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<p>Good models of industrial robots are necessary in a variety of applications, such as mechanical design, performance simulation, control, diagnosis, supervision and offline programming. This motivates the need for good modelling tools. In the first part of this thesis the forward kinematic modelling of serial industrial robots is studied. The first steps towards a toolbox are implemented in the Maple programming language.</p><p>A series of possible applications for the toolbox can be mentioned. One example is to estimate the pose of the robot tool using an extended Kalman filter by means of extra sensors mounted on the robot. The kinematic equations and the relations necessary for the extended Kalman filter can be derived in the modelling tool. Iterative learning control, ILC, using an estimate of the tool position can then improve the robot performance.</p><p>The second part of the thesis is devoted to ILC, which is a control method that is applicable when the robot performs a repetitive movement starting from the same initial conditions every repetition. The algorithm compensates for repetitive errors by adding a correction signal to the reference. Studies where ILC is applied to a real industrial platform is less common in the literature, which motivates the work in this thesis.</p><p>A first-order ILC filter with iteration-independent operators derived using a heuristic design approach is used, which results in a non-causal algorithm. A simulation study is made, where a flexible two-mass model is used as a simplified linear model of a single robot joint and the ILC algorithm applied is based on motor-angle measurements only. It is shown that when a model error is introduced in the relation between the arm and motor reference angle, it is not necessary that the error on the arm side is reduced as much as the error on the motor side, or in fact reduced at all.</p><p>In the experiments the ILC algorithm is applied to a large-size commercial industrial robot, performing a circular motion that is relevant for a laser-cutting application. The same ILC design variables are used for all six motors and the learning is stopped after five iterations, which is motivated in practice by experimental results. Performance on the motor side and the corresponding performance on the arm side, using a laser-measurement system, is studied. Even though the result on the motor side is good, it is no guarantee that the errors on the arm side are decreasing. One has to be very careful when dealing with resonant systems when the controlled variable is not directly measured and included in the algorithm. This indicates that the results on the arm side may be improved when an estimate of, for example, the tool position is used in the ILC algorithm.</p> / <p>Bra modeller av industrirobotar behövs i en mängd olika tillämpningar, som till exempel mekanisk design, simulering av prestanda, reglering, diagnos, övervakning och offline-programmering. I första delen av avhandlingen studeras modellering av framåtkinematiken för en seriell robot och implementeringen av ett modelleringsverktyg, en toolbox, för kinematikmodellering i Maple beskrivs ingående.</p><p>Ett antal möjliga tillämpningar för toolboxen kan nämnas. Ett exempel är att med hjälp av extra sensorer monterade på roboten och ett så kallat extended Kalmanfilter förbättra skattningen av positionen och orienteringen för robotverktyget. De kinematiska ekvationerna och sambanden som behövs för extended Kalmanfiltret kan beräknas med hjälp av modelleringsverktyget. Reglering genom iterativ inlärning - iterative learning control, ILC - där en skattning av verktygspositionen används, kan sedan förbättra robotens prestanda.</p><p>Andra delen av avhandlingen är tillägnad ILC. Det är en reglermetod som är användbar när roboten utför en repetitiv rörelse som startar från samma initialvillkor varje gång. Algoritmen kompenserar för de repetitiva felen genom att addera en korrektionsterm till referenssignalen. Studier där ILC är tillämpad på en verklig industriell plattform är mindre vanligt i litteraturen, vilket motiverar arbetet i avhandlingen.</p><p>Ett första ordningens ILC-filter med iterationsoberoende operatorer används. ILC-algoritmen är framtagen enligt ett heuristiskt tillvägagångssätt, vilket resulterar i en ickekausal algoritm. I en simuleringsstudie med en flexibel tvåmassemodell som en förenklad linjär modell av en enskild robotled, används en ILC-algoritm baserad endast på motorvinkelmätningar. Det visar sig att när ett modellfel introduceras i sambandet mellan arm- och motorvinkelreferensen, är det inte säkert att felet på armsidan minskar så mycket som felet på motorsidan, eller minskar överhuvudtaget.</p><p>I experiment tillämpas ILC-algoritmen på en stor kommersiell industrirobot som utför en cirkelrörelse som är relevant för en laserskärningstillämpning. Samma designvariabler används för alla sex motorerna och inlärningen stoppas efter fem iterationer, vilket är motiverat i praktiken genom experimentella resultat. Prestanda på motorsidan studeras, och motsvarande prestanda på armsidan mäts med ett lasermätsystem. Trots goda resultat på motorsidan finns det inga garantier för minskande fel på armsidan. Stor försiktighet krävs när experimenten innefattar ett resonant system där den reglerade variabeln inte är mätt explicit och inkluderad i algoritmen. Detta visar på möjligheten att förbättra resultaten på armsidan då en skattning av till exempel verktygspositionen används i ILC-algoritmen.</p> / Report code: LiU-TEK-LIC-2008:1.

