JP2002096232A - Controlling method for machine tool - Google Patents

Controlling method for machine tool

Info

Publication number
JP2002096232A
JP2002096232A JP2000287424A JP2000287424A JP2002096232A JP 2002096232 A JP2002096232 A JP 2002096232A JP 2000287424 A JP2000287424 A JP 2000287424A JP 2000287424 A JP2000287424 A JP 2000287424A JP 2002096232 A JP2002096232 A JP 2002096232A
Authority
JP
Japan
Prior art keywords
value
traveling plate
step
parallel link
link mechanism
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP2000287424A
Other languages
Japanese (ja)
Inventor
Hiromitsu Ota
浩充 太田
Original Assignee
Toyoda Mach Works Ltd
豊田工機株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Toyoda Mach Works Ltd, 豊田工機株式会社 filed Critical Toyoda Mach Works Ltd
Priority to JP2000287424A priority Critical patent/JP2002096232A/en
Publication of JP2002096232A publication Critical patent/JP2002096232A/en
Pending legal-status Critical Current

Links

Abstract

PROBLEM TO BE SOLVED: To provide a controlling method for a machine tool capable of controlling a parallel link mechanism with high accuracy. SOLUTION: Position and attitude of a traveling plate after driven and controlled by command values for the position and attitude of the traveling plate are acquired as actual measured values by a step S10. A compliance value is determined based on the actual measured values acquired and the command values by a step S12. The determined compliance value is applied to a transformation formula for transforming the command values imparted in an orthogonal coordinate system into output values of an actuator by a step S14. As a result, a prescribed parameter included in the transformation formula has the application of the compliance value based on the actual measured values and thereby an error included in the output values of the actuator by the transformation formula can be reduced. Therefore, the parallel link mechanism can be controlled with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for controlling a machine tool, and more particularly to a method for controlling a machine tool using a parallel link mechanism.

[0002]

2. Description of the Related Art Conventionally, as a machine tool using a parallel link mechanism, there is a "tool hand and a machine tool using the same" disclosed in JP-A-9-66480. According to this, a command value of a position and a posture of a tool tip given in an orthogonal coordinate system is converted into an output value of each actuator (rotation angle of each servo motor).

That is, in the case of a machine tool using a parallel link mechanism as shown in FIG. 15, command values (x,
y, z, A, B, C) from the command value (U,
The conversion to u, V, v, W, w) is performed as follows on the u axis, for example.

First, an equation of a straight line in a rectangular coordinate system of a u-axis (ball screw 4u) fixed to the base 1 at a predetermined angle K is obtained, and then a first command value (x, y, z,
The coordinates Tu of the ball joint 7u when the traveling plate 2 is moved to (A, B, C) are calculated in a rectangular coordinate system. Thereafter, an equation of a sphere having a radius R (length R of the rod 5u) centered on the coordinates Tu is obtained, and an intersection of the sphere and the straight line is calculated from the equation of the sphere and the previously obtained straight line equation. The distance between the intersection and the origin Ou of the u-axis is determined, and this value is set as a command value u1 converted into an output coordinate system.

In this conversion, in addition to the predetermined angle K of the ball screw 4 fixed to the base 1 and the length R of the rod 5, an offset value depending on the mounting position of the ball screw 4 with respect to the base 1, a traveling plate A mechanism parameter such as an offset value depending on the mounting position of the rod 5 with respect to 2 is required, and a design value is generally used for each.

However, according to the machine tool of this type of parallel link mechanism, the above-mentioned mechanical parameters are set to design values due to machining errors and assembly errors of mechanical parts such as the ball screw 4, rod 5, and ball joints 6, 7. , And there is at least an error. Therefore, the error of the mechanism parameter causes an error in the conversion from the command value of the rectangular coordinate system to the output value of the actuator, and an error occurs in the actual position and posture control of the tool tip. Had occurred.

[0007] The present applicant has solved such a problem by using a "method of controlling a machine tool" disclosed in Japanese Patent Application Laid-Open No. H11-114777. That is, based on a command value for the position and orientation of the traveling plate and an actual measured value of the position and orientation of the traveling plate after drive control based on the command value, a parameter for correcting an error in drive control is calculated, and the orthogonal coordinate system is calculated. Is converted into the output value of the actuator based on the parameter, and the actuator is controlled. Thereby, the command value given in the rectangular coordinate system is converted into an output value of the actuator based on a parameter for correcting an error in drive control, and the parallel link mechanism is driven by the actuator controlled by the output value. Even if there are machining errors or assembly errors in the mechanical parts that make up the link mechanism,
The parallel link mechanism can be controlled with high accuracy.

[0008]

However, since the mechanical components constituting the parallel link mechanism have their own weights, their own weights cause elastic deformation of the traveling plate, rod, ball screw, and the like. The present inventor has confirmed through experiments that the amount of elastic deformation changes when the load balance distributed to each axis changes depending on the position and posture of the traveling plate and the like.

That is, as shown in FIG. 16, the axial load of the rod 5u when the angle of the A-axis (the rotation angle around the x-axis) is changed at the origin position is small and uniform when the angle is 0 °. Has been confirmed to become largely non-uniform as the angle increases. This means that a change in the load due to the position or posture of the traveling plate 2 or the like may cause a change in the amount of elastic deformation of each part, and may also cause a decrease in positioning accuracy. Therefore, the "method of controlling a machine tool" disclosed in the above-mentioned publication does not consider such a change in the amount of elastic deformation due to a change in the position and orientation, and therefore, the positioning based on the change in the amount of elastic deformation. A decrease in accuracy cannot be sufficiently prevented.

