Thesis (Ph. D.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 174-192). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 53-58). Also available on the World Wide Web.

Mechanical compliance will be an essential component for agile robots as they begin to leave the laboratory settings and join our world. The most crucial finding of this dissertation is showing how lessons learned from soft robotics can be adapted into traditional robotics to introduce compliance. Therefore, it presents practical knowledge on how to build soft bodied sensor and actuation modules: first example being soft-bodied curvature sensors. These sensors contain both standard electronic components soldered on flexible PCBs and hyperelastic materials that cover the electronics. They are built by curing multi-material composites inside hyper elastic materials. Then it shows, via precise sensing by using magnets and Hall-effect sensors, how closed-loop control of soft actuation modules can be achieved via proprioceptive feedback. Once curvature sensing idea is verified, the dissertation describes how the same sensing methodology, along with the same multi-material manufacturing technique can be utilized to construct soft bodied tri-axial force sensors. It shows experimentally that these sensors can be used by traditional robotic grippers to increase grasping quality. At this point, I observe that compliance is an important property that robots may utilize for different types of motions. One example being Raibert's 2D hopper mechanism. It uses its leg-spring to store energy while on the ground and release this energy before jumping. I observe that via soft material design, it would be possible to embed compliance directly into the linkage design itself. So I go over the design details of an extremely lightweight compliant five-bar mechanism design that can store energy when compressed via soft ligaments embedded in its joints. I experimentally show that the compliant leg design offers increased efficiency compared to a rigid counterpart. I also utilize the previously mentioned soft bodied force sensors for rapid contact detection (~5-10 Hz) in the hopper test platform. In the end, this thesis connects soft robotics with the traditional body of robotic knowledge in two aspects: a) I show that manufacturing techniques we use for soft bodied sensor/actuator designs can be utilized for creating soft ligaments that add strength and compliance to robot joints; and b) I demonstrate that soft bodied force sensing techniques can be used reliably for robotic contact detection.

Legged locomotion provides robots with the capability of adapting to different terrain conditions. General complex terrain traversal methodologies solely rely on proprioception which readily leads to instability under dynamical situations. Biological legged locomotion utilizes somatosensory feedback to sense the real-time interaction of the feet with ground to enhance stability. Nevertheless, limited attention has been given to sensing the feet-terrain interaction in robotics. This project introduces a paradigm shift in robotic walking called sensitive walking realized through the development of a compliant bipedal platform. Sensitive walking extends upon the success of sensitive manipulation which utilizes tactile feedback to localize an object to grasp, determine an appropriate manipulation configuration, and constantly adapts to maintain grasp stability. Based on the same concepts of sensitive manipulation, sensitive walking utilizes podotactile feedback to enhance real-time walking stability by effectively adapting to variations in the terrain. Adapting legged robotic platforms to sensitive walking is not as simple as attaching any tactile sensor to the feet of a robot. The sensors and the limbs need to have specific characteristics that support the implementation of the algorithms and allow the biped to safely come in contact with the terrain and detect the interaction forces. The challenges in handling the synergy of hardware and sensor design, and fabrication in a podotactile-based sensitive walking robot are addressed. The bipedal platform provides contact compliance through 12 series elastic actuators and contains 190 highly flexible tactile sensors capable of sensing forces at any incident angle. Sensitive walking algorithms are provided to handle multi-legged locomotion challenges including stairs and irregular terrain.

Studien är skriven på uppdrag av den studerade organisationen och är en del i det förbättringsarbete som organisationens HR-funktion genomför. Uppdraget har syftat till att undersöka avdelningschefers uppfattning gällande behovet av HR-stöd i deras arbete. Syftet specificeras utifrån studiens tre forskningsfrågor; (1) Vilka HR-uppgifter ansvarar avdelningscheferna över i deras arbete? (2) Inom vilka HR-uppgifter anser sig avdelningscheferna ha behov av stöd? (3) Hur kan behovet av stöd bemötas enligt avdelningscheferna? Vi har genomfört 10 semistrukturerade intervjuer med organisationens avdelningschefer. Resultatet av vår studie har visat att av de sex HR-uppgifter som avdelningschefer utför önskas stöd i fyra av dessa. Behovet av stöd varierar mellan och inom specifik HR-uppgift och bemötandet av detta behov önskas enligt avdelningscheferna ske via tydliggörande av rollerna och utifrån tre former av stöd; rådgivnings-, kunskaps- och avlastningsstöd. En organisering av HR bör därför bottna i vilket behov linjecheferna har utifrån vardera stödform och hur dessa kan variera. En förutsättning för detta är att  goda relationer skapas så att HR upplevs som tillgängliga där rollerna och förväntningarna är uttalade.

