WO2011018497A1 - A device and method for capacitive linear displacement measurement - Google Patents
A device and method for capacitive linear displacement measurement Download PDFInfo
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- WO2011018497A1 WO2011018497A1 PCT/EP2010/061749 EP2010061749W WO2011018497A1 WO 2011018497 A1 WO2011018497 A1 WO 2011018497A1 EP 2010061749 W EP2010061749 W EP 2010061749W WO 2011018497 A1 WO2011018497 A1 WO 2011018497A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
- G01D5/244—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
- G01D5/249—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains using pulse code
- G01D5/2497—Absolute encoders
Abstract
The present invention provides a device and process for capacitive linear displacement measurement, wherein the strip electrodes are arranged on the base in a line equidistantly, and every N continuous strip electrodes compose a spatial period, and a first group of signal lines is composed by N signal lines, wherein N is an integer greater than or equal to 2; in the absolute displacement measurement mode, the N signal lines in said first group of signal lines take turns in being loaded with excitation signals in one signal generation period; the connection between each strip electrode and the first group of signal lines causes all the excitation signal combinations detected at all displacement positions by the reading unit in the absolute displacement measurement mode to be different from one another; the reading unit moves along the strip electrodes, outputting the signal combinations detected at the strip electrodes which it covers, and providing the absolute displacement value corresponding to the signal combination to the displacement determining unit. The present invention enables simpler absolute displacement measurement at a low cost and delivers strong resistance to interference.
Description
Description
A device and method for capacitive linear displacement measurement
Technical Field
The present invention relates to displacement measurement technology, and more particularly to a device and method for capactive linear displacement measurement.
Background Technology
The existing methods for capacitive linear displacement measurement can be mainly divided into incremental displacement measurement and absolute displacement measurement. Thanks to its low cost, simple process and high measurement accuracy, incremental displacement measurement has been used very widely; however, incremental displacement measurement can only obtain the relative displacement, and when there is a need to obtain the absolute displacement, we need to obtain the absolute reference point at powering up, and the process of obtaining the absolute reference point often requires moving the reading unit so it passes through the location of the reference point and records the information of the location. Such a process is time-consuming, and in some cases, it is not permitted to move the reading unit. The absolute displacement measurement can be made to obtain the absolute displacement value directly without obtaining the reference point, but the technique is complicated with low measurement accuracy.
Firstly, the principles of incremental displacement measurement and absolute displacement measurement are briefly described. The displacement measurement devices of both modes include a displacement scale unit and a reading unit.
The displacement scale unit in the incremental displacement measurement contains strip electrodes that are arranged uniformly and have the same shape, size and the same electrical
conductivity, that is, they must be identical. The width and gap of the strip electrodes are the same in order to mark the scale of the displacement. A spatial period is set by a fixed number N, and every continuous N strip electrodes are set as a spatial period, and each strip electrode is loaded with signals of a fixed phase difference within the spatial period. The reading unit and the strip electrodes it covers will form capacitance which can sense the signals loaded to the strip electrodes; the displacement of the reading unit in relation to the reference point will modulate the signals of the strip electrodes covered by the reading unit, thus causing the changes in the phase of the sensed signals. By using the corresponding relationship between the relative displacement and the phase of the signal read, it is possible to ob- tain the relative displacement information by obtaining the phase values of the output signals.
The absolute displacement requires that the signals read by the reading unit at every displacement position should differ from each other, that is, it requires that each scale should be distinguishable.
Currently, the incremental displacement measurement method is an established technology that is used widely, but the abso- lute displacement measurement technology is still under development and there are mainly the following two absolute displacement measurement methods in the prior art:
The first method: the incremental displacement measurement and absolute displacement measurement on the evenly distributed electrodes are achieved by means of spatial multiplexing. In this approach, each electrode in a string of evenly distributed electrodes in the displacement scale unit is cut into an upper part and a lower part. For an odd number of strip electrodes, the cutting position satisfies the periodic sinusoidal curve, and for an even number of strip electrodes, the cutting position satisfies the periodic cosine curve. In the incremental displacement measurement, both the upper part
and the lower part of each electrode will be loaded with the same signal, and when the cutting gap is small enough, each electrode can be seen as an incremental measurement scale. In the absolute displacement measurement, both upper and lower parts of each electrode will be loaded with signals that have the opposite phase, the signals sensed by the reading unit with a certain displacement will depend on the area difference between the upper part and the lower part of each electrode covered by the reading unit, which results in differ- ence in the phase values of the signals output by the reading unit with each displacement. By using the corresponding relationship between the absolute displacement and the phase of the signals output by the reading unit, it is possible to obtain the absolute displacement information by obtaining the phase values of the output signals.
The second method: the displacement scale unit contains multiple lines of evenly distributed and parallel electrodes, and at each position, the reading units can cover multiple lines of electrodes. When the absolute displacement measurement is taken, every line of electrodes comprises electrode groups connecting to both positive signal and negative signal. At each displacement, the polarity combination of the signals recorded by the electrodes covered by the reading unit is different. Based on the corresponding relationship between the displacement and the polarity combination, it is possible to obtain the absolute displacement information by obtaining the polarity combination output by the read signals .
