Development and dynamic modeling of a new hybrid thermo-piezoelectric micro-actuator.

International audienceThis paper presents a new hybrid micro-actuator based on the combination of piezoelectric and thermal effects. The proposed actuator can perform both a high stroke coarse positioning through the thermal actuation, and a high resolution fine positioning through the piezoelectric actuation. The micro-actuator structure is a unimorph piezoelectric cantilever, which also constitutes a thermal bimorph that is very sensitive to temperature variation. While electrical voltage is used to control the piezoelectric actuation, we use a Peltier module to provide the temperature variation and to control the thermal functioning. In order to understand the behavior of the hybrid actuator, a model is developped. For better precision but at the same time for model simplicity, the thermal part is modeled with the thermal network whereas the Prandtl-Ishlinskii hysteresis approach is used to model the nonlinearity of the piezoelectric part. Finally, a series of experimental results validate the developed model

Development and Force/Position control of a new Hybrid Thermo-Piezoelectric MicroGripper dedicated to micromanipulation tasks.

International audienceA new microgripper dedicated to micromanipulation and microassembly tasks is presented in this paper. Based on a new actuator, called thermo-piezoelectric actuator, the microgripper presents both a high range and a high positioning resolution. The principle of the microgripper is based on the combination of the thermal actuation (for the coarse positioning) and the piezoelectric actuation (for the fine positioning). In order to improve the performances of the microgripper, its actuators are modeled and a control law for both the position and the manipulation force is synthesized afterwards. A new control scheme adapted for the actuators of the hybrid thermo-piezoelectric microgripper is therefore proposed. To prove the interest of the developed microgripper and of the proposed control scheme, the control of a pick-and-release task using this microgripper is carried out. The experimental results confirm their efficiency and demonstrate that the new microgripper and the control law are well suited for micromanipulation and microassembly applications

Dry etching of single crystal PMN-PT piezoelectric material.

International audienceDuring the last decade, the applications of PMN-PT spread significantly. Unlike PZT, the appropriate microtechnologies for PMN-PT Piezo-MEMS aren't fully documented in the literature. This paper deals with the PMN-PT etching by inductively coupled plasma (ICP) technique, also known as DRIE. The paper quantitatively presents the etching parameters of PMN-PT by the Ar/C4F8 gas combination and reports some related useful experience

Research concerning the Ramp and Sinusoidal Command Signals of the Piezoelectric Miniactuators.

International audienceIn this paper is presented a mini-system with compliant minigripper and piezoelectric actuation. The piezoelectric actuator is controlled with ramp and sinus signals. The response of the mini-system is predicted by the finite elements method. The displacement of the compliant minigripper and piezoactuator are analyzed. In the end is presented a comparison of the experimental results for same actuator but for two different types of the signals with theoretical results

Quasistatic displacement self-sensing method for cantilevered piezoelectric actuators.

International audiencePiezoelectric meso- and microactuator systems required for manipulation or assembly of microscale objects demand reliable force and/or displacement information. Available sensors are prone to dimension restrictions or precision limitation. Self-sensing method, based on the electric charge measurement, may represent a solution in terms of cost-effectiveness and integration, the actuator performing simultaneously as its own sensor. This paper presents a self-sensing method dedicated to free uni- and bimorph piezocantilevers but can also be adapted to other piezoactuator types. The integrated electric current, used to convert the charge, can be compensated against piezoelectric material nonlinearities to provide accurate displacement information. The advantages relative to existing self-sensing methods consist in the ability to keep this displacement information for long-term periods more than a thousand seconds and in the reduction in signal noise. After introductive issues related to the method the base principle allowing the estimation of tip displacement is presented. Then, the identification procedure of the estimator parameters is depicted and representative experimental results are shown. Finally, a series of aspects related to electronic circuits are discussed, useful for successful system implementation

Actuated MOEMS Micro-Mirror based on PMN-PT Piezoelectric Material.

International audienceThis paper investigates the use of a PMN-PT [001] piezoelectric actuator to be integrated in smart Micro-Opto-Electrical-Mechanicals Systems (MOEMS). Unlike most piezoelectric materials, PMN-PT [001] can generate large-stroke out-of-plane displacement. This is due to its very high longitudinal piezoelectric coefficient of tu to 4500 pm/V. After an introduction on MOEMS actuation and a short description of the Reconfigurable Free Space Micro-Optical Bench (RFS-MoB) in which the studied actuator may be included is presented, a bulk actuator is proposed. FEM simulations are then presented highlighting some tradeoffs : increased displacement with the reduction in size while decreasing the optical aberration. It was observed that for actuators with a smaller surface than 800 x 800 µm2 and 200 µm thick, displacement larger than 325 nm is largely achievable and that the size of the usable area of the actuator varies in size with the applied voltage

Battery powered cost effective TDS logger intended for water testing.

International audienceThe paper presents a cost-effective device designed for measuring and monitoring the TDS (total dissolved solids) level of drinkable, surface (lakes, rivers) and/or industrial waters. Providing a first reading of potential water pollutions, the device is dedicated to the sectors of environment and consumer protection. The device was implemented and a series of continuous measurements is depicted, discovering some abnormalities in the quality of Targoviste city water utility

Duo-bimorph actuator made of PMN-PT [011] : 3D modeling, development and characterization.

International audienceThis paper reports the development of a duo-bimorph cantilevered actuator made of PMN-PT material and intended for large-stroke micro-scale manipulation. The principle of operation is piezoelectric, but with a series of material-induced particularities: PMN-PT is reputed for its very high piezoelectric and electromechanical coupling characteristics, but exhibits a lower coercive field which prevents driving in a fully bipolar manner. Instead of the uniaxial [001] plate, by using the anisotropic [011] cut, a positive transverse d31 piezoelectric coefficient may be exploited. This allows the extension of the structure with the applied voltage, which is particularly beneficial for micro-gripping. After an introductory part in piezo-materials and duo-bimorph structures, a comprehensive static three-dimensional displacement modeling is provided by means of constitutive matrix equations. The actuator micro-manufacturing is presented, followed by the experimental characterization. Compared to the classical PZT structures, the actuation is increased by a factor of two, up to 600 μm in the transversal plane and up to 20 μm longitudinally. Some perspectives related to 3 DoF (Degrees of Freedom) micro-manipulation tasks are finally approached

The metrology and applications of PSD (position sensitive detector) sensors for microrobotics.

International audienceThe position sensitive (or sensing) detectors (PSD) are special special monolithic PIN photodiodes featuring a series of lateral electrodes in order to achieve a 1D or 2D displacement measurement of an optical spot. Compared to the discrete array sensors, the PSD have many advantages including high positioning resolution, fast response time and very simple analogue signal conditioning circuits. This paper investigates the metrology of a two-dimensional PSD working alternately in direct or indirect (reflective) mode. The possible applications consist in precise assembly of optical MEMS micromirrors or fast tracking of an object over a pneumatic smart-surface. The first results showed a good linearity and a fast response time, which successfully enable such applications for PSD sensors