bluuebunny/crossref_metadata_2025 huggingface dataset:
Trajectory generation and control for automatic manipulation
Authors: Hayward Vincent , Daneshmend Laeeque , Nilakantan Ajit
Published: March 2009

A method is described to convert information available at manipulator programming level into trajectories which are suitable for tracking by a servo control system. This process generates trajectories in real time which comply with general dynamic and kinematic constraints. Tracking accuracy will depend mainly on the acceleration demand of the nominal trajectory setpoints - the actuator output demands, in particular, must remain bounded. Our scheme takes into consideration at the trajectory computation level the dynamics of the underlying system, dynamically available information acquired through sensors, and various types of constraints, such as manipulators. It has been developed in the context of a multi-manipulator programming and control system called Kali and developed at McGill University.
A prototype ground-remote telerobot control system
Authors: Backes Paul G. , Beahan John , Long Mark K. , Steele Robert D. , Bon Bruce , Zimmerman Wayne
Published: March 2009

A local-remote telerobot control system is described which is being developed for time-delayed groundremote control of space telerobotic systems. The system includes a local site operator interface for interactive command building and sequencing for supervised autonomy and a remote site: the Modular Telerobot Task Execution System (MOTES), to provide the remote site task execution capability. The local site system also provides stereo graphics overlay on video with interactive update of the remote environmental model. The operator selects objects in the environment to interact with and skill types to specify the tasks to be performed, such as grasping a module or opening a door.
Path planning and control of a mobile base with nonholonomic constraints
Authors: Jagannathan S. , Zhu S. Q. , Lewis F. L.
Published: March 2009

Motion Planning and control of mobile vehicles with nonholonomic constraints are in their infancy. A systematic approach for modeling and base; motion control of a mobile vehicle is presented. A nonlinear coordinate transformation that takes into account the complete dynamics with nonholonomic constraints is used in order to obtain a linear system in space coordinates. An input-output feedback linearization inner loop is subsequently designed to transform this system into a linear-point mass system in the coordinates corresponding to the control objectives. A rigorous yet simple approach to motion planning through optimization techniques is presented for these mobile vehicles. The resulting Cartesian trajectory generated from the motion planning algorithm is employed as the reference trajectory in the outer loop, which is designed based on a Lyapunov function candidate. The net result is a base motion controller that gives capabilities to these mobile vehicles not only for tracking a Cartesian trajectory but also to achieve a desired final orientation (docking angle).
Dynamic control with adaptive identification for free-flying space robots in joint space
Authors: Shin Jin-Ho , Lee Ju-Jang
Published: March 2009

In this paper, a joint space dynamic control scheme with an adaptive identifier is proposed for free-flying space robots. The control in Cartesian space poses a measurement problem which is critical from a point of view of implementation. In order to overcome this problem, a joint space control is developed. An inverse kinematics algorithm is proposed so as to control free-flying space robots in joint space. Since the inverse kinematic solutions for space robots depend on the dynamic parameters as well as the kinematic.parameters, the accurate estimation of all the unknown parameters is essential to make joint space control possible. Therefore, an off-line adaptive parameter identification is performed for free-flying space robots. Simulation results are given to show the validity and the effectiveness of the presented adaptive identification and dynamic control scheme.
Mobile robot guidance using a short-lived heat trail
Authors: Russell R. Andrew
Published: March 2009

This paper describes a novel form of navigation aid for mobile robots. It is suggested that a robot lay a heated trail to mark its path. This information about the robot trajectory can be used to assist a robot when it performs area coverage operations such as floor cleaning or allow a robot to follow the path previously taken by itself or another robot. Prototype devices for laying and tracking a heat trail are described and details of their performance are given. A mobile robot has been equipped to lay and track a heat trail.
Analysis of static equilibrium of a parallel manipulator
Authors: Pang Hyunsok , Shahinpoor Mohsen
Published: March 2009

An analysis is presented in this paper for the equilibrium of a class of parallel manipulators resembling the Stewart platform in a general form. General coordinates and 4 x 4 homogeneous transformations are employed to arrive at exact expressions for the force distribution in all six legs given the general 6-dimensional wrench (generalized force) at the upper platform of a parallel manipulator. Numerical examples are carried out to examine the validity of the approach and the accuracy of the numerical technique employed.
A new scheme for hybrid force-position control
Authors: Perdereau Véronique , Drouin Michel
Published: March 2009

Many robotic tasks require the end-effector to come into contact with the external environment. In such complex tasks, the manipulator is constrained by the environment, and certain DOFs are lost for motion. The contact forces must be controlled in constraint directions, while the tip position is simultaneously controlled in the free directions.
Grasping, coordination and optimal force distribution in multifingered mechanisms
Authors: Gorce P. , Villard C. , Fontaine J. G.
Published: March 2009

In the field of multifingered mechanisms the control/command problem is mainly a problem o1 coordination. The problem is not only to coordinate joints of a chains but also to coordinate the different chains together.