However, in the above first approach, the absolute displacement measurement is taken by obtaining the analog quantity, which will be easily affected by the inclination of the reading unit. As the actual installation and movement of the reading unit will not be completely parallel with the displacement scale unit, the measured absolute displacement will be varied due to the inclination degree of the reading unit, and its resistance to interference is weak. In addition, each
electrode needs to be cut in a specific position, resulting in a complicated manufacturing process and high cost. In the second approach, as it contains multiple lines of electrodes, a large number of electrodes is therefore needed, leading to high cost and complexity in connecting each electrode to the signal line of the specified polarity.
In view of this, the object of the present invention is to provide a device and method for capacitive linear displace- ment measurement to enable simpler absolute displacement measurement that is low in cost and strong in interference resistance .
A device for capacitive linear displacement measurement, which includes: a displacement scale unit, a reading unit and a displacement determining unit; said displacement scale unit includes a base, M identical strip electrodes and a first group of signal lines, wherein M is an integer greater than or equal to 4; said M strip electrodes are arranged on said base in a line equidistantly, and every N continuous strip electrodes form a spatial period; said first group of signal lines comprises N signal lines, wherein N is an integer greater than or equal to 2; in the absolute displacement measurement mode, the N signal lines of said first group of signal lines take turns in being loaded with excitation signals in one signal generation period; the connection between said each strip electrode and said first group of signal lines causes all the excitation signal combi- nations detected at each displacement by the reading unit in the absolute displacement measurement mode to be different from one another; said reading unit is used to move along the M strip elec- trodes, and cover R strip electrodes in the absolute displacement measurement mode, detecting the excitation signals loaded to the strip electrodes that it covers and outputting
the detected signal combinations, wherein R is an integer greater than or equal to N; said displacement determining unit is used to determine the displacement value corresponding to the signal combination output by said reading unit in the absolute displacement measurement mode, according to the predetermined corresponding relationship between the displacement value and the signal combination.
In addition, said displacement scale unit further includes a second group of signal lines comprising another N signal lines; in the incremental displacement measurement mode, said first group of signal lines and second group of signal lines are loaded with carrier signals of the same waveform, and the phase difference between the carrier signals loaded to the signal lines in each group of the signal lines in turn and
360°
spaced is N ; the connection between said each strip electrode and said first group and second group of signal lines causes the phases of the excitation signals loaded to the strip electrodes which take the same turn in each spatial period to be the same in the incremental displacement measurement mode; said reading unit is further used for covering KN strip electrodes in the incremental displacement measurement mode, and outputting the detected signals, wherein K is an integer greater than or equal to 1; said displacement determining unit is further used to determine the displacement value corresponding to the phase of the signal output by said reading unit in the incremental displacement measurement mode according to the corresponding relationship between the signal phase and displacement value.
Furthermore, the device further includes: a signal generator, which is used to load the excitation signals in turn to
the N signal lines in said first group of signal lines in one signal generation period in the absolute displacement measurement mode after receiving the measurement instruction; after receiving the measurement instructions in the incremental displacement measurement mode, the signal generator loads the carrier signals of the same waveform to said first group of signal lines and second group of signal lines at the same time and the phase difference between the carrier signals loaded to the signal lines in each group in turn and spaced
360°
is N •
The device further includes: a mode switching unit, for switching said reading unit and said displacement determining unit to the incremental displacement measurement mode or absolute displacement measurement mode at the same time.
In this case, said reading unit includes: an absolute measurement pick-up area and an incremental measurement pick-up area; said absolute measurement pick-up area comprises at least one rectangular sensing area, and covers a total of R strip electrodes for outputting the detected signal combinations in the absolute displacement measurement mode; said rectangular sensing areas have a non-conductive separation area between them; said incremental measurement pick-up area includes K sensing areas of special shapes, and each sensing area covers N strip electrodes for outputting the detected signal in the incre- mental displacement measurement mode; said special shapes have inconstant amplitudes in the lengthwise direction of the strip electrodes.
In this case, said displacement determining unit includes: a decoder and a table checker;
said decoder is used for decoding the signal combination output by the reading unit in the absolute displacement measurement mode into the binary absolute code, and providing it to said table checker; in the incremental displacement measure- ment mode, the decoder determines the phase of the signal output by said reading unit, and provides it to said table checker; said table checker is used to determine the displacement value corresponding to the received absolute code according to the predetermined corresponding relationship between the absolute code and the displacement value; the table checker is further used to determine the displacement value corresponding to the phase of the received signal according to the predetermined corresponding relationship between the signal phase and displacement value.
Specifically, said N is 4, and the strip electrodes which take the same turn in each spatial period are connected to the signal lines in the first group or the second group of signal lines corresponding to the turn; said signal generator loads the excitation signals in turn to the four signal lines in the first group of signal lines by the method of time-sharing multiplexing in one signal generation period in the absolute displacement measurement mode; and in the incremental displacement measurement mode, the signal generator loads the carrier signals to the signal lines in the first group of signal lines and the second group of signal lines at the same time, and the phase difference between the carrier signals loaded to the signal lines in each group of signal lines in turn and spaced is 90° .
Preferably, said excitation signal is a pulse signal;
Said carrier signal is: a trigonometric signal or a square wave signal .
