UAS LiDAR Hot Swapping
Hot Swapping Best Practices
Last updated
Hot Swapping Best Practices
Last updated
PLS does not recommend hot-swapping batteries as SOP for UAS LiDAR acquisition, but we still provide the user the option on most of our lidar systems. Attached to the Nav box is a power input connector that has a split connection. Typically the primary source of power will come from the aircraft itself and the LiDAR does not need a secondary battery to perform acquisition, but, during a hot swap you can use this second connection to provide temporary battery power to the system while the UASs batteries are being replaced. This will allow the LiDAR to continuously run, reducing the time it would take to get airborne again and return on acquisition.
If a client wants to incorporate hot swapping into their acquisition technique, This is PLSs official best-practices suggestions:
When performing the Hot-Swap, the aircraft should NOT be stationary on the ground for longer than 2 minutes, anything greater than 2 minutes could result in excessive MEMs IMU drift that will result in ambiguous trajectory results during post-processing. If static time exceeds 2 minutes, the LiDAR should be powered down to stop data collection and treat the previous data collection as one mission, and start a new mission for the remainder of the flight acquisition.
PLS recommends performing a kinematic alignment and figure-8 at the beginning and end of each flight during the hot swapping to ensure that each flight can be processed individually if the need arises. PLS also recommends separating the mission for a battery swap at the end or beginning of a flight line and avoid departing the trajectory in the middle of a flight line. If your flight does depart in the middle of a flight line, you should overlap your trajectories by at least 100 ft (30m) or restart the flightline from the beginning for an unbroken trajectory after battery swap.
Ensure you have compatible software for processing data individually (LiDARMill NavLab must be able to process the entire trajectory, as no splitting is possible).
Avoid obstructing the LiDAR GNSS antenna while swapping batteries. If it is impossible not to obstruct or move the GNSS receiver during the battery swap, the LiDAR should be powered down to stop data collection and treat the previous data collection as one mission, and start a new mission for the remainder of the flight acquisition.
Avoid moving the UAV unusually on the ground or in the air post hot-swap. The aircraft should be armed, climb vertically until clear of all objects and sent on mission. To make this process as seamless as possible, have the kinematic line begin and end at the takeoff location.
Ensure the back-up battery is installed prior to shutting down, turning on, or disconnecting the main batteries from the UAS. Once the aircraft is on and the back-up battery is no longer necessary remove it from the LiDAR.
Pros of using Hot-Swap technique:
Can save time if implemented properly
Can increase acquisition and processing efficiency if you can prevent drift
A more “automated” approach to LiDAR acquisition.
Cons of using Hot-Swap technique:
If not conducted properly can hurt the quality of the entire data set.
If an improper shutdown of the system occurs during the acquisition it could corrupt the entire data collection.
This type of acquisition method creates unnecessary stress during the acquisition process which could result in poor operational best-practices.