This paper presents a general and efficient method for implementing the control/command of such systems, taking into account the force distribution problem. To solve this problem it is necessary to pay great attention to dynamic effects. To do this, we broke down the Inverse Dynamic Model (I.D.M.) problem into two main levels; One level is devoted to I.D.M. computation; it can be called the Finger Level (F.L.). As we wanted to divide up the work to be done as much as possible, we subdivided the Finger Level according to the number o1 kinematic chains. In addition, we considered a second level, the Coordinator. This level has to control all the chains using the Fingers-to-Object-Interaction Model (F.O.LM.).

Next, we will also introduce new grasping systems: Polyvalent Gripper Systems (P.G.S). There are a new solution to multicomponent assembly problems. As they can be equipped with several multifingered mechanisms, they can also use the control/command scheme.
Formulation and numerical solution of elastic robot dynamic motion with maximum load carrying capacities
Authors: korayem M.H. , Basu A.
Published: March 2009

This paper presents a new formulation as well as numerical solution for the problem of finding a point-to-point trajectory with maximum load carrying capacities for flexible manipulators. For rigid manipulators, the major limiting factor in determining the maximum allowable load (mass and mass moment of inertia) is the joint actuator capacity, while the flexibility exhibited by light weight robots or by robots operating at a higher speed dictates the need for an additional constraint to be imposed for situations where precision tracking is required, that is, the allowable deformation at the end effector. The Lagrangian assumed mode method was used to model the manipulator and load dynamics, including both joint and deflection motions. An Iterative Linear Programming (ILP) method is then used to determine the maximum allowable load of elastic robot subject to both constraints, while a general computational procedure for the multiple-link case given arbitrary trajectories is presented in detail. Symbolic derivation and simulation by using a PC-based symbolic language MATHEMATICA® was carried out for a two-link planer robot and the results further confirm the necessity of the dual constraints.

Rough joint flexibility is the dominant source of compliance in today's commercial robots in future robots containing light weight flexible arms link flexibility may become most important. Hence this paper stresses link flexibility rather than joint flexibility.
On numerical techniques for kinematics problems of general serial-link robot manipulators
Authors: Sasaki Shinobu
Published: March 2009

This paper addresses widely applicable methods for solving the kinematics problem of any class of serial-link robot manipulators. First, the position and orientation of the manipulator hand, the Jacobian matrix and their symbolic generation are clearly presented using recursive relations. Second, the inverse problem to such formulations is posed as an unconstrained non-linear optimization one, where numerical techniques for the overdetermined and underdetermined kinematic problems are considered separately to derive consistent arm solutions. On the basis of several proposals on step lengths involved to maintain good numerical stability, the results of computer simulation show that performance is sufficiently reliable.
Path finding and grasp planning for robotic assembly
Authors: Lee Byung R. , Ro Paul I.
Published: March 2009

This paper focuses on developing a planning strategy for robotic assembly. At first, channel and junction are defined by using half-spaces, and free-space inside the female part is approximately decomposed by channels and junctions. Then, a simple and efficient algorithm to find the assembly path of the male part is developed, in which any path between the shortest and safest paths can be easily found by just changing the clearance gap between the male and female parts. Next, the robot arm is considered in the path planning, in which a feasible grasp angle region is obtained to avoid a collision between the robot arm and the female part during the assembly process. An optimum grasping angle can be found in the feasible grasping angle region by applying a proper performance index. Finally, a simple robotic assembly using the algorithm is numerically demonstrated.
Experimental results for a robust position and force controller implemented on a direct drive robot
Authors: Bridges M. M. , Cai J. , Dawson D. M. , Grabbe M. T.
Published: March 2009

In this paper we present the results obtained from the implementation of a robust position/force controller on a two-degree-of-freedom direct drive robot. The controller is based on the theoretical work presented in references 1 & 2, which guarantees Globally Uniformly Ultimately Bounded (GUUB) position tracking error and bounded force tracking error. The controller accomplishes this stability result in spite of robot model uncertainty and only requires; joint position and velocity measurements, end-effector force measurements, and bounds on the model parameters. Experimental results described in this paper serve to verify the theoretical claims.
The modification of pre-planned manipulator paths to improve the gross motions associated with the pick and place task
Authors: Sanders David A.
Published: March 2009

