bluuebunny/crossref_metadata_2025_split huggingface dataset:
Collision-avoidance control for redundant articulated robots
Authors: Rahmanian-Shahri N. , Troch I. 
Published: March 2009

SummaryA new mathematical formulation of robot and obstacles is presented such that for on-line collision recognition only robot joint positions in the workspace are required. This reduces calculation time essentially because joint positions in workspace can be computed every time from the joint variables through robot geometry. It is assumed that the obstacles in the workspace of the manipulator are represented by convex polygons. For every link of the redundant robot and every obstacle a boundary ellipse is defined in workspace such that there is no collision if the robot joints are outside this ellipsis.In addition to this, a collision avoidance method is presented which allows the use of redundant degrees of freedom such that a manipulator can avoid obstacles while tracking the desired end-effector trajectory. The method is based on the generalized inverse with boundary ellipse functions as optimization criteria. The method permits the tip of the hand to approach any arbitrary point in the free space while the kinematic control algorithm maximizes the boundary ellipse function of the critical link. The effectiveness of the proposed methods is discussed by theoretical considerations and illustrated by simulations of the motion of three- and four-link planar manipulators between obstacles.
A virtual sensor implementation for a flexible assembly machine
Authors: Rowland J. J. , Nicholls H. R. 
Published: March 2009

SummaryWe describe a sensor integration system which we have designed and implemented for a large fully-integrated flexible assembly machine. The machine was developed by a consortium to explore the design and implementation issues involved. The sensor integration system was designed for execution on a multiple transputer architecture, and co-ordinates all the sensory information in the machine. It uses the concept of virtual sensing to provide sensory data at an appropriate level of abstraction to the machine supervisor, which controls execution of the assembly tasks.
Kinematics, kinematic constraints and path planning for wheeled mobile robots
Authors: Wang Yongji , Linnett J.A. , Roberts J. 
Published: March 2009

SUMMARYThe problem associated with planning a collision-free path for a wheeled mobile robot (WMR) moving among obstacles in the workspace is investigated in this paper. A kinematic model, including the general nonholonomic constraint equation, is developed first, followed by the analysis of some general maneuvering characteristics of the WMR. The analytic solutions to the typical path curves, such as circle and straight line, which are important in the path planning problem, are also derived. From the analysis of the established kinematic model, some factors which affect the path planning problem for a WMR and therefore must be taken into account are revealed and the general description of the path planning problem for a WMR is formuated. In conclusion, a possible architecture of the algorithm for a practical WMR is presented.
Bang bang motion control of a Cartesian crane
Authors: DeSantis R. M. , Krau S. 
Published: March 2009

SUMMARYA motion controller for an overhead Cartesian crane in three-dimensional Euclidean (3-D) space is designed under the constraint that the control action belong to a discrete set of assigned values. The design approach rests upon a two-step procedure: first, a constraintfree motion controller is determined that satisfies the required dynamic specifications; second, this controller is replaced with an equivalent controller satisfying the discrete action constraint. The first step is implemented by means of a heuristic 3-D extension of a well-proven 2-D controller, the second step by applying recent sliding mode results. Numerical simulations illustrate the properties of the resulting feedback system under both nominal and perturbed operating conditions.
Towards a virtual reality-assisted movement diagnostics - an outline
Authors: Medved Vladimir 
Published: March 2009

The paper proposes a concept of a movement diagnostics system of enhanced performances. The existing system, using electromyographic (EMG) and ground reaction force signals as inputs, has been applied primarily to sports locomotion evaluation and testing, providing suitable quantitative criteria. The proposed enhancement relies on movement simulation facility, incorporating subject-specific anatomical and functional data on the neuro-musculo-skeletal system of extremities. Reflecting the principles of anthropomorphic robotics, the computer graphics simulation is conceptualized to generate artificial (synthesized) movement patterns in virtual reality.By comparing synthesized and measured signals the suitable feedback information is provided that may be used to enhance the overall system's performance. Using the power of computer technology and computer graphics, a user-friendly system of high ergonomic potentials is thus devised, in order to enhance the quality and efficacy of diagnostic procedure. The bioengineering principles used and the merging of measurement with simulation in the process of operation define a powerful instrument applicable to both healthy and pathological movement assessment.
Air jets imaging tactile sensing device for automation applications
Authors: Benhadj R. , Dawson B. 
Published: March 2009

SummaryThis paper details the design principles of operation of a pneumatic proximity-to-tactile sensing device for part handling and recognition in a flexible manufacturing environment. The sensing device utilises a densely packed line array of piezoresistive pressure sensors, providing continuous variable outputs. The sensing plane of the device incorporates a corresponding line array of air jets which develop an air cushion when striking a target of interest. The back pressure levels from these air jets form the basis for the task of target detection and recognition.
On avoiding singularities in redundant robot kinematics
Authors: Tchoń Krzysztof , Matuszok Aleksander 
Published: March 2009

