Many motions in mobile manipulators are conducted quasi-static and non-periodically at low speed. Due to these motions’ features, about 90% of the required torque at actuators is generated by the gravitational force. In other words, reducing the gravitational torque can dramatically improve the efficiency of the actuator. Moreover, the payload on the end-effector is varied during the tasks, leading to the variation of the required gravitational torque even in the same mobile manipulator.

We are developing a variable gravity compensation module that can compensate for the gravitational torque and adjust the degree of compensation according to the payload variation. Furthermore, by combining the variable gravity compensation module with customized high-power and compact actuators, we present a novel approach to energy-efficient actuators in the robotic field.

There is a limit to the optimal design of the robot platform due to a low power density and a large volume of the form factor of conventional actuators. Therefore, we are developing new actuators having novel transmission mechanisms for low-profile and high bandwidth performances. Currently, we are developing two types of actuators that can be applied to consumer robots, including wearable robots.