What is an electro-hydrostatic actuator (EHA)?
An electro-hydrostatic actuator (EHA) combines an electric motor, a pump and a hydraulic cylinder in a single unit. It produces hydraulic force from electrical power, without connecting to a central hydraulic line.
How does an EHA work?
- The driver turns the electric motor according to the control command.
- The motor turns a bidirectional pump.
- The pump moves oil from one side of the cylinder to the other, and the piston moves.
- Speed and direction are set mainly by the motor’s speed and direction of rotation rather than by a valve.
- Position and pressure sensors give feedback to the control loop.
EHA compared with a servo valve actuator
In a servo valve system, a central power unit supplies pressurised oil and the valve throttles it to control motion. In an EHA, each actuator has its own oil circuit and motion is controlled through the motor, which reduces the need for long hydraulic lines.
Advantages
- Reduces the need for central hydraulic lines and long piping
- Power is carried by electrical cable
- Uses energy mainly when motion is needed
- Can be replaced and tested as a single unit
Where is it used?
- Flight control surfaces in aviation
- Defence systems
- Electric construction machinery and industrial applications
What is checked in EHA testing?
EHA testing monitors motor drive, phase currents, position tracking, pressure and temperature behaviour together. It verifies that the control software works properly with the motor, valves and sensors.
Frequently asked questions
What is the difference between an EHA and an electromechanical actuator (EMA)?
An EHA transfers motor power to the cylinder through oil. An EMA transfers it through mechanical parts such as gears and a ball screw.
Why is FOC used in an EHA?
FOC (field-oriented control) controls the motor’s phase currents according to rotor position, which lets motor torque be adjusted precisely.
To drive and test EHAs
MotorTech EHA offers FOC-controlled 3-phase motor drive, poppet valve outputs, and LVDT and pressure inputs.