Obstacle Avoidance: URC 2026 Rover

Obstacle avoidance and GPS/IMU navigation for the Wisconsin Robotics 2026 University Rover Challenge (URC) rover. Fork of WisconsinRobotics/WRoverSoftware_25-26; this README covers the parts I wrote.

Demo

Rover detects and avoids an obstacle during the SAR run. The avoidance worked, but motion was jerky and took ~5 s (see Limitations).

My contributions

Package	Role
navigation	Depth-camera obstacle avoidance. Projects depth into a GPS-shifted 9×9 m local occupancy grid (0.1 m cells), builds a polar histogram (4° sectors), and picks a free valley VFH+-style (hysteresis thresholds, 0.5 m robot-radius inflation, target-weighted cost). Outputs a 4-value drive command.
gps_tools	TODO
wr_imu_compass	TODO

How it works

depth + RGB + GPS + compass heading + waypoint
 -> ground removal (height + slope < 30°) -> obstacle points
 -> project into persistent local grid (shifts with GPS, slow decay)
 -> inflate by robot radius -> smoothed polar histogram
 -> hysteresis -> open valleys -> best sector (5x target + 1x heading cost)
 -> low-pass -> P controller -> drive command

Validation

• VFH+ (Vector Field Histogram+: bins obstacle density by direction and steers into the best free gap) worked in testing on a kart.
• Did not carry over to the rover. Suspected cause: poor localization (not verified).

Limitations / future work

• Heading controller was P-only (proportional gain, no integral or derivative term), likely contributing to jerky motion.
• Next: add a D term using IMU gyro yaw rate (not differentiated heading error, which amplifies noise); log pose vs. ground truth to test the localization hypothesis; re-run VFH+ on the rover.

Setup

Upstream GNSS/RTK setup from the team repo.

Installation

Install the ublox package with:

sudo apt update
sudo apt install ros-[distro]-ublox-dgnss

Running the Node

After setting up RTK on the base with ublox, make each base start receiving RTK and publishing the corrected topics:

ros2 run ublox_dgnss_node ublox_dgnss_node --ros-args -r __ns:=/rover1 -p device_serial_string:="'1'"

• Replace /rover1 with your desired output topic namespace.
• Replace "'1'" with your device's specific id.

Output Topics

For this example, the output topic is /rover1/ubx_nav_pvt, of type UBXNavPVT, importable from the installed ublox-gps package:

from ublox_ubx_msgs.msg import UBXNavPVT

Running base station launch scripts

Configure RTK on the base station:

./run_rtk_base_station.sh POLE_LAT POLE_LON POLE_ALT DISTANCE BEARING
# Example
./run_rtk_base_station.sh 38.221704 -110.421456 1309.99 0 0

Run the path planning, spiral planning, and base station controller:

./run_state_machine_base_station.sh LIDAR_PATH
# Example
./run_state_machine_base_station.sh ~/motel.laz