Planar motor rotor displacement measuring device and its measuring method

Abstract

A planar motor rotor displacement measuring device and its measuring method are provided. The motor is a moving-coil type planar motor. The device comprises probes, two sets of sine sensors, two sets of cosine sensors, a signal lead wire and a signal processing circuit. The method is arranging two sets of magnetic flux density sensors within a magnetic field pitch τ along two vertical movement directions in the rotor located in the sine magnetic field area. Sampled signals of the four sets of sensors are respectively processed with a frequency multiplication operation, four subdivision signals are obtained, the zero-crossing points of the four subdivision signals are detected, and then two sets of orthogonal pulse signals are generated. The pulse number of the orthogonal pulse signals is counted, and phase difference of the two sets of orthogonal pulse signals is respectively detected.

Claims

1. A planar motor rotor displacement measuring device, wherein the planar motor is a moving-coil type planar motor comprising a stator (1) and a rotor (3) on the stator (1), the stator (1) includes a magnetic steel array (2), and a coil array (4) is arranged on the lower surface of the rotor (3), characterized in that: the displacement measuring device comprises a probe (5), two sets of sine sensors, two sets of cosine sensors, a signal lead wire (6) and a signal processing circuit (7); the probe (5) is arranged at the edge of the rotor (3) which is located in a sine magnetic field area generated by the magnetic steel array of the stator of the moving-coil type planar motor; the two sets of sine sensors include an x-direction sine sensor set (8) and a y-direction sine sensor set (10), the two sets of cosine sensors include an x-direction cosine sensor set (9) and a y-direction cosine sensor set (11); a plurality of sensors are arranged in the probe (5) including a reference sensor (12), wherein m.sub.y sensors in total including the reference sensor (12) are uniformly arranged within one magnetic field pitch τ along an x-direction, forming the y-direction sine sensor set and m.sub.x sensors in total including the reference sensor (12) are uniformly arranged within one magnetic field pitch τ along a y-direction, forming the x-direction sine sensor set; wherein, beginning at a distance of τ/4 from the reference sensor (12) in the y-direction, m.sub.y sensors are uniformly arranged within one magnetic field pitch τ along the x-direction, forming the y-direction cosine sensor set; wherein, beginning at the distance of τ/4 from the reference sensor (12) in the x-direction, m.sub.x sensors are uniformly arranged within one magnetic field pitch τ along the y-direction, forming the x-direction cosine sensor set, where m.sub.x=2, 3, 4, . . . , m.sub.y=2, 3, 4, . . . ; wherein the signal processing circuit (7) is connected with an output of the probe (5) via the signal lead wire (6); wherein the signal processing circuit (7) includes an analog signal processing unit and a digital signal processing unit; and wherein the magnetic field pitch τ is a spatial period of the sine magnetic field of the planar motor.

