摘要:

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,

ISSN:0741-2223    

DOI:10.1002/rob.4620120402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThis article presents a unified method for the velocity and acceleration analyses of general parallel robotic manipulators. In this method, the governing velocity and acceleration equations of the robot are formulated in the joint space by considering it as a tree‐type mechanism subjected to Cartesian velocity and acceleration constraints. The procedures for solving the direct and the inverse analysis problems are established based on the generalized coordinate partitioning technique and the full pivoting Gaussian elimination method. These procedures take into account the overconstrained kinematic loops and redundant joints, and are applicable to either fully parallel robots or hybrid series‐parallel robots without any modifications. In addition, a set of generalized recursive formulas for computing the forward Cartesian velocity and acceleration transformations are developed. These formulas are also useful for efficient evaluating the complex nonlinear terms of the governing acceleration equations. ©1995 John Wiley&Sons,

ISSN:0741-2223    

DOI:10.1002/rob.4620120403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThis article examines the grasping quality problem and suggests a formulation that can capture the major mechanisms that generate the human grasping quality sense. Here, the quality of a grasp is examined from the gripper, object, and grasping‐configuration perspectives. These perspectives are incorporated into the formulation by selecting an appropriate objective function that is minimized subject to constraints that represent the geometry, friction, and force‐balance conditions of a grasp. The quality of a grasp is depicted as a polar plot that demonstrates the dependency of grasping quality on the external‐loading direction. The suggested grasping quality measures possess characteristics that are in agreement with basic human intuition. In particular this article proves that the three proposed quality measures are improved when the number of contact points is increased. In summary, the suggested grasping quality formulation captures some of the physical mechanisms that characterize a human grasp, and therefore it may lead to a powerful mathematical model of the human grasping quality sense. ©1995 John Wiley&Son

ISSN:0741-2223    

DOI:10.1002/rob.4620120404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper presents internalposition error correction(IPEC)—a new method for accurate and reliable dead‐reckoning with mobile robots. The IPEC method has been implemented on our recently developedmulti‐degree‐of‐freedom(MDOF) mobile platform, a vehicle in which two differential‐drive mobile robots (called trucks) are physically connected through acompliant linkage.In addition to its four wheel encoders, the MDOF platform has one linear and two rotaryinternalencoders, which allow measurement of the relative distance and bearing between the two trucks. During operation, both trucks perform conventional dead‐reckoning with their wheel encoders. But, in addition, the IPEC method uses information from the internal encoders to detect and correct dead‐reckoning errors as soon as they occur.Our system, calledcompliant linkage autonomous platform with position error recovery(CLAPPER), requires neither external references (such as navigation beacons, artificial landmarks, known floorplans, or satellite signals), nor inertial navigation aids (such as accelerometers or gyros). Nonetheless, the experimental results included in this article show one to two orders of magnitude better positioning accuracy than systems based on conventional dead‐reckoning. The CLAPPER corrects not only systematic errors, such as different wheel diameters, but also non‐systematic errors, such as those caused by floor roughness, bumps, or cracks in the floor.These features are made possible by exploiting the newgrowth‐rate conceptfor dead‐reckoning errors that is introduced in this article for the first time. The growth‐rate concept distinguishes between certain dead‐reckoning errors that develop slowly and other dead‐reckoning errors that develop quickly. Based on this concept, truck A frequently measures a property withslow‐growingerror characteristics on reference truck B (thus admitting a small error) to detect afast‐growingerror on truck A (thus correcting a large error), and vice

ISSN:0741-2223    

DOI:10.1002/rob.4620120405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe redundancy resolution problem for kinematically redundant serial chain manipulators is addressed. In this article we present a generalization of the geometry‐based rate allocation algorithm, developed initially for only a minimum norm solution, to obtain the optimal joint rate solution for any specified objective function, with or without weightage. This generalization is made possible through a physial interpretation of the common pseudoinverse‐based gradient solution scheme, and by developing a modified formulation for the objective function as a minimum criterion not with respect to the origin of the joint rate space, but with respect to another point in the joint rate space represented by the gradient of the specified objective. Application examples of the algorithm including procedures of solution are demonstrated using 7R manipulators with two generic types of geometry. Moreover, a closed form optimal solution for the class of 7R anthropomorphic arms is also given. ©1995 John Wiley&Sons,

ISSN:0741-2223    

DOI:10.1002/rob.4620120406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:0741-2223    

DOI:10.1002/rob.4620120401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY