JPH0894385A - Detector for detecting position of moving member - Google Patents

Abstract

PURPOSE: To perform highly accurate detection by finding a ratio of a plurality of sine waveforms having specific angle dislocations, obtaining a triangular waveform which linearly changes for the change of the position of a moving member, and interpolating the position of the moving member on the basis of a composed triangular wave. CONSTITUTION: Signals A1, B1 which A/D-convert two analog signals Va, Vb mutually having the dislocation of a 90 deg. phase are prepared from an MR element output amplification part 8. In a control part 11, an A/D conversion value of each analog signal is converted into a difference from the intermediate level, ratios of signals themselves is calculated, and K1 and K2 are obtained. A triangular wave of a large amplitude is obtained by connecting K1 and K2 at the intersection thereof in the control part 11, and interpolation calculation is performed. In the interpolation calculation, the values of K1 are divided into four cases, and a minute distance Δd between pulses is calculated. And a final moved distance D is calculated by an approximately moved distance d and the minute moved distance Δd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving member position detecting device for detecting the position of an object, and more particularly to a moving member position detecting device for obtaining a signal from a detector for position detection as a sine wave.

[0002]

2. Description of the Related Art Conventionally, as a typical method of a linear encoder, an optical method using a main scale and a subscale having minute slits that transmit and block light, and an N pole and an S pole with a minute width are perforated. There is known a magnetic system in which a magnet magnetized in the above is detected by a magnetic detection element.

In either method, a sine wave can be obtained as a detection signal. The comparison between the intermediate level of the detection signal and the analog signal represented by the sine wave is performed, and when the signal crosses the intermediate level, it is converted into a pulse signal,
The number of times of the pulse signal is counted to detect the movement amount.

In order to increase the detection resolution of the moving amount, the slit width of the scale may be reduced in the case of the optical system, and the magnetized width of the magnet to be magnetized may be reduced in the magnetic system.

However, the smaller the slit width of the scale and the finer the magnetizing width, the smaller the signal from the detector and the lower the SN ratio. Further, in the case of the optical system, the gap between the main scale and the sub-scale, and in the case of the magnetic system, the gap between the magnetized magnet and the magnetic detection element becomes small, and the allowable fluctuation range thereof becomes very small. As a result, very strict dimensional accuracy is required for the element and scale configurations, and there is a limit to increase the detection resolution.

Therefore, apart from converting the analog signal into a digital signal at the midpoint level, an interpolation method is known in which the analog signal is finely divided and the digital signals are finely divided to increase the detection resolution. There is. Here, the interpolation means dividing the periodic signal output to obtain phase information finer than the frequency of the signal.

However, since the signal obtained by the detector is a sine wave and has a portion that changes substantially linearly and a portion that the polarity of the signal reverses while changing gently, the resolution cannot be uniformly improved. A method for solving such a problem is, for example, Nikkei Mechanical May 31, 1993.
It is disclosed in the Japanese issue. FIG. 10 is a diagram for explaining the interpolation method disclosed in Nikkei Mechanical. Here, a rod-shaped permanent magnet and three ferromagnetic film resistance elements (hereinafter abbreviated as MR elements) are used as the position sensor.

Referring to FIG. 10, the outputs of the three MR elements are combined to obtain a sawtooth waveform output. Since the position is detected using only the portion where the voltage change is large with respect to the phase change, accurate interpolation becomes possible.

[0009]

In the conventional position sensor detection method devised to improve the resolution, since the outputs of three MR elements are used, the number of circuits increases and the cost increases. there were. Further, according to this method, when the signal level changes, the amplitude of the triangular waveform also changes, which causes a detection error.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a position detecting device for a moving member, which can improve the resolution and can stably obtain high detection accuracy. .

[0011]

SUMMARY OF THE INVENTION A position detecting device for a moving member according to the present invention moves while moving and outputs first and second sinusoidal signals whose phases are shifted from each other by 90 ° according to the position. Member, means for obtaining the ratio of the first and second output signals, means for synthesizing continuous triangular waveforms based on the value of the ratio, and means for interpolating the position of the moving member based on the synthesized triangular wave. Including and

[0012]

By calculating the ratio of two sinusoidal waveforms that are offset by 90 °, it is possible to obtain a triangular waveform that changes linearly with respect to the change in the position of the moving member. Further, since the ratio of the signals is taken, even if there is a change in the amplitude of the analog signal, they are canceled by each other.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a position detecting device for a moving member according to the present invention will be described below based on the case where this device is used as a lens position detector. This lens position detecting device uses an MR element whose resistance changes with a change in magnetic field.

