少自由度并联系泊单元的机构设计及尺度优化

Mechanism Design and Dimensional Optimization of a Low-Degree-of-Freedom Parallel Mooring Unit

摘要:

船舶的自动化系泊系统工作载荷大、波浪补偿运动速度快，采用全自由度并联机构作为系泊装置的时候需要较多的油缸作为作动器，由于油缸载荷大、数量多，对液压系统提出了苛刻的流量和功率要求。为此提出一种少自由度的2UPU-2SPU并联单元，在船艏艉各1套组合形成双并联机构可实现船舶自动系泊的需求。对该机构的工作空间、运动学和力学性能进行综合分析和优化。运用旋量理论分析2UPU-2SPU并联单元的运动特性；基于运动和力的传递/约束特性，划分优质工作空间以避免发生机构的传递奇异和约束奇异。推导了机构单元的规则优质工作空间体积指标、全局传递/约束指标和全局刚度性能指标。以这3类指标为目标函数，采用SPEA2多目标优化算法进行尺度优化求解，并各自针对动态性能和静态性能偏好，应用层次分析法选取出目标性能较优的解。该系泊系统特别考虑了安装条件约束和协同组合运动的方式，单元机构主要通过地脚螺栓体系即可完成在码头上的安装。

Abstract:

The automated mooring system of a vessel is subject to large operational loads and requires fast wave-compensation motions. When a full-degree-of-freedom parallel mechanism is used as the mooring device， a large number of hydraulic cylinders are needed as actuators. Due to the high loads and large quantity of cylinders， stringent requirements are imposed on the flow rate and power capacity of the hydraulic system. To address this issue， a low-degree-of-freedom 2UPU-2SPU parallel unit is proposed. By installing one such unit at both the bow and stern of the ship， a dual parallel mechanism configuration is formed that meets the requirements of automated mooring. A comprehensive analysis and optimization of the workspace， kinematic behavior， and mechanical performance of the proposed mechanism are conducted. Screw theory is employed to analyze the motion characteristics of the 2UPU-2SPU parallel unit. Based on the transmission and constraint characteristics of motion and force， a high-quality workspace is defined to avoid transmission singularities and constraint singularities. The regular high-quality workspace volume index， global transmission/constraint indices， and global stiffness performance indices of the mechanism unit are derived. Taking these three categories of indices as objective functions， dimensional optimization is conducted using the SPEA2 multi-objective optimization algorithm. Furthermore， in accordance with preferences for dynamic and static performance， the analytic hierarchy process （AHP） is applied to select solutions with superior overall performance. The proposed mooring system explicitly considers installation constraints and coordinated combined motion. The unit mechanisms can be installed on the quay primarily through an anchor-bolt system， facilitating practical deployment.