JPH11194813A - Operation command generating method for industrial machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operation command generating method for an industrial machine which enables accurate arcuate interpolation at a corner part. SOLUTION: In this method, track control is carried out on the basis of interpolation and a speed specified by an operation program as to an industrial machine having more than one axis. The track error E between a corner point which comes into contact with each straight line at a corner part from linear interpolation to linear interpolation and is specified in the program and an actual operation result is specified by the operation program and the error E is classified into a route error αE by a command part and a route error (1-α)E by a servo part by a specified method (S100 to S104), and an arc radius R is so found (S105) so that command track has the error αE by the command part, the operation speed is so found (S106) so that the error (1-α)E by the servo part is reached, and an arc interpolation part based upon the determined arc radius R and operation speed V is generated, thereby generating a command track (S107).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for controlling an industrial machine having a plurality of axes in accordance with an operation program, and more particularly to a method for creating an operation command.

[0002]

2. Description of the Related Art Conventionally, when trajectory control is performed on an industrial machine having a plurality of axes having a configuration as shown in FIG. 2, when linear interpolation sections are connected at a certain corner point, linear interpolation Although the speed of the section is specified, but it is not possible to pass the corner point at a finite speed, the motor, amplifier, etc. can output acceleration by reducing the speed to 0 or turning inward at a certain radius Command to the servo controller was created so as to obtain a proper value. For example, trajectories Pi-1 and Pi as shown in FIG.
Considering the case where a locus passing through Pi + 1 is interpolated by a machine having X and Y axes, the sections Pi-1 to Pi (i-th
Section) and Pi to Pi + 1 (the (i + 1) th section) are specified by the operation program to operate at the operation speed V. In such a case, the speed in the X direction at the point Pi is normally reduced when the trajectory is specified to pass through the Pi. Then, since the acceleration in the (i + 1) -th section starts after the speed becomes completely zero as a result of the deceleration, the cycle time becomes longer. In applications where speed is related to work quality (e.g., gluing, painting, etc.), it leads to significant quality degradation. Therefore, in such a case, for example, a circular interpolation is inserted between PiF and PiB so as to make a smooth speed change even if the accuracy of the trajectory is somewhat sacrificed, and a command to make an inward rotation (FIG. 6). (Dotted line). At this time, it is necessary to determine the radius and speed of the inward turning command. According to the technique disclosed in Japanese Patent Application Laid-Open No. Hei 7-152417, the path and feed speed of the tool are controlled in accordance with a machining program. In the "Tool path and feed rate control method of the numerical control device", the circular arc that touches each straight line at the corner part from the straight line to the straight line, and the path error with the programmed path is equal to or less than the specified allowable error amount. Forming a feed rate corresponding to the arc to form an arc block, and automatically inserting the arc block into a machining program, thereby reducing a mechanical shock while keeping a path error within a certain range at a corner portion. Is disclosed.

[0003]

However, in the above conventional example, the radius of the circular arc is determined by the designated error E, and then the command speed V is determined by the radius R and the inward error amount ΔR which is predetermined as a set constant. Can be That is, first, the path error due to the circular interpolation command is determined without considering the response of the servo unit. After that, based on the circular arc command, the error ΔR determines the speed V in consideration of only the servo section. As a result, there has been a problem that the error in the command section and the error in the servo section are larger than the error E initially specified by the delay of the servo section, as shown by the one-dot chain line in FIG. Therefore, an object of the present invention is to provide a method for creating an operation command for an industrial machine that can create an operation command that operates with a specified error E regardless of the speed even if the servo unit is delayed. .

