A Study on the Motion of Micro-Parts on a Saw-Tooth Surface by the PTV Method

This study investigates the motion of micro parts on several vibratory plates with saw-tooth surface profile driven by a piezoelectric actuator. The surfaces are made of carbide, brass, and zirconia with the same profiles as a saw-tooth. The velocity and position of micro-parts are time-dependently measured by the particle tracking velocimetry (PTV) method where the Canny edge detection technique is used. In the present experiment, 2012-type micro-parts whose dimensions are 2.0 × 1.2 × 0.6 mm3 in length, width, and depth, respectively, are employed. The mass of each micro-part is 7.5 mg. Using a high-speed camera, the tracked longitudinal displacement resolution is found to be about 0.01 mm, which is small in comparison with the length of each micro-part. The obtained results show that unidirectional motion can be attained by the present feeder system. For the same oscillating frequencies and amplitudes applied to the sawtooth surfaces, the motion behavior of micro-parts varies for different experiments and surfaces. This implies that the motion of micro-parts is affected by uncertain causes. However, the probability distribution of the micro-parts’ velocity can be approached by a Gaussian distribution.

Stability and Bifurcation Analysis of Periodic Motions in a Periodically Forced Duffing Oscillator

In this paper, the analytical, approximate solutions of period-1 motions in the nonlinear damping, periodically forced, Duffing oscillator is obtained. The corresponding stability and bifurcation analysis of the HB2 approximate solution of period-1 motions in the forced Duffing oscillator is carried out. Numerical illustrations of period-1 motions are presented.

An Experimental Study of Acid Exposed Fibre Reinforced Plastic Gratings

Fibre Reinforced Plastics (FRPs) generally have greater advantages over conventional materials for their structural properties. However, the service life can significantly be shortened if the fibre reinforced plastics are exposed to adverse environmental conditions especially acid vapour, humidity and high temperature. In many chemical industrial plants in Australia and elsewhere fibre reinforced plastic gratings are used as structural components of stairs and passages where they are subjected to varying degrees of fluosilicic acid, a byproduct of the industrial manufacturing process. As currently no experimental data on the effects of fluosilicic acid on FRPs is available in the public domain, it is difficult to predict the service life of FRPs with some certainty. In order to understand the structural strength of fluosilicic acid exposed FRPs, an experimental study was undertaken. A series of specimens from various locations of a chemical plan in Australia were acquired and studied. Some new specimens (not exposed to acid, humidity and high temperature) were also studied to provide a benchmark for the comparison. The results indicated that the long time exposure to harsh environment and acid vapour can significantly deteriorate the flexural strength and service life of FRPs.

Analysis of Vibration Characteristics for Last Stage Blade With Friction Contact Surfaces of Steam Turbine

Friction damping devices such as under platform dampers are installed for modern turbine blades to suppress dynamic vibrations of the blades. In order to secure the reliability of the blades, it is important to predict the dynamic response and friction damping characteristics accurately. In this present paper, the dynamic response and friction damping characteristics of a last stage blade (LSB) of a steam turbine with contact surfaces at the cover, tie-boss and blade root was investigated. Especially, it is focused on the effect of the non-uniform normal contact forces at the contact surface. To investigate the effect of non-uniform normal contact forces, an analysis method was developed. Analysis model of the LSB with contact surfaces was discretized by finite elements. Tangential forces at the contact surfaces were modeled by multi-DOF macro-slip modeling. The non-linear frequency responses of the LSB were obtained by using the harmonic balance method. Using this analysis method, the relationship between the contact surface behavior and the dynamic response was studied.

Frequency-Weighted Variable-Length Controllers Using Anytime Control Strategies

This paper considers an anytime strategy to implement controllers that react to changing computational resources. The anytime controllers developed in this paper are suitable for cases when the time scale of switching is in the order of the task execution time, that is, on the time scale found commonly with sporadically missed deadlines. This paper extends the prior work by developing frequency-weighted anytime controllers. The selection of the weighting function is driven by the expectation of the situations that would require anytime operation. For example, if the anytime operation is due to occasional and isolated missed deadlines, then the weighting on high frequencies should be larger than that for low frequencies. Low frequency components will have a smaller change over one sample time, so failing to update these components for one sample period will have less effect than with the high frequency components. An example will be included that applies the anytime control strategy to a model of a DC motor with deadzone and saturation nonlinearities.

Design Optimization Method for MR-Brake Actuators

MR-brakes work by varying viscosity of a magnetorheological (MR) fluid inside the brake. This electronically controllable viscosity leads to variable friction torque generated by the actuator. A properly designed MR-brake can have a high torque-to-volume ratio which is quite desirable for an actuator. However, designing an MR-brake is a complex process as there are many parameters involved in the design which can affect the size and torque output significantly. The contribution of this study is a new design approach that combines the Taguchi design of experiments method with parameterized finite element analysis for optimization. Unlike the typical multivariate optimization methods, this approach can identify the dominant parameters of the design and allows the designer to only explore their interactions during the optimization process. This unique feature reduces the size of the search space and the time it takes to find an optimal solution. It normally takes about a week to design an MR-brake manually. Our interactive method allows the designer to finish the design in about two minutes. In this paper, we first present the details of the MR-brake design problem. This is followed by the details of our new approach. Next, we show how to design an MR-brake using this method. Prototype of a new brake was fabricated. Results of experiments with the prototype brake are very encouraging and are in close agreement with the theoretical performance predictions.

