JP4448219B2 - Dynamic deflection correction method in motion controller and motion controller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dynamic deflection correction method and a motion controller in a motion controller used for position control of a feed drive mechanism or the like of a machine tool.
[0002]
[Prior art]
A feed drive mechanism of a machine tool or the like linearly moves a driven part (moving object) such as a work table by a feed screw mechanism such as a ball screw driven by a servo motor, as shown in FIG. Can be represented by a model. In FIG. 3, T is a motor generated torque (Nm), θb is a motor rotation angle (rad), Jb is a rotary member total inertia (NmS ² ) of the feed drive mechanism, and Tb is a rotating portion friction torque (Nm) of the feed drive mechanism. , R is the rotation / linear conversion coefficient (m / rad) of the feed drive mechanism, K is the axial stiffness (N / m) of the feed drive mechanism, M is the amount of axially moving substance (Kg) of the feed drive mechanism, and Xt is The position (m) of the moving object and Ct are the friction coefficients (Ns / m) of the axially moving object such as the linear guide portion of the feed drive mechanism. Incidentally, the total rotary inertia Jb referred to here is the total of the rotor inertia of the servo motor, the coupling inertia of the feed screw portion, and the ball screw inertia.
[0003]
The servo control system that performs position control detects the rotational position (motor position) of the servo motor with a rotary encoder, calculates the deviation between the motor position detected by the rotary encoder and the command value, and makes the deviation zero. In other words, position control is performed so as to follow the position command.
[0004]
Therefore, if the axial rigidity K of the feed drive mechanism is infinite, the position of the moving object such as the work table is also correctly moved to the command position. However, the stiffness K is a finite value, and the feed drive mechanism produces axial deflection. For this reason, even if the motor rotation position is correctly controlled, an error occurs in the table position. Deflection occurs in correlation with inertial force and frictional force due to mass M.
[0005]
The error of reciprocation due to the deflection of the feed drive mechanism is called lost motion and is corrected by backlash correction. For backlash correction, the amount of lost motion is measured in advance under certain conditions, and this value is set as a parameter in the servo controller.When the servo controller reverses the axis movement direction, the servo motor is moved by an amount corresponding to the set value. This is done by driving extra.
[0006]
[Problems to be solved by the invention]
Lost motion is caused by the deflection of the feed drive mechanism in the axial direction due to the effects of frictional force and inertial force, whereas the optimum lost motion amount changes due to changes in the frictional force and inertial amount of the driven part. The driven part is normally supported by a guide mechanism, and friction exists in the guide mechanism. This frictional force changes depending on the moving speed, the mass of the load placed on the work table, and the like. The part has a mass, and an inertial force is generated when accelerating or decelerating. The inertial force also changes depending on the mass of the driven part. Therefore, the actual lost motion amount changes as the feed conditions change, so the optimum correction amount changes due to changes in the frictional force and inertial force of the driven part, which cannot be handled by the conventional backlash correction, resulting in a lost motion error. .
[0007]
In addition, in the conventional backlash correction, the correction amount is switched only when the moving direction is reversed, but the actual lost motion amount changes when the acceleration and friction force change, so the amount of lost motion during movement changes. It cannot be handled, and a lost motion error occurs.
[0008]
The present invention was made to solve the above-mentioned problems, and even when the amount of deflection of the drive system changes dynamically due to frictional force, mass change, etc. of the driven part, this is compensated appropriately. It is an object of the present invention to provide a dynamic deflection correction method in a motion controller and a motion controller used to implement the dynamic deflection correction method so as to obtain high positioning accuracy.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a dynamic deflection correcting method in a motion controller according to the present invention is a dynamic deflection correcting method in a motion controller that drives and controls a driven part that moves linearly by a feed screw mechanism driven by a servo motor. In this embodiment, the amount of deflection of the drive machine portion including the feed screw mechanism and the driven portion is estimated, the position command given to the servo motor is corrected based on the estimated amount of deflection, and the movement error of the driven portion is corrected. It is to reduce.
