JPS6123213A - Robot controller - Google Patents

Abstract

PURPOSE:To eliminate the variance of follow-up time by detecting the delay amounts of each robot element to compare them with each other and giving the command value to the element having the largest delay amount at the normal time and then to other elements with delays respectively. CONSTITUTION:A delay amount calculation means 3 of a controller 1 reads actual positions theta'1 and theta'2 and compares them with the command values of a command value memory means 2 for calculation of delay amounts d1 (X axis) and d2 (Y axis). Then the command value D2 of the normal time is given to a Y axis 21 of the large delay amount d2. While the command value D1 is applied to an X axis 11 with a delay given to the time progress of the difference (d2- d1). Both D1 and d2 are shown by equations I, and the actual positions are shown by equations II. Thus the mutual position relation between both X and Y axes realizes the command value at the same time point although the delay d2 is given to the time progress.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a robot control device for controlling a robot having two or more degrees of freedom with high precision.

"Conventional technology" In order to control the robot with high precision, the arm wrist,
Conventionally, follow-up performance has been improved by reducing the moment of inertia of robot elements such as a swivel table or by increasing the gain of servo control/lz-p.

``Problem to be solved by the invention'' In a robot with two or more robot elements, each robot element usually has different dynamic characteristics, so it is necessary to reduce the moment of inertia of each robot element, Even if the tracking performance is improved by increasing the gain,
The followability of each robot element is often different from each other.

However, if the followability of each robot element is different from each other, the delay of each robot element with respect to the target position will differ as time progresses, resulting in a time-series deviation in the actual position of each robot element. This causes the problem that the composite position deviates from the taught position, resulting in poor positional accuracy.

"Means for Solving the Problem" The robot control device of the present invention includes a command value storage means for teaching and storing a group of command values to be sequentially given to each robot element as time progresses, and a command value storage means for each robot. Delay amount calculation means that calculates the amount of delay of each robot element by comparing the command value given to the element at the previous time and the current value of each robot element read from the position sensor, and the calculated delay of each robot element. The quantities are compared with each other, and for the robot element with the largest amount of delay, a command value is retrieved from the command value storage means and applied to that robot element according to the normal progression of time, while on the other hand, the command value is given to that robot element with the amount of delay that is not the maximum. Each of the above-mentioned means comprises a command value delaying means for extracting a command value from the command value storage means and applying it to the robot element according to a time that is delayed by a larger amount as the amount of delay becomes smaller for the robot element. can be configured using, for example, a microcomputer system.

"Operation" In the robot control device of the present invention, a command value is given to the robot element with the largest follow-up delay out of each robot element according to the normal progression of time, but a command value is given to the robot element with the smaller follow-up delay. , the command value is given at a slower rate of time than usual. If the amount of time delay is taken to be the difference between the follow-up delay time of the robot and the maximum follow-up delay time, then the follow-up delay amount of the robot element will substantially match the maximum follow-up delay amount. The same can be said for other robot elements, so that the mismatch in follow-up delay for all robot elements is eventually resolved, and time-based discrepancies between the positions of each robot element are prevented.

"Example" Hereinafter, the example shown in the drawings will be described. Here, FIG. 1 is a diagram illustrating the configuration of a system consisting of a robot control device according to an embodiment of the present invention and an example of a robot controlled by the robot, and FIG. 2 is a diagram illustrating the principle of operation of the system shown in FIG. 1. FIG. 3 is a flowchart of the main part of the operation of the robot control device shown in FIG. 1, and FIG. 4 is an explanatory diagram of the delay amount calculation process.

In FIG. 1, the robot 10 has an X axis of 11 degrees and a Y axis of 21 degrees.
and Z-axis 31, each axis 11
．． 21.31, drive mechanism 12.22.32, position sensor 13, 23.33, detection circuit 14.24.3
4 and 4 individually.

The robot control device 1 includes: a command value storage means 2 and a delay N;
It includes a calculation means 3 and a command value delay means 4.

First, with reference to FIG. 2, the principle of this control device 1 will be explained. If you try to move the robot's wrist 10 (not shown) in time T from the current point P to point P2, in the conventional case, the command value for the χ axis 11 is the same.

is given by the equation 0 as time t progresses.

However, -1r -(X2 X'l) /T, β-
(Y2-Y,)/T.

D;-χπ +T・t...■Similarly, Y
The command value D2 to the axis 21 is given by equation 0.

D2 = Y, +β・t... ■However, if the X-axis 11 has a follow-up delay amount d, and the Y-axis 21 has a follow-up delay amount d2, then the position sensor 13.2
The actual positions θ1' and θ2' read in step 3 are as shown in equations ① and ②.

θ1' -Xl +r・ (t-dl)...■θ,
, '-Y, 10β・ (-t-d2)...■Here a,
<d2, the X-axis 11 automatically moves ahead when viewed from the Y-axis 21, and in FIG. 2, the points i, p, and P2. As a result, they are not connected by a straight line (indicated by a broken line) but by a curved line (indicated by a two-dot chain line). This means that the work is out of line with the intended work line.

On the other hand, in the control device 1 of the present invention, the delay amount calculation means 3 reads the actual positions θ1' and θ-r', compares them with the command values stored in the command value storage means 2, and calculates the follow-up delay amount d1.
Calculate 5d2. Then, the command value delay means 4 compares the follow-up delay amounts dl and d2, and the follow-up delay amount d2 is the larger one.
The command value D2 is given to the Y-axis 21 which has a smaller follow-up delay amount d1 according to the normal progression of time, but the time progresses by the follow-up delay amount difference (d2 d+) to the X-axis which has the smaller follow-up delay amount d1. Delays the command value and gives the command value.

That is, instead of the conventional formulas ■ and ■, DI=X1 +r H(t a2+d+ )'''■'
D2 =Y+ +-B-t...■
'. As a result, formulas ■ and ■ are θI ' -x, +γ・ (t d2 +d
, -d+ )...■'θ2'=Y1 +β・ (t dz) ・・
・■' becomes. If we rearrange Equation 07, θ,'=x, +γ・ (t d2)...
■'', so if (t-a2) is set as t', θ,'
=X, +'7-t'...■θ
, '=Y, +β・t' ...■, and although time is delayed by time d2, if we pay attention to the mutual positional relationship of the X-axis and Y-axis at the same time, we can see that the command value that was faithfully taught This means that you can execute

To illustrate the above in FIG. 2, in the conventional device, for example, point Q
2 becomes point 02' in this control device 1, and it can be seen that an actual work line (solid line) faithful to the intended work line (broken line) can be obtained.

Now, FIGS. 3(a), 3(b), 3(c), and 3(d) are flowcharts of the operation of the control device 1. However, generalizations have been made, such as setting the number of robot elements to N and taking into account sections in which exceptional movements (for example, reversals) occur.

First, referring to FIG. 3(a), before the "start", a group of command values θmi is taught and stored in the command value storage unit @2. Here, m is the number of the robot element, and i is a variable meaning time, where m=1 to N and i=1 to J.

When the "start" is performed, the delay amount dm of all robot elements is set to 0 as "initialization", and the maximum delay amount dm is set to 0.

And the tentative maximum delay amount d~' is set to O. Then, the time is set to i=1, and the robot element number is set to m=l.

As shown in Fig. 3(b), the "speed change point check" checks whether there is a speed change in the progress of the robot element at a time (i + α) that is α ahead of the current time j, and also checks whether there is a speed change in the progress of the robot element. If there is a change, this is a routine that sets an interval in which special processing should be performed depending on the type of change. If there is no speed change and the robot element moves at a constant speed, no section is set.

"Calculation of command value Dm and delay amount d, n" sets the command value D□ to be output to the robot element, and the delay l
This is a routine to calculate dm. As shown in FIG. 3(c), when the current time i belongs to an interval in which special processing should be performed, D□□ and dm are calculated by special processing determined for each interval, and If it does not belong to the section that should be processed, D
mL and dm are calculated.

In order to simplify the explanation, a description will be given of the "uniform speed progression process" which is the most prominent feature of the present invention, and a description of special processes will be omitted.

In the "uniform speed progression process", as shown in Fig. 3(d), at a time (a, , -G) earlier than the current time i, that is, at a time (i - d m + d m). The correspondingly stored command value θm (l − J , +J m) is read out and set as the command value 1)m. If there is no delay in all robot elements, d,... = O, dm-〇, so I) mt-θmL, and the stored command value θII
ILs are retrieved in sequence according to the normal progression of time. Furthermore, if the robot element has the largest amount of delay, d m = d 1. l, so DmL
”'θmL, and in this case as well, the stored command value θ, Ili is retrieved as normal time progresses. However, if the delay Mdl, l is neither 0 nor the maximum, the above To (d.

−d□) is delayed and the memory command value θm
('t-J-'+Jm') is extracted.

Next, in order to newly calculate the delay Md1l+, the stored command value θm (L-am) that is d, . This is the estimated value that is closest to the current value. Furthermore, the stored command values θ, , l (□-a-I) one control period before the estimated position A are taken out and used as the moving direction discrimination value B. Furthermore, the output signal θlN1' of the position sensor is read. This is the current value.

In the specific process of calculating the amount of delay, since the directions of magnitude comparison are different, the estimated position A and the moving direction determination value B are compared, and the flow shown in FIG. 3(d) is branched into two. However, since the principles are the same, only the case where A>B is Yes will now be explained.

As shown in FIG. 4, A>B means that the command value data is changing in an increasing direction. Therefore, when comparing 8 and 01□′, if θ
0. ' is at the cl or C7 position shown in Figure 4, then A
≧θ1llL', so the current position θ1. ′ is later than or equal to the estimated position. Therefore, the process branches to a process of increasing or preserving the delay tdm. On the other hand, if θ1llL' is at the position C3 shown in Fig. 4, A<0m1', which means that the delay is getting smaller, so proceed to the process of reducing the delay amount dm. Branch out. Since the process of increasing or preserving and the process of decreasing are the same in principle, now A≧θ1.
Only the case where Ili' is Yes will be explained.

First, θML' is at the position of CI shown in Figure 2, and A≧θm
If l□', then dIll is increased by .

At this time, it is normally unlikely that the delay amount dm exceeds the elapsed time i up to the current time i, but if it does, dm is exceptionally decreased by 16, that is, the original value of d is maintained. Further, dm is increased by 1, a corresponding change in the command value is checked, and if there is no change, the original values of dl and l are exceptionally maintained in the same way as above. Furthermore, even when dm exceeds a predetermined upper limit value, the original value of d4 is similarly maintained.

When the delay amount dWl does not exceed the elapsed time i up to the present time and does not exceed the upper limit value, the estimated position A is determined using the increased dll. In other words, shift the estimated position A by one control cycle to the previous position, that is, position B shown in FIG. 4, and then compare A and θ If A≧θ1,′, the process returns to increasing dm by 1 again. If this is repeated, A will gradually decrease, and eventually A≧°θ□' will no longer hold true. Therefore, the value obtained by subtracting 1 from the current d□ is set as a new d□. In addition, when A = θl, l', dm is added by LJ to A
Since ≧θI, 1□′ no longer holds, that d□
1 is subtracted from , and in the end, the original values of d,,l are preserved.

Now, the command value is determined as described above. When □ and the delay amount d are calculated, the process returns to the flow shown in Fig. 3(a), and next, d
ll is compared with the provisional maximum delay amount d MIX', and if larger, the provisional maximum delay amount d~' is updated.

As a result, when one process is performed from m=l to m=N, d my' holds the maximum value among the delay amounts of each robot element. d m' is set as the maximum delay amount d at the next time (i+1).

The command values D and E are output to the corresponding robot elements in the "servo control" process. This "servo control" processing is similar to conventionally known processing, so a description thereof will be omitted.

When the above processing is completed for m=1 to N and i=1 to J, all stored command values θml have been output for the robot element with the largest delay amount d, 11. However, since time is delayed for robot elements with smaller delay amounts d and n, storage command values θI and li that have not yet been output are left. Therefore, in terms of the processing procedure, the above processing is further repeated with the current time i set to J. As a result, the delay amount dm of each robot element
will gradually become smaller, so let's call it 6. By Chi, 17
, d, is a predetermined small value ε. When it becomes smaller,
It is assumed that the final destination position has actually been reached, and the operation is terminated.

As another embodiment, instead of setting the time delay to (1-dwy '' dm) as in the above embodiment, a value S□ specific to the robot element is determined, and (+ d-+
dm S+a) that is delayed. The way to determine this S,11 is, for example, the dead time of one robot element is T, and the time constant of a delay element is Tm.
', then Sm=0 for the robot element with the maximum T, +T,' among all robot elements, and for other robot elements, the robot element's Tm + Tl11'
An example of this is to define the difference between Twl+T, , ' of the largest robot element as the SII of the robot element.

As yet another example, the time delay method may be changed to (+ −
5-3m) that is delayed. Here, q is converted into an integer by rounding down, for example. According to this example, the time delay method is set to load d, , +d
Since the delay amount is smaller than when using wl-sm), the sensitivity becomes smaller but smoother.

"Effects of the Invention" The robot control device of the present invention includes a command value storage means that is taught and stores a group of command values to be sequentially given to each robot element as time progresses; A delay amount calculation means that calculates the amount of delay of each robot element by comparing the command value given to the robot element with the current value of each robot element read from the position sensor, and mutual comparison of the calculated amount of delay of each robot element. Then, for the robot element with the maximum amount of delay, command 4fj is retrieved from the command value storage means and given to that robot element according to the normal progression of time, while for the robot element with the amount of delay that is not the maximum, the command 4fj is given to that robot element. The device is equipped with a command value delaying means that retrieves a command value from the command value storage means and applies it to the robot element according to the time delayed by a larger amount of delay as the amount of delay becomes smaller. According to this, the following delay of each robot element is reduced. Since it is possible to eliminate variations in the amounts and match them, there is no time-based deviation between the positions of each robot element, and the position accuracy can be significantly improved.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the configuration of a system consisting of a robot control device according to an embodiment of the present invention and an example of a robot controlled by it, and Fig. 2 is an explanatory diagram of the principle of operation of the system shown in Fig. 1. , FIG. 3 is a flowchart of the main part of the operation of the robot control device shown in FIG. 1, and FIG. 4 is an explanatory diagram of the delay amount calculation process. (Explanation of symbols) 1... Robot control device 2... Command value storage means 3... Delay amount calculation means, 4... Command A1? - delaying means 10...robot 11.2], 31...robot element 13.23.33...position sensor.

Claims (1)

[Claims] 1. A robot control device comprising a plurality of robot elements, each of which moves according to a command value, and a position sensor that detects and outputs the current value of the robot elements, comprising: (a ) a command value storage means that is taught and stores a group of command values to be sequentially given to each robot element as time progresses; (b) a command value that is given to each robot element at a previous time and read from the position sensor; and (c) a delay amount calculating means that calculates the amount of delay of each robot element by comparing the current value of each robot element with the current value of each robot element. For a robot element with a delay amount, the command value is retrieved from the command value storage means and given to that robot element as time progresses normally, while for a robot element with a delay amount that is not the maximum, the smaller the delay amount, the more the command value is given to the robot element. A control device for a robot, comprising a command value delaying means for extracting a command value from the command value storage means and applying it to the robot element according to a greatly delayed time.