PRE2019 4 Group9

Group members

Name	Student ID	Department
Pim Claessen	0993712	Applied Physics
Bengt Frielinck	1269593	Automotive
Matthijs Marinus	1000921	Software Science
Max Opperman	1232427	Computer Science and Engineering
Thomas Willems	1022753	Software Science

Goedemorgen Lambert Rooijakkers

Problem Statement

From the beginning of mankind some 2 million years ago, humans have never lived in a more connected, safe world. People can travel the world by plane and car and we have a system to protect and help us from danger and misfortune. However this is modern way of live has not completely eliminated all dangers. Due to our connected world death by road accident is a common occurrence definitely under younger ages. In these accidents people can get stuck inside or under a car. The current tools used to free this people are hydraulic pumps, spreaders and cutters. While these can effectively help free people they also take quite some time to set up and use, time that isn't always there. This is why we propose the use of an actively powered exoskeleton. Firetrucks can be equipped with this exoskeleton and firemen can put it on while driving to the emergency. This will provide instant superhuman strength for any situation. In the case of a person being stuck under a car, the car can be lifted the moment the firemen arrive and valuable minutes are saved that are normally needed to set up a hydraulic jack. Firemen are only 1 example of the emergency workers benefiting from the super human strenght given by an active exoskeleton. The flexible design we propose can improve rescue workers effectiveness in all areas, for example disaster areas, where lifting rouble and carrying people all day puts a heavy strain on workers bodies. In this report a concept design for such a flexible, multipurpose, active exoskeleton will be given

User Group

We will be designing our exoskeleton for use by emergency responders. In most situations these will be firefighters. However we will keep other use cases in mind for example for police officers or search and recue operations. Firefighters have an incredibly difficult and dangerous job. Typical firefighter emergency scenario’s include medical emergencies, vehicle accidents, building collapse and of course putting out fires among others. These are difficult, strenuous activities often carried out in very adversarial conditions. It is then not surprising that one of the mayor causes of death for firefighters is overexertion, being struck by objects or getting caught/trapped . Our exoskeleton should help alleviate this group by reducing the amount of physical exertion firefighters have to undergo while performing our jobs. We also hope the exoskeleton can provide the firefighters with the extra boost in strength to free themselves or people they are helping in dangerous situation. The exoskeleton should also serve as a type of shield by taking some of the blows of various objects hitting the firemen since the exoskeleton will cover a large part of their bodies. It will also help them carry people much easier out of dangerous situations, or move heavy objects trapping people. You could also think about tall buildings which are on fire. Firemen have to carry equipment up a large set of stairs. Currently there is already an exoskeleton design who helps firemen carry up to 40kg of weight making this task much easier and faster . It should also be applicable in traffic accidents where victims are stuck in folded cars. Often firemen are called in these scenarios to cut open the car. This is a difficult process and having an exoskeleton to bend or break critical parts should be a tremendous help.

Another great user group are search and rescue workers. After natural disaster these people are deployed to find and help people who are in danger. This usually involves freeing people from under a large pile of debris from collapsed buildings or other items. These operations usually take a long time and a lot of equipment. Shows a company who has developed and exoskelton already for this case allowing the user to have extra power to move debris or objects for a long period of time under harsh conditions. These are defenitly some of the features we want to equip or exoskeleton with.

Police officers could also benefit from using this type of technoglogy. As explained in police officers often have to carry heavy equipment like gun vests or gun belts with them. This coupled with long standing hours causes a lot of police offers to eventually develop health problems in their back or legs causing them to become unemployed. If they were to carry and exoskelton during long work hours we could alleviate some of this repetetive strain.

User research

We are trying to contact our local fire- and police departments to interview some people about exoskeletons and how they would use this technology. For the first interview the Brandweer Eindhoven Centrum Eindhoven (040-2203203) was contacted who forwarded our call to a fireman at the station. We asked him the following questions after which we will write a summarized answer of the conversation:

1. Do you know of any exoskeleton suits currently in use or development at any firestations in the Netherlands?

As far as he was aware, the use of this particular technology was not in use anywhere. He had only seen it use in medical applications thus far.

