Workspace Control Research Articles

Workspace control system of underwater tele-operated manipulators on an ROV

This paper presents a control technique for structured undersea tasks that require a high degree of precision. The overall efficiency of tele-operated underwater manipulation is improved by reducing the burden on the human operator. A new workspace-control system composed of a computer and input devices in workspace was developed to support the operator. The computer transforms the desired velocity of end-effector in workspaces to desired joint angles by solving the inverse kinematics of the slave manipulators. The desired joint angles are transferred to the slave controller through RS-485 serial communication, and be followed by the slave manipulator. The developed master system provides advantages in conducting structured tasks(coring, drilling, underwater connector mating, etc.) that require precise control of the end-effector’s motion and attitude. The existing master system, however, is more useful for unstructured tasks than newly developed master system. By combining the two master systems, the work efficiency of the underwater tele-operated manipulator system was improved. This paper presents the development of the workspace-control system and a working strategy to alleviate operator’s burden in underwater works. Experimental results are presented to evaluate the effectiveness of the proposed method using underwater manipulators mounted on the KORDI deep-sea ROV Hemire.

Siemens Multileaf Collimator Characterization and Quality Assurance Approaches for Intensity-Modulated Radiotherapy

Application of the multileaf collimator (MLC) has evolved from replacing blocks to create treatment fields to creating photon fluence modulation for intensity-modulated radiotherapy (IMRT). Multileaf collimator system performance requirements are far more stringent for such applications and will require increased performance for future applications, such as motion tracking. This article reviews Siemens MLC systems, including a technical description and dosimetric characteristics of 56-, 82-, and 160-leaf designs. Routine quality assurance of MLC for IMRT necessitates frequent and critical assessment of MLC leaf position calibration errors that can present in many different ways (e.g., accuracy, reproducibility, longevity, hysteresis, and collimator/gantry angle dependencies). Several techniques for measuring these errors are presented, along with qualitative and quantitative techniques for analyzing results. In particular, increased accuracy of leaf position measurement at variable gantry angles is enabled by spatial transformations to electronic portal imaging device position quantified by calibration protocols introduced with megavoltage cone beam. Measured values of X-ray transmission (intra-leaf, inter-leaf, and through abutting leaf pairs) and penumbra (leaf end, leaf tongue, leaf groove) are presented with an evaluation of their characterization by a treatment-planning system. The dosimetric impact of planning system model inadequacies is demonstrated for collimator scatter, dose profile values within 30 mm of the field edge, and the resultant effect demonstrated on clinical cases. Finally, a description of automated quality assurance delivery, analysis, and calibration protocols applicable for the specific vendor's system is provided.

Ｏｐｅｎ ＭＲＩ環境下手術支援マニピュレータのためのてこ―平行リンク式位置姿勢伝達機構 運動学と可動領域解析，剛性実験

We would propose a novel mechanism of a surgical manipulator, which works in Open MRI guided surgery and assists surgeon (s) in precise positioning and handling of surgical devices. This mechanism can transmit 3 translational and 3 rotational motions from the outside to the inside of MR imaging area by using leverage and parallelogram mechanism. Such a remote actuation is significantly helpful because the strong and sensitive magnet of MR denies the accessibility of magnetic and electric devices and materials to the imaging area. In this paper, the basic ideas of mechanism were introduced and its forward and inverse kinematics was formulated firstly. Secondly, a non-MR-compatible prototype was made to reveal mechanical problems. Thirdly, the workspace of the prototype was numerically analyzed. Fourthly, the stiffness of the prototype was experimentally evaluated. These results concluded trade-off between stiffness and workspace. Fifthly, our new idea of workspace control for mechanical safety was preliminary discussed.

マルチレート制御とむだ時間補償に基づくビジュアルサーボ

This paper presents a visual servoing of robot manipulator based on intersample disturbance rejection with switching scheme and dead-time compensation. First, multirate intersample disturbance rejection algorithm is reviewed, which was proposed by authors for general digital control system with restricted sampling frequency. Second, the novel feedforward scheme is proposed with open-loop estimation and switching function, which enables the disturbance rejection without any sacrifice of the closed-loop characteristics. Third, new precise formulation of delay problems in visual servoing is established as the image processing latency, the difference between sampling period of camera signal and control period of joint servo system, and delay of inner-loop joint servo system. By introducing the workspace controller and nonlinear perspective transformation, the proposed intersample disturbance rejection controller becomes applicable to the visual servoing problem of 2 DOF manipulator with moving object points. Finally, the advantages of the proposed control system are verified through simulations and experiments.

