Accelerometer Based Wheelchair for Physically Handicapped Person

In our country of 1.3 billion populations, we still have more than 1% population of elderly or disabled people, which need support for personal mobility. Our project has a goal to meet their requirement of mobility with smart technology. The problem with them is that their legs bones get weaker or get a break due to an accident and cause pain while moving, so we are using hand or head-tilt motions to move a wheelchair. The tilt is sensed by accelerometer and equivalent voltage is developed, that voltage is sensed by Arduino and converts them into an equivalent signal for the relay. Based on the Arduino signal, the relay drives the corresponding motor. The motion of the motor causes the wheelchair to move in a certain direction. This gives features to the user to control the motion of the wheelchair by hand or head tilt. We have used the ultrasonic smart sensor to control the braking of the wheelchair based on the distance between the wheelchair and obstacles. If the difference distance is less than 20 cm then Arduino sends a braking signal to relay and motor halt, this decreases the speed and after 2-3 seconds the wheelchair finally gets a stop. This helps the user from a major and minor accident on the road, with the help of smart techniques. LCD shows the difference distance for forward and backward on display for the user. These features make the wheelchair simple, safe, and smart for the user.

Components required:

Arduino nano,

Relay 5V,

Wood Board for Mechanical assembly,

4 DC gear motor 24V,2A,

Batteries 12V,4A,

Aluminum plate,

Glove,

Adxl 335 modules,

Wheelchair wheels,

Chair with screws for fixing,

12V,5V Regulator IC.

The block diagram consists of the sensor unit, power supply, Arduino, relay, LCD, and motors. Arduino has inputs from the automatic seat belt mechanism for detection of the seat belt is worn by the user or not. When the user wears a seat belt, Arduino senses, and turns on the system. Then the welcome message is displayed and the user asked to select the mode of operation. There are three modes of operation and are selected by manual switches. Once the mode is selected then it starts sensing the change in the output of the accelerometer sensor and correspondingly changes the input signal for relay by Arduino. Based on the Arduino signal, the relay drives the motor in a particular direction until the Arduino changes the relay input. The ultrasonic sensor is used to measure the distance of obstacle near the wheelchair, this information is displayed on LCD and store in Arduino for braking. When the distance is less than 20 cm, Arduino generates a braking signal to relay and it stops the movement of the wheelchair. There is two power supply used for Arduino and motor supply, Arduino has a supply of 5v and the motor has a supply of 24v.

Development of wheelchair start from mechanical frame assembly. An acrylic or wooden board can be used for the bottom frame of the wheelchair. Then the board is cut in frame size of 24 * 36 inches,24 inches is length and 36 inches are the width of the frame.

The motor is mounted on frame board with help of L bracket. By leaving space of 2 inches on length side and drill hole for mounting the motor. When drilling is over then we place the L bracket and starting putting a screw and then fix the motor by its screw-on shaft body. After that wires are extended by joining other extension wire and connecting it to relay output.

A four-leg chair is used to make the system more stable during operating on the road. These legs edge is drilled with hole and place on frame and drilling is also done on the frame. After that chair is fixed on a frame by screw bolt.

A power supply switch is used to provide supply to the motor and if any short circuit happens then turn off the system supply by this switch. These switches and LCD are firstly fixed on a wooden board and then fix on the rest pad of the chair by drilling hole and then fixing it by a screw bolt.

For building a seat belt mechanism, aluminum handle section is used and bend over an edge. Two handles are used and a nylon belt is used and fixed at Chair shoulder position. The handle is fixed at the seating edge of the chair.

Two ultrasonic sensors are used for forwarding and backward distance measurement. They are fixed at the center edge of a wheelchair with screw.

Two wooden boards of size 2 * 6 inches are used for leg rest pad. These are fixed on wheelchair edge in v shape position.

