This paper presents a model-based approach for the first time to identify the crack location for the hinge-based planar RRR compliant mechanism, a parallel micro-motion stage driven by piezoelectric (PZT) actuators. However, cracks more likely occur on a flexure hinge because it usually undergoes a periodic deformation in service, which eventually compromises mechanism's performance, positioning accuracy for instance. In this work, the pseudo-rigid-body method is used to develop kinematic and dynamic models of the RRR mechanism both in healthy and damaged conditions, where the crack is considered in terms of the rotational compliance of a flexible hinge. The crack location is determined by measuring PZT elongations, which represents the driving toque deviation because of the crack presence. Numerical simulation is conducted to verify the proposed approach, and the results show good match of the identified crack location with the assumed location. Finally, experiments on the RRR mechanism with a prefabricated crack is performed to further validate the proposed models; the experimental results yield a good consistence.

In this paper, a planar 3-DOF XYγ parallel micromanipulator with monolithic structure is presented. The micromanipulator is driven by three piezoelectric (PZT) actuators. To achieve highly accurate control, a new approach investigating the relationship among input-force, payload, stiffness, and displacement (IPSD model) of the XYγ micromanipulator is proposed in analytical style, and the analytical expression of the relationship between driving voltages of PZT actuators and outputs of end-effector is deduced based on the IPSD model. Finally, in order to verify the IPSD model, the simulations by finite element method and experiment are performed. The micromanipulator can be used to do microtasks that need the manipulator perform only planar motion, such as microoperation and microassembly, and the proposed IPSD model is useful for both digital control and design of the XYγ micromanipulator.