CN115727747A - Absolute straight line position positioning device and method - Google Patents

Abstract

An absolute position-to-linear positioning device and method belong to the field of linear encoders. The invention aims to solve the problems that long-distance displacement measurement cannot be realized, absolute position identification is difficult to realize and the technical cost is overhigh. The invention adopts the inductive detection principle and mainly comprises a scale and a reading head; the scale is provided with a certain regular coding pattern, the movable reading head is provided with an exciting coil, a reading head circuit generates exciting waves with alternating voltage, the exciting waves are transmitted to the scale pattern through the exciting coil to generate eddy currents and transmit electromagnetic waves, the reading head is correspondingly provided with a plurality of induction coils which respectively induce the electromagnetic waves on the scale, and a section of coding information in a region corresponding to the scale can be obtained. The position of the segment code in the global title and thus the absolute position of the reading head can be obtained by using a table look-up method. The scale of the invention adopts single code channel coding, has simple hardware and high reliability, and removes the detection coil group of the fuzzy code through a two-stage evaluation mechanism to obtain the correct segment coding information and the corresponding absolute position.

Description

Absolute straight line position positioning device and method

Technical Field

The invention belongs to the field of linear encoders, and particularly relates to a device and a method for positioning an absolute straight line position.

Background

Linear encoders are sensors that convert linear displacement into an electrical signal, and encoders can be classified into contact type and non-contact type according to the reading mode. Contact is generally not suitable for high speed applications and is not considered for reasons of durability. Non-contact linear encoders typically include a stationary scale and a sliding read head. The static ruler is provided with scale information, the sliding reading head is generally arranged on a measured object and moves along with the measured object, and a displacement signal is output by comparing the scale information with the scale information of the static ruler.

The magnetic grid ruler linear encoder (magnetic grid ruler for short) is measured by the magnetoelectric conversion principle, and the magnetic grid ruler is accurately magnetized to be a ruler with N poles and S poles at equal intervals on the surface layer of a magnetic material or a magnetic coating layer of a non-magnetic material. When there is relative movement between the magnetic grid base rule and the magnetic head, a sine wave-shaped induction potential is generated in the output winding of the magnetic head according to the electromagnetic induction principle, and the magnitude of the induction potential is in direct proportion to the speed of the relative movement, and the displacement can be obtained after filtering, amplifying, shaping, subdividing and counting.

The working principle of the inductive encoder is similar to that of a rotary transformer, and the encoder is adopted in the invention. The linear inductive encoder consists of a stator and a rotor, wherein the stator is internally provided with a power supply circuit and an angle signal processing circuit. The stator is provided with an excitation wave transmitting coil, the rotor is provided with a specially designed metal pattern, alternating electromagnetic waves transmitted by the stator form an eddy current in the metal pattern of the rotor, and an electromagnetic field generated by the eddy current changes along with the movement of the rotor. The stator is also provided with a receiving coil which can detect the electromagnetic field, and the displacement of the rotor can be obtained through a demodulation circuit. Unlike the rotary transformer, the inductive type employs a PCB wiring coil instead of a wire winding.

The traditional method for acquiring displacement and position by utilizing the inductance measurement principle is proposed decades ago, corresponding electric periodic displacement is obtained by two groups of scales with different scales in a short stroke, and an absolute position can be obtained by combining the two groups of electric periodic displacement by adopting a vernier method. If the stroke is to be increased, multiple segments of the scale can be spliced together. In use, by reading the segment code of the scale, the position of the segment of the scale in the global is obtained, thereby realizing the positioning of long stroke. When the binary pseudo-random code is read by the method, the induction coil can press on a fuzzy area on the scale, namely a metal area partially pressing on the scale and a non-metal area partially pressing on the scale, so that the read signal is between '1' and '0', and wrong coded information can be obtained. In addition, the calibration operation increases the complexity and workload of the program, and causes troubles in production and use.

