This thesis work contains a litterature study about electrical motors in general and how PWM-patterns for brushless DC-motors can be made. A suitable method has been implemented as a simulation model in VHDL. A simulation model of a brushless DC-motor which describes the phasecurrents, torque and angular velocity has also been made. The motor model made simulations easier for the complete PWM-system. The design was synthesised and tested with a prototypeboard including a SPARTAN II FPGA. In order to test the design, a powerstage and a motor was included. The tests showed that the design was working as expected according to the previous simulations. A study about an alternative way to control a brushless DC-motor has also been made. This alternative is best suited when the generated back-EMK for the motor is sinusoidal. A simulation model for a part of a system like this has been made, and it has been synthesised in order to examine if it is possible to implement using a FPGA availible today.

This thesis presents, analyzes and suggests solutions to the dead-lock problem of the sensorless variable speed drive NFO Sinus. Friction, measurement, parameter estimation and quantization effects are believed possible origins of this problem and is hence studied. A short introduction to ¯eld oriented control of the asynchronous AC motor and the NFO Control strategy is also included. The report is published at LiTH as ISRN LiTH-ISY-EX--06/3945--SE and at LTH under ISRN LUTFD2/TFRT--5780--SE.

In developing a method of quantifying stability in the lumbar spine Cholewicki and McGill (1996) have also broached the notion of sufficient stability, where too much stiffness (and stability) would hinder motion. Thus people highly skilled at maintaining stability may use different and optimal strategies, where <i>sufficient</i> stability is maintained. The purpose of this work was to explore the contributors to <i>sufficient</i> stability, how they coordinate and relate to injury mechanisms. This work represents a cascade of investigations where. 1) To explore the balance of various sources of stiffness and their effect on the critical load and post-buckling behaviour, simulations were undertaken where the buckled configuration of the spine was predicted and its stability in this new configuration was assessed. 2) The various sources of stiffness contributing to stability in the lumbar spine have been in some cases found to be deficient. The question of how these deficiencies place individuals at risk of instability, if at all, remains unresolved. A challenged breathing task was used to determine if there was a difference in stabilizing potential between healthy individuals and low back pain sufferers. Given that differences in stabilizing potential are apparent, several tasks which included a predetermined motor strategy, such as 3)pressurizing the abdomen and 4) abdominal hollowing vs. muscle bracing, were evaluated to determine if individuals can utilize motor strategies to augment stability. The stabilizing potential of abdominal pressure (IAP) and its interaction with muscle activation was evaluated. Some individuals are more skilled at stabilizing their lumbar spine than others. Some consciously controlled motor strategies are better stabilizers than others. These strategies highlight the relative contributions of various components (posture, passive tissue, muscle activation, and load) in that no single muscle dominates stability and IAP appears to augment stability beyond muscle activation alone. The margin of safety is considerable and depends on the task at hand, but it is possible to speculate on which tissues are at greatest risk of injury.

This research study examined the design of a virtual keyboard that can be used for text entry with a rotary controller, particularly when users may differ in age and experience with a particular system. I specifically examined the shape and letter arrangement on the virtual keyboard to help determine the best features to use in a design. Two keyboard shapes, an Oval and a Plus, were selected to represent different aspects of the shape. Two keyboard arrangements, Alphabetic and a Standard QWERTY-based ordering, were selected to represent a well-known and less familiar arrangement. In the experiment, older and younger adults entered words over two consecutive days. Most of the time, they used either the Oval or the Plus, but they also used the alternate shape at specific points during their practice session to allow assessment of their ability to transfer what they had learned. At the end of the second day, they also used a variation of the practiced arrangement to examine how well they had learned the letter arrangement. Text entry performance on both shapes improved as a function of practice, demonstrating that participants could learn even unfamiliar devices and virtual keyboards to complete a word entry task. No overall shape effects were found for any level of performance, but shape did affect how participants learned and performed the word entry task. In particular, unique visual features on a shape may facilitate memorization of letter/visual cue mappings. These shape features are particularly important for older adults, as younger adults seem to develop a mental model that helps them memorize letter locations on either shape. With practice, older adults could achieve optimal performance levels with an Alphabetic keyboard on the Plus shape that has the more visually unique corners. In general, alphabetic ordering is best not only because it helped visual search, but also because it facilitated better movement planning. Overall, designers should consider creating unique visual features on a virtual keyboard that will blend with the compatibility and allowed movements for the selected device to create an effective virtual keyboard.

