Working Principle of Electro-Hydraulic Actuators

Electro-hydraulic actuators are highly efficient automation devices that control hydraulic systems through electrical signals. They are widely used in applications requiring high force and precise control, such as industrial automation, aerospace, and petrochemical industries. This article will delve into their working principles, including input signal processing, hydraulic power generation, and precise control of actuator components.

Input Signal and Target Position Setting

The input signals for electro-hydraulic actuators typically consist of standard current signals (e.g., 4-20 mA). These signals are transmitted through a control system to the Position Control Processor (PCP). The PCP converts the received electrical signals into target positions based on the set stroke and signal range. This process ensures that the actuator can accurately position itself according to external control commands, adapting to various operational requirements. For instance, when adjusting valve openings or controlling fluid levels, the PCP will modify the position based on real-time signals to maintain system stability and responsiveness.

Current Position Monitoring and Error Detection

To achieve precise control, electro-hydraulic actuators are equipped with high-precision feedback components that continuously monitor the current position. These components typically include position sensors or encoders that provide accurate positional data. The PCP compares the target position with the current position and calculates the error. If the error exceeds a user-defined deadband, the PCP activates the motor for necessary corrections. This mechanism ensures rapid response to changes in external signals while maintaining high operational accuracy, meeting the stringent precision demands of industrial applications. Additionally, the system records operational data for subsequent analysis and optimization.

Components and Functions of the Hydraulic Power Module

The core component of an electro-hydraulic actuator is the hydraulic power module, which consists of several key elements:

Electric Motor: Provides the mechanical energy required by the system, usually using high-efficiency motors to enhance energy utilization and reduce consumption.
Hydraulic Pump: Converts the mechanical energy from the motor into hydraulic oil pressure. The selection of the hydraulic pump is critical to system performance, as a high-quality pump enhances response speed and operational efficiency.
Flow Matching Valve (FMV): Controls the direction and flow rate of the hydraulic oil to achieve precise piston movement. The FMV can automatically adjust flow rates under different operating modes, optimizing response speed and ensuring stable operation in various conditions.
Oil Reservoir: Stores hydraulic oil, ensuring continuous operation and stable pressure to prevent system failures due to insufficient oil supply.
Heater and Cooler: Regulate the temperature of the hydraulic oil, ensuring it operates within the optimal range to enhance system reliability and efficiency. Proper temperature management also extends the lifespan of the hydraulic oil.
Bypass Solenoid Valve: Provides an alternative pathway in case of system failure, enhancing safety and preventing incidents caused by hydraulic oil backflow.

Precise Movement of the Piston

During operation, the hydraulic pump drives the piston by pressurizing hydraulic oil. For instance, to move the piston to the left, the pump changes the rotation direction to pressurize the hydraulic oil through the A port of FMV-2. This action causes the valve core of FMV-2 to become unbalanced under pressure differential, opening the passage connected to the cylinder body. As a result, high-pressure liquid flows into the right chamber of the cylinder, pushing the piston to the left, while the hydraulic oil on the left side returns to the pump's inlet through a check valve. This design ensures precise piston movement and maintains stable performance under varying operational conditions.
Once the piston reaches the target position, the pump stops, and two switch valves close, allowing hydraulic oil to remain in the cylinder, thus stabilizing the position. This design ensures that the electro-hydraulic actuator can maintain precise positioning even without motor drive, reducing energy consumption and extending system lifespan. Consequently, the actuator can sustain the required operational state for extended periods, significantly enhancing equipment reliability and cost-effectiveness.

Position Holding and Fault Diagnosis

The design of the electro-hydraulic actuator ensures that hydraulic oil can be retained in the cylinder during idle states, facilitating long-term stable operation. Additionally, the Position Control Processor is equipped with fault diagnosis capabilities, allowing real-time monitoring of the actuator's operational status and detection of potential faults. This fault detection system can automatically identify anomalies during operation and issue timely alerts to ensure safe operation. Any faults are displayed as error codes on the monitoring screen for quick localization and troubleshooting, enhancing system reliability. Through data recording and analysis, technicians can further optimize the system and reduce the frequency of faults.

Key Advantages

The primary advantages of electro-hydraulic actuators include:

High Force and Load Capacity: Hydraulic systems can provide greater thrust than pneumatic or electric systems, making them suitable for heavy-duty applications, particularly in scenarios requiring the overcoming of high resistance, such as opening heavy valves or moving large machinery.

Rapid Response: The instantaneous nature of hydraulic power allows the actuators to respond quickly, meeting dynamic control requirements and excelling in rapidly changing operational environments.

Precise Control: The combination of feedback systems and electronic control enables high-precision positioning and control, ensuring the maintenance of operational accuracy in complex operations, suitable for demanding industrial applications.

Conclusion

Electro-hydraulic actuators demonstrate powerful performance in complex applications through efficient signal processing, hydraulic power generation, and precise execution control. Although hydraulic systems can be relatively complex, through thoughtful design and effective control, electro-hydraulic actuators can meet demands for high efficiency and precision, becoming indispensable components of modern industrial automation systems. As technology continues to advance, their application prospects across various industries are becoming increasingly expansive, particularly in today's era of intelligent manufacturing and heightened automation. Electro-hydraulic actuators will continue to play an irreplaceable role in these developments.