JP2005241317A - Support mechanism for multichannel sensor which is robust against thermal external disturbance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a support mechanism for a displacement sensor such that uncertainty in the measurement result is minimized, when a measurement system in which the plurality displacement sensors having unknown temperature characteristics are combined is designed. <P>SOLUTION: The support position for the displacement sensor is defined so that a neutral surface of an object to be measured is at approximately the center of the measurement range of the plurality of displacement sensors. A jig for supporting the mutual position/posture of these displacement sensors employs a material and a structure such that the effect of the thermal displacement due to the effect of temperature variation can be managed or negligible, and supports it at the displacement sensor support position. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to position measurement such as the dimension of an object to be measured, and more particularly to position measurement for measuring the surface shape of an object to be measured using a plurality of displacement sensors such as displacement.

Conventionally, for example, when measuring information between two measurement surfaces using a plurality of displacement sensors, a plurality of displacement sensors that detect one piece of displacement information are used, and the positions and orientations of these displacement sensors are constrained to each other. Build a sensor system with the desired functions and degrees of freedom using jigs.
By the way, in such position measurement, there is a problem that an error factor such as an unexpected temperature drift occurs due to the interaction between the fluctuation of the displacement sensor itself with respect to the thermal fluctuation and the fluctuation of the jig. That is, in the case of such position measurement, it is necessary to obtain a displacement sensor whose behavior is controlled with respect to temperature fluctuations and to adopt a jig design structure that is less affected by temperature fluctuations.

In reality, the behavior of the displacement sensor with respect to temperature fluctuations is often black-boxed, and the range in which this temperature compensation is performed afterwards is limited. For jigs, materials whose linear expansion coefficient is controlled are used. Measures are taken such as designing with or selecting a material with high thermal conductivity.
However, if the behavior of the displacement sensor with respect to the temperature remains unknown, even if the behavior of the jig with respect to the temperature is managed, the measurement system as a whole could not obtain the expected performance against temperature fluctuations. .
JP2003-121131A

An object of the present invention is to obtain a displacement sensor support mechanism that minimizes the uncertainty of measurement results when designing a measurement system in which a plurality of displacement sensors having unknown temperature characteristics are combined.
Here, the “neutral plane” as used in this specification defines a virtual plane when the measurement target plane is idealized and regarded as one plane, and is mathematically defined by a least square plane, for example. I will call the face.

  In order to achieve this object, in the present invention, the support position of the displacement sensor is determined so that the neutral surface of the measurement object is approximately the center of the measurement range of the plurality of displacement sensors, and the position and orientation of these displacement sensors are mutually determined. It is proposed that the jig that supports can be supported at the displacement sensor support position by using a material and a structure that can manage or ignore the influence of thermal displacement due to the influence of temperature fluctuation.

According to the present invention, even if the displacement sensor exhibits an unknown behavior, the behavior with respect to the temperature variation of the entire measurement system combining a plurality of displacement sensors is determined by the temperature variation of the jig itself, Measurement uncertainty of the entire measurement system can be minimized.
In addition, even if the behavior of the displacement sensor with respect to temperature fluctuation is known and any compensation for temperature fluctuation is possible, this effect of the present invention is not impaired and contributes to the reduction of measurement uncertainty. it can. In other words, even if accuracy compensation for temperature variation of the displacement sensor is performed, according to the guidelines for calculating the uncertainty of ISO, it is necessary to escape from the need to enter measurement uncertainty due to residual compensation. I can't. Specifically, in the calculation of measurement uncertainty, when the same equipment, algorithm, etc. are employed, the smaller the amount to be compensated for, the smaller the contribution of uncertainty due to compensation residue, resulting in Measurement uncertainty is minimized. In other words, according to the present invention, regardless of whether the temperature characteristics of the displacement sensor are unknown or known, if a mechanism that supports the neutral position with respect to the temperature fluctuation is employed, the measurement uncertainty of the entire measurement system is minimized. If a mechanism in which the contribution of temperature fluctuation is managed and predictable in the jig design or the contribution is minimized in terms of material mechanics, the measurement uncertainty can be further reduced.

In a preferred embodiment of the invention described below,
1) In position measurement that measures the surface shape of a measurement object using a plurality of displacement sensors that obtain information on the relative position and orientation of each other, the displacement sensor substantially matches the position of the neutral plane determined by the surface shape. Multi-channel sensor support mechanism that is tolerant to thermal disturbances supported at the support position of support jigs such as
2) The support jig is a multi-channel sensor support mechanism that is tough against thermal disturbance and is composed of a material with a coefficient of linear thermal expansion that is negligibly small in the target position measurement.
3) Multi-channel sensor support mechanism that is robust to thermal disturbances, in which the linear thermal expansion coefficient of the support jig is known, and compensation by thermal expansion is performed by a temperature detection signal of a temperature sensor different from the displacement sensor
4) Using the detection signal of the temperature sensor and the detection signal of the displacement sensor, the effective linear expansion coefficient of the support jig is estimated recursively, and the multi-channel is robust against thermal disturbance that compensates for the position measurement result. A sensor support mechanism is described.

