Characterization, modeling and robust control of a nonlinear 2-dof piezocantilever for micromanipulation/microassembly

Piezoelectric cantilevers have proved their performances for actuating microgrippers dedicated to micromanipulation and microassembly tasks. While the control of one degree-of-freedom (dof) piezocantilevers have been well whelmed, the control of multi-dof one has not been addressed. Indeed, to assemble complex structures, the use of multidof microgrippers is recognized. Unfortunately, strong coupling between the axis and nonlinearities indeniably limit their performances. This paper deals with the modeling and control of a piezocantilever that has 2 degrees of freedom: in-plane and out of plane deflections. While such a characteristic allows the microgrippers perform both orientation and translation during micromanipulation/microassembly tasks, the strong coupling between the two dof makes difficult their control. Moreover, nonlinearities (hysteresis and creep) raise when the piezocantilever is used in high deformation. To overcome these, we consider the coupling as a disturbance, model the nonlinearities with the quadrilateral approximation and we apply a robust H_¿ controller that accounts them. The experiments show the efficiency of the synthesized controller and the obtained performances are convenient for micromanipulation/ microassembly tasks.