Design and control of mechanical systems with reduced mobility

对更快的生产机械的追求要求设计和开发能够以特殊类型的运动移动有效载荷的机械系统，缺少全部六个刚体的一些自由度。这一领域的工作已经产生了所谓的低移动性机器人（LMR）。这种类型的典型机器被称为SCARA（选择性顺应性装配机器人臂）系统，用于传送扁平工件，如出现在现代电子产品（手机、iPod等）中的那些。它们在两个最大尺寸位于平行平面的两个姿态之间移位。这一特征要求抑制围绕两个独立水平轴的倾斜，从而导致具有四个自由度的运动，已知需要具有群的代数性质的位移，所述群被称为刚体位移群的Schoenflies子群。这些位移是由服务员的托盘所经历的：沿着沿着三个独立方向的平移，但是一个单一的旋转，即围绕固定方向的轴，通常是垂直的。传统的SCARA系统，其特征在于三个平行轴的销接头和一个平行于前述轴的方向的滑动接头，在串联阵列中，已经存在了大约25年。它们的技术已经成熟，它们的性能已经达到其物理极限，这促使自世纪之交以来发展了替代形态，即平行的，具有多达四个四肢连接固定基座和移动平台。后者携带夹持器。这只是LMR的一个例子;还有更多。这些系统的设计和控制提出了有趣的挑战，因为他们的加工和装配精度的极端要求。这里提出了应对这些挑战的强有力的手段。拟议工作中采用的理念在于申请人在过去六年中进行的理论设计工作。

The quest for faster production machinery has called for the design and development of mechanical systems capable of moving a payload with motions of a special kind, short of some degrees of freedom of the total six of rigid bodies. Work in this area has given rise to what is known as low-mobility robots (LMR). Typical machines of this kind are what is known as SCARA (Selective-Compliance Assembly Robot Arm) systems, for the transfer of flat workpieces, as those appearing in modern electronic products (cell phones, iPods, etc.) that are displaced between two poses in which their two largest dimensions lie in parallel planes. This feature calls for a suppression of tilting about two independent horizontal axes, thereby leading to motions with four degrees of freedom, known to entail displacements endowed with the algebraic property of a group, what is called the Schoenflies subgroup of the rigid-body displacement group. These displacements are those undergone by the tray of a waiter: translations along three independent directions, but one single rotation, namely, about an axis of fixed direction, usually vertical. Conventional SCARA systems, featuring three pin joints of parallel axes and one sliding joint of direction parallel to the foregoing axes, in a serial array, have been around for about 25 years. Their technology has reached maturity, their performance having reached its physical limits, which has prompted, since the turn of the century, the development of alternative morphologies, namely, parallel, with up to four limbs connecting a fixed base with a moving platform. The latter carries the gripper. This is but one example of LMR; there are many more. The design and control of these systems pose interesting challenges because of the extreme demands in the accuracy of their machining and assembly. Robust means to face these challenges are proposed here. The philosophy adopted in the proposed work lies in the theoretical design work conducted by the applicant in the last six years.