Loop Interface for Local Set Point Override in Digital Control Systems
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Solution Overview
Problem
Existing control systems for field devices lack the ability to locally adjust and override set points in a control loop without the need for continuous connection to a host device, limiting remote and emergency control capabilities.
Innovation Solution
A loop interface is introduced that allows users to view and adjust set points directly within the control loop, overriding host connections if necessary, enabling local control and operation of digital control loops without relying on a connected host device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a host device is used to adjust set points remotely, then centralized control capability is improved, but local control capability deteriorates
Solution Approach 1:
The control system is segmented into two independent interfaces: a host device interface for centralized control and a local loop interface for local control. Each interface can operate independently, allowing the system to maintain centralized control capabilities while simultaneously enabling local control when needed, thus resolving the contradiction between centralized and local control capability.
Solution Approach 2:
The local loop interface acts as an intermediary between the user and the loop controller. It can receive set point inputs locally and override host control when necessary, serving as a mediator that enables local control capability without eliminating centralized control functionality. The intermediary allows the system to switch between centralized and local control modes as needed.
2Adaptability or versatility
If the loop controller is located remotely at field locations, then operational flexibility is improved, but ability to adjust set points deteriorates
Solution Approach 1:
The system separates the loop controller (located remotely for operational flexibility) from the set point adjustment interface. By providing a local loop interface at or near the field location, users can adjust set points locally without needing to access the remote controller physically or maintain continuous host connection, thus maintaining both operational flexibility and ease of adjustment.
Solution Approach 2:
The local loop interface enables the remote control system to serve itself by providing autonomous set point adjustment capability at the field location. Users can directly input and modify set points locally without requiring external host device intervention, allowing the remotely located controller to maintain full operational capability including set point adjustment independently.
3Extent of automation
If host connection is maintained for setup, then centralized configuration capability is improved, but independent operation capability deteriorates
Solution Approach 1:
The local loop interface is pre-configured with the ability to receive and process set point inputs independently. During initial setup, the host device can configure the interface, but the interface is preliminarily prepared to operate autonomously. This preliminary configuration enables the system to maintain centralized configuration capability while ensuring independent operation capability is already in place and functional.
Solution Approach 2:
The system dynamically switches between host-connected and independent operation modes. The local loop interface can operate in host-dependent mode during setup and maintenance, then switch to independent operation mode when the host disconnects. This dynamic capability allows the system to have both centralized configuration capability when needed and independent operation capability when the host is unavailable.
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AI summary
Example methods and apparatus to interface with a control loop are disclosed. An example apparatus includes a loop controller to control a control loop, a sensor to provide a measurement value to the loop controller, a device controller to adjust a control device based on an output from the loop controller, and a loop interface to receive a set point value and send the set point value to the loop controller, wherein the loop interface is different from a host device communicatively coupled to the loop controller.