CN106500641A - The thermal deformation error compensating method of articulated coordinate machine - Google Patents

Abstract

The invention provides a thermal deformation error compensation method of an articulated coordinate measuring machine, comprising the following steps: 1) establishing a mathematical model of the influence of temperature on the structural parameters of the articulated coordinate measuring machine; 2) placing the articulated coordinate measuring machine in In a temperature-controllable thermostatic chamber, set the room temperature to 15° and wait for 2 hours; 3) Use an articulated coordinate measuring machine to measure the designed special calibration plate; 4) Adjust the temperature of the thermostatic chamber to 20° and wait for 2 hours Measure the calibration plate again; 5) continue to heat up, and conduct a set of measurement experiments every 5° until the temperature rises to 40°; 6) calculate the error of each group of data according to the nominal value of the special calibration plate, and use the joint type The self-calibration method of the structural parameters of the coordinate measuring machine calibrates the structural parameters at each temperature; 7) In the constant temperature room, under different temperature gradients, the calibration plate is measured again, so as to calculate the compensation effect of f(T) verify.

Description

Compensation Method for Thermal Deformation Error of Articulated Coordinate Measuring Machine

technical field

The invention relates to a temperature compensation technology of a coordinate measuring machine, in particular to a thermal deformation error compensation method of an articulated coordinate measuring machine.

Background technique

Articulated coordinate measuring machine is a multi-degree-of-freedom non-orthogonal three-dimensional coordinate measuring machine, usually with 6 degrees of freedom. It is modeled on human joints, and consists of three measuring arms and a measuring head connected in series through six rotating joints. Compared with the traditional orthogonal three-coordinate measuring machine, the joint-type coordinate measuring machine has the characteristics of large measurement range, convenience and flexibility, and simple mechanical structure. However, because articulated coordinate measuring machines are often used in industrial sites such as workshops, the temperature of the working environment varies greatly. Affected by the ambient temperature, the articulated coordinate measuring machine undergoes thermal deformation, which leads to errors in the measurement results. The articulated coordinate measuring machine is a precise coordinate measuring tool, and the series structure will amplify the error, and the error caused by thermal deformation cannot be ignored. Compensating the thermal deformation error of the articulated coordinate measuring machine can effectively improve the accuracy of the measurement results.

Some literatures published successively in recent years have proposed different methods to compensate the thermal error of the articulated coordinate measuring machine: "Research on temperature error correction technology of the articulated three-coordinate measuring machine" simplifies the measuring arm of the articulated coordinate measuring machine into a detailed The long rod model uses the one-dimensional linear expansion coefficient of the material to correct its thermal deformation error; "Research on Thermal Deformation Error Modeling and Correction of Articulated Coordinate Measuring Machine" studies the thermal deformation error of articulated coordinate measuring machine, And the error model is corrected based on the neural network algorithm; "Thermal deformation error and correction of articulated coordinate measuring machine" establishes the thermal deformation error model of articulated coordinate measuring machine by using a single hidden layer with backpropagation feed-forward neural network, and through Experiments verify the effectiveness of the model. The research focuses on simulation analysis, model simplification, etc., and there are few studies on the thermal deformation error of the whole machine.

Therefore, it is necessary to study a method capable of compensating the thermal deformation error of the articulated coordinate measuring machine.

Contents of the invention

The object of the present invention is to provide a thermal deformation error compensation method of an articulated coordinate measuring machine, comprising the following steps: 1) establishing a mathematical model of the influence of temperature on the structural parameters of an articulated coordinate measuring machine:

