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Occupational Risk Factors Associated With Tremor

The cause of ET is not known but some studies suggests that part of the brain control muscle movement doesn’t work properly, sometimes it is  referred to as familial when more than one member of a family are affected, this suggest that genes play an important role on its cause. ET is non-work related and there is no evidence that the use of vibrated electric power tolls can cause ET. A recent study by the US National Library of Medicine, National Institute of Health to examine whether repetitive mechanical movement may be related to the development of Carpal Tunnel Syndrome (CTS) in PD with unilateral hand tremor using neurophysiological methods. The result showed that hand tremor in PD patients was not directly related to the development of CTS. In contrast, more frequent use of hand without tremor may induce mechanical loading and may be associated with CTS in the hand without tremor. (National Institute of Health, 2004)

A recent study by Edlund M., Burström L., Hagberg M., Lundström R., Nilsson T., Sandén H., and Wastensson G. (2014) at Goteborg University, Sweden. The study was conducted to investigate the possible increase in hand tremors in relation to Hand-Arm Vibration (HAV) exposure to tools and work area. The study concluded that there was no evidence of exposure– response association between HAV exposure and measured postural tremor. Increase in age and nicotine use appeared to be the strongest predictors of tremor.

Non Occupational Risck Factors Associated With Tremor

Gender:

According to several studies, most female affected with ET disorder have their head and voice are significantly affected more than any parts of the body. On the other hand, males have their hands affected more than any other parts of the body. This study conducted by a group of neurological doctors and researchers to test the hypothesis that variability in ET clinical expression is influenced by gender and age. The examination included 450 ET patients and the result showed that head/voice tremor was notably more common among female ET patients.  Men had more common ET tremor on hand (Hubble J., Busenbark K., Pahwa R., Lyons K., and Koller W. 1997).

Age:   

There is no exact age at which ET can take place. In General, the occurrence of ET increases with age. ET is more common in people age 40 and older (Louis E., and Ferreira J. 2010). A study on 1214 of participants of 12 young and 14 old was conducted by group of researchers in the School of Physiotherapy and Exercise Science in corporation with Applied Cognitive Neuroscience Research Centre, Griffith University, Queensland, Australia, and School of Human Movement and Exercise Science, University of Western Australia, Crawley. This study concluded that even though tremor outlined to be the same among all age groups, older patients demonstrated higher tremor amplitude on their hands and fingers. Also a higher EMG motion across all postural conditions (National Institute of Neurological Disorders and Stroke, 2014).  As per the International ET Foundation, one out of five people over age 65 are affected with ET.

Alcohol:

People who drink more alcohol everyday are more likely to be at risk of developing ET. In a study by the Spanish Research Group, they “assessed lifetime alcohol consumption and neurological symptoms in more than 3,000 people aged 65 years or older.  At initial assessment, more than half (1,838 people; 56%) of the participants were found to have had at least one alcoholic drink per day over their lifetime.  During the subsequent 3 years, 76 people developed essential tremor” (Louis E., and Ferreira J. 2010). Another study suggests that ET can be reduced for 45 to 60 minutes after the digestion of alcohol. This could cause chronic alcoholism in addition to tremor can worsen when the effect of alcohol is over. (Kiriyama T).

Smoking Cigarettes/Chewing Tobacco:

Even though some specialists insist that excessive amount of nicotine or caffeine can cause tremor. A group of researchers demonstrated the effects of cigarette smoking and oral nicotine on hand tremor. The study was applied on thirty three people of two age groups, and different gender, and the study included three experiments. There was a noticeable increase in hand tremor after smoking a cigarette and chewing a 4 mg nicotine gum.

On the other hand, a study on 2008 was conducted on 3,348 participants in Spain by a group of researchers from the department of neurology at Columbia University, New York and department of neurology University Hospital Madrid, Spain. 3,271 of the participants were ordinary people (392 among whom were smokers), and 77 participants have incident ET (5 among whom were smokers). This study verified relationship between baseline heavy cigarette smoking and lower risk of incident ET. Two previous studies examined smoking habits in prevalent ET cases and non-ET cases smokers (Striano P., Elefante A., and Coppola A. 2007).  Although the proportion of ET cases and non-ET smokers did not differ, the number of cigarette packs per year was significantly lower in ET cases. The second of these studies focused on the association between smoking and prevalent ET. In this study, ever smokers were one- half as likely to have ET when compared with never smokers (Jacob F. 2010).