[0004]

According to one aspect of the present invention, there is provided a method for controlling a trajectory in an industrial machine having a plurality of axes by interpolation and speed specified by an operation program. And the trajectory error E between the corner point specified in the program and the actual operation result at the corner portion from linear interpolation to linear interpolation.
Is specified by an operation program, and the error E is determined by a method specified in advance by a path error αE by the command unit,
Divided into the path error (1-α) E by the servo unit, the arc radius R is determined so that the command trajectory is at the error αE by the command unit, and the operation speed is determined so as to obtain the error (1-α) E by the servo unit. A command locus is created by forming an arc interpolation portion consisting of the determined arc radius R and the operation speed V. According to this configuration, since the error E at the corner is divided into the path error αE by the command unit and the path error (1−α) E by the servo unit, accurate trajectory control to achieve the specified operation trajectory can be performed. Will be possible. The invention according to claim 2 is characterized in that the value of α is determined to a value that maximizes the operating speed of the corner.
According to this configuration, it is possible to accurately follow the designated trajectory and to perform an operation near the corner portion as fast as possible. Further, according to the invention described in claim 3, the radius R
Amount of contraction ΔR in the radial direction when the circular arc is commanded at the speed V
Is given by the equation ΔR =
Approximately expressed by (V / K) ² / (2R), and when the coefficient K is smaller than V / R, ΔR = R−R / (1+ (V / K) ² / R ² ) ^{1 / 2} , characterized by According to this configuration, even if the ratio between the delay coefficient K of the servo unit and V / R changes, accurate correction control can be performed correspondingly.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. 1 to 5 are views according to a first embodiment of the present invention. FIG. 1 shows the first embodiment of the present invention.
FIG. 2 is a flowchart of the operation of the operation command creating method for an industrial machine according to the embodiment, and FIG. 2 is a configuration diagram of the industrial machine in FIG. FIG. 3 is an explanatory diagram of a trajectory error E in the operation command creating method shown in FIG. 1, and FIG. 4 is an explanatory diagram of errors L and ΔR in the operation command creating method shown in FIG. FIG. 5 is a block diagram showing an approximation of the servo unit shown in FIG. In FIG. 2, a multi-axis industrial machine having an X-axis and a Y-axis (here, two axes are shown, but the number of axes is not particularly limited) of machine axes driven by the servomotor 23 is The NC program control by the control device (numerical control device) 20 is performed. The NC program (operation program) control reads the operation program stored in the program memory and specifies the machining trajectory of the X-axis and Y-axis tools for each machining axis for the machining shape of the workpiece, the tool feed speed, and the like. Then, the tool is controlled so as to faithfully follow the designated path at the designated speed. Numerical control device 20
In the trajectory control according to the present invention, in particular, for the control of the corner portion from linear interpolation to linear interpolation, the trajectory error between the corner point in contact with each straight line and the actual operation result becomes E by circular interpolation in the operation command creating section 21. An arc trajectory with a large radius R is created, and control is performed so that continuous machining can be performed smoothly.
In the present embodiment, for the circular interpolation, the operation command creation unit 21 generates an error αE by the command unit based on the trajectory error E and the division ratio α specified in the operation program.
And an error (1−α) E by the servo unit, determine an arc radius R and an operation speed V, transmit each axis operation command to the servo controller unit 22, and the servo controller unit 22 By driving the Y-axis servo motor 23 and feeding back the operation data of the servo unit,
It is configured so as to accurately follow the arc trajectory of the corner-specified route and smoothly perform the machining at the designated machining speed. Note that FIG. 2 is a common diagram with the conventional example because the configuration of the industrial machine as hardware on which the operation command program of the present invention runs is shown.

