JP2011113475A - Numerical control device and machine tool including the numerical control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a numerical control device that achieves high followability to a position command and a machine tool including the numerical control device. <P>SOLUTION: In a first multiplication part 14 of an FF generation part 30 in the numerical control device 4, a "value 1" is determined by multiplying a constant 1 by a velocity determined by a first velocity calculation part 13. In a second multiplication part 17, a constant 3 is assumed to be zero, and an acceleration found by an acceleration calculation part 15 is not used. In a fourth multiplication part 25, a constant 5 is defined to be zero, and a jerk calculated by a jerk calculation part 23 is not used. Then, a constant 6 of a primary LPF 19 and a constant 7 of a primary LPF 20 are defined to be time constants, and a "value 2" is calculated by subtracting a value determined by processing a velocity calculated by a second velocity calculation part 18 with the primary LPF 19 and the primary LPF 20 from the velocity calculated by the second velocity calculation part 18. In a third multiplication part 22, "a value 3" is determined by multiplying the "value 2" by the predetermined constant 8. By a first adder 12, the "value 1" and the "value 3" are added together to be added to an output of a position loop multiplier 10 as an FF command. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a numerical control device that controls a machine tool by executing a numerical control program and a machine tool including the device.

  Conventionally, a machine tool uses a numerical control program (hereinafter referred to as an “NC program”) to move and rotate a table, a spindle, or the like by motor control to process a workpiece. In this case, the machine tool needs to shorten the machining time (cycle time) of the workpiece. When the machine tool is operated by the NC program, it performs machining and positioning operations continuously. When the machine tool performs the above-described operation, the machine tool often reaches the target position of the current operation and executes the next operation. Therefore, in the control of the motor that moves each axis of the machine tool, if the followability with respect to the position command (movement command) is good, the next operation can be executed quickly, resulting in a short cycle time.

  If the gain of the feedforward (FF) command is increased as a means for improving the followability, the followability to the position command is improved. However, when the gain of the feedforward command is increased to 100%, problems such as overshoot that exceed the target position occur. As a means for solving this problem, in the invention described in Patent Document 1, followability is improved by passing a feedforward command through a low-pass filter.

Japanese Patent No. 3899824

  However, the invention described in Patent Document 1 has a problem that sufficient followability has not yet been realized, although the followability to the position command is improved to some extent.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a numerical control device that can realize high followability to a position command and a machine tool including the device.

  A numerical control apparatus according to a first aspect of the present invention obtains a position deviation between a position detection means for detecting a position of a motor to be controlled and a position of the motor fed back from the position detection means and a position command. A first subtracting means; a position loop multiplying means for multiplying the position deviation by a position proportional gain; a first speed calculating means for differentiating the position command to obtain a speed component; and a predetermined output at the first speed calculating means And a numerical control device for adding the output of the first multiplication means as a feedforward command to the output of the position loop multiplication means and outputting the same to the motor amplifier. Acceleration calculating means for obtaining an acceleration command by differentiating, second multiplying means for multiplying the output of the acceleration calculating means by a predetermined constant, and speed command by differentiating the position command Second speed calculating means to be obtained; a low-pass filter for filtering the output of the second speed calculating means; a second subtracting means for subtracting the output of the low-pass filter from the output of the second speed calculating means; Third feed means for multiplying the output of the subtracting means by a predetermined constant; the output of the second multiplication means and the output of the third multiplication means are added to the output of the first multiplication means; First adding means for calculating.

  In the numerical control device according to the first aspect, by adding the velocity component and the acceleration component to the feedforward command, it is possible to improve the position deviation of the motor to be controlled and bring it close to almost zero. Therefore, at the same time when the position command is completed, the termination condition is satisfied and the movement cycle time can be shortened. Further, since the position deviation is almost zero during movement, the movement path can be moved according to the position command. Therefore, the path error can be improved.

  The numerical control device includes jerk calculating means for differentiating the output of the acceleration calculating means to obtain a jerk component, and fourth multiplying means for multiplying the output of the jerk calculating means by a predetermined constant, The first addition means adds the output of the first multiplication means, the output of the second multiplication means, the output of the third multiplication means, and the output of the fourth multiplication means, and outputs a feedforward command You may make it do.

  In this case, in addition to the speed component and the acceleration component, the jerk component can also be added to the feedforward command, so that the position deviation of the motor to be controlled can be further improved and the position deviation can be made closer to zero. it can.

