PRE2019 3 Group6

Group members

David van Son	1005864
Susanne Louvenberg	1238843
Jur Janssen	1247069
Bas Ohlen	0963529
Jeroen Meijs	1008703

Problem statement

In our current society is the sitting position the most frequent body posture, especially in the office working industry. Many professions require working behind a desk. Students also experience those working conditions. Jans, Proper, and Hildebrandt (2007) found that working adults in the Netherlands can spend up to 12 hours sitting down on a workday. Because people are sitting more hours a day, much research is done to determine the consequences of sitting for longer periods of time.

There has been done research about long-term health risk of long occupational sitting. Health risk as body fatness, cancer, type 2 diabetes, cardio-vascular disease, and mortality are examined to their connection with occupational sitting. However, they conclude that there is insufficient evidence of a causal relationship between those conditions.

However, other research does shows that occupational sitting increases pain. Medical and ergonomic field studies indicate that sitting posture can be the cause of muscle, connective tissues of tendons, ligaments, and join capsules pain. Chronic pain and troubles may be the result of static load for longer periods of time. The degrees of pain increased as the time of occupational sitting increases. A study by Womersley, L and May, S (2006) showed that people with backache sat for longer periods of uninterrupted sitting compared to the no backache group of people. The sitting posture also determines the effects of occupational sitting. In their same study the group with postural backache also had a more flexed relaxed sitting posture. Other research confirms this result because slumped sitting position and poor shoulder posture (e.g. rounded shoulders, and head forward) causes pain due to mechanical changes that affect the function of the median nerve. Shoulder protraction reduces the nerve movement and other joints are moved. In response to moving other joints, the nerve dynamics is altered which changes the local blood supply. This is harmful for the nerve function and causes the risk of neck and shoulder pain.

Backache and neck pain are one of the most frequent cause of invalidity in industry in most Western countries. Kuoppala and colleagues (2008) showed in a systematic review that promoting ergonomics and a good sitting position reduces the absences from work. This stresses the importance of a good sitting position, because it reduces pain for individuals but also decreases work absences for the company.

Marshall, and Gyi (2010) mention: “Environmental influences such as no support for the feet, low-friction seating material, or poor desk height can all create additional muscle work. Poor design forces the adoption of awkward and inefficient working postures that can ultimately lead to discomfort, pain, and chronic disability if adverse conditions persist.”. In addition to the environment influencing the sitting posture another research states that individuals with neck pain have a different perception of a ‘good’ sitting position. Their sitting position is slightly different, and even a small change in head position can result in an increase of the lead on supporting structures and muscle activity. This indicates that it is important to impose a sitting position on people to accomplish a good sitting position that decreases the chances of pain.

To conclude, it is of importance to have a chair that provides a good sitting position to reduce the effects of occupational sitting. However, every person has a different physique, which means that one chair would not fulfil the needs of different users. Most chairs can be to some extent be adjusted at the users wishes. But as stated above, users who experience backache do not always have the correct idea of a ‘good’ sitting position. In the current working environment, employees do not have a fixed sitting position because of flex-work spaces. Therefore, the user needs to adjust the chair every day to have a good sitting position. To overcome all the problems stated above, this project envisions an automatic chair that helps the user with establishing a good sitting position.

Our Solution

To overcome all the problems stated above, this project envisions an automatic chair that helps the user with establishing a good sitting position. This chair has the possibility to automatic adjust the sitting position of the user. When the user wants to use the automatic chair, he or she needs to login. This is to know which user uses the chair and therefore which unique position chair needs to take. This can be done by scanning the user’s student or company card. Besides some other personal information, this card will have some details about your body part lengths. With this information, the automatic chair can adjust the sitting position for a particular user in the best sitting position to overcome backache.

Scenarios

The following two scenarios describe the importance of this project and the end user that is envisioned.

