CN103278110B - A kind of compensation method to guide rail coupling error - Google Patents

Abstract

The invention discloses a compensation method for guide rail coupling error. By using two displacement measuring devices to measure the Y-axis positions of two measuring points with fixed distances on the sliding table, the sliding table at multiple measuring points relative to the initial The deflection angle and displacement of the position, and finally use the deflection angle and displacement to compensate the movement of the guide rail, realize the coupling error detection and compensation of the guide rail, and improve the accuracy of the guide rail; the present invention uses a laser interferometer or a laser displacement sensor to cooperate with a plane mirror. The displacement of two points of the sliding table is measured to further improve the measurement accuracy; the present invention obtains the fitting curve of the deflection angle and the displacement by using multi-position measurement of the sliding table, and uses the two curves to compensate the movement of the guide rail, so that The compensation curve is closer to the real guideway error, thereby improving the position accuracy of the guideway.

Description

A Compensation Method for Rail Coupling Error

technical field

The invention relates to high-precision detection of coupling errors of guide rails, in particular to a method for compensating guide rail coupling errors.

Background technique

With the continuous development of manufacturing and precision machining technology, the requirements for the motion accuracy of guide rails are increasing. Therefore, how to quickly and accurately detect various errors of the linear guide rail and perform error compensation plays an extremely important role in improving the motion accuracy of the motion platform.

Due to errors such as straightness error, yaw error, pitch error, roll error, verticality error between the X-axis and Y-axis, and installation error of the guide rail, when the slide table moves along the X-axis direction, it will be in the X-axis direction. The vertical direction Y direction of the direction produces a position offset ΔY(X), which is called coupling error. As a result, there is a deviation between the actual position and the theoretical position of the guide rail, especially for the guide rail of the machine tool, the coupling error leads to the error between the actual position and the ideal position between the tool and the workpiece, such as in the outer circle of the car, the surface of the workpiece to be machined The normal direction is the sensitive direction of machining error, and in this direction, the relative position error between the tool and the workpiece will be mapped to the machining error to the greatest extent. Machining experiment data shows that in conventional turning, the coupling error can reach the micron level, but in high-precision machining, the coupling error can usually reach the sub-micron level. Therefore, the coupling error, as a sensitive direction error, has no influence on the machining accuracy of the outer circle of the car. Neglect, must be compensated to improve machining accuracy.

Since the actual contact position between the slide table and the guide rail is in dynamic change during the movement, and there is a deviation from the ideal position, the angle of the slide table is deflected during the movement along the guide rail, and the rotation center of the angle error is on the guide rail. The location also changes dynamically. When compensating the error, if only the displacement compensation is performed and the angular deflection of the guide rail is ignored, it will inevitably cause loss of precision and reduce the effect of error compensation.

Contents of the invention

In view of this, the present invention provides a guide rail coupling error compensation method, which can detect and compensate the guide rail including displacement and angle coupling errors, thereby improving the motion accuracy of the guide rail.

A kind of compensation method of guide rail coupling error of the present invention, comprises the steps:

A. Fix the micro-motion platform on the slide table of the guide rail, and place the driven object on the micro-motion platform;

B. Drive the sliding table to move from the initial position of the guide rail, so that the geometric center of the sliding table at the initial position is the origin, the moving direction of the sliding table at the initial position is the x-axis, and the direction perpendicular to the x-axis is the y-axis; when the sliding table moves N measurement positions are set during the process, and at each measurement position, two fixed displacement measurement devices are used to measure the displacement of two points on the slide table with a distance of L in the y-axis direction relative to the initial position; N is an integer greater than 0;

C. Then calculate the deflection angle of the sliding table relative to the x-axis at the measurement position according to the displacement of the two points and the distance L between the two points, and the displacement of the geometric center of the sliding table in the y-axis direction relative to the initial position at this time;

D. Count the deflection angle and the displacement of the geometric center of the slide table at all measurement positions, and perform curve fitting to obtain the deflection angle curve and the displacement curve of the geometric center of the slide table;

E. Invert the deflection angle curve and displacement curve of the slide table and input it to the micro-motion platform to make it perform coupling error compensation on the motion of the driven object.

