CAREER: Planning and Control for Overconstrained Mechanisms

摘要在许多操作任务中，多点接触是常见的。例如用于分布式或微操作、车辆和传统机器人抓取的阵列。尽管所有这些应用都得到了极大的关注，但以前的工作还没有提供一种分析方法来处理接触状态中的内在不确定性--表示给定触点是卡住、滑动还是脱离接触的状态。接触态之间的这些非光滑跃迁对动力学有很大的影响；因此，系统地减轻非光滑效应所带来的负面影响是很重要的。此外，这些系统经常被过度驱动，因此每个接触接口都是独立铰接的。这导致了名义上运动过约束的机构--也就是说，不能同时满足所有点接触之间的运动关系。哪个约束被打破对摩擦和法向力建模的细节很敏感，因此有必要估计当前的接触状态，并将其纳入运动规划和控制。这项研究的目标是产生混合估计器、运动规划算法和控制策略，它们将协同工作，以确保在非结构化环境中面对多个接触界面时的性能和稳定性。将开发一个过约束的多点机械手原型，并将规划和控制方法应用于该系统，以演示对摩擦界面的细节不敏感的操作。制造通常涉及为了组装的目的而需要重新定位和重新定向对象。为了实现这一点，经常使用多个执行器，这些执行器由于摩擦相互作用而与物体发生粘滞和滑动接触。致动器的物理特性，特别是它们与物体的相互作用，是出了名的难以精确建模。因此，迫切需要对这些低水平细节不敏感的操纵策略。此外，许多车辆，如最初的火星漫游车，都有一个机械设计，保证一些车轮在运行过程中一定会打滑。然而，哪个车轮打滑取决于未知的环境条件。因此，在这种情况下，也需要开发即使在环境引起的重大不确定性存在的情况下也能保证工作的运动规划策略。该项目将通过制定在面对内在不确定性时保证业绩的战略来促进这些需求。短期内，该项目将有助于宏观规模的制造和车辆控制，长期而言，可能会影响微观规模的制造。

AbstractMultiple point contact is common in many manipulation tasks. Examplesinclude arrays for distributed or micro manipulation, vehicles, andtraditional robotic grasping. Although all of these applications havereceived a great deal of attention, no previous works have provided ananalytical approach capable of dealing with the inherent uncertainties inthe contact state--the state that represents whether a given contact issticking, slipping, or is out of contact. These nonsmooth transitionsbetween contact states have a dramatic impact on the dynamics; hence, itis important to systematically mitigate the negative performance thesenonsmooth effects induce. Moreover, these systems are often overactuated,so that each contact interface is independently articulated. This leadsto mechanisms that are nominally kinematically overconstrained--that is,the kinematic relationships between all the point contacts cannot besimultaneously satisfied. Which constraint is broken is sensitive todetails of friction and normal force modeling, so it is necessary toestimate the current contact state and incorporate the contact state intothe motion planning and control. The goal of this research is toproduce hybrid estimators, motion planning algorithms, and controlstrategies that will work in concert to guarantee performance andstability in the face of multiple contact interfaces in an unstructuredenvironment. An overconstrained multiple point manipulator prototype willbe developed and planning and control methods will be applied to thissystem to demonstrate manipulation that is not sensitive to theparticulars of the frictional interfaces.Manufacturing often involves the need to reposition and reorient objectsfor purposes of assembly. To accomplish this, multiple actuators areoften used, and these actuators experience stick and slip contact with theobject due to frictional interactions. The physics of the actuators and,in particular, their interaction with the object are notoriously difficultto model accurately. Hence, there is a strong need for manipulationstrategies that are not sensitive to these low-level details. Moreover,many vehicles, such as the original Mars rover, have a mechanical designthat guarantees that some of the wheels must slip during operation.However, which wheels slip is dependent on unknown environmental conditions. Hence, in this situation as well there is a need to develop motion planning strategies that are guaranteed to work even in the presence of substantial uncertainty arising from the environment. This project will contribute to these needs by developingstrategies that have guaranteed performance in the face of inherentuncertainty. In the short term this project will contribute to macro-scalemanufacturing and vehicle control, and in the long-term will likely impactmicro-scale manufacturing.