We report on the design, optimization, and performance evaluation of a new wheel-leg hybrid robot. This robot utilizes a novel transformable wheel that combines the advantages of both circular and legged wheels. To minimize the complexity of the design, the transformation process of the wheel is passive, which eliminates the need for additional actuators. A new triggering mechanism is also employed to increase the transformation success rate. To maximize the climbing ability in legged-wheel mode, the design parameters for the transformable wheel and robot are tuned based on behavioral analyses. The performance of our new development is evaluated in terms of stability, energy efficiency, and the maximum height of an obstacle that the robot can climb over. With the new transformable wheel, the robot can climb over an obstacle 3.25 times as tall as its wheel radius, without compromising its driving ability at a speed of 2.4 body lengths/s with a specific resistance of 0.7 on a flat surface.

Wheel Transformer: A Wheel-Leg Hybrid Robot With Passive Transformable Wheels

A wheel drive mechanism is simple, stable, and efficient, but its mobility in unstructured terrain is seriously limited. Using a deformable wheel is one of the ways to increase the mobilit...

Origami Wheel Transformer: A Variable-Diameter Wheel Drive Robot Using an Origami Structure

Morphology plays an important role in behavioral and locomotion strategies of living and artificial systems. There is biological evidence that adaptive morphological changes can not only extend dynamic performances by reducing tradeoffs during locomotion but also provide new functionalities. In this article, we show that adaptive morphology is an emerging design principle in robotics that benefits from a new generation of soft, variable-stiffness, and functional materials and structures. When moving within a given environment or when transitioning between different substrates, adaptive morphology allows accommodation of opposing dynamic requirements (e.g., maneuverability, stability, efficiency, and speed). Adaptive morphology is also a viable solution to endow robots with additional functionalities, such as transportability, protection, and variable gearing. We identify important research and technological questions, such as variable-stiffness structures, in silico design tools, and adaptive control systems to fully leverage adaptive morphology in robotic systems.

Adaptive Morphology: A Design Principle for Multimodal and Multifunctional Robots

http://biorolab.synology.me/pdf/Journal%20papers/2014%20JBE.pdf

A Bio-Inspired Hopping Kangaroo Robot with an Active Tail

This report is on the design, control strategy, implementation, and performance evaluation of a novel leg–wheel transformable robot called TurboQuad, which can perform fast gait/mode coordination and transitions in wheeled mode, in legged trotting, and in legged walking while in motion. This functionality was achieved by including two novel setups in the robot that were not included in its predecessor, Quattroped. First, a new leg–wheel mechanism was used, in which the leg/wheel operation and its in situ transition can be driven by the same set of motors, so the actuation system and power can be utilized efficiently. Second, a bio-inspired control strategy was applied based on the central pattern generator and coupled oscillator networks, in which the gait/mode generation, coordination, and transitions can be integrally controlled. The robot was empirically built and its performances in the described three gaits/modes as well as the transitions among them were experimentally evaluated and will be discussed in this paper.

TurboQuad: A Novel Leg–Wheel Transformable Robot With Smooth and Fast Behavioral Transitions

This paper reports on the design, integration, and performance evaluation of a novel four-leg/four-wheel transformable mobile robot, Quattroped. In contrast to most hybrid platforms that have separate mechanisms and actuators for wheels and legs, this robot is implemented with a unique transformation mechanism that directly switches the morphology of the driving mechanism between the wheels (i.e., a full circle) and 2 degrees of freedom leg (i.e., combining two half circles as a leg), so that the same system of actuation power can be efficiently utilized in both wheeled and legged modes. The design process, mechatronics, software infrastructure, behavioral development, and leg-wheel dynamic characteristics are described. The performance of the robot is evaluated in various scenarios, including driving and turning in wheeled mode, driving, step and bar crossing, irregular terrain passing, and stair climbing in legged mode. Taking advantage of the leg-wheel combination on a single platform, the comparison of the wheeled and legged locomotion is also discussed.

Quattroped: A Leg--Wheel Transformable Robot

We introduce the design of a leg-wheel hybrid platform Quattroped. Comparing to most hybrid platforms which have separate mechanisms of wheels and legs, this robot is implemented with a transformation mechanism which directly changes the morphology of wheels (i.e. a full circle) into 2 degree-of-freedom legs (i.e. combining two half-circles as a leg). The mechatronics, software infrastructure, and the initial experimental test of the robot are also reported.

/pdf/design-of-a-leg-wheel-hybrid-mobile-platform-1mfmvf3ovk.pdf

Design of a leg-wheel hybrid mobile platform

This video submission presents the experimental validation and testing of a leg-wheel hybrid mobile robot Quattroped. By combining the smooth and efficient motion of wheels on the flat ground with the great mobility of legs on rough terrains, the design of the robot aims for agile and versatile yet efficient locomotion in both natural and artificial environments. Compared to most hybrid platforms, which have separate mechanisms of wheels and legs, this robot is implemented with a transformation mechanism that directly changes the morphology of wheels (i.e., a full circle) into half-circle legs, each with 2 active degrees-of-freedom (i.e., combining two half circles as a leg ). The experimental testing includes flat terrain driving and turning in the wheeled mode, leg-wheel mode switching, and step crossing, bar crossing, natural rough terrain walking, and stair climbing in the legged mode.

Experimental validation of a leg-wheel hybrid mobile robot Quattroped

A mobile platform including a body, hybrid leg-wheels and driving mechanisms is provided. The hybrid leg-wheels are disposed around the body for carrying the body moving on a working surface. The driving mechanisms are disposed between the corresponding hybrid leg-wheels and the body. Each driving mechanism includes a driving axle connecting the corresponding hybrid leg-wheels and the body. Each driving mechanism provides the corresponding hybrid leg-wheel a rotational degree of freedom and a linear translational degree of freedom, wherein the rotational degree of freedom and a linear translational degree of freedom are driven independently. The rotational degree of freedom allows the hybrid leg-wheels rotating along an axis of the driving axle, and the linear translational degree of freedom allows the hybrid leg-wheels translating with respect to the driving axle, wherein the rotational direction is substantially perpendicular to the translational direction.

Shuan-Yu Shen

Papers

Quattroped: A Leg--Wheel Transformable Robot

Design of a leg-wheel hybrid mobile platform

Experimental validation of a leg-wheel hybrid mobile robot Quattroped

Leg-wheel hybrid mobile platform