Criteria of type complexity for legged robots

Abstract Type characteristics limit the performance of legged robots. In this paper, the type-complexity criteria for legged robots are proposed to evaluate the structure-related performance at the conceptual-design stage. Firstly, the incidence relation (IR) is used to represent the structural features of legged robots, where the General-Function (GF) set is used to characterize the end-effector of the robot and the incidence-relation matrix is used to characterize the input-output transformation. Secondly, the theoretical basis of type complexity is proposed and demonstrated. On this basis, two types of complexity criteria are defined according to the incidence relation of legged robots. The output complexity reflects the magnitude of the robot drive load, while the input complexity reflects the uniformity of the drive load. These two kinds of complexity point out the distribution of the robot actuation under the specific operation requirements, which is determined by the robot topology, reflecting the advantages and disadvantages of the robot structure. Finally, the theoretical calculations, model simulations, and prototype experiments are carried out for three typical legged-robot types. The correctness and usefulness of the type-complexity criteria are validated and demonstrated.