Final Performance Test

Performance Test #3: Energy Optimization

In preparation for the final performance test, the group wanted to minimize the energy used during each run. The GoFor(); command was kept constant throughout trials since it was shown to be more consistent, but the times needed for each section of the track were modified. Shown in the graph below, modifications to times did not alter the amount of Joules used per run. However, the modifications in times were done after another issue occurred with the Arduino board. Similar to the last issue with only one motor working, the team needed to take time to brainstorm reasons as to why this issue persisted. The motor chip was replaced again and the metal clips were positioned even further than the Arduino board to decrease interference. The wires connecting the motors and ports were also split again after finding one was slightly looser. After these adjustments, the times used in the GoFor(); command were not accurate. Thus, the group spent more time trying to perfect the code so the AEV would stop within the gate using only coasting. The group had tested earlier in the Preliminary R&D that power braking consumes more energy, so the group wanted to continue with coasting throughout the entirety of the track. However, it was observed that when the AEV was coasting down the hill back to the loading dock with the caboose, it had a hard time stopping with the excess weight using only coasting. The group decided to implement power braking at the bottom of the hill for just a second or two so that the AEV would not bump into the end of the track so much that it would disrupt its passengers. This power braking can be seen in the graph below on the orange line. It is the skinny sharp increase in power at the end of the run. Although adding more energy, the group concluded that it was miniscule amount of energy to sacrifice for the safety of the passengers. Also seen by the graph, the overall run of the final trial was 59 seconds. This was longer than most other group’s runs, so the team wanted to move forward in the performance testing to try to decrease the time as much as possible. They considered using power braking to decrease the time of the run and therefore decrease the overall cost of the project, but they wanted to focus on energy first and foremost since energy efficiency was their approach. After several considerations, the group decided to stick with their code consisting of mostly coasting with the exception of power braking at the end since the trial only used 220.75J, which was lower value than most other groups. The group was still struggling with consistency in the AEV when trying to stop in the gate by the end of Performance Test #3. Moving forward, the group wanted to keep two separate codes for the two different classrooms while keeping the battery voltage as consistent as possible. Other possible sources of error could have been any sort of draft or change in temperature in the room that was could the AEV to travel faster or slower than normal. The group also considered if continuous usage of the AEV throughout a class period helped the AEV perform more consistently as it typically performed more consistent towards the end of the class rather than the beginning.

 

Performance Test #4: Final Testing

The group completed three successful runs of the final performance test. The AEV was inconsistently coasting up the hill and was not stopping between the gate every run, so the group decided to implement manual braking during the tests and sacrifice accuracy errors. Although accuracy errors were lost, the use of manual braking decreased the time costs since the group was able to increase the speed of the AEV as it traveled towards each gate checkpoint. Using manual braking also decreased energy costs since no power braking was needed. The group noticed these trends after the first test and increased the speed of the AEV as it traveled up both hills to decrease the time of the run. As seen by the Cost Analysis table below, the second run was lower in time by 4 seconds and lower in energy by 2.35J after the group allowed the AEV to run for an extra second or two, enabling it to coast towards the gate checkpoint at a faster rate.

The average cost form energy and time combined was $431,882. With capital costs, the AEV was $587,682 overall. The group was $87,682 over the desired budget. This was mostly due to time being higher than desired since coasting was implemented rather than power braking. With more time, the group would have worked to decrease the time as much as possible while keeping the same amount of energy used since each second was $1,500 and each Joule used was $5,000. After the run with lower energy and time with higher speed going into the gate, the group would want to explore decreasing the time the AEV runs for by allowing the GoFor(); command to run during flat portions of the track instead of coasting and then apply manual braking. The manual braking only cost the group 2 accuracy points out of a total 40 points. The deduction was minimal, so the team would want to explore the benefits of continuing the manual braking and decreasing the time of the runs. The cost of the AEV was not the main focus of the group, but it was a large factor in how the group approached the design of the AEV. The reflectance sensors were taken off and the smallest base was used to reduce capital costs. The two-motor design was used since it improved efficiency and decreased time of each run as discovered in Performance Test #1 and the motor quantity analysis in the Advanced R&D.

 

Citations

The Ohio State University Advance Energy Vehicle Design Project: Mission Concept Review

            (MCR) and​ Deliverables. 2018, Apr 10. www.carmen.osu.edu.

 The Ohio State University Advance Energy Vehicle Design Project: Lab Manual Preliminary

            Research and Design. 2018, Apr 10. www.carmen.osu.edu.

The Ohio State University Advance Energy Vehicle Design Project: Advance Research and

            Development and Performance Tests. 2018, Apr 10. www.carmen.osu.edu.