The ontogeny of the enzyme LDH has been studied in two species of amphibians (Amblystoma gracile and Rana aurora) as it provides a sensitive gauge of the state of differentiation of the organism, since the number and proportions of LDH isozymes present exhibit temporal and species specificity, thereby reflecting the degree of activity of the controlling genes. The presence of LDH in all stages of both species examined was established by assaying embryo homogenates for LDH activity, and the LDH was resolved into isozymic patterns by the methods of starch gel and disc electrophoresis. Specific enzyme activity for each developmental stage was correlated with the morphological events then occurring and the isozyme patterns obtained were discussed in terms of showing an increase in complexity during ontogeny and in terms of the current LDH isozyme hypothesis. A modified hypothesis was advanced to account for some of the experimental findings. / Science, Faculty of / Zoology, Department of / Graduate

High-performing legged robots require complex spatial leg designs and controllers to simultaneously implement propulsion, maneuvering and stabilization behaviors. Looking to nature, tails assist a variety of animals with these functionalities separate from the animals' legs. However, prior research into robotic tails primarily focuses on single-mass pendulums driven in a single plane of motion and designed to perform a specific task. In order to justify including a robotic tail on-board a legged robot, the tail should be capable of performing multiple functionalities in the robot's yaw, pitch and roll directions. The aim of this research is to study bioinspired articulated spatial robotic tails capable of implementing maneuvering and stabilization behaviors in quadrupedal and bipedal legged robots. To this end, two novel serpentine tails designs are presented and integrated into prototypes to test their maneuvering and stabilizing capabilities. Dynamic models for these two tail designs are formulated, along with the dynamic model of a previously considered continuum robot, to predict the tails' motion and the loading they will apply on their legged robots. To implement the desired behaviors, outer- and inner-loop controllers are formulated for the serpentine tails: the outer-loop controllers generate the desired tail trajectory to maneuver or stabilize the legged robot, and the inner-loop controllers calculate control inputs for the tail that implement the desired tail trajectory using feedback linearization. Maneuvering and stabilizing case studies are generated to demonstrate the tails' ability to: (1) generate yaw angle turning in both a quadruped and a biped, (2) improve the quadruped's ability to reject an externally applied roll moment disturbance that would otherwise destabilize it, and (3) counteract the biped's roll angle instability when it lifts one of its legs (for example, during its gait cycle). Tail simulations and experimental results are used to implement these case studies in conjunction with multi-body dynamic simulations of the quadrupedal and bipedal legged platforms. Results successfully demonstrate the tails' ability to maneuver and stabilize legged robots, and provide a firm foundation for future work implementing a tailed-legged robot. / Ph. D.

Bipedal robots offer a uniquely flexible platform capable of navigating complex, human-centric environments. This makes them ideally suited for a variety of missions, including disaster response and relief, emergency scenarios, or exoskeleton systems for individuals with disabilities. This, however, requires significant advances in humanoid locomotion and control, as they are still slow, unnatural, inefficient, and relatively unstable. The work of this dissertation the state of the art with the aim was of increasing the robustness and efficiency of these bipedal walking platforms. We present a series of control improvements to enable reliable, robust, natural bipedal locomotion that was validated on a variety of bipedal robots using both hardware and simulation experiments. A huge part of reliable walking involves maximizing the robot's control authority. We first present the development of a model predictive controller to both control the ground reaction forces and perform step adjustment for walking stabilization using a mixed-integer quadratic program. This represents the first model predictive controller to include step rotation in the optimization and leverage the capabilities of the time-varying divergent component of motion for navigating rough terrain. We also analyze the potential capabilities of model predictive controllers for the control of bipedal walking. As an alternative to standard trajectory optimization-based model predictive controls, we present several optimization-based control schemes that leverage more traditional bipedal walking control approaches by embedding a proportional feedback controller into a quadratic program. This controller is capable of combining multiple feedback mechanisms: ground reaction feedback (the "ankle strategy"), angular momentum (the "hip strategy"), swing foot speed up, and step adjustment. This allows the robot to effectively shift its weight, pitch its torso, and adjust its feet to retain balance, while considering environmental constraints, when available. To enable the robot to walk with straightened legs, we present a strategy that insures that the dynamic plans are kinematically and dynamically feasible to execute using straight legs. The effects of timing on dynamic plans are typically ignored, resulting in them potentially requiring significantly bending the legs during execution. This algorithm modifies the step timings to insure the plan can be executed without bending the legs beyond certain angle, while leaving the desired footsteps unmodified. To then achieve walking with straight legs we then presented a novel approach for indirectly controlling the center of mass height through the leg angles. This avoids complicated height planning techniques that are both computationally expensive and often not general enough to consider variable terrain by effectively biasing the solution of the whole-body controller towards using straighter legs. To incorporate the toe-off motion that is essential to both natural and straight leg walking, we also present a strategy for toe-off control that allows it to be an emergent behavior of the whole-body controller. The proposed approach was demonstrated through a series of simulation and experimental results on a variety of platforms. Model predictive control for step adjustment and rough terrain is illustrated in simulation, while the other step adjustment strategies and straight leg walking approaches are presented recovering from external disturbances and walking over a variety of terrains in hardware experiments. We discuss many of the practical considerations and limitations required when porting simulation-based controller development to hardware platforms. Using the presented approaches, we also demonstrated a important concept: using whole-body control frameworks, not every desired motion need be directly commanded. Many of these motions, such as toe-off, may simply be emergent behaviors that result by attempting to satisfy other objectives, such as desired reaction forces. We also showed that optimization is a very powerful tool for walking control, able to determine both stabilizing inputs and joint torques. / Ph. D.

