CN109597352B - Numerical control machine tool and control system and method thereof - Google Patents

Numerical control machine tool and control system and method thereof Download PDF

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CN109597352B
CN109597352B CN201710944310.2A CN201710944310A CN109597352B CN 109597352 B CN109597352 B CN 109597352B CN 201710944310 A CN201710944310 A CN 201710944310A CN 109597352 B CN109597352 B CN 109597352B
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main shaft
machine tool
temperature
spindle
fem
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CN109597352A (en
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佘丰客
任超
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Siemens AG
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Siemens AG
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
    • G05B19/404—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
    • G05B19/19—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/37—Measurements
    • G05B2219/37431—Temperature
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/45—Nc applications
    • G05B2219/45136—Turning, lathe
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/49—Nc machine tool, till multiple
    • G05B2219/49169—Compensation for temperature, bending of tool
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/49—Nc machine tool, till multiple
    • G05B2219/49206—Compensation temperature, thermal displacement, use measured temperature
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/49—Nc machine tool, till multiple
    • G05B2219/49219—Compensation temperature, thermal displacement

Abstract

The invention provides a control method realized by an industrial host of a numerical control machine tool, the numerical control machine tool also comprises a machine tool controller, a cutter used for cutting a workpiece and a spindle connected with the cutter, the spindle is internally provided with a motor, and the control method comprises the following steps: acquiring at least one working parameter of the numerical control machine tool from the machine tool controller; determining temperature distribution information of the main shaft according to the acquired at least one working parameter; calculating the deformation of the main shaft according to the determined temperature distribution information of the main shaft; and sending a control command to the machine tool controller to control the machine tool controller to adjust the driving feed amount of the tool according to the calculated deformation amount of the main shaft. The invention analyzes the deformation of the main shaft by adopting the finite element model of the simulation main shaft, thereby improving the calculation accuracy.

Description

Numerical control machine tool and control system and method thereof
Background
With the development of Numerical Control (CNC) technology, CNC machines can process increasingly precise parts. The precision of the precision part obviously puts higher requirements on the error control of the tool driving feed amount, and the deformation of a main shaft caused by heat generation in the machining process of a main shaft of a numerical control machine tool is an important factor for causing the error of the tool feed amount. Therefore, in the numerical control machine tool, it is general to eliminate such an influence on the driving feed amount of the tool due to the deformation of the spindle.
In the conventional technology, sensors are usually used to actually detect the heating degree of a spindle of a numerical control machine tool, and these sensors are usually installed on the numerical control machine tool to detect the spindle temperature from the outside of the spindle, or a spindle manufacturer directly embeds a temperature sensor in the spindle, so that an industrial host connected with the numerical control machine tool can directly read the spindle temperature measured by the sensor in the spindle during the processing of a controller of the numerical control machine tool, and estimate the deformation of the spindle according to the actually measured spindle temperature, thereby determining the driving feed amount of a tool according to the estimated variable phase amount of the spindle.
Although the problem of correcting spindle distortion is well solved by using a temperature sensor, it is not suitable for use in some environments. For example, cutting debris or cutting fluid may corrode the wiring of the sensor and even affect the sensing element of the sensor, thereby often rendering the sensor inoperable.
Disclosure of Invention
The invention provides an improved numerical control machine tool and a control system thereof, which are not required to measure the temperature of a main shaft of the numerical control machine tool through a sensor in the process of machining parts by the numerical control machine tool, so that the problems of inaccurate temperature measurement and inaccurate cutter driving feed amount caused by abnormal sensor are solved.
The inventors have found a relationship between an operation parameter of a numerical control machine tool and a temperature distribution of a spindle through a great deal of experiments and studies. Therefore, the temperature distribution parameters of the main shaft are determined according to the operation parameters of the numerical control machine tool, the deformation of the main shaft is calculated according to the determined temperature distribution parameters, and finally the driving feed amount of the cutter is determined. The problem of inaccurate cutter driving feed caused by inaccurate temperature measurement of the sensor is effectively solved. The accurate prediction of the temperature of the main shaft is realized, and the numerical control machine tool has a wider application environment.
According to an aspect of the present invention, there is provided a method for controlling a numerically controlled machine tool, the numerically controlled machine tool further comprising a machine tool controller, a tool for cutting a workpiece, and a spindle connected to the tool, the spindle having a motor built therein, the spindle being driven by the motor to perform a cutting operation of the tool, the method comprising: acquiring at least one working parameter of the numerical control machine tool from the machine tool controller, wherein the at least one working parameter is used for representing the state of the numerical control machine tool in the machining process; determining first temperature distribution information of the main shaft according to the acquired at least one working parameter; calculating the deformation of the main shaft according to the determined first temperature distribution information of the main shaft; and determining the driving feed amount of the tool according to the calculated deformation amount of the main shaft. According to the scheme, the problem of inaccurate cutter driving feed amount caused by inaccurate temperature measurement of the sensor is effectively avoided.
Preferably, determining first temperature distribution information of the spindle according to the acquired at least one working parameter includes: determining the first temperature distribution information of the main shaft according to the obtained at least one working parameter based on a finite element model FEM of the main shaft; according to the determined first temperature distribution information of the main shaft, calculating the deformation amount of the main shaft comprises the following steps: and calculating the deformation amount of the main shaft based on the FEM of the main shaft by taking the first temperature distribution information of the main shaft as a boundary condition of the FEM. By utilizing the scheme, the structure characteristics of the main shaft are fully considered, and the accurate estimation of the temperature of the main shaft and the deformation of the main shaft is realized by establishing a finite element model for the main shaft in advance, so that the more accurate control of the feed amount of the cutter is realized.
Preferably, wherein determining the first temperature distribution information of the main shaft based on the at least one acquired operating parameter based on a finite element model FEM of the main shaft comprises: determining the self-heating H of the motor according to the acquired at least one working parameterrotorAnd the cutting heat H of the toolcut(ii) a Self-heating H of the motor to be determinedrotorAnd the cutting heat H of the toolcutAnd calculating to obtain the first temperature distribution information of the main shaft as an input boundary condition of the FEM. Preferably, wherein the at least one parameter comprises: the motor comprises a working voltage U, a working current I, a cutting torque T applied to the spindle by the motor and a rotating speed V of the spindle, wherein the self-heating Hrotor and the cutting heat Hcut of the motor are calculated by the following formula, and the Hrotor is T V, and U I-Hcut. By utilizing the scheme, the temperature can be accurately predicted.
Preferably, before acquiring at least one operating parameter of said numerically controlled machine tool from said machine tool controller, a calibration process is further included, the calibration process including: acquiring temperature information of the spindle in operation through at least one temperature sensor which is preset inside or outside the spindle, and synchronously acquiring at least one working parameter of the numerical control machine tool from the machine tool controller;
determining second temperature distribution information of the numerical control machine tool according to the at least one synchronously acquired working parameter of the numerical control machine tool; and determining the FEM of the main shaft according to the acquired temperature information and the determined second temperature distribution information of the numerical control machine tool. Through the calibration process, the accuracy of the temperature and the deformation amount predicted by the finite element model can be ensured.
Preferably, the determining the FEM of the principal axis comprises: determining at least one calibration factor for calibrating the calculated amount of deformation of the spindle when applied to the FEM, based on the acquired temperature information and the determined second temperature distribution information of the numerically controlled machine tool.
Preferably, wherein said determining at least one calibration factor comprises: determining the second temperature distribution information of the main shaft according to the at least one synchronously acquired working parameter based on the FEM of the main shaft in the calibration process; comparing the acquired temperature information with the determined second temperature distribution information of the main shaft to determine the at least one calibration factor, wherein the at least one calibration factor is used for indicating a temperature deviation between the acquired actual temperature of the main shaft and the temperature of the main shaft determined according to the synchronously acquired at least one parameter. The invention further improves the precision control of the cutter driving feed amount by correcting the deformation amount by using the calibration factor.
Preferably, the control method further includes: detecting an actual error of the workpiece processed based on the driving feed amount; based on the actual error, performing calibration processing on the FEM, including: acquiring temperature information of the spindle in operation through at least one temperature sensor which is preset inside or outside the spindle, and synchronously acquiring at least one working parameter of the numerical control machine tool from the machine tool controller; determining at least one calibration factor for calibrating the calculated amount of deformation of the spindle when applied to the FEM, based on the collected temperature information and second temperature distribution information determined synchronously with the at least one operating parameter. Therefore, the machine tool can be maintained conveniently during the use period of the machine tool, and the machining precision is ensured.