[0010]
In the dynamic deflection correcting method in the motion controller according to the present invention, the thrust of the driven part is measured by a thrust sensor, and the deflection amount is estimated from the thrust measurement value by the thrust sensor, or the value of the rotating object inertia and the rotation The friction coefficient of the system is set as a parameter, and the rotating object friction torque and rotating object inertia acceleration torque are calculated from the differential value of the parameter setting value and position command value, and the rotating object friction torque, rotating object inertia acceleration torque, and motor generation are calculated. The thrust of the driven part is calculated from the torque command value of the servo system representing the torque, and the deflection amount is estimated from the calculated thrust value.
[0011]
In order to achieve the above object, a motion controller according to the present invention is a motion controller that drives and controls a driven part that moves linearly by a feed screw mechanism driven by a servo motor. A deflection amount estimating means for estimating a deflection amount of a drive machine portion including a portion, and a position command correcting means for correcting a position command given to the servomotor based on the deflection amount estimated by the deflection amount estimation means. It is what.
[0012]
The motion controller according to the present invention has a thrust sensor for measuring the thrust of the driven part, and the deflection amount estimation means inputs a thrust measurement value by the thrust sensor and estimates the deflection amount from the thrust measurement value. To do.
[0013]
In addition, the motion controller according to the present invention has a parameter setting unit for setting parameters of the rotating object inertia and the friction coefficient of the rotating system, and the deflection amount estimation means inputs the parameter setting value from the parameter setting unit. The torque command value of the servo system is input as a representative value of the position command value and the motor generated torque, and the rotating object friction torque and the rotating object inertia acceleration torque are calculated from the parameter setting value and the differential value of the position command value, The thrust of the driven part is calculated from the rotating object friction torque, the rotating object inertia acceleration torque, and the torque command value, and the deflection amount is estimated from the calculated thrust value.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
(Embodiment 1)
FIG. 1 shows a first embodiment of a motion controller and a feed driving mechanism of a machine tool whose position is controlled by the motion controller according to the present invention.
[0015]
The feed drive mechanism of a machine tool has a work table 102 that is guided by a linear guide 101 on a fixedly arranged bed 100 and moves linearly in the horizontal direction in the drawing. The bed 100 rotatably supports a ball screw 107 by brackets 103 and 104 and bearing members 105 and 106, and a ball screw nut 108 that is screwed into the ball screw 107 is attached to the work table 102.
[0016]
The ball screw 107 is drivingly connected to the servo motor 110 by a coupling 109 and is rotationally driven by the servo motor 110. A rotary encoder 111 that detects the rotational position (motor position) of the servo motor 110 is attached to the servo motor 110.
[0017]
A thrust sensor 112 that measures the thrust of the driven portion (work table 102) is attached to the attachment portion of the ball screw nut 108 of the feed drive mechanism. The thrust sensor 112 can measure both the direction in which the thrust increases and the direction in which the thrust decreases.
[0018]
The motion controller (servo controller) includes a table position coordinate conversion unit 11 that converts the rotation position of the servo motor 110 detected by the rotary encoder 111 into table position coordinates and outputs a position field signal, and a table position coordinate conversion unit 11. The position command correction unit 12 that performs dynamic deflection correction by subtracting an estimated deflection amount described later from the table position indicated by the position field signal, and the deviation between the table position corrected by the position command correction unit 12 and the position command value is calculated. A position deviation calculator 13 for generating a speed command such that the position deviation becomes zero, and a differentiator 15 for differentiating the table position of the table position coordinate converter 11 to generate a speed feedback signal. And the speed command value output from the position controller 14 and the table shifter from the differentiator 15. A speed deviation calculation unit 16 that calculates a deviation from the speed, a speed controller 17 that generates a torque command so that the speed deviation becomes zero, and a torque command given by the speed controller 17 according to the torque command value The current command creating unit 18 for creating the current command and the servo amplifier 19 to which the current command is given from the current command creating unit 18 are configured.
[0019]
The motion controller includes a deflection amount estimation unit 20 that calculates an estimated deflection amount. The deflection amount estimation unit 20 receives the thrust measurement value from the thrust sensor 112 and performs the following calculation to estimate the deflection amount ΔX (m) of the feed drive mechanism.
