Logan InvenTeam Energy Management System for a Prosthetic Limb

Logan InvenTeam Energy Management System for a Prosthetic Limb

During the 2018-19 school year, Logan High School in La Crosse, Wisconsin was one of 15 schools in the nation to be selected as an InvenTeam and awarded a grant through the Lemelson-MIT program.

The Logan InvenTeam designed and built an energy harvesting system to extend the battery life for vacuum socket units in above and below knee prostheses. This will greatly improve an amputee’s freedom by extending the time he/she can use the limb without being restricted to plugging it into a wall socket to recharge.

The Amputee Coalition of America estimates that there are 185,000 new lower extremity amputations each year just within the United States and that there is an estimated population of 2 million American amputees. Many removed limbs are replaced by prosthetics.

By harvesting heel strike energy while walking, the system extends operating battery life beyond the current 24 hours. The invention is mounted by a prosthetic outfitter within the natural contour of the prosthetic foot and lower leg, requiring no prosthetic modification. The user will notice minimal to no change in the feel or use of the modified prosthetic. The system device weighs 376 grams with a total volume of 491 cm3. Current is generated using heel strike deflections with durations of 10-100 msec with 20 lbf. Energy harvesting is done using two spring coupled fast responding coreless rotor DC motors, which generate from 12 to 18 V and 25 to 100 mA. Rectification and charge storage in a capacitor array, subsequent power conversion, and regulation with a charge controller for the battery completes the power system. A Bluetooth™ communication link allows the user to monitor the energy storage system using a compatible cell phone and app

DESIGNED AND FABRICATED BY THE LOGAN INVENTEAM: 

Caitlin Coffey, Alex Magnuson, Thomas Kujak, Tanner Boge, Seth Petersen, Austin Sather, Avery Schams, Paige Treakle, and Thaying Vang


INSTRUCTORS: Joanne Cappuccio, Logan HS English Language Learning Dept. & Steve Johnston, Logan HS Technology and Engineering Dept.


CONTRIBUTORS (TECHNICAL EXPERTISE):
David Foye, Electrical Engineering Consultant
Dr. Scott Escher, MD-Gundersen Health System
Clint Accinni, 5280 Prosthetics, LLC
Mike Wettestein, Industrial Automation
Bob Loper, Branch Manager and CPO - Hanger Clinic
Joe Van Der Bosch, CPO - Limb Lab
Art Butterworth, Mechanical Engineering Consultant
William Beres, Patent Consultant
Gary Moe, Guest Speaker (Amputee)
Justin Pitz, Logan HS Technology and Engineering Instructor
Ryan Schreiner, Logan HS Technology and Engineering Instructor
Terry Curtis, Logan HS Technology and Engineering Instructor


Engineering Blog: http://loganrangeressystemprostheticlimb.blogspot.com

YouTube Video link: https://www.youtube.com/watch?v=kUZrXbu30p0

Media links for the Energy Management System for a Prosthetic Limb project:

https://loganrangeressystemprostheticlimb.blogspot.com/

https://wxow.com/news/top-stories/2018/10/26/logan-students-earn-invention-g
rant/

https://www.news8000.com/news/students-building-new-prosthetic-technology-us
ing-95k-grant-1/827806963 

https://www.wsaw.com/content/news/Local-school-is-one-of-15-in-the-nation-to-receive-prestigious-grant-498759541.html

https://lacrossetribune.com/news/local/education/la-crosse-logan-high-school
-inventeam-developing-major-advancement-for/article_8b02e99d-a25a-527d-b797-
e116fd8429ab.html

https://www.news8000.com/news/logan-students-learn-how-to-invent-new-technology/1005549286

https://www.businesswire.com/news/home/20181024005138/en/High-School-Teams-Receive-Lemelson-MIT-InvenTeam%E2%84%A2-Grant

https://www.facebook.com/LaCrosseSchools/

https://lemelson.mit.edu/teams/inventeam

From Media Day 5.22.19 :

WKBT News
https://www.news8000.com/news/la-crosse-logan-students-show-off-completed-pr
osthetic-limb/1080143129

