Elastokinetics modeling and characteristic analysis of the parallel robot mechanism

This paper focuses a new 4-UPS-RPS five degree of freedom (DOF) spatial parallel robot mechanism with independent intellectual property rights obtained. Based on KED method and together with finite element method, Lagrange equation and substructure modeling method, the elastokinetics analytical model of this parallel robot mechanism is established under the ideal situation. Subsequently, the research results, such as elastokinetics model, stress and frequency characteristic analysis, are obtained. Combined with typical examples, key design parameters which significantly influence the dynamic characteristics of the system, are explicated. The work done in this paper lays a solid foundation for the dynamic optimum design of parallel robot mechanism and the physical prototype development

Dynamic analysis of constrained object motion for mechanical transfer of live products

This thesis is motivated by practical problems encountered in handling live products in the poultry processing industry, where live birds are manually transferred by human labors. As the task of handling live products is often unpleasant and hazardous, it is an ideal candidate for automation. To reduce the number of configurations and live birds to be tested, this thesis focuses on developing analytical models based on the Lagrange method to predict the effect of mechanical inversion on the shackled bird. Unlike prior research which focused on the effect of different inversion paths on the joint force/torque of a free-falling shackled bird, this thesis research examines the effect of kinematic constraints (designed to support the bird body) on the shackled bird. Unlike free-falling, the imposed kinematic constraints enable the shackled bird to rotate about its center of mass, and thus minimize wing flapping. In this thesis, birds are geometrically approximated as ellipsoids while the lower extremity is modeled as a pair of multi-joint serial manipulators. With the constraint equations formulated into a set of differential algebraic equations, the equations of motion as well as Lagrange multipliers characterizing kinematical constraints are numerically solved for the bird motion, specifically the position, velocity, and orientation and hence the forces and torques of the joints. The dynamic models are verified by comparing simulation results against those obtained using a finite element method. The outcomes of this thesis will provide some intuitive insights essential to design optimization of a live-bird transfer system.M.S.Committee Chair: Kok-Meng Lee; Committee Member: Bruce Webster; Committee Member: Shreyes Melkot

Modeling, Analysis, Force Sensing and Control of Continuum Robots for Minimally Invasive Surgery

This dissertation describes design, modeling and application of continuum robotics for surgical applications, specifically parallel continuum robots (PCRs) and concentric tube manipulators (CTMs). The introduction of robotics into surgical applications has allowed for a greater degree of precision, less invasive access to more remote surgical sites, and user-intuitive interfaces with enhanced vision systems. The most recent developments have been in the space of continuum robots, whose exible structure create an inherent safety factor when in contact with fragile tissues. The design challenges that exist involve balancing size and strength of the manipulators, controlling the manipulators over long transmission pathways, and incorporating force sensing and feedback from the manipulators to the user. Contributions presented in this work include: (1) prototyping, design, force sensing, and force control investigations of PCRs, and (2) prototyping of a concentric tube manipulator for use in a standard colonoscope. A general kinetostatic model is presented for PCRs along with identification of multiple physical constraints encountered in design and construction. Design considerations and manipulator capabilities are examined in the form of matrix metrics and ellipsoid representations. Finally, force sensing and control are explored and experimental results are provided showing the accuracy of force estimates based on actuation force measurements and control capabilities. An overview of the design requirements, manipulator construction, analysis and experimental results are provided for a CTM used as a tool manipulator in a traditional colonoscope. Currently, tools used in colonoscopic procedures are straight and exit the front of the scope with 1 DOF of operation (jaws of a grasper, tightening of a loop, etc.). This research shows that with a CTM deployed, the dexterity of these tools can be increased dramatically, increasing accuracy of tool operation, ease of use and safety of the overall procedure. The prototype investigated in this work allows for multiple tools to be used during a single procedure. Experimental results show the feasibility and advantages of the newly-designed manipulators

