This paper discusses the Ohio University Virtual Haptic Back (VHB) project, including objectives, implementation, and initial evaluations. Haptics is the science of human tactile sensation and a haptic interface provides force and touch feedback to the user from virtual reality. Our multimodal VHB simulation combines high-fidelity computer graphics with haptic feedback and aural feedback to augment training in palpatory diagnosis in osteopathic medicine, plus related training applications in physical therapy, massage therapy, chiropractic therapy, and other tactile fields. We use the PHANToM haptic interface to provide position interactions by the trainee, with accompanying force feedback to simulate the back of a live human subject in real-time. Our simulation is intended to add a measurable, repeatable component of science to the art of palpatory diagnosis. Based on our experiences in the lab to date, we believe that haptics-augmented computer models have great potential for improving training in the future, for various tactile applications. Our main project goals are to: 1. Provide a novel tool for palpatory diagnosis training; and 2. Improve the state-of-the-art in haptics and graphics applied to virtual anatomy.

A dynamic model is presented for omnidirectional wheeled mobile robots, including wheel/motion surface slip. We derive the dynamics model, experimentally measure friction coefficients, and measure the force to cause slip (to validate our friction model). Dynamic simulation examples are presented to demonstrate omnidirectional motion with slip. After developing an improved friction model, compared to our initial model, the simulation results agree well with experimentally-measured trajectory data with slip. Initially, we thought that only high robot velocity and acceleration governed the resulting slipping motion. However, we learned that the rigid material existing in the discontinuities between omnidirectional wheel rollers plays an equally important role in determining omnidirectional mobile robot dynamic slip motion, even at low rates and accelerations.

Abstract—This paper describes a test-bed for technology that unifies agent based computing and adaptive resource management for dynamic real-time systems. We describe a unified framework that combines a hybrid agent based architecture with explicit resource adapting mechanisms. I.

The naturally-transitioning rate-to-force controller (NTRFC) is presented for remote teleoperation of manipulators. Our goal is to provide a single controller which handles free motion, constrained motion, and the transition in-between without any artificial changes. In free motion the displacement of the master device is proportional to the commanded Cartesian rate of the remote manipulator. In contact the displacement of the human operator's hand is proportional to the wrench exerted on the environment by the remote manipulator. The transition between free rate motion and applied-wrench contact with the environment requires no changes in control mode or gains and hence is termed natural. Furthermore, in contact, if the master enables force reflection, the wrench of the human operator's hand exerted on the master is proportional to the wrench exerted on the environment by the remote manipulator. This paper demonstrates the NTRFC concept via a simple 1-DOF model and then discusses experimental implementation and results from a remote Merlin manipulator teleoperated via the force-reflecting PHANToM interface.

A control architecture is presented for real-time, sensor-based, shared control of remote, multiple-manipulator telerobotic systems. The system allows teleoperation, autonomy, or a combination (shared, telerobotic control). The rate-based system accepts control inputs from a variety of sources (joystick position or velocity, automated path planner position or velocity, machine vision, force/moment) simultaneously for all Cartesian axes. The system has been experimentally implemented and has proven effective in laboratory simulations of remote space tasks.

A novel controller, the naturally-transitioning rate-to-force controller (NTRFC), is presented for remote telerobotic systems. The controller involves shared control with a resolved-rate algorithm running concomitantly with a force accommodation algorithm, for all Cartesian axes. When the manipulator motion is unconstrained, it performs like a rate controller, where the hand controller displacement is proportional to the manipulator rate. When the manipulator contacts the environment, the control naturally transitions to a force controller, where the hand controller displacement is proportional to the manipulator force exerted. The force accommodation enables stable equilibrium in contact, with suitable gains. The transition requires no controller change and is thus termed natural. If a force reflecting hand controller is used in conjunction with the NTRFC, the force of the operator's hand is proportional to the manipulator force exerted. The NTRFC has been shown to possess excellent control characteristics for simulated Space tasks in the laboratory.

Local performance optimization for joint limit avoidance and manipulability maximization is presented using the Jacobian matrix pseudoinverse and objective function gradient projection into the Jacobian null space. Real-time performance optimization is achieved for a member of the class of 8-joint redundant manipulators having a 3-axis spherical shoulder, a single elbow joint, and a 4-axis spherical wrist. Symbolic solutions are used for both full and partitioned Jacobian matrix pseudoinverses and objective function gradients. Results are presented to demonstrate the effectiveness of the performance optimization. A kinematic limitation of this class of manipulators and its effect on redundancy resolution is discussed.< >