JPH0549437B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) Although the present invention is an articulated robot, it is equipped with operation means for the Cartesian coordinate system in addition to the operation means for the joint system, so that it functions as if it were a robot for the Cartesian coordinate system. This paper relates to the improvement of a moving articulated robot.

(Prior technology) Many of the workpieces that are processed by industrial robots have processing lines that extend at right angles when welding or seaming, so robots work continuously along these processing lines. will be carried out. Therefore, as the applications of articulated robots spread and they are used for such tasks, even articulated robots are required to operate like robots in a Cartesian coordinate system, and controlled objects such as end effectors are It would be advantageous if it could be operated to move in the axial direction of the orthogonal coordinates, or if position and orientation data could be captured in the orthogonal coordinate system and interpolation for moving along the machining line could be easily performed. For this reason, although it is an articulated robot, the operation panel is equipped with not only operation switches for the joint system, but also operation switches for the rectangular coordinate system such as X, Y, Z, φ, and θ, and changeover switches for these operation switches. Many of the devices are equipped with means for capturing information even in a rectangular coordinate system and for performing coordinate transformation between the two coordinate systems.

As an example, in an articulated welding robot as shown in FIG. A second shaft 21 is rotatably provided on the arm 17, a third shaft 23 is rotatably provided on the second shaft 21, and a welding torch as a controlled object is attached to the tip of the third shaft. 27 are provided, and the rotation angle (synonymous with joint angle) of each arm or axis α1, α2, α
By controlling α4 and α5, the welding torch is moved to the desired position and welding is performed, but the operation panel is equipped with switches for operating the joint system and Cartesian coordinate system. The control device has built-in coordinate conversion means for converting the amount of operation given in the rectangular coordinate system into the amount of operation of the joint system.

However, in such robots, when the position and posture data of the controlled object are given in a rectangular coordinate system, there is a problem in that the values of the joint angles for giving the position and posture cannot be uniquely determined. In other words, referring to FIG. 2B, which schematically shows the robot in FIG. 1, the bent states of the first arm 11 and the second arm 17 are (hereinafter, Since the joint angles that define the position and posture of these arms are also α2, α3 (first state) and α2′, α3′ ( (2nd state) This makes it difficult to decide which position and posture each arm should take, so to date, articulated robots have resolved this ambiguity by restricting them so that they can only take one position or the other. For this reason,
In such a robot, there is an object in the path of movement of the arms, which becomes an obstacle in the first state, but in the second state.
Even if the condition would not cause a problem, it is not possible to reverse these conditions, so when a problem occurs, the user has to remove the workpiece, change its orientation, attach it, and start the work again. for example,
Obstacle 28 is located at the position shown in Figure 2B.
If the welding torch 27 is moved in the direction of the arrow, the second arm 17 will collide with the obstacle 28 if the arms 11 and 17 are bent. but,
Since it is not possible to reverse the workpiece to the above state, the workpiece was removed to avoid collision.

In other words, while it eliminated ambiguity and made it easier to control, it also reduced flexibility and narrowed the range of motion. Therefore, attempts were made to widen the operating range by enabling reversal between the two states mentioned above, and this was reported in Japanese Patent Application Laid-Open No. 57-27689 and Japanese Patent Application No. 56-54789.
This is proposed in the application No. 173484 (Japanese Unexamined Patent Publication No. 173484/1984). By the way, such a reversal of the state is, for example, according to the example shown in FIG. 2B, moving from the state shown in the figure to the state shown in FIG.
This is done by going through the states shown in Figure 2 G in sequence and then moving to the state shown in Figure 2. However, in the range of E to G in Figure 2 where the inversion is performed, it is dangerous to operate in a rectangular coordinate system because the arms will swing around. This range is called the critical zone and is operated using the joint system.

However, these critical zones were set by the operator who visually checked the state of the robot's arms and shafts and judged each time based on his/her experience, so much depended on the skill level of the operator. This was one of the reasons why articulated robots were difficult to operate.

(Problem to be Solved) This invention was made with attention to these circumstances, and the robot itself identifies the critical zone in the articulated robot as described above,
There is an articulating robot that facilitates operation when the arm is reversed by displaying the information.

(Means for Solving the Problems) This invention provides that, for one position, one posture, or one position/posture of a controlled object, among the arms or shafts that sequentially support the controlled object, adjacent arms or A joint mechanism that can bend the axis in two ways, a drive means for driving the joint mechanism, a drive command means for giving a drive command to the drive means, an operation input means using a joint system, an operation input means using a rectangular coordinate system, For an articulated robot equipped with a means for switching these inputs and a storage means for capturing the input information, functional calculations are performed using variables such as each joint angle and the length of the main part of each arm or axis. critical zone identification means for identifying that the arm or axis is within a critical zone during transition from one state to the other of two bending states; It is equipped with a display means to indicate that it is within the zone.

The above-mentioned bent states of the arms or shafts include not only the case where the arms are bent together as shown in FIG. 2B described in the description of the prior art, but also cases such as shown in FIG. 2C and FIG. 2D.

FIG. 2C shows the case of the second axis 21 and the third axis 23, and the welding torch 27 has the same posture for the two states of these axes. Also, the second
Figure D shows the case of the rotating body 5 and the first shaft 11, and the position of the welding torch 27 is the same for the two states of these shafts.

For functions that use joint angles or the length of the main part of the arm or axis as variables to identify whether the arm or axis is within the critical zone, both variables and expressions must be applied to the connection state of each arm or axis. These functional operations identify that the arm or axis is within the critical zone, so identifying the critical zone is not as easy as relying on the operator's visual recognition of the arm or axis. Not only does it eliminate variations and become stable, but it can also be displayed on the display means, so the operator can easily identify the critical zone and appropriately switch the operation input means.

(Example) Hereinafter, the present invention will be described with reference to a multi-joint robot similar to that shown in FIG. An example implemented in a welding robot that can take two different types will be described.

