JPH0126828B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an articulated robot, and particularly to an articulated robot suitable for teaching in a rectangular coordinate system and driving in an articulated coordinate system. BACKGROUND OF THE INVENTION Articulated robots have traditionally been used for manipulators or other automatic machines. An example of such an articulated robot is the one disclosed in Japanese Unexamined Patent Publication No. 49-50376. FIG. 14 is a schematic mechanical diagram showing an example of such an articulated robot, and for ease of understanding, the position and orientation of the end effector EE in a two-dimensional plane (X-Z plane) are shown here. We are considering an articulated robot that can control As shown in the figure,
This multi-jointed robot has four arms _A1 to _A4 connected sequentially by three joints _E1 to _E3 , and an end effector EE is attached to the tip arm _A4 . ing. When controlling this multi-jointed robot, the joint angles of each joint _E1 to _E3 are specified, thereby setting the position and posture of the end effector EE to desired values. Teaching methods for multi-joint robots for such control include teaching the joint angles of each joint _E1 to _E3 (teaching in a multi-joint coordinate system), and teaching the position and posture of the end effector EE. is taught in a rectangular coordinate system (X-Z system),
There is a method in which the joint angles of each joint E ₁ to _{E 3} are obtained through coordinate transformation from a rectangular coordinate system to a multi-joint coordinate system. In applications where the end effector EE often moves in a straight line, such as for welding or seaming, a method that allows teaching and playback to be performed as if it were a Cartesian coordinate system robot is used. ing. However, in the teaching method described above, even if the position and orientation of the end effector EE are specified in the Cartesian coordinate system, the values of each joint angle in the multi-joint coordinate system may not be uniquely determined. One of the causes of this situation is redundant degrees of freedom, that is, degrees of freedom necessary and sufficient to freely transform the position and orientation of the end effector EE within a predetermined range (hereinafter referred to as "adapted degrees of freedom"). ”) may have more degrees of freedom. In this case, there are naturally a plurality (infinite number) of states for setting the end effector EE in the same position and posture. However, even if the number of degrees of freedom itself is a matching degree of freedom, the above situation may occur. For example, in the example shown in Figure 14, a total of three degrees of freedom are the "adaptation degrees of freedom": two degrees of freedom for positioning in the two-dimensional plane, and one degree of freedom for positioning in the two-dimensional plane. Yes, the articulated robot shown is
This degree of freedom of adaptation is ensured by E ₁ to _{E 3} .
Nevertheless, the end effector shown
For the same position and posture of the EE, it can take two states: the joint state shown by the solid line (right bent state) and the joint state shown by the broken line (left bent state). As is easily understood, such a situation does not occur in an X-Z rectangular coordinate robot (not shown), but is a situation unique to an articulated robot.
It should be noted that, as can be easily seen, this situation occurs when a robot has four or more arms connected by three or more joints, regardless of whether it is a two-dimensional articulated robot or a three-dimensional articulated robot. Occurs only if it exists. If joint E ₂ in Figure 14 is removed, 2
It is clear that the above situation no longer occurs when it comes to joints. If such a situation exists, indeterminacy remains in the above coordinate transformation, so conventionally, for example, joint _E2 in Fig. 14 is subjected to coordinate transformation with the condition that it only bends to the right. I was getting used to it.
In this way, the coordinate transformation becomes unambiguous, and
The above uncertainty will be resolved. [Problem to be Solved by the Invention] However, if teaching or playback is performed with the multi-jointed robot shown in FIG.
