scholarly journals Role of digit placement control in sensorimotor transformations for dexterous manipulation

2017 ◽  
Vol 118 (5) ◽  
pp. 2935-2943 ◽  
Author(s):  
Daisuke Shibata ◽  
Marco Santello
Keyword(s):  
Force Feedback ◽  
Force Production ◽  
Passive Movement ◽  
Position Estimation ◽  
Accurate Estimation ◽  
Dexterous Manipulation ◽  
Motor Commands ◽  
Sensorimotor Transformations ◽  
Sensorimotor Mechanisms ◽  
Digit Position

Dexterous manipulation relies on the ability to modulate grasp forces to variable digit position. However, the sensorimotor mechanisms underlying such critical ability are not well understood. The present study addressed whether digit force-to-position modulation relies entirely on feedback of digit placement and force, or on the integration of such feedback with motor commands responsible for digit positioning. In two experiments, we asked 25 subjects to estimate the index fingertip position relative to the thumb (perception test) or to grasp and lift an object with an asymmetrical mass distribution while preventing object roll (action test). Both tests were performed after subjects’ digits were placed actively or passively at different distances (active and passive condition, respectively) and without visual feedback. Because motor commands for digit positioning would be integrated with position and force feedback in the active condition, we hypothesized this condition to be characterized by greater accuracy of digit position estimation and digit force-to-position modulation. Surprisingly, discrimination of digit position and force-to-position modulation was statistically indistinguishable in the active and passive conditions. We conclude that voluntary commands for digit positioning are not essential for accurate estimation of finger position or modulation of digit forces to variable digit position. Thus digit force-to-position modulation can be implemented by integrating sensory feedback of digit position and voluntary commands of digit force production following contact. NEW & NOTEWORTHY This study was designed to understand the sensorimotor mechanisms underlying digit force-to-position modulation required for manipulation. Surprisingly, estimation of relative digit position and force-to-position modulation was accurate regardless of whether the digits were passively or actively positioned. Therefore, accurate estimation of digit position does not require an efference copy of active digit positioning, and the hypothesized advantage of active over passive movement on estimation of end-point position appears to be task and effector dependent.

scholarly journals The Effects of Spinal Manipulation on Motor Unit Behavior

2021 ◽  
Vol 11 (1) ◽  
pp. 105
Author(s):  
Lucien Robinault ◽  
Aleš Holobar ◽  
Sylvain Crémoux ◽  
Usman Rashid ◽  
Imran Khan Niazi ◽  
...  
Keyword(s):  
Motor Unit ◽  
Conduction Velocity ◽  
Spinal Manipulation ◽  
Maximum Voluntary Contraction ◽  
Force Production ◽  
Movement Control ◽  
Position Sense ◽  
Joint Position Sense ◽  
Voluntary Contraction ◽  
Passive Movement

Over recent years, a growing body of research has highlighted the neural plastic effects of spinal manipulation on the central nervous system. Recently, it has been shown that spinal manipulation improved outcomes, such as maximum voluntary force and limb joint position sense, reflecting improved sensorimotor integration and processing. This study aimed to further evaluate how spinal manipulation can alter neuromuscular activity. High density electromyography (HD sEMG) signals from the tibialis anterior were recorded and decomposed in order to study motor unit changes in 14 subjects following spinal manipulation or a passive movement control session in a crossover study design. Participants were asked to produce ankle dorsiflexion at two force levels, 5% and 10% of maximum voluntary contraction (MVC), following two different patterns of force production (“ramp” and “ramp and maintain”). A significant decrease in the conduction velocity (p = 0.01) was observed during the “ramp and maintain” condition at 5% MVC after spinal manipulation. A decrease in conduction velocity suggests that spinal manipulation alters motor unit recruitment patterns with an increased recruitment of lower threshold, lower twitch torque motor units.

scholarly journals Optical Enhancement of Exoskeleton-Based Estimation of Glenohumeral Angles

2016 ◽  
Vol 2016 ◽  
pp. 1-20 ◽  
Author(s):  
Camilo Cortés ◽  
Luis Unzueta ◽  
Ana de los Reyes-Guzmán ◽  
Oscar E. Ruiz ◽  
Julián Flórez
Keyword(s):  
Estimation Method ◽  
Position Estimation ◽  
Accurate Estimation ◽  
Joint Angles ◽  
Estimation Errors ◽  
Marker Position ◽  
Human Movements ◽  
Posture Estimation ◽  
Kinematic Models ◽  
Method Accuracy

