JPH02251720A - Interpolating method of encoder - Google Patents

Abstract

PURPOSE:To make it possible to obtain an accurate interpolating signal by obtaining the offset values, the amplitudes and the phase differences of the signals in a phase A and a phase B outputted from encoders, and obtaining the two signals whose amplitudes are equal and phase differences are deviated by 90 degrees. CONSTITUTION:Two signals in a phase A and a phase B outputted from encoders are converted into digital signals in A/D converters 12a and 12b. The signals are inputted in an operator 14 (constituted of microprocessors and the like). The operator 14 obtains the amplitudes and the offset values in the respective phases based on the maximum values and the minimum values in the respective phases. The signal data of the phase A and the phase B wherein there is no offset and the amplitudes are equal are obtained. The phase difference is obtained based on the signal data in the phase A and the phase B, and the phase difference is corrected. The signal data in the phase A and the phase B wherein the phase is deviated by 90 degrees are computed. An interpolating signal theta based on the computed signal data in the phase A and the phase B is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an encoder for detecting the rotational position of a motor or the moving position of a table of a machine tool.

BACKGROUND ART As encoders for detecting rotational positions such as the rotational position of a rotor in a motor, there are known magnetic encoders that detect rotational positions using magnetically sensitive elements, photoencoders that use photoelectric elements, and the like.

From these encoders, the A, phase is 90 degrees out of phase.

A B-phase sine wave is obtained, and the rotation position and direction of one rotation are determined from the A-phase and B-phase sine wave signals. Furthermore, this A
An interpolated signal is also created from the phase and eight-phase sine wave signals.

Ideally, the output from the encoder is a sine wave or a COS wave with a phase shift of 90 degrees, but in reality it is a phase A,
As shown in the following equations (1) and (2), the amplitude, offset, and phase difference of the eight phases are not ideal.

A-KASinθ+OA...(1)
B-K 5in (θ+a) +O-・-” (2)
B B Note that K and K are the amplitudes of A phase and B phase, and OA.

8B OB is the offset value of the A phase and B phase (DC component), and α is the phase difference (α-90 degrees in the ideal state).

Therefore, conventionally, the amplitudes KA and K and the offset 0.0. The phase difference α is adjusted to be 90 degrees. And ideal A phase-K sin θ.

Assuming that the B phase-K CO5θ signal is obtained,
The interpolated signal θ was obtained by calculating the following equation (3).

B-tan-1 (K S In6 ) ・−・−
(3) K CO3θ Problems to be Solved by the Invention By polygon adjustment, etc., the amplitudes of the A-phase and B-phase output signals from the encoder are made the same as the off-cert values OA and OB, and the phase difference α Adjusting the angle to exactly 90 degrees is extremely difficult and requires time and effort.
Also, by adjusting these parameters, the ideal K si
It is very difficult to drive the signals to nθ and Kcosθ. Furthermore, the encoder itself undergoes temperature changes and changes over time, and it is extremely difficult to adapt to these temperature changes and changes over time and always obtain ideal signals.

Therefore, the object of the present invention is to improve the amplitude and offset.

An object of the present invention is to provide an encoder interpolation method in which a phase difference is automatically adjusted by a processor and an accurate interpolation signal can be obtained.

Means for Solving the Problems The present invention converts two signals, A phase and B phase output from an encoder, into digital signals and inputs them to a processor,
The processor is the maximum value of each phase.

Find the amplitude and offset value of each phase from the minimum value, find the A phase and B phase signal data with the same amplitude and no offset from the found offset value and amplitude, and calculate the phase from the A phase and B phase signal data. The above problem can be solved by determining the phase difference, performing phase difference correction, calculating signal data of phase A and phase B with a 90 degree phase shift, and creating an interpolated signal from the calculated signal data of phase A and phase B. solved.

Let the two signals from the operational encoder be A-phase and B-phase signals as shown by equations (1) and (2).

A-KAsinθ+OA −・−−−(1)
B−KBsin(θ+a)+OB−−(2
) Then, the rotary disk of the encoder rotates, and the above (1)
, A-phase and B-phase signals as shown in equation (2) are output, and when these are converted into digital signals and input to the processor, the processor receives the A-phase signals.

The maximum values AlaX, Bmax and the minimum values Amtn, 31+n of the B-phase signal are determined. Once these maximum and minimum values are found, since the A-phase and B-phase signals are sine waves, the offset value of each phase is 0. 0, the amplitude is found.

