Cedrat Technologies, innovation in mechatronics

Actuators in space are broadly used to operate satellites’ platform and payload devices. Despite their common utilisation, actuators still represent critical subsystems as their failure might often lead to severe, when not catastrophic, effects on the spacecraft operations. Environmental conditions to which actuators are exposed in space are generally not favourable: operating temperature ranges and deep vacuum are certainly the most critical ones.

In the context of the ATLID instrument [1] embedded in the EarthCARE mission (Earth Cloud, Aerosol and Radiation Explorer), a Beam Steering Assembly is deviating a pulsed high energy UV laser beam to compensate the pointing misalignment between the emission and reception paths of ATLID with a very high stability and high resolution. Within the EarthCARE mission, led by ESA, Astrium is responsible for the ATLID instrument. The BSA development, manufacture and tests were assigned by Astrium to Sodern, an EADS filial.

Ongoing developments of instruments reveal the need for fast and precise mechanisms [1]. These requirements are all the more significant when large payloads of hundreds grams, such as mirrors, optical plates, corner cubes or antennas are involved in the motion. Indeed, highly dynamic kinematics coupled with large inertia lead to parasitic reaction forces that interfere on the accurate measurement.

In this study, a characterization of hysteresis in a piezoceramic stack actuator similar to those employed in an actively controlled flap (ACF) system is performed to assess the effects of hysteresis on system performance. The effect of unmodeled actuation hysteresis may significantly reduce vibration and noise reduction capabilities. A hysteresis model based on the classical Preisach model has been developed from experimental data.

Within the frame of a project called DTP RPA (Développement Technique Probatoire Rotor à Pale Active), also known as Active Blade Concept, carried out in cooperation between ONERA, Eurocopter, DLR and Eurocopter Deutschland, a four-bladed Mach-scaled rotor was tested in December 2005 in ONERA S1 Modane wind-tunnel. The main objective of this test was to validate the concept of using active flaps located on the trailing edge of the blades of the main rotor of a helicopter to decrease the vibration level generated by this rotor.

ABC is the acronym for ‘’Active Blade Concept’’ and represents a 38% Mach scaled model rotor of the Advanced Technology Rotor (ATR) of Eurocopter Germany (ECD, [4]). In contrast to the ATR the model rotor is fully articulated. Specifically, it is equipped with a flap at the trailing edge of each blade, which is driven by a piezoelectric actuator. The ABC project is a cooperation between the French ONERA and the German DLR within the research concept ‘’The Active Rotor’’.

Optical instruments such as interferometers and optical delay lines are sensitive to external vibrations and require a strong isolation of vibrations. Some products for active, semi active or passive isolation exist but are rather large which makes them much more suitable for lab applications than to embedded applications as meet in Space, Aircraft or Military applications in general, or in the space ICE CNES experiment. These requirements have driven the development of a new type of Electrically-Tunable Low-Frequency Miniature Suspension.