Self-stable one-legged hopping using a curved foot

Reduction of the system complexity is currently one of the main challenges for efficient and versatile legged robot locomotion. In this paper, we present a new one legged hopping robot called CHIARO, which is equipped with a curved foot. Even though the robot has no sensory feedback and consists of only two rigid bodies and one spring loaded joint with parallel actuation, it is able to achieve stable forward-hopping over a wide range of parameters and forward-speeds. Operating at natural hopping frequency, the parallel actuation shows good efficiency. This paper presents an approach to determine stability and efficiency of a highly non-linear mechanical system. By implementing a two dimensional numerical model, taking into account ground contact forces by a Newtonian kinematic impact- and coulomb friction law, we conducted a thorough parameter analysis based on a series of simulations. The comparison of the simulation and real world experiments shows good accordance, which qualifies the simulation for parameter optimization including prediction of robot stability and efficiency.