CN106706008B - Differential capacitance encoder - Google Patents

Abstract

The invention relates to a differential capacitance encoder, which comprises a static disc, a transmitting area, a receiving area, a moving disc and a processing circuit; the static disc comprises a transmitting area and a receiving area, and the transmitting area and the receiving area are arranged on two sides of the circumference of the static disc; the emission area is provided with a rough division excitation pole and a fine division excitation pole; the receiving area comprises a coarse division receiving area and a fine division receiving area; the processing circuit comprises a signal excitation module and a signal acquisition module which are respectively connected to the two sides of the static disc, a signal demodulation module connected with the signal acquisition module and a signal filtering module connected with the signal demodulation module. Compared with the common capacitance encoder, the differential capacitance encoder fully utilizes the area resources of the dynamic disc and the static disc, so that the differential capacitance encoder is smaller in size and can be suitable for more use occasions; meanwhile, the signal-to-noise ratio of the signal is improved, and the anti-interference capability of the differential capacitance encoder is enhanced.

Description

Differential Capacitive Encoder

technical field

The invention relates to the technical field of encoders, in particular to a differential capacitance encoder.

Background technique

An encoder is a device that compiles and converts signals or data into signal forms that can be used for communication, transmission and storage. The encoder converts angular displacement or linear displacement into an electrical signal, the former is called a code disc, and the latter is called a yardstick.

Encoders are generally divided into optical encoders, magnetic encoders and capacitive encoders. Capacitive encoders have some basic advantages over optical and magnetic encoders. However, due to the complex structure, large size and poor adaptability of the capacitive encoder in the prior art, it is difficult to be applicable to many different usage occasions.

Contents of the invention

Based on this, the present invention provides a differential capacitive encoder, which has a simple structure, a small volume, and is easy to realize miniaturization.

In order to realize the purpose of the present invention, the present invention adopts following technical scheme:

A differential capacitance encoder, comprising a static disk, a moving disk arranged relative to the static disk, and a processing circuit connected to the static disk; the static disk is provided with a transmitting area and a receiving area, and the transmitting area The receiving area is set on opposite sides of the stationary disk; the transmitting area is provided with a number of coarse-divided excitation poles and fine-divided excitation poles arranged along its radial direction; the receiving area includes a coarse-divided receiving area and the subdivision receiving area; the coarse division excitation pole, the subdivision excitation pole, the coarse division reception area and the subdivision reception area are all arranged in a fan ring shape; the coarse division reception area and the coarse division reception area The subdivided excitation poles are located on the same ring on the static disk, and the subdivided receiving area and the subdivided excitation poles are located on the same annular ring on the static disk; the surface of the moving disk is printed with continuous etc. A plurality of repeating patterns, the repeating patterns constitute a complete circular electrode ring, including a coarse electrode ring and a finer electrode ring; the processing circuit includes a signal excitation module and a signal excitation module respectively connected to both sides of the static plate An acquisition module, a signal demodulation module connected to the signal acquisition module, and a signal filtering module connected to the signal demodulation module.

For the above differential capacitance encoder, the transmitting area and the receiving area on the static disk are set on both sides of the circumference of the static disk, and the moving disk saves the reflection ring in the moving disk of the general capacitance encoder, but directly uses A part of the area of the electrode ring is used as an induction pole, and another part is used as a reflection pole. Compared with the general capacitive encoder, the differential capacitive encoder of the present invention makes full use of the area resources of the dynamic and static discs, making the differential capacitive encoder smaller in size and adaptable to more occasions; meanwhile, it also improves The signal-to-noise ratio of the signal enhances the anti-interference ability of the differential capacitance encoder.

In one of the embodiments, the stationary disk is arranged concentrically with the moving disk, and the moving disk is located directly above the static disk.

In one of the embodiments, each four consecutive excitation electrodes is taken as a cycle for the coarse-division excitation pole and the fine-division excitation pole.

In one of the embodiments, the signal excitation module uses a sine wave signal with a frequency higher than 10 kHz as the excitation signal, and the excitation signal is respectively loaded on each excitation electrode group, and the phase difference between two adjacent excitation electrodes is 90 Spend.

In one embodiment, the shape of the repeating pattern is a sinusoidal waveform.

In one of the embodiments, a shielding area is further provided between the transmitting area and the receiving area.

In one of the embodiments, both the static disc and the movable disc are annular PCB boards.

In one of the embodiments, the shielding area is a solder resisting part of the PCB.