Disclosure of Invention

The invention adopts the inductance principle to measure the linear absolute position, and aims to solve the problems that long-distance displacement measurement cannot be realized, absolute position addressing is not easy to realize, and the technical cost is overhigh. The following technical scheme is provided:

the invention relates to a device and a method for positioning an absolute linear position, wherein the device mainly comprises a scale (1) and a reading head (2); the scale (1) is provided with a certain regular coding pattern, a pseudo-random code consisting of a plurality of '0's and '1's is generally adopted, the coding pattern '1' is made of metal, namely a metal area (11), and the coding pattern '0' is made of nonmetal, namely a nonmetal area (12);

the reading head (2) is provided with an exciting coil (3), a reading head circuit can generate exciting waves with alternating voltage, the exciting waves are transmitted to the scale (1) through the exciting coil (3), eddy currents are generated in a metal area (11) of the coding pattern of the scale (1) and electromagnetic waves are transmitted, the reading head (2) is correspondingly provided with two groups of a plurality of induction coils, each group can be composed of but not limited to 7 coils, namely A1-A7 and B1-B7, the electromagnetic waves generated on the scale (1) are correspondingly induced, and a section of coding information in the corresponding area of the scale can be obtained by analyzing the amplitude of the induction voltage; when the metal pattern is correspondingly arranged on the scale below the induction coil, electromagnetic waves emitted by eddy currents in the metal pattern are received by the induction coil, and the signal amplitude is greater than a certain threshold value, the output is high level and is marked as '1'; on the contrary, when the corresponding nonmetal pattern on the scale below the induction coil is not received by the induction coil, and the signal amplitude is zero or less than a certain threshold, the output is low level, which is marked as "0"; then, a position of the segment code in the global code is obtained by using a table look-up or other matching method, so that the absolute position of the reading head can be determined.

Preferably, the scale (1) can be manufactured in a number of ways, one of which is a printed circuit board, with metal, such as copper, remaining at the coding pattern "1" and etched away where the coding pattern "0" is.

Preferably, the pseudo-random code uses a "shift register" in a computer algorithm, and the algorithm of "shifting" the previous and the next position multiple times is used to determine that each position is a unique code, so long as the coding rules in the global position code do not have repeated segments, the absolute position of the read head can be determined.

Preferably, when a certain group of coils are pressed on the fuzzy area of the scale pattern, namely partially pressed on the metal area and partially pressed on the non-metal area, the amplitude of the signal induced on the group of coils is between the coding pattern "1" and the coding pattern "0", the coding information of the group of patterns cannot be reliably judged; at this time, the other group of coils still falls on the non-fuzzy area of the pattern, namely all the coils are pressed on the metal area or all the coils are pressed on the non-metal area, and the group can reliably judge the coded information of the pattern; although at least one of the two sets of induction coils will sample non-ambiguous encoded information, it is necessary to establish a reliable selection mechanism and be the key for accurately obtaining encoded information, and a method for implementing the selector is described as follows:

let Ai be the signal amplitude obtained by the ith induction coil of the A group at the current position, and similarly define Bi; when i =1 to 7, that is, the group a has 7 induction coils, and the group B also has 7 induction coils, generally, the number of the group a and the group B induction coils is equal, and the number N is determined by the total length L of the absolute positioning address and the width Pitch of the unit code, and the relationship is as follows:

L＝Pitch*(2**N)

when the scale is designed, the sum of the widths of two adjacent induction coils (such as A1 and B1) of the group A and the group B is less than or equal to the unit width of codes on the scale, so that whether the reading head is at any position on the scale, at least one of the two adjacent induction coils does not fall into a fuzzy area, or the amplitude of at least one induced signal is accurate;

taking fig. 1 as an example, the read head has 14 induction coils, and the signal amplitudes of the 14 induction coils can be compared to find out the maximum value MAX and the minimum value MIN, which correspond to 1 and 0, respectively;

MAX＝Max(A1,A2,…A7,B1,B2,…B7)

MIN＝Min(A1,A2,…A7,B1,B2,…B7)

after finding MAX and MIN in this way, each sensing signal amplitude can be converted to a number between 0 and 1: namely, it is