Fleur studies the bachelor Applied Mathematics at the TU/e. She needs to attend lectures and study for many hours a week to learn the courses. This means she spends about 5 hours a day on occupational sitting. Her days consist of meetings, lectures, and individual studying, which means she switches from different chairs very often. However, she does not take the time to adjust the chair to her optimal sitting position. Most of the time, Fleur only changes the height of the chair. But she started to notice that she is experiencing backache. She realizes this pain is coming from a bad sitting position. Therefore, she is enthusiastic about the new automatic chairs on the University. Since the new chairs arrived Fleur has been using the automatic chair every time, which is easy for her because of the login system. She is experiences way less backache compared to before. The chair made it easier to adjust the chair which she did not completely did before. Besides, the automatic chair made her more aware of her sitting position.

Thomas is 56-year-old and works already 30 years at the Rabobank. He has a job which requires him to work behind a computer every day. He experiences occupational sitting for around 8 hours a day. In the past, Thomas experienced shoulder and neck pain. However, he searched for help and understood it was because of the many hours sitting in a bad position. From then on, he started to adjust to chair as much as possible to have a better sitting position. He has been doing this for almost 10 years already. As a result, he experiences far less backache than before. But a few years ago, the Rabobank started to use flexible working spaces. Which means Thomas needs to switch places every day. This is very annoying for him, because he needs to adjust the chair each day again. Because he does this in the most optimal way, it takes him 5 frustrated minutes. Thomas would really like to see the automatic chair in his office. This means he does not have to struggle each day with adjusting his chair.

Objectives

There are different types of users involved in this product. Primary, secondary, and tertiary users have different views on how this automatic chair needs to function. Different objectives are specified for those user groups.

Primary user objectives (office workers, students).

• The primary user can ‘activate’ the chair to automatically go in the good sitting position.
• The primary user can manually change the sitting position of the chair.
• The primary user can use the chair like a regular chair, and thus without the automatic option.
• The primary user can login to the chair with his/her card.

Secondary user objectives (companies, universities).

• The secondary user can install the automatic system on their regular chairs.
• The secondary user can replace the automatic chair with regular chairs.
• The secondary user can explain the usage of the automatic chair to the primary user.
• The secondary user can gain the needed information (lengths) of the primary user for the automatic chair to function.

Tertiary user objectives (technicians for installation and maintenance).

• The tertiary user can repair the automatic chair at the location of the secondary user.
• The tertiary user can install the automatic chair at the location of the secondary user.
• The tertiary user can repair the automatic chair without hinder to the primary user.

Product Requirements (NOT done, working progress)

The following list of requirements help to structure the project process and ensures traceability.

• The chair needs to be reliable for the user. (specify reliable)
• The chair needs to be safe to use. (specify safe)
• The chair needs to automatically adjust more efficiently (less time) than the user itself could do. (how much time less)
• The chair needs to know the user’s physique. (what physique)
• The chair needs to know what the good position is for the user. (what is the good position)
• The chair needs to automatically change the position of the user.
• The chair needs to be able to be manually changed in the same manner as the user currently does.
• The chair needs to be comfortable for the user. (what is comfortable)
• The interface between the automatic chair and the user needs to be understandable for the user (universally understood). (when does the user understand it)

Survey

A questionnaire was done to examine the primary user’s perspective of our project. This survey consisted of questions regarding the users sitting behavior and about our solution to a bad sitting position. The goal of this survey was to find out whether the user would like to use such an automatic chair to begin with. It also served as a start to know the focus of this project.

The survey is linked here.[1]

State-of-the-Art

Posture effect on performance

Posture plays an important role in performance. Poor posture can lead to worse task performance while also adding stress to the spine and balance muscles .

Posture is also a tell-tale sign of engagement, it is even possible to estimate engagement purely on posture.

Currently it is possible to detect sitting posture using a regular office chair equipped with force transducers. It is also possible to detect posture using mobile devices, which is more accurate but also more intrusive.

Using a posture assistance device, it is possible to correct posture and thereby improve performance, even in a dynamic environment, such as surgery .

In this paper research two groups were studied, symptomatic and asymptomatic office workers. All subjects demonstrated an 10% increase in forward head posture from their relaxed sitting postures with the computer display. No substantial evidence for posture changing over a working day was found. .

The higLink titleh complained of musculoskeletal disorders is due to awkward postures, unsuitable workstation and lack of knowledge related to the areas to apply in everyday routine and it shows that working postures have a direct contribution on musculoskeletal disorders complained by the office workers in Putrajaya. .