An interestingly study presented the possibility of using nicotine to reduce the effect of Parkinson’s Disease. There is no strong evidence that supports this study, and there is no agreement on nicotine daily dosage and method, or process of using such a subject 20.

Emotional Stress:

Stress exist in our daily life and anyone can experience stress anywhere and at any time, when the stress takes place, the body starts to respond to that change mentally, physically, and emotionally. The reaction to stress vary from one person to another, some people emotional reaction to stress can include sadness, anger, less concentration, and mood change. Other people could have unintentional reaction to stress like sweaty palms, shaking, and loss or gain weight. Other people might develop rest tremor by the stress of work interview, during exam, at anger or extreme fatigue. This is called physiological tremor. There are studies suggest that emotional stress can make vocal tremor even worst. Approximately 25% of individual with Essential tremor have vocal tremor (Hansen C., Snyder S., Qiu X., Brooks L., & Moreau D. 2012).

Diagnosis of Tremor:

According to the National Organization for Rare Disorders (NORD): ET is a highly variable disorder. Age of onset, progression, tremor distribution, and severity can vary greatly from one individual to another (Louis E., and Ferreira J. 2010). There are symptoms associated with ET that doctors can observe during medical exams, such as uncontrollable shaking hands and arms, shaking voice and slight head shaking. Part of the face may appear panicked, and in the worst case is the unbalanced and abnormality. In rare cases, tremor can occur in the feet or legs. The diagnosis of ET is achieved by a review of the patient’s history and a physical examination. Thus, there is no particular test to confirm a clinical diagnosis of ET. To aid in the diagnosis, several clinical criteria have been proposed, including those by the Consensus Statement on Tremor by the Movement Disorder Society (Deuschl et al. 1998), which were modified slightly by the Tremor Research Group (Elble 2000). The history review of the disease should consider the age of the patient, the disease progression over time, the use of caffeinated beverages, tobacco, alcohol, and the use of any medication for ET treatment.

The physical examination can include Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) scans. During the exam, the characteristic of the movement should be evaluated precisely to confirm that the involuntary movements are rhythmic and oscillatory. It is important to distinguish ET patients from those with PD. Patients with PD often manifest a mild to moderate postural tremor or kinetic tremor (Koller et al. 1989; Jankovic et al. 1999). It is also important to distinguish ET from enhanced physiological tremor. Enhanced physiological tremor is an 8–12 Hz postural and kinetic tremor that may occur in the limbs and voice (but not the head) and may be further exacerbated by emotion and by medications. While the amplitude of kinetic tremor in ET is generally higher and the frequency lower than that of enhanced physiological tremor, mild ET and severe enhanced physiological tremor may have similar tremor amplitudes (Elble R. 2005).

The final stage of ET assessment is the lab evaluation. Thus, if symptoms or signs of hyperthyroidism are present, then thyroid function tests should be performed. In younger patients (i.e., under 40 years old) with no family history of ET or dystonia, the possibility of Wilson disease should be explored with a serum ceruloplasmin, which may be reduced; this is usually not an issue in older patients (Louis E., and Ferreira J. 2010).

Treatment of Tremor:

Tremor treatment can involve:

• Non-Surgical Treatment (Medications): All medications which doctors prescribe for essential tremor disorder have side effects, so the decision to treat ET patients with medications can only be taken if the level of discomfort outweighs the side effects of treatment.  Side effects of common medications include: Drowsiness and nausea caused by Topamax, fatigue and sedation Caused by Xanax (Mayo Clinic), slow heart rate and drop in blood pressure caused by Beta-blockers (Harvard Medical School, 2004).  

Non-Medical Therapy: This includes physical therapy and exercises to enhance muscle strength. The other therapy treatment can involve adaption of wrist weight or using wide grip pen. Although physical therapies can improve coordination and muscle control of some individuals, these therapies are long time treatments and can’t remain with patients all day long. Since anxiety and stress typically make the tremor worse, non-medical relaxation performances and biofeedback can be effective in some patients.