Ai = (Ai-MIN)/(MAX-MIN), where i =1,N

Bi = (Bi-MIN)/(MAX-MIN), where i =1,N

The signal amplitude measurement of the induction coil needs signal amplification, filtering, and circuits or devices from analog quantity to digital quantity, and the specific implementation may have a certain difference, for example, sometimes the signal amplitude obtained by sampling analysis is 0.95, and in fact, it also corresponds to the code 1 pattern; the sampling analysis results in a signal amplitude of 0.1, which in fact also corresponds to a pattern code 0 pattern; the method needs to be capable of accommodating a certain measurement error; in engineering, a threshold mechanism can be established by adopting a statistical method, wherein the threshold mechanism is considered to be 1 between the threshold and 1, and the threshold mechanism is considered to be 0 between 0 and the threshold; specifically, the signal amplitudes of the plurality of induction coils corresponding to the pattern 1 encoded on the sampling scale at the plurality of non-blurred regions may be sampled, the signal amplitudes of the plurality of samplings form a set VH, and the maximum value VHmax and the minimum value VHmin may be found, so that the threshold corresponding to the amplitude 1 is

VH＝VHmin/VHmax

That is, the signal obtained by the induction coil between VH and 1 can be considered as 1;

correspondingly, the signal amplitudes of the induction coils corresponding to the pattern 0 encoded on the sampling scale at the positions of the non-fuzzy areas can be sampled, and the signal amplitudes VL of the non-fuzzy areas sampled for multiple times form a set to find the maximum value VLmax, so that the threshold corresponding to the amplitude 0 is

VL＝VHmax

That is, the signal obtained by the induction coil can be considered as 0 between VH and 1;

generally, this tolerance is reasonable at 10%, and the engineering design is easy to implement, which is described below as an example, i.e. the signal amplitude is greater than 0.9 and regarded as 1, and the signal amplitude is less than 0.1 and regarded as 0;

the signals obtained by a certain group of sensors are judged to be correct code values through a two-stage non-fuzzy code evaluation mechanism: the first stage, evaluating the group of scores V of the non-fuzzy codes by directly analyzing the signal amplitude of the corresponding induction coil, adding 1 to the group of scores V when the signal amplitude of a certain induction coil can be judged to be 1 or 0, and keeping the group of scores V unchanged when the signal amplitude of a certain coil cannot be determined to be 1 or 0, traversing all the coil signal amplitudes corresponding to the group by the method, and obtaining the total group of scores V;

in the first stage, by comparing the scores V of the group A and the group B, when the score V of the group B is large, the group B is selected, otherwise, the group A is selected;

on the basis of the first-stage judgment, a second stage is added to confirm the authenticity of the first-stage judgment;

setting the signal amplitude difference between any two adjacent induction coils in the same group as delta, wherein delta Ai is the absolute value of the difference between the signal amplitude of the i +1 th induction coil in the group A and the signal amplitude of the i-th induction coil in the group A:

Δ Ai = | Ai +1-Ai | wherein i =1,n-1

Similarly,. DELTA.Bi =. DELTA.Bi + 1-Bi. Where i =1,N-1

Observing the magnitude of this signal drop Δ, it can be seen that there are only two possibilities if the corresponding two induction coils do not fall within the ambiguity region:

the delta value is close to 1, namely the code values respectively detected by the two induction coils are different, one is 1, and the other is 0;

(II) the delta value is close to 0, namely the code values detected by the two induction coils are the same, and are either 1 or 0; if the two corresponding induction coils fall in the fuzzy area, the delta value is between 0 and 1, then the delta values corresponding to the group A and the group B can be compared, and the corresponding non-fuzzy code score V can be evaluated again, which is as follows:

if group a is selected in the first stage, Δ Ai and Δ Bi +1 continue to be compared,

if Δ Ai is greater than 0.5 and Δ Ai is greater than or equal to Δ Bi +1, the group A unambiguous code score V plus one,

otherwise, adding one to the B group non-fuzzy code score V;

if Δ Ai is less than 0.5 and Δ Ai is less than or equal to Δ Bi +1, the group a non-ambiguous code score V plus one,

otherwise, adding one to the B group non-fuzzy code score V;

if group B is selected in the first stage, Δ Ai and Δ Bi continue to be compared,

if Δ Bi is greater than 0.5 and Δ Bi is greater than or equal to Δ Ai, adding one to the B-group unambiguous code score V, otherwise, adding one to the a-group unambiguous code score V;

if Δ Bi is less than 0.5 and Δ Bi is less than or equal to Δ Ai +1, the B group non-ambiguous code score V plus one, otherwise, the A group non-ambiguous code score V plus one;

traversing all corresponding delta values to obtain corresponding total scores V of the non-fuzzy codes, and comparing the scores V of the group A and the group B, wherein when the score V of the group B is large, the group B is selected, otherwise, the group A is selected;

when the two-stage selection results are consistent, the set of measured code values is valid.