Description of drawings

Fig. 1 is the structure schematic diagram of the stationary disk and the moving disk of the differential capacitive encoder of a preferred embodiment of the present invention;

Fig. 2 is the schematic diagram of connection between the static disk and the processing circuit of the differential capacitive encoder shown in Fig. 1;

Fig. 3 is an enlarged schematic diagram of circle A shown in Fig. 2;

Notes on drawings:

10-static disc, 20-transmitting area, 21-coarse excitation pole, 22-subdivision excitation pole, 30-receiving area, 31-coarse division receiving area, 32-subdivision receiving area, 40-moving disc, 41- Coarse division electrode ring, 42-subdivision electrode ring, 50-shielding area, 60-signal excitation module, 70-signal acquisition module, 80-signal demodulation module, 90-signal filtering module.

Detailed ways

In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the associated drawings. Preferred embodiments of the invention are shown in the accompanying drawings. However, the present invention can be embodied in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

It should be noted that when an element is referred to as being “fixed” to another element, it can be directly on the other element or there can also be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or intervening elements may also be present.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field of the invention. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention.

Please refer to FIG. 1 to FIG. 3 , which show a differential capacitive encoder in a preferred embodiment of the present invention, which is installed on the shaft of the motor. The differential capacitance encoder is a two-piece reflective circular capacitance encoder, including a static disk 10, a moving disk 40 arranged relative to the static disk 10, and a processing circuit connected to the static disk; The static disc 10 is provided with a transmitting area 20 and a receiving area 30 ; Both the static disc 10 and the moving disc 40 are annular PCB boards, the static disc 10 is stationary, and the moving disc 40 is installed concentrically with the crankshaft of the motor and moves along with the motor. Shafts rotate synchronously.

The transmitting area 20 and the receiving area 30 are located on the side of the static plate 10 facing the moving plate 40 ; , and the coverage area of the transmitting area 20 is larger than the coverage area of the receiving area 30 . In this embodiment, the transmitting area 20 and the receiving area 30 are separately arranged on the opposite sides of the static disk 10, compared with the general capacitive encoders where both the transmitting area and the receiving area are arranged on the circumference of the static disk. On the same side, the differential capacitive encoder in this embodiment has a reduced ring width, which makes the differential capacitive encoder smaller in size and can be adapted to more application occasions.

The emission area 20 is provided with a plurality of coarse division excitation poles 21 and subdivision excitation poles 22 arranged along its radial direction, and the coarse division excitation poles 21 and the subdivision excitation poles 22 are arranged in a uniform fan ring shape. The ring width of the coarse-division excitation pole 21 is the same as that of the fine-division excitation pole 22; the ring width is the width of a sector ring, and the ring width=(outer diameter-inner diameter)/2. The coarse fractionation excitation pole 21 is close to the inner circumference of the static disk 10, and the fine division excitation pole 22 is close to the outer circumference of the static disk 10, that is, the coarse division excitation pole 21 and the fine division excitation pole are respectively Set on adjacent inner and outer rings. The coarse-division excitation poles 21 and the fine-division excitation poles 22 constitute a group or a cycle with an even number of excitation electrodes, such as four, six, eight, and so on. In this embodiment, the coarse-dividing excitation pole 21 and the fine-division excitation pole 22 take every four consecutive excitation electrodes as a period.

The receiving area 30 includes a coarse receiving area 31 and a subdivided receiving area 32, both of which are arranged in a fan ring shape. The coarse receiving area 31 is close to the inner circumference of the static plate 10, and the finer receiving area 32 is closer to the outer circumference of the static plate 10, that is, the coarse receiving area 31 and the finer receiving area 32 They are respectively arranged on the adjacent inner ring and outer ring. The ring width of the coarse separation receiving area 31 is equal to the ring width of the coarse separation excitation pole 21, and the coarse separation reception area 31 and the coarse separation excitation pole 21 are located in the same ring on the stationary disk 10 superior. The ring width of the subdivided receiving area 32 is equal to the ring width of the subdivided excitation pole 22, and the subdivided receiving area 32 and the subdivided excitation pole 22 are located in the same ring on the stationary disk 10 superior.

The moving plate 40 can rotate synchronously around the shaft of the motor, and its surface is printed with a plurality of continuous repeating patterns, and the shape of the repeating pattern is a sine wave; in other embodiments, it can also be a cosine wave, a square Waveform or sawtooth waveform, etc. The repeating pattern constitutes a complete circular electrode ring, including a coarse electrode ring 41 and a subdivided electrode ring 42, the coarse electrode ring 41 is close to the inner circumference of the moving disk 40, and the subdivided electrode ring 42 is close to The outer circumference of the moving disk 40 . The coarse-dividing electrode ring 41 and the fine-dividing electrode ring 42 have at least one peak/trough of the waveform on the same starting point on the circumference.