WXOW News
https://wxow.com/news/top-stories/2019/05/22/logan-high-school-students-crea
te-self-sufficient-prosthetic-limb/

WEAU News
https://www.weau.com/content/news/Local-high-school-group-shows-off-new-inve
ntion-that-could-benefit-amputees-510293821.html


WIZM news
https://www.wizmnews.com/2019/05/22/logan-students-spend-year-building-speci
al-prosthetic-leg/

Media Day 5.22.19

Media Day

Date: 5.22.19
Location: Logan HS
Time: 9:20-9:40 AM

We hosted a media day at Logan HS to demonstrate our Energy Management System for a Prosthetic Limb invention and practice our presentation for EurekaFest. Attendance was very good and we had a number of sponsors, parents, business partners and politicians that show up along with three TV Channels and one radio channel.

We started off by doing the 10 min presentation that we will be doing at EurekaFest. We had it timed down to around 9 min. and we were right on. We then opened up for questions from the audience afterwards. We did not have many questions which probably meant we either did a great job of explaining the problem and our solution, or people were just hesitant to ask questions. We think people we just more hesitant in a larger group to ask questions.

We then broke into small groups (hardware, software, sustainability, finance, etc...) where people could walk around and ask questions in a smaller more comfortable setting and interact with the team. We received a lot of positive feedback on the invention and some suggestions for improving our presentation.

Mr. Bob Loper from Hanger Clinic was in attendance which we were happy to see as Mr. Loper is a Certified Prosthetist and this would be the first time he had seen our design. Hanger Clinic had donated a lot of equipment for us to test with and use. He was very impressed and was pleased with the solution we came up with.

After about 45 min. we wrapped things up and thanked people for attending. Interviews with the media went on for another 30 minutes.

Overall it was nice to put closure on this part for our team and community members. We are looking forward to EurekaFest and are beginning to change focus to trip packing and preparation.

Thank you Lemelson-MIT Program for giving us this opportunity!

Logan InvenTeam presenting.

Nice audience in attendance.

Austin being interviewed and showing off the cell phone interface he created.

Work Day 5.15.19

Work Day

Date: 5.15.19
Location: Logan HS
Time: Morning about 3 hours
Students: Austin and Paige
Goal: Create and adhere stickers to simulator to promote the team and the Lemelson-MIT program.

Just some detail work that needed to be done on the tester. Paige and Austin made stickers for the tester to "dress" it up a little bit. This was the first time they had done this so using the vinyl cutter, weeding, and taping the stickers was a learning experience and they had fun doing it. A welcome change of pace from soldering or working with oscopes and multimeters to test faults.

Paige and Austin getting stickers ready.

Austin starting to adhere the sticker.

Stickers on and the simulator with a green screen for photo editing.

Austin putting on a sticker.

Work Night 5.9.19

Work Night

Date: 5.9.19
Location: Logan HS
Time: 5:15-7:15 PM
Goal: Change over generators on the heel strike simulator (limb tester) and work on EurkaFest PP.
Students: Paige, Caitlin, Tanner, Seth, Thomas and Alex.

The work night and week leading up to it was mostly positive steps for the team as we progress toward EurekaFest.

We finally finished the essential testing of different generator outputs and have come to the conclusion that the 18 V generators (as a reminder we are using stock DC coreless motors as our generators) give us the highest output for current and efficiency. The new 12 V motors have a stronger gearhead that will withstand the torque placed on them from the tester better, but the output is lower than we anticipated. These were the new motors we ordered from India which looked very promising specification wise on paper, but did not test as well as the 18 V motors. The only way we could find out if they would work well was to test them.

We also wanted to try to switch the 8-1 gearheads to the 18 V generators but they would not swap out as the pinion gear inside was not the same size and had a different gear pitch. So we are going with the lighter duty 8-1 gearhead. We have changed over our heel strike simulator to demonstration mode now which will not load the limb as much and should be easier on the gearing. It is much quieter running now as the knee joint does not lock out. We still can demonstrate outputs using an oscope.

During this process we tested out a variety of spring combinations to determine if different spring strength would make a large impact on our outputs. We came to the conclusion that is does make a difference but the size spring (9 kg / 20 lbs) we are currently using gives us the best output without stressing the components.

