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.

Interaction stability is an important concern in variable admittance control, and it is a prerequisite for achieving the desired compliant interaction with humans or uncertain environments. Different variable admittance controllers with essential stability analyses are required for multiple interaction scenarios in a complex task, where stability analysis is the major difficulty. In this article, we propose a unified stability-guaranteed variable admittance control architecture to decrease the control system complexity, in which we represent the admittance control model as a port-Hamiltonian (pH) system and design an energy tank with the optimization theory. The advantages of the proposed architecture are reflected in several aspects: 1) compatibility with common strategies; 2) perturbation resistance; and 3) passivity as a natural property. As the dissipated energy from the pH system is injected into the energy tank while the energy in the tank is used to support the interaction and perturbation resistance, the best passive approximation of the desired behaviors is generated, which can avoid the control signal failure (control signal failure denotes that the unexpected input $u=0$ occurs due to a lack of energy in the tank). Three different groups of experiments are conducted to verify the feasibility, perturbation resistance, and practicality of the proposed architecture.