Development of Chain Motor with Shape Variability and Its Application to a Humanoid

Abstract

The enhancement of output torque is crucial for robots performing high-load operations, and various methods have been proposed to achieve this. However, in robots with elongated frames, such as humanoid robots, the limited space available for actuators and transmission components restricts the application of existing methods. In this paper, we propose the Chain Motor, an electric actuator with shape variability. Shape variability refers to the ability of the actuator to change its form during operation. This capability enables a denser arrangement of motors even under spatial constraints imposed by the frame geometry, which improves output torque. For instance, actuators can be placed across adjacent frames and deform in response to joint rotation. We evaluated the performance of the developed Chain Motor by measuring torque characteristics. Furthermore, by applying the Chain Motor to the elbow joint of a humanoid robot, we demonstrated its ability to facilitate high-load operations.