On the use of forward kinematic models in visually guided hand position control—analysis based on ISLES model

Nonhuman primates have been used extensively to study eye-head coordination and eye-hand coordination, but the combination—eye-head-hand coordination—has not been studied. Our goal was to determine whether reaching influences eye-head coordination (and vice versa) in rhesus macaques. Eye, head, and hand motion were recorded in two animals with search coil and touch screen technology, respectively. Animals were seated in a customized “chair” that allowed unencumbered head motion and reaching in depth. In the reach condition, animals were trained to touch a central LED at waist level while maintaining central gaze and were then rewarded if they touched a target appearing at 1 of 15 locations in a 40° × 20° (visual angle) array. In other variants, initial hand or gaze position was varied in the horizontal plane. In similar control tasks, animals were rewarded for gaze accuracy in the absence of reach. In the Reach task, animals made eye-head gaze shifts toward the target followed by reaches that were accompanied by prolonged head motion toward the target. This resulted in significantly higher head velocities and amplitudes (and lower eye-in-head ranges) compared with the gaze control condition. Gaze shifts had shorter latencies and higher velocities and were more precise, despite the lack of gaze reward. Initial hand position did not influence gaze, but initial gaze position influenced reach latency. These results suggest that eye-head coordination is optimized for visually guided reach, first by quickly and accurately placing gaze at the target to guide reach transport and then by centering the eyes in the head, likely to improve depth vision as the hand approaches the target. NEW & NOTEWORTHY Eye-head and eye-hand coordination have been studied in nonhuman primates but not the combination of all three effectors. Here we examined the timing and kinematics of eye-head-hand coordination in rhesus macaques during a simple reach-to-touch task. Our most novel finding was that (compared with hand-restrained gaze shifts) reaching produced prolonged, increased head rotation toward the target, tending to center the binocular field of view on the target/hand.

Download Full-text

Asymmetric generalization in adaptation to target displacement errors in humans and in a neural network model

Journal of Neurophysiology ◽

10.1152/jn.00483.2014 ◽

2015 ◽

Vol 113 (7) ◽

pp. 2360-2375 ◽

Cited By ~ 1

Author(s):

Stephanie Westendorff ◽

Shenbing Kuang ◽

Bahareh Taghizadeh ◽

Opher Donchin ◽

Alexander Gail

Keyword(s):

Neural Network ◽

Network Model ◽

Neural Network Model ◽

Visual Target ◽

Hand Position ◽

Prediction Errors ◽

Visually Guided ◽

Target Error ◽

Adaptation Mechanisms ◽

Simulation Results

Different error signals can induce sensorimotor adaptation during visually guided reaching, possibly evoking different neural adaptation mechanisms. Here we investigate reach adaptation induced by visual target errors without perturbing the actual or sensed hand position. We analyzed the spatial generalization of adaptation to target error to compare it with other known generalization patterns and simulated our results with a neural network model trained to minimize target error independent of prediction errors. Subjects reached to different peripheral visual targets and had to adapt to a sudden fixed-amplitude displacement (“jump”) consistently occurring for only one of the reach targets. Subjects simultaneously had to perform contralateral unperturbed saccades, which rendered the reach target jump unnoticeable. As a result, subjects adapted by gradually decreasing reach errors and showed negative aftereffects for the perturbed reach target. Reach errors generalized to unperturbed targets according to a translational rather than rotational generalization pattern, but locally, not globally. More importantly, reach errors generalized asymmetrically with a skewed generalization function in the direction of the target jump. Our neural network model reproduced the skewed generalization after adaptation to target jump without having been explicitly trained to produce a specific generalization pattern. Our combined psychophysical and simulation results suggest that target jump adaptation in reaching can be explained by gradual updating of spatial motor goal representations in sensorimotor association networks, independent of learning induced by a prediction-error about the hand position. The simulations make testable predictions about the underlying changes in the tuning of sensorimotor neurons during target jump adaptation.

