8,294 research outputs found
Natural ZMP trajectories for biped robot reference generation
The control of a biped humanoid is a challenging
task due to the hard-to-stabilize dynamics. Walking reference
trajectory generation is a key problem. Linear Inverted
Pendulum Model (LIPM) and Zero Moment Point (ZMP)
Criterion based approaches in stable walking reference
generation are reported. In these methods, generally, the ZMP
reference during a stepping motion is kept fixed in the middle of
the supporting foot sole. This kind of reference generation lacks
naturalness, in that, the ZMP in the human walk does not stay
fixed, but it moves forward under the supporting foot. This paper
proposes a reference generation algorithm based on the LIPM
and moving support foot ZMP references. The application of
Fourier series approximation simplifies the solution and it
generates a smooth ZMP reference. A simple inverse kinematics
based joint space controller is used for the tests of the developed
reference trajectory through full-dynamics 3D simulation. A 12
DOF biped robot model is used in the simulations. Simulation
studies suggest that the moving ZMP references are more energy
efficient than the ones with fixed ZMP under the supporting foot.
The results are promising for implementations
Optimal Auctions with Simultaneous and Costly Participation
We study the optimal auction problem with participation costs in the symmetric independent private values setting, where bidders know their valuations when they make independent participation decisions. After characterizing the optimal auction in terms of participation cutoffs, we provide an example where it is asymmetric. We then investigate when the optimal auction will be symmetric/asymmetric and the nature of possible asymmetries. We also show that, under some conditions, the seller obtains her maximal profit in an (asymmetric) equilibrium of an anonymous second price auction. In general, the seller can also use non-anonymous auctions that resemble the ones that are actually observed in practice.
Investigation of phase-equivalent potentials by a halo transfer reaction
Using the supersymmetric quantum mechanics we investigate the wave
function-sensitive properties of the supersymmetric potentials which have
received a lot of attention in the literature recently. We show that a
superdeep potential and its phase-equivalent shallow-partner potential give
very similar "rms" values for the weakly bound systems such as the deuteron and
11Be nuclei. Although the corresponding eigenstates differ in the node-number,
our investigation on the 11Be(p,d)10Be single nucleon halo transfer reaction at
35 MeV show that also other physical quantities such as the cross section
angular distributions calculated using these wave functions reflect the nodal
structure rather weakly. This lends support to two nearly equivalent treatments
of the Pauli principle.Comment: 20 pages article in LaTEX (uses standard article.sty). Figures can be
obtained from author(s). Please check "http://www1.gantep.edu.tr/~ozer" for
other studies of Nuclear Physics Group at University of Gaziante
New exact treatment of the perturbed Coulomb interactions
A novel method for the exact solvability of quantum systems is discussed and
used to obtain closed analytical expressions in arbitrary dimensions for the
exact solutions of the hydrogenic atom in the external potential , which is based on the recently introduced supersymmetric
perturbation theory.Comment: 6 pages article in LaTEX (uses standard article.sty). No Figures.
Please check "http://www1.gantep.edu.tr/~ozer/" for other studies of Nuclear
Physics Group at University of Gaziante
Ratifiability of Efficient Collusive Mechanisms in Second-Price Auctions with Participation Costs
We investigate whether efficient collusive bidding mechanisms are affected by potential information leakage from bidders' decisions to participate in them within the independent private values setting. We apply the concept of ratifiability introduced by Cramton and Palfrey (1995) and show that when the seller uses a second-price auction with participation costs, the standard efficient cartel mechanisms such as preauction knockouts analyzed in the literature will not be ratified by cartel members. A high-value bidder benefits from vetoing the cartel mechanism since doing so sends a credible signal that she has high value, which in turn discourages other bidders from bidding in the seller's auction.Auctions, collusion, ratifiability
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