Showing papers by "J.E. Colgate published in 2002"

Validating a novel approach to rendering fingertip contact sensations

Abstract: "Fingertip haptics" refers to the direct exploration of a virtual environment with the fingertips, rather than via an intermediate grasped object, such as a stylus or thimble. We hypothesize that a key psychophysical aspect of finger-tip haptics is the relative motion - slip - that occurs between the fingertip and surface. This paper investigates a novel approach to rendering slip at the finger pad. Our approach uses a rotating drum or sphere to render the velocity, of a surface as it passes beneath the fingertip. We construct a prototype device in one degree of freedom and test two groups of 14 subjects on their ability to sense the nature of the fingertip contact sensation (i.e., whether an actual surface or a rotating drum renders the contact sensation). The experimental results show strong justification of our mechanical approach to rendering relative velocity, at the fingertip. The results also raise several key issues for investigation in subsequent studies including the roles of vibration and apparatus dynamics.

Enriching Freshman Design Through Collaboration With Professional Designers

Abstract: Engineering educators over the last fifteen years have increasingly emphasized the teaching of design. As a result, design courses are not only being offered as a capstone experience in engineering majors; they are increasingly found at the freshman and sophomore level. This latter development has sparked a controversy about whether it is desirable, or even possible, to teach design to freshmen. As Carol McConica explains, in a 1996 edition of Chemical Engineering Education, "Freshman design courses are problematic because students do not yet have the fundamental engineering background necessary to solve real problems."

Cobot implementation of 3D virtual surfaces

Abstract: Cobots are devices for human/robot interaction, in which axes of motion are coupled to one another by computer-controlled continuously variable transmissions rather than individually driven by servomotors. We have recently built a 3R parallelogram cobot. Here we present a control method for the display of virtual surfaces and for free-mode in which the cobot endpoint moves as if it were unconstrained. We show experimental results on the performance of the cobot in these modes.

Toward improved CVTs: theoretical and experimental results

Abstract: Revolute-jointed cobots depend on continuously variable transmissions (CVTs). CVTs constrain the speed ratio between two shafts to a particular value within a continuous range. The spherical CVT is well suited to cobots, but like other point contact transmissions, achieving good performance is challenging. We have studied the contact mechanics of the spherical CVT under certain simplifying assumptions. Results of the calculations are compared to experimental measurements of an instrumented CVT. Improved CVT performance may require better control of compliance and contact forces in the CVT. Results for the contact forces under load conditions are shown. We conclude with a discussion of design implications for improved CVTs.Copyright © 2002 by ASME

Kinematic constraints for assisted single-arm manipulation

Abstract: Of several possible forms of human-robot collaborative manipulation, we focus on the case where the human and the robot jointly manipulate a common load. In our formulation, the robot's role is to provide a constraint surface to guide the motion of the load. The value of this form of interaction, in terms of ergonomics, accuracy, or speed, depends on how humans make use of such constraints. We are studying natural single-arm manipulation of a load constrained to move along a guide rail. In this paper we present results of experiments showing that subjects apply significant forces against the rail, depending on the configuration of the arm and the orientation of the rail. These forces are unnecessary for the manipulation task, and we hypothesize that humans apply forces against the constraint to simplify the manipulation task.

The Learning Cobot

Abstract: Cobots (COllaborative roBOTS) are passive devices that assist humans by guiding motion along software-defined paths. This paper introduces intuitive and efficient tools to design such paths. The operator creates a guiding path by walk-through path programming , tracing a path in free mode. A B-spline fit to this path becomes the guideway. The operator can locally define and modify the B-spline guiding path by moving the control points on a dedicated graphical user interface using a computer mouse. During movement, the operator avoids obstacles and handles sensing errors by using the elastic path planner to deviate from the guiding path. Collaborative learning lets the operator optimize a guiding path in a few tries to adapt it to the specific task and environment. These tools have been implemented and extensively tested on the Scooter cobot.Copyright © 2002 by ASME