Design and Fabrication of Android Controlled Powered Wheelchair

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1 Design and Fabrication of Android Controlled Powered Wheelchair Jayashree P. Wakalkar 1, Akshay Ingale 2, Amol Wadhi 3, Nikhil Sawarkar 4, Vishal Belekar 5, Shrikant Peshatwar 6 B.E. Students, Department of Mechanical Engineering, Guru Nanak Institute of Technology, Kalmeshwar Road, Nagpur, India 1,2,3,4,5 Assistant Professor, Department of Mechanical Engineering, Guru Nanak Institute of Technology, Kalmeshwar Road, Nagpur, India 6 Abstract: Powered wheelchairs depend upon a power source for starting up and to continue their movement. A control system is essential to control the direction of the wheelchair movement through voice and/or eye movement, joystick, etc. User undependability, safety and comfort are of primary concern while designing a wheelchair. It is hypothesized that a wheelchair benefits its user with its ability to perform work with ease and comfort sufficient to cater with the utility requirement from the user. It is in this view that we have chosen our wheelchair to be controlled using Android application through mobile which is the current trend in the society we live in. A feature of being operated by mobile increases its prospect of being an independently maneuvering (no-push feature), easy-to-use conveyance to a user. In this paper, our project has been discussed. Keywords: Android, Maneuverability, Motorized, Pro-E, Wireless. I. INTRODUCTION A wheelchair is a mobility device designed for shifting patients, moving physically challenged people from one place to another with the help of attendee or by means of self propelling. Of 6.5 billion people around the world, about 10% people i.e., 650 million are physically handicapped, of which 10% i.e., 65 million people depend upon wheelchairs for their living. Furthermore, wheelchairs are utilized according to the nature of handicap i.e., their purpose to service varies from user to user. Wheelchairs are the most common assistive or mobility devices for enhancing mobility with dignity. The wheelchair is divided into two different types based on the power used for mobility- manually powered wheelchairs and electric powered wheelchairs. Manual powered wheelchairs are driven by manual powered which are again classified into foldable and non-foldable with or without commode design. Motorized wheelchair or electric-powered wheelchair is a wheelchair that is propelled by means of an electric motor rather than manual power. Motorized wheelchairs are useful for those who are not able to impel a manual wheelchair or who may need to employ a wheelchair for distances or over terrain which would be strenuous in a manual wheelchair. They may also be used not just by people with conventional mobility impairments, but also by people with cardiovascular and fatigue based conditions. Electric wheelchairs have enhanced the quality of life for many people with physical disabilities through the mobility they afford. The selection of power chair will rely on many factors; including the kind of surface setting the chair will be driven over, the need to settle thresholds and curbs, and clearance widths in accustomed environment. The most fundamental job of the chair is to take input from the user, usually in the form of a small joystick, and decipher that motion into power to the wheels to move the person in the preferred direction. The last few years have seen abundant improvements and models that give the user unmatched control of the wheelchair in terms of both user effort and vehicle aptitude. Mobile phones today have become an essential entity for many, and so for any mobile based application there is a great reception. In this scenario making a mobile phone operated wheel chair would prove significant. Conventionally, wireless control robots utilize RF circuits, which had limitations like limited range, limited frequency ranges & controls. But mobile phone controlled wheel chair can hold up these limitations. It has a robust control, unlimited range (coverage area of service provider), no fear of interfering with other controllers & we can have as much as 12 controls. Because of the growing demand of android with its easy installation, availability and low cost makes it the

