Bouc-Wen modeling and inverse multiplicative structure to compensate hysteresis nonlinearity in piezoelectric actuators.

International audienceA new approach to compensate the strong hysteresis nonlinearity in piezoelectric materials is proposed. Based on the inverse multiplicative scheme, the approach avoids models inversion as employed in existing works. The compensator is therefore simple to implement and does not require additional computation as soon as the direct model is available. The proposed compensation technique is valuable for hysteresis that are modeled with the Bouc-Wen set of equations

Performances inclusion for stable interval systems.

International audienceThis paper presents the performances inclusion on time and frequency domains of SISO stable interval systems. We demonstrate that an interval transfer function included in another interval transfer function will have its performances also included in those of the second one.While the results may be intuitive, the paper provides an analytical demonstration by using interval arithmetic and related tools. These results are of great interest for robust performances analysis and for controller design in parametric uncertain systems

Combining self-sensing with an Unkown-Input-Observer to estimate the displacement, the force and the state in piezoelectric cantilevered actuators.

International audienceSelf-sensing techniques is defined as the use of an actuator as a sensor at the same time. The main advantage of such techniques is the embeddabil- ity and the packageability of the systems. This paper deals with the development of a self-sensing technique able to estimate the displacement, the force and the state in piezoelectric cantilevered actuators. The main novelties relative to previous works are: 1) three signals (displacement, force and states) are provided at the same time instead of only two (displacement and force), 2) and these three signals are provided in a complete way, i.e. low and high frequency information can be provided (instead of exclusively low or high frequency). It is therefore possible to further use the measurement for a displacement control or for a force control by using the output feedback methods or by using modern control methods (state-feedback). In order to allow such measurement possibilities, the proposed approach consists in combining an unknown- input-observer (UIO) with the classical electrical cir- cuit of a self-sensing. The experimental results confirm the effectiveness of the proposed approach

Modeling and compensation of multivariable creep in multi-DOF Piezoelectric Actuators.

International audienceThe scope of this paper is the model- ing, identi cation and compensation of multivariable creep in piezoelectric actuators. Based on the inverse multiplicative scheme, we propose an approach to model and reduce the creep when the actuators have multiple degrees of freedom. The approach is simple to compute and easy to implement. The experimental results demonstrate the e ciency of the proposed approach on piezoelectric actuators

Force estimation in a piezoelectric cantilever using the Inverse-Dynamics-Based UIO technique.

International audienceThis paper presents the estimation of the force applied by a piezocantilever dedicated to micromanipulation/ microassembly. Relative to previous works, the presented method avoids the reliance on the force dynamics on the characteristics of the microobjects. Furthermore, the estimation is a closed-loop kind technique so that convergency can be ensured efficiently. To perform these, we consider the force at the tip of a piezocantilever as an unknown input and we use an Unknown Input Observation technique. We especially use the Inverse-Dynamics-Based UIO technique because it is well suited for a piezocantilever model. The experiments show that the performances of the observer are convenient for micromanipulation/ microassembly tasks

Presentation and improvement of an AFM-based system for the measurement of adhesion forces.

International audienceThe aim of this paper is the presentation and improvement of an AFM-based system dedicated to measure adhesion forces. Because an AFM-lever presents a high linearity and a high resolution, it can be used to characterize forces that appears between two micro-objects when their relative distance is small. In this paper, an AFM is used to evaluate the adhesion forces versus the distance. Especially, the pull-off and the Van Der Waals forces can be quantified. Unfortunately, the presence of the hysteresis on the piezotube distorts the measurement and makes the whole system imprecise. Hence, a Prandtl-Ishlinskii hysteresis compensator is introduced. To show the efficiency of the improved measurement system, experiments on different materials where performed

Principle, characterization and control of a new hybrid thermo-piezoelectric microactuator.

International audienceThis paper presents a new actuator based on a unimorph piezocantilever and on the thermal bimorph principle, called hybrid thermopiezoelectric actuator. The main advantage of the proposed actuator is the high range of positioning from the thermal actuation and the high resolution and bandwidth from the piezoelectric one. A characterization and linear modeling are proposed. Finally, we propose an adapted control law to manage the two possible actuation types

Force control in piezoelectric microactuators using self scheduled H∞ technique.

International audienceIn micromanipulation and microassembly tasks, the manipulated micro-objects do not always have the same characteristics, such as compliance. Thus, both the static and dynamic models representing the force behavior respect to input sollicitations depend on the characteristics of of the manipulated micro-object. As a result, it is hard to synthesize a single controller able to ensure desired performances for all set of micro-objects, especially when their compliance range is very large. In this paper, we propose to model and control the manipulation force applied by piezoelectric microactuators by using a parameter dependent approach such that desired performances are ensured for all kind of manipulated objects. The resulting controller is said self-scheduled and easy to implement from numerical point of view. First, we derive a model that is dependent on the characteristics of the manipulated micro-object. The strong hysteresis nonlinearity of the piezoelectric microactuator was compensated and the derived model is therefore linear. Afterwards, we design a self-scheduled controller using H technique. In order to ensure the desired performances (micrometric accuracy, tens of millisecon∞d of settling time) for any manipulated micro-objects, a parameter dependent controller is designed respect to the continuum of models. Finally, the efficiency of the proposed design procedure will be illustrated from experimental results

Piezoelectric systems for precise and high dynamic positioning: design, modeling, estimation and control

This HDR synthesizes the works I have carried out at the department of AS2M of the FEMTO-STInstitute as well as the different administrative, editorial and teaching activities. The research works(supervised, in collaboration, ...) deal with the: design, development, modeling, control and signalsmeasurement and estimation in piezoelectric based systems devoted to precise and highly dynamicpositioning applications. The systems behaviors include linear and nonlinear phenomena (hysteresisand creep) and badly damped vibrations which greatly compromise the performances of thepositioning tasks, and which pose great challenge in their control. The proposed control techniquesenclose feedforward and feedback schemes. In feedback schemes, mainly robust techniques arestudied: H-infinity techniques and interval control techniques. In the use of intervals, new theoreticalresults are also proposed and are applied to different applications: design, control, structuralanalysis. Innovative measurement techniques have also been proposed to estimate the signals inpiezoelectric systems by accounting for the limited space, the high dynamics and the high precisionrequirements. The last part of the HDR poses questions and wonders if these different developmentsand endeavors would not be profitable for the development of other applications than precise andhighly dynamic positioning

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