Therefore, the present applicant solves such a technical problem by controlling the parallel link mechanism in consideration of elastic deformation by the “parallel link mechanism control method and control device” according to the earlier application. Solved. That is, the mechanism parameters are corrected based on the amount of elastic deformation generated respectively from the forces applied to the traveling plate, the plurality of rods, and the plurality of actuators according to the target position and posture, and the tool unit of the tool unit is corrected based on the corrected mechanism parameters. The position information of a plurality of actuators corresponding to the target position is obtained. As a result, even if the load balance distributed to each axis changes due to a change in the position and posture, it is possible to prevent a decrease in positioning accuracy due to a change in the amount of elastic deformation.

However, the present applicant has come to know from the subsequent examination that the earlier application has the following technical problems. That is, in this “parallel link mechanism control method and control device”, the inverse conversion is performed by changing the mechanism parameters according to the target position and orientation, but the amount of change in the mechanism parameters depends on each member. It is determined by multiplying the applied force by the compliance value of each member (a value indicating the softness of the mechanism). As the compliance value, a design value estimated in advance is used. Therefore, when the inverse conversion is performed using the compliance value based on such a design value, there is a problem that even if a decrease in the positioning accuracy can be prevented to some extent, a demand for a stricter positioning accuracy cannot be sufficiently satisfied. . That is, if the compliance value for correcting the mechanism parameter includes an error, the correction of the mechanism parameter may be insufficient, and a positioning error may occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a method of controlling a machine tool capable of controlling a parallel link mechanism with high accuracy.

[0013]

According to a first aspect of the present invention, there is provided a method for controlling a machine tool, comprising: a base fixed externally; and a traveling base held on the base via a parallel link mechanism. A plate, a tool attached to the traveling plate, a plurality of actuators for driving the parallel link mechanism, and a control device for controlling the actuator by converting a command value given in a rectangular coordinate system into an output value of the actuator. A method of controlling the machine tool comprising: a first step of acquiring as a measured value the position and orientation of the traveling plate after drive control by a command value for the position and orientation of the traveling plate; and A second step of obtaining a compliance value based on the actually measured value obtained in the step and the command value; And a third step of applying the compliance value obtained in the second step to a conversion equation for converting a command value given in the rectangular coordinate system into an output value of the actuator. I do.

According to a second aspect of the present invention, in the control method for a machine tool according to the first aspect, the compliance value is one of mechanism parameters related to the base, the traveling plate, the parallel link mechanism, and the plurality of actuators. Thus, a technical feature is that the mechanical parameters are determined at the same time as the mechanical parameters determined based on the measured values and the command values.

Further, in the method of controlling a machine tool according to a third aspect, in the first or second aspect, in the second step, the compliance value is optimized by a predetermined convergence calculation. .

According to the first aspect of the present invention, in the first step, the position and orientation of the traveling plate after the drive control based on the command values for the position and orientation of the traveling plate are obtained as actual measurement values, and in the second step,
A compliance value is obtained based on the measured value and the command value obtained in the first step, and the compliance value obtained in the second step is converted into a command value given in a rectangular coordinate system into an output value of the actuator in a third step. Applied to the conversion formula. Thereby, since the predetermined parameter included in the conversion formula is applied with the compliance value based on the actually measured value, the error included in the output value of the actuator by the conversion formula can be reduced.

According to the second aspect of the present invention, the compliance value is a mechanism parameter obtained based on an actual measurement value and a command value among mechanism parameters relating to the base, the traveling plate, the parallel link mechanism, and the plurality of actuators; Required at the same time. Thereby, the compliance value can be obtained in parallel with the predetermined processing for obtaining such a mechanism parameter.

According to the third aspect of the present invention, in the second step, the compliance value is optimized by a predetermined convergence calculation. Thus, the accuracy of the compliance value obtained in the second step can be improved.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for controlling a machine tool according to the present invention will be described below with reference to the drawings. FIG.
FIG. 1 is a diagram showing a configuration of an entire machine tool to which a machine tool 10 of the present embodiment is applied.

The machine tool 10 is mounted on a ceiling of a gate-shaped frame 50 via a supporting column 51.
Table 52 is located below the table. A workpiece (not shown) is placed on the table 52 at the time of machining, and a measurement jig 60 or a surface plate is placed on the table 52 when measuring the position and orientation of the traveling plate 12 as actual measurement values as described later. .

The machine tool 10 is essentially for mounting a tool (not shown) in place of the measuring device 40 shown in the figure and moving the tool to a desired position by movement control by the control device 70 to machine the workpiece. However, here, the present embodiment of the machine tool 10 at the time of adjustment before factory shipment or at the time of on-site adjustment, that is, the measuring device 40 used for calculating the mechanism parameters and the compliance value from the actually measured values of the position and orientation of the traveling plate 12 and the like are described. Machine tool 10 mounted
And its control method will be described.

As shown in FIG. 2, the machine tool 10 mainly includes
A base 11 fixed to the outside by a support column 51, a traveling plate 12 for mounting a tool such as a measuring instrument 40 and a drill, and six arms 14U, 14u connecting the traveling plate 12 to the base 11 described above. 14V,
14v, 14W, and 14w. (Hereinafter, unless otherwise specified, “14U, 14u, 14V, 14
Descriptions such as "v, 14W, 14w" are collectively described as "14U-w". )

The base 11 is a hexagonal flat plate member, and three sets of support portions 11U and 11u, 11V and 11
v, 11W and 11w are provided at equal intervals. Each support 11U-w has an arm 14 to be described later.
Uw are mounted radially in three directions as a set of two parallel Uw.