2 most preferable over application such as Arduino, and operating systems such as joy stick, voice and vision based recognition for the movement of wheelchair. II. LITERATURE REVIEW The research and analysis of motorized wheelchairs dates back in time with several scientists and researchers evaluating the automation in its operation. Nirmal T.M [1] investigated the control of a wheelchair through voice, eye motion and a joystick to prove beneficial for physically and mentally handicapped people. This paper evaluates different units of an automatic wheelchair viz. Controlling unit, Sensor unit and Remote unit. The controlling of the wheelchair is made through voice, eye motion and a joystick. A servo-controlled robotic arm assists the patient to pick and place the objects. The environmental and body condition of the patient are checked through different sensors such as temperature, PIR, humidity, obstacle and heart beat sensors. The result of the sensors are displayed in the LCD which is at a remote distance and it informs the doctor, concerned person of any drastic changes in the heart beats of the user by a GSM module through an sms. In remote unit, a PIC16F877 microcontroller is used in the sensor motor to control the wheelchair movement. A VR module is concerned with voice recognition and a joystick for the convenience of the patient for wheelchair movement. A short range controlling of wheelchair is possible through an Xbee. Humaira Salmin et al [2] did work to upgrade a normal wheelchair into a joystick-controlled electromechanical wheelchair and to make the total prototype as cost-effective and less expensive as possible. A microcontroller based control system is applied with two dc gear motors to control the rear end wheels. The main objective of the project was to run the wheelchair automatically in all possible directions- forward, backward, left and right by using a joystick. A 40-pin PIC18F4520 micro-controller was operated smoothly to ensure EWC's movement in desired direction after receiving command signal from the joystick. Each rear wheel of EWC is attached with a DC gear motor which acquires required power from dry-cell battery connected to respective motors. Arvind Prasad et al [3] provided information about the usage of wheelchairs based on renewable energy systems. The renewable energy systems which are discussed in this paper are batteries and solar panels. It also gives a report on the efficiency and durability of batteries and solar panels. Explanatory material is followed by a worked example and problems with answers. Mohan Kumar R. et al [4] designed a wheelchair which gives multiple options to the user and attendee by providing provisions for an ease of defecation, cleaning and changing of clothes. Adjustable back rest, arm rest, leg rest provides comfort for the patient while resting. The adjustable arm rest provides an ease of shifting the patient from chair to the bed or to the vehicle. A facility is provided for keeping food plate, water bottle, etc. Additional to this, an alarm facility is provided to inform the attendee if there is a need of his / her presence to the patient. III. FORMULATION OF WORK As mentioned before, the main objective of our project is to make a wheelchair that could be controlled via Bluetooth, also backrest could be inclined. But before talking about the control and inclination mechanism we have to understand the various engineering considerations while designing such a project. The project is made considering the calculations. So many changes were made while building the actual wheelchair. Primarily the prototype was modeled using Pro/Engineer software. This helped us to understand the basic structure of the vehicle. Figure 1 3D model of wheelchair Figure 2 3D model of wheelchair (Colour filled image)

3 Scenario of Hardware: Microcontroller 89s51 Motor Driver L293D Motor 1 Motor 2 Figure 3 Block diagram indicating signal flow to components We are using an 8051 microcontroller (89s51) that requires 5 volt supply. Here we are using battery which gives 12 volt output. We are using IC7805 that gives 5 volt at the output. This 5 volt is applied to the 8051 microcontroller. We have used a battery as we have to generate 5 volt and 12 volt DC supply. So, we have used a 12 volt, 500 ma battery which means its output will be 12 volts with current rating of 500 ma. We have used a filter capacitor to remove signal from the output of battery. In this project, the wheelchair is controlled by a mobile phone that connects to a Bluetooth decoder attached to the PCB which is mounted on the wheelchair. The PCB is designed on the Easily Applicable Graphical Layout Editor i.e., EAGLE software. Figure 4 PCB in our project Two separate voltage regulators are used after the filter capacitor so as to generate constant DC voltage supply of 5 volts and 12 volts. We have used 7805 and 7812 as voltage regulators. Both of them are three terminal, positive linear DC output voltage regulator pin IC namely input, ground and output. We have to give output of filter capacitor to the input of regulator, and we get 5 volts and 12 volts supply at the output pin of the respective regulator. The Bluetooth decoder placed on wheelchair should be paired and connected with the Android mobile. Each key of the mobile is assigned for a particular task. This way the wheelchair can be controlled through mobile. Once the connection is established, if any button is pressed, a code corresponding to the button pressed is sent to the decoder. The received command is processed by the microcontroller with the help of Bluetooth decoder and is displayed on the LCD screen. A motor driver IC seeks the voltage signal from the 5 V voltage regulator converts it into 12 V and delivers it to the motor for driving it. The L293D is a quadruple bidirectional motor driver IC that can drive current of up to 600 ma with a voltage range of 4.5 to 36 volts. We have used two motors of 12 volts, 100 rpm, and producing 15 kg-cm (i.e., N-m) torque each to drive the wheels. Scenario of Software: Algorithms: Step 1: Start Step 2: Clear all the registers

