JPH0546563B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a robot control device, and in particular to a so-called force relief control that allows the movable parts of a vertically articulated robot to be moved freely by external force. The present invention relates to a robot control device that can perform the desired control.

[Conventional technology]

In recent years, various industrial robots have come to be used on factory production lines, and assembly robots are also being put into practical use.

However, in order to place a robot on a continuous line, which has traditionally been widely used in assembly work lines, to assemble objects (workpieces) that flow continuously on a conveyor, it is necessary to It is necessary to synchronize the movements between
It is extremely difficult to simultaneously control the work of the robot itself and synchronize it with the conveyor.

Therefore, while the robot is performing a certain task, if the movable parts such as arms are placed in a "relaxed state" where they can be moved freely by external force, the robot can follow the movement of the workpiece on the conveyor without any particular synchronous control. be able to.

As a conventional robot control device capable of such force-relaxation control, there is a device described in, for example, Japanese Patent Application Laid-Open No. 58-206389.

This device cuts off the drive current to an actuator, such as a motor, that drives a pre-specified movable part among multiple movable parts in a multi-axis robot, thereby allowing the movable part to be freely moved by an external force. This is what I did to get it.

However, in conventional robot control devices capable of stress relief control, the drive current (power) to the motor that drives the robot, for example, is cut off. Not only is it necessary to use a large and expensive magnetic switch with a large contact capacity, but it also requires measures to prevent inrush current flowing into the motor when the contacts are turned on and off, and frequent maintenance of the contacts. There were some problems, such as the need to do so.

Therefore, in order to control movable parts such as arms in robots, the drive current of the motor that drives the movable part is generally controlled in accordance with a command value based on the deviation between the speed command value and the speed feedback value from the speed detection system of the movable part. Therefore, by setting the command value based on the deviation between the speed command value and the speed feedback value to zero, regardless of the actual speed command value and speed feedback value, it is possible to The present applicant previously filed a patent application for a robot control device that allows parts to be moved freely by external force (Japanese Patent Application No. 265353/1982).

In this way, a compact and inexpensive relay switch with small contact capacity can be used as the switching control means for zeroing the command value based on the deviation, and when the contacts are switched, an inrush current is generated in the motor. Since there is no flow, there is no need to take preventive measures, and the number of times the contacts need to be maintained is reduced, so the above-mentioned problems can be solved.

[Problem that the invention seeks to solve]

However, even in such a robot control device, the drive current of the motor that drives each axis of the movable part of the robot is reduced to zero, and the robot is in a relaxed state. This can only be applied to horizontally articulated robots that have vertical joints that rotate movable parts in a vertical plane. There was a problem that it could not be applied because of the

The object of the present invention is to solve this problem and to enable strain relief control even for vertically articulated robots.

[Means for solving problems]

Therefore, the control device for a vertically articulated robot according to the present invention controls each movable part according to the command value based on the deviation between the speed command value output from the speed command system and the speed feedback value output from the speed detection system. In a control device for a vertically articulated robot that controls the drive current of a motor, the gravitational moment applied to the vertical joint axis of each movable part is calculated according to the posture of each movable part, and the gravitational moment is applied to the calculated gravitational moment. a gravity balance compensation circuit that outputs a compensation command value for generating shaft torque that can be resisted; a speed pseudo value corresponding to the speed command value such that the command value becomes zero; and a feedback pseudo value corresponding to the speed feedback value. a pseudo value output means for outputting a value, a current supply circuit that supplies a drive current to a motor of each movable part based on the command value or the compensation command value, and when an actuation signal is output, , the speed command system and the speed detection system are separated and connected to the pseudo value output means, and the gravity balance compensation circuit is connected to the current supply circuit, and the deviation between the speed pseudo value and the feedback pseudo value is A command value of zero and a compensation command value based on the speed control system are applied to the current supply circuit, while when a non-operation signal is output, the pseudo value output means is separated and the speed command system and the speed detection system are connected to each other. a command value control circuit that connects and disconnects the gravity balance compensation circuit from the current supply circuit, and supplies the current supply circuit with a command value based on the deviation between the speed command value and the feedback value; The present invention is characterized in that it has a switching circuit that selectively outputs an activation signal or a non-activation signal.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

First, the structure and operation of the robot used in this embodiment will be explained with reference to FIG.