  In the numerical control device, the low-pass filter may be provided in a plurality of stages. By providing a plurality of low-pass filters, position control delay compensation can be further improved.

  A machine tool according to a second aspect includes the numerical control device described above. A machine tool provided with the above numerical control device can improve the positional deviation of the motor of each axis that is a control target, and can bring the positional deviation closer to zero. Therefore, at the same time when the position command is finished, the finish condition can be satisfied and the machining cycle time can be shortened. Further, since the position deviation is almost zero during movement, the movement path can be moved according to the position command. Therefore, the path error can be improved.

1 is a block diagram showing an electrical configuration of a numerical control device 4 and a machine tool 1 according to a first embodiment. It is a figure which shows the result of having measured the position control when the feedforward gain in the conventional numerical control apparatus is 50%. FIG. 3 is an enlarged view of FIG. 2. It is a figure which shows the result of having measured the position control operation | movement by FF command based on the speed calculated | required from the position command. It is a figure which shows the result of having measured the position control operation | movement which made the addition value of the speed calculated | required from the position instruction | command and the result of having passed the said speed | rate through 1st-order LPF to FF instruction | command. It is a figure which shows the result of having measured the position control operation | movement which made the addition value of the speed calculated | required from the position instruction | command, the said speed | rate through primary LPF, and acceleration to FF instruction | command. It is a figure which shows the result of having measured the speed calculated | required from the position command, the result of having passed the said speed to primary LPF, and the position control operation | movement which made the addition value of an acceleration and jerk the FF command. It is a block diagram which shows the electrical structure of the numerical control apparatus 4 and machine tool 1 of 2nd Embodiment.

  Hereinafter, a first embodiment of a machine tool and a numerical control device in which a numerical control device according to the present invention is used will be described with reference to the drawings. These drawings are used for explaining the technical features that can be adopted by the present invention, and the numerical control device and the configuration of the machine tool described are not intended to be limited only to them. It is just an illustrative example.

  As shown in FIG. 1, the machine tool 1 is provided with a motor 2 and an encoder 3. The machine tool 1 includes a spindle motor, an X-axis motor, a Y-axis motor, and a Z-axis motor (not shown). The motor 2 represents one of the X-axis motor, the Y-axis motor, and the Z-axis motor. It is assumed that the same control is performed for the other motors. The motor 2 is provided with an encoder 3 that detects the position of the output shaft of the motor 2 to be controlled.

  The machine tool 1 is connected to a numerical controller 4 that controls a motor 2 (main shaft motor, X-axis motor, Y-axis motor, Z-axis motor) of the machine tool 1. The numerical controller 4 includes a position controller 5 and a motor amplifier 6 that controls the motor 2 of the machine tool 1. The position controller 5 is provided with an FF generator 30 that generates a feed forward (hereinafter referred to as “FF”) command.

  The numerical controller 4 outputs an FF command from the FF generator 30 so that the position command input from the position command input unit 11 and the position of the output shaft of the motor 2 fed back from the encoder 3 coincide with each other. It is configured to perform control. The motor amplifier unit 6 includes a speed control unit 7 that performs speed control of the motor 2 and a torque control unit 8 that performs torque control of the motor 2.

  The FF generation unit 30 of the position control unit 5 includes a position command input unit 11 that inputs a position command, and a first speed calculation unit 13 that calculates a speed component by differentiating the position command input from the position command input unit 11. And a first multiplication unit 14 that multiplies the output of the first speed calculation unit 13 by a predetermined constant 1. The constant 1 is a value determined in advance for each machine tool 1 so that the positional deviation of the machine tool 1 approaches zero.

  The position control unit 5 includes an acceleration calculation unit 15 that calculates the acceleration component by differentiating the position command input from the position command input unit 11 twice, and a moving average that averages the output of the acceleration calculation unit 15. A filter 16 and a second multiplier 17 that multiplies the output of the moving average filter 16 by a predetermined constant 3 are provided. The constant 2 of the moving average filter 16 is a time constant determined in advance so that the positional deviation of the machine tool 1 approaches zero. The constant 3 is a value determined in advance for each machine tool 1 so that the positional deviation of the machine tool 1 approaches zero.

