Design and Manufacturing of Segway Report Download – Mechanical Project

Design Description

Design Constraints
The Segway design had to be self contained and turned on and off by a switch. Thus, the batteries, or power source, must be on the cart itself. The container that was used as the mass in the competition had a 6 inch diameter base, so the cart had to be designed with a top plate large enough to hold the container. The maximum distance of the top plate from the floor had to be less than 6 inches. This height does not
include the vertical handlebar post which had to be removable and between the lengths of 7 to 9 inches. The cart also had to be rigid enough to hold and balance a mass of up to 2 kg. The two cart wheels had to have diameters between 0.5 and 6 inches. To test the balance of the cart, it was necessary to enable a maximum free range of motion to 60 degrees in both directions of the wheel axle.
The cost of the finished cart could not exceed the specified budget of $200.00 and the weight of the cart should not have exceeded 1 kg. The incentive to keep costs and weight low was included into the final score estimate with the score improving as those parameters were reduced. Another important component of calculating the final score was the time to execute a motion from the start of the motion to the end. The tape paths that the robot had to follow during the competition grew increasingly complex to test the cart’s agility and success of design.

Mechanical Design

A 0.975 kg, 6 inch tall with 6 inch wheel diameter design was developed with consideration of the competition constraints. The polycarbonate-framed cart was designed with a two 12V DC direct drive motor system in which the shafts of the motors acted as the wheel axles. Through circuit calculations, a 9V battery was identified as suitable to power the 8-bit ATMega32 board used to control the functions
of the cart. Nine AAA batteries were calculated to supply enough power to drive the motors.

Photoresistors were used to detect the black electrical tape path on the day of the competition and infrared sensors were incorporated into the design to act as balance sensors.

For the purpose of aesthetics and identifying the Segway, handlebars were produced but were not included in the final mass of the cart or attached during the actual competition. The final cart design is shown in Figure.

Conclusion
The cart followed the entire length of the tape path, 3 meters, during the final competition while carrying the mass. After the competition, the Segway was also tested to see if it could follow non-linear tape paths. Without a mass, the cart performed with excellence. It followed any curved path where the lighting was not too dark or too bright.
It was theorized that a lower center of mass would help the Segway balance. This was evident in competition when the carts with lower center of masses were more successful in balancing the mass. The designed Segway did not use encoders, which did not hinder its
performance. The provided photoresistors were sufficient feedback systems for allowing the carts to follow the lines.
The design of the Segway could have improved by adjusting for different light conditions. When the lighting was too bright or dark, it got confused and hesitated or did not react to any. The center of mass for this design could have also been lowered by adding additional
weight or lowering the top plate to hang below the wheel axles.

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Design and Manufacturing of Segway Report Download – Mechanical Project