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Showing papers in "Robotica in 1998"


Journal ArticleDOI
01 Nov 1998-Robotica
TL;DR: The algorithm is used to establish design guidelines and a globally optimal architecture for a planar haptic interface from both a kinematic and dynamic perspective and to choose the optimum geometry for a 6-DOF Stewart Platform.
Abstract: A new global isotropy index (GII) is proposed to quantify the configuration independent isotropy of a robot's Jacobian or mass matrix. A new discrete global optimization algorithm is also proposed to optimize either the GII or some local measure without placing any conditions on the objective function. The algorithm is used to establish design guidelines and a globally optimal architecture for a planar haptic interface from both a kinematic and dynamic perspective and to choose the optimum geometry for a 6-DOF Stewart Platform. The algorithm demonstrates consistent effort reductons of up to six orders of magnitude over global searching with low sensitivity to initial conditions.

120 citations


Journal ArticleDOI
01 Mar 1998-Robotica
TL;DR: This article deals with the kinematic calibration of the Delta robot and a measurement set-up is presented which allows to determine the end-effector's position and orientation with respect to the base.
Abstract: This article deals with the kinematic calibration of the Delta robot. Two different calibration models are introduced: The first one takes into account deviations of all mechanical parts except the spherical joints, which are assumed to be perfect (“model 54”), the second model considers only deviations which affect the position of the end-effector, but not its orientation, assuming that the “spatial parallelogram” remains perfect (“model 24”). A measurement set-up is presented which allows to determine the end-effector's position and orientation with respect to the base. The measurement points are later be used to identify the parameters of the two calibration model resulting in an accuracy improvement of a factor of 12.3 for the position and a factor of 3.7 for the prediction of the orientation.

120 citations


Journal ArticleDOI
01 Sep 1998-Robotica
TL;DR: A critical review of the well-known resolved-acceleration technique for the tracking control problem of robot manipulators in the task space is provided and an alternative Euler angles feedback scheme is proposed which shows an advantage in terms of avoidance of representation singularities.
Abstract: The goal of this paper is to provide a critical review of the well-known resolved-acceleration technique for the tracking control problem of robot manipulators in the task space. Various control schemes are surveyed and classified according to the type of end-effector orientation error; namely, those based on Euler angles feedback, quaternion feedback, and angle/axis feedback. In addition to the assessed schemes in the literature, an alternative Euler angles feedback scheme is proposed which shows an advantage in terms of avoidance of representation singularities. An insight into the features of each scheme is given, with special concern to the stability properties of those schemes leading to nonlinear closed-loop dynamic equations. A comparison is carried out in terms of computational burden. Experiments on an industrial robot with open control architecture have been carried out, and the tracking performance of the resolved-acceleration control schemes in a case study involving the occurrence of a representation singularity is evaluated. The pros and cons of each scheme are evidenced in a final discussion focused on practical implementation issues.

92 citations


Journal ArticleDOI
01 Sep 1998-Robotica
TL;DR: The design requirements, the methods of detection of the signals and the training required to operate the hand are outlined, and more than one degree of freedom can be controlled and a greater and more natural functional range is possible.
Abstract: The current designs of commercial artificial hands have a low level of innovation. As feedback to the user is difficult to achieve reliably, most devices are simple in design and operation, and limited in functional range. If information on the state of the hand, the forces and any slippage that is occurring is fed back to a microcontroller then more than one degree of freedom can be controlled and a greater and more natural functional range is possible. This paper describes the development of such a device. It outlines the design requirements, the methods of detection of the signals and the training required to operate the hand.

82 citations



Journal ArticleDOI
01 Sep 1998-Robotica
TL;DR: Several simulation results of specific task-oriented variants of the basic path planning problem using the proposed genetic algorithm using a bit-string encoding of selected graph vertices show higher or at least equally well performance for the genetic algorithm.
Abstract: A genetic algorithm for the path planning problem of a mobile robot which is moving and picking up loads on its way is presented. Assuming a findpath problem in a graph, the proposed algorithm determines a near-optimal path solution using a bit-string encoding of selected graph vertices. Several simulation results of specific task-oriented variants of the basic path planning problem using the proposed genetic algorithm are provided. The results obtained are compared with ones yielded by hill-climbing and simulated annealing techniques, showing a higher or at least equally well performance for the genetic algorithm.

