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Alice Open Source Exoskeleton 2021 Update

Open Source, Child-Focused Leg Exoskeleton for accessibility in developing communities.

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This exoskeleton was developed following the team's participation in Cybathlon 2016 (Switzerland).

Noticing that high efficacy was countered by low accessibility due to specialized components and required tools, it seemed necessary to create a simplified alternative which would require only off-the-shelf material and manufacturing processes found in developing countries.

Alice has been developed through years of work and investment in México and France and her design and control codes are now available to everyone for use and collaborative development under the Attribution Non-Commercial CC License (CC BY-NC).

Alice addresses manufacturing, material and cost restrictions specifically encountered in Latin America and other developing countries, promoting successful exoskeleton deployment within budget-restricted communities.

Furthermore, the exoskeleton proposes a specialized combination of hardwaresoftware and operation conditions focused on reducing complexity while achieving the minimum required functionality for previously-unattended patients.


Her Clinical Validation

ALICE has successfully been deployed with patients exhibiting different medical conditions and covering a diversity of socio-economic backgrounds primarily in Monterrey, México.

A total of 12 pediatric subjects have participated in short-term clinical usage which has proved beneficial in improving patient psychology as well as due to potential positive impacts in blood circulation and internal organ functioning.

Conditions exhibited by users included Muscular Dystrophy (MD), Cerebral Palsy (CP), Spinal Muscular Atrophy (SMA), and Cephalic Disorder (CD).


Mechanics:
The system features only 4 DOFs powered by automotive DC 26Nm actuators as well as a significant portion of parts manufactured on PLA and commercial 3D-Printing composites.

Programming:
Motion is achieved through simplified PID controllers designed and implemented over low-cost electronics and in conjunction with non-specialized actuators + basic potentiometer-based feedback. Controllers are designed to counter actuator nonlinearities through customized filtering, anti-windup algorithms, and static friction compensations.

Operation Layout:
ALICE operates using a decentralized layout where the power source and system operation modules are separated from the exoskeleton. Standard automotive 12V Lithium / Lead batteries and a PC or Mac running Arduino IDE are enough to successfully operate the exoskeleton in safety-compliant clinical contexts.


Patents:

1. (2019, China) CN201930193288.2 Electromechanical Structure for Pediatric Mobility.

2. (2019, México) MX/f/2019/000922 Estructura electromecánica para movilidad pediátrica.

A basic model of ALICE can be constructed with a material budget of ~1,500 EUR.

ALICE OSE 2020 Render 3. may 2020.JPG

Render showing the assembly of the lower part of the legs in Alice's 2020 version.

JPEG Image - 596.25 kB - 01/10/2021 at 12:57

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1.2 ALICE OSE 2020 Leg Structure Manufacturing Sheet. oct 2020.JPG

Mechanical sketch for the manual construction of the lower-leg aluminum profiles used to build Alice in its 2020 version. Right and Left leg are identical.

JPEG Image - 119.82 kB - 01/10/2021 at 12:55

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(DEC2018) AliceOnyx - Adaptador Braces.STL

Sample mechanical part to be constructed in Nylon+CF or ABS+CF composite filament. In the 2018 model, this component served as a connection point between the ergonomic brace holding the users' legs and the aluminum profile comprising the exoskeleton's leg.

Standard Tesselated Geometry - 191.98 kB - 01/10/2021 at 12:53

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(DEC2018) AliceOnyx - Tapa_RodillaIzq.STL

Sample mechanical part to be constructed in Nylon+CF or ABS+CF composite filament. This part mates opposite to "AliceOnyx - Efector_Fijo..." to ensure the lower part of the leg moves without going out of its intended position as the moving part of the DC motor rotates.

Standard Tesselated Geometry - 57.11 kB - 01/10/2021 at 12:52

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(DEC2018) AliceOnyx - Efector_Fijo_Rodilla_Izq.STL

Sample mechanical part to be constructed in Nylon+CF or ABS+CF composite filament. This part connects the fixed part of the DC motor with the upper part of the leg, which corresponds to an aluminum profile.

