Patent Publication Number: US-2023140330-A1

Title: Angle measurement system based on magnetic method and measurement method therefor

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to an angle measurement system based on a magnetic method and a measurement method therefor. 
     Description of the Related Art 
     An angle measurement system based on a magnetic method is a system for measuring an angle of a magnet attached to a rotor of a motor. In this case, the magnet provided with two tracks TR 1  and TR 2  may be used in order to increase resolution of angle measurement. A magnetic encoder may include a magnet and an angle measurement system that measures an angle according to rotation of the magnet. 
       FIG.  1    is an explanatory view of an angle measurement system based on a magnetic method and provided with two tracks TR 1  and TR 2 . An encoder chip C is preferably attached while having a gap with respect to the magnet provided with the two annular tracks TR 1  and TR 2 . In addition, the encoder chip C includes sensors H 1  and H 2  capable of measuring a magnetic field of each of the two tracks TR 1  and TR 2 . 
     When a motor rotates, the magnetic fields change, and angle information according to the rotation of the magnet, that is, rotation angles of the motor, may be measured by measuring the changed magnetic fields by the sensors H 1  and H 2 . 
     SUMMARY OF THE INVENTION 
     The present disclosure is devised in order to solve the technical problems as described above, and an objective of the present disclosure is to provide an angle measurement system based on a magnetic method and a measurement method therefor capable of measuring an absolute angle at a time when a motor is stopped and/or rotated with high resolution. 
     An angle measurement system configured to use a magnet and provided with a first track and a second track is configured to include an absolute angle calculation unit for calculating an absolute angle of a position of the magnet by using a 1-1th digital signal obtained by measuring a magnetic field signal of the first track and converted into a digital signal, a 1-2th digital signal obtained by measuring the magnetic field signal of the first track and converted into a digital signal, a 2-1th digital signal obtained by measuring a magnetic field signal of the second track and converted into a digital signal, and a 2-2th digital signal obtained by measuring the magnetic field signal of the second track and converted into a digital signal. In addition, the 1-1th digital signal and the 1-2th digital signal are sinusoidal signals having a phase difference of 90 degrees from each other, and the 2-1th digital signal and the 2-2th digital signal are sinusoidal signals having a phase difference of 90 degrees from each other. 
     An absolute angle of the position of the magnet may be configured to include at least one piece of data including: main section values obtained by dividing one rotation of 360 degrees of the magnet into a first main section to a fourth main section, which are four 90 degree sections; sub-section values obtained by dividing each of the first main section to the fourth main section into a plurality of sections by a value using the phase difference between the magnetic field signal of the first track and the magnetic field signal of the second track; first signal section values obtained by dividing the magnetic field signal of the first track into four first signal sections by using a sign of the 1-1th digital signal and a sign of the 1-2th digital signal; and lower section values calculated by the 1-1th digital signal and the 1-2th digital signal for each first signal section value. 
     Specifically, the absolute angle calculation unit may be configured to include: a main section value calculator for calculating main section values that divides one rotation of 360 degrees of the magnet into the first main section to the fourth main section, which are the four 90 degree sections; an angle output part for outputting absolute angle data of a position of the magnet comprising the main section values; a first signal section value calculator for calculating first signal section values obtained by dividing the magnetic field signal of the first track into four first signal sections by using a sign of the 1-1th digital signal and a sign of the 1-2th digital signal; and a lower section value calculator for calculating lower section values by the 1-1th digital signal and the 1-2th digital signal for each first signal section value. 
     In addition, the absolute angle calculation unit may be configured to further include: a first difference value calculator for calculating a 1-1th difference value to 1-4th difference value, which are values each embedding the phase difference between the magnetic field signal of the first track and the magnetic field signal of the second track by using the 1-1th digital signal, the 1-2th digital signal, the 2-1th digital signal, and the 2-2th digital signal; a data converter for converting each of the 1-1th difference value to the 1-4th difference value into a 1-1th signed difference value to a 1-4th signed difference value, which are signed values; and a shift difference value calculator for calculating a 1-1th shift difference value to a 1-4th shift difference value, which are obtained by phase shifting each of the 1-1th difference value to the 1-4th difference value by 45 degrees by using a plurality of the 1-1th signed difference value to the 1-4th signed difference value. 
     The main section values may be calculated by using values each embedding the phase difference between the magnetic field signal of the first track and the magnetic field signal of the second track. 
     In addition, the absolute angle calculation unit may be configured to further include a sub-section value calculator for calculating sub-section values corresponding one of the 1-1th shift difference value to the 1-4th shift difference value to a 1-1th sub-section to a 1-Mth sub-section for each main section value. 
     In addition, the absolute angle calculation unit may be configured to further include: a first shift section value calculator for calculating a first signal section value shifted by one section by shifting the first signal section value by one first signal section in a first direction; a second shift section value calculator for calculating a first signal section value shifted by two sections by shifting the first signal section value by two first signal sections in the first direction; and a third shift section value calculator for calculating a first signal section value shifted by three sections by shifting the first signal section value by three first signal sections in the first direction, wherein the first direction is either a left direction or a right direction of a register used as the first signal section value calculator. 
     In addition, the absolute angle calculation unit may be configured to further include: a first signal section period calculator for calculating, by using the first signal section values, a first signal section period in which the four first signal sections are repeated; a second signal section value calculator for calculating second signal section values divided into four second signal sections by using a sign of the 2-1th digital signal and a sign of the 2-2th digital signal; and a second difference value calculator for calculating each second difference value that is a difference of a change point between the corresponding first signal section value and the second signal section value by sequentially using one of the unshifted first signal section value, the first signal section value shifted by one section, the first signal section value shifted by two sections, and the first signal section value shifted by three sections, wherein the main section values are calculated by using the second difference values. 
