Diego C. Ruspini

The haptic display of complex graphical environments

Force feedback coupled with visual display allows people to interact intuitiv ely with complex virtual environments. For this synergy of haptics and graphics to flourish, however, haptic systems must be capable of modeling environments with the same richness, complexity and interactivity that can be found in existing graphic systems. To help meet this challenge, we have developed a haptic rendering system that allows for the efficient tactile display of graphical information. The system uses a common high-level framework to model contact constraints, surface shading, friction and tex ture. The multilevel control system also helps ensure that the haptic device will remain stable even as the limits of the renderer’s capabilities are reached.

Coordination and decentralized cooperation of multiple mobile manipulators

Mobile manipulation capabilities are key to many new applications of robotics in space, underwater, construction, and service environments. This article discusses the ongoing effort at Stanford University for the development of multiple mobile manipulation systems and presents the basic models and methodologies for their analysis and control. This work builds on four methodologies we have previously developed for fixed-base manipulation: the Operational Space Formulation for task-oriented robot motion and force control; the Dextrous Dynamic Coordination of Macro/Mini structures for increased mechanical bandwidth of robot systems; the Augmented Object Model for the manipulation of objects in a robot system with multiple arms; and the Virtual Linkage Model for the characterization and control of internal forces in a multi-arm system. We present the extension of these methodologies to mobile manipulation systems and propose a new decentralized control structure for cooperative tasks. The article also discusses experimental results obtained with two holonomic mobile manipulation platforms we have designed and constructed at Stanford University.

Vehicle/arm coordination and multiple mobile manipulator decentralized cooperation

Mobile manipulation capabilities are key to many new applications of robotics in space, underwater construction, and service environments. This article discusses the ongoing effort at Stanford University for the development of multiple mobile manipulation systems and presents the basic models and methodologies for their analysis and control. This work builds on four methodologies we have previously developed for fixed-base manipulation: the operational space formulation for task-oriented robot motion and force control; the dextrous dynamic coordination of macro/mini structures for increased mechanical bandwidth of robot systems; the augmented object model for the manipulation of objects in a robot system with multiple arms; and the virtual linkage model for the characterization and control of internal forces in a multi-arm system. We present the extension of these methodologies to mobile manipulation systems and propose a new decentralized control structure for cooperative tasks. The article also discusses experimental results obtained with two holonomic mobile manipulation platforms we have designed and constructed at Stanford University.

Force Strategies for Cooperative Tasks in Multiple Mobile Manipulation Systems

Mobile manipulation capabilities are key to many new applications of robotics in space, underwater, construction, and service environments. This article discusses the ongoing effort at Stanford University for the development of multiple mobile manipulation systems and presents the basic models and methodologies for their analysis and control. This work builds on four methodologies we have previously developed for fixed-base manipulation: the Operational Space Formulation for task-oriented robot motion and force control; the Dextrous Dynamic Coordination of Macro/Mini structures for increased mechanical bandwidth of robot systems; the Augmented Object Model for the manipulation of objects in a robot system with multiple arms; and the Virtual Linkage Model for the characterization and control of internal forces in a multi-arm system. We present the extension of these methodologies to mobile manipulation systems and propose a new decentralized control structure for cooperative tasks. The article also discusses experimental results obtained with two holonomic mobile manipulation platforms we have designed and constructed at Stanford University.

Robotics and interactive simulation

As applications of robots extend into everyday human life, new approaches to simulating interactions between them and their environments are emerging at the intersection of the physical and virtual worlds.

Human-Centered Robotics and Interactive Haptic Simulation

A new field of robotics is emerging. Robots are today moving towards applications beyond the structured environment of a manufacturing plant. They are making their way into the everyday world that people inhabit. This paper focuses on models, strategies, and algorithms associated with the autonomous behaviors needed for robots to work, assist, and cooperate with humans. In addition to the new capabilities they bring to the physical robot, these models and algorithms and, more generally, the body of developments in robotics is having a significant impact on the virtual world. Haptic interaction with an accurate dynamic simulation provides unique insights into the real-world behaviors of physical systems. The potential applications of this emerging technology include virtual prototyping, animation, surgery, robotics, cooperative design, and education among many others. Haptics is one area where the computational requirement associated with the resolution in real time of the dynamics and contact forces of the virtual environment is particularly challenging. This paper describes various methodologies and algorithms that address the computational challenges associated with interactive simulaThe International Journal of Robotics Research Vol. 23, No. 2, February 2004, pp. 167-178, DOI: 10.1177/0278364904041325 ©2004 Sage Publications tions involving multiple contacts and impacts between human-like

Collision/Contact Models for Dynamic Simulation and Haptic Interaction

In this paper we present a general framework for the dynamic simulation and haptic exploration of complex virtual environments. This work builds on previous developments in simulation, haptics, and operational space control. The relations between the dynamic models used in simulation and the models originally developed for robotic control are also presented. This framework has been used to develop a simulator that can model complex interaction between generalized articulated mechanical systems and permit direct “hands-on” interaction with the virtual environment through a haptic interface.

Dynamic Models for Haptic Rendering Systems

To create a compelling interactive virtual experience, haptic systems must incorporate methods to allow for the specification of and interaction with complex dynamic environments. In this paper we discuss some of the issues encountered and the solutions developed for incorporating dynamic motion in our haptic rendering library “HL.” The objective in the development of this library is to provide haptic capabilities to users who may have little or no familiarity with robotics, haptics or control.

Haptic display for human interaction with virtual dynamic environments

Haptics is an emerging technology that permits direct “hands-on” interaction with a virtual environment. A haptic device uses mechanical actuators to physically push a users finger or hand to give the sensation that he or she would have when interacting with a real physical environment. These force feedback systems have many applications, from training a surgeon to perform an operation, to assisting a child in understanding the behavior of a lever or pulley. In this paper we discuss methods and techniques to allow realistic and robust haptic interactions between a human and a complex dynamic virtual environment. Beyond modeling object penetration constraints, this work demonstrates how shading, friction, texture, and dynamics can be generated to create compelling and realistic virtual worlds.

Dynamic simulation of interactive robotic environment

A dynamic simulation package, which can accurately model the interactions between robots and their environment, has been developed. This package creates a virtual environment where various controllers and workcells may be tested. The simulator is divided in two parts: local objects that compute their own dynamic equations of motion, and a global coordinator that resolves interactive forces between objects. This simulator builds upon previous work on dynamic simulation of simple rigid bodies and extends it to correctly model and efficiently compute the dynamics of multi-link robots.<<ETX>>