4 Step 3: Turn off all the motors Step 4: Initialize LCD Step 5: Display WELCOME message on LCD Step 6: Read the BLUETOOTH input Step 7: Check if BLUETOOTH input is = 2 Step 8: If YES, then move motor in forward direction Step 9: If NO, then check BLUETOOTH input is = 4 Step 10: If YES, then motor 1 will STOP & motor 2 will move in forward direction (i.e., wheelchair will move in left direction) Step 11: If NO, then check BLUETOOTH input is = 6 Step 12: If YES, then motor 2 will STOP & motor 1 will move in forward direction (i.e., wheelchair will move in right direction) Step 13: If NO, then check BLUETOOTH input is = 8 Step 14: If YES, then move motor in reverse direction Step 15: If NO, then check BLUETOOTH input is = 5 Step 16: If YES, then both the motors will turn off (i.e., wheelchair will stop) Step 17: Go to step 6 to repeat the sequence IV. WORKING OF PROJECT The wheelchair is controlled by Android application. So when an Android mobile is synchronized i.e., connected to the wheelchair via Bluetooth decoder, a Bluetooth Device Control screen is featured as a display. In the application, each device represents different components of the wheelchair i.e., Device 1 represent the left motor and Device 2 represents the right motor. Rear wheels are mounted on the shaft of these motors. So when both the devices are switched ON both the motors run together and the wheelchair follows a straight line path. When Device 2 is switched OFF, the right wheel stands still, while, the other wheel continues to move and the wheelchair turns right. And when the Device 1 is switched OFF, the left wheel stands still and the wheelchair turns left. (a) (b) (c) Figure 5 Bluetooth device control screen under various operating conditions Figures (a), (b) and (c) represent the Bluetooth device control screen under various operating conditions where, (a) : Both motors switched OFF (b) : Left motor switched ON (right turn) (c) : Both motors switched ON (moves straight)

5 V. CALCULATIONS Dimensions of chair Height of chair = 26 inches = cm = mm Length of chair = 24 inches = cm = mm Width of chair = 14 inches = cm = mm Drive wheel diameter = 4 inches = cm = mm 1) Motor selection: a) Actual torque acting by considering the weight of wheelchair: Total weight of wheelchair = 10 kg = 10 * 9.81 = 98.1 N The total weight on drive wheels is 50% of the total weight of the wheelchair. Therefore, Total weight on drive wheels = N This weight is divided into two because of two drive wheels as = 49.05/2 = N Net Force acting on each drive wheel, F1 = N Torque required, T = F1 * R = * (101.6/2) = N-mm = N-m b) Total torque required: We have two drive wheels in this chair so two motors are required separately for each wheel. Total Torque, T = T1 + T2 = N-m c) Power required for each drive wheel: P = (2π*N*T)/60 P = (2π*100*1.245)/60 = W Therefore, a 15 kg-cm torque, 100 rpm motor should be used. 2) RPM of Caster wheel: Let D1 = Diameter of Drive wheel in mm D2 = Diameter of Caster wheel in mm N1 = Speed of Drive wheel in rpm N2 = Speed of Caster wheel in rpm By using equation, Π*D1*N1 = Π*D2*N2 D1/D2 = N2/N /30 = N2/100 Therefore, N2 = rpm 3) Velocity of wheels: a) Drive wheel (V1): V1 = (Π*D1*N1)/60 = (Π*101.6*100)/60 = * 10-3 m/sec = m/sec b) Velocity of Caster wheel (V2): V2 = (Π*D2*N2)/60 = (Π*30*338.66)/60 = * 10-3 m/sec = m/sec And Mean velocity, V = m/sec 4) Diameter of Drive wheel shaft (d1):

