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.

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.

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.

scholarly journals A dual-loop tracking control approach to precise nanopositioning

2018 ◽  
Vol 25 (3) ◽  
pp. 666-674 ◽  
Author(s):  
Mohammed Altaher ◽  
Douglas Russell ◽  
Sumeet S. Aphale
Keyword(s):  
Closed Loop ◽  
Reference Signal ◽  
Open Loop ◽  
Performance Criteria ◽  
Control Technique ◽  
Loop Control ◽  
Control Approach ◽  
First Order ◽  
Integral Controller ◽  
Double Integrator

Nanopositioners are mechanical devices that can accurately move with a resolution in the nanometer scale. Due to their mechanical construction and the piezoelectric actuators popularly employed in nanopositioners, these devices have severe performance limitations due to resonance, hysteresis and creep. A number of techniques to control nanopositioners, both in open-loop and closed-loop, have been reported in the literature. Closed-loop techniques clearly outperform open-loop techniques due to several desirable characteristics, such as robustness, high-bandwidth, absence of the need for tuning and high stability, along with others. The most popular closed-loop control technique reported is one where a damping controller is first employed in an inner loop to damp the mechanical resonance of the nanopositioner, thereby increasing achievable bandwidth. Consequently, a tracking controller, typically an Integral controller or a proportional–integral controller, is implemented in the outer loop to enforce tracking of the reference signal, thereby reducing the positioning errors due to hysteresis and creep dynamics of the employed actuator. The most popular trajectory a nanopositioner is forced to track is a raster scan, which is generated by making one axis of the nanopositioner follow a triangular trajectory and the other follow a slow ramp or staircase. It is quite clear that a triangle wave (a finite velocity, zero acceleration signal) cannot be perfectly tracked by a first-order integrator and a double integrator is necessary to deliver error-free tracking. However, due to the phase profile of the damped closed-loop system, implementing a double integrator is difficult. This paper proposes a method by which to implement two integrators focused on the tracking performance. Criteria for gain selection, stability analysis, error analysis, simulations, and experimental results are provided. These demonstrate a reduction in positioning error by 50%, when compared to the traditional damping plus first-order integral tracking approach.

A near-optimal decentralized control approach for polynomial nonlinear interconnected systems

2020 ◽  
pp. 014233122097743
Author(s):  
Mohamed Sadok Attia ◽  
Mohamed Karim Bouafoura ◽  
Naceur Benhadj Braiek
Keyword(s):  
Optimal Control ◽  
Closed Loop ◽  
Sufficient Conditions ◽  
Open Loop ◽  
System Stability ◽  
Gronwall Lemma ◽  
Interconnected System ◽  
Control Approach ◽  
State Dependent ◽  
And Control

This article tackles the decentralized near-optimal control problem for the class of nonlinear polynomial interconnected system based on a shifted Legendre polynomials direct approach. The proposed method converts the interconnected optimal control problems into a nonlinear programming one with multiple constraints. In light of the formulated NLP optimization, state and control coefficients are used to design a nonlinear decentralized state feedback controller. Overall closed-loop system stability sufficient conditions are investigated with the help of Grönwall lemma. The triple inverted pendulum case is considered for simulation. Satisfactory results are obtained in both open-loop and closed-loop schemes with comparison to collocation and state-dependent Riccati equation techniques.

Regulation of Hydrogen Peroxide Dosage in a Heterogeneous Photo-Fenton Process

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2167
Author(s):  
Karla Estefanía Saldaña-Flores ◽  
René Alejandro Flores-Estrella ◽  
Victor Alcaraz-Gonzalez ◽  
Elvis Carissimi ◽  
Bruna Gonçalves de Souza ◽  
...  
Keyword(s):  
Gallic Acid ◽  
Organic Compounds ◽  
Closed Loop ◽  
Transfer Functions ◽  
Direct Synthesis ◽  
Synthesis Method ◽  
Open Loop ◽  
Fenton Process ◽  
Control Approach ◽  
Curve Method

