JPS6227610A - Detecting method of absolute position - Google Patents

Abstract

PURPOSE:To detect the accurate (AR) position, by performing linear correction of temperature change in power transmitting system such as feeding shaft of an AR position detector, and performing non-linear correction of the temperature change in a position converter. CONSTITUTION:To an output shaft 58 of a motor 50, a ball screw 59 in a power transmitting system, which moves a table 51 back and forth in the direction of an axis X, is linked. A phase type AR position detector 54 is linked to the other end. An output PA on the secondary side from the detector 54 is fed back to a position converter 53. The output is converted into the position data. The data is sent to a CPU 57. Temperature sensors 60-62 are attached to the detector 54, the converter 53 and the screw 59. The signals from the sensors are converted into the temperature data 63 and sent to the CPU 57. Then the amounts of movement per unit temperature of the detector 54 and the screw 59 and the amount of movement of the converter at each temperature are obtained beforehand. The temperature is changed and the offset amount is obtained by the CPU 57. The offset amount is corrected with respect to the AR position. Then, the actual AR position can be computed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to converting data detected by a phase modulation type or amplitude modulation type absolute position detector into position data by a position converter. , when determining the absolute position from this position data, correct the error due to phase shift or amplitude fluctuation due to temperature change, and obtain the accurate absolute position. Available for

[Background technology and its problems]

-m, position data obtained from an absolute position detector using a phase transition (modulation) method or an amplitude modulation method such as a resolver, indantosin, or magnescale may undergo a phase shift due to temperature rise of the absolute position detector or position converter. and amplitude fluctuations.

Furthermore, when used in an NC device or the like, thermal displacement occurs on the machine shafts due to temperature rise in power transmission systems such as feed shafts and cutting shafts, causing apparent phase shifts and amplitude fluctuations.

Therefore, when calculating the absolute position based on the obtained position data, there is a problem in that errors occur depending on these temperature changes.

[Purpose of the invention]

An object of the present invention is to provide a method for correcting errors caused by these temperature increases and detecting a more accurate absolute position.

[Means and actions for solving problems] Therefore,
In the present invention, linear correction is performed for temperature changes in the power transmission system such as absolute position detectors, feed shafts of NC devices, cutting shafts, etc., and nonlinear correction is performed for temperature changes of the position converter. By doing so, the aim is to detect accurate absolute position.

Specifically, after the position of the drive source that moves the driven member via the power transmission system is detected by an absolute position detector, this data is converted to position data by a position converter, and the position of the driven member is determined from this position data. In the absolute position detection method for calculating the absolute position of a member, the position data obtained by the position converter or the absolute position calculated from this position data is detected by the absolute position detector, the position converter, and the power transmission system. It is characterized in that it is corrected in response to at least one temperature change.

〔Example〕

FIG. 1 shows an embodiment in which the present invention is applied to position control of a table of an NG machine tool. In the figure, a ball screw 59 as a power transmission system for moving a table 51 as a driven member forward and backward in the X-axis direction is connected to one end of an output shaft 58 of a motor 50 as a drive source. Phase type absolute position detector 5 on the other end side
4 are connected.

An electric wire 55 is connected to the absolute position detector 54 from the driver circuit 52 for supplying excitation current to its negative excitation winding. On the other hand, the secondary output from the absolute position detector 54 connects the electric wire 56 to i! A feed bank is also provided to the position transducer 53. The feed bank signal P^ is converted into position data by the position converter 53, and then sent to the central processing unit (hereinafter referred to as
It is called CPU. )57.

In addition, an absolute position detector 54 and a position converter 53
, for each of the ball screws 59! ffsey+60.
61.62 are installed. The signal θd from the temperature sensor 60 is sent through the electric wire 60A, and the signal θC from the temperature sensor 61 is sent through the electric wire 61A to the temperature sensor 6.
The signal θb from 2 is passed through the electric wire 62A to A/2, respectively.
The signal is supplied to a D converter 63. The signals θd and θC1θb supplied to the A/D converter 63 are each converted into temperature data, and then sent to the CPU 57 via the line 64 in the same manner as described above.

Based on the obtained position data and temperature data θd, θC1θb, the CPU 57 performs a correction corresponding to the temperature change T in a procedure described later, and calculates an accurate absolute position.

When temperature = 25°C (normal temperature) In Fig. 1, when the temperature T detected by each temperature sensor 60, 61, 62 is 25°C (normal temperature), in order to move the table 51 in the X direction , the motor 50 is θ
. Fig. 2 shows the image rotated by a degree.

In FIG. 2, a feedback signal PA from an absolute position detector 54 is converted into position data P, (θ) by a position converter 53.

For example, the motor 50 is θ. The position data obtained when rotated is α. It is expressed as Furthermore, the CPU 57 calculates the absolute position X based on the obtained position data PA(θ). For example, the motor 50 is θ. The absolute position obtained when rotated by degrees is calculated as Xo. However, since the temperature T = 25°C is used as the reference temperature here, there is no phase shift with respect to the position data.
The position data PA(θ) is assumed to be a digital quantity of 2000 base counts that changes linearly with respect to the feedback signal PA.

゛When T≠25°C In Fig. 1, if the temperature T of the absolute position detector 54, position transducer 53, and ball screw 59 increases and the feed bank signal PA causes a phase shift, the surface In order to move the table 5I in the X direction in the same way as the top,
motor 50 at θ. When rotated by degrees, the obtained position data Pa(θ) and absolute position X are respectively α.

+XO no longer matches.

As shown in Figure 3, when the temperature T≠25℃,
Position data P at the position where the rotation angle of the motor 50 is 0 point
This is because a'(θ) becomes ε (≠O).