Further, the two displacement measuring devices adopt two laser interferometers, two laser displacement sensors or one laser displacement sensor and one laser interferometer.

Further, in the step B, the plane mirror is fixed on the slide table, the laser interferometer or the laser displacement sensor is controlled to emit the laser beam to the plane mirror, and the projection of the two laser beams on the plane mirror is respectively controlled during the movement of the plane mirror with the slider. The displacement of the point along the y-axis direction is measured, so as to realize the measurement of the displacement of the slide table in the y-axis direction.

Further, the laser interferometer includes a quarter-wave plate, two corner mirrors, a beam splitter and a laser source; wherein, the quarter-wave plate, the beam splitter and the laser source are arranged in sequence on the plane mirror In front of the reflector, the quarter-wave plate is perpendicular to the optical axis of the laser source, and the beam splitter is at an angle of 45° to the optical axis of the laser source; two corner mirrors are placed on both sides of the beam splitter, and two The angle between the two reflective surfaces is 45°, which is used to receive the reflected laser light from the beam splitter.

Further, the solution process of the inclination angle θ of the slide table relative to the x-axis and the relative displacement in the y-axis direction is as follows: at each measurement position, two displacement measuring devices respectively measure the displacement of two points on the slider, The measured data of each point are A _ij and B _ij respectively, where i represents the number of measurements, i=1,2,...,n; j represents the number of measurement points for each test j=1,2,..., m;

For the measured value of the first displacement measuring device A _ij , the n sets of data at each measuring point are respectively summed and averaged, namely: The obtained average value of each point is fitted with a straight line, and the obtained straight line equation is: Y _j = kX _j + a, and the coupling error at each measurement point is ΔY _1j (X) = A' _j -Y _j ;

The measured value of the second displacement measuring device is B _ij , and the n sets of data at each measuring point are respectively summed and averaged: The obtained average value of each point is fitted with a straight line, and the obtained straight line equation is: Y' _j = k'X' _j + b, and the coupling error at each measurement point is ΔY _2j (X) = B' _j -Y'_j;

Then at the jth measurement position, the inclination angle of the slide table relative to the x-axis is:

$\mathrm{the\; tan}{\mathrm{\θ}}_j=\frac{\mathrm{\Δ}{Y}_{2j}\left(x\right)-\mathrm{\Δ}{Y}_{1j}\left(x\right)}{L},$ θ _j ≈ tanθ _j ;

Among them, L is the distance between two measurement points in the x-axis direction;

At the jth measurement position, the displacement of the geometric center of the sliding table in the y-axis direction relative to the initial position is:

Y _Cj =ΔY _2j (X)-(X _2j -X _Cj )θ _j ;

Among them, X _2j represents the x-axis coordinate of the second measurement point at the j-th measurement position, and X _Cj represents the x-axis coordinate of the geometric center of the sliding table.

Furthermore, when the laser interferometer is used as the displacement measurement device, the measured value is A _ij , and the actual measured value is The n groups of data at each measurement point are respectively summed and the average value is: A' _j =(A' _1j +A' _2j +...+A' _nj )/n.

The present invention has following beneficial effects:

1), the present invention uses two displacement measuring devices to measure the Y-axis positions of two fixed-distance measurement points on the slide table, so as to obtain the deflection angle and displacement of the slide table at multiple measurement points relative to the initial position, Finally, the deflection angle and displacement are used to compensate the movement of the guide rail, which realizes the coupling error detection and compensation of the guide rail, and improves the accuracy of the guide rail;

2), the present invention uses a laser interferometer or a laser displacement sensor in conjunction with a plane mirror to measure the displacement of two points on the sliding table, further improving the measurement accuracy;

3) The present invention obtains the fitting curve of deflection angle and displacement by using multi-position measurement on the slide table, and uses two curves to compensate the movement of the guide rail, so that the compensation curve is closer to the real guide rail error, thereby improving the position of the guide rail. precision.