2. Do you see any use and/or neccesity for an exoskeleton?

In his honest opinion not really, at least not for the work he carried out. We informed him of some of the death report numbers of firemen usually dieing from overexaustion or getting stuck in dangerous situations. He however did not share these conceners and in his opinion it would not be really neccecary.

3. Could you think of any situation where an exoskeleton might be practical?

The only situation where he think it might be helpful is extinguish fires over longer periods of time since this can be quite exhausting but further than that, for the work he carried out he still feeled like it would be unnecessary.

4. What are your biggest concerns for the use of this technology?

The main issue he saw, and mainly why he would not really see the benefit of this technology is that in his opinion it would take too long to get into. In high pressure situation every second is of essence which they train a lot and his perception of exoskeletons was that they take a really long time to get into. Time, that in his opinion, you do not really have. Furthermore he thought that something that covered most of your body would be too bothersome to use. He gave the example of climbing a fence for example for which you need quite a lot of flexibility or when you are walking through a house you do not want to keep bumping into objects.

5. What are your main requirements if you would use this technology?

His main requirements followed from the previous question. If he had to use it he would not want it to hinder him in his movements and it should also be very easy to get in and out of. '

Through some private contacts we were able to arrange an interview with William Elseman, a volunteer fireman. I started the interview by introducing William to the subject of exoskeletons and our plans to design one for use by the fire department. I also told him some of our ideas for the design, e.g. being used for carrying rubble/people or assisting with long hosing times.

1. Do you know of any exoskeleton suits currently in use or development at any fire stations in the Netherlands?

“No, I’ve never heard of this technology being used by any fire department.”

2. Would you want to use this kind of technology? What do you think of the uses we propose?

“Well, the most important thing to understand is that our biggest concern is always our own safety. You don’t enter a building if you’re not sure you can get out and when we arrive at the scene with six people, we leave with six people. Because of this carrying rubble would never be a good application for an exoskeleton. Once a building has burned down so far that it starts collapsing, we won’t enter. Instead we would probably have a crane or a ‘Bobcat’ (a brand of crane vehicle) move the rubble. I do agree that it can be very useful in carrying people out of buildings though, as it can be quite a challenge to carry, wel… ‘larger’ people out of a building. Normally when we enter a building the most restricting factor is the amount of oxygen in our tanks. The more effort something takes (e.g. hosing a fire or heavy lifting), the more oxygen we use, resulting in less time we can spend inside the building. If an exoskeleton would reduce some of these efforts, it could greatly extend the time we could be active inside a building.”

3. Could you think of another situation where an exoskeleton might be practical?

“A lot of other jobs we do is what is called “Technische Hulpverlening” (THV). This is needed at heavy car crashes for example. When we need to break open a car or cut two cars apart, etc., we use hydraulic equipment. These hydraulic shears are very heavy and can sometimes require two people to operate. I think an exoskeleton might be a perfect application for this type of situation. Another thing I can think of is when we are dealing with large house fires we often deploy a water cannon, which is incredibly heavy. Again, being able to carry such heavy equipment by yourself would help a lot.”

4. Are there any last concerns you have for such an exoskeleton?

“First of all, keep in mind that when dealing with fires, we already have heavy gear on our backs, namely our oxygen tanks. There’s not much room for battery packs or any other equipment or electronics. Secondly, make sure the fireman operating the exoskeleton is still able to reach his communications device and that none of the electronics interfere with the signal. Communication is very important when dealing with these dangerous, high pressure situations.”

I ended the interview by thanking William for his time, after which he suggested he could try to get me in contact with one of his superiors at the volunteer fire department. We got confirmation we can contact this next user and intend to conduct an extra interview to ask further about the specific requirements for an exoskeleton used for THV.

Use Case

After conducting the interviews we decided that the best use case for our exoskeleton would be support in “Technische Hulpverlening”. This mostly includes decreasing the effort of carrying heavy equipment like hydraulic shears. From the interviews we learned that for really high pressure scenarios like rescuing people from burning houses, an exoskeleton would first of all not really be necessary, as told to us by the first fireman we interviewed, and also that putting on the exoskeleton would probably cost too much valuable time. Instead we moved to support carrying heavy equipment like William Elseman suggested. The goal of our exoskeleton is that working with heavy equipment can both be done by one man (wearing the exoskeleton) instead of two or more and also that this will take much less effort decreasing the risk of injuries from accidents by not being able to handle the equipment properly because of its weight and long term injuries from working with heavy equipment for long periods of time.