In FIG. 1, a fixing member 1 is fixed to the ground, for example, and a cylindrical base 3 having a relatively low height is attached to the fixing member 1. A relatively tall cylindrical rotating body 4 is provided at the upper end of the cylindrical base 3 so as to be rotatable around a rotating shaft (not shown). In the hollow part of this cylindrical rotating body 4,
Although not shown, a vertical rotating shaft is provided, and a rotating member 5 is provided above the cylindrical rotating member 4 so as to rotate integrally therewith. This cylindrical rotating body 4, and thus the rotating body 5, is rotationally driven about a joint angle α1 by a motor, which will be described later, although not shown. The rotating body 5 has a support member 7 extending substantially perpendicularly and in parallel from its upper surface. A rotary arm 11 is supported by this support member 7 by a horizontal shaft 9 so as to be rotatable about a joint angle α2. Although not shown, the rotating arm 11 is rotationally driven by a motor that will be described later. Further, in relation to the rotating arm 11, a balance mechanism 13 is provided to balance the rotational state of the rotating arm. Although not shown, this balance mechanism 13 includes, for example, a tension spring,
It is configured to rotate together with the cylindrical rotating body 4.

At the tip of the rotating arm 11, a rotating arm 17 is supported by a shaft 15 parallel to the axis 9 so as to be rotatable with respect to the arm 11, that is, about a joint angle α3.
Although not shown, this rotating arm 17 is rotationally driven by a motor that will be described later. At one free end of the pivoting arm 17 is a shaft 19 parallel to the shaft 9;
A rotating shaft 21 is rotatably supported on the rotating arm 17, that is, about a joint angle α4. Although not shown, this rotation shaft 21 is rotationally driven around the shaft 19 by a motor, which will be described later. Rotation axis 21
includes a rotating shaft 23 that supports the torch fixture 25.
is rotatably supported coaxially with respect to the rotation shaft 21. Although not shown, this rotating shaft 23 is driven to rotate relative to the rotating shaft 21, that is, about a joint angle α5, by a motor that will be described later. A welding torch 27 is attached to the torch fixture 25 . In this way, this automatic welding device includes the rotating body 5,
Respective joint angles α1, α2, α3, α of the rotating arm 11, rotating arm 17, rotating shaft 21, and rotating shaft 23
4 and α5, the attitude of the welding torch 27 and the position of its tip, that is, the welding point P, are controlled.

The rectangular coordinate system XYZ is the absolute system coordinates of the robot R, and its Z axis is provided to coincide with the rotation axes (not shown) of the rotating bodies 4 and 5. The Y axis is
It is provided perpendicularly to the rotation center line of the joint angle α1 in a horizontal plane including the horizontal axis 9. The X-axis is provided in a horizontal plane including the horizontal axis 9 to coincide with the center line of rotation of the joint angle α1. Further, the orientation angle and attitude angle θ of the torch 27 are determined as shown.

Furthermore, since this robot R is a multi-joint robot, the joint control system is limited to a multi-joint system (α system).

FIG. 3 is a schematic block diagram showing one embodiment of the present invention. In this embodiment, the operation panel 100
is provided. The operation panel 100 is provided with a mode changeover switch 101 for instructing whether to operate in an operating mode such as automatic welding equipment. This mode changeover switch 101 can be set by selectively switching between manual mode (M), test mode (T), and auto mode (A). The operation panel 100 further includes a push button switch 103.
is provided. The pushbutton switch 103 is operated to give a start command for the auto mode and also to give a teaching command in the teaching mode. Second mode selector switch 1
05 is for selectively setting either linear interpolation operation (L), circular interpolation operation (C), or weaving operation (W). Furthermore, the speed setting device 11
1 is provided. This speed setting device 111 is for commanding the speed at which the welding torch 27 and therefore the welding point P should move. 113 is an indicator lamp, and the joint angle is critical zone CZ
Displays what has happened. The operation panel 100 includes two groups of manual switches 11.
9,121,123,125 and 127 and 129,131,133,135 and 137
is provided. The switches 119 to 127 are
It is operated to control the position of the welding equipment in a rectangular coordinate system, that is, an XYZ system. On the other hand, the switches 129 to 137 are operated to control their positions in a multi-joint system, that is, an α system. In other words, each joint angle α1
α5 is used to directly control α5.
To this end, the operation panel 100 is provided with a system changeover switch 117 for selecting which of the group of switches 119 to 127 or the group of switches 129 to 137 is to be enabled. Therefore, this system changeover switch 117
By switching the switch 117 to the left (in FIG. 3), the group of manual switches 119 to 127 is enabled, and by switching the switch 117 to the right, the group of manual switches 129 to 137 is activated.
group is activated.

These manual switches 119 to 127
and 129 to 137 can each take three positions, and the position shown by the solid line in FIG. 3 is the neutral position. Switches 119, 121, and 123 each have X
used to control the Y-axis and Z-axis,
The direction away from the origin of the rectangular coordinate is the up direction (U), and the direction approaching the origin is the down direction.
(D). Also, switch 12
5 is used to control the orientation angle φ of the welding torch 27, and a switch 127 is used to control the attitude angle θ of the welding torch 27. These switches 125 and 127 then adjust the angles φ and θ associated with the welding torch in a clockwise direction (C), respectively.
Or can be controlled counterclockwise (CC). Similarly, the manual switches 129 to 137 of the multi-joint system, that is, the α system, change the rotation angles α1 to α5 of each arm or shaft, respectively, in the clockwise direction (C).
Or can be controlled counterclockwise (CC). The operating means has been described above, and the teaching means is comprised of at least the above-mentioned operating means and the CPU 31, which will be described later. Data is exchanged between the operation panel 100 including each of these components and the data bus 55 via an interface (not shown).

