Kyong-Sok Chang

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.

Robots in Human Environments: Basic Autonomous Capabilities

This article discusses the basic capabilities needed to enable robots to operate in human-populated environments for accomplishing both autonomous tasks and human-guided tasks. These capabilities are key to many new emerging robotic applications in service, construction, field, underwater, and space. An important characteristic of these robots is the “assistance” ability they can bring to humans in performing various physical tasks. To interact with humans and operate in their environments, these robots must be provided with the functionality of mobility and manipulation. The article presents developments of models, strategies, and algorithms concerned with a number of autonomous capabilities that are essential for robot operations in human environments. These capabilities include: integrated mobility and manipulation, cooperative skills between multiple robots, interaction ability with humans, and efficient techniques for real-time modification of collision-free path. These capabilities are demonstrated on two holonomic mobile platforms designed and built at Stanford University in collaboration with Oak Ridge National Laboratories and Nomadic Technologies.

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.

ProVAR assistive robot system architecture

This paper describes the implementation of a robot control architecture designed to combine a manipulation task design environment with a motion controller that uses the operational space formulation to define and implement arm trajectories and object manipulation. The ProVAR desktop manipulation system is an assistive robot for individuals with a severe physical disability, such as quadriplegia as a result of a high-level spinal cord injury. ProVAR allows non-technical operators access to the robots capabilities through a direct-manipulation simulation/preview user interface. The novel interface concept is based on two built-in characters to play the roles of helpful consultant and down-to-earth robot arm. This team-based interface concept was chosen to maximize user performance and comfort in controlling the inherently complex mechatronic technology. This paper describes our design decisions and rationale.

Operational space dynamics: efficient algorithms for modeling and control of branching mechanisms

This paper discusses intuitive and efficient ways to model and control the dynamics of highly redundant branching mechanisms using the operational space formulation. As the complexity of mechanisms increases, their modeling and control become increasingly difficult. The operational space formulation provides a natural framework for these problems since its basic structure provides dynamic decoupling among multiple tasks and posture behaviors. Efficient recursive algorithms are presented for the computation of the operational space dynamics of branching mechanisms with multiple operational points. The application of these algorithms results in a significant increase in the interactivity and usability of dynamic control of complex branching mechanisms. The experimental results are presented using real-time dynamic simulation.

The augmented object model: cooperative manipulation and parallel mechanism dynamics

The augmented object model provided the basis for effective cooperation between multiple robots. These robots were assumed to have a single serial-chain structure. In this paper we discuss the augmented object model in the context of mechanisms involving multiple branches such as humanoid robots and parallel mechanisms. An application of the proposed model in the dynamic modeling of a holonomic mobile base and experimental results using real-time dynamic simulation are presented to illustrate the effectiveness of the proposed approach.

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

Manipulator control at kinematic singularities: a dynamically consistent strategy

This paper presents a general strategy for manipulator control at kinematic singularities. When a manipulator is in the neighborhood of singular configurations, it is treated as a redundant mechanism in the subspace orthogonal to the singular directions of the end-effector. Control in this subspace is based on operational forces, while null space joint torques are used to deal with the control in the singular directions. Decoupled behavior is guaranteed by using the dynamically consistent force/torque relationship. Two different types of kinematic singularities are identified and strategies dealing with these singularities are developed. Experimental results of the implementation of this approach on a PUMA 560 manipulator are presented.