Problems of interference with the IP (eg workpiece) arise. That is, when moving the end effector EE in the (-Z) direction from the illustrated state,
Arm A ₂ interferes with the obstacle IP. To avoid this, it would be possible to have joint _E2 bend to the left, but this is prohibited due to the above restrictions. Therefore, it is necessary to temporarily remove the obstacle IP, which reduces the efficiency of the work. Even if control were performed to allow only left turns, the position of the obstacle IP may change, so this would not fundamentally solve the above problem. In this way, in conventional articulated robots, limits are placed on the possible range of joint angles in order to ensure the unambiguousness of coordinate transformation. There was a problem that it required complicated work. (Conversely,
If the obstacles are not removed, the robot's range of motion will be significantly restricted. ) Such problems occur not only in two-dimensional articulated robots with adapting degrees of freedom as illustrated in Fig. 14, but also in three-dimensional articulated robots with adapting degrees of freedom (an example of which will be described later). It has become a common problem. [Object of the Invention] The present invention is intended to overcome the above-mentioned problems in the prior art, and is aimed at an articulated robot with adaptable degrees of freedom, and is intended to solve the problem of the robot and the obstacle without requiring the task of removing the obstacle. It is an object of the present invention to provide an articulated robot that can prevent interference with the robot and that has fewer restrictions on the robot's operating range. [Means for Solving the Problems] As shown in FIG. 1A, the articulated robot of the present invention includes (a) an articulated mechanism, (b) a drive means, (c) an operation input means, and (d) a storage means. , (e) Drive command signal generating means. Among these, the multi-joint mechanism is specified by the following conditions (a-1) to (a-4). (a-1) Contains four or more arms articulated sequentially by three or more joints. (a-2) An end effector is attached to the distal arm. (a-3) A necessary and sufficient degree of freedom to arbitrarily change the position and posture of the end effector within a predetermined position range and posture range is ensured by the connection through the above-mentioned joints. This is a condition of having the "adaptation degree of freedom" described above, and will be referred to as "adaptation degree of freedom condition" below. For example, when arbitrarily performing three-dimensional positioning and attitude determination in three-dimensional space, the roll angle Rl in the Euler angle representation in Fig. 1B,
Considering the case where there is no need for a degree of freedom to independently change only the roll angle Rl of the end effector EE among the pitch angle P _t and the yaw angle Y _w , two degrees of freedom are required for the posture. total,
3 (position) + 2 (posture) = 5 is the adaptation degree of freedom. "Necessary and sufficient" means that the degree of freedom for adaptation is neither less than nor greater than the above degree of freedom (that is, there is no redundant degree of freedom). (a-4) When each combination of joint angle values of each joint is called a joint angle state, there are multiple joint angle states in which the position and posture of the end effector are the same (hereinafter referred to as This condition is called the ``multivalent state condition''). In the example of FIG. 14 described above, the right-turning state and the left-turning state are "multiple joint angle states" that bring the end effector to the same position and posture. It has been known that there are various multi-joint mechanisms that satisfy such multivalent state conditions (examples will be described later). The driving means (b) is a means coupled to each joint to drive each joint. During teaching, the operation input means (c) inputs (c-1) position and orientation data DP representing the commanded position and commanded orientation of the end effector, and (c-2) the aforementioned commanded position and commanded orientation. This is for operating and inputting state designation data DS that selectively designates which of the joint angle states is to be realized. That is, in addition to the commanded position and commanded orientation of the end effector, which of a plurality of functional angle states is to be used to realize the commanded position and orientation is specified by the operational input. In addition, the storage means (d) stores the position/orientation data DP and state designation data inputted in this manner.
It is a means to remember the DS. Further, the drive command signal generation means (e) generates the state designation data DS based on the position/orientation data DP and the state designation data DS read from the storage means.
This means generates a drive command signal for making the position and orientation of the end effector coincide with the commanded position and commanded orientation, respectively, while maintaining the joint angle state specified by , and outputs it to the driving means. That is, in the present invention, in FIG. 1, in addition to the position and orientation data DP, the state designation data
The DS is operated as an input during teaching, and when driving a multi-joint mechanism during playback, etc., the state specification data DS can be used to specify the joint state and generate a drive command signal. It is characterized by its unique structure. [Operation] At each teaching point, the operator determines which of the plurality of joint angle states to realize during teaching based on the situation of obstacles existing around the multi-joint mechanism. The operator inputs state designation data indicating the selected joint angle state together with position and orientation data from the operation input means, and these data are stored in the storage means. Since the command position and command orientation are indicated by position and orientation data, the state designation data does not need to include the absolute value of each joint angle. That is, any data is sufficient as long as it is sufficient to specify one of the plurality of joint angle states allowed when the command position and command posture are given. During playback, the drive command signal generation means reads the data from the storage means and generates a drive command signal for setting the end effector at the command position and orientation while taking the state specified by the state designation data; It outputs it to the driving means. The drive means drives each joint accordingly, so that the end effector moves to the commanded position and commanded posture while avoiding obstacles and the like. [Embodiment] A Mechanical configuration of the embodiment FIG. 2 is a perspective view showing the mechanical configuration of the articulated robot RB, which is an embodiment of the present invention. This multi-joint robot RB is formed as a welding robot and is equipped with a multi-joint mechanism JM having the following members. First, a fixing member 1 is fixed on the ground in order to support the multi-joint mechanism JM on the ground.
A cylindrical base 3 is attached to the fixed member 1. A cylindrical rotating body 4 is provided at the upper end of the cylindrical base 3 so as to be freely rotatable around a rotating shaft (not shown). A vertical rotating shaft (not shown) is provided in the hollow portion of this cylindrical rotating body 4, and a rotating body 5 is provided above this cylindrical rotating body 4 and supported so as to rotate integrally therewith.
The cylindrical rotary body 4 and the rotary body 5 are connected to a first motor (not shown), and are driven to rotate at a rotation angle _α1 . The rotating body 5 has support members 7a and 7b extending substantially perpendicularly and parallel to each other from its upper surface. A rotating arm 11 is supported by the support members 7a, 7b so as to be rotatable about a rotation angle _α2 by a horizontal shaft 9. Note that this rotating arm 11
is coupled to a second motor (not shown) and rotationally driven by the motor. Further, a balance mechanism 13 is provided for balancing the rotating arm 11 when it rotates. A rotary arm 17 is rotatably supported at the tip of the rotary arm 11 by a shaft 15 parallel to the shaft 9 (rotation angle α ₃ ). This rotating arm 17 is rotationally driven by a third motor (not shown).