Preferably, said base is a flexible printed circuit board, and said strip electrodes and the signal lines are printed on said base by using roll-to-roll technology. A method for capacitive linear displacement measurement, which is used in a device that comprises a displacement scale unit, a reading unit and a displacement determining unit, wherein said displacement scale unit includes: a base, M identical strip electrodes and a first group of signal lines, wherein M is an integer greater than or equal to 4; said M strip electrodes are arranged on said base in a line equidis- tantly, and every N continuous strip electrodes comprise a spatial period; said first group of signal lines comprises N signal lines, wherein N is an integer greater than or equal to 2; in the absolute displacement measurement mode, the N signal lines in said first group of signal lines take turns in being loaded with the excitation signals in one signal generation period; the connection between said each strip electrode and said first group of signal lines causes all the excitation signal combinations detected at each displacement by the reading unit in the absolute displacement measurement mode to be different from one another; the method includes: said reading unit moves along said M strip electrodes and outputs the detected signal combination of the R strip electrodes covered in the absolute displacement measurement mode, wherein R is an integer greater than or equal to N; said displacement determining unit determines the displace- ment value corresponding to the signal combination detected by said reading unit in the absolute displacement measurement mode according to the predetermined corresponding relationship between the displacement value and the signal combination .
Furthermore, said displacement scale unit further includes a second group of signal lines comprising another N signal lines; in the incremental displacement measurement mode, the
signal lines in said first group of signal lines and second group of signal lines are loaded with carrier signals of the same waveform at the same time, and the phase difference between the carrier signals loaded to the signal lines in each
360°
group of signal lines in turn and spaced is N ; the connection between said each strip electrode and said first group and second group of signal lines also causes the strip electrodes which take the same turn in each spatial period to be loaded with the same signal phases in the incremental dis- placement measurement mode; the method further includes: said reading unit outputs the signals detected by the KN strip electrodes covered in the incremental displacement measurement mode, wherein K is an integer greater than or equal to 1 ; said displacement measurement unit determines the displacement value corresponding to the signal phase output by said reading unit in the incremental displacement measurement mode according to the corresponding relationship between the signal phase and displacement value.
Preferably, the method further includes: obtaining the final displacement measurement value by combining the displacement value determined in the absolute measurement mode and the displacement value determined in the incremental displacement measurement mode by said displacement determining unit.
As we can see from the above description, the present inven- tion enables the reading unit to output the signal combinations of the R strip electrodes covered in the absolute displacement measurement mode in one signal period by loading the excitation signals in turn to the strip electrodes in each spatial period in one signal period, and makes it possi- ble to achieve the absolute displacement measurement using only one line of strip electrodes by uniquely identifying the absolute displacement of the reading unit with the signal
combinations. Compared to the second method of the prior art which uses multiple lines of strip electrodes, the present invention reduces the wiring complexity and floor space to greatly simplify the construction of the device. Compared to the first method of the prior art, the present invention is simpler to implement by eliminating the complex cutting process. In addition, the method of obtaining signal combinations in one signal period in the absolute displacement measurement method of the present invention is in fact a method of digi- tal acquisition of absolute codes, which is insensitive to the inclination degree of the reading unit, resulting in stronger interference resistance than the first method of the prior art. Description of the Drawings
Figure 1 shows a structural diagram of the device provided by the embodiment of the present invention.
Figure 2 shows an exemplary diagram of the device provided by the embodiment of the present invention.
Figure 3a is a schematic drawing showing the excitation signals generated by the signal generator provided by the embodiment of the present invention.
Figure 3b is a schematic drawing showing the displacement of the pick-up area provided by the embodiment of the present invention . Figure 3c shows the waveforms of the signals output by the reading unit on the basis of Figure 3a and Figure 3b provided by the embodiment of the present invention.
Figure 4 is a schematic drawing of the printed circuit board of the displacement scale unit provided by the embodiment of the present invention.
Exemplary Embodiments
In order to make the objective, technical solutions and advantages of the present invention more evident, the following gives a detailed description of the present invention in com- bination with the drawings and particular embodiments.
Firstly, the device provided by the present invention is described for easy understanding. Figure 1 shows a structural diagram of the device provided by the embodiment of the pre- sent invention. As shown in Figure 1, the device may include: a displacement scale unit 100, reading unit 110 and displacement determining unit 120.
In this case, the displacement scale unit 100 includes: base 101, M identical strip electrodes 102, signal lines 103 and signal generator 104, wherein M is an integer greater than or equal to 4.
M strip electrodes are arranged on the base 101 in a line equidistantly, and the base is made of dielectric materials. All strip electrodes have the same shape, size and electrical conductivity.
Every N continuous strip electrodes of M strip electrodes 102 is set as a spatial period, and N signal lines in the signal lines 103 comprise a first group of signal lines, for example, the signal lines in the upper side of the strip electrodes 102 shown in the drawing, wherein N is an integer greater than or equal to 2.
After receiving the measurement instruction in the absolute displacement measurement mode, the signal generator 104 loads the excitation signals in turn to the N signal lines in the first group of signal lines within a signal generation period in order to load the excitation signals to each strip electrode connected to the signal lines of the first group.
The reading unit 110 moves along the strip electrodes 102 arranged in a line, and covers R strip electrodes in the absolute displacement measurement mode, and can detect the excitation signals loaded to the covered strip electrodes, and output the signal combinations detected; wherein R is an integer greater than or equal to N; the values of R can be determined according to the range of the absolute displacement measurement . The signal combination in the reading unit 110 can be represented by a binary code, and will be further described later on .
