JP4090666B2 - Numerical control system and position command value correction device used therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a numerical control system such as a so-called NC machining system, NC robot system, NC transport system, and position command value correction device used therefor, and in particular, a simple setting of lost motion that occurs when a control object is driven in reverse. It is related with the improvement for correct | amending with high precision.
[0002]
[Prior art]
FIG. 12 is a block diagram showing the configuration of a conventional numerical control system. In the figure, 1 is a table to which a workpiece (workpiece) or a tool is fixed, 2 is a ball screw nut fixed to the lower surface of the table 1, 3 is a ball screw fitted to the ball screw nut 2, and 4 is this A servo motor 5 that rotationally drives the ball screw 3 is an encoder that detects the amount of rotation of the servo motor 4.
[0003]
6 is a position command value output means for outputting a position command value, 7 is a reversal detection means for detecting a reversal of the control direction of the table 1 based on the position command value and outputs a reversal detection signal, and 23 is a position when the reversal is detected. Lost motion correction gain calculating means 10 for outputting a correction signal and 10 are position addition means for adding the position correction signal to the position command value. Further, 11 is a position control means for outputting a speed command value corresponding to the distance between the target position indicated by the output of the position addition means 10 and the current position indicated by the detected rotation amount of the encoder 5, and 12 is according to the speed command value. A speed control means for outputting a current command value; 24, a friction correction gain calculating means for outputting a current command correction value having a constant magnitude when an inversion detection signal is input; and 14, a current command value for correcting the current command value. Reference numeral 15 denotes current adding means for adding values, and 15 is current control means for supplying the servo motor 4 with a current having a current value corresponding to the output of the current adding means 14.
[0004]
Next, the operation will be described.
When the position command value is output from the position command value output means 6, the reverse detection means 7 detects the reverse of the control direction of the table 1 based on this position command value. In the case of inversion, an inversion detection signal having a positive or negative magnitude 1 is output according to the control direction after inversion. On the contrary, when not inverted, an inversion detection signal having the same sign size 1 as before is output. A position correction signal is output from the lost motion correction gain calculation means 23 based on the inversion detection signal, a current command value obtained by adding the position correction signal is input to the position control means 11, and a speed command value is output from the position control means 11. The current command value is output from the speed control means 12. Similarly, a current correction value is output from the friction correction gain calculation unit 24 based on the inversion detection signal, and a current command value obtained by adding the current correction value is input to the current control unit 15, and the servo motor 4 is based on the current command value. Drives the ball screw 3 and the table 1 moves by an amount corresponding to the amount of rotation.
[0005]
With such a configuration, the table 1 is not only moved accurately in one direction by the servo motor 4, but also has a rattling between the ball screw 3 and the ball screw nut 2. Even if the direction is switched, it can be compensated by correcting it with the position command correction value or the like, and for example, machining accuracy such as perfect circle machining can be improved.
[0006]
However, in such a conventional numerical control system, the lost motion correction gain is a constant value, and the sign of the calculated lost motion correction amount changes, but its absolute value is constant. Therefore, in an actual product, there is a problem that the amount of lost motion that changes depending on the position, speed, and lubrication state of the linear motion guide mechanism cannot be corrected appropriately.
[0007]
FIG. 13 is a diagram for explaining the relationship between the position and the amount of lost motion. In FIG. 2A, reference numeral 25 denotes a linear motion guide, and 26 denotes a bearing fixed to the linear motion guide 25 and supporting the ball screw 3. FIG. 5B is a characteristic diagram showing a typical relationship between the table position and the friction amount in the case of the configuration. In the case of such a bearing structure, the ball screw 3 is pivotally supported by a pair of bearings 26 installed at both ends thereof. At this time, the distance from the table 1 to the ball screw 3 at the position of the ball screw nut 2, the bearing In some cases, the distance from the table 1 to the ball screw 3 at the position 26 is slightly different. In such a case, the closer the ball screw nut 2 is to the bearing 26, the more friction is generated, and the rotational load of the ball screw 3 increases. Will end up. As a result, the amount of friction changes so that the ball screw nut 2 is minimized at the position farthest from the bearings 26 at both ends, and increases as it approaches the both ends.
[0008]
When the linear guide 25 is a sliding guide, the guide surface of the linear guide 25 and the table 1 are in contact with each other when the speed is low, and the table 1 rises from the guide surface as the speed increases. It is known that friction is reduced. This phenomenon greatly depends on the state of the lubricating oil supplied to the sliding guide. Especially when the temperature changes, the viscosity coefficient of the lubricating oil changes and the friction changes.
[0009]
Japanese Patent Laid-Open No. 4-362603 proposes a conventional numerical control system that varies the lost motion correction gain. FIG. 14 is a block diagram showing the configuration of the conventional numerical control system. In the figure, reference numeral 27 includes a main control unit 27a, a control program storage unit 27b, a lost motion correction amount calculation unit 27c, a multilayer neural network type estimation unit 27d, an output unit 27e, an input unit 27f, and a coupling weight coefficient calculation unit 27g. An axis control unit that outputs a control signal based on the control program stored in the control program storage unit 27b and the rotation detection amount, 28 is an amplifier that amplifies the control signal and supplies it to the servo motor 4, and 29 is an axis control unit 27. It is a function generation part which outputs a function when training.
[0010]
Next, the operation will be described.
When the shaft control unit 27 outputs a control signal based on the control program and the rotation detection amount in the state where the training of the axis control unit 27 is completed based on the output of the function generation unit 29, the control signal is output from the amplifier 28. Based on the amplified control signal, the servo motor 4 rotates, and the table 1 performs linear motion according to the rotation. Then, the amount of rotation of the servo motor 4 is detected by the encoder 5, the new position of the table 1 is grasped by the axis control unit 27 based on the amount of rotation detected by the encoder 5, and the next control signal is output.
[0011]
With such a configuration, the amount of lost motion correction can be changed according to the position and speed at that time using a multilayer neural network, so a fixed lost motion correction amount is simply added to the position command. Compared to the above, the lost motion can be corrected with high accuracy regardless of the position, speed, lubrication state of the guide and the like.
