scholarly journals Electrotactile feedback improves performance and facilitates learning in the routine grasping task

2016 ◽  
Vol 26 (3) ◽  
Author(s):  
Milica Isaković ◽  
Minja Belić ◽  
Matija Štrbac ◽  
Igor Popović ◽  
Strahinja Došen ◽  
...  
Keyword(s):  
Force Control ◽  
Closed Loop ◽  
Feedforward Control ◽  
Open Loop ◽  
Spatial Coding ◽  
Accuracy And Precision ◽  
Array Electrode ◽  
Grasping Force ◽  
Four Levels ◽  
And Training

Aim of this study was to investigate the feasibility of electrotactile feedback in closed loop training of force control during the routine grasping task. The feedback was provided using an array electrode and a simple six-level spatial coding, and the experiment was conducted in three amputee subjects. The psychometric tests confirmed that the subjects could perceive and interpret the electrotactile feedback with a high success rate. The subjects performed the routine grasping task comprising 4 blocks of 60 grasping trials. In each trial, the subjects employed feedforward control to close the hand and produce the desired grasping force (four levels). First (baseline) and the last (validation) session were performed in open loop, while the second and the third session (training) included electrotactile feedback. The obtained results confirmed that using the feedback improved the accuracy and precision of the force control. In addition, the subjects performed significantly better in the validation vs. baseline session, therefore suggesting that electrotactile feedback can be used for learning and training of myoelectric control.

Study of Dominant Performance Characteristics in Robot Transmissions

1993 ◽  
Vol 115 (3) ◽  
pp. 472-482 ◽  
Author(s):  
H. Schempf ◽  
D. R. Yoerger
Keyword(s):  
Force Control ◽  
Closed Loop ◽  
Stability Margin ◽  
Viscous Friction ◽  
Open Loop ◽  
Phase Lag ◽  
Stability Margins ◽  
Loop Bandwidth ◽  
Hard Contact ◽  
Following Error

Six different transmission types suitable for robotic manipulators were compared in an experimental and theoretical study. Single-degree-of-freedom mechanisms based on the different transmissions were evaluated in terms of force control performance, achievable bandwidth, and stability properties in hard contact tasks. Transmission types considered were (1) cable reducer, (2) harmonic drive, (3) cycloidal disk reducer, (4) cycloidal cam reducer, (5) ball reducer, and (6) planetary/cycloidal gear head. Open loop torque following error, attenuation and phase lag, and closed loop bandwidth and stability margin were found to be severely dominated by levels of inertia, stiffness distribution and variability, stiction, coulomb and viscous friction, and ripple torque. These aspects were quantified and shown to vary widely among all transmissions tested. The degree of nonlinearity inherent in each transmission affected its open and closed loop behavior directly, and limited the effectiveness of controller compensation schemes. Simple transmission models based on carefully measured transmission characteristics are shown to predict stability margins and achievable force-control bandwidths in hard contact to within a 5 to 15 percent error margin.

Design and Assessment of an Adaptive Intermittent Cervical Traction Modality With EMG Biofeedback

1996 ◽  
Vol 118 (4) ◽  
pp. 597-600 ◽  
Author(s):  
M. Y. Lee ◽  
M. K. Wong ◽  
F. T. Tang ◽  
W. H. Chang ◽  
W. K. Chiou
Keyword(s):  
Force Control ◽  
Closed Loop ◽  
Traction Force ◽  
Open Loop ◽  
Emg Biofeedback ◽  
Paraspinal Muscle ◽  
Myoelectric Activity ◽  
Emg Signal ◽  
Cervical Traction ◽  
And Control

An intermittent cervical traction modality with closed-loop traction force control based on EMG biofeedback was developed and used for clinical study. This system consists of a EMG scanner, on-line self-adjusted traction force controller, audio/video alarm system, real time therapeutic status display, computer interface hardware, and control software. Twenty-four subjects with diagnosed cervical radiculopathy and muscle spasm symptom who were randomly divided into two groups served as subjects in this study. The control and experimental groups were treated with conventional open loop and new EMG biofeedback closed loop traction control protocols respectively. The results of this study indicate that the average reductions in paraspinal EMG signal during traction after 7 weeks treatment for experimental and control groups were 71 and 50 percent, respectively (p < 0.001). These results not only support the clinical use of intermittent, sitting traction to produce cervical paraspinal muscle relaxation, but also revealed that the average myoelectric activity of cervical paraspinal muscle during traction was reduced as traction force increased over the 7-week duration of traction treatment. Through EMG biofeedback traction force control, muscle injury, neck soreness, or pain after traction may be avoided.

Disturbance Observer Based Closed Loop Force Control for Haptic Feedback

2007 ◽  
Author(s):  
Abhishek Gupta ◽  
Marcia K. O’Malley ◽  
Volkan Patoglu
Keyword(s):  
Force Control ◽  
Disturbance Observer ◽  
Closed Loop ◽  
Force Feedback ◽  
Haptic Feedback ◽  
Open Loop ◽  
Contact Forces ◽  
Force Sensing ◽  
Haptic Interfaces ◽  
Simulation Fidelity

Most commonly used impedance-type haptic interfaces employ open-loop force control under the assumption of pseudostatic interactions. Advanced force control in such interfaces can increase simulation fidelity through improvement of the transparency of the device, and can further improve robustness. However, closed loop force-feedback is limited both due to the bandwidth limitations of force sensing and the associated cost of force sensors required for its implementation. In this paper, we propose the use of a nonlinear disturbance observer for estimation of contact forces during haptic interactions. This approach circumvents the traditional drawbacks of force sensing while exhibiting the advantages of closed-loop force control in haptic devices. The feedback of contact force information further enables implementation of advanced robot force control techniques such as robust hybrid impedance and admittance control. Simulation and experimental results, utilizing a PHANToM Premium 1.0A haptic interface, are presented to demonstrate the efficacy of the proposed approach.