Standard Tesselated Geometry - 216.78 kB - 01/10/2021 at 12:52

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View all 7 files

  • 1 × ABS+CF 3D-Printing Filament (Nanovia)
  • 1 × White PLA 3D-Printing Filament (ColorFabb)
  • 1 × 26Nm 12V DC Motor 226-3005 (AM Equipment)
  • 1 × Mega 2560 R3 Microcontroller (Arduino)
  • 1 × G2 High-Power Motor Driver 18v17 (Pololu)

View all 10 components

  • Talking Motors

    Jesús Tamez-Duque02/19/2021 at 18:00 0 comments

    During the building of the pediatric exoskeleton, some actuator evaluations were done in order to decide for the best option. The state-of-the-art Brushless DC motors by Maxon Group (Switzerland) joined with strain weave gears by Harmonic Drive LLC (United States) combinations were compared to DC Motors by SIEMENS (Germany) and AM Equipment (United States). Even though the state-of-the-art combination is undeniably better in performance, both SIEMENS and AM equipment 26Nm DC actuators were found to be appropriate exoskeleton implementations

    AM Equipment DC actuators were finally deemed the best option for continuous system production and deployment due to technological characteristics, price and overall product availability within the Mexican market. 

    Four actuators were used and covered hip and knee Degrees of Freedom; this reduced complexity and weight while maintaining minimum functionality required for standing and walking tasks.

    We have been searching for different alternatives and similar motors to make sure people outside The US and especially in Europe have easier access to low-cost actuators but we haven’t been able to find other suppliers with similar options and reliability. Let us know if you find any !

  • Open-Loop and Closed-Loop control

    Jesús Tamez-Duque02/05/2021 at 22:31 0 comments

    On the first version of Alice, in order to ensure user's safety, we opted for an incremental approach in the control scheme. Because of this we decided to start with a very simple control system that manipulated every step separately, instead of a complete routine. 

    This control scheme consisted of an Open-Loop strategy to minimize the risk in case our sensors failed. In the newest Alice version we have made improvements to ensure robustness on sensors and a good signal quality through digital filters. These changes allowed us to increase the automatization of Alice’s movements through a Closed-Loop algorithm (PID), replacing the Open-Loop strategy. This whole process resulted in 3 different functions: stand-up, walk through 4 movements and sit down. 

    The PID control scheme was designed and integrated using potentiometer-based feedback referencing joint angles in real time. Third-order Butterworth filtering, anti-windup algorithms, and static friction compensations were implemented to account for potentially larger amounts of noise, mechanical resistance, and overall system nonlinearities. Controller tuning is analogous for the left- and right-side actuators; position mapping parameters are set individually per joint. 

    To maximize the access through Open Source platforms, the whole control algorithm was implemented on Arduino, creating some custom libraries. We believe that this will allow more people to implement it; however, we are getting to the maximum memory available on Arduino. Following upgrades should consider memory optimization.

  • Material Evolution

    Jesús Tamez-Duque01/30/2021 at 00:09 0 comments

    One of the most important evolutions undergone was focused on the joints, which are the unions between the motor and the profiles transmitting the movements to the legs. These unions were constantly getting broken when mechanically-demanding movements were performed. Throughout the years some partial solutions for this problem have been tested focused on local manufacturing, considering limited budgets, in order to find the right design, components combination and operation conditions.

    Aiming to maximize the material resistance, while keeping the manufacturing process simple, we started using 3D printed pieces on PLA for the first iteration,  (although we suspected the resistance would not be what we needed) because we knew it would still provide valuable information to move forward. This material was later replaced with Aluminum but it was found to be very expensive to make all the parts out of this material. The next material candidate we tried was Nylon + Carbon Fiber, which merged the advantages of PLA and Aluminum, but its sensitivity to humidity and abrasiveness were too high. Finally, we came up with the best solution (so far): ABS + Carbon Fiber. One of the nice properties of this material is its low plastic deformation and abrasiveness together with its humidity resistance; additionally, it profits from a nicer finish. 

    Because of the nature and difficulties that 3D Printing presents, it seems like iterations and manual destruction are not only a practical approach but maybe an appropriate process in finding the desired balance between manufacturing process and material resistance.

    We can currently advise you to use ABS + Carbon Fiber, but please let us know if you find something else which might work even better! 

