Cedrat Technologies, innovation in mechatronics

Good limitations of the current in a circuit using an electromechanical breaker suppose a very fast opening of the contacts. Due to the fact that the electrodynamic repulsive forces do not generate enough acceleration, an actuator has to be used to improve the breaker performances. Since a traditional reluctant magnetic device is too slow for the application concerned, a propeller based on the Thomson effect has been chosen. FLUX2D simulations make possible a good understanding of the propeller’s operation and thus the improvement of its design.

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.

The DTT35XS is a new piezo mechanism coming from CEDRAT TECHNOLOGIES lab in February 2002. It comes from a development for space needs defi ned with the CNES (the French space agency), and for which a first application was found in the frame of “PHARAO”. This mechanism is based on two pairs of APA35XS, Amplifi ed Piezo Actuators displaying 35 µm of stroke each, arranged in cross configuration. The mechanism allows both a defl ection of +/- 2 mrad around the X and Y axis and a vertical displacement of 35 µm in the Z direction.

The XY200M is an XY piezo stage coming from CEDRAT TECHNOLOGIES lab and which was newly designed according to space needs defined with CNES (the French space agency). This XY stage benefi ts from the heritage of a former XY stage developed for ESA (European Space Agency) in the frame of Rosetta / Midas space mission which will launch in the beginning of 2003. It is based on two pairs of APA200M, Amplifi ed Piezo Actuators displaying 200 µm of stroke each, arranged in cross configuration around a central ring.

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.

As future astronomic missions will require more and more stringent resolution requirements, the high demand for an environment clean of vibrations and disturbance appears. This also leads to the need for high precision steering devices for fine pointing of sensitive optics with the highest possible accuracy. Several methods exist to reduce vibration levels: the first consists in isolating the sensitive system from the perturbation and the second in damping the structure vibration modes. Therefore, two Stewart platforms have been designed, manufactured and tested. The first is a soft hexapod that provides 6 degree-of-freedom (DOF) active isolation and the second is a stiff hexapod that provides active damping to whatever flexible payload attached/mounted to it. In addition, both hexapods have steering capabilities.

This paper reviews some concepts used for active vibration control and vibration isolation. It is divided into two parts. Part 1 reviews some control strategies based on collocated control systems, which offer promising results for space and civil engineering applications. Part 2 (starting at section 4) is focused on automobile applications.