Computational Design of Closed-Chain Linkages: Hopping Robot Driven by Morphological Computation

The main advantages of legged robots over wheeled ones are their abilities to traverse on uneven terrain due to the use of intermittent contacts and an ability to shift the center of mass relative to the contact location. A robot's leg design can be implemented by using an open-chain mechanism actuated with high-density torque actuators though this solution needs a vast energy budget. An alternative way to design a leg mechanism is the application of morphological computation principle. According to the principle, most of the desired robot's behavior can be delegated to the mechanics with minimum control effort needed to excite, stabilize or augment it. Within this paper, we have proposed a method to synthesize a leg for hopping robots. Due to optimization of mechanical structure, geometric parameters, mass distribution, and elasticity allocation, our method allows getting an energy-efficient robot with minimal control system complexity, which is accomplished via series elastic allocation and active variable length link. Based on this approach, we have designed a hopping robot with two low performance actuators that can achieve hopping, running, and, in the case of a biped or quadruped robot, walking motion. The paper describes a synthesized leg linkage and overviews prototype design, control strategy, and test results of a physical prototype.