The goal of this thesis is to design the steering vehicle system by joystick. The main function of the steering vehicle system is drivers can operate the joystick with electrical control to accomplish steering motion. In this paper , the main design framework of the steering vehicle system is divided into three stages of the experiment, vehicle architecture, vehicle dynamic simulation and vehicle test results . The overall system is modified Go-kart as a platform, develop a suitable joystick framework in the vehicle, and apply the encoder on the joystick, which transfer the control information into the position signal, to be the input command of steering motor control program. According to the steering by wire for brushless DC servo motor control strategy, the system control architecture achieve the goal by embedded-DSP. And to test double-lane change by Go-kart. Experimental results recorded by gyroscope can compare the steering situation of joystick with steering wheel.

When top sports performers fail or “choke” under pressure, everyone asks: why? Research has identified a number of conditions (e.g. an audience) that elicit choking and that moderate (e.g. trait-anxiety) pressure – performance relation. Furthermore, mediating processes have been investigated. For example, explicit monitoring theories link performance failure under psychological stress to an increase in attention paid to a skill and its step-by-step execution (Beilock & Carr, 2001). Many studies have provided support for these ideas. However, so far only overt performance measures have been investigated which do not allow more thorough analyses of processes or performance strategies. But also a theoretical framework has been missing, that could (a) explain the effects of explicit monitoring on skill execution and that (b) makes predictions as to what is being monitored during execution. Consequently in this study, the nodalpoint hypothesis of motor control (Hossner & Ehrlenspiel, 2006) was taken to predict movement changes on three levels of analysis at certain “nodalpoints” within the movement sequence. Performance in two different laboratory tasks was assessed with respect to overt performance (the observable result, for example accuracy in the target), covert performance (description of movement execution, for example the acceleration of body segements) and task exploitation (the utilization of task properties such as covariation). A fake competition (see Beilock & Carr, 2002) was used to invoke pressure. In study 1 a ball bouncing task in a virtual-reality set-up was chosen. Previous studies (de Rugy, Wei, Müller, & Sternad, 2003) have shown that learners are usually able to “passively” exploit the dynamical stability of the system. According to explicit monitoring theories, choking should be expected either if the task itself evokes an “active control” (Experiment 1) or if learners are provided with explicit instructions (Experiment 2). In both experiments, participants first went through a practice phase on day 1. On day 2, following the Baseline Test participants were divided into a High-Stress or No-Stress Group for the final Performance Test. The High-Stress Group entered a fake competition. Overt performance was measured by the Absolute Error (AE) of ball amplitudes from target height; covert performance was measured by Period Modulation between successive hits and task exploitation was measured by Acceleration (AC) at ball-racket impact and Covariation (COV) of impact parameters. To evoke active control in Exp. 1 (N=20), perturbations to the ball flight were introduced. In Exp. 2 (N=39) half of the participants received explicit skill-focused instructions during learning. For overt performance, results generally show an interaction between Stress Group and Test, with better performance (i. e. lower AE) for the High-Stress group in the final Performance Test. This effect is also independent of the Instructions that participants had received during learning (Exp. 2). Similar effects were found for COV but not for AC. In study 2 a visuomotor tracking task in which participants had to pursuit a target cross that was moving on an invisible curve. This curve consisted of 3 segments of 6 turning points sequentially ordered around the