Abstract not found

In this paper, we survey the work in robotic grasping related areas that has been done over the last two decades, with a bias toward the development of the theoretical framework and analytical results in this area. In addition we assess the state of the art in this area and outline some of the important open problems.

In this paper, we introduce a robust controller that uses contact position and normal feedback to generate contact configurations for statically stable grasps. The approach uses a context sensitive composition of two controllers that minimize force and moment residuals in the grasp configuration. We show that equilibria in the composite controller correspond to optimal contact configurations for 2 and 3 contacts on regular, convex polygons. The preimage is used to generalize the controller to arbitrary object geometries by learning a policy for compensation and to address object recognition, and contact (de)allocation. 1 Introduction Grasping and manipulation tasks with dextrous hands introduce formidable challenges to traditional planning and control techniques. These tasks include a broad range of contexts; dextrous hands are expected to be flexible with respect to varying object geometry, the hand mechanism itself is highly redundant, and the environments in which they are e...

Research in robotic grasping has flourished in the last 25 years. A recent survey by Bicchi [1] covered over 140 papers, and many more than that have been published. Stemming from our desire to implement some of the work in grasp analysis for particular hand designs, we created an interactive grasping simulator that can import a wide variety of hand and object models and can evaluate the grasps formed by these hands. This system, dubbed “GraspIt!,” has since expanded in scope to the point where we feel it could serve as a useful tool for other researchers in the field. To that end, we are making the system publicly available (GraspIt! is available for download for a variety of platforms from

The form--closure and force--closure properties of robotic grasping are investigated. Loosely speaking, these properties are related to the capability of the robot to inhibit motions of the workpiece in spite of externally applied forces. In this paper, form--closure is considered as a purely geometric property of a set of unilateral (contact) constraints, such as those applied on a workpiece by a mechanical fixture, while force--closure is related with the capability of the particular robotic device being considered to apply forces through contacts. The concepts of partial form-- and force--closure properties are introduced and discussed, and an algorithm is proposed to obtain a synthetic geometric description of partial form--closure constraints. While the literature abounds with form--closure tests, proposed algorithms for testing force--closure are either approximate or computationally expensive. This paper proves the equivalence of force--closure analysis with the study of the equ...

Geometric uncertainty is unavoidable when programming robots for physical applications. We propose a stochastic framework for manipulation planning where plans are ranked on the basis of expected cost. That is, we express the desirability of states and actions with a cost function and describe uncertainty with probability distributions. We illustrate the approach with a new design for a programmable parts feeder, a mechanism that orients two-dimensional parts using a sequence of open-loop mechanical motions. We present a planning algorithm that accepts an n-sided polygonal part as input and, in time O(n²), generates a stochastically optimal plan for orienting the part.

Three important problems in the study of grasping and manipulation by multifingered robotic hands are: (a) Given a grasp characterized by a set of contact points and the associated contact models, determine if the grasp has force closure; (b) If the grasp does not have force closure, determine if the ngers are able to apply a specified resultant wrench on the object; and (c) Compute "optimal" contact forces if the answer to problem (b) is affirmative. In this paper, based on an early result by Buss, Hashimoto and Moore, which transforms the nonlinear friction cone constraints into positive definiteness of certain symmetric matrices, we further cast the friction cone constraints into linear matrix inequalities (LMIs) and formulate all three of the problems stated above as a set of convex optimization problems involving LMIs. The latter problems have been extensively studied in optimization and control community and highly efficient algorithms with polynomial time complexity are now available for their solutions. We perform simulation studies to show the simplicity and efficiency of the LMI formulation to the three problems.

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, multi-rigid-body 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...

This paper introduces a grasp synthesis algorithm that can use any grasp prototype as the starting point in a search for a good grasp. The algorithm makes the given prototype more effective by generalizing it for a specific task. This generalization step expands the range of application of the prototype to a wide variety of target object geometries, while ensuring that the resulting grasps are appropriate for the intended task. An example whole-hand grasp synthesized for the Salisbury hand is shown at the end of the paper. 1 Introduction It has been very difficult to successfully automate the processes of acquiring and manipulating objects using today's robotic hands. Because many successful grasps are whole-hand, or enveloping grasps, one tempting solution is to develop prototypes, such as a generic cylinder grasp, to be applied to common objects, an approach motivated by studies of human grasping (e.g. see Napier [17], and Jeannerod [10]). Prototype grasps benefit from requiring ver...

In this thesis, we investigate modeling, control, and coordination of mobile manipulators. A mobile manipulator in this study consists of a robotic manipulator and a mobile platform, with the manipulator being mounted atop the mobile platform. A mobile manipulator combines the dextrous manipulation capability offered by fixed-base manipulators and the mobility offered by mobile platforms. While mobile manipulators offer a tremendous potential for flexible material handling and other tasks, at the same time they bring about a number of challenging issues rather than simply increase the structural complexity. First, combining a manipulator and a platform creates redundancy. Second, a wheeled mobile platform is subject to nonholonomic constraints. Third, there exists dynamic interaction between the manipulator and the mobile platform. Fourth, manipulators and mobile platforms have different bandwidths. Mobile platforms typically have slower dynamic response than manipulators. The objectiv...