Autonomous Quadcopter Platform

Hardware Setup

WARNING: Experience with flying Remotely Controlled Quad­Copter is required.

Binding Procedure

Binding is required the first time the craft is used with a new transmitter. It is done
using the following procedure.

To place Rx into binding mode, pace a wire jumper across PCB board “Term 8” Pins 1
& 4. This will force the Rx into binding mode.

Connect the 4­Cell 4aH Li­Po battery to the craft using the yellow xt­60 battery
connectors at the bottom of the craft.

Wait for the orange “Bind Led” on the Radio Receiver (Rx) to begin flashing rapidly.

Follow binding procedure on DSM2 Tx of choice.

Bind LED will stop flashing and burn solid once Tx & Rx are bound.

Remove jumper from PCB“Term 8”.

Power Cycle Craft to confirm bind. Bind LED will turn on solid when communication
between Tx and Rx is established.

Prepping the Craft for Flight

Before the flying craft ensure that it is in good flying condition. Visually inspect the
Craft for wear and disconnected wires, repair using attached documentation.

  1. Power on the DSM2 Compatible Transmitter (Tx).
  2. Place the “Channel 5” (Often referred to as the Gear Switch) into “Position 0”. The
    setting with a 1000uS on time for Channel 5. This places the craft in direct user
    control.
  3. Install the 4­Cell 4Ah Li­Po battery on to the craft, using the included Velcro strip.
  4. Plug the yellow xt­60 battery connector to the power lead of the craft.
  5. The orange “Bind Led” on the Radio Receiver (Rx) will change to solid orange once a
    radio link between the Tx & Rx is established.
  6. Before flying, the CC3D must be armed. This is done by giving a full Throttle down and
    a full Yaw CCW command on the left Tx stick. Hold this position and observe blue
    status LED on CC3D. Unit will flash rapidly for 5 seconds and go dark. Unit is now
    armed, and will respond immediately to Tx stick inputs.
  7. To disarm the craft, giving a full Throttle down and full Yaw CW command on the left
    Tx stick. Additionally, unit will self disarm after 30 seconds of non­activity from the Tx.

Programming the CC3D

The CC3D is responsible for leveling the craft. Before it can do that, it must first be
configured to talk with the hardware. This is done using the OpenPilot Ground Control
Software.

Download the OpenPilot GCS software version 15.02.01 from
https://wiki.openpilot.org/display/WIKI/OpenPilot+Downloads. Install the program using the
default location and settings.
Start the OpenPilot GCS program, at the welcome screen connect the CC3D to the computer
using the mini USB port. On the welcome screen, use the vehicle setup wizard to configure
the craft’s hardware settings. This will define the motor outputs and the Transmitter inputs.
One important point where the P15230 Craft differs from the configuration wizard is in the
Input settings. The current version of the OpenPilot GCS used pin 8 for the PPM input. The
Craft is configured to use pin 3. To change this setting navigate to the “Configure pane” on the
bottom of the screen. Click the “Hardware Button” at the top left. From there click the input
drop down and select “PPM+NoOneShot”. Click the save button on the bottom right of the
page to save the configuration. IMPORTANT, The OpenPilot program and the CC3D must be
restarted to take effect. From here the Transmitter may be configured using the “Transmitter
Setup Wizard”. This is located on the “Configure/Input” pane. Click the “Start Transmitter
Startup Wizard” button, when complete click save on the bottom right hand corner of the
page.

Additional References

Here is some additional information pertaining to flying an RC Quad­Copter. This
information links to 3rd party sites. This material is linked to often by the RC community, but is
unvetted by the MSD Team.
http://myfirstdrone.com/how­to­fly­a­quadcopter/ ­ Tutorial on Flight Introduction to Controls
https://www.youtube.com/watch?v=P3E2pQnEDRI ­ Tutorial on Flight Video (Part 1)
https://vimeo.com/90043790 ­ Tutorial on Flight Video (Part 2)
http://blog.oscarliang.net/quadcopter­tutorial­how­to­fly­drone/ ­ Additional Tutorial
http://www.uavcoach.com/how­to­fly­a­quadcopter­guide/ ­ Detailed review on RC
Terminology

Software Setup

Starting Program

At start the default program will run once the start push button is pressed. This will run
the compiled program ‘lmnoCopter’ located in the mainProg folder on the Raspberry Pi. The
teensy will automatically run its program at power on. When a program is ran from the start
button press all console output is directed to a log file timestamped and located in the logs
folder within the mainProg folder.