This data bus 55 further includes a CPU 31.
and memory 33 are connected. The memory 33 includes a ROM for storing a system program for the CPU 31, a storage area and a flag area necessary for calculations and other processing in the CPU 31, and a RAM for storing a user program. The data bus 55 includes a plurality of drive circuits 351, 352, 353, 354 and 355 (in this embodiment, five corresponding to the five rotation angles α1 to α5) and a plurality of (in this embodiment, five) drive circuits 351, 352, 353, 354 and 355. )
Incremental encoder 531, 532, 5
33, 534 and 535 are connected, respectively. In this FIG. 3, the drive circuit 351 is
It is depicted in more detail on behalf of the others. here,
The configuration of this drive circuit 351 will be explained.
Regarding the remaining drive circuits 352 to 355,
It should be pointed out in advance that a similar configuration can be adopted.

The drive circuit 351 includes a command position buffer 37 into which command position information from the CPU 31 is loaded;
A feedback counter 39 is provided for counting pulse signals from a corresponding incremental encoder 531. Command position buffer 3
The content of 7 is the minuend, and the content of the feedback counter 39 is the subtractive number, and the content of the subtractor 41 is
given as two inputs. The output of the subtracter 41 is given to a D/A converter 43. Therefore, a voltage signal corresponding to the difference between the command position and the current position is derived from the D/A converter 43. The output of the D/A converter 43 is sent to the servo amplifier 4.
5. It is given as a drive signal to the servo motor 49 via the command limiter 47. Note that the output of the command limiter 47 is further provided to a null signal detection circuit 51. This Null signal is
This is a zero signal obtained from the servo amplifier 45 when the position is controlled by the servo system, and derives a region very close to the target position, that is, the timing at which the motor 49 almost stops. Therefore, this
The output of the null signal detection circuit 51 is sent via the data bus 55 as a signal indicating that the controlled object controlled by the servo motor 49 has reached the command position loaded into the command position buffer 37.
It is given to the CPU 31. As described above, the joint angle control means is composed of at least the CPU 31.

In the above configuration, the implementation of FIG. 3 and therefore FIG. 1 will be explained below with reference to the flow diagrams shown in FIGS. An example operation or operation will be explained.

First, the manual mode for teaching will be explained. The CPU 31 has an internally provided timer that receives a clock from a clock source, and the timer generates an output at certain fixed time intervals in response to the clock. and,
In the CPU 31, if there is an output from the timer, an interrupt is generated (step S1).
01). In the first step S103, manual switches 119, 1 for each axis of the operation panel 100 are activated.
21, 123, 125 and 127 and 12
9, 131, 133, 135 and 137 are all maintained in the neutral position. In other words, this step S103
Now, these manual switches 119 to 1
37 is being operated. In the following step S105, it is determined whether the system changeover switch 117 (FIG. 3) has been switched to the α system. That is, in the present invention, the articulated robot is configured so that the joint angle can be in a first state where the joint angle is bent to one side and a second state where the joint angle is bent to the other side. When only two states are taken, that is, when there is no inversion of states, the system changeover switch 117 is switched to the XYZ system. This is because the welding lines of a workpiece (not shown) often extend perpendicularly to each other, so it is easier for the operator to command the torch 27 (Fig. 1) in a rectangular coordinate system. This is because it is easy to move along the welding line, and it is easy to perform interpolation calculations. Conversely, the joint angle is the first
When there is a change from the state (or the second state) to the second state (or the first state), that is, when the state is reversed, the system changeover switch 117 is switched to the α system. In this way, it is possible to manually operate the joint angle in two ways, and therefore to perform teaching.

Therefore, if it is determined in step S105 that the system changeover switch 117 has been switched to the XYZ system, in the following step S107, the position or orientation information is increased or decreased in accordance with the operating direction of the switch operated in the XYZ system. do. That is, in this step S107, based on the signal from the operation panel 100, the operated manual switches 119, 121, 123, 12
Based on the operating direction (U, D, C, or CC) of 5 or 127 and the speed set by the speed determiner 111, the position or attitude information (basic amount) corresponding to the above-mentioned timer time is increased or decreased. And if you give information in the XYZ system like this,
In the following step S109, α from the XYZ system is
Perform coordinate transformation to the system. Such a coordinate transformation is
This will be explained in detail later along with the coordinate transformation in step S115, which will be described later. During the coordinate transformation in step S109, flags YFLG1, YFLG2 and
The code of YFLG3 (details will be described later) is taken into account.

In addition, in the robot R of this embodiment, α1 has a controllable range of 240°, but it is 0°, that is, the arm 11 is
When rotating in the CC direction with the state parallel to the positive direction of the axis as a boundary, it is defined as 1, and when rotating in the C direction, it is defined as +. α2 has a controllable range of, for example, 120°, or, for example, a state where it is bent in one direction (D direction) with 0° (i.e., the arm 11 is vertical) as a border, and a state where it is bent in the other direction (U direction). The ivy state is defined as +. Furthermore, α3 has a controllable range of, for example, 270°, but a state in which the arms 11 and 17 are bent in one direction (D direction) with the boundary at 180° (that is, a straight state of the arms 11 and 17) is defined as −, and the other state (U A state in which the material is bent in the direction (direction) is defined as +. Similarly, α5 has a movable range of 360°, and is negative when rotating in the CC direction and positive when rotating in the C direction.

In this way, the system changeover switch 117
If the system has been switched to the XYZ system, the position or orientation information of the XYZ system given in step S107 is set to the above-mentioned flags YFLG1, YFLG2,
Considering the sign of YFLG3, it is converted into α-system information in step S109 (coordinate conversion means) and used as a command value. Next, in step S110, the joint angles α1, α2, α
2, α3, α4, and α5, it is determined whether the arm or axis is in the critical zone, and if it is in the critical zone, indicator lamp 1 is displayed.
13 lights up. Regarding identification of the critical zone in step S110, step S1
This will be explained in detail later along with the coordinate transformation of 09.

Then, in step S110, the display lamp 113
Unless it is lit, the α-system information obtained in step S109 is equally divided and outputted by the angle interpolation means in the subsequent step S111, and the respective joint angles are driven and controlled.