FIG. 1 is a block diagram showing the arrangement of a lens position detecting apparatus according to this embodiment. Referring to FIG. 1, the lens position detecting device includes an MR element 5 on which a lens 4 is mounted,
A magnetized magnet rod 6 that performs position detection integrally with the MR element 5, an MR element output amplification section 8 that processes an output signal from the MR element, a pulse signal conversion section 9, and an A / D conversion section 10
And a control unit 11.

The driving of the lens 4 in the optical axis direction is performed by controlling the piezoelectric actuator 3 by the piezoelectric actuator driving section 7. The position of the lens 4 is detected by the combination of the MR element 5 and the magnetized magnet rod. The output signal from the MR element 5 is amplified by the MR element output amplification section 8. The pulse signal converter 9 compares the amplified signal with the intermediate level of the above signal to convert it into a pulse signal. Also, MR
The output signal from the element 5 is also input to the A / D conversion unit 10 to perform digital value conversion, and the control unit 11 performs interpolation calculation.

FIG. 2 is a diagram showing the characteristics of the resistance change of the MR element with respect to the magnetic field. The X axis in the figure represents the strength of the magnetic field,
The Y axis represents the resistance value. The relationship between the signal magnetic field of the MR element and the output signal is also shown in the figure.

FIG. 3 is a diagram showing the relationship between the magnetized magnet of the MR element used in this embodiment and the output signal. Since the magnetizing magnet rod 6 is magnetized as shown in (b), its magnetic field changes as shown in (a). Two pairs of MR elements 5a and 5b are arranged on this, as shown in (c). As a result, as shown in (d), a pair of MR elements 5a to V
The sine wave indicated by a is output, and a Vb sine wave signal that is 90 ° out of phase with Va is obtained from the other pair of MR elements 5b. Based on the signal thus obtained, a Vad signal which is a pulse signal of Va as shown in (e) and a Vbd signal which is a pulse signal of Vb as shown in (f) are obtained. Based on the rising and falling edges of the above signal, the pulse signal converter 9 obtains an output signal of λ / 8 pitch as shown in (g).

FIG. 4 is a diagram showing respective circuits of the MR element 5, the MR element output amplifying section 8 and the pulse signal converting section 9 shown in FIG. With reference to FIG. 4, the output of the MR element 5 is amplified by the operational amplifiers 81 and 82 of the MR element output amplification section 8, and the comparators 91 and 92 of the pulse signal conversion section 9 are amplified.
Thus, pulse signals Vad and Vbd are obtained. Here, the operational amplifiers 81 and 82 amplify the output signal from the MR element 5 about 50 times.

FIG. 5 is a flow chart showing a method for detecting the lens position. A method for detecting the lens position will be described with reference to FIG. The signal output from the pulse signal conversion unit 9 is input to the pulse counter provided inside the control unit 11. The count value of this input pulse signal is called and the value is set to n (step # 1,
The following steps are abbreviated). Since the moving amount of the lens per pulse of the pulse signal is λ / 8 as shown in FIG. 3, the approximate moving distance d can be calculated by n * λ / 8. However, λ is the distance from the N pole of the magnetizing magnet to the adjacent N pole (Fig. 3
(B)).

Next, a method of calculating the moving distance between pulses will be described. The A / D converted values of the analog signals Va and Vb from the MR element output amplifier 8 are A1 and B1, respectively, and the value corresponding to the intermediate level A / D converted value of the analog signals Va and Vb is Vr (# 3).

In the control unit 11, the A / D converted value of the analog signal is A2 = A1-Vr, B2 = B1-
The value is converted from the intermediate level of the signal to its value by the calculation formula of Vr (# 4), and the ratio of each signal is calculated by K1 = A2 / B.
2, K2 = B2 / A2 (# 5).

FIG. 6 shows how the ratio values K1 and K2 calculated in # 4 and # 5 described above change. As can be seen from FIG. 6, K1 is a function of monotonic increase in λ / 4 period, and K2 is a graph of monotonic decrease in the same period. By connecting K1 and K2 at their intersections in the control section 11, a triangular waveform having a large amplitude can be obtained. The control unit 11 performs interpolation calculation using this triangular waveform.

In the interpolation calculation, the minute distance Δd between the pulses is calculated by the calculation formulas # 7 to # 10 in four cases according to the value of K1. Specifically, K
When 1 is 0 or more and 1 or less (0 ≦ x ≦ λ / 16), 1 <K1 (λ / 16 <x <λ / 8) according to the equation (1)
Then K1 ≦ −1 (λ / 8 <x <3 according to the equation (2).
When λ / 16), −1 <K1 <0 according to the equation (3).
When (3λ / 8 <x <λ / 4), Δd is calculated by the equation (4). In addition, in FIG. 6, # 7 to # 1 in FIG.
The part corresponding to 0 is specified.