  The FF generator 30 also includes a second speed calculator 18 for differentiating the position command input from the position command input unit 11 to calculate a speed component, and a primary low-pass filter for compensating for position control delay ( Hereinafter, the output of the primary LPF 20 is subtracted from the speed calculated by the first speed LPF 20 and the first low-pass filter (hereinafter referred to as “first-order LPF”) 20 and the second speed calculator 18. A second subtractor 21 and a third multiplier 22 for multiplying the output of the second subtractor 21 by a predetermined constant 8 are provided. The constants 6 and 7 of the primary LPFs 19 and 20 are time constants determined in advance so that the positional deviation of the machine tool 1 approaches zero. The constant 8 is a value determined in advance for each machine tool 1 so that the positional deviation of the machine tool 1 approaches zero.

  Further, the position controller 5 differentiates the output of the moving average filter 16 to calculate a jerk, a moving acceleration filter 24 that averages the output of the jerk calculating unit 23, and a moving average. A fourth multiplier 25 for multiplying the output of the filter 24 by a predetermined constant 5; The constant 4 of the moving average filter 24 is a time constant determined in advance so that the positional deviation of the machine tool 1 approaches zero. The constant 5 is a value determined in advance for each machine tool 1 so that the positional deviation of the machine tool 1 approaches zero.

  Further, the position control unit 5 subtracts a feedback value of the encoder 3 that detects the position of the output shaft of the motor 2 from the position command input from the position command input unit 11, and obtains a position deviation; A position loop multiplier 10 that multiplies the position deviation output from the first subtractor 9 by a coefficient Kp of a position proportional gain, and a first adder that adds the output of the position loop multiplier 10 and the FF command from the FF generator 30. 12 is provided, and the output of the first adder 12 is input to the motor amplifier unit 6. The coefficient Kp is a predetermined value predetermined for each apparatus.

Next, the primary LPF 19 and the primary LPF 20 will be described. The primary LPF 19 and the primary LPF 20 are “X: input value”, “Y: output value”, “T: time constant”, “A: intermediate value for calculation”, and subscript numbers are time (nth cycle). ) Is expressed by the following arithmetic expression.
1st period A ₁ = X ₁ Y ₁ = A ₁ / T
2nd period A ₂ = X ₂ + A ₁ −Y ₁ Y ₂ = (A ₂ + Y ₁ ) / T
・
・
n period A _n = X _n + A _n−1 −Y _n−1 Y _n = (A _n + Y _n−1 ) / T

The moving average filter 16 has a moving average filter 24 with “X: input value”, “Y: output value”, “T: time constant”, and the subscript number is time (nth cycle). It is expressed by the following arithmetic expression.
1st cycle Y ₁ = X ₁ / T
2nd cycle Y ₂ = (X ₁ + X ₂ ) / T
3rd period Y ₃ = (X ₁ + X ₂ + X ₃ ) / T
・ ・
・ ・
n-th cycle Y _n = (X ₁ + X ₂ +... + X _n ) / T
n + 1 period Y _{n + 1} = (X ₂ + X ₃ +... + X _{n + 1} ) / T

Next, regarding the relationship between the position command, the speed calculated by the first speed calculation unit 13 or the second speed calculation unit 18, the acceleration calculated by the acceleration calculation unit 15, and the jerk calculated by the jerk calculation unit 23 explain. The speed calculated by the first speed calculation unit 13 or the second speed calculation unit 18 is obtained by the following equation.
Speed = position command in current cycle−position command in previous cycle Note that acceleration and jerk are calculated in the same way.
An example of the calculation result is shown in Table 1.

  Next, the position control of the machine tool 1 in the conventional numerical control device and the numerical control device 4 of the present embodiment will be described with reference to FIGS. As shown in FIG. 2 to FIG. 3, in the position control when the feedforward gain is 50% in the conventional numerical control apparatus, the position deviation is large and the position deviation is far from zero. The unit of velocity on the left vertical axis in FIGS. 2 to 7 is “mm / msec”, the unit of position deviation on the right vertical axis is the number of delayed pulses of the motor 2, and the horizontal axis is , Time “msec”.

