This paper proposes a new type of energy-efficient actuator called variable gravity compensation module integrated actuator (VGCA). VGCA improves the energy efficiency by compensating the gravitational torque at the target joint. Additionally, the variability of compensation torque can further improve the energy efficiency by dealing with the variation of payload, which is required in many robotic applications. As a core part of the VGCA, a compact variable gravity compensation module, called CVGCm, is a cylindrical compact modular unit based on the cam and variable pivot of the lever mechanism. By the theoretically designed cam and lever profiles, the CVGCm can generate a non-linear compensation torque and energy-free variability. First, the functional principles of CVGCm and VGCA are explained. Next, implementation detail and manufacturing of VGCA are introduced. Subsequently, the power estimation model of the actuator is explained based on the Lagrangian method. The experimental results showed that the CVGCm achieved a rapid change of the compensation torque in the compact module. Furthermore, compared to the actuator without CVGCm, VGCA showed a 63.1% reduction of current in static motion and a 64.0% reduction of power in dynamic motion.

Funding Information
*  The Samsung Research Funding & Incubation Center of Samsung Electronics under Project Number SRFC-IT1903-02.
*  The Chung-Ang University Graduate Research Scholarship of 2019