The first of the two AR&D tests performed by Group F was that of Power Braking vs Coasting. Power Braking and Coasting are the two primary methods of stopping the AEV’s forward motion, and theses tests were performed in order to determine which of the two was the more effective method to adopt for future testing.
Power braking is the process of stopping the motor’s forward motion, and reversing the motors in order to provide a short, controlled burst of backwards thrust. This backwards thrust from the propellers is sufficient to entirely halt the AEV.
Coasting, the other method used to stop the AEV’s motion, is the process of simply turning off the drive motors at a very specifically calculated time. The AEV’s forward momentum will then carry the AEV to the intended stopping point.
Both the Power Braking and the Coasting methods were each tested with a uniform program in order to gauge the efficacy of each. This data was then collected and graphed, and the results can be seen below:
Graphs:
Coasting Graphs – Plot of distance (red line) and energy consumption (blue line) vs time.
Power braking graphs – plot of distance (red line) and energy consumption (blue line) vs time:
Both Power Braking and Coasting have their pros and cons. As can be seen from the graphs above, the Power Braking is a much more immediate stop to the AEV’s motion. By the time the current being provided to the motors has been cut, the AEV’s forward motion has already all but ceased. In contrast, the Coasting data shows that the “Distance” value continues to increase, even after the motors have ceased moving. What this means is that the Power Braking allows for much more precise control over where the AEV stops moving, as opposed to the Coasting which requires careful measurements and synchronization in order to get the AEV to stop at the intended point.
However, the Power Braking also uses up considerably more power than does the Coasting. Where the Power Braking requires the motors to keep running for a short period after the intended forward motion has been reached – the portion of the energy graph after the large spike – the Coasting method stops using energy far earlier, and does not involve the large spike in energy consumption. This makes the Coasting far more efficient than the Power Braking, however the discrepancy in control still exists.
In light of this data obtained, Group F has opted to go with Power Braking method in order to take advantage of the more precise control afforded by it. However, Group F may reevaluate this decision at a future time depending on upcoming testing of the final design.