If the indicator lamp 113 is lit in step S110, this indicates that the arm or shaft is in the critical zone as described above, so return all operation switches to neutral and switch the system. Switch the switch to the α system and enable the switches 129 to 137. When the results of these operations are confirmed in steps S103 and S105, the process moves to step S113. Also, when operating in the α system from the beginning, the process moves to step S113 after the judgments in steps S103 and S105 described above are made. In step S113, the operated switches 129, 131, 13 in the α system are
The command value corresponding to the above-mentioned timer time is increased or decreased based on the operating direction of 3, 135 or 137 and the speed set by the speed setter 111. In this way, when the command value is given in the α system, in the subsequent step S115, for the interpolation calculation described later,
The coordinates are transformed from the α system to the XYZ system, and the state of the joint angles is identified. This coordinate transformation and identification will also be described later. Then, step S113
It outputs and drives according to the α-system command value given by (step S111). In this way, when driven by the α system, the CPU 31
1 to α5 are given to corresponding drive circuits 351 to 355, respectively. Each drive circuit 351 to 355 controls each joint angle α1 to α5 shown in FIG. 1 based on a command from the CPU 31.

When teaching, use the operation panel 100
Press the start button 103. That is, by setting the mode selection switch 101 to manual mode (M) and pressing the start button 103,
A teaching interrupt occurs to the CPU31. In the CPU 31, when such an interrupt occurs, the position information and flag at that time are
The contents of YFLG1, YFLG2, and YFLG3 are stored in a predetermined storage area of the memory 33. That is, during teaching, in step S117, previous steps S107 and S115 (fourth
Store the coordinate position of the XYZ system in Figure). In this way, when teaching, the XYZ system is memorized. This is because, as mentioned above, it is convenient for interpolation calculations. Then, step S119
In step S119 or S115,
The contents of flags YFLG1, YFLG2 and YFLG3 in (Fig. 4) are stored. YFLG1,
The contents of YFLG2 and YFLG3 will be shown in detail in the coordinate transformation section below.

Next, the operation in the auto mode of this embodiment will be explained with reference to FIG. In the case of auto mode, mode selection switch 101 on operation panel 100 is set to auto mode (A).
Then, the start button 103 is pressed. depending on,
In step S121, the CPU 31 resets a step counter (not shown) formed at an appropriate storage location in the memory 33, and then resets the step counter (not shown) in step S121.
23, the step counter is incremented. Then, in step S125,
From the memory 33, the CPU 31 selects the step M incremented in step S123 from among the command information of each previously taught step.
Read and load the command information. In the following step S127, it is checked whether the loaded command information of step M includes a linear interpolation command. This can be determined based on whether identification information representing linear interpolation has been loaded together with command position information.

In the case of linear interpolation, the target position is set as the command position of step M in the subsequent step S129, and then linear interpolation is performed in step S131.

Here, the linear interpolation subroutine will be explained with reference to FIG. In the linear interpolation subroutine, in the first step S151, the current position and the target position are internally calculated in the XYZ system. That is, internal division ΔS = command speed V x time t (for example, 0.2
seconds), and calculate the linear interpolation point for each ΔS.
In the following step S153, it is determined whether such internal division calculation has been completed. Otherwise, in step S155, the previous step S
109 (Figure 4), the coordinate transformation from the XYZ system to the α system is performed using flags YFLG1, YFLG2 and
This is done considering YFLG3. Continued step S157
In , α-based interpolation calculations are performed. That is,
In step S151, linear interpolation points are calculated every 0.2 seconds to find the internal division ΔS, but in order to connect these ΔS more smoothly, interpolation is performed between them using the α system. That is, interpolation is performed equally between two points separated by ΔS for each axis from α1 to α5. This allows for very smooth control. In the following step S159,
It is determined whether the internal division using the α system in step S157 has been completed. If so, the process returns to the previous step S151, and if not, the output is driven in the α system in the subsequent step S161. Note that when it is determined in the previous step S153 that internal division has ended, the current position information is updated with the target position information and the process returns to the main routine (step S163).

In FIG. 6, when it is determined in step S127 that it is not linear interpolation, in the following step S133, it is determined whether or not it is the first circular interpolation command among a series of circular interpolation command information, that is, n=1 at the command point Cn.
Decide whether or not. If n=1, linear interpolation should be used until then, and the previous step S12
Move on to 9. Further, if the circular interpolation information is continuous at three or more locations, circular interpolation points are calculated in the following step S135. However, in the case of circular interpolation of the second point (for example, C ₂ in FIG. 14), the next circular interpolation point (for example, C ₄ in FIG. 14) is calculated as the first circular interpolation point. Then, the calculated interpolation point position is set as the target position (step S137). Furthermore, in this embodiment, linear interpolation is further performed in step S139. This is due to the following reasons. Step S1
In step 35, circular interpolation points are calculated to have a pitch of, for example, 5 mm, and linear interpolation is further performed between the calculated interpolation points to enable even smoother control. Calculation for circular interpolation requires more calculation processing time than linear interpolation, but in order to save such calculation time and make it possible to use a cheaper microcomputer, this example , the circular interpolation points are relatively coarse, and the interpolation between the interpolation points is more finely interpolated by a linear interpolation routine (FIG. 7), resulting in fine and precise control even using an inexpensive computer. When the linear interpolation is completed, the command position for circular interpolation is stored in a storage step S141.
Determine whether C _o has been reached. in that case,
Returning to step S123, a step counter (not shown) is incremented. Otherwise, the process returns to step S135.

In addition, in both the case of the above-mentioned linear interpolation and the case of circular interpolation, the angles φ and θ of the torch 27 (FIG. 1) are each independently and equally interpolated.

Here, with reference to FIGS. 8 to 10, from the α system calculated in step 115 of FIG.
Coordinate transformation to the XYZ system and flag determination will be explained. In this embodiment, a microcomputer, for example, is used as the CPU 31, and recent microcomputers have improved performance and are now capable of high-speed calculations. Therefore,
In this embodiment, what was conventionally processed using approximate calculations is now processed with regular calculations with high accuracy.

