In week 7, research and development continued on the AEV. The energy and analysis study was conducted during lab, providing a better look at the forces that affect the AEV.
To start the energy analysis, the AEV was first measured to be .263 kg. Then, the following code was run to the AEV while the vehicle ran on a straight track.
Energy Analysis Code
energyAnalysis
//code given by lab manual
motorSpeed(4, 30);
goFor(4);
motorSpeed(4, 0);
goFor(10);
Following the run on the straight track, data was extracted from Matlab and used in calculations for an Excel Spreadsheet. Sensor accuracy, propeller and friction forces, distance vs time and velocity vs time graphs were all calculated.
The wheel count system was then verified to be accurate. The measured distance on the track was found to be 269 inches (or 6.83 m). The data gathered in the arduino board was analyzed in Excel. The error measure in marks was found to be .32% error (off by 2 Marks), proving the AEV to accurately measure it’s location
The following plots were then generated in MatLab:
Distance vs Time
The AEV followed a relatively linear pattern for distance versus time. The AEV covered distance at a higher rate in the beginning, maintained the pattern in the middle, but eventually stopped moving around 10.5 seconds; this was the point where the AEV stopped entirely due to braking but the sensors continued to gather data.
Velocity vs Time
The velocity vs time graph was derived from the distance versus time graph. The AEV increased velocity incrementally in very defined steps, leading to a “staircase type” plot. The velocity peak is around the center of the graph, where everything after is decreasing speed. This relationship is to be expected, as the AEV will run slower once the power supply is cut off and it is no longer accelerating. One notable observation is the oscillation between steps. Since the AEV measures distance incrementally via the reflectance sensors, fluctuations are expected to be seen in the graph.
Forces Calculated
- AEV mass: 263 g
- AEV motorSpeed: 30%
- Propeller Force: 10.0 gmf (gram-force)
- Friction Force: 3.1 gmf (gram-force)
- Net: 6.9 gmf (gram-force)
Overall, the AEV experienced a low friction force compared to the propeller force. This allowed the AEV to operate with a net force of 6.9 gmf. It is important to compare the propeller force against friction force, as a high net force could negate a strong propeller force. Further research could be conducted in minimizing the friction force the AEV experiences.
Our force calculations compared very well to Team B’s. When running their 264 g AEV at 25% speed, a 10.7 gmf propeller force was negated by a 3.9 gmf friction force, resulting in a similar net force of 6.8 gmf. At lower speeds, their AEV experienced a similar force but also a higher friction force. While this shows our AEV to overcome friction better, their propeller force output of 10.7 gmf was higher, demonstrating that considerations must be made to our AEV propellers. Ultimately, increasing propeller force without increasing friction is our primary goal.
Motor Configuration Code
reverse();
motorSpeed(4,25);
goFor(2);
motorSpeed(4,20);
goToAbsolutePosition(100);
reverse(4);
motorSpeed(4,30);
goFor(1.5);
brake(4);
Motor Configuration Graphs
Configuration One
Configuration Two
The main difference between the two configurations was the motor placement. Configuration one consisted of one motor on the left side of the AEV, and configuration two consisted of one motor in the middle. It is clear from the graphs that configuration two was more energy efficient. This occurs because the motor is set in the middle of the base, meaning the AEV will be moved straight down the track. Due to the fact that the motor in the first configuration was set to the left side of the base, energy was wasted when the AEV was being propelled straight down the track.