Torque Measurement of 3-DOF Haptic Master Operated by Controllable Electrorheological Fluid
Abstract This work presents a torque measurement method of 3-degree-of-freedom (3-DOF) haptic master featuring controllable electrorheological (ER) fluid. In order to reflect the sense of an organ for a surgeon, the ER haptic master which can generate the repulsive torque of an organ is utilized as a remote controller for a surgery robot. Since accurate representation of organ feeling is essential for the success of the robot-assisted surgery, it is indispensable to develop a proper torque measurement method of 3-DOF ER haptic master. After describing the structural configuration of the haptic master, the torque models of ER spherical joint are mathematically derived based on the Bingham model of ER fluid. A new type of haptic device which has pitching, rolling, and yawing motions is then designed and manufactured using a spherical joint mechanism. Subsequently, the field-dependent parameters of the Bingham model are identified and generating repulsive torque according to applied electric field is measured. In addition, in order to verify the effectiveness of the proposed torque model, a comparative work between simulated and measured torques is undertaken.
Damping characteristics and flow behaviors of an ER fluid with a piston sine vibration in a viscous damper
The damping characteristics and flow behaviors of ER fluids inside a piston–cylinder viscous damper subjected to external electric fields are studied based on experiment, theoretical analysis and numerical simulation. The viscous damper is a closed system with an inner piston and an outer cylinder, which is designed and constructed in our laboratory. In the experiment, the test ER fluid is enclosed in the gap of a piston–cylinder system. To examine the damping characteristics of the test ER fluid, a piston sine vibration experiment is performed with accompanying theoretical analyses. In addition, in order to investigate the ER flow behaviors inside the damper, a numerical simulation is carried out. The present study discloses the damping characteristics and the fluid mechanism of the ER fluid in the piston–cylinder damper with an applied external electric field.
Convergence Anatomization of Aquaculture Production in Leading Fish-Producing Countries During the Period of 1997-2013
Growth and national importance of aquaculture production is empirically assessed as an important indicator of development. The present article aims to test whether the major aquaculture producing countries of the world are converging over time. The authors have applied the absolute and conditional beta convergence and sigma convergence approaches on the data of FAO for the period 1997-2013. The results show that there is an absolute beta convergence and sigma convergence among 25 major aquaculture producing countries; negative sign of coefficient of conditional beta convergence with per capita income is also noticed. It implies, the growth rates of aquaculture for developed nations are declining with rise in per capita income and backward fish-intensive countries are catching up with the giant producers like China and India. The cross-country variations are also going down which means that the countries' development gaps are getting narrowed by means of growth of aquaculture resources.