  Next, a case where the FF command is generated based on the speed obtained by the first speed calculation unit 13 in the FF generation unit 30 of the numerical controller 4 of the present embodiment will be described. In this case, the first multiplication unit 14 of the FF generation unit 30 of the numerical control device 4 multiplies the speed obtained by the first speed calculation unit 13 by a constant 1 which is a predetermined constant, and obtains “value 1 " Next, “constant 3 = 0” of the second multiplication unit 17 is set, and the acceleration obtained by the acceleration calculation unit 15 is not used. Further, “constant 8 = 0” of the third multiplication unit 22 is set, and the speed obtained by the second speed calculation unit 18 is not used. Further, the jerk obtained by the jerk calculator 23 is not used as “constant 5 = 0” of the fourth multiplier 25. In this case, “value 1” obtained by multiplying the speed obtained by the first speed calculation unit 13 by a predetermined constant 1 is added to the output of the position loop multiplier 10 by the first adder 12 as an FF command. Is done. In the position control in this case, as shown in FIG. 4, the position deviation is improved between the central portions (150 msec to 250 msec).

  Next, when the FF generation unit 30 of the numerical control device 4 of the present embodiment generates an FF command based on the speed obtained by the first speed calculation unit 13 and the speed obtained by the second speed calculation unit 18 Will be explained. The first multiplication unit 14 of the FF generation unit 30 of the numerical controller 4 multiplies the speed obtained by the first speed calculation unit 13 by a constant 1 that is a predetermined constant to obtain “value 1”. Further, “constant 3 = 0” of the second multiplication unit 17 is set, and the acceleration obtained by the acceleration calculation unit 15 is not used. Further, the jerk obtained by the jerk calculator 23 is not used as “constant 5 = 0” of the fourth multiplier 25. Next, the constant 6 of the first order LPF 19 and the constant 7 of the first order LPF 20 are set as time constants, and the speed obtained by the second speed computation section 18 from the speed obtained by the second speed computation section 18 is calculated by the primary LPF 19 and the primary LPF 20. “Value 2” is obtained by subtracting the processed value. The third multiplier 22 multiplies “value 2” by a predetermined constant 8 to obtain “value 3”. “Value 1” and “value 3” are added, and the first adder 12 adds to the output of the position loop multiplier 10 as an FF command. In the position control in this case, as shown in FIG. 5, the position deviation is not only improved to approach 0 in the central part (150 msec to 250 msec), but also improved in the vicinity of 100 msec and 350 msec. ing.

  Next, in the FF generation unit 30 of the numerical control device 4 of the present embodiment, the speed obtained by the first speed computation unit 13, the speed obtained by the second speed computation unit 18, and the acceleration computation unit 15 A case where the FF command is generated based on the acceleration will be described. The first multiplication unit 14 of the FF generation unit 30 of the numerical controller 4 multiplies the speed obtained by the first speed calculation unit 13 by a constant 1 that is a predetermined constant to obtain “value 1”. Further, the jerk obtained by the jerk calculator 23 is not used as “constant 5 = 0” of the fourth multiplier 25. Next, the constant 6 of the first order LPF 19 and the constant 7 of the first order LPF 20 are set as time constants, and the speed obtained by the second speed computation section 18 from the speed obtained by the second speed computation section 18 is calculated by the primary LPF 19 and the primary LPF 20. “Value 2” is obtained by subtracting the processed value. The third multiplier 22 multiplies “value 2” by a predetermined constant 8 to obtain “value 3”. The constant 2 of the moving average filter 16 is set as a time constant, and the acceleration obtained by the acceleration calculator 15 is processed by the moving average filter 16 to obtain “value 4”. The second multiplier 17 multiplies “value 4” by a predetermined constant 3 to obtain “value 5”. “Value 1”, “value 3”, and “value 5” are added, and the first adder 12 adds to the output of the position loop multiplier 10 as an FF command. In the position control in this case, as shown in FIG. 6, the position deviation is further improved by approaching 0 between 70 msec and 320 msec.

