Papers by Veljko Potkonjak
Mathematics and Computers in Simulation, vol.54,pp. 147-157, 2000
This paper is concerned with the trajectory definition in robot tasks. Successful task operation ... more This paper is concerned with the trajectory definition in robot tasks. Successful task operation does not necessarily imply the maximum quality of its outcome. It is sufficient to keep the task quality at a given lower level, and optimize a certain secondary criterion. Here, the kinematics of the task is
defined using a 'biomechanical' secondary performance criterion, which modifies the kinematics using the 'learn from humans'' principle so as to resemble the behavior of a human worker human worker. Two task examples are successfully treated applying this technique, namely handwriting and spray-coating tasks.
Journal of Intelligent and Robotic Systems, vol. 35,no. 4, 353-364, 2002
This part of the paper examines numerically the possibility of modeling ''robot fatigue'' being ... more This part of the paper examines numerically the possibility of modeling ''robot fatigue'' being representative of a human psycho-physical state that can be applied to robots. Temperatures of driving motors are suggested as analogs to fatigue in muscles.
Contribution to a computer-aided choice of D.C. motors for manipulation robots
Robotica, 1986
Mechanism and Machine Theory, 1983
In the paper are presented the basic ideas of computer-aided design of manipulation robots based ... more In the paper are presented the basic ideas of computer-aided design of manipulation robots based on adopted optimizational criteria and on set constraints of strengths, as well as on actuator capabilities. Using complete models of manipulator dynamics, a simulation programme was derived, giving at its output the optimal design parameters of manipulator. An algorithm was formed, optimizing simultaneously two of the several significant manipulator parameters. In one case these a~ two diameters of circular cross-section segments, in another, one is a diameter and the other the reducing ratio of the DCmotor type actuator.
Journal of Intelligent and Robotic Systems, 1992
The concept of distributed positioning is based on the separation of the required end-effector mo... more The concept of distributed positioning is based on the separation of the required end-effector motion into two components according to a criterion. The external-to-internal transformation of the motion is made in such a way that some of the joints become responsible for the first and others for the second component. Thus, the redundancy could be compensated and the unique solution of the inverse kinematics achieved. If the separation is made according to the acceleration criterion, then the ‘smooth’ and the ‘fast’ components of the end-effector motion are obtained. The paper shows that this concept results in the improvement of robot dynamic capabilities.
Mathematical modelling of a redundant anthropomorphic arm (Part I
Robotics and Autonomous Systems, 1992
Simulation of a redundant anthropomorphic arm (Part II
Robotics and Autonomous Systems, 1992
Robotics and Computer-integrated Manufacturing, 1990
Based on the SCARA concept, accepted worldwide, this paper considers the possibility of realizing... more Based on the SCARA concept, accepted worldwide, this paper considers the possibility of realizing SCARA with a full circle working area. The basis of the approach is a mechanism with two eccentrically positioned rotating discs instead of two joined links. In this way, apart from a circular working area and some other advantages, the installation of several tools (hands) is also facilitated. This paper analyzes the advantages of the proposed solution and the possibilities of its realization.
International Journal of Humanoid Robotics, 2006
This paper elaborates a generalized approach to the modeling of human and humanoid motion. Instea... more This paper elaborates a generalized approach to the modeling of human and humanoid motion. Instead of the usual inductive approach that started from the analysis of different situations of real motion (like bipedal gait and running; playing tennis, soccer, or volleyball; gymnastics on the floor or using some gymnastic apparatus; etc.) and tried to make a generalization, the considered deductive approach started with formulating a completely general problem and derived different real situations as special cases. The paper first explains the general methodology. The concept and the software realization are verified by comparing the results with the ones obtained by using a "classical" software for one well known particular problem -biped walk. The applicability and potentials of the proposed method are demonstrated by simulation of a selected example. The simulated motion included a landing on one foot (after a jump), the impact, a dynamically balanced single-support phase, and the overturning (falling down) when the balance is lost. It was shown that the same methodology and the same software can cover all these phases.