2. A planar motor rotor displacement measuring method using the device of claim 1, characterized in that, the method includes: 1) processing, by the analog signal processing unit of the signal processing circuit, sampled signals of the x-direction sine sensor set, sampled signals of the x-direction cosine sensor set, sampled signals of the y-direction sine sensor set and sampled signals of the y-direction cosine sensor set, so as to obtain an x-direction sine measurement signal S.sub.X0, an x-direction cosine measurement signal C.sub.X0, a y-direction sine measurement signal S.sub.Y0 and a y-direction cosine measurement signal C.sub.Y0, respectively; 2) processing the x-direction sine measurement signal S.sub.X0 and the x-direction cosine measurement signal C.sub.X0 with the following n.sub.X frequency multiplication operations by the digital signal processing unit of the signal processing circuit, so as to obtain an x-direction sine subdivision signal S.sub.Xn.sub.X and an x-direction cosine subdivision signal C.sub.Xn.sub.X: $S_{X1}=2*S_{X0}*C_{X0},C_{X1}=C_{X0}*C_{X0}-S_{X0}*S_{X0},S_{X2}=2*S_{X1}*C_{X1},C_{X2}=C_{X1}*C_{X1}-S_{X1}*S_{X1},\mathrm{.Math.},S_{{\mathrm{Xn}}_X}=2*S_{X,n_X-1}*C_{X,n_X-1},C_{{\mathrm{Xn}}_X}=C_{X,n_X-1}*C_{X,n_X-1}-S_{X,n_X-1}*S_{X,n_X-1}$ where S.sub.X1, C.sub.X1, S.sub.X2, C.sub.X2, . . . , S.sub.X,n.sub.X.sub.-1 and C.sub.X,n.sub.X.sub.-1 are intermediate variables, n.sub.X=1, 2, 3, . . . ; while, the y-direction sine measurement signal S.sub.Y0 and the y-direction cosine measurement signal C.sub.Y0 are processed with the following n.sub.Y frequency multiplication operations by the signal processing circuit, so as to obtain a y-direction sine subdivision signal S.sub.Yn.sub.Y and a y-direction cosine subdivision signal C.sub.Yn.sub.Y: $S_{Y1}=2*S_{Y0}*C_{Y0},C_{Y1}=C_{Y0}*C_{Y0}-S_{Y0}*S_{Y0},S_{Y2}=2*S_{Y1}*C_{Y1},C_{Y2}=C_{Y1}*C_{Y1}-S_{Y1}*S_{Y1},\mathrm{.Math.},S_{{\mathrm{Yn}}_Y}=2*S_{Y,n_Y-1}*C_{Y,n_Y-1},C_{{\mathrm{Yn}}_Y}=C_{Y,n_Y-1}*C_{Y,n_Y-1}-S_{Y,n_Y-1}*S_{Y,n_Y-1}$ where S.sub.Y1, C.sub.Y1, S.sub.Y2, C.sub.Y2, . . . , S.sub.Y,n.sub.Y.sub.-1 and C.sub.Y,n.sub.Y.sub.-1 are intermediate variables, n.sub.Y=1, 2, 3, . . . ; 3) detecting zero-crossing points of the x-direction sine subdivision signal S.sub.Xn.sub.X and the x-direction cosine subdivision signal C.sub.Xn.sub.X obtained at step 2) by the digital signal processing unit of the signal processing circuit respectively, generating a set of x-direction orthogonal pulse signals, that is, an x-direction sine pulse signal A.sub.X and an x-direction cosine pulse signal B.sub.X; while, the zero-crossing points of the y-direction sine subdivision signal S.sub.Yn.sub.Y and the y-direction cosine subdivision signal C.sub.Yn.sub.Y obtained at step 2) are detected respectively, generating a set of y-direction orthogonal pulse signals, that is, a y-direction sine pulse signal A.sub.Y and a y-direction cosine pulse signal B.sub.Y; 4) if the x-direction sine subdivision signal S.sub.Xn.sub.X>0, then the output of the x-direction sine pulse signal A.sub.X is of high level; if the x-direction sine subdivision signal S.sub.Xn.sub.X<0, then the output of the x-direction sine pulse signal A.sub.X is of low level; and if the x-direction sine subdivision signal S.sub.Xn.sub.X=0, then the output of the x-direction sine pulse signal A.sub.X remains unchanged; if the x-direction cosine subdivision signal C.sub.Xn.sub.X>0, then the output of the x-direction cosine pulse signal B.sub.X is of high level; if the x-direction cosine subdivision signal C.sub.Xn.sub.X<0, then the output of the x-direction cosine pulse signal B.sub.X is of low level; and if the x-direction cosine subdivision signal C.sub.Xn.sub.X=0, then the output of the x-direction cosine pulse signal B.sub.X remains unchanged; 5) if the y-direction sine subdivision signal S.sub.Yn.sub.Y>0, then the output of the y-direction sine pulse signal A.sub.Y is of high level; if the y-direction sine subdivision signal S.sub.Yn.sub.Y<0, then the output of the y-direction sine pulse signal A.sub.Y is of low level; and if the y-direction sine subdivision signal S.sub.Yn.sub.Y=0, then the output of the y-direction sine pulse signal A.sub.Y remains unchanged; if the y-direction cosine subdivision signal C.sub.Yn.sub.Y>0, then the output of the y-direction cosine pulse signal B.sub.Y is of high level; if the y-direction cosine subdivision signal C.sub.Yn.sub.Y<0, then the output of the y-direction cosine pulse signal B.sub.Y is of low level; and if the y-direction cosine subdivision signal C.sub.Yn.sub.Y=0, then the output of the y-direction cosine pulse signal B.sub.Y remains unchanged; 6) counting the pulse numbers of the x-direction sine pulse signal A.sub.X or the x-direction cosine pulse signal B.sub.X obtained at step 3) by the digital signal processing unit of the signal processing circuit, and detecting a phase difference between the x-direction sine pulse signal A.sub.X and the x-direction cosine pulse signal B.sub.X; taking one pulse of the x-direction sine pulse signal A.sub.X or the x-direction cosine pulse signal B.sub.X as an x-direction displacement resolution $\frac{\tau }{2^{n_X}}$ n.sub.X=1, 2, 3, . . . , if the phase of the x-direction sine pulse signal A.sub.X is behind the phase of the x-direction cosine pulse signal B.sub.X, then it indicates that it is the forward displacement; and if the phase of the x-direction sine pulse signal A.sub.X is ahead of the phase of the x-direction cosine pulse signal B.sub.X, then it indicates that it is the backward displacement, in such a way, the x-direction displacement of the rotor of the planar motor is measured; 7) counting the pulse numbers of the y-direction sine pulse signal A.sub.Y or the y-direction cosine pulse signal B.sub.Y obtained at step 3) by the digital signal processing unit of the signal processing circuit, and detecting the phase difference between the y-direction sine pulse signal A.sub.Y and the y-direction cosine pulse signal B.sub.Y; taking one pulse of the y-direction sine pulse signal A.sub.Y or the y-direction cosine pulse signal B.sub.Y as a y-direction displacement resolution $\frac{\tau }{2^{n_Y}}$ n.sub.Y=1, 2, 3, . . . , and if the phase of the y-direction sine pulse signal A.sub.Y is behind the phase of the y-direction cosine pulse signal B.sub.Y, then it indicates that it is the forward displacement; and if the phase of the y-direction sine pulse signal A.sub.Y is ahead of the phase of the y-direction cosine pulse signal B.sub.Y, then it indicates that it is the backward displacement, in such a way, the y-direction displacement of the rotor of the planar motor is measured.