Next, the details of the control of the circular arc interpolation at the corner will be described with reference to the flowchart of the command creation sequence of FIG. FIG. 6 used to explain the conventional example.
A case where the present invention is applied when the points Pi-1, Pi and Pi + 1 shown in FIG. The following command generation sequence for the circular arc interpolation control of the corner by the operation command generation unit 21 according to the present embodiment is started (S10).
0). First, the operation command creating unit 21 reads the trajectory error E specified in the operation program (S101). The error E in this case, as shown in FIG. 3, indicates the distance between the point where the circular motion locus approaches the point Pi and Pi. Next, a division ratio α for dividing the trajectory error E into a command component and a servo delay component is read from the operation program (S102). The division ratio α will be described later. A straight line Pi-1 as shown in FIG.
角 Pi and the straight line Pi + 1 are determined (S10
3). Since the positions of the teaching points Pi-1, Pi, and Pi + 1 are stored in the operation program, the angle θ can be easily obtained from this value. Subsequently, the angle coefficient β is obtained from the following equation (1) (S104). β = (1 / cos (θ / 2)) − 1 (1) At this time, when performing circular interpolation, the distance L between the circular arc (dotted line shown in FIG. 4) and the point Pi in the command is a circular arc. Is R, the following equation (2), L = R · β (2) is obtained. It is well known that the amount of contraction in the radial direction when a circular arc having a radius R is commanded at a speed V is approximately expressed by the following equation (3). ΔR = (V / K) ² / (2R) (3) where K is a coefficient representing the delay of the servo unit. When the servo unit can be approximated as shown in FIG. Kp. When the first-order lag filter is included in the servo section as shown in FIG. 5B, K = 1 / (1 / Kp ² + Tf ² ) ^1/2 . The sum of equations (2) and (3) is the motion trajectory and the point P
It is the distance to i, and this becomes the designated trajectory error E, which means that L + ΔR = E (4). At this time, the ratio between L and ΔR is arbitrary, but in the present embodiment, it is the value of α read in S102. That is, L = α · E (5) ΔR = (1−α) E (6) Next, the radius R is calculated using the equations (2) and (5) (S105). R = E · α / β (7) From this equation (7), equation (6) and equation (3), an equation for calculating the velocity V is derived (S106). V = KE · (2α (1−α) / β) ^1/2 (8) Finally, the command trajectories PiF to PiB to be circularly interpolated by the radius R and the velocity V obtained as described above are calculated. It is inserted into the operation program (S107). After the completion of the circular interpolation processing (S108), the operation program is interpreted as including a circular section, and a normal operation is performed.

Next, a second embodiment of the present invention will be described. The second embodiment relates to a method for determining the division ratio α shown in S102 of FIG. This α
Is arbitrary, but in the present embodiment, the condition is determined such that the speed V obtained in S106 by the operation of the operation command creating unit 21 is maximized. By doing so, the motion trajectory is also held at the designated E, and it is possible to operate near Pi at the highest possible speed and smoothly. Each drawing is common to the first embodiment. Substituting the equations (2) and (3) into the equation (4), R · β + (V / K) ² / (2R) = E (9) When this is modified, V ² = −2βK ² [[R− {E / (2β)}] ² − {E / (2β)} ² ] (10) From this equation (10), the condition that the speed V becomes maximum is: R = E / (2β) (11), and V at this time is as follows: V = KE · (2β) ^1/2 (12) Here, comparing Expression (11) and Expression (7), both of which represent R, it can be seen that α = 0.5 (13). Therefore, the result of the second embodiment is equivalent to setting α = 0.5 in the processing of S102, and α = 0.5 is derived as the optimal division ratio.

Next, a third embodiment of the present invention will be described. In the description of the first and second embodiments so far, the radius error when the arc is commanded at the speed V is approximated by the equation (3), but when K is smaller than (V / R), , This approximation does not hold. Therefore, the third embodiment relates to correction control under the condition that K is smaller than (V / R). Each drawing is common to the first and second embodiments. In the case of the third embodiment, a similar expression is modified using the following expression instead of Expression (3) as ΔR. ΔR = R−R / ｛1+ (V / K) ² / R ² ｝ ^1/2 (14) As a result, instead of the expression (8) in S106 in FIG. R [R ² / {R- (1-α) E} -1] ^1/2 (15) where R is the equation (7) used in S105, and the others are the same as in FIG. The same processing is performed. Further, a method of obtaining the maximum V in this case is to substitute the equation (2) and the equation (14) into the equation (4) to obtain R · β + R−R / ｛1+ (V / K) ² / R ² ｝ ^{1 / 2} = E (16) When the relationship between R and V at this time is modified, V = [{RK · (1-E / R + β)} ² −1] ^1/2 (17) ). Using this equation, V may be determined to be the maximum by repeated calculation or the like in the range of R> 0.