• Surgical Treatment: Various forms of surgical treatment can be used to control the ET disorder when medications are ineffective. This can include Deep Brain Simulation (DBS) by implanting electrodes within specific areas in the brain. This device produces electrical pulses to interrupt signals from the thalamus. There is no guarantee that the tremor will be completely relieved with DBS (Johns Hopkins Medicine). There are also some after surgery side effects that includes weakness, problems with balance, difficulty speaking, and headache. This surgery is costly. According to some experts, a surgical efficiency loss cases have been reported over time after DBS surgery. There are also gradual worsening of the disease cases following DBS surgery. (Oxford Brain Journal, 2012).

Surgical Lesion – Placing a surgical lesion in an area of the brain called the ventral intermediate thalamus (VIM) has been used to treat ET for decades. Between 80 and 90 percent of patients have benefited from this surgery. On the other hand, this surgery is only effective to control tremor on one side of the body. It is very dangerous to use this procedure to control tremor on both sides of the body due to the increased threat of developing speech problems (Johns Hopkins Medicine). 

III. Research Objectives

Customer Segmentation and Value Proposition

There are several practices that need to be considered when developing a new product or service. Among those practices are the customer segmentation and value proposition.

Importance of Customer Segmentation and Value Proposition

We all agree that customers differ in the way they think, their lifestyles, purchasing habits, and other attributes. There is no one solution that is considered to be suitable for all customers. Thus, one-size-fits–all approach is a bad practice and far from reality. Customer segmentation is a very important factor that needs to be considered when developing a new product or service. Another important factor that needs to be considered when developing a new product or service is the value proposition. This is because regardless of what we do, we always have bigger competitors. This competition even goes bigger when product or business moves across borders and overseas.

Customer Segmentation

Customer segmentation is the process of dividing customers into small groups who are similar in gender, age, educational level, or specific needs. This measurable segmentation helps in serving and assisting the customers effectively. It is also a useful technique to communicate with targeted customers through sales and marketing channels.  This project is considered to be a need-based segmentation where the customers are hand tremor patients. This does not include the severe case of tremor patients who suffer from head shaking, face change, and speak with difficulty. The customers included according to this segmentation will be:

• Hand tremor patients

• Both genders

• All ages

Value Proposition

Value proposition of a product is the key element that makes it attractive and valuable to customers. It is the most persuasive reason that guides the customers to a particular product. There are many important promises that this product can give to tremor patients. It assures them with many benefits they can receive by using this product:

• This product is very cheap and the prototype costs less than forty dollars. Unlike other tremor suppression products that may cost hundreds or even thousands of dollars.

• Unlike other tremor cancellation systems available today. This product can be used for writing, eating, holding knife, fork, or cup.

• This product will improve quality of life of hand tremor patients by reducing the hand vibration.

• This product is portable and can be used anywhere, any time, and by any patient. It does not involve mechanical, or stationary monitoring system.

• This product is light. Unlike other tremor passive suppression system that uses heavy weight to counteract the tremor generated by patient’s hand. This product uses light electronics components which are assembled on top of a glove.

Vibration

Vibration is a continuous shaking movement about an equilibrium point, it exists in many electrical, pneumatic, hydraulic systems, structures, and in most machines. In some applications, vibration is necessary and can be useful such as in musical instruments, body vibration therapy devices, loudspeakers, and mobile phones. On the other hand, there are many situations in which vibration can play a critical role in reducing machine performance, reliability, and cause energy losses.  Some industrial applications require a vibration-free environment and the process cannot be completed if any vibration exists. For example, semiconductor wafers production lines. Vibration of many mechanical devices such as pneumatic drills, grinders, and sanders always create dangerous noise that is disturbing, harmful, and has a negative impact on human health. When vibration exceeds the normal level of any mechanical machine, it can affect its lifetime and can be worn out rapidly due to imbalance or looseness of some mechanical parts. In a human being, some people suffer from vibration of one or more parts of their bodies. This unwanted vibration has a destructive impact on those patients, and makes their daily life activities very challenging and frustrating.

