exo skelton

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WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON Dept. of ECE KSIT Page 1 CHAPTER 1 INTRODUCTION 1.1 INTRODUCTION In medicine, a coma [1] is a state of unconsciousness lasting more than six hours, in which a person cannot be awakened; fails to respond normally to painful stimuli, light, or sound; lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as being comatose. For a patient to maintain consciousness, two important neurological components must function. The first is the cerebral cortexthe grey matter that covers the outer layer of the brain. The other is a structure located in the brainstem, called reticular activating system (RAS). Injury to either or both of these components is sufficient to cause a patient to experience a coma. Traumatic brain injury [2] can cause a variety of complications, health effects that are not TBI themselves but that result from it. The risk of complications increases with the severity of the trauma; however even mild traumatic brain injury can result in disabilities that interfere with social interactions, employment, and everyday living. Coma may result from a variety of conditions like 1. Intoxication (such as drug abuse, overdose or misuse of over the counter medications, prescribed medication, or controlled substances). 2. Metabolic abnormalities 3. Central nervous system diseases 4. Strokes , Head trauma caused by vehicle injuries 5. Deliberately induced by pharmaceutical agents during major neurosurgery, to preserve higher brain functions following brain trauma, or to save the patient from extreme pain during healing of injuries or diseases. 6. Lack of oxygen resulting from cardiac arrest TBI may cause emotional or behavioural problems and changes in personality. Emotional symptoms that can follow TBI include emotional instability, depression, anxiety, hypomania, mania, apathy, irritability, and anger. TBI

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  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

    Dept. of ECE KSIT Page 1

    CHAPTER 1

    INTRODUCTION

    1.1 INTRODUCTION

    In medicine, a coma [1] is a state of unconsciousness lasting more than six hours,

    in which a person cannot be awakened; fails to respond normally to painful stimuli, light,

    or sound; lacks a normal sleep-wake cycle and does not initiate voluntary actions. A

    person in a state of coma is described as being comatose.

    For a patient to maintain consciousness, two important neurological components

    must function. The first is the cerebral cortexthe grey matter that covers the outer layer

    of the brain. The other is a structure located in the brainstem, called reticular activating

    system (RAS). Injury to either or both of these components is sufficient to cause a patient

    to experience a coma.

    Traumatic brain injury [2] can cause a variety of complications, health effects that

    are not TBI themselves but that result from it. The risk of complications increases with

    the severity of the trauma; however even mild traumatic brain injury can result in

    disabilities that interfere with social interactions, employment, and everyday living.

    Coma may result from a variety of conditions like

    1. Intoxication (such as drug abuse, overdose or misuse of over the counter

    medications, prescribed medication, or controlled substances).

    2. Metabolic abnormalities

    3. Central nervous system diseases

    4. Strokes , Head trauma caused by vehicle injuries

    5. Deliberately induced by pharmaceutical agents during major neurosurgery, to

    preserve higher brain functions following brain trauma, or to save the patient from

    extreme pain during healing of injuries or diseases.

    6. Lack of oxygen resulting from cardiac arrest

    TBI may cause emotional or behavioural problems and changes in

    personality. Emotional symptoms that can follow TBI include emotional

    instability, depression, anxiety, hypomania, mania, apathy, irritability, and anger. TBI

    http://en.wikipedia.org/wiki/Depression_(mood)http://en.wikipedia.org/wiki/Hypomaniahttp://en.wikipedia.org/wiki/Mania

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

    Dept. of ECE KSIT Page 2

    appears to predispose a person to psychiatric disorders including obsessive compulsive

    disorder, alcohol or substance abuse or substance dependence, clinical depression, bipolar

    disorder, phobias, panic disorder, and schizophrenia.

    Behavioural symptoms that can follow TBI include disinhibition, inability to control

    anger, impulsiveness and lack of initiative, inappropriate sexual activity, and changes in

    personality. Different behavioural problems are characteristic of the location of injury; for

    instance, frontal lobe injuries often result in disinhibition and inappropriate or childish

    behaviour, and temporal lobe injuries often cause irritability and aggression.

    Complications that result from a coma may be of two types complications during

    coma state and complications after recovering the traumatic brain injury (TBI).

    Post TBI complications include cognitive disabilities like

    memory loss

    post traumatic amnesia

    communication problems

    sensory deficits

    emotional and behavioural problems

    post traumatic ellipse

    Parkinsons disease etc.

    During coma a patient may suffer from pressure sores, pneumonia, progressive

    multiple organ failure, muscular degradation and reduced rate of blood flow.

    1.2 MOTIVATION

    At the present different medications are used to decrease brain swelling, treat

    infections, and prevent seizures. If a persons intracranial pressure is very high or difficult

    to control, medication may be used to put the person into a medication induced coma to

    prevent more swelling.

    Some preventive rehabilitation may be initiated in the Intensive Care Unit such as

    body positioning, splinting, and range of motion (a therapist moves the persons body

    limbs). Sometimes surgery may be necessary to remove blood clots and pressure.

    http://en.wikipedia.org/wiki/Obsessive_compulsive_disorderhttp://en.wikipedia.org/wiki/Obsessive_compulsive_disorderhttp://en.wikipedia.org/wiki/Substance_abusehttp://en.wikipedia.org/wiki/Substance_dependencehttp://en.wikipedia.org/wiki/Clinical_depressionhttp://en.wikipedia.org/wiki/Bipolar_disorderhttp://en.wikipedia.org/wiki/Bipolar_disorderhttp://en.wikipedia.org/wiki/Phobiashttp://en.wikipedia.org/wiki/Panic_disorderhttp://en.wikipedia.org/wiki/Schizophreniahttp://en.wikipedia.org/wiki/Frontal_lobehttp://en.wikipedia.org/wiki/Temporal_lobehttp://en.wikipedia.org/wiki/Aggression

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    Anti-Embolism Stockings (TED Hose) are worn on the persons legs to help

    prevent embolisms (blood clots) from forming and to assist in circulation of blood and

    fluids in the legs. The stockings are long (up to the thighs) and made of tight elastic

    material.

    Sequential Compression Stockings (Kendalls) are worn on the persons legs to help

    prevent blood pooling. These are plastic leg wraps operated by a machine to inflate and

    deflate around the persons legs.

    1.3 AIM OF THE PROJECT

    To design and develop a web controlled leg exoskeleton used to assist the blood

    circulation and avoid the muscular degeneration in the legs of the comatose and be

    extended for physiotherapy. This project presents a new generic technology aiming to

    solve two main problems in the comatose i.e. the muscular degradation and the decreased

    blood flow rate.

    1.4 OVERVIEW OF THE PROJECT

    To overcome this problem a mechanical structure is designed which keeps the

    muscles alive and makes sure that the rate of the blood flow is not decreased. This being

    an electro-mechanical technology avoids intrusion to the body in any sense. The design is

    made general such that it and is wearable by people with any foot size and hence reduces

    the cost of treatment.

    The greatest challenge faced is achieving accuracy in angular control as well as

    design the structure for variable foot sizes and shapes. The structure must be

    mechanically sturdy and as light as possible. The force to push and pull the foot must be

    within permissible limits and the action of the robotic exoskeleton must not cause any

    injuries.

    Care must be taken in providing the angle of motion as well as the number of

    iterations performed by the foot. This is provided by the doctor either manually near the

    patient or remotely through a secure webpage. The input angle must not exceed the

    physically possible angle of motion of the patients foot. To provide all of these at the

    most economic price and greater quality becomes a challenge of its own.

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    1.5 CONTRIBUTIONS

    This project aims to concentrate on the comatose and the bedridden patients. It

    provides a solution to two major problems that are

    Muscular degeneration

    Lack of blood circulation

    It keeps the muscles active by externally exercising the calf muscles and also aids

    for the venous shoot of the blood back to the heart. When used in physiotherapy, it

    provides energy to weakened muscles thus helping in rehabilitation of the patient. This

    device along with the feature of web control provides an immense contribution in the

    medical field with a major advantage being that the cost is less than 150 USD.

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    CHAPTER 2

    LITERATURE SURVEY

    2.1 RELATED WORKS

    This section gives an overview about the works that run in parallel with the

    proposed work. Each of these below mentioned works have different strategies but are not

    designed for the coma patients or the bed ridden. The advantages and drawbacks are also

    mentioned below. The new devise called cybernetic assistive leg exoskeleton is built

    keeping in mind the drawbacks of the related work.

    2.1.1 LOPES (LOWER EXTREMITY POWERED EXOSKELETON) ROBOT FOR

    INTERACTIVE GAIT CORRECTION

    These robots replace the physical training effort of a therapist. This may be useful

    in cases where a therapists effort is very intensive leading to limitations in availability or

    even injuries. In the general setting of these robotic systems, a therapist is still responsible

    for the nonphysical interaction and observation of the patient by maintaining a

    supervisory role of the training, while the robot carries out the actual physical inter-action

    with the patient. The LOPES robot for interactive gait correction is as shown in Fig.2.1.

    Fig 2.1 Model of LOPES

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    Thus, the LOPES [3] robot is a combination of an exoskeleton robot for the legs

    and an externally supporting end-effector robot for the pelvis. The robot is an exoskeleton

    that moves in parallel with the legs of a person walking on a treadmill, at pelvis height

    flexibly connected to the fixed world. It allows a selective corrective or supportive torque

    to be applied to the leg-joints and the pelvis of patients who are walking on their own

    effort.

    2.1.2 BLEEX (BERKLEY LOWER EXTREMITY EXOSKELETON)

    Heavy objects are typically transported using wheeled vehicles. However, many

    environments, such as rocky terrains and staircases, pose significant challenges to

    wheeled vehicles. Thus legged locomotion becomes an attractive method of

    transportation within these settings, since legs can adapt to a wide range of extreme

    terrains. The Berkeley Lower Extremity Exoskeleton shown in Fig 2.2 [4] (commonly

    referred to as BLEEX) is the first field-operational robotic system which is worn by its

    operator and provides its wearer the ability to carry significant loads on his/her back with

    minimal effort over any type of terrain. BLEEX is comprised of two powered

    anthropomorphic legs, a power supply, and a backpack-like frame on which a variety of

    heavy payloads can be mounted.

    BLEEX provides load carrying capability through legged locomotion guided by

    human interaction, but instead of actively driving the vehicle, BLEEX shadows the

    operators movement as he/she wears it like a pair of artificial legs. By combining the

    strength capabilities of robotics with the navigation intelligence and adaptability of

    humans, BLEEX allows heavy loads to be carried over rough, unstructured, and uncertain

    terrains.

    BLEEX is the first energetically autonomous lower extremity exoskeleton capable

    of carrying a payload. BLEEX demonstrates to support up to 75 kg (exoskeleton weight +

    payload), walk at speeds up to 1.3 m/s, and shadow the operator through numerous

    manoeuvres without any human sensing or pre-programmed motions.

    LOPES provide unhindered walking in the device and that any torques/forces

    needed to impose a gait pattern can be achieved. Also, limb orientations of the robot and

    the walking subject agree well, sufficient for stable implementation of training and lower

    level control.

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    Fig 2.2 Model of BLEEX

    LOPES provide unhindered walking in the device and that any torques/forces

    needed to impose a gait pattern can be achieved. Also, limb orientations of the robot and

    the walking subject agree well, sufficient for stable implementation of training and lower

    level control.

    The BLEEX method does not concentrate on any kind of patients and the LOPES

    concentrate on the patients recovered from the bed ridden state. The hardware required

    invisibly very large and the cost of implementation is very high.

    2.2 PROPOSED METHODOLOGY

    The proposed methodology is to build a generic shaped mechanical structure for

    the foot that accepts inputs from a control unit to move the foot in the desired manner. It

    also provides flexibility in controlling the method of giving inputs. This method rules out

    the problem of weakened nerve endings which result when electric pulses are provided to

    activate the muscles since it is a complete mechanical structure. The device is adaptable

    and rugged thus provides longevity. The key concepts used in the project is as follows

    Scotch Yoke mechanism This is a simple method of converting circular motion to

    linear motion or vice versa. To move the foot front and back this method becomes very

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    helpful since it converts the circular motion of the servo motor to linear motion of the

    shaft that connects to the foot. In this method the (DOF) degree of freedom is restricted to

    one by the holders on the side of the connecting shaft.

    Pulse Width Modulation (PWM) Pulse Width Modulation, or PWM, is a technique for

    getting analog results with digital means. Digital control is used to create a square wave, a

    signal switched between on and off. This on-off pattern can simulate voltages in between

    full on (5 Volts) and off (0 Volts) by changing the portion of the time the signal spends on

    versus the time that the signal spends off. The duration of "on time" is called the pulse

    width.

    Servo control The servo motor is controlled by a train of pulses having a particular

    period. The Ton time of the pulse determine the angular position of the servo shaft. A

    standard servo motor with a voltage specification of 5V requires a pulse width of 1.5ms to

    rotate to 90o position while keeping a period of 20mS constant.

    GPIO control in Raspberry Pi Raspberry Pi consists of 21 general purpose input

    output pins [5]. Control and configuration of these pins are of key importance. The

    manufacturer of the board decides the pin configuration based on which the libraries to be

    invoked in python also differ. These libraries in python help to configure the GPIO pins

    as per our requirements.

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    CHAPTER 3

    WEB BASED CYBERNETIC ASSISTIVE LEG

    EXOSKELETON

    This chapter describes the block diagram with the necessary hardware components

    and their specifications. The block diagram consist of a Raspberry Pi acting as control

    unit , inbuilt PWM module, buffer circuit , servo motor or the actuator along with a power

    module to power the servo motor. All of these are used to control the foot board strapped

    on the patient there by controlling the foot movement. Figure 3.1 shows the block

    diagram of the web based cybernetic assistive leg exoskeleton.

    Fig 3.1 Block diagram

    The inputs to the control unit are the angle at which the foot should move and also

    the number of times it should move. The angle input is converted to appropriate pulse

    width to get the required angle movement of the foot board while the number of iterations

    are directly mapped to the number of times the foot board should move .The resulting

    PWM signal from the module is given to the servo motor through the buffer circuit. The

    servo when powered using a power module or an adapter providing the necessary current

    requirement moves at the angle provided by the user.

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    3.1 CONTROL UNIT - RASPBERRY PI

    The Raspberry Pi [6] is a credit card sized single board computer developed by the

    Raspberry Pi Foundation. It is a capable little computer which can be used for many of

    the things that desktop PC does like spreadsheets, playing high definition video etc. Fig

    3.2 shows the Raspberry Pi board diagram.