In the figure, 1 is a vertically articulated robot, which has a lumbar axis 3 erected perpendicularly to a base 2 fixed on a pedestal (not shown), and a shoulder axis fixed at right angles to the lumbar axis. A first arm (upper arm) 5 connected to a motor 4, and an elbow shaft 6 at the tip of the first arm.
A second arm (lower arm) 7 is rotatably connected by a wrist shaft 8 at the tip of the second arm 7.
It consists of a hand 9 etc. which are rotatably connected by. This is schematically shown in FIG. 3.

The waist shaft 3 is a horizontal joint shaft that is rotated in the direction of arrow A in a horizontal plane by the motor 10.

The first arm 5 is moved in the direction of the arrow B by the motor 4, the second arm 7 is moved in the direction of the arrow C by the motor 11, and the hand 9 is moved in the direction of the arrow C by the motor 11. The shoulder axis, elbow axis 6, and wrist axis 8, which rotate in the direction of arrow D in a vertical plane and connect these, are vertical joint axes.

Note that the motors 4, 10, 11 and the wrist shaft drive motor (not shown) that rotates the hand 9 all use DC servo motors. The reduction gear that transmits the driving force of each of these motors is
Use one with relatively high reverse transfer efficiency.

Further, a tachogenerator for detecting the rotation speed and a potentiometer for detecting the rotation angle are attached to the output shaft of each of these motors.

The hand 9 has a holder 12 connected to the wrist shaft 8.
A nut runner 14 is provided with a socket 14a on the tip of which is tightened by holding a bolt in a piston rod that prevents the air cylinder 13 from rotating.
Further, a pair of limit switches 15 and 16 are attached to the holder 12, and are operated by a dog 14b attached to the nut runner 14 to detect the upper limit position and lower limit position of the nut runner 14. I'm trying to make it possible.

On the other hand, 17 is a container conveyor (hereinafter simply referred to as "conveyor"), on which a workpiece 18 such as an engine block, which is fixed in a predetermined position at a predetermined posture, is placed, and the workpiece 18 is moved along the arrow E within the work area of the robot 1. It is designed to be conveyed in the direction at a predetermined speed.

A bolt 19 (for example, a bolt for fixing a head cover to a cylinder head) to be worked on is set on the workpiece 18 conveyed by the conveyor 17.
Use hand 9 to tighten nut runner 1.
4 is to be performed by the robot 1 to which it is attached.

Furthermore, 20 is a bolt passage detector fixed to the upper end of a stay 21 installed on the floor, and is conveyed by the conveyor 17 when the robot 1 is waiting at a predetermined position as shown in the figure. It is detected when the bolt 19 on the workpiece 18 passes.

Note that as this bolt passage detector 20, for example, a reflective photoelectric switch or the like is used.

Moreover, the bolt 19 of this bolt passage detector 20
The positional relationship between the detection position and the nut runner 14 is such that when the bolt passage detector 20 detects the passage of the bolt 19 and when the nut runner 14 is lowered to the lowering limit, the apex socket 14a detects the bolt 19.
Build a relationship where you can relate to each other.

Instead of the bolt passage detector 20, a dog is provided at a predetermined position on the conveyor 17 corresponding to the bolt 19, and the dog hits a limit switch attached to a fixed part at a predetermined position along the conveyor 17. Passage of the bolt 19 may be detected by turning on this limit switch.

Next, an embodiment of the control device for the robot 1 shown in FIG. 2 will be described with reference to FIG.

In FIG. 1, numeral 23 is a central processing section using a microcomputer or the like, and is in charge of overall control of the robot 1.

