Patent Description:
The invention belongs to the technical field of precision measurement, in particular, to an orthogonal trigonometric function double excitation-based encoder and an operation method thereof.

In the field of industrial machinery automation and CNC machining, when displacement feedback and high-precision processing and measurement for some mechanical structures are performed, encoders are often required for devices in feedback of precise positions and angles.

Currently, in the market, rulers or scales such as fiber gratings, magnetic scales, and capacitive gratings are mainly used as grating encoders, during whose movement the regular periodic changes of a certain physical quantity are used to form grating lines evenly distributed along the space, and a displacement pulse signal sent every time a grating interval passes is accumulated to obtain the displacement. The fiber grating is currently the most widely used grating encoder with high precision and mature technology, and widely used in digital high-precision mechanical measuring instruments and equipment such as high-end CNC machine tools, coordinate measuring machines, and gear measuring centers. It can be seen that the fiber grating sensor technology is the basis and key component to ensure the performance of the mechanical system. However, the fiber grating encoder has high requirements for the working environment, especially sensitive to dusty environment, oily environment, etc.; its anti-seismic ability is poor, its cost performance is low, and it is easily affected by foreign supply channels, so that its application range is relatively narrow, and it is difficult to equip it on a large scale. For decades, our country has invested a lot of manpower and material resources, but it still does not have the ability to manufacture high-end fiber grating encoders, and the equipment can only rely on imports.

In recent years, due to the improvement of domestic scientific research level and technology, an idea for an encoder of exchanging high-precision time measurement for physical changes in space has been born, which takes advantage of the current high-exponential time measurement level (i.e., the measurement accuracy of time is higher than the accuracy of physical quantities) to obtain high-precision angular displacement changes so as to design a high-precision encoder. Since this kind of encoder uses time as a "scale", the physical scale on the fiber grating disc is omitted, and the use of fragile fiber grating discs is avoided, so that it has advantages in high precision, shock resistance, economy, and ability to work in harsh environments. The most important thing is to solve the problems of supply chain and intellectual property rights, so that the domestic encoder industry sees hope.

However, the current time grating displacement encoders basically use single excitation, i.e., single single-frequency sine wave excitation, which is implemented by a phase shift method of <MAT>. The single excitation can only achieve a single calculation reference phase, and the internal and external reference signals can only be divided by using the periodic signal of 2π as the calculation parameter, so that the calculation error is larger when the rotor rotates at high speed and low speed. When the signal source is interfered, the interference signal will be directly superimposed on the source signal. When the frequency of the interference source is close to the frequency of the source, the problems caused are difficult to deal with and the anti-interference ability is low. The patent application <CIT> double-channel differential absolute time grating angular displacement encoder which comprises a rotor and a stator, wherein the rotor and the stator are coaxially and parallelly arranged.

In view of this, it is necessary to provide an orthogonal trigonometric function double excitation-based encoder and an operation method thereof which has a high precision and a strong anti-interference ability.

The embodiment of the invention uses the method of orthogonal trigonometric function double excitation, i.e., combining the sine wave and the cosine wave and obtaining the combined signals by shifting <MAT> and <MAT> in phase. Since the combination is performed by two excitations, synchronous phase differences between the source signals y<NUM>, and y<NUM> and between the combined signals Y and F(t) may be simultaneously detected, and an absolute angle value is calculated by comparing the phase difference. With the phase shift of <MAT>, internal reference signals may be based on π or 2π as a reference period, i.e., combination of (external π, internal π) and (external π, internal 2π) may effectively reduce calculation errors during high-speed and low-speed rotation. Even if the phase and frequency of the source signal are disturbed, it will only appear as low-frequency interference or DC interference on the combined signals, because the center frequency of the combined signal is twice the center frequency of the source signal. In this way, it is easy to pass through the band-pass filter, and the interference signal may be eliminated, so that a relatively clean signal may be obtained for phase comparison, thereby reducing the system errors.

In order that the objectives, technical schemes and advantages of the present invention will become more apparent, the present invention will be described in more detail with reference to the drawings and examples above. It should be understood that the specific embodiments described herein are only for illustrating but not for limiting the present invention.

As shown in <FIG> and <FIG>, an encoder of orthogonal trigonometric function double excitation according to an embodiment of the invention is shown, which includes a stator <NUM> and a rotor <NUM> that are arranged coaxially and in parallel.

