CN107024907B - Embedded full-life-cycle machine tool thermal error compensation system and method - Google Patents

Abstract

The invention discloses an embedded full life cycle machine tool thermal error compensation system and method. The output end of the temperature sensor is connected with the programmable logic controller through the temperature filtering and conditioning circuit, the programmable logic controller is connected with the memory chip, the PLC controller and the core controller, and the host computer is connected with the core controller. Connected, the system and method can accurately realize thermal error compensation of the machine tool, and the operation is relatively simple.

Description

An embedded full life cycle machine tool thermal error compensation system and method

technical field

The invention belongs to the field of thermal error compensation of numerically controlled machine tools, and relates to an embedded full life cycle machine tool thermal error compensation system and method.

Background technique

With the improvement of parts machining accuracy and machine tool assembly technology, the errors caused by traditional machine tools due to manufacturing and assembly have dropped significantly, while thermal errors, which were not the main factor before, accounted for 40% to 70% of modern machining errors. Error compensation technology is getting more and more attention. Among the two methods of thermal balance design and thermal error reverse compensation, the second method is widely used due to its short development cycle and good versatility. Thermal error reverse compensation requires a high-efficiency, high-precision, high-reliability compensation device. For example, the patent with the application number of 201511020629.3 and the title of "A Precision CNC Machine Tool Thermal Error Measurement and Temperature Compensation System" discloses a method using a temperature sensor It is a device that calculates compensation through comprehensive modeling with an inductive displacement sensor, and converts the compensation amount into a motor drive signal to control the movement of the shaft. This device is suitable for most machine tools, and the modeling is more accurate and has high precision. However, in the actual machining of parts, due to the difficulty in the arrangement of the inductive sensor during machining, the implementability is poor, and it needs to be wired with the servo motor driver. inconvenient. Another example is the patent application number 201610036937.3, titled "An artificial intelligence compensator and compensation method for thermal deformation error of machine tools", which discloses a compensation model calculation device based on artificial intelligence, which can be calculated according to the experimental data of the laser interferometer and the data of the temperature sensor. Automatically learn to model. This system has strong adaptability and can be used for experimental modeling of various machine tools, but there are two problems. The first is that a laser interferometer needs to be used to measure the error in each experiment. For a single machine tool, the laser interferometer can be used to measure the error. Accurate measurement and modeling, but now the consistency of thermal error of machine tools has not been verified, one by one experiment is required for a large number of machine tools, and it is very difficult to conduct experiments for machine tools that have been sold, which is not conducive to the convenience of users. The second is that the network port needs to be occupied for a long time for communication. When the actual machine tool is used for processing, the network port needs to perform other operations, which will cause great inconvenience to the machine tool user to arrange work. In the existing compensation devices, the establishment of the model must be carried out by the "five-point method" experimental measurement error by eddy current or by the laser interferometer to measure the error. This kind of measurement is very suitable as a factory experimental method, but for users, it is necessary to Experiments with machine tools need to pay the price of stopping production of machine tools and even production lines, which is not conducive to large-scale promotion. In the sending of compensation amount, it needs to be realized by occupying the network port or other PLC panel communication ports. However, when the PLC is used, these ports have other operations to be completed. How to reasonably arrange the operation process requires a high level of operation of the processing workers. In terms of model establishment, although the above measurement device can establish a relatively accurate thermal error model, the thermal error model of the machine tool will change with the use of the machine tool, and the model needs to be corrected in time. The operation of the above modeling experiment is complicated and repetitive. Experimentation is expensive and affects the effect of actual use. To sum up, a real-time thermal error compensation system with simple structure, high precision, simple operation and suitable for use in factory production lines is needed now.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the above shortcomings of the prior art, and to provide an embedded full life cycle machine tool thermal error compensation system and method.

In order to achieve the above purpose, the embedded full life cycle machine tool thermal error compensation system according to the present invention includes a host computer, a PLC controller, a core controller, a programmable logic controller, a temperature filtering and conditioning circuit, a memory chip, and a machine tool for collecting data. A temperature sensor for temperature, wherein the output end of the temperature sensor is connected with a programmable logic controller through a temperature filtering and conditioning circuit, the programmable logic controller is connected with a memory chip, a PLC controller and a core controller, and the host computer and the core control connected to the device.

The programmable logic controller and the PLC controller are connected through the I/O port.

The core controller and the host computer are connected through the USB interface, the RS232 interface and the network port.

The temperature sensor is a PT100 platinum thermal resistance.

