Kinematic singularity elimination and deployment dynamics of a gear-synchronized truss-type deployable structure

Large deployable structures are promising for offshore buoy systems that require compact transportation and reliable in-service deployment. From a structural mechanics perspective, however, practical deployment is complicated by thickness-induced geometric offsets, synchronization constraints, and gravity-coupled dynamic effects. This study proposes a gear-synchronized truss-type deployable structure and investigates its kinematic and dynamic behavior. A closed-loop kinematic model is first established to characterize the effect of panel thickness on the deployment path. The results show that the original mechanism may encounter a Type II singularity near the fully deployed state, causing motion bifurcation and loss of deterministic motion. To resolve this issue, a drive-topology reconfiguration strategy is proposed. A rigid-flexible coupled dynamic model is then developed to examine the deployment response under different deployment durations, gravity orientations, and passive torsion-spring inputs. The deployment-duration analysis shows that slower deployment reduces transient stress, while the stress-reduction benefit becomes less pronounced in the longer-duration range. The horizontal attitude is identified as the most unfavorable gravity condition for the present configuration. For passive deployment, the analysis reveals a dynamic bottleneck effect and shows that the rate-determining joint may shift when the torsion-spring preload distribution is changed. A scaled prototype is used to qualitatively verify the feasibility of the proposed design and the consistency of the deployment sequence, while stress, torque, and time-history responses are evaluated numerically. The study offers useful insight into the design and analysis of thick-panel deployable truss structures with synchronized constraints.