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Autonomous Quadrotor Project Anzhelka User Manual

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Autonomous Quadrotor Project
Cody Lewis
Luke De Ruyter
srlm@anzhelka.com
ilukester@anzhelka.com
May 29, 2012
And when he [Herod] had apprehended him [Peter], he put him in
prison, and delivered him to four quaternions of soldiers to keep
him; intending after Easter to bring him forth to the people.
–Acts 12:14, King James Bible, Cambridge Edition
1

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Summary of Contents for Autonomous Quadrotor Project Anzhelka

  • Page 1 Autonomous Quadrotor Project Cody Lewis Luke De Ruyter srlm@anzhelka.com ilukester@anzhelka.com May 29, 2012 And when he [Herod] had apprehended him [Peter], he put him in prison, and delivered him to four quaternions of soldiers to keep him; intending after Easter to bring him forth to the people.

  • Page 2: Abstract

    Abstract This project discusses the design of a four rotor autonomous aerial vehicle platform called the Anzhelka Project. The system is based on the open source Elev-8 quadrotor mechanical hardware platform and the Parallax P8X32A mi- crocontroller. In this paper we discuss the preparation that we have done in order to create a stable, autonomous vehicle.

  • Page 3: Table Of Contents

    TABLE OF CONTENTS TABLE OF CONTENTS Table of Contents Abstract Revisions Table of Contents 1 Introduction 1.1 Quadrotor Mathematics ..... . . 1.2 Executive Summary .

  • Page 4: Table Of Contents

    Protocol String Table ....8 User Interface 8.1 Anzhelka Terminal ......9 Testing 9.1 Hardware Testing .

  • Page 5: Introduction

    1 INTRODUCTION Introduction A quadrotor, also known as a quadrotor helicopter or quadcopter, is a mutltirotor aerial vehicle that has four rotors mounted on a rigid frame to provide lift. Quadrotor designs first appeared in the 1920s, but were abandoned because of bad performance and high pilot work load.

  • Page 6: Executive Summary

    Executive Summary Figure 2: Rendering of the Open Source Elev-8 quadrotor platform used in the Anzhelka project (image courtesy of Parallax). This senior design project’s goal is to create an autonomous quadrotor that can be used to film outdoor sports such as mountain biking, snowboarding, and skiing.

  • Page 7: Design Objectives And System Overview

    After watching countless videos from Go Pro cameras from a single perspectives and partial views of the subject, project Anzhelka was created. Anzhelka will allow users to be able to capture video angles that were once unattainable without costing thousands of dollars. Anzhelka will allow users to capture video with the same ease as using a Go Pro camera, but without the single perspective and jitter from traditional methods.

  • Page 8: Current Project Status

    Development Environment and Tools The Anzhelka project software was developed for the most part using a Linux system. All code and other project files are hosted on the project Git repository ([1]).
  • Page 9 This folder stores all the relevant datasheets in the datasheet subdirectory, and any other project documentation that is deemed to fit. Note that most documentation probably belongs in the Anzhelka wiki on [1]. The datasheet and reports folders contain the reference datasheets for each component and the various generated reports of the project, respectively.

  • Page 10: Development Cycle

    fly the quadrotor other programs need to be stored in the extra folder. This folder stores the Anzhelka Terminal files and the Thrust/Torque test stand files for example.

  • Page 11: Definitions And Acronyms

    files could be easily merged. All project files are open source under the MIT license and can be downloaded freely. Definitions and Acronyms Anzhelka Terminal $ATxxx Anzhelka Terminal Communication String BSTC Brad’s Spin Tool Compiler EEPROM Electrically Erasable Programmable Read-Only Memory Electronics Speed Controller...

  • Page 12: Assumptions

    Realistic Constraints Every system has constraints and Anzhelka is no exception. The most im- portant constraint is the life of the battery. If each motor consumes 15 amps on average then that is a current drain of 60 amps from the motor battery.

