Data synchronization in a cooperative distributed control system
AssigneeSchneider Electric USA, Inc.
InventorsRodney B. Washington, Pierre Colle
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Abstract
A data synchronization method and apparatus are provided for a distributed control system where multiple controllers can control a plurality of actuators or sensors. The actuators or sensors are assigned to logical groups that share a common state. One of the actuators or sensors within a logical group serves as a reference device for a state variable. Before taking a control action, the controllers read the current value of the state variable from the reference device. Data synchronization is maintained by one or more refresh master controllers.
Claims7
A method of updating a state variable implemented by a controller in a distributed control system having multiple controllers, said method comprising:
- determining, by the controller, a reference device for a logical group of actuators and sensors,
- wherein said reference device is one of said actuators and sensors of said logical group and wherein a current state for any of the actuators or sensors within the logical group is determined by reading a current value of a state variable shared by all of the actuators and sensors of the logical group from the reference device;
- reading, by the controller, a current value of the state variable from the reference device in the logical group to perform a control action;
- calculating, by the controller, a new value for the state variable;
- sending, by the controller, a command to each actuator and sensor in the logical group to set the state variable to the new value,
- wherein a state of the state variable is subject to control by a plurality of the multiple controllers;
- periodically sending a refresh command to each actuator and sensor in the logical group to set the state variable to a predetermined state;
- and
- verifying that the controller is designated as a refresh master controller for the state variable before sending the refresh command.
A controller in a distributed control system, said controller comprising:
- a communications interface for communicating over a network with a plurality of distributed actuators and sensors in a logical group;
- and
- a command processor configured to:
- determine a reference device for a logical group of actuators and sensors,
- wherein said reference device is one of said actuators and sensors of said logical group and wherein a current state for any of the actuators or sensors within the logical group is determined by reading a current value of a state variable shared by all of the actuators and sensors of the logical group from the reference device;
- read a current value of the state variable from the reference device in the logical group to perform a control action;
- calculate a new value for the state variable;
- send a command to each actuator and sensor in the logical group to set the state variable to the new value,
- wherein a state of the state variable is subject to control by a plurality of the multiple controllers;
- periodically send a refresh command to each actuator and sensor in the logical group to set the state variable to a predetermined state;
- and
- verify that the controller is designated as a refresh master controller for the state variable before sending the refresh command.
A method of data synchronization in a distributed control system having multiple controllers, said method comprising:
- assigning a set of actuators and sensors to a logical group having one or more shared state variables,
- wherein each of the actuators and sensors in the set is controlled by a plurality of the multiple controllers;
- assigning one of the actuators and sensors to serve as a reference device for the logical group of actuators and sensors;
- determining, by one of the multiple controllers, a current state for any of the actuators or sensors within the logical group by reading a current value of at least one of the one or more shared state variables from the reference device to perform a control action;
- and
- designating a selected one of the controllers as a refresh master controller for the state variables, and storing an identity of the refresh master controller in memory of the reference device.
A distributed control system comprising:
- a plurality of actuators and sensors assigned to a logical group that shares one or more common state variables;
- and
- a plurality of distributed controllers each for controlling each of the plurality of sensors and actuators of the logical group, wherein the plurality of controllers are configured to:
- assign one of the actuators and sensors to serve as a reference device for the logical group of actuators and sensors;
- determine a current state for any of the actuators or sensors within the logical group by reading a current value of at least one of the one or more shared state variables from the reference device to perform a control action;
- and
- designate a selected one of the controllers as a refresh master controller for the state variables, and store an identity of the refresh master controller in memory of the reference device.
Dependencies are inferred from the claim text.