CN101968641A - Error correction system of machine tool XY plane - Google Patents

Abstract

The invention discloses a machine tool XY plane error correction system, which belongs to the technical field of machine tool system error correction control. The system hardware includes a servo driver controlled by a host computer and a programmable controller, and a servo motor connected to the servo driver, and works on an XY plane. The platform is driven by a servo motor through a screw, and the upper computer is equipped with a system error identification module and a fitting compensation module for the XY plane of the machine tool; the present invention cooperates with the system software and hardware, and the upper computer function module can identify the machine tool Accurate error model data, timely compensation by the system, can make the machine tool achieve ideal control accuracy, and at the same time, the compensation data setting of the numerical control system is simple and convenient.

Description

A Machine Tool XY Plane Error Correction System

the

technical field

The invention relates to a machine tool system error correction control technology, in particular to a machine tool XY plane system error correction control technology.

Background technique

The error compensation of the machine tool is an effective measure to improve the precision of the machine tool, which has important practical significance. At present, at home and abroad, the error compensation of machine tools is mainly completed by the numerical control CNC system (the main foreign CNC numerical control system manufacturers include SIEMENS, FANAC, FAGOR, etc.). Its error compensation mainly includes pitch compensation and backlash compensation. During pitch compensation, the CNC system automatically superimposes the average position deviation of the target position Pi on the interpolation command, so that the error is partially offset and the error compensation is realized. During backlash compensation, it is necessary to measure the average reverse difference of each target position Pi, and input it into the system as the compensation parameter of the machine tool. When the system controls the reverse movement of the coordinates, it will automatically let the coordinate axis move in the reverse direction first, and then proceed according to the instruction. movement, thereby compensating for errors.

When the CNC control system is used in the machine tool, the CNC controller needs to control the servo driver on the hardware, and then the servo driver controls the servo motor. In this way, the integrated system is expensive and the control structure is complicated. For lathes with relatively simple functions (such as precision drilling machines), if a CNC controller is used, many complex functions of the CNC controller are not used in the application device, resulting in a great waste of resources. When the CNC system compensates, the average position deviation of the target position Pi is superimposed on the interpolation command. In this way, the error value of the compensation point between adjacent target positions is relatively large, and with the distance between adjacent target positions The position accuracy of the compensation point will also become worse if the value is increased. At the same time, the current popular CNC control system (such as: SIEMENS-840D numerical control system, etc.), its pitch error compensation adopts the absolute compensation method, and the compensation data can be set by executing the program. The method is intuitive but the operation steps are very cumbersome.

Contents of the invention

The purpose of the present invention is to provide a machine tool XY plane error correction system that can achieve the required control precision without using the CNC controller and without changing the hardware structure of the original system. .

The technical solution of the present invention is: a machine tool XY plane error correction system, the system hardware includes a servo driver controlled by a host computer and a programmable controller, and a servo motor connected to the servo driver, and the XY plane working platform is controlled by a servo motor through a wire Rod drive, the upper computer is equipped with a system error identification module and a fitting compensation module for the XY plane of the machine tool;

The system error identification module obtains the XY plane system error model of the machine tool through a number of given command positions and the actual measurement position of the tool on the machine tool in the XY plane of the machine tool;

The fitting compensation module, after receiving the given position signal, uses the XY plane system error model of the machine tool obtained by the system error identification module to fit and calculate the feedforward amount and correct the output position, and transmit the corrected output position to to the servo drive.

The system error identification module includes:

Feed position data conversion sub-module, this module converts several feed positions that need to be input into a data format that the machine tool system can recognize;

Automatic point-to-point feed position subroutine submodule, this module instructs the tool to automatically feed according to the feed position and number input into the machine tool processing data reference area;

The tool actual feed position measurement and data format conversion sub-module measures the actual feed position of the machine tool tool on the XY plane through a laser interferometer. This module converts the measurement data format of the laser interferometer into a data format that the machine tool system can recognize;

的求取：Deviation calculation correction sub-module, this module calculates the error value between the feed position of each input point and its actual feed position, modifies the input feed position, inputs the modified feed position into the system, performs iterative process calculation, and records the corresponding data , until the error meets the requirements, so as to obtain the XY plane system error model of the machine tool. The calculation method is as follows, that is, the model function

to obtain:

，其对应输入变量

。对于函数

，可转换为方程

，由此，过程转换为方程的求解。set each given position

, which corresponds to the input variable

. for functions

, which can be converted into the equation

, thus, the process is transformed into the solution of the equation.

