Title of Thesis: DESIGN AND CONTROL OF A VEHICLE FOR NEUTRAL BUOYANCY SIMULATION OF SPACE OPERATIONS
Degree Candidate: Joseph Douglas Graves
Degree and Year: Master of Science, 1997
Thesis directed by: Assistant Professor Robert M.
Department of Aerospace Engineering
This thesis describes the design, control and testing of the
Ranger Neutral Buoyancy Vehicle flight control system. Four major
topics are covered: (1) vehicle design; (2) flight control operator
interface; (3) estimation and control; and (4) experimental results.
The work in this thesis focuses on controlling the vehicle attitude.
The vehicle design section covers the details of the hardware that is
related to vehicle flight control. Sensor and actuator
characteristics are described, along with the overall structure of
the data management system. The flight control operator interface
section describes the variety of means available for the operator to
direct and observe the behavior of vehicle. Interfaces for many
functions are described, including controller selection and tuning,
trajectory control, simulation, data recording, and analysis. The
estimation and control section describes the vehicle dynamic model,
and the methods chosen for describing its attitude and angular
velocity. Estimation of vehicle attitude and angular velocity are
then discussed, followed by a description of estimator inaccuracies.
Controller error metrics are developed, along with three types of
tracking attitude control algorithms. An advanced PD controller
commands the vehicle motion based on the current attitude and angular
velocity error. The next controller adds nonlinear compensation by
using a model of the system dynamics to compute the torque necessary
to autonomously follow the specified trajectory. Finally, an adaptive
controller is presented that uses observations of the vehicle
behavior to update its estimates of the vehicle dynamic parameters. A
discussion of the hardware in the loop vehicle flight simulator is
accompanied by a comparison of its performance with actual vehicle
operations. This section ends with a discussion of the trajectory
generation system and a description of the vehicle auto balance
algorithm. The experimental results section describes the initial
tuning of these controllers and evaluation of their performance.