3. The planar motor rotor displacement measuring method of claim 2, characterized in that, n.sub.X described at step 2) is determined as follows: given that the B.sub.XM is the magnitude of the magnetic induction intensity in the x-direction of the sine magnetic field generated by the magnetic steel array of the stator of the planar motor, and v.sub.x is the noise in the sensor measurement in the x-direction, then the maximized number of times of the frequency multiplication operations in the x-direction is $n_X=\left[{\log }_2\left(\frac{B_{\mathrm{XM}}}{v_x}\right)-3\right]$ n.sub.Y described at step 2) is determined as follows: given that the B.sub.YM is the magnitude of the magnetic induction intensity in the y-direction of the sine magnetic field generated by the magnetic steel array of the stator of the planar motor, and v.sub.y is the noise in the sensor measurement in the y-direction, then the maximized number of times of frequency multiplication operations in the y-direction is $n_Y=\left[{\log }_2\left(\frac{B_{\mathrm{XM}}}{v_y}\right)-3\right].$

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic view of the overall structure of the displacement measuring device according to the present invention.

(2) FIG. 2 is a bottom view seen from bottom to top of the probe in which m.sub.x=m.sub.y=4 according to the present invention.

(3) FIGS. 3a and 3b are waveform schematic views of the x-direction sine and cosine measurement signals, x-direction sine and cosine subdivision signals and x-direction sine and cosine pulse signals when n.sub.x=4 according to the present invention.

(4) FIGS. 4a and 4b are schematic views of two sets of orthogonal pulse signals of the rotor displacement during the measurement according to the present invention.

(5) The main numerals used in the drawings are: 1 stator 2 magnetic steel array 3 rotor 4 coil array 5 probe 6 signal lead wire 7 signal processing circuit 8 x-direction sine sensor set 9 x-direction cosine sensor set 10 y-direction sine sensor set 11 y-direction cosine sensor set 12 reference sensor

MODE FOR THE INVENTION

(6) In the following, the embodiments of the invention will be further described in detail in conjunction with the accompanying drawings.

