Affordable and Lightweight Exoskeleton Legs Used To Help Patients With Lower-body Paralysis Walk

Summary

Video https://youtu.be/Awqo6-ct1bQ

After people suffer from a stroke or spinal chord injury, 90% of patients are left with paralysis. This problem can be fixed with walking exoskeleton systems. In Vietnam, costs can be said to be the biggest problem,  where having to spend tens of thousands of dollars on a developed walking system is too much for patients' family to spend. This project is aimed at minimize the suffering and help people with lower-body paralysis to be able to walk on their own as well as aid them mentally, making them feel better about themselves.

I tested different types DC of motors and their power output to find out which option is the best to use. The final motor includes an reduction gear which in total, has a torque of 300Nm. The exoskeleton is controlled by rotating each motor to a certain position, holding it, and returning it to normal. Experiments on accuracy and durability were also carried out.

The result of my project is an exoskeleton weighing only 9.3KG, which can be dissembled into 3 parts, and costing only $700. These statistics are better than most exoskeletons available, some even being the best out of the range. My hypothesis is fully supported, and it even goes more than that. 

In the future, I hope to test my device on people with paralysis, and see how my device actually works are patients, not me. It will help me come to conclusions that could aid me in developing my device.

Question / Proposal

Can a walking-assist exoskeleton system be made that is lightweight, affordable, portable, and effective to help patients will lower-body paralysis walk?

Background on Walking Exoskeletons

Over the last century, technology and development had enabled humans to advance hugely. About a decade ago, patients will paralysis will never be able to walk again. Now, with the help of exoskeleton systems, people with lower-body paralysis still have the hope of being able to walk again.

Exoskeletons nowadays are have gone through major improvements,but they are still too expensive for many people whom need them. Walking exoskeletons nowadays cost around $80,000, and weigh at least 12KG. With the average family in Vietnam making only $750 per month, having a pair of walking exoskeletons will be near impossible.

Hypothesis 

My hypothesis is that a walking exoskeleton systems can be created in which people with limited income and training can purchase and use. The cost of the exoskeleton will be at $1000 highest. Also, the exoskeleton must also be lightweight, functional, portable. and most importantly, affordable for a normal person (male and female) to use.

Steps towards achieving my hypothesis this target include being able to create a strong frame, joint system, controlling motors using encoders, and splitting the exoskeleton into smaller parts for portability.

One of the main features my exoskeleton will need to be portability. Ideally, the exoskeleton will be split into 3 parts: the circuit and battery, and each of the 2 legs.

Research

Paralysis In Vietnam

Through the course of my research, I found out that in Vietnam, there are more than 750 000 people living with paralysis. This means for very 1000 people, there are 18 who are paralyzed in some way. Current products walking exoskeletons are too expensive: normal ones costing around $80 000, while the cheapest product available, Phoenix, (SuitX) is $40 000. For people in my country, any of these exoskeletons could cost more than their entire life savings! Vietnam is only an economically developing country, hence its people do not make as much as others in developed countries, and can afford less wants.

Current Exoskeletons

I found out that there are some currently present products which are aimed to help the walking of paralyzed patients:

1) REX Exoskeleton by Rex Robotics

This Exoskeleton is unique, letting the user walk without the use of crutches. This device can be used for people with severe impairments, like spinal chord injury. 

This product, however, costs $110 000, and is very heavy, hence it will be too expensive for poorer patients to buy and transported. In addition, the size of REX Exoskeleton is too much for it to be easily transported without being damaged.

2) Japanese Walking Assist by Honda

This device is a walking assist device, but the user must be able to walk normally. The device sole purpose is to help with power in the user's stride. Thus, the Japanese Walking Assist is unable to help people with paralysis, as they are unable to initiate the action of walking. 

Apart from these mentioned devices, some other products available include:

  • Phoenix by SuitX
  • The American Esko by Esko Bionics
  • ReWalk

Looking at already present devices, I found that there are no suitable device which is light-weight, portable, and affordable to people whom are poor and unable to purchases anything with a price tag of several thousand dollars. This had shaped my project to aiming to create an exoskeleton device that satisfies the mentioned categories for paralyzed people with unhopeful financial conditions.

With my exoskeleton created, I believe that many people all over the world would have a new joy in their life, and be able to walk on their own again. As I intend to create my exoskeleton costing under $1000, funds can be more easily raised for the purchase of a device via donations or charity.

Human Walking Motion

Upon extensive research, I found out that making an exoskeleton leg that helps people walk must require knowledge about the human walking motion. In short, the main actions of the walking motion include:

  1. Lifting heel up
  2. Lifting lower portion of leg up 
  3. Life thigh to the front
  4. Releasing the lower-leg and thigh

Taking into account each step of the walking motion, I will replicate these actions on the motors to help users walk as naturally as possible.