We spent some time cleaning up connections on the tester and making things look better. Alex is finishing up a LED display that will light up when certain voltages are run into it. This will give our audience a visual other than just saying we are now charging a 1000 mAh battery.

We are working on the our presentation and Paige is organizing who will speak on each slide. Caitlin provided some more information on sustainability and we found out more information on recycling motors that we did not know about. The rotor in a motor is very valuable as far as recycling is concerned.

Seth and Tanner worked on the conceptual design for the next generation generator system. They are working with a local mechanical engineer on it. Tanner also updated our finances.

Austin has the software program in order and just needs to document it for patent purposes.

Next week is final exams for our seniors so work time will be cut back to allow them time to prepare. We will still spend some time getting ready for our May 22nd media day.

Austin and Paige getting the tester ready for painting.

Tape added to protect the electronics of the tester.

Primer coat is going on in our finish room at Logan.

Almost done.

Paint job finished.

The numbers on the springs indicate how many pounds each spring is.

Paige doing wire management on the tester.

Seth and Tanner working on next generation design.

Alex working on a LED display for the a visual representation of our electrical output.

Chart on peak generator Volts to how many pounds of force the spring is.

Work Night 5.2.19

Work Night
Date: 5.2.19
Location: Logan HS
Time: 5:15-7:30 PM
Students: Paige, Caitlin, Austin, Tanner, Seth, Thomas and Alex.
Goal: Continue to test to see which motor configuration gives us the most efficient output and test our new Bluetooth module.

We spent some time on Wed. morning working on the tester and mounting our new smaller Bluetooth module so we did not have to do it tonight. The new module is much smaller than the original one Austin designed which used an Arduino Uno. We are not using an Arduino Nano which gives us the same functionality and is 75% smaller which helps us with the over all scale of the electronics. Austin did a nice job designing and programming this.

During the work night we had to first troubleshoot a generator problem as one generator was not operating properly. Our output was confusing which led us to figuring out it was incorrectly wired into a terminal block. We relabeled the terminals so that would not occur again. Part of the problem with all the testing we are doing is nothing is permanent yet. This meaning we are moving components around in testing to see which ones give the the most efficient charging combination. Once we have that combination down, we can permanently label and connect the components.

We started testing with the 12 V generators under load. The idea is to run up the charging circuit while under load, see how it performs and collect data as we do that. Right now it appears the 18 V generators give us the best output although we still want to try one 12 V generator with a 18 V generator. The method is the same for each set of generators we test and an oscilloscope is a key to measuring that output. Alex, Thomas and Austin worked on this.

Paige also spent some time working on the EurekaFest Powerpoint. Seth and Tanner worked on our next generation harvesting system conceptual drawing. This is just a concept on how we could improve the mechanical design. We will not have time to fabricate it, but is could be a next step.

The highlight of the night was testing the new Bluetooth module. This would be the first time we installed it in the charging system. It had been bench tested to simulate functionality but you never know what will happen until you install it in the system. We started the heel strike simulator and within 13 seconds the Bluetooth module had enough electricity to kick on and start showing voltage readings! This was faster than expected. We also got some baseline data on how long we can maintain the reading and how much the Bluetooth mod drains from the capacitor storage. We have it programmed to sample a voltage and go into sleep mode so it does not continue to drain electrical storage. Caitlin worked more on the App interface to clean it up and make it look presentable.

Next week we start to paint the tester and do more work on the Provisional Patent.

Picture of the top of the Bluetooth module

Picture of back of Bluetooth module.

The Bluetooth module is now attached in the bottom right corner of the mounting plate.

Paige working on the EurkaFest Powerpoint.

Caitlin working on the App interface design.

Alex wiring in the Bluetooth module. Not much room to terminate connections.

App interface draft that Caitlin is working on.

Work Night 4.25.19

Work Night

Date:4.25.19
Location: Logan HS
Time: 5:15-7:15 PM
Students: Avery, Tanner, Seth, Alex, Paige, Thomas and Austin
Goal: Test new generator configuration under load.

