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Impedance Control (impedance + control)
Selected AbstractsLeft Ventricle Afterload Impedance Control by an Axial Flow Ventricular Assist Device: A Potential Tool for Ventricular RecoveryARTIFICIAL ORGANS, Issue 9 2010Francesco Moscato Abstract Ventricular assist devices (VADs) are increasingly used for supporting blood circulation in heart failure patients. To protect or even to restore the myocardial function, a defined loading of the ventricle for training would be important. Therefore, a VAD control strategy was developed that provides an explicitly definable loading condition for the failing ventricle. A mathematical model of the cardiovascular system with an axial flow VAD was used to test the control strategy in the presence of a failing left ventricle, slight physical activity, and a recovering scenario. Furthermore, the proposed control strategy was compared to a conventional constant speed mode during hemodynamic changes (reduced venous return and arterial vasoconstriction). The physiological benefit of the control strategy was manifested by a large increase in the ventricular Frank,Starling reserve and by restoration of normal hemodynamics (5.1 L/min cardiac output at a left atrial pressure of 10 mm Hg vs. 4.2 L/min at 21 mm Hg in the unassisted case). The control strategy automatically reduced the pump speed in response to reduced venous return and kept the pump flow independent of the vasoconstriction condition. Most importantly, the ventricular load was kept stable within 1%, compared to a change of 75% for the constant speed. As a key feature, the proposed control strategy provides a defined and adjustable load to the failing ventricle by an automatic regulation of the VAD speed and allows a controlled training of the myocardium. This, in turn, may represent a potential additional tool to increase the number of patients showing recovery. [source] Robust impedance control of a hydraulic suspension systemINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 8 2010Mohammad Mehdi FatehArticle first published online: 2 JUN 200 Abstract A novel robust impedance control approach is developed to control dynamic behavior of a vehicle subject to road disturbances. This behavior is predetermined as an impedance rule to achieve passenger comfort and vehicle handling by the use of a hydraulically actuated suspension system. Impedance control law is simple, free of model and efficient to apply for a broad range of road conditions. Moreover, it relates comfort to handling. This control approach can provide a desired comfort when passing a bump, and both desired comfort and handling after passing a bump. Robust position and force controls are used to implement the robust impedance control with the presence of uncertainties. A transformed proportional,integral,derivative control is proposed to perform the robust control. The system stability is analyzed and analytical results are confirmed by simulations. A quarter-car model of suspension system and a nonlinear model of hydraulic actuator are used to simulate the control system. Copyright © 2009 John Wiley & Sons, Ltd. [source] Reconfigurable ankle rehabilitation robot for various exercisesJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue S1 2006Jungwon Yoon This paper presents a reconfigurable ankle rehabilitation robot to cover various rehabilitation exercise modes. The designed robot can allow desired ankle and foot motions, including toe and heel raising as well as traditional ankle rotations, since the mechanism can generate relative rotation between the fore and rear platforms as well as pitch and roll motions. In addition, the robotic device can be reconfigured from a range of motion (ROM)/strengthening exercise device to a balance/proprioception exercise device by simply incorporating an additional plate. Further, the action of the device is twofold in the sense that while a patient's foot is fastened firmly to the ROM/strengthening device for task specific training, that person can also stand on the balance/proproception device. To perform each mode of ROM, strengthening, and proproception exercises, a unified position-based impedance control is systematically developed taking into account the desired position and velocity. © 2005 Wiley Periodicals, Inc. [source] Interactive force control of an operator,mobile manipulator coordination systemJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 4 2002Jae H. Chung In this article, a new type of coordination control called interactive force control is developed for an operator,mobile manipulator coordination system (OMMCS) based on a base force/torque sensor. In the interactive force control scheme, a robust force control of the manipulator and impedance control of the mobile platform are integrated to achieve smooth interaction between the operator, the manipulator, and the mobile platform. In simulation, the developed methods are compared for control performance in tracking and force regulation. Simulation results show the promise of the developed control scheme, which utilizes robust force control based on a base force/torque sensor. © 2002 Wiley Periodicals, Inc. [source] On singular behaviors of impedance-based repeatable control for redundant robotsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 4 2001Chau-Chang Wang This article addresses the association between the unstiffening phenomena in structural mechanics and the algorithmic singularities encountered in the impedance-based repeatable control algorithms used to command redundant manipulators. It is well known that velocity control schemes such as the pseudoinverse control schemes do not guarantee repeatability for redundant manipulators. In other words, for a closed end-effector trajectory, the joints do not, in general, exhibit a closed trajectory. One way to overcome this problem is to model each joint with compliance and incorporate a second-order correction term for the pseudoinverse. With this model, the joint configuration adopted by the manipulator at a given point in task space is one which minimizes the artificial potential energy of the system and is locally unique. In terms of statics, this is equivalent to saying that the elastic structure reaches its static equilibrium under external load. Keep this analogy in mind. We know that the impedance control commands the manipulator to mimic the behavior of an elastic articulated chain. For any phenomena observable on a real elastic structure, we should be able to find its counterpart embedded in the impedance control. In this article, we analyze the performance of such repeatable control algorithms from the point of view of structure mechanics. Singularities in the algorithm are examined and their significance in mechanics are also discussed. © 2001 John Wiley & Sons, Inc. [source] | ||||||||||