That is, a servo control section for the motor 4 that drives the shoulder shaft that rotates the first arm 5, which is composed of a position command register 24, a position control section 25, a speed control section 26, a current control section 27, etc. , just like this servo control section, the position command register 3
4. A servo control unit for the motor 11 that drives the elbow shaft 6 that rotates the second arm 7, which is configured by a position control unit 35, a speed control unit 36, a current control unit 37, etc., and is not shown. However, in addition to controlling the servo control section for the waist shaft drive motor 10 and the servo control section for the wrist shaft drive motor, which are configured similarly to these servo control sections, the hand 9 shown in FIG. The attached air cylinder 13 and nut runner 14 are controlled, that is, the air cylinder 13 controls the raising and lowering of the nut runner 14, and its built-in motor controls the rotation and stopping of the socket 14a.

Next, in the servo control section for the motor 4, the target position command value of the first arm 5 from the central processing section 23 is written into the position command register 24 while being updated one after another.

The position control unit 25 outputs the target position command value of the first arm 5 written in the position command register 24 and the position feedback signal (voltage) from the potentiometer 30 attached to the output shaft of the motor 4 to A. outputs a speed command value Sa based on the deviation from the value converted into a digital value by the /D converter 31, that is, the current position value of the first arm 5 (corresponding to the angle θ ₁ in FIG. 3); Each time the target position command value and the current position value match and positioning is completed, this is notified to the central processing unit 23, and the central processing unit 23 uses this to measure the timing for outputting the next target position command value. . Note that the central processing unit 23, position command register 24, and position control unit 25
constitutes a speed command system.

The speed control section 26 includes a command value control circuit 4 which will be described later.
A current command value S ₁ is output based on the deviation between the speed command value Sa from the position control unit 25 inputted via the motor 5 and the speed feedback value from the tachogenerator 29 attached to the output shaft of the motor 4. This tachogenerator 29 constitutes a speed detection system.

The current control section 27 inputs the current command value _S1 from the speed control section 26 via the addition circuit 32, and calculates the current command value S1 based on the deviation from the current feedback value from the current detector 28 that detects the drive current flowing to the motor 4. A drive current is applied to the motor 4.

Therefore, the servo control section for the motor 4, which is composed of the position command register 24, the position control section 25, the speed control section 26, the current control section 27, etc., has a command value control circuit 45 which will be described later. As long as the speed command value and the speed feedback value from the tachometer generator 29 are output as they are to the speed control unit 26, the motor 4 is driven based on the target position command value from the central processing unit 23, and the first arm 5. Playback control (positioning control)
can do.

Each part 34-42 which constitutes a servo control part for motor 11 which drives the second arm 7 is also each part 24-3 which constitutes a servo control part for motor 4 mentioned above.
The command value control circuit 45, which will be described later, directly receives the speed command Sb output from the position control section 35 and the speed feedback value output from the tachometer generator 39 attached to the output shaft of the motor 11. As long as the output is to the speed control section 36, the motor 11 is driven based on the target position command value from the central processing section 23, and the second
The arm 7 can be controlled playback (positioning control).

Furthermore, the servo control units for the motor 10 that rotationally drives the waist shaft 3 and the wrist shaft drive motor function similarly to drive each motor, respectively, and can playback control the waist shaft 3 and hand 9. .

The air cylinder drive circuit that controls the air cylinder 13 shown in FIG.
It is switched by a command from 3, and the direction of air supply is changed to raise and lower the air. The rotation and stopping of the socket 14a is as follows:
The nut runner 1 is activated by the command from the central processing unit 23.
This is done by controlling the power supply to the motor built in 4.

The command value control circuit 45 has 10 switching switches that are switched depending on whether the relay coil L is energized or de-energized.
SW ₁ to _{SW 10} (4 changeover switches inserted in the servo control section for motor 10 and wrist shaft drive motor)
SW ₅ to SW ₈ are composed of electromagnetic relays (not shown).

