Minimum effort factor approach for sensor-based control of a four-joint 6-dof redundant manipulator

A sensor-driven control model and a minimum effort control algorithm in terms of time and energy expended during the execution of a movement strategy are described and validated for a multijointed cooperating robotic manipulator. Considering smooth, human-like (anthropomorphic) movements, using joint motion profiles achievable in real time as well as sensory information from all joints, and evaluating the total work expended by each manipulator joint during the execution of a movement strategy, a minimum effort motion trajectory is synthesized to precisely and efficiently position the robotic arm end-effector. This sensor-based approach significantly reduces the computational requirements for such cooperative motion. The minimum effort control algorithm generates several human-like arm movement strategies and selects the best strategy on the basis of expendable effort. The algorithm has an inherent basis to deal with obstacles in an efficient way. Detailed examples are described from the simulation studies. © 1994 John Wiley & Sons, Inc.     

Effective-capacity-based stochastic delay guarantees for systems with time-varying servers, with an application to IEEE 802.11 WLANs

Many network applications rely on stochastic QoS guarantees. With respect to loss-related performance, the effective bandwidth/capacity theory has proved useful for calculating loss probabilities in queues with complex input and server processes and for formulating simple admission control tests to ensure associated QoS guarantees. This success has motivated the application of the theory for delay-related QoS too. However, up until now this application has been justified only heuristically for queues with variable service rate. The paper fills this gap by establishing rigorously that the effective bandwidth/capacity theory may be used for the asymptotically correct calculation and enforcement of delay tail-probabilities in systems with variable rate servers too. Subsequently, the paper applies the general results to IEEE 802.11 WLANs, by representing each IEEE 802.11 station as an On/Off server and employing the effective capacity function for this model. Comparison of analytical results with simulation validates the effectiveness of the On/Off IEEE 802.11 model for delay-related QoS, complementing earlier results on loss-related performance.     

Modular Reconfigurable Robots in Space Applications

Robots used for tasks in space have strict requirements. Modular reconfigurable robots have a variety of attributes that are well suited to these conditions, including: serving as many different tools at once (saving weight), packing into compressed forms (saving space) and having high levels of redundancy (increasing robustness). In addition, self-reconfigurable systems can self-repair and adapt to changing or unanticipated conditions. This paper will describe such a self-reconfigurable modular robot: PolyBot. PolyBot has significant potential in the space manipulation and surface mobility class of applications for space.     

Relations between environmental black carbon sorption and geochemical sorbent characteristics

Pyrogenic carbon particles in sediments (soot and charcoal, collectively termed "black carbon" or BC) appear to be efficient sorbents of many hydrophobic organic compounds, so they may play an important role in the fate and toxicity of these substances. To properly model toxicant sorption behavior, it is important to (i) quantify the magnitude of the role of BC in sorption and (ii) elucidate which geochemical BC characteristics determine the strength of environmental BC sorption. Sorption isotherms of d10-phenanthrene (d10-PHE) were determined over a wide concentration range (0.0003-20 microg/L), for five sediments with widely varying characteristics. From the sorption isotherms, we determined Freundlich coefficients of environmental BC sorption, K(F,BCenv. These varied from 10(4.7) to 10(5.5). From the data, it could be deduced that BC was responsible for 49-85% of the total d10-PHE sorption at a concentration of 1 ng/L. At higher concentrations, the importance of BC for the sorption process diminished to <20% at 1 microg/L and 0-1% at 1 mg/L. There were no significant relationships between BC sorption strength and the tested geochemical BC characteristics [the fraction of small (<38 microm) BC particles, the BC resistance to high-temperature oxidation, the fraction of biomass-derived BC, the native polycyclic aromatic hydrocarbon and total organic carbon contents]. Because of the limited variation in BC sorption strength with widely varying BC characteristics, the presented BC sorption coefficients may putatively be used as generic starting points for environmental modeling purposes.