Cedrat Technologies, innovation in mechatronics

Piezo-electric motors have been successfully developed for various applications like autofocus drives in camera lenses and handling equipment for semiconductor production. Their high speed and accurate positioning capability, combined with a favourable holding torque in unpowered condition, make piezomotors also very attractive for actuation purposes in spacecraft mechanisms. The paper introduces a new concept of a versatile ultrasonic piezomotor. The testing campaign carried out on the designed rotating piezomotor has validated the vacuum compatibility and the lifetime of the motor in air.

The focus of this research was to create a linear motor that could easily be packaged and still perform the same task of the current DC motor linear device. An incremental linear motor design was decided upon, for its flexibility in which the motor can be designed. To replace the current motor it was necessary to develop a high force, high speed incremental linear motor. To accomplish this task, piezoelectric actuators were utilized to drive the motor due their fast response times and high force capabilities.

Piezo-electric motors have been successfully developed for various applications like autofocus drives in camera lenses and handling equipment for semiconductor production. Their high speed and accurate positioning capability, combined with a favourable holding torque in unpowered condition, make piezo motors also very attractive for actuation purposes in spacecraft mechanisms. However, so far only a few studies have been reported considering their suitability for actual use in space.

The applications of piezoelectric actuators are spreading in various fields such as precise micro-positioning, shape control or vibration generation, control or damping.

Implementation of 3D capabilities on ultrasonic imaging systems tantalizingly proves the high interest for this diagnosing modality. However, to become a clinical tool, 3D ultrasound has to spend further technological efforts in acquisition performance and probe size to deliver on the fly, quality volumetric images as well as current functionalities.

Existing piezo motors such as travelling wave motors present several technical limitations, they are not useable for linear drive, they cannot be easily adapted to specific rotational needs and the development of customised solution is expensive. The proposed Ultrasonic Piezo Drive (UPD) aims at overcoming these limitations. It is a shell-based stator using multilayered piezoceramics in d33 mode. Excited at only 1-10V, it produces an ultrasonic elliptical vibration large enough to direct drive any type of second body by friction. Tangential driving properties of UPD20 are typically in the range of 100-200mm/s max speed and 15-30N max force.

We are delighted in announcing the successful test of our LPM20 linear piezoelectric motor, carried out in June this year at the CNES (French Agency Space), Toulouse in vacuum conditions.Developed for positioning applications, the piezoelectric motor has proved to be a very interesting solution thanks to its high massive force, its zero consumption at rest and its high precision. For space applications, it is a question of obtaining an identical behaviour in ambient and in vacuum conditions. However, the friction drive that is the key to the functioning of the piezoelectric motor, limits the lifespan and poses tribology problems.