This paper presents research work which crosses the divide between “Path Planning” and “Trajectory Generation & Tracking”. These subjects have tended to develop along two parallel lines, in isolation from each other. The work uses the Lagrange formulation for the three major joints of an industrial manipulator. Simple planning rules are developed from this formulation. The rules are used to select new paths for a manipulator rather than to improve preplanned trajectories. The method has been applied to pick and place tasks requiring gross motions of the manipulator and the results are presented. It is shown that using this method, pre-planned manipulator paths can be modified to improve the gross motions associated with the pick and place task.
Optimal conditions for inverse kinematics of a robot manipulator with redundancy
Authors: Cho Dong Kwon , Choi Byoung Wook , Chung Myung Jin
Published: March 2009

The algorithms of inverse kinematics based on optimality constraints have some problems because those are based only on necessary conditions for optimality. One of the problems is a switching problem, i.e., an undesirable configuration change from a maximum value of a performance measure to a minimum value may occur and cause an inverse kinematic solution to be unstable. In this paper, we derive sufficient conditions for the optimal solution of the kinematic control of a redundant manipulator. In particular, we obtain the explicit forms of the switching condition for the optimality constraintsbased methods. We also show that the configuration at which switching occurs is equivalent to an algorithmic singularity in the extended Jacobian method. Through a numerical example of a cyclic task, we show the problems of the optimality constraints-based methods. To obtain good configurations without switching and kinematical singularities, we propose a simple algorithm of inverse kinematics.
On the optimum design of Stewart platform type parallel manipulators
Authors: Bhattacharya Soumya , Hatwal H. , Ghosh A.
Published: March 2009

This paper studies the static rigidity behaviour of a parallel manipulator with legs modelled as elastic members under axial loading. Structurally, a parallel module is more rigid compared to a serial module and is expected to take heavier payloads. Therefore, a guidance for design of such parallel manipulators is needed which leads to maximum rigidity over the workspace. In the present work, the authors propose the concept of the flexibility ellipsoid for a parallel system. Various scalar measures of rigidity are formulated on the basis of the proposed ellipsoid. An algorithm, involving multiple objective nonlinear programming technique, is implemented to decide upon some important design parameters of a generalised six degrees of freedom Stewart platform type parallel manipulator. It is observed that irrespective of the other parameters, parallel manipulators with the legs pairwise joined at the top platform possess the highest rigidity. Moreover, there exists certain kinematic dimensions for which the designed parallel system is completely free from all sorts of singularity.
A high torque to weight ratio robot actuator
Authors: Bobrow James E. , Desai Jayesh
Published: March 2009

A light-weight, high-torque actuator with accurate torque control capability is described. The actuator uses a small hydrostatic transmission to achieve the advantage of large gear reduction from a high speed DC motor, and retains accurate joint torque sensing and control capabilities with no backlash. A disadvantage of the actuator is that is introduces extra dynamics which must be accounted for in robot control systems. It is shown that state feedback enables closed loop control of joint torque, with full back drivability, through an effective gear ratio of 485:1 for the experimental system. The actuator can therefore be used for both position control and output force control, which is essential for modern robot control algorithms. A mathematical model of the system is presented in this paper along with experimental results.
Mobile robot localization using a single rotating sonar and two passive cylindrical beacons
Authors: Beom H. R. , Cho H. S.
Published: March 2009

This paper proposes a new method of estimating the position and heading angle of a mobile robot moving on a fiat surface. The proposed localization method utilizes two passive beacons and a single rotating ultrasonic sensor. The passive beacons consist of two cylinders with different diameters and reflect the ultrasonic pulses coming from the sonar sensor mounted on the mobile robot. The sonar sensor, again, mounted on a pan-tilt device then receives the reflected pulses while scanning over a wide area. The geometric parameter set of beaconis acquired from the sonar scan data obtained at a single mobile robot location using a new data processing algorithm. The presented algorithm is especially suitable for processing the sonar scan data obtained by ultrasonic sensor with wide beam spread. From this parameter set, the position and heading angle of the mobile robot is determined directly. The performance and validity of the proposed method are evaluated using two beacons and a single sonar sensor attached at the pan-tilt device mounted on a mobile robot, named LCAR, in our laboratory.
A meta-study of PUMA 560 dynamics: A critical appraisal of literature data
Authors: Corke Peter I. , Armstrong-Hélouvry Brian
Published: March 2009

The paper presents a meta-study of the kinematic, dynamic and electrical parameters for the PUMA 560 robot. Parameter values which have been reported in the literature are transformed into a single system of units and coordinates, and differences in the data and measurement techniques are discussed. New data have been gathered and are presented where the record was incomplete.
A unified approach to mathematical modelling of robotic manipulator dynamics
Authors: Vukobratović M.K. , Filaretov V.F. , Korzun A.I.
Published: March 2009

