WO2018073873A1

WO2018073873A1 - Servo control device

Info

Publication number: WO2018073873A1
Application number: PCT/JP2016/080744
Authority: WO
Inventors: 佐藤　剛; 智哉藤田; 章田辺
Original assignee: 三菱電機株式会社
Priority date: 2016-10-17
Filing date: 2016-10-17
Publication date: 2018-04-26
Also published as: JP6333495B1; JPWO2018073873A1

Abstract

This servo control device (100) controls a motor (6) connected via a drive transmission mechanism to an object to be driven, and is provided with: a servo control unit (1) which calculates and outputs a torque command (201) to the motor (6) on the basis of a position command (200) and an amount of error correction (206) so that a machine edge position (203), which is a position of the object to be driven, is dictated by the position command (200); a movement direction detection unit (2) which detects the direction of movement of the machine edge position (203) on the basis of the position command (200); a skew amount calculation unit (3) which calculates an amount of skew (205) from the machine edge position (203) and a motor edge position (202), which is a position of the motor (6), and outputs the calculated amount of skew (205); and a correction amount calculation unit (4) which calculates said amount of error correction (206), using the amount of skew (205) as calculated when the direction of movement of the machine edge position (203) is reversed, and also using the mechanical characteristics of the object to be driven and the drive transmission mechanism.

Description

Servo control device

The present invention relates to a servo control device that drives a servo motor.

In the servo control device of a machine tool, the actuator is controlled so that the position of a driven body such as a table or a tool for fixing the workpiece follows the command. Examples of the actuator to be driven include a rotary motor and a linear motor. In a machine tool, control for driving a tool position with respect to a workpiece so as to accurately follow a command path, which is a commanded path, is referred to as path control or contour motion control, and is a numerical control device and a servo control device attached thereto. Is precisely executed by. The machine device to be controlled has a plurality of axes, and the servo motors constituting each axis are driven by the respective servo control devices.

Friction, backlash, and lost motion that exist in the mechanical system become disturbance factors for trajectory control in the servo control device, and cause follow-up errors. A typical example is a tracking error that occurs when the moving direction of the driven body along the feed axis is reversed at the arc quadrant switching position when an arc locus is commanded. If this error is displayed with the amount of error enlarged in the radial direction, it becomes a projection-like error outside the locus, so it is called a quadrant projection. When a tracking error such as a quadrant projection occurs, streaks or scratches are generated on the processed surface, which is not preferable.

In the conventional servo control device, in order to suppress the quadrant protrusion, when the moving direction of the driven body along the feed shaft is reversed, the servo control device is set in advance to compensate for each factor of backlash, elastic deformation, and static friction. The correction amount is added to the speed command (see Patent Document 1).

Japanese Patent No. 2607773

However, since friction and elastic deformation change depending on control conditions such as command speed or command trajectory, the method disclosed in Patent Document 1 needs to set a correction amount each time the control conditions such as command speed or command trajectory change. is there. In addition, since friction changes depending on environmental factors such as temperature, it is necessary to reset the correction amount each time the environmental factors change. For this reason, in order to perform high-accuracy correction on a command trajectory in which various control conditions are combined, it is necessary to readjust the correction amount with respect to the control conditions and environmental factors during processing, which requires a lot of trouble. There was a problem of requiring.

In addition, the correction amount and the correction time differ depending on the machine configuration, and even if the machines have the same configuration, there are individual differences. Therefore, there is a problem that it is necessary to adjust the correction amount for each machine, which takes time. Furthermore, when a servo control device that controls the position of a driven body using a drive transmission mechanism such as a rotary motor and a ball screw is controlled by a fully closed loop, the position measured by a position detector attached in the vicinity of the driven body The deviation from the position of the driven body calculated from the rotation angle measured by the rotation angle detector attached to the rotation motor that drives the mechanical system greatly affects the tracking error when the moving direction is reversed. Therefore, there is a problem that a sufficient correction effect cannot be obtained depending on the command locus.

The present invention has been made in view of the above, and an object of the present invention is to provide a servo control device capable of suppressing a tracking error with respect to a command locus of a machine end position when the moving direction of a driven body is reversed. And

In order to solve the above-described problems and achieve the object, the present invention is a servo control device for controlling a motor connected to a driven body via a drive transmission mechanism, based on a position command and an error correction amount. A servo control unit that calculates and outputs a torque command to the motor so that the machine end position, which is the position of the driven body, follows the position command, and detects the direction of movement of the machine end position based on the position command And a moving direction detecting unit. The present invention relates to a torsion amount calculation unit that calculates and outputs a torsion amount from a machine end position and a motor end position that is a motor position, a torsion amount when a moving direction is reversed, a driven body, and a drive transmission mechanism And a correction amount calculation unit that calculates an error correction amount using the mechanical characteristics of.

The servo control device according to the present invention has an effect that it is possible to suppress a tracking error with respect to the command locus of the machine end position when the moving direction of the driven body is reversed.

The figure which shows the structure of the numerical control apparatus concerning Embodiment 1 of this invention. The figure which shows the structure of the motor and mechanical system concerning Embodiment 1. FIG. The figure which shows the structure of the servo control part concerning Embodiment 1. FIG. The figure which shows the structure of the moving direction detection part concerning Embodiment 1. FIG. The figure which shows the structure of the twist amount calculating part concerning Embodiment 1. FIG. FIG. 3 is a diagram illustrating a configuration of a correction amount calculation unit according to the first embodiment. The motor and the mechanical system according to the first embodiment are modeled by a two-inertia system The motor and the mechanical system according to the first embodiment are modeled by a two-inertia system A diagram showing a two-inertia system model of a motor and a mechanical system according to the first embodiment in a block diagram The figure which shows the locus of the machine end position when the circular arc position command is given to the servo controller The figure which shows the locus of the machine end position when the circular arc position command is given to the servo controller The figure which shows the structure of the numerical control apparatus concerning Embodiment 2 of this invention. The figure which shows the structure of the moving direction detection part concerning Embodiment 2. FIG. The figure which shows the structure of the corrected amount calculating part concerning Embodiment 2. FIG. The figure which shows the structure of the numerical control apparatus concerning Embodiment 3 of this invention. The figure which shows the structure of the servo control part concerning Embodiment 3. The figure which shows the hardware constitutions in the case of implement | achieving the function of the numerical control apparatus concerning Embodiment 1-4 from a computer

Hereinafter, a servo control device according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of a numerical control apparatus 101 according to the first embodiment of the present invention. The numerical control device 101 includes a position command generation unit 5 that generates a position command 200 and a servo control device 100 that outputs a torque command 201 based on the position command 200. The servo control device 100 is connected to the motor 6 and the mechanical system 7, and drives the mechanical system 7 that is a control target by giving a torque command 201 to the motor 6. When the mechanical device to be controlled by the numerical control device 101 has a plurality of axes, the servo control device 100, the motor 6, and the mechanical system 7 are provided on each axis, but only one axis is shown in FIG.

The servo control device 100 includes a servo control unit 1 that outputs a torque command 201, a movement direction detection unit 2 that outputs a movement direction signal 204, a twist amount calculation unit 3 that outputs a twist amount 205, and an error correction amount 206. And an output correction amount calculation unit 4.

FIG. 2 is a diagram illustrating the configuration of the motor 6 and the mechanical system 7 according to the first embodiment. The motor 6 includes a servo motor 61 and a motor end position detector 62. A specific example of the motor end position detector 62 is a rotary encoder. The motor end position detector 62 is attached to the servo motor 61 and detects a motor end position 202 that is the rotation angle of the servo motor 61.

The mechanical system 7 includes a coupling 70 that transmits the power of the servo motor 61, a ball screw 71 that is rotationally driven by the servo motor 61, a ball screw nut 72 that converts the rotation of the ball screw 71 into a linear motion, and a ball screw. And a table 73 which is a driven body fixed to the nut 72. The ball screw 71 is connected to the servo motor 61 via the coupling 70. The ball screw nut 72 is fitted to the ball screw 71, and the table 73 and the ball screw nut 72 are driven together. The coupling 70, the ball screw 71, and the ball screw nut 72 constitute a drive transmission mechanism from the motor 6 to the table 73. Therefore, the mechanical system 7 includes a driven body and a drive transmission mechanism.

The machine tool having the numerical control device 101 further includes a linear encoder having a machine end position detector 74 and a scale 75. A specific example of the scale 75 is a glass surface having a grid-like scale. The machine end position detector 74 reads the scale 75 and outputs it as a signal. The signal output from the machine end position detector 74 is converted into the machine end position 203 that is the position of the table 73 that is the driven body, and is output to the servo control device 100.

Assuming that the detection unit of the rotation angle detected by the motor end position detector 62 is degrees, multiply the motor end position 202 by a ball screw lead, which is a table movement amount per rotation of the servo motor 61, at 360 degrees. The rotation angle can be converted into the length of the table 73 in the moving direction. Here, the moving direction is a direction along the axis that the servo control device 100 is in charge of, and the direction of the moving direction can be either positive or negative. In the following description, a value converted into the moving direction of the table 73 is used as the motor end position 202.

