Abstract

Parallel robots are preferred over serial robots owing to their enhanced accuracy and rigidity which comes from their higher stiffness. However, there are applications both in industry and in healthcare where higher accuracy is required alongside high compliance (reduced stiffness). Accuracy and compliance being conflicting to each other are difficult to achieve simultaneously. To address this issue, an intrinsically compliant 6-dof parallel robot is proposed in this work. Kinematic and analytical modeling is performed for its conceptual design to obtain the Jacobian matrix and thereby map the joint and Cartesian spaces. Robot’s structure design is analyzed, and the wrench analysis is also carried out to estimate the link forces and stiffness. It is shown that by small changes in the proposed robot design; its compliance can be altered making it suitable for a range of applications. It is also shown mathematically that the robot design can be optimized to maintain higher accuracy together with higher compliance. To carry out design optimization, three important performance criteria, namely; global condition number (for higher accuracies), norm of link forces (to reduce actuator power requirement) and robot compliance (for response to an external wrench) are mathematically formulated. Later, a multi-criteria optimization is performed using an evolutionary algorithm to simultaneously optimize these performance criteria. From the final robot design selected, it is evident that a higher robot compliance with optimal condition number and link forces can be achieved.

摘要

并联机器人比串联机器人更受欢迎，因为它们具有更高的刚度和更高的刚度。然而，在工业和医疗保健领域的应用中，需要更高的精度以及高顺应性（降低刚度）。相互冲突的准确性和合规性很难同时实现。为了解决这个问题，一个本质上兼容的 6-自由度在这项工作中提出了并联机器人。对其概念设计进行运动学和分析建模以获得雅可比矩阵，从而映射关节和笛卡尔空间。分析了机器人的结构设计，并进行了扳手分析，以估计连杆受力和刚度。结果表明，拟议机器人设计的微小变化；它的合规性可以改变，使其适用于一系列应用。数学上还表明，可以优化机器人设计以保持更高的精度和更高的合规性。进行设计优化，三个重要的性能标准，即；全局条件数（以获得更高的精度），连杆力规范（以减少执行器功率要求）和机器人顺应性（用于响应外部扳手）在数学上制定。随后，使用进化算法执行多标准优化，以同时优化这些性能标准。从最终选择的机器人设计中，很明显可以实现更高的机器人符合最佳条件数和连杆力。