No description available.

No description available.

No description available.

This thesis examines the neurobiological components of the motor control system and relates it to current control theory in order to develop a novel framework for models of motor control in the brain. The presented framework is called the Neural Optimal Control Hierarchy (NOCH). A method of accounting for low level system dynamics with a Linear Bellman Controller (LBC) on top of a hierarchy is presented, as well as a dynamic scaling technique for LBCs that drastically reduces the computational power and storage requirements of the system. These contributions to LBC theory allow for low cost, high-precision control of movements in large environments without exceeding the biological constraints of the motor control system.

This thesis examines the neurobiological components of the motor control system and relates it to current control theory in order to develop a novel framework for models of motor control in the brain. The presented framework is called the Neural Optimal Control Hierarchy (NOCH). A method of accounting for low level system dynamics with a Linear Bellman Controller (LBC) on top of a hierarchy is presented, as well as a dynamic scaling technique for LBCs that drastically reduces the computational power and storage requirements of the system. These contributions to LBC theory allow for low cost, high-precision control of movements in large environments without exceeding the biological constraints of the motor control system.

The evolution of aircraft has led into a large increase in the demand for electrically integrated subsystems. Part of this demand is the transformation of a centralized hydraulic systems to independently operated electrical subsystems. The result of this overhaul will decrease aircraft weight, increase reliability, reduce aircraft lifetime maintenance and cost, and help to increase the control of power distribution. This thesis proposes the design methodology of a multi-pole permanent magnet (PM) motor with a capability to operate at high temperature. High temperature capability is one of the key requirements to implement electromechanical actuation for aircraft flight control, replace hydraulic actuation system, especially in tactical military aircraft, due to the hot environment and lack of heat sink. Temperature effects on motor materials are reviewed. The need for high power density is considered in the design. The motor design is confirm by ANYSYS RMXprt software. Along with the motor design, a voltage control method is also designed for the motor. Integrated electrical simulation results of the motor and controller to follow highly dynamic flight profiles are provided to show the stroke tracking, input power (including regenerative power), and winding copper loss. Experimentation set-up of EMA and experimental uncertainties are also discussed.

<p>The control of unimanual and bimanual tasks is a highly orchestrated process in which primary motor cortex (M1) and primary somatosensory cortex (SI) play key roles. While somatic cortices are known to aid in the control of hand movements, the neural mechanisms by which they act remain largely unknown. One mechanism which is thought to mediate the control of hand movements between bilateral M1s is called interhemispheric inhibition (IHI), a neurophysiological mechanism by which one M1 is able to inhibit the contralateral M1, reducing the occurrence of unwanted movements, or enabling the performance of two differing tasks. Previous research suggests that IHI may be one mechanism by which SI aids in the control of hand movements and this thesis further examined this relationship. Two experiments were performed to investigate the influence of SI on IHI. Experiment 1 investigated the effects of direct modulation of SI cortical excitability on IHI. Experiment 2 investigated the effects of peripheral somatosensory inputs on IHI. The collective results of Experiments 1 and 2 suggest that SI can indeed modulate IHI from either the cortical or peripheral level, with increases in IHI seen following either intervention. Further, it was found that SI selectively modulates only the short latency phase of IHI (SIHI) as well as that mixed afferent inputs were most effective in altering SIHI. The novel findings of this thesis suggest that SI is indeed capable of aiding in the control of motor outputs and thus may be a possible target in future rehabilitative strategies.</p> / Master of Science in Kinesiology