AB A O-<Aviax +Am1n)/2 -・-
---(4) O= <Blax + [3m1n)/2
−= (5)K −(Alax −AIi
n)/2 = (6) 8K −<Blax −8m1n)/2
”----(7) Then, subtract the obtained A-phase offset l1lIOA from the A-phase input signal, that is, equation (1), and from the B-phase input signal, that is, equation (2),
Subtract the offset value O obtained from equation (5) and get K /KB
By multiplying by B A , as shown in the following equation (8) and (9), the correction signal A of the A phase and B phase with equal amplitude and no offset is obtained.
'B' is obtained.

A′ −A OA = K As1nθ ・−
...-(8)B'-(KA/ni,) (B-0,
)−KAsin(θ+(Z) −−−−
(9) If we assume a Lissajous waveform with the signal A' shown in equations (8) and (9) above on the vertical axis and the signal 8' on the horizontal axis, it will be an ellipse as shown in Figure 4. A figure is obtained (note that if the value of α is 90 degrees, it will be a circle, but since the value of α is around 90, it will be an ellipse figure.) Next, the distance from the center to the top of the ellipse is 1 below, When determining r (referred to as the radius of the ellipse), the following equation (10) is obtained.

r − (A/ 2 + B/ 2 > 17
2.2.2 = K A (S l n O + sin (θ + α month 1/2... (10) The radius r of this ellipse is the radius r of the ellipse, which is the radius of the ellipse at both ends on the major axis and at both ends on the minor axis. becomes a local maximum or minimum value.

Therefore, by finding the square r2 of the radius r of the ellipse, we get the following (1
1) It becomes like the formula.

Differentiating equation (11) with respect to θ, -K 2(sin 2θ+5in(2θ+2α))^ =2 to 2sin(2θ+(2) cosaA
(12) Since the value of α is near 90 degrees, COSα is not “0”.

Therefore, the point where the differential of 2 is "0" is sin (2
θ-1-a) -0-...-(13) Therefore, 2θ+
Since equation (13) becomes [0] when α-nπ, θ=-α/2. θ−(π/2)−(α/2).

When θ-π-(α/2) and θ-(3π/2)-(α/2), the radius r of the ellipse becomes the maximum and minimum, and the maximum and minimum values of the radius r are given by Equation (10). Therefore, θ=-α/2 or θ
-π-(α/2), r-KAl 5in(α/2
) I x co-(14) θ-(π/2)-(α/2) or θ-(3π/2)-(α/2), r-KAI C03((Z/2) l xrΣ・=
(15). That is, when the value of phase difference α is smaller than 90 degrees, C03((2/2) is 5in(α/
2) Since it is larger than the maximum value of the radius r of the ellipse (major axis)
rsax, the minimum value (minor axis) rain is the next (16th
) and Equation (11).

rsax −ar”2°−K cos(α/2)
”・ (16)^ rain-C7-Ksin(α/2) -117)
Also, when the value of phase difference α is larger than 90 degrees, rsa
x-f-Σ-Ksin(α/2) ・(1
8) ＾ rain-C-Kcos (α/2) ・(19)
becomes.

As a result, when α<90, that is, the long axis r wa
x is the first. 3rd quadrant (A'> O, B'> O or A
'<O,B'<0), the (16th).

From equation (11), a −2−jan” (−LuL) ・・・・・・
・(20) When laX α>90, that is, the long axis r laX is the second,
Third quadrant (A'> O, B'< O or A+ < 0.
8'> 0), −1rlaX α=2・tan (−−〒−)・・・・・・(21
) rug10 , the phase difference α is determined.

Next, if we calculate the value B, which is obtained by subtracting COSα・A′ from B′ in equation 9 and dividing it by sin α, we get
As shown in the equation, it is possible to obtain a signal B'' having the same amplitude and a phase difference of 90 degrees with respect to the correction signal A'.

B"-(B'-cos a-A')/s
in a-(K 5in(θ+a) -K sin
θ-cos a ) /sin aA
^ = KACO3θ ・・・・・・(22
) Therefore, from Equation (22) and Equation (8) above, it follows. As a result, the A phase input to the processor.

By performing the above processing on the eight-phase digital signal, the interpolated signal θ can be obtained.

Embodiment FIG. 2 is a block diagram of an embodiment of the present invention. In the figure, 10a and 10b are differential amplifiers, which output A-phase signals output from the detection element of the encoder with a phase shift of 180 degrees. A, A, and B phase signal B.

Amplify the difference between A and B, remove the offset (DC component) of A phase signal A, A and B phase signal B, which are 180 degrees out of phase, and output A phase signal A and B phase signal B. are doing.

