1,218 research outputs found

    An inverse kinematics algorithm for a highly redundant variable-geometry-truss manipulator

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    A new class of robotic arm consists of a periodic sequence of truss substructures, each of which has several variable-length members. Such variable-geometry-truss manipulator (VGTMs) are inherently highly redundant and promise a significant increase in dexterity over conventional anthropomorphic manipulators. This dexterity may be exploited for both obstacle avoidance and controlled deployment in complex workspaces. The inverse kinematics problem for such unorthodox manipulators, however, becomes complex because of the large number of degrees of freedom, and conventional solutions to the inverse kinematics problem become inefficient because of the high degree of redundancy. A solution is presented to this problem based on a spline-like reference curve for the manipulator's shape. Such an approach has a number of advantages: (1) direct, intuitive manipulation of shape; (2) reduced calculation time; and (3) direct control over the effective degree of redundancy of the manipulator. Furthermore, although the algorithm was developed primarily for variable-geometry-truss manipulators, it is general enough for application to a number of manipulator designs

    Mechanics of human locomotor system

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    (Bio)mehanički modeli ljudskog tela su važna oruđa u razumevanju osnovnih principa čovekovog pokreta i koordinacije, pri čemu,istovremeno modeli imaju široku primenu za industrijske, naučne i medicinske svrhe. U ovom radu su predstavljeni i razmatrani (bio)mehanički modeli ljudske ruke (7 SS), gornjeg dela tela i desne ruke (15 SS) i noge (2 SS).Takođe je prikazan jedan (bio)mehanički model celog ljudskog tela.Na kraju je sprovedena simulacija ravanskog mehaničkog modela ruke (5SS) u zadatku pisanja u MATLAB okruženju.(Bio)mechanical models of human body are important tools in understanding the functional principles of human movement and coordination as well as they have widespread applications for the industrial, scientific and medical purposes. In this paper (bio)mechanical models of the upper human limb (arm, forearm and hand, 7 degree-of- freedoms ( DOFs)), upper torso and right arm (15 DOFs) and of the leg with (2DOFs) are presented, where model of upper human limb is discussed in detail. Also, multi-chain (bio)mechanical model of a human body anthropomorphic locomotion configuration, is introduced. At last, simulations in MATLAB environment are performed and the results of kinematical and dynamical model of an anthropomorphic arm (5 DOFs) in the task of writing are presented

    Optimal control of redundant robots in human-like fashion

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    U ovom radu je predložen jedan novi vid upravljanja redundantnim robotskim sistemom. To je ostvareno primenom pogodnog kinematičkog i dinamičkog kriterijuma zasnovanim na biološkim principima tj. na načinu koji je sličan i svojstven čoveku. Ovde je dinamički model robotskog sistema dat u formi Langranžeovih jednačina druge vrste u kovarijatnom obliku.Nekoliko kriterijuma je uvedeno koji su funkcija generalisanih koordinata, brzina vektora ubrzanja kao i vektora upravljanja respektivno. Konačno, efikasnost predloženog optimalnog upravljanja na način sličan čoveku je demonstrirana na robotu sa četiri stepena slobode.This paper suggests a new optimal control of a redundant robotic system. It is achieved using suitable kinematic and dynamic criteria based on biological principles, i.e. in human-like fashion. Here, a dynamical model of robotic system is given in the form of Langrange's equations of second kind in covariant form. Several criteria are introduced which are the function of generalized coordinates, velocities, accelerations and control vectors, respectively. Finally, the effectiveness of suggested optimal control in human-like fashion is demonstrated with a robot with four degrees of freedom as the illustrative example