In the displacement scale unit 100, each strip electrode is connected to the signal lines in a way that ensures that the signal combinations detected by the reading unit 110 in the absolute displacement measurement mode at each displacement position are different. The displacement determining unit 120 is for determining the displacement value corresponding to the signal combination output by the reading unit 110 in the absolute displacement measurement mode according to the predetermined corresponding relationship between the displacement value and the signal combination.
Moreover, in addition to achieving the above absolute displacement measurement, the device provided by the present invention can also realize the incremental displacement meas- urement, in which case, the signal line 103 may comprise 2N signal lines, and the other N lines belong to the second group of signal lines, for example, the signal lines in the lower side of the strip electrode 102 shown in the drawing. After receiving the measuring instruction in the incremental displacement measurement mode, the signal generator 104 will load the carrier signals of the same waveform to the two groups of signal lines at the same time, and the phase dif-
ference between the carrier signals loaded to the signal lines in each group of signal lines in turn and spaced is
360°
N . In this case, the carrier signals loaded in the incremental displacement measurement mode can be sinusoidal signal or square-wave signal.
The reading unit 110 also moves along the strip electrodes arranged in a line, detecting the signals loaded to the covered strip electrodes, and in the incremental displacement measurement, it covers KN strip electrodes and outputs the detected signals, wherein K is an integer greater than or equal to 1. When K is greater than 1, the signal strength detected by the reading unit 110 can be strengthened, thus improving the detecting performance of the reading unit 110.
In order to enable the device to make the incremental displacement measurement at the same time, the connection relationship between each strip electrode 102 and the signal lines 103 causes the phase of signals loaded to the strip electrodes which take the same turn in each spatial period in the incremental displacement measurement to be the same.
In the incremental displacement measurement mode, the displacement determining unit 120 determins the displacement value corresponding to the signal phase output by the reading unit 110 according to the corresponding relationship between the signal phase and displacement value.
In addition, the device further includes: a mode switching unit 130 for switching the measuring mode of reading unit
110, signal generator 104 and displacement determining unit 120, that is, switching to the absolute displacement measurement mode or incremental displacement measurement mode. The mode switching unit 130 can be set separately, or be presented in the form of a switch that is set in the displace-
ment scale unit 100. In Figure 2, it is set in the displacement scale unit 100.
Note that the signal generator 104 in the above said device can be set in the capacitive linear displacement measurement device as shown in Figure 1, and can also be additionally set outside the device, that is, using the existing signal generator to provide the corresponding excitation or carrier signals to the capacitive linear displacement measurement de- vice.
In order to make the above said device more apparent, below we suppose that N is 4, that is, we take 4 strip electrodes as a spatial period, the number M of the strip electrodes ar- ranged in a line is far more than 4 in order to ensure the measurement range. Figure 2 shows an exemplary diagram of the device in this embodiment. As shown in Figure 2, the reading unit 110 in the device may include two pick-up areas: absolute measurement pick-up area 111 and incremental measurement pick-up area 112.
Firstly, we describe the absolute displacement measurement:
The absolute measurement pick-up area 111 is composed of at least one rectangular sensing area, which is covered by R strip electrodes in total, for outputting the detected signal combination in absolute displacement measurement mode in sequence in a signal generation period. In Figure 2, the two rectangular areas of the shaded parts in absolute measurement pick-up area 111 are sensing areas, each of which can cover 4 strip electrodes, and both sensing areas can cover 8 strip electrodes in total, the signal combinations output in absolute displacement measurement mode is 8, the displacement measuring range that can be measured is (2 - 8 )x L , L being the sum of the width of a strip electrode and the spacing between the strip electrodes. The specific number of the pickup areas can be set according to the required displacement measuring range.
There is a separation area between sensing areas of the absolute pick-up area 111 to prevent the interference of the signals between the two sensing areas. There may be an output line in every sensing area, which provides the detected signals to the displacement determining unit 120 respectively to compose the 8-bit signal combinations.
The reading unit 110 faces the displacement scale unit 110, and moves along the strip electrode 102 arranged in a line. The strip electrodes 102 arranged in a line are set in the center of the base 101, with the same width of the electrodes as well as the same gap. More optimally, the width and the gap of the electrodes also remain the same so that every width and gap can serve as a scale. The 8 signal lines 103 are divided into two groups, one located in the upper side of the strip electrodes, and the other located in the lower side of the strip electrodes. Every 4 continuous strip electrodes compose a spatial period, the strip electrodes in the same arrangement in every spatial period are connected to the corresponding signal lines in the same arrangement in the upper or lower part. We mark the strip electrodes in a spatial period with A, B, C and D; the strip electrode marked A can connect the signal line that is nearest to the strip elec- trode in the upper or lower part; the strip electrode marked B can connect the signal line that is the second nearest to the strip electrode in the upper or lower part; the strip electrode marked C can connect the signal line that is the third nearest to the strip electrode in the upper or lower part; and the strip electrode marked D can connect the signal line that is farthest from the strip electrode in the upper or lower part.
Suppose the signal generator 104 loads the excitation signals to the signal lines in the upper part in sequence in absolute displacement measurement mode, in this embodiment, we take the example of a loading pulse signal. It can also be other signal types, but we must be sure that when we connect the
signal lines in each strip electrode, the connection methods of the strip electrode and the signal lines in the upper part make the 8-bit signal combinations obtained at all displacement positions by the absolute measurement pick-up area III in the reading unit 110 be different. In specific implementations, we can determine the 8-bit signal combination at first, and connect the signal lines of the various strip electrodes according to the 8-bit signal combinations, then record the corresponding relationship between the signal com- binations and the displacement value for use by the displacement determining unit 120.
