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Abstract

A computer-implemented building automation system is provided with an asynchronous object-oriented operating environment that is able to provide support for synchronous object execution with respect to real time, including those used to maintain closed-loop control over a system. The operating environment for supporting standard objects includes a clock mechanism for maintaining time and a scheduling mechanism for initiating the methods associated with the standard objects. A control method (i.e. PID control method) of a first standard object is scheduled for execution at a predefined schedule time with the schedule mechanism, and at some later time is initiated by the schedule mechanism. Upon execution, the control method determines an actual time of initiation by reading the clock mechanism and adjusts its control method using this actual time when the actual time exceeds the schedule time. More specifically, the actual time is determined by reading an elapsed time from the clock mechanism and computing a difference between this elapsed time and a start time that was determined by reading the clock mechanism at the time the control method was scheduled.

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First Claim