Development of a digital electronic rebalance loop for a dry tuned-rotor two degree-of-freedom gyroscope

Digital electronic rebalance loops were designed and implemented in brassboard form to capture both X and Y axes of the Kearfott Gyroflex. The loops were width-modulated binary types using a 614.4 kHz keying signal and a 2.4 kHz sample frequency. The loops were designed for a torquing rate of 2 deg/sec (70.6 mA torquing current) and a data resolution of 23.4 milli-arc-sec per data pulse. Design considerations, implementation details, and preliminary experimental results are presented

The design and analysis of single flank transmission error tester for loaded gears

To strengthen the understanding of gear transmission error and to verify mathematical models which predict them, a test stand that will measure the transmission error of gear pairs under design loads has been investigated. While most transmission error testers have been used to test gear pairs under unloaded conditions, the goal of this report was to design and perform dynamic analysis of a unique tester with the capability of measuring the transmission error of gears under load. This test stand will have the capability to continuously load a gear pair at torques up to 16,000 in-lb at shaft speeds from 0 to 5 rpm. Error measurement will be accomplished with high resolution optical encoders and the accompanying signal processing unit from an existing unloaded transmission error tester. Input power to the test gear box will be supplied by a dc torque motor while the load will be applied with a similar torque motor. A dual input, dual output control system will regulate the speed and torque of the system. This control system's accuracy and dynamic response were analyzed and it was determined that proportional plus derivative speed control is needed in order to provide the precisely constant torque necessary for error-free measurement

The design and analysis of single flank transmission error testor for loaded gears

Due to geometrical imperfections in gears and finite tooth stiffnesses, the motion transmitted from an input gear shaft to an output gear shaft will not have conjugate action. In order to strengthen the understanding of transmission error and to verify mathematical models of gear transmission error, a test stand that will measure the transmission error of a gear pair at operating loads, but at reduced speeds would be desirable. This document describes the design and development of a loaded transmission error tester. For a gear box with a gear ratio of one, few tooth meshing combinations will occur during a single test. In order to observe the effects of different tooth mesh combinations and to increase the ability to load test gear pairs with higher gear ratios, the system was designed around a gear box with a gear ratio of two

A Two-Degree-Of-Freedom Time-Optimal Solution for Hard Disk Drive Servo Problems

This paper deals with the hard disk drive (HDD) servo problems. A novel discrete time-optimal control solution is proposed in a two-degree-of-freedom (2DOF) structure, employing both the feedback and feedforward controllers. The time-optimal feedback controller, derived from a simple, double integral plant model, shows remarkable robustness and disturbance rejection in the presence of resonant modes, measurement noises and position and torque disturbances. It eliminates the needs for two separate controllers for track-seeking and track-following operations. The proposed feedforward controller in this 2DOF structure proves to be quite beneficial in reducing the seek time. It also allows the feedback controller to be tuned more aggressively, which helps to improve the quality of track following. The proposed control scheme offers a novel basic control structure for HDD servo, upon which numerous further improvements can be made. It is successfully tested in simulation on an industrial 13.0-kTPI HDD

A Two-Degree-Of-Freedom Time-Optimal Solution for Hard Disk Drive Servo Problems

This paper deals with the hard disk drive (HDD) servo problems. A novel discrete time-optimal control solution is proposed in a two-degree-of-freedom (2DOF) structure, employing both the feedback and feedforward controllers. The time-optimal feedback controller, derived from a simple, double integral plant model, shows remarkable robustness and disturbance rejection in the presence of resonant modes, measurement noises and position and torque disturbances. It eliminates the needs for two separate controllers for track-seeking and track-following operations. The proposed feedforward controller in this 2DOF structure proves to be quite beneficial in reducing the seek time. It also allows the feedback controller to be tuned more aggressively, which helps to improve the quality of track following. The proposed control scheme offers a novel basic control structure for HDD servo, upon which numerous further improvements can be made. It is successfully tested in simulation on an industrial 13.0-kTPI HDD

