Bio-inspired kinematics of reconfigurable linkage structures

Abstract

Bio-inspired design provides promising prototype developments in architecture and engineering with innovative and sustainable characteristics. In design and nature, motion is one of the major biological strategies that can be considered in different design scales. Natural organisms may act as role models in providing kinematic principles to structures subjected to time-varying external conditions. Along these lines, the present study refers to a linkage structure typology development and kinematics mechanism application based on the particular function and kinematics of the human fingers. The linkage structure consists of cross hybrid rigid bars interconnected in series that are additionally integrated with a secondary system of struts and two continuous diagonal cables. The kinematics mechanism corresponds to the effective crank–slider approach that stepwise reduces a planar linkage system to an externally actuated 1-DOF system, in order to adjust the joint angles from the initial to the target values for its complete reconfiguration. The two ends of the linkage structure are supported on the ground, through a pivot joint on one end and a linear sliding block on the other end. Each intermediate joint is equipped with brakes. Two linear motion actuators placed on the ground, are associated to the cables. A reconfiguration of the linkage structure can be accomplished through different control sequences and an optimal one can be selected based on specific criteria, such as lowest maximum required brake torques and actuators motion. A simulation study refers to the preliminary kinematics and the comparative Finite-Element Analysis of a group of planar linkage systems of eight cross hybrid rigid aluminum bars of constant and variable length. The systems have an overall length of 12.0 m in their initial, almost flat configuration, and a respective span of 6.0 m in their specific arch-like target configuration. The study discusses main characteristics of the kinematics approach and demonstrates its potential to build upon aspects of flexibility and controllability through a high degree of modularity and simple actuation requirements for actual scale structures.