Nonlinear Response Compensation of Flexure-Hinge Based Guiding Mechanism Using Bi-Linear Control Input

The flexure-hinge (FH) based guiding mechanism, such as fast tool servo (FTS) or micro-lens-array punching machine, is widely used in micro/nano precision engineering, due to their good linearity of stiffness. The major design advantage of FHs for this application was the absence of backlash and friction in the direction of the motion. This provides very smooth, high-precision operating characteristics without inducing evident wear which is commonly associated with high speeds or continuous operation. The dynamic model of FH can be simplified as a spring-mass-damping system, both the stiffness and frequency of a mechanism play significant roles in its dynamic performance. However, the relationship between dynamic response and the input function is nonlinear. In order to achieve precision displacement output under different excitation frequency, nonlinear input compensation should be considered. In this paper, an innovative method is provided to handle this kind of problem, where the stiffness of the guiding mechanism can be adjusted, such that the output amplitude scale can be remained the same at any excitation frequency, therefore, it become a linear system, the input is very easy to control. The tension stiffening is used to change the stiffness and thus the frequency, and the relationship between the change rate of frequency and tension force is also revealed. Finally, the control strategy is given, and an example is given to show the efficient of the presented method.