In this work, a classical linear control approach for the peroxide (H2O2) dosage in a photo-Fenton process is presented as a suitable solution for improving the efficiency in the treatment of recalcitrant organic compounds that cannot be degraded by classical wastewater treatment processes like anaerobic digestion. Experiments were carried out to degrade Lignin, Melanoidin, and Gallic acid, which are typical recalcitrant organic compounds present in some kinds of effluents such as vinasses from the Tequila and Cachaça industries. Experiments were carried in Open-Loop mode for obtaining the degradation model for the three compounds in the form of a Transfer Function, and in Closed-Loop mode for controlling the concentration of each compound. First-order Transfer Functions were obtained using the reaction curve method, and then, based on these models, the parameters of Proportional Integral controllers were calculated using the direct synthesis method. In the Closed-Loop experiments, the Total Organic Carbon removal was 39% for lignin, 7% for melanoidin, and 29% for Gallic acid, which were greater than those obtained in the Open-Loop experiments.

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.

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.

scholarly journals A Clamping Force Estimation Method Based on a Joint Torque Disturbance Observer Using PSO-BPNN for Cable-Driven Surgical Robot End-Effectors

Sensors ◽  
2019 ◽  
Vol 19 (23) ◽  
pp. 5291 ◽  
Author(s):  
Zhengyu Wang ◽  
Daoming Wang ◽  
Bing Chen ◽  
Lingtao Yu ◽  
Jun Qian ◽  
...  
Keyword(s):  
Disturbance Observer ◽  
Estimation Method ◽  
Surgical Robot ◽  
Joint Torque ◽  
Force Sensing ◽  
Clamping Force ◽  
Force Estimation ◽  
Cable Tension ◽  
One Dimensional ◽  
End Effectors

The ability to sense external force is an important technique for force feedback, haptics and safe interaction control in minimally-invasive surgical robots (MISRs). Moreover, this ability plays a significant role in the restricting refined surgical operations. The wrist joints of surgical robot end-effectors are usually actuated by several long-distance wire cables. Its two forceps are each actuated by two cables. The scope of force sensing includes multidimensional external force and one-dimensional clamping force. This paper focuses on one-dimensional clamping force sensing method that do not require any internal force sensor integrated in the end-effector’s forceps. A new clamping force estimation method is proposed based on a joint torque disturbance observer (JTDO) for a cable-driven surgical robot end-effector. The JTDO essentially considers the variations in cable tension between the actual cable tension and the estimated cable tension using a Particle Swarm Optimization Back Propagation Neural Network (PSO-BPNN) under free motion. Furthermore, a clamping force estimator is proposed based on the forceps’ JTDO and their mechanical relations. According to comparative analyses in experimental studies, the detection resolutions of collision force and clamping force were 0.11 N. The experimental results verify the feasibility and effectiveness of the proposed clamping force sensing method.

Contact Force Estimation for an Elastic Beam Using Optimal High-Gain Disturbance Observer

2010 ◽  
Author(s):  
Yan Liu ◽  
Dirk So¨ffker
Keyword(s):  
Contact Force ◽  
Disturbance Observer ◽  
Elastic Beam ◽  
High Gain ◽  
Contact Forces ◽  
Force Estimation ◽  
Input Estimation ◽  
System States ◽  
Unknown Input Estimation ◽  
Noisy Measurements

This contribution presents a contact force estimation approach based on an optimal high-gain disturbance observer for an elastic beam using noisy measurements. The reconstruction of contact forces as an example for unknown input estimation represents a class of typical mechanical engineering problems related to the estimation of unknown effects for disturbance rejection or accommodation or fault diagnosis and isolation. The high-gain disturbance observers applied here is able to estimate estimate unknown external inputs together with system states. But choosing observer gains is a difficult task because of the influence of measurement noise. The important advantage of the proposed approach in comparison with classical high-gain disturbance observer is the self adjustment of the observer gains according to the actual estimation situation. Estimation results based on real measurements from known high-gain disturbance observer and the proposed optimal one are compared. It can be shown that the proposed algorithm allows optimized disturbance observer gains calculation, being able to be situatively adapted.

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