The Direct Simulation Monte Carlo (DSMC) method is used to numerically simulate and design a micronozzle with improved performance. Thrust calculations using the DSMC method demonstrate that the coaxial micronozzles can achieve milli-Newton thrust levels with specific impulses on the order of 45 s using argon in a cold gas expansion. Improved micronozzle designs of coaxial microthrusters are al...

In this paper, a Dynamic Sliding Mode Controller (DSMC) is proposed for trajectory tracking control of a nonholonomic Wheeled Mobile Robot (WMR) in which the centroid doesn't coincide to the connection center of driving wheels. This robust controller is designed based on the developed dynamical model of WMR in Cartesian coordinates, therefore, the application limits in polar coordinates is remo...

In the present investigation, slip-continuum and molecular (DSMC) flow models have been used to compare the drag coefficient on a confined microsphere over a range of Knudsen numbers between 0.01 and 0.4. The simulations consider a fixed Reynolds number (Re=0.125) and a range of blockage ratios from 2.0 up to 13.0. Two separate problem formulations have been studied; the first considers flow pa...

Both the particle based Direct Simulation Monte Carlo (DSMC) method and a compressible Navier-Stokes based continuum method are used to investigate the flow inside micronozzles and to predict the performance of such devices. For the Navier-Stokes approach, both slip and no-slip boundary conditions are applied. Moreover, the two methods have been coupled to be used together in a hybrid particle-...

The direct simulation Monte Carlo (DSMC) method is applied here to model the electron-beam (e-beam) physical vapor deposition of copper thin films. A suitable molecular model for copper-copper interactions have been determined based on comparisons with experiments for a 2D slit source. The model for atomic copper vapor is then used in axi-symmetric DSMC simulations for analysis of a typical e-b...

Rarefied helium and nitrogen flow expanding into vacuum through 150μm high and 1.5 cm long channels is studied experimentally and numerically with the DSMC method. Different types of channel walls are examined, both polished and rough with well characterized roughness shaped as triangles and rectangles. The pressure varies from 200 to 13,000 Pa, with the gas mean free path being both much large...

The advent of highly efficient and superior digital devices and fast microprocessors for control application has opened the field of discrete time controller design. This paper presents an exciting application of magnetic levitation system using discrete sliding mode control. There is a limited volume of literature available for discrete sliding mode control as applied to magnetic levitation sy...

A recently developed high-order velocity-slip boundary condition is validated for gas micro ows, by comparing predictions of the new model against the Ž rst-order slip condition and the direct-simulation Monte Carlo (DSMC) results. Numerical solutions of gas  ow through microchannels and backward-facing step geometry are presented. The backwardfacing step geometry is a suitable testbed for st...

This paper presents a discrete sliding mode observer (DSMO) for state estimation of a class of a second order underactuated system. The estimated states are used to implement the discrete sliding mode control (DSMC). Modified Bartoszewicz’s reaching law is used to synthesize a DSMC. A partially filled liquid container motion coupled with liquid slosh constitutes a class of second order underact...