We have been having more difficulties with our limb tester. We blew a 12.5 microFarad capacitor and need to order a new one. The capacitor is used in motor startup for the tester. All testing stopped until we got it back up and working. Also, some of the bearing and moving parts needed to be greased and refitted with normal wear and tear occurring from use over the course of the year.

Once we fixed the tester we were able to start collecting new data on our 18 V generators and new 12 V generators to see which ones would give us the highest current output. We finished the night by getting most of the data collected and still have to try a mixed configuration (one 18 V and one 12 V generator) wired together to see how that looks. Once all the data is collected we can make a decision on which configuration is the most efficient for us. Keep in mind that our generators are really stock DC motors that we are re-purposing for this application.

Software has made some nice advances and our wireless (Bluetooth) connection is now configured for 2 voltage inputs and one enable (on/off) switch. Bench testing was positive on the setup so we will mount the new board this week and then test it next week with the limb tester and full charging circuit. If that is function, we will have made hit all our targeted goals.

We are still progressing on the patent application. Work is slow as it is new for us. Our industry contacts  have been very helpful here as some of them are patent holders and are very willing to help us with the terminology and process.

New 12 V motors that came in from India. Notice the packaging.

The new motors came with this envelope indicating they were the first motors Portescape had made of this variety. They are still stock motors, but apparently they were the first run.

Motors after we added the pinion gear and extension wiring and shielding. Notice the manufacturing label on them indicating 001 and 002.

Paige and Austin working on the wireless connection circuit board amid the clutter of pizza and treats.

Tanner, Seth and Avery working on the design for the production concept.

Wave form output for our 18 V motors through the charging system. The yellow line indicates the capacitor charging and the blue line indicates the duration of the constant voltage supplied.

Seth measuring Thomas' forehead...not sure what that has to do with the project, but it looks like they are having fun.

Wave form output with our new 12 V motor output through our charging system. The blue line indicates some transient activity is happening toward the end of the wave form. 

Work Night 4.11.19

Work Night 

Date: 4.11.19
Location: Logan HS
Time: 5:15-7:15 PM
Students: Tanner, Seth, Alex, Paige, Austin, Thaying, Avery and Thomas.
Goal: Test the new charging circuit for functionality.

We needed to test the updated charging circuit and had a problem with one generator outputing the correct voltage. It seemed one of the generators was not functioning properly. When we cycled the tester, we were only seeing one output on the oscope. We felt it was a mechanical malfunction, but after some testing we determined both generators were functioning in the new mount we 3D printed with the (gray) supports we added for additional strength. It had to be wiring or some other electrical issue which we will have to trace down next week.

The new 12 V motors will hopefully be in next week with the 8:1 gearhead. We are hoping this adds to the durability of the generator system. The current motors we are using have a plastic gearhead.

Team members also worked on the patent information. We feel something that makes our system unique is the fact that our design does not change need to change foot of the artificial limb by adding motors or gears as in some other designs. This keeps the cost low and increases simplicity . It will work on any Freedom foot which we were told is the most popular prosthetic foot. The only thing that may need to be modified is re-3D print the heel adapter for the size of the heel. Which would cost pennies.

We also spent some time redesigning the charging port that goes in the vacuum pump. The current one is proprietary and is big and bulky. We needed to design a more streamlined one that would not be so bulky. Students found a way to modify the current adapter by doing some cutting and drilling some new openings and then using epoxy...at least that is the current plan.

UPDATE 4.15.19
We worked on troubleshooting the motor and electronics to try to trace down the fault in the circuit that was giving us zero output from one of our generators. It turns out one of the green terminal blocks was mislabeled and therefore we wired one of the generators in wrong. This was the reason we showed no output from that generator on the oscope. When we corrected it you can see the output was back to what we expected. In fact, it worked exceptionally well. The output was giving us the voltages we needed and was charging the caps and we demonstrated that by lighting up some LED's to show how the system worked. Using our safe (low charge) setting we were able to light the LED's in about 15 sec.

The oscope shows the output from our generators to our storage system.  This is important because it shows
the success of our charging system. Now we just have to tweak the software.

New supports for the motors in gray.

Thomas and Alex working on the LED array.

Seth, Tanner and Avery working on redesigning the charging adapter for the vacuum pump.