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This paper presents a micro X-Y stage with new comb drives arrangements for large displacements. In-plane motion applications, the side instability of movable comb drives will lead to limited travel distance of itself, consequently limits the maximum displacement of the microstage. To overcome the instability and extend the displacement, several means are implemented. Firstly, the gaps between the fingers are increased to decrease the unbalanced force generated by fixed fingers at both sides. Secondly, a proper design of the spring structure with high axial and lateral stiffness ratio is presented by utilizing both the theoretical calculations and finite element method (FEM). The conventional comb-drive actuators consist of one set of movable comb drives and one set of fixed comb drives next to the moving parts. When the voltage is applied to fixed parts, it will attract the movable comb drives by the electrostatic force and accordingly drive the whole microstage. When they are used in the micro X-Y stage structures, the fixed comb drives are always arranged on the same side as the direction of movement, as nearly all the comb-drive actuators give the microstage the pulling force. The new arrangements of the comb drives are composed of one set of movable comb drives and two sets of fixed ones which are located at each side of the movable combs drives. By using this arrangement, in addition to the original pulling forces, the comb-drive actuators can provide additional pushing forces to the microstage, therefore additional displacements can be achieved which are as big as the displacements generated by the original pulling forces. It makes the driving force more symmetric for the platform. In addition, the arrangement saves the area yet generates the same driving force when compared with the conventional structure, making the device more compact. The feasibility of this arrangement is verified numerically using FEM, the simulation results are consistent with the values derived from the mathematical model. The results show an obviously enhanced displacement and a compact layout, approximate 150µm large displacements in both X and Y directions are obtained under driving voltage 49.5 V. |