Emergency gates are important safety feature of hydropower plants. They are used to close the flow in order to protect power plant equipment in case of emergency. In this diploma the-sis are realized CDF simulations of emergency closure of wheel-mounted gate on two-dimensional model of the Slapy hydropower plant. Simulations were performed for the case of constant lowering gate speed and for the case of gravitational closure. Dynamic mesh was used to enable the gate motion. The 6DOF method was used for the case of gravitational clo-sure and user defined function was defined to control movement of the gate. User defined function include gravitational force, hydrodynamic forces and friction force. Simulations were used to verify forces acting on gate and volume flow through gate during closing process. In case of gravitational closure the speed and orientation of closing process and closing process time were determined.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: There are several ports around the world currently experiencing problems with moored vessel motions. Extreme vessel motions are mainly caused by long waves, which can become trapped inside a harbour basin. The extreme motions can cause downtime in port operations and in some instances cause mooring lines to break. Methods and procedures currently available to measure motions of moored vessels require vessel specific information as input. The implementation of these methods is seen as impractical to implement on every vessel visiting the port and require the physical measurement of some points on the vessel and/or the placement of some kind of measurement device on the vessel. A new Six Degree of Freedom (6DOF) motion measurement system for a moored vessel is presented in this document. The system analyses a video image sequence from one camera. The method estimates the 3D rigid motion for an object of known size by using a Pose from Orthography and Scaling with ITerations (POSIT) algorithm. The object for which the motion is estimated is located on the deck of the vessel and within the camera field of view. Geometric rigid body calculations allow for the calculation of camera perspective rotations and translation of an object on the vessel. Further geometric calculations allow for converting camera perspective motions to the 6DOF object motions. The primary objective of this study was to validate and verify the motions obtained from two proof-of-concept tracking systems. For evaluation purposes, the validation was done by using a small scale physical model set-up in a hydraulics laboratory and using a known method as reference. The Keoship system from the Council for Scientific and Industrial Research (CSIR) is currently one of the most accurate small scale vessel motion measurement systems and was used as reference. The first method tested was the tracking of a 2D LED rectangle mounted on the vessel. This method tracked a 2D object and was primarily used as a stepping stone to measure movement of a 3D object. The second method tracked a 3D object on the vessel. Each tracking method was tested for four different wave conditions with each condition additionally repeated twice as repeatability tests, resulting in a total of 12 tests for each tracking method. When comparing the 2D LED tracking and 3D Object tracking data to data measured with the Keoship system, results show that in general, the 3D Object tracking data compared better to the Keoship data. Tests under controlled conditions enabled a direct estimation of the absolute accuracy of the two developed methods. The verification and accuracy test results, indicated that the 2D LED tracking system should not be pursued further. The results also indicated that for prototype motions exceeding 0.6 m (i.e. storm events) the 3D Object tracking system would have an accuracy close to the maximum allowable accuracy criterion of 0.1 m. This makes the system viable at its current proof-of-concept stage for further development which would enable rapid deployment during a storm event in a prototype situation. / AFRIKAANSE OPSOMMING: Daar is verskeie hawens regoor die wêreld wat tans bewegings probleme op gemeerde skepe ervaar. Hierdie buitensporige bewegings word veroorsaak deur lang periode golwe wat binne die hawe bekkens vasgekeer word. Dit kan daartoe lei dat hawe bedrywighede tot stilstand kom en in ernstige gevalle ook veroorsaak dat meringslyne breek. Huidige metodes vir die meet van skeepsbewegings op vasgemeerde skepe, vereis skeep spesifieke inligting as inset. Die toepassing van hierdie metodes op elke skip wat die hawe besoek, word as onprakties beskou, aangesien dit die fisiese meting van sekere punte op die skip behels. In sekere gevalle is dit selfs nodig om meet toestelle op die skip te plaas. In hierdie dokument word ‘n nuwe metode aangebied om die ses grade van vryheid bewegings vir ‘n vasgemeerde skip te meet. Hierdie stelsel analiseer ‘n video beeld reeks van een kamera. Die metode bereken die 3D rigiede beweging van ‘n voorwerp, waarvan die grootte bekend is. ’n ‘Pose from Orthography and scaling with Iterations’ (POSIT) algoritme word hiervoor gebruik. Die voorwerp waarvoor beweging gemeet word is op die dek van die skip en in kamera sig. Rigiede geometriese voorwerp berekeninge word gebruik om die rotasie en translasie vanuit ‘n kamera perspektief te bereken. Verdere geometriese berekeninge maak dit moontlik om die bewegings vanuit die kamera perspektief te omskep in die ses grade van vryheid bewegings van die voorwerp. Die hoof doelwit van hierdie ondersoek was om die gemete bewegings van twee beweging stelsels te valideer en te verifieer. Die validasie en verifiëring was in ‘n hidrolise laboratorium met ‘n klein skaal model opstelling getoets. ‘n Meet metode van skeepsbeweging op klein skaal wat reeds bekend is, is gebruik as ‘n verwysingsraamwerk waarteen die metings vergelyk kan word. Die Keoship stelsel van die Wetenskaplike Nywerheids Navorsings Raad (WNNR) is tans een van die mees akkurate klein skaal skeepsbeweging meet stelsels, en was as verwysing gebruik. Die eerste bewegings metode is getoets op ‘n 2D reghoek vervaaridig uit ligstralede diodes. Hierdie metode het die 2D voorwerp gevolg en is hoofsaaklik gebruik as ‘n boublok om die beweging van ‘n 3D voorwerp te volg. Die tweede metode het die beweging van ‘n 3D voorwerp op ‘n skip gevolg. Vir elke meet metode was daar vier verskillende golf toestande. Elke golf toestand was ook ‘n verdere twee keer herhaal vir herhaalbaarheids doeleindes. Saam met die herhaalbaarheids toetse was daar in totaal, 12 toetse vir elkeen van die twee metodes gedoen. Met die Keoship metode as verwysing, bewys hierdie toetse dat die 3D metode beter resultate lewer as die 2D metode. Toetse onder beheerde toestande, het dit moontlik gemaak om die absolute akkuraatheid van albei sisteme wat ontwikkel was, te evalueer. Verifikasie en akuraatheids toetse het aangedui dat verdere ontwikkeling van die 2D metode gestuit moet word. Die resultate het ook aangedui dat die 3D metode ‘n akuraatheid baie na aan die maatstaf van 0.1 m sal hê wanneer prototipe bewegings 0.6 m oorskrei (b.v. gedurende ‘n storm). Dit sal die oplossing lewensvatbaar maak by die huidige bewys van konsep fase vir die verdere ontwikkeling wat vinnige ontplooiing gedurende ‘n storm sal moontlik maak.