    Fig 3.2 Raspberry Pi B model

    3.1.1 FEATURES OF RASPBERRY PI

    Broadcom BCM2835 system on chip with ARM processor

    Clock speed is 700MHz. It can be over clocked to 800MHz

    512 MB RAM

    It uses SD card for booting and persistent storage

    Operating systems supported by Raspberry Pi are Linux, RISC OSand FreeBSD

    It provides 2 USB ports via the built in integrated 3-port USB hub

    14 HDMI resolution video outputs

    10/100 Mbits/s Ethernet USB adapter on third port of the USB hub

    21 GPIO pins with multiplexed functions

    Power rating of 700mA(3.5W)

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    Power source is a 5V microUSB or GPIO header

    Size of the board is 85.60 mm 56 mm

    The Processor at the heart of the Raspberry Pi is the same processor that is found

    in the iPhone 3G and the Kindle 2, so the capabilities of the Raspberry Pi as comparable

    to those powerful little devices. This chip is a 32 bit, 700 MHz System on a Chip, which

    is built on the ARM11 [7] architecture. ARM chips come in a variety of architectures

    with different cores configured to provide different capabilities at different price points.

    The Model B has 512MB of RAM and the Model A has 256 MB. (The first batch of

    Model Bs had only 256MB of RAM.). The Secure Digital (SD) Card slot is used in Pi

    and has no hard drive; everything is stored on an SD Card. There is a need for some sort

    of protective case since the solder joints on the SD socket may fail if the SD card is

    accidentally bent. On the Model B there are two USB 2.0 ports, but only one on the

    Model A. Some of the early Raspberry Pi boards were limited in the amount of current

    that they could provide. Some USB devices can draw up 500mA.

    The original Pi board supported 100mA or so, but the newer revisions are up to

    the full USB 2.0 specifications. The model B has a standard RJ45 Ethernet port. The

    Model A does not, but can be connected to a wired network by a USB Ethernet adapter

    (the port on the Model B is actually an on board USB to Ethernet adapter). WiFi

    connectivity via a USB dongle is another option. The HDMI port provides digital video

    and audio output.14 different video resolutions are supported, and the HDMI signal can

    be converted to DVI (used by many monitors), composite (analog video signal usually

    carried over a yellow RCA connector), or SCART (a European standard for connecting

    audio-visual equipment) with external adapters.

    Status LEDs: The Pi has five indicator LEDs that provide visual feedback.

    Table 3.1 Status LEDs of RPi

    ACT Green Lights when SD card is accessed

    PWR Red Hooked up to 3.3V

    FDX Green On if network adapter if full duplex

    LNX Green Network activity light

    100 Yellow On if network connection is 100Mbps

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    3.2 PWM MODULE

    Pulse-width modulation (PWM) [8], as it applies to motor control, is a way of

    delivering energy through a succession of pulses rather than a continuously varying

    (analog) signal. By increasing or decreasing pulse width, the controller regulates energy

    flow to the motor shaft. The motors own inductance acts like a filter, storing energy

    during the on cycle while releasing it at a rate corresponding to the input or reference

    signal. In other words, energy flows into the load not so much the switching frequency,

    but at the reference frequency. The main advantage of PWM is that power loss in the

    switching devices is very low. When a switch is off there is practically no current, and

    when it is on, there is almost no voltage drop across the switch. Power loss, being the

    product of voltage and current, is thus in both cases close to zero. PWM also works well

    with digital controls, which, because of their on/off nature, can easily set the needed duty

    cycle.

    Raspbian provides Raspberry Pi with a library to configure PWM known as

    WiringPi. The WiringPi library appears to support both hardware PWM output on one

    GPIO pin and software PWM on any of the other GPIO pins. Meanwhile the Raspberry Pi

    GPIO.PWM library does PWM by controlling the GPIO pins via Direct Memory Access

    controller (DMA). Effectively this is a halfway house between hardware and software

    PWM, providing a 1us timing resolution compared to 100us with WiringPis software

    PWM. Which of these is suitable for your applications depends on how many PWM

    outputs you need and what performance you want out of those outputs. If the application

    is tolerant of low timing resolution and high jitter then you could use software or DMA

    assisted timing loop. If there is a need for higher precision / lower jitter PWM then you

    may need hardware assistance.

    When we need to control a servo motor with hard real-time response requirements

    then we need to use the Hardware PWM. Even then, there may be problems ensuring a

    real-time response for the servo loop which ties encoder input to PWM output. A

    stable servo loop needs to read encoders at a regular rate (low jitter), write out revised

    PWM output values at a regular rate and the latency between these should be fixed (low

    jitter overall) or you will have to under-tune your motor to prevent it becoming unstable

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    under load. This is hard to do with a multi-tasking operating system without low level

    support.

    3.3 74HC245 BUFFER IC

    The 74HC245 as shown in Fig 3.3 is a high speed Si-gate CMOS device. It is

    octal bi-directional bus interface and has non-inverting 3 states outputs. The values on the

    output enable and direction pins decide the direction of input and output. The table below

    illustrates the functional description. A low on both output enable and direction will have

    the As input passed to B. Figure below shows the pin diagram of 74HC245.

    Fig 3.3 Internal circuitry of 74HC245

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    Table 3.2 Truth table for 74HC245

    H=High voltage level

    L=Low voltage level

    X= dont care

    Z= High impedance OFF-state

    3.4 ACTUATOR

    The actuator part is the mechanical designed part of the project. It helps mimic the

    natural action of the foot and keeps the muscles alive. The design is based on the Scotch

    Yoke mechanism.

    3.4.1 SERVO MOTOR

    A servo motor shown in Fig 3.4 has greater number of poles which allows a

    stepper motor to move accurately and precisely between each pole and also to be operated

    without any position feedback for many applications. It can be controlled by simple Pulse

    Width Modulation. In addition, servo motors are quite, available in AC and DC drive, and

    do not vibrate or suffer from resonance issues. The most important advantage being that it

    is light weighted since the entire hardware with the motor is placed on the subjects leg

    and hence the weight of the system should not be more.

    3.4.2 FEATURES OF SELECTED SERVO MOTOR

    Torque: 9kg @ 4.8v

    Weight: 51g

    Speed: 0.21 / 60o @ 4.8v

    INPUT INPUT/OUTPUT

    OE DIR An Bn

    L L A=B Input

    L H Input B=A

    H X Z Z

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    Voltage: 4.8v~6v

    Plug: JR style

    Features:

    Metal Gears

    Dual Ball-race

    Fig 3.4 Servo motor

    3.5 POWER MODULE

    The power module is used to power up the Raspberry Pi and servo motor. Since

    the servo is powered from the power module and not from the Raspberry Pi, there is no

    back noise flowing from servo to the Raspberry Pi. This module converts the incoming

    12V to 5V required to power the Raspberry Pi. It consists of KA7805 regulator, 2.2uF

    capacitors, 100Uf capacitors, IN4007 diode and 330ohm resistor.

    The KA7805 is a three-terminal positive regulator with several fixed output

    voltages, making them useful in a wide range of applications. These employ internal

    current limiting, thermal shut down and safe operating area protection, making it

    essentially indestructible. If adequate heat sinking is provided, they can deliver over 1A

    output current. Although designed primarily as fixed voltage regulators, these devices can

    be used with external components to obtain adjustable voltages and currents. Fig 3.5

    shows the KA7805 Regulator.

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    3.5.1. FEATURES

    Output Current up to 1A

    Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V

    Thermal Overload Protection

    Short Circuit Protection

    Output Transistor Safe Operating Area Protection

    Fig 3.5 KA7805 Regulator

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    CHAPTER 4

    SOFTWARE AND WEBPAGE DESIGN

    The underlying software platforms and their utilization are of key importance

    while developing any project. The webpage design and their considerations are given in

    the following section for implementation of the proposed system.

    4.1 NOOBS

    NOOBS stands for New out of the Box Software installer which is an image file

    you have to download and copy onto the newly formatted 8 GB SD card. This software

    helps to start the Raspberry Pi and gives you list of operating systems to choose from

    during installation. This also contains several other software packages which help in the

    functioning of the Raspberry Pi.

