Mark Ovinis

Experimental Study of Low Velocity Impact Response of Carbon/Basalt Hybrid Filament Wound Composite Pipes

In this study, the impact damage resistance of carbon/basalt hybrid fiber reinforced polymer pipes was experimentally investigated under low velocity impact loading. The composite pipes, composed of thin plastic liner of HDPE wrapped with eight layers of plies at constant winding angle of [±55∘/902∘/±55∘/902∘], were fabricated through filament winding technique. Eight pipe configurations with different stacking sequence and fiber content proportion were studied. Specimens cut from the original pipes were tested in a drop weight impact machine under two levels of impact energies, 50J and 100J, in order to predict the impact response and induced damage resistance of the pipe. The damage of the tested pipes was assessed based on the force-displacement, force-time histories, the energy absorption mechanism, as well as the micrographs captured by scanning electron microscope (SEM) for the specimens. The results indicate that the impact resistance behavior was highly affected by the stacking sequence of the lay...

Autonomous patrol and surveillance system using unmanned aerial vehicles

Unmanned aerial vehicles (UAVs) are increasingly popular for civil applications due to their flight capabilities and mobility. This paper proposes an indoor autonomous patrol and surveillance system using unmanned aerial vehicles. The system consists of six components: (1) a low cost vision-based pose estimation of UAVs, (2) vision-based state estimation, (3) UAV patrol path planning, (4) UAV controller to desired waypoints, (5) manual joystick controller and (6) assignment of priority hierarchy to multiple control inputs of a robot. The components were integrated successfully and the designed system was experimented in an indoor setup. Results has shown that the proposed system is suitable and feasible to be used as an autonomous patrol and surveillance agent for indoors use.

Image-Based Technique for Turbulent Flow Segmentation

Turbulent flow segmentation from image data is a challenging problem. This is due to the un-defined edge and the complex flow nature of turbulence. In this paper, an image-based technique is proposed for turbulent flow segmentation from image. The proposed technique segments the flow region based on enhancing the input image intensity at flow edges and by defining a thresholding value to differentiate between flow region and image background. To test the image-based segmentation technique, a turbulent buoyant jet was experimentally simulated at different nozzle flow rates which have a Reynolds numbers of 960, 1560, and 3210. Then, a video camera was used to record the jet flow data. Then, the image-based technique was applied to segment the flow region and estimate the jet penetration area. As a result, the turbulent flow region was segmented well for all cases of nozzle flow rates. Moreover, application of the image-based technique for jet penetration estimation showed a good agreement with the previous work, in which the jet propagated linearly over time.

Investigation on the dynamic stability of an underwater glider using CFD simulation

Dynamic stability is an important consideration for an underwater glider because its slow motion makes it susceptible to underwater currents. This is compounded by its weak propulsion system whereby it self-propels by shifting its net buoyancy either positive or negative during forward motion. In this paper, steady state Computational Fluid Dynamic (CFD) simulation was used to evaluate the dynamic stability of a low-speed underwater glider. Fluid domains were generated for different flow velocities and angles of attack, for both rectilinear and rotary motions. For rectilinear motion, a straight line resistance test was replicated the tow tank resistance test. For rotary motion, a rotating arm setup was replicated and various angular velocities were numerically simulated. Hydrodynamic derivatives were obtained by extracting the slopes of the lift force and moment data points. The results showed that the dynamic stability of glider improved as the velocity and mass of the glider increases.

U-model based depth control of underwater glider

Controlling underwater glider brings a unique challenge for control engineers and academic researcher. The dynamics, nonlinearity and multivariable nature of glider plus the highly turbulent underwater disturbances has disregarded many effective control techniques. The Internal Model Control (IMC) structure, where the controller implementation includes explicit model of the plant has shown to be very effective for control of stable plants in process industries. The inherent capabilities of IMC to perform robustly and reject disturbances make it attractive to be used in applications like underwater robotics. In this paper adaptive IMC based on U-model is investigated for controlling depth of underwater Glider. U-model is an adaptive modeling framework that models system based on current control term only. This implies that the control law can be synthesized simplistically using Internal Model Control (IMC). Hence inverse of polynomial expression based on u(t-1) is computed using Newton-Raphson method. The effectiveness of U-model based IMC is illustrated with aid of simulation for depth control of glider. Furthermore, performance of proposed controller is compared with PID. Results show that U-model methodology performs better than PID in terms of settling time.

Underwater gliders control strategies: A review

Underwater Gliders (UGs) are a type of Autonomous Underwater Vehicle (AUV) that uses buoyancy engines, an energy efficient locomotion, primarily for oceanography. In this paper, control strategies for existing underwater gliders are reviewed. A total of 50 papers indexed by Scopus with keywords control and underwater gliders were reviewed from 1989 to 2014. The majority of gliders use classical controllers, which cannot dynamically compensate for un-modeled hydrodynamic forces and unknown variations in water current and wind. With increasing operational depths and larger payloads, control strategies will become an increasingly important aspect for these gliders. Control strategies implemented in underwater gliders were reviewed and alternative control strategies are proposed.

Comparative analysis of multi-resolution optical flow techniques for flow rate estimation

In April 20, 2010, the largest amount of oil in history leaked into the Gulf of Mexico (GoM) due to the oil rig explosion. For the fact of the lack of accurate technique for estimating the volume of oil spilled in this incident, ad-hoc techniques were employed from other fields e.g. Particle Image Velocimetry (PIV) from fluid dynamic experiment. Of the different techniques employed, the technique by Crone based on optical plume velocimetry was the most accurate. However, the accuracy of estimation differs depending on the choice of algorithms. In this work, a comparative analysis of optical flow algorithms based on image warping theory and on Lucas and Kanades algorithm was performed. Crones experimental setup was replicated and a video camera was used to record the flow. The two algorithms were used to estimate flow rate. To improve estimation accuracy, a multi-resolution framework was used. Optical flow based on image warping outperforms that based on Lucas and Kanade in representing the velocity fields in all regions of flow. Moreover, a comparison between the estimated flow rates with actual flow rates resulted in a non-zero crossing of 0.064 and 0.128 m/s for image warping and Lucas and Kanade respectively.