CN112817274A - Machine tool acceleration and deceleration time optimization method and system based on load inertia - Google Patents

Abstract

The invention discloses a method and system for optimizing acceleration and deceleration time of a machine tool based on load inertia, belonging to the technical field of numerical control machining. Deceleration time parameter, process the first workpiece, and obtain state data during processing to identify the initial load inertia corresponding to each line of G code; based on the initial load inertia and machine tool motion control strategy, adjust each line of G code Corresponding acceleration and deceleration time parameters, obtain the acceleration and deceleration time parameter table after the first optimization; use the acceleration and deceleration time parameter table after the first optimization to process the next workpiece, and obtain the acceleration and deceleration time after the second optimization. Deceleration time parameter table; until the last workpiece is machined. In this way, the present invention can rapidly optimize the acceleration and deceleration time parameters of the numerical control system, thereby realizing the improvement of the processing quality and efficiency of the numerical control system to the greatest extent.

Description

A method and system for optimizing acceleration and deceleration time of machine tool based on load inertia

technical field

The invention belongs to the technical field of numerical control machining, and more particularly relates to a method and system for optimizing acceleration and deceleration time of a machine tool based on load inertia.

Background technique

The manufacturing industry is the foundation of the development of the national economy, and the development of CNC machine tools is the foundation of the development of the manufacturing industry. With the continuous improvement of the performance requirements of high-end CNC machine tools in the manufacturing industry, especially the requirements for machine tools to improve production efficiency and reduce production costs on the premise of ensuring the quality of parts processing, the machine tool feed system is developing in the direction of high speed and precision. The high-speed spindle must also cooperate with the high-speed feed system in order to give full play to the many advantages of high-speed cutting.

The acceleration/deceleration time parameter determines the acceleration (jerk) of the machine axis movement. The larger the acceleration/deceleration parameter, the smaller the acceleration (jerk), and the longer the time it takes for the machine axis to reach the specified speed. In order to achieve the requirements of high-speed and high-precision machining, it is necessary to reasonably set the acceleration and deceleration time constants under different machining feed states. Reasonable acceleration and deceleration time constants can prevent overshoot during high-speed rotation of the spindle and shorten the machining time during low-speed rotation. At the same time, the acceleration and deceleration time constants are also affected by the load inertia of the machine tool feed system. When the load inertia does not match the acceleration and deceleration time constants, the frequent acceleration and deceleration of the machine tool in the high speed and acceleration state will impact the machine tool, stimulate the vibration mode of the machine tool feed system, and affect the machining quality of the workpiece.

In order to improve production efficiency, shorten unnecessary processing time, and improve product quality, the optimization of machining process parameters has received extensive attention and research. Quantity, milling width and other process parameters. Acceleration and deceleration time constants are often out of consideration. At the same time, the inertia identification of the machine tool feed system, and the parameter self-tuning based on this, only focuses on the adjustment of the servo parameters, ignoring the optimization of the acceleration and deceleration time constants.

During machine tool processing, under the influence of factors such as different feed speeds, back-feeding amount, processing materials, etc., the load inertia of the feed system is different. Therefore, it is necessary to identify the inertia of the machine tool to identify the system under different conditions. Inertia, adjust the acceleration and deceleration time constant of the system according to the load inertia. At present, the research and achievements on optimizing the acceleration and deceleration time constants according to the load inertia are still very weak.

SUMMARY OF THE INVENTION

In view of the above defects or improvement needs of the prior art, the present invention provides a method and system for optimizing the acceleration and deceleration time of a machine tool based on the load inertia. Deceleration time parameters, realize the optimization of the acceleration and deceleration time parameters of the machine axis.

In order to achieve the above object, on the one hand, the present invention provides a method for optimizing the acceleration and deceleration time of a machine tool based on the load inertia, including the following steps:

S1. Identify the non-cutting interval and the cutting interval in the G code by analyzing the processed G code;

S2. Use the initial acceleration and deceleration time parameters to process the first workpiece, and obtain the status data during the processing to identify and obtain the initial load inertia corresponding to each line of G code;

S3. Based on the initial load inertia and the machine tool motion control strategy, adjust the acceleration and deceleration time parameters corresponding to each line of G code, and obtain the first optimized acceleration and deceleration time parameter table; wherein, the acceleration and deceleration corresponding to the non-cutting interval The time parameter is not adjusted;

S4. Use the first optimized acceleration and deceleration time parameter table to process the next workpiece, and repeat steps S2 and S3 to obtain the second optimized acceleration and deceleration time parameter table until the last workpiece is processed.

