HEAD MOTION CONTROLLED POWER WHEELCHAIR

Quadriplegia or tetraplegia is a condition that occurs when a part of the spinal cord inside the neck has been injured. This injury causes loss of feeling and movement in the arms, legs, and trunk. The damage affects the nerve fibers passing through the injured area and may impair part or all of the corresponding muscles and nerves below the injury site. Spinal injuries occur most frequently in the neck (cervical) and lower back (thoracic and lumbar) areas. A thoracic or lumbar injury can affect physiologic functions. A cervical injury may affect breathing as well as movements of the upper and lower limbs. For Severe Quadriplegics, the only residual movement present is the head so it is mandatory to use this movement to enhance the mobility of the patient to control the movement of the wheelchair.

NEED:

          It is well recognized that the lack of mobility is one of the most limiting disabilities that estimated 50,000

individuals who don’t have use of their arms and legs (quadriplegics) encounter. Without a means to free move around, they are totally dependent on others. The goal of independent living cannot possibly be achieved in this manner. Therefore, it is their priority to be able to mechanically move their bodies under their own command.

EXISTING SYSTEM:

Earlier, the system which used just controls the movement of the wheel chair automatically by using the keypad alone.  It does not detect the object opposite to it. This is one drawback by using this system. To avoid this we go for a new system. Modern power wheelchairs for quadriplegics commonly use one of two control mechanisms. The first involves controlling the wheelchair with a controller that lies in the mouth, while the other is known as a “Sip and Puff” system which requires user to suck or blow air through tubes in front of the mouth to control wheelchair functions. These control options are expensive and also interfere directly with the user’s ability to communicate while operating the chair.

PROPOSED SYSTEM:

          This paper describes a head controlled assist system developed using an electronic and mechanical arrangement (MEMS) controlled by a Programmable Interface Controller. Sensor accelerometer placed on the patient’s head sensed the tilt made by the head. This tilt corresponded to the analog voltage. Using this voltage, control signals were generated for four directions of the wheelchair.

The ultrasonic sensor here used to detect the objects opposite to the wheel chair, if any object means it intimates through LCD. All these control information are fetched in the microcontroller using embedded C coding.  Control of the robot is done by using the relays; relays are the electromagnetic switch which activates the motors that used in the robot according to the given instruction by microcontroller.

BLOCK DIAGRAM:

Fig. shows the overall structure of the assist system that is composed of Sensor design, the Electronic module and the Mechanical module. The Sensor design comprises of Tri-axis Accelerometer and signal conditioning unit (S.C.U). The electronic module has a PIC Microcontroller and the mechanical module consists of a Driver IC and Motors. The Tri-Axis Accelerometer is an integrated module that can sense gravitational (g) force of ±3g on three axes (X, Y, and Z). A switch placed on the headrest of the wheelchair is meant for the purpose of ON and OFF action. Acquiring measurements from the module is simplified through a synchronous serial interface. Single and multi-axis models are available to detect magnitude and direction of the acceleration as a vector quantity. Single axis measures the force in any of the three directions namely X, Y or Z. Due to this disadvantage, tri-axis accelerometer is used for this application. Based on the sensitivity, accuracy and supply voltage, acceleration to voltage conversion is performed. The Electronic module comprises a homework board that has an 8-bit flash based Programmable Interface Controller, an EEPROM with a fixed program, a Voltage regulator and reset circuitry to control the operation of the Assist system.

HARDWARE REQUIREMENTS:

Ø  PIC Microcontroller.

Ø  Ultrasonic sensor.

Ø  Accelerometer Sensor.

Ø  S.C.U.

Ø  Relays with Driver unit.

Ø  Robot Mechanism.

Ø  LCD.

SOFTWARE REQUIREMENTS:

Ø  Embedded C

Ø  MPLAB IDE or CCS C Compiler

CONCLUSION:

The head movement based assist system was developed with an idea of serving the people affected with high level Quadriplegia. In this case, the assist system has proven to be of a simple implementation and of low cost. The result obtained clearly implies that the system is easy to handle by the patients. This paper can be further extended to thought recognition module for controlling the speed and movement of the wheelchair, Obstacles on the pathway can be identified and the directions of the movement can be controlled using ultrasonic sensor.

REFERENCES:

[1] Henrik Vie Christensen a and Juan Carlos Garcia b,"Infrared Non-Contact Head Sensor, for Control of Wheelchair Movements,” Book Title Book Editors IOS Press, 2003.

[2] James M Ford,Saleem J.Sheredos, “ Ultrasonic Head Controller For Powered Wheelchair,” Journal of Rehabilitation Research and Development, vol. 32 No. 3, October 1995 Pages 280—284.

[3] Margarida Urbano, José Fonseca, Urbano Nunes, Luís Figueiredo, "Adaptation of Powered Wheelchairs for Quadriplegic Patients with Reduced Strength, "ETFA 2008 - 13th IEEE Conference On Emerging Technologies & Factory Automation, Hamburg, 15-18September.

4] Smith B, Buckett JR, Peckham PH, et al. “An Externally Powered, Multichannel implantable Stimulator for Versatile Control of Paralyzed Muscle,” IEEE Trans Biomed Eng 1987;Pages 499-508.

[5] A Ferreira, R L Silva, W C Celeste, T F BastosFilho and M Sarcinelli Filho, ”Human –Machine Interface Based on Muscular and Brain Signal Applied to a Robotic Wheelchair,”Journal of NeuroEngineering And Rehabilitation 2008, 5:10.

[6] Chris Aimone, Ryan Fung, Ashish Khisti, Meghal Varia,” HEAD Mounted Control System,” in press.

[7] Roberto Merletti , Philip A. Parker. “Electromyography- Physiology, Engineering and Non-invasive Applications”.