According to another aspect of the present invention, there is provided a control system for a numerically controlled machine tool including a machine tool controller, a tool for cutting a workpiece, and a spindle connected to the tool, wherein a motor is built in the spindle, and the spindle is driven by the motor to perform a cutting operation of the tool, the control system including: the temperature determining unit is used for acquiring at least one working parameter of the numerical control machine tool from the machine tool controller and determining the temperature distribution information of the main shaft according to the acquired at least one working parameter, wherein the at least one working parameter is used for indicating the state of the numerical control machine tool in the machining process; a deformation calculation unit for calculating the deformation of the spindle according to the determined temperature distribution information of the spindle;
and the driving feed amount determining unit is used for determining the driving feed amount of the tool according to the calculated deformation amount of the main shaft.
According to another aspect of the present invention, there is provided a control system of a numerically controlled machine tool, comprising: at least one memory to store instructions; and the at least one processor is used for calling the instruction to execute the control method of any one numerical control machine tool.
According to another aspect of the present invention, there is provided a machine-readable medium having stored thereon instructions, which when executed by a machine, cause the machine to perform any one of the aforementioned control methods of a numerical control machine.
Drawings
FIG. 1 shows a schematic diagram of a machine tool control system according to one embodiment of the invention;
FIG. 2 shows a schematic diagram of a machine tool control system according to another embodiment of the invention;
FIG. 3 shows a schematic diagram of spindle temperature simulation using a finite element model;
FIG. 4 is a schematic diagram showing spindle deflection simulation using a finite element model;
FIG. 5 shows a machine tool control diagram according to one embodiment of the invention;
FIG. 6 shows a machine tool control diagram according to one embodiment of the invention.
Detailed Description
Preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
As shown in fig. 1, there is shown a schematic diagram of a control system 100 for a CNC machine according to one embodiment of the present invention. The CNC machine includes a machine controller 101, which may be a Programmable Logic Controller (PLC), for example, a tool for cutting a workpiece to be machined, a spindle connected to the tool, and a driving motor built in the spindle, wherein the spindle is driven by the motor to complete a cutting action of the tool. It will be appreciated that CNC machines may have multiple drive motors and multiple tools. In the following description, one tool and a built-in motor are described as an example, but the control method of the present invention is also applicable to a case of a plurality of tools.
In this example, the control system 100 may be implemented by an industrial host installed on a machine tool. As shown in fig. 1, the control system 100 is connected to a machine tool controller 101, and includes a temperature determination unit 102, a deformation calculation unit 103, and a drive feed amount calculation unit 104. It will be readily understood to those skilled in the art that the control system 100 also includes other subsystems or components, but for simplicity, other subsystems or components included in the control system 100 are not shown in the figures. On a numerically controlled machine tool, a machine tool controller 101 controls the driving feed amount of a tool according to the parameter of a workpiece to be machined under the control of an industrial host. Since the thermal deformation of the main shaft is caused during the machining process (due to various factors). Such thermal deformation of the spindle adversely affects the predetermined tool driving feed amount originally set in accordance with the parameters of the workpiece. Therefore, the control system 100 of the present invention takes into account the influence of the spindle heat generation when the controller 101 actually outputs the actual feed amount of the tool.
To this end, the control system 100 is provided with a temperature determination unit 102 to determine the degree of heat generation on the spindle and output temperature information. In this example, the temperature determination unit 102 reads at least one operating parameter of the machine tool from the machine tool controller 101. The operating parameter may refer to any factor directly or indirectly related to spindle heating, which is indicative of the state of the CNC machine during machining. The temperature determination unit 102 may determine temperature distribution information H of the main shaft using the at least one operation parameter. The deformation amount information D of the spindle can be calculated by the deformation calculating means 103 using the determined temperature distribution information H. The drive feed amount calculation unit 104 adjusts the drive feed amount of the tool corresponding to the machining parameter of the workpiece to be machined, i.e., removes the deformation amount D from the drive feed amount as the actually output tool feed amount, based on the calculated deformation amount information D, and generates a control command indicating the adjusted drive feed amount. The drive feed amount calculation unit 104 then supplies the control command to the machine tool controller 101, and the machine tool controller 101 controls the cutting of the tool with the adjusted drive feed amount according to the control command.
