Abstract

  

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. Sanner
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.