65 citations


Journal ArticleDOI
01 Jul 1998-Robotica
TL;DR: In this article, a hybrid approach to optimize the counterweight balancing of a robot arm is presented, which combines an artificial intelligence technique called the GA and the weighted min-max multiobjective optimization method.
Abstract: This paper presents a hybrid approach to optimize the counterweight balancing of a robot arm. A new technique that combines an artificial intelligence technique called the genetic algorithm (GA) and the weighted min-max multiobjective optimization method is proposed. These techniques are included in a system developed by the authors, called MOSES, which is intended to be used as a tool for engineering design optimization. The results presented here show how the new proposed technique can get better trade-off solutions and a more accurate Pareto front for this highly non-convex problem using an ad-hoc floating point representation and traditional genetic operators. Finally, a methodology to compute the ideal vector using a genetic algorithm is presented. It is shown how with a very simple dynamic approach to adjust the parameters of the GA, it is possible to obtain better results than those previously reported in the literature for this problem.

48 citations


Journal ArticleDOI
01 Sep 1998-Robotica
TL;DR: Functional aspects are stressed as a basis for technical implementations, with special attention to the ergonomics of interactive control of the manipulator-wheelchair system in unstructured human environments.
Abstract: Realisations and concepts are presented on the control of the MANUS wheelchair-mounted telemanipulator arm by severely disabled persons with few residual functions Functional aspects are stressed as a basis for technical implementations, with special attention to the ergonomics of interactive control of the manipulator-wheelchair system in unstructured human environments Adaptability of the control is accentuated, both with respect to abilities and impairments of the individual user and with respect to characteristics of the environment and the task to be executed Some methods to improve adaptability are discussed, and the need for standard interfacing methods is underlined Control configurations in actual daily use by persons with different severe disabilities are presented in some detail A first implementation of integrated chin joystick control of MANUS manipulator and electric wheelchair, in daily use by a person with a C4/C5 spinal cord lesion, is reported as an example

45 citations


Journal ArticleDOI
01 Sep 1998-Robotica
TL;DR: It is experimentally demonstrated that the proposed control laws realize higher acceleration and lower reaction force than other force display systems.
Abstract: In this paper, we develop a force display system using parallel wire mechanism for virtual sports training with high speed motion. We firstly point out a control issue of the force display system driven by parallel wire mechanism. Based on the analysis, control laws are proposed to improve performance of the force display system. It is experimentally demonstrated that the proposed control laws realize higher acceleration and lower reaction force than other force display systems. Using the experimental result, the performance of the system is evaluated quantitatively.

41 citations


Journal ArticleDOI
Ick-Chan Shim1, Yong-San Yoon1
01 Mar 1998-Robotica
TL;DR: The minimization of the ∞-norm of the joint torques subject to the feasibility constraint is shown to improve the performances through the simulations of a 3-link planar redundant manipulator.
Abstract: The minimization of the joint torques based on the ∞-norm is proposed for the dynamic control of a kinematically redundant manipulator. The ∞-norm is preferred to the 2-norm in the minimization of the joint torques since the maximum torques of the actuators are limited. To obtain the minimum ∞-norm torque solution, we devised a new algorithm that uses the acceleration polyhedron representing the end-effector's acceleration capability. Usually the minimization of the joint torques has an instability problem for the long trajectories of the end-effector. To suppress this instability problem, an inequality constraint, named the feasibility constraint, is developed from the geometrical relation between the required end-effector acceleration and the acceleration polyhedron. The minimization of the ∞-norm of the joint torques subject to the feasibility constraint is shown to improve the performances through the simulations of a 3-link planar redundant manipulator.

