Design of kinematically-redundant two-module robots

当需要精确定位时(如在机床中或在对准工作台中)，并联机器人因其高刚性而成为首选。然而，并联机器人的主要缺点之一是它们的工作空间相对较小，这进一步受到所谓类型2奇点的存在的限制。当并联机器人接近于类型2奇异构形时，其末端执行器承受载荷的能力会显著降低。由于这些奇点，很少有公司能够提出创新的设计，大多数公司坚持流行的六足，它经常过度设计(例如，太大)，不适合手头的应用程序。 分而治之的策略很有希望实现负担得起的高精度机器人系统。申请人不是设计单一的n自由度(n-DOF)并联机器人，而是选择使用两个独立的机器人，一个具有i个自由度的机器人旨在操纵刀具(可能是串联机器人)，另一个具有j个自由度的机器人用于夹持工件。此外，这个两模块机器人系统在运动学上是冗余的，这意味着i和j的和将大于n。 提出的研究方案背后的主要思想是使用具有一到两个运动学冗余度的两个机器人(至少其中一个是平行的)的组合，即ij=n1或ij=n2，以完全消除奇点问题。因此，该方案的第一个目标是开发一种系统的方法，用于分析导致具有大工作空间和降维奇异性流形的运动冗余设计的几何条件。将特别关注低自由度混合自由度空间并联机构，这已被证明是机床的极佳选择。第二个目标是为现有的串联式和并联式机器人设计次级模块。最后，第三个目标将是为这些两模块机器人开发新的低成本自动校准技术。

When precise positioning is needed (as in a machine tool, or in an alignment table), parallel robots are a choice of predilection due to their high rigidity. However, one of the major disadvantages of parallel robots is their relatively small workspace, which is further limited by the presence of so-called Type 2 singularities. When a parallel robot is close to a Type 2 singular configuration, its ability to withstand loads with its end-effector is significantly compromised. Because of these singularities, very few companies have managed to come up with innovative designs and most stick to the popular hexapod, which is often overdesigned (e.g., too big) for the application at hand. The divide-and-concur strategy is promising for achieving affordable high-accuracy robot systems. Instead of designing a single n-degree-of-freedom (n-DOF) parallel robot, the applicant would opt for the use of two separate robots, one with i DOFs aimed at manipulating the tool (possibly being a serial robot) and another with j DOFs for holding the workpiece. Furthermore, this two-module robot system will be kinematically redundant, which means that the sum of i and j will be greater than n. The main idea behind the proposed research program is to use a combination of two robots (at least one of which is parallel) with one or two degrees of kinematic redundancy, i.e., i + j = n + 1 or i + j = n + 2, in order to completely eliminate problems with singularities. The first objective of the proposed program is therefore to develop a systematic approach for analysing the geometric conditions leading to kinematically redundant designs with large workspace and singularity manifolds of reduced dimension. Particular attention will be paid to lower-mobility spatial parallel mechanisms with mixed DOFs, which have proven to be an excellent choice for machine tools. The second objective will be designing secondary modules for existing serial and parallel robots. Finally, the third objective will be the development of novel low-cost automated calibration techniques for these two-module robots.