Further, identifying the load inertia specifically includes:

其中，

为k时刻的机床速度，

为k时刻的电磁转矩，T为转置符号，

为k-1时刻的负载惯量估计值；(1) Calculate the estimated output value at time k:

in,

is the machine tool speed at time k,

is the electromagnetic torque at time k, T is the transpose sign,

is the estimated value of the load inertia at time k-1;

其中，y(k)为系统实际输出；将所述误差e(k)反馈到辨识算法中，通过修正项对上一时刻的负载惯量估计值

进行修正，从而得到k时刻的负载惯量估计值

(2) Calculation error

Among them, y(k) is the actual output of the system; the error e(k) is fed back to the identification algorithm, and the estimated value of the load inertia at the previous moment is estimated by the correction term

Correction is made to obtain the estimated value of load inertia at time k

估算出k时刻的负载转矩T_L(k)，然后利用

T_L(k)、

估算k+1时刻的负载惯量估计值

(3) Use the estimated value of load inertia at time k

Estimate the load torque T _L (k) at time k, and then use

T _L (k),

Estimate the estimated value of the load inertia at time k+1

(4) Loop iteration until the corresponding criterion function takes the minimum value.

Further, the adjusted acceleration and deceleration time parameters are expressed as:

Among them, t is the initial acceleration and deceleration time parameter of the benchmark; J is the load inertia of the machine tool in the non-processing state; J ^' is the load inertia identified during the operation of the machine tool; m is the adjustment proportional coefficient, which is related to the machine tool motion control strategy and machining instructions.

Further, the state data during the processing includes the current and speed of the machine tool.

Further, a machine tool motion control strategy is selected according to processing requirements and processing conditions, and the machine tool motion control strategy includes linear acceleration and deceleration, exponential acceleration and deceleration, and S-curve acceleration and deceleration.

On the other hand, the present invention provides a system for optimizing the acceleration and deceleration time of a machine tool based on load inertia, including:

The analysis module is used to identify the non-cutting interval and the cutting interval in the G code by analyzing the processed G code;

The identification module is used to process the first workpiece by using the initial acceleration and deceleration time parameters, and obtain the status data during the processing, so as to identify the initial load inertia corresponding to each line of G code;

The optimization module is used to adjust the acceleration and deceleration time parameters corresponding to each line of G codes based on the initial load inertia and the machine tool motion control strategy, and obtain the acceleration and deceleration time parameter table after the first optimization; wherein, the non-cutting interval corresponds to The parameter of acceleration and deceleration time is not adjusted;

The iteration module is used to process the next workpiece by using the acceleration and deceleration time parameter table after the first optimization, and repeat the operations of the identification module and the optimization module to obtain the acceleration and deceleration time parameters after the second optimization. table; until the last workpiece is machined.

Further, the identification module is specifically used for,

其中，

为k时刻的机床速度，

为k时刻的电磁转矩，T为转置符号，

为k-1时刻的负载惯量估计值；(1) Calculate the estimated output value at time k:

in,

is the machine tool speed at time k,

is the electromagnetic torque at time k, T is the transpose sign,

is the estimated value of the load inertia at time k-1;

其中，y(k)为系统实际输出；将所述误差e(k)反馈到辨识算法中，通过修正项对上一时刻的负载惯量估计值

进行修正，从而得到k时刻的负载惯量估计值

(2) Calculation error

Among them, y(k) is the actual output of the system; the error e(k) is fed back to the identification algorithm, and the estimated value of the load inertia at the previous moment is estimated by the correction term

Correction is made to obtain the estimated value of load inertia at time k

估算出k时刻的负载转矩T_L(k)，然后利用

T_L(k)、

估算k+1时刻的负载惯量估计值

(3) Use the estimated value of load inertia at time k

Estimate the load torque T _L (k) at time k, and then use

T _L (k),

Estimate the estimated value of the load inertia at time k+1

(4) Loop iteration until the corresponding criterion function takes the minimum value.