     The absolute angle calculation step may be configured to further include a sub-section value calculator for calculating sub-section values respectively corresponding the first main section to the fourth main section into P sections of a 2-1th sub-section to a 2-Pth sub-section by using a value obtained by dividing the second difference values by the first signal section period. 
     According to the angle measurement system based on the magnetic method and the measurement method therefor of the present disclosure, the absolute angle at the time when the motor is stopped and/or rotated may be measured with the high resolution. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is an explanatory view of an angle measurement system based on a magnetic method and provided with two tracks. 
         FIG.  2    is a block diagram illustrating the angle measurement system based on the magnetic method according to an exemplary embodiment. 
         FIG.  3    is a block diagram illustrating an absolute angle calculation unit according to a first exemplary embodiment. 
         FIG.  4    is an explanatory view illustrating first signal section values. 
         FIG.  5    illustrates waveform diagrams of a 1-1th difference value to a 1-4th difference value, a 1-1th signed difference value to a 1-4th signed difference value, and a 1-1th shift difference value to a 1-4th shift difference value. 
         FIG.  6    is an explanatory view illustrating sub-section values. 
         FIG.  7    is a block diagram illustrating an absolute angle calculation unit according to a second exemplary embodiment. 
         FIG.  8    is an explanatory view illustrating a first signal section value calculator, a first shift section value calculator, a second shift section value calculator, and a third shift section value calculator. 
         FIG.  9    is an explanatory view illustrating a process of calculating second difference values. 
         FIG.  10    is a waveform diagram illustrating a result of the calculated second difference values. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, an angle measurement system based on a magnetic method and a measurement method therefor according to an exemplary embodiment of the present disclosure is described in detail with reference to the accompanying drawings. 
     Naturally, it is apparent that the following exemplary embodiment of the present disclosure are not intended to limit or restrict the scope of the present disclosure, but only to embody the present disclosure. What can be easily inferred by those skilled in the art to which the present disclosure pertains from the detailed description and examples of the present disclosure is construed as belonging to the scope of the present disclosure. 
     The angle measurement system based on the magnetic method is a system for measuring an angle of a magnet attached to a rotor of a motor. In this case, in order to increase resolution used to measure the angles, the magnet provided with two annular tracks TR 1  and TR 2  as shown in  FIG.  1    may be used. A magnetic encoder may include the magnet and the angle measurement system that measures the angle according to the rotation of the magnet. 
     That is, preferably, the magnet used in the magnetic encoder for measuring the angle of the present disclosure includes: a first track TR 1  of an annular shape in which N poles and S poles are alternately and repeatedly connected to each other; and a second track TR 2  of an annular shape foamed to contact with an inner side or an outer side of the first track TR 1  and provided with a plurality of unit poles connected to each other. Alternatively, the second track TR 2  may be configured in a form in contact with an upper side or a lower side of the first track TR 1 . 
     In addition, each of the plurality of unit poles is the same size and has one polarity of a plurality of polarities including an N pole and a S pole. That is, each of the unit poles may be the N pole or the S pole. 
     However, unlike  FIG.  1   , in the magnet used in the magnetic encoder for measuring the angle of the present disclosure, it is preferable that the number of pairs of N poles and S poles included in each of the two tracks TR 1  and TR 2  differs, so that after a point where an N pole and a S pole in each of the two tracks TR 1  and TR 2  coincide is passed, the N poles and the S poles in the two tracks TR 1  and TR 2  are configured to be gradually shifted from alignment as an angle increases. 
     Specifically, in the magnet used in the magnetic encoder for measuring the angle of the present disclosure, in a case where U numbers of pairs of N poles and S poles are alternately and repeatedly connected to each other in the first track TR 1  and W numbers of pairs of N poles and S poles are alternately and repeatedly connected to each other in the second track TR 1 , when the number U and the number W are different from each other, unit pole positions of the N poles or S poles of the first track TR 1  and second track TR 2  are slightly shifted from each other according to the rotation of the motor, and thus a phase difference occurs between a magnetic field signal of the first track TR 1  and a magnetic field signal of the second track TR 2 . For reference, the first track TR 1  and the second track TR 2  may be designed respectively as in a case where the number U is 32 and the number W is 31. 
       FIG.  2    is a block diagram illustrating the angle measurement system  1000  based on the magnetic method according to the exemplary embodiment. The angle measurement system  1000  based on the magnetic method according to the exemplary embodiment may be implemented in a form of the encoder chip C shown in  FIG.  1   . 
     As may be seen from  FIG.  2   , the angle measurement system  1000  based on the magnetic method according to the exemplary embodiment is configured to include a sensor device  100  and an angle measurement device  200 . 
     The sensor device  100  may be configured to include at least one 1-1th sensor H 11 , at least one 1-2th sensor H 12 , at least one 2-1th sensor H 21 , and at least one 2-2th sensor H 22 . 
     Various magnetic sensors such as a Hall sensor, a magnetoresistive element, and the like may be used for the at least one 1-1th sensor H 11 , at least one 1-2th sensor H 12 , at least one 2-1th sensor H 21 , and at least one 2-2th sensor H 22 , which are included in the sensor device  100 . 
     Each of the at least one 1-1th sensor H 11  and the at least one 1-2th sensor H 12  measures the magnetic field signal of the first track TR 1 . In this case, when it is assumed that the at least one 1-1th sensor H 11  measures the magnetic field signal of the first track TR 1  in response to a sine signal, the at least one 1-2th sensor H 12  may measure the magnetic field signal of the first track TR 1  in response to a cosine signal. That is, an output of the at least one 1-1th sensor H 11  and an output of the at least one 1-2th sensor H 12  are sinusoidal signals, and the at least one 1-1th sensor H 11  and the at least one 1-2th sensor H 12  may be arranged so as to have a phase difference of 90 degrees from each other. 
     For reference, when the magnetic field signal of the first track TR 1  is measured in a form of a sine signal and a cosine signal, it is preferable that two 1-1th sensors H 11  and two 1-2th sensors H 12  are arranged respectively when differential signals are used in the angle measurement device  200 . 
