Exploiting Passive Stability for Hierarchical Control

The dynamics of a Spring Loaded Inverted Pendulum (SLIP) \template” [1] approximate well the center of mass (COM) of running animals, humans, and of the robot RHex [2]. Running control can therefore be ierarchically structured as a high level SLIP control and the anchoring of SLIP in the complex morphology of the physical system. Analysis of the sagittal plane lossless SLIP model has shown that it includes parameter regions where its gait is passively stabilized, i.e. with the discrete control input | the leg touchdown angle | held constant. We present numerical evidence to suggest that an open loop \clock” excitation of a high degree of freedom hexapedal robot model can lead to asymptotically stable limit cycles that \anchor” [1] the SLIP model in its self stabilizing regime. This motivates the search for completely feedforward SLIP locomotion control strategies, which we now speculate may be successfully used to elicit a self-stabilizing running robot such as RHex. For more information: Kod*La

A simply stabilized running model

Abstract. The spring-loaded inverted pendulum (SLIP), or monopedal hopper, is an archetypal model for running in numerous animal species. Although locomotion is generally considered a complex task requiring sophisticated control strategies to account for coordination and stability, we show that stable gaits can be found in the SLIP with both linear and “air ” springs, controlled by a simple fixed-leg reset policy. We first derive touchdown-to-touchdown Poincaré maps under the common assumption of negligible gravitational effects during the stance phase. We subsequently include and assess these effects and briefly consider coupling to pitching motions. We investigate the domains of attraction of symmetric periodic gaits and bifurcations from the branches of stable gaits in terms of nondimensional parameters

Microbiological and plant engineering aspects of phosphate biological removal

Biological models and microbial populations involved in phosphate removal from wastewater are reviewed and compared

The Tyre-Soil Effects on the Manoeuvrability of a City-Car

Eco-compatibility aims at drastic changes of people transportation means and, to grant proper mobility levels, the electrically-powered city-car concept provides effective solutions. This quite obviously leads to distributed actuation, with separately driven wheels and inconsistencies appear unless redundancy and tyre/road interaction are properly mastered. The paper deals with the dynamics of such kind of vehicle moving from the behaviour of driven wheels (with compliant tyre and varying soil interactions); then a twin powered axle or train are investigated, as basic reference to describe the dynamics of a four wheels platform, driven by redundant actuation on varying friction soils. On these premises, a city car manoeuvre stability can be stated for low speed tasks over urban roads. Results are obtained, after modelling the wheel dynamics, with resort to computer simulation, based on the SIMULINK package; the kinematics constraints are introduced and the varying tyre-soil coupling conditions are relate d with the driving torque options

PHOSPHORUS REMOVAL IN FLUIDIZED-BED BIOLOGICAL REACTOR (FBBR)

The biological phosphorus removal in fluidized bed biological reactor (FBBR) has been investigated. The feasibility of excess phosphorus uptake, assured by exposition of biomass to anaerobic-aerobic conditions, has been demonstrated on a bench-scale biofilm reactor working as sequencing batch reactor (SBR) and the limiting parameters have been established. Although the reactor worked effectively, it took several weeks for both acclimatization of biomass and selection of a biofilm rich in poly-P-bacteria. The highest phosphate uptake rates have been observed when strict anaerobic conditions were reached during the anaerobic phase. Using a fluidized bed, a thin biofilm, characterized by high surface/volume ratio and hence highly disposed towards substrate uptake, has been obtained and the overall phosphorus abatement, referred to the biomass present in the reactor, proved particularly effective

Italian standards for the design and construction of maritime structures

Three Italian Standards for port and coastal structure design and construction are here presented. The first refers to the design and construction of the defence structures of the erosive beaches, second to design and construction of the maritime dikes, third to the design and construction of the big cranes and handling machines in the port areas

Restricted Urban Traffic Guidance of District-Dispatchers with Four Powered Wheels

n° 3/4 Marzo-April

Phosphorus removal in fluidized bed biological reactor (FBBR)

The biological phosphorus removal in fluidized bed biological reactor (FBBR) has been investigated. The feasibility of excess phosphorus uptake, assured by exposition of biomass to anaerobic-aerobic conditions, has been demonstrated on a bench-scale biofilm reactor working as sequencing batch reactor (SBR) and the limiting parameters have been established