Cedrat Technologies, innovation in mechatronics

In Inertia Drive Motors, generated motion is based on stick-slip principle. Current analytical models are predictive enough to calculate qualitatively their optimal performances, such as maximal step size and speed, with relatively few input parameters. Butn they do not take into account the contact life and temporal evolution of parameters as friction factor all along lifetime of IDM. So analytical models reach their limitswhen precise predictions are necessary.

Many applications and more specifically space projects would have use of a stable sub-micrometre positioning actuator. In order to meet this need, Cedrat Technologies has designed the new FSPA brand. This linear stepping actuator offers sub-micrometric positioning resolution along 5mm stroke combined with high actuation force (>100N) and the ability to hold its position without power. Starting from the FSPA, a special version is being developed for the IASI-NG space instrument. This light (500g), fully redundant actuator is designed to achieve 150μm stroke with locking at rest, 60 N force with a 25-50 nm step resolution and resistance to launching. The paper presents the base FSPA actuator and the new high performance space variant.

Modular Stepping Piezo Actuators (MSPA) use the stick-slip principle to combine high resolution positioning (<μm) with long stroke (>cm). These motors provide unlimited motion in both rotation and translation. Fine mode allows precise positioning (<10nm). Since it is a module, it easily fits any existing devices requiring up to 25N of driving force with a speed up to 50mm/s. This motor module benefits the use of space qualified Amplified Piezo Actuators (APA®). It is then deemed a good candidate for severe environments such as vacuum, cryo, vibrations, nonmagnetic etc… This paper presents three technical challenges encountered for the development of MSPA product. The first one is the issue of noise resulting from stick-slip actuation below ultrasonic frequencies. The second is the miniaturization at low voltage: One is macro size (sugar cube) working at 45V is characterized, the other is micro size (grain of rice) powered at low voltage below 60V. The third challenge is the successful and reliable integration of the module within new customer applications and new Cedrat Technologies’ products.

Stepping Piezoelectric Actuators (SPA’s) – based on the Piezoelectric Friction-Inertial Actuation (PFIA) principle – are made from Cedrat Technologies Amplified Piezoelectric Actuators (APA). They use the stickslip principle to couple high resolution positioning (<µm), long stroke (>cm) and low volume (<15cm3). These motors are used in optronic, medical and military applications. However, current rubbing contact between the shaft and clamp limits the potential evolution of SPA’s. In this paper, a new concept: called Module SPA (MSPA) – offering long stroke capabilities (>10cm), allowing easier multi-DoF mechanism developments and miniaturization possibilities – is presented. Results obtained on three innovative engineering models – linear long stroke, rotary and three-DoF actuators – are presented, giving the reader actual benefits of this concept and allow addressing new applications such as consumer goods and medical devices.

Typical holding force of piezo motors is defined by friction force, required to make motor move. However, increase of friction force is not inconsequent for motor performances in terms of speed, max motion force and lifetime (tribology). In this paper, a new motor, offering high resolution positioning and holding position when unpowered, is presented. Based on a Stepping Piezo Actuator [1] at its core, this new design decouples the outer forces from the most sensitive parts of the motor. This allows the motor to propose a high force/mass ratio and sustain even higher forces without supply. Results obtained on prototype are presented, giving the reader the benefits of proposed technology.

In Inertia Drive Motors, generated motion is based on stick-slip principle. Current analytical models are predictive enough to calculate qualitatively their optimal performances, such as maximal step size and speed, with relatively few input parameters. But, they do not take into account the contact life and temporal evolution of parameters as friction factor all along lifetime of IDM. So, analytical models reach their limits when precise predictions are necessary. This investigation aims at understand wear mechanisms to model temporal evolution of friction. Such an understanding requires the reconstitution of the contact life through the evaluation of 1st and 3rd body flows. To do so, a new IDM-representative tribometer is designed. First bodies - coated TA6V and polymer - are not see-through. They are replaced alternatively by an intermediate transparent first body to observe the contact dynamically and in-situ. Friction factor, step size and mean speed are also measured. Preliminary results shows that wear profiles from real IDM and tribometer are similar. Direct observations bring out particles of TA6V coating are firstly snatched, then moves in contact and finally trigs others particle detachments.

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.