CN106706008B

CN106706008B - Differential capacitance encoder

Info

Publication number: CN106706008B
Application number: CN201710139261.5A
Authority: CN
Inventors: 杜昭辉; 杨艺榕; 庄德津; 罗日辉
Original assignee: Dongguan Yingdong Electromechanical Technology Co ltd; Siemens AG
Current assignee: Dongguan Yingdong Electromechanical Technology Co ltd; Siemens AG
Priority date: 2017-03-09
Filing date: 2017-03-09
Publication date: 2023-08-04
Anticipated expiration: 2037-03-09
Also published as: CN106706008A

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 capacitance encoder

Technical Field

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

Background

An encoder is a device that compiles, converts, or communicates, transmits, and stores signals or data into a signal form. The encoder converts angular displacement, referred to as a code wheel, or linear displacement, referred to as a code scale, into an electrical signal.

Encoders are commonly classified into optical encoders, magnetic encoders, and capacitive encoders. Capacitive encoders have some fundamental advantages over optical and magnetic encoders. However, the capacitive encoder in the prior art has a complex structure, a large volume and poor adaptability, and is difficult to be suitable for various different use occasions.

Disclosure of Invention

Based on the above, the differential capacitance encoder provided by the invention has a simple structure and a small volume, and is easy to realize miniaturization.

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

a differential capacitance encoder comprises 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, and the repeated patterns form an electrode ring with a complete circumference and comprise a rough electrode ring and a fine electrode ring; 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.

According to the differential capacitance encoder, the transmitting area and the receiving area on the static disc are arranged on two sides of the circumference of the static disc in a distinguishing way, the reflecting ring in the movable disc of the general capacitance encoder is omitted, and part of the area of the electrode ring is directly used as an induction pole, and the other part of the area of the electrode ring is used as a reflecting pole. Compared with a 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.

In one embodiment, the stationary disc and the movable disc are coaxially arranged, and the movable disc is located right above the stationary disc.

In one embodiment, the roughly divided excitation electrode and the finely divided excitation electrode have four excitation electrodes each in succession as one period.

In one embodiment, the signal excitation module adopts sine wave signals with the frequency higher than 10kHz as excitation signals, the excitation signals are respectively loaded on each excitation electrode group, and the phase difference between two adjacent excitation electrodes is 90 degrees.

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

In one embodiment, a shielding region is further disposed between the transmitting region and the receiving region.

In one embodiment, the stationary disc and the movable disc are both circular-ring-shaped PCB boards.

In one embodiment, the shielding region is a solder resist portion of the PCB.

Drawings

FIG. 1 is a schematic diagram of a static disc and a dynamic disc of a differential capacitive encoder according to a preferred embodiment of the present invention;

FIG. 2 is a schematic diagram illustrating connection of a stator plate of the differential capacitive encoder shown in FIG. 1 to a processing circuit;

FIG. 3 is an enlarged schematic view of circle A shown in FIG. 2;

the drawings are marked with the following description:

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

Detailed Description

In order that the invention may be readily understood, a more complete description of the invention will be rendered by reference to the appended drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It will be understood that when an element is referred to as being "fixed to" another element, it can be directly on the other element or intervening elements may also be present. 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 defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Referring to fig. 1 to 3, a differential capacitive encoder according to a preferred embodiment of the present invention is mounted on a shaft of a motor. The differential capacitance encoder is a two-piece reflective circular capacitance grid encoder and comprises a static disc 10, a movable disc 40 arranged relative to the static disc 10 and a processing circuit connected with the static disc; the static disc 10 is provided with a transmitting area 20 and a receiving area 30; the stationary plate 10 and the movable plate 40 are coaxially arranged, and the movable plate 40 is positioned right above the stationary plate 10. The static disc 10 and the movable disc 40 are circular ring-shaped PCB boards, the static disc 10 is stationary, and the movable disc 40 and a shaft of the motor are concentrically mounted and synchronously rotate along with the shaft.