The changeover switch SW ₁ of this command value control circuit 45,
The movable contacts c of SW ₂ are each connected to the input side of the speed control unit 26, each fixed contact a is connected to the ground, and each fixed contact b is connected to the output side of the position control unit 25 and the tachogenerator 29, respectively. .

Further, the movable contacts c of the changeover switches SW ₃ and SW ₄ are connected to the input side of the speed control section 36, respectively, each fixed contact a is connected to the ground, and each fixed contact b is connected to the position detection section 36.
5 and the tachometer generator 39, respectively.

When SW1 to SW4 mentioned above are connected to the fixed contact b side, a speed command system and a speed detection system are connected to the speed control parts 26 and 36, respectively, and these are connected to the fixed contact a side. When the speed control section 26, 36 has a command value of zero, a pseudo value output means is connected to output a speed pseudo value corresponding to the speed command value and a feedback pseudo value corresponding to the speed feedback value, respectively. That will happen.

Changeover switches SW ₅ , SW ₆ and SW ₇ (not shown),
SW ₈ is also connected in exactly the same way in the servo control section for the motor 10 and the servo control section for the wrist shaft drive motor, respectively.

The changeover switches SW ₉ and SW ₁₀ are configured to receive a compensation command value output from a gravity balance compensation circuit 50, which will be described later.
CS ₁ and CS ₂ are inserted into lines input to adder circuits 32 and 42, respectively, and are used as open/close switches.

Note that the diode D connected to both ends of the relay coil L is a flywheel diode.

In this command value control circuit 45, when the relay coil L is not energized, the movable contacts c of each of the changeover switches _SW1 to _SW10 are respectively switched to the fixed contact b side,
The actual speed command value and speed feedback value are passed through as they are, and the servo control section for each motor is operated as originally intended, but the relay coil L
When energized, the movable contact piece c of each switch SW ₁ to _{SW 10} switches to the fixed contact a side as shown in the figure, and the input is sent to the speed control unit 26, 36, ... in the servo control unit for each motor. Both the speed command value and the speed feedback value to be used are set to zero (earth value), and the current command values S ₁ , S ₂ , ... based on the deviations are expressed in other words, regardless of the deviation between the actual speed command value and speed feedback value. Then, it becomes zero regardless of the movement of the motors 4, 11, etc.

In this way, if the current command value is set to zero regardless of the actual speed command value and speed feedback value, position and speed feedback control will no longer be effective, so each motor 4, 10, 11, etc. will be in a free state, and Therefore, the waist shaft 3, first arm 5, second arm 7, and hand 9 of the robot 1 shown in FIG. 2 can be freely moved by external force.

However, in this case, if the drive current of each motor is completely reduced to zero, the first and second arms 5,
7 and hand 9 rotates each vertical joint axis, and the posture of these movable parts collapses, making it impossible to work. Therefore, a gravity balance compensation circuit 50 is provided, which corrects the gravity balance. I try to maintain my posture so that I don't lose my posture, but the details will be explained later.

In addition, each changeover switch of the command value control circuit 45
Even when the movable contacts c of SW ₁ to _{SW 10} are switched to the fixed contact b side, the deviation between the speed command value and the speed feedback value becomes zero when positioning is completed, but at this time the position and speed feedback control is not performed. Because of this, when an external force is applied to the first and second arms 5, 7, etc. and the motors 4, 11, etc. are rotated from the stopped position, a rotational force is immediately generated to return them to their original positions.

In addition, in this command value control circuit 45, when the current command values S ₁ , S ₂ , ... are functioning to be zero (in this embodiment, when the relay coil L is excited), it is in the operating state. That's what it means.

Reference numeral 46 denotes a switching circuit, which includes switching switches 47 and 48 inserted into the power supply circuit of the power supply V _CC and an ascent limit switch 15 attached to the hand 9 of the robot 1.
It is composed of. The limit switch 15 is of a normally closed type and is turned off when the nut runner 14 reaches its upper limit and is struck by the dog 14b.

