Electronics and Software Subsystems roughly comprise of

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Control Systems for rover

Written primarily for closed loop operation of Arm and Steer

  • All 6 wheels are driven independently from GPIO pins of Raspberry Pi 3 in open loop, 4 steering wheels (Front and Rear) are steered using closed loop control (see fig. on left)
  • Steering is controlled by Roboclaw Motor Drivers onto which we employ a Type II control system, to track ramp input (see fig. on left, tracking of i/p, dotted line, is done by o/p, solid purple), while drive is controlled by Hercules motor Drivers
  • We are working towards getting a state space description of the same, so that we can employ Inverse Kinematics or LQR control for the arm, using Moveit! motion planning plugin (see fig. on left)

Autonomous Operation of Rover

The rover navigates autonomously from one GPS coordinate to other, avoiding obstacles coming in path

  • Surrounding mapping is done using SLAM; requires a high-power LIDAR for visualising the map
  • The whole system is up and running on Gazebo in a simulated environment and the algorithm is being improved for better performance. (video on right)
  • We are working to employ the algorithm on our smaller prototype of the rover first, and then later shift to main rover

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Base Station GUI

Implemented over multiple machines in a distributed manner (pic on left), using RQT dashboard, providing visual feedback of IP Cameras, APM and other on board sensors.

  • URDF Visualisation: As a first step towards automating the system, an URDF of rover (pic on left) was made, which helps us translate what rover is doing on field onto the GUI and autonomous node.
  • Plotting GPS data from APM module (pic on left): GPS lat long received from APM using mavros library is mapped onto RViZ aerialmapdisplay plugin using QT gui.
  • IP Camera interfacing with GUI: RTSP stream of IP camera is obtained using opencv and using ROS-OpenCV bridge, stream is converted to image message. The GUI widget ‘Image View’, is used to visualise the message.
  • Currently working towards incorporating rover diagnostics into GUI, by plotting various critical sensor data using RQT plot, storing data in ROS bags for analysis, and raising appropriate warnings and errors occuring in on-board code, on GUI

Wireless Communications

Establishment of Wireless Communications between Rover and Base Station, over 1 km non LOS range

  • We are using commercial off-the-shelf PoE wireless bridges (Ruckus P300) which operate in 5.6 GHz band (IEEE 802.11ac), and have maximum EIRP of 36 dBm, compliant with FCC UNII-1 regulations.
  • These have been tested to give 1 km non-LOS range, and use adaptive channel selection techniques (Ruckus ChannelFly) to shift to a different channel once the current channel starts degrading, to tolerate interference.
  • Video feed is obtained via IP cameras on board and telemetry is achieved by passing messages between ROS nodes running on board (which interface with various sensors) and nodes running on base station (which interface with GUI).
  • We also have 900 MHz Xbee modules as a backup link for the communication systems, which have been interfaced with ROS framework as well.

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Power Distribution and BMS

  • The entire rover will be powered by a 24 Volt custom battery pack consisting 3.7 Volts lipo cells
  • 24V - 12V and 24V - 5V DC-DC buck converters are used on a custom made PCB to distribute power for every components
  • A Capacitor bank is used on the PCB to compensate for the effect of back EMF generated from the motors and actuators
  • We are designing a Battery Management System for cell balancing and monitor the health of lipo cells during charging and discharging

Documentation and Code Storage

  • The team uses Github primarily for code storage and documentation.
  • Have a look at iitbmartian github organisation for all our codes and latest updates.
  • All the repositories have well documented README's which indicate how to set-up and debug the code
  • Also, we contributed to a small, application intensive wiki page on ROS for Web and Coding Club (WNCC) Wiki.