(7) Referring to FIGS. 1 and 2, the planar motor described in the invention is a moving-coil type planar motor comprising a stator 1 and a rotor 3 on the stator 1; the stator 1 includes a magnetic steel array 2, and a coil array 4 is arranged on the lower surface of the rotor 3; the displacement measuring device comprises a probe 5, two sets of sine sensors, two sets of cosine sensors, a signal lead wire 6 and a signal processing circuit 7; the probe 5 is arranged at the edge of the rotor 3 which is located in the sine magnetic field area formed by the magnetic steel array of the stator of the moving-coil type planar motor; the two sets of sine sensors include an x-direction sine sensor set 8 and a y-direction sine sensor set 10, the two sets of cosine sensors include an x-direction cosine sensor set 9 and a y-direction cosine sensor set 11; the sensors are arranged in the probe 5 in such a manner, firstly, a sensor is arranged in the probe 5 as the reference sensor 12, m.sub.y sensors in total including the reference sensor 12 are uniformly arranged within a magnetic field pitch τ along the x-direction, forming the y-direction sine sensor set; taking the reference sensor 12 as the first sensor, m.sub.x sensors in total including the reference sensor 12 are uniformly arranged within a magnetic field pitch τ along the y-direction, forming the x-direction sine sensor set; beginning at the distance τ/4 from the reference sensor 12 in the y-direction, m.sub.y sensors are uniformly arranged within a magnetic field pitch τ along the x-direction, forming the y-direction cosine sensor set; beginning at the distance τ/4 from the reference sensor 12 in the x-direction, m.sub.x sensors are uniformly arranged within a magnetic field pitch τ along the y-direction, forming the x-direction cosine sensor set, where m.sub.x=2, 3, 4, . . . , m.sub.y=2, 3, 4, . . . ; the signal processing circuit 7 is connected with the output of the probe 5 via the signal lead wire 6; the signal processing circuit 7 includes an analog signal processing unit and a digital signal processing unit; and the magnetic field pitch τ is the spatial period of the sine magnetic field of the planar motor.

(8) Referring to FIGS. 3a and 3b, taking the case in which the rotor 3 is in the uniform motion along the x-direction as an example, the waveforms of the x-direction sine measurement signal S.sub.X0, the x-direction sine subdivision signal S.sub.X4, the x-direction sine pulse signal A.sub.X, and the waveforms of the x-direction cosine measurement signal C.sub.X0, the x-direction cosine subdivision signal C.sub.X4, and the x-direction cosine pulse signal B.sub.X during the rotor movement when n.sub.X=4 are presented respectively.

(9) Referring to FIGS. 4a and 4b, the measurement of the x-direction displacement with the x-direction sine pulse signal A.sub.X and the x-direction cosine pulse signal B.sub.X, and the measurement of the y-direction displacement with the y-direction sine pulse signal A.sub.Y and the y-direction cosine pulse signal B.sub.Y are presented respectively.

(10) The planar motor rotor displacement measuring method described in the invention includes the following steps:

(11) 1) sampled signals of the x-direction sine sensor set, sampled signals of the x-direction cosine sensor set, sampled signals of the y-direction sine sensor set and sampled signals of the y-direction cosine sensor set are processed by the analog signal processing unit of the signal processing circuit, so as to obtain the x-direction sine measurement signal S.sub.X0, the x-direction cosine measurement signal C.sub.X0, the y-direction sine measurement signal S.sub.Y0 and the y-direction cosine measurement signal C.sub.Y0 respectively;

(12) 2) the x-direction sine measurement signal S.sub.X0 and the x-direction cosine measurement signal C.sub.X0 are processed with n.sub.X frequency multiplication operations by the digital signal processing unit of the signal processing circuit so as obtain the x-direction sine subdivision signal S.sub.Xn.sub.X and the x-direction cosine subdivision signal C.sub.Xn.sub.X:

(13) $S_{X1}=2*S_{X0}*C_{X0},C_{X1}=C_{X0}*C_{X0}-S_{X0}*S_{X0},S_{X2}=2*S_{X1}*C_{X1},C_{X2}=C_{X1}*C_{X1}-S_{X1}*S_{X1},\mathrm{.Math.},S_{{\mathrm{Xn}}_X}=2*S_{X,n_X-1}*C_{X,n_X-1},C_{{\mathrm{Xn}}_X}=C_{X,n_X-1}*C_{X,n_X-1}-S_{X,n_X-1}*S_{X,n_X-1},$
where S.sub.X1, C.sub.X1, S.sub.X2, C.sub.x2, . . . , S.sub.X,n.sub.X.sub.-1 and C.sub.X,n.sub.X.sub.-1 are intermediate variables, n.sub.X=1, 2, 3, . . . ;
also, the y-direction sine measurement signal S.sub.Y0 and the y-direction cosine measurement signal C.sub.Y0 are processed with n.sub.Y frequency multiplication operations by the signal processing circuit so as to obtain the y-direction sine subdivision signal S.sub.Yn.sub.Y and the y-direction cosine subdivision signal C.sub.Yn.sub.Y:

(14) $S_{Y1}=2*S_{Y0}*C_{Y0},C_{Y1}=C_{Y0}*C_{Y0}-S_{Y0}*S_{Y0},S_{Y2}=2*S_{Y1}*C_{Y1},C_{Y2}=C_{Y1}*C_{Y1}-S_{Y1}*S_{Y1},\mathrm{.Math.},S_{{\mathrm{Yn}}_Y}=2*S_{Y,n_Y-1}*C_{Y,n_Y-1},C_{{\mathrm{Yn}}_Y}=C_{Y,n_Y-1}*C_{Y,n_Y-1}-S_{Y,n_Y-1}*S_{Y,n_Y-1},$
where S.sub.Y1, C.sub.Y1, S.sub.Y2, C.sub.Y2, . . . , S.sub.Y,n.sub.Y.sub.-1 and C.sub.Y,n.sub.Y.sub.-1 are intermediate variables, n.sub.X=1, 2, 3, . . . ;

(15) 3) the zero-crossing points of the x-direction sine subdivision signal S.sub.Xn.sub.X and the x-direction cosine subdivision signal C.sub.Xn.sub.X obtained at step 2) are detected by the digital signal processing unit of the signal processing circuit respectively, generating a set of x-direction orthogonal pulse signals, that is, the x-direction sine pulse signal A.sub.X and x-direction cosine pulse signal B.sub.X; also, the zero-crossing points of the y-direction sine subdivision signal S.sub.Yn.sub.Y and the y-direction cosine subdivision signal C.sub.Yn.sub.Y obtained at step 2) are detected respectively, generating a set of y-direction orthogonal pulse signals, that is, the y-direction sine pulse signal A.sub.Y and y-direction cosine pulse signal B.sub.Y;

(16) 4) if the x-direction sine subdivision signal S.sub.Xn.sub.X>0, then the output of the x-direction sine pulse signal A.sub.X is of high level; if the x-direction sine subdivision signal S.sub.Xn.sub.X<0, then the output of the x-direction sine pulse signal A.sub.X is of low level; and if the x-direction sine subdivision signal S.sub.Xn.sub.X=0, then the output of the x-direction sine pulse signal A.sub.X remains unchanged; if the x-direction cosine subdivision signal C.sub.Xn.sub.X>0, then the output of the x-direction cosine pulse signal B.sub.X is of high level; if the x-direction cosine subdivision signal C.sub.Xn.sub.X<0, then the output of the x-direction cosine pulse signal B.sub.X is of low level; and if the x-direction cosine subdivision signal C.sub.Xn.sub.X=0, then the output of the x-direction cosine pulse signal B.sub.X remains unchanged;

(17) 5) if the y-direction sine subdivision signal S.sub.Yn.sub.Y>0, then the output of the y-direction sine pulse signal A.sub.Y is of high level; if the y-direction sine subdivision signal S.sub.Yn.sub.Y<0, then the output of the y-direction sine pulse signal A.sub.Y is of low level; and if the y-direction sine subdivision signal S.sub.Yn.sub.Y=0, then the output of the y-direction sine pulse signal A.sub.Y remains unchanged; and if the y-direction cosine subdivision signal C.sub.Yn.sub.Y>0, then the output of the y-direction cosine pulse signal B.sub.Y is of high level; if the y-direction cosine subdivision signal C.sub.Yn.sub.Y<0, then the output of the y-direction cosine pulse signal B.sub.Y is of low level; and if the y-direction cosine subdivision signal C.sub.Yn.sub.Y=0, then the output of the y-direction cosine pulse signal B.sub.Y remains unchanged;

