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<p> The performance index in teleoperation, transparency, is often defined as linear scaling of force and position between the master/ operator and slave/ environment. Motivated by applications involving soft tissue manipulation such as robotic surgery, the transparency objective is generalized in this thesis to include static nonlinear and linear-time-invariant filter mappings between the master I slave position and force signals. Lyapunov-based adaptive motion/ force controllers are proposed to achieve the generalized transparency objectives. Using Lyapunov stability theory the mapped position and force tracking errors are shown to converge in the presence of dynamic uncertainty in the master I slave robots and user I environment dynamics. Given a priori known bounds on unknown dynamic parameters, a framework for robust stability analysis is proposed that uses stability of Lur'ePostinkov systems and Nyquist/Bode envelopes of interval plant systems. Methods for finding the required Nyquist/Bode envelopes are presented in this thesis. A comprehensive stability analysis is performed under different sets of generalized mappings. For nonlinear mapping of either position or force, robust stability depends on stability of an equivalent Lur'e-Postinikov system. Stability results of such systems are discussed in this thesis. In particular, the on and off-axis circle theorems are utilized. Using these theorems, sufficient teleoperation stability regions are obtained that are far less conservative than those obtained from passivity. In the special case of LTI filtered force and position mappings the exact robust stability regions are obtained by showing stability of the relevant closed-loop characteristic polynomial. The proposed robust stability test uses the phase values of a limited set of extremal polynomials. </p> <P> To demonstrate the utility of the generalized performance measures, a stiffness discrimination tele-manipulation task is considered in which the user compares and contrasts the stiffness of soft environments via haptic exploration in the presence and absence of visual feedback. Using adaptive psychophysical perception experiments a nonlinear force mapping is shown to enhance stiffness discrimination thresholds. The design guidelines for this enhanced nonlinear force mapping are reported in this thesis. Generalized nonlinear and linear filtered mappings are achieved in experiments with a two-axis teleoperation system where the details of implementation are given. </p> / Thesis / Master of Applied Science (MASc)

Low back pain (LBP) is a substantial secondary disability among persons with lower-limb amputation (LLA). Abnormal mechanics of movement subsequent to LLA may increase the stability demands on the spinal column, and repetitive exposures to such abnormal movements may alter trunk passive properties and/or the coordination of surrounding trunk muscle responses. Further, preferential use of the sound limb may lead to asymmetries in these behaviors. Spine biomechanics (e.g., loading and stability) are substantially influenced by trunk passive properties and neuromuscular control, and alterations in these behaviors are associated with abnormal mechanics of the spinal column and an increased LBP risk. However, there is limited evidence regarding whether prolonged repeated exposures to abnormal gait and movement resulting from LLA and subsequent repeated use of a prosthetic device affect these trunk behaviors. Eight males with unilateral LLA and a matched sample of non-amputation controls completed three studies in which several measures of trunk passive properties, neuromuscular control, and spine biomechanics were quantified using laboratory experiments and biomechanical analyses. Each study involved a distinct task to investigate potential alterations and/or asymmetries in trunk passive properties and neuromuscular control. The first study used a seated balance task to assess trunk postural control and stability. The second study used multidirectional trunk perturbations to assess trunk mechanical and neuromuscular behaviors. Finally, the third study used controlled quasi-static trunk movements to assess load-sharing mechanisms between active and passive low back tissues. Significant alterations and asymmetries in trunk passive properties and trunk neuromuscular responses were present among participants with LLA, specifically reduced and asymmetric trunk stiffness and reflex response; decreased and asymmetric passive contributions to trunk movements; and increased trunk muscle activities. Significant increases in trunk postural sway and trunk muscle activities were also present during seated stability measures. Such alterations in these behaviors may be a result of repetitive exposures to abnormal gait and movement subsequent to LLA and the use of a prosthetic device, and could play a contributing role in the development of LBP in this population. Future work should investigate the temporal relationship between altered trunk behaviors and repeated exposure to abnormal gait and movement subsequent to LLA, to better identify critical years for rehabilitation and preventative care. / Ph. D.

