Robot – DIY Database

Robotic vehicles can have a wide variety of drive mechanisms that range from a simple tricycle setup all the way to crawling legs. Alex Le’s project leverages the reliability of LEGO blocks with the customizability of 3D-printed pieces to create a highly mobile omnidirectional robot called Swervebot, which is controllable over Wi-Fi thanks to an Arduino Nano ESP32.

The base mechanism of a co-axial swerve drive robot is a swerve module that uses one axle + motor to spin the wheel and another axle + motor to turn it. When combined with several other swerve modules in a single chassis, the Swervebot is able to perform very complex maneuvers such as spinning while moving in a particular direction. For each of these modules, a pair of DC motors were mounted into custom, LEGO-compatible enclosures and attached to a series of gears for transferring their motion into the wheels. Once assembled into a 2×2 layout, Le moved onto the next steps of wiring and programming the robot.

The Nano ESP32 is attached to two TB6612 motor drivers and a screen for displaying fun, animated eyes while the robot is in-motion or idling. Controlling the swerve bot is easy too, as the ESP32 hosts a webpage full of buttons and other inputs for setting speeds and directions.

For more details on the Swervebot, you can read Le’s write-up here on Instructables.

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A vehicle’s wheel diameter has a dramatic effect on several aspects of performance. The most obvious is gearing, with larger wheels increasing the ultimate gear ratio — though transmission and transfer case gearing can counteract that. But wheel size also affects mobility over terrain, which is why Gourav Moger and Huseyin Atakan Varol’s prototype mobile robot, called Improbability Roller, has the ability to dynamically alter its wheel diameter.

If all else were equal (including final gear ratio), smaller wheels would be better, because they result in less unsprung mass. But that would only be true in a hypothetical world on perfectly flat surfaces. As the terrain becomes more irregular, larger wheels become more practical. Stairs are an extreme example and only a vehicle with very large wheels can climb stairs.

Most vehicles sacrifice either efficiency or capability through wheel size, but this robot doesn’t have to. Each of its wheels is a unique collapsing mechanism that can expand or shrink as necessary to alter the effective rolling diameter. Pulley rope actuators on each wheel, driven by Dynamixel geared motors by an Arduino Mega 2560 board through a Dynamixel shield, perform that change. A single drive motor spins the wheels through a rigid gear set mounted on the axles, and a third omni wheel provides stability.

This unique arrangement has additional benefits beyond terrain accommodation. The robot can, for instance, shrink its wheels in order to fit through tight spaces. It can also increase the size of one wheel, relative to the other, to turn without a dedicated steering rack or differential drive system.

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