Robust tuning of robot control systems

The computed torque control problem is examined for a robot arm with flexible, geared, joint drive systems which are typical in many industrial robots. The standard computed torque algorithm is not directly applicable to this class of manipulators because of the dynamics introduced by the joint drive system. The proposed approach to computed torque control combines a computed torque algorithm with torque controller at each joint. Three such control schemes are proposed. The first scheme uses the joint torque control system currently implemented on the robot arm and a novel form of the computed torque algorithm. The other two use the standard computed torque algorithm and a novel model following torque control system based on model following techniques. Standard tasks and performance indices are used to evaluate the performance of the controllers. Both numerical simulations and experiments are used in evaluation. The study shows that all three proposed systems lead to improved tracking performance over a conventional PD controller

The effect of bandwidth on telerobot system performance

The purpose of the experiment was to determine the effect that various slave-joint bandwidths have on telerobot system performance. The telerobot system consisted of a slave arm controlled by a master. The slave incorporated an impedance loop to provide local compliance in addition to the compliance provided by the operator via force feedback. Three joint bandwidths, 0.5, 1.0, and 2.0 Hz, were used. The performance measures were the task completion time and the sums of the squared forces and moments exerted on the environment. The task consisted of peg-in-hole insertion and removal. The results of the experiment indicate a significant performance decrease at 0.5-Hz bandwidth relative to the 1- and 2-Hz bandwidths. There was no significant change in performance between the 1- and 2-Hz bandwidths

A GIS Hub at Pace University

The Thinkfinity Grant is to use technology to develop a GIS Hub at Pace University. The Hub is intended to show the larger community the work done at Pace and to show that our students and faculty are using GIS to solve geographically-based problems for communities and organizations. It also is intended to serve as a site from which users can download data to make their own maps and as a place where the larger community can find examples of maps and have the ability to manipulate maps

A Modeling approach for analysis and improvement of spindle-holder-tool assembly dynamics

The most important information required for chatter stability analysis is the dynamics of the involved structures, i.e. the frequency response functions (FRFs) which are usually determined experimentally. In this study, the tool point FRF of a spindle-holder-tool assembly is analytically determined by using the receptance coupling and structural modification techniques. Timoshenko’s beam model is used for increased accuracy. The spindle is also modeled analytically with elastic supports representing the bearings. The mathematical model is used to determine the effects of different parameters on the tool point FRF and to identify contact dynamics from experimental measurements. The applications of the model are demonstrated and the predictions are verified experimentally

Influence de la position de l'outil sur le comportement dynamique en fraisage de parois minces

Vibratory problems encountered when milling a thin walled structure affect the surface quality of the finished workpiece and to a lesser extent, the life of the tool and the spindle. This is why, it is necessary to be able to limit these problems by an appropriate choice of the cutting conditions. The stability lobes theory allows to choose the suitable cutting conditions according to the dynamic behaviour of the workpiece and the tool. We introduce here the variations of dynamic behaviour due to the tool position, in order to obtain optimum cutting conditions all along the machining. This general implementation of the classical stability lobes graph leads us to represent the lobes in three dimensions. These theoretical results are compared with experimental milling of thin walled structure, in down-milling

Novel supermultiplets of SU(2,2|4) and the AdS_5/CFT_4 duality

We continue our study of the unitary supermultiplets of the N=8, d=5 anti-de Sitter (AdS_5) superalgebra SU(2,2|4), which is also the N=4 extended conformal superalgebra in d=4. We show explicitly how to go from the compact SU(2)XSU(2)XU(1) basis to the non-compact SL(2,C)XD basis of the positive energy unitary representations of the conformal group SU(2,2) in d=4. The doubleton representations of the AdS_5 group SU(2,2), which do not have a smooth Poincare limit in d=5, are shown to represent fields with vanishing masses in four dimensional Minkowski space. The unique CPT self-conjugate irreducible doubleton supermultiplet of SU(2,2|4)is simply the N=4 Yang-Mills supermultiplet in d=4. We study some novel short non-doubleton supermultiplets of SU(2,2|4) that have spin range 2 and that do not appear in the Kaluza-Klein spectrum of type IIB supergravity or in tensor products of the N=4 Yang-Mills supermultiplet with itself. These novel supermultiplets can be obtained from tensoring chiral doubleton supermultiplets, some of which we expect to be related to the massless limits of 1/4 BPS states. Hence, these novel supermultiplets may be relevant to the solitonic sector of IIB superstring and/or (p,q) superstrings over AdS_5 X S^5.Comment: Minor modifications to clarify the role of central charge and the outer automorphism group U(1)_Y in the representation theory of SU(2,2|4); typos corrected; 28 pages; Late