x-axis. Participants learned two short movement sequences which were then concatenated to form a single sequence. It was expected that under pressure, this sequence should “fall apart” at the point of concatenation. Overt Performance was assessed by the Root Mean Square Error between target and pursuit cross as well as the Absolute Error at the turning points, covert performance was measured by the Latency from target to pursuit turning and task exploitation was measured by the temporal covariation between successive intervals between turning points. Experiment 3 (intraindividual variation) as well as Experiment 4 (interindividual variation) show performance enhancement in the pressure situation on the overt level with matching results on covert and task exploitation level. Thus, contrary to previous studies, no choking under pressure was found in any of the experiments. This may be interpreted as a failure in the experimental manipulation. But certainly also important characteristics of the task are highlighted. Choking should occur in tasks where performers do not have the time to use action or thought control strategies, that are more relevant to their “self” and that are discrete in nature. / Wenn Top-Athleten im Wettkampf versagen fragt sich jeder: warum? Die Forschung hat dazu einerseits Bedingungen identifiziert (z.B. die Anwesenheit von Publikum), die „Versagen“ auslösen und die Beziehung Druck- Leistung moderieren. Zudem wurden vermittelnde Prozesse gefunden wie zum Beispiel die bewusste Aufmerksamkeitsfokussierung („explicit monitoring“) auf die Ausführung der Bewegung (Beilock & Carr, 2001). Obwohl es gerade für diese Vorstellungen einige Befunde gibt, wurde bislang fast ausschließlich das Bewegungsresultat („overt performance“) untersucht, nicht aber Variablen, die Aussagen über die Bewegungsausführung zulassen. Zudem fehlt ein theoretischer Rahmen, der Vorhersagen zulässt darüber, (a) welche Veränderungen der Bewegungsausführung unter Druck zu erwarten sind und (b) welchen Stellen der Bewegung bewusst fokussiert werden. Darum wurde für diese Studie die „Knotenpunkthypothese motorischer Kontrolle“ (Hossner & Ehrlenspiel, 2006) herangezogen um auf drei Analyse-Ebenen zu ermöglichen Vorhersagen an Knotenpunkten der Bewegung zu treffen. Leistung wurde entsprechend auf einer overt-Ebene (beobachtbare Bewegungsresultat, z.B. Treffgenauigkeit), einer covert-Ebene (z.B. raum-zeitliche Verlaufe von Gelenkwinkeln) und einer task-exploitation-Ebene (z.B. die Covariation von Ausführungsparametern) untersucht. Für die Manipulation einer „Druck-Bedingung“ wurde ein Pseudowettkampf (nach Beilock & Carr, 2002) verwendet. Für die Experimente 1 und 2 wurde eine semi-virtueller „ball bouncing“-Aufgabe verwendet, für die sich gezeigt hat (de Rugy, Wei, Müller, & Sternad, 2003), dass Lernende tatsächlich in der Lage sind, die dynamische Stabilität der Aufgabe zunehmend auszunutzen. Angenommen wurde, dass Versagen unter Druck erscheinen sollte, wenn die Aufgabe entweder eine „aktive Kontrolle“ verlangt (Experiment 1) oder aber die Lernenden explizite Instruktionen während der Lernphase erhalten. Allerdings zeigen die Ergebnisse beider Experimente nur Leistungsverbesserungen unter Druck-Bedingungen auf overt-Ebene, die mit entsprechenden Verbesserungen auf covefrt- und task-exploitation-Ebene einhergehen. Für die Experimente 3 und 4 wurde eine visuomotorische Tracking-Aufgabe verwendet in der die Probanden zunächst zwei kleinere Bewegungssequenzen erlernten, bevor diese zu einer großen Sequenz verbunden wurde. Unter Druck sollte diese Gesamtsequenz „auseinander brechen“. Jedoch zeigt sich auch hier in beiden Experimenten eine Resultatsverbesserung unter Druck (gegenüber Kontrollbedingungen bzw. –gruppen) auf overt wie auf covert-Ebene. Im Gegensatz zu vielen vorangehenden Studien zeigte sich kein „Choking under Pressure“. Sicherlich stellt sich zunächst die Frage nach der Validität der Druckmanipulation, die aber zumindest für die beiden ersten Experimente gesichert scheint. Relevanter scheint demnach eine Inspektion der Aufgabe. Hier dürfte es sein, dass diskrete Aufgaben, die einen Einsatz von Handlungskontroll-Strategien nicht erlauben und die von größerer „Selbst“-Relevanz sind, eher unter Druck beeinträchtigt werden.

