Coupled dynamical system based arm–hand grasping model for learning fast adaptation strategies

Performing manipulation tasks interactively in real environments requires a high degree of accuracy and stability. At the same time, when one cannot assume a fully deterministic and static environment, one must endow the robot with the ability to react rapidly to sudden changes in the environment. These considerations make the task of reach and grasp difficult to deal with. We follow a Programming by Demonstration (PbD) approach to the problem and take inspiration from the way humans adapt their reach and grasp motions when perturbed. This is in sharp contrast to previous work in PbD that uses unperturbed motions for training the system and then applies perturbation solely during the testing phase. In this work, we record the kinematics of arm and fingers of human subjects during unperturbed and perturbed reach and grasp motions. In the perturbed demonstrations, the target’s location is changed suddenly after the onset of the motion. Data show a strong coupling between the hand transport and finger motions. We hypothesize that this coupling enables the subject to seamlessly and rapidly adapt the finger motion in coordination with the hand posture. To endow our robot with this competence, we develop a coupled dynamical system based controller, whereby two dynamical systems driving the hand and finger motions are coupled. This offers a compact encoding for reach-to-grasp motions that ensures fast adaptation with zero latency for re-planning. We show in simulation and on the real iCub robot that this coupling ensures smooth and “human-like” motions. We demonstrate the performance of our model under spatial, temporal and grasp type perturbations which show that reaching the target with coordinated hand–arm motion is necessary for the success of the task.     

Segmented object manufacturing

Rapid Prototyping (RP) is a technology based on a “divide-and-conquer” strategy that enables automatic physical realization of a design without any special tooling. However, existing RP processes suffer from staircase defects since they are all based on 2.5-axis kinematics. To minimize the error due to staircase defects parts are normally built from very thin layers typically with thickness values of 0.010 to 0.300 mm. Therefore, hundreds of layers are required to produce a typical object making RP a slow and costly process. To overcome these limitations, a new RP process called Segmented Object Manufacturing (SOM) is proposed in this paper. SOM makes use of three-axis kinematics in conjunction with a novel slicing method. Slicing in SOM is based on certain visibility-based considerations and is independent of the part accuracy. Since only a few thick layers are used in the SOM technique, a part can be produced faster and cheaper with an accuracy comparable to that of CNC machining.     

A comparative dielectric relaxation study of PMN–PT and PMN–PZ ceramics using impedance spectroscopy

AC-impedance spectroscopic studies in the temperature range of 30–400 °C are carried out on solid solutions of lead magnesium niobate (PMN) with lead titanate (PT) and lead zirconate (PZ), both of them in the 65/35 atomic ratio. For PMN–PT this corresponds to the morphotropic phase boundary composition (with normal ferroelectric behaviour), and for PMN–PZ it is near the phase boundary between normal ferroelectric and relaxor ferroelectric compositions. The variation of dielectric permittivity with temperature at different frequencies shows normal ferroelectric and relaxor-like dependence for PMN–PT and PMN–PZ, respectively. Temperature-dependent spectroscopic modulus plots reveal a much broader peak for PMN–PZ compared to that for PMN–PT, which is consistent with the dielectric behaviour. PMN–PT shows nearly ideal Debye behaviour below T_m (the temperature of the permittivity maximum) and the behaviour departs from ideality above T_m, whereas non-ideal Debye behaviour is seen both below and above T_m for PMN–PZ. Complex modulus plots fit well with two depressed semicircles and three depressed semicircles, respectively, for PMN–PT and PMN–PZ. The relaxation observed in the spectroscopic plots around 1 MHz for PMN–PT has been assigned to polarisation relaxation expected for normal-sized domains. No such relaxation could be observed for PMN–PZ around 1 MHz because of the mesoscopic domain sizes.     

