M. Overmars, A. Rao, O. Schwarzkopf, and C. Wentink, Immobilizing polygons against a wall, Proc. 11th Ann. ACM Symp. on Computational Geometry (1995), pp. 29-38.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....produced by Brost and Goldberg s algorithm correspond to fixture vise configurations where one of the fixture plates contains a single peg. Recently, Overmars et al. introduced a point edge fixturing paradigm wherein objects are immobilized by a combination of one edge and two point contacts [10]. They prove that their fixturing paradigm is complete in the sense that their system can fixture all appropriately sized polygons whose convex hulls do not have parallel edges. They also present an algorithm for designing modular fixtures for given polygonal objects. Notice that this fixture ....

M. Overmars, A. Rao, O. Schwarzkopf, and C. Wentink. Immobilizing polygons against a wall. In Symposium on Computational Geometry, pages 29--38, Vancouver, BC, June 1995. ACM, ACM Press.

....in form closure (4 in 2D, 7 for polyhedra) 96, 84] but efficient algorithms are still needed. In modular fixturing, where fixture elements are constrained to a regular lattice, recent results suggest a number of open questions about the existence of solutions for classes of fixtures and parts [154, 142, 115]. When there is uncertainty in part pose or applied forces, minimizing the number of grasp points can be posed as a convex set covering problem. Recently, CG researchers have described efficient and probably practical algorithms for near optimal grasps. This goes beyond the previous works which ....

Overmars, M., Rao, A., Schwarzkopf, O., Wentink, C. Immobilizing polygons against a wall, ACM Symp. Comput. Geom. (1995), Vancouver, BC.

....workpiece, which is a prerequisite for fixturing. We use the term minimal to characterize fixture toolkits which incorporate a single degree of freedom and where fixture elements are placed in a finite number of locations. Wallack and Canny [18, 21] Brost and Goldberg [2] and Overmars et al. [16] developed fixture design algorithms for minimal modular fixture toolkits: the fixture vise (Figure 1) the translating clamp, and the translating clamp and wall toolkits respectively. In this report, we generalize these complete fixture design algorithms [18, 21, 2, 16] i.e. we present a ....

....Goldberg [2] and Overmars et al. 16] developed fixture design algorithms for minimal modular fixture toolkits: the fixture vise (Figure 1) the translating clamp, and the translating clamp and wall toolkits respectively. In this report, we generalize these complete fixture design algorithms [18, 21, 2, 16], i.e. we present a generic complete fixture design algorithm for minimal fixture toolkits. Figure 1: Wallack and Canny s fixture vise toolkit. 1.1 Object Recognition from Sparse Probe Data Object recognition is a classical problem in machine vision and robotics. Although object recognition is ....

M. Overmars, A. Rao, O. Schwarzkopf, and C. Wentink. Immobilizing polygons against a wall. In Symposium on Computational Geometry, pages 29--38, Vancouver, BC, June 1995. ACM, ACM Press.

....useful grasps, and grasp quality metrics; the reader is referred to [4, 8, 10] for an overview of these results. Mishra s [5] analysis of the toe clamp toolkit sparked renewed interest in the field of robotics. Recently, Wallack and Canny [10, 11] Brost and Goldberg [1] and Overmars et al. [6] proposed modular fixturing toolkits which incorporated peg hole devices (fixture tables) and a single degree of freedom, as well as complete fixture design algorithms. Wallack and Canny s [10, 11] and Brost and Goldberg s [1] algorithms share many similarities: both algorithms handle polygonal ....

M. Overmars, A. Rao, O. Schwarzkopf, and C. Wentink. Immobilizing polygons against a wall. In Symposium on Computational Geometry, pages 29--38, Vancouver, BC, June 1995. ACM, ACM Press.

....kit consists of a latticed workholding plane, three locators, and one clamp, the algorithm in [BG96] finds all possible placements of a given part on the workholding surface where form closure can be achieved, along with the corresponding positions of the locators and the clamp. The algorithm in [ORSW95] computes the form closure fixtures of input polygonal parts using a kit containing one edge fixture, one locator, and one clamp. An algorithm for fixturing an assembly of parts that are not rigidly fastened together is proposed in [Mat95] A large number of fixturing contacts are first scattered ....

M. Overmars, A. Rao, O. Schwarzkopf, and C. Wentink. Immobilizing polygons against a wall. In Proc. ACM Symp. on Comput. Geom., pages 29--38, 1995.

....placed at grid holes and a fourth nger that is placed on a horizontal or vertical line through these holes. Their algorithm for this modular setting runs in O(n d ) time, where d is the diameter of the part in grid units. Other results on the computation of modular grasps are reported in [9, 17, 18, 19, 20, 21, 22]. The key feature of our approach to solving the problem of computing all 2nd order immobility and form closure grasps is that we rst identify all triples or quadruples of edges that induce at least one 2nd order immobility or form closure grasp. Note that trying all triples and quadruples ....