Since the construction of each arm 14U-w is the same, the arm 14U is constituted by a rod 15U and a guide 20U. The length is set to a predetermined length L. The guide 20U includes a base 22U,
The servo motor 25U includes a slide table 26U, a ball screw 24U, and a motor position detecting encoder 31U.

The base 22U is a member having a U-shaped cross section.
It is fixed to the support portion 11U of the base 11 radially at an inclination (for example, 45 degrees). A slide table 26U is slidably supported on the base 22U in the longitudinal direction. The base 22U has a ball screw 2 screwed with a nut (not shown) of the slide table 26U.
4U is rotatably supported, fixed to the base 22U and connected to the ball screw 24U.
By driving 5U, the ball screw 24U is rotated, and as a result, the slide table 26U is moved to the base 22U.
Move in the longitudinal direction.

A rod 15U is connected to the slide table 26U by a ball joint 16U, and the rod 15U can swing three-dimensionally with respect to the slide table 26U with the ball joint 16U as a fulcrum. The other end of the rod 15 is connected to the traveling plate 12U by a ball joint 17U, and the rod 15U can swing three-dimensionally with respect to the traveling plate 12U with the ball joint 17U as a fulcrum.

The traveling plate 12 is a flat plate member having a hexagonal shape smaller than the base 11, and the other end of the rod 15U is connected on the same plane by a ball joint 17U. The lower part of the traveling plate 12 has a shape to which a tool such as a measuring instrument 40 and a drill can be attached.

As shown in FIG. 3, the control device 70
U71, memory 72, interface (I / F) 73,
74 and 75. The memory 72 stores a program for executing a process for calculating a mechanism parameter and a compliance value, which will be described later, and an actual machining process.

The interface 73 includes a digital servo unit 8 for driving the aforementioned servo motor 25U-w.
1 to 86 are connected. Each of the digital servo units 81 to 86 drives a servo motor 25U-w based on a command value from the CPU 71, and performs feedback control by output from each motor position detection encoder 31U-w. Then, by moving the slide table 26U-w driven by the servo motor 25U-w to a desired position, as a result, the traveling plate 12 connected via the six rods 15U-w is moved to the desired position. And posture.

The interface 74 stores a keyboard (KB) 76 for inputting processing data and the like to be described later, an image display (CRT) 77 for displaying the processing data and the current state of the machine tool 10, and the processing data. An external storage device (for example, a hard disk) 78 is connected. The input / output data is exchanged with the CPU 71. The measuring device 40 and the like described below are connected to the interface 75, and are configured to output data input from these devices to the CPU 71.

As shown in FIG. 4 and FIG.
Are mainly dial gauges 44, 45, 46, a mirror 49 attached to the lower portion of the traveling plate 12,
It comprises goniometers 47 and 48 attached to the upper part of the traveling plate 12. Then, the positional error amounts of the traveling plate 12 in the x-axis, y-axis, and z-axis directions are measured by the dial gauges 44, 45, and 46, respectively, and the angle error amounts of the A-axis, B-axis, and C-axis are measured by the angle meter 4.
7, 48, and a mirror 49 is used for measurement.

The dial gauges 44, 45, and 46 are mounted on the traveling plate 12 via the support portion 41. The mounting position is determined when the traveling plate 12 at the time of measurement moves to a predetermined position as described later. Each of the measuring units 44 a, 45 a, and 46 a is set at a position where the measuring jig 60 can abut on the reference pin 63. The position error amount in the x-axis direction measured by the dial gauge 44, the position error amount in the y-axis direction measured by the dial gauge 45, and the position error amount in the z-axis direction measured by the dial gauge 46 are determined by a control device described later. 70 and are used to calculate mechanism parameters and compliance values.

The mirror 49 is also attached to the traveling plate 12 via the support portion 41, and is positioned so as to be able to reflect the laser beam emitted from the direction perpendicular to the plane of FIG. The laser beam reflected on the mirror surface 49a of the mirror 49 is received by a sensor (not shown) to measure the C-axis angle error.

On the other hand, the goniometers 47 and 48 mounted on the upper part of the traveling plate 12 detect the tilting state of the traveling plate 12, thereby detecting the A axis and the B axis, respectively.
The angle error of the shaft is measured. The angle error of the A axis measured by the goniometer 47 and the angle error of the B axis measured by the goniometer 48 are also output to the control device 70, and are combined with the angle error of the C axis by the sensor described above. To calculate mechanism parameters and compliance values.

As shown in FIG. 6, the measuring jig 60 used in the measuring device 40 is, for example, a plate 61 formed in a disk shape and a plurality (for example, nine) provided on the surface thereof.
And a reference pin 63. The position where the reference pin 63 is provided and the posture (shape such as length and thickness) of the reference pin 63 are determined according to predetermined conditions, and are arranged at equal intervals on the same circumference, for example.