Among them, Δa _i , Δd _i , Δα _i , Δθ _i , ΔI are the errors of joint length, measuring arm length, joint torsion angle, joint rotation angle and probe length respectively, f _ai (T), f _di (T), f _αi (T), f _I (T), and f _θi (T) are temperature error functions; 2) Place the articulated coordinate measuring machine in a temperature-controlled constant room, set the room temperature to 15° and wait for 2 hours; 3) Use an articulated coordinate measuring machine to measure the designed special calibration plate, measure the designated taper hole on the special calibration plate 100 times at each position, and try to use a variety of different postures during the measurement; 4) Adjust the constant temperature When the temperature of the chamber reaches 20°, wait for 2 hours and then measure the calibration plate again; 5) Continue to raise the temperature, and conduct a set of measurement experiments every 5° until the temperature rises to 40°; 6) According to the nominal value of the special calibration plate The error of each group of data is calculated, and the structural parameters at each temperature are calibrated by the self-calibration method of the structural parameters of the joint type coordinate measuring machine. According to the standard value of the structural parameters of the articulated coordinate measuring machine, calculate the structural parameter errors at each temperature, and use the polynomial fitting method to fit the temperature error function to obtain the corresponding error function f(T); 7) at constant temperature In the chamber, under different temperature gradients, the calibration plate is measured again, and the specified cone hole is measured 30 times at each position, and the structural parameters are corrected with the f(T) fitted above to obtain According to the corresponding structural parameters, the corrected coordinate values are calculated with the corrected structural parameters, and the error of the measurement results of the articulated coordinate measuring machine before and after the correction is calculated, so as to verify the compensation effect of f(T).

Preferably, the error function model is: f(T)=kT ³ +mT ² +nT+b. Where k, m, n, b are constants to be fitted.

Preferably, the temperature gradient in step 7) is 17°, 23°, 28°, 33° and 38°.

Preferably, the temperature gradient in step 7) is 15°, 18°, 21°, 24° and 27°.

Preferably, the temperature gradient in step 7) is 15°, 18°, 23°, 30° and 37°.

It should be understood that both the foregoing general description and the following detailed description are exemplary illustrations and explanations, and should not be used as limitations on the claimed content of the present invention.

Description of drawings

With reference to the accompanying drawings, more objects, functions and advantages of the present invention will be clarified through the following description of the embodiments of the present invention, wherein:

FIG. 1 schematically shows the structure diagram of an articulated coordinate measuring machine.

Fig. 2 is a structural schematic diagram of a special calibration plate used in the present invention.

Fig. 3 is a schematic diagram of the placement position of the special calibration plate of the present invention during use.

detailed description

The objects and functions of the present invention and methods for achieving the objects and functions will be clarified by referring to the exemplary embodiments. However, the present invention is not limited to the exemplary embodiments disclosed below; it can be implemented in various forms. The essence of the description is only to help those skilled in the relevant art comprehensively understand the specific details of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or similar components, or the same or similar steps.

Figure 1 is a schematic diagram of an articulated coordinate measuring machine. The articulated coordinate measuring machine 100 includes: a base 110 , three measuring arms 107 , 108 , 109 , rotating joints 101 , 102 , 103 , 104 , 105 , 106 and a probe 111 . On the base 110, six rotatable joints 101, 102, 103, 104, 105, 106 connected in series by three sections of measuring arms 107, 108, 109 form a space open chain structure, and the end of the open chain structure is the measuring machine The measuring head 111.

The thermal deformation error caused by temperature on the articulated coordinate measuring machine is converted into the influence of temperature on the structural parameters of the articulated coordinate measuring machine. The mathematical model is established as follows:

Among them, Δa _i , Δd _i , Δα _i , Δθ _i , and ΔI are the errors of joint length, measuring arm length, joint torsion angle, joint rotation angle and probe length, respectively. f _ai (T), f _di (T), f _αi (T), f _I (T), f _θi (T) are temperature error functions.

The articulated coordinate measuring machine was placed in a temperature-controlled constant room, and the room temperature was set at 15°. Wait for more than 2 hours for the articulated coordinate measuring machine and the room temperature to reach thermal equilibrium, and use the articulated coordinate measuring machine to measure the designed special calibration plate, which is shown in Figure 2. In order to cover the entire measurement space as much as possible, the positioning of the calibration board is shown in Figure 3. Perform 100 measurements on the designated taper hole on the special calibration plate at each position, and try to use a variety of different postures during the measurement. Then adjust the temperature of the thermostatic chamber to 20°, wait for 2 hours and then measure the calibration plate again. Continue to raise the temperature, and conduct a set of measurement experiments every 5° until the temperature rises to 40°. After completing the experiment, a total of 7 sets of experimental data corresponding to different temperatures were obtained. Table 1 shows some experimental data of the same point at different temperatures.