If the signal generator 104 received the measurement instruction after it was switched to absolute displacement measure- ment mode by the mode switching unit 130, we should load the pulse signals to the 4 signal lines in the upper part in sequence by adopting the method of time-sharing multiplex in a signal generation period, as shown in Figure 3a, generate a group of pulse signals at 4 moments, namely tl, t2, t3 and t4 respectively in a signal generating period, the pulse signals generated at tl are loaded in the signal line that is the nearest to the strip electrode, the pulse signals generated at t2 are loaded in the signal line that is the second nearest to the strip electrode, the pulse signals generated at t3 are loaded in the signal line that is the third nearest to the strip electrode, the pulse signals generated at t4 are loaded in the signal line that is the farthest from the strip electrode and, in this way, we can load the pulse signals to the strip electrode marked A at tl, and load the pulse sig- nals to the strip electrode marked B at t2, load the pulse signals to the strip electrode marked C at t3, and load the pulse signals to the strip electrode marked D at t4.
If the position of the absolute measurement pick-up area 111 in the reading unit 110 is as shown in Figure 3b, the waveform of the signals detected by the reading unit 110 is as shown in Figure 3c. The reading unit 110 outputs the detected signals to the decoder 121 in the displacement determining
unit 120, then the decoder 121 decodes the received signals, supposing the signals that can be detected are decoded to 1, and the signals that can not be detected are decoded to 0, then the signal combinations detected by the reading unit 110 in absolute displacement measurement mode at the 4 moments in sequence in a signal generating period are decoded into 8-bit of binary absolute code 10110101. Namely, the pulse signals loaded to the strip electrode connected with the signal lines in the upper part are decoded into 1, and the pulse signals (there may be noise) loaded to the strip electrode connected with the signal lines in the lower part are decoded into 0.
The decoder 121 sends the decoded absolute codes to the table checker 112, which determines the corresponding displacement value of the absolute codes according to the corresponding relationship between the predetermined absolute codes and the displacement value, the displacement value being the current absolute displacement value of the reading unit. The above said absolute codes are binary digital codes, which can better resist external interference compared to analog signal, and the encoding method is simpler and more reliable, and the identical nature of the strip electrodes is not destroyed at the same time, the present invention can be real- ized by using only one line of strip electrodes, and the connection is simple and easy for processing and manufacturing.
In addition, the number of the binary code determines how many absolute codes can be used, and thus the absolute unique measurement length can be determined, a long measurement length often requiring binary codes greater than 4 bits; generally, metric length requires absolute codes greater than 8 bits . It can be seen that, the measurement of the absolute displacement actually takes the width of the strip electrodes as the measurement accuracy, as the width of the electrode is often in mm; therefore, the accuracy of the absolute dis-
placement value is also in mm, the measurement accuracy being coarse. However, this can be made up through incremental displacement measurement, which can measure high accuracy relative displacement. At last, we can combine the displacement value measured through absolute displacement measurement with the displacement value measured through incremental displacement measurement as the final high accuracy displacement value . The above is the description of the absolute displacement measurement conducted by the device. Below we describe the incremental displacement measurement conducted by the device.
When the signal generator 104 is switched to the incremental displacement measurement mode under the instruction of the mode switching unit 130, if it receives measurement instruction, it will load the carrier signals of the same waveform to the signal lines in the upper and lower parts at the same time, the phase difference of the loading carrier signals for the signal lines on the upper part in turn and spaced is
360°
N , the phase difference of the loading carrier signals for the neighboring siganl lines on the lower part in turn and
360°
spaced is N , and makes the signal phase loaded on the strip electrodes which have the same sequence in every spa- tial period the same. The carrier signal can be sinusoidal signal, cosine signal, square wave signal, etc.
For instance, the signal generator 104 loads the sinusoidal function with an interval of 90 phase in sequence on the signal lines in the upper and lower parts, specifically:
load the signal V0COS ( (Ot ) on the signal line that is nearest to the strip electrode in the upper and lower parts, load the signal V0COS ( ftrt+90° ) on the signal line that is the second nearest to the strip electrode in the upper and lower parts, load the signal V0COS ( ύΛ+\$0°) on the signal line that is the third nearest to the strip electrode in the upper and lower parts, and load the signal V0COS ( ftrt+270° ) on the sig-
nal line that is farthest from the strip electrode in the upper and lower parts. In this way, all the strip electrodes marked A are loaded with the signal V0COS ( ύ)t ), all the strip electrodes marked B are loaded with the signal
V0COS ( θΛ+90° ), all the strip electrodes marked C are loaded with the signal V0COS ( oA +180° ), and all the strip electrodes marked D are loaded with the signal V0COS ( θA+270° ).
When the reading unit 110 is switched to incremental dis- placement measurement mode under the instruction of the mode switching unit 130, it uses the incremental measurement pickup area 112. The incremental measurement pick-up area 112 can include K sensing areas with specific shape, K being an integer greater than or equal to 1. In this case, every sensing area covers N strip electrodes, that is a spatial period, outputting the detected signals in incremental displacement measurement mode. The signals output in incremental displacement measurement mode can use an output line different from that used by the signals output in absolute measurement mode.