Method / Testing and Redesign

Designing The Physical Components Of The System

For my exoskeleton system to work well and meet my targets, it must have some key components: the frame, the motor, the circuit board, and the encoders to control the motor. Each part of the suit must be designed perfectly for the final product to meet my demanding targets. The following is the process to making/choosing each item on the agenda.

 

The Frame

The first step of making the exoskeleton was the frame. The frame has to be strong enough to support the weight of the user and fit the user's body. The frame of my exoskeleton device has the following properties: 

  • Made of a an alloy of aluminum called AA5251, which has a tensile strength of 310 MPa, and a shear strength of 165 MPa. This means the frame can support the weight of an adult with ease.
  • The shape of the exoskeleton is designed to to have curves that wrap around the natural shape of the leg. This enables easier attachment of the leg to the frame and a more comfortable wear.
  • A plastic pad on the feet stops the exoskeleton from slipping up the user.
  • The whole exoskeleton is designed so that it can be separated into 3 separate components, and be connected together very easily using wires like the image below.

Image: Wires Used to connect modules together

Motors

The motor is one of the key components: it will spin and allow each joint of the exoskeleton to rotate, enabling the user to walk. The process of choosing the right motor was very time consuming, as I had to measure the torque and potential of each motor. The following are results from tests I did to decide which motor to choose. 

Table comparing motors

From these results, I chose the DC motor with 300Nm torque after being attached to the speed reducer. as its size enables it to easily mount onto the joint I have made. This torque is enough to bring a patient's leg up when they are leaning over crutches.

 

 

 

 

 

Above: Motor 2

The Encoder

The encoder used is essential in making the motor turn the right direction for the leg joint to rotate. The encoders enable the turning of motors to different angles and back as commanded. Properties of this encoder include: 

  • High durability
  • High accuracy: 1000P/R. This enables accurate rotation of the motor, which could be an important factor when having patients with different conditions using the exoskeleton. The turn needs to be accurate so no damaged is caused.
  • Repetitiveness: this encoder can perform accuracy tests with high levels of accuracy repeatedly.

Power

24V was need for the motors. However, 24V batteries are expensive, so I used 2x 12V cell instead. This provided enough voltage and lasted up to 5 hours periodic running.

Above: two 12V cells

 

The voltage to needed to power the Circuit board is only 5V, so I used a Voltage Regulator Module to reduce the 24V supply to 5V (below).

 

 

Results

Whole Exoskeleton Suit Statistics:

In conclusion, we have created an walking exoskeleton which is capable of helping patients walk. The exoskeleton weighs 9.3KG, which I have been able to achieve by using a light-weight aluminum frame and components. What is making the exoskeleton unable to achieve a lighter weight is the 2 12V batteries that are packed into the backpack.

Above: Whole Circuit Box For One Side

Encoders

The encoders used in this exoskeleton are basically rings with black and transparent marks on them. This ring is attached to the armature of each motor and as the motor spins, the reader can count the rotations on the ring and know the position of the motor. Processing and reacting to this means that without having to use a servo or stepper motor, a DC motor can be controlled to turn at a certain angle.

Control

The exoskeleton is operated by a RF remote. By pressing a button representing a function on this remote, a signal is transmitted to the RF reader in the backpack, and the reader will relay the message to the Ardruino Board. A response will then be coordinate by the Ardruino to control the 4 H-Bridge Modules which control the distribution of the 24V supply to control the motor. The speed of the motor rotating can also be altered: changing the analog signal of the PWM channel can lessen or increase the current going into the motor hence it is possible to increase or decrease the rotation speed. 

Above: RF remote and reader & H-Bridge Module

Disassembly & Assembly of Exoskeleton

One of the aims of the project was to make the exoskeleton portable, which would help the process of transportation and wearing for the user. The exoskeleton consists of 3 parts: the backpack, containing the circuit and battery, and 2 legs. The attachment of each leg to the backpack requires only the plugging of 2 wire heads together.  

Image: Disassembling & folding the exoskeleton up ​

Exoskeleton in operation

Operation of the exoskeleton is also well. To stimulate the walking of any feet, the user must press a button on the remote. A is used for stepping forward, while B is used for stepping back. C is a special mode where the exoskeleton while continuously walk at a preset rate, according to the user's wants.

 

 

Tests

Motor Accuracy

This test proves how the motor is very accurate, all because of the high accuracy encoder. A preset angle was determined, and the angle of the motor armature was measured after it rotated. The accuracy of the motor is 100% within 5o.

 

Battery Lifetime

This test measured the voltage in the battery after the motors were given a loop code, with 15 second breaks between each rotation. This effectively showed that the battery used has enough power for 5 hours of usage, more than other exoskeletons available.

Encoder Consistency

This test showed that the encoder has a very high accuracy, important for the accurate turning of the motor.

 

Conclusion

Summary:

The overall results show that the exoskeleton is a success. In making the whole exoskeleton the total cost was only $700, not even a fraction of other exoskeletons. This means that I have successfully made by suit cheap enough for common people to afford.

