Common Workspace Research Articles

Synchronised Web Applications for Product Development in the 21st Century

Product development continues to be at the core of manufacturing industries and the heartland of global competition in the 21st century. The e-commerce technologies will have a profound impact on the practice and performance of product development. This paper examines the roles of web applications in collaborative product design and manufacture. The emphasis is placed not only upon the geographical and disciplinary dimensions, but also on the time dimension of collaboration. A case study is used to demonstrate how synchronised web applications can be used to facilitate collaborative product definition. The project team members share the common workspace that maintains the integrity and consistency of product and process information.

A model-based error recovery scheme for a multi-robot system

A work cell with multiple robots increases manufacturing flexibility and productivity. Robots in the work cell equipped in a sparse area usually share a motion path, resources and workspace. In this paper, an embedded Markov chain model for a multi-robot system that has a common workspace is constructed on the basis of the concept of a multi-processor system. With the presented model, we measure the performance of error recovery schemes under different workloads and analyze the sensitivity of the execution time with respect to the robot speed. We verify the presented model with an experimental multi-robot work cell. This study is useful in evaluating the performance of a robotic work cell and presents a guide for designing a complex work cell.

A Common Work Space to Support the Air Traffic Control

This paper deals with the research of means to build a Human-Machine Cooperation in the Air Traffic Control. The experiment described aims at evaluating a principle of dynamic allocation of conflict resolution on a large scale simulator of air traffic control. Artificial and human agents have to cooperate to exchange information, to take decision and to command the air traffic. To analyse and define cooperation between agents, the know-how and the know-how-to-cooperate are defined. These concepts give a structure which allows to build a Common Work Space to support more efficiently the cooperation.

TOGA—A customizable service for Data-Centric collaboration

Collaboration in cooperative information systems, like concurrent design and engineering, exploits common work and information spaces. In this paper we introduce the TOGA service (Transaction-Oriented Group and Coordination Service for Data-Centric Applications), which offers group management facilities and a push model for change propagation w.r.t. shared data, thus allowing for group awareness. Through TOGA's customizability and its layered architecture the service can be adapted to a variety of different collaboration scenarios. Multiple communication protocols (CORBA, UDP/IP, TCP/IP) are supported as well as basic transaction properties. Our approach enables both, firstly, the evolution of a set of separate applications to form a cooperative information system, i.e., it provides a technique towards component-oriented system engineering. Secondly, it can be exploited as a basic service within collaboration frameworks to effectively manage common work and information spaces. In this paper we report on design issues, implementation aspects, and first experiences gained with the TOGA prototype and its exploitation in an activity coordination and collaboration framework system.

Multi-Agent Systems: A Survey from the Robot-Soccer Perspective

ABSTRACTOne of the most challenging goals in artificial intelligence (AI) is the development of artificial intelligent autonomous agents with human-level performance. The past few years has witnessed a tremendous interest in research and discussions on intelligent agents. With the ever increasing number of robots in an industrial environment, scientists and technologists are often faced with issues on cooperation and coordination among different robots and their self governance in a common work-space. This has led to developments in multi-robot cooperative autonomous systems. With an aim to study issues such as group architecture, resource conflict, origin of cooperation, learning and geometric problems, groups of robots are constructed. The proponents of multi-robot autonomous systems needed a model to validate the theories being proposed and to test their efficacy and efficiency. It is no surprise that they started focussing on robot soccer. Robot soccer makes heavy demands in all the key areas of robot...

Design of Self-Learning Hierarchical Fuzzy Logic for Guidance and Control of Multirobot Systems

Increased application of fuzzy logic to complex control raises a need for a structured methodological approach to developing fuzzy logic systems, which are currently developed based on individualistic bases and cannot face the challenge of interacting with other (fuzzy) systems in a dynamic environment. We propose designing self-learning hierarchical fuzzy logic control based on the integration of evolutionary algorithms and fuzzy logic to provide an integrated knowledge base for intelligent control and collision avoidance among multiple robots. Robots are considered point masses moving in common work space. Evolutionary algorithms are used as an adaptive method for learning the fuzzy knowledge base of control systems and learning, mapping, and interaction between fuzzy knowledge bases of different fuzzy logic systems.

Planar Curve Routing for Tethered-Robot Motion Planning

The following problem appears in robotics. A number of small, circular robots live in a common planar workspace. Each is attached by a flexible cable of finite length to a point on the boundary of this workspace. Each robot has a target point in the workspace it must reach. When a robot has reached its target, its cable will have been dragged out into the workspace and possibly pushed and bent by other robots. The cables remain taut at all times and may not overlap, but may bend around other robots. When only the target points are specified for the robots, their motion can produce arbitrarily complex cable configurations. The more complex a cable configuration is, the more restrictive it is to the motion of the robots. To keep restrictions on the robots' motions at a minimum, it is necessary to specify, in addition to the target points, a configuration of the cables that is as simple as possible but allows all robots to reach their targets. The problem of finding the simplest cable configuration for a given set of target points is shown to reduce to the problem of finding a minimal set of nonintersecting routes in a Euclidean graph whose nodes are the robots' cable line. That no set of edges can intersect any other set of edges is an unusual characteristic of this graph problem. This consideration leads to interesting geometric analysis used to determine which relative placements of the graph edges represent overlapping cable lines. An algorithm is suggested that uses an exhaustive search method with pruning to find a set of nonintersecting routes in the graph that is minimal according to a chosen criterion. The algorithm has been implemented and tested; examples of its performance are given.