<p>Many daily motor tasks involve the precise control of both force level and motor timing. The neural mechanisms concurrently managing these movement parameters remain unclear, as the dominant focus of previous literature has been to examine each in isolation. As a result, little is understood regarding the contribution of various sensory modalities to force output and interval production in sequential motor tasks. This thesis uses a sequential force production task to investigate the roles of visual and somatosensory feedback in the timed control of force. In Chapter 2 we find that removal of visual force feedback resulted in specific force output errors, but leaves motor timing behavior relatively unaffected according to predictions of the two-level timing model by Wing and Kristofferson (1973). In Chapter 3, we show that force output errors exhibited in the absence of a visual reference may be related to the processing of reafferent somatosensation from self-generated force pulses. The results of Chapter 4 reveal evidence that force errors exhibited following visual feedback removal are consistent with a shift in the perceived magnitude of force output and that the direction of error may be determined by prior task constraints. In Chapter 5 we find evidence of effector-specificity in the processing of and compensation for reafferent somatosensation. Lastly, in Chapter 6 we find that the interplay between audition and somatosensation in the control of sound level by the vocal effectors resembles that which is observed between vision and somatosensation in the control of force by the distal effectors.</p> / Doctor of Philosophy (PhD)

<p>Maintaining upright posture is seemingly an automatic task in younger adults, but it may require additional resources in late adulthood due to decreases in sensorimotor and cognitive functions. The thesis used a dual-task paradigm to investigate age-related changes in relation to the secondary task and context-dependent factors attributes to postural control. The postural task involved visuomotor tracking. Successfully performing the visuomotor task necessitated proper sensory feedback, motor response, and sensorimotor integration. Moreover, we used silent counting as a cognitive task to investigate attentional demands on postural control and age-related difference in cognitive processing.</p> <p>We first investigated the relative contributions of visual feedback delay and cognitive task load on postural dynamics as well as age-related difference in this effect. Our results supported distinct timescale mechanisms for postural control. Moment-to-moment center of pressure fluctuations are dependent on cognitive performance during delayed visual feedback postural control. Also, we demonstrated the increased role of vision with age in postural control. Next, we investigated whether postural control improved when performing a cognitive task with an internal focus of attention. We found that devoting less attention internally by performing a cognitive dual-task enhanced postural control in young adults. Yet, the age-related declines diminish the attentional allocation ability. Lastly, we investigated how older and younger adults differ in employing sensorimotor strategies in a dual-task situation. Our results suggested that age-related changes in postural control may degrade the flexible coordination of the sensory feedback and motor execution. Furthermore, diminished cognitive and attentional capacities may alter postural performance in dual-task conditions.</p> <p>This thesis adds to the current understanding of the role of sensorimotor processing, attentional influence and age in the control of posture. Our data provide convergent evidence that deterioration of peripheral sensorimotor systems and reduced flexibility in central information processing are responsible for the age-related differences in postural control. <strong></strong></p> / Doctor of Philosophy (PhD)

<p>The primary somatosensory cortex (SI) is important for hand function and influences motor circuitry in the primary motor cortex (M1). Areas 3a, 1 and 2 of SI have direct connectivity with M1. Much of our present knowledge of this connectivity and its relevance to hand function is based on animal research. However, less is known about the neural mechanisms that underpin hand function in humans. The present study investigated the influence of SI on corticospinal excitability as well as inhibitory and excitatory neural circuitry within M1 before and after continuous theta-burst stimulation (cTBS). Additionally, stimulation parameters influence the direction and magnitude of cTBS after-effects. Thus, current direction and frequency of cTBS were manipulated. Two experiments were performed. In Experiment 1, motor-evoked potentials (MEPs) were recorded from the first-dorsal interosseous (FDI) muscle bilaterally before and after 50 Hz cTBS over left SI. In a second condition, the orientation of cTBS was reversed. Experiment 2 measured MEPs, short-latency intracortical inhibition (SICI) and intracortical facilitation (ICF) from the right FDI following a modified 30 Hz cTBS over left SI or M1. The results of Experiment 1 and 2 demonstrate that SI influences M1 circuitry such that MEPs are facilitated following cTBS over SI. However, MEPs are suppressed when the current direction is reversed. CTBS at 30 Hz delivered over M1 suppressed excitatory circuitry that generates MEPs and ICF. The findings from the thesis suggest that SI influences hand motor circuitry and is likely a mechanism by which somatosensory information modulates hand motor function.</p> / Bachelor of Science (BSc)