Backdrivability is a key characteristic of robotic reducers; however, a long-standing lack of theoretical research has constrained its engineering application. Hysteresis, as an inherent characteristic of reducers, can effectively reflect the dynamic behavior during rotational motion. This paper systematically studies the backdrivability of reducers based on hysteresis characteristics. Combining the practical needs of robotic applications, the definition of back drive is clarified, emphasizing that its core lies in the rotation angle and energy absorption capacity. By establishing a correlation model between hysteresis characteristics and backdrivability, generalized polynomial and analytical expressions are proposed: lost motion is introduced as a key indicator, utilizing numerical changes in the hysteresis curve to evaluate the rotation angle; the area enclosed by the hysteresis curve is used to characterize the energy absorption capacity of the reducer during back drive, and statistical analysis methods along with torque-energy curves are employed to evaluate overall and instantaneous energy consumption performance, respectively. Experiments compared the backdrivability of two reducers made of different materials. The results indicate that geometric errors, elastic deformation, and material properties all significantly influence back-driving behavior.
Cao et al. (Sun,) studied this question.