41 citations


Journal ArticleDOI
01 Nov 1998-Robotica
TL;DR: This paper concerns the modeling and control of a mobile manipulator which consists of a robotic arm mounted upon a mobile platform and a variable structure control approach is employed to minimize the harmful effect of the wheel slip on the tracking performance.
Abstract: This paper concerns the modeling and control of a mobile manipulator which consists of a robotic arm mounted upon a mobile platform. The equations of motion are derived using the Lagrange-d'Alembert formulation for the nonholonomic model of the mobile manipulator. The dynamic model which considers slip of the platform's tires is developed using the Newton-Euler method and incorporates Dugoff's tire friction model. Then, the tracking problem is investigated by using a well known nonlinear control method for the nonholonomic model. The adverse effect of the wheel slip on the tracking of commanded motion is discussed in the simulation. For the dynamic model, a variable structure control approach is employed to minimize the harmful effect of the wheel slip on the tracking performance. The simulation results demonstrate the effectiveness of the proposed control algorithm.

Journal ArticleDOI
01 May 1998-Robotica
TL;DR: Lagrange's impact model is used to derive a general form of impact equations for an industrial manipulator performing peg-in-hole assembly and the impact equations of a SCARA robot are obtained and utilized to investigate how the system parameters affect force impulse and departure angle in the assembly of a peg with a chamfered hole.
Abstract: This paper presents an approach for analyzing the dynamics of initial impact during robotic parts mating represented by peg-in-hole assembly. Lagrange's impact model is used to derive a general form of impact equations for an industrial manipulator performing peg-in-hole assembly. Specific impact equations can then be generated for a given robot to analyze part motions and contact forces in the mating of parts. The impact equations of a SCARA robot are obtained and utilized to investigate how the system parameters affect force impulse and departure angle in the assembly of a peg with a chamfered hole. The resulting information is useful to robot manufacturers in design of robotic equipment and to robot users in determining optimal operational conditions. It is also useful for building an intelligent robot controller capable of deciding on proper values of operation parameters.

Journal ArticleDOI
01 Jul 1998-Robotica
TL;DR: Evaluated aspects of a generalized predictive control technique to an electro-hydraulic positioning actuator demonstrate good performance and the promise of the technique, and successful control tests could be performed repetitively.
Abstract: This paper reports the results of an experimental study, which was conducted to evaluate the performance and implementation aspects of a generalized predictive control (GPC) technique to an electro-hydraulic positioning actuator. Poor dynamics and high nonlinearities form part of the difficulty in the control of hydraulic functions which make the application of adaptive controls an attractive solution. The applicability of GPC to the position control of hydraulic manipulator has been investigated through computer simulations in the literature. However, there is no experimental record of applying this technique to an actual hydraulic system. A suitable plant model is established and recursive U-D factorization technique is adopted for on-line estimation of time-varying plant parameters. Experimental results are obtained from a laboratory electrohydraulic actuator test stand. Various benchmark tests, comprising step and tracking inputs, demonstrate good performance and the promise of the technique. In spite of significant actuator dynamics (control voltage saturation, flow nonlinearity and dry frictional nonlinearity in the hydraulic actuator), successful control tests could be performed repetitively.

Journal ArticleDOI
01 May 1998-Robotica
TL;DR: Geometric and quasi-static analyses of multiple-peg insertions are presented and a possible contact-state enumeration, geometric conditions for each contact- state, and the force-moment equations for static-equilibrium states of two dimensional dual-peg inserts are derived.
Abstract: Reliable flexible assembly workstations depend ultimately on the physics of assembly tasks performed. Multiple-peg insertions, as a practical assembly class, is complicated by the large number and kind of interaction between mating parts.In this article, geometric and quasi-static analyses of multiple-peg insertions are presented. First, a possible contact-state enumeration, geometric conditions for each contact-state, and the force-moment equations for static-equilibrium states of two dimensional dual-peg insertions are derived. The jamming diagrams and the taxonomy of dual-peg insertions are obtained. Then, an experiment to verify the analysis is presented.

Journal ArticleDOI
01 Jan 1998-Robotica
TL;DR: It is shown that the Adaptive FeedForward Controller AFFC) is well suited for learning the parameters of the dynamic equation, even in the presence of friction and noise.
Abstract: In this paper, nine adaptive control algorithms are compared. The best two of them are tested experimentally. It is shown that the Adaptive FeedForward Controller AFFC) is well suited for learning the parameters of the dynamic equation, even in the presence of friction and noise. The resulting control performance is better than with measured parameters for any trajectory in the workspace. When the task consists of repeating the same trajectory, an adaptive look-up-table MEMory, introduced and analyzed in this paper, is simpler to implement and results in even better control performance.

