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Dynamics and control of flexible manipulatorsVakil, Mohammad 24 July 2008 (has links)
Flexible link manipulators (FLM) are well-known for their light mass and small energy consumption compared to rigid link manipulators (RLM). These advantages of FLM are even of greater importance in applications where energy efficiency is crucial, such as in space applications. However, RLM are still preferred over FLM for industrial applications. This is due to the fact that the reliability and predictability of the performance of FLM are not yet as good as those of RLM. The major cause for these drawbacks is link flexibility, which not only makes the dynamic modeling of FLM very challenging, but also turns its end-effector trajectory tracking (EETT) into a complicated control problem. <p>The major objectives of the research undertaken in this project were to develop a dynamic model for a FLM and model-based controllers for the EETT. Therefore, the dynamic model of FLM was first derived. This dynamic model was then used to develop the EETT controllers. <p>A dynamic model of a FLM was derived by means of a novel method using the dynamic model of a single flexible link manipulator on a moving base (SFLMB). The computational efficiency of this method is among its novelties. To obtain the dynamic model, the Lagrange method was adopted. Derivation of the kinetic energy and the calculation of the corresponding derivatives, which are required in the Lagrange method, are complex for the FLM. The new method introduced in this thesis alleviated these complexities by calculating the kinetic energy and the required derivatives only for a SFLMB, which were much simpler than those of the FLM. To verify the derived dynamic model the simulation results for a two-link manipulator, with both links being flexible, were compared with those of full nonlinear finite element analysis. These comparisons showed sound agreement. <p>A new controller for EETT of FLM, which used the singularly perturbed form of the dynamic model and the integral manifold concept, was developed. By using the integral manifold concept the links lateral deflections were approximately represented in terms of the rotations of the links and input torques. Therefore the end-effector displacement, which was composed of the rotations of the links and links lateral deflections, was expressed in terms of the rotations of the links and input torques. The input torques were then selected to reduce the EETT error. The originalities of this controller, which was based on the singularly perturbed form of the dynamic model of FLM, are: (1) it is easy and computationally efficient to implement, and (2) it does not require the time derivative of links lateral deflections, which are impractical to measure. The ease and computational efficiency of the new controller were due to the use of the several properties of the dynamic model of the FLM. This controller was first employed for the EETT of a single flexible link manipulator (SFLM) with a linear model. The novel controller was then extended for the EETT of a class of flexible link manipulators, which were composed of a chain of rigid links with only a flexible end-link (CRFE). Finally it was used for the EETT of a FLM with all links being flexible. The simulation results showed the effectiveness of the new controller. These simulations were conducted on a SFLM, a CRFE (with the first link being rigid and second link being flexible) and finally a two-link manipulator, with both links being flexible. Moreover, the feasibility of the new controller proposed in this thesis was verified by experimental studies carried out using the equipment available in the newly established Robotic Laboratory at the University of Saskatchewan. The experimental verifications were performed on a SFLM and a two-link manipulator, with first link being rigid and second link being flexible.<p>Another new controller was also introduced in this thesis for the EETT of single flexible link manipulators with the linear dynamic model. This controller combined the feedforward torque, which was required to move the end-effector along the desired path, with a feedback controller. The novelty of this EETT controller was in developing a new method for the derivation of the feedforward torque. The feedforward torque was obtained by redefining the desired end-effector trajectory. For the end-effector trajectory redefinition, the summation of the stable exponential functions was used. Simulation studies showed the effectiveness of this new controller. Its feasibility was also proven by experimental verification carried out in the Robotic Laboratory at the University of Saskatchewan.
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TIP trajectory tracking of flexible-joint manipulatorsSalmasi, Hamid 12 February 2010 (has links)
In most robot applications, the control of the manipulators end-effector along a specified desired trajectory is the main concern. In these applications, the end-effector (tip) of the manipulator is required to follow a given trajectory. Several methods have been so far proposed for the motion control of robot manipulators. However, most of these control methods ignore either joint friction or joint elasticity which can be caused by the transmission systems (e.g. belts and gearboxes). This study aims at development of a comprehensive control strategy for the tip-trajectory tracking of flexible-joint robot manipulators. While the proposed control strategy takes into account the effect of the friction and the elasticity in the joints, it also provides a highly accurate motion for the manipulators end-effector.
