Despite decades of designing mobile robots for locomotion in unstructured terrains, no system can operate with the fluidity and ease of animals in these conditions. When compared with animals, mobile robots are neither very mobile nor maneuverable. More generally, mobile robots suffer from a lack of versatility, which extends the mobility and maneuverability concepts to include the ability to operate in and transition among multiple domains (e.g. terrestrial, scansorial, aerial, and aquatic). We are interested in understanding the relationship between a robot's design and its versatility. We then use that understanding to help design systems with high versatility and low mechanical complexity.
Our most successful design is the HyTAQ Robot(Hybrid Terrestrial and Aerial Quadrotor), a novel mobile robot capable of both aerial and terrestrial locomotion. Flight is achieved through a quadrotor configuration; four actuators provide the required thrust. Adding a rolling cage to the quadrotor makes terrestrial locomotion possible using the same actuator set and control system. Thus, neither the mass nor the system complexity is increased by inclusion of separate actuators for terrestrial and aerial locomotion. During terrestrial locomotion, the robot only needs to overcome rolling resistance and consumes much less energy compared to the aerial mode. This solves one of the most vexing problems of quadrotors and rotorcraft in general — their short operation time. Experimental results show that the hybrid robot can travel a distance 4 times greater and operate almost 6 times longer than an aerial only system. It also solves one of the most challenging problems in terrestrial robot design—obstacle avoidance. When an obstacle is encountered, the system simply flies over it.