Has the advantages that: the invention can be manufactured by a circuit board process, has low production cost, adopts single code channel coding on the scale, has simple hardware and high reliability, does not need to add other code channels or measuring means, and can accurately and reliably eliminate the detection coil group of the fuzzy code by a two-stage evaluation mechanism to obtain the correct segment of coding information and the corresponding absolute position.

Drawings

FIG. 1 is a schematic scale of an absolute linear position locating device;

FIG. 2 shows the amplitude of the sampled signal and the analysis result of each set of induction coils when the device scale is in position;

FIG. 3 shows the amplitude of the sampled signal and the analysis result of each set of induction coils when the scale of the device is at the second position;

FIG. 4 shows the amplitude of the sampling signal and the analysis result of each set of induction coils when the scale of the device is at the third position;

FIG. 5 shows the amplitude of the sampled signal and the analysis result of each set of induction coils when the scale of the device is at the fourth position;

FIG. 6 is a schematic diagram of an apparatus and method for absolute linear position location.

Detailed Description

The first specific implementation way is as follows: referring to fig. 1, the present embodiment is specifically described, and the device and the method for absolute linear position positioning according to the present invention are mainly composed of a scale (1) and a reading head (2), as shown in fig. 1; the scale (1) is provided with a certain regular coding pattern, a pseudo-random code consisting of a plurality of '0's and '1's is generally adopted, the coding pattern '1' is made of metal, namely a metal area (11), and the coding pattern '0' is made of nonmetal, namely a nonmetal area (12);

the reading head (2) is provided with an exciting coil (3), a reading head circuit can generate exciting waves with alternating voltage, the exciting waves are transmitted to the scale (1) through the exciting coil (3), eddy currents are generated in a metal area (11) of a coding pattern of the scale (1) and electromagnetic waves are transmitted, the reading head (2) is correspondingly provided with two groups of a plurality of induction coils, each group is composed of 7 coils, namely A1-A7 and B1-B7, correspondingly induces electromagnetic waves generated on the scale (1), and a section of coding information in a corresponding area of the scale can be obtained by analyzing the amplitude of the induction voltage; when the metal pattern is correspondingly arranged on the scale below the induction coil, electromagnetic waves emitted by eddy currents in the metal pattern are received by the induction coil, and the signal amplitude is larger than a certain threshold value, the output is high level and is marked as '1'; on the contrary, when the corresponding nonmetal pattern on the scale below the induction coil is not received by the induction coil, and the signal amplitude is zero or less than a certain threshold, the output is low level, which is marked as "0"; taking the position of the reading head 2 in fig. 1 as an example, the segment read by the group a coils according to the sequence of A1, A2, A3, A4, A5, A6, A7 is encoded as 1011001; the group B coils can also obtain the segment code as 1011001. Then, a position of the segment code in the global code is obtained by using a table look-up or other matching method, so that the absolute position of the reading head can be determined.

The second embodiment is as follows: this embodiment is further illustrative of an absolute linear position positioning apparatus and method described in the first embodiment, and the scale (1) can be manufactured in various ways, one of which is a printed circuit board, where metal such as copper remains at the code pattern "1" and metal is removed by etching where the code pattern "0" remains. As shown in fig. 1, the corresponding code for scale 1 is 0101100101, which is understood to be a portion of the entire scale, which is considered herein to be an open head segment.

The third concrete implementation mode: this embodiment is to further explain an apparatus and a method for positioning an absolute linear position according to the first embodiment, in which a pseudo-random code uses a "shift register" in a computer algorithm, and determines that each position is a unique code by an algorithm of "shifting" a previous position and a subsequent position multiple times, and the absolute position of a reading head can be determined as long as a coding rule in a global position code does not have a repeated segment.

The fourth concrete implementation mode: this embodiment is a further description of the device and method for absolute linear position positioning described in the first embodiment, in which when a certain set of coils is pressed on the fuzzy area of the scale pattern, for example, when the reading head (2) is moved to the position shown in fig. 2, i.e., partially pressed on the metal area, and partially pressed on the non-metal area, the amplitude of the signal induced on the set of coils is between the code pattern "1" and the code pattern "0", the encoded information of the set of patterns cannot be reliably determined; at this time, the other group of coils a still falls on the non-fuzzy area of the pattern, i.e. all the coils are pressed on the metal area or all the coils are pressed on the non-metal area, and then the group can reliably judge that the coded information of the pattern is 1011001; although at least one of the two sets of induction coils will sample non-ambiguous encoded information, it is necessary to establish a reliable selection mechanism and be the key for accurately obtaining encoded information, and a method for implementing the selector is described as follows:

let Ai be the signal amplitude obtained by the ith induction coil of the A group at the current position, and similarly define Bi; when i =1 to 7, that is, the group a has 7 induction coils, and the group B also has 7 induction coils, generally, the number of the group a and the group B induction coils is equal, and the number N is determined by the total length L of the absolute positioning address and the width Pitch of the unit code, and the relationship is as follows:

L＝Pitch*(2**N)

when the scale is designed, the sum of the widths of two adjacent induction coils (such as A1 and B1) of the group A and the group B is less than or equal to the unit width of codes on the scale, so that whether the reading head is at any position on the scale, at least one of the two adjacent induction coils does not fall into a fuzzy area, or the amplitude of at least one induced signal is accurate;

taking fig. 1 as an example, the read head has 14 induction coils, and the signal amplitudes of the 14 induction coils can be compared to find out the maximum value MAX and the minimum value MIN, which correspond to 1 and 0, respectively;

MAX＝Max(A1,A2,…A7,B1,B2,…B7)

MIN＝Min(A1,A2,…A7,B1,B2,…B7)

after finding MAX and MIN in this way, each sense signal amplitude can be converted to a number between 0 and 1: namely, it is

Ai = (Ai-MIN)/(MAX-MIN), where i =1,N

Bi = (Bi-MIN)/(MAX-MIN), where i =1,N

The signal amplitude measurement of the induction coil needs signal amplification, filtering, and circuits or devices from analog quantity to digital quantity, and the specific implementation may have a certain difference, for example, sometimes the signal amplitude obtained by sampling analysis is 0.95, and in fact, it also corresponds to the code 1 pattern; the sampling analysis results in a signal amplitude of 0.1, which in fact also corresponds to a pattern code 0 pattern; the method needs to be capable of accommodating a certain measurement error; in engineering, a threshold mechanism can be established by adopting a statistical method, wherein the threshold mechanism is considered to be 1 between the threshold and 1, and the threshold mechanism is considered to be 0 between 0 and the threshold; specifically, the signal amplitudes of the plurality of induction coils corresponding to the pattern 1 encoded on the sampling scale at the plurality of non-blurred regions may be sampled, the signal amplitudes of the plurality of samplings form a set VH, and the maximum value VHmax and the minimum value VHmin may be found, so that the threshold corresponding to the amplitude 1 is

VH＝VHmin/VHmax

That is, the signal obtained by the induction coil between VH and 1 can be considered as 1;

correspondingly, the signal amplitudes of the induction coils corresponding to the pattern 0 encoded on the sampling scale at the positions of the non-fuzzy areas can be sampled, and the signal amplitudes VL of the non-fuzzy areas sampled for multiple times form a set to find the maximum value VLmax, so that the threshold corresponding to the amplitude 0 is