In a preferred embodiment of the present invention, the temperature determining unit 102 determines the temperature distribution information H of the spindle according to the acquired at least one operating parameter based on a finite element model FEM established in advance for the spindle. The FEM fully considers the structural characteristics of the main shaft, utilizes finite element analysis to simulate the main shaft, can more accurately determine the temperature distribution of the main shaft, and the finite element analysis calculation is abbreviated as
Figure BDA0001426893890000071
As previously mentioned, the operational parameters obtained when calculating the temperature distribution in the present invention may be various possible factors that affect spindle heating, including various parameters that affect spindle operation. In this example, the operation voltage U and the operation current I of the motor read from the machine tool controller 101, and the torque T and the spindle rotation speed V applied to the workpiece by the tool during the operation of the spindle will be described. In the machining process, frictional heat, that is, cutting heat, is generated when a tool coupled to the spindle cuts a workpiece, and self-heating is generated during operation of a motor built in the spindle, all of which are inevitably conducted to the spindle, so that, in this example, the temperature determining unit 102 generates self-heating H by the operation of the motorROTORAnd tool cutting toolHeat of cutting H generated during machiningCUTAs a boundary constraint condition of the finite element model FEM, the temperature distribution information H of the main axis is estimated. More specifically, as shown by the dashed line box in fig. 1, the temperature determination unit 102 includes a first calculation unit 1021 and a second calculation unit 1022. The temperature determination unit 102 receives from the machine tool controller 101 the operating parameters of the machine tool, including the operating voltage U and the operating current I of the motor, the torque T applied to the workpiece by the tool when the spindle is in operation, and the spindle rotational speed V. The first calculation unit 1021 calculates the self-heating and cutting heat of the motor on the spindle using the received machine tool operation parameters. The first calculation unit 1021 calculates the self-heating H of the motor by using the working voltage U, the working current I, the cutting torque T and the spindle rotation speed VROTORAnd heat of cutting HCUTWherein
HCUT＝T*V
HROTOR＝U*I-HCUT
Then, the second calculation unit 1022 uses HCUTAnd HROTORThe temperature distribution H of the spindle is calculated as a boundary condition of the finite element model FEM of the spindle, i.e.
Figure BDA0001426893890000072
Here, the
Figure BDA0001426893890000073
Represents a calculation function of the finite element model FEM and supplies the temperature H to the deformation calculation unit 103. Then, the deformation calculation unit 103 calculates the deformation amount D of the spindle from the calculated temperature H. The driving feed amount calculation unit 104 adjusts the driving feed amount of the tool based on the calculated deformation amount information D, and generates a control command. The machine tool controller 101 controls the cutting of the tool with the adjusted drive feed amount according to the control command, thereby achieving precise machining of the workpiece.
In another embodiment of the present invention, the deformation calculation unit 103 also uses the finite element model FEM of the main shaft when calculating the deformation amount D of the main shaft using the temperature information H received from the temperature determination unit 102. Deformation calculation unit 103Calculating a deformation amount D of the main shaft, namely, a deformation amount D of the main shaft, by using the temperature information of the main shaft as a boundary condition of the FEM in the FEM of the main shaft
Figure BDA0001426893890000081
Wherein H1,H2,. Hm denotes the temperature of multiple points on the determined temperature profile of the spindle. The drive feed amount calculation unit 104 adjusts the drive feed amount of the tool based on the calculated deformation amount information D, i.e., removes the deformation amount D from the drive feed amount as the actually output tool feed amount, and generates a control command indicating the adjusted drive feed amount. The machine tool controller 101 controls the tool cutting with the adjusted drive feed amount according to the control command. . Due to the fact that the irregular structure characteristics of the main shaft and the characteristic that heat distribution on the main shaft is uneven are fully considered, accurate estimation of deformation of the main shaft can be achieved by the FEM.
The invention adopts finite element model analysis and has the advantages that: by simulating the real spindle structure, the accurate solution of spindle heat distribution and the simulation calculation of spindle deformation are realized. Different from simple formula processing in the prior art, the calculation result precision of the finite element model is higher. It should be noted that in the present invention, the main spindle is used as the main body of the finite element analysis model, and as for the way of establishing the finite element model for the main body determined in this way, the existing model provided by the main spindle supplier can be adopted, or the model can be constructed by itself according to the actual product parameters, and for the sake of brevity, a more detailed discussion is not provided here.
FIG. 3 illustrates an exemplary schematic of a spindle temperature H distribution on a finite element model established for a spindle according to an embodiment. It can be seen from this figure that the temperature on the spindle varies along the spindle, with the junction with the tool on the spindle (i.e. to the left in the figure) having the greatest temperature, for example 179.86 ℃ under certain experimental conditions, and a minimum temperature of 153.17 ℃ at the far end. The model well shows the temperature distribution of each part on the main shaft.
Fig. 4 shows a distribution of spindle deformation D on a finite element model built for a spindle according to an embodiment. It can be seen that the spindle has the greatest amount of deformation at the interface with the tool, for example, 0.9062mm under the same experimental conditions as described above, while the interface with the motor at the distal end has zero deformation. The model shows well the deformation distribution of the sections on the spindle.