（即机床对应输出点）的对应理想输入变量作为求取过程初始值点，引入迭代算法，则机床实际输出即为

，

，可以通过激光干涉仪实际测量得到。上位计算机通过

（W为迭代次数）的误差值计算，对输入

值进行修正，得到

进入下一次迭代过程。对测量数据进行分析，当满足相应国家标准(如VDI3441、JIS6330、GB10931-89等)时，过程结束，这样可得到机床XY平面系统误差模型函数

。Match the machine tool system to each given position

(that is, the corresponding output point of the machine tool) corresponds to the ideal input variable As the initial value point of the calculation process, the iterative algorithm is introduced, and the actual output of the machine tool is

,

, which can be actually measured by laser interferometer . upper computer through

(W is the number of iterations) the error value is calculated for the input

The value is corrected to get

into the next iteration process. Analyze the measurement data, and when the corresponding national standards (such as VDI3441, JIS6330, GB10931-89, etc.) are met, the process ends, so that the XY plane system error model function of the machine tool can be obtained

.

The difference between the identification method of the system error identification module and the existing method is that the input feed position of the machine tool is continuously corrected through the iterative calculation process, so as to obtain the input feed position value corresponding to the ideal output feed position where the error is allowed . And establish the functional relationship between the ideal output feed position and the input feed position, and use this function relationship as a model when there is a systematic error in the machine tool. The error model obtained by this identification method can integrate error factors such as machine tool pitch error and system installation.

Principle of system error identification module:

When the hardware structure of the screw drive system of the machine tool is stable and the system setting is within a reasonable range, it can be considered that the position error of the machine tool is unique and repeatable. The actual displacement of the system (including the system pitch error, backlash error, and system error caused by the installation process) is taken as the expected value point of the system series, and as the output point of the system function. According to the computational mathematics principle, the function input feed position of the system function at each output feed position can be solved.

为输入位置，为实际输入指令的位置点

，即输入的进给位置，

为机床实际输出进给位置。

为高次函数，其阶数与机床系统误差相关（包括：齿轮间隙误差、丝杆误差、安装误差）。在区间，即机床正常工作范围内，函数

是连续的，对于指定的函数值

有唯一的输入变量

与之对应。Let the model function of the input and output of the machine tool be ;in

is the input position, and is the position point where the command is actually input

, that is, the input feed position,

The feed position is actually output for the machine tool.

It is a high-order function, and its order is related to the error of the machine tool system (including: gear clearance error, screw error, installation error). in interval , that is, within the normal working range of the machine tool, the function

is continuous, for the specified function value

has a unique input variable

Corresponding.

在区间连续，给定

个点

，已知

，

，可寻找一函数

，作为

的近似表达式，使满足

Thus, the function

in interval continuous, given

points

,A known

,

, one can find a function

, as

Approximate expressions for

， 

                      （1.1）

,

(1.1)

个互异节点

上的函数值

满足式（1.1）的

次多项式是存在且唯一的。It can be known from the mathematical theorem of calculation that: in a given

distinct nodes

function value on

Satisfies formula (1.1)

Degree polynomials exist and are unique.

即为机床系统实用的计算模型函数。Therefore, it is possible to obtain

It is the practical calculation model function of the machine tool system.

The measuring device in the measuring and recording sub-module of the actual feed position of the cutter of the present invention measures the actual feed position of the cutter by an off-line method of a laser interferometer. Other actual position measuring devices can also be used.

The fitting compensation module of the present invention includes:

Feed position data conversion sub-module: This module converts the feed position that needs to be input into a data format that the machine tool system can recognize; 

Feed-forward calculation and output sub-module of feed position: This module performs fitting operation with the corresponding machine tool XY plane system error model according to the feed position of each input point to obtain the feed-forward amount, and obtains the feed-forward amount according to the feed-forward amount. Input the actual required feed displacement of the point, and transmit each actual required feed displacement to the servo driver to control the output displacement of the servo motor.

