Configuration-based compliance control of kinematically redundant robot arm Part II: Experimental validation

U okviru ovog rada koji se sastoji iz dva dela, prikazuje se novi pristup upravljanja popustljivošću vrha robota, odnosno elastomehaničkom interakcijom vrha robota i njegovog okruženja, primenom kinematske redundanse umesto aktuacione. U prvom delu ovaj pristup je prikazan kroz koncipiranje metode upravljanja krutošću promenom konfiguracije - Configuration-based Stiffness Control (CSC), za slučaj kinetosatičke konzistentnosti, primenom projekcije gradijenta optimizacione funkcije koja minimizira Euklidovu normu nedijagonalnih elemenata matrice krutosti robota izražene u unutrašnjim koordinatama. U drugom delu predložena metoda upravljanja popustljivošću je testirana simulacionim eksperimentima, koristeći kao simulacionu platformu dva posebna slučaja najjednostavnijih kinematski redundantnih robotskih ruku: Slučaj 1 - eksperimenti sa jednodimenzionim radnim prostorom (m = 1) i minimalno mogućom redundansom, r = (n - m) = 1, i Slučaj 2 - eksperimenti sa jednodimenzionim radnim prostorom (m = 1) i minimalno mogućom hiperredundansom, r = 2 i r > m. U oba slučaja singulariteti i ograničenja u opsezima pokretljivosti zglobova nisu razmatrani.This two-part paper presents an approach to the control of robot endpoint compliance, i.e., elasto-mechanical interaction between a robot and its environment using kinematic redundancy instead of actuation redundancy. In Part I this approach is developed by proposing the Configuration-based Stiffness Control (CSC) method for kinetostatically consistent control of robot compliant behaviour, based on the gradient projection of the cost function which minimizes the norm of off-diagonal elements of the jointspace matrix. In Part II validity of the proposed compliance control method is tested by simulation experiments using as a simulation platform two specific cases of most simple kinematically redundant robot arms: Case 1 - experiments with onedimensional taskspace (m=1) and minimal possible redundancy, r = (n - m) = 1, and Case 2 - experiments with onedimensional taskspace (m=1) and minimal possible hyper-redundancy, r = 2 and r > m. In both cases the singularity and joint limits were not considered

Compliant behaviour of redundant robot arm: Experiments with null-space

This paper presents theoretical and experimental aspects of Jacobian nullspace use in kinematically redundant robots for achieving kinetostatically consistent control of their compliant behavior. When the stiffness of the robot endpoint is dominantly influenced by the compliance of the robot joints, generalized stiffness matrix can be mapped into joint space using appropriate congruent transformation. Actuation stiffness matrix achieved by this transformation is generally nondiagonal. Off-diagonal elements of the actuation matrix can be generated by redundant actuation only (polyarticular actuators), but such kind of actuation is very difficult to realize practically in technical systems. The approach of solving this problem which is proposed in this paper is based on the use of kinematic redundancy and nullspace of the Jacobian matrix. Evaluation of the developed analytical model was done numerically by a minimal redundant robot with one redundant d.o.f. and experimentally by a 7 d.o.f. Yaskawa SIA 10F robot arm

The photoelectrochemical cell with hydrogen accumulation at the conditions of natural insolation

The film photoanodes based on CdSe and NT-TiO2/CdSe have been formed by the electrochemical and painting methods. It is shown that the introduction of graphene oxide into the structure of the semiconductor CdSe film promotes absorption of light and leads to improvement in their characteristics by 25-30 %. The compatibility of the cathode based on composite of hydrogen-sorbing intermetallic alloys LaNi4.5Mn0.5 + LaNi3.5Al0.7Mn0.8 with current-conductive additives in pair with the CdSe photoanode is shown. It was found that 95 – 98 % of the total current generated under the influence of sunlight at the anodes was used on the formation and accumulation of hydrogen by cathodes

Analytical and finite element modeling in the calculation and design of reinforcements of stretched elements by fiber-reinforced polymers based on high-strength fiber using adhesive joints

Subject . Analysis of applicability and effectiveness of various complexity level models in design of reinforcement of stretch elements by gluing on their surface high-strength fiber reinforced polymers (HSFRP). Research objectives. Determine the necessary level of complexity of the calculation model based on the comparison of calculation results obtained on models of various complexity within the elastic behavior of the reinforced element and analysis of features of its elastoplastic behavior in case of its overload. Materials and methods. Few relatively simple variants of HSFRP-reinforcement structures with application of four Finite Element Method (FEM) simulation models of varying complexity and an analytic approach. Plane and spatial Finite Element (FE) models with PC LIRA (SCAD) and FEMAP (NASTRAN) apply in considered series of numerical experiments. Comparative analysis of results of elastic FEM calculation based on various FE models with the results obtained using analytical expressions. A number of diagrams and tables represent the results of calculations. Nonlinear FEM analysis reveals some features of the reinforced elements response under extreme loads. Results. The effect of various factors on the bonded joint behavior observed, the equations and formulae for the analysis and design are applied, the analytical approach based numerical results well correspond with those obtained using FEM. A number of nonlinear FEM calculations discover some features of elastic-plastic response of joints. Conclusions. All the considered here FE models within the limits of elastic design are quite compatible mutually and with an approximate analytical approach as well. The least timeand effort-expensive for the stage of preliminary assessment of the various parameters effect on the glued joint behavior in the elastic design of the stretched elements reinforcement is an analytical approach allowing instantaneously obtain the resulting main components of stresses and forces in the components of joint to scroll through parameter values. FEM simulation for elastic calculation is expedient for verification of results. The simplified plain FEM simulation seems to be quite reliable here. In inelastic state of the reinforced element material yet, the features of its stress-strain distribution not observable in the elastic stage of its loading and requiring special attention and refined FEM simulation may dominate

