CN102538685A - Displacement detection system with twist error correcting function - Google Patents

Abstract

The invention relates to a displacement detection system, in particular to a displacement detection system with a twist error correcting function. The problem that the measurement precision of a measuring instrument cannot be fully used because of the mechanical structure precision or the mounting precision of a machine tool while the traditional measurement technology is designed according to the measurement precision of the measuring instrument is solved. The system comprises a first standard raster, a second standard raster, a sampling control module, a first position signal probing system, a second position signal probing system and a position analyzing module, wherein the first position signal probing system and the second position signal probing system send sampling signals through the sampling control module together; and the position analyzing module weighs the two displacement signals and averagely calculates the displacement value of a moving body by analyzing and comparing the displacement signals from the first position signal probing system and the second position signal probing system. The displacement detection system is used for improving reading stability and self-detection ability of a measurement system, and eliminating or reducing a twist error to the greatest extent at the same time.

Description

Displacement detection system with the function of correcting torsion error

technical field

The invention relates to a displacement detection system, in particular to a displacement detection system with the function of correcting torsion errors. Measuring system for measuring lengths with high precision and stability.

Background technique

The grating line displacement measurement system is mainly used as the position feedback element in the closed-loop control in the numerical control. Its accuracy and reliability affect the machining accuracy. The advantage of the full-closed loop compared with the semi-closed loop is mainly that it can eliminate transmission errors. For machining tool position and workpiece Direct measurement of position. The accuracy of grating rulers at home and abroad has been able to meet higher measurement accuracy requirements, but the installation accuracy of domestic machine tools is not high enough, making it difficult for the high-precision advantages of high-precision measuring instruments to be fully utilized in their own numerical control systems. One of the reasons is that there are various influencing factors in the numerical control system, including that the motion of the moving body on the slider is not an absolute linear motion, and there are still errors in the measurement of displacement. If the problem of matching with the machine tool cannot be handled well, then the advantages of full closed-loop machining cannot be brought into play, and its stability and accuracy may not be as good as semi-closed-loop systems with high installation precision. This situation hinders the research on high-precision CNC systems, making People have great difficulties in refitting machine tools.

The general way to solve the measurement error is to improve the accuracy of each component of the system and the accuracy of the grating ruler to reduce the measurement error, but the long-term operation accuracy and stability of the system still need to correct the deviation that occurs during operation.

Contents of the invention

In order to solve the existing displacement measurement technology, the present invention is mainly designed for the measurement accuracy of the measuring instrument itself. Although it can achieve high measurement accuracy, due to the mechanical structure accuracy or installation accuracy of the machine tool itself, the measuring instrument itself cannot The measurement accuracy cannot be fully utilized. In order to improve the stability of the system displacement measurement on the basis of the accuracy of the existing machine tool design, minimize the deviation caused by the non-linearity of the orbital motion, and reduce the requirements for installation accuracy , providing a displacement detection system with the function of correcting torsion errors.

A displacement detection system with the function of correcting torsion error, the system includes a first standard grating, a second standard grating, a sampling control module, a first position signal detection system, a second position signal detection system and a position analysis module; the sampling control module Send out the acquisition signal, the first position signal detection system and the second position signal detection system collect the displacement signals of the moving body relative to the first standard grating and the second standard grating respectively, and obtain the first position signal and the second position signal, The position analysis module performs weighted average calculation on the first position signal and the second position signal to obtain the corrected displacement value of the moving body, and outputs the displacement value of the moving body through the result output module.

Beneficial effects of the present invention: the displacement detection system of the present invention uses two first position signal detection systems and a second position signal detection system respectively installed on two rails, and the two detection systems correspond to the movement of the moving body at the two The moving displacement on a track, then by comparing the two displacement values obtained, the torsion of the moving body during the movement can be analyzed to obtain the corrected displacement measurement value, which is difficult to do through a position detection system alone. arrived. The invention is used to improve the reading stability and self-inspection ability of the measurement system, and simultaneously eliminate or minimize the torsion error.

Description of drawings

Fig. 1 is a structural diagram of a displacement detection system with a function of correcting torsion error according to the present invention;

2 is a schematic diagram of the position of the displacement detection system with the function of correcting the torsion error described in the present invention under ideal conditions;

Fig. 3 is a schematic diagram of the position of the displacement detection system with the function of correcting the torsion error under the non-ideal condition.

Detailed ways

1 to 3 to illustrate this embodiment, the displacement detection system with the function of correcting torsional errors, the system includes a first standard grating 101, a second standard grating 201, a sampling control module 10, a first position signal detection system 21, a second Two position signal detection system 22 and position analysis module 30;

The position analysis module 30 receives position signals from the first position signal detection system 21 and the second position signal detection system 22, and the first position signal detection system 21 and the second position signal detection system 22 are unified by the sampling control module 10 The acquisition signal is sent out, and the position analysis module 30 analyzes and compares the displacement signals of the moving body 300 obtained from the first position signal detection system 21 and the second position signal detection system 22 relative to the first standard grating 101 and the second standard grating 201, The weighted average of the two displacement signals is used to calculate the displacement value of the moving body 300 .

The first standard grating 101 and the second standard grating 201 described in this embodiment are fixed on the first track 100 and the second track 200 respectively, and position information is marked on the first standard grating 101 and the second standard grating 201 In order to obtain absolute position information, at least one of the first standard grating 101 and the second standard grating 201 has a pattern marking absolute position information. When the first position signal detection system 21 and the second position signal detection system 22 are fixed on the moving body, the first position signal detection system 21 and the second position signal detection system 22 place the first standard grating 101 and the second standard grating 201 The information on the length above is scanned into the first position signal detection system 21 and the second position signal detection system 22 respectively, and the first position signal detection system 21 and the second position signal detection system 22 scan by means of photoelectric scanning. The first position signal detection system 21 and the second position signal detection system 22 are CMOS (Complementary Metal Oxide Semiconductor), photocell array or CCD.