During this study several approaches have been developed, implemented and verified experimentally/numerically for the tip trajectory tracking of robot manipulators. To compensate for the elasticity of the joints two methods have been proposed; they are a composite controller whose design is based on the singular perturbation theory and integral manifold concept, and a swarm controller which is a novel biologically-inspired controller and its concept is inspired by the movement of real biological systems such as flocks of birds and schools of fishes. To compensate for the friction in the joints two new approaches have been also introduced. They are a composite compensation strategy which consists of the non-linear dynamic LuGre model and a Proportional-Derivative (PD) compensator, and a novel friction compensation method whose design is based on the Work-Energy principle. Each of these proposed controllers has some advantages and drawbacks, and hence, depending on the application of the robot manipulator, they can be employed. For instance, the Work-Energy method has a simpler form than the LuGre-PD compensator and can be easily implemented in industrial applications, yet it provides less accuracy in friction compensation. In addition to design and develop new controllers for flexible-joint manipulators, another contribution of this work lays in the experimental verification of the proposed control strategies. For this purpose, experimental setups of a two-rigid-link flexible-joint and a single-rigid-link flexible-joint manipulators have been employed. The proposed controllers have been experimentally tested for different trajectories, velocities and several flexibilities of the joints. This ensures that the controllers are able to perform effectively at different trajectories and speeds.
Besides developing control strategies for the flexible-joint manipulators, dynamic modeling and vibration suppression of flexible-link manipulators are other parts of this study. To derive dynamic equations for the flexible-link flexible-joint manipulators, the Lagrange method is used. The simulation results from Lagrange method are then confirmed by the finite element analysis (FEA) for different trajectories.
To suppress the vibration of flexible manipulators during the manoeuvre, a collocated sensor-actuator is utilized, and a proportional control method is employed to adjust the voltage applied to the piezoelectric actuator. Based on the controllability of the states and using FEA, the optimum location of the piezoelectric along the manipulator is found. The effect of the controllers gain and the delay between the input and output of the controller are also analyzed through a stability analysis.
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Acquisition and tracking of weak GPS signals as received by cellular telephonesGrant, Howard Alexander 25 January 2011 (has links)
This thesis investigates the suitability of global navigation satellite system (GNSS) signals for cellular phone location. The requirement is to determine and report the location of a phone during an emergency call.<p>
The thesis analyzes acquisition and tracking techniques suitable for very weak signals as received by a cellular phone indoors. The L1 and L5 signals from GPS satellites and the L1 signal from Galileo satellites are considered. It is shown that long integration times and coherent integration are required for the weakest expected signals. Long coherent integration times require a precise knowledge of the Doppler shift due to the range rate of the satellite. The tolerance to Doppler shift can be increased by using FFTs in the analysis of the data. Non-coherent averaging techniques improve the Doppler tolerance but compared to coherent averaging, the loss of signal to noise ratio is too large for the weakest signals.<p>
Coherent averaging of the GPS L1 signal requires data removal that can be accomplished with assistance from the cellular network. The GPS L5 and Galileo L1 signals include a data-less or pilot channel. The GPS L5 pilot channel includes a 20 bit Neuman Hoffman code with a bit period of 1 ms. This code has to be acquired or removed before coherent averaging. Similarly the Galileo pilot channel includes a 25 bit short code.<p>
Once code acquisition has been accomplished, it is necessary to track the signals from at least four satellites for long enough to compute a position estimate. A discussion of tracking techniques is included to show the signal to noise ratio limitations for adequate tracking accuracy.<p>
The results show that GNSS signals are suitable for cellular phone location in a large number of situations. Increased receiver sensitivity would permit location in additional situations. In rural situations GNSS may be the only available option.
