Abstract: Human mobility exoskeletons have been in development for several years and are becoming increasingly efficient. Unfortunately, user comfort was not always a priority design criterion throughout their development. To further improve this technology, exoskeletons should operate and deliver assistance without causing discomfort to the user. For this, improvements are necessary from an ergonomic point of view. The device’s control method is important when endeavoring to enhance user comfort. Exoskeleton or rehabilitation device controllers use methods of control called interaction controls (admittance and impedance controls). This paper proposes an extended version of an admittance controller to enhance user comfort. The control method used consists of adding an inner loop that is controlled by a proportional-integral-derivative (PID) controller. This allows the interaction force to be kept as close as possible to the desired force trajectory. The force-tracking admittance controller modifies the actuation force of the system in order to follow both the desired motion trajectory and the desired relative force between the user and the exoskeleton.
Abstract: A mechanical wave or vibration propagating through
granular media exhibits a specific signature in time. A coherent
pulse or wavefront arrives first with multiply scattered waves (coda)
arriving later. The coherent pulse is micro-structure independent i.e.
it depends only on the bulk properties of the disordered granular
sample, the sound wave velocity of the granular sample and hence
bulk and shear moduli. The coherent wavefront attenuates (decreases
in amplitude) and broadens with distance from its source. The
pulse attenuation and broadening effects are affected by disorder
(polydispersity; contrast in size of the granules) and have often been
attributed to dispersion and scattering. To study the effect of disorder
and initial amplitude (non-linearity) of the pulse imparted to the
system on the coherent wavefront, numerical simulations have been
carried out on one-dimensional sets of particles (granular chains).
The interaction force between the particles is given by a Hertzian
contact model. The sizes of particles have been selected randomly
from a Gaussian distribution, where the standard deviation of this
distribution is the relevant parameter that quantifies the effect of
disorder on the coherent wavefront. Since, the coherent wavefront is
system configuration independent, ensemble averaging has been used
for improving the signal quality of the coherent pulse and removing
the multiply scattered waves. The results concerning the width of the
coherent wavefront have been formulated in terms of scaling laws. An
experimental set-up of photoelastic particles constituting a granular
chain is proposed to validate the numerical results.
Abstract: In order to design a suitable control scheme for human extremity exoskeleton, the interaction force control scheme with traditional PI controller was presented, and the simulation study of the electromechanical system of the human extremity exoskeleton was carried out by using a MATLAB/Simulink module. By analyzing the simulation calculation results, it was shown that the traditional PI controller is not very suitable for every movement speed of human body. So, at last the fuzzy self-adaptive PI controller was presented to solve this problem. Eventually, the superiority and feasibility of the fuzzy self-adaptive PI controller was proved by the simulation results and experimental results.
Abstract: Grinding operation is performed in order to obtain desired surfaces precisely in machining process. The needed relative motion between the cutting tool and the workpiece is generally created either by the movement of the cutting tool or by the movement of the workpiece or by the movement of both of them as in our case. For all these cases, the coherence level between the movements and the interaction forces is a key influential parameter for efficient grinding. Therefore, in this work, spectral coherence analysis has been performed to investigate the coherence level between grinding interaction forces and the movement of the workpiece on our robotic-grinding experimental setup in METU Mechatronics Laboratory.
Abstract: The objective of this work is to study the effect of two
key factors - external magnetic field and applied current density
during template-based electrodeposition of nickel nanowires using an
electrode distance of 20 mm. Morphology, length, crystallite size and
crystallographic characterization of the grown nickel nanowires at an
electrode distance of 20mm are presented. For this electrode distance
of 20 mm, these two key electrodeposition factors when coupled was
found to reduce crystallite size with a higher growth length and
preferred orientation of Ni crystals. These observed changes can be
inferred to be due to coupled interaction forces induced by the
intensity of applied electric field (current density) and external
magnetic field known as magnetohydrodynamic (MHD) effect during
the electrodeposition process.
Abstract: The electrical interaction between two axisymmetric
spheroidal particles in an electrolyte solution is examined numerically.
A Galerkin finite element method combined with a Newton-Raphson
iteration scheme is proposed to evaluate the spatial variation in the
electrical potential, and the result obtained used to estimate the
interaction energy between two particles. We show that if the surface
charge density is fixed, the potential gradient is larger at a point, which
has a larger curvature, and if surface potential is fixed, surface charge
density is proportional to the curvature. Also, if the total interaction
energy against closest surface-to-surface curve exhibits a primary
maximum, the maximum follows the order (oblate-oblate) >
(sphere-sphere)>(oblate-prolate)>(prolate-prolate), and if the curve
has a secondary minimum, the absolute value of the minimum follows
the same order.
Abstract: The quantum mechanics simulation was applied for
calculating the interaction force between 2 molecules based on atomic level. For the simple extractive distillation system, it is ternary
components consisting of 2 closed boiling point components (A,lower boiling point and B, higher boiling point) and solvent (S). The
quantum mechanics simulation was used to calculate the intermolecular force (interaction force) between the closed boiling
point components and solvents consisting of intermolecular between
A-S and B-S.
The requirement of the promising solvent for extractive distillation
is that solvent (S) has to form stronger intermolecular force with only
one component than the other component (A or B). In this study, the
systems of aromatic-aromatic, aromatic-cycloparaffin, and paraffindiolefin
systems were selected as the demonstration for solvent
selection. This study defined new term using for screening the solvents called relative interaction force which is calculated from the
quantum mechanics simulation. The results showed that relative
interaction force gave the good agreement with the literature data
(relative volatilities from the experiment). The reasons are discussed. Finally, this study suggests that quantum mechanics results can improve the relative volatility estimation for screening the solvents leading to reduce time and money consuming
Abstract: Sensorized instruments that accurately measure the interaction forces (between biological tissue and instrument endeffector) during surgical procedures offer surgeons a greater sense of immersion during minimally invasive robotic surgery. Although there is ongoing research into force measurement involving surgical graspers little corresponding effort has been carried out on the measurement of forces between scissor blades and tissue. This paper presents the design and development of a force measurement test apparatus, which will serve as a sensor characterization and evaluation platform. The primary aim of the experiments is to ascertain whether the system can differentiate between tissue samples with differing mechanical properties in a reliable, repeatable manner. Force-angular displacement curves highlight trends in the cutting process as well the forces generated along the blade during a cutting procedure. Future applications of the test equipment will involve the assessment of new direct force sensing technologies for telerobotic surgery.