Further, the adjusted acceleration and deceleration time parameters are expressed as:

Among them, t is the initial acceleration and deceleration time parameter of the benchmark; J is the load inertia of the machine tool in the non-processing state; J ^' is the load inertia identified during the operation of the machine tool; m is the adjustment proportional coefficient, which is related to the machine tool motion control strategy and machining instructions.

Further, the state data during the processing includes the current and speed of the machine tool.

Further, a machine tool motion control strategy is selected according to processing requirements and processing conditions, and the machine tool motion control strategy includes linear acceleration and deceleration, exponential acceleration and deceleration, and S-curve acceleration and deceleration.

In general, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

(1) The present invention is based on the command domain, realizes the optimization of the acceleration and deceleration time parameters of the current G code line of the machine tool by identifying the system load inertia in real time under each processing state, and matching the appropriate acceleration and deceleration time parameters according to the load inertia; In the next round of processing, when the G code runs to this line, the optimized parameter values are automatically retrieved. In this way, the present invention can rapidly optimize the acceleration and deceleration time parameters of the numerical control system, thereby realizing the improvement of the processing quality and efficiency of the numerical control system to the greatest extent.

(2) The present invention provides an operating man-machine interaction interface integrated in the numerical control system, which provides a processing state information graph based on an instruction sequence, collects the current state data in real time during the processing, and identifies the load inertia of the machine tool online according to the processing data. , and draws the instruction sequence curve graph at the same time, including two forms of wave and column. The waveform diagram is the identification result of the load inertia, and the identification result of the load inertia tends to be stable with the increase of the identification period. The waveform diagram is convenient to observe the result of the identification of the load inertia. Below the waveform graph, the bar graph observes the axis with the behavior of processing the G code program, optimizes the acceleration and deceleration time parameters of each line, and displays the optimized result from time to time. The bar graph of the machine axis motion G code line and other G code lines To distinguish, the acceleration and deceleration time of the axis motion line only needs to be optimized and adjusted. In this way, the present invention is highly seamlessly integrated with the numerical control system, all data interactions are carried out in the internal data of the data system, and the parameter optimization is synchronized with the numerical control system cycle, which avoids tedious and constant manual adjustment, thereby greatly shortening the acceleration and deceleration time. The parameter optimization cycle ensures the timeliness and effectiveness of parameter optimization.

Description of drawings

1 is a flowchart of a method for optimizing acceleration and deceleration time of a machine tool based on load inertia provided by the present invention;

Figure 2 shows the speed change curves of three acceleration and deceleration control strategies; among them, (a), (b), (c) are linear acceleration and deceleration, exponential acceleration and deceleration, and S-shaped (bell-shaped) acceleration and deceleration; T is Time to accelerate from 0 to a specified speed or decelerate from a specified speed to 0; in S-type acceleration and deceleration, the acceleration process first changes to acceleration, the acceleration starts to increase from 0, increases to a stable value, starts to accelerate at a constant speed, and then changes to deceleration , T2 is the acceleration change (increase or decrease) time, T1 is the time from the start of acceleration to the end of the uniform acceleration stage, calculated from the set speed and T1;

Fig. 3 is the curve waveform display diagram of the load inertia identification result of the present invention; wherein, N1, N2, N3... Inertia identification is carried out on the line, and with the collected data, the inertia identification results gradually converge, and the identification results are stable; in non-axis movement, inertia identification is not performed on the machine tool feed system, and the identification result curve is a horizontal line;

Fig. 4 is a columnar display diagram of the optimization curve of acceleration and deceleration time parameters based on the load inertia of the present invention; wherein, N1, N2, N3... The deceleration time parameter, the light bar chart indicates that the line program is an axis movement program and needs to modify the acceleration and deceleration time parameters, and the dark bar chart indicates that it is a non-axis movement line program, and the acceleration and deceleration time parameters do not need to be modified; the ordinate Y axis Represents the current acceleration/deceleration time parameter value, and the height of each histogram is determined by the load inertia identified by the G code line and the selected acceleration/deceleration control strategy;

