Toward low impact docking: an admittance control approach integrated with contact proprioception

Purpose Low impact docking presents significant challenges, particularly in achieving accurate contact force perception and effective compliant control in uncertain space environments. The purpose of this study is to develop a robust, compliant and durable docking system to address the potential needs of future space missions. Design/methodology/approach A proprioceptive low impact docking system (PLIDS) is designed for contact proprioception and compliant control. Its mechanical structure comprises a base, an end-effector and six identical joint branches, each integrating a quasi-direct-drive actuator (QDA) with high back drivability and an equivalent Hooke joint. An efficient dynamics model incorporating friction was then derived using the principle of virtual work. Furthermore, a three-layer cascaded admittance control framework was developed, consisting of an inner joint motion loop, a middle admittance loop and an outer contact monitoring loop. Each layer operates at a distinct frequency and serves a dedicated function, collectively enabling high-accuracy contact perception, real-time motion planning and compliant control. Findings The ground test experiments confirm its feasibility for low impact docking applications, with contact forces and moments as low as 1032 N and 240 Nm, respectively. Moreover, the collision detection experiments show the proposed PLIDS achieves high-precision force estimation, with errors below 47 N and 40 Nm. Originality/value This research pioneers the integration of proprioceptive and compliant control into the design and control of the PLIDS, significantly enhancing its adaptability and compliance. The developed methodology provides critical technical support for space missions such as manned spaceflight, deep space exploration and on-orbit servicing.