Soft-Legged Wheel-Based Robot with Terrestrial Locomotion Abilities

Ali Sadeghi,Alessio Mondini,Barbara Mazzolai,Emanuela Del Dottore,Anand Kumar Mishra

doi:10.3389/frobt.2016.00073

Abstract

In recent years robotics has been influenced by a new approach, soft-robotics, bringing the idea that safe interaction with user and more adaptation to the environment can be achieved by exploiting easily deformable materials and flexible components in the structure of robots. In 2016, the soft-robotics community has promoted a new robotics challenge, named RoboSoft Grand Challenge, with the aim of bringing together different opinions on the usefulness and applicability of softness and compliancy in robotics. In this paper we describe the design and implementation of a terrestrial robot based on two soft legged wheels. The tasks predefined by the challenge were set as targets in the robot design, which finally succeeded to accomplish all the tasks. The wheels of the robot can passively climb over stairs and adapt to slippery grounds using two soft legs embedded in their structure. The soft legs, fabricated by integration of soft and rigid materials and mounted on the circumference of a conventional wheel, succeed to enhance its functionality and easily adapt to unknown grounds. The robot has a semi stiff tail that helps in the stabilization and climbing of stairs. An active wheel is embedded at the extremity of the tail in order to increase the robot maneuverability in narrow environments. Moreover two parallelogram linkages let the robot to reconfigure and shrink its size allowing entering inside gates smaller than its initial dimensions.

Highlights

Terrestrial locomotion has been since long a topic of research for enhancing the development of autonomous systems in uneven environments for instance for mines detection (Hirose and Kato, 1998; Nonami et al, 2003), rescue operations (Murphy, 2004), and exploration of hostile environments (Bellingham and Rajan, 2007)
Wheels excel on prepared surface such as rails and roads but they fail in unstructured environments where instead legged locomotion can overcome unexpected obstacles and rough terrains (Raibert, 1986)
The emergent soft-robotics community has started to provide some novel ideas for solving common problems by providing compliancy in the structure

Summary

INTRODUCTION

Terrestrial locomotion has been since long a topic of research for enhancing the development of autonomous systems in uneven environments for instance for mines detection (Hirose and Kato, 1998; Nonami et al, 2003), rescue operations (Murphy, 2004), and exploration of hostile environments (Bellingham and Rajan, 2007). Rone and Ben-Tzvi (2014) proposed a continuum hybrid actuated tail structure (tendon and rod driving mechanisms) able to generate forces in the x-, y- and z-directions for improving stabilization in locomotion in presence of external disturbances Another example of soft robot is presented in Walker et al (2012). We proposed a novel design for a wheel-leg-based locomotion exploiting a soft-solution approach in particular for improving the climbing of stairs and passing slippery grounds in a passive manner This aim was obtained by employing a combination of hard and soft components in the design of the wheel, allowing the change of stiffness for a better adaptation to different conditions. A multi-gait approach for the locomotion in different situations is proposed, which can take advantage of an actuated tail with variable stiffness, useful for passing stairs and for fine tuning the robot direction

DESIGN CRITERIA

MATERIALS AND METHODS

EXPERIMENTS AND RESULTS