625 research outputs found
On the generation of sequential unitary gates from continuous time Schrodinger equations driven by external fields
In all the various proposals for quantum computers, a common feature is that
the quantum circuits are expected to be made of cascades of unitary
transformations acting on the quantum states. A framework is proposed to
express these elementary quantum gates directly in terms of the control inputs
entering into the continuous time forced Schrodinger equation.Comment: 10 page
Design Optimization, Analysis, and Control of Walking Robots
Passive dynamic walking refers to the dynamical behavior of mechanical devices that are able to naturally walk down a shallow slope in a stable manner, without using actuation or sensing of any kind. Such devices can attain motions that are remarkably human-like by purely exploiting their natural dynamics. This suggests that passive dynamic walking machines can be used to model and study human locomotion; however, there are two major limitations: they can be difficult to design, and they cannot walk on level ground or uphill without some kind of actuation.
This thesis presents a mechanism design optimization framework that allows the designer to find the best design parameters based on the chosen performance metric(s). The optimization is formulated as a convex problem, where its solutions are globally optimal and can be obtained efficiently.
To enable locomotion on level ground and uphill, this thesis studies a robot based on a passive walker: the rimless wheel with an actuated torso. We design and validate two control policies for the robot through the use of scalable methodology based on tools from mathematical analysis, optimization theory, linear algebra, differential equations, and control theory
Relative Critical Points
Relative equilibria of Lagrangian and Hamiltonian systems with symmetry are
critical points of appropriate scalar functions parametrized by the Lie algebra
(or its dual) of the symmetry group. Setting aside the structures - symplectic,
Poisson, or variational - generating dynamical systems from such functions
highlights the common features of their construction and analysis, and supports
the construction of analogous functions in non-Hamiltonian settings. If the
symmetry group is nonabelian, the functions are invariant only with respect to
the isotropy subgroup of the given parameter value. Replacing the parametrized
family of functions with a single function on the product manifold and
extending the action using the (co)adjoint action on the algebra or its dual
yields a fully invariant function. An invariant map can be used to reverse the
usual perspective: rather than selecting a parametrized family of functions and
finding their critical points, conditions under which functions will be
critical on specific orbits, typically distinguished by isotropy class, can be
derived. This strategy is illustrated using several well-known mechanical
systems - the Lagrange top, the double spherical pendulum, the free rigid body,
and the Riemann ellipsoids - and generalizations of these systems
Kinematic Performance Measures and Optimization of Parallel Kinematics Manipulators: A Brief Review
This chapter covers a number of kinematic performance indices that are instrumental in designing parallel kinematics manipulators. These indices can be used selectively based on manipulator requirements and functionality. This would provide the very practical tool for designers to approach their needs in a very comprehensive fashion. Nevertheless, most applications require a more composite set of requirements that makes optimizing performance more challenging. The later part of this chapter will discuss single-objective and multi-objectives optimization that could handle certain performance indices or a combination of them. A brief description of most common techniques in the literature will be provided
Dimensional synthesis of a spherical parallel manipulator based on the evaluation of global performance indexes
In this work, the dimensional synthesis of a spherical Parallel Manipulator (PM) with a -1S kinematic chain is presented. The goal of the synthesis is to find a set of parameters that defines the PM with the best performance in terms of workspace capabilities, dexterity and isotropy. The PM is parametrized in terms of a reference element, and a non-directed search of these parameters is carried out. First, the inverse kinematics and instantaneous kinematics of the mechanism are presented. The latter is found using the screw theory formulation. An algorithm that explores a bounded set of parameters and determines the corresponding value of global indexes is presented. The concepts of a novel global performance index and a compound index are introduced. Simulation results are shown and discussed. The best PMs found in terms of each performance index evaluated are locally analyzed in terms of its workspace and local dexterity. The relationship between the performance of the PM and its parameters is discussed, and a prototype with the best performance in terms of the compound index is presented and analyzed
Manipulator Performance Measures - A Comprehensive Literature Survey
Due to copyright restrictions of the publisher this item is embargoed and access to the file is restricted until a year after the publishing date.The final publication is available at www.springerlink.comPerformance measures are quintessential to the design, synthesis, study and
application of robotic manipulators. Numerous performance measures have been
defined to study the performance and behavior of manipulators since the early days of
robotics; some more widely accepted than others, but their real significance and
limitations have not always been well understood. The aim of this survey is to review
the definition, classification, scope, and limitations of some of the widely used
performance measures. This work provides an extensive bibliography that can be of
help to researchers interested in studying and evaluating the performance and
behavior of robotic manipulators. Finally, a few recommendations are proposed based
on the review so that the most commonly noticed limitations can be avoided when new
performance measures are proposed.http://link.springer.com/article/10.1007/s10846-014-0024-y
Kinematics and Robot Design I, KaRD2018
This volume collects the papers published on the Special Issue “Kinematics and Robot Design I, KaRD2018” (https://www.mdpi.com/journal/robotics/special_issues/KARD), which is the first issue of the KaRD Special Issue series, hosted by the open access journal “MDPI Robotics”. The KaRD series aims at creating an open environment where researchers can present their works and discuss all the topics focused on the many aspects that involve kinematics in the design of robotic/automatic systems. Kinematics is so intimately related to the design of robotic/automatic systems that the admitted topics of the KaRD series practically cover all the subjects normally present in well-established international conferences on “mechanisms and robotics”. KaRD2018 received 22 papers and, after the peer-review process, accepted only 14 papers. The accepted papers cover some theoretical and many design/applicative aspects
Bridges Between Subriemannian Geometry and Algebraic Geometry
We consider how the problem of determining normal forms for a specific class
of nonholonomic systems leads to various interesting and concrete bridges
between two apparently unrelated themes. Various ideas that traditionally
pertain to the field of algebraic geometry emerge here organically in an
attempt to elucidate the geometric structures underlying a large class of
nonholonomic distributions known as Goursat constraints. Among our new results
is a regularization theorem for curves stated and proved using tools
exclusively from nonholonomic geometry, and a computation of topological
invariants that answer a question on the global topology of our classifying
space. Last but not least we present for the first time some experimental
results connecting the discrete invariants of nonholonomic plane fields such as
the RVT code and the Milnor number of complex plane algebraic curves.Comment: 10 pages, 2 figures, Proceedings of 10th AIMS Conference on Dynamical
Systems, Differential Equations and Applications, Madrid 201
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