Given the association between RULA (rapid upper limb assessment) score and the prevalence of the problems, reducing RULA score by designing ergonomic workstation may reduce the prevalence of WMSDs (work-related musculoskeletal disorders) among the workers. .

Computer use increases risk of developing musculoskeletal disorders. Such an increase is mediated by ergonomic factors such as mouse use, remaining seated for prolonged periods, adoption of inadequate or uncomfortable postures, performing certain PC tasks, and psychosocial factors. .

Research ergonomic chair

Ergonomic guidelines ergonomic chair

The ergonomic guidelines for an ergonomic chair are

• Chair sears should have correct height. Both feet should be supported. When a chair is too high, it creates undue pressure at the knee/thigh. While, if it is too short the knee will be higher than the hip sockets.
• Width and depth of chair seats should conform to the users dimensions.
• Flat uncontoured seats are preferred to discourage a slouched or C-shaped posture.
• Lumbar support by providing low- or mid-back support can help hold good posture and prevent pain to the spine and neck.
• Head support, if provided, can help ease stress for the neck muscles and provide support for seating over extended periods.
• Arm rests provide support for reading, typing, painting, and similar activities.

Research on Ergonomic Design and Evaluation of Office Backrest Curve

Survey

There is already many research done to the ergonomic design of an office chair. Also research is done to the complaints of people who is using an office chair a lot. A questionnaire (link to source) was used to find out what the most common complaints were. A group of persons (2000) working in the IT sector were questioned the following questions:

• Sitting posture most commonly used by employees in employees’ minds;
• Which indicators of office chairs can cause discomfort?
• What kinds of discomfort does office chair lead to?
• Importance of office chair parts and the score of each part.

Sitting posture most commonly used by employees

Results

As can be seen in Figure ?? the most used sitting posture is the relax posture. The survey shows that 50.3% subjects consider the backrest is very important. The waist supporting, a part of the backrest, cause to 58.09% of the people pain in the back when sitting in an office chair for a long time. The neck supporting, a part of the backrest, causes to 57.23% of the users pain in the neck. These two indicators are causing the most discomfort comparing to the other indicators. The Chair back inclination angle (36.01%) and Hardness and softness of chair back (31.83%) are also causing discomfort. So the shape and material of the backrest is not optimal. When the back of the user can not fit well in the back of the chair, the backrest cannot be supported by the seat, and it will cause neck and shoulder pain eventually. Users’ heads and necks leaning forward and cannot get pillow’s supporting, when they keep a relaxed sitting posture, which are also reasons of neck and shoulder soreness. So the backrest is the most important part of an office chair.

Construct of spine and chair backrest

Spinal Measurement

A test was done to see whether the shape of an office chairs corresponds to the shape of a spine. A spinal measurement was done by the participants and an office chair backrest measurement was done. Four different chairs were investigated. The ergonomics requirements for office chairs that were given are:

• Headrest height: 628.3 – 675.1 mm. (This range ranges from P50 females to P50 males with high cervical spine point in sitting posture.) (P50 stands for normal height);
• Waist support height: ≥ 210 mm;
• Waist support depth: 20 – 40 mm;
• Effective back width: ≥ 360 mm;
• Seat back height: ≥ 460 mm.

When the chairs and the spine of an average person were investigated the results can be seen in Figure ??. In the figure the shape of the spine of an average person can be seen. Also the shape of the four tested chairs. The spine and backrest is divided into three parts: head and neck, back and waist. None of the four chairs do conform to the curve of the spine when the human body is sitting upright. All the four chairs do have waist support, but they do not fully consistent with the human waist, only chair B does fit. Furthermore the most serious differences are at the head and neck area, following is the upper back. The results of this study show that most of the existing office chair designs do not conform to the shape of the human spine in the office state. The main problems are the unreasonable depth of waist and the excessive distance between backrest and headrest and human body.

Suggestions made by the paper

From the survey, it is also found that the chair backrest is mainly used for relaxation, and cannot play an effective supporting role in the working. In the design of office chair, it is suggested to design the back of the chair according to the shape of the human spine, or to match the curve of the back of the chair with the shape of the spine in the sitting position, so as to support the human body as comprehensively as possible in the work.

