Mechanism Design

A Novel Continuous Alternate Motion Mechanism With Two Input Wheels

by Francesco Pescarmona

Csr: Constrained selfish routing in ad-hoc networks

by Christine Bassem

Near-efficient equilibria in contribution-based competitive grouping

by Anna Gunnthorsdottir

published as: Gunnthorsdottir, A., R. Vragov, S. Seifert & K. McCabe (2010). Near-efficient equilibria in contribution-based competitive grouping. Journal of Public Economics, 94, 987-994.

We introduce a formal account of the efficiency-enhancing effects of contribution-based grouping. We find that a... more We introduce a formal account of the efficiency-enhancing effects of contribution-based grouping. We find that a somewhat complicated equilibrium, rather than off-equilibrium psychological motives, account for the effect in our case. Experimental subjects are able to coordinate this asymmetric equilibrium via simultaneous decisions, without communicating, and apparently without learning.

Compliant mechanisms for an active cardiac stabilizer: lessons and new requirements in the design of a novel surgical tool

by Lennart Rubbert

FINITE ELEMENT ANALYSIS OF A HIGHLY PARALLEL ROBOTIC SURFACE

by Chris Salisbury

Published in the proceedings of the global IMECE2011 conference.

A  novel  three-dimensional  robotic  surface  is  devised  and more A  novel  three-dimensional  robotic  surface  is  devised  and
implemented  using  triangular  modules.  Each  module  is
connected  by  a  passive  sixbar  mechanism  that  mimics  the
constraints of a spherical joint at each triangle intersection. The
finite element method (FEM) is applied to the static loading of
this  device  using  linear  three  dimensional  (6  degrees  of
freedom) beam elements to calculate the cartesian displacement
and force and the angular displacement and torque at each joint.
In this way, the traditional methods of finding joint forces and
torques  are  completely  bypassed.  An  effiecient  algorithm  is
developed  to  linearly  combine  local  stiffness  matrices  into  a
full structural stiffness matrix for the easy application of loads.
This is then decomposed back into the local matrices to easily
obtain joint variables used in the design and open-loop control
of the surface.

DYNAMIC FINITE ELEMENT ANALYSIS OF A HIGHLY PARALLEL ROBOTIC SURFACE

by Chris Salisbury

Published in the proceedings of the SMASIS2011 conference.

A  novel  three-dimensional  robotic  surface  is
devised  using ... more A  novel  three-dimensional  robotic  surface  is
devised  using  triangular  modules  connected  by
revolute  joints  that  mimic  the  constraints  of  a
spherical  joint  at  each  triangle  intersection.  The
finite  element  method  (FEM)  is  applied  to  the
dynamic  loading  of  this  device  using  three
dimensional    (6    degrees    of    freedom)    beam
elements  to  not  only  calculate  the  cartesian
displacement  and  force,  but  also  the  angular
displacement and torque at each joint. In this way,
the traditional methods of finding joint forces and
torques  are  completely  bypassed.  An  effiecient
algorithm  is  developed  to  linearly  combine  local
mass  and  stiffness  matrices  into  a  full  structural
stiffness  matrix  for  the  easy  application  of  loads.
An  analysis  of  optimal  dynamic  joint  forces  is
carried  out  in  Simulink®  with  the  use  of  an
algebraic Ricatti equation.

Mars Science Laboratory CHIMRA: A Device for Processing Powdered Martian Samples

by Daniel Sunshine

The CHIMRA is an extraterrestrial sample acquisition and processing device for the Mars Science Laboratory that... more The CHIMRA is an extraterrestrial sample acquisition and processing device for the Mars Science Laboratory that emphasizes robustness and adaptability through design configuration. This work reviews the guidelines utilized to invent the initial CHIMRA and the strategy employed in advancing the design; these principles will be discussed in relation to both the final CHIMRA design and similar future devices. The computational synthesis necessary to mature a boxed-in impact-generating mechanism will be presented alongside a detailed mechanism description. Results from the development testing required to advance the design for a highly-loaded, long-life and high-speed bearing application will be presented. Lessons learned during the assembly and testing of this subsystem as well as results and lessons from the sample-handling development test program will be reviewed.

Ng, Irene C.L. and Robert J. Kwortnik Jr, (2008) “Balancing Cruise Revenue Sources: The Case of Empress Cruise Lines” Case Research Journal, Vol. 27, No. 2, pp105-127

by Irene C L Ng

Ng, Irene and Yip, Nick K. T.(2011) 'Mechanism design in an integrated approach towards revenue management: the case of Empress Cruise Lines', The Service Industries Journal, 31: 3, 469 — 482

by Irene C L Ng

This paper investigates an integrated form of revenue management through the case of Empress Cruise Lines (ECL). The... more This paper investigates an integrated form of revenue management through the case of Empress Cruise Lines (ECL). The case highlights a multidisciplinary approach towards
how demand and supply factors should be integrated in the form of four decision sets in revenue management decisions – the value set, the segmentation set, the sensitivity set and the forecasting/allocation set. Also, the use of mechanism design allows the firm to separate markets for better forecasting of revenue from each segment. The case also shows that segments could be incentivized to behave differently, and to behave in alignment with ECL’s policies so that capacity could be optimally allocated and revenue maximized.

