A new approach to G1 filling of n-sided holes with free-form boundary curves (e.g., polynomial, rational, sinusoidal or other parametric forms) is presented. It has no intrinsic limitation but adequate freedoms for shape adjustment and optimization. The given n-sided hole is filled by rotating a cubic Bézier curve C around a fixed unit vector nc at a fixed center point c of the hole. C's two end points fall on the hole boundary and c respectively. nc is C's normal at c. In this way n triangular surfaces are generated in G0 contact. Then each crease between two adjacent triangular surfaces is smoothed by sweeping another cubic Bézier curve along the crease. Thus n leafy blending patches are produced to replace the overlapped parts of the triangular surfaces. The proposed algorithm is applied to some typical examples of hole-filling on free-form surfaces, such as blending and decoration.

This correspondence deals with the dynamic force distribution (DFD) problem, i.e., computing the contact forces to equilibrate a dynamic external wrench on the grasped object. The sum of the normal force components is minimized for enhancing safety and saving energy. By this optimality criterion, the DFD problem can be transformed into a linear programming (LP) problem. Its objective function is the inner product of the dynamic external wrench and a vector, and the constraints on the vector, given by a set of linear inequalities, define a polytope. The solution to the LP problem can always be attained at the vertex of the polytope called the solution vertex. We notice that the polytope is determined by the grasp configuration. Along with the direction change of the dynamic external wrench, only the solution vertex moves to an adjacent vertex sequentially, whereas the polytope with all its vertices remains unchanged. Therefore, the polytope and the adjacencies of each vertex can be computed in the offline phase. Then, in the online phase, simply search the adjacencies of the old solution vertex for the new one. Without lost of optimality, such a DFD algorithm runs a thousandfold faster than solving the LP problem by the simplex method in real time.

This paper addresses a shortcut in the ray-shooting based algorithm proposed by Liu. His algorithm provides an efficient force-closure test of 3D frictional grasps, which is formulated as a linear programming (LP) problem. We prove that the optimal objective value of the LP formulation indicates the force-closure property of grasps directly. Thus computing Q, d/sub 1/, and d/sub 2/ can be omitted.

This paper presents a general algorithm for computing the optimal dynamic force distribution in multifingered grasping. It consists of two phases. In the offline phase, we select a spanning set for the required dynamic resultant wrench and find a corresponding spanning set for the total contact force. Then, in the online phase, the total contact force is obtained by decomposition of the resultant wrench into the former spanning set and a coefficient vector followed by positive combination of the latter spanning set with the vector. To make the online computation as simple as possible, iterative operation is executed offline and only arithmetic operation is employed online. To improve the grasping quality, the two spanning sets are selected elaborately.

Most industrial grippers now in use are two-fingered. Among them the parallel-jaw gripper is the simplest. It can partially remove the pose uncertainty of an object through grasping, such as the orientation uncertainty. This paper addresses a new type of grippers with the finger configuration of four circles instead of two parallel lines. It has a number of important advantages. Especially, it achieves form-closure and confines the object to a locally unique pose, so as to remove the pose uncertainty completely. It allows the gripped object to reach this pose freely without loss of required friction in the direction perpendicular to the grasping plane. More information can be acquired for identifying the object and its grasp mode. As a result the identification can be performed at one grasp. The key parameter of a symmetric four-pin gripper is the distance (span) between two pin centers on each finger, which depends upon the object shape and impacts the closure property, Based on a new approach to the grasp geometry, selection and limitations of the span are illustrated.

A general dynamic force distribution (DFD) algorithm for multifingered grasping is presented. Based on the convexity and cone property of contact constraints, the optimal internal force is defined. Determination of the contact force is divided into two phases: (1) determine the direction of the optimal internal force during grasp planning and (2) determine the manipulation force and compensation factor during task manipulation. The total computation cost consists of off-line numerical iterations and on-line analytical computations. Only the latter is related to the real-time control. The algorithm can directly deal with the nonlinear and/or coupled constraints and well overcome the temporal discontinuity.

Formulates the force distribution for soft multi-fingered hands as choosing a suitable internal force such that the total contact force satisfies the frictional constraints. As a first step, the direction of the optimal internal force is defined based on the grasp locations. Implementation of the algorithm is divided into two phases: (1) determine the direction of the internal force during grasp planning; (2) determine the magnitude of the internal force during task manipulation. The total computation cost consists of off-line numerical iterations and online analytical computations. Only the latter is related to the real-time control. An example shows that the proposed algorithm can efficiently deal with the soft frictional constraints and well overcome the temporal discontinuity.

This paper deals with the problem of the equivalence of internal and interaction forces in multifingered grasping. The dimensions of these two force spaces are analyzed. It is shown that the internal force space can be more generally expressed as the direct sum of the interaction and parallel force spaces. Under certain conditions, the parallel force space disappears and the internal and interaction force spaces become coincident. In this sense, the internal force can be equivalently characterized by the interaction force or pairs of equal and opposite collinear forces. The necessary and sufficient conditions for this equivalent characterization, which depends upon the number of contacts and the distribution of their locations, are derived. The algebraic structure of the parallel force spaces is given. Some illustrative examples are also presented.

Presents a hypothesis testing method called double bound testing which is used for statistical decision-making, specifically for binary decisions. A probability decision space is defined to increase the decision flexibility. Based on the decision reached by each sensor, a combination rule is also formulated to give the global decision for the multisensor system. The proposed method offers three options for decision snaking, rather than the classical binary options. An experiment on 2D object identification was performed to demonstrate the proposed strategy.

The difference between the sum of squared deviations and the maximum deviation was studied. The popular least square method refers to the former, but the criterion of many engineering geometrical problems, including fitting problems, often refers to the latter. As a typical case study this paper presents a new approach to the optimization of the automobile panel fitting aiming at minimizing the maximum deviation, based on a systematic analysis of the differential adjusting motion's impact on the variations of gaps/flushes. Comparative calculations show: the conventional least square method may lead to a result with the maximum deviation over thirty percent higher than the actual optimal solution, obtained by the new method. Moreover, the latter can cope with different tolerances of different seams explicitly.

A general scenario of disassembly is figured out, starting from the authors' past study of the internal structures of machines and devices, based on a mechanical engineer's point of view. The authors argue that among all data relevant to assembly, the key data for generating assembly sequences are the liaison type and the assembly direction. From these data many important geometrical, topological and technological constraints can be inferred that can be used as criteria for reducing the user's input data and the information to be extracted from the CAD database. These criteria minimize the possible decompositions at each stage of disassembly, and may even guide the search towards the best plan. A fast planner has been implemented in PROLOG, giving a user friendly system capable of generating optimal assembly plans very quickly, with a computational cost roughly proportional to the number of parts in the final assembly.>

Presents a framework of an online knowledge based error recovery system for robotized assembly, which deals with problems of execution monitoring, sensor processing, failure diagnosis and recovery. The system is of modular and hierarchical structure. Techniques have been integrated into each functional module. Based on the presented framework, the authors have also investigated the way to implement the proposed system in their testbed. The prototype has been realized at the first stage using V+ as the main tool.>