ActiveErgo .

In this paper an active approach is made to improve ergonomics by combining sensing and self-actuating workspace furniture. The areas posture sensing, ergonomics reminders, and active furniture were combined.

Posture sensing

• Accelerometers in wearable devices can track partial body postures;
• Flex sensors can detect head tilt, and arm angles;
• Capacity sensors and piezoelectric sensor are used in chairs to detect bad postures on pressure distribution;
• Vision-based monitoring systems can detect sitting postures;
• Geometric features can determine incline angle of user’s head;
• Face detection is used to calculate distance between face and screen;
• Microsoft Kinect sensors can provide skeletal tracking, also measure the user’s body dimensions.

Ergonomic reminders

• The prototype uses real-time feedback displayed on the display screen. The system provides real-time directions to guide users on how to adjust chair position and height.

The 6 posture angles that require personalization in a computer workspace

Active furniture

• The prototype uses a motorized desk for automated height adjustment, and dual robotic arms to provide automated adjustment based on sensor data on monitor height and distance.

Ergonomic Guidelines

The ergonomic guidelines are based on the figure on the right.

• Maximum forward head tilt of 15°. (1)
• Upper arms are vertical and forearms are horizontal. (3 – 4)
• Thighs are horizontal and knees are at 90°. (5 – 6)
• Vertical viewing angle of 15-20° below the horizontal, with the first line on screen at about or just below eye level. (2)

Result from 21-person field research

Field study

The two users that were tested are desktop and laptop users. In the figure can be seen that the upper arm angles (mean=26.5°, SD=11.7°) deviates the most. This is because of excessive chair distance to the desk/keyboard. The forearm angles (mean=13.4°, SD = 8.7°) are caused by incorrect desk/keyboard height. Another interesting thing was that laptop users had significantly higher forward head tilt angle compared to desktop users (mean=6.58° vs. 0.88°). None of the participants fully met the guidelines to within a margin of 10°. This was surprising because the company provided ergonomic chairs, desks, and monitors, and also offered optional ergonomics training to the employers.

Future work

A prototype was made but needed some improvements. The improvements that were needed are:

• Deviations during Actual Tasks. For future work, an extended field study would be needed to observe the deviation from the initial postures. We also envisioned active approaches supporting continuous posture and activity monitoring for helping users maintain ergonomic postures throughout the day.
• Clothing variety. They did not specify participants on what type of clothes.
• Improved Skeletal Sensing and Full Automation. The prototype currently requires users to perform two specific postures for the Kinect SDK. But it should be on normal walking and standing postures. The prototype still requires manual chair height and position adjustments. This should be automatic
• Activating Postures. The current system is static in the sense that it stops making adjustments once everything is properly configured. Explore using active furniture to actively encourage users to switch to different postures

Conclusion

So the ergonomic guidelines were given in different sources. It became clear that despite of using ergonomic chairs people still get all kinds of discomforts, caused by different parts of the office chair. For this project it will not be able to work on all those different parts. One part of the chair must be chosen and this will be improved. Based on the studied papers most people have discomforts in their back, head and neck, caused by a bad shaped backrest. So the part that we are going to improve is the backrest. This backrest must meet all ergonomic guidelines and will be designed in a way that it more closely resembles a human spine and that it can be adjusted automatically, based on the user. There is already tried to make an automatic workplace, so these sources can be useful for this project.

Brainstorm

When we started brainstorming, we asked ourselves the question: how can we assist in making people sit better? We thought of different ways by which we could accomplish this goal. The ideas that we came up with differed mainly in the amount of autonomy of the user. The idea where the user would have the most autonomy, is to launch an information campaign that raises awareness of the problem. In this case, the user would be able to decide for himself/herself whether he/she does something with the information. The idea where the user would be the least atonomous, is the idea of a seating police. We imagined a scenario similar to stories of the D.D.R., where citizens monitored each other. In our case, this seating police would consist of many normal users, who could spy on others to see if they're seating like they're supposed to. Then, a warning or punishment could be given to force people to sit in a healthy way. While these ideas are on the ends of the spectrum of user autonomy, we also thought of more balanced solutions. These ideas came down to warning the user of his/her bad seating position, either actively or passively. In this solution, the user retains his/her autonomy for the most part, while being nudged in the direction of a healthy seating position.

