CN214040073U - Absolute type capacitive grating sensor measuring system - Google Patents
Absolute type capacitive grating sensor measuring system Download PDFInfo
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- CN214040073U CN214040073U CN202022780144.7U CN202022780144U CN214040073U CN 214040073 U CN214040073 U CN 214040073U CN 202022780144 U CN202022780144 U CN 202022780144U CN 214040073 U CN214040073 U CN 214040073U
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Abstract
The utility model discloses an absolute type grid sensor measurement system, including measurement signal processing unit and absolute type grid sensor unit and the data processing unit who is connected with measurement signal processing unit, measurement signal processing unit is equipped with parallelly connected optional first grid IC1 and second grid IC2, absolute type grid sensor unit contains first increment type grid sensor group and second increment type grid sensor group, and wherein every group increment type grid sensor's component structure all is unanimous with increment type grid sensor, all along measuring axis synchronous motion, all has the characteristic of data uniqueness in the single pitch to the pitch of two sets of increment type grid sensor is close, and the difference of the pitch number that two sets of increment type grid sensor passed through is less than or equal to 1 in absolute type grid sensor's effective measuring range. The system has the advantages of low cost, no measurement speed limit, strong anti-interference capability, no loss of power failure data, low power consumption, wide application range and easy batch production.
Description
Technical Field
The utility model relates to a displacement measurement technique specifically is an absolute type capacitive grating sensor measurement system.
Background
The conventional sensors commonly used in displacement measurement include various types such as gratings, magnetic gratings, ball grids, photoelectric encoders, capacitors and the like, wherein the capacitive grating displacement sensor is widely applied to the fields of linear and angular displacement measurement due to the characteristics of simple structure, small volume, micro power consumption, low cost and the like. The sensor is an incremental capacitive grating sensor which adopts eight modulation pulse driving signal excitation sources, a clustered distribution structure and a phase discrimination type. Although incremental capacitive-gate sensors have been widely used for over 30 years, the following problems have been present:
1. speed limitation: because the sensor needs to accumulate displacement data continuously, but is limited by power consumption, and the frequency of the sensor cannot be too high, the measuring response speed of the sensor has a limit value, and the measuring speed of the sensor is 3m/s @300KHz at present;
2. weak anti-interference capability and easy error: because displacement data are obtained by continuously accumulating the sensors, once calculation is wrong or interference exists, data confusion is caused, and measurement errors occur;
3. the application field is narrow: the sensor needs to work continuously, the accumulated power consumption is large, power failure data are lost, and the sensor cannot be applied to certain monitoring fields.
Based on these disadvantages, incremental capacitive sensors are gradually eliminated, and a small number of products using absolute capacitive sensor technology are sporadically produced in the market.
The absolute type capacitive grating displacement sensor is originated by the Japan Sanfeng company, the technical implementation method of the absolute type capacitive grating displacement sensor is disclosed in patent documents with application numbers of CN89106051.0, US5053715, CN92101246.2 and CN93117701.4 respectively, then Guilin Guangdong is improved on the basis of the patent documents, an absolute type capacitive grating displacement sensor scheme with independent intellectual property rights is provided, the technical implementation method of the Guilin Guangdong is disclosed in Chinese patent document with application number of CN201010254159.8, the methods are basically the same, not only the phase differences generated after the relative motion of a plurality of groups of channels are detected, the phase differences are compared, the absolute displacement data are obtained through complex calculation, the channels in the methods are composed of bars with different periods of thickness, middle thickness and thin thickness and different figures, and according to the technical implementation principle and the structural characteristics of the methods, the accuracy requirements of the sensor on the matching errors of bar lines, mechanical components and assembly and the like are very high, the sensor in the methods and technologies is composed of three groups of signals to form different channels, grid bar patterns are too complex, the resolution cannot be improved in a pitch reduction mode like an incremental capacitive grating sensor, and therefore the absolute type capacitive grating displacement sensor is rarely used in products such as dial gauges.
The method is basically the same, and a group of rough sensors working at a single-pitch state are added on the basis of the original sensor to serve as the pitch number positioning of the subdivided sensor by utilizing the characteristic of data uniqueness of the incremental capacitive grating sensor in the single pitch, and then the data of the subdivided sensor is combined to obtain absolute displacement data. The absolute type capacitive sensor implemented in this way suffers from the following problems:
1. the rough-dividing sensor can only work in one pitch, so that a clustering structure of a conventional incremental grating sensor is not available, an average effect is avoided, the error of the rough-dividing sensor is very large, the pitch of the subdivided sensor cannot be very small for eliminating the influence of the error on the positioning of the pitch number of the subdivided sensor, and the resolution of the sensor cannot be very high finally;
2. the rough-dividing sensor can only work in one pitch, so the measuring range of the sensor is limited, and the sensor can not be popularized and applied to a large-measuring-range digital display indicating meter and a digital display caliper.
SUMMERY OF THE UTILITY MODEL
The utility model aims at the not enough of prior art, and provide an absolute type capacitive grating sensor measurement system. The system has the advantages of low cost, no measurement speed limit, strong anti-interference capability, no loss of power failure data, low power consumption, wide application range and easy batch production.
Realize the utility model discloses the technical scheme of purpose is:
the absolute type capacitive grating sensor measuring system comprises a measuring signal processing unit, an absolute type capacitive grating sensor unit and a data processing unit, wherein the absolute type capacitive grating sensor unit and the data processing unit are connected with the measuring signal processing unit, the measuring signal processing unit is provided with a first capacitive grating IC1 and a second capacitive grating IC2 which are connected in parallel and can be selected, the absolute type capacitive grating sensor unit comprises a first incremental type capacitive grating sensor group and a second incremental type capacitive grating sensor group, the composition structure of each incremental type capacitive grating sensor group is consistent with that of the incremental type capacitive grating sensors, the incremental type capacitive grating sensors synchronously move along a measuring axis, the single pitch has the characteristic of data uniqueness, the pitches of the two incremental sensors are close to each other, the difference of the number of the pitches of the two incremental sensors in the effective range of the absolute type capacitive grating sensor is less than or equal to 1, and the data processing unit is provided with a microprocessor MCU and a time-sharing switching gating circuit connected with the microprocessor MCU, The key and display unit, the microprocessor MCU control time-sharing switch gate circuit, and read the data in the single pitch of two groups of sensors, then compare the data difference of two groups of sensors, calculate the same pitch number that two groups of sensors pass through, and combine the data in the single pitch of one group of sensors, obtain the absolute displacement data finally.
The first capacitive gate IC1 and the second capacitive gate IC2 are both incremental capacitive gate dedicated ICs, for example, SN6602, in which an oscillation circuit, a frequency division circuit, a data processing circuit, a phase discrimination and calculation circuit, a demodulation and amplification circuit, and an 8-way driving circuit are disposed, and the data processing circuit transmits displacement data to the microprocessor MCU through a data line.
The absolute type capacitive grating sensor unit is composed of two groups of incremental linear displacement capacitive grating sensors when used for absolute linear displacement measurement, and is composed of two groups of incremental circular capacitive grating sensors when used for absolute angular displacement measurement.
The first structure of the absolute type capacitive gate sensor unit is as follows: the first incremental capacitive gate sensor group and the second incremental capacitive gate sensor group are two groups of sensors which are mutually independent, and the two groups of sensors are arranged on a measuring axis in a parallel or serial mode.
The second structure of the absolute type capacitive gate sensor unit is as follows: the first incremental capacitive grating sensor group and the second incremental capacitive grating sensor group are combined into a group of absolute capacitive grating sensors, electrodes of the two groups of incremental capacitive grating sensors are arranged in the absolute capacitive grating sensors in parallel in a reflection type two-piece structure or a transmission type three-piece structure according to the arrangement method of the original incremental capacitive grating sensors, a measurement signal processing unit selects a capacitive grating special IC, a microprocessor MCU controls a time-sharing switch gating circuit, 8 paths of driving signals of the capacitive grating special IC are sent to emitting electrodes of the two groups of sensors in a time-sharing mode, or output signals of the two groups of sensors are sent to the capacitive grating special IC in a time-sharing mode for processing.
In the technical scheme, the mathematical model is defined as follows: setting the pitch of an incremental capacitive grating sensor as P, according to the principle of the incremental capacitive grating sensor, outputting data of the sensor as NT + a, wherein N is the number of pitches through which the sensor passes, T is pitch output data, the resolution of the sensor is P/T, a is data in a single pitch, the value of a is between 0 and (T-1), according to the characteristic of uniqueness of the data in the single pitch of the incremental capacitive grating sensor, the data a and the positions of the sensor in the single pitch have one-to-one correspondence, and setting the value of a shift amount in the sensor as W, setting W as NP + aP/T (1), and in the incremental sensor, continuously accumulating the data processing part to obtain the number of pitches N; in an absolute sensor, the absolute sensor attribute determines that the pitch number N, which is obtained by calculating the data difference a between two sets of sensors, cannot be obtained by a continuous accumulation method, and the specific method is as follows:
two groups of incremental sensors G1、G2Combined (two sets of sensors have the same T value) and synchronously moved along the measuring axis, and P is set2>P1Then G is1Data a of1Ahead of a2As can be seen from equation (1), when W ═ P2When a is1＝(P2-P1)T/P1(ii) a When W is 2P2When a is1＝2(P2-P1)T/P1By analogy, when W is NP2And N is equal to N1＝N2，G1Advance G2Less than one pitch, then a1＝N(P2-P1)T/P1At this time a2All are 0, the data difference a ═ a1-a2＝a1From this, it is possible to obtain: A/N ═ P2-P1)T/P1(2) A/N is the data difference increase rate, and formula (2) is that2Special displacement point NP at 02Deducing, verifying by combining specific data, and setting two groups of incremental sensor parameters, wherein the pitches are P respectively15.12mm and P2When the output data T of one pitch is 512 at 5.24mm, the value of the output data is between 0 and 511, and the data a of two groups of incremental capacitive grating sensors at each point is shown in table 1 according to the formula (1):
TABLE 1
When a is1>a2When N is present1＝N2(ii) a When a is1<a2When N is present1-1＝N2Not only G1Advance G2Entering the next pitch, making the pitch equal to N2When calculating the data difference A, the data a1Shall be a1+512, as can be seen from table 1, the two sets of data differences a are linearly varying and the rate of increase of the values is about 12 per pitch; substituting the two groups of sensor parameters into the formula (2), wherein the data difference increase rate A/N is 12 after counting, and the values of the two are equal, so that when the difference between the number of pitches passed by the two groups of sensors is less than or equal to 1, the pitch number N can be obtained by comparing and calculating the data difference of the two groups of sensors.
As the displacement W increases, the data difference A also increases and gradually approaches the maximum value 511 of the data difference A, and when the value increases again from 0, as indicated by the data "225.0" in Table 1, the sensor G is activated1Has advanced G2One pitch, which results in the inconsistency of the two sensor pitches, exceeds the effective range of the absolute type capacitive grating sensor, and the pitch can not be calculated by using the formula (2) singly, but it can be seen that the subsequent section from the moment follows the same rule, and only the initial state is changed, as long as the initial state is changedThe zone recording device is added for distinguishing, the zone recording device is regarded as a superposition of a plurality of absolute sensors, the pitch number in any measuring range can be calculated, and the measuring range of the sensor is expanded infinitely. As can be seen from equation (2), when the data difference a is again reduced to 0, the pitch number N is equal to P1/(P2-P1) (i.e., T/(A/N)), where the displacement value W is NP2＝P1P2/(P2-P1) When the effective range L of the absolute type capacitive sensor is set, L is equal to P1P2/(P2-P1) (3)。
The essential condition in the technical scheme is that the pitches of two groups of incremental capacitive grating sensors forming the absolute capacitive grating sensor unit are close, and the difference of the number of the pitches passed by the two groups of incremental capacitive grating sensors in the effective measuring range of the absolute capacitive grating sensor is less than or equal to 1.
In the technical scheme, the calculation processing process of the microprocessor MCU comprises the following steps: the CPU calculates the data difference increase rate A/N according to the pitch isoparametric of two groups of incremental capacitive grating sensors through a formula (2) and stores the data difference in the RAM, the CPU subtracts two groups of read data a to obtain a data difference A, if A <0, the data difference is corrected to be A + T, then the data difference is divided by the A/N to obtain a pitch number N, finally the pitch number N is substituted into the formula (1), the absolute displacement data of the point is obtained through calculation, and then the related data are calculated according to the product requirements and displayed through the LCD.
The technical scheme has the advantages that:
1. absolute displacement data can be obtained only by using displacement data of two groups of incremental capacitive grating sensors in a single pitch through simple calculation, and according to the characteristic of uniqueness of the data of the sensors in the single pitch, the data read at any time is only data related to the positions of the sensors, so that the problems of measurement speed limitation, weak anti-interference capability, power failure data loss and the like of the traditional capacitive grating sensors in the prior art are solved;
2. two groups of incremental capacitive grating sensors are adopted, the sensor structure which is the same as that of the prior art is used, and the existing mature technology can be used for measuring circuits and processing technologies, so that the limit of the prior art on too high requirements on grating lines, mechanical components and assembly precision is avoided, and the large-batch production is easy;
3. inheriting and developing the characteristic that the incremental capacitive grating sensor is easy to achieve high precision and high resolution, and is easy to apply to products such as a dial indicator and a ten-thousandth indicator;
4. time-sharing control is adopted, so that the circuit can work intermittently, and the power consumption can be effectively reduced;
5. the sensor has more flexibility by adopting a microprocessor control circuit and processing data, and can be applied to various measuring tool products by only carrying out simple program processing according to the requirement.
The system has the advantages of low cost, no measurement speed limit, strong anti-interference capability, no loss of power failure data, low power consumption, wide application range and easy batch production.
