Doc-20190119-wa0007.docx

WHEEL CHAIR

ABSTRACT Mobility aids that are currently available in developing countries do not fully meet users’ needs. People require a device that is maneuver able within the home and that can travel long distances on rough roads. In this work we present the Leveraged Freedom Chair (LFC), a wheelchairbased mobility aid capable of navigating virtually any terrain, from rural walking paths to within the home, by optimally utilizing upper body power for propulsion through a variable-speed lever drive train. Instead of using multiple gears to change speed, the user varies mechanical advantage by sliding his hands up and down the levelers. Changing user geometry instead of machine geometry enables the lever system to be made from a simple assembly of low-cost bicycle parts. This insures the LFC can be manufactured and repaired anywhere in the developing world.

SYSTEM DESCRIPTION The LFC achieves a multi-speed, fixed gear ratio drive train with the lever system shown in Fig. 2. Unlike most gear trains, which operate in varied states to obtain multiple ratios, the LFC’s drive train exists in only one state; it is the user who changes his hand position to change the mechanical advantage of the device. If more torque at the wheel is needed to climb a hill, the user simply slides his hands up the levers and away from the pivots, as shown in Fig. 2a. If more speed is required, the user moves his hands closer to the lever pivots, as shown in Fig. 2b, achieving a greater angular deflection with every push stroke.

Figure 2. LFC variable mechanical advantage drive train a. Low gear: moving hands high on the levers produces high torque. b. High gear: moving hands low on the levers high angular speed.

3.1 BLOCK DIAGRAM

3.2 WORKING Two modified Shaft is used with sprocket. This Sprocket is joined with chain which is connected with another smaller cassette that is mounted directly on handle shaft. Whenever the handle shaft rotates then the sprocket of rear spindle starts rotating and thus the wheel starts moving. In this wheelchair the chain is used to transmit power to drive wheel. A wooden tray is attached underneath the seat to mount the shaft and sprocket gear. The control circuitry is placed underneath the seat which is covered in a box. After completing the connection of the mechanical equipment, the structure of wheel chair which is implemented.