Vibration Cancellation Techniques

According to Hansen, Snyder, Qiu, Brooks, and Moreau (2012) vibration and noise are related and share many common concepts and depends on each other. For that reason, vibration control and noise control have been treated in a combined manner by researchers (p. xvii).  There are two techniques used in the industry to cancel and control vibration; the active control and the passive control. In the active control method, there are some sensors, actuators, and logic controls involved in the design.  The sensors measure the vibration and then the feedback logic controls the actuators to generate the necessary force to counteract the unwanted vibration motion. In contrast, the passive control system acts passively- without requiring any power supply. The damping action mainly counts on the properties of materials used in the system. Both active and passive damping techniques mainly use three methods for cancelling vibration. These methods are vibration damping, vibration isolation, and anti-vibration.

Active vibration damping system:

This is a closed loop system that involves sensors, actuators, and a feedback controller. This method is used when there is a need for a greater performance or when the passive technique is ineffective. Instead of using spring as in passive method, active damping uses electromagnetic generated force. This method is effective when there are several vibration sources involved, it is capable of damping all vibration at once.

Active vibration isolation system:

In this process, the vibration sensitive area is isolated from the source of vibration. The design of this system involves a feedback circuit to control the vibration isolation process. The feedback circuit consists of sensors to detect displacement, velocity, and acceleration. As well as actuator for power generation, amplifier, and microcontroller. Active vibration isolation is usually used in small structure systems such as medical devices, photonics, and semiconductor industry.

Active anti-vibration system:

This method is used when the unwanted vibration area cannot be isolated from the vibration source, and also when the vibration is not amplified by the mechanical structure. In this technique, an out of phase force with equal frequency and amplitude is generated to interfere with the vibration source in order to minimize it or cancel it.  

Passive vibration damping system:

Unlike active technique, passive system does not involve electronic components. In this method, the structural design of the system generates a potential energy. This energy acts as a control force to absorb the vibration. There are several passive damping materials used today. These materials include viscoelastic materials, oil, rubber, and a spring. Viscoelastic material carries the properties of both liquid and solid. It converts the absorbed vibration energy into heat.

Passive vibration isolation system:

In this method, the natural frequency of the system is kept lower than the excitation level. It mainly contains of a rubber pad or mechanical spring, a mass, and a damper. This technique is used in large scale structures and equipment. Some area of applications are heavy load pumps, large air conditioning unit, compressors, building and large structures, and car suspension systems.

Passive anti-vibration system:

This method is used whenever the sensitive area cannot be isolated from the vibration source. This system uses a Tuned Mass Absorber (TMA) where a swinging spring-mass is attached to the targeted part of the structure in order to reduce mechanical vibration amplitude. This technique is widely used in car’s crankshaft pulley to control the angular vibration. AMT technique is also used in the solid fuel booster of spacecraft and many other applications.

IV. METHOD AND PROCEDURES

The Glove Design

The glove is designed for the right hand although it can be built for the left hand as well. As indicated in figure 2, there are five main modules involved in the design of this glove.

Glove Module

The first module is the glove with connection wires installed on the glove. These wires are arranged in a way that make them easy to be connected to vibration motors from one end, and to the output pins of Arduino from the other end.

Figure 2

The hand glove, different module and parts

Tremor Simulation Module

This module is built to provide and simulate human hand shaking. The difficulty to provide a vibration machine that satisfies our need for this project was the main reason behind building this module. All vibration machines available in the College of Engineering and Applied Science at WMU were too big and could not be used for this project. Another alternative was to provide a tremor simulation device made specifically for hand tremor study and analysis. This system was expensive. The solution was to build a simulation module. This module included a small 3-5V dc motor, plastic bottle covers, Velcro strap, 9V battery, clay, and power supply circuit. The power supply circuit is also used to supply the necessary voltage to run the vibration motors. The strength of the vibration depends on the size of the plastic cover and the location of the hole made in the cover as indicated in figure 3. The bigger the plastic cover the more clay it can take, and the weaker the vibration will be and vice versa. A heavy material, such as a little stone or a piece of metal can be added to make the plastic cover heavier. If the hole made in the plastic cover far from center, the stronger the vibration will be and vice versa.