The embedded full life cycle machine tool thermal error compensation method of the present invention includes the following steps:

The user inputs the ideal size of the workpiece to the upper computer, and the upper computer builds a compensation model according to the ideal size of the workpiece, and stores the established compensation model in the memory chip;

The core controller generates a temperature collection instruction, and sends the temperature collection instruction to the programmable logic controller, and the programmable logic controller collects the temperature through a temperature sensor according to the temperature collection instruction, wherein the temperature sensor collects the temperature of the machine tool. Temperature information, the temperature information of the machine tool is filtered and conditioned by the temperature filtering and conditioning circuit and then input into the programmable logic controller, the PLC controller obtains the running state of the machine tool, and when the machine tool is running, the PLC controller specifies the I/O The port generates a high-level signal, and then the high-level signal is input into the programmable logic controller and read by the core controller. The core controller controls the programmable logic controller from the memory chip according to the high-level signal. The heating formula of the compensation model is extracted from the computer, and the temperature information of the machine tool is substituted into the heating formula of the compensation model to obtain the thermal error compensation value of the machine tool, and then the thermal error compensation value of the machine tool is sent to the upper computer and the PLC controller; when the machine tool is not running When the PLC controller designates the I/O port to generate a low-level signal, the low-level signal is input into the programmable logic controller and read by the core controller, and the core controller is based on the low-level signal. Control the programmable logic controller to extract the cooling formula of the compensation model from the memory chip, and substitute the temperature information of the machine tool into the cooling formula of the compensation model to obtain the thermal error compensation value of the machine tool, and then send the thermal error compensation value of the machine tool to the upper computer and PLC controller;

The core controller performs thermal error compensation of the machine tool according to the thermal error compensation value of the machine tool, and completes the thermal error compensation of the embedded full-life cycle machine tool.

The user inputs the size of the workpiece to the upper computer, and the upper computer constructs a compensation model according to the size of the workpiece, and stores the constructed compensation model in the memory chip. The specific operations are as follows:

1) The user inputs the ideal size of the workpiece into the upper computer, and the upper computer takes the ideal size of the workpiece as the error calculation benchmark, and sets the allowable tolerance zone;

2) When a workpiece is processed, the size of the workpiece is measured, and the measured size of the workpiece is input into the host computer;

3) The host computer calculates the compensation amount according to the measured size of the workpiece and the ideal size of the workpiece, and stores the temperature, size and compensation amount of the workpiece at the same time;

4) The host computer uses the multi-objective particle swarm intelligent algorithm to calculate the compensation model according to the temperature, size and compensation amount of the workpiece, and then stores the compensation model in the memory chip.

The present invention has the following beneficial effects:

In the specific operation of the embedded full life cycle machine tool thermal error compensation system and method of the present invention, a compensation model is constructed first, and then the compensation model is stored in the memory chip, and then the temperature information of the machine tool is used according to the operating state of the machine tool. The cooling formula of the compensation model and the heating formula of the compensation model are compensated in real time, and the compensation thermal error compensation value is obtained, and then the thermal error compensation value of the machine tool is sent to the upper computer and the PLC controller, and the size calculation compensation value is recorded while processing is realized. It is suitable for mass production conditions such as production lines, and at the same time realizes accurate compensation of thermal errors of machine tools.

Description of drawings

Fig. 1 is the structural representation of the present invention;

FIG. 2 is a schematic diagram of the present invention.

Among them, 1 is a PLC controller, 2 is a host computer, 3 is a programmable logic controller, 4 is a core controller, 5 is a temperature filter conditioning circuit, 6 is a memory chip, and 7 is a temperature sensor.

Detailed ways

Below in conjunction with accompanying drawing, the present invention is described in further detail:

Referring to FIG. 1, the embedded full life cycle machine tool thermal error compensation system according to the present invention includes a host computer 2, a PLC controller 1, a core controller 4, a programmable logic controller 3, a temperature filter conditioning circuit 5, and a memory chip 6 And a temperature sensor 7 for collecting the temperature of the machine tool, wherein the output end of the temperature sensor 7 is connected with the programmable logic controller 3 through the temperature filtering and conditioning circuit 5, and the programmable logic controller 3 is connected with the memory chip 6 and the PLC controller 1. It is connected with the core controller 4, and the upper computer 2 is connected with the core controller 4.

The programmable logic controller 3 and the PLC controller 1 are connected through the I/O port; the core controller 4 and the host computer 2 are connected through the USB interface, the RS232 interface and the network port; the temperature sensor 7 is a PT100 platinum thermal resistance.

