An Active-Passive Compliance Strategy for Robotic Plugging and Unplugging of Rocket Electrical Connectors

Plugging and unplugging rocket electrical connectors (RECs) are crucial technical processes for checking the electrical performance of the system before a launching mission. Due to the complexity of their structures, plugging and unplugging RECs face several demanding requirements. Specifically, the precise insertion force and the damage caused by the separation force should be taken into consideration. To deal with this issue, an active-passive compliance strategy (APCS) is proposed for plugging RECs precisely and compliantly during the insertion phase and minimizing the instantaneous unplugging impact at the separation moment. The APCS incorporates double passivity as follows: 1) an assisted plugging-unplugging device (APUD) is designed for mechanical passive compliance; and 2) an active compliance control framework is proposed to achieve control compliance (an energy tank is designed to preserve the passivity of the system) while complementing the mechanical passive compliance of the APUD. Furthermore, 80 contrastive experiments with 11 metrics are conducted to verify and evaluate the feasibility and reliability of the proposed strategy. The corresponding results demonstrate that the APCS makes the insertion subtask successful with a mean stable force error of 0.234 $N$ and a stability variance of 0.860 $N^{2}$ and minimizes the separation force effectively.