Cedrat Technologies, innovation in mechatronics

The performances offered by Magnetics Resonance Imaging (MRI) are widely recognized and used by practitioners. Mainly used for diagnostic issues, MRI becomes more and more an interventional tool in image-assisted classic or robotic surgery. However, constraints imposed by the MRI strong magnetic field and strong magnetic gradients in terms of material and architecture are often obstacles to MRI guided robotics. Designers have to deal with the few choices offered to them to build a robot which will be able to respond to severe specifications, in terms of space limitations, magnetic field sensitivity and image impact. Piezoelectric micro-motors are good candidates to fulfil these requirements in several fields of applications.

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.

Stepping Piezoelectric Actuators (SPA) are new long-stroke linear piezoelectric motors for micro/nano positioning applications benefiting of the advantages and the heritage of the APA. SPA are formed of only 4 parts: the well-established Amplified Piezoelectric Actuators (APA), a front mass, a clamp and a rod.

Abstract: Stepping Piezoelectric Actuators (SPA) are new small long-stroke linear piezoelectric motors for micro/nano positioning applications benefiting of the advantages and the heritage of the APA. SPA is formed of only 4 parts: the well-established Amplified Piezoelectric Actuators (APA), a front mass, a clamp and a rod. SPA operates by accumulation of small steps, using inertial mode, impact forces and stick-slip effects, allowing performing long strokes (> 10mm). Main advantages induced by the choice of the APA above a usual inertial drive mechanism (IDM) are high reliability, low peak current (<0.1A), relatively high speed (> 20mm/s), useful forces (from 1N for XS to 30N for SM type) and nano positioning mode.

Piezomotors are well known in various applications where high precision actuation is required like AFM or handling equipment for semiconductor production. Their specific low speed in direct drive and high torque characteristics combined with high holding torque in off power conditions make them very attractive for any positioning application and especially space mechanisms where low electrical consumption is always sought. A new concept of rotating stepping piezomotor has been developed in the frame of the LISA space project where the mechanism of the telescope orientation was addressed.