    4.2 RASPBIAN

    Raspbian is a Debian-based free operating system optimized for the Raspberry Pi

    hardware. Debian uses the Linux kernel (the kernel is the core of an OS) and contains a

    wide range of application software and some pre-compiled software bundles.

    4.3 HTML & CSS

    HTML or Hypertext Mark-up Language is the standard mark-up language used to

    create web pages. The purpose of a web browser is to read HTML documents and

    compose them into visible or audible web pages. The browser does not display the HTML

    tags, but uses the tags to interpret the content of the page. HTML describes the structure

    of a website semantically along with cues for presentation, making it a mark-up

    language rather than a programming language. HTML elements form the building blocks

    of all websites. HTML allows images and objects to be embedded and can be used to

    create interactive pages. It provides a means to create structured documents by denoting

    structural semantics for text such as headings, paragraphs, lists, links, quotes and other

    items. It can embed scripts written in languages such as JavaScript which affect the

    behaviour of HTML web pages.

    http://en.wikipedia.org/wiki/Markup_languagehttp://en.wikipedia.org/wiki/Web_pagehttp://en.wikipedia.org/wiki/Web_browserhttp://en.wikipedia.org/wiki/Markup_languagehttp://en.wikipedia.org/wiki/Markup_languagehttp://en.wikipedia.org/wiki/Programming_languagehttp://en.wikipedia.org/wiki/Websitehttp://en.wikipedia.org/wiki/Img_(HTML_element)http://en.wikipedia.org/wiki/Structured_documenthttp://en.wikipedia.org/wiki/Semantichttp://en.wikipedia.org/wiki/Hyperlinkhttp://en.wikipedia.org/wiki/Scripting_languagehttp://en.wikipedia.org/wiki/JavaScript

  • WEB BASED CYBERNETIC ASSISTIVE LEG EXOSKELETON

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    Cascading Style Sheets (CSS) is a style sheet language used for describing

    the look and formatting of a document written in a mark-up language. While most often

    used to style web pages and interfaces written in HTML and XHTML, the language can

    be applied to any kind of XML document, including plain XML, SVG and XUL. CSS is a

    cornerstone specification of the web and almost all web pages use CSS style sheets to

    describe their presentation. CSS is designed primarily to enable the separation of

    document content from document presentation, including elements such as

    the layout, colours, and fonts. This separation can improve content accessibility, provide

    more flexibility and control in the specification of presentation characteristics, enable

    multiple pages to share formatting, and reduce complexity and repetition in the structural

    content.

    4.4 PYTHON

    Python is a widely used general-purpose, high-level programming language. The

    language provides constructs intended to enable clear programs on both a small and large

    scale. Python supports multiple programming paradigms, including object-

    oriented, imperative programming, functional programming or procedural styles. It

    features a dynamic type system and automatic memory management and has a large and

    comprehensive standard library Like other dynamic languages, Python is often used as

    a scripting language.

    4.5 NEED FOR SSH

    Secure Shell (SSH) is a cryptographic network protocol for secure data

    communication, remote command-line login, remote command execution, and other

    secure network services between two networked computers. It connects, via a secure

    channel over an insecure network, a server and a client running SSH server and SSH

    client programs, respectively.

    The best-known application of the protocol is for access to shell

    accounts on Unix-like operating systems, but it can also be used in a similar fashion for

    accounts on Windows. It was designed as a replacement for Telnet and

    other insecure remote shell protocols such as the Berkeley rsh and rexec protocols, which

    send information, notably passwords, in plaintext, rendering them susceptible to

    interception and disclosure using packet analysis. The encryption used by SSH is

    http://en.wikipedia.org/wiki/General-purpose_programming_languagehttp://en.wikipedia.org/wiki/High-level_programming_languagehttp://en.wikipedia.org/wiki/Programming_paradigmhttp://en.wikipedia.org/wiki/Object-oriented_programminghttp://en.wikipedia.org/wiki/Object-oriented_programminghttp://en.wikipedia.org/wiki/Imperative_programminghttp://en.wikipedia.org/wiki/Functional_programminghttp://en.wikipedia.org/wiki/Dynamic_typehttp://en.wikipedia.org/wiki/Memory_managementhttp://en.wikipedia.org/wiki/Standard_libraryhttp://en.wikipedia.org/wiki/Dynamic_languagehttp://en.wikipedia.org/wiki/Scripting_languagehttp://en.wikipedia.org/wiki/Network_protocolhttp://en.wikipedia.org/wiki/Data_communicationhttp://en.wikipedia.org/wiki/Data_communicationhttp://en.wikipedia.org/wiki/Command-line_interfacehttp://en.wikipedia.org/wiki/Loginhttp://en.wikipedia.org/wiki/Network_servicehttp://en.wikipedia.org/wiki/Secure_channelhttp://en.wikipedia.org/wiki/Secure_channelhttp://en.wikipedia.org/wiki/SSH_serverhttp://en.wikipedia.org/wiki/SSH_clienthttp://en.wikipedia.org/wiki/SSH_clienthttp://en.wikipedia.org/wiki/Shell_accounthttp://en.wikipedia.org/wiki/Shell_accounthttp://en.wikipedia.org/wiki/Unix-likehttp://en.wikipedia.org/wiki/Microsoft_Windowshttp://en.wikipedia.org/wiki/Telnethttp://en.wikipedia.org/wiki/Computer_securityhttp://en.wikipedia.org/wiki/Unix_shellhttp://en.wikipedia.org/wiki/Remote_Shellhttp://en.wikipedia.org/wiki/Remote_Process_Executionhttp://en.wikipedia.org/wiki/Passwordhttp://en.wikipedia.org/wiki/Plaintexthttp://en.wikipedia.org/wiki/Packet_analyzerhttp://en.wikipedia.org/wiki/Encryption

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    intended to provide confidentiality and integrity of data over an unsecured network, such

    as the Internet.

    SSH uses public-key cryptography to authenticate the remote computer and allow

    it to authenticate the user, if necessary. There are several ways to use SSH; one is to use

    automatically generated public-private key pairs to simply encrypt a network connection,

    and then use password authentication to log on.

    Another is to use a manually generated public-private key pair to perform the

    authentication, allowing users or programs to log in without having to specify a password.

    In this scenario, anyone can produce a matching pair of different keys (public and

    private). The public key is placed on all computers that must allow access to the owner of

    the matching private key (the owner keeps the private key secret). While authentication is

    based on the private key, the key itself is never transferred through the network during

    authentication. SSH only verifies whether the same person offering the public key also

    owns the matching private key. In all versions of SSH it is important to verify

    unknown public keys, i.e. associate the public keys with identities, before accepting them

    as valid. Accepting an attacker's public key without validation will authorize an

    unauthorized attacker as a valid user.

    SSH also supports password-based authentication that is encrypted by

    automatically generated keys. In this case the attacker could imitate the legitimate side,

    ask for the password and obtain it (man-in-the-middle attack). However this is only

    possible if the two sides have never authenticated before, as SSH remembers the key that

    the remote side previously used. Password authentication can be disabled.

    In our project SSH is performed for two major reasons

    Remote login- When SSH is performed, Raspberry Pi it gives us the flexibility of

    using the Raspberry Pi over the local area network from a remote location using a

    laptop or desktop and execute commands.

