CAREER: Planning and Control for Overconstrained Mechanisms

该教师早期职业发展（CAREER）计划研究的目标是产生混合估计器，运动规划算法和控制策略，这些策略将协同工作，以保证在非结构化环境中面对多个接触界面时的性能和稳定性。 一个过约束的多点机械手原型将开发和规划和控制方法将被应用到这个系统中，以证明操作是不敏感的摩擦界面的细节。 多点接触在许多操作任务中很常见。 示例包括用于分布式或微操作的阵列、车辆和传统的机器人抓取。 虽然所有这些应用程序已经收到了很大的关注，没有以前的作品提供了一个分析方法，能够处理的固有的不确定性的接触状态-状态，代表是否一个给定的接触是粘，滑动，或脱离接触。这些接触状态之间的非光滑过渡的动态有显着的影响，因此，重要的是要系统地减轻这些非光滑效应诱导的负面性能。 此外，这些系统通常被过度致动，使得每个接触界面被独立地铰接。 这导致机构名义上运动过约束-也就是说，所有点接触之间的运动关系不能同时满足。 由于摩擦力和法向力建模的细节对哪一个约束被打破很敏感，因此有必要估计当前的接触状态，并将接触状态纳入运动规划和控制中。制造业通常需要重新定位和重新定向对象以进行装配。 为了实现这一点，通常使用多个致动器，并且这些致动器由于摩擦相互作用而经历与物体的粘滞和滑动接触。 众所周知，致动器的物理特性，特别是它们与物体的相互作用，很难精确建模。因此，强烈需要对这些低级细节不敏感的操纵策略。 此外，许多车辆，如最初的火星探测器，具有机械设计，确保某些车轮在运行期间必须滑动。 然而，哪些车轮打滑取决于未知的环境条件。 因此，在这种情况下，也有必要开发运动规划策略，即使在存在由环境引起的大量不确定性的情况下，也能保证工作。 该项目将通过制定在面临内在不确定性的情况下保证业绩的战略来促进这些需求。在短期内，该项目将有助于宏观规模的制造和车辆控制，从长远来看，可能会影响微观规模的制造。

The goal of this Faculty Early Career Development (CAREER) Program research is to produce hybrid estimators, motion planning algorithms, and control strategies that will work in concert to guarantee performance and stability in the face of multiple contact interfaces in an unstructured environment. An overconstrained multiple point manipulator prototype will be developed and planning and control methods will be applied to this system to demonstrate manipulation that is not sensitive to the particulars of the frictional interfaces. Multiple point contact is common in many manipulation tasks. Examples include arrays for distributed or micro manipulation, vehicles, and traditional robotic grasping. Although all of these applications have received a great deal of attention, no previous works have provided an analytical approach capable of dealing with the inherent uncertainties in the contact state--the state that represents whether a given contact is sticking, slipping, or is out of contact. These nonsmooth transitions between contact states have a dramatic impact on the dynamics; hence, it is important to systematically mitigate the negative performance these nonsmooth effects induce. Moreover, these systems are often overactuated, so that each contact interface is independently articulated. This leads to mechanisms that are nominally kinematically overconstrained--that is, the kinematic relationships between all the point contacts cannot be simultaneously satisfied. Which constraint is broken is sensitive to details of friction and normal force modeling, so it is necessary to estimate the current contact state and incorporate the contact state into the motion planning and control.Manufacturing often involves the need to reposition and reorient objects for purposes of assembly. To accomplish this, multiple actuators are often used, and these actuators experience stick and slip contact with the object due to frictional interactions. The physics of the actuators and, in particular, their interaction with the object are notoriously difficult to model accurately. Hence, there is a strong need for manipulation strategies that are not sensitive to these low-level details. Moreover, many vehicles, such as the original Mars rover, have a mechanical design that 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 developing strategies that have guaranteed performance in the face of inherent uncertainty. In the short term this project will contribute to macro-scale manufacturing and vehicle control, and in the long-term will likely impact micro-scale manufacturing.