Development of a Compact Robust Passive Transformable Omni-Ball for Enhanced Step-Climbing and Vibration Reduction (2403.14160v2)

Abstract: This paper introduces the Passive Transformable Omni-Ball (PTOB), an advanced omnidirectional wheel engineered to enhance step-climbing performance, incorporate built-in actuators, diminish vibrations, and fortify structural integrity. By modifying the omni-ball's structure from two to three segments, we have achieved improved in-wheel actuation and a reduction in vibrational feedback. Additionally, we have implemented a sliding mechanism in the follower wheels to boost the wheel's step-climbing abilities. A prototype with a 127 mm diameter PTOB was constructed, which confirmed its functionality for omnidirectional movement and internal actuation. Compared to a traditional omni-wheel, the PTOB demonstrated a comparable level of vibration while offering superior capabilities. Extensive testing in varied settings showed that the PTOB can adeptly handle step obstacles up to 45 mm, equivalent to 35 $\%$ of the wheel's diameter, in both the forward and lateral directions. The PTOB showcased robust construction and proved to be versatile in navigating through environments with diverse obstacles.

• The paper presents a novel PTOB design that improves step-climbing and minimizes vibrations through an innovative three-spherical-cap structure.
• It demonstrates enhanced performance by negotiating obstacles up to 45 mm high and adapting efficiently to uneven surfaces with a passive sliding mechanism.
• Experimental results confirm that the design achieves stable vibration levels while integrating actuators compactly for superior mobile robotics applications.

Overview of Passive Transformable Omni-Ball Development

The paper introduces a novel locomotion mechanism, the Passive Transformable Omni-Ball (PTOB), designed to improve the capabilities of omnidirectional wheels. The PTOB focuses on enhancing step-climbing, minimizing vibrations, and increasing robustness, especially for applications demanding high maneuverability on uneven terrain. This paper presents both the PTOB's design features and its implications for applications in robotics and other fields where traditional wheel mechanisms might fall short due to limitations in handling diverse and challenging surfaces.

Key Design Innovations

The PTOB is based on the existing Omni-ball, yet it incorporates several significant improvements. A principal innovation is expanding the conventional two-segment design to three spherical cap structures. This adjustment aims to provide sufficient space along the rotational axis for actuator integration, which is pivotal in achieving in-wheel integration while minimizing structural gaps that could compromise performance.

Another critical feature introduced in the PTOB is the sliding mechanism within the spherical cap-shaped wheel units. This passive sliding structure allows the wheels to adjust during interaction with step-like obstacles, drastically improving step-climbing capabilities. Experimental results show that the PTOB excels in handling steps that are 35% of the wheel's diameter, significantly outperforming the Omni-ball's prior achievements.

Experimental Validation

The research demonstrates the PTOB's effectiveness through several experiments, contrasting it primarily against the conventional Omni-ball and Single Omni-wheel. Noteworthy among these is the vibration assessment during various motion patterns. The PTOB achieves comparable levels of vibrations to legacy systems, thereby confirming its viability for stable locomotion under typical operational conditions.

Step-climbing tests underscore PTOB's superiority as it adeptly negotiates steps up to 45 mm in height, capitalizing on its unique structural features. Additionally, tests conducted over various terrains, including gap-crossing and cable-passage scenarios, further establish the PTOB's robustness and adaptability.

Implications and Future Prospects

From a theoretical standpoint, the PTOB architecture introduces a paradigm shift in how actuator integration and passive mechanical adjustments can collaboratively enhance wheel performance on omnidirectional platforms. Practically, its development could substantially impact the design of mobile robots, particularly those operating in environments where surface irregularities are prevalent, such as search-and-rescue or autonomous delivery systems.

The PTOB also opens new avenues for wheel-based robots that require enhanced mobility without significant design changes to existing chassis structures. With its compact and robust construction, it provides opportunities for significant reductions in size and weight of mobile robotic platforms, which are crucial for increasing operational efficiency and broadening application scopes.

Looking forward, further refinement of the PTOB is necessary to address operational challenges, such as camouflaging potential gaps that might entrap foreign objects. Moreover, integrating more sophisticated control algorithms to optimize phase alignment and movement efficiency remains a promising area for future research. The quest for balancing torque, size, and actuator force within this novel structure presents an ongoing challenge that will likely fuel continued innovations in robotic mobility solutions.