Cedrat Technologies, innovation in mechatronics

Many applications require long-term position stability, which relates to the notion of absolute precision over time. Until now, the long-term stability of strain gages (SG) for position measurement was questionable. Using its extensive know-how of strain gages integration and new instrumentation equipment, Cedrat Technologies has managed to demonstrate nanometric position stability of a closed-loop piezo-mechanism with integrated strain gages sensors. This technology opens a wide range of new possibilities for industrial, aeronautical, and space applications.

Tuned mass dampers are simple and efficient devices for suppression of machine tool chatter, which is one of the principal effects limiting productivity in many machining processes. However, their effectiveness depends on a proper tuning of the damper dynamics to the dynamics of the machine. This involves the dynamic characterisation of the machining process, in order to identify the critical resonance frequency, and the possibility of matching the resonance frequency of the damper to frequency. The difficulty of meeting these two requirements has been limiting the use of tuned mass dampers in industrial applications.

The MRF actuators are new electromechanical components using Magneto Rheological Fluids (MRF). These smart fluids are characterized by their ability to change their rheological properties versus applied magnetic field. They can switch from a liquid to an almost solid body. This effect is reversible and operates within a few milliseconds. MRF are used to create controllable dampers, smart shock absorbers or brakes. After having developed several MRF actuators with an original characteristic (presenting a blocking force at rest), Cedrat Technologies was asked to develop a very challenging new MRF damper which goal can be summed up with a few words: “small size and high force”.

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.

Actuation is used in all vehicles (aircraft, spacecraft, ground vehicles, etc) to control the position and/or attitude of the vehicle, and also to deploy or retract equipment, particularly for embedded optic instruments (cameras, telescopes). As such, the actuation is a safety critical system, particularly when humans could be catastrophically affected by failures within the system. Applications for actuation are flight controls, landing gear, rotors, suspension, antennae steering, valves, scanning, positioning using hydraulic, electromechanical, magnetic and piezo actuators. In aircraft there is a common goal to reduce the number of hydraulic actuators in vehicles and eventually to replace them completely by electric actuators.

Stepping Piezo Actuators (SPA) are long stroke linear piezoelectric actuators capable to reach long stroke (typ. >10mm) with an important resolution (typ. <1nm). It has been proposed to use Amplified Piezo Actuator into inertial stepper motor to build the SPA. This piezo motor showed good behaviour, with relatively high speed (up to 70mm/s), force (from 0.2N to 20N) and low consumption (down to 700mW).

It is well known that the Amplified Piezo Actuators (APA) offer large strains in static conditions and at resonance. Because many applications as shakers, anti-vibration and motors would benefit also of large dynamic strain below resonance, the maximum strain of the APA has been theoretically and experimentally investigated in this wide frequency range. The tested actuator is the APA30uXS currently used in the SPA30uXS new inertial micro piezo motor.