12a and 12b are analog-to-digital conversion i! (below,
An A/D converter) converts the A-phase signal A and the B-phase signal B into digital quantities. The A-phase signal A and the B-phase signal B are input to a processor 14 composed of a microprocessor, etc., and the microprocessor (hereinafter, CP
U) is a predetermined period, and the above A-phase signal A of the input signal,
It reads the B-phase signal B, performs processing to be described later, and outputs an interpolated signal θ.

FIGS. 1(a) to (C) show the arithmetic unit 14 in this embodiment.
1 is a flowchart of processing performed by the CPU of
The CPU No. 4 performs this process at predetermined intervals.

First, when the NN is turned on to the machine that uses this encoder and the power is turned on to the encoder and the computing unit 14, etc.,
The CPU performs initialization processing and initializes registers, flags, counters, etc. provided in the memory in the arithmetic unit 14. That is, the signals SA of the A phase and B phase input to the dancer 14,
Registers AlaX and B that store the respective maximum values of B
A register A11n that sets sax to the minimum value that the register can store and stores the minimum values of the A phase and B phase signals A and B.
.

The maximum value that can be stored in each register is set in Bmtn, and the register rgiax stores the maximum value and minimum value of the distance r from the center of the ellipse obtained by the above-mentioned equation (10).
, set ri+in to "0" and input signals A and B.
The registers D and D', which store the quadrant position on the elliptical locus detected from , are set to "0", the flag P and CPE are set to rOJ, and the counter CT is set to "0".

The CPU is shown in Figure 1 (a) to (cl).
Start.

First, input signals A and B are read (step 101).

Note that the A-phase and B-phase signals are (1).

Offset value OA as explained in equation (2).

O, the amplitude is KA, and the phase difference α (α is approximately 90
It is a sine wave signal of degrees). Next, it is determined in step 102 whether the value to the signal is smaller than the value of register A*aX.
), at the beginning, the value of register A igax is initialized and the minimum value is stored, so from step 102 to step 1
Proceed to 03 and read the signal A into the register A
Set the value of Then, the value of signal A is set to register A.
Step 104 to determine whether the value is greater than the win value.
), at the beginning, the maximum value is stored in the register A sin during initialization, so the process proceeds to step 105, and the value of the signal loaded into the register As1n&:fi is stored (step 105).

Similarly, the read value of signal B and register Bmax,
The values of Bg+in are compared, and initially, the minimum value is stored in the register f3 wax and the maximum value is stored in the register B win during initialization, so the register 3max.

The read values and the value of signal B are stored in B11n (steps 106 to 109).

Next, registers Ag+ax, Aatn, 3ma
x.

The calculations of equations (4) to (7) are performed from the value stored in B sin (step 110), and the offset value OA is obtained.

Find OB, amplitude KA, and use these values and input signal A.
, B, the v4 calculation of equations (8) and (9) is performed to obtain correction signals A' and B' (step 111). Then, the radius r of the ellipse is determined by calculating equation (10) from the obtained correction signals A' and B' (step 112).
＞, In addition, at the beginning, 76, laX -Asin -A,
Since 3max = 3min-8, the correction signal @A'
, 8' is rOJ, and the radius r of the ellipse is also "0".

Next, the radius r and rlaX of the obtained ellipse.

It is compared with the value of r sin, but at the beginning rlaX is initialized.
.

r sin is set to ``0'' and initially the radius of the ellipse r
is also “0”, so steps 113, 118°120
However, in step 120, the flag P is initialized to "0".
”, so the process goes to step 122 and the step (
21) Calculate the equation to find the phase difference α, which is the true maximum value rlaX of the radius r of the ellipse.

Since the minimum value r giin has not been determined, this phase difference α is not a correct value. Then, the calculation of equation (22) is performed (step 123), but in this case as well, the correct B
” cannot be calculated.Next, it is determined whether the flag CPE is “1” or not, and since the flag CPE is initially initialized to “0”, the process moves from step 124 to step 125, and the correction is performed. From the signs of signals A' and B', the radius r of the ellipse is
Detects the quadrant where A'-8' -0 currently exists.
Therefore, "0" is stored in register D that stores the quadrant.

Then, the combination of D' is determined from the value of this register D and the register D' (initially D'-0) which stores the quadrant in which the radius r of the ellipse exists in the previous cycle. (D, D') - (0,0), the process moves to step 131 via steps 127 and 129, stores the value of register D in register D', and then
) is performed to output a temporary interpolation signal θ (step 127).

Although this interpolation signal θ is not a correct value, it is output as a signal to operate the device.

Next, the value of counter CT exceeds 4, or
Step 133) to determine whether it is smaller than -4, starting with C
Since it is T-0, the processing for this cycle is ended.