FIG. 5 is a schematic diagram of a process of online modification of acceleration and deceleration time parameters provided by the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

Referring to FIG. 1, the present invention provides a method for optimizing the acceleration and deceleration time of a machine tool based on the load inertia, including the following steps:

Step 1: First, identify the non-cutting interval and cutting interval in the G code by analyzing the processed G code. For the non-cutting process such as G00, each motion axis mainly completes the task of rapid traverse positioning. In this case, the static load inertia will not change; for the cutting process, due to the cutting force of the tool, the dynamic load inertia of the machine tool axis will change; therefore, the load inertia needs to be identified separately in these two cases, according to different load inertia, Optimize the acceleration and deceleration time constants of different axes, such as fanuc system 1620/1621 parameters.

Step 2: The machine tool motion control strategy is the acceleration and deceleration control strategy (such as linear acceleration and deceleration (continuous speed), exponential acceleration and deceleration, S-curve acceleration and deceleration (continuous acceleration), etc.), usually the CNC system will manually adjust the acceleration and deceleration according to different processing needs. Strategies such as linear/bell acceleration and deceleration for fanuc systems. Different acceleration and deceleration control strategies will cause different shocks and vibrations to the machine tool during the machining process, which will affect the machining quality of the workpiece. For occasions with low requirements on machining accuracy, such as rough machining, or for auxiliary motions such as start-stop, advance and retreat, etc., linear acceleration and deceleration control is adopted, which mainly ensures the continuity of speed. In addition, the transition of speed is not smooth enough, and the motion accuracy is low. Compared with linear acceleration and deceleration, exponential acceleration and deceleration have better smoothness and high movement progress, and there is still a sudden acceleration of acceleration at the start and end points of acceleration and deceleration, which has a certain flexible impact. During manual feed movement. The acceleration of S-shaped acceleration and deceleration is continuously changed at any point, thus avoiding the flexible impact, the smoothness of the speed is very good, the motion precision is high, the requirements for the machine tool and the system are relatively high, and it is suitable for high-speed and high-precision machining occasions. The choice of the specific acceleration and deceleration strategy needs to be selected according to the experience of the processing personnel and the actual processing requirements and processing conditions. Different acceleration and deceleration strategies adjust the acceleration and deceleration time differently. As shown in Figure 2, according to the acceleration and deceleration control strategy set by the system, the acceleration and deceleration time parameters are optimized according to the inertia change.

Step 3: Obtain the data in the processing process through the processing of the first workpiece. This step does not modify the acceleration and deceleration time parameters of the system. The present invention needs to identify the inertia first, and optimize the acceleration and deceleration time parameters according to the inertia. The first choice of inertia identification needs to obtain the state data of the machine tool during cutting, so it is necessary to test a workpiece, and obtain the initial inertia and the optimized acceleration and deceleration time parameters through this workpiece. Parts machined after this part can be iteratively identified and optimized. The result of inertia identification is shown in Figure 3, which is displayed in real time on the man-machine interface. Through the acquired current data during the machining process, according to the torque constant (if the motor does not provide the torque constant, it can also be calculated based on the maximum current, maximum torque or stall current and stall torque) to calculate the electromagnetic rotation during the acceleration of the shaft motion. moment.

The dynamic model of the mechanical part of the servo system is described by differential equations as follows:

Among them: T _e - the electromagnetic torque of the motor; ω _r - the motor speed (rad/s); J _m - the moment of inertia of the servo motor; J _L - the equivalent moment of inertia of the motor rotor; T _L - the load torque of the servo motor .

The main process of inertia identification is to use the measurable input and output data of the system. From the above formula, it can be seen that the measurable data involved in inertia identification are current, speed and other data. According to a certain criterion, the load inertia is estimated.

In offline identification, _TL in the differential equation can be eliminated by designing periodic excitation signals, but in online identification during machining, the machine tool is running according to the actual machining program, and the _TL term cannot be eliminated, only by performing obtained by an iterative method. First, the load inertia and load torque are initialized, and the precise value is gradually approached by an iterative method.