Automatic seat belt and glove based button used short circuit concept and connected to 5v. The LCD is connected to Arduino Nano in 4-bit interfacing mode and it will display a welcome message on the start of a wheelchair. After that mode selection of wheelchair is done using gloves button. The gloves are connected to 0,1,2,3 pin of Arduino and the accelerometer is connected to A0, A1 of Arduino. When accelerometer is tilted, the acceleration is converted to X-axis and Y-axis voltages. Based on it the movement of a wheelchair is done. Direction of acceleration is converted to motion of wheelchair with a help of relay connected to 4,5,6,7 pins of Arduino and it is connected in a manner that the signal is converted into 4 direction motion of wheelchair like forward, backward, left, right. DC motor is connected directly to relay at no connection, open connection, common terminal. Ultrasonic trigger pin is connected to pin no 13 of Arduino and echo is connected to 10,11 pin of Arduino. It is used for automatic braking when an obstacle is detected within a range of 20 cm and it displays the distance on LCD. LCD data pins are connected to A2, A3, A4, A5 and enable pin is connected to 9 pin, register select is connected to pin no 10

The algorithm flow operation of wheelchair is done in following manner

1. Start by connecting the power supply of 24 V and 5 V.

2. Connect the Seatbelt, if not connected then go to 16.

3. Check if the accelerometer is in stable condition?

4. Switch on motor supply switch.

5. Select the mode of operation by glove button, the processor execute on 6, 9, 12 and if not selected then go to 16.

6. Mode 1 selected, then

7. Move the accelerometer in the direction we want to move the wheelchair.

8. Accelerometer moves or tilt his position thus gives the analog signal to Arduino and convert it inappropriate

digital level, so as to move the motors of the wheelchair.

9. Mode 2 selected, then

10. Based on glove button is pressed in the direction, we want to move the wheelchair.

11. Arduino senses change in glove switch mode on/off and convert it inappropriate digital level, so as to move the motors of the wheelchair.

12. Mode 3 selected, then

13. Move accelerometer in the direction we want to move the wheelchair.

14. Accelerometer moves or tilt his position thus gives an analog signal to Arduino and convert it in

appropriate digital level, and check for ultrasonic difference distance.

15. Ultrasonic sensors are used to detect the obstacle. If any obstacle is detected then it

gives the signal to Arduino and it applies braking operation and will stop the motors.

16. The wheelchair is in the rest position.

17. Remove the Seatbelt.

Efforts were made to make the system compact and wearable, minimum wires have been used and this reduces the system complexity. The Arduino is the heart of the system and therefore needs to be programmed properly. Various gestures were tested and the outputs were studied to check if the right signal is sent to relay. The wheelchair model works on the switching relays & motors with an accelerometer sensor placed on the patient’s hand. Arduino with the accelerometer is used to send tilt signal to the wheelchair in terms of motion i.e., left or right, front or back. Here relay acts as a switching circuit. According to the relay operation, the wheelchair will move in that corresponding direction. The proper interfacing of all components according to the circuit diagram gives us hardware circuitry for prototype wheelchair with hand-based gesture and glove based control with automatic braking for the safety of patients.

We had implemented an automatic wheelchair, which has various advantages. It is operating in three different modes i.e. manual mode, accelerometer and accelerometer with braking mode. Also, there are two ultrasonic sensors that increase the accuracy of the wheelchair and provide automatic braking. This Wheelchair is economical and can be affordable to common people. With the development of this project, it can be successfully implemented on a larger scale for the handicapped people. The low cost of the assembly makes it really a bonus for the general public. We can also add new technology in this wheelchair. From the above-obtained results, we conclude that the developed of all three control modes of a wheelchair is tested and works satisfactorily in an indoor environment with minimum assistance to the physically disabled person. It has a good response to the accelerometer activating the motors connected to the wheels of the chair. The speed and distance covered by a wheelchair can be further improved if the gear system connected to motors is replaced by a crank and pinion joint which has less friction and mechanical wear & tear. The running cost of this system is much lower as compared to other systems used for the same purpose.