(18) 6) the pulse numbers of the x-direction sine pulse signal A.sub.X or the x-direction cosine pulse signal B.sub.X obtained at step 3) are counted by the digital signal processing unit of the signal processing circuit, and the phase difference between the x-direction sine pulse signal A.sub.X and the x-direction cosine pulse signal B.sub.X is detected; taking one pulse of the x-direction sine pulse signal A.sub.X or the x-direction cosine pulse signal B.sub.X as an x-direction displacement resolution

(19) $\frac{\tau }{2^{n_X}}$
where n.sub.X=1, 2, 3, . . . ; if the phase of the x-direction sine pulse signal A.sub.X is behind the phase of the x-direction cosine pulse signal B.sub.X, then it indicates that it is the forward displacement; if the phase of the x-direction sine pulse signal A.sub.X is ahead of the phase of the x-direction cosine pulse signal B.sub.X, then it indicates that it is the backward displacement, in such a way, the x-direction displacement of the rotor of the planar motor is measured;

(20) 7) the pulse numbers of the y-direction sine pulse signal A.sub.Y or the y-direction cosine pulse signal B.sub.Y obtained at step 3) are counted by the digital signal processing unit of the signal processing circuit, and the phase difference between the y-direction sine pulse signal A.sub.Y and the y-direction cosine pulse signal B.sub.Y is detected; taking one pulse of the y-direction sine pulse signal A.sub.Y or the y-direction cosine pulse signal B.sub.Y as an y-direction displacement resolution

(21) 0$\frac{\tau }{2^{n_Y}}$
n.sub.Y=1, 2, 3, . . . ; if the phase of the y-direction sine pulse signal A.sub.Y is behind the phase of the y-direction cosine pulse signal B.sub.Y, then it indicates that it is the forward displacement; if the phase of the y-direction sine pulse signal A.sub.Y is ahead of the phase of the y-direction cosine pulse signal B.sub.Y, then it indicates that it is the backward displacement, in such a way, the y-direction displacement of the rotor of the planar motor is measured.

(22) n.sub.X described at step 2) can be determined as follows:

(23) given that the B.sub.XM is the magnitude of the magnetic induction intensity along the x-direction of the sine magnetic field generated by the magnetic steel array of the stator of the planar motor, and v.sub.x is the noise in the sensor measurement noise along the x-direction, then the maximized number of times of frequency multiplication operations along the x-direction is

(24) $n_X=\left[{\log }_2\left(\frac{B_{\mathrm{XM}}}{v_x}\right)-3\right];$

(25) n.sub.Y described at step 2) can be determined as follows:

(26) given that the B.sub.YM is the magnitude of the magnetic induction intensity along the y-direction of the sine magnetic field generated by the magnetic steel array of the stator of the planar motor, and v.sub.y is the noise in the sensor measurement along the y-direction, then the maximized number of times of frequency multiplication operations along the y-direction is

(27) $n_Y=\left[{\log }_2\left(\frac{B_{\mathrm{YM}}}{v_y}\right)-3\right].$

(28) The embodiment:

(29) for example, m.sub.x=m.sub.y=4, the magnetic field pitch τ=35.35 mm, according to the formula of the maximized number of times of frequency multiplication operations, taking n.sub.X=n.sub.Y=4, the device and method of the invention are implemented.

