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Towards The Enhancement Of Biped Locomotion And Control TechniquesYuksel, Basak 01 August 2008 (has links) (PDF)
The omnipresent tendency to &ldquo / live easy&rdquo / is a sign of our need for automatization. To enable for such a &ldquo / comfortable and safe&rdquo / world, the automatic systems have to be developed that satisfies the necessities of life. Biologically inspired robots, especially the humanoids, are thus the key, and research in this area focuses on the improvement of such systems. Lately, it has been shown by high dexterity examples that the humanoid robots achieved to a mature level even if there are still open issues to be improved, especially in the control and stability of the bipeds. The purpose of this thesis is to study biped locomotion in different floor conditions, such as stairs and obstacles / to improve the research done in this area / to contribute to the development of autonomous biped robots, dynamic modeling, gait planning, supervisory and guidence control, stability analysis of
biped robots / and to implement new control algorithms for biped locomotion, especially by using optimization and high level intelligent control techniques. The locomotion aimed to be realized results from complex, high-dimensional, nonlinear and dynamically related interactions between the robot and its environment. The mathematical modeling of the physical system is realized based on a 5-link 7 DOF biped robot model walking on a 3D planar surface and the dynamic simulation is performed using MATLAB. In terms of control, several different methods applied, comparison and the performance of each method are given. The 3D dynamic simulation software is developed, which allows the user to operate the biped systems within a 3D virtual environment.
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Design, Fabrication And Implementation Of A Vibration Based Mems Energy Scavenger For Wireless MicrosystemsSari, Ibrahim 01 September 2008 (has links) (PDF)
This thesis study presents the design, simulation, micro fabrication, and testing steps of microelectromechanical systems (MEMS) based electromagnetic micro power generators. These generators are capable of generating power using already available environmental vibrations, by implementing the electromagnetic induction technique. There are mainly two objectives of the study: (i) to increase the bandwidth of the traditional micro generators and (ii) to improve their efficiency at low frequency environmental vibrations of 1-100 Hz where most vibrations exist.
Four main types of generators have been proposed within the scope of this thesis study. The first type of generator is mainly composed of 20 parylene cantilevers on which coils are fabricated, where the cantilevers are capable of resonating with external vibrations with respect to a stationary magnet. This generator has dimensions of 9.5× / 8× / 6 mm3, and it has been shown that 0.67 mV of voltage and 56 pW of power output can be obtained from a single cantilever of this design at a vibration frequency of 3.45 kHz. The second type generator aims to increase the bandwidth of the traditional designs by implementing cantilevers with varying length. This generator is sized 14× / 12.5× / 8 mm3, and the mechanical design and energy generation concept is similar to the first design. The test results show that by using 40 cantilevers with a length increment of 3 & / #956 / m, the overall bandwidth of the generator can be increased to 1000 Hz. It has also been shown that 9 mV of constant voltage and 1.7 nW of constant power output can be obtained from the overall device in a vibration frequency range of 3.5 to 4.5 kHz. The third type is a standard large mass coil type generator that has been widely used in the literature. In this case, the generator is composed of a stationary base with a coil and a magnet-diaphragm assembly capable of resonating with vibrations. The fabricated device has dimensions of 8.5× / 7× / 2.5 mm3, and it has been considered in this study for benchmarking purposes only. The test results show that 0.3 mV of voltage and 40 pW of power output can be obtained from the fabricated design at a vibration frequency of 113 Hz. The final design aims to mechanically up-convert low frequency environmental vibrations of 1-100 Hz to a much higher frequency range of 2-3 kHz. This type of generator has been implemented for the first time in the literature. The generator is composed of two parts / a diaphragm-magnet assembly on the top, and 20 cantilevers that have coils connected in series at the base. The diaphragm oscillates by low frequency environmental vibrations, and catches and releases the cantilevers from the tip points where magnetic nickel (Ni) areas are deposited. The released cantilevers then start decaying out oscillations that is at their damped natural frequency of 2-3 kHz. It has been shown with tests that frequency up-conversion is realized in micro scale. The fabricated device has dimensions of 8.5× / 7× / 2.5 mm3, and a maximum voltage and power output of 0.57 mV and 0.25 nW can be obtained, respectively, from a single cantilever of the fabricated prototype at a vibration frequency of 113 Hz.
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Angular Acceleration Assisted Stabilization Of A 2-dof Gimbal PlatformOzturk, Taha 01 October 2010 (has links) (PDF)
In this thesis work construction of the angular acceleration signal of a 2-DOF gimbal
platform and use of this signal for improving the stabilization performance is aimed.
This topic can be divided into two subtopics, first being the construction of angular
acceleration and the second being the use of this information in a way to improve
system performance. Both problems should be tackled in order to get satisfactory
results. The most important output of this work is defined as the demonstration of
the improvements obtained both theoretically and on experimental setup. Although
the system to be studied is a two axis gimbal platform, the results obtained can be
applied to other servo control problems. It is possible to define different performance
criteria for a servo control problem and different techniques will be addressed with
different control objectives. For this thesis work, the performance criterion is defined
as the stabilization performance of the platform. As a result, disturbance rejection
characteristics of the controller emerges as the main topic and methods for rejecting
these disturbances such as the friction torques and externally applied moments are
focused on throughout the studies. As expected, remarkable improvement is achieved
as a result of the use of acceleration feedback.
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MicroRNA-212/132 Family is Involved in the Regulation of Long-Term Spatial Memory and Synaptic RemodelingErikci, Erdem 26 February 2014 (has links)
No description available.
