This paper describes the integration of several techniques for cooperative control of both tele-operated and autonomous redundant manipulators with overlapping workspaces. Motivating this research is a tele-operated surgical manipulator(s) supported by autonomous robot(s) that insert/remove items from the surgical workspace. The dynamic and unpredictable location of obstacles in a small workspace requires a complete strategy to avoid collisions when completing critical tasks and minimizes the need for user (i.e. the surgeon) intervention to make path planning decisions or resolve impasse situations. Three techniques are integrated into the decision-making for the manipulators: an intelligent and intuitive EEF velocity scaling, coordinated null-space optimization across affected manipulators, and collision detection. Central to all three techniques is an estimated time- to-collision formulation that combines distances between objects with their higher order properties, thus only objects currently moving towards each other are included in the collision avoidance techniques. The use of multiple techniques derived from the terms of a single metric results in a computationally efficient strategy for tele-operated and autonomous manipulators sharing the same workspace.

In this paper, a metrology method is presented to calibrate modular robots. It is to perform metrology at the modular level and measure the kinematic parameters of each module so that the acquired information may be used for obtaining an "as built" model every time either a modular robot is reconfigured or maintenance has been made. Based on the product-of-exponentials formula and the modified dyad kinematics, two calibration models with or without the interface error compensation are proposed. The success of this method is based on two key technologies; the first key is an accurate and interchangeable standardized interface and the second key is to develop a state-of-the-art 3-D metrology system which is accurate, flexible, and easy to use. This paper presents these topics with kinematic models for modular robot calibration.

Robotic systems are often used for remote operations in Department of Energy Environmental Management applications because they allow the removal of personnel from dangerous environments. Typically, these systems are operated in pure teleoperation mode by a human operator. While these systems are capable of performing many tasks, their performance can be greatly enhanced through the use of telerobotics (a combination of teleoperation, automation, and decision making). This paper describes an analytical approach to decision making for robotic systems used in remote operations. This approach utilizes redundancy in the system or the task to improve the overall system performance based on analytical criteria. The approach is illustrated by application to the dual arm telerobot at Oak Ridge National Laboratory (ORNL) and the pit viper system at Pacific Northwest National Laboratory (PNNL). In both instances, decision making clearly reduces the operator involvement in tedious tasks while improving performance.

In this paper, a simple and approximate formulation to be used in the initial phase of modular interface design is presented, which relates the design parameters such as contact stiffness, geometry dimensions and dimensional tolerances to the final relative position and orientation of connected interfaces. Specifically, the concept of contact spring from former research is adopted to obtain approximate single-step solutions for over-constrained multi-DOF connection problems. The primary purpose of this method is to efficiently obtain an initial set of design parameter values, including tolerances, out of many possible choices that a designer have faced.

This work introduces a new architecture for a parallel, six degree of freedom manipulator. The kinematic analysis of this redundant manipulator is provided. The proposed parallel mechanism allows easy implementation of redundant actuators, and has relatively large workspace in comparison to conventional six degree of freedom parallel devices. The kinematic analysis performed forms the basis for the introduction of design criteria for the manipulator. Several design criteria are introduced and their use is illustrated by example design involving an initial geometric parameter analysis of the manipulator.

The objective of the paper is to develop a structural compliance model for a general serial manipulator that includes both joint and link compliance sources in any general distribution of revolute and prismatic joints. A primary feature is that special consideration is given to modeling the variable focal compliance properties of a robot containing one or more prismatic joints. A more reliable method for placing the link compliance frames is also introduced. An improved linear quasi-static compliance model for serial robot structure comprised of both revolute and/or prismatic joint is provided.

This paper presents a simulation and analysis of partial failure recovery using nonlinear programming techniques. Previous techniques have shown partial failure recoveries that were limited by their use of a single criterion. The technique shown maintains the torque constraints imposed by the failure while minimizing additional performance criteria. One advantage of this technique is that it allows the robot to avoid parametric and mathematical limits by means of imposing additional performance criteria.

This study introduces a criteria-based methodology for grasp synthesis. The method allows the use of multiple performance criteria both at the finger and the hand levels, which are used to generate a preliminary grasp and an optimum grasp, respectively. The approach offers reduced complexity by decomposing grasp synthesis into manageable phases. A case study using a physical hand demonstrates the effectiveness of the method.

