Omnidirectional Bike: Balancing on Spheres

Omnidirectional Bike: Balancing on Spheres

The pursuit of unconventional vehicle designs continues with the creation of an omnidirectional bike that balances on two spheres. This project builds upon previous iterations, which included designs with omni wheels and mecanum wheels, each presenting unique challenges in achieving multidirectional movement.

Design and Mechanics

This iteration uses two rigid balls, referred to as "walking globes," driven by omni wheels. Each ball is propelled by three omni wheels, with two wheels powered and the third acting as an idler. This configuration is intended to allow for both sideways and forward/backward movement. However, the design introduces concerns about potential slippage between the wheels and the balls, which could affect the bike's maneuverability.

• Omni Wheels: These wheels, with their ability to slide sideways, are crucial for enabling lateral movement.
• Walking Globes: Rigid spheres that serve as the base for balancing and movement.
• Drive System: Utilizing O-drives with 8325 motors, the system aims to control position, velocity, and torque for precise movement.

Challenges and Solutions

Several challenges were encountered during the construction and testing phases:

1. Traction and Slippage: Initial tests revealed concerns about the traction between the omni wheels and the balls. To address this, the design allows for motorizing the third idler wheel if necessary.
2. Static Electricity: The buildup of static electricity between the balls and omni wheels caused glitches and disruptions. Grounding the chassis and metal components helped mitigate these issues.
3. Forward Acceleration: The initial design struggled with forward acceleration, leading to wheel spin. An additional drive unit was added to the rear wheel to improve acceleration.
4. Centrifugal Force: When driving in circles, the bike tended to drift outwards due to centrifugal force. A "steer to lean" control was implemented, which adjusts the balance point to counteract the outward drift.

Construction and Components

The bike's frame is constructed from 4040 T-slot aluminum extrusion, allowing for adjustability and modularity. Custom aluminum plates, manufactured by PCBWay, are used to attach the motor reduction units to the frame. 3D-printed parts, created using Lulzbot 3D printers and 3DFuel filament, provide the necessary structure and tolerancing for bearings and other components.

Handlebar Controls

Custom-designed twist grips were implemented for steering and forward/backward movement. The steering mechanism uses a hall effect sensor to detect the twist grip's position, allowing for precise control of the bike's direction.

Future Improvements

Despite the progress made, there's room for further refinement. One area for improvement is the wheel design for better forward/backward motion. Resolving the high velocity wheel popping issue is also a key consideration.

Concluding Thoughts

The omnidirectional bike represents an ambitious attempt to redefine personal mobility. The project highlights the complexities of balancing and controlling movement on spheres, offering insights into the challenges and potential solutions in unconventional vehicle design. Which path will future development take?

Comments are closed.