Model Identification and Control of Autonomous Ground Vehicles

Autonomous Ground Vehicles (AGV) are mobile robotic platforms used in variety of applications to execute tasks which could be dangerous for humans to operate. Recently, autonomous cars are discussed in carrying passengers from point to point without human interaction. Sophisticated controllers are required to operate autonomous vehicles while responding to both normal and hazardous driving conditions. Dangerous conditions which might be easily perceivable by sensors in the system require controllers that can readily benefit from the new sensory information. In this thesis, we address this problem by asserting that the design of controllers and corresponding calibration and local planning methods are required to quickly adapt to changes in both the dynamic model of vehicle as well as changes in environment. A full pipeline of calibration, local planner and model predictive controller has been developed and tested in simulation and on physical platform. Properties of a high fidelity model and a simpler model has been studied and their pros and cons has been discussed. Also, a calibration algorithm has been developed to calibrate parameters of dynamic models based on informativeness of robot's motion. Next, A local planning algorithms has been developed to plan vehicle's reference path between consecutive waypoints and finally a model predictive controller has been designed to stabilizes the vehicle to the reference path. A theoretical proof for stability of proposed controller is given. One of the goals behind this work has been design of an adaptive method in a sense that system can quickly adapt to changes in robot's model or environment

Fundamental asymmetric lamb wave ( a0 ) interaction with rectangular notch using elastodynamic finite integration technique (EFIT)

Fundamental asymmetric lamb wave’s interactions with rectangular notches in a steel plate are investigated in this paper. Elastodynamic finite integration technique previously mainly used to study wave propagation in elastic media is adopted to study lamb wave interaction with defects. Simulation examples are presented to illustrate the reflection and transmission coefficients’ variations with defect’s height, for both symmetric and asymmetric modes. Results show as the depth of notch increases reflection coefficients for both symmetric mode and asymmetric mode increase. However, when the depth of notch increases transmission coefficient for asymmetric mode decreases which means the main part of transmitted energy is carried by symmetric mode generated when the fundamental asymmetric mode interacts with defect. This simulation could be a valuable tool for the research of lamb wave’s applications in nondestructive testing (NDT) field, as the problem of lamb wave interaction with discontinuities can be used to study defect sizing problem

A fibrous scaffold for in vitro culture and experimental studies of Physcomitrium patens

Abstract The model moss, Physcomitrium patens, is routinely cultured on cellophane placed over a solid nutrient medium. While this culture method is convenient for moss propagation, it is not suitable for studying how topographical features and mechanical cues from the environment influence the growth and development of moss. Here, we show that P. patens can be grown on fibrous scaffolds consisting of nanoscale, randomly oriented fibers composed of polyvinylidene tri‐fluoroethylene (NRP). The moss adheres tightly to NRP in contrast to the lack of adhesion to cellophane. Adhesion to the scaffold is associated with slower tip growth of moss protonema for some time, followed by an increase in tip growth rate that is equivalent to that on cellophane. In addition, the orientation of the first subapical cell division plane differs between NRP‐grown and cellophane‐grown protonema. Nonetheless, moss colonies grown on NRP did not show signs of nutrient or photosynthetic stress and developed normal gametophores. Together, these data establish NRP as a suitable substrate for the culture of P. patens and to probe the influence of mechanical forces on tip growth and cell division of moss

Image-based computational hemodynamic analysis of an anterior communicating aneurysm treated with the Woven EndoBridge device

Background: The Woven EndoBridge (WEB) aneurysm embolization device is a relatively recent developed intrasaccular flow disruptor committed to intracranial wide-neck and complex aneurysm occlusion. In this study, we aimed to assess hemodynamic profiles of an AcomA aneurysm treated with WEB Single Layer (WEB-SL) to shed light on the understanding of hemodynamic alterations in the context of a recanalized aneurysm. Methods: Image-Based computational fluid dynamics (CFD) was used to simulate pre and post-treatment blood flow of an anterior communicating aneurysm treated with WEB-SL. The simulated velocity field was used to visualize and quantify velocity, wall shear stress (WSS), and pressure distributions. Results: Following WEB deployment, infiltration of flow and mean velocity magnitude were decreased considerably within the aneurysm sac. WSS was the only measured index that demonstrated a dual hemodynamic pattern; it reduced along the superior half of the aneurysm sac while slightly increased in the neck region. At one-year follow-up, angiography showed recanalization of the aneurysm, and the WEB had been pushed to the dome. Conclusions: All assessed hemodynamic parameters reduced significantly from pre to post-WEB placement in the sac of AcomA aneurysm; however, recanalization may happen secondary to filling the proximal portion of the WEB-SL and increased WSS in the neck of the aneurysm. Conduction of larger studies is warranted to elaborately investigate the potential role of CFD techniques for correlating the hemodynamics indices with clinical outcomes