Figure 3

The hand tremor simulation module

Arduino-Uno3 Module

Melgar and Diez (2012) described Arduino as an open-source development board based on ATMEGA microcontroller. It was introduced on 2005 at the Interaction Design Institute Ivera, Italy. Unlike other microcontrollers, there are Arduino clones which are less expensive, have a simple programming environment. The open-source software is easy to be used by beginners who do not have any programming experiences. Arduino software can run on Windows, Mac, or Linux. It is published as an open source and is written on programming language similar to C/C++. Any experience programmer can modify and extend Arduino programming capability. Any inexperienced circuit designer can develop and extend his/her own Arduino or Arduino shield boards (p.2).

Figure 4

Arduino Uno R3 Pinout Diagram.

As seen on figure 4, Arduino hardware includes the main board that houses the ATMEGA microcontroller. It has other built in Integrated Circuits (IC’s) modules like memory, a user interface chip, and 5V voltage regulator chip. The power supply can be connected through the DC power input that can handle any DC voltage between 7 to 12 volts. There are 14 digital pins numbered from 0 to 13 for sending or receiving digital signals. These pins can be used as INPUT or OUTPUT depending on their need in the application. Six of the digital pins (0 to 5) can be used for Pulse Width Modulation (PWM) purposes. Beside the power connector, there are 4 pins for power connection through wires or batteries. These pins are 3.3V, 5V, and 2 pins for ground (GND). There are also six analog input pins which are used for receiving the analog signals and convert them to digital signal.

Accelerometer and Gyroscope

The advancement in new technology helped researchers to develop tiny microscopic and sophisticated sensors. The use of these sensors are becoming increasingly significant in many applications around us in our life. These sensors have been essential for the development of navigational system, tablets, mobile phones, consumer virtual reality, medical devices, space, and military applications. The most common of these sensors are the accelerometer and the gyroscope.

Accelerometer is a device that measures the magnitude of linear acceleration along any axis. By using the microscopic crystal built in it, accelerometer can detect an object movement when it changes its position from standstill to any velocity.  When this acceleration (vibration) occurs, the crystal inside accelerometer goes under stress and generates a voltage. The amount of generated voltage depends on the level of vibration and can be used to determine position data history of that object.

We can better understand how accelerometer works by reviewing our high school mathematics and physics background. We have learned that velocity is defined as the rate of change of the position of an object with respect to time. The acceleration is defined as the rate of change of the velocity of the same object with respect to time. The rate of change with respect to time is known as derivative. According to this, velocity is considered the derivative of the position and acceleration is considered the derivative of the velocity. Based on that if the acceleration of an object is given, then the preceding position data of that object can be found easily by applying double integration on the acceleration, therefore:

If velocity V  = ʃ (a) dt  and  position   S = ʃ (v) dt

 S = ʃ (ʃ (a) dt) dt

Gyroscope (Gyro) measures the rate of rotation of an object (orientation) around any axis X, Y, or Z using the principle of angular momentum. In other words, gyroscope is used to determine how fast an object can spin about an axis (angular velocity), which is represented in rotation per minutes (RPM).  The mechanical gyro as displayed in figure 5 consists of a high speed, free spinning wheel called a rotor. The rotor is surrounded by three suspended frame rings called gimbals that have almost frictionless bearing. If the gyro is tipped, the gimbals will change their orientations in order to keep the rotor spinning along the same original axis and same direction.

The capability of the rotor to remain stationary regardless of any change in gimbals axis made gyroscope to become useful in many applications.

