DISPLAYING TIME-CRITICAL MESSAGES IN A MULTITASKING ROBOT CONTROL SYSTEM
Original Publication Date: 1994-Feb-28
Included in the Prior Art Database: 2004-Apr-06
Xerox Disclosure Journal
Robot controllers commonly employ multitasking computer environments in order to execute assembly programs. Multiple programs or processes may be executed concurrently on the controllers used for robotic assembly systems, for example and Adept Robot Controller. Resources used by the processes, such as memory, external devices, communication ports, and the controller's serial terminal must be shared by different processes. Typically, only one process may have control over a limited resource at any one time, and the remaining processes needing the resource must wait until the resource is available. Unfortunately, processes which function in real-time environments can seldom wait for critical resources. As an example, if a process needs to write a message to the serial terminal associated with the robot controller while another process has control of the terminal, the process needing access must wait until the process currently accessing the terminal relinquishes it. Thus, the waiting process may remain in an idle state, possibly missing events which should be monitored, while waiting for the shared terminal resource. Alternatively, the waiting process, upon determining that the terminal is unavailable, may forgo the display of a message until a later time. Unfortunately, for critical processes, neither of these scenarios is desirable.