....These problems are then solved eciently by applying data structures [1] from the eld of computational geometry. For each of the reported triples or quadruples we can compute the (non empty) set of induced 2nd order immobility grasps and form closure grasps in constant time. Overmars et al. [9] (see also [21] proposed to extend the set of contacts for holding parts with line contacts (or walls) and studied the computation of form closure grasps involving one line and two points in a modular setting. We extend our results for four point contacts to the case of one line and two points, ....

M. Overmars, A. Rao, O. Schwarzkopf, and C. Wentink, Immobilizing polygons against a wall, Proc. 11th Ann. ACM Symp. on Computational Geometry (1995), pp. 29-38.

....to the survey by Bose and Toussaint [2, 5] In assembly, the emphasis is on planning tasks so as to put parts together to form the final product. Interesting geometric problems arise in almost every step of automatic assembly planning. Assembly sequencing [24] part orienting [9] fixturing [18], and welding [17] are just a few of many examples. Although these manufacturing and assembly processes may be totally different from one another, some of them raise similar geometric problems that can be generally termed separability problems [22] This is the case in the manufacturing process ....

M. Overmars, A. Rao, O. Schwarzkopf, and C. Wentink. Immobilizing polygons against a wall. In Proc. 11th Annu. ACM Sympos. Comput. Geom., pages 29--38, 1995.

....[2] and the survey by Bose and Toussaint [4] In assembly, the emphasis is on planning tasks so as to put parts together to form the nal product. Interesting geometric problems arise in almost every step of automatic assembly planning. Assembly sequencing [27] part orienting [11] xturing [21], and welding [19] are just a few of many examples. Although these manufacturing and assembly processes may be di erent from one another, some of them raise similar geometric problems that can be generally termed separability problems [25] This is the case in the manufacturing process that we ....

Mark Overmars, Anil Rao, Otfried Schwarzkopf, and Chantal Wentink. Immobilizing polygons against a wall. In Proc. 11th Annu. ACM Sympos. Comput. Geom., pages 29-38, 1995.

....of four of these points yield form closure for the part. The unit square can be placed such that its vertices all lie on grid points and thus the intended contact points are actually on grid lines, which means that the four clamps can indeed be placed such that form closure is obtained. Nguyen [22] showed how to find sets of 4 edge segments on an arbitrary polygon such that if we place a point contact somewhere on every of these four segments, the part is in form closure. Such segments are now called Nguyen segments. Zhuang and Goldberg also showed that a convex polygonal part is fixturable ....

....objects) Some of the algorithms can be extended or changed such that additional cases can be dealt with as well. Here we give a short overview of a Figure 32: Three different models for a vise combined with an edge fixel. number of known extensions. Computation of Nguyen regions Nguyen [22] introduced an algorithm to compute Nguyen regions of an object in a model with four point contacts. Nguyen regions define possible placements of the point contacts, such that form closure is obtained if we place at least one contact in every region. Since the Nguyen regions are independent of a ....

M. Overmars, A. Rao, O. Schwarzkopf, and C. Wentink. Immobilizing polygons against a wall. In ACM Symposium on Computational Geometry, pages 29--38, June 1995.

....and by Charles University Grants No. 193,194. In assembly, the emphasis is on planning tasks so as to put parts together to form the final product. Interesting geometric problems arise in almost every step of automatic assembly planning. Assembly sequencing [26] part orienting [11] fixturing [20], and welding [19] are just a few of many examples. Although these manufacturing and assembly processes may be totally different from one another, some of them raise similar geometric problems that can be generally termed separability problems [24] This is the case in the manufacturing process ....

M. Overmars, A. Rao, O. Schwarzkopf, and C. Wentink. Immobilizing polygons against a wall. In Proc. 11th Annu. ACM Sympos. Comput. Geom., pages 29-- 38, 1995.

....[3] and the survey by Bose and Toussaint [6] In assembly, the emphasis is on planning tasks so as to put parts together to form the final product. Interesting geometric problems arise in almost every step of automatic assembly planning. Assembly sequencing [27] part orienting [11] fixturing [21], and welding [19] are just a few of many examples. Although these manufacturing and assembly processes may be different from one another, some of them raise similar geometric problems that can be generally termed separability problems [25] This is the case in the manufacturing process that we ....

M. Overmars, A. Rao, O. Schwarzkopf, and C. Wentink. Immobilizing polygons against a wall. In Proc. 11th Annu. ACM Sympos. Comput. Geom., pages 29--38, 1995.

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