ΔX = F / K (1)
[0020]
However, F: Thrust value measured by thrust sensor 112 (N)
K: Equivalent rigidity of feed drive mechanism (N / m)
[0021]
By subtracting this deflection amount ΔX (m) from the position feedback value obtained from the measurement result by the rotary encoder 111, the displacement due to the deflection in the axial direction is corrected. As a result, the value to be compared with the position command is a value reflecting an error occurring between the table position calculated from the motor rotation position due to the deflection of the feed drive mechanism due to the frictional force or inertial force of the guide portion, etc. The actual table position can be correctly controlled.
[0022]
The estimated deflection amount can be corrected by adding it to the position command side.
[0023]
(Embodiment 2)
FIG. 2 shows a second embodiment of a motion controller and a feed driving mechanism of a machine tool whose position is controlled by the motion controller according to the present invention. 2, parts corresponding to those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and description thereof is omitted.
[0024]
In this embodiment, a parameter setting unit 21 for setting parameters of the rotating object inertia value Jb (Nms ² ) and the friction coefficient Cb (Ns / rad) of the rotating system is provided, and the deflection amount estimating unit 22 The parameter setting value is input from the setting unit 21, and the torque command value output from the speed controller 17 is input as a representative value of the position command value and the motor generated torque Tm.
[0025]
The deflection amount estimation unit 22 calculates the rotating object friction torque Tb from the friction coefficient Cb of the rotating system and the differential value dθ / dt of the position command value, and the differential value d ² of the position command value of the rotating object inertia value Jb. The rotor inertia acceleration torque Ta is calculated from θ / dt ^2, the thrust F ′ of the driven part is calculated from the rotor friction torque Tb, the rotor inertia acceleration torque Ta, and the torque command value (Tm), and the calculated thrust value The amount of deflection is estimated from F ′.
[0026]
Here, the motor generated torque Tm is the sum of the following values.
(1) Rotating friction torque Tb (Nm)
(2) Rotating object inertia acceleration torque Ta (Nm)
(3) Axial moving friction torque Tc (Nm)
When the axial frictional force is Fc (N), Tc = R · Fc.
(4) Axial moving object acceleration torque Tam (Nm)
Tam = R · A · M where M (Kg) is the amount of moving substance in the axial direction, and A (m / s ² ) is the acceleration.
Therefore, the motor generated torque Tm (Nm) is
Tm = Tb + Ta + Tc + Tam (2)
It can be considered that this value is substantially equal to the torque command value.
[0027]
Various types of friction such as Coulomb friction and viscous friction can be considered as rotational friction. Here, a case where viscous friction occurs is considered. Rotation object inertia value Jb (Nms ² ) and rotation system friction coefficient Cb (Ns / rad) are set as parameters. As a result, the following calculation processing is performed by the deflection amount estimation unit 22.
The thrust of the work table is obtained by multiplying Tc + Tam by 1 / R and converting it in the axial direction. The value of Tc + Tam is obtained by modifying equation (2) and Tc + Tam = Tm−Tb−TA (3)
Can be obtained as follows.
[0028]
In order to obtain the rotating object friction torque Tb and the rotating object inertia acceleration torque Ta, first, the position command value is differentiated to obtain dθ / dt and d ² θ / dt ² . From this, the rotating object friction torque Tb and the rotating object inertia acceleration torque Ta are obtained by the following equations.
Tb = Cb (dθ / dt) (4)
Ta = Jb (d ² θ / dt ² ) (5)
By subtracting these values from the motor-generated torque Tm and dividing by the rotation / linear conversion coefficient R of the feed drive mechanism, the work table thrust F ′ can be calculated. Using this value, the deflection amount ΔX ′ is obtained from the equation (1), as in the first embodiment.
[0029]
The differential operation can actually be replaced by a difference operation by digital operation. In addition, although viscous friction is given as an example of rotating object friction, various frictional forces can be dealt with if the generation pattern of rotating object frictional force can be set with parameters.
[0030]
In addition, when the position of the machine is detected directly with a linear scale, etc., the inversion delay of the machine occurs due to the effect of the lost motion, and the inversion delay can be eliminated even for the phenomenon that deteriorates the machining accuracy, which is large An effect is obtained.
