Wireless Plant Control With Error-Adaptive Command Retransmission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Networked Control Systems (NCS) face challenges with packet loss and time delays in wireless communication, leading to unstable control loops and performance issues, as existing solutions do not effectively merge wireless communication and control system technologies to optimize performance.
Innovation Solution
A networked control system that includes a receiver, controller, state observer, and transmitter, where the state observer determines the number of wireless transmissions based on control error to ensure reliable packet delivery and reduce network congestion, and a scheduler prioritizes packet transmission times based on control errors to minimize total control error across multiple plants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If control commands are transmitted over wireless network, then system flexibility and remote control capability are improved, but packet loss and time delays occur leading to unstable control loops
Solution Approach 1:
The system dynamically adjusts the transmission rate based on the current control error magnitude. When control error is large, transmission rate increases to ensure timely delivery of corrective commands. When control error is small, transmission rate decreases to reduce network congestion. This dynamic adaptation resolves the contradiction by making the system responsive to actual control needs rather than using fixed transmission rates.
Solution Approach 2:
The patent changes the transmission parameter (transmission rate) based on the control error parameter. By mapping control error magnitude to transmission rate, the system adapts its communication behavior to the control performance requirements, thereby maintaining stability while enabling remote operation.
2Reliability
If transmission rate is increased to compensate for packet loss, then reliability of control command delivery is improved, but network congestion increases
Solution Approach 1:
The system uses dynamic transmission rate adjustment where the transmission rate is proportional to the control error magnitude. This prevents unnecessary high transmission rates when control error is small, thereby avoiding network congestion while maintaining sufficient reliability when control error is large.
Solution Approach 2:
The system applies partial action by transmitting at higher rates only when necessary (large control error) rather than continuously at maximum rate. This selective approach ensures reliability only when needed, avoiding the excessive network traffic that would cause congestion.
3Stability of the object's composition
If remote controller runs slower to ensure stable control loops, then control loop stability is maintained, but transient response and performance deteriorate
Solution Approach 1:
The remote controller dynamically adjusts its operating speed based on control error magnitude. When control error is large, the controller operates faster to provide timely reference inputs and shape transient response. When control error is small, it operates slower to maintain stability. This dynamic speed adjustment resolves the contradiction between stability and transient performance.
4Reliability
If multiple packets are transmitted to ensure delivery, then packet delivery reliability is improved, but network congestion and latency increase
Solution Approach 1:
The system transmits multiple packets only when control error is large, applying partial action rather than continuously. This reduces the total number of retransmissions and decreases network latency while maintaining sufficient delivery reliability for critical control moments.
Data Source
AI summary
A networked control system for controlling at least one plant includes a receiver configured to receive a feedback signal indicative of a current state of a controlled variable of a plant over a wireless link and a controller configured to determine a control command based on a control error between a reference state of the controlled variable and the current state of the control variable. The system also includes a processor configured to determine, based on a function of the control error, a number of transmission times a packet with the control command needs to be transmitted over the wireless link, and a transmitter configured to transmit the packet over the wireless link the number of transmission times.