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. 

Week 2

      This week was the first time we had a Monday class meeting for capstone. We confirmed our budget with Dr. Gordon (it is $600) and updated him on the progress of our project. Max Murphy worked on Arduino code for the motor while the rest of the team went to Josh Park's office and created a 3D scan of the foot. This will be used to 3D print a foot/ankle "brace" that fits onto Isaac's leg.

Josh Park holding the 3D scanner to scan Isaac's foot.

It was found that wearing a sock made it difficult to complete and align the different scans, so the process was redone. The colored dots helped with alignment. 

An example of the 3D scan rendering.

This was the completed scan, which Josh sent us later in the week as an .STL file.

    Later in the week, we went to the shop again and constructed a new bracket for testing the motor. We also constructed a "shield" that will help stop anything that flies off during testing (if something should fly off). The force transducer is able to screw onto the side of the bracket, which will hopefully allow us to accurately measure the forces generated.

A sheet of metal was bent to fit over a 2x4 piece of wood. The motor will be mounted to the sheet metal.

Another view of the set-up. The motor is now mounted so that it will spin horizontally, rather than vertically.

The force transducer can be attached directly to the test bracket.

This is an example of how the set-up would be used during testing. The "shield" is open at the top as the weight would be unlikely to fly out of the top if the screw were to break. This also allows us to use the tachometer while the motor is running.

     We attempted to test out the motor; however, the screw we were using hit the side of the shield and broke. We placed an order with Dr. Gordon for a brass plate from McMaster-Carr. Once the brass arrives, we would like to go to the shop and mill out the following object.

The object we plan to mill out of the stock brass piece.

This object combines both the "arm" and the "weight" portion, so that we will no longer have to use a small M3 screw and mass. This should make the system much stronger and less prone to breaking/shearing off. The round end with holes in it is where the system will mount to the motor. Brass was chosen because it has a high density and is also able to be machined with our equipment. We are hoping to receive the brass early on during Week 4 and be able to mill out our shape, as most of our testing is at a stand-still until this step occurs.
     We also continued to work on the Arduino code that controls the motor, and also started discussing how we plan to attach the elastic bands to the harness. As of right now, we are planning on sewing the elastic bands; we will fold the elastic band over itself to create a loop. This loop would then allow the ban to be taken off the harness if need be. This will likely be delayed until further in the semester, however, as testing the motor is our number one priority for the time being.

Week 1(?); First Post of Second Semester

     This is the first week of class since Christmas break. Over break, we ordered parts for our project, which were waiting when school resumed. Below is a picture of the items we ordered.

The items ordered over Christmas break.

     We double checked that we received all of the items, and then started constructing the base plate in order to test the motor. We went to Wes' shop and got his help to do this. We bent a sheet of aluminum to create a 90-degree bend, and also punched holes into the metal in order to anchor the motor to the plate.

The above pictures show our team fabricating the test bracket in the lab.

     Once the test bracket was constructed, we began our motor testing. We started out by using a 50 mm screw and spinning it by itself at different speeds (increased incrementally). We then added a small mass and repeated the process, and slowly worked up to larger masses. The mass sets were threaded onto the screw via the hole in their centers. We used the tachometer to measure the RPM of each different combination. The motor was spun via an Arduino and motor controller (as shown on the order form), with much of the code being found/written by Max.

This shows the set-up with one of the smaller masses being attached to the motor.

The motor test bracket as shown from the back (held down by a clamp).

Using the tachometer to measure the RPM of the spinning mass. 

Max used Arduino code and a motor controller to control the motor's speed. 

The results from the testing can be seen in the picture below:

The "scary" sections were when the motor hit a harmonic and vibrated in a scary-fashion, which didn't allow for proper readings.

     We also met up to discuss our options for mounting the mass to the motor, as well as the motor system to the ankle. During our testing, we had found that the head of the 50 mm screw sheared off, launching the mass into the air. Obviously we do not want this, so we explored several alternative options for attaching the weights to the motor safely. Some ideas were using a bigger screw, welding a screw/rod to the motor, redoing the bracket to change the resonant frequencies, using a bike cable rather than screw, and machining out a solid piece that would serve as both the mass and the "arm." We felt that the last two ideas were the best, but we think that there will be difficulties with both options. Therefore, we are hoping to discuss them with our tech adviser and/or Wes before purchasing anything.

Ideas of how to attach the mass and motor configuration together. 

     For attaching the motor to the ankle/leg, we want something that is cost-effective (re: not expensive), but that also provides stability. Our current ankle brace would not be sufficient on its own as it would allow a lot of room for movement once the motor started spinning. Ideas we contemplated were 3D printing "shin guards" and then Velcro cinching them down, buying a sturdy boot (such as a ski boot or work boot), or purchasing a sturdier ankle brace. We believe we will try to 3D print material, as this would not count against our budget. However, we would again like to consult with both the tech adviser and Josh Park before making a decision.

Ideas of how to attach the motor configuration to the ankle.