Δd = (λ / 16) * K1 (1) Δd = λ / 16 (2-K2) (2) Δd = − (λ / 16) * K2 (3) Δd = (λ / 16) * (K1 + 2) (4) Then, the final movement distance D is calculated from the rough movement distance d and the minute movement distance Δd (# 11).

FIG. 7 is a graph corresponding to FIG. 6 showing the calculation result of the ratio between the respective signals when the signal amplitude changes. As can be seen from the figure, even if the amplitude fluctuates, the triangular waveform synthesized from the ratio calculation result has no effect. That is, even if the amplitude of the sine waveform varies, they are canceled by each other, so that a stable triangular waveform can always be obtained and the detection resolution can be stably improved.

FIG. 8 is a magnetized magnet rod 6 for detecting the end position in the moving direction of the lens 4 shown in FIG.
FIG. 3 is a diagram showing the configuration of and the signal waveform of the MR element 5 obtained at that time. FIG. 8A shows the case where the ordinary magnetizing magnet rod 6a is used, FIG. 8B shows the case where the notch grooves 21 are provided at both ends of the magnetizing magnet rod 6b, and FIG. 8C shows the notch. It is a figure which shows the case where the magnetized magnet rod 6c which stuck the thin iron plate on the groove | channel 21 is used.

As can be seen from the signal waveforms shown in FIGS. 8B and 8C, the signal is generated when the magnetic field is not applied to the MR element 5 by the notch groove 21 or the thin iron plate 22 provided thereon. Is constant at the intermediate level 24. Therefore, by detecting this level 24, the end position of the lens 4 can be detected. Further, when this structure is used, the end position can be visually recognized, so that the mounting position of the magnetized magnet rod 6 can be mechanically adjusted.

FIG. 9 shows a lens 4 using the structure shown in FIG.
5 is a flowchart showing a method of detecting the end position of the. Referring to FIG. 9, first, a value corresponding to an A / D converted value at an intermediate level between analog signals Va and Vb is set to Vr (#
20). The piezoelectric actuator driver 7 is controlled to move the lens 4 in a fixed direction (# 21). The analog signals Va and Vb from the MR element output amplifying section 8 are A / D converted into A1 and B1 respectively (# 22). Then A
It is determined whether both 1 and B1 are equal to Vr (# 2
3) If they are not equal, the process returns to # 22, and if they are equal, it is determined to be the end position of the lens 4, and the lens drive is stopped (# 2).
4).

Although the notch groove 21 is provided at the end position in the above embodiment, it may be provided at a desired position to be detected.

[0030]

As described above, according to the present invention, 90 °
By obtaining the ratio of the two shifted sine waveforms, it is possible to obtain a triangular waveform that linearly changes with respect to the change of the position of the moving member, and it is possible to improve the detection resolution. Further, since the ratio of the signals is taken, even if there is a change in the amplitude of the analog signal, they are canceled by each other, so that a stable triangular waveform is always obtained and the detection resolution can be stably improved.

As a result, it is possible to provide a position detecting device for a moving member which can improve the resolution and can stably obtain high detection accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing characteristics of resistance change of an MR element with respect to a magnetic field.

FIG. 3 is a diagram showing an output signal waveform with respect to a magnetized magnet of an MR element used in this example, and a signal obtained by a pulse signal conversion unit.

FIG. 4 is a circuit diagram showing an MR element, an MR element output amplification section, and a pulse signal conversion section.

FIG. 5 is a flowchart showing a lens position detection method.

FIG. 6 is a diagram showing a relationship between two signal waveforms obtained from the MR element and a ratio between the signals.

FIG. 7 is a diagram showing a relationship of ratios of respective signals when the signal amplitude varies.

FIG. 8 is a diagram showing a configuration example of a magnetizing magnet for detecting the end position of the lens and one signal waveform of the MR element.

FIG. 9 is a flowchart showing a method for detecting the end of the lens position.

FIG. 10 is a diagram showing a detection method of a conventional position sensor.

[Explanation of symbols]

 3 Piezoelectric actuator 4 Lens 5 MR element 6 Magnetizing magnet rod 7 Piezoelectric actuator drive section 8 MR element output amplification section 9 Pulse signal conversion section 10 A / D conversion section 11 Control section

Claims (1)

[Claims] 1. A moving member that outputs first and second sine wave signals whose phases are shifted from each other by 90 ° according to the position while moving, and a ratio of the first and second sine wave signals. A position detecting device for a moving member, comprising: a means for obtaining, a means for combining continuous triangular waveforms based on the value of the ratio, and a means for interpolating the position of the moving member based on the combined triangular wave.