Many a robotic pitch-roll wrist uses a bevel-gear differential train to drive the gripper. The innovative design of pitch-roll wrists using spherical cam-roller pairs is currently underway at McGill University's Centre for Intelligent Machines, with the aim of overcoming the drawbacks of bevel-gear trains. This innovative design relies on Speed-o-Cam, a new concept of speed-reduction mechanisms based on cams and pure-rolling contact, intended to replace gears and harmonic drives in applications where backlash, friction, and flexibility cannot be tolerated. The new mechanism consists mainly of a spherical conjugate cam subassembly and two roller-carrying disks. / We start with a study of cam curvature, with special focus on its machinability. Drawing from experience, we introduce the hypothesis that high curvature changes of a cam profile are at the source of the concentration of machining errors. As a consequence, the machining accuracy of the concave regions in a cam profile is substantially lower than that of its convex regions. To produce a more accurate cam we developed the geometric condition that guarantees a fully convex spherical cam profile. / The optimum design of the pitch-roll mechanism based on cam-roller pairs is reported here. The optimization is intended to simplify the subassembly of spherical conjugate cams of the old design by means of a layout of two pairs of spherical mechanisms of the Stephenson type and two conjugate cams mounted on distinct shafts. We focus on the optimum design of both the spherical cam-roller mechanism and the spherical Stephenson mechanism.

The Large Adaptive Reflector is a Canadian design for a new radio telescope. The receiver is held at the focus of the reflector by an aerostat tethered to the ground by multiple tethers. One of the main goals in the design of this system is the minimization of the motion of the receiver. Most perturbations are produced by the action of the wind on the aerostat and transmitted to the confluence point via the leash that connects the aerostat to the receiver. For that reason, this work focused on leash-related stabilization techniques. Computer simulations were used to evaluate the benefits of different passive and active methods. Among the passive approaches studied were the use of a constant force spring and of a passive heave compensator. The active methods evaluated included aerostat pitch control and active heave compensation. One of the more promising approaches, a leash made of bungee cable, was evaluated experimentally on a prototype of the system in Penticton, BC. Finally, a pitch control mechanism was designed. This mechanism displaces the leash attachment point on the harness to pitch the aerostat nose up or down.

Kinematically redundant manipulators composed of a rigid-link, rigid-joint robot and a structurally flexible arm on top of which the former is located constitute a new paradigm of long-reach manipulation systems. In order to have the end-effector of such a system faithfully follow a preplanned path, one should be able to reliably monitor the motions of the flexible submanipulator due to its elastic deformations. To this end, it is proposed that redundant point-acceleration measurements made on the rigid-robot base be used in an extended Kalman filter to estimate the flexural states of the flexible submanipulator. More specifically, this is done by processing the above-mentioned acceleration data in a novel pose and twist estimation technique, formulated in this thesis, to obtain those of the tip of the flexible arm; the pose and the twist data are then utilized as the measured outputs for the observer. Of course, the state-output relations should be linearized; the linearization is performed in closed-form. / The mathematical models of the flexible and the rigid submanipulators are derived separately, each through the premultiplication of the transpose of the kinematic-constraint matrix by the assembled set of the link Lagrange equations; this matrix is the natural orthogonal complement of the kinematic-constraint wrench. Obviously, the reaction wrench acting between the rigid-robot base and the end-effector of the flexible submanipulator couples the two sets of dynamics equations. This wrench can be determined by substituting the twist-rate of the base, i.e., its angular and translational accelerations, into the dynamics equations of the rigid submanipulator and, subsequently, solving them. Then, considering the wrench as a time-dependent input for the flexible arm, we take the flexible-arm dynamics as the modelled dynamics in the observer. The reduced-order dynamics helps dramatically reduce the required floating-point operations within the observer. / Two redundancy-resolution techniques, namely, rigid-link redundancy resolution and flexible-link redundancy resolution, are discussed. Whereas the former assumes all the links to be rigid, the latter takes the flexibility effects into account. In both approaches, the self-motion of the system is computed so as to minimize the forces exciting its lowest "modal coordinates" while imposing a proportional damping on the flexural dynamics.

