A "Double V-shaped" Eightbar Linkage And Its Associated Fulleroid-like DPMS And Application

“Made in China 2025 strategy”has been put forward by China government in 2014.The main aim of this significant national strategic plan is to comprehensively improve and further the quality and level of China's manufacturing industry based on the general trend of international industrial reform in the metabolically new global environment.Being the important parts of the“Made in China 2025 strategy”,“High-end Equipment Manufacturing Innovation Project”has been proposed as the optimization and upgrading of product-quality are carried out closely around the crucial links in key areas of manufacturing.For the high-end equipment innovation project like smart civil aircrafts design and control?aerospace engineering designing and manufacturing?ocean engineering equipment developing and the deployment of ground mobile robots,they all need to face the challenge of“space problem”which means they have to consider about the variable space in case of developing the multifunctional devices and relevant equipment.As being one of the very important branches of the deployable structure/mechanism,the deployable polyhedral mechanisms?DPMs?have the shape of the related polyhedrons which can be expanded and folded without changing the assembly.Based on this particular characterization,DPMs has become the forefront of the designing and manufacturing of high-end equipment.This thesis,for the first time,presents an overconstrained spatial eightbar linkage as a deployable unit and by using this unit,a synthesizing method based on regular polyhedrons and semi-regular polyhedrons has been proposed.One of the investigated deployable Fulleroid-like hexahedral mechanism can be used as the body of a quadcopter so that a novel deployable quadcopter with its dynamic model and PID control have been proposed and studied in this thesis.The main works of this thesis are shown below,?1?Presents a single-plane symmetry spatial eightbar linkage which consists of four identical“V-shaped”links and four identical straight links,all the links are connected to each other by using revolute joints.This eightbar linkage is a parallel mechanism which is able to be decomposed into two kinematic linkage chains,both the two kinematic chains own one base?V-shaped link?and one moveable platform?another V-shape link?.By following the Convention of Denavit-Hartenberg method,the homogeneous coordinates of the joints in each kinematic chains are obtained.In addition,when the joints angles are satisfying a certain requirement,the moveable platform is able to carry out a straight-line motion.?2?Change the previous eightbar linkage into a novel eightbar linkage by replacing two V-shape links into two straight links.This new eightbar linkage is similar to the Sarrus linkage,and by comparison with the Sarrus linkage,each chain of the linkage has one extra revolute joint together with an extra link,this spatial eightbar linkage is also an overconstrained one whose mobility is calculated and verified by using screw theory.There are two cases for the eightbar to implement a straight-line motion.The first one is pretty simple just give the ground inputs and satisfy?₁₁=?₂₁,?₁₂=?₂₂,?₁₃=?₂₃,similar to the Sarrus linkage.The second case is to satisfy the revolute angles?₁₁=?₂₄,?₁₂=?₂₃,?₁₃=?₁₂ and given the inputs,the double V-shaped links are able to perform a straight-line motion while the two straight links not connected to V-shaped links can carry out a double helix motion.Inspired by the special motions,this double V-shaped linkage is chosen as the deployable unit for synthesizing and constructing the DPMs.?3?Based on the motion characterization of this double V-shaped linkage,the author proposed a synthesizing method by implanting the eightbar linkage into edges and faces by using the Platonic polyhedrons as the bases.The tetrahedron and hexahedron are chosen as two typical examples.By further detailed design,the deployable tetrahedral mechanism and hexahedral mechanism are synthesized.The synthesized polyhedral mechanisms are similar to the Fulleroid mechanism,so the author named them as deployable Fulleroid-like Platonic mechanisms.The mobility of the two deployable Fulleroid-like Platonic mechanisms is one and both can be calculated by using screw theory after the constraint matrices are obtained by drawing the constraint graphs.Motion simulations proved that the deployable Fulleroid-like Platonic mechanisms are moving as expected during the expanding and folding process:the facet components perform screw motions about the corresponding virtual axes and the vertex components execute radially reciprocating motions along their associated virtual axes towards or outwards the virtual centers.?4?Unlike the Platonic polyhedrons,the vertex of Archimedean solids is constructed by two or three different faces.Based on the cuboctahedron and truncated tetrahedron,by taking the same synthesizing method and screw theory introduced previously,two typical deployable Fulleroid-like Archimedean mechanisms are synthesized and analyzed.Without loss of generality,this synthesizing method can be naturally extended and generalized based on other bases from the group of Archimedean polyhedrons.They are all mobility one and regard on the motion features,the different facet components perform screw motions about the corresponding virtual axes and the vertex components execute radially reciprocating motions along their associated virtual axes towards or outwards the virtual centers.?5?Based on the overconstrained feature of the synthesized mechanisms and the characterization of the straight-line movement of the vertex components,a linear actuator can be placed along the virtual axis?the trace of vertex component?for actuating the mechanism to expand and fold.The dynamic expressions of four mechanisms as aforementioned can be obtained by calculating the kinetic energy.?6?An adapting application based on the deployable Fulleroid-like hexahedral mechanism was designed by replacing vertex with a sphere surface vertex so that the mechanism could be able to fold into a cell.The design can be used as a deployable carrier for developing and improving the existing robotic structures,thanks to the high expansion ratio of the mechanism.The carrier can load sensing system or equip micro crawling devices/wheels.A prototype of the proposed deployable carrier was built through 3D printing technology.In addition,the proposed deployable hexahedral mechanism was applied in the development of a reconfigurable quadrotor with static structural analyses and dynamic simulations of the fully-expanded configuration,intermediate configuration and fully-folded configuration being carried out.Moreover,a PID control system based on the three angle inputs and altitude input is investigated.The results show that the PID controllers are stable and fast respond.