An Architecture for Form Feature Modeling for Concurrent, Cooperative and Consistent Product Design.

Concurrent, cooperative and consistent product design by multiple designers and engineers is a key concept for success in a quickly changing market. For such design, the product modeling system is considered to be the common work space that integrates both design activities and design information from multiple designers and engineers. In this paper a framework of feature-based modeling is proposed to support concurrent, cooperative and consistent product design involving functional design, machining, assembly and maintenance. The framework defines a mechanism for interpreting shape descriptions from the viewpoint of different applications into a unified representation. With this mechanism, designers and engineers can deal cooperatively with product shapes in an environment of concurrent engineering. Based on this framework, a feature-based modeling system has been developed and an example of implementation is briefly introduced.

二本指マイクロハンドの設計と微細作業

A prototype two-fingered micro hand is designed and is applied to the actual micro tasks. First, we discuss a concept of a two-fingered micro hand based on human usage of a pair of chopsticks. The two-fingered micro hand should be designed by considering the effective work space, or the common work space of two fingers, as well as the simplicity of its cooperation control for each finger. Our proposed prototype has two 6 DOF parallel mechanisms in series in order to realize similar motion in our chopsticks usage. We applied the prototype to practical micro manipulation tasks, and we succeeded in picking up a glass ball having size of 2 [μm] and placing it in arbitrary position under a microscope by human teleoperation.

A Collision-Space Approach to Trajectory Planning of Coordinated Robots

This contribution presents a geometric approach for detecting collisions in a multi-robot system. The approach is based on the fact that in any multi-robot system each robot occupies a certain slice of the common workspace at a certain time, which is a restricted area for any other robot involved. The multi-robot operation is collision free as long as the occupied workspace slices do not intersect. The proposed collision area is the set of all configurations causing an intersection of these workspace slices. By knowing these configurations at any instance of time, trajectory planning can be done easily by avoiding the configurations that are part of the collision area. In the following an efficient geometric approach for collision free trajectory planning is presented.

Optimal assignment of robot tasks with precedence for muliti‐robot coordination by disjunctive graphs and state‐space search

AbstractAn approach to optimal assignment of tasks with precedence relationships to multiple robots is proposed. The robots are assumed to share a common workspace and work cooperatively to accomplish a given process plan consisting of a set of tasks. The optimal task assignment is defined to be the one that results in spending the least amount of time to complete the plan under the criterion that no robot collision will occur when the assigned tasks are performed. The ordering of the tasks in the process plan is described by a topological tree, which is then expanded to form a larger state‐space tree without redundant tree paths. Each path in the expanded tree represents a partially developed assignment of the tasks to the robots, and a graph formulation scheme is presented for estimating the cost of the assignment. A collision‐free motion schedule for each robot based on each task assignment can be obtained by finding the minimaximal path in a disjunctive graph formulated by the scheme. By using the A* algorithm, a search method for finding the optimal assignment with the minimum cost is presented. Some heuristic rules are also proposed to speed up the search process. Simulation results are illustrated to show the effectiveness of the proposed approach. © 1995 John Wiley & Sons, Inc.

CAD-based generation of collision-free paths for robotic manipulators

Abstract The use of a CAD system can improve the overall efficiency of automated factories. This paper describes the utilization of a CAD system devoted to the off-line generation of collision-free paths for robotic manipulators. This tool is first applied in the case of a robotic manipulator in a moderately cluttered environment, next it is utilized it for planning collision-free paths for two robotic manipulators sharing a common workspace. The implemented off-line programming system is written in C, in X/Windows environment. In this way portability is effectively achieved. Simulation results show the effectiveness of the proposed approach.

Integration of task planning and motion control in a multi-robot assembly workcell

Most of the existing multi-robot systems emphasize only one of two aspects, namely, plan generation and plan monitoring. There is a missing link between producing a multi-agent plan and its control during actual execution. The existence of this gap between planning and control precludes the possibility of automatically regenerating the execution plan to recover from unexpected error conditions and greatly limits the flexibility of the system. This paper describes a multi-robot task planning and execution system which successfully solves the integration problem by a two-phase five-layer structure. The concept of a finite-state automaton has been used as a tool to combine planning with simultaneous execution of parallel action. The developed system has been demonstrated for the assembly of a dishwasher power unit in a real experiment using a multi-robot assembly workcell consisting of an ADEPT I and a PUMA 560 robot placed close to each other so as to share a common workspace.