Drawings
FIG. 1 is a schematic block diagram of an embodiment;
FIG. 2 is a schematic block diagram of a first specific application circuit of FIG. 1;
FIG. 3 is a schematic block diagram of a second specific application circuit of FIG. 1;
FIG. 4 is a schematic diagram of a first reflective two-piece absolute linear displacement capacitive sensor in an embodiment;
FIG. 5 is a schematic diagram of a first reflective two-piece absolute type circular capacitive grating sensor in an embodiment;
FIG. 6 is a diagram of a second exemplary embodiment of a two-piece reflective absolute linear displacement capacitive sensor;
FIG. 7 is a diagram showing a second reflective two-piece absolute type circular capacitive grating sensor according to an embodiment;
FIG. 8 is a schematic diagram of an exemplary embodiment of a three-piece absolute linear displacement capacitive sensor;
FIG. 9 is a schematic diagram of an exemplary embodiment of a transmissive three-piece absolute type circular capacitive grating sensor;
FIG. 10 is a schematic diagram illustrating the displacement of an incremental capacitive sensor according to an embodiment;
FIG. 11 is a schematic diagram of the displacement of an absolute capacitive sensor in an embodiment.
In the figure, 1-1, a first fixed grid plate, 2-1, a first movable grid plate, 11-1, a first receiving electrode, 12-1, a first emitter, 13-1, a first reflector, 21-1, a second receiver, 22-1, a second emitter, 23-1, a second reflector, 01-1, a first shield, 02-1, a second shield 1-2, a second fixed grid plate, 2-2, a second movable grid plate, 11-2, a third receiver, 12-2, a third emitter, 13-2, a third reflector, 21-2, a fourth receiver, 22-2, a fourth emitter, 23-2, a fourth reflector, 01-2, a third shield, 02-2, a fourth shield 1-3, a third fixed grid plate, 2-3, a third movable grid plate, 31-3, a fifth receiver, 12-3, a fifth emitter, 33-3, a fifth reflector, 22-3, a sixth emitter, 01-3, a fifth shield, 02-3, a sixth shield, 1-4, a fourth fixed grid, 2-4, a fourth movable grid, 31-4, a sixth receiver, 12-4, a seventh emitter, 33-4, a sixth reflector, 22-4, an eighth emitter, 01-4, a seventh shield, 02-4, an eighth emitter, 3-5, a first emitter, 4-5, a first shielding spacer, 5-5, a first receiver, 11-5, a seventh receiver, 12-5, a ninth emitter, 14-5, a first transmission window, 21-5, an eighth receiver, 22-5, a tenth emitter, 24-5 of a second group of transmission windows, 02-5 of a ninth shield, 01-5 of a tenth shield, 03-5 of an eleventh shield, 3-6 of a second emission plate, 4-6 of a second shield partition, 5-6 of a second receiving plate, 11-6 of a ninth receiver, 12-6 of an eleventh emitter, 14-6 of a third group of transmission windows, 21-6 of a tenth receiver, 22-6 of a twelfth emitter, 24-6 of a fourth group of transmission windows, 02-6 of a twelfth shield, 01-6 of a thirteenth shield, and 03-6 of a fourteenth shield.
Detailed Description
The contents of the present invention will be further described with reference to the accompanying drawings and examples, but the present invention is not limited thereto.
Example (b):
referring to fig. 1, an absolute type capacitive grating sensor measuring system includes a measuring signal processing unit, an absolute type capacitive grating sensor unit connected with the measuring signal processing unit, and a data processing unit, wherein the measuring signal processing unit is provided with a first capacitive grating IC1 and a second capacitive grating IC2 which are connected in parallel and selectable, the absolute type capacitive grating sensor unit includes a first incremental type capacitive grating sensor group and a second incremental type capacitive grating sensor group, the incremental type capacitive grating sensors in each group have the same composition structure as the incremental type capacitive grating sensors and synchronously move along a measuring axis, the incremental type capacitive grating sensors in each group have the characteristic of data uniqueness within a single pitch, the pitches of the two groups of incremental sensors are close to each other, the difference of the number of pitches passed by the two groups of incremental sensors within the effective range of the absolute type capacitive grating sensor is less than or equal to 1, and the data processing unit is provided with a microprocessor MCU and a time-sharing switch gating circuit connected with the microprocessor MCU, The key and display unit, the microprocessor MCU control time-sharing switch gate circuit, and read the data in the single pitch of two groups of sensors, then compare the data difference of two groups of sensors, calculate the same pitch number that two groups of sensors pass through, and combine the data in the single pitch of one group of sensors, obtain the absolute displacement data finally.
In this example, the first capacitive gate IC1 and the second capacitive gate IC2 are both SN6602, an oscillation circuit, a frequency division circuit, a data processing circuit, a phase discrimination and calculation circuit, a demodulation and amplification circuit, and an 8-way driving circuit are arranged in the SN6602, and the data processing circuit transmits displacement data to the microprocessor MCU through a data line.
In this example, the absolute type capacitive grating sensor unit is composed of two incremental linear displacement capacitive grating sensors when the absolute type capacitive grating sensor unit is used for absolute linear displacement measurement, and is composed of two incremental circular capacitive grating sensors when the absolute type capacitive grating sensor unit is used for absolute angular displacement measurement.