A new method for computer forming of dynamic equations of open-chain mechanical robot configurations is presented. The algorithm used is of a numeric-iterative type, based on mathematical apparatus of screw theory, which has enabled elimination of the unnecessary computations in the process of dynamic model derivation. In addition to conventional kinematic schemes of robotic manipulators, the branched kinematic chains which have recently found their application in the locomotion of robotic mechanisms were also treated. Both the inverse and direct problems of dynamics were addressed. A comparative analysis was carried out of the numerical complexity of various existing algorithms of numeric-iterative type dealing with the problems of spatial active mechanisms dynamics. It has been shown that the proposed method regardless of its generality, approaches by its models complexity symbolic models, which are valid for particular robotic mechanisms only where they achieve a high degree of efficiency.
Inverse kinematics of six-degree of freedom “general” and “special” manipulators using symbolic computation
Authors: Mavroidis C. , Ouezdou F. B. , Bidaud P.
Published: March 2009

This paper presents an algorithm that solves the inverse kinematics problem of all six degrees of freedom manipulators, “general” or “special”. A manipulator is represented by a chain of characters that symbolizes the position of prismatic and revolute joints in the manipulator and the special geometry that may exist between its joint axes. One form of the loop closure equation is chosen and the Raghavan and Roth method is used to obtain symbolically a square matrix. The determinant of this matrix yields the characteristic polynomial of the manipulator in one of the kinematic variables. As an example of the use of this algorithm we present the solution to the inverse kinematics problem of the GMF Arc Mate welding manipulator. In spite of its geometry, this industrial manipulator has a non-trivial solution to its inverse kinematics problem.
Observer-based sliding mode control of a robotic manipulator
Authors: Jezernik Karel , Curk Boris , Harnik Jože
Published: March 2009

This paper presents a new approach for the design of variable structure control (VSC) of nonlinear systems. The approach is based on estimation of joint acceleration signals with introduction of load estimation with the asymptotic observer. The control system is insensitive to parameter variations for a chosen switching hypersurface in conditions when it is reached by the dynamic motion with the required dynamics. The parameter insensitive response provided by this control method is demonstrated on the model of the SCARA robot. Simulation results confirm the validity of accurate tracking capability and the robust performance.
Fusing sensor information using fuzzy measures
Authors: Odeberg Hans
Published: March 2009

In a measurement system with intelligent, distributed sensor processes, complementary observations from different sensor need be combined with each other. This paper describes a method based on fuzzy measures, in which a global ‘fusion algorithm’ questions the sensors as to their support and opinion of a hypothesis. The sensor opinions are clustered into groups based on their support of each others' opinions, and fused using a new fuzzy operator.
A hierarchical strategy for planning crab gaits of a quadruped walking robot
Authors: Lee Yun Jung , Bien Zeungnam
Published: March 2009

A method of planning crab gaits for a quadruped walking robot is proposed. In the conventional gait study, one of the major concerns has been the foothold selection based on a prescribed body motion, but, in the paper, we consider the body motion planning problem under the assumption that a set of irregular footholds is given, and propose a hierarchical strategy. The strategy can be divided into three stages: first, a feasible range of the body movement is sought under the kinematic limit and the stability constraint. Next, a swing-leg sequence is selected with the aid of a proposed measure of traversability. Finally, an optimal sequence of the body motion is planned by the proposed procedure of otpimizing the gait stability margin. To verify the efficiency of the proposed method, simulation results are presented.
A vision system for mobile robot navigation
Authors: Boudihir M. Elarbi , Dufaut M. , Husson R.
Published: March 2009

A new vision system architecture has been developed to support the visual navigation of an autonomous mobile robot. This robot is primarily intended for urban park inspection, so it should be able to move in a complex unstructured environment. The system consists of various modules each ensuring a specific task involved in autonomous navigation. Task coordination focuses on the central module called the supervisor which triggers each module at the time appropriate to the current situation of the robot. Most of the processing time is spent with the scene exploration module which is based on the Hough transform to extract the dominant straight features. This module operates in two modes: the initial phase which forms the type of processing applied to the first image acquired in order to initiate navigation, and the continuous following mode which ensures the processing of subsequent images taken at the end of the blind distance. In order to rely less on visual data, a detailed map of the environment has been established, and an algorithm is used to make a scene prediction based on robot position provided by the localization system. The predicted scene is used to validate the objects detected by the knowledge base. This knowledge base uses the acquired and predicted data to construct a scene model which is the main element of the vision system.
Trajectory control of robotic manipulators by using a feedback-error-learning neural network
Authors: Hamavand Zaryab , Schwartz Howard M.
Published: March 2009