VL＝VHmax

That is, the signal obtained by the induction coil can be considered as 0 between VH and 1;

generally, this tolerance is reasonable at 10%, and the engineering design is easy to implement, which is described below as an example, i.e. the signal amplitude is greater than 0.9 and regarded as 1, and the signal amplitude is less than 0.1 and regarded as 0;

the signals obtained by a certain group of sensors are judged to be correct code values through a two-stage non-fuzzy code evaluation mechanism: the first stage, evaluating the group of scores V of the non-fuzzy codes by directly analyzing the signal amplitude of the corresponding induction coil, adding 1 to the group of scores V when the signal amplitude of a certain induction coil can be judged to be 1 or 0, and keeping the group of scores V unchanged when the signal amplitude of a certain coil cannot be determined to be 1 or 0, traversing all the coil signal amplitudes corresponding to the group by the method, and obtaining the total group of scores V;

in the first stage, by comparing the scores V of the group A and the group B, when the score V of the group B is large, the group B is selected, otherwise, the group A is selected;

on the basis of the first-stage judgment, a second stage is added to confirm the authenticity of the first-stage judgment;

setting the signal amplitude difference between any two adjacent induction coils in the same group as delta, wherein delta Ai is the absolute value of the difference between the signal amplitude of the i +1 th induction coil in the group A and the signal amplitude of the i-th induction coil in the group A:

Δ Ai = | Ai +1-Ai | where i =1, n-1

Similarly, Δ Bi = | Bi +1-Bi | where i =1,N-1

Observing the signal amplitude difference Δ, it can be seen that there are only two possibilities if the corresponding two induction coils do not fall into the ambiguity region:

the delta value is close to 1, namely the code values respectively detected by the two induction coils are different, one is 1, and the other is 0;

(II) the delta value is close to 0, namely the code values detected by the two induction coils are the same, and are either 1 or 0; if the two corresponding induction coils fall in the fuzzy area, the delta value is between 0 and 1, then the delta values corresponding to the group A and the group B can be compared, and the corresponding non-fuzzy code score V can be evaluated again, which is as follows:

if group a is selected in the first stage, Δ Ai and Δ Bi +1 continue to be compared,

if Δ Ai is greater than 0.5 and Δ Ai is greater than or equal to Δ Bi +1, group a non-ambiguous code score V plus one,

otherwise, adding one to the scores V of the B group of non-fuzzy codes;

if Δ Ai is less than 0.5 and Δ Ai is less than or equal to Δ Bi +1, the group A unambiguous code score V plus one,

otherwise, adding one to the B group non-fuzzy code score V;

if group B is selected in the first stage, Δ Ai and Δ Bi continue to be compared,

if Δ Bi is greater than 0.5 and Δ Bi is greater than or equal to Δ Ai, adding one to the B-group unambiguous code score V, otherwise, adding one to the a-group unambiguous code score V;

if Δ Bi is less than 0.5 and Δ Bi is less than or equal to Δ Ai +1, the B group non-ambiguous code score V plus one, otherwise, the A group non-ambiguous code score V plus one;

traversing all corresponding delta values to obtain corresponding total scores V of the non-fuzzy codes, and comparing the scores V of the group A and the group B, wherein when the score V of the group B is large, the group B is selected, otherwise, the group A is selected;

when the two-stage selection results are consistent, the set of measured code values is valid.

The fifth concrete implementation mode is as follows: the present embodiment is further described with reference to the device and method for positioning an absolute linear position described in the fourth embodiment, and as shown in fig. 2 to 6, feasibility analysis is performed on the sampled signal amplitudes and results of each set of the induction coils at the first position, the second position, the third position, and the fourth position, respectively, and the results of simulation analysis on several typical positions can be determined according to the table in the figure.

Claims (4)

1. An absolute position-to-line positioning device and method is characterized in that the device mainly comprises a scale (1) and a reading head (2); the scale (1) is provided with a regular coding pattern, a pseudo random code consisting of a plurality of '0's and '1's is generally adopted, the coding pattern '1' is made of metal, namely a metal area (11), and the coding pattern '0' is made of nonmetal, namely a nonmetal area (12);