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Modeling And Control Of A Stabilization SystemAfacan, Kamil 01 December 2004 (has links) (PDF)
Elevation axis model of a barrel stabilization system is constructed. The
nonlinearities which are considered in the model are orifice flow
characteristics, coulomb friction, hard-stop limits, kinematics of the system
and unbalance on the barrel. A Simulink® / model for the servo valve,
actuation system and barrel is constructed. Servo valve identification is
made via the actual test data. Compressibility of the hydraulic fluid is taken
into consideration while modeling the actuation system. Friction model is
simulated for different cases. Controller of the system is constructed by two
PIDs, one for each of the velocity and the position loops. Velocity feed
forward can reduce the time to make a quick move by the system. The
disturbance is evaluated from a given road profile and disturbance feed
forward is applied to the system.
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On-line Controller Tuning By Matlab Using Real System ResponsesPektas, Seda 01 December 2004 (has links) (PDF)
This thesis attempts to tune any controller without the mathematical model knowledge of the system it is controlling. For that purpose, the optimization algorithm of MATLAB® / 6.5 / Nonlinear Control Design Blockset (NCD) is adapted for real-time executions and combined with a hardware-in-the-loop simulation provided by MATLAB® / 6.5 / Real-Time Windows Target (RTWT). A noise-included model of a DC motor position control system is obtained in MATLAB® / / SIMULINK first and simulated to test the modified algorithm in some aspects. Then the presented methodology is verified using the physical plant (DC motor position control system) where tuning algorithm is driven mainly by the real system data and the required performance parameters specified by a user defined constraint window are successfully satisfied. Resultant improvements on the step response behavior of DC motor position control system are shown for two case studies.
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Development Of A Stereo Vision System For An Industrial RobotBayraktar, Hakan 01 January 2005 (has links) (PDF)
The aim of this thesis is to develop a stereo vision system to locate and
classify objects moving on a conveyor belt. The vision system determines the
locations of the objects with respect to a world coordinate system and class of the
objects. In order to estimate the locations of the objects, two cameras placed at
different locations are used. Image processing algorithms are employed to extract
some features of the objects. These features are fed to stereo matching and
classifier algorithms. The results of stereo matching algorithm are combined with
the calibration parameters of the cameras to determine the object locations.
Pattern classification techniques (Bayes and Nearest Neighbor classifiers) are
used to classify the objects. The linear velocity of the objects is determined by
using an encoder mounted to the shaft of the motor driving the conveyor belt. A
robot can plan a sequence of motion to pick the object from the conveyor belt by
using the output of the proposed system.
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3-d Humanoid Gait Simulation Using An Optimal Predictive ControlOzyurt, Gokhan 01 September 2005 (has links) (PDF)
In this thesis, the walking of a humanoid system is simulated applying an optimal predictive control algorithm. The simulation is built using Matlab and Simulink softwares. Four separate physical models are developed to represent the single support and the double support phases of a full gait cycle. The models are three dimensional and their properties are analogous to the human&rsquo / s. In this connection, the foot models in the double support phases include an additional joint which connects the toe to the foot. The kinematic relationships concerning the physical models are formulated recursively and the dynamic models are obtained using the Newton &ndash / Euler formulation.
The computed torque method is utilized at the level of joints. In the double support phase, the redundancy problem is solved by the optimization of the actuating torques. The command accelerations required to control the gait are obtained by applying an optimal predictive control law.
The introduced humanoid walker achieves a sustainable gait by tuning the optimization and prediction parameters. The control algorithm manages the tracking of the predefined walking pattern with easily realizable joint accelerations. The simulation is capable of producing all the reaction forces, reaction moments and the values of the other variables. During these computations, a three dimensional view of the humanoid walker is animated simultaneously. As a result of this study, a suitable simulation structure is obtained to test and improve the mechanical systems which perform bipedal locomotion. The modular nature of the simulation structure developed in this study allows testing the performance of alternative control laws as well.
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Modeling And Real-time Control System Implementation For A Stewart PlatformAlbayrak, Onur 01 November 2005 (has links) (PDF)
This work focuses on modeling and real-time control of a motion simulator for dynamic testing of a two-axis gyro-stabilized head mirror used in modern tanks. For this purpose, a six-degree-of freedom Stewart Platform which can simulate disturbances on the stabilized head mirror during operation of the tank is employed.
Mathematical models of the Stewart Platform are constructed using MATLAB and ADAMS. Control system infrastructure is constructed and real-time control system elements are employed. Controller tuning is achieved by using the developed mathematical models in MATLAB. These parameters are applied in the real-time control system and fine tuning is achieved. Accuracy of the motion simulator is tested by mounting an Inertial Measurement Unit on the Stewart Platform. Further control system strategies are discussed by means of simulation.
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Design, Construction And Preliminary Testin Of An Aeroservoelastic Test Apparatus To Be Used In Ankara Wind TunnelUnal, Sadullah Utku 01 February 2006 (has links) (PDF)
In this thesis, an aeroservoelastic test appratus is designed to investigate the flutter phenomena in a low speed wind tunnel environment. Flutter is an aeroelastic instability that may occur at control surfaces of aircrafts and missiles. Aerodynamic, elastic, and inertial forces are involved in flutter. A mathematical model using aeroelastic equations of motion is derived to investigate flutter and is used as a basis to design the test setup. Simulations using this mathematical model are performed and critical flutter velocities and frequencies are found. Stiffness characteristics of the test setup are determined using the results of these simulations. The test setup is a two degrees of freedom system, with motions in pitch and plunge, and is controlled by a servomotor in the pitch degree of freedom. A NACA 0012 airfoil is used as a control surface in the test setup. Using this setup, the flutter phenomena is generated in Ankara Wind Tunnel (AWT) and experiments are conducted to validate the results of the theoretical aeroelastic mathematical model calculations.
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