Disturbance-Observer-Based Force Estimation for Haptic Feedback

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Abhishek Gupta ◽  
Marcia K. O’Malley
Keyword(s):  
Force Control ◽  
Disturbance Observer ◽  
Closed Loop ◽  
Haptic Feedback ◽  
Open Loop ◽  
Contact Forces ◽  
Haptic Interface ◽  
Force Sensing ◽  
Force Estimation ◽  
Control Approach

In this paper, we propose the use of a nonlinear disturbance-observer for estimation of contact forces during haptic interactions. Most commonly used impedance-type haptic interfaces employ open-loop force control under the assumption of pseudostatic interactions. Advanced force control in such interfaces can increase simulation fidelity through improvement of the transparency of the device. However, closed-loop force feedback is limited both due to the bandwidth limitations of force sensing and the associated cost of force sensors required for its implementation. Using a disturbance-observer, we estimate contact forces at the tool tip, then use these estimates for closed-loop control of the haptic interface. Simulation and experimental results, utilizing a custom single degree-of-freedom haptic interface, are presented to demonstrate the efficacy of the proposed disturbance-observer (DO)-based control approach. This approach circumvents the traditional drawbacks of force sensing while exhibiting the advantages of closed-loop force control in haptic devices. Results show that the proposed disturbance-observer can reliably estimate contact forces at the human-robot interface. The DO-based control approach is experimentally shown to improve haptic interface fidelity over a purely open-loop display while maintaining stable and vibration-free interactions between the human user and virtual environment.

scholarly journals Virtual Grasping: Closed-Loop Force Control Using Electrotactile Feedback

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Nikola Jorgovanovic ◽  
Strahinja Dosen ◽  
Damir J. Djozic ◽  
Goran Krajoski ◽  
Dario Farina
Keyword(s):  
Closed Loop ◽  
Feedforward Control ◽  
Human Subjects ◽  
Real Life ◽  
Sensory Substitution ◽  
Vibrotactile Stimulation ◽  
Loop Control ◽  
Control Robustness ◽  
Grasping Force ◽  
Virtual Grasping

Closing the control loop by providing somatosensory feedback to the user of a prosthesis is a well-known, long standing challenge in the field of prosthetics. Various approaches have been investigated for feedback restoration, ranging from direct neural stimulation to noninvasive sensory substitution methods. Although there are many studies presenting closed-loop systems, only a few of them objectively evaluated the closed-loop performance, mostly using vibrotactile stimulation. Importantly, the conclusions about the utility of the feedback were partly contradictory. The goal of the current study was to systematically investigate the capability of human subjects to control grasping force in closed loop using electrotactile feedback. We have developed a realistic experimental setup for virtual grasping, which operated in real time, included a set of real life objects, as well as a graphical and dynamical model of the prosthesis. We have used the setup to test 10 healthy, able bodied subjects to investigate the role of training, feedback and feedforward control, robustness of the closed loop, and the ability of the human subjects to generalize the control to previously “unseen” objects. Overall, the outcomes of this study are very optimistic with regard to the benefits of feedback and reveal various, practically relevant, aspects of closed-loop control.

On closed-loop equilibrium strategies for mean-field stochastic linear quadratic problems

2020 ◽  
Vol 26 ◽  
pp. 41
Author(s):  
Tianxiao Wang
Keyword(s):  
Optimal Control ◽  
Closed Loop ◽  
Optimal Control Problems ◽  
Mean Field ◽  
Open Loop ◽  
Time Inconsistency ◽  
Control Problems ◽  
Linear Quadratic ◽  
Linear Quadratic Optimal Control ◽  
Equilibrium Strategies

This article is concerned with linear quadratic optimal control problems of mean-field stochastic differential equations (MF-SDE) with deterministic coefficients. To treat the time inconsistency of the optimal control problems, linear closed-loop equilibrium strategies are introduced and characterized by variational approach. Our developed methodology drops the delicate convergence procedures in Yong [Trans. Amer. Math. Soc. 369 (2017) 5467–5523]. When the MF-SDE reduces to SDE, our Riccati system coincides with the analogue in Yong [Trans. Amer. Math. Soc. 369 (2017) 5467–5523]. However, these two systems are in general different from each other due to the conditional mean-field terms in the MF-SDE. Eventually, the comparisons with pre-committed optimal strategies, open-loop equilibrium strategies are given in details.

Comparison of Dc-Dc SEPIC, CUK and Flyback Converters Based LED Drivers

2020 ◽  
pp. 99-107
Author(s):  
Erdal Sehirli
Keyword(s):  
Integrated Circuit ◽  
Closed Loop ◽  
Input Voltage ◽  
Open Loop ◽  
Current Sensor ◽  
Switching Frequency ◽  
Led Driver ◽  
Advantages And Disadvantages ◽  
Led Drivers ◽  
Conduction Mode

This paper presents the comparison of LED driver topologies that include SEPIC, CUK and FLYBACK DC-DC converters. Both topologies are designed for 8W power and operated in discontinuous conduction mode (DCM) with 88 kHz switching frequency. Furthermore, inductors of SEPIC and CUK converters are wounded as coupled. Applications are realized by using SG3524 integrated circuit for open loop and PIC16F877 microcontroller for closed loop. Besides, ACS712 current sensor used to limit maximum LED current for closed loop applications. Finally, SEPIC, CUK and FLYBACK DC-DC LED drivers are compared with respect to LED current, LED voltage, input voltage and current. Also, advantages and disadvantages of all topologies are concluded.

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