When conducting THV, firefighters don’t use oxygen tanks and thus have no equipment on their backs, giving us a lot more freedom in design and making it a lot more feasible to be able to get in and out of the exoskeleton quickly. In THV firefighters also don’t experience extreme heats like in house fires, so our concerns for extreme heat resistance can be put aside.

From the user research we can make the following list of user requirements which we will reference in the system requirements such that our requirements are relevant to user needs.

• [UR01] - The exoskeleton shall not hinder the user in its required movements
  • [UR01.a] - The exoskeleton shall not restrict easy access to the communications device of the fireman

The needs for this requirement was clearly expressed by the first interviewed fireman. One of his main objections to using an exoskeleton would be that he feared that the exoskeleton would hinder him while carrying out movements that required a higher degree of agility. Not taking this requirement into account would certainly result in our exoskeleton being unusable in practise. Extra attention in regards to the movement of the exoskeleton must be paid to sub-requirement a, as mentioned by William.

• [UR02] The exoskeleton shall be easy to get into.

Another critical factor that the fireman expressed which would turn him off to the idea of using an exoskeleton would be the time it would take to get into one. When firemen get sent out for an emergency every minute is of the essence and if the exoskeleton takes too long to get into, then in all reality it would not really be usable. Technische hulpverlening scenarios are usually not immediately life or death so it does not have to be seconds however also not more than a few minutes.

• [UR03] The exoskeleton will make the user able to lift heavy equipment by himself without straining effort.

This requirement shall have the benefit that one man instead of two are needed for jobs thereby decreasing the amount of firemen required and also caters to our goal of reducing the amount of effort it takes to carry out these tasks.

State of the Art

We probably have to pull different innovations from all kinds of different types of exoskeletons. From different parts of the body to different types of exoskeletons (varying goals). shows that currently, a problem many exoskeletons face is the tradeoff between rigidness and agility. Often a more rigid skeleton can provide more stability/force but in practice is quite cumbersome. The exoskeleton in is an example of an exoskeleton designed for firemen. It provides support for the back and shoulders and is a good example of something we would like to achieve, alleviate some of the heavy work. Discuses some positive/negatives of a back support exoskeleton mostly used in the treatment of SCI (spinal cord injury). The interesting part of this article is that it also discusses some of the dangers involved in using an exoskeleton like bone fractures and skin shearing. Furthermore, it also discusses how tailor-made most exoskeletons are and that most take a lot of practice to get used to. The last problem it brings up is that they also take a lot of time to get into. These are all problems we are going to have to think about in our project. Article shows the relevancy of this topic. It talks about a so called AFA exoskeleton which is currently being developed specifically for firemen. It should give a fireman the ability to carry loads up to 100kg while in only weighs 23 kg itself where most of the weight is being transferred to the floor. One of its main uses is that you can replace 2-3 firemen, which is typically needed to hold and control the motion of a firehose, by 1 fireman who can operate and move it all by itself.

Talks about the impact exoskeletons could have on police work. A lot of injuries over the long term are caused by repetitive strain from carrying gun belts, bullet-resistant vests, and long periods of standing. As is the case for firemen, who also carry a lot of gear and are likely to have to stand for long periods of time, our ES should alleviate this repetitive strain keeping the emergency responders in better health for a longer time. Displays another great possible use case exoskeletons, some of which we want to replicate in our model. It involves an exoskeleton designed for dangerous and heavy search and rescue work under extreme conditions. It allows the user to carry heavy objects with greater ease and for longer periods of time helping with moving debris or heavy objects. This is also a functionality we want to have.

Requirements

Within the design of an exoskeleton, multiple required features should be present, depending on the user of the exoskeleton. Keeping in mind that the users of the exoskeleton will be emergency services we came up with the following requirements respecting the requirements ISO 29148 for systems (and software) engineering. Note that these requirements can be altered in a later stage if we find them to be unreachable for our system. Some of these requirements are linked to user requirements which are specific to cater to the needs of users, others are requirements we felt would be most beneficial to practical and useful exoskeleton to be used in real life.