Using the measuring device 40 and the measuring jig 60 configured as described above, the position and orientation of the traveling plate 12 are measured as follows. First, command values (x, y, z, A, B, and C) of the rectangular coordinate system of each reference pin provided on the measurement jig 60 are input to the control device 70. For example, in the present embodiment, nine command values are input to the reference pins 63. Next, the orthogonal coordinate system command value of the first reference pin 63 is converted into the output coordinate system command value (U, u, V, v,
W, w) is converted to the output command value of each servo motor 25U.
Then, the traveling plate 12 to which the measuring device 40 is attached is moved to the target position of the first reference pin 63. Traveling plate 1
2 is completed, the x-axis, the y-axis, and the z-axis of the traveling plate 12 are controlled by the dial gauges 44, 45, 46, the goniometers 47, 48, and the sensors constituting the measuring device 40.
The axial position error amount and the A-axis, B-axis, and C-axis angle error amounts are respectively measured. By performing the same measurement for the second and subsequent reference pins 63, the measurement of the tool tip coordinates at a plurality of points (9 points in the present embodiment) is completed.

As an example of an alternative to the measuring device 40, there is one using a double ball bar (hereinafter referred to as "DBB"). The DBB will be described next with reference to FIGS. As shown in FIG.
The DBB 160 measures the displacement of a bar having balls attached to both ends, that is, the displacement of the distance between two points.
By attaching this to the lower surface of the traveling plate 12, the distance between the traveling plate 12 and the fixed point S is measured. Thereby, a mechanism parameter and a compliance value are estimated.

As shown in the cross section in FIG.
Is composed of a bar 162 provided with balls (iron balls) 164 and 166 at both ends, and the ball 164 and the bar 162 are connected by a spherical joint using a permanent magnet. The bar 162 includes a pair of bars 162A and 162B that are contractably combined, and a detection device 168 that outputs the contracted displacement amount is provided therein. This detection device 186
The length of the bar 162, that is, the distance r between the center of the ball 164 and the center of the ball 166 is detected based on the amount of displacement from.

Here, the traveling plate 12 is
The jig 140 is attached, and a fixing point S1 is provided on a table (not shown) provided on the table 52 shown in FIG. The tip of the first jig 140 and the fixing point S1 is the ball 1 of the DBB 160.
64 and 166 are magnetized.

By tilting the DBB 160 by about 45 °, errors in the traveling plate 12 not only in the x and y directions but also in the z direction can be detected from the distance r (see FIG. 7). In this state, the traveling plate 12 is moved to draw a circle. FIG. 8B is a plan view of this drawn circle (command value) (FIG. 7 viewed from above). And
The trajectory actually drawn by the traveling plate 12 is shown in FIG.
It is shown in (C). As shown in the figure, the trajectory deviates from the circle on the command value in accordance with the error amount of the mechanism parameter described above. For this reason, some points of the moving distance r of the traveling plate 12 are obtained, and the mechanism parameters and the compliance value are estimated from the measured distance r by the least square method so as to minimize the error.

The measurement by the DBB 160 will be described in more detail with reference to FIGS. Here, three points (fixed points S1, S2, S3) are taken as fixed points and measurement is performed. As shown in FIG. 10, the fixed points S1, S
2, the fixed point S2 and the fixed point S3 of the machine tool 1
It is taken parallel to the y-axis of 0, so that the fixed points S1, S2, S3 are equilateral triangles. Here, the fixed points S1, S2, S
By making 3 an equilateral triangle with a side of 300 mm, a length of 300
The position is calibrated by the DBB 160 of mm, and the distance between the fixed points is set accurately.

Then, as shown in FIG. 9, each of the fixing points S is fixed by using a jig 143 capable of holding the ball 164 of the DBB 160 at three positions not on the same straight line.
The distances between 1, S2, and S3 and three points that are not on the same straight line are measured by drawing a circle as shown in the figure. As a result, the distance from the fixed points S1, S2, S3, which are known coordinates, to the tool tip can be measured at three points. Based on the measured distance r, the mechanism parameters and the compliance value are estimated as described later.

Next, with reference to FIGS. 11 to 14, a description will be given of a process of calculating a mechanism parameter and a compliance value, and further performing an inverse transformation using the calculated mechanism parameter and the compliance value to obtain an actuator coordinate.

[1] Step S10 As shown in FIG. 11, first, in step S10, a process of acquiring measurement data for calibration is performed. In this process, the above-described machine tool 10 is controlled based on the actuator coordinates obtained by the inverse transformation in consideration of the elastic deformation, and data is acquired by the measuring device 40 or the DBB 160.

Here, a series of processes for obtaining the actuator coordinates by the inverse transformation in consideration of the elastic deformation is shown in FIG.
This will be described with reference to FIGS. Note that this inverse transformation is usually performed to obtain the actuator coordinates with respect to the target tool tip coordinates. Specifically, the following equations (1) to (5) are used.
It is calculated as shown in

[0046]

(Equation 1)

(Equation 2)

(Equation 3)

(Equation 4)

(Equation 5) Here, RL and SA used in the above equations (1), (3) to (5) are used.
1, SA2, BO1, BO2, BO3, SL, SO, J
As shown in FIG. 5, O, TO, TPO1, TPO2, and TPO3 are parameters representing the geometrical dimensions of the machine.
This is called a “mechanism parameter”. Equation (2)
X, y, and z used in FIG. 13 represent positions in the rectangular coordinate system shown in FIGS. 13 and 14, and A, B, and C represent rotations about the x, y, and z axes.

