Novel Layered Multi Angular Gearless Transmission (L-MAGT) Mechanism for Agile Manipulation

This paper introduces a multi-axis power transfer mechanism that is applicable when actuators and their corresponding joints are placed separately in a manipulator. In particular, in this work, the humanoid arm is considered the primary target of application. A modified Hobson joint, termed the Multi Angular Gearless Transmission (MAGT), serves as the central mechanism. The system transmits power through the elbow to the wrist without requiring direct placement of the actuator in the distal part of the manipulator. The design uses a layered MAGT (L-MAGT) to convey coaxial inputs. In this study, L-MAGT which employs three layers is applied to implement a wrist with three axes. After L-MAGT transmits inputs, the coupled wrist 3 axes structure converts them into roll, yaw, and pitch motion of the wrist. This approach reduces the weight of the actuator in the distal part of the manipulator. The weight reduction in the distal part leads to more agile manipulation of the manipulator. Furthermore, the MAGT ensures constant velocity transmission across varying elbow angles, eliminating the velocity fluctuation typically associated with universal joints, such as the Cardan joint. Experimental validation using a 3D printed prototype and a motion capture system shows that the mechanism achieves its intended range of motion and maintains acceptable repeatability, despite some backlash and compliance introduced by 3D printed components. The results confirm the feasibility of this mechanism for humanoid arms and manipulators. The proposed mechanism, which passes through a joint with variable angles, offers a novel multi-axis power transfer mechanism solution to manipulator design.