This paper examines the commonalities of manual controllers used in robotics for teleoperation. These include devices ranging from simple joysticks to force-reflecting controllers. The similarities in functionality and behaviour of these controllers is further exploited to develop a reusable software architecture for manual controller interfacing. The development of this architecture is based on object-oriented design. The application of this design philosophy led to the development of a hierarchy of software components that are manual controller independent and also have a standardized interface. Reusability of these components is supported through generality and extensibility. The key design requirements for this architecture were: open-system, reusable, application independent, extensive error-handling and safety checking, applicability to real-time control and simulation, and reduction in program development time. This paper discusses the software analysis and design issues that were faced to meet the architecture requirements. Further, this architecture is demonstrated using four different manual controllers and a teleoperated dual-arm robotic manipulator.

This paper describes a program (RAMP) which facilitates robot design analysis, project management, and design documentation. Requirements for such a program are proposed, and the literature is investigated. Design of the program is discussed in an object-oriented manner, and the system-level objects are described. The extent and method of implemented analysis objects is presented in more detail. Examples of use are discussed in terms of component selection, deflection analysis, and end-effector position error. Finally, the future augmentation of RAMP is described.

Dual-arm robotic systems with cooperating manipulators possess redundancy in drivability providing the opportunity for choice, or resource allocation, a fundamental quality of an intelligent machine. Criteria are necessary to make effective use of dual-arm robotic system resources, as well as to enhance performance. Decision-making criteria are presented which are based on parameters inherent to the two cooperating manipulators, and parameters intrinsic to cooperative modes of operation in dual-arm robots, thus the criteria are formulated at multiple levels within the dual-arm robotic system. Interactive computer graphics is used to investigate multi-level criteria with an example 17 degree-of-freedom robot performing cooperative dual-arm robotic operations.>

The establishment of a unique infrastructure for distributed robotics and remote operations research within an educational environment is reported. The distributed laboratory consists of sites at four universities and NASA's Johnson Space Center. The distributed laboratory configuration provides the opportunity to quantitatively study the effects of various system components and technologies on overall telerobotic task performance. The ability to execute representative inspection and manipulation tasks with multiple control, robot, and performance/workload monitoring sites simultaneously connected has been demonstrated. Operations are carried out on a routine basis. During the process, needs for hardware and software standards development have been identified. The current implementation provides a basis for linking government, industrial, and university facilities to realize a truly collaborative research and development environment, enabling graduate students to experience educational opportunities that would otherwise not be possible.>

Previous implementations of robot force control seldom produced satisfactory results, and researchers in the past have experienced significant instability problems associated with their force controllers. When a manipulator is constrained to an environment (force-controlled), geometric stability due to the manipulator configuration and the force-controlled direction is shown to be a significant factor in overall system stability. This exploratory study points out a rather intuitive, geometrically based stability and analyzes the phenomenon both analytically and graphically. Sequential joint self-motion algorithms for kinematically redundant manipulators are suggested for reduced transitional impact and greater stability in the ensuing force-controlled operation.>

The micromanipulator is a device to enhance robot accuracy by allowing small, fast position corrections to be introduced near the end effector of a standard industrial robot. The objective of this paper is to discuss global issues for the design, manufacture, and implementation of this module. The kinematic and dynamic modeling method of the parallel mechanism is presented. The optimum geometric parameters for performing a given task are synthesized, based on the modeling simulation. Internal force, local maximum stress, and the deflection analyses are performed for critical loading cases to allow design of the hardware components. Design principles which address local and global objectives for the design of a micromanipulator are discussed, from the optimization point of view. The concept of designing a flexural joint to have low stiffness, low inertia, low friction, and no backlash while maintaining a kinematically sound system is discussed in detail. Finally, to eliminate the need for an external force sensor, an integral 6 DOF force sensing system would be included in the final design.>

Establishing the complete dynamic model of a manipulator arm requires precise knowledge of the system mass and stiffness properties. An experimental procedure based on the modal analysis concept to identify the dynamic parameters of industrial manipulator arms is presented. The mass and stiffness content of an industrial robot are extracted from the modal behavior of the arm utilizing a general mathematical model for serial manipulators. The validity of the parameters is verified by comparison of the measured vibration behavior of the arm with the behavior of the proposed model. Some suggestions to improve the performance and operating speed of the robot by increasing the structural integrity of the system are presented.>