For example, the U axis shown in FIGS. 13 and 14 will be described. BO1, BO2, BO3 are slides 22
13 (A), (B), and FIG. 14 show the distances (base offsets) in the x, y, and z directions from the starting point of the base 11 to the center of the base 11.
(A)), TPO1, TPO2, and TPO3 represent distances (TP offset) in the x, y, and z directions from the ball joint 17U connecting the traveling plate 12 and the rod 15U to the center of the traveling plate 12 (FIG. 13). (A), (C), FIG. 14 (B)).

SA1 is composed of slide 22U and xy
The angle formed by the plane (slider mounting angle) and SA2 represent the angle formed by the slide 22U and the xz plane (slider mounting angle), respectively (FIGS. 13A, 13B, and 14A).
). However, on the V (v) axis and the W (w) axis, 1
These are the distance and angle as viewed from the coordinate system rotated by 20 ° and 240 °.

Further, RL is the length of the rod 15U (rod length), JO is the offset value (joint offset) of the ball joint 16U connecting the slide 22U and the rod 15U from the center of the ball screw 24, and SO is the actuator shaft. , SL represents the length of the slide 22 (slider length), and TO represents the amount of protrusion (TP offset) from the traveling plate 12 to the tip of the tool (FIG. 5A). in this way,
Each parameter is defined for the U axis, but each parameter is defined for the other axes (u axis, V axis, v axis, W axis, and w axis) in the same manner as the U axis.

Since the inverse transformation is performed based on the above equations (1) to (5), each parameter in these equations is replaced by a mechanism parameter and a compliance value optimized by the processing described later. (Motor 25U-w, ball screw 2)
The error included in the output value of 4) can be reduced.

As shown in FIG. 12, first, the mechanism parameters are set to initial values (S20), and then the inverse transformation is performed in a no-load state, that is, a state in which the elastic deformation is ignored, and the actuator coordinates are calculated (S22). Next, after calculating the unit vector in the rod axis direction and the angle of each joint from the calculated actuator coordinates (S24, S26), the force applied to each member is decomposed into the axial direction and the bending direction (S24).
28).

Here, it is determined whether or not the difference between the determined force and the previously determined force is sufficiently small, that is, whether the difference is within the range of the allowable error ε (S30). If it is within the range of the allowable error ε (No in S30), the process ends (EN
D) If not (Yes in S30), the amount of elastic deformation of each member due to the difference in force is calculated (S32), and the value of the mechanism parameter is corrected (S34). The modified mechanism parameters are used in the next S36. In calculating the amount of elastic deformation of each member due to the difference in force in step S32, the force applied to each member is multiplied by the compliance value of each member. As the first compliance value, a design value estimated in advance is used.

In the last step S36, the inverse transformation is performed using the corrected mechanism parameters, and the actuator coordinates are calculated again. Then, based on the obtained actuator coordinates, the processing of steps S24 to S36 is repeated again. That is, the convergence calculation is repeated until the difference between the forces obtained in step S28 becomes sufficiently small, that is, until the difference falls within the range of the allowable error. Accordingly, the amount of elastic deformation in step S32 can be more accurately obtained, and thus the actuator coordinates can be appropriately obtained by inverse transformation in consideration of the elastic deformation. After controlling by using the inverse transformation in consideration of such elastic deformation, the measuring device 40 or D
The process of acquiring data by the BB 160 is performed in step S1.
Performed with 0.

[2] Step S12 Next, in step S12, a process for optimizing the mechanism parameters and the compliance values is performed. That is, the relationship (forward conversion equation) between the tool tip coordinates acquired in step S10, the actuator coordinates, the mechanism parameters, and the compliance values is defined as shown in the following equation (6).

[0055]

(Equation 6) x, y, z, A, B, and C indicate tool tip coordinates, d indicates actuator coordinates (U, u, V, v, W, w), pk indicates mechanism parameters, and pc indicates compliance values.

Next, when both sides of the above equation (6) are fully differentiated with respect to changes in mechanism parameters and compliance values, the following equation is obtained.
The relational expression shown in (7) is obtained. In the following mathematical formulas, those expressed corresponding to the tool tip coordinates (x, y, z, A, B, C) (for example, formula (7)) are as follows:
Since x, y, z, A, B, and C can be similarly described, x will be described below as a representative, and y,
The description of z, A, B, and C is omitted.

(Equation 7)

Then, regarding this equation (7), the tool tip seat
X is the measured value of the targetm, The nominal value of the mechanism parameter is pk
N, The nominal value of the compliance value is pcNAnd d
x is the position error of the tool tip δx = g (d, pkN, P
cN) -Xm, Dpki, Dpc iEach parameter
Data error δpki= PkNi-Pki, Δpcj= PcNj
-PcjIs replaced by the following equation (8):
It is.

[0058]

(Equation 8) The above equation (8) is an approximate equation that is satisfied when the parameter error is sufficiently small.

Here, the partial differential coefficient ∂g / ∂p of the above equation (8)
Since i cannot be calculated directly, the value of the error g at a certain position d is obtained by a convergence calculation such as Newton's method from an inverse transformation equation, and p i + Δp i / 2, p i −Δp i / 2
Is replaced with the difference value of the error g in. Then,
The difference relational expression shown in (9) is obtained.

[0060]

(Equation 9)

Then, the parameter error δp
The least squares method is applied using k i and δpc j as unknown variables. That is, the tool tip position error δx obtained from the measured value
And a tool tip position error δx ′ calculated from the estimated parameter errors δpk i ′ and δpc i ′ (δx−δ
x ′) is represented by the following equation (10).