A rotating shaft 21 is rotatably supported at one free end of the rotating arm 17 by a shaft 19 parallel to the shaft 9 (rotating angle α ₄ ). This shaft 21 is rotationally driven around the shaft 19 by a fourth motor (not shown). A rotary shaft 23 that supports a torch fixture 25 is rotatably supported on the shaft 21 coaxially with the shaft 21 (rotation angle α ₅ ). This shaft 23
is connected to a fifth motor (not shown), and is rotationally driven about the shaft 21 by this motor. A welding torch 27 as an end effector is attached to the torch fixture 25. In this way, this welding multi-joint robot RB includes a rotating body 5, a rotating arm 11, and a rotating arm 1.
7. _{The posture} and _{position of} the welding torch ₂₇ (specifically is the position of the welding point P at the tip)
control. The control device for the articulated robot PB is the second one.
It is not shown in the figure, and will be described later. B Properties of Multi-joint Mechanism JM Here, in what manner the above-mentioned multi-joint mechanism JM satisfies the "compatibility degree of freedom condition" and the "state multivalence condition" will be explained. (B-1) Compatible degrees of freedom conditions The articulated robot RB shown in FIG. 2 is constructed with the intention of arbitrarily changing the position and posture of the welding torch 27 within a three-dimensional space. Therefore, 3 degrees of freedom per position,
Two degrees of freedom are required for each pose, and a total of five degrees of freedom are the necessary and sufficient degrees of freedom (ie, adaptation degrees of freedom). The articulated robot RB shown in Fig. 2 has five degrees of freedom regarding the rotation angles α ₁ to α ₅ .
The positioning in three spatial directions and the two postures θ and φ can be arbitrarily performed. Therefore, it can be seen that the articulated robot RB has a degree of freedom of adaptation in the three-dimensional spatial domain. The length of each arm is also determined to ensure the necessary range. (B-2) Multivalent state condition Figure 3 is a simplified schematic diagram of the multi-joint mechanism JM. In this multi-joint mechanism JM, the joint angle state where the position and posture of the welding torch 27 are the same (that is,
There are four combinations of joint angles α ₁ to _{α 5} . That is, as shown in FIG. 4A, the joint (axis 15) between arms 11 and 17 is first adjusted while keeping the positions of axes 9 and 19 constant.
There are two joint angle states depending on whether the angle is a mountain fold A ₊ (solid line) or a valley fold A _- (dashed line). Further, as shown in FIG. 4B, a welding torch 27
There are also two joint angle states: a state B _- (solid line) in which the arm 21 is on the side of the fixed member 1, and a state B ₊ (broken line) in which the arm 21 is on the side farther from the fixed member 1. Although joint α ₅ is not a bent joint, in state B _- the arm 21 is tilted inward (toward the fixed member 1 side), so state B _- is called an "inward folded state", and state B ₊
Here, we will call this the "outward bending state" to mean that the arm 21 is tilted outward. In this specification, joint angle states that are distinguished by differences in the rotational directions of a given joint will be referred to as "bent states." One of the states is specified by specifying the "bending direction" of the joint. Furthermore, the entirety of a plurality of joint angle states (four states in the example considered here) in which the position and posture of the welding torch 27 are the same is referred to as a "conjugate state." Since the joint angle state options (A ₊ , A _- ) and (B ₊ , B _- ) in Figs. 4A and 4B are independent, A ₊ A total of four bending states can be taken: B ₊ , A ₊ and B _- , A _- and B ₊ , A _- and B _- . In fact, FIG. 6 shows examples of the four bending states described above when the position and orientation of the welding torch 27 are set to the same value Q. In these four states,
Not only the joint angles α ₃ and α ₅ are different, but the other joint angles are also different from each other, but the joint angle α ₃
They are mutually distinguished by the state of α 5 and α ₅ . What should be noted here is that these four bending states are not four states arbitrarily selected from a large number of states, but if the position and orientation of the welding torch 27 are specified and fixed, the positions can be changed. This means that only these four states exist for postures. Therefore, it is not possible to maintain the same position and attitude of the welding torch 27, for example, in a state intermediate between a and b in FIG. 6. In other words, after specifying the position and orientation of the welding torch 27 (abstractly indicated by the symbol Q in the figure), select and specify which of these four bent states (conjugate states) it is in. , joint angle α ₃
And not only α ₅ but also all joint angle values are uniquely determined. In such an embodiment, the multi-joint mechanism JM
is an example of a mechanism that satisfies the "multivalent state condition". (B-3) Critical Zone Here, I will explain the definition of "critical zone" that will be needed later. As an example, the second
Looking at the rotating arms 11 and 17 in the figure, the relationship between these arms 11 and 17 at any value of the rotating angle α ₃ can be classified as shown in FIG. In FIG. 7, a indicates that arms 11 and 17 are connected to axis
They are arranged almost linearly with respect to each other.