The embedded full life cycle machine tool thermal error compensation method of the present invention includes the following steps:

The user inputs the ideal size of the workpiece into the upper computer 2, and the upper computer 2 builds a compensation model according to the ideal size of the workpiece, and stores the established compensation model in the memory chip 6;

The core controller 4 generates a temperature collection instruction, and sends the temperature collection instruction to the programmable logic controller 3, and the programmable logic controller 3 collects the temperature through the temperature sensor 7 according to the temperature collection instruction, wherein the temperature The sensor 7 collects the temperature information of the machine tool, and the temperature information of the machine tool is filtered and conditioned by the temperature filtering and conditioning circuit 5 and then input to the programmable logic controller 3, and the PLC controller 1 obtains the running state of the machine tool. , the PLC controller 1 specifies the I/O port to generate a high-level signal, and then the high-level signal is input into the programmable logic controller 3 and read by the core controller 4, and the core controller 4 according to the high-level signal The level signal controls the programmable logic controller 3 to extract the heating formula of the compensation model from the memory chip 6, and substitute the temperature information of the machine tool into the heating formula of the compensation model to obtain the thermal error compensation value of the machine tool, and then send the thermal error compensation value of the machine tool. To the host computer 2 and the PLC controller 1; when the machine tool is not running, the PLC controller 1 specifies the I/O port to generate a low-level signal, and inputs the low-level signal to the programmable logic controller 3 And read by the core controller 4, the core controller 4 controls the programmable logic controller 3 to extract the cooling formula of the compensation model from the memory chip 6 according to the low-level signal, and substitutes the temperature information of the machine tool into the cooling of the compensation model. Formula, get the thermal error compensation value of the machine tool, and then send the thermal error compensation value of the machine tool to the upper computer 2 and the PLC controller 1;

The core controller 4 performs thermal error compensation of the machine tool according to the thermal error compensation value of the machine tool, and completes the thermal error compensation of the embedded full life cycle machine tool.

The operation mode of transmitting instructions between the core processor and the programmable logic controller 3 is the same as the mode of accessing the memory chip 6, and the command format is as follows:

Operation type + (operation address) + operation content + (data)

The memory chip 6 stores the temperature information of the machine tool after compensation in partitions, and the starting address index of each partition data will be uniformly stored in the delimited position of the memory chip 6 to facilitate the acquisition of machine tool temperature data at a specified time. In actual operation, the lower computer first reads the storage address of the last data before storing the data, and searches for the unused empty storage area after the storage address of the last data, and then establishes the address of this data storage in the empty storage area. .

The I/O interface of the PLC controller 1 is isolated from the I/O interface of the lower computer through the optocoupler.

The system compensation workflow is as follows: when the host computer 2 stores the compensation model in the memory chip 6 through the core controller 4 and the programmable logic controller 3 through the USB interface or the RS232 serial port, the programmable logic controller 3 obtains the temperature each time. data, the core controller 4 will perform a temperature compensation on the temperature data through the compensation model, wherein the storage format of the compensation model in the NandFlash chip is as follows:

Axis number + compensation coefficient 1 + compensation coefficient 2 + ... compensation coefficient n + offset adjustment value

The formula for calculating the compensation value is as follows:

temperature1*compensation coefficient1+temperature2*compensation coefficient2...temperaturen*compensation coefficientn+offset adjustment value;

In addition, the host computer 2 proposes the temperature information of the machine tool in the storage chip 6, draws the temperature curve of the machine tool according to the temperature information of the machine tool, and at the same time plays back and checks the temperature information of the machine tool, and establishes the relationship between the temperature information of the machine tool and the workpiece error to establish a model.

The invention uses the multi-objective intelligent algorithm particle swarm algorithm to calculate the compensation model. Specifically, the objective function and constraint conditions are determined according to the structural characteristics of the machine tool, the thermal characteristics of the machine tool material and the working environment of the machine tool, and then combined with the particle swarm algorithm and the multi-objective regression analysis. The compensation model is obtained, wherein the calculation process of the objective function and the constraint conditions is:

The framework of the basic multi-objective intelligent algorithm particle swarm algorithm is:

x=[x ₁ ,x ₂ ,...,x _D ] ^T

minf(x)={f ₁ (x),f ₂ (x),...,f _m (x)}

st x∈S={xg _j (x)≤0,j=1,2,…,p}

Among them: compensation model temperature coefficient x=[x ₁ , x ₂ ,...,x _D ] ^T , D is determined by the number of selected thermal key points, and the number of thermal key points varies with the change of the bed structure;

f _k (x) is the kth objective function, that is, the criterion for search optimization;

g _j (x)≤0, g _j (x) is the jth inequality constraint, which can be omitted;

S is the feasible region of the decision variable.