In addition, it should be noted that, as the realization of the measurement in incremental displacement measurement mode depends on the different signal phases output from the different relative displacement positions, sensing for the sig- nals on the strip electrode by the reading unit 110 is realized actually through the principle of capacitors, and a sensing area covers the strip electrodes in a spatial period. If the coverage area of the various strip electrodes is the same, then the offset of a spatial period will not produce different phase values, therefore, if the offset occurring in a spatial period can produce the difference in phase value, then the area of all the strip electrodes covered in every offset position will have deviation. This can be realized through using a sensing area of a specific shape, the special shape needing to have inconstant amplitude in the lengthwise direction of the strip electrode, for example, following a certain functional relationship, such as sinusoidal function,
cosine function, triangular wave function, etc. The sensing area in incremental measurement pick-up area 112, as shown in Figure 2, takes the example of following the sinusoidal function in the amplitude in the lengthwise direction of the strip electrode.
The signals output by the reading unit 110 in incremental displacement measurement mode are actually the synthesized signal of the various strip electrodes detected in the cur- rent displacement position, and the phase of the synthesized signal and the relative displacement of the reading unit form a linear relationship, with which the displacement determining unit 120 in incremental displacement measurement mode can determine the relative displacement value according to the signal phase output by the reading unit 110. Generally, the reference point of the relative displacement value is the starting point of the spatial period of the current displacement . In this mode, the decoder 121 in the displacement determining unit 120 will determine the signal phase output by the reading unit 110 in absolute displacement measurement mode, and provide it to the table checker 122; the table checker 122 will determine the corresponding displacement value of the received signal phase according to the predetermined corresponding relationship between the signal phase and the displacement value.
The incremental measurement mode determines the relative dis- placement value by obtaining the phase of the output signals, and the accuracy of the displacement value obtained in this way is very high, which can measure a displacement smaller than the width of the strip electrode, and can reach the level of μm. In the present invention, the final measured displacement value can be the integration of the absolute displacement value measured in absolute displacement measurement mode with the relative displacement value measured in incremental displacement measurement mode, the width level of
the strip electrode measured in absolute displacement measurement mode being less than the displacement of the width of the strip electrode measured through the incremental displacement measurement mode. In the specific combination, we should first determine the starting value of the spatial period of the absolute displacement value measured in absolute displacement measurement mode, and obtain the final displacement measurement value by adding the starting value of the spatial period with the relative value measured in incre- mental displacement measurement mode.
The displacement scale unit 100 in the present invention is generally manufactured in the form of a printed circuit board (PCB) . If we make the circuit on a hard base 101, the proc- essing technology cannot produce a scale with the length of several meters, the processing length usually being no more than 1 meter. However, if we use flexible printed circuit board (FPCB), we can produce a long scale once. As shown in Figure 4, the strip electrode 102 and signal line 103 printed on the front side of the flexible base 101 by roll-to-roll technology, and the conducting wire 105 on the back side will connect strip electrode 102 and signal line 103 through pin connection. This design method of double sides and single layer is suitable for manufacturing with roll-to-roll tech- nology, which enables the processing length to reach several meters to several tens of meters.
We can see from the above description that the method and device provided by the present invention have advantages as follows:
1) The present invention makes the reading unit output the signal combinations of the covered R strip electrodes in sequence in absolute displacement measurement mode within a signal period through the method of loading the excitation signals to the strip electrodes in sequence within the various spatial periods in a signal period, and we can identify the absolute displacement of the reading unit through the
signal combinations, so that we can conduct the absolute displacement measurement simply through the single line of strip electrodes, compared to the multiple lines of electrodes in the second approach of the existing technology, which reduces the complexity of the connection and the space occupancy levels, greatly simplifying the construction of the device; further, compared to the first approach of the existing technology, it leaves out the complex cutting processes, and can realize the absolute displacement measurement more easily.
2) What the present invention obtains by means of absolute displacement measurement is signal combinations in a signal period, in fact, this is a kind of digital mode of gaining absolute code, and it is insensitive to the inclination de- gree of the reading unit, and as compared to the first approach of the existing technology, it has a stronger anti- interference ability.
3) In addition to the absolute displacement measurement, the present invention makes it possible to re-construct the same device for the incremental displacement measurement as the unity of the strip electrodes is not destroyed, so as to incorporate the advantage of high accuracy of the incremental displacement measurement to greatly improve the measuring ac- curacy of the absolute displacement measurement.
4) The present invention only needs a single line of strip electrodes, and does not need complex manufacturing processes, making it more cost-effective than the two methods in the prior art. In addition, the present invention may use roll-to-roll printing technology to make a device with a longer scale.
The above only describes preferred embodiments of the present invention, and is not intented to restrict the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the pre-
sent invention should be included in the scope of protection of the present invention.
Claims
1. A device for capacitive linear displacement measurement, which includes: a displacement scale unit, a reading unit and a displacement determining unit; characterized in that, said displacement scale unit includes a base, M identical strip electrodes and a first group of signal lines, wherein M is an integer greater than or equal to 4; said M strip electrodes are arranged on said base in a line equidistantly, and every N continuous strip electrodes compose a spatial period; said first group of signal lines comprises N signal lines, wherein N is an integer greater than or equal to 2; in the absolute displacement measurement mode, the N signal lines in said first group of signal lines take turns in being loaded with excitation signals in one signal generation period; the connection between said each strip electrode and said first group of signal lines causes all the excitation signal combinations detected at all displacement positions by the reading unit in the absolute displacement measurement mode to be dif- ferent from one another;
said reading unit is used to move along the M strip electrodes and cover R strip electrodes in the absolute displacement measurement mode, detecting the excitation signals loaded to the strip electrodes that it covers, and outputting the detected signal combinations, wherein R is an integer greater than or equal to N;
said displacement determining unit is used to determine the corresponding displacement value for a signal combination output by said reading unit in the absolute displacement measurement mode, by using the predetermined corresponding relationship between the displacement value and the signal combination .