The position command generator 5 numerically controls the machine end position 203 by generating a position command 200 based on the machining program. The machining program is a program in which a tool for machining a workpiece and how to move the mechanical system 7 are described in a series of formats by an instruction such as a G code. In the machining program, the moving distance and moving speed of the tool and the mechanical system 7 with respect to the workpiece are determined. The position command generator 5 calculates a position command 200 for each axis based on the machining program, and outputs it to the servo control device for each axis.

The servo control device 100 receives the position command 200 generated by the position command generation unit 5 and is obtained from the motor end position 202 detected by the motor end position detector 62 and the signal output by the machine end position detector 74. The machine end position 203 is acquired. The servo control device 100 uses the motor end position 202 and the machine end position 203 as position feedback, generates a torque command 201 so that the machine end position 203 follows the position command 200, and outputs the torque command 201 to the motor 6.

FIG. 3 is a diagram illustrating a configuration of the servo control unit 1 according to the first embodiment. The servo control unit 1 includes a position control unit 11, a speed control unit 12, a differential calculation unit 13, subtracters 14 and 16, and an adder 15.

The subtractor 14 obtains a position deviation that is a difference between the position command 200 and the machine end position 203 and outputs the position deviation to the position control unit 11. The position control unit 11 executes position control processing such as proportional control with respect to the position deviation, and calculates and outputs a speed command. The adder 15 adds a speed command and an error correction amount 206 calculated by the correction amount calculation unit 4 described later and outputs the result. The differential calculation unit 13 differentiates the motor end position 202 and outputs a motor end speed that is a differential value of the motor end position 202. The subtracter 16 obtains a speed deviation that is a difference between the output of the adder 15 and the motor end speed, and outputs the speed deviation to the speed control unit 12. The speed control unit 12 executes a predetermined speed control process such as proportional integral control with respect to the speed deviation, and calculates and outputs a torque command 201 that causes the machine end position 203 to follow the position command 200.

FIG. 4 is a diagram illustrating a configuration of the moving direction detection unit 2 according to the first embodiment. The moving direction detection unit 2 includes a position control simulation unit 21, an integration calculation unit 22, a sign calculation unit 23, and a subtracter 24. The movement direction detection unit 2 simulates the response of the machine end position 203 based on the position command 200 and outputs a movement direction signal 204 indicating the direction of the movement direction of the table 73.

The subtractor 24 obtains the difference between the position command 200 and the model position that is the output of the integral calculation unit 22 and outputs the difference to the position control simulation unit 21. The position control simulation unit 21 simulates the position control unit 11 of the servo control unit 1. The position control simulation unit 21 executes the same position control processing as the position control unit 11 on the difference between the position command 200 input from the subtractor 24 and the model position, and uses the obtained speed command as a model speed. Output. The model speed output by the position control simulation unit 21 corresponds to the calculated value of the speed in the table 73. The integration calculation unit 22 obtains a calculated value of the machine end position 203 by integrating the model speed and outputs it as a model position. The sign calculation unit 23 detects whether the moving direction of the table 73 is positive or negative based on the model speed, takes a positive or negative sign according to the moving direction, and the absolute value is “1”. The movement direction signal 204 which is a step-like signal is output. Thereby, the timing at which the moving direction of the table 73 is reversed can be accurately detected. The sign calculation unit 23 outputs the same movement direction signal 204 as the previous time when the model speed becomes 0, and outputs “0” as the movement direction signal 204 in the initial state.

FIG. 5 is a diagram illustrating a configuration of the twist amount calculation unit 3 according to the first embodiment. The twist amount calculation unit 3 includes

differential calculation units

31 and 32, a unit conversion unit 33, and subtractors 34 and 35. The torsion amount calculation unit 3 receives the motor end position 202 and the machine end position 203 as inputs, and calculates and outputs a torsion amount 205 caused by friction for each calculation cycle. The torsion amount 205 is an amount based on a deviation between the motor end position 202 and the machine end position 203. This deviation includes a component caused by frictional force and a component caused by inertial force. The component resulting from the inertia force is a component due to elastic deformation of the mechanical system 7. In the torsion amount calculation unit 3, in order to calculate the torsion amount 205 as a deviation due to friction, a deviation due to inertial force is obtained and removed from the deviation between the motor end position 202 and the machine end position 203.

The motor end position 202 is second-order differentiated by the

differential operation units

31 and 32 connected in series, and the motor end acceleration am of the motor 6 is calculated and output to the unit conversion unit 33. The unit conversion unit 33 calculates and outputs a deviation due to inertial force by multiplying the input motor end acceleration am of the motor 6 by a predetermined coefficient. The coefficient will be described later. The subtractor 34 obtains a deviation between the motor end position 202 and the machine end position 203 and outputs it to the subtractor 35. The subtractor 35 subtracts the deviation of the component caused by the inertial force output by the unit conversion unit 33 from the entire deviation inputted, thereby calculating and outputting the twist amount 205 that is the deviation of the component caused by friction. To do. As a result, the torsion amount 205 due to friction can be calculated with high accuracy.

FIG. 6 is a diagram illustrating a configuration of the correction amount calculation unit 4 according to the first embodiment. The correction amount calculation unit 4 includes a correction gain calculation unit 41 and a mechanical characteristic filter 42. The correction amount calculation unit 4 receives the twist amount 205 output from the twist amount calculation unit 3 and the movement direction signal 204 output from the movement direction detection unit 2 and outputs an error correction amount 206.

The correction gain calculation unit 41 can determine that the moving direction is reversed when the direction of the moving direction of the table 73 changes based on the moving direction signal 204. When the moving direction of the table 73 is reversed, that is, when the moving direction signal 204 changes from “+1” to “−1”, or when the moving direction signal 204 changes from “−1” to “+1”. A correction gain is calculated based on the twist amount 205 at that time. As a specific example of the correction gain calculation method, the correction gain is calculated by multiplying the twist amount 205 by the correction magnification. The correction gain is set to 0 except when the moving direction of the table 73 is reversed. Then, the correction gain calculation unit 41 outputs an impulse signal whose amplitude is the magnitude of the correction gain to the mechanical characteristic filter 42. Therefore, the correction gain calculation unit 41 outputs an impulse signal having the amplitude of the correction gain as an amplitude to the mechanical characteristic filter 42 when the moving direction of the table 73 is reversed. The mechanical characteristic filter 42 filters the output of the correction gain calculation unit 41 with a transfer function type filter that represents mechanical characteristics, and corresponds to the elapsed time after the moving direction of the table 73 to be controlled is reversed. An error correction amount 206 is calculated and output. The setting of the mechanical characteristic filter 42 will be described later.

Next, the principle of correction in the servo control apparatus 100 according to the first embodiment will be described. 7 and 8 are diagrams in which the motor 6 and the mechanical system 7 according to the first embodiment are modeled by a two-inertia system. 7 and 8, K is the spring constant of the elastic element of the mechanical system 7, C is the viscous friction coefficient of the damping element of the mechanical system 7, Jm is the inertia of the motor 6, and Jl is the mechanical system 7 , FM is a friction force acting on the motor 6, and FL is a friction force acting on the mechanical system 7. 7 and 8, the position of Jm imitates the motor end position 202, and the position of Jl imitates the machine end position 203. The reason why Jm and Jl are separated through the elastic element is that a deviation occurs between the motor end position 202 and the machine end position 203 due to elastic deformation caused by the frictional force generated between the motor 6 and the mechanical system 7. It expresses that.

7 and 8, the horizontal direction on the paper surface indicates the movement direction of the motor end position 202 and the machine end position 203, and both show how the movement of the machine end position 203 follows the movement of the motor end position 202. ing. FIG. 7 shows a case where the motor end position 202 and the machine end position 203 are moved in the + direction of the movement direction, and FIG. 8 shows that the motor end position 202 and the machine end position 203 are moved in the − direction of the movement direction. Shows the case. In FIG. 7, the force by the elastic element acting in the + direction on Jl and the frictional force FL are balanced. On the other hand, in FIG. 8, the force by the elastic element acting in the negative direction on Jl and the frictional force FL are balanced. When the direction of the moving direction of the table 73 is reversed, the positional relationship between the motor end position 202 and the machine end position 203 is reversed, so the positions of Jm and Jl are changed from FIG. 7 to FIG. 8 or from FIG. 8 to FIG. The relationship also changes. As a result, the direction of the force due to the elastic element acting on Jl is reversed, and the acting direction of the frictional force FL is also reversed.

FIG. 9 is a block diagram showing a two-inertia system model of the motor 6 and the mechanical system 7 according to the first embodiment. Tm is a torque output from the servo motor 61 in accordance with the torque command 201, xl is a variable indicating the machine end position 203, xm is a variable indicating the motor end position 202, and s is a Laplace operator representing differentiation. . xm, respectively those of xl and FL and Laplace _transform, when X M, _{X L} and _{F L,} the value obtained by Laplace transform a deviation between the motor end position 202 and the machine end position 203, the following equation (1) Represented.

Here, A _M is one where the motor end acceleration am the differentiating unit 32 and output to Laplace transform. The motor end acceleration am is a value obtained by second-order differentiation of the motor end position 202. Further, ω _n is a resonance frequency of the mechanical system 7, and ζ is a damping coefficient of the mechanical system 7.

The first term in parentheses on the right side of the last line of Equation (1) is a term due to frictional force, and the second term in parentheses is a term due to inertial force. When the moving direction of the table 73 is reversed, the sign of the twist amount, which is a deviation due to the frictional force of the first term, is reversed with the reversal of the acting direction of the frictional force. When the moving direction of the table 73 is reversed, it is necessary to move the motor end position 202 steeply in a stepwise manner to reverse the moving direction. However, only the feedback control causes a delay in the movement of the motor end position 202. As a result, the reversal of the moving direction of the machine end position 203 is delayed, and a tracking error of the machine end position 203 with respect to the position command 200 occurs. The tracking error Et of the machine end position 203 corresponding to the elapsed time since the direction of the movement direction of the motor end position 202 is reversed is expressed by the following formula (2) because the amount of change in the frictional force at the time of reversal is 2FL. It is.

In the servo control device 100 according to the first embodiment, the follow-up error is suppressed by compensating the follow-up error Et represented by Expression (2). The second term in parentheses on the right side of the last line of Equation (1) is a deviation caused by inertial force. Therefore, the twist amount calculation unit 3 removes the deviation due to the inertial force of the second term from the entire deviation as described above. From Equation (1), the coefficient multiplied by the unit conversion unit 33 may be the reciprocal 1 / ω _n ^{2 of the} square of the resonance frequency of the mechanical system 7. The resonance frequency ω _n can be identified by examining the frequency response characteristics.

As described above, the torsion amount 205 output from the torsion amount calculation unit 3 is a deviation caused by the frictional force and is a value corresponding to FL / K. The correction gain calculation unit 41 calculates the correction gain by doubling the twist amount 205.

Further, the tracking error Et at the machine end position 203 depends on the spring constant K and the viscous friction coefficient C indicating the mechanical characteristics of the mechanical system 7. For this reason, it is necessary to perform correction in consideration of the mechanical characteristics of the mechanical system 7. According to Expression (2), the mechanical characteristic filter 42 may be set as a transfer function type filter Gf (s) represented by the following Expression (3). Gf of formula (3) (s) is the transfer function multiplied by K to transfer characteristics from the friction force F _L acting on the mechanical system 7 to torsion amount of 2 inertia model shown in FIGS.

10 and 11 are diagrams showing the locus of the machine end position when an arc-shaped position command is given to the servo control device. In both FIG. 10 and FIG. 11, a clockwise arc-shaped position command is given to two axes of the X axis and the Y axis which are orthogonal to each other. In order to realize the arc-shaped position command, it is necessary to provide the servo control device 100, the motor 6, and the mechanical system 7 according to the first embodiment for each of the X axis and the Y axis.

FIG. 10 shows the locus of the machine end position when feedback control for the position command is executed without correcting the follow-up error Et of the machine end position 203. The broken line in FIG. 10 indicates the command locus, and the solid line indicates the locus of the machine end position. The locus error at the position where the moving direction along the Y axis is reversed is displayed in an enlarged manner, and a large protrusion is generated. This is a quadrant projection caused by the tracking delay.

FIG. 11 is a diagram illustrating an effect when the correction by the servo control device 100 according to the first embodiment is executed. Also in FIG. 11, the broken line indicates the command locus and the solid line indicates the locus of the machine end position, as in FIG. 10, but the quadrant protrusion is suppressed by the correction at the position where the moving direction along the Y axis is reversed. Therefore, the broken line and the solid line overlap.

As described above, according to the servo control device 100 according to the first embodiment, the twist amount 205 is always obtained, and the error correction amount 206 is calculated using the twist amount 205 when the moving direction is reversed. The tracking error Et of the machine end position 203 caused by the friction force when the moving direction is reversed can be accurately corrected, and robust correction is performed for control conditions such as command speed or command trajectory and environmental factors such as temperature. There is an effect that becomes possible.

Furthermore, according to the servo control apparatus 100 according to the first embodiment, the error correction amount 206 is calculated by using the mechanical characteristic filter 42 in which the mechanical characteristic of the mechanical system 7 is represented by a transfer function type filter. Thus, there is an effect that the tracking error Et of the machine end position 203 at the time of reversing the moving direction of the table 73 can be accurately corrected.

