Design of a Concentrically Stacked Modular Actuator with Forced Air Cooling for Multi-DOF Robotic Systems

This paper proposes a concentrically stacked modular (CoSMo) actuator with rotary electric motors to implement multi-degree-of-freedom (multi-DOF) robotic systems with high power densities. The CoSMo actuator shows a novel design concept, which enables the actuator module with an integrated radiator to be combined in series and cooled by a single fan. This unique system has elevated thermal characteristics owing to the heatsink sharing effect. This enables the module to carry higher current by decreasing the temperature-rise rate. Also, the proposed design concept reduces the number of components required for cooling and allows the actuator to be placed concentrically, which contributes to the system having low mechanical impedance and higher power output per unit mass. The thermal characteristics and feature of the CoSMo actuator were analytically and numerically verified by simulation using a simplified model. To advance the thermal characteristics of the system further, the adequate actuator types for the CoSMo actuator were analyzed and a prototype was fabricated based on the analysis. Through the experiment using the prototype, we verified that the maximum continuous current that can be applied to the CoSMo actuator is up to about three times greater than the rated current in a forced air-cooling environment.