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Control Systems, IEEE

Issue 1 • Date Feb. 1997

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Displaying Results 1 - 10 of 10
  • Robust approximation and control

    Publication Year: 1997 , Page(s): 80 - 87
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1054 KB)  

    An algorithmic procedure has been implemented. Its input data are the frequency samples of a MIMO high order (possibly infinite dimensional) model and its output is a controller for that system. The procedure considers the approximation error as additive uncertainty and designs for robust performance of a mixed sensitivity problem by using H/sup /spl infin// optimal control. For cases where not only modeling uncertainty but also other types of uncertainties are considered, μ-synthesis can be used to design for robust performance From a practical point of view, the same procedure can be used for robust identification. This is the case when the values of H(j/spl omega//sub k/) are corrupted by additive bounded noise and the uniform bound on the noise is small enough. This is an important practical extension of this methodology, because a controller can be obtained directly from experimental data. Although there are assumptions which should be made concerning the identified plant, these are less restrictive than the knowledge of a mathematical model of the (possibly) infinite dimensional system as is the case in the approximation procedure. View full abstract»

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  • Position-based impedance control of an industrial hydraulic manipulator

    Publication Year: 1997 , Page(s): 46 - 52
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2564 KB)  

    This article addresses the problem of impedance control in hydraulic manipulators. Whereas most impedance and hybrid force/position control formulations have focused on electrically driven robots with controllable actuator torques, torque control of hydraulic actuators is a difficult task. A position-based impedance controller (PBIC) is proposed and demonstrated on an existing industrial hydraulic robot (a Unimate MKII-2000). A nonlinear proportional-integral (NPI) controller is first developed to meet the accurate positioning requirements of this impedance control formulation. The NPI controller is shown to make the manipulator match a range of second-order target impedances. Various experiments in free space and in environmental contact, including a simple impedance modulation experiment, demonstrate the feasibility and the promise of the technique. Finally, explanation of an experimentally observed behaviour is offered, suggesting a basic limitation to the implementation of impedance control View full abstract»

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  • Tactile feedback for multifingered dynamic grasping

    Publication Year: 1997 , Page(s): 63 - 71
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3740 KB)  

    Dynamic grasping force control for a multifingered hand is proposed and investigated. The grasping force of the finger is dynamically adjusted according to the tactile feedback so that each fingertip force always stays inside the friction cone detected by the tactile sensor and the fingertips maintain firm contact without any undesired slip nor detaching from the object while grasping it. The proposed method allows real-time control of the hand since it requires few numerical calculations. In order to enable the tactile feedback, a finger-shaped tactile sensor using an optical waveguide capable of detecting the contact location and the surface normal of the contacted object is developed. Finally, the validity of the proposed method is confirmed experimentally using a two-fingered hand with tactile sensors View full abstract»

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  • A distributed control system for flexible materials handling

    Publication Year: 1997 , Page(s): 22 - 28
    Cited by:  Papers (14)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    In this research, we are developing a materials handling system where many small, simple actuators cooperate to convey large objects with three degrees of freedom in a plane. The actuators, or cells, are arranged in a regular array which is fixed to a planar surface, and objects are passed over the array. Such an array provides very flexible materials handling in which many objects can be conveyed simultaneously in different directions. The array is coordinated in a distributed manner, rather than by a central controller. Each manipulator has its own controller, and each controller communicates with its neighbours. In this article, modeling and control methods, and a real-time communication network and language are developed. Simple tests on hardware and in simulation are presented View full abstract»

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  • Recent developments in a mechatronics-oriented design project laboratory

    Publication Year: 1997 , Page(s): 72 - 79
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3196 KB)  

    This article describes a senior-level undergraduate course in mechatronics/design for mechanical engineers at Polytechnic University in Brooklyn, NY, and presents an overview of the projects developed as part thereof. It is a two-semester course sequence, mandatory for all undergraduate students. Teams are typically formed by groups of three students, and a project is assigned to them at the beginning of the academic year. The assigned projects are related to the design and control of mechanical systems. The teams have a limited budget to complete the project, and can use the available resources at the Instrumentation Laboratory. The projects involve significant effort in microprocessor interfacing, signal processing, and power control for actuators. The anticipated theoretical results are analyzed and compared to the obtained experimental data. The teams submit five bimonthly reports and make a final presentation. The outcome of the best projects has been presented in regional conferences and published in several journals. The projects presented in the paper concern AGVs, heating and ventilation, process temperature control, DC motors, gear transmissions, and solar panel tracking View full abstract»