6 Material of wheel is PVC Therefore the tensile stress value of material, Sut = 15 MPa a) Shear stress, Fs = 0.75 * Sut = 0.75 * 15 = MPa b) Torque transmitted by shaft, T = (Π*Fs*d1 3 )/ = (Π*11.25* d1 3 )/16 d1 3 = mm d1 = mm 5) Battery selection Minimum Battery voltage = Drop across IC required output voltage = 3 V + 5 V = 8 V So at the input of 7805 we require 8 V with margin Consider drop across diode 0.7 V. So 1 diode conducts a drop of 0.7 V = 0.7 V + 8 V = 8.7 V So battery required should be greater than 8.7 volt Therefore, a 12 volt battery should be selected. Result of Testing 1 st Condition: No load on the wheelchair 2 nd Condition: 5 kg load on the wheelchair 3 rd Condition: 10 kg load on the wheelchair 4 th Condition: 15 kg load on the wheelchair VI. EXPERIMENTAL RESULTS Table 1 Results of testing for various parameters at various loads Sr. No. Particulars 1 st Condition 2 nd Condition 3 rd Condition 4 th Condition 1 Drive wheel speed (rpm) Caster wheel speed (rpm) Torque (N-m) Power (W) Velocity of Drive wheel (m/sec) Total weight of wheelchair (kg) 10+0= = = =25 + dummy weight for trial (kg) (a) (b) Figures (a) and (b) show the fabricated prototypes of the wheelchair that we made

7 Table 2 List of components Sr. No. Name of component Specification Quantity Function 1 Capacitor 1000 µf 1 To store energy 100 µf 2 To remove the signal from the output 10 µf 1 of battery 104 pf 2 2 Microcontroller AT89s51, 1 It transmits the signal to the motor driver low power, high IC s to operate the motors performance CMOS, 8-bit, volts 3 IC L293D CM To convert 5 volts into 12 volts which is which is required to drive the motor To drive current upto 600 ma (without heat sink) with voltage range of upto 4.5 to 36 volts 4 Voltage regulator To generate a constant DC voltage supply of 5 volts and 12 volts 5 Resistor 10 k-ohm 2 To source the current along with 100 k-ohm 2 microcontroller 330 k-ohm 2 6 Crystal oscillator MHz 1 To provide the required clock pulses MHz 1 7 LCD 16 alpha x 2 num 1 To display various messages and commands received 8 Motor 12 volts, 100 rpm, 2 To generate torque 15 kg-cm torque To drive the driver wheels (i.e., N-m) 9 Wheel PVC, 4 inches 2 To impart movement to the wheelchair 10 Caster wheel PVC, 2 inches 2 To stabilize the wheelchair while the drive-wheels propel it 11 Battery 12 volts, 500 ma 1 It is the main component of the power supply module To generate and supply DC voltage to the motors 12 Chassis 2 x 2 cm hollow 1 To provide a power base to the square section wheelchair VII. ADVANTAGES AND DISADVANTAGES Advantages 1) The most important advantage of our project is that a person with disability can easily bring the chair lying far from him towards himself by simply giving command/s through his mobile 2) Because of its light weight and small size, it can be easily carried to different places while travelling 3) Reduces the dependency of user on others to move around and also, no manual effort is required to push chair as the chair is power driven 4) This wheel chair is easy to operate and cheaper in cost as compared to others that exist in the market Disadvantages 1) Complete dependency on mobile for drive. Mobile must be fully charged for a longer operation 2) Requires android mobile only and other systems won t support a mobile that operates on ios, Windows etc. Applications 1) In hospitals for patients 2) For short outdoor travelling 3) For old age people 4) For temporary use (those who met with small accidents)

