Our top priority is safety, which involves the safety of passengers as well as the whole transportation system. One of the potential cause of danger to passengers is when the AEV approaches the gate, there might be a sudden speed change and the passengers might get hurt due to inertia. Our solution is that the AEV would first coast before the gate, and after the AEV triggers the gate sensor, there will be a power brake to effectively stop the AEV. This solution is also firmly backed by higher energy efficiency as well as higher accuracy. Compared with the sole power braking method, which would use 66 joules energy and take 8.17 seconds to fully stop since the start point, the new approach only uses 44 joules energy and 7.48 seconds to stop. The group has decided to ensure safety first, with potentially higher energy efficiency as well as accuracy pursued. Therefore, the Coasting-Power Braking approach has been used every time the AEV should stop.
Another approach we employed to enhance the AEV performance accuracy is that, we used position-constrained methods to control the coasting period instead of using time-constrained methods. Before this change in program design, the performance of AEV during test runs showed a high inconsistency between distance traversed until it braked. However, after using position based methods, the AEV could accurately and stably arrive at desired location. Backed by solid data, in the three tests runs observed, the AEV traveled 4.14 (m), 4.23 (m), and 3.95 (m), with a small standard deviation being 0.12 (m).
Other than optimized program design evolution, our group also referred to some scientific research and changed our AEV hardware design based on our research findings. It has been suggested that the push-pull propeller configuration is preferred considering aerodynamic efficiency over different configurations including pull, push, and pull-push configurations [1]. We changed our design to a more balanced shape well-suited to a push-pull configuration, which helped us to cut the general percent power from 40% to 35% speed.
Supported by solid data results, our evolution of general design will confidently live up to our top priority — safety, as well as other missions including accuracy and overall comfort. Our design will be an effective solution to the local community transportation problem, which is to connect residents from Linden to Easton/Polaris with more opportunities in the future!
References:
[1] Comparison of wing–propeller interaction in tractor and pusher configuration. 2018, March 23. http://journals.sagepub.com/doi/full/10.1177/1756829316638206