    Reuse existing resources- To operate a Raspberry Pi we need to connect an USB

    keyboard, USB mouse and a monitor. When we perform SSH we can login to the

    Raspberry Pi (remotely) using the keyboard, mouse, monitor of the laptop or

    desktop from which we are logging in thus reducing the hardware drastically.

    Thus the only required hardware is a LAN cable connected to the Raspberry Pi.

    http://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Public-key_cryptographyhttp://en.wikipedia.org/wiki/Authenticationhttp://en.wikipedia.org/wiki/Passwordhttp://en.wikipedia.org/wiki/Public_keyhttp://en.wikipedia.org/wiki/Public-key_cryptography#Associating_public_keys_with_identitieshttp://en.wikipedia.org/wiki/Man-in-the-middle_attack

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    4.5.1 NETSCANNER

    It helps in Network scanning which is a procedure for identifying active hosts on a

    network. Scanning procedures, such as ping sweeps and port scans, return information

    about which IP addresses map to live hosts that are active on the Internet.

    4.5.2 RDP (Remote Desktop Protocol)

    Remote Desktop Protocol (RDP) is a proprietary protocol developed

    by Microsoft, which provides a user with a graphical interface to connect to another

    computer over a network connection. The user employs RDP client software for this

    purpose, while the other computer must run RDP server software.

    4.6 Bonjour

    Bonjour is Apple's implementation of Zero-configuration networking (Zeroconf),

    a group of technologies that includes service discovery, address assignment,

    and hostname resolution. Bonjour locates devices such as printers, other computers, and

    the services that those devices offer on a local network using multicast Domain Name

    System (mDNS) service records.

    Bonjour provides a general method to discover services on a local area network.

    The software is widely used throughout OS X, and allows users to set up a network

    without any configuration. As of 2010 it is used to find printers and file-sharing servers.

    iTunes uses Bonjour to find shared music, iPhoto to find shared photos, iChat,

    Adobe Creative Suite 3, Proteus, Adium, Fire, Pidgin, Skype, Vine Server,

    and Elgato EyeTV to share local recordings with multiple clients, the Gizmo5 to find

    other users on the local network, TiVo Desktop to find digital video recorders and shared-

    media libraries, SubEthaEdit and e to find document collaborators, Contactizer to find

    and share contacts, tasks, and events information, and Things & OmniFocus to

    synchronize projects and tasks across the Mac desktop and the iPad, iPhone or iPod

    touch. It is used by Safari to find local web servers and configuration pages for local

    devices, and by Asterisk to advertise telephone services along with configuration

    parameters to VoIP phones and dialers. Software such as Bonjour Browser or iStumbler,

    both for Mac OS X, or Zeroconf Neighbourhood Explorer for Windows, can be used to

    view all services declared by these applications. Apple's "1Remote" application for

    iPhone and iPod Touch also uses Bonjour to establish connection to iTunes libraries via

    Wi-Fi.

    http://searchcio-midmarket.techtarget.com/definition/hosthttp://searchmidmarketsecurity.techtarget.com/definition/port-scanhttp://searchwindevelopment.techtarget.com/definition/IP-addresshttp://searchcio-midmarket.techtarget.com/definition/hosthttp://en.wikipedia.org/wiki/Proprietary_protocolhttp://en.wikipedia.org/wiki/Microsofthttp://en.wikipedia.org/wiki/Graphical_user_interfacehttp://en.wikipedia.org/wiki/Apple_Inc.http://en.wikipedia.org/wiki/Zero-configuration_networkinghttp://en.wikipedia.org/wiki/Service_discoveryhttp://en.wikipedia.org/wiki/Link-local_addresshttp://en.wikipedia.org/wiki/Hostname_resolutionhttp://en.wikipedia.org/wiki/Local_area_networkhttp://en.wikipedia.org/wiki/Multicast_DNShttp://en.wikipedia.org/wiki/Multicast_DNShttp://en.wikipedia.org/wiki/Local_area_networkhttp://en.wikipedia.org/wiki/IPhotohttp://en.wikipedia.org/wiki/Adobe_Creative_Suitehttp://en.wikipedia.org/w/index.php?title=Proteus_(instant_messenger)&action=edit&redlink=1http://en.wikipedia.org/wiki/Adiumhttp://en.wikipedia.org/wiki/Fire_(instant_messenger)http://en.wikipedia.org/wiki/Pidgin_(software)http://en.wikipedia.org/wiki/Skypehttp://en.wikipedia.org/wiki/Elgatohttp://en.wikipedia.org/wiki/Gizmo5http://en.wikipedia.org/wiki/TiVohttp://en.wikipedia.org/wiki/SubEthaEdithttp://en.wikipedia.org/wiki/E_(editor)http://en.wikipedia.org/wiki/Contactizerhttp://en.wikipedia.org/wiki/Things_(application)http://en.wikipedia.org/wiki/OmniFocushttp://en.wikipedia.org/wiki/Safari_(web_browser)http://en.wikipedia.org/wiki/Asterisk_PBXhttp://en.wikipedia.org/wiki/Bonjour_Browserhttp://en.wikipedia.org/wiki/IStumbler

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    Bonjour only works within a single broadcast domain, which is usually a small

    area, without special DNS configuration. Mac OS X, Bonjour for Windows

    and AirPort Base Stations may be configured to use Wide Area Bonjour which allows for

    wide area service discovery via an appropriately configured DNS server.

    Applications generally implement Bonjour services using standard TCP/IP calls,

    rather than in the operating system. Although Mac OS X provides various Bonjour

    services, Bonjour also works on other operating systems. Apple has made the source code

    of the Bonjour multicast DNS responder, the core component of service discovery,

    available as a Darwin open source project. The project provides source code to build the

    responder daemon for a wide range of platforms, including Mac OS 9, Mac OS X, Linux,

    *BSD, Solaris, VxWorks, and Windows. Apple also provides a user-installable set of

    services called Bonjour for Windows and Java libraries. A number of Windows programs

    use Zeroconf, including Adobe Systems Creative Suite 3, iTunes, Cerulean

    Studios' Trillian Pro 3, Ruckus Music.

    http://en.wikipedia.org/wiki/Broadcast_domainhttp://en.wikipedia.org/wiki/Computer_configurationhttp://en.wikipedia.org/wiki/AirPorthttp://en.wikipedia.org/wiki/TCP/IPhttp://en.wikipedia.org/wiki/Multicasthttp://en.wikipedia.org/wiki/Darwin_(operating_system)http://en.wikipedia.org/wiki/Open_sourcehttp://en.wikipedia.org/wiki/Mac_OS_9http://en.wikipedia.org/wiki/Linuxhttp://en.wikipedia.org/wiki/BSDhttp://en.wikipedia.org/wiki/Solaris_(operating_system)http://en.wikipedia.org/wiki/VxWorkshttp://en.wikipedia.org/wiki/Microsoft_Windowshttp://www.apple.com/bonjour/http://en.wikipedia.org/wiki/Adobe_Systemshttp://en.wikipedia.org/wiki/Adobe_Creative_Suitehttp://en.wikipedia.org/wiki/Trillian_(instant_messenger)

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    CHAPTER 5

    ELECTRICAL AND MECHANICAL DESIGN

    REQUIREMENTS

    5.1 MECHANICAL DESIGN

    As we are developing a mechanical structure for the motion of the foot for coma

    patients or otherwise patients who are bedridden or in intensive care, the structure must

    be sturdy. The material used must not cause any rashes or sores, the device must be such

    that it is easily put on the foot or removed, it should be as light as possible and must also

    be applicable to variable foot sizes and shapes. This poses a challenge in terms of design.

