Electrical computers and digital data processing systems: input/ – Interrupt processing – Processor status
Reexamination Certificate
2000-01-12
2001-10-09
Beausoleil, Robert (Department: 2781)
Electrical computers and digital data processing systems: input/
Interrupt processing
Processor status
C710S268000, C709S241000, C709S241000
Reexamination Certificate
active
06301634
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a robot controller and its control method. In particular the invention relates to improved robot controllers using generic personal computer operating systems that execute the processing associated with the occurrence of events on a real time basis.
2. Description of the Related Art
Most conventional robot controllers and their control methods are designed to control the operation of specific manipulators such as SCARA-type manipulators and cartesian coordinate manipulators. For these purposes the conventional robot controllers employ independently developed robot control operating systems (“OS”).
In recent years, however, there has been an increased demand for robot controllers that are capable of controlling the entire system, such as controlling peripheral devices or communicating with external devices, beyond controlling the operation of manipulators. In such cases, an OS that incorporates a multi-tasking function must be used as a robot controller OS. To meet this need either proprietary OS or generic real time operating systems (pSOS, VxWorks, VTRX, OS-
9
, etc.) are used in most cases.
It should be noted that “pSOS” is a registered trademark of Integrated Corporation, “VxWorks” is a registered trademark of WindRiver Systems Corporation, and “VRTX” is a registered trademark of MicroTech Research Corporation.
Because the control of manipulators and peripheral devices requires real time processing, an important requirement for a robot controller OS is the ability to ensure real time processing.
The development of proprietary operating systems capable of ensuring real time processing requires a vast amount of labor. On the other hand, while generic real time operating systems provide such real time processing capabilities, their high cost can be an economic drawback.
Recently, low-cost, high functionality personal computer operating systems have become available and are widely used. If such a personal computer operating system can be used for a robot controller, it is possible to achieve both substantial reductions in developmental labor and costs. This approach offers the additional advantages of ease of training from the standpoint of users, further reductions in developmental leadtimes because of the availability of a full complement of developmental tools, and the possibility of extending applications through the use of off-the-shelf hardware and software.
However, even though low-cost personal computers and PC-oriented operating systems offer multi-tasking capabilities, their task-switching operations are slow. A reduction in switching intervals is impossible, and it is therefore difficult to ensure real time processing.
As noted previously, because the control of manipulators and peripheral devices in a robot controller requires real time processing, if an operating system takes a long time between the occurrence of an event and the startup of the task that processes the event, the system falls short of being fully practical for a robot controller.
Another complicating factor is that, if any of the aforementioned personal computers or PC-oriented operating systems is used, the length of time between the occurrence of an event and the startup of the task that processes the event can vary greatly depending on the timing at which the event occurs. This fact tends to reduce the quality of the processing in terms of reproducibility.
OBJECTS OF THE INVENTION
Therefore, it is an object of the present invention to overcome the aforementioned problems.
Another object of the present invention is to provide high-speed task switching and a reduction in boot time or task startup time variability in the aforementioned personal computers and PC operating systems (so-called non-real time operating systems). A further object is to provide robot controllers developed with less manpower, having higher levels of functionality, improved ease of user learning, and greater expansion potential through the use of off-the-shelf hardware and software, while fully utilizing the various advantages inherent in the aforementioned personal computer operating systems.
A further object of the present invention is to provide a robot controller and its control method using a generic personal computer and a generic operating system for personal computers.
SUMMARY OF THE INVENTION
The robot drive controller of the present invention comprises a task-switching unit that includes a pre-emptive multi-tasking function and a real time control unit that effects control by commanding the task-switching unit to switch tasks so that the processing in response to the occurrence of an event is executed in real time. The real time control unit detects events on a regular basis at fixed time intervals that are short enough for the execution of real time processing. The robot drive controller comprises an event drive unit that performs event drive processing and directs the task-switching unit to switch to the task that executes processing associated with the detected event.
In the present context the term “pre-emptive” generally refers to the division of CPU processing into fixed time slices so that the OS assigns CPU time to applications according to a priority scheme. In other words, the term encompasses the case in which, before an application completes its processing and relinquishes the CPU, the OS seizes processing control at each unit time and switches the CPU to another application, i.e. pre-empts the unfinished application. Consequently, when multiple applications are executed in a pre-emptive multi-tasking scheme, it is not necessary for an application to wait until another application completes processing and releases the CPU. This substantially reduces the amount of wait time that the user experiences and thus improves the apparent efficiency of the computer.
In the present invention events are detected at fixed intervals so that the task that executes processing associated with an event can be driven in a timely manner. Therefore, by performing event drive processing at each interval that is short enough to handle events on a real time basis, the processing for handling events will be executed in real time.
The real time control unit of the present invention comprises an external interrupt generation unit that generates interrupt signals at the fixed intervals by using an external timer. The event drive unit performs the event drive processing in synchronization with the interrupt signals that are generated by the external interrupt generation unit.
In the real time control method of the present invention, processing that is associated with the occurrence of an event in a robot controller employs a generic operating system that includes a pre-emptive multi-tasking function. The control method comprises an external interrupt generation step that uses an external timer to generate interrupt signals on a regular basis at fixed time intervals that are short enough for the execution of real time processing. The control method further comprises an event drive step that detects events in synchronization with the interrupt signals that are generated in the external interrupt generation step and that performs event drive processing in which the generic operating system is directed to switch to the task that executes processing associated with the detected event.
In this manner, an external timer can be used to generate external interrupt signals at fixed time intervals sufficiently short to respond to the occurrence of events in real time. Therefore, by performing event drive processing in synchronization with the interrupt signals, even generic personal computers and generic operating systems for PCs that are not presently capable of ensuring the aforementioned fixed time intervals (by means of time slices or of internal interrupts using a system timer) can now control event-responding processing in real time.
In the present invention, the task-switching unit, comprises a time-slice unit that slices or divides time into the fixed time
Gomi Kazuhiro
Miyazawa Hiroshi
Okuyama Masayuki
Shioda Toshimi
Yokoshima Norio
Beausoleil Robert
Phan Raymond N
Seiko Epson Corporation
Watson Mark P.
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