How to design fault-tolerant control for regulating valves

In modern industrial control systems, the regulating valve, as an important part of the executive mechanism, its operating reliability directly affects the stability and safety of the entire system. Especially in key industrial fields such as chemicals, electricity, and oil, once the regulating valve fails, it may lead to system loss of control, product quality decline, and even trigger safety accidents. Therefore, designing an effective regulating valve fault-tolerant control strategy is the key to improving the robustness and reliability of the system.

One, Common Fault Types of Control Valves

Before designing a fault-tolerant control system, it is necessary to first clarify the typical fault types that may occur in control valves. These mainly include:

1. Sticking fault: The valve is stuck at a certain opening and cannot respond to control signals;
2. Leakage fault: Poor sealing leads to medium leakage, affecting control accuracy;
3. Hysteresis and Dead Zone: Valve response lag or dead zone causes poor control sensitivity;
4. Abnormal driving signal: Such as interruption of gas source or electrical signal, causing the valve to fail to operate.

Two, Basic Ideas of Fault Tolerant Control

Fault Tolerant Control (FTC) aims to maintain system stability and as much control performance as possible even after partial system failure. The design for control valves mainly includes the following steps:

# 1. Fault Detection and Diagnosis (FDD)

By collecting parameters such as valve opening, flow, and pressure through sensors, and combining state observers, model matching, or neural network algorithms, real-time monitoring and fault identification of valve status can be achieved. For example, the method based on residual analysis can effectively identify abnormal behaviors such as valve jamming or leakage.

# 2. Fault-tolerant Controller Design

Once a fault is detected, the controller should be able to adaptively adjust the control strategy. Common methods include:

- Model reconstruction: Dynamically adjust the control model according to the type of fault;
- PID parameter self-tuning: Optimize PID parameters under fault conditions to reduce control errors;
- Multi-model switching control: Preset multiple control models and switch automatically according to the fault state;
- Robust control technology: Adopt methods such as H∞ control and sliding mode control to enhance the system's tolerance to uncertainty and faults.

# 3. Redundant Channels and Redundant Design

For critical systems, redundant design can be adopted, such as setting backup valves or parallel execution structures. When the main valve fails, the control system automatically switches to the backup channel to ensure continuous operation of the system.

Three, Matters to be aware of in practical applications

In engineering practice, when implementing fault-tolerant control of control valves, the following factors need to be considered:

- The system has high real-time requirements, and the FDD module needs to be fast and accurate;
- The complexity of the control algorithm should not be too high to adapt to the computational capability of the field controller;
- Compatibility with DCS and PLC systems;
- Regular maintenance and self-inspection mechanisms are also important means to ensure fault-tolerant capability.

Four, Conclusion

With the continuous improvement of industrial automation levels, the fault-tolerant control design of control valves has become an important direction of research on system safety and reliability. Through means such as fault detection, adaptive control, and redundant configuration, the operation stability of control valves under abnormal working conditions can be effectively improved, ensuring the safety and efficiency of the production process. In the future, with the development of artificial intelligence and big data technology, fault-tolerant control will evolve towards a more intelligent and self-learning direction, providing stronger protection for industrial control systems.