[0012]
[Problems to be solved by the invention]
Since the conventional numerical control system and the position command value correction device used therefor are configured as described above, in order to perform optimal lost motion correction according to the position, speed, lubrication state of the guide, etc., the position, Assuming the expected usage environment of the speed and the lubrication state of the guide, it is necessary to reproduce each combination of the usage environment over the whole and let the multilayer neural network learn, in particular, multiple factors It is necessary to reproduce and learn a large number of operating environments as the amount of lost motion correction that can be corrected with high accuracy is considered. There are problems such as becoming complicated.
[0013]
Further, in a slide guide or the like that is suitably used as a member that regulates the moving direction of the table 1 to be controlled in such a conventional numerical control system, the lubrication state varies depending on the season or date, and the temperature change or slip Although it also fluctuates due to aging of the guide surface, the lost motion due to such fluctuation cannot be corrected.
[0014]
And it is not realistic to do such work for each product with different ways of occurrence of deviation due to assembly error, so the data to be learned by this multilayer neural network is common to many products As a result, it is realistic to achieve a certain level of accuracy by using average data for multiple products with different ways of generating deviations. There are also issues such as being unable to do so.
[0015]
The present invention has been made to solve the above-described problems, and the lost motion correction amount that can be corrected with high accuracy can be set with a small amount of measurement. It is an object of the present invention to obtain a numerical control system capable of setting a lost motion correction amount with high accuracy regardless of position, speed, guide lubrication state, etc. while measuring the amount of motion, and a position command value correction device used therefor. .
[0016]
[Means for Solving the Problems]
The position command value correction apparatus according to the present invention is a position command value correction apparatus that corrects a position command value used for numerical control of a controlled object. The position command value correction apparatus receives the position command value and performs control based on increase or decrease of the position command value. A reversal detecting means for detecting reversal of the direction and outputting reversal detection information; and a storage means for storing a friction amount for each position of the controlled object measured in advance, and the friction at the position based on the current position of the controlled object. The friction amount output means for selecting and outputting the amount, and the inversion detection signal as well as the friction amount output from the friction amount storage means are input, and a position command correction value that varies depending on the friction amount is generated. Position command correction value output means for outputting and calculation means for performing correction calculation of the position command value using the position command correction value.
[0017]
The position command correction device according to the present invention is a position command value correction device that corrects a position command value used for numerical control of an object to be controlled. The position command value is input, and a control direction is determined based on increase or decrease of the position command value. Inversion detection means for detecting inversion and outputting inversion detection information, and storage means for storing the friction amount for each position of the controlled object measured in advance, and the friction amount at the position based on the current position of the controlled object A friction amount output means for selecting and outputting, and a storage means for storing a spring coefficient for each position of the controlled object measured in advance, and selecting and outputting the spring coefficient at the position based on the current position of the controlled object The friction coefficient output from the friction amount storage means and the inversion detection signal are input together with the spring coefficient output means to perform, the spring coefficient output from the spring coefficient storage means, and the spring coefficient and the friction A position command correction value output means for generating and outputting a position command correction value that varies depending on the position, and a calculation means for performing a correction calculation of the position command value using the position command correction value. .
[0018]
In the position command value correction apparatus according to the present invention, the friction amount output means operates the control object based on a predetermined schedule, and the position information of the control object at that time and the command value to the drive means for driving the control object, Friction amount calculating means for calculating the friction amount at each position based on the above, and the storage means stores the friction amount for each position of the control target calculated by the friction amount calculating means.
[0019]
In the position command value correcting apparatus according to the present invention, the friction amount calculation means calculates the friction amount when the controlled object is operated based on a certain position command value.
[0020]
The position command value correction apparatus according to the present invention is a position command value correction apparatus that corrects a position command value used for numerical control of a controlled object. The position command value correction apparatus receives the position command value and performs control based on increase or decrease of the position command value. The command value for the inversion detection means for detecting the inversion of the direction and outputting the inversion detection information and the drive means for driving the controlled object are inputted, and the position command correction value is generated using the arithmetic expression based on the modeling of the controlled object. Output position command correction value output means, and calculation means for performing a correction calculation of the position command value using the position command correction value.
[0021]
In the position command value correction apparatus according to the present invention, the position command correction value output means is different depending on the speed of the control target using the arithmetic expression based on the modeling of the control target when the information on the current speed of the control target is input. A position command correction value to be a value is generated and output.
[0022]
The numerical control system according to the present invention includes a position command value output means for outputting a position command value used for numerical control of a controlled object, and the position command value is input, and the position based on the inversion detection signal of the controlled object. The position command value correcting device for correcting the command value, current command value generating means for generating a current command value based on the corrected position command value output from the position command value correcting device, and the current command value A current command value correction device that corrects the current command value using a predetermined friction correction gain based on the inversion detection signal of the control target, and a correction that is output from the current command value correction device Current Drive means for driving the controlled object based on the command value.
[0023]
In the numerical control system according to the present invention, the current command value correction device calculates a friction correction gain based on the position command correction value generated by the position command value correction device, and the current command value is calculated using the friction correction gain. Is to correct.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below.
Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration for one axis of an NC machining system according to Embodiment 1 of the present invention. In the figure, 1 is a table (control target) to which a workpiece (workpiece) or a tool is fixed, 2 is a ball screw nut (driving means) fixed to the lower surface of the table 1, and 3 is fitted with the ball screw nut 2. The combined ball screw (driving means) 4 is a servo motor (driving means) for rotationally driving the ball screw 3, and 5 is an encoder for detecting the amount of rotation of the servo motor 4. The ball screw 3 and the ball screw nut 2 convert the rotational motion of the servo motor 4 into a linear motion, and the table 1 includes a drive transmission member such as the ball screw 3 and the ball screw nut 2 and a linear motion guide mechanism (guide rail) (not shown). According to the above, setting control is performed at a predetermined position, or the moving operation is performed in a target trajectory.