     Similarly, each of at least one 2-1th sensor H 21  and at least one 2-2th sensor H 22  measures a magnetic field signal of the second track TR 2 . In this case, when it is assumed that the at least one 2-1th sensor H 21  measures the magnetic field signal of the second track TR 2  in response to a sine signal, the at least one 2-2th sensor H 22  may measure the magnetic field signal the second track TR 2  in response to a cosine signal. That is, an output of the at least one 2-1th sensor H 21  and an output of the at least one 2-2th sensor H 22  are sinusoidal signals, and the at least one 2-1th sensor H 21  and the at least one 2-2th sensor H 22  may be arranged so as to have a phase difference of 90 degrees. 
     For reference, when the magnetic field signal of the second track TR 2  is measured in the form of a sine signal and a cosine signal, it is preferable that two 2-1th sensor H 21  and two 2-2th sensors H 22  are arranged respectively when the differential signals are used in the angle measurement device  200 . 
     The angle measurement device  200  may be configured to include an analog-to-digital conversion unit  210  and absolute angle calculation units  230   a  and  230   b . Each of the analog-to-digital conversion unit  210  and the absolute angle calculation units  230   a  and  230   b  may be configured to include at least one of a circuit, a processor, and a memory. 
     The analog-to-digital conversion unit  210  serves to receive an input of analog signals that are outputs of a plurality of sensors H 11  and H 12  to convert the input analog signals to digital signals of a 1-1th digital signal and a 1-2th digital signal, thereby outputting the digital signals. In addition, The analog-to-digital conversion unit  210  serves to receive an input of analog signals that are outputs of a plurality of sensors H 21  and H 22  to convert the input analog signals to digital signals of a 2-1th digital signal and a 2-2th digital signal, thereby outputting the digital signals. The analog-to-digital conversion unit  210  may be provided with a separate analog-to-digital converter for each of the 1-1th digital signal, the 1-2th digital signal, the 2-1th digital signal, and the 2-2th digital signal. Alternatively, in one analog-to-digital converter, the analog-to-digital conversion unit  210  may share the analog-to-digital converter in a way of converting the plurality of the 1-1th digital signal, the 1-2th digital signal, the 2-1th digital signal, and the 2-2th digital signal by using a multiplexer. 
     Specifically, the analog-to-digital conversion unit  210  serves to receive the input of the analog signals of the output of the at least one 1-1th sensor H 11  and the output of the at least one 1-2th sensor H 12 , which respectively measure the magnetic field signal of the first track TR 1 , convert the input analog signals to the digital signals of the 1-1th digital signal and the 1-2th digital signal, and output the digital signals. In addition, the 1-1th digital signal and the 1-2th digital signal are sinusoidal signals and have a phase difference of 90 degrees from each other. 
     Similarly, the analog-to-digital conversion unit  210  serves to receive the input of the analog signals of the output of the at least one 2-1th sensor H 21  and the output of the at least one 2-2th sensor H 22 , which respectively measure the magnetic field signal of the second track TR 2 , convert the input analog signals to the digital signals of the 2-1 digital signal and the 2-2 digital signal, and output the digital signals. In addition, the 2-1th digital signal and the 2-2th digital signal are sinusoidal signals and have a phase difference of 90 degrees from each other. 
     The absolute angle calculation units  230   a  and  230   b  serve to calculate an absolute angle of a position of the magnet by using the 1-1th digital signal, the 1-2th digital signal, the 2-1th digital signal, and the 2-2th digital signal. The absolute angle of the position of the magnet refers to an angle rotated from a reference position of the magnet. 
     The absolute angle of the position of the magnet is configured to include at least one piece of data, including: main section values obtained by dividing one rotation of 360 degrees of the magnet into four 90 degree sections, which are a first main section to a fourth main section; sub-section values obtained by dividing each of the first main section to the fourth main section into a plurality of sections by a value using a phase difference between a magnetic field signal of a first track and a magnetic field signal of a second track; first signal section values obtained by dividing the magnetic field signal of the first track into four first signal sections by using a sign of a 1-1th digital signal and a sign of a 1-2th digital signal; and lower section values calculated by the 1-1th digital signal and the 1-2th digital signal for each of the first signal section values. 
       FIG.  3    is a block diagram illustrating an absolute angle calculation unit  230   a  according to a first exemplary embodiment. 
     As may be seen from  FIG.  3   , the absolute angle calculation unit  230   a  according to the first exemplary embodiment may be configured to include a main section value calculator  231   a , a first signal section value calculator  232   a , a first difference value calculator  233   a , a data converter  234   a , a shift difference value calculator  235   a , a sub-section value calculator  237   a , a lower section value calculator  238   a , and an angle output part  239   a.    
     For reference, the absolute angle calculation unit  230   a  according to the first exemplary embodiment may be used to calculate a rotation angle of a motor at a stopped position when the rotation of the motor is stopped. 
     The main section value calculator  231   a  calculates the main section values for dividing one rotation of 360 degrees of the magnet into a first main section to a fourth main section, which are four 90 degree sections. For reference, the main section values may be calculated by various methods. 
     In addition, the first signal section value calculator  232   a  uses a sign of a 1-1th digital signal and a sign of a 1-2th digital signal, so as to calculate first signal section values obtained by dividing the magnetic field signal of the first track TR 1  into four first signal sections. 
       FIG.  4    is an explanatory view illustrating the first signal section values. 
     As may be seen from  FIG.  4   , the first signal section values are values obtained by dividing the magnetic field signal of the first track TR 1  into four first signal sections by using, i.e., combining, the sign of the 1-1th digital signal and the sign of the 1-2th digital signal. 
     For example, in a case where it is assumed that a first signal section value is set as a 2-bit signal, the first signal section value may be set to “00” when a sign of a 1-1th digital signal and a sign of a 1-2th digital signal are both positive numbers, and the first signal section value may be set as “01” when the sign of the 1-1th digital signal and the sign of the 1-2th digital signal are respectively positive and negative. Similarly, the first signal section value may be set to “10” when the sign of the 1-1th digital signal and the sign of the 1-2th digital signal are both negative numbers, and the first signal section value may be set as “11” when the sign of the 1-1th digital signal and the sign of the 1-2th digital signal are respectively negative and positive. 
     The first difference value calculator  233   a  may calculate a 1-1th difference value to a 1-4th difference value as respective unsigned values, by using the 1-1th digital signal, the 1-2th digital signal, the 2-1 digital signal, and the 2-2 digital signal. 
     The 1-1th difference value to the 1-2th difference value may be calculated by a preset [Equation 1]. 
         P (1−1)={SIN(α)−SIN(β)} 2 +{COS(α)−COS(β)} 2  
 
         P (1−2)={SIN(α)−SIN(β)} 2 +{COS(α)−COS(β_ B )} 2    [Equation 1]
 
     In Equation 1, P(1−1) to P(1−2) respectively represent a 1-1th difference value to a 1-2th difference value, SIN(α) represents a 1-1th digital signal, COS(α) represents a 1-2th digital signal, SIN(β) represents a 2-1th digital signal, cos(β) represents a second digital signal, and β_B represents an inverted signal of β, that is, −β. 
     In addition, the 1-3th difference value is a signal obtained by inverting the 1-1th difference value, and the 1-4th difference value is a signal obtained by inverting the 1-2th difference value. That is, the 1-1th difference value to the 1-4th difference value are values each having a phase difference by 90 degrees in turn. 
     For reference, when a trigonometric equation is used, the 1-1th difference value may be expressed as in Equation 2 below. 
     
       
         
           
             
               
                 
                   
                     P 
                     ⁡ 
                     ( 
                     
                       1 
                       - 
                       1 
                     
                     ) 
                   
                   = 
                   
                     
                       
                         
                           { 
                           
                             
                               SIN 
                               ⁡ 
                               ( 
                               α 
                               ) 
                             
                             - 
                             
                               SIN 
                               ⁡ 
                               ( 
                               β 
                               ) 
                             
                           
                           } 
                         
                         2 
                       
                       + 
                       
                         
                           { 
                           
                             
                               COS 
                               ⁡ 
                               ( 
                               α 
                               ) 
                             
                             - 
                             
                               COS 
                               ⁡ 
                               ( 
                               β 
                               ) 
                             
                           
                           } 
                         
                         2 
                       
                     
                     = 
                     
                       
                         
                           
                             SIN 
                             2 
                           
                           ( 
                           α 
                           ) 
                         
                         - 
                         
                           2 
                           ⁢ 
                           
                             SIN 
                             ⁡ 
                             ( 
                             α 
                             ) 
                           
                           ⁢ 
                           
                             SIN 
                             ⁡ 
                             ( 
                             β 
                             ) 
                           
                         
                         + 
                         
                           
                             SIN 
                             2 
                           
                           ( 
                           β 
                           ) 
                         
                         + 
                         
                           
                             COS 
                             2 
                           
                           ( 
                           α 
                           ) 
                         
                         - 
                         
                           2 
                           ⁢ 
                           
                             COS 
                             ⁡ 
                             ( 
                             α 
                             ) 
                           
                           ⁢ 
                           
                             COS 
                             ⁡ 
                             ( 
                             β 
                             ) 
                           
                         
                         + 
                         
                           
                             COS 
                             2 
                           
                           ( 
                           β 
                           ) 
                         
                       
                       = 
                       
                         
                           2 
                           - 
                           
                             2 
                             ⁢ 
                             
                               { 
                               
                                 
                                   
                                     COS 
                                     ⁡ 
                                     ( 
                                     α 
                                     ) 
                                   
                                   ⁢ 
                                   
                                     COS 
                                     ⁡ 
                                     ( 
                                     β 
                                     ) 
                                   
                                 
                                 + 
                                 
                                   
                                     SIN 
                                     ⁡ 
                                     ( 
                                     α 
                                     ) 
                                   
                                   ⁢ 
                                   
                                     SIN 
                                     ⁡ 
                                     ( 
                                     β 
                                     ) 
                                   
                                 
                               
                               } 
                             
                           
                         
                         = 
                         
                           2 
                           ⁢ 
                           
                             { 
                             
                               1 
                               - 
                               
                                 COS 
                                 ⁡ 
                                 ( 
                                 
                                   α 
                                   - 
                                   β 
                                 
                                 ) 
                               
                             
                             } 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     2 
                   
                   ] 
                 
               
             
           
         
       
     
     As may be seen from [Equation 2], each of the 1-1th difference value to the 1-4th difference value is a value embedding (α-β), which is a phase difference between a magnetic field signal of the first track TR 1  and a magnetic field signal of the second track TR 2 . 
     The data converter  234   a  serves to convert each of the 1-1th difference value to the 1-4th difference value into the 1-1th signed difference value to the 1-4th signed difference value, which are signed values. 
     Specifically, each of the 1-1th signed difference value to the 1-4th signed difference value may be calculated as in Equation 3 below. 
       SignP(1−1)= P (1−1)− P 1(SUM)
 
       SignP(1−2)= P (1−2)− P 1(SUM)
 
       SignP(1−3)= P (1−3)− P 1(SUM)
 
       SignP(1−4)= P (1−4)− P 1(SUM)  [Equation 3]
 
     In [Equation 3], SignP(1−1) to SignP(1−4) respectively represent a 1-1th signed difference value to 1-4th signed difference value, P(1−3) represents a 1-3th difference value, P(1−4) represents a 1-4th difference value, and P1(SUM) may be expressed as in Equation 4 below. 
     
