Actuators are key elements of air- and spacecrafts. In the recent years the concept of the more-electric aircraft pushed the development of electrical actuation systems to substitute hitherto used hydraulic actuators in a broad range of applications such as flight control, landing gear and brake actuation.
The presented project ADLAND (AST3-CT-2004-502793) dealt with evaluating the options for adaptive shock absorbers to be applied in aircraft landing gears. Analytical design procedures were developed to simulate different potential design options and a best practice solution determined. The different hardware components regarding adaptive shock absorbers were then developed and tested with regard to adaptive landing gear model. The objectives of the project were: to develop a concept of adaptive shock-absorbers, to develop new numerical tools for design of adaptive absorbers and for simulation of the adaptive structural response to an impact scenario, to develop technology for actively controlled shock-absorbers applicable in landing gears, to design, produce and perform repetitive impact tests of the adaptive landing gear model with high impact energy dissipation effect, to design, produce and test in flight the chosen full-scale model of the adaptive landing gear.
Proof mass dampers are currently used in aircraft structures, but are not active, which introduce performance limitations. Proof Mass Actuators based on spring-mass structures are an interesting technique for active vibration control, but it is difficult to design them for operation below 100 Hz, especially if high dynamic forces are required. The proof of concept of a Tunable Proof Mass Actuator (TPMA) based on a pendulum structure has been assessed into the Mesema FP6 EC project targeting an Helicopter application.
MRF actuators are new electromechanical components using Magneto Rheological Fluids (MRF). When submitted to a high enough magnetic field, MRF switch from a liquid to a near solid body. These new developed MRF actuators were developed in order to reach three aims: to offer a blocking force at rest which can be strongly reduced by applying a current, to provide an electrically-controllable resistive force over a stroke of 30 mm, to perform the control of the force in a very short time, typically in a few milliseconds.
To meet the demand of controllable millimeter-stroke actuators, there are two possible starting points. One is to consider improvement of moving coil actuators, the other is to consider improvement of moving iron actuators. Following this approach and using its experience on the different types of magnetic actuators, Cedrat Technologies has developed new specific Moving Iron Controllable Actuators, called MICA. This actuator circumvents previous controllability limitations of standard Moving Iron actuators while keeping their high forces capabilities. Compared with moving coils of the same force, the MICA are twice less in mass while requiring 3 times less electric power. Another significant advantage of the MICA is a much better heat dissipation and reliability as the MICA coil is fixed into the iron stator.
Short Abstract The MRF actuators are new electromechanical components using Magneto Rheological Fluids (MRF). When submitted to a high enough magnetic field, MRFs switch from a liquid to an almost solid body. The purpose of the new developed MRF actuators is to reach three aims: to offer a blocking force at rest, which can be strongly reduced by applying a current, to provide an electrically- controllable resistive force over a stroke of 30 mm, to perform the control of the force in a very short time, typically in a few milliseconds.
There is a strong demand of controllable actuators for both traditional and new applications. A controllable actuator should be able to accelerate, break, inverse the motion of the load, all along the stroke. It means the force produced by the actuator should be proportional (at least roughly) to the applied electric excitation, and in particular, the sign of the actuation force could be changed all along the stroke.
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