The stator <NUM> includes an auxiliary ruler region <NUM>, a main ruler region <NUM>, an inner ring DA region <NUM> and an inner ring DB region <NUM> which are sequentially arranged from outside to inside. The auxiliary ruler region <NUM> is located at an outer ring, and is annularly and uniformly divided into a plurality of first emission sheets <NUM> with a center of circle of the stator <NUM> as a center. Every <NUM> first emission sheets <NUM> is a group, and every two groups of first emission sheets <NUM> are used as a phase shift period of 2π. An inner end of each group of first emission sheets <NUM> forms a closed fan shape protruding inward, and each group of first emission sheets <NUM> is arranged radially and symmetrically between groups. When the rotor <NUM> rotates, the auxiliary ruler region <NUM> of the stator as an emission region verifies a zero point of a critical point of the auxiliary ruler region <NUM> of the rotor <NUM> as an induction region to perform boundary compensation. The main ruler region <NUM> is located inside the auxiliary ruler region <NUM>, and is annularly and uniformly divided into a plurality of second emission sheets <NUM> with a center of circle of the stator <NUM> as a center. Every <NUM> second emission sheets <NUM> is a group, and two groups of second emission sheets <NUM> are used as a phase shift period of 2π. An inner end of each group of second emission sheets <NUM> jointly forms an arc protrusion protruding toward the center of circle, and two groups of second emission sheets <NUM> are arranged radially and symmetrically between groups. When the rotor <NUM> rotates, the main ruler region <NUM> of the stator as an emission region verifies a zero point of a critical point of the main ruler region <NUM> of the rotor <NUM> as an induction region to perform boundary compensation. The inner ring DA region <NUM> and the inner ring DB region <NUM> are signal receiving rings, and the annular areas of the inner ring DA region <NUM> and the inner ring DB region <NUM> are equal to ensure that electric field signals of the rotor <NUM> may be uniformly induced and received during operation.

The rotor <NUM> includes an auxiliary ruler region <NUM>, a main ruler region <NUM>, an inner ring ZA region <NUM> and an inner ring ZB region <NUM> which are sequentially arranged from outside to inside. The auxiliary ruler region <NUM> is located at an outer ring with a center of circle of the rotor <NUM> as a center, and includes a plurality of first induction sheets <NUM> distributed annularly. Each of the first induction sheets <NUM> is a closed symmetrical figure divided by a hyperbola. A closed area at both ends of the figure is small, and the closed area gradually increases toward the center, forming an approximately elliptical shape with small ends and a large middle. Arc lengths of both ends of the first induction sheet <NUM> are equal, and radians thereof coincide with a radian of the inner ring of the rotor <NUM>; the first induction sheet <NUM> covers two first emission sheets <NUM> in a dimensionally circumferential span. In the embodiment, the first induction sheet <NUM> is inclined at a certain angle, i.e., with a distal end inclined counterclockwise and a proximal end inclined clockwise. Such graphic design may ensure that the rotor <NUM> may evenly induce the electric field signals from the stator <NUM> when rotating, and will induce error compensation signals when covering the auxiliary ruler region <NUM> of the stator <NUM>, which is convenient for calculation. The main ruler region <NUM> of the rotor <NUM> is located inside the auxiliary ruler region <NUM> and axially corresponds to the main ruler region <NUM> of the stator <NUM>. The main ruler region <NUM> is centered on the center of the rotor <NUM>, is evenly distributed annularly, and is divided into a plurality of second induction sheets <NUM>. Every two second induction sheets <NUM> is a group, as a phase shift period of 2π. One of the second induction sheets <NUM> covers two second emission sheets <NUM> in a circumferential span, and a rotating arc length of the second induction sheet <NUM> is twice that of the second emission sheet <NUM> of the stator <NUM>. The annular areas of the inner ring DA region <NUM> and the inner ring DB region <NUM> are equal to ensure that electric field signals of the rotor <NUM> may be uniformly induced and received during operation, and the electric field signals are transmitted to the inner ring DA region <NUM> and the inner ring DB region <NUM> of the stator <NUM>.

The working principle of the embodiment of the invention is described in detail now: first, the system generates a double excitation signal source: <MAT> <MAT> wherein A<NUM> and A<NUM> are the signal amplitude, f is the frequency, and t is the time. the signal sources are combined: <MAT> wherein A = A<NUM>*A<NUM>. The combined signal source is shifted through <MAT> and <MAT>; in phase, and the calculation method of <MAT> is the same as that of <MAT>, so only <MAT> is discussed.

Thus, the following signals are obtained through the phase shift of <MAT>: <MAT> <MAT> <MAT> <MAT> similarly, Y(<NUM>) = Y(π), <MAT>.

Assuming that the speed of the rotor at a certain time t is V, then the angle by which the rotor is rotated may be expressed as:
<MAT>
wherein <MAT>, R is the radius of the rotor, and ω is the angular velocity of the rotor.

Then the electric field induced on the rotor should be expressed as:
<MAT>
Therefore, the electric field signals acting on the induction sheet are expressed as:
<MAT>
<MAT>
<MAT>
<MAT>
Finally, a formula for the relationship between angular space and time is obtained through spacetime transformation:
<MAT>
There are a total of <NUM> combinations according to the arrangement order of the induction sheets, and the formulas are finally simplified as:
<MAT>
wherein E is the amplitude of the signal, k is a constant coefficient, Deg(t) is the angle of rotation by which the rotor is rotated after the time t, and fc is the frequency of the combined signal.

Let θ = Deg(t), and the initial angle of the rotor is θ<NUM>, then the following may be obtained:
<MAT>
If the rotor starts rotating from the zero scale, θ<NUM> = <NUM>, then the following may be obtained:
<MAT>
When the rotor is stationary, with an initial angle of θ = <NUM>, the following may be obtained:
<MAT>
In this way, regardless of whether the rotor is stationary or moving, the system may obtain the sine wave based on the phase change of the relative angle between the rotor and the stator.