  • Page 13: Safety

    4-40 5/8” Standoff $0.46 $5.52 DIY Drones Propellers 10x4.5 1 push 1 pull $6.00 $12.00 Pololu CHR-UM6-LT IMU Sensor $149.99 $149.99 Anzhelka Power control board $166.60 $166.60 Tower Hobbies Eagle Tree RPM sensor $13.79 $55.16 Total $789.48 Safety When dealing with any robotic system one must take extreme cautions in order to ensure the safety of everyone.

  • Page 14: System Design

    4 SOFTWARE INTRODUCTION had yet to complete. With these two resources set up and with the help of keeping an open schedule the team has been able to successfully coordinate and maximize productivity. System Design The system is fairly simple. The general system architecture consists of the central Propeller microcontroller interfacing with a number of different devices.
  • Page 15 4.1 Propeller 4 SOFTWARE INTRODUCTION Each core, called a COG, is identical with equal access to all chip resources. The Propeller has a central RAM area called the HUB which is COG accessible in a round robin fashion. Figure 5: The functional architecture of the Parallax Propeller (courtesy of Parallax).

  • Page 16: Programming

    4.2 Control Loop Frequency 4 SOFTWARE INTRODUCTION the Spin interpreter, must fit in 496 instructions or less in order to fit into the COG RAM. The Propeller does not have provisions for fetching PASM instructions from other locations besides COG RAM. For Spin code the compiled interpretable bytes are stored in the HUB RAM, and are fetched and decoded by the Spin interpreter.
  • Page 17 Now we need to consider the software control loop. We’ve broken the math into three blocks: attitude control, altitude control, and motor control. The equations can be found in the Anzhelka mathematics document [3]. The attitude control block and altitude control block can be done in parallel, and their output fed into the motor control block.

  • Page 18: Other Software Notes

    4.3 Other Software Notes 5 QUADROTOR PROTOTYPE CONSTRUCTION Our estimates show that we can have an inner control loop of 260Hz, and if we parallelize the moment and altitude calculations as shown above then we can get about 40Hz faster for a control loop frequency of 300 Hz. Also of interest is that the quadrotor control loop has a response time of 3.3 milliseconds.

  • Page 19: Frame

    5.1 Hardware 5 QUADROTOR PROTOTYPE CONSTRUCTION Item Mass(Grams) Frame 450g Each propeller Motor (black) Motor (red) ESC (black) ESC (red) 5000MAH Battery 410g 8000MAH Battery 650g 5.1.1 Frame The quadrotor frame that we are using for this project is the open source Elev-8 frame from Parallax ([6])The resin plates are constructed out of a ma- terial called Delin [9] made by DuPont...

  • Page 20: Power Board Pcb

    5.1 Hardware 5 QUADROTOR PROTOTYPE CONSTRUCTION Figure 6: PWM vs RPM under no load. They are nearly the same on the PWM up and down. Figure 7: Volts vs RPM under no load. As you can see that the current is linear with the voltage.
  • Page 21 5.1 Hardware 5 QUADROTOR PROTOTYPE CONSTRUCTION * Switching regulators for the logic voltages * Power distribution for motor ESCs * Current and voltage sensing for all motors * Level shifting for 5v interfacing * 8 free channel of ADC * 8 free servo channels * I/O headers for I2C, IMU, SD card, and XBee * Mounting holes for BoE formfactor, quickstart, SD card, and IMU PCBs are very difficult in the ways of being able to produce something...

  • Page 22: Thrust/Torque Test Stand Construction

    5.2 Software 5 QUADROTOR PROTOTYPE CONSTRUCTION around time, but at a much larger cost. Choosing one in China provides for a much cheaper product, but at a slower turn around time. The fabrication house in China that we selected (iTeadStudio) took nearly a month for a full turn around.

  • Page 23: Rotation Speed

    5.2 Software 5 QUADROTOR PROTOTYPE CONSTRUCTION (a) The thrust/torque test stand. (b) The motor mounting is on the left and torque measurement arm is the bronze piece on the right. Figure 10: Brushless motor test stand 5.2.1 Rotation Speed In order to determine the amount of thrust that a motor is producing the platform must be able to measure the RPM of the motor.