Informing

• Raise awareness/informing people about a healthy seeting position
• Measure the current way the user sits and give information on how to improve

Nudging

• Passively warning
  • Built in display or light which shows if you have the correct setting on your chair.

• Actively warning
  • A light
  • Notification on your phone
  • Vibrating chair

Paternalism

• Annoying beeping sound like with seatbelts in a car
• Only allowed to use computer if sitting like you are supposed to
• Seating police

Based on the survey that we held, most people are already aware of their bad seating position. An information campaign would therefore have little to no effect, as the problem doesn't seem to be a lack of awareness. The survey also found that people value their atonomy. They want to be able to adjust their seats themselves, without others interfering or limiting their options. Thesre findings point us in the direction of a seat that encourages the user to adjust their seating position to be healthy. We think that the idea of passively warning the user fits this best. The reason that this fits better than actively warning, is that the users who value autonomy, which seem to be all of them, won't want to sit on actively warning chairs. This means that they will probably sit somewhere else, where they can be free of interference and sit how they want. This will most likely result in them sitting unhealthily, which is not what we want.

Approach, Milestones and Delivarables

Approach

Our approach is that we start by gathering information regarding our topic, the state of the art and the relevance of our research. We will then hold a survey among people who use adjustable chairs often, in which we want to find out which part(s) of the chair they most often adjust. Using this data, we will research which parts are in most need of being monitored. Then we will determine possible ways of warning the user, and make prototype(s) of these systems. We will then test which way is preferred by the user, and which way gives the best results. Combining these results, we will conclude which way would be best for a user warning system.

Milestones

• Evaluation of the best working posture.
• Made and held the survey
• Determined the most relevant adjustable parts of a chair
• Determined the sensors that are needed to detect a person’s working posture.
• Made a prototype of the user warning system
• Full test evaluation of the user warning system
• User evaluation of the user warning system

Deliverables

• This Wiki page containing all our research and findings.
• Survey results about the adjustable chair.
• A prototype of the user warning system.
• Test and user evaluation of the user warning system.
• A presentation at the end of the project.

Pressure sensors

Sensor

For our product we want to make a mat with pressure sensors in it. This mat can be put on the office chair. This way we don't have to make a whole new chair. Inside the pressure mat 9 (this can be changed later) sensors will be placed equally divided in a 3x3 structure. Before we can make a choice on which sensors we are going to use, the sensors used in the papers are investigated. The sources that are given by the different sensors are the papers that have used that sensor

Load cells

Load cells have different kind of ranges, there are loads cells that have a range of 5-10 kg (55mm x 12.7mm x 12.7mm), but also up to 200 kg (150mm x 38mm x 24mm). The working of a load cell is not ideal for our situation. On both sided (up and front) a piece should be mounted. Then a force will be applied on one plate than the straight bar will deform and based on the deformation the pressure can be translated into an electrical signal. The price of load cells ranges from €10 - €15. [[2]]

Force transducers

Force transducers are used for dynamic, short-duration static and impact force measurements. So it can measure tensile and compressive forces, this can be option for our product. The maximum compression is about 80kg, this enough because the transducers will be divided over the whole seat. The dimensions are 19.05mm x 15.93mm. [[3]]

Force sensing resistor

A force sensing resistor (or force sensitive resistor, FSR) is a material whose resistance changes when a force, pressure or stress is applied. These FSR’s have a maximum range of 10kg, it is not sure if this is enough. The weight of a person will be divided over the whole seat, so if enough resistors are used than 10kg can be enough. There are different kinds of resistors. A square FSR (44x38mm) of €9.95 or a circular (12.5mm) of €6.95. [[4]] There is also another one, this one is much more expensive, €21.95. But this one has a much bigger range because the resistance can be adjusted, the maximum can be set up to 300 kg. But for our product a maximum of 10kg seems enough so the circular FSR with a diameter of 12.5mm seems the best choice. [[5]]

Pressure mat

Now the materials for the pressure mat must be investigated. The material must be comfortable because a person must sit on it and the FSR's must be placed into sheet.

Polyether SG35 or SG40

This material is often used for seat cushions and the hardness is medium. The material is very cheap for a 300x400x30mm piece the price is €1.80.

Koudschuim HR40

This material is often used for chairs and matrasses. The material is very cheap for a 300x400x40mm piece the price is €3.00. Minimum height is of this material is 40mm. It doesn’t really matter which of these two products we choose, because both materials are sufficient for our project. Also two thin mats can be bought and than the FSR's can be placed between those two mats.

Circuit

The circuit diagram is shown in [6]. The circuit makes use of a voltage divider structure. This divides the voltage between the pressure sensor and the resistor. Since the pressure sensor's resistance increases when the force increases, the voltage across it also increases. This voltage is measured by the Arduino's ADC, which it then outputs to the PC as a value between 0 and 255 (1 byte). The analog multiplexers (MUX) enable us to use more than 6 different sensors.

Who is doing what

Week 1

Name	Time spent	Break-down
David	11 h	Introductory lecture (2h), Brainstorm (1h), Studied papers (4h), Wrote summary (1h), Group meeting (2h), formatting wiki page (1h)
Jur	10 h	Introductory lecture (2h), Group meeting (2h), Studied papers [7-10] and made summary (4h), Brainstorm about possible topics (1h), Approach/Milestones/Deliverables (1h)
Jeroen	9 h	Introductory lecture (2h), Group meeting+brainstorm (2.5h), Studied papers(4h), Made user requirements (0.5h)
Bas	9 h	Introductory lecture (2h), Group meeting (2h), Brainstorm (1h), Studied papers, Update wiki(4h),
Susanne	10.5 h	Introductory lecture (2h), Brainstorm (0.5h), Group meeting (2h), Studied papers (2h), Wrote problem statement (4h)

Week 2

Name	Time spent	Break-down
David	8.5h	Tutor meeting (0.5h), Group meeting1 (1.5), rewrote approach, milestones and deliverables (2h), Group meeting2 (1.5h), Enquête (2h), data analysis (1h)
Jur	12h	Tutor meeting (0.5h), Group meeting (1.5h), [Search papers, summarize, make ready for Wiki, put on Wiki] (8h), enquête (2h)
Jeroen	h
Bas	h
Susanne	10.5h	Tutor meeting (0.5h), Group meeting1 (1.5), Made enquête (1h), Group meeting2 (1.5h), Enquête (2h), Wrote objectives and requirements (3h), Wrote our solution (1h)

Week 3

Name	Time spent	Break-down
David	h	Group meeting1 (1.5h), data analysis of survey (2h), add survey to wiki (0.5h), rewrite approach, milestones and delivarables (0.5h), Group meeting2 (1.5h), design electric circuit (2h), make prototype of circuit and program arduino (8h), write code documentation (h)
Jur	11h	Group meetings 1 and 2 (3h), Tutor meeting (0.5h), Research sensors -> what is already used -> which is the best for us (5h), Research material mat (1h), Write parts for sensor and mat on the Wiki (1.5h)
Jeroen	h	sensoren onderzoeken, wat bestaat er al
Bas	h	brainstorm over het waarschuwen (manieren/ pros & cons)
Susanne	h	Tutor meeting (0.5h), Group meeting1 (1.5h), Rewrite our solution, Rewrite requirements (1h), Write two scenarios (1h), Group meeting2 (1.5h), Rewrite state-of-the-art and add assumptions, Look at possible chairs to use as prototype

Week 4

Name	Time spent	Break-down
David	h
Jur	h
Jeroen	h
Bas	h
Susanne	h

Week 5

Name	Time spent	Break-down
David	h
Jur	h
Jeroen	h
Bas	h
Susanne	h

Week 6

Name	Time spent	Break-down
David	h
Jur	h
Jeroen	h
Bas	h
Susanne	h

Week 7

Name	Time spent	Break-down
David	h
Jur	h
Jeroen	h
Bas	h
Susanne	h

Week 8

Name	Time spent	Break-down
David	h
Jur	h
Jeroen	h
Bas	h
Susanne	h