In FIG. 7b, the arms 11 and 17 are bent in such a way that the axis 15 points upwards, just as it is shown in FIG. And the seventh
FIG. 7c shows a situation that is just the opposite of FIG. 7b. Furthermore, in FIG. 7d, the bending of the arms 11 and 17 is much smaller than in the state shown in FIG. 7b. Similarly, Figure 7e
In this case, the bending (absolute value of joint angle α ₃ ) is very small compared to the state shown in FIG. 7c. The situations shown in FIGS. 7d and 7e can be handled in substantially the same way as in FIG. 7a. The "critical zone" refers to cases where the degree of bending of the two arms is very small as shown in Figure 7 d and Figure 7 e, or there is no bending at all as shown in Figure 7 a. The zone has a predetermined number of minute widths.
Therefore, the states shown in FIGS. 7a, d, and e are called "states in the critical zone." The critical zone thus defined for arms 11 and 17 is as shown in FIG. 4A.
It is a zone that must be passed through when reversing the joint angle state between A ₊ and A _- . In addition, Fig. 7a shows the boundary (critical) state between the mountain fold state and the valley fold state,
Because the zone is centered around this boundary state, it is called the "critical zone." Similarly, a critical zone can also be defined for the case where the joint angle state is reversed between states B _- and B ₊ in FIG. 4B. As already explained, the inwardly bent state B _- and the outwardly bent state B ₊ are two states that are distinguished depending on whether or not the arm 21 is on the fixed member 1 side with respect to the welding torch 27 . Therefore, the critical zone here is set in the middle when changing the joint angle state between these two bent states. Specifically, the welding torch 27 and torch fixture 25 in FIG.
The intermediate posture when inverted between the _states shown by The entire posture around these reference postures is defined as a critical zone. (Since Figure 2 shows the process of changing only the posture, the position of the welding torch is different between states 27a and 25a and states 27b and 25b, but in reality, the position of the welding torch is the same. The two states are states B _- and B ₊ .For this, the fourth
As already described in Figure B. ) In addition, when reversing the state between the conjugate states B _- and B ₊ , there is an option to change the joint angle α ₅ clockwise or counterclockwise, but here, The posture is changed by rotating in a direction in which the rotation angle α ₅ changes less. However, when the amount of change in the rotation angle α ₅ is the same in both directions as in the illustrated example, the rotation is performed in one direction specified in advance. And in each case, the conjugate state
The state reversal between B _- and B ₊ is made to occur through the critical zone. The meaning of the critical zone defined as above in controlling the multi-joint mechanism JM will be described later. C. Configuration of Control Device (C-1) General Configuration FIG. 8 is a schematic block diagram of the control device 200 used in the embodiment. In the figure, an operation panel 100 is provided with a mode changeover switch 101 for instructing in which operation mode the welding robot should be operated. This mode changeover switch 101 can selectively switch and set any one of manual mode (M), test mode (T), and auto (reproduction) mode (A). Of these,
The manual mode is a mode for teaching operations, and the test mode is a mode for checking teaching data while moving the robot step by step. Furthermore, the auto mode is a mode in which the robot continuously moves to perform work based on teaching data. The operation panel 100 is further provided with a push button switch 103 and a switch group 105. The pushbutton switch 103 gives a command to start the auto mode, and
Operated to give teaching commands in manual mode. switch group 10
The three pushbutton switches belonging to No. 5 are operated when instructing the welding robot to perform a linear interpolation operation, a weaving operation, and a circular interpolation operation, respectively. The speed setter 111 is for commanding the speed at which the welding torch 27 (and therefore the welding point P) should move. The operation panel 100 is further provided with two manual switch groups 121 and 131. The switch group 121 is operated to control the position of the welding robot in a rectangular coordinate system, that is, an XYZ system. On the other hand, switch group 13
1 is used to directly control each rotation angle α ₁ to α ₅ . For this purpose, this operation panel 100 includes switch groups 121 and 1.
Select which of the 31 to enable. A system switching switch 117 is provided. Each of the switches belonging to these manual switch groups 121 and 131 has three
The position shown by the solid line in FIG. 8 is the neutral position. The three switches labeled X, Y, and Z are used to control the movement of the welding torch 27 in positive or negative directions parallel to the X, Y, and Z axes, respectively. Further, two switches labeled θ and φ are used to change the orientation degree φ and (in a narrow sense) attitude angle θ of the welding torch 27 clockwise or counterclockwise, respectively.