This paper presents a neural network based control strategy for the trajectory control of robot manipulators. The neural network learns the inverse dynamics of a robot manipulator without any a priori knowledge of the manipulator inertial parameters nor any a priori knowledge of the equation of dynamics. A two step feedback-error-learning process is proposed. Strategies for selection of the training trajectories and difficulties with on-line training are discussed.
Design of a robust dynamic gait of the biped using the concept of dynamic stability margin
Authors: Seo Young-Jin , Yoon Yong-San
Published: March 2009

A computational technique for designing a physically realizable robust dynamic gait for a planar biped robot is developed. Firstly, a feasible set of gaits was constructed to satisfy the periodicity of the biped locomotion. Then the concept of dynamic, stability margin is introduced based on the robustness of a gait with respect to the external disturbances. Using that margin, we can assess the robustness of each dynamic gait in the feasible set. It is found that the parameter, called foot strike time margin, representing the readiness of the foot strike has a close positive correlation with the dynamic stability margin. We obtain a robust gait with respect to the external disturbance by maximizing the foot strike time margin. The robustness of the optimal gait is confirmed by the behavior of the gait after application of linear impulse as well as by the examination of the largest eigenvalue at the perturbed state.
Parametric study and sensitivity analysis of automated vehicles
Authors: Mehrabi M. G. , Cheng R. M. H. , Hemam A.
Published: March 2009

This paper presents a parametric study of automated vehicles using the sensitivity theory. A sixth order dynamic model of an axisymmetric vehicle is developed in the state space format to represent its 3 degrees-of-freedom motion in the lateral, yaw and roll modes. Variations of the important parameters of the vehicle are grouped into three separate vectors: with the elements consisting of inertia, stiffness and damping, and geometric-kinematic parameters respectively. The effect of every element of these vectors on the state variables is studied carefully, a comparison being made among the state variables to reveal the relative influence of the parameter-induced variations. This helps better understanding which mode of the system is more affected by changes in particular parameters and the severity in the transient response and in the steady-state response. Then the effects of a particular vector on the performance of the system is studied.
A new neural network control technique for robot manipulators
Authors: Jung Seul , Hsia T. C.
Published: March 2009

A new neural network (NN) control technique for robot manipulators is introduced in this paper. The fundamental robot control technique is the model-based computed-torque control which is subjected to performance degradation due. to model uncertainty. NN controllers have been traditionally used to generate a compensating joint torque to account for the effects of the uncertainties. The proposed NN control approach is conceptually different in that it is aimed at prefiltering the desired joint trajectories before they are used to command the computed-torque-controlled robot system (the plant) to counteract performance degradation due to plant uncertainties. In this framework, the NN controller serves as the inverse model of the plant, which can be trained on-line using joint tracking error. Several variations of this basic technique is introduced; Back-propagation training algorithms for the NN controller have been developed. Simulation results have demonstrated the excellent tracking performance of the proposed control technique.
Robotic grasping of complex shapes: is full geometrical knowledge of the shape really necessary?
Authors: Rodrigues M. A. , Li Y. E. , Lee M. H. , Rowland J. J.
Published: March 2009

This paper aims at contributing to a sub-symbolic, feedback-based “theory of robotic grasping” where no full geometrical knowledge of the shape is assumed. We describe experimental results on grasping 2D generic shapes without traditional geometrical processing. Grasping algorithms are used in conjunction with a vision system and a robot manipulator with a three-fingered gripper is used to grasp several different shapes. The altorithms are run on the shape as it appears on the computer screen (i.e. directly from a vision system). Simulated gripper ringer with virtual sensors are configured and positioned on the screen whose inputs are controlled by moving their position relative to the image until an equilibrium is reached among the control systems involved.
Three methods of training multi-layer perceptrons to model a robot sensor
Authors: Pham D. T. , Sagiroglu S.
Published: March 2009

This paper discusses three methods of training multi-layer perceptrons (MLPs) to model a six-degrees-of- freedom inertial sensor. Such a sensor is designed for use with a robot to determine the location of objects it has to pick up. The sensor operates by measuring parameters related to the inertia of an object and computing its location from those parameters. MLP models are employed for part of the computation. They are trained to output the orientation of the object in response to an input pattern that includes the period of natural vibration of the sensor on which the object rests. After reviewing the working principle of the sensor, the paper describes the three MLP training methods (backpropagation, optimisation using the Levenberg-Marquardt algorithm, evolution based on the genetic algorithm) and presents the experimental results obtained.
Near Time-Optimal Collision-Free Motion Planning of Robotic Manipulators Using an Evolutionary Algorithm
Authors: Rana A.S. , Zalzala A.M.S.
Published: March 2009