    5.1.1 DESIGN SPECIFICATIONS

    The greatest challenge of the design is that the exoskeleton must be wearable for

    any type of foot, irrespective of age, gender or shape of the leg. Furthermore, the

    flexibility of the feet varies from person to person. For comatose patients there is a loss of

    flexibility in the various joints and weakening of the muscles in the legs as well as

    chances of swelling in the feet. Keeping these restrictions in mind the design of the

    mechanical structure of the exoskeleton becomes complex.

    As per the requirements of the doctor:

    The total angular motion of the feet must be in the range of 40 to 50 degrees.

    The total weight of the exoskeleton should not exceed 2 Kg.

    The foot should only have one degree of freedom for its motion.

    Accurate angular control up to 5 degrees.

    Fasteners for variable foot sizes.

    Durability.

    The torque while pushing or pulling the foot must not exceed the permissible

    limit.

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    5.1.2 SCOTCH YOKE MECHANISM

    The Scotch Yoke mechanism shown in Fig 5.1, also known as the slotted link

    mechanism is a reciprocating motion mechanism , converting the linear motion of the

    slider to rotational motion or vice versa. The servo motors shaft is connected to a disc of

    calculated radius. The stub point on the disc moves inside a linear grid and there by

    converts a circular motion into linear motion. The ends of the linear shaft of the grid are

    restricted for a 1D motion. Figure below shows the pictorial view of the mechanism. It

    has many advantages over standard crankshaft and connecting rod mechanism like higher

    torque operation with smaller cylinder size, smother operation. The speed of motion

    follows that of a sine wave with the speed reaching a maximum at the middle of the travel

    and momentarily coming to a complete stop at each end of the travel.

    Fig 5.1 Scotch Yoke mechanism design

    5.1.3 SCOTCH YOKE MECHANISM DESIGN

    The Scotch Yoke mechanism, [9] though simple compared to other techniques

    involves lot of calculations. To calculate the scotch yoke travel, the pin must rotate at a

    diameter of the total displacement required. Considering the ankle bone (malleolus) as the

    centre of the arc and radius as the average height of the foot from that point, the

    displacement can be calculated which provides the required angular movement. Fig 5.2

    shows the side view of Scotch yoke mechanism. Let S be the displacement and hence

    the diameter of the path of the pin to be found. The radius of the pin is referred to as

    crank. Therefore, S can be written as,

    S= twice the length of the crank.

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    Let r be the distance from the malleolus bone to the tip and let be the total

    angle specified by the doctor for the motion of the foot. Then, by using the equation

    S=r. -------- Eq 5.1

    We can calculate the crank length. On calculating the term r (length of the foot

    from malleolus joint and the tip of the foot) of many individuals, it is found that the

    average value is around 14cm. The angle is to be in the range of 40o to 50

    o as

    specified by the doctor. We have chosen a total angle movement of 45o. In radians, 45

    o is

    equal to 0.785rad. Having these values,

    S= (14cm) x (0.785)

    = 10.99cm (11cm approximately)

    Hence, S should be of 11cm to provide a total angular motion of 45 o

    . While

    calculating for the term r, the length of the foot from malleolus to the tip is considered.

    The malleolus joint is made the origin as the ankle rotates over that joint and the tip of the

    foot is considered as the force required in moving the foot (i.e. push and pull) is less as

    the distance increases, from the equation

    T=F X L ---------- Eq 5.2

    Where, T is the torque

    F is the force applied at the point and

    L is the distance between the origin and the point.

    Fig 5.2 Scotch yoke side view: 1- clamp, 2- crank, 3 - pin, 4 - shaft and 5 - slider

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    The slider slit length should be equal to the length of crank diameter and the

    diameter of the pin for proper motion. This comes around 12.5cm and the width being

    equal to the pin diameter as shown in the diagram.

    The length of the shaft was decided based on the average shin bone length of few

    individuals. Similarly, other measurements such as the dimensions of the foot plate were

    also carried out the same way. Fig 5.4 shows the design of the crank shaft. Two rods run

    parallel from the end of the shin guard to a point on the foot plate. These rods ensure that

    the entire system lies in one plane. The points on the foot plate where these rods are

    connected are the pivot points, on which all other calculations are made. The distance

    between the tip of the plate and this point is the term r.

    Figures 5.5 and 5.6 depict the footplate and the C-cup and their measurements.

    The total size of the footplate was decided based on the average foot size measured from

    a survey of 30 people aged between 15 to 30 years but the pivot point of 14 cm from the

    top of the plate was calculated to achieve the required angular range i.e. its equal to the

    value of r from equation 5.1. The C-cup was designed similarly from the same survey

    for the average dimensions around the ankle. The height of the cup was obtained by

    measuring the calf muscle sizes from the same survey.

    Fig 5.3 Design of the disc

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    Fig 5.4 Design of crank shaft mechanism

    Fig 5.5 Foot plate design

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    Fig 5.6 C-cup design

    5.1.4 ANGULAR CONTROL DESIGN

    Servo motors [10] are known for their accurate angle control. We send pulse

    width modulation signals for controlling the angle of rotation of the motor. It is observed

    that, for our design, 180 o

    in servo motor (maximum angle of rotation) corresponds to 45 o

    angular movement of the foot. Servo motors take in a PWM signal having a period of

    20ms. The duty cycle decides the angle to which the motor has to rotate. Every 0.2ms

    increase in the duty cycle gives 10 o increase in the angle of rotation starting from 0.4ms.

    For a Ton time of 1.4ms the angle of rotation is 90o, for 1.2ms, it is 70

    o and so on. The

    factors which affect the angle control are: size of the disk, position of the pivot point on

    the foot plate, position and size of the pin and the length of the shaft. All of these factors

    are kept constant. Hence, the only way to control the rotation is by changing the duty

    cycle which is done programmatically. This control is given to the doctor who decides the

    angle of rotation of the foot based on the patients condition.

    The angles provided for the movement of the foot plate are 5, 10, 15, 20, 25

    degrees. These cannot be fed directly since the motion of the foot plate and the motor are

    not similar, also as the PWM signal has to be sent for the angle control of the motor, there

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    is a need to convert the angle movement required to the corresponding angle of the motor.

    This should further be converted to pulse width signal before feeding it to Raspberry Pi.

    It is measured that, when a pulse of width 0.5ms is sent, the motor is rotated to 0o

    and when 2.3ms is sent, it rotates to 180o. It stays at 90

    o when a pulse of 1.5ms is sent and

    so on. Based on this, we can calculate the pulse required to be sent to obtain other angles.

    The measurements of the scotch yoke mechanism follow a sine wave. Therefore the

    displacement is more for a small change in angle near the peaks compared to other

    regions. This makes the angle calculations complex. The initial offset position is taken to

    be 85o which can be set by sending a pulse of 1.45mS.

    For 25o, the motor moves forward by 25

    o and backwards by 20

    o. For 20

    o, it moves

    20o in both the directions from the initial offset position. This is similar with other angles

    too. The following table shows the pulse widths required to obtain different angles.

    Table 5.1 Pulse width required for different angles

    Angle (in Degrees) Forward pulse (ms) Backward pulse (ms)

    25 2.3 0.6

    20 1.9 0.95

    15 1.75 1.125

    10 1.65 1.25

    5 1.55 1.35

    It is observed that for every 1.2cm displacement, 5o movement of the foot plate is

    obtained. The offset point is 0.6cm away from the centre of the disc. The displacements

    considered are taken from this point only. 1.2cm displacement in both the directions

    together gives 10o motion, which is labelled as 5

    o representing that it moves 5

    o in one

    direction. The corresponding pulse width is as mentioned in the table.

