On-the-fly state synchronization in a distributed system

A method for synchronizing a second sheet transportation process to a first sheet transportation process, wherein state data regarding input to, and output of, a model of the first sheet transportation process is available to the second sheet transportation process after a delay period, the method comprising:

• beginning a data collection period;
• determining a data collection state count to be a number of state times having a total duration at least as long as the delay period;
• receiving delayed state data points regarding the input to and output of the model, wherein the output of the model includes at least one of a sheet position, a sheet speed and a sheet trajectory;
• storing the delayed state data points received during the data collection period;
• ending the data collection period after receiving and storing a delayed state data point after the data collection period has persisted for a number of state times at least as large as the data collection state count;
• determining at least one of a current position, speed and trajectory of the sheet, from a current state of the model calculated from at least some of the stored state data points and predetermined information regarding a behavior of the state of the model;
• and
• setting a current state for an output value of the sheet transportation controller according to the determined at least one of a current position, speed and trajectory of the sheet, thereby synchronizing the second sheet transportation process to the first sheet transportation process.

A method for synchronizing a second process to a first process, wherein state data regarding input to and output of a model of the process is available to the controller after a delay period, the method comprising:

• beginning a data collection period;
• receiving delayed state data points regarding the input to and output of the model;
• storing the delayed state data points received during the data collection period;
• ending the data collection period after receiving and storing required information for determining a current state of the model based on forward propagation;
• using the stored required information and information regarding the behavior of the model to forward propagate the model from a state at a point after the beginning of the data collection period to the current state, thereby determining the current state of the model;
• and
• setting a current state of the second process according to the determined current state of the model, thereby synchronizing the controller to the process.

A system that is operative to control a process, the system comprising:

• a model of the process;
• a communications path associated with a communications delay;
• a controller that is operative to control a portion of the process;
• and
• a supervisor that is operative to activate the controller at a time appropriate for the controller to prepare for controlling the portion of the process, wherein, the controller receives information regarding states of the model of the process over the communications path after the communications delay, and wherein the controller is operative to initialize and maintain a local copy of the model for use in determining appropriate control actions, wherein the controller is operative to initialize the local copy of the model by using delayed information regarding prior states of the model to determine a starting prior state of the model and to forward propagate the model from the starting prior state to a current state of the model, thereby synchronizing the local copy of the model to the model of the process.

A document processing system comprising:

• a first xerographic marking engine;
• a sheet transport system that is operative to at least transport a sheet of print media to or from the first xerographic marking engine.
• a model of a sheet transportation process;
• a communications path associated with a possibly variable communications delay;
• a controller that is operative to control a portion of the sheet transportation process;
• and
• a supervisor that is operative to activate the controller at a time appropriate for the controller to prepare for controlling the portion of the sheet transportation process, wherein, the controller receives information regarding states of the model of the sheet transportation process over the communications path after the communications delay, and wherein the controller is operative to initialize and maintain a local copy of the model of the sheet transportation process for use in determining appropriate control actions, wherein the controller is operative to initialize the local copy of the model of the sheet transportation process by using delayed information regarding prior states of the model of the sheet transportation process to determine a starting prior state of the model and to forward propagate the model from the starting prior state to a current state of the model, thereby synchronizing the local copy of the model of the sheet transportation process to the model of the sheet transportation process.