The moving disc 40 in this embodiment omits the reflective ring in the common capacitive encoder moving disc, but directly uses a part of the area of the electrode ring as the sensing pole, and the other part as the reflecting pole. The sensing pole overlaps with the emission area 20 projection on the static disk 10 to generate capacitive coupling, the induction pole is excited from the emission area 20 to generate an induction electrical signal, and the reflection pole and the static disk The projection of the receiving area 30 on 10 overlaps, and the receiving area 30 receives the electrical signal reflected by the reflector, that is, the modulation signal, and outputs the modulation signal for analysis.

In order to avoid direct coupling between the transmitting area 20 and the receiving area 30, and between the excitation poles in the transmitting area 20, a shielding area 50 is also provided between the transmitting area 20 and the receiving area 30, further Specifically, the shielding area 50 in this embodiment is the solder resist portion of the PCB.

The processing circuit in this embodiment includes a signal excitation module 60 and a signal acquisition module 70 respectively connected to both sides of the static disk 10, a signal demodulation module 80 connected to the signal acquisition module 70, and a signal demodulation module 80 connected to the signal demodulation module 70. The signal filtering module 90 of the modulation module 80. The signal excitation module 60 generates four channels of sine wave excitation signals, which are loaded on the respective excitation electrode groups of the coarse-division excitation pole 21 or the fine-division excitation pole 22 . In this embodiment, the signal excitation module 60 uses a sine wave signal with a frequency higher than 10 kHz as the excitation signal, and the excitation signal is respectively loaded on each excitation electrode group, and the phase offset corresponding to the signal of each excitation electrode is respectively 0, 90, 180 and 270 degrees, that is, the phase difference between two adjacent excitation electrodes is 360/4=90 degrees.

The signal collection module 70 is electrically connected to the receiving area 40 on the static disk 10 to collect the modulated signal reflected from the reflector 24 . When the differential capacitive encoder is powered on, an excitation signal is first loaded to the coarse division excitation pole 31 through a multi-channel control switch, and the signal acquisition module 70 is connected to the coarse division receiving area 31 at this time, A coarsely divided modulation signal can be obtained; and then the multi-channel control switch is switched to load an excitation signal to the subdivided receiving area 32 to obtain a subdivided modulated signal. Since the amplitude of the modulated signal is weak, it needs to be amplified to increase the signal amplitude to hundreds of millivolts to thousands of millivolts, so the signal acquisition module 70 includes an operational amplifier. Assuming that the first excitation electrode on a certain excitation electrode group is named A, after the relative rotation of the moving plate 20 and the static plate 10 occurs, the electrical signal charge that can be received by the signal acquisition module 70 is Among them, K is a coefficient, which is related to many printings, such as the amplitude of the excitation signal, the area of the excitation electrode strip, the air gap between the moving plate and the static plate, the dielectric constant of the air gap, etc. Generally, in a specific design and working environment, K is approximately a constant .

The signal demodulation module 80 is electrically connected to the signal acquisition module 70. The signal demodulation module 80 receives the amplified modulated signal and multiplies it with the excitation signal to separate the excitation signal and the displacement signal. In this embodiment, a sinusoidal excitation signal is used, the modulation signal is multiplied by the sinusoidal excitation signal, and the signal result includes a trigonometric function and a displacement of twice the frequency of the excitation signal cosine function of /> Compared to a signal at twice the frequency of the excitation signal, the shift / cosine function of is a direct current flow, and the high-frequency component is removed by the signal filtering module 90 to obtain /> Similarly, when the excitation source is a cosine excitation signal, the modulated signal received by the signal demodulation module 80 is multiplied by the cosine excitation signal, and the signal result includes a trigonometric function and displacement of twice the frequency of the excitation signal The sine function /> Compared to a signal at twice the frequency of the excitation signal, the shift / The sine function /> is a direct current flow, and the high-frequency component is removed by the signal filtering module 90 to obtain /> In this embodiment, the signal filtering module 90 is a low-pass filter. Obtain the displacement by the above method /> After the sine and cosine signals, the displacement can be solved by various calculation methods. The existing products on the market can directly accept this sine and cosine signals as the output of the encoder. This technology is quite mature, so the present invention will not go into details Intermediate calculation process.