Haptic devices and haptic rendering is an important topic in the burgeoning field of virtual reality applications. In this thesis, I describe the design and implementation of a cutting force model integrating a haptic device, the PHANToM, with a high &ndash / powered computer. My goal was to build a six degree &ndash / of &ndash / freedom force model to allow user to interact with three &ndash / dimensional deformable objects. Methods for haptic rendering including graphical rendering, collision detection and force feedback are illustrated, implementation of haptic rendering system is introduced, and application is evaluated to explore the effectiveness of the system.

The CAREN-Extended system is a fully immersive virtual environment (VE) that can provide stability-challenging scenarios in a safe, controlled manner. Understanding gait biomechanics when stability is challenged is required when developing quantifiable metrics for rehabilitation assessment. The first objective of this thesis was to examine the VE’s technical aspects to ensure data validity and to design a stability-challenging VE scenario. The second and third objectives examined walking speed changes and kinematic strategies when stability was challenged for able-bodied and unilateral transtibial amputees. The results from this thesis demonstrated: 1) understanding VE operating characteristics are important to ensure data validity and to effectively design virtual scenarios; 2) self-paced treadmill mode for VEs with multiple movement scenarios may elicit more natural gait; 3) gait variability and trunk motion measures are useful when quantitatively assessing stability performance for people with transtibial amputations.

<p>Real-time MRI scanning is used to visualize tissue and organs in motion. The real-time approach requires new interaction techniques to facilitate interaction with the scanning plane. The aim of this thesis is to investigate the use of input with six degrees of freedom – 6DOF. An overview over existing 6DOF input devices is given. Three devices are chosen for implementation and evaluation, Flock of Birds, SpaceBall and SpaceMouse. </p><p>A simulator application is developed to test the different input devices. The simulator purpose is to imitate the real-time scanning situation. To be able to evaluate speed andaccuracy of the different interaction techniques, methods for measuring time and error are developed. A statistical survey is done on two different tasks to gather data of the interaction. The data is analyzed and the result is that the test subjects find the SpaceMouse superior to the other devices thanks to its kinesthetic feed-back properties and ergonomic benefits. However, the statistical data shows that Flock of Birds is the fastest device and no great difference is showed in accuracy between Flock of Birds and SpaceMouse. SpaceBall was the device that generated the least satisfying data.</p>

A dynamic flight model of a jet trainer aircraft is developed in MATLAB-SIMULINK. Using a six degree of freedom mathematical model, non-linear simulation is used to observe the longitudinal and lateral-directional motions of the aircraft following a pilot input. The mathematical model is in state-space form and uses aircraft stability and control derivatives calculated from the aircraft geometric and aerodynamic characteristics. The simulation takes the changes in speed and altitude into consideration due to pilot input and demonstrates the non-linearity of the aircraft motion. The results from the simulation are compared with the results from flight characteristics manual of the actual aircraft to validate the mathematical model used. The simulation is carried out for a number of airspeed and altitude combinations to examine the effect of changing speed and altitude on the aircraft dynamic response.

