A computational neural and biomechanical system for human bicycle pedaling is developed in order to study the interaction between the central nervous system and the biomechanical system. It consists of a genetic algorithm, artificial neural network, muscle system, and skeletal system. Our first finding is that the genetic algorithm is a robust tool to formulate human movement. We also find that our developed models are able to handle mechanical perturbation and neural noise. In addition, we observe variability and repeatability of pedaling motion with or without perturbation and noise. Movement phase dependent feedback nature is seen through computation too. This system shows many human movement qualities and is useful for further neural and motor control investigations. / text

One of the greatest challenges in controlling robotic hands is grasping and manipulating objects in unstructured and uncertain environments. Robotic hands are typically too rigid to react against unexpected impacts and disturbances in order to prevent damage. The human hands have great versatility and robustness due, in part, to the passive compliance and damping. Designing mechanical elements that are inspired by the nonlinear joint compliance of human hands is a promising solution to achieve human-like grasping and manipulation. However, the exact role of biomechanical elements in realizing joint stiffness is unknown. We conducted a series of experiments to investigate nonlinear stiffness and damping of the metacarpophalangeal (MCP) joint at the index finger. We designed a custom-made mechanism to integrate electromyography sensors (EMGs) and a motion capture system to collect data from 19 subjects. We investigated the relative contributions of muscle-tendon units and the MCP capsule ligament complex to joint stiffness with subject-specific modeling. The results show that the muscle-tendon units provide limited contribution to the passive joint compliance. This findings indicate that the parallel compliance, in the form of the capsule-ligament complex, is significant in defining the passive properties of the hand. To identify the passive damping, we used the hysteresis loops to investigate the energy dissipation function. We used symbolic regression and principal component analysis to derive and interpret the damping models. The results show that the nonlinear viscous damping depends on the cyclic frequency, and fluid and structural types of damping also exist at the MCP joint. Inspired by the nonlinear stiffness of the MCP joint, we developed a miniaturized mechanism that uses pouring liquid plastic to design energy storing elements. The key innovations in this design are: a) a set of nonlinear elasticity of compliant materials, b) variable pulley configurations to tune the stiffness profile, and c) pretension mechanism to scale the stiffness profile. The design exhibits human-like passive compliance. By taking advantage of miniaturized joint size and additive manufacturing, we incorporated the novel joint design in a novel robotic manipulator with six series elastic actuators (SEA). The robotic manipulator has passive joint compliance with the intrinsic property of human hands. To validate the system, we investigated the Cartesian stiffness of grasping with low-level force control. The results show that that the overall system performs a great force tracking with position feedback. The parallel compliance decreases the motor efforts and can stabilize the system. / text

This is an interdisciplinary research project in which the methods of biomechanical and design engineering are focused upon a problem in orthopaedics. The anterior cruciate ligament (ACL) is the major ligament in the knee and is often torn during athletic competition as well as every day activity. The ACL is made up of two functional bundles, which help to stabilize the knee. Until recently, ACL reconstruction only replaced one of these bundles; however, research shows that both bundles should be replaced to more fully restore normal knee functionality. The aim of the research was, therefore, to evaluate the mechanical aspects of the double-tunnel-double-bundle ACL reconstruction technique. The research was directed towards designing a new and improved surgical device to improve ACL reconstruction: The current study used a computational model and experimental testing to explore the mechanical parameters of the tendon graft and knee bones to investigate the effects of double tunnel drilling in tibia and femur during ACL reconstruction. The thesis presents the findings of research into three aspects of double-tunnel-double-bundle ACL reconstruction. The first aspect of the study involves clinical and computational analysis of a single-tunnel-singlebundle (SB) ACL reconstructed knee with a double-tunnel-double-bundle (DB) ACL reconstructed example. The study tried to show the advantage of the DB technique over the conventional SB technique. The anatomical geometries of both SB and DB examples were used to create a finite element model and investigate the relative merits of single and double tunnelling, the variations of graft pretension, and tunnel placement on bone stress. The experimental and computational results of both methods were compared and discussed. The second study investigated whether tripling a tendon when using suspensory fixation provides inferior graft strength and a greater cyclical elongation than a doubled tendon graft with suspensory fixation. The tensile stress was found to be lower in the third strand than in the doubled portion. The study was focussed on the mechanical assessment of two different methods of tripling tendons when using suspensory fixation. The third aspect of the study focussed on the design of a new device for fixation of the femoral tripled tendon graft in DB ACL reconstruction technique. The study describes a series of designs and prototypes that were iteratively developed and experimentally tested, leading to a novel tripled tendon graft device. The function of the new device was compared with the conventional methods and tested with a number of animal tendons and bones. The new device with a tripled tendon graft resulted in higher pull-out strength and less graft elongation than that seen using a conventional tripling method.

