Predictor-Based Control for Intermittent Wireless Process Measurements
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Solution Overview
Problem
Process control systems face challenges with wireless communication networks due to reliability concerns, power consumption, and the need for frequent updates of process variable measurements, which can lead to reduced efficiency and equipment damage.
Innovation Solution
A control technique that uses predictors like Kalman filters or Smith predictors to estimate process variables from intermittent or slow feedback signals, ensuring continuous control by providing updated estimates to the controller during each execution cycle, regardless of the frequency of measurement updates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wireless communication networks are used to transmit process variable measurements, then installation flexibility and reduced wiring complexity are improved, but communication reliability and data update frequency deteriorate
Solution Approach 1:
The patent introduces a predictor as an intermediary component that receives intermittent process variable measurements from wireless field devices and generates continuous estimates. This mediator bridges the gap between the unreliable wireless communication and the control system's need for continuous data, allowing wireless installation flexibility while maintaining control reliability through mathematical estimation.
2Use of energy by moving object
If wireless field devices transmit measurements less frequently to reduce power consumption, then energy usage is reduced, but measurement precision and control accuracy deteriorate
Solution Approach 1:
The patent applies preliminary action by having the predictor generate continuous process variable estimates before actual measurements are received. The predictor uses process models and available data to proactively create estimates that maintain control accuracy, allowing field devices to transmit measurements less frequently for reduced power consumption while the predictor ensures continuous precision.
3Measurement precision
If process controllers execute control routines at high frequency to maintain control accuracy, then control precision is improved, but computational load and processing time requirements worsen
Solution Approach 1:
The patent uses copying by creating a mathematical model copy of the process behavior through the predictor. Instead of requiring the actual process to provide continuous measurements, the predictor creates a copy/estimate of the process variable using process models, control inputs, and intermittent measurements. This reduces computational load while maintaining control accuracy.
4Adaptability or versatility
If traditional control algorithms are modified to handle intermittent measurements, then adaptability to wireless systems is improved, but system complexity and implementation difficulty worsen
Solution Approach 1:
The patent applies segmentation by separating the intermittent measurement handling function from the control algorithm itself. The predictor is segmented as a independent preprocessing component that converts intermittent measurements into continuous estimates, while the control algorithm remains unchanged. This segmentation maintains adaptability to wireless systems without increasing control algorithm complexity.
Data Source
AI summary
A control technique that enables the use of slow or intermittently received process variable values in a predictor based control scheme without the need to change the control algorithm includes a controller, such as a PID controller, and a predictor, such as a model based predictor, coupled to receive intermittent feedback in the form of, for example, process variable measurement signals from a process. The predictor, which may be an observer like a Kalman filter, or which may be a Smith predictor, is configured to produce an estimate of the process variable value from the intermittent or slow process feedback signals while providing a new process variable estimate to the controller during each of the controller execution cycles to enable the controller to produce a control signal used to control the process.