Week 13

     This was our final week before the presentation. We did not meet on Monday as classes were cancelled for Easter Break. This week we updated our Deliverable 7 (which summarized the testing done and which requirements specifications were met). We also submitted our final design notebook this week. Finally, we spent time working on the final presentation. An image of the first slide can be seen below.

The title slide of our presentation.

Week 12

     This week, we continued working on our poster (the draft was due Wednesday). This involved adding more pictures of relevant topics and including some text elaborating on some of the topics. One of the things that we tried to keep in mind while creating the poster was that Dr. Gordon (our adviser) wanted very little text. Therefore, we tried to keep the explanations short and succinct, with the idea that more detail could be given to interested parties when we present the poster and our project. This also included rearranging the poster so that it was a bit more chronological and aesthetically pleasing. The draft submitted to Dr. Gordon can be seen below.

This is the draft of the poster that was submitted to Dr. Gordon.

     We also spent some time this week trying to get the Arduino to run off of battery power. Currently, our system needs to be plugged into a laptop via USB to run. However, Arduinos are intended to be used un-tethered as well, and can store code in their internal memory. We bought a 9V battery to power the Arduino. However, we ran into some issues where the code would not run once the Arduino had been unplugged from the computer. We consulted a few people who have more experience using Arduinos, and their opinions were that something might be wrong with our board. We will look into the problem, and possibly use another Arduino board for the time being.

Week 11

     This week during class Dr. Gordon did not have much feedback for our group, aside from saying that he felt like our project was in a good place and that we had made good progress thus far. During the remainder of the class (and for the rest of the week), we started working on our poster. The poster is similar to a conference-style poster and will be printed out to be displayed at the end of the year at the engineering showcase and graduation ceremony. It is due on Wednesday of Week 12, but we started getting some of the basic content that we want on it.

This was one of the example templates given to students.

This is a basic outline of the sections and images that we would like to include on our poster. We are waiting to hear back from our adviser if CBU will allow us to change the heading border to a style similar to this (we feel as though it is more visually appealing/professional-looking).

Week 10

     During class this week, we met with Dr. Gordon to discuss our progress on the project and then glued the bearings to the "arm" of the brace so that they did not move around. We believe that this was one of the reasons why we had issues last week while testing the new dual system.
     Once the glue had dried, we tested the dual system using the force plate. Isaac was also available for testing, so the leg brace was worn by its intended user (the current leg brace was customized to fit Isaac's leg). The glue seemed to help immensely, as the system worked far better this week.
     As stated in previous blog posts, our target is 140 N, as our research has shown that this amount of force should be sufficient to completely prevent bone density loss while in space. We were able to reach and exceed this amount of force during testing. The results for some of the testing we did can be seen below. (All of the data was gathered from Isaac standing vertically on the force plate.)

Data from testing summarized in a table. As can be seen, we generated approximately 205 N of force for some of the trials.

The data in the table was obtained from saving the data points during test and graphing them in a plot. This allowed the peak-to-peak force to estimated.

As can be seen from the two plots, the peak-to-peak force for different motor speeds (given in "Arduinos") may be estimated.

     This testing showed that we can reach our target force, which is encouraging. However, one of the issues we ran into was that the system was a bit uncomfortable to wear. We will look into addressing this, whether we need to make the brace more comfortable (such as by adding foam as a cushion) or decreasing the amount of time that the system needs to be worn during each use. 

     We also revised and reprinted the motor casing this week. The previous case had very tight tolerances, so the spinning brass masses were very close to the side/wall of the casing. We found that when we put the lid on the original case, it would push the sides in, which would interfere with the spinning masses. Our second version is slightly bigger to accommodate this, and has a shorter lid to help avoid the issue as well. The second revision of the case can be seen in the images below. (We did not have a chance to use the new casing as it was printed at the very end of the week. It will be incorporated into the system at the beginning of Week 11).

View of the new motor casing with the lid off.

The motor casing with the lid on.

Week 9

     This week, we gathered all of the parts we needed to assemble our second prototype (revision 2). We then went to the shop to press-fit the pin and various components (bearings, gears, etc) into the "arm" portion of the newly designed brace. This can be seen in the pictures below.