    Optimal control of redundant robots in human-like fashion

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    U ovom radu je predložen jedan novi vid upravljanja redundantnim robotskim sistemom. To je ostvareno primenom pogodnog kinematičkog i dinamičkog kriterijuma zasnovanim na biološkim principima tj. na načinu koji je sličan i svojstven čoveku. Ovde je dinamički model robotskog sistema dat u formi Langranžeovih jednačina druge vrste u kovarijatnom obliku.Nekoliko kriterijuma je uvedeno koji su funkcija generalisanih koordinata, brzina vektora ubrzanja kao i vektora upravljanja respektivno. Konačno, efikasnost predloženog optimalnog upravljanja na način sličan čoveku je demonstrirana na robotu sa četiri stepena slobode.This paper suggests a new optimal control of a redundant robotic system. It is achieved using suitable kinematic and dynamic criteria based on biological principles, i.e. in human-like fashion. Here, a dynamical model of robotic system is given in the form of Langrange's equations of second kind in covariant form. Several criteria are introduced which are the function of generalized coordinates, velocities, accelerations and control vectors, respectively. Finally, the effectiveness of suggested optimal control in human-like fashion is demonstrated with a robot with four degrees of freedom as the illustrative example

    Performance of modified jatropha oil in combination with hexagonal boron nitride particles as a bio-based lubricant for green machining

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    This study evaluates the machining performance of newly developed modified jatropha oils (MJO1, MJO3 and MJO5), both with and without hexagonal boron nitride (hBN) particles (ranging between 0.05 and 0.5 wt%) during turning of AISI 1045 using minimum quantity lubrication (MQL). The experimental results indicated that, viscosity improved with the increase in MJOs molar ratio and hBN concentration. Excellent tribological behaviours is found to correlated with a better machining performance were achieved by MJO5a with 0.05 wt%. The MJO5a sample showed the lowest values of cutting force, cutting temperature and surface roughness, with a prolonged tool life and less tool wear, qualifying itself to be a potential alternative to the synthetic ester, with regard to the environmental concern

    Studies on Trajectory Tracking of Two Link Planar Manipulator

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    In robotic manipulator control situations, high accuracy trajectory tracking is one of the challenging aspects. This is due to nonlinearities in dynamics and input coupling present in the robotic arm. In the present work, a two link planar manipulator revolving in a horizontal plane is considered. Its kinematics, Jacobian analysis, dynamic equations are obtained from modelling. It is proposed to use this manipulator for following a desired trajectory by using an effective control method. Initially, computed torque control scheme is used to obtain the end effector motions. The dynamic equations are solved by numerical method and the joint space results are used to obtain the error and its derivative. This linearized error dynamic control uses constant gains and an attempt is made to obtain a correct set of gains in each error cycle to refine the control performance. A scaled prototype is made with aluminium links and joint servos. A mechatronic system with an arduino microcontroller board is employed to drive the servos in incremental fashion as per the tracking point and its inverse kinematics. The computer results are shown for two trajectories namely a straight line and spline. The errors are reported as a function of time and the corresponding joint torques computed in each time step are plotted. Finally to illustrate the mechatronic control system on the prototype, a path containing three points is considered and corresponding errors and repeatability are presented

    Bio-inspired kinematical control of redundant robotic manipulators

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    Purpose – This paper aims to propose an innovative kinematic control algorithm for redundant robotic manipulators. The algorithm takes advantage of a bio-inspired approach. Design/methodology/approach – A simplified two-degree-of-freedom model is presented to handle kinematic redundancy in the x-y plane; an extension to three-dimensional tracking tasks is presented as well. A set of sample trajectories was used to evaluate the performances of the proposed algorithm. Findings – The results from the simulations confirm the continuity and accuracy of generated joint profiles for given end-effector trajectories as well as algorithm robustness, singularity and self-collision avoidance. Originality/value – This paper shows how to control a redundant robotic arm by applying human upper arm-inspired concept of inter-joint dependency

    A novel closed-form solution for the inverse kinematics of redundant manipulators through workspace analysis