The conventional structure of an absolute type capacitive sensor unit is: the first incremental capacitive gate sensor group and the second incremental capacitive gate sensor group are two groups of sensors which are mutually independent, and the two groups of sensors are arranged on a measuring axis in a parallel or serial mode.
The absolute type capacitive grating sensor unit in the embodiment has a structure that a first incremental type capacitive grating sensor group and a second incremental type capacitive grating sensor group are combined into a group of absolute type capacitive grating sensors, and electrodes of the two groups of incremental type capacitive grating sensors are arranged in the absolute type capacitive grating sensors in parallel in a reflection type two-piece structure or a transmission type three-piece structure according to the arrangement method of the original incremental type capacitive grating sensors.
In this example, the measurement signal processing unit is composed of a capacitive gate IC, and the microprocessor MCU controls the time-sharing switch gating circuit, so that the function of processing the measurement signals of two incremental capacitive gate sensors by using one capacitive gate IC can be realized, thereby avoiding mutual interference between signals caused by using two capacitive gate ICs, and reducing the cost.
As shown in FIG. 4, the first absolute type linear displacement capacitive sensor is an absolute type linear displacement capacitive sensor with a reflective two-piece structure, which comprises a first fixed grid plate 1-1 and a first movable grid plate 2-1, wherein a first receiving electrode 11-1, a first emitting electrode 12-1, a second emitting electrode 22-1 and a second receiving electrode 21-1 are sequentially arranged on the first fixed grid plate 1-1 perpendicular to a measuring axis, a first shielding electrode 01-1 for shielding at intervals is arranged between the electrodes, the first emitting electrode 12-1 and the second emitting electrode 22-1 are respectively electrode grids with two rows of close pitches and uniformly distributed along the measuring axis, a first reflecting electrode 13-1 and a second reflecting electrode 23-1 are correspondingly arranged at the projection positions of the receiving electrode and the emitting electrode on the first movable grid plate 2-1 on the first fixed grid plate 1-1, a second shielding electrode 02-1 which plays a role of shielding at intervals is arranged between the first reflecting electrode 13-1 and the second reflecting electrode 23-1, wherein the first receiving electrode 11-1, the first emitting electrode 12-1 and the first reflecting electrode 13-1 form a first incremental capacitive grating sensor group; the second receiving electrode 21-1, the second emitting electrode 22-1 and the second reflecting electrode 23-1 form a second incremental capacitive grating sensor group, as shown in fig. 2, the first emitting electrode 12-1 and the second emitting electrode 22-1 are connected in parallel to 8 driving circuits in a capacitive grating IC, eight modulation pulse driving signals are subjected to twice capacitive coupling of the first reflecting electrode 13-1 and the second reflecting electrode 23-1, phase modulation signals containing position information along with axial movement of the movable grating plate 2-1 are coupled to the first receiving electrode 11-1 and the second receiving electrode 21-1, are electrically connected to two input ends of a gating circuit, and are finally transmitted to the capacitive grating IC for signal processing in a time-sharing manner through the gating circuit controlled by the microprocessor MCU.
The electrode patterns of the first absolute type linear displacement capacitive sensor are expanded along the circumference by taking a rotating shaft as the center of a circle, the pitch of each electrode is calculated according to the angle of the center of the concentric circle of the arc pair, and the reflective two-piece absolute type circular capacitive sensor structure is formed, the reflective two-piece absolute type circular capacitive sensor is applied to angular displacement measurement, as shown in figure 5, the reflective two-piece absolute type circular capacitive sensor structure comprises a second fixed grid plate 1-2 and a second movable grid plate 2-2, wherein the second fixed grid plate 1-2 is sequentially provided with a fourth receiving electrode 21-2, a fourth emitting electrode 22-2, a third emitting electrode 12-2, a third receiving electrode 11-2 and a third shielding electrode 01-2 among electrodes from the center of a circle to the outside, the second movable grid plate 2-2 is sequentially provided with a fourth reflecting electrode 23-2, a third reflecting electrode 13-2 and a fourth shielding electrode 02-2 among the electrodes from the center of a circle to the outside, the third receiving electrode 11-2, the third emitting electrode 12-2 and the third reflecting electrode 13-2 form a first incremental capacitive grating sensor group; the fourth receiving electrode 21-2, the fourth emitting electrode 22-2 and the fourth reflecting electrode 23-2 form a second incremental capacitive-gate sensor group.
