Multiple-degree-of-freedom compliant mechanism possessing nearly uncoupled dynamics: experimental findings

Micromanipulation has enabled numerous technological breakthroughs in recent years, from advances in biotechnology to micro-component assembly. Micromanipulators commonly use piezoelectric actuators (PZT) and a compliant mechanism to provide fine motions with position resolution in the nanometre or even sub-nanometre range. Parallel compliant mechanisms are used to provide motion with multiple degrees-of-freedom (DOF) as parallel mechanisms provide greater rigidity and positioning accuracy than serial mechanisms. However, parallel mechanisms with multiple DOF often have dynamic behavior that is coupled, non-linear and highly complex. This leads to difficulties in modeling and controller design, often requiring sophisticated control techniques such as model-based or neural networks to provide fast, accurate control. This paper presents the findings of an experimental study into the dynamics of a particular 3 DOF compliant mechanism, specifically considering actuator-space coupling at a range of frequencies and poses. It was expected that the dynamics would be coupled as a dynamic model developed for this mechanism suggested this to be the case. However the experimental results reveal the surprising and useful finding that this mechanism possesses almost completely uncoupled dynamics for the operating bandwidth of the manipulator. This result simplifies the problem of controller design and suggests that the micromanipulator could be effectively controlled using simple independent joint control without requiring development of a decoupling controller.