Update: Jason 2018-12-09

This week, I focused on three different things

  • Analyzing experimental torque disturbance data and its comparison to simulation
  • Preparation and presentation for a meeting with a potential sponsor
  • Preliminary velocity data analysis using CTA (constant temperature anemometer)

1. Torque disturbance data analysis

I started analysis on torque disturbance data. I had fixed a bug in my python script, which caused a huge order of magnitude for the disturbance torque. Although the order of magnitude became more plausible, still we have an issue with the result.

Fig. 1. 1. X-direction torque 2. Y-direction torque 3. Z-direction torque (with fan on)

Problem is that there is a very small lag between the disturbance torque and the motor torque. Since the command torque is proportional to the error of angular velocity (\underline{n_{B}}=-\frac{\underline{J_{B}^{B}}}{\tau_{\omega}}\left(\underline{\hat{\omega}}-\underline{\omega_{cmd}}\right)), we would expect some lags. However, the level of lag is very small, as it is shown in the graph. I looked at Karan’s data, and similar level of small lag was observed.

In order to figure out the reason, I ran a simulation with a torque input (10 [mNm], x-direction only) from 27-31 [s], and results are shown.

Fig 2. Simulation results with a torque input (Position, velocity, angular velocity, and motor forces)

Fig 3. Torque results, x-direction (enlarged)  

Fig 4. Torque results, overall

However, as one can see from the position plot, I was adding too much torque input, which resulted in very high magnitude of the torque.

I will try to make a similar simulation of our experiment, to properly compare the results with our experimental data next week.

2. CTA preliminary test

I also started collecting velocity data of the jet utilizing CTA. As an initial stage, I manually hold the sensor and measured center-line velocity.

Fig 5. Flow velocity measurement description

Results are as follows;

Fig 6. Jet velocity w.r.t time.

  • While I will need further analysis of the experimental data, \left\langle u'^{2}\right\rangle for example, I have noticed that the voltage of hot-wire circuit is not consistent. I will need to conduct further experiment to figure out the consistency of our sensor.
  • Also, I will compare the experimental jet velocity with theoretical values, and see whether there is a self-similarity as well.

This week, I have learned that

  • Thorough, logical way of analyzing/reasoning the given data
  • Utilizing/connecting the knowledge that I have learned from the class

Next week (Specifically, before the general progress meeting Dec/19, considering my hectic schedule on finals/project) I am planning to finish the tasks that I stated Section 1 and 2.

In a month, I will finish the flow characterization on drone so that I can aim the results to upcoming conferences.