Then the objective function and constraints in the present invention are:

为各温度理论计算系数，根据机床理想结构的膨胀系数计算得到；目标函数f₂(X)的意义是粒子群算法产生的系数与理论值有足够的接近度；约束条件g₁的意义是系数与理论膨胀系数之差的绝对值必须小于1。Among them: the meaning of objective function f ₁ (X) is that the compensation amount calculated by the product of temperature and coefficient is the closest to the measurement error curve;

The theoretical calculation coefficient for each temperature is calculated according to the expansion coefficient of the ideal structure of the machine tool; the meaning of the objective function f ₂ (X) is that the coefficient generated by the particle swarm algorithm is close enough to the theoretical value; the meaning of the constraint condition g ₁ is the coefficient The absolute value of the difference from the theoretical expansion coefficient must be less than 1.

The workpiece real-time modeling module of the software of the host computer 2 is obtained by the user by inputting the workpiece size in the host computer 2 to compensate the thermal error of the machine tool in real time. The specific modeling steps are as follows:

1) Before the machine tool starts processing, arrange the temperature sensor 7 to the temperature measuring point, and connect the core controller 4 to the upper computer 2;

2) The processor inputs the ideal size of the workpiece into the host computer 2 as the error calculation benchmark, and sets the allowable tolerance zone;

3) Each time a workpiece is processed, input the measured workpiece size into the host computer 2;

4) The host computer 2 inputs the compensation value according to the change of the workpiece size. Specifically, when the change of m consecutive workpieces exceeds the preset value, the host computer 2 calculates the compensation amount, and the compensation value is set to n dimensions exceeding the preset value. The mean value of the error of the set workpiece or the preset fixed value;

5) The host computer 2 records the temperature, size and compensation operation information, stores and generates files, and the file format is as follows:

Size + temperature + plus compensation error + uncompensated error + current compensation value + total compensation value

6) After the processing is completed, the host computer 2 uses the multi-objective particle swarm intelligence algorithm to calculate a new compensation model according to the saved file and the temperature data file, and stores the compensation model in the memory chip 6 .

The whole life cycle compensation module of the temperature compensation system is an extension function in addition to the above basic modeling, and the lower computer can record the whole life cycle operation status of the machine tool and the model change to the NandFlash memory chip 6 . If the user finds that the existing model deviates, he can run the real-time modeling of the workpiece or the offline modeling program to establish a new model to replace the original model according to the changes in the operating conditions of the machine tool. The model change record will be stored in the NandFlash memory chip 6 and used as a The learning samples of the full life cycle model will be established in the future. If the same type of machine tool has enough life cycle status and error and model correction change data, the data mining algorithm can be used to directly find out the law through the compiled software and automatically switch the model according to the machine tool running time. The full life cycle modeling method is as follows:

1) The user establishes the quantitative form of each feature of the machine tool, the features include bed type, working environment, working temperature, processing type and frequency of use; quantification refers to the numerical expression of the indicators described in text;

2) Cluster analysis of different machine tools according to quantitative indicators, and cluster machine tools with similar indicators into a group of samples;

3) Use data mining technology to classify the whole life cycle thermal error variation law of a group of samples and accumulate them as knowledge;

4) According to the given quantitative index of the machine tool to be subjected to thermal error compensation, the compensation formula of the learning sample machine tool closest to the working condition is imported into the memory chip 6 of the machine tool to be subjected to thermal error compensation, and the core processor calculation is changed according to the usage time. The compensation model used realizes the error compensation of the whole life cycle of the machine tool.

Claims (5)

1. The utility model provides an embedded full life cycle machine tool thermal error compensation method, characterized in that, based on embedded full life cycle machine tool thermal error compensation system, embedded full life cycle machine tool thermal error compensation system includes host computer (2), PLC controller (1), core controller (4), programmable logic controller (3), temperature filtering conditioning circuit (5), memory chip (6) and is used for gathering temperature sensor (7) of lathe temperature, wherein, the output of temperature sensor (7) is connected with programmable logic controller (3) through temperature filtering conditioning circuit (5), programmable logic controller (3) are connected with memory chip (6), PLC controller (1) and core controller (4), host computer (2) are connected with core controller (4), including the following step:

a user inputs the ideal size of the workpiece into the upper computer (2), the upper computer (2) constructs a compensation model according to the ideal size of the workpiece, and the constructed compensation model is stored into the storage chip (6);