SummaryFor redundant robot kinematics with a degree of redundancy 1 a self-motion vector field is examined whose equilibrium points lie at singular configurations of the kinematics, and whose orbits determine the self-motion manifolds. It is proved that the self-motion vector field is divergence-free. Locally, around singular configurations of corank 1, the self-motion vector field defines a 2-dimensional Hamiltonian dynamical system. An analysis of the phase portrait of this system in a neighbourhood of a singular configuration solves completely the question of avoidability or unavoidability of this configuration. Complementarily, sufficient conditions for avoidability and unavoidability are proposed in an analytic form involving the self-motion Hamilton function. The approach is illustrated with examples. A connection with normal forms of kinematics is established.
Control of grasp stiffness using a multifingered robot hand with redundant joints
Authors: Choi H. R. , Chung W. K. , Youm Y. 
Published: March 2009

SummaryThis paper addresses a method of satisfactorily controlling the grasp of objects. Emphasis is placed on achieving the desired stiffness of a grasped object as accurately as possible, especially when the fingers have redundant joints. A model describing the relation between stiffness and force is derived. Based upon this model, a hierarchical control scheme of the grasp stiffness, called decentralized object stiffness control (DOSC) is proposed. DOSC is composed of a fingertip stiffness synthesis (FSS) algorithm and orthogonal stiffness decomposition control (OSDC). Employing the proposed FSS always achieves the desired grasp stiffness by solving the constrained least square problem. The computed fingertip stiffness is achieved by OSDC. It offers a feasible way of controlling the fingertip stiffness as well as maintaining the stability of the finger configuration by modulating the joint stiffness. The developed control method is implemented on a two-fingered planar robot hand one finger of which has a redundant joint. The effectiveness of the control method is confirmed experimentally.
Modeling and path-tracking control of a mobile wheeled robot with a differential drive
Authors: DeSantis R. M. 
Published: March 2009

SummaryTopics relevant to modeling and control of mobile wheeled robots with a differential drive are discussed by assuming a motion that is planar and free from lateral and longitudinal slippages, and by taking into account dynamic and kinematic properties of the vehicle. Based on the concept of geometric path-tracking, a controller is designed that is a memoryless function of the lateral, heading, and velocity path-tracking offsets. If these offsets are kept small and the assigned tracking velocity is constant, then this controller may be given a linear, time-invariant and decoupled PID (Proportional + integral + derivative) structure.
A novel differential shape memory alloy actuator for position control
Authors: Gorbet Robert B. , Russell R. Andrew 
Published: March 2009

SummaryThis paper discusses a novel design for a rotary differential NiTi shape memory alloy actuator, which incorporates a mobile heat sink. The new mechanism is described in detail, and its performance in a position control system is compared with that of the same actuator without heat sink. Experimental results are presented which show an improvement in actuator response time, as well as closed-loop bandwidth. The design of the mechanism gives enhanced performance, without the increased power consumption associated with fixed heat sinks.
Force control for walking on soft terrains
Authors: Lehtinen Hannu 
Published: March 2009

SUMMARYForce control of walking machines is essential in a natural soft and uneven terrain. A load adaptive PI force control method for the hydraulic actuation system of MECANT I has been developed. The I term of the controller is changed according to the desired load. Force control satisfies the support requirement also when a leg penetrates the terrain. A method to distribute support forces in an optimal manner has been developed. A rule based altitude controller and a dead-zone and saturation based attitude controller calculates the desired body forces. Walking tests on uneven wet sand fields show the useful applicability of the method.
Trajectory planning of multiple coordinating robots using genetic algorithms
Authors: Sun Shudong , Morris A.S. , Zalzala A.M.S. 
Published: March 2009

SUMMARYThe paper focuses on the problem of trajectory planning of multiple coordinating robots. When multiple robots collaborate to manipulate one object, a redundant system is formed. There are a number of trajectories that the system can follow. These can be described in Cartesian coordinate space by an nth order polynomial. This paper presents an optimisation method based on the Genetic Algorithms (GAs) which chooses the parameters of the polynomial, such that the execution time and the drive torques for the robot joints are minimized. With the robot's dynamic constraints taken into account, the pitimised trajectories are realisable. A case study with two planar-moving robots, each having three degrees of freedom, shows that the method is effective.
Improving the accuracy of a vibratory sensor using Kalman filtering
Authors: Pham D.T. , Hafeez K. 
Published: March 2009