If the movable contact i of the changeover switch 48 is switched to the fixed contact g side as shown in the figure, the command value control circuit will be activated when the limit switch 15 is off (when the nut runner 14 is in the raised position). 45 is de-energized, and when the limit switch 15 is on, the relay coil L is energized.

Moreover, if the movable contact piece i of the changeover switch 48 is switched to the fixed contact h side, the limit switch 15
Regardless of whether the command value control circuit 45 is on or off, the command value control circuit 45 can be activated or deactivated by the changeover switch 47.

In addition, in this embodiment, the relay coil L
The excitation of the command value control circuit 45 corresponds to the operation of the command value control circuit 45, but the fixed contacts a of the changeover switches SW ₁ to _{SW 10}
By reversing the connections between and b, it is also possible to make the de-energization of the relay coil correspond to the operation of the command value control circuit 45.

Next, a detailed example of the gravity balance compensation circuit 50 will be explained with reference to FIG.

This gravity balance compensation circuit 50 includes a CPU (central processing center) 51 and a program memory.
A memory 52 including ROM and RAM as data memory, and a pair of A/D converters 53 and 54.
and D/A converters 55 and 56.

The gravity balance compensation circuit 50 corresponds to the rotation angle θ ₁ (see FIG. 3) of the first arm 5 from the horizontal position output from the potentiometer 30 attached to the output shaft of the motor 4. The voltage signal is converted into a digital value by the A/D converter 53 and read into the CPU 51, and the second arm 7 relative to the first arm 5 is output from the potentiometer 40 similarly attached to the output shaft of the motor 11. The voltage signal corresponding to the rotation angle θ ₂ (see Fig. 3) is
converted into a digital value by the D converter 54
Read into CPU51.

The length _{l 1} from the single axis 4a to the center of gravity of the first arm 5 of the robot 1 and the total length are stored in the memory 52 in advance.
l ₂ , the length from the elbow axis 6 of the second arm 7 to the center of gravity l ₃
and the total length l ₄ , each weight W ₁ , W ₂ , W ₃ of the first arm 5, second arm 7, and hand 9 (see Figure 3),
The CPU 51 calculates the moments of gravity M(A) and M(B) at the shoulder axis 4a and the elbow axis 6, which are the vertical joint axes, by performing the following calculations. Compensation command values CS ₁ and CS ₂ to generate shaft torque that can withstand it are D/A
It is converted into an analog signal via converters 55 and 56 and output.

M(A)=K ₁ cosθ ₁ +K ₂ sin(θ ₁ +θ ₂ −90°) M(B)=K ₂ sin(θ ₁ +θ ₂ −90°) However, K ₁ =l ₁ W ₁ +l ₂ ( W ₂ + W ₃ ) K ₂ = l ₃ W ₂ + l ₄ W ₃ is given. Since K ₁ and K ₂ are constants,
It is preferable to store this in the memory 52 in advance.

CPU in this gravity balance compensation circuit 50
The operation flow of 51 is shown in FIG.

In this way, the compensation command values CS ₁ , CS 2 outputted from the gravity balance compensation circuit 50 are changed to the changeover switches SW ₉ , CS ₂ of the command value control circuit 45 during strain relief control.
input to the adder circuits 32 and 42 via SW ₁₀ ,
Current command value output from speed control units 26 and 36
Even if S ₁ and S ₂ are zero, the current control units 27 and 37
The drive current for gravity compensation is controlled by motors 4 and 1.
1 to generate an axial torque that can resist the weight of the first and second arms 5, 7 and the hand 9,
The first and second arms 5 and 7 can maintain their postures while maintaining gravity balance.

In this embodiment, the air cylinder 13 and nut runner 14 of the hand 9 are always held vertically (vertically) in a relaxed state, and the weight of the hand 9 applied to the wrist shaft 8 always acts in the vertical direction, so the moment is Since no gravity is generated and its own weight is supported by the workpiece 18, no gravity compensation is performed.