[0025]
6 is a position command value output means for outputting a position command value for numerically controlling the position in the predetermined one axis direction of the table 1 based on a machining program or the like, and 7 is a position command value input. Based on the increase / decrease of the value, it is determined whether or not the control direction of the relevant axis direction of the table 1 is reversed, and when reversed, the positive or negative magnitude 1 corresponding to the increase / decrease direction of the position command value after the reversal is determined. A reversal detecting means for outputting a step-shaped reversal detection signal and outputting a step-shaped reversal detection signal having the same sign size 1 as the previous determination result when not reversing, and 8 represents a friction amount for each position of the table. Friction amount storage means (friction amount output means) 9 for inputting the detected rotation amount of the encoder 5 and outputting the friction amount at the position of the table 1 estimated based on the detected rotation amount. A reversal detection signal is input together with the amount of friction, and the reversal detection signal is corrected to a magnitude corresponding to the friction amount with a friction correction gain corresponding to the dynamic friction of the servo motor 4, the ball screw 3 and the table 1. Lost motion correction gain calculation means (position command correction value output means) 10 for outputting as a position correction signal is a position addition means (calculation means) for adding the position correction signal to the position command value.
[0026]
In the lost motion correction gain calculation means 9, the current position determined based on the detected rotation amount of the encoder 5 is p, and the friction amount function stored in the friction amount storage means 8 as the friction amount of the current position. Is f (p) and the position command correction value (lost motion correction amount) is LM, the position command correction value is generated based on the calculation shown in the following equation 1. However, K is a constant representing the relationship between the friction amount and the position command correction value, and corresponds to a spring coefficient (a constant value in this embodiment).
LM = f (p) / K Equation 1
[0027]
The spring coefficient K is set according to the following procedure. First, in a state where the table 1 is moved at a constant position and a constant speed, the amount of lost motion of the table 1 is measured using a position measuring means such as a contact displacement meter, and the final motion to the servo motor 4 is measured. Record the supply current value. Next, the spring coefficient K is obtained by substituting these data into the following equation 2. However, Kt is a torque constant of the servomotor 4 and is generally known as the specification of the servomotor 4, i (p1) is a current value supplied to the servomotor 4 at the table position p1, and LM (p1 ) Is the amount of lost motion of the table 1 at the table position p1.
K = Kt × i (p1) / LM (p1) Equation 2
[0028]
11 is inputted with the output of the position adding means 10 and the detected rotation amount of the encoder 5, and the speed according to the distance between the target position shown in the output of the position adding means 10 and the current position shown in the detected rotation amount of the encoder 5. Position control means (current command value generation means) for outputting a command value, 12 is speed control means (current command value generation means) for outputting a current command value to the servo motor 4 according to the speed command value, and 13 is inverted. Friction correction gain calculation means (current command value) that outputs a current command correction value that is a correction torque amount that cancels the friction that acts on the servo motor 4 by correcting the detection signal with a friction correction gain of a constant magnitude. Correction device ), 14 is a current adding means (current command value) for adding the current command correction value to the current command value. Correction device , 15 is a current control means (drive means) that receives the output of the current addition means 14 and supplies a current having a current value corresponding to the output to the servo motor 4.
[0029]
Incidentally, the friction amount storage means 8 measures a current command value in a reference operation in advance, and stores a friction amount depending on a position estimated from the current command value. For example, each drive shaft is caused to perform a constant-velocity linear motion at a sufficiently low speed at which the influence of speed and acceleration does not appear greatly in the current value of the servomotor 4, and the position of the table 1 at that time is measured using the encoder 5, The final supply current value to the servo motor 4 is measured, the amount of friction at each position is calculated using the following equation 3, and stored. However, Kt is a torque constant of the servo motor 4 and is generally known as a specification of the servo motor 4, and i (p) is a current value supplied to the servo motor 4 at the position p.
f (p) = Kt × i (p) Equation 3
[0030]
In order to obtain the relationship of the above formula 2, it is necessary to measure the position of the table such as a contact-type displacement meter at any one point p1 at least once before product shipment. The lost motion LM is a difference between the position of the motor measured by the encoder 5 and the position of the table measured by a contact displacement meter or the like, and accuracy of micron or less is required. On the other hand, at the stage of the above formula 3, the position accuracy may be on the order of about 1 mm, for example, and the motor position detection using the encoder 5 is sufficient. Since the spring coefficient K is a fixed value, it is not necessary to measure thereafter, and no means for measuring the position of the table is necessary. Although the detection of the motor position by the encoder 5 is easy, the detection of the table position is complicated because an extra instrument is required.
[0031]
FIG. 2 is an explanatory diagram showing an example of the relationship between the position of the table 1 stored in the friction amount storage means and the friction amount according to Embodiment 1 of the present invention. FIG. 4A shows a friction amount distribution graph in which the horizontal axis indicates the position and the vertical axis indicates the friction amount, and FIG. 4B shows the measurement data on which the graph is based. In the figure, the amount of friction gradually increases as the position of the table 1 moves from the central part of the shaft to both ends.
[0032]
Next, the operation will be described.
When a position command value is output from the position command value output means 6 based on a machining program or the like, the inversion detection means 7 reverses the control direction in the relevant axial direction of the table 1 based on the increase / decrease in the value of the position command value. Determine whether or not. Then, when not inverted, a step-like inversion detection signal having the same sign as the previous determination result is output, and when inverted, a stepwise inversion detection signal having a positive or negative magnitude 1 corresponding to the control direction of the axis after inversion is output. On the other hand, the friction amount at the current position of the table 1 estimated based on the detected rotation amount is output from the friction amount storage means 8, and the lost motion correction gain calculation means 9 is inverted so as to have a magnitude corresponding to this friction amount. The magnitude of the detection signal is corrected, and the position addition means 10 adds the position correction signal and the position command value. The position control means 11 outputs a speed command value corresponding to the distance between the target position indicated by the added value and the current position indicated by the detected rotation amount of the encoder 5. Further, while the current command value corresponding to the speed command value is output from the speed control means 12, the friction correction gain calculation means 13 corrects the magnitude of the inversion detection signal and outputs a current command correction value. These are added in the current adding means 14, and this added current command value is input to the current control means 15, the output current of the current control means 15 is supplied to the servo motor 4, and the servo motor 4 rotationally drives the ball screw 3, The table 1 moves together with the ball screw nut 2 to the position command value at the speed command speed.
