Determining an object’s spatial pose (including orientation and position) plays a fundamental role in a variety of applications, such as automatic assembly, indoor navigation, and robot driving. In this paper, we design a fine-grained pose sensing system called Tag-Compass that attaches a single tag to an object (whose size may be small) and identifies the tagged object’s pose by determining the spatial orientation and position of the tag. We exploit the polarization properties of the RF waves used in the communications between an RFID reader and the tag on the object. Polarization mismatch between the tag and the reader’s antenna affects the received signal strength at the reader. From the measured signal strength values, we are able to deduce the tag’s pose through a series of transformations and deviation minimization. We propose a system design for Tag-Compass and implement a prototype. We evaluate the performance of Tag-Compass through extensive experiments using the prototype. The experimental results show that Tag-Compass provides accurate estimate of object orientation with a median error of just 2.5° when the tag’s position is known and a median error of 3.8° when the tag’s position is unknown. In the latter case, Tag-Compass will provide an estimate of tag position as a byproduct of orientation sensing, with an accuracy comparable to the state of the art. It is practically appealing to find both the orientation and the position of an object using a single method, instead of having to deploy two different methods.

中文翻译：

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带有单个RFID标签的姿势感应

确定对象的空间姿势（包括方向和位置）在各种应用中起着基本作用，例如自动组装，室内导航和机器人驾驶。在本文中，我们设计了一种称为Tag-Compass的细粒度姿势检测系统，该系统将单个标签附加到对象（其大小可能很小），并通过确定标签的空间方向和位置来识别被标记对象的姿势。我们利用极化RFID阅读器与对象标签之间的通信中使用的RF波的特性。标签和阅读器天线之间的极化不匹配会影响阅读器处的接收信号强度。根据测得的信号强度值，我们可以通过一系列变换和偏差最小化来推断标签的姿态。我们提出了Tag-Compass的系统设计并实现了原型。我们通过使用原型的大量实验来评估Tag-Compass的性能。实验结果表明，Tag-Compass可以准确地估计对象的方向，当已知标签位置时，中值误差仅为2.5°，而当未知标签位置时，中值误差为3.8°。在后一种情况下，标签罗盘将提供标签位置的估计值，作为方向感应的副产品，其精度可与现有技术相媲美。实际上，使用一种方法而不是必须使用两种不同的方法来查找对象的方向和位置是很有吸引力的。