Description of drawings

Fig. 1 is a schematic diagram of the present invention.

Fig. 2 is a principle diagram of error calculation in the present invention.

Fig. 3 is the experimental verification result of the present invention.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and examples.

The invention provides a method for compensating guide rail coupling errors, the method comprising the following steps:

Fix the micro-motion platform on the slide table of the guide rail, and place the driven object on the micro-motion platform;

Drive the sliding table to move from the initial position of the guide rail, so that the geometric center of the sliding table at the initial position is the origin, the direction of the guide groove of the guide rail is the x-axis, and the direction perpendicular to the x-axis is the y-axis; set N during the movement of the sliding table Measuring position. At each measuring position, two fixed displacement measuring devices are used to measure the displacement of two points on the sliding table with a distance of L in the y-axis direction relative to the initial position;

Among them, N is an integer greater than or equal to 0, and the value is selected according to actual needs. The larger the value of N, the more test positions, the more test samples, and the more accurate the final curve fitting result.

Then calculate the deflection angle of the sliding table at the measurement position relative to the initial position, and the displacement of the geometric center of the sliding table relative to the initial position at this time according to the displacement of the two points and the distance L between the two points;

Count the deflection angle and displacement of the slide table at all measurement positions, and perform curve fitting to obtain the deflection angle curve and displacement curve of the slide table;

The deflection angle curve and the displacement curve of the slide table are reversed and then input to the micro-motion platform to make it perform coupling error compensation on the motion of the driven object.

Among them, the micro-motion platform has more than three degrees of freedom, and can move in the x-axis and y-axis directions and rotate in the horizontal plane.

In the present invention, at each measurement position, the displacement of two points in the y-axis direction can be accomplished by using various instruments or devices, for example, by using a displacement sensor to measure it. In order to improve the measurement accuracy, a laser interferometer can also be used to achieve it. In order to cooperate with the measurement of the laser interferometer, a plane mirror is fixed on the slide table, and the laser interferometer is controlled to emit laser beams to the plane mirror. During the movement of the plane mirror, the two laser beams are respectively The projection point on the plane mirror is measured relative to the displacement of the y-axis, so as to realize the measurement of the displacement of the slide table relative to the y-axis.

Although the measurement accuracy of the laser interferometer is high, due to the high cost of using two sets of laser interferometers, other displacement measurement devices can also be used in the case of low precision requirements, such as using a laser displacement sensor to emit laser beam, it is possible to measure the displacement of the laser projection point. It is also possible to use two laser displacement sensors as the two displacement measuring devices.

Wherein, as shown in Figure 1, taking the laser interferometer and the laser displacement sensor as two displacement measuring devices as an example, the laser interferometer of the present invention includes a quarter wave plate, two corner mirrors, a beam splitter and Laser source; the quarter-wave plate, the beam splitter and the laser source are arranged sequentially in front of the reflective surface of the plane mirror, the quarter-wave plate is perpendicular to the optical axis of the laser source, and the beam splitter forms an angle of 45° with the optical axis of the laser source; Two pyramid reflectors are respectively placed on both sides of the beam splitter, and the included angle between the two reflection surfaces in the corner cone reflector is 45° for receiving reflected laser light from the beam splitter. The working principle of the laser interferometer is: after the laser light emitted by the laser source in the laser interferometer enters the beam splitter, it is split by the front surface of the beam splitter:

All the way is reflected by the front surface to the second corner mirror on the left, after being reflected twice by the second corner mirror, it is reflected again to the front surface of the beam splitter, and after being reflected by the front surface, it is received by the receiver of the laser source. as a reference beam;

