Work Night
Date: 12.20.18
Location: Logan HS
Time: 4:30-7:00
Students: Paige, Avery, Austin, Caitlin, Seth, Thomas and Alex
Goal: Work on mounting assembly for generator, test motors and motor windings and research Nano vs. Uno for software.
We made significant progress tonight in a number of areas. Paige updated the Engineering Journal book and outlined steps for the patent process.
Avery, Caitlin and Austin revisited the Arduino current/voltage divider parameters and looked into switching from Uno to Nano to scale down in size. They will have to test the Bluetooth communications for compatibility. Caitlin is making progress on the MIT App for the cellphone interface.
Seth took measurements and began to design the mounting mechanism for the generator and gears. We decided to just print this in segments to see how it would fit before doing a full 30 hour 3D print. Seth has named this the "Mark III" after the Iron Man movies.
Thomas and Alex tested motor resistance and voltage output for a variety of different motors and logged it in a database. We are looking for the perfect motor which will give us low resistance, high voltage and high current output. This is difficult to find due to compromises.So far we have seen that the ideal generator is: small, able to generate 15 to 25 V without complicated gear train, low winding resistance- able to deliver high charging current in a short time and low bearing losses.
Thomas then worked on designing a rectifier circuit in Multisim to test different motor wave form outputs. Alex worked on soldering a gear to a motor which was unsuccessful and then used epoxy which worked very well after it dried.
We will next meet on 12/27 from 10:00- Noon over the holiday break.
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| Seths generator mount with bearing openings cut in. |
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| Thomas and Alex testing motors. |
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| Paige updating the Engineering Journal. |
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| Thomas demonstrating his rectifier circuit for the team. |
Video of the 3D printer working on the generator mount.
Seth showing the first generation of the generator mounting assembly.
Thomas showing how Multisim is used to simulate a rectifier circuit.
Other notes:
Some notes on the idea generation and further direction and the Logan technology project.
First, if we continue to present relevant problems to solve, and solutions are feasible, the students will likely react.
On December 20 we tried to outline apparent intellectual property domains of the work so far:
1)
prosthetic leg energy recovery system for recharging battery power
2)
unilateral prosthetic foot mounted energy recovery generator system
3)
prosthetic leg energy recovery system monitor and controller hardware
4)
prosthetic leg energy recovery system monitoring controller software/logic
These elements could be combined in and intellectual property description in whatever manner is appropriate. They are listed separately here for further development in idea content.
The further steps we have identified for meeting basic goals recorded as:
1)
complete equipment of the first tester configuration to demonstrate heel strike based energy recovery; this includes adding mechanical linkage, generator, and electronics to demonstrate a complete system
2)
supply one or more generators suitable for number one
3)
assemble electronics circuit modules for power conversion, battery charging regulation, the microprocessor operation; and display or communication elements sufficient to support display
4)
provide necessary frame reinforcement and other provisions to stabilize mechanical operation
5)
consider desired improvements for a new model; fabricated of welded aluminum by an outside shop
The last item noted was a possible improvement of the tester to be able to demonstrate a more complete gait including loaded rolling of the foot from fore foot to heel.
At this point if the project is completed meeting these goals, project success would only be limited by the extent of battery recharge that is achieved, and integral communication is supported. The still may be limited by how well the team can find an adequate generator element and provide effective mechanical linkages to engage the generator, possibly including forefoot strike as well as heel strike.
A further possibility is that a second generator could be added, taking advantage of the structure of the carbon fiber bilateral foot design. The second generator could be identical to give further generating capacity, or it could be designed with a different time constant to allow for different gait speeds if necessary.
Of course if a single generator is found which will meet the need, this bilateral approach may not be necessary for charging purposes only.
Another question the team’s been exploring is what is the role of the software and communication system. The obvious first answer is that it is to report the health and operation of the charging system. This does open up the possibility that the data that is available may be useful for other purposes.
At this point, we have heard team members discussing measurement of charging system voltages and the sequencing of processor operations.
So, in total, the prosthetic user would have available information about battery condition as well as the added information of the performance or operation of the charging system. The expectation is that this would improve prosthetic use by allowing simpler management of the vacuum puck charging system.
The team has been asking what other sensors are information might be needed. Before expanding that, it might be useful to think about what used to be made of the data that will already be available!
So possible data to transmit might consist of:
- peak generator voltage/average generator voltage/generation duration/energy generated
- charging current delivered(milliampere hours?)
- Battery condition/battery capacity
Additional information which may be relatively easy to together may include:
- number of generations cycles/steps, or steps per hour(user useful measurement), or steps per day(indicating prosthetic use)
- average generated energy per step(a possible indication of activity level)
- characteristics of apparent gait, including gait interval or symmetry, and intensity or duration(note that these measures may be of use by a therapist or clinician)
Additional information that might be available if a bilateral generation system is used, and with additional data taking sophistication:
- generation waveform transmission, which will include some information of gait details. This would require sampled data taking by the processor and package transmission
- sampling in discriminating data between the two generators, to detect asymmetries in foot loading
- if some of these data elements can be included, with processing and reports delivered by an external computer system.
Intellectual property may become:
1)
prosthetic leg energy recovery system for recharging battery power providing clinical diagnostics
2)
bilateral prosthetic foot mounted energy recovery generator system
3)
prosthetic leg energy recovery system monitor and controller hardware providing clinical data
4)
prosthetic leg energy recovery system monitoring controller software/logic providing clinical data and diagnostics
So with very little additional effort, it is possible to show the potential value of the data that is being provided. Some research papers which describe the clinical practice of helping patients achieve improved gait using the prosthetic legs and the therapy process as they adapt to them.
It also points out that a further interview or discussion with a therapist or clinician should verify some of these goals by practicing medical personnel.