  • Page 24: Pulse Width Modulation

    5.2 Software 5 QUADROTOR PROTOTYPE CONSTRUCTION single motor. The sensor converts the brushless motor signals to a series of pulses where each pulse is proportional to a rotation. The Propeller does not measure the signal directly from a brushless motor control line because there are very high voltages and back EMF from the motor which creates a very nasty environment for the 3.3v microcontroller.

  • Page 25: Uart Serial Communication

    ρn Above, we have the two equations that define how the propellers affect our quadrotor system. These equations can be found in context in the Anzhelka Project quadrotor mathematics document ([3]). The form that 6.1 and 6.2 are in now makes it convenient for us to measure the constants K and K : if we...

  • Page 26: Implementation Details

    Anzhelka Data and Command Exchange Protocol The Anzhelka project uses a protocol called $ATXXX to facilitate data and command exchange between different subsystems. $ATXXX is very similar to NMEA-0183 where data is exchanged via sentences prefaced with a sentence code.

  • Page 27: Protocol Implementation Details

    Data strings are prefaced with $ADxxx (short for Anzhelka Data type xxx). Note that the only defined whitespace in a string is a single space after the sentence code, and a newline (ASCII characters LF and CR) after each string.

  • Page 28: User Interface

    Currently, the only user interface is via the Anzhelka Terminal. Anzhelka Terminal The Anzhelka project uses a PC based GUI platform called Anzhelka Ter- minal (AT) to display realtime system states and to allow for parameter tuning. AT is written in Python and uses the WxWidgets Python branch WxPython for the GUI.

  • Page 29: Testing

    Testing Testing is a critical part of any project, and the Anzhelka project is no exception. All hardware and software is tested thoroughly to ensure correctness. As more time passes we will work on developing automated tests, including regression tests once the project becomes mature.

  • Page 30: Motors/Propellers

    9.1 Hardware Testing 9 TESTING 9.1.2 Motors/Propellers The motors and propellers would also need to be tested and matched to ensure the best performance. We can assemble all of our motors and propellers and then we can test them for torque and thrust ratings. Once we have all of the results we can then match the motors with nearly the same characteristics together.

  • Page 31: Maintenance Plan

    10 MAINTENANCE PLAN all the components are in working order. One of the easiest ways to accomplish this is to develop test code that will run on the hardware and will give you a set of known outputs. Having something that will test all components several times under different inputs and outputs is key to insure that the PCB is in good working order.

  • Page 32: For The Next Year

    11.1 Realistic Constraints on Time and Money The Anzhelka project is relatively unconstrained in time and money. We each work roughly 20-40 hours a week on the project, for a total of 23 weeks. This gives approximately 1400 hours of total time investment in the project.

  • Page 33: Anzhelka Marketing

    Delrin pieces. The PCB has a white solder mask to contrast with the black color of the frame. The Anzhelka Terminal GUI was designed to be intuitive and easy to use, even without any experience. Functionality is divided into tabs for easy access.

  • Page 34: Ethics

    Ethics Unmanned aerial vehicles(UAVs) are a very controversial current topic. The Anzhelka project is part of a subset of UAVs; namely, vertical take and and landing (VTOL). UAVs can assist in surveillance, inspect structures, creating aerial photographs, rescuers in a disaster situation, transporting goods, and many other situations.

  • Page 35: Acknowledgements

    14 ACKNOWLEDGEMENTS [3] C. Lewis, L De Ruyter, ”Quadrotor Mathematics For Simpletons,” 2012, available at "http://code.anzhelka.com" [4] E. Stingu, F. Lewis, ”Design and Implementation of a Structured Flight Controller for a 6DoF Quadrotor Using Quaternions,” Mediterranean Con- ference on Control & Automation, pp. 1233-1238, June 2009.

  • Page 36: Appendices

    15 APPENDICES W9GFO (Rich Harman) Laser cutting of the Derlin Frame Parts Gene Shermen Machinist Dale Holtkamp Machinist Elmar Palma Workshop Dr. Philip Brisk Consulting Dr. Ping Liang Consulting Dr. Roman Chomko Consulting Dr. Kastner Consulting Tom Wypych Consulting Frank Lewis Algorithms Emanuel Stingu Algorithms...

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