FIG. 8 is a schematic diagram of the articulated robot R shown in FIG. 1 viewed from the side. Figure 9 is a schematic diagram of the same articulated robot R seen from the top, Figure A is a diagram of the state shown in Figure 8 viewed from the top, and Figure B is a diagram of Figure A seen from the top.
FIG. 3 is a detailed view of the vicinity of the origin when a rotation angle α1 is given in FIG. 10 is a schematic diagram of the dimensions of the rotating shaft 23, the torch mounting bracket 25, and the torch 27 of the multi-jointed robot R shown in FIG.

In FIGS. 8 to 10, angles α1 to α5 respectively correspond to angles α1 to α5 in FIG. The rotation angle is shown, and α3 is the rotation angle of the rotation arm 17. Also, the angle α4 is
Indicates the rotation angle of the shaft 21 with respect to the vertical axis, angle α4
E indicates the rotation angle of the shaft 21 with respect to the rotation arm 17. The angle α5 indicates the rotation angle of the shaft 23. angle α6
is constant.

Further, α1 indicates the length component from the lower end of the fixed member 1 to the axis 9, α2 indicates the length from the axis 9 to the axis 15, α3 indicates the length component from the axis 15 to the axis 19, and α4 represents the length component from axis 19 to point B where the extension line of welding torch 27 and the extension line of axis 21 intersect. α5 to α8 indicate the dimensions of the rotating shaft 23, the torch mounting bracket 25, and the torch 27.

Further, point P is the tip of the welding torch 27, that is, the welding point, and point B is the intersection of the extension line of the welding torch 27 and the extension line of the shaft 21. Point Q is the intersection of axis 19 in FIG. 1 with a plane parallel to pivot arms 11, 17 and 21 in FIG. 1 and including point B. Point F is the intersection of the plane parallel to the rotating arms 11, 17 and the rotating axis 21 and including point B and the axis 15 in FIG.
Point G also points to the rotating arms 11, 17 and the rotating shaft 2.
The plane parallel to 1 and containing point B and the axis 9 in FIG.
It is the intersection with and points B, Q, F and G
are on the same plane, and let this plane be the surface RS where the robot exists.

Furthermore, the orthogonal coordinates XYZ are also the same as the coordinates XYZ in FIG. 1, and are assumed to be an absolute system. Cartesian coordinates
The Z axes of XYZ are provided to coincide with the rotation center (not shown) of the joint angle α1. O is the origin of the rectangular coordinates XYZ. The rectangular coordinates X'Y'Z' are the coordinates of the robot system, and the origin is located at point G on the robot. e1 and e5 are rectangular coordinates XYZ, respectively
Indicates the deviation of the origin G of the rectangular coordinates X'Y'Z' from the origin of .

Also, the rectangular coordinates αβγ are the coordinates of the torch system,
Point B is the origin.

Here, the rectangular coordinate system is expressed by each translational axis component and angular component (X, Y, Z, φ, θ), and the angular coordinate system is expressed by the angular component (α1, α2, α
3, α4, α5).

When each angle α1 to α5 is given in Figure 8, the X-axis component Px, Y-axis component Py, and Z-axis component Pz about point P are as follows from the relationships in Figures 9 and 10. . However, hereinafter "sinαi" will be expressed as "si" and "cosαi" will be expressed as "ci".

Px＝c ₁ {a ₂ s ₂ + a ₃ s ₂₊₃ + (a ₄ − a ₇ ) s ₄ −e ₄ c ₄ c ₅ + e ₅ } + s ₁ (e ₄ s ₅ −e ₁ ) Py＝S ₁ {a ₂ s ₂ +a ₃ s ₂₊₃ +(a ₄ −a ₇ )s ₄ −e ₄ c ₄ c ₅ +e ₅ }−c ₁ (e ₄ s ₅ −e ₁ ) Pz＝a ₁ +a ₂ c ₂ + a ₃ c ₂ + 3 + (a ₄ − a ₇ ) c ₄ + e ₄ s ₄ c ₅ Also, the orientation angle φ and attitude angle θ of the torch 27
is as follows, where tx, ty, and tz are the directional coarcs to each axis.

θ=tan ^-1 (txy/-tz) = tan ^-1 (ty/tx) However, tx=c ₁ (c ₄ c ₅ s ₆ + s ₄ c ₆ ) - s ₁ s ₅ s ₆ ty=s ₁ ( _{c4c5s6 + s4c6 ) + c1s5s6tz = c4c6 − s4c5s6txγ} = ⁽ _{t2x + ty2 ) 1/2} ^.

That is, in the coordinate transformation from the α system to the XYZ system in step S115 in FIG.
XYZ position information is required.

Note that when the system changeover switch 117 is switched so that the robot R operates in the α system, as described above, for example, in step S115,
Coordinate transformation is performed from the α system to the XYZ system, but when operating in the α system in this way, the angles α1 and α2, and the angle α2
With respect to α3 and angles α4 and α5, whether they are in the first state or the second state is determined by flags as follows.

First, a flag is set to determine whether the angles α1 and α2 are in the first state or the second state.
The contents of YFLG1 are determined by the sign of the following equation.

YFLG1=e ₅ +a ₂ s ₂ +a ₃ s ₂₊₃ +a ₄ S _4First state YFLG1≧0 Second state YFLG1<0 Next, determine whether the angles α2 and α3 are in the first state or the second state. The state of flag YFLG2 to be determined is determined as follows depending on the sign of the following equation.

YFLG2=α3 First state YFLG2≧0 Second state YFLG2<0 Furthermore, the state of flag YFLG3, which determines whether the angles α4 and α5 are in the first state or the second state, is determined by the sign of the following equation. It is determined as follows.

YFLG3=π/2−|α5| First state YFLG3≧0 Second state YFLG3<0 Next, coordinate transformation from the XYZ system to the α system (flag YFLG1 ,YFLG2,
considering the sign of YFLG3) and step S11
Identification of the critical zone at 0 will be further explained with reference to FIGS. 11 to 13.