采用逐渐逼近的方法，在k时刻，根据k-1时刻对象参数估计值

转矩估计值T_L(k-1)以及输入的数据

(根据电流计算的电磁转矩)，来计算出当前时刻的输出估计值(机床速度)：

To obtain an estimate of the moment of inertia

Using the method of gradual approximation, at time k, according to the estimated value of the object parameters at time k-1

Torque estimate _TL (k-1) and input data

(Electromagnetic torque calculated according to the current), to calculate the estimated output value (machine tool speed) at the current moment:

y(k)为系统实际输出。然后将输出估计误差反馈到辨识算法中去，通过修正项对上一时刻的估计值

进行修正，计算出k时刻的估计值。利用k时刻负载惯量的估计值

估算出k时刻的负载转矩T_L(k)，然后利用

T_L(k)、

去估算k+1时刻的值。Calculate the estimation error

y(k) is the actual output of the system. Then the output estimation error is fed back to the identification algorithm, and the estimated value at the previous moment is estimated by the correction term.

Correction is made to calculate the estimated value at time k. Using the estimated value of the load inertia at time k

Estimate the load torque T _L (k) at time k, and then use

T _L (k),

to estimate the value at time k+1.

也已经逼近系统的实际输出值y(k)，转动惯量的估计值

也基本接近实际的参数值。This loop iterates until the corresponding criterion function takes the minimum value, then the estimated output value

The actual output value y(k) of the system has also been approximated, the estimated value of the moment of inertia

It is also basically close to the actual parameter value.

Regarding the initial values of load inertia and load torque, a range can be estimated based on experience. Generally, the minimum equivalent moment of inertia of the system is the factory value of rotor inertia in the motor parameter manual, and the equivalent value of load inertia does not exceed 10 times of rotor inertia. ; The equivalent torque of the motor load is 0 at no-load (non-cutting stage), and the maximum does not exceed 3 times the rated torque of the motor, so an empirical range of load inertia and load torque can be obtained [J _min , J _max ] and [T _Lmin ,T _Lmax ], the initial value can be determined within this range.

Step 4: Match the appropriate acceleration/deceleration time constant according to the identified inertia result and the selected acceleration/deceleration control strategy. The initial acceleration and deceleration time parameters set according to the servo parameters of the machine tool are t, and the acceleration and deceleration time parameters adjusted according to the identified inertia are as follows:

Among them, t is the initial acceleration and deceleration time parameter as the reference; J is the inertia of the machine tool in the non-processing state; J ^′ is the load inertia identified during the operation of the machine tool; m is the adjustment ratio related to the acceleration and deceleration control strategy, processing command speed, etc. The coefficient is obtained according to the processing experience.

Generate the optimized acceleration/deceleration time parameters and machine axis information corresponding to each line of G code. The generation sequence of the optimization result of the acceleration and deceleration time constant lags behind the inertia identification result by one line of G code. Because the load inertia identification result of this row needs to be obtained first, the acceleration and deceleration time constants can be further matched and optimized. The optimization results are shown in Figure 4. The display of the optimization results is one G code line behind the identification results in timing.

Step 5: Modify the acceleration and deceleration time parameters online. The optimization results generated during the complete machining process of the previous workpiece will be saved in a parameter table. When the next workpiece is machined, the acceleration and deceleration time parameters will be modified according to the machining process, as shown in Figure 5.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (10)

1. A machine tool acceleration and deceleration time optimization method based on load inertia is characterized by comprising the following steps:

s1, analyzing the processed G code to identify a non-cutting section and a cutting section in the G code;

s2, processing the first workpiece by using the initial acceleration and deceleration time parameter, and acquiring state data in the processing process to identify and obtain the initial load inertia corresponding to each row of G codes;

s3, adjusting acceleration and deceleration time parameters corresponding to each row of G codes based on the initial load inertia and a machine tool motion control strategy to obtain an acceleration and deceleration time parameter table after first optimization; wherein, the acceleration and deceleration time parameter corresponding to the non-cutting interval is not adjusted;

s4, processing the next workpiece by utilizing the first optimized acceleration and deceleration time parameter table, and repeating the steps S2 and S3 to obtain a second optimized acceleration and deceleration time parameter table; until the last workpiece is machined.