Embodiment 2. FIG.
FIG. 12 is a diagram showing a configuration of the numerical controller 301 according to the second embodiment of the present invention. The numerical control device 301 includes a position command generation unit 5 that generates a position command 200 and a servo control device 300 that outputs a torque command 201 based on the position command 200. In FIG. 12, the same components as those in FIG. 1 according to the first embodiment are given the same names and reference numerals as those in the first embodiment, and the description thereof is omitted. In the following, the difference between the numerical control device 301 and the numerical control device 101 according to the first embodiment will be mainly described.

FIG. 13 is a diagram illustrating a configuration of the moving direction detection unit 320 according to the second embodiment. The movement direction detection unit 320 includes a differential calculation unit 324 in addition to the position control simulation unit 21, the integration calculation unit 22, the sign calculation unit 23, and the subtractor 24. The movement direction detector 320 simulates the response of the machine end position 203 based on the position command 200 and outputs a model acceleration 207 in addition to outputting a movement direction signal 204 indicating the direction of the movement direction of the mechanical system 7. To do.

The differentiation calculation unit 324 calculates a model acceleration 207 that is a calculated value of the acceleration at the machine end position 203 by differentiating the model speed output from the position control simulation unit 21. The movement direction detection unit 320 outputs the model acceleration 207 together with the movement direction signal 204 to the correction amount calculation unit 340.

FIG. 14 is a diagram illustrating a configuration of the correction amount calculation unit 340 according to the second embodiment. The correction amount calculation unit 340 includes a correction gain calculation unit 341, a mechanical characteristic filter 42, and a correction magnification table 343. The correction magnification table 343 is a table showing correction magnifications T0, T1,..., Tn corresponding to reference model accelerations a0, a1,. A correction magnification corresponding to the model acceleration 207 received by the correction amount calculation unit 340 in the correction magnification table 343 is input to the correction gain calculation unit 341. Depending on the mechanical characteristics of the mechanical system 7, the necessary correction amount changes depending on the acceleration of the table 73 at the time of reversal, and thus the correction magnification is changed depending on the model acceleration 207. The correction gain calculation unit 341 calculates the correction gain by multiplying the twist amount 205 and the correction magnification when the movement direction signal 204 changes, as in the first embodiment.

As described above, in the second embodiment, the correction magnification is determined based on the model acceleration 207 that is the state quantity of the servo control device 300 at the time of inversion. As the state quantity on which the correction magnification depends, other state quantities of the servo control device 300 may be used instead of the model acceleration 207 depending on the structure or characteristics of the mechanical system 7. As a specific example of the other state quantity, a calculated value related to the position or speed other than the acceleration calculated from the position command 200 using any model may be used. Further, as the state quantity, a history of a position feedback value that is an actual measurement value such as the motor end position 202 or the machine end position 203 at the time of reversal, and a speed feedback value that is a differential value of the position feedback value may be used. A specific example of the history of the speed feedback value is the maximum speed of the speed feedback value within a certain time before inversion. Further, the temperature or temperature of the motor 6 or the mechanical system 7 may be used as the state quantity. The correction magnification may depend on two or more of the state quantities described above.

As described above, according to the servo control device 300 according to the second embodiment, the correction magnification is changed according to the state quantity of the servo control device 300, so that it is based on the mechanical characteristics of the mechanical system 7 for each control condition. There is an effect that can be corrected. Furthermore, robust correction can be made against changes in environmental factors.

Embodiment 3 FIG.
FIG. 15 is a diagram illustrating a configuration of a numerical control device 401 according to the third embodiment of the present invention. The numerical control device 401 includes a position command generation unit 5 that generates a position command 200 and a servo control device 400 that outputs a torque command 201 based on the position command 200. In FIG. 15, the same components and elements as those in FIG. In the following, differences between the numerical control device 401 and the numerical control device 101 according to the first embodiment will be mainly described.

The servo control device 400 further includes a vibration command generation unit 8 and a machine model identification unit 9 in addition to the components of the servo control device 100. The vibration command generator 8 outputs a vibration command 208 to the servo controller 410 when identifying the machine model. Here, the machine model is a transfer function that depends on the mechanical characteristics of the mechanical system 7 and is a transfer function from the motor end position 202 to the machine end position 203.

FIG. 16 is a diagram illustrating a configuration of the servo control unit 410 according to the third embodiment. The

subtractors

43 and 45 and the adder 44 perform the same operations as the

subtracters

14 and 16 and the adder 15 of FIG. In FIG. 16, an adder 46 is further provided. The vibration command 208 is input to the adder 46 and output as a torque command 201, and the motor 6 is driven to vibrate the mechanical system 7. When this vibration is performed, the position command 200 and the error correction amount 206 are both set to zero. As long as the vibration command 208 is input to the servo control unit 410, unlike FIG. 16, the vibration command 208 may be input to the position control unit 11 as the position command 200, or input to the speed control unit 12 as a speed command. Also good. In these cases, the same vibration effect can be obtained.

