JP2000084878A - Control device for robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out the direct teaching work with a favorable control property by restraining the inertia moment around a joint to the minimum reducing the operation force of a teacher without using an expensive sensor and special device. SOLUTION: This is provided with third state feedback control means 13, 15 for making the position limit value giving a width to the negative side for the position order to a first state feedback control means 11 to the order value of a servo system, a first adjuster 18a for adjusting the output of second state feedback control means 12, 14 in response to a position deviation, a second adjuster 18b for adjusting the output of the third state feedback control means in response to the position deviation, a means 19 for adding the output value of the first adjuster and the output value of the second adjuster to the torque control part or the speed control part of the first state feedback control means, a means 16 for obtaining a position order correction value in response to the output value of the first adjuster and the output value or state of the second adjuster and a means 17 for obtaining the order value from the position order correction value to the first state feedback control means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a robot controller capable of performing a teaching operation with a simple structure in direct teaching for teaching an operation to an industrial robot or the like.

[0002]

2. Description of the Related Art A conventional direct teaching of an industrial robot is a method of mechanically canceling the robot's own weight, that is, a joint which generates a torque in the opposite direction with the same magnitude as the torque applied to the joint by the link weight. The mechanism is designed so that the torque applied to the joint is reduced to zero by providing it on the opposite side of the link. This mechanism reduces the force of the human to move the robot. There is also a method of outputting a torque in the opposite direction to the actuator of the joint instead of the weight (for example, see Japanese Patent Application Laid-Open No. 9-38877). As another means, when the teacher pushes the robot tip in the direction in which the robot tip is to be moved by the force sensor attached to the robot tip, the force sensor detects the pressing force and pushes the robot tip in the direction to cancel the pressing force. The servomotor moves to drive. For this reason, there is a method (for example, see Japanese Patent Application Laid-Open No. 7-41566) in which the position and posture of the robot tip can be changed only by applying a light force to the robot.

[0003]

However, in the first method, the weight is balanced by the weight of the first method, the weight of the entire robot is increased by the weight of the weight as compared with that of a normal robot, and the handleability is reduced. However, the moment of inertia around the joints becomes large, and the control performance of the robot decreases, and there is a problem that the teacher needs a large force to operate. Japanese Patent Application Laid-Open No. Hei 9-38877, which is the second system, uses a system in which a torque in the opposite direction is output to the joint actuator to cancel the torque corresponding to gravity. If it occurs, there is a risk of runaway. In addition, it is difficult for the instructor to move the robot tip with a force greater than the friction generated in the drive part of the robot and the moment of inertia around the joints, and to perform minute positioning, and the physical load is extremely large. is there. In Japanese Patent Application Laid-Open No. 7-41566, which is the third method, a force sensor is attached to the end of the robot. However, the force sensor is generally expensive, and a large number of cables for transmitting signals and electric power are required. And there is a risk that the force sensor may be mechanically damaged. Therefore, the present invention provides a direct teaching operation in which the robot itself is lightweight, minimizes the moment of inertia around the joints, has good controllability, and reduces the operating force of the instructor without using expensive sensors or special devices. The purpose is to do.

[0004]

According to the present invention, in order to solve the above-mentioned problems, as shown in FIG. 1, in a robot controller provided with a control circuit of a motor for driving each joint of the robot, a position control gain or A first state feedback control means for a position and a speed in which the speed control gain is set smaller than usual, and a position limit value having a width on the positive side with respect to a position command to the first state feedback control means are servo-controlled. A second state feedback control unit that sets a system command value; and a position limit value that has a width on the negative side with respect to a position command to the first state feedback control unit. (3) a state feedback control means, and a first adjuster for adjusting an output of the second state feedback control means according to a position deviation of the second state feedback control means. A second adjuster for adjusting an output of the third state feedback control means in accordance with a position deviation of the third state feedback control means, and an output value of the first adjuster and an output value of the second adjuster. Means for adding to the torque control portion or speed control portion of the first state feedback control means, and a position command correction value according to the output value of the first regulator and the output value or state of the second regulator. Means for obtaining a command value to the first state feedback control means from the position command correction value.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first specific embodiment of the present invention will be described with reference to FIG. FIG. 2 is a control block diagram in which the control of the present invention is applied to a normal position / speed control system. In the conventional direct teaching method using a force sensor, a teacher operates the robot by holding the tip of the robot, applying an operating force, and detecting the direction with a force sensor. Here, if the direction of the operating force of the instructor can be detected without using a force sensor, it is possible to give a command to operate the robot arm in the same direction. The position and speed control system can be made sufficiently low rigidity (flexible) by reducing the gain of each joint and stopping the speed deviation integral term when the robot arm is stopped. Then, it is possible to recognize a direction of the operating force as a switch by causing a position shift (deviation with respect to a command) for each joint of the robot arm by the operating force (external force) of the instructor and detecting the position shift. . However, it is difficult for the instructor to intuitively determine the detection by performing only the process of detecting whether the positional deviation of each joint exceeds the set width. In addition, when the position of the joint of the robot arm is displaced more than necessary, it is difficult to detect the direction of the operating force of the instructor, and the interference between the tip of the robot and the work is likely to occur. Therefore, in the present invention, a position monitoring position / speed control loop is used in addition to a normal position / speed control loop. If the instructor applies an operating force and the positional deviation exceeds the set width, a command is output from the position monitoring position / speed control loop in a direction to suppress the operation. Can operate only for the width set for detection. Accordingly, the instructor can intuitively understand the position shift detection determination, and the instructor can use each joint as a switch. The robot arm can be operated without using a special sensor by using a method of updating the position command in the same direction or adding a fixed amount of torque using the direction of the position shift detection as information. It is.

