Drawbar Testing
Drawbar tests simulate hillclimbing and traction in tough terrain. It isn't too different than a tractor pull. Weights apply resistance through pulleys, and that pull is measured by a load cell. 'Steepness' is adjusted by moving an onboard weight (the one with the orange stripe that is riding on the aluminum beam) from front to back. This proportions weight between front and back wheels for testing. Weight naturally shifts aft during steep ascent, and that shift contributes substantially to climbing failure.
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Drawbar Pull (DP) setup
Once again, I am happy to see the DP set up on your team's rover. However, I notice that the drawbar is connected to the wheel hub for these tests - and is perfectly ok for generating a DP vs. Slip plot on an even surface at the end of the test. However, whilst using the weight shift to emulate slope gradeability, I think it may not be accurate if the current set up is used.
In my opinion most of the reactions come from the wheel-soil interaction at the wheel-ground contact patch. Hence, the drawbar connection links should be attached as close to the wheel-ground contact patch as possible to record accurate forces during weight shifting. I am not sure about the magnitude of accuracy or inaccuracy between the two setups, but thought might be of mutual interest to discuss it here.
Ricky8midnightmoon
Rover Locomotion Engineer