No description available.

Posterior pedicle screw and rod fixation has become standard in the treatment of oncological resections requiring stabilization, deformity correction and unstable thoracolumbar fractures. Given the high mechanical stress at the points of highest instability, some clinicians have utilized dual rods on each side to augment the construct. The added advantage of this type of construct has not been previously evaluated in-vitro. The goal of this study is to evaluate the biomechanical advantage of a dual rod construct in the thoracolumbar spine, using a burst fracture cadaveric model. Methods: Seven fresh human cadaveric (T9-L3) spines were tested in normal conditions, after an iatrogenic T12 burst fracture, and successively after laminectomy and standard two rod pedicle screw stabilization (two level above and two below) and two different dual rod overlapping constructs. Pure moment torque was applied quasistatically, while 3D motion was measured optoelectronically. Thoracolumbar range of motion was measured during flexion, extension, left / right lateral bending, and left / right axial rotation. Results: All constructs significantly stabilized the simulated burst fracture in all modes of testing. There was no statistically significant difference, however, in the ability to restrict motion between the 3 different constructs, either from T10-L2, or across the fracture segment of T11-L1. Conclusions: There does not appear to be a biomechanical advantage to using dual rods over standard single rods for immediate fixation in an unstable segment. Whether dual rods protect the construct against long-term failure is not yet known.

Osseointegrated titanium implants have become a commonly used method in edentulous jaws and today there are success rates in the magnitude of 82 % in the lower jaw and 98 % in the upper. During first year after implantation a fully normal marginal bone loss of 1-2 mm occurs. If the bone loss continues there is a risk of implant failure. High tensions in bone and inflammation caused by bacteria are possible reasons for this problem. It has been shown that a leakage of bacterias occurs between the parts of the implant and there are theories that this has effects on the marginal bone loss. The aim of this thesis has been to increase the knowledge about microbial leakage with help of in vitro tests and virtual simulations. The goal was to create a test method to measure differences of microbial leakage in two implant systems. The developed test method includes an in vitro test of six implants and Finite Element Analysis. The test method is the product of a process with several small tests. The final test method measures leakage of a coloured fluid with a spectrophotometer. The results are then compared with the virtual simulations to draw conclusions and find explanations how the implants are functioning. The result of test on six implants, four Ospol and two Nobel Replace, indicates that there are differences in the magnitude of microleakage in different implant systems in due to the implant-abutment interface. No conclusions can be drawn before the test method is refined and more implants are tested.

Grip kinetics are emerging as an important measure in clinical assessments of handwriting pathologies and fine motor rehabilitation as well as in biometric and forensic applications. The signature verification literature in particular has extensively examined the spatiotemporal, kinematic, and axial pressure characteristics of handwriting, but has minimally considered grip kinetics. Therefore, the focus of this thesis was to investigate the variability of grip kinetics in adults during signature writing. To address this goal, a database of authentic and well-practiced bogus signatures were collected with an instrumented pen that recorded the forces applied to its barrel. Four different analytical studies were conceived. The first study investigated the intra- and inter-participant variability of grip kinetic topography on the pen barrel based on authentic signatures written over 10 days. The main findings were that participants possessed unique grip force topographies even when the same grasp pattern was employed and that participants could be discriminated from each other with an average error rate of 1.2% on the basis of their grip force topographies. The second study examined the stability of different grip kinetic features over an extended period of a few months. The analyses revealed that intra-participant variation was generally much smaller than inter-participant variations even in the long term. In the third study, grip kinetics associated with authentic and well-practiced bogus signatures were compared. Differences in grip kinetic features between authentic and bogus signatures were only observed in a few participants. The kinetics of bogus signatures were not necessarily more variable. The variation of grip kinetic profiles between participants writing the same bogus signature was evaluated in the fourth study and an average error rate of 5.8% was achieved when verifying signatures with kinetic profile-based features. Collectively, the findings of this thesis serve to inform future applications of grip kinetic measures in biometric, clinical and industrial applications.

<p> The purpose of this study was to evaluate energy expenditure (EE) during powered exoskeleton&ndash;assisted walking in persons with paraplegia. Five male participants with paraplegia, aged 37&ndash;61 years, were recruited for this study. Able&ndash;bodied (AB) subjects were matched for height (&plusmn;12.7 cm) weight (&plusmn;6.8 kgs) and age (&plusmn;5 yrs) were recruited to serve as a control group. EE measurements were obtained for 6 minutes while: seated, standing, walking, and seated recovery for three trials (Pre, Mid, Post) over 60 sessions. A portable metabolic cart was used to obtain all metabolic measurements. The results from this study suggest that over the course of 60 sessions, powered exoskeletal&ndash;assisted walking can: significantly improve an individual's oxygen consumption (p=0.04), significantly decrease RPE (p&lt;0.001), and significantly increase the distance traveled per 6MWT (p=0.02). These improvements may potentially further enhance the quality of life of persons with paraplegia. </p>

<p> Movement presents a unique challenge for snakes (suborder Serpentes), which utilize limbless locomotion to move in terrestrial and aquatic environments. Lateral undulation, the fastest and most commonly used type of snake locomotion, has been extensively studied in both contexts due to its prevalence in the animal kingdom. However, the effects of speed on locomotor kinematics have only been studied in aquatic conditions. During swimming, snakes are known to increase speed by increasing wavelength and amplitude while maintaining constant frequency. Additionally, amplitude in aquatic environments increases from the anterior to the posterior regions of the body. The mechanism for increasing speed in a terrestrial context is unknown, despite the fact that the majority of snakes reside in terrestrial areas. Therefore, I compared terrestrial locomotor kinematic data with existing aquatic swimming data to determine whether kinematic differences exist for increasing speed in different environments. In this study, Eastern Garter Snakes, <i>Thamnophis sirtalis </i> (<i>n</i>=4), were filmed utilizing lateral undulation at two different speeds with 120fps high-speed video. I examined speed effects on locomotion by conducting detailed comparisons of key kinematic and performance variables including wavelength, amplitude, frequency and segmental angles of the waves created during lateral undulation.</p><p> The speed effects of terrestrial locomotion were found to differ from aquatic locomotor pattern in wavelength; the mean wavelength observed in our terrestrial trials increased significantly as speed increased. Other variables, including frequency, amplitude and growth of amplitude from head to tail, exhibited similar patterns to aquatic locomotion. This study provides insight into the mechanisms by which snakes generate locomotor complexity from a simple body plan.</p>

Grip kinetics are emerging as an important measure in clinical assessments of handwriting pathologies and fine motor rehabilitation as well as in biometric and forensic applications. The signature verification literature in particular has extensively examined the spatiotemporal, kinematic, and axial pressure characteristics of handwriting, but has minimally considered grip kinetics. Therefore, the focus of this thesis was to investigate the variability of grip kinetics in adults during signature writing. To address this goal, a database of authentic and well-practiced bogus signatures were collected with an instrumented pen that recorded the forces applied to its barrel. Four different analytical studies were conceived. The first study investigated the intra- and inter-participant variability of grip kinetic topography on the pen barrel based on authentic signatures written over 10 days. The main findings were that participants possessed unique grip force topographies even when the same grasp pattern was employed and that participants could be discriminated from each other with an average error rate of 1.2% on the basis of their grip force topographies. The second study examined the stability of different grip kinetic features over an extended period of a few months. The analyses revealed that intra-participant variation was generally much smaller than inter-participant variations even in the long term. In the third study, grip kinetics associated with authentic and well-practiced bogus signatures were compared. Differences in grip kinetic features between authentic and bogus signatures were only observed in a few participants. The kinetics of bogus signatures were not necessarily more variable. The variation of grip kinetic profiles between participants writing the same bogus signature was evaluated in the fourth study and an average error rate of 5.8% was achieved when verifying signatures with kinetic profile-based features. Collectively, the findings of this thesis serve to inform future applications of grip kinetic measures in biometric, clinical and industrial applications.