Stable path planning for reconfigurable robots over uneven terrains

University of Technology Sydney. Faculty of Engineering and Information Technology.Autonomous mobile robots are required to find safe and feasible routes in the environment when operating over challenging terrains. The most influential tip-over stability measures are based on two criteria; the robot’s centre of mass (CM) and the support polygon defined by the convex area spanned between the ground contact points. The force angle (FA) stability margin is employed in this work given its widespread use and simple geometric interpretation. A method to compute the contact points between a tracked robot and rugged terrain and predict robot’s stability axes on 3D meshed maps reconstructed from 3D point clouds using the open dynamics engine (ODE) is presented. The validity and the need for stability computations based on the proposed contact points prediction algorithm is established through experiments over two common indoor obstacles i.e. ramps and stairs. An analytical strategy to generate stable paths for reconfigurable robots whilst also meeting additional navigational objectives is hereby proposed. The suggested solution looks at minimizing the length of the traversed path and the energy expenditure in changing postures, and also accounts for additional constraints in terms of sensor visibility and traction. A statistical analysis of stability prediction to account for the uncertainties associated with the actual robot’s dynamic model, its localisation in the ground, and the terrain models is introduced. Probability density function (PDF) of contact points, CM and the FA stability measure are numerically estimated, with simulation results performed on the ODE simulator based on uncertain parameters. Two techniques are presented: a conventional standard Monte Carlo (SMC) scheme, and a structured unscented transform (UT) which results in significant improvement in computational efficiency. A novel probabilistic stability criterion derived from the cumulative distribution of the FA margin is introduced that allows a safety constraint to be dynamically updated by available sensor data as it becomes available. The advantages of planning with probabilistic stability is demonstrated using a grid based A* algorithm as well as a sampling based RRT planner. The validity of the proposed approach is evaluated with a multi-tracked robot fitted with a manipulator arm and a range camera using two challenging 3D terrains data sets: one obtained whilst operating the robot in a mock-up urban search and rescue arena, and a second one from a publicly available on-line data from a quasi-outdoor rover testing facility

Application of microsatellite markers to study the genetic structure of stellate sturgeon populations (Acipenser stellatus Pallas, 1771) in the south Caspian Sea

Population genetic structure of stellate sturgeon (Acipenser stellatus) in 197 adult specimens from four fishery regions along the Iranian coastline of the southern Caspian Sea was investigated using microsatellite markers. Out of 15 microsatellite primers, 11 loci were produced, in which 10 of them were polymorphic and 1 was monomorph. Totally, 184 alleles were identified and on average 13.1 alleles per locus were found (ranged 8 to 18 alleles). All sampled regions contained unique alleles. Average observed and expected heterozygosity was 0.667 and 0.854, respectively and significant genetic differences between 4 regions were observed (p≤0.01). Deviations from Hardy-Weinberg equilibrium were found in most cases. Population differentiation test was modest and significant (p≤0.01). Based on FST estimate (p≤0.01), more than one population of stellate sturgeon is identified in the south Caspian Sea. Therefore, fishery management for restocking and conservation of gene pool is highly recommended

Cross-species amplification of Clupeidae microsatellite DNA markers in common kilka, Clupeonella cultriventris from the Caspian Sea

Common kilka Clupeonella cultriventris (Nordmann, 1840) is a brackish water and small pelagic fish species and is one of the most abundant fishes that live gregariously in the Caspian Sea. A total of 60 specimens of adult common kilka were sampled from two seasons. Fifteen pairs of microsatellites previously developed for A. sapidissima, C. pallasi, C. harengus, and S. pilchardus were tested for cross-species amplification on the common kilka. In this study, only five primer pairs were used successfully. Analyses revealed that the average of alleles per locus was 14.4. The average observed and expected heterozygosity was 0.153 and 0.888, respectively. All loci significantly deviated from H–W equilibrium. These results together with significant Rst. values for genotypic differences support the existence of different genetic populations along the Caspian Sea coast (Guilan Province)

Exact analysis of heat convection in viscoelastic FENE-P fluids through isothermal slits and tubes

In this article, two exact analytical solutions for heat convection in viscoelastic fluid flow through isothermal tubes and slits are presented for the first time. Herein, a Peterlin type of finitely extensible nonlinear elastic (FENE-P) model is used as the nonlinear constitutive equation for the viscoelastic fluid. Due to the eigenvalue form of the heat transfer equation, the modal analysis technique has been used to determine the physical temperature distributions. The closed form solution for the temperature profile is obtained in terms of a Heun Tri-confluent function for slit flow and then the Frobenius method is used to evaluate the temperature distribution for the tube flow. Based on these solutions, the effects of extensibility parameter and Deborah number on thermal convection in FENE-P fluid flow have been studied in detail. The fractional correlations for reduced Nusselt number in terms of material modulus are also derived. Here, it is shown that by increasing the Deborah number from 0 to 100, the Nusselt number is enhanced by 8.5% and 13.5% for slit and tube flow, respectively

A statistical approach for uncertain stability analysis of mobile robots

Stability prediction is an important concern for mobile robots operating in rough environments. Having the capacity to predict areas of instability means pro-actively being able to plan safer traversable paths. The most influential tip-over stability measures are based on two criteria, the robot's center of mass (CM) and the supporting polygon (SP) defined by the convex area spanned between the ground contact-points. However, there is significant uncertainty associated with many parameters in the planning pipe-line: the actual robot kino-dynamic model, its localisation in the ground, and the terrain models, particularly in uneven terrain. This article proposes a statistical analysis of stability prediction to account for some of the uncertainties. This is accomplished using the force angle (FA) stability measure for a reconfigurable multi-tracked vehicle fitted with flippers, a manipulator arm and a sensor head. Probability density function (PDF) of contact-points, CM and the FA stability measure are numerically estimated, with simulation results performed on the open dynamics engine (ODE) simulator based on uncertain parameters. Two techniques are presented: a conventional Monte Carlo scheme, and a structured unscented transform (UT) which results in significant improvement in computational efficiency. Experimental results on maps obtained from a range camera fitted on the sensor head while the robot traverses over a ramp and a series of steps are presented that confirms the validity of the proposed probabilistic stability prediction method. © 2013 IEEE