In the next cycle, the input signals A and B are read again (step 101), and if the value of the read signal is larger than the value stored in the register A*aX, the value of the read signal A is stored in the register A*aX. Also, the value of signal A is
If it is smaller than the value of sin, the value of signal A is stored in register A sin. Similarly, if the value of the read signal B is greater than the value of the register BlaX, the register 31a
Store the value of signal@B in X, and if it is smaller than register B gcin, store it in register 3m1n (step 102
~109).

Next, calculate the offset value o, o, , oscillation [KA, by calculating the equations (4) to (7) (Sterap 110).
, calculate the corrected signal @A' by calculating the equations (8) and (9).
, B' are determined (step 111), and the radius r of the ellipse is determined by calculating equation (10) (step 112).

Next, compare the radius r of the ellipse found with the value of the register rlaX that stores the maximum value of the radius r.
x-0) (step 113), if the calculated radius r is large, store this radius r in the register r wax (step 114), the correction signal A' calculated in step 111
, B', the quadrant in which the radius (maximum value) exists is determined (step 115). That is, A'>0.8'>
If 0, the first quadrant; if A'> O, B'< Q, the second quadrant; if A'<0.8'< O, the third quadrant;
A'<O.

If D′〉0, it is the fourth quadrant, and the first. If it is in the third quadrant, flag P is set to "0", and if it is in the second quadrant. If it is the fourth limit, set the flag P to NJ (steps 116 and 117), and compare the value of the register r laX that stores the minimum value of the radius with the calculated radius r (step 118), and set the calculated radius r If is smaller, the value of this radius r is stored in the register r sin (step 119).

Then, if the value of the flag P is "0", the equation (20) is calculated, and if the value of the flag P is "1", the equation (21) is calculated to calculate the phase difference α.
(steps 120 to 122), calculate the value of B" by calculating equation (22) (step 123), and then:
Step 124) Determine whether flag CPE is "1" or not.
, since the flag CPE has not yet been set to "1", the quadrant of the radius of the ellipse is found from the signs of the correction signals A' and B' (step 125), and this quadrant and the quadrant D' found in the previous cycle are (step 127)
．． 129), since it is D'-〇 for up to two cycles after initialization, the process advances to step 131, and the above-mentioned process 1! i!
The processes of steps 132 and 133 are performed to complete the process of the cycle.

Thus, if the above processing is performed for each round mN1, step 10
By processing steps 1 to 109, registers AIaX, A
The maximum and minimum values of the signals A and B so far are stored in s1n, 3sax, and 31in, and in the processing of steps 110 to 119, the maximum and minimum values of the radius of the ellipse are stored in register rlaX.

It will be stored in r lin. Furthermore, depending on the direction of rotation of the rotary disk of the encoder, the radius r of the ellipse in FIG. The combination (D, D') is (2,1)(3,2)(4,3)(
1, 4), and when such a combination is detected (step 127), "1" is added to the counter CT (step 128). Also, if it is clockwise, the combination (D, D
) is (4,1)(3,4)(2,3)(1,2), and when such a combination is detected, step 12
9) , subtract "1" from the counter CT (step 1
30).

Then, when the value of the counter CT exceeds 4 in step 133 or becomes smaller than -4 (step 133), which means that the radius r of the ellipse has turned approximately -, in step 134 Set flag CPE to "1".

Then, the fact that the radius r of the ellipse has turned approximately - means that the maximum value of the signals A and B, the small It value, and the maximum value and minimum value of the radius of the ellipse are sin to each register AlaX.

3max, Bg+in, rg+ax, r-
This means that it is stored in in. Then, when the maximum value of the radius of the ellipse appears through the processing of steps 115 to 117, that is, the long axis position of the ellipse is at the first. If it is in the third quadrant, the flag P is set to "0", and the second.
If it is in the fourth quadrant, it is set to 1°1. As a result, the flag P is set to "0" and the major axis is the first. When it is in the third quadrant and the phase difference α is less than 90 degrees,
Calculation 211 of equation (20) is performed to obtain the phase difference α (step 121). Also, flag P is set to "1",
The long axis is the second. If it is in the fourth quadrant and the phase difference α exceeds 90 degrees, the phase difference α is determined by performing the expression (21) (step 122). Then, the calculation of equation (22) is performed using the obtained phase difference α and the correction signal A'B' obtained in step 111 (step 123), and IB
Since the flag CPE has already been set to "1", the process proceeds from step 124 to step 126, where equation (24) is calculated to obtain and output the interpolated signal θ. In addition, in this case, the maximum value and minimum value Amax, Aitin, during one cycle of the A-phase and B-phase signals are
Since 8i+ax, 8sin, the maximum value rlaX, and the minimum value rwin of the radius r of the ellipse have been determined, this interpolation signal θ is different from the interpolation signal determined in step 132 and is a correct interpolation signal.