• When in passive-mode, the exoskeleton shall change to active-mode when the “change mode” button is pressed within 100ms.
• When in active-mode, the exoskeleton shall change to passive-mode when the “change mode” button is pressed within 100ms.

- We want both an active and passive mode, between which the user should be able to switch. If used appropriately, this will result in less battery power being used. When the exoskeleton is not used to support the user in lifting, the passive mode ensures that the batteries are not drained. In active mode, the exoskeleton aids with picking up things. To maximize the time that the exoskeleton can assist the user the switching between modes is needed. If there is only an active mode the batteries shall be drained before the user can even experience any assistance from the exoskeleton.

• When in passive-mode, the exoskeleton shall carry at least its weight. [UR01]

- The exoskeleton should not put extra weight on the user when standing still. This means that the exoskeleton can stand on its own and the user will only have to carry parts of the exoskeleton when moving. For example, when moving the right arm, the user will only feel like they are carrying the arm due to the force needed to move the exoskeleton from one position to another. Once the arm is in position and is kept still, the exoskeleton shall support itself again and no carry weight is felt by the user.

• When in passive-mode, the exoskeleton shall move freely without restricting the movement of the user. [UR01]

- This means that when the passive-mode is on, the hinges and other pivoting points will not be fixed in one position. They will give in when the user makes a movement.

• When in active-mode, the exoskeleton shall be powered by batteries.

- A remote battery pack in a vehicle with a cable may be used, depending on the required work needed and weight that needs to be lifted.

• When in active-mode, the exoskeleton shall ensure that the user perceives the weight being lifted in a ratio of 15:1. [UR03]

- This ratio of 15:1 is a bit less than the Raytheon XOS 2. However, this exoskeleton uses hydraulics rather than batteries.

• The exoskeleton shall not hinder the movement of the arms and legs in normal usage, meaning that movement of arms and legs should go unhindered until full extension of the arms and complete folding of the legs, such as a fireman's suit does not hinder all movement of the user's arms and legs. The exoskeleton, should not impede the user in normal operation, the user should be able to move as in a normal firemen's suit. Normal operations include carrying a hose near pelvis height and should height. [UR01]
• The exoskeleton without batteries shall weigh at most 40 kg. The user should be able to move in the exoskeleton with the other required equipment, such as a fireman's suit. Using materials that are lightweight, the user will not feel encumbered while in the exoskeleton. Potential materials that can be used are fiberglass or carbon fiber, as these materials offer high strength while being lightweight. With previous models, made of carbon fiber and aluminum or steel, a weight of 23 kgs was reached. Therefore a weight of 40 kgs should be in range. With regard to cost, a mix of composites and aluminum is the best course of action. Specific strength is an important factor, as the strength to weight relation is important. [UR01]

Force requirement: Average weight male is 85kg, 5.7% of this weight is in the arms. 3.25% in the upper arms, 1.87 in the lower arms and 0.65% in the hands. The total weight of 1 arm is then 0.0285*85=2.42k. With the use of a passive system connected in the middle of the upper arm, and the weight pulling down from the elbow joint the following conclusions can be drawn. (sketch below) The upper arm, lower arm and hand are in order 17.2, 15.7 and 5.75 percent of the total height of an average male. The ratio between these parts is 2.99 : 2.73 : 1. In the figure this is the ratio between A : B : C. The formula to calculate the supporting force relative to the force of the load (work) is the following:

Fsup=dACFwork/dAFsup

To keep a stretched arm in place horizontally using the lengths above with the supportive brace mounted exactly in the middle between A and B gives: Fsup=3.83 Fwork For the average male using the weights above the maximum force becomes: Fsup=3.83*1.73=6.62 Kg. For a more accurate force needed the weight integral over the length of the arm must be taken, however for the most cases the exoskeleton is used a load will be lifted as seen in the sketch below of figure X. This makes the weight of the arm negligible and the total workforce can be seen as pulling from point C. In this case a new force ratio applies: Fsup=2 Fwork and for the case of only holding the arm up the force needed isFsup=2*1.73=3.45 Kg. In order for the exoskeleton to feel good and not push the users arms up when putting it on and actively “fighting” the mechanism when no load is placed upon the system this is the maximum lift it can provide if the supporting force is passive. In order to give more lift assistance while remaining manageable and free to move while no load is present, an on off switch is needed. The equipment is governed by European standard EN13204 and has a maximum weight of 20 Kg, for a ~50% weight reduction the system should supply ~20 Kg of lift.