[0033]
As described above, according to the first embodiment, the reversal detection means 7 that receives the position command value, detects reversal of the control direction based on the increase / decrease of the position command value, and outputs a reversal detection signal. From the friction amount storage means 8 for storing the friction amount for each position of the control object measured in advance and selecting and outputting the friction amount at the position based on the current position of the table 1. And the lost motion correction gain calculating means 9 for generating and outputting a position command correction value that changes in accordance with the friction amount when the inversion detection signal is input. The position adding means 10 for performing the correction calculation of the position command value using the position command correction value is provided, and the position command value used for numerical control of the table 1 is corrected. By storing the amount of friction for each position of the table 1, the position command correction value at each position is determined based on the amount of friction that differs for each position where the inversion occurs in the control direction of the table 1. Command value correction calculation can be performed.
[0034]
Accordingly, different amounts of friction are obtained according to the position of the table 1, and the position command value can be corrected based on this, so that rattling caused by play between the ball screw nut 2 and the ball screw 3 (backlash) Even if there is elastic deformation that depends on the relationship between the rigidity and friction of these drive transmission members, the position command value is corrected using a fixed position command correction value when the control direction of the table 1 is simply reversed. Compared with the case where the calculation is performed, there is an effect that the lost motion can be corrected with high accuracy and the position can be controlled with high accuracy.
[0035]
Further, since the position command correction value corresponding to the position of the table 1 is generated and the position command value is corrected using this, the position command correction value based on the relationship model between the position of the table 1 and the friction amount is generated. The friction amount storage means 8 can store the friction amount corresponding to the position of the table 1 only by measuring the relationship between the position of the table 1 and the friction amount under a certain condition. Therefore, it is not necessary to perform measurement for all combinations in which all parameters are changed as in the conventional position command value correction apparatus using a multilayer neural network, and the position command correction value can be set with a small number of measurements.
[0036]
Furthermore, since the amount of friction can be set with such a small amount of measurement, even if each measurement is performed for each product, there is no tremendous effort. A position command correction value that can be corrected well can be set, and there is an effect that higher precision than in the past can be realized.
[0037]
Embodiment 2. FIG.
FIG. 3 is a block diagram showing a configuration for one axis of the NC machining system according to the second embodiment of the present invention. In the figure, reference numeral 16 denotes the amount of movement of the table 1 determined based on the detected rotation amount when the detected rotation amount of the encoder 5 is input together with the friction amount from the friction amount storage means 8 and a reverse detection signal is input. In response to this, lost motion correction gain calculation means (position command correction value output means) that generates and outputs a position command correction value using the following equation (4). However, g (v) is a function representing increase / decrease of the lost motion amount depending on the current speed. The other configuration is the same as that of the first embodiment, and the description is omitted.
LM = f (p) × g (v) / K Equation 4
[0038]
FIG. 4 is an explanatory diagram showing the relationship between the speed of the table 1 and the amount of friction according to Embodiment 2 of the present invention. FIG. 4A is a friction distribution graph in which the horizontal axis is speed and the vertical axis is the lost motion coefficient g (v) in the above equation 4, and FIG. 4B is measurement data on which the graph is based. In the figure, when the speed of the table 1 increases, the friction amount gradually decreases to a certain speed range, the lost motion coefficient g (v) decreases, and the speed exceeds the speed range. As the value increases, the amount of friction gradually increases and the lost motion coefficient g (v) also increases.
[0039]
Next, the operation will be described.
When the reverse detection signal is input from the reverse detection means 7, the lost motion correction gain calculation means 16 uses the above equation 4 to determine the position according to the moving speed of the table 1 determined based on the friction amount and the detected rotation amount. A command correction value is generated and output. Other operations are the same as those in the first embodiment, and a description thereof will be omitted.
[0040]
As described above, according to the second embodiment, the lost motion correction gain calculation means 16 receives the detected rotation amount from the encoder 5 and uses the calculation formula based on the table drive system modeling to calculate the speed of the table 1. Since the position command correction value that is different depending on the position is generated and output, the friction amount of the different table 1 can be corrected with the position command correction value according to the speed, and only the position of the table 1 is considered. There is an effect that the position can be controlled with higher accuracy than when the position command correction value is used.
[0041]
In addition, the position and speed of the table 1 are separated and considered based on the modeling of the driving system of the table 1 without taking into account all parameters collectively as in the position command value correction apparatus using the conventional multilayer neural network. Therefore, even if the number of factors to be taken into account increases in this way, the contents of the friction amount storage means 8 and the parameters of the arithmetic expression are set with a small measurement regardless of the number of factors. There is an effect that it is possible to accurately correct the deviation.
[0042]
Embodiment 3 FIG.
FIG. 5 is a block diagram showing a configuration for one axis of the NC machining system according to the third embodiment of the present invention. In the figure, reference numeral 17 denotes a spring coefficient that stores in advance a spring coefficient for each position of the table and outputs the above-described spring coefficient at the position of the table 1 estimated based on the detected rotation amount of the encoder 5. The storage means (spring coefficient output means) 18 receives the detected rotation amount of the encoder 5 together with the friction amount from the friction amount storage means 8, and when the reverse detection signal is input, the determination is made based on the detected rotation amount. This is a lost motion correction gain calculation means (position command correction value output means) that generates and outputs a position command correction value using the following equation 5 according to the position of the table 1. However, k (p) is stored in the spring coefficient storage means 17 as a spring coefficient that changes depending on the current position. The other configuration is the same as that of the first embodiment, and the description is omitted.
LM = f (p) / k (p) Equation 5
[0043]
FIG. 6 is an explanatory diagram showing the relationship between the position of the table 1 and the spring coefficient according to Embodiment 3 of the present invention. FIG. 4A shows a spring coefficient distribution graph in which the horizontal axis is the position and the vertical axis is the spring coefficient k (p) in the above equation 5, and FIG. 4B is measurement data that is the basis of the graph. And what is shown in the figure has a characteristic that the spring coefficient k (p) gradually decreases as the position of the table 1 increases.
[0044]
The spring coefficient distribution function k (p) is set by the following procedure. First, while moving the table 1 over the entire operating range at a constant speed, the amount of lost motion of the table 1 is measured using a position measuring means such as a contact displacement meter, and the current supplied to the servo motor 4 is also measured. Record. Next, by substituting these data into the following formula 6, a spring coefficient distribution function k (p) is obtained. Here, Kt is a torque constant of the servo motor 4, i (p) is a current value supplied to the servo motor 4 at the table position p, and LM (p) is a lost motion amount of the table 1 at the table position p. The spring coefficient distribution graph is plotted.
k (p) = Kt × i (p) / LM (p) Equation 6
[0045]
Next, the operation will be described.