On the problem of multiple mobile robots cluttering a workspace

We consider the problem of multiple mobile robots navigating in a common workspace. Initially, based on the premise that the costs of operation of the robots can be ignored, results regarding the probability of collision of two point robots in the workspace are derived. Obviously, these results depend on the geometry of the workspace, and hence they are derived for workspaces with various geometries. The results are then extended for two robots of finite dimensions. The question “Are k + 1 robots better than k?” is then considered. Based on two modes of operation, namely, the batch-scheduled mode and the list-scheduled mode, various theoretical results are derived. If the costs of operation of the robots can be ignored, based on various computational results obtained, we conjecture that the answer to the question is in the affirmative in both modes of operation. Finally, by using the model of computation which includes the costs of operation of the robots, the problem is revisited. We have shown that for various geometries and revenue to cost ratios, there are optimal finite values for the number of robots that can operate within the workspace. Expressions for these optimal values have been derived.

Fast Collision-Free Motion Planning for Robots by Using Direct Kinematic Solutions

Abstract A fast algorithm is presented in this article for steering robots sharing a common workspace. In order to avoid collisions, robot motions are coordinated using a hierarchical strategy, which attributes different levels of priority to robots where highest priority is attained by obstacles. Obstacles are modelled as virtual closed mechanical chains. With this approach, avoiding obstacles and collision avoidance with other robots can be handled by a unified approach. The efficiency of this method is demonstrated through a number of examples which encompass different number of robots and obstacles.

Motion planning for multiple robots with multi-mode operations via disjunctive graphs

SUMMARYA new approach to motion planning for multiple robots with multi-mode operations is proposed in this paper. Although sharing a common workspace, the robots are assumed to perform periodical tasks independently. The goal is to schedule the motion trajectories of the robots so as to avoid collisions among them. Rather than assigning the robots with different priorities and planning safe motion for only one robot at a time, as is done in most previous studies, an efficient method is developed that can simultaneously generate collision-free motions for the robots with or without priority assignment. Being regarded as a type of job-shop scheduling, the problem is reduced to that of finding a minimaximal path in a disjunctive graph and solved by an extension of the Balas algorithm. The superiority of this approach is demonstrated with various robot operation requirements, including “non-priority”, “with-priority”, and “multicycle” operation modes. Some techniques for speeding up the scheduling process are also presented. The planning results can be described by Gantt charts and executed by a simple “stop-and-go” control scheme. Simulation results on different robot operation modes are also presented to show the feasibility of the proposed approach.

Collision-free motion planning for two articulated robot arms using minimum distance functions

SummaryThis paper presents a collision-free motion planning method of two articulated robot arms in a three dimensional common work space. Each link of a robot arm is modeled by a cylinder ended by two hemispheres, and the remaining wrist and hand is modeled by a sphere. To describe the danger of collision between two modeled objects, minimum distance functions, which are defined by the Euclidean norm, are used. These minimum distance functions are used to describe the constraints that guarantee no collision between two robot arms. The collision-free motion planning problem is formulated as a pointwise constrained nonlinear minimization problem, and solved by a conjugate gradient method with barrier functions. To improve the minimization process, a simple grid technique is incorporated. Finally, a simulation study is presented to show the significance of the proposed method.

Adaptive collision-free path-following control for two robots with prismatic joints

An adaptive control strategy based on a collision-free path-finding (CFPF) algorithm is proposed for two robots with prismatic joints. In systems with two or more robots operating in a common workspace, the arm of each robot is considered a moving obstacle. Taking into account the geometry of potential collision space, a simple CFPF algorithm is developed for two robots with prismatic joints. An adaptive control scheme is used to control each robot to follow the desired path computed by the CFPF algorithm at each sampling-time step. This approach is investigated by computer simulation and the results show that such a method can provide the efficient operation of the two-robot system.

Collision–Free Trajectory Planning for Two Robot Arms

SUMMARYAn approach for collision–free trajectory planning along designated paths of two robots in a common workspace is presented. Specifically, in order to describe potential collision between the links of two robots along the designated paths, explicit forms of virtual obstacle are adopted, according to which links of one robot are made to grow while the other robot is forced to shrink as a point on the path. Then, a notion of virtual coordination space is introduced to visualize all the collision–free coordinations of two trajectories. Assuming that a collision–free coordination curve between the two robots is given via a virtual coordination space, the minimum time collision–free trajectory pair for the two robots is sought considering dynamic constraints of torque and velocity bounds of actuators of the two robots.

Collision detection between the wrists of two robot arms in a common workspace

Detecting collisions for planning collision-free motion of the wrists of two robot arms in a common workspace is discussed in this paper. A collision-free motion can be obtained by detecting collisions along the preplanned trajectories using a sphere model for the wrist of each robot and then modifying the paths and/or trajectories of one or both robots to avoid the collision. In this paper, a collision detection algorithm is described and its role in collision avoidance is discussed. Collision detection is based on the premise that (1) the wrists of robots move monotonically on their preplanned straight line trajectories and (2) collisions never occur between the two wrists at the beginning points or end points.