Journal ArticleDOI
01 Sep 1998-Robotica
TL;DR: A picture is drawn of the RR situation in Europe and aspects to move forward are discussed, including how to support people with severe disabilities in their daily life.
Abstract: Rehabilitation Robotics (RR) is a challenging field with a high potential to support people with severe disabilities in their daily life. In the past years this field developed in Europe with a European dimension. European consortia have been supported in technical development and investigations. Also, several robotic aids have been sold and installed in Europe and support end users in their daily life. However, the breakthrough on the market is still outstanding. This paper tries to draw a picture of the RR situation in Europe and discusses aspects to move forward. Particular reference is given to TIDE (Technology Initiative for Disabled and Elderly people of European Union) and the special interest group on RR (SIG-1) of the AAATE (Association for the Advancement of Assistive Technology in Europe).

Journal ArticleDOI
01 Sep 1998-Robotica
TL;DR: This paper addresses the possibility of designing some assistive technologies using impedance elements that can adapt to the user and the circumstances and proposes two impedance elements based on magnetic particle brakes and detuning the P-D controller in a servo-motor mechanism.
Abstract: A person with a moderate or severe motor disability will often use specialised or adapted tools to assist their interaction with a general environment. Such tools can assist with the movement of a person's arms so as to facilitate manipulation, can provide postural supports, or interface to computers, wheelchairs or similar assistive technologies. Designing such devices with programmable stiffness and damping may offer a better means for the person to have effective control of their surroundings.This paper addresses the possibility of designing some assistive technologies using impedance elements that can adapt to the user and the circumstances. Two impedance elements are proposed. The first, based on magnetic particle brakes, allows control of the damping coefficient in a passive element. The second, based on detuning the P-D controller in a servo-motor mechanism, allows control of both stiffness and damping. Such a mechanical impedance can be modulated to the conditions imposed by the task in hand. The limits of linear theory are explored and possible uses of programmable impedance elements are proposed.


Journal ArticleDOI
01 Jan 1998-Robotica
TL;DR: Two alternative controllers are developed in this paper, a computed-torque controller and a quadratic optimal controller, which are very relevant to larger manipulators, because it can be readily expanded by adding simple controllers for the other rigid links.
Abstract: Manipulators with some flexible links are attractive because they avoid the severe control problems associated with the large inertia forces generated when the large-mass, rigid links in conventional robot manipulators move at high speed. In fact only two of the links within a typical six degrees of freedom revolute-geometry industrial robot cause significant inertia forces, and so only these two links need to be flexible. The development of a two-flexible-link system controller is therefore very relevant to larger manipulators, because it can be readily expanded by adding simple controllers for the other rigid links. Two alternative controllers are developed in this paper, a computed-torque controller and a quadratic optimal controller. Simulations confirm the superior performance of the latter.

Journal ArticleDOI
01 May 1998-Robotica
TL;DR: This work has developed a constraint based methodology for case combination that allows its application across a wide range of problems and provides an efficient adaptation methodology that ensures convergence upon a solution if one exists.
Abstract: The frequent use of past experience by human engineers when solving new problems has led to an interest in the use of case based reasoning (CBR) to help automate engineering design. In engineering design it often occurs that many past exp eriences must be combined to solve a new problem, and thus the process of case based adaptation must efficiently and systematically combine information from many sources. We have developed a constraint based methodology for case combination that allows its application across a wide range of problems. We have shown that our approach provides an efficient adaptation methodology that ensures convergence upon a solution if one exists, provides a uniform representation of cases, and is generalizable beyond just one domain. Our technique is implemented in a case based reasoning system called COMPOSER, which ha s been tested in two design domains: assembly sequence design and configuration design.

Journal ArticleDOI
01 Jan 1998-Robotica
TL;DR: The controller proved robustness and good performance under rough conditions and in the manner of hybrid control, directions of a task frame can be selected to be force, impedance or position controlled.
Abstract: Common geared industrial robots call for force control methods with special properties such as good rejection of frictional disturbances, smoothness of corrective motions, and more. A new method is presented which meets these requirements and provides a high control bandwidth. In the manner of hybrid control, directions of a task frame can be selected to be force, impedance or position controlled. A joint-based inner position loop and a superimposed predictive force controller are used. Practical results include data from a robotic grinding facility. Here, the controller proved robustness and good performance under rough conditions.