In the above example of the present invention, the temperature distribution of the spindle and the amount of deformation of the spindle are calculated using the finite element model FEM established in advance for the spindle. Optionally, in practice, the finite element model FEM may be further calibrated before the at least one operating parameter of the machine tool is obtained from the machine tool controller 101. Fig. 2 shows a schematic diagram of a machine tool control system 100 with calibration functionality.
As shown in fig. 2, the control system 100 includes a calibration module 105 shown by a dashed box, in addition to the temperature determination unit 102 for estimating the temperature of the spindle, the deformation calculation unit 103 for calculating the deformation amount of the spindle, and the drive feed amount calculation unit 104, which are the same as those of fig. 1. As shown, the calibration module 105 includes at least one sensor 106 and a model calibration unit 107. Presetting the at least one temperature sensor 106 inside or outside the main shaft, then operating the machine tool, and acquiring temperature information of the main shaft in operation in real time through the sensor 106 during the operation of the CNC machine tool.
In synchronization with the acquisition of the temperature information by the sensor 106, the temperature determination unit 102 synchronously acquires the at least one working parameter of the CNC machine from the machine controller 101, and uses the temperature distribution information H determined by the at least one working parameter according to an initial finite element model FEM established in advance for the spindle. The at least one operating parameter may include, but is not limited to, the operating voltage U and the operating current I of the motor discussed in the previous embodiments, the torque T applied to the workpiece by the tool when the spindle is in operation, the spindle speed V, and the like.
The model calibration unit 107 receives the actually acquired temperature from the sensor 106 and the temperature distribution information determined with the at least one operating parameter from the temperature determination unit 102, from which collected temperature information and the determined temperature distribution information the degree of error of the determined temperature distribution information with respect to the actual temperature of the spindle may be determined. The model calibration unit 107 may adjust the initial finite element model FEM previously established for the spindle according to the degree of error. After one or more adjustments, when the error meets a predetermined requirement, the model calibration unit 107 stores the calibrated FEM in the temperature determination unit 102 and the calculation unit 103, respectively, to update the initial FEM model stored therein.
Since the temperature distribution information determined by the temperature determining unit 102 using at least one operating parameter may have an error with the actual spindle temperature, in another preferred embodiment of the present invention, at least one calibration factor λ may be further set for the finite element model in the deformation calculating unit 103, and the deformation amount D estimated by the deformation calculating unit 103 is corrected using the at least one calibration factor λ, so as to reflect the deformation amount of the spindle more truly. As shown in fig. 2, the model calibration unit 107 may generate the calibration factor λ, which indicates the degree of the error, from the error of the temperature distribution information determined using the at least one operating parameter with respect to the actual temperature of the main shaft, which may be stored in the deformation calculation unit 103. Similarly to the foregoing, the temperature determination unit 102 calculates the spindle temperature distribution information H based on at least one parameter acquired from the machine tool controller using the updated finite element model. The deformation calculation unit 103 uses the updated finite element model FEM function using the main shaft temperature distribution H calculated by the temperature determination unit 102 as a boundary constraint condition
Figure BDA0001426893890000101
Calculating the deformation D of the main shaft, and further using the calibration factor lambda to correct the deformation D or directly using the calibration factor for adjusting the finite element function
Figure BDA0001426893890000102
Thereby generating a corrected deformation amount D'. The driving feed amount calculation unit 104 adjusts the driving feed amount of the tool based on the calculated deformation amount information D', generates a control command, and supplies the control command to the machine tool controller 101. The machine tool controller 101 controls the tool cutting using the adjusted drive feed amount in accordance with the control command.
The above embodiment is a scheme of generating the calibration factor λ using the deviation between the actual temperature and the calculated temperature. Alternatively, it is also possible to generate a signal reflecting the deviation between the actual deformation amount of the main shaft and the deformation amount calculated by the deformation calculation unit 103 by directly measuring the actual deformation amount and comparing it with the deformation amount calculated by the deformation calculation unit 103, and supply the signal to the deformation calculation unit 103 as the calibration factor λ.