the core controller (4) generates a temperature acquisition instruction and sends the temperature acquisition instruction to the programmable logic controller (3), the programmable logic controller (3) acquires the temperature through the temperature sensor (7) according to the temperature acquisition instruction, wherein the temperature sensor (7) acquires the temperature information of the machine tool, the temperature information of the machine tool is filtered and conditioned by the temperature filtering and conditioning circuit (5) and then is input into the programmable logic controller (3), the PLC controller (1) acquires the running state of the machine tool, when the machine tool is in machining operation, the PLC controller (1) designates an I/O port to generate a high level signal, then the high level signal is input into the programmable logic controller (3) and read by the core controller (4), the core controller (4) controls the programmable logic controller (3) to extract a temperature rise formula of a compensation model from the storage chip (6) according to the high level signal, substituting the temperature information of the machine tool into a temperature rising formula of the compensation model to obtain a machine tool thermal error compensation value, and then sending the machine tool thermal error compensation value to the upper computer (2) and the PLC (1); when the machine tool is not in machining operation, the PLC (1) designates an I/O port to generate a low level signal, the low level signal is input into the programmable logic controller (3) and read by the core controller (4), the core controller (4) controls the programmable logic controller (3) to extract a cooling formula of the compensation model from the memory chip (6) according to the low level signal, temperature information of the machine tool is substituted into the cooling formula of the compensation model to obtain a thermal error compensation value of the machine tool, and then the thermal error compensation value of the machine tool is sent to the upper computer (2) and the PLC (1);

the core controller (4) performs thermal error compensation on the machine tool according to the thermal error compensation value of the machine tool to complete embedded full-life-cycle machine tool thermal error compensation;

calculating a compensation model by using a multi-objective intelligent algorithm particle swarm algorithm, specifically, determining a target function and a constraint condition according to the structural characteristics of a machine tool, the thermal characteristics of a machine tool material and the working environment of the machine tool, and then obtaining the compensation model by combining the particle swarm algorithm and multi-objective regression analysis, wherein the calculation process of the target function and the constraint condition is as follows:

the basic multi-target intelligent algorithm particle swarm optimization framework is as follows:

x＝[x₁,x₂,…,x_D]^T

min f(x)＝{f₁(x),f₂(x),…,f_m(x)}

s.t. x∈S＝{x|g_j(x)≤0,j＝1,2,…,p}

wherein: temperature coefficient x ═ x for compensation model₁,x₂,…,x_D]^TD is determined by the number of the selected thermal key points, and the number of the thermal key points is different along with the change of the structure of the machine tool; f. of_k(x) Searching the optimal criterion for the kth objective function; g_j(x)≤0，g_j(x) Is the jth inequality constraint condition; s is a decision variable feasible region; the objective function and the constraint are:

wherein: objective function f₁The meaning of (X) is that the compensation quantity calculated by the product of the temperature and the coefficient is closest to the measurement error curve;

calculating coefficients for each temperature theory according to the expansion coefficient of the ideal structure of the machine tool; objective function f₂(X) has the meaning that the coefficients generated by the particle swarm algorithm are sufficiently close to theoretical values; constraint g₁The meaning of (1) is that the absolute value of the difference between the coefficient and the theoretical expansion coefficient must be less than 1.

2. The embedded full-life-cycle machine thermal error compensation method of claim 1, characterized in that the programmable logic controller (3) is connected with the PLC controller (1) through an I/O port.

3. The embedded full-life-cycle machine tool thermal error compensation method according to claim 1, wherein the core controller (4) is connected with the upper computer (2) through a USB interface, an RS232 interface and a network interface.

4. The embedded full-life cycle machine thermal error compensation method of claim 1, characterized in that the temperature sensor (7) is PT100 platinum thermistor.

5. The thermal error compensation method of the embedded full-life-cycle machine tool according to claim 1, characterized in that the user inputs the size of the workpiece into the upper computer (2), the upper computer (2) constructs the compensation model according to the size of the workpiece, and the specific operations of storing the constructed compensation model into the memory chip (6) are:

1) a user inputs the ideal size of the workpiece into the upper computer (2), the upper computer (2) takes the ideal size of the workpiece as an error calculation reference, and an allowable tolerance band is set;

2) when a workpiece is machined, the size of the workpiece is measured actually, and the measured size of the workpiece is input into an upper computer (2);

3) the upper computer (2) calculates compensation quantity according to the actual measurement size of the workpiece and the ideal size of the workpiece, and simultaneously stores the temperature, the size and the compensation quantity of the workpiece;

4) the upper computer (2) calculates a compensation model by using a multi-target particle swarm intelligent algorithm according to the temperature, the size and the compensation quantity of the workpiece, and then stores the compensation model into the storage chip (6).

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