Autopilot creation

This is a Bachelor thesis that deals with aircraft autopilots using FS as a bed test. It shows how to tune a PID using several methods. The methods can be used to tune FS standard autopilot but in this case a separated one was made. The reader needs some Laplace transform knowledge to follow the equations but I believe that basic Mathematical analysis and the graphs will be enough to understand.

The author is Andrea Saccomanno and myself as tutor.

Autopilot.pdf

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . 6

CHAPTER 1 . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 9

1.2 Principles of flight control . . . . . . . . . . . . . . . . . 9

1.3 Flight control surfaces . . . . . . . . . . . . . . . . . . 11

1.3.1 Fighter aircraft . . . . . . . . . . . . . . . . . . . 12

1.3.2 Commercial aircraft . . . . . . . . . . . . . . . . . 13

1.4 Flight control systems . . . . . . . . . . . . . . . . . . . 15

1.4.1 Mechanical systems . . . . . . . . . . . . . . . . . 16

1.4.2 Hydromechanical systems . . . . . . . . . . . . . . 17

1.4.3 Fly-by-wire systems . . . . . . . . . . . . . . . . . 18

1.5 Aircraft navigation and positioning systems . . . . . . . . . 19

1.5.1 Global Positioning System (GPS) . . . . . . . . . . . 20

1.5.2 Autopilot systems . . . . . . . . . . . . . . . . . . 21

CHAPTER 2 . . . . . . . . . . . . . . . . . . . . . . . . . . 25

2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 26

2.2 Control Systems . . . . . . . . . . . . . . . . . . . . . 26

2.2.1 Open-Loop (Feedforward) Control Systems . . . . . . . 27

2.2.2 Closed-Loop (Feedback) Control Systems . . . . . . . . 27

2.2.3 System Transfer Function . . . . . . . . . . . . . . 28

2.3 Proportional-Integral-Derivative (PID) Controller . . . . . . . 29

2.3.1 Basic modes of a PID algorithm . . . . . . . . . . . . 30

2.3.2 Proportional (P) algorithm . . . . . . . . . . . . . . 31

2.3.3 Proportional Integral (PI) algorithm . . . . . . . . . . . 31

2.3.4 Proportional Integral Derivative (PID) algorithm . . . . . . 32

2.3.5 Effects of Proportional, Integral and Derivative action . . . 33

2.3.5.1 Windup . . . . . . . . . . . . . . . . . . 36

2.3.5.2 Setpoint limitation . . . . . . . . . . . . . . 38

2.3.5.3 Incremental Algorithms . . . . . . . . . . . . 38

2.3.5.4 Back-calculation and Tracking . . . . . . . . . 39

2.3.5.5 Controllers with a Tracking Mode . . . . . . . . 42

2.3.6 PID Tuning . . . . . . . . . . . . . . . . . . . . 43

2.3.6.1 Ziegler-Nichols Methods . . . . . . . . . . . 46

2.3.6.2 Cohen-Coon Method . . . . . . . . . . . . . 48

CHAPTER 3 . . . . . . . . . . . . . . . . . . . . . . . . . . 50

3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 51

3.2 Autopilot specification . . . . . . . . . . . . . . . . . . 51

3.2.1 Heading controller specifications . . . . . . . . . . . . 51

3.2.2 Altitude controller specifications . . . . . . . . . . . . 53

3.2.3 GPS Navigation controller specifications . . . . . . . . . 54

3.3 Autopilot design . . . . . . . . . . . . . . . . . . . . . 54

3.3.1 Microsoft® Flight Simulator and the plug-in FSUIPC . . . . 55

3.3.2 The function Plotter . . . . . . . . . . . . . . . . . 58

3.3.3 Heading controller design . . . . . . . . . . . . . . . 60

3.3.4 Altitude controller design . . . . . . . . . . . . . . . 70

3.3.5 GPS navigation controller design . . . . . . . . . . . . 75

3.4 Controller implementation . . . . . . . . . . . . . . . . . 77

3.4.1 The function lateral . . . . . . . . . . . . . . . . . 77

3.4.2 The function longitudinal . . . . . . . . . . . . . . . 81

3.4.3 The function navigation . . . . . . . . . . . . . . . 84

CHAPTER 4 . . . . . . . . . . . . . . . . . . . . . . . . . . 86

4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 87

4.2 Experiment description . . . . . . . . . . . . . . . . . . 87

4.2.1 Test #1: lateral controller testing . . . . . . . . . . . . 88

4.2.2 Test #2: longitudinal controller testing . . . . . . . . . . 98

4.2.3 Test #3: navigation controller testing . . . . . . . . . . 124

4.2.4 Test #4: lateral + longitudinal controllers testing . . . . . . 132

4.2.5 Test #5: navigation + longitudinal controllers testing . . . . 141

CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . 152

APPENDIX A . . . . . . . . . . . . . . . . . . . . . . . . . . 154

BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . 157