the reading head (2) is provided with an exciting coil (3), a reading head circuit can generate exciting waves with alternating voltage, the exciting waves are transmitted to the scale (1) through the exciting coil (3), eddy currents are generated in a metal area (11) of a coding pattern of the scale (1) and electromagnetic waves are transmitted, the reading head (2) is correspondingly provided with two groups of a plurality of induction coils, each group can be composed of but not limited to 7 coils, namely A1-A7 and B1-B7, the electromagnetic waves generated on the scale (1) are correspondingly induced, and a section of coding information in the corresponding area of the scale can be obtained by analyzing the amplitude of the induction voltage; when the metal pattern is correspondingly arranged on the scale below the induction coil, electromagnetic waves emitted by eddy currents in the metal pattern are received by the induction coil, and the signal amplitude is greater than a certain threshold value, the output is high level and is marked as '1'; otherwise, when the corresponding non-metal pattern on the scale below the induction coil is not received by the induction coil and the signal amplitude is zero or less than a certain threshold, the output is a low level, and is marked as '0'; the position of the segment code in the global title is then obtained using a look-up table or other matching method, so that the absolute position of the reading head can be determined.

2. An absolute linear position positioning device and method according to claim 1, characterized in that the scale (1) can be manufactured in many ways, one of which is a printed circuit board, where metal such as copper remains at the coding pattern "1" and where the coding pattern "0" is etched away.

3. An absolute linear position locating device and method according to claim 1, characterized in that the pseudo random code uses the "shift register" in the computer algorithm, and each position is determined to be a unique code by the algorithm of "shifting" the previous position and the next position several times, so long as the coding rule in the global code does not have the repeated segment, the absolute position of the reading head can be determined.

4. The apparatus and method for absolute linear position location according to claim 1, wherein when a set of coils is pressed on the fuzzy region of the scale pattern, i.e. partially on the metal region and partially on the non-metal region, the amplitude of the signal induced on the set of coils is between the code pattern "1" and the code pattern "0", the code information of the set of patterns cannot be reliably judged; at this time, the other group of coils still falls on the non-fuzzy area of the pattern, namely all the coils are pressed on the metal area or all the coils are pressed on the non-metal area, and the group can reliably judge the coded information of the pattern; although at least one of the two groups of induction coils must sample non-fuzzy coding information, a reliable selection mechanism needs to be established and is also the key for accurately obtaining coding information, and a method for realizing the selector is introduced as follows:

let A _i Similarly define B for the amplitude of the signal obtained at the current position for the ith induction coil of group A _i (ii) a When i =1 to 7, that is, the group a has 7 induction coils, and the group B also has 7 induction coils, generally, the number of the group a and the group B induction coils is equal, and the number N is determined by the total length L of the absolute positioning address and the width Pitch of the unit code, and the relationship is as follows:

L＝Pitch*(2**N)

when the scale is designed, the sum of the widths of two adjacent induction coils (such as A1 and B1) of the group A and the group B is less than or equal to the unit width of codes on the scale, so that whether the reading head is at any position on the scale, at least one of the two adjacent induction coils does not fall into a fuzzy area, or the amplitude of at least one induced signal is accurate;

taking fig. 1 as an example, the read head has 14 induction coils, and the signal amplitudes of the 14 induction coils can be compared to find out the maximum value MAX and the minimum value MIN, which correspond to 1 and 0, respectively;

MAX＝Max(A1,A2,…A7,B1,B2,…B7)

MIN＝Min(A1,A2,…A7,B1,B2,…B7)

after finding MAX and MIN in this way, each sensing signal amplitude can be converted to a number between 0 and 1: i.e., ai = (Ai-MIN)/(MAX-MIN), where i =1,n

Bi = (Bi-MIN)/(MAX-MIN), where i =1,N

The signal amplitude measurement of the induction coil needs signal amplification, filtering, and circuits or devices from analog quantity to digital quantity, and the specific implementation may have a certain difference, for example, sometimes the signal amplitude obtained by sampling analysis is 0.95, and in fact, it also corresponds to the code 1 pattern; the sampling analysis results in a signal amplitude of 0.1, which in fact also corresponds to a pattern code 0 pattern; the method needs to be capable of accommodating a certain measurement error; in engineering, a threshold mechanism can be established by adopting a statistical method, wherein the threshold mechanism is considered to be 1 between the threshold and 1, and the threshold mechanism is considered to be 0 between 0 and the threshold; specifically, the signal amplitudes of the plurality of induction coils corresponding to the pattern 1 encoded on the sampling scale at the plurality of non-blurred regions may be sampled, the signal amplitudes of the plurality of samplings form a set VH, and the maximum value VHmax and the minimum value VHmin may be found, so that the threshold corresponding to the amplitude 1 is

