A Survey of Wheeled-Legged Robots

The community in legged robotics focuses on bio-inspired robots, although there are some human inventions that nature could not recreate. One of the most significant examples is the wheel which has made our transportation system more efficient and faster. Inspired by this human-made evolution, we present a survey of wheeled-legged robots, allowing robotic systems to be efficient on flat as well as versatile on challenging terrain. This enhancement, however, comes at the cost of increased complexity due to additional degrees of freedom at the end-effector, which empowers motions along the rolling direction. The missing examples in nature make designing templates that capture the underlying locomotion principles cumbersome, making hybrid locomotion challenging. This paper reviews some of the novel locomotion frameworks overcoming these challenges.