JPS62284408A - Speed control method for industrial robot - Google Patents

Abstract

PURPOSE:To attain accerelation corresponding to the posture of a robot without exceeding overload by using a maximum allowable speed with the highest efficiency for plural arm axes to execute computer operation and controlling a servocontrol part based on the operated result. CONSTITUTION:The angular speeds of respective arm axes of an industrial robot are inputted from a switch part 14 to the CPU 10 through an input port 13. The CPU 10 receives a synthetic speed (v) consisting of a marginal speed omegamax determined by the maximum speeds omega of respective arm axes and the performance of a driving source, calculates k=omegamax/omega of each arm axis and recognizes the maximum allowable speed kminv consisting of the minimum result kmin. Consequently, the CPU 10 calculates the robot leading positions p1-pn following the passage of time and controls servocontrol parts 11, 12 by respective calculated output signals. Thus, the driving capacity of arm axis driving sources can be utilized at their maximum and high efficiency corresponding to the posture of the robot can be attained without overload.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a speed control method for an industrial robot. Then, computer calculations are performed using the most efficient allowable maximum speed (or acceleration) for multiple bracelets, and servo control is performed based on the results to maximize the drive capacity of the drive source and achieve industrial This is to achieve speedup that corresponds to the robot's posture.

(Prior art) Among industrial robots, welding robots and painting robots require absolute linear speed. With the exception of spot welding, in arc welding it is necessary to specify an absolute linear velocity in order to accurately trace a continuous weld line and evenly compensate for the amount of penetration and distortion of the material due to heat. Also, in painting work, it is essential to travel at a specified linear speed in order to create a uniform coating and obtain a beautiful finish. On the other hand, transfer robots and assembly port pots often require high speeds to the fullest capacity rather than absolute linear speeds, and welding robots and painting robots often require During the air cut section, there are similar requirements for transfer robots, so a maximum speed that depends on the robot's posture is required.

(Problem to be solved by the invention) In a conventional robot, its speed is, for example, Im/s.
ec, etc., and was played back at a specified speed. In Figure 1, point A Oo
, YA, ZA) Empty point B (XB, YB
, 2B), and if the speed is V, then the position P after seconds is expressed as follows.The position P of the robot was determined every extremely short time (several aS).

For example, like the robot in FIG. 1, S1. S 2゜S
Assuming that the robot is made up of three joints in Figure 3, as long as this robot moves in a straight line at a constant speed, Sl should move fastest at point N, which is closest to the center, and slowest at point B, which is farthest from the center. There is.

In this case, especially near the N point, the robot is not necessarily able to operate at the specified speed because it is limited by the limit speed of St.
The same can be said of the other 52.33 joints other than S1.

(Means for solving the problem) When the robot moves from one teaching point to the next teaching point, the speed should be automatically reduced based on the point with the heaviest load on the axis with the heaviest load. It is necessary to ensure that the system is able to operate at the specified speed without stopping midway due to abnormal loads, and that it operates most faithfully to the specified speed. As a specific means for this purpose, when the combined speed of the robot is V, let the maximum speed of each of the plurality of arm axes be ω, find the ratio to the limit speed ωIax determined by the ability of the drive source, and calculate the speed for each of the obtained arm axes. The minimum of the ratios is set as the maximum permissible speed kmin, and this is used to calculate the control, and the servo control unit is controlled based on the result to maximize the driving efficiency and force for each bracelet. This has enabled the robot's arm to move faster in response to different postures. Examples will be described below.

(Example) Examples of the present invention shown in the drawings will be explained in detail below. In FIG. 1, the moving angular velocity of the axis Sl of a robot arm having three axes 31, 32 and S3 is 1, for example, the tip of the arm is at the teaching point A.
From point (coordinates: XA, YA, ZA) to teaching point B (coordinates:
XB, YB.

When moving to ZB), it becomes maximum at point N.

Let this maximum angular velocity be ωi. Furthermore, although the shaft S1 is driven by a motor or the like, there is naturally a limit to the driving ability of the driving power source such as the motor, and therefore, there is also a limit to the angular velocity of the shaft S1.

This critical angular velocity is ω, saw. Now, let us assume that the ratio between this maximum angular velocity ωl and the limit angular velocity ωl la summer is 1.

k1=□ ω1, and in this case, 1 is ω, which exceeds ω1■ax l+
31 or -1 top number 1 10 thoughts) 1
For example, if ni = 2, then ω1 = ω, laX, which means that the maximum angular velocity of axis SL, 0, is its limit angular velocity ω.
l means half of laX, in other words axis 5
This means that there is room to increase the angular velocity ω□ of 1, that is, to increase the speed (high efficiency). Therefore, the angular velocity ω1 is set to (ωI Ila!) until the driving capacity is equal to
(kl = 1). Then, when k1=1, the axis S1 is the ability - the angular velocity of 0 weight = ωI■a! It will be driven by

The above description relates to the axis Sl, but the following 2. , is obtained.

ω2 maX (r)
5 maXk2==, ks=□ω2
ω5 Here,
If the minimum of k, , 2 and 3 is kain, then kminv is the maximum allowable speed when moving from point A to point B. Now, for example, , , , and 3
are respectively 1.53.1.02.1.38, then 2 is the smallest, that is, the maximum angular velocity ω2 of the axis S2 is the limit angular velocity ω211a of the axis S2! In other words, the axis S2 is driven with the highest efficiency (angular velocity), and the other axes St and S3 are driven with still room for higher efficiency (higher speed). This means that it has been done. Here, if we drive the robot in Figure 1 at the maximum value of kt instead of the minimum value of 2, then the axes S2, S
Regarding 3, the margin will be increased, in other words, the robot will be driven more leisurely and the efficiency of the robot work will be reduced.

Also, suppose k sin = 1. which is smaller than kmin @ k2 = 1.02. If the robot is driven as an office worker, the axis S1. S2 and S3 are overloaded, especially the axis si with the largest value of k (k, = 1.53).
This will result in an abnormal load.

For this reason, as the maximum allowable speed ratio Kmin,
, to 2. 2 is selected as the smallest of the two.

FIG. 2 is for explaining the operation of the central processing unit CPU that controls the robot. Reference numeral 10 indicates a switch 14, which is an operation panel for inputting angular velocity as an input device of the CPU. In addition to inputting acceleration, the input keys on this operation panel also include a "%" key that allows input in percentage display.

In the CPU, the above-mentioned maximum allowable speed k sin is calculated from the composite speed V.
v is recognized. When the maximum permissible speed kminv is recognized, the position P of the robot tip is calculated as P+ +P2. according to the calculation formula as time passes t,, t2 ---- tn. --P n is C
The calculated output signal is calculated by the PU and the calculated output signal is
Output from U and 11.12 servo control section 1.2--
one is controlled. 13 is an input port. As a result of the robot being controlled based on the maximum speed ksinv in this way, the capacity of the robot arm driving point is effectively utilized, and the inconvenience of one of the axes being stopped due to abnormal load is eliminated. Ru.

Although the embodiments described above relate to angular velocity, the same consideration can be given to velocity and acceleration in addition to angular velocity. For example, in the case of acceleration, when the resultant acceleration is α, the maximum acceleration α1, α2−−αn and the limit acceleration α, l1a with respect to the axis S1.52−−−Sn
X, α7+1aX---αnff1a! and the ratio a1. Find a2---an, al, a2---an
C
Can be used for PU calculations. Furthermore, it goes without saying that it is applicable not only to the linear motion described above but also to circular arc motion.

(Effects of the Invention) As described above, according to the present invention, computer calculations are performed using the most efficient allowable maximum speed (acceleration) for multiple bracelets, taking into account the drive capacity of the arm shaft drive source of an industrial robot. By controlling the servo control unit based on the calculation results, it is possible to make maximum use of the drive capacity of the arm axis drive source, which allows it to respond to the robot's posture without exceeding overload. High speed (high efficiency) is achieved.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the state when the robot moves linearly at a constant speed from teaching point A to B. Figure 2 is a block diagram explaining the operation of the central processing unit CPU that controls the speed of the robot. be. Reference numeral 1.2 in the drawing: Servo control section. 10: cPU, 11. 12 + sabot control unit, 13:
Input port, 14: Switch i, part A, B, N: teaching point,

Claims (1)

[Claims] When the combined speed of the industrial robot is v, the ratio when ω is the maximum speed for each of the plurality of arm axes and ωmax is the limit speed determined by the capability of the drive source; k = (ωmax )/ω, and the obtained ratio for each arm axis, k_1, k_2
---When the minimum speed among kn is kmin, the allowable maximum speed is kminv, and this is used to perform calculations for robot control, and the servo control section is controlled based on the calculation results. The driving capacity of the drive source for a plurality of arm axes is utilized to the maximum, thereby making it possible to increase the speed of movement of the arm of the robot corresponding to the posture of the robot without causing overload. speed control method for industrial robots.