In Robot-Assisted Rehabilitation (RAR) the accurate estimation of the patient limb joint angles is critical for assessing therapy efficacy. In RAR, the use of classic motion capture systems (MOCAPs) (e.g., optical and electromagnetic) to estimate the Glenohumeral (GH) joint angles is hindered by the exoskeleton body, which causes occlusions and magnetic disturbances. Moreover, the exoskeleton posture does not accurately reflect limb posture, as their kinematic models differ. To address the said limitations in posture estimation, we propose installing the cameras of an optical marker-based MOCAP in the rehabilitation exoskeleton. Then, the GH joint angles are estimated by combining the estimated marker poses and exoskeleton Forward Kinematics. Such hybrid system prevents problems related to marker occlusions, reduced camera detection volume, and imprecise joint angle estimation due to the kinematic mismatch of the patient and exoskeleton models. This paper presents the formulation, simulation, and accuracy quantification of the proposed method with simulated human movements. In addition, a sensitivity analysis of the method accuracy to marker position estimation errors, due to system calibration errors and marker drifts, has been carried out. The results show that, even with significant errors in the marker position estimation, method accuracy is adequate for RAR.

Design and Modeling of an Electro-Rheological Fluid Based Haptic Interface

2000 ◽  
Author(s):  
C. Mavroidis ◽  
C. Pfeiffer ◽  
J. Celestino ◽  
Y. Bar-Cohen
Keyword(s):  
Analytical Modeling ◽  
Force Feedback ◽  
Haptic Interface ◽  
Dexterous Manipulation ◽  
End Effector ◽  
Jet Propulsion ◽  
Field Robots ◽  
Rutgers University ◽  
Modeling And Experiments ◽  
Human Operators

Abstract In this project, Rutgers University has teamed with the Jet Propulsion Laboratory (JPL) to pursue the development and demonstration of a novel haptic interfacing capability called MEMICA (remote MEchanical MIrroring using Controlled stiffness and Actuators). MEMICA is intended to provide human operators intuitive and interactive feeling of the stiffness and forces at remote or virtual sites in support of space, medical, underwater, virtual reality, military and field robots performing dexterous manipulation operations. The key aspect of the MEMICA system is a miniature Electrically Controlled Stiffness (ECS) element that mirrors the stiffness at remote/virtual sites. The ECS elements make use of Electro-Rheological Fluid (ERF), which is an Electro-Active Polymer (EAP), to achieve this feeling of stiffness. Forces applied at the robot end-effector due to a compliant environment will be reflected to the user by this ERF device where a change in the system viscosity will occur proportionally to the force to be transmitted. This paper describes the analytical modeling and experiments that are currently underway to develop an ERF based force feedback element.

scholarly journals Bayesian Estimation of the Axial Position in Astigmatism-Based Three-Dimensional Particle Tracking

2009 ◽  
Vol 2009 ◽  
pp. 1-6 ◽  
Author(s):  
Joshua W. Shaevitz
Keyword(s):  
Bayesian Estimation ◽  
Particle Tracking ◽  
Single Particle ◽  
Functional Form ◽  
Three Dimensional ◽  
Position Estimation ◽  
Single Particle Tracking ◽  
Axial Position ◽  
Accurate Estimation ◽  
Image Set

Accurate estimation of the axial position of a molecule using a single lateral image remains a challenge in fluorescent single particle tracking. Here, a principled algorithm for the Bayesian estimation of the axial position of a molecule in three-dimensional astigmatism-based particle tracking is proposed. This technique uses the data from a calibration image set to derive the position without assuming a functional form for the abberated defocusing curve. Using a calibration image set from forty 57 nm beads, the axial position is calculated, and the error associated with position estimation is discussed. This method is compared to previously published algorithms.

scholarly journals GNSS Signal Processing with EKF and UKF for Stationary User Position Estimation

2021 ◽  
Vol 17 ◽  
pp. 75-80
Author(s):  
Mert Sever ◽  
Chingiz Hajiyev
Keyword(s):  
Signal Processing ◽  
Kalman Filter ◽  
Unscented Kalman Filter ◽  
Measurement Data ◽  
Position Estimation ◽  
Accurate Estimation ◽  
Important Process ◽  
Moving Platforms ◽  
Linearization Methods ◽  
Nonlinear Motion

Precise and accurate estimation of state vectors is an important process during position determination. In this study, Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF) of stationary user, state vectors defined in Earth Centered Inertial (ECI) coordinate system, accompanied by GNSS measurement data. It is aimed to make estimations with methods. EKF and UKF methods were compared with each other. In this study, the effects of nonlinear motion analysis and linearization methods on state vector estimations were investigated. Thanks to this study, estimations of the positioning information required during the specific tasks of many moving platforms have been made.