The transmitting area 20 and the receiving area 30 are positioned on one surface of the static disc 10 facing the dynamic disc 40; the emitting area 20 and the receiving area 30 each occupy a circular ring on one side of the static disc 10, and the coverage area of the emitting area 20 is larger than that of the receiving area 30. In this embodiment, the transmitting area 20 and the receiving area 30 are separately disposed on opposite sides of the fixed disk 10, and compared with a common capacitive encoder, the transmitting area and the receiving area are disposed on the same side of the circumference of the fixed disk, and the differential capacitive encoder in this embodiment has a reduced loop width, so that the differential capacitive encoder is smaller in size and can be adapted to more use occasions.

The emission area 20 is provided with a plurality of rough division excitation poles 21 and subdivision excitation poles 22 which are arranged along the radial direction of the emission area, the rough division excitation poles 21 and the subdivision excitation poles 22 are arranged in a uniform sector ring shape, and the ring width of the rough division excitation poles 21 is the same as the ring width of the subdivision excitation poles 22; the ring width is the width of a fan ring, the ring width= (outer diameter-inner diameter)/2. The rough-division excitation pole 21 is close to the inner side of the circumference of the static disc 10, and the sub-division excitation pole 22 is close to the outer side of the circumference of the static disc 10, namely, the rough-division excitation pole 21 and the sub-division excitation pole are respectively arranged on an adjacent inner ring and an adjacent outer ring. The roughly divided excitation electrodes 21, the finely divided excitation electrodes 22 are grouped in an even number of excitation electrodes or a cycle, such as four, six, eight, etc. In this embodiment, the roughly divided excitation electrodes 21 and the finely divided excitation electrodes 22 are each one cycle of four consecutive excitation electrodes.

The receiving area 30 includes a coarse receiving area 31 and a fine receiving area 32, and the coarse receiving area 31 and the fine receiving area 32 are arranged in a fan-ring shape. The rough-divided receiving area 31 is close to the inner side of the circumference of the static disc 10, and the sub-divided receiving area 32 is close to the outer side of the circumference of the static disc 10, namely, the rough-divided receiving area 31 and the sub-divided receiving area 32 are respectively arranged on the adjacent inner ring and the adjacent outer ring. The ring width of the rough reception area 31 is equal to that of the rough excitation pole 21, and the rough reception area 31 and the rough excitation pole 21 are positioned on the same ring on the stationary disc 10. The ring width of the subdivision receiving area 32 is equal to the ring width of the subdivision excitation pole 22, and the subdivision receiving area 32 and the subdivision excitation pole 22 are on the same ring on the stator disk 10.

The movable disk 40 can synchronously rotate around the shaft of the motor, and a plurality of continuous repeated patterns are printed on the surface of the movable disk, wherein the repeated patterns are in a sine wave shape; in other embodiments, the waveform may be a cosine waveform, a square waveform, a sawtooth waveform, or the like. The repeated pattern forms a complete circumferential electrode ring, and comprises a rough split electrode ring 41 and a fine split electrode ring 42, wherein the rough split electrode ring 41 is close to the inner circumferential side of the movable disk 40, and the fine split electrode ring 42 is close to the outer circumferential side of the movable disk 40. The rough split electrode ring 41 and the fine split electrode ring 42 have at least one wave-shaped peak/trough circumferentially starting at the same point.

The movable disk 40 in this embodiment omits the reflective ring in a typical capacitive encoder movable disk, and instead directly uses a portion of the area of the electrode ring as the sense electrode and another portion as the reflective electrode. The sensing electrode is in projection overlapping with the transmitting area 20 on the static disk 10, and is in capacitive coupling, the sensing electrode is excited by the transmitting area 20 to generate a sensing electric signal, the reflecting electrode is in projection overlapping with the receiving area 30 on the static disk 10, and the receiving area 30 receives the electric signal reflected by the reflecting electrode, namely a modulation signal, and outputs the modulation signal for analysis.