In the embodiments of the present invention described above, a multi-axis industrial machine in which the drive shaft has an orthogonal coordinate system has been described as an example. However, a machine in which the drive shaft is not orthogonal (for example, a vertical multi-joint industrial machine). It is needless to say that the present invention can also be applied to a robot for use in an automobile. In this case, the servo delay of each axis does not exactly coincide with the servo delay amount in the work coordinate system X, Y. However, even in such a case, the literature "Goto, Nakamura, Kura: Journal of the Society of System Control Information, Vol. .7, No. 3, P103, 199
As described in “4 years”, the servo delay in the working coordinate system is considered to be almost equal to K representing the servo delay of each axis in a certain range. It can be well adapted using similar algorithms as in the case.

[0010]

As described above, according to the first aspect of the present invention, the error E at the corner portion can be determined by a method specified in advance by the path error αE by the command portion and the path error (1) by the servo portion. -Α) E, so that there is an effect that control based on the motion trajectory as specified in the circular arc interpolation becomes possible. According to the second aspect of the present invention, the division ratio α is determined to be a value that maximizes the operation speed of the corner portion. Therefore, work can be performed by protecting the trajectory and maximizing the operation speed. This has the effect of being more efficient. According to the third aspect of the present invention, when the coefficient K representing the delay of the servo is smaller than (V / R), the trajectory control is performed by switching the approximate expression of ΔR. Even if the ratio between (V / R) and (V / R) changes, there is an effect that a wide range of correction control can be performed accurately in response to a change in condition.

[Brief description of the drawings]

FIG. 1 is a flowchart of an operation of an operation command creating method for an industrial machine according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of the industrial machine in FIG.

FIG. 3 is an explanatory diagram of a trajectory error in the operation command creating method shown in FIG. 1;

FIG. 4 is an explanatory diagram of errors L and ΔR in the operation command creating method shown in FIG. 1;

FIG. 5 is a block diagram showing an approximation of the servo unit shown in FIG. 2;

FIG. 6 is an explanatory diagram of a trajectory error in a conventional operation command creation method.

[Explanation of symbols]

 Reference Signs List 20 control device 21 operation command creation unit 22 servo controller unit 23 servo motor

Claims (3)

[Claims] 1. A method for trajectory control by an interpolation and a speed specified by an operation program in an industrial machine having a plurality of axes, wherein the tangent to each straight line at a corner portion from linear interpolation to linear interpolation and specified in a program The trajectory error E between the set corner point and the actual operation result is specified by an operation program, and the error E is determined by a method specified in advance by a path error αE by the command unit and a path error (1-α) E by the servo unit. The radius of the arc R is determined so that the command trajectory becomes equal to the error αE of the command unit, and the operation speed is determined so as to obtain the error (1−α) E by the servo unit. A method for creating an operation command for an industrial machine, comprising forming an arc interpolation portion consisting of V and creating a command trajectory. 2. The method according to claim 1, wherein α is determined to a value that maximizes the operation speed of the corner portion. 3. The contraction amount ΔR in the radial direction when the circular arc having the radius R is instructed at the speed V is represented by the following formula: ΔR = (V / K) ² / (2R), where K is a coefficient representing the delay of the servo unit. It is represented approximately, and when the coefficient K is smaller than V / R, it is represented by a formula ΔR = RR / (1+ (V / K) ² / R ² ) ^1/2 . Item 1. The operation command creation method for an industrial machine according to Item 1.