Moreover, the function of this gravity balance compensation circuit 50 is provided in the central processing unit 23 of FIG.
The CPU may perform time-sharing processing.

Furthermore, if the gravity balance compensation circuit 50 is always operated and the output compensation command values CS ₁ and CS ₂ are constantly input to the addition circuits 32 and 42 to maintain gravity balance, the speed control units 26 and 36 The current command values S ₁ , S ₂ from the above can be reduced accordingly, making it difficult to cause hunting, etc., and making it possible to easily move the movable part both downward and upward at the same speed.

Next, using the control device shown in FIG. 1 that is capable of switching between playback control and stress relief control as described above, the robot 1 shown in FIG. bolt 19
The operation for tightening will be explained with reference to the flowchart of FIG.

It is assumed that the teaching work necessary to make the robot 1 perform the tightening work described below has been performed in advance.

Further, the nut runner 14 attached to the hand 9 of the robot 1 is normally at the upper limit position, and the limit switch 15 is turned off by being struck by the dog 14b. In the following explanation, the first
It is assumed that the changeover switch 48 in the changeover circuit 46 in the figure is switched to the contact g side.

In this state, since the switching circuit 46 cuts off the power to the relay coil L of the command value control circuit 45, the movable contacts c of each of the switching switches SW ₁ to SW ₁₀
are all switched to the fixed contact b side, and the waist shaft 3,
Playback control of the motors 4, 10, 11, etc. that rotate the first and second arms 5, 7 and hand 9, respectively, is possible.

Therefore, in step 1 of FIG.
11, etc., to move the first and second arms 5, 7, etc. to their original positions (which may be any retracted position).

Next, the nut runner 14 attached to the hand 9
In step 2, the motors 4, 11, etc. are replayed so that the socket 14a of the bolt 19 on the workpiece 18 conveyed by the conveyor 17 is located at the working point, which is a predetermined standby position on the movement trajectory of the bolt 19 on the workpiece 18. The robot is controlled to take a predetermined standby posture as shown in FIG.

In this state, the bolt passage detector 20 detects the workpiece 1.
When the bolt passage detector 20 detects the passage of the bolt 19 on the bolt 19, the detection signal is input to the central processing unit 23 in FIG. Judgment is YES
Then, in step 4, the air cylinder 13 is driven to lower the nut runner 14.

When the nut runner 14 starts to descend, the upper limit switch 15 is immediately turned on, so that the relay coil L of the command value control circuit 45 is energized by the switching circuit 46, and each of the switching switches SW ₁ -
Since SW ₁₀ is switched as shown in Fig. 1, the drive motors 4, 10, 11, etc. of each axis are all free, and the movable parts such as the first and second arms 5, 7, etc. are freed when subjected to external force. Although the motors are in a relaxed state where they can move freely, the compensation command value from the gravity balance compensation circuit 50 causes a drive current to flow through the motors 4 and 11 to generate shaft torque that resists the moment due to their own weight. , the gravitational balance is maintained and the postures of the first and second arms 5, 7 do not collapse.

When the nut runner 14 descends to its lower limit, the socket 14a comes to grip the bolt 19 on the workpiece 18 conveyed by the conveyor 17, and at the same time, the lower limit switch 16 is struck by the dog 14b and is activated. Then, based on that signal, the decision in step 5 becomes YES, and in step 6, the nut runner 14 is driven to open the socket 14.
Rotate a and tighten bolt 19.

In this way, the socket 14 of the nut runner 14
The conveyor 17 is moving the workpiece 18 while a is tightening the bolt 19 with the bolt 19 in the jaw, but each of the waist shaft 3 and the first and second arms 5, 7 of the robot 1, etc. Since the movable part is in a state where it can be freely moved by external force, the hand 9 can move in the horizontal direction following the movement while tightening the bolt 19.

Then, by measuring the time since the start of tightening or the tightening torque, it is determined in step 7 whether or not tightening of the bolt 19 has been completed, and when the tightening has been completed, the nut runner 14 is driven in step 8. At the same time, the nut runner 14 is raised by driving the air cylinder 13.