Geometric Motion Control for a Kinematically Redundant Robotic Chain: Application to a Holonomic Mobile Manipulator

AbstractFor kinematically redundant robotic manipulators, the extra degrees of freedom available allows freedom in the generation of the trajectories of the end‐effector. In this paper, for this scope, we use techniques for motion control of rigid bodies on Riemannian manifolds (and Lie groups in particular) to design workspace control algorithms for the end‐effector of the robotic chain and then to pull them back to joint space, all respecting the different geometric structures of the two underlying model spaces. The trajectory planner makes use of geometric splines. Examples of the different kinds of curves that are obtained via the De Casteljau algorithm in correspondence of different metric structures in SE(3) are reported. The feedback module, instead, consists of a Lyapunov based PD controller defined from a suitable notion of error distance on the Lie group. The motivating application of our work is a holonomic mobile manipulator for which simulation results are described in detail. © 2003 Wiley Periodicals, Inc.

Configuration space as a means for augmenting human performance in teleoperation tasks

This paper considers an approach to operator-guided real time motion control of robot arm manipulators that's based on the use of configuration space (C-space). The goal is to improve operator performance in a complex environment with obstacles, In such tasks, traditional teleoperation techniques, which are all based on control in work space (W-space), suffer from human errors tied to deficiencies in human spatial reasoning. The C-space approach transforms the problem into one humans are much better equipped to handle-moving a point in a maze-and results in a significant improvement in performance: shorter path, less time to complete the task, and virtually no arm-obstacle collisions. Versions of the approach are described for two-dimensional (2-D) and three-dimensional (3-D) tasks, and tools are developed to efficiently interface the human and machine intelligence. Effectiveness of the C-space approach is demonstrated by a series of experiments, showing an improvement in performance on the order of magnitude in the 2-D case and a factor of two to four in the 3-D case, compared to usual work space control.

Workspace Control Diagrams and Head-Mounted Displays as Alternatives to Multiple Monitors in Information-Rich Environments

In environments such as Navy command and control, supervision and multi-tasking are often hindered by a shortage of screen space. An obvious solution is to use more or larger monitors. An inexpensive and practical alternative is to use an interface that allows rapid switching between workspaces (screens of information), providing, in effect, a large virtual desktop. One potentially effective switching interface is a workspace control diagram—a meaningful arrangement of buttons, each of which provides access to and information for a particular workspace. In Experiment 1, participants best performed a task that required frequent navigation among workspaces using two real monitors but were nearly as proficient when using one monitor with a workspace control diagram operated by hot keys. In Experiment 2, participants performed concurrent tracking and monitoring tasks about equally using four monitors with all workspaces visible and using two monitors with a workspace control diagram. Additionally, we discuss the potential of a much more radical workstation design alternative: head-mounted displays.

Supporting Software Development Processes in Adele 2

After years using of Adele, a configuration management system, it became apparent that it lacks activity-related concepts and mechanisms like work environment control, user coordination and synchronization, method and tool control, etc. It was also clear that considerable work is required to adapt a Software Engineering Environment (SEE) to user requirements. Using this experience, Adele 2 has beeen implemented to provide a general support for defining and managing dynamic aspects of a SEE and facilitate the building of new SEEs. This paper describes, using an example (work space control), the concepts and mechanisms involved. We show how close integration of an activity manager with a software engineering database fulfills the basic requirements and how a high level task manager coupled to a configuration manager can be developed.

Work-space robot controllers

SUMMARYIn regard to work-space controller design, a derivation of the relationships between the operational approach and the decoupling method is introduced. The given generating rules, which are valid for nonredundant robots, permit the design of a Position-Speed-Acceleration controller or hybrid Force-PSA controllers.