       
         
           
             
               
                 
                   
                     P 
                     ⁢ 
                     1 
                     ⁢ 
                     
                       ( 
                       SUM 
                       ) 
                     
                   
                   = 
                   
                     
                       1 
                       4 
                     
                     ⁢ 
                     
                       { 
                       
                         
                           P 
                           ⁡ 
                           ( 
                           
                             1 
                             - 
                             1 
                           
                           ) 
                         
                         + 
                         
                           P 
                           ⁡ 
                           ( 
                           
                             1 
                             - 
                             2 
                           
                           ) 
                         
                         + 
                         
                           P 
                           ⁡ 
                           ( 
                           
                             1 
                             - 
                             3 
                           
                           ) 
                         
                         + 
                         
                           P 
                           ⁡ 
                           ( 
                           
                             1 
                             - 
                             4 
                           
                           ) 
                         
                       
                       } 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                         
                     4 
                   
                   ] 
                 
               
             
           
         
       
     
     The shift difference value calculator  235   a  calculates a 1-1th shift difference value to a 1-4th shift difference value, which are obtained by phase shifting each of the 1-1th difference value to the 1-4th difference value by 45 degrees by using a plurality of the 1-1th signed difference value to the 1-4th signed difference value. 
     Specifically, the 1-1th shift difference value to the 1-4th shift difference value may be calculated as in Equation 5 below. 
       ShiftP(1−1)=SignP(1−4)−SignP(1−3)
 
       ShiftP(1−2)=SignP(1−4)−SignP(1−3)
 
       ShiftP(1−3)=SignP(1−4)−SignP(1−3)
 
       ShiftP(1−4)=SignP(1−4)−SignP(1−3)   [Equation 5]
 
     In Equation 5, ShiftP(1−1) to ShiftP(1−4) respectively represent a 1-1th shift difference value to a 1-4th shift difference value. In addition, B SignP(1−4) represents a value obtained by inverting the 1-4th signed difference value. 
       FIG.  5    illustrates waveform diagrams of the 1-1th difference value to the 1-4th difference value, the 1-1th signed difference value to the 1-4th signed difference value, and the 1-1th shift difference value to the 1-4th shift difference value, which are respectively calculated by the first difference value calculator  233   a , the data converter  234   a , and the shift difference value calculator  235   a.    
     As may be seen from  FIG.  5   , each of the 1-1th difference value to the 1-4th difference value has a maximum value at 90 degrees, 180 degrees, 270 degrees, and 360 degrees during one rotation of 360 degrees of the magnet, and appears in the form of a sine wave with a period of 360 degrees. 
     For reference, the main section values may be calculated by using values calculated by using the 1-1th difference value to the 1-4th difference value. Specifically, the main section values may be calculated by using the 1-1th signed difference value to the 1-4th signed difference value, which are the values using the 1-1th difference value to the 1-4th difference value. However, each of the 1-1th signed difference value to the 1-4th signed difference value also include a phase difference between the magnetic field signal of the first track TR 1  and the magnetic field signal of the second track TR 2 . That is, the main sections value may be calculated by using each value embedding the phase difference between the magnetic field signal of the first track and the magnetic field signal of the second track. 
     For example, the main section values may be set as “00”, “01”, “10”, and “11” with two bits by comparing a value of all four bits, in which a sign of each of the 1-1th signed difference value to the 1-4th signed difference value is expressed as one bit, with a reference value 1 to a reference value 4. 
     For each main section value, the sub-section value calculator  237   a  calculates sub-section values that correspond one of the 1-1th shift difference value to 1-4th shift difference value to the 1-1th sub-section to 1-Mth sub-section. Here, M is a natural number greater than or equal to two. 
       FIG.  6    is an explanatory view illustrating sub-section values. 
     That is, with respect to a first main section, sub-section values cause the 1-1th shift difference values to correspond to respective three bits, i.e., a 1-1th sub-section to a 1-8 sub-section, which are eight sub-sections. 
     That is, the sub-section values may represent the respective 1-1th sub-section to 1-8th sub-section as “000” to “111” with three bits. For example, when a relevant 1-1th shift difference value corresponds to the 1-1th sub-section, a corresponding sub-section value becomes “000”. 
     Similarly, with respect to a second main section, sub-section values cause the 1-2 shift difference values to correspond to respective three bits, i.e., a 1-1th sub-section to a 1-8th sub-section, which are eight sub-sections. 
     That is, the sub-sections to be allocated are determined according to magnitudes of respective the 1-1th shift difference value to the 1-4th shift difference value. 
     The lower section value calculator  238   a  calculates lower section values calculated by the 1-1th digital signal and the 1-2th digital signal for each first signal section value. That is, the lower section values are values for dividing each of the first signal section values into K lower angle values. Here, K is a natural number greater than or equal to four. 
     Specifically, in the lower sections, each lower section is expressed as K number of lower angle values for each first signal section value. For example, when the number of first signal sections is four, a first lower section value to a fourth lower section value may be calculated. In addition, the first lower section value to the fourth lower section value are values in which each of the lower section values is expressed by Y bits. When a first signal section value is “00”, a first lower section value is used and K is 2 Y . That is, the lower section values are the values for dividing the respective first signal section values into K lower angle values. When Y is 16, K becomes 2 16 . 
     The lower section values may be calculated as the first lower section value to the fourth lower section value as shown in the following [Equation 6] according to the first signal section values. For example, the first lower section value may be used when a first signal section value is “00”, the second lower section value may be used when the first signal section value is “01”, the third lower section value may be used when the first signal section value is “10”, and the fourth lower section value may be used when the first signal section value is “11”. 
         L (1−1)=SIN(α)+COS(α_ B )
 
         L (1−2)=SIN(α_ B )+COS(α_ B )
 
         L (1−3)=SIN(α)+COS(α_ B )
 
         L (1−4)=SIN(α_ B )+COS(α_ B )  [Equation 6]
 