When the nut runner 14 rises to its upper limit, the upper limit switch 15 is turned off, so the relay coil L of the command value control circuit 45 is de-energized, and the changeover switches SW ₁ to _{SW 10} are all switched to the contact b side. , the drive motors 4, 11, etc. for each axis all return to a state in which playback control is possible.

By the time the playback control returns to a state where it is possible, the movable parts of the robot 1 have moved from the standby position, so the position control parts for each motor have a position deviation corresponding to the movement. It's accumulating. Therefore, when playback control becomes possible, each movable part immediately begins to return to the working point before movement, but the upper limit switch 15
When the is turned off, the process returns from step 9 to step 1, and the process of moving to the initial original position is performed again, so each movable part such as the first and second arms 5, 7 returns to the working point and moves as a result. Return to the original position and repeat the above operation again.

In this way, the nut runner 14
While the bolts 19 of 8 are being tightened, each movable part of the robot 1 relaxes and follows the movement of the workpiece 18, thereby greatly simplifying the following work, which conventionally required very complicated control. can be easily realized.

In addition, when the conveyor 17 is stopped and the bolts 19 on the stationary workpiece 18 are tightened, the changeover switch 48 in the changeover circuit 46 is used.
is switched to the contact h side, and the changeover switch 47
If the rest position of the bolt 19 and the above-mentioned work point are matched by switching to the contact e side, the sixth
By omitting the determination of bolt passage in step 3 in the figure, the bolt 19 can be tightened while it is stationary.

Furthermore, if the changeover switch 48 is switched to the contact h side, the first and second arms 5, 7, etc. can be applied with external force at any time by switching the changeover switch 47 to the contact d side as necessary. This allows it to be in a relaxed state where it can be moved freely.

In the above embodiment, an example was described in which the current command value is set to zero by switching both the actual speed command value and the speed feedback value to zero values that are unrelated to positioning control. The current command value can also be made zero by switching both values to mutually equal predetermined values that are unrelated to positioning control. Alternatively, the current command value may be directly switched to the zero value.

Further, the gravity balance compensation circuit 50 in the above-described embodiment calculates the gravity compensation value by calculating the gravity compensation value according to the data corresponding to the angles θ ₁ and θ ₂ in FIG. 3 from the potentiometers 30 and 40. However, in advance, the optimal gravity compensation value for each vertical joint axis according to each angle θ ₁ and θ ₂ is stored in memory 5 in Fig. 4.
2 as a table, and the CPU 51 may read the gravity compensation value from the table in accordance with the input angle data.

In any case, in particular the second arm 7 of the elbow shaft 6
The gravity compensation value for the moment due to the self-weight at the end is slightly smaller than the value that perfectly balances it,
It may be preferable to leave a slight pressing force on the hand 9 due to its own weight, since this can prevent tools such as the nut runner 14 from coming off the workpiece (the bolt 19 in this embodiment).

〔Effect of the invention〕

As explained above, according to this invention,
Control of a vertically articulated robot that controls the drive current of the motor of each moving part according to the command value based on the deviation between the speed command value output from the speed command system and the speed feedback value output from the speed detection system. In the device, a gravitational moment applied to a vertical joint axis of each movable part is calculated according to the posture of each movable part, and a compensation command value is output for generating an axial torque capable of resisting the calculated gravitational moment. a gravity balance compensation circuit that outputs a speed pseudo value corresponding to the speed command value and a feedback pseudo value corresponding to the speed feedback value such that the command value becomes zero, and the command value. Alternatively, if the current supply circuit that supplies the drive current to the motor of each movable part based on the compensation command value and the operation signal is output, the speed command system and the speed detection system are separated, and the speed command system and the speed detection system are separated. The gravity balance compensation circuit is connected to the pseudo value output means, and the gravity balance compensation circuit is connected to the current supply circuit, and a zero command value and a compensation command value based on the deviation between the speed pseudo value and the feedback pseudo value are transmitted to the current supply circuit. On the other hand, if an inoperation signal is output, the pseudo value output means is disconnected and connected to the speed command system and the speed detection system, and the gravity balance compensation circuit is disconnected from the current supply circuit. , a command value control circuit that provides the current supply circuit with a command value based on the deviation between the speed command value and the feedback value; and a switching circuit that selectively outputs an activation signal or a non-operation signal to the command value control circuit. Therefore, when an operation signal is output from the switching circuit, shaft torque corresponding to the compensation command value output from the gravity balance compensation circuit is output from the motor of each movable part.