Since the two-chip capacitor is susceptible to electromagnetic interference or noise interference from the motor, in this embodiment, the coarse receiving area 31 and the subdivided receiving area 32 are fully utilized to suppress background noise. Please refer to FIG. 2 again, the signal acquisition module 70 adopts a bipolar op amp, the positive input of the bipolar op amp is connected to the subdivided receiving area 32, and the negative input of the bipolar op amp is connected to the coarse Sub-receiving area 31. When the subdivision excitation pole 22 is working under load, the subdivision receiving area 32 collects the subdivided modulation signal and its background noise signal, and at this time, only the background noise signal is received on the coarse division receiving area 31 , and no effective signal is received. Generally speaking, the background noise received by the subdivided receiving area 32 is roughly equivalent to that received by the coarsely divided receiving area 31. In the bipolar operational amplifier, the background noise is suppressed and the effective signal is amplified. . In the same way, when the coarse division excitation pole 21 is working under load, the coarse division receiving area 31 collects the coarse modulation signal and its background noise signal, and at this moment, only the background noise signal is received in the subdivision receiving area 32 The noise signal does not receive the effective signal. In the bipolar op amp, the background noise is suppressed and the effective signal is amplified. By using this method, without increasing the area and size of the static disk 10, background noise interference is effectively suppressed, and the performance and reliability of the differential capacitive encoder are improved.

For the above differential capacitance encoder, the transmitting area and the receiving area on the static disk are set on both sides of the circumference of the static disk, and the moving disk saves the reflection ring in the moving disk of the general capacitance encoder, but directly uses A part of the area of the electrode ring is used as an induction pole, and another part is used as a reflection pole. Compared with the general capacitive encoder, the differential capacitive encoder of the present invention makes full use of the area resources of the dynamic and static discs, making the differential capacitive encoder smaller in size and adaptable to more occasions; meanwhile, it also improves The signal-to-noise ratio of the signal enhances the anti-interference ability of the differential capacitance encoder.

The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, should be considered as within the scope of this specification.

The above-mentioned embodiments only express several implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but should not be construed as limiting the patent scope of the invention. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (8)

1. The differential capacitance encoder is characterized by comprising a static disc, a movable disc arranged relative to the static disc and a processing circuit connected with the static disc; the static disc is provided with a transmitting area and a receiving area, and the transmitting area and the receiving area are arranged on two opposite sides of the static disc; the emission area is provided with a plurality of rough-division excitation poles and fine-division excitation poles which are arranged along the radial direction of the emission area; the receiving area comprises a coarse division receiving area and a fine division receiving area; the rough division exciting electrode, the subdivision exciting electrode, the rough division receiving area and the subdivision receiving area are all arranged in a fan ring shape; the rough division receiving area and the rough division exciting electrode are positioned on the same circular ring on the static disc, and the subdivision receiving area and the subdivision exciting electrode are positioned on the same circular ring on the static disc; the surface of the movable disk is printed with a plurality of continuous repeated patterns, the repeated patterns form an electrode ring with a complete circumference and comprise a rough division electrode ring and a subdivision electrode ring, the rough division electrode ring is close to the inner side of the circumference of the movable disk, the subdivision electrode ring is close to the outer side of the circumference of the movable disk, and at least one wave crest/wave trough of the rough division electrode ring and the subdivision electrode ring are at the same starting point on the circumference; the processing circuit comprises a signal excitation module and a signal acquisition module which are respectively connected to the two sides of the static disc, a signal demodulation module connected with the signal acquisition module and a signal filtering module connected with the signal demodulation module.

2. The differential capacitive encoder of claim 1, wherein the stationary plate is coaxially disposed with the movable plate, the movable plate being located directly above the stationary plate.

3. The differential capacitive encoder according to claim 1, wherein the roughly divided excitation pole and the finely divided excitation pole have four excitation electrodes each in succession as one cycle.

4. The differential capacitive encoder according to claim 1, wherein the signal excitation module uses a sine wave signal with a frequency higher than 10kHz as the excitation signal, the excitation signal being respectively applied to each excitation electrode group, and a phase difference between two adjacent excitation electrodes is 90 degrees.

5. The differential capacitive encoder of claim 1, wherein the shape of the repeating pattern is a sinusoidal waveform.

6. The differential capacitive encoder of claim 1, wherein a shielding region is further provided between the transmitting region and the receiving region.

7. The differential capacitive encoder of claim 6, wherein the stationary plate and the movable plate are circular-ring-shaped PCBs.

8. The differential capacitive encoder of claim 7, wherein the shielding region is a solder resist portion of a PCB.