     In Equation 6, L(1−1) to L(1−4) respectively represent the first lower section value to the fourth lower section value. In addition, α_B represents an inverted signal of α, that is, −α. 
     The angle output part  239   a  outputs absolute angle data of the positions of the magnet. For example, when the first track TR 1  has 32 pairs of N poles and S poles alternately and repeatedly connected to each other and the second track TR 2  has 31 pairs of N poles and S poles alternately and repeatedly connected to each other, the absolute angle data calculated by the angle output part  239   a  may include the following bits. 
     main section values: values each constituting the uppermost two bits and divide one rotation of 360 degrees of the magnet into the first main section to the fourth main section, which are the four 90 degree sections. 
     sub-section values: values that constitute lower bits of each main section value, and constitute three bits of data for each main section value. That is, the sub-section values calculate the absolute angle with resolution of 11.25 degrees obtained by dividing one main section of 90 degrees by eight. 
     first signal section values: values that are calculated by using the sign of the 1-1th digital signal and the sign of the 1-2th digital signal, and constitute lower two bits of respective sub-section values. That is, the absolute angle is calculated with resolution of 2.8125 degrees obtained by dividing 360 degrees by a value obtained by calculating (32 pairs of poles×four first signal sections). 
     lower section values: values calculated by the 1-1th digital signal and the 1-2th digital signal for each first signal section value. The lower section values constitute lower 16 bits of respective first signal section values. 
       FIG.  7    is a block diagram illustrating an absolute angle calculation unit  230   b  according to a second exemplary embodiment. 
     As may be seen from  FIG.  7   , the absolute angle calculation unit  230   b  according to the second exemplary embodiment may be configured to include: a main section value calculator  231   b , a first signal section value calculator  232   b , a first shift section value calculator  233   b _ 1 , a second shift section value calculator  233   b _ 2 , a third shift section value calculator  233   b _ 3 , a first signal section period calculator  234   b , a second difference value calculator  235   b , a second signal section value calculator  236   b , a sub-section value calculator  237   b , a lower section value calculator  238   b , and an angle output part  239   b.    
     For reference, the absolute angle calculation unit  230   b  according to the second exemplary embodiment may be used to calculate a rotation angle of a motor at a corresponding rotation position when the motor is rotating. 
     In addition, when each component of the absolute angle calculation unit  230   b  according to the second exemplary embodiment is used with the same name as that of each component of the absolute angle calculation unit  230   a  according to the first exemplary embodiment, unless otherwise stated, it is natural that each component of the absolute angle calculation unit  230   b  includes all the features of the same name component of the absolute angle calculation unit  230   a  according to the first exemplary embodiment. 
     The main section value calculator  231   b  calculates the main section values for dividing one rotation of 360 degrees of the magnet into a first main section to a fourth main section, which are the four 90 degree sections. For reference, the main section values may be calculated by various methods. 
       FIG.  8    is an explanatory view illustrating the first signal section value calculator  232   b , the first shift section value calculator  233   b _ 1 , the second shift section value calculator  233   b _ 2 , and the third shift section value calculator  233   b _ 3 . 
     The first signal section value calculator  232   b  uses the sign of the 1-1th digital signal and the sign of the 1-2th digital signal, so as to calculate and store the first signal section values obtained by dividing the magnetic field signal of the first track TR 1  into four first signal sections. When being expressed with two bits, the first signal section values may be expressed as “00”, “01”, “10”, and “11”. 
     The first shift section value calculator  233   b _ 1  shifts a first signal section value by one first signal section in a first direction, so as to calculate the first signal section value shifted by one section. In addition, the second shift section value calculator  233   b _ 2  shifts a first signal section value by two first signal sections in the first direction, so as to calculate the first signal section value shifted by two sections. In addition, the third shift section value calculator  233   b _ 3  shifts a first signal section value by three first signal sections in the first direction, so as to calculate the first signal section value shifted by three sections. 
     The first direction is either a left direction or a right direction of a register used as the first signal section value calculator  232   b.    
     The second signal section value calculator  236   b  uses a sign of the 2-1th digital signal and a sign of the 2-2th digital signal, so as to calculate and store second signal section values obtained by dividing the magnetic field signal of the second track TR 2  into four second signal sections. When being expressed with two bits, the second signal section values may be expressed as “00”, “01”, “10”, and “11”. 
     That is, the second signal section values may also be set by the same method as the first signal section values. 
     By using the first signal section values, the first signal section period calculator  234   b  serves to calculate a first signal section period in which four first signal sections are repeated. For example, the first signal section period may be calculated by using respective first signal section values from a time point when a current “00” is started to a time point when the next “00” is started. By calculating the first signal section period, the rotation speed of the motor may be reflected, and thus respondence may be available according to the speed of the motor. 
     The second difference value calculator  235   b  sequentially uses one of an unshifted first signal section value, a first signal section value shifted by one section, a first signal section value shifted by two sections, a first signal section value shifted by three sections, so as to calculate each second difference value, which is a difference of a change point between the corresponding first signal section value and second signal section value. 
       FIG.  9    is an explanatory view illustrating a process of calculating second difference values, and  FIG.  10    is a waveform diagram illustrating a result of the calculated second difference values. 
     Each second difference value is a value corresponding to the phase difference between the magnetic field signal of the first track TR 1  and the magnetic field signal of the second track TR 2 . That is, each second difference value is a value obtained from a difference between the number of pairs of N poles and S poles constituting the first track TR 1  and the number of pairs of N poles and S poles constituting the second track TR 2 . When a value corresponding to a second difference value of 90 degrees is calculated, second difference values are consecutively calculated by using the other one from one of the unshifted first signal section value, the first signal section value shifted by one section, the first signal section value shifted by two sections, and the first signal section value shifted by three sections. 
