During the 2016-2017 academic year the Robotics and Automation Society at the University of Pittsburgh designed and built a drone to compete in Mission 7 of the International Aerial Robotics Competition. The team competed at the American venue and was awarded “Best System Design” and achieved the highest score at the venue.
This post will explore from a technical perspective the current capabilities of 2017’s entry, the overall design of the system, and the challenges facing the team in the 2017-2018 academic year.
The drone is currently capable of estimating its absolute position in the vertical direction and its absolute horizontal velocity. We are capable of reliable and controlled autonomous takeoff and landing as well as horizontal translation under velocity control. Velocity control allows us to fly pseudo-waypoints (requesting a velocity for an amount...
Our IARC Mission 7 team this past year used an RPLIDAR A2 made by Slamtec for obstacle detection. For a little background information, the drone flies in an open gymnasium and must avoid four moving ground robots with tall PVC pipes on top.
The installation and setup process were fairly painless. We have used both the NVIDIA Jetson TX1 and TX2 with this sensor. The default configuration of Linux4Tegra does not include the kernel module for communicating with the CP210x usb-to-serial converter included with the RPLIDAR. To set up this kernel module, we followed the instructions here.
After that was done, everything worked flawlessly with the ROS packages provided by Slamtec here.
We had no problems with noisy or invalid data coming out of the sensor; we were easily able to cluster the data into individual obstacles that could then be fed into our obstacle avoidance code....
For our 5kg custom autonomous quadrotor built over the past year, we used KDE Direct ESCs, motors, and props. Specifically, we designed our propulsion system to provide approximately 10kg of thrust using the following combination:
- 515Kv, 535W Brushless Motors (KDE2814XF-515)
- 35A ESCs (KDEXF-UAS35)
- Triple-bladed 12.5x4.3 Carbon Fiber propellers (KDE-CF125-TP)
The ESCs were fantastic and incredibly responsive. The synchronous rectification and regenerative braking features do feed large transients back into the system, but the only problem this caused occured when we had a connection (external to KDE’s electronics) between our control electronics and our motor power system. We were able to diagnose the problem with KDE’s help, and adding an opto-isolation barrier completely solved any problems.
The motors were also very reliable and well-constructed. We had one extremely bad crash from approximately 15m which broke the bearings on one motor, but they have otherwise been good....