VH＝VHmin/VHmax

That is, the signal obtained by the induction coil between VH and 1 can be considered as 1;

correspondingly, the signal amplitudes of the induction coils corresponding to the pattern 0 encoded on the sampling scale at the positions of the non-fuzzy areas can be sampled, and the signal amplitudes VL of the non-fuzzy areas sampled for multiple times form a set to find the maximum value VLmax, so that the threshold corresponding to the amplitude 0 is

VL＝VHmax

That is, the signal obtained by the induction coil can be considered as 0 between VH and 1;

generally, this tolerance is reasonable at 10%, and the engineering design is easy to implement, which is described below as an example, i.e. the signal amplitude is greater than 0.9 and regarded as 1, and the signal amplitude is less than 0.1 and regarded as 0;

the signals obtained by a certain group of sensors are judged to be correct code values through a two-stage non-fuzzy code evaluation mechanism: the first stage, evaluating the group of scores V of the non-fuzzy codes by directly analyzing the signal amplitude of the corresponding induction coil, adding 1 to the group of scores V when the signal amplitude of a certain induction coil can be judged to be 1 or 0, and keeping the group of scores V unchanged when the signal amplitude of a certain coil cannot be determined to be 1 or 0, traversing all the coil signal amplitudes corresponding to the group by the method, and obtaining the total group of scores V;

in the first stage, the scores V of the group A and the group B are compared, when the score V of the group B is large, the group B is selected, otherwise, the group A is selected;

on the basis of the first-stage judgment, a second stage is added to confirm the authenticity of the first-stage judgment;

setting the signal amplitude difference between any two adjacent induction coils in the same group as delta, wherein delta Ai is the absolute value of the difference between the signal amplitude of the i +1 th induction coil in the group A and the signal amplitude of the i-th induction coil in the group A:

Δ Ai = | Ai +1-Ai | where i =1, n-1

Similarly,. DELTA.Bi =. DELTA.Bi + 1-Bi. Where i =1,N-1

Observing the magnitude of this signal drop Δ, it can be seen that there are only two possibilities if the corresponding two induction coils do not fall within the ambiguity region:

the delta value is close to 1, namely the code values respectively detected by the two induction coils are different, one is 1, and the other is 0;

(II) the delta value is close to 0, namely the code values detected by the two induction coils are the same, and are either 1 or 0; if the two corresponding induction coils fall in the fuzzy area, the delta value is between 0 and 1, then the delta values corresponding to the group A and the group B can be compared, and the corresponding non-fuzzy code score V can be evaluated again, which is as follows:

if group A is selected in the first stage, continue to compare Δ Ai to Δ Bi +1,

if Δ Ai is greater than 0.5 and Δ Ai is greater than or equal to Δ Bi +1, group a non-ambiguous code score V plus one,

otherwise, adding one to the B group non-fuzzy code score V;

if Δ Ai is less than 0.5 and Δ Ai is less than or equal to Δ Bi +1, the group A unambiguous code score V plus one,

otherwise, adding one to the B group non-fuzzy code score V;

if group B is selected in the first stage, Δ Ai and Δ Bi continue to be compared,

if Δ Bi is greater than 0.5 and Δ Bi is greater than or equal to Δ Ai, the B group non-ambiguous code scores V plus one, otherwise, the a group non-ambiguous code scores V plus one;

if Δ Bi is less than 0.5 and Δ Bi is less than or equal to Δ Ai +1, the B group non-ambiguous code score V plus one, otherwise, the A group non-ambiguous code score V plus one;

traversing all corresponding delta values to obtain corresponding total scores V of the non-fuzzy codes, and comparing the scores V of the group A and the group B, wherein when the score V of the group B is large, the group B is selected, otherwise, the group A is selected;

when the two-stage selection results are consistent, the set of measured code values is valid.

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