As shown in FIG. 6, the absolute type linear displacement capacitive grating sensor with the second reflective two-plate structure comprises a third fixed grating plate 1-3 and a third movable grating plate 2-3, wherein a fifth emitter 12-3, a fifth receiver 31-3, a sixth emitter 22-3 and a fifth shielding 01-3 between each electrode are sequentially arranged on the third fixed grating plate 1-3 perpendicular to a measuring axis, the fifth emitter 12-3 and the sixth emitter 22-3 are respectively two rows of electrode gratings with close pitches and are uniformly distributed along the measuring axis, a fifth reflector 33-3 and a sixth shielding 02-3 are correspondingly arranged at the projection positions of each electrode on the third fixed grating plate 1-3 on the third movable grating plate 2-3, the fifth receiving electrode 31-3, the fifth emitting electrode 12-3 and the fifth reflecting electrode 33-3 form a first incremental capacitive gate sensor group; the fifth receiving electrode 31-3, the sixth emitting electrode 22-3 and the fifth reflecting electrode 33-3 form a second incremental capacitive gate sensor group. Because the measurement signal comes from the same capacitive grating IC, there is no electrical interference between the two sets of sensors, the receiver and the reflector are both combined into one, and when the area of the sensor is the same, the area of each electrode in fig. 6 is enlarged compared with that in fig. 4, and the intensity of the measurement signal is increased, as shown in fig. 3, the microprocessor MCU controls the 8 paths of time-sharing gating circuit to transmit the eight paths of modulated pulse driving signals of the capacitive grating IC to the fifth emitter 12-3 or the sixth emitter 22-3 in a time-sharing manner, and along with the axial movement of the third movable grating 2-3, the phase modulation signal containing the position information is capacitively coupled to the fifth receiver 03-3 twice through the fifth reflector 04-3, and finally transmitted to the capacitive grating IC for signal processing.
The electrode pattern of the second absolute type linear displacement capacitive sensor is expanded along the circumference by taking the rotating shaft as the center of a circle, the pitch of each electrode is calculated according to the central angle of the concentric circle of the arc pair, and the structure of the reflective two-piece absolute type circular capacitive sensor is formed, as shown in fig. 7, the structure comprises a fourth fixed grid plate 1-4 and a fourth movable grid plate 2-4, wherein an eighth emitter 22-4, a sixth receiver 31-4, a seventh emitter 12-4 and a seventh shield 01-4 between each electrode are sequentially arranged on the fourth fixed grid plate 1-4 from the center of a circle to the outside, a sixth reflector 33-4 and an eighth shield 02-4 are correspondingly arranged on the projection position of each electrode on the fourth fixed grid plate 1-4 on the fourth movable grid plate 2-4, and a sixth receiver 31-3, a seventh emitter 12-3 are correspondingly arranged on the projection position of each electrode on the fourth movable grid plate 2-4, The sixth reflector 33-3 forms a first incremental capacitive gate sensor group; the sixth receiving electrode 31-3, the eighth emitting electrode 22-3 and the sixth reflecting electrode 33-3 form a second incremental capacitive gate sensor group.
As shown in FIG. 8, the transmission type three-piece absolute type linear displacement capacitive grating sensor is composed of a first emitting plate 3-5, a first shielding partition plate 4-5 and a first receiving plate 5-5, wherein the grating surfaces of the first emitting plate 3-5 and the first receiving plate 5-5 are oppositely and fixedly arranged at intervals, the first shielding partition plate 4-5 moves along the measuring axial direction between the first emitting plate 3-5 and the first receiving plate 5-5 at intervals, two rows of grating electrodes, namely, a ninth emitting electrode 12-5 and a tenth emitting electrode 22-5 which have close pitches and are uniformly distributed along the measuring axis are arranged on the first emitting plate 3-5 and are perpendicular to the measuring axis, a ninth shielding electrode 02-5 is arranged between the first emitting plate and the tenth emitting electrode, a seventh receiving electrode 11-5 and an eighth receiving electrode 21-5 are arranged on the first receiving plate 5-5 at the projection positions corresponding to the ninth emitting electrode 12-5 and the tenth emitting electrode 22-5, a tenth shielding electrode 01-5 is arranged between the first shielding electrode and the second shielding electrode for shielding at intervals, a first group of transmission windows 14-5 and a second group of transmission windows 24-5 corresponding to a ninth emitting electrode 12-5 and a tenth emitting electrode 22-5 are arranged on the first shielding clapboard 4-5, an eleventh shielding electrode 03-5 is arranged between the first shielding electrode and the second shielding electrode and is connected with the ground wire, and the ninth emitting electrode 12-5, the first group of transmission windows 14-5 and a seventh receiving electrode 11-5 form a first incremental capacitive grating sensor group; the tenth emitter 22-5, the second set of transmission windows 24-5 and the eighth receiver 21-5 form a second incremental capacitive-gate sensor set. As shown in FIG. 2, the ninth emitter 12-5 and the tenth emitter 22-5 are connected in parallel to the 8-way driving circuit in the capacitive gate IC, the eight-way modulated pulse driving signal can be coupled to the seventh receiver 11-5 and the eighth receiver 21-5 only through the first set of transmission windows 14-5 and the second set of transmission windows 24-5, the phase modulation signal containing the position information along with the axial movement of the shielding partition 4-5 is coupled to the seventh receiver 11-5 and the eighth receiver 21-5, and is electrically connected to two input ends of the gating circuit, and finally the gating circuit is controlled by the microprocessor MCU to be time-shared and sent to the capacitive gate IC for signal processing.
