JP2001292586A - Motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly protect an element or the like which is arranged around a motor from heat generation, by enhancing the accuracy of the prediction of the extent of temperature rise around the motor. SOLUTION: This controller is provided with a current sensor which detects an output current value i to a serve motor for driving each shaft (arm) of the body of a robot. The rotational speed r of each serve motor is detected by an encoder. A robot controller samples the output current i for each current sensor and the rotational speed r for each encoder, separately for each shafts (S1-S3) and obtains an average current 1 and an average rotational speed R from n pieces of sampling values (S4). Then, it computes a temperature rise ΔT, using both of those average current I and the average rotational speed R (S5), and compares the temperature rise ΔT with a set value Tmax (S6), and when the temperature rise ΔT is larger than a set value Tmax (S6: Y), it stops the drive of a servo motor (S7).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device for controlling a motor in a system such as a robot that outputs the rotation of the motor via a rotation transmitting mechanism.

[0002]

For example, in an industrial articulated robot, a motor (servo motor with an encoder) for driving each axis (arm) is built in a robot body composed of articulated arms. Then, the driving force is transmitted to the arm via a rotation transmission mechanism such as a speed reducer provided at the joint, for example. Further, the servo motors of the respective axes are driven and controlled by a robot controller including a microcomputer or the like.

By the way, in this type of robot,
In order to protect the elements of the encoder which are relatively weak to heat, the degree of temperature rise of the motor is estimated from the output current value to the motor of each axis. Control has been performed to limit the operation of the robot so as not to exceed the allowable use temperature.

However, the cause of the temperature rise around the motor is not only the heat generated by the motor itself, but also the heat generated by a sliding portion such as an oil seal portion of the speed reducer during high-speed operation of the motor. If the heat generation is large, it is not possible to accurately estimate the degree of temperature rise by estimating the degree of temperature rise only from the output current value to the motor as in the past, and the temperature around the motor will be reduced to the allowable operating temperature of the element. May be exceeded. Incidentally, for example, it is conceivable to provide a temperature sensor to detect the temperature around the actual motor. However, this leads to complication of the configuration including the wiring, as well as insufficient reliability, and It is not realistic to adopt.

The present invention has been made in view of the above circumstances, and has as its object to improve the accuracy of estimating the degree of temperature rise around a motor, and to generate heat from elements and the like arranged around the motor. It is an object of the present invention to provide a motor control device capable of satisfactorily protecting the motor.

[0006]

In order to achieve the above-mentioned object, a motor control device according to the present invention provides a motor control device which detects a current value of an output current to a motor and a rotation speed of the motor. It is configured to estimate the degree of temperature rise in the surroundings (the invention of claim 1). Here, factors of the temperature rise around the motor are roughly classified into heat generation of the motor itself and heat generation in the rotation transmission mechanism. At this time, the heat generated by the motor increases according to the output current value (torque) to the motor, and the heat generated by the rotation transmission mechanism increases according to the rotation speed of the motor.

Therefore, according to the first aspect of the present invention, unlike the case of estimating the degree of temperature rise around the motor only from the output current value to the motor, the degree of temperature rise taking into account heat generation in the rotation transmission mechanism is also considered. Can be estimated,
This provides an excellent effect that the accuracy of estimating the degree of temperature rise around the motor can be improved, and that the elements disposed around the motor can be well protected from heat generation.

More specifically, the heat value of the motor itself is:
It is almost proportional to the square of the output current value (torque) to the motor,
The amount of heat generated by the rotation transmission mechanism is substantially proportional to the square root (half) of the rotation speed of the motor. Therefore, the temperature rise value can be obtained by the following equation based on the average output current value and the average rotation speed (the invention of claim 2).

[0009]

(Equation 1) According to this, it is possible to estimate a more accurate temperature rise value. Note that the constants A and B can be experimentally obtained in advance according to actual use conditions and the like.

If the control of stopping the driving of the motor is performed so that the estimated temperature rise does not exceed the set upper limit value (invention of claim 3), elements such as elements disposed around the motor can be controlled. Protection from heat generation can be reliably and effectively performed. In addition, as a means for protecting the elements and the like from heat generation, it is also conceivable to reduce the driving speed of the motor or to forcibly cool by, for example, blowing air from a cooling fan device.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to control of a motor for driving each axis of an industrial articulated robot will be described below with reference to the drawings. First, FIG. 5 schematically shows the appearance of the main body 1 of the articulated (6-axis) robot according to the present embodiment.
Has a six-axis robot arm on a base 2 and a tool such as a hand (not shown) attached to the tip of the robot arm.

Specifically, a first arm 3 extending upward is connected to the base 2 so as to be rotatable (turnable) around a vertical axis J1. The lower end of the second arm 4 extending upward is connected to be rotatable about a horizontal axis J2. A base end of a third arm 5 is connected to a tip end of the second arm 4 so as to be rotatable about a horizontal axis J3.
The base end of the arm 6 is connected so as to be coaxially rotatable about the axis J4. A fifth arm 7 is rotatably connected to the distal end of the fourth arm 6 about an axis J5, and a flange portion to which a tool such as the hand is detachably attached is provided on the distal end surface of the fifth arm 7. 8 is provided so as to be coaxially rotatable about the axis J6.

As will be shown later as a part (first arm 3), servomotors 9 to 14 (see FIG. 2) for driving the respective axes and robot A belt transmission mechanism for transmitting the rotation of the servo motors 9 to 14 to the respective arms 3 to 8 at a joint of the shaft;
A rotation transmission mechanism including a bearing, a speed reducer, an oil seal, and the like is provided.

Further, as shown in FIG. 2, the servo motors 9 to 14 are provided with encoders 15 to 20 which also function as rotation speed detecting means. The robot body 1 is connected to a robot controller 21 composed of a microcomputer or the like. As will be described later, the servo motors 9 to 14 of the respective axes are controlled by the robot controller 21 to perform various operations (assembly work). Is to be performed.

Here, the first of the robot arms is
The configuration of the arm 3 (joint with the second arm 4) will be described as a representative. As shown in FIG. 4, the first arm 3 is configured by covering a left side portion of a metal (casting) frame 3 a with a cover 3 b, and an encoder for driving the second arm 4 is provided at a lower portion inside the first arm 3. A servo motor 10 with 16 is disposed rightward. A drive pulley 22 is attached to an output shaft of the servo motor 10. The lower left wall of the frame 4a of the second arm 4 is rotatably connected to the upper part of the right wall of the frame 3a of the first arm 3, and the driving force of the servomotor 10 is transmitted. ing.

That is, a circular assembling opening 3c is provided in the upper part of the right side wall of the frame 3a, and a speed reducer 23 is provided therein as described later. This reduction gear 23
Is, for example, a hollow harmonic drive, and as is well known, a hollow wave generator 24 including an elliptical cam and a ball bearing on the outer periphery thereof, and a cup-shaped flex spline (elastic gear) disposed on the outer periphery thereof. ) 25, and a circular spline (internal gear) 26 meshing with the outer periphery thereof. On the other hand, a hollow shaft 27 is provided on the lower left wall of the frame 4a of the second arm 4 so as to protrude leftward. The axis of the hollow shaft 27 is the shaft J2.
Matches.

A bearing 2 made of, for example, a cross roller bearing is provided on an inner peripheral portion of the mounting opening 3c of the frame 3a.
The frame 4a of the second arm 4 is supported by the bearing 28 so as to be rotatable about an axis J2. At this time, the outer ring 28a of the bearing 28, the flex spline 25, and the support member 29 are fixed to the frame 3a in a so-called co-tightened state. On the other hand, the inner race 28b of the bearing 28, the circular spline 26, and the closing member 30 are fixed to the frame 4a in a so-called co-tightened state. Further, the outer ring 2 is provided on the right side surface of the bearing 28.
An oil seal 31 is provided between the inner ring 8a and the inner ring 28b.

Further, the wave generator 24 includes:
The hollow shaft 27 is arranged with a small gap on the outer periphery thereof, and the left and right ends in the axial direction of the outer periphery are formed in the bearing 32 and the closing member 30 provided between the inner periphery of the support member 29 and the inner periphery thereof, respectively. It is rotatably supported by a bearing 33 provided between itself and the peripheral part. At this time, an oil seal 34 is provided on the left side of the bearing 32, and an oil seal 35 is provided on the right side of the bearing 33.

A driven pulley 36 is rotatably provided on the outer periphery of the tip (left end) of the hollow shaft 27, and the driven pulley 36 is connected to the wave generator 24. Further, a timing belt 37 is stretched between the driving pulley 22 and the driven pulley 36. As a result, the rotation of the servo motor 10 is transmitted to the driven pulley 36 via the timing belt 37 to rotate the wave generator 24 at high speed, and the rotation is reduced by the speed reducer 23 and transmitted to the second arm 4. It is becoming so.

At this time, the oil seal 31 prevents dust and water droplets from entering the inside of the speed reducer 23, and also prevents the oil seal 31 and the oil seal 34 from entering.
And 34 prevent the internal lubricating oil (not shown) from leaking to the outside. In addition, the hollow shaft 27
Inside, a wiring 38 (partially shown by imaginary lines) is passed. Further, although detailed illustration and description are omitted, similar reduction gears are provided for the joints of the other arms 4 to 8 so that the rotation of the servo motors 9 to 14 is transmitted at a reduced speed. .

FIG. 2 schematically shows an electrical configuration centered on the robot controller 21. The robot controller 21 includes a main CPU board 39 for controlling the entire robot main body 1, and each servo controller. It is provided with servo drivers 40 to 45 for controlling the motors 9 to 14, respectively. At this time, the main CPU board 39 outputs a position command signal to each of the servo drivers 40 to 45 based on the operation program, and the servo drivers 40 to 45 control the servo motors 9 to 14 based on the position command signal. It is designed to be driven.

The servo drivers 40 to 45 receive the position (rotational speed) detection signals of the encoders 15 to 20 and perform feedback control. Further, current sensors 46 to 51 are provided on the current supply lines to the servomotors 9 to 14, and their current detection signals are input to the servo drivers 40 to 45. Therefore, the encoders 15 to 20 function as rotation speed detecting means, and the current sensors 46 to 5
1 functions as current detecting means for detecting the output current value to the servo motors 9 to 14.

As will be described later in the flow chart description, the robot controller 21 (each of the servo drivers 40 to 45) uses the software configuration to output an output current value to each of the servo motors 9 to 14, It functions as temperature estimating means for estimating the degree of temperature rise around the servo motors 9 to 14 based on both speeds.

Here, the factors of the temperature rise around the servo motors 9 to 14 are roughly classified into the following.
It is considered that heat is generated by itself and heat generated by the rotation transmission mechanism. At this time, the heat generated by the servo motors 9 to 14 increases according to the output current value (torque), and the heat generated by the rotation transmission mechanism increases according to the rotation speed of the servo motors 9 to 14. More specifically, servo motors 9 to
The heating value of the servomotor 9-14 is substantially proportional to the square of the output current value (torque) of the servomotors 9-14, and the heating value of the rotation transmission mechanism is the square root (1/2) of the rotation speed of the servomotors 9-14. It is almost proportional to Servo motor 9-1
4 shows the relationship among the average output current value, the average rotation speed, and the temperature rise value.

Therefore, more specifically, in this embodiment,
The robot controller 21 controls each axis (servo motors 9 to
14) For each, an output current value i from each of the current sensors 46 to 51 and a rotation speed r from each of the encoders 15 to 20
Are sampled at predetermined time intervals, and an average current value I and an average rotation speed R are obtained from a predetermined number (unit time) of sampling values. Then, the temperature rise value ΔT is calculated by the following equation.

[0026]

(Equation 2) The constants A and B are experimentally determined in advance according to actual use conditions.

Further, the robot controller 21 converts the estimated temperature rise value ΔT into a predetermined set value Tma.
x (for example, set to 70K), and when the temperature rise value ΔT is larger than the set value Tmax, the servo drivers 40 to 45 stop driving the servo motors 9 to 14, and thus the operation of the robot body 11. Is to be stopped. Therefore, the robot controller 21
However, it also functions as stopping means.

Next, the operation of the above configuration will be described with reference to FIG. The arms 3 to 8 of each axis of the robot main body 1 are operated according to a predetermined work program by controlling the servo motors 9 to 14 of each axis by the robot controller 21 and repeatedly execute various works. The flowchart of FIG. 1 shows a processing procedure of estimating a temperature rise value in each axis executed by the robot controller 21 when the robot main body 1 operates.

That is, in step S1, each current sensor 4
The output current value i from 6 to 51 is detected (sampled), and in the next step S2, the rotational speed r by each of the encoders 15 to 20 is detected (sampled). These samplings are repeatedly executed at a predetermined time interval until the predetermined number n is reached (step S3). When a predetermined number of samplings have been performed (Yes in step S3), in the next step S4, the average current value I is calculated by the equation of I = Σi / n, and the average rotation speed R is calculated as R = Σ
It is calculated by the equation of r / n.

Then, in the next step S5, the temperature rise value ΔT is estimated (calculated). The calculation of ΔT is performed by the following equation as described above.

(Equation 2)

In this case, as described above, the servo motor 9
The heating value of the servomotors 9 to 14 is substantially proportional to the square of the output current value (torque) of the servomotors 9 to 14, and the heating value of the rotation transmission mechanism is determined by the square root (half-square) of the rotation speed of the servomotors 9 to 14. ), It is possible to estimate an accurate temperature rise value ΔT.

In the next step S6, the calculated temperature rise value ΔT is compared with a set value Tmax (for example, 70K), and if the temperature rise value ΔT is equal to or less than the set value Tmax (N
o), the processing from step S1 is repeated. On the other hand, when the temperature rise value ΔT exceeds the set value Tmax (Yes in step S6), the driving of the servomotors 9 to 14 is stopped in step S7. In this case, the temperature rise value ΔT of any one of the servomotors 9 to 14 is equal to the set value Tmax.
, The driving of the entire robot body 1 is stopped.

Thus, more accurate peripherals of the servo motors 9 to 14 (arms 3 and 14) taking into account both the heat generated by the servo motors 9 to 14 themselves and the heat generated by the rotation transmitting mechanism.
８8) can be estimated. Then, the calculated temperature rise value ΔT is equal to the set value Tmax.
Control is performed to stop the driving of the servo motors 9 to 14 when it exceeds
The protection of the zero element and the like can be performed reliably and effectively. By the way, by setting the set value Tmax to 70K, the ambient temperature of the servo motors 9 to 14 can be set to about 90 ° C.
At most, it can be suppressed to 95 ° C. or less.

As described above, according to the present embodiment, unlike the prior art in which the degree of temperature rise around the motor is estimated only from the output current value to the motor, the temperature in consideration of heat generation in the rotation transmission mechanism is also considered. The degree of rise can be estimated, and the accuracy of estimation of the degree of temperature rise around the servomotors 9 to 14 can be improved. As a result, it is possible to obtain an excellent effect that the elements disposed around the servomotors 9 to 14 can be well protected from heat generation.

In the above embodiment, when the estimated temperature rise value ΔT exceeds the set value Tmax, the servo motor 9
-14 are controlled, but as a means for protecting elements and the like around the motor from heat generation,
In addition, reduce the driving speed of the motor, or
For example, forcible cooling by blowing air from a cooling fan device or the like may be considered. In addition, the present invention is not limited to robots, and can be applied to various devices including motors, for example, and can be appropriately modified and implemented without departing from the scope of the invention.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a procedure of estimating a temperature rise value according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the robot.

FIG. 3 is a diagram showing a relationship between an average output current value and an average rotation speed of a motor and a temperature rise value.

FIG. 4 is a longitudinal sectional front view showing a configuration of a first arm portion.

FIG. 5 is a side view showing the appearance of the articulated robot.

[Explanation of symbols]

In the drawing, 1 is a robot body, 3 to 8 are arms, 9 to 14
Is a servomotor (motor), 15 to 20 are encoders (rotation speed detecting means), 21 is a robot controller (temperature estimating means, stopping means), 23 is a speed reducer, 28 and 3
2, 33 are bearings, 31, 34, 35 are oil seals, 4
Numerals 0 to 45 denote servo drivers, and numerals 46 to 51 denote current sensors (current detecting means).

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Claims (3)

[Claims] 1. A device for controlling the motor in a system for outputting rotation of the motor via a rotation transmission mechanism, wherein current detection means for detecting an output current value to the motor, and rotation of the motor. Rotation speed detection means for detecting a speed; estimating a temperature rise degree around the motor based on both the current value detected by the current detection means and the rotation speed detected by the rotation speed detection means. And a temperature estimating means. 2. The motor control device according to claim 1, wherein said temperature estimating means obtains a temperature rise value by the following equation based on an average output current value and an average rotation speed. (Equation 1) 3. The apparatus according to claim 1, further comprising a stop unit for stopping the driving of the motor such that a degree of temperature rise estimated by the temperature estimating unit does not exceed a set upper limit value. Motor control device.