Real-time MRI scanning is used to visualize tissue and organs in motion. The real-time approach requires new interaction techniques to facilitate interaction with the scanning plane. The aim of this thesis is to investigate the use of input with six degrees of freedom – 6DOF. An overview over existing 6DOF input devices is given. Three devices are chosen for implementation and evaluation, Flock of Birds, SpaceBall and SpaceMouse. A simulator application is developed to test the different input devices. The simulator purpose is to imitate the real-time scanning situation. To be able to evaluate speed andaccuracy of the different interaction techniques, methods for measuring time and error are developed. A statistical survey is done on two different tasks to gather data of the interaction. The data is analyzed and the result is that the test subjects find the SpaceMouse superior to the other devices thanks to its kinesthetic feed-back properties and ergonomic benefits. However, the statistical data shows that Flock of Birds is the fastest device and no great difference is showed in accuracy between Flock of Birds and SpaceMouse. SpaceBall was the device that generated the least satisfying data.

The successful prediction of spacecraft motion is often heavily based upon assumptions used to simplify the problem without compromising solution accuracy. For many analyses, a primary assumption used is the decoupling of trajectory and attitude dynamics when calculating trajectories. In cases where spacecraft or objects have high area to mass ratios, non-conservative effects such as atmospheric drag and solar radiation pressure can greatly perturb spacecraft translational motion based on rotational state. A modular, six degree of freedom (6DOF) simulation with coupled orbit and attitude dynamics has been developed to model spacecraft and orbits of arbitrary geometries. First, the basis for the modular rotational and translational equations of motion are introduced. Next, formulations are provided for the gravity gradient torque, solar radiation pressure, aerodynamic, and non-spherical gravity potential sources of perturbations, and the Marshall Engineering Thermosphere atmospheric model used is described. A first test case is performed using the 6DOF simulation to simulate the deorbit of the spacecraft Lightsail 1, which flew in 2015. Next, predictive cases are demonstrated using the simulation for a theoretical sail-boom-rocket combination representative of a debris removal scenario, and for the Aerodynamic Deorbit Experiement, which will demonstrate a passively stable drag sail technology and characterize its effectiveness on orbit. All simulation cases have had aerodynamic perturbation formulations compared against high fidelity Direct Simulation Monte Carlo runs, and suggestions have been made for the future development of the simulation tool.

No description available.

The purpose of this thesis was to design, construct and control a robotic arm with six degrees of freedom. The arm should be able to do simple tasks such as pick and place with good accuracy and without using external sensors. This thesis investigates the precision and the strength of the constructed robot arm. The arm was constructed using 3D printed parts and commonly available hardware such as threaded rods, bearings, screws and nuts. Each axis uses a combination of pulleys and belts in order to achieve desired torque. A differential transmission was implemented in four of the axes in order to combine the power of the motors and reduce weight in the upper parts of the arm. The robot is driven by six stepper motors that are controlled by a combination of RAMPS 1.4 shield and Arduino Mega 2560 microcontroller. The user can manipulate each axis by sending commands to the Arduino through an USB cable. The commands are generated with the help of a simple user interface written in Python. Experiments have shown that the arm has an average error increase of 0.0289-0.1356 mm for each movement, depending on the chosen speed. The maximum amount ofweight that the arm can hold in the worst case scenario is 0.84 kg. / Syftet med denna avhandling var att designa, konstruera och kontrollera en robotarm med sex frihetsgrader. Armen ska kunna utföra enkla uppgifter som pick-and-place med god noggrannhet och utan användning av externa sensorer. Denna avhandling underosöker precisionen och styrkan hos den konstruerade robotarmen. Armen konstruerades med 3D-printade delar och läattillgänglig hårdvara som gängstänger, lager, skruvar och muttrar. Varje axel använder en kombination av kuggremskivor och kuggremmar för att uppnå önskat moment. En differentialväxel användes i fyra av axlarna för att kombinera motorernas moment och minska vikten i armens övre delar. Roboten drivs av sex stegmotorer som styrs av en kombinationav RAMPS 1.4-shield och Arduino Mega 2560 mikrokontroller. Användaren kan styra varje axel genom att skicka kommandon till Arduinon via en USB-kabel. Kommandona genereras med hjälp av ett enkelt användargränssnitt skrivet i Python. Experiment har visat att armen har en genomsnittlig felökning på 0,0289-0,1356 mm för varje rörelse, beroende på vald hastighet. Den högsta vikt som armen i värsta fallkan håalla är 0,84 kg.