When a reversal detection signal is input from the reversal detection unit 7 in a state where a spring coefficient corresponding to the current position is output from the spring coefficient storage unit, the lost motion correction gain calculation unit 18 receives the output from the friction amount storage unit 8. A position command correction value is generated from a certain friction amount and a spring coefficient which is an output from the spring coefficient storage means 17 using the above formula 5, and is output. Other operations are the same as those in the first embodiment, and a description thereof will be omitted.
[0046]
As described above, according to the third embodiment, the lost motion correction gain calculation means 18 uses the friction amount that changes according to the position of the control target and the spring coefficient that changes according to the position of the control target. Since the command correction value is generated and output, even if the spring coefficient for each position of the control target changes, the position command correction value can be calculated accordingly, and only the variation in the friction amount of the control target is considered. There is an effect that the position can be controlled with higher accuracy than when the position command correction value is used.
[0047]
In addition, the change in the amount of friction due to the position of the table 1 and the change in the spring coefficient due to the position of the table 1 are separated without taking into account all the parameters as in the conventional position command value correction device using a multilayer neural network. Thus, even if the number of factors to be taken into account increases in this way, each product can be set while setting the storage contents of the correction amount storage means 8 and the parameters of the arithmetic expression with a small measurement. There is an effect that each shift can be accurately corrected.
[0048]
In addition, as shown in FIG. 7, the same effect can be acquired also on the assumption of the structure of NC processing system of Embodiment 2. FIG. In the figure, reference numeral 19 denotes the detected rotation amount when the detected rotation amount of the encoder 5 is input together with the friction amount from the friction amount storage means 8 and the spring coefficient from the spring coefficient storage means 17, and when the reverse detection signal is input. This is a lost motion correction gain calculation means (position command correction value output means) that generates and outputs a position command correction value using the following equation 7 in accordance with the speed of the table 1 determined based on it. The other configuration is the same as that of the second embodiment, and the description is omitted.
LM = f (p) × g (v) / k (p) Equation 7
[0049]
Further, in the above description, an example in which the friction amount and the spring coefficient depending on the position of the control target are displayed in a tabular form is shown, but an approximate function extracted from tabular data may be used. Alternatively, for the spring coefficient depending on the position of the controlled object, the following equation 8 based on the mechanical system model of the controlled object may be used. However, A and B are constants for converting the current position into a spring coefficient.
k (p) = 1 / (A × p + B) Equation 8
[0050]
Embodiment 4 FIG.
FIG. 8 is a block diagram showing a configuration for one axis of an NC machining system according to Embodiment 4 of the present invention. In the figure, reference numeral 20 denotes a predetermined schedule in which the detected rotation amount of the encoder 5 and the final supply current value to the servo motor 4 are input, and are grasped based on power activation, predetermined continuous operation time, user instruction, and the like. It is a function derivation unit (friction amount calculation unit) that performs an update process of the content stored in the friction amount storage unit 8. Specifically, the function deriving means 20 outputs, for example, a position command value for moving the table 1 at a constant speed much lower than the normal use speed over the entire movement range, while the position command value output means 6 outputs the position command value. On the basis of the position information and the supply current value in Table 1, the friction amount at each position is calculated using the above equation 3, and this is stored in the friction amount storage means 8. The other configuration is the same as that of the first embodiment, and the description is omitted.
[0051]
Next, the operation will be described.
When the update processing timing of the content stored in the friction amount storage unit 8 comes based on the above schedule, the function deriving unit 20 specifically sets, for example, the table 1 at a constant speed much lower than the normal use speed over the entire movement range. While the position command value to be moved at the position is output from the position command value output means 6, the friction amount at each position is calculated based on the position information of the table 1 and the supply current value at that time, and this is calculated as the friction amount storage means 8. Remember me. Other operations are the same as those in the first embodiment, and a description thereof will be omitted.
[0052]
As described above, according to the fourth embodiment, the table 1 is operated based on a predetermined schedule, the position information of the table 1 at that time, and the final current command to the servo motor 4 that drives the table 1 Function derivation means 20 for calculating the friction amount at each position based on the value, and the friction amount storage means 8 stores the friction amount for each position of the table 1 calculated by the function derivation means 20. The amount storage means 8 can store a position command correction value corresponding to the environment and state at that time.
[0053]
Therefore, even if the lubrication state of the linear motion guide changes in accordance with temperature change or aging change, and as a result, the amount of friction at each position of the table 1 changes, that is, the lubrication state of the linear motion guide mechanism changes. Even so, the stored content of the friction amount storage means 8 can be updated accordingly, so that the lost motion can be accurately performed regardless of the temperature change or aging change, and the guide lubrication state change. There is an effect that can be corrected.
[0054]
According to the fourth embodiment, the function deriving means 20 calculates the friction amount when the table 1 is operated based on a constant position command value, so that the substantially constant speed over the entire movement range. Thus, it is possible to obtain the friction amount when the table 1 is moved, to prevent the friction amount from being changed due to the speed change, and to improve the accuracy of the friction amount and the position command correction value according to the position of the table 1. There is an effect that can be done.
[0055]
Embodiment 5. FIG.
FIG. 9 is a block diagram showing a configuration for one axis of the NC machining system according to the fifth embodiment of the present invention. In the figure, reference numeral 21 denotes a friction correction gain that is calculated based on the position command correction value. When an inversion detection signal is input, the magnitude is corrected by this friction correction gain using the following equation 9 to obtain a current. Friction correction gain calculation means (current command value correction device) that outputs as a command correction value. Here, fc is a friction correction amount, LM is a lost motion correction amount, and K is a spring coefficient indicating the relationship between the lost motion correction amount and the friction amount. The other configuration is the same as that of the first embodiment, and the description is omitted.
fc = LM × K (formula 9)
[0056]
Next, the operation will be described.