[0062]

(Equation 10)

Therefore, the difference (δx
−δx ′) is optimized to minimize the parameter. Here, with respect to the tool tip position errors .delta.x k obtained from k measurements, the following equation (11), (12), defining the respective matrix shown in (13), the parameter error E p for determining a minimum of 2 It is calculated by the following equation (14) using the multiplication method.

[0064]

[Equation 11]

(Equation 12)

(Equation 13)

[Equation 14]

From this result, the first estimated value p (1) of the parameter is obtained by the following equation (15).

(Equation 15)

The parameters obtained in this way are replaced with nominal values, and the calculations by the equations (8) to (15) are subtracted by the difference (δ
x−δx ′) is sufficiently reduced. That is, the convergence calculation is performed until the difference (δx−δx ′) becomes smaller than the predetermined value. Thus, the accuracy of the compliance value optimized in step S12 can be increased.

When the above-mentioned measured value is measured by the DBB 160, the above equation (6) is replaced by the following equation (16). In this case, r indicates the distance r measured by the DBB 160 (see FIGS. 7 and 8).

[0068]

(Equation 16)

When only the compliance value is obtained, the mechanism parameter pk can be similarly obtained by the above-described equations by setting the mechanism parameter pk to a constant.

[3] Step S14 Next, in step S14, a process of replacing the optimized mechanism parameters and the like with the parameters in the inverse conversion equation is performed. That is, the mechanism parameters and the compliance values optimized in step S12 are calculated using the above-described equations (1) to (1).
A process for replacing each parameter in the inverse transformation equation by (5) is performed. In the present embodiment, for example, RL, SA1, SA
2, BO1, BO2, BO3, SL, SO, JO, T
Each parameter of O, TPO1, TPO2, and TPO3 is to be replaced.

As described above, according to the control method according to the present embodiment, in step S10, the position and orientation of the traveling plate 12 after the drive control based on the command values for the position and orientation of the traveling plate 12 are used as measured values. In step S12, a compliance value is obtained based on the obtained measured value and command value in step S12, and in step S14, the obtained compliance value is converted from a command value given in a rectangular coordinate system to an output value of an actuator. Applies to equations (Equations (1)-(5)).
Thereby, predetermined parameters (for example, RL, SA1, SA2, BO1, BO2, BO) included in the conversion formula
3, SL, SO, JO, TO, TPO1, TPO2, T
Since PO3) receives the compliance value based on the actually measured value, it is possible to reduce an error included in the output value of the actuator by the conversion formula. Therefore, there is an effect that the parallel link mechanism can be controlled with high accuracy.

Further, according to the control method according to the present embodiment, the compliance value is determined by the base 11, the traveling plate 12, the arm 14U-w, the rod 15U-w, the ball joint 16U-w, 17U-w, and the guide 20U.
Among the mechanical parameters related to -w, the base 22U-w, the ball screw 24U-w, the slide table 26U-w, the servomotor 25U-w, etc., the mechanical parameters obtained based on the actually measured values and the command values are the same. Required at the time. Thereby, the compliance value can be obtained in parallel with the predetermined processing for obtaining such a mechanism parameter. Therefore, there is an effect that high-precision control of the parallel link mechanism can be performed at high speed.

Further, according to the control method according to the present embodiment, in step S12, the obtained parameters are replaced with nominal values, and the calculation by the equations (8) to (15) is performed by the difference (δx
The compliance value is optimized by the convergence calculation repeated until −δx ′) becomes sufficiently small. Thereby, the accuracy of the compliance value obtained in step S12 can be improved. Therefore, there is an effect that the control of the parallel link mechanism can be further improved.

[0074]

According to the first aspect of the present invention, in the first step, the position and the posture of the traveling plate after the drive control based on the command values for the position and the posture of the traveling plate are acquired as the actually measured values.
A compliance value is obtained based on the measured value and the command value obtained in the first step, and the compliance value obtained in the second step is converted into a command value given in a rectangular coordinate system into an output value of the actuator in a third step. Applied to the conversion formula. Thereby, since the predetermined parameter included in the conversion formula is applied with the compliance value based on the actually measured value, the error included in the output value of the actuator by the conversion formula can be reduced. Therefore, there is an effect that the parallel link mechanism can be controlled with high accuracy.

According to the second aspect of the present invention, the compliance value includes a mechanism parameter obtained based on an actual measurement value and a command value among mechanism parameters relating to the base, the traveling plate, the parallel link mechanism, and the plurality of actuators; Required at the same time. Thereby, the compliance value can be obtained in parallel with the predetermined processing for obtaining such a mechanism parameter. Therefore, there is an effect that high-precision control of the parallel link mechanism can be performed at high speed.

According to the third aspect of the invention, in the second step, the compliance value is optimized by a predetermined convergence calculation. Thus, the accuracy of the compliance value obtained in the second step can be improved. Therefore, there is an effect that the control of the parallel link mechanism can be further improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a mechanical configuration of an entire machine tool controlled by a machine tool control method according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a mechanical configuration of the machine tool shown in FIG.

FIG. 3 is a block diagram illustrating a configuration of a control device of the machine tool illustrated in FIG. 1;

FIG. 4 is an explanatory view showing a measuring device and a reference pin used in the control method of the machine tool according to the embodiment.

FIG. 5 is a view taken in the direction of the arrow V in FIG. 4;

FIG. 6 is a plan view showing a measuring jig used in the control method according to the embodiment.

FIG. 7 is a schematic diagram showing another measuring device (DBB) used in the control method according to the embodiment.

