Engineering in Practice

Hi folks..

Guess it's time to discuss some cool engineering stuff..

Let's talk about automation - Intelligent Bicycle Transmission. This novel design of Intelligent Bicycle Transmission (IBT) [(C) Arpit et al.] system provides superior efficiency to bicycle riders since it allows the rider to maintain the preferred cadence range. The system is very simple and economic yet provides an automatic gear shifting option to the cyclist at fairly accurate level. The gear manipulation in the case of a bicycle is not a simple linear progression from a lower gear to a higher gear as in a motorized vehicle, for example a car. It is instead a function of the ratio of the front gear size to the rear gear size, both of which are variable. Since years, many designs for the automated transmission have evolved; however the excessive cost and the inadequate efficiency kept the urgency and the scope of the improved designs alive. This motivated the brainstorming by a group of so called engineers who, at that point of time, were not able to think of anything better to design and fabricate!;)

I. Cadence and gearing
Bicycle’s motion is dependent on the input power being delivered by the rider in the form of pedaling. Pedaling involves rotation of a front sprocket due to pressure applied by the rider’s feet. This motion is then transmitted to the rear wheels through a chain mechanism and rear sprocket (a smaller gear attached to the rear wheels). Cycling involves different riding conditions, each having their own power requirements. For instance, while racing, more speed is desirable whereas for city commuting, comfort is preferred over speed.
II. Design of Transmission System
Based upon the theory of preferred cadence, an approach for the design of transmission system is suggested as follows: The implementation of the algorithm required fulfilling of three steps: (a) Design of two sensor devices A and B that measure the angular velocities accurately and their output is in the form of parameters that can be inputted to an electronic control unit (ECU), (b) Design of an ECU that receives the output of the sensors and controls the motion of the actuator that causes the shifting of the gear and (c) Design of an actuator that shifts the gear system as per the signals generated by the ECU. The schematic of the algorithm is shown below:

A. Sensor Devices

In the presented design, two sensors have been used. Sensor A has been used to measure cadence and Sensor B to measure angular velocity of the rear wheel. From the experimental results, it is found that a voltage range of [1.3, 1.7] V is obtained by the sensor A for the preferred cadence.
B. Electronic Control Unit
The designed ECU has two main sections: (a) Actuator Control Circuit, (b) Motor Driver Circuit.
C. Actuator

In the proposed system, a derailleur with 5 speeds or gears is used having following specifications. CAD/CAM schematic of the actual actuatuor was used in designing of IBT (drawn on Solidworks s/w) .

This is the abstract of the original work. However,  disclosure of detailed designs and discussion are beyond the scope of this article due to the rights reserved with IEEE.