The other path passes through the beam splitter, as the measured beam, passes through the 1/4 wave plate, and the measured light changes from linearly polarized light to circularly polarized light. Reflected by the plane reflector, when the reflected light beam returns to the beam splitter, it passes through the 1/4 wave plate, and the vibration direction of the light is turned by 90°, so that the light cannot pass through the beam splitting surface of the beam splitter and can only be reflected to the right. side of the first corner cube mirror. It is reflected upward by the corner mirror, and then passes through the 1/4 wave plate to the plane mirror. When the reflected beam returns to the beam splitter again, the polarization direction is rotated by 90° because it passes through the 1/4 wave plate twice, so The light beam is no longer reflected on the beam splitting surface but directly transmitted. The measured beam is coaxial with the returned reference beam, and the combined signal is sent to the laser source receiver. The laser interferometer obtains the displacement of the projection point of the laser on the plane mirror according to the optical path difference between the reference beam and the measured beam. The light emitted by the high-precision laser displacement sensor is directly reflected back to the receiver by the plane mirror, and the displacement of its laser projection point can also be obtained.

The solution process of the inclination angle θ of the geometric center of the slide table relative to the initial position and the relative displacement Y _C in the Y-axis direction is as follows: the data of each point measured by the laser interferometer and the laser displacement sensor are A _ij and B _ij respectively, where, i represents the number of measurements, i=1,2,...,n; j represents the number of measurement points for each test j=1,2,...,m.

For the measured value A _ij of the laser interferometer, the n sets of data of each measurement point are respectively summed and averaged, because the optical path of the laser interferometer is measured as a double optical path, so the displacement of the plane mirror in the vertical direction of the moving direction is Fit the average value of each point to a straight line, and the obtained straight line equation is: Y _j = kX _j + a, where X _j and Y _j are the variables of the straight line equation, k is the slope of the straight line, a is a constant, and the specific straight line The equation is determined, and the coupling error at each measurement point is ΔY _1j (X)=A' _j -Y _j ;

The measurement value of the laser displacement sensor is B _ij , and the n sets of data at each measurement point are summed and averaged: The obtained average value of each point is fitted with a straight line, and the obtained straight line equation is: Y' _j = k'X' _j + b, and the coupling error at each measurement point is ΔY _2j (X) = B' _j -Y' _j .

The schematic diagram of the coupling error calculation principle is shown in Figure 2, the plane mirror moves along a straight line, the geometric center of the plane mirror is C (X _C , Y _C ), the distance between two points X1 and X2 on the plane mirror is L, ΔY _1j (X) and ΔY _2j (X) respectively correspond to the displacement deviation of the two points relative to the initial position, and θ is the deflection angle of the plane mirror at this time. By measuring the deviation ΔY _1j (X) and ΔY _2j (X) of two points on the plane mirror relative to the reference position and the deflection angle θ of the plane mirror, the linear equation of the plane mirror at any time can be obtained, that is, the position and angle information of the plane mirror, which is the coupling error basis for compensation.

At the jth measurement position, the inclination angle of the slide table relative to the initial position is:

$\mathrm{the\; tan}{\mathrm{\θ}}_j=\frac{\mathrm{\Δ}{Y}_{2j}\left(x\right)-\mathrm{\Δ}{Y}_{1j}\left(x\right)}{L},$ θ _j ≈ tanθ _j ;

At the jth measurement position, the displacement of the geometric center of the sliding table in the y-axis direction relative to the initial position is:

Y _Cj =ΔY _2j (X)-(X _2j -X _Cj )θ _j ;

Among them, X _2j represents the x-axis coordinate of the second measurement point at the j-th measurement position, and X _Cj represents the x-axis coordinate of the geometric center of the sliding table.

The obtained error curve is fitted and inverted to obtain the error compensation curve equation, which is input into the control program of the micro-motion platform, and the deflection angle of each point is input into the control program of the micro-motion platform. When the linear motion table moves again, the micro-motion platform performs error compensation motions at intervals or time according to the error compensation curve equation. While compensating the linear motion, the micro-motion platform also compensates the angle deviation.

