Hydrostatic Actuator
Core technology of Sinotest, the seceret of long using life
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The hydrostatic actuator eliminates the need for sealing gaskets by utilizing a specially designed hydrostatic bearing unit. This design enables the piston rod to self-regulate, ensuring constant alignment and central guiding between the piston rod and cylinder housing. While the bearings center the piston, all sliding surfaces within the actuator remain separated by a pressurized oil film. Unlike conventional bearings, this oil film is present before piston movement begins and is maintained even under lateral forces, effectively eliminating friction and wear. As a result, the hydrostatic actuator delivers exceptional performance for testing applications that demand the highest levels of control and measurement accuracy.
Key Features of the Hydrostatic Actuator
The SINOTEST hydrostatic actuator delivers exceptional performance across a comprehensive range of operating parameters. Specifically:
Capacity: 10 kN – 20,000 kN
Frequency: 0.01 – 400 Hz
Working pressure: 21 MPa / 28 MPa
Speed: 6 m/s, with customized options reaching up to 20 m/s
Consequently, this hydrostatic servo actuator provides laboratories with a versatile, high-performance platform suitable for both quasi-static and high-frequency dynamic testing applications.
For laboratories and testing facilities that require ultra-high precision, the SINOTEST hydrostatic actuator is an ideal choice.
AVAILABLE MODELS
ML series hydrostatic torsion servo actuator
Capacity(10-20000kN)
- ML10/25/50
- ML100/200/300/500
- ML1000/2000
MR series hydrostatic liner servo actuator
- MR.500/1000.100
- MR.2000/3000.100
- MR.5000.100
- MR.10000.100
- MR.25000.100
PL&PR series servo actuator
- Capacity: PL series: 10-2000KN
- Gap sealing technology
- Cost effective
PR series: 500-25000NM
Video of the Hydrostatic cylinder
SINOTEST’s hydrostatic system demonstration
SINOTEST’s hydrostatic cylinder for simulation motorcycle testing
Application of the Hydrostatic cylinder
The hydrostatic cylinder consistently outperforms conventional units in long-duration, high-accuracy test procedures.
Detailed Technical Specification
The SINOTEST hydrostatic actuator portfolio encompasses four distinct series, each engineered with unique performance characteristics for specific testing requirements.
ML Series – Hydrostatic Servo Actuator
As the flagship linear actuator, the ML series features a relative sliding surface with almost no friction, achieving a starting pressure of ≤ 0.001 MPa. Furthermore, it delivers high frequency response up to 400 Hz, speeds up to 6 m/s, and an uninterrupted working lifespan exceeding 100,000 hours. In addition, the piston rod withstands lateral loads of 5% of the rated load when in neutral position, while hydrostatic bearings remain in a pure liquid lubrication state for high transmission efficiency. Notably, the series features high sensitivity, high control accuracy, good accuracy retention, and high motion precision. Moreover, the relative sliding surface between the hydrostatic bearing and the piston rod is filled with a high-stiffness, high-load-bearing hydrostatic support oil film, which keeps the piston rod in the center position of the hydrostatic bearing at all times—delivering high seismic resistance, high coordination and synchronization, and automatic centering function. Finally, the special self-lubricating coating makes the hydrostatic support servo actuator repairable for extended service life.
MR Series – Hydrostatic Swing Servo Actuator
Designed for oscillatory motion, the MR series adopts hydrostatic bearings for sealing the oil chamber, achieving high speed, high precision, and frictionless operation. Specifically, the working frequency reaches 300 Hz with a swing angle of ± 50°, and can be customized according to user needs. Furthermore, the relative swinging surface has almost no friction, while the series is characterized by high frequency response, high speed, and long lifespan. In addition, hydrostatic bearings are always in a pure liquid lubrication state, delivering high transmission efficiency, high sensitivity, high control accuracy, good precision retention, and high motion accuracy. Moreover, the MR series possesses high seismic resistance and high coordination synchronization. As with the ML series, the special self-lubricating coating provides repairability for reliable long-term operation.
PL Series – Dynamic Electro-Hydraulic Servo Linear Actuator
As a core component for dynamic loading, the PL series generates force and displacement in electro-hydraulic servo systems, primarily used in dynamic, static, and fatigue testing applications. Specifically, the actuator comprises servo cylinders, displacement sensors, and servo valves to achieve various closed-loop controls. Manufactured according to the standard hydrostatic servo actuator process, the PL series features external dimensions and connection dimensions fully consistent with standard models. Furthermore, its dynamic characteristics and service life are comprehensively superior to traditional friction pair servo actuators. Additional advantages include high cylinder body strength with resistance to resonance, gap sealing technology combined with a special self-lubricating coating that minimizes friction, excellent sealing performance, and high cost-effectiveness for laboratories seeking reliable dynamic loading solutions.
PR Series – Dynamic Electro-Hydraulic Servo Swing Actuator
Similarly manufactured using hydrostatic bearing technology, the PR series swing servo actuator is dimensionally interchangeable with standard hydrostatic swing servo actuators. Furthermore, its dynamic characteristics and lifespan comprehensively surpass traditional friction pair swing servo actuators. Key features include high cylinder body strength with resistance to resonance, gap sealing technology with a special self-lubricating coating for low friction, excellent sealing performance, and high cost-effectiveness. Ultimately, the PR series offers laboratories a reliable, long-life solution for oscillatory loading in demanding test environments.