Dynamics of anthropomorphic painting robot: Quality analysis and cost reduction
Robotics and Autonomous Systems, 2000
KNAW Narcis. Back to search results. Publication Dynamics of Anthropomorphic Painting Robot: Qual... more KNAW Narcis. Back to search results. Publication Dynamics of Anthropomorphic Painting Robot: Quality Analysis and Cost Reduction (2000). Pagina-navigatie: Main. Title, Dynamics of Anthropomorphic Painting Robot: Quality Analysis and Cost Reduction. ...
Mechanism and Machine Theory, 1979
In this paper is presented the common basic features of the method for automatic setting of dynam... more In this paper is presented the common basic features of the method for automatic setting of dynamic equations of active spatial mechanisms in the form of open chains. The paper is divided into two pads. In the first part, beside the theoretical basis of the computer methods, the version at the basis of the fundamental theorems of mechanics is presented. Second part of the paper contains the new result, relating to the procedures based on Gibbs--Appel's and Lagrange's equations. Finally is given the comparison of the three method's efficiency, representing the complete possibility for computer forming of the dynamic differential equations of spatial active chains.
IEEE Robotics & Automation Magazine, 2003
How far away is “artificial man
IEEE Robotics & Automation Magazine, 2001
All through craft history and technological progress, several attempts have been made to build a ... more All through craft history and technological progress, several attempts have been made to build a device that looks and behaves as humans do. In modern times, it was Karel Capek's imagination that first captured the idea of a true artificial man, a robot (the very root of ro-bot derived ...
Journal of Intelligent and Robotic Systems, 2007
This work is concerned with the modeling and analysis of a complex humanoid robotic system walkin... more This work is concerned with the modeling and analysis of a complex humanoid robotic system walking on an immobile/mobile platform. For this purpose, a software package was synthesized which allows one to select configuration of both the humanoid and the platform. Each joint of the biped and platform can be defined by the user via the motor state (active or locked) and gear type (rigid or elastic). The user can also form very diverse configurations of the humanoid and platform. The software package forms a mathematical model. By selecting system’s parameters the simulation allows user to analyze dynamic behavior of the biped of selected configuration, walking on either an immobile or mobile platform of selected configuration. In the moment when the biped steps on the platform, the latter, by its dynamics, acts on the biped dynamics, and the biped on the other hand, by its characteristics, influences dynamics of the platform motion. These two complex contacting systems form a more complex system, whose mathematical model has to encompass all the elements of coupling between the humanoid joints and platform joints. The phenomenon of coupling is analyzed first on a humanoid robotic system with all rigid elements, which is in contact with the platform mechanism having also all rigid elements. It has been shown that coupling is more influenced when elasticity elements are included into the configuration. Insufficient knowledge of coupling characteristics may present a serious disturbance to the system in the robotic task realization. The deviation of the ZMP (Zero-Moment Point) from the reference trajectory is presented, which implies the need for the synthesis of new control structures for stabilizing biped motion on the immobile/mobile platform. The reference trajectory may be defined in very different ways and from several aspects. Reference trajectory of each joint can be defined so to encompass or not encompass elastic deformations. The control structure for the biped walking on the platform should be defined so that it satisfies the requirement for the ZMP to be within the given boundaries in every sampling instant, which guarantees dynamic balance of the locomotion mechanism in the real regime. The control is defined as CR (Centralized Reference control, calculated from the reference state), plus LO (control via local feedbacks of motor motion with respect to position and velocity). In the case of the biped motion on a mobile platform CR control is defined separately under the real conditions of unknown characteristics of coupling between the two complex systems, as well as unknown elasticity properties. The analysis of simulation results of the humanoid robot motion on a mobile platform gives evidence for all the complexity of this system and shows how much system parameters (choice of trajectory, configuration, geometry, elasticity characteristics, motor, etc.) influence stabilization of its humanoid motion.
