Kinematic Modeling and Analysis of a Walking Machine (Robot) Leg Mechanism on a Rough Terrain

Many manmade machines and mechanisms including robots function based on the concept of nature-inspired design so that they can perform their intended duties by mimicking the working mechanisms of animals and insects. Accordingly, walking machines (robots) use wheels and tracks to cross rough terrain efficiently and in a stable way than more conventional robots. Legged walking robots in particular get a discontinuous contact with the ground that provides them the capability to select tractions such that obstacles or holes are escaped. This article reports a study conducted on kinematic modelling and analysis of a walking machine (robot) leg mechanism that can operate on rough terrain. Its kinematic mechanisms is analyzed using the Denavit-Hartenberg (DH) convention approach. Symbolic computations are also implemented to parametrically optimize the motion parameters of the robot leg mechanism. The equation of motion is derived from the dynamic analysis using the Euler-Lagrange method which involves kinetic and potential energy expressions. In order to validate the performance of the robot leg mechanism and motion behaviors, kinematic motion analysis in SolidWorks and MATLAB are used. The leg mechanism used is effective for rough terrain areas because it is capable of walking on terrain with different amplitudes due to surface toughness and aerodynamics.publishedVersio

Longitudinal river zonation in the tropics: examples of fish and caddisflies from endorheic Awash river, Ethiopia

Primary Research PaperSpecific concepts of fluvial ecology are well studied in riverine ecosystems of the temperate zone but poorly investigated in the Afrotropical region. Hence, we examined the longitudinal zonation of fish and adult caddisfly (Trichoptera) assemblages in the endorheic Awash River (1,250 km in length), Ethiopia. We expected that species assemblages are structured along environmental gradients, reflecting the pattern of large-scale freshwater ecoregions. We applied multivariate statistical methods to test for differences in spatial species assemblage structure and identified characteristic taxa of the observed biocoenoses by indicator species analyses. Fish and caddisfly assemblages were clustered into highland and lowland communities, following the freshwater ecoregions, but separated by an ecotone with highest biodiversity. Moreover, the caddisfly results suggest separating the heterogeneous highlands into a forested and a deforested zone. Surprisingly, the Awash drainage is rather species-poor: only 11 fish (1 endemic, 2 introduced) and 28 caddisfly species (8 new records for Ethiopia) were recorded from the mainstem and its major tributaries. Nevertheless, specialized species characterize the highland forests, whereas the lowlands primarily host geographically widely distributed species. This study showed that a combined approach of fish and caddisflies is a suitable method for assessing regional characteristics of fluvial ecosystems in the tropicsinfo:eu-repo/semantics/publishedVersio