.

The working method of the eddy current absolute encoder provided in the above embodiments of the present invention includes differential processing, tangent calculation, phase calculation, phase difference calculation, angle calculation and communication output, as shown in FIG. 5 .

The specific process is as follows:

(1) Differential processing:

For the analog signals output by two adjacent planar coils in each group of four groups of planar coils in the eight planar coils, differential processing (and direct subtraction) is performed to obtain four differential signals, each Two difference frequency signals of one code channel can effectively suppress the interference of the space point magnetic field, improve the signal quality, improve the measurement accuracy and anti-interference ability, namely:

ΔW1S=W1Sp-W1Sn, ΔW1C=W1Cp-W1Cn

ΔW2S=W2Sp-W2Sn, ΔW2C=W2Cp-W2Cn

(2) Calculate the tangent:

For the four differential signals ΔW1S, ΔW1C, ΔW2S, and ΔW2C obtained after differential processing, the two differential signals on the same code channel are subjected to ratio processing to obtain the tangent values of the two code channels respectively. which is:

Tan1=ΔW1S/ΔW1C, Tan2=ΔW2S/ΔW2C

(3) Calculate the phase:

The two tangent values Tan1 and Tan2 obtained after calculating the tangent are respectively subjected to arctangent calculation, so as to obtain the phase values of the two code channels respectively. which is:

Φ1=arctan(Tan1)=arctan(ΔW1S/ΔW1C),

Φ2＝arctan(Tan2)＝arctan(ΔW2S/ΔW2C),

(4) Calculate the phase difference:

The two phase values Φ1 and Φ2 obtained after phase calculation are differentially calculated (that is, directly subtracted), so as to obtain the phase difference of the two code channels. which is:

(5) Calculate the angle:

The phase difference of the two code channels obtained after calculating the phase difference Multiplied by a fixed constant k, the final measured angle value θ can be obtained; the constant k is proportional to the product of the measured wavelengths λ1 and λ2 of the two code channels, and is proportional to the difference between the measured wavelengths λ1 and λ2 of the two code channels Inversely proportional, the proportionality coefficient is 1/(2π). which is:

k=(λ1*λ2)/[2π*(λ1-λ2)]

(6) Communication output:

Output the angle value obtained after calculating the angle θ to the host computer through the interface socket.

The eddy current absolute encoder and its working method provided by the above embodiments of the present invention are composed of an annular encoding disc and an annular reading disc, which are relatively concentrically arranged, parallel to each other, and separated by a small distance. A plurality of reflective conductors are arranged on the surface of the code disc, distributed on two concentric circular code tracks, and the number of reflectors in the two code tracks is different. The reading disc is designed with eight planar coils, which are distributed on two concentric circular code tracks. Each code track is divided into two groups. The spacing between the groups of planar coils is an odd multiple of 1/4 of the measurement wavelength. The planar coil is manufactured using PCB technology, so that it can form an integrated component with the measurement circuit. The angle value is obtained by calculating the phase difference of the two code tracks. The eddy current absolute encoder and its working method provided by the above embodiments of the present invention can not only realize absolute angle measurement, but also have the characteristics of low cost, anti-vibration, wide temperature range, and insensitivity to magnetic targets and magnetic field changes, and can be applied to In a variety of complex and strong interference environments.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (10)

1. An eddy-current absolute encoder, characterized in that: it comprises a ring-shaped coding disk and a ring-shaped reading disk which are relatively concentric and arranged in parallel, and a distance is provided between the coding disk and the reading disk; wherein: The surface of the code disc is provided with two concentric ring code tracks a, and multiple reflective conductors with different numbers are respectively arranged on the two ring code track a; multiple reflective conductors on the same ring code track a have the same The shape and size are evenly distributed along the circumference, and the fan angle corresponding to the interval between two adjacent reflective conductors in the circumferential direction is called the measurement wavelength of the code track; The surface of the reading disc is provided with two ring code tracks b corresponding to the two ring code tracks a on the code disc, and the measurement wavelength of the two ring code tracks b is the same as that of the corresponding ring code track a; Four planar coils are respectively arranged on the ring code track b; the shape and size of the four planar coils on the same ring code track b are the same, and the four planar coils are divided into two groups, and the two planar coils in each group are on the circumference The spacing in the directions is an even multiple of the 1/2 measurement wavelength of the code track, and the circumferential spacing of the two groups of planar coils is an odd multiple of the 1/4 measurement wavelength of the code track. 2. The eddy-current absolute encoder according to claim 1, characterized in that: the reading disc is also provided with a measuring circuit, the measuring circuit forms an integrated assembly with the planar coils, and provides excitation signals for all the planar coils, At the same time, changing parameters of the planar coil are acquired and corresponding electrical signals are output, and the electrical signals are used to obtain the measured angular position. 3. The eddy current absolute encoder according to claim 2, characterized in that: the measuring circuit uses an exciter to provide an excitation signal for the planar coil and directly outputs an analog signal; the number of the exciter is the same as that of the planar coil , where each planar coil corresponds to an exciter. 4. The eddy current absolute encoder according to claim 1, characterized in that: the reading plate is further provided with an interface socket, and the interface socket is used for connecting an external power supply and outputting measurement results. 5. The eddy current absolute encoder according to any one of claims 1 to 4, characterized in that: the reflective conductor is made of metal and is prepared by a PCB manufacturing method or a mechanical processing method. 6. The eddy current absolute encoder according to any one of claims 1 to 4, characterized in that the planar coil is prepared by a multi-layer PCB manufacturing method. 7. The eddy current absolute encoder according to any one of claims 1 to 4, characterized in that: the distance between the encoding disk and the reading disk is 0.5mm. 8. The eddy current absolute encoder according to any one of claims 1 to 4, characterized in that: the outer diameter and inner diameter of the encoding disc and the reading disc are respectively the same or similar. 9. A working method of the eddy current absolute encoder according to any one of claims 1-8, characterized in that: comprising the steps of: S1, Differential processing: Differential processing is performed on the analog signals output by the excitation of two planar coils in each group of planar coils on the reading panel to obtain four differential signals; S2, calculate the tangent: for the four-way differential signal obtained after the differential processing, perform ratio processing on the two-way differential signals on the same ring code track b, so as to obtain the tangent values of the two ring code track b respectively; S3, calculate the phase: perform the arctangent calculation on the two tangent values obtained after calculating the tangent respectively, so as to obtain the phase values of the two ring code tracks b; S4, calculate the phase difference: perform differential calculation on the two phase values obtained after calculating the phase, so as to obtain the phase difference between the two ring code tracks b; S5, calculate the angle: multiply the phase difference of the two circular code tracks b obtained after calculating the phase difference by a fixed constant to obtain the final measured angle value; the product of the constant and the measured wavelengths of the two circular code tracks b It is directly proportional to, and inversely proportional to the difference between the measured wavelengths of the two ring code tracks b, and the proportional coefficient is 1/(2π). 10. The working method of the eddy current absolute encoder according to claim 9, characterized in that: it also comprises the steps of: S6, communication output: output the measured angle value obtained after calculating the angle to the host computer through the interface socket set on the reading panel.