Head motion based wheelchair

SUBMITTED BYNAVEEN YADAVNIVEDIKA GUPTAPRIYANK MISHRASUNEEL Kr SAVITA

GUIDED BY- NEERAJ MARWAHA

INTRODUCTIONThe objective of this project was to design a power

wheelchair with a novel control system for quadriplegics with head or hand mobility. The control system translates the position of the user's hand into speed and directional control of the wheelchair. Hand movement was measured using accelerometer sensor-based motion- tracking of an sensor array on the back of the user's hand.

PICMicrocontroller with

Analog to digital converter

Amplifier

Left H Bridge

Right H Bridge

Left Motor

Right Motor

Amplifier Amplifier

x-axis sensor

y-axis sensor

z-axis sensor

BLOCK DIAGRAM

OPERATIONAL AMPLIFIER(LM358)

•LM158/LM258/LM358 low power dual operational amplifier are used.•Dual supplies are used(+1.5V to + 16V).

FEATURES-•Available in micro SMD chip sized package.•Large dc voltage gain(100dB).•Wide Bandwidth(unity gain- 1MHz).

ADVANTAGES-•Compatible with all forms of logic.•Eliminates need for dual supplies.

The LM358 is available in 8-Bump micro SMD chip sized package and consists of two independent high gain, internally frequency compensated operational amplifier. It can be operated from a single supply and also split power supplies.

OUTPUT1INPUT1(-)

INPUT1(+)

GND

VCC

OUTPUT2

INPUT2(-)

INPUT2(+)

ACCELEROMETERAccelerometer sensor can measure static(earthgravity) or dynamic acceleration in all three axis.Application of the sensor is in various fields and manyapplications can be developed using this sensor.Accelerometer sensor measures level of accelerationwhere it is mounted this enable us to measureacceleration/deceleration of object like car or robot, ortilt of a platform with respected to earth axis, orvibration produced by machines. Sensor provides 0Goutput which detect linear free fall. Sensitivity can beadjusted in two ranges.

One accelerometer sensor can sense the two different tilts. Based on the ground position each tilt will generate an output as a voltage. The sensor used in this automatic system generates an output voltage which varies between 2.5V to 3.5V is given to microcontroller as an analog input. Then it converted into digital signal using ADC of controller.

ACCELEROMETER SENSOR

Sensor accelerometer placed on the patient’s head sensed the tilt mode by the head. This tilt corresponded to the analog voltage. Using this voltage, control signals were generated for four directions of the wheelchair.

Acceleration is a vector force which has direction and measured in meters per second. Earth produces gravitational acceleration on all objects on earth. Bymonitoring the three axis acceleration one can measure the level of tilt of any platform.

Features Simple to use Analoge output for each axis +5V operation @1ma current High Sensitivity (800mV/g @ 1.5g)Selectable Sensitivity (+- 1.5g, +- 6g) 0 g detect for free fall detectionRobust design, high shock survivabilityLow Cost

GESTURE RECOGNITIONHand gesture recognition is based on information fusion of

three-axis accelerometer.• Starting and ending points of gesture segments are

detected by the intensity of sensor signal.

Gesture recognition

MicrocontrollerThe microcontroller that has been used for this project

is PIC16F877A. It is an eight bit microcontroller. It has been programmed using PIC C compiler. Microcontroller contains many peripherals like ten bit ADC module, three timers, Capture, compare and PWM module. Ten bit ADC is used in this project. When any analog value is given, the converter generates the digital results of the corresponding values. The A/D conversion of the analog input signal results in a corresponding 10-bit digital number. It uses successive approximation type conversion. The A/D module has inputs that are software selectable to some combination of VDD and VSS.

MOTOR DRIVER ICL293D is a dual H-Bridge driver, so with one IC

we can interface two DC motors which can be controlled in both clockwise and counter clockwise direction and a motor with fixed direction of motion. All I/Os are used to connect four motors . L293D has output current of 600mA and peak output current of 1.2A per channel. Moreover for protection of circuit from back EMF output diodes are included IC. The output supply has a wide range from 4.5V to 36V, which makes L293D a best choice for DC motor driver.

CURRENT FLOW THROUGH MOTOR

CONTINUE…Driver IC has four switching elements within

the bridge. These four elements are often called, high side left, high side right, low side right, and low side left (when traversing in clockwise order).

The switches are turned on in pairs, either high left and lower right, or lower left and high right, but never both switches on the same "side" of the bridge.

AXIS OF ACCELERATIONa single axis measured, you can only know the force in either X, Y, or Z directions, but not all.

Axis ofacceleration

FINAL MODULE

RESULT When a person wears a band fixed with

accelerometer and tilts his head the wheelchair moves in corresponding directions based on the head movement.

When the person bends his finger the wheelchair moves in corresponded direction based on the bend of the finger.

CONCLUSION As the accelerometer glove based automated

system has been presented which would be very helpful for physically challenged persons and for the persons who cannot move their body except head and fingers. Also the accelerometer sensor is calibrated such that it produces particular analog voltage for a corresponding tilt.PIC is programmed for analog to digital conversion using PIC C compiler.

REFERENCESwww.flexpoint.com Datasheet of PIC16F877 http://www.sunram.com

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