Synthesis of Multiple Degrees-of-Freedom Compliant Parallel Mechanisms Using Improved Beam-Based Structural Optimization Method

This paper presents the development of a three degrees-of-freedom (DOF) compliant parallel mechanism (CPM) with spatial motions, i.e., two rotations about the X and Y axes and one translation along the Z axis (θX-θY-Z). Such CPM is synthesized by the improved beam-based structural optimization method. The obtained results suggest that the proposed CPM is able to produce totally decoupled motions illustrated by a diagonal stiffness/compliance matrix, a large workspace of ±22,5 degrees × ±22,5 degrees × ±9,6 mm, fast dynamic response with the first natural frequency of ~100 Hz and high stiffness ratios between actuating and non-actuating directions (with stiffness ratios of 6210 and 2706 for translations and rotations respectively). Finite element analysis (FEA) is employed to evaluate the actual performance of the synthesized CPM with Ti6Al4V material in order to verify the correctness of the synthesis method. The effectiveness of the improved beam-based structural method is demonstrated by the good agreement between the simulation and predicted data with the highest deviations are 8.8% and 6.7% for the stiffness and dynamic properties respectively. In addition, some comparisons are carried out to investigate the advantages as well as disadvantages of the proposed CPM and existing designs. The comparison results show that the 3-DOF CPM presented in this paper has many merits compared to its counterparts. It can be used in various applications, e.g., the micro/nano positioners and alignment systems in precision engineering field due to its good mechanical properties (high stiffness ratios and fast dynamic behavior), large work range and fully-decoupled motion characteristic.