Research Log
After arriving in Rome, I was introduced to my research subject, a four wheeled model of a lunar rover. The current radius of its wheels was creating interference whenever the rover traversed inclined obstacles, so I used geometric reasoning to determine the minimum size adjustment required to successfully traverse an obstacle up to a grade of 30 degrees. Using the manufacturer's motor specifications and data, as well as estimated coefficients of friction, I was able to determine the maximum radius the wheels could have without stalling the motors due to overloaded motor torque. With this information I was able to proceed with modeling a wheel with a new radius in CREO Parametric CAD software to be manufactured using 3D printing technology. Early desired wheel characteristics include a wheel built in segments due to the limited size of the 3D printer, symmetric but multi-directional tread, and a rounded profile to aid in turning.
Week One: 5/18/18
Week Two:5/25/18
The initial CAD draft of the wheel was modeled and reviewed by midweek. Much of the inner geometry was kept the same so that the wheel would be compatible with the motor mounts. I increased the thickness of the wheel to account for the greater size, and because I had observed some deterioration in the rover's current wheels. To accommodate the size of the 3D printer test bed, the wheel was designed as an assembly of three radially symmetric interlocking parts. At Dr. Curti's suggestion, an inner guard was added to keep out accumulating dust from the test bed surface. The design was finalized but complications with the 3D printer delayed manufacturing.
Reflection: What are some initial cultural barriers that you are experiencing during your first few days conducting research abroad?
The biggest cultural barrier I have faced so far is unfamiliarity with language, both Italian and English. While the lab I work in uses English as a professional language for documentation, day to day conversations are still in Italian. I occasionally need to ask to borrow tools from other labs, which requires conversational Italian. It can take some time to coherently discuss technical topics, as well as make sure there are no misunderstandings due to language barriers. Reliable transportation has also been a little frustrating. Since the only way to reach the university campus is by bus and Roman buses are notoriously unreliable, it has taken some time to fully understand Rome public transport. There have been several instances where it has taken me over two hours to get to work due to a late bus. Luckily, everyone in the lab is understanding and working hours are flexible. I recently received a key to the lab so that I can go to work whenever I need to, which is especially helpful now that I have long 3D print jobs to complete.
Week Three:6/1/18
After several test prints, I was able to determine the optimal print settings using the expertise of coworkers and past part print files. I have tried to print parts as continuous as possible, however the operating hours of public transportation can interfere with my printing schedule. Each wheel part takes about 15 hours to print, with additional time afterwards for cooling. After each part is completed, support filament is trimmed away and sanded to produce a smoother surface. The dimensions of critical part features are verified inspected to ensure a close fitted final assembly. By the end of the week, a full wheel was able to be assembled, but the 3D printer had begun to malfunction again.
Due to the malfunctioning 3D printer, manufacturing was set back by four days. During that time I familiarized myself with the Python scripts used to control the rover, as some of the code for processing optical and sensory input was contained on a micro SD card that had been recently damaged. Depending on the progress of my research I may try to rewrite the missing code, however my main focus remains the rover's general locomotion. After a few unsuccessful attempts, I continued printing the component parts of the wheel assembly, and ran out of usable filament by the end of the week.
Week Four:6/8/18
Reflection: What are some adjustments, if any, that you have made to transition into your new environment?
Since moving to Rome, I have had to make some minor adjustments to my habits and schedule. As I mentioned before, securing reliable public transport has been a challenge. This is also the first time I have been without a car in my adult life. I have to generously allot travel time in order to compensate for late or missing buses, and have occasionally had to buy extra train tickets because I couldn't find the correct platform. The times where I have to speak Italian quickly are usually when buying metro passes and groceries, so I've learned Italian phrases specific to these situations to minimize confusion. I am using a lot more hand motions than I normally use in order to provide another medium of communication to a non-native English speaker and keep misunderstandings to a minimum. Fortunately, my work is relatively straight forward and I have a significant amount of background knowledge, so I haven't had to make any adjustments in my professional environment.
Week Five:6/15/18
I finished printing enough component parts for two wheel assemblies, which will be used to verify that the wheel design meets the necessary physical requirements and can effectively transmit torque from the motor to the wheel. The component parts for each wheel assembly were bolted together and glued with a fast acting adhesive specific to plastics. After the glue cured overnight, the wheel bearings were press fit into the wheels, and the entire assembly was attached to the motor shaft. Initial testing is promising, however, new hardware is needed to exert enough axial force to properly fix the wheels to the motor shaft. A silicon sealant between the motor shaft adapter and the wheel assembly may be beneficial as well.
Week Six:6/22/18
Week Six:6/22/18
I managed to fix the hardware issue by scavenging for odd spacers and washers around the lab, so the hardware joining the wheels to the motor now exerts the required axial force. After testing out the rover both on the ground and on the lunar environment, I proceeded to start manufacturing the remaining two wheels, following the same protocols for assembly as before. New washers for the wheels were ordered and will replace the temporary spacers. Issues with the 3D printer set back manufacturing, so wheel assembly will take place next week.