Thermoforming is a process of forming thermoplastic sheets into three-dimensional shapes by heating it to tender soft and pliable, and then, forcing the sheet into or over the shape of a mold by applying differential pressure or vacuum. Sheet reheat is the most important step in thermoforming because its result can affect all subsequent processing steps. In order to develop an advanced in-cycle and cycle-to-cycle control strategy, one needs to track the desired sheet temperature profiles throughout the reheat cycle, and identify and characterize the process and material parameters that vary from cycle-to-cycle and batch-to-batch. Absorptivity of the polymer sheet material and the heat flux incident on the sheet are the two important factors that need to be monitored and estimated properly in order to integrate into the absorptivity based model for the sheet reheat phase. Estimation of the heat flux can be used to generate the heat gain matrix relating the energy given to the heating elements and temperature of the sheet. This thesis develops methods to estimate absorptivity and heat flux in order to improve model based control systems.

Morphological and clinical signs of lumbar intervertebral disc disruption are pronounced in the posterior and postero-lateral inner annulus fibrosus. The regional intervertebral disc predisposition to disruption suggests that intradiscal stresses and strains may also be region specific and possibly initiate the disruption. Quantitative data describing intradiscal deformations have been limited to the mid-sagittal plane using techniques that compromise the intervertebral disc integrity. No experimental study has quantified intradiscal strain patterns. The initial objectives of the present work were to use experimental cadaveric methods and finite element techniques to develop and validate methods of measuring intradiscal deformations and strains along the complete mid-transversal plane using a fine wire grid. / Subsequently, these methods were used to quantify intradiscal deformations and strains in healthy and degenerated intervertebral discs during sub-maximal loads. Eighteen healthy and degenerated intervertebral discs were subjected with wires placed within and beads glued along their mid-traversal plane surface, to compression, extension, flexion and lateral bending. Cramo-caudal radiographs at unloaded and loaded steps documented wire and bead positions. Intradiscal nucleus pulposus displacements, circumferential, radial and shear strains in the annulus fibrosus and transitional zone under load were compared among all anatomical regions and between healthy and degenerated intervertebral discs. / The methods develop to estimate intradiscal strains from intradiscal wire intersection displacements demonstrated a relative overall accuracy of 2.9% (i.e. percent error from theoretical estimations). Generally, intradiscal circumferential and radial strains decreased from the transitional zone to the annulus fibrosus and increased at the side of bending during all bending conditions. Circumferential and radial strain peaks were observed in the postero-lateral regions even in healthy intervertebral discs during extension and lateral bending. Shear strains were generally uniform within the healthy intervertebral disc. Degeneration significantly increased intradiscal circumferential, radial and shear strains during all bending conditions (particularly in the postero-lateral regions). The increased nucleus pulposus migration in degenerative intervertebral discs appeared to have caused the increases in circumferential and radial strains and to some extent perhaps increases in shears strains. / The inner postero-lateral annulus fibrosus is predisposed to excessive normal circumferential and radial strains early on which coincide with morphological changes observed in the same regions. This observation suggests a predisposition to failure likely due to an inability of resisting delaminating normal strains. Furthermore, the increased nucleus pulposus migration observed in degenerated intervertebral discs appears to shift the pivot point during bending movements more posterior, which consequently forces the postero-lateral regions to consistently experience higher circumferential and radial strains. These effects may contribute to the segmental instability observed in degenerated motion segments prior to intervertebral disc failure.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 1246. Adviser: Jonathan Dantzig. Includes bibliographical references (leaves 123-129) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 1250. Adviser: C. Liu. Includes bibliographical references (leaves 179-184) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 1262. Adviser: Anthony M. Jacobi. Includes bibliographical references (leaves 110-116) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 1274. Adviser: Anthony M. Jacobi. Includes bibliographical references (leaves 102-109) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 1277. Adviser: Joseph Bentsman. Includes bibliographical references (leaves 184-187) Available on microfilm from Pro Quest Information and Learning.