Discrete Mechanics and Optimal Control Applied to the Compass Gait Biped

This paper presents a methodology for generating locally optimal control policies for simple hybrid mechanical systems, and illustrates the method on the compass gait biped. Principles from discrete mechanics are utilized to generate optimal control policies as solutions of constrained nonlinear optimization problems. In the context of bipedal walking, this procedure provides a comparative measure of the suboptimality of existing control policies. Furthermore, our methodology can be used as a control design tool; to demonstrate this, we minimize the specific cost of transport of periodic orbits for the compass gait biped, both in the fully actuated and underactuated case

Songlines and Navigation in Wardaman and other Australian Aboriginal Cultures

We discuss the songlines and navigation of the Wardaman people, and place them in context by comparing them with corresponding practices in other Australian Aboriginal language groups, using previously unpublished information and also information drawn from the literature. Songlines are effectively oral maps of the landscape, enabling the transmission of oral navigational skills in cultures that do not have a written language. In many cases, songlines on the earth are mirrored by songlines in the sky, enabling the sky to be used as a navigational tool, both by using it as a compass, and by using it as a mnemonicComment: accepted by JAH

UbiqBIOPARC: A GPS and WIFI Based Context-Aware System for an Enhanced Guide Experience

This document discusses and evaluates the use of GPS, WIFI and iPhone SDK based technologies to develop UbiqBIOPARC, a context-aware system in a particular context: a new generation zoological park that has been created based on the zooimmersion concept, submersing the visitor totally in the savage habitats. It offers appropriate contextual information to users, depending on their preferences and the environment in which they are positioned. UbiqBIOPARC is a context-aware application that provides information to zoo visitors. It combines the flexibility of iPhone SDK with the connectivity provided by WIFI, the location capabilities of GPS and the orientation offered by a compass integrated in the device. In this document the overall architecture and the implementation steps followed to create this application are presented. We also demonstrate that a new approach to build context-aware applications with the aid of GPS and compass features is possible. Finally, several experiments have been carried out in order to evaluate performance and system behavior. In particular, system reaction time and data download time are under study. Besides power consumption in different modes such as GPS, local, WIFI and compass modes is evaluated.Sorribes Díaz, JV. (2010). UbiqBIOPARC: A GPS and WIFI Based Context-Aware System for an Enhanced Guide Experience. http://hdl.handle.net/10251/14544Archivo delegad

Intrinsic Polarized Strangeness and Lambda Polarization in Deep-Inelastic Production

We propose a model for the longitudinal polarization of Lambda baryons produced in deep-inelastic lepton scattering at any xF, based on static SU(6) quark-diquark wave functions and polarized intrinsic strangeness in the nucleon associated with individual valence quarks. Free parameters of the model are fixed by fitting NOMAD data on the longitudinal polarization of Lambda hyperons in neutrino collisions. Our model correctly reproduces the observed dependences of Lambda polarization on the kinematic variables. Within the context of our model, the NOMAD data imply that the intrinsic strangeness associated with a valence quark has anticorrelated polarization. We also compare our model predictions with results from the HERMES and E665 experiments using charged leptons. Predictions of our model for the COMPASS experiment are also presented

Artificial Spill Generator at COMPASS

openThe Artificial Spill Generator firmware for controlling, monitoring, and generating accelerator timing signals, has been developed for the DAQ system of CERN SPS M2 beamline experiments COMPASS and AMBER, within the frame of the Summer Student Program. In this work, the COMPASS experimental context is described, reporting its field of research, the main purposes of its creation, and the architecture of its spectrometer setup. A more detailed presentation of its Trigger and DAQ systems is also produced, providing a description of the bigger architecture in which the Artificial Spill Generator was first devised and eventually deployed. The structure and behaviour of the M2 beam line of CERN SPS exploited by COMPASS is explained, providing links with the functioning of the FPGA-based continuously run- ning DAQ currently used in the experiment. Moreover, the hardware and software monitoring tools of the DAQ are presented, making comments on how they interact with the Artificial Spill Generator. Eventually, the logic and the behavior of the firmware are reported in detail, explaining the different tasks and measurements associated with such a module. After having passed all the required tests, the Artificial Spill Generator firmware has been programmed into an FPGA board, which is currently still implemented in COMPASS and AMBER DAQ systems, improving their acquisition performances

Processing of sky compass cues and wide-field motion in the central complex of the desert locust (Schistocerca gregaria)

1. Polarization-sensitive neurons of the locust central complex show azimuthdependent responses to unpolarized light spots. This suggests that direct sunlight supports the sky polarization compass in this brain area. / 2. In the brain of the desert locust, neurons sensitive to the plane of celestial polarization are arranged like a compass in the slices of the central complex. These neurons, in addition, code for the horizontal direction of an unpolarized light cue possibly representing the sun. We show here that horizontal directions are, in addition to E-vector orientations from dorsal direction, represented in a compass-like manner across the slices of the central complex. However, both compasses are not linked to each other but seem to interact in a cell specific nonlinear way. Our study confirms the role of the central complex in signaling heading directions signaling and shows that different cues are employed for this task. / 3. Visual cues are essential for animal navigation and spatial orientation. Many insects rely on celestial cues for spatial orientation, including the sky polarization pattern. In desert locusts neurons encoding the plane of polarized light (E-vector) are located in the central complex (CX), a group of midline-spanning neuropils. Several types of CX neuron signalling heading direction represent zenithal Evectors in a topographic manner across the slices of the CX and, likely, act as an internal sky compass. Because animals experience optic flow stimulation during flight, we asked whether progressive wide-field motion affects the responses of CX neurons to polarized light. In most neurons, progressive motion disadapted the response to the preferred E-vector (i.e. the E-vector eliciting strongest firing), whereas the response to the anti-preferred E-vector remained comparatively unaffected. This suggests context-dependent gain modulation in sky compass signalling. Three types of compass neuron were responsive to motion simulating body rotation around the yaw axis. Depending on arborization domains in the CX and rotation direction these neurons were strongly excited or inhibited. As proposed for Drosophila, they may be involved in shifting compass signal activity across the slices of the CX as the animal turns enabling it to keep track of its heading

Compass

https://digitalcommons.georgiasouthern.edu/armstrong-compass/1017/thumbnail.jp