The function of fitting compensation: when the system enters a required ideal feed position, according to the system error identification module, the feedforward amount of the feed position is calculated and determined, and the determined feedforward amount is added to the control system to achieve Error correction for compensation purposes. The essence of the fitting compensation method of the fitting compensation module is different from the existing method is that when the machine tool is required to reach a certain ideal feed position, the system performs fitting calculation according to the identified system error model to obtain This requires the feedforward amount corresponding to the feed position, and the determined feedforward amount is added to the control system to achieve the purpose of error correction and compensation. The model fitting calculation adopts the piecewise quadratic Lagrange interpolation method.

Fit compensation method principle:

，得到其有限点的函数值。对连续函数

在任意点的值，采用分段二次Lagrange插值。方法近似度为：Known according to the system error identification module: system model function

, get the function value of its finite point. for continuous functions

The value at any point is interpolated using piecewise quadratic Lagrange. The method approximation is:

     

     

There are formulas:

成立。

established.

The technical effect of the present invention: the present invention cooperates with the software and hardware of the system, and the functional module of the host computer can identify the accurate error model data of the machine tool, and through the timely compensation of the system, the machine tool can achieve the ideal control accuracy. At the same time, the numerical control system sets the compensation Data is simple and convenient. the

Description of drawings

The invention will be illustrated by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a control principle block diagram of the present invention;

Fig. 2 is a schematic flow chart of the system error identification function module described in the preferred embodiment of the present invention;

Fig. 3 is a schematic flow chart of the fitting compensation module described in the preferred embodiment of the present invention;

Fig. 4 is a schematic diagram of errors when the machine tool system is not compensated;

Fig. 5 is a schematic diagram of the error after the machine tool system performs a system error identification to form a data model and fits and compensates;

Fig. 6 is a schematic diagram of the error after the machine tool system performs 4 system error identifications to form a data model and fits and compensates.

Detailed ways

All features disclosed in this specification, or steps in all methods or processes disclosed, may be combined in any manner, except for mutually exclusive features and/or steps.

Any feature disclosed in this specification (including any appended claims, abstract and drawings), unless expressly stated otherwise, may be replaced by alternative features which are equivalent or serve a similar purpose. That is, unless expressly stated otherwise, each feature is one example only of a series of equivalent or similar features.

As shown in Figure 1, a machine tool XY plane error correction system, the system hardware includes a servo drive based on the host computer and programmable controller control, and a servo motor connected to the servo drive, the XY plane working platform is controlled by the servo motor through the screw drive, the upper computer is provided with a system error identification module and a fitting compensation module for the XY plane of the machine tool; Measure the position to obtain the XY plane system error model of the machine tool; after receiving the given position signal, the fitting compensation module uses the XY plane system error model of the machine tool obtained by the system error identification module to fit and calculate the feedforward amount and Correct the output position and send the corrected output position to the servo drive.

As shown in Figure 2, the system error identification module includes:

，转换成机床系统可以识别的数据格式；Feed position data conversion sub-module, this module will need to input several feed positions

, converted into a data format that the machine tool system can recognize;

Automatic point-to-point feed position subroutine submodule, this module instructs the tool to automatically feed according to the input feed position and number;

The tool actual feed position measurement and data format conversion sub-module measures the actual feed position of the machine tool tool on the XY plane through a laser interferometer. This module converts the measurement data format of the laser interferometer into a data format that the machine tool system can recognize;

，直到误差符合要求，从而得到机床XY平面系统误差模型。Deviation calculation correction sub-module, this module calculates the error value between the feed position of each input point and its actual feed position, modifies the input feed position, inputs the modified feed position into the system, performs iterative process calculation, and records the corresponding data

, until the error meets the requirements, so as to obtain the XY plane system error model of the machine tool.

的求取：The calculation method is as follows, that is, the model function

to obtain:

。对于函数

，可转换为方程

，由此，过程转换为方程的求解。set each given position , which corresponds to the input variable

. for functions

, which can be converted into the equation

, thus, the process is transformed into the solution of the equation.