Optimal Configuration of Ultrasonic Sensors in a 3D Position Estimation System Using Genetic Algorithms

2001 ◽  
Author(s):  
Probir Kumar Ray ◽  
Nishant Unnikrishnan ◽  
Ajay Mahajan
Keyword(s):  
Autonomous Vehicles ◽  
Wave Theory ◽  
Position Estimation ◽  
Optimal Placement ◽  
Accurate Estimation ◽  
Delay Term ◽  
Electronic Circuitry ◽  
3D Space ◽  
The Difference ◽  
Estimation System

Abstract This paper provides a genetic algorithm based approach to calculate the optimal placement of receivers in a 3D position estimation system that uses the difference in the time-of-arrivals (TOA) of an ultrasonic wave from a transmitter to the different receivers fixed in 3D space. This is a different approach to traditional systems that use the actual time-of-flights (TOF) from the transmitter to the different receivers and triangulate the position of the transmitter. The new approach makes the system more accurate, makes the transmitter independent of the receivers and does not require the need of calculating the time delay term that is inherent in traditional systems due to delays caused by the electronic circuitry. This paper presents a thorough analysis of receiver configurations in the 2D and 3D system that lead to singularities, i.e. locations of receivers that lead to formulations that can not be solved due to a shortage of information. It provides guidelines of where not to place receivers, and further, presents a detailed analysis of locations that are optimal, i.e. locations that lead to the most accurate estimation of the transmitter positions. The results presented in this paper are not only applicable to ultrasonic systems, but all systems that use wave theory, e.g. infrared, laser, etc. This work finds applications in virtual reality cells, robotics, guidance of indoor autonomous vehicles and vibration analysis.

scholarly journals Higher-Order Sliding Mode Observer for Speed and Position Estimation in PMSM

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Suneel K. Kommuri ◽  
Kalyana C. Veluvolu ◽  
M. Defoort ◽  
Yeng C. Soh
Keyword(s):  
Sliding Mode ◽  
Permanent Magnet Synchronous Motor ◽  
Estimation Method ◽  
Higher Order ◽  
Position Estimation ◽  
Accurate Estimation ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Three Phase ◽  
Low Pass

This paper presents a speed and position estimation method for the permanent magnet synchronous motor (PMSM) based on higher-order sliding mode (HOSM) observer. The back electromotive forces (EMFs) in the PMSM are treated as unknown inputs and are estimated with the HOSM observer without the need of low-pass filter and phase compensation modules. With the estimation of back EMFs, an accurate estimation of speed and rotor position can be obtained. Further, the proposed method completely eliminates chattering. Experimental results with a 26 W three-phase PMSM demonstrate the effectiveness of the proposed method.

Omnidirectional Vision Based Mobile Robot Hierarchical SLAM

2011 ◽  
Vol 464 ◽  
pp. 95-98
Author(s):  
Mao Hai Li ◽  
Li Ning Sun ◽  
Ming Qiang Pan
Keyword(s):  
Mobile Robot ◽  
Particle Filter ◽  
Position Estimation ◽  
Medium Size ◽  
Accurate Estimation ◽  
Omnidirectional Vision ◽  
Alignment Algorithm ◽  
Feature Maps ◽  
Topological Graph ◽  
Local Map

A hierarchical mobile robot simultaneous localization and mapping (SLAM) method that allows us to obtain accurate maps of large environments is proposed. The local map level is composed of a set of local metric feature maps that are guaranteed to be statistically independent. The global level is a topological graph whose arcs are labeled with the relative location between local maps. An estimation of these relative locations is maintained with local map alignment algorithm, and more accurate estimation is calculated through a global minimization procedure using the loop closure constraint. The local map is built with Rao-Blackwellised particle filter (RBPF). The particle filter is used to extend the path posterior by sampling new poses that integrate the current observation which drastically reduces the uncertainty about the robot pose. The landmark position estimation and update is also implemented through Kalman filter. Omnidirectional vision mounted on the robot tracks the 3D natural point landmarks, which are structured with matching Scale Invariant Feature Transform (SIFT) feature pairs. The matching for multi-dimension SIFT features is implemented with a KD-Tree. Experimental results on real robot in a medium size, real indoor environment show the practicality and efficiency of our proposed method.

A μ-Synthesis Based Control for Compliant Maneuvers

2006 ◽  
Vol 128 (4) ◽  
pp. 914-921
Author(s):  
Yutaka Uchimura ◽  
H. Kazerooni
Keyword(s):  
Control System ◽  
Force Feedback ◽  
Controller Design ◽  
Force Sensor ◽  
Force Estimation ◽  
Dexterous Manipulation ◽  
Human Dynamics ◽  
Physical Strength ◽  
Human Power ◽  
Central Control System

This paper deals with a system, which is subjected to very uncertain factors: human and environment. These independent uncertainties are dealt with explicitly on the framework of μ-synthesis. We also describe a controller design, which enables a robust force feedback without using a force sensor. The model of human dynamics, environments, and actuators are modeled associated with uncertainties described in the form of weighting functions. A controller is designed based on the μ-synthesis so that it maintains robust performance against uncertainties in both environment and human dynamics, which contributes to dexterous manipulation. The controller described here is implemented on the human power extender, which is worn by a human and amplifies the human’s physical strength, while the human’s intelligence remains as the central control system for manipulation. Experimental results conducted on the extender showed that the force estimation worked fine and the control system performed as desired.

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