| Meso/micro grasping of tiny soft objects such as biological tissues or biopsy, which ranges from hundreds to thousands micro-millimeters in dimension, plays a significant role in the fields of tele-surgery, minimally invasive surgery (MIS), and biomedical instrumentation. In this dissertation, a proposed novel piezoelectric forceps actuator (PFA) is fabricated to improve one of the existing surgery tools used in MIS. One of the advantages of the PFA over conventional MIS forceps lies in that it can be remotely controlled to achieve precision deflection and grasping force. Furthermore, it does not have any moving parts such as gears and hinges, and hence avoids problems in operation like friction, backlash, lubrication, leakage and sterilization. A new general piezoelectric laminated slightly curved beam model is derived to predict the natural frequencies of the PFA, and verified with experimental results. By setting the curvature of the proposed model to zero (i.e., the radius of curvature goes to infinity) and neglecting stretch-bend couple, a piezoelectric laminated straight beam model can be derived. With a distributed transfer function formulation for the proposed models, the effects of the layer number, the layer thickness and the bending stiffness on natural frequencies, deflection, bending moment and output force of the system can be investigated. Based on solid mechanics and Castiliagno's theorems, radius of curvature displacement and grasping force models of the PFA is derived and verified with experimental results. Finally, the control system formulations of the PFA based on the distributed transfer function method (DTFM) and Rayleigh-Ritz method are provided to show the usefulness of the proposed models for further used in control system design and analysis. |
