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Control Systems Magazine, IEEE

Issue 2 • Date Feb. 1990

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Displaying Results 1 - 8 of 8
  • Manipulation and dynamic mechanical testing of microscopic objects using a tele-micro-robot system

    Page(s): 3 - 9
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    A microrobot having two high-performance parallel drive limbs which has been developed for manipulation, surgery, and dynamic mechanical testing of very small objects such as single living cells is described. The end points of each limb move in overlapping spherical workspaces of 1-mm diameter with minimum open- and closed-loop movements of 1 nm and 10 nm, respectively. The displacement bandwidth of all six microrobot axes exceeds 1 kHz for small displacements. A three-dimensional laser vision system with a resolution of 50 to 100 nm has been developed to provide the microrobot with volume images containing magnitude, phase, polarization, and spectral information. A macro version of the microrobot has been built to permit force-reflecting teleoperation of the microrobot. The telemicrorobot system permits both microscopic objects and continuum models to be felt. A high-performance parallel computer has been designed, and partially constructed, to meet the substantial computational and control requirements of the telemicrorobot system.<> View full abstract»

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  • Design and characterization of a linear motion piezoelectric micropositioner

    Page(s): 10 - 15
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    Small, lightweight, fast micropositioners provide fast, precise motion for applications in precision manufacturing. A description is given of the design and characterization of a precise linear micropositioner. The device is constructed from a number of piezoelectric plates placed on both sides of a sliding mass. Actuation of the plates in an accordion fashion provides a linear displacement of +or-0.36 mm. In addition, the device has a force capability of over 80 g, as well as position and force sensing capabilities. The dynamic performance of the device is characterized, and initial tests show that it has a second-order system behavior with nonlinear response. The device resolution is affected by the performance of the capacitive-type position sensor and varies from 3 mu m to less than 0.6 mu m.<> View full abstract»

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  • A family of robot control strategies for intermittent dynamical environments

    Page(s): 16 - 22
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    A formalism is developed for describing and analyzing a very simple representative class of robotic tasks that require dynamical dexterity-among them, the task of juggling. The authors review their empirical success to date with a new class of control algorithms for this task domain, called mirror algorithms. The formalism for representing the task domain and encoding within it the desired robot behavior enables them to prove that a suitable mirror algorithm is correct with respect to a specified task.<> View full abstract»

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  • Control strategies for tendon-driven manipulators

    Page(s): 23 - 28
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    Two antagonist control algorithms are presented. These algorithms are used to control manipulator links antagonistically driven by two actuators via tendons. They have been simulated and experimentally shown to produce better active and passive performance for an electric test system than control algorithms developed earlier. There are two fundamental differences between the control algorithms and earlier ones. First, the new algorithms allow both positive and negative (push and pull) commands to be given to the actuators. Previous systems generated only pull commands, ensuring that tendons would not go slack and give rise to backlash and other problems. The new controllers allow push commands to the actuators, but still do not allow tendons to go slack. Second, each actuator, in addition to being fed back its respective tendon force, is fed back both positive nd negative manipulator joint torques. This feature allows both actuators to respond simultaneously to torque errors.<> View full abstract»

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  • Adaptive control of a single-link flexible manipulator

    Page(s): 29 - 33
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    A method for controlling single-link lightweight flexible manipulators is proposed. The objective is to control the tip position of the flexible manipulator in the presence of joint friction and changes in payload. Both linear and nonlinear frictions are overcome by using a very robust control scheme for flexible manipulators. The control scheme is based on two nested feedback loops: an inner loop, to control the position of the motor, and an outer loop, to control the tip position. Compensation for changes in load is achieved by decoupling the dynamics of the system and then applying a very simple adaptive control for the tip position. This results in a simple control law that needs minimal computing effort and, thus, can be used for real-time control of the flexible arms.<> View full abstract»

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  • Scheduling jobs with simple precedence constraints on parallel machines

    Page(s): 34 - 40
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    A methodology is presented for scheduling jobs on identical, parallel machines. Each job comprises a small number of operations that must be processed in a specified order. The objective is to minimize the total weighted quadratic tardiness of the schedule, subject to capacity and precedence constraints. The procedure presented is an efficient near-optimal method based on the Lagrangian relaxation technique and the list-scheduling concept. In addition, the resulting job-interaction information can be used to provide quick answers to what-if questions and to reconfigure the schedule to reincorporate new jobs and other dynamic changes. This scheduling methodology has been implemented in a knowledge-based scheduling system. Typical sizes of problems involve 35 to 40 machines and 100 to 200 jobs, each with 3 to 5 operations.<> View full abstract»

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  • Experiments in identification and control of flexible-link manipulators

    Page(s): 41 - 46
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    A report is presented on an ongoing effort for end-point position control of flexible-link manipulators under realistic conditions in laboratory setups consisting of one- and two-link manipulators. The authors treat modeling, identification, and control of flexible-link manipulators that are required to carry payloads, possibly unknown and varying, while undergoing disturbance effects from the environments and the workspace. The various identification and control techniques being investigated are summarized, with emphasis on the ability of the controller to adjust to changes in dynamics, payload, and working environment. It is found that time-domain methods offer identified model structures that are readily available for control design, whereas frequency-domain methods, particularly the time-varying transfer function estimation approach developed for this application, are more desirable when rapid controller tuning is required.<> View full abstract»

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  • Communication and control for distributed microsystems

    Page(s): 48 - 50
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    The authors introduce communication and control issues in the design of systems composed of distributed microsensors and microactuators. They examine reliability and bandwidth in the context of distributed microsystem design and suggest areas for further research and development. It is shown that communication networks for closed-loop microsystems must exhibit high speed while having a minimum number of wires and a simple interconnection scheme. Until such networks are constructed, the performance of distributed microsystems will fall short of expectations. The lessons learned from robot sensing are discussed.<> View full abstract»

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Aims & Scope

This Magazine ceased publication in 1990. The current retitled publication is IEEE Control Systems.

Full Aims & Scope