The electrode pattern of the transmission type three-piece absolute type linear displacement capacitive grating sensor is expanded along the circumference by taking a rotating shaft as the center of a circle, the pitch of each electrode is calculated according to the central angle of a concentric circle which is opposite to the arc of the electrode, so that the transmission type three-piece absolute type circular grating sensor structure is formed, the transmission type three-piece absolute type circular grating sensor is applied to angular displacement measurement, as shown in figure 9, and comprises a second emission plate 3-6, a second shielding partition plate 4-6 and a second receiving plate 5-6, wherein the second emission plate 3-6 is sequentially provided with a twelfth emission electrode 22-6, an eleventh emission electrode 12-6 and a twelfth shielding electrode 02-6 between the electrodes from the center of a circle to the outside, the second shielding partition plate 4-6 is sequentially provided with a fourth group of transmission windows 24-6, a third group of transmission windows 14-6 and a fourteenth shielding electrode 03-6 from the center of a circle to the outside, the second receiving plate 5-6 is provided with a tenth receiving electrode 21-6, a ninth receiving electrode 11-6, a thirteenth shielding electrode 01-6 between the electrodes, an eleventh emitting electrode 12-6, a third group of transmission windows 14-6 and a ninth receiving electrode 11-6 in sequence from the circle center to the outside to form a first incremental capacitive grating sensor group; and the twelfth emitter 22-6, the fourth group of transmission windows 24-6 and the tenth receiver 21-6 form a second incremental capacitive-gate sensor group.
In this example, the mathematical model is defined as: setting the pitch of an incremental capacitive grating sensor as P, according to the principle of the incremental capacitive grating sensor, the sensor output data as NT + a, wherein N is the number of pitches through which the sensor passes, T is pitch output data, the resolution of the sensor is P/T, a is data in a single pitch, the value of a is between 0 and (T-1), according to the characteristic of uniqueness of the data in the single pitch of the incremental capacitive grating sensor, the data a and the positions of the sensor in the single pitch have a one-to-one correspondence relationship, as shown in FIG. 10, if the value of the shift amount in the sensor is W, W is NP + aP/T (1), and in the incremental sensor, the data processing part is required to be continuously accumulated to obtain the number of pitches N; in an absolute sensor, the absolute sensor attribute determines that the pitch number N cannot be obtained by a continuous accumulation method, and in this example, the pitch number N is obtained by calculating the data difference a between two sets of sensors, and the specific method is as follows:
two groups of incremental sensors G1、G2Combined (two sets of sensors having the same value of T) and moved synchronously along the measuring axis, as shown in FIG. 11, let P2>P1，G1Data ahead of G2As can be seen from equation (1), when W ═ P2When a is1＝(P2-P1)T/P1(ii) a When W is 2P2When a is1＝2(P2-P1)T/P1By analogy, when W is NP2And N is equal to N1＝N2，G1Advance G2Less than one pitch, then a1＝N(P2-P1)T/P1At this time a2Data difference A ═ a ═ 01-a2＝a1From this, it is possible to obtain: A/N ═ P2-P1)T/P1(2) A/N is the data difference increase rate, and formula (2) is that2Special displacement point NP at 02Deducing, verifying by combining specific data, and setting two groups of incremental sensor parameters, wherein the pitches are P respectively15.12mm and P2When the output data T of one pitch is 512 at 5.24mm, the value of the output data is between 0 and 511, and the data a of two groups of incremental capacitive grating sensors at each point is shown in table 1 according to the formula (1):
TABLE 1
When a is1>a2When N is present1＝N2(ii) a When a is1<a2When N is present1-1＝N2Not only G1Advance G2Entering the next pitch, making the pitch equal to N2Then when calculating the data difference A, the data should be a1+512, as can be seen from table 1, the two sets of data differences a are linearly varying and the rate of increase of the values is about 12 per pitch; substituting the two groups of sensor parameters into the formula (2), wherein the data difference increase rate A/N is 12 after counting, and the values of the two are equal, so that when the difference between the number of pitches passed by the two groups of sensors is less than or equal to 1, the pitch number N can be obtained by comparing and calculating the data difference of the two groups of sensors.