2. The device as claimed in claim 1, characterized in that said displacement scale unit further includes a second group of signal lines comprising another N signal lines; in the incremental displacement measurement mode, said first group of signal lines and second group of signal lines are loaded with carrier signals of the same waveform, and the phase difference between the carrier signals loaded to the signal lines
360° in each group of signal lines in turn and spaced is N ; the connection between said each strip electrode and said first group and second group of signal lines causes the strip electrodes that take the same turn in each spatial period to be loaded with the same phase of carrier signals in the incremental displacement measurement mode;
said reading unit is further used to cover KN strip elec- trodes in the incremental displacement measurement mode, and output the detected signals, wherein K is an integer greater than or equal to 1 ;
said displacement determining unit is further used to determine the displacement value corresponding to the phase of the signal output by said reading unit in the incremental displacement measurement mode by using the corresponding relationship between the signal phase and displacement value.
3. The device as claimed in claim 2, characterized in that the device further includes: a signal generator, which is used to load the excitation signals in turn to the N signal lines in said first group of signal lines in one signal generating period after receiving the measurement instruction in the absolute displacement measurement mode; at the same time the signal lines in said first group and second group of signal lines are loaded with carrier signals of the same waveform after receiving the measurement instruction in the incremental displacement measurement mode, and the phase difference between the carrier signals loaded to the signal lines in each group of signal lines in turn and spaced is
360°
N
4. The device as claimed in claim 2, characterized in that the device further includes: a mode switching unit, which is used to switch both said reading unit and said displacement determining unit to the incremental displacement measurement mode or to the absolute displacement measurement mode.
5. The device as claimed in claim 2, characterized in that said reading unit includes: an absolute measurement pick-up area and incremental measurement pick-up area;
said absolute measurement pick-up area comprises at least one rectangular sensing area that covers a total of R strip electrodes, and is used to output the detected signal combinations in the absolute displacement measurement mode; said rectangular sensing areas have a non-conductive separation area between them;
said incremental measurement pick-up area includes K sensing areas of special shapes, and each sensing area covers N strip electrodes for outputting the detected signals in the incremental displacement measurement mode; said special shapes have inconstant amplitudes in the lengthwise direction of the strip electrodes.
6. The device as claimed in claim 2, characterized in that said displacement determining unit includes: a decoder and a table checker;
said decoder is used for decoding the signal combinations output by said reading unit in the absolute displacement measurement mode into binary absolute codes, and providing the codes to said table checker; in the incremental displace- ment measurement mode, the decoder determines the phase of the signals output by said reading unit, and provides it to said table checker;
said table checker is used for determining the displacement value corresponding to the received absolute code according to the predetermined corresponding relationship between the absolute code and the displacement value; the table checker determines the displacement value corresponding to the phase of the received signal according to the predetermined corresponding relationship between the signal phase and displace- ment value.
7. The device as claimed in claim 3, characterized in that N is 4, the strip electrodes that take the same turn in each spatial period are connected to the signal lines in the first group or second group of signal lines corresponding to the turn;
said signal generator loads the excitation signal in turn to the four signal lines in the first group of signal lines by the method of time-sharing multiplexing in one signal generation period in the absolute displacement measurement mode; the signal lines in the first group and the second group of signal lines are loaded at the same time with carrier signals in the incremental displacement measurement mode, and the phase difference between the carrier signals loaded to the signal lines in each group of signal lines in turn and spaced is 90° .
8. The device as claimed in any one of claims 2 through 7, characterized in that said excitation signal is a pulse signal;
said carrier signal is: a trigonometric signal or square wave signal .
9. The device as claimed in any one of claims 1 through 7, characterized in that said base is a flexible printed circuit board, and said strip electrodes and signal lines are printed on said base using roll-to-roll technology.
10. A method for capacitive linear displacement measurement, which is used in the device comprising a displacement scale unit, a reading unit and a displacement determining unit, wherein said displacement scale unit includes: a base, M identical strip electrodes and a first group of signal lines, wherein M is an integer greater than or equal to 4; said M strip electrodes are arranged on said base in a line equidis- tantly, and every N continuous strip electrodes form a spatial period, wherein said first group of signal lines com- prises N signal lines, wherein N is an integer greater than or equal to 2; in the absolute displacement measurement mode, the N signal lines of said first group of signal lines take turns in being loaded with excitation signals in one signal generation period; the connection between said each strip electrode and said first group of signal lines causes all the excitation signal combinations detected at different displacement positons by the reading unit in the absolute dis- placement measurement mode to be different from another; the method includes:
said reading unit moves along said M strip electrodes and outputs the signal combinations detected at the covered R strip electrodes in the absolute displacement measurement mode, wherein R is an integer greater than or equal to N; said displacement determining unit determines the displacement value corresponding to the signal combination detected by said reading unit in the absolute displacement measurement mode, according to the predetermined corresponding relation- ship between the displacement value and the signal combination .