Tensegrity structures consist of isolated compression members (rigid bars) suspended by a continuous network of tension members (cables). Tensegrity structures can be used as variable geometry truss (VGT) mechanisms by actuating links to change their length. This paper will present a new method of position finding for tensegrity structures that can be used for actuation as VGT mechanisms. Tensegrity structures are difficult to understand and mathematically model. This difficulty is primarily because tensegrity structures only exist in specific stable tensegrity positions. Previous work has focused on analysis based on statics, dynamics, and virtual work approaches. This work considers tensegrity structures from a kinematic viewpoint. The kinematic approach leads to a better understanding of the conditions under which tensegrity structures exist in the stable positions. The primary understanding that comes from this kinematic analysis is that stable positions for tensegrity structures exist only on the boundaries of nonassembly of the structure. This understanding also allows the tensegrity positions to be easily found. This paper presents a method of position finding based on kinematic constraints and applies that method to several example tensegrity structures. / Master of Science

Determining the locations of devices in mobile ad-hoc networks (MANETs), wireless sensor networks (WSNs), and cellular networks has many important applications. In MANETs, which are useful in disaster recovery, rescue operations, and military communications, location information is used to enable location-aided routing and geodesic packet forwarding. In WSNs, whose applications include environmental monitoring (e.g., for precision agriculture) and asset tracking in warehouses, not only is location information useful for the self-organization of the network, but in addition, tying locations to the sensor observations is crucial for adding meaning to the sensed data. In cellular networks, location information is used to provide subscribers with location-based services in addition to providing public service answering points with potentially life-saving location information during emergency calls. These applications are largely not new, which is evidenced by the fact that the literature is quite rich with localization studies presented over the span of many years. Because of this, it may be surprising to learn that there is a lack of analyses concerning the fundamental factors impacting localization performance. Fundamentally, localization performance depends upon three factors: (i) the number of devices participating in the localization procedure, (ii) the locations of the participating devices, and (iii) the quality of the positioning observations gathered from the participating devices. For the most part, these factors cannot reasonably be considered deterministic. Instead, at any point in time, random effects within a network and its surroundings will determine these factors for individual positioning scenarios. Unfortunately, there are currently no analytical approaches for characterizing localization performance over these random factors. Instead, researchers either provide analytical results for a deterministic set of factors or use complex system-level simulations to obtain general performance insights. While the latter certainly averages over the random factors, the validity of the results is limited by the simulation assumptions. Any change in a network parameter requires running a new time-consuming simulation. In this dissertation, we address current deficiencies in several ways. We present a new model for tractably analyzing network localization fundamentals. This is demonstrated through fundamental analyses of hearability and geometry. Further, collaboration among non-reference devices has recently garnered increasing interest from the research community as a means to (i) improve positioning accuracy and (ii) improve positioning availability. We present fundamental analyses of both of these potential benefits. As a result of our work, we not only characterize several key performance metrics, we also demonstrate that there exist new tractable ways to analyze localization performance. / Ph. D.

No / Almost all studies in health research control or investigate socioeconomic position (SEP) as exposure or confounder. Different measures of SEP capture different aspects of the underlying construct, so efficient methodologies to combine them are needed. SEP and ethnicity are strongly associated, however not all measures of SEP may be appropriate for all ethnic groups. Methods We used latent class analysis (LCA) to define subgroups of women with similar SEP profiles using 19 measures of SEP. Data from 11,326 women were used, from eight different ethnic groups but with the majority from White British (40%) or Pakistani (45%) s, who were recruited during pregnancy to the Born in Bradford birth cohort study. Results Five distinct SEP subclasses were identified in the LCA: (i) "Least socioeconomically deprived and most educated" (20%); (ii) "Employed and not materially deprived" (19%); (iii) "Employed and no access to money" (16%); (iv) "Benefits and not materially deprived" (29%) and (v) "Most economically deprived" (16%). Based on the magnitude of the point estimates, the strongest associations were that compared to White British women, Pakistani and Bangladeshi women were more likely to belong to groups: (iv) "benefits and not materially deprived" (relative risk ratio (95% CI): 5.24 (4.44, 6.19) and 3.44 (2.37, 5.00), respectively) or (v) most deprived group (2.36 (1.96, 2.84) and 3.35 (2.21, 5.06) respectively) compared to the least deprived class. White Other women were more than twice as likely to be in the (iv) "benefits and not materially deprived group" compared to White British women and all ethnic groups, other than the Mixed group, were less likely to be in the (iii) "employed and not materially deprived" group than White British women. Conclusions LCA allows different aspects of an individual’s SEP to be considered in one multidimensional indicator, which can then be integrated in epidemiological analyses. Ethnicity is strongly associated with these identified subgroups. Findings from this study suggest a careful use of SEP measures in health research, especially when looking at different ethnic groups. Further replication of these findings is needed in other populations.

Yes / When lying supine, due to the reaction force from the mattress acting mostly through the heel, an external knee-extension joint-torque is induced that keeps the knee fully extended. This torque becomes zero if the feet are hung over the end of the support. This study investigated, in patients with knee-osteoarthritis (knee-OA) who routinely sleep supine, whether a change to such a sleeping position would ameliorate the knee pain and associated physical problems they suffer. Patients were recruited (General-Practitioners Centre, UK) over a 9-month period; those eligible (51/70) were randomly allocated to an intervention (65% female; age 71.5 [11.3] yrs; BMI, 29.20 [5.54] kg/m2; knee-OA severity, 20 mild–mod/3 severe) or control group (63% female; age, 68.3 [9.7] yrs; BMI, 28.69 [5.51] kg/m2; knee-OA severity, 17 mild–mod/2 severe). The primary outcome was improvements (0 [worst] to 100 [best]) in knee pain at 3 months and was rated in the Knee-Injury-and-Osteoarthritis-Outcome-Score questionnaire (KOOS). Secondary outcomes were improvements (0–100) in the other four KOOS-subscales. There were no differences between groups in KOOS outcomes at baseline, and there were no changes in KOOS outcomes in the control group at 3 months. Relative to the baseline KOOS values in Knee-Pain (50.1), Symptoms (52.5), Activities-of-Daily-Living (53.8) and Quality-of-Life (31.5), were all seen to improve at 3 months in the intervention group (by between 11.9 and 12.9); however, when comparing to controls, only the improvements in the subscale Activities-of-Daily-Living (which improved by 12.2) were statistically significant. Findings indicate that for those with knee-OA who routinely sleep supine, sleeping with the feet over the end of the mattress (to prevent the knee being pushed into/held in full extension) can help ameliorate the physical problems they suffer.

Motion of an image across the retina degrades visual accuracy, thus eye position must be held stationary. The horizontal eye velocity-to-position neural integrator (PNI), located in the caudal hindbrain of vertebrates, is believed to be responsible since the neuronal firing rate is sustained and proportional to eye position. The physiological mechanism for PNI function has been envisioned to be either (1) network dynamics within or between the bilateral PNI including brainstem/cerebellar pathways or (2) cellular properties of PNI neurons. These hypotheses were investigated by recording PNI neuronal activity in goldfish during experimental paradigms consisting of disconjugacy, commissurectomy and cerebellectomy.In goldfish, the eye position time constant ([tau]) is modifiable by short-term (~1 hr) visual feedback training to either drift away from, or towards, the center of the oculomotor range. Although eye movements are yoked in direction and timing, disconjugate motion during [tau] modification suggested separate PNIs to exist for each eye. Correlation of PNI neural activity with eye position during disconjugacy demonstrated the presence of two discrete neuronal populations exhibiting ipsilateral and conjugate eye sensitivity. During monocular PNI plasticity, [tau] was differentially modified for each eye corroborating coexistence of distinct neuronal populations within PNI.The hypothesized role of reciprocal inhibitory feedback between PNI was tested by commissurectomy. Both sustained PNI activity and [tau] remained with a concurrent nasal shift in eye position and decrease in oculomotor range. [tau] modification also was unaffected, suggesting that PNI function is independent of midline connections.The mammalian cerebellum has been suggested to play a dominant role for both [tau] and [tau] modification. In goldfish, cerebellar inactivation by either aspiration or pharmacology both prevented and abolished [tau] modifications, but did not affect eye position holding. PNI neurons still exhibited eye position related firing and modulation during training.By excluding all network circuitry either intrinsic or extrinsic to PNI, these results favor a cellular mechanism as the major determinate of sustained neural activity and eye position holding. By contrast, while cerebellar pathways are important for sustaining large [tau] (>20s), they are unequivocally essential for [tau] modification.