▪FOB
▪CIF
▪Package: Wooden case
Hydrostatic Derivatives and Ultra-Precision Applications
Beyond standard actuators, SINOTEST has fully mastered hydrostatic wear reduction technology across a range of derivative products, based on the hydrostatic decoupling platform.
Low-Friction Multi-Degree-of-Freedom Decoupling Platform
The hydrostatic decoupling platform provides precision motion control across multiple degrees of freedom, enabling frictionless, high-stiffness operation for demanding testing and positioning applications. Specifically:
One degree of freedom focuses on rotating bearing products, including long-life accompanying test bearings, high-stiffness support bearings, low-friction ball bearings, and low-friction guide sleeves.
Furthermore, two degrees of freedom extends into planar motion, covering flat sliding table products, horizontal vibration tables, compression shear platforms, wear-reducing sliding shoes, and rotary tables for major equipment and scientific instruments.
In addition, three degrees of freedom encompasses spherical hydrostatic turntables, spherical flipping products, attitude simulators, multi-degree-of-freedom decoupling systems, and hydrostatic ball products.
Consequently, this multi-degree-of-freedom hydrostatic platform serves as a versatile foundation for laboratories and manufacturers requiring ultra-precise, low-friction motion control across a wide range of spatial configurations.
Ultra precision machine tool hydrostatic module
In addition, through the accumulation of specialized hydrostatic machine tool component technology, SINOTEST upgrades traditional mechanical bearing machine tools and provides hydrostatic components for ultra-precision CNC machine tools.
Key features include high stiffness, high speed, high precision, and long lifespan. Applications cover hydrostatic spindles, grinding machine hydrostatic electric spindles, lathe hydrostatic electric spindles, CNC center hydrostatic electric spindles, heavy-duty hydrostatic spindles, friction torque measurement hydrostatic spindles, hydrostatic guide rails, machine tool hydrostatic guide rails, hydrostatic turntables, and hydrostatic screws.
ACTUATOR ATTACHMENT
Seamless Swivel
The seamless swivel features a spherical bearing with Longxi self-lubricating joint bearings, installed at both the front and rear ends of the servo actuator. Specifically, it ensures tracking of the loading direction and avoids lateral forces on the actuator, thereby extending service life. Key features include a pre-tightening adjustment mechanism for bearing clearance, rotating supports suitable for alternating loads, a rotation range of ± 90 degrees, and a tilt angle of ± 7 degrees. Capacity: 25–2000 kN.
Spherical Swivel
Similarly, the spherical swivel adopts a spherical structure with an annular lubricating oil groove, also installed at actuator ends for loading direction follow-up and lateral force avoidance. Furthermore, it offers low friction, high dynamic characteristics, high resistance to alternating loads, and long service life. Additional features include a pre-tightening adjustment mechanism for gap regulation under alternating loads, a rotation angle of ± 10 degrees, and a shaft capable of 360 degree rotation. Capacity: 25–630 kN.
The History of Hydraulic Transmission
Hydraulic transmission uses liquid as the working medium and converts energy through liquid pressure. Since the late 18th century, when Britain manufactured the world’s first hydraulic press, hydraulic transmission technology has undergone over two hundred years of development.
Early Foundations (1650–1795)
In 1650, Pascal proposed the principle of hydrostatic transmission, revealing that pressure applied to a static liquid in a closed container is uniformly transmitted to all points. Subsequently, in 1795, Joseph Bramah of England applied this principle to industrial practice and successfully manufactured the world’s first hydraulic press using water as the working medium, marking the birth of hydraulic transmission technology.
From Water to Oil (1905–1930s)
In 1905, the working medium was changed from water to oil, which further improved the effectiveness of hydraulic transmission. Although the technology was born early, widespread application was not achieved until the 1930s.
World War II and Post-War Expansion (1940s–1950s)
During World War II, the application of hydraulic transmission and control devices in weapons significantly improved performance and promoted rapid development. After the war, hydraulic technology quickly shifted from military to civilian use, and with the continuous improvement of industry standards and component standardization, it gradually gained widespread application in mechanical manufacturing, engineering machinery, agricultural machinery, and automobile manufacturing.
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After the 1960s, with the vigorous development of atomic energy, space technology, computer technology, and microelectronics, hydraulic technology achieved significant breakthroughs and became an important pillar for automated production across various fields of the national economy.
Advantages and Future
Today,hydraulic transmission is recognized for its good lubrication, flexible liquid delivery, excellent speed regulation, and high transmission stability. **Compared with** mechanical transmission, hydraulic transmission offers significant advantages: oil as the transmission medium provides good lubrication; working fluid can be flexibly transported through pipelines; rotational motion is easily converted to linear motion; and stepless speed regulation with a transmission ratio up to 1:1000 is achievable. Moreover, hydraulic transmission supports load control, speed control, and direction control, enabling centralized, remote, and automatic control. Finally, the standardization, serialization, and universality of hydraulic components make design, manufacturing, and application more convenient.
**As for** the linear actuator in electro-hydraulic servo fatigue testing machines, it has evolved through three stages: sealing ring, gap seal, and hydrostatic bearing seal.Currently, all three types remain in market use, each with corresponding performance indicators. However, hydrostatic linear servo actuators offer faster frequency response, better resistance to lateral forces, lower friction coefficients, and support for higher response frequencies—making them the actuator of choice for high-speed, high-operation, and long-lifespan applications.
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