Overview of CERES Cloud Properties Derived From VIRS AND MODIS DATA

Simultaneous measurement of radiation and cloud fields on a global basis is recognized as a key component in understanding and modeling the interaction between clouds and radiation at the top of the atmosphere, at the surface, and within the atmosphere. The NASA Clouds and Earth s Radiant Energy System (CERES) Project (Wielicki et al., 1998) began addressing this issue in 1998 with its first broadband shortwave and longwave scanner on the Tropical Rainfall Measuring Mission (TRMM). This was followed by the launch of two CERES scanners each on Terra and Aqua during late 1999 and early 2002, respectively. When combined, these satellites should provide the most comprehensive global characterization of clouds and radiation to date. Unfortunately, the TRMM scanner failed during late 1998. The Terra and Aqua scanners continue to operate, however, providing measurements at a minimum of 4 local times each day. CERES was designed to scan in tandem with high resolution imagers so that the cloud conditions could be evaluated for every CERES measurement. The cloud properties are essential for converting CERES radiances shortwave albedo and longwave fluxes needed to define the radiation budget (ERB). They are also needed to unravel the impact of clouds on the ERB. The 5-channel, 2-km Visible Infrared Scanner (VIRS) on the TRMM and the 36-channel 1-km Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua are analyzed to define the cloud properties for each CERES footprint. To minimize inter-satellite differences and aid the development of useful climate-scale measurements, it was necessary to ensure that each satellite imager is calibrated in a fashion consistent with its counterpart on the other CERES satellites (Minnis et al., 2006) and that the algorithms are as similar as possible for all of the imagers. Thus, a set of cloud detection and retrieval algorithms were developed that could be applied to all three imagers utilizing as few channels as possible while producing stable and accurate cloud properties. This paper discusses the algorithms and results of applying those techniques to more than 5 years of Terra MODIS, 3 years of Aqua MODIS, and 4 years of TRMM VIRS data

Disruptive Innovationen für Unternehmen

Wie häufig bündelt auch hier der englische Begriff zahllose deutsche Entsprechungen, die von „Störung“ über „Bruch“, „Riss“ und „Spaltung“ bis zu „Zersprengen“ reichen. Dieses Spektrum gibt zum Inhalt einen ersten Anhaltspunkt, denn Disruption kann sich in all diesen Dimensionen zeigen. Verschiedene Theorien liefern zudem Erklärungen für die Geschehnisse rund um Disruption. Die bekannteste Theorie stammt vom Professor der ‚Harvard Business School‘, Clayton Christensen. Er nutzt den Begriff „Disruptive Innovation“ und erklärt mit seiner Theorie den Erfolg von Unternehmen wie Netflix, Apple und Co. Eine Betrachtung der Grundüberlegungen seiner Theorie kann nicht ausbleiben, wenn man sich mit dem Thema näher beschäftigen und die Fragen nach der Bedeutung von Disruption für das eigene Unternehmen diskutieren möchte

Hierarchical Production Planning for General Jobs Shops : Part 1 : Modeling

The study is divided into two parts. In part 1, we provide an extensive bibliographical study on the subject and introduce a two-level hierarchical production planning model. The whole model is composed of the low level model, the high level model, and the links between both. These models are supposed to be known. We provide a mathematical formulation of the production planning problem and an iterative algorithm to solve it. In the second part of the study, we will provide several numerical examples, including an industrial application. We will also provide a comparison of the hierarchical approach and the monolithic approach in terms of efficiency, memory requirement and computational complexity