8A is a schematic sectional view of a DBB, FIG. 8B is an explanatory view showing a trajectory based on a movement command value of the parallel link mechanism, and FIG. 8C is an actual diagram of the parallel link mechanism. FIG. 4 is an explanatory diagram showing a movement locus.

FIG. 9 is a schematic diagram showing a measurement state of a parallel link mechanism using a DBB.

FIG. 10 is a plan view showing fixed points of a parallel link mechanism using a DBB.

FIG. 11 is a flowchart illustrating processing of a control method according to the present embodiment.

FIG. 12 is a flowchart illustrating control of a parallel link mechanism performed when acquiring measurement data for calibration.

FIG. 13 is an explanatory diagram showing each mechanism parameter relating to the parallel link mechanism. FIG. 13 (A) shows mechanism parameters SA1,
RL, BO1, TO, SO, JO, clearly shown in FIG.
3 (B) clearly shows the mechanism parameter BO3, FIG.
(C) specifies TPO3.

FIG. 14 is an explanatory diagram showing each mechanism parameter relating to the parallel link mechanism. FIG. 14 (A) shows a mechanism parameter SA2;
FIG. 14 (B) shows the mechanism parameter T
PO1 and TPO2 are specified.

FIG. 15 is a schematic diagram illustrating a coordinate system of a machine tool using a parallel link mechanism.

FIG. 16 is a characteristic diagram showing a load change in the rod axis direction when the angle of the A axis is changed at the origin position of the parallel link mechanism.

[Explanation of symbols]

Reference Signs List 10 machine tool 11 base 12 traveling plate 14U-w arm (parallel link mechanism) 15U-w rod (parallel link mechanism) 16U-w ball joint (parallel link mechanism) 17U-w ball joint (parallel link mechanism) 20U-w Guide (Parallel Link Mechanism) 22U-w Base (Parallel Link Mechanism) 24U-w Ball Screw (Parallel Link Mechanism, Actuator) 25U-w Servo Motor (Actuator) 26U-w Slide Table (Parallel Link Mechanism) 40 Measuring Instrument 63 Reference Pin 70 Control device 140 First jig 142 Second jig 160 DBB S10 (first step) S12 (second step) S14 (third step)

Claims (3)

[Claims]
1. A base fixed to the outside, a traveling plate held on the base via a parallel link mechanism, a tool attached to the traveling plate, and a plurality of actuators for driving the parallel link mechanism A control device that converts a command value given in a rectangular coordinate system into an output value of the actuator and controls the actuator, comprising: a command for a position and a posture of the traveling plate. A first step of obtaining the position and orientation of the traveling plate after the drive control based on the measured values as measured values, and a second step of obtaining a compliance value based on the measured values and the command values obtained in the first step. And the compliance value obtained in the second step is
A third step of applying a command value given in the Cartesian coordinate system to a conversion formula for converting the command value into an output value of the actuator.
2. A mechanism parameter obtained based on the actually measured value and the command value among mechanism parameters related to the base, the traveling plate, the parallel link mechanism, and the plurality of actuators. 2. The control method for a machine tool according to claim 1, wherein the control method is obtained at the same time.
3. The control method for a machine tool according to claim 1, wherein in the second step, the compliance value is optimized by a predetermined convergence calculation.
JP2000287424A 2000-09-21 2000-09-21 Controlling method for machine tool Pending JP2002096232A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2000287424A JP2002096232A (en) 2000-09-21 2000-09-21 Controlling method for machine tool

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2000287424A JP2002096232A (en) 2000-09-21 2000-09-21 Controlling method for machine tool

Publications (1)

Publication Number Publication Date
JP2002096232A true JP2002096232A (en) 2002-04-02

Family

ID=18771169

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2000287424A Pending JP2002096232A (en) 2000-09-21 2000-09-21 Controlling method for machine tool

Country Status (1)

Country Link
JP (1) JP2002096232A (en)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1775077A2 (en) * 2005-10-17 2007-04-18 Shin Nippon Koki Co., Ltd. Parallel kinematic machine, calibration method of parallel kinematic machine, and calibration program product
US7208029B2 (en) 2003-07-31 2007-04-24 Nissan Motor Co., Ltd. Exhaust gas cleaning system
JP2007268682A (en) * 2006-03-31 2007-10-18 Jtekt Corp Control method of space 3-degree-of-freedom parallel mechanism and space 3-degree-of-freedom parallel mechanism
US7356937B2 (en) * 2005-03-01 2008-04-15 Shin Nippon Koki Co., Ltd. Method for calibrating parallel kinematic mechanism, method for verifying calibration, program product for verifying calibration, method for taking data, and method for taking correction data for spatial posturing correction
WO2008068989A1 (en) * 2006-12-07 2008-06-12 Ihi Corporation Parallel link conveying device and method of controlling the same
US7520156B2 (en) 2005-05-16 2009-04-21 Okuma Corporation Calibration method for a parallel kinematic mechanism machine
CN102069393A (en) * 2011-02-18 2011-05-25 上海工程技术大学 Three-degree-of-freedom parallel mechanism for virtual-axis machine tool and robot
CN102145457A (en) * 2011-02-11 2011-08-10 上海工程技术大学 Three-rotational freedom parallel mechanism for virtual axis machine tool and robot
WO2011156941A1 (en) * 2010-06-17 2011-12-22 上海磁浮交通发展有限公司 Method for realizing the spatial transformation from machining points to reference points of installation survey
EP2957383A1 (en) * 2014-06-18 2015-12-23 Kabushiki Kaisha Toshiba Machine tool
EP2829367A4 (en) * 2012-03-23 2016-10-26 Ntn Toyo Bearing Co Ltd Link actuation device
TWI585363B (en) * 2015-12-01 2017-06-01 國立清華大學 Double ball-bar system and errors compensation method thereof for measurement