8 VIII. SCOPE OF FUTURE WORK Although this project has many advantages, it was proposed that the wheelchair could be powered by solar energy. A different mechanism can be implemented to replace the nut-bolt angle plate setup for inclination of the backrest of the wheelchair, and also to make it work for the purpose of stretcher on requirement. The square tabular frame is proposed to be replaced with that of a circular cross-section. In addition to this, features such as controlling through voice recognition could also be implemented. IX. CONCLUSION The requirement, ease and comfort of a user play a vital role in deciding the features for a wheelchair. The wheelchair has to be modeled and designed keeping in mind other aspects as well as feasibility, material properties, design parameters and cost. A collective approach of Bluetooth technology, power electronics and design facilitated in the making of an easily operated, light weighted, and relatively cheap vehicle with reduced manual effort and travel time. Our project would benefit 2.1 million handicapped all across the country. REFERENCES [1] Nirmal T. M., Wheelchair for Physically and Mentally Disabled Persons, International Journal of Electrical and Electronics Research ISSN , vol. 2, no. 2, 2014 [2] Salmin Humaira, Rakibul Hafiz, Kundu Pratik Kumar, Shuvo B.M. Fahmid Jahur, Nasiruzzaman K.B.M. and Rahman Md. Moshiour, Design and Implementation of an Electric Wheel-Chair to Economize it with Respect to Bangladesh, International Journal of Multidisciplinary Sciences and Engineering, vol. 5, no. 2, 2014 [3] Prasad A., Shah S., Ruparelia P., Sawant A., Powered Wheelchairs, International Journal of Scientific & Technology Research ISSN , vol. 2, no. 11, 2013 [4] R. Mohan Kumar, S. Lohit, Mishra Manas and Md. Ahamed Basheer, Design of Multipurpose Wheel Chair for Physically Challenged and Elder People, SASTECH, vol. 11, no. 1, 2012 [5] Tadakamalla Shanmukh Anirudh and Jyoti Pragyan Satpathy, Design of Motorised Wheelchair, Thesis 110ID0259 and 110ID0625, Bachelor of Technology in Industrial Design, NIT Rourkela, pp , 2014 [6] Lewis Edward, Lamontagne Mario, Barclay Hugh, John Thomas and Martel Guy, A technique for the determination of centre of gravity and rolling resistance for tilt-seat wheelchairs, Journal of Rehabilitation Research and Development, vol. 28, no. 3, pp , 1991 [7] Armstrong W., Borg J., Krizack M., Lindsley A., Mines K., Pearlman J., Sheldon S. and Reisinger K., Guidelines on the provision of Manual Wheelchairs in less resourced settings, WHO Library Cataloguing-in-Publication Data ISBN , pp , 2008 ACKNOWLEDGEMENT In an endeavour to undergo the intricacies of this project and at various stages when we were in need of guidance, we are grateful to all those who helped us and wish to thank them. We thank with gratitude Assistant Professor Rupesh Khorgade whose co-guidance has been a vital part of our publication work. We are thankful to the entire Mechanical Engineering staff for supporting us in all possible manners. We express our sincere gratitude towards our Project Guide, Er. S.V. Peshatwar (Assistant Professor Mechanical Department) who guided us, instilled self-confidence within us and provided motivation throughout. We also express our sincere gratitude towards our Project In-charge, Er. S.N. Khekale under whose supervision our project could be completed in time. We would also like to thank the Head of Department of Mechanical Engineering, Dr. Prashant Washimkar, and also the Staff Members of Department whose help and inspiration proved beneficial to us. We thank with immense gratitude our honourable Principal of Guru Nanak Institute of Technology, Dr. N. M. Kanhe who has always been our source of motivation. The first author Jayashree P. Wakalkar is thankful to Mr. Nilesh Wakalkar, M.Sc. Physics student from Mumbai University for his valuable suggestions and criticism.last but not the least we are thankful to our families for their enduring support, faith and motivation which made possible the best of team work

9 More images of the wheelchair