In this paper, we propose a novel performance metric for articulated robotic mechanisms called the sensor observability analysis and the resulting sensor observability index. The goal is to analyse and evaluate the performance of robot-mounted distributed directional or axial-based sensors to observe specific axes in task space as a function of joint configuration. For example, joint torque sensors are often used in serial robot manipulators and assumed to be perfectly capable of estimating end effector forces, but certain joint configurations may cause one or more task-space axes to be unobservable as a result of how the joint torque sensors are aligned. The proposed sensor observability analysis provides a method to analyse the cumulative quality of a robot configuration to observe the task space, akin to forward kinematics for sensors. The resultant metrics can then be used in optimization and in null-space control to avoid sensor observability singular configurations or to maximize sensor observability in particular directions. Parallels are drawn between sensor observability and the traditional kinematic Jacobian for the particular case of joint torque sensors in serial robot manipulators. Compared to kinematic analysis using the Jacobian in serial manipulators, sensor observability analysis is shown to be more generalizable in terms of analysing non-joint-mounted sensors and can potentially be applied to sensor types other than for force sensing, e.g., link-mounted proximity sensors. Simulations and experiments using a custom 3-DOF robot and the Baxter robot demonstrate the utility and importance of sensor observability in physical interactions.

翻译：本文提出了一种用于关节机器人机构的新型性能指标——传感器可观测性分析及其导出的传感器可观测性指数。该指标旨在分析和评估机器人上安装的分布式定向或轴向传感器，在任务空间中观测特定轴的能力随关节构型的变化。例如，关节力矩传感器常用于串联机器人操作臂，且通常被认为能够完美估计末端执行器所受的力，但由于关节力矩传感器的对齐方式，某些关节构型可能导致任务空间中的一个或多个轴不可观测。所提出的传感器可观测性分析提供了一种方法，可分析机器人构型观测任务空间的累积质量，类似于传感器的正向运动学。由此得出的指标可用于优化和零空间控制，以避免传感器可观测性奇异构型，或在特定方向上最大化传感器可观测性。针对串联机器人操作臂中关节力矩传感器的特定情况，本文建立了传感器可观测性与传统运动学雅可比矩阵之间的类比关系。与串联操作臂中使用雅可比矩阵的运动学分析相比，传感器可观测性分析在分析非关节安装传感器方面更具泛化能力，并可能适用于除力传感以外的其他传感器类型，例如连杆安装的接近传感器。使用定制三自由度机器人和Baxter机器人进行的仿真和实验，展示了传感器可观测性在物理交互中的实用性和重要性。