Thesis--Universität Dresden, 2008. / Includes bibliographical references.

Equine-assisted therapy is a nontraditional form of physical therapy that involves riding horses as a form of rehabilitation. Limited access to these riding programs justifies a need to develop a horseback riding simulator capable of simulating the gaits, bend, and collection of the horse. Research involving the development of horseback riding simulators is limited, but the available research does show promising results in the ability to aid in physical therapy. A two-dimensional model and simulation was developed using MATLAB. Using the results from the simulation, a horseback riding simulator was designed, fabricated and tested. The physical simulator was capable of simulating a walk, trot, and canter, bend to the left or right, and collection of the gait. The purpose of the testing of the horseback riding simulator was to evaluate the similarity of the physical simulator to the gaits of the data collected from a real horse. The results from the testing are compared with the kinematic data from the MATLAB simulation. The biomechanical effect on the hip flexion angle is also evaluated when the system simulates bend and collection of the horse’s back. The motion data was collected using a Vicon system. Four cameras were set up to collect the data from the five reflective markers that were placed on the rider. The kinematic results of the horseback riding simulator were compared to the computer simulation using the measurements of the inclination of the ellipse, the major axis of the ellipse, and the frequency. The results from the hip flexion angles shows that the test that simulated bend only results in a significant increase in the hip flexion angle compared to the tests without bend. Simulated collection does not change the hip flexion angles of the rider. Future work on the horseback riding simulator is needed in order to increase the safety so that a person with a disability would be able to use it as part of their physical therapy. Adaptive programming of the system is also necessary to make the horseback riding simulator more similar to that of a real horse.

This research presents the initial studies and results on shield design for Shape-Shifting Surfaces (SSSs) seeking maximum compression and maximum expansion of a unit-cell. Shape-Shifting Surfaces (SSSs) are multilayered surfaces that are able to change shape while maintaining their integrity as physical barriers. SSSs are composed of polygonal unit-cells, which can change side lengths and corner angles. These changes are made possible by each side and corner consisting of at least two different shields, or layers of material. As the layers undergo relative motion, the unit-cell changes shape. In order for the SSS to retain its effectiveness as a barrier, no gaps can open between different layers. Also, the layers cannot protrude past the boundaries of the unit-cell. Based on these requirements, using equilateral triangle unit-cells and triangular shields, a design space exploration was performed to determine the maximum deformation range of a unit-cell. It was found that the triangular shield that offered maximum expansion and compression ratio is a right triangle with one angle of 37.5 degrees and its adjacent side equal to 61% of the side of the unit-cell. The key contribution of this paper is a first algorithm for systematic SSS shield design. Possible applications for SSSs include protection, by creating body-armor systems; reconfigurable antennas able to broadcast through different frequencies; recreational uses, and biomedical applications.

This dissertation describes the development and effectiveness of a mathematical model used to predict the behavior of cantilever beams whose loading conditions include parallel combinations of evenly distributed loads and endpoint forces. The large deflection of cantilever beams has been widely studied. A number of models and mathematical techniques have been utilized in predicting the endpoint path coordinates and load-deflection relationships of such beams. The Pseudo-Rigid-Body Model (PRBM) is one such method which replaces the elastic beam with rigid links of a parameterized pivot location and torsional spring stiffness. In this paper, the PRBM method is extended to include cases of a constant distributed load combined with a parallel endpoint force. The phase space of the governing differential equations is used to store information relevant to the characterization of the PRBM parameters. Correction factors are also given to decrease the error in the load-deflection relationship and extend the angular range of the model, thereby further aiding compliant mechanism design. The calculations suggest a simple way of representing the effective torque caused by a distributed load in a PRBM as a function of easily calculated model parameters.