（即机床对应输出点）的对应理想输入变量

作为求取过程初始值点，引入迭代算法，则机床实际输出即为

，

，可以通过激光干涉仪实际测量得到

。上位计算机通过

（W为迭代次数）的误差值计算，对输入值进行修正，得到进入下一次迭代过程。对测量数据进行分析，当满足相应国家标准(如VDI3441、JIS6330、GB10931-89等)时，过程结束，这样可得到模型函数

。Match the machine tool system to each given position

(that is, the corresponding output point of the machine tool) corresponds to the ideal input variable

As the initial value point of the calculation process, the iterative algorithm is introduced, and the actual output of the machine tool is

,

, which can be actually measured by laser interferometer

. upper computer through

(W is the number of iterations) the error value is calculated for the input The value is corrected to get into the next iteration process. Analyze the measurement data. When the corresponding national standards (such as VDI3441, JIS6330, GB10931-89, etc.) are met, the process ends, so that the model function can be obtained

.

；其中

为输入量，为实际输入指令的位置点

，即待进给的给定位置，

为机床实际输出位置。

为高次函数，其阶数与机床系统误差相关（包括：齿轮间隙误差、丝杆误差、安装误差）。在区间

，即机床正常工作范围内，函数

是连续的，对于指定的函数值

有唯一的输入变量与之对应。Let the model function of the input and output of the machine tool be

;in

is the input quantity, and is the position point of the actual input command

, which is the given position to be fed,

It is the actual output position of the machine tool.

It is a high-order function, and its order is related to the error of the machine tool system (including: gear clearance error, screw error, installation error). in interval

, that is, within the normal working range of the machine tool, the function

is continuous, for the specified function value

has a unique input variable Corresponding.

在区间

连续，给定

个点

，已知，

，可寻找一函数

，作为

的近似表达式，使满足Thus, the function

in interval

continuous, given

points

,A known ,

, one can find a function

, as

Approximate expressions for

， 

                      （1.1）

,

(1.1)

个互异节点

上的函数值

满足式（1.1）的

次多项式

是存在且唯一的。It can be known from the mathematical theorem of calculation that: in a given

distinct nodes

function value on

Satisfies formula (1.1)

degree polynomial

exists and is unique.

即为机床系统实用的计算模型函数。Therefore, it is possible to obtain

It is the practical calculation model function of the machine tool system.

The measurement device in the actual feed position measurement and recording sub-module described in this embodiment adopts a laser interferometer.

As shown in Figure 3, the fitting compensation module described in this embodiment includes:

Feed position data conversion sub-module: This module converts the feed position that needs to be input into a data format that the machine tool system can recognize; 

Feed-forward calculation and output sub-module of feed position: This module performs fitting operation with the corresponding machine tool XY plane system error model according to the feed position of each input point to obtain the feed-forward amount, and obtains the feed-forward amount according to the feed-forward amount. Input the actual required feed displacement of the point, and transmit each actual required feed displacement to the servo driver to control the output displacement of the servo motor.

The role of fit compensation:

When the system enters a required ideal position, according to the system error identification module, the feedforward amount of the position is calculated and determined, and the determined feedforward amount is added to the control system to achieve the purpose of error correction and compensation.

Fit compensation method principle:

，得到其有限点的函数值。对连续函数

在任意点的值，采用分段二次Lagrange插值。方法近似度为：Known according to the system error identification module: system model function

, get the function value of its finite point. for continuous functions

The value at any point is interpolated using piecewise quadratic Lagrange. The method approximation is:

     

     

There are formulas:

成立。

established.

Due to the cooperation of the software and hardware of the above system, the upper computer function module can identify the precise error model data of the machine tool, and through the timely compensation of the system, the machine tool can achieve the ideal control accuracy. At the same time, the numerical control system is simple and convenient to set the compensation data.

In order to verify the actual effect of the present invention, a comparative test is carried out on the machining accuracy before and after the adoption of this embodiment. A laser interferometer is used to measure the actual feed position, and the measurement position interval is 20mm.

