A ball bearing is widely used in the precision machine, and the ball is its major component. The sphericity and the surface roughness of the ball significantly influence the bearing per-formance and reliability. First, this study considers the gyro-scopic effect and modifies the theoretical model of magnetic fluid grinding to analyze the kinematics characteristics of ball grinding process. According to the apparent changes in the spin angle and the shaft angular speed, the theoretical analysis qualitatively predicts the onset of skidding between contacts. Moreover, the gyroscopic effect is helpful to the randomizing for the ball motion. Second, the grinding trajectory on ball is theoretically analyzed for the new self-developed grinding machine to ob-tain the high efficiency and high precision grinding of balls. Results show that the grinding trajectory is uniform when the spin angle stably changes from 0 to 2p periodically.

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Farrokh Ayazi; Committee Member: Jennifer Michaels; Committee Member: Levent Degertekin; Committee Member: Paul Hasler; Committee Member: W. Marshall Leach. Part of the SMARTech Electronic Thesis and Dissertation Collection.

The ARIES Unmanned Underwater Vehicle (UUV) currently uses an Inertial Measurement Unit (IMU) with an inherent rotation rate error bias of 10 degrees/hour. Then need for a more accurate IMU for long term missions has led to the purchase of the Honeywell HG1700 IMU. The HG1700 is a ring laser gyroscope designed specifically as part of the navigation software in multiple U.S. missiles. The objective of this research is to perform numerous bench tests on the HG1700 to test its capabilities and to begin the process of implementing the IMU into the ARIES unmanned underwater vehicle. Specifically, the IMU is tested for correct setup configurations, angle of rotation accuracies, the rotation rate error bias, and positional accuracies. Also, guidelines for integrating the IMU with the current software in the ARIES vehicle are discussed.

Among the many safety hazards facing chainsaw operators, the phenomenon known as kickback is the most dangerous. Kickback occurs when the chain at the tip of the chainsaw is caused to stop abruptly, and transfers the energy of the cutting chain to motion of the saw. The saw will rotate backward toward the operator rapidly. The limited amount of published research on the topic of chainsaw kickback was conducted to develop standardized testing for consumer chainsaws. Modern chainsaws are equipped with safety measures such as low-kickback cutting chains and hand-guard braking mechanisms. These mechanisms have greatly improved the safety of chainsaws, but their inherent mechanical simplicity leaves room for improvement. The current work presents the research that analyzed the possible methods for detecting kickback electronically. Phase 1 of this work utilized a set of two accelerometers and a single gyroscope to determine if it is possible to distinguish a kickback event from normal cutting operations. A method for applying weighting coefficients to the three sensor readings, then summing the three signal values was optimized to obtain the greatest margin between kickback and normal cutting. The result of this study was that kickback is most easily identified by using only a gyroscope and setting a threshold. Phase 2 focused on detecting kickback as early as possible. Three methods were attempted: Signal Differentiation, a Simplified Bag of Words method, and applying a Support Vector Machine with selective undersampling and a stack of classifier vectors. Signal differentiation, while detecting the kickback events earlier, also suffered from many false positives. The Bag of Words method was unsuccessful in creating results different than the threshold method from Phase 1. The Support Vector Machine classification was able to detect kickback an average of 19.4 ms before the simple threshold method with no occurrence of either false positives or false negatives. This method is the most reliable and provides the greatest likelihood of detecting kickback early. / Graduation Date: 2013

Thesis (M.A. Sc.)--University of Toronto, 2004. / Adviser: Chris Damaren.

Thesis (M.S. in Astronautical Engineering)--Naval Postgraduate School, Dec. 2004. / Thesis Advisor(s): Brij N. Agrawal. Includes bibliographical references (p. 103-104). Also available online.

Thesis (M.S. in Applied Science (Physical Oceanography))--Naval Postgraduate School, June 2005. / Thesis Advisor(s): Anthony J. Healey, Edward B. Thornton. Includes bibliographical references (p. 49). Also available online.

This study investigates energy harvesting characteristics from a spinning device that consists of a proof mass that is supported by two orthogonal elastic structures with the piezoelectric material. Deformation in the piezoelectric structures due to vibration of the proof mass generates voltages to power electrical loads. The governing equations for this electromechanically coupled device are derived using Newtonian mechanics and Kirchhoff's voltage law. The case where the device rotates at a constant speed and is subjected to sinusoidal base excitation is examined in detail. The energy harvesting behavior is investigated for devices with identical piezoelectric support structures (called tuned devices). Closed-form expressions are derived for the steady state response and power harvested. For nonzero rotation speeds, these devices have multifrequency dynamic response and power harvested due to the combined vibration and rotation of the host system. The average power harvested for one oscillation cycle is calculated for a wide range of operating conditions to quantify the devices' performance. Resonances do not occur for cases when the base excitation frequency is fixed and the rotation speed varies. For cases of fixed rotation speed and varying base excitation frequency, however, resonances do occur. The number and location of these resonances depend on the electrical circuit resistances and rotation speed. Resonances do not occur at speeds or frequencies predicted by resonance diagrams, which are commonly used in the study of rotating system vibration. These devices have broadband speed energy harvesting ability. They perform equally well at high and low speeds; high speeds are not necessary for their optimal performance. The impact of the chosen damping model on energy harvesting characteristics for tuned devices is investigated. Two common damping models are considered: viscous damping and structural (hysteretic) damping. Closed-form expressions for steady state dynamic response and power harvested are derived for models with viscous and structural damping. The average power harvested using the model with structural damping behaves similarly at high speeds and low speeds, and at high resistances and low resistances. For the viscous damping model, however, the average power harvested is meaningfully different at high speeds compared to low speeds, and at high resistances compared to low resistances. The characteristics of devices with nonidentical piezoelectric support structures (called mistuned devices) are investigated numerically. Similar to spinning tuned devices, mistuned devices have multifrequency dynamic response and power harvested. In contrast to tuned devices, high amplitude average power harvested occurs near speeds and base excitation frequencies predicted by resonance diagram.

In this master thesis the gyroscopic stabilization of a two-wheeled amphibious concept vehicle is investigated. The key idea is to neutralize external torques applied on the vehicle by the counter torque produced from the two gyroscopes attached on the vehicle. Here the gyroscopes are used as actuators, not as sensors. When a torque is applied in order to rotate a gyroscope whose flywheel is spinning, then the gyroscope precesses and it generates a moment, orthogonal to both the torque and the spinning axis. This phenomenon is known as gyroscopic precession. As the vehicle leans from its upright position we expect to generate sufficient gyroscopic reaction moment to bring the vehicle back and get it stabilized.   We first derive the equations of motion based on Lagrangian mechanics. It is worth mentioning that we only consider the control dynamics of a static vehicle. This is the so called regulator problem where we try to counteract the effects of disturbances. The trajectory tracking (servo problem) and the water-travelling can be considered as an extension of the current project. We linearize the dynamics around an equilibrium and we study the stability of the linearized model. We then design an LQG controller, a Glover-McFarlane controller and a cascade PID controller. Regarding the implementation part, we only focus on the cascade PID controller. The results from both simulations and experiments with a small-scale prototype are presented and discussed. / <p>MARINTEKNIKDAGAR PÅ KTH 2015</p>

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