It should be noted here that the calibration module 105 is not an essential module of the CNC machine control system, and it may be detachably installed in the control system 100 as a separate module or selectively activated in the control system 100 for calibrating the machine control system before the machine is actually run or shipped. Once the calibration of the finite element model FEM is completed by the calibration module 105 and/or the calibration factor λ is determined, the calibration module 105 may be removed or disabled. During normal operation, the temperature determination unit 102 and the deformation calculation unit 103 may directly use the calibrated finite element model, and the deformation calculation unit 103 may directly correct the deformation amount D by using the calibration factor λ. During the use of the machine tool or after the machine tool is shipped, if the machine tool is abnormal, for example, when it is determined that a large error exists in the machined workpiece, the calibration module 105 is installed or activated again and the calibration mode is started to recalibrate the finite element model FEM and/or generate a new calibration factor λ ', and the deformation calculation unit 103 and the temperature determination unit 102 are updated again by using the recalibrated finite element model FEM and the new calibration factor λ', so that the machine tool is calibrated.
Alternatively, the calibration module 105 may be constituted by only the model calibration unit 107, with the temperature sensor 106 being placed outside the calibration module 105. Thus, according to an embodiment of the present invention, the calibration module 105 may be integrated with the temperature determination unit 102, the deformation calculation unit 103, and the drive feed amount calculation unit 104. At calibration, the calibration process described above may be implemented by activating a calibration module internal to the control system 100 while utilizing the external sensor 106.
In addition, a control system of a numerical control machine tool is also provided, including: at least one memory to store instructions; and the at least one processor is used for calling the instruction to execute the control method of the numerical control machine tool provided by the embodiment of the invention. The control system may be considered an alternative implementation of the control system 100. Wherein the temperature determination unit, the deformation calculation unit, the drive feed amount determination unit, the calibration unit, and the like in the control system 100 may be regarded as a part of the instructions.
FIG. 5 illustrates a control flow diagram for an industrial host, according to one embodiment of the invention. As shown, after the machine tool is started, machine tool operating parameters are received from the machine tool controller 101 at step 501. In step 502, the temperature determination unit 102 determines temperature distribution information of the spindle according to the acquired operating parameters. Here again, as an example, the operating voltage U and the operating current I of the motor and the cutting torque T applied by the tool via the spindle and the spindle rotational speed V are used as operating parameters, and the temperature determination unit 102 calculates the temperature distribution information H of the spindle on the basis of the operating parameters using a finite element model FEM established for the spindle. The temperature determination unit 102 calculates the self-heating Hrotor of the motor and the cutting heat Hcut of the tool using the operating parameters, and then applies the self-heating Hrotor and the cutting heat Hcut as boundary conditions to the finite element model, thereby calculating the temperature H of the spindle. In step 503, the deformation calculation unit 103 takes the calculated temperature H as the FEM function of the finite element model
Figure BDA0001426893890000121
The boundary constraint condition (D) of (2) is calculated. In step 504, the drive feed amount calculation unit 104 generates a control command using the deformation amount D calculated by the deformation calculation unit 103, and controls the sameA command is given to the machine tool controller 101, and the machine tool controller 101 adjusts the driving feed amount of the tool by using the deformation amount D according to the control command, thereby achieving accurate control of the feed amount.
Further, in step 503, the deformation calculation unit 103 may also correct the deformation amount D using an internally stored calibration factor λ, thereby outputting a corrected deformation amount D'. In step 504, the drive feed amount calculation unit 104 generates a control command using the corrected deformation amount D'. Further, the machine tool controller 101 controls the cutting of the tool according to the adjusted tool driving feed amount based on the control command.
FIG. 6 shows a schematic flow chart for calibrating a finite element model. As shown in fig. 6, at step 601, at least one machine tool operating parameter is received from the machine tool controller 10. In step 602, the temperature determination unit 102 determines boundary conditions that can be suitable for the finite element model FEM using at least one machine tool operating parameter, for example, calculates a maximum temperature Hmax and a minimum temperature Hmin of the spindle heat generation, and further estimates the temperature distribution H of the spindle by using the maximum temperature Hmax and the minimum temperature Hmin as input boundary conditions of the finite element model of the spindle. Meanwhile, in step 603, the measured actual temperature H' of the spindle is received from the sensor 106 previously provided outside or inside the spindle. In step 604, the model calibration unit 107 compares the estimated temperature H with the actual temperature H 'and determines the degree of error between the estimated temperature H and the actual temperature H'. In step 605, when the model calibration unit 107 determines that the error is large, which indicates that the fitting effect of the estimated temperature H and the actual temperature H' is poor, for example, the error difference is larger than a certain threshold, the initial finite element model FEM is calibrated (for example, the internal parameters of the FEM are adjusted), and then the step 601 is returned to, and the above steps 602 and 605 are repeated by using the calibrated FEM. If it is determined in step 605 that the temperature error is lower than the threshold, it means that the current finite element model FEM satisfies the temperature simulation calculation requirements, and thus the calibrated FEM is stored in the deformation calculation unit 103 and the temperature calculation unit 102. Alternatively, in step 606, a signal reflecting the temperature error between the estimated temperature H and the actual temperature H' may also be generated, and provided to the deformation calculation unit 103 as the calibration factor λ and stored.
