FOX-VPS Servo Actuators are specifically designed to provide the highest levels of fidelity in the application of controlled power. This is particularly important when used in precision testing systems such as:

  • Material Testing
  • Fatigue (Endurance) Testing
  • Durability Testing
  • Systems (Dynamic) Testing
  • Tensile Testing
  • Compression Testing
  • Motion (Synergistic) Simulation

Material Testing:

Material testing often utilises servo actuators to apply static, quasi-static or dynamic loads to a specimen of the material to be analysed. These applications and materials are often very diverse in characteristics and the magnitude of forces required. The new FOX-VPS F210 & F280 actuators have been designed to test materials of greatly varying stiffness, for example; Concrete, metals, composites, elastomers and adhesive bonding.

Fatigue Testing:

Fatigue or Endurance testing usually involves long test periods and very high levels of control accuracy often with multiple channel synchronised loading requirements. The test equipment needs to be both reliable and offer consistent performance. System safety is of paramount importance and great care is taken to avoid any failures due to system malfunction. A failure in the loading of the article under test, possibly resulting in damage must be avoided. Due to the complexity and cost of the specimen an unacceptable loading spectrum could well be very expensive and time consuming. Our design team has experience of supplying actuators with control manifolds for this ‘active’ testing application that incorporate sophisticated hydraulic safety circuitry to some of the most demanding and complex fatigue test rigs in the aerospace industry.

Durability Testing:

Durability testing is usually associated with vehicles where road test recorded ‘real time’ loading is applied to the specimen. The complex loading patterns often required for components or complete vehicles tests can result in off axis loads being produced which result in lateral (or side) loading being experienced by the actuators. Also the number of loading cycles, velocities and accelerations are often high requiring the testing Servo Actuators to be very robust with high PV capacity bearings. FOX-VPS actuators are heavy duty units designed to operate in arduous conditions, however if necessary we engineer the actuators for the specific duty requirement. For instance if the off axis loads are too high Hydrostatic bearings are incorporated.

Systems Testing:

Systems or Dynamic testing also involves long periods of cyclic loading and requires actuators with low frictional characteristics to provide accurate ‘reactive’ forces to the customers ‘active’ system. A typical example is an aircraft actuator that needs to operate against a realistic load. This requires the ‘reacting’ actuator to simulate the reaction load as faithfully as possible. Aircraft Undercarriage Cycling System Tests usually incorporate a number of ‘reactive’ actuators that are attached to the landing gear legs or doors. Not only do the testing actuators have to accurately reproduce the loads seen in operation but they also have to be cycled in a ‘free wheeling’ mode imposing as small a reaction force as possible. To achieve this they need an associated control circuitry that allows un-impeded across piston oil flow .

Tensile Testing:

Elastic and Extension testing of materials is readily achieved across a wide loading range using closed loop servo control. Suitably sized actuators are capably of applying accurate dynamic loads to facilitate determination of the characteristics of the specimen under test. These types of testing systems often utilise a servo actuator to provide tensile testing of high volume parts for statistical analysis. Extension testing requires accurately controlled dynamics to determine material idiosyncracies.

Compression Testing:

Controlled compressive testing of structures and materials is also readily achieved with Servo Hydraulic equipment. Very stiff materials such as Concrete and steel girders need to be tested to ascertain their performance under static or cyclic compressive loading. Test actuators can be operated in groups to apply rhythmic cyclic sequence loading to simulate the passing of a wheel over a road surface and for qualifying rail substrate aggregates composition after tamping.

Motion Simulation:

Motion simulations utilise servo actuators to provide motion cues to a system that is intended to reproduce a dynamic activity and often involves human operatives. To realistically mimic a motion and to convince those aboard the simulator of the authenticity of the action the actuators need to have minimum frictional characteristics especially when the motion direction changes. This is an application where the actuators are usually run under positional rather than load control so it is important that the actuators readily accommodate a displacement device.


Based on many years of experience in this market sector FOX-VPS engineers are able to offer consultation on various aspects of servo actuator configuration and application. Our range of Servo Actuators are fully compatible with all leading control systems and can be easily adapted to work with bespoke control systems.


FOX-VPS ranges of Servo Actuators have been designed to provide test engineers with a highly comprehensive user friendly range that is cost effective and flexible. They are suitable for a wide range of testing applications, for example.

  • Automotive component and chassis testing
  • Aerospace structural, dynamic and systems testing
  • Formula 1 suspension and component tests
  • Civil Engineering laboratory structural testing
  • Defence equipment durability testing
  • Material Testing