The kinematic motor redundancy of the human legs provides more local degrees of freedom than are necessary to achieve low degree of freedom performance variables like leg length and orientation. The purpose of this dissertation is to investigate how the neuromuscular skeletal system simplifies control of a kinematically redundant system to achieve stable locomotion under different conditions. I propose that the neuromuscular skeletal system minimizes step to step variance of leg length and orientation while allowing segment angles to vary within the set of acceptable combinations of angles that achieves the desired leg length and orientation. I find that during human hopping, control of the locomotor system is organized hierarchically such that leg length and orientation are achieved by structuring segment angle variance. I also found that leg length and leg orientation was minimized for a variety of conditions and perturbations, including frequency, constrained foot placement, and different speeds. The results of this study will give valuable information on interjoint compensation strategies used when the locomotor system is perturbed. This work also provides evidence for neuromuscular system strategies in adapting to novel, difficult tasks. This information can be extended to give insight into new and different areas to focus on during gait rehabilitation of humans suffering from motor control deficits in movement and gait.

This study uses ultrasound to image onset velar stop consonant articulation in words. By examining tongue body placement, the extent of velar closure variation across vowel contexts provides for the measurement of anticipatory coarticulation while productions within the same vowel context provide measurement of extent of token-to-token variation. Articulate Assistant Advanced 2.0 software was used to semi-automatically generate midsagittal tongue contours at the initial point of maximum velar closure and was used to fit each contour to a curved spline. Patterns of lingual coarticulation and measures of speech motor stability, based on curve-to-curve distance (Zharkova, Hewlett, & Hardcastle, 2011), are investigated to compare the speech of typically fluent speakers to the speech of people who stutter. Anticipatory coarticulation can be interpreted as a quantitative measure indicating the maturity of the speech motor system and its planning abilities. Token-to-token variability is examined from multiple velar vowel productions within the same vowel context, describing the accuracy of control, or stability, of velar closure gestures. Measures for both speaking groups are examined across the lifespan at stages during speech development, maturation, and aging. Results indicate an overall age effect, interpreted as refinement, with increased speech stability and progressively more segmental (less coarticulated) productions across the lifespan. A tendency toward decreased stability and more coarticulated speech was found for younger people who stutter, but this difference was small and absent among older adults. Outcomes of this study suggest the articulatory maturation trajectories of people who stutter may be delayed, but overall maturation of the speech mechanism is evident by older adulthood for typically fluent speakers and those who stutter. Applications to intervention are discussed in closing.

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

Motor noise and redundancy are vexing issues in motor control; yet their understanding provides great insights on underlying control mechanisms that govern movement. They provide glimpses into how the nervous system organizes and regulates movement within the motor control system. Understand of motor control could spur new advances in motor control could lead to better development of rehabilitation process and technology to counteract debilitating affects of neuromuscular disorders and motor readjustment with prostheses. However, before such process and technology could be developed and adapted for clinical use, a deeper understanding of motor control is needed to unravel the neural roadmap that regulates and generates movement. New theory of motor control could precipitate the development of more robust control mechanisms for robotic-human interaction. This work aims at expanding a more rigorous analytical and mathematical framework to understand how these control mechanisms reconcile redundancy and stochastic noise in human motor control. / text