Abstract
As a type of multiconfiguration mechanism that can operate in an under-actuated state, metamorphic mechanisms were proposed more than two decades ago and attracted significant interest. Studies on structural synthesis of metamorphic mechanisms tend to focus more on metamorphic techniques and the structural synthesis of source mechanisms for metamorphic mechanisms. By designing different constraint architectures of metamorphic joints, multistructures can be obtained from the same source metamorphic mechanism. To determine the constraint architectures of metamorphic joints and their different assembly combinations, a kinematic status matrix and a corresponding constraint status matrix are constructed based on the metamorphic cyclogram of a source mechanism. According to the equivalent resistance gradient model and the constraint status matrix, an equivalent resistance matrix for the metamorphic joints is proposed. A structural synthesis matrix of the metamorphic mechanism is then obtained from the equivalent resistance matrix by deducing the constraint form vectors of the metamorphic joints. Furthermore, a kinematic diagram synthesis of the source metamorphic mechanism of a planar single-loop metamorphic mechanism is proposed, which is based on only the 14 one- or zero-degrees-of-freedom linkage groups. The entire structural design method of a metamorphic mechanism is based on the structural synthesis matrix and is presented as a systematic process. Finally, the proposed structural design approach is illustrated by two examples to verify its feasibility and practicality. This study provides an effective method for designing a practical multi-mobility and multiconfiguration planar single-loop metamorphic mechanism with a single actuator.
Highlights
A fundamental tenet of mechanism design is to minimize the number of actuators required to perform a given operational task
Li et al [36, 37] studied the structural synthesis of compliant metamorphic mechanisms based on adjacency matrix operations, which can be used in the design of new compliant metamorphic mechanisms
Which constraint forms and structures of metamorphic joints should be selected? How many architectures of metamorphic mechanisms correspond to the different metamorphic joints? Based on the equivalent resistance gradient model of metamorphic mechanisms proposed in Ref. [28], this study investigates the relationship between kinematic status, resistant forces, and constraint forms and structures of metamorphic joints
Summary
A fundamental tenet of mechanism design is to minimize the number of actuators required to perform a given operational task. Wei and Dai [31] presented a novel approach for synthesizing metamorphic parallel mechanisms with the ability to reconfigure motion between 1R2T and 2R1T, and the Lie group was introduced to study type synthesis using the transformation configuration space for reconfigurable parallel mechanisms [32]. The combinations are assembled to obtain structures for a multi-DOF planar metamorphic mechanism with a single actuator to satisfy the functional and operational requirements for a practical working task.
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