The solution according to the invention allows the following advantages to be achieved:
since the temperature of the spindle is estimated from the operating parameters of the machine tool, the dependence on sensors is avoided, which not only improves the environmental suitability of the machine tool of the invention, but also the reliability of the entire machine tool due to the reduction of such components. In addition, according to a preferred embodiment of the present invention, by sufficiently considering the structural features of the main shaft, accurate estimation of the deformation amount of the main shaft is achieved by previously establishing a finite element model for the main shaft, thereby achieving more precise control of the tool feeding amount. In the conventional technology, the detected spindle temperature is used for calculating the spindle deformation, which is usually obtained by using a simple formula, and the characteristics of the spindle structure and the like are not considered, so that the problem of low precision exists. The invention calculates the temperature of the main shaft and the deformation of the main shaft by simulating the structural characteristics of the main shaft, improves the calculation accuracy, realizes the accurate control of the cutter, and accordingly improves the processing precision of the whole machine tool.
Preferred embodiments of the present invention have been described above with reference to examples. It is understood that the units shown in fig. 1 and 2 can be implemented by software, hardware (e.g., integrated circuit, FPGA, etc.), or a combination of software and hardware. Further, although the temperature determination unit and the deformation calculation unit are shown separately from the machine tool controller, it is obvious that the temperature determination unit and the deformation calculation unit may be implemented integrally with the machine tool controller. For example, the present invention may also be implemented by a computing device executing instructions stored on a machine-readable medium, the instructions being executable to implement a method according to the present invention.
It will be understood by those skilled in the art that various changes and modifications may be made to the embodiments disclosed above without departing from the spirit of the invention. Accordingly, the scope of the invention should be determined from the following claims.

Claims (10)

1. A method for controlling a numerically controlled machine tool, the numerically controlled machine tool further comprising a machine tool controller, a tool for cutting a workpiece, and a spindle connected to the tool, the spindle having a motor disposed therein, the spindle being driven by the motor to perform a cutting operation of the tool, the method comprising:
acquiring at least one working parameter of the numerical control machine tool from the machine tool controller, wherein the at least one working parameter is used for representing the state of the numerical control machine tool in the machining process;
determining first temperature distribution information of the spindle according to the acquired at least one working parameter, including: determining the first temperature distribution information of the main shaft according to the acquired at least one working parameter based on a Finite Element Model (FEM) of the main shaft;
calculating the deformation amount of the main shaft according to the determined first temperature distribution information of the main shaft, wherein the calculation comprises the following steps: calculating a deformation amount of the main shaft based on the FEM of the main shaft with the first temperature distribution information of the main shaft as a boundary condition of the FEM;
determining the driving feed amount of the cutter according to the calculated deformation amount of the main shaft;
wherein the finite element model FEM is determined by:
acquiring temperature information of the spindle in operation through at least one temperature sensor which is preset inside or outside the spindle, and synchronously acquiring at least one working parameter of the numerical control machine tool from the machine tool controller;
determining second temperature distribution information of the numerical control machine tool according to the at least one synchronously acquired working parameter of the numerical control machine tool;
determining the FEM of the spindle according to the acquired temperature information and the determined second temperature distribution information of the numerical control machine tool, including: determining at least one calibration factor for calibrating the calculated amount of deformation of the spindle when applied to the FEM, based on the acquired temperature information and the determined second temperature distribution information of the numerically controlled machine tool.
2. The control method of claim 1, wherein determining the first temperature distribution information of the spindle from the acquired at least one operating parameter based on a Finite Element Model (FEM) of the spindle comprises:
determining the self-heating H of the motor according to the acquired at least one working parameterrotorAnd the cutting heat H of the toolcut；
Determining the self-heating H of the motorrotorAnd the cutting heat H of the toolcutAnd calculating to obtain the first temperature distribution information of the main shaft as an input boundary condition of the FEM.
3. The method of claim 1, wherein said determining at least one calibration factor comprises:
determining the second temperature distribution information of the main shaft according to the at least one synchronously acquired working parameter based on the FEM of the main shaft in the calibration process;
comparing the acquired temperature information with the determined second temperature distribution information of the main shaft to determine the at least one calibration factor, wherein the at least one calibration factor is used for indicating a temperature deviation between the acquired actual temperature of the main shaft and the temperature of the main shaft determined according to the synchronously acquired at least one parameter.
