For the vehicle to move forward the engine has to be connected to driving wheels so as to propel the vehicle. The engine rotates at relatively high speeds, while the wheels are required to turn at slower speeds. The torque requirements of the vehicle vary as per the prevailing conditions of load, terrain etc. Gear box provides different gear ratios between the engine and the driving wheels, to suit the varying road conditions such as when climbing hills, traversing rough road or sandy road or pulling a load. The required gear shift for providing varying torque requirements can be obtained either manually or automatically. Automatic gear shifting mechanism is a concept implementing an embedded control system for actuating the gears automatically without human intervention. The automation is achieved by using a microcontroller and suitable sensor and actuator hardware. Whenever the speed of the vehicle increases or decreases beyond a pre-defined set of values, the microcontroller based control system actuates the clutch as well as the gear and helps maintain a steady operation of the automobile. The concept of automatic gear change is applied in this work to a 4-stroke, manual transmission motorcycle. The clutch is actuated by means of a DC Motor actuated mechanism and gear lever is actuated by means of the spring loaded solenoid actuator, both controlled by a microcontroller based circuit, programmed to read the signals from an inductive proximity sensor which senses the actual speed of the wheel. The system design and development is described in this paper with control circuit and control logic.
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