JPH04339206A - Detection of position - Google Patents

Abstract

PURPOSE:To enable highly accurate detection of the position of a moving object by determining the sine value of a phase error under specified conditions utilizing a 2-phase AC signal value corresponding to the movement of the moving object to correct the phase error by the sine value. CONSTITUTION:2-phase AC detection means comprising a gear 2 and magnetic sensors 3 and 4 fastened on a moving object 1 detects 2-phase AC signals Ea and Eb having a phase difference of 90 deg.. Instantaneous values of the signals Ea and Eb are sampled by an instantaneous value detection means 10. When a phase error is generated in the signals Ea and Eb. Ea= Vcos and Eb=Vsin (theta+alpha) (V: rotational speed of the gear 2 and theta: position within one tooth of the gear 2). With a phase error detection means 30, for example, a point is determined to meet dEb/dEa=0 based on data per cycle of instantaneous values of the signals Ea and Eb and sinalpha is calculated by a specified formula. A phase error correction section 9 corrects errors alpha of the signals Ea and Eb utilizing the sinalpha to detect 40 the position theta.

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] [Industrial Application Field] The present invention relates to a position detection method using a two-phase alternating current signal. [Prior Art] FIG. 5 shows a conventional position detection method. FIG. 1 is a schematic configuration diagram of a reluctance magnetic rotary encoder. A two-phase AC detection means consisting of a gear 2 fixed to the moving body 1 and magnetic sensors 3 and 4 having permanent magnets detects a two-phase AC signal Ea'=Vco having a phase difference of 90 degrees from each other.
Detect sθ and Eb'=Vsinθ. An instantaneous value detection means 10 consisting of a sample-and-hold (S/H) circuit 5 and an analog-to-digital (A/D) conversion circuit 6 detects two-phase AC signals Ea' and Eb from the two-phase AC detection means.
The instantaneous value of ′ is sampled and converted to digital. Interpolation signal detection means 20 consisting of a divider 7 and an arctangent calculator 8
is based on the instantaneous values of the two-phase AC signals Ea' and Eb' from the instantaneous value detection means 10.
/Vcosθ), the position θ within one tooth of the gear 2 is detected. [0003] Problems to be Solved by the Invention In the encoder that implements the conventional position detection method described above, due to variations in the characteristics of each element of the magnetic sensor, installation errors, etc., the actually detected two-phase AC signal Since the phase difference deviates from 90° and differs from the appropriate value, there is a drawback that highly accurate position detection cannot be performed. There are encoders that deal with this situation by installing a phase error correction circuit using an operational amplifier, etc. However, since the phase error correction circuit requires adjustment of variable resistors, etc., human adjustment errors may occur. However, there has been a drawback that stable and highly accurate position detection cannot be performed at all times due to deterioration of characteristics due to aging of circuit elements. Furthermore, the present applicant has proposed an encoder having a function of automatically correcting phase errors (Japanese Patent Application No. 1-310236). For example, Figure 4
In the Lissajous diagram when the two-phase AC signal includes an amplitude error Vβ/Vα and a phase error α as shown in
If you know the three points xi and yi (i=1 to 3), you can use equation 1, equation 2,
Since the values of a, b, and e can be found using equation 3,
Using these values, the amplitude error Vβ/Vα can be calculated from equations 4 and 5.
and phase error α to perform automatic correction. [Formula 1] a=(y22-y32)x1y1+(y3
2-y12)x2y2
+(y12-y22)x3y3
[Math. 2] b=(x22-x32)x1y1+(x3
2-x12)x2y2
+(x12-x22)x3y3 [Formula 3] e=(x22-x32)y12+(x32
-x12)y22
+(x12-x22)y32 [Formula 4] [Formula 5] However, the above calculation formula is complicated, and if there are fluctuations in the DC component (offset error) in addition to the amplitude error and phase error, these errors can be The calculation formula for detection becomes even more complex. Therefore, if points xi and yi contain minute errors, the calculated amplitude error, phase error, and offset error values will differ from the actual values, and noise will be mixed in at the detection timing. Similarly, there is a problem in that errors occur in the calculation results, making it impossible to perform highly accurate position detection. The present invention was made in view of the above-mentioned circumstances, and an object of the present invention is to provide a position detection method that can perform accurate position detection. [0004] The present invention relates to a method for detecting the position of a moving body using two-phase AC signals Ea and Eb corresponding to the distance traveled by the moving body. The above-mentioned object of the invention is to obtain 2 such that dEa/dEb=0 or dEb/dEa=0, where α is a phase error that is an error of the phase difference between the two-phase AC signals Ea and Eb from a predetermined value.
