The model and design of a Spring-Embedded Planetary Dual-Motor Actuator to reduce energy losses

Abstract

The electrification of many mobile applications such as wearable robots has led to the need for carrying batteries to store electrical energy. However, low-efficient actuators require larger batteries that have to be carried along, which limits the range and performance of such devices. In addition, collaborating with robots require safe cobots and actuators. To address this challenge, parallel and series elastic actuators have been adopted in many applications to increase safety and energy efficiency. Meanwhile, some industries, including the automotive industry, have put much research effort into dual motor actuation to decrease the energy consumption of the overall drivetrain.In this paper, we introduce a Spring-Embedded Planetary Dual-Motor Actuator (SEP-DMA) which combines both technologies using a planetary gear unit and a spring. We derive and validate a dynamic model for all possible configurations and discuss their operating modes, including active and passive actuation. To demonstrate the potential of the actuator, we compare it with a traditional stiff actuator consisting of a gearbox and electric motor. The former shows a 40% decrease in the overall energy consumption for a standard task of lifting and oscillating a mass.