Toward the Development of an Interactive Modeling, Simulation, Animation, and Real- Time Control (MoSART) Hardware/Software Testbed for a Tilt-Wing Rotorcraft John S. Koenig Arizona State University, Tempe AZ IEEE Student Member # IEEE Region 6, Southwest Area, Student Paper Contest San Diego, CA Saturday March 27th, 1999

Introduction Motivation Contributions of Work Test Stand Pitch Dynamics Controller Design MoSART Environment Utility of Environment Summary and Future Work

Motivation High Speed Autonomous Rotorcraft Vehicle (HARVee) Project at ASU –Tilt-wing aircraft which combines the benefits of a helicopter and an airplane –NEED: Automatic control for safe hover flight

Motivation Hardware Test Stand –Lab-scale test bed for control system development –NEED: Mathematical modeling, simulation, and real-time control

Nonlinear and linear model development –1 DOF Test Stand Pitch Dynamics Linear controller design Tilt-Wing Software Environment –Open-loop and closed-loop simulation Modeling, Simulation, Animation, and Real-Time Control (MoSART) –Interactive tool for control system design –Can be connected to hardware to form integrated hardware/software testbed Contributions of Work

Test Stand Description Four degrees-of-freedom Replicates all hover mode control inputs (except has only two main engines) Fully constrained and contained Modeling Second order, non-linear model –1 DOF pitch dynamics –Three Point-Mass Representation

Three Point-Mass Model Non-linear model: Where,

Incorporate known parameters: Linearize (sin , for small angles): Determine transfer function: Model Development

Open-Loop Stability Plant Transfer function: Root Locus Plot: Open-Loop Poles at s=±5

Controller Design - Part One Controller design proceeds in two parts –Part One - Series Compensation P Step K1K1 Chose K 1 such that: K 1 is given the following form:

Controller Design - Part One

Controller Design Closed-loop transfer function has the form: Derivative action [(s+a) term] produces large magnitude response to a high-frequency input. Controller output when s is very large:

Eliminate overshoot by employing a feed-forward loop. Step Controller Design - Part Two

K 1 (s) and K 2 (s) are improper and the following modifications are made to make them strictly proper: Closed-loop transfer function now takes the form: Controller Design

MoSART Environment System specific, interactive software environment for Modeling, Simulation, Animation, and Real-Time Control (MoSART) Runs on Pentium PC platform under Windows 95/NT Written in C++, using Microsoft Foundation Classes (MFC) and Direct-3D Utilizes MATLAB for analysis purposes

MoSART Environment Environment structured around four modules: –Program Interface Module (PIM) –Simulation Module (SIM) –Graphical Animation Module (GAM) –Help-Instruct Module (HIM)

Program Interface Module Interactive System Diagram –Block diagram representation of system –Point-and-click access Standard Windows 95/NT Interface –User Friendly –Menus –Multiple windows –Control toolbars

Simulation Module Numerical Simulation –Fast compiled C++ –Faster than real-time simulation is possible On-the-fly Parameter Editing –Change model –Edit controller parameters –Adjust reference commands (step, sinusoid, etc.) –Different integration methods (Euler, 4th order Runge-Kutta) Dynamic linking to MATLAB engine

Graphical Animation Module 3-D Animation (Direct-3D) –Texture-mapped, light-shaded polygons Visualization Tools –Real-time 3-D and graphing windows

Help-Instruct Module On-line Help –Instructions on using the environment HTML/PDF Documents –Model documentation/references –On-line tutorials

Utility of Environment Open-loop simulation –3-D visualization of unstable system –Change between linear and non-linear models –Utilize MATLAB for data analysis and comparison

Utility of Environment Controller Design - Series and Feed-Forward –Animation Visualize positive and negative aspects of a design –Series controller = large overshoot (negative) –Series+feed-forward = small overshoot (positive) –Graphing Windows Real-time plotting of user-specified parameters –Pitch angle vs. time Utilize MATLAB engine for analysis –Such as comparing the linear and nonlinear responses

Utility of Environment Controller Design - High vs. Low Gain –MATLAB processing of data gives precise measure of linear error –(k) and (a) values adjusted with with point- and-click interface –Effects of controller changes can be seen in seconds

Future Work Link hardware test stand with MoSART environment –Hardware/software testbed will be an effective control system design tool –Provides real-time control of actual hardware Mathematical model development –4 DOF test stand dynamics –6 DOF tilt-wing rotorcraft dynamics

Summary Linear and nonlinear models developed –1 DOF pitching dynamics Linear controller developed –Tested using linear and nonlinear models MoSART software environment –Simulation, Animation, Analysis, Control –Interactive tool for controller design