SUMMARYThis paper presents a Kalman filtering technique for reducing errors in locating 3-D objects using a sensor system. The location information is employed to control the motion of an industrial robot to pick up the objects. The sensor consists of a rigid platform mounted on a flexible column. Each object to be located is placed on the sensor. The static deflections and natural frequencies of vibrations of the sensor are measured and processed to determine the position and orientation of the object. In practice, the sensor signals obtained are corrupted with noise leading to errors in location determination. A Kalman filter is used to reduce the noise present in the sensor system.
Simplification of manipulator dynamic formulations utilizing a dimensionless method
Authors: Lin Yueh-Jaw , Zhang Hai-Yan 
Published: March 2009

SUMMARYThis paper presents a new approach for simplifying dynamic equations of motion of robot manipulators by using a nondimensionalization scheme. With this approach the dynamic analysis is done in a nondimensional space. That is, it is required to establish a dimensionless coordinate system in which the dynamic equations of motion of manipulators are formulated. The characteristic parameters of the manipulators are then defined by choosing proper physical quantities as basic units for nondimensionalization. Within the nondimensional space the Lagrange method is applied to the manipulator to obtain a set of general dimensionless equations of motion. This dimensionless dynamic formulation of manipulators leads to an easier way to simplify the dynamic formulation by neglecting insignificant terms using the order of magnitude comparison. The dimensionless dynamic model and its simplified version of PUMA 560 robot are implemented using the proposed approach. It is found that the simplified dynamic model greatly reduces the computation burden of the inverse dynamics. Simulation results also show that the simplified model is extremely accurate. This implies that the proposed nondimensional simplification emethod is reliable.
Measurement of robustness for biped locomotion using a linearized Poincaré map
Authors: Cheng M. -Y. , Lin C. -S. 
Published: March 2009

SUMMARYMany studies on control of dynamic biped walking have been done in the past two decades. While the biped dynamics is highly nonlinear, the stability analysis, if done, is usually based on a linearized model. The validity of the linearized model may become questionable if the walking involves states that are too far away from the operating point. In this paper, an approach for evaluating the robustness based on the linearized Poincare map is suggested and examined. The Poincare map is a useful tool to investigate the periodic motion of a dynamic system. Using the Poincare“ map, one can study an associated discrete time map instead of studying the continuous time system directly. Investigation of stability of a periodic motion can be reduced to the study of the stability of a fixed point of the Poincaré map. The computational method that results in a measurement for evaluating the robustness of biped locomotion is developed. Our simulation study has verified that the suggested measurement is a good indicator.
Manipulating robots along helical trajectories
Authors: Selig J. M. , Ovseevitch A. I. 
Published: March 2009

SUMMARYCurrent industrial robots are highly non-linear systems. However, the control strategies in most commercially available robots largely ignore the non-linearity. The resulting linear approximations are only valid at low speeds. Any improvement would allow robots to move faster and hence be more productive. There has been much academic research into robot control, but this has almost always separated the control and the trajectory planning. In this work we seek to combine these tasks and hence simplify the computations required. We investigate how to control a general robot in such a way that it's gripper follows straight line, circular or helical paths. These simple paths are both one parameter subgroups for the group of proper rigid motions and geodesies for certain metrics on the group. This suggests a non-linear feedback control law which turns the closed loop dynamics of the robot into the equations for geodesies. Although these equations are not completely stable we are able to modify the control law so that the resulting closed loop dynamics are stable. Hence, the end-effector of the robot will follow straight line, helical or circular trajectories.
A method for controlling robotic contact tasks
Authors: Payandeh Shahram 
Published: March 2009

SUMMARYIn robotic tasks where the manipulator has to make transition from free space motion to constrained one, there always exists a inevitable impact phase (contact transition phase). Examples can be the autonomous exploratory motion of the end-effector in a cluttered environment, or grasping and manipulation of objects using dexterous mechanical end-effector. A number of controllers have been proposed in the literature with various discussions on their practical implications. In this paper a simple and efficient controller is proposed for the robotic contact tasks. The controller is based on the notion of switching control law where the structure of the controller remains unchanged during the phase transition and only the magnitudes of its gains are changed. The proposed control law maintans the stable performance during the impact phase of the manipulator when making contact with general environment. In addition, the controller exhibits stable and robust performance during the post-contact phase with the desired contact force regulation. The stability of the proposed controller is shown using the Lyapunov method which guarantees the exponential rate of convergence of the state during the contact transition to post-contact phase. Experimental results are presented to demonstrate the practicality of the proposed controller.
Static and dynamic modelling of a two-flexible-link robot manipulator
Authors: Morris A.S. , Madani A. 
Published: March 2009

SUMMARYThis paper is addressed at the difficulty of accurately modelling a two-flexible-link manipulator system, which is a necessary pre-requisite for future work developing a high-performance controller for such manipulators. Recent work concerned with the development of an accurate single-flexible-link model is first reviewed and then the expansion of a single-link model into a two-flexible-link system in a way which properly takes into account the coupling and interactions between the two links is discussed. The method of approach taken is to calculate the elastic and rigid motions of the links separately and then to combine these according to the principle of superposition. The application of the model developed is demonstrated in a simulated two-flexiblelink system.
Causal inverse dynamics of a flexible hub-arm system through Liapunov's second method
Authors: Ata Atef , Elkhoga Salwa , Shalaby Mohamed , Asfour Shihab 
Published: March 2009