The problem of portability is also solved in the making of the exoskeleton: wires from the bag can be connect to the legs easily, in less than 20 seconds. As a result, the exoskeleton leg can be easily disassembled and packed into a small space. This is great if patients need to transport the exoskeleton to a rehabilitation center or while they are traveling.

The total weight of the exoskeleton suit is 9.3KG. This is lighter that any other exoskeletons available. The lightweight of the exoskeleton means there will be no drag on the wearer and the experience in the exoskeleton will be as natural as possible.

The operation of the exoskeleton is to my expectations: the encoders worked well at the accuracy rate of 100%, while sufficient power from the motor enabled my legs to be lifted when I leaned slightly over the crutches. I can feel the hard force of the motors on my legs, so it means the motors will be capable of lifting other patients of size like me (1m74, 65KG). 

The battery lifetime can be up to 5 hours, meaning the exoskeleton can be used for daily activities without worrying about running out of battery.

The exoskeleton can be adjusted for different patients, changing the stride or how long the time of walk is. As a result this device can help a wide range of people with different needs.

With noticeable changes and fruitful practical results, I can confidently say that my exoskeleton can help patients with lower-body paralysis walk again. The exoskeleton has the following properties:

  • Lightweight (9.3KG)
  • Portability: separate into 3 parts
  • Functional: can operate effective for up to 5 hours
  • Affordable: only $700
  • Effective: can lift 1m74, 65KG male
  • Durable
  • Adjustable

All these positive results show that the outcome of my research and making supports my thesis that an affordable, working, portable and lightweight exoskeleton can be made to help patients with paralysis walk.

Tests Variables

I did my encoder test reliably by attaching the protractor to the encoder itself. The motor accuracy test is kept reliable by reading values at exactly 90o. All test to do with current was carefully monitored and all other factors were kept the same. In all I think that I have made my tests are reliable and fair as it can be, so recorded values are all accurate. I think that all my experiments were fair.

Moving Forward

In the future, I will program the exoskeleton to be able to walk up stairs, and stand up from a wheel chair. I will also find better power sources that could last up to 8 hours.

I want my exoskeleton to help ay as possible and make the world a better place.

About me

My name is Quoc Anh, and I am from Vietnam.

My interest in STEM aroused when I was young, when I used to be occupied with model trains for hours and hours. I love their design and how they function. My interest in trains is still around even these days! I love traveling by train. 

Apart from doing things in the area of STEM, I love playing sports. I like to think that soccer is my main sport, but I will play any other sport any time!

In the future, my plans are to go to a technology university in the US, and study to become an engineer, where by then I can invent more things for the world!

Winning will show me that my hardwork and devotion is to a fruitful result, and it means I can get one step closer to helping millions of lives all over the world whom are stuck to their chairs and beds to walk a gain. I will do everything in my power to get my exoskeletons readily available to people in need of them.

Health & Safety

During my test and time working around the exoskeleton, I had access to the following saftety equipments:

  • First Aid Kit
  • Supervision by an adult incase of emergency/accident
  • Electric source with a Residual-Current Breaker Installed 
  • Appropriate frame to hold the exoskeleto

When planning my test and conducting them, I managed all the safety aspect before proceeding, like the power source and making sure there are no short circuits etc. 

All aspects of my work had no public costs, no toxins or harmful emmisions were given into the environment, and so no animal, humans, or organisms were harmed during the course of my work.

Bibliography, references, and acknowledgements

Bibliography

  • https://www.spinalcord.com/types-of-paralysis

  • https://www.vietnamonline.com/az/average-salary.html

  • https://rewalk.com/

  • https://www.eyecomtec.com/3016-Statistics-about-Paralysis

  • https://www.azom.com/article.aspx?ArticleID=2863

  • https://exoskeletonreport.com/product/rex/

  • https://www.spinalcord.com/types-of-paralysis

  • https://www.thingiverse.com/

  • www.instructables.com/

  • https://hshop.vn/products/encoder-1000-xung-omron-e6b2-cwz6c-chinh-hang

  • https://en.wikipedia.org/wiki/Shear_strength

  • https://www.suitx.com/phoenix-medical-exoskeleton

  • https://tradingeconomics.com/vietnam/wages

  • https://newatlas.com/suitx-phoenix-exoskeleton/41678/

  • https://en.wikipedia.org/wiki/Orthotics

  • https://en.wikipedia.org/wiki/Gait_(human)

Acknowledgements

Through the process of making this exoskeleton, I greatly appreciate my mother for purchasing all the equipments I needed, and encouraging every step of the way. Without her, this project would have never got anywhere close to finishing. 

My sister helped me in assembling some of the components, and she was supportive. I greatly appreciate her.

Software Used

I used an open source program called Ardruino to do all the programming for my exoskeleton.