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Force Control (force + control)

Distribution by Scientific Domains

Engineering	73%

Selected Abstracts

Prevention of Stick-Slip Vibrations by Passive Normal Force Control

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003
Martin Rudolph
The classical stick-slip oscillator is extended by an additional degree of freedom which couples the slipping motion to the normal force. Using this, the effective friction force can be altered without changing the friction-velocity characteristic. The paper deals with the optimization problem of finding parameters of the additional system that prevent stick-slip motion or minimize the amplitude of the residual limit cycle. Another goal is to increase the decay rate of vibration. Results were achieved by numerical integration based on analytical investigations. [source]

Myoelectric Hand Prosthesis Force Control Through Servo Motor Current Feedback

ARTIFICIAL ORGANS, Issue 10 2009
Tálita Saemi Payossim Sono
Abstract This paper presents the prehension force closed-loop control design of a mechanical finger commanded by electromyographic signal (EMG) from a patient's arm. The control scheme was implemented and tested in a mechanical finger prototype with three degrees of freedom and one actuator, driven by arm muscles EMG of normal volunteers. Real-time indirect estimation of prehension force was assessed by measuring the DC servo motor actuator current. A model of the plant comprising finger, motor, and grasped object was proposed. Model parameters were identified experimentally and a classical feedback phase-lead compensator was designed. The controlled mechanical finger was able to provide a more accurate prehension force modulation of a compliant object when compared to open-loop control. [source]

Force control between nanostructures by coupling of spatially separated polaritons

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2006
Takuya Iida
Abstract We theoretically propose a novel metrology technique based on the photomediated force control between nano-objects. In order to demonstrate the potential of this concept, we develop the general theoretical framework based on the Lorentz force equation and the nonlocal theory to obtain a concise analytical expression of the interparticle radiation force (IRF) due to the induced fields from polaritons in different nano-objects. This expression clearly shows how IRF reflects the electromagnetic coupling of spatially separated polaritons and contains information on the other nanostructure. This means that IRF can be used to access the multidirectional information of quantum properties in the target nanostructure. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Position/Force Control of an Underwater Mobile Manipulator

JOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 12 2003
Lionel Lapierre
This paper proposes a new control method applied to an underwater vehicle equipped with a robot manipulator. This control method is based on force control to stabilize the platform when the manipulator works in free or constrained space. The torque produced by the arm on the platform is estimated with a force sensor installed between the base of the manipulator and the vehicle. This allows correcting the position errors of the platform using an external force control loop. This paper presents this control law and shows some simulation results. © 2003 Wiley Periodicals, Inc. [source]

Sensorimotor memory and grip force control: does grip force anticipate a self-produced weight change when drinking with a straw from a cup?

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2003
Dennis A. Nowak
Abstract We examined whether self-generated weight changes are anticipated by adequate grip force adjustments when repeatedly lifting an instrumented manipulandum. Subjects lifted a cup filled with 500 mL of water prior to and following drinking two portions of water with a straw without touching it. One half of the subjects drank from and lifted an uncovered cup receiving constant visual information about its filling level and the other half of the subjects drank from a covered cup without such visual feedback. During the lifts immediately following the drinking procedures, grip force scaling was erroneously programmed for the heavier weight of the preceding lift as was obvious from an inadequately high rate of grip force development. Vision had only a minor influence on the rate of grip force increase. The influence of vision on the scaling of peak grip force was more pronounced. More accurate force scaling was obtained with an increasing number of lifts performed under each weight condition, indicating an ongoing force adjustment process probably based on sensory feedback. We conclude that self-generation of a change in the weight of an object to be lifted is not, in itself, sufficient to elicit a predictive grip force output. Rather, accurate feedback information associated with the self-generated weight change is essential to update internal models related to the mechanical object properties. This assumption was confirmed in pilot experiments; when subjects lifted the cup after having poured water from it, they accurately scaled their fingertip force to the self-produced weight change. Here, direct sensory feedback from the grasping fingers could signal the weight change and update internal models while pouring water from the cup. Our data support the hypothesis that the sensorimotor system planning and processing predictive fingertip force can operate independently of higher-level cognitive and perceptual systems. [source]