Summary of the research for the batteries

Prismatic lithium-Ion batteries have the highest energy density [Wh/Kg] of around 160 Wh/Kg and a volumetric energy density of around 360 Wh/L.

Weight car with hinge point (the arm of force can be neglected in the correct lift and with locking mechanism)

Example SUV specs: 3000kg 5m x 2m x 1.75m

The force needed for a sideway tip = 14715N

Energy needed sideway tip = (max 29430 J) → for 5min active lifting +- 15kg batteries

Materials

For the materials, we have to take into account the previous statement about weight and heat resistance. In addition to this, we also have to take into account the strength of the material. It has to be a solid material that is quite stiff. The following materials were found with these properties:

Material	Tensile Yield Strength	Compressive Yield Strength	Density	Hardness (Brinell, Knoob, Rockwell C, Vickers)	Rigidity	Melting Point	Further Notes
Titanium Grade 6	827 MPa	830 MPa	4480 kg/m³	320, 363, 36, 349	48.2 GPa	<= 1590 °C. However, 2.80 MPa at temperature 540 °C with time >= 3.60e+6 sec	517 MPa Tensile Strength at temperature 427°C
Titanium Beta C	825 MPa	-	4820 kg/m³	304, 330, 32, 318	-	1555 - 1650 °C	Due to Wikipedia indicating that this material has the tensile strength of 1400 MPa we researched this material. However, we found that it was incorrect.
Titanium Grade 5 Annealed at 700-785°C	880 MPa	970 MPa	4430 kg/m³	334, 363, 36, 349	42.1 GPa	1604 - 1660 °C. However, 150 MPa at temperature 455 °C during >=360000 sec	Tensile Strength is 620 MPa at 427°C
Titanium Grade 5 Solution Treated 900-955°C, Aged 540°C	1100 MPa	1070 MPa	4430 kg/m³	379, 414, 41, 396	-	1604 - 1660 °C. However, 210 MPa at temperature 455 °C during >=23400 sec	This has been treated at a slightly higher temperature than the above, resulting in recrystallization (as explained here).
Carbon Fiber Reinforced Carbon Composite (CFC) (Light)	68.9 MPa	172 MPa*	1650 kg/m³	-	-	400 °C	* We use the value for compressive strength on a plane of CFC for this.
Carbon Fiber Reinforced Carbon Composite (CFC)	103 MPa	200 MPa*	1750 kg/m³	-	-	400 °C	* We use the value for compressive strength on a plane of CFC for this.

Note: we also looked at grades below grade 5 for titanium. However, we quickly found out that the density is higher for those than for titanium grade 5, hence they are not mentioned here.

The most viable materials that were researched is Titanium Grade 5, either the annealed or tempered variant. The version we choose depends on the ease with which we can import both variants in Fusion. We have a slight preference for the version that has been treated at a higher temperature.

CAD

A prototype of the lower leg and shoe modeled in Fusion 360, from two angles. A rough draft where many changes still need to be made.

Approach, milestones & deliverables

Approach

Our current goal for the end deliverable is a model for an exoskeleton that helps emergency services. Due to the COVID-19 situation, the process of the actual building of the model will be difficult in the given time span. The aim is to have a full-body exoskeleton that has both a passive and active mode to preserve battery. We want to achieve this by reaching the milestones as mentioned below. In short, we want to do research on what has already been achieved in the field of exoskeletons and how they operate. After that, we want to start designing our model and elaborate on our design choices in a report. This model will be made using CAD software which we yet have to determine. Since we have plans for a full-body exoskeleton we will distribute this work amongst two of our group members. The rest of the group will work more on the research and design choices of the project. If we find out that this distribution of work is not working out for us, we will alter it accordingly.

Milestones

Week	Milestone
Week 1	Research on possible projects and prepare for the first meeting
Week 2	Summarize papers & more research First design decisions
Week 3	Learn CAD Elaborate research on design decisions
Week 4	First CAD concept designs Finish research & write the report
Week 5	Finalize design Elaborate design sections in the report
Week 6	Finalize CAD models Finish design sections in the report
Week 7	Finish video presentation Final report on the wiki page
Week 8	Video presentation and peer review

Deliverables

Our deliverables will be:

• A concept design for a flexible, multipurpose exoskeleton that uses passive and active technology for use by emergency services.
• A report on the wiki page containing a detailed description of the design as well as all of the research, findings, and results of the project.
• A video presentation presenting our research, findings, and design.

Task distributions

Bengt and Matthijs will focus on learning CAD and visualizing our designs. As mentioned before, there will be somebody (Max) who can help with this if there are too few group members assigned to this task. Max, Pim, and Thomas will do research on how the exoskeleton will be made. This consists of e.g. the materials, electronic circuits, and passive mechanisms.

Logbook

Week 1:

Name (ID)	Hours	Work done
Matthijs Marinus (1000921)	8	Intro lecture[1h] Meetings [3h], Finding/Researching different topics [4h]
Bengt Frielinck (1269593)	8	Intro lecture[1h] Meetings [3h], Finding/Researching different topics [4h]
Pim Claessen (0993712)	7	Intro lecture[1h] Meetings [3h], Finding/Researching different topics [3h]
Max Opperman (1232427)	7	Intro lecture[1] Meetings [3h], Finding/Researching different topics [3h]
Thomas Willems (1022753)	7	Intro lecture[1] Meetings [3h], Finding/Researching different topics [3h]

Week 2:

Name (ID)	Hours	Work done
Matthijs Marinus (1000921)	11	Meetings[30m], Researching new topic for user groups [2h], Writing user groups/SoTA part/updating wiki page[3h30m], Installing CAD Fusion360/Doing tutorials on modelling[5h]
Bengt Frielinck (1269593)	9	Communications[30m],Researching[2h], Writing requirements and revision[2h30m], CAD Training[4]
Pim Claessen (0993712)	3.5	Meetings[2h], Writing Problem Statement [30m], Research [2h]
Max Opperman (1232427)	9	Meetings[2h], Writing Approach, Milestones and Deliverables/updating wiki page[3h], Writing requirements[2hr], Research on lifting abilities for requirements [1hr], Research on how to write proper requirements [1hr]
Thomas Willems (1022753)	4	Meetings[2h], Writing Approach, Milestones and Deliverables/updating wiki page[2h]

Week 3:

Name (ID)	Hours	Work done
Matthijs Marinus (1000921)	10.15	Meetings [2h], Contacting Eindhoven firedeparments, Interview [45min], Write on wiki (small update SoTa, writing user requirments form interview, researching/elaborating requirements) [4h], CAD tutorials [3:30h])
Bengt Frielinck (1269593)	10	Meetings [2h], Requirements[2h],CAD Tutorials[6h], CAD prototype[2h]
Pim Claessen (0993712)		Meetings [1.5h], Writing out requirements [2h], Researching batteries and exoskeletal joints [2h]
Max Opperman (1232427)	8	Meetings [2h], Writing requirements [4h], Editing wiki [2h]
Thomas Willems (1022753)	6	Meetings [2h], Contacting police- and firedepartments [2.5], Writing interview questions [1h], Editing wiki [30m]

Week 4:

Name (ID)	Hours	Work done
Matthijs Marinus (1000921)	7h30	Meetings [2h], Research upper body skeletons [3h], Research CAD simulations and tutorials [2h30m]
Bengt Frielinck (1269593)	7h	Meetings [2h], Requirements[1 h],CAD Tutorials[2h], CAD prototype[2h]
Pim Claessen (0993712)
Max Opperman (1232427)	7	Meetings [2h], Writing requirements (elaboration and link to use cases; research + calculations for heat and materials) [3h], Editing wiki [2h]
Thomas Willems (1022753)	7	Meetings [2h], Interviewing William Elseman [2h], writing user research [2h], editing wiki [1h]

Week 5:

Name (ID)	Hours	Work done
Matthijs Marinus (1000921)
Bengt Frielinck (1269593)
Pim Claessen (0993712)
Max Opperman (1232427)
Thomas Willems (1022753)

Week 6:

Name (ID)	Hours	Work done
Matthijs Marinus (1000921)
Bengt Frielinck (1269593)
Pim Claessen (0993712)
Max Opperman (1232427)
Thomas Willems (1022753)