When the XY plane error correction system of the machine tool described in this embodiment is not added, the actual measurement of the machining accuracy from 0 to 1600mm, the schematic diagram of the error value is shown in Figure 4, and the maximum error range is: -0.094477mm, +0.130328mm, that is ( -94.477μm, +130.328μm).

By using the machine tool XY plane error correction system described in this embodiment, a system error identification (without process iteration) is performed, and after the system error model is formed, the feedforward amount is calculated through fitting compensation, and the corrected actual value is obtained. The output feed displacement, and then the actual output feed displacement is transmitted to the servo driver, the servo driver controls the output displacement of the servo motor, and the actual feed displacement of the machine tool is measured with a laser interferometer. The measurement position interval is 20mm, and the machining accuracy of 0 to 1600mm is actually measured. The error is shown in Figure 5. The maximum error range is: -0.081854mm; +0.037439mm, that is ( -81.854μm, +37.439μm).

By adopting the machine tool XY plane error correction system described in this embodiment, four system error identifications (that is, three process iterations) are performed, and after the system error model is formed, the feedforward amount is calculated by the fitting compensation module, and The corrected actual output feed displacement is then transmitted to the servo driver, the servo driver controls the output displacement of the servo motor, and the actual feed displacement of the machine tool is measured with a laser interferometer. The measurement position interval is 20mm, and the machining accuracy of 0 to 1600mm is actually measured. The error is shown in Figure 6. The maximum error range is: -0.024969mm; +0.026406mm, that is ( -24.969μm, +26.406μm).

It can be seen from the actual measurement and verification that the invention can significantly improve the positioning accuracy of the machine tool, without adding system hardware, automatic completion of identification and compensation, simple operation, and good application prospects.

The present invention is not limited to the foregoing specific embodiments. The present invention extends to any new feature or any new combination disclosed in this specification, and any new method or process step or any new combination disclosed.

Claims (4)

1. lathe XY plane error update the system, system hardware comprises the servo-driver based on host computer and Controlled by Programmable Controller, and the servomotor that is connected with servo-driver, XY plane workbench is driven by screw mandrel by servomotor, it is characterized in that: be provided with systematic error recognition module and match compensating module to lathe XY plane in the described host computer;

Described systematic error recognition module is fixed a cutting tool in the actual measurement location of lathe XY plane correspondence by some given locations of instruction and lathe, draws lathe XY planar system error model;

Described match compensating module, behind the reception given position signal, by the lathe XY planar system error model that described systematic error recognition module is drawn, The Fitting Calculation goes out the feedforward amount and with the outgoing position correction, revised outgoing position is passed to servo-driver.

2.2, a kind of lathe XY plane error update the system according to claim 1, it is characterized in that: described systematic error recognition module comprises:

Supplying position data-switching submodule, this module will need some supplying positions of importing, and converting machine tool system to can the recognition data form;

Automatic point-to-point supplying position subroutine submodule, this module instruction cutter is automatically according to described supplying position and the number auto-feed that is input to machine tooling data base zone;

The actual supplying position of cutter is measured and the Data Format Transform submodule, by laser interferometer machine tool is measured at the actual supplying position in XY plane, this module is that machine tool system can the recognition data form with the measurement data format conversion of laser interferometer;

Deviation calculation correction submodule, this module is calculated the error amount of the supplying position supplying position actual with it of each input point, revise the supplying position of input, with amended supplying position input system, carrying out iterative process calculates, the record corresponding data meets the requirements up to error, thereby obtains lathe XY planar system error model.

3.3, a kind of lathe XY plane error update the system according to claim 2, it is characterized in that: described laser interferometer adopts off-line method to measure the actual supplying position of cutter.

4.4, according to claim 1 or 2 or 3 described a kind of lathe XY plane error update the systems, it is characterized in that: described match compensating module comprises:

Supplying position data-switching submodule: the supplying position that this module will need to import converts machine tool system to can the recognition data form;

Supplying position feedforward amount is calculated, output sub-module: this module is according to the supplying position of each input point, carry out the match computing with corresponding lathe XY planar system error model, draw the feedforward amount, obtain the actual required feeding displacement of each input point according to described feedforward amount, and each actual required feeding displacement passed to servo-driver, control servomotor output displacement.

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