Adaptive robust force control for vehicle active suspensions

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 2 2004
Supavut Chantranuwathana
Abstract In this paper, the modular adaptive robust control (MARC) technique is applied to design the force loop controller of an electro-hydraulic active suspension system. A key advantage of this modular design approach lies in the fact that the adaptation algorithm can be designed for explicit estimation convergence. The effect of parameter adaptation on force tracking performance can be compensated and thus it is possible to guaranteed certain control performance. Experimental results from a quarter-car active suspension test rig show that when realistic external disturbances and measurement noises exist, the modular design achieves a better estimate than the non-modular ARC design. The improved estimation was found to result in control signals with slightly lower magnitude while maintaining similar tracking performance. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Position/Force Control of an Underwater Mobile Manipulator

Planning and controlling cooperating robots through distributed impedance

JOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 6 2002
Jérôme Szewczyk
This article presents distributed impedance as a new approach for multiple robot system control. In this approach, each cooperating manipulator is controlled by an independent impedance controller. In addition, along selected degrees of freedom, force control is achieved through an external loop, to improve control of the object's internal loading. Extensive stability analysis is performed, based on a realistic model that includes robot impedance and object dynamics. Experiments are performed using two cooperating industrial robots holding an object through point contacts. Force and position control actions are suitably dispatched to achieve both internal loading control and object position control. Individual impedance parameters are specified according to the theoritical stability criterion. The performance of the system is demonstrated for transportation and contact tasks. © 2002 Wiley Periodicals, Inc. [source]

Interactive force control of an operator,mobile manipulator coordination system

JOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 4 2002
Jae 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]

Robust force control of a flexible arm with a nonsymmetric rigid tip body

JOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 5 2001
Yoshifumi Morita
In this article, we discuss modeling and robust control of bending and torsional vibrations and contact force of a flexible arm with a nonsymmetric rigid tip body. By using Hamilton's principle and the Lagrange multiplier method, dynamic equations of the constrained flexible arm are derived. Since the flexible arm has the nonsymmetric tip body, the bending and torsional vibrations are coupled. As the obtained boundary conditions of the distributed parameter system are nonhomogeneous, we introduce a change of variables to derive homogeneous boundary conditions. By using the eigenvalues and the correpsonding eigenfunctions related to the distributed parameter system, we derive a finite-dimensional modal model. To compensate for the spillover instability, we construct robust controllers of an optimal controller with a low-pass property and an H, controller. Some experiments have been carried out to show the effectiveness of the proposed robust controllers. © 2001 John Wiley & Sons, Inc. [source]

Position and force tracking of a two-manipulator system manipulating a flexible beam

JOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 4 2001
Dong Sun
This article discusses the issue of hybrid position and force control of a two-manipulator system manipulating a flexible beam in trajectory tracking. Unlike our previous approach of set-point position control in the trajectory tracking, the system coordinates are hard to be regulated to the desired states with nonzero tracking velocities under continuous feedback control. In this study, we design a hybrid position and force tracking controller while using saturation control to compensate for the effect of beam vibration dynamics on the tracking performance. All parameters and states used in the controller are readily available so that the proposed method is feasible to implement. Under the proposed controller, the tracking error asymptotically converges to a predetermined boundary. Simulation results demonstrate the validity of the proposed approach. © 2001 John Wiley & Sons, Inc. [source]

Force control between nanostructures by coupling of spatially separated polaritons

Robust impedance control of a hydraulic suspension system

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 8 2010
Mohammad 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]

A position/force control for a robot finger with soft tip and uncertain kinematics

JOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 3 2002
Zoe Doulgeri
We consider the position and force regulation problem for a soft tip robot finger in contact with a rigid surface under kinematic and dynamic parametric uncertainties. The reproducing force is assumed to be related to the displacement through a nonlinear function whose characteristics are unknown, but both the actual displacement and force can be directly measured. Kinematic uncertainties concern the rigid surface orientation and the contact point location. Kinematic parameters involved in the contact point location concern the length from the last joint to the contact point and the rest of the link lengths in the general case. An adaptive controller with a composite update parameter law is proposed, and the asymptotic stability of the force and estimated position errors under dynamic and kinematic uncertainties is shown for the planar case. Simulation results for a three-degrees-of-freedom planar robotic finger are presented. © 2002 Wiley Periodicals, Inc. [source]