Planet Arduino

Omni wheels, sometimes referred to by the trademarked Mecanum name, are special wheels lined with rollers. Thanks to the orientation of the rollers, a vehicle equipped with four omni wheels (each driven independently) can move in any direction by vectoring each wheel relative to the others. A typical setup includes four omni wheels, but James Bruton proved that even a single one is useful when he built this strange self-balancing bicycle robot.

This robot is part of a larger project exploring full-sized self-balancing bicycles. It’s a small robot meant for experimenting with some unusual concepts. The front wheel is an omni wheel with its own motor and an axle that is perpendicular to that of the rear wheel, which is a conventional wheel driven by a second motor. The orientation of the omni wheel means that the robot can move the front end left and right easily, providing the inverted pendulum dynamic for self-balancing. When the robot needs to drive forward or backward, the rear motor provides propulsion and the omni wheel rollers spin freely.

As with other self-balancing robots, this requires fast and precise PID control to stay upright. An Arduino Mega 2560 board takes frequent readings from an IMU (inertial measurement unit) and detects if the robot tilts too far to one side. When it does, it turns the omni wheel motor in one direction or the other, measured by an encoder, to correct itself and balance. Commands sent from Bruton’s own custom remote tell the Arduino when it should rotate the rear drive motor. Steering commands influence the balancing routines, allowing the robot to lean or pivot in order to make a turn.

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Wheeled robots normally have wheels that move in a single axis and steer by using either differential speeds or by pivoting some kind of guide wheel. However, this leads to some drawbacks, the most obvious being an inability to move in really tight spaces. When presented with this challenge, YouTuber James Bruton came up with a great design for a highly mobile robot platform that employs a novel setup to move in any direction. Inspired by the work of researchers at Osaka University in Japan, the omni wheel uses a single drive shaft to spin, yet nearly every surface has a way to move along the ground. 

After designing his robot in Fusion 360 and 3D printing each part, Bruton assembled the wheels and added a pulley to each drive shaft which could be spun by a motor sitting directly above. An Arduino Mega is tasked with controlling each of the three BTS7960 motor drivers and it receives commands via an nRF24L01 radio module. All of the drive components are powered by a single 3-cell LiPo battery pack, while the main board is supplied current by a USB battery bank. 

By spinning certain wheels at the correct speed, straight line motion can be produced, as shown in the video below. Bruton tested his robot by driving over carpet, tile, aluminum extrusions, and even a plastic lid, which did very well across everything except the lid. This robot has countless potential uses, such as a garbage collection device for around the house. 

Code and design files for the project are available on GitHub.

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Omni wheels normally contain a number of rollers arranged on their circumference, allowing them to slide left and right and perform various tricks when combined with others. The rollers on UCLA researchers Junjie Shen and Dennis Hong’s OmBURo, however, are quite different in that they are actually powered, enabling a single wheel to accomplish some impressive feats on its own.

These powered rollers give OmBURo the ability to move in both longitudinal and lateral directions simultaneously, balancing as a dual-axis wheeled inverted pendulum. 

Control is accomplished via an Arduino Mega along with an IMU and encoders for its two servo motors —one tasked with driving the wheel backwards and forwards, the second for actuating the rollers laterally via helical gears and a flexible shaft. 

As seen in the video below, the robot can follow different paths via remote control, and even balance on an inclined plane. More informaton on the impressive build is available in the Shen and Hong’s research paper here.

A mobility mechanism for robots to be used in tight spaces shared with people requires it to have a small footprint, to move omnidirectionally, as well as to be highly maneuverable. However, currently there exist few such mobility mechanisms that satisfy all these conditions well. Here we introduce Omnidirectional Balancing Unicycle Robot (OmBURo), a novel unicycle robot with active omnidirectional wheel. The effect is that the unicycle robot can drive in both longitudinal and lateral directions simultaneously. Thus, it can dynamically balance itself based on the principle of dual-axis wheeled inverted pendulum. This letter discloses the early development of this novel unicycle robot involving the overall design, modeling, and control, as well as presents some preliminary results including station keeping and path following. With its very compact structure and agile mobility, it might be the ideal locomotion mechanism for robots to be used in human environments in the future.

Omni wheels normally contain a number of rollers arranged on their circumference, allowing them to slide left and right and perform various tricks when combined with others. The rollers on UCLA researchers Junjie Shen and Dennis Hong’s OmBURo, however, are quite different in that they are actually powered, enabling a single wheel to accomplish some impressive feats on its own.

These powered rollers give OmBURo the ability to move in both longitudinal and lateral directions simultaneously, balancing as a dual-axis wheeled inverted pendulum. 

Control is accomplished via an Arduino Mega along with an IMU and encoders for its two servo motors —one tasked with driving the wheel backwards and forwards, the second for actuating the rollers laterally via helical gears and a flexible shaft. 

As seen in the video below, the robot can follow different paths via remote control, and even balance on an inclined plane. More informaton on the impressive build is available in the Shen and Hong’s research paper here.

A mobility mechanism for robots to be used in tight spaces shared with people requires it to have a small footprint, to move omnidirectionally, as well as to be highly maneuverable. However, currently there exist few such mobility mechanisms that satisfy all these conditions well. Here we introduce Omnidirectional Balancing Unicycle Robot (OmBURo), a novel unicycle robot with active omnidirectional wheel. The effect is that the unicycle robot can drive in both longitudinal and lateral directions simultaneously. Thus, it can dynamically balance itself based on the principle of dual-axis wheeled inverted pendulum. This letter discloses the early development of this novel unicycle robot involving the overall design, modeling, and control, as well as presents some preliminary results including station keeping and path following. With its very compact structure and agile mobility, it might be the ideal locomotion mechanism for robots to be used in human environments in the future.

Retired maker “lingb” created an omni-bot, with four wheels that allow sliding motion in the X/Y plane courtesy of their perpendicular rollers. While that alone would have been a fun build, he also attached a pen, along with a servo-based lifting mechanism, turning this robot into a free-range plotter!

The device is controlled by an Arduino Uno and Bluetooth module, and takes movement commands via a linked smartphone or tablet. Four 28BYJ-48 stepper motors with ULN2003 drivers move each wheel, though outputs are shared between opposite motors to save on I/O. 

This means that rotating the robot isn’t possible, but as shown in the video below, this isn’t needed to plot straight and curved lines with good accuracy.

Omni wheels are devices that look like wheels with extra rollers positioned along their circumference. This allows robots to move forwards and backwards, as well as slide and spin depending on how the wheels are powered. Maker Jeremy S. Cook decided to create his own version, and after some consideration and careful design work, constructed a cylindrical frame out of MDF and PLA.

The Roomba-like unit features an Arduino Nano, which controls four NEMA 17 stepper motors via Easy Driver boards, while a Bluetooth module enables smartphone operation. Once a few intermittent motion issues are worked out, the stepper motors should provide precise positioning for further robotics experimentation.

Code for the build can be found here.