Journal ArticleDOI
01 Mar 1998-Robotica
TL;DR: In the presence of the constraint uncertainties under investigation, the desired position and constraint force can be guaranteed with global asymptotic convergence.
Abstract: In this paper, the global stability problem for constrained robot motions in the presence of constraint uncertainties is investigated. We focus on the uncertainties in the constraint functions and their effects on the global stability. PD type controllers are used and conditions for global stability are developed using Lyapunov's direct approach. In the presence of the constraint uncertainties under investigation, the desired position and constraint force can be guaranteed with global asymptotic convergence. The developed conditions for feedback gain selections clearly show the effects of the constraint uncertainties. For the case when the velocity measurements are not available, conditions for global stability regulation are also established and the robot controller uses only the measurements of the position angles. Finally, we consider the case where the robot joints are flexible and global stability conditions are given.

Journal ArticleDOI
01 Jul 1998-Robotica
TL;DR: The CAIR-2 robot as mentioned in this paper is an intelligent mobile robot with three major parts: Behaviors, Planner, and Coordinator, which consists of a flexible human interface and a planner itself.
Abstract: One of the most difficult challenges in mobile robotics is real-world navigation. A real world can change suddenly and this change makes the robot relinquish planning actions in advance. In order to overcome such a change, behavior-based navigation was introduced. However, it had a difficulty in planning deliberate actions and in communicating with humans.We propose a new control strategy combining both the merits of behavior-based and planner-based approaches. The architecture consists of three major parts: Behaviors, Planner, and Coordinator. The Planner plays two important roles: 1) as a flexible human interface and 2) as the planner itself. The Coordinator serves as an interface between Behaviors and Planner and guides Behaviors to accomplish meaningful tasks according to the guidelines from the Planner and the Position estimator.We also provide a brief description of the intelligent mobile robot CAIR-2 and for '95 IJCAI/AAAI Robot Competition and Exhibition when the robot was placed first in the Office Delivery event.

Journal ArticleDOI
01 Jul 1998-Robotica
TL;DR: This paper investigates the trajectory generation problem for a four-wheel-steering tractor/semi-trailer system, and it is shown that this nonholonomic constraint problem can be converted into one of finding fitting-functions satisfying certain necessary boundary conditions.
Abstract: A basic problem in the development of an intelligent vehicle/highway system (IVHS), or an autonomous mobile robot system (AMRS) is to find suitable input controls which can be used to drive the vehicle between any two configurations. In this paper a trajectory generation problem for a four-wheel-steering tractor/semi-trailer system is investigated, and it is shown that this nonholonomic constraint problem can be converted into one of finding fitting-functions satisfying certain necessary boundary conditions. Proposals for control laws are presented and simulation results for a lane change manoeuvre are given.

Journal ArticleDOI
Makoto Suzuki1, Ken Masamune1, Lin-Jong Ji1, Takeyoshi Dohi1, Hideo Yano 
01 Sep 1998-Robotica
TL;DR: An interface method using force sensors is examined and concluded that it can detect the user's motion at the beginning of a walk and can be used to assist walking of elderly people.
Abstract: This paper presents a prototype development of a robot arm to assist walking of elderly people. For effective use in Japanese houses, a robot arm mounted on a rail was designed. Force sensors were used to provide an easy-to-use interface. Thresholds of forces were determined to detect the user's intention to walk as well as for safety considerations. Applying a step by step motion, the arm could follow the rhythmical walking of the subject. We examined an interface method using force sensors and concluded that it can detect the user's motion at the beginning of a walk.