The machine model identification unit 9 uses the measured values of the motor end position 202 and the machine end position 203 when the motor 6 is driven by the vibration command 208 to vibrate the mechanical system 7, and uses the measured values from the motor end position 202 to the machine end. The transfer function Gm (s) up to position 203 is identified. When the motor 6 and the mechanical system 7 are modeled by a two-inertia system as shown in FIGS. 7 and 8, the transfer function Gm (s) is expressed by the following formula (4).

Based on the measured values of the motor end position 202 and the machine end position 203, the machine model identification unit 9 uses a method such as a least square method, a spectrum analysis method, or a subspace method to transfer the transfer function of Equation (4). Gm (s) can be identified. Using Jl, C, and K calculated from the identified transfer function Gm (s), the transfer function type filter Gf (s) given by Equation (3) is determined. The machine model identification unit 9 outputs the transfer function type filter Gf (s) thus obtained to the correction amount calculation unit 4 as a mechanical characteristic filter 209. The correction amount calculation unit 4 uses the transfer function type filter Gf (s) received as the mechanical characteristic filter 209 for the mechanical characteristic filter 42, and calculates and outputs an error correction amount 206 based on this. By using the error correction amount 206, the servo control unit 410 can perform robust correction suitable for the mechanical characteristics of the mechanical system 7.

As described above, the servo control device 400 according to the third embodiment further includes the vibration command generation unit 8 and the machine model identification unit 9, so that a new sensor is not added. 7 has the effect of automatically identifying a transfer function representing the mechanical characteristics of No. 7.

Embodiment 4 FIG.
The configuration of the numerical control device 401 and the servo control unit 410 according to the fourth embodiment is the same as that of the third embodiment shown in FIGS. 15 and 16.

The vibration command generator 8 of the servo control device 400 according to the fourth embodiment performs vibration while moving the motor 6 and the mechanical system 7. Therefore, the vibration command 208 is a signal obtained by adding the movement component and the vibration component. The moving component is a command to move in one direction at a constant speed. Then, the vibration command 208 to which a random vibration signal is added as a vibration component at the timing when the speed is constant is used. The moving component may be another command such as a reciprocating motion, and the excitation component may be a sine sweep signal that changes the frequency of the sine wave stepwise.

Similarly to the third embodiment, the machine model identification unit 9 uses the actual measurement values of the motor end position 202 and the machine end position 203 when the vibration command 208 is vibrated, from the motor end position 202 to the machine end position 203. The transfer function Gm (s) up to is identified. However, in the fourth embodiment, since the vibration command 208 includes a movement component and an excitation component, the machine model identification unit 9 determines the movement component from the measured values of the motor end position 202 and the machine end position 203. And the transfer function Gm (s) is identified from the measured values of the motor end position 202 and the machine end position 203 with respect to the vibration component. As a specific example of the method for removing the moving component, the measured values of the motor end position 202 and the machine end position 203 when the vibration command 208 of only the moving component is given in advance are measured, and the measured motor end position 202 is measured. Further, the actual measurement value of the machine end position 203 is subtracted from the actual measurement values of the motor end position 202 and the machine end position 203 when the vibration command 208 including the vibration component is given. A method for identifying the transfer function Gm (s) represented by Expression (4) from the measured values of the motor end position 202 and the machine end position 203 from which the moving component has been removed, and a transfer function type filter given by Expression (3) The method for determining Gf (s) is the same as in the third embodiment.

As described above, in the servo control device 400 according to the fourth embodiment, the mechanical model identifying unit 9 removes the influence of the frictional force by performing vibration using the vibration command 208 including the moving component and the vibration component. Identification becomes possible. When vibration is performed in a state where the mechanical system 7 is stopped, in the mechanical system 7 having a large frictional force, the vibration amplitude at the machine end position 203 becomes small due to the influence of friction, and the transfer function type filter Gf (s) is reduced. Although there is a case where the measurement cannot be performed with high accuracy, according to the servo control device 400 according to the fourth embodiment, since the vibration command 208 includes a moving component, the transfer function type filter Gf (representing the mechanical characteristics of the mechanical system 7) The effect that s) can be identified more accurately is obtained.

