JP2009101444A - Method of controlling position of rotating structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of controlling the position of a rotating structure capable of making a contribution over the achievement of accurate machining by accurately controlling the position. <P>SOLUTION: This method of controlling the position of a rotating structure comprises a first step of determining a coefficient of torsional rigidity K<SB>θR</SB>by calculating based on a predetermined function selected or pre-determined from a pre-determined table according to the position to be controlled R of the rotating structure 1, a second step of calculating an angular error Δθ using the determined coefficient of torsional rigidity K<SB>θR</SB>, and a third step of outputting the angular error Δθ as a correction amount. Since the coefficient of torsional rigidity K<SB>θR</SB>is selected according to the position to be controlled, the deformed amount of the rotating structure at each position can be accurately estimated, and the accurate positional control can be performed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control method for controlling the position of a rotating structure provided in, for example, a multi-axis machine tool.

In recent years, since products with higher added value are required, the use of multi-axis machine tools is increasing, and improvement of machining accuracy in the multi-axis machine tools is desired. Therefore, in order to enable highly accurate position control (rotation angle control), for example, a control device as described in Patent Document 1 has been devised.
Hereinafter, a control device described in Patent Document 1 and a position control method in the control device will be described. The control device described in Patent Document 1 includes a rotation speed detector and a rotation angle detector in the vicinity of the rotation shaft, and the control obtained from the rotation speed detector and the like assuming that the rotation shaft is a spring and a rigid body. A rotational angle error amount due to torsional deformation is estimated based on the information, and the torque command value is corrected based on the estimated value.

Japanese Patent Publication No. 6-38212

  Here, strictly speaking, when the rotating structure is rotated, the entire structure is not similarly deformed in the same manner, and therefore, the rotation angle error amount may be different for each position of the rotating structure. However, since the control method described in Patent Document 1 does not consider the situation, there is a difference between the calculated estimated amount and the actual rotational angle error amount at the specific position (control target position) of the rotating structure. The situation that it occurs occurs, and there is a problem that the reliability of the position control is poor.

  Therefore, the present invention has been made in view of the above problems, and can perform position control with high accuracy and can contribute to the realization of more accurate machining and the like. Is to provide.

  In order to achieve the above object, the present invention provides a position control method for correcting an angular error, which is an error in the rotating shaft of the rotating structure, based on a torque command output to a drive unit that rotates the rotating structure. The first step of determining the torsional stiffness coefficient by selection from a preset table or calculation based on a preset predetermined function according to the control target position of the rotating structure, and the determination The second step of calculating the angle error using the torsional rigidity coefficient and the third step of outputting the angle error as a correction amount are executed.

  According to the present invention, the position to be controlled is input to the angle error estimation device, the torsional stiffness coefficient at the position to be controlled is selected or calculated, and the angle error Δθ is calculated (estimated) using the torsional stiffness coefficient. Thus, the rotational operation of the drive unit is controlled while taking into account the angle error Δθ. Therefore, compared with the conventional position control that does not calculate the angle error according to the position to be controlled, it is possible to perform position control with higher reliability, and it is possible to improve the positioning accuracy and hence the processing accuracy. .

  Hereinafter, a position control method according to an embodiment of the present invention will be described.

First, the rotating structure 1 to be controlled by the control device will be described. FIG. 1 is an explanatory view showing the rotating structure 1, and FIG. 2 is an explanatory view schematically showing the rotating structure 1. In FIG. 2, the X-axis direction in FIG. 1 is shown as the front and back direction of the paper.
The rotating structure 1 is a trunnion-structured biaxial unit installed in a machine tool such as a 5-axis control vertical machining center, for example, and an X-axis with pivot shafts 4 and 4 supported by bearings (not shown) as an axis. And a trunnion 2 that can swing (rotate) around an A axis parallel to the head and a table 3 that can rotate on the trunnion 2.

On the other hand, a control device for controlling the operation of the trunnion 2 will be described with reference to FIG. FIG. 3 is a block diagram showing a control mechanism related to the rotation operation around the A axis.
As shown in FIG. 3, the control device is provided in the NC position command input from the NC device 10 and the motor (drive unit) 11 that rotates the trunnion 2 in connection with the control of the rotation operation of the trunnion 2 around the A axis. A position control loop is built so that the deviation from the position feedback signal from the angle detector 12 is zero. The speed control loop in which the speed control signal obtained by differentiating the position feedback signal by the differentiator 13 and the output signal from the position control unit 14 is compared by the speed control unit 15 is provided inside the position control loop. Is assembled. The torque command signal output from the speed control unit 15 is transmitted to the motor 11 via the torque / current control unit 16.