[0031]
【The invention's effect】
As understood from the above description, according to the dynamic deflection correction method and motion controller in the motion controller according to the present invention, the deflection amount of the drive machine portion including the feed screw mechanism and the driven portion is estimated, and the estimated The position command given to the servo motor is corrected based on the amount of deflection, and the movement error of the driven part is reduced, so even if the amount of deflection of the feed drive mechanism changes dynamically, this can be corrected appropriately, and the machine tool Machining accuracy is improved. In addition, the effects of changes in the weight of the load, changes in the frictional force of the guide portion, etc. can be eliminated. In particular, parameters that define the friction of the rotating system, the inertia value of the rotating system, and the axial rigidity are required as parameters, and these are less affected by the load and are therefore affected by changes in the load. Absent. Further, the deflection due to the processing reaction force is automatically corrected.
[0032]
Further, in the case where the thrust of the driven part is measured by the thrust sensor and the deflection amount is estimated from the thrust measurement value by the thrust sensor, it is not necessary to perform a complicated calculation for the estimation of the deflection amount, and it can be handled at high speed.
[0033]
In addition, the rotary object inertia value and the friction coefficient of the rotary system are set as parameters, and the rotary object friction torque and the rotary object inertia acceleration torque are calculated from the differential values of the parameter setting value and the position command value. A thrust sensor is not particularly required for calculating the thrust of the driven part from the torque command value of the servo system representing the inertia inertia acceleration torque and the motor generated torque, and estimating the deflection amount from the calculated thrust value.
[Brief description of the drawings]
FIG. 1 is a block diagram showing Embodiment 1 of a motion controller and a feed driving mechanism of a machine tool whose position is controlled by the motion controller according to the present invention.
FIG. 2 is a block diagram showing Embodiment 2 of a motion controller and a feed driving mechanism of a machine tool whose position is controlled by the motion controller according to the present invention;
FIG. 3 is a dynamic model diagram of a feed driving mechanism.
[Explanation of symbols]
11 Table position coordinate conversion unit 12 Position command correction unit 13 Position deviation calculation unit 14 Position controller 15 Differentiator 16 Speed deviation calculation unit 17 Speed controller 18 Current command generation unit 19 Servo amplifier 20 Deflection amount estimation unit 21 Parameter setting unit 22 Deflection amount estimation unit 100 Bed 101 Linear guide 102 Work table 107 Ball screw 108 Ball screw nut 109 Coupling 110 Servo motor 111 Rotary encoder 112 Thrust sensor

Claims (2)

In a dynamic deflection correction method in a motion controller that drives and controls a driven part that moves linearly by a feed screw mechanism driven by a servo motor,
Rotation object inertia value and friction coefficient of rotation system are set as parameters, and rotation object friction torque and rotation object inertia acceleration torque are calculated from the differential value of these parameter setting value and position command value. The thrust of the driven part is calculated from the torque command value of the servo system representing the material inertia acceleration torque and the motor generated torque, and the deflection of the drive machine part including the feed screw mechanism and the driven part is calculated from the thrust calculation value. A dynamic deflection correction method in a motion controller, wherein an amount is estimated, a position command given to the servomotor is corrected based on the estimated deflection amount, and a movement error of the driven portion is reduced. In a motion controller that drives and controls a driven part that moves linearly by a feed screw mechanism driven by a servo motor,
A deflection amount estimating means for estimating a deflection amount of a drive machine portion including the feed screw mechanism and the driven portion;
Position command correcting means for correcting a position command given to the servo motor based on the deflection amount estimated by the deflection amount estimating means;
It has a parameter setting unit that sets the parameter of the rotating object inertia and the friction coefficient of the rotating system,
The deflection amount estimation means inputs a parameter setting value from the parameter setting unit, and also inputs a servo command torque command value as a representative value of the position command value and motor generated torque, and the parameter setting value and the position command value. Rotating object friction torque and rotating object inertia acceleration torque are calculated from the differential value of, and the thrust of the driven part is calculated from the rotating object friction torque, rotating object inertia acceleration torque and the torque command value, and the calculated thrust value A motion controller characterized by estimating the amount of deflection more.

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