During teaching or interpolation control, the target position is each translational axis component (Px,
Py, Pz) and angle components (θ, ), calculations are required to convert these into the α system, that is, the drive amount of each rotation axis.

The translational components of the orthogonal coordinate XYZ system of point B are Bx, By, and Bz as described above.

In addition, for the following, the orientation angle and attitude angle θ are
COS and SIM are displayed as follows.

_c = cos _s = sin θ _c = cos θ θ _s = sin θ First, the calculation for determining the angle α1 will be explained with reference to FIG.

FIG. 11 is a schematic diagram of the articulated robot R viewed from above. In Figure 11, α1, e ₁ , e
The symbols 5, B, G and RS are taken as in FIG. 9 and have the same meanings. However, point F,
Q and P are omitted. The line OG' is a line drawn from the origin O of the XYZ coordinates to the surface RS where the robot exists, and the point G' is the intersection of this perpendicular line and the surface RS.
By the way, regarding this robot R, the angle α2 can be taken in the + direction, so when one joint angle α1 is taken in the + direction and in the unidirectional direction, point B comes to point Ba and point Bb, respectively. Then, when point B is at point Ba, it is in the positive direction with respect to line OG', and when it is at point Bb, it is in the negative direction with respect to line OG'. In each case, the angle is as shown below. The calculation formula for α1 will change.

The angle α1 is found as follows.

The X-axis component Bx and Y-axis component By of point B are as follows.

Bx=α5θ _{s c} +Px By=α5θ _{s s} +Py Based on these Bx and By, the length component W ₁ and angle components W ₂ and W ₃ in FIG. 11 are determined.

W ₁ =(B ² _x +B ² _y −e ² ₁ ) ^1/2 W ₂ =tan ⁻¹ e ₁ /W ₁ W ₃ =tan ⁻¹ By/Bx Here, determination using the flag YFLG1 is required. Flag YFLG1 is at point B in Figure 11.
It switches when it matches G', that is, when it reaches directly above the robot R. And the flag of
YFLG1 switches, that is, joint angle α2 and α1
is from the first state to the second state or from the second state to the first state
Area where the state changes (critical zone CZ)
The entry into is determined by the following formula, where ε ¹ is a specified positive number.

(B ² _x +B ² _y −e ² ₁ ) ^1/2 <ε ₁ Then, if the vehicle is in the critical zone CZ, the display lamp 103 on the operation panel 100 lights up.

Therefore, when YFLG1≧0 α ₁ =W ₃ −W ₂ When YFLG1<0 α ₁ =W ₃ +W ₂ −π For a certain joint angle α1, when point B is at point Ba and when point Bb The calculation formula for determining the joint angle α1 is different depending on when the joint angle α1 is.

When point B comes to point Ba, the joint angle α1 can also be α'1, as shown by the broken line in FIG. In this case, since point G' also comes to G'', point B is in the negative direction with respect to G', and the flag YFLG
1 becomes -, and the joint angle α2 also becomes different. That is, for the same position of the torch 27, at least two joint angles are taken in two ways. Then, when joint angle α1 is α′ ₁ , point B is Ba
When it is at a point, the joint angle α′ ₁ is calculated using the above formula, and when it is at a point B′b, it is calculated using the above formula.

Next, calculations for determining the angles α4 and α5 will be explained with reference to FIG. 12.

FIG. 12A is a schematic diagram mainly showing the Q point portion of the articulated robot R in FIG.
represents the coordinates of the torch system. Point Q is determined from the torch angles φ, θ and α1 given by FIG. 12A. In this case, from the (αβγ) system, (X′Y′Z′)
Perform the conversion to a system. And α ² + β ² = e ₃ ² , γ
= ^- 〓 Find the intersection of the circle ₈ and the plane y′=0.

α β γ 1=θ _c 0 θ _s 0 1 −θ _s 0 θ _s 1φ _c φ _s −φ _s φ _s 1 1 x′ y′ z′ 1 α β γ 1=θ _c 0 θ _s 0 −θ _c φ _s φ _c −θ _s φ _s 0 −θ _s 0 θ _c 0 0 0 0 1X′ Y′ Z′ 1 Therefore, α, β, and γ are respectively given by the following equations.

α=θ _c φ _c x′−θ _c φ _s y′−θ _s z′ β=θ _s x′+φ _c y′ γ=θ _s φ _c x′−θ _s φ _s y′+θ _c z′ and , y'=0, α, β, and γ further become as follows.

α=θ _c φ _c x′−θ _s z′ β=φ _s x′ γ=θ _s φ _c x′+θ _c z′ Also, from γ=−a ₈ , the following equation (2) is given, α ² + β ² = e ₃ ² gives the following equation (3).

θ _s φ _c x′+θ _c z′+α ₈ =0 …(2) θ _c ² φ _c 2x′2−2θ _c φ _c θ _s x′z′ +θ _s ² z′ ² +φ _s ² x′ ² = e ² ₃ ...(3) By substituting z′=−(θ _s φ _c x′+α ₈ )/θ _c into the above equation (3), the following equation is obtained.

(φ _c ² + θ _c ² φ _s ² )x′ ² +2α ₈ θ _s φ _c x′ + (α ₈ ² 〓 _s ² −e ₃ ² θ _c ² )=0 When determining the discriminant WD in the above equation, discriminant
The WD is as follows.