When a reverse detection signal is output from the reverse detection means 7 and a position correction signal is output from the lost motion correction gain calculation means 9 based on the reverse detection signal, the friction correction gain calculation means 21 is based on the position command correction value. Then, the friction correction gain is calculated, the magnitude of the inversion detection signal is corrected by this friction correction gain, and a current command correction value is output. Other operations are the same as those in the first embodiment, and a description thereof will be omitted.
[0057]
As described above, according to the fifth embodiment, the friction correction gain is calculated based on the position command correction value generated by the lost motion correction gain calculation means 9, and the current command value is calculated using this friction correction gain. Since the friction correction gain calculating means 21 for correcting the friction amount is provided, the increase / decrease in the friction amount depending on the position of the table 1 can be offset by the friction correction gain, and the position correction accuracy is deteriorated due to the increase / decrease in the friction amount. There is an effect that can be prevented.
[0058]
In addition, as shown in FIG. 10, the same effect can be acquired also on the premise of the configuration of the NC machining system of the second embodiment.
[0059]
Embodiment 6 FIG.
FIG. 11 is a block diagram showing a configuration for one axis of an NC machining system according to Embodiment 6 of the present invention. In the figure, reference numeral 22 denotes the final supply current value to the servo motor 4 and the detected rotation amount of the encoder 5, and when the reverse detection signal is input, the table 1 is determined based on the detected rotation amount. Lost motion correction gain calculation means (position command correction value output means) that generates and outputs a position command correction value using the following equation 10 in accordance with the moving speed. Where f is the estimated friction amount in terms of the servo motor axis, Kt is the torque constant of the servo motor 4, i is the current command value to the servo motor 4, J is the inertia in terms of the servo motor axis including all moving parts, ddΘ Is the angular acceleration of the servomotor 4, C is the viscous friction coefficient in terms of the servomotor shaft, and dΘ is the angular velocity of the servomotor 4. The other configuration is the same as that of the second embodiment, and the description is omitted.
f = Kt × i−J × ddΘ−C × dΘ Equation 10
[0060]
The inertia J and the viscous friction coefficient C are the position (angle), speed (angular velocity), acceleration (angular acceleration) and thrust (when the sine wave motion having an appropriate maximum speed is applied to the drive shaft of the servo motor 4. Servo motor torque) is calculated by the following equation group 11 using the least square method. However, [] ′ is a transposed matrix, [τ] is an m-row column vector composed of time series data of servo motor torque, B is a sign sign (dΘ) of angular acceleration ddΘ and angular velocities dΘ and dΘ, respectively. A matrix of m rows × 3 columns composed of m row column vectors, and A is an inverse matrix of 3 rows × 3 columns calculated from the matrix B.
[J C f] ′ = A [τ]
B = [ddΘ dΘ sign (dΘ)]
τ = Kt × i (Expression group 11)
[0061]
Next, the operation will be described.
When the reverse detection signal is output from the reverse detection means 7, the lost motion correction gain calculation means 22 calculates the final supply current value to the servo motor 4 at that time and the current speed determined from the detected rotation amount of the encoder 5. The position command correction value is generated based on Equation 10 above. Other operations are the same as those in the second embodiment, and a description thereof will be omitted.
[0062]
As described above, according to the sixth embodiment, the inversion detection means 7 that receives the position command value, detects the inversion of the control direction based on the increase / decrease in the position command value, and outputs the inversion detection signal; A final supply current value for the servo motor 4 that drives the table 1 is input, and a lost motion correction gain calculating unit 22 that generates and outputs a position command correction value using an arithmetic expression based on modeling of the table 1; The position adding means 10 for correcting the position command value using the position command correction value is provided, and the position command value used for the numerical control of the table 1 is corrected. It is possible to perform correction calculation of position command values having different values for each position where the inversion of the table 1 occurs.
[0063]
Accordingly, the position command value can be corrected according to the friction amount of the different table 1 depending on the position. Therefore, when the table 1 is simply reversed, the position command value is corrected using a fixed position command correction value. There is an effect that the position can be controlled with higher accuracy than in the case of performing it.
[0064]
In addition, since the position command correction value based on the relational model between the position of table 1 and the amount of friction can be generated, all the parameters are changed as in the conventional position command value correction device using a multilayer neural network. It is not necessary to perform the measurement for the combination of the above, and the parameters of the arithmetic expression can be set with a small number of measurements.
[0065]
Furthermore, since the calculation formula can be set with such a small number of measurements, even if each measurement is performed for each product, there is no tremendous effort. Since a position command correction value that can be corrected well can be set, there is an effect that an unprecedented high accuracy can be realized.
[0066]
Finally, if the amount of friction changes according to the environment and state at that time, the final supply current value to the servo motor 4 that changes accordingly is input to the lost motion correction gain calculation means 22. Even if the lubrication state of the linear motion guide changes according to a temperature change or a secular change, and as a result, the amount of friction at each position of the table 1 changes, a position command correction value corresponding to the change can be calculated. Therefore, there is an effect that the deviation can be corrected with high accuracy irrespective of the temperature change and the secular change, and regardless of the change in the lubrication state of the linear motion guide.
[0067]
According to the sixth embodiment, the lost motion correction gain calculating means 22 generates and outputs a position command correction value that becomes a different value depending on the speed of the table 1 using an arithmetic expression based on the modeling of the table 1. Therefore, the friction amount of the table 1 that differs depending on the speed can be corrected with the position command correction value, and the position can be controlled with higher accuracy than when the position command correction value considering only the position of the table 1 is used. There is an effect that can.
[0068]
In addition, the position and speed of the table 1 can be separated and considered based on the modeling of the table 1 without having to consider all parameters collectively as in the conventional position command value correction apparatus using the multilayer neural network. Therefore, even if the number of factors to be considered increases, the lost motion can be accurately corrected for each product while setting the calculation formula parameters with a small number of measurements. There is.
[0069]
In the above embodiment, the current position of the table 1 is determined based on the detected rotation amount of the encoder 5, but it may be determined using the position command value output from the position command value output means 6. Similar effects can be obtained.