All of the pictures above show the second prototype being assembled. The pin fits through two holes in the "arm" and holds one of the brass weights, a gear, and bearings. The vise was used to press-fit the entire assembly together. 

     The final assembly, with the motor casing attached is shown below. (The lid is not placed on the box to show the fit of the assembly.

 

     During the week we also tried to test the system. We went to Dr. Kim's lab and used the force plate again, with the user standing on the force plate while wearing the system. However, the test was conducted the Friday before spring break, when Isaac (the normal wearer) was gone. Kimberli wore the brace during testing, and there was still quite a bit of wiggle that we had hoped to eliminate with the double-mass system. It was unclear whether the design did not address the issue as well as hoped, or if the wiggle was produced because the brace did not fit well on Kimberli. (The brace was custom-designed for Isaac's foot, and was significantly larger than Kimberli's.) This is one thing that needs to be double checked after break when all of the group members return.
     Another problem was experienced during testing. The upper mass hit the lower gear when it spun. We will either need to add a bit of clearance or file down the lower gear to reduce this problem.It was also found that the upper gear sometimes became out of alignment, so that the gears were not always opposite of each other. Both of these problems are likely due to the fact that the bearings (on the pin) are somewhat loose and will need to be glued to the brace to reduce movement.

As can be seen, the brace sits much lower on the foot/ankle as it was big on Kimberli's leg. (Isaac was not available for testing.)

Video of one of the tests performed while standing on the force plate.

Week 8

     This week we ordered another LiPo battery for the motor, as the previous one died from being plugged in for too long to the low- voltage checker. We also received the stock brass we had ordered and used the CNC machine to mill out our second brass weight. (We had tried to do this last week, but the stock came loose and we were unable to use it.)

We now have two of the brass weights that are this size (Revision 2). 

     The rest of the week each person worked on his or her Broader Impacts essay that was due at the beginning of Week 9. These were individual assignments and consisted of a 1,500 paper that discussed the social, economic, safety, and environmental implications of the project in both a local and global context.

Week 7

     During class this week, we presented our midterm presentation. This included a summary of what has been up to this point, as well as future testing and actions to be taken. Our presentation was slightly different than most other groups', as we will not have as much testing to do (since we are unable to take our project to space or perform bed-rest studies). Therefore, much of our presentation focused on the redesign that we are working on, and how it will be incorporated into the current prototype. Further details about the redesign may be seen below and in the previous blog post. An example of one of our slides may be seen in the image below.

This is one of the slides that was included in our midterm presentation.

     The rest of the week, we ordered parts that will be used in our redesign, such as pins (for holding one of the brass weights) and ball bearings. The redesign consists of two brass masses spinning in opposite directions. These will be spun by the motor and a gear system, and held in place by a large "arm" on the leg brace. The reasoning behind this is that the opposite spin should cancel out the forces (and thus the wiggle) around the leg. This would result in force only being transmitted along the z-directions, or along the bones of the leg. (The CAD images for this overall system may be seen in the previous week's blog post.)
     Isaac also worked on the MasterCAM for milling the second set of brass weights this week. Dr. Hekman agreed to meet with us and help us use the CNC machine in Bourns Lab again. We were using the same piece of brass stock before, as the remaining brass was just long enough to machine our new parts.

     We experienced an issue during milling however, where one end of the brass stock was not supported as well as we had believed it to be. This left one end free to move around during milling, which caused one of the new brass weights to be cut incorrectly and unusable for our purposes. We were able to cut one of the new weights out successfully (see the image below), but will need to purchase more brass in order to mill the second one. (One advantage to buying new brass stock, however, is that we can get the thickness that we want, rather than having to face off a large portion of the brass.)

The successful brass weight that was created. This part was easier to mill than the original, since the entire piece was the same height.

     We also sent our redesigned leg brace (with the large arm to support the gears) to Josh Park for 3D printing. The leg brace finished printing successfully late during the week, but we were not able to test anything as we are missing the second brass weight. The motor casing had also been sent to Josh for printing, but will not be available until next week. Additionally, the gears for the redesign were 3D printed from SLS nylon from an outside source (Jake's parents), which should be stronger than if they were made out of PLA (as is the leg brace). These may be seen in the images below. 

The redesigned portion of the leg brace. The large "arm" will hold/guide the two spinning masses. 

The gears to be used in the redesign.