WD=α ₈ ² θ _s ² φ _c ² − (φ _c ² + θ _c ² φ _s ² ) (α ₈ ² θ _s ² −
e ₃ ² θ _c ² ) =α ₈ ² θ _s ² φ _c ² −α ₈ ² θ _s ² φ _c ² +e ₃ ² θ _c ² φ _c ² −α ₈
² θ _s ² θ _c ² φ _s ² +e ₃ ² θ _c ⁴ φ _s ² = e ₃ ² θ _c ² (φ _c ² + θ _c ² φ _s ² ) − α ₈ ² θ _s ² θ _c ² φ _s ²
=θ _c ² {e ₃ ² (φ _c ² +φ _s ² θ _c ² )−α ₈ ² θ _s ² φ _s ² } Therefore, if the value of this discriminant WD is negative, point Q exists. It would be impossible. Also, if WA=φ _c ² + θ _c ² φ _s ² WB=α ₈ θ _s φ _c WC=α ₈ ² θ _s ² −e ₃ ² θ _c ² , then the x' coordinate of point Q is x'= −WB±(WB ² −WA×WC) ^1/2 /WA. The corresponding value of z′ is determined by x′=−(θ _s φ _c x′+α ₈ )/θ _c .

On the other hand, if x′ is found in the region of θ≦45°, and z′ is found in the region of θ>45°, then from equation (2) above,
Obtain x′=−(θ _c z′+α ₈ )/θ _s φ _c and set the gap as above (3
) to the expression. Then, the following formula is obtained.

(φ _c ² +θ _c ² φ _s ² )z′ ² +2α ₈ θ _c z′+φ _c ² (α
₈ ² θ _c ² −e ₃ ² θ _s ² ) + α ₈ ² φ _s ² = 0 Then, in the same way as finding x', Wa = φ _c ² + θ _c ² φ _s ² Wb = α ₈ θ If _c Wc = φ _c2 (α ₈ ² θ _c ² + e ₃ ² θ _s ² ) + α ₈ ² φ _s ² , then the discriminant WD is given by the following equation.

WD=Wb ² −Wa×Wc Therefore, the X-axis component x and the z-axis component Qz of point Q
are given by the following equations.

It is expressed as Qz=z′=−Wb±√WD/Wa Qx=x′=−(θ _c z′+α ₈ )/θ _s φ _c . In either case, the coordinates of point Q are
There are two points, Q ₁ (x′1, z′1) and Q ₂ (x′2, z′2).
These two different points are in the first state or the second state, respectively.
It corresponds to the state.

FIG. 12B shows the first state and the second state representatively for the case where θ=0°. However, Fig. 12B schematically shows the tip of the articulated robot R from point Q, and the plane RS (x'z' plane) where the robot exists is the xz plane
It is assumed to have been translated in parallel in the axial direction. Furthermore, flag determination is required regarding the first state and the second state. Flag YFLG3 switches. In other words, the fact that joint angles α4 and α5 have entered the region (critical zone CZ) where they switch from the first state to the second state or from the second state to the first state is expressed by the following equation, where ε ₃ is a specified integer. Desired.

π/2 | α ₅ | < ε ₃ And if it enters the critical zone CZ,
The display lamp 113 on the operation panel lights up.

Such flag YFLG3 code and torch 2
Regarding the attitude angle θ of 7, for example, when 0≦θ<1.0, the sign of ± in the above equation regarding Qz is + when YFLG3≧0 and − when YFLG3<0.

Here, with the origin as point B, the coordinates of the robot system (x', y', z') and the coordinates of point Q (Qx', Qy', Qz')
From this, determine angles α ₄ and α ₅ . First, since Qy'=0, α ₄ is given by the following equation.

α ₄ = tan ^-1 (-Qx)/(-Qz) Then, in order to find the angle α ₅ , from the robot coordinate system (x′, y′, z′), each (x″, y″, z″
)
seek. Then, in this (x″, y″, z″) system, (α
β γ)=(0 0 −1).

x″ y″ z″ 1=c ₄ 0 s ₄ 1 −s ₄ 0 c ₄ 1φ _c −φ _S φ _s φ _c 1 1θ _c 0 −θ _s 1 θ _s 0 θ _c 10 0 −1 0 c ₄ φ _c −φ _{s 4} φ _c 0 c ₄ φ _s φ _c s ₄ φs 0 −s ₄ 0 c ₄ 0 0 0 0 1=−θ _s 0 −θ _c 0 Therefore, x″ and y″ are respectively It is given by the following formula.

x″=−c ₄ φ _c θ _s +s ₄ θ _c y″=φ ₂ θ _s Then, if the reference line of angle α ₅ is the angle from the vertical line as shown in Figure 12C, then this angle α ₅ is given by the following formula.

α ₅ =tan ⁻¹ (−φ _s θ _s /c ₄ φ _c θ _s −s ₄ θ _c ) Next, the calculation for determining the angles α ₂ and α ₃ will be explained with reference to FIG. 13.

FIG. 13 is a schematic diagram of the multi-jointed robot R seen from the side, and the tip from point Q is not shown.
Figure A is the main view, and Figure B is a top view of Figure A. Angles α ₁ , α ₂ , α ₃ , points G, F, Q, line segments α ₁ , α ₂ , α ₃ , e ₁ , e ₅ are taken in the same way as in Figures 8 and 9, and the same have meaning. l ₁ and l ₂ are supplementary line segments, and W ₁ , W ₂ , and W ₃ are supplementary angle components.

First, when the position of point Q is found in the absolute coordinate system, each axis component Qx, Qy, Qz of this Q is given by the following equations.

Qx＝Bx＋x′cosα ₁ Qy＝By＋x′sinα ₁ Qz＝Bz＋z′ On the other hand, the coordinates of point G are (−e ₁ sinα ₁ +e ₅ cosα ₁ ,
e ₁ cosα ₁ + e ₅ sinα ₁ , α ₁ ), so the length component l ₁ ,
l ₂ and angle component W ₁ are each expressed by the following equations.

l ₁ = ± {(Qx+e ₁ s ₁ −e ₅ c ₁ ) ² + (Qy−e ₁ c ₁ −e ₅ s ₁ ) ² } ^1/2 l ₂ = {l ₁ ² + (Qz−α ₁ ) ² } ^1/2 W ₁ =tan ^-1 Qz−α ₁ /l _1And if WA=(α ₂ ² +l ₂ ² −α ³ ₂ )/2α ₂ l ₂ , then the angular component W2 is given by the following equation. Given.