11. The method as claimed in claim 10, characterized in that said displacement scale unit further includes a second group of signal lines, wherein said second group of signal lines comprises another N signal lines, and, in the incremental displacement measurement mode, said first group of signal lines and second group of signal lines are loaded with carrier signals of the same waveform at the same time, and the phase difference between the carrier signals loaded to the signal lines in each group of signal lines in turn and spaced
360°
is N ; the connection between said each strip electrode and said first group and second group of signal lines also causes the strip electrodes which take the same turn in each spatial period to be loaded with the same signal phases in the incremental displacement measurement mode; the method further includes :
said reading unit outputs the signals detected at the covered KN strip electrodes in the incremental displacement measure- ment mode, wherein K is an integer greater than or equal to 1; said displacement measurement unit determines the displacement value corresponding to the phase of the signal output by said reading unit in the incremental displacement measurement mode according to the corresponding relationship between the signal phase and displacement value.
12. The method as claimed in claim 11, characterized in that, the method further includes: obtaining the final displacement measurement value by combining the displacement value determined in the absolute measurement mode and that determined in the incremental displacement measurement mode by said displacement determining unit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE112010003273.4T DE112010003273B4 (en) | 2009-08-13 | 2010-08-12 | An apparatus and method for capacitive linear displacement measurement |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009101623403A CN101995208B (en) | 2009-08-13 | 2009-08-13 | Capacitive linear displacement measuring device and method |
| CN200910162340.3 | 2009-08-13 |
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| Publication Number | Publication Date |
|---|---|
| WO2011018497A1 true WO2011018497A1 (en) | 2011-02-17 |
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| Application Number | Title | Priority Date | Filing Date |
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| PCT/EP2010/061749 WO2011018497A1 (en) | 2009-08-13 | 2010-08-12 | A device and method for capacitive linear displacement measurement |
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| Country | Link |
|---|---|
| CN (1) | CN101995208B (en) |
| DE (1) | DE112010003273B4 (en) |
| WO (1) | WO2011018497A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014101031A1 (en) * | 2012-12-27 | 2014-07-03 | Siemens Aktiengesellschaft | Linear capacitive encoder and position determing method |
| EP2527796A3 (en) * | 2011-05-27 | 2017-05-17 | Siemens Aktiengesellschaft | Capacitive rotary encoder and method for sensing a rotation angle |
| CN113008120A (en) * | 2019-12-19 | 2021-06-22 | 重庆理工大学 | Capacitive linear displacement sensor and movable ruler thereof |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104075740B (en) * | 2013-03-27 | 2016-11-02 | 西门子公司 | A kind of capacitance type rotary encoder and the method determining absolute rotation angle |
| CN104236437B (en) * | 2014-08-26 | 2017-09-29 | 广东盈动高科自动化有限公司 | Absolute linearity displacement measuring device |
| CN105300262B (en) * | 2015-11-12 | 2017-12-15 | 重庆理工大学 | Grating straight-line displacement sensor during a kind of absolute type |
| CN113523836A (en) * | 2021-06-10 | 2021-10-22 | 上海铂世光半导体科技有限公司 | Wear-resistant conductive diamond positioner |
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| DE3832929C1 (en) * | 1988-09-28 | 1989-08-24 | Voest-Alpine Automotive Ges.M.B.H., Linz, At | |
| EP0635700A1 (en) * | 1993-07-22 | 1995-01-25 | Marco Dr. Brandestini | Absolute digital position encoder |
| WO2006002311A2 (en) * | 2004-06-23 | 2006-01-05 | Fe Technical Services, Inc. | Capacitive sensing techniques |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1017746B (en) * | 1988-05-31 | 1992-08-05 | 株式会社三丰 | Capacitance-type measuring device for absolute measurement of positions |
-
2009
- 2009-08-13 CN CN2009101623403A patent/CN101995208B/en active Active
-
2010
- 2010-08-12 WO PCT/EP2010/061749 patent/WO2011018497A1/en active Application Filing
- 2010-08-12 DE DE112010003273.4T patent/DE112010003273B4/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3832929C1 (en) * | 1988-09-28 | 1989-08-24 | Voest-Alpine Automotive Ges.M.B.H., Linz, At | |
| EP0635700A1 (en) * | 1993-07-22 | 1995-01-25 | Marco Dr. Brandestini | Absolute digital position encoder |
| WO2006002311A2 (en) * | 2004-06-23 | 2006-01-05 | Fe Technical Services, Inc. | Capacitive sensing techniques |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2527796A3 (en) * | 2011-05-27 | 2017-05-17 | Siemens Aktiengesellschaft | Capacitive rotary encoder and method for sensing a rotation angle |
| WO2014101031A1 (en) * | 2012-12-27 | 2014-07-03 | Siemens Aktiengesellschaft | Linear capacitive encoder and position determing method |
| CN113008120A (en) * | 2019-12-19 | 2021-06-22 | 重庆理工大学 | Capacitive linear displacement sensor and movable ruler thereof |
| CN113008120B (en) * | 2019-12-19 | 2023-09-22 | 通用技术集团国测时栅科技有限公司 | Capacitive linear displacement sensor and movable ruler thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| CN101995208B (en) | 2012-06-27 |
| CN101995208A (en) | 2011-03-30 |
| DE112010003273T5 (en) | 2013-01-03 |
| DE112010003273B4 (en) | 2014-08-21 |
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