## 3 Experimental Results
### Battery Characterization  
The Crazyllie 2.0 has a flight time of around 7 min [9] without any additional equipment. At first, the flight time was measured first without the camera and video transmission module mounted on the vehicle and then the flight time was measured with the module mounted and turned on, thus contributing to the effective flight time both by its net weight and by the power required for indoor operation. The results from measuring the battery level with and without the camera module activated can be seen in Figure 10. Based on these results, it can hover in place for roughly 6.7 min until the battery voltage level drops below 3.0 Volts.  
In Figure 11, a similar experiment was conducted but this time with the camera and transmission module mounted on-board the Crazyllie 2.0 and with the power to the module turned on. The intention of this experiment was to assess how the battery life is influenced by only its contribution by weight, excluding the power consumption for the operation of the module. However, at this point the battery had reached too many charge cycles to be able to maintain a similar operational time as for the previous experiments, making the battery discharge more rapidly and thus decreasing the effective flight time substantially.  
\begin{table}
\begin{tabular}{c c c} \hline \hline x [cm] & y [cm] & \(\
abla\) [degrees] \\ (\(\mu\) = 1.88, \(\sigma\) = 5.65) & (\(\mu\) = -2.27, \(\sigma\) = 4.99) & (\(\mu\) = 0.085, \(\sigma\) = 4.06) \\ \hline \(-\)7.7 & 1.0 & 0.12 \\ 7.3 & \(-\)7.1 & \(-\)10.67 \\ 3.5 & \(-\)3.4 & 5.19 \\ \(-\)6.1 & 0.5 & 0.38 \\ 3.6 & 9.2 & 1.44 \\ 7.0 & \(-\)2.5 & 1.75 \\ 5.1 & \(-\)6.2 & 0.34 \\ \(-\)4.3 & \(-\)1.7 & 1.1 \\ 4.9 & \(-\)5.2 & 0.14 \\ 5.5 & \(-\)7.3 & 1.06 \\ \hline \hline \end{tabular}
\end{table}
Table 11: Results of the targeted landing experiment. The mean value \(\mu\) and the standard deviation \(\sigma\) are indicated for each respective parameter.  
Figure 10: Changes in the effective flight time of the MAV with and without the camera module.  
Therefore, we cannot compare the results between the different measurements directly, but we can observe how other parameters influence the flight time. As the battery level decrease, the duty cycle of the PWM signal given as input to the metal-oxide-semiconductor field-effect (MOSFET) transistors which drive the motors must increase in order to keep the vehicle in equilibrium at the specified height, because the thrust generated by each motor must add up to support the total weight of the platform.  
The plot in Figure 11 shows how the duty cycle of the PWM signal increases as the battery voltage decreases in order to keep the quadcopter stable and at a constant height. This means that since the thrust output from each motor will determine the position (in this case, the height) of the quadcopter, by increasing the cycle frequency the quadcopter is able to remain in its original pose, but this will also entail in an increased power consumption. We can also see from the graph that the readings from the on-board temperature sensor increase with the time of operation. This is interesting because it allows us to reason about the losses in the system that appear as heat losses. The internal resistance in the battery will cause the temperature in the battery to increase over time during operation and will cause the voltage to drop; however, since the sensor measures the ambient temperature, we cannot conclude that the increase in temperature is subject to only the heat generated by the battery, as it may also originate from, e.g., friction or other losses from the brushless motors which generate heat.