As shown in fig. 11, when W ═ N +1) P2When (N +1) P2>(N+2)P1Sensor G1Has advanced G2One pitch, combined with the data in Table 1, increases as the amount of displacement W increases, and the difference A gradually approaches the maximum value 511 of the difference A, when the value increases again from 0, as indicated by the data "225.0" in Table 1, at which time the sensor G is activated1Has advanced G2One pitch leads to the inconsistency of the two groups of sensor pitches, and at this time, the effective range of the absolute type capacitive grating sensor is exceeded, the pitch number cannot be calculated by using the formula (2) singly, but it can be seen that from this point, the subsequent section follows the same rule, only the initial state is changed, and as long as the section recording device is added for distinguishing, and the section recording device is regarded as the superposition of a plurality of absolute type sensors, the pitch number in any range can be calculated, so that the range of the sensor is expanded infinitely. As can be seen from equation (2), when the data difference a is again reduced to 0, the pitch number N is equal to P1/(P2-P1) (i.e., T/(A/N)), where the displacement value W is NP2＝P1P2/(P2-P1) When the effective range L of the absolute type capacitive sensor is set, L is equal to P1P2/(P2-P1)(3)。
In this example, the pitches of the two incremental capacitive grating sensors forming the absolute capacitive grating sensor unit are close, and the difference between the number of the pitches passed by the two incremental capacitive grating sensors in the effective range of the absolute capacitive grating sensor is less than or equal to 1, and the effective range L is calculated according to the formula (3).
In this example, the calculation processing procedure of the microprocessor MCU: the CPU calculates the data difference increase rate A/N according to the pitch isoparametric of two groups of incremental capacitive grating sensors through a formula (2) and stores the data difference in the RAM, the CPU subtracts two groups of read data a to obtain a data difference A, if A <0, the data difference is corrected to be A + T, then the data difference is divided by the A/N to obtain a pitch number N, finally the pitch number N is substituted into the formula (1), the absolute displacement data of the point is obtained through calculation, and then the related data are calculated according to the product requirements and displayed through the LCD. Because the sensor has a certain degree of data error, one decimal is reserved firstly when the pitch number N is calculated, and then the accurate pitch number N is corrected by combining the data of the sensor, for example, when the decimal of N is more than 0.9, if the data of the sensor is less than 0.1T, the pitch number is corrected to be N +1 firstly, and then the shift data W is calculated; when the decimal of N is less than 0.1, if the data of the sensor is more than 0.9T, the pitch number is corrected into N-1, and then the displacement data W is calculated, the method is applied to high-precision products with small measuring range and needing precision calibration, such as a dial indicator, a ten-thousandth meter and the like, the data difference A of each point and the corresponding pitch number N are also stored in a ROM when the precision of each point is calibrated, after the data difference A is calculated by a CPU, the pitch number N is compared through a table look-up program, so that the redundant calculation and correction processes of the pitch number can be omitted, the accurate displacement data can be quickly calculated, and the effects of reducing power consumption and improving the precision of the products are achieved.
Claims (5)
1. The absolute type capacitive grating sensor measuring system is characterized by comprising a measuring signal processing unit, an absolute type capacitive grating sensor unit and a data processing unit, wherein the absolute type capacitive grating sensor unit and the data processing unit are connected with the measuring signal processing unit, the measuring signal processing unit is provided with a first capacitive grating IC1 and a second capacitive grating IC2 which are connected in parallel and can be selected, the absolute type capacitive grating sensor unit comprises a first incremental type capacitive grating sensor group and a second incremental type capacitive grating sensor group, the composition structure of each incremental type capacitive grating sensor group is consistent with that of the incremental type capacitive grating sensors, the incremental type capacitive grating sensors all synchronously move along a measuring axis, the absolute type capacitive grating sensor group has the characteristic of data uniqueness in a single pitch, the pitches of the two incremental type capacitive grating sensors are close to each other, and the difference of the number of the pitches of the two incremental type capacitive grating sensors passing through in the effective range of the absolute type capacitive grating sensor is not more than 1.
2. The absolute capacitive-gate sensor measurement system according to claim 1, wherein the first capacitive-gate IC1 and the second capacitive-gate IC2 are both capacitive-gate dedicated ICs.
3. The absolute type capacitive grating sensor measuring system according to claim 1, wherein the absolute type capacitive grating sensor unit consists of two sets of incremental linear displacement capacitive grating sensors when used for absolute linear displacement measurement, and consists of two sets of incremental circular capacitive grating sensors when used for absolute angular displacement measurement.
4. The absolute capacitive-gate sensor measuring system according to claim 1, wherein the first incremental capacitive-gate sensor group and the second incremental capacitive-gate sensor group are two independent groups of sensors, and the two groups of sensors are arranged on the measuring axis in a parallel or serial manner.
5. The absolute capacitive grating sensor measuring system according to claim 1, wherein the first incremental capacitive grating sensor group and the second incremental capacitive grating sensor group are combined into one absolute capacitive grating sensor group, and electrodes of the two incremental capacitive grating sensors are arranged in the absolute capacitive grating sensor in a reflective two-piece structure or a transmissive three-piece structure in parallel according to an arrangement method of the original incremental capacitive grating sensors.
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