Projects

A list of some of my more interesting engineering projects :

PRESSURE AND FLOW CONTROL

Volume Delivery and Gas Mixing Control System
Two flow feedback control loops for precision
volume control and ratio-metric control of oxygen concentration. Application: Critical Care Life Support.
Involved in interface design for hot-film anemometer type flow sensors, stepper motor actuated flow
delivery and exhaust valves.

Pressure Regulation System Cascade Control for regulating pressure in an infant patient circuit within
plus or minus 0.5 cm H2O.

Pressure Tracking System Dual valve actuation/ split frequency band control for precision pressure
tracking in an infant critical care ventilator.

Flow Valve Actuator Position Control Prototype high speed, robust voice coil control for a valve
actuator. Application: exhaust valve for critical care ventilator.

Lung/Circuit Simulation Models  A complete library of VisSim simulation models providing a quick and
low cost alternative in development and evaluation of new control methods for critical care ventilation.

Ventilator Controls Testbed Established several windows based Hardware-in-the-Loop testbeds for
servo design and verification reducing turnaround from months to weeks.

Controls & Software Development for Adult Patient Ventilator Controls simultaneously regulate flow
and pressure, substantially reducing the imposed inspiratory work of breathing. Coding was done in
assembly language on an Intel 8031 processor using a Nohau's in-circuit emulator for debug.

Designed and built
Prototype PAV Ventilator in joint effort with a Japanese university hospital for
assessment of clinical efficacy and a new product.

Pressure Control design for the Adult Bird 8400 ventilator providing increased marketability. Project was
completed in 1/3 the expected time by using a hardware in the loop simulation to first prove feasibility of
the control design. My first HILS project using VisSim.

Ventilator Work of Breathing Platform  Wrote an interactive Matlab script for including data acquisition
interface to measure pressure and flow, and process the information for display and quantitative analysis
of pressure volume loops.

Estimation of Lung Mechanics Parameters Wrote a Matlab script that acquires flow and pressure data,
and using a recursive least squares estimator, determined real time circuit compliance, lung compliance
and ET tube resistance

Adaptive Inverse Model Control of Pressure Based Ventilation Designed and developed an
adaptive controller for pressure based ventilation breath types. The controller results in uniform, fast
tracking of pressure trajectories for all PBV breath types, and over all patient and connecting circuit
loading from neonate to large adult.

Virtual Patient Simulator Designed and developed a hardware in the loop system that simulates patient,
patient connecting circuit, and ventilator valves and sensors. The simulation is connected to ventilator
electronics and software controls and can be used to emulate a real patient connected to the ventilator.
Parameters can be varied real time to simulate the course of an illness. Also valve, sensor and connecting
circuit faults can be simulated and tested against the software system for FMECA studies.

MOTION CONTROL SYSTEMS

Motion Control Blockset
Designed and implemented motion control blockset for the simulation software,
VisSim , including the following:

  • High fidelity non-linear models of 3 phase AC induction motors, permanent magnet synchronous
    motors, linear model of DC machines, and stepper motor models.

  • Models of PWM servo amplifiers for brush and brushless motors.

  • Models for full, half-step and microstep control of stepper motors.

  • Discrete time controller models (PID, PI, PD, I – feed forward) and filter models for feedback control.

  • Translational and rotational dynamic load models including gear coupling, non-linear affects such as
    Coulomb and Stribeck friction components.

  • A field oriented controller (FOC) block model for AC induction motor speed control including models
    for space vector PWM, current model, and Clarke’s and Park’s transformations

  • High fidelity motion sensor models including encoders, servo potentiometers, tachometer
    generators, LVDT, etc.

  • Authored user manual block reference and tutorials including a machine tool application of speed
    control of an AC induction motor and position feedback, 2-axis control of camera line of sight using
    a DC brushless motor.

POINTING & TRACKING CONTROL SYSTEMS

Designed and built an Optical Gimbal. A precision pivot-less gimbaled mirror for line of sight stabilization
using a piezoelectric actuator triad with a laser and quadrature detector for angular position feedback.
Achieved angular precision of less than 1 microradian.

Target tracking system for CCD Designed prototype target tracking system for CCD camera using
General Scanning 2 axis galvanometer actuators and Datacube's VME image pipeline processor
components. Programmed control and imaging interface using 68000 assembly language.

Active Structural Control Designed a control system for damping flexible modes using the disturbance
accomodation control method. Project was done on a fixed-fixed beam designed such that the primary
bending mode was near the primary torsional mode. The control involved use of reaction mass
components, relative position sensors, and accelerometers. The controller was programmed on a systolic
system's systolic array processor. Efficiency of control and spillover were studied.

Telescope Tracking System Gimbal torquer control with 20 bit encoder feedback for pointing and
tracking a 12 inch reflector telescope. Application: acquisition and tracking of low earth orbit satellites for
orbit determination.

Air to Air Free Space Laser Communications System A pair of gimbaled laser communications
transceivers used to communicate secure > 1 Gbit/sec data rates between aircraft. Here I developed the
feedback controls for gyro stabilized tracking of the gimbaled receivers, turret positioning controls and
navigation for gimbal acquisition of the LOS, and fast steering mirror controls for laser pointing.  The
system never flew due to budget limitations, however was proven effective on a Stewart Table simulating
aircraft motion and disturbance with mutual acquisition and tracking over a 50 km test range at White
Sands Missile range.

UNDERWATER DIVING & LIFE SUPPORT SYSTEMS

Physiology Laboratory
Built and operated a laboratory to test the performance of rescue and survival
equipment on human subjects. Involved treadmill tests with overhead sensor platform for measuring
oxygen, carbon dioxide and temperature. Programmed HP computer and interface to HP3497 data
acquisition and control system

Work of Breathing Tests Built and operated a test system in a man rated hyperbaric chamber to
measure and compare the imposed work of breathing between competitor's sport diving regulators.

Diving Regulator Design Mechanical design of a balanced 2nd stage underwater sport diving regulator
achieving stable, low effort operation (Aqualung Royal)

Rebreather Designs Designed and prototyped a closed circuit, mixed gas breathing apparatus for fire
rescue using a novel lithium nitrate tri-hydrate phase transition heat capacitor(SCEBA-60, U.S. Bureau of
Mines). Designed lithium hydroxide scrubbers for a 2 hr. rescue rebreather (
LP-120) and a 4 hour closed
circuit system for army CBW applications

Cousteau Expedition Support Provided design and working drawing package of a shark cage and
equipment platform for the Cousteau society and their expedition to Clipperton Island.
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