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    © 2017 Elsevier Ltd This work addresses the inverse kinematic problem for redundant serial manipulators. Its importance relies on its effect in the programming and control of redundant robots. Besides, no general closed-form techniques have been developed so far. In this paper, redundant manipulators are reduced to non-redundant ones by selecting a set of joints, denoted redundant joints, and parametrizing its joint variables. This selection is made through a workspace analysis which also provides an upper bound for the number of different closed-form solutions for a given pose. Once these joints have been identified several closed-form methods developed for non-redundant manipulators can be applied for obtaining the analytical solutions. Finally, particular instances for the parametrized joints variables are determined depending on the task to be executed. Different criteria and optimization functions can be defined for that purpose.Peer ReviewedPostprint (author's final draft

    A Bio-Inspired Tensegrity Manipulator with Multi-DOF, Structurally Compliant Joints

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    Most traditional robotic mechanisms feature inelastic joints that are unable to robustly handle large deformations and off-axis moments. As a result, the applied loads are transferred rigidly throughout the entire structure. The disadvantage of this approach is that the exerted leverage is magnified at each subsequent joint possibly damaging the mechanism. In this paper, we present two lightweight, elastic, bio-inspired tensegrity robotics arms which mitigate this danger while improving their mechanism's functionality. Our solutions feature modular tensegrity structures that function similarly to the human elbow and the human shoulder when connected. Like their biological counterparts, the proposed robotic joints are flexible and comply with unanticipated forces. Both proposed structures have multiple passive degrees of freedom and four active degrees of freedom (two from the shoulder and two from the elbow). The structural advantages demonstrated by the joints in these manipulators illustrate a solution to the fundamental issue of elegantly handling off-axis compliance.Comment: IROS 201

    Biologically inspired control and modeling of (bio)robotic systems and some applications of fractional calculus in mechanics

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    U ovom radu, prezentovane su primene biološki inspirisanog modeliranja i upravljanja (bio)mehaničkim (ne)redundantnim mehanizmima, kao i novodobijeni rezultati autora u oblasti primenjene mehanike koji su zasnovani na primeni računa necelobrojnog reda. Prvo, predloženo je korišćenje biološkog analogona-sinergije zahvaljujući postojanju nepromenljivih odlika u izvršavanju funkcionalnih pokreta. Drugo, model (bio)mehaničkog sistema može se dobiti primenom drugog biološkog koncepta poznatim pod nazivom distribuirano pozicioniranje (DP), koji je zasnovan na inercijalnim svojstva i pokretanju zglobova razmatranog mehaničkog sistema. Takođe,predlaže se korišćenje drugih bioloških principa kao što su: princip minimalne interakcije, koji ima glavnu ulogu u hijerarhijskoj strukturi upravljanja i princip samopodešavanja (uvodi lokalne pozitivnu/negativnu povratnu spregu u upravljačkoj petlji i to sa velikim pojačanjem), koji omogućava efikasno ostvarivanje upravljanja na bazi iterativnog prirodnog učenja. Takođe, novi, nedavno publikovani rezultati autora su takođe predstavljeni u oblasti stabilnosti, elektro-viskoelastičnosti i teoriji upravljanja a koji su zasnovani na korišćenju računa necelobrojnog reda.In this paper, the applications of biologically inspired modeling and control of (bio)mechanical (non)redundant mechanisms are presented, as well as newly obtained results of author in mechanics which are based on using fractional calculus. First, it is proposed to use biological analog-synergy due to existence of invariant features in the execution of functional motion. Second, the model of (bio)mechanical system may be obtained using another biological concept called distributed positioning (DP), which is based on the inertial properties and actuation of joints of considered mechanical system. In addition, it is proposed to use other biological principles such as: principle of minimum interaction, which takes a main role in hierarchical structure of control and self-adjusting principle (introduce local positive/negative feedback on control with great amplifying), which allows efficiently realization of control based on iterative natural learning. Also, new, recently obtained results of the author in the fields of stability, electroviscoelasticity, and control theory are presented which are based on using fractional calculus (FC)
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