A technique for open-loop minimum time planning of time-histories of control torques for robotic manipulators subject to constraints on the control torques using evolutionary algorithm is presented here. Planning is carried out in joint space of the manipulator and the path is represented as a string of via-points connected by cubic spline polynomial functions. Repeated path modification is done by using the evolutionary algorithm to search for a time-optimal path. Time taken to traverse over a particular path is calculated by reducing the dynamic equations of motion over that path in terms of a path parameter and then calculating the time optimal-control over that path.
A configuration space based approach for robotic assembly sequencing
Authors: Bhatia Praveen , Zalzala A.M.S. , Ghosh Amitabh
Published: March 2009

This paper describes a compact assembly sequencer for automatic robotic assembly using a configuration space-based path planner. Connection graph of the assembly is constrained by the feasibility information made available from the analysis of local disassembly paths tried by the robot's path planner. Free space of the robot performing assembly is explicitly used to generate the disassembly constraints. We show with the help of a ball pen assembly how the sequencing is performed with this representation.
Effect of payloads contact upon the coupled dynamic response of two cooperating robots
Authors: Shagal G. , Meguid S.A.
Published: March 2009

The coupled dynamic response of two cooperating robots handling two flexible payloads is treated using a new algorithm. In this algorithm, the dynamic equations describing the system are obtained using Lagrange's method for the rigid robot links and the finite element method for the flexible payloads. The contact between the flexible payloads is modelled using the penalty function method and a contact search algorithm is employed to identify the contact region.
Adaptive hybrid force/position control for the Space Station Alpha robotic operations
Authors: Kalaycioglu S. , Brown A.
Published: March 2009

The Space Station Alpha is the most significant international space project of this century and the largest international technology development project ever undertaken. The space robot manipulators will be a substantial part of the space station and will perform tasks such as assembly as well as maintenance of the station. Therefore the robot manipulators need a very sophisticated real-time control capability for gross and fine motions (i.e. compliant motions) during various operations. Moreover, the proposed dual-arm robot system servicing the Space Station requires automated motion coordination, synchronization of the arms, and controlled mechanical interaction with fixed and moving objects involved in various tasks.
Optimal turning gait of a quadruped walking robot
Authors: Cho D. J. , Kim J. H. , Gweon D. G.
Published: March 2009

The analysis of the gait mode is an important step for constructing a walking robot. In this study an optimal turning gait of a four-legged walking robot is proposed, which maximizes walking speed keeping walking stability larger than a certain required value. To obtain an optimal gait algorithm, for body trajectory of the robot, maximum walking speed, feasible gait modes and stability margin are analyzed for a quadruped walking robot designed in this study. The proposed gait is sufficiently flexible, as to permit crab walking, turning walking and a pure rotational walking about a robot's geometric center. The validity of the proposed gait algorithm is confirmed by many simulations.
Coordinated-motion control of heavy-duty industrial machines with redundancy
Authors: Singh N. , Zghal H. , Sepehri N. , Balakrishnan S. , Lawrence P. D.
Published: March 2009

An implementation of a real-time scheme suitable for coordinated-motion control of a class of teleoperated industrial machines with redundancy is presented. An efficient gradient projection technique is adopted for the numerical solution. The scheme utilizes the redundancy to avoid the joint limits by minimizing a hyperbolic function of the joint distances from the mid-range. This new performance criterion is shown to be advantageous over similar criteria; both the joint-limit avoidance capability and the resulting joint velocity profiles can be adjusted by the appropriate choice of parameters introduced in the criterion. Previous criteria are shown to be special cases of the new criterion. Furthermore, the scheme includes a novel algorithm which incorporates the bounded joint velocities. The joint motions are determined considering both the required task in terms of the desired end-effector speed and the dynamic considerations, such as hydraulic circuit interdependency and power limitations.

The feasibility and effectiveness of the implementation of the scheme is first tested through simulations of a Kaiser Spyder-like excavator machine on a PC-486 micro-computer. The robustness and real-time response of the scheme are then validated on a real-time excavator-based graphics simulator interfaced to a human operator through a joystick.
Robot performance measurement and calibration using a 3D computer vision system
Authors: Preising B. , Hisa T. C.
Published: March 2009

Present day robot systems are manufactured to perform within industry accepted tolerances. However, to use such systems for tasks requiring high precision, various methods of robot calibration are generally required. These procedures can improve the accuracy of a robot within a small volume of the robot's workspace. The objective of this paper is to demonstrate the use of a single camera 3D computer vision system as a position sensor in order to perform robot calibration. A vision feedback scheme, termed Vision-guided Robot Control (VRC), is described which can improve the accuracy of a robot in an on-line iterative manner. This system demonstrates the advantage that can be achieved by a Cartesian space robot control scheme when end effector position/orientation are actually sensed instead ofcalculated from the kinematic equations. The degree of accuracy is determined by setting a tolerance level for each of the six robot Cartesian space coordinates. In general, a small tolerance level requires a large number of iterations in order to position the end effector, and a large tolerance level requires fewer iterations. The viability of using a vision system for robot calibration is demonstrated by experimentally showing that the accuracy of a robot can be drastically improved. In addition, the vision system can also be used to determine the repeatability and accuracy of a robot in a simple, efficient, and quick manner. Experimental work with an IBM Electric Drive Robot (EDR) and the proposed vision system produced a 97 and a 145 fold improvement in the position and orientation accuracy of the robot, respectively.
Path constrained time-optimal motion of a cooperative two robot system
Authors: Cho Hye-Kyung , Lee Bum-Hee , Ko Myoung-Sam
Published: March 2009