  • The Open Source Program

    Jesús Tamez-Duque01/22/2021 at 22:08 0 comments

    Since the beginning, our aim was to create as much -real- impact as possible. Any Pediatric Exoskeleton is already a big deal which can surely benefit many children, but we couldn’t stop thinking that even if prices were accessible, there would always be someone we wouldn’t be able to get to.

    We decided to propose an Open Source Model paired with a Sharing and Collaborating Program to ensure that the design wouldn’t just go into a repository where people wouldn’t really know what to do with it. An exoskeleton is a complex machine which can really make use of a bit of instruction and support in order to be successfully built and run. We want to help makers around the world really get into the technology, and we want to push collaboration beyond our own capabilities as well!

    Because of the children-focused nature of Alice, and due to the fact that it operates with high levels of current with moving parts which could very well damage someone’s limbs if not operated properly, we provide free access to the codes, designs and reference material after a screening process which ensures only people with basic engineering experience and aptitude attempt to build and use the device. We want to make sure Alice helps children, and we want to make sure nobody is damaged through what we have made.

    If you want to build your own exoskeleton, make sure to request full access through this link.

    We have a growing community in Italy, Greece, the USA, Chile, México, India, Ecuador, and more; and we would love to have you with us!

    See you there and until the next log! :)

  • Clinical Success and our Golden Pilot

    Jesús Tamez-Duque01/16/2021 at 09:33 0 comments

    Our pilot was born with Muscular Dystrophy; unable to move his legs. This forced him to depend on wheelchairs and brought additional complications spanning body and mind. Unable to walk on his own, independence became something unusual for him.

    In 2018, his grandmother heard of our project but our exoskeleton was not ready for him. We asked them to wait so we could be sure that Alice would be safe enough for him to wear. His grandmother was patient -yet insistent- and wrote back to us every month for the next ~12 months. After about a year of testing, detailing, and getting the appropriate clinical permissions, we were finally able to give them some good news.

    In 2019, he made a first attempt at standing up and walking with the help of Alice, but he didn’t manage to do it. On his second try the day after, however, he was able to stand, walk, and wave for a photo without the help of anyone else.

    This was an important day for the team, because we proved that Alice could indeed support children with high disability and up to 50kg + ~1.4m… but it was way more important because it made us feel that what we were doing could actually achieve something significant for others. He was one of 10 children who participated within our first user tests.

  • We are back !

    Jesús Tamez-Duque01/05/2021 at 17:46 0 comments

    Since the last post, a lot has happened. We have moved from the early prototype we showed you in PLA to a still-simple but patient-compliant clinical device; and we definitely want to keep sharing it in Open Source with you !

    During this time, we have created new designs, new codes, and new electronic / mechanical combinations which have made it possible to even test a couple of prototypes in hospitals so we can now say that Alice has been validated with patients. We have also been working on creating and growing an Open Source program to help more people make their own exoskeletons. You can also bet we have been drinking lots of coffee during the whole process.

    We know it has taken us a while but we can finally sit down and write about it, so we will soon be uploading more posts to tell you some of things that happened during this process and to share all of the details you need to know to make your own patient-validated exoskeleton.

    Stay tuned, we will be trying to make a new post every week !

    PS: Here’s a sneak peak of the use of Alice with patients.

View all 6 project logs

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Laurent C wrote 01/15/2021 at 20:34 point

Really fabulous, what a hope to be able to move to where you want. The world of "iron man" is near...

  Are you sure? yes | no

Jesús Tamez-Duque wrote 01/24/2021 at 22:25 point

We surely hope so ! :) Hopefully it will be a world accessible to many more than just Tony Stark hahaha :P

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Laurent C wrote 01/15/2021 at 20:34 point

Really fabulous, what a hope to be able to move to where you want. The world of "iron man" is near ...   

  Are you sure? yes | no

Dan Maloney wrote 01/04/2021 at 23:13 point

That's both tragic and beautiful. Very exciting to see what can be accomplished with hobbyidt-grade tools and materials. Well done!

  Are you sure? yes | no

Jesús Tamez-Duque wrote 01/05/2021 at 16:50 point

Thanks, @Dan Maloney! Indeed, we're really happy to be able to actually help patients using materials which are available to a larger range of people. Stay tuned as we will soon add more details about the prototyping and construction process :)

  Are you sure? yes | no

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