In order to avoid direct coupling between the emitter region 20 and the receiver region 30, and between each exciting electrode in the emitter region 20 and the exciting electrode, a shielding region 50 is further disposed between the emitter region 20 and the receiver region 30, and further, the shielding region 50 in this embodiment is a solder mask 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 two sides of the stationary plate 10, a signal demodulation module 80 connected to the signal acquisition module 70, and a signal filtering module 90 connected to the signal demodulation module 80. The signal excitation module 60 generates four-way sine wave excitation signals which are respectively loaded on each excitation electrode group of the rough division excitation electrode 21 or the subdivision excitation electrode 22. In this embodiment, the signal excitation module 60 uses a sine wave signal with a frequency higher than 10kHz as an excitation signal, 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 acquisition module 70 is electrically connected to the receiving area 40 on the stationary plate 10, and acquires the modulated signal reflected from the reflector 24. When the differential capacitance encoder is powered on, an excitation signal is firstly loaded to the coarse-division excitation electrode 31 through a multi-path control switch, and the signal acquisition module 70 is connected with the coarse-division receiving area 31 at the moment, so that a coarse-division modulation signal can be obtained; then the multi-path control switch is switched to subdivide and receiveThe area 32 is loaded with an excitation signal, resulting in a finely divided modulation signal. Because the modulated signal is weak in amplitude and requires amplification to increase the signal amplitude to hundreds to thousands of millivolts, the signal acquisition module 70 includes an op-amp. Assuming that a first excitation electrode of a certain excitation electrode group is designated as a, after the movable disk 20 and the stationary disk 10 perform relative rotation movement, the electric signal charge received by the signal acquisition module 70 isWhere K is a coefficient that is related to many prints, such as excitation signal amplitude, excitation electrode stripe area, air gap between moving and stationary plates, air gap dielectric constant, etc., and generally is approximately constant under certain design and operating circumstances.

The signal demodulation module 80 is electrically connected to the signal acquisition module 70, and the signal demodulation module 80 receives the amplified modulated signal, and multiplies the amplified modulated signal by the excitation signal to separate the excitation signal and the displacement signal. In this embodiment, a sinusoidal excitation signal is used, the modulated signal is multiplied by the sinusoidal excitation signal, and the signal result includes a trigonometric function and displacement of twice the frequency of the excitation signalCosine function of +.>Said displacement +.>Cosine function of (2)Is a direct current, and the high frequency component is removed by the signal filtering module 90, thereby obtaining +.>Similarly, when the excitation source is cosine excitation signal, the signal demodulation module80 with a cosine excitation signal, the signal result comprising a trigonometric function of twice the frequency of the excitation signal and a displacement +.>Is +.>Said displacement +.>Is +.>Is a direct current, and the high frequency component is removed by the signal filtering module 90, thereby obtaining +.>In this embodiment, the signal filtering module 90 is a low-pass filter. The displacement is obtained by the above method>After the sine and cosine signals of the encoder are calculated by various calculation modes, the existing products in the market can directly accept the sine and cosine signals as the output of the encoder, and the technology is quite mature, so that the invention does not need to describe an intermediate calculation process.

Since the two-chip capacitor is easily interfered by electromagnetic interference of the motor or noise thereof, the coarse receiving area 31 and the fine receiving area 32 are fully utilized in the embodiment, so as to realize background noise suppression. Referring again to fig. 2, the signal acquisition module 70 employs a bipolar op-amp, the positive input of which is connected to the sub-divided receiving area 32, and the negative input of which is connected to the coarse-divided receiving area 31. When the subdivided driving pole 22 is in load operation, the subdivided modulation signals and the background noise signals thereof are collected by the subdivided receiving region 32, and at this time, only the background noise signals are received by the coarse receiving region 31, and no effective signals are received, generally, the subdivided receiving region 32 is approximately equivalent to the background noise received by the coarse receiving region 31, and in the bipolar operational amplifier, the background noise is suppressed, and the effective signals are amplified. Similarly, when the coarse exciter 21 is in load operation, the coarse receiving area 31 collects coarse modulated signals and background noise signals thereof, and only background noise signals are received in the fine receiving area 32, and no effective signals are received, so that background noise is suppressed and effective signals are amplified in bipolar operational amplification. With this method, the background noise interference is effectively suppressed and the performance and reliability of the differential capacitive encoder are improved without increasing the area and size of the stationary plate 10.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims

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.