This paper presents a systematic approach to the time-optimal motion planning of a cooperative two robot system along a prescribed path. First, the minimum-time motion planning problem is formulated in a concise form by parameterizing the dynamics of the robot system through a single variable describing the path. The constraints imposed on the input actuator torques and the exerted forces on the object are then converted into those on that variable, which result in the so-called admissible region in the phase plane of the variable. Considering the load distribution problem that is also involved in the motion, we present a systematic method to construct the admissible region by employing the orthogonal projection technique and the theory of multiple objective optimization. Especially, the effects of viscous damping and state-dependent actuator bounds are incorporated into the problem formulation so that the case where the admissible region is not simply connected can be investigated in detail. The resultant time-optimal solution specifies not only the velocity profile, but also the force assigned to each robot at each instant. Physical interpretation on the characteristics of the optimal actuator torques is also included with computer simulation results.
Dynamic modeling and simulation of two cooperating structurally-flexible robotic manipulators
Authors: Krishnamurthy K. , Yang L.
Published: March 2009

A dynamic model for two three-link cooperating structurally-flexible robotic manipulators is presented in this study. The equations of motion are derived using the extended Hamilton's principle and Galerkin's method, and must satisfy certain geometric constraints due to the closed chain formed by the two manipulators and the object. The dynamic model presented here is for the purpose of designing controllers. Therefore, a low-order model which captures all the major effects is of interest. Computer simulated results are presented for the case of moving an object along an elliptical path using the two cooperating flexible manipulators.
A semi-flexible kinematic model for serial manipulators
Authors: Cléroux Louise , Gourdeau Richard , Cloutier Guy M.
Published: March 2009

Structural and control flexibilities affect the absolute precision of serial manipulators. A semi-flexible kinematic model is developed, to improve the absolute static precision. It expands the solid body model by incorporating a spring effect for each joint and a beam effect for each link. Simulation results confirm the adequacy of the model. The dependencies existing between the articulate posture of the manipulator, the effects of the external efforts and the gravitational load on the global structure are properly described. The identifiability of the added parameters is explored on a RR planar robot. It requires efforts and pose errors to be known in the tool frame only.
Global optimal control of redundant robot
Authors: Gotlih Karl , Troch Inge , Jezernik Karel
Published: March 2009

A global optimal control algorithm was developed with the aim of finding a control which satisfies some special requirements in the sense of obtaining singular position free movement of the redundant robot mechanism. The solution of the developed global optimal control algorithm is a boundary value problem. The additional constraints in the boundary value problem were constructed with the use of an optimization process. The usefulness of the developed global optimal control algorithm is demonstrated by the example of the 3 DOFs planar redundant robot mechanism of SCARA type.
Hybrid external control for two robot coordinated motion
Authors: Perdereau Véronique , Drouin Michel
Published: March 2009

In the field of robotic applications based on the coordinated motion of two manipulators, it seems that very few control schemes work efficiently. The best way to achieve the simultaneous control of object trajectory and forces applied to it, is to implement control schemes that are extended versions of one arm hybrid force'position control. The aim of this paper is not to review all existing solutions but rather to analyze and compare them from simulation results with a new solution presented here. The control scheme is an application of the one arm hybrid external control that we had previously developed. The main results of this theory are summarized in this paper. This radically new approach for a cooperation task has some advantages compared to other methods mentioned in this paper.
Active visual sensing of the 3-D pose of a flexible object
Authors: Byun Jong-Eun , Nagatat Tadashi
Published: March 2009

This paper presents an active visual method for determining the 3-D pose of a flexible object with a hand-eye system. Some simple and effective on-line algorithms to overcome various exceptional situations in chaincoding or determine the object pose more precisely are developed. The pose of a flexible object can be easily changed because of the flexible nature and the prediction of the pose is almost impossible. A new sensing pose is computed by using the image coordinates of the points on the border line of an image window and the current pose of a hand-eye system for the cases that the flexible object is extended outside the window. In a case of exceptional overlapping, a new sensing pose is computed by using the image coordinates of four extreme image points and the current pose of the hand-eye system. Through a chaincoding process on the skeletonized images, the stereo matching problem of two images is transformed into the matching of the curvature representations of the two skeletonized images. The 3-D pose of a flexible object is computed by using the results of this matching and the camera and hand-eye parameters calibrated beforehand. The initial sensing results are used in computing a new sensing pose to determine the object more precisely.
An Advanced Robot Control Scheme Using ANN and Fuzzy Theory Based Solutions
Authors: Rudas Imre J. , Bitó János F. , Tar József K.
Published: March 2009

