Modeling And Integrated Design Of A Novel 5-DOF Hybrid Robot

Driven by many practical needs for innovation and development of robotized cells for on-site manufacturing and assembly of large structural components,this dissertation investigates the integrated design methodology of a novel 5-DOF hybrid robot especially designed and developed for machining,milling and drilling.The contents cover a wide range of spectrum in terms of type synthesis and criteria to select suitable robot mechanisms,parametric kinematic and dynamic modeling,integrated design and performance prediction,as well as prototype development and experimental verification.The following contributions have been made.(1)Type synthesis and robot mechanism innovationA simple and highly visible approach for type synthesis of a family of over-constrained 1T2R(T--Translation,R--Rotation)parallel mechanisms is proposed.This family features a spatial limb combined a member of a class of planar symmetrical linkages,the latter connected by a revolute joint either to the machine frame at its base link or to the platform at its output link.Criteria for selecting suitable mechanisms from among numerous candidates are then developed by considering the realistic practical requirements of the movement capability,the limb structural rationality,the modular reconfigurability,as well as the algorithm simplicity of inverse/forward displacement analyses.Exploitation of the proposed robot mechanisms and evaluation criteria leads to a novel 5-DOF hybrid module named Tri Mule with a compact,lightweight yet rigid design particularly suitable for configuring various robotized manufacturing cells and systems.Various scenarios are also provided to illustrate its potential application.(2)Modeling methods and performance assessmentsBased mainly on screw theory incorporated with structural mechanics,a complete and comprehensive theoretical package is developed for analytical and semi-analytical modeling of kinematics(including workspace,position,velocity and acceleration),statics,rigid and flexible body dynamics of the Tri Mule robot.A set of comprehensive local and global indices are then proposed for evaluating the performances that are essentially required for robot machining.The influences on these indices of the design parameters are investigated in depth using response surface analysis.The results offer a critical guideline for the integrated design of the hybrid robot.(3)Integrated design methodologyIn order to reduce design complicity and to improve design efficiency,three important strategies are developed for the integrated design of the Tri Mule robot.They are the hierarchical design strategy at A/C wrist and 1T2 R mechanism levels,the associative design strategy driven by a group of key parameters,and the optimal design strategy using a set of performance indices defined at the reference configuration.Consequently,an overall design framework is established under which the design procedure can sequentially be implemented by three closely connected steps,i.e.the conceptual design of all mechanical parts at a subassembly level,the optimal design of the key parameters of the A/C wrist and the 1T2 R mechanism,and the pose-varying performance prediction across the entire task workspace using CAD-CAE integration technology.With the results verified by CAD/CAE software,a full size prototype of the Tri Mule-600 robot is built.A set of experiments is carried out to test its comprehensive performances about workspace envelope,speeding and accelerating capabilities,FRFs(frequency response functions)at the robot TCP(tool center point),etc.The experimental results show that the maximum acceleration of 1G and maximum speed of 60 m/min of the robot TCP can be achieved within a relatively large workspace having envelope/footprint volume ratio of 2.7.The experiments also show that the minimum lateral stiffness of the robot TCP is superior to 2.1 N ?m and its first-order natural frequency is higher than 24 Hz within 80% of the task workspace.Currently,a test bench has been built to demonstrate the realistic applicability of the Tri Mule robot for mirror milling of thin wall aluminum alloy structures and for orbital drilling of Ti/CRFP/Al stacks.The outcomes of this dissertation not only offer a complete theoretical fundamental for integrated design of the Tri Mule robot,but also demonstrate its potential application to the high-end manufacturing.