A Vibration-Based Structural Damage Detection Method and its Applications to Engineering Structures

Two major challenges associated with a vibration-based damage detection method using changes in natural frequencies are addressed: accurate modeling of structures and the development of a robust inverse algorithm to detect damage, which are defined as the forward and inverse problems, respectively. To resolve the forward problem, new physics-based finite element modeling techniques are developed for fillets in thin-walled beams and for bolted joints, so that complex structures can be accurately modeled with a reasonable model size. To resolve the inverse problem, a logistic function transformation is introduced to convert the constrained optimization problem to an unconstrained one, and a robust iterative algorithm using the Levenberg-Marquardt method is developed to accurately detect the locations and extent of damage. The new methodology can ensure global convergence of the iterative algorithm in solving under-determined system equations and deal with damage detection problems with relatively large modeling error and measurement noise. It is applied to various engineering structures including lightning masts, a space frame structure and one of its components, and a pipeline. The exact locations and extent of damage can be detected in the numerical simulation, and the locations and extent of damage can be successfully detected in experimental damage detection.

Design, Construction and Control of a Remotely Operated Vehicle (ROV)

This is report of design, construction and control of “Ariana-I”, an Underwater Remotely Operated Vehicle (ROV), built in Shiraz University Robotic Lab. This ROV is equipped with roll, pitch, heading, and depth sensors which provide sufficient feedback signals to give the system six degrees-of-freedom actuation. Although its center of gravity and center of buoyancy are positioned in such a way that Ariana-I ROV is self-stabilized, but the combinations of sensors and speed controlled drivers provide more stability of the system without the operator involvement. Video vision is provided for the system with Ethernet link to the operation unit. Control commands and sensor feedbacks are transferred on RS485 bus; video signal, water leakage alarm, and battery charging wires are provided on the same multi-core cable. While simple PI controllers would improve the pitch and roll stability of the system, various control schemes can be applied for heading to track different paths. The net weight of ROV out of water is about 130kg with frame dimensions of 130×100×65cm. Ariana-I ROV is designed such that it is possible to be equipped with different tools such as mechanical arms, thanks to microprocessor based control system provided with two directional high speed communication cables for on line vision and operation unit.

Time Integration Incorporated Sensitivity Analysis With Generalized-α Method for Multibody Dynamics Systems

The topology optimization method is extended for the optimization of geometrically nonlinear, time-dependent multibody dynamics systems undergoing nonlinear responses. In particular, this paper focuses on sensitivity analysis methods for topology optimization of general multibody dynamics systems, which include large displacements and rotations and dynamic loading. The generalized-α method is employed to solve the multibody dynamics system equations of motion. The developed time integration incorporated sensitivity analysis method is based on a linear approximation of two consecutive time steps, such that the generalized-α method is only applied once in the time integration of the equations of motion. This approach significantly reduces the computational costs associated with sensitivity analysis. To show the effectiveness of the developed procedures, topology optimization of a ground structure embedded in a planar multibody dynamics system under dynamic loading is presented.

Simulation and Visualization of Dynamic Systems Using MATLAB, Simulink, Simulink 3D Animation, and SolidWorks

There are many approaches to simulating and visualizing a dynamic system. Our focus is on developing/understanding and trading-off three different approaches that are relatively easy to implement with inexpensive, commonly available software using combinations of MATLAB, Simulink, Simulink 3D Animation, SolidWorks (basic), SolidWorks (Motion Manager) in addition to several common animation players such as Windows (Live) Movie Maker or the resident animation capability within MATLAB. The “SolidWorks Design Table” approach entails creating MATLAB/Simulink driven time-dependent assembly configurations, associated graphics files (e.g. JPG, TIFF) and then effectively “playing” them sequentially with animation software. The “SolidWorks Motor” approach utilizes SolidWorks’ Motion Manager capability (an add-on), whereby each spatially time-dependent geometric system variable is driven by a “motor” based on MATLAB/Simulink time-dependent data and an animation file can be generated from within Motion Manager. Lastly, in the “Simulink 3D Animation” approach, SolidWorks data is brought into the MATLAB environment and modified with V-Realm Builder (VRML Editor) supplied within the Simulink 3D Animation toolbox to define geometric constraints prior to inclusion as an animation VR Sink block within the Simulink model of the dynamic system. In each case, detailed procedures are provided. To exercise these three different approaches and permit comparisons, a benchmark problem was posed: parallel-parking of a four-wheeled vehicle possessing front wheel steering. Comparisons were then made and the recommended approach depends on such issues as the software background of the developer, the animation quality standard (e.g. framerate), and relative ease of implementation.