A 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. Note to Practitioners-The works presented in this paper are motivated by the need of high performances systems dedicated to pick-transport-and-place tasks and their control. These tasks are one of the main base of the microassembly and micromanipulation applications. While pick-and-place tasks were successfully performed with classical microgrippers, they were very rarely automated. This is mainly due to the fact that automation in the micro/nanoworld is a new issue and the litterature only concerns the local control of microactuators and microrobots for the moment. Furthermore, existing microgrippers are limited to small range of positioning, making them hardly adapted for pick-and-place for large distance. The core of this paper is to fulfil the requirement of high range, high resolution, and controlled microgrippers. For that, a microgripper based on a combination of the thermal and the piezoelectric actuations is developed. To improve the positioning accuracy and to control the manipulation force during a pick-and-place task, a new control scheme adapted for the actuators of the new microgripper is proposed. It is noticed that the proposed control scheme can also be applied to classical microgrippers as it is a generalization.

Piezoelectric 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.