Study of the generator/motor operation of induction machines in a high frequency link space power system

Static power conversion systems have traditionally utilized dc current or voltage source links for converting power from one ac or dc form to another since it readily achieves the temporary energy storage required to decouple the input from the output. Such links, however, result in bulky dc capacitors and/or inductors and lead to relatively high losses in the converters due to stresses on the semiconductor switches. The feasibility of utilizing a high frequency sinusoidal voltage link to accomplish the energy storage and decoupling function is examined. In particular, a type of resonant six pulse bridge interface converter is proposed which utilizes zero voltage switching principles to minimize switching losses and uses an easy to implement technique for pulse density modulation to control the amplitude, frequency, and the waveshape of the synthesized low frequency voltage or current. Adaptation of the proposed topology for power conversion to single-phase ac and dc voltage or current outputs is shown to be straight forward. The feasibility of the proposed power circuit and control technique for both active and passive loads are verified by means of simulation and experiment

A Multirate Control Strategy to the Slow Sensors Problem: An Interactive Simulation Tool for Controller Assisted Design

[EN] In many control applications, the sensor technology used for the measurement of the variable to be controlled is not able to maintain a restricted sampling period. In this context, the assumption of regular and uniform sampling pattern is questionable. Moreover, if the control action updating can be faster than the output measurement frequency in order to fulfill the proposed closed loop behavior, the solution is usually a multirate controller. There are some known aspects to be careful of when a multirate system (MR) is going to be designed. The proper multiplicity between input-output sampling periods, the proper controller structure, the existence of ripples and others issues need to be considered. A useful way to save time and achieve good results is to have an assisted computer design tool. An interactive simulation tool to deal with MR seems to be the right solution. In this paper this kind of simulation application is presented. It allows an easy understanding of the performance degrading or improvement when changing the multirate sampling pattern parameters. The tool was developed using Sysquake, a Matlab-like language with fast execution and powerful graphic facilities. It can be delivered as an executable. In the paper a detailed explanation of MR treatment is also included and the design of four different MR controllers with flexible structure to be adapted to different schemes will also be presented. The Smith's predictor in these MR schemes is also explained, justified and used when time delays appear. Finally some interesting observations achieved using this interactive tool are included.This work was supported in part by the Spanish Ministry of Economy and Competitiveness under Project DPI2012-31303. The authors J. Salt, A. Cuenca, are grateful to Grant TEC2012-31506, from the Spanish Ministry of Education. The work of A. Cuenca was supported in part by the Spanish Ministerio de Economia under Grant DPI2011-28507-C02-01.Salt Llobregat, JJ.; Cuenca Lacruz, ÁM.; Palau, F.; Dormido, S. (2014). A Multirate Control Strategy to the Slow Sensors Problem: An Interactive Simulation Tool for Controller Assisted Design. Sensors. 14(3):4086-4110. https://doi.org/10.3390/S140304086S4086411014