Comments on “Design and analysis of a totally decoupled 3-DOF spherical parallel manipulator” by D. Zhang and F. Zhang (Robotica, Available on CJO 19 Nov, 2010, doi:10.1017/S0263574710000652)

by Marco Carricato

Robotica, Vol. 29, No. 7, December 2011, pp. 1101-1103.

Comments on the paper:
“Design and analysis of a totally decoupled 3-DOF spherical parallel manipulator”,
by... more Comments on the paper:
“Design and analysis of a totally decoupled 3-DOF spherical parallel manipulator”,
by D. Zhang and F. Zhang,
published on Robotica, 2011, Vol. 29, Issue 07, pp.1093-1100
(Available on CJO 19 Nov, 2010, doi:10.1017/S0263574710000652).

Important issues concerning the design of decoupled and isotropic orientational parallel manipulators are critically discussed.

An experimental comparison of sequential first-and second-price auctions with synergies

by Marc Vorsatz

joint with Kasper Leufkens and Ronald Peeters, Unpublished Working Paper, 2007.

The presence of synergies in recurrent procurement auctions leads to an exposure problem and asymmetries among... more The presence of synergies in recurrent procurement auctions leads to an exposure problem and asymmetries among bidders. We consider sequential first- and second-price auctions with synergies in a setting with four bidders. In a series of experiments we compare the performance of the two pricing formats for three different sizes of the synergy. We find that for small synergies, the first-price auction performs better in terms of efficiency, revenue, and the probability on losses. However, once the synergy factor becomes very large the performance of the two different pricing formats becomes more similar. We also find that even though the potential total surplus that can be divided between buyers and seller increases in the synergy factor, subjects’ earnings within a pricing rule do not significantly change in the synergy factor. Finally, we observe that the two pricing formats give rise to different price trends within the auction sequence. In general, our results provide support for the common use of first-price instead of second-price auctions for public procurement.

Preference Intensities and Risk Aversion in School Choice: A Laboratory Experiment

by Marc Vorsatz

joint with Flip Klijn and Joana Pais, Unpublished Working Paper, 2010.

We experimentally investigate in the laboratory two prominent mechanisms that are employed in school choice programs... more We experimentally investigate in the laboratory two prominent mechanisms that are employed in school choice programs to assign students to public schools. We study how individual behavior is influenced by preference intensities and risk aversion. Our main results show that (a) the Gale-Shapley mechanism is more robust to changes in cardinal preferences than the Boston mechanism independently of whether individuals can submit a complete or only a restricted ranking of the schools and (b) subjects with a higher degree of risk aversion are more likely to play "safer" strategies under the Gale-Shapley but not under the Boston mechanism. Both results have important implications for the efficiency and the stability of the mechanisms.

Size approval voting

by Marc Vorsatz

joint with Jorge Alcalde Unzu, Working Paper, published in Journal of Economic Theory 144: 1187-1210, 2009.

We propose a new class of voting procedures, called Size Approval Voting, according to which, the effective weight of... more We propose a new class of voting procedures, called Size Approval Voting, according to which, the effective weight of a vote from a given individual depends on how many other candidates that individual votes for. In particular, weights are assumed to be non-negative and weakly decreasing in the number of approved candidates. Then, for a given profile of individual votes, all candidates with the maximal sum of weighted votes are elected. We show in our axiomatic analysis that the family of all Size Approval Voting procedures is characterized by a set of natural properties.

Persistent Screw Systems of Dimension Three.

by Marco Carricato

13th World Congress in Mechanism and Machine Science, Guanajuato, México, 19-25 June, 2011.

In 1978, Hunt found a set of vector subspaces of screws that guarantee `full-cycle mobility' of mechanisms.
They... more In 1978, Hunt found a set of vector subspaces of screws that guarantee `full-cycle mobility' of mechanisms.
They are subalgebras of the Lie algebra se(3) of the Euclidean group and they are at the basis of most families of mechanisms with special motion capabilities.
Recently, a more general concept was presented.
Persistent screw systems (PSSs) are not subalgebras of se(3), but they still exhibit relevant properties for full-cycle motions, namely the invariance of both the space dimension and the pitch of the principal screws.
For this reason, they are believed to play an important role in both mobility analysis and mechanism synthesis.
This paper provides the detailed derivation and the comprehensive classification of PSSs of dimension three.

Persistent Screw Systems

by Marco Carricato

In: Advances in Robot Kinematics: Motion in Man and Machine, eds. J. Lenarčič and M.M. Stanišić, Springer, Dordrecht, 2010, pp. 185-194.