     That is, it is assumed that the number of pairs of N poles and S poles constituting the first track TR 1  is 32, and the number of pairs of N poles and S poles constituting the second track TR 2  is 31. A second difference value is calculated by using a first signal section value, and the second difference value is consecutively calculated until an eighth magnet pair of the first track TR 1  where a second difference value is 90 degrees. When the second difference value becomes 90 degrees, a second difference value is calculated by using a first signal section value shifted by three sections, and the second difference value is consecutively calculated until a 16th pole pair of the first track TR 1  where the second difference value becomes 90 degrees. Similarly, when the second difference value becomes 90 degrees, a second difference value is calculated by using a first signal section value shifted by two sections, and the second difference value is consecutively calculated until a 24th pole pair of the first track TR 1  where the second difference value becomes 90 degrees. Finally, when the second difference value becomes 90 degrees, a second difference value is calculated by using a first signal section value shifted by one section, and the second difference value is consecutively calculated until a 32th pole pair of the first track TR 1  where the second difference value becomes 90 degrees. 
     In summary, each second difference value appears in a form of repeating a linear function having a maximum value at 90 degrees. Each of the four 90-degree sections represents a value calculated by a difference of the change point by one of the values, including: the first signal section value and the second signal section value; the first signal section value and the second signal section, which are shifted by one section; the first signal section value and the second signal section, which are shifted by two sections; and the first signal section value and the second signal section, which are shifted by three sections. 
     Main section values may be calculated by using second difference values. For example, by setting the second difference value at intervals of 90 degrees, the main section values are set as a first main section to a fourth main section. That is, a section in which the second difference value is initially from 0 degrees to 90 degrees may be set as the first main section, and a section in which the second difference value is next from 0 degrees to 90 degrees may be set as the second main section. The first main section to the fourth main section may be set as “00”, “01”, “10”, and “11” by the respective main section values of two bits. 
     The sub-section value calculator  237   b  uses values obtained by dividing the second difference values by the first signal section period, so as to calculate sub-section values that are values corresponding the first main section to the fourth main section to P sections of a 2-1th sub-section to a 2-Pth sub-section. That is, the sub-section values are values obtained by normalizing the second difference values divided by the first signal section period, regardless of the motor speed. Here, P is a natural number greater than or equal to two. 
     For example, the sub-section values correspond to the second difference values, which are normalized with respect to the first main section, to the 2-1th sub-section to the 2-8th sub-section, which are eight pieces of 3-bit sub-sections. That is, the sub-section values may respectively represent the 2-1th sub-section to the 2-8th sub-section as “000” to “111” with three bits. In addition, when a normalized relevant second difference value corresponds to the 2-1th sub-section, a sub-section value becomes “000”. That is, the sub-sections to be allocated are determined according to magnitudes of the normalized second difference values. 
     The lower section value calculator  238   b  calculates lower section values calculated by the 1-1th digital signal and 1-2th digital signal for each first signal section value. 
     The angle output part  239   b  outputs absolute angle data including bits of the main section values, the sub-section values, the first signal section values, and the lower section values. 
     An angle measurement method based on a magnetic method according to the exemplary embodiment will be described. 
     Since the angle measurement method based on the magnetic method according to the exemplary embodiment uses the above-described angle measurement system  1000 , it is natural that even when there is no separate description, the method includes all the features of the angle measurement system  1000 . In addition, each step of the angle measurement method based on the magnetic method according to the exemplary embodiment may be performed by at least one or a combination of an analog circuit, a digital circuit, a processor, and a memory. 
     The angle measurement method based on the magnetic method includes: a first analog-to-digital conversion step S 10  of outputting a 1-1th digital signal and a 1-2th digital signal, which are digital signals, by receiving an input of an output of at least one 1-1th sensor H 11  and an output of at least one 1-2th sensor H 12 , which are for measuring a magnetic field signal of a first track TR 1 ; a second analog-to-digital conversion step S 20  of outputting a 2-1th digital signal and a 2-2th digital signal, which are digital signals, by receiving an input of an output of at least one 2-1th sensor H 21  and an output of at least one 2-2th sensor H 22 , which are for measuring a magnetic field signal of a second track TR 2 ; and absolute angle calculation steps S 30 A and S 30 B of calculating an absolute angle of a position of a magnet by using the 1-1th digital signal, the 1-2th digital signal, the 2-1th digital signal, and the 2-2th digital signal. 
     That is, the first analog-to-digital conversion step S 10  is configured to receive the input of the analog signals from a plurality of sensors H 11  and H 12  that have measured the magnetic field signal of the first track TR 1 , and convert the analog signals into the digital signals. The second analog-to-digital conversion step S 20  is configured to receive the input of the analog signals from a plurality of sensors H 21  and H 22  that have measured the magnetic field signal of the second track TR 2 , and convert the analog signals into the digital signals 
     In addition, the 1-1th digital signal and the 1-2th digital signal are sinusoidal signals having a phase difference of 90 degrees from each other. Similarly, the 2-1th digital signal and the 2-2th digital signal are sinusoidal signals having a phase difference of 90 degrees from each other. 
     An absolute angle of a position of a magnet is configured to include at least one piece of data, including: a main section value obtained by dividing one rotation of 360 degrees of the magnet into four 90 degree sections, which are a first main section to a fourth main section; sub-section values obtained by dividing each of the first main section to the fourth main section into a plurality of sections by a value using a phase difference between a magnetic field signal of a first track and a magnetic field signal of a second track; first signal section values obtained by dividing the magnetic field signal of the first track into four first signal sections by using a sign of a 1-1th digital signal and a sign of a 1-2th digital signal; and lower section values calculated by the 1-1th digital signal and the 1-2th digital signal for each of the first signal section values. 
     The absolute angle calculation step S 30 A according to the first exemplary embodiment will be described. 
     Since the absolute angle calculation step S 30 A according to the first exemplary embodiment uses the absolute angle calculation unit  230   a  according to the first exemplary embodiment described above, even though there is no separate description, it is natural that the absolute angle calculation step S 30 A includes all the features of the absolute angle calculation unit  230   a  according to the first exemplary embodiment. 
     The absolute angle calculation step S 30 A according to the first exemplary embodiment includes: a main section value calculation step S 31 A, a first signal section value calculation step S 32 A, a first difference value calculation step S 33 A, a data conversion step S 34 A, a shift difference value calculation step S 35 A, a sub-section value calculation step S 36 A, a lower section value calculation step S 37 A, and an angle output step S 38 A. 