Journal ArticleDOI
01 May 1998-Robotica
TL;DR: This paper presents a method of analyzing and evaluating the assemblability of a product under given tolerance specifications in order to provide a tool to aide for tolerance design.
Abstract: The design of tolerances should take the functionality, manufacturability, assemblability and cost effectiveness of a product into consideration. This paper presents a method of analyzing and evaluating the assemblability of a product under given tolerance specifications in order to provide a tool to aide for tolerance design. Introduced is the range of feasible displacement of a part of an assembly as a result of the accumulation of clearances between mating parts along the serial as well as parallel chain of assembly, which can play a role of compensating for the pose error of the corresponding part due to the accumulation of tolerances. Assemblability is determined by the probability that all the parallel as well as serial chains of the assembly can be f ormed successfully under given statistical properties of tolerances. This requires to numerically compute the probability that a pair of mating parts forming a parallel chain can align themselves within the error margin defined by their mating clearance, accounting for the possible compensation of the ranges of pose errors associated with the mating parts due to tolerance accumulations by the ranges of feasible displacements of the mating parts due to clearance accumulations. Simulation results are shown.


Journal ArticleDOI
01 Mar 1998-Robotica
TL;DR: Three curves, a quintic polynomial, a cubicPolynomial and a triangular function are developed to perform the parallel transfer manoeuvre which forms the basis of several important manoeuvres such as reverse parking, moving off, negotiating a stationary obstacle, overtaking a moving vehicle, and changing lane.
Abstract: One of the most fundamental problems in the development of an intelligent highway system or an autonomous mobile robot system for factory use is to find the necessary input control variables for smooth and safe movement of the vehicle, or robot, between any two configurations. In this paper it is demonstrated that this problem can be converted into one of finding a fitting function which satisfies the boundary conditions. Three curves, a quintic polynomial, a cubic polynomial and a triangular function are developed to perform the parallel transfer manoeuvre which forms the basis of several important manoeuvres such as reverse parking, moving off, negotiating a stationary obstacle, overtaking a moving vehicle, and changing lane. A detailed discussion of the effect of the vehicle's steering angle limit on the feasibility of these manoeuvres is presented. Simulation results using three typical vehicles, a long commercial vehicle, an ordinary car, and a small laboratory robot, travelling along three curves are also presented and discussed. Based on the comparative study, some suggestions for further work are made. Compared with other methods, this approach is simple and provides excellent simulation of human driver techniques. The paper concludes with a focused discussion about the integration of these techniques with satellite based GPS systems for automated vehicle guidance on highways.

Journal ArticleDOI
01 Mar 1998-Robotica
TL;DR: A neural network based algorithm for tim e-optimal trajectory planning is introduced that utilises neural networks for representing the inverse dynamics of the robot.
Abstract: Planning appropriate trajectories can significantly increase the productivity of robot systems. To plan realistic time-optimal trajectories, the robot dynamics have to be described precisely. In this paper, a neural network based algorithm for tim e-optimal trajectory planning is introduced. This method utilises neural networks for representing the inverse dynamics of the robot. As the proposed neural networks can be trained with data obtained from exciting the robot with given torque inputs, they will capture the complete dynamics of the robot system. Threfore, the trajectories generated will be mo re realistic than those obtained by using nominal dynamic equations based on nominal parameters. Time-optimal trajectories are generated for a PUMA robot to demonstrate the proposed method.

Journal ArticleDOI
Seon-Jae Kim1, Youn-sik Park1
01 Nov 1998-Robotica
TL;DR: The self-motion can be utilized to regulate flexibility and effectively reduce the end-effector tracking error, and the effectiveness and applicability have been demonstrated through numerical simulation with three-link planar robotic manipulators possessing flexible links.
Abstract: This paper focuses on overcoming the problem of tracking control in structurally flexible redundant manipulators by utilizing their self-motion capabilities. In the proposed algorithm, the self-motion is evaluated in order to nullify the dominant modal force of flexural motion that is induced by a rigid body motion.The flexure motions of manipulators, which are induced by joint motion, cause undesired inaccuracy in end-effector tracking. In-plath planning states, joint trajectories are so designed as not to excite but to damp out the flexure motions. The self-motion, inherent in redundant manipulators, can alter joint motion, influencing the flexure motion (by exciting and damping the flexure modes), while not affecting end-effector motion at all. Therefore, the self-motion can be utilized to regulate flexibility and effectively reduce the end-effector tracking error.The effectiveness and applicability of the proposed algorithm have been demonstrated through numerical simulation with three-link planar robotic manipulators possessing flexible links.