Approaches to the synthesis, modelling and optimisation of spatial translational compliant parallel mechanisms

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Li, Haiyang
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University College Cork
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The main facets of designing compliant mechanisms are synthesis, modelling and optimization. This thesis focuses on these three aspects of designing compliant mechanisms with a particular emphasis on spatial translational compliant parallel mechanisms (XYZ CPMs). In this thesis, a constraint and position identification (CPI) synthesis approach, a constraint‐force‐based (CFB) modelling approach and a position‐spacereconfiguration (PSR) approach are proposed. Subsequently, two PSR‐based optimization approaches are presented. A large number of XYZ CPMs can be synthesized using the proposed CPI approach. Each of the synthesized XYZ CPMs can provide decoupled translations along the X‐, Y‐ and Z‐axes, and can be actuated by three groundmounted linear actuators. Furthermore, the motion characteristics of a synthesized XYZ CPM can be analysed, based on an analytical model that can be derived using the proposed CFB approach. Such motion characteristics can include cross‐axis coupling, lost motion, parasitic motion and actuation stiffness. If the motion characteristics of an XYZ CPM need to be improved, the XYZ CPM can be reconfigured using the PSR approach. For example, two PSR‐based optimization approaches are detailed, which are used to reduce parasitic motions of XYZ CPMs and to reconfigure a non‐symmetric XYZ CPM into a symmetric XYZ CPM, respectively. Such PSR‐based optimization approaches can be employed to optimize both the geometrical dimension and the geometrical shape of an XYZ CPM. Therefore, an XYZ CPM can be synthesized using the CPI approach, modelled using the CFB approach, and then optimized using the PSR‐based approaches. In order to demonstrate the use of these proposed approaches, several examples of XYZ CPMs are synthesized, modelled and optimized. These design examples are also verified by FEA simulations and/or experimental tests. Several prototypes of the obtained XYZ CPMs are fabricated, and a control system for one of the prototypes is also presented. It is important to note that the proposed CFB approach, PSR approach and PSR‐based optimization approaches can also be employed to model, reconfigure and optimize other types of compliant mechanisms in addition to XYZ CPMs.
Compliant mechanism , Structure synthesis , Analytical modelling , Shape and dimension optimisation , Spatial translation , Spatial deformation
Li, H. 2016. Approaches to the synthesis, modelling and optimisation of spatial translational compliant parallel mechanisms. PhD Thesis, University College Cork.
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