Vol. 1, No. 3 (2017): Regular Issue

Due to different chip formation mechanisms, increased tool-radius to feed-rate ratio, and higher spindle speeds, micro-milling is a highly nonlinear process which can produce multiple and broadband frequencies that negatively impact the process. Micro-milling is investigated through the development and analysis of a nonlinear micromilling dynamic model. A lumped mass-spring-damper system is assumed for modeling the dynamic properties of the tool. The force mechanism utilized is a slip-line field model that provides the advantage of being highly dynamic by accounting for the constantly changing effective rake angle and slip-line variables. Accurate prediction of the chip thickness is important in correctly predicting the dynamics of the system since the force mechanism and its variables are a function of the chip thickness. A novel approach for calculating the instantaneous chip thickness which accounts for the tool jumping out of the cut and elastic recovery of the workpiece is presented. The derivation for the effective rake angle is given and the helical angle is accounted for resulting in a three dimensional micro-milling model. The model generates the high frequency force components that are seen in experimental data available in literature. The effect that the helical angle and system stiffness has on the resulting cutting forces is also investigated. It is shown that dynamic instability has the greatest impact on tool performance and improving the dynamic response is a necessity for achieving high speed ultra-stable micro-machining.

Development of autonomous drive or control technology for vehicles such as a car or a railway train has become major trends, so there is great need for a 3D measuring system which detects terrains or obstructs on forward area of the vehicle. The authors developed a simplified receiver optical system for the line scan type laser scanner which is one of the 3D measurement methods using laser ranging and mirror scanning. The developed receiver enables to acquire the 3D data with wider FOV (field of view) without a receiver scanner mirror. The receiver optics can spatially resolve the measured area horizontally and can measure the whole vertical FOV without scanning. The composition of the receiver optical system was obtained by an optical simulation. After an evaluation system was constructed combining a laser transmitter, a processing unit and the developed receiver, the performance tests were carried out under indoor and outdoor conditions. In this paper, the main objective is an evaluation of the FOV enlargement function of the developed receiver in vertical direction. And it also describes about the 3D measurement performance of the system using the receiver. The results of tests showed that the vertical FOV was extended 6.6 times with the receiver than a conventional one as designed. And it was verified that the system had 3D measurement capability with target distance error of -0.10 ∼ +0.18m in outdoor test.

Axisymmetric convective flow in porous media is frequently encountered in nature and industry applications. In recent years, Lattice Boltzmann method has been developed as a powerful tool for such kind of flow and heat transfer. Despite its success in many problems regarding to porous flow, the existing LB model for the axisymmetric thermal flow in porous media at the representative volume scale suffers from a serious drawback. That is, it can not handle the cases where the heat capacitance of porous media varies spatially obviously. In this paper, a generalized LB model for axisymmetric temperature field is proposed to remedy this shortcoming. Chapman-Enskog analysis demonstrates that the energy equation in the cylindrical coordinates system can be recovered by the proposed model. Natural convection in a vertical annulus filled with saturated porous media, natural convection in a vertical annulus without porous media, have been carried out, and the results predicted by the present LB model agree well with the existing numerical data. More, natural convection in a vertical annulus with spatially varying heat capacitance shows that the present model can address the problem where the heat capacitance varies spatially obviously successfully.

This paper presents a simple method of steering control strategy for a class of Nonholonomic wheeled mobile robots. The strategy is based on adaptive Backstepping technique and does not require the conversion of the model into a “chained form”, and so it does not depend on any special transformation methods. Control laws have been developed for five different types of mobile robot models. The control laws and the adaptive laws are derived in the sense of Lyapunov functions, so that the closed loop system’s stability can be guaranteed.

This paper presents a simple and systematic approach to steer an underwater vehicle model by considering two different cases: (i) when all actuators are functional, and (ii) when one actuator is not working. In first case, the model of an underwater vehicle is steered by using adaptive Backstepping technique. The first actuator is necessary for the operation of the system so any of the other three actuators can be non-operational. So, the second case itself contains three different cases. Adaptive Backstepping is then used to steer the system with one non-working actuator. The synthesis method is general, in that it applies to a large class of drift free, completely controllable systems, for which the associated controllability Lie algebra is locally nilpotent.

In the present paper, a problem of a free rigid body motion in mechanical system is analyzed from a video capture webcam (Sony Cybershot 10.1 M.P). The problem subjected to kinematic characteristics and relative trajectories are theoretically and analytically solved. Subsequently, the solution is quantitatively verified by a new experiment procedure, constructed by the authors. The geometrical treatments of the absolute experimental trajectories of two points of the body, allow determining the relative trajectory of a point from the other point. The kinematic parameters optimization, i.e., translational velocity, instantaneous velocity of rotation and initial kinematic conditions, are obtained, solving non-linear least-squares problems, based on Levenberg-Marquardt’s algorithm. On the other hand, the response surfaces of the objective function and the sensitivity analysis of the different initial estimates of the analytical model parameters are also discussed. The comparison of the theoretical study results with experimental output shows that there are instruments to directly verify rather abstract mathematical theories even on the general mechanics program. Moreover, combining the theoretical description of the problem with an appropriate laboratory experiment and computational optimization procedures, gives a more exhaustive view of the physical problem as a whole.