J. Kenneth Salisbury

Application of Change Detection to Dynamic Contact Sensing

The forces of contact during manipulation convey substan tial information about the state of the manipulation. Textures, slip, impacts, grasping, and other contact conditions produce force and position signatures that can be used for identifying the state of contact. This article addresses the fundamental problems of interpreting the force signals without any addi tional context on the state of manipulation. Techniques based on forms of the generalized sequential likelihood ratio test are used to segment individual strain signals into statistically equivalent pieces. The results of the segmentation are designed to be used in a higher level procedure that will interpret the results within a manipulation context. We report on our ex perimental development of the segmentation algorithm and on its results for detecting and labeling impacts, slip, changes in texture, and condition. The sequential likelihood ratio test is reviewed, and some of its special cases and optimal properties are discussed. Finally, we conclude by discussing extensions to the techniques and lessons for sensor design.

Making graphics physically tangible

Robotics Institute of Carnegie University using a simulation system that takes large time steps in a stable way and couples a technique for enforcing constraints on individual cloth particles with an implicit integration method.

Mechanical Design for Whole-Arm Manipulation

This paper describes the performance requirements and mechanical design of an arm designed and built at MIT for whole-arm manipulation. Whole-arm manipulation began as a research objective to explore the benefits of manipulating objects with all surfaces of a robotic manipulator — not just the fingertips of an attached robotic hand. The need for robust environment contact by all surfaces of the robotic hardware prompted a re-evaluation of traditional manipulator design requirements and spurred the invention of new transmission mechanisms for robots.

Determination of Manipulator Contact Information from Joint Torque Measurements

Measurements of the net forces acting on a structure can provide information necessary to determine the location of contacts through which the external forces act, under appropriate assumptions. One practical application of this idea resulted in the contact-resolving force-sensing fingertips developed by Salisbury and Brock. These fingertip sensors employ a 6-axis force sensor under a fingertip shell to measure the net applied force. It has been demonstrated that this type of sensor supplies enough information to determine the location and force components of contacts which transmit pure forces. Bicchi recently extended this analysis to permit the same sensor to also measure a moment exerted about the contact normal.

Cooperative control of multiple robots to manipulate objects

This paper addresses the problem of using multiple robots together as a hand to reorient objects in the plane. A planner is described which generates a sequence of intermediate object motions and robot grasps, called a grasp gait, sufficient to achieve a final desired object orientation. These gaits are implemented using 3 phantom haptic interfaces, modified to act as robot fingers. The core control structure of the implementation is presented. Finger force and position errors, as well as object position errors, are discussed, and additional control algorithms are developed to correct for these errors. These gaits are demonstrated to be robust to small disturbances using the additional control algorithms.

Toward Dexterous Gaits and Hands

This paper deals with planning and executing large-scale reorientations of grasped planar objects using a three-fingered robot hand. We begin by presenting a method for planning a gait, a series of finger motions and regrasps, that can reorient any two-dimensional convex object by any desired amount. The implementation of these gait plans is then discussed, including the control algorithms that were used and how effective they were in achieving the desired orientation. We then discuss the limitations of our approach and present ideas to improve both the algorithms and the hardware. We conclude with a discussion of components of a new modular hand mechanism intended to support future work on spatial reorientation grasp gaits.