FIG. 17 is a diagram illustrating a hardware configuration when the functions of the numerical control device according to the first to fourth embodiments are realized by a computer. When the functions of the

numerical control devices

101, 301, and 401 are realized by a computer, the functions of the

numerical control devices

101, 301, and 401 are, as shown in FIG. 17, a CPU (Central Processing Unit) 51, a memory 52, an interface 53, and a dedicated device. This is realized by the circuit 54. Some of the functions of the

numerical control devices

101, 301, and 401 are realized by software, firmware, or a combination of software and firmware. Software or firmware is described as a program and stored in the memory 52. The CPU 51 implements the functions of each unit by reading and executing the program stored in the memory 52. That is, the

numerical control devices

101, 301, and 401 are programs that, as a result, execute steps of the

numerical control devices

101, 301, and 401 when the functions of the respective units are executed by the computer. A memory 52 for storing is provided. These programs can also be said to cause a computer to execute the procedures or methods of the

numerical control apparatuses

101, 301, and 401. Here, the memory 52 is a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Nonvolatile Memory, or an EEPROM (Electrically Erasable Memory) A semiconductor memory, a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, and a DVD (Digital Versatile Disk) are applicable.

The CPU 51 reads out and executes the program stored in the memory 52, thereby realizing the functions of the position command generation unit 5, the correction

amount calculation units

4 and 340, the twist amount calculation unit 3, and the movement

direction detection units

2 and 320. . The interface 53 has a function for receiving the motor end position 202 and the machine end position 203. A specific example of the dedicated circuit 54 is an inverter circuit of the

servo control units

1 and 410. As described above, the

numerical control devices

101, 301, and 401 can realize the above-described functions by hardware, software, firmware, or a combination thereof.

The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

1,410 Servo control unit, 2,320 Movement direction detection unit, 3 Twist amount calculation unit, 4,340 Correction amount calculation unit, 5 Position command generation unit, 6 Motor, 7 Mechanical system, 8 Excitation command generation unit, 9 Machine model identification unit, 11 position control unit, 12 speed control unit, 13, 31, 32, 324 differential operation unit, 21 position control simulation unit, 22 integral operation unit, 23 sign operation unit, 33 unit conversion unit, 41, 341 Correction gain calculation unit, 42, 209 mechanical characteristic filter, 51 CPU, 52 memory, 53 interface, 54 dedicated circuit, 61 servo motor, 62 motor end position detector, 70 coupling, 71 ball screw, 72 ball screw nut, 73 Table, 74 Machine end position detector, 75 scale, 100, 300, 400 Servo control , 101, 301, 401 numerical control device, 200 position command, 201 torque command, 202 motor end position, 203 machine end position, 204 movement direction signal, 205 twist amount, 206 error correction amount, 207 model acceleration, 208 vibration Command, 343 Correction magnification table.

Claims

A servo control device for controlling a motor connected to a driven body via a drive transmission mechanism,
A servo control unit that calculates and outputs a torque command for the motor based on a position command and an error correction amount so that a machine end position that is the position of the driven body follows the position command;
A moving direction detector that detects the direction of the moving direction of the machine end position based on the position command;
A torsion amount calculation unit that calculates and outputs a torsion amount from the machine end position and a motor end position that is the position of the motor;
A correction amount calculation unit that calculates the error correction amount using the twist amount when the moving direction is reversed, and mechanical characteristics of the driven body and the drive transmission mechanism;
A servo control device comprising:
2. The servo according to claim 1, wherein the twist amount calculation unit calculates the twist amount by removing a component due to an inertial force included in a deviation from a deviation between the machine end position and the motor end position. Control device.
The servo control device according to claim 1, wherein the mechanical characteristic is a transmission characteristic from a frictional force acting on the driven body and the drive transmission mechanism to the torsion amount.
The said moving direction detection part calculates | requires the calculated value of the speed of the said to-be-driven body by simulating the said servo control part, and detects the direction of the said moving direction based on the said calculated value. 4. The servo control device according to any one of 3 to 3.
The correction amount calculation unit calculates the error correction amount by filtering an impulse signal having an amplitude that is a correction gain obtained by multiplying the twist amount by a correction magnification based on the mechanical characteristics. The servo control device according to any one of claims 1 to 4.
The correction magnification depends on at least one of a value calculated from the position command, the machine end position, the motor end position, the motor temperature, the temperature of the driven body, the temperature of the drive transmission mechanism, and the air temperature. The servo control device according to claim 5, wherein the servo control device is changed.
An excitation signal generation unit that generates an excitation signal to be input to the servo control unit;
A machine model identification unit for identifying a transfer function from the motor end position to the machine end position from the measured value of the motor end position and the machine end position when the excitation signal is input to the servo control unit When,
The servo control device according to claim 1, further comprising:
The servo control device according to claim 7, wherein the excitation signal is a signal obtained by adding a movement component and an excitation component.