While amputee gait has been studied in great detail, the influence of prosthetic foot sagittal and coronal plane stiffness on amputee walking biomechanics is not well understood. In order to investigate the effects of sagittal and coronal plane foot stiffness on amputee walking, a framework for manipulating the stiffness of a prosthetic foot needs to be developed. The sagittal and coronal plane stiffness of a low profile carbon fiber prosthetic foot was manipulated through coupling with selective-laser-sintered prosthetic ankles. The carbon fiber foot provided an underlying non-linear stiffness profile while the ankle modified the overall stiffness of the ankle-foot combination. A design of experiments was performed to determine the effect of four prosthetic ankle dimensions (keel thickness, keel width, space between the ankle top and bottom faces, and the location of the pyramid connection) on ankle-foot sagittal and coronal plane stiffness. Ankles were manufactured using selective laser sintering and statically tested to determine stiffness. Two of the dimensions, space between the ankle top and bottom faces and the location of the pyramid connection, were found to have the largest influence on both sagittal and coronal plane stiffness. A third dimension, keel thickness, influenced only coronal plane stiffness. A number of prosthetic ankle-foot combinations were created that encompassed a range of sagittal and coronal plane stiffness levels that were lower than that of the low profile carbon fiber foot alone. To further test the effectiveness of the framework to manipulate sagittal and coronal plane stiffness, two ankle-foot combinations, one stiffer than the other in the sagittal and coronal planes, were used in a case study analyzing amputee walking biomechanics. Differences in stiffness were large enough to cause noticeable changes in amputee kinematics and kinetics during turning and straight-line walking. Future work will expand the range of ankle-foot stiffness levels that can be created using this framework. The framework will then be used to create ankle-foot combinations to investigate the effect of sagittal and coronal plane stiffness on gait mechanics in a large sample of unilateral transtibial amputees. / text

Advances in graphics and robotics have increased the importance of tools for synthesizing humanoid movements to control animated characters and physical robots. There is also an increasing need for analyzing human movements for clinical diagnosis and rehabilitation. Existing tools can be expensive, inefficient, or difficult to use. Using simulated physics and motion capture to develop an interactive virtual reality environment, we capture natural human movements in response to controlled stimuli. This research then applies insights into the mathematics underlying physics simulation to adapt the physics solver to support many important tasks involved in analyzing and synthesizing humanoid movement. These tasks include fitting an articulated physical model to motion capture data, modifying the model pose to achieve a desired configuration (inverse kinematics), inferring internal torques consistent with changing pose data (inverse dynamics), and transferring a movement from one model to another model (retargeting). The result is a powerful and intuitive process for analyzing and synthesizing movement in a single unified framework. / text

Background: Most traffic safety research projects require accurate real world data which is collected in different databases around the world. This is especially important since the results of these projects form the basis for new crash test procedures and standards. In many of these databases the involvement of the frontal structures of the car in frontal crashes is coded by using the SAE J224 practice (Society of Automobile Engineers). There were indications that by using this practice the database would contain an overestimate of the car frontal structure involvement in real world crashes. One purpose of this thesis is therefore to develop a new method for real world crash investigations to better address this issue. One purpose was also to adopt this method in a data collection of fatal crashes in Sweden and examine injury causation mechanisms. Studies shows that the commonly used Hybrid III dummy is not fully reproducing the kinematical behavior observed in frontal sled test with belted PMHS (Post Mortem Human Subject). A human FE-model (Finite Element) might be able to reproduce the behavior evidenced with the PMHS in order to study upper body kinematics in certain types of frontal collision events. Method: A new data collection method was developed with the purpose to examine actual load paths active in the car front during a frontal crash. An important purpose was to examine if there was a relation between these load paths and injury producing mechanisms. This was done in an examination and analysis of 61 fatally injured occupants in 53 car frontal crashes in a sample area covering 40 % of the population of Sweden. Sample period was one year (1st October 2000 to 30th September 2001). An existing human FE-model was developed and validated with respect to upper body kinematics by using existing frontal belted PMHS tests. This was done by building a FE-model of the seat and seat belt used in the PMHS tests. Results: A generic car structure was developed which was used in the data collection methodology. By adopting this new method, Small Overlap (SO) crashes emerged as the most common crash configuration (48 %) among belted frontal fatalities. The injury producing mechanism in SO crashes is characterized by occupant upper body impacts in the side structure (door, a-pillar) of the car. This upper body kinematics is induced by both the crash pulse and the asymmetrical three point belt system. Current crash test procedures are not designed to fully estimate the performance of neither car structures nor restraints in SO crashes. In order to develop a better tool for reproducing this kinematical behavior a FE-model of a human body was refined and validated for belted conditions. This validation was performed with satisfying result. Conclusions: This study showed that by adopting new methods of data collecting new areas of traffic safety could be considered. In this study SO (48 %) crashes emerged as the most common crash configuration for belted frontal fatalities. Approximately ¼ of the fatalities occurred in a crash configuration comparable to current barrier crash test procedures. The body kinematics of PMHS in the SO crashes can be replicated and studied by using a FE-model of a human body in the collision load case model. With this tool possible collision counter measures could be evaluated for the SO crash configuration.

Using various molecular line and continuum emission criteria, we have selected a sample of six isolated, dense concentrations of molecular gas, i.e., “cores”, which are either starless (L694-2, L429, L1517B, and L1689-SMM16) or contain a protostellar Very Low Luminosity Object (VeLLO) and are currently experiencing gravitational collapse (L1014 and L1521F). Studying the molecular emission from dense gas tracers toward this sample of cores will help us gain a more detailed image of the internal physical conditions of dense cores and their evolution. We observed the cores in our sample in NH3 (1,1) and (2,2) emission using the Green Bank Telescope (GBT) and in N2H+ (1−0) emission using the Nobeyama Radio Observatory (NRO). L429 shows the most complicated structure among the cores in our sample. Also, the maxima of molecular line integrated intensities and dust continuum emission toward L429 show a significant offset. The rest of the cores in our sample are roughly round and the morphologies of line integrated intensities follow that of the corresponding continuum emission closely. Cores in our sample have gas kinetic temperatures ∼ 9 − 10 K and therefore show comparable thermal velocity dispersions. L429 and L1517B are, respectively, the most turbulent and most quiescent cores in our sample. Finally, L1521F is the most centrally concentrated core of our sample. L1689-SMM16 is the least previously studied core in our sample and had not yet been probed in molecular emission. Jeans and virial analyses made using updated measurements of core mass and size confirm that L1689-SMM16 is prestellar, i.e., gravitationally bound. It also has accumulated more mass compared to its corresponding Jeans mass in the absence of magnetic fields and therefore is a “super-Jeans” core. The high levels of X(NH3)/X(N2H+) and deuterium fractionation reinforce the idea that the core has not yet formed a protostar. Comparing the physical parameters of the core with those of a Bonnor-Ebert sphere reveals the advanced evolutionary stage of L1689-SMM16 and shows that it might be unstable to collapse. We do not detect any evidence of infall motions toward the core, however. Instead, red asymmetry in the line profiles of HCN (1−0) and HNC (1−0) indicates expansion of the outer layers of the core at a speed of ∼ 0.2 − 0.3 km s−1. For a gravitationally bound core, expansion in the outer layers might indicate that L1689-SMM16 is experiencing oscillations. Radiative transfer modelling of NH3 emission toward L694-2 and L1521F at low and high spatial resolutions show that the less evolved core, L694-2, is best described by relatively constant radial profiles of temperature and fractional NH3 abundance. On the other hand, L1521F, which contains a protostellar VeLLO, is best described by a radial abundance profile that is enhanced toward the core centre and a radial temperature profile that decreases toward the core centre. Comparison of our results with previous studies on L1544, a well-studied starless core, imply that as dense cores evolve and progress toward the moment of collapse, they become more centrally concentrated. As a result, the gas temperatures at their centres decrease, leading to increase in levels of CO depletion factor and increase in NH3 fractional abundance toward the centre. / Graduate