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The Weakly Identifying System for Doorway MonitoringJenkins, Christopher James 10 May 2007 (has links)
The System Architecture for Tracking Individuals (SAFTI) is an indoor person location tracking system designed for use in the field of pervasive computing. SAFTI provides location tracking in environments where cameras are too privacy invasive, where tracking devices are too costly, insecure or inconvenient, and where usability is a high priority. While many location tracking systems satisfy each of these constraints individually, SAFTI satisfies all three constraints simultaneously. Upon entering and exiting SAFTI buildings, users submit identification credentials. Once inside the building, using SAFTI is effortless - simply passing through doorways is sufficient for supplying SAFTI with the information it needs to perform location tracking. An integral part of SAFTI is the Weakly Identifying System for Doorway Monitoring (WISDOM). These instrumented doorways contain a variety of infrared, ultrasonic and pressure sensors that detect the direction of passage and measure each user's body size and shape. We quantify the measurement and identification accuracy of WISDOM by analyzing data collected from a user study containing 530 passes through a WISDOM prototype from 10 different subjects. We combine the results from WISDOM with large publicly available anthropometric databases to evaluate how accurately SAFTI performs location tracking with respect to building size, density of occupants, and matching algorithm used. / Dissertation
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Implicit, Eclipsed, but Functional: the Development of Orthographic Knowledge in Early ReadersKaefer, Tanya January 2009 (has links)
<p>Although most models of reading development present orthographic knowledge as a more advanced and later developing form of knowledge than phonological knowledge, this dissertation presents a model of the development of orthographic knowledge in which generalized orthographic knowledge, the knowledge of symbol patterns within and across words, develops early, at the same time as phonological knowledge and before lexicalized representations of a whole word. However, because phonological and generalized orthographic knowledge are not fully integrated, phonological knowledge masks orthographic knowledge in typical measures of literacy. </p><p>In study 1 pre-readers' knowledge of the elements that make up words was tested using eye-tracking as a measure of implicit knowledge. We find that pre-reading children as young as 3 have implicit orthographic knowledge regarding the elements that make up words. This supports the prediction that generalized orthographic knowledge develops before lexicalized knowledge. </p><p>In study 2, children's creative spellings were used to gauge children's implicit knowledge of letter patterns in a naturalistic setting. We find that kindergarteners in particular tend to rely on phonology over orthography when the two are in conflict. This supports the hypothesis that phonological knowledge can mask orthographic knowledge.</p><p>In study 3, children were asked to decode non-words and their implicit knowledge of letter patterns was measured using eye tracking. I found that early readers show some implicit knowledge when decoding, This supports the hypothesis that generalized orthographic knowledge can be measured in literacy tasks under certain testing conditions. </p><p>In study 4, children's phonological and orthographic knowledge was tested directly by asking children to sound out and select the best word. Results show that sensitivity to orthographic violations is decreased when phonology is introduced. This is a direct test of the hypothesis that phonological knowledge can mask orthographic knowledge, and findings support this hypothesis. </p><p>These results suggest that pre-readers show generalized orthographic knowledge before lexicalized knowledge and concurrently with phonological knowledge. Furthermore, this generalized orthographic knowledge initially presents itself implicitly, and in many early literacy tasks the orthographic domain is dominated by phonological concerns. Essentially, orthographic and phonological knowledge develop at the same time; however, until children learn to integrate the two dimensions of written language, they rely on one source over the other.</p> / Dissertation
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Target Tracking by Information Filtering in Cluster-based UWB Sensor NetworksLee, Chih-ying 19 August 2011 (has links)
We consider the topic of target tracking in this thesis. Target tracking is one of the applications in wireless sensor networks (WSNs). Clustering approach prolongs sensor¡¦s lifetime and provides better data aggregation for WSNs. Most previous researches assumed that cluster regions are disjointed, while others assigned overlapping cluster regions, and utilized them in some applications, including inter-cluster routing and time synchronization. However, in overlapping clustering, processing of redundant sensing data may impair system performance. We present a regular distributed overlapping WSN in this thesis. The network is based on two kinds of sensors: (1) high-capability sensors, which are assigned as cluster heads (CHs), responsible for data processing and inter-cluster communication, (2) normal sensors, which are in a larger number when comparing with the high-capability sensors, the function of normal sensors are to provide data to the CHs. We define several operating modes of CHs and sensors. WSN works more efficient under the settings. Since a target may be located in the overlapping region, redundant data processing problem exists. To solve the problem, we utilize Cholesky decomposition to decorrelate the measurement noise covariance matrices. The correlation will be eliminated during the process. In addition, we modify extended information filter (EIF) and adapt to the decorrelated data. The CHs track the target, fuse the information from other CHs, and implement distributed positioning. The simulations are based on ultra-wideband (UWB) environment, we have verified that the proposed scheme works more efficient under the setting of different modes. The performance with decorrelated measurement is better than that with correlated ones.