W2=cos ^-1 (WA)=tan ^-1 {(1-WA2) ^1/2 /WA} Also, if WB=(α ₂ ² + α ₃ ² −l ₂ ² )2α ₂ α ₃ ,
The angular component W3 is given by the following equation.

W3=tan ^-1 {(1-WB2) ^1/2 /WB} Therefore, angles α ₂ and α ₃ are given by the following equations, respectively.

α ₂ =π/2−W ₁ ±W ₂ α ₃ =±(π−W ₃ ) Here, the sign of the flag YFLG2 is related to how to take ± in the above equation regarding the angles α ₂ and α ₃ . When flag YFLG2 switches, that is, when joint angles α ₂ and α ₃ enter the region (critical zone CZ) where they switch from the first state to the second state or from the second state to the first state, ε ₂ is specified. As a positive number, it can be calculated using the following formula.

｜α ₃ ｜＜ε ₂ If you enter the critical zone, the operation panel 1
The display lamp 113 above 00 lights up.

Then, according to the sign of the flag YFLG2, the angle α ₂
and α ₃ can be determined in two ways as follows.

When YFLG2≧0, α ₂ =π/2−W ₁ −W ₂ α ₃ =π−W ₃ When YFLG2<0, α ₂ =π/2−W ₁ +W ₂ α ₃ =W ₃ −π In this way, Then, coordinate transformation is performed from the XYZ system to the α system, and the critical zone is identified. At this time, the joint angles α ₁ , α ₂ , α ₃ ,
α ₄ and α ₅ are uniformly selected from two possible states.

As described above, according to the present invention, when the articulated robot R shown in FIG. In the process of coordinate conversion to information, it is determined whether the state of the arm and axis, that is, the state of the joint angle, is in the critical zone to obtain the position or posture of the welding torch 27 specified by this information. Can be displayed. Therefore, the decision to switch the system selection switch 117 to the α system or the XYZ system can be easily made not only by visually checking the arms and axes of the robot, but also by checking the display on the operation panel 100. The effect of being able to do this is demonstrated. Moreover, as a result, the effect of facilitating the teaching operation is exhibited.

Although this embodiment shows the case of teaching playback, it goes without saying that it can be implemented simply in manual mode operation like a manipulator.

As shown in FIG. 1, the above is a polygon system configured so that at least two joint angles can take two different states when the welding torch, which is a controlled object, is controlled to the same position or the same posture. Although this embodiment is applied to an articulated robot, it is also possible to implement the present invention in a multi-jointed robot in which the two joint angles described above can only be in a uniform state. In that case as well, the area where it is appropriate to provide the position or orientation information of the controlled object by providing the position or orientation information of the controlled object in a rectangular coordinate system, that is, the limit of the operating range in this case. This has the effect of making it easy to determine that the area is within the range.

Furthermore, as another embodiment, it is possible to implement the present invention in a polar coordinate robot in which position or orientation information of a controlled object is given by selecting either a rectangular coordinate system or a polar coordinate system. In this case, as in the above-described embodiments, it is possible to easily determine a region in which it is appropriate to provide position or orientation information of a controlled object using a rectangular coordinate system.

Note that the implementation of the present invention is not limited to the above-mentioned embodiments, and each structure may be replaced with an equivalent one, and such a case also falls within the technical scope of the present invention.

As described above, according to the present invention, the control device itself can identify and display whether the arm or axis of the articulated robot is within the critical zone, instead of determining whether the arm or axis of the articulated robot is within the critical zone. When reversing the bending state of the shaft from one state to the other, the operation can be appropriately switched between the Cartesian coordinate system and the joint system. This makes the articulated robot easier to operate, and the troublesome work of removing the workpiece to avoid obstacles on the moving path of the articulated mechanism is reduced, allowing efficient robot operation.

[Brief explanation of the drawing]

The drawings show the background and embodiments of this invention, and FIG. 1 is an illustrative view of an articulated robot that serves as the background of this invention and shows an embodiment of this invention. Moreover, FIG. 2 is a schematic diagram showing the background of this invention. FIG. 3 is a block diagram showing the control system of this articulated robot. In Figure 3, 31...CPU, 33...Memory, 119-1
27...Switches used to operate in the orthogonal coordinate system, 129-137...Switches used to operate in the multi-joint system, 117...System selection switch, 103...Teaching operation switch, 35
1 to 355...Drive circuit. FIG. 4 is a flow diagram of manual mode.
In FIG. 4, step S107... operating means, step S1
09, S110...Joint angle control means, step S
113...Operation means. FIG. 5 is a teaching flow diagram. Fifth
In the figure, step S117, step S11
9...Teaching means. FIG. 6 is a flow diagram of auto mode. 6th
In the figure, S121 to S141...Joint angle control means FIG. 7 is a flowchart of the subroutine in FIG. 6. In FIG. 7, steps S151 to S1
59...Joint angle control means. 8 to 14 are schematic diagrams showing embodiments of the present invention regarding the articulated robot of FIG. 1.

Claims (1)

[Claims] 1. For one position, one posture, or one position/posture of a controlled object, the bending states of adjacent arms or shafts that sequentially support the controlled object are defined as 2. A joint mechanism that can be used in various ways, a drive means for driving this joint mechanism, a drive command means for giving a drive command to this drive means, an operation input means using a joint system, an operation input means using a rectangular coordinate system, and a method for inputting these input means. An articulated robot comprising a switching means, a storage means for receiving input information from the input means, and a coordinate conversion means between a rectangular coordinate system and a joint system, wherein each joint angle of the joint mechanism, the main point of the arm or axis is performs a functional operation using the length of the part as a variable, and identifies that the arm or shaft is in a critical zone between transitions from one of the two bent states to the other; The articulated robot comprises a critical zone identifying means, and a critical zone displaying means for displaying that the arm or shaft is within the critical zone based on the output of the identifying means.