Starting the Craft

With the crafts onboard computers started the user may use the transmitter to toggle
between autonomous and user controlled operation. For safety purposes, the Teensy is
unable to arm the CC3D, thus the CC3D must be armed by the user. In­order to do this the
craft is first placed into Direct Control Mode. This is done by placing Channel 5 into POS­0.
With the craft under direct user control, the user may now arm the CC3D. This procedure is
covered in steps 6 & 7 of “Prepping the Craft for Flight”.
Notes about direct user control. In Channel 5 :POS­0 the unit is programmed for direct
user control and self stabilization. Stick inputs correspond to displacement angles. that is 0%
stick movement corresponds to 0° displacement, and 100% stick movement corresponds to
11° displacement. All controls are limited to 11° from level.
Notes about autonomous control. In Channel 5: POS­1 the unit is programmed for
autonomous control. Commands from the onboard computers are passed to the CC3D.
a. Note: POS­1 initiates Auto Hover Mode with Rev03 Firmware

Environment Setup on New Hardware

When starting with a blank teensy and Raspberry pi, the programs should be loaded
and installed as follows. Additionally the Teensy program must be modified when binding to a
new Tx.

Teensy Program

Developing Environment

Download the Arduino Sketch environment from arduino.cc. Install version 1.6.4.
Install the Teensyduino version 1.23 addon from
https://www.pjrc.com/teensy/td_download.html. Follow installation guide and add All libraries
when given the option.

Add Arduino Libraries

Within the Arduino Sketch environment the jmPID and sharedi2cCom libraries should be previously installed. This is done by adding the jmPID and sharedi2cCom folders into the PATH_TO_ARDUINO_WORKSPACE/Arduino/libraries folder. Additionally
DEFINED_VALUES.h must be placed into the PATH_TO_CODE/Teensy­Rev04 folder. In
order for Arduino sketch to recognize these libraries the IDE should be restarted.

Load Program onto Teensy

Within the Arduino Sketch environment press the verify button. The compiler will compile the program and assure that all libraries and include files are in the proper place. When the program compiles successfully, click the upload button within the Arduino Sketch environment. the TeensyDuino add on will pop up. At this time press the black button located on the Teensy Development board. The TeensyDuino will show a progress bar as it uploads the new code to the Teensy. At its completion the TeensyDunio addon will say Upload Complete.

New Tx Setup with the Teensy

The Teensy microcontroller is configured to emulate the user’s Tx. Each Tx has its
own offsets and errors around neutral. The Teesny must be configured to emulate these
offsets and errors in­order for the CC3D tuning to work with the craft. These offsets may be
determined using the following method.
Download the OpenPilot GCS software version 15.02.01 from
https://wiki.openpilot.org/display/WIKI/OpenPilot+Downloads. Install the program using the
default location and settings.
Start the OpenPilot GCS program, at the welcome screen connect the CC3D to the computer
using the mini USB port. Click the Configure Tab at the bottom left hand corner of the window.
This will bring up the configuration page. Click the input tab at the top left of the window to
bring up a live telemetry of the current inputs. The neutral column will contain the offset value.
To compute this offset, for throttle subtract 1000 from the neutral value. Here it is 100. For the
Roll, Pitch, and Yaw channels subtract 1500 from the neutral value. Here it is 15, 19, 19.

CC3D Program

Installing the Program

The CC3D is configured using the OpenPilot Ground Control Software. Download the OpenPilot GCS software version 15.02.01 from https://wiki.openpilot.org/display/WIKI/OpenPilot+Downloads. Install the program using the default location and settings.