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  • Variable damping impedance control of a bilateral telerobotic system

    Publication Year: 1997 , Page(s): 37 - 45
    Cited by:  Papers (21)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2444 KB)  

    Damping and stiffness control in a telerobotic system allows the programmer to define the master and slave dynamics to suit a given task. Unfortunately, many requirements for good teleoperation produce conflicting choices of desired dynamic parameters for different tasks. It is proposed here that the master and slave damping and stiffness matrices be functionally dependent on sensed and commanded values of force and velocity, with no previous knowledge of the environment required. A strategy has been devised which provides better quality teleoperation under a variety of circumstances than is achievable with constant dynamics. Tracking in free space and along a surface by the slave can be maintained while impact forces are minimized with this strategy. The variable damping algorithm has been implemented on a 7-degree-of-freedom Robotics Research Corporation manipulator with position input from a 6-degree-of-freedom Kraft master hand controller, and tracking and impact performance is illustrated View full abstract»

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  • Teleoperation based on the adjoint Jacobian approach

    Publication Year: 1997 , Page(s): 53 - 62
    Cited by:  Papers (18)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4180 KB)  

    In this article we introduce a method for telecontrol of nonredundant slave arms based on the adjoint Jacobian approach. Cartesian velocity command inputs are used to teleoperate the slave arm smoothly within the whole workspace, including the vicinity of singularities. Moreover, teleoperation at a codimension one singularity is also possible, yielding specific motion patterns. Those include the motion through the singularity, resulting in a reconfigured kinematic chain. The method presented here is, in fact, an alternative to the singularity-consistent null space based approach developed earlier. We discuss some implementation details and provide simulation and experimental data derived during teleoperation of a virtual planar 2R arm and the wrist of a real robot View full abstract»

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  • An actively compliable probing system

    Publication Year: 1997 , Page(s): 14 - 21
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1340 KB)  

    A new probing mechanism and an associated active compliance control algorithm have been developed for in-circuit test of a PCB (printed circuit board). Commercially available robotic probing devices are incapable of controlling contact force generated when a rigid probe contacts with a solder joint at high speed. This uncontrollable excessive contact force often makes some defects on the surface of the solder joint, which is plastically deformable over some limited contact force. This force also makes unstable contact motions resulting in unreliable test data. To overcome these problems, we propose a serially connected macro and micro manipulator equipped with active compliance capability for safe and reliable in-circuit test. Moreover, with this probe the depth of penetration onto a solder joint can be regulated after contact. This article describes the design characteristics, modeling, and control scheme of the newly proposed devices. The comparison of conventional passive compliance and force feedback control methods with the proposed control scheme for the contact force control is presented. The results obtained from a series of experiments clearly show the effectiveness of the proposed system View full abstract»

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  • Visions of control

    Publication Year: 1997 , Page(s): 88 - 89
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    Technological disciplines are defined by their visions no less than their practices. The long-term, even futuristic, projections of the former serve as beacons, illuminating (it is hoped) the trail for researchers and practitioners who, at any time, are likely to be mired in their quotidian tasks. This is particularly true in the re-engineered world, where the next deadline, milestone, or deliverable may become an all-consuming pursuit-a succession of impermanent efforts that are likely to produce a permanent myopia. Immediate concerns may be necessary stepping stones, but grand visions can become the casualties of their reductive, analytic pursuits. Paradoxically, the greater the successes on the staging grounds, the more remote the ultimate goal can appear. And even research, the activity explicitly chartered with maintaining the long-term perspective, can be compromised View full abstract»

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  • Control for slosh-free motion of an open container

    Publication Year: 1997 , Page(s): 29 - 36
    Cited by:  Papers (52)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2548 KB)  

    This article describes two methods for controlling the surface of a liquid in an open container as it is being carried by a robot arm. Both methods make use of the fundamental mode of oscillation and damping of the liquid in the container as predicted from a boundary element model of the fluid. The first method uses an infinite impulse response filter to alter the acceleration profile so that the liquid remains level except for a single wave at the beginning and end of the motion. The motion of the liquid is similar to that of a simple pendulum. The second method removes the remaining two surface oscillations by tilting the container parallel to the beginning and ending wave. A double pendulum model is used to determine the trajectory for this motion. Experimental results of a FANUC S-800 robot moving a 230 mm diameter hemispherical container of water are presented View full abstract»

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Jonathan P. How
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