The configuration of the position monitoring position / speed control loop will be described below. In the inner loop of the normal position / speed control, the proportional / integral control is performed.
By setting the position loop gain and the speed loop gain of 1 sufficiently small and stopping the speed integration term, the displacement can be flexibly caused by the operating force of the teacher, that is, the external force. Here, it is assumed that the constantly acting force is compensated by the static compensation element. First position / speed control loop 11
A predetermined setting value α is added to or subtracted from the position command, and a position command having a width corresponding to the setting value α, that is, an operation restriction, is created by the operation restriction setting means 14 and 15. Another second (positive side) and third (negative side) position monitoring position / speed control loops 12 and 13 which receive the operation limit value as input are configured. Here, the set value only needs to be large enough that when the joint axis of the robot 31 moves to the set value, the movement is recognized from the outside. The position loop gain and the speed loop gain of the second and third position monitoring position / speed control loops 12 and 13 are set sufficiently large, and the speed integral term is made effective to constitute a high rigidity control system. Here, the operation of the second (positive side) position monitoring position / speed control loop 12 will be described in detail as an example. This position monitoring position / speed control loop 1
2 operates when the robot arm 31 exceeds the operation limit. When the position command changes in the normal control state, the robot arm 31 is controlled by the first position / speed control loop 11.
Moves, and the robot arm 31 is moved by the external force when an external force greater than the servo rigidity acts. When the robot arm 31 exceeds the operation limit angle, the position monitoring position / speed control loop 12 starts functioning by the operation of the adjuster 18. The function of the adjuster 18 is a block that is determined only by the operation limit angle and the current position of the robot arm, regardless of the motion of the robot 31 due to its own weight or the motion moved by another person. The motion limit angle and the joint angle of the robot arm are determined by the sign of the deviation of the position / velocity control system,
While the adjuster 18 is negative (i.e., while the joint angle exceeds the operation limit angle), the position monitoring position / speed control loop 12 continues to function, and the robot arm 31 rarely exceeds the operation limit, and Even when a large force is applied carelessly, the operation of the robot arm 31 can be limited to a narrow range. FIG. 5 shows the actual robot arm 31.
Shows an example in which operation restrictions are provided. The direction of the operating force of the instructor can be determined by detecting that the robot arm is on the 31 operation limit angle by the operation direction determining means 16. Therefore, by paying out the position command correction amount in the same direction to the position command generation means 17, the teacher can operate the robot arm 31 with a light force. As another means, a similar effect can be obtained by adding a method of adding a fixed amount of torque to the torque command of the first position / speed control loop 11. At this time, it is possible to operate the robot with high rigidity by using a means for switching the control of the first position / speed control loop 11 from the present method to the ordinary position control.

Next, a second embodiment of the present invention will be described with reference to FIG.
And will be described. In the first specific embodiment, the position loop gain and the speed loop gain of the first position / velocity control loop 11 are set sufficiently small to provide flexibility. In this specific example, the generated torque is limited at the torque command stage (see A in FIG. 3), so that the robot 31 can flexibly operate with respect to an externally applied force. That is, when a torque larger than the restricted torque acts from the outside, the joint of the robot 31 starts to flexibly respond to the acting force. Here, too, it is assumed that the constantly acting force is compensated by the static compensation element. Other implementation methods are the same as in the first specific example. Further, in the first and second specific embodiments, a position / speed control loop is formed in the working coordinate system of the robot instead of the position / speed control loop in the joint coordinate system. here,
By using a small displacement correspondence such as a Jacobi matrix, a force torque command in the working coordinate system is converted into a torque command in the joint coordinate system, and the motor of the robot is operated. With this configuration, it is also possible to detect a position shift of the robot on the work coordinate system, and it is possible to obtain the same effect as the position / speed control loop of the joint coordinate system. In the first and second specific embodiments, the gravity compensation calculation is performed by calculating a required torque from the joint angle of the robot arm, the position of the center of gravity of the arm, and the weight, for example. It is added to the output value of the loop 11.

Next, a second embodiment of the present invention will be described with reference to FIG. 4 showing an example of use in a handling operation. Normally, the motor capacity and the speed reducer of the serial link type robot 31 are smaller than the tip shaft, so that the serial link type robot 31 can be operated more flexibly with respect to the externally applied force than the root motor and the speed reducer. Therefore, the direction of the operating force of the instructor is detected on the three axes on the tip side, and the robot arm on the three axes on the root side is controlled based on the information on the direction. Hereinafter, a description will be given of a handling operation performed by the 6-axis serial link robot 31 as an example. Usually, in the handling operation, the workpiece is handled with the flange surface of the distal end shaft of the robot 31 facing downward in the vertical direction. Therefore, even in this control method, the position command of each joint is created such that the flange surface of the robot faces downward. The three axes of R, B, and T in the posture shown in FIG. 4 are orthogonal to each other.
As a method of detecting the direction of the operation force, the axis that operates based on the information detected due to the operation restriction of the T axis is the S axis whose operation plane is parallel. Similarly, the axis that operates according to the information on the operation restriction on the B axis is the L axis on the same plane, and the axis that operates based on the information on the operation restriction on the R axis is not on the same plane.
Set the axis. Since the T-axis and the S-axis are on the same plane, when the teacher pushes the operating handle 33 attached to the hand 32 as the end effector in the Y direction in the drawing, the T-axis operates flexibly and the position shifts. Begins to occur. The operating direction of the instructor is detected by shifting the position of the T axis until the operation limit is reached, and the first position / speed control loop 11 of the S axis is detected.
Or a fixed amount of torque is added to the torque command of the first position / speed control loop 11. Therefore, the robot arm 31 operates in the Y direction in which the teacher applies a force to the operation handle 33. In addition, since the position / speed control system of the T-axis has flexibility, the operating force applied to the operating handle 33 by the instructor is relaxed.
Returning to the position of the initial position command, the payout of the command to the S axis is also completed. The same control is performed for the B axis and the L axis, and the R axis and the U axis.

Here, when it is desired to operate the R, B, and T axes independently, the control axis changeover switch 3 provided on the handle is provided.
With 4 or the like, it is also possible to switch and operate the three axes on the distal end side / three axes on the root side. At this time, the rotation directions of the R axis and the U axis do not match, but the operation handle 3 is also provided in the Y direction of the hand.
By adding 3, the instructor can operate without feeling uncomfortable. Alternatively, if the U-axis operation switch 35 is provided above and below the operation handle 33, only one operation handle 33 is required, and it is possible to configure with a minimum number of sensors (that is, switches and the like).

As another operating means, the direction of operation based on the direction detected by the information of the operation restriction of the T axis is set in the Y direction of the working coordinates, and the robot tip is moved linearly in the Y direction. Similarly, by giving an operation command of the robot in the X direction of the work coordinate in the information of the operation restriction of the B axis and in the Z direction of the work coordinate in the information of the operation restriction of the R axis, the robot is linearly operated in the work coordinate system. It is possible. FIG. 6 is a schematic block diagram of the robot control device. The robot controller 40 includes a processor board 41, and the processor board 41 includes a processor 41a, a ROM 41b,
There is a RAM 41c and nonvolatile memories 41d and 41e. The processor 41a controls the entire robot controller 40 according to the ROM 41b. Various data are stored in the RAM 41c. Non-volatile memory 41d, 4
In 1e, an operation program of the robot 31 and a program according to the present invention are loaded from the ROM 41b.
Each operation and each calculation of the position monitoring position / speed control loop shown in FIGS. 1 to 3 are functions of software that the processor 41a reads and executes a program in the nonvolatile memory 41d. Processor board 41 is bus 4
3. The digital servo control circuit 42 is coupled to the bus 43, and drives the servo motors 22a, 22b, 22c, 22d, 22e and 22f via the servo amplifier 21 according to a command from the processor board 41. These servo motors are built in the robot 31 and operate each axis of the robot 31. The serial port 44 is connected to the bus 43 and is connected to the teaching operation panel 47 and other RS232C devices 48. The teaching operation panel 47 is used for inputting teaching points to the robot. Also, I
Input / output of data and signals with the outside is performed via / O46. 45 is a large capacity memory.

[0011]

As described above, according to the present invention, a joint coordinate system position / speed loop for position deviation monitoring is configured separately from a normal joint coordinate system position / speed loop, and the position monitoring position / speed loop is constructed. By using the output of the operation restriction from the loop as the operation switch, it is possible to configure a direct teaching device that does not require a special sensor and can determine that the instructor is operating intuitively.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention.

FIG. 2 shows a first specific embodiment of the present invention.

FIG. 3 shows a second specific embodiment of the present invention.

FIG. 4 is a work application example of the present invention.

FIG. 5: Operating range of the robot

FIG. 6 is a hardware configuration diagram for realizing the present invention.

[Explanation of symbols]

 11 First position control speed loop 12 Second position control speed loop positive side 13 Second position control speed loop negative side 14 Positive side operation restriction setting unit 15 Negative side operation restriction setting unit 16 Operation direction setting unit 17 Position command Generation means 18 Adjuster 21 Amplifier 22 Motor 23 Encoder 31 Robot 32 End effector 33 Operation handle 34 Control axis switch 35 U-axis operation switch 40 Robot controller 41 Processor board 41 a Processor 41 b ROM 41 c RAM 41 d, 41 e Non-volatile memory 42 digital servo control circuit 43 bus 44 serial port 45 large capacity memory 46 I / O 47 teaching operation panel 48 RS232C device A torque limiter

Claims (5)

[Claims] 1. A robot control device having a control circuit for a motor for driving each joint of a robot, comprising: first state feedback control means for position and speed in which a position control gain or a speed control gain is set smaller than usual; A second state feedback control unit that uses a position limit value having a width on the positive side with respect to a position command to the first state feedback control unit as a command value of the servo system; and the first state feedback control. A third state feedback control means that uses a position limit value having a width on the negative side with respect to a position command to the means as a command value of the servo system, and an output of the second state feedback control means to a second A first adjuster that adjusts according to a positional deviation of the state feedback control means; and a third state feedback means for outputting an output of the third state feedback control means. A second adjuster for adjusting the output value of the first adjuster and the output value of the second adjuster according to a position deviation of the torque control means, a torque control portion or a speed control of the first state feedback control means. Means for adding a position command correction value according to an output value of the first adjuster and an output value or state of the second adjuster; and a first state feedback from the position command correction value. A robot control device comprising means for obtaining a command value to a control means. 2. A robot control device having a control circuit for a motor for driving each joint of a robot, comprising: a first state feedback control means for a position and a speed in which a position control gain or a speed control gain is set smaller than usual; A second state feedback control unit that uses a position limit value having a width on the positive side with respect to a position command to the first state feedback control unit as a command value of the servo system; and the first state feedback control. A third state feedback control means that uses a position limit value having a width on the negative side with respect to a position command to the means as a command value of the servo system, and an output of the second state feedback control means to a second A first adjuster that adjusts according to a positional deviation of the state feedback control means; and a third state feedback means for outputting an output of the third state feedback control means. A second adjuster for adjusting the output value of the first adjuster and the output value of the second adjuster according to a position deviation of the torque control means, a torque control portion or a speed control of the first state feedback control means. Means for adding to a portion, and a command addition value of the first state feedback control means for controlling another joint axis according to the output value of the first adjuster and the output value or state of the second adjuster. A robot control device comprising: means for deriving by calculation or calculation; and means for adding the command addition value to a command value of the first state feedback control means of the other joint axis. 3. The control device for a robot according to claim 1, further comprising means for providing a torque limit after the first state feedback control means. 4. The apparatus according to claim 1, further comprising means for partially replacing means for issuing a command value to said first state feedback control means with a switch or a force sensor provided at a tip of said robot. The control device of the described robot. 5. The robot control device according to claim 1, further comprising means for controllably compensating for a torque acting on the robot arm and a weight of a load gripped by the robot.