Program control system in multitask environment

A program control system in a multitask environment to execute a plurality of programs in parallel. The system includes a program execution control device for controlling an execution of a plurality of programs, a first program and a second program which are mutually related, a subtask execution recognition device for recognizing a subtask execution command in the first program, and a resumption control device for resuming the first program in response to both a wait command in the first program and an end command in the second program of the task associated with the task of the first program. When the subtask execution command is recognized by the subtask execution recognition device while the first program is being executed, the second program is also executed. When the end command in the second program is detected while the first program is in a wait state under the wait command, the resumption control means allows the program execution control means to resume the first program.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
The present invention relates to a program control system in a multitask 
environment, and more particularly, to a program control system in a 
multitask environment which can be applied to a control unit for a 
numerically controlled machine tool, an industrial robot, or the like to 
facilitate execution, halt, recommencement, and termination of a program. 
(2) Description of the Related Art 
Conventionally, a control unit for a numerically controlled tool machine, 
an industrial robot, or the like often executes only one program in 
normal, and therefore the peripheral devices thereof are configured so as 
to be operated by a single task. The term "program" herein used means a 
program which has been prepared by a user and generally called a user 
program, operation program, work program, teaching program or the like. 
Such a program. will be simply called as a program hereinafter. 
Recently, a multitasking operation to simultaneously run a plurality of 
programs has become popular in the field of numerical control units or 
industrial robots. Taking a case of a certain manufacturing line for 
machining workpieces, if there is used a system comprising an apparatus 
for picking out a workpiece from a warehouse, a machine for transferring 
the picked out workpiece to a working table, and a machine tool for 
machining the transferred workpiece, for example, three programs, each of 
which performs the respective corresponding function, are executed 
simultaneously. These three programs run in parallel synchronizing with a 
digital input signal, each of the programs, however, essentially runs as 
an completely separate program. 
In the case mentioned above, in order to execute, halt, recommence, or 
terminate individual programs, it is necessary to either individually or 
simultaneously select the programs to be controlled for a start or end of 
the programs. For example, if the first and the second programs are in the 
halt state, in order to recommence execution of the programs from this 
state, first, the first program is selected by some way, concretely, for 
example, by moving a cursor using a teaching console or by using a signal 
inputted from an external device, then recommenced. Next, the second 
program is selected likewise to be executed. Or, all programs in halt are 
recommenced at a time. 
In a conventional program control system, a plurality of programs are 
individually selected and then controlled, even though in a multitask 
environment where the plurality of programs can be executed in parallel. 
That is, the conventional system takes a form such that a program control 
system in a single task environment where only one program is executed at 
a time is simply extended. 
To execute programs in the multitask environment, the above mentioned 
procedure such as controlling programs after individually selecting can be 
time-consuming and problematic, and tends to cause an operational error. 
In addition, the conventional system is not well matched to a current 
automated system in which input/output of a digital signal from an 
external device is used to execute, halt, recommence, or terminate 
execution of a program. That is, the system configuration for controlling 
the programs by a digital signal from the external device is designed for 
use with the single tasking operation, and is therefore, usually not well 
adopted to the multitask operation as it is. 
A further disadvantage of the above mentioned procedure for starting and 
terminating all the programs is that this procedure lacks for flexibility 
and a system cannot be configured freely though in the multitask 
environment where a flexible system can be organized. For example, when 
execution of a program is recommenced from the halt state, even though 
there is a robot which has already finished its work in a series of works 
such as in a manufacturing line and which is therefore not necessary to be 
recommenced, all the program must be recommenced at a time and can not be 
executed individually and selectively. 
SUMMARY OF THE INVENTION 
The invention aims to remedy these disadvantages and to provide a program 
control system in a multitask environment where a plurality of programs 
can be executed in parallel, wherein a program which is related to and 
associated with a certain program is allowed to be executed automatically 
by executing the program. 
To solve the above mentioned problems, a program control system in a 
multitask environment is provided wherein operational programs respective 
for machine tools or industrial robots are allowed to be executed in 
parallel in an environment where a plurality of programs can be executed, 
comprising a program execution control means for controlling execution of 
a plurality of programs, a first program which is activated as an 
originating task by the program execution control means, a subtask 
execution recognition means for recognizing an execution command of a 
subtask in the first program, a second program which is activated as a 
subtask by the program execution control means in response to the 
recognition of execution of the subtask by the subtask execution 
recognition means, and a resumption control means for resuming the first 
program by the program execution control means in response to both a wait 
command in the first program indicating the first program to be in a wait 
state and an end command in the second program indicating that the task in 
the second program associated with the task in the first program is 
finished. 
According to the system mentioned above, the first program selected from 
among relevant programs is executed as an originating task by the program 
execution control means. Then, if a subtask execution command of the first 
program, which specifies execution of a subtask, is reached, the subtask 
execution recognition means recognizes the command and the program 
execution control means begins execution of the second program, during 
which the first program is executed continuously. If a wait command of the 
first program is directed, under which the first program can not be 
resumed until an end of the second program, this is notified to the 
resumption control means. Then, when completion of the second program is 
notified to the resumption control means, the program execution control 
means resumes execution of the first program which has been in the wait 
state. 
The above and other objects, features and advantages of the present 
invention will become apparent from the following description when taken 
in conjunction with the accompanying drawings which illustrate preferred 
embodiments of the present invention by way of example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A preferred embodiment of the present invention will now be described 
hereinafter with reference to the drawings. 
FIG. 1 is a block diagram illustrating a configuration of a program control 
system in accordance with the present invention. Referring to FIG. 1, the 
reference numeral 1 designates a program execution control means which is 
adapted to control execution of a first program 2 and a second program 3. 
The first program 2 contains a subtask execution command 21 and a wait 
command 22. The subtask execution command 21 is adapted to be recognized 
by a subtask execution recognition means 4 and the wait command 22 is 
adapted to be detected by a resumption control means 5. The second program 
3 contains an end command 31 and the resumption control means 5 is adapted 
to comply with the end command 31. Outputs of the subtask execution 
recognition means 4 and the resumption control means 5 are connected to an 
input to control the program execution control means 1. 
In order to activate the programs, it is necessary to activate the first 
program 2 and the second program 3 for multitasking. In actual activation 
operation, however, both the first and the second programs can be 
activated only by selecting and activating the first program 2, which is 
the same way as with a single tasking. The first program 2 selected in 
this way is activated as an originating task by the program execution 
control means 1. 
When the subtask execution command 21 of the first program 2 is reached 
while the first program 2 is executed, the command 21 is recognized by the 
subtask execution recognition means 4 and notified to the program 
execution control means 1. In response to the notification, the program 
execution control means 1 activates the second program 3 as a subprogram 
of the first program 2, during which the execution of the first program 2 
is continued. 
When the wait command 22 under which the first program is not resumed until 
an end of execution of the second program is directed, this is notified to 
the resumption control means 5. When the second program 3 is executed to 
the end, the end command 31 of the second program 3 is transferred to the 
resumption control means 5. In response to the wait command 22 of the 
first program 2 and the end command 31 of the second program 3, the 
resumption control means 5 controls the program execution control means 1 
to resume the first program 2 from the wait state. 
When the first program 2 is in activation and the subtask execution command 
21 of the first program 2 is reached as mentioned above, the first program 
2 becomes a parent program of the second program 3 and the second program 
3 becomes a child program of the first program 2, thereby a set membership 
is automatically provided. Accordingly, only by indicating halt, 
resumption, and termination of execution to the first program 2 which is a 
parent program, the indication is transferred to the second program 3 to 
which a set membership is held with the first program, and automatically 
reflected to the second program 3. 
Similarly, if the other subtask execution command to execute a third 
program is contained in the first program 2 or the second program 3 and is 
directed, a new set membership is provided therebetween and the third 
program is executed by the subtask execution recognition means 4 and the 
program execution control means 1. Thus, the third program stands to the 
first program 2 in the relation of grandchild, and if execution of the 
third program is activated, for example, from the second program 3, then 
the operation to the parent program is applied and reflected to the 
grandchild program. 
Therefore, if the programs held in a set membership relation are grouped, 
in a certain system, the whole group is activated by selecting and 
activating only the parent of the group. 
On the other hand, when the programs are controlled from an external 
device, finally, what is necessary is to control the parent program only, 
and therefore such a system can be used in an environment prepared for the 
single tasking operation as it is. 
FIG. 2 is a diagram of a robot system for illustrating an application 
example of the present invention. Referring to FIG. 2, a robot control 
unit 60 is adapted to control a sealing robot 61, a workpiece loader 62, 
and a workpiece supply machine 63 and provided with a program A for 
controlling the sealing robot 61, a program B for controlling the 
workpiece loader 62, and a program C for controlling the workpiece supply 
machine 63. 
Workpieces 64 are sequentially supplied by the workpiece supply machine 63 
and moved to the position where the workpiece loader 62 picks up the 
workpiece 64 with the hand for loading. The workpiece 64 moved to the 
position mentioned above is set in position on a jig 66 by the workpiece 
loader 62. Then the sealing robot 61 performs a predetermined sealing 
operation using its sealing gun. 
FIG. 3 is a flow chart illustrating one example of a program execution of a 
robot control unit. Programs to control the robot system exemplified in 
FIG. 2 are the program A, program B, and program C. In this robot control 
unit 60, activation of the system is commanded only to the program A. 
In the program A, the program B is activated as a subtask in step S11, 
thereby a set membership relation is automatically held between the 
program A and the program B. Then, in step S12, the sealing robot 61 is 
moved to its operation start position. In Step S13, it is determined 
whether the workpiece 64 is set in position on the jig 66. If the 
workpiece 64 is set in position, flow advances to step S14 and the sealing 
robot 61 seals the workpiece 64 using a sealing gun 67. 
When activated by the program A, the program B is executed in parallel to 
execution of the program A. When the program B is activated, first, the 
program C is activated as a subtask in step S21. Thereby a set membership 
relation is automatically held in step S21. Then, in step S22, the 
workpiece loader 62 is controlled and moved to the loading position of the 
workpiece 64 which is supplied by the workpiece supply machine 63. In step 
S23, it is determined whether the workpiece 64 reaches to the loading 
position. If the workpiece 64 reaches to the position, then flow advances 
to Step S24 and the workpiece loader 62 uses the loading hand 65 to pick 
up the workpiece 64 from the workpiece supply machine 64 and sets the 
workpiece 64 in position on the jig 66. At this time, a workpiece set 
completion signal is turned on in the program B. The workpiece set 
completion signal is directed before determination in step S13 of the 
program A. 
When activated by the program B, the program C is executed in parallel to 
execution of the program A and program B. In step S31 of the program C, 
the work supply machine 63 is controlled to move the workpieces 64 to the 
position where the workpieces 64 are sequentially loaded by the workpiece 
loader 62 and when a workpiece reaches to the position, a workpiece supply 
completion signal is turned on. The workpiece supply completion signal is 
directed before determination in step S13 of the program B. 
FIGS. 4(A), 4(B), and 4(c) are diagrams which comprise a representation of 
examples of program of a robot control unit. FIGS. 4(A), 4(B), and 4(C) 
are respective examples of the program A, program B, and program C. 
According to the example of the program A, the program B is activated by 
the command of the first line, and the sealing robot 61 is moved to its 
operation start position ("P 1!") by the command of the second line. 
After the sealing robot 61 is moved to the start position, the third line 
makes the sealing robot 61 wait until the workpiece set completion signal 
(SDO 1!) is turned on. When the workpiece set completion signal is turned 
on, a series of sealing operations is performed from the sealing start 
operation (SS) to the sealing end operation (SE) through the 4th to 20th 
lines. 
According to the example of the program B, the program C is activated by 
the first line, and the workpiece loader 62 is moved to its workpiece 
loading position ("P 1!") by the second line. After the workpiece loader 
62 is moved to the position, the third line makes the workpiece loader 62 
wait until the workpiece supply completion signal (SDO 2!) is turned on. 
When the workpiece supply completion signal is turned on, a macro program 
named "PICK WORKPIECE" to pick up a workpiece is accessed and executed by 
the 4th line. Then the 5th line allows the workpiece loader 62 to take the 
workpiece 64 to the jig 66, and the 6th line accesses and executes the 
macro program named "SET WORKPIECE" to set the workpiece 64 on the jig 66. 
Then the 7th line turns on the workpiece set completion signal (SDO 1!). 
According to the example of the program C, in response to the activation 
command from the program B, the first line accesses and executes a macro 
program named "MOVE WORKPIECE" to move the workpiece 64 to the loading 
position of the workpiece loader 62. When the workpiece 64 is moved to the 
loading position of the workpiece loader 62, the second line turns on the 
work supply completion signal(SDO 2!). 
As mentioned heretofore, in accordance with the present invention, since a 
set membership is provided for a plurality of programs related mutually, 
the plurality of the programs are activated only by activating the 
originating program, thereby activation of the programs is facilitated. 
In addition, the load put on the program control in the multitask 
environment is largely reduced without impairing flexibility of the 
system, and therefore occurrence of an operational error can be prevented. 
Further, on constructing an automated system, it is possible to use 
equipment and control software which has been prepared for the 
conventional single task environment without changing. 
The foregoing is considered as illustrative only of the principles of the 
present invention. Further, since numerous modifications and changes will 
readily occur to those skilled in the art, it is not desired to limit the 
invention to the exact construction and applications shown and described, 
and accordingly, all suitable modifications and equivalents may be 
regarded as falling within the scope of the invention in the appended 
claims and their equivalents.