Therefore, by finding the offset amount δ of the absolute position X corresponding to the position data C at the position where the rotation angle of the motor 50 is 0 point, and correcting the absolute position .

In the next section, we will show this correction method and calculate the absolute position
Of the γ agency feed bank signals θd and θC1θb of the absolute rising W based on 'e4jLM positive, which calculates 0, the temperature sensor 60
, 62, the feedback signals θd, θb from the temperature T
According to the change of θd and θb cc T , indicating linear operation. By the way, the A/D converter 63
As shown in Figure 4 (A) and (B'), the linear phase shifts θd(T) and θb are obtained by
(T), θd (T), θb(T
) CcTθd (T) = D (T-25) θb (T) = B (T-25) ・・・・・・(
1), and using the constant R and B, linear temperature change (T-
25) can be obtained.

Furthermore, since the feedback signal θC from the temperature sensor 61 operates nonlinearly according to changes in the temperature T, a discrete phase shift amount, cc (Ti), is made to correspond to a minute temperature section as shown in FIG. Similarly to equation 1), by setting cc(T)=θc(Ti) --(2), the amount of phase shift with respect to temperature change of the position converter 53 can be determined.

From the above, from equations (1) 2 and (2), temperature T≠25℃
When , the position data PA (θ) = ε corresponding to the 0 point is ε = θd (T) + θb (T) + θc (T) = D
(T-25) +B (T-25)+θc (Ti)
......It is represented by (3).

Furthermore, the offset of the absolute position for this ε)
As for Iδ, it fluctuates linearly, so δ0 ε ,゛, δ=C(D (T-25)+B (T-25
)+θc(Ti)) =Co (T 25) +Cs (T 25)+C
θc(Ti) ・・・・・・(4) (However,
Co-C-DSCa=C-B), and the offset Iδ for the position data ε can be obtained.

From the above, the absolute position X1 obtained by this offset amount δ is corrected to obtain the actual absolute position ffX. The calculation results in the following formula.

X o ”
... (5) That is, proportionality constant Cゎ = amount of movement per unit temperature of the detector, C8 - amount of movement per unit temperature of the ball screw, C・θ
c (Ti) - The amount of movement of the position transducer at each temperature Ti is determined in advance, and the offset amount δ is determined by the CPU 57 using the temperature T (and Ti) as a parameter.
By correcting this offset Iδ with respect to the absolute position X, the actual absolute position can be calculated.

In the above description, the ball screw 59 is used as the power transmission system in FIG. 1, but any system may be used as the power transmission system as long as the driven member can be driven by rotation from the motor 50.

Further, the absolute position detector is not limited to the rotary type described in the above embodiment, but may be a linear type absolute position detector.

Furthermore, not only the phase modulation type absolute position detector but also an amplitude modulation type absolute 1 position detector may be used.

In addition, in the above embodiment, the absolute position X1 is corrected by the offset δ, and the actual absolute position
was calculated. However, in the present invention, the position data PA (
A similar effect can be expected by correcting θ) with ε obtained by equation (3) to obtain actual position data, and then obtaining the absolute position from the corrected position data.

Furthermore, in equation (4), there was a term for calculating the offset amount assuming that the temperature T changes continuously. However, in the present invention, the offset amount δi at the temperature T1 is calculated all discretely, and δi=Co (Ti -25) + Cg (Ti-25) +C・θC(Ti) (However, i=1.2, 3 . . , N) may be prepared as N parameters.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a detection method capable of correcting errors caused by temperature changes and detecting a more accurate absolute position.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a circuit configuration for correcting temperature change T when detecting an absolute position by the method of the present invention, and FIG.
A waveform diagram illustrating the position data and absolute position that can be taken as = 25°C, Figure 3 is for temperature correction from the position data and absolute position that can be taken as temperature T≠25°C (arbitrary temperature) using the device in Figure 1. 4 is a waveform diagram showing the amount of phase shift for the signal obtained from the detector and the temperature sensor of the ball screw in the device of FIG. 1, and FIG. 5 is a waveform diagram of the position transducer in the device of FIG. FIG. 3 is a waveform diagram showing a discrete phase shift amount with respect to temperature obtained from a temperature sensor. 50... Motor as a driving source, 51... Table as a driven member, 52... Driver circuit, 53...
...Position converter, 54...Absolute position detector, 57...CPU, 59...Ball screw as a power transmission system, 63...A/D converter.

Claims (5)

[Claims] (1) After detecting the position of the drive source that moves the driven member via the power transmission system with an absolute position detector, this data is converted to position data by a position converter, and from this position data, the position of the drive source that moves the driven member via the power transmission system is detected. In the absolute position detection method of calculating the absolute position, position data obtained by the position converter or the absolute position calculated from this position data is detected by at least one of the absolute position detector, the position converter, and the power transmission system. An absolute position detection method characterized by making corrections according to two or more temperature changes. (2) In claim 1, the absolute position is characterized in that after calculating the absolute position from the position data obtained by the position converter, the absolute position is corrected according to the temperature change. Detection method. (3) The absolute position according to claim 1, wherein the position data obtained by the position converter is corrected according to the temperature change, and then the absolute position is calculated from the corrected value. Detection method. (4) In any one of claims 1 to 3, the position data or absolute position is
A method for detecting an absolute position, characterized in that correction is performed continuously or discretely in response to temperature changes in at least one of the absolute position detector and the power transmission system. (5) In any one of claims 1 to 4, the position data or absolute position is
A method for detecting an absolute position, characterized in that correction is performed discretely and non-linearly in accordance with temperature changes of the position converter.