Download Full-text

Kinematic Analysis and Design of a Six-Degrees of Freedom 3-RRPS Mechanism for Bone Reduction Surgery

Journal of Medical Devices ◽

10.1115/1.4049057 ◽

2020 ◽

Vol 15 (1) ◽

Author(s):

Terence Essomba ◽

Sinh Nguyen Phu

Keyword(s):

Degrees Of Freedom ◽

Vertical Axis ◽

Velocity Model ◽

Analysis And Design ◽

Six Degrees Of Freedom ◽

Bone Fragments ◽

Kinematic Models ◽

Surgery First ◽

Forward Kinematic ◽

Classical Mechanism

Abstract Robot-assisted bone reduction surgery consists in using robots to reposition the bone fragments into their original place prior to fracture healing. This study presents the application of a 3-RRPS augmented tripod mechanism with six degrees-of-freedom for longitudinal bone reduction surgery. First, the inverse and forward kinematic models of the mechanism are investigated. Particularly, the forward kinematic is solved by applying Sylvester's dialytic method. Second, the velocity model is studied and its singular configurations are identified. The workspace of the 3-RRPS mechanism is then outlined and compared with the Stewart platform, which is a classical mechanism for the targeted application. The results show that this mechanism provides a larger workspace, especially its rotation angle about the vertical axis, which is an important aspect in the bone reduction. A series of simulations on the numerical and graphic software is performed to verify the entire analysis of the parallel mechanism. A physiguide and mscadams software are used to carry out a simulation of a real case of femur fracture reduction using the proposed mechanism to validate its suitability. Finally, a robotic prototype based on the mechanism is manufactured and experimented using an artificial bone model to evaluate the feasibility of the mechanism.

Download Full-text

Dynamic Modeling and Analysis of Lifting Mechanism for Forging Manipulator

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.278-280.633 ◽

2013 ◽

Vol 278-280 ◽

pp. 633-640 ◽

Cited By ~ 2

Author(s):

Jian Ming Hu ◽

Wen Hua Ding ◽

Hua Deng

Keyword(s):

Dynamic Models ◽

Position Control ◽

Dynamic Equations ◽

Modular Approach ◽

Modeling And Analysis ◽

Forging Process ◽

Adams Software ◽

Forging Manipulator ◽

Forward Kinematic ◽

Open Die Forging

The kinematic and dynamic behaviors of lifting mechanism for a forging manipulator are investigated. The forward kinematic equations are established. Then, based on the modular approach combined with equivalent dynamic ideal, the dynamic equations are deduced. Moreover, all the equations have been verified by the simulation on a virtual prototype with the ADAMS software and the experiments on a forging manipulator. The results show that the calculated values are well in agreement with the real measurements. Finally, both kinematic and dynamic models are analyzed, and it is found that the force produced by the kinetic energy has very weak effect on the results in comparison with the gravity. The results provide the foundation of gripper’s position control in automatic open-die forging process.

Download Full-text

Reach Adaptation and Final Position Control Amid Environmental Uncertainty After Stroke

Journal of Neurophysiology ◽

10.1152/jn.00870.2006 ◽

2007 ◽

Vol 97 (4) ◽

pp. 2824-2836 ◽

Cited By ~ 69

Author(s):

Robert A. Scheidt ◽

Tina Stoeckmann

Keyword(s):

