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Mechanical Engineering Commons

Open Access. Powered by Scholars. Published by Universities.®

1991

University of Pennsylvania

Keyword

Articles 1 - 5 of 5

Full-Text Articles in Mechanical Engineering

An Approach To Simultaneous Control Of Trajectory And Interaction Forces In Dual-Arm Configurations, Xiaoping Yun, Vijay R. Kumar Oct 1991

An Approach To Simultaneous Control Of Trajectory And Interaction Forces In Dual-Arm Configurations, Xiaoping Yun, Vijay R. Kumar

Departmental Papers (MEAM)

Multiple arm systems, multifingered grippers, and walking vehicles all have two common features. In each case, more than one actively coordinated articulation interacts with a passive object, thus forming one or more closed chains. For example, when two arms grasp an object simultaneously, the arms together with the object and the ground (base) form a closed chain. This induces kinematic and dynamic constraints and the resulting equations of motion are extremely nonlinear and coupled. Furthermore, the number of actuators exceeds the kinematic mobility of the chain in a typical case, which results in an underdetermined system of equations. An approach ...


Active Control Of Convection, Jonathan Singer, Haim H. Bau Aug 1991

Active Control Of Convection, Jonathan Singer, Haim H. Bau

Departmental Papers (MEAM)

It is demonstrated theoretically that active (feedback) control can be used to alter the characteristics of thermal convection in a toroidal, vertical loop heated from below and cooled from above. As the temperature difference between the heated and cooled sections of the loop increases,t he flow in the uncontrolled loop changes from no motion to steady; time independent motion to temporally oscillatory, chaotic motion. With the use of a feedback controller effecting small perturbations in the boundary conditions, one can maintain the no-motion state at significantly higher temperature differences than the critical one corresponding to the onset of convection ...


Breakdown Of A Wire-To-Plane Discharge: Transient Effects, Milind A. Jog, Ira M. Cohen, Portonovo S. Ayyaswamy Aug 1991

Breakdown Of A Wire-To-Plane Discharge: Transient Effects, Milind A. Jog, Ira M. Cohen, Portonovo S. Ayyaswamy

Departmental Papers (MEAM)

A wire-to-plane discharge during the early phases of breakdown has been studied. The discharge has been modeled in a prolate spheroidal coordinate system with the wire shape taken as a hyperboloid of revolution. Four simultaneous coupled, time-dependent, nonlinear partial differential equations describe the electrical discharge. These are the conservation equations for ion and electron densities, the energy equation for electron temperature, and Poisson’s equation for the self-consistent electric field. By solving this formulation subject to appropriate initial and boundary conditions, charged particle densities and temperature variations have been obtained as the ionization progresses in the discharge. The results show ...


Controlling A Chaotic System, Jonathan Singer, Y-Z Wang, Haim H. Bau Mar 1991

Controlling A Chaotic System, Jonathan Singer, Y-Z Wang, Haim H. Bau

Departmental Papers (MEAM)

Using both experimental and theoretical results, this Letter describes how low-energy, feedback control signals can be successfully utilized to suppress (laminarize) chaotic flow in a thermal convection loop.


The Effect Of An Adjacent Viscous Fluid On The Transmission Of Torsional Stress Waves In A Submerged Waveguide, Jin O. Kim, Yuzhou Wang, Haim H. Bau Mar 1991

The Effect Of An Adjacent Viscous Fluid On The Transmission Of Torsional Stress Waves In A Submerged Waveguide, Jin O. Kim, Yuzhou Wang, Haim H. Bau

Departmental Papers (MEAM)

The effects of an adjacent fluid's viscosity and density on the characteristics of torsional stress waves transmitted in a waveguide with a circular cross section are studied theoretically and experimentally. Expressions for the torsional waves speed, dispersion relations, and attenuation are obtained as functions of the adjacent fluid's viscosity and density. The theoretical results are compared with experimental observations. It is demonstrated that a devices similar to the one described herein can be used as a rugged, real-time, on-lines sensor for measuring the viscosity of a fluid with a known density. Such a sensor can measure the viscosity ...