    The angle of the motor is decided by taking the inverse cosine function on the

    linear displacement and the radius of the disc which acts as hypotenuse when a triangle is

    drawn using the linear displacement, radius of the disc and the altitude of the point under

    consideration as the sides. Based on the angle obtained, pulse width to be sent is decided.

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    For example, to get 20o motion (40

    o in total- 20

    o on each side) of the foot, the

    motor should rotate from 25o

    to 140o. The corresponding pulse widths are 0.95ms and

    1.9ms. For 15o motion (30

    o in total- 15

    o on each side), the motor should rotate from 52.5

    o

    to 125o.

    5.2 MATERIAL ANALYSIS

    In the field of medicine, the materials used, play a very important role. They must

    be selected such that they do not cause any harm to the patient when used. We have

    chosen aluminium for the fabrication of the exoskeleton.

    Aluminium (or aluminium) [11] is a chemical element in the boron group with

    symbol Al and atomic number 13. Aluminium is the second-most used metal after steel,

    largely because it is versatile. It is a silvery white, soft, ductile metal. It is noted for its

    low density and for the ability to resist corrosion due to the phenomenon of passivation.

    The advantages of aluminium which encouraged us to use this material are:

    Light weight

    Corrosion resistance

    Electrical and thermal conductivity

    Ductility

    In addition to these, it is harmless to the skin even though it is kept in contact for a long

    time.

    5.3 ELECTRICAL DESIGN

    5.3.1 NEED FOR BUFFER CIRCUIT

    The 74HC245 buffer IC [12] is used to isolate the Raspberry Pi from the servo

    motor. The PWM signal from the Raspberry Pi is fed to the input side of the buffer and

    the output is connected to the servo input. Thus the buffer IC avoids the back currents

    flowing to the Raspberry Pi and thus the heating of the Raspberry Pi board. This also

    avoids the noise signal generated from the back EMF of the servo to reach the Raspberry

    Pi.

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    5.3.2 NEED FOR THE POWER REGULATION

    The voltage specification of the servo motor is 4.8V to 6.2V. The power regulator

    steps down the 220V AC to 5V DC which is used to power the servo motor. The

    Raspberry Pi sources a current of 50mA from all the GPIO pins while the servo requires

    1A of current for its operation. Trying to draw such huge amount of current from the

    Raspberry Pi damages the Raspberry Pi since it does not have current limiting circuit for

    protection.

    5.3.3 SERVO MOTOR vs. STEPPER MOTOR

    Selecting between a servo motor and a stepper motor can be quite a challenge

    involving the balancing of several design factors. Cost considerations, torque, speed,

    acceleration, and drive circuitry all play a role in selecting the best motor for our

    application. Even though servo motors are expensive when compared to stepper, they

    have their own advantages.

    Servo motors are generally an assembly of four things: a DC motor, a gearing set,

    a control circuit and a position-sensor. Servo motors are designed for more specific tasks

    where position needs to be defined accurately such as controlling the rudder on a boat or

    moving a robotic arm or robot leg within a certain range.

    In servo motors the angle of rotation is limited to 180o back and forth. Servo

    motors receive a control signal that represents an output position and applies power to the

    DC motor until the shaft turns to the correct position, determined by the position sensor.

    PWM is used for the control signal of servo motors. However, unlike DC motors its the

    duration of the positive pulse that determines the position, rather than speed, of the servo

    shaft. A neutral pulse value dependant on the servo (usually around 1.5ms) keeps the

    servo shaft in the centre position. Increasing that pulse value will make the servo turn

    clockwise, and a shorter pulse will turn the shaft anticlockwise. The servo control pulse is

    usually repeated every 20 milliseconds, essentially telling the servo where to go, even if

    that means remaining in the same position. When a servo is commanded to move, it will

    move to the position and hold that position, even if external force pushes against it. The

    servo will resist from moving out of that position, with the maximum amount of resistive

    force the servo can exert being the torque rating of that servo.

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    Stepper motors have a large number of poles, magnetic pairs of north and south

    poles generated either by a permanent magnet or an electric current, typically 50 to 100

    poles which make them bulky for equipment that are smaller in size. In comparison, servo

    motors have very few poles, often 4 to 12 in total. Each pole offers a natural stopping

    point for the motor shaft. For applications where high torque is needed, servo motors

    shine. They maintain their torque rating at high speed. They are more efficient than

    stepper motors with efficiencies between 80-90%. A servo motor can supply roughly

    twice their rated torque for short periods, providing a well of capacity to draw from when

    needed. In addition, servo motors are quite, available in AC and DC drive, and do not

    vibrate or suffer from resonance issues. Stepper motors are not as good as servo motors in

    accelerating a load.

    5.4 WEB DESIGN

    One of the great features of the Raspberry Pi is the built-in Ethernet connection,

    which opens up many possibilities for web-connected projects. This enables this small

    device to be able to operate as a web server, ideal for running custom web applications.

    Since the Raspberry Pi can also be connected to a host of other sensors and devices

    through the GPIO ports, this opens up the possibility of creating web-controlled devices.

    Since Python [13], [14] is the main programming language for controlling the

    Raspberry Pi, the ideal web server for the device is a Python-based web framework. This

    means that the code for controlling the Raspberry Pi's GPIO could be integrated right into

    the code for the web server.

    The webpage is designed using HTML [15] as the coding platform as it is simple

    to use and compatible with any browser. Designing an effective web site requires more

    than just gathering relevant information and posting it on the web. Like a good paper or

    research presentation, a quality web project demands as much attention to the selection,

    organization, and presentation of material as to the underlying research itself. It is

    important to be both clear and engaging in every aspect of site design.

    As the webpage is designed for a particular application, utility and accessibility

    assume more importance than visual design. It is also preferable to keep the graphics

    mostly to a minimum - mostly text, little or no graphics enables quick loading, does not

    require lots of memory or a high end graphic card. Letting the user see clearly what

    http://components.about.com/od/Components/a/Stepper-Motor-Basics.htm

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    functions are available is a fundamental principle of successful user interface design. It

    doesnt really matter how this is achieved. What matters is that the content is well-

    understood and visitors feel comfortable with the way they interact with the system. As

    the user to the web interface is the doctor, there is a need to keep the webpage simple,

    effective and must be designed in such a way that future expansions, such as an addition

    of a pulse oxymeter or a health monitor can be easily incorporated into the existing page

    without affecting the functionality.

    An optimal solution for effective writing while displaying on the web page is to

    Use short and concise phrases (come to the point as quickly as possible),

    Use simplified layout (categorize the content, use multiple heading levels, use visual

    elements and bulleted lists which break the flow of uniform text blocks), Such that

    any new user can also quickly understand and access the webpage without difficulty.

    To setup the Raspberry Pi as a server, we need to setup bonjour services and then

    configure the board to host the webpage by accessing the pico.conf file. There are two

    ways of performing the next step, you can either install an apache based framework or

    use various web framework platforms for python such as flask, pylon, django and

    cherrypy. We have used the Flask framework as it provides easier accessibility, and can

    connect the HTML frontend with the python script in the backend.

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    CHAPTER 6

    IMPLEMENTATION AND RESULTS

    6.1 BASIC ASSUMPTIONS

    There are a few basic assumptions that we have to make with respect to the

    implementation of the device. These include:

    The patient is in the Intensive care unit and the status of the patient is known and

    updated to the doctor.

    The nurse can strap on the exoskeleton and power-on the system without any

    technical know-how.

    The doctor has access to the Local area network.

    After the conclusion of the iterations, the doctor may or may not instruct the nurse

    to remove the exoskeleton after the operation.