Similarly, α system manual switch group 131
By operating the rotation angle α ₁ to α ₅ of each arm or axis can be changed. The display lamp 113 and pushbutton switch 115 provided on the operation panel 100 are one of the features of this embodiment, and these will be described later. Then, between the operation panel 100 including each of these components and the data bus 55,
Data is exchanged via an interface (not shown). This data bus 55 further includes a CPU
31 and memory 33 are connected. memory 3
3 is for storing the system program and user program of CPU31.
Contains ROM, storage areas and flag areas necessary for calculations and other processing in the CPU 31
Includes RAM. The drive command signal generation means and storage means which are the constituent elements of this invention are realized by these CPU 31 and memory 33. The data bus 55 includes five drive circuits 351 to 35 corresponding to five rotation angles α ₁ to α ₅ .
5, and five rotary encoders 531 coupled to each joint to detect each joint angle α ₁ to _{α 5}
~535 are respectively concatenated. The drive circuits 351 to 355 are multi-joint mechanisms.
It is for driving the first to fifth motors (not shown) respectively connected to each joint of the JM, and has a built-in well-known feedback control circuit. Based on the drive command signal given from the CPU 31 and each joint angle detected by the rotary encoders 531 to 535, each motor (and therefore each joint)
to drive. (C-2) Indicator lamp 113 and switch 115 The indicator lamp 113 lights up only when the joint angles α ₃ and α ₅ of the multi-joint mechanism JM are in the respective critical zones described above. That is, the light is turned on when the relationship between the arms 11 and 17 in FIG. 7 is as shown in a, d, or e in the figure, and the attitude near the welding torch is near the state shown by the solid line 27 in FIG. 2. do,
Inform the operator. As will be explained later, in this example, it is a multi-joint mechanism.
This corresponds to the fact that JM allows inversion between conjugate states only when the state is in the critical zone. In addition, the display lamp 113
may be replaced by a notification buzzer, or may be used in conjunction with it. Push button switch 115 is a switch for instructing reversal between conjugate states by pressing it. As already mentioned,
In the multi-joint mechanism JM of this embodiment, there are four conjugate states shown in FIG. 6 for the same position and posture of the welding torch 27. Therefore, in principle, any one of these four conjugate states can be selected, but in this embodiment, only two states, "A ₊ and B ₊ state" are allowed, and "A ₊ "and B _- state" and "A _- and B ₊ state" are prohibited. Therefore, either the "A ₊ and B ₊ state" (hereinafter referred to as "up state U") or the "A _- and B _- state" (hereinafter referred to as "down state D") Therefore, it is sufficient to be able to externally input whether the commanded position and commanded posture are to be achieved by using a single pushbutton switch 1.
15 is sufficient. In this embodiment, instead of specifying the up state or down state for each teaching point one by one,
Press the push button switch 11 only when you want to reverse the state between the UP state and the DOWN state.
Make sure to press 5. Therefore, in this embodiment, "state designation data" is provided in the form of "bending direction reversal designation data" that collectively designates the bending direction of joints α ₃ and α ₅ . Note that the bending state at the first teaching point is determined in advance. The state reversal command by pressing the pushbutton switch 115 is issued by the display lamp 113.
It is enabled only when is lit (in other words, within the critical zone). It is the axis (joint) 15 as shown in Figure 7b and c.
If the state is reversed when the absolute value of the joint angle α ₃ in be. D Teaching Operation Based on the above preparations, the teaching operation of welding robot RB will be explained with reference to FIGS. 9A and 9B. First, prior to the process shown in FIG. 9A, the system changeover switch 11 provided on the operation panel 100 is
7 to the XYZ system. This is related to the fact that the weld lines on the workpiece often run at right angles to each other. In other words,
When the operator moves the welding torch 27 along the welding line during the teaching operation (manual mode), the rectangular coordinate system allows this movement to be performed more easily, and it also makes it easier to move the welding torch 27 in the replay mode later. This is because interpolation calculations and the like of . Thereafter, the operator sets the moving speed of the welding torch 27 during regeneration on the speed setting device 111, and uses the switch group 121 to instruct the direction in which the welding torch 27 should move. A timer is provided inside the CPU 31 to generate an output at predetermined time intervals. Then, when an output from this timer is generated and the switch operation as described above is performed, the CPU 31 determines what happens when the welding torch 27 is moved by a predetermined minute distance in the direction specified by the switch group 121. Once the command position and command posture of the welding torch 27 are
Find it using the XYZ system. Then, by converting the coordinates thereof, command values in the multi-joint system (α system) are calculated (steps S1, S3, and S5). In calculating this command value, whether to adopt the up state or the down state is based on the criterion that the bending state is the same as the bending state at the previous command value. Therefore, at the stage of coordinate transformation in step S5, it is not necessary to input the state designation data (folding direction reversal designation data) using the switch 115. Next, in step S7, it is determined whether the joint angle state calculated in this way is within the critical zone. For example, for the joint angle α ₃ , if the absolute value is less than a predetermined minute value when the angle is measured in the direction shown in FIG. 7, it is within the critical zone. and,
If it is within the critical zone, CPU31
Write logic 1 to the critical zone flag CZF included in the RAM of the memory 33, and set this flag.
Set CZF (step S9). In the following step S11, the CPU 31 determines whether the command value at the previous teaching point was in the critical zone. The determination in step S11 is made by checking the contents of the flag CZF that was taught last time. Next, in step S13, the CPU 31 determines whether there is a state reversal instruction, that is, whether the push button switch 115 of the operation panel 100 has been operated. That is, when the state before entering the critical zone is, for example, the up state U, and it is necessary to change it to the down state D next, the reversing switch 115 is operated. This reversing switch 115
is pressed after the operator confirms that the display lamp 113 is lit. When this state reversal instruction is detected, the CPU 31
In the following step S17, the up-down flag UDF in the RAM is inverted. For this flag UDF, for example, logic 1 may be written in the up state U, and logic 0 may be written in the down state D. On the other hand, in step S7, if the current command value is not in the critical zone, in the following step S15, logic 0 is written in the critical zone flag CZF and it is reset. Therefore, when considering a chain of command values (i-1), i, i', (i+1) as abstractly shown in FIG. , i′) consecutively and the latter command value
The flag UDF is inverted only when the switch 115 is pressed at i'. Conversely, when you want to invert the state, use 2
After giving a command value within the critical zone twice in succession, switch 115 is pressed when inputting a later command value.
Press . Thereafter, in step S19, the position and orientation command values of the XYZ system are coordinate-transformed according to the state of the up-down flag UDF, and the command values of the multi-joint system, that is, _α1 to _α5 , are calculated anew. Since the articulated mechanism JM satisfies the multivalue state condition, this coordinate transformation is multivalued (that is, a transformation with multiple solutions), but according to the up-down flag UDF, those multiple solutions Choose one. For example, when the flag UDF is "1", it is sufficient to find a solution that realizes the A ₊ B ₊ state (up state). The values of α ₁ to _{α 5} thus obtained are given to drive circuits 351 to 355 as drive command signals, and these drive circuits 351 to 355
Drives a motor connected to each joint. Therefore, in the example of FIG. 10A, the bending state is reversed when the welding torch 27 moves from the command value i to i'. Since state reversal when moving from command value i' to (i+1) is prohibited (determination result in step S7 becomes "No"), for example, down state D It remains as it is. Note that the command value i' is normally treated as a dummy point for inverting the flag CDF. In other words,
Later teaching data storage processing (Figure 9B)
In this case, data regarding the command value i' is not stored as teaching data. Then, only the command values (i-1), i, and (i+1) are stored as teaching data. This is because the bending state is reversed between the respective positions of the command value i and (i+1) during playback, which will be described later.
During teaching (manual mode), the CPU 31 cannot know the contents of the command value (i+1) until it is input, so the state is inverted at the dummy point i' in the critical zone for the time being. It is. Therefore, the dummy point i' is set only for state reversal in the manual mode, and its position and orientation instruction value may be the same as the instruction value i. Such processing is repeated every time a timer output is generated, and thereby the welding torch 27 sequentially moves along the trajectory intended by the operator. Then, in this manual mode, each time the position and orientation of the welding torch 27 become desired (teaching point), the process moves to storing the teaching data. Storage processing of this teaching data (9th B)
), the start button 103 on the operation panel 100 is pressed. That is, by setting the mode selection switch 101 to manual mode (M) and pressing the start button 103, the CDU
31 is interrupted for storing teaching data. When the interrupt occurs, the CPU 31 stores the position and orientation information and the states of the flags CZF and UDF at that time in a predetermined storage area of the memory 33 as teaching data. In addition, the following describes the flags CZF and UDF in the system, and the flags CZF and UDF stored for each teaching point in this way.
In order to distinguish them from UDF, the latter are expressed as "CZF _a " and "UDF _a ". The position and orientation information taught here is
This is XYZ type information. This is because, as described above, this is convenient for easier operation and calculations for interpolation control, for example. Therefore, in this embodiment, the position and orientation data input in the XYZ system is stored in the memory 33 together with the flags CZF _a and UDF _a , and the command value in the α system calculated in step S19 is It is not stored as data. E. Reproduction Operation Next, the reproduction operation (auto mode operation) of the multi-jointed robot RB using the teaching data obtained as described above will be explained with reference to FIG. Note that this auto mode operation is
Although this is performed after the test operation under the test mode, a description of this test operation will be omitted. In the case of auto mode, the operation panel 100
Set the mode setting switch 101 to auto mode A. And start button 1
Press 03. From the memory 33, the CPU 31
One piece of teaching data is read out (step S31). Steps S33 to S39 of the following steps
are the command position and command orientation at the teaching point just read out (hereinafter simply referred to as "target value").
