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28
Orienting Polygonal Parts without Sensors
, 1992
"... In manufacturing, it is often necessary to orient parts prior to packing or assembly. We say that a planar part is polygonal if its convex hull is a polygon. We consider the following problem: given a list of n vertices describing a polygonal part whose initial orientation is unknown, find the short ..."
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Cited by 205 (41 self)
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In manufacturing, it is often necessary to orient parts prior to packing or assembly. We say that a planar part is polygonal if its convex hull is a polygon. We consider the following problem: given a list of n vertices describing a polygonal part whose initial orientation is unknown, find the shortest sequence of mechanical gripper actions that is guaranteed to orient the part up to symmetry in its convex hull. We show that such a sequence exists for any polygonal part by giving an O#n log n# algorithm for finding the sequence. Since the gripper actions do not require feedback, this result implies that any polygonal part can be oriented without sensors.
Geometric Reasoning about Mechanical Assembly
 Artificial Intelligence
, 1994
"... In which order can a product be assembled or disassembled? How many hands are required? How many degrees of freedom? What parts should be withdrawn to allow the removal of a specified subassembly? To answer such questions automatically, important theoretical issues in geometric reasoning must be ..."
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Cited by 66 (18 self)
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In which order can a product be assembled or disassembled? How many hands are required? How many degrees of freedom? What parts should be withdrawn to allow the removal of a specified subassembly? To answer such questions automatically, important theoretical issues in geometric reasoning must be addressed. This paper investigates the planning of assembly algorithms specifying (dis)assembly operations on the components of a product and the ordering of these operations. It also presents measures to evaluate the complexity of these algorithms and techniques to estimate the inherent complexity of a product. The central concept underlying these planning and complexity evaluation techniques is that of a "nondirectional blocking graph," a qualitative representation of the internal structure of an assembly product. This representation describes the combinatorial set of parts interactions in polynomial space. It is obtained by identifying physical criticalities where geometric int...
The mechanics of fine manipulation by pushing
 in IEEE International Conference on Robotics and Automation
, 1992
"... This paper presents a method for determining the possible instantaneous motions of a sliding object during multiple contact pushing. The approach consists of two components: a kinematic analysis considering kinematic motion constraints, and a force analysis considering force constraints on the motio ..."
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Cited by 41 (8 self)
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This paper presents a method for determining the possible instantaneous motions of a sliding object during multiple contact pushing. The approach consists of two components: a kinematic analysis considering kinematic motion constraints, and a force analysis considering force constraints on the motion. A new representation of the support friction of a sliding object is presented, and the results of the force analysis are independent of the exact support distribution of the object. The analysis results in a new manipulation primitive: stable rotational pushing. This primitive may be used for precise placement operations by pushing. 1.
Prediction of the Quasistatic Planar Motion of a Contacted Rigid Body
 IEEE Transactions on Robotics and Automation
, 1995
"... Planning the motion of bodies in contact requires a model of contact mechanics in order to predict sliding, rolling, and jamming. Such a model typically assumes that the bodies are rigid and that tangential forces at the contacts obey Coulomb's law. Though, usually assumed to be constant, the static ..."
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Cited by 24 (9 self)
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Planning the motion of bodies in contact requires a model of contact mechanics in order to predict sliding, rolling, and jamming. Such a model typically assumes that the bodies are rigid and that tangential forces at the contacts obey Coulomb's law. Though, usually assumed to be constant, the static and dynamic coefficients of friction vary in space and time and are difficult to measure accurately. In this paper, we study a quasistatic, multirigidbody model for planar systems, in which the coefficients of friction are treated as independent variables. Our analysis yields inequalities defining regions in the space of friction coefficients for which a particular contact mode (i.e., a particular combination of sliding, rolling, or separating at the contacts) is feasible. The geometrical interpretation of these inequalities leads to a simple graphical technique to test contact mode feasibility. This technique is then used to generate a nontrivial example in which several contact modes ar...
On Motion Planning in Changing, PartiallyPredictable Environments
 International Journal of Robotics Research
, 1997
"... We present a framework for analyzing and computing motion plans for a robot that operates in an environment that both varies over time and is not completely predictable. We first classify sources of uncertainty in motion planning into four categories, and argue that the problems addressed in this ..."
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Cited by 23 (4 self)
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We present a framework for analyzing and computing motion plans for a robot that operates in an environment that both varies over time and is not completely predictable. We first classify sources of uncertainty in motion planning into four categories, and argue that the problems addressed in this paper belong to a fundamental category that has received little attention. We treat the changing environment in a flexible manner by combining traditional configuration space concepts with a Markov process that models the environment. For this context, we then propose the use of a motion strategy, which provides a motion command for the robot for each contingency that it could be confronted with. We allow the specification of a desired performance criterion, such as time or distance, and determine a motion strategy that is optimal with respect to that criterion. We demonstrate the breadth of our framework by applying it to a variety of motion planning problems. Examples are computed...
