Abstract not found

Force feedback coupled with visual display allows people to interact intuitively 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 texture. 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. CR Categories and Subject Descriptors: C.3 [Special Purpose and Application-Based Systems]: Real-time Systems

The transformation from high level task specification to low level motion control is a fundamental issue in sensorimotor control in animals and robots. This paper describes a control scheme called Virtual Model Control that addresses this issue. Virtual Model Control is a motion control language that uses simulations of imagined mechanical components to create forces, which are applied through real joint torques, thereby creating the illusion that the virtual components are connected to the robot. Due to the intuitive nature of this technique, designing a Virtual Model Controller requires the same skills as designing the mechanism itself. A high level control system can be cascaded with the low level Virtual Model Controller to modulate the parameters of the virtual mechanisms. Discrete commands from the high level controller would then result in fluid motion. Virtual Model Control has been applied to a physical bipedal walking robot. A simple algorithm utilizing a simple set of virtua...

Consideration of dynamics is critical in the analysis, design, and control of robot systems. This article presents an extensive study of the dynamic properties of several important classes of robotic structures and proposes a number of general dynamic strategies for their coordination and control. This work is a synthesis of both previous and new results developed within the task-oriented operational space formulation. Here we introduce a unifying framework for the analysis and control of robotic systems beginning with an analysis of inertial properties based on two models that independently describe the mass and inertial characteristics associated with linear and angular motions. To visualize these properties, we propose a new geometric representation, termed the belted ellipsoid, that displays the magnitudes of the mass/inertial properties directly rather than their square roots. Our study of serial macro/mini structures is based on two models of redundant mechanisms. The first is a ...

Abstract Research in motion planning has been striving to develop faster planning algorithms in order to be able to address a wider range of applications. In this paper a novel real-time motion planning framework, called decomposition-based motion planning, is proposed. It is particularly well suited for planning problems that arise in service and field robotics. It decomposes the original planning problem into simpler subproblems, whose successive solution empirically results in a large reduction of the overall complexity. A particular implementation of decomposition-based planning is proposed. Experiments with an eleven degree-of-freedom mobile manipulator are presented. 1 Introduction Recent advances in the area of robot motion planning have resulted in the successful application of these techniques to diverse domains, such as assembly planning, virtual prototyping, drug design, and computer animation. Much of the progress can be attributed to the introduction of probabilistic roadmap techniques [10] and their various extensions [1, 2, 8, 9]. Despite these advances, however, some areas of application have still remained out of reach for automated planning algorithms. Applications requiring robots with many degrees of freedom to operate in highly dynamic and unpredictably changing environments fall into that category. To operate robustly and safely in dynamic environments the ability to modify the planned motion in real time is necessary. The planning techniques for high-dimensional configuration spaces described in the literature, however, do not generate plans in real time.

Walking is an easy task for most humans and animals. Two characteristics which make it easy are the inherent robustness (tolerance to variation) of the walking problem and the natural dynamics of the walking mechanism. In this thesis we show how understanding and exploiting these two characteristics can aid in the control of bipedal robots. Inherent robustness allows for the use of simple, low impedance controllers. Natural dynamics reduces the requirements of the controller. We present a series of simple physical models of bipedal walking. The insight gained from these models is used in the development of three planar (motion only in the sagittal plane) control algorithms. The first uses simple strategies to control the robot to walk. The second exploits the natural dynamics of a kneecap, compliant ankle, and passive swing-leg. The third achieves fast swing of the swing-leg in order to enable the robot to walk quickly (1.25 m s ). These algorithms are implemented on Spring Flamingo...

This paper reviews some of the accomplishments in the field of robot dynamics research, from the development of the recursive Newton-Euler algorithm to the present day. Equations and algorithms are given for the most important dynamics computations, expressed in a common notation to facilitate their presentation and comparison. 1

Mobile manipulation capabilities are key to many new applications of robotics in space, underwater, con-struction, and service environments. This article dis-cusses 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 Formula-tion 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 manipu-lation 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 decen-tralized control structure for cooperative tasks. The ar-ticle also discusses experimental results obtained with two holonomic mobile manipulation platforms we have designed and constructed at Stanford University. 1

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 ...

The transformation from high level task specification to lowlevel motion control is a fundamental issue in sensorimotor control in animals and robots. This thesis develops a control scheme called virtual model control which addresses this issue.