Micro motion stages with flexure hinges-design and control

The developments in micro and nano technologies brought the need of high precision micropositioning stages to be used in micro/nano applications such as cell manipulation, surgery, aerospace, micro fluidics, optical systems, micromachining and microassembly etc. Micro motion stages with flexible joints called compliant mechanisms are built to provide the needed accuracy and precision. This thesis aims to build compliant planar micro motion stages using flexure hinges to be used as micropositioning devices in x-y directions by applying new control methods. First 3- RRR planar parallel kinematic structure is selected which is also popular in the literature. Then the mechanism is developed to have a new structure which is a 3-PRR mechanism. The necessary geometric parameters are selected by using Finite Element Analysis (FEA). The displacement, stress and frequency behaviors of the mechanisms are compared and discussed. Modeling of the flexure based mechanisms is also studied for 3-PRR compliant stage by using Kinetostatic modeling method which combines the compliance calculations of flexure hinges with kinematics of the mechanism. Piezoelectric actuators and optical 2d position sensor which uses a laser source are used for actuation and measurement of the stages. After the experimental studies it's seen that the results are not compatible with FEA because of the unpredictable errors caused by manufacturing and assembly. We have succeeded to eliminate those errors by implementing a control methodology based on Sliding Mode Control with Disturbance Observer which is also based on Sliding Mode Control using linear piezoelectric actuator models. Finally, we have extracted experimental models for each actuation direction of the stage and used those models instead of piezoelectric actuator models which lowered our errors in the accuracy of our measurement and ready to be used as a high precision micro positioning stage for our micro system applications

Concepts for elastic parallel manipulators for the control of structural vibrations

Im Vordergrund der vorliegenden Arbeit steht die Unterdrückung von Schwingungen in der Roboterstruktur eines elastischen parallelen Manipulators. Um dieses Ziel zu realisieren, soll eine Strukturregelung entwickelt werden, die grundsätzlich über die Kenntnis der Bewegungsgleichungen des zu regelnden Manipulators verfügen muss, da diese Art von Maschinen im Allgemeinen zur Klasse der nichtlinearen Systeme gehört. Deswegen müssen, um die gestellte Aufgabe zu erfüllen, grundsätzlich zwei Hauptprobleme gelöst werden: - Modellierung eines elastischen parallelen Manipulators - Entwurf einer modellbasierten Regelung Parallele Manipulatoren werden in der Literatur und in der Praxis vorwiegend als Starrkörpersysteme behandelt. Die für diese Klasse von Robotern entwickelten Methoden können zumeist nicht ohne arbeitsaufwendige Modifikationen auf die elastischen parallelen Manipulatoren übertragen werden. Aus diesem Grund werden im Rahmen dieser Arbeit, basierend auf den am häufigsten eingesetzten und hier beschriebenen Standardmethoden, neue Verfahren und Lösungsansätze entwickelt und vorgestellt. Zu diesen neuen Lösungen gehören - eine Methode zur Herleitung der direkten Kinematik, - zwei Methoden zur Bestimmung des Arbeitsraumes, - eine Methode zur Herleitung der Jacobimatrix, - eine Methode zur verteilten Berechnung der direkten Dynamik und - ein modellbasiertes nichtlineares Regelungsverfahren. Die neuen Konzepte werden auf Basis des ebenen elastischen parallelen Manipulators Fünfgelenk analysiert und diskutiert. Durch Simulationen und Experimente werden die hier vorgeschlagenen Lösungen anschließend bestätigt. Anhand der gewonnenen Ergebnisse wird das Potential der neuen Verfahren aufgezeigt, wodurch eine gute Basis für ihre aufgabenorientierte roboterbezogene Weiterentwicklung und Optimierung geschaffen wird.The main aim of this study is the damping of vibration within the structure of an elastic parallel robot. In order to achieve this aim, the control of the manipulator's structure needs to be developed. Basically the equations of motion of the elastic manipulator need to be known for the control strategy, as generally this type of machine belongs to non-linear systems. Therefore, in order to complete this task, two main problems need to be solved: - The modelling of an elastic parallel manipulator - The design of a model-based control Parallel manipulators are mainly treated as rigid-body systems both in theory and in practise. Those methods developed for these types of robots mostly cannot be transfered directly to the elastic parallel manipulators. For this reason in the course of this study, based on the most commonly used standard methods as described here, new techniques and approaches are developed and presented. These new techniques include: - A method for the derivation of direct kinematics - Two methods to determine a manipulator's workspace - A method to derive a Jacobian matrix - A method for the distributed/simultaneous calculation of direct dynamics - A model-based controller algorithm These new concepts are analysed and discussed on the basis of a Five-Bar planar elastic parallel manipulator. Through simulations and experiments, the solutions suggested here, can subsequently be confirmed. Based on the acquired results, the potential of the new techniques will be shown, whereby a good basis for further task- and manipulator-orientated development and optimisation will be achieved