     The main section value calculation step S 31 A calculates the main section values for dividing one rotation of 360 degrees of the magnet into a first main section to a fourth main section, which are four 90 degree sections. For reference, the main section value may be calculated by various methods. 
     The first signal section value calculation step S 32 A uses a sign of a 1-1th digital signal and a sign of a 1-2th digital signal, so as to calculate the first signal section values obtained by dividing the magnetic field signal of the first track TR 1  into four first signal sections. 
     In addition, the first difference value calculation step S 33 A uses the 1-1th digital signal, the 1-2th digital signal, the 2-1th digital signal, and the 2-2th digital signal, so as to calculate a 1-1th difference value to a 1-4th difference value, which are values embedding a phase difference between the magnetic field signal of TR 1  and the magnetic field signal of the second track TR 2 . Each of the 1-1th difference value to the 1-4th difference value is calculated as an unsigned value with no sign. 
     In the data conversion step S 34 A, the 1-1th difference value to the 1-4th difference value are respectively converted to the 1-1th signed difference value to the 1-4th signed difference value, which are signed values. The shift difference value calculation step S 35 A calculates a 1-1th shift difference value to a 1-4th shift difference value, which are obtained by phase shifting each of the 1-1th difference value to the 1-4th difference value by 45 degrees by using a plurality of the 1-1th signed difference value to the 1-4th signed difference value. 
     For reference, the main section values may be calculated by using values calculated by using the 1-1th difference value to the 1-4th difference value. Specifically, the main section value may be calculated by using the 1-1th signed difference value to the 1-4th signed difference value, which are the values using the 1-1th difference value to the 1-4th difference value. However, each of the 1-1th signed difference value to the 1-4th signed difference value also embed a phase difference between the magnetic field signal of the first track TR 1  and the magnetic field signal of the second track TR 2 . That is, the main section value may be calculated by using each value embedding the phase difference between the magnetic field signal of the first track and the magnetic field signal of the second track. 
     For each main section value, the sub-section value calculation step S 36 A calculates sub-section values that correspond one of the 1-1th shift difference value to 1-4th shift difference value to the 1-1th sub-section to 1-Mth sub-section. M is a natural number greater than or equal to two. 
     The lower section value calculation step S 37 A calculates lower section values calculated by the 1-1th digital signal and the 1-2th digital signal for each first signal section value. The lower section values are values for dividing each first signal section value into K lower angle values. Here, K is a natural number greater than or equal to four. 
     The angle output step S 38 A outputs absolute angle data of the positions of the magnet including the main section values. Specifically, the absolute angle data calculated in the angle output step S 38 A may include bits of the main section values, the sub-section values, the first signal section values, and the lower section values. 
     The absolute angle calculation step S 30 B according to the second exemplary embodiment will be described. 
     Since the absolute angle calculation step S 30 B according to the second exemplary embodiment uses the absolute angle calculation unit  230   b  according to the second exemplary embodiment described above, even though there is no separate description, it is natural that the absolute angle calculation step S 30 B includes all the features of the absolute angle calculation unit  230   b  according to the second exemplary embodiment. 
     The absolute angle calculation step S 30 B according to the second exemplary embodiment includes a main section value calculation step S 31 B, a first signal section value calculation step S 32 B, a first shift section value calculation step S 33 B  1 , a second shift section value calculation step S 33 B_ 2 , a third shift section value calculation step S 33 B_ 3 , a first signal section period calculation step S 34 B, a second signal section value calculation step S 35 B, a second difference value calculation step S 36 B, a sub-section value calculation step S 37 B, a lower section value calculation step S 38 B, and an angle output step S 39 B. 
     The main section value calculation step S 31 B calculates main section values dividing one rotation of 360 degrees of a magnet into a first main section to a fourth main section, which are four 90 degree sections. 
     In addition, the first signal section value calculation step S 32 B uses a sign of a 1-1th digital signal and a sign of a 1-2th digital signal, so as to calculate first signal section values obtained by dividing a magnetic field signal of a first track TR 1  into four first signal sections. 
     The first shift section value calculation step S 33 B  1  shifts a first signal section value by one first signal section in a first direction, so as to calculate the first signal section value shifted by one section. In addition, the second shift section value calculation step S 33 B_ 2  shifts a first signal section value by two first signal section in the first direction, so as to calculate the first signal section value shifted by two sections. The third shift section value calculation step S 33 B_ 3  shifts a first signal section value by three first signal sections in the first direction, so as to calculate the first signal section value shifted by three sections. The first direction is either a left direction or a right direction of a register used for calculating the first signal section value. 
     The first signal section period calculation step S 34 B calculates, by using the first signal section values, a first signal section period in which four first signal sections are repeated. 
     The second signal section value calculation step S 35 B uses a sign of a 2-1th digital signal and a sign of a 2-2th digital signal, so as to calculate second signal section values divided into four second signal sections. In addition, the second difference value calculation step S 36 B sequentially uses one of an unshifted first signal section value, a first signal section value shifted by one section, a first signal section value shifted by two sections, a first signal section value shifted by three sections, so as to calculate each second difference value, which is a difference of a change point between the corresponding first signal section value and the second signal section value. 
     In addition, the main section values are calculated by using the second difference values. 
     The sub-section value calculation step S 37 B uses values obtained by dividing the second difference values by the first signal section period, so as to calculate sub-section values corresponding each of the first main section to the fourth main section to P sections of a 2-1th sub-section to a 2-Pth sub-section. Here, P is a natural number greater than or equal to two. 
     The lower section value calculation step S 38 B calculates lower section values on the basis of the 1-1th digital signal and the 1-2th digital signal for each first signal section value. The lower section values are values for dividing each first signal section value into K lower angle values. K is a natural number greater than or equal to four. 
     The angle output step S 39 B outputs absolute angle data of the position of the magnet including the main section values. Specifically, the absolute angle data calculated in the angle calculation step S 39 B may include bits of main section values, sub-section values, first signal section values, and lower section values. 
     As described above, according to the angle measurement system  1000  based on the magnetic method and the measurement method therefor of the present disclosure, it may be confirmed that the absolute angle at the time when the motor is stopped and/or rotated may be measured with the high resolution.