Doctor of Philosophy

dissertationParalysis due to spinal cord injury or stroke can leave a person with intact peripheral nerves and muscles, but deficient volitional motor control, thereby reducing their health and quality of life. Functional neuromuscular stimulation (FNS) has been widely studied and employed in clinical devices to aid and restore lost or deficient motor function. Strong, selective, and fatigue-resistant muscle forces can be evoked by asynchronously stimulating small independent groups of motor neurons via multiple intrafascicular electrodes on an implanted Utah slanted electrode array (USEA). Determining the parameters of asynchronous intrafascicular multi-electrode stimulation (aIFMS), i.e., the per-electrode stimulus intensities and the interelectrode stimulus phasing, to evoke precise muscle force or joint motion presents unique challenges because this system has multiple-inputs, the n independently stimulated electrodes, but only one measurable output, the evoked endpoint isometric force or joint position. This dissertation presents three studies towards developing robust real-time control of aIFMS. The first study developed an adaptive feedforward algorithm for selecting aIFMS per-electrode stimulus intensities and interelectrode stimulus phasing to evoke a variety of isometric ankle plantar-flexion force trajectories. In simulation and experiments, desired step, sinusoidal, and more-complex time-varying isometric forces were successfully evoked. The second study developed a closed-loop feedback control method for determining aIFMS per-electrode stimulus intensities to evoke precise single-muscle isometric ankle plantar-flexion force trajectories, in real-time. Using a proportional closed-loop force-feedback controller, desired step, sinusoid, and more complex time-varying forces were evoked with good response characteristics, even in the presence of nonlinear system dynamics, such as muscle fatigue. The third study adapted and extended the closed-loop feedback controller to the more demanding task of controlling joint position in the presence of opposing joint torques. A proportional-plus-velocity-plus-integral (PIV) joint-angle feedback controller evoked and held desired steps in position with responses th a t were stable, consistent, and robust to disturbances. The controller evoked smooth ramp-up (concentric) and ramp-down (eccentric) motion, as well as precise slow moving sinusoidal motion. The control methods developed in this dissertation provide a foundation for new lower-limb FNS-based neuroprostheses that can generate sustained and coordinated muscle forces and joint motions that will be desired by paralyzed individuals on a daily basis. proportional-plus-velocity-plus-integral (PIV) joint-angle feedback controller evoked and held desired steps in position with responses th a t were stable, consistent, and robust to disturbances. The controller evoked smooth ramp-up (concentric) and ramp-down (eccentric) motion, as well as precise slow moving sinusoidal motion. The control methods developed in this dissertation provide a foundation for new lower-limb FNS-based neuroprostheses that can generate sustained and coordinated muscle forces and joint motions that will be desired by paralyzed individuals on a daily basis

Design of the Annular Suspension and Pointing System (ASPS) (including design addendum)

The Annular Suspension and Pointing System is an experiment pointing mount designed for extremely precise 3 axis orientation of shuttle experiments. It utilizes actively controlled magnetic bearing to provide noncontacting vernier pointing and translational isolation of the experiment. The design of the system is presented and analyzed

Control System Design, Analysis, and Simulation of a Photovoltaic Inverter for Unbalanced Load Compensation in a Microgrid

This thesis presents a control scheme for a single-stage three-phase Photovoltaic (PV) converter with negative sequence load current compensation. In this thesis a dual virtual impedance active damping technique for an LCL filter is proposed to address the issue of LCL filter resonance. Both inverter-side current and the capacitor current are used in the feedback loop. Using both signals provides higher DC rejection than using capacitor current alone. The proposed active damping scheme results in a faster transient response and higher damping ratio than can be obtained using inverter-side current alone. The feedback gains can be calculated to achieve a specified damping level. A method of determining the gains of the Proportional and Resonant current controller based on frequency response characteristics is presented. For a specified set of gain and phase margins, the controller gains can be calculated explicitly. Furthermore, a modification is proposed to prevent windup in the resonator. A numerically compensated Half-Cycle Discrete Fourier Transform (HCDFT) method is developed to calculate the negative sequence component of the load current. The numerical compensation allows the HCDFT to accurately estimate the fundamental component of the load current under off-nominal frequency conditions. The proposed HCDFT method is shown to have a quick settling time that is comparable to that obtained with conventional sequence compensation techniques as well as immunity to harmonics in the input signal. The effect of unbalance compensation on the PV power output depending on the irradiance and the operational region on the power-voltage curve is examined. Analysis of the DC link voltage ripple shows the region of operation on the P-V curve affects the amplitude of the DC link voltage ripple during negative sequence compensation. The proposed control scheme is validated by simulation in the Matlab/Simulink® environment. The proposed control scheme is tested in the presence of excessive current imbalance, unbalanced feeder impedances, and non-linear loads. The results have shown that the proposed control scheme can improve power quality in a hybrid PV-diesel microgrid by reducing both voltage and current imbalance while simultaneously converting real power from a PV array