Furthermore, the angle of the control device, the torque command T _m output from the speed control unit 15 inputs the angle error estimator 20 calculates the angular error Δθ by elastic deformation of the trunnion 2, and to output a correction signal A correction loop is built, and the torsional stiffness coefficient _KθR is set in the table in advance in the angle error estimation device 20 so as to correspond to each point on the trunnion 2 (or on the table 3), that is, for each control target position R. Has been. Then, when the torque command _Tm is input to the angle error estimation device 20, the corresponding torsional stiffness coefficient _KθR is selected from the table based on the control target position R calculated and input based on the NC position command, The angle error Δθ is calculated by the following equation (1) and output as a correction amount. It should be noted that the rotational angular acceleration α is also calculated and input to the angle error estimating device 20 based on the NC position command. Further, the control target position R is a distance from the rotation center of the position to be corrected as shown in FIG. 2, and is calculated by the control target calculation unit 21 based on the NC position command. Furthermore, J _m in the following formula (1) is an inertia in the turning shaft portion 4 and the bearing.

Here, when describing a specific calculation of the angle error [Delta] [theta] based on FIG. 2, when calculating the angular error [Delta] [theta] ₁ in the controlled object position R _1, stiffness coefficient twisting in the controlled object position R ₁ stored in the table K _θR1 is selected, and the angle error Δθ ₁ is calculated from Δθ ₁ = (T _m −J _m · α) / K _θR1 . On the other hand, when calculating the angular error [Delta] [theta] ₂ in the controlled object position _{R 2,} select the stiffness coefficient K _Shitaaru2 torsion in the controlled object position _{R 2} stored in the _{table, Δθ 2 = (T m -J} m · α) The angle error Δθ _{2 is} calculated from / K _θR2 .

According to the position control method as described above, the control target position R input to the angle error estimating apparatus 20, selected from the table which is previously set the torsional rigidity coefficient K _.theta.R in the controlled object position R, the torsional rigidity The angle error Δθ is calculated (estimated) using the coefficient K _θR . Then, the rotational operation of the motor 11 is controlled while taking into account the angle error Δθ. Therefore, as compared with the conventional control device that does not calculate the angle error according to the control target position R, it is possible to perform position control with higher reliability, and to improve the positioning accuracy, and thus the processing accuracy. it can.

In addition, the structure which concerns on the control apparatus of this invention is not limited to the aspect as described in the said embodiment, It can change suitably as needed in the range which does not deviate from the meaning of this invention.
For example, in the above embodiment, the angle estimation error device stores in advance the torsional stiffness coefficient _KθR corresponding to each control target position, and the corresponding torsional stiffness coefficient _KθR corresponding to the input control target position. However, instead of this configuration, a predetermined function capable of calculating the torsional stiffness coefficient _KθR using the position to be controlled as a variable is stored in the angle estimation error device, and the angle error estimation device is The torsional stiffness coefficient _KθR may be calculated using a predetermined function based on the input control target position. In the above embodiment, the reference point for specifying the control target position R is the rotation center of the rotating structure. However, the reference point is provided on the table, and the control target position is specified by the distance from the reference point. May be.
Further, in estimating the angular error due to the elastic deformation of the control target position of the rotating structure, for each type of force resulting from the elastic deformation (for example, concentrated weighting such as gravity, rotational angular acceleration, external force and load weight), by selecting (calculated) by a function or a table torsional rigidity coefficient K _theta used, it is also possible to further improve the accuracy of the estimated angle error.
Further, the configuration of the rotating structure is not limited to the trunnion as described above, and there is no problem even if the table is a trunnion that does not turn.

It is explanatory drawing which showed the rotating structure. It is explanatory drawing which showed the rotation structure typically. It is the block block diagram which showed the control mechanism of the control apparatus.

Explanation of symbols

  1 .... Rotary structure 2 .... Trunnion 3 .... Table 4 .... Rotating shaft 10 .... NC device 11 .... Motor 12 .... Angle detector 13 .... Differentiator 14 ... -Position control unit, 15 ... Speed control unit, 16 ... Torque / current control unit, 20 ... Angle error estimation device, 21 ... Control target position calculation unit.

Claims (1)

A position control method for correcting an angular error, which is an error in the rotating shaft of the rotating structure, based on a torque command output to a drive unit that rotates the rotating structure,
A first step of determining a torsional stiffness coefficient by a selection from a preset table or a calculation based on a preset predetermined function according to a control target position of the rotating structure;
A second step of calculating an angle error using the determined torsional stiffness coefficient;
A position control method for a rotating structure that executes a third step of outputting the angle error as a correction amount.

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