Cheng Wei

Clearance in joints caused by assemblage, manufacturing errors, and wear is inevitable, which will affect the dynamic performance of the dual-manipulator system on spacecraft. The motion of the dual-manipulator system with clearances in imperfect joints is the motion of dual-manipulator system with ideal joints. In this paper, the dynamic responses and motion accuracy ofdual-manipulator system on spacecraft considering clearance effects are investigated numerically. The imperfect joint with clearance is considered as contact force constraint and the mathematical model of revolute joint with clearance is established, where the normal contact force is established using nonlinear continuous contact force model and the friction effect is considered using modified Coulomb friction model. Then, a dual-manipulator system on spacecraft with clearance joints is used as the numerical example to implement the investigation. The effects of clearances on dynamic responses and motion accuracy of the dual-manipulator system are presented and discussed via different case studies. Numerical simulation results indicate that clearances present significant effects on the dynamic performances of dual-manipulator system due to contact and impact in clearance joints. The motion accuracy and stability of the dual-manipulator system are obviously reduced. The investigation in this work clearly shows the effects of clearances on dynamic performance of the dual-manipulator system on spacecraft, which is the basis for robust control system design of dual-manipulator system.

The anthropomorphic hand plays a crucial role in human-machine interaction tasks. However, there are very few hands that realize multimodal perception with high degrees of freedom (DOF) in a low-cost way. Here, we present a dexterous hand that achieves multimodal sensing solely through a camera. The hand has 18 DOF but does not require any position or force sensors, making it cost-effective and easy to manufacture. We develop an integrated forearm for the hand that provides both actuation and multimodal sensing information simultaneously. This includes the 18 joint angles, 5 fingertip positions and contact forces, and information on object softness and contour. The core principle of perception is that the camera can track the displacement and tension of all tendons simultaneously. The multimodal perception model is developed by characterizing tendon properties and coupling them with the hand dynamics. Experiments indicate that our hand has potential in multimodal sensing and dexterity.

This paper investigates flexible multibody dynamic modeling and a staged deployment strategy for large-scale spinning tethered satellite systems, targeting deployment instability, inefficiencies, and tension-induced fracture risks. A nonlinear flexible multibody model is constructed using the absolute nodal coordinate formulation within an arbitrary Lagrangian–Eulerian framework, enabling accurate large-deformation modeling of the tether with geometric nonlinearity. This model surpasses traditional massless/rigid rod models by integrating tether mass distribution, flexible dynamics, and satellite attitude dynamics. A two-stage deployment strategy is proposed based on tether safe tension thresholds. Stage 1 optimizes deployment velocity to eliminate libration angles, ensuring stability while maintaining deployment efficiency. Stage 2 employs dynamic angular velocity tracking and torque compensation to reduce tether tension, prioritizing deployment safety. Numerical simulations validate the model’s accuracy and the strategy’s effectiveness, showing significant tension reduction compared to the single-stage strategy and suppressing libration angle oscillations within ±0.5°. The impact of space environmental forces on deployment stability across different orientations is analyzed, highlighting the necessity of force compensation for parallel-to-ground configurations. This research integrates dynamics and control, providing a practical solution for safe and efficient deployment of the spinning tethered satellite system.