  FIG. 1 shows a conventional measurement system for measuring a gap between two substantially parallel planes using two contact displacement meters. Contact type displacement systems 3 and 4 (displacement sensors) installed between the measured surfaces 1 and 2 are arranged so as to face each other, and the respective measuring elements 5 and 6 are arranged on the measurement surface of the contact type displacement meters 3 and 4. The device is set to contact at a substantially neutral position. The support jig 7 that supports the contact displacement gauges 3 and 4 that are displacement sensors is connected to a scanning mechanism (not shown) that is separately designed, thereby changing the detection position (moving up and down in the figure). ) Information is obtained in the gap across the entire surface to be measured. In general, the displacement sensor behaves in a black box in many cases, and even if it can be grasped in advance, the measurement uncertainty due to thermal disturbance is the largest error factor in the configuration of FIG. It becomes. On the other hand, even if the temperature compensation of the displacement sensor is performed by some method, if the amount to be compensated itself has the magnitude of the maximum uncertainty factor, the uncertainty due to the compensation residue is included. Obviously, this has worsened the measurement uncertainty of the measurement system.

FIG. 2 shows a multi-channel sensor support mechanism according to the present invention. In this embodiment as well, the gap between two substantially parallel planes is measured as in the case of FIG. That is, the non-contact type displacement gauges 3 and 4 (displacement sensors) are installed between the measurement surfaces 1 and 2 in a back-to-back state, and these measurement surfaces are placed in opposition to the corresponding measurement surfaces.
Further, the non-contact displacement meters 3 and 4 are fixed to the support blocks 5 and 6 fixed to the support jig 7 so that the vicinity of the approximate center of the measurement range coincides with the neutral surface of each surface to be measured.

The thermal behavior of the support blocks 5 and 6 is a factor that mainly contributes to the uncertainties in the scanning direction orthogonal to the measurement value of the gap. Therefore, the thermal displacement is controlled or not measured. Does not make a significant contribution to the uncertainty. The support jig 7 is connected to a separately designed scanning mechanism (not shown), thereby changing the detection position to obtain information on the gap over the entire surface to be measured, as in FIG.
The support jig 7 can be designed with a member having a sufficiently low linear expansion coefficient or a member having a known linear expansion coefficient and good thermal conductivity. In other words, a material with a small coefficient of linear expansion is a measure to minimize the thermal displacement itself caused by temperature fluctuations. A member with a known coefficient of linear expansion and good thermal conductivity generates thermal displacement, The quantity can be accurately predicted and compensated.

  In the case of the support jig 7 having a known linear expansion coefficient and good thermal conductivity, the problem of the contribution of uncertainty due to the residue of compensation is compared with that of a displacement sensor having a plurality of members and complicated mechanisms inside. It can be made much smaller. Specifically, since the support jig 7 itself can be designed in a substantially block shape, it means that a uniform and single material and a simple and two-dimensional cross-sectional shape can be adopted. It is well known in the block gauge measurement widely used for a long time as a standard for geometric measurement that the block-shaped member can predict the thermal displacement with relatively high accuracy.

Compensation for thermal displacement can be performed using the linear expansion coefficient of the support jig 7 obtained in advance and a temperature sensor attached to the support jig 7 in advance, and the accuracy compensation process using the information follows ISO guidelines. It can also withstand uncertainty calculations.
Of course, when the support jig is formed by using a material whose linear expansion coefficient can be ignored, it is not necessary to compensate for thermal displacement.

  Further, in the embodiment of the present invention shown in FIG. 2, since the displacement sensor is supported at a position substantially corresponding to the neutral position defined by the object to be measured, an error factor due to temperature variation of the displacement sensor itself. Is also minimized.

  When the linear expansion coefficient of the support jig 7 is unknown, it has been said that the error due to the linear expansion of the support jig 7 cannot be compensated for in general. A method of regressively estimating and compensating for the effective linear expansion coefficient of the support jig using a plurality of displacement sensor signals may be employed.

This is a model of a conventional measurement system when a gap between two substantially parallel planes is measured using two contact displacement meters. 3 is a model of a measurement system using two non-contact displacement sensors according to the present invention.

Explanation of symbols

1, 2 Surface to be measured 3, 4 Non-contact displacement meter (displacement sensor)
5,6 Support block 7 Support jig

Claims (4)

  In the position measurement in which the surface shape of the measurement object is measured using a plurality of displacement sensors that obtain information on the relative positions and orientations of each other, the displacement sensor substantially matches the position of the neutral plane determined by the surface shape. A multi-channel sensor support mechanism that is tough against thermal disturbances, and is supported at a support position of a support jig.   2. The support mechanism for a multi-channel sensor tough against thermal disturbance according to claim 1, wherein the support jig is made of a material having a linear thermal expansion coefficient that is negligibly small in a target position measurement.   2. The thermal disturbance according to claim 1, wherein a linear thermal expansion coefficient of the support jig is known, and compensation by thermal expansion is performed by a temperature detection signal of a temperature sensor different from the displacement sensor. Multi-channel sensor support mechanism. 4. The position measurement result is compensated by regressively estimating an effective linear expansion coefficient of the support jig using the detection signal of the temperature sensor and the detection signal of the displacement sensor. Multi-channel sensor support mechanism that is tough against thermal disturbances.

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