Position Control ◽

Dynamic Environment ◽

Sensory Information ◽

Hand Position ◽

Stroke Survivors ◽

Final Position ◽

Applied Forces ◽

Position Regulation ◽

Hemiparetic Stroke ◽

Neurologically Intact

We characterized how hemiparetic stroke survivors and neurologically intact individuals adapt reaching movements to compensate for unpredictable environmental perturbations. We tested the hypotheses that like unimpaired subjects, hemiparetic stroke survivors adapt using sensory information obtained during only the most recent movements and that the reliability of target acquisition decreases as the degree of sensorimotor impairment increases. Subjects held the handle of a two-joint robotic arm that applied forces to the hand while reaching between targets in a horizontal plane. The robot simulated a dynamic environment that varied randomly in strength from one trial to the next. The trial sequence of perturbations had a nonzero mean value corresponding to information about the environment that subjects might learn. Stroke subjects were less effective than control subjects at adapting reaches to the perturbations. From a family of potential adaptation models, we found that the compensatory strategy patients used was the same as that used by neurologically intact subjects. However, analysis of model coefficients found that the relative weighting of prior perturbations and prior movement errors on subsequent reach attempts was significantly depressed poststroke. Regulation of final hand position was also impaired in the paretic limbs. Measures of trajectory adaptation and final position regulation deficits were significantly dependent on the integrity of limb proprioception and the amount of time poststroke. However, whereas model coefficients varied systematically with impairment level poststroke, variability of final positioning in the contralesional limb did not. This difference suggests that these two aspects of limb control may be differentially impaired poststroke.

Download Full-text

A new serial approach of the forward kinematic model of spherical parallel manipulators for real-time applications

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406216688027 ◽

2017 ◽

Vol 232 (4) ◽

pp. 677-684 ◽

Cited By ~ 1

Author(s):

Houssem Saafi ◽

Margot Vulliez ◽

Said Zeghloul ◽

Med Amine Laribi

Keyword(s):

Real Time ◽

Model Calculation ◽

Computing Time ◽

Kinematic Model ◽

Parallel Manipulators ◽

Parallel Structures ◽

Kinematic Models ◽

Real Time Applications ◽

Critical Singularity ◽

Forward Kinematic

Parallel architectures are increasingly used as haptic devices to provide low inertia, high stiffness and compactness. Thus, spherical parallel manipulators have been developed to generate the three rotational movements in a sufficient workspace. However, these parallel structures have complex kinematic models and can suffer from critical singularity issues. This paper proposes a serial approach to solve the forward kinematic model of a spherical parallel manipulator, which is used as a haptic device in minimally invasive surgery. The new forward kinematic model is based on the serial positioning of the three sensors on one leg rather than placing the three sensors on the three actuated base joints. The forward kinematic model calculation is thus simplified to be suitable for real-time applications (computing time around 5 µs) without cost increase. Parallel singularity effects are removed using this approach and the accuracy of the forward kinematic model is highly enhanced. Simulations were carried out to show the benefits of this approach. The resulting errors of the forward kinematic model calculation due to measurement noises do not exceed 0.2° along the workspace. Experiments were carried out to demonstrate the control of a surgical robot.

Download Full-text

Simulation of Droplet Position Control in Digital Microfluidic Systems

Journal of Dynamic Systems Measurement and Control ◽

10.1115/1.4000077 ◽

2009 ◽

Vol 132 (1) ◽

Cited By ~ 7

Author(s):

Biddut Bhattacharjee ◽

Homayoun Najjaran

Keyword(s):

Position Control ◽

Digital Microfluidics ◽

Control Analysis ◽

Operational Parameters ◽

Microfluidic Systems ◽

Analysis And Design ◽

Significant Research ◽

Biochemical Analyses ◽

Digital Microfluidic ◽

Semi Empirical

Digital microfluidic systems (DMSs) are emerging with high potential to serve as true labs-on-a-chip (LOCs) systems for various chemical and biochemical analyses. Significant research efforts have been devoted toward the design and fabrication of improved LOC systems. Due to design, fabrication, and also runtime uncertainties, feedback control schemes must be incorporated to ensure reliability and accuracy of LOCs for practical use. This paper introduces the basics of the control analysis and design of the DMS, which is a relatively unexplored area in digital microfluidics. Based on the semi-empirical models of the droplet dynamic system, simulation results of the closed-loop position control of a droplet between two adjacent cells of a DMS are presented. The dynamic response is analyzed and discussed in relation to the operational parameters of a DMS.

Download Full-text