This paper introduces a design technique for complex robotic systems called interfaces-first design. Interfaces-first design develops information interfaces based on the characteristics of information flow in the system, and then builds subsystem interfaces from combinations of these information interfaces. This technique is applied to a dual-arm workcell combining a graphical user interface, an on-line motion planner, real-time vision, and an on-line simulator. The system is capable of performing object acquisition from a moving conveyor belt and carrying out simple assemblies, without the benefit of pre-planned schedules nor mechanical fixturing. The information characteristics of this system are analyzed, and divided into three interfaces: world state, task command, and motion commands. Detailed descriptions of the resulting interfaces are provided. The paper concludes with experimental results from the workcell. Both single-arm and dual-arm actions are discussed.

Real-time system software is notoriously hard to share and reuse. This paper walks through the methodology and application of ControlShell, a component-based programming system real-time system software development. ControlShell combines graphical system-building tools, an execution-time configuration manager, a real-time matrix package, and an object name service into an integrated development environment. It targets complex systems that require on-line reconfiguration and strategic control. ControlShell takes advantage of functional object hierarchies to enable code sharing and reuse. It gains flexibility by supporting easy interconnectivity of these objects. It features a unique configuration control system for changing operating modes. The paper concludes by examining the application of this framework to a dual-arm robotic workcell that is able to pick objects from a moving conveyor and perform simple assemblies,.

The network data delivery service (NDDS) is a novel network data-sharing system. NDDS builds on the model of information producers (sources) and consumers (sinks). Producers generate data at their own discretion, unaware of prospective consumers. Consumers "subscribe" to data-updates without concern for who is producing them. The routing protocol is connectionless and nearly "stateless", thus network reconfigurations, node failures, etc. are handled naturally. This scheme is particularly effective in systems (such as distributed control systems) where information is of a repetitive nature. NDDS provides support for multiple producers, reliable data-delivery, consumer update guarantees, notifications vs. polling for updates, dynamic binding of producers and consumers, distributed queries, and user-defined data types. NDDS is integrated into the ControlShell real-time framework and is being used in several robotic applications as an effective means of information sharing between sensor systems, robot controllers, planners, graphical user interfaces, and simulators.>

The dynamic control module of the Dynamic and Strategic Control of Cooperating Manipulators (DASCCOM) project for aerospace robotics is presented. The cooperative manipulation problem is analyzed from a systems perspective, and the desirable features of a control system for cooperative manipulation are discussed. A control policy is developed that enforces a controlled impedance not of the individual arm endpoints, but of the manipulated object itself. A parallel implementation for a multiprocessor system is presented. The controller fully compensates for the system dynamics and directly controls the object internal forces. Most importantly, it presents a simple, powerful, intuitive interface to higher level strategic control modules. Experimental results from a dual two-link-arm robotic system show the effectiveness of the object impedance controller compared to other strategies, both for free-motion slews and environmental contact.>

The authors present the dynamic control module of the Dynamic and Strategic Control of Cooperative Manipulators project at Stanford University's Aerospace Robotics Laboratory. First, the cooperative manipulation problem is analyzed from a systems perspective, and the desirable features of a control system for cooperative manipulation are discussed. Next, a control policy is developed that enforces a controlled impedance not of the individual arm endpoints, but of the manipulated object itself. A parallel implementation for a multiprocessor system is presented. The controller fully compensates for the system dynamics and directly controls the object internal forces. Most importantly, it presents a simple, powerful, intuitive interface to the strategic controller. Experimental results for a dual two-link arm robotic system are presented to verify the controllers performance, for both free-motion slews and environmental contact.>