AUTOPILOT DESIGN

Autopilot Design for Light Aircraft- CESSNA 172

Introduction3

Problem Statement3

Purpose of the study4

Aims & Objectives4

Significance of the study5

Rationale of the study5

Literature Review6

Methodology7

System Overview7

Specifications8

Design Procedure9

Trim And Pitch Of Light Aircraft10

References18

Autopilot Design for Light Aircraft- CESSNA 172

Introduction

In this report, we will present the design and construction of a test platform for digital autopilots, as well as a reference design and implementation of a 2-axis autopilot for use with this platform. The platform will be targeted at the educational market (for use in control systems laboratory courses), and builders of unmanned aerial vehicles (such as participants in the annual Aerial Robotics Competition). The platform will consists of a micro-controller board, which hosts the autopilot, and a PC running the commercial X-Plane flight simulator. The two components are interfaced via Ethernet. With this set-up, autopilot prototypes can be tested with X-Plane's sophisticated flight- and atmospheric models(Blakelock, 2009 pp. 7-61). The reference 2-axis autopilot is designed for small aircraft and features altitude control, vertical speed control, as well as a wing leveler. The functionality of the platform is demonstrated by comparing the response of a Cessna 172 under control of the autopilot to the expected theoretical response obtained from SIMULINK simulation using the linearized model.

Problem Statement

Aircraft Autopilots are often used in university control system courses and textbooks as motivating examples. Unfortunately, most university laboratory settings do not make it possible for students to gain hands-on experience in the design, implementation, and testing of such systems. While students could always design an autopilot in a simulation package such as Matlab/Simulink, they generally lack the opportunity to see how their newly designed autopilot performs on a realistically simulated aircraft in a realistic environment (Russel 2010, pp. 105-108).

Purpose of the study

The principal aim of this project is to design an autopilot system for a light aircraft. The design would need to consider the problems of auto-pilot runaway, interaction with other automatic systems (such as auto-elevator trim) and the interaction with the pilot.

Aims & Objectives

The first goal was to create a platform on which digital autopilots can be implemented and tested. The platform is to consist of a microcontroller that hosts the autopilot code and interfaces with an advanced PC-based flight simulator. To facilitate entering settings into the autopilot, a hardware user interface consisting of a keypad and LCD display is also required.

The second goal was to design an autopilot for a Cessna 172SP Skyhawk airplane, and then implement and test it on the platform. We chose to create a 2-axis autopilot consisting of an altitude and vertical speed controller, as well as a wing-leveler. The purpose of the altitude and vertical speed controllers is to cause the airplane to climb or descend at a desired vertical speed until a desired target altitude is reached and then keep the airplane at this altitude until a new command is issued. At the same time, the wing-leveler will, as the name implies, keep the airplane in level flight. The design of the wing-leveler will not be discussed in this report, ...