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Application of an Omnidirectional Camera to Detection of Moving Objects in 3D SpaceHsu, Chiang-Hao 29 August 2011 (has links)
Conventional cameras are usually small in their field of view (FOV) and make the observable region limited. Applications by such a vision system may also limit motion capabilities for robots when it comes to object tracking. Omnidirectional camera has a wide FOV which can obtain environmental data from all directions. In comparison with conventional cameras, the wide FOV of omnidirectional cameras reduces blind regions and improves tracking ability. In this thesis, we assume an omnidirectional camera is mounted on a moving platform, which travels with planar motion. By applying optical flow and CAMShift algorithm to track an object which is non-propelled and only subjected to gravity. Then, by parabolic fitting, least-square method and Levenberg-Marquardt method to predict the 3D coordinate of the object at the current instant and the next instant, we can finally predict the position of the drop point and drive the moving platform to meet the object at the drop point. The tracking operation and drop point prediction can be successfully achieved even if the camera is under planar motion and rotation.
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Interactive Stereoscopic Installation: A Photographic CollageKannapurakkaran, Shyam 2010 August 1900 (has links)
The research involves the creation of an interactive installation showcasing the
dynamic nature of human visual observation of a still photograph. Using an eye
tracker as an input device, the data collected is used to create a photographic collage
in stereoscopic 3D. The installation is artistically inspired by selected photographic
works of artists David Hockney, Maurizio Galimberti, Joyce Neimanas and Cubist
painters especially Picasso. One of the key factors in their work that is adapted in this
research, is the representation of the way eyes search points of interest demonstrated
in what they painted/photographed. The installation will demonstrate an expressive
representation of the viewers' experience of looking at a photograph. This will be
achieved by applying certain manipulations of the photograph based on the input
obtained from the viewer using an eye tracker. The eye tracker collects information
about the location and number of instances of where the viewer is when observing
a photograph. This is fed into software that processes the data and determines the
location and the size of the area of the photograph and amount of the manipulation
to be applied to that area. These two constitute the artistic rules that are used to
create the end product the photo collage. The individual pieces of the collage will be
arranged in a virtual 3D model by the artist and will be projected in stereoscopic 3D.
The development of this installation progressed through multiple case studies and
optimization based on ease of use, cost and availability of resources. This process is
intended to be a framework for artists working in interactive visual media.
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A Study of Real-Time Face Tracking with an Active CameraXie, Yao-Zhang 03 July 2005 (has links)
In this research we develop a Real-time face tracking system by single pan-tilt camera. The system includes face detection, deformable template tracking and motion control. We refer a method to search the facial features by using the genetic algorithm searching technique, the learning algorithm for face detector is based on AdaBoost. In the face tracking, we refer a tracking way to combine with detection and tracking. In the pan-tilt camera control part, two fuzzy logic controllers are designed to control the tracking and handling of moving face. We achieve a more robust tracking way than the single-template by renewing face-template continuously. Finally in our tests, the system can track the face of people in 30-frame per second under complex environment by using the personal computer.
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Design of Sliding Surface for A Class of Mismatched Uncertain Systems to Achieve Output TrackingChiu, Wen-chi 09 August 2005 (has links)
Based on the Lyapunov stability theorem, a methodology of designing an adaptive sliding mode control (ASMC) scheme is proposed in this thesis for a class of linear dynamic systems with matched and mismatched perturbations. Firstly, by utilizing a pseudo control input in the design of a novel sliding surface function, one can not only suppress the mismatched perturbations in the sliding mode, but also achieve the objective of output tracking. In addition, the accuracy of output tracking can be adjusted through the designed parameter embedded in this pseudo controller. Then, a sliding mode controller is derived to guarantee the existence of the sliding mode in a finite time by using adaptive mechanism, which is used to overcome the lumped perturbations so that the upper bound of perturbations is not required. Finally, two illustrative examples are given to demonstrate the validity of the results.
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