Find sin α based on the values of phase AC signals Ea and Eb, and calculate the two-phase AC signals Ea and E based on the sin α.
This is achieved by correcting the phase error α of b and detecting the position of the moving object based on the corrected two-phase AC signal. [0005] In the present invention, since the locus of the two-phase AC signal is utilized, the phase error can be corrected using a simple calculation formula. [Embodiment] FIG. 1 is a schematic configuration diagram showing an example of a reluctance magnetic rotary encoder that implements the position detection method of the present invention, corresponding to FIG. The explanation will be omitted. Assuming that a phase error α occurs in the two-phase AC signals Ea and Eb output from the two-phase AC detection means, the two-phase AC signals Ea and Eb are calculated as shown in equations 6 and 7.
It is expressed as [Equation 6] Ea=Vcosθ [Equation 7] Eb=Vsin (θ+α) At this time, the Lissajous figure of the two-phase AC signals Ea and Eb becomes an ellipse as shown in FIG. 3, and dEa/dEb=0 or dEb/dEa= Points that are 0 are P1, P2, P3, P
4, these coordinates are P1(V, Vs
in α), P2 (V sin α, V), P3 (-V, -V
sin α), P4(-Vsin α, -V). Then, as shown in the flowchart of FIG. 2, the phase error detection means 30 detects one period of the instantaneous values of the two-phase AC signals Ea and Eb detected by the instantaneous value detection means 10 (i=1 to N (N is an integer)). ) (step S1), and based on these data, calculate dEb/dEa=0 using equations 8 and 9.
Point P1 (V, Vsin α) = (Eai, Ebi)
(Step S2). [Formula 8] [Formula 9] Ea>0 Then, sin α is calculated and stored using Equations 10 and 11 (Step S3). [Equation 10] sin α=Vsin α/V=Ebi/V [Equation 11] The phase error correction unit 9 constituting the position detecting means 30 uses the calculated sin α and Equation 12 and Ebi/V to calculate Ebi/V using Equation 14. According to equation 15, two-phase AC signals Ea and Eb
The phase error α is corrected (step S4). [Formula 12] sin(θ+α)=sinθco
sα+cosθsinα [Formula 13] [Formula 14] Ea'=Ea=Vcosθ [Formula 15] Eb'=Vsinθ
=(Vsin(θ+α)−Vco
sθ・sinα)/cosα
=(Eb-Ea・sinα)/cosα The divider 7 and the arctangent calculator 8 that constitute the position detection means 40 are as follows.
Two-phase AC signals Ea' and Eb' from the phase error correction section 9
Based on the instantaneous value of θ=tan-1(Eb'/Ea')
The position θ within one tooth of gear 2 is detected by the calculation of (
Step S5), all processing ends. [0008] In the above-described embodiment, Equation 15 was used as the correction formula for the phase error α, but if the phase error α is small, cosα=k (k is a constant) may be used. In addition, since the phase error α does not constantly change, the phase error detection means 9 does not need to constantly detect the phase error α, but only at a certain time, and at other times. may be corrected using the value detected immediately before. Further, in this embodiment, a reluctance type magnetic rotary encoder has been described, but the present invention is not limited to this, and a linear encoder of a linear movement type may be used. In addition, it is not limited to the magnetic type, but other types,
For example, even an optical type can be applied as long as it uses a two-phase AC signal. [0009] As described above, according to the position detection method of the present invention, a stable and highly accurate position can be automatically detected at all times, so the man-hours for adjustment etc. can be reduced and the cost can be reduced. It is possible to reduce the

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an encoder that implements the position detection method of the present invention.

FIG. 2 is a flowchart illustrating the position detection method of the present invention.

FIG. 3 is a diagram showing a Lissajous diagram of a two-phase AC signal used in the position detection method of the present invention.

FIG. 4 is a diagram showing a Lissajous diagram of a two-phase AC signal used in a conventional position detection method.

FIG. 5 is a schematic configuration diagram showing an example of an encoder that implements a conventional position detection method.

[Explanation of symbols]

9 Phase error correction section 30 Phase error detection means 40 Position detection means

Claims (1)

[Claims] Claim 1: When detecting the position of the moving body using two-phase AC signals Ea and Eb corresponding to the moving distance of the moving body, the phase difference between the two-phase AC signals Ea and Eb is determined from a predetermined value. When the phase error is α, dEa/
Find sin α based on the values of two-phase AC signals Ea and Eb where dEb=0 or dEb/dEa=0, and calculate the si
A position detection method characterized in that the phase error α of the two-phase AC signals Ea and Eb is corrected based on nα, and the position of the moving object is detected based on the corrected two-phase AC signal.