19-06-2012, 04:51 PM
JOYSTIC AND SENSOR CONTROLLED WHEEL CHAIR
PROJECT ON JOYSTIC AND SENSOR CONTROLLED WHEEL CHAIR[1][1].docx (Size: 401.88 KB / Downloads: 66)
INTRODUCTION
Since the first folding, tubular steel wheelchair was invented in 1932 and the first electric wheelchair was designed in the 1950’s, the functionalities of the manual and electric wheelchair have been improved significantly. The electric wheelchairs have become more efficient, quieter and lower-maintenance in general. They also grant users more freedom with less assistance including in the control, styles, range or travel distance, maneuverability, seating and other user options. In contrast, the mobility of the manual wheelchair was limited by the user’s physical condition and restricted his or her daily Activities. This disparity in performance is reflected in a difference in cost: electric wheelchairs typically range between $1600 and $7500, while the basic manual wheelchairs cost around $100 to $500. After researching various existing motors, we noticed that a standard bike could be converted into an electric bike by installing hub motors, which cost around $300 per wheel. The conversion is very convenient and allows a much greater range of travel. Also, cars’ windshield wiper motors can also be used to provide as much torque as the hub motors with a more competitive cost. Therefore, a manual wheel chair can be possibly converted into an electric wheel chair by adding the suitable motors.
OBJECTIVES
The primary aim of the project is to convert a manual wheel chair into an electrical one under a competitive budget. As it is mentioned previously in the background section, a price difference of 1000 dollars or more exists between electric and manual wheel chairs. Our project cost has to be less than the difference in order to be viable while achieving the functionalities.
The second objective of this design is flexibility. The users can easily disassemble chair to convert the wheel chair from electric to manual. It will greatly benefit the users with higher mobility level. If they want to exercise their arms, it can be achieved by taking off the MWA. This is the reason why we have to ensure the design has to be mounted in a way that can be disassembled without other assistance.
JOYSTICK STEERING CONTROL
The joystick steering control method of the MWA system. The control option other than sensors the joystick control is much simpler and user friendly.
The mini-joystick with two channel inputs takes in x and y direction and speed information and encodes them as voltage variations. Those two channels of voltage signals get converted to digital by the Analog-to-Digital Converter built into the microcontroller. There are design algorithms in the micro-controller to extract the speed and direction information from the joystick input.
Finally, the speed and direction will bemapped to the command words to output to the propulsion system. The joystick was the only user interface for the steering control in our original design. Initially, plan to design and build a joystick tailored to the application from basic potentiometers. After researching the current joystick designs, the problem has become time consuming and cost inefficient we need two potentiometers for x and y axis flexibilities, RC components and a circuit board. The joystick identified with two axes and two potentiometers. It will be sufficient for our implementation. As a result part reduced to integrating the joystick into the rest of the control system.
METHODOLOGY
The foremost focuses is to design a joystick steering control handheld device that will allow the user to select the speed and direction of the wheel chair. Control signals will be provided by the joystick and sensors to the propulsion system of the wheel chair. Please refer to Figure 4: General Project Block Diagram for the relationship among components of the project.
General description
The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash Programmable and Erasable Read Only Memory (PEROM). The device is manufactured using Atmel’s high density nonvolatile memory technology and is compatible with the industry standard MCS-51™ instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications.