The Integrate operator uses a discrete-time approach, providing periodic updates of variables based on a rate, which may be changed dynamically by external inputs. Complex behavior emerges from the interaction of devices that have simple models of internal continuous processes. This environment supports incremental model development, maintenance, and reuse. IMC-sequencer software monitored and controlled the model rather than the skills layer and hardware. The model included diverse components and systems for processing O 2 and CO 2 gases in a plant-growth chamber, crew chamber, and incinerator, and for storing gases and transferring them between chambers.
Rectangles are devices, and elongated ovals are activities.
Modes are indicated by the text in the rectangles and ovals, or by icons that indicate device modes. The product gas-transfer system model. The modeled devices include the chambers, various gas processors that convert O 2 to CO 2 or vice versa, gas concentrators, and PGT hardware that directs and regulates flow and pressure. The modeled activities include discrete and continuous control of the hardware that directs and regulates flow and pressure, schedules for crops and human activities, and some manual procedures. The activity models represent control by the 3T planning or skills tiers, local controllers, or human operators.