In 1978, Hunt found a set of vector subspaces of screws that guarantee `full-cycle mobility' of linkages and exhibit... more In 1978, Hunt found a set of vector subspaces of screws that guarantee `full-cycle mobility' of linkages and exhibit remarkable properties. They are subalgebras of the Lie algebra se(3) of the Euclidean group and they are at the basis of most families of mechanisms with special motion capabilities. This paper proves the existence of screw systems that, though not being subalgebras of se(3), still exhibit important properties for full-cycle motions, namely the invariance of both the space dimension and the pitch of the principal screws. Such systems are named persistent and they are believed to play an important role in both mobility analysis and mechanism synthesis.

Singularity-Free Fully Isotropic Translational Parallel Manipulators

by Marco Carricato

Ph. D. dissertation.

Parallel mechanisms show desirable characteristics such as a large payload to robot weight ratio, considerable... more Parallel mechanisms show desirable characteristics such as a large payload to robot weight ratio, considerable stiffness, low inertia and high dynamic performances. In particular, parallel manipulators with fewer than six degrees of freedom have recently attracted researchers’ attention, as their employ may prove valuable in those applications in which a higher mobility is uncalled-for.
The attention of this dissertation is focused on translational parallel manipulators (TPMs), that is on parallel manipulators whose output link (platform) is provided with a pure translational motion with respect to the frame.
The first part deals with the general problem of the topological synthesis and classification of TPMs, that is it identifies the architectures that TPM legs must possess for the platform to be able to freely translate in space without altering its orientation.
The second part studies both constraint and direct singularities of TPMs. In particular, special families of fully-isotropic mechanisms are identified. Such manipulators exhibit outstanding properties, as they are free from singularities and show a constant orthogonal Jacobian matrix throughout their workspace. As a consequence, both the direct and the inverse position problems are linear and the kinematic analysis proves straightforward.

Position Analysis of a New Family of 3-DOF Translational Parallel Manipulators

by Marco Carricato

ASME Journal of Mechanical Design, Vol. 125, No.2, June 2003, pp. 316-322.

This article presents the position analysis of a new family of 3-limbed 3-dof parallel manipulators, whose output... more This article presents the position analysis of a new family of 3-limbed 3-dof parallel manipulators, whose output links exhibit a motion of pure translation with respect to the base. Each limb contains four passive revolute joints and an active prismatic pair, which can be mounted anywhere along the kinematic chain or replaced by a fifth revolute one. A univariate polynomial has been found that solves the direct position problem wherever the actuators are placed. The inverse analysis has been carried out in closed-form for all possible locations of the actuated joints. Finally, numerical examples are pro-vided.

A Family of 3-DOF Translational Parallel Manipulators

by Marco Carricato

ASME Journal of Mechanical Design, Vol. 125, No.2, June 2003, pp. 302-307.

This article addresses parallel manipulators with fewer than six degrees of freedom, whose use may prove valuable in... more This article addresses parallel manipulators with fewer than six degrees of freedom, whose use may prove valuable in those applications in which a higher mobility is uncalled for. In particular, a family of 3-dof manipulators containing only revolute joints or at the most revolute and prismatic ones is studied. Design and assembly conditions sufficient to provide the travelling platform with a pure translational motion are determined and two sub-families that fulfill the imposed constraint are found: one is already known in the literature, while the other is original. The new architecture does not exhibit rotation singularities, i.e. configurations in which the platform gains rotational degrees of freedom. A geometric interpretation of the translation singularities is provided.

Kinematics of a Family of Translational Parallel Mechanisms With Three 4‐DOF Legs and Rotary Actuators

by Marco Carricato

Journal of Robotic Systems, Vol. 20, No. 7, 2003, pp. 373–389.

This paper focuses on the kinematics of a family of translational parallel mechanisms equipped with three 4-dof legs... more This paper focuses on the kinematics of a family of translational parallel mechanisms equipped with three 4-dof legs and rotary actuators. The direct and the inverse position problems are solved in analytical form, the velocity analysis is carried out, the workspace is determined and the loci of both kinematic singularities and isotropic configurations are derived. Furthermore, the problem of singularity avoidance by means of actuator redundancy is addressed and some solutions are proposed. Two special architectures are finally considered as case studies: in the first, the three actuation axes are mutually orthogonal, in the second, two actuation axes are parallel to each other and the third is perpendicular to them. The comparison of the two architectures on the basis of kinematic considerations allows for the selection of the second one as a preferable solution.

On the Topological and Geometrical Synthesis and Classification of Translational Parallel Mechanisms

by Marco Carricato

11th World Congress in Mechanism and Machine Science, April 1–4, 2004, Tianjin, China, pp. 1624-1628.

This paper focuses on translational parallel mechanisms (TPMs), that is on parallel manipulators whose platform is... more This paper focuses on translational parallel mechanisms (TPMs), that is on parallel manipulators whose platform is provided with a pure translational motion with respect to the frame. It approaches, in a geometric way, the problem of the kinematic synthesis and classification of TPMs and it systematizes many architectures presented in the literature into a general frame. It provides a survey of the state of the art on such a topic.