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.

Week 6

     One of the things we did this week was redesign the electronics casing so that it was smaller. Our client/adviser agreed that only one motor unit would be sufficient for demonstration (in addition, an extra leg brace for the other leg could be printed, allowing the astronaut to simply switch the motor system between the two). Since the old casing was designed to hold two of everything, the new casing is about half the width. It also includes holes for the "kill switch" to be easily accessible, as well as a port through which the microUSB on the Arduino can be accessed. The updated casing can be seen in the images below.

The Arduino's microUSB can easily be accessed, as well as the "kill switch" that will stop the motor.

This view shows all of the components placed in the casing. The lid (not pictured) slides onto the box via notched grooves, as in Revision 1 of the casing.

     We also finished designing the double weight system this week, which is the redesign that attempts to minimize the wiggle produced when the motor is run. This system uses two brass masses, each roughly half the size as the original brass weight. The masses are spun in opposite directions, via the motor and two attached gears. As can be seen in the image below, this system is much bulkier than the original system, but will hopefully vastly reduce the axial rotation created. 

The redesign will also attach to the leg brace via a long "arm."

This view shows the two brass weights and the gears more clearly.

The entire system will have a casing around it, to help improve safety. This makes the overall system much bulkier, but will hopefully help reduce/eliminate the wiggle.

     This week we also went to Dr. Kim's lab to use the force plate again. We were trying to see if the force generated was transmitted to the upper leg/femur. One way we thought to test this was to have Isaac sit on the force plate with his legs raised in the air. We then collected readings will his legs straight and locked, and then with his legs bent. We were hoping to see similar readings for both cases. However, the data we received was inconclusive and would require additional testing/possible testing with the redesigned system.

Isaac standing on the force plate with the motor system on his left leg. Shown in his hand is the new electronics casing (he did not wear it as he did not have a belt).

Isaac sitting on the force plate with his legs bent and his feet elevated  above the ground.

     Finally, we updated Deliverable 6, turned in the Midterm Notebook, and worked on the Midterm presentation this week. The midterm presentation will be presented on Monday at the beginning of Week 7 (Feb 27, 2017).

Week 5

     During class this week, we were able to spend a good amount of time talking to Dr. Gordon and showing him our progress thus far. We were also able to run the motor system (with Isaac wearing it on his leg). The main concern with the motor system currently is that it produces a fair amount of wiggle in the leg. This could become uncomfortable; however, if the astronaut is only wearing the device for short periods (15 minutes) at a time, then this may not be the highest priority, so long as the system works. The second concern with the wiggle is that excess force may be getting transmitted in the horizontal directions (rather than vertically, along the axis of the leg). This could be tested and checked by running the system on the force plate again, however, as it has the ability to record force in the x, y, and z-directions. (Additionally, Dr. Kim was able to show us a way to export the data this week).

The motor system shown on Isaac's leg. The entire system (and leg) wiggled/vibrated when the motor was turned on. 

     Dr. Gordon suggested another method that could be used to help combat the wiggle. He suggested spinning two weights at once, and using gears to mechanically ensure that the motors were in phase. Since the class is scheduled to allow a couple weeks for testing and verification, and since our system has very few ways to test it, he thought that we would have the time to be able to look into and possibly do this. As for our current progress, Dr. Gordon felt that we were in a good spot for the semester.
     We had been planning on purchasing the items needed to create a second motor assembly for the right leg, but we decided to postpone this (possibly indefinitely) in case we need the budget for gears or additional brass, and because it would be possible to switch the same unit between the two different legs (running them at different times). However, we did purchase some additional items, most of which will be used for our current set-up. This includes the items shown in the table below.

Items ordered this week.

     We also created an up-to-date budget that includes all of our purchases to date and the amount of money spent so far. To date, we have spent $370.49, out of an original $600. This budget was part of the requirements for Deliverable 6.
     Additionally, a box was designed in Solidworks to hold all of the electronic components (for testing, we have simply been having the user hold them). The box has a loop on the back that will fit around the wearer's belt loop, and can be worn at the back. There is a lid that slides on and off via notched grooves in the box, and holes for wires to enter and exit the box. The next version of the box will need an additional hole for the on/off switch to stick through, making it easily accessible to the user. The size of the box was determined by the size of the components that will need to be placed in the box. This can be seen in the images below.