Morphometric and meristic variations in bream (Abramis brama orientalis, Berg, 1949) during larval development

This study was conducted to examine morphometric and meristic characteristics alongside pigmentation patterns of bream larvae, Abramis brama orientalis, in four stages of larval development. Morphological characters including total length (TL), standard length (SL), notochord length (NL), head length (HL), head depth (HD), eye diameter (ED) and mouth width (MW) were examined from hatching time through 30 days after hatching (DAH). The results showed morphometric variations in the different larval stages. Growth and development of fins occurred mainly at the Post Flexion stage with the completion of caudal fin at 9 mm TL and pelvic fin at 13.33 mm TL. At all larval stages, the highest concentration of pigments was seen on dorsal, ventral and somewhat on the lateral sides of body in descending order. The highest density of melanophores at larvae yolk sac stage was observed on the yolk sac and the back of head zone, while at preflexion and flexion stages melanophores were dominant on the back of head and on the skin folds which resulted from yolk absorption. At post flexion stage, high density of melanophores was found on the back of the head, bases of fins and caudal fin, while less concentrations of these cells were evident on the lateral sides of fish' body. In conclusion, a clear change in the growth and main morphological characters were observed in postflexion stage. This may be due to the main development of fins, which would suggest enhanced swimming capabilities and also prey capture efficiencies

The effect of adding gentamicin to contrast media for prevention of cholangitis after biliary stenting for non-calculous biliary obstruction, a randomized controlled trial

Aim: Cholangitis is the most common infectious complication of ERCP. In vitro studies showed that addition of aminoglycosides to contrast medium was effective in reducing cholangitis but the results of clinical trials are conflicting. We studied the effect of adding gentamicin to contrast medium in reducing the rate of post-ERCP cholangitis in patients with non-calculous obstructive jaundice. Methods: All patients with non-calculous obstructive jaundice who underwent endoscopic biliary stenting at the Shariati Hospital, Tehran, between December 2009 and October 2010 were enrolled in the study. Gentamicin (10 mg) or distilled water was added to each 10 cc contrast medium during ERCP. Intravenous antibiotics were administered before and after the procedure in all patients. After ERCP and stent deployment, patients were followed for 72 h for symptoms and signs of cholangitis. Results: A total of 114 patients were eligible for the study. Of these, 57 patients were included in each group. Cholangiocarcinoma was the most prevalent diagnosis. The obstruction was relieved in all patients by stenting. Five patients in each group (8. 8 %) developed cholangitis. There was no significant difference in the incidence of cholangitis between the two groups (p = 1. 000). Conclusions: With adequate drainage of the obstructed biliary tract by proper stenting, adding gentamicin to contrast media had no significant effect on incidence of post-ERCP cholangitis. © 2012 Indian Society of Gastroenterology

Effects of viscous dissipation on miscible thermo-viscous fingering instability in porous media

The thermo-viscous fingering instability associated with miscible displacement through a porous medium is studied numerically, motivated by applications in upstream oil industries especially enhanced oil recovery (EOR) via wells using hot water flooding and steam flooding. The main innovative aspect of this study is the inclusion of the effects of viscous dissipation on thermal viscous fingering instability. An Arrhenius equation of state is employed for describing the dependency of viscosity on temperature. The normalized conservation equations are solved with the finite element computational fluid dynamics code, COMSOL (Version 5) in which glycerol is considered as the solute and water as the solvent and the two-phase Darcy model employed (which couples the study Darcy flow equation with the time-dependent convection-diffusion equation for the concentration). The progress of finger patterns is studied using concentration and temperature contours, transversely averaged profiles, mixing length and sweep efficiency. The sweep efficiency is a property widely used in industry to characterize how effective is displacement and it can be defined as the ratio of the volume of displaced fluid to the total volume of available fluid in a porous medium in the displacement process. The effects of Lewis number, Brinkman number and thermal lag coefficient on this instability are examined in detail. The results indicate that increasing viscous dissipation generates significant enhancement in the temperature and a marked reduction in viscosity especially in the displaced fluid (high viscous phase). Therefore, the mobility ratio is reduced, and the flow becomes more stable in the presence of viscous dissipation

Effects of Zataria multiflora and Eucalyptus globolus essential oils on haematological parameters and respiratory burst activity in Cyprinus carpio

The present study was undertaken to investigate the effects of Zataria multiflora and Eucalyptus globolus essential oils on some haematological parameters and respiratory burst activity in common carp (Cyprinus carpio). 260 fish (30±5g) were randomly distributed in 13 treatment groups; each one in three replicates and different doses of essential oils in 16-17ºC were administrated. The fish were sampled on day 1, 2, 8, 15 and 22 after the 8-day trial. Haematological parameters (red blood cell count, haematocrit) and respiratory burst activity were then evaluated in all treatment groups. The results suggest that essential oils especially Zataria multiflora in dietary intake significantly enhanced respiratory burst activity of blood neutrophlis (P< 0.05). Meanwhile, essential oils had moderate effects on RBC and haematocrit. Significant increases in RBC and haematocrit levels were just noted in T11 treatment group (P< 0.05). This study indicates that dietary administration of Zataria multiflora and Eucalyptus globolus essential oils could be used to promote the health status of common carp during temperature stress