Therefore, if the compensation command value is set so that this axis torque balances the calculated moment of gravity of the vertical joint axis, the vertical joint axis will remain stationary.
On the other hand, if the compensation command value is set so that this is not balanced on purpose, it will be possible to apply a slight pressing force to the workpiece due to its own weight, allowing various operations to follow the movement of the conveyor on a continuous line. It is easily possible to have the robot perform the task while the robot is moving.

Furthermore, a compact and inexpensive electromagnetic relay with a small contact capacity can be used as a command value control means, which not only reduces the number of times of contact maintenance, but also prevents inrush current from flowing to the motor when switching contacts. Therefore, there is no need to take preventive measures.

[Brief explanation of the drawing]

Fig. 1 is a block configuration diagram of a control device showing an embodiment of the present invention, Fig. 2 is an external view of the robot and its surroundings to explain the structure and operation of a vertically articulated robot to which this invention is applied, and Fig. 3 The figure is also a schematic diagram for explaining the moment of gravity applied to the vertical joint axis of the robot, FIG. 4 is a block circuit diagram showing a specific example of the gravity balance compensation circuit 50 in FIG. 1, and FIG. CPU in diagram
FIG. 6 is a flowchart showing an example of the operation of the central processing unit 23 in FIG. 1... Vertical multi-joint robot, 3... Waist axis,
4, 10, 11... DC servo motor, 5... First arm, 6... Elbow shaft, 7... Second arm, 8...
... Wrist axis, 9 ... Hand, 13 ... Air cylinder, 14 ... Nut runner, 15, 16 ... Limit switch, 17 ... Container conveyor, 18 ... Work, 19 ... Bolt, 20 ...
Bolt passage detector, 23... central processing section, 29,
39... Tachometer generator, 30, 40... Potentiometer, 45... Command value control circuit, 46...
...Switching circuit, 50...Gravity balance compensation circuit.

Claims (1)

[Claims] 1. Control the drive current of the motor of each movable part according to the command value based on the deviation between the speed command value output from the speed command system and the speed feedback value output from the speed detection system. In a control device for a vertically articulated robot, a gravitational moment applied to a vertical joint axis of each movable part is calculated according to a posture of each movable part, and an axial torque capable of resisting the calculated gravitational moment is generated. a gravity balance compensation circuit that outputs a compensation command value for the rotational speed; and a pseudo value that outputs a speed pseudo value corresponding to the speed command value and a feedback pseudo value corresponding to the speed feedback value such that the command value becomes zero. an output means; a current supply circuit that supplies a drive current to the motor of each movable part based on the command value or the compensation command value; and when an operation signal is output, the speed command system and the speed detection circuit; The gravity balance compensation circuit is connected to the current supply circuit, and a zero command value and a compensation command are generated based on the deviation between the speed pseudo value and the feedback pseudo value. value to the current supply circuit, while if an inoperation signal is output, the pseudo value output means is disconnected and connected to the speed command system and speed detection system, and the gravity balance compensation circuit is connected to the speed command system and speed detection system. a command value control circuit which separates the current supply circuit from the current supply circuit and supplies the current supply circuit with a command value based on the deviation between the speed command value and the feedback value; and selecting an activation signal or a non-operation signal to the command value control circuit. 1. A control device for a vertically articulated robot, characterized by comprising a switching circuit that outputs a vertically articulated robot.