The electronics box with lid.

The electronics box with lid. There is a hole for wires on the bottom of the box and a loop through which a belt can fit through.

The lid is slid off to show the contents of the box. It will hold the motor battery, Arduino battery case, breadboard (with Arduino and other components), and motor controllers). 

     We also started looking at and designing the double-weight system this week, and worked on Deliverable 6 (due 2/20). We decided that the gears for the double-weight system can be 3D printed for now.

Week 4

     During the class meeting, we showed Dr. Gordon the current components we have for our project. The prototype was not in its final stage yet, as the brass had not been ordered yet and the 3D printed leg braces needed to be redone. Dr. Gordon had two main things to talk about: he wanted us to talk with Dr. Hekman (the vibrations professor) to see if enough force will actually be transmitted axially along the leg/bone as we are hoping. He also had a possible redesign that he wanted us to consider. The image below shows the proposed redesign.

The circle on the left side represents the motor, which would be connected by links to a "track" on the leg (shown on the right side of the picture.)

     The redesign would allow linear motion along the leg, ensuring that (at least most of) the force would be transmitted in the desired directions, rather than in all directions due to the rotational manner. Three concerns that were immediately brought up were that this system would likely be bigger/bulkier than the current design, that excess heat would likely be generated between the "track"and "slider," and that there would be a higher likelihood of material/structural failure (given our budget and machining capabilities). However, Dr. Gordon encouraged us to spend some time this week thinking over the two designs and coming up with a concrete decision by Week 5. 

     An Excel mathematical model was created for the redesign, with some of the reference equations being drawn from Wikipedia. These were used to calculate the acceleration with respect to the crank angle. This can be seen in the images below:

Equations used (credit: Wikipedia). 

The results from the mathematical model. 

     The CAD files for the leg braces were also updated and sent to Josh for 3D printing. The leg braces remain largely the same to the ones created last week, except they are scaled slightly larger for better fit and also have the motor mount on the opposite side now (so that the motor is mounted to the outer part of the ankle, rather than the instep). 

     Isaac and Jake created a MasterCAM file for milling the brass once it arrived. (It arrived late Thursday evening.) We set up a time with Dr. Hekman to help us mill the brass weight on Friday morning, as we are not permitted to use the CNC machine on our own. 

Setting up the CNC machine to mill out our piece from stock brass. 

Dr. Hekman helping us use the CNC machine.

The completed brass part that will be used in the motor system. This design is far less likely to shear off, as the screw and mass set did. 

     We could not run the full tests as the leg braces had not finished printing yet, but we tested out the new brass weight with the motor and casing. We ran the motor at slow speeds, but found that the rotations per minute were very close to the values we got from previous testing with the screw and offset mass (both tests were measured with a tachometer). 

The brass part mounted to the motor via screws. The brass part can spin freely without hitting the case.

The lid now fits onto the motor casing, as we removed the bulky bracket that was used to hold the screw and mass arrangement. 

The other side of the case. The metal washer is where the casing will be attached to the leg braces once they are printed.

The motor spinning with the brass piece on it (shown without the cover for observation purposes). 

    We also looked into what types of hand stitching are the strongest, as we are planning on sewing loops into the elastic bands and attaching them to the harness. Through a general internet search, it was found that back stitching is the strongest hand stitching method. None of us are very experienced at sewing, so we practiced sewing a back stitch of extra pieces of the elastic band. Based on our preliminary attempts, we agreed that the stitch seemed to be strong enough for what we are intending.  

Example of a back stitch (credit: http://sewing.wikia.com/wiki/Back_Stitch). 