(30) The device can be seen from FIG. 1, the planar motor described in the invention is a moving-coil type planar motor comprising a stator 1 and a rotor 3 on the stator 1, the stator 1 includes a magnetic steel array 2, and a coil array 4 is arranged on the lower surface of the rotor 3; the displacement measuring device comprises a probe 5, two sets of sine sensors, two sets of cosine sensors, a signal lead wire 6 and a signal processing circuit 7; the probe 5 is arranged at the edge of the rotor 3 which is located in the sine magnetic field area generated by the magnetic steel array of the stator of the moving-coil type planar motor; the two sets of sine sensors include an x-direction sine sensor set 8 and a y-direction sine sensor set 10, the two sets of cosine sensors include an x-direction cosine sensor set 9 and a y-direction cosine sensor set 11; a probe 5 is arranged at the edge of the rotor which is located in the sine magnetic field area generated by the magnetic steel array of the stator of the moving-coil type planar motor; referring to FIG. 2, the sensors are arranged in the probe 5 in such a manner, firstly, one sensor is arranged in the probe 5 as the reference sensor 12, and then one sensor is arranged every τ/4 along a pitch τ within the magnetic field, i.e., the x-direction, 4 sensors in total including the reference sensor are arranged, forming the y-direction sine sensor set; taking the reference sensor as the first sensor, one sensor is arranged every τ/4 along another pitch τ within the magnetic field, i.e., the y-direction, 4 sensors in total including the reference sensor are arranged, forming the x-direction sine sensor set; beginning at the distance τ/4 from the reference sensor 12 in the y-direction, one sensor is arranged every τ/4 along the x-direction, 4 sensors in total, forming the y-direction cosine sensor set; beginning at the distance τ/4 from the reference sensor 12 in the x-direction, one sensor is arranged every τ/4 along the y-direction, 4 sensors in total, forming the x-direction cosine sensor set, where τ/4 is 8.8375 mm.

(31) The method includes:

(32) 1) sampled signals of the x-direction sine sensor set, sampled signals of the x-direction cosine sensor set, sampled signals of the y-direction sine sensor set and sampled signals of the y-direction cosine sensor set are processed by the analog signal processing unit of the signal processing circuit, so as to obtain the x-direction sine measurement signal S.sub.X0, the x-direction cosine measurement signal C.sub.X0, the y-direction sine measurement signal S.sub.Y0 and the y-direction cosine measurement signal C.sub.Y0 respectively;

(33) 2) the x-direction sine measurement signal S.sub.X0 and the x-direction cosine measurement signal C.sub.X0 are processed with n.sub.X=4 frequency multiplication operations, i.e. 2.sup.4 subdivision operations by the digital signal processing unit of the signal processing circuit:
S.sub.X1=2*S.sub.X0*C.sub.X0,C.sub.X1=C.sub.X0*−C.sub.X0−S.sub.X0*S.sub.X0,
S.sub.X2=2*S.sub.X1*C.sub.X1,C.sub.X2=C.sub.X1*−C.sub.X1−S.sub.X1*S.sub.X1,
S.sub.X3=2*S.sub.X2*C.sub.X2,C.sub.X3=C.sub.X2*−C.sub.X2−S.sub.X2*S.sub.X2,
S.sub.X4=2*S.sub.X3*C.sub.X3,C.sub.X4=C.sub.X3*−C.sub.X3−S.sub.X3*S.sub.X3,
so as to obtain the x-direction sine subdivision signal S.sub.X4 and the x-direction cosine subdivision signal C.sub.X4, where S.sub.X1, C.sub.X1, S.sub.X2, C.sub.X2, S.sub.X3 and C.sub.X3 are intermediate variables, also, the y-direction sine measurement signal S.sub.Y0 and the y-direction cosine measurement signal C.sub.Y0 are processed with n.sub.Y=4 frequency multiplication operations, i.e. 2.sup.4 subdivision operations by the signal processing circuit:
S.sub.Y1=2*S.sub.Y0*C.sub.Y0,C.sub.Y1=C.sub.Y0*C.sub.Y0−S.sub.Y0*S.sub.Y0,
S.sub.Y2=2*S.sub.Y1*C.sub.Y1,C.sub.Y2=C.sub.Y1*C.sub.Y1−S.sub.Y1*S.sub.Y1,
S.sub.Y3=2*S.sub.Y2*C.sub.Y2,C.sub.Y3=C.sub.Y2*C.sub.Y2−S.sub.Y2*S.sub.Y2,
S.sub.Y4=2*S.sub.Y3*C.sub.Y3,C.sub.Y4=C.sub.Y3*C.sub.Y3−S.sub.Y3*S.sub.Y3,
so as to obtain the y-direction sine subdivision signal S.sub.Y4 and the y-direction cosine subdivision signal C.sub.Y4, where S.sub.Y1, C.sub.Y1, S.sub.Y2, C.sub.Y2, S.sub.Y3 and C.sub.Y3 are intermediate variables;

(34) 3) The zero-crossing points of the x-direction sine subdivision signal S.sub.X8 and the x-direction cosine subdivision signal C.sub.X8 are detected by the digital signal processing unit of the signal processing circuit respectively, generating a set of x-direction orthogonal pulse signals, that is, the x-direction sine pulse signal A.sub.X and x-direction cosine pulse signal B.sub.X; also, the zero-crossing points of the y-direction sine subdivision signal S.sub.Y8 and the y-direction cosine subdivision signal C.sub.Y8 are detected respectively, generating a set of y-direction orthogonal pulse signals, that is, the y-direction sine pulse signal A.sub.Y and y-direction cosine pulse signal B.sub.Y;

(35) 4) referring to FIGS. 3a and 3b, if the x-direction sine subdivision signal S.sub.X8>0, then the output of the x-direction sine pulse signal A.sub.X is of high level; if the x-direction sine subdivision signal S.sub.X8<0, then the output of the x-direction sine pulse signal A.sub.X is of low level; if the x-direction sine subdivision signal S.sub.X8=0, then the output of the x-direction sine pulse signal A.sub.X remains unchanged; and if the x-direction cosine subdivision signal C.sub.X8>0, then the output of the x-direction cosine pulse signal B.sub.X is of high level; if the x-direction cosine subdivision signal C.sub.X8<0, then the output of the x-direction cosine pulse signal B.sub.X is of low level; if the x-direction cosine subdivision signal C.sub.X8=0, then the output of the x-direction cosine pulse signal B.sub.X remains unchanged;

(36) 5) if the y-direction sine subdivision signal S.sub.Y8>0, then the output of the y-direction sine pulse signal A.sub.Y is of high level; if the y-direction sine subdivision signal S.sub.Y8<0, then the output of the y-direction sine pulse signal A.sub.Y is of low level; if the y-direction sine subdivision signal S.sub.Y8=0, then the output of the y-direction sine pulse signal A.sub.Y remains unchanged; and if the y-direction cosine subdivision signal C.sub.Y8>0, then the output of the y-direction cosine pulse signal B.sub.Y is of high level; if the y-direction cosine subdivision signal C.sub.Y8<0, then the output of the y-direction cosine pulse signal B.sub.Y is of low level; if the y-direction cosine subdivision signal C.sub.Y8=0, then the output of the y-direction cosine pulse signal B.sub.Y remains unchanged;

(37) 6) referring to FIG. 4a, the pulse number of the x-direction cosine pulse signal B.sub.X is counted by the digital signal processing unit of the signal processing circuit, and the pulse number at time t is 4 with respect to time 0, indicating the displacement is

(38) $4*\frac{\tau }{2^n}=4*\frac{35.35\mathrm{mm}}{2^8}=0.5523\mathrm{mm}\mathrm{long},$
and the phase of the x-direction sine pulse signal A.sub.X is ahead of the phase of the x-direction cosine pulse signal B.sub.X, indicating the backward displacement, so in FIG. 4a, the displacement in the x-direction at time t with respect to time 0 is −0.5523 mm;

(39) referring to FIG. 4b, the pulse number of the y-direction sine pulse signal A.sub.Y is counted by the digital signal processing unit of the signal processing circuit, and the pulse number at time t is 3 with respect to time 0, indicating the displacement is

(40) $3*\frac{\tau }{2^n}=3*\frac{35.35\mathrm{mm}}{2^8}=0.4143\mathrm{mm}\mathrm{long},$
and the phase of the y-direction sine pulse signal A.sub.Y is behind the phase of the y-direction cosine pulse signal B.sub.Y, indicating the forward displacement, so in FIG. 4b, the displacement in the y-direction at time t with respect to time 0 is +0.4143 mm;

(41) Through the above steps, on condition that the zero-crossing points are able to be detected, it only requires simple subtraction and multiplication to extract the displacement information contained in the magnetic field signals, and differently from the prior art, the components configured for generating signals containing the displacement information are not required, simplifying the installation of hardware and reducing the cost, and at the same time, the displacement measurement of the rotor of the planar motor of long moving range and high preciseness is still guaranteed.

(42) Only some preferred embodiments of the present invention are described in the above. Without departing from the scope of the invention disclosed in the claims, various modification, addition and substitution should be considered as in the scope of protection of the invention.