Reflection: Describe an experience(s) in the community that helped you learn something about the culture of your host country.
This week is the festival of Peter and Paul, which is a local holiday in Rome honoring the city's patron saints. Most shops and offices close for the day, and there are several different celebrations all around the city, from a canoe regatta on the Tiber River to fireworks and street carnivals. It’s also an important event for the catholic church, with many dedicated services in Rome's local churches. There's also the Pallium Mass at St. Peter's Basilica, which is a special service where Pope Francis blesses the pallium, a white stole that is placed around newly appointed church officials. In St. Peter's Square there are beautiful "infiorata" floral tapestries, a tradition dating back to the 1600s. I went to a street fair at the Basilica of St. Paul's Outside the Walls with a few friends and it was great to see how the streets outside a normally quiet abbey transformed with families and fair food. Rome has a lot of traditions that date back of hundreds of years, but to me the most interesting part of these celebrations and holidays is how they continue to be celebrated by people today who value their significance to their culture while also modernizing them through their participation.
Week Seven:6/29/18
The 3D printer hasn't worked properly since last week. I spent several days trying different settings and printing configurations. I recently had to replace the spool of filament in the printer, so there is a chance that impurities in the filament could be the issue. Additional prints with different brands of filament also failed, which leads me to believe that there is a mechanical issue with the printer. In the event that further printer problems prevent me from finishing the wheels during my tenure in Rome, I wrote an assembly guide so that the wheels could be completed in my absence. Until the printer starts to work, I will research and develop a traction control algorithm to improve mobility and decrease slip.
Week Eight:7/6/18
As the issues with the 3D printer continue to persist, I tried rebuilding the extruder assembly and replacing the nozzle, as I had noticed that the filament unloaded from the extruder appeared to be piling back on itself and clogging the nozzle. In some instances the filament looked burnt from staying inside the chamber of the nozzle for an extended time. When I was replacing the nozzle, I noticed that the chamber was filled with burnt plastic debris, so it could have been a contributing factor to the printer issues. Replacing the nozzle significantly improved extrusion, but I still haven't been able to successfully print any more parts. While developing the traction control algorithm, I was told that the motor encoders attached to each drive wheel had an analog output, which would not interface with the Raspberry Pi without an analog to digital signal converter. I found a suitable converter chip and a decoding function to incorporate into the rover's code, but I can't do much else until I have the chip to connect the encoders to the Raspberry Pi controlling the rover.
Reflection: Has there been any cultural differences that you've experienced that have made you aware of your own culture?
Probably the biggest cultural difference that sparks awareness of my own culture is how I speak. Italian as a language is very heavy on vowels, and contains no silent letters. When I was beginning to learn Italian, I found it was difficult to pronounce words with multiple vowels in a row such as 'biglietteria' or even 'aeroporte,' as you had to individually pronounce each letter in the word. For this reason, there are certain things I will avoid saying simply because it is too hard. But apart from simple grammar rules and pronunciation guides, a lot of people I've met in Rome find an American accent to be funny, especially when trying unsuccessfully to speak Italian. My mother recently arrived in Rome to visit me, and we've laughed a lot about these proununciation struggles. One of my goals in the beginning of the summer was to speak to someone in Italian without them responding in English. While I do still get responses in English, I am getting more responses in Italian now, so hopefully this is a sign of improvement.
Week Nine:7/13/18
I managed to reach out to the supplier of the motor encoders, who provided me with additional documentation and coding tutorials that proved the encoder output was digital and not analog. This allowed me to begin working on applying slip control. Using the Tektronix TDS 2014 Oscilloscope, I measured the output frequencies of the motor encoder while the rover was suspended in midair to establish the motor's output rotational speed when it was only subjected to the load conditions of its own weight, similar to the load conditions of a wheel in slip. By establishing a simulated wheel slip frequency for each speed command in the rover's piloting script (i.e. low, medium, high,) the piloting script can be altered to adjust speed commands according to an increase in encoder frequency indicative of wheel slip. Next, I wired the encoders to connect to the RPi's GPIO pins and began to modify the piloting script.
Week Ten:7/20/18
I wrote guides for all rover subsystems I worked on and organized my files. I continued altering the piloting script and added explanatory comments. In my spare time, I created an alternate version of the rover wheel part file with a diamond tread pattern optimized for sandy surfaces. Since I hadn't been able to manufacture the remaining two rover wheels due to printer malfunction, I created the diamond tread pattern part file so that there would be a multi-directional, printable part that could be used for all rover wheels in case the lab acquired a new 3D printer or borrowed one for a brief period of time. After uploading my files to the common lab drive, I briefed my principal investigator and all others in the lab that were involved with my project.
