Position-based high backdrivable control using load-side encoder and backlash

Abstract

The demand for robots working with humans, known as collaborative robots, has increased recently. Collaborative robots must be human-friendly; they must ensure safety and flexibly follow human's instructions. In the industry, as the cost of high-resolution encoders has decreased, the number of devices with load-side encoders has significantly increased. However, studies on control methods using load-side encoder information are limited. Therefore, in this paper, a high backdrivable control method for geared mechatronic systems is proposed using load-side encoder information and backlash. The proposed high backdrivable control method utilizes the idling characteristics of backlash, by precise position control using both motor-side and load-side encoders. The performance of the proposed method is verified and compared to impedance control. Moreover, the advantages of employing a load-side encoder to collaborative robots are demonstrated by simulations and experiments.