Reloading the P15230 PID Settings

The CC3D uses PID control law to level and stabilize the craft in flight. The craft has previously been tuned by the team for stable flight. These values are already loaded on the CC3D but may be re­loaded in the following way. Start the OpenPilot GCS program, at the welcome screen connect the CC3D to the computer using the mini­USB port. Click the system tab at the bottom of the window. Click File/Import UAV Setting. From the file browser window select the path to the P15230_CC3D File. Click Select, to load the settings onto the CC3D. NOTE: This will override the Tx calibration, and will require calibrating.

Calibrating the Tx

Calibration of the Tx can be completed using the Transmitter Setup Wizard. This software will walk the user through calibrating the CC3D to their particular transmitter. This will recompute new maximum and minimum values. Access the Transmitter Setup Wizard by clicking the configuration tab at the bottom of the screen. Click the “Start Transmitter Setup Wizard” button. When the program is complete, Click the Save button at the bottom right of the screen.

Raspberry Pi Program
Connecting to the Pi
Most file transfers onto and from the pi was done via Secure Shell login on a shared
network between the connecting computer and the Raspberry Pi. This can be done in
Windows environments using shell clients such as Putty or through interfaces provided in
MATLab and Simulink. In a Unix Environment, this can be done via the Terminal prompt.
For this section, connection was done via a Unix terminal prompt with host computer
enabling shared ethernet as a DHCP host for the Raspberry Pi.
To login:
$ ssh [email protected]_IP
You now should have access to the Pi’s terminal command prompt.
To transfer files via secure shell to Pi:
$ scp path_to_file/file [email protected]_IP:path_to_pi_file/file
To transfer files via secure shell from Pi:
$ scp [email protected]_IP:path_to_pi_file/file path_to_file/file
Setup Pi LIbraries
Enable I2C
If you can’t find the I2C device on the Raspberry Pi, it may need to be manually removed from
the blacklist that Raspbian supplied with its OS. To check if the driver is enabled on the Pi’s
command prompt enter:
$ ls /dev/
If “i2c­1” is not listed check for other i2c named devices. If there is an I2C device of a different
name, this name with have to be edited from the file (device handler) used to the openi2cBus
function in the masteri2cCom source file. If no i2c device is listen it will have to be enabled.
Follow the Adafruit tutorial to enable this device as
https://learn.adafruit.com/adafruits­raspberry­pi­lesson­4­gpio­setup/configuring­i2c .
Add Source Files to Pi
Copy startup scripts
The startup scripts that run the program from the pushbutton press should be copied to the
home folder of the logged in user. This can be done via the command from your host Unix
machine:
$scp start [email protected]_IP:/home/PIUSERNAME/
If the crontab isn’t modified to reference these files, it can be added to the crontab by;

  1. making a cron log directory:
    $ cd #go to home directory
    $ mkdir logs #create log directory
  2. open cron:
    $ sudo crontab ­e
  3. edit to run script at reboot:
    @reboot sh /home/PIUSERNAME/start/launcher.sh > /home/PIUSERNAME/logs/cronlog 2>&1
    Copy Main Program
    To transfer the main programs source code use the command:
    $scp mainProg [email protected]_IP:/home/PIUSERNAME/c_code/
    Changing Program
    Programs to Build
    From the Makefile provided in the mainProg folder many compile options are identified
    mostly for testing during system integration.
    Adding Programs
    To add programs to the source make sure that the Makefile is modified to compile and
    link those programs properly.
    Referencing Programs For Button Start
    The startup script runs the program compiled under the name ‘lmnoCopter’, to change
    the program that runs at the button press either the executable created in the Makefile could
    be modified to rename its executable, the executable could be manually renamed, or the
    reference in the lmnoCopter.sh script could be changed.
    Compile Program
    The Makefile makes re­compiling easy. On the Pi’s command prompt just run the command
    make and whatever component to compile. The compile time can take up to 2 minutes from
    original source.
    $ make comlink: creates the main file that allows the user to send PPM packets of throttle,
    pitch, roll, and yaw values from the Pi to the Teensy slave device which will generate the PPM
    signals to send to the flight controller on the platform.
    $ make test_sonar: creates the comlink program with the option of requesting incoming
    data from the teensy which includes the four connected sonar sensors as well as current and
    voltage sensing readings.
    $ make test_acc: creates the test_acc program that displays all reading from the IMU in
    10 polls spaced 1 second a piece.
    $ make all: creates the lmnoCopter program. This is the program in progress for applying
    autonomy for indoor waypoint navigation. Currently the craft has no localization method and
    forward and hover commands are unimplemented.
    $ make avoidance: creates the avoidance program, which is a following program for the
    craft. The craft tries to maintain a constant distance from a sensed object on the back sonar
    sensor.
    Potential Add-Ons to Program
  4. Finalize Flight Control
    a. Tuning of Flight Controls (CC3D, Teensy PID, RPi PID)
    b. Face Tracking or Alternative Following UAS with distance locking
    c. WiFi Positioning Integration To UAS For Indoor Flight
    d. GPS Positioning Integration To UAS For Outdoor Flight
  5. Indoor Mapping (2D or 3D)
    a. LIDAR Integration To UAS
    Errors In Program
    Though status LEDs are not currently configured for the RPi, the I2C communications status
    came be read by the main program reading the uint8_ti2cComStatusvariable. A bit within that
    variable serves as a flag for the teensy slave , the compass and accelerometer slave sensors,
    the barometer slave sensor, and the gyroscope slave sensor. Each bit is defined below:

defineCOMSTATUS_COM_ACC (0x01)

defineCOMSTATUS_BARO (0x02)

defineCOMSTATUS_GYRO (0x04)

defineCOMSTATUS_TEENSY (0x08)

Localization Program
Necessary Hardware

  1. Three 2.4 GHz routers
  2. One 2.4 GHz WiFi USB receiver
    Software
    The software was designed to be used in conjunction with the A* search algorithm’s grid
    layout of an area of known size. There must be three WiFi routers at ground level, each with
    known coordinates on the Asearch grid. The first part of the code takes the recorded signal strength of a router and calculates a distance based on the formula found here: http://stackoverflow.com/questions/11217674/how­to­calculate­distance­from­wifi­route r­using­signal­strength The 27.55 term is a constant based on both the units of the frequency of the signal and the units of the distance from the router. In this case, the frequency is measured in megahertz and the distance in meters, so 27.55 is used. More information on this constant can be found here: http://en.wikipedia.org/wiki/Free­space_path_loss#Free­space_path_loss_in_decibels The main function first tries to connect to each router (referred to as A, B, and C) in order based on a counter variable that increments once all calculations are finished for the currently connected router. In order to connect to the routers, the proper SSID and password must be entered in the code itself, replacing the terms “Router A/B/C” and “wifipassword” with the appropriate values. Once connected to a router, the frequency of the signal, and the signal strength at the craft’s location. Once it has these parameters, the calculations from above are run to convert the signal strength into a distance. This process is repeated until all three routers have a recorded distance. After all three distances have been recorded, these are used in geometry­based equations to pin­point the craft’s coordinates on the A search grid. The process is then repeated.
    For best results, place Router A at <0,0,0>, Router B at an adjacent corner, and Router C on
    the far side, halfway between the endpoints.
    Issues
    First, WifI has been found to be unreliable for this purpose. NFC or bluetooth hotspots with
    dedicated connections to the Pi would be preferable. This will eliminate the need to cycle
    through connections. The method of obtaining the distance from each hotspot will need to be
    changed to reflect the change in hardware.
    Using WiFi, the 2.4GHz routers are not the most optimal choice. 5GHz routers would be much
    more preferable as the signal strength changes more noticeably with distance, allowing for
    more accurate distance calculations than the current set­up. If the included WiFi receiver is
    used, there will not be a need to replace it for a 5GHz compatible model, as this is already
    supported.

Source: Autonomous Quadcopter Platform

Scroll to Top
Read previous post:
Raspberry Pi: Access the GPIO interface with Java

table of contents Raspberry Pi: Access the GPIO interface with JavaSet up the working environmentDesign of a GPIO-JNI workerAn oscilloscope...

Close