A methodology that can intelligently search a CAD database of 2.5D machinable components and retrieve components and sub-pieces with similar shape characteristics has been presented. The proposed methodology has the potential to reduce both the development time and cost of new designs by effectively re-using existing designs more efficiently. This is accomplished by searching a database of parts with their associated plans and extracting parts of those plans that are required for the query part. These plan parts can subsequently be merged to develop the entire plan for the query part. The methodology utilizes qualitative matrices to represent the spatial relationship between the maximal features of the query component. These feature-spatial relationship pairs are matched against those present in existing components within the database. The query can be relaxed based upon TAH structures that allow for generalizing of features and spatial relationships to allow for the best match to be found if no exact match is found.

Recent research uses qualitative contact models for compliant motion planning and control. Although these methods have great potential, generation of qualitative contact models of nonconvex polyhedra is difficult. Qualitative contact models could be generated in a generate-and-test fashion if a predicate were available for verifying contact hypotheses. In general, a contact hypothesis does not fully constrain the relative configuration of the objects making verification of the hypothesis difficult. This paper presents an optimization-based method to verify geometric feasibility of contact hypotheses that do not fully constrain the relative configuration. This method has been implemented and applied to test contact hypotheses of nontrivial object pairs.

This paper looks at the control of mechanical impedance of the so-called Gough-Stewart class of parallel platforms. Two methods of compliance control are presented. One is based on global potential energy functions that have previously been applied to controlling serial manipulators and electrodynamically levitated platforms. The second method uses the exponential map to associate finite displacements of the platform from equilibrium with twist displacements. Compliant wrenches are then proportional to the twist displacements. Control of spatial damping is addressed as well, justifying the classification as impedance control. Control algorithms and simulation results are given.

Looks at the control of mechanical impedance of the so-called Gough-Stewart class of parallel platforms. Two methods of compliance control are presented. One is based on global potential energy functions that have previously been applied to controlling serial manipulators and electrodynamically levitated platforms. The second uses the exponential map to associate finite displacements of the platform from equilibrium with screw displacements. Compliant wrenches are then proportional to the screw displacements. Control of spatial damping is addressed as well, justifying the classification as impedance control. Control algorithms and simulation results are given.

The increased use of Computer Aided Design (CAD) tools have resulted in the obvious need to efficiently retrieve specific and groups of similar parts from CAD databases for group technology (GT) applications; Current classification and retrieval methods from CAD databases are typically code based. The disadvantage of such a retrieval scheme is application dependency. We propose an application independent scheme and utilize it in retrieving similarly shaped parts on the basis of form-features and the inter-feature relationships. We address the issues of completeness of spatial interactions vocabulary and multiple interpretations for a part.

Mechanical impedance is the dynamic generalization of stiffness, and determines interactive behavior by definition. Although the argument for explicitly controlling impedance is strong, impedance control has had only a modest impact on robotic manipulator control practice. This is due in part to the fact that it is difficult to select suitable impedances given tasks. A spatial impedance controller is presented that simplifies impedance selection. Impedance is characterized using "spatially affine" families of compliance and damping, which are characterized by nonspatial and spatial parameters. Nonspatial parameters are selected independently of configuration of the object with which the robot must interact. Spatial parameters depend on object configurations, but transform in an intuitive, well-defined way. Control laws corresponding to these compliance and damping families are derived assuming a commonly used robot model. While the compliance control law was implemented in simulation and on a real robot, this paper emphasizes the underlying theory.

Development and evaluation of teleoperators and haptic virtual environment technologies require objective quantitative measures of haptic quality. In this paper a theoretical framework and experimental procedures are introduced for quantitative assessment of haptic perception. Human haptic perception of objects is distorted and uncertain as well. Perceptual distortion is defined to be a systematic bias of perception with respect to an objective standard. Perceptual uncertainty is defined to be a measure of statistical distribution of percepts. A set of mathematical tools is presented to quantify perceptual distortion and uncertainty. Two experiments are presented which apply these tools to investigate the fundamental structure of human haptic perception.>