Thesis (M.S.)--Humboldt State University, 2009. / Includes bibliographical references (leaves 44-46). Also available via Humboldt Digital Scholar.

According to documented statistics, intersections are among the most hazardous locations on roadway systems. Many studies have extensively analyzed safety of signalized intersections, but did not put their major focus on the most frequent type of intersections, unsignalized intersections. Unsignalized intersections are those intersections with stop control, yield control and no traffic control. Unsignalized intersections can be differentiated from their signalized counterparts in that their operational functions take place without the presence of a traffic signal. In this dissertation, multiple approaches of analyzing safety at unsignalized intersections were conducted. This was investigated in this study by analyzing total crashes, the most frequent crash types at unsignalized intersections (rear-end as well as angle crashes) and crash injury severity. Additionally, an access management analysis was investigated with respect to the different median types identified in this study. Some of the developed methodological techniques in this study are considered recent, and have not been extensively applied. In this dissertation, the most extensive data collection effort for unsignalized intersections was conducted. There were 2500 unsignalized intersections collected from six counties in the state of Florida. These six counties were Orange, Seminole, Hillsborough, Brevard, Leon and Miami-Dade. These selected counties are major counties representing the central, western, eastern, northern and southern parts in Florida, respectively. Hence, a geographic representation of the state of Florida was achieved. Important intersections' geometric and roadway features, minor approach traffic control, major approach traffic flow and crashes were obtained. The traditional negative binomial (NB) regression model was used for modeling total crash frequency for two years at unsignalized intersections. This was considered since the NB technique is well accepted for modeling crash count data suffering from over-dispersion. The NB models showed several important variables affecting safety at unsignalized intersections. These include the traffic volume on the major road and the existence of stop signs, and among the geometric characteristics, the configuration of the intersection, number of right and/or left turn lanes, median type on the major road, and left and right shoulder widths. Afterwards, a new approach of applying the Bayesian updating concept for better crash prediction was introduced. Different non-informative and informative prior structures using the NB and log-gamma distributions were attempted. The log-gamma distribution showed the best prediction capability. Crash injury severity at unsignalized intersections was analyzed using the ordered probit, binary probit and nested logit frameworks. The binary probit method was considered the best approach based on its goodness-of-fit statistics. The common factors found in the fitted probit models were the logarithm of AADT on the major road, and the speed limit on the major road. It was found that higher severity (and fatality) probability is always associated with a reduction in AADT, as well as an increase in speed limit. A recently developed data mining technique, the multivariate adaptive regression splines (MARS) technique, which is capable of yielding high prediction accuracy, was used to analyze rear-end as well as angle crashes. MARS yielded the best prediction performance while dealing with continuous responses. Additionally, screening the covariates using random forest before fitting MARS model was very encouraging. Finally, an access management analysis was performed with respect to six main median types associated with unsignalized intersections/access points. These six median types were open, closed, directional (allowing access from both sides), two-way left turn lane, undivided and mixed medians (e.g., directional median, but allowing access from one side only). Also, crash conflict patterns at each of these six medians were identified and applied to a dataset including median-related crashes. In this case, separating median-related and intersection-related crashes was deemed significant in the analysis. From the preliminary analysis, open medians were considered the most hazardous median type, and closed and undivided medians were the safest. The binomial logit and bivariate probit models showed significant median-related variables affecting median-related crashes, such as median width, speed limit on the major road, logarithm of AADT, logarithm of the upstream and downstream distances to the nearest signalized intersection and crash pattern. The results from the different methodological approaches introduced in this study could be applicable to diagnose safety deficiencies identified. For example, to reduce crash severity, prohibiting left turn maneuvers from minor intersection approaches is recommended. To reduce right-angle crashes, avoiding installing two-way left turn lanes at 4-legged intersections is essential. To reduce conflict points, closing median openings across from intersections is recommended. Since left-turn and angle crash patterns were the most dominant at undivided medians, it is recommended to avoid left turn maneuvers at unsignalized intersections having undivided medians at their approach. This could be enforced by installing a left-turn prohibition sign on both major and minor approaches.