Due to the essential development of different means of numerical computation in the last years, new prospects have been opened for realization of different advanced control methods as conventional reasoning, fuzzy rule or ANN-basedAIcontrols. However, it can clearly be seen, that each of these methods have significant technological limits making it expedient to seek compromises between the application of such methods and certain particular hardware solutions designed for a concrete problem. The aim of this paper is to show that in quite wide a range of practically important control tasks appropriate hardware solutions can be elaborated and combined with the above methods.
A 4-degrees-of-freedom microrobot with nanometer resolution
Authors: Breguet J.-M. , Renaud Ph.
Published: March 2009

A new type of microrobot is described. Its simple and compact design is believed to be of promise in the microrobotics field. Stepping motion allows speeds up to 4mm/s. Resolution smaller than 10 nm is achievable. Experiments in an open-loop motion demonstrated a repeatability better than 50µm on a 10 mm displacement at an average speed of 0.25 mm/s. A position feedback based on a microvision system will be developed in order to achieve a submicron absolute position accuracy.
Local joint control in cooperating manipulator systems - force distribution and global stability
Authors: Luecke Greg R. , Gardner John F.
Published: March 2009

Almost all industrial robot applications in use today are controlled using a control law that is simple and computationally efficient, local joint error feedback. When two or more open chain manipulators cooperate to manipulate the same object - such as in mechanical grippers, walking machines, and cooperating manipulator systems - closed kinematic chain, redundantly actuated mechanisms are formed. Control approaches for this type of system focus on the more computationally intensive computed torque or inverse plant control laws, due to the concern over instability caused by the unspecified distribution of control forces in the redundant actuator space, and due to the constrained motion caused by the closed kinematic chains.
Historical perspectives and state of the art in joint force sensory feedback control of manipulation robots
Authors: Stockić Dragan , Vukobratović Miomir
Published: March 2009

The application of the joint force sensory feedback in both the gross and fine motion control of manipulation robots is considered in the paper. One of the objectives of the paper is to give a historical overview how the idea of the joint force sensory feedback has appeared and developed in the past two decades. The control schemes, which include joint torque sensory feedback, are surveyed in the paper. The main advantages of this approach are discussed: the joint torque feedback offers an elegant way to compensate for the effects of the robot dynamics without real time computation of the robot dynamics, the control schemes are robust in respect of parameter variations. Various problems regarding design and implementation of joint torque sensor are also considered. Special emphasis is given to the application of this approach in hybrid position/force control schemes.
Introduction to the special issue on robotics for health care
Authors: Kassler Michael
Published: March 2009

Robots in the 20th century have been valued mainly for their enhancement of productivity. According to Professor Ichiro Kato of Waseda University, 21st-century robots will be valued because they enhance amenity. The development of robot systems for health care, detailed in this special issue of Robotica, is an affirmation of this forecast.

Several factors have combined to cause this development, although economic factors are paramount. Industrialised countries, where robots are most likely to be used, face an ageing population-a result of lower birth rates, reduced infant mortality and increased life expectancy. This ‘ageing society' is expected to have enormous impact upon these countries’ health and social security systems which devote a large proportion of their resources to the care of older people.
Early experience in the use of the ‘Handy 1’ robotic aid to eating
Authors: Topping Mike
Published: March 2009

More than 50 ‘Handy 1’ robotic aids are now in use that enable some handicapped people to feed themselveswithout assistance from a carer. The benefits of thisdevice include much greater control of the eating process by the user as well as the development of eating skills. The article describes the genesis of this device and its subsequent development and early evaluation.
Development and methodology for the formal evaluation of the Neil Squire Foundation robotic-assistive appliance
Authors: Birch Gary E.
Published: March 2009

It is expected that an appropriate robotic appliance can play a major role in providing long periods of independence, which in turn will lead to improved quality of life, for people who are severely physically limited. As part of its research programme over the past several years the Neil Squire Foundation has been developing a workstation-based robotic assistive appliance (RAA) for use by such persons. We feel that robotic aids initially will have their most profound impact when applied in a vocational environment. Although other rehabilitation researchers have similar interests there is a great need for the utility of robots in these environments to be more fully substantiated and assessed. A formal evaluation process currently is under way in an attempt to quantify and to understand the cost/benefit results of using the RAA in office situations.