4. A method for controlling a numerically controlled machine tool, the numerically controlled machine tool further comprising a machine tool controller, a tool for cutting a workpiece, and a spindle connected to the tool, the spindle having a motor disposed therein, the spindle being driven by the motor to perform a cutting operation of the tool, the method comprising:
acquiring at least one working parameter of the numerical control machine tool from the machine tool controller, wherein the at least one working parameter is used for representing the state of the numerical control machine tool in the machining process;
determining first temperature distribution information of the spindle according to the acquired at least one working parameter, including: determining the first temperature distribution information of the main shaft according to the acquired at least one working parameter based on a Finite Element Model (FEM) of the main shaft;
calculating the deformation amount of the main shaft according to the determined first temperature distribution information of the main shaft, wherein the calculation comprises the following steps: calculating a deformation amount of the main shaft based on the FEM of the main shaft by taking the first temperature distribution information of the main shaft as a boundary condition of the FEM;
determining the driving feed amount of the cutter according to the calculated deformation amount of the main shaft;
detecting an actual error of the workpiece processed based on the driving feed amount;
based on the actual error, performing calibration processing on the FEM, including:
acquiring temperature information of the main shaft in operation through at least one temperature sensor which is arranged inside or outside the main shaft in advance, and synchronously acquiring at least one working parameter of the numerical control machine tool from the machine tool controller;
determining at least one calibration factor for calibrating the calculated amount of deformation of the spindle when applied to the FEM, based on the acquired temperature information and second temperature distribution information determined synchronously with the at least one operating parameter.
5. A control system of a numerically controlled machine tool, the numerically controlled machine tool comprising a machine tool controller, a tool for cutting a workpiece, and a spindle connected to the tool, wherein a motor is built in the spindle, and the spindle is driven by the motor to complete a cutting operation of the tool, the control system comprising:
a temperature determining unit, configured to obtain at least one working parameter of the cnc machine from the machine controller, and determine first temperature distribution information of the main shaft according to the obtained at least one working parameter based on a finite element model FEM of the main shaft, where the at least one working parameter is used to indicate a state of the cnc machine during a machining process;
a deformation calculation unit that calculates a deformation amount of the main shaft based on the FEM of the main shaft with the first temperature distribution information of the main shaft as a boundary condition of the FEM;
a driving feed amount determining unit for determining a driving feed amount of the tool based on the calculated deformation amount of the spindle; and
a calibration unit comprising:
at least one temperature sensor which is arranged inside or outside the main shaft in advance and is used for collecting the actual temperature information of the main shaft in operation,
the model calibration unit is used for receiving second temperature distribution information of the main shaft synchronously calculated by the temperature determination unit by utilizing the at least one working parameter synchronously acquired from the machine tool controller, and determining the FEM according to the acquired actual temperature information and the calculated second temperature distribution information of the main shaft;
wherein the temperature determination unit determines at least one calibration factor for calibrating the calculated deformation amount of the main shaft when applied to the FEM, based on the acquired temperature information and the determined second temperature distribution information.
6. The control system of claim 5, wherein the temperature determination unit further comprises:
a first calculating unit for calculating a self-heating Hrotor of the motor and a cutting heat Hcut of the tool according to the acquired at least one operating parameter,
and the second calculation unit is used for calculating and obtaining the first temperature distribution of the spindle by using the motor self-heating Hrotor and the cutter cutting heat Hcut as input boundary conditions of the finite element model based on the finite element model FEM.
7. The control system of claim 5, wherein the temperature determination unit further:
determining second temperature distribution information of the main shaft according to the at least one working parameter obtained synchronously based on the FEM of the main shaft in the calibration process;
comparing the collected temperature information with second temperature distribution information of the main shaft determined according to the at least one synchronously obtained working parameter to determine the at least one calibration factor, wherein the at least one calibration factor is used for indicating a temperature deviation between the collected actual temperature of the main shaft and the temperature of the main shaft determined according to the at least one synchronously obtained parameter.
8. A numerically controlled machine tool comprising a control system as claimed in any one of claims 5 to 7.
9. A control system for a numerically controlled machine tool, comprising:
at least one memory to store instructions;
at least one processor configured to invoke the instructions to perform the method of any of claims 1-4.
10. A machine-readable medium having stored thereon instructions which, when executed by a machine, cause the machine to perform the method of any one of claims 1 to 4.
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