    6.2 PROCEDURE TO BE FOLLOWED BY THE NURSE

    First, the nurse has to strap on the exoskeleton and power it on. The nurse or any

    ward assistant can strap it without any technical expertise of how the device has to

    function. The system needs to be fastened such that the shaft of the scotch yoke

    mechanism stays parallel to the shin bone of the leg at all times and that the alignment of

    the leg with the system is in the same line. The leg is lifted up using the c-cup mechanism

    described before. This is done to ensure that the mechanical action of the foot is

    unrestricted by the bed. The height of the c-cup is such that the foot is inclined to a

    required angle and designed such that the heel of the foot is free to move forward and

    backward. Assuming that the patient has neither consciousness nor control over his/her

    body great care is taken to keep the entire leg aligned in one direction so that the

    movement of the feet can properly exercise the calf muscles without any hindrance.

    6.3 PROCEDURE TO BE FOLLOWED BY THE DOCTOR

    After the exoskeleton is powered on and the Raspberry Pi boots up, there are two methods

    using which the doctor can control the operation.

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    1. Through the web interface: The Raspberry Pi is configured as a server. It hosts

    its own website which can be accessed via the LAN or if a domain name is

    brought, through a WAN like the Internet. At the user end, the doctor can connect

    to this server via a webpage and is required to input two parameters for the

    operation of the exoskeleton i.e. the angle range to which the foot has to move

    back and forth as well as the number of times the iteration or the action has to

    occur. The webpage request for valid identification of the doctor before permitting

    him to access the device. Then it requests for the different inputs. Once valid

    inputs are received the webpage transfers control to the processor of the Raspberry

    Pi.

    2. By directly accessing command line of the Raspberry Pi: The presence of a

    technician or a trained nurse may be required in this method to operate the

    exoskeleton. The technician can access the Raspberry Pi directly by connecting a

    monitor and keyboard or by using SSH can remotely access the systems

    command line and execute the source code for the required parameters. These

    parameters are given by the doctor.

    Once the inputs are received by the board different procedures and functions

    are called depending on the method of access.

    6.4 FLOWCHART OF WEB CONTROL

    Fig 6.1 shows the flowchart of the entire program. The various steps and the flow

    of control in the main program when the system is accessed through the web interface are

    as follows:

    Step 1: Initialize and call various python and Raspberry Pi libraries such as RPi.

    GPIO, Wiring Pi, Time and sys.

    Step 2: Initialize GPIO pins and various modules associated with it. Configure the

    board programmatically to follow a particular pin configuration for the Raspberry

    Pi i.e. BCM mode or BOARD mode.

    Step 3: Run the host webpage function. It is the empty webpage setup by the host.

    It has a static local address when accessed through LAN but if accessed through

    WAN, every time the Raspberry Pi is booted, it is assigned a dynamic IP address

    thats linked to the static local address.

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    Step 4: If the webpage is called, load the webpage or else wait. The webpage acts

    as the user interface. When the user accesses the webpage using the local address,

    the webpage is called.

    Fig 6.1 Flow chart of the entire program

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    Step 5: Calling Homepage. Fig 6.2 shows the flowchart of the homepage function

    Step 6: Call the python script at the backend. The user inputs are taken by the

    python script and run accordingly. Fig 6.3 shows the python script function.

    The various steps and the flow of control when the Homepage is called

    Step 1: As soon as the Homepage is called, it loads the source code. This acts as

    the primary user interface. The doctor is asked to input various parameters.

    Step 2: The parameters such as the angular control range and the number of

    iterations for the action are taken as input. These inputs are passed on to the

    python script.

    Step 3: Returns control to the main program.

    Fig 6.2 Flow chart of the function homepage

    The various steps of the python script at the back-end

    Step 1: Initialize iteration variables i and j.

    Step 2: Accept user input values and set iteration and pulse value.

    Step 3: Initialize each iterative loop for the desired action and execute the loops.

    Step 4: Generate PWM signal as per the required Ton time.

    Step 5: Return control to user interface.

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    Fig 6.3 Flow chart of the python script

    6.5 RESULTS

    The major objective of this chapter is to verify the design of the exoskeleton and

    examine the results produced by it. It is important to note that the following results

    represent that the concept and design is working. Various screen shots of the web

    interface and images of the different positions of the footplate are presented. Actual

    implementation of the exoskeleton on the comatose requires testing and approval by

    various medical bodies and the Government of India. It involves various procedures and

    license grants which we are yet to obtain. But, rest assured, the concept and the study of

    the effects on the human body and muscles show great promise that the main objective is

    achievable, as soon as permission for testing on the target demographic is granted. The

    following sets of images i.e. Figures 6.6 6.10 represent the web interface and the

    various stages during input, operation and end of operation and Figure 6.11 shows the

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    webpage with details about the team. The Doctor logs on to the webpage and enters the

    angular range from and to which the foot has to move, then he is required to enter the

    number of times this action has to be performed. After which he is directed to a waiting

    page when the action is carried out by the mechanism. Fig 6.4 shows the proposed

    exoskeleton model. Fig 6.5 shows the designed C-cup.

    Fig 6.4 Proposed exoskeleton model

    Fig 6.5 Designed C-cup

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    Fig 6.6 User interface Homepage

    Fig 6.7 User interface selecting the angle

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    Fig 6.8 User interface selecting the number of iterations

    Fig 6.9 Features of the project displayed

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    Fig 6.10 End of operation

    Fig 6.11 Page about the team

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    CHAPTER 7

    CONCLUSIONS AND FUTURE WORK

    This new idea of bringing out an electromechanical assistive structure helps solve

    the medical field problems in a simpler way. The results obtained by this method are

    consistent and efficient. The design has been successful in mimicking the natural action

    of the foot externally. This method improves the blood circulation in bedridden patients

    without resorting to invasive procedures and drugs which may be harmful. By exercising

    the calf muscles thoroughly the exoskeleton decreases the chances of muscular atrophy

    and the improvement of the rate of circulation also prevents embolism formation. The

    manufacture of the prototype along with the required components is very economical and

    the design is found to be applicable to variable foot sizes and patients of different ages

    from 15 years old and up.

    This project shows immense promise and can be further extended to new stages. A

    few of the possible enhancements are discussed below:

    Implementation and testing on comatose would be the first step out of many. The

    next goal of the project is to provide a feedback from the leg using sensors to

    communicate vital information and also know the condition of the patient. This is

    the higher stage of the project and will provide an easier method to monitor the

    patient regularly.

    A health monitoring system can be added by interfacing a pulse oxymeter to

    measure the oxygen saturation and the monitor the blood circulation. This would

    remove the need for the use of Doppler scans to monitor the blood circulation.

    The Raspberry Pi can be configured to log data and monitor status of the patient.

    By developing and implementing the right sensors, signals can also be tapped

    from nerve endings in the leg to track the body status. This can also be used to

    study the human brain when a person is in coma. Hence, it can help in

    understanding the human brain but this would be very difficult and require a

    dedicated amount of time to be implemented.

    The same concept can be further implemented on Wide Area Network by buying

    domain name. This provides a greater area through which the device can be operated. The

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    design can also be used to provide rehabilitation for the patients who need physiotherapy

    by simple changes in the design. Thus the work can be implemented on both comatose

    and in post TBI cases as well.

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    [4] Zoss.A , H. Kazerooni, Andre chu ; On the Mechanical Design of the Berkeley

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    [9] Scotch yoke mechanism, YouTube,

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    [10] Servo motor control ,Wikipedia,

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    [11] Aluminium and its properties , Wikipedia,

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