To sum up, the above are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (4)

1. a compensation method of guide rail coupling error, is characterized in that, comprises the steps: A. Fix the micro-motion platform on the slide table of the guide rail, and place the driven object on the micro-motion platform; B. Drive the sliding table to move from the initial position of the guide rail, so that the geometric center of the sliding table at the initial position is the origin, the moving direction of the sliding table at the initial position is the x-axis, and the direction perpendicular to the x-axis is the y-axis; when the sliding table moves N measurement positions are set during the process, and at each measurement position, two fixed displacement measurement devices are used to measure the displacement of two points on the slide table with a distance of L in the y-axis direction relative to the initial position; N is an integer greater than 0; C. Then calculate the deflection angle of the sliding table relative to the x-axis at the measurement position according to the displacement of the two points and the distance L between the two points, and the displacement of the geometric center of the sliding table in the y-axis direction relative to the initial position at this time; D. Count the deflection angle and the displacement of the geometric center of the slide table at all measurement positions, and perform curve fitting to obtain the deflection angle curve and the displacement curve of the geometric center of the slide table; E. Invert the deflection angle curve and displacement curve of the slide table and input it to the micro-motion platform to make it perform coupling error compensation on the motion of the driven object; The two displacement measuring devices adopt two laser interferometers, two laser displacement sensors or a laser displacement sensor and a laser interferometer; In the step B, the plane mirror is fixed on the sliding table, the laser interferometer or the laser displacement sensor is controlled to emit the laser beam to the plane mirror, and the projection points of the two laser beams on the plane mirror along the y The displacement in the axial direction is measured, so as to realize the measurement of the displacement of the slide table in the y-axis direction. 2. the compensation method of a kind of guide rail coupling error as claimed in claim 1, is characterized in that, described laser interferometer comprises quarter-wave plate, two mirror mirrors, beam splitter and laser source; Wherein, The quarter-wave plate, the beam splitter and the laser source are arranged sequentially in front of the reflective surface of the plane mirror, the quarter-wave plate is perpendicular to the optical axis of the laser source, and the beam splitter is at an angle of 45° to the optical axis of the laser source; Two pyramid reflectors are respectively placed on both sides of the beam splitter, and the angle between the two reflection surfaces in the corner cone reflector is 45°, which is used to receive the reflected laser light from the beam splitter. 3. The compensation method of a kind of guide rail coupling error as claimed in claim 1 or 2, it is characterized in that, the solution process of the inclination angle θ of the slide table relative to the x-axis and the relative displacement in the y-axis direction is: in each At the measurement position, two displacement measurement devices measure the displacement of two points on the slider respectively, and the measured data of each point are A _ij and B _ij respectively, where i represents the number of measurements, i=1,2,... ,n; j represents the number of measurement points for each test j=1,2,...,m; For the measured value of the first displacement measuring device A _ij , the n sets of data at each measuring point are respectively summed and averaged, namely: The obtained average value of each point is fitted with a straight line, and the obtained straight line equation is: Y _j = kX _j + a, and the coupling error at each measurement point is ΔY _1j (X) = A' _j -Y _j ; The measured value of the second displacement measuring device is B _ij , and the n sets of data at each measuring point are respectively summed and averaged: The obtained average value of each point is fitted with a straight line, and the obtained straight line equation is: Y' _j = k'X' _j + b, and the coupling error at each measurement point is ΔY _2j (X) = B' _j -Y'_j; Then at the jth measurement position, the inclination angle of the slide table relative to the x-axis is: Among them, L is the distance between two measurement points in the x-axis direction; At the jth measurement position, the displacement of the geometric center of the sliding table in the y-axis direction relative to the initial position is: Y _Cj =ΔY _2j (X)-(X _2j -X _Cj )θ _j ; Among them, X _2j represents the x-axis coordinate of the second measurement point at the j-th measurement position, and X _Cj represents the x-axis coordinate of the geometric center of the sliding table. 4. the compensation method of a kind of guide rail coupling error as claimed in claim 3, is characterized in that, when adopting laser interferometer as displacement measuring device, measured value is A _ij , then actual measured value is The n groups of data at each measurement point are respectively summed and the average value is: A' _j =(A' _1j +A' _2j +...+A' _nj )/n.