Figure 5

Figure 5 the mechanical gyroscope

In modern electronics technology, a microscopic gyros are used to reach the same outcome of the mechanical gyros. These microscopic gyros use a different principle of operation and structure than those used in mechanical ones. In recent years, two other kind of gyros were introduced and found their way in many applications. These are optical gyro and vibration gyro and the last one is the most common in advanced technology. According to a study in in 2011, Armenise, Ciminelli, Dell’ Olio, and Passaro suggest that all vibration gyros are based on Coriolis Effect. This effect occurs when an object moves on a spinning system and experiences a force perpendicular to the direction of rotational motion. This force causes the object to deflect right or left instead of going straight. The vibration angular degree can be simply represented by two degree-of-freedom spring mass damper structure (p. 12). These gyros are made out of different materials like crystal, ceramic, and silicon. Their structures can also take several shapes like double-t, tuning fork, and h-shape depending on their use and applications. Gyroscopes are used in aircraft navigational systems, large boats, unmanned vehicles, camera-shake correction, game controller, motion sensing, and car navigational systems.  

Combining accelerometer and gyroscope together can lead to a very powerful sensing capabilities and give a quicker, more accurate position and orientation determination. These micro size devices are called Micro-Electro-Mechanical Systems (MEMS) and involve tiny mechanical and electronic parts. MEMS become very significant in applications where the highly accurate and complex movement of an object is required. Based on their uses and applications, they can vary from being very simple structure without any moving parts, to extremely complex with tens of integrated parts. The integrated mechanical parts can comprise springs, levers, and vibrating structures. The integrated electrical parts can comprise capacitors, resistors, inductors, and transistors. In 2011, Armenise, Ciminelli, Dell’Oio, and Passaro in their study showed that the reduction in power consumption, size, cost, and weight made MEMS the optimal choice for small-scale controlling technologies (p. 97). Figure 5 shows the MEMS accelerometer/gyro sensor used in this project. This sensor is called GY-52, and contains three accelerometers and three gyros in one single chip.

The GY-521 is a breakout board that contains a Micro Processor Unit 6050 (MPU6050), KB33 voltage regulator, pull-up resistors in both clock line (SCL) and data line (SDA) line, and the auxiliary I2C lines. The MPU6050 consists of 3 MEMS accelerometer and 3 MEMS gyros. The accelerometer range: ±2, ±4, ±8, ±16g, and the gyro rang: 250, 500, 1000, 2000/s. The MPU has a 16-bit analog to digital converter for each channel which makes it very accurate by capturing the x, y, and z channel at the same time. The MPU6050 is integrated with a Digital Motion Processor (DMP). DMP performs a fast calculation of 6-axis positions and gives a precise reading of the motion at any time. This will offload the timing and the processing power required by MPU 6050. The KB33 voltage regulator enables GY-521 to be connected to any voltage source between 3.3-5 DCV. The auxiliary line I2C is a serial protocol for 2-wire interface to connect low speed devices such as microcontroller and analog to digital converter in integrated system. It also can be used to allow MPU6050 to act as master to other devices such as a microcontroller if needed. (MPU-6000 and MPU-6050 Product Specification, 2013).

Figure 6

GY-521 board

The number of sensors built inside MEMS is referred to as Degree Of Freedom (DOF). The GY-521 contains 3-axis accelerometer, and 3-axis gyros; hence it has 6 degree of freedom.

Vibration Motors

Although vibration motors have been around for many decades, they became widely spread in mobile phone vibration alerting in the 90’s.  These motors are also used in different products and applications, such as Global Positioning System (GPS) tracker, medical instruments, haptic feedback devices, automotive industry, and many more. Based on their applications, vibration motors can vary in shapes (Coin/Cylinder/Spring) and sizes (Diameter 3 mm to 48 mm).

Coin vibration motors are small, thin, and light weight motors and have no external moving parts. Figure 6 indicates the internal construction of coin motor which consists of a magnet, weight, and a rotor with commutation points attached with a coil. The power supply brushes are attached to the magnet. One end of the commutation points is in contact with the brushes, and the other end is attached to the small electric wires. Once the power is connected, the electrical coils in the rotor will be energized which in turn produces a magnetic field. This magnetic field is capable of rotating the motor and producing a force that causes the weight to displace. The repeated displacement generates the vibration. If the voltage applied to the motor is increased, both the speed of the motor and the vibration frequency will increase. (Coin vibration motor, Precision Microdrivers).

Figure 7 displays the direction of spinning of the vibration motor. If the shaft in Y axis, the vibration will take place in X, and Z axis.

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