With the increasing amount of space debris, it is necessary to develop space debris active cleaning technology. The space netted pocket system is a flexible mechanism system which can be used to capture a non-cooperative target flexibly due to the advantages of having a stable structure, strong adaptability and a large capture range. In this paper, the dynamics of the space netted pocket system capturing a non-cooperative target are investigated. The dynamics model of the space netted pocket system is established based on the absolute nodal coordinate formulation (ANCF). The mathematic model of the closing rope is modeled using an ANCF flexible cable dynamics model. Then, the contact collision force model is presented to describe the collision characteristics during the space netted pocket system capturing the target. Finally, the dynamic characteristics of the space netted pocket system capturing the non-cooperative target are analyzed and discussed for different capturing strategies. The simulation results indicate that the target is captured successfully and the target contacts and collides with the rope net in the capturing process, which is subjected to contact and collision forces.

The identification of space debris’s dynamic parameters is a prerequisite for detumbling and capture operations. In this paper, a novel method for identifying dynamic parameters based on the rope net flexible collision and vision data is proposed, which combines the advantages of full dynamic parameter estimation (contact method) and safety (non-contact method). The point cloud data before and after collision is obtained by LiDAR, and the transformation matrix of point clouds and debris motion data are calculated by point cloud registration. Before the collision, using the motion model-based optimization, the real-time position of the debris center of mass is estimated. And the transformation matrix between visual and debris-fixed coordinates are calculated by the mass center position and transformation matrix of the point cloud. Then, using the debris dynamic model and parameters’ characteristics, the normalized dynamic parameters are estimated. An identification method of net node position changes based on the flexible collision characteristics of rope nets is proposed, which is used to obtain the momentum of the rope net after the collision. Based on the conservation of linear momentum and angular momentum of the satellite-net system, the true values of the mass and the principal moment of inertia of the debris are estimated. The true values of the kinetic energy and momentum can be obtained by substituting the true values of the principal moment of inertia into the normalized parameters, and the full dynamic parameters of large space debris is estimated. Simulations of identifying full dynamic parameters have been performed; the results indicate that this method can provide accurate and real-time true values of dynamic parameters for the detumbling and capture mission.

The space flexible netted pocket capture system provides a flexible and stable solution for capturing non-cooperative space objects. This paper investigates the control problem for the capture of non-cooperative targets undergoing motion. A dynamic model of the capturing net is established based on the absolute nodal coordinate formulation (ANCF) and equivalent plate–shell theory. A contact collision force model is developed using a spring–damper model. Subsequently, a feedforward controller is designed based on the estimated collision force from the dynamic model, aiming to compensate for the collision effects between the target and the net. By incorporating the collision estimation data, an extended state observer is designed, taking into account the collision estimation errors and the flexible uncertainties. A sliding mode feedback controller is then designed using the fast terminal sliding mode control method. Finally, simulation analysis of target capture under different motion states is conducted. The results demonstrate that the spacecraft system’s position and attitude average flutter amplitudes are less than ${10}^{-2}$ m and ${10}^{-2}$ deg. In comparison to standard sliding mode control, the designed controller reduces the attitude jitter amplitude by an order of magnitude, thus demonstrating its effectiveness and superiority.