SUMMARYThe main objective of this work is to study the performance of a flexible single hub-arm system. The equations of motion are derived using the extended Hamilton principle. The Liapunov functional is used as a condition for the stability analysis. The Liapunov functional is considered as the sum of the internal energy of the flexible beam. The required drive torque was obtained directly through the solution of the inverse dynamic problem. Although the flexible link is nonminimum phase in nature, the use of Liapunov and the PD controller guarantee the causality for the stable case. The effects of tip mass as well as its inertia in the case of stable and asymptotic stable systems were investigated to ensure the validity of this procedure.
Kinematic calibration using the product of exponentials formula
Authors: Okamura Koichiro , Park F.C. 
Published: March 2009

SUMMARYWe present a method for kinematic calibration of open chain mechanisms based on the product of exponentials (POE) formula. The POE formula represents the forward kinematics of an open chain as a product of matrix exponentials, and is based on a modern geometric interpretation of classical screw theory. Unlike the kinematic representations based on the Denavit- Hartenberg (D-H) parameters, the kinematic parameters in the POE formula vary smoothly with changes in the joint axes, ad hoc methods designed to address the inherent singularities in the D-H parameters are therefore unnecessary. Another important advantage is that simple closed-form expressions can be obtained for the derivatives of the forward kinematic equations with respect to the kinematic parameters. After introducing the POE formula, we derive a least-squares kinematic calibration algorithm for general open chain mechanisms. Simulation results with a 6-axis open chain are presented.
Secondary school specialization in robotics and FMS: A practical experience (a viewpoint)
Authors: Miljakovic-Jevtic I. , Potkonjak Veljko 
Published: March 2009

SUMMARYThis paper deals with the problems of the education of the staff in robotics and flexible automation at the secondary school level. It deals with an experiment which aims at training technicians for robotics and flexible manufacturing systems. The experiment began in 1989. and now the second generation of students that studies according to the curricula of this experiment has completed the education. Previous experience, especially from the standpoint of the result of the students and problems that arise during the realization of the experiment, are analyzed in this text.
Mobile microrobots
Authors: Shimoyama Isao , Yasuda Takashi , Miura Hirofumi , Kubo Fujisawa Yayoi , Ezura Yuichi 
Published: March 2009

SUMMARYThis paper discusses suitable mechanisms and functions of a mobile microrobot from the point of view ofscale effects. Several assumptions are made using animalscaling. A large scale model is shown to demonstrate these mechanisms. Moreover, microsized models have been built on silicon wafers by using polysilicon as rigidplates and polyimide as elastic joints. The results showthat suitable mechanisms and functions may be different from those of a conventional robot.
A discrete-event systems approach to modeling dextrous manipulation
Authors: Ricker S.L. , Sarkar N. , Rudiet K. 
Published: March 2009

SUMMARYTo perform dextrous manipulation efficiently, it is necessary to coordinate the interactions of many component processes. This paper investigates one approach to coordination: discrete-event systems. The applicability of discrete-event systems to the modeling of dextrous manipulation tasks is studied. Discrete-event control theory offers formal methods for determining whether a coordinator of the components can be generated. A representative dextrous manipulation task, the planar Grasp-Lift-Replace task of Howe and Cutkosky, is presented as a discrete-event process. The task is extended to include two-fingered exploratory procedures. The effectiveness of the discrete-event system approach is illustrated through simulations of several test cases.
Simultaneous velocity, impact and force control
Authors: Zotovic Stanisic Ranko , Valera Fernández Ángel 
Published: March 2009

SUMMARYIn this paper, we propose a control method to achieve three objectives simultaneously: velocity regulation during free motion, impact damping and finally force reference tracking. During impact, the parameters are switched in order to dissipate the energy of the system as fast as possible and the optimal switching criteria are deduced. The possibility of sliding regimes is analysed and the theoretical results are verified in simulations.
Trends in the Diffusion of Selected Medical Technology in the Federal Republic of Germany
Authors: Schicke R. K. 
Published: March 2009

AbstractThis article contends that the German social and economic situation is conducive to the rapid diffusion of innovative medical technology. While there is public control over hospital facilities, the pluralistic health care system and decentralized government responsibilities contribute to an essentially laissez faire regulatory environment. There is perfunctory planning and regulation for major medical expenditures, but the essential constraints are financial. This is no comprehensive program for the assessment of diagnostic technologies and the effective imposition of guidelines depends on the cooperative effort of various financing organizations, professional interests, and public pressure groups.