2. The method for optimizing acceleration/deceleration time of a machine tool based on load inertia according to claim 1, wherein the step of identifying the load inertia specifically comprises:

(1) calculating an output estimation value at the k moment:

wherein,

is the machine speed at the moment k,

is the electromagnetic torque at time k, T is the transposed symbol,

the estimated value of the load inertia at the moment k-1 is obtained;

(2) calculating error

Wherein y (k) is the actual output of the system; feeding the error e (k) back to an identification algorithm, and estimating the load inertia value of the last moment by a correction term

Correcting to obtain estimated value of load inertia at time k

(3) Using estimated value of load inertia at time k

Estimating the load torque T at time k_L(k) Then use

T_L(k)、

Estimating load inertia estimated value at k +1 moment

(4) And circularly iterating until the corresponding criterion function takes the minimum value.

3. The method for optimizing acceleration/deceleration time of a machine tool based on load inertia according to claim 1 or 2, wherein the adjusted acceleration/deceleration time parameter is expressed as:

wherein t is a reference initial acceleration and deceleration time parameter; j is the load inertia of the machine tool in a non-processing state; j' is the load inertia identified during the operation of the machine tool; and m is an adjusting proportionality coefficient and is related to a machine tool motion control strategy and a machining instruction.

4. The method of claim 1, wherein the in-process state data includes current and speed of the machine tool.

5. The method for optimizing acceleration/deceleration time of a machine tool based on load inertia according to claim 1, wherein a machine tool motion control strategy is selected according to the processing requirement and the processing condition, and the machine tool motion control strategy comprises linear acceleration/deceleration, exponential acceleration/deceleration and S-shaped curve acceleration/deceleration.

6. A machine tool acceleration and deceleration time optimization system based on load inertia is characterized by comprising:

the analysis module is used for identifying a non-cutting interval and a cutting interval in the G code by analyzing the processed G code;

the identification module is used for processing the first workpiece by utilizing the initial acceleration and deceleration time parameter and acquiring state data in the processing process so as to identify and obtain the initial load inertia corresponding to each row of G codes;

the optimization module is used for adjusting acceleration and deceleration time parameters corresponding to each row of G codes based on the initial load inertia and a machine tool motion control strategy to obtain an acceleration and deceleration time parameter table after first optimization; wherein, the acceleration and deceleration time parameter corresponding to the non-cutting interval is not adjusted;

the iteration module is used for processing the next workpiece by utilizing the first optimized acceleration and deceleration time parameter table, and repeatedly executing the operation of the identification module and the optimization module to obtain a second optimized acceleration and deceleration time parameter table; until the last workpiece is machined.

7. The system of claim 6, wherein the identification module is configured to identify the machine tool acceleration and deceleration time based on the load inertia,

(1) calculating an output estimation value at the k moment:

wherein,

is the machine speed at the moment k,

is the electromagnetic torque at time k, T is the transposed symbol,

the estimated value of the load inertia at the moment k-1 is obtained;

(2) calculating error

Wherein y (k) is the actual output of the system; feeding the error e (k) back to an identification algorithm, and estimating the load inertia value of the last moment by a correction term

Correcting to obtain estimated value of load inertia at time k

(3) Using estimated value of load inertia at time k

Estimating the load torque T at time k_L(k) Then use

T_L(k)、

Estimating load inertia estimated value at k +1 moment

(4) And circularly iterating until the corresponding criterion function takes the minimum value.

8. The load inertia-based acceleration/deceleration time optimization system of claim 6 or 7, wherein the adjusted acceleration/deceleration time parameter is expressed as:

wherein t is a reference initial acceleration and deceleration time parameter; j is the load inertia of the machine tool in a non-processing state; j' is the load inertia identified during the operation of the machine tool; and m is an adjusting proportionality coefficient and is related to a machine tool motion control strategy and a machining instruction.

9. The system of claim 6, wherein the in-process state data comprises machine current, speed.

10. The system for optimizing acceleration/deceleration time of a machine tool based on load inertia according to claim 6, wherein the motion control strategy of the machine tool is selected according to the processing requirement and the processing condition, and comprises linear acceleration/deceleration, exponential acceleration/deceleration and S-shaped curve acceleration/deceleration.

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