     Our 3D printed parts finished printing over the weekend, so we were able to fully assemble our prototype for the first time. We also did some preliminary testing of the motor system while Isaac was wearing it on his leg and standing on Dr. Kim's force plate. The force plate is able to record force in the x,y, and z directions.  The data could not be exported, however, so further testing will have to be done once Dr. Kim is available to help us. Despite not being able to export the data and get a concrete value, it appeared as though enough force was being generated in the z-direction to continue on with this design . These tests were performed at low speeds, so we are confident that with further testing and refining, we can reach our desired goal of force transmitted axially along the leg. Because of this, we have decided to stick with our current design rather than pursuing the redesign.

Isaac wearing the system on his leg while standing on the force plate.

Close-up view of the motor system. The final version will likely use Velcro straps or a ratchet system rather than duct tape to hold the system to the leg. Additionally, future versions will secure the wires so that they are not dangling. 

This is a screenshot of the program screen during testing with the force plate. The force in the z-direction is currently shown. Although it is difficult to tell, each division is 150 N. The peak-to-peak measurement appears to be about half of this, which would equate to ~75 N.  

Week 3

    During class this week, Isaac and Max worked on Solidworks files for the project. They concentrated on finishing the foot brace from the 3D scans of Isaac's foot, as well as creating the motor casing that would attach to the brace. Jake and I (Kim) went to the shop to create a mount that the force transducer could be mounted to. The mount was created out of a large block of steel scrap metal and holes were drilled/counter-bored into it so that screws could be inserted into the mount and attach to the force transducer (while sitting flush with the surface). This mount can be seen in the picture below.

Picture showing the force transducer mount with counter-bored holes (this side would be facing down once the force transducer was screwed on). 

     The next day we met as a team to continue working on Solidworks and also test the motor with the new mount for the force transducer. We anchored the force transducer to the plate and then used a nut to tighten the force transducer shaft onto the motor mount. However, the force transducer shaft sheared off while we were tightening the nut. This was extremely unfortunate, as this rendered the force transducer inoperable.

The nut with part of the sheared off screw stuck inside it.

The sheared-off shaft/post on the force transducer.

     Since we could no longer use the force transducer (and we had already done testing and gathered data using the tachometer alone), we emailed the professor regarding next steps and continued working on the CAD files. The finalized assembly (which includes both the leg brace pieces and the motor casing) can be seen in the images below. The large cylinder shape is the motor casing, which serves multiple purposes. Not only will it help prevent the weight from hitting or injuring something if it were to break, but it will also prevent the astronaut from accidentally hitting the motor against things while moving around within the spacecraft and working. The two halves of the leg brace provide a sturdy surface to attach the motor to. Since the shape is customized to the user's leg, it will hopefully be more comfortable to wear while also limiting the amount of movement of the brace. The two parts of the brace will be cinched down with Velcro straps. The parts were all sent to Josh for 3D printing (the leg braces requested at 70% infill, and the casing at 30% infill). 

This image and the one above show the leg brace/motor mount assembly. 

     Dr. Gordon was able to meet with the team on Thursday morning, where we discussed the broken force transducer and next steps for the project. Dr. Gordon suggesting emailing the company to see how expensive and how long it would take to repair the existing force transducer. This was done, with pictures of the broken shaft and the diagnostics screen sent to the company. The technician who answered hinted that the force transducer was not being used as intended. He did not specify how long the repair would take, but said that it was more complicated than it seemed and that he would need to wait for parts from the manufacturer. This repair would also require mailing the force transducer to Utah. We will discuss this in class with Dr. Gordon before sending it out.

     On Friday, Max met with Dr. Kim about possibly using his force plate or force sensor for our testing while we do not have access to the force transducer. The rest of the team picked up the 3D printed parts from Josh and went to Wes' shop. We cut out small squares of sheet metal that will eventually be used as the inserts to help anchor the motors to the foot braces. Jake and I ground the squares down to the desired size (~40 mm^2), while Isaac sanded part of the leg brace, as there had been a misprint. We also drilled holes into the square inserts for the motor's screws.

Jake grinding down the metal inserts to the correct size.

Caliper showing the size of the metal insert.

Isaac sanding the foot brace.

Next week, we will try to assemble the parts we have and also order and mill the brass weight.