Reactive Algorithms for Grasping Using a Modified Parallel Jaw Gripper
 Proc. IEEE Intl. Conf. on Robotics and Automation
, 1994
"... We consider the problem of grasping an unknown polygonal flat object using a parallel jaw gripper. Here we propose to equip a standard gripper with several lightbeam sensors (close to each jaw) and describe a reactive grasping algorithm. This is done by probing the object to locate a good grasp pos ..."
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Cited by 16 (5 self)
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We consider the problem of grasping an unknown polygonal flat object using a parallel jaw gripper. Here we propose to equip a standard gripper with several lightbeam sensors (close to each jaw) and describe a reactive grasping algorithm. This is done by probing the object to locate a good grasp position, and then grasping, without moving the object significantly. The goal is to do as little motion as possible to find a grasp. This algorithm can be viewed in a competitive framework, where our algorithm is competing against any algorithm which already knows the object. 1 Introduction In the past, the usual approach to grasping has been to assume an accurate model of the object to be grasped and from such a model, an offline geometric algorithm determines a set of grip points, where the fingers are then placed. (See Mishra, Schwartz and Sharir [MSS87]). Once the grip points have been determined, the geometry of the object is deemed irrelevant and the grasp is determined and maintained ...
Part pose statistics: estimators and experiments
 IEEE Transactions on Robotics and Automation
, 1999
"... Abstractâ€”Many of the most fundamental examples in probability involve the pose statistics of coins and dice as they are dropped on a flat surface. For these parts, the probability assigned to each stable face is justified based on part symmetry, although most gamblers are familiar with the possibili ..."
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Cited by 14 (2 self)
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Abstractâ€”Many of the most fundamental examples in probability involve the pose statistics of coins and dice as they are dropped on a flat surface. For these parts, the probability assigned to each stable face is justified based on part symmetry, although most gamblers are familiar with the possibility of loaded dice. In industrial part feeding, parts also arrive in random orientations. We consider the following problem: given part geometry and parameters such as center of mass, estimate the probability of encountering each stable pose of the part. We describe three estimators for solving this problem for polyhedral parts with known center of mass. The first estimator uses a quasistatic motion model that is computed in time O(n log n) for a part with n vertices. The second estimator has the same time complexity but takes into account a measure of dynamic stability based on perturbation. The third estimator uses repeated Monte Carlo experiments wit(15ra05goldberg)h a mechanics simulation package. To evaluate these estimators, we used a robot and computer vision system to record the pose statistics based on 3595 physical drop experiments with four different parts. We compare this data to the results from each estimator. We believe this is the first paper to systematically compare alternative estimators and to correlate their performance with statistically significant experiments on industrial parts.
A RISC approach to Sensing and Manipulation
, 1993
"... This paper is about sensing and manipulation strategies using simple, modular robot hardware. RISC robotics is an attempt to fuse automation and robotic technologies. It uses traditional automation hardware such as paralleljaw grippers and optical beam sensors, together with geometric planning and ..."
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Cited by 12 (2 self)
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This paper is about sensing and manipulation strategies using simple, modular robot hardware. RISC robotics is an attempt to fuse automation and robotic technologies. It uses traditional automation hardware such as paralleljaw grippers and optical beam sensors, together with geometric planning and sensing algorithms. RISC systems should be costeffective and reliable, and easy to setup and reconfigure. They should also be flexible enough to support small batch sizes and rapid changes in part design needed in forthcoming flexibleagile manufacturing systems. The RISC acronym, borrowed from computer architecture, suggests the parallels between the two technologies. RISC robots perform complex operations by composing simple elements. The elements may be individual light beam sensors, grouped together to form an array for recognition. Or a complex manipulation task may be performed via a sequence of grasp steps by different grippers specialized for acquisition and placement. This paper emphasizes three areas: (i) RISC sensing, primarily optical beam sensing (ii) RISC manipulation using simple paralleljaw grippers or minimal configurations of fingers (iii) Computeraided design of RISC workcells.
Estimating the friction parameters of pushed objects
 In Proc. of the 1993 IEEE/RSJ Int'l Conference on Intelligent Robots and Systems
, 1993
"... In order to plan manipulation of an object by pushing, a robot must have a model of the geometry and the friction properties of the object. This paper presents an approach to estimating the relevant friction parameters by performing experimental pushes and observing the resultant motion. Recognition ..."
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Cited by 11 (1 self)
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In order to plan manipulation of an object by pushing, a robot must have a model of the geometry and the friction properties of the object. This paper presents an approach to estimating the relevant friction parameters by performing experimental pushes and observing the resultant motion. Recognition of objects based on their friction parameters is also explored. 1.
Sensor placement design for object pose determination with three lightstripe range finders
 In Proceedings of 1994 IEEE Int. Conf. on Robotics and Automat
, 1994
"... interpreted as representing the o cial policies, either expressed or implied, of the U.S. government. ..."
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Cited by 10 (0 self)
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interpreted as representing the o cial policies, either expressed or implied, of the U.S. government.