多模式并联机构操作模式变换方法研究

Operation Mode Transformation Method of Multi-mode Parallel Mechanism

多模式并联机构可通过改变操作模式来满足不同功能性、适应性要求。为更好地实现多模式机构不同模式间的平稳变换,提出一种多模式并联机构的操作模式变换方法。首先,基于Study参数和代数几何对多模式并联机构进行可重构分析,获得机构的各种操作模式和变换位形;其次,对实际需要的操作模式和变换位形的合理驱动空间进行分析求解,将所有变换位形的驱动空间求交集,得到机构的驱动空间,并优选出最优的驱动组合;最后,采用TCI(整体运动/力约束性能指标)确定近似约束奇异空间,在该空间内采用冗余驱动的方式,使机构平稳实现操作模式之间的变换。以SNU 3-UPU机构为例,分析了3T模式与2T1R模式之间的变换过程,并通过仿真验证了该方法的正确性。

The multi-mode parallel mechanism could change the operation mode to meet the requirements of different functional and adaptive tasks.In order to realize the stationary transformation preferably between different modes,an operation mode transformation method of multi-mode parallel mechanism was proposed.Firstly,to obtain various operation modes and transformation configurations of the mechanism,the dual quaternion was used to describe the position of moving platform systematically,and the reconfigurable analysis of the multi-mode parallel mechanism was carried out based on the algebraic geometry,that was the polynomial constraint equations were established by using study parameters,and further prime decomposition was performed.Secondly,the reasonable actuation spaces of the operation modes and the transformation configurations of actual demand were analyzed and solved by preferring base pairs or moving pairs close to the base as the driving pairs.The actuation spaces of the mechanism were obtained by intersecting all the actuation spaces of the transformation configurations,and the optimal combination of actuators was selected according to the principles that the least actuators were used to realize the most operation modes and the mechanism had good performance.Finally,TCI(Total constraint index)was adopted to determine the approximate constraint singular space(κ<0.3),and redundancy actuation was adopted in this space to make the mechanism realize the transformation between operation modes smoothly.Taking SNU 3-UPU mechanism as an example,seven operation modes and four transformation configurations were obtained,the transformation process between 3T mode and 2T1R mode was analyzed,and the correctness of the method was verified by simulation.