Table 1 Partial experimental data of the same point at different temperatures

The error of each group of data is calculated according to the nominal value of the special calibration plate, and the structural parameters at each temperature are calibrated by the self-calibration method of the structural parameters of the joint type coordinate measuring machine. According to the standard values of the structural parameters of the articulated coordinate measuring machine, the structural parameter errors at each temperature are calculated respectively. The temperature error function is fitted by the method of polynomial fitting, and the corresponding error function f(T) is obtained. The error function model is: f(T)=kT ³ +mT ² +nT+b. Where k, m, n, b are constants to be fitted.

In the thermostatic chamber at 17°, 23°, 28°, 33° and 38°, measure the calibration plate again, and measure the designated cone hole 30 times at each position. Use the f(T) fitted above to correct the structural parameters to obtain the corresponding structural parameters at each temperature, and use the corrected structural parameters to calculate the corrected coordinate values. The error of the measurement result of the articulated coordinate measuring machine before and after correction is calculated to verify the compensation effect of f(T).

In the thermostatic chamber at 15°, 18°, 21°, 24° and 27°, measure the calibration plate again, and measure the designated cone hole 30 times at each position. Use the f(T) fitted above to correct the structural parameters to obtain the corresponding structural parameters at each temperature, and use the corrected structural parameters to calculate the corrected coordinate values. The error of the measurement result of the articulated coordinate measuring machine before and after correction is calculated to verify the compensation effect of f(T).

In the thermostatic chamber at 15°, 18°, 23°, 30° and 37°, measure the calibration plate again, and measure the designated cone hole 30 times at each position. Use the f(T) fitted above to correct the structural parameters to obtain the corresponding structural parameters at each temperature, and use the corrected structural parameters to calculate the corrected coordinate values. The error of the measurement result of the articulated coordinate measuring machine before and after correction is calculated to verify the compensation effect of f(T).

Other embodiments of the invention will be apparent to and understood by those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The description and examples are considered exemplary only, with the true scope and spirit of the invention defined by the claims.

Claims (5)

1. A thermal deformation error compensation method of an articulated coordinate measuring machine, comprising the steps of: 1) Establish a mathematical model of the influence of temperature on the structural parameters of the articulated coordinate measuring machine: $\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&Delta;a</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; \&Delta;d</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; \&Delta;\&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; \&Delta;\&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; \&theta;</span>}\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>\\ \mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>\end{array}\right.$ Among them, Δa _i , Δd _i , Δα _i , Δθ _i , Δl are the errors of joint length, measuring arm length, joint torsion angle, joint rotation angle and probe length respectively, f _ai (T), f _di (T), f _αi (T), f _l (T), f _θi (T) are temperature error functions; 2) Place the articulated coordinate measuring machine in a temperature-controllable constant temperature room, set the room temperature to 15° and wait for 2 hours; 3) Use an articulated coordinate measuring machine to measure the designed special calibration plate, measure the designated taper hole on the special calibration plate 100 times at each position, and try to use a variety of different postures during the measurement; 4) Adjust the temperature of the thermostatic chamber to 20°, wait for 2 hours and measure the calibration plate again; 5) Continue to heat up, and carry out a set of measurement experiments every 5° until the temperature rises to 40°; 6) Calculate the error of each group of data according to the nominal value of the special calibration plate, and use the self-calibration method of the structural parameters of the joint type coordinate measuring machine to calibrate the structural parameters at each temperature. According to the standard value of the structural parameters of the articulated coordinate measuring machine, the structural parameter errors at each temperature are calculated respectively, and the temperature error function is fitted by the polynomial fitting method to obtain the corresponding error function f(T); 7) Under different temperature gradients in the thermostatic chamber, measure the calibration plate again, measure the designated cone hole 30 times at each position, and use the f(T) fitted above to correct the structural parameters The corresponding structural parameters at each temperature are obtained, the corrected coordinate values are calculated with the corrected structural parameters, and the error of the measurement results of the articulated coordinate measuring machine before and after correction is calculated to verify the compensation effect of f(T). 2. The error compensation method according to claim 1, wherein the error function model is: f(T)=kT ³ +mT ² +nT+b. Where k, m, n, b are constants to be fitted. 3. The error compensation method according to claim 1, wherein the temperature gradient in step 7) is 17°, 23°, 28°, 33° and 38°. 4. The error compensation method according to claim 1, wherein the temperature gradient in step 7) is 15°, 18°, 21°, 24° and 27°. 5. The error compensation method according to claim 1, wherein the temperature gradient in step 7) is 15°, 18°, 23°, 30° and 37°.