Design and control of multibody mechanical systems

提高生产力需要快速、高效的机器人机械系统，能够以一种特殊的运动移动有效载荷，这种运动不包括某些刚体运动，这就产生了所谓的低移动性机器人或机制。这些需要运动学循环，因为它们具有并行架构。因此，这些系统本质上是过度约束的，因为任何制造和装配误差都会使环路闭合不可能或限制其自由度。专家设计师使用额外的关节来科普这一特点，缺点是刚度，因此，精度，是妥协。在未来五年的研究计划中，我们将研究低移动性机器人的设计和控制。在设计方面，我们会引入复杂性作为主要的设计准则，因为它可以处理设计过程的概念阶段的有限信息。通过为机器的每个性能方面、精度、刚度和可组装性分配复杂性度量，我们将能够面对当前的行业挑战。这里的主要思想是在所有致动器之间尽可能均匀地分配负载，同时针对具有几何、运动和机械对称性的机械结构。结果应该是机械系统在任何运动方向上具有相同的精度和刚度特性，以及相同的固有频率。然而，功能要求可能使其不可能满足上述理想条件。在这种情况下，应该针对性能尽可能接近前述理想的机器达成妥协。在控制方面，我们也将使用复杂性作为主要的设计标准，这将使我们能够产生最简单的控制系统架构，一个接近相同的单输入，单输出控制子系统的并行阵列，一个用于有效载荷的每个运动方向。

Productivity-enhancement has called for fast, efficient robotic mechanical systems capable of moving a payload with motions of a special kind, that exclude some rigid-body motions, which has given rise to what is known as lower-mobility robots or mechanisms. These entail kinematic loops, as they bear a parallel architecture. As a consequence, these systems are inherently overconstrained, in that any manufacturing and assembly errors either make loop-closure impossible or limit their degree of freedom. Expert designers use extra joints to cope with this feature, the downside being that stiffness, and hence, precision, are compromised. In the research program proposed here for the next five years we will investigate the design and control of lower-mobility robots. On the design side, we will introduce complexity as a main design criterion, for it can handle the limited amount of information available at the conceptual stage of the design process. By assigning a complexity measure to each of the machine performance aspects, precision, stiffness and assemblability, we will be able to face the current challenges of industry. The main idea here is to distribute the load as uniformly as possible among all actuators, while aiming at a mechanical structure with geometric, kinematic and mechanical symmetries. The outcome should be a mechanical system with the same precision and stiffness properties in any direction of motion, and the same natural frequencies. However, functional requirements may make it impossible to meet the foregoing ideal conditions. In this case, a compromise should be reached in aiming at machines whose performance lies as closely as possible to the foregoing ideal. On the control side, we will also use complexity as a major design criterion, which will allow us to produce the simplest control-system architecture, one approaching a parallel array of identical single-input, single-output control subsystems, one for each motion direction of the payload.