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7208029B2 (en) 2003-07-31 2007-04-24 Nissan Motor Co., Ltd. Exhaust gas cleaning system
EP1698954B1 (en) * 2005-03-01 2011-11-23 Shin Nippon Koki Co., Ltd. Method for calibrating parallel kinematic mechanism
US7356937B2 (en) * 2005-03-01 2008-04-15 Shin Nippon Koki Co., Ltd. Method for calibrating parallel kinematic mechanism, method for verifying calibration, program product for verifying calibration, method for taking data, and method for taking correction data for spatial posturing correction
US7520156B2 (en) 2005-05-16 2009-04-21 Okuma Corporation Calibration method for a parallel kinematic mechanism machine
EP1775077A3 (en) * 2005-10-17 2009-03-11 Shin Nippon Koki Co., Ltd. Parallel kinematic machine, calibration method of parallel kinematic machine, and calibration program product
EP1775077A2 (en) * 2005-10-17 2007-04-18 Shin Nippon Koki Co., Ltd. Parallel kinematic machine, calibration method of parallel kinematic machine, and calibration program product
JP2007268682A (en) * 2006-03-31 2007-10-18 Jtekt Corp Control method of space 3-degree-of-freedom parallel mechanism and space 3-degree-of-freedom parallel mechanism
WO2008068989A1 (en) * 2006-12-07 2008-06-12 Ihi Corporation Parallel link conveying device and method of controlling the same
WO2011156941A1 (en) * 2010-06-17 2011-12-22 上海磁浮交通发展有限公司 Method for realizing the spatial transformation from machining points to reference points of installation survey
CN103026310A (en) * 2010-06-17 2013-04-03 上海磁浮交通发展有限公司 Method for realizing the spatial transformation from machining points to reference points of installation survey
CN102145457A (en) * 2011-02-11 2011-08-10 上海工程技术大学 Three-rotational freedom parallel mechanism for virtual axis machine tool and robot
CN102069393A (en) * 2011-02-18 2011-05-25 上海工程技术大学 Three-degree-of-freedom parallel mechanism for virtual-axis machine tool and robot
EP2829367A4 (en) * 2012-03-23 2016-10-26 Ntn Toyo Bearing Co Ltd Link actuation device
US9522469B2 (en) 2012-03-23 2016-12-20 Ntn Corporation Link actuation device
EP2957383A1 (en) * 2014-06-18 2015-12-23 Kabushiki Kaisha Toshiba Machine tool
US9636794B2 (en) 2014-06-18 2017-05-02 Kabushiki Kaisha Toshiba Machine tool
TWI585363B (en) * 2015-12-01 2017-06-01 國立清華大學 Double ball-bar system and errors compensation method thereof for measurement
US10209048B2 (en) 2015-12-01 2019-02-19 National Tsing Hua University Double ball-bar measuring system and errors compensation method thereof

Similar Documents

Publication Publication Date Title
US9833897B2 (en) Calibration and programming of robots
US9908238B2 (en) Method and system for determination of at least one property of a manipulator
Borm et al. Determination of optimal measurement configurations for robot calibration based on observability measure
CN103250025B (en) The error of the measurement obtained using coordinate positioning apparatus by correction
CN102015221B (en) A method and a system for determining the relation between a robot coordinate system and a local coordinate system located in the working range of the robot
US7813830B2 (en) Method and an apparatus for performing a program controlled process on a component
EP1446636B1 (en) Dynamic artefact comparison
US6822412B1 (en) Method for calibrating and programming of a robot application
EP2559965B1 (en) Method of error compensation in a coordinate measuring machine
US9645217B2 (en) System and method for error correction for CNC machines
EP2188586B1 (en) Method of aligning arm reference systems of a multiple- arm measuring machine
KR910005508B1 (en) Measuring and analysing method of numerical controller
ES2290497T3 (en) System and process for measuring, compensating and checking heads of a numerically controlled tool machine and / or tables.
DE60311527T3 (en) Workpiece inspection process and device
US7254506B2 (en) Method of calibrating a scanning system
US8155789B2 (en) Device, method, program and recording medium for robot offline programming
JP3827548B2 (en) Scanning probe calibration method and calibration program
EP0042960B1 (en) Method and apparatus for calibrating a robot
DE69736348T2 (en) Robot fuel control system with visual sensor for communication work
EP2722136A1 (en) Method for in-line calibration of an industrial robot, calibration system for performing such a method and industrial robot comprising such a calibration system
JP4658337B2 (en) Rotating device for scanning head of coordinate measuring device
JP5244786B2 (en) Differential calibration
JP5448634B2 (en) Machine error identification method and program
US7899577B2 (en) Measuring system and calibration method
US5239855A (en) Positional calibration of robotic arm joints relative to the gravity vector

Legal Events

Date Code Title Description
RD04 Notification of resignation of power of attorney

Free format text: JAPANESE INTERMEDIATE CODE: A7424

Effective date: 20050922

A711 Notification of change in applicant

Free format text: JAPANESE INTERMEDIATE CODE: A712

Effective date: 20060301