The first position signal detection system 21 in this embodiment is a photocell array, which is fixed on the moving body, and the second position signal detection system 22 is a photocell array, which is fixed on the moving body. At least any one of the first position signal detection system 21 and the second position signal detection system 22 has an absolute position signal detection function.

The first standard grating 101 and the second standard grating 201 described in this embodiment may be reflective gratings or transmissive gratings. The receiving chips of the first position signal detection system 21 and the second position signal detection system 22 may be silicon photocells or CCDs.

This embodiment is further described in conjunction with FIG. 3. When the system has a certain movement deviation and a certain twist, the twist angle is represented as α in the figure, and the first position signal detection system 21 and the second position signal detection system 22 They all move along their respective orbits 100 and 200, and do not twist with the twisting of the moving body, forming the shape in Figure 3. In this way, the displacement values moving on the two orbits are different, and after the position analysis module After the position subdivision module of 30, the readings corresponding to track 100 and track 200 are respectively X1 and X2. In combination with FIG. 2, assuming that the distance between the reticle lines 101 and 201 on the two tracks is expressed as L, the position shown in FIG. 3 can be relationship to obtain the center of the moving body (in this example, it is assumed that the shape and position of the moving body are symmetrical with respect to the two rails, so that the center point of the moving body is on a line equidistant from the two rails, and does not move with the twisting motion, that is, does not The displacement value of a point equidistant from two orbits) can be expressed as:

X＝(X1+X2)/2 ①

The twist angle α can be calculated by the following formula:

α＝arctan[(X1-X2)/L] ②

For the convenience of description, the shape of the moving body is assumed to be a rectangle in this example, but it does not affect the extension of the conclusion. Assuming that the running displacement of the moving body is X, then the readings of the two reading heads will be:

X1＝X+L*tan(α)/2 ③

X2＝X-L*tan(α)/2 ④

In this way, the position X of the fixed point can be expressed as formula ①, and the value obtained in formula ① is independent of the torsion angle α, which is a small deflection angle, for example, the angle of α is 10′.

The rationality of the above calculation formula is analyzed below,

For the convenience of description, the shape of the moving body is assumed to be a rectangle in this example, but it does not affect the extension of the conclusion. Assuming that the running displacement of the moving body is X, then the readings of the two reading heads will be formula ③ and formula ④ respectively

For example, X1 is equal to 20.345mm, and X2 is equal to 20.355mm. In this way, X is 20.350mm calculated by formula ①. If L is equal to 200mm, the deflection angle α is calculated by formula ② to be equal to 10.3 arc seconds, and the error is reduced by about 5 microns.

In this way, in the present invention, only one processing circuit is needed, by adding a reading system, two standard gratings are fixed on the two tracks, two independent position values are obtained through the reading system, and the fixed point in the analysis system is compared The position, using this position to indicate the position of the system, effectively overcomes the measurement error caused by the torsion of the moving body, and at the same time can monitor the amount of torsion through the angle α, and the measurement method is simple. This measurement method can effectively improve the measurement accuracy and measurement reliability, and is especially suitable for environments where the installation accuracy is not high enough but the measurement accuracy is high, without requiring high requirements for installation equipment and methods.

In addition, the measurement method in the present invention can also be used in the following situations, using a certain track as the track used in normal use, while the other track is used to check and correct the position value, only a certain period of detection is required. The measured value of the previous track is corrected, so that the installation error is taken into account at the same time. The value obtained by the first track includes the overall error of the system other than the reading system itself, not just the correction of the grating ruler itself.

Claims (5)

1. A displacement detection system with the function of correcting torsional errors, the system includes a first standard grating (101), a second standard grating (201), a sampling control module (10), a first position signal detection system (21), a second A position signal detection system (22) and a position analysis module (30); it is characterized in that the sampling control module (10) sends a collection signal, and the first position signal detection system (21) and the second position signal detection system (22) Respectively collect displacement signals of the mobile body (300) relative to the first standard grating (101) and the second standard grating (201), to obtain a first position signal and a second position signal, and the position analysis module (30) A weighted average calculation is performed on the first position signal and the second position signal to obtain a corrected displacement value of the mobile body (300), and the displacement value of the mobile body (300) is output through a result output module. 2. The displacement detection system with the function of correcting torsion error according to claim 1, characterized in that, the system also includes a first track (100) and a second track (200), and the first standard grating (101) and the second standard grating (201) are respectively fixed on the first track (100) and the second track (200), and there is at least one mark on the standard grating in the first standard grating (101) and the second standard grating (201) A pattern with absolute position information. 3. The displacement detection system with the function of correcting torsion error according to claim 1 or 2, characterized in that, the first standard grating (101) and the second standard grating (201) are reflective gratings or transmissive gratings . 4. The displacement detection system with the function of correcting torsion error according to claim 1, characterized in that, the first position signal detection system (21) and the second position signal detection system (22) are respectively fixed on the moving body ( 300), the first position signal detection system (21) and the second position signal detection system (22) are photocell arrays, CCD or CMOS. 5. The displacement detection system with the function of correcting torsion error according to claim 1, characterized in that at least one position signal is provided in the first position signal detection system (21) and the second position signal detection system (22) The detection system has the detection function of the absolute position signal.

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