Design optimization of active scanning probe using parallel link mechanism

A 3-dof active scanning probe using a translational parallel mechanism (TPM) is proposed. The TPM proposed in this study employs a small touching force control and can be used as a probing device for coordinate measurement, working within an area of a few cubic millimeters. In this paper, the characteristics of the mechanism, optimization of design, prototyping, and accuracy of the TPM are introduced. In the proposed optimization TPM design, the manipulability of the mechanism is equal in all directions. This implies that the positional sensitivities of the TPM share an isotropic relationship. The positional resolution of the mechanism becomes less than 1.0 μm in a cubic working range with side length of 1.6 mm. An experimental mechanism using the proposed design is introduced. In order to evaluate the accuracy of the TPM, we have developed an experimental system for the measurement of the position of the TPM using image processing. By applying mechanical parameters calibration, the accuracy of the absolute position of the TPM has been improved to 3.4 μm.