By calculating θ, the changes in the current relative angle value of the rotor and stator may be obtained, and the absolute angle value of the rotor and stator may be calculated according to the zero point of the system signal of y<NUM>,y<NUM>,Y.

In combination of <FIG>, the above working principle is implemented by the following steps:
In the first step, the digital signal source generates two excitation signals, sine signals and cosine signals, and the function is expressed as formula (<NUM>, <NUM>).

In the second step, the two excitation signals are shifted in phase digitally to obtain two groups of signals with a phase difference of<MAT>.

In the third step, the product of two signals is obtained by digitally combining, and the function is expressed as formula (<NUM>).

In the fourth step, the output and amplification are performed through digital-to-analog conversion to obtain <NUM> groups of combined signals with a phase difference of <MAT>, and the function is expressed as formula (<NUM>, <NUM>, <NUM>, <NUM>).

In the fifth step, the combined signal (Y(<NUM>), <MAT>) is respectively applied to the N<NUM> second emission regions of the main ruler region of the stator, and circulated clockwise in the order of (Y(<NUM>), <MAT>), as shown in <FIG>). N<NUM> is a multiple of <NUM>.

In the sixth step, the main ruler region (Zm<NUM>, Zm<NUM>) of the rotor is circulated sequentially, and each of the second induction sheets in the main ruler region of the rotor covers the two second emission sheets in the main ruler region of the rotor, i.e., <MAT>, Zm<NUM> = <MAT>, which is circulated sequentially.

In the seventh step, the induction signals of the main ruler region (Zm<NUM>, Zm<NUM>) of the rotor is fed back to the inner ring DA region and the inner ring DB region of the stator through the inner ring ZA region and the inner ring ZB region, as shown in <FIG>.

In the eighth step, the induction signals of the inner ring DA region and the inner ring DB region of the stator are combined, amplified, filtered, and are subjected to digital phase identification to calculate the current angle area of the main ruler region.

The auxiliary ruler region is implemented by the following steps as further description:.

As shown in <FIG>, the working content and flow of the software are described as below:.

The embodiment of the invention uses the method of orthogonal trigonometric function double excitation, i.e., combining the sine wave and the cosine wave and obtaining the combined signals by shifting
<MAT>
and
<MAT>
in phase. Since the combination is performed by two excitations, synchronous phase differences between the source signals y<NUM> and y<NUM> between the combined signals Y and F(t) may be simultaneously detected, and an absolute angle value is calculated by comparing the phase difference. With the phase shift of <MAT>, internal reference signals may be based on π or 2π, i.e., combination of (external π, internal π) and (external π, internal 2π) may effectively reduce calculation errors during high-speed and low-speed rotation. Even if the phase and frequency of the source signal are disturbed, it will only appear as low-frequency interference or DC interference on the combined signals, because the center frequency of the combined signal is twice the center frequency of the source signal. In this way, it is easy to pass through the band-pass filter, and the interference signal may be eliminated, so that a relatively clean signal may be obtained for phase comparison, thereby reducing the system errors.

Claim 1:
An orthogonal trigonometric function double excitation-based encoder, comprising a stator (<NUM>) and a rotor (<NUM>), wherein the stator (<NUM>) is arranged coaxially and in parallel with the rotor (<NUM>); the stator comprises an auxiliary ruler region, a main ruler region, an inner ring DA region and an inner ring DB region which are sequentially arranged from outside to inside; the rotor (<NUM>) includes an auxiliary ruler region, a main ruler region, an inner ring ZA region and an inner ring ZB region which are sequentially arranged from outside to inside; the auxiliary ruler region of the stator (<NUM>) is annularly and uniformly divided into a plurality of first emission sheets (<NUM>), every four consecutive first emission sheets (<NUM>) form a group, and every two groups of first emission sheets (<NUM>) are configured to be used for signals of one period; the main ruler region of the stator (<NUM>) is annularly and uniformly divided into a plurality of second emission sheets (<NUM>), every two consecutive second emission sheets (<NUM>) form a group, and every two groups of second emission sheets (<NUM>) are configured to be used for signals of one period; the auxiliary ruler region of the rotor (<NUM>) is annularly divided into a plurality of first induction sheets (<NUM>), and one first induction sheet (<NUM>) covers two continuous first emission sheets (<NUM>); the main ruler region of the rotor (<NUM>) is annularly divided into a plurality of second induction sheets, and one second induction sheet covers two continuous second emission sheets (<NUM>) in a circumferential span; a rotating arc length of the second induction sheet is twice that of the second emission sheet of the stator (<NUM>);
wherein:
an outer end of the first induction sheet (<NUM>) is inclined counterclockwise, and an inner end thereof is inclined clockwise; and
characterized in that
the first induction sheet (<NUM>) is a closed symmetrical figure formed by hyperbola division, and a closed area of both ends of the first induction sheet (<NUM>) is small, and wherein the closed area gradually increases toward a center point thereof, forming an approximately elliptical shape with small ends and a large middle.