This is for determining whether to make the bending state at the previous target value the same as the bending state at the previous target value, or to make it the opposite. As described above, the instruction contents of the bending state at each target value are stored as the up-down flag UDF _a in accordance with the operation input during teaching. Therefore, the current bending state can be determined depending on whether the up-down flag UDF _a stored at each teaching point is inverted between the previous and current target values. As already explained in the section "(C-3) Critical Zone", in order to suppress the large movement of each joint, in this embodiment, the state is limited only when the joint angle state is within the critical zone. Allow inversion. More specifically, (a) the previous target value is within the critical zone, (b) the current target value is outside the critical zone, and (c) the state is changed due to the inversion of flag UDF _a . Only when reversal is instructed, the bending state at the previous target value is reversed to become the current bending state. In other words, in Figure 10B, regardless of whether the previous target value was inside or outside the critical zone, the current target value is within the critical zone (as shown in Figure 10B), or if the previous and current target values are different from each other. If both target values are outside the critical zone (Fig. 10B), state reversal is prohibited, and state reversal is permitted only in the case of Fig. 10B, which satisfies the above (a) to (c). Therefore,
State reversal is allowed between the command value i and (i+1) in Figure 10A (as mentioned above, the command value i' is a dummy point and is not stored as teaching data. do not have). In addition,
FIG. 10B shows a situation that occurs as a result of pressing the switch 115 even though the display lamp 103 is not lit, and is treated as an error. The above-mentioned situations can be identified by referring to the flags UDF _a and CZF _a . This identification process is the step shown in Figure 11.
S33 to S37, and the symbols ~ in FIG. 11 correspond to those in FIG. 10B. Note that criteria other than this example may be used to determine in what cases inversion is permitted. If the state reversal is permitted, that is, the reversal of the folded state is instructed in the subsequent step S39. This is done by rewriting the up-down flag UDF in the system in accordance with the value _of the up-down flag UDF a read this time (the value stored in the teaching step in FIG. 9B). In the following step S41, preliminary calculations for interpolation control are performed. For example, in the case of linear interpolation, this is a process of calculating the interpolation pitch between two consecutive teaching points based on the command speed and the like. After that, the CPU 31
Sequentially calculate interpolation points based on the interpolation pitch etc. obtained by preliminary calculation (step
S43). Since the target value is expressed in the XYZ system,
Interpolation calculations in the XYZ system, which are important in practice, can be easily performed. Then, in step S45, each joint angle α ₁ ~ is adjusted to make the welding torch 27 match the given position and posture while taking the bent state indicated by the up-down flag UDF in the system.
Find the value of _α5 . For example, when the up-down flag UDF indicates up, that is, the A ₊ B ₊ state (up state), each joint angle α ₁ is set to the command position and command posture in the A ₊ B ₊ state.
The value of ~α ₅ is determined by coordinate transformation from the command position and command orientation in the XYZ system. Then, a drive command signal for realizing the values of each joint angle α ₁ to _{α 5} is generated and output drive is performed by outputting it to each motor (step S47). Thereby, the articulated mechanism
JM uses the welding torch 27 in the specified bent state.
is moved so that its position and orientation match the commanded position and commanded orientation, respectively, in the above-mentioned folded state. Steps S43, S45, and S47 are repeated until the welding torch 27 reaches the target position (steps
S49). Then, such processing is sequentially repeated for each target position, and when the welding work end point is reached, the regeneration processing is completed (step S51). F. Summary of Examples In this way, the value of the flag UDF is determined by the state specification data (folding direction reversal instruction data) input in the form of pressing the switch 115, and based on this, the same position and orientation are determined. By selecting one of a plurality of corresponding joint angle states (bent states A ₊ B ₊ and A _- B _- ), the multi-joint mechanism JM can be driven to avoid obstacles. . It can be understood from the fact that step S19 in FIG. 9 is executed in accordance with the flag UDF that such drive control can be applied to movement control of the multi-joint mechanism JM during teaching as well as during playback. G. Modification The multi-joint mechanism to which this invention can be applied is not limited to the above embodiment. For example, each mechanism shown in FIG. 12 can take two states, a state shown by a solid line and a state shown by a broken line, even when the respective positions and postures of arms T1 and T2 are specified. It is easy to understand what can be done. Therefore, multi-joint mechanisms including these mechanisms can satisfy the "multivalent stateability condition." Furthermore, the multi-joint mechanism shown in Figure 13A also satisfies the multivalent stateability condition and the adaptive degrees of freedom condition, and it has been known for a long time that various such mechanisms exist. . Furthermore, as shown in FIG. 13B, the rotating arm 17 in FIG. 2 can be rotatably attached to the rotating arm 11 about an axis perpendicular to the axis 9. Further, as shown in FIG. 13C, the shaft 21 in FIG. 2 may be used as a rotation shaft, and a rotation shaft may be attached to the end thereof. In other words, if there are three joints, three-dimensional positioning is possible.
In such a case, once the target position is determined, a variety of conditions may be easily conceived. For example, the position of a point or axis corresponding to axis 19 in FIG. 2 is controlled using a rectangular coordinate system, and
1 and 23 may be controlled using a joint coordinate system. In addition, in the above example, four joint angle states
Among A ₊ B ₊ , A ₊ B _- , A _- B ₊ , A _- B _- , A ₊ B ₊ and
Although only two states, A _- B _-, are used, two sets of flags CZF and UDF are provided, and two sets of conjugate states (A ₊ , A _- ) and (B ₊ , B _- ) can be independently set. The joint angle state may be specified so that all of the above four joint angle states can be selected. In this case, for example, as long as the joint angle α ₃ is within the critical zone (A ₊ , A _- )
It is sufficient to allow reversal between states. Note that even in the case of an articulated robot with redundant degrees of freedom, the joint angle state must be specified in some way, but in this case, in order to specify one state from an infinite number of conjugate states, a method such as the one in this invention is used. It is very difficult to use simple specification processing. Furthermore, providing redundant degrees of freedom makes the mechanism that much more complex. Therefore, in a multi-joint mechanism with adaptive degrees of freedom, this invention requires only one bending state to be specified from a finite number of bending states (usually only a few states). The technology is qualitatively different from that of the previous version. [Effects of the Invention] As explained above, according to the present invention, for a multi-joint mechanism that satisfies the adaptive degrees of freedom condition and the multivalent state condition, one of a plurality of joint angle states is determined by state specification data. Since drive control can be performed while arbitrarily selecting one, the multi-joint mechanism can be driven while adjusting the joint angle state so as to avoid obstacles. Therefore, interference between the robot and the obstacle can be prevented without requiring any work to remove the obstacle. Further, since the joint angle state can be specified arbitrarily among the plurality of joint angle states, there are fewer restrictions on the robot's motion range.

[Brief explanation of drawings]

FIG. 1A is a block diagram explaining the configuration of the present invention, FIG. 1B is an explanatory diagram of degrees of freedom regarding the posture of the end effector, and FIG. An explanatory diagram of the mechanism,
3 to 6 are explanatory diagrams of the multivalent state condition in the example, FIG. 7 is an explanatory diagram of the critical zone, and FIG. 8 is a block diagram of the control device used in the example. FIG. 9 is a flowchart showing the teaching operation, FIG. 10 is an explanatory diagram of state reversal conditions, FIG. 11 is a flowchart showing the reproducing operation, and FIGS. 12 and 13 are schematic diagrams of modifications of the present invention. Mechanism diagram, FIG. 14 is a schematic diagram of a two-dimensional multi-joint mechanism that satisfies the multivalent state condition. RB...Multi-joint robot, JM...Multi-joint mechanism,
27...Welding torch (end effector), 10
0...Control panel, 115...Push button switch for state reversal, _α1 to _α5 ...Rotation angle (joint angle).

Claims (1)

[Scope of Claims] 1. An articulated robot characterized by comprising each of the following elements (a) to (c). (a) Multi-jointed mechanism that satisfies all of the following conditions (a-1) to (a-4): (a-1) Four or more joints connected sequentially by three or more joints. (a-2) An end effector is attached to the distal arm; (a-3) To arbitrarily change the position and posture of the end effector within a predetermined position range and posture range, respectively. The degree of freedom necessary and sufficient for
(a-4) When each combination of joint angle values of the joints is referred to as a joint angle state, the positions and postures of the end effectors must be the same. (b) A driving means coupled to each of the joints to drive each joint; (c) During teaching of the multi-joint robot, the following (c-1) ) and (c-2): (c-1) Position and orientation data expressing the commanded position and commanded attitude of the end effector; (c-2) The commanded position and state designation data for selectively designating which of the plurality of joint angle states the commanded posture is to be realized by, (d) the position and orientation data input by the operation input means and the state designation. storage means for storing data: (e) Based on the position/posture data and the state specification data read from the storage means, the end effector is controlled to take the joint angle state specified by the state specification data; A drive command signal generation means for generating a drive command signal for making a position and orientation coincide with the command position and the command orientation, respectively, and outputting the generated drive command signal to the drive means. 2. The position/posture data is operationally inputted at each of a plurality of teaching points, and the plurality of joint angle states existing at each of the teaching points are mutually identified by the bending direction of a predetermined joint, and the state Claim 1, wherein the specified data is folding direction reversal instruction data that is input when reversing the folding direction at the current teaching point with respect to the folding direction at the previous teaching point. Multi-jointed robot. 3. The operation input means enables operation input for validating the operation input of the folding direction reversal instruction data at the current teaching point only when the command position and command orientation at the previous teaching point are within a predetermined range. 3. The articulated robot according to claim 2, further comprising a means for converting the robot to an articulated robot.