Auto-Discovering Configurations for Service Management

Determining service configurations is essential for effective service management. In this paper we describe a model-driven approach for service configuration auto-discovery. We develop metrics for performance and scalability analysis of such auto-discovery mechanisms. Our approach addresses several problems in auto-discovery: specification of what services to discover, how to efficiently distribute service discovery, and how to match instances of services into related groups. We use object-oriented models for discovery specifications, a flexible bus-based architecture for distribution and communication, and a novel multi-phased, instance matching approach. We have applied our approach to typical e-commerce services, Enterprise Resource Planning applications, like SAP, and Microsoft Exchange services running on a mixture of Windows and Unix platforms. The main contribution of this work is the flexibility of our models, architecture and algorithms to address discovery of a multitude of services.     

Effect of EGR on the exhaust gas temperature and exhaust opacity in compression ignition engines

In diesel engines, NOx formation is a highly temperature-dependent phenomenon and takes place when the temperature in the combustion chamber exceeds 2000 K. Therefore, in order to reduce NOx emissions in the exhaust, it is necessary to keep peak combustion temperatures under control. One simple way of reducing the NOx emission of a diesel engine is by late injection of fuel into the combustion chamber. This technique is effective but increases fuel consumption by 10–15%, which necessitates the use of more effective NOx reduction techniques like exhaust gas recirculation (EGR). Re-circulating part of the exhaust gas helps in reducing NOx, but appreciable paniculate emissions are observed at high loads, hence there is a trade-off between NOx and smoke emission. To get maximum benefit from this trade-off, a paniculate trap may be used to reduce the amount of unburnt particulates in EGR, which in turn reduce the paniculate emission also. An experimental investigation was conducted to observe the effect of exhaust gas re-circulation on the exhaust gas temperatures and exhaust opacity. The experimental setup for the proposed experiments was developed on a two-cylinder, direct injection, air-cooled, compression ignition engine. A matrix of experiments was conducted for observing the effect of different quantities of EGR on exhaust gas temperatures and opacity     

An interactive method for extracting grammar from programs

The grammar of the language in which some given code is written is essential for developing automated tools for maintenance, reengineering, and program analysis. Frequently grammar is available for a language but not for its variants that are implemented by various vendors and in which the given code may be written. In this work we address the problem of obtaining the grammar from source code, which can then be used for generating tools for the programs. We propose an incremental method for obtaining grammar for a particular language variant, from a set of programs written in the language variant and an approximate grammar (presumably of the standard language) with some user interaction. We also present the design of a tool for implementing this approach and our experience in working with grammars of C, C++ and COBOL. Copyright © 2004 John Wiley & Sons, Ltd.     

Note: Compact high voltage pulse transformer made using a capacitor bank assembled in the shape of primary

The experimental results of an air-core pulse transformer are presented, which is very compact (<10 Kg in weight) and is primed by a capacitor bank that is fabricated in such a way that the capacitor bank with its switch takes the shape of single-turn rectangular shaped primary of the transformer. A high voltage capacitor assembly (pulse-forming-line capacitor, PFL) of 5.1 nF is connected with the secondary of transformer. The transformer output voltage is 160 kV in its second peak appearing in less than 2 μS from the beginning of the capacitor discharge. The primary capacitor bank can be charged up to a maximum of 18 kV, with the voltage delivery of 360 kV in similar capacitive loads.     

Structural,optical and electrical properties of silicon nanocrystals embedded in SixC1−x/SiC multilayer systems for photovoltaic applications

In this work we present a structural, optical and electrical characterization of Si_xC_1?x/SiC multilayer systems with different silicon content. After the deposition process, an annealing treatment was carried out in order to induce the silicon nanocrystals formation. By means of energy-filtered transmission electron microscopy (EFTEM) we observed the structural morphology of the multilayers and the presence of crystallized silicon nanoprecipitates for samples annealed up to 1100 °C. We discuss the suitability of optical techniques such as Raman scattering and reflectance and transmittance (R&T) for the evaluation of the crystalline fraction of our samples at different silicon excess ranges. In addition, the combination of R&T measurements with simulation has proved to be a useful instrument to confirm the structural properties observed by EFTEM. Finally, we explore the origin of the extremely high current density revealed by electrical measurements, probably due to the presence of an undesired defective SiC_yO_z ternary compound layer, already supported by the structural and optical results. Nevertheless, the variation of the electrical measurements with the silicon amount indicates a small but significant contribution from the multilayers.