Mechanism design and workspace analysis of a hexapod robot with changeable morphology

Abstract

Here, the morphology of a legged robot refers to the standing/crawling pose of the robot and the forward/backward orientation of the knee, which are related to the configurations of all leg mechanisms. The standing/crawling pose of the robot determines the body height and the leg supporting region size, which are related to the obstacle-traversing and arch-traversing capability. The proper knee orientation can reduce the leg-ground interference risk and then help for selecting good foothold. Therefore, the terrain adaptability can be enhanced if the morphology of the legged robot is changable. Motivated by this, a hexapod robot with changeable morphology is designed in this study. For the leg mechanism, a double-parallelogram transmission mechanism is used to implement the forward/backward orientation changes of the knee. The hexapod robot can transform between the crawling morphology and the standing morphology, and can also transform among four standing morphologies (i.e., the knee-elbow, knee-knee, elbow-knee, and elbow-elbow morphology). The appropriate robot morphology can be determined according to the terrain type. The lateral reachable body workspaces are derived analytically for different morphology, which is useful for the motion planning. Simulations are used to verify the design and analysis of the hexapod robot.