Below, steps 101 to 124 and step 1 for each cycle
26 processes are performed to output an interpolated signal θ for each synchronization.

In the above embodiment, after the power is turned on, the A phase and B phase are
Find the maximum value and minimum value of the phase signal, the maximum value and minimum value of the radius r of the ellipse, and calculate the offset values 0 and O of the A-phase and B-phase signals.
, amplitude, and phase AB
Since the phase difference does not change frequently, and may change due to changes in temperature or changes over time, these offset values of 0.0B and amplitude KA may be adjusted as necessary.

8 and phase difference α, and in normal processing, an interpolation signal may be output based on the already determined offset value and amplitude 9 phase difference.

In this case, a non-volatile RAM is provided in the arithmetic unit 14, and an offset value of 0. 0,
Store amplitude, , and phase difference α AB
In addition, for example, a parameter adjustment command is provided as a command to the CPU of the calculation unit 114, and when this parameter adjustment command is input, the CPU of the calculation unit 14
performs steps 101 to 123 in FIG. 1, proceeds from step 123 to step 125, and performs steps 125 to 133 until the value of counter CT exceeds 4 or becomes smaller than -4. Repeat the above process. As a result, one cycle of signals of A phase and B phase is captured, and a maximum of 1iAsa of A phase and B phase is captured.
x, 131aX, minimum value As1n, B11n
From these values, the (4)th to (7th)
), the offset value is 0.0. .

The amplitude KA is determined and stored in the nonvolatile RAM.

Furthermore, from the signs of the correction signals A' and B' when the value of the radius r of the ellipse takes the maximum value @ r la If it is smaller than 90 degrees, the second
0) to find the phase difference α, and when it is larger than 90rx, calculate the equation (21) to find the phase difference α, which is stored in the non-volatile RAM, and the parameter adjustment process ends.

In normal processing, the processing shown in the flowchart of FIG. 3 is performed at predetermined intervals, and an interpolation signal θ is output.

First, read input signals A and Bt (step 201),
Signal A is read with an offset value of 0.0 and an amplitude stored in non-volatile RAM.

Calculate equations (8) and (9) from the values of AB A B to obtain correction signals A' and B' (step 202), and store the obtained correction signals A' and B' in the nonvolatile RAM. Calculate equation (22) from the stored phase difference α to obtain B I
The value of f is determined (step 203), and the calculation of equation (24) is performed using the determined B'' and the value of the correction signal A' to determine and output the interpolated signal θ (step 204).

Thereafter, the above process is repeated for each period, and the interpolated signal θ is obtained for each synchronization.
Output. Also, when temperature changes or secular changes occur, the above-mentioned parameter adjustment process is performed to set the offset value to 0A, 0. , amplitude KA.

What is necessary is to find the value of the K32 phase difference α and update these values stored in the nonvolatile RAM.

Effects of the Invention The present invention automatically determines the offset value, amplitude, and phase difference of the A-phase and B-phase signals output from the encoder, and calculates the offset value, amplitude, and phase difference of the A-phase and B-phase signals output from the encoder. Since the signal is determined, an accurate interpolation signal can be obtained from these two signals. As a result, there is no need for analog adjustment using a volume or the like for offset, amplitude, and phase difference adjustment as in the prior art, and the accuracy of the interpolation signal is improved.

Furthermore, it is possible to cope with temperature changes and secular changes, and to obtain accurate interpolated signals.

[Brief explanation of drawings]

FIGS. 1(a) to (C) are operation flowcharts of one embodiment of the present invention, FIG. 2 is a block diagram of main parts of an encoder implementing the same embodiment, and FIG. 3 is a diagram of another embodiment of the present invention. The operation flowchart in FIG. 4 is an explanatory diagram of the surge waveforms of the correction signals A' and B' obtained in the embodiment of the present invention. 10a, 10b...Differential amplifier, 12a, 12b...Analog-digital converter, 14
...A stick player. Part 1 (a) Part 1

Claims (1)

[Claims] The two signals of phase A and phase B output from the encoder are converted into digital signals and input to the processor, and the processor calculates the amplitude and offset value of each phase from the maximum and minimum values of each phase. Find the A-phase and B-phase signal data with the same amplitude and no offset from the offset value and amplitude, find the phase difference from the A-phase and B-phase signal data, perform phase difference correction, and calculate the 90 degree phase shift. 1. An interpolation method for an encoder, characterized in that A-phase and B-phase signal data are calculated, and an interpolation signal is created from the calculated A-phase and B-phase signal data.