The incorporation of multiple criteria in the operation of redundant manipulators is considered. The criteria investigated in the literature are categorized, and an alternative set of criteria categories is proposed. Criteria normalization and prioritization are discussed. Simulation results for a spatial seven-degree-of-freedom manipulator incorporating four criteria along a self-motion trajectory are given. An animation package for visualizing the simulation results and examining the tradeoffs between criteria is described. The study is intended as a first step toward a decision-making framework that will be used to investigate how a comprehensive set of criteria might be combined to enhance the operation of redundant manipulators.>

A modeling procedure for a completely general kinematic system and a stiffness formulation technique for antagonistically actuated systems are given, in a format which is directly applicable to the design of high-stiffness robotic manipulator controllers. The formulation is developed in terms of kinematic influence coefficients. This involves some generalization of an existing modeling technique so that hybrid manipulator systems (combinations of parallel and serial manipulator systems) can be systematically treated. Antagonistic stiffness, which is developed extensively, is seen to be very promising for the design and control of future manipulators with high precision requirements under various operational disturbances.>

A novel approach for the control of task-space stiffness characteristics in systems consisting of a superabundance of kinematically dependent inputs is proposed. When there are more input actuations than operational degrees of freedom, internal preloads can be generated that produce effective restoring forces in the face of displacement or disturbances imposed on the system. Examples of this excessive actuation can be found in certain modes of structurally overconstrained parallel manipulators and in antagonistically structured serial manipulators. The input loads are synthesized offline (prior to operation) and entered as a feedforward component so that the desired effective loads on objects are obtained, and (simultaneously) significant disturbances at the task level can be largely rejected in an open-loop fashion. This reduces the burden and shortcomings of standard feedback schemes. Moreover, a layered feedback scheme is used to compensate for small perturbations and unmodeled dynamics. The open-loop task-based stiffness control scheme as applied to structurally parallel mechanism/robotic linkage systems is investigated. The scheme's applicability as a programmable active compliance device is also discussed.>

A method of deflection analysis for a general serial manipulator which considers end-effector, gravity, and inertial loads is described. The conceptualized manipulator can have many degrees of freedom and be of the most general geometry. The analysis returns end-effector error based on a quasistatic approach. Thus, small oscillations (due to vibrations) are ignored and the inertial loads are considered applied loads. A kinematic analysis based on geometric influence coefficients is used to obtaining resultant joint loads. A flexibility analysis sufficient to describe general link deformation is performed to yield the local link deformations. These local values are transformed to end-effector deflections through the use of the kinematic influence coefficients as a first order approximation. End-effector deflection due to flexibilities in the joint actuators is addressed. A description of the generalized end-effector spring is presented.>

It is essential for the robust control of a dynamic system to employ a characterization of its inertia content in the control formulation. One such characterization is described for the nonlinear time-varying system of a robotic manipulator in the form of pipelined modeling software which is implemented on a medium-sized array processor to run in real time. The time-varying inertia content of the manipulator is expressed in terms of kinematic influence coefficients which are represented by explicit functions of only the generalized coordinates. Properties of these influence coefficients are employed to reduce the computation effort necessary to generate the modeling coefficients. To efficiently pipeline this algorithm, the structure inherent in the problem is exploited to allow extensive use of data-dependent addressing which is employed to compute multiple "small" operations within a single pipeline. The resulting software consists of two portions-- an off-line portion generates integer offset vectors to direct the addressing of the on-line portion in computing the modeling coefficients. The real-time algorithm is fourth-order in the number of links requiring 7.5 ms on a modest-sized array processor to compute the modeling coefficients of a general six-link manipulator.

Current industrial robots deflect as much as 25 times their specified accuracy due to their capacity load. This paper presents the local optimization criteria for the distribution of actuator stiffness (or compliance) of a given manipulator configuration to enhance the overall stiffness of the structure and to guarantee a specified level of precision under a known magnitude of machining load resulting from drilling, routing, riveting, etc. Position dependent kinematic influence coefficients [2] form a convenient basis for the compliance matrix for demonstration of the role of significant physical parameters and efficient computation in the analysis and design process. Specific examples dealing with optimal distribution of actuator compliance are presented. The techniques developed in this paper and the previous work [6,7] can greatly reduce the design cycle time for accurate, reliable manipulators, and makes adjustment of the distribution of system parameters to enhance controllability more feasible, especially when precision control under external disturbance is required.