STRATUS PROJECTMIDTERM
PRESENTATION
Ryan RasmussenMaggie Krause
Jiajun Yang
Hardware Progress•Mechanical assembly complete
•Received APM case and power module last week
•Connected wi-fi module in January but have encountered several problems so far
Hardware Problems APM and Xbee Explorer not compatible without modification
Dr. Detweiler removed a diode and soldered additional resistors
First wi-fi module is no longer functional, now using spare We are not sure how it broke, possibly hooked up incorrectly?
Initially used TCP connection, but discovered that when the connection is lost, it was very difficult to recover Now using UDP, which requires connecting to module with static IP
Several connection problems when working in NIMBUS Lab Sponsors said they have always encountered wi-fi problems in the building We don’t have the same problems when using outside the lab
Progress First semester was focused on assembly and choosing
communication hardware
This semester is focused on software with two major goals Direct connection to phone, which will display copter status and send
basic commands Adding node to existing NIMBUS framework to allow the lab’s ROS
system to communicate with the copter’s MAVlink system
Separation of tasks NIMBUS Integration – Maggie iOS App – Jiajun Android App - Ryan
NIMBUS Integration: ROS Overview Robot Operating System (ROS)
Open-source "meta-operating system" for communicating with robots
Built to be modular and adaptableProvides a host of command-line tools for
testing and developmentrosmake, rosrun, roslaunch, rxgraph, etc.
ROS Concepts Uses a Computation Graph: a network of
communicating nodes Node: A process that performs a specific
computation Topic: A stream of messages published by a node
and subscribed to by one or many nodes Message: a data structure with typed fields, used
for sending info or commands Others: Manifests, stacks, services, bags
NIMBUS ROS System Runs on Linux, uses ROS system
MITAscTec MITAscTec
Collection of packages for communicating with and monitoring drones
Capabilities:○ GUI interface for sending state-based
commands○ Integration with Vicon infrared camera
system in NIMBUS lab and GPS for positioning
○ Remote access capabilities○ Serial communication with drone using
XBee module
I/O cluste
r
State machine
Control cluster
Drone
Progress: MAVLink/ROS Node Integration Quadcopter uses MAVLink protocol, but
MITAscTec uses AscTec protocolNeed for intermediate node to translate
Integrating an open-source nodeInstall MAVLink/ROS packageDetermine placement of new node and create launch
files specifying node and topic configurationMAVLink/ROS package:
○ Outbound data translated from AscTec protocol to MAVLink
○ Inbound data translated from MAVLink to AscTec protocol
Progress: Integration
Sending commands:ROS command input/a/robot_trans translates command to AscTec, /a/robot_prot
handles AscTec protocolMAVLink node translates AscTec to MAVLink and sends
commands, receives data similarly
Future Plans: Integration Test MAVLink inbound node by receiving
status/heartbeat (no outbound components) Test MAVLink outbound node with Vicon launch
configuration (Relies on input from Vicon camera system)
Make alterations to MAVLink/ROS node based on differences between MAVLink and ArduCopter protocols
Build other launch configurations once MAVLink/ROS node is tested
iOS App Status Ability to communicate with APM using UDP
When app starts, it detects heartbeat from APM and extracts APM system ID, which is then used to request a data stream that contains status information
App also accesses iPhone GPS to get current location which will be used to implement “Follow Me” function
iOS App Implementation MAVlink is a messaging library only available in C
iOS Objective-C allows for easy integration of MAVlink library with no modificationThinking more on the stream pack(ByteBuffer) when send and receive
Using open source iOS code (AsyncUdpSocket) to implement UPD communicationEasy to sent with the port and IP address, and receive Objective-C type Data with action immediately.
Wrote the phone GPS class with the Objective-C framework.
Next Plan Done on the display part Available for send actually command. Test outside with iPhone.
Android App Status Ability to communicate using UDP and display all copter status info Notifies user if connection is lost All commands are implemented, but so far only Arm/Disarm is
confirmed to be working Access to Android GPS for “Follow Me” coordinates
Android App Implementation Attempted to implement MAVlink library using JNI
Ended up writing Java classes to implement messages and commands Only implement messages we need (about 15) Involved working with raw byte data (ByteArray, ByteBuffer)
Wrote custom class for UDP connection that implements InputStream Same functions as TCP InputStream (avoid refactoring code)
Utilizing Android AsyncTask Main thread is reserved for UI AsyncTask allows you to easily launch tasks in a new thread One thread is dedicated to receiving and unpacking UDP communication Each command launches an AsyncTask to send command and wait for
acknowledgement from APM
Setbacks/Problems Testing commands must be done outside
Requires GPS Weather not cooperative Requirement from sponsors that at least 2 people are present
How did wi-fi module break?
Replacing parts after crashes is time consuming. Currently need to replace at least one motor
Setbacks/Problems ctd... ArduCopter does not implement all MAVlink commands
Makes potentially easy commands much harder to implement (Takeoff)
ArduCopter has made several modifications that are not documented Requires going through source code in detail May add difficulty to implementation of NIMBUS node
Implemented commands on Android currently not working Takeoff and Land commands were not working as of last week Guided Mode vs. Auto Mode? ArduCopter does not implement MAVlink Takeoff command, which may require
sending mission script to copter and changing flight mode and throttle level
DEMO