Mechanism and Machine Theory, 1999
Modelling the dynamics of contact tasks is carried out in a completely general way. Two dynamic s... more Modelling the dynamics of contact tasks is carried out in a completely general way. Two dynamic systems are brought into contact and the relevant dynamic eects analysed. The eects are: rigid-bodycontact force, elastodynamics in contact zone, friction in contact points, elastic deformation in torque transmission, impact, etc. The general model is then applied to some more concrete problems in order to discuss some eects in detail. The control strategy is considered for each concrete problem and the simulation results are presented. The work is organized in two parts dedicated to ®rst the general model, and second model application and simulation. # 1998 Elsevier Science Ltd. All rights reserved. Mechanism and Machine Theory 34 (1999) 923±942 0094-114X/99/$ -see front matter # 1998 Elsevier Science Ltd. All rights reserved. PII: S 0 0 9 4 -1 1 4 X ( 9 7 ) 0 0 0 9 1 -8 PERGAMON
Journal of Robotic Systems, 1986
Part II of this article elaborates one practical problem: peg-in-hole problem in assembly manipul... more Part II of this article elaborates one practical problem: peg-in-hole problem in assembly manipulation. The theory of constrained gripper motion explained in Part I is used to solve the dynamics of the assembly manipulation problem.
A Generalized Approach to Modeling Dynamics of Human and Humanoid Motion
Journal of Intelligent and Robotic Systems, 2004
The questions when and why one needs to use mathematical models, and especially the models of dyn... more The questions when and why one needs to use mathematical models, and especially the models of dynamics, represent a still unresolved issue. A general answer would be that dynamic modeling is needed as a tool when designing structure of the system and its control unit. In this case we talk about simulation. The other application is in on-line control of the system – the so-called dynamic control. While for simulation one should generally use the best available model, the control can be based on a reduced dynamics, depending on a particular task. This article considers humans and humanoid robots and addresses a rather important question: what are dynamic effects that one should take care of when modeling and simulating a human or a humanoid? The article suggests the key topics for work and tries to justify them. As a final result a General Human/Humanoid-Dynamics Simulator is seen.
Robotics and Computer-integrated Manufacturing, 2001
This paper (Part II) investigates the motion of a redundant anthropomorphic arm during the writin... more This paper (Part II) investigates the motion of a redundant anthropomorphic arm during the writing task. Two approaches are applied. The "rst is based on the concept of distributed positioning which is suitable to model the`writinga task before the occurrence of fatigue symptoms. The second approach uses the concept of`virtual fatiguea (<F) which is a variable that dynamically behaves in a way analogous to the biological fatigue. <F enables the arm to recon"gure itself and take postures appropriate for the current level of fatigue. The study includes the analysis of legibility and inclination of handwriting, and a set of simulation results that show most practical aspects of robot human-like performance.
International Journal of Humanoid Robotics, 2008
The work considers some aspects of the problem of generating and preserving of two-legged gait be... more The work considers some aspects of the problem of generating and preserving of two-legged gait bearing in mind the requirements for a higher degree of similarity with human gait (anthropomorphism) and robustness to the constantly present small disturbances during the walk. Reference motion was synthesized by semi-inverse method, varying the mode of ZMP traveling along a path selected in advance on the foot-ground surface. It was found that different ways of ZMP motion along the path has a decisive role in the trunk deflection in the sagittal plane. Also, the problem of classification of disturbances and their compensation during the gait is discussed in detail. The significance of the multi-link trunk in the gait synthesis and its role in the compensation of disturbances is also considered.
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Papers by Veljko Potkonjak
defined using a 'biomechanical' secondary performance criterion, which modifies the kinematics using the 'learn from humans'' principle so as to resemble the behavior of a human worker human worker. Two task examples are successfully treated applying this technique, namely handwriting and spray-coating tasks.