FESOM_coastal

There is a growing need in the high quality estimations of long-term dynamics and circulation features in the coastal areas to answer major present and future societal, ecosystem and other questions, because of changing climate. On long time scales, the coastal dynamics change not only because of variable forcing, but also due to exchanges with the evolving global ocean. Over recent years, considerable efforts have been invested into developing regional models and applying them to the coastal areas. These models are used by different institutions to study currents, sediment transport and ecosystem dynamics. They are well-established tools equipped with necessary parameterizations and modules that may be required in shelf or coastal modeling. However, they are regional models with open boundaries. When it comes to applying them to study long-term trends and variability in the regional sea, they have to be coupled to a large-scale modeling system. However, numerical algorithms used by global models can be insufficient to simulate coastal dynamics. There are issues related to vertical advection and mixing, stability in case of very thin sigma layers, absence of wetting/drying option etc. One more point is the choice of time step in case of highly varying resolution. Coastal refinement can be added to the global models, but at the same time they will lose efficiency. Unstructured-mesh coastal models are too dissipative and expensive to simulate global circulation at present. A way out of this situation is coupling global and coastal models (one or two ways nesting). To reach this goal we present a coastal branch of the global model FESOM (Danilov et al. 2004, Wang et al. 2014). FESOM is a well-established large-scale ocean circulation model which is tested in numerous applications and participates in ocean model intercomparison project (see CORE-II virtual special issue of Ocean Modelling). It is the first model worldwide which provides multi-resolution functionality to large-scale ocean modeling, allowing one to bridge the gap between the scales and has the finite volume version at the current stage. FESOM_coastal treats the input/output characteristics in the same manner and share partly physical core with the global solution. It supports full coastal functionality, has cell-vortex finite volume discretization and works on any configurations of triangular, quadrangular or hybrid meshes

Evaluation and Application of Newly Designed Finite Volume Coastal Model FESOM-C, Effect of Variable Resolution in the Southeastern North Sea

A newly developed coastal model, FESOM-C, based on three-dimensional unstructured meshes and finite volume, is applied to simulate the dynamics of the southeastern North Sea. Variable horizontal resolution enables coarse meshes in the open sea with refined meshes in shallow areas including the Wadden Sea and estuaries to resolve important small-scale processes such as wetting and drying, sub-mesoscale eddies, and the dynamics of steep coastal fronts. Model results for a simulation of the period from January 2010 to December 2014 agree reasonably well with data from numerous regional autonomous observation stations with high temporal and spatial resolutions, as well as with data from FerryBoxes and glider expeditions. Analyzing numerical solution convergence on meshes of different horizontal resolutions allows us to identify areas where high mesh resolution (wetting and drying zones and shallow areas) and low mesh resolution (open boundary, open sea, and deep regions) are optimal for numerical simulations

Механистичка идентификација модела силе при ортогоналном резању

У раду је описана идентификација параметара модела сила при ортогоналном резању рендисањем, уз примену двокомпонентног динамометра са мерним тракама за мерење сила. За мерење попречне и уздужне компоненте силе резања, мерне траке су постављене на осам места на полупрстену тела сензора. Сигнали силе резања су снимљени коришћењем модула за аквизицију и обрађивани помоћу MATLAB софтверског пакета. Резултати добијени при различитим параметрима резања (променљива дубина резања и променљива ширина резања) показују да се динамометар може користити за поуздано мерење сила при обради резањем, док експериментална верификација показује да се идентификовани модел може користити за предикцију сила при различитим обрадама резањем, уз задржавање исте геометрије алата и истог материјала обратка.The paper describes the identification of model parameters of cutting forces during orthogonal cutting, using a two-component dynamometer with strain gauges to measure force. For measuring radial and extensive components of cutting force, strain gauges were installed at eight positions on the body of the ring sensor. Cutting force signals are recorded using a data acquisition module and processed by MATLAB software package. The results obtained under different cutting parameters (variable cutting depth and variable cutting width) show that the dynamometer can be used for reliable measurements of the cutting forces, and experimental verification shows that the identified model can be used to predict the forces under different types of machining, maintaining the same tool geometry and the same workpiece material