Optimal Design and Tracking Control of a Superelastic Flexure Hinge Based 3-PRR Compliant Parallel Manipulator

Abstract

A major obstacle that restricts the application of notched flexure hinge based compliant mechanism is its limited motion range. This paper presents the optimal design and tracking control of a superelastic flexure hinge based 3-PRR compliant parallel manipulator (CPM) to achieve high precision planar motion within centimeter's translation range and up to 10 degrees' rotational range. Firstly, a novel asymmetric ellipse-parabola (AEP) notch shape is proposed, and the geometric parameters of the AEP superelastic flexure hinge are acquired via multi-objective optimization to obtain desirable transmission performance. Secondly, a nominal inverse kinematic model of the CPM is established, and the dimension parameters of the 3-PRR manipulator are synthesized to maximize the dexterity of the CPM over the regular workspace. Thereafter, a disturbance observer based inverse kinematic control scheme (DOB-IKM) is proposed to suppress the model mismatches and external disturbances of the 3-PRR CPM, where the unmodeled factors of the system are approximated through an online learning radical basis function neural network (RBFNN) and the external disturbances of the CPM is observed and compensated by a disturbance observer (DOB). Finally, a prototype of the 3-PRR CPM is manufactured, and experimental tests show the effectiveness of the proposed control scheme and the superiority of the 3-PRR CPM.