[0070]
【The invention's effect】
As described above, according to the present invention, in the position command value correction device that corrects the position command value used for the numerical control of the controlled object, the position command value is input, and control is performed based on the increase or decrease of the position command value. A reversal detecting means for detecting reversal of the direction and outputting reversal detection information; and a storage means for storing a friction amount for each position of the controlled object measured in advance, and the friction at the position based on the current position of the controlled object. The friction amount output means for selecting and outputting the amount, and the inversion detection signal as well as the friction amount output from the friction amount storage means are input, and a position command correction value that varies depending on the friction amount is generated. Since the position command correction value output means for outputting and the calculation means for performing the correction calculation of the position command value using the position command correction value are provided, the amount of friction for each position of the control target measured in advance in the storage means is provided. Remembered In Rukoto, can be based on the amount of friction different value for each position where the inversion of the control target occurs, the correction operation of the position command value by using the optimum position command correction value at each position.
[0071]
Therefore, since the position command value can be corrected according to the friction amount of the control object that differs depending on the position, when the control object is reversed, the position command value is corrected using a fixed position command correction value. There is an effect that the position can be controlled with higher accuracy than in the case of performing it.
[0072]
Further, since a correction value corresponding to the position of the control target is generated and the position command value is corrected using this, a position command correction value based on a relational model between the position of the control target and the friction amount is generated. The position command correction value corresponding to the position of the controlled object can be stored in the storage means only by measuring the relationship between the position of the controlled object and the friction amount under a certain condition. Therefore, it is not necessary to perform measurement for all combinations in which all parameters are changed as in the conventional position command value correction apparatus using a multilayer neural network, and the position command correction value can be set with a small number of measurements.
[0073]
Furthermore, since the position command correction value can be set with such a small number of measurements, even if each measurement is performed for each product, it does not take a lot of time and effort. Since it is possible to set a position command correction value that can correct motion with high accuracy, there is an effect that it is possible to achieve higher accuracy than in the past.
[0074]
According to the present invention, the spring coefficient output means further comprises a storage means for storing a spring coefficient for each position of the controlled object measured in advance, and selects and outputs the spring coefficient at the position based on the current position of the controlled object. And the lost motion correction gain calculating means generates and outputs a position command correction value using a friction amount that changes according to the position of the control target and a spring coefficient that changes according to the position of the control target. Even if the spring coefficient for each position of the control target changes, the position command correction value can be calculated accordingly, and it is more accurate than using a position command correction value that takes into account only the variation in the friction amount of the control target. There is an effect that the position can be well controlled.
[0075]
According to this invention, the friction amount output means operates the control target based on a predetermined schedule, and each position is determined based on the position information of the control target at that time and the command value to the drive means that drives the control target. And a storage means for storing the friction amount for each position of the controlled object calculated by the friction amount calculation means. The corresponding position command correction value can be stored. Therefore, even if the lubrication state of the guide changes according to temperature change or aging change, and as a result, the amount of friction at each position to be controlled changes, the position command correction value of the storage means is updated accordingly. Therefore, there is an effect that the lost motion can be corrected with high accuracy regardless of the temperature change or the secular change and the change in the lubrication state of the guide.
[0076]
According to the present invention, the friction amount calculation means calculates the friction amount when the control target is operated based on the constant position command value, so that the control target is controlled at a substantially constant speed over the entire moving range. It is possible to obtain the amount of friction in a state where the position is moved, to prevent a change in the amount of friction accompanying a speed change, and to improve the accuracy of the correction amount and the position command correction value according to the position of the control target. is there.
[0077]
According to the present invention, in the position command value correction device for correcting the position command value used for numerical control of the controlled object, the position command value is input, and the reversal of the control direction is detected based on the increase or decrease of the position command value. Position command for generating a position command correction value by using an arithmetic expression based on modeling of the control object, and a command value for the inversion detection means for outputting the reversal detection information and the drive means for driving the control object Since the correction value output means and the calculation means for performing the correction calculation of the position command value using the position command correction value are provided, each position where the inversion of the control object has occurred using the calculation formula based on the modeling of the control object Thus, it is possible to perform correction calculation of position command values having different values.
[0078]
Therefore, since the position command value can be corrected according to the friction amount of the control object that differs depending on the position, when the control object is reversed, the position command value is corrected using a fixed position command correction value. There is an effect that the position can be controlled with higher accuracy than in the case of performing it.
[0079]
In addition, since it is possible to generate a position command correction value based on a relational model between the position of the controlled object and the amount of friction, all of the parameters that have been changed are changed as in the conventional position command value correction device using a multilayer neural network. It is not necessary to perform the measurement for the combination of the above, and the parameters of the arithmetic expression can be set with a small number of measurements.
[0080]
Furthermore, since the calculation formula can be set with such a small number of measurements, even if each measurement is performed for each product, there is no tremendous effort. Since a position command correction value that can be corrected well can be set, there is an effect that an unprecedented high accuracy can be realized.
[0081]
Finally, the position command correction value output means receives the command value for the drive means for driving the controlled object that changes in accordance with the amount of friction depending on the environment and state at that time. Even if the lubrication state of the product changes according to temperature change or secular change, and as a result, the amount of friction at each position to be controlled changes, the position command correction value can be calculated accordingly. There is an effect that the lost motion can be corrected with high accuracy regardless of the temperature change or aging change of the guide and the change of the lubrication state of the guide.
[0082]
According to this invention, the position command correction value output means receives position control information that is input with information about the current speed of the control target, and has different values depending on the speed of the control target using an arithmetic expression based on modeling of the control target. Since the correction value is generated and output, the friction amount of the control target that differs depending on the speed can be corrected with the position command correction value, rather than using the position command correction value that only considers the position of the control target. There is an effect that the position can be controlled with high accuracy.
[0083]
Moreover, it is possible to separate and consider the position and speed of the controlled object based on the modeling of the controlled object without having to consider all the parameters at once like the position command value correction device using the conventional multilayer neural network. Therefore, even if the number of factors to be taken into account increases in this way, the lost motion of each product can be accurately set for each product while setting the memory contents and parameters of the calculation formula with a small number of measurements. There is an effect that can be corrected.
[0084]
According to the present invention, the position command value output means for outputting the position command value used for the numerical control of the controlled object and the position command value are input, and the position command value is obtained based on the inversion detection signal of the controlled object. The position command value correcting device for correcting, a current command value generating means for generating a current command value based on the corrected position command value output from the position command value correcting device, and the current command value are input, A current command value correction device that corrects the current command value using a predetermined friction correction gain based on the inversion detection signal of the control object, and a correction output from the current command value correction device Current Drive means for driving the control object based on the command value, so that a position command correction value can be generated with data based on a small number of measurements, and when the control object is simply inverted, a constant position command correction is performed. There is an effect that the position can be controlled with higher accuracy than when the position command value is corrected using the value.
[0085]
According to this invention, the current command value correction device calculates a friction correction gain based on the position command correction value generated by the position command value correction device, and corrects the current command value using this friction correction gain. Therefore, the increase / decrease of the friction amount depending on the position of the table can be offset by this friction correction gain, and there is an effect that the deterioration of the position correction accuracy due to the increase / decrease of the friction amount can be prevented.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration for one axis of an NC machining system according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing an example of a relationship between a position of a table stored in a friction amount storage unit and a friction amount according to Embodiment 1 of the present invention.
FIG. 3 is a block diagram showing a configuration for one axis of an NC machining system according to a second embodiment of the present invention.
FIG. 4 is an explanatory diagram showing the relationship between the speed of a table and the amount of friction according to Embodiment 2 of the present invention.
FIG. 5 is a block diagram showing a configuration for one axis of an NC machining system according to a third embodiment of the present invention.
FIG. 6 is a diagram for explaining a relationship between a position and a spring coefficient according to Embodiment 3 of the present invention.
FIG. 7 is a block diagram showing a modification of the NC machining system according to the third embodiment of the present invention.
FIG. 8 is a block diagram showing a configuration for one axis of an NC machining system according to a fourth embodiment of the present invention.
FIG. 9 is a block diagram showing a configuration for one axis of an NC machining system according to a fifth embodiment of the present invention.
FIG. 10 is a block diagram showing a modification of the NC machining system according to the fifth embodiment of the present invention.
FIG. 11 is a block diagram showing a configuration for one axis of an NC machining system according to a sixth embodiment of the present invention.
FIG. 12 is a block diagram showing a configuration of a conventional numerical control system.
FIG. 13 is a diagram illustrating a relationship between a position and a lost motion amount.
FIG. 14 is a block diagram showing a configuration of a conventional numerical control system.
[Explanation of symbols]
1 table (control object), 2 ball screw nut (drive means), 3 ball screw (drive means), 4 servo motor (drive means), 5 encoder, 6 position command value output means, 7 reverse detection means, 8 friction amount storage means (Friction amount output means), 9, 16, 18, 19, 22 Lost motion correction gain calculation means (position command correction value output means), 10 Position addition means (calculation means), 11 Position control means (current command value generation means) ), 12 Speed control means (current command value generation means), 13 Friction correction gain calculation means (current command value correction device), 14 Current addition means (current command value correction device), 15 Current control means (drive means), 17 Spring coefficient storage means (spring coefficient output means), 20 function derivation means (friction amount calculation means), 21 friction correction gain calculation means (current command value correction device).

Claims (8)

In a position command value correction device that corrects a position command value used for numerical control of a controlled object,
Reversal detecting means for inputting the position command value, detecting reversal of the control direction based on increase or decrease of the position command value, and outputting reversal detection information;
A storage means for storing the friction amount for each position of the control object measured in advance, and a friction amount output means for selecting and outputting the friction amount at the position based on the current position of the control object;
The position command correction value output means for generating and outputting a position command correction value that is different from the friction amount output from the friction amount storage means and is input according to the friction amount;
A position command value correction apparatus comprising: a calculation means for performing a correction calculation of the position command value using the position command correction value. In a position command value correction device that corrects a position command value used for numerical control of a controlled object,
Reversal detecting means for inputting the position command value, detecting reversal of the control direction based on increase or decrease of the position command value, and outputting reversal detection information;
A storage means for storing the friction amount for each position of the control object measured in advance, and a friction amount output means for selecting and outputting the friction amount at the position based on the current position of the control object;
A storage means for storing a spring coefficient for each position of the control object measured in advance, and a spring coefficient output means for selecting and outputting the spring coefficient at the position based on the current position of the control object;
The friction amount output from the friction amount storage means and the inversion detection signal are input together with the spring coefficient output from the spring coefficient storage means, and a position command correction value that varies depending on the spring coefficient and the friction amount is generated. Position command correction value output means for outputting
A position command value correction apparatus comprising: a calculation means for performing a correction calculation of the position command value using the position command correction value. The friction amount output means operates the control target based on a predetermined schedule, and calculates the friction amount at each position based on the position information of the control target at that time and the command value to the drive means for driving the control target. A friction amount calculation means is provided,
The position command value correction apparatus according to claim 1 or 2, wherein the storage means stores the friction amount for each position of the control target calculated by the friction amount calculation means. 4. The position command value correction device according to claim 3, wherein the friction amount calculation means calculates a friction amount when the controlled object is operated based on a fixed position command value. In a position command value correction device that corrects a position command value used for numerical control of a controlled object,
Reversal detecting means for inputting the position command value, detecting reversal of the control direction based on increase or decrease of the position command value, and outputting reversal detection information;
Position command correction value output means for inputting a command value for the driving means for driving the control object, and generating and outputting a position command correction value using an arithmetic expression based on modeling of the control object;
A position command value correction apparatus comprising: a calculation means for performing a correction calculation of the position command value using the position command correction value. The position command correction value output means receives information related to the current speed of the control target, and generates a position command correction value that varies depending on the speed of the control target using an arithmetic expression based on modeling of the control target. 6. The position command value correction apparatus according to claim 1, wherein the position command value correction apparatus outputs the position command value. Position command value output means for outputting a position command value used for numerical control of the controlled object;
The position command value correction device according to claim 1 or 5, wherein the position command value is input, and the position command value is corrected based on the inversion detection signal of the control target.
Current command value generation means for generating a current command value based on the corrected position command value output from the position command value correction device;
A current command value correction device that receives the current command value and corrects the current command value using a predetermined friction correction gain based on the inversion detection signal of the control target;
Numerical control system comprising a driving means for driving said controlled object based on the corrected current command value output from the current command value correcting unit. The current command value correction device calculates a friction correction gain based on the position command correction value generated by the position command value correction device, and corrects the current command value using the friction correction gain. Item 8. The numerical control system according to Item 7.

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