Improved Admittance Control Based Berthing System for Robotic On-Orbit Refueling Mission

The growing demand for accurate and reliable on-orbit refueling missions has prompted the development of advanced solutions. In response, this paper introduces an innovative berthing system that utilizes a 6-degree-of-freedom robotic arm. The primary objective of this system is to enhance the precision and dependability of on-orbit refueling operations. To achieve improved force tracking performance, an enhanced admittance control approach is proposed, which incorporates a proportional-derivative controller. This integration enhances the traditional admittance control method and ensures precise interaction between the robotic arm and the target spacecraft during the berthing process. The effectiveness of the proposed berthing system and control algorithm is validated through extensive experimentation. The results demonstrate significant improvements in the system's fast response capability and reduction in force overshoot. Notably, when employing the designed berthing system and the improved admittance control algorithm, the maximum contact force remains below 20N, and the maximum contact torque is limited to 0.8Nm. These outcomes underscore the system's ability to achieve safe and reliable berthing operations in on-orbit refueling missions.