JP2000222004A - Robot controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a robot controller capable of obtaining stable and also fast position control by eliminating following errors due to human intervention and obtaining an appropriate servo gain corresponding to a gain. SOLUTION: This controller is provided with a load moment of inertia estimating part 5 which estimates the moment of inertia on the basis of an output of a position detector detecting the rotational position of a servomotor and has a gain switching part 6 which finds the load moment of inertia being its estimation results and outputs it to a servo controller. Thus, the load moment of inertia can be estimated even when the fluctuation of a load occurs. A microprocessor can automatically select an appropriate servo gain in accordance this estimated load moment of inertia, i.e., a stable and optimum serve gain all the time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a robot controller for controlling a servo system for driving a robot mechanism with at least one servomotor, and more particularly to an improvement in dynamic characteristics during operation of a robot.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a schematic configuration of a conventional robot controller. In FIG. 1, a robot mechanism 2 including a servomotor is a part that actually performs a work or a part that drives a load 1 to be worked, and the robot mechanism 2 is controlled by a servo control device 3. The servo control device 3 forms a servo loop system for driving a robot mechanism, as described later. Further, the servo control device 3 is controlled by a robot control device 4 which is a high-order control device including a high-order microprocessor for processing a position distribution amount and a robot language.

FIG. 5 shows an example of a servo loop system for driving a robot mechanism by the servo controller 3. The servo loop system includes a position control loop 100, a speed control loop 110, and a current control loop 12 for controlling a given command value.
Has zero. Among these, the position control loop 100 is proportional control, speed control loop 110 and current control loop 1
Reference numeral 20 denotes a proportional integral control. The servo motor 140 is controlled by the signal amplified by the power amplifier 130 to which the output of the current control loop is given, and the current flowing through the servo motor 140 is fed back to the current control loop 120 and detected by the position detector 150. The rotational position of the servo motor is fed back to the position control loop 100 and also fed back to the speed control loop 110 via the differential element 160. Therefore, the position control system includes the current control loop and the speed control loop as a minor loop as a whole.

In general, in a servo system, adjustments are made with some allowance for load fluctuations in a mechanical portion, for example, changes in load weight. That is, the gain is reduced to some extent so that no vibration or the like occurs even when the load increases.

[0005] However, if such a marginal adjustment is made in a system that requires high-speed positioning, such as a robot, the positioning time determined by the reciprocal of the gain increases, and high-speed operation cannot be performed. is there.

For this reason, conventionally, in order to satisfy conflicting demands of high-speed positioning and stability at the time of load change, programming has been performed in which a gain is switched according to the load of the load. That is, in such a gain switching programming, when the load is light, the gain is switched to a high gain, and when the load is heavy, the gain is switched to a low gain.

Conventionally, such servo system gain switching is performed by an operator calculating the moment of inertia of a load through a microprocessor included in the robot controller 4 and switching the gain to an appropriate gain in a robot program for the load. I do programming to write instruction words. Therefore, the servo system switches the gain only when the operator describes a gain switching command and the microprocessor issues a gain switching command in response to this command.

[0008]

As described above, in the conventional robot controller, in order to achieve both high-speed positioning and stability at the time of a load change, an operator calculates a moment of inertia of a load and sends the program to a program. There is a problem that a complicated operation such as a description of a gain switching instruction must be performed. In addition, if the load changes without a switching command being issued in the event of a programming error, phenomena such as overshoot and oscillation occur, and the dynamic characteristics are greatly reduced.

Further, when the load conveyed by the robot changes due to a change in the line or the like, there is a problem that the gain switching command must be reviewed sequentially.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is intended to eliminate a following error caused by human intervention and obtain a stable and high-speed position control by obtaining an appropriate servo gain according to a load. It is an object of the present invention to provide a robot control device capable of performing the following.

[0011]

According to the present invention, there is provided a robot control apparatus for controlling a servo system including at least one servomotor for driving a robot mechanism, comprising: a load estimating means for estimating a load on the robot mechanism; Switching control means for switching a servo gain for the servo control device so as to follow the load estimated by the load estimating means.

According to the present invention, the servo system is provided with a mechanism for dynamically estimating the moment of inertia of the current load, and the servo gain according to the load is appropriately selected from the estimated moment of inertia. A stable and high-speed follow-up control can be performed by obtaining an appropriate servo gain according to the load without human intervention.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the basic concept of a robot control device according to the present invention. In FIG. 1, since the load 1, the robot mechanism 2, the servo control device 3, and the robot control device 4 are completely the same as those in FIG. 4, detailed description thereof will be omitted.

4 is different from FIG. 4 in that a load estimating unit 5 for estimating a moment of inertia, which is a control parameter in the servo control device, is provided. The point is that a gain switching unit 6 for obtaining an appropriate gain for the device and outputting it to the servo control device is provided.

In the present invention, by combining the two mechanisms of the load estimating section 5 and the gain switching section 6, the load inertia moment is estimated even when a load fluctuates as described later. An appropriate servo gain can always be automatically selected by the microprocessor in accordance with the set load inertia moment, and an optimum servo gain can be automatically selected.

FIG. 2 is a block diagram showing a configuration for specifically realizing the functional configuration shown in FIG.

The system memory 11 stores a system program for executing a robot program and a system program for executing a gain switching function. Top C
The PU 12 executes the robot program according to the system program read from the system memory 11 and executes the gain switching function, and includes both elements of the robot control device 4 and the gain switching unit 6 in FIG.

The dual port memory 13 is a host CPU 1
This is a bidirectional memory for exchanging data between the servo control CPU 2 and the servo control CPU 14 described below. As a practical matter, the memory may be provided on either the servo control CPU side or the host CPU side.

The servo control CPU 14 corresponds to the servo control device 3 and the load estimating unit 5 in FIG. 1 and performs servo control (motor position control) and estimation of a load inertia moment which is a feature of the present invention. At this time, a necessary program is read from the servo system memory 15 in which a system program for executing the servo control and a servo system program for executing the moment of inertia estimation function are stored and executed.

The servo control CPU 14 controls the servo motor 14
When performing the control of 0, first, a command is issued to the power amplifying unit 130, and the power amplifying unit 130 controls the current flowing through the servomotor 140 by switching the transistors included therein.

A position detector 150 for detecting the rotation angle of the motor is attached to the rotation axis of the servo motor 140, and the detected rotation angle data of the motor is sent to the servo control CPU 14, and as described above, Position control is performed.

FIG. 3 is a block diagram showing an example of a servo loop system for driving a robot mechanism by the servo controller 3 according to the present invention. This figure shows the configuration of the servo loop of the position control system similar to that of FIG. 5, and the same components as those of FIG. 5 are denoted by the same reference numerals. This control system is a control system for driving a servo motor in accordance with a command, and includes a position control loop 100, a speed control loop 110, a current control loop 1
30. Among them, the position control loop 100 is a proportional control, and the speed control loop 110 and the current control loop 130 are a proportional integral control. The servo motor 140 is controlled by the signal amplified by the power amplifier 130,
The current flowing through the servomotor 140 is the current control loop 12
0, the rotational position of the servomotor is detected by the position detector 150, and the position data is fed back to the position control loop, and also fed back to the speed control loop 110 via the differential element 160. As a whole, the position control system includes a current control loop and a speed control loop as minor loops. Such a control system is constituted by a microprocessor.

[0024]

(Equation 1) For (c) noise reduction, the estimated value I _m obtained through the low-pass filter 180, and calculates the final estimate.
At the time of passing through the low-pass filter, the calculation of 1 / (Ts + 1) (2) is performed using s as a Laplace operator. At this time, the cut-off frequency of the low-pass filter is set to about a fraction of the position loop gain.

The final estimated value I is sent to the host CPU 12 via the dual port memory 13. (2) Gain Switching Mechanism The host CPU 12 dynamically switches the gain so that an appropriate gain is obtained based on the estimated load value. This switching is performed according to the following procedure.

(A) First, a set of two gains, a gain Gmin when there is no load (only the mechanical part of the robot) and a gain Gmax when the load is the maximum, is read. This set of gains is obtained in advance by actual measurement or simulation by a robot system including a mechanism. Note that this reading is 1 when the power is turned on.
Only the number of times is sufficient.

(B) Based on the estimated load inertia moment I, the following calculation is performed to calculate the optimum gain G for the current load.

G = (I × (Gmin−Gmax)) / (Imax−Imin) (3) where I: estimated load inertia moment, Gmax: gain at maximum load, Gmin: gain at minimum load Gain, generally Gmin ≧ Gmax: Imax: inertia moment at maximum load, Imin: inertia moment at minimum load (Imax ≧ I ≧ Imin).

(C) The calculated gain is transmitted to the servo control CPU via the dual port memory 13.

Note that (Gmin-Gmax)) / (Im
ax-Imin) is a known constant value, so that the calculated optimum gain G is proportional to the estimated load inertia moment I.

As described above, according to this embodiment, the load inertia moment is estimated based on the position data obtained by the position detector, and the optimum gain is obtained based on the estimated load inertia moment. Therefore, when the estimated value of the load inertia moment is large, the gain is set large, and when the estimated value of the load inertia moment is small, the gain is set small. Can be.

In the above embodiment, the servo control C
The PU estimates the load inertia moment, and the upper CPU takes charge of gain switching. However, this is not always necessary. When the upper CPU performs servo control, the upper CPU also performs the load inertia moment estimation function. Can be.

Conversely, the estimation of the inertia moment of the load and the switching of the servo gain can be performed on the servo control CPU side.

Further, in the present embodiment, the upper CPU and the servo control CPU are in a one-to-one relationship in the above example, but a single upper CPU is provided with a plurality of different dual port memories via different dual port memories. It is also possible to connect a servo CPU and control by these.

Further, in this embodiment, the optimum gain is obtained by using the known inertia moment and gain at the time of minimum load and the inertia moment and gain at the time of maximum load. A so-called look-up table format for reading out the optimum gain value stored in the memory according to the value may be used.

Further, in the embodiment, the moment of inertia is used as the load to be estimated, but another appropriate physical quantity representing the load can be used.

[0037]

According to the present invention, the load moment of inertia is estimated from the detected position of the servomotor, and the gain is switched based on the moment. Thus, the gain switching conventionally described by a human is performed. Functions are automated,
Since a complicated operation of describing and adjusting the switching command every time the load changes is not required, there is no need for a program coating error and no gain adjustment is required.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic concept of a robot control device according to the present invention.

FIG. 2 is a block diagram showing a configuration for specifically realizing the functional configuration shown in FIG. 1;

FIG. 3 is a block diagram showing an example of a robot loop driving servo loop system by the servo control device 3 according to the present invention.

FIG. 4 is a block diagram showing a schematic configuration of a conventional robot control device.

FIG. 5 is a block diagram showing an example of a robot mechanism driving servo loop system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Load 2 Robot mechanism 3 Servo controller 4 Robot controller 5 Moment of inertia estimation part 6 Gain switching part 11 System memory 12 Upper CPU 13 Dual port memory 14 Servo control CPU 15 Servo system memory 100 Position control loop 110 Speed control loop 120 Current Control loop 130 Power amplifier 140 Servo motor 150 Position detector 160, 170 Differential element 180 Load estimation mechanism 190 Low-pass filter

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) KK20 KK23 KK24 LL03 MM05

Claims (3)

[Claims] 1. A robot controller for controlling a servo system including at least one servomotor for driving a robot mechanism, wherein: a load estimating means for estimating a load on the robot mechanism; and a load estimated by the load estimating means. Switching control means for switching a servo gain for the servo control device so as to follow the servo control. 2. The apparatus according to claim 1, further comprising: a position detecting means for detecting a rotational position of the servomotor, wherein the load estimating means calculates an estimated load inertia from a ratio between a torque command value and an angular acceleration obtained from an output of the position detecting means. 2. A method for determining a moment.
4. The robot control device according to item 1. 3. The robot control device according to claim 2, wherein said switching control means obtains an optimum gain in accordance with an output of said load estimating means and instructs it as a command value. .