  Next, in the FF generation unit 30 of the numerical control device 4 of the present embodiment, the speed obtained by the first speed computation unit 13, the speed obtained by the second speed computation unit 18, and the acceleration computation unit 15 A case where the FF command is generated based on the acceleration and the jerk obtained by the jerk calculation unit 23 will be described. The first multiplication unit 14 of the FF generation unit 30 of the numerical controller 4 multiplies the speed obtained by the first speed calculation unit 13 by a constant 1 that is a predetermined constant to obtain “value 1”. Next, the constant 6 of the first order LPF 19 and the constant 7 of the first order LPF 20 are set as time constants, and the speed obtained by the second speed computation section 18 from the speed obtained by the second speed computation section 18 is calculated by the primary LPF 19 and the primary LPF 20. “Value 2” is obtained by subtracting the processed value. The third multiplier 22 multiplies “value 2” by a predetermined constant 8 to obtain “value 3”. The constant 2 of the moving average filter 16 is set as a time constant, and the acceleration obtained by the acceleration calculator 15 is processed by the moving average filter 16 to obtain “value 4”. The second multiplier 17 multiplies “value 4” by a predetermined constant 3 to obtain “value 5”. Further, the jerk calculation unit 23 calculates the jerk from the acceleration output from the moving average filter 16. Using the constant 4 of the moving average filter 24 as a time constant, the jerk obtained by the jerk calculating unit 23 is processed by the moving average filter 24 to obtain “value 6”. The fourth multiplier 25 multiplies “value 6” by a predetermined constant 5 to obtain “value 7”. “Value 1”, “value 3”, “value 5”, and “value 7” are added, and the first adder 12 adds to the output of the position loop multiplier 10 as an FF command. In the position control in this case, as shown in FIG. 7, the position deviation is further improved by approaching 0 between 50 msec and 400 msec.

  As described above, in the numerical control device 4 of the present embodiment, the position deviation of the motor 2 of the machine tool 1 can be improved by adding the speed component to the FF command. Further, the position deviation of the motor 2 of the machine tool 1 can be further improved by adding the speed component and the acceleration component to the FF command. Further, by adding the velocity component, the acceleration component, and the jerk component to the FF command, the position deviation of the motor 2 of the machine tool 1 can be greatly improved.

In addition, this invention is not limited to the said embodiment, A various change is possible. For example, as in the second embodiment shown in FIG. 8, only the first-order LPF 19 may be used as the low-pass filter. In addition, the moving average filter 16 and the moving average filter 24
Is not necessarily provided. The numerical control device 4 includes a CPU, a ROM, and a RAM, and may be realized by software, or may be realized by a hard logic circuit or the like.

DESCRIPTION OF SYMBOLS 1 Machine tool 2 Motor 3 Encoder 4 Numerical control apparatus 5 Position control 6 Motor amplifier part 7 Speed control part 8 Torque control part 9 1st subtractor 10 Position loop multiplier 11 Position command input part 12 1st adder 13 1st speed Calculation unit 14 First multiplication unit 15 Acceleration calculation unit 16 Moving average filter 17 Second multiplication unit 18 Second speed calculation unit 19 Primary LPF
20 Primary LPF
21 Second subtractor 22 Third multiplication unit 23 Jerk calculation unit 24 Moving average filter 25 Fourth multiplication unit 30 FF generation unit

Claims (4)

Position detecting means for detecting the position of the motor to be controlled;
First subtracting means for obtaining a position deviation between the position of the motor and the position command fed back from the position detecting means, position loop multiplying means for multiplying the position deviation by a position proportional gain, and differentiating the position command. A first speed calculating means for obtaining a speed component; a first multiplying means for multiplying an output of the first speed calculating means by a predetermined constant; and an output of the first multiplying means as a feedforward command. In the numerical controller that adds to the output and outputs to the motor amplifier,
Acceleration calculation means for differentiating the position command twice to obtain an acceleration command;
Second multiplication means for multiplying the output of the acceleration calculation means by a predetermined constant;
Second speed calculation means for differentiating the position command to obtain a speed command;
A low-pass filter for filtering the output of the second speed calculation means;
Second subtracting means for subtracting the output of the low-pass filter from the output of the second speed calculating means;
Third multiplication means for multiplying the output of the second subtraction means by a predetermined constant;
And a first addition unit for calculating the feedforward command by adding the output of the second multiplication unit and the output of the third multiplication unit to the output of the first multiplication unit. Numerical control unit. Jerk calculation means for differentiating the output of the acceleration calculation means to obtain a jerk component;
A fourth multiplication means for multiplying the output of the jerk calculation means by a predetermined constant;
The first addition means adds the output of the first multiplication means, the output of the second multiplication means, the output of